RU2775742C2 - Method for production of transparent electrodes - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: invention relates to a method for the production of a transparent electrode or a transparent thermal cable including silver nanowires. The transparent electrode or the transparent thermal cable is obtained by transfer of a silver nanowire formed on glass substrate to polymer and flexible film. When the silver nanowire transferred to polymer and flexible film is treated with an iodine mixture, the surface of the silver nanowire changes color.

EFFECT: providing a method for the production of a transparent electrode or a transparent thermal cable with low surface resistance, good flexibility and improved visibility.

6 cl, 15 dwg

Description

Technical field

The present invention relates to a method for producing a transparent electrode or a transparent thermal cable, including silver nanowires.

State of the art

Electrodes are widely used in various fields. The role of the electrode is to transfer the electrical charge to each electrical element and thus it serves to transfer energy to drive each electrical element. Therefore, it is very important that the resistivity and stability are as low as possible. In general, metals such as silver and copper are the main materials for making an electrode, and transparent electrodes such as TDI are widely used in displays.

The transparent electrode is an electronic component having a high transparency of 80% or more, and thus it is widely used in electronic fields such as displays, liquid crystal front electrodes, organic light emitting diode (OLED) electrodes, touch screens, solar cells and optoelectronic devices. Indium tin oxide (hereinafter referred to as "ITO") is commonly used as the transparent electrode in these devices. OIO electrodes have many advantages such as optical transparency, electrical conductivity and environmental stability.

However, since the RIO electrodes used in existing touch screen panels (TSPs) are less flexible and difficult to use for flexible or curved flexible displays, graphene, CNTs (carbon nanotubes) and silver nanowires (AgNW) are gaining attention as new replacement materials. OIO films.

Among them, silver nanowires are electrodes with high conductivity and electrical conductivity. Therefore, there is a growing demand for transparent electrodes incorporating silver nanowires.

Brief description of the invention

This summary is intended to introduce a number of concepts in a simplified form, which are further described in the following detailed description of the invention. This summary is not intended to identify key features or essential features of the claimed subject matter, and is not intended to be used as a means of determining the scope of the claimed subject matter.

The purpose of the present invention is to provide a method for producing a transparent electrode or a transparent thermal cable having low surface resistance, good flexibility and improved visibility.

In accordance with an embodiment of the present invention, a method for producing transparent electrodes is provided, including preparing a base substrate; forming a silver nanowire in contact with one surface of the base substrate; heating the base substrate and the silver nanowire at a given temperature; applying an uncured polymer to one surface of the base substrate to coat the silver nanowire; placing a flexible film on the uncured polymer; applying a predetermined pressure between the placed flexible film and the base substrate; irradiating the flexible film with light of a certain wavelength and curing the uncured polymer to convert it into a cured polymer; separating the base substrate and the cured polymer so that the silver nanowire is separated from the base substrate and bonded to the cured polymer, whereby a silver nanowire assembly including the silver nanowire, the cured polymer, and the flexible film is formed; exposing the silver nanowire assembly to an iodine mixture for a predetermined period of time to change the color of only a portion of the surface of the silver nanowire to gray or black, and annealing the silver nanowire assembly exposed to the iodine mixture.

In one embodiment of the present invention, the base substrate may be a glass substrate.

In one embodiment of the present invention, the base substrate may be a plate with a granite surface.

In one embodiment of the present invention, the flexible film may include PET.

In one embodiment of the present invention, the set temperature may be from 200°C to 300°C.

In one embodiment of the present invention, a given pressure may be applied by rolling a roller. The Brinell hardness of the roller can range from 30 to 50.

In one embodiment of the present invention, the iodine mixture may include a chloride-based mixture. The iodine mixture may further include potassium.

In one embodiment of the present invention, the portion of the silver nanowire that is changed to gray or black may be silver chloride.

In one embodiment of the present invention, annealing can be carried out at a temperature of from 100°C to 150°C for 2-5 minutes.

