JP7638882B2 - Method for producing transparent conductive film - Google Patents

Description

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

Conventionally, in image display devices having touch sensors, transparent conductive films obtained by forming a metal oxide layer such as ITO (indium tin oxide) on a transparent resin film have been widely used as electrodes for the touch sensors. However, transparent conductive films having such metal oxide layers tend to lose conductivity when bent, making them difficult to use in applications requiring flexibility such as flexible displays.

On the other hand, transparent conductive films containing metal nanowires are known as highly flexible transparent conductive films. Metal nanowires are wire-shaped conductive materials with nanometer-sized diameters. In transparent conductive films made of metal nanowires, the metal nanowires form a mesh-like structure, so that a small amount of metal nanowires can form good electrical conduction paths, and openings are formed in the gaps between the meshes, achieving high light transmittance. On the other hand, because the metal nanowires are wire-shaped, they tend to be arranged in an oriented state, which creates the problem of conductive anisotropy in transparent conductive films containing metal nanowires.

Special Publication No. 2009-505358 Patent No. 6199034

The present invention has been made to solve the above problems, and its object is to provide a method for producing a transparent conductive film that contains metal nanowires but has small conductive anisotropy.

The method for producing a transparent conductive film of the present invention is a method for producing a transparent conductive film comprising a substrate and a transparent conductive layer arranged on one side of the substrate, and includes a coating step of coating the substrate with a transparent conductive layer forming composition containing metal nanowires while transporting the elongated substrate to form a coating layer, and an air blowing step of blowing air onto the coating layer, the air blowing step including blowing air in a direction different from the transport direction of the substrate.
In one embodiment, the air blowing step is performed in two or more directions.
In one embodiment, the direction of air blowing in the air blowing step as viewed from the coating layer surface side of the substrate includes a direction from the inner side in the width direction of the substrate to both outer sides in the width direction.
In one embodiment, the direction of air blowing in the air blowing step as viewed from the coating layer surface side of the substrate includes directions from both outer sides in the width direction of the substrate toward the inner side in the width direction.
In one embodiment, the air blowing step is a spiral air blowing step.

The present invention provides a method for producing a transparent conductive film with small conductive anisotropy.

1A to 1E are schematic plan views illustrating the air blowing direction in the air blowing process in one embodiment of the present invention. 1A' to 1E' are schematic plan views illustrating the air blowing direction in the air blowing process in one embodiment of the present invention. 1 is a schematic cross-sectional view of a transparent conductive film obtained by a manufacturing method according to one embodiment of the present invention.

A. Overview of the manufacturing method of the transparent conductive film The manufacturing method of the transparent conductive film of the present invention includes a coating step of forming a coating layer by coating a composition for forming a transparent conductive layer containing metal nanowires on a long-sized substrate while transporting the substrate, and a blowing step of blowing air on the coating layer. According to the manufacturing method of the present invention, a transparent conductive film including a substrate and a transparent conductive layer disposed on one side of the substrate is obtained. The manufacturing method of the present invention may include any other appropriate steps in addition to the above-mentioned coating step and blowing step. In one embodiment, the manufacturing method may further include a drying step of drying the coating layer after the blowing step. In another embodiment, the blowing step is a step that can dry the coating layer, and the transparent conductive layer is formed through the blowing step.

Typically, the substrate in a roll state is unwound and transported while performing the above-mentioned coating process and air blowing process (as well as other processes such as a drying process, if necessary) to form a long transparent conductive film comprising the substrate and a transparent conductive layer disposed on one side of the substrate. In one embodiment, the transparent conductive film is wound up after formation. In the present invention, the air blowing in the air blowing process includes air blowing in a direction different from the substrate transport direction. The concept of a direction different from the substrate transport direction includes a direction different from the substrate transport direction as viewed from the substrate's coating layer surface side; a direction that is not parallel to the substrate surface; and a direction different from the substrate transport direction as viewed from the substrate's coating layer surface side and not parallel to the substrate surface. In one embodiment, the air blowing in a direction different from the substrate transport direction is a direction different from the substrate transport direction as viewed from the substrate's coating layer surface side and parallel or not parallel to the substrate surface. In another embodiment, the air blown in a direction different from the substrate transport direction is a direction different from the substrate transport direction when viewed from the coating layer side of the substrate, or a direction that is approximately parallel to the substrate transport direction, and is not parallel to the substrate surface. In this specification, the term "non-parallel direction" means that the angle with respect to the reference direction/plane (substrate surface) is 5° or less.

