Field emission cold cathode

Details Field emission cold cathode Field emission cold cathode

1999-11-02

2002-07-02

Patel, Nimeshkumar D. (Department: 2879)

Electric lamp and discharge devices

Discharge devices having a multipointed or serrated edge...

C313S336000, C313S351000, C313S495000, C313S496000, C313S497000

Reexamination Certificate

active

06414421

ABSTRACT:

The present application claims priority to Japanese Patent Application No. 10-315691 filed on Nov. 6, 1998, the specification, claims, drawings and summary of which is hereby incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a field emission cold cathode.
2. Description of the Related Art
With respect to current control, a field emission cold cathode can be grouped into two groups. A current is controlled by means of a resistor in one of the groups, and by means of a transistor in the other group. Hereinbelow are explained typical field emission cold cathodes with respect to how a current is controlled and with respect to a current limiting device.
Japanese Unexamined Patent Publication No. 5-47296 has suggested a field emission cold cathode including a current limiting device comprised of a resistor, and emitter cones to which the current limiting device is electrically connected.
FIG. 1
illustrates the suggested field emission cold cathode. The illustrated field emission cold cathode is comprised of an electrically conductive substrate
9
, an insulating layer
5
formed on the substrate
9
, a gate electrode
2
formed on the insulating layer
5
, and a plurality of emitter cones
6
formed at a surface of the substrate
9
in an gate opening
1
formed throughout the gate electrode
2
and the insulating layer
5
. Each of the emitter cones
6
has a resistor
13
therebelow.
Japanese Unexamined Patent Publication No. 5-144370 has suggested a field emission cold cathode including a current limiting device comprised of a resistor, and a gate electrode electrically connected to the current limiting device.
FIGS. 2A and 2B
illustrate the suggested field emission cold cathode. The illustrated field emission cold cathode is comprised of an electrically conductive substrate
9
, an insulating layer
5
formed on the substrate
9
, a gate electrode
2
formed on the insulating layer
5
, and a plurality of emitter cones
6
formed at a surface of the substrate
9
in an gate opening
1
formed throughout the gate electrode
2
and the insulating layer
5
. The gate electrode
2
is comprised of a highly resistive layer
23
, and a lowly resistive layer
22
formed on the highly resistive layer
23
in the form of a mesh.
Japanese Unexamined Patent Publication No. 4-284324 has suggested a field emission cold cathode as illustrated in FIG.
3
. The suggested field emission cold cathode is comprised of an electrically conductive substrate
9
, an insulating layer
5
formed on the substrate
9
, a gate electrode
2
formed on the insulating layer
5
, a plurality of emitter cones
6
formed at a surface of the substrate
9
in an gate opening
1
formed throughout the gate electrode
2
and the insulating layer
5
, a power-feeding line
7
formed on the insulating layer
5
, and a connector
18
electrically connecting the gate electrode
2
to the power-feeding line
7
.
Japanese Unexamined Patent Publication No. 5-67441 has suggested a field emission cold cathode including a current limiting device comprised of a transistor.
FIG. 4
illustrates the suggested field emission cold cathode. The illustrated field emission cold cathode is comprised of an electrically conductive substrate
9
, an insulating layer
5
formed on the substrate
9
, a gate electrode
2
formed on the insulating layer
5
, a plurality of emitter cones
6
formed at a surface of the substrate
9
in an gate opening formed throughout the gate electrode
2
and the insulating layer
5
, and a transistor including a base
19
and an emitter
20
, formed in the substrate
9
.
Japanese Unexamined Patent Publication No. 10-12128 has suggested a field emission cold cathode including a current limiting device having trenches.
FIG. 5
illustrates the suggested field emission cold cathode. The illustrated field emission cold cathode is comprised of an electrically conductive substrate
9
including a current flow limