JP2017165993A - Metal nanowire and method for producing the same, metal nanowire dispersion liquid and transparent conductive film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal nanowire which makes it possible to obtain a nanowire film that is composed of metal having migration resistance and oxidative degradation resistance and also has sufficiently excellent transparency and conductivity and a transparent conductive film comprising the nanowire film.SOLUTION: A metal nanowire is composed of nickel and platinum, the molar ratio between the nickel and platinum (nickel/platinum) is 5,000-100,000, and the metal nanowire is substantially free from a polymer layer.SELECTED DRAWING: None

Description

  The present invention relates to a metal nanowire and a production method thereof, a metal nanowire dispersion liquid and a transparent conductive film.

  In recent years, transparent conductive films have been widely used as transparent electrodes in accordance with the expansion of the solar cell market and the growing demand for touch panels due to the rapid spread of smartphones and tablet terminals. As the transparent conductive film, a transparent conductive film is often used from the viewpoint of weight reduction, thinning, and flexibility, and most of them are ITO films using indium tin oxide as a conductive layer.

  However, the ITO film has a problem in color tone due to low light transmittance in the long wavelength region. In addition, since ITO is a semiconductor, there is a limit to achieving high conductivity. Furthermore, ITO has a problem in bendability because the conductive layer has poor bendability. For this reason, there has been a demand for a flexible film having higher transmittance and higher conductivity.

  Therefore, various transparent conductive films using metal nanomaterials such as carbon nanotubes, conductive polymers, fine metal wires constituting a mesh structure, and silver nanowires have been proposed as next-generation transparent conductive films.

  Among these, carbon nanotubes and conductive polymers are as conductive as semiconductors, and therefore, satisfactory conductivity cannot be obtained as the next-generation transparent conductive film. Moreover, although the transparent conductive film which consists of a metal mesh structure has very high electroconductivity, there existed a problem that a metal fine wire could be visually observed. On the other hand, transparent conductive films using metal nanowires are attracting attention because they can achieve both conductivity and transparency.

  Silver nanowires are widely used as metal nanowires used for transparent conductive films because of their high conductivity and easy manufacturing method. However, although silver has a high conductivity, it is a metal material that is very likely to cause ion migration. Therefore, the electrical conductivity adversely affects the insulation of the film base and the insulation between the wirings. Therefore, the transparent conductive film using silver nanowires as a conductive material has a problem that reliability of a device or the like is lowered.

  Therefore, a method has been proposed in which the surface of the silver nanowire is coated with another metal material by plating or the like to impart ion migration resistance and improve stability (Patent Documents 1 and 2). However, the proposed method has a problem that the manufacturing method is complicated due to the plating process. Furthermore, since this method is difficult to uniformly plate the nanowire surface, there is a problem not only in unevenness of ion migration resistance but also in electrical characteristics such as conductivity.

As a nanowire made of a metal material other than silver, copper (1.7 × 10 ⁻⁸ Ω · m (20), which is the volume resistivity value next to silver (1.6 × 10 ⁻⁸ Ω · m (20 ° C.)). ° C)) has been proposed (Patent Document 3). Usually, nanowires are in the form of a dispersion and are coated to obtain a transparent conductive film. However, since copper nanowires have very low oxidation degradation resistance, they are difficult to handle with dispersions and are very susceptible to degradation. Therefore, it was very difficult to industrially realize the process of coating copper nanowires in the form of a dispersion.

  In addition to silver and copper, technologies related to nanowires such as nickel, iron, and cobalt have been proposed (Patent Documents 4 to 7). The nanowires such as nickel described in Patent Documents 4 and 5 are not supposed to be obtained in the form of a dispersion, but are entangled three-dimensionally. I couldn't. Moreover, since the nanowire described in Patent Document 6 uses a porous material as a template, there is a problem in productivity and environmental adaptability such as alumina waste liquid and chromium waste liquid. Furthermore, since it has deteriorated due to the chromic acid / phosphoric acid solution treatment or the like, gold plating or the like is required to obtain conductivity.

