Method for manufacturing transparent conductive film

Abstract

To provide a transparent conductive film that includes metal nanowires and has excellent conductivity.SOLUTION: A production method for a transparent conductive film according to the present invention includes: a coating step for applying a transparent conductive layer formation composition that includes metal nanowires onto a substrate so as to form a coating layer; a leaving step for leaving the coating layer alone for a prescribed time; and a blowing step for blowing air onto the coating step after the leaving step, wherein the thickness Tb of the coating layer when commencing blowing in the coating step is 25-90% of the thickness Ts of the coating layer in the coating step.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing a transparent conductive film. [Background technology]

[0002] Conventionally, in image display devices with 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 with such metal oxide layers tend to lose conductivity when bent, making them difficult to use in flexible displays. However, there is a problem in that it is difficult to use in applications where flexibility is required.

[0003] Meanwhile, 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, allowing a small amount of metal nanowires to form good electrical conduction paths. Furthermore, openings are formed in the gaps between the meshes, achieving high light transmittance. Improvements in the conductivity that are essentially required for conductive films are also being investigated for such transparent conductive films containing metal nanowires. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2009-505358 [Patent Document 2] Patent No. 6199034 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made to solve the above-mentioned problems, and its object is to provide a method for producing a transparent conductive film containing metal nanowires and having excellent conductivity. [Means for solving the problem]

[0006] The method for producing a transparent conductive film of the present invention includes a coating step of forming a coating layer by applying a transparent conductive layer-forming composition containing metal nanowires to a substrate, a leaving step of leaving the coating layer for a predetermined period of time, and an air blowing step of blowing air onto the coating layer after the leaving step, wherein the thickness Tb of the coating layer when air blowing is started in the coating step is 25% to 90% of the thickness Ts of the coating layer in the coating step. In one embodiment, the thickness Ts of the coating layer in the coating step is 10 μm to 50 μm. In one embodiment, the difference between the thickness Tb of the coating layer when air blowing is started in the coating step and the thickness Ts of the coating layer in the coating step is 2 μm to 12 μm. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a method for producing a transparent conductive film that contains metal nanowires and has excellent conductivity. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic cross-sectional view of a transparent conductive film obtained by a production method according to one embodiment of the present invention. [Figure 2] FIG. 1 is a graph showing the results of an example and a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0009] A. Overview of transparent conductive film manufacturing method The method for producing a transparent conductive film of the present invention includes a coating step of coating a substrate with a transparent conductive layer-forming composition containing metal nanowires to form a coating layer, a leaving step of leaving the coating layer for a predetermined period of time, and a blowing step of blowing air onto the coating layer after the leaving step. According to the production method of the present invention, a transparent conductive film is obtained that includes a substrate and a transparent conductive layer disposed on one side of the substrate. The production method of the present invention may include any other appropriate steps in addition to the coating step and the blowing step. In one embodiment, the production 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 a transparent conductive layer is formed via the blowing step.

[0010] In one embodiment, the manufacturing method can be carried out while the substrate is being transported. Typically, the coating step, leaving step, and air blowing step (and other steps such as a drying step, if necessary) are carried out while the substrate in a roll state is unwound and transported, to form a long transparent conductive film including 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.

[0011] B. Coating process As described above, in the coating step, a composition for forming a transparent conductive layer containing metal nanowires is applied to the substrate by any appropriate method to form a coating layer. In one embodiment, the composition for forming a transparent conductive layer containing metal nanowires is applied to the substrate while the long substrate is being transported to form a coating layer.

[0012] (base material) Any appropriate material can be used as the material for the substrate. Specifically, for example, a polymer substrate such as a film or 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 productivity can be significantly improved by continuous production using a roll.

[0013] The material constituting the 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; and cellulose resins. Among these, polyester resins, cycloolefin resins, and acrylic resins are preferred. These resins are excellent in transparency, mechanical strength, thermal stability, and moisture-blocking properties. The thermoplastic resins may be used alone or in combination of two or more. Optical films used in polarizing plates, such as low-retardation substrates, high-retardation substrates, retardation plates, and brightness-enhancing films, can also be used as the substrate.

[0014] The thickness of the substrate is preferably 20 μm to 200 μm, and more preferably 30 μm to 150 μm.

