KR20180004585A - A Conductive Film and Method for Preparing the Same - Google Patents

Abstract

The present invention relates to a transparent conductive film. The transparent conductive film according to the present invention comprises a nanowire assembly of which position is adjusted. The conductive film can implement sufficient conductivity while using less nanowires than existing conductive film consisting of nanowires.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a conductive film,

The present application relates to a conductive film and a method of manufacturing the same.

One of the most widely used materials for transparent electrode materials used in displays and touch panels is indium tin oxide (ITO). Although the film formed from indium tin oxide has an advantage of being excellent in conductivity and transmittance, it has a disadvantage that it is expensive to manufacture due to the use of expensive indium, and it is difficult to realize a large-area flexible display.

As a means for replacing ITO, a conductive film in which metal nanowires are dispersed is used, as shown in Fig. In order for the nanowire-dispersed film to be conductive, a contact point between the randomly dispersed nanowires, that is, a conductive path, must be sufficiently formed, which must include an excess of nanowires. However, when the content of the nanowires is increased, not only the manufacturing efficiency is lowered but also the haze of the film is increased and the sheet resistance of the film is increased.

One object of the present application is to provide a conductive film having excellent conductivity even with a small amount of nanowires.

Another object of the present invention is to provide a conductive film having excellent transparency and low film resistance.

It is still another object of the present invention to provide a conductive film having a reduced manufacturing cost and excellent processability.

These and other objects of the present application can be resolved entirely by the present application, which is described in detail below.

In one example of this application, the present application relates to a conductive film. The conductive film may comprise a substrate, and nanowire assemblies provided on the substrate. 2 schematically shows a conductive film according to an example of the present application.

The conductive film may include a plurality of nanowire aggregates having a closed annular shape as a plan view. The term " closed annular shape " as used herein refers to a state in which a plurality of nanowires are bonded together via a cured compound of a curable compound to form a single nanowire aggregate, It may mean a circle, an ellipse, a polygon, or the like, in which both ends are in contact with each other and are round or angular.

The form of the planar figure of each nanowire aggregate is not particularly limited as long as it has a closed annular shape. In one example, each nanowire assembly may be circular, elliptical, polygonal, or amorphous. In addition, a plurality of nanowire aggregates provided on one substrate may have the same or different planar morphologies.

Each nanowire aggregate may have a contact or a tangent to adjacent nanowire aggregates depending on the planar shape of the aggregate. The contact or tangential line may provide a conductive path for the conductive film. When manufactured by the manufacturing method of the present invention described below, since each nanowire aggregate can be arranged so that the areas do not overlap each other, even if there is a contact or a tangent line between adjacent nanowire aggregates, Is in contact with other nanowire assemblies is excluded from the arrangement of the nanowire assemblies of the present application.

In one example, the nanowire aggregates can be positioned so that their areas do not overlap with adjacent nanowire aggregates sharing contacts or tangents. The term " area of the nanowire aggregate " in the present application can mean the internal area of each aggregate enclosed by the closed annulus when the conductive film is viewed from above or below the normal direction thereof. In the present application using the manufacturing method described below, the conductive films of the present application provide sufficient conductive paths even with only a small amount of nanowires, because each aggregate is arranged so that the areas between the nanowire aggregates do not overlap, As shown in Fig.

Each of the nanowire assemblies may include a plurality of nanowires and a cured product of the curable compound. Specifically, through the post-drying curing process described below, a plurality of nanowires can be joined together via a cured compound of a curable compound to form a nanowire aggregate having a circular, elliptical, polygonal, or amorphous closed annular shape have.

 The kind of the curable compound is not particularly limited so long as it has at least one heat or photocurable functional group. In one example, the curable functional group may be selected from an acrylate group, an epoxy group, a hydroxyl group, an isocyanate group, a carboxyl group, an alkenyl group, an alkynyl group, an acid anhydride group, a nitrile group or an amine group.

In one example, the individual nanowires for forming the nanowire aggregate may have a length in the range of 0.01 [mu] m to 500 [mu] m, and a diameter in the range of 0.01 [mu] m to 10 [mu] m.

