CN114503224A - Method for producing transparent conductive film - Google Patents

Method for producing transparent conductive film Download PDF

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Publication number
CN114503224A
CN114503224A CN202080069191.0A CN202080069191A CN114503224A CN 114503224 A CN114503224 A CN 114503224A CN 202080069191 A CN202080069191 A CN 202080069191A CN 114503224 A CN114503224 A CN 114503224A
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transparent conductive
substrate
air blowing
conductive film
coating layer
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长濑纯一
桥本尚树
长原一平
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Nitto Denko Corp
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Nitto Denko Corp
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
    • B05D3/04—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by exposure to gases
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B13/00—Apparatus or processes specially adapted for manufacturing conductors or cables
    • H01B13/30—Drying; Impregnating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D5/00—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures
    • B05D5/06—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures to obtain multicolour or other optical effects
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D5/00—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures
    • B05D5/12—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures to obtain a coating with specific electrical properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
    • B05D7/24—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials for applying particular liquids or other fluent materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B13/00—Apparatus or processes specially adapted for manufacturing conductors or cables
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B5/00—Non-insulated conductors or conductive bodies characterised by their form
    • H01B5/14—Non-insulated conductors or conductive bodies characterised by their form comprising conductive layers or films on insulating-supports
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D2252/00—Sheets
    • B05D2252/02—Sheets of indefinite length

Abstract

The invention provides a method for manufacturing a transparent conductive film with small conductive anisotropy even containing metal nanowires. The method for producing a transparent conductive film of the present invention comprises: a coating step of forming a coating layer by coating a transparent conductive layer forming composition containing metal nanowires on a long base material while conveying the base material; and an air blowing step of blowing air to the coating layer to dry the coating layer and thereby form the transparent conductive layer on the substrate, wherein the air blowing in the air blowing step includes air blowing in a direction different from a conveying direction of the substrate when viewed from the coating layer surface side of the substrate.

Description

Method for producing transparent conductive film
Technical Field
The present invention relates to a method for producing a transparent conductive film.
Background
Conventionally, in an image display device having a touch sensor, a transparent conductive film obtained by forming a metal oxide layer such as ITO (indium tin composite oxide) on a transparent resin film has been often used as an electrode of the touch sensor. However, the transparent conductive film including the metal oxide layer is liable to lose conductivity by bending, and thus has a problem that it is difficult to use the transparent conductive film for applications requiring bendability, such as flexible displays.
On the other hand, as a transparent conductive film having high flexibility, a transparent conductive film including metal nanowires is known. The metal nanowire is a linear conductive material having a diameter of a nanometer size. In the transparent conductive film composed of metal nanowires, the metal nanowires are in a mesh shape, and thus a good electrical conduction path is formed with a small amount of metal nanowires, and openings are formed in gaps of the mesh, thereby achieving high light transmittance. On the other hand, since the metal nanowires are linear, they are easily arranged in an oriented state, and thus there is a problem that conductive anisotropy occurs in the transparent conductive film including the metal nanowires.
Documents of the prior art
Patent document
Patent document 1: japanese Kokai publication Hei 2009-505358
Patent document 2: japanese patent No. 6199034
Disclosure of Invention
Problems to be solved by the invention
The present invention has been made to solve the above problems, and an object thereof is to provide a method for producing a transparent conductive film having small conductive anisotropy even when containing metal nanowires.
Means for solving the problems
The method for producing a transparent conductive film according to the present invention is a method for producing a transparent conductive film including a substrate and a transparent conductive layer disposed on one side of the substrate, the method for producing a transparent conductive film including: a coating step of forming a coating layer by coating a composition for forming a transparent conductive layer containing metal nanowires on the base material while conveying the long base material; and an air blowing step of blowing air to the coating layer, the air blowing step including air blowing in a direction different from the conveying direction of the substrate.
In one embodiment, the air blowing in the air blowing step is performed in two or more directions.
In one embodiment, the direction of air blowing in the air blowing step when viewed from the coating layer surface side of the base material includes a direction from the inner side in the width direction of the base material toward both outer sides in the width direction.
In one embodiment, the direction of air blowing in the air blowing step when viewed from the coating layer surface side of the base material includes a direction from both outer sides of the base material in the width direction toward the inner side of the base material in the width direction.
