JP2011009074A - Electron-emitting element, electron-emitting device, self-luminous device, and image display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electron-emitting element which can control the emission position of electrons and emission quantity per unit area or the like in the thin-film electrode, and can maintain electron emission characteristics for a long period by avoiding a situation where an electrode on the electron emission side is gradually lost accompanying electron emission.SOLUTION: The electron-emitting element 1 includes an electron acceleration layer 4 between an electrode substrate 2 and a thin-film electrode 3. The electron acceleration layer 4 includes a particulate layer 105 containing insulator particulates located on the electrode substrate 2 side and includes depositions 107... of conductive particulates arranged separated on the surface of the particulate layer 105. An electron emission part 108 consisting of a physical defect is formed on each deposition 107. The total surface area of the plurality of depositions 107 against the surface area of the particulate layer 105 is 5% or more and 90.6% or smaller, and the thickness of the thin-film electrode 3 is established to be 100 nm or more and 500 nm or smaller.

Description

  The present invention relates to an electron-emitting device that emits electrons by applying a voltage, and an electron-emitting device, a self-luminous device, and an image display device including the electron-emitting device.

  As a conventional electron-emitting device, a Spindt type electrode, a carbon nanotube (CNT) type electrode, and the like are known. Such an electron-emitting device has been studied for application in the field of FED (Field Emission Display), for example. In such an electron-emitting device, a voltage is applied to the sharp portion to form a strong electric field of about 1 GV / m, and electrons are emitted by the tunnel effect.

  However, since these two types of electron-emitting devices have a strong electric field in the vicinity of the surface of the electron-emitting portion, the emitted electrons easily obtain large energy by the electric field and easily ionize gas molecules. There is a problem that positive ions generated by ionization of gas molecules are accelerated and collided in the direction of the surface of the electron-emitting device due to a strong electric field, and the electron-emitting device is destroyed by sputtering.

  Also, oxygen in the atmosphere generates ozone prior to the generation of ions because dissociation energy is lower than ionization energy. Since ozone is harmful to the human body and oxidizes various things with strong oxidizing power, there is a problem of damaging members around the electron-emitting device. In order to cope with such a problem, it is necessary to use an expensive ozone-resistant material for the peripheral member.

  On the other hand, MIM (Metal Insulator Metal) and MIS (Metal Insulator Semiconductor) type electron-emitting devices are known as other types of electron-emitting devices. These are surface emission type electron-emitting devices that accelerate electrons using the quantum size effect and strong electric field inside the electron-emitting device to emit electrons from the planar device surface. Since these emit electrons accelerated by the electron acceleration layer inside the device, a strong electric field is not required outside the device. Therefore, in the MIM type and MIS type electron-emitting devices, as in the Spindt-type, CNT-type, and BN-type electron-emitting devices, there is a problem of being destroyed by sputtering due to ionization of gas molecules and a problem of generating ozone. Can be overcome.

  For example, in Patent Document 1, an insulator film in which fine particles such as metal are dispersed is provided between two electrodes, electrons are injected from one electrode (substrate electrode) into the insulator film, and the injected electrons are injected. Has been disclosed in which an electron is emitted through the other electrode (electron emission side electrode) having a thickness of several tens of thousands to 1,000 mm.

JP-A-1-298623 (published on December 1, 1991) Japanese Patent Laid-Open No. 1-279557 (published on November 9, 1991)

  However, in the configuration of the MIM type electron-emitting device disclosed in Patent Document 1, the position where current flows in the insulator film and the electron-emitting portion from which electrons are emitted are accidentally generated in the electrode surface on the electron-emitting side. It cannot be set arbitrarily. Therefore, it is impossible to control the electron emission position in the electrode on the electron emission side, the emission amount per unit area, and the like.

  However, among these, the amount of electron emission can also be controlled by changing the voltage applied between the two electrodes, and the electron emission amount is reduced at a low voltage, and the electron emission amount is increased at a high voltage. it can. However, since the element disclosed in Patent Document 1 has an extremely small amount of electron emission when a low voltage is applied and the electron emission efficiency is remarkably lowered, when it is desired to narrow down the amount of electron emission extremely small, Controlling the amount of release is not a realistic countermeasure.

  Furthermore, in the configuration of the MIM type electron-emitting device disclosed in Patent Document 1, there is a problem that the electrode on the electron emission side is reverse sputtered by the emitted electrons. Reverse sputtering means that the electrode on the electron emission side becomes a target for sputtering by emitted electrons. By being reverse sputtered by the emitted electrons, the metal material constituting the electrode on the electron emission side is gradually but gradually lost, and the electrode on the electron emission side eventually functions as an electrode. It will be lost. This phenomenon applies not only to MIM type electron-emitting devices but also to all electron-emitting devices in which the electrode on the electron emission side is a solid electrode.

  The present invention has been made in view of the above problems, and is an electron-emitting device capable of controlling the electron emission position in a thin film electrode, the amount of emission per unit area, and the like, and the electrode on the electron emission side emits electrons. Thus, an electron-emitting device capable of maintaining the electron emission characteristics for a long period of time by avoiding the situation of gradually disappearing along with the above is provided.

  In order to solve the above-described problems, an electron-emitting device of the present invention has an electron acceleration layer between an electrode substrate and a thin film electrode arranged to face each other, and a voltage is applied between the electrode substrate and the thin film electrode. Is applied to accelerate the electrons in the electron acceleration layer to emit the electrons from the thin film electrode, and the electron acceleration layer has a fine particle layer containing insulating fine particles. The fine particle layer is provided with a single substance or a mixed substance that enhances the ease of electricity flow in the thickness direction of the fine particle layer so that the application positions are discrete when viewed from the upper surface of the fine particle layer. In the electron acceleration layer, a conductive path that passes through the electron acceleration layer in the thickness direction and a path exit serving as an electron emission portion that supplies the electrons to the thin film electrode is formed in advance, and the fine particle layer Said alone against the surface area of The total surface area of conferring part of the quality or substance mixture is not more than 90.6% more than 5%, and wherein the thickness of said thin film electrode is 100nm or more 500nm or less.

  According to the above configuration, by applying a voltage between the electrode substrate and the thin film electrode, a current flows in the electron acceleration layer, and a part of the current becomes a ballistic electron by the strong electric field formed by the applied voltage, and the thin film Released from the electrode side.

  Here, electrons are not emitted from an arbitrary portion on the thin film electrode side, but are emitted from an electron emission portion formed in advance in an electron acceleration layer located in the lower layer of the thin film electrode. The electron emission portion is an exit of a conductive path formed in the electron acceleration layer and passing through the electron acceleration layer in the thickness direction. Electrons emitted from the thin film electrode pass through the conductive path to the thin film electrode. Given and released. Such a conductive path (preliminarily formed conductive path) is caused by the action of a single substance or a mixed substance, which is imparted to the fine particle layer containing the insulating fine particles and enhances the flow of electricity in the thickness direction of the fine particle layer. It can be easily formed by a forming process in the atmosphere.

  In the atmosphere forming process, a DC voltage is applied between the electrode substrate and the thin film electrode in the atmosphere to form a conduction path for the current in the element that flows from the electrode substrate side to the thin film electrode side through the fine particle layer. It is processing to do.

  Since the conductive path is formed in the electron acceleration layer in advance by the forming process in the atmosphere, a new conductive path is not formed by voltage application to the element required for the subsequent electron emission operation in vacuum. The in-element current flows through a previously formed conductive path. As a result, the conductive path functions stably during electron emission. On the other hand, applying a voltage in a vacuum to an element that has not been subjected to the forming process in the atmosphere and has not previously been formed with a conductive path is a process of forming a conductive path and an electron emission process. It is. That is, electrons are emitted while forming a conductive path. The formation of the conductive path formed under such conditions is not constant, and is newly formed each time a voltage is applied in a vacuum. Therefore, every time a voltage is applied in a vacuum, the conductive state of the element changes, and stable electron emission characteristics cannot be obtained.

  Thus, in the above configuration, electrons are not emitted from any part of the electron acceleration layer, but a part from which electrons are emitted is specified as the electron emission part of the electron acceleration layer. Therefore, in the thin film electrode, the portion reversely sputtered by the emitted electrons is limited to a portion located directly above the electron emitting portion or a portion located near the electron emitting portion. Therefore, except for the portion located just above or near the electron emission portion in the thin film electrode, it is not exposed to electrons, the metal material constituting the thin film electrode is reverse sputtered by the emitted electrons, and disappears with time, Ultimately, the function as an electrode is not lost.

