TWI709448B - Nanowire and production method thereof, nanowire dispersion and transparent and electrically conductive film - Google Patents

Abstract

The present invention provides a nanowire, which can give a nanowire film that is sufficiently excellent in both transparency and electrical conductivity. The present invention relates to a nanowire having such a particle-connecting shape that particles are interconnected unidimensionally, wherein the nanowire satisfies the formula: 1.5 ≦ A/B ≦ 2.5 when regarding a diameter of one nanowire, a maximum value is referred to as A (nm) and a minimum value is referred to as B (nm).

Description

Nanowire and its manufacturing method, nanowire dispersion and transparent conductive film

The present invention relates to a nanowire, a method for manufacturing the nanowire, a nanowire dispersion and a transparent conductive film.

In recent years, with the expansion of the solar battery market and the rapid spread of smart phones and tablet terminals, the demand for touch panels has increased, and transparent conductive films have been widely used for transparent electrodes. From the viewpoints of weight reduction, thinning, and flexibility, transparent conductive films are mostly used transparent conductive films. At present, almost ITO films using indium tin oxide as the conductive layer are used.

However, ITO films have low light transmittance in the long-wavelength region, so they have color tone problems. In addition, since ITO is a semiconductor, there is a limit to high conductivity. In addition, because ITO lacks the flexibility of the conductive layer, there is a problem with the flexibility. Therefore, a flexible film with higher transmittance and high conductivity is required.

Therefore, the current next-generation transparent conductive film has various proposals that use metal nanomaterials such as carbon nanotubes, conductive polymers, thin metal wires that make up the mesh structure, and silver nanowires.

Among them, the conductivity of carbon nanotubes and conductive polymer-based semiconductors is equivalent to that of the next-generation transparent conductive film. In addition, although the transparent conductive film composed of a metal mesh structure can achieve very high conductivity However, there are problems such as visible metal wires. On the other hand, transparent conductive films using metal nanowires are attracting attention because they have both conductivity and transparency.

The metal nanowire used in the transparent conductive film is known as a metal nanowire made of silver, copper, gold, nickel, etc. For example, the nanowire disclosed in Patent Document 1 has a diameter variation coefficient of 30% or less and contains at least one metal selected from the group consisting of gold, nickel, and copper. In addition, for example, Patent Document 2 discloses a copper nanowire whose ends are spherical. In addition, for example, Patent Document 3 discloses a metal nanowire and a metal nanowire dispersion liquid containing a polymer compound layer on the surface of the metal nanowire.

[Prior Technical Literature] [Patent Literature]

Patent Document 1: Japanese Patent Laid-Open No. 2012-238592

Patent Document 2: Japanese Patent Special Form 2013-513220

Patent Document 3: International Publication No. 2015/163258

However, the conventional nanowires can improve conductivity when the diameter is thicker, but there is a problem of reduced transparency. On the other hand, when the diameter is thinner, although the transparency is improved, the conductivity is decreased. Or easily cut off.

In order to solve the above-mentioned problems, the present invention aims to provide a nanowire that can obtain a nanowire film that is sufficiently excellent in both transparency and conductivity, and a dispersion thereof.

The inventors of the present invention found that by controlling the nanowire to a specific shape, the conductivity loss and visible light shielding in the nanowire can be minimized, and high transparency can be achieved. With high conductivity, the present invention has been completed.

That is, the gist of the present invention is as follows.

(I) A type of nanowire, which is a nanowire with a shape of one-dimensional connection of particles connected by a plurality of particles; among them, the maximum diameter of one nanowire is A(nm) and the minimum When set to B(nm), the above-mentioned nanowire system satisfies the following formula (1): 1.5≦A/B≦2.5 (1)

(II) The nanowire as described in (I), wherein A is 50~500nm and B is 10~200nm.

(III) The nanowire as described in (I), wherein the nanowire system satisfies the following formula (2): A+B≦350nm (2)

(IV) The nanowire as described in any one of (I) to (III), wherein the nanowire has a length of 10 μm or more and 40 μm or less.

(V) The nanowire as described in any one of (I) to (IV), wherein the nanowire is a metal nanowire.

(VI) The nanowire as described in any one of (I) to (V), wherein the nanowire is made of nickel.

(VII) A complex nanowire, which is a complex nanowire in which a plurality of particles are connected in a one-dimensional connection, and contains the nanowire described in any one of (I) to (VI).

(VIII) A complex nanowire, which is a complex nanowire with a shape of particles connected in one-dimensional connection by a plurality of particles, wherein the maximum diameter of one nanowire is A(nm) and the minimum When set to B(nm), the above complex nanowire system satisfies the following formula (1-1): 1.5≦A/B average value≦2.5 (1-1)

(IX) The plural nanowires as described in (VII) or (VIII), wherein the average value of A is 50 to 500 nm, and the average value of B is 10 to 200 nm.

(X) The complex nanowire as described in any one of (VII) to (IX), wherein the complex nanowire system satisfies the following formulas (1-2) and (1-3): 1.5≦A/ Maximum value of B≦2.5 (1-2)

1.5≦A/B minimum value≦2.5 (1-3)

(XI) The complex nanowire described in any one of (VII) to (X), wherein the complex nanowire system satisfies the following formula (2-1): the average value of A+B≦350nm (2 -1)

(XII) The complex nanowire as described in any one of (VII) to (XI), wherein the complex nanowire system satisfies the following formulas (2-2) and (2-3): A+B Maximum ≦350nm (2-2)

The minimum value of A+B≦350nm (2-3)

(XIII) The plural nanowires as described in any one of (VII) to (XII), wherein the plural nanowires have an average length of 10 μm or more and 40 μm or less.

