JP2006228499A - Electron emitter and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electron emitter having stable electron emission characteristics. <P>SOLUTION: The electron emitter has a forming body 4 including a carbon nanotube (nano carbon material) 6 on the surface of a conductive substrate 2, and exposes the tip of the carbon nanotube 6 to a uniform height by flatly machining the surface of the forming body 4 and then performing roughening. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electron emitter that emits electrons by applying an electric field, and a method of manufacturing the same.

  In general, a display device using an electron emitter is arranged on the cathode side and emits electrons toward the anode side by an electric field applied to the anode side to collide with the phosphor on the anode side. Thus, the phosphor is excited to emit light (see Patent Document 1). Such an electron emitter is also called a cold cathode, can efficiently emit electrons even at room temperature, has a high electron emission effect on applied voltage, and has high brightness, wide viewing angle, and long life. Due to its high responsiveness, it has been applied to a large and thin display device, and its development has been earnestly advanced. Among these electron emitters, attention is focused on electron emitters using nanocarbon materials such as carbon nanotubes. Since this nanocarbon material has a large aspect ratio, it is easy to emit electrons in a low electric field, the electron emission characteristics are stable, and a high-density light emitting point can be provided to a display device. Have been developed for implementation on the display device. Manufacturing methods for this type of electron emitter include dry deposition methods such as chemical vapor deposition (CVD), which forms a carbon thin film on a substrate by thermal reaction and chemical reaction using hydrocarbon gas as a source gas, There is a wet film forming method in which a carbon material is mixed and dispersed in a resin solvent, printed as a paste on a substrate, and then baked to evaporate the solvent component and place the nanocarbon material on the substrate.

  However, the CVD method requires a large-scale and expensive apparatus, and even if such a large-scale and expensive apparatus is used, the manufacturing process is large and the manufacturing process is complicated, and the nanocarbon material is placed on the substrate. It is difficult to grow to a uniform and uniform length, and it is difficult to obtain an electron emission characteristic, that is, a light emission characteristic capable of stably emitting a phosphor in a display device.

On the other hand, in the printing method, since it is not necessary to grow the nanocarbon material directly on the substrate, there is no need to use a large-scale and expensive apparatus as in the CVD method, but the nanocarbon material is randomly formed on the substrate in a paste form. When the solvent component is removed by baking, the nanocarbon material is arranged unevenly on the substrate, and electron emission occurs due to electric field concentration at the tip. As a nanocarbon material, the electron emission characteristic of the whole becomes an extremely unstable electron emitter. In addition, the irregularity of the nanocarbon material means that the density is lowered, the emission point density is lowered, the electron beam emission density of the electron source for exciting the fluorescent film is low, and there is unevenness. The screen is dark and the displayed image is uneven, resulting in a significant deterioration in image quality.
JP 2001-23552 A

  Accordingly, the present invention is to provide an electron emitter in which electron emission characteristics as a whole are stabilized in a method of applying a nanocarbon material by printing or the like.

  1st invention provides the molded object solidified from the paste containing nanocarbon material on the substrate surface, and after the surface of the molded object is flattened to a predetermined or less surface roughness, the surface roughness is equal to or greater than the above surface roughness. An electron emitter characterized by being roughened by surface roughness. The nanocarbon material may include carbon nanotubes, fullerenes, carbon nanohorns, nanoparticles, carbon nanowalls, and the like. The nanocarbon material may be any material as long as it has a shape capable of emitting electrons in part, and the shape is not particularly limited. For example, the nanocarbon material may have a tube shape, a linear shape, a disc shape, a spherical shape, or the like. Is included. The molded body can be obtained, for example, by providing a paste on the surface of the substrate by applying a printing method, a slurry method, an ink method or the like, and firing the paste-like substance. The molded body can be flattened to a surface with a surface roughness of a predetermined level or less by mechanical polishing or chemical mechanical polishing. The surface of the molded body can be roughened to a surface roughness of a predetermined level or more by etching or the like.

  According to the first invention, a molded body containing a nanocarbon material is provided on the surface of the substrate, and after the surface flattening process is performed on the molded body, the surface roughening process is performed. It is possible to expose the tip of the carbon material evenly over the entire surface, so that the nanocarbon material on the entire surface of the molded body emits electrons almost evenly, and the electron emission characteristics are extremely stabilized. An emitter can be provided. Therefore, in the first invention, since it is not necessary to grow the nanocarbon material on the substrate, it is not necessary to use a large-scale and expensive apparatus as in the CVD method, and the nanocarbon material is not uniform inside the molded body. Even if it exists, the tip of the nanocarbon material that is exposed on the surface of the molded body and is used for electron emission can be aligned at a uniform height from the substrate. The electric field is evenly concentrated on the tip, so that it is possible to improve the efficiency and stability of electron emission and make the emission intensity uniform in the surface.

  2nd invention provides the molded object solidified from the paste containing nanocarbon material on the substrate surface, and after the surface of the molded object is flattened to a predetermined or less surface roughness, the surface roughness is equal to or greater than the above surface roughness. An electron emitter characterized by being roughened by surface roughness.

