KR20220072837A - Method for manufacturing transparent conductive film - Google Patents

Abstract

Provided is a method for manufacturing a transparent conductive film containing metal nanowires and having low conduction anisotropy. A method for producing a transparent conductive film of the present invention includes a coating step of forming an application layer by applying a composition for forming a transparent conductive layer containing metal nanowires to the substrate while conveying a long substrate, and drying the application layer and a drying step of forming a transparent conductive layer on the substrate, wherein the average inclination angle θa of the surface of the substrate is 0.5° or more.

Description

Method for manufacturing transparent conductive film

The present invention relates to a method for producing a transparent conductive film.

BACKGROUND ART Conventionally, in an image display device having a touch sensor, a transparent conductive film obtained by forming a metal oxide layer such as ITO (indium-tin composite oxide) on a transparent resin film is used as an electrode of the touch sensor. However, the transparent conductive film provided with this metal oxide layer easily loses electroconductivity by bending|flexion, and there exists a problem that it is difficult to use for uses which require flexibility, such as a flexible display.

On the other hand, as a transparent conductive film with high flexibility, the transparent conductive film containing a metal nanowire is known. A metal nanowire is a wire-like conductive substance whose diameter is a nanometer size. In a transparent conductive film composed of metal nanowires, when the metal nanowires become mesh-like, a good electrical conduction path is formed with a small amount of metal nanowires, and openings are formed in the gaps between the meshes to achieve high light transmittance. . On the other hand, since a metal nanowire is a wire form, it is easy to arrange|position in the state which has orientation, Therefore, there exists a problem that electrically conductive anisotropy arises in the transparent conductive film containing a metal nanowire.

Japanese Patent Publication No. 2009-505358 Japanese Patent No. 6199034

The present invention has been made in order to solve the above problems, and an object thereof is to provide a method for manufacturing a transparent conductive film containing metal nanowires and having small conductive anisotropy.

A method for producing a transparent conductive film of the present invention includes a coating step of forming an application layer by applying a composition for forming a transparent conductive layer containing metal nanowires to the substrate while conveying a long substrate, and drying the application layer and a drying step of forming a transparent conductive layer on the substrate, wherein the average inclination angle θa of the surface of the substrate is 0.5° or more.

In one embodiment, the average space|interval Sm of the unevenness|corrugation of the surface of the said base material is 0.4 mm or less.

According to another aspect of the present invention, a transparent conductive film is provided. This transparent conductive film is equipped with a base material and the transparent conductive layer arrange|positioned on one side of the base material, The average inclination angle (theta)a of the surface of the base material is 0.6 degree or more.

ADVANTAGE OF THE INVENTION According to this invention, the method of manufacturing a transparent conductive film with small electrically conductive anisotropy can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic sectional drawing of the transparent conductive film by one Embodiment of this invention.

A. Manufacturing method of transparent conductive film

The method for producing a transparent conductive film of the present invention comprises: an application step of forming an application layer by applying a composition for forming a transparent conductive layer containing metal nanowires to the substrate while conveying a long substrate; and a drying step of forming a transparent conductive layer on the substrate. Typically, the application process and drying process are performed while feeding the base material in a roll state and conveying the base material, and as shown in FIG. The long transparent conductive film 100 provided with the transparent conductive layer 20 is formed. In one embodiment, the said transparent conductive film is wound up after a drying process.

A-1. application process

As mentioned above, in an application|coating process, the composition for transparent conductive layer formation containing a metal nanowire is apply|coated to the said base material, conveying a long base material, and an application layer is formed.

(write)

The average inclination angle θa of the surface of the substrate is 0.5° or more. In the present invention, by using the substrate whose surface shape is specified as described above, the metal nanowires are well dispersed in the coating layer, the orientation of the metal nanowires is disturbed, and as a result, a transparent conductive film with small conductive anisotropy can be manufactured. In addition, in this specification, the surface of a base material is a surface in which formation of an application layer is scheduled.

