JP6334076B2 - Nanowire and manufacturing method thereof, nanowire dispersion and transparent conductive film - Google Patents

Description

  The present invention relates to a nanowire and a production method thereof, a 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 problems, such as a metal fine wire being visible. On the other hand, transparent conductive films using metal nanowires are attracting attention because they can achieve both conductivity and transparency.

  As a metal nanowire used for a transparent conductive film, a metal nanowire made of silver, copper, gold, nickel or the like is known. For example, Patent Document 1 discloses a nanowire containing at least one metal selected from the group consisting of gold, nickel, and copper having a diameter variation coefficient of 30% or less. Further, for example, Patent Document 2 discloses a copper nanowire having spherical ends. Moreover, for example, Patent Literature 3 discloses a metal nanowire dispersion liquid including a metal nanowire and a polymer compound layer that the metal nanowire has on the surface.

JP 2012-238593 A Special table 2013-513220 International Publication No. 2015/163258

  However, conventional nanowires increase in conductivity when the diameter is large, but decrease in transparency. On the other hand, when the diameter is small, the transparency increases, but the conductivity decreases or is easily cut. There was a problem.

  This invention solves the said subject, Comprising: It aims at providing the nanowire which can obtain the nanowire film | membrane which was excellent in both transparency and electroconductivity, and its dispersion liquid. is there.

  The present inventors have found that by controlling the nanowire to a specific shape, the conductive loss in the nanowire and the shielding of visible light can be reduced as much as possible, and both high transparency and high conductivity can be achieved. The invention has been reached.

That is, the gist of the present invention is as follows.
(I) One nanowire having a particle connection shape in which a plurality of particles are connected one-dimensionally,
The nanowire characterized by the said nanowire satisfy | filling following formula (1) when the maximum value of the diameter in one nanowire is set to A (nm) and the minimum value is set to B (nm).
1.5 ≦ A / B ≦ 2.5 (1)
(II) A is 50 to 500 nm,
The nanowire according to (I), wherein B is 10 to 200 nm.
(III) The nanowire according to (I), wherein the nanowire satisfies the following formula (2).
A + B ≦ 350nm (2)
(IV) The nanowire according to any one of (I) to (III), wherein the nanowire has a length of 10 μm to 40 μm.
(V) The nanowire according to any one of (I) to (IV), wherein the nanowire is a metal nanowire.
(VI) The nanowire according to any one of (I) to (V), wherein the nanowire is made of nickel.
(VII) A plurality of nanowires having a particle connection shape in which a plurality of particles are connected one-dimensionally,
A plurality of nanowires including the nanowire according to any one of (I) to (VI).
(VIII) A plurality of nanowires having a particle connection shape in which a plurality of particles are connected one-dimensionally,
The plurality of nanowires satisfying the following formula (1-1) when the maximum diameter of one nanowire is A (nm) and the minimum value is B (nm).
1.5 ≦ A / B average value ≦ 2.5 (1-1)
(IX) The average value of A is 50 to 500 nm,
The nanowire according to (VII) or (VIII), wherein the average value of B is 10 to 200 nm.
(X) The plurality of nanowires according to any one of (VII) to (IX), wherein the plurality of nanowires satisfy the following formulas (1-2) and (1-3).
1.5 ≦ maximum value of A / B ≦ 2.5 (1-2)
1.5 ≦ A / B minimum value ≦ 2.5 (1-3)
(XI) The plurality of nanowires according to any one of (VII) to (X), wherein the plurality of nanowires satisfy the following formula (2-1).
Average value of A + B ≦ 350 nm (2-1)
(XII) The plurality of nanowires according to any one of (VII) to (XI), wherein the plurality of nanowires satisfy the following formulas (2-2) and (2-3).
Maximum value of A + B ≦ 350 nm (2-2)
Minimum value of A + B ≦ 350 nm (2-3)
(XIII) The plurality of nanowires according to any one of (VII) to (XII), wherein the plurality of nanowires have an average length of 10 μm to 40 μm.
(XIV) The plurality of nanowires according to any one of (VII) to (XIII), wherein the plurality of nanowires are metal nanowires.
(XV) The plurality of nanowires according to any one of (VII) to (XIV), wherein the plurality of nanowires are made of nickel.
(XVI) A method for producing a plurality of nanowires according to (XIV) or (XV),
A method for producing a plurality of nanowires, comprising reducing metal ions in a magnetic field.
(XVII) A nanowire dispersion liquid in which a plurality of nanowires according to any one of (VII) to (XV) are dispersed.
(XVIII) A transparent conductive film containing a plurality of nanowires according to any one of (VII) to (XV).