(XIV) The plural nanowires as described in any one of (VII) to (XIII), wherein the plural nanowires are metal nanowires.

(XV) The plural nanowires as described in any one of (VII) to (XIV), wherein the plural nanowires are made of nickel.

(XVI) A method of manufacturing complex nanowires, as described in (XIV) or (XV), includes: reducing metal ions in a magnetic field.

(XVII) A nanowire dispersion liquid in which the plural nanowires described in any one of (VII) to (XV) are dispersed.

(XVIII) A transparent conductive film containing the plural nanowires described in any one of (VII) to (XV).

According to the nanowire of the present invention, a nanowire film that can achieve both high transparency and high conductivity can be obtained.

Figure 1 is a TEM image of the nickel nanowire produced in Example 1.

2 is a graph of the surface resistance and transmittance of the nanowires of Example 1 and the nanowires of Comparative Examples 1 and 2.

3 is a graph of the surface resistance and transmittance of the nanowires of Example 2 and the nanowires of Comparative Examples 3 and 4.

4 is a graph showing the surface resistance and transmittance of the nanowire of Example 3 and the nanowire of Comparative Example 5.

5 is a graph of the surface resistance and transmittance of the nanowire of Example 4 and the nanowire of Comparative Example 6.

6 is a graph showing the surface resistance and transmittance of the nanowire of Example 5 and the nanowire of Comparative Example 7.

FIG. 7 is a graph showing the surface resistance and transmittance of the nanowire of Example 6 and the nanowire of Comparative Example 8. FIG.

(Nanowire)

The present invention provides a nanowire having a shape of particles connected by a plurality of particles, especially nanoparticles, in a one-dimensional connection. The particle connection shape, in other words, refers to a shape in which a plurality of particles are connected in series and continuously connected to form a linear shape. The particles at the two ends are connected to one or more adjacent particles, and the other particles are connected to two or more adjacent particles. In this particle connection shape, the concave portion is usually formed by the connection portion (the boundary portion of the particle), and the convex portion is formed by the particle portion. The concave portion and the convex portion are continuously repeated in the connection direction of the particle (the direction of the long side of the nanowire). . Generally, a transparent conductive film composed of nanowires has a thicker shape, the more conductivity is improved, but the transparency is lowered. On the other hand, the smaller the shape of the nanowire, the lower the conductivity, but the higher the transparency. The nanowire with a particle-connected shape of the present invention has repeated irregularities in the longitudinal direction, the concave portion can reduce visible light shielding and the loss of transparency (light transmittance) can be suppressed, and the convex portion can suppress the loss of conductivity. As a result, both high transparency and high conductivity have been achieved overall. The nanowire of the present invention is not strictly necessary, and it is definitely necessary to have the particle connection shape as described above, as long as the concave and convex portions are continuously repeated in the longitudinal direction of the nanowire and have a specific concave-convex relationship as described later.

Each particle system constituting the nanowire of the present invention has an approximately spherical shape. The so-called abbreviated spherical shape not only refers to a spherical shape with a circular cross-section, but also covers a three-dimensional shape with a cross-section of a polygonal shape or an ellipse of a triangle or more, or a composite shape thereof.

The nanowire of the present invention has a specific concave-convex relationship. In detail, the nanowire of the present invention sets the maximum diameter of one nanowire as A (nm) and the minimum value as B (nm), and satisfies the following formula (1), thereby improving transparency. From the viewpoint of performance and conductivity, it is preferable to satisfy the following formula (1'), and more preferably 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), if the A/B value is less than 1.5, it is difficult to balance high transparency and high conductivity, and either transparency or conductivity may decrease. If the A/B value exceeds 2.5, the nanowire is likely to be cut even if the stress is weak. Therefore, the nanowire may be cut due to the stress during dispersion or film formation and the conductivity may decrease. In the present invention, it is preferable that one nanowire satisfy the above formula. Even if a rod-shaped nanowire with a certain cross-sectional shape in the longitudinal direction is mixed and used thicker and thinner, it is still difficult to balance high transparency and high conductivity, and either transparency or conductivity will be reduced. situation.

The maximum diameter A of the nanowires of the present invention is usually 50~500nm, especially 50~400nm. From the viewpoint of improving transparency and conductivity, it is preferably 50~300nm, more preferably 50~200nm, special The best is 60~200nm, the best is 60~150nm.

The minimum diameter B of the nanowire of the present invention is usually 10~200nm, especially 20~200nm. From the viewpoint of improving the transparency and conductivity, it is preferably 30~150nm, more preferably 30~90nm, special The best system is 40~90nm.

The diameter in the present invention refers to the vertical cross-sectional diameter in the long side direction of the nanowire, and the maximum and minimum diameter can be read by the TEM image of the nanowire. The nanowire of the present invention provides a nanowire that does not have the maximum diameter A at the end. The so-called end is the place within 100nm from the end point of the nanowire.

The nanowire of the present invention is also A+B usually 500nm or less, especially 80~500nm. From the viewpoint of improving transparency and conductivity, especially transparency, it is preferable to satisfy the following formula (2), more preferably The system satisfies the following formula (2'), and the particularly good system satisfies the following formula (2").