The average inclination angle θa of the surface of the substrate is preferably 0.8° or more, more preferably 1° or more, still more preferably 1.2° or more, and particularly preferably 1.4° or more. If it is such a range, the effect of the said this invention becomes more remarkable. The upper limit of the average inclination angle θa is, for example, 3° (preferably 2.5°, more preferably 2°). In this specification, average inclination angle (theta)a is defined by following formula (1).

θa = tan ^-1 Δa ... (1)

In the above formula (1), Δa is the lowest point of the vertices and valleys of neighboring mountains in the reference length L of the roughness curve prescribed in JIS B 0601 (1994 edition), as shown in the following formula (2) It is a value obtained by dividing the sum (h1 + h2 + h3 ... + hn) of the difference (height h) by the reference length L. The roughness curve is a curve obtained by removing a surface undulation component longer than a predetermined wavelength from a cross-sectional curve with a phase difference compensation high-pass filter. In addition, the said cross-sectional curve is the outline which appears on the cut-out surface when a target surface is cut|disconnected on the plane perpendicular to the target surface.

Δa = (h1 + h2 + h3 ... + hn)/L ... (2)

The average spacing Sm of the unevenness on the surface of the substrate is preferably 0.4 mm or less, more preferably 0.3 mm or less, still more preferably 0.25 mm or less, particularly preferably 0.2 mm or less, and most preferably is 0.15 mm or less. As the average spacing Sm of the irregularities increases, the orientation of the metal nanowires can be reduced, and a transparent conductive film having particularly small conductive anisotropy can be manufactured. In addition, when the average interval Sm of the unevenness is increased, even if the average inclination angle θa is relatively small (for example, the average inclination angle θa = 0.6° to 1°), a remarkable effect of decreasing the conductive anisotropy can be obtained. The lower limit of the average spacing Sm of the unevenness is, for example, 0.03 mm (preferably 0.04 mm). The definition of the average inclination angle θa is based on JIS B 0601 (1994 edition).

Arithmetic mean surface roughness Ra of the surface of the said base material becomes like this. Preferably it is 0.05 micrometer - 3 micrometers, More preferably, they are 0.1 micrometer - 1.5 micrometers. If it is such a range, a transparent conductive film with especially small electrically conductive anisotropy can be manufactured. The definition of arithmetic mean surface roughness Ra is based on JISB0601 (1994 edition).

The thickness of the substrate is preferably 20 µm to 200 µm, more preferably 30 µm to 150 µm.

The total light transmittance of the substrate is preferably 30% or more, more preferably 35% or more, and still more preferably 40% or more.

Any suitable material may be used as the material constituting the substrate. Specifically, for example, a polymer substrate such as a film or a plastic substrate is preferably used. It is because it is excellent in the smoothness of a base material and the wettability with respect to the composition for transparent conductive layer formation, and productivity can be improved significantly by continuous production with a roll.

The material constituting the substrate is typically a polymer film containing a thermoplastic resin as a main component. As a thermoplastic resin, For example, polyester-type resin; Cycloolefin resins, such as polynorbornene; acrylic resin; polycarbonate resin; Cellulose-type resin etc. are mentioned. Among them, a polyester-based resin, a cycloolefin-based resin or an acrylic resin is preferable. These resins are excellent in transparency, mechanical strength, thermal stability, moisture shielding property, and the like. You may use the said thermoplastic resin individually or in combination of 2 or more types. In addition, it is also possible to use an optical film such as that used for a polarizing plate, for example, a low retardation substrate, a high retardation substrate, a retardation plate, a brightness improving film, etc. as a substrate.

As a method of conveying the substrate, any suitable method may be employed. For example, conveyance by a conveyance roll, conveyance by a conveyance belt, these combinations, etc. are mentioned. A conveyance speed is 5 m/min - 50 m/min, for example.

(Metal Nanowire)

The metal nanowire refers to a conductive material made of a metal, having a needle-like shape or a filamentous shape, and having a diameter of nanometers. The metal nanowire may be linear or curved. When the transparent conductive layer composed of metal nanowires is used, the metal nanowires become mesh-like, so that even a small amount of metal nanowires can form a good electrical conduction path, and a transparent conductive film with low electrical resistance can be obtained. In addition, when the metal nanowires become mesh-like, openings are formed in the gaps between the meshes, and a transparent conductive film with high light transmittance can be obtained.