In another example, the nanowire may include at least one of Ag, Au, Cu, Pt, Pd, Ni, Co, Rh, Iridium (Ir), ruthenium (Ru), and iron (Fe), but the material of the nanowire is not limited to these metals.

In another example, the nanowire may be a nanowire surface modified with a hydrophobic organic material. The hydrophobic organic substance may be, for example, a hydrophobic hydrocarbon-based compound as an organic matter having a relative affinity for the hydrophobic solvent higher than that for the hydrophilic solvent, as described below. More specifically, it may be a parylene, a polypropylene-based compound, a surfactant having a carbon chain with a long alcohol, a vegetable oil, or a hydrophilic-hydrophobic group at the same time.

The substrate on which a plurality of nanowire aggregates are arranged may be a light-transmitting substrate. More specifically, the substrate may be a substrate having a transmittance to visible light of 50% or more. In the present application, the term " visible light " may mean light in the wavelength range of 380 nm to 780 nm.

As an example of the light-transmitting base layer, there can be mentioned a glass base layer or a transparent polymer base layer. As the glass substrate layer, a base layer such as soda lime glass, barium / strontium-containing glass, lead glass, aluminosilicate glass, borosilicate glass, barium borosilicate glass or quartz can be used. As the polymer base layer, ), PEN (polyethylene naphthalate), PC (polycarbonate), acrylic resin, PET (poly (ethylene terephthalate)), PES (polyether sulfide) The kind of the material forming the substrate is not particularly limited as far as the transmittance to the visible light mentioned can be realized.

In one example, to improve the conductivity, the substrate may further comprise a metal oxide such as an indium based composite oxide. For example, ITO (Indium Tin Oxide), In 2 O 3 (indium oxide), IGO (indium galium oxide), FTO (Fluor doped Tin Oxide), AZO (Aluminium doped Zinc Oxide), GZO (Galium doped Zinc Oxide) , Indium doped tin oxide (ATO), indium doped zinc oxide (IZO), niobium doped titanium oxide (NTO), zinc oxide (ZnO), cesium tungsten oxide (CTO), and the like.

The conductive film according to the present application is excellent in transparency and conductivity. In one example, the conductive film may have, for example, a transmittance of 50 to 99% for visible light and a haze of 50% or less. Since the haze is better as the haze is lower, the lower limit is not particularly limited, and may be, for example, 0.5% or more. The transmittance and haze can be measured by a known apparatus or method such as a Nippon Denshoku haze meter apparatus. In addition, the conductive film may have sufficient conductivity even with a small amount of nanowires. For example, the conductive film of the present application may have a low surface resistance in the range of 0.1? /? To 1,000? / ?. The surface resistance can be measured by a known apparatus or method such as a 4-point probe.

In another example of this application, the present application relates to a method of making a conductive film. The method for manufacturing the conductive film includes: a nanowire; And one or more heat- or light-curable functional group-containing compounds; a coating solution containing a droplet adsorbed on the surface; applying the coating solution onto the substrate; and drying and curing the coating solution.

In one example, the droplets may be formed by emulsification. More specifically, the droplet may be formed by adding a nanowire surface-modified with a hydrophobic organic substance to a mixture of a phase-separated hydrophilic and hydrophobic solvent. That is, when the hydrophobic solvent and the hydrophilic solvent are simply mixed, the mixture of the hydrophobic solvent and the hydrophilic solvent is separated into two layers due to the phase separation, but the nanowire surface-modified with the hydrophobic organic material is a kind of Since it acts as a surfactant, after the nanowire surface-modified with the hydrophobic organic material, the droplet can be formed while the initial shape of the phase-separated mixture is changed into an emulsion form.

In the present application, the terms " hydrophobic " and " hydrophilic " For example, in the case of hydrophobic solvents and hydrophilic solvents, hydrophilic solvents can be mixed with water (water-miscible), while hydrophobic solvents can be phase-separated without being mixed with water . The hydrophilic solvent and the hydrophobic solvent are not particularly limited as far as they are emulsified particles, that is, a solvent capable of forming a droplet when they are mixed together with the surfactant, when they are mixed with only two solvents. . In addition, as described below, any solvent having a boiling point to such an extent as to be able to be evaporated through drying at room temperature or at a warm condition can be used.

