JP2006294525A - Electron emission element, its manufacturing method and image display device using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electron emission element capable of reducing luminance dispersion and deterioration speed and having a uniform height; to provide its manufacturing method; and to provide a field emission type display (image display device) having high image quality, excellent efficiency, high resolution and high durability by using the electron emission element. <P>SOLUTION: This electron emission element is characterized by forming, on an electrode, spherical fine particles D comprising: oxidized diamond fine particles A each having oxidized surface; a transition metal catalyst B supported to the surfaces of the oxidized diamond fine particles A; and a nano-carbon material C radially grown from the transition metal catalyst B. Its manufacturing method and this field emission type display (image display device) using the electron emission element are also provided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electron-emitting device that emits electrons by using a field electron emission phenomenon, a method for manufacturing the same, and an image display device using the same, and more particularly, fine particles provided with fibrous carbon such as carbon nanotubes. The present invention relates to an electron-emitting device that has the characteristics of reducing luminance variation and deterioration rate as an electron-emitting source, a manufacturing method thereof, and an image display device using the electron-emitting device.

In recent years, there has been an increasing demand for thinner image display devices (or displays) and higher brightness, higher contrast, and wider viewing angle of the images. Along with this, development of micron-sized micro-electron emission devices as active electron sources for displays has been active.
Conventionally, as the electron-emitting device, a “heat emission type” element that emits electrons by applying a high voltage to a material such as tungsten heated to a high temperature has been used. However, in recent years, it is necessary to heat the material to a high temperature. Therefore, “cold cathode type” electron-emitting devices capable of emitting electrons even at a low voltage have been actively researched and developed. There are various types of such cold cathode type electron-emitting devices, but generally there are field emission type (FE type) and the like. In the FE type electron-emitting device, electrons are emitted from a cone-shaped protrusion made of silicon (Si) or molybdenum (Mo) by applying a voltage to the gate electrode and applying an electric field to the electron-emitting portion. .

As such a cold cathode type electron-emitting device, a new and advantageous cathode structure for a field emission display (FED) having features such as high-speed response and low power consumption has been clarified (for example, Patent Document 1).
In Patent Document 1, diamond that can have a negative electron affinity by performing a specific treatment is to be used as an electron emission source. As a configuration, diamond particles are used instead of a diamond film. We are trying to realize the simplification and cost reduction. Specifically, a conductive layer to be an electrode is formed on the substrate, and an electron emission portion made of diamond particles is further formed thereon. Diamond particles have a negative electron affinity due to a predetermined treatment. An electron extraction electrode is provided so as to face the diamond particles, and by applying a potential to the electron extraction electrode, electrons are extracted from the electron emission portion made of the diamond particles. Here, since the electron affinity of the surface of the diamond particles is negative, the electrons entering the diamond particles from the conductive layer are expected to be easily emitted from the diamond particles. As a result, it is expected that electrons can be taken out without applying a high voltage to the opposing electron extraction electrode, and since the electron emission portion is configured using diamond particles, It can be formed at a low cost.

Carbon nanotubes, on the other hand, have higher electrical conductivity than metals, good or moderate electrical conductivity (good conductors or semiconductors), chemically stable surfaces, and light weight that is comparable to that of diamonds. Due to their chemical and mechanical properties, they are likely to be applicable to future nanotechnology such as field emission electron sources, nanoscale electronic devices, chemical storage systems, mechanical reinforcements, etc.
Conventionally, as a carbon nanotube production method, as a gas phase method, a method by arc discharge in a gas atmosphere containing a carbon raw material such as hydrocarbon, a laser evaporation method in which graphite is irradiated by laser irradiation and formed by evaporation And a method in which a gas serving as a carbon raw material such as acetylene is pyrolyzed on a substrate on which a catalyst of cobalt metal or nickel metal is disposed (for example, see Patent Document 2). Recently, a method capable of producing a nanocarbon material at a significantly lower cost than a conventional arc discharge method has been proposed (for example, see Patent Document 3). In Patent Document 3, 0.1 g of a catalyst containing 5 wt% of nickel oxide as a metal component as a catalyst and diamond oxide having a particle diameter of 15 to 100 nm as a carrier is packed in a small fixed bed flow system reaction tube. A carbon nanotube having a hollow structure with a diameter of 15 to 100 nm is obtained by keeping the layer constant at 600 ° C. and performing a reaction by flowing methane as a raw material gas at a flow rate of 20 ml / min for 60 minutes. There has been proposed a method for obtaining an efficient and good carbon fiber by controlling the type and shape of the nanofiber.
However, in the method of Patent Document 3, since the nanocarbon material does not grow isotropically using diamond fine particles as nuclei and spherical fine particles cannot be obtained, the present inventors have previously made Japanese Patent Application No. 2004-2004. No. 153129 proposes a novel spherical fine particle (ie, marimocarbon) in which a nanocarbon material is grown radially with diamond as a core, which can make the characteristics of the material using the nanocarbon material fine particle uniform, and a method for producing the same. Yes.