Figures 1(a) to (e) are schematic plan views illustrating the air blowing direction in the air blowing process in one embodiment of the present invention. Figures 1(a') to (e') are schematic views illustrating the air blowing direction in the air blowing process in one embodiment of the present invention. Figure 1(a') is a schematic front view of Figure 1(a) (viewed from the transparent conductive film winding side), and Figure 1(b') is a schematic front view of Figure 1(b). Figure 1(c') is a schematic side view of Figure 1(c), and Figure 1(d') is a schematic side view of Figure 1(d). Figure 1(e') is a schematic front view of Figure 1(e).

In one embodiment, as shown in Figures 1(a) and (b), the air blowing direction in the air blowing process as viewed from the coating layer 21 side of the substrate 10 is a direction different from the substrate conveying direction as viewed from at least the coating layer side of the substrate, and the air blowing is performed in two or more directions.

1(a), the direction of the air blowing process (also referred to as the air blowing direction X) as viewed from the coating layer 21 side of the substrate 10 includes directions from both outer sides of the substrate 10 in the width direction to the inside of the width direction. In this embodiment, the angle between the substrate conveying direction A and the air blowing direction X is greater than 0° and less than 180°, preferably 30° to 150°, more preferably 60° to 120°, even more preferably 60° to 100°, even more preferably 60° to 95°, even more preferably 75° to 95°, and particularly preferably 85° to 95°. The wind may be blown in a fan-like manner from the outside of the substrate 10 in the width direction to the inside of the width direction.

In the embodiment shown in FIG. 1(b), the direction of air blowing in the air blowing process as viewed from the coating layer 21 side of the substrate 10 (also referred to as air blowing direction X) includes a direction from the inner side of the substrate 10 in the width direction to both outer sides in the width direction. In this embodiment, the angle between the substrate conveying direction A and the air blowing direction X is greater than 0° and less than 180°, preferably 30° to 150°, more preferably 60° to 120°, even more preferably 60° to 100°, even more preferably 60° to 95°, even more preferably 75° to 95°, and particularly preferably 85° to 95°. The wind may be blown in a fan-like manner from the inner side of the substrate 10 in the width direction to the outer side in the width direction.

In addition to the embodiment shown in Fig. 1(a) and (b), an embodiment in which air is blown in two or more directions can also be mentioned, as shown in Fig. 1(c) and (d), in which air is blown in a spiral shape (i.e., air is made to flow as a spiral flow). When air is blown in a spiral shape, the direction X' of the spiral axis of the air as seen from the coating layer 21 side of the substrate 10 may be parallel to the transport direction A of the substrate as shown in Fig. 1(c), or may not be parallel. In one embodiment, the angle between the direction X' of the spiral axis of the air as seen from the coating layer 21 side of the substrate 10 and the transport direction A of the substrate is preferably 0° to 60°, more preferably 0° to 45°, and even more preferably 0° to 30°. In another embodiment, the angle between the direction X' of the spiral axis of the air as seen from the coating layer 21 side of the substrate 10 and the transport direction A of the substrate is preferably 60° to 120°, more preferably 80° to 100°. In yet another embodiment, the angle between the direction X' of the helical axis of the wind as viewed from the coating layer 21 surface side of the substrate 10 and the transport direction A of the substrate is preferably 120° to 180°, more preferably 150° to 180°. When wind is blown in a spiral shape, the direction Z' of the helical axis of the wind as viewed from the side of the substrate 10 may be parallel to the transport direction A of the substrate (FIG. 1(c')), or may not be parallel. In one embodiment, the angle between the direction Z' of the helical axis of the wind as viewed from the side of the substrate 10 and the transport direction A of the substrate is preferably 0° to 60°, more preferably 0° to 30°. In another embodiment, the angle between the direction Z' of the helical axis of the wind as viewed from the side of the substrate 10 and the transport direction A of the substrate is preferably 60° to 120°, more preferably 80° to 100° (FIG. 1(d')). In this specification, in order to distinguish it from wind that blows in a spiral shape, wind that blows in a substantially constant direction rather than in a spiral shape, such as the winds shown in Figures 1(a), (b) and (e), is referred to as "rectified wind."

