JP2004107162A - Method for manufacturing carbon fiber, electron emitter having carbon fiber and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a carbon fiber 15 in which a film of a catalyst metal 13 on a substrate 11 is heated to form a catalyst particles 14 to which carbon is deposited for growth, wherein the density of the obtained carbon fiber 15 can be controlled. <P>SOLUTION: An alloy layer 12 is intervened between the substrate 11 and the catalyst metal 13, wherein the alloy layer 12 comprises at least a metal selected from Si, Al, Au, Ag, Cu and Pt and a metal selected from W, Mo, Ta, Ti and Cr. The density of the catalyst 14 is controlled by the composition ratio of the alloy layer 12, thereby controlling the density of the obtained carbon fiber 15. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention has a method for producing a carbon fiber which can be used for, for example, a hydrogen absorbing material of a hydrogen storage device, an electron emitting member of an image display device of a television broadcast or an image display device of a personal computer, and a carbon fiber using the method. The present invention relates to a method for manufacturing an electron-emitting device and an image display device.
[0002]
[Prior art]
Recently, carbon fibers such as CNT (Carbon Nano Tube) and GNF (Graphite Nano Fiber) have been actively used as electron emission members and hydrogen storage members of cold cathode electron sources. Carbon fibers such as CNT and GNF are characterized in that they have a nanometer-sized diameter and a length in the order of microns, and are extremely sharp and have a large aspect ratio. When a carbon fiber is used as an electron-emitting member of a cold cathode electron source and an extraction electrode is provided opposite to the cold cathode and a positive voltage is applied, an electric field enhancement effect occurs at the tip of the carbon fiber, resulting in an extremely high voltage of about several V / um. Electron emission can be generated only by applying a low electric field intensity.
[0003]
There is a trend to use this carbon fiber as an electron source for FED (Field Emission Display). The FED is a self-luminous display device provided with one or a plurality of field emission (FE) electron-emitting devices per pixel. If the self-luminous display device is used, the luminance is about the same as that of a CRT. Power consumption can be achieved, and an image display device that is thinner and lighter than a CRT can be manufactured.
[0004]
Conventionally, an arc discharge method or a CVD (chemical vapor deposition) method has been used for producing carbon fibers such as CNT and GNF. Above all, in the CVD method, carbon fibers can be easily obtained simply by spraying metal fine particles serving as a catalyst for carbon fiber growth on a substrate and heating the substrate in an atmosphere such as hydrocarbons. Has attracted attention as a way to create.
[0005]
In the above-mentioned CVD method, a method of spraying catalytic metal fine particles on a substrate is generally used. A thin film of a metal to be a catalyst is deposited on a substrate and the fine particles are heated. It is a method to make it. Although this method is a method that can easily produce catalyst metal fine particles, depending on the combination of the types of the catalyst metal and the substrate, all of the catalyst metal is diffused into the substrate during the heat treatment, and the catalyst metal is diffused. Fine particles may not be produced. In order to solve the above problem, a technique has recently been known in which a metal thin film such as TiN for suppressing the reaction between the catalyst metal and the substrate is interposed between the substrate and the catalyst particles to arrange carbon fibers ( For example, see Patent Document 1).
[0006]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2001-303250
[Problems to be solved by the invention]
However, in the related art, the density of catalyst particles [the density in the present specification refers to the quantity (number or number) per unit area. ] Has not been sufficiently discussed. Controlling the density of the catalyst particles at the surface will also control the density of the carbon fibers growing from the catalyst particles.
[0008]
Recently, in order to use carbon fiber as an electron source, it is necessary to efficiently generate electric field concentration, and it has been found that there is a density of carbon fiber suitable for causing electric field concentration efficiently. A technique for controlling the density of carbon fiber has been required.
[0009]
The present invention has been made in view of the above-mentioned conventional problems, and a method for producing a carbon fiber in which a catalyst metal film on a substrate is heated to form catalyst particles, and carbon is attached to and grown on the catalyst particles. An object of the present invention is to make it possible to control the density of carbon fiber.
