JP2010267583A - Electron emission element and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electron emission element which can effectively emit a stable electron in a vacuum and the atmosphere in a simple manufacturing process and can restrain generation of toxic substances such as ozone and NOx. <P>SOLUTION: In the electron emission element where a first conductive member and a second conductive member are formed to face each other and an electron is emitted by applying voltage between the conductive members, the electron emission element has an insulating member and insulated film nanoparticles in a three-dimensional space between the conductive members at approximate uniformity, and the insulated film nanoparticles are formed on the insulating member at the approximate uniformity. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electron-emitting device that can emit electrons by applying a voltage.

  Conventionally, as a field emission display element, a microemitter such as silicon or molybdenum having a sharp tip is known. However, carbon nanotubes (Carbon Nano-Tube: CNT), which are conductive fibers, have a nano-level diameter, high aspect ratio, high current density, high toughness, high heat resistance and high resistance due to the developed graphite structure. Since it has chemical stability, it is expected to be a field emission display device superior to the aforementioned metallic microemitter.

In Japanese Patent Laid-Open No. 2001-35424, a sword mountain-like member having a large number of protrusions 102 formed on one surface of a substrate 101 is produced. The substrate 101 is an Al ₂ O ₃ single crystal plate, and the protrusions 102 are zinc oxide. By forming the metal thin film 103 on the entire surface of the sword-like member on the protrusion 102 side, a large number of protrusion-shaped electron emitters 104 are obtained. The tip of the protrusion 102 is convex, and the radius of curvature indicating the sharpness (a value calculated by approximating the apex portion to a quadratic curve within a predetermined range) is 10 μm or less. A manufacturing method is simpler than that of a Spindt-type element, and a light emitting device with high luminous efficiency is obtained (see FIG. 11).

  Japanese Patent Application Laid-Open No. 2001-236879 is a method in which a base layer is formed on a cathode 105 or not, a catalyst layer 106 is formed, and a carbon nanotube 107 is grown on the catalyst layer by a Spindt method. When the separation layer is etched and removed by forming a non-reactive layer on the catalyst layer outside the microcavity and growing the carbon nanotubes 107 only on the catalyst layer 106 inside the microcavity. However, since the external carbon nanotube 107 does not exist, the carbon nanotube 107 does not flow into the microcavity. Thereby, it is disclosed that the production cost is increased while the production yield is increased (see FIG. 12).

These electron emission principles will be described. When a strong electric field is applied to the solid surface, the potential barrier on the surface confining the electrons in the solid becomes low and thin, and the electrons are released into the vacuum by the tunnel effect. In order to emit electrons, a strong electric field of the order of 10 ⁷ V / cm must be applied to the surface. In order to realize such a strong electric field, a metal needle having a sharp tip is usually used. When a negative voltage is applied to the needle, the electric field concentrates at the sharp tip and the required strong electric field is obtained. A Spindt-type emitter is produced by applying a semiconductor processing technique such as etching the needle. Carbon nanotube emitters are manufactured by kneading and coating CNT elements in resin, etc. (1) Sharp tip and large aspect ratio, (2) Chemically stable, (3) Mechanically tough (4) It has excellent physicochemical properties as a field emission emitter material, such as (4) no diffusion of atoms and excellent stability at high temperatures, and (5) conductivity. .

JP 2001-35424 A JP 2001-236879 A

The spint type electron-emitting device disclosed in Japanese Patent Application Laid-Open No. 2001-35424 and the CNT (carbon nanotube) type electron-emitting device disclosed in Japanese Patent Application Laid-Open No. 2001-236879 also have complicated manufacturing methods. That is, the Spindt-type electrode must have a sharp curvature using a metal such as Al ₂ O ₃ as a substrate and an advanced etching technique, and a complicated and highly accurate manufacturing technique is required. . In the carbon nanotube type electron-emitting device, carbon nanotubes are grown, or the grown carbon nanotubes are applied in a paste form, and electrons are emitted from the tips of the carbon nanotubes having a sharp curvature. However, it was difficult to grow carbon nanotubes uniformly on the substrate, and the manufacturing apparatus was complicated. In addition, the method of applying carbon nanotubes in a paste form is simple, but the electron emission position varies, a uniform electron emission current cannot be obtained, and the electron emission efficiency is poor.

  Since these electron-emitting devices are all formed in a plane, it cannot be said that the three-dimensional space is effectively utilized, and the efficiency of electron emission with respect to the input power is poor.

  As a result of diligently examining the problems described above, we created an electron-emitting device by self-organizing action in a simple process of applying a solution containing nanoparticles at room temperature and drying it. We found that electrons were emitted by a new electron emission principle. As a result, there is no need to bake at high temperatures, low power consumption, large area display such as field emission display (FED), electron beam irradiation device, light source, electronic component manufacturing device, electron beam such as electronic circuit components An object of the present invention is to provide an electron-emitting device that can be used as a source.