  In addition, in the configuration in which the single substance or the mixed substance is applied to the entire surface of the fine particle layer, when the conductive path is formed by performing the forming process, the conductive path is formed in the portion where the current easily flows, and the electron emission portion Is determined accidentally. If the electron emission part is accidentally formed, the electron emission part is arbitrarily arranged on the surface of the thin film electrode to control the electron emission position in the thin film electrode, or to control the emission amount per unit area. I can't. The electron emission amount can also be controlled by changing the voltage applied between the electrode substrate and the thin film electrode. The electron emission amount is reduced at a low voltage, and the electron emission amount is increased at a high voltage. it can. However, the device of the present invention has an extremely small amount of electron emission when a low voltage is applied, and the electron emission efficiency is significantly reduced. For this reason, when it is desired to narrow down the electron emission amount extremely small, the control of the electron emission amount by the applied voltage is not used.

  On the other hand, according to the above configuration, the single substance or the mixed substance is provided so that the application positions when viewed from the upper surface of the fine particle layer are discrete. When the conductive path is formed, the conductive path through which the current in the element flows is formed with respect to the individual, single substance or mixed substance application parts discretely arranged from the electrode substrate side. An electron emitting portion is formed on the surface. In this way, by adopting a configuration in which the single substance or the mixed substance application portion is discretely arranged, the electron emission portion can be arbitrarily arranged in the thin film electrode surface, and electrons are emitted in the thin film electrode. It is possible to control the position, the discharge amount per unit area, and the like.

  By the way, the applicant of the present invention has further studied the above configuration in which a single substance or a mixed substance is discretely applied to the fine particle layer. In order to operate stably for a long time, the electron emission portion relative to the surface area of the thin film electrode is used. And the thickness of the thin film electrode was found to be important.

  In other words, when the number of electron emission portions relative to the surface area of the thin film electrode is small, a portion other than the electron emission portion in the electron acceleration layer, that is, a single substance or a mixed substance is not applied during continuous driving (during long driving). It has been found that the fine particle layer portion and the thin film electrode thereon are likely to be selectively destroyed, and the surface conduction is lost with continuous driving, and the electron emission is eventually interrupted.

  This phenomenon is caused by destruction of the fine particle layer other than the electron emission portion, and a very small amount of current flows into the fine particle portion where the current does not flow (portion other than the current path forming portion). This is considered to be due to the accumulation of electric charge and finally the breakdown of the fine particle layer.

  In addition, even if the number of electron emission portions relative to the surface area of the thin film electrode is sufficiently large, if the thickness of the thin film electrode is not sufficient during continuous driving, even if the applied voltage is low, the application part of the single substance or mixed substance is destroyed. As a result, it was found that the electron emission was interrupted.

  Therefore, in the above-described configuration, the total surface area of the single substance or mixed substance application portion with respect to the surface area of the fine particle layer is 5% to 90.6%, and the thickness of the thin film electrode is 100 nm to 500 nm.

  By setting the total surface area of the applied portion of the single substance or mixed substance to the surface area of the fine particle layer within the above range, the problem that the portion other than the electron emission portion in the electron acceleration layer is selectively destroyed during continuous driving is avoided. can do. In addition, by setting the thickness of the thin film electrode within the above range, both the single substance or the mixed substance application portion or the thin film electrode on the single substance or the mixed material are destroyed during continuous driving without inhibiting electron emission through the thin film electrode. Can be avoided.

  Here, it is more preferable that the lower limit of the total surface area of the single substance or the mixed substance applied portion with respect to the surface area of the fine particle layer is 10% or more. According to this, it is possible to more reliably avoid the problem that a portion other than the electron emission portion in the electron acceleration layer is selectively destroyed during continuous driving.

  Similarly, the lower limit of the thickness of the thin film electrode is more preferably 160 nm or more. According to this, the problem that both the single substance or the mixed substance application portion or the thin film electrode thereon is destroyed during continuous driving can be avoided more reliably.

  Thus, the electron-emitting device of the present invention is an electron-emitting device capable of controlling the electron emission position in the thin film electrode, the emission amount per unit area, and the like, and the material constituting the electron-emitting side electrode In addition to being able to maintain the electron emission characteristics for a long period of time by avoiding the situation where the electron emission gradually disappears with the emission of electrons, it is difficult for charge accumulation to occur in parts other than the electron emission part, and the amount of emission current Thus, an element capable of stable electron emission even in continuous driving while maintaining a high state is obtained.

In the electron-emitting device of the present invention, the single substance or the mixed substance is conductive fine particles, and the conductive fine particles are deposited on the surface of the fine particle layer to form a deposit,
The deposit of the conductive fine particles may have a configuration in which a physical defect serving as the electron emission portion is provided.

  The single substance or the mixed substance can be, for example, conductive fine particles. Application of the conductive fine particles to the fine particle layer is realized by depositing conductive fine particles on the surface of the fine particle layer to form a deposit. The deposit of the conductive fine particles is provided with a physical defect that becomes an electron emission portion in the formation of the conductive path.

  In the electron-emitting device of the present invention, it is preferable that the fine particle layer further includes a binder resin for binding the insulating fine particles.

  According to the above configuration, since the insulating fine particles are bound to each other by the binder resin in the fine particle layer, the mechanical strength of the electron-emitting device can be increased. Further, when the single substance or the mixed substance is conductive fine particles, the fine particle layer is hardened with a binder resin, so that the conductive fine particles are more easily deposited on the surface of the fine particle layer than entering the fine particle layer. The configuration of the electron-emitting device of the present invention can be easily realized.

  In the electron-emitting device of the present invention, the conductive fine particles may be a noble metal. As described above, since the conductive fine particles are precious metals, it is possible to prevent element deterioration such as oxidation of the conductive fine particles by oxygen in the atmosphere. Therefore, the lifetime of the electron-emitting device can be extended.

  In the electron-emitting device of the present invention, the conductive fine particles may further include at least one of gold, silver, platinum, palladium, and nickel. As described above, since the conductive fine particles contain at least one of gold, silver, platinum, palladium, and nickel, the deterioration of the elements such as oxidation of the conductive fine particles due to oxygen in the atmosphere is further reduced. Can be effectively prevented. 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 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.

  An electron-emitting device according to the present invention includes any one of the above-described electron-emitting devices and a power supply unit that applies a voltage between the electric electrode substrate and the thin-film electrode.

  As already described in the electron-emitting device, the electron-emitting device of the present invention is an electron-emitting device capable of controlling the electron emission position in the thin film electrode, the amount of emission per unit area, and the like. In addition to being able to maintain the electron emission characteristics for a long period of time by avoiding the situation where the electrode of the electrode gradually disappears with the emission of electrons, it is difficult for charge accumulation to occur in parts other than the electron emission part, and the emission Since it is an electron-emitting device capable of stable electron emission even in continuous driving while maintaining a high current amount, an electron-emitting device configured using such an electron-emitting device has an electron emission position, It is an electron-emitting device that can control the amount of emission per unit area, etc., and avoids the situation where the material constituting the electrode on the electron emission side gradually disappears as the electron is emitted. Long-term maintenance is possible In addition to the lying, hardly accumulated charges in a portion other than the electron-emitting portion is generated while the amount of emission current is maintained high, it becomes stable electron emission can electron emission device in continuous operation.

  Further, a self-luminous device constructed using such an electron emission device of the present invention is also included in the scope of the present invention.

  In the electron-emitting device of the present invention, as described above, the electron acceleration layer has a fine particle layer containing insulating fine particles, and the fine particle layer is a single material that increases the ease of electricity flow in the thickness direction of the fine particle layer. The substance or the mixed substance is applied so that the application position when viewed from the upper surface of the fine particle layer is discrete, and the electron acceleration layer is a conductive path passing through the electron acceleration layer in the thickness direction. In addition, a conductive path is formed in advance so that the path exit becomes an electron emission portion that gives the electrons to the thin film electrode, and the total surface area of the application part of the single substance or the mixed substance with respect to the surface area of the fine particle layer is 5% or more 90.6 %, And the thickness of the thin film electrode is 100 nm or more and 500 nm or less.

  Thus, the electron-emitting device of the present invention is an electron-emitting device capable of controlling the electron emission position in the thin film electrode, the emission amount per unit area, and the like, and the material constituting the electron-emitting side electrode In addition to being able to maintain the electron emission characteristics for a long period of time by avoiding the situation where the electron emission gradually disappears with the emission of electrons, it is difficult for charge accumulation to occur in parts other than the electron emission part, and the amount of emission current Thus, it is possible to obtain an electron-emitting device capable of stably emitting electrons even in continuous driving while maintaining a high state.

