KR20090121954A - Carbon nanotube conductive film and preparing method thereof - Google Patents

Abstract

PURPOSE: A carbon nanotube conductive film and this manufacturing method are provided to obtain the excellent stability, the high permeability, a high-conductivity by using the urethane binder. CONSTITUTION: The carbon nanotube conductive film comprises as follows. The binder layer(20) is formed in the surface of the substrate(10) and substrate which is made of the acryl class binder. The transparent conductive film(30) consisting of the carbon nanotube adhered to the binder layer is included. The manufacturing method of the carbon nanotube conductive film comprises as follows. The substrate is prepared. The binder layer of the acryl or the urethane polymer is coated on the substrate. The carbon nanotube solution is coated on the binder layer surface with spray.

Description

Carbon nanotube conductive film and preparation method thereof

The present invention relates to a carbon nanotube conductive film, and more particularly, to adopt an optimal binder to improve adhesion stability to a substrate to be coated and to improve moisture resistance of the surface of the conductive film when manufacturing the carbon nanotube transparent conductive film. It relates to a nanotube conductive film and a method of manufacturing the same.

Carbon Nanotubes (CNT) form a tube where one carbon is combined with another carbon atom in a hexagonal honeycomb pattern to form a tube. The diameter of the tube is extremely small, at the level of nanometers (nm). .

Carbon nanotubes have excellent mechanical, electrical, and excellent field emission characteristics. In addition, since the shape of the semiconductor has the characteristics of the semiconductor and the energy gap varies depending on the diameter, it is attracting attention in the electronics, biotechnology, and medicine. In addition, the electrical properties of carbon nanotubes are so dramatic that they are not comparable to other materials currently known.

When the carbon nanotubes are formed in a thin conductive film on a plastic or glass substrate, they can be used as transparent electrodes because they exhibit high transmittance and conductivity in the visible light region. Accordingly, carbon nanotube conductive film is an alternative to ITO (Indium Tin Oxide) transparent electrode, which is currently used as a transparent electrode such as a field emission display (FED), a flat panel display (FPD), and a touch panel. I am attracting attention.

In particular, the carbon nanotube conductive film coated on the plastic substrate is attracting attention as a next-generation display because it has a merit that the electrical property does not change even when the film is folded or bent because it is stable to external impact or stress, compared to the metal oxide thin film ITO transparent electrode. It is being researched as a transparent electrode for flexible display.

The carbon nanotube conductive film should satisfy the characteristics of high transparency and low sheet resistance and at the same time have excellent adhesion stability. In addition, the carbon nanotube conductive film must satisfy the stability of the environment at high temperature and high humidity.

However, when manufacturing the conventional carbon nanotube conductive film, there was a problem that does not satisfy the adhesion stability of the carbon nanotube transparent conductive film. In addition, when manufacturing a conventional carbon nanotube conductive film, there was a problem that does not satisfy the stability to high temperature and high humidity.

The present invention was created in order to solve the conventional problems as described above, in manufacturing a carbon nanotube transparent conductive film using a spray coating method, to increase the adhesion stability and moisture resistance of the electrode, the carbon having a low permeability and sheet resistance value An object of the present invention is to provide a method for manufacturing a nanotube conductive film and a carbon nanotube conductive film.

The present invention to achieve the above object, the substrate; A binder layer formed on the surface of the substrate and comprising a polymer; It provides a carbon nanotube conductive film comprising a; and a transparent conductive film made of carbon nanotubes attached to the binder layer.

In addition, the present invention provides a method for manufacturing a substrate comprising: providing a substrate; Coating a binder layer made of an acryl-based or urethane-based polymer on the surface of the substrate; It provides a carbon nanotube conductive film manufacturing method comprising a; spray coating a carbon nanotube solution on the surface of the binder layer.

