Method for manufacturing transparent conductive film

Abstract

The present invention provides a method for manufacturing a transparent conductive film containing metal nanowires and exhibiting excellent conductivity. The method for manufacturing the transparent conductive film of the present invention includes: a coating step, wherein a transparent conductive layer forming composition comprising metal nanowires is coated onto a substrate to form a coating layer; a placement step, wherein the coating layer is placed for a predetermined time; and an air supply step, wherein air is supplied to the coating layer after the placement step; wherein the thickness Tb of the coating layer at the start of air supply in the air supply step is 25% to 90% relative to the thickness Ts of the coating layer in the coating step.

Description

Technical Field

[0001] This invention relates to a method for manufacturing a transparent conductive film. Prior Technology

[0002] Previously, in image display devices with touch sensors, the electrodes for the touch sensors were often transparent conductive films formed by depositing metal oxide layers such as ITO (Indium Tin Oxides) on a transparent resin film. However, transparent conductive films with such metal oxide layers are prone to losing conductivity due to bending, which makes them unsuitable for applications requiring flexibility, such as flexible displays.

[0003] On the other hand, transparent conductive films with high flexibility are known to include metal nanowires. Metal nanowires are linear conductive materials with a diameter of nanometers. In transparent conductive films composed of metal nanowires, the metal nanowires form a mesh, creating good conductive paths from a small number of wires. Furthermore, openings are formed in the gaps between the meshes, achieving high light transmittance. Further research has been conducted on improving the conductivity inherently required for conductive films in the presence of such metal nanowires. [Previous Technical Documents] [Patent Literature]

[0004] [Patent Document 1] Japanese Patent Publication No. 2009-505358 [Patent Document 2] Japanese Patent No. 6199034 Summary of the Invention

[0005] [The problem the invention aims to solve]

[0006] The present invention was made to solve the above-mentioned problems, and its purpose is to provide a method for manufacturing a transparent conductive film containing metal nanowires and having excellent conductivity. [Technical means to solve the problem]

[0007] The method for manufacturing the transparent conductive film of the present invention includes: a coating step, wherein a transparent conductive layer forming composition comprising metal nanowires is coated on a substrate to form a coating layer; a placement step, wherein the coating layer is placed for a predetermined time; and an air supply step, wherein air is supplied to the coating layer after the placement step; wherein the thickness Tb of the coating layer at the start of air supply in the coating step is 25% to 90% relative to the thickness Ts of the coating layer in the coating step. In one embodiment, the thickness Ts of the coating layer in the above coating step is 10 μm to 50 μm. In one embodiment, the difference between the thickness Tb of the coating layer when air supply begins 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]

[0008] According to the present invention, a method for manufacturing a transparent conductive film containing metal nanowires and exhibiting excellent conductivity can be provided. Simple Explanation of the Diagram

[0009] 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. Figure 2 is a graph showing the results of the embodiments and comparative examples. Implementation

[0010] [A.] [An overview of the manufacturing method of transparent conductive films] [] The manufacturing method of the transparent conductive film of the present invention includes: a coating step, wherein a transparent conductive layer forming composition comprising metal nanowires is coated onto a substrate to form a coating layer; a placement step, wherein the coating layer is placed for a predetermined time; and an air supply step, wherein air is supplied to the coating layer after the placement step. According to the manufacturing method of the present invention, a transparent conductive film having a substrate and a transparent conductive layer disposed on one side of the substrate is obtained. In addition to the coating step and the air supply step described above, the manufacturing method of the present invention may also include any other suitable steps. In one embodiment, the manufacturing method may further include a drying step for drying the coating layer after the air supply step. In another embodiment, the air supply step is a step that dries the coating layer, and the transparent conductive layer is formed through the air supply step.

[0011] In one embodiment, the manufacturing method described above can be performed while the substrate is being transported. Typically, while releasing and transporting the substrate in a roll, the coating step, placement step, and air supply step (and, if necessary, other steps such as drying) are performed to form a strip-shaped transparent conductive film having a 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.

[0012] [B.] [Coating Steps] [] As described above, in the coating step, a coating layer is formed by coating the substrate with a transparent conductive layer forming composition containing metal nanowires using any suitable method. In one embodiment, a coating layer is formed by coating the substrate with a transparent conductive layer forming composition containing metal nanowires while conveying a strip-shaped substrate.