In one embodiment, the air blowing in the air blowing step is a spiral air blowing.
Effects of the invention
According to the present invention, a method for manufacturing a transparent conductive film having small conductive anisotropy can be provided.
Drawings
Fig. 1(a) to (e) are schematic plan views illustrating air blowing directions in an air blowing step according to an embodiment of the present invention. The following (a ') to (e') are schematic diagrams illustrating the blowing direction in the blowing step according to one embodiment of the present invention.
Fig. 2 is a schematic cross-sectional view of a transparent conductive film obtained by a manufacturing method according to an embodiment of the present invention.
Detailed Description
A. Outline of method for producing transparent conductive film
The method for producing a transparent conductive film of the present invention comprises: a coating step of coating a transparent conductive layer forming composition containing metal nanowires on a long base material while conveying the base material to form a coating layer; and an air blowing step of blowing air to the coating layer. According to the production method of the present invention, a transparent conductive film including a substrate and a transparent conductive layer disposed on one side of the substrate can be obtained. The production method of the present invention may include any appropriate other steps in addition to the coating step and the blowing step. In one embodiment, the above-described production method may further include a drying step of drying the coating layer after the air blowing step. In another embodiment, the air blowing step is a step of drying the coating layer, and the transparent conductive layer is formed through the air blowing step.
Typically, the coating step and the air blowing step (and other steps such as a drying step, if necessary) are performed while the base material in a rolled state is fed and conveyed, and a long transparent conductive film including the base material and a transparent conductive layer disposed on one side of the base material is formed. In one embodiment, the transparent conductive film is wound after formation. In the present invention, the air blowing in the air blowing step includes air blowing in a direction different from the conveying direction of the base material. The direction different from the transport direction of the substrate includes: a direction different from the conveying direction of the substrate when viewed from the coated layer side of the substrate; a direction non-parallel to the substrate surface; and a concept in which the coating layer side of the substrate is different from the conveying direction of the substrate and is not parallel to the surface of the substrate when viewed from the coating layer side. In one embodiment, the air blow in a direction different from the conveyance direction of the substrate is a direction different from the conveyance direction of the substrate and parallel or non-parallel to the surface of the substrate when viewed from the coating layer surface side of the substrate. In another embodiment, the air blowing in a direction different from the conveyance direction of the substrate is a direction different from the conveyance direction of the substrate or a direction substantially parallel to the conveyance direction of the substrate when viewed from the coating layer surface side of the substrate, and is a direction not parallel to the surface of the substrate. In the present specification, the term "nonparallel direction" means that the angle with respect to the direction/plane (substrate surface) serving as a reference is 5 ° or less.
Fig. 1(a) to (e) are schematic plan views illustrating air blowing directions in an air blowing step according to an embodiment of the present invention. Fig. 1(a ') to (e') are schematic diagrams illustrating the blowing direction in the blowing step according to the embodiment of the present invention. Fig. 1(a ') is a schematic front view of fig. 1(a) (a view when viewed from the transparent conductive film winding side), and fig. 1 (b') is a schematic front view of fig. 1 (b). FIG. 1(c ') is a schematic side view of FIG. 1(c), and FIG. 1 (d') is a schematic side view of FIG. 1 (d). Fig. 1 (e') is a schematic front view of fig. 1 (e).
In one embodiment, as shown in fig. 1(a) and (b), the air blowing direction in the air blowing step when viewed from the coating layer 21 surface side of the substrate 10 is a direction different from the conveying direction of the substrate at least when viewed from the coating layer surface side of the substrate, and the air blowing is performed in two or more directions.
In the embodiment shown in fig. 1(a), the direction of air blowing in the air blowing step (also referred to as the air blowing direction X) when viewed from the coating layer 21 surface side of the substrate 10 includes a direction from both outer sides in the width direction of the substrate 10 toward the inner side in the width direction. In this embodiment, the angle formed by the conveyance direction a of the base material and the air blowing direction X is greater than 0 ° and less than 180 °, preferably from 30 ° to 150 °, more preferably from 60 ° to 120 °, still more preferably from 60 ° to 100 °, still more preferably from 60 ° to 95 °, still more preferably from 75 ° to 95 °, and particularly preferably from 85 ° to 95 °. Further, the air from the outside of the width direction of the base material 10 toward the inside of the width direction may be blown in a fan shape.