  In patent document 7, in order to improve the dispersibility of nanowires, such as nickel, the nanowire surface is coat | covered with the high molecular compound. In order to form a polymer compound film, it is essential to produce nanowires in the presence of the polymer compound, so that the production solution has a high viscosity, and the workability during production has been reduced. Further, the dispersion medium was limited by the polymer compound coating. In addition, there is a problem that the conductivity of the nanowire is slightly lowered. For this reason, when the coating amount of the nanowire dispersion liquid was increased to obtain a predetermined surface resistance value in the transparent conductive film, the transmittance of the film was remarkably lowered. Thus, nanowires such as nickel require some technique or treatment to improve dispersibility, but transparent conductive films obtained from such nanowires have excellent transparency and excellent conductivity. Both could not be realized.

JP2013-151752A JP2013-155440A Special table 2013-513220 JP 2007-284716 A International Publication No. 2014/147785 Pamphlet JP 2012-238292 A International Publication No. 2015/163258 Pamphlet

  The present invention has been made in view of such prior art, and an object of the present invention is to provide a metal nanowire composed of a metal having migration resistance and oxidation degradation resistance and sufficiently excellent in dispersibility. It is.

  The present invention also provides a nanowire film composed of a metal having migration resistance and oxidation degradation resistance and sufficiently excellent in both transparency and conductivity and a transparent conductive film provided with the nanowire film. An object of the present invention is to provide a metal nanowire and a dispersion thereof.

  The present inventors have found that the dispersibility of the resulting nanowire is improved by using nickel and platinum in combination and setting the molar ratio within a specific range, and have reached the present invention.

That is, the gist of the present invention is as follows.
(1) A metal comprising nickel and platinum, the molar ratio of nickel and platinum (nickel / platinum) being 5,000 to 100,000, and having substantially no polymer layer Nanowire.
(2) The metal nanowire according to (1), wherein an average length of the metal nanowire is 5 to 40 μm.
(3) A method for producing a metal nanowire according to (1) or (2),
A method for producing metal nanowires comprising reducing nickel ions and platinum ions in a magnetic field.
(4) A metal nanowire dispersion liquid in which the metal nanowires according to (1) or (2) are dispersed.
(5) A transparent conductive film comprising the metal nanowire according to (1) or (2).
(6) The transparent conductive film according to (5), comprising a metal nanowire film having a surface resistance value of 100Ω / □ or less and a transmittance of 85% or more.

The metal nanowire of the present invention is composed of a metal having migration resistance and oxidation deterioration resistance, and is sufficiently excellent in dispersibility.
The conductive film containing the metal nanowire of the present invention is sufficiently excellent in both transparency and conductivity.

The graph of the surface resistance value of the nanowire film | membrane produced from the nanowire produced in Examples 1 and 3 and Comparative Examples 1 and 4 and the transmittance | permeability is shown.

(Metal nanowires)
The metal nanowire of the present invention (hereinafter sometimes simply referred to as “nanowire”) is composed of nickel and platinum. Metal nanowires are composed of nickel and platinum means that metal nanowires are composed essentially of nickel and platinum, and nickel and platinum can be detected and quantified by ICP emission analysis. It is. In the present invention, the nanowire does not have to be strictly composed only of nickel and platinum, and other than nickel and platinum, as long as the effects of the present invention are not impaired during the synthesis of the metal nanowire and its raw material. These substances may be included as impurities. In the nanowire of the present invention, platinum is not detected by ESCA. Therefore, the platinum does not exist in the nanowire surface layer but exists inside. The measurement conditions by ESCA are as follows: X-ray source: monochrome Al-Kα, X-ray output: 200 W, photoelectron emission angle: 75 °, pass energy: 58.70 eV, peak derived from platinum The presence or absence was confirmed.

  In the present invention, the nanowire has substantially no polymer layer. The nanowire has substantially no polymer layer. Even if the nanowire is stained with a phosphotungstic acid dyeing method and observed with a transmission electron microscope at a magnification of 600,000 times or more, the surface of the nanowire This means that no polymer layer is observed. The polymer layer is a form in which the polymer continuously covers the surface of the nanowire in the circumferential direction. In the present invention, the nanowire or nanowire dispersion may have a polymer that does not have such a layer form. The circumferential direction of the nanowire is the circumferential direction of the nanowire in a cross section perpendicular to the longitudinal direction of the nanowire.