  In order to solve the above-described problems, the electron-emitting device of the present invention is formed such that the first conductive member and the second conductive member face each other, and a voltage is applied between the conductive members. An electron-emitting device that emits electrons, having an insulating member and insulating coating nanoparticles substantially uniformly in a three-dimensional space between the first and second conductive members, and the insulating coating nanoparticles being insulated It is characterized by being formed substantially uniformly on the sex member. In the examples described later, one type of insulating member is used, but even when several types of insulating members are used, they are included in a substantially uniform category. The same applies to nanoparticles.

  According to the above configuration, the electron acceleration layer including the insulating member and the insulating film nanoparticles is provided between the electrode substrate and the thin film electrode. By coating a thin film insulating member around the nanoparticles, it is possible to make the oxidation generation reaction of the nanoparticles less likely to occur, and it is possible to use the device in an atmospheric pressure state. In addition, the insulating coating nanoparticles can be scattered around the insulating member by the self-organizing action, and the efficiency of the electron-emitting device can be improved.

  This electron acceleration layer is a thin film layer in which an insulating member and nanoparticles having high antioxidation power are densely assembled, and has semiconductivity. When a voltage is applied to the semiconductive electron acceleration layer, a current flows in the electron acceleration layer, and a part thereof is emitted as ballistic electrons by the strong electric field formed by the applied voltage.

  In addition, since a conductor having a high anti-oxidation power is used as the nanoparticle, it is difficult to cause element deterioration due to oxidation by oxygen in the atmosphere, and thus it can be stably operated even at atmospheric pressure.

  In addition, since the insulating member and the insulating coating nanoparticles can adjust the resistance value and the amount of electrons generated in the electron acceleration layer, the value of the current flowing through the electron acceleration layer and the amount of electron emission can be controlled. Furthermore, since the insulating member can also have a role of efficiently releasing Joule heat generated by the current flowing through the electron acceleration layer, the electron-emitting device can be prevented from being destroyed by heat.

  Since the electron-emitting device of the present invention has the above-described configuration, it does not generate a discharge even when operated not only in a vacuum but also in an atmospheric pressure, and therefore hardly generates harmful substances such as ozone and NOx, and the electron-emitting device is oxidized. Does not deteriorate. Therefore, the electron-emitting device of the present invention has a long life and can be operated continuously for a long time even in the atmosphere. Therefore, according to the present invention, it is possible to provide an electron-emitting device that can stably emit electrons not only in a vacuum but also in an atmospheric pressure and suppress generation of harmful substances such as ozone and NOx.

  In the electron-emitting device of the present invention, in addition to the above-described configuration, a part of the formed insulating coating nanoparticles are aggregated to a size that does not cause dielectric breakdown, and a plurality of aggregates are formed. It is said. That is, it is preferable that the insulating coating nanoparticles are formed on the insulating member, but the size is such that dielectric breakdown does not occur when voltage is applied to the first conductive member and the second conductive member. The insulating coating nanoparticles may be aggregated.

  According to the above configuration, in addition to the above effects, electrons having more energy may be emitted between the agglomerated insulating coating nanoparticles, and the degree of aggregation may be such that dielectric breakdown does not occur. .

  The electron-emitting device of the present invention has the following characteristics in detail.

  In the configuration, the conductor forming the nanoparticles may include at least one of gold, silver, platinum, palladium, and nickel. As described above, since the conductor that forms the nanoparticles includes at least one of gold, silver, platinum, palladium, and nickel, elements such as oxidation of the nanoparticles by oxygen in the atmosphere are included. Deterioration can be prevented more effectively. Therefore, the lifetime of the electron-emitting device can be extended more effectively.

  In the electron-emitting device of the present invention, in addition to the above configuration, the average diameter of the nanoparticles must be smaller than the size of the insulating member because it is necessary to control conductivity, and is 3 to 20 nm. preferable. Thus, by setting the average diameter of the nanoparticles to be smaller than the particle diameter of the insulating member, preferably 3 to 20 nm, a conductive path by the nanoparticles is not formed in the electron acceleration layer, and the electrons Dielectric breakdown is less likely to occur in the acceleration layer. Although there are many unclear points in principle, electrons are efficiently generated by using nanoparticles having a particle diameter in the above range.

In the electron-emitting device of the present invention, in addition to the above configuration, the insulating member may include at least one of SiO ₂ , Al ₂ O ₃ , and TiO ₂ . Or it may contain an organic polymer. When the insulating member contains at least one of SiO ₂ , Al ₂ O ₃ , and TiO ₂ , or contains an organic polymer, the insulating property of these substances is high, and thus the electron acceleration layer It is possible to adjust the resistance value to an arbitrary range. In particular, when an oxide (SiO ₂ , Al ₂ O ₃ , and TiO ₂ ) is used as an insulating member, and a conductor having high anti-oxidation power is used as a nanoparticle, device deterioration due to oxidation by oxygen in the atmosphere Therefore, the effect of stably operating even at atmospheric pressure can be more remarkably exhibited.

