KR101064943B1 - Carbon nano tube electrode manufacturing method - Google Patents

Abstract

The present invention relates to a method for manufacturing an organic-free carbon nanotube electrode using an aerosol deposition technique.

The present invention (a) aerosolizing the carbon nanotube raw material; And (b) forming an electrode made of a carbon nanotube thin film by spray-depositing the aerosolized carbon nanotubes by vacuum expansion on a substrate; It provides a carbon nanotube electrode manufacturing method comprising a.

Carbon nanotube, electrode, cathode, backlight unit, display

Description

Carbon nano tube electrode manufacturing method

The present invention relates to a method for manufacturing an organic-free carbon nanotube electrode using an aerosol deposition technique.

There are three main methods for manufacturing an emitter by forming a carbon nanotube layer on an electrode of a BLU or FED.

The first method is a chemical vapor deposition (CVD) method in which a catalyst is formed on a cathode electrode and a substrate is heated so that the carbon nanotubes grow in the catalyst part while the hydrocarbon precursor is broken by thermal-chemical action. Most of the carbon nanotubes grow in the catalyst section and grow perpendicular to the cathode electrode. However, vertically grown carbon nanotubes are prone to collapse and have the disadvantage of requiring additional catalytic process and expensive CVD equipment technology.

The second method is to disperse the carbon nanotubes in the liquid phase through chemical treatment or to mix the polymer or photoresist and then coat the cathode. This method is very inexpensive and is currently used by many companies. However, due to the deterioration of the properties of carbon nanotubes embedded in the polymer and durability and contamination of the polymer itself, it is an obstacle to commercialization. Moreover, due to the high resistance of the polymer carriers, the emitter portion becomes hot and degrades and contaminates the vacuum inside the device (increased getter technology dependence).

The third method is to form a film by spraying a chemically dispersed carbon nanotube solution on the substrate under atmospheric pressure using an air brush as in the second method. That is, it is similar to the general spray painting technique used by painters. This method, like the second method, has similar problems with weak bonding force and polymer binder between substrate and carbon nanotubes.

Therefore, ideally, a technique for forming a carbon nanotube thin film having a direct chemical bond between cathode-CNT and CNT-CNT without a binder on a cathode is urgently required as a core technology for increasing the quality and life of a BLU or FED device.

An object of the present invention is to provide a high quality / high clean electrode having a direct bond between a cathode electrode and a carbon nanotube at room temperature without using a polymer binder by developing an energy-saving, eco-friendly low-cost process.

The above object can be achieved by aerosolizing a carbon nanotube raw material and then accelerating the aerosol at high speed according to a vacuum expansion principle to impinge a substrate to obtain a carbon nanotube thin film and apply it as an electrode.

Before aerosolizing the carbon nanotube raw material, the carbon nanotube may be further physically modified or chemically pretreated to perform surface modification. An example of this is ball milling.

In the forming of the carbon nanotube thin film by impinging the carbon nanotube aerosol on the substrate, a reactive gas for inducing some chemical reactions may be introduced.

According to the present invention (a) does not include a separate binder resin, (b) most of the carbon nanotubes are directly bonded (chemically bonded) side by side on the substrate, (c) these carbon nanotubes at one or both ends of the upper layer Protruding or protruding carbon nanotube stops, (d) the field emission is caused by the protruding portion of the carbon nanotubes, it is possible to manufacture a field emission-type carbon nanotube emitter. The field emission type carbon nanotube emitter can be applied to the development of high quality, long life, energy saving, eco-friendly BLU, FED.