  In the nanowire of the present invention, nickel is present in a molar ratio of 5,000 to 100,000 with respect to 1 mol of platinum. The molar ratio (nickel / platinum) is preferably 10,000 to 75,000, more preferably 20,000 to 50, from the viewpoint of further improving the dispersibility of the nanowires and the transparency and conductivity of the transparent conductive film. , 000. The source of the effect is unknown, but nanowires with excellent dispersibility can be produced at the specific nickel / platinum molar ratio. As a result, a transparent conductive film that is sufficiently excellent in both transparency and conductivity can be obtained. When the nickel / platinum molar ratio is less than 5,000 or exceeds 100,000, the dispersibility of the nanowire is impaired, and the nanowire becomes thicker, the nanowire becomes shorter, and the nanowire becomes shorter. There is a problem that is mainly caused by nanowires.

  The average length of nanowire is not specifically limited, It can select suitably according to a use with reaction conditions, For example, it is 5-40 micrometers. Usually, the longer the nanowire, the better the conductivity of the resulting nanowire film or the like, and conversely, the film made of a short nanowire is inferior in conductivity. On the other hand, in the case of long nanowires, cutting of the nanowires occurs due to stress applied during dispersion and film formation, and performance such as transmittance and surface resistance of the resulting nanowire film may not be stable. Therefore, a preferable average length is 10 μm to 35 μm, particularly 10 μm to 30 μm.

  The average diameter of the nanowire is not particularly limited, and can be appropriately selected depending on the use depending on the reaction conditions, and is, for example, 40 to 300 nm. In general, in the case of thin nanowires, the nanowire is cut by stress applied during dispersion and film formation as described above, and the performance of the obtained nanowire film, such as transmittance and surface resistance, may not be stable. Moreover, a thick nanowire may be inferior in the transmittance | permeability of the nanowire film | membrane obtained. Therefore, a preferable average diameter is 50 nm to 200 nm, and more preferably 50 nm to 150 nm.

  The shape of the nanowire is not particularly limited as long as it is linear. For example, the nanowire may have a rod shape having a substantially constant cross-sectional shape in the longitudinal direction, or a particle in which a plurality of substantially spherical particles are one-dimensionally connected. The connection shape may be sufficient. In other words, the particle connection shape is a shape in which a plurality of substantially spherical particles are connected in series and continuously, the particles at both ends are connected to one or more adjacent particles, and the other particles are adjacent to each other. It is connected with two or more particles. From the viewpoint of further improving the transparency of the transparent conductive film, the nanowire preferably has a particle-connected shape. In the case of a particle-connected shape, the average diameter is calculated by taking the average of the minimum and maximum diameters of one nanowire as the diameter of the nanowire.

(Method for producing metal nanowires)
The nanowire of this invention can be manufactured with the following method, for example.
Specifically, the nanowire of the present invention can be obtained by reducing nickel ions and platinum ions at a predetermined ratio in a magnetic field. The manufacturing method is shown below.

  In order to reduce nickel ions in a magnetic field, it is preferable to dissolve a nickel salt in a solvent. The nickel salt may be in any form that is soluble in the solvent used and can supply nickel ions in a reducible state. For example, nickel chloride, sulfate, nitrate, acetate and the like can be mentioned. These salts may be hydrates or anhydrides.

  The concentration of nickel ions to be reduced is preferably 15 μmol / g or less. If the concentration of nickel ions is 15 μmol / g or less, it is possible to suppress the occurrence of three-dimensional aggregation of nanowires (generation of a nonwoven fabric form).

  The concentration of platinum ions to be reduced is not particularly limited as long as nanowires having the above-described molar ratio of nickel / platinum can be obtained. The concentration varies depending on the reaction conditions. Under any reaction condition, the nickel / platinum molar ratio in the nanowire is usually set to 5,000 or more unless the molar ratio of nickel ions / platinum ions contained in the reaction solution is greater than 5,000. Cannot be satisfied.

  The composition of the platinum ion is not particularly limited, and there is no problem even if it is a complex shape. For example, the target nanowire can be produced by using chloroplatinic acid.

  As a method for reducing nickel ions and platinum ions, it is preferable to use a reducing agent. In this production method, the reducing agent is preferably one that can reduce nickel ions with a ferromagnetic structure, such as hydrazine, hydrazine monohydrate, ferrous chloride, hypophosphorous acid, borohydride salt, Aminoboranes, lithium aluminum hydride, sulfites, hydroxylamines (eg, diethylhydroxylamine), zinc amalgam, diisobutylaluminum hydride, hydroiodic acid, ascorbic acid, oxalic acid, formic acid, ferrous chloride, hypochlorous acid Examples include phosphoric acid, borohydride salts, aminoboranes, ascorbic acid, oxalic acid, and formic acid. A preferred reducing agent is hydrazine or hydrazine monohydrate.

  The concentration of the reducing agent, particularly hydrazine monohydrate, is preferably 0.05 to 0.5% by mass with respect to the reaction solution. If the amount is less than 0.05% by mass, the reduction reaction may be insufficient, and the reaction may stop in the middle and nanowires may not be formed. Moreover, when exceeding 0.5 mass%, nanowire may aggregate by the influence of the residual reducing agent (especially hydrazine monohydrate).

  As the reaction solvent, polyols such as ethylene glycol and propylene glycol are preferable. In the case of polyols, the nickel salt and the reducing agent can be dissolved, and boiling does not occur even at the reaction temperature, so that the reaction can be performed with good reproducibility.

  In order to reduce nickel ions and platinum ions, it is necessary to control pH and temperature. Although the pH and temperature differ depending on the reducing agent, for example, when the reduction reaction is performed using hydrazine monohydrate in ethylene glycol, the temperature is preferably 70 to 100 ° C. and the pH is preferably 11 to 12. .

  As the magnetic field applied when reducing nickel ions and platinum ions, the central magnetic field of the reaction vessel is preferably about 10 to 200 mT. Nanowires are not generated when the magnetic field is weak. Moreover, since it is difficult to generate a strong magnetic field, it is not realistic.

  In the present invention, it is not necessary to add a polymer compound to the reaction solution. By adding a polymer compound at the time of nanowire production, it becomes possible to produce nanowires with excellent dispersibility. However, as described above, the dispersion medium is limited due to the formation of the polymer compound film. However, there is a problem that the conductivity of the nanowire is lowered.

  In order to control the average diameter and average length of nanowires, a complexing agent may be added to the reaction solution. However, when the reducing agent is small or the reducing power is weak, the reduction reaction is inhibited and the yield is reduced. It is preferable not to use a complexing agent because it causes a decrease.

  The reduction time of the reduction reaction is not particularly limited as long as the nanowire having the above dimensions can be produced, and is, for example, 10 minutes to 1 hour. Then, nickel nanowire can be obtained by refine | purifying and collect | recovering nanowire by centrifugation, filtration, adsorption with a magnet, etc.

  Since the nanowire produced by the above production method is oxidized during production and purification, it is preferable to further perform a reduction treatment. The reduction treatment may be performed at about 150 ° C. in a polyol solvent such as ethylene glycol. Thereby, a peak derived from a metal simple substance can be confirmed on the nanowire surface by ESCA.

(Metal nanowire dispersion and method for producing the same)
The present invention also provides a dispersion in which the nanowires are dispersed. The concentration of nanowires in the dispersion is not particularly limited, and is preferably about 0.01 to 2.0% by mass from the viewpoint of further improving dispersibility. The concentration is a ratio with respect to the total amount of the dispersion. Although it does not specifically limit as a dispersion medium, Since it has polar groups, such as a hydroxyl group which it has on the nanowire surface, polar organic solvents, such as alcohols, such as ethylene glycol and isopropanol, acetone, acetonitrile, DMSO, and DMF Is more preferable.

  The nanowire dispersion liquid of the present invention may contain additives such as a binder, an antioxidant, a wetting agent, and a leveling agent, as long as the performance is not deteriorated.