[0015] The total light transmittance of the substrate is preferably 30% or more, more preferably 35% or more, and even more preferably 40% or more.

[0016] Any appropriate method can be used to transport the substrate. For example, transportation by transport rolls, transportation by transport belt, a combination of these, etc. The transport speed is, for example, 5 m / min to 50 m / min.

[0017] (metal nanowires) Metal nanowires are conductive materials made of metal, shaped like needles or threads, and nanometer-sized diameters. Metal nanowires may be linear or curved. By using a transparent conductive layer made of metal nanowires, the metal nanowires form a mesh, allowing even a small amount of metal nanowires to form an excellent electrical conduction path, resulting in a transparent conductive film with low electrical resistance. Furthermore, the mesh-like shape of the metal nanowires allows openings to be formed in the gaps between the meshes, resulting in a transparent conductive film with high light transmittance.

[0018] 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 high aspect ratio, the metal nanowires can be well intersected, enabling a small number of metal nanowires to exhibit high conductivity. As a result, a transparent conductive film with high light transmittance can be obtained. In this specification, the "thickness of the metal nanowire" refers to the diameter of the metal nanowire when the cross section is circular, the minor axis of the metal nanowire when the cross section is elliptical, and the longest diagonal of the metal nanowire when the cross section is polygonal. The thickness and length of the metal nanowire can be confirmed using a scanning electron microscope or a transmission electron microscope.

[0019] The thickness of the metal nanowires is preferably less than 500 nm, more preferably less than 200 nm, particularly preferably 10 to 100 nm, and most preferably 10 to 50 nm. Within this range, a transparent conductive layer with high light transmittance can be formed.

[0020] 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. If the length is within this range, a transparent conductive film with high conductivity can be obtained.

[0021] Any suitable metal can be used as the metal constituting the metal nanowires, as long as it is a conductive metal. Examples of metals constituting the metal nanowires include silver, gold, copper, and nickel. 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.

[0022] Any suitable method can be used to produce the metal nanowires. Examples include reducing silver nitrate in solution, applying a voltage or current from the tip of a probe to the surface of a precursor, drawing the metal nanowires from the tip of the probe, and continuously forming the metal nanowires. In the method of reducing silver nitrate in 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. Uniformly sized silver nanowires can be mass-produced, for example, according to the methods described in Xia, Y. et al., Chem. Mater. (2002), 14, 4736-4745 and Xia, Y. et al., Nano Letters (2003), 3(7), 955-960.

[0023] (Composition for forming transparent conductive layer) The composition for forming a transparent conductive layer contains metal nanowires. In one embodiment, the composition for forming a transparent conductive layer is prepared by dispersing the metal nanowires in any appropriate solvent. Examples of such solvents include water, alcohol-based solvents, ketone-based solvents, ether-based solvents, hydrocarbon-based solvents, and aromatic solvents. The composition for forming a transparent conductive layer may further contain additives such as a resin (binder resin), a conductive material other than metal nanowires (e.g., conductive particles), and a leveling agent. The composition for forming a transparent conductive layer may also contain 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 crosslinker, a thickener, inorganic particles, a surfactant, and a dispersant.

[0024] 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 effects of the present invention are significant. The viscosity of the composition for forming a transparent conductive layer can be measured using a rheometer (for example, Anton Paar's MCR302).

[0025] The dispersion concentration of the metal nanowires in the composition for forming a transparent conductive layer is preferably 0.01% by weight to 5% by weight, and within this range, the effects of the present invention are significant.

[0026] The transparent conductive layer-forming composition may be applied by any suitable method, such as spray coating, bar coating, roll coating, die coating, inkjet coating, screen coating, dip coating, letterpress printing, intaglio printing, or gravure printing.

[0027] The basis weight of the coating layer is preferably 0.3 g / m 2 ~30g / m 2 and more preferably 1.6 g / m 2 ~16g / m 2 Within this range, the metal nanowires are dispersed well by the air blowing in the air blowing step, and a transparent conductive film with smaller conductive anisotropy can be produced.