It is a schematic diagram which shows the structure of the electron emission apparatus using the electron emission element of one Embodiment of this invention. It is a schematic diagram of the plane of the electron acceleration layer in the electron-emitting device with which the electron-emitting apparatus of FIG. 1 was equipped. FIG. 2 is a schematic diagram showing a deposit of conductive fine particles deposited in a discrete manner and a cross section in the vicinity thereof in an electron acceleration layer in the electron emission device provided in the electron emission device of FIG. 1. FIG. 2 is an explanatory view showing a surface state of a deposit of conductive fine particles that are discretely deposited in an electron acceleration layer in the electron-emitting device provided in the electron-emitting device of FIG. 1. (A)-(b) is explanatory drawing which expands and shows the surface state of one deposit in which the conductive fine particles are discretely deposited of the electron acceleration layer in the electron-emitting device shown in FIG. It is explanatory drawing which shows the measurement system of the electron emission experiment implemented with respect to an electron emission element. Sample No. It is a figure which shows the result of having performed stepwise voltage application in the vacuum with respect to the electron-emitting device of 1 Example, and measuring the element internal current of an electron-emitting device. Sample No. It is a figure which shows the result of having measured the time change of the electric current in an element, and an electron emission current by making applied voltage + 16V with respect to the electron emission element of 1 Example. Sample No. It is a figure which shows the result of having measured the time change of the electric current in an element | device and an electron emission current in continuous 100 hours, with an applied voltage + 16.5V with respect to the electron-emitting element of 1 Example, and is a sample as a comparative example. No. It is a figure which writes and shows the result of 4 Example (applied voltage + 18.0V) together. Sample No. It is a figure which shows the result of having measured the time change of the electric current in an element, and an electron emission current by making applied voltage + 13V with respect to the electron emission element of the comparative example 2 of 3B. Sample No. It is a figure which shows the result of having measured the element internal current with respect to the electron-emitting element of the comparative example 4 of 5. FIG. Sample No. 2 is a photomicrograph of the electron-emitting device 1 of Example 1. It is a figure which shows an example of the self-light-emitting device using the electron emission apparatus of FIG. It is a figure which shows another example of the self-light-emitting device using the electron emission apparatus of FIG. It is a figure which shows another example of the self-light-emitting device using the electron emission apparatus of FIG. It is a figure which shows another example of the image display apparatus which comprises the self-light-emitting device using the electron emission apparatus of FIG.

  Embodiments and examples of an electron-emitting device and an electron-emitting device according to the present invention will be described below 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 1]
FIG. 1 is a schematic diagram showing a configuration of an electron emission device 10 using an electron emission element 1 according to an embodiment of the present invention.

  As shown in FIG. 1, an electron emission device 10 includes an electron emission element 1 and a power source 7 according to an embodiment of the present invention. The electron-emitting device 1 includes an electrode substrate 2 serving as a lower electrode, a thin film electrode 3 serving as an upper electrode, and an electron acceleration layer 4 sandwiched therebetween. A voltage is applied between the electrode substrate 2 and the thin film electrode 3 by a power source 7.

  When a voltage is applied between the electrode substrate 2 and the thin film electrode 3, a current flows through the electron acceleration layer 4 between the electrode substrate 2 and the thin film electrode 3, and a part thereof is a strong electric field formed by the applied voltage. Are emitted from the electron acceleration layer 4 as ballistic electrons and emitted from the thin film electrode 3 side to the outside of the device.

  The electrons emitted from the electron acceleration layer 4 pass through (transmit) the thin film electrode 3 or the holes of the thin film electrode 3 caused by the influence of irregularities on the surface of the electron acceleration layer 4 positioned below the thin film electrode 3. It passes through the gap and is released to the outside.

  As described above, in the configuration in which electrons are emitted from every part of the electron acceleration layer 4 located below the thin film electrode 3, the thin film electrode 3 located on the electron emission side is reverse sputtered by the emitted electrons, and the thin film electrode 3. Has a problem that it disappears with time and eventually loses its function as an upper electrode. Further, in the configuration in which the electron emission portion is accidentally formed in the surface of the thin film electrode 3, there is a problem that the electron emission position in the thin film electrode 3, the emission amount per unit area, and the like cannot be controlled.

  In order to solve such a problem, in the electron-emitting device 1 of the present embodiment, an electron emission portion is provided at an arbitrary position of the electron acceleration layer 4 instead of emitting electrons from the entire surface of the electron acceleration layer 4. Electrons are emitted only from a specific portion of the electron acceleration layer 4.

  That is, the electron acceleration layer 4 has a fine particle layer 105 containing insulating fine particles, and the fine particle layer 105 is made of a single material or a mixed material that enhances the flow of electricity in the thickness direction of the fine particle layer. The electron acceleration layer 4 is a conductive path that passes through the electron acceleration layer 4 in the thickness direction, and the path exits electrons into the thin film. A conductive path serving as an electron emission portion to be applied to the electrode 3 is formed in advance, and the total surface area of the applied portion of the single substance or the mixed substance with respect to the surface area of the fine particle layer 105 is 5% or more and 90.6% or less. Is set to 100 nm or more and 500 nm or less. Here, the pre-formation of the conductive path means that the voltage is applied to the element 1 in a vacuum and before driving, that is, it is formed in the manufacturing process of the electron-emitting element 1. It is.

  According to the above configuration, electrons are not emitted from an arbitrary location on the thin film electrode 3 side, but are emitted from an electron emission portion formed in advance in the electron acceleration layer 4 positioned below the thin film electrode 3. The electron emission portion is an exit of a conductive path formed in advance in the electron acceleration layer 4 and passing through the electron acceleration layer 4 in the thickness direction. It is given to the thin film electrode 3 through the path and emitted.

  As described above, in the electron-emitting device 1, instead of being emitted from an arbitrary portion of the electron acceleration layer 4, the emitted portion corresponds to an electron in the electron acceleration layer 4 corresponding to the exit of the conductive path formed in advance. Specific to the discharge part. Therefore, in the thin film electrode 3, the portion reversely sputtered by the emitted electrons is limited to a portion located directly above the electron emitting portion or a portion located in the vicinity of the electron emitting portion, and other portions. Then, the metal material constituting the thin film electrode is not reversely sputtered by the emitted electrons and disappears with time, and the function as the electrode is not lost.

  In addition, since the single substance or the mixed substance is provided so that the application positions when viewed from the upper surface of the fine particle layer 105 are discrete, it is possible to arbitrarily arrange the electron emission portion in the thin film electrode surface. Thus, it is possible to control the electron emission position in the thin film electrode, the emission amount per unit area, and the like.

  Furthermore, the total surface area of the application part of the single substance or the mixed substance with respect to the surface area of the fine particle layer is 5% or more and 90.6% or less, and the thickness of the thin film electrode is 100 nm or more and 500 nm or less. Thereby, it is possible to avoid the problem that the portion other than the electron emission portion in the electron acceleration layer is selectively destroyed during continuous driving, and also during continuous driving without hindering electron emission through the thin film electrode. The problem that both the single substance or the mixed substance application part or the thin film electrode thereon is destroyed can be avoided. More specific description will be given below.

  FIG. 1 shows the electron-emitting device 1 in the case where the single substance or the mixed substance that enhances the ease of electricity flow in the thickness direction of the fine particle layer 105 in the electron acceleration layer 4 is the conductive fine particles 6. As shown in FIG. 2, the conductive fine particles 6 are discretely deposited on the surface of the fine particle layer 105 to form partial deposits 107. The application of the conductive fine particles 6 to the fine particle layer 105 is realized by depositing the conductive fine particles 6 on the surface of the fine particle layer 105 to form partial deposits 107. Each deposit 107 is provided with a physical defect serving as an electron emission portion in forming a conductive path. FIG. 2 is a top view of the electron acceleration layer 4 formed on the electrode substrate 2.

  3 shows a schematic diagram of a cross section of the electron acceleration layer 4 having a structure including the deposits 107 of the conductive fine particles 6. The deposits 107 of the conductive fine particles 6 are deposited in a dome shape on the fine particle layer 105 including the insulating fine particles 5. The conductive fine particles 6 are deposited on the surface (upper surface) of the fine particle layer 105 without being mixed with the insulating fine particles 5 at the interface between the deposits 107 and the fine particle layer 105.

  As a method for depositing the conductive fine particles 6 on the surface of the fine particle layer 105 without being mixed with each other, the conductive fine particles 6 and the insulating fine particles 5 may have the same size, or in the fine particle layer 105, the insulating fine particles 5 may be mutually connected. This can be realized by binding using a binder resin. In particular, in the configuration in which the fine particle layer 105 is hardened with a binder resin, the particle diameters of the insulating fine particles 5 and the conductive fine particles 6 can be selected without considering the mixing of the conductive fine particles 6 into the fine particle layer 105. Increases freedom. Further, there is an advantage that the mechanical strength of the electron-emitting device 1 itself is increased.

  In each deposit 107, an electron emission portion 108 made of a physical defect is formed. Although not shown, a conductive path is formed under the electron emission portion 108. Here, the electron emission portion 108 and the conductive path are formed by a forming process in the atmosphere.

  In general, the forming process is a process for forming a conductive path by applying an electric field to an electron-emitting device generally configured in an MIM type, as described in Patent Document 2, for example. The forming process is decisively different from normal dielectric breakdown: a) diffusion of the electrode material into the insulator layer, b) crystallization of the insulator substance, c) formation of a conductive path called a filament, d) insulation This is an accidental growth of a conductive path (current path) explained in various theories such as a stoichiometric shift of a body material.