The carbon nanotube conductive film and the conductive film manufacturing method according to the present invention increase the adhesion stability and intrinsic properties of the conductive film by coating an acrylic binder on a substrate coated with carbon nanotubes, and using a urethane-based binder at high temperature and high humidity. By increasing the durability of the carbon nanotubes, it is a very useful invention to obtain the effect of excellent stability, high permeability, high conductivity, high moisture resistance and the like after coating.

Hereinafter, the technical configuration of the present invention according to the accompanying drawings in detail.

1 is for explaining the configuration of a conductive film according to an embodiment of the present invention.

The carbon nanotube conductive film according to the present invention includes a substrate 10, a binder layer 20, and a transparent conductive film 30.

The substrate 10 is a substrate of the conductive film, and may be adopted among those having planar characteristics such as glass, a polymer film, and a membrane. Specific examples of the polymer film include polyethylene terephthalate (PET) film.

The binder layer 20 is formed on the surface of the substrate 10. The binder layer 20 may be coated on the substrate 10 using bar coating, roll coating, dip coating, spin coating, or the like. In particular, the binder layer 20 is first coated on the substrate 10 before the carbon nanotubes are coated, and stably bonded to the substrate 10, or after the carbon nanotubes are coated, the substrate 10. Can be coated, but the former method is more preferred.

In particular, the acrylic binder has high transparency and excellent adhesive stability as a binder, and the urethane-based binder has excellent water resistance and high moisture resistance. The acrylic binder has the characteristics of the original thermoplastic, and has a characteristic of softening when the temperature is raised. The urethane-based binder also has the same characteristics by using a kind having a characteristic of the thermoplastic.

Therefore, the binder layer 20 is present in a state in which the polymer is softened by the temperature of the hot plate used in spray coating of carbon nanotubes.

The transparent conductive film 30 is formed by spray coating a carbon nanotube (CNT), which is a conductive material, on the polymer of the binder layer 20. The transparent conductive film 30 should maintain transparency and conductivity, which are characteristics of the conductive film. To this end, the transparent conductive film 30 should be connected to the conductive material carbon nanotubes without disconnection, and the carbon nanotubes should be coated as thin as possible. In order to satisfy these two characteristics, the transparent conductive film 30 having a predetermined pattern is formed using a spray coating method. When the carbon nanotube solution is sprayed onto the substrate at a constant pressure by spray coating, a small drop of water forms a pattern of coffee ring on the substrate as a whole. When the substrate becomes a hard surface, the water droplets on the substrate due to the pressure of the spray The phenomenon may occur, but when the solution under pressure on the softened substrate falls, the pattern is fixed into the substrate, which is advantageous in forming a carbon nanotube pattern coating.

The transparent conductive film 30 is preferably selected from single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, and bundled carbon nanotubes, or a combination thereof, but is not necessarily limited thereto.

Figure 2a is an electron scanning microscope picture of the unstabilized carbon nanotube conductive film according to an embodiment of the present invention, Figure 2b is an electron scanning microscope picture of a stabilized carbon nanotube conductive film according to an embodiment of the present invention .

As shown in FIGS. 2A and 2B, the binder layer 20 is made of a thermoplastic polymer, and the transparent conductive film 30 is stabilized by the binder layer 20 while maintaining a predetermined pattern. That is, as described above, a part of the carbon nanotubes is buried on the surface of the binder layer 20 softened on the substrate 10, thereby improving the adhesion stability of the electrode.

For the characteristics of the transparency and the sheet resistance of the transparent electrode, it is preferable to adopt an acrylic binder.

Meanwhile, the binder layer 20 has a thickness of 0.5 to 2 micrometers (μm). If the thickness of the coating is thinner than 0.5㎛, the properties related to the adhesion stability is lowered. If the thickness is thicker than 2㎛, the carbon nanotubes are embedded in the thermoplastic resin when the carbon nanotubes are coated, and the electrical properties may be degraded. Transparency is also affected.