In one embodiment, as shown in FIG. 1(e), the air blowing direction in the air blowing process as viewed from the coating layer 21 side of the substrate 10 is different from the substrate conveying direction, and the air blowing is performed in one direction. In this embodiment, the angle between the substrate conveying direction A and the air blowing direction X is greater than 0° and less than 90°, or greater than 90° and less than 180°, and is preferably 30° to 60° or 120° to 150°. The air may be blown in a fan-like manner.

When the rectified air is blown to the coating layer 21, the air blowing direction Z in the air blowing process as viewed from the side of the substrate 10 may be parallel to the substrate surface (FIGS. 1(a') and (b')), or may not be parallel (FIG. 1(e')). The angle between the air blowing direction Z in the air blowing process as viewed from the side of the substrate 10 and the conveying direction A of the substrate surface is preferably 0° to 60°. In one embodiment, the air blowing direction Z in the air blowing process as viewed from the side of the substrate 10 is approximately parallel to the substrate surface (i.e., the angle between the air blowing direction Z and the substrate surface is 10° or less). In this way, a transparent conductive layer with excellent surface smoothness is formed. In another embodiment, the angle between the air blowing direction Z in the air blowing process as viewed from the side of the substrate 10 and the substrate surface is greater than 10° and less than 60°.

In the present invention, by blowing air in a specific direction during the air blowing process, the orientation of the metal nanowires is disturbed, and as a result, a transparent conductive film with small conductive anisotropy can be produced. This effect becomes more pronounced by blowing air in two or more directions. Furthermore, by blowing air in two or more directions, a transparent conductive film with significantly high dispersion uniformity of the metal nanowires can be obtained.

B. Coating Step As described above, in the coating step, a coating layer is formed by coating a transparent conductive layer-forming composition containing metal nanowires onto a long-sized substrate while the substrate is being transported.

(Substrate)
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. This is because the substrate has excellent smoothness and wettability with respect to the transparent conductive layer forming composition, and the productivity can be significantly improved by continuous production using a roll.

The material constituting the above-mentioned substrate is typically a polymer film mainly composed of a thermoplastic resin. Examples of thermoplastic resins include polyester resins; cycloolefin resins such as polynorbornene; acrylic resins; polycarbonate resins; cellulose resins, etc. Among them, polyester resins, cycloolefin resins, and acrylic resins are preferred. These resins are excellent in transparency, mechanical strength, thermal stability, and moisture shielding properties. The above-mentioned thermoplastic resins may be used alone or in combination of two or more kinds. In addition, optical films such as those used in polarizing plates, such as low retardation substrates, high retardation substrates, retardation plates, and brightness enhancement films, can also be used as substrates.

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

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

Any suitable method may be used to transport the substrate. For example, transport by a transport roll, transport by a transport belt, or a combination of these may be used. The transport speed is, for example, 5 m/min to 50 m/min.

(Metal Nanowires)
Metal nanowires are conductive materials made of metal, shaped like needles or threads, and with a diameter of nanometers. Metal nanowires may be straight or curved. By using a transparent conductive layer made of metal nanowires, the metal nanowires can be made into a mesh shape, 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. Furthermore, by making the metal nanowires into a mesh shape, openings can be formed in the gaps of the mesh, so that a transparent conductive film with high light transmittance can be obtained.

The ratio of the thickness d to the length L of the metal nanowire (aspect ratio: L/d) is preferably 10 to 100,000, more preferably 50 to 100,000, and particularly preferably 100 to 10,000. By using metal nanowires with such a large aspect ratio, the metal nanowires can be well crossed, and high conductivity can be achieved with a small amount of metal nanowires. As a result, a transparent conductive film with high light transmittance can be obtained. In this specification, the "thickness of the metal nanowire" means the diameter when the cross section of the metal nanowire is circular, the short axis when the cross section is elliptical, and the longest diagonal when the cross section is polygonal. The thickness and length of the metal nanowire can be confirmed by a scanning electron microscope or a transmission electron microscope.

The thickness of the metal nanowires 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. Within this range, a transparent conductive layer with high light transmittance can be formed.

The length of the metal nanowires is preferably 1 μm to 1000 μm, more preferably 10 μm to 500 μm, and particularly preferably 10 μm to 100 μm. Within this range, a transparent conductive film with high conductivity can be obtained.

Any suitable metal may be used as the metal constituting the metal nanowires, so long as it is a conductive metal. Examples of metals constituting the metal nanowires include silver, gold, copper, nickel, and the like. Materials obtained by plating these metals (e.g., gold plating) may also be used. Among these, silver, copper, or gold are preferred from the viewpoint of conductivity, and silver is more preferred.