[0010]
[Means for Solving the Problems]
The present inventors insert an alloy layer between the catalyst particles and the substrate, determine that the reaction between the catalyst metal and the alloy can be determined by the composition ratio of the alloy, and control the number of catalyst particles per unit area. I found it. Possible reasons for this control include the difference in the diffusion rate of the catalyst metal in the alloy phase and the presence of an unreacted phase in the alloy base material. It is considered that the density is controlled by the inter-reaction.
[0011]
As the amount of the catalyst metal reacting with the alloy increases, the probability of forming catalyst particles on the alloy surface decreases, and the number of catalyst particles existing on the alloy surface also decreases. By controlling the reaction between the catalyst metal and the alloy, the density of the catalyst particles can be controlled. As a result, if the density of the catalyst particles is controlled by controlling the reaction of the catalyst metal, the density of the carbon fibers is also controlled because one carbon fiber grows from one catalyst particle.
[0012]
That is, a first aspect of the present invention is to provide a method for producing a carbon fiber capable of controlling the density of the carbon fiber,
(A) An alloy layer containing at least a metal selected from Si, Al, Au, Ag, Cu and Pt and a metal selected from W, Mo, Ta, Ti and Cr on a substrate Arranging the
(B) forming catalyst particles on the alloy layer;
(C) forming a carbon fiber by bringing a gas containing carbon into contact with the catalyst particles and heating;
And a method for producing a carbon fiber.
[0013]
A first aspect of the present invention is that the carbon fiber is a carbon nanotube or a graphite nanofiber,
The catalyst particles are made of Ni, Fe, Co, Pd, Pt or an alloy thereof;
The step of forming the catalyst particles comprises a step of attaching a catalyst metal on the alloy layer, and a step of heating the catalyst metal at 400 ° C. to 900 ° C.
Is included as a preferable embodiment.
[0014]
A second aspect of the present invention is to provide a method for manufacturing an electron-emitting device having carbon fibers, in which parameters such as a threshold voltage of the electron-emitting device can be controlled.
(A) An alloy layer containing at least a metal selected from Si, Al, Au, Ag, Cu and Pt and a metal selected from W, Mo, Ta, Ti and Cr on a substrate Arranging,
(B) forming catalyst particles on the alloy layer;
(C) forming a carbon fiber by bringing a gas containing carbon into contact with the catalyst particles and heating;
And a method for manufacturing an electron-emitting device having carbon fibers.
[0015]
Further, a third aspect of the present invention is a method for manufacturing an image display device having a plurality of electron-emitting devices and a light-emitting member which emits light by irradiation of electrons from the electron-emitting devices, wherein the electron-emitting devices are formed of carbon fibers. And a method for manufacturing an image display device characterized by being manufactured by a method for manufacturing an electron-emitting device having the following.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
(Method of manufacturing carbon fiber)
FIG. 1 is an explanatory view showing an example of the method for producing a carbon fiber of the present invention.
[0017]
In FIG. 1, 11 is a substrate, and 12 is an alloy layer.
[0018]
First, as shown in FIG. 1A, an alloy layer 12 is formed on a substrate 11 by vapor deposition or the like.
[0019]
As the substrate 11, other than quartz, a metal such as W, Mo, Ta or the like, or an insulator such as soda lime glass or alumina can be used. The alloy forming the alloy layer 12 includes at least a metal selected from Si, Al, Au, Ag, Cu, and Pt and a metal selected from W, Mo, Ta, Ti, and Cr. Is used.
[0020]
Next, as shown in FIG. 1B, a catalyst metal 13 is provided on the alloy layer 12. The attachment of the catalyst metal 13 is performed by forming the catalyst metal 13 on the alloy layer 12 by, for example, a sputtering method. As the catalyst metal 13, it is preferable to use Co, Ni, Fe, Pd, Pt or an alloy thereof. By using these, the catalyst particles 14 (see FIG. 4C) described below can be formed of Co, Ni, Fe, Pd, Pt or an alloy thereof, and the carbon fibers 15 (FIG. 1D) (See Reference).
[0021]
Further, as shown in FIG. 1C, the substrate 11 on which the catalyst metal 13 film is formed on the alloy layer 12 is heated in a hydrogen atmosphere to generate catalyst particles 14. The density of the catalyst particles 14 can be controlled by the composition ratio of the metal constituting the alloy layer 12.