  The formation of a conductive path (preliminarily formed conductive path) by the forming process in the atmosphere is such that the deposits 107 of the conductive fine particles 6 on the surface of the fine particle layer 105 flow in the thickness direction of the fine particle layer 105. By increasing the ease, it can be easily formed by a forming process in the atmosphere.

  Since the conductive path is formed in advance in the electron acceleration layer 4, a new conductive path is not formed by voltage application to the element required for the subsequent electron emission operation in vacuum, and the current in the element is It flows through a pre-formed conductive path. As a result, the conductive path functions stably during electron emission. On the other hand, applying a voltage in a vacuum to an element in which a conductive path is not formed in advance is a process for forming a conductive path and an electron emission process. That is, electrons are emitted while forming a conductive path. The formation of the conductive path formed under such conditions is not constant, and is newly formed each time a voltage is applied in a vacuum. Therefore, every time a voltage is applied in a vacuum, the conductive state of the element changes, and stable electron emission characteristics cannot be obtained.

  In addition, since the conductive fine particles 6 are discretely deposited on the surface of the fine particle layer 105 and the partial deposits 107 are discretely arranged, the electron emission position is controlled, The amount of discharge per unit area can be controlled.

  In the forming process step in the atmosphere, a current flows from the electrode substrate 2 side to the thin film electrode 3 side, aiming at a portion where the current of the deposit 107 of the conductive fine particles 6 easily flows, and a conductive path (current path) is formed. Is done. If the deposit of the conductive fine particles 6 is planar, the electron emission portion 108 is accidentally determined on the surface of the planar deposit, and the position and the number of the formed portions are not determined. If the electron emission portion 108 is accidentally formed on the surface of the electron acceleration layer 4 in this way, the electron emission position cannot be controlled, and the emission amount per unit area cannot be controlled.

  The electron emission amount can also be controlled by changing the voltage applied between the electrode substrate 2 and the thin film electrode 3, and the electron emission amount is small at a low voltage, and the electron emission amount is large at a high voltage. Can be operated. However, the device disclosed in this specification has an extremely small amount of electron emission when a low voltage is applied, and the electron emission efficiency is remarkably lowered. For this reason, when it is desired to narrow down the electron emission amount extremely small, the control of the electron emission amount by the applied voltage is not used.

  On the other hand, in the configuration as shown in FIG. 2 in which the conductive fine particles 6 are discretely deposited and the partial deposits 107 are discretely arranged, the conductive path formed by the forming process in the atmosphere is The individual deposits 107 are formed from the electrode substrate 2 side, and the electron emission portions 108 are formed in the individual deposits 107. Therefore, by controlling the arrangement of the deposits 107, the electron emission portion can be arranged at an arbitrary position on the surface of the electron acceleration layer 4, and the electron emission position in the plane of the electron emission element 1 or It is possible to control the discharge amount per unit area. Needless to say, the arrangement of the deposits 107 is not limited to a regular arrangement as shown in FIG. 2, but may be a random arrangement.

  Further, in the above configuration, since the electron emission portion is specified as the electron emission portion 108 of the deposit 107, the portion reversely sputtered by the emitted electrons in the thin film electrode 3 is a portion located directly above the electron emission portion 108. In addition, it is limited to the portion located in the vicinity of the electron emitting portion 108 and is not exposed to the emitted electrons except for the portion located in the thin film electrode 3 directly above or near the electron emitting portion 108. Therefore, the function as the upper electrode of the thin film electrode 3 can be maintained even during long-term driving.

  By the way, in the configuration in which electrons are emitted from the electron emission portions 108 of the deposits 107 arranged discretely, in order to operate stably for a long time, the number of electron emission portions with respect to the surface area of the thin film electrode 3, and the thin film electrode A thickness of 3 is important.

  That is, when the number of electron emission portions with respect to the surface area of the thin film electrode 3 is small, the deposit 107 of the conductive fine particles 6 is formed on the surface other than the electron emission portion in the electron acceleration layer, that is, on the surface during continuous driving (long-time driving). The portion of the fine particle layer 105 not disposed and the thin film electrode 3 thereon are easily destroyed selectively, the surface conduction is lost with continuous driving, and the electron emission is eventually interrupted. Such a phenomenon is caused by destruction of the fine particle layer 105 other than the electron emission portion, and a very small amount of current flows into a portion where current does not flow, and charges are accumulated by continuous driving. This is considered to be caused by the dielectric breakdown of the fine particle layer 105.

  Further, even if the number of electron emission portions with respect to the surface area of the thin film electrode 3 is sufficiently large, when the thin film electrode 3 is not sufficiently thick during long-time driving (continuous driving), the deposit 107 is destroyed even if the applied voltage is low. As a result, it was also found that electron emission was interrupted.

  Therefore, in the electron-emitting device 1, the total surface area of the deposit 107 with respect to the surface area of the fine particle layer 105 is 5% to 90.6%, and the thickness of the thin-film electrode 3 is 100 nm to 500 nm.

  By setting the total surface area of the deposit 107 with respect to the surface area of the fine particle layer 105 to 5% or more, a portion other than the electron emission portion in the electron acceleration layer 4 is selectively destroyed during long-time driving (continuous driving). Can be avoided. Here, the upper limit is set to 90.6%. When the upper limit is exceeded, the deposits 107 come close to each other and are connected to each other to form a planar arrangement, and the deposits 107 can be arranged discretely. This is because it becomes difficult. In the electron-emitting device in which the deposit 107 is arranged in a planar shape, an abnormal increase in the electron-emitting portion occurs in the aging process, the device cannot withstand the accompanying increase in current in the device, the device breaks down, and electron emission occurs in a short time. May be lost.

  Further, by setting the thickness of the thin film electrode 3 to 100 nm or more, it is possible to avoid the problem that the deposit 107 or both the deposit 107 and the thin film electrode 3 thereon is destroyed during continuous driving. If the thickness is less than 100 nm, the electrode film is likely to be broken during continuous driving, which may result in poor conduction. If the upper limit is 500 nm, a higher voltage is required at the time of the forming process in the atmosphere, and there is a risk of lack of controllability, and the gas of the thin film electrode 3 that separates the deposit 107 from the atmosphere. This is because the molecular permeability is lost and the forming process cannot be performed, that is, electrons may not be emitted.

  Here, the lower limit of the total surface area of the deposit 107 with respect to the surface area of the fine particle layer 105 is more preferably 10% or more. According to this, it is possible to more reliably avoid the problem that a portion other than the electron emission portion in the electron acceleration layer is selectively destroyed during continuous driving.

  Similarly, the lower limit of the thickness of the thin film electrode 3 is more preferably 160 nm or more. According to this, during the continuous driving, it is possible to more reliably avoid the problem that the deposits 107, or both the deposits 107 and the thin film electrode 3 thereon are destroyed.

  As long as the method of forming the deposit 107 is a method that enables discrete deposition of the conductive fine particles 6, in addition to the ink jet method using an ink jet head, a spray coating method using a mask, or a maskless conductive fine particle 6 is used. An electrostatic spraying method or the like that can scatter the liquid droplets can be used. However, in consideration of controllability of the application position and reproducibility of the application amount, application by the ink jet method is preferable.

  FIG. 4 shows a surface photograph of a certain deposit 107. This is formed by the ink jet method, but the partial deposit 107 formed in a dome shape by the ink jet method causes a so-called coffee ring phenomenon in the drying process, and the central portion of the circle is depressed, and the outer peripheral portion Solidify with the ring slightly raised. Note that FIG. 4 is an image of the deposit 107 before the forming process, so the electron emission portion 108 is not formed, and the surface of the deposit 107 is smooth.

  In the above description, the conductive fine particles 6 have been presented as a single substance or a mixed substance that enhances the ease of electricity flow in the thickness direction of the fine particle layer 105 in the electron acceleration layer 4. However, as another example, an electron pair is provided. A configuration in which a basic dispersant in which an electron donor is introduced as a substituent is imparted to the fine particle layer 105 is also conceivable.

  By applying a basic solution containing a basic dispersant to the fine particle layer 105, the identification represented by the electron donating group contained in the basic solution is applied to the surface of the insulating fine particles 5 constituting the fine particle layer 105. (For example, a phenyl group or a vinyl group which is a π electron system, and an alkyl group, an amino group, or the like). Giving a specific substituent to the surface of the insulating fine particles 5 not only facilitates electric conduction of the particle surface through them, but also the surface of water molecules or oxygen molecules in the atmosphere from atmospheric conditions. Adhesion further facilitates this electrical conduction phenomenon. As a result, like the deposits 107 of the conductive fine particles 6, a constant conductive path can be formed in the fine particle layer 105 by the forming process in the atmosphere. In the case of a basic solution, unlike the conductive fine particles 6, it does not stay on the surface of the fine particle layer 105 but is diffused into the fine particle layer 105, and there are discrete portions where the basic solution is diffused. Become.