[0028] The thickness Ts of the coating layer in the coating step is preferably 10 μm to 50 μm, more preferably 13 μm to 40 μm, even more preferably 13 μm to 30 μm, and particularly preferably 13 μm to 20 μm. Within these ranges, a transparent conductive film with particularly excellent conductivity can be obtained. The thickness Ts (hereinafter also referred to as the initial thickness Ts of the coating layer) refers to the thickness (wet thickness) of the coating layer immediately after coating. The thickness Ts (wet thickness) of the coating layer can be measured using an optical interference film thickness meter (for example, the "FLAME-S Spectrometer" manufactured by Ocean Insight).

[0029] C. Leaving process As described above, the leaving step is a step of leaving the coating layer for a predetermined period of time. More specifically, it is a step of leaving a laminated structure including a substrate and a coating layer in a windless environment at 25°C or below (preferably 20°C to 25°C). In this specification, a windless environment refers to a state in which the wind speed (relative wind speed in the case of transporting a substrate) is less than 0.5 m / s. Furthermore, in this specification, "leaving" refers to reducing the thickness of the coating layer in a windless environment, and is a concept that also includes an operation of reducing the thickness of the coating layer while transporting a laminated structure including a substrate and a coating layer.

[0030] The time for leaving the coating layer is, for example, 1 to 300 seconds. The time for leaving the coating layer corresponds to the time from the formation of the coating layer in the previous step until the start of air blowing in the subsequent step.

[0031] In the present invention, a transparent conductive film with excellent conductivity can be obtained by leaving the coating layer for a predetermined time and then performing the subsequent air blowing step. When comparing the transparent conductive film obtained by the manufacturing method of the present invention with a transparent conductive film obtained by drying the coating layer without air blowing, or a transparent conductive film obtained by blowing air onto the coating layer immediately after coating, the transparent conductive film obtained by the manufacturing method of the present invention has superior conductivity per unit weight of metal nanowires. According to the manufacturing method of the present invention, leaving the coating layer for a predetermined time makes it possible to favorably adjust the flow of the metal nanowires in the coating layer, which is thought to increase the number of contact points between the metal nanowires, thereby achieving the above-mentioned effects.

[0032] The thickness of the coating layer after the leaving step (thickness Tb of the coating layer when air blowing is started in the air blowing step) is preferably more than 1 μm, and more preferably 2 μm or more. In other words, it is preferable to end the leaving step before the thickness of the coating layer becomes 1 μm or less (preferably less than 2 μm). In this way, the flow of the metal nanowires in the coating layer can be favorably adjusted, and more contact points between the metal nanowires can be created.

[0033] In one embodiment, the standing time is determined based on the thickness Ts of the coating layer in the coating step and the thickness of the coating layer after the standing step (the thickness Tb of the coating layer when air blowing is started in the air blowing step). In one embodiment, the thickness Tb of the coating layer when air blowing is started in the air blowing step is 25% to 90%, more preferably 27% to 89%, and even more preferably 30% to 88% of the thickness Ts of the coating layer in the coating step. Within this range, the flow of the metal nanowires in the coating layer can be favorably adjusted, increasing the number of contact points between the metal nanowires, and thereby producing a transparent conductive film with high conductivity per unit weight of metal nanowires.

[0034] In one embodiment, the coating layer is preferably left until the thickness thereof becomes 2 μm to 12 μm thinner than the initial thickness Ts of the coating layer, more preferably until the thickness thereof becomes 4 μm to 11 μm thinner than the initial thickness Ts of the coating layer, even more preferably until the thickness thereof becomes 6 μm to 10 μm thinner than the initial thickness Ts of the coating layer, and preferably until the thickness thereof becomes 6 μm to 9 μm thinner than the initial thickness Ts of the coating layer. Within these ranges, the flow of the metal nanowires in the coating layer can be preferably adjusted, and the number of contact points between the metal nanowires can be increased.

[0035] Furthermore, when the initial thickness Ts of the coating layer is 10 μm to 13 μm, it is preferable to leave the coating layer until the thickness Tb of the coating layer reaches 2.5 μm to 9 μm, and more preferably until the thickness Tb of the coating layer reaches 3 μm to 5 μm. Furthermore, when the initial thickness Ts of the coating layer is greater than 13 μm but less than 16 μm, it is preferable to leave the coating layer until the thickness Tb of the coating layer reaches 4 μm to 12 μm, and more preferably until the thickness Tb of the coating layer reaches 5 μm to 7 μm. Furthermore, when the initial thickness Ts of the coating layer exceeds 16 μm (preferably greater than 16 μm but not greater than 30 μm, more preferably greater than 16 μm but not greater than 20 μm), it is preferable to leave the coating layer until the thickness Tb of the coating layer reaches 6 μm to 14 μm, and more preferably until the thickness Tb of the coating layer reaches 7 μm to 9 μm. Within these ranges, the flow of the metal nanowires in the coating layer can be favorably adjusted, and the number of contact points between the metal nanowires can be increased.