In the embodiment shown in fig. 1(b), the direction of air blowing in the air blowing step (also referred to as air blowing direction X) when viewed from the coating layer 21 surface side of the substrate 10 includes a direction from the width direction inside toward the width direction outside of the substrate 10. In this embodiment, the angle formed by the conveyance direction a of the base material and the blowing direction X is greater than 0 ° and less than 180 °, preferably 30 ° to 150 °, more preferably 60 ° to 120 °, still more preferably 60 ° to 100 °, still more preferably 60 ° to 95 °, still more preferably 75 ° to 95 °, and particularly preferably 85 ° to 95 °. Further, the air from the width direction inside toward the width direction outside of the base material 10 may be blown in a fan shape.
As an embodiment in which air is blown in two or more directions, in addition to the embodiments shown in fig. 1(a) and (b), there may be mentioned an embodiment in which air is blown in a spiral shape (that is, air is caused to flow in a spiral flow) as shown in fig. 1(c) and (d). In the case of blowing air in a spiral shape, the direction X' of the spiral axis of the air when viewed from the coating layer 21 surface side of the substrate 10 may be parallel to the conveyance direction a of the substrate as shown in fig. 1(c) or may not be parallel thereto. In one embodiment, the angle formed by the direction X' of the helical axis of the wind and the conveyance direction a of the substrate when viewed from the coating layer 21 surface side of the substrate 10 is preferably 0 ° to 60 °, more preferably 0 ° to 45 °, and still more preferably 0 ° to 30 °. In another embodiment, the angle formed by the direction X' of the helical axis of the wind and the conveyance direction a of the substrate when viewed from the coating layer 21 surface side of the substrate 10 is preferably 60 ° to 120 °, and more preferably 80 ° to 100 °. In still another embodiment, the angle formed by the direction X' of the helical axis of the wind and the conveyance direction a of the substrate when viewed from the coating layer 21 surface side of the substrate 10 is preferably 120 ° to 180 °, and more preferably 150 ° to 180 °. In the case of blowing air in a spiral shape, the direction Z 'of the spiral axis of the air when viewed from the side surface side of the substrate 10 may be parallel to the substrate conveyance direction a (fig. 1 (c')) or may not be parallel. In one embodiment, the angle formed by the direction Z' of the helical axis of the wind and the transport direction a of the substrate when viewed from the side surface side of the substrate 10 is preferably 0 ° to 60 °, and more preferably 0 ° to 30 °. In another embodiment, the angle formed by the direction Z 'of the helical axis of the wind and the transport direction a of the substrate when viewed from the side surface side of the substrate 10 is preferably 60 ° to 120 °, more preferably 80 ° to 100 ° (fig. 1 (d')). In the present specification, in order to distinguish from the air blown out in a spiral shape, the air blown out not in a spiral shape but in a substantially constant direction as in the case of the air shown in fig. 1(a), (b), and (e) is referred to as rectified air.
In one embodiment, as shown in fig. 1(e), the air blowing direction in the air blowing step when viewed from the coating layer 21 surface side of the substrate 10 is a direction different from the conveying direction of the substrate, and the air blowing is performed in one direction. In this embodiment, the angle formed by the conveyance direction a of the base material and the air blowing direction X is greater than 0 ° and less than 90 ° or greater than 90 ° and less than 180 °, and preferably 30 ° to 60 ° or 120 ° to 150 °. Further, the wind may be blown in a fan shape.
When the rectified wind is blown toward the coating layer 21, the blowing direction Z in the blowing step when viewed from the side surface side of the substrate 10 may be parallel to the substrate surface (fig. 1(a ') and (b ')), or may be non-parallel (fig. 1(e ')). The angle formed by the air blowing direction Z in the air blowing step and the conveyance direction a of the surface of the base material when viewed from the side surface side of the base material 10 is preferably 0 ° to 60 °. In one embodiment, the blowing direction Z in the blowing step when viewed from the side surface side of the base material 10 is substantially parallel to the base material surface (i.e., the angle formed by the blowing direction Z and the base material surface is 10 ° or less). This makes it possible to form a transparent conductive layer having excellent surface smoothness. In another embodiment, the angle formed by the blowing direction Z in the blowing step and the surface of the base material when viewed from the side surface side of the base material 10 is greater than 10 ° and 60 ° or less.