In one example, the hydrophobic solvent is a solvent that is immiscible with water (H ₂ O), and may mean, for example, a solvent having a dipole moment of 1.6D or less, and the hydrophilic solvent includes water (H ₂ O) 1.7D or more daily, but is not limited thereto. In a non-limiting example, methylene chloride (MC), n-hexane or toluene may be used as the hydrophobic solvent, and water or ethyl acetate may be used as the hydrophilic solvent.

The surface modification method for the nanowires put into the mixture is not particularly limited. In one example, the surface modification may mean coating the surface of the nanowire with a hydrophobic organic material, such as by mixing and stirring the hydrophobic organic and nanowires in a particular solvent Or by surface treatment. A surface treatment method for surface modification of nanowires is widely known, and a detailed description thereof will be omitted.

For the surface modification of the nanowire, a hydrophobic organic substance having a relative affinity to the above-mentioned hydrophobic solvent higher than that of the hydrophilic solvent may be used. As the hydrophobic organic substance, for example, a hydrophobic hydrocarbon-based compound may be used. More specifically, a hydrophobic polymer such as PE, PP, PS, PVdF, PTFE, PET, PMMA or PAN, or a water-insoluble polymer may be used. In some cases, the hydrophilic polymer may include a polar or hydrophilic functional group, Compounds may be used. For example, if the surface of the nanowire, which is an intermediate product, is already relatively hydrophilic by pre-surface treatment in view of the physical properties such as the dispersibility of the nanowire, because it requires a polar bond such as hydrogen bond at the time of surface modification of the nanowires according to the organic matter, in the side chain or the end of the hydrocarbon chain, _{-COOH, -NH 2, -OH, -SH} , = O, -OCN, or -NO ₂ And the like, or a hydrophobic carbon-based material containing a fluorine substituent may be used. Examples of the material containing a polar functional group as described above include, for example, compounds containing -NH ₂ , such as tetradecylamine, hexadecylamine, octadecylamine, and the like. The kind of the hydrophobic organic substance is not particularly limited as long as it contains a polar functional group such as the functional group mentioned above and is hydrophobic as a whole organic substance.

In one example, the manufacturing method of the present application can be made by further adding an amphipathic polymer to a mixture of a hydrophobic solvent and a hydrophilic solvent. The amphipathic polymer can further enhance the interfacial stability of the droplet. The amphipathic polymer may refer to a substance that may exist at the interface of a hydrophilic and hydrophobic solvent, because it has both a hydrophobic part and a hydrophilic part in one polymer. For example, a hydrophobic portion formed by the hydrocarbon backbone and a hydrophilic portion such as a hydroxy group may be bonded to the terminal or side chain of the main chain. The amphipathic polymer used in the present application may also be adsorbed with the nanowires at the boundary of the droplet, that is, at the interface of the hydrophilic solvent and the hydrophobic solvent.

In one example, the amphipathic polymer may be a compound having at least one heat or photocurable functional group. The heat or photocurable functional group is not particularly limited and may be, for example, an acrylate group, an epoxy group, a hydroxyl group, an isocyanate group, a carboxyl group, an alkenyl group, an alkynyl group, an acid anhydride group, a nitrile group or an amine group. The epoxy group may mean a cyclic ether having three ring constituent atoms, and may be used to include a glycidyl group and the like. When the exemplified curable functional group is used, the kind of the amphipathic polymer that can be used is not particularly limited. For example, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, Dipentaerythritol hexaacrylate, 1,4-butylene glycol diacrylate, 1,6-hexane diol diacrylate, or polyethylene glycol diacrylate, can be used.

The method of applying the droplet-containing mixture prepared from the above, that is, the coating solution onto the substrate is not particularly limited. For example, well-known coating methods such as spin coating, dip coating, spray coating or bar coating may be used.