  According to the nanowire of this invention, the nanowire film | membrane which can make high transparency and high electroconductivity compatible can be obtained.

4 is a TEM image of nickel nanowires produced in Example 1. FIG. The graph of the surface resistance value of the nanowire of Example 1, and the nanowire of Comparative Examples 1 and 2 and the transmittance | permeability. The graph of the surface resistance value of the nanowire of Example 2, and the nanowire of Comparative Examples 3 and 4 and the transmittance | permeability. The graph of the surface resistance value of the nanowire of Example 3, and the nanowire of the comparative example 5 and the transmittance | permeability. The graph of the surface resistance value of the nanowire of Example 4, and the nanowire of the comparative example 6 and the transmittance | permeability. The graph of the surface resistance value of the nanowire of Example 5, and the nanowire of the comparative example 7, and the transmittance | permeability. The graph of the surface resistance value of the nanowire of Example 6, and the nanowire of the comparative example 8 and the transmittance | permeability.

(Nanowire)
The present invention provides a single nanowire having a particle connection shape in which a plurality of particles, particularly nanoparticles, are connected one-dimensionally. In other words, the particle connection shape is a linear shape as a whole, in which a plurality of particles are connected in series and continuously. Each particle at both ends is connected to one or more adjacent particles, and each other particle is connected to two or more adjacent particles. In such a particle connection shape, a concave portion is usually formed at the connecting portion (particle boundary portion), a convex portion is formed at the particle portion, and a concave portion and a convex portion are formed in the particle connecting direction (longitudinal direction of the nanowire). Is repeated continuously. In general, a transparent conductive film made of nanowires has higher conductivity as the nanowire is thicker, but the transparency is lowered. On the other hand, the thinner the nanowire shape is, the lower the conductivity is, but the transparency is improved. In the nanowire having the particle-coupled shape of the present invention, the concave portion reduces visible light shielding by suppressing the loss of transparency (light transmittance) by repeatedly having concave and convex portions in the longitudinal direction, and the convex portion is conductive. Reduces sexual loss. As a result, compatibility between high transparency and high conductivity is achieved as a whole. The nanowire of the present invention does not have to have the above-mentioned particle connection shape strictly and clearly, but the concave and convex portions are continuously repeated in the longitudinal direction of the nanowire, and will be described later. What is necessary is just to have such a specific uneven | corrugated relationship.

  Each particle constituting the nanowire of the present invention has a substantially spherical shape. The substantially spherical shape includes not only a spherical shape having a circular cross section, but also a three-dimensional shape having a cross section of a polygon more than a triangle, an ellipse, or a composite shape thereof.

The nanowire of this invention has a specific unevenness | corrugation relationship. Specifically, the nanowire of the present invention satisfies the following formula (1) when the maximum value of the diameter of one nanowire is A (nm) and the minimum value is B (nm), and is transparent and conductive. From the viewpoint of further improvement, it is preferable to satisfy the following formula (1 ′), and it is more preferable to satisfy the following formula (1 ″).
1.5 ≦ A / B ≦ 2.5 (1)
1.5 ≦ A / B ≦ 2 (1 ′)
1.55 ≦ A / B ≦ 1.75 (1 ″)

  In Formula (1), when the value of A / B is less than 1.5, it becomes difficult to achieve both high transparency and high conductivity, and either transparency or conductivity is lowered. When the value of A / B is more than 2.5, the nanowire is easily cut even with a weak stress. Therefore, the nanowire is cut by the stress at the time of dispersion or film formation, and the conductivity is lowered. In the present invention, the above formula is preferably satisfied by one nanowire. Even if rod-shaped nanowires having a substantially constant cross-sectional shape in the longitudinal direction are used in a mixture of thick and thin, it is difficult to achieve both high transparency and high conductivity. One side falls.

  In the nanowire of the present invention, the maximum value A of the diameter is usually 50 to 500 nm, particularly 50 to 400 nm, and preferably 50 to 300 nm, more preferably 50 to 200 nm, from the viewpoint of further improving transparency and conductivity. More preferably, it is 60-200 nm, Most preferably, it is 60-150 nm.