  Here, the insulating member may be fine particles, and the average diameter is preferably 10 to 1000 nm, and more preferably 12 to 110 nm. In this case, the dispersion state of the particle diameter may be broad with respect to the average particle diameter. For example, fine particles having an average particle diameter of 50 nm may have a particle diameter distribution in the region of 20 to 100 nm. By making the average diameter of the insulating member, which is the fine particle, preferably 10 to 1000 nm, more preferably 12 to 110 nm, heat conduction can be efficiently conducted from the inside of the nanoparticles smaller than the size of the insulating member to the outside. Thus, Joule heat generated when current flows in the device can be efficiently released, and the electron-emitting device can be prevented from being destroyed by heat. Furthermore, the resistance value in the electron acceleration layer can be easily adjusted.

  In the electron-emitting device of the present invention, in addition to the above configuration, the ratio of the insulating member in the electron acceleration layer is preferably 80 to 95% by weight. When the ratio of the insulating member in the electron acceleration layer is 80 to 95% by weight, the resistance value in the electron acceleration layer can be appropriately increased, and a large amount of electrons flow at a time. The emission element can be prevented from being destroyed.

  In the electron-emitting device of the present invention, in addition to the above configuration, the thickness of the electron acceleration layer is preferably 12 to 6000 nm, and more preferably 300 to 6000 nm. By making the layer thickness of the electron acceleration layer preferably 12 to 6000 nm, more preferably 300 to 6000 nm, the electron acceleration layer can be made uniform, and the resistance of the electron acceleration layer can be adjusted in the layer thickness direction. It becomes possible. As a result, electrons can be uniformly emitted from the entire surface of the electron-emitting device, and electrons can be efficiently emitted outside the device.

  In the electron-emitting device of the present invention, in addition to the above configuration, the thin film electrode may include at least one of gold, silver, carbon, tungsten, titanium, aluminum, and palladium. By containing at least one of gold, silver, carbon, tungsten, titanium, aluminum, and palladium in the thin film electrode, electrons generated in the electron acceleration layer are efficiently tunneled due to the low work function of these materials. Thus, more high-energy electrons can be emitted outside the electron-emitting device.

  In addition to the above structure, the insulating film of the insulating film nanoparticles of the electron-emitting device of the present invention is characterized in that it has a thickness capable of tunneling electrons. This is because electrons cannot be emitted from the conductor to the outside unless the thickness allows electrons to tunnel, and the basic function as an electron-emitting device cannot be realized.

  In the electron-emitting device of the present invention, in addition to the above configuration, the insulating coating of the insulating coating nanoparticles includes at least one of alkane, alcohol, fatty acid, alkanethiol, hydrocarbon-based silane compound, and organic surfactant. Also good. An insulating film made of such an organic material contributes to improving the dispersibility of the nanoparticles in the dispersion during device creation. Therefore, abnormal path formation of current based on the aggregates of nanoparticles is formed. In addition to making it difficult to occur, the composition of the particles due to oxidation of the nanoparticles present around the insulating member itself does not change, so that the electron emission characteristics are not affected. Therefore, the lifetime of the electron-emitting device can be extended more effectively.

  The method for manufacturing an electron-emitting device according to the present invention has the following features and effects.

  That is, a step of forming an insulator member and insulating coating nanoparticles on the first conductive member, a step of dispersing insulating coating nanoparticles on the insulating member, and a step of forming the second conductive member It is characterized by having. By using such a manufacturing method, it can be formed on an insulating member in a self-organizing manner, and an electron-emitting device can be efficiently produced with a minimum use energy without going through a high-temperature firing step.

  The step of dispersing the particles in the dispersion solution is characterized in that the nanoparticles are arranged at substantially uniform intervals by the self-organizing action of the particles in the solvent. By making such a manufacturing method, as is clear from the SEM photographs in the examples, nanoparticles can be scattered in a three-dimensional structure, and the interval is about 10 to 30 nm, and the electron emission efficiency Self-organized at optimum intervals to improve Since this can be produced by a simple method of leaving at room temperature or after heating at a temperature lower than the boiling point of the solvent, little energy is required for production.

  The step of forming the insulating film nanoparticles on the insulating member includes a step of mixing the insulating member and the insulating film nanoparticles in a solvent to form a solution, and dispersing the particles in the dispersion solution, and allowing the particles to stand at room temperature. Alternatively, it can be allowed to stand after heating at a temperature lower than the boiling point of the solvent, whereby self-assembly can be effectively expressed.

  As described above, according to the electron-emitting device of the present invention, an electron-emitting device can be easily prepared by simply applying an electron acceleration layer between electrodes and drying at room temperature, and the electron-emitting efficiency is remarkably high. It is possible to provide a device with an easy area.

  As described above, the electron-emitting device of the present invention has an insulating member and insulating coating nanoparticles between the first conductive member and the second conductive member, and the insulating coating nanoparticles are It is the structure formed in the insulating member. The insulating coating nanoparticles are formed almost uniformly on the insulating member by a self-organizing action. Accordingly, the three-dimensional space between the first conductive member and the second conductive member is substantially uniformly formed. This is a thin film layer and has semiconductivity. When a voltage is applied to the semiconductive electron acceleration layer, a current flows in the electron acceleration layer, and a part of the electron is emitted from the nano metal particles by a strong electric field formed by the applied voltage. In addition, since a conductor having high anti-oxidation power is used as the metal fine particles, it is difficult to cause element degradation due to oxidation by oxygen in the atmosphere, and therefore it can be stably operated even under atmospheric pressure.

