WO2009107694A1 - Process for producing metal nanowire, and dispersion and transparent electroconductive film comprising the produced metal nanowire - Google Patents

Process for producing metal nanowire, and dispersion and transparent electroconductive film comprising the produced metal nanowire Download PDF

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Publication number
WO2009107694A1
WO2009107694A1 PCT/JP2009/053489 JP2009053489W WO2009107694A1 WO 2009107694 A1 WO2009107694 A1 WO 2009107694A1 JP 2009053489 W JP2009053489 W JP 2009053489W WO 2009107694 A1 WO2009107694 A1 WO 2009107694A1
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metal
dispersion
metal nanowires
transparent conductive
producing
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PCT/JP2009/053489
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French (fr)
Japanese (ja)
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高広 北野
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株式会社クラレ
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/14—Ultrafiltration; Microfiltration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D63/00—Apparatus in general for separation processes using semi-permeable membranes
    • B01D63/02—Hollow fibre modules
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/02—Elements
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/60—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape characterised by shape
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B7/00—Single-crystal growth from solutions using solvents which are liquid at normal temperature, e.g. aqueous solutions
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2315/00—Details relating to the membrane module operation
    • B01D2315/10—Cross-flow filtration

Definitions

  • the present invention relates to a method for producing metal nanowires, and more specifically, a method for producing metal nanowires including a step of removing impurities by a cross-flow filtration method.
  • a dispersion liquid in which the obtained metal nanowires are dispersed and a transparent conductive film made of the metal nanowires are dispersed and a transparent conductive film made of the metal nanowires.
  • a transparent conductive film used for a transparent electrode or the like has been mainly dry coating such as sputtering.
  • these methods are batch-type, the manufacturing cost is high, and a manufacturing method capable of continuous production is desired.
  • a high temperature is required at the time of coating, and there is a drawback that a resin substrate such as a plastic film cannot be used.
  • Patent Documents 1 and 2 As a method for solving this problem, wet coating is considered, and a network structure using noble metal fine particles has been proposed as one of material candidates (Patent Documents 1 and 2).
  • Patent Document 1 requires a vapor deposition process in a vacuum system, and it is necessary to pre-treat the substrate before the metal vapor deposition process. is there.
  • Patent Document 2 is an excellent method in which wet coating such as spin coating is possible and can be produced continuously, but there is a problem that a plastic substrate cannot be used because a firing process is essential.
  • Non-Patent Document 1 discloses a method for producing silver nanowires by polyol reduction. Although this method is one of the very effective methods for producing metal nanowires, centrifugation is employed as a method for separating silver fine particles generated as a by-product. The method of recovering metal nanowires as a precipitate by centrifugation is a convenient method for recovery, but in order to produce a transparent conductive film, silver nanowires that have been recovered once in a solid state must be dispersed again in a solvent. .
  • the silver nanowires once collected in a solid state are entangled with each other, and are not easily loosened, making it difficult to produce a dispersion of silver nanowires.
  • an object of the present invention is to provide a method for producing metal nanowires with little entanglement and a transparent conductive film using the same.
  • the present invention that solves the above-mentioned problems is a method for producing metal nanowires that includes a step of cross-flow filtering a dispersion in which crude metal nanowires are dispersed.
  • the metal nanowire is preferably a silver nanowire, and more preferably the silver nanowire is produced by a polyol reduction method.
  • the cross flow filtration method is preferably an internal pressure type circulation filtration method using a hollow fiber membrane, and in particular, the internal pressure type circulation filtration method using a hollow fiber membrane is a hollow fiber membrane having a pore diameter of 0.5 ⁇ m or more. It is more preferable to use Moreover, in the internal pressure type circulation filtration using the hollow fiber membrane, it is more preferable that the flow rate of the dispersion liquid in which the crude metal nanowires are dispersed is 50 mm / second or more and 500 mm / second or less in linear velocity.
  • the dispersion solvent of the dispersion in which the crude metal nanowires are used used in the cross flow filtration method is any one of methyl alcohol, ethyl alcohol, 1-propanol, 2-propanol, and 1-butanol.
  • the metal nanowire obtained by the present invention has a short-axis length of 10 nm to 500 nm and a long-axis length of 1 ⁇ m to 100 ⁇ m.
  • the present invention also provides a dispersion obtained by dispersing the metal nanowires obtained by the above-described production method in a dispersion solvent, wherein the solid content concentration is 0.1% by mass or more and 20% by mass or less. It is a dispersion.
  • the dispersion solvent is preferably a single or mixed solvent selected from methyl alcohol, ethyl alcohol, 1-propanol, 2-propanol, 1-butanol, water, and ethylene glycol.
  • this invention is a transparent conductive film containing the transparent conductive layer which consists of metal nanowire obtained by the manufacturing method of above-described this invention, and the intersection part of several metal nanowire which comprises a transparent conductive layer is especially joined. It is preferable. More preferably, the intersections are joined by pressure bonding or plating.
  • the manufacturing method of the metal nanowire which concerns on this invention can obtain the metal nanowire with few entanglements of metal nanowires. For this reason, there is little loss of metal nanowire and it can manufacture with a high yield. It is also easy to scale up. Moreover, since there are few entanglements of metal nanowires, a dispersion liquid with less entanglement of metal nanowires can be easily produced. For this reason, a highly concentrated dispersion liquid can be made. Further, the solvent of the dispersion can be easily changed. In addition, since a dispersion liquid with less entanglement of metal nanowires can be used, a transparent conductive film with less aggregate and high transmittance can be obtained.
  • FIG. 2 is a result of scanning microscope observation of silver nanowires obtained in Example 1.
  • FIG. 2 is a result of scanning microscope observation of silver nanowires obtained in Example 1.
  • FIG. 3 is a diagram illustrating an example of a pressurizing method performed in Example 1.
  • FIG. It is a scanning microscope observation result of the transparent conductive film obtained in Comparative Example 1. It is the figure which compared the length distribution of the silver nanowire obtained in Example 1 and Comparative Example 1.
  • the present invention is a method for producing metal nanowires that includes a step of removing impurities by a cross-flow filtration method.
  • the material of the metal nanowire used in the present invention is a metal. It does not include ceramics such as metal oxides and nitrides. Specific examples include iron, cobalt, nickel, copper, zinc, ruthenium, rhodium, palladium, silver, cadmium, osmium, iridium, platinum, and gold, and copper, silver, platinum, and gold are preferable from the viewpoint of conductivity. Silver is more preferred.
  • the shape of the metal nanowire used in the present invention is not particularly limited as long as the ratio of the length in the minor axis direction to the length in the major axis direction (hereinafter sometimes referred to as aspect ratio) is 10 or more. However, since handling becomes difficult when the aspect ratio is too large, the ratio is preferably 10,000 or less, and more preferably 1,000 or less.
  • a linear metal nanowire is preferable.
  • the straight metal nanowire means that the shape is a rod shape, and does not include a branched shape or a shape in which particles are connected in a bead shape. However, if the metal nanowire has low rigidity and is bent or bent like a banana, it is included in the straight metal nanowire.
  • the length of the metal nanowire in the minor axis direction is preferably 1 nm or more and 1 ⁇ m or less, and more preferably 10 nm or more and 500 nm or less. This is because if the length in the minor axis direction is too large, the transmittance decreases, and if it is too small, synthesis becomes difficult.
  • the length in the major axis direction is preferably 1 ⁇ m or more and 1 mm or less, and more preferably 10 ⁇ m or more and 100 ⁇ m or less. This is because if the length in the major axis direction is too short, the conductivity is lowered, and if it is too long, handling becomes difficult.
  • the shape and size of the metal nanowire can be confirmed with a scanning electron microscope or a transmission electron microscope.
  • the metal nanowire can be synthesized by a known method.
  • a method of reducing silver nitrate in a solution or a method in which an applied voltage or current is applied to the precursor surface from the tip of the probe to pull out the metal nanowire at the tip of the probe and continuously form the metal nanowire (Patent Document) 4) and the like.
  • silver nitrate is reduced in solution by a method of reducing nanofibers composed of metal complexed peptide lipids (Patent Document 5) or a method called polyol reduction, while heating in ethylene glycol.
  • Examples include a method of reducing (Patent Document 6), a method of reducing in sodium citrate (Non-Patent Document 1), and the like.
  • the method of reducing with heating in ethylene glycol is preferable because metal nanowires with high crystallinity can be obtained most easily.
  • the cross-flow filtration method in the present invention represents a filtration method in which a supply liquid flows along a membrane surface, and a permeate passing through the membrane flows in a direction perpendicular to the supply liquid.
  • Specific examples include a flat membrane method and a hollow fiber membrane method, but a hollow fiber membrane method is preferable from the viewpoint of scale-up and ease of handling.
  • the pore size of the filtration membrane used in the present invention varies depending on the particle size of impurities contained in the liquid to be filtered, but is preferably 0.1 ⁇ m or more and 1 ⁇ m or less, preferably 0.2 ⁇ m or more and 1 ⁇ m or less, and preferably 0.2 ⁇ m or more and 1 ⁇ m or less. And more preferably 0.5 ⁇ m or more and 1 ⁇ m or less.
  • the linear velocity is preferably 10 mm / second or more and 1000 mm / second, and more preferably 50 mm / second or more and 500 mm / second or less.
  • the linear velocity represents the supply amount of the supply liquid with respect to the long fiber direction of the hollow fiber membrane.
  • the linear velocity of 10 mm / second represents the supply amount of 10 mm per second with respect to the long fiber direction of the hollow fiber membrane.