The ratio (aspect ratio: L/d) of the thickness d to the length L of the metal nanowire is preferably 10 to 100,000, more preferably 50 to 100,000, and particularly preferably 100 to 10,000. As described above, when a metal nanowire having a large aspect ratio is used, the metal nanowire crosses favorably, and high conductivity can be expressed with a small amount of the metal nanowire. As a result, a transparent conductive film with high light transmittance can be obtained. In addition, in this specification, "thickness of a metal nanowire" means the diameter when the cross section of the metal nanowire is circular, and in the case of an elliptical shape, it means the short diameter, and in the case of a polygon, the longest diagonal is it means. The thickness and length of a metal nanowire can be confirmed with a scanning electron microscope or a transmission electron microscope.

The thickness of the metal nanowire is preferably less than 500 nm, more preferably less than 200 nm, particularly preferably 10 nm to 100 nm, and most preferably 10 nm to 50 nm. If it is such a range, a transparent conductive layer with high light transmittance can be formed.

The length of the metal nanowire is preferably 1 µm to 1000 µm, more preferably 10 µm to 500 µm, and particularly preferably 10 µm to 100 µm. If it is such a range, a transparent conductive film with high electroconductivity can be obtained. Moreover, when the length of a metal nanowire is the said range, the effect obtained by specifying the surface shape of a base material as mentioned above becomes large.

As the metal constituting the metal nanowire, any suitable metal may be used as long as it is a conductive metal. As a metal which comprises the said metal nanowire, silver, gold|metal|money, copper, nickel, etc. are mentioned, for example. Moreover, you may use the material which gave plating process (for example, gold plating process) to these metals. Among them, from the viewpoint of conductivity, silver, copper, or gold is preferable, and silver is more preferable.

Any suitable method may be employed as a method for manufacturing the metal nanowire. For example, a method of reducing silver nitrate in a solution, applying a voltage or current from the tip of the probe to the surface of the precursor, withdrawing a metal nanowire from the tip of the probe, and continuously forming the metal nanowire, etc. are mentioned. have. In the method of reducing silver nitrate in solution, silver nanowires can be synthesized by liquid-phase reduction of silver salts such as silver nitrate in the presence of polyol such as ethylene glycol and polyvinylpyrrolidone. Silver nanowires of uniform size are described in, for example, Xia, Y. et al., Chem. Mater. (2002), 14, 4736 - 4745, Xia, Y. et al. , Nano letters (2003) 3(7), 955 - 960, mass production is possible.

(Composition for forming a transparent conductive layer)

The composition for forming a transparent conductive layer contains metal nanowires. In one embodiment, a metal nanowire is disperse|distributed to arbitrary appropriate solvents, and the composition for transparent conductive layer formation is prepared. Examples of the solvent include water, alcohol solvents, ketone solvents, ether solvents, hydrocarbon solvents, aromatic solvents, and the like. Moreover, the composition for transparent conductive layer formation may further contain additives, such as resin (binder resin), conductive materials other than metal nanowire (for example, electroconductive particle), and a leveling agent. In addition, the composition for forming a transparent conductive layer includes a plasticizer, a heat stabilizer, a light stabilizer, a lubricant, an antioxidant, an ultraviolet absorber, a flame retardant, a colorant, an antistatic agent, a compatibilizer, a crosslinking agent, a thickener, inorganic particles, a surfactant, and a dispersant. Additives may be included.

The viscosity of the composition for forming a transparent conductive layer is preferably 5 mP·s/25°C to 300 mP·s/25°C, more preferably 10 mP·s/25°C to 100 mP·s/25°C . If it is such a range, the effect obtained by specifying the surface shape of a base material as mentioned above becomes large. The viscosity of the composition for transparent conductive layer formation can be measured with a rheometer (For example, MCR302 of Anton Parr Corporation).

The dispersion density|concentration of the metal nanowire in the composition for transparent conductive layer formation becomes like this. Preferably they are 0.01 weight% - 5 weight%. If it is such a range, the effect of this invention becomes remarkable.

