1. Field of the Invention
The present invention relates to an electron source for emitting an electron beam and a manufacture method of the electron source, as well as an image forming device such as a display for forming an image by irradiation of an electron beam and a manufacture method of the image forming device.
2. Related Background Art
Known hitherto are two kinds of electron emitting elements, i.e., a thermo-electron source and a cold cathode electron source. As a cold cathode electron source, there are electron emitting elements of field emission type (hereinafter abbreviated as FE), metal/insulating layer/metal type (hereinafter abbreviated as MIM), and surface conduction type.
Known as examples of FE are W. P. Dyke & W. W. Dolan, "Fieldemission", Advance in Electron Physics, 8, 89 (1956), C. A. Spindt, "Physical Properties of thin-film field emission cathodes with Molybdenium cones", J. Appl. Phys., 47, 5428 (1976), etc.
Known as examples of MIM are C. A. Mead, "The tunnel-emission amplifier", J. Appl. Phys., 32, 646 (1961), etc.
Known as examples of an electron emitting element of surface conduction type are M. I. Elinson, Radio Eng. Electron Phys., 10 (1965), etc.
Here, the term "electron emitting element of surface conduction type" means an element which utilizes a phenomenon of causing electron emission when a thin film of small area is formed on a base plate (substrate) and a current is supplied to flow parallel to the film surface. As electron emitting elements of surface conduction type, in addition to the above-cited element by Elinson using an SnO.sub.2 thin film, there have been reported an element using an Au thin film [G. Dittmer: "Thin Solid Films", 9,317 (1972)], an element using an In.sub.2 O.sub.3 /SnO.sub.2 thin film [M. Hartwell and C. G. Fonstad: "IEEE Trans. ED Conf.", 519 (1975)], an element using a carbon thin film [Hisashi Araki et. al.: "Vacuum", Vol. 26, No. 1, p. 22 (1983)], etc.
As a typical element configuration of those electron emitting elements of surface conduction type, FIG. 28 shows a configuration of the above element reported by M. Hartwell, et. al. In FIG. 28, denoted by 231 is an insulating base plate and 232 is an electron emitting portion forming thin film which is of a thin film of metal oxide or the like formed by sputtering into a H-shaped pattern. An electron emitting portion 233 is formed by an electrifying process called `forming` described later. 234 is referred to as an electron emitting portion including thin film.
In such an electron emitting element of surface conduction type, it has conventionally been generally known to form the electron emitting portion forming thin film 232 into the electron emitting portion 233 beforehand by an electrifying process called `forming` prior to start of electron emission. The term `forming` means a process of by applying a voltage across the electron emitting portion forming thin film 232 to effect an electrifying process so that the electron emitting portion forming thin film is locally broken, deformed or denatured, thereby forming the electron emitting portion 233 which is caused to have an electrically high-resistance state. With the electron emitting element of surface conduction type thus subjected to the `forming` process, electrons are emitted from the electron emitting portion 233 by applying a voltage to the electron emitting portion including thin film 234 and flowing a current through the element.
However, the above prior art electron emitting elements of surface conduction type have accompanied various problems in realizing practical use. Therefore, the applicant has conducted intensive studies aiming at various improvements and has solved the problems in practical use as follows.
For example, the applicant has proposed a novel electron emitting element of surface conduction type that, as shown in FIG. 27, a fine particle film 244 is arranged as the electron emitting portion forming thin film between electrodes 242 and 243 on a base plate 241, and the fine particle film 244 is subjected to the electrifying process to form an electron emitting portion 245 (Japanese Patent Application Laid-Open No. 2-56822).
As an example in which numerous electron emitting elements of surface conduction type are formed in an array, there have been proposed an electron source having a number of rows in each of which electron emitting elements of surface conduction type are arrayed in parallel and these individual elements are interconnected at their both ends by wires (e.g., Japanese Patent Application Laid-Open No. 64-31332 filed by the applicant).
Meanwhile, particularly in the field of image sensing devices including displays, flat type displays using liquid crystals have recently been employed in place of CRT's. But liquid crystal displays are not emission type and hence have had such a problem as requiring backlights or the like. For this reason, displays of emissive type have been demanded.
In order to satisfy such a demand, a display in combination of an electron source which comprises an array of numerous electron emitting elements of surface conduction type, and a fluorescent material which emanates a visible light upon impingement of electrons emitted from the electron source has been proposed as an image forming device (e.g., U.S. Pat. No. 5,066,883 assigned to the applicant). This is an emissive type display which enables even a large-screen device to be relatively easily manufactured, and which is superior in display quality.
In a variety of image forming devices including the above-mentioned display, a larger screen size and higher fineness are inevitably demanded and expected. However, for an electron source in which numerous electron emitting elements are formed into an array as mentioned above, the following problems, for example, may be caused due to troubles particularly encountered in manufacture:
1) defect or failure of electron emitting elements themselves, PA1 2) disconnection of common wires or short circuit between adjacent wires, and PA1 3) failure of interlayer insulation in areas where common wires cross each other. PA1 the electron emitting element includes a plurality of electron emitting portions electrically connected in parallel, the electrical connection being made through a thermally cut-off member. PA1 forming a pluraltiy of electron emitting portions electrically connected in parallel on the base plate, PA1 checking the plurality of electron emitting portions to detect electron emission characteristics, and PA1 cutting off the electrical connection in that electron emitting portion on which the electron emission characteristic has been found not normal as a result of the checking step. PA1 the electron emitting element includes an electron emitting portion connected to voltage supply means through a thermally cut-off member, and an electron emitting portion forming film which includes a thermally connecting member. PA1 forming an electron emitting portion connected to voltage supply means, and an electron emitting portion forming film on the base plate, PA1 checking the electron emitting portion to detect an electron emission characteristics, and PA1 cutting off the connection in that electron emitting portion on which the electron emission characteristic has been found not normal as a result of the checking step, PA1 connecting the electron emitting portion forming film to the voltage supply means, and PA1 forming an electron emitting portion in the electron emitting portion forming film. PA1 said electron emitting element includes an electron emitting portion connected to voltage supply means, the connection being performed by using a thermally connecting member.