The binder layer 20 may be directly coated on a transparent substrate, but it is also possible to directly use a transparent polymer substrate including an acrylic binder layer. The concentration of the binder layer 20 should be adjusted in a range that does not affect the transmittance of the conductive film, and for this purpose, the change in the original transmittance value of the substrate 10 to be coated with carbon nanotubes is satisfied within 0.5%. do.

As such, the carbon nanotubes are coated on the substrate 10 to which the binder layer 20 is coated by a spray method, and the electrode is manufactured by adjusting sheet resistance according to the use thereof. Depending on the thickness of the carbon nanotube to be coated and the type of substrate, the base substrate heat treatment temperature is different when spraying. Surface stabilization of the electrodes is confirmed using the ASTM D3359 method (Tape test), a US standard method. After measuring the sheet resistance of the electrode surface and measuring the sheet resistance of the same surface after the tape test, check the surface stability.

In addition, the binder layer 20 preferably has an acrylic resin content of 20% or more.

On the other hand, the acrylic resin is preferably to include one or more components used in general industrial, such as alkyl acrylate, methacrylate having an alkyl group having 1 to 12 carbon atoms.

On the other hand, another feature of the carbon nanotube conductive film according to the present invention will be described.

To this end, the carbon nanotube conductive film according to the present invention includes a substrate 10, a binder layer 20, and a transparent conductive film 30.

The substrate 10 is a substrate of the conductive film, and may be adopted among those having planar characteristics such as glass, a polymer film, and a membrane. Specific examples of the polymer film include polyethylene terephthalate (PET) film.

The binder layer 20 is formed on the surface of the substrate 10 and is made of a urethane-based polymer. The binder layer 20 may be coated on the substrate 10 using bar coating, roll coating, dip coating, spin coating, or the like. In particular, the binder layer 20 is first coated on the substrate 10 before the carbon nanotubes are coated, and stably bonded to the substrate 10, or after the carbon nanotubes are coated, the substrate 10. Can be coated, but the former method is more preferred.

The transparent conductive film 30 is formed by spray coating a carbon nanotube (CNT), which is a conductive material, on the polymer of the binder layer 20. The transparent conductive film 30 should maintain transparency and conductivity, which are characteristics of the conductive film. To this end, the transparent conductive film 30 should be connected to the carbon nanotubes, which are conductive materials without disconnection, and the carbon nanotubes should be coated as thinly as possible. In order to satisfy these two characteristics, a spray coating method is used to form a transparent conductive film 30 having a predetermined pattern connected to each other.

The transparent conductive film 30 is preferably selected from single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, and bundled carbon nanotubes, or a combination thereof, but is not necessarily limited thereto.

Meanwhile, the binder layer 20 has a thickness of 0.5 to 2 micrometers (μm). If the coating thickness is thinner than 0.5 μm, the properties related to the adhesion stability are lowered. If the thickness is thicker than 2 μm, the carbon nanotubes are buried a lot in the binder layer 20 in the thermal stabilization step after spray coating. And the transparency of the substrate 10 is also affected.

The binder layer 20 may be directly coated on a transparent substrate, but it is also possible to directly use a transparent polymer substrate including a urethane-based binder layer. The concentration of the binder layer 20 should be adjusted in a range that does not affect the transmittance of the conductive film, for this purpose adjusted so that the change in the original transmittance value of the substrate 10 to be coated with carbon nanotubes is within 0.5%. do.

As such, the carbon nanotubes are coated on the substrate 10 to which the binder layer 20 is coated by a spray method, and the electrode is manufactured by adjusting sheet resistance according to the use thereof. Depending on the thickness of the carbon nanotubes and the type of the substrate to be coated, the heat treatment temperature and time for the surface stabilization after electrode production is different. The high temperature and high humidity stabilization of the electrode is maintained in a constant temperature and humidity chamber at 65 ° C, 95%, R.H., and 240hr, which is a test method of the conductive film, and then the sheet resistance on the surface of the electrode is measured and the change value is checked to compare the stabilization degree.