The method for producing a conductive film according to the present application may include drying the coating solution containing a droplet applied on a substrate before curing the coating solution. More specifically, the manufacturing method according to the present application can provide a precursor on a substrate capable of forming a nanowire aggregate, as described below, by drying the coating solution containing droplets applied to the substrate. That is, since the drying for the coating solution evaporates not only the hydrophobic or hydrophilic solvent included in the droplet but also the hydrophilic or hydrophobic solvent of the opposite nature surrounding the droplet in the coating solution, after the drying step, Only the nanowire and amphipathic polymer that were present at the spherical droplet interface remain on the substrate forming a network of planar shapes such as circular, elliptical, polygonal, or amorphous. The term " network of planar shapes " in the present application may mean that after the solvent evaporation, the nanowires and the amphipathic polymer aggregate in a specific planar morphology.

Conditions for drying the coating solution are not particularly limited. For example, drying can be carried out at room temperature in the range of 18 ° C to 25 ° C without heating or heating, and depending on the type of solvent or polymer used, or other circumstances, heating or heating conditions, Or more, 70 ° C or more, or 100 ° C or more. The upper limit of the drying temperature is not particularly limited, but may be 150 DEG C or lower, for example.

After drying, heat or photo-curing may take place. Through the curing, the network shape of the planar figure shape formed by the precursor of the nanowire aggregate, that is, the nanowire and the amphipathic polymer, can be stabilized. Specifically, since the amphipathic polymer includes a curable functional group as mentioned above, the curing is carried out so that the nanowires are bonded via the cured amphipathic polymer, and thus the polymer is bonded to the nanowire such as circular, oval, polygonal, or amorphous A conductive network in the form of planar features may be fixed on the substrate, thereby forming a nanowire aggregate.

In one example, a radical initiator may be used for the curing. In one example, a radical initiator may be added upon formation of the mixture for droplet formation. The kind of the radical initiator is not particularly limited, and various kinds of radical initiators known in the art can be used without limitation. The content of the radical initiator is not particularly limited.

The kind of the substrate is the same as that mentioned above, and the method of producing the substrate is not particularly limited. In one example, when the substrate comprises a metal oxide such as ITO (Indium Tin Oxide), the substrate may be provided by a known method such as sputter deposition.

The present application can provide a conductive film capable of ensuring a sufficient conductive path even with a small amount of nanowires. In addition, the present application can provide a conductive film having excellent performance, high transparency, and low surface resistance, as well as excellent performance.

Figure 1 schematically illustrates a nanowire conductive film according to the prior art.
Fig. 2 schematically shows a conductive film produced according to an example of the present application.
3 is a microscope image of a droplet produced according to an embodiment of the present application.
FIG. 4 is a microscope image of a comparative photograph taken before and after the drying and curing step according to the embodiment of the present application. FIG. 4A is a microscope image of a droplet taken after coating a coating liquid on a substrate, and FIG. 4B is a microscope image of a nanowire aggregate formed after drying and curing the applied coating liquid.

Hereinafter, the present application will be described in detail by way of examples. However, the scope of protection of the present application is not limited by the following embodiments.

Example

Surface with hydrophobic material Reformed Of silver nano wire  Produce

Hexadecylamine was mixed in a weight ratio of 1: 1 to an isopropanol (IPA) solution containing silver nanowires in an amount of 0.08 wt%. The silver nanowires used were those of Aiden, which had a width of 30 nm or less, a length of 30 μm or less, and a specific resistance of 10 ^-6 Ω.cm. The mixed solution was stirred for 24 hours, and the surface-modified silver nanowires were precipitated with a centrifuge (5000 rpm, 10 minutes) and separated from unreacted hexadecylamine solution.

The nanowires were then dispersed in toluene (1 wt%). The surface modification to hydrophobicity was confirmed by the dispersion of toluene.