  In addition, since the insulating member and the insulating coating nanoparticle can adjust the resistance value and the amount of electrons generated in the electron acceleration layer, it is possible to control the value of the current flowing through the electron acceleration layer and the amount of electron emission. Furthermore, since the insulating member can also have a role of efficiently releasing Joule heat generated by the current flowing through the electron acceleration layer, the electron-emitting device can be prevented from being destroyed by heat.

  Since the electron-emitting device of the present invention has the above-described configuration, it does not generate a discharge even when operated not only in a vacuum but also in an atmospheric pressure, and therefore hardly generates harmful substances such as ozone and NOx, and the electron-emitting device is oxidized. Does not deteriorate. Therefore, the electron-emitting device of the present invention has a long life and can be operated continuously for a long time even in the atmosphere. Therefore, according to the present invention, it is possible to provide an electron-emitting device that can stably emit electrons not only in a vacuum but also in an atmospheric pressure and suppress generation of harmful substances such as ozone and NOx.

It is a schematic diagram which shows the structure of the electron-emitting element of one Embodiment of this invention. FIG. 2 is an enlarged view of a cross section in the vicinity of a fine particle layer in the electron-emitting device of FIG. 1. It is explanatory drawing explaining the process of forming an insulating film nanoparticle in an insulating member. It is a figure which shows the measurement system of an electron emission experiment. It is a figure showing the graph which shows the electron emission current in a vacuum. It is a figure showing the graph which shows the electric current in an element at the time of the electron emission in a vacuum. It is a figure showing the graph which shows the electron emission current and the element internal current in air | atmosphere. It is a figure which shows the time-dependent change of the electron emission current in air | atmosphere, and the element internal current. It is a SEM photograph of the electron acceleration layer with the best electron emission performance. It is a SEM photograph of the electron acceleration layer in a comparative example. It is explanatory drawing which shows a prior art. It is explanatory drawing which shows a prior art.

  Hereinafter, embodiments of the electron-emitting device of the present invention will be specifically described with reference to FIGS. Note that the embodiments and examples described below are merely specific examples of the present invention, and the present invention is not limited thereto.

Embodiment
FIG. 1 is a schematic diagram showing the configuration of an embodiment of an electron-emitting device of the present invention. As shown in FIG. 1, an electron-emitting device 1 according to the present embodiment is sandwiched between an electrode substrate (first conductive member) 2 and a thin film electrode (second conductive member) 3 which are lower electrodes. And an existing electron acceleration layer 4. In addition, the substrate 2 and the thin film electrode 3 are connected to a power source 7 so that a voltage can be applied between the substrate 2 and the thin film electrode 3 arranged to face each other. The electron-emitting device 1 applies a voltage between the substrate 2 and the thin film electrode 3, thereby causing a current to flow between the substrate 2 and the thin film electrode 3, that is, the electron acceleration layer 4. Electrons are transmitted through the thin film electrode 3 or emitted from the gaps of the thin film electrode 3 by the strong electric field formed by. The electron-emitting device is composed of the electron-emitting device 1 and the power source 7.

  The substrate 2 serving as the lower electrode serves as a support for the electron-emitting device. Therefore, any material can be used without particular limitation as long as it has a certain degree of strength, has good adhesion to a directly contacting substance, and has appropriate conductivity. Examples thereof include metal substrates such as SUS, Ti, and Cu, semiconductor substrates such as Si, Ge, and GaAs, insulator substrates such as glass substrates, and plastic substrates. For example, if an insulator substrate such as a glass substrate is used, a conductive material such as a metal is attached to the interface with the electron acceleration layer 4 as an electrode, so that the substrate 2 can be used as a lower electrode. The conductive material is not particularly limited as long as a noble metal material excellent in conductivity can be formed into a thin film using magnetron sputtering or the like. An ITO thin film widely used for transparent electrodes is also useful as an oxide conductive material. In addition, for example, a metal thin film in which a Ti film is formed to 200 nm on a glass substrate surface and a Cu film is further formed to a 1000 nm thickness may be used in that a tough thin film can be formed. Never happen.

  The thin film electrode 3 applies a voltage in the electron acceleration layer 4. Therefore, any material that can be applied with voltage can be used without particular limitation. However, from the standpoint that electrons accelerated and become high energy in the electron acceleration layer 4 are transmitted with as little energy loss as possible and emitted, a material having a low work function and capable of forming a thin film is higher. The effect can be expected. Examples of such a material include gold, silver, carbon, tungsten, titanium, aluminum, palladium, and the like whose work function corresponds to 4 to 5 eV. In particular, assuming operation at atmospheric pressure, gold without oxide and sulfide formation reaction is the best material. In addition, silver, palladium, tungsten, and the like, which have a relatively small oxide formation reaction, are materials that can withstand actual use without problems. The film thickness of the thin-film electrode 3 is important as a condition for efficiently emitting electrons from the electron-emitting device 1 to the outside, and is preferably in the range of 10 to 55 nm. The minimum film thickness for causing the thin film electrode 3 to function as a planar electrode is 10 nm. If the film thickness is less than this, electrical conduction cannot be ensured. On the other hand, the maximum film thickness for emitting electrons from the electron-emitting device 1 to the outside is about 100 nm. If the film thickness exceeds this, the thin film electrode 3 often recaptures the electron acceleration layer 4 due to absorption or reflection of electrons. As a result, the element cannot be driven with low power consumption.