  As the antioxidant, those having no antioxidant or by-product remaining after coating are preferable, and examples thereof include hydrazines and hydroxylamines. Further, the concentration of the antioxidant in the dispersion is not particularly limited, but is preferably about 0.01 to 2.0% by mass in order to prevent a decrease in dispersibility due to the antioxidant.

  The nanowire dispersion liquid of the present invention can be obtained by adding the above-described nanowires to a dispersion medium containing a desired additive and stirring.

(Use of metal nanowire dispersion)
A film, a laminate, a wiring, and the like can be formed by applying the nanowire dispersion liquid of the present invention to a substrate and drying it. Examples of the substrate include a glass substrate, a polyethylene terephthalate film, a polycarbonate film, a cycloolefin film, a polyimide film, and a polyamide film.

  The coating method is not particularly limited, but for example, wire bar coater coating, film applicator coating, spray coating, gravure roll coating method, screen printing method, reverse roll coating method, lip coating, air knife coating method, curtain flow coating method, dip coating Method, die coating method, spray method, letterpress printing method, intaglio printing method, and ink jet method.

  In this invention, a nanowire film | membrane is a nanowire layer which does not contain a binder, and is useful for the use of a transparent conductive film. The nanowire film can be formed by applying the nanowire dispersion of the present invention containing no binder onto a substrate and drying. In the present invention, when a nanowire film is formed on a substrate and used as a transparent conductive film, a photocurable resin or the like is applied on the nanowire film so that the nanowire film is not peeled off from the substrate. be able to. The transparent conductive film usually includes a base material and a nanowire film formed on the base material.

  In the present invention, since the nanowire film is sufficiently excellent in transparency and conductivity, the transparent conductive film is also sufficiently excellent in transparency and conductivity. When the coating amount of the nanowire dispersion liquid is increased in order to obtain a good surface resistance value in the nanowire film or the transparent conductive film, the transmittance of the film generally decreases significantly. However, when the nanowire dispersion liquid of the present invention is used, even if the coating amount is increased in order to achieve a sufficiently low surface resistance value, the decrease in transmittance is sufficiently suppressed. Therefore, the nanowire and nanowire film | membrane of this invention are useful as a electrically conductive material of a transparent conductive film, especially the transparent conductive film for touchscreens (transparent electrode for touchscreens). The nanowire dispersion liquid of the present invention has a transmittance of 85% or more, preferably 88% or more even when the coating amount is increased in order to achieve a surface resistance value of 100Ω / □ or less, for example. Can be obtained.

In the present invention, when the nanowire film is used as a conductive material for a transparent conductive film, particularly a transparent conductive film for a touch panel (transparent electrode for touch panel), the basis weight of the nanowire film is usually 1 to 30 g / m ² , preferably Is 5 to 20 g / m ² .

  EXAMPLES Next, although an Example demonstrates this invention, this invention is not limited by these inventions.

A. Evaluation Method Evaluation methods used in Examples and Comparative Examples are as follows.

(1) Nickel / platinum molar ratio of nanowires Nanowires were collected from the obtained nanowire dispersion. The collected nanowires were mixed with a mixed solution of concentrated hydrochloric acid and concentrated nitric acid and heated to 160 ° C., and then concentrated hydrochloric acid was added and heated to 200 ° C. to dissolve the nanowires. The dissolved solution was quantified for nickel concentration and platinum concentration by calibration curve method quantitative analysis using an ICP emission analyzer (iCAP6500 Duo ICP). The molar ratio of nickel / platinum was calculated from the quantitative value. Each nanowire was measured three times, and the average value is shown in Table 1.

(2) Presence / absence of polymer in nanowires Nanowires were collected from the obtained nanowire dispersion. The collected nanowires were collected by filtration, washed with water and dried, and then immersed in 5% phosphotungstic acid staining solution for 3 minutes. Next, using a grid with a support film, observation was performed at 600,000 times with a transmission electron microscope.
○: No polymer layer (stained material) was observed;
X: A polymer layer (dyed product) was observed.