A+B≦350nm (2)

80nm≦A+B≦350nm (2')

100nm≦A+B≦250nm (2")

The length of the nanowire will affect the conductivity and transparency of the transparent conductive film made from the nanowire. If the nanowires are too short, the number of contacts between the nanowires per unit area increases, resulting in a decrease in the conductivity of the transparent conductive film. If the nanowires are too long, the dispersibility of the nanowires will be reduced, and thus the produced transparent conductive film is prone to unevenness, 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, particularly 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 the present invention may be made of a conductive material. For example, it may be a metal nanowire, a semiconductor or a conductive polymer nanowire. From the viewpoint of conductivity, the nanowire of the present invention is preferably a metal nanowire. In addition, the metal nanowire of the present invention is preferably composed of one or more metals selected from the group consisting of nickel, cobalt, and iron from the viewpoint of the manufacturing method. In addition, the nanowire of the present invention is preferably composed of nickel and/or cobalt (especially nickel). If it belongs to the above-mentioned shape nanowire made of nickel and/or cobalt, it can have the same level of transparency and conductivity as the commercially available silver nanowire, and a transparent conductive film with excellent ion migration resistance can be obtained. The so-called nanowire is composed of nickel and/or cobalt, which means that the nanowire is essentially composed of only nickel and/or cobalt, and nickel and cobalt can be quantified by ICP emission analysis or fluorescent X-ray. In this case, the nanowire is not strictly necessary to be composed only of nickel and/or cobalt. When the nanowire and its raw materials are synthesized, the effect of the present invention may not be impaired, and nickel and/or cobalt may be contained in the form of impurities. Substances other than cobalt.

(Plural nanowires)

The plural nanowires of the present invention include the aforementioned nanowires. Regarding the shape and size of nanowires, it is impossible to grasp all nanowires in dispersions or transparent conductive films in reality. The present invention evaluates any part of all the nanowires in the dispersion or the transparent conductive film. If the above conditions are satisfied, it is confirmed that the transparency and conductivity are further improved.

The plural nanowires of the present invention specifically have a particle connection shape, and when the maximum diameter of one nanowire is A (nm) and the minimum is B (nm), the following formula (1-1) is satisfied From the viewpoint of further improving transparency and conductivity, it is preferable to satisfy the following formula (1-1'), and more preferably to satisfy the following formula (1-1").

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 when it exceeds 2.5, it is the same as when the A/B value is less than 1.5 and when it exceeds 2.5 in the above formula (1), respectively.

In the plural nanowires of the present invention, the average value of the maximum diameter A is usually 50~500nm, especially 50~400nm. From the viewpoint of improving transparency and conductivity, it is preferably 50~300nm, more preferably 50~200nm, especially best 60~200nm, best 60~150nm. The so-called average value of A is the average value of A for any 100 nanowires.

In the plural nanowires of the present invention, the average value of the minimum diameter B is usually 10~200nm, especially 20~200nm. From the viewpoint of improving transparency and conductivity, it is preferably 30~150nm, more preferably 30~90nm, especially good 40~90nm. The so-called average value of B refers to the average value of B for any 100 nanowires.

The plural nanowires of the present invention further improve the transparency and conductivity From the viewpoint of, it is better to satisfy the following formulas (1-2) and (1-3), more preferably to satisfy the following formulas (1-2') and (1-3'), and especially to satisfy the following formulas (1-2) ") and (1-3").

1.5≦A/B maximum value≦2.5 (1-2)

1.55≦A/B maximum value≦2.2 (1-2')

1.65≦A/B maximum value≦1.85 (1-2")

1.5≦A/B minimum value≦2.5 (1-3)

1.5≦A/B minimum value≦1.9 (1-3')

1.45≦A/B minimum value≦1.65 (1-3")

The so-called maximum value of A/B refers to the maximum value of A/B for any 100 nanowires.

The so-called minimum value of A/B refers to the minimum value of A/B for any 100 nanowires.

In the plural nanowires of the present invention, the average value of A+B is usually 500 nm or less, especially 80 to 500 nm. From the viewpoint of improving transparency and conductivity (especially transparency), it is preferable to satisfy the following formula ( 2-1). The better system satisfies the following formula (2-1'), and the particularly best system satisfies the following formula (2-1").

The average value of A+B≦350nm (2-1)

80nm≦A+B average value≦350nm (2-1')

100nm≦A+B average value≦250nm (2-1")

The so-called average value of A+B refers to the average value of A+B for any 100 nanowires.

In the plural nanowires of the present invention, the maximum value of A+B is usually 520 or less, particularly 90 to 520 nm, and the minimum value of A+B is usually 480 or less, particularly 70 to 480 nm. The plural nanowires of the present invention have improved transparency and conductivity From the viewpoint of, it is better to satisfy the following formulas (2-2) and (2-3), more preferably to satisfy the following formulas (2-2') and (2-3'), and especially to satisfy the following formulas (2- The best system of 2") and (2-3") satisfies the following formulas (2-2"') and (2-3"').

The maximum value of A+B≦350nm (2-2)

The minimum value of A+B≦350nm (2-3)

80nm≦A+B maximum value≦350nm (2-2')

80nm≦A+B minimum value≦350nm (2-3')

100nm≦A+B maximum value≦350nm (2-2")

80nm≦A+B minimum value≦250nm (2-3")

100nm≦A+B maximum value≦250nm (2-2"')

100nm≦A+B minimum value≦250nm (2-3"')

The so-called maximum value of A+B refers to the maximum value of A+B for any 100 nanowires.

The so-called minimum value of A+B refers to the minimum value of A+B for any 100 nanowires.

In the plural nanowires of the present invention, the average diameter is from the viewpoint of improving transparency and conductivity, preferably 40~300nm, more preferably 50~200nm, particularly preferred 50~180nm, most preferably 70~180nm .

The average diameter is taken with a transmission electron microscope at 600,000 magnifications for the nanowires dried on a grid with a supporting film, and the average diameter of the nanowires at any 100 locations in 10 fields of view is measured.

In the plural nanowires of the present invention, the average length is from the viewpoint of further improving transparency and conductivity, preferably 10 μm or more and 40 μm or less, more preferably 15 μm or more and 40 μm or less, particularly preferably 15 μm or more and 30 μm or less, Best system 20μm Above and below 30μm.