  The electron acceleration layer 4 should just contain the metal microparticles which consist of conductors and have high antioxidant power, and the insulating member larger than the said metal microparticle size. In the present embodiment, the insulating member will be described as insulating fine particles 5 that are fine particles having an average diameter larger than the average diameter of the metal fine particles 6. However, the configuration of the electron acceleration layer 4 is not limited to the one described above. For example, the insulating member is formed on the substrate 2 and has a plurality of openings that penetrate in the thickness direction of the layer. The opening may contain metal fine particles.

  In this embodiment, the electron acceleration layer 4 includes insulating fine particles 5 and metal fine particles 6. Therefore, hereinafter, the electron acceleration layer 4 is referred to as a fine particle layer 4.

  Here, as the metal species of the metal fine particles 6, any metal species can be used on the operation principle of generating electrons. However, for the purpose of avoiding oxidative degradation when operated at atmospheric pressure, it is necessary to be a metal having high antioxidation power, and a noble metal is preferable, and examples thereof include materials such as gold, silver, platinum, palladium, and nickel. Such metal fine particles 6 can be prepared by using known fine particle production techniques such as sputtering and spray heating, and also use commercially available metal fine particle powders such as silver nanoparticles produced and sold by Applied Nano Laboratory. Is possible. The principle of electron generation will be described later.

  Here, the average diameter of the metal fine particles 6 needs to be smaller than the size of the fine particles 5 of the insulator described below because it is necessary to control the conductivity, and is more preferably 3 to 10 nm. Thus, by setting the average diameter of the metal fine particles 6 to be smaller than the particle diameter of the insulating fine particles 5, preferably 3 to 20 nm, no conductive path is formed by the metal fine particles 6 in the fine particle layer 4. Insulation breakdown in the fine particle layer 4 hardly occurs and electrons are generated efficiently.

  An insulating member may be present around the metal fine particle 6 or may be an adhering substance that adheres to the surface of the metal fine particle 6. The adhering substance is an insulating material that coats the surface of the metal fine particle 6. It may be a film. In this case, when the insulating member having a thickness of several nanometers is an insulating film for coating the metal fine particles 6, and the insulating film is covered by the oxide film of the metal fine particles 6, the thickness of the oxide film is desired due to oxidative degradation in the air In order to avoid oxidative degradation when operated at atmospheric pressure, an insulating film made of an organic material is preferable. For example, alkane, alcohol, fatty acid, alkanethiol, hydrocarbon type Examples include materials such as silane compounds and organic surfactants. It can be said that the thickness of the insulating coating is advantageously as thin as possible because electrons can be taken out by the tunnel effect. In this embodiment, a thickness of about 1 nm is used.

The insulating fine particles 5 can be used without particular limitation as long as the material has insulating properties. However, the weight ratio of the insulating fine particles 5 to the entire fine particles constituting the fine particle layer 4 is 80 to 95% as shown in the experimental results described later, and the size is to obtain a heat radiation effect superior to the metal fine particles 6. The diameter of the fine metal particles 5 is preferably 10 to 1000 nm, more preferably 12 to 110 nm. Therefore, the material of the insulating fine particles 5 is practically SiO ₂ , Al ₂ O ₃ , or TiO ₂ . However, using small-sized silica particles with surface treatment increases the surface area of the silica particles in the solvent and increases the solution viscosity compared to using spherical silica particles with a larger particle diameter. Therefore, the film thickness of the fine particle layer 4 tends to increase slightly. The material of the insulating fine particles 5 may be fine particles made of an organic polymer. For example, highly crosslinked fine particles (SX8743) made of styrene / divinylbenzene manufactured and sold by JSR Corporation, or made by Nippon Paint Co., Ltd. The fine sphere series of styrene / acrylic fine particles manufactured and sold can be used. Here, two or more different types of particles may be used as the insulating fine particles 5, particles having different particle size peaks may be used, or a single particle having a broad particle size distribution. A thing may be used.

  Further, since the role of the insulator does not depend on the shape of the fine particles, a sheet substrate made of an organic polymer may be used for the insulating member, or an insulating layer formed by applying an insulating member by any method. However, the sheet-like substrate or the insulator layer needs to have a plurality of fine holes penetrating in the thickness direction. As a sheet-like substrate material satisfying such requirements, for example, a membrane filter new clipper (made of polycarbonate) manufactured and sold by Whatman Japan Co., Ltd. is useful.

