Display having an electron emitting device

Details Display having an electron emitting device Display having an electron emitting device

1999-09-13

2002-07-16

Patel, Nimeshkumar D. (Department: 2879)

Electric lamp and discharge devices

With luminescent solid or liquid material

Vacuum-type tube

C313S292000, C315S169100, C315S169200

Reexamination Certificate

active

06420825

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an image-forming apparatus such as a display apparatus using electron beams and, more particularly, it relates to an image-forming apparatus comprising spacers arranged within the envelope of the apparatus to internally support the envelope against the atmospheric pressure.
2. Related Background Art
There have been known two types of electron-emitting devices, which are the thermionic electron source and the cold cathode electron source. Cold cathode electron sources refer to the field emission type (hereinafter referred to as the FE type), the metal/insulation layer/metal type (hereinafter referred to as the MIM type) and the surface conduction electron-emitting type (hereinafter referred to as the SCE type).
Examples of SCE type device include the one proposed in M. I. Elinson, Radio Eng. Electron Pys., 10 (1965).
An SCE type device is realized by utilizing the phenomenon that electrons are emitted out of a thin film with a small area formed on a substrate when an electric current is forced to flow in parallel with the film surface. While Elinson proposes the use of SnO
2
thin film for a device of this type, the use of Au thin film is proposed in G. Dittmer: “Thin Solid Films”, 9, 317 (1972) whereas the use of In
2
O
3
/SnO
2
thin film and that of carbon thin film are also discussed respectively in M. Hartwell and C. G. Fonstad: “IEEE Trans. ED Conf.”, 519 (1975) and H. Araki et al.: “Vacuum”, Vol. 26, No. 1, p. 22 (1983).
FIG. 30
of the accompanying drawings schematically illustrates a typical surface conduction electron-emitting device proposed by M. Hartwell. In
FIG. 30
, reference numeral
3001
denotes an insulating substrate. Reference numeral
3004
denotes an electron-emitting region-forming thin film, which is a thin metal oxide film prepared by sputtering, using an H-shaped pattern, in which an electron-emitting region
3005
is produced when it is subjected to an electrically energizing process referred to as “energization forming” as will be described hereinafter. In
FIG. 30
, a pair of device electrodes are separated by a length L of 0.5 to 1 [mm] and have a width W of 0.1 [mm].
Conventionally, an electron emitting region
3005
is produced in a surface conduction electron-emitting device by subjecting the electron-emitting region-forming thin film
3004
of the device to an electrically energizing process, which is referred to as energization forming. In the energization forming process, a constant DC voltage or a slowly rising DC voltage that rises typically at a very slow rate of 1V/min. is applied to given opposite ends of the electron-emitting region-forming thin film
3004
to partly destroy, deform or transform the film and produce an electron-emitting region
3005
which is electrically highly resistive. Thus, the electron-emitting region
3005
is part of the electron-emitting region-forming thin film
3004
that typically contains a fissure or fissures therein so that electrons may be emitted from the fissure and its vicinity. The electron-emitting region-forming thin film
3004
including the electron-emitting region produced by energization forming will be referred to as the electron-emitting region-containing thin film. Note that, once subjected to an energization forming process, a surface conduction electron-emitting device comes to emit electrons from its electron emitting region
3005
whenever an appropriate voltage is applied to the electron-emitting region-containing thin film
3004
to make an electric current run through the device.
Examples of FE type device include those proposed by W. P. Dyke & W. W. Dolan, “Field emission”, Advance in Electron Physics, 8, 89 (1956) and C. A. Spindt, “PHYSICAL Properties of thin-film field emission cathodes with molybdenum cones”, J. Appl. Phys., 47, 5284 (1976).
FIG. 31
of the accompanying drawings shows a schematic cross sectional view of a device proposed by C. A. Spindt et al., which is a typical FE type device. Referring to
FIG. 31
, it comprises a substrate
3010
, an emitter wiring layer
3011
made of a conductive material, a conical emitter
3012
, an insulation layer
3013
and a gate electrode
3014
. The device emits electrons from the tip of the conical emitter
3012
as an appropriate voltage is applied to the conical emitter
3012
and the gate electrode
3014
.
While the FE type device illustrated and described above has a multilayer structure, the emitter and the gate electrode may alternatively be arranged on the substrate substantially in parallel with the plane of the substrate.
Examples of MIM type device are disclosed in papers including C. A. Mead, “The tunnel-emission amplifier”, J. Appl. Phys., 32, 646 (1961).
FIG. 32
of the accompanying drawings shows a schematic cross sectional view of a typical MIM type device, Referring to
FIG. 32
, it comprises a substrate
3020
, a lower metal electrode
3021
, a thin insulation layer
3022
having a thickness of about 10 [nm] and an upper metal electrode having a thickness of about 30 [nm].
The MIM type device emits electrons from the surface of the upper electrode
3023
as an appropriate voltage is applied between the upper electrode
3023
and the lower electrode
3021
.
Contrary to a thermionic device, a cold cathode device is adapted to emit electrons at low temperature and hence does not need a heater. Consequently, the former has a simplified structure if compared with the latter and, therefore, it is possible to prepare very small cold cathode devices, which are relatively free from problems such as a thermally molten substrate if they are densely arranged on a substrate. Additionally, while the responsiveness of a thermionic device is defined by that of the heater used for it, a cold cathode device is free from such a problem and hence a highly responsive cold cathode device can be realized without difficulty.
In view of the above listed advantages and other advantages, efforts have been paid to develop electron beam apparatus, image-forming apparatus in particularly, comprising cold cathode devices.
Particularly, the surface conduction electron-emitting device provides a remarkable advantage that a large number of devices can be arranged over a large area because of the structural simplicity they have. Studies have been made to exploit this advantage for various applications. Applications of surface conduction electron-emitting devices include electrically charged beam sources and display apparatus.
Applications of surface conduction electron-emitting devices arranged in numbers include electron sources realized by arranging surface conduction electron-emitting devices in parallel rows and connecting them through the opposite ends of each of the devices by means of wires to form a matrix of devices (see, inter alia, Japanese Patent Application Laid-Open No. 1-031332 filed by the applicant of the present patent application). While flat panel type display apparatus utilizing liquid crystal have been replacing CRTs in the field of image-forming apparatus including display apparatus, they have a drawback that they are not of the emission type and hence required to be provided with a back light. Therefore, there has been a strong demand for emission type display apparatus. Emission type display apparatus capable of displaying high quality images include image-forming apparatus having a large display screen that can be realized with relative ease by combining an electron source comprising a large number of surface conduction electron-emitting devices and fluorescent bodies adapted to emit visible light by electrons emitted from the devices (see, inter alia, U.S. Pat. No. 5,066,883 issued to the application of the present patent application).
An electron beam appratus that can be used for image-forming apparatus as described above typically comprises an envelope for maintaining vacuum within the apparatus, an electron source arranged in the envelope, targets to be irradiated with respective electron beams e

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