[0022]
For example, an alloy of W and Si has a phase having a strong bond at a composition ratio of WSi ₂ , and therefore, if the composition ratio is small and W is large, the ratio of unstable Si atoms is large. Further, the metal to be the catalyst metal 13 such as Ni, Co, Fe, Pd, and Pt has a formation temperature of NiSi of 400 ° C., a formation temperature of CoSi of 400 ° C., and a formation temperature of Pd ₂ Si of 200 ° C. Thus, it is easily silicidized with Si at a low temperature.
[0023]
On the other hand, metals such as W, Mo, and Ta are alloyed with the catalyst metal 13 even at the heating temperature of the growth temperature (400 ° C. to 900 ° C.) used for CVD growth of the carbon fiber 15 (see FIG. 1D). Does not change. Therefore, it is considered that when the substrate 11 is heated, the catalyst metal 13 reacts with the alloy 12 having unstable Si atoms, and the amount of the catalyst metal 13 existing on the surface decreases, and the density of the catalyst particles 14 decreases.
[0024]
As a heating method, a lamp annealing method, a resistance heating method, or the like can be used. The heating temperature is preferably from 400 ° C. to 900 ° C. in order to easily control the density of the catalyst particles 14.
[0025]
Finally, as shown in FIG. 1 (d), the substrate 11 having the alloy layer 12 and the catalyst particles 14 is heated in a gas atmosphere containing carbon, so that carbon fibers 15 grow from the catalyst particles 14. The carbon fibers 15 can be generated at a density substantially corresponding to the density of the catalyst particles 14. As the gas containing carbon, a vapor of an organic solvent such as ethanol or acetone can be used, but a hydrocarbon gas such as acetylene, ethylene, methane, propane, or propylene is preferable.
[0026]
In the above steps, when carbon is deposited and grown on the catalyst particles 14 on the alloy layer 12 of the substrate 11 to form carbon fibers 15, the density of the catalyst particles 14 is controlled by changing the composition of the alloy layer 12, Accordingly, the density of the growing carbon fiber 15 can be controlled. In addition, carbon nanotubes or graphite nanofibers can be obtained as the carbon fibers 15.
[0027]
(Method of manufacturing electron-emitting device having carbon fiber)
FIG. 2 is an explanatory view showing an example of a method for manufacturing an electron-emitting device having a carbon fiber according to the present invention.
[0028]
In FIG. 1, 11 is a substrate, and 12 is an alloy layer. The substrate 11 and the alloy layer 12 are the same as those described in the method for producing carbon fiber.
[0029]
As shown in FIG. 2A, a substrate 11 provided with an alloy layer 12 by vapor deposition or the like is prepared, and further, a region is limited on the alloy layer 12 using a metal mask (not shown), and a catalyst metal 13 is formed. Is formed by a sputtering method or the like. The catalyst metal 13 is also the same as that described in the method for producing carbon fiber.
[0030]
Next, as shown in FIG. 2B, the alloy layer 12 is patterned so as to become the gate electrode 17 and the cathode electrode 18 of the electron-emitting device later. At this time, the catalyst metal 13 is left on the gate electrode 17 and the cathode electrode 18. The distance between the gate electrode 17 and the cathode electrode 18 is generally about 1 to 100 μm, preferably 1 to 20 μm.
[0031]
Patterning can be performed by a commonly used etching technique. For example, it can be performed by forming a resist into a desired shape by photolithography, dry-etching the catalyst metal 13 and the alloy layer 12 using the resist as a mask, and finally removing the resist with a stripping solution or the like. .
[0032]
Next, as shown in FIG. 2C, a film of the catalyst metal 13 is formed on the alloy layer 12 patterned in the shape of the gate electrode 17 and the cathode electrode 18 as described in the method of manufacturing the carbon fiber. By heating the formed substrate 11 in a hydrogen atmosphere to generate catalyst particles 14 and further heating in a gas atmosphere containing carbon, carbon fibers 15 can be grown from the catalyst particles 14.