  Examples of commercially available basic dispersants that can be applied to the present invention include various trade names such as trade names manufactured by Avicia: Solsperse 9000, 13240, 13940, 20000, 24000, 24000GR, 24000SC, 26000, 28000, 32550, 34750, and 31845. Solsperse dispersant, trade name manufactured by Big Chemie: Dispersic 106, 112, 116, 142, 161, 162, 163, 164, 165, 166, 181, 182, 183, 184, 185, 191, 2000, 2001, Ajinomoto Product names manufactured by Fine Techno Co., Ltd .: Addisper PB711, PB411, PB111, PB821, PB822, product names manufactured by Fuka Chemicals: EFKA-47, 4050, and the like.

  Further, in the case of a basic solution, it does not stay on the surface of the fine particle layer 105, but is diffused in the fine particle layer 105. Therefore, in the fine particle layer 105 to which the basic solution is applied, a conductive path is formed by an atmospheric forming process. Is formed, the electron emission portion made of physical defects as formed in the deposits 107 of the conductive fine particles 6 is not formed, and only the exit of the conductive path becomes the electron emission portion. Therefore, from the viewpoint of protecting the electron emission portion and realizing long-term driving, it is necessary to form the electron emission portion hard, such as the deposit 107 of the conductive fine particles 6, so that the electron emission portion is solidified. A method is preferable in which a substance is mixed and applied in a basic solution and an electron emission portion is formed in a solid substance deposit, such as a deposit 107 of the conductive fine particles 6.

  Next, the material of each part in such an electron-emitting device 1 will be described.

  In addition to the function as an electrode, the electrode substrate 2 serves as a support for the electron-emitting device. Therefore, any substrate can be used without particular limitation as long as the substrate has a certain degree of strength, good adhesion to a directly contacting substance, and appropriate conductivity. Specifically, for example, a metal substrate such as SUS, Ti, or Cu, or a semiconductor substrate such as Si, Ge, or GaAs can be used. In addition, a conductive material such as a metal may be attached as an electrode to the surface of an insulating substrate such as a glass substrate or a plastic substrate (interface with the electron acceleration layer 4). The conductive substance to be attached to the surface of the insulating substrate is not particularly limited as long as it has excellent conductivity and can be formed into a thin film using magnetron sputtering or the like. It is preferable to use a conductor having high strength, and it is more preferable to use a noble metal. 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 having a thickness of 200 nm is formed on the surface of a glass substrate and a Cu film having a thickness of 1000 nm may be used may be used because a strong thin film can be formed. However, it is not limited to these materials and numerical values.

  The thin film electrode 3 can be used without particular limitation as long as it can be applied with a voltage. However, from the viewpoint of transmitting electrons that are accelerated and become high energy in the electron acceleration layer 4 without loss of energy as much as possible, it is higher if the material has a low work function and can form a thin film. 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. Further, as already described, the film thickness of the thin-film electrode 3 is in the range of 100 nm to 500 nm in the present invention.

As materials for the insulating fine particles 5 constituting the fine particle layer 105 in the electron acceleration layer 4, materials such as SiO ₂ , Al ₂ O ₃ , and TiO ₂ become practical. 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 electron acceleration layer 4 tends to increase slightly. Further, as the insulating fine particles 5, fine particles made of an organic polymer may be used.

  As the insulating fine particles 5, two or more kinds of particles of different materials may be used, particles having different particle size peaks may be used, and further, a single particle having a broad particle size distribution. A thing may be used. However, as described above, the deposits 107 of the conductive fine particles 6 are formed on the fine particle layer 105. At the interface between the deposits 107 and the fine particle layer 105, the two layers need to be separated even if there is little mutual mixing. Therefore, when the single substance or the mixed substance that enhances the flow of electricity in the thickness direction of the fine particle layer is the conductive fine particles 6, the insulating fine particles 5 are mixed according to the particle diameter of the conductive fine particles 6. You need to choose not to happen. However, when the binder resin that binds the insulating fine particles 5 to each other is used, the binder resin prevents the conductive fine particles 6 from entering, so that the particle diameter of the insulating fine particles 5 is smaller than when the binder resin is not used. Some margin can be expected.

  Further, the layer thickness of the fine particle layer 105 preferably has a thickness sufficient to absorb the solvent used when the conductive fine particles 6 are applied and diffuse it into the fine particle layer 105. Although this will be described in detail later, for the purpose of suitable manufacturing, a step of applying a basic solution to the entire surface of the electron acceleration layer 4 in which the conductive fine particles 6 are deposited on the fine particle layer 105 is added. It is. When the basic solution is applied in a state where the deposits 107 in the electron acceleration layer 4 are not completely solidified, the conductive fine particles 6 constituting the deposits 107 flow out into the basic solution. Therefore, the deposits 107 should be completely solidified when the basic solution is applied. In order to completely solidify the deposits 107, it is necessary to absorb and diffuse the solvent used in applying the conductive fine particles 6 in the fine particle layer 105. Therefore, it is necessary that the fine particle layer 105 has a void enough to absorb the solvent and has a layer thickness sufficient to absorb and diffuse the solvent. This also applies to the case where a basic solution containing a basic dispersant is used as the single substance or the mixed substance for increasing the ease of electricity flow in the thickness direction of the fine particle layer, and a solid substance is mixed therewith. is there.

  On the other hand, as the material of the conductive fine particles 6, any conductor can be used as long as it enhances the flow of electricity in the thickness direction of the fine particle layer 105 in the portion where the conductive fine particles 6 are arranged. However, if the conductor has high anti-oxidation power, it is possible to avoid oxidative degradation when operated at atmospheric pressure. Here, the high antioxidant power means that the oxide forming reaction is low. In general, the larger the negative value ΔG [kJ / mol] value of the oxide formation free energy obtained by thermodynamic calculation, the easier the oxide formation reaction occurs. Examples of the conductor having a high antioxidation power include materials such as noble metals such as gold, silver, platinum, palladium, and nickel.

  Such conductive fine particles 6 can be prepared using a known fine particle production technique such as sputtering or 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 particle diameter of the conductive fine particles needs to be a particle diameter that does not cause the deposits to be electrically blown away. Experiments have confirmed that the reverse sputtering phenomenon can be prevented if the average particle diameter is 5 nm.

  Further, a small insulator material that is an insulator material smaller than the average particle diameter of the conductive fine particles 6 may be present around the conductive fine particles 6, and this small insulator material adheres to the surface of the conductive fine particles 6. The adhering substance may be an insulating film that coats the surface of the conductive fine particles 6 as an aggregate having a shape smaller than the average diameter of the conductive fine particles 6. As the small insulator material, any insulator material can be used on the principle of operation of generating ballistic electrons. However, when the insulating material smaller than the size of the conductive fine particle 6 is an insulating film that coats the conductive fine particle 6, and the insulating film is covered by the oxide film of the conductive fine particle 6, the thickness of the oxide film due to oxidative degradation in the atmosphere. In order to avoid oxidative degradation when operated at atmospheric pressure, an insulating film made of an organic material is preferable. For example, materials such as alcoholate, fatty acid, and alkanethiol are listed. It is done. It can be said that the thinner the insulating coating, the more advantageous.

  The binder resin used for the fine particle layer 105 is not particularly limited as long as it has good adhesion to the electrode substrate 2, can disperse the insulating fine particles 5, and has insulating properties. Examples of the binder resin 15 include tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, phenyltriethoxysilane, hexyltrimethoxysilane, decyltrimethoxysilane, hydrolyzable group-containing siloxane, Vinyltrimethoxysilane, vinyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxy Propyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysila N-2 (aminoethyl) 3-aminopropyltrimethoxysilane, N-2 (aminoethyl) 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-tri Ethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, N-phenyl-3-aminopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-mercaptopropyltri Examples include methoxysilane, bis (triethoxysilylpropyl) tetrasulfide, and 3-isocyanatopropyltriethoxysilane. These resin binders can be used alone or in combination of two or more.

  Next, an embodiment of a method for manufacturing the electron-emitting device 1 in which the conductive fine particles 6 are deposited on the fine particle layer 105 will be described.

  First, a dispersing agent and the insulating fine particles 5 are added to a dispersion solvent, and the insulating fine particles 5 are dispersed by an ultrasonic dispersing device to obtain an insulating fine particle dispersed solution. The dispersion method is not particularly limited, and the dispersion method may be performed by a method other than the ultrasonic disperser. As a dispersion solvent for dispersing the insulating fine particles 5, any insulating solvent that can effectively disperse the insulating fine particles 5 and evaporate after coating can be used without particular limitation. For example, toluene, benzene, xylene, hexane, tetradecane, or the like can be used. Any dispersant may be used as long as it is compatible with the dispersion solvent and can disperse the insulating fine particles 5.

  Next, the fine particle dispersion solution prepared as described above is applied onto the electrode substrate 2 to form the fine particle layer 105 in the electron acceleration layer 4. As a coating method, for example, a spin coating method can be used. The insulator fine particle dispersion is dropped onto the electrode substrate 2 and a thin film to be the fine particle layer 105 is formed by using a spin coating method. A predetermined film thickness can be obtained by repeating the dropping of the insulating fine particle dispersion solution on the electrode substrate 2, the film formation by the spin coating method, and the drying a plurality of times. In addition to the spin coating method, for example, a dropping method, a spray coating method, or the like can be used for forming the fine particle layer 105.