  The thinner the fine particle layer 4 is, the stronger the electric field is applied, so that electrons can be accelerated by applying a low voltage. However, the layer thickness of the electron acceleration layer can be made uniform and the resistance of the electron acceleration layer can be adjusted in the layer thickness direction. Therefore, the layer thickness of the fine particle layer 4 is preferably 100 to 1000 nm, more preferably 300 to 6000 nm. If the thickness is less than 100 nm, contact between the electrodes or dielectric breakdown due to application of a high voltage may occur. If the thickness is 6000 nm or more, a high electric field necessary for electron emission cannot be applied. Become.

  Next, the principle of electron emission will be described. FIG. 2 is an enlarged schematic view of the cross section in the vicinity of the fine particle layer 4 of the electron-emitting device 1. As shown in FIG. 2, most of the fine particle layer 4 is composed of insulating fine particles 5, and metal fine particles 6 are formed in the gaps. The ratio of the insulating fine particles 5 to the metal fine particles 6 in FIG. 2 is such that the weight ratio of the insulating fine particles 5 to the total weight of the insulating fine particles 5 and the metal fine particles 6 corresponds to 80% to 95%.

  Since the fine particle layer 4 is composed of the insulating fine particles 5 and a small number of metal fine particles 6, it has semiconductivity. Therefore, when a voltage is applied to the fine particle layer 4, a very weak current flows. The voltage-current characteristics of the fine particle layer 4 show so-called varistor characteristics, and the current value is rapidly increased as the applied voltage increases. Part of this current is emitted from the metal particles by a strong electric field in the fine particle layer 4 formed by the applied voltage, and is transmitted through the thin film electrode 3 or through the gap to be emitted to the outside of the electron-emitting device 1. .

  Next, an embodiment of a method for generating the electron-emitting device 1 will be described. First, a fine particle layer 4 is formed by applying a dispersion solution in which insulating fine particles 5 and metal fine particles 6 are dispersed on a substrate 2 by using a spin coating method. Here, the solvent used in the dispersion solution can be used without particular limitation as long as the insulating fine particles 5 and the metal fine particles 6 can be dispersed and dried after coating. For example, toluene, benzene, xylene, hexane, Tetradecane or the like can be used.

  In particular, in order to disperse the insulating coating nanoparticles, a nonpolar solvent (a solvent having a small relative dielectric constant, such as hexane) is preferable. However, water and the like are typical polar solvents, but can be used because they have cost merit. The reason for using a nonpolar solvent is that it is better to shield the charge of the nanoparticles in order to prevent the nanoparticles from attracting with the charge or the like of the nanoparticles. In addition, the viscosity of the solvent affects the ease of movement of the nanoparticles, and therefore affects the dispersibility. In particular, a solvent having a relative dielectric constant of 5 or less (hexane 1.9, toluene 2.3, xylene 2.3) is preferable.

  In addition, for the purpose of improving the dispersibility of the metal fine particles 6, an alcoholate treatment may be performed as a pretreatment. A predetermined film thickness can be obtained by repeating film formation and drying by a spin coating method a plurality of times. The fine particle layer 4 can be formed by a method such as a dropping method or a spray coating method in addition to the spin coating method. Then, the thin film electrode 3 is formed on the electron acceleration layer 4. For forming the thin film electrode 3, for example, a magnetron sputtering method may be used.

  That is, the insulator and insulating coating nanoparticles are dissolved in a solvent, the nanoparticles are dispersed by an ultrasonic cleaner, and the coating is performed on the first conductive member. Then, it is left at room temperature and the solvent is slowly removed. With the simple process as described above, an electron acceleration layer can be formed without the need for high-temperature treatment.

Further, in the electron-emitting device 1, when the insulating member in the electron acceleration layer (corresponding to the insulating fine particles 5 in the fine particle layer 4) is formed as a layer, it can be generated as follows. First, an insulating member (hereinafter referred to as a sheet-like insulating member) having a plurality of openings penetrating in the thickness direction of the layer is laminated on the substrate 2, or on the substrate 2. A coating solution in which an insulating member is dissolved / dispersed is applied to form an insulating layer. As the sheet-like insulating member, for example, a sheet-like substrate made of an organic polymer, SiO ₂ , and Al ₂ O ₃ can be used. Examples of the material that forms the insulator layer include SiO ₂ , Al ₂ O ₃ , and TiO ₂ or an organic polymer can be used.

Here, the plurality of openings can be formed by using a punching method using a blade or a laser drilling method using high-energy laser irradiation as long as it is an organic polymer, and from SiO ₂ and Al ₂ O _3. A desired opening can be formed on the formed material using an anodizing method, particularly a hydroporous reaction method using a surfactant as a template for forming a nanoporous structure of SiO ₂ . The opening needs to have a diameter larger than that of the metal fine particles used, and is preferably 50 to 50 nm. A plurality of openings are formed in the insulating layer formed by laminating the substrate 2 with the sheet-like insulating member provided with such openings, or by applying a coating solution in which the insulating member is dissolved / dispersed.

  Here, in the above, the sheet-like insulating member provided with the opening is laminated on the substrate 2, but after the sheet-like insulating member is laminated on the substrate 2, the opening is provided on the sheet-like insulating member. It may be formed.