The present invention is an aerosol chamber in which carbon nanotube raw material is stored; A deposition chamber having a substrate disposed therein and having an exhaust unit for exhausting an internal gas; An aerosol transport tube having one end communicating with the aerosol chamber, the other end penetrating the deposition chamber, and an injection nozzle coupled to the end of the deposition chamber; Aerosol opening and closing means provided in the middle of the pipeline of the aerosol transport pipe; And a flow rate controller for sucking external general air and supplying the aerosol chamber to the aerosol chamber. A method of manufacturing a carbon nanotube electrode made by a pulsed aerosol deposition apparatus comprising a: (a) supplying external general air sucked by the flow rate control unit into the aerosol chamber as a transport gas to supply the carbon nanotube raw material; Aerosolization; And (b) accelerating the aerosolized carbon nanotubes by a vacuum expansion principle to form a thin film of carbon nanotubes by spray deposition on a substrate disposed in a deposition chamber in communication with the aerosol chamber. Including, but the step (b) increases the injection rate of the aerosolized carbon nanotubes by inducing a reduced pressure of the deposition chamber by intermittently opening and closing the aerosol transport pipe to the aerosol opening and closing means, aerosolized carbon It provides a method of manufacturing a carbon nanotube electrode, characterized in that the finely dispersed carbon nanotube aerosol particles are deposited on the substrate by passing through the porous membrane in the aerosol chamber before the nanotube is injected into the deposition chamber.

In step (a), the transport gas may be supplied to the aerosol chamber in which the carbon nanotube raw material is stored so that the carbon nanotubes may be aerosolized. The transport gas is external general air sucked by the flow control unit. In addition, in step (b), the aerosolized carbon nanotubes may be injected into the deposition chamber 12 in communication with the aerosol chamber 1 by the aerosol transport tube 10 and the substrate disposed therein. The substrate may be coated with a transparent conductive film or an opaque conductive film, which is the same in all the embodiments described below.

1 is a schematic diagram of a continuous aerosol deposition apparatus, in which an aerosol chamber 1 and a deposition chamber 12 are provided. The carbon nanotube raw material 2 is introduced into the aerosol chamber 1, and the transport gas is quantitatively input from the outside. The transport gas may be introduced by adjusting the quantity by the flow control unit 4 shown in FIG. The transport gas is injected into the carbon nanotube raw material 2 in the aerosol chamber 1 through the gas transport pipe (5). By transport gas injection, the carbon nanotube particles are dispersed in a gaseous phase to form a carbon nanotube aerosol (9). The generated carbon nanotube aerosol is vacuum expansion principle to the deposition chamber 12 through the nozzle 11 of the tip through the tube connecting the aerosol chamber 1 and the deposition chamber 12, that is, the aerosol transport tube 10. By spraying at high speed. The carbon nanotube aerosol accelerated at high speed hits the substrate 14 and deposition occurs. The substrate is fixed to the substrate holder 15, the substrate holder 15 may be configured to enable the distance between the substrate and the nozzle through the holder height adjusting unit 16. The gases in the deposition chamber 12 are continuously exhausted through the exhaust 17. Acceleration of carbon nanotubes increases as the exhaust velocity (pumping speed) through the exhaust portion is increased, and the acceleration at the moment of discharge from the nozzle is maximized. On the other hand, the base material, that is, the substrate may be designed to be movable in the x, y, z axis in connection with a driving device such as a piezo material or a motor. Alternatively or in parallel thereto, the driving device may be driven to move the nozzle unit in association with the nozzle unit.

Meanwhile, in the present invention, the aerosol transport pipe 10 may be intermittently opened and closed to induce a reduced pressure of the deposition chamber 12 to increase the injection speed of the aerosolized carbon nanotubes. 2 is a schematic diagram of a pulsed aerosol deposition apparatus configured to practice the present invention. In the device shown in FIG. 1, carbon nanotubes are deposited on a substrate by a continuous carbon nanotube flow, while FIG. 2 shows that a carbon nanotube is a substrate by an intermittent pulsed carbon nanotube flow. Is deposited. This technique uses the principle of the cluster source. The method of obtaining an intermittent pulse beam may be performed by intermittently blocking the supply of external transport gas or intermittently blocking the injection of aerosolized carbon nanotubes. These two methods may be applied simultaneously or sequentially. It may be.

The pulse aerosol deposition apparatus shown in FIG. 2 includes a raw material supply unit 3 and a deposition chamber 12. The raw material supply unit 3 disperses the gas transport pipe 5 and carbon nanotube raw material powder for introducing and supplying a transport gas (external general air) from the outside to form gaseous particulates, and then form the aerosol transport pipe 10. An aerosol chamber 1 for transporting through. The raw material supply unit 3 and the deposition chamber 12 may have a structure bound through a separate fastening means 13 as shown in FIG. In FIG. 2, carbon nanotube raw material powder is left in the aerosol chamber 1, and a porous diaphragm 6 is provided in the upper space inside the aerosol chamber 1. In addition, in order to introduce the transport gas into the aerosol chamber 1, the gas opening and closing is controlled by the flow rate adjusting unit 4 mounted on the gas transportation pipe 5, and the aerosol opening and closing is similarly applied to the aerosol transportation pipe 10. By means of the means 7, the transport gas is introduced in pulse form (deposition time: Δt1, rest period: Δt2 adjustment) to generate gas phase dispersion of the raw material powder in the form of a pulse, or aerosol fine particles in the form of a pulse It may collide with (14).