  According to the second invention, in addition to having the same effect as the first invention, the tip of the nanocarbon material over the entire surface of the molded body is obtained by the relationship between the surface roughness of the surface flattening and the surface roughening. It is possible to accurately align the heights, and it is possible to further improve the efficiency and stability of electron emission and make the emission intensity uniform in the surface.

  The surface of the molded body is preferably flattened to a surface roughness of 10 nm at maximum by polishing. The surface of the molded body is preferably roughened to a surface roughness of 10 nm to 20 μm by etching. By setting such surface roughness, the arrangement density of the nanocarbon material exposed from the surface of the molded body can be improved, and the emission intensity can be further improved.

  According to a third aspect of the present invention, there is provided a coating step of applying a paste containing a nanocarbon material on a substrate surface, a firing step of firing the paste to obtain a molded body containing the nanocarbon material, A method of manufacturing an electron emitter, comprising: a flattening step for flattening a surface; and a surface roughening step for roughening the surface of the molded body to a surface roughness greater than or equal to a predetermined level. The application may include printing, spraying, ink method, and the like.

  The flattening method is not particularly limited. For example, there is a method of flattening by polishing. The planarization is preferably a step of polishing the surface of the molded body to a maximum surface roughness of 10 nm. The surface roughening method is not particularly limited, but the surface can be roughened by etching, for example. The surface of the molded body is preferably roughened to a surface roughness of 10 nm as a minimum.

  In the manufacturing method of the present invention, it is possible to manufacture an electron emitter that is inexpensive and has excellent light emission characteristics.

  According to the present invention, an electron emitter having extremely stable electron emission characteristics can be provided.

  Hereinafter, an electron emitter and a manufacturing method thereof according to embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a sectional view of an electron emitter according to an embodiment. The electron emitter includes a conductive substrate 2 and a molded body 4 formed on the surface of the substrate 2 by printing. The substrate 2 is made of a semiconductor such as silicon, a metal, or the like. Moreover, when the board | substrate 2 is comprised from insulating materials, such as glass, the electroconductive material is provided in the board | substrate 2, and it is good for the substrate surface to have electroconductivity. The substrate 2 may have at least a surface having conductivity. The substrate 2 is on the cathode electrode side in the field emission display device. The molded body 4 includes carbon nanotubes 6 that are examples of nanocarbon materials for electron emission. The entire or almost entire surface of the molded body 4 is processed to be substantially flat with a surface roughness of a predetermined level or less, and the entire surface or substantially the entire surface is roughened to a surface roughness equal to or greater than the surface roughness by the above-described flat processing. Has been. When the surface is patterned on the substrate 2 to form an electron emitter, the entire surface is the entire surface or almost the entire surface corresponding to the pattern. The nanocarbon material is not limited to the carbon nanotube, and may include, for example, fullerene, carbon nanohorn, nanoparticle, carbon nanowall, and the like. Examples of the flattening process of the surface of the molded body include mechanical polishing, chemical mechanical polishing, a combination thereof, and others. The roughening process of the surface of the molded body 4 includes etching or other appropriate roughening process. As the etching, an etching method (half etching) such as dry etching or wet etching can be preferably used. In this etching, the carbon nanotubes are hardly etched, and the binder material constituting the molded body can be easily etched. For example, when the molded body contains glass, etching with an alkaline solution can be applied.

  Since the molded body 4 is obtained by firing a paste containing carbon nanotubes 6, the carbon nanotubes 6 are aggregated by van der Waals attraction at this paste stage to form bundles, and the carbon nanotubes 6 are in-plane. Therefore, it is impossible to obtain uniform electron emission characteristics. Therefore, in the paste stage, it is possible to perform a dispersion treatment with ultrasonic waves or the like so that the carbon nanotubes 6 are preferably evenly dispersed. Further, for example, ITO (indium tin oxide) 8 which makes the carbon nanotubes 6 hard to be burned out so that the carbon nanotubes 6 are not burned off by heat at the time of baking of the paste can be used as a conductive material in the paste. The carbon nanotube 6 can make an electrical back contact with the substrate 2 by the ITO 8.

  In addition to the carbon nanotube 6, the paste material has a viscosity dissolved in an inorganic binder material (low-melting glass particles, a conductive material, etc.) and a vehicle (resin such as ethyl cellulose, terpineol, butyl carbitol, etc.). Solution) and a paste having fluidity. Low melting glass particles include bismuth, zinc and lead materials. The vehicle can be removed by heating using a material having good decomposition and volatility. The inorganic binder material is for maintaining a solid state after firing. The paste material can be mixed with a dispersing agent that enhances the dispersibility of the carbon nanotubes or an anti-aggregating agent that prevents aggregation of the nanocarbon material. Ultrasonic treatment can be applied to increase the dispersibility of the nanocarbon material. The nanocarbon material is, for example, a carbon nanotube. In addition to the above, inorganic binder materials include titanium oxide and others.