In accordance with an embodiment of the present invention, a method for manufacturing transparent electrodes is provided, including: preparing a base substrate; forming a silver nanowire in contact with one surface of the base substrate; heating the base substrate and the silver nanowire at a given temperature; changing the color of a portion of the silver nanowire to gray or black by exposing the silver nanowire to an iodine mixture for a predetermined period of time; applying an uncured polymer to one surface of the base substrate to coat the color changed silver nanowire; placing a flexible film on the uncured polymer; applying a predetermined pressure between the placed flexible film and the base substrate; irradiating the flexible film with light of a certain wavelength and curing the uncured polymer to convert it into a cured polymer; separating the base substrate and the cured polymer so that the color-changed silver nanowire is separated from the base substrate and bonded to the cured polymer, whereby a silver nanowire assembly comprising the color-changed silver nanowire, the cured polymer, and the flexible film is formed, and annealing the silver nanowire assembly.

In accordance with an embodiment of the present invention, a silver nanowire is placed on a flexible film to obtain a transparent electrode or thermal cable with improved flexibility.

In addition, the silver nanowire has a low surface resistivity to provide a transparent electrode or a transparent thermal cable that can be realized over a large area.

In addition, the clouding (haze) phenomenon when viewed with the naked eye is reduced to provide a transparent electrode or a transparent thermal cable with improved visibility.

In addition, the silver nanowire is located at a certain depth on the flexible film to provide a transparent electrode or transparent thermal cable with increased durability.

Brief description of the drawings

In FIG. 1 is an example illustrating the arrangement of silver nanowires on a base substrate.

In FIG. 2A and in FIG. 2B are examples illustrating the application of heat to the silver nanowires shown in FIG. one.

In FIG. 3 is an example illustrating the deposition of an uncured polymer to coat silver nanowires on the base substrate shown in FIG. one.

In FIG. 4 is an example illustrating the placement of a flexible film on the uncured resin shown in FIG. 3.

In FIG. 5A is an example illustrating the application of pressure to the assembly shown in FIG. 4, using the RL roller.

In FIG. 5B is a diagram illustrating a comparison of the processing quality of flexible films as a function of the hardness of the roller shown in FIG. 5A.

In FIG. 6 is an example illustrating the use of ultraviolet light to cure an uncured polymer.

In FIG. 7 is an example illustrating the separation of the silver nanowire assembly from the base substrate.

In FIG. 8A is an example illustrating the assembly of a silver nanowire.

In FIG. 8B is an example illustrating a cross section taken along line I-I' in FIG. 8A.

In FIG. 9 is an example illustrating the processing of the silver nanowire assembly shown in FIG. 8A with a solution including an iodine mixture.

In FIG. 10A is an example illustrating the assembly of a silver nanowire treated with an iodine mixture.

In FIG. 10B is an example illustrating a cross section taken along line II-II' in FIG. 10A.

In FIG. 11 is a flowchart illustrating a method for producing a transparent electrode according to an embodiment of the present invention.

Detailed description of the invention

The following is a detailed description, which helps to obtain a complete understanding of the methods, devices and/or systems described in this document. However, various changes, modifications, and equivalents to the methods, devices, and/or systems described herein will be apparent to those skilled in the art. The sequences of operations described in this document are only examples and are not limited to those set forth in this document, on the contrary, they can be changed, as it is obvious to a person skilled in the art, except for the stages necessarily carried out in a certain order. In addition, descriptions of functions and constructions that are well known to a person skilled in the art may be omitted for greater clarity and brevity.

The terms used in the description are only intended to describe certain embodiments and do not limit the present invention in any way. Unless expressly stated otherwise, expressions in the singular include the plural. As used herein, an expression such as "comprising" or "consisting of" is intended to denote a feature, amount, step, operation, element, part, or combination thereof, and is not to be construed as excluding the presence or possibility of one or more other characteristics, quantity, stages, operations, elements, their parts or combinations.

In the drawings, the proportions and dimensions of the components have been enlarged to effectively describe the technical content.