The so-called average length refers to the average length of any 200 nanowires.

The plural nanowires of the present invention may be composed of the same material as the above-mentioned nanowires. For example, it may be a metal nanowire, a semiconductor or a conductive polymer nanowire. From the viewpoint of conductivity, the nanowire of the present invention is preferably a metal nanowire. In addition, the metal nanowire of the present invention is preferably composed of one or more metals selected from the group consisting of nickel, cobalt, and iron from the viewpoint of the manufacturing method. In addition, the plural nanowires of the present invention are preferably composed of nickel and/or cobalt, particularly nickel.

The plural nanowires of the present invention preferably have a dispersible form in a solvent. The so-called dispersible form in a solvent means that the nanowire is added to the dispersion medium described below at a concentration of 0.1 to 2.0% by mass and stirred for just 1 minute. There is no form of agglomerate state visually, and it is preferably a nanowire There is no cut-off state.

Preferably, the plural nanowires of the present invention do not substantially have a polymer layer. The so-called nanowire does not actually have a polymer layer, it means that the nanowire is dyed by the phosphotungstic acid dyeing method, and even if it is observed at about 600,000 times with a transmission electron microscope, there is no on the surface of the nanowire. A polymer layer was observed. The so-called polymer layer is a form in which the polymer continuously covers the surface of the nanowire in the circumferential direction. The nanowire of the present invention may have a polymer that does not have such a layer form, but it is preferable not to have it from the viewpoint of improving dispersibility. The so-called circumferential direction of the nanowire refers to the circumferential direction of the nanowire perpendicular to the long side of the nanowire.

(Method of manufacturing nanowire)

The following describes the manufacturing method of plural nanowires, but of course it can also be manufactured A nanowire of the present invention. Below, unless otherwise stated, nanowires refer to plural nanowires.

The nanowires (especially metal nanowires) of the present invention can be manufactured according to the following method, for example. In detail, metal ions, especially nickel ions, are reduced in a magnetic field. The manufacturing method is illustrated below.

In order to reduce metal ions (such as nickel ions) in a magnetic field, it is best to dissolve the metal salt in a solvent. The shape (morphology) of the metal salt can be as long as it can be dissolved in the solvent used and can supply metal ions in a reducible state. The metal salt series can be, for example, chlorides, sulfates, nitrates, acetates, etc. of metals (especially nickel). These salts may be hydrates or anhydrates.

From the viewpoint of the shape control of the nanowire, the reduced metal ion concentration is preferably set at 1.5-20μmol/g, more preferably at about 1.5-15μmol/g, with respect to the total amount of the reaction solution. It is about 1.5~10μmol/g. If the concentration of metal ions is below 20μmol/g, the three-dimensional aggregation of nanowires can be inhibited (the formation of non-woven fabrics). If the concentration of metal ions is above 1.5 μmol/g, nanowires meeting the above-mentioned shape can be produced.

The method of reducing metal ions preferably uses a reducing agent. In this manufacturing method, the reducing agent system can include, for example: hydrazine, hydrazine monohydrate, ferrous chloride, hypophosphorous acid, boron hydride, aminoboranes, lithium aluminum hydride, sulfites, hydroxylamines (for example: Diethylhydroxylamine), zinc amalgam (zinc amalgam), diisobutyl aluminum hydride, hydroiodic acid, ascorbic acid, oxalic acid, formic acid, ferrous chloride, hypophosphorous acid, boron hydride, aminoboranes, ascorbic acid, Oxalic acid, formic acid. Preferred reducing agents are hydrazine and hydrazine monohydrate.

The concentration of the reducing agent (especially hydrazine monohydrate) is usually 0.05 to 1.0% by mass relative to the reaction solution. From the viewpoint of suppressing the formation of non-woven fabrics, Preferably, it is 0.1 to 0.5 mass%.

The reaction solvent is preferably polyhydric alcohols such as ethylene glycol and propylene glycol. Polyols can dissolve metal salts (especially nickel salts) and reducing agents, and will not boil even at the reaction temperature, so the reaction can be produced with good reproducibility.

In order to reduce metal ions (such as nickel ions), pH and temperature must be controlled. Although the pH and temperature vary according to the reducing agent, for example, when hydrazine monohydrate is used in ethylene glycol to perform the reduction reaction, the temperature is preferably 70°C to 100°C, and the pH is preferably 11-12.

From the viewpoint of shape control of the nanowire, the central magnetic field of the reaction vessel is preferably about 10 to 200 mT, and more preferably 80 to 180 mT for the magnetic field applied when reducing metal ions. If the magnetic field is weak, nanowires will not be generated. Moreover, because the generation of a strong magnetic field is very difficult, it is not feasible.

In the present invention, it is not necessary to add a polymer compound to the reaction solution. By adding a polymer compound during the production of nanowires, nanowires with excellent dispersibility can be produced. However, there may be cases where the above-mentioned irregularities are not likely to occur due to the polymer compound.

In order to control the surface unevenness, average diameter and average length of the nanowire, it is also possible to add a nucleating agent and/or a complexing agent to the reaction solution according to the type of metal ion and reducing agent to be reduced.

The crystal nucleating agent can be, for example, a salt of a precious metal such as gold, silver, platinum, palladium, rhodium, iridium, ruthenium, and osmium. Specific examples of the noble metal salt may include chloroplatinic acid, chlorauric acid, and palladium chloride. Preferably, the crystal nucleating agent is a salt of platinum (especially chloroplatinic acid).

The amount of crystal nucleating agent is to obtain the transparency and conductivity of the present invention The enhancement effect is mentioned before, and the rest is not particularly limited. For example, relative to 1 mol of the noble metal ion of the crystal nucleating agent, the number of reduced metal ions is 5,000-10,000,000, preferably 10,000-10,000,000.