  Thereafter, the metal fine particles 6 coated with an insulating film are filled in the openings of the sheet-like insulating member. At this time, for example, the electron acceleration layer 4 is formed by allowing a solution in which the metal fine particles 6 coated with an insulating film are dispersed to permeate the openings and naturally dry. The metal fine particles 6 with the insulating coating may be directly infiltrated into the opening by a method such as air blowing, suction, or rubbing without being dispersed in a solvent. Then, the thin film electrode 3 is formed on the electron acceleration layer 4 thus formed. For forming the thin film electrode 3, for example, a magnetron sputtering method may be used.

  Examples of electron emission according to the present invention will be described below.

  As an example, an electron emission experiment using the electron-emitting device according to the present invention will be described with reference to FIGS. In addition, this experiment is an example of implementation and does not limit the content of the present invention.

  In this example, five types of electron-emitting devices 1 were prepared by changing the composition of the insulating fine particles 5 in the fine particle layer 4 and the metal fine particles 6 having the insulating member (adhesive substance) attached to the surface.

  A 30 mm square SUS substrate was used as the substrate 2, and the fine particle layer 4 was deposited on the substrate 2 using a spin coating method. The solution containing the fine particles 5 of the insulator used in the spin coating method and the fine metal particles 6 having an insulating member attached to the surface is obtained by dispersing each particle using toluene as a solvent. The mixing ratio of the insulating fine particles 5 dispersed in the toluene solvent and the metal fine particles 6 having the insulating member attached to the surface is the weight of the insulating fine particles 5 with respect to the total amount of the insulating fine particles 5 and the metal fine particles 6 charged. The ratio was set to 70, 80, 90, and 95%, respectively.

  Silver nanoparticles (average diameter 10 nm, of which the insulating coating alcoholate is 1 nm thick) were used as the metal fine particles 6 having the insulating member attached to the surface, and spherical silica particles (average diameter 110 nm) were used as the insulating fine particles 5. .

  A method for preparing a solution in which each fine particle is dispersed will be described with reference to FIG. 3 mL of toluene solvent is put into a 10 mL reagent bottle, and 0.5 g of silica particles is put therein. Here, the reagent bottle is put on an ultrasonic disperser to disperse the silica particles. Thereafter, 0.055 g of silver nanoparticles are additionally added, and ultrasonic dispersion treatment is similarly performed. In this way, a dispersion solution in which the blending ratio of the insulating fine particles (silica particles) is 90% is obtained.

  The film forming condition by the spin coating method was that the substrate was rotated at 500 RPM for 5 seconds and then at 3000 RPM for 10 seconds after the dispersion solution was dropped onto the substrate. This film forming condition was repeated three times, three layers were deposited on the substrate, and then naturally dried at room temperature. The film thickness was about 1500 nm.

After the fine particle layer 4 is formed on the surface of the substrate 2, the thin film electrode 3 is formed using a magnetron sputtering apparatus. Gold was used as the film forming material, the layer thickness of the thin film electrode 3 was 12 nm, and the area was 0.28 cm ² .

For the electron-emitting device manufactured as described above, an electron emission experiment was performed using a measurement system as shown in FIG. In the experimental system of FIG. 4, the counter electrode 8 is arranged on the thin film electrode 3 side of the electron-emitting device 1 with the insulator spacer 9 interposed therebetween. The electron-emitting device 1 and the counter electrode 8 are each connected to a power source 7, and a voltage V1 is applied to the electron-emitting device 1 and a voltage V2 is applied to the counter electrode 8. An electron emission experiment was conducted by placing such an experimental system in a vacuum of 1 × 10 ⁻⁸ ATM, and an electron emission experiment was conducted by placing such an experimental system in the atmosphere. The results of these experiments are shown in FIGS.

FIG. 5 is a graph showing a result of measuring an electron emission current when an electron emission experiment is performed in a vacuum. Here, V1 = 1 to 10V and V2 = 50V. As shown in FIG. 5, in a vacuum of 1 × 10 ⁻⁸ ATM, no electron emission was observed when the weight ratio of silica particles was 70%, whereas currents due to electron emission were 80, 90, and 95%. Observed. The value was about 10 ⁻⁷ A when a voltage of 10 V was applied.

  FIG. 6 is a graph showing the result of measuring the current in the device when the electron emission experiment was performed in a vacuum as described above. Also here, V1 = 1 to 10V and V2 = 50V as described above. From FIG. 6, it can be seen that when the ratio of silica particles is 70%, the resistance value is insufficient and dielectric breakdown occurs (the current value is shaken out and sticks to the upper part of the graph). When the compounding ratio of the metal fine particles is increased, a conductive path is easily formed by the metal fine particles, and a large current flows through the fine particle layer 4 at a low voltage. For this reason, it is considered that the conditions for generating ballistic electrons are not satisfied.

  FIG. 7 shows the measurement of the electron emission current and the current in the device when an electron emission experiment was performed in the atmosphere with V1 = 1 to 15 V and V2 = 200 V using an electron emitting device having a silica particle ratio of 90%. It is a graph which shows a result.