In other words, the transport gas enters the aerosol chamber 1 through the gas transport pipe 5 in the form of a pulse through the flow rate adjusting unit 4. At this time, the gas introduced in the form of pulse blows the carbon nanotube raw material (2) to the opposite side in an instant to aerosolize the carbon nanotube raw materials. Only the tube aerosol 9 particles exit the porous diaphragm 6 and are discharged through the aerosol transport tube 10 and finally accelerated into the deposition chamber 12 through the nozzle 11 at its end. That is, the carbon nanotube aerosol particles supplied through the aerosol transport tube 10 are accelerated and deposited on the substrate 14 fixed to the substrate holder 15. The substrate holder 15 may be installed to move up and down by the height adjusting unit 16. At this time, the aerosol transport pipe 10 may be provided with an aerosol opening and closing means (7). In the present invention, the flow rate control unit 4 and the aerosol opening and closing means 7 for interlocking the gas can be interlocked, for example, after opening the flow rate adjusting unit 4 to introduce the transport gas into the aerosol chamber 1. The flow control unit 4 may be closed and the aerosol opening and closing unit 7 may be opened so that the aerosolized carbon nanotube raw material may be introduced into the deposition chamber 12 through the aerosol transport pipe 10. Of course, in the present invention, the raw material may be introduced into the deposition chamber 12 by opening the aerosol opening and closing means 7 while the flow rate control unit 4 is open. Alternatively, in the present invention, only the aerosol opening and closing means 7 without the flow control unit 4 may be introduced to the carbon nanotube raw material in a pulse by the operation of the aerosol opening and closing means (7). At this time, the gas introduced into the deposition chamber 12 together with the carbon nanotube aerosol 9 is exhausted by the exhaust unit 17. In addition, a separate sample container (not shown) may be installed outside the raw material supply unit 3 to supply a sample continuously or discontinuously when the raw material supply unit 3 is short of raw materials. In the conventional aerosol deposition method, a vacuum pump is provided in the deposition chamber, and in FIG. 2, the illustration of the vacuum pump is omitted. As described above, in the present invention, the piezoelectric material is added to the substrate to enable precise fine movement along the x, y, and z axes.

Hereinafter, a method of depositing aerosolized carbon nanotubes on a substrate at high speed will be described.

The thermal spraying method is a method of obtaining a coating by activating a base powder at a high temperature by using plasma or thermal energy and injecting a high temperature / high pressure compressed air directly into the base material through a nozzle. Such spraying methods have typically been used in the field of ceramic coatings for aircraft or large structures. However, work must be done in fireproof clothing in an enclosed space, and there are serious disadvantages of noise pollution, sparks, air pollution and energy waste.

Recently, the coating method of the metal nanoparticles using the cold spray method, which has been developed by the thermal spraying method, has received much attention, which is related to the direct wiring of the metal nanoparticles. Cold spraying is a method of spraying compressed air through a nozzle similarly to a thermal spraying method and forming a coating by hitting a metal particle at a high speed with a base material at room temperature. At this time, the compressed gas container is heated to several hundred degrees to obtain a high pressure gas. It doesn't just go through the powder activation process like plasma in thermal spraying. Due to the resistive gas pressure in the deposition zone, ultra-fast acceleration is required, which requires a unique nozzle design, high temperature / high pressure compressed gas retention technology, and severe noise generation during coating.