  In the nanowire of the present invention, the minimum value B of the diameter is usually 10 to 200 nm, particularly 20 to 200 nm, and preferably 30 to 150 nm, more preferably 30 to 90 nm, from the viewpoint of further improving transparency and conductivity. More preferably, it is 40-90 nm.

  In the present invention, the diameter means a diameter in a cross section perpendicular to the longitudinal direction of the nanowire, and the maximum value and the minimum value of the diameter can be read in a TEM image of the nanowire. The nanowire of the present invention provides a maximum value A of the diameter where it is not an end in one nanowire. The end portion is within 100 nm from the end of the nanowire.

In the nanowire of the present invention, A + B is usually 500 nm or less, particularly 80 to 500 nm, and preferably satisfies the following formula (2) from the viewpoint of further improvement in transparency and conductivity, particularly transparency, It is more preferable to satisfy the following formula (2 ′), and it is more preferable to satisfy the following formula (2 ″).
A + B ≦ 350nm (2)
80 nm ≦ A + B ≦ 350 nm (2 ′)
100 nm ≦ A + B ≦ 250 nm (2 ″)

  The length of the nanowire affects the conductivity and transparency of the transparent conductive film prepared from the nanowire. If the nanowire is too short, the number of contacts between the nanowires per unit area increases, and the conductivity of the transparent conductive film decreases. If the nanowires are too long, the dispersibility of the nanowires decreases, so that the produced transparent conductive film tends to be uneven, and uniform transparency and conductivity cannot be obtained. Therefore, in the present invention, the length of the nanowire is preferably 10 μm or more and 40 μm or less, more preferably 15 μm or more and 40 μm or less, further preferably 15 μm or more and 30 μm or less, and most preferably 20 μm or more and 30 μm or less.

  The nanowire of this invention should just be comprised from the material which has electroconductivity, For example, a metal nanowire may be sufficient and the nanowire of a semiconductor or a conductive polymer may be sufficient as it. The nanowire of the present invention is preferably a metal nanowire from the viewpoint of conductivity. Furthermore, it is preferable that the metal nanowire of this invention is comprised from 1 or more types of metals selected from the group which consists of nickel, cobalt, and iron from the point of a manufacturing method. Furthermore, it is preferable that the nanowire of this invention is comprised from nickel and / or cobalt, especially nickel. If it is the nanowire of the said shape comprised from nickel and / or cobalt, it can obtain the transparent conductive film which has transparency and electroconductivity equivalent to the commercially available silver nanowire, and is excellent in ion migration tolerance. it can. The nanowire is composed of nickel and / or cobalt means that the nanowire is substantially composed only of nickel and / or cobalt, and the nickel and cobalt are analyzed by ICP emission analysis or fluorescent X-ray. Is quantifiable. In this case, the nanowire does not have to be strictly composed of only nickel and / or cobalt, and other than nickel and cobalt, as long as the effects of the present invention are not impaired during the synthesis of the nanowire and its raw material. These substances may be included as impurities.

(Multiple nanowires)
The plurality of nanowires of the present invention includes the above-described nanowires. It is practically impossible to grasp the shape and dimensions of the nanowires for all the nanowires in the dispersion or transparent conductive film. In the present invention, any part of the nanowires in the dispersion or the transparent conductive film is evaluated, and if the above conditions are satisfied, it is confirmed that a further improvement effect of transparency and conductivity can be obtained. ing.

Specifically, the plurality of nanowires of the present invention have a particle-connected shape, and when the maximum value of the diameter of one nanowire is A (nm) and the minimum value is B (nm) In order to satisfy the following formula (1-1) and further improve transparency and conductivity, the following formula (1-1 ′) is preferably satisfied, and the following formula (1-1 ″) is satisfied. Is more preferable.
1.5 ≦ A / B average value ≦ 2.5 (1-1)
1.5 ≦ A / B average value ≦ 2 (1-1 ′)
1.55 ≦ A / B average value ≦ 1.75 (1-1 ″)

  The average value of A / B is the average value of A / B for any 100 nanowires.

  In the formula (1-1), when the average value of A / B is less than 1.5 and more than 2.5, when the A / B value is less than 1.5 in the formula (1) and 2 Same as above.

  In the plurality of nanowires of the present invention, the average value of the maximum value A of the diameter is usually 50 to 500 nm, particularly 50 to 400 nm, and from the viewpoint of further improving transparency and conductivity, preferably 50 to 300 nm. Preferably it is 50-200 nm, More preferably, it is 60-200 nm, Most preferably, it is 60-150 nm. The average value of A is the average value of A for any 100 nanowires.