[0033]
After the growth of the carbon fiber, as shown in FIG. 2D, an anode electrode 16 is provided so as to face above the gate electrode 17 and the cathode electrode 18, and the gate electrode 17, the cathode electrode 18, and the anode electrode 16 are disposed. In the three-terminal electron-emitting device described above, a desired current density can be emitted by applying voltages Va and Vg to the anode electrode 16 and the gate electrode 17. Further, by changing the composition of the alloy layer 12, the density of the catalyst particles 14 is controlled, and accordingly, the density of the growing carbon fiber is controlled. As a result, the characteristics of the electron-emitting device can be controlled. It becomes.
[0034]
2C and 2D, the carbon fibers 15 are grown on both the gate electrode 17 and the cathode electrode 18. However, it is not necessary to provide the carbon fibers 15 on the gate electrode 17. When the carbon fiber 15 is provided only on the cathode electrode 18, when the catalyst metal 13 is formed on the alloy layer 12, for example, a metal mask (not shown) is used so that the catalyst metal 13 is not formed on a portion to be the gate electrode 17. do it.
[0035]
The electron-emitting device described with reference to FIG. 2 has a three-terminal structure. However, only the cathode electrode 18 is formed without forming the gate electrode 17, and the carbon fiber 15 is grown on the cathode electrode 18. An electron-emitting device having a diode structure in which electrons are extracted only by the electrode 16 may be used.
[0036]
(Method of manufacturing image display device)
An image forming apparatus can be configured by combining a plurality of electron-emitting devices and a light-emitting member that emits light by irradiation of electrons from the electron-emitting devices. When manufacturing the image display device, if the electron-emitting device is an electron-emitting device having the carbon fiber and the electron-emitting device having the carbon fiber is manufactured by the above-described manufacturing method, the electron-emitting device can be adjusted according to the performance of the image display device. The image display device can be manufactured while controlling the characteristics of the image display device.
[0037]
【Example】
Example 1
This embodiment will be described with reference to FIG.
[0038]
As shown in FIG. 1A, a substrate 11 on which an alloy layer 12 was deposited was prepared. As the substrate 11, a quartz plate was used, and as the alloy layer 12, an alloy having a composition ratio of W of 20% by weight and Si of 80% by weight was used.
[0039]
Next, as shown in FIG. 1B, a catalyst metal 13 was deposited on the alloy layer 12 to a thickness of about 5 nm by a sputtering method. Co was used as the catalyst metal 13.
[0040]
Next, as shown in FIG. 1C, the substrate 11 having the alloy layer 12 and the catalyst metal 13 was heated at 500 ° C. for about 20 minutes in a hydrogen atmosphere. Then, it was confirmed that catalyst particles 14 having a diameter of 10 nm to 50 nm were formed on the substrate 11 at a density of 10 ⁸ particles / cm ² .
[0041]
When a similar experiment was performed using WSi _{2 for the} alloy layer 12, it was confirmed that the catalyst particles 14 were formed at a density of about 1 × 10 ¹⁰ particles / cm ² . When the same experiment was performed using an alloy containing 10 wt% of W and 90 wt% of Si for the alloy layer 12, catalyst particles 14 were formed at a density of about 5 × 10 ⁷ particles / cm ^2. Was confirmed. Further, similar results were obtained even when the alloy composition was MoSi, TaSi, TiSi, or CrSi.
[0042]
Although the lamp annealing method was used as the heating method, similar results were obtained with other heating methods such as the resistance heating method.
[0043]
Finally, as shown in FIG. 1D, when the substrate 11 having the alloy layer 12 and the catalyst particles 14 was heated at 500 ° C. for about 20 minutes in an ethylene atmosphere, the carbon fibers 15 (graphite nano Fibers) were grown and produced on the surface at a density of 10 ⁸ fibers / cm ² .
[0044]
Example 2
This embodiment will be described with reference to FIG.
[0045]
As shown in FIG. 2A, a substrate 11 on which an alloy layer 12 was deposited was prepared. As the substrate 11, soda lime glass was used. As the alloy layer 12, an alloy having a composition ratio of W of 40% by weight and Au of 60% by weight was used.
[0046]
An area was limited on the alloy layer 12 using a metal mask (not shown), and a catalyst metal 13 was deposited by sputtering to a thickness of about 5 nm. Ni was used as the catalyst metal 13.