  • the linear velocity is too high, the metal nanowire may be damaged, and if it is too low, the efficiency may be lowered.
  • washing solvent used in the crossflow filtration method
  • methyl alcohol, ethyl alcohol, 1-propanol, 2-propanol, 1- Butanol, water, or a mixed solvent thereof is preferable. It is also possible to change the solvent during filtration.
  • the present invention also provides a dispersion of metal nanowires obtained by the above production method.
  • a process of taking out the metal nanowires once in a solid state is necessary, and therefore, a process of redispersion is necessary or the metal nanowires are damaged at the time of redispersion.
  • the method for producing metal nanowires according to the present invention solves these problems, and in principle there is no decrease in yield in this step.
  • the solid concentration of the metal nanowire dispersion according to the present invention is preferably 0.01% by mass or more and 50% by mass or less, more preferably 0.1% by mass or more and 20% by mass or less, and more preferably 1% by mass or more and 10% by mass or less. preferable. If the solid content concentration is too small, the number of times of coating until the desired resistance value is increased, and if the solid content concentration is too large, the metal nanowires may be damaged during handling.
  • the solvent of the dispersion of the metal nanowires according to the present invention is not particularly limited, but methyl alcohol, ethyl alcohol, 1-propanol, 2-propanol from the viewpoint of workability during coating and preferred solvent types in the crossflow filtration step. More preferably, it is a single or mixed solvent selected from 1-butanol, water, and ethylene glycol.
  • the present invention also provides a transparent conductive film containing metal nanowires obtained by the above production method.
  • the transparent conductive film according to the present invention is not particularly limited as long as the transparent conductive layer containing at least the metal nanowire is laminated on the base material, but in a range not impairing the effects of the present invention, a protective layer, an undercoat layer, There may be a hard coat layer, an antistatic layer, an antiglare layer, an antireflection layer, a color filter layer, a retardation film layer and the like.
  • a specific layer structure a layer structure in which a protective layer and an antireflection layer are laminated on a transparent conductive layer as shown in FIGS. 1 and 2, and a transparent conductive film is formed on a hard coat layer as shown in FIG. And a layer configuration in which an antiglare layer is provided on the side opposite to the transparent conductive layer as shown in FIG.
  • a protective layer on the transparent conductive layer.
  • thermoplastic resins such as polyester resin, cellulose resin, vinyl alcohol resin, vinyl resin, cycloolefin resin, polycarbonate resin, acrylic resin, ABS resin, photocurable resin, and heat
  • a known coating material such as a curable resin can be used.
  • the material of the protective layer is preferably the same material as the base material from the viewpoint of adhesion.
  • the base material is a polyester resin
  • the protective layer is preferably a polyester resin.
  • the thickness of the protective layer is too thick, the contact resistance of the transparent conductive layer increases, and if it is too thin, the effect as a protective layer cannot be obtained, and is preferably 1 nm or more and 1 ⁇ m or less, and preferably 10 nm or more and 100 nm or less.
  • the substrate is not particularly limited as long as it is in the form of a sheet or film.
  • ceramics such as glass and alumina, metals such as iron, aluminum and copper, polyester resins, cellulose resins, vinyl alcohol resins, and chlorides.
  • vinyl resins cycloolefin resins, polycarbonate resins, acrylic resins, ABS resins, and other thermoplastic resins, photo-curing resins, thermosetting resins, etc., and emphasizing transparency when using the transparent conductive film according to the present invention.
  • the total light transmittance of the said base material is 80% or more, Specifically, glass, a polyester resin, a polycarbonate resin, an acrylic resin, a cellulose resin etc. are mentioned.
  • the preferable range of the thickness of the base material varies depending on the use, but is preferably 500 ⁇ m or more and 10 mm or less in the case of a sheet, and preferably 10 ⁇ m or more and 500 ⁇ m or less in the case of a film.
  • components other than metal nanowires can be added to the transparent conductive layer as long as the effects of the present invention are not impaired.
  • Photocurable resin, binder components such as epoxy-based, melamine-based, and silicon-based thermosetting resins, surfactants, pigments, and the like.
  • the blending ratio of other components such as metal nanowire and binder can be arbitrarily changed according to the application, but if the blending ratio of metal nanowire is too small, there is a risk that the conductivity will decrease, so the transparent conductive layer
  • the weight ratio of the metal nanowires in the whole is preferably 10% by mass or more and 100% by mass or less, and more preferably 30% by mass or more and 60% by mass or less.
  • the intersections of the metal nanowires are joined. This is because the contact resistance between the linear metal nanowires is lowered by joining the intersections, and as a result, the surface resistance value of the transparent conductive layer is lowered.
  • the intersection portion between the linear metal nanowires is a portion where the linear metal nanowires appear to overlap each other when the transparent conductive layer in which the linear metal nanowires are dispersed in a network is viewed from directly above. It is preferable that the intersections are joined by pressure bonding or plating. Being crimped represents a state in which the intersection portion is deformed and the contact areas of the linear metal nanowires are increased.
  • being plated refers to a state in which the intersection portion of the linear metal nanowires is thicker than before plating and the contact area is increased. In the present invention, it is not necessary that all the intersections are joined, and may be a part. This is because even if it is a part, the effect of lowering the surface resistance value of the transparent conductive layer can be obtained. Whether or not the intersection part of the linear metal nanowires is pressure-bonded or plated can be confirmed by the presence or absence of deformation of the intersection part with a scanning electron microscope or a transmission electron microscope.
  • the surface resistance value of the transparent conductive film according to the present invention is preferably 0.1 ⁇ / ⁇ or more and 100000 ⁇ / ⁇ or less, and more preferably 1 ⁇ / ⁇ or more and 1000 ⁇ / ⁇ or less. This is because if the surface resistance value is too high, the possibility of being used as an electrode is lowered, and if the surface resistance value is too low, the transmittance is lowered in exchange and the possibility of being unavailable as an optical member is increased.
  • the total light transmittance of the transparent conductive film used in the present invention varies depending on the substrate to be used, the total light transmittance is preferably 60% or more and 99% or less, and more preferably 70% or more and 90% or less.
  • the total light transmittance of a transparent conductive film here refers to the total light transmittance as a transparent conductive film including a substrate, not the total light transmittance of only the transparent conductive layer. This is because if the total light transmittance is too high, the surface resistance value becomes too high in exchange and the possibility of being used as an electrode is reduced, and if the total light transmittance is too low, the possibility of being usable as an optical member is reduced. .
  • Example 1 In a 1 L three-necked flask, 333.9 g of ethylene glycol (manufactured by Wako Pure Chemical Industries, Ltd.), 48 ng of sodium chloride (manufactured by Wako Pure Chemical Industries, Ltd.), 41 ng of tris (2,4-pentanedionate) iron (III) (manufactured by Aldrich) was heated to 160 ° C.
  • the resulting crude silver nanowire dispersion was subjected to pressure-type hollow fiber membrane filtration (trade name Midi cross crossflow module membrane area 80 cm 2 pore size 0.5 ⁇ m hollow fiber diameter 0.5mm Spectrum Co.).
  • the cleaning solvent is 2-propanol (manufactured by Wako Pure Chemical Industries, Ltd.), and the linear velocity is 150 mm / sec.
  • the filtration was concentrated to obtain 20 g of a 2-propanol dispersion of purified silver nanowires.
  • 2-propanol is added to the obtained dispersion of purified silver nanowires to obtain a solid content concentration of 3.0% by mass, and then a PET film (product name: Cosmo Shine A4100, manufactured by Toyobo Co., Ltd.) is 18 ⁇ m in wet film thickness. Bar coated on top. The laminate was dried at 80 ° C. for 3 minutes.
  • a PET film with a release layer (trade name: Cosmo Shine K1572 manufactured by Toyobo Co., Ltd.) is stacked on the laminated film so that the release layer is in contact with the transparent conductive layer, and as shown in FIG. The surface was rubbed with a pestle to apply pressure to the transparent conductive layer surface. The results are shown in Table 1.
  • Example 2 A diameter of the hollow fiber is 1mm as internal pressure type hollow fiber membrane using a (trade name Midi cross crossflow module membrane area 60cm 2 pore size 0.5 ⁇ m Spectrum Co.), is carried out except that the linear velocity 500 mm / sec The same operation as in Example 1 was performed. The results are shown in Table 1.
  • Example 3 2-propanol is added to the resulting purified silver nanowire dispersion to adjust the solid concentration to 0.1% by mass, and then a PET film (trade name: Cosmo Shine A4100, manufactured by Toyobo Co., Ltd.) is 18 ⁇ m in wet film thickness. Bar coated on top.
  • a PET film (trade name: Cosmo Shine A4100, manufactured by Toyobo Co., Ltd.) is 18 ⁇ m in wet film thickness. Bar coated on top.
  • Example 4 2-propanol is added to the resulting purified silver nanowire dispersion to adjust the solid concentration to 0.1% by mass, and then a PET film (trade name: Cosmo Shine A4100, manufactured by Toyobo Co., Ltd.) is 18 ⁇ m in wet film thickness. Bar coated on top.
  • a PET film trade name: Cosmo Shine A4100, manufactured by Toyobo Co., Ltd.
  • Example 5 A polyester resin (trade name Byron UR-4800, manufactured by Toyobo Co., Ltd.) was spray-coated on the transparent conductive film obtained in Example 1 so that the film thickness was 10 nm. When the obtained film was subjected to a cross-cut test (JIS K5400), it was 100/100 and no peeling was observed. Table 1 shows the results of the surface resistance and the total light transmittance of the transparent conductive film obtained.