  In the plurality of nanowires of the present invention, the average value of the minimum value B of the diameter is usually 10 to 200 nm, particularly 20 to 200 nm. From the viewpoint of further improving transparency and conductivity, preferably 30 to 150 nm. Preferably it is 30-90 nm, More preferably, it is 40-90 nm. The average value of B is the average value of B for any 100 nanowires.

The plurality of nanowires of the present invention preferably satisfy the following formulas (1-2) and (1-3) from the viewpoint of further improving transparency and conductivity, and the following formulas (1-2 ′) and ( 1-3 ′) is preferable, and it is preferable that the following formulas (1-2 ″) and (1-3 ″) are satisfied.
1.5 ≦ maximum value of A / B ≦ 2.5 (1-2)
1.55 ≦ maximum value of A / B ≦ 2.2 (1-2 ′)
1.65 ≦ maximum value of A / B ≦ 1.85 (1-2 ″)
1.5 ≦ A / B minimum value ≦ 2.5 (1-3)
1.5 ≦ Minimum value of A / B ≦ 1.9 (1-3 ′)
1.45 ≦ minimum value of A / B ≦ 1.65 (1-3 ″)

The maximum value of A / B is the maximum value of A / B for any 100 nanowires.
The minimum value of A / B is the minimum value of A / B for any 100 nanowires.

In the plurality of nanowires of the present invention, the average value of A + B is usually 500 nm or less, particularly 80 to 500 nm. From the viewpoint of further improving transparency and conductivity, particularly transparency, the following formula (2-1 ) Is preferably satisfied, the following formula (2-1 ′) is more preferably satisfied, and the following formula (2-1 ″) is more preferably satisfied.
Average value of A + B ≦ 350 nm (2-1)
80 nm ≦ A + B average value ≦ 350 nm (2-1 ′)
100 nm ≦ A + B average value ≦ 250 nm (2-1 ″)

  The average value of A + B is the average value of A + B for any 100 nanowires.

The plurality of nanowires of the present invention further has a maximum value of A + B of usually 520 or less, particularly 90 to 520 nm, and a minimum value of A + B is usually 480 or less, particularly 70 to 480 nm. The plurality of nanowires of the present invention preferably satisfy the following formulas (2-2) and (2-3) from the viewpoint of further improving transparency and conductivity, and the following formulas (2-2 ′) and ( 2-3 ′) is more preferable, the following formulas (2-2 ″) and (2-3 ″) are more preferably satisfied, and the following formulas (2-2 ′ ″) and (2- More preferably, 3 ′ ″) is satisfied.
Maximum value of A + B ≦ 350 nm (2-2)
Minimum value of A + B ≦ 350 nm (2-3)
80 nm ≦ maximum value of A + B ≦ 350 nm (2-2 ′)
80 nm ≦ A + B minimum value ≦ 350 nm (2-3 ′)
100 nm ≦ A + B maximum value ≦ 350 nm (2-2 ″)
80 nm ≦ minimum value of A + B ≦ 250 nm (2-3 ″)
100 nm ≦ A + B maximum value ≦ 250 nm (2-2 ′ ″)
100 nm ≦ minimum value of A + B ≦ 250 nm (2-3 ′ ″)

The maximum value of A + B is the maximum value of A + B for any 100 nanowires.
The minimum value of A + B is the minimum value of A + B for any 100 nanowires.

  In the plurality of nanowires of the present invention, the average diameter is preferably 40 to 300 nm, more preferably 50 to 200 nm, still more preferably 50 to 180 nm, and most preferably 70 to 180 nm, from the viewpoint of further improving transparency and conductivity. preferable.

  As for the average diameter, nanowires dried on a grid with a support film were photographed with a transmission electron microscope at a magnification of 600,000 times, and the average value of nanowire diameters at arbitrary 100 points in 10 fields of view was measured.

  In the plurality of nanowires of the present invention, the average length is preferably 10 μm or more and 40 μm or less, more preferably 15 μm or more and 40 μm or less, and further preferably 15 μm or more and 30 μm or less from the viewpoint of further improving transparency and conductivity. 20 μm or more and 30 μm or less is more preferable.

  The average length is the average length for any 200 nanowires.