The following describes embodiments of the invention in more detail with reference to the accompanying drawings, in which like components are shown with the same or corresponding reference numbers, regardless of the drawing number, and redundant explanations are omitted.

In FIG. 1-fig. 10B shows examples illustrating a method for producing transparent electrodes according to an embodiment of the present invention. In FIG. 11 is a flowchart illustrating a method for producing a transparent electrode according to an embodiment of the present invention.

In FIG. Figure 1 shows an example illustrating the arrangement of silver nanowires on a BP base substrate.

The base substrate of the PSU can be a glass substrate or a plate with a granite surface. Glass substrates and plates with a granite surface have high thermal stability. Thus, it is advantageous that deformation does not occur even if a high temperature of 200° C. or more is used later in the heat treatment.

Silver nanowires NP are placed directly on the base BP substrate. Here, a method such as pour coating, rod coating, slot die coating, applicator, spin coating, or spray coating can be used.

According to an embodiment of the present invention, when coating silver nanowires using a spin coater, after applying the paste of the silver nanowire to a glass substrate, the spin coater is operated at a speed of 1000 to 3000 rpm to deposit the silver nanowires . If there are deviations from the above condition, it is impossible to deposit silver nanowires NP on the BP base substrate with a uniform thickness.

According to an embodiment of the present invention, when the silver nanowires are coated with a rod coater, the coating can be carried out at a speed of 1 to 100 cm/sec.

According to an embodiment of the present invention, when silver nanowires are coated using a spray coating apparatus, a nozzle size of 0.2 to 0.3 at a pressure of 1 to 5 kgf/cm ² can be used to coat the silver wires on base substrate.

According to an embodiment of the present invention, when the silver nanowires are coated using an applicator, the silver nanowire paste can be dropped in a row, and then the silver nanowires can be spread at 1-100 cm/s.

When the above conditions are not met, NR silver nanowires cannot be deposited on a base OD substrate with a uniform thickness.

You can use a silver nanowire NP size from 1 to 100 nm in diameter and from 2 to 100 μm in length. If the diameter is less than 5 nm, the mechanical stability becomes very weak, so it can be easily broken and it is difficult to maintain a stable mesh shape. On the other hand, if it exceeds 100 nm, the transparency (light transmittance) rapidly decreases to 70% or less.

If the length is less than 2 μm, since the length of the silver nanowires constituting the network becomes too short, more silver nanowires are needed, the transparency decreases, and the electrical conductivity deteriorates due to the plurality of contact points. On the other hand, if the length exceeds 100 μm, the production of silver nanowires becomes difficult, and the silver nanowires may break easily due to their long length during their deposition.

In FIG. 2A and in FIG. 2B are examples showing the application of heat to the silver nanowires shown in FIG. one.

The heating can be carried out by using a torch, micropulse photon heating, continuous photon heating, microwave heating, or heating in an oven.

As shown in FIG. 2B, when heat is applied, the conductivity of the contact part of the CN of the first silver nanowire NP1 and the second silver nanowire NP2 increases, which reduces the specific surface resistance of the silver nanowires NP as a whole. More specifically, the contact part of the CN of the first NP1 silver nanowire and the second NP2 silver nanowire, which is not a simple physical contact, slightly melts and becomes flexible, resulting in an expansion of the contact area, and this further improves the overall resistance. In addition, as the tensioned silver nanowires become flexible with heat, they become closer to the BP base substrate, resulting in a wider contact area and further improving adhesion.

The heat applied to the silver NP nanowires may be from about 100 to 300°C, preferably from about 200 to 300°C. When the temperature is less than 200°C, the surface resistance of the silver NP nanowires may not be low enough. On the other hand, at a temperature of more than 300°C, a part of the base substrate of the BP or silver nanowires of the NP can be damaged due to high temperature.

It is possible to carry out processing even at temperatures above 200°C only if the base substrate of the PSU is a glass substrate or a plate with a granite surface. On the other hand, if the PB base substrate is a substrate including a resin, heat may cause deformation when processed at such a high temperature.

