JP5300193B2 - Method for manufacturing electron-emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of an electron emission substance capable of surely constituting an electron emission part with a required structure under a lower temperature condition, and a display device. <P>SOLUTION: In the manufacturing method of the electron emission element containing a carbon material and shaped in a fibrous or tubular form forming graphite nanotube 21 with an end face 22a of a graphene sheet 22 exposed at a side part on a conductive catalyst layer 12 with conductivity, the conductive catalyst layer 12 is heated, mixture gas is guided in around the conductive catalyst layer 12, and plasma is generated to carry out CVD. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a method for manufacturing an electron-emitting device and a display device, and more particularly to a method capable of lowering the temperature of a manufacturing process.

As a kind of display device, a field emission display (hereinafter referred to as “FED”) using an electron-emitting device is known (see, for example, Patent Document 1). This type of display device includes an electron-emitting device and a display unit that are arranged at regular intervals. The electron-emitting device is configured, for example, by forming a cathode electrode layer on a glass substrate, and forming an electron-emitting layer having an electron-emitting material and a gate electrode on the cathode electrode layer. On the other hand, the display unit includes an anode electrode layer formed to oppose the electron emission unit. When a predetermined voltage is applied to the cathode electrode layer, the gate electrode layer, and the anode electrode layer in a reduced pressure state, electrons are emitted from the electron emission portion, and the display portion emits light by colliding with the display portion. As the electron emission portion, graphite nanotube (GNT), graphite nanofiber (GNF) carbon nanotube (CNT), or the like is used. Generally, GNT and GNF are manufactured by a thermal CVD method, and the heating temperature at that time is set to 500 ° C. or higher (see, for example, Patent Document 2). CNTs are formed using a plasma CVD method, and the heating temperature at that time is about 600 ° C.
Japanese Patent Laying-Open No. 2004-186015 (FIG. 1) JP 2001-288625 A (FIG. 2)

  In the electron-emitting device, it is required to form an electron-emitting portion having a desired structure. However, the above method requires a high temperature environment in order to obtain the desired structure.

  Therefore, an object of the present invention is to make it possible to reliably configure an electron emission portion having a desired structure in a lower temperature environment.

According to one aspect of the present invention, there is provided a method for manufacturing an electron-emitting device in which an electron-emitting device including a carbon material and having a fibrous or tubular shape is formed on a conductive catalyst layer. In a reduced-pressure atmosphere, a mixed gas is introduced around the catalyst layer, and plasma is generated to perform CVD to form the electron-emitting portion and the heating portion when forming the electron-emitting portion. By controlling the temperature and the mixing ratio of the mixed gas, the shape or size of the catalyst nuclei is controlled , the size of the catalyst nuclei is 50 nm or more, and graphite nanotubes are used as the electron emission portions. It is characterized by forming .

Another aspect is characterized in that the size of the core of the catalyst is 10 nm or more and less than 50 nm, and a graphite nanofiber is formed as the electron emission portion.

  According to the present invention, it is possible to reliably configure an electron-emitting device having a desired structure in a lower temperature environment. Further, according to the present invention, a display device having such an electron-emitting device can be configured.

[First Embodiment]
First, the image display device 1, the electron-emitting device 10 and the like according to the first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a perspective view showing a portion corresponding to one pixel of the entire image display device 1. FIG. 2 is an enlarged cross-sectional view showing a portion A of the image display device 1 of FIG. FIG. 3 is a cross-sectional view showing the electron emission portion of FIG. Arrows X, Y, and Z in FIGS. 1, 2, and 3 indicate three directions orthogonal to each other. In each figure, the configuration is appropriately enlarged, reduced, or omitted for explanation.

  As shown in FIG. 1, an image display device 1 as an example of a display device includes an electron-emitting device 10 and a display unit 30 that emits light by electrons emitted from the electron-emitting device 10. The electron-emitting device 10 and the display unit 30 are joined to face each other with a predetermined gap secured.