(3) Dispersibility of nanowires Nanowires were collected from the obtained nanowire dispersion. The recovered nanowires were added to any solvent of isopropanol (IPA), acetone, and ethyl acetate, and the dispersibility was evaluated as follows. As the defibrating treatment, the dispersion was stirred for 10 minutes.
○: Good (dispersed without defibrating treatment);
Δ: Yes (dispersed by defibration treatment) (no problem in practical use);
X: Impossible (it did not disperse even after fibrillation treatment).
In “possible” and “impossible”, the dispersion state immediately after the end of the defibrating process was observed.

(4) Measurement of nanowire diameter A nanowire dispersion was dried on a grid with a support film, and the resulting nanowire was photographed at a magnification of about 100,000 to 1,000,000 times with a transmission electron microscope. One nanowire The maximum value and the minimum value of the diameter at 100 were measured for arbitrary 100 pieces. The average diameter of the nanowires was calculated from the value, and the results are summarized in Table 1.

(5) Measurement of nanowire length The nanowire dispersion was dried on a sample stage, and the obtained nanowire was photographed with a scanning electron microscope at a magnification of 2000 to 6000 times to measure the nanowire length. The average length was calculated from the arbitrary 200 nanowire lengths, and the results are summarized in Table 1.

  Examples 1 and 3 and Comparative Examples 1 and 4 were also evaluated as follows.

(6) Measurement of surface resistance value and transmittance of nanowire film The obtained nanowire dispersion liquid was applied onto a slide glass with an applicator to obtain five nanowire films having different transmittances (coating amounts).
About the surface resistance value of the obtained nanowire film | membrane, it measured with Mitsubishi Chemical Analytech Co., Ltd. resistivity meter MCP-T610.
About the transmittance | permeability, the light transmittance in wavelength 550nm was measured for the slide glass as the blank value. Therefore, the transmittance is the transmittance of only the nanowire film.
Each surface resistance value and transmittance are plotted to create FIG. Table 2 lists the five surface resistance values obtained and the corresponding transmittance.

Example 1
Nickel chloride hexahydrate 0.30 g (1.27 mmol) was added to ethylene glycol to make a total amount of 50 g. This solution was heated to 90 ° C. to dissolve nickel chloride.
On the other hand, 0.40 g of sodium hydroxide and 30.7 μg (59.4 nmol) of chloroplatinic acid hexahydrate were added to ethylene glycol to make a total amount of 49.9 g. This solution was heated to 90 ° C. to dissolve sodium hydroxide and chloroplatinic acid.
After all the compounds in each solution were dissolved, 0.1 g of hydrazine monohydrate was dissolved in a solution containing sodium hydroxide, and then the two solutions were mixed.
The mixed solution was immediately put in a magnetic circuit capable of applying a magnetic field of 150 mT at the center, and the magnetic field was applied, and the mixture was left to stand for 15 minutes while maintaining at 90 to 95 ° C. to carry out a reduction reaction. The pH was 11.5.
After the reaction, the nanowires were collected with a neodymium magnet and purified and recovered. The collected nanowire was mixed with 30 g of ethylene glycol and heated at 150 ° C. for 3 hours. After heating, nickel nanowires were obtained by collecting again with a magnet.
The obtained nanowire was added to isopropanol contained in hydrazine monohydrate to obtain a nanowire dispersion liquid having a nanowire concentration of 0.5 mass% and a hydrazine monohydrate concentration of 0.5 mass%.

Example 2
Nickel chloride hexahydrate 0.30 g (1.27 mmol) was added to ethylene glycol to make a total amount of 50 g. This solution was heated to 90 ° C. to dissolve nickel chloride.
On the other hand, 0.40 g of sodium hydroxide and 15.4 μg (29.7 nmol) of chloroplatinic acid hexahydrate were added to ethylene glycol to make a total amount of 49.9 g. This solution was heated to 90 ° C. to dissolve sodium hydroxide and chloroplatinic acid.
After all the compounds in each solution were dissolved, 0.1 g of hydrazine monohydrate was dissolved in a solution containing sodium hydroxide, and then the two solutions were mixed.
The mixed solution was immediately put in a magnetic circuit capable of applying a magnetic field of 150 mT at the center, and the magnetic field was applied, and the mixture was left to stand for 15 minutes while maintaining at 90 to 95 ° C. to carry out a reduction reaction. The pH was 11.5.
After the reaction, the nanowires were collected with a neodymium magnet and purified and recovered. The collected nanowire was mixed with 30 g of ethylene glycol and heated at 150 ° C. for 3 hours. After heating, nickel nanowires were obtained by collecting again with a magnet.
A nanowire dispersion was obtained in the same manner as in Example 1 except that the nanowire obtained in this example was used.