In FIG. 3 is an example illustrating the deposition of an uncured P-N polymer to coat the silver nanowires of NP on the BP base substrate shown in FIG. one.

The uncured P-N polymer may be a liquid material in the form of a gel and may be applied in a thin layer about 3 µm or less thick by stick or by pouring.

The uncured P-N polymer can be cured by exposure to light in a certain wavelength range, and in particular can be cured by exposure to ultraviolet (UV) light.

The uncured P-N polymer may be a material having excellent optical characteristics such as light transmission. Since the NP silver nanowire according to an embodiment of the present invention is intended to provide a transparent electrode, other materials may also be required to maintain high light transmission to provide a transparent electrode.

In FIG. 4 is an example illustrating the placement of a flexible HP film on the uncured P-N resin shown in FIG. 3.

The flexible HP film may include polyethylene terephthalate (PET). Since the flexible film HP has flexibility, it is preferable to mount the transparent electrode on a flexible display device such as a foldable display device, a roll-up display device, or a movable display device.

In FIG. 5A is an example illustrating the application of pressure to the assembly (HP, P-L, VP) shown in FIG. 4 using a RL roller. In FIG. 5B is a diagram illustrating a comparison of the processing quality of flexible films as a function of the hardness of the roller of FIG. 5A.

In order to transfer the NP silver nanowires on the BP base substrate to the uncured P-N polymer and flexible HP film, to the (HP, P-N, OP) assembly shown in FIG. 4, pressure is applied using the RL roller.

The Brinell hardness of the RL roller may be from 30 to 50, preferably about 40. When the Brinell hardness of the RL roller is less than 30, the hardness may not be sufficient to move the NR silver nanowires. On the other hand, when the Brinell hardness of the RL roller is more than 50, wrinkling may occur on the HP flexible film due to clumping or wrinkling, which deteriorates the processing quality.

As shown in FIG. 5B, the flexible film HP has a number of wrinkles on its surface, which cannot provide a clear view to clearly see the object behind it when the Brinell hardness of the RL roller is 80. On the other hand, the surface of the flexible film HP can be smooth to provide a clear visibility to clearly see the object behind it when the Brinell hardness of the RL roller is 40.

Pressure can be applied with the RL roller so that the thickness of the uncured P-N polymer can be between 4 and 6 µm. When the thickness of the uncured PN polymer is less than 4 µm, it may be too thin and the NP silver nanowires may be damaged. On the other hand, when the thickness of the uncured P-N resin is more than 6 µm, wrinkling may occur due to thermal stress in subsequent processes. Therefore, the thickness of the uncured P-N polymer is preferably about 4 to 6 microns, taking into account subsequent processes.

In FIG. 6 is an example illustrating the use of ultraviolet light to cure an uncured P-N polymer.

The light source emitting ultraviolet light may be a lamp or an LED.

An uncured P-N polymer can be cured within seconds by an acrylic polymerization reaction under ultraviolet (UV) light. The uncured P-N polymer can also be cured with light in a certain wavelength range other than ultraviolet light, but curing is not limited to this.

The uncured P-N polyether can be cured to convert to the corresponding cured P-O polymer, whereby the silver nanowires (see FIG. 3) coated with the uncured P-N polymer can be attached to the cured RS-H polymer.

In FIG. 7 is an example illustrating the separation of the SNR silver nanowire assembly from the BP base substrate.

When the cured P-O polymer and flexible HP film are separated from one end of the BP base substrate, the NR silver nanowires can be separated from the BP base substrate and transferred onto the cured P-O polymer.

When both the cured P-O polymer and the flexible HP film are separated from the main substrate OP, an SNR silver nanowire assembly can be obtained, including a silver nanowire NP, a cured P-O resin, and a flexible HP film.

On FIG. 8A is an example illustrating the assembly of a silver nanowire. On FIG. 8B is an example illustrating a cross section taken along line I-I' in FIG. 8A.