Any suitable method may be employed as a method of applying the composition for forming the transparent conductive layer. Examples of the coating method include spray coating, bar coating, roll coating, die coating, inkjet coating, screen coating, dip coating, embossing printing method, intaglio printing method, and gravure printing method.

The weight of the coating layer is preferably 0.3 g/m 2 to 30 g/m 2 , and more preferably 1.6 g/m 2 to 16 g/m 2 . If it is such a range, the effect obtained by specifying the surface shape of a base material as mentioned above becomes large.

The film thickness of the said application layer becomes like this. Preferably they are 1 micrometer - 50 micrometers, More preferably, they are 2 micrometers - 40 micrometers.

A-2. drying process

As mentioned above, in a drying process, the said application layer is dried, and a transparent conductive layer is formed on the said base material.

As a drying method of the application layer, any suitable drying method (eg, natural drying, air drying, heat drying) can be employed. For example, in the case of heat drying, the drying temperature is typically 80°C to 150°C, and the drying time is typically 1 to 20 minutes.

You may perform arbitrary appropriate processes after a drying process. For example, when the composition for transparent conductive layer formation containing binder resin is used, you may perform hardening process by ultraviolet irradiation etc.

B. Transparent conductive film

A transparent conductive film is formed by said manufacturing method. BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic sectional drawing of the transparent conductive film by one Embodiment of this invention. The transparent conductive film 100 includes a substrate 10 and a transparent conductive layer 20 disposed on one side of the substrate 10 .

The surface resistance value of the transparent conductive film is preferably 0.1 Ω/□ to 1000 Ω/□, more preferably 0.5 Ω/□ to 300 Ω/□, particularly preferably 1 Ω/□ to 200 Ω/□. □ is. The ratio (TD/MD) of the surface resistance value in TD (direction orthogonal to MD) to the surface resistance value in MD (transport direction) of the transparent conductive film is preferably 0.7 to 1.5, and more Preferably it is 0.8-1.2, More preferably, it is 0.9-1.1. A surface resistance value can be measured with "resistivity automatic measurement system MCP-S620 type/MCP-S521 type" by Mitsubishi Chemical Analytech.

The haze value of the transparent conductive film is preferably 20% or less, more preferably 10% or less, and still more preferably 0.1% to 5%.

The total light transmittance of the transparent conductive film is preferably 30% or more, more preferably 35% or more, and particularly preferably 40% or more.

The average inclination angle θa of the surface of the substrate is 0.6° or more, preferably 0.8° or more, more preferably 1° or more, still more preferably 1.2° or more, and particularly preferably 1.4° or more. If it is such a range, the effect of the said this invention becomes more remarkable. The upper limit of the average inclination angle θa is, for example, 3° (preferably 2.5°, more preferably 2°). In addition, the said average inclination angle (theta)a of the surface of a base material is measured before formation of a transparent conductive layer.

The average spacing Sm of the unevenness on the surface of the substrate is preferably 0.4 mm or less, more preferably 0.3 mm or less, still more preferably 0.25 mm or less, particularly preferably 0.2 mm or less, and most preferably is 0.15 mm or less. In addition, the average space|interval Sm of the said unevenness|corrugation of the surface of a base material is measured before formation of a transparent conductive layer.

Arithmetic mean surface roughness Ra of the surface of the said base material becomes like this. Preferably it is 0.05 micrometer - 3 micrometers, More preferably, they are 0.1 micrometer - 1.5 micrometers. In addition, the said arithmetic mean surface roughness Ra of the surface of a base material is measured before transparent conductive layer formation.

The weight per unit area of the transparent conductive layer is preferably 0.001 g/m 2 to 0.09 g/m 2 , more preferably 0.005 g/m 2 to 0.05 g/m 2 .

The content ratio of the metal nanowires in the transparent conductive layer is preferably 0.1 parts by weight to 50 parts by weight, more preferably 0.1 parts by weight to 30 parts by weight with respect to 100 parts by weight of the binder resin constituting the transparent conductive layer. is part by weight. If it is such a range, the transparent conductive film excellent in electroconductivity and light transmittance can be obtained.