In addition, the binder layer 20 preferably has a urethane resin content of 20% or more. On the other hand, the urethane resin may include a composite of a polyol, diisocyanate, chain extender.

On the other hand, the conductive film manufacturing method according to the present invention comprises the steps of providing a substrate 10, coating a binder layer 20 made of an acrylic or urethane-based polymer on the surface of the substrate 10, and the binder layer Spray coating a carbon nanotube solution on the surface of the substrate (10) coated with (20).

As such, by adding the binder layer 20 therebetween without directly coating the carbon nanotubes on the substrate 10, the stability of the carbon nanotube electrodes can be improved. In this case, the binder layer 20 is first coated on the substrate 10, and then carbon nanotubes are coated on the binder layer 20. In addition, the carbon nanotubes are coated so that a portion of the carbon nanotubes is permeated into the binder layer 20. Therefore, the carbon nanotubes are firmly fastened to the substrate 10 while maintaining a constant pattern, thereby improving the bonding stability while maintaining the properties such as conductivity and transparency of the carbon nanotubes.

This method (base coating) has an effect of lowering the sheet resistance value than the method of coating the carbon nanotubes on the substrate 10 and then coating the binder layer 20 (top coating). This is because the top coating method results in covering the surface of the carbon nanotubes, thereby increasing the sheet resistance of the electrode.

The carbon nanotube solution may be formed by mixing a carbon nanotube, a dispersant, and a solvent.

As a dispersant, any one can disperse carbon nanotubes in a solvent such as water. Specific examples include sodium dodecyl sulfate (SDS), Triton X (Sigma), Tween20 (Polyoxyethyelene Sorbitan Monooleate), and CTAB (Cetyl Trimethyl Ammonium Bromide). The content of the dispersant is preferably 0.1 to 10000 parts by weight based on 1 part by weight of carbon nanotubes, and particularly preferably 0.1 to 500 parts by weight.

As a solvent, water, ethanol, methanol, isopropanol, 1,2-dichlorobenzene, chloroform, dimethylformamide, acetone and mixtures thereof are used, and the solvent content is 1 weight of carbon nanotubes. It is preferably 10 to 80000 parts by weight based on parts.

As such, the spray-coated carbon nanotubes are preferably formed of a plurality of cyclic patterns in which portions are connected to each other. 3 is an optical micrograph of a pattern shape appearing after the carbon nanotube spray coating according to an embodiment of the present invention. The cyclic pattern herein means a cyclic ring.

The annular pattern is that when the liquid and the material having different evaporation rates are mixed in the liquid drop, the liquid in the outer edge evaporates, and the liquid inside the drop moves outward while occupying the empty space. Most of the particles come from the edges of the liquid droplets. The pattern may be obtained by adjusting a factor such as spray pressure, substrate temperature, etc. of the coating solution to obtain an annular ring pattern having a certain size and shape. Therefore, the carbon nanotubes are connected to the entire surface coated with the solution without breaking, thereby forming a highly transparent carbon nanotube conductive film.

Hereinafter, the present invention will be described in more detail with reference to the following examples, but the present invention is not limited only to the following examples.

Example 1 and Example 2

PET film was selected as a transparent substrate on which carbon nanotubes are to be coated. Thereafter, acrylic binders (A and B) were coated on the PET by a dip coating method, and the coating solution was dried. The PET was placed on a heating plate heated to a temperature of 70 ° C., and an experimental spray device (Anest Iwata W-100) was prepared and coated with a spray spray on the prepared substrate using a carbon nanotube dispersed solution (base coating).

After spraying the film was confirmed by the pattern of the spray through a microscope (OLYMPUS BX51) and the sheet resistance value and transmittance of the transparent electrode were measured. 3 is a pattern shape appearing after spray coating the carbon nanotubes, it can be seen that the pattern shape is maintained in the acrylic binder as it is. The sheet resistance and transmittance of the transparent electrode are shown in Table 1.