In the present invention, the orientation of the metal nanowires is disturbed by setting the direction of the wind in the blowing step to a specific direction, and as a result, a transparent conductive film having low conductive anisotropy can be produced. Such an effect is more remarkable by blowing air in two or more directions. Further, if air is blown in two or more directions, a transparent conductive film having remarkably high dispersion uniformity of the metal nanowires can be obtained.
B. Coating step
As described above, in the coating step, while the long-sized base material is conveyed, the composition for forming a transparent conductive layer containing the metal nanowires is coated on the base material to form the coating layer.
(substrate)
Any suitable material may be used for the material constituting the substrate. Specifically, for example, a polymer substrate such as a film or a plastic substrate can be preferably used. This is because the smoothness of the substrate and the wettability with respect to the composition for forming a transparent conductive layer are excellent, and the productivity can be greatly improved by continuous production using a roll.
The material constituting the substrate is typically a polymer film containing a thermoplastic resin as a main component. Examples of the thermoplastic resin include: polyester resins, cycloolefin resins such as polynorbornene, acrylic resins, polycarbonate resins, cellulose resins, and the like. Among them, polyester-based resins, cycloolefin-based resins, or acrylic resins are preferable. These resins are excellent in transparency, mechanical strength, thermal stability, moisture barrier property, and the like. The thermoplastic resins may be used alone or in combination of two or more. In addition, an optical film used for a polarizing plate, for example, a low retardation substrate, a high retardation substrate, a retardation plate, a luminance improving film, or the like may be used as the substrate.
The thickness of the substrate is preferably 20 to 200. mu.m, more preferably 30 to 150. mu.m.
The total light transmittance of the substrate is preferably 30% or more, more preferably 35% or more, and further preferably 40% or more.
As a method of conveying the substrate, any suitable method may be adopted. Examples thereof include conveyance by a conveyance roller, conveyance by a conveyance belt, and a combination thereof. The transport speed is, for example, 5 m/min to 50 m/min.
(Metal nanowire)
The metal nanowire is a conductive material having a material of metal, a needle-like or wire-like shape, and a diameter of nanometer. The metal nanowire may be linear or curved. When the transparent conductive layer made of metal nanowires is used, the metal nanowires are formed into a mesh shape, whereby a good electrical conduction path can be formed even with a small amount of metal nanowires, and a transparent conductive film with low resistance can be obtained. Further, by forming the metal nanowires in a mesh shape and forming openings in gaps of the mesh, a transparent conductive film having high light transmittance can be obtained.
The ratio of the thickness d to the length L (aspect ratio: L/d) of the metal nanowire is preferably 10 to 100000, more preferably 50 to 100000, and particularly preferably 100 to 10000. When such a metal nanowire having a large aspect ratio is used, the metal nanowire is favorably crossed, and high conductivity can be exhibited by a small amount of the metal nanowire. As a result, a transparent conductive film having high light transmittance can be obtained. In the present specification, the "thickness of the metal nanowire" means a diameter of the metal nanowire when the cross section of the metal nanowire is circular, a short diameter of the metal nanowire when the metal nanowire is elliptical, and a longest diagonal line when the metal nanowire 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 500nm, more preferably less than 200nm, particularly preferably 10 to 100nm, and most preferably 10 to 50 nm. In such a range, a transparent conductive layer having high light transmittance can be formed.
The length of the metal nanowire is preferably 1 to 1000. mu.m, more preferably 10 to 500. mu.m, and particularly preferably 10 to 100. mu.m. Within such a range, a transparent conductive film having high conductivity can be obtained.
As the metal constituting the metal nanowire, any appropriate metal may be used as long as it is a conductive metal. Examples of the metal constituting the metal nanowire include: silver, gold, copper, nickel, and the like. In addition, a material obtained by subjecting these metals to plating treatment (for example, gold plating treatment) may be used. Among them, silver, copper, or gold is preferable, and silver is more preferable, from the viewpoint of conductivity.