[0036] D. Air blowing process Air can be blown toward the coating layer by any appropriate method. In one embodiment, air can be blown toward the coating layer using an air blower arranged above the coating layer (opposite the substrate) and / or to the side. The air blowing direction can be any appropriate direction. For example, the air blowing direction may be at a predetermined angle (e.g., 10° to 170°) relative to the surface of the coating layer, or may be approximately parallel to the surface of the coating layer (e.g., less than 10° relative to the surface of the coating layer). Alternatively, air may be blown in a spiral pattern. The air blowing direction can be adjusted, for example, by providing a louver on the air blower and adjusting the direction of the louver. In one embodiment, the air blowing direction is determined by the opening direction of the louver. When blowing spiral air, an air blower equipped with a spiral air direction plate at the air outlet can be used.

[0037] The wind speed of the wind 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, making it possible to produce a transparent conductive film with excellent conductivity. Furthermore, 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 refers to the wind speed at the time when the wind reaches the coating layer.

[0038] 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, etc. 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 when it reaches the coating layer.

[0039] The air blowing time is preferably 1 to 10 minutes, more preferably 2 to 5 minutes. Within this range, the metal nanowires are well dispersed, making it possible to produce a transparent conductive film with smaller anisotropy of electrical conductivity. Specifically, by determining the area to be blown so that the air blowing time falls within the above range, the metal nanowires can be properly dispersed throughout the entire coating layer. Furthermore, a transparent conductive film with excellent surface smoothness and thickness uniformity can be obtained.

[0040] In the air blowing step, air may be blown in multiple stages. For example, air may be blown in stages into zones that are divided into zones with different wind directions, wind speeds, temperatures, etc.

[0041] After the air blowing step, 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 irradiation may be performed. Furthermore, after the transporting step, a drying step may be performed. Examples of drying methods include oven heating and natural drying.

[0042] E. Transparent conductive film A transparent conductive film is formed by the above manufacturing method. Figure 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. The transparent conductive film 100 includes a substrate 10 and a transparent conductive layer 20 disposed on one side of the substrate 10. The transparent conductive layer 20 includes metal nanowires (not shown).

[0043] The surface resistance 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 / □, and most preferably 1 Ω / □ to 150 Ω / □. The surface resistance can be measured using Mitsubishi Chemical Analytech's "Automatic Resistivity Measurement System MCP-S620 / MCP-S521."

[0044] The surface resistance value of the transparent conductive film of the present invention is preferably 90% or less, more preferably 85% or less, and even more preferably 80% or less, of the surface resistance value of a comparative conductive film obtained in the same manner as the transparent conductive film except that the above-mentioned air blowing step is not performed.

[0045] The haze value of the transparent conductive film is preferably 20% or less, more preferably 10% or less, and even more preferably 0.1% to 5%.

[0046] 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.

[0047] The basis weight of the transparent conductive layer is preferably 0.001 g / m2 ~0.09g / m 2 and more preferably 0.005 g / m 2 ~0.05g / m 2 is.

[0048] The thickness of the transparent conductive layer is preferably 2 μm to 10 μm, more preferably 3 μm to 9 μm, and even more preferably 4 μm to 8 μm.

[0049] The content of the metal nanowires in the transparent conductive layer is preferably 0.1 to 50 parts by weight, 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 conductivity and light transmittance can be obtained.