The aerosol deposition method used in the present invention is based on the principle of vacuum expansion, the basis of which is based on the cluster beam source which is widely used in the basic science field. Supersonic cluster source by a vacuum injection of gas into a pulse or ultrashort 10 ³ - 10 ⁴ to obtain the acceleration in m / s. The reason for using the pulse method is to maintain high vacuum. Carrier gas intermittently entering a high vacuum state can obtain the best acceleration force by the pressure difference and the pumping speed of the pump. If a large amount of gas enters, such as in a spray or cold spray method, it is impossible to maintain a vacuum. The cluster source also during the aerosol is deposited on the substrate ^10-4 - maintaining the 10 ^-5 torr, and the AD method maintains a low pressure of 5-20torr.

The AD method uses heavier powders, so it doesn't gain tremendous acceleration like a cluster source, but it can produce a good deposition film even at subsonic speeds. An example is a 4 nm aerosol deposition method (Huh et. Al. Appl. Phys. Lett. 91, 093118, 2007). This paper presents an example in which 4 nm particles are accelerated to about 200m / s by a vacuum expansion principle and collide on a silicon substrate to have direct bonding between the substrates and the particles. Therefore, even when the aerosol is carbon nanotubes, it is possible to form a direct bond between the CNT-cathode electrode and the CNT-CNT by the same vacuum expansion principle. The aerosol deposition method is, above all, very quiet compared to the spraying method or the cold spray method, and is an environmentally friendly energy saving process technology compared to the CVD, PVD, spraying method, and cold spray method. Unlike the cluster source, it can be implemented with low vacuum technology.

의 운동 에너지(k)를 가지고 기판위에 충돌하는 도시한 것이다. [도 3]의 (a)는 탄소나노튜브가 수직 혹은 약간 비슴듬하게 기판에 충돌하는 경우를 보여준다. 탄소나노튜브가 기판에 충돌하는 순간 탄소나노튜브의 속도 v는 거의 0이 된다. 즉, 탄소나노튜브 선단부의 전진력 또는 움직임은 기판에 의하여 제지당하게 된다. 그 후 위쪽 기다란 꼬리 같은 탄소나노튜브 부분은 관성력에 의하여 계속 앞으로 전진하려한다. 따라서 탄소나노튜브 선단부측에서는 힘의 균형에 의하여 큰 굴곡현상이 일어나 탄소나노튜브가 접히고(bending) 접힌 탄소나노튜브 뒷부분들이 강하게 기판을 때리며 요동치게 된다(탄소나노튜브의 탄성계수는 매우 뛰어나 쉽게 구부려 질 수 있음). 이 과정에서 기판과의 직접적인 결합이 일어난다. 따라서 탄소나노튜브가 수직으로 기판에 박힌채 형태를 유지하기는 매우 어렵다. 그러나 기계적으로 절단된 짧은 탄소나노튜브들인 경우는 수직으로 기판에 서 있을 수 있다. 3 is a schematic view showing a simple phenomenon of deposition phenomenon when manufacturing a carbon nanotube electrode through the present invention. 3 is a carbon nanotube

It is shown to impinge on a substrate with its kinetic energy (k). (A) of FIG. 3 shows a case where the carbon nanotubes collide with the substrate vertically or slightly. The moment the carbon nanotubes strike the substrate, the velocity v of the carbon nanotubes becomes almost zero. That is, the forward force or movement of the carbon nanotube tip is restrained by the substrate. Afterwards, the carbon nanotube section, like the long tail, tries to move forward with inertia. Therefore, the carbon nanotubes are bent at the tip of the carbon nanotubes due to the balance of forces, causing the carbon nanotubes to bend and the back of the folded carbon nanotubes to strike the substrate strongly (the elastic modulus of the carbon nanotubes is very excellent and easily bent Can be lost). In this process, direct bonding with the substrate occurs. Therefore, it is very difficult to keep the shape of the carbon nanotubes embedded in the substrate vertically. However, mechanically cut short carbon nanotubes can stand vertically on the substrate.