As the method for producing the metal nanowire, any appropriate method can be adopted. For example, a method of reducing silver nitrate in a solution; and a method of applying a voltage or a current from the tip of the probe to the surface of the precursor, drawing the metal nanowire from 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 a liquid phase in the presence of a polyhydric alcohol such as ethylene glycol and polyvinylpyrrolidone. Silver nanowires of uniform size can be produced in large quantities, for example, according to the methods described in Xia, Y.et al, chem.Mater. (2002), 14, 4736-.
(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 metal nanowires in any suitable solvent. Examples of the solvent include: water, alcohol solvents, ketone solvents, ether solvents, hydrocarbon solvents, aromatic solvents, and the like. The composition for forming a transparent conductive layer may further contain additives such as a conductive material (for example, conductive particles) other than the resin (binder resin) and the metal nanowires, and a leveling agent. The composition for forming a transparent conductive layer may further 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 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 mPs/25 to 300 mPs/25 ℃, and more preferably 10 mPs/25 to 100 mPs/25 ℃. In such a range, the effect obtained by setting the direction of the wind in the air blowing step to a specific direction is increased. The viscosity of the composition for forming a transparent conductive layer can be measured by a rheometer (for example, MCR302 by Anton Paar).
The dispersion concentration of the metal nanowires in the composition for forming a transparent conductive layer is preferably 0.01 to 5 wt%. Within such a range, the effect of the present invention is remarkable.
As a method for applying the composition for forming a transparent conductive layer, any appropriate method can be used. Examples of the coating method include: spray coating, bar coating, roll coating, die coating, inkjet coating, screen coating, dip coating, relief printing, gravure printing, and the like.
The weight per unit area of the coating layer is preferably 0.3g/m2～30g/m2More preferably 1.6g/m2～16g/m2. In such a range, the metal nanowires can be dispersed well by air blowing in the air blowing step, and a transparent conductive film having a smaller conductive anisotropy can be produced.
The thickness of the coating layer is preferably 1 to 50 μm, more preferably 2 to 40 μm.
C. Air blowing process
As described above, in the air blowing step, air is blown to the coating layer side, and the orientation of the metal nanowires in the coating layer is set to an appropriate orientation. The direction of the air blow is as explained in item a.
The air supply to the coating layer may be performed by any suitable method. In one embodiment, the air blowing to the coating layer may be performed using an air blower disposed above (on the side opposite to the substrate) and/or on the side of the coating layer. The air blowing direction may be adjusted by providing a louver in the air blower, for example, and by the direction of the louver. In one embodiment, the air blowing direction is defined by the opening direction of the louver. In the case of blowing the spiral wind, a blower having a spiral wind direction plate at the wind blowing port may be used.
The wind speed is preferably 0.5 to 10m/s, more preferably 1 to 5 m/s. In such a range, the metal nanowires are well dispersed, and a transparent conductive film having smaller conductive anisotropy can be produced. Further, a transparent conductive film having excellent surface smoothness and thickness uniformity can be obtained. The wind speed may be appropriately set according to the solvent and the like contained in the composition for forming a transparent conductive layer. In the case of using the composition for forming a transparent conductive layer prepared from water, the wind speed is preferably 0.5 to 10m/s, more preferably 1 to 5 m/s. In the present specification, the wind speed refers to the wind speed at the time when the coating layer is reached.
The temperature of the air is preferably 10 to 50 ℃, more preferably 15 to 30 ℃. The wind speed may be appropriately set according to the solvent and the like contained in the composition for forming a transparent conductive layer. When a composition for forming a transparent conductive layer prepared from water is used, the temperature of the air is preferably 10 to 50 ℃, more preferably 15 to 30 ℃. In the present specification, the temperature of the wind refers to the temperature of the wind at the time when the wind reaches the coating layer.
The air blowing time is preferably 1 minute to 10 minutes, more preferably 2 minutes to 5 minutes. In such a range, the metal nanowires are well dispersed, and a transparent conductive film having smaller conductive anisotropy can be produced. Specifically, if the blown area is determined so that the blowing time falls within the above range, the metal nanowires can be appropriately dispersed throughout the coating layer, and a transparent conductive film having a smaller conductive anisotropy can be produced. Further, a transparent conductive film having excellent surface smoothness and thickness uniformity can be obtained.