Any suitable method can be used as the method for producing the metal nanowires. For example, there is a method of reducing silver nitrate in a solution, a method of applying a voltage or current from the tip of a probe to the surface of a precursor, drawing out a metal nanowire at the tip of the probe, and continuously forming the metal nanowire. In the method of reducing silver nitrate in a solution, silver nanowires can be synthesized by reducing a silver salt such as silver nitrate in the liquid phase in the presence of a polyol such as ethylene glycol and polyvinylpyrrolidone. Silver nanowires of uniform size can be mass-produced according to the methods described in, for example, Xia, Y. et al., Chem. Mater. (2002), 14, 4736-4745, and Xia, Y. et al., Nano letters (2003) 3(7), 955-960.

(Composition for forming transparent conductive layer)
The transparent conductive layer forming composition includes metal nanowires. In one embodiment, the transparent conductive layer forming composition is prepared by dispersing the metal nanowires in any suitable solvent. Examples of the solvent include water, alcohol-based solvents, ketone-based solvents, ether-based solvents, hydrocarbon-based solvents, and aromatic solvents. The transparent conductive layer forming composition may further include additives such as a resin (binder resin), a conductive material other than the metal nanowires (e.g., conductive particles), and a leveling agent. The transparent conductive layer forming composition may also include additives such as 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.

The viscosity of the composition for forming a transparent conductive layer is preferably 5 mP·s/25°C to 300 mP·s/25°C, and more preferably 10 mP·s/25°C to 100 mP·s/25°C. Within this range, the effect obtained by directing the air in a specific direction during the air blowing process is greater. The viscosity of the composition for forming a transparent conductive layer can be measured using a rheometer (e.g., Anton Paar's MCR302).

The dispersion concentration of the metal nanowires in the composition for forming a transparent conductive layer is preferably 0.01% to 5% by weight. Within this range, the effects of the present invention are remarkable.

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

The coating layer preferably has a basis weight of 0.3 g/m ² to 30 g/m ² , and more preferably 1.6 g/m ² to 16 g/m ^2. Within such a range, the metal nanowires are well dispersed by air blowing in the air blowing step, and a transparent conductive film with smaller conductive anisotropy can be produced.

The thickness of the coating layer is preferably 1 μm to 50 μm, and more preferably 2 μm to 40 μm.

C. Air Blowing Step As described above, in the air blowing step, air is blown toward the coating layer to properly align the metal nanowires in the coating layer. The air blowing direction is as described in Section A.

Air can be blown to the coating layer by any suitable method. In one embodiment, air can be blown to the coating layer using a blower arranged above (the side opposite to the substrate) and/or to the side of the coating layer. The air blowing direction can be adjusted, for example, by providing a louver on the blower and adjusting the direction of the louver. In one embodiment, the air blowing direction is determined by the opening direction of the louver. In addition, when blowing a spiral wind, a blower equipped with a spiral wind direction plate at the blower outlet can be used.

The wind speed is preferably 0.5 m/s to 10 m/s, more preferably 1 m/s to 5 m/s. Within this range, the metal nanowires are well dispersed, and a transparent conductive film with smaller conductive anisotropy can be produced. In addition, a transparent conductive film with excellent surface smoothness and thickness uniformity can be obtained. The wind speed can be appropriately set depending on the solvent contained in the transparent conductive layer forming composition. When a transparent conductive layer forming composition prepared with water is used, the wind speed is preferably 0.5 m/s to 10 m/s, more preferably 1 m/s to 5 m/s. In this specification, the wind speed means the wind speed at the time when it reaches the coating layer.

The temperature of the air is preferably 10°C to 50°C, and more preferably 15°C to 30°C. The air speed can be appropriately set depending on the solvent contained in the composition for forming a transparent conductive layer. When a composition for forming a transparent conductive layer prepared with water is used, the temperature of the air is preferably 10°C to 50°C, and more preferably 15°C to 30°C. In this specification, the temperature of the air means the temperature of the air at the time it reaches the coating layer.

The air blowing time is preferably 1 to 10 minutes, and more preferably 2 to 5 minutes. Within this range, the metal nanowires are well dispersed, and a transparent conductive film with smaller conductive anisotropy can be produced. Specifically, if the air blowing area is determined so that the air blowing time falls within the above range, the metal nanowires can be properly dispersed throughout the coating layer, and a transparent conductive film with smaller conductive anisotropy can be produced. In addition, a transparent conductive film with excellent surface smoothness and thickness uniformity can be obtained.