[0013] (Substrate) The material constituting the above-mentioned substrate can be any suitable material. Specifically, for example, polymeric substrates such as films and plastic substrates are preferred. This is because the substrate has excellent smoothness and wettability relative to the composition for forming the transparent conductive layer, and productivity can be greatly improved by using continuous production with rollers.

[0014] The materials constituting the aforementioned substrate are, in a representative sense, polymer films primarily composed of thermoplastic resins. Examples of thermoplastic resins include polyester resins, cyclic olefin resins such as polynorbornene, acrylic resins, polycarbonate resins, and cellulose resins. Among these, polyester resins, cyclic olefin resins, or acrylic resins are preferred. These resins exhibit excellent transparency, mechanical strength, thermal stability, and moisture-blocking properties. The aforementioned thermoplastic resins can be used alone or in combination of two or more. Furthermore, for optical films such as polarizers, low-phase-difference substrates, high-phase-difference substrates, phase-difference plates, and brightness-enhancing films can also be used as substrates.

[0015] The thickness of the aforementioned substrate is preferably 20 μm to 200 μm, and more preferably 30 μm to 150 μm.

[0016] The total light transmittance of the aforementioned substrate is preferably 30% or more, more preferably 35% or more, and even more preferably 40% or more.

[0017] Any suitable method can be used as the method for conveying the substrate. For example, examples include conveying by conveying rollers, conveying by conveying belts, and combinations thereof. The conveying speed is, for example, 5 m / min to 50 m / min.

[0018] (Metal nanowires) Metal nanowires refer to conductive materials made of metal, shaped like needles or wires, with a diameter of nanometers. Metal nanowires can be straight or curved. When a transparent conductive layer composed of metal nanowires is used, the nanowires form a mesh, allowing even a small number of nanowires to create good conductive paths, resulting in a transparent conductive film with low resistance. Furthermore, by forming a mesh, openings can be created between the mesh openings, resulting in a transparent conductive film with high light transmittance.

[0019] The aspect ratio (L / d) of the aforementioned metal nanowires is preferably 10 to 100,000, more preferably 50 to 100,000, and particularly preferably 100 to 10,000. Using metal nanowires with such a large aspect ratio allows for good intersecting of the nanowires, enabling higher conductivity with a smaller number of nanowires. As a result, a transparent conductive film with high light transmittance can be obtained. Furthermore, in this specification, the term "thickness of the metal nanowire" refers to its diameter when the cross-section of the metal nanowire is circular, its minor axis when it is elliptical, and its longest diagonal when it is polygonal. The thickness and length of the metal nanowires can be confirmed using a scanning electron microscope or a transmission electron microscope.

[0020] The thickness of the aforementioned 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. If it falls within this range, a transparent conductive layer with high light transmittance can be formed.

[0021] The length of the aforementioned metal nanowires is preferably 1 μm to 1000 μm, more preferably 10 μm to 500 μm, and even more preferably 10 μm to 100 μm. Within this range, a transparent conductive film with high conductivity can be obtained.

[0022] As for the metal constituting the aforementioned metal nanowires, any suitable metal can be used as long as it is a conductive metal. Examples of metals constituting the aforementioned metal nanowires include silver, gold, copper, and nickel. Furthermore, materials that have undergone plating treatment (e.g., gold plating) on ​​these metals can also be used. From the viewpoint of conductivity, silver, copper, or gold are preferred, with silver being more preferred.

[0023] As a method for manufacturing the aforementioned metal nanowires, any suitable method can be employed. For example, methods such as reducing silver nitrate in solution and applying voltage or current to the surface of a precursor from the tip of a probe, pulling out metal nanowires using the tip of the probe, and continuously forming the metal nanowires can be exemplified. In the method of reducing silver nitrate in solution, silver nanowires can be synthesized by reducing silver salts such as silver nitrate in the liquid phase in the presence of polyols 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.

[0024] (Composition for forming a transparent conductive layer) The composition for forming a transparent conductive layer includes metal nanowires. In one embodiment, the composition for forming a transparent conductive layer is prepared by dispersing the metal nanowires in any suitable solvent. Examples of such solvents include water, alcohol-based solvents, ketone-based solvents, ether-based solvents, hydrocarbon-based solvents, and aromatic solvents. Furthermore, the composition for forming a transparent conductive layer may also include additives such as resins (adhesive resins), conductive materials other than metal nanowires (e.g., conductive particles), and leveling agents. Additionally, the composition for forming a transparent conductive layer may include additives such as plasticizers, heat stabilizers, light stabilizers, lubricants, antioxidants, ultraviolet absorbers, flame retardants, colorants, antistatic agents, compatibilizers, crosslinking agents, tackifiers, inorganic particles, surfactants, and dispersants.