In one embodiment, the above-described air blowing is performed on the substrate (substrate on which the coating layer is formed) on the conveying roller. Thus, the metal nanowires are well dispersed, and a transparent conductive film having less conductive anisotropy can be manufactured. Further, a transparent conductive film having excellent surface smoothness and thickness uniformity can be obtained.
In the air blowing step, air blowing may be performed in multiple stages. For example, the air may be blown in stages by dividing the air into different sections such as wind direction, wind speed, and temperature. The thickness of the coating layer may be reduced by, for example, oven heating or natural drying before the air blowing step. The weight per unit area of the coating layer at the start of the air blowing step is preferably 0.001g/m2～0.09g/m2More preferably 0.005g/m2～0.05g/m2。
Any appropriate treatment may be performed after the air blowing step. For example, when a composition for forming a transparent conductive layer containing a binder resin is used, curing treatment by ultraviolet irradiation or the like may be performed. Further, the drying step may be performed after the air blowing step. Examples of the drying method include oven heating and natural drying.
D. Transparent conductive film
The transparent conductive film is formed by the above-described manufacturing method. Fig. 2 is a schematic cross-sectional view of a transparent conductive film obtained by a manufacturing method according to an 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 value of the transparent conductive film is preferably 0.1. omega./□ to 1000. omega./□, more preferably 0.5. omega./□ to 300. omega./□, and particularly preferably 1. omega./□ to 200. omega./□. The ratio (TD/MD) of the surface resistance value in TD (direction orthogonal to MD) to the surface resistance value in MD (conveying direction) of the transparent conductive film is preferably 0.7 to 1.5, more preferably 0.8 to 1.2, and particularly preferably 0.9 to 1.1. The surface resistance value can be measured by "automatic resistivity measuring system MCP-S620 model. MCP-S521 model" of MITSUBISHI CHEMICAL ANALYTECH.
The haze value of the transparent conductive film is preferably 20% or less, more preferably 10% or less, and further preferably 0.1% to 5%.
The total light transmittance of the transparent conductive film is preferably 30% or more, more preferably 35%, and particularly preferably 40% or more.
The weight per unit area of the transparent conductive layer is preferably 0.001g/m2～0.09g/m2More preferably 0.005g/m2～0.05g/m2。
The content ratio 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, based on 100 parts by weight of the binder resin constituting the transparent conductive layer. Within such a range, a transparent conductive film having excellent conductivity and light transmittance can be obtained.
Examples
The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples at all. The evaluation methods of the examples are as follows. The thickness was measured by using a scanning electron microscope "S-4800" manufactured by hitachi high and new technologies, in which a cross section was formed by cutting with a microtome after embedding with an epoxy resin.
(1) Surface resistance value
The surface resistance values (surface resistance values in MD and TD) of the transparent conductive film were measured by the eddy current method using a non-contact surface resistance tester manufactured by NAPSON corporation, trade name "EC-80". The measurement temperature was set at 23 ℃.
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-.
The silver nanowires obtained above were dispersed in pure water to a concentration of 0.2 wt%, and dodecyl pentaethylene glycol was dispersed in pure water to a concentration of 0.1 wt%, to obtain a composition for forming a transparent conductive layer.
[ example 1]
A PET film (trade name "S100" made of mitsubishi resin) was used as a base material. The composition for forming a transparent conductive layer, prepared in production example 1, was coated on the substrate using a bar coater (product name "bar coater No. 16", manufactured by first Classification Co., Ltd.) while conveying the substrate using a conveying roll to form a film having a thickness basis weight of 0.015g/m2And a wet film thickness of the coating layer of 15 μm. Then, while the substrate on which the coating layer was formed was conveyed, a flow-regulated air was blown to the coating layer to dry the coating layer, thereby 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), air blowing is performed from the center toward both ends of the base material in directions from the width direction inner side toward both width direction outer sides, and the angle formed by the conveying direction a of the base material and the air blowing direction X (the air blowing direction when viewed from the coating layer surface side) is set to 90 °, and the angle formed by the conveying direction a of the base material and the air blowing direction Z (the air blowing direction when viewed from the coating layer side) is set to 0 °. The wind speed was set at 2m/s, and the wind temperature was set at 25 ℃. The air blowing time (drying time) was set to 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 air blowing was performed in a direction from both outer sides of the base material toward the inner side in the width direction as shown in fig. 1 (a). An angle formed by the conveyance direction a of the substrate and the air blowing direction X (air blowing direction when viewed from the coating layer surface side) is 90 °, and an angle formed by the conveyance direction a of the substrate and the air blowing direction Z (air blowing direction when viewed from the coating layer side) is 0 °. The wind speed was 2m/s, and the wind temperature was 25 ℃. The air blowing time (drying time) was set to 2 minutes.