  An electron-emitting device 10 shown in FIGS. 1 and 2 includes a substrate 11, a plurality of conductive catalyst layers 12 formed on the substrate 11, and an insulating layer 13 formed on the substrate 11 and the conductive catalyst layer 12. And a plurality of gate electrodes 14 formed on the insulating layer 13. An emitter hole 15 is formed in the insulating layer 13 and the gate electrode 14, and a carbon layer 20 as an example of an electron emission layer is formed on the conductive catalyst layer 12 in the emitter hole 15.

  The substrate 11 is made of glass, silicon, or the like to a thickness of about 1 mm, and has a predetermined area necessary for displaying an image. Here, for example, three conductive catalyst layers 12 are formed in parallel on the substrate 11 corresponding to one pixel. For example, the conductive catalyst layer 12 is made of a catalyst metal such as nickel and has a thickness of about 200 nm and is formed in a rectangular shape that extends in the Y direction.

As shown in FIGS. 1 and 2, the insulating layer 13 is made of silicon oxide (SiO ₂ ) or the like, and is formed on the upper surface of the substrate 11 and the conductive catalyst layer 12. The three gate electrodes 14 are formed of a metal such as aluminum in a rectangular shape extending in the X direction described above, and are arranged at positions corresponding to three-color phosphors 33 to 35 described later. These gate electrodes 14 are connected to a drive circuit and subjected to matrix control.

  As shown in FIG. 1, a plurality of circular emitter holes 15 are formed in a portion where the gate electrode 14, the insulating layer 13, and the conductive catalyst layer 12 intersect and overlap each other. Here, as shown in FIG. 2, the emitter hole 15 is formed by removing only the gate electrode 14 and the insulating layer 13 by etching or the like.

  As shown in FIGS. 2 and 3, a carbon layer 20 as an electron emission layer is formed on the conductive catalyst layer 12 exposed in the emitter hole 15.

  The carbon layer 20 includes graphite nanotubes 21 as a large number of electron emission portions that are intertwined with each other. As shown in FIG. 4, the graphite nanotube 21 is a cylindrical substance having a carbon material as a main component and the end face 22 a of the graphene sheet 22 exposed on the outer surface. The graphite nanotubes 21 are formed in a columnar shape having a through hollow portion 21a in which a graphene sheet 22 is laminated via a conductive catalyst layer 12 of nickel which is a catalyst metal and filled with hollow or amorphous carbon at the center. FIG. 4 shows a state in which a plurality of graphite nanotubes 21 are upright to facilitate the explanation of the configuration. The graphite nanotube 21 is 10 times longer than the diameter in the axial direction, for example, has a diameter of about 50 nm and a length of about 1 μm, has a large allowable current density, and emits electrons when a low voltage is applied under reduced pressure. To do. Electrons are emitted from the end face 22 a of the graphene sheet 22 exposed at the side wall 21 b of the graphite nanotube 21. The graphite nanotube 21 is located at a lower height than the gate electrode 14.

On the other hand, in FIGS. 1 and 2, the display unit 30 includes an anode substrate 31, an anode electrode 32 formed on the anode substrate 31, and three colors of R, G, and B applied to the surface of the anode electrode 32. Phosphors 33-35. Here, the anode substrate 31 is made of a transparent material such as glass, which is the same material as the substrate 11, in order to improve sealing with the substrate 11. The anode electrode 32 is formed on the surface facing the substrate 11 and is made of a metal such as aluminum. The anode electrode 32 is connected to the drive circuit. On the other hand, the three color phosphors 33 to 35 have the rectangular shape extending in the X direction described above, and are arranged corresponding to the gate electrode 14, respectively. Thus, a predetermined gap is ensured for bonding. The gap is in a reduced pressure state of about 10 ⁻⁸ Torr, for example, and this reduced pressure state is maintained by a getter (not shown).

Hereinafter, a method for manufacturing the electron-emitting device 10 of the present embodiment described above will be described with reference to FIG. 1 or FIG.
First, nickel is formed on the substrate 11 by sputtering or the like to form the conductive catalyst layer 12. Next, the insulating layer 13 is formed on the conductive catalyst layer 12 and the entire upper surface of the substrate 11 on which the conductive catalyst layer 12 is not formed. Next, a metal such as aluminum different from the catalyst metal used in the conductive catalyst layer 12 is formed on the surface of the insulating layer 13 by sputtering or the like, thereby forming the gate electrode 14.