[0025] The viscosity of the composition for forming the transparent conductive layer is preferably 5 mP·s / 25℃ to 300 mP·s / 25℃, more preferably 10 mP·s / 25℃ to 100 mP·s / 25℃. Within this range, the effects of the present invention become significant. The viscosity of the composition for forming the transparent conductive layer can be measured using a rheometer (e.g., Anton Paar's MCR302).

[0026] The dispersion concentration of the metal nanowires in the composition for forming the transparent conductive layer is preferably 0.01% to 5% by weight. Within this range, the effects of the present invention become significant.

[0027] As a coating method for the above-mentioned composition for forming a transparent conductive layer, any suitable method can be used. Examples of coating methods include spraying, rod coating, roller coating, die coating, inkjet coating, screen coating, dip coating, letterpress printing, gravure printing, and gravure printing.

[0028] The weight per unit area of ​​the above-mentioned coating layer is preferably 0.3 g / m² to 30 g / m², more preferably 1.6 g / m² to 16 g / m². If it is within this range, then by means of air supply in the air supply step, a transparent conductive film with well-dispersed metal nanowires and less conductive anisotropy can be manufactured.

[0029] The thickness Ts of the coating layer during the coating process 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 this range, a transparent conductive film with exceptionally 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 interferometer (e.g., the "FLAME-S spectrometer" manufactured by Ocean Insight).

[0030] [C.] [Placement Steps] [] The placement step, as described above, involves placing the coating layer for a specified time. More specifically, it involves placing the laminate containing the substrate and coating layer in an environment below 25°C (preferably 20°C to 25°C) and in a windless state. In this specification, "windless state" refers to a state where the wind speed (relative wind speed when transporting the substrate) is less than 0.5 m / s. Furthermore, in this specification, "placement" refers to reducing the coating layer thickness in a windless state, and also includes the concept of reducing the coating layer thickness while transporting the laminate containing the substrate and coating layer.

[0031] The time for placing the coating layer is, for example, 1 second to 300 seconds. The time for placing the coating layer is equivalent to the time from the formation of the coating layer in the previous step to the start of air supply in the subsequent step.

[0032] In this invention, by placing the coating layer for a predetermined time before proceeding with the next air-blowing step, a transparent conductive film with excellent conductivity can be obtained. Comparing the transparent conductive film obtained by the above manufacturing method with a transparent conductive film obtained by drying the coating layer without airflow, or a transparent conductive film obtained by immediately air-blowing the coating layer after coating, the transparent conductive film obtained by the above manufacturing method exhibits superior conductivity per unit weight of metal nanowires. It is believed that by placing the coating layer for a predetermined time according to the manufacturing method of this invention, the flow of metal nanowires in the coating layer can be better adjusted, increasing the number of contact points between the metal nanowires, thus achieving the effects described above.

[0033] The thickness of the coating layer after the placement step (the coating layer thickness Tb at the start of the air supply step) is preferably greater than 1 μm, more preferably greater than 2 μm. That is, it is preferable to end the placement step before the coating layer thickness becomes less than 1 μm (preferably less than 2 μm). If this is done, the flow of the metal nanowires in the coating layer can be better adjusted, resulting in more contact points between the metal nanowires.

[0034] In one embodiment, the placement time is determined based on the thickness Ts of the coating layer during the coating step and the thickness of the coating layer after the placement step (the thickness Tb of the coating layer when air supply begins in the air supply step). In one embodiment, the thickness Tb of the coating layer when air supply begins in the air supply step is 25% to 90% of the thickness Ts of the coating layer during the coating step, more preferably 27% to 89%, and even more preferably 30% to 88%. If this range is met, the flow of the metal nanowires in the coating layer can be better adjusted, the contact points between the metal nanowires increase, and thus a transparent conductive film with high conductivity per unit weight of metal nanowires can be obtained.

[0035] In one embodiment, it is preferable to place the coating layer during a period when its thickness is 2 μm to 12 μm thinner than the initial thickness Ts of the coating layer; more preferably, during a period when its thickness is 4 μm to 11 μm thinner than the initial thickness Ts of the coating layer; even more preferably, during a period when its thickness is 6 μm to 10 μm thinner than the initial thickness Ts of the coating layer; and most preferably, during a period when its thickness is 6 μm to 9 μm thinner than the initial thickness Ts of the coating layer. With this range, the flow of the metal nanowires in the coating layer can be better adjusted, resulting in more contact points between the metal nanowires.