[0047]
Next, as shown in FIG. 2B, the alloy layer 12 was patterned so as to become the gate electrode 17 and the cathode electrode 18 of the electron-emitting device later. At this time, the catalytic metal 13 was left on the gate electrode 17 and the cathode electrode 18 so that the distance between the gate electrode 17 and the cathode electrode 18 was 5 μm.
[0048]
For patterning, a resist is formed in the shape of the gate electrode 17 and the cathode electrode 18 by photolithography, the catalyst metal 13 and the alloy layer 12 are dry-etched using the resist as a mask, and finally, the resist is removed with a stripper. I went by. Dry etching was performed at 50 sccm Ar, 1 Pa, and 500 W.
[0049]
Next, as shown in FIG. 2C, the substrate 11 having the alloy layer 12 and the catalyst metal 13 was heated at 600 ° C. for about 20 minutes in a hydrogen atmosphere. Then, it was confirmed that catalyst particles 14 having a diameter of 20 nm to 50 nm were formed on the substrate 11 at a density of 10 ⁸ particles / cm ² .
[0050]
When the substrate 11 having the alloy layer 12 and the catalyst particles 14 was heated at 600 ° C. for about 20 minutes in an ethylene atmosphere, it was observed that carbon fibers 15 (graphite nanofibers) grew from the catalyst particles 14.
[0051]
Lastly, as shown in FIG. 2D, an anode electrode 16 is provided so as to face a position 2 mm away from the substrate 11 to constitute an electron-emitting device, and a voltage of 10 kV is applied to the anode electrode 16. At the same time, a voltage of 30 V was applied to the gate electrode 17 to emit electrons. In the case where a Ti electrode is used instead of the alloy layer 12, a voltage of 10 kV is applied to the anode electrode 16 and a voltage of 50 V is required for the gate electrode 17 in order to obtain electron emission at the same current density as described above. did.
[0052]
【The invention's effect】
As described above, according to the method for producing a carbon fiber of the present invention, the density of the obtained carbon fiber can be controlled. In addition, when an electron-emitting device having carbon fibers is manufactured using this, characteristics of the obtained electron-emitting device can be controlled. Further, according to the method of manufacturing an image display device of the present invention, it is possible to perform manufacturing by controlling the characteristics of the electron-emitting device according to the performance of the image display device.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing one example of a method for producing a carbon fiber of the present invention.
FIG. 2 is an explanatory view showing an example of a method for manufacturing an electron-emitting device having a carbon fiber according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 Substrate 12 Alloy 13 Catalyst metal 14 Catalyst particle 15 Carbon fiber 16 Anode electrode 17 Gate electrode 18 Cathode electrode

Claims (6)

A method for producing a carbon fiber, wherein (A) at least a metal selected from Si, Al, Au, Ag, Cu and Pt and a metal selected from W, Mo, Ta, Ti and Cr on a substrate. Arranging an alloy layer containing the metal and
(B) forming catalyst particles on the alloy layer;
(C) forming a carbon fiber by bringing a gas containing carbon into contact with the catalyst particles and heating;
A method for producing a carbon fiber, comprising: The method according to claim 1, wherein the carbon fiber is a carbon nanotube or a graphite nanofiber. 3. The method according to claim 1, wherein the catalyst particles are made of Ni, Fe, Co, Pd, Pt or an alloy thereof. 4. The method according to claim 1, wherein the step of forming the catalyst particles comprises a step of attaching a catalyst metal on the alloy layer and a step of heating the catalyst metal at 400 to 900 ° C. 2. The method for producing a carbon fiber according to claim 1. A method for manufacturing an electron-emitting device having carbon fibers,
(A) An alloy layer containing at least a metal selected from Si, Al, Au, Ag, Cu and Pt and a metal selected from W, Mo, Ta, Ti and Cr on a substrate Arranging,
(B) forming catalyst particles on the alloy layer;
(C) forming a carbon fiber by bringing a gas containing carbon into contact with the catalyst particles and heating;
A method for producing an electron-emitting device having a carbon fiber, comprising: A method for manufacturing an image display device, comprising: a plurality of electron-emitting devices; and a light-emitting member that emits light when irradiated with electrons from the electron-emitting devices, wherein the electron-emitting devices are manufactured by the manufacturing method according to claim 5. A method for manufacturing an image display device, comprising:

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