As described above, a field emission display (FED) requires a good electron emission material, and as this electron emission material or electron emission element, a carbon nanotube or a nanocarbon material (nanocarbon material) is used. (For example, refer to Patent Documents 4 to 8.)
Specifically, Patent Document 4 discloses a method for manufacturing an electron emission source. A bundle paste in which a bundle composed of a plurality of carbon nanotubes gathered in a viscous solution having conductivity is prepared. A first step of forming a pattern made of a paste on the substrate, and irradiating the pattern surface with a laser selectively removes substances other than the bundle on the pattern surface. And a second step of forming an electron emission source for selectively removing carbon components other than the carbon nanotubes on the surface to emit electrons from the carbon nanotubes. In this structure, the surface of the printed pattern surface is irradiated with a laser so that the silver particles and the binder on the surface Can be removed, and the bundle can be exposed, and in addition, by this laser irradiation, the carbon nanotubes are exposed on the exposed bundle surface, so that electrons that are resistant and can emit more electrons The emission source can be made more easily.
Moreover, in patent document 5, it is an electron emission element provided with the 1st electrode and the electron emission part arrange | positioned on this 1st electrode, Comprising: This electron emission part is particle | grains or its aggregate. An electron-emitting device is proposed in which the particle includes a carbon material having a six-carbon ring structure. With this structure, a particle or a particle aggregate particularly including a carbon material having a six-carbon ring structure is proposed. By using the current collector as the electron emission portion, the electron emission device can be manufactured at low cost and can emit electrons efficiently. The carbon material having a six-carbon ring structure contains, for example, graphite or carbon nanotube as a main component.

Patent Document 6 discloses a carbon ink, an electron-emitting device, a method for manufacturing the electron-emitting device, and an image display device. The image display device includes carbon particles having at least a six-membered ring, and includes an organic binder and a solvent. A carbon ink containing support particles that are made into a paste and support a part of the carbon particles is applied to a predetermined position of a conductor patterned on the substrate, and further fired. With this configuration, carbon ink and an electron-emitting device with high field emission efficiency and a manufacturing method thereof are provided in an inexpensive and mass-productive process called printing, and a good electron-emitting device is provided for use in an image display device. Further, the present invention provides a configuration of an image display device that has high image quality and high efficiency by using the electron-emitting device.
Further, Patent Document 7 discloses an electron-emitting device, an electron-emitting source, a manufacturing method thereof, an image display apparatus using the same, and a manufacturing method thereof, and an electron capable of stably obtaining a large current by driving at a low voltage. In order to provide an emission device and a method for manufacturing the emission device, the electron emission device includes a conductive layer, and a fibrous object (for example, carbon) that is fixed to the conductive layer so as to bury part of the conductive layer. System materials and carbon nanotubes). In addition, this electron-emitting device selectively removes the conductive paste contained in the surface portion of the applied mixture, for example, by applying a mixture of the conductive paste and the fibrous object on the substrate. Then, it can be manufactured by a manufacturing method including a removing step of exposing a part of the fibrous object.
Further, in Patent Document 8, an electron emission composite particle in which a plurality of individual electron emission materials can exist in a state perpendicular to the substrate, a manufacturing method thereof, an electron emission source and a manufacturing method thereof, and an electron emission composite particle are disclosed. A composition for forming an emitter of an electron emission display device is proposed and selected from the group consisting of a metal, an oxide and a ceramic material in order to provide an electron emission device having excellent electron emission characteristics when electron emission starts at a low operating voltage. And a matrix particle 2 made of at least one kind of substance, and an individual 3 of a carbon-based substance that is partially embedded in the matrix particle 2 and the other part protrudes on the surface. Release composite particles and the like are disclosed.