  The plurality of nanowires of the present invention need only be made of the same material as the nanowire described above, and may be, for example, a metal nanowire, or a nanowire of a semiconductor or a conductive polymer. Good. The nanowire of the present invention is preferably a metal nanowire from the viewpoint of conductivity. Furthermore, it is preferable that the metal nanowire of this invention is comprised from 1 or more types of metals selected from the group which consists of nickel, cobalt, and iron from the point of a manufacturing method. Furthermore, the plurality of nanowires of the present invention is preferably composed of nickel and / or cobalt, particularly nickel.

  The plurality of nanowires of the present invention preferably have a form that can be dispersed in a solvent. A form dispersible in a solvent is a form in which the nanowire is added to a dispersion medium described later at a concentration of 0.1 to 2.0% by mass and stirred for 1 minute, so that there is no aggregate by visual observation. It is preferable that the nanowire is not cut.

  The plurality of nanowires of the present invention preferably have substantially no polymer layer. The nanowire has substantially no polymer layer. Even if the nanowire is stained with a phosphotungstic acid staining method and observed with a transmission electron microscope at a magnification of about 600,000 times, 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 may have a polymer that does not have such a layer form, but it is preferably not present from the viewpoint of improving dispersibility. 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.

(Manufacturing method of nanowire)
Hereinafter, although the manufacturing method of several nanowire is demonstrated, it is clear that one nanowire of this invention can also be manufactured. Hereinafter, unless otherwise specified, the nanowire is a plurality of nanowires.

  The nanowire (especially metal nanowire) of this invention can be manufactured, for example with the following method. Specifically, metal ions, particularly nickel ions are reduced in a magnetic field. The manufacturing method is shown below.

  In order to reduce metal ions (for example, nickel ions) in a magnetic field, it is preferable to dissolve the metal salt in a solvent. The shape (form) of the metal salt may be any form that is soluble in the solvent used and can supply metal ions in a reducible state. Examples of the metal salt include metal (especially nickel) chloride, sulfate, nitrate, acetate, and the like. These salts may be hydrates or anhydrides.

  The concentration of metal ions to be reduced is preferably 1.5 to 20 μmol / g, more preferably about 1.5 to 15 μmol / g, based on the total amount of the reaction solution, from the viewpoint of nanowire shape control. Preferably, it is more preferably about 1.5 to 10 μmol / g. When the concentration of metal ions is 20 μmol / g or less, it is possible to suppress the occurrence of three-dimensional aggregation of nanowires (generation of a nonwoven fabric form). When the concentration of metal ions is 1.5 μmol / g or more, nanowires satisfying the above shape can be produced.

  As a method for reducing metal ions, it is preferable to use a reducing agent. In this production method, examples of the reducing agent include hydrazine, hydrazine monohydrate, ferrous chloride, hypophosphorous acid, borohydride salts, aminoboranes, lithium aluminum hydride, sulfites, hydroxylamines. (Eg, diethylhydroxylamine), zinc amalgam, diisobutylaluminum hydride, hydroiodic acid, ascorbic acid, oxalic acid, formic acid, ferrous chloride, hypophosphorous acid, borohydride salts, aminoboranes, ascorbic acid, Examples include oxalic acid and formic acid. Preferred reducing agents are hydrazine and hydrazine monohydrate.

  The addition concentration of the reducing agent, particularly hydrazine monohydrate, is usually 0.05 to 1.0% by mass with respect to the reaction solution, and 0.1 to 0. 5 mass% is preferable.

  As the reaction solvent, polyols such as ethylene glycol and propylene glycol are preferred. In the case of polyols, metal salts (particularly nickel salts) and reducing agents 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 metal ions (for example, nickel 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 metal ions, the central magnetic field of the reaction vessel is preferably about 10 to 200 mT, particularly 80 to 180 mT, from the viewpoint of shape control of the nanowire. 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. Although a nanowire excellent in dispersibility can be produced by adding a polymer compound at the time of producing the nanowire, the above-described unevenness may be difficult to occur due to the polymer compound.

  In order to control the surface irregularities, average diameter, and average length of the nanowire, a nucleating agent and / or a complexing agent may be added to the reaction solution according to the type of metal ion to be reduced and the reducing agent.

  Examples of the nucleating agent include salts of noble metals such as gold, silver, platinum, palladium, rhodium, iridium, ruthenium and osmium. Specific examples of the noble metal salt include chloroplatinic acid, chloroauric acid, and palladium chloride. Preferred nucleating agents are platinum salts, especially chloroplatinic acid.