In one embodiment, the above air is blown onto the substrate (substrate on which the coating layer is formed) on the transport roll. In this way, the metal nanowires are well dispersed, and a transparent conductive film with smaller conductive anisotropy can be produced. In addition, a transparent conductive film with excellent surface smoothness and thickness uniformity can be obtained.

In the air blowing process, air may be blown in multiple stages. For example, air may be blown in stages by dividing the zones so that the wind direction, wind speed, temperature, etc. are different. In addition, the thickness of the coating layer may be reduced by oven heating, natural drying, etc., before the air blowing process. The basis weight of the coating layer at the start of the air blowing process 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 .

After the air blowing process, any appropriate treatment may be performed. For example, when a transparent conductive layer forming composition containing a binder resin is used, a curing treatment such as ultraviolet light irradiation may be performed. In addition, after the delivery process, a drying process may be performed. Examples of drying methods include oven heating and natural drying.

D. Transparent Conductive Film A transparent conductive film is formed by the above manufacturing method. Figure 2 is a schematic cross-sectional view of a transparent conductive film obtained by a manufacturing method according to one embodiment of the present 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 of the transparent conductive film is preferably 0.1 Ω/□ to 1000 Ω/□, more preferably 0.5 Ω/□ to 300 Ω/□, and particularly preferably 1 Ω/□ to 200 Ω/□. The ratio (TD/MD) of the surface resistance in TD (direction perpendicular to MD) to the surface resistance in MD (transport direction) of the transparent conductive film is preferably 0.7 to 1.5, more preferably 0.8 to 1.2, and even more preferably 0.9 to 1.1. The surface resistance can be measured using Mitsubishi Chemical Analytech's "Automatic Resistivity Measurement System MCP-S620/MCP-S521."

The haze value of the above transparent conductive film is preferably 20% or less, more preferably 10% or less, and even 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 basis weight of the transparent conductive layer is preferably 0.001 g/m ² to 0.09 g/m ² , and more preferably 0.005 g/m ² to 0.05 g/m ² .

The content of the metal nanowires in the transparent conductive layer is preferably 0.1 to 50 parts by weight, and more preferably 0.1 to 30 parts by weight, relative to 100 parts by weight of the binder resin constituting the transparent conductive layer. Within this range, a transparent conductive film with excellent electrical conductivity and light transparency can be obtained.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. The evaluation methods in the examples are as follows. The thickness was measured using a scanning electron microscope "S-4800" manufactured by Hitachi High-Technologies Corporation after embedding in epoxy resin and cutting with an ultramicrotome to form a cross section.

(1) Surface Resistance Value The surface resistance values (MD and TD surface resistance values) of the transparent conductive film were measured by an eddy current method using a non-contact surface resistance meter (product name "EC-80") manufactured by Napson Corporation. The measurement temperature was 23°C.

[Production Example 1] Preparation of a composition for forming a transparent conductive layer Silver nanowires were synthesized based on the method described in Chem. Mater. 2002, 14, 4736-4745.
The silver nanowires obtained above were dispersed in pure water to a concentration of 0.2% by weight, and dodecyl-pentaethylene glycol was dispersed to a concentration of 0.1% by weight, to obtain a composition for forming a transparent conductive layer.

[Example 1]
A PET film (manufactured by Mitsubishi Plastics, product name "S100") was used as the substrate. While this substrate was being transported using a transport roll, the composition for forming a transparent conductive layer prepared in Production Example 1 was applied onto the substrate using a bar coater (manufactured by Daiichi Rika Co., Ltd., product name "Bar Coater No. 16") to form a coating layer having a thickness of 0.015 g/m ² and a wet film thickness of 15 μm. Thereafter, while transporting the substrate on which the coating layer was formed, rectified air was blown onto the coating layer to dry the coating layer, forming a transparent conductive layer, and a transparent conductive film including the substrate and the transparent conductive layer was obtained.
As shown in Fig. 1(b), the air was blown from the center of the substrate to both ends from the inside toward both outside in the width direction, and the angle between the substrate conveying direction A and the air blowing direction X (air blowing direction as seen from the coating layer surface side) was 90°, and the angle between the substrate conveying direction A and the air blowing direction Z (air blowing direction as seen from the side of the coating layer) was 0°. The wind speed was 2 m/s, and the air temperature was 25°C. The air blowing time (drying time) was 2 minutes.
The obtained transparent conductive film was subjected to the above evaluation (1). The results are shown in Table 1.