Example

Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited at all to these Examples. The evaluation method in an Example is as follows. In addition, thickness was formed by cutting with an ultra microtome after embedding process with an epoxy resin, and it measured using the Hitachi High-Technologies company scanning electron microscope "S-4800".

(1) the shape of the surface of the substrate

In accordance with JIS B0601 (1994 edition), the average uneven distance Sm (mm) and the arithmetic mean surface roughness Ra (µm) were measured. Specifically, a glass plate (manufactured by MATSUNAMI, MICRO SLIDE GLASS, product number S, thickness 1.3 mm, 45 mm 50 mm) was bonded to the surface on the opposite side to the measurement surface with an adhesive to prepare a sample. A scanning speed of 0.1 mm using a stylus type surface roughness measuring instrument (manufactured by Kosaka Laboratories Co., Ltd., high-precision fine shape measuring instrument, trade name “SURFcoder ET4000”) having a measuring needle with a radius of curvature R of the tip (diamond) of R = 2 µm) Under the conditions of /sec, a cutoff value of 0.8 mm, and a measurement length of 4 mm, the surface shape of the anti-glare layer in the sample is measured in a constant direction, the average interval Sm of the irregularities is obtained, and the average slope from the obtained surface roughness curve The angle θa (°) was calculated.

(2) Surface resistance value

The surface resistance value (the surface resistance value of MD and TD) of the transparent conductive film was measured by the eddy current method using the Napson Co., Ltd. non-contact surface resistance meter, brand name "EC-80". The measurement temperature was 23 degreeC.

[Production Example 1] Preparation of a composition for forming a transparent conductive layer

Chem. Mater. 2002, 14, based on the method described in 4736 - 4745, silver nanowires were synthesized.

In pure water, 0.2 weight% of the silver nanowire obtained above and dodecyl-pentaethylene glycol were disperse|distributed so that it might become a density|concentration of 0.1 weight%, and the composition for transparent conductive layer formation was obtained.

[Example 1]

PET film (manufactured by Toray Corporation, trade name "U40", thickness: 23 µm), 100 parts by weight of an acrylic monomer (manufactured by Osaka Organic Chemical Industry, trade name "Viscoat #300", solid content 56 wt%), and particles (Sekisui) A coating solution containing 30 parts by weight of Hwaseong Co., Ltd., trade name "Tech Polymer SSX-105"), 0.5 parts by weight of an initiator (manufactured by BASF, trade name "Irgacure 127"), and 35 parts by weight of butyl acetate, It dried at 100 degreeC for 2 minute(s), after that, 300 mJ ultraviolet-ray was irradiated, and the base material A (thickness: 20 micrometers) was formed on the PET film.

The composition for forming a transparent conductive layer prepared in Production Example 1 was applied on the substrate A peeled from the PET film using a bar coater (manufactured by Daiichi Rika Co., Ltd., product name “Bar Coater No. 16”), and heated at 120°C. It was dried for 2 minutes in a blow dryer, the transparent conductive layer was formed, and the transparent conductive film provided with a base material and a transparent conductive layer was obtained. Moreover, the average inclination angle (theta)a of the surface on which the transparent conductive layer of the base material A was formed was 1.5 degrees, and the average space|interval Sm of unevenness|corrugation was 0.05 mm.

The obtained transparent conductive film was subjected to the above evaluation (2). A result is shown in Table 1.

[Example 2]

Instead of 30 parts by weight of particles (manufactured by Sekisui Chemical Co., Ltd., trade name "Tech Polymer SSX-105"), 5 parts by weight of particles (manufactured by Soken Chemical, trade name "SX-350H") is used, and a thixotropic agent ( The base material B (thickness: 20 micrometers) was formed like Example 1 except having added 0.2 weight part of Kunimine Kogyo company make, brand name "SAN"). Then, by the method similar to Example 1, the transparent conductive layer was formed, and the transparent conductive film provided with a base material and a transparent conductive layer was obtained. Moreover, the average inclination angle (theta)a of the surface on which the transparent conductive layer of the base material D was formed was 0.9 degrees, and the average space|interval Sm of unevenness|corrugation was 0.15 mm.