The reduction time of the reduction reaction is set before the nanowire of the present invention can be produced, and the rest is not particularly limited. From the viewpoint of controlling the shape of the nanowire, for example, 10 minutes to 1 hour, preferably 10 minutes to 30 minutes . Then, the metal nanowire can be obtained by refining and recovering the nanowire by centrifugal separation, filtration, adsorption by magnet, etc.

The nanowires produced by the above-mentioned production methods are oxidized during production and refining, so it is better to further reduce them. The reduction treatment system only needs to be heated to about 150°C in a polyol solvent such as ethylene glycol. In this way, ESCA can be used to confirm the spikes originating from the single metal on the surface of the nanowire.

(Nanowire dispersion and its manufacturing method)

The present invention also provides a dispersion liquid dispersed by the aforementioned nanowires. The concentration of the nanowire in the dispersion is not particularly limited, but from the viewpoint of further enhancing the dispersibility, it is preferably about 0.01 to 2.0% by mass. The concentration is the ratio to the total amount of the dispersion. The dispersion medium is not particularly limited. Since the surface of the nanowire has polar groups such as hydroxyl groups, it is more preferable to use alcohols such as ethylene glycol and isopropanol, and polar organic solvents such as acetonitrile, DMSO, and DMF.

The nanowire dispersion of the present invention may also contain additives such as binders, antioxidants, wetting agents, leveling agents, etc., before the performance is reduced, but preferably does not contain binders.

Antioxidants are preferably those that do not leave antioxidants or by-products after coating, such as hydrazines and hydroxylamines. In addition, the concentration of the antioxidant in the dispersion is not particularly limited. In order to prevent the degradation of the dispersibility due to the antioxidant, it is preferably 0.01 to 2.0 About mass%.

The nanowire dispersion system of the present invention can be obtained by adding the aforementioned nanowires to a dispersion medium containing the required additives and stirring.

(Use of nanowire dispersion)

The nanowire dispersion of the present invention is applied to a substrate and dried to form a film, a laminate, and wiring. Examples of substrate systems include glass substrates, polyethylene terephthalate films, polycarbonate films, cycloolefin films, polyimide films, and polyamide films.

The coating method is not particularly limited, and examples include: bar coating, film drip coating, spray coating, gravure roll coating, screen printing, reverse roll coating, and lipstick coating. Type coating, air knife coating method, curtain flow coating method, dip coating method, die coating method, spraying method, relief printing method, gravure printing method, inkjet method.

In the present invention, the nanowire film is a nanowire layer without a binder, which can be effectively used for transparent conductive film applications. The nanowire film is formed by coating the nanowire dispersion of the present invention without a binder on a substrate and drying it. 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 coated on the nanowire film to prevent the nanowire film from being removed from the substrate. Flaking on. The transparent conductive film usually contains a substrate and a nanowire film formed on the substrate.

In the present invention, since the transparency and conductivity of the nanowire film are very excellent, the transparent conductive film is also sufficiently excellent in transparency and conductivity. In nanowire films or transparent conductive films, if the coating amount of the nanowire dispersion is increased in order to obtain a good surface resistance value, the transmittance of the film will generally decrease significantly. However, when the nanowire dispersion of the present invention is used, even if the coating is increased in order to achieve a sufficiently low surface resistance value The amount can still fully suppress the decrease in penetration rate. Therefore, the nanowire and nanowire film system of the present invention can be effectively used as a transparent conductive film, particularly a conductive material of a transparent conductive film for touch panels (transparent electrodes for touch panels).

In the present invention, when the surface resistance of the nanowire film system is 100Ω/□, a penetration rate of 85% or more, preferably 88% or more, and more preferably 91% or more is achieved. The transmittance at a surface resistance of 100Ω/□ is based on the method that the surface resistance of the nanowire film becomes approximately 100Ω/□, and the surface resistance and transmittance of five types of nanowire films that vary the coating amount are measured. , Can be obtained by reading from the graph of surface resistance and transmittance. The detailed measurement method of the surface resistance and transmittance of the nanowire film is shown in the examples.

In the present invention, when the nanowire film is used as a transparent conductive film, particularly a conductive material for a transparent conductive film for touch panels (transparent electrodes for touch panels), the apparent density of the nanowire film is usually 1~ 30mg/m ² , preferably 5-20mg/m ² .

[Example]

Next, the present invention will be described using embodiments, but the present invention is not limited by these inventions.

The evaluation methods used in the examples and comparative examples are as follows.

(1) Determination of the average diameter of the nanowire

For the nanowires dried on a grid with a supporting film, a transmission electron microscope was used to shoot at 600,000 times, and the average diameter of the nanowires at any 100 locations in 10 fields of view was measured.

(2) Measurement of nanowire diameter

The nanowire obtained by drying the dispersion on a grid with a supporting film The transmission electron microscope photographs nanowires at 100,000 to 1,000,000 times, and measures the maximum and minimum diameters of one nanowire for any 100 nanowires. From this value, the A value, B value, A/B value, and A+B value of each nanowire were calculated, and the results are summarized in Table 1.

(3) Measurement of nanowire length

The nanowires obtained by drying the dispersion on the sample table are photographed with a scanning electron microscope at 2000 to 6000 times to measure the length of the nanowires. The average length is calculated from a total of 200 arbitrary lengths of nanowires, and the results are summarized in Table 2.

(4) Measurement of surface resistance and transmittance of nanowire film

The obtained nanowire dispersion was coated on a carrier glass using a dripper to obtain 5 nanowire films with different penetration rates (coating amounts).

The surface resistance value of the obtained nanowire film was measured using a resistivity meter MCP-T610 manufactured by Mitsubishi Chemical Analytech.