  Further, an emitter hole 15 is formed at a predetermined position so that the catalytic metal is exposed through the gate electrode 14 and the insulating layer 13. Specifically, first, a mask having a circular opening is placed on the gate electrode 14. Thereafter, using the mask, the gate electrode 14 is dry-etched with a predetermined etching gas to be opened. Next, dry etching is performed until the insulating layer 13 reaches the conductive catalyst layer 12 with a predetermined etching gas, whereby an emitter hole 15 having a predetermined shape is formed.

After forming the emitter hole 15, the substrate 11 is introduced into the plasma CVD apparatus shown in FIG. 5 and heated to 400 to 450 ° C. to decompose the mixed gas of CH ₄ (methane) and H ₂ (hydrogen) with plasma. Then, the carbon layer 20 is formed on the exposed conductive catalyst layer 12.

  The plasma CVD apparatus is a vacuum container provided with a heater 24, a substrate support portion 25, and the like. This plasma CVD apparatus has an adjustment function capable of adjusting a pressure, a gas type, a gas flow rate, an RF power, a heater temperature, a processing time, and the like as conditions for the plasma CVD process.

Here, first, the substrate 11 on which the conductive catalyst layer 12 is formed is placed on the substrate support portion 25 in the plasma CVD apparatus 23, and as a pretreatment, a discharge treatment is performed with only hydrogen gas for about 10 minutes. Next, a predetermined flow rate of methane gas is added to perform this process. Here, the plasma type is a microwave excitation type. Here, the pressure, gas flow ratio, and temperature are set to the following conditions as shown in the upper part of FIG. That is, the internal pressure of the container is 4 kPa, and CH ₄ and H ₂ are used as gas types. The gas flow rate of CH ₄ is 10 [sccm], and the gas flow rate of H ₂ is 80 [sccm]. Further, the temperature of the heater 24 is set to 400 ° C., the RF power is set to 400 W, and the processing time is set to 30 minutes.

  When exposed to plasma CVD under the above conditions, the nickel conductive catalyst layer 12 formed in a film shape on the substrate 11 has a structure having a granular nickel catalyst core 12a as a catalyst core having a predetermined size. Become. As shown in the upper part of FIG. 7, the size and shape of the catalyst core 12a are determined in accordance with the plasma processing conditions. Here, for example, the catalyst core 12a has a sharp diamond shape with a curvature radius of about 5 nm or less. And about 100 nm in size. Since the conductive catalyst layer 12 is composed of a catalyst metal such as nickel, it acts as a catalyst layer, so that a carbon substance grows directly on the conductive catalyst layer 12 based on the catalyst core 12a. As shown in FIG. 7, the structure of the carbon material as the electron emission portion that grows depends on the size and shape of the catalyst core 12a. Here, graphite nanotubes 21 shown in FIG. 4 grow on the basis of a diamond-shaped catalyst nucleus 12a having a size of about 100 nm. Thus, in the emitter hole 15 where the conductive catalyst layer 12 is exposed, a large number of graphite nanotubes 21 are formed on the conductive catalyst layer 12 in a random direction, and the carbon layer 20 is configured.

  On the other hand, the anode electrode 32 is formed on the anode substrate 31 made of a transparent material such as glass, and the phosphors 33 to 35 are applied to the anode electrode 32 to manufacture the display unit 30. Further, the periphery of the substrate 11 and the periphery of the anode substrate 31 are joined with a sealing material in a state where a predetermined gap is secured via the spacer. Thus, the electron-emitting device 10 and the display unit 30 are joined, and the image display device 1 is completed.