It is very interesting to look at the phenomenon of the back of carbon nanotubes colliding with the substrate. The kinetic energy k of carbon nanotubes is converted into collision energy (E _impact ) at the moment of contact with the substrate, and various phenomena occur for carbon nanotubes to consume this impact energy (E _impact ). The disappearance of kinetic energy can be divided into five categories. Firstly, energy absorption by the substrate during collision, secondly CNT-substrate, CNT-CNT bond formation, thirdly CNT bending / defect formation / deformation, fourthly CNT fluctuation, fifthth generation of thermal energy (Friction, etc.) can be mentioned. Among them, bond formation and fluctuation are very important. Bond formation means that a pure carbon nanotube structure without organic matter or binder can be prepared. The rocking phenomenon is a phenomenon in which a strong swing on a substrate causes chemical bonds, folds, deformations, and complete loss of energy. As a result, even carbon nanotubes deposited side by side on a substrate have a significant amount of protrusions. (B) of FIG. 3 is a diagram illustrating a case where the carbon nanotubes collide with the substrate side by side. In order to dissipate the _impact energy (E _impact ) at the moment when the entire carbon nanotubes hit the substrate, a process similar to (a) of FIG. 4 is performed. As a result, the carbon nanotubes collide with the substrate to form mostly lying carbon nanotubes (“b” in FIG. 3) and have local protrusions (“a” in FIG. 3). That is, the protruding portion by one or both ends or intermediate folding of the carbon nanotubes is formed by aerosol deposition. When carbon nanotubes exit the aerosol chamber, there is a high probability that they will fly perpendicularly to the substrate by hydrodynamics, but when they expand and impinge on the substrate, they will be very low pressure and the direction of the carbon nanotubes colliding as the carrier gas movement is hindered by the substrate. It is expected to be disordered.

In another aspect, the present invention provides a carbon nanotube cathode manufacturing method characterized in that the carbon nanotube thin film patterning process by spray deposition of carbon nanotubes after the mask is disposed on the substrate. That is, in the present invention, by installing a mask having a predetermined pattern on the upper surface of the substrate, the carbon nanotube aerosol can be deposited only at a desired position of the substrate.

In addition, the resist surface formed by a lithography process on the surface of the electrode may be further deposited and then etched using a conventional lift-off method.

4 is a schematic diagram of an embodiment of a BLU or FED manufactured using the invention. In the illustrated example, the lower substrate and the upper substrate are spaced apart to face each other. In between, a spacer is provided. The interior space can be maintained in vacuum or filled with a suitable gas. The upper substrate may be, for example, a glass substrate coated with ITO (anode). A fluorescent film is coated on the anode on the upper substrate. A separate thin conductive film may be coated on the surface of the fluorescent film to prevent phosphor aging and to reflect light from the fluorescent material and to be exported through the upper glass substrate. The phosphor layer may have a suitable pattern against the underlying emitter.

The lower substrate may be, for example, a metal or ITO coated glass substrate. An emitter is formed on the lower electrode cathode by forming a continuous carbon nanotube film or a carbon nanotube layer etched through a predetermined patterning process through the AD method. A patterned insulating film is provided between the emitters, and a gate electrode is formed on the provided insulating film. In the BLU, when a predetermined voltage is applied to the cathode electrode, the gate electrode, and the anode electrode, electrons are emitted from the emitter by a voltage applied between the cathode electrode and the gate electrode. At this time, the electrons are emitted from the locally protruded carbon nanotubes. In addition, there is no organic matter and plays a role of cold sound tube by reducing contact resistance to the minimum by direct coupling between electrode-CNT and CNT-CNT.

Meanwhile, the carbon nanotube raw material further includes at least one raw material selected from the group consisting of nanoparticles, nanowires, nanorods, nanobelts, and powders. It is possible to further include a modified release carbon particles.

In addition, the carbon nanotube raw material may be a doped with impurities such as boron (B), phosphorus (P). In addition, the carbon nanotube raw material may be applied to the chemically surface modification. In addition, the aerosolization of the carbon nanotube raw material may be subjected to a grinding step.

In summary, the present invention relates to a method for manufacturing a field emission-free carbon nanotube electrode using an aerosol deposition technique, an apparatus for uniformly dispersing carbon nanotubes in the gas phase (aerosol chamber) and carbon dispersed therein The nanotube aerosol is provided with a method of producing a field emission emitter electrode by impinging on the cathode by the vacuum expansion acceleration principle. Carbon nanotube aerosol deposition can be carried out by the continuous method (CFM) or pulse method (CFM). The transport gas does not need to be heated in particular, and the distance between the nozzle and the substrate is preferably 30 cm or less, and the deposition angle between the nozzle and the substrate is not a problem. In addition, the aerosol chamber is mixed with the material of the other components to form a mixed aerosol and then deposited on the substrate by the vacuum expansion acceleration principle to produce a carbon nanotube-containing composite thin film.

