Electron beam emitting apparatus with potential defining...

Details Electron beam emitting apparatus with potential defining... Electron beam emitting apparatus with potential defining...

2000-10-31

2004-02-17

Patel, Vip (Department: 2879)

Electric lamp and discharge devices

With luminescent solid or liquid material

Vacuum-type tube

C313S496000, C313S310000, C315S169100, C315S169300

Reexamination Certificate

active

06693376

ABSTRACT:

This application is a continuation of International Application No. PCT/JP00/01193, filed Mar. 1, 2000, which claims the benefit of Japanese Patent Application No. 11-053793, filed Mar. 2, 1999.
TECHNICAL FIELD
The invention disclosed in the present application relates to electron beam emitting apparatus and image-forming apparatus. More particularly, the invention concerns the electron beam emitting apparatus and image-forming apparatus provided with a lot of electron-emitting devices.
BACKGROUND ART
There are two types of electron-emitting devices known heretofore, thermionic emission sources and cold-cathode emission sources, and there are also the known image-forming apparatus making use of these electron sources.
The image-forming apparatus illustrated in
FIG. 11
is known as a plane type image-forming apparatus using the thermionic emission source.
FIG. 11
is a schematic structural diagram of the image-forming apparatus using the conventional thermionic emission source.
This image-forming apparatus has a plurality of anodes
1502
, which are arranged in parallel on an insulating substrate
1501
and the surface of which is coated with a material that emits fluorescence upon collision of an electron beam therewith (phosphor), a plurality of filaments
1503
, which are arranged in parallel and opposite to the anodes
1502
, and a plurality of grid electrodes
1504
, which are arranged perpendicular to the anodes
1502
and filaments
1503
between the anodes
1502
and the filaments
1503
, and these anodes
1502
, filaments
1503
, and grid electrodes
1504
are held in a transparent vessel
1505
. The vessel
1505
is hermetically bonded (hereinafter referred to as “sealed”) to the insulating substrate
1501
so as to be able to keep the inside in vacuum, and the inside of the envelope constructed of the vessel
1505
and the insulating substrate
1501
is kept in the vacuum of about 1.3×10
−4
Pa.
The filaments
1503
emit electrons when heated in vacuum and, with application of respectively appropriate voltages to the grid electrodes
1504
and to the anodes
1502
, the electrons emitted from the filaments
1503
collide with the anodes
1502
, whereupon the phosphor on the anodes
1502
emits fluorescence. Light-emitting positions can be controlled by matrix addressing of the lines of anodes
1502
(in the X-direction) and the lines of grid electrodes
1504
(in the Y-direction), whereby an image can be displayed through the vessel
1505
.
The image-forming apparatus using the thermionic emission source, however, has the following problems: (1) power consumption is large, (2) it is difficult to implement large-capacity display because of slow modulation speed, and (3) variation occurs readily among the devices, and it is not easy to realize a large screen, because the structure becomes complex. Thus there are also the image-forming apparatus using the cold-cathode emission source instead of the thermionic emission source.
The cold-cathode emission sources include field emission type (hereinafter referred to as “FE type”), metal/insulator/metal type (hereinafter referred to as “MIM type”), surface conduction electron-emitting devices, and so on.
Examples of the known FE type devices are those described in W. P. Dyke & W. W. Dolan, “Field emission”, Advance in Electron Physics, 8, 89 (1956), or in C. A. Spindt, “Physical Properties of thin-film field emission cathodes with molybdenum cones”, J. Appl. Phys., 47, 5248, (1976), and so on.
An example of the image-forming apparatus using this FE type electron source will be described referring to FIG.
12
.
FIG. 12
is a schematic, structural diagram to show the conventional image-forming apparatus with the FE type electron source, partly enlarged.
As illustrated in
FIG. 12
, this image-forming apparatus has an electron source
2001
, in which many electron-emitting devices are formed, and a face plate
2003
opposed to the electron source
2001
. The electron source
2001
is comprised of a lot of micropoints
2013
, which are formed in an electrically connected state through electric conductors
2012
on an insulating substrate
2011
, and a grid
2015
, which has apertures corresponding to the micropoints
2013
and which is supported on the insulating substrate
2011
while being electrically insulated from the micropoints
2013
by insulating layer
2014
. The bottoms of the micropoints
2013
have the diameter and height of about 2 &mgr;m and the diameter of the apertures in the grid
2015
is also about 2 &mgr;m.
The face plate
2003
is comprised of the phosphor
2032
, which is laid on the inner surface of glass sheet
2031
, and an electroconductive film
2033
, which covers the phosphor
2032
and which acts as an acceleration electrode to which a voltage for accelerating electrons emitted from the micropoints
2013
is applied.
In the above structure, the distance is very small between the tips of the micropoints
2013
and the grid
2015
(not more than 1 &mgr;m), and the tips of the micropoints
2013
are of a pointed shape. Therefore, a strong electric field (not less than 10
7
V/cm) capable of field electron emission can be created between the micropoints
2013
and the grid
2015
even by the potential difference of not more than 100 V. The amount of electron emission from one micropoint
2013
is approximately several &mgr;A. Since it is possible to form approximately several ten thousand micropoints
2013
per mm
2
, an electron-emitting device corresponding to one pixel is normally composed of a set of about several thousand to several ten thousand micropoints
2013
in the image-forming apparatus. Therefore, the electron emission amount can be over several mA per electron-emitting device corresponding to one pixel.
The potentials at the grid
2015
and at the micropoints
2013
are set, for example, as follows: the earth potential (0 V) is applied to the grid
2015
and a negative potential (about −100 V) is applied through the conductor
2012
to the micropoints
2013
, which implements electron emission. Further, a potential equal to or greater than that at the grid
2015
is applied through the conductive film
2033
to the face plate
2003
, whereby the electrons emitted from the electron source
2001
come to collide with the phosphor
2032
to excite the phosphor and effect light emission thereof.
For controlling luminous points of this emission, there are provided a plurality of row wires
2041
formed of an array of X-directional beltlike conductors
2012
, each being electrically connected to a plurality of micropoints
2013
, and column wires
2042
of the grid
2015
electrically connected in the Y-direction, and an image can be displayed in such a manner that matrix addressing is implemented so as to apply a voltage over a desired electron emission start voltage to desired areas out of a plurality of electron-emitting device areas
2010
formed at intersections of this matrix wire pattern from external power supplies
2043
,
2044
, thereby selecting positions where the electrons impinge upon the phosphor
2032
to which the voltage is applied through the conductive film
2033
from an acceleration voltage supply
2045
.
On the other hand, examples of the known MIM devices are those described in C. A. Mead, “Operation of Tunnel-emission Devices”, J. Appl. Phys., 32,646 (1961) and so on.
Examples of the surface conduction electron-emitting devices are those described in M. I. Elinson, Radio Eng. Electron Phys., 10, (1965) and so on.
The surface conduction electron-emitting devices are the electron-emitting devices making use of the phenomenon that electron emission occurs when electric current flows in parallel to the surface in small-area thin film formed on a substrate. The surface conduction electron-emitting devices reported heretofore include those using thin films of SnO
2
reported by aforementioned Elinson et al., those using thin films of Au [G. Dittmer: “Thin Solid Films,” 9,317 (1972)], those using thin films of In
2
O
3
/SnO
2
[M. Hartwell a

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