Regarding the transmittance, the carrier glass was set to a blank value, and the light transmittance at a wavelength of 550 nm was measured. Therefore, the penetration rate is only that of the nanowire film.

The corresponding transmittances of the obtained surface resistance values of the 5 sheets are described in Table 3 to Table 8, and the graphs are shown in Figures 2 to 7. 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 approximately the same in a way that enables effective comparison.

[Example 1]

0.25 g (1.05 mmol) of nickel chloride hexahydrate was added to ethylene glycol so that the total amount was 50 g. The 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 so that the total amount was 49.9 g. The solution was heated to 90°C to dissolve sodium hydroxide and chloroplatinic acid.

After the compound in each solution was completely dissolved, 0.1 g of hydrazine monohydrate was dissolved in the solution containing sodium hydroxide, and then the two solutions were mixed.

The mixed solution is immediately placed in a magnetic circuit that can apply a 150mT magnetic field toward the center, applying the magnetic field, and standing for 15 minutes while maintaining a state of 90~95°C to perform a reduction reaction. The pH is 11.5. The concentration of nickel ions in the reaction solution is 10 μmol/g.

After the reaction, the nanowires are collected using neodymium magnets and taken out to be refined and recycled. The recovered nanowires were mixed with 30 g of ethylene glycol and heated at 150°C for 3 hours. After heating, the magnet is used for recycling to obtain nickel nanowires.

The obtained nanowire was added to isopropanol containing hydrazine monohydrate to prepare a nanowire dispersion adjusted to a nanowire concentration of 0.5% by mass and a hydrazine monohydrate concentration of 0.5% by mass.

The TEM image of the nanowire produced in this embodiment is shown in FIG. 1.

[Example 2]

0.20 g (0.84 mmol) of nickel chloride hexahydrate was added to ethylene glycol so that the total amount was 50 g. The 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 so that the total amount was 49.9 g. The solution was heated to 90°C to dissolve sodium hydroxide and chloroplatinic acid.

After the compound in each solution was completely dissolved, 0.1 g of hydrazine monohydrate was dissolved in the solution containing sodium hydroxide, and then the two solutions were mixed.

The mixed solution is immediately placed in a magnetic circuit that can apply a 150mT magnetic field toward the center, applying the magnetic field, and standing for 15 minutes while maintaining a state of 90~95°C to perform a reduction reaction. The pH is 11.5. The concentration of nickel ions in the reaction solution was 8.4 μmol/g.

After the reaction, the nanowires are collected using neodymium magnets and taken out to be refined and recycled. The recovered nanowires were mixed with 30 g of ethylene glycol and heated at 150°C for 3 hours. After heating, the magnet is used for recycling to obtain nickel nanowires.

The obtained nanowire was added to isopropanol containing hydrazine monohydrate to prepare a nanowire dispersion adjusted to 0.5% by mass of nanowire and 0.5% by mass of hydrazine monohydrate.

[Example 3]

0.20 g (0.84 mmol) of nickel chloride hexahydrate was added to ethylene glycol so that the total amount was 50 g. The 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 so that the total amount was 49.9 g. The solution was heated to 90°C to dissolve the sodium hydroxide.

After the compound in each solution was completely dissolved, 0.1 g of hydrazine monohydrate was dissolved in the solution containing sodium hydroxide, and then the two solutions were mixed.

The mixed solution is immediately placed in a magnetic circuit that can apply a 150mT magnetic field toward the center, applying the magnetic field, and standing for 15 minutes while maintaining a state of 90~95°C to perform a reduction reaction. The pH is 11.5. The concentration of nickel ions in the reaction solution was 8.4 μmol/g.

After the reaction, the nanowires are collected using neodymium magnets and taken out to be refined and recycled. The recovered nanowires were mixed with 30 g of ethylene glycol and heated at 150°C for 3 hours. After heating, the magnet is used for recycling to obtain nickel nanowires.

The obtained nanowire was added to isopropanol containing hydrazine monohydrate to prepare a nanowire dispersion adjusted to a nanowire concentration of 0.5% by mass and a hydrazine monohydrate concentration of 0.5% by mass liquid.

[Example 4]

0.20 g (0.84 mmol) of nickel chloride hexahydrate and 50 mg (0.17 mmol) of trisodium citrate dihydrate were added to ethylene glycol so that the total amount was 50 g. The 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 so that the total amount was 49.9 g. The solution was heated to 90°C to dissolve the sodium hydroxide.

After the compound in each solution was completely dissolved, 0.1 g of hydrazine monohydrate was dissolved in the solution containing sodium hydroxide, and then the two solutions were mixed.

The mixed solution is immediately placed in a magnetic circuit that can apply a 150mT magnetic field toward the center, applying the magnetic field, and standing for 15 minutes while maintaining a state of 90~95°C to perform a reduction reaction. The pH is 11.5. The concentration of nickel ions in the reaction solution was 8.4 μmol/g.

After the reaction, the nanowires are collected using neodymium magnets and taken out to be refined and recycled. The recovered nanowires were mixed with 30 g of ethylene glycol and heated at 150°C for 3 hours. After heating, the magnet is used for recycling to obtain nickel nanowires.

The obtained nanowire was added to isopropanol containing hydrazine monohydrate to prepare a nanowire dispersion adjusted to a nanowire concentration of 0.5% by mass and a hydrazine monohydrate concentration of 0.5% by mass.

[Example 5]

0.20 g (0.84 mmol) of nickel chloride hexahydrate and 100 mg (0.34 mmol) of trisodium citrate dihydrate were added to ethylene glycol so that the total amount was 50 g. The 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 so that the total amount was 49.9 g. The solution was heated to 90°C to dissolve the sodium hydroxide.