Closed-ring Nanowire  Preparation of Conductive Film Having Aggregate

As described above, a toluene solution in which silver nanowires surface-modified with a hydrophobic polymer was dispersed, an amphiphilic hexanediol diacrylate (Sigma-Aldrich, CAS No. 13048-33-4), and a radical initiator Irgacure 907 1: 0.1 (toluene solution with hexane-diol dispersed in AgNW: Irgacure 907), and mixed with water using Voltex (2000 rpm, 1 hour), and the surface-modified silver nanowires were adsorbed at the interface To form droplets. 3 is a microscope image of the droplet produced from the above.

Thereafter, the solution containing the liquid droplet was coated on a PET substrate having a thickness of 100 nm by a bar coater (bar number: 18), dried in an oven at 80 ° C for 2 minutes and irradiated with a UV lamp (Fusion UV inc., H bulb) at a power of 1,000 mJ / cm < ² > to cure the film. The microscope image of the droplet on the substrate immediately after the solution application is shown in Fig. 4A, and the microscope image of the nanowire aggregate formed after drying and curing of the solution is shown in Fig. 4B.

Claims (18)

materials; And a plurality of nanowire aggregates provided on the substrate and having a closed annular shape,
Wherein the nanowire aggregate is arranged such that areas of the aggregates do not overlap with each other.
The film electrode according to claim 1, wherein the nanowire aggregate has a contact or a tangent line with an adjacent aggregate.
The film electrode according to claim 1 or 2, wherein the nanowire aggregate has the same or the same plan shape as the nanowire aggregate.
The film electrode according to claim 3, wherein the nanowire aggregate has a planar shape of a circle, an ellipse, a polygon, or an amorphous shape.
The film electrode according to claim 3, wherein the nanowire assembly comprises a cured product of a curable compound and a plurality of nanowires, wherein the nanowires are bonded to each other via a cured product of the curable compound.
The method of claim 5, wherein the curable compound comprises at least one heat or photo-curable functional group, and the heat or photo-curable functional group is at least one of an acrylate group, an epoxy group, a hydroxyl group, A nitrile group, or an amine group.
6. The film electrode of claim 5, wherein the nanowire has a length in the range of 0.01 to 500 microns and a diameter in the range of 0.01 to 10 microns.
The film electrode according to claim 5, wherein the nanowire is a nanowire surface-modified with a hydrophobic organic substance.
The nanowire of claim 1, wherein the nanowire is selected from the group consisting of Ag, Au, Cu, Pt, Pd, Ni, Co, Rh, Wherein the film electrode comprises at least one metal selected from the group consisting of iridium (Ir), ruthenium (Ru), and iron (Fe).
The film electrode according to claim 1, wherein the substrate is transparent glass or polymer.
The film electrode according to claim 1, wherein the haze is in the range of 0.5% to 50%, and the surface resistance is in the range of 0.1 Ω / □ to 1,000 Ω / □.
Nanowires; And at least one heat or photo-curable functional group-containing compound, a droplet-containing coating solution adsorbed on the surface is coated on a substrate, and the film is dried and cured.
13. The method of claim 12, wherein the droplet is prepared by adding the nanowire to a mixture of a hydrophilic solvent and a hydrophobic solvent, and the nanowire is a nanowire surface-modified with a hydrophobic organic substance.
The method of claim 13, wherein the at least one heat or photo-curable functional group-containing compound is an amphipathic polymer,
Wherein at least one heat or photocurable functional group-containing compound is further added to the mixture of the hydrophilic solvent and the hydrophobic solvent.
15. The method of claim 14, wherein the drying causes the hydrophilic solvent and the hydrophobic solvent to evaporate, and wherein the nanowire and the amphipathic polymer are in the form of a circular, elliptical, polygonal, or amorphous conductive film ≪ / RTI >
15. The method of producing a conductive film according to claim 14, wherein the drying is performed at room temperature or under heating.
15. The method of producing a conductive film according to claim 14, wherein a radical initiator is further added to the mixture of the hydrophilic solvent and the hydrophobic solvent.
The method of claim 17, wherein the heat or photo-curable functional group is selected from an acrylate group, an epoxy group, a hydroxyl group, an isocyanate group, a carboxyl group, an alkenyl group, an alkynyl group, an acid anhydride group, a nitrile group, or an amine group, Curing or photo-curing.

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