However, in the electron-emitting devices and the manufacturing methods thereof disclosed in Patent Documents 4 to 7, a carbon material such as carbon nanotubes is applied to an electrode substrate together with a conductive paste and the like, and carbon nanotubes and the like are formed only by the application process. An effective electron-emitting device is not formed because it is laid down or buried in the paste. Therefore, an effective electron-emitting device is formed by exposing the carbon nanotubes and the like by employing a removal process.
In such a method, the height of the carbon nanotubes and the like becomes uneven, and as a result, the luminance of the field emission display (FED) is varied, or the electric field is concentrated on the carbon nanotubes having a high height. Therefore, there was a problem that it was destroyed from there and accelerated deterioration.

JP-A-7-282715 JP 2000-86217 A JP 2004-277241 A JP 2000-36243 A JP 2000-90813 A JP 2000-204304 A JP 2000-208027 A JP 2004-311407 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide a uniform height electron-emitting device capable of reducing luminance variation and deterioration rate, and a method for manufacturing the same, in view of the problems of the conventional electron-emitting device for field emission display (FED). Is to provide. Another object of the present invention is to provide a field emission display (image display device) that uses the electron-emitting device and has high image quality and efficiency, and high resolution and durability.

  As a result of intensive studies to achieve the above object, the inventors of the present invention produced spherical fine particles having a uniform diameter to which carbon nanotubes and the like were added, and the spherical fine particles were converted into a conductive viscous solution, for example, a conductive paste. At the same time, when applied on the electrode, the conventional technique required a process of removing the conductive paste or the like, but an electron-emitting device having a uniform height can be formed only by the application process and the drying process. The present inventors have found that, when the electron-emitting device is applied to a field emission display (FED), luminance variation and deterioration rate can be reduced. The present invention has been completed based on these findings.

That is, according to the first aspect of the present invention, the oxidized diamond fine particles (A) whose surfaces are oxidized, the transition metal catalyst (B) supported on the surfaces of the oxidized diamond fine particles (A), and the transition metal catalyst (B An electron-emitting device characterized in that spherical fine particles (D) composed of a nanocarbon material (C) grown radially from (2) are formed on an electrode.
According to the second invention of the present invention, in the first invention, the transition metal catalyst (B) is Ni or Co, and the nanocarbon material (C) is a carbon nanotube. An electron-emitting device is provided.
Furthermore, according to the third invention of the present invention, in the first invention, the transition metal catalyst (B) is Pd, and the nanocarbon material (C) is a coin stacked carbon nanograph. An electron-emitting device is provided.

According to a fourth aspect of the present invention, there is provided the electron-emitting device according to any one of the first to third aspects, wherein the spherical fine particles (D) have a diameter of 1 to 50 μm.
According to the fifth invention of the present invention, in any one of the first to fourth inventions, the spherical fine particles (D) are formed on the surface of the oxidized diamond fine particles (A) whose surface is oxidized by the transition metal catalyst (B). Is suspended in a gas phase composed of hydrocarbons and stirred, and heated to a catalytic reaction temperature at which the nanocarbon material is synthesized to grow the nanocarbon material on the surface of the diamond catalyst fine particle. An electron-emitting device is provided.

According to a sixth aspect of the present invention, there is provided the electron-emitting device according to any one of the first to fifth aspects, wherein the spherical fine particles (D) are formed in a single layer on the electrode. The
According to a seventh aspect of the present invention, there is provided the electron-emitting device according to any one of the first to sixth aspects, wherein the spherical fine particles (D) are fixed on the electrode with a conductive paste. Provided.

On the other hand, according to the eighth aspect of the present invention, the oxidized diamond fine particles (A) whose surfaces are oxidized, the transition metal catalyst (B) supported on the surfaces of the oxidized diamond fine particles (A), and the transition metal catalyst (B A conductive ink composition comprising spherical fine particles (D) composed of a nanocarbon material (C) grown radially from (1).
According to a ninth aspect of the present invention, there is provided the conductive ink composition according to the eighth aspect, wherein the spherical fine particles (D) are uniformly dispersed in the conductive paste. .