  The amount of the nucleating agent is not particularly limited as long as the transparency and conductivity improving effect of the present invention is obtained. For example, the number of moles of metal ions to be reduced with respect to 1 mole of noble metal ions of the nucleating agent. The amount is preferably 5,000 to 10,000,000, particularly 10,000 to 10,000,000.

  The reduction time of the reduction reaction is not particularly limited as long as the nanowire of the present invention can be produced, and is, for example, 10 minutes to 1 hour, preferably 10 minutes to 30 minutes, from the viewpoint of shape control of the nanowire. Then, metal 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. As the reduction treatment, it may be heated to 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.

(Nanowire dispersion and manufacturing method thereof)
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 to the total amount of the dispersion. The dispersion medium is not particularly limited, but has a polar group such as a hydroxyl group on the surface of the nanowire. Therefore, alcohols such as ethylene glycol and isopropanol, and polar organic solvents such as acetonitrile, DMSO, and DMF are 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 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).

  In the present invention, the nanowire film achieves a transmittance of 85% or more, preferably 88% or more, more preferably 91% or more when the surface resistance value is 100Ω / □, for example. The transmittance when the surface resistance value is 100 Ω / □ is, for example, the surface resistance value and transmission of five types of nanowire films in which the coating amount is changed so that the surface resistance value of the nanowire film is about 100 Ω / □. It can be obtained by measuring the rate and reading from the graph of surface resistance and transmittance. Detailed measurement methods of the surface resistance value and transmittance of the nanowire film are as shown in the Examples.

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 touch panel (transparent electrode for touch panel), the basis weight of the nanowire film is usually 1 to 30 mg / m ² , preferably there 5~20mg / ^{m 2.}

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

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

(1) Measurement of average nanowire diameter Nanowires dried on a grid with a support film were photographed with a transmission electron microscope at a magnification of 600,000 times, and an average value of nanowire diameters at arbitrary 100 points in 10 fields of view was obtained. Measured.

(2) Measurement of nanowire diameter The dispersion liquid was dried on a grid with a support film, and the obtained nanowire was photographed with a transmission electron microscope at a magnification of about 100,000 to 1,000,000 times to obtain a nanowire 1 The maximum value and the minimum value of the diameter in the book were measured for 100 arbitrary numbers. The A value, B value, A / B value, and A + B value for each nanowire were calculated from the values, and the results are summarized in Table 1.

(3) Measurement of nanowire length The dispersion was dried on a sample stage, and the obtained nanowire was photographed at a magnification of 2000 to 6000 times with a scanning electron microscope to measure the nanowire length. The average length was calculated from arbitrary 200 nanowire lengths, and the results are summarized in Table 2.

(4) 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.
The obtained surface resistance values and the corresponding transmittances are shown in Tables 3 to 8 and shown in FIGS. The examples and comparative examples described in each table or figure are a combination of examples and comparative examples in which the average diameter and average length of the nanowires are substantially equivalent so that a significant comparison is possible.

Example 1
0.25 g (1.05 mmol) of nickel chloride hexahydrate 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. The concentration of nickel ions in the reaction solution was 10 μmol / g.
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 nanowire obtained was added to isopropanol contained in hydrazine monohydrate to prepare a nanowire dispersion liquid having a nanowire concentration of 0.5 mass% and a hydrazine monohydrate concentration of 0.5 mass%.
A TEM image of the nanowire produced in this example is shown in FIG.

Example 2
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. The concentration of nickel ions in the reaction solution was 8.4 μmol / g.
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 prepare a nanowire dispersion liquid containing 0.5% by mass of nanowire and 0.5% by mass of hydrazine monohydrate.

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 was added to ethylene glycol to make a total amount of 49.9 g. This solution was heated to 90 ° C. to dissolve sodium hydroxide.
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. The concentration of nickel ions in the reaction solution was 8.4 μmol / g.
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 nanowire obtained was added to isopropanol contained in hydrazine monohydrate to prepare a nanowire dispersion liquid having a nanowire concentration of 0.5 mass% and a hydrazine monohydrate concentration of 0.5 mass%.