Example 3
Nickel chloride hexahydrate 0.20 g (0.84 mmol) was added to ethylene glycol to make a total amount of 50 g. This solution was heated to 90 ° C. to dissolve nickel chloride.
On the other hand, 0.40 g of sodium hydroxide and 30.7 μg (59.4 nmol) of chloroplatinic acid hexahydrate were added to ethylene glycol to make a total amount of 49.9 g. This solution was heated to 90 ° C. to dissolve sodium hydroxide and chloroplatinic acid.
After all the compounds in each solution were dissolved, 0.1 g of hydrazine monohydrate was dissolved in a solution containing sodium hydroxide, and then the two solutions were mixed.
The mixed solution was immediately put in a magnetic circuit capable of applying a magnetic field of 150 mT at the center, and the magnetic field was applied, and the mixture was left to stand for 15 minutes while maintaining at 90 to 95 ° C. to carry out a reduction reaction. The pH was 11.5.
After the reaction, the nanowires were collected and collected by a neodymium magnet and purified. The collected nanowire was mixed with 30 g of ethylene glycol and heated at 150 ° C. for 3 hours. After heating, nickel nanowires were obtained by collecting again with a magnet.
A nanowire dispersion was obtained in the same manner as in Example 1 except that the nanowire obtained in this example was used.

Comparative Example 1 (International Publication No. 2015/163258 Pamphlet)
In ethylene glycol, 0.40 g (1.68 mmol) of nickel chloride hexahydrate and 50 mg (0.17 mmol) of trisodium citrate dihydrate were dissolved. Furthermore, 0.32 g of sodium hydroxide, 3.0 g of dried product of Pitzkol K120L made by Daiichi Kogyo Seiyaku, and 0.92 ml of 0.054M chloroplatinic acid aqueous solution were dissolved in this order, and ethylene glycol was added to a total amount of 75 g Added.
On the other hand, 0.10 g of sodium hydroxide and 50 mg (0.17 mmol) of trisodium citrate dihydrate were dissolved in ethylene glycol. Furthermore, 1.0 g of dried Pitzkor K120L and 1.25 g of hydrazine monohydrate were dissolved in this order, and then ethylene glycol was added to a total amount of 25 g to prepare a reducing agent solution.
Each of the two liquids was heated to 90 to 95 ° C., mixed while maintaining the temperature, a magnetic field of 150 mT was applied to the center of the reaction solution, and the reaction was allowed to stand for 1 hour and 30 minutes to perform a reduction reaction. The pH was 11.5.
In order to purify and collect the nanowires from the obtained reaction solution, 100 g of the reaction solution was diluted 10 times with ethylene glycol, and the nanowires were collected and collected with a neodymium magnet and purified and collected. The collected nanowire was mixed with 30 g of ethylene glycol and heated at 150 ° C. for 3 hours. After heating, nickel nanowires were obtained by collecting again with a magnet.
A nanowire dispersion was obtained in the same manner as in Example 1 except that the nanowire obtained in this comparative example was used.