  Next, a dispersing agent and the conductive fine particles 6 are added to a dispersion solvent, and the conductive fine particles 6 are dispersed by applying an ultrasonic dispersing device to obtain a conductive fine particle dispersion solution B. The dispersion method is not particularly limited, and the dispersion method may be performed by a method other than the ultrasonic disperser. As a dispersion solvent for dispersing the conductive fine particles 6, any conductive solvent can be used without particular limitation as long as the conductive fine particles 6 can be effectively dispersed and evaporated after coating. For example, toluene, benzene, xylene, hexane, tetradecane, or the like can be used. Any dispersant may be used as long as it has good compatibility with the dispersion solvent and can disperse the conductive fine particles 6.

  As the conductive fine particle dispersion solution B, a conductive fine particle dispersion solution in which the conductive fine particles 6 are previously dispersed in a dispersion solvent may be used. However, since the coating solution has a clay limitation depending on the coating method, a commercially available conductive fine particle dispersion solution may be used within the limitation.

  The conductive fine particle dispersion solution B is discretely applied to the surface of the fine particle layer 105 to deposit the conductive fine particles 6. As the coating method for discrete deposition, an ink jet method is most preferable, but a spray coating method using a mask, an electrostatic spraying method capable of scattering droplets of the conductive fine particles 6 without using a mask, or the like may be used.

  When the deposit 107 of the conductive fine particles 6 discretely arranged on the fine particle layer 105 is formed, the thin film electrode 3 is further formed thereon so as to cover the entire surface. For forming the thin film electrode 3, for example, a magnetron sputtering method can be used. In addition to the magnetron sputtering method, for example, an inkjet method, a spin coating method, a vapor deposition method, or the like can be used for forming the thin film electrode 3.

  Next, in the atmosphere, a forming process is performed in which a DC voltage is applied between the electrode substrate 2 and the thin film electrode 3 to physically partially destroy the deposit 107 of the conductive fine particles 6. As a result, the electron emission portion 108 is formed in the deposit 107.

  In performing the forming process, it is preferable that the DC voltage applied between the electrode substrate 2 and the thin film electrode 3 is increased stepwise. This is because if a voltage that generates a required electric field is applied between the electrode substrate 2 and the thin film electrode 3 at once, the element may break down. By increasing the voltage stepwise, the forming process can be performed without causing dielectric breakdown.

In the forming process, the voltage applied between the electrode substrate 2 and the thin film electrode 3 has an electric field strength generated between the electrode substrate 2 and the thin film electrode 3 of 1.9 × 10 ^{7 to} 4.1 ×. It is preferable to set to 10 ⁷ [V / m]. This is because when the electric field strength is less than 1.9 × 10 ⁷ [V / m], the forming process cannot be performed, or even when it is formed, the formation of the conductive path is insufficient, and the voltage required for electron emission is applied. However, if the current in the device does not become a sufficient amount to obtain electron emission, and if the electric field strength exceeds 4.1 × 10 ⁷ [V / m], a large-scale dielectric breakdown is likely to occur. It will be destroyed. This is because once such a process has been followed, even if a voltage required for electron emission is applied, the current in the device will not flow at all, or even if it flows, it will not be in a state sufficient to obtain electron emission. .

  In manufacturing the electron-emitting device 1 of the present invention, more preferably, the fine particle layer 105 in the electron acceleration layer 4 is formed on the entire surface of the electron acceleration layer 4 in which the deposits 107 are formed on the fine particle layer 105. Applying a basic solution containing the basic dispersant described above as a single substance or mixed substance other than the conductive fine particles 6 to increase the ease of the flow of electricity in the thickness direction, and then forming the thin film electrode 3. .

  The deposits 107 are formed by depositing the conductive fine particles 6 on the fine particle layer 105, and the density of the conductive fine particles 6 is high. On the other hand, in the fine particle layer 105, although a part of the conductive fine particles 6 may permeate near the interface, the existence ratio is extremely low. Therefore, in such an electron acceleration layer 4, it is not easy to form a conductive path even if a DC voltage is applied in the forming process.

  However, by applying the basic solution to the electron acceleration layer 4 as described above, the electron emission portion 108 is formed in the forming process step with good reproducibility, small energy, and mild process conditions. It has been confirmed that a conductive path can be formed.

  By applying the basic solution to the fine particle layer 105 having the deposits 107 on the surface, as described above, the electric conduction on the particle surface is facilitated, and the atmospheric water is used from the atmospheric condition. The surface attachment of molecules or oxygen molecules further facilitates this electrical conduction phenomenon. As a result, the forming process can be performed easily and reliably.

  Here, the application method of the basic solution may be any method that can uniformly coat a very small amount of solution without breaking the electron acceleration layer 4 on which the deposits 107 on the surface of the fine particle layer 105 are arranged. Examples include spin coating and dropping.

  Further, although the basic solution is applied, it is possible to apply it to the fine particle layer 105 before forming the conductive fine particle deposits 107... It is considered that the procedure of applying the basic solution after arranging 107... Facilitates the formation of a current path in the forming process.

  This is due to the following reason. FIGS. 5A to 5C are photographs showing the surface of a certain deposit 107 in which the conductive fine particles 6 are discretely arranged. Among these, Fig.5 (a) shows the surface state of the deposit 107 before basic solution application | coating (before forming process). A black line that goes around the edge can be seen at the edge. FIG. 5B is a photograph of the surface state of the deposit 107 immediately after the application of the basic solution (before the forming process), focusing on the edge. As can be seen from comparison with FIG. 5A, it can be seen that a second black line is formed around the edge portion. FIG. 5C is a photograph of the surface state of the deposit 107 immediately after the application of the basic solution (before the forming process), focusing on the ring part that is most prominent. As can be seen from comparison with FIG. 5 (a), it can be confirmed that a part of the ring that is most swelled is damaged, and a blue substance pool can be confirmed in the central recess.

  As a result of such observation, the applicant of the present application can scratch the surface of the deposits 107 by applying the basic solution after arranging the deposits 107. It is considered that the electric current flows aiming at the scratch on the surface, and as a result, the formation of the conductive path is facilitated.

[Example 1]
In a 10 mL reagent bottle, 2.0 g of ethanol solvent and 0.5 g of tetramethoxysilane KBM-04 (manufactured by Shin-Etsu Chemical Co., Ltd.) are placed, and spherical silica particles AEROSIL R8200 having an average diameter of 12 nm as an insulator substance (Evonik EXA Japan Co., Ltd.) 0.5 g of company) was added, and the reagent bottle was put on an ultrasonic disperser to obtain a silica particle dispersion solution.

  The silica particle dispersion is dropped onto a 25 mm square glass substrate having an ITO thin film on the surface as the electrode substrate 2, and then a silica particle layer is formed under the conditions of 8000 rpm and 10 s using a spin coating method. By drying at room temperature for a time, a silica particle layer corresponding to the fine particle layer 105 is obtained.

A tetradecane dispersion solution (manufactured by ULVAC, Inc., average particle diameter of silver fine particles of 5.0 nm, silver fine particle solid content concentration of 54%) in which silver nanoparticles as conductive fine particles 6 are dispersed on the surface of the silica particle layer is so-called inkjet. A silver particle dome, which is a deposit 107 of silver nanoparticles, was formed at a landing diameter of 26 μm and a density of about 20,400 particles / cm ² by discrete ejection using a head. At this time, the ejection conditions of the inkjet head were such that the ejection volume was 4 pL, the ejection was performed in a zigzag pattern, and the minimum distance at the landing position was 62 μm. At this time, the total surface area of the silver particle dome relative to the surface area of the silica particle layer, that is, the landing density is 11%.

  A basic solution is applied to the silica particle layer having a large number of silver particle domes using a spin coating method. In the basic solution, 3 mL of toluene solvent was put into a 10 mL reagent bottle, 0.03 g of Ajisper PB821 (manufactured by Ajinomoto Fine Techno Co., Ltd.), a basic dispersant (basic functional group-containing copolymer), was added, It is obtained by dispersing through a sonic disperser. This basic solution was dropped on the silica particle layer, and then applied under conditions of 1000 rpm and 10 s using a spin coating method.

Finally, a surface electrode as a thin film electrode 3 having a film thickness of 160 nm is formed on the surface of the Syria particle layer on which the silver particle dome is formed by using a magnetron sputtering apparatus. A thick film sample No. 1 was obtained. Gold was used as the film forming material for the surface electrode, and the electrode area was 0.014 cm ² . The number of silver particle domes existing in the surface electrode is about 290.