Example 3 and Example 4

PET film was selected as a transparent substrate on which carbon nanotubes are to be coated. Thereafter, a urethane-based binder (A, B) was coated on the PET by a dip coating method, and the coating solution was dried. The PET was placed on a heating plate heated to a temperature of 70 ° C., and an experimental spray device (Anest Iwata W-100) was prepared and coated with a spray spray on the prepared substrate using a carbon nanotube dispersed solution (base coating).

After spraying the film was confirmed by the pattern of the spray through a microscope (OLYMPUS BX51) and the sheet resistance value and transmittance of the transparent electrode were measured. The sheet resistance and transmittance of the transparent electrode are shown in Table 1.

Comparative Example 1

PET film was selected as a transparent substrate on which carbon nanotubes are to be coated. Thereafter, PET was placed on a heating plate heated to a temperature of 70 ° C., and an experimental spray device (Anest Iwata W-100) was prepared and coated with a spray spray on the prepared substrate using a carbon nanotube dispersed solution. An acrylic binder was coated on the top surface of the carbon nanotube film by a dip coating method and then dried (top coating).

Comparative Example 2

PET film was selected as a transparent substrate on which carbon nanotubes are to be coated. Thereafter, PET was placed on a heating plate heated to a temperature of 70 ° C., and an experimental spray device (Anest Iwata W-100) was prepared and coated with a spray spray on the prepared substrate using a carbon nanotube dispersed solution. The urethane-based binder was coated on the top surface of the carbon nanotube film by a dip coating method and then dried (top coating).

Comparative Example 3

PET film was selected as a transparent substrate on which carbon nanotubes are to be coated. Thereafter, a fluorine-based binder (PVDF) was coated on the PET by a dip coating method, and the coating solution was dried. The PET was placed on a heating plate heated to a temperature of 70 ° C., and an experimental spray device (Anest Iwata W-100) was prepared and coated with a spray spray on the prepared substrate using a carbon nanotube dispersed solution (base coating).

Comparative Example 4

PET film was selected as a transparent substrate on which carbon nanotubes are to be coated. Thereafter, a melamine-based binder (PVDF) was coated on the PET by a dip coating method, and the coating solution was dried. The PET was placed on a heating plate heated to a temperature of 70 ° C., and an experimental spray device (Anest Iwata W-100) was prepared and coated with a spray spray on the prepared substrate using a carbon nanotube dispersed solution (base coating).

 Coating substrate  Binder type  Coating method  Sheet resistance (Ω / □)  Permeability (%) Stability test sheet resistance change High temperature and high humidity (240hr) 65 ° C, 95%, R.H. Before attaching tape After attaching tape Before test After test Example 1 PET Acrylic series A base 500 81 500 500 500 770 Example 2 PET Acrylic series B base 500 82 500 500 500 945 Example 3 PET Urethane Series A base 500 80 500 600 500 650 Example 4 PET Urethane Series B base 500 80 500 600 500 600 Comparative Example 1 PET Acrylic series A top 1 × 10 ³ 82 1 × 10 ³ 1 × 10 ³ 1 × 10 ³ 2 × 10 ³ Comparative Example 2 PET Urethane Series A top 1 × 10 ³ 80 1 × 10 ³ 1 × 10 ³ 1 × 10 ³ 1 × 10 ³ Comparative Example 3 PET PVDF Series base 500 80 500 700 500 937 Comparative Example 4 PET Melamine series base 500 80 500 650 500 945

For reference, the tape test was performed for the adhesion stability test of the film, and the surface stability was confirmed by checking the conductivity of the film before and after the tape test. In addition, the surface state was confirmed by an electron scanning microscope to check the mutual bonding state between the binder and the carbon nanotubes on the surface of the film. In addition, for durability test for high temperature and high humidity using a thermo-hygrostat, each sample was maintained at 65 ° C., 95%, and R.H. for 240 hours, and the sheet resistance values before and after the test were compared.