  • Example 6 A butyral resin (trade name: MOWITAL B60H, manufactured by KSE) was added to the 3% by mass silver nanowire dispersion obtained in Example 1 so that the concentration of the silver nanowires relative to the solid content was 37.5% by mass, and PET film (Product name: Cosmo Shine A4100 manufactured by Toyobo Co., Ltd.) was applied with a wet film thickness of 30 ⁇ m and dried at 80 ° C. for 3 minutes to obtain a laminated film. A pressure was applied to the surface of the transparent conductive layer in the same manner as in Example 1 for the obtained laminated film. When the obtained film was subjected to a cross-cut test (JIS K5400), it was 100/100 and no peeling was observed. The results are shown in Table 1.
  • the obtained silver nanowire dispersion was bar-coated on a PET film (trade name: Cosmo Shine A4100, total light transmittance 92%, manufactured by Toyobo Co., Ltd.) so as to have a wet film thickness of 3 ⁇ m.
  • the laminate film was obtained by drying at 80 ° C. for 3 minutes.
  • pressure was applied to the transparent conductive layer surface. The results are shown in Table 1.
  • FIG. 1 shows a method for producing metal nanowires according to the method of the present invention
  • FIG. 8 shows a method for producing metal nanowires according to the prior art.
  • Example 1 and Comparative Example 1 when Example 1 and Comparative Example 1 are compared, the yields of metal nanowires are 59% and 4%, respectively. Therefore, it is clear that the method for producing metal nanowires by the method of the present invention has a higher yield than the conventional method.
  • the surface resistance value (device name: manufactured by Loresta EP Dia Instruments Co., Ltd.), total light transmittance, and haze value (device name direct reading haze computer, manufactured by Suga Test Instruments Co., Ltd.) of the obtained transparent conductive film were measured. The results are shown in Table 1.
  • FIG. 9 shows the length distribution of the silver nanowires obtained in Example 1 and Comparative Example 1. From the above results, it can be seen that the mode value of Example 1 is 6 ⁇ m to 8 ⁇ m, and the mode value of Comparative Example 1 is 2 ⁇ m to 4 ⁇ m. That is, it can be seen that the production method of the present invention can selectively produce long metal nanowires compared to the conventional method.

Abstract

Disclosed is a process for producing a metal nanowire that is less likely to cause entangling. Also disclosed is a transparent electroconductive film using the metal nanowire. The process for producing a metal nanowire comprises the step of subjecting a dispersion containing a crude metal nanowire dispersed therein to cross flow filtration. The metal nanowire is preferably a silver nanowire, more preferably a silver nanowire prepared by a polyol reduction method. Further, preferably, the cross flow filtration is internal pressure circulation filtration using a hollow fiber membrane. More preferably, the internal pressure circulation filtration using the hollow fiber membrane uses a hollow fiber membrane having a pore diameter of not less than 0.5 μm.

Description

金属ナノワイヤの製造方法並びに得られた金属ナノワイヤよりなる分散液および透明導電膜Method for producing metal nanowire, and dispersion and transparent conductive film obtained from metal nanowire
　本発明は金属ナノワイヤの製造方法に関するものであり、より詳しくはクロスフローろ過法により不純物を取り除く工程を含む金属ナノワイヤの製造方法である。また、得られた金属ナノワイヤが分散した分散液および該金属ナノワイヤからなる透明導電膜である。 The present invention relates to a method for producing metal nanowires, and more specifically, a method for producing metal nanowires including a step of removing impurities by a cross-flow filtration method. In addition, a dispersion liquid in which the obtained metal nanowires are dispersed and a transparent conductive film made of the metal nanowires.
　近年液晶ディスプレイやプラズマディスプレイの利用が増えており、これらのデバイスに必須の部材である透明電極膜の需要も増えている。従来透明電極等に用いられる透明導電膜はスパッタリング法などの乾式コーティングが主流であった。しかしながらこれらの方法はバッチ式のため製造コストが高く、連続生産可能な製造方法が望まれている。また、コーティング時に高温が必要であり、プラスチックフィルムなどの樹脂基板を使用することができないという欠点があった。 In recent years, the use of liquid crystal displays and plasma displays has increased, and the demand for transparent electrode films, which are essential members for these devices, has also increased. Conventionally, a transparent conductive film used for a transparent electrode or the like has been mainly dry coating such as sputtering. However, since these methods are batch-type, the manufacturing cost is high, and a manufacturing method capable of continuous production is desired. In addition, a high temperature is required at the time of coating, and there is a drawback that a resin substrate such as a plastic film cannot be used.
　この問題を解決する方法として湿式コーティングが考えられ、材料候補の１つとして貴金属微粒子を用いたネットワーク構造が提案されている（特許文献１および２）。 As a method for solving this problem, wet coating is considered, and a network structure using noble metal fine particles has been proposed as one of material candidates (Patent Documents 1 and 2).
　しかしながら特許文献１に開示された方法は、真空系での蒸着工程が必須であり、また、金属の蒸着処理の前に基板に前処理を施す必要があるため製造コストが高くなるという問題点がある。 However, the method disclosed in Patent Document 1 requires a vapor deposition process in a vacuum system, and it is necessary to pre-treat the substrate before the metal vapor deposition process. is there.
　一方、特許文献２の方法はスピンコートなどの湿式コートが可能であり、連続で作製できるという優れた方法であるが、焼成工程が必須であるためプラスチック基板が使えないという問題点がある。 On the other hand, the method of Patent Document 2 is an excellent method in which wet coating such as spin coating is possible and can be produced continuously, but there is a problem that a plastic substrate cannot be used because a firing process is essential.
　さらに、いずれの方法も金属微粒子を数珠上につなげて配線を構成しており、ネットワークの形状は不定形である。このため、ある２点間に配線を構成するときにおいて不必要な部分にも配線が伸びてしまい、結果として全光線透過率の低い透明導電膜しか得られないという課題が残されていた。 Furthermore, in both methods, metal fine particles are connected on a bead to form a wiring, and the shape of the network is indefinite. For this reason, when the wiring is formed between two points, the wiring extends to an unnecessary portion, and as a result, there remains a problem that only a transparent conductive film having a low total light transmittance can be obtained.
　そこで本発明者は、上記課題を解決すべく金属ナノワイヤを用いた透明導電膜について新たに発明した（特許文献３）。
　金属ナノワイヤの製造方法にはいくつかあるが、ポリオール還元による製造方法も有力な方法の１つである。非特許文献１にポリオール還元による銀ナノワイヤの製造方法が開示されている。この方法は非常に有効な金属ナノワイヤの製造方法の１つであるが、副生成物として発生する銀微粒子を分離する方法として遠心分離を採用している。遠心分離によって金属ナノワイヤを沈殿物として回収する方法は回収するには便利な方法であるが、透明導電膜を作製するためには一旦固体状態で回収した銀ナノワイヤを再び溶媒に分散しなければならない。 Therefore, the present inventor newly invented a transparent conductive film using metal nanowires in order to solve the above problems (Patent Document 3).
Although there are several methods for producing metal nanowires, a method using polyol reduction is one of the promising methods. Non-Patent Document 1 discloses a method for producing silver nanowires by polyol reduction. Although this method is one of the very effective methods for producing metal nanowires, centrifugation is employed as a method for separating silver fine particles generated as a by-product. The method of recovering metal nanowires as a precipitate by centrifugation is a convenient method for recovery, but in order to produce a transparent conductive film, silver nanowires that have been recovered once in a solid state must be dispersed again in a solvent. .
　ところが、一旦固体状態で回収した銀ナノワイヤはお互いに絡みあっており、容易にほぐれず、銀ナノワイヤの分散液を作ることが困難であった。 However, the silver nanowires once collected in a solid state are entangled with each other, and are not easily loosened, making it difficult to produce a dispersion of silver nanowires.
国際特許出願公開２００３／０１６２０９公報International Patent Application Publication No. 2003/016209 国際特許出願公開２００３／０６８６７４公報International Patent Application Publication No. 2003/068674 特願２００７－２３６９４８号明細書Japanese Patent Application No. 2007-236948 Specification 特開２００４－２２３６９３公報JP 2004-223893 A 特開２００２－２６６００７公報JP 2002-266007 A 米国特許出願公開２００５－０５６１１８公報US Patent Application Publication No. 2005-056118
　従って本発明の課題は絡み合いの少ない金属ナノワイヤの製造方法及びこれを用いた透明導電膜を提供することである。 Therefore, an object of the present invention is to provide a method for producing metal nanowires with little entanglement and a transparent conductive film using the same.
　そこで、本発明者は、鋭意検討した結果、クロスフローろ過法により不純物を取り除く工程を含むことによって絡み合いの少ない金属ナノワイヤが得られることを見出し、さらに検討を重ねた結果、上記課題を解決し得る透明導電膜を完成するに至った。 Therefore, as a result of intensive studies, the present inventors have found that a metal nanowire with less entanglement can be obtained by including a step of removing impurities by a cross-flow filtration method, and as a result of further studies, the above problems can be solved. A transparent conductive film was completed.
　すなわち上記課題を解決する本発明は、粗金属ナノワイヤが分散した分散液をクロスフローろ過する工程を含む金属ナノワイヤの製造方法である。本発明において前記金属ナノワイヤは銀ナノワイヤであることが好ましく、特に該銀ナノワイヤがポリオール還元法によって作製されたものであることがより好ましい。 That is, the present invention that solves the above-mentioned problems is a method for producing metal nanowires that includes a step of cross-flow filtering a dispersion in which crude metal nanowires are dispersed. In the present invention, the metal nanowire is preferably a silver nanowire, and more preferably the silver nanowire is produced by a polyol reduction method.