  Next, a direct current voltage was applied to the electron-emitting device obtained under the manufacturing conditions so far in the atmosphere to form a conductive path (current path) in the silver particle dome. The maximum value of the voltage at this time was + 20V, and the voltage was increased under the condition that it takes 3 seconds to increase the voltage by 1V in steps of 0.1V.

During such voltage application, the silver particle dome has a light emission phenomenon that can be visually discerned on the surface of the element. In exchange for this phenomenon, a part of the silver particle dome lacks the electron emission portion 108. Or a crack is formed. Since the defect generated in the silver particle dome becomes a current path when a voltage is applied next, the voltage application process in the atmosphere applies an electric field to an electron-emitting device configured in a general MIM type. In addition, it is considered that a current path formation mechanism similar to a so-called “forming process” for forming a current path is developed.
[Comparative Example 1]
On the other hand, when the tetradecane dispersion solution in which silver nanoparticles are dispersed is discretely ejected onto a silica particle layer using an inkjet head, the impact density of the silver nanoparticles is 2 to 3.5% of the surface of the silica particle layer. Sample no. Sample No. 1 under the same conditions as those of the electron-emitting device 1 of FIG. Two electron-emitting devices were produced. This sample No. In the case of 2 electron-emitting devices, the number of silver particle domes existing in the surface electrode having an area of 0.014 cm ² is about 55 to 100. This condition is a condition for an electron-emitting device having a sparse conductive fine particle dome. Sample No. The electron-emitting device 2 is an electron-emitting device having a sparse silver particle dome and a thick surface electrode.
[Comparative Example 2]
Except that a surface electrode as a thin film electrode 3 having a film thickness of 40 nm is formed on the surface of the Syria particle layer on which the silver particle dome is formed using a magnetron sputtering apparatus, sample No. Sample No. 1 under the same conditions as those of the electron-emitting device 1 of FIG. 3A and 3B electron-emitting devices were prepared. This sample No. In the case of 3A and 3B electron-emitting devices, the number of silver particle domes existing in the surface electrode having an area of 0.014 cm ² is about 290, the silver particle domes are dense, and the surface electrode is a thin film electron-emitting device. It is.
[Comparative Example 3]
When the tetradecane dispersion solution in which silver nanoparticles are dispersed is discretely ejected onto a silica particle layer using an inkjet head, the impact density of the silver nanoparticles covers 2 to 3.5% of the surface of the silica particle layer. The surface electrode as a thin film electrode 3 having a film thickness of 40 nm was formed on the surface of the Syria particle layer on which the silver particle dome was formed using a magnetron sputtering apparatus. Sample No. 1 under the same conditions as those of the electron-emitting device 1 of FIG. 4 electron-emitting devices were prepared. This sample No. The electron-emitting device 4 is an electron-emitting device in which the silver particle dome is sparse and the surface electrode is a thin film.
[Comparative Example 4]
Sample No. except that no forming process was performed in the air. Sample No. 1 under the same conditions as those of the electron-emitting device 1 of FIG. 5 electron-emitting devices were prepared. This sample No. 5 is an electron-emitting device in which the silver particle dome is dense and the surface electrode is a thick film, but the current path and the electron-emitting portion 108 are not formed.

  Sample no. An electron emission experiment was performed on each of the electron-emitting devices 1 to 5. The electron emission experiment was performed using the measurement system shown in FIG.

In the measurement system of FIG. 6, the counter electrode 8 is disposed on the thin-film electrode 3 side of the electron-emitting device 1 with an insulator spacer 9 (diameter: 1 mm) interposed therebetween. A voltage V1 is applied between the electrode substrate 2 and the thin film electrode 3 of the electron-emitting device 1 by the power source 7A, and a voltage V2 is applied to the counter electrode 8 by the power source 7B. In-device current (in-device current density) I1 per unit area flowing between the thin film electrode 3 and the power source 7A was measured by placing the measurement system in a vacuum of 1 × 10 ⁻⁸ ATM.

FIG. 7 shows the result of examining the electron emission characteristics of the electron-emitting device 1 of sample No. 1 in Example 1 in a vacuum. At an applied voltage of 17 V to the surface electrode, an electron emission current of 1.24 × 10 ⁻⁴ [A / cm ² ] was obtained as an electron emission current per unit area.

  FIG. 8 shows the results of examining the time variation of each current when +16 V was applied to the electron-emitting device 1 of sample No. 1 in Example 1 in vacuum and continuously driven. When +16 V was applied for continuous driving, about 30 minutes after the start of voltage application, a sudden increase in current occurred and intermittent light emission occurred at the silver particle dome on the surface of the silica particle layer. At this time, no conspicuous fracture marks were formed on the silver fine particle dome, but each current value maintained a stable state after reaching a peak once. In particular, the amount of electron emission is high and stable.

  FIG. 9 shows the electron-emitting device 1 of sample No. 1 in Example 1. The result of examining the time-dependent change of the electron emission amount (time change of each current) when +16.5 V is applied in vacuum and continuously driven for 100 hours is shown. For comparison, Sample No. 2 in which the silver particle dome is sparse and the film thickness of the surface electrode is 40 nm. The change with time of the electron emission amount of the electron emission element of 4 is listed simultaneously. This sample No. The driving voltage of the electron-emitting device 4 is + 18V.

  The amount of electron emission after 20 hours of continuous drive is the same value regardless of the density of the silver particle dome, but the sample No. In the electron emitting device No. 4, the electron emission amount became a pulse after 80 hours of continuous driving, and the electron emission was stopped after about 84 hours. On the other hand, dense sample No. With one element, stable electron emission was possible up to 100 hours.

  On the other hand, although the surface electrode is thick, the sample No. In the electron-emitting device 2, when continuously driven for a long time, the places other than the presence of the silver particle dome (silica particle layer and the surface electrode deposited on the surface) were destroyed during the driving. This breakdown tends to increase with time, and eventually the conductivity of the surface electrode is lost and electron emission from the device is lost. It is considered that this breakdown is caused by the dielectric breakdown of the silica particle layer due to the flow and accumulation of a very small amount of current accompanying a strong electric field in the silica particle layer where no current flows.

  On the other hand, sample No. 1 has a thick surface electrode and a dense silver particle dome. In the electron emitting device 1 of 1, the same breakdown did not occur. This is because the accumulation of charges in the silica particle layer where current does not flow is likely to occur in the same way as in the case where the silver particle dome is sparse. It is believed that some of the charge will sequentially leak into the silver particle dome before the charge reaches an amount sufficient to destroy the silica particle layer. As a result, it is presumed that dielectric breakdown on a scale that destroys the silica particle layer is less likely to occur.

  Although the silver particle dome is dense, the surface electrode is a thin film sample No. When a 3A electron-emitting device is continuously driven at an applied voltage of, for example, + 18V, a few minutes after the start of driving, the current flowing in the device and the emission current rapidly increase to a value that far exceeds the power supply capability. However, no voltage was applied to the element.

  It was confirmed that the silver particle dome on the surface of the element repeatedly emitted pulsed light intermittently during the rapid increase of current, and that some of the dome was destroyed.

  In FIG. This time, the result of continuously driving the electron-emitting device of 3B with a lower applied voltage of + 13V is shown. FIG. 9 shows the time variation of each current when the applied voltage is +13 V in an electron-emitting device having a dense silver particle dome and a thin surface electrode thickness of 40 nm. A few minutes after the start of driving, the current flowing through the device and the emission current rapidly increased to values far exceeding the power supply capability, and no voltage was applied to the device. Under this condition, a rapid increase in current occurred about 8 hours after the start of voltage application, and the electron emission stopped immediately after this phenomenon occurred.

  From this, it is impossible to realize a stable operation of the element for a long time only by increasing the density of the silver particle dome. When the surface electrode corresponding to the thin film electrode 3 is thin, even if the driving voltage is low, even if the surface driving is continuous. It was found that a few minutes after the start of driving, the current flowing through the device and the emission current rapidly increased to a value far exceeding the power supply capability, and no voltage was applied to the device.

  Although this physical phenomenon cannot be clearly described, this phenomenon is not observed in the sample No. 1 of Example 1. As in the case of the electron-emitting device 1, it was possible to cope with the problem by increasing the film thickness of the surface electrode and setting the driving voltage to a voltage lower than + 18V.

  In this way, by increasing the density of silver nano, increasing the film thickness of the thin film electrode, and further reducing the driving voltage, stable electron emission over a long time while maintaining a high emission current amount. It becomes an element to be made possible.

FIG. 11 shows the sample No. of Comparative Example 5 in which the forming process in the atmosphere is not performed. 5 shows the measurement results of the electron-emitting device 5. In the element not subjected to the forming process, the current value in the element at the applied voltage +20 V was 1.2 × 10 ⁻⁶ A / cm ² . Sample No. of Comparative Example 3 in which the silver particle dome is sparse and the surface electrode is thin. Compared with the electron-emitting device 4, the current in the device increased, but no electron emission occurred from the device.