As can be seen from Table 1, according to Examples 1 and 2 according to the base coating using the acrylic (A, B) binder, it was confirmed that the sheet resistance value is low, the conductivity is good, the permeability is excellent and the stability is very excellent. According to Examples 3 and 4, as a result of base coating using a urethane series (A, B) binder, it was confirmed that the stability is superior to the acrylic series in the environment of high temperature and high humidity.

On the other hand, according to Comparative Example 1 as a result of the top coating using an acrylic binder, it was confirmed that the sheet resistance value is high, the conductivity is lowered and not stable even in the environment of high temperature and high humidity. According to Comparative Example 2 as a result of the top coating using a urethane-based binder, it was confirmed that the conductivity is reduced due to the high sheet resistance. According to Comparative Example 3, as a result of base coating using a fluorine series (PVDF) binder, a higher sheet resistance value was obtained than that of an acrylic series or a urethane series. According to Comparative Example 4, as a result of base coating using a melamine-based binder, a higher sheet resistance value was obtained compared to an acryl-based or urethane-based.

Although the present invention has been described with reference to the embodiments illustrated in the drawings, this is merely exemplary, and any person skilled in the art to which the present invention pertains may have various modifications and equivalent other embodiments. Will understand. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

1 is for explaining the configuration of a conductive film according to an embodiment of the present invention,

Figure 2a is an electron scanning micrograph of the unstabilized carbon nanotube conductive film according to an embodiment of the present invention,

Figure 2b is an electron scanning micrograph of the stabilized carbon nanotube conductive film according to an embodiment of the present invention,

3 is an optical micrograph of a pattern shape appearing after the carbon nanotube spray coating according to an embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

10: substrate 20: binder layer

30: transparent conductive film

Claims (13)

temperament; A binder layer formed on the surface of the substrate and comprising an acrylic binder; And And a transparent conductive film made of carbon nanotubes attached to the binder layer. The method according to claim 1, The binder layer is a carbon nanotube conductive film, characterized in that the content of the acrylic resin 20% or more. The method according to claim 1, The acrylic resin, Carbon nanotube conductive film, characterized in that at least one of alkyl acrylate, methacrylate having an alkyl group having 1 to 12 carbon atoms is adopted. temperament; A binder layer formed on the surface of the substrate and formed of a urethane series; And And a transparent conductive film made of carbon nanotubes attached to the binder layer. The method according to claim 4, The binder layer is a carbon nanotube conductive film, characterized in that the content of the urethane resin 20% or more. The method according to claim 4, The urethane resin, Carbon nanotube conductive film comprising a compound of polyol, diisocyanate, chain extender. The method according to any one of claims 1 to 6, The carbon nanotubes, Carbon nanotube conductive film, characterized in that the portion is buried in the polymer surface of the binder layer to maintain a certain shape. The method according to any one of claims 1 to 6, The binder layer is carbon nanotube conductive film, characterized in that formed in a thickness of 0.5 ~ 2 micrometers (㎛). The method according to any one of claims 1 to 8, The binder layer is a carbon nanotube conductive film, characterized in that the content of the acrylic resin 20% or more. The method according to any one of claims 1 to 6, The transparent conductive film, Carbon nanotube conductive film, characterized in that the single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, bundle type carbon nanotubes, or a combination thereof. The method according to any one of claims 1 to 6, The substrate is, Carbon nanotube conductive film, characterized in that at least one of glass, polymer film, membrane is adopted. Providing a substrate; Coating a binder layer made of an acryl-based or urethane-based polymer on the surface of the substrate; Spray coating a carbon nanotube solution on the surface of the binder layer; Carbon nanotube conductive film manufacturing method comprising a. The method according to claim 12, The carbon nanotube conductive film manufacturing method, characterized in that the coating so that a part of the binder layer soaking.

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