　本発明において、クロスフローろ過法が中空糸膜を用いた内圧型循環ろ過法であることが好ましく、特に中空糸膜を用いた内圧型循環ろ過法が、孔径が０.５μｍ以上の中空糸膜を用いることがより好ましい。
　また、前記中空糸膜を用いた内圧型循環ろ過において、粗金属ナノワイヤが分散した分散液の流速が線速度で５０ｍｍ／秒以上５００ｍｍ／秒以下であることがより好ましい。
　さらに、前記クロスフローろ過法において用いられる、粗金属ナノワイヤが分散した分散液の分散溶媒が、メチルアルコール、エチルアルコール、１－プロパノール、２－プロパノール、１－ブタノールのいずれかであることが好ましい。 In the present invention, the cross flow filtration method is preferably an internal pressure type circulation filtration method using a hollow fiber membrane, and in particular, the internal pressure type circulation filtration method using a hollow fiber membrane is a hollow fiber membrane having a pore diameter of 0.5 μm or more. It is more preferable to use
Moreover, in the internal pressure type circulation filtration using the hollow fiber membrane, it is more preferable that the flow rate of the dispersion liquid in which the crude metal nanowires are dispersed is 50 mm / second or more and 500 mm / second or less in linear velocity.
Furthermore, it is preferable that the dispersion solvent of the dispersion in which the crude metal nanowires are used used in the cross flow filtration method is any one of methyl alcohol, ethyl alcohol, 1-propanol, 2-propanol, and 1-butanol.
　本発明により得られる金属ナノワイヤは、その短軸方向の長さが１０ｎｍ以上５００ｎｍ以下、かつ長軸方向の長さが１μｍ以上１００μｍ以下である。
　また本発明は、上記した製造方法によって得られた金属ナノワイヤが分散溶媒に分散させられて得られる分散液であって、固形分濃度が０．１質量％以上２０質量％以下である金属ナノワイヤの分散液である。特に前記分散溶媒が、メチルアルコール、エチルアルコール、１－プロパノール、２－プロパノール、１－ブタノール、水、エチレングリコールから選ばれる単一あるいは混合溶媒であることが好ましい。 The metal nanowire obtained by the present invention has a short-axis length of 10 nm to 500 nm and a long-axis length of 1 μm to 100 μm.
The present invention also provides a dispersion obtained by dispersing the metal nanowires obtained by the above-described production method in a dispersion solvent, wherein the solid content concentration is 0.1% by mass or more and 20% by mass or less. It is a dispersion. In particular, the dispersion solvent is preferably a single or mixed solvent selected from methyl alcohol, ethyl alcohol, 1-propanol, 2-propanol, 1-butanol, water, and ethylene glycol.
　また本発明は、上記した本発明の製造方法によって得られた金属ナノワイヤからなる透明導電層を含む透明導電膜であり、特に透明導電層を構成する複数の金属ナノワイヤ同士の交点部分が接合されているのが好ましい。前記交点部分の接合は、圧着によりされているかまたはメッキによりされているのがより好ましい。 Moreover, this invention is a transparent conductive film containing the transparent conductive layer which consists of metal nanowire obtained by the manufacturing method of above-described this invention, and the intersection part of several metal nanowire which comprises a transparent conductive layer is especially joined. It is preferable. More preferably, the intersections are joined by pressure bonding or plating.
　本発明に係る金属ナノワイヤの製造方法は金属ナノワイヤ同士の絡まりが少ない金属ナノワイヤを得ることができる。このため金属ナノワイヤのロスが少なく、高収率で製造できる。またスケールアップも容易である。また金属ナノワイヤの絡まりが少ないので金属ナノワイヤの絡まりが少ない分散液が容易に作ることができる。このため高濃度の分散液を作ることができる。さらに分散液の溶媒の変更も容易に可能である。
　また金属ナノワイヤの絡まりが少ない分散液を利用できるので凝集塊が少なく、透過率の高い透明導電膜を得ることができる。 The manufacturing method of the metal nanowire which concerns on this invention can obtain the metal nanowire with few entanglements of metal nanowires. For this reason, there is little loss of metal nanowire and it can manufacture with a high yield. It is also easy to scale up. Moreover, since there are few entanglements of metal nanowires, a dispersion liquid with less entanglement of metal nanowires can be easily produced. For this reason, a highly concentrated dispersion liquid can be made. Further, the solvent of the dispersion can be easily changed.
In addition, since a dispersion liquid with less entanglement of metal nanowires can be used, a transparent conductive film with less aggregate and high transmittance can be obtained.
本発明で用いる層構成の例を示す図であるIt is a figure which shows the example of the layer structure used by this invention 本発明で用いる層構成の例を示す図であるIt is a figure which shows the example of the layer structure used by this invention 本発明で用いる層構成の例を示す図であるIt is a figure which shows the example of the layer structure used by this invention 本発明で用いる層構成の例を示す図である。It is a figure which shows the example of the layer structure used by this invention. 実施例１で得られた銀ナノワイヤの走査型顕微鏡観察結果である。2 is a result of scanning microscope observation of silver nanowires obtained in Example 1. FIG. 実施例１で得られた銀ナノワイヤの走査型顕微鏡観察結果である。2 is a result of scanning microscope observation of silver nanowires obtained in Example 1. FIG. 実施例１で行った加圧方法の例を示す図である。3 is a diagram illustrating an example of a pressurizing method performed in Example 1. FIG. 比較例１で得られた透明導電膜の走査型顕微鏡観察結果である。It is a scanning microscope observation result of the transparent conductive film obtained in Comparative Example 1. 実施例１および比較例１で得られた銀ナノワイヤの長さ分布を比較した図である。It is the figure which compared the length distribution of the silver nanowire obtained in Example 1 and Comparative Example 1. FIG.
発明を実施するための形態BEST MODE FOR CARRYING OUT THE INVENTION
　本発明はクロスフローろ過法により不純物を取り除く工程を含むことを特徴とする金属ナノワイヤの製造方法である。 The present invention is a method for producing metal nanowires that includes a step of removing impurities by a cross-flow filtration method.
　本発明に用いる金属ナノワイヤの材質は金属である。金属の酸化物や窒化物等のセラミックは含まない。具体的には鉄、コバルト、ニッケル、銅、亜鉛、ルテニウム、ロジウム、パラジウム、銀、カドミウム、オスミウム、イリジウム、白金、金が挙げられ、導電性の観点から銅、銀、白金、金が好ましく、銀がより好ましい。 The material of the metal nanowire used in the present invention is a metal. It does not include ceramics such as metal oxides and nitrides. Specific examples include iron, cobalt, nickel, copper, zinc, ruthenium, rhodium, palladium, silver, cadmium, osmium, iridium, platinum, and gold, and copper, silver, platinum, and gold are preferable from the viewpoint of conductivity. Silver is more preferred.
　本発明に用いる金属ナノワイヤの形状は、短軸方向の長さと長軸方向の長さの比（以下、これをアスペクト比と称することがある。）が１０以上のものであれば特に制限はないが、アスペクト比が大きすぎると取扱が困難となるので上記比は１００００以下が好ましく、１０００以下がより好ましい。 The shape of the metal nanowire used in the present invention is not particularly limited as long as the ratio of the length in the minor axis direction to the length in the major axis direction (hereinafter sometimes referred to as aspect ratio) is 10 or more. However, since handling becomes difficult when the aspect ratio is too large, the ratio is preferably 10,000 or less, and more preferably 1,000 or less.
　特に、直線状金属ナノワイヤであることが好ましい。直線状金属ナノワイヤとは形状が棒状であることを意味し、分岐している形状や、粒子を数珠状に繋げた形状は含まない。ただし金属ナノワイヤの剛性が低く、バナナ状に湾曲していたり、折れ曲がったりしている場合には直線状金属ナノワイヤに含むものとする。 In particular, a linear metal nanowire is preferable. The straight metal nanowire means that the shape is a rod shape, and does not include a branched shape or a shape in which particles are connected in a bead shape. However, if the metal nanowire has low rigidity and is bent or bent like a banana, it is included in the straight metal nanowire.
　上記金属ナノワイヤの短軸方向の長さは１ｎｍ以上１μｍ以下が好ましく、１０ｎｍ以上５００ｎｍ以下がより好ましい。短軸方向の長さが大きすぎると透過率が低下し、小さすぎると合成が困難となるからである。長軸方向の長さは１μｍ以上１ｍｍ以下であることが好ましく、１０μｍ以上１００μｍ以下であることがより好ましい。長軸方向の長さが短すぎると導電性が低下し、長すぎると取扱が困難となるからである。
　金属ナノワイヤの形状や大きさは走査型電子顕微鏡や透過型電子顕微鏡によって確認することができる。 The length of the metal nanowire in the minor axis direction is preferably 1 nm or more and 1 μm or less, and more preferably 10 nm or more and 500 nm or less. This is because if the length in the minor axis direction is too large, the transmittance decreases, and if it is too small, synthesis becomes difficult. The length in the major axis direction is preferably 1 μm or more and 1 mm or less, and more preferably 10 μm or more and 100 μm or less. This is because if the length in the major axis direction is too short, the conductivity is lowered, and if it is too long, handling becomes difficult.