Next, the operation of the image display apparatus 1 according to the present embodiment will be described with reference to FIGS. 1 and 2.
When predetermined voltages Va (for example, 1 to 15 KV) and Vd (for example, 0 to 100 V) are respectively applied to the anode electrode 32, the conductive catalyst layer 12 as the cathode electrode, and the gate electrode 14 (see FIG. 2 above). An electric field is generated. Here, since the end face 22a of the graphene sheet 22 exposed on the side wall 21b of the graphite nanotube 21 as the carbon material grown on the conductive catalyst layer 12 is thin, electric lines of force concentrate here. As a result, a strong electric field is obtained and drawn out by this electric field, and electrons are emitted from the side wall 21b of the graphite nanotube 21 as the carbon material. The electrons are guided to the gate electrode 14 and enter the anode electrode 32 on which the phosphors 33 to 35 are applied. Thus, the phosphors 33 to 35 are excited and emit light. A desired image is displayed through the transparent anode substrate 31 by this light emission. Here, light emission can be controlled by matrix control of the voltage applied to the gate electrode 14, and gradation display for each pixel is possible.

  The electron-emitting device 10 and the image display device 1 according to the present embodiment have the following effects.

  By setting the size or shape of the catalyst core 12a which is a catalyst particle, the substrate temperature when forming the graphite nanotube 21 can be lowered to about 400 ° C. to 450 ° C. by forming it by the plasma CVD method. The electron emission portion can be formed directly on the substrate 11. Moreover, since the heat-resistant conditions required for the substrate 11 can be relaxed, the cost of the substrate 11 can be reduced.

  Further, as shown in FIGS. 6 and 7, for example, as described later in the second to fourth embodiments, by changing the size of the catalyst core 12a, carbonaceous materials having different structures can be created separately. Is possible. In addition, since the size and shape of the catalyst core can be easily determined by adjusting the gas flow rate and the temperature, a plurality of types of carbon materials can be easily created using a common apparatus. Therefore, it is possible to reliably manufacture the graphite nanotube 21 that can emit electrons from the side wall portion 21b and has high electron emission properties.

  Furthermore, it becomes possible to perform plasma processing at a high pressure of about 4 kPa by using microwaves. Therefore, it is possible to reduce the cost required for decompression compared to the case where processing is performed at a low pressure.

[Second Embodiment]
Next, a graphite nanotube 21 as an electron emission portion according to a second embodiment of the present invention and a manufacturing method thereof will be described with reference to FIG. FIG. 4 is an enlarged cross-sectional view showing a part of the carbon layer 20. In each drawing, the configuration is appropriately enlarged, reduced, or omitted for explanation. Note that the configuration and the like of the image display device 1 of the present embodiment are the same as those of the first embodiment, and a description thereof will be omitted.

In this embodiment, the pressure, gas flow rate ratio, and temperature in this process are set to the following conditions as shown in FIG. That is, the internal pressure of the container is 4 kPa, and CH ₄ and H ₂ are used as gas types. The gas flow rate of CH ₄ is 10 [sccm], and the gas flow rate of H ₂ is 80 [sccm]. Further, the temperature of the heater 24 is set to 450 ° C., the RF power is set to 400 W, and the time of this processing is set to 30 minutes.

  When exposed to plasma CVD under the above conditions, the nickel conductive catalyst layer 12 formed in a film shape on the substrate 11 has a structure having granular catalyst nuclei 12a having a predetermined size. As shown in FIG. 7, the size and shape of the catalyst core 12a are determined depending on the conditions of the plasma treatment. Here, for example, the shape of the catalyst core 12a has a radius of curvature of about 5 nm or less. It is formed to a size of about 100 nm. Since the conductive catalyst layer 12 is composed of a catalyst metal such as nickel, it acts as a catalyst layer, so that a carbon substance grows directly on the conductive catalyst layer 12 based on the catalyst core 12a. As shown in FIG. 7, the structure of the growing carbon material depends on the size of the catalyst core 12a. Here, the graphite nanotubes 21 are grown on the basis of the diamond-shaped catalyst core 12a having a size of about 50 to 100 nm. Thus, in the emitter hole 15 where the conductive catalyst layer 12 is exposed, graphite nanotubes 21 as a large number of electron emitting materials are formed on the conductive catalyst layer 12 in random directions, and the carbon layer 20 is configured.

  The graphite nanotube 21 formed under the above conditions has a diameter of 50 nm to 100 nm and a length of about 1 μm, has a large allowable current density, and emits electrons when a low voltage is applied under reduced pressure. Electrons are emitted from the end face 22 a of the graphene sheet 22 exposed at the side wall 21 b of the graphite nanotube 21.