[0036] Furthermore, when the initial thickness Ts of the coating layer is 10 μm to 13 μm, it is preferable to place the coating layer until the thickness Tb of the coating layer becomes 2.5 μm to 9 μm, more preferably, until the thickness Tb of the coating layer becomes 3 μm to 5 μm. Also, when the initial thickness Ts of the coating layer exceeds 13 μm but does not reach 16 μm, it is preferable to place the coating layer until the thickness Tb of the coating layer becomes 4 μm to 12 μm, more preferably, until the thickness Tb of the coating layer becomes 5 μm to 7 μm. Furthermore, when the initial thickness Ts of the coating layer exceeds 16 μm (preferably exceeding 16 μm but less than 30 μm, more preferably exceeding 16 μm but less than 20 μm), it is preferable to place the coating layer until the thickness Tb of the coating layer becomes 6 μm to 14 μm, and more preferably, until the thickness Tb of the coating layer becomes 7 μm to 9 μm. Within this range, the flow of the metal nanowires in the coating layer can be better adjusted, resulting in more contact points between the metal nanowires.

[0037] [D.] [Air Supply Procedure] [] Air supply to the coating layer can be performed by any suitable method. In one embodiment, air supply to the coating layer can be performed using a blower positioned above (opposite to the substrate) and / or to the side of the coating layer. The air supply direction can be set to any suitable direction. For example, it can be set to an air supply direction at a predetermined angle (e.g., 10° to 170°) relative to the coating layer, or it can be air supplied approximately parallel to the coating layer (e.g., less than 10° relative to the coating layer). Alternatively, a spiral-shaped airflow can be supplied. The air supply direction can be adjusted, for example, by providing a light-shielding body to the blower and adjusting the direction of the light-shielding body. In one embodiment, the air supply direction can be defined by the opening direction of the light-shielding body. Furthermore, in the case of supplying a spiral-shaped airflow, a blower with a spiral-shaped airflow vane at the air outlet can be used.

[0038] The wind speed mentioned above 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 can be well dispersed, resulting in 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 according to the solvents contained in the transparent conductive layer forming composition. When using a transparent conductive layer forming composition prepared from water, the wind speed mentioned above is preferably 0.5 m / s to 10 m / s, more preferably 1 m / s to 5 m / s. Furthermore, the wind speed referred to in this specification refers to the wind speed at the point in time when the coating layer is reached.

[0039] The preferred temperature of the airflow is 10°C to 50°C, more preferably 15°C to 30°C. The airflow speed can be appropriately set according to the solvents contained in the composition for forming the transparent conductive layer. When using a composition for forming a transparent conductive layer prepared from water, the preferred airflow temperature is 10°C to 50°C, more preferably 15°C to 30°C. Furthermore, the airflow temperature referred to in this specification refers to the airflow temperature at the point in time of reaching the coating layer.

[0040] The air supply time is preferably 1 to 10 minutes, more preferably 2 to 5 minutes. Within this range, a transparent conductive film with well-dispersed metal nanowires and less conductive anisotropy can be manufactured. Specifically, by specifying the air supply area within the above range, the metal nanowires can be appropriately dispersed throughout the coating layer. Furthermore, a transparent conductive film with excellent surface smoothness and thickness uniformity can be obtained.

[0041] In the air supply process, air supply can also be carried out in multiple stages. For example, air supply can be carried out in stages by dividing the area according to different methods such as wind direction, wind speed, and temperature.

[0042] Alternatively, any appropriate treatment can be performed after the air supply step. For example, when using a composition for forming a transparent conductive layer containing an adhesive resin, a curing treatment using ultraviolet irradiation or the like can be performed. Furthermore, a drying step can also be performed after the air supply step. Examples of drying methods include oven heating and natural drying.

[0043] [E.] [Transparent conductive film] [] A transparent conductive film is formed by the above-described 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).

[0044] The surface resistivity of the transparent conductive film is preferably 0.1 Ω / □ to 1000 Ω / □, more preferably 0.5 Ω / □ to 300 Ω / □, even more preferably 1 Ω / □ to 200 Ω / □, particularly preferably 1 Ω / □ to 150 Ω / □, and most preferably 20 Ω / □ to 100 Ω / □. The surface resistivity can be measured using the "Automatic Resistivity Measurement System MCP-S620" or "MCP-S521" from Mitsubishi Chemical Analytech.