[Example 2]
A conductive film was obtained in the same manner as in Example 1, except that the air was blown from both outer sides of the substrate toward the inside in the width direction as shown in Fig. 1 (a). The angle between the substrate conveying direction A and the air blowing direction X (air blowing direction as seen from the coating layer surface side) was 90°, and the angle between the substrate conveying direction A and the air blowing direction Z (air blowing direction as seen from the side of the coating layer) was 0°. The air speed was 2 m/s, and the air temperature was 25°C. The air blowing time (drying time) was 2 minutes.
The obtained transparent conductive film was subjected to the above evaluation (1). The results are shown in Table 1.

[Example 3]
A coating layer was formed on the substrate in the same manner as in Example 1. Thereafter, while conveying the substrate on which the coating layer was formed, a spiral flow was blown onto the coating layer using a circulator to dry the coating layer, forming a transparent conductive layer, and a transparent conductive film including the substrate and the transparent conductive layer was obtained. The wind was blown in such a manner that the direction X' of the spiral axis as viewed from the coating layer surface side of the substrate was parallel to the conveying direction A of the substrate, and the direction Z' of the spiral axis as viewed from the side surface side of the substrate was parallel to the conveying direction A of the substrate, as shown in FIG. 1(c) and (c'). The wind speed was 2 m/s, and the wind temperature was 25° C. The blowing time (drying time) was 2 minutes.
The obtained transparent conductive film was subjected to the above evaluation (1). The results are shown in Table 1.

[Example 4]
A coating layer was formed on the substrate in the same manner as in Example 1. Thereafter, while conveying the substrate on which the coating layer was formed, a spiral flow was blown from above the coating layer using a circulator to dry the coating layer, forming a transparent conductive layer, and a transparent conductive film including the substrate and the transparent conductive layer was obtained. The wind was blown at an angle of 90° between the direction X' of the spiral axis as viewed from the coating layer surface side of the substrate and the conveying direction A of the substrate, as shown in Figs. 1(d) and (d'). The wind speed was 2 m/s, and the wind temperature was 25°C. The wind blowing time (drying time) was 2 minutes.
The obtained transparent conductive film was subjected to the above evaluation (1). The results are shown in Table 1.

[Example 5]
As shown in Fig. 1(e), the air was blown from the left side of the substrate, with the angle between the substrate conveying direction A and the air blowing direction X (air blowing direction as seen from the coating layer surface side) being 40°, and the angle between the substrate conveying direction A and the air blowing direction Z (air blowing direction as seen from the side of the coating layer) being 0°. The air speed was 2 m/s, and the air temperature was 25°C. The air blowing time (drying time) was 2 minutes.
[Comparative Example 1]
A coating layer was formed in the same manner as in Example 1. Thereafter, the substrate on which the coating layer was formed was placed in an oven at an oven temperature of 100° C. for 2 minutes to obtain a transparent conductive film. The obtained transparent conductive film was subjected to the above evaluation (1). The results are shown in Table 1.

10: Substrate 20: Transparent conductive layer 100: Transparent conductive film

Claims (4)

A method for producing a transparent conductive film comprising a substrate and a transparent conductive layer disposed on one side of the substrate, the method comprising the steps of:
a coating step of coating a transparent conductive layer-forming composition containing metal nanowires onto the substrate while transporting the substrate in a long shape to form a coating layer;
and a blowing step of blowing air onto the coating layer,
The blowing step includes blowing air in a direction different from the transport direction of the base material,
The blowing step is performed in two or more directions.
A method for producing a transparent conductive film. The method for producing a transparent conductive film according to claim 1, wherein the air blowing step includes blowing air in a direction different from the conveying direction of the substrate as viewed from at least the coating layer side of the substrate. The method for producing a transparent conductive film according to claim 1 or 2, wherein the direction of air blowing in the air blowing step as viewed from the coating layer side of the substrate includes a direction from the inner side in the width direction of the substrate to both outer sides in the width direction. The method for producing a transparent conductive film according to claim 1 or 2, wherein the direction of air blowing in the air blowing step as viewed from the coating layer side of the substrate includes directions from both outer sides in the width direction of the substrate toward the inner side in the width direction.

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