The obtained transparent conductive film was subjected to the above evaluation (1). The results are shown in table 1.
[ example 3]
In the same manner as in example 1, a coating layer was formed on the substrate. Then, while the substrate on which the coating layer was formed was conveyed, a spiral flow was sent to the coating layer by using a circulator to dry the coating layer, thereby 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(c) and (c '), the air blowing is performed such that the direction X ' of the screw axis when viewed from the coating layer surface side of the substrate is parallel to the conveyance direction a of the substrate, and the direction Z ' of the screw axis when viewed from the side surface side of the substrate is parallel to the conveyance direction a of the substrate. The wind speed was set at 2m/s and the wind temperature was set at 25 ℃. The air blowing time (drying time) was set to 2 minutes.
The obtained transparent conductive film was subjected to the above evaluation (1). The results are shown in table 1.
[ example 4]
In the same manner as in example 1, a coating layer was formed on the substrate. Then, while the substrate on which the coating layer was formed was conveyed, a spiral flow was sent from above the coating layer by using a circulator to dry the coating layer, thereby 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(d) and (d '), blowing is performed so that the angle formed by the direction X' of the screw axis and the conveyance direction a of the substrate when viewed from the coating layer surface side of the substrate is 90 °. The wind speed was set at 2m/s and the wind temperature was set at 25 ℃. The air blowing time (drying time) was set to 2 minutes.
The obtained transparent conductive film was subjected to the above evaluation (1). The results are shown in table 1.
[ example 5]
The air blowing method was performed from the left side of the substrate as shown in fig. 1(e), and the angle formed by the transport direction a of the substrate and the air blowing direction X (the air blowing direction when viewed from the coating layer surface side) was set to 40 °, and the angle formed by the transport direction a of the substrate and the air blowing direction Z (the air blowing direction when viewed from the coating layer side) was set to 0 °. The wind speed was 2m/s, and the wind temperature was 25 ℃. The air blowing time (drying time) was set to 2 minutes.
Comparative example 1
A coating layer was formed in the same manner as in example 1. Then, the substrate on which the coating layer was formed was put into an oven at an oven temperature of 100 ℃ 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.
TABLE 1
Figure BDA0003574550110000121
Description of the symbols
10 base material
20 transparent conductive layer
100 transparent conductive film

Claims (6)

1. 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 for manufacturing the transparent conductive film comprises the following steps:
a coating step of forming a coating layer by coating a composition for forming a transparent conductive layer containing metal nanowires on the base material while conveying the long base material; and
an air blowing step of blowing air to the coating layer,
the air blow in the air blow step includes air blow in a direction different from the conveying direction of the base material.
2. The method for manufacturing a transparent conductive film according to claim 1,
the air blow in the air blow step includes at least air blow in a direction different from the conveyance direction of the substrate when viewed from the coating layer surface side of the substrate.
3. The method for producing a transparent conductive film according to claim 1 or 2,
the air blowing in the air blowing step is performed in two or more directions.
4. The method for manufacturing a transparent conductive film according to claim 3,
the direction of air blowing in the air blowing step when viewed from the coating layer surface side of the substrate includes directions from the inner side in the width direction of the substrate to both outer sides in the width direction.
5. The method for manufacturing a transparent conductive film according to claim 3,
the direction of air blowing in the air blowing step when viewed from the coating layer surface side of the base material includes a direction from both outer sides of the base material in the width direction toward the inner side of the base material in the width direction.
6. A transparent conductive film according to claim 1,
the air supply in the air supply process is spiral air supply.
CN202080069191.0A 2019-10-02 2020-09-28 Method for producing transparent conductive film Pending CN114503224A (en)

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