According to a tenth aspect of the present invention, there is provided an electron-emitting device comprising a step of applying the conductive ink composition according to the eighth or ninth aspect of the invention onto an electrode and a step of drying the same. A manufacturing method is provided.
According to an eleventh aspect of the present invention, there is provided an image display device comprising the electron-emitting device according to any one of the first to seventh aspects.

  According to the electron-emitting device and the method of manufacturing the same according to the present invention, in the conventional technology, the luminance variation of the field emission display (FED) is caused, or the electric field is concentrated on the carbon nanotube having a high height. However, there was a problem that the material was destroyed and the deterioration was accelerated. However, novel spherical fine particles in which nanocarbon materials such as carbon nanotubes were formed in a radial pattern (hereinafter referred to as spherical fine particles depending on the form thereof). Therefore, there is an effect that it is possible to provide an electron-emitting device having characteristics of reducing luminance variation and deterioration rate.

Hereinafter, the electron-emitting device and the manufacturing method thereof according to the present invention will be described in detail for each item.
The electron-emitting device of the present invention comprises oxidized diamond fine particles (A) having an oxidized surface, a transition metal catalyst (B) supported on the surface of the oxidized diamond fine particles, and a nanocarbon material (C) radially grown from the transition metal catalyst. The spherical fine particles (D) are formed on a predetermined electrode.

1. Method for Producing Spherical Fine Particles (Marimo Carbon) (D) As described above, the detailed production method and production apparatus for spherical fine particles (D), that is, marimo carbon, are described in Japanese Patent Application No. 2004-153129. This will be briefly described below.
As the production apparatus, a fluidized gas phase synthesis apparatus is used, and the marimocarbon production apparatus is composed of a vertically disposed reaction tank containing diamond catalyst fine particles and hydrocarbons provided at the lower and upper parts of the reaction tank, respectively. An inlet for introducing the gas, a discharge outlet for discharging the gas, a heating device disposed so as to surround the reaction tank, and a filter that allows the gas to pass without passing through the diamond catalyst particles. Moreover, you may have a mixing apparatus for mixing reaction auxiliary gas and dilution gas with the gas which consists of hydrocarbons.

In order to produce marimocarbon using the above fluidized gas phase synthesizer, the following process is performed. Diamond catalyst fine particles in which the surface of oxidized diamond fine particles whose surfaces are oxidized are supported by a transition metal catalyst are arranged on a filter. For the method for producing the diamond catalyst fine particles, see Patent Document 3.
The hydrocarbon as a raw material is a hydrocarbon having 1 to 30 carbon atoms, and may include unsaturated hydrocarbons such as ethylene and acetylene in addition to saturated hydrocarbons such as methane, ethane and propane.
In addition, the raw material hydrocarbon may be introduced and reacted alone on the catalyst, or may be introduced and reacted together with the carrier gas on the catalyst. As such a carrier gas, a reducing gas such as hydrogen or carbon monoxide, or a gas obtained by mixing an inert gas such as nitrogen with the reducing gas can be used.

A gas composed of hydrocarbons is introduced at a predetermined flow rate from the inlet and discharged from the outlet. The predetermined flow rate of the gas is a flow rate at which the diamond catalyst fine particles float in the reaction vessel and is stirred. If the reaction vessel is made of fused silica, the flow rate is set by checking the state with the naked eye. The particle diameter of the diamond fine particles may be 500 nm or less, and if it is too large, it is difficult to float. The temperature is preferably in the range of 400 to 600 ° C. when Ni, Cr or Pd is used as the catalyst and methane is used as the hydrocarbon gas. Moreover, since the particle diameter of the produced marimocarbon increases in proportion to the time of floating and stirring at a predetermined temperature, the reaction time may be set according to the purpose of use. In the case of the electron-emitting device of the present invention, the diameter of marimocarbon, that is, the spherical fine particles (D) is preferably 1 to 50 μm, and the reaction time is preferably 3 hours.
The commercially available diamond surface is not only completely carbon but also oxygen and the like. Accordingly, when oxidized under a predetermined condition to make the diamond surface uniform, “oxidized diamond” is generated. Apparently, the diamond oxide is not much different from the first commercially available product, but since it has been treated to a certain degree, it is not affected by the lot of the commercial product, and the optimum diamond is prepared as a catalyst support in the present invention. Can do. “Diamond” as a carrier in the present invention is used to include “diamond diamond” that has been treated in this manner.