  In this embodiment, the same effects as those of the electron-emitting device 10 and the image display device 1 according to the first embodiment described above can be obtained.

[Third Embodiment]
Next, a graphite nanofiber 26 and a carbon nanotube 27 as an electron emission portion according to a third embodiment of the present invention, and a manufacturing method thereof will be described with reference to FIGS. 8 and 9 are enlarged cross-sectional views showing a part of the carbon layer 20. In each drawing, the configuration is appropriately enlarged, reduced, or omitted for explanation. Note that, in the image display device 1 of the present embodiment, the configuration of the portions other than the graphite nanofibers 26 and the carbon nanotubes 27 as the electron emission portions are the same as those of the image display device 1 of the first embodiment, and therefore will be described. Is omitted.

In this embodiment, the pressure, gas flow rate ratio, and temperature in this process are set to the following conditions as shown in FIG. That is, the internal pressure of the container is 4 kPa, and CH ₄ and H ₂ are used as gas types. The CH4 gas flow rate is 5 [sccm], and the H2 gas flow rate is 80 [sccm]. Further, the temperature of the heater 24 is set to 450 ° C., the RF power is set to 400 W, and the time of this processing is set to 30 minutes.

  When exposed to plasma CVD under the above conditions, as shown in FIG. 8 or FIG. 9, the nickel conductive catalyst layer 12 formed on the substrate 11 in the form of a film has granular catalyst nuclei 12b having a predetermined size. / 12c. As shown in FIG. 7, the size and shape of the catalyst core 12b / 12c are determined depending on the conditions of the plasma treatment. Here, diamond-shaped catalyst nuclei 12b having a size of about 10 to 50 nm as shown in FIG. 8 or spherical catalyst nuclei 12c having a size of about 10 nm as shown in FIG. 9 are formed. Since the conductive catalyst layer 12 is made of nickel, which is a catalyst metal, as a catalyst layer, a carbon material as an electron emission portion directly grows on the conductive catalyst layer 12 on the basis of the catalyst core 12b / 12c. Since the structure of the carbon material that grows as shown in FIG. 7 depends on the size and shape of the catalyst nucleus 12b / 12c, here, when based on the diamond-shaped catalyst nucleus 12b having a size of about 10 to 50 nm, When the graphite nanofiber 26 shown in FIG. 8 grows and is based on the spherical catalyst core 12c having a size of about 10 nm, the carbon nanotube 27 shown in FIG. 9 grows. Thus, in the emitter hole 15 where the conductive catalyst layer 12 is exposed, a large number of graphite nanofibers 26 or carbon nanotubes as electron emission portions are formed on the conductive catalyst layer 12 in random directions, and the carbon layer 20 is configured. Is done.

  The graphite nanofibers 26 formed under the above conditions are a fibrous substance whose main component is a carbon material and whose end face 22a of the graphene sheet 22 is exposed on the side wall part 26b. The graphite nanofiber 26 has a structure in which small pieces of graphene sheets 22 having a shape along the surface shape of the core of the catalyst metal are stacked via the catalyst metal. The graphite nanofiber 26 is 10 times longer than the diameter in the axial direction, for example, about 10 nm to 50 nm in diameter and about 1 μm in length, has a large allowable current density, and is applied with a low voltage under reduced pressure. Emits electrons. Electrons are emitted from the end face 22 a of the graphene sheet 22 exposed at the side wall portion 26 b of the graphite nanofiber 26.

  The carbon nanotubes 27 formed under the above conditions have a structure in which the graphene sheet 22 is rounded into a cylindrical shape. The carbon nanotube 27 is 10 times longer in the axial direction than the diameter, for example, has a diameter of about 10 nm and a length of about 1 μm, has a large allowable current density, and is applied with a low voltage under reduced pressure. Release. Electrons are emitted from the end face 22 a of the graphene sheet exposed at the tip 27 b of the carbon nanotube 27. Here, as shown in FIG. 10, an electric field is formed perpendicularly to the surface of the conductive catalyst layer 12 in order to align the direction of the growing carbon nanotubes 27, and the direction of the carbon nanotubes stands on the brush toward the anode electrode 32 side. You may arrange to do.