[0050] Preferably, the amount of metal nanowires in the transparent conductive layer is x (g / m 2 The relationship between the electrical conductivity y (1 / Ω) and the electrical conductivity y (1 / Ω) is expressed by the following formula (1): y = a × x (1) In formula (1), a is preferably 0.7 or more, more preferably 0.75 or more, more preferably 0.77 or more, and even more preferably 0.79 or more. Within this range, a transparent conductive film with excellent conductivity can be obtained. The larger the above a, the better, but its upper limit is, for example, 2.0. The greater the amount of silver, the higher the conductivity, but the haze also increases and transparency is impaired. The conductivity is the reciprocal of the above surface resistance value. [Example]

[0051] 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 used in the examples are as follows. The thickness was measured using an optical interference film thickness meter ("FLAME-S Spectrometer" manufactured by Ocean Insight).

[0052] (1) Surface resistance 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 Co., Ltd. The measurement temperature was 23°C.

[0053] (2) Haze value The haze value of the transparent conductive film was measured according to the method defined in JIS 7136 using a haze meter (manufactured by Murakami Color Science Laboratory, product name "HN-150").

[0054] [Production Example 1] Preparation of composition for forming 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 wt % and dodecyl-pentaethylene glycol to a concentration of 0.1 wt %, to obtain a composition for forming a transparent conductive layer.

[0055] [ reference 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 transparent conductive layer-forming composition 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. 6") to form a coating layer with a thickness (initial thickness of the coating layer, Ts) of 13 μm. Thereafter, the substrate was left to stand until the thickness of the coating layer (thickness of the coating layer at the start of the air blowing process, Tb) reached 11.7 μm (i.e., Tb / Ts = 0.9) (standing step). Next, air was blown from the center of the substrate to both ends in a direction from the inside in the width direction to both outside in the width direction. The angle between the transport direction of the substrate and the air blowing direction (air blowing direction as seen from the coating layer surface side) was 90°, and the angle between the transport direction of the substrate and the air blowing direction (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 set to 2 minutes. The obtained transparent conductive film was subjected to the above evaluations (1) and (2). The results are shown in Table 1.

[0056] Example 2 、3、5、6、8、 9 ;Reference examples 4, 7; Comparative Examples 1 to 6 The initial thickness Ts of the coating layer and the thickness Tb of the coating layer when starting the air blowing process (at the start of the air blowing) were as shown in Table 1. reference A transparent conductive film was obtained in the same manner as in Example 1. The obtained transparent conductive film was subjected to the above-mentioned evaluations (1) and (2). The results are shown in Table 1. Furthermore, the relationship between the thickness Tb of the coating layer at the start of air blowing and the surface resistance value of the obtained transparent conductive film is shown in Figure 2.

[0057] Comparative Example 7 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. 6") to form a coating layer with a thickness of 13 μm. Thereafter, the substrate with the coating layer formed thereon 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-mentioned evaluations (1) and (2). The results are shown in Table 1.

[0058] [Comparative Example 8] 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. 8") to form a coating layer with a thickness of 15 μm. Thereafter, the substrate with the coating layer formed thereon 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-mentioned evaluations (1) and (2). The results are shown in Table 1.

[0059] Comparative Example 9 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. 10") to form a coating layer with a thickness of 17 μm. Thereafter, the substrate with the coating layer formed thereon 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-mentioned evaluations (1) and (2). The results are shown in Table 1.

[0060] [Table 1]

[0061] As is clear from Table 1 and Figure 2, the production method of the present invention allows a transparent conductive film with excellent conductivity to be obtained by carrying out a leaving step. Furthermore, by optimizing the thickness of the coating layer at the start of air blowing (optimizing the leaving time) according to the initial thickness of the coating layer, the conductivity effect becomes more pronounced. [Explanation of symbols]

[0062] 10 Base material 20 Transparent conductive layer 100 Transparent conductive film

Claims

1. a coating step of coating a substrate with a transparent conductive layer-forming composition containing metal nanowires to form a coating layer; a leaving step of leaving the coating layer for a predetermined period of time; and a blowing step of blowing air onto the coating layer after the leaving step, a thickness Tb of the coating layer at the time when air blowing is started in the air blowing step is 40% to 70% of a thickness Ts of the coating layer in the coating step; The thickness Ts of the coating layer in the coating step is 10 μm to 30 μm. A method for producing a transparent conductive film.

2. a difference between a thickness Tb of the coating layer at the time when air blowing is started in the air blowing step and a thickness Ts of the coating layer in the coating step is 2 μm to 12 μm; The method for producing the transparent conductive film according to claim 1 .

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