As shown in FIG. 7, a current of about 10 ⁻¹⁰ A was observed in the atmosphere when a voltage of V1 = 15 V was applied.

  Further, FIG. 8 uses an electron-emitting device having a silica particle ratio of 90% as in FIG. 7, and here, when it is continuously driven in the atmosphere by applying voltages of V1 = 15V and V2 = 200V, It is a graph which shows the result of having measured the electron emission current and the element internal current. As shown in FIG. 8, the current was stably released even after 6 hours.

FIG. 9 shows an SEM photograph of the electron acceleration layer for particles mixed at a ratio of 90% of silica having the best electron emission performance. According to FIG. 9, it was observed that a large number of the alcoholate-coated nanometal particles adhered to the silica particles (the portions that appear white in the figure) and were uniformly formed on the silica particles at substantially uniform intervals. Here, since the SEM photograph is observed from the second conductive member side as it is without pre-processing and charged up, the photographing is performed with the observation mode set to several seconds.
(Comparative example)
In the same manner as in Example 1, toluene was used as the solvent, silver nanoparticles (average diameter: 10 nm, of which the insulating coating alcoholate was 1 nm thick) as insulating metal particles 6, and silica particles (average diameter) as insulating particles 5. 100 nm) was mixed and dispersed at a ratio of 90 w% of silica particles to the whole particles (silver nanoparticles and silica particles) to prepare solution A. Further, toluene was used as a solvent, silica particles (average diameter: 100 nm) as the insulating fine particles 5 were charged in the same weight as the solution A, and the solution B was prepared without using silver nanoparticles. Using these solutions, one layer of solution A was deposited by spin coating at 500 RPM · 5 sec + 3000 RPM · 10 sec, and then two layers of solution B were deposited at the same rotational speed. In order to develop a self-organizing action, it was naturally dried at room temperature without firing. The film thickness was about 500 nm as in Example 1. Although conducted emission experiments in the same manner as in Example 1, the electron emission was lower as compared with Examples 10 ^-10 voltage application of 10V.

  FIG. 10 shows an SEM photograph of the electron acceleration layer of this electron-emitting device. According to FIG. 10, it was found that the alcoholate film nanoparticles were not formed on the silica particles on the uppermost surface (second conductive member side).

  The present invention relates to an electron-emitting device. As an application example, it can be applied as a display such as a field emission display (FED), an electron beam source such as an electron beam irradiation device, a light source, an electronic component manufacturing device, and an electronic circuit component.

1 Electron-emitting device 2 First conductive member (electrode substrate)
3 Second conductive member (thin film electrode)
4 Fine particle layer (electron acceleration layer)
5 Insulator fine particles (insulating material)
6 Metal fine particles (insulating coating nano-particles)
7 Power supply (power supply section)
8 Counter electrode 9 Insulator spacer

Claims (9)

In the electron-emitting device in which the first conductive member and the second conductive member are formed so as to face each other, and a voltage is applied between the conductive members to emit electrons.
An electron having an insulating member and insulating coating nanoparticles substantially uniformly in a three-dimensional space between the conductive members, and the insulating coating nanoparticles are formed substantially uniformly on the insulating member. Emitting element.   When a voltage is applied to the first conductive member and the second conductive member, the insulating coating nanoparticles are aggregated to form a plurality of aggregates so that dielectric breakdown does not occur. The electron-emitting device according to claim 1.   3. The electron-emitting device according to claim 1, wherein the conductor portion forming the insulating coating nanoparticle contains at least one substance of gold, silver, platinum, palladium, and nickel. .   The electron-emitting device according to any one of claims 1 to 3, wherein an average diameter of a conductor portion forming the insulating coating nanoparticle is 3 to 20 nm. The insulating member _{is, SiO 2, Al 2 O 3} , and includes at least one of TiO _2, or characterized in that it comprises an organic polymer, according to any one of claims 1 to 4 Electron emission device. A method of manufacturing an electron-emitting device, wherein a first conductive member and a second conductive member are formed so as to face each other, and a voltage is applied between the conductive members to emit electrons.
A step of forming insulating coating nanoparticles on the insulating member, a step of forming insulating member and insulating coating nanoparticles on the first conductive member, and a step of forming the second conductive member. A method for manufacturing an electron-emitting device.   The step of forming the insulating film nanoparticles on the insulator member includes a step of mixing the insulator member and the insulating film nanoparticles in a solvent to form a dispersion solution, and dispersing the particles in the dispersion solution. The method for manufacturing an electron-emitting device according to claim 6.   8. The method of manufacturing an electron-emitting device according to claim 7, wherein in the step of dispersing the particles in the dispersion solution, the nanoparticles are arranged at substantially uniform intervals by a self-organizing action between the particles in the solvent. .   9. The step of forming the insulating film nanoparticles on the insulator member includes a step of leaving at room temperature or after heating at a temperature not higher than the boiling point of the solvent, according to any one of claims 6 to 8. A method for manufacturing an electron-emitting device.