The shape and size of the metal nanowire can be confirmed with a scanning electron microscope or a transmission electron microscope.
　上記金属ナノワイヤは公知の方法によって合成することができる。例えば溶液中で硝酸銀を還元する方法や、前駆体表面にプローブの先端部から印加電圧又は電流を作用させプローブ先端部で金属ナノワイヤをひき出し、該金属ナノワイヤを連続的に形成する方法（特許文献４）等が挙げられる。溶液中で硝酸銀を還元する方法としては具体的には金属複合化ペプチド脂質から成るナノファイバーを還元する方法（特許文献５）や、ポリオール還元と呼ばれる方法であって、エチレングリコール中で過熱しながら還元する方法（特許文献６）、クエン酸ナトリウム中で還元する方法（非特許文献１）等が挙げられる。中でも、エチレングリコール中で過熱しながら還元する方法が最も容易に結晶性の高い金属ナノワイヤを入手できるので好ましい。 The metal nanowire can be synthesized by a known method. For example, a method of reducing silver nitrate in a solution, or a method in which an applied voltage or current is applied to the precursor surface from the tip of the probe to pull out the metal nanowire at the tip of the probe and continuously form the metal nanowire (Patent Document) 4) and the like. Specifically, silver nitrate is reduced in solution by a method of reducing nanofibers composed of metal complexed peptide lipids (Patent Document 5) or a method called polyol reduction, while heating in ethylene glycol. Examples include a method of reducing (Patent Document 6), a method of reducing in sodium citrate (Non-Patent Document 1), and the like. Among them, the method of reducing with heating in ethylene glycol is preferable because metal nanowires with high crystallinity can be obtained most easily.
　本発明におけるクロスフローろ過法とは、供給液を膜面に沿って流し、膜を透過する透過液が供給液とは垂直方向に流れるろ過方式を表す。具体的には平膜方式や中空糸膜方式が挙げられるが、スケールアップおよび取り扱いの容易性の観点から中空糸膜方式が好ましい。 The cross-flow filtration method in the present invention represents a filtration method in which a supply liquid flows along a membrane surface, and a permeate passing through the membrane flows in a direction perpendicular to the supply liquid. Specific examples include a flat membrane method and a hollow fiber membrane method, but a hollow fiber membrane method is preferable from the viewpoint of scale-up and ease of handling.
　本発明において用いるろ過膜の孔径はろ過する液体に含まれる不純物の粒径によっても異なるが、０．１μｍ以上１μｍ以下が好ましく、０．２μｍ以上１μｍ以下が好ましく、０．２μｍ以上１μｍ以下が好ましく、０．５μｍ以上１μｍ以下がより好ましい。 The pore size of the filtration membrane used in the present invention varies depending on the particle size of impurities contained in the liquid to be filtered, but is preferably 0.1 μm or more and 1 μm or less, preferably 0.2 μm or more and 1 μm or less, and preferably 0.2 μm or more and 1 μm or less. And more preferably 0.5 μm or more and 1 μm or less.
　本発明において中空糸膜を用いる場合、線速度は１０ｍｍ／秒以上１０００ｍｍ／秒が好ましく、５０ｍｍ／秒以上５００ｍｍ／秒以下がより好ましい。ここで線速度とは中空糸膜の長繊維方向に対する供給液の供給量を表し、例えば線速度が１０ｍｍ／秒とは中空糸膜の長繊維方向に対し１秒間に１０ｍｍ進む量の供給量を表す。本発明において線速度が大きすぎると金属ナノワイヤが損傷する可能性があり、小さすぎると効率が低下する危険性がある。 In the present invention, when a hollow fiber membrane is used, the linear velocity is preferably 10 mm / second or more and 1000 mm / second, and more preferably 50 mm / second or more and 500 mm / second or less. Here, the linear velocity represents the supply amount of the supply liquid with respect to the long fiber direction of the hollow fiber membrane. For example, the linear velocity of 10 mm / second represents the supply amount of 10 mm per second with respect to the long fiber direction of the hollow fiber membrane. To express. In the present invention, if the linear velocity is too high, the metal nanowire may be damaged, and if it is too low, the efficiency may be lowered.
　クロスフローろ過法において用いる洗浄溶媒に特に制限はないが、溶媒によってはろ過膜を溶解したり破損させたりする危険性があるので、メチルアルコール、エチルアルコール、１－プロパノール、２－プロパノール、１－ブタノール、水、またはこれらの混合溶媒であることが好ましい。また、ろ過途中で溶媒を変更することも可能である。 There is no particular limitation on the washing solvent used in the crossflow filtration method, but there is a risk of dissolving or damaging the filtration membrane depending on the solvent. Therefore, methyl alcohol, ethyl alcohol, 1-propanol, 2-propanol, 1- Butanol, water, or a mixed solvent thereof is preferable. It is also possible to change the solvent during filtration.
　また本発明は上記製造方法によって得られた金属ナノワイヤの分散液を提供する。従来の金属ナノワイヤの分散液の製造方法では、一旦固体状態で金属ナノワイヤを取り出す工程が必要であったため、再分散させる工程が必要であったり、再分散時に金属ナノワイヤが損傷したりするなどの問題点があった。この点に対し本発明による金属ナノワイヤの製造方法はこれら問題点を解決し、原理的にはこの工程での収率低下はない。 The present invention also provides a dispersion of metal nanowires obtained by the above production method. In the conventional method for producing a dispersion liquid of metal nanowires, a process of taking out the metal nanowires once in a solid state is necessary, and therefore, a process of redispersion is necessary or the metal nanowires are damaged at the time of redispersion. There was a point. On the other hand, the method for producing metal nanowires according to the present invention solves these problems, and in principle there is no decrease in yield in this step.
　本発明による金属ナノワイヤの分散液の固形分濃度は０．０１質量％以上５０質量％以下が好ましく、０．１質量％以上２０質量％以下がより好ましく、１質量％以上１０質量％以下がより好ましい。固形分濃度が小さすぎると所望の抵抗値になるまでの塗工回数が増え、固形分濃度が大きすぎると取扱時に金属ナノワイヤが損傷する可能性がある。 The solid concentration of the metal nanowire dispersion according to the present invention is preferably 0.01% by mass or more and 50% by mass or less, more preferably 0.1% by mass or more and 20% by mass or less, and more preferably 1% by mass or more and 10% by mass or less. preferable. If the solid content concentration is too small, the number of times of coating until the desired resistance value is increased, and if the solid content concentration is too large, the metal nanowires may be damaged during handling.
　本発明による金属ナノワイヤの分散液の溶媒は特に制限はないが塗工時の作業性や、上記クロスフローろ過工程での好ましい溶媒種の観点からメチルアルコール、エチルアルコール、１－プロパノール、２－プロパノール、１－ブタノール、水、エチレングリコールから選ばれる単一あるいは混合溶媒であることがより好ましい。 The solvent of the dispersion of the metal nanowires according to the present invention is not particularly limited, but methyl alcohol, ethyl alcohol, 1-propanol, 2-propanol from the viewpoint of workability during coating and preferred solvent types in the crossflow filtration step. More preferably, it is a single or mixed solvent selected from 1-butanol, water, and ethylene glycol.
　また本発明は上記製造方法によって得られた金属ナノワイヤを含む透明導電膜を提供する。本発明による透明導電膜は基材上に少なくとも上記金属ナノワイヤを含む透明導電層が積層されたものであれば特に制限はないが、本発明の効果を損なわない範囲において、保護層、下塗り層、ハードコート層、帯電防止層、アンチグレア層、反射防止層、カラーフィルター層、位相差膜層等があっても良い。具体的層構成としては図１および図２に示すように透明導電層上に保護層や反射防止層が積層されている層構成、図３に示すようにハードコート層上に透明導電膜が形成されている層構成、図４に示すように透明導電層とは反対面側にアンチグレア層が設けられている層構成等が挙げられる。 The present invention also provides a transparent conductive film containing metal nanowires obtained by the above production method. The transparent conductive film according to the present invention is not particularly limited as long as the transparent conductive layer containing at least the metal nanowire is laminated on the base material, but in a range not impairing the effects of the present invention, a protective layer, an undercoat layer, There may be a hard coat layer, an antistatic layer, an antiglare layer, an antireflection layer, a color filter layer, a retardation film layer and the like. As a specific layer structure, a layer structure in which a protective layer and an antireflection layer are laminated on a transparent conductive layer as shown in FIGS. 1 and 2, and a transparent conductive film is formed on a hard coat layer as shown in FIG. And a layer configuration in which an antiglare layer is provided on the side opposite to the transparent conductive layer as shown in FIG.