After the compound in each solution was completely dissolved, 0.1 g of hydrazine monohydrate was dissolved in the solution containing sodium hydroxide, and then the two solutions were mixed.

The mixed solution is immediately placed in a magnetic circuit that can apply a 150mT magnetic field toward the center, applying the magnetic field, and standing for 15 minutes while maintaining a state of 90~95°C to perform a reduction reaction. The pH is 11.5. The concentration of nickel ions in the reaction solution was 8.4 μmol/g.

After the reaction, the nanowires are collected using neodymium magnets and taken out to be refined and recycled. The recovered nanowires were mixed with 30 g of ethylene glycol and heated at 150°C for 3 hours. After heating, the magnet is used for recycling to obtain nickel nanowires.

The obtained nanowire was added to isopropanol containing hydrazine monohydrate to prepare a nanowire dispersion adjusted to a nanowire concentration of 0.5% by mass and a hydrazine monohydrate concentration of 0.5% by mass.

[Example 6]

0.25 g (1.05 mmol) of nickel chloride hexahydrate was added to ethylene glycol so that the total amount was 50 g. The 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 so that the total amount was 49.9 g. The solution was heated to 90°C to dissolve sodium hydroxide and chloroplatinic acid.

After the compound in each solution was completely dissolved, 0.1 g of hydrazine monohydrate was dissolved in the solution containing sodium hydroxide, and then the two solutions were mixed.

The mixed solution is immediately placed in a magnetic circuit that can apply a 100mT magnetic field toward the center, apply the magnetic field, and stand for 15 minutes at a state of 90~95℃ to perform a reduction reaction. should. The pH is 11.5. The concentration of nickel ions in the reaction solution is 10 μmol/g.

After the reaction, the nanowires are collected using neodymium magnets and taken out to be refined and recycled. The recovered nanowires were mixed with 30 g of ethylene glycol and heated at 150°C for 3 hours. After heating, the magnet is used for recycling to obtain nickel nanowires.

The obtained nanowire was added to isopropanol containing hydrazine monohydrate to prepare a nanowire dispersion adjusted to a nanowire concentration of 0.5% by mass and a hydrazine monohydrate concentration of 0.5% by mass.

[Comparative Example 1]

The silver nanowire dispersion (Agnws-90) manufactured by AGS Material was added to isopropanol containing hydrazine monohydrate to prepare the nanowires with a concentration of 0.5% by mass and 0.5% by mass of hydrazine monohydrate. % Nanowire dispersion.

[Comparative Examples 2, 3 and 5~7]

According to the same method as in Japanese Patent Laid-Open No. 2012-238592, metal ions are reduced without using a magnetic field to produce nanowires. The obtained nanowire is 50 mg of nanowire, mixed with 30 g of ethylene glycol, and heated at 150°C for 3 hours. After heating, the nanowire is recovered with a magnet, and the obtained nanowire is added to isopropanol containing hydrazine monohydrate to produce a nanowire with a concentration of 0.5% by mass and 0.5% by mass of hydrazine monohydrate. Nanowire dispersion.

[Comparative Example 4]

0.3 g (1.26 mmol) of nickel chloride hexahydrate was added to ethylene glycol so that the total amount was 50 g. The 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 so that the total amount was 49.9 g. The solution was heated to 90°C to dissolve sodium hydroxide and chloroplatinic acid.

After the compound in each solution was completely dissolved, 0.1 g of hydrazine monohydrate was dissolved in the solution containing sodium hydroxide, and then the two solutions were mixed.

The mixed solution is immediately placed in a magnetic circuit that can apply a 150mT magnetic field toward the center, applying the magnetic field, and standing for 15 minutes while maintaining a state of 90~95°C to perform a reduction reaction. The pH is 11.5. The concentration of nickel ions in the reaction solution was 12.6 μmol/g.

After the reaction, the nanowires are collected using neodymium magnets and taken out to be refined and recycled. The recovered nanowires were mixed with 30 g of ethylene glycol and heated at 150°C for 3 hours. After heating, the magnet is used for recycling to obtain nickel nanowires.

The obtained nanowire was added to isopropanol containing hydrazine monohydrate to prepare a nanowire dispersion adjusted to a nanowire concentration of 0.5% by mass and a hydrazine monohydrate concentration of 0.5% by mass.

[Comparative Example 8]

According to the same method as International Publication No. 2015/163258, a nanowire dispersion was prepared. The following methods are used in detail.

Dissolve 0.40 g (1.68 mmol) of nickel chloride hexahydrate and 50 mg (0.17 mmol) of trisodium citrate dihydrate in ethylene glycol. In addition, it was dissolved in order: 0.32 g of sodium hydroxide, 3.0 g of the dried product of PITZCOL K120L manufactured by Daiichi Kogyo Pharmaceutical, and 0.92 ml of 0.054 M chloroplatinic acid aqueous solution, and ethylene glycol was added so that the total amount became 75 g.

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. Also, sequentially dissolve the dry matter of PITZCOL K120L 1.0 g and 1.25 g of hydrazine monohydrate, and then ethylene glycol was added so that the total amount became 25 g to prepare a reducing agent solution.

After the above two liquids are heated to 90-95°C, they are mixed while maintaining the temperature, a 150mT magnetic field is applied to the center of the reaction solution, and the reaction solution is allowed to stand for 1 hour and 30 minutes to perform the reduction reaction. The pH is 11.5.

In order to be able to purify and recover the nanowires from the obtained reaction liquid, 100 g of the reaction liquid was diluted to 10 times with ethylene glycol, and then the nanowires were collected by neodymium magnets for purification and recovery. The recovered nanowires were mixed with 30 g of ethylene glycol and heated at 150°C for 3 hours. After heating, the magnet is used for recycling to obtain nickel nanowires.