Example 4
Nickel chloride hexahydrate 0.20 g (0.84 mmol) and trisodium citrate dihydrate 50 mg (0.17 mmol) were 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 was added to ethylene glycol to make a total amount of 49.9 g. This solution was heated to 90 ° C. to dissolve sodium hydroxide.
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. The concentration of nickel ions in the reaction solution was 8.4 μmol / g.
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 nanowire obtained was added to isopropanol contained in hydrazine monohydrate to prepare a nanowire dispersion liquid having a nanowire concentration of 0.5 mass% and a hydrazine monohydrate concentration of 0.5 mass%.

Example 5
Nickel chloride hexahydrate 0.20 g (0.84 mmol) and trisodium citrate dihydrate 100 mg (0.34 mmol) were added to ethylene glycol to 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 was added to ethylene glycol to make a total amount of 49.9 g. This solution was heated to 90 ° C. to dissolve sodium hydroxide.
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. The concentration of nickel ions in the reaction solution was 8.4 μmol / g.
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 nanowire obtained was added to isopropanol contained in hydrazine monohydrate to prepare a nanowire dispersion liquid having a nanowire concentration of 0.5 mass% and a hydrazine monohydrate concentration of 0.5 mass%.

Example 6
0.25 g (1.05 mmol) of nickel chloride hexahydrate 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 100 mT at the center, and the magnetic field was applied, and the mixture was allowed to stand for 15 minutes while maintaining at 90 to 95 ° C. to carry out a reduction reaction. The pH was 11.5. The concentration of nickel ions in the reaction solution was 10 μmol / g.
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 nanowire obtained was added to isopropanol contained in hydrazine monohydrate to prepare a nanowire dispersion liquid having a nanowire concentration of 0.5 mass% and a hydrazine monohydrate concentration of 0.5 mass%.

Comparative Example 1
The silver nanowire dispersion (Agnws-90) manufactured by AGS Material is added to isopropanol contained in hydrazine monohydrate, and the nanowire concentration is 0.5 mass% and the hydrazine monohydrate concentration is 0.5 mass%. A nanowire dispersion was prepared.

Comparative Examples 2, 3 and 5-7
By the same method as in Japanese Patent Application Laid-Open No. 2012-238592, metal wires were reduced without using a magnetic field, and nanowires were produced. The obtained nanowire was mixed with 30 g of ethylene glycol with respect to 50 mg of nanowire, and heated at 150 ° C. for 3 hours. After heating, the nanowires are collected with a magnet, and the obtained nanowires are added to isopropanol contained in hydrazine monohydrate, and the nanowire concentration is 0.5 mass% and the hydrazine monohydrate concentration is 0.5 mass%. A nanowire dispersion was prepared.

Comparative Example 4
Nickel chloride hexahydrate 0.3 g (1.26 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. The concentration of nickel ions in the reaction solution was 12.6 μmol / g.
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 nanowire obtained was added to isopropanol contained in hydrazine monohydrate to prepare a nanowire dispersion liquid having a nanowire concentration of 0.5 mass% and a hydrazine monohydrate concentration of 0.5 mass%.

Comparative Example 8
A nanowire dispersion was prepared in the same manner as in International Publication No. 2015/163258. Specifically, the following method was used.
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 order, and ethylene glycol was added so that the total amount became 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 dry product of 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.
The nanowire obtained was added to isopropanol contained in hydrazine monohydrate to prepare a nanowire dispersion liquid having a nanowire concentration of 0.5 mass% and a hydrazine monohydrate concentration of 0.5 mass%.

  Tables 1 to 9 show the evaluation results of the nanowires obtained in Examples and Comparative Examples, and nanowire dispersions. Evaluation results are shown in Tables 3 to 8 for each combination of Examples and Comparative Examples in which the average diameter and average length of the nanowires are substantially equivalent, and graphs of the surface resistance value and transmittance of the nanowires are shown in FIG. This is shown in FIG. In each figure, “1.E + 01” means “10”, “1.E + 02” means “100”, and “1.E + 03” means “1000”.

For each example, the transmittance (T) when the surface resistance value was 100 Ω / □ was read from each graph, shown in Table 9, and evaluated according to the following ranking.
A: 91% ≦ T (best);
○: 88% ≦ T <91% (better);
Δ: 85% ≦ T <88% (good).

  The nanowires of Examples 1 to 6 satisfy the above-described formula (1-1): average of A / B values, formula (2-1): average of A + B values, and average length of nanowires. Therefore, the nanowire film composed of these nanowires has sufficient surface resistance and transmittance than the conventional nickel nanowire or nanowire film composed of nanowires with similar average length and average diameter. It was excellent.