　特に透明導電層との密着性が低い基材を用いる場合や、透明導電層の膜強度が低い場合には、透明導電層上に保護層を設けることが好ましい。保護層に用いる材料に特に制限はないが、ポリエステル樹脂、セルロース樹脂、ビニルアルコール樹脂、ビニル樹脂、シクロオレフィン系樹脂、ポリカーボネート樹脂、アクリル樹脂、ＡＢＳ樹脂等の熱可塑性樹脂、光硬化性樹脂および熱硬化性樹脂などの公知のコーティング材料を用いることができる。保護層の材料は、密着性の観点からは基材と同じ材料が好ましく、例えば基材がポリエステル樹脂の場合は保護層がポリエステル樹脂であることが好ましい。保護層の膜厚は、厚すぎると透明導電層の接触抵抗が大きくなり、薄すぎると保護層としての効果が得られないので１ｎｍ以上１μｍ以下が好ましく、１０ｎｍ以上１００ｎｍ以下が好ましい。 In particular, when a substrate having low adhesion to the transparent conductive layer is used, or when the film strength of the transparent conductive layer is low, it is preferable to provide a protective layer on the transparent conductive layer. There are no particular restrictions on the material used for the protective layer, but thermoplastic resins such as polyester resin, cellulose resin, vinyl alcohol resin, vinyl resin, cycloolefin resin, polycarbonate resin, acrylic resin, ABS resin, photocurable resin, and heat A known coating material such as a curable resin can be used. The material of the protective layer is preferably the same material as the base material from the viewpoint of adhesion. For example, when the base material is a polyester resin, the protective layer is preferably a polyester resin. If the thickness of the protective layer is too thick, the contact resistance of the transparent conductive layer increases, and if it is too thin, the effect as a protective layer cannot be obtained, and is preferably 1 nm or more and 1 μm or less, and preferably 10 nm or more and 100 nm or less.
　基材としてはシート状、フィルム状のものであれば特に制限はないが、例えば、ガラス、アルミナなどのセラミックや、鉄、アルミ、銅等の金属、ポリエステル樹脂、セルロース樹脂、ビニルアルコール樹脂、塩化ビニル樹脂、シクロオレフィン系樹脂、ポリカーボネート樹脂、アクリル樹脂、ＡＢＳ樹脂等の熱可塑性樹脂、光硬化性樹脂、熱硬化性樹脂などが挙げられ、本発明による透明導電膜を使用するに際し透明性を重視する場合は、上記基材の全光線透過率が８０％以上であることが好ましく、具体的にはガラス、ポリエステル樹脂、ポリカーボネート樹脂、アクリル樹脂、セルロース樹脂などが挙げられる。 The substrate is not particularly limited as long as it is in the form of a sheet or film. For example, ceramics such as glass and alumina, metals such as iron, aluminum and copper, polyester resins, cellulose resins, vinyl alcohol resins, and chlorides. Examples include vinyl resins, cycloolefin resins, polycarbonate resins, acrylic resins, ABS resins, and other thermoplastic resins, photo-curing resins, thermosetting resins, etc., and emphasizing transparency when using the transparent conductive film according to the present invention. When it does, it is preferable that the total light transmittance of the said base material is 80% or more, Specifically, glass, a polyester resin, a polycarbonate resin, an acrylic resin, a cellulose resin etc. are mentioned.
　上記基材の厚みは用途によって好ましい範囲は異なるが、シート状であれば５００μｍ以上１０ｍｍ以下が好ましく、フィルム状であれば１０μｍ以上５００μｍ以下が好ましい。 The preferable range of the thickness of the base material varies depending on the use, but is preferably 500 μm or more and 10 mm or less in the case of a sheet, and preferably 10 μm or more and 500 μm or less in the case of a film.
　また、透明導電層には本発明の効果を損なわない範囲において金属ナノワイヤ以外の成分を加えることができる。具体的にはポリエステル樹脂、セルロース樹脂、ポリエーテル樹脂、ビニルアルコール樹脂、ビニル樹脂、シクロオレフィン系樹脂、ポリカーボネート樹脂、アクリル樹脂、ＡＢＳ樹脂、天然高分子等の熱可塑性樹脂、アクリル系やオキセタン系などの光硬化性樹脂、エポキシ系やメラミン系、シリコン系などの熱硬化性樹脂などのバインダー成分、界面活性剤、顔料等が挙げられる。 Moreover, components other than metal nanowires can be added to the transparent conductive layer as long as the effects of the present invention are not impaired. Specifically, polyester resin, cellulose resin, polyether resin, vinyl alcohol resin, vinyl resin, cycloolefin resin, polycarbonate resin, acrylic resin, ABS resin, thermoplastic resin such as natural polymer, acrylic resin, oxetane resin, etc. Photocurable resin, binder components such as epoxy-based, melamine-based, and silicon-based thermosetting resins, surfactants, pigments, and the like.
　金属ナノワイヤとバインダーなど他の成分の配合比率は用途に応じて任意に変更することが可能であるが、金属ナノワイヤの配合比が少なすぎると導電性が低下する危険性があるので、透明導電層全体に占める金属ナノワイヤの重量比は１０質量％以上１００質量％以下が好ましく、３０質量％以上６０質量％以下がより好ましい。 The blending ratio of other components such as metal nanowire and binder can be arbitrarily changed according to the application, but if the blending ratio of metal nanowire is too small, there is a risk that the conductivity will decrease, so the transparent conductive layer The weight ratio of the metal nanowires in the whole is preferably 10% by mass or more and 100% by mass or less, and more preferably 30% by mass or more and 60% by mass or less.
　本発明による透明導電膜は金属ナノワイヤ同士の交点部分が接合されていることが好ましい。交点部分を接合することによって直線状金属ナノワイヤ間の接触抵抗が下がり、その結果透明導電層の表面抵抗値が下がるからである。直線状金属ナノワイヤ同士の交点部分とは、直線状金属ナノワイヤが網目状に分散している透明導電層を真上から見て、直線状金属ナノワイヤが重なって見える部分のことである。交点部分の接合は、圧着またはメッキによってされているのが好ましい。圧着されているとは当該交点部分が変形し、直線状金属ナノワイヤの接触面積が互いに大きくなっている状態を表す。また、メッキされているとは直線状金属ナノワイヤの交点部分がメッキする前に比べ太くなり、接触面積が増えている状態を指す。
　なお、本発明においては当該交点部分がすべて接合されている必要はなく、一部分であっても良い。一部分であっても、透明導電層の表面抵抗値を下げる効果が得られるからである。
　直線状金属ナノワイヤ同士の交点部分が圧着またはメッキされているか否かは走査型電子顕微鏡や透過型電子顕微鏡によって当該交点部分の変形の有無によって確認することができる。 In the transparent conductive film according to the present invention, it is preferable that the intersections of the metal nanowires are joined. This is because the contact resistance between the linear metal nanowires is lowered by joining the intersections, and as a result, the surface resistance value of the transparent conductive layer is lowered. The intersection portion between the linear metal nanowires is a portion where the linear metal nanowires appear to overlap each other when the transparent conductive layer in which the linear metal nanowires are dispersed in a network is viewed from directly above. It is preferable that the intersections are joined by pressure bonding or plating. Being crimped represents a state in which the intersection portion is deformed and the contact areas of the linear metal nanowires are increased. Moreover, being plated refers to a state in which the intersection portion of the linear metal nanowires is thicker than before plating and the contact area is increased.
In the present invention, it is not necessary that all the intersections are joined, and may be a part. This is because even if it is a part, the effect of lowering the surface resistance value of the transparent conductive layer can be obtained.
Whether or not the intersection part of the linear metal nanowires is pressure-bonded or plated can be confirmed by the presence or absence of deformation of the intersection part with a scanning electron microscope or a transmission electron microscope.
　本発明による透明導電膜の表面抵抗値は０．１Ω／□以上１０００００Ω／□以下であることが好ましく、１Ω／□以上１０００Ω／□以下であることがより好ましい。表面抵抗値が高すぎると電極等として利用できる可能性が低下し、表面抵抗値が低すぎると引き替えに透過率が低下し、光学部材として利用できなくなる可能性が高くなるからである。 The surface resistance value of the transparent conductive film according to the present invention is preferably 0.1Ω / □ or more and 100000Ω / □ or less, and more preferably 1Ω / □ or more and 1000Ω / □ or less. This is because if the surface resistance value is too high, the possibility of being used as an electrode is lowered, and if the surface resistance value is too low, the transmittance is lowered in exchange and the possibility of being unavailable as an optical member is increased.
　本発明に用いる透明導電膜の全光線透過率は用いる基材によっても異なるが、全光線透過率が６０％以上９９％以下であることが好ましく、７０％以上９０％以下であることがより好ましい。ここでいう透明導電膜の全光線透過率は透明導電層のみの全光線透過率ではなく、基材も含めた透明導電膜としての全光線透過率を指す。
　全光線透過率が高すぎると引き替えに表面抵抗値が高くなりすぎて電極等として利用できる可能性が低下し、全光線透過率が低すぎると光学部材として利用できる可能性が低下するからである。 Although the total light transmittance of the transparent conductive film used in the present invention varies depending on the substrate to be used, the total light transmittance is preferably 60% or more and 99% or less, and more preferably 70% or more and 90% or less. . The total light transmittance of a transparent conductive film here refers to the total light transmittance as a transparent conductive film including a substrate, not the total light transmittance of only the transparent conductive layer.
This is because if the total light transmittance is too high, the surface resistance value becomes too high in exchange and the possibility of being used as an electrode is reduced, and if the total light transmittance is too low, the possibility of being usable as an optical member is reduced. .
＜実施例１＞
　１Ｌ３口フラスコにエチレングリコール（和光純薬工業社製）３３３．９ｇ、塩化ナトリウム（和光純薬工業社製）４８ｎｇ、トリス（２，４－ペンタンジオネート）鉄（III）（アルドリッチ社製）４１ｎｇを投入し１６０℃に加熱した。
　上記混合溶液中にエチレングリコール（和光純薬工業社製）２００ｇ、塩化ナトリウム（和光純薬工業社製）２９ｎｇ、トリス（２，４－ペンタンジオネート）鉄（III）（アルドリッチ社製）２５ｎｇ、硝酸銀（和光純薬工業社製）２．８８ｇからなる混合溶液とエチレングリコール（和光純薬工業社製）２００ｇ、塩化ナトリウム（和光純薬工業社製）２．１ｍｇ、トリス（２，４－ペンタンジオネート）鉄（III）（アルドリッチ社製）１２８ｎｇ、ポリビニルピロリドン（Ｍｗ．５５０００　アルドリッチ社製）３．１ｇからなる溶液を６分間で滴下し３時間攪拌し粗銀ナノワイヤを得た。 <Example 1>
In a 1 L three-necked flask, 333.9 g of ethylene glycol (manufactured by Wako Pure Chemical Industries, Ltd.), 48 ng of sodium chloride (manufactured by Wako Pure Chemical Industries, Ltd.), 41 ng of tris (2,4-pentanedionate) iron (III) (manufactured by Aldrich) Was heated to 160 ° C.