As shown in FIG. 8B, the silver nanowires can be fixed in a mold embedded in the cured P-O polymer. Such an embedded shape can be obtained by coating the silver nanowires with uncured P-N polymer (see FIG. 3) during transfer.

The thickness H1 of the cured P-O resin may be 4 to 6 µm, similar to the thickness of the uncured P-N resin described in FIG. 5. The reason is described above. However, if necessary, the thickness H1 of the cured P-O resin may be 4 to 15 µm.

The thickness H2 of the flexible HP film can be between 50 and 100 µm. The flexibility may decrease when the thickness H2 of the flexible HJ film becomes larger than this range.

In FIG. 9 is an example illustrating the processing of the silver nanowire assembly shown in FIG. 8A with an OP treatment solution containing an iodine mixture. In FIG. 10A is an example illustrating a silver nanowire assembly treated with an iodine mixture. In FIG. 10B is an example illustrating a cross section taken along line II-II' in FIG. 10A.

The OP treatment solution may include an iodine mixture, and it may include a chloride-based mixture.

An iodine mixture containing a chloride-based mixture can react with the silver NP nanowires, and accordingly, the corresponding silver chlorides can form on the surface of the silver NP nanowires, so that the surface of the silver NP nanowire can become gray or black. Areas where the color of NP silver nanowires is changed can be called IC areas of a changed color.

The clouding phenomenon, which is caused by an optical effect, darkening the clarity of the assembly of the SNR silver nanowire as a whole, making it cloudy, can be reduced by color-changed IC regions.

The mass fraction of the mixture based on chloride in the iodine mixture can be from 20 to 30%. When the mass fraction of the chloride-based mixture deviates from this range, precipitation from the iodine mixture may be formed on the surface of the SNR silver nanowire assembly, thus the haze phenomenon can be enhanced.

When potassium is added to the iodine mixture in a certain ratio, this can contribute to a discoloration. The mass ratio of the iodine mixture and potassium may be from about 1:1 to 1:5. When this ratio is less than this range, the increase in the color change rate may be small. On the other hand, when the ratio is larger than this range, the haze problem may be exacerbated.

The SNR silver nanowire assembly exposed to an iodine mixture to form color-changed IC regions can be annealed. When the SNR silver nanowire assembly is treated with an iodine mixture and the surface resistivity of the SNR silver nanowire increases by about 10%, the increased resistance can be reduced by the annealing process.

The annealing process can be carried out using a dead end furnace or an IR furnace.

In one embodiment of the present invention, when annealing is carried out using a dead-end furnace, heating to about 100-150°C for about 10 to 60 minutes can be carried out.

In one embodiment of the present invention, when annealing is carried out using an IR oven, heating to about 100-150°C for about 1 to 20 minutes can be carried out.

In the annealing process, when the annealing temperature and the annealing time are smaller than the lower value of these ranges, the surface resistivity is not sufficiently reduced. On the other hand, when the annealing temperature and the annealing time are larger than the upper value of these ranges, the SNR silver nanowire assembly may be damaged by heating.

More specifically, when annealing is carried out using an IR oven, the annealing time can be adjusted depending on the degree of increase in the surface resistivity. For example, when the specific surface resistance of the silver nanowires NR increases by about 10% due to treatment with iodine mixture, heating can be carried out for about 2 minutes at a temperature of 100 to 150°C, and when the specific surface resistance of the silver nanowires NR increases by about 20 % due to treatment with an iodine mixture, heating can be carried out for about 5 minutes at a temperature of from 100 to 150°C.

In FIG. 11 is a flowchart illustrating a method for producing a transparent electrode according to an embodiment of the present invention, which combines the operations described in FIG. 1-10V.

The step (S100) of obtaining the base substrate and forming the silver nanowires S110) may correspond to FIG. one.

The heating and cooling step (S120) may correspond to FIG. 2A and FIG. 2B.

The step (S130) of applying the uncured resin may correspond to FIG. 3.

The flexible film placement step (S140) may correspond to FIG. four.