  If Ni or Co is selected as the transition metal, the nanocarbon material constituting marimocarbon becomes carbon nanotubes, and if Pd is chosen, the nanocarbon material constituting marimocarbon becomes coin-stacked carbon nanographite. What is necessary is just to set a transition metal according to the objective. In the case of the electron-emitting device of the present invention, Ni is preferred.

  According to this method, since the diamond catalyst fine particles are suspended and stirred in the reaction vessel, nanocarbon materials having the same length grow radially over the entire surface of the diamond catalyst fine particles, as shown in FIG. The marimo-like fine particles are obtained.

2. Electron-emitting device and method for producing the same The electron-emitting device of the present invention is obtained by applying a conductive ink composition in which the above spherical fine particles (marimocarbon) are uniformly dispersed in a conductive viscous solution, that is, a coating step. Is manufactured.

First, an electrode is produced by forming a conductive paste on a substrate such as a glass substrate using a thick film technique. The conductive paste is preferably made of highly viscous ITO (Indium Tin Oxide). Alternatively, it may be made of a metal material such as aluminum or chromium. As the thick film technology, a screen printing method, a slurry method, or the like can be used. In particular, when the conductive paste is made of ITO, the conductive paste of ITO preferably contains a solid component at a certain ratio or more. At this time, the conductive paste suitable for printing has a viscosity in the range of 10,000 to 100,000 cps, and the solid component in the conductive paste is preferably present at 10 to 80% by weight.
The screen printing method is a method in which a conductive paste is extruded onto a substrate (substrate) to be printed through a mesh of screen mesh using a squeegee or a rubber roller. Since this is simple and the plate making process for forming a pattern is relatively easy, it is widely used for printing in various fields.
The screen printing of the conductive paste includes a process of fixing the substrate and the screen mesh to a screen printer and printing the conductive paste on the substrate using a squeegee.

Next, a conductive ink composition is applied on the formed electrode. The conductive ink composition is obtained by uniformly dispersing the spherical fine particles (marimocarbon) in a conductive viscous solution such as a silver paste. The conductive ink composition is preferably applied to the upper side of the electrode and formed into a film by the screen printing method or the slurry method.
In the prior art, as a method for manufacturing an electron-emitting device,
(I) forming a cathode electrode on the substrate;
(Ii) forming a conductive layer mixed with a conductive material on the cathode electrode;
And (iii) a step of etching the conductive layer with an acid to expose a conductive substance in the conductive layer to form an electron emission portion, and in many cases, an electron is formed when an emitter is formed. In order to expose a nanocarbon material that emits, for example, carbon nanotubes (CNT), on the surface of the emitter, a removal step of a conductive paste or the like was essential. Since the thickness is constant, only the coating process and the drying process can expose a nanocarbon material having an electron emission action, such as carbon nanotubes (CNT), on the surface of the emitter, thereby forming an electron-emitting device having a uniform height.

  The conductive viscous solution is preferably a conductive paste, particularly preferably a silver paste, and the composition ratio of the conductive ink composition is 0.5 to 0.8 silver when spherical fine particles (marimocarbon) are set to 1. And 2 to 20 binders.

3. Field emission display (FED)
A field emission display (FED) according to the present invention can be manufactured using the electron-emitting device of the present invention. As shown in FIG. 3, the field emission display (FED) is constructed by forming a vacuum vessel with two substrates (insulators) (6, 12) on the upper and lower sides, and using an electron emission source on the lower surface in the vessel. An emitter, a cathode (cathode) (8), and a Kate electrode (9) are provided. On the other hand, an anode (anode) (10) and a light emitting phosphor (11) for electrons to reach the upper surface are provided. The emitter of the present invention is used for the emitter. An image display device forms an image by emitting light from the phosphor layer with electrons emitted from the electron-emitting device.
Conventionally, it was difficult to produce a sharp and uniform tip shape with good reproducibility, and there were problems such as destruction of the emitter. However, in the present invention, the electron emission can be obtained at a relatively low voltage. By applying the electron-emitting device of the invention as an emitter, a field emission display (FED) has good display characteristics and can reduce luminance variation and deterioration rate.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples of the present invention, but the present invention is not limited to these Examples.