In the mixed solution, 200 g of ethylene glycol (manufactured by Wako Pure Chemical Industries, Ltd.), 29 ng of sodium chloride (manufactured by Wako Pure Chemical Industries, Ltd.), 25 ng of tris (2,4-pentandionate) iron (III) (manufactured by Aldrich), A mixed solution composed of 2.88 g of silver nitrate (manufactured by Wako Pure Chemical Industries, Ltd.), 200 g of ethylene glycol (manufactured by Wako Pure Chemical Industries, Ltd.), 2.1 mg of sodium chloride (manufactured by Wako Pure Chemical Industries, Ltd.), Tris (2,4-pentane) A solution consisting of dionate) iron (III) (manufactured by Aldrich) 128 ng and polyvinyl pyrrolidone (Mw. 55000, manufactured by Aldrich) 3.1 g was added dropwise over 6 minutes and stirred for 3 hours to obtain crude silver nanowires.
　得られた粗銀ナノワイヤ分散液を内圧型中空糸膜ろ過（商品名　ミディクロス・クロスフローモジュール　膜面積８０ｃｍ２　孔径０．５μｍ　中空糸直径０．５ｍｍ　スペクトラム社製）に供した。洗浄溶媒は２－プロパノール（和光純薬工業社製）、線速度は１５０ｍｍ／秒である。１５００ｍｌのろ液が排出された時点でろ過を濃縮し、２０ｇの精製銀ナノワイヤの２－プロパノール分散液を得た。 The resulting crude silver nanowire dispersion was subjected to pressure-type hollow fiber membrane filtration (trade name Midi cross crossflow module membrane area 80 cm 2 pore size 0.5μm hollow fiber diameter 0.5mm Spectrum Co.). The cleaning solvent is 2-propanol (manufactured by Wako Pure Chemical Industries, Ltd.), and the linear velocity is 150 mm / sec. When 1500 ml of filtrate was discharged, the filtration was concentrated to obtain 20 g of a 2-propanol dispersion of purified silver nanowires.
　得られた精製銀ナノワイヤの走査型電子顕微鏡にて観察した結果を図５、６に記す。この結果より本実施例に用いた銀ナノワイヤの長軸方向の長さが３μｍ以上３０μｍ以下であり、短軸方向の長さが１００ｎｍ以上３００ｎｍ以下であることが分かった。また得られた精製銀ナノワイヤの２－プロパノール分散液の固形分濃度を測定したところ８．５質量％であることが分かった。銀ナノワイヤの収率は５９％（＝２０×０．０８５／２．８８）であった。 Results of observation of the obtained purified silver nanowire with a scanning electron microscope are shown in FIGS. From this result, it was found that the length in the major axis direction of the silver nanowire used in this example was 3 μm or more and 30 μm or less, and the length in the minor axis direction was 100 nm or more and 300 nm or less. Further, when the solid content concentration of the obtained purified silver nanowire in a 2-propanol dispersion was measured, it was found to be 8.5% by mass. The yield of silver nanowires was 59% (= 20 × 0.085 / 2.88).
　得られた精製銀ナノワイヤの分散液に２－プロパノールを加えて固形分濃度を３．０質量％にした後ウェット膜厚で１８μｍになるようにＰＥＴフィルム（商品名：コスモシャインＡ４１００　東洋紡社製）上にバーコートした。８０℃で３分間乾燥し積層体を得た。積層膜上に離型層付きＰＥＴフィルム（商品名：コスモシャインＫ１５７２　東洋紡社製）を離型層が透明導電層に接するように重ね、図７に示すように離型層付きＰＥＴフィルム側からメノウ製乳棒で擦り、透明導電層面に圧力をかけた。結果を表１に記す。 2-propanol is added to the obtained dispersion of purified silver nanowires to obtain a solid content concentration of 3.0% by mass, and then a PET film (product name: Cosmo Shine A4100, manufactured by Toyobo Co., Ltd.) is 18 μm in wet film thickness. Bar coated on top. The laminate was dried at 80 ° C. for 3 minutes. A PET film with a release layer (trade name: Cosmo Shine K1572 manufactured by Toyobo Co., Ltd.) is stacked on the laminated film so that the release layer is in contact with the transparent conductive layer, and as shown in FIG. The surface was rubbed with a pestle to apply pressure to the transparent conductive layer surface. The results are shown in Table 1.
＜実施例２＞
　内圧型中空糸膜として中空糸の直径が１ｍｍのもの（商品名　ミディクロス・クロスフローモジュール　膜面積６０ｃｍ２　孔径０．５μｍ　スペクトラム社製）を用いて、線速度を５００ｍｍ／秒にした以外は実施例1と同様の操作を行った。結果を表１に記す。 <Example 2>
A diameter of the hollow fiber is 1mm as internal pressure type hollow fiber membrane using a (trade name Midi cross crossflow module membrane area 60cm 2 pore size 0.5μm Spectrum Co.), is carried out except that the linear velocity 500 mm / sec The same operation as in Example 1 was performed. The results are shown in Table 1.
＜実施例３＞
　得られた精製銀ナノワイヤの分散液に２－プロパノールを加えて固形分濃度を０．１質
量％にした後ウェット膜厚で１８μｍになるようにＰＥＴフィルム（商品名：コスモシャ
インＡ４１００　東洋紡社製）上にバーコートした。 <Example 3>
2-propanol is added to the resulting purified silver nanowire dispersion to adjust the solid concentration to 0.1% by mass, and then a PET film (trade name: Cosmo Shine A4100, manufactured by Toyobo Co., Ltd.) is 18 μm in wet film thickness. Bar coated on top.
＜実施例４＞
　得られた精製銀ナノワイヤの分散液に２－プロパノールを加えて固形分濃度を０．１質量％にした後ウェット膜厚で１８μｍになるようにＰＥＴフィルム（商品名：コスモシャインＡ４１００　東洋紡社製）上にバーコートした。 <Example 4>
2-propanol is added to the resulting purified silver nanowire dispersion to adjust the solid concentration to 0.1% by mass, and then a PET film (trade name: Cosmo Shine A4100, manufactured by Toyobo Co., Ltd.) is 18 μm in wet film thickness. Bar coated on top.
＜実施例５＞
　実施例１で得られた透明導電膜上にポリエステル樹脂（商品名バイロンＵＲ－４８００　東洋紡社製）を膜厚が１０ｎｍになるようにスプレーコートした。
　得られたフィルムをクロスカット試験（ＪＩＳ　Ｋ５４００）に供したところ１００／１００であり剥がれは見られなかった。
　得られた透明導電膜の表面抵抗値、全光線透過率の結果を表１に記す。 <Example 5>
A polyester resin (trade name Byron UR-4800, manufactured by Toyobo Co., Ltd.) was spray-coated on the transparent conductive film obtained in Example 1 so that the film thickness was 10 nm.
When the obtained film was subjected to a cross-cut test (JIS K5400), it was 100/100 and no peeling was observed.
Table 1 shows the results of the surface resistance and the total light transmittance of the transparent conductive film obtained.
＜実施例６＞
　実施例１で得られた３質量％の銀ナノワイヤ分散液にブチラール樹脂（商品名　ＭＯＷＩＴＡＬ　Ｂ６０Ｈ　ＫＳＥ社製）を固形分に対する銀ナノワイヤの濃度が３７．５質量％になるように添加し、ＰＥＴフィルム（商品名：コスモシャインＡ４１００　東洋紡社製）上にウェット膜厚３０μｍで塗工、８０℃で３分間乾燥し積層膜を得た。
　得られた積層膜に対し実施例１と同様の方法にて透明導電層面に圧力をかけた。得られたフィルムをクロスカット試験（ＪＩＳ　Ｋ５４００）に供したところ１００／１００であり剥がれは見られなかった。結果を表１に記す。 <Example 6>
A butyral resin (trade name: MOWITAL B60H, manufactured by KSE) was added to the 3% by mass silver nanowire dispersion obtained in Example 1 so that the concentration of the silver nanowires relative to the solid content was 37.5% by mass, and PET film (Product name: Cosmo Shine A4100 manufactured by Toyobo Co., Ltd.) was applied with a wet film thickness of 30 μm and dried at 80 ° C. for 3 minutes to obtain a laminated film.
A pressure was applied to the surface of the transparent conductive layer in the same manner as in Example 1 for the obtained laminated film. When the obtained film was subjected to a cross-cut test (JIS K5400), it was 100/100 and no peeling was observed. The results are shown in Table 1.
