JPH087747A - Field emission cathode device - Google Patents

Abstract

(57) [Summary] [Purpose] A field emission cathode device that can obtain a large beam current sufficient to operate an image pickup tube and has a function of gradually increasing or decreasing the beam current while keeping the electron beam diameter small is realized. To do. A plurality of cold cathodes 3 have their tips located on an arc of radius R centering on a focusing point O of the electron beam emitted from each cold cathode 3, and pass through the tips of the cold cathodes 3. The center line (symmetry axis) of the tip portion is arranged so as to coincide with a straight line radially extending from the focusing point O, and a plurality of gate electrodes 4 are provided on both sides of the tip portion of the cold cathode 3 and at the focusing point of the electron beam. One of the end faces is arranged on a circular arc of radius R centering on O or along the circular arc of radius R in a positional relationship close to that. Further, the two anodes are centered on the focusing point O of the electron beam. The electron beam passing region (anode aperture) 6 is left on both sides so as to coincide with the arc of P (P <R).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a field emission cathode element (cathode element using a cold cathode) used in, for example, an image pickup tube of a television, and more particularly, to an image pickup tube by simultaneously driving a plurality of field emission cathode elements. A beam current that is large enough to operate can be obtained, and a beam adjusting function that can gradually increase or decrease the beam current while keeping the electron beam diameter small is provided.

[0002]

2. Description of the Related Art The emission current of a conventional field emission cathode device is 1
Since it is about several μA per cathode element, it is necessary to drive a plurality of elements at the same time when a larger current is required. This situation will be described taking the case of an image pickup tube as an example. The hot-cathode electron gun has been used for the image pickup tube so far, but instead of this hot-cathode electron gun, if a minute field emission cold cathode having an electron emission region by a sharp tip with a radius of curvature of about several tens nm is used. , As compared with the above-mentioned hot cathode electron gun, it is an extremely small electron source, and as a result,
It is expected that the resolution of the image pickup tube can be improved significantly.

[0003]

However, in the image pickup tube, only about 1/4 of the electrons emitted from the cathode contributes to the reading of the signal charge on the photoconductive surface, and therefore, the publication of the patent application on the field emission cathode element ( As described in Japanese Patent Application Laid-Open No. 4-312752, "Electron tube apparatus"), simply by replacing, for example, one vertical field emission cathode element in place of a conventional hot cathode electron gun, an image can be obtained. The dynamic range is limited to about 2 to 3 μA as the beam current.
Therefore, when reading a signal charge larger than this,
It becomes necessary to drive a plurality of field emission cathode devices at the same time.

Here, in simultaneously driving a plurality of field emission cathode devices, it is not possible to reduce the device spacing to 1 μm or less by the conventional microfabrication technology by photolithography of the cathode devices, so a plurality of devices are driven. When widening the operation of the image pickup tube, it is difficult to set the electron source size to 1 μφ or less. That is,
In the case of widening the dynamic range, there is a problem in that the high resolution characteristics of the sharp tip must be sacrificed.

In order to solve the above-mentioned problems, an object of the present invention is to provide a field emission cathode capable of gradually increasing or decreasing the beam current while simultaneously driving a plurality of cathodes and keeping the electron beam diameter small. It is intended to obtain an element, and the obtained field emission cathode element has a large depth of focus and is capable of emitting an almost parallel electron beam.

[0006]

In order to achieve the above object, the field emission cathode device of the present invention is a field emission cathode device comprising a plurality of cold cathodes having a sharp tip shape. The center line of the tip portion of the cold cathode and the straight line extending radially from the focusing point of the electron beam emitted from the cold cathode are coincident with each other, and the tip portion is the focusing portion. While being arranged so as to be positioned on an arc of the same radius centered on a point, each of the plurality of cold cathodes is sandwiched by gate electrodes arranged adjacent to each other in the arc direction centered on the focusing point, In addition, two positive and negative arcs are formed on the arc around the focusing point near the focusing point so that each electron beam emitted from the plurality of cold cathodes forms an anode aperture for focusing on the focusing point. There is characterized in that it is arranged.

Further, the field emission cathode device of the present invention is characterized in that the cold cathode, the gate electrode and the anode are respectively formed on the same insulator substrate.