  The surface of the molded body 4 is flattened so that the surface roughness is at most 10 nm, preferably less. The surface of the molded body 4 is roughened to a surface roughness of at least 10 nm, preferably more than that, by etching after the planarization. In FIG. 1, for the sake of understanding, the surface roughness of the molded body 4 is exaggerated by the concave portions 4 a and the convex portions 4 b. On the concavo-convex surface of the molded body 4, the concave portions 4 a are concave portions between the carbon nanotubes 6 and are portions removed by the etching, and the convex portions 4 b are portions that remain without being etched. When the carbon nanotubes 6 are positioned, the carbon nanotubes 6 are exposed in a state of protruding from the surface of the molded body 4, thereby obtaining electron emission characteristics.

  In the electron emitter according to the embodiment having the above configuration, the surface of the molded body 4 is polished and the electron emission surface has a substantially constant height from the surface of the substrate 2. The amount of electron emission from 6 becomes constant, and the light emission characteristics become uniform. In addition, since the surface of the molded body 4 is processed to a predetermined surface roughness and the carbon nanotubes 6 are exposed from the electron emission surface having the surface roughness, the electric field concentration is further improved and the electron emission characteristics are stable. Turn into.

  A method of manufacturing the electron emitter according to the embodiment will be described with reference to FIG. FIG. 2 shows a process flow of the manufacturing method, and FIGS. 3 to 5 are sectional views showing each process. As shown in the process flow, this manufacturing method includes coating (including baking), planarization, and surface roughening. Further, the coating process is shown in FIG. 3 together with the baking process, the flattening process is shown in FIG. 4, and the surface roughening process is shown in FIG. Further, in FIGS. 3 to 5, each step is indicated by (a) and (b), and (b) conceptually exaggerates and shows a part of (a).

  With reference to FIGS. 3A and 3B, in the first application step, a paste (viscous solution) is applied to the surface of the substrate 2. The paste includes carbon nanotubes 6, the above-described inorganic binder (molding aid), and a vehicle. At the time of application, the paste surface has a surface shape with a large undulation with respect to the substrate surface, and the carbon nanotubes 6 are a mixture of vertically oriented and other oriented carbon nanotubes in the paste. It is. After applying the paste, the paste is baked at a predetermined temperature. By this firing, the paste is solidified to form the molded body 4. The surface roughness of the molded body 4 is not uniform and has a rough surface, and the tips of the carbon nanotubes 6 are uneven in height from the surface of the substrate 2 and the electron emission characteristics are extremely poor. In addition, since a part of the carbon nanotube 6 is embedded in the molded body 4, the carbon nanotubes 6 that can emit electrons are limited, and the electron emission characteristics are stable, such as the amount of electron emission is reduced. Do not turn. Therefore, in the present embodiment, the following flattening and surface roughening are further performed.

  That is, referring to FIGS. 4A and 4B, in the next flattening step, the surface of the molded body 4 is mechanically polished or a slurry-like abrasive is supplied to the surface of the polishing pad to form a thin plate. The surface roughness Ra (arithmetic mean roughness of Japanese Industrial Standard JIS-B0601) is 10 nm by chemical and mechanical polishing (CMP) for polishing the surface of the workpiece and chemical mechanical polishing (CMP) for combining them mechanically. Planarize below. Since this mechanical polishing is possible by a well-known method, the details are omitted. By this flattening, the surface of the molded body 4 becomes a mirror surface. By this polishing, the surface height of the molded body 4 becomes uniform. Next, referring to FIGS. 5A and 5B, in the final surface roughening step, the surface of the molded body 4 is roughened to a surface roughness Ra of 10 nm or more by wet etching or dry etching. Through the above steps, the electron emitter shown in FIG. 1 can be manufactured.

  The present invention is not limited to the above-described embodiment, and includes various changes or modifications within the scope described in the claims.

It is sectional drawing of the electron emitter which concerns on embodiment of this invention. It is a figure which shows the manufacture flow of the electron emitter of FIG. FIG. 2 is a process diagram for applying and firing the electron emitter of FIG. 1. FIG. 2 is a planarization process diagram of the electron emitter of FIG. 1. It is a surface roughening process drawing of the electron emitter of FIG.

Explanation of symbols

2 Substrate 4 Molded body 6 Carbon nanotube (nanocarbon material)

Claims (3)

  An electron emitter characterized in that a molded body solidified from a paste containing a nanocarbon material is provided on a substrate surface, and the surface of the molded body is flattened and then roughened.   A molded body solidified from a paste containing a nanocarbon material is provided on the substrate surface, and the surface of the molded body is flattened to a surface roughness of a predetermined level or less and then roughened to a surface roughness of the above-mentioned surface roughness or higher. An electron emitter characterized by that. An application step of applying a paste containing a nanocarbon material to the substrate surface;
A firing step of firing a paste to obtain a molded body containing a nanocarbon material;
A flattening step of flattening the surface of the molded body to a predetermined surface roughness;
A surface roughening step in which the surface of the molded body is roughened to a surface roughness of a predetermined level or more;
A method for manufacturing an electron emitter, comprising:

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