[0045] The surface resistance value of the transparent conductive film of the present invention is preferably 90% or less of the surface resistance value of the comparative conductive film obtained in the same manner as the transparent conductive film, except that the above-mentioned air supply step is not performed, more preferably 85% or less, and even more preferably 80% or less.

[0046] The haze value of the above-mentioned transparent conductive film is preferably below 20%, more preferably below 10%, and even more preferably 0.1% to 5%.

[0047] The total light transmittance of the aforementioned transparent conductive film is preferably 30% or more, more preferably 35% or more, and especially preferably 40% or more.

[0048] The unit area weight of the transparent conductive layer is preferably 0.001 g / m² to 0.09 g / m², more preferably 0.005 g / m² to 0.05 g / m².

[0049] 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.

[0050] The content ratio of the metal nanowires in the aforementioned transparent conductive layer relative to 100 parts by weight of the adhesive resin constituting the transparent conductive layer is preferably 0.1 parts by weight to 50 parts by weight, and more preferably 0.1 parts by weight to 30 parts by weight. If it is within this range, a transparent conductive film with excellent conductivity and light transmittance can be obtained.

[0051] Preferably, the relationship between the amount of metal nanowires x (g / m²) and the conductivity y (1 / Ω) in the above-mentioned transparent conductive layer is the relationship of the following equation (1): y = a × x···(1) In equation (1), α is preferably 0.7 or higher, more preferably 0.75 or higher, even more preferably 0.77 or higher, and still more preferably 0.79 or higher. Within this range, a transparent conductive film with excellent conductivity can be formed. The larger α is, the better, but its upper limit is, for example, 2.0. The more silver present, the higher the conductivity, but correspondingly, the haze increases, leading to impaired transparency. The conductivity is the reciprocal of the surface resistance value mentioned above. Example

[0052] The present invention will now be specifically described using examples, but the invention is not limited to these examples. The evaluation methods in the examples are as described below. Furthermore, the thickness is measured using an optical interferometer (a "spectrometer FLAME-S" manufactured by Ocean Insight).

[0053] (1) Surface resistivity The surface resistance values ​​(MD and TD values) of transparent conductive films were measured using a non-contact surface resistivity meter (trade name "EC-80") manufactured by Napson Corporation, by means of the eddy current method. The measurement temperature was set to 23°C.

[0054] (2) Haze value The haze value of the transparent conductive film was measured using a haze meter (manufactured by Murakami Color Science Research Institute Co., Ltd., trade name "HN-150") according to the method specified in JIS 7136.

[0055] [Manufacturing Example 1] Preparation of a Composition for Forming a Transparent Conductive Layer Silver nanowires were synthesized using the method described in Chem. Mater. 2002, 14, 4736-4745. The silver nanowires obtained above were dispersed in pure water at a concentration of 0.2% by weight and dodecyl-pentanediol at a concentration of 0.1% by weight to obtain a composition for forming a transparent conductive layer.

[0056] [Example 1] A PET film (manufactured by Mitsubishi Resin, trade name "S100") was used as the substrate. While the substrate was being transported using a conveyor roller, a rod coater (manufactured by Daiichi Riko Co., Ltd., product name "Rod Coater No. 6") was used to coat the substrate with the transparent conductive layer forming composition prepared in Manufacturing Example 1, forming a coating layer with a thickness (initial coating thickness Ts) of 13 μm. Then, the substrate was left to stand until the coating layer thickness (coating layer thickness Tb at the start of air supply during the air supply step) reached 11.7 μm (i.e., Tb / Ts = 0.9) (standing step). Subsequently, air was supplied from the center of the substrate to both ends in a direction from the inside to the outside in the width direction. The angle between the substrate transport direction and the air supply direction (air supply direction viewed from the coating layer side) was set to 90°, and the angle between the substrate transport direction and the air supply direction (air supply direction viewed from the coating layer side) was set to 0°. Also, the wind speed is set to 2 m / s, and the wind temperature is set to 25℃. Also, the air supply time (drying time) is set to 2 minutes. The resulting transparent conductive film was used for the above evaluations (1) and (2). Table 1 shows the results.

[0057] [Examples 2-9, Comparative Examples 1-6] Except that the initial thickness Ts of the coating layer and the thickness Tb of the coating layer at the start of air supply (when air supply begins) are as shown in Table 1, a transparent conductive film was obtained in the same manner as in Example 1. The obtained transparent conductive film was subjected to the above evaluations (1) and (2). Table 1 shows the results. Also, Figure 2 shows the relationship between the thickness Tb of the coating layer at the start of air supply and the surface resistance value of the obtained transparent conductive film.