The field emission cathode device of the present invention is characterized in that the insulator substrate is an SOI substrate.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. 1 (a), 1 (b) and 1 (c) show an example of a field emission cathode device according to the present invention, in which each cathode device is an insulator substrate, for example, SOI (Silicon on Insulator).
The top view formed on the substrate, the cross-sectional view cut along the dotted line OT of FIG. 1 (a) and the dotted line O- of FIG. 1 (a).
It is a cross-sectional view cut along S and shown. In this embodiment, as shown in FIGS. 2B and 2C, various electrodes (cold cathode, gate electrode, and anode) that compose the cathode element are formed.
Is formed by photolithography or the like on an insulator substrate (SOI substrate) in which the silicon oxide film 2 is formed on the surface of the silicon substrate 1.

Next, the arrangement of the electrodes constituting the present invention will be described. As shown in FIG. 1 (a), the electrodes constituting the field emission cathode device of the present invention are composed of a plurality of cold cathodes 3, a plurality of gate electrodes 4 and two anodes 5. First, a plurality of cold cathodes 3
Are their tips located on an arc of radius R centering on the focal point O of the electron beam emitted from each cold cathode 3, and passing through the center of the tip of the cold cathode 3 ( The axis of symmetry) is arranged so as to coincide with a straight line radially extending from the focusing point O (indicated by a dotted line in FIG. 1A in the trajectory of the electron beam). The number of cold cathodes 3 is determined according to the size of the device to be manufactured, the processing accuracy of the device, and the increase / decrease scale of the beam current.

The plurality of gate electrodes 4 are for extracting electron beams from the plurality of cold cathodes 3, respectively, and are arranged on both sides of the tip of the cold cathode 3 and have a radius R with the focusing point O of the electron beam as the center. One end surface is aligned with the arc, or is arranged along the arc having a radius R in a positional relationship close to it.

Further, the two anodes coincide with each other on an arc having a radius P (P <R) centered on the focusing point O of the electron beam, and the electron beam passage region (anode aperture) 6 shown in the figure is left. It is placed on both sides of it. The materials of the cold cathode 3, the gate electrode 4 and the anode 5 are S of the substrate.
The OI film can be used as it is, but a refractory metal such as tungsten W or another material may be used.

As described above, each cold cathode 3 and each gate electrode 4
The electron beam emitted by the electric field due to the voltage applied between the electric field between the anode 5 and the gate electrode 4, Therefore, the movement is performed so as to focus toward the point O. The cold cathode 3, the gate electrode 4 and the anode 5
The potentials and the like to be applied to are the same as those in the case of the conventional field emission cathode, and therefore description thereof is omitted.

[0014]

According to the field emission cathode device of the present invention, if the size of the cold cathode, the gate electrode and the anode is about several microns and the anode aperture is about 1 micron, the depth of focus is large and the electron beam is almost parallel. Therefore, the diameter of the electron beam emitted from many cold cathodes can be suppressed to 1 μm or less. The divergence angle and depth of focus of the electron beam are radiuses R and P.
It is possible to have an adjusting function by appropriately setting each of. From the above, by using the conventional processing technology by lithography in the fabrication of silicon devices as it is, (1) an electron beam with a large depth of focus and a small divergence angle can be obtained, and (2) while keeping the electron beam diameter small, the beam current Can be changed stepwise.

[Brief description of drawings]

FIG. 1 is a diagram showing a structure of a field emission cathode device of the present invention.

[Explanation of symbols]

 1 Silicon Substrate 2 Silicon Oxide Film 3 Cold Cathode 4 Gate Electrode 5 Anode 6 Anode Aperture

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shiro Sato 1-10-11 Kinuta, Setagaya-ku, Tokyo Inside the Japan Broadcasting Corporation Broadcasting Technology Laboratory

Claims (3)

[Claims] 1. A field emission cathode device comprising a plurality of cold cathodes having a sharp tip shape, wherein each of the plurality of cold cathodes passes through the tip of the cold cathode and is the center of the tip of the cold cathode. The line and the straight line extending radially from the focusing point of the electron beam emitted from the cold cathode are aligned, and the tip portion is arranged so as to be located on an arc of the same radius with the focusing point as the center. , Each of the plurality of cold cathodes is sandwiched by gate electrodes arranged adjacent to each other in an arc direction centered on the focusing point, and each electron beam emitted from the plurality of cold cathodes is at the focusing point. A field emission cathode device, characterized in that two anodes are arranged on an arc around the focusing point in the vicinity of the focusing point so as to form an anode aperture for focusing. 2. The field emission cathode device according to claim 1, wherein the cold cathode, the gate electrode and the anode are formed on the same insulator substrate. 3. The field emission cathode device according to claim 2, wherein the insulator substrate is an SOI substrate.