Comparative Example 2 (International Publication No. 2014/147885 pamphlet)
Ion exchange of 1.18 g (5.00 mmol) of nickel chloride hexahydrate, 0.55 g (1.87 mmol) of trisodium citrate dihydrate, and 5.18 mg (0.01 mmol) of chloroplatinic acid hexahydrate After adding and dissolving in water, 10M NaOH aqueous solution was added dropwise to adjust the pH to 12.5 to make a total volume of 50 ml.
On the other hand, 2.50 g (0.05 mol) of hydrazine monohydrate and ion-exchanged water were mixed, and then a 10 M NaOH aqueous solution was added dropwise to adjust the pH to 12.5 to a total volume of 50 ml.
The two solutions were heated to 80 ° C., and the two solutions were mixed. The mixed solution was immediately placed in the center in a magnetic circuit to which a magnetic field of 100 mT could be applied, the magnetic field was applied, and the mixture was allowed to stand for 15 minutes while being maintained at 80 to 85 ° C. to perform a reduction reaction. The pH was 12.5.
After the reaction, the aggregated nanowires were collected and removed, and purified and recovered by washing with ion exchange water.
A nanowire dispersion was obtained in the same manner as in Example 1 except that the nanowire obtained in this comparative example was used.

Comparative Example 3
Nanowires were produced in the same manner as in Example 1 except that the amount of chloroplatinic acid hexahydrate used for the preparation of the chloroplatinic acid solution was reduced to 15.4 ng (29.7 pmol).

Comparative Example 4
Example 1 except that 2 g of a dried product of Pitzkor K120L made by Daiichi Kogyo Seiyaku was dissolved in the nickel chloride solution, and 2 g of a dried product of Pitzkor K120L made by Daiichi Kogyo Seiyaku was dissolved in the chloroplatinic acid solution. Nanowires were manufactured by the same method.

Comparative Example 5
Nanowires were produced by the same method as in Example 1 except that the chloroplatinic acid solution was not used.

  The evaluation results of the nanowires obtained in Examples and Comparative Examples are shown in Tables 1 to 3.

  The nanowire of Examples 1-3 is a nanowire comprised by the molar ratio of nickel / platinum prescribed | regulated by this application. For this reason, even if the treatment of the polymer film or the like is not performed, it has excellent dispersibility and can be dispersed in a solvent such as acetone and ethyl acetate in which conventional nanowires cannot be dispersed. The dispersibility of the nanowires of Examples 1 and 2 was particularly excellent.

Since Examples 1 and 3 did not have a coating film of a polymer compound, the obtained nanowire film had a lower surface resistance value and a higher transmittance than Comparative Example 1 having an equivalent nanowire length.
For example, using the nanowire dispersions of Examples 1 and 3, even when the coating amount is increased in order to achieve a surface resistance value of 100Ω / □ or less, a transmittance of 85% or more, particularly 88% or more is obtained. A nanowire film having the same could be obtained (see FIG. 1).
Further, for example, when the coating amount is increased in order to achieve a surface resistance value of 100Ω / □ or less using the nanowire dispersion liquid of Comparative Example 1, the transmittance becomes 83.1% or less, and transparency and conductivity A nanowire film having both excellent properties could not be obtained (see FIG. 1).

  In Comparative Examples 1 and 2, since the molar ratio of nickel / platinum was smaller than the range specified in the present application, the nanowire was inferior in dispersibility or limited in the dispersible solvent species.

The average length of Comparative Example 2 could not be measured accurately.
In Comparative Examples 3 and 5, the average length could not be measured because the nanowires were aggregated so that the starting point and the ending point were not known.

  The nanowire of the present invention is useful as a conductive material for a transparent electrode and a transparent conductive film, particularly a flexible transparent conductive film such as a transparent conductive film for a touch panel.

Claims (6)

  A metal nanowire comprising nickel and platinum, having a molar ratio of nickel and platinum (nickel / platinum) of 5,000 to 100,000 and having substantially no polymer layer.   The metal nanowire of Claim 1 whose average length of the said metal nanowire is 5-40 micrometers. A method for producing a metal nanowire according to claim 1 or 2,
A method for producing metal nanowires comprising reducing nickel ions and platinum ions in a magnetic field.   A metal nanowire dispersion liquid in which the metal nanowires according to claim 1 or 2 are dispersed.   The transparent conductive film containing the metal nanowire of Claim 1 or 2.   The transparent conductive film according to claim 5, comprising a metal nanowire film having a surface resistance value of 100Ω / □ or less and a transmittance of 85% or more.

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