  In addition, in FIG. 1 shows a photomicrograph of the electron-emitting device 1 of FIG. From FIG. 12, it can be considered that the silver particle dome (silver dome layer) has the same or slightly thicker layer thickness as the silica particle layer. Even if the coating conditions are changed, the silica particle layer is formed at around 1 μm (a little over 1 μm when the spin speed is low, and a little under 1 μm when the spin speed is high). From this, the height of the silver dome is I guess it is about 1 μm.

[Embodiment 2]
FIGS. 13 to 15 show examples of self-luminous devices according to the present invention, in which the self-luminous devices are configured by the electron-emitting device 10 using the electron-emitting device 1 according to one embodiment of the present invention described in the first embodiment. Respectively.

  A self-emitting device 31 shown in FIG. 13 includes a light emitting unit 36 in addition to the electron emitting device 10 including the electron emitting element 1 and a power source 7 that applies a voltage to the electron emitting element 1. The light emitting unit 36 has a structure in which an ITO film 33 and a phosphor 32 are laminated on a glass substrate 34 serving as a base material. The light emitting unit 36 is disposed at a distance from the position facing the electron-emitting device 1.

As the phosphor 32, an electron excitation type material corresponding to red, green, and blue light emission is suitable. For example, Y ₂ O ₃ : Eu, (Y, Gd) BO ₃ : Eu in red, Zn ₂ SiO ₄ : Mn, BaAl ₁₂ O ₁₉ : Mn in green, and BaMgAl ₁₀ O ₁₇ : Eu ²⁺ in blue can be used. It is. The phosphor 32 is formed on the surface of the glass substrate 34 on which the ITO film 33 is formed, and preferably has a thickness of about 1 μm. The thickness of the ITO film 33 is 150 nm in the present embodiment, as long as it is a film thickness that can ensure conductivity.

  In forming the phosphor 32, it is preferable to prepare a kneaded product of an epoxy resin serving as a binder and finely divided phosphor particles and form the film by a known method such as a bar coater method or a dropping method.

  Here, in order to increase the emission luminance of the phosphor 32, it is necessary to accelerate the electrons emitted from the electron-emitting device 1 toward the phosphor 32. In order to realize such acceleration, as shown in FIG. 13, a power source 35 is provided between the electrode substrate 2 of the electron-emitting device 1 and the ITO film 33 of the light emitting unit 36 to form an electric field for accelerating electrons. A configuration that allows voltage application to be applied is preferable. At this time, the distance between the phosphor 32 and the electron-emitting device 1 is preferably 0.3 to 1 mm, the applied voltage from the power source 7 is preferably 18 V, and the applied voltage from the power source 35 is preferably 500 to 2000 V.

  A self-luminous device 31 ′ shown in FIG. 14 includes a phosphor (light emitter) 32 in addition to the electron emitter 10 including the electron emitter 1 and a power source 7 that applies a voltage to the electron emitter 1. In the self-luminous device 31 ′, the phosphor 32 has a planar shape and is disposed on the surface of the electron-emitting device 1. Here, the phosphor 32 layer formed on the surface of the electron-emitting device 1 is prepared as a coating liquid composed of a kneaded material with the phosphor particles finely divided as described above, and is formed on the surface of the electron-emitting device 1. To do. However, since the electron-emitting device 1 itself has a structure that is weak against external force, there is a risk that the device may be damaged if film forming means by the bar coater method is used. Therefore, a method such as a dropping method or a spin coating method may be used.

  A self-luminous device 31 ″ shown in FIG. 15 includes a phosphor (light emitter) in the electron acceleration layer 4 of the electron emitter 1 in addition to the electron emitter 10 including the electron emitter 1 and a power source 7 that applies a voltage to the electron emitter. ) Fluorescent fine particles are mixed in as 32 '. In this case, the fine particles of the phosphor 32' may also be used as the insulating fine particles 5. However, the aforementioned phosphor fine particles generally have low electric resistance, The electrical resistance is clearly lower than that of the insulating fine particles 5. Therefore, when the fluorescent fine particles are changed to the insulating fine particles 5 and mixed, the mixing amount of the fluorescent fine particles must be kept small. When spherical silica particles (average diameter 110 nm) are used as the insulating fine particles 5 and ZnS: Mg (average diameter 500 nm) is used as the phosphor fine particles, a weight mixing ratio of about 3: 1 is appropriate.

  In the self-luminous devices 31, 31 ′, 31 ″, the electrons emitted from the electron-emitting device 1 collide with the phosphors 32, 32 to emit light. Since the electron-emitting device 1 has an improved electron emission amount, The self-light-emitting devices 31, 31 ′, 31 ″ can emit light effectively. The self-luminous devices 31, 31 ', 31' 'can be more efficiently light-emitted by increasing the electron emission current by vacuum sealing.

Further, FIG. 16 shows an example of an image display apparatus according to the present invention provided with the self-luminous device according to the present invention. An image display device 140 shown in FIG. 16 includes the self-luminous device 31 ″ shown in FIG. 15 and a liquid crystal panel 330. In the image display device 140, the self-luminous device 31 ″ is installed behind the liquid crystal panel 330. And used as a backlight. When used in the image display device 140, the applied voltage to the self-luminous device 31 ″ is preferably 20 to 35 V, and for example, 10 μA / cm ² of electrons are emitted per unit time at this voltage. The distance between the self-light emitting device 31 ″ and the liquid crystal panel 330 is preferably about 0.1 mm.

When the self-luminous device 31 shown in FIG. 13 is used as the image display apparatus according to the present invention, the self-luminous devices 31 are arranged in a matrix, and an image is formed and displayed as an FED by the self-luminous device 31 itself. It can also be a shape. In this case, the applied voltage to the self-luminous device 31 is preferably 20 to 35 V, and it is sufficient that, for example, 10 μA / cm ² of electrons are emitted per unit time at this voltage.

  The electron-emitting device according to the present invention can ensure electrical continuity, flow a sufficient current in the device, and emit ballistic electrons from the thin film electrode. Therefore, for example, it can be suitably applied to an image display device or the like by combining with a light emitter.

DESCRIPTION OF SYMBOLS 1 Electron emission element 2 Electrode substrate 3 Thin film electrode 4 Electron acceleration layer 5 Insulator fine particle 6 Conductive fine particle 7 Power supply (power supply part)
7A power source 7B power source 8 counter electrode 9 insulator spacer 10 electron emission device 31, 31 ', 31 "self-emitting device 32, 32' phosphor (luminescent material)
33 ITO film 34 Glass substrate 35 Power source 36 Light emitting part 107 Deposit 108 Electron emitting part 330 Liquid crystal panel

Claims (11)

An electron acceleration layer is provided between the electrode substrate and the thin film electrode arranged opposite to each other, and a voltage is applied between the electrode substrate and the thin film electrode to accelerate electrons in the electron acceleration layer. An electron-emitting device that emits the electrons from the thin film electrode,
The electron acceleration layer has a fine particle layer containing insulating fine particles, and the fine particle layer includes an electrode substrate in the fine particle layer that is made of a single substance or a mixed substance that enhances the flow of electricity in the thickness direction of the fine particle layer. It is given so that the application position when viewed from the upper surface of the fine particle layer with the side as the lower surface is discrete,
In the electron acceleration layer, a conductive path that passes through the electron acceleration layer in the thickness direction, a conductive path serving as an electron emitting portion whose path exit gives the electrons to the thin film electrode is formed in advance.
The total surface area of the application part of the single substance or mixed substance with respect to the surface area of the fine particle layer is 5% or more and 90.6% or less,
An electron-emitting device, wherein the thin-film electrode has a thickness of 100 nm to 500 nm. The single substance or mixed substance is conductive fine particles,
The conductive fine particles are deposited on the surface of the fine particle layer to form a deposit,
The electron-emitting device according to claim 1, wherein the deposit of the conductive fine particles is provided with a physical defect serving as the electron-emitting portion.   3. The electron-emitting device according to claim 1, wherein a total surface area of the application part of the single substance or the mixed substance with respect to a surface area of the fine particle layer is 10% or more.   The electron-emitting device according to any one of claims 1 to 3, wherein the thickness of the thin film electrode is 160 nm or more.   The electron-emitting device according to claim 1, wherein the fine particle layer includes a binder resin that binds the insulating fine particles to each other.   The electron-emitting device according to claim 2, wherein the conductive fine particles are a noble metal.   The electron-emitting device according to claim 2, wherein the conductive fine particles include at least one of gold, silver, platinum, palladium, and nickel.   The electron-emitting device according to any one of claims 1 to 7, wherein the thin-film electrode includes at least one of gold, silver, carbon, tungsten, titanium, aluminum, and palladium.   The electron-emitting device according to claim 1, and a power supply unit that applies a voltage between the electrode substrate and the thin-film electrode in the electron-emitting device. Electron emission device.   A self-luminous device comprising the electron-emitting device according to claim 9 and a light emitter, wherein the light-emitting device emits electrons by emitting electrons from the electron-emitting device.   An image display apparatus comprising the self-luminous device according to claim 10.