＜比較例１＞
　実施例１で得られた粗銀ナノワイヤを遠心分離（装置名　高速冷却遠心機ＣＲ２２ＧII　日立工機社製　３０００Ｇ×５分間）し、残渣を水と２－プロパノールの混合溶液（５０／５０ｖｏｌ％）９ｇに分散させた。
　得られた精製銀ナノワイヤの走査型電子顕微鏡にて観察した結果を図４に記す。
　また得られた精製銀ナノワイヤの２－プロパノール分散液の固形分濃度を測定したところ１．３質量％であることが分かった。銀ナノワイヤの収率は４％（＝９×０．０１３／２．８８）であった。 <Comparative Example 1>
The crude silver nanowire obtained in Example 1 was centrifuged (device name: high speed cooling centrifuge CR22GII manufactured by Hitachi Koki Co., Ltd., 3000 G × 5 minutes), and the residue was 9 g of a mixed solution of water and 2-propanol (50/50 vol%). Dispersed.
The result of observing the obtained purified silver nanowire with a scanning electron microscope is shown in FIG.
Further, when the solid content concentration of the obtained purified silver nanowire in a 2-propanol dispersion was measured, it was found to be 1.3% by mass. The yield of silver nanowires was 4% (= 9 × 0.013 / 2.88).
　得られた銀ナノワイヤ分散液をウェット膜厚で３μｍになるようにＰＥＴフィルム（商品名：コスモシャインＡ４１００　東洋紡社製　全光線透過率９２％）上にバーコートした。８０℃で３分間乾燥し積層膜を得た。
　実施例１と同様に透明導電層面に圧力をかけた。
　結果を表１に記す。 The obtained silver nanowire dispersion was bar-coated on a PET film (trade name: Cosmo Shine A4100, total light transmittance 92%, manufactured by Toyobo Co., Ltd.) so as to have a wet film thickness of 3 μm. The laminate film was obtained by drying at 80 ° C. for 3 minutes.
In the same manner as in Example 1, pressure was applied to the transparent conductive layer surface.
The results are shown in Table 1.
[評価]
　図１は本発明の方法による金属ナノワイヤの製造方法であり、図８は従来技術による金属ナノワイヤの製造方法である。これらを比較すると図８では銀ナノワイヤの凝集物が見られるのに対し図１では同様の凝集物がほとんどないことが分かる。従って、本発明の方法による金属ナノワイヤの製造方法は従来の方法に比べて絡まりの少ない金属ナノワイヤが得られることが明確である。 [Evaluation]
FIG. 1 shows a method for producing metal nanowires according to the method of the present invention, and FIG. 8 shows a method for producing metal nanowires according to the prior art. When these are compared, it can be seen that aggregates of silver nanowires are seen in FIG. 8, whereas there are almost no similar aggregates in FIG. Therefore, it is clear that the metal nanowire manufacturing method according to the method of the present invention can yield metal nanowires with less entanglement than the conventional method.
　また、実施例１と比較例１を比較すると金属ナノワイヤの収率はそれぞれ５９％と４％である。従って本発明の方法による金属ナノワイヤの製造方法は従来の方法に比べて高収率であることが明確である。
　得られた透明導電膜の表面抵抗値（装置名：ロレスタＥＰ　ダイアインスツルメンツ社製）、全光線透過率、ヘイズ値（装置名直読ヘーズコンピュータ、スガ試験機社製）を測定した。結果を表１に記す。 Moreover, when Example 1 and Comparative Example 1 are compared, the yields of metal nanowires are 59% and 4%, respectively. Therefore, it is clear that the method for producing metal nanowires by the method of the present invention has a higher yield than the conventional method.
The surface resistance value (device name: manufactured by Loresta EP Dia Instruments Co., Ltd.), total light transmittance, and haze value (device name direct reading haze computer, manufactured by Suga Test Instruments Co., Ltd.) of the obtained transparent conductive film were measured. The results are shown in Table 1.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　図９に実施例１と比較例１で得られた銀ナノワイヤの長さ分布を記す。上記結果より、実施例１の最頻値は６μｍから８μｍであり、比較例１の最頻値は２μｍから４μｍであることが分かる。すなわち、本発明の製造方法は従来法に比べ長い金属ナノワイヤを選択的に製造できることが判る。 FIG. 9 shows the length distribution of the silver nanowires obtained in Example 1 and Comparative Example 1. From the above results, it can be seen that the mode value of Example 1 is 6 μm to 8 μm, and the mode value of Comparative Example 1 is 2 μm to 4 μm. That is, it can be seen that the production method of the present invention can selectively produce long metal nanowires compared to the conventional method.

Claims (15)

  1. 粗金属ナノワイヤが分散した分散液をクロスフローろ過する工程を含むことを特徴とする金属ナノワイヤの製造方法。 A method for producing metal nanowires, comprising a step of cross-flow filtering a dispersion in which crude metal nanowires are dispersed.
  2. 金属ナノワイヤが銀ナノワイヤであることを特徴とする請求項１記載の金属ナノワイヤの製造方法。 The method for producing a metal nanowire according to claim 1, wherein the metal nanowire is a silver nanowire.
  3. 銀ナノワイヤがポリオール還元法によって作製されたものであることを特徴とする請求項２記載の金属ナノワイヤの製造方法。 The method for producing a metal nanowire according to claim 2, wherein the silver nanowire is produced by a polyol reduction method.
  4. クロスフローろ過法が中空糸膜を用いた内圧型循環ろ過法であることを特徴とする請求項１～３のいずれか１項に記載の金属ナノワイヤの製造方法。 The method for producing metal nanowires according to any one of claims 1 to 3, wherein the crossflow filtration method is an internal pressure type circulation filtration method using a hollow fiber membrane.
  5. 中空糸膜の孔径が０.５μｍ以上であることを特徴とする請求項４記載の金属ナノワイヤ製造方法。 The method for producing metal nanowires according to claim 4, wherein the hollow fiber membrane has a pore diameter of 0.5 µm or more.
  6. 中空糸膜を用いた内圧型循環ろ過において、粗金属ナノワイヤが分散した分散液の流速が線速度で５０ｍｍ／秒以上５００ｍｍ／秒以下であることを特徴とする請求項４または５に記載の金属ナノワイヤの製造方法。 The metal according to claim 4 or 5, wherein the flow rate of the dispersion liquid in which the crude metal nanowires are dispersed is 50 mm / second or more and 500 mm / second or less in linear velocity circulation filtration using a hollow fiber membrane. A method for producing nanowires.
  7. クロスフローろ過法において用いられる、粗金属ナノワイヤが分散した分散液の分散溶媒がメチルアルコール、エチルアルコール、１－プロパノール、２－プロパノール、１－ブタノールのいずれかであることを特徴とする請求項１～６のいずれか１項に記載の金属ナノワイヤの製造方法。 The dispersion solvent of the dispersion in which the crude metal nanowires are dispersed used in the cross-flow filtration method is any one of methyl alcohol, ethyl alcohol, 1-propanol, 2-propanol, and 1-butanol. 7. The method for producing a metal nanowire according to any one of 1 to 6.
  8. 得られた金属ナノワイヤの短軸方向の長さが１０ｎｍ以上５００ｎｍ以下、かつ長軸方向の長さが１μｍ以上１００μｍ以下であることを特徴とする請求項１～７のいずれか１項に記載の製造方法。 The length of the short axis direction of the obtained metal nanowire is 10 nm or more and 500 nm or less, and the length of the long axis direction is 1 μm or more and 100 μm or less, according to any one of claims 1 to 7 Production method.
  9. 得られた金属ナノワイヤの長軸方向の長さを２μｍ単位で度数分布表示したときに最頻値が４μｍ以上２０μｍ以下であることを特徴とする請求項１～８のいずれか１項に記載の製造方法。 The mode value is 4 μm or more and 20 μm or less when the length of the obtained metal nanowire in the long axis direction is displayed in a frequency distribution in units of 2 μm. Production method.
  10. 請求項１～９のいずれか１項に記載の製造方法によって得られた金属ナノワイヤが分散溶媒に分散させられて得られる分散液であって、固形分濃度が０．１質量％以上２０質量％以下である金属ナノワイヤの分散液。 A dispersion obtained by dispersing the metal nanowires obtained by the production method according to any one of claims 1 to 9 in a dispersion solvent, wherein the solid concentration is 0.1% by mass or more and 20% by mass A dispersion of metal nanowires as follows.
  11. 分散溶媒がメチルアルコール、エチルアルコール、１－プロパノール、２－プロパノール、１－ブタノール、水、エチレングリコールから選ばれる単一あるいは混合溶媒であることを特徴とする請求項１０に記載の分散液。 The dispersion liquid according to claim 10, wherein the dispersion solvent is a single or mixed solvent selected from methyl alcohol, ethyl alcohol, 1-propanol, 2-propanol, 1-butanol, water, and ethylene glycol.
  12. 請求項１～９のいずれか１項に記載の金属ナノワイヤの製造方法によって得られた金属ナノワイヤからなる透明導電層を含む透明導電膜。 A transparent conductive film comprising a transparent conductive layer made of metal nanowires obtained by the method for producing metal nanowires according to any one of claims 1 to 9.
  13. 透明導電層を構成する複数の金属ナノワイヤ同士の交点部分が接合されていることを特徴とする請求項１２に記載の透明導電膜。 The transparent conductive film according to claim 12, wherein intersections of a plurality of metal nanowires constituting the transparent conductive layer are joined.
  14. 前記交点部分の接合が圧着によりされている請求項１３に記載の透明導電膜。 The transparent conductive film according to claim 13, wherein the intersection portions are joined by pressure bonding.
  15. 前記交点部分の接合がメッキによりされている請求項１３に記載の透明導電膜。 The transparent conductive film according to claim 13, wherein the intersection portion is joined by plating.
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