Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
2001-09-14
2002-11-26
Vu, David (Department: 2821)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C313S309000, C313S351000
Reexamination Certificate
active
06486609
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a cold-cathode type electron-emitting element that brings about the field emission of electrons and to an image display device constructed using the same.
BACKGROUND ART
In recent years, accompanying increasing demands for a reduction in the thickness of displays and improved compactness, the development of microminiature electron-emitting elements capable of high-speed operation has become very active.
In the development of electron-emitting elements, research and development was first focused on the thermal emission type, but in recent years, research and development of the cold cathode type, which without requiring heating at high temperatures, can emit electrons even at a low voltage, has become extensive. Against this background and building on prior art, a cold-cathode type element structure capable of obtaining a stable, high current at low voltage and low power consumption and bringing about the emission of electrons from a selected location was proposed in the Japanese Unexamined Patent Publication No. H10-199398.
This element, as is shown in FIG.
8
(
a
), takes on a structure such that a graphite layer
212
, serving as the cathode electrode, is deposited in a line formation on a substrate
211
, and on top of this, an electron-emitting layer
213
comprising a carbon nanotube layer is provided. In addition, an insulating region
214
is provided on both sides of the electron-emitting layer
213
, and on top of this, a grid electrode
215
with a line formation is disposed so that it is orthogonal to the electron-emitting layer
213
.
With this kind of structure, when a positive voltage is applied to the grid electrode
215
and a negative voltage to the cathode electrode
212
, an electric field is generated at the sections where the electrodes intersect, and electrons are pulled from the intersecting sections of the cathode electrode. Therefore, by selecting a line to which to apply a voltage, it is possible to bring about the emission of electrons from a selected location. In addition, because the electron-emitting layer is made of carbon nanotubes, which have excellent discharge characteristics, a stable, large current can be obtained in a low vacuum and at a low voltage.
However, with this element structure, there are the following inherent problems:
1) Because the restricting of the pulling of electrons is accomplished only by the potential difference between the cathode and the grid, in order to pull electrons from the cathode, sufficient voltage must be applied to the grid electrode. Thus, it is difficult to realize a sufficiently low operation voltage.
2) Because an electric field is generated between the opposing surfaces of the intersecting cathode electrode and the grid electrode, many electrons emitted from the cathode electrode surface end up flowing into the grid electrode, which is the opposing surface. Therefore, the number of electrons that arrive at the anode, which is disposed above the grid electrode, is not more than the small portion that passes through the central portion of the electron passage hole. Thus, the usage efficiency of the emitted electrons is low.
3) The anode electrode is disposed above the grid electrode, but when a potential is supplied to the anode electrode, an electric field concentration arises at the edge portions of the grid electrode, and thus the generating of abnormal discharge from the edge portions of the grid
215
tends to occur. Abnormal discharge causes a considerable deterioration in the reliability of the electron-emitting device.
DISCLOSURE OF THE INVENTION
The present invention was developed to solve the foregoing and other problems. The inventors of the present invention, through intense research, discovered that electrons could be very efficiently pulled from an electron-emitting material (the cathode electrode) by combining an electric field between the anode electrode and the cathode electrode and an electric field between the grid electrode and the cathode electrode and that abnormal discharge from the edge portions of the grid electrode could be prevented by adjusting the placement and shape of the grid electrode. The inventors thus achieved the present invention. The present invention has the following construction.
(1) An electron-emitting element is provided comprising an electron conveying member, a cathode electrode comprising an electron-emitting member fixed to the electron conveying member, an anode electrode disposed such that it is spaced from the cathode electrode, and a grid electrode disposed between the cathode electrode and the anode electrode and having an electron passage opening, wherein the spatial positioning of the three members, the cathode electrode, the anode electrode and the grid electrode, and their respective shapes are constructed such that an electric field existing between the grid electrode and the anode electrode emanates from the electron passage opening to the cathode electrode side, and the emanated electric field and an electric field existing between the cathode electrode and the grid electrode interact with each other to form a combined electric field, and electron-emission controlling means is provided for varying the intensity of the combined electric field by varying the potential of at least one of the cathode electrode, the anode electrode, and the grid electrode to control the number of electrons emitted from the cathode electrode.
This construction is characterized in that a combined electric field is formed from the electric field that emanated to the cathode electrode side and the electric field generated between the cathode electrode and the grid electrode and the field emission of electrons from the cathode electrode is controlled by varying the intensity of the combined electric field. Compared with conventional field emission elements, an element employing this control method makes remarkably efficient field emission possible. Thus, at a low operating voltage, there is good response and stable electron emission can be brought about. The basic principle of this kind of electron-emitting element of the present invention is described with reference to FIG.
1
.
In an electron-emitting element of the present invention, in order to form a combined electric field, the spatial positioning and shapes of the three members, the cathode electrode, the anode electrode, and the grid electric, are appropriately adjusted, and by utilizing the electron-emission controlling means, the intensity of the combined electric field is controlled to control the number of electrons emitted from the cathode electrode. The characteristics and technical significance of this combined electric field is made clear by FIG.
1
.
FIG. 1
shows the concept that supposing a voltage much lower than but with the same polarity as that of the anode electrode is applied to the grid electrode, the state of the combined electric field is as represented by equipotential surfaces
10
. As is shown in
FIG. 1
, an electric field existing between a grid electrode
3
and the anode electrode emanates from the electron passage opening of the grid electrode
3
to the cathode electrode side and this emanated electric field interacts with an electric field generated between a cathode electrode
2
and the grid electrode
3
to form a protruding set of equipotential surfaces on the cathode electrode side. This set of equipotential surfaces is the combined electric field.
A combined electric field region
11
of
FIG. 1
designates the range of the effect of the emanating electric field, in other works the range of the combined electric field. The respective intervals of the group of equipotential surfaces within the combined electric field region
11
are, as shown in
FIG. 1
, the most narrow on the line (valley line) connecting the points (valleys) of each equipotential surface, and as the distance from the valley line increases to either the right or the left, the equipotential surface intervals widen. In other words, the group of points on the valley
Akiyama Koji
Kurokawa Hideo
Shiratori Tetsuya
Matsushita Electric Industries, Inc.
Parkhurst & Wendel L.L.P.
Vu David
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