The obtained nanowire was added to isopropanol containing hydrazine monohydrate to prepare a nanowire dispersion adjusted to a nanowire concentration of 0.5% by mass and a hydrazine monohydrate concentration of 0.5% by mass.

The evaluation results of the nanowires and nanowire dispersions obtained in the Examples and Comparative Examples are shown in Tables 1 to 9. The examples and comparative examples in which the average diameter and average length of the nanowires are approximately the same are combined. The evaluation results are shown in Tables 3 to 8, and the surface resistance and transmittance graphs of the nanowires are shown in Figs. 2 to 2 7 shown. 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) at a surface resistance value of 100Ω/□ was read from each graph, and as shown in Table 9, the evaluation was performed according to the following grades.

◎: 91%≦T (optimal); ○: 88%≦T<91% (excellent); △: 85%≦T<88% (good).

The nanowires of Examples 1 to 6 satisfy the above formula (1-1): average A/B value, formula (2-1): average A+B value, and average length of the nanowire. Therefore, the nanowire film composed of these nanowires has a surface resistance under the nanowire film composed of conventional nickel nanowires or similar average length and average diameter nanowires. The value and penetration rate are sufficiently excellent.

In particular, the nanowires of Examples 1 and 4 completely satisfy the above formulas (1-2) and (1-3): the maximum and minimum values of A/B, and the formulas (2-2) and (2- 3): The maximum and minimum values of A+B. Therefore, the nanowire film is composed of the nanowires of Examples 1 and 4. Even if the surface resistance is lower, a higher penetration rate can still be achieved.

Comparative Example 1 is a general silver nanowire. The volume specific resistance value is irrelevant to the fact that silver exhibits a lower value than nickel, because it does not satisfy the shape specified by the present invention. Therefore, compared with the nickel nanowire of Example 1 with the same average diameter and average length, The surface resistance and penetration rate are both poor. The surface resistance and transmittance graphs of the nanowire of Example 1 and the nanowire of Comparative Example 1 are shown in FIG. 2.

Comparative Examples 2 to 8 are nickel nanowires with the average diameter and average length equivalent to the respective examples, but because they do not meet the shape specified in the present invention, they are compared with those with the same average diameter and average length. Under the nickel nanowires of each embodiment, the surface resistance and the penetration rate are both poor. The surface resistance and transmittance graphs of the nanowires of each example and the nanowires of the comparative examples are shown in Figures 2-7.

(Industrial availability)

The nanowires of the present invention are effectively used as conductive materials for transparent electrodes and transparent conductive films, particularly conductive materials for flexible transparent conductive films such as transparent conductive films for touch panels.

Claims (16)

A type of nanowire, a nanowire with a shape of one-dimensional connection of multiple particles connected by particles; among them, the maximum diameter of a nanowire is set to A(nm) and the minimum is set to B (nm), and the maximum diameter A is the maximum diameter of the one nanowire at the end that is not within 100nm from the endpoint, the nanowire system satisfies the following formula (1): 1.5≦A/ B≦2.5 (1); the above-mentioned nanowire is a metal nanowire; the above-mentioned nanowire does not substantially have a polymer layer. For example, the nanowire of claim 1, where A is 50~500nm and B is 10~200nm. Such as the nanowire of claim 1 or 2, wherein the above-mentioned nanowire satisfies the following formula (2): A+B≦350nm (2). The nanowire according to claim 1 or 2, wherein the nanowire has a length of 10 μm or more and 40 μm or less. Such as the nanowire of claim 1 or 2, wherein the aforementioned nanowire is made of nickel. A complex nanowire is a complex nanowire having a shape of one-dimensional connection of particles connected by a plurality of particles. The above-mentioned complex nanowire is a metal nanowire and contains any one of claims 1 to 5 Rice noodles. A complex nanowire, a complex nanowire with a shape of one-dimensional connection of particles connected by a plurality of particles, in which the maximum diameter of a nanowire is set to A(nm) and the minimum is set to B (nm), and the maximum diameter A is the maximum diameter of the one nanowire at the end that is not within 100nm from the endpoint, the complex nanowire system satisfies the following formula (1-1): The average value of 1.5≦A/B≦2.5 (1-1); the aforementioned plural nanowires are metal nanowires; the aforementioned nanowires have substantially no polymer layer. Such as the complex number of nanowires in claim 6 or 7, where the average value of A is 50~500nm, and the average value of B is 10~200nm. For example, the complex number of nanowires in claim 6 or 7, where the aforementioned complex number of nanowires satisfies the following formulas (1-2) and (1-3): the maximum value of 1.5≦A/B≦2.5 (1-2) The minimum value of 1.5≦A/B≦2.5 (1-3). Such as the complex number of nanowires in claim 6 or 7, where the aforementioned complex number of nanowires satisfies the following formula (2-1): the average value of A+B≦350nm (2-1). Such as the complex number of nanowires in claim 6 or 7, where the aforementioned complex number of nanowires satisfies the following formulas (2-2) and (2-3): the maximum value of A+B≦350nm (2-2) A+ The minimum value of B≦350nm (2-3). Such as the plural nanowires of claim 6 or 7, wherein the plural nanowires have an average length of 10 μm or more and 40 μm or less. Such as the plural nanowires of claim 6 or 7, wherein the plural nanowires are made of nickel. A method for manufacturing a plurality of nanowires is the method for manufacturing a plurality of nanowires according to any one of Claims 6 to 13, including: reducing metal ions in a magnetic field. A dispersion of nanowires in which plural of claims 6 to 13 are dispersed Nanowire. A transparent conductive film containing plural nanowires according to any one of Claims 6 to 13.

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