  In particular, in the nanowires of Examples 1 and 4, the above formulas (1-2) and (1-3): the maximum and minimum values of A / B values, and formulas (2-2) and (2-3) ): All of the maximum and minimum values of the A + B values are satisfied. Therefore, the nanowire film composed of the nanowires of Examples 1 and 4 achieved a higher transmittance even with a lower surface resistance value.

  Comparative Example 1 is a general silver nanowire. Although the volume resistivity value is lower than that of nickel, silver does not satisfy the shape defined in the present invention. Therefore, the nickel nanowire of Example 1 having the same average diameter and average length has The surface resistance and transmittance were inferior. A graph of the surface resistance value and the transmittance of the nanowire of Example 1 and the nanowire of Comparative Example 1 is shown in FIG.

  Comparative Examples 2 to 8 are nickel nanowires having an average diameter and an average length corresponding to each example, but do not satisfy the shape defined in the present invention, and therefore each example having the same average diameter and average length. The surface resistance and transmittance were inferior to the nickel nanowires in the examples. The graph of the surface resistance value and the transmittance | permeability of the nanowire of the comparative example corresponding to the nanowire of each Example is shown to FIGS.

  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 (17)

One nanowire having a particle connection shape in which a plurality of particles are connected one-dimensionally,
The maximum value of the diameter of one nanowire is A (nm), the minimum value is B (nm), and the maximum value A of the diameter is a diameter where the one nanowire is not within 100 nm from the end. The nanowire satisfies the following formula (1),
The nanowire is a metal nanowire;
The nanowire characterized by not having a polymer layer substantially.
1.5 ≦ A / B ≦ 2.5 (1) A is 50 to 500 nm,
The nanowire according to claim 1, wherein B is 10 to 200 nm. The nanowire according to claim 1 or 2, wherein the nanowire satisfies the following formula (2).
A + B ≦ 350nm (2)   The nanowire according to claim 1, wherein the nanowire has a length of 10 μm or more and 40 μm or less. The nanowire according to any one of claims 1 to 4 , wherein the nanowire is made of nickel. A plurality of nanowires having a particle connection shape in which a plurality of particles are connected one-dimensionally,
The plurality of nanowires are metal nanowires;
The some nanowire containing the nanowire in any one of Claims 1-5 . A plurality of nanowires having a particle connection shape in which a plurality of particles are connected one-dimensionally,
The maximum value of the diameter of one nanowire is A (nm), the minimum value is B (nm), and the maximum value A of the diameter is a diameter where the one nanowire is not within 100 nm from the end. When the plurality of nanowires satisfy the following formula (1-1),
The plurality of nanowires are metal nanowires;
A plurality of nanowires, wherein the nanowires have substantially no polymer layer.
1.5 ≦ A / B average value ≦ 2.5 (1-1) The average value of A is 50 to 500 nm,
The nanowire according to claim 6 or 7 , wherein an average value of B is 10 to 200 nm. The plurality of nanowires according to any one of claims 6 to 8 , wherein the plurality of nanowires satisfy the following formulas (1-2) and (1-3).
1.5 ≦ maximum value of A / B ≦ 2.5 (1-2)
1.5 ≦ A / B minimum value ≦ 2.5 (1-3) The plurality of nanowires according to any one of claims 6 to 9 , wherein the plurality of nanowires satisfy the following formula (2-1).
Average value of A + B ≦ 350 nm (2-1) The plurality of nanowires according to any one of claims 6 to 10 , wherein the plurality of nanowires satisfy the following formulas (2-2) and (2-3).
Maximum value of A + B ≦ 350 nm (2-2)
Minimum value of A + B ≦ 350 nm (2-3) The plurality of nanowires according to any one of claims 6 to 11 , wherein the plurality of nanowires has an average length of 10 µm or more and 40 µm or less. The plurality of nanowires according to any one of claims 6 to 12 , wherein the plurality of nanowires is made of nickel. A method for producing a plurality of nanowires according to any one of claims 6 to 13 ,
A method for producing a plurality of nanowires, comprising reducing metal ions in a magnetic field.   Using a reducing agent for the reduction,
  The manufacturing method of several nanowire of Claim 14 whose density | concentration with respect to the reaction solution of the said reducing agent is 0.05-1.0 mass%. A nanowire dispersion liquid in which a plurality of nanowires according to any one of claims 6 to 13 are dispersed. Transparent conductive film including a plurality of nano wire according to any one of claims 6 to 13.

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