The obtained transparent conductive film was subjected to the above evaluation (2). A result is shown in Table 1.

[Example 3]

A base material C (thickness: 20 µm) was formed in the same manner as in Example 2 except that the addition amount of the particles (manufactured by Soken Chemical Co., Ltd., trade name “SX-350H”) was 10 parts by weight. Then, by the method similar to Example 1, the transparent conductive layer was formed, and the transparent conductive film provided with a base material and a transparent conductive layer was obtained. Moreover, the average inclination angle (theta)a of the surface on which the transparent conductive layer of the base material C was formed was 1.5 degrees, and the average space|interval Sm of unevenness|corrugation was 0.12 mm.

The obtained transparent conductive film was subjected to the above evaluation (2). A result is shown in Table 1.

[Comparative Example 1]

The same as in Example 1, except that a PET film (manufactured by Toray Corporation, trade name "U40", thickness: 23 µm, average inclination angle: 0.1°, average spacing of concavities and convexities Sm: 0.04 mm) was used as the substrate B instead of the substrate A instead of the substrate B. and a transparent conductive film was obtained. The obtained transparent conductive film was subjected to the above evaluation (2). A result is shown in Table 1.

[Comparative Example 2]

Example 1 except that 15 parts by weight of particles (manufactured by Sekisui Chemical Co., Ltd., trade name "Technopolymer SSX-101") was used instead of 30 parts by weight of particles (manufactured by Sekisui Chemical Co., Ltd., trade name "Tech Polymer SSX-105") It carried out similarly to the above, and the base material D (thickness: 20 micrometers) was formed. Then, by the method similar to Example 1, the transparent conductive layer was formed, and the transparent conductive film provided with a base material and a transparent conductive layer was obtained. In addition, the average inclination angle (theta)a of the surface on which the transparent conductive layer of the base material D was formed was 0.3 degree, and the average space|interval Sm of unevenness|corrugation was 0.19 mm.

The obtained transparent conductive film was subjected to the above evaluation (2). A result is shown in Table 1.

[Reference Example 1]

On PET film, 100 parts by weight of an acrylic monomer (manufactured by Osaka Organic Chemical Industry, trade name "Viscoat #300", solid content 56% by weight) and particles (manufactured by Sekisui Chemical Co., Ltd., trade name "Tech Polymer SSX-101") 10 weight A coating solution containing part and 0.5 parts by weight of an initiator (manufactured by BASF, trade name "Irgacure 127") and 35 parts by weight of butyl acetate was coated, dried at 100° C. for 2 minutes, and then UV light of 300 mJ was applied. It was irradiated, and the base material C (thickness: 20 micrometers) was formed on the PET film.

On the base C peeled from the PET film, the composition for forming a transparent conductive layer prepared in Production Example 1 was applied using a bar coater (manufactured by Daiichi Rika Co., Ltd., product name “Bar Coater No. 16”), and heated at 120°C. It was dried for 2 minutes in a blow dryer, the transparent conductive layer was formed, and the transparent conductive film provided with a base material and a transparent conductive layer was obtained. Moreover, the average inclination angle (theta)a of the surface on which the transparent conductive layer of the base material C was formed was 0.1 degree, and the average space|interval Sm of unevenness|corrugation was 0.27 mm.

As a result of subjecting the obtained transparent conductive film to the said evaluation (2), the surface resistance value of MD was 41 (ohm), and the surface resistance value of TD was 62 (ohm).

10 ; write
20 ; transparent conductive layer
100 ; transparent conductive film

Claims (3)

A coating step of forming an application layer by applying a composition for forming a transparent conductive layer containing metal nanowires to the substrate while conveying a long substrate;
a drying step of drying the application layer to form a transparent conductive layer on the substrate;
The average inclination angle θa of the surface of the substrate is 0.5° or more,
A method for producing a transparent conductive film. The method of claim 1,
The manufacturing method of the transparent conductive film whose average spacing Sm of the unevenness|corrugation of the surface of the said base material is 0.4 mm or less. A substrate and a transparent conductive layer disposed on one side of the substrate,
The average inclination angle θa of the surface of the substrate is 0.5° or more,
Transparent conductive film.

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