[Example 1]: Production of spherical fine particles (marimocarbon) and electron-emitting device First, commercially available diamond powder having a particle size of 500 nm or less was used, and Ni, Co, or Pd was impregnated according to the method of Patent Document 3. Each supported diamond catalyst fine particle was prepared. 1-5 g of diamond catalyst fine particles, a flow rate of methane gas of 50-200 ml / min, a reaction temperature of 400-600 ° C., and using a fluidized gas phase synthesizer, spherical fine particles (marimocarbon) as shown in FIG. 1 are produced. did. With the diamond catalyst fine particles (1) as the core, nanofibers (2) having a nano-sized diameter grow radially.

  Next, the spherical fine particles (marimocarbon) prepared using the diamond catalyst fine particles impregnated and supported with Ni were uniformly dispersed in the conductive paste to prepare a conductive ink composition. This conductive ink composition was applied onto an ITO electrode formed on glass and dried to produce an electron-emitting device (see FIG. 2). Similarly, a conductive ink composition using spherical fine particles (marimocarbon) produced using diamond catalyst fine particles impregnated and supported with Co or Pd was produced, and an electron-emitting device was produced according to the same procedure.

  The electron-emitting device fabricated as described above was used as an emitter of a field emission display (FED) cathode (see FIG. 3). As a cold cathode of FED, it is placed facing the anode coated with phosphor in vacuum, and when voltage is applied, electrons are drawn out in the vacuum and accelerated to collide with the phosphor and excited light can be emitted. It was.

  Since the electron-emitting device of the present invention has an excellent function of reducing luminance variation and deterioration rate, it can be used for FED, imaging device, electron beam device, microwave traveling wave tube, lighting device, organic light emitting device, and electrochemical device. It is likely to be applicable as a key device.

It is a figure which shows the structure of the spherical fine particle (marimo carbon) based on this invention. It is a schematic diagram explaining the electron-emitting device of this invention. It is a figure explaining the field emission display which concerns on this invention.

Explanation of symbols

1 transition metal-supported diamond 2 nanocarbon material such as carbon nanotube (CNT)
DESCRIPTION OF SYMBOLS 3 Conductive paste 4 Electrode 5 Transition metal catalyst 6 Substrate, for example, glass substrate 7 Spherical fine particle 8 Cathode 9 Gate electrode 10 Anode 11 Phosphor 12 Insulator 13 Electron 14 Gate voltage 15 Anode voltage

Claims (11)

  Oxidized diamond fine particles (A) having an oxidized surface, a transition metal catalyst (B) supported on the surface of the oxidized diamond fine particles (A), a nanocarbon material (C) radially grown from the transition metal catalyst (B), An electron-emitting device characterized by forming spherical fine particles (D) comprising:   The electron-emitting device according to claim 1, wherein the transition metal catalyst (B) is Ni or Co, and the nanocarbon material (C) is a carbon nanotube.   The electron-emitting device according to claim 1, wherein the transition metal catalyst (B) is Pd, and the nanocarbon material (C) is a coin-laminated carbon nanographite.   The electron-emitting device according to any one of claims 1 to 3, wherein the spherical fine particles (D) have a diameter of 1 to 50 µm.   The spherical fine particles (D) are obtained by suspending and stirring the diamond catalyst fine particles in which the transition metal catalyst (B) is supported on the surface of the oxidized diamond fine particles (A) whose surfaces are oxidized in a gas phase composed of hydrocarbons. The electron-emitting device according to claim 1, wherein the electron-emitting device is formed by heating to a catalytic reaction temperature at which the nanocarbon material is synthesized and growing the nanocarbon material on the surface of the diamond catalyst fine particles.   6. The electron-emitting device according to claim 1, wherein the spherical fine particles (D) are formed in a single layer on the electrode.   The electron-emitting device according to any one of claims 1 to 6, wherein the spherical fine particles (D) are fixed on the electrode with a conductive paste.   Oxidized diamond fine particles (A) having an oxidized surface, a transition metal catalyst (B) supported on the surface of the oxidized diamond fine particles (A), a nanocarbon material (C) radially grown from the transition metal catalyst (B), A conductive ink composition comprising spherical fine particles (D) comprising:   The conductive ink composition according to claim 8, wherein the spherical fine particles (D) are uniformly dispersed in the conductive paste.   A method for producing an electron-emitting device, comprising: a step of applying the conductive ink composition according to claim 8 or 9 on an electrode; and a step of drying the conductive ink composition.   An image display device comprising the electron-emitting device according to claim 1.

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