The pressure application step (S150) may correspond to FIG. 5A and FIG. 5V.

The UV irradiation step (S160) may correspond to FIG. 6.

The step (S170) of separating the silver nanowire assembly may correspond to FIG. 7-fig. 8B.

The step (S180) of reacting with the iodine mixture may correspond to FIG. 9-fig. 10V.

In one embodiment of the present invention, the step (S180) of reacting with the iodine mixture can be performed between the step (S120) of heating and cooling and the step (S130) of applying the uncured polymer. In this case, the area of the NP silver nanowires that reacts with the iodine mixture can be expanded, which improves visibility.

The annealing step (S190) is not shown separately, but is described above.

Although the description is presented with reference to specific embodiments, it should be understood that various changes and modifications may be made by those skilled in the art without departing from the spirit and scope of the embodiment presented herein as defined by the appended claims and equivalents. Accordingly, the examples described herein are only intended to explain the invention, and are not intended to limit the invention. The scope of the present invention is defined by the following claims, and it is to be understood that all features equivalent to those set forth in the following claims fall within the scope of the present invention.

Industrial Application

Transparent electrodes, which are not easily recognized by the human eye, are widely used in fields related to various electrical devices, including display devices.

Therefore, the method of obtaining a transparent electrode with low surface resistivity and improved visibility according to the present invention can be widely used in industry.

Claims (26)

1. A method for producing transparent electrodes, including: - preparation of the base substrate, - formation of a silver nanowire in contact with one surface of the base substrate, - heating the base substrate and the silver nanowire at a given temperature, - applying an uncured polymer to one surface of the base substrate to coat the silver nanowire, - placement of a flexible film on an uncured polymer, - application of a given pressure between the placed flexible film and the base substrate, - irradiating the flexible film with light of a certain wavelength and curing the uncured polymer to convert it into a cured polymer, separating the main substrate and the cured polymer so that the silver nanowire is separated from the base substrate and bonded to the cured polymer, whereby a silver nanowire assembly is formed, including the silver nanowire, the cured polymer and the flexible film, exposing the assembly of the silver nanowire to an iodine mixture comprising a mixture based on chloride and potassium for a predetermined period of time to convert only part of the surface of the silver nanowire to silver chloride, which is gray or black in color, and keep the other part of the silver nanowire conductive, and - annealing the assembly of silver nanowire, under the influence of iodine mixture at a temperature of from 100°C to 110°C for 2-5 minutes, where a given pressure is applied by rolling a roller having a Brinell hardness of 30 to 50. 2. The method of claim 1 wherein the base substrate is a glass substrate. 3. The method of claim 1 wherein the base substrate is a granite surface substrate. 4. The method of claim 1 wherein the flexible film comprises PET. 5. The method of claim. 1, in which the set temperature is from 200°C to 300°C. 6. A method for producing transparent electrodes, including: - preparation of the base substrate, - formation of a silver nanowire in contact with one surface of the base substrate, - heating the base substrate and the silver nanowire at a given temperature, obtaining a color-changed silver nanowire by exposing the silver nanowire to an iodine mixture including a mixture based on chloride and potassium for a predetermined period of time to convert only part of the surface of the silver nanowire into silver chloride, which is gray or black in color, and maintaining the conductivity of the other pieces of silver nanowire, - applying an uncured polymer to one surface of the base substrate to coat the color changed silver nanowire, - placement of a flexible film on an uncured polymer, - applying a predetermined pressure between the placed flexible film and the base substrate, - irradiating the flexible film with light of a certain wavelength and curing the uncured polymer to convert it into a cured polymer, separating the base substrate and the cured polymer so that the silver nanowire is separated from the base substrate and bonded to the cured polymer, whereby a silver nanowire assembly is formed including the color-changed silver nanowire, the cured polymer, and the flexible film, and - annealing the silver nanowire assembly at a temperature of 100°C to 110°C for 2-5 minutes, where a given pressure is applied by rolling a roller having a Brinell hardness of 30 to 50.

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