[0058] [Comparative Example 7] PET film (manufactured by Mitsubishi Resin, trade name "S100") was used as the substrate. While the substrate was being conveyed using a transfer roller, a rod coater (manufactured by Daiichi Riko Co., Ltd., product name "Rod Coater No. 6") was used to coat the substrate with the transparent conductive layer forming composition prepared in Manufacturing Example 1, forming a coating layer with a thickness of 13 μm. Then, the substrate with the coated layer was placed in an oven at 100°C for 2 minutes to obtain a transparent conductive film. The obtained transparent conductive film was used for the evaluations (1) and (2) described above. Table 1 shows the results.

[0059] [Comparative Example 8] PET film (manufactured by Mitsubishi Resin, trade name "S100") was used as the substrate. While the substrate was being conveyed using a transfer roller, a rod coater (manufactured by Daiichi Riko Co., Ltd., product name "Rod Coater No. 6") was used to coat the substrate with the transparent conductive layer forming composition prepared in Manufacturing Example 1, forming a coating layer with a thickness of 15 μm. Then, the substrate with the coated layer was placed in an oven at 100°C for 2 minutes to obtain a transparent conductive film. The obtained transparent conductive film was used for the evaluations (1) and (2) described above. Table 1 shows the results.

[0060] [Comparative Example 9] PET film (manufactured by Mitsubishi Resin, trade name "S100") was used as the substrate. While the substrate was being conveyed using a transfer roller, a rod coater (manufactured by Daiichi Riko Co., Ltd., product name "Rod Coater No. 10") was used to coat the substrate with the transparent conductive layer forming composition prepared in Manufacturing Example 1, forming a coating layer with a thickness of 17 μm. Then, the substrate with the coated layer was placed in an oven at 100°C for 2 minutes to obtain a transparent conductive film. The obtained transparent conductive film was used for the evaluations (1) and (2) described above. Table 1 shows the results.

[0061] [Table 1] Initial thickness Ts (μm) of the coating layer The thickness of the coating layer, Tb (μm), at the start of air supply. Tb / Ts resistance (Ω / □) Haze (%) Example 1 13 11.7 0.9 112 0.4 Example 2 13 9.1 0.7 100 0.4 Example 3 13 5.2 0.4 94 0.4 Example 4 15 13.5 0.9 74 0.5 Example 5 15 10.5 0.7 70 0.5 Example 6 15 6 0.4 62 0.5 Example 7 17 15.3 0.9 55 0.7 Example 8 17 11.9 0.7 49 0.7 Example 9 17 6.8 0.4 48 0.6 Comparative Example 1 13 13 1 112 0.4 Comparative Example 2 13 1 0.08 120 0.5 Comparative Example 3 15 15 1 76 0.6 Comparative Example 4 15 1 0.07 76 0.6 Comparative Example 5 17 17 1 60 0.7 Comparative Example 6 17 1 0.06 62 0.6 Comparative Example 7 13 - - 126 0.6 Comparative Example 8 15 - - 77 0.6 Comparative Example 9 17 - - 67 0.6

[0062] As shown in Table 1 and Figure 2, according to the manufacturing method of the present invention, a transparent conductive film with excellent conductivity can be obtained by performing a placement step. Furthermore, by optimizing the coating thickness at the start of air supply (optimizing the placement time) based on the initial thickness of the coating layer, the conductivity effect is further enhanced.

[0063] 10: Substrate 20: Transparent conductive layer 100: Transparent conductive film

Claims

1. A method for manufacturing a transparent conductive film, comprising: a coating step, wherein a transparent conductive layer forming composition comprising metal nanowires is coated onto a substrate to form a coating layer; a placement step, wherein the coating layer is placed for a predetermined time; and an air supply step, wherein air is supplied to the coating layer after the placement step; wherein the thickness Tb of the coating layer at the start of air supply in the air supply step is 40% to 70% of the thickness Ts of the coating layer in the coating step; and the thickness Ts of the coating layer in the coating step is 10 μm to 30 μm.

2. The method for manufacturing the transparent conductive film as claimed in claim 1, wherein the difference between the thickness Tb of the coating layer at the start of air supply in the air supply step and the thickness Ts of the coating layer in the coating step is 2 μm to 12 μm.

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