  In this embodiment, the same effects as those of the electron-emitting device 10 and the image display device 1 according to the first embodiment described above can be obtained.

  In each of the above embodiments, the conductive catalyst layer 12 is illustrated as being made of nickel. However, the conductive catalyst layer 12 may be made of a catalyst metal including iron, cobalt, molybdenum, platinum and the like. Also in these cases, the same effects as those in the above embodiments can be obtained by adjusting the shape and size of the catalyst metal particles.

As a raw material gas at the time of forming the electron emission part, a carbon-based mixed gas such as methane (CH ₄ ), ethylene (C ₂ H ₄ ), acetylene (C ₂ H ₂ ), etc., a mixture of the carbon-based mixed gas and hydrogen gas Gas can be used. A gas obtained by vaporizing methanol, ethanol, acetone, toluene, or the like, or a mixed gas of the vaporized gas and hydrogen gas may be used.

  Each condition can be appropriately changed according to the conditions such as the apparatus and the gas used.

  In the above embodiment, the conductive catalyst layer 12 is formed on the substrate 11 such as glass or silicon. However, a conductive substrate having a thickness of about 0.1 mm may be used, for example.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

1 is a perspective view schematically showing a part of an image display device according to a first embodiment of the present invention. Sectional drawing which expands and shows typically the principal part of the image display apparatus. The side view which shows typically the principal part of FIG. 1 is a cross-sectional view schematically showing a configuration of a graphite nanotube according to a first embodiment of the present invention. The figure which shows the plasma CVD processing apparatus concerning the 1st thru | or 3rd embodiment of this invention. The figure which shows the plasma CVD process conditions concerning the 1st thru | or 3rd embodiment of this invention. The figure which shows a response | compatibility with the plasma CVD process conditions concerning the 1st thru | or 3rd Embodiment of this invention, and the structure of an electron emission part. Sectional drawing which shows typically the structure of the graphite nanofiber concerning 3rd Embodiment of this invention. Sectional drawing which shows typically the structure of the carbon nanotube concerning 4th Embodiment of this invention. Sectional drawing which expands and shows typically the principal part of the image display apparatus concerning the modification of 4th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image display apparatus, 10 ... Electron emission element, 11 ... Substrate, 12 ... Conductive catalyst layer,
12a, 12b, 12c ... catalyst core, 20 ... carbon layer,
21 ... Graphite nanotube, 21b ... Side wall part, 22 ... Graphene sheet,
22a ... end face, 23 ... CVD device, 26 ... graphite nanofiber, 26b ... side wall part, 27 ... carbon nanotube, 30 ... display part.

Claims (3)

A method of manufacturing an electron-emitting device that forms an electron-emitting portion that includes a carbon material and has a fibrous or tubular shape on a conductive catalyst layer,
Heating the catalyst layer;
In a reduced pressure atmosphere, a mixed gas is introduced around the catalyst layer,
Generate plasma and perform CVD to form the electron emission part,
In forming the electron emission portion, by controlling the temperature during the heating and the mixing ratio of the mixed gas, the shape or size of the core of the catalyst is controlled ,
A method for manufacturing an electron-emitting device , wherein a size of a nucleus of the catalyst is 50 nm or more, and a graphite nanotube is formed as the electron-emitting portion . A method of manufacturing an electron-emitting device that forms an electron-emitting portion that includes a carbon material and has a fibrous or tubular shape on a conductive catalyst layer,
Heating the catalyst layer;
In a reduced pressure atmosphere, a mixed gas is introduced around the catalyst layer,
Generate plasma and perform CVD to form the electron emission part,
In forming the electron emission portion, by controlling the temperature during the heating and the mixing ratio of the mixed gas, the shape or size of the core of the catalyst is controlled,
A method for manufacturing an electron-emitting device, wherein a size of a nucleus of the catalyst is 10 nm or more and less than 50 nm, and a graphite nanofiber is formed as the electron-emitting portion. Wherein upon heating, method of manufacturing an electron-emitting device according to claim 1 or 2, wherein said catalyst layer is characterized in that it is heated below 450 ° C. 400 ° C. or higher.

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