The structure of the carbon nanotube emitter thus manufactured has the following characteristics in that it is a conventional carbon nanotube emitter. That is, (1) no organic matter or catalyst is required, and (2) most carbon nanotubes form a direct bond with the substrate side by side, and (3) carbon nanotubes fold at one or both ends of the carbon nanotubes or in the middle. Due to the formation of a large number of protrusions, (5) the presence of protrusions by intermediate folding of the deposited carbon nanotubes, (6) field emission at the protrusions is very effective, and (7) direct chemistry with the cathode electrode. Heat generated by bonding can be suppressed, and (8) high vacuum / high cleanness, which is an essential element in the cold cathode tube, can be maintained.

1 is a schematic diagram of a continuous aerosol deposition apparatus.

2 is a schematic diagram of a pulsed aerosol deposition apparatus configured to practice the present invention.

3 is a schematic diagram illustrating a phenomenon in which carbon nanotubes collide with a substrate and are deposited.

Figure 4 is a schematic diagram of an embodiment of a BLU or FED manufactured using the present invention.

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

1: aerosol chamber 2: carbon nanotube raw material

3: raw material supply part 4: flow control part

5: gas transportation pipe 6: porous membrane

7: aerosol opening and closing means 9: aerosol

10: aerosol transport pipe 11: nozzle

12 deposition chamber 13 fastening means

14 substrate 15 substrate holder

16: holder height adjusting unit 17: exhaust unit

Claims (10)

An aerosol chamber in which carbon nanotube raw materials are stored; A deposition chamber having a substrate disposed therein and having an exhaust unit for exhausting an internal gas; An aerosol transport tube having one end communicating with the aerosol chamber, the other end penetrating the deposition chamber, and an injection nozzle coupled to the end of the deposition chamber; Aerosol opening and closing means provided in the middle of the pipeline of the aerosol transport pipe; And A flow rate adjusting unit which sucks external general air and supplies it to the aerosol chamber; As a carbon nanotube electrode manufacturing method made by a pulsed aerosol deposition apparatus comprising a, (a) aerosolizing the carbon nanotube raw material by supplying external general air sucked by the flow control unit into the aerosol chamber as a transport gas; And (b) accelerating the aerosolized carbon nanotubes by a vacuum expansion principle, thereby spray-depositing a substrate disposed in a deposition chamber in communication with the aerosol chamber to form an electrode made of a thin film of carbon nanotubes; Including, In step (b), the aerosol transport pipe is intermittently opened and closed by the aerosol opening and closing means to induce a reduced pressure of the deposition chamber to increase the injection speed of the aerosolized carbon nanotubes, and aerosolized carbon nanotubes are deposited. A method of manufacturing a carbon nanotube electrode, characterized in that the finely dispersed carbon nanotube aerosol particles are deposited on the substrate by passing through the porous diaphragm in the aerosol chamber before being injected into the chamber. delete delete delete In claim 1, In the step (b), the carbon nanotube electrode manufacturing method is characterized in that the carbon nanotube thin film is patterned by spray deposition of carbon nanotubes after disposing a mask on the substrate. The method of claim 1 or 5, In the step (a), the carbon nanotube raw material further includes heterogeneous carbon particles, wherein the heterogeneous carbon particles are nanoparticles, nanowires, nanorods, nanorods, Carbon nanotube electrode manufacturing method characterized in that it further comprises at least one raw material selected from the group consisting of nanobelt (Nanobelt) and powder type. The method of claim 1 or 5, The step (a) is a carbon nanotube electrode manufacturing method, characterized in that the impurity is doped to the carbon nanotube raw material. The method of claim 1 or 5, Step (a) is a carbon nanotube electrode manufacturing method characterized in that the carbon nanotube raw material is chemically modified. The method of claim 1 or 5, The step (a) is a carbon nanotube electrode manufacturing method, characterized in that the grinding step before the aerosolization of the carbon nanotube raw material. The method of claim 1 or 5, The substrate applied in the step (b) is a carbon nanotube electrode manufacturing method, characterized in that the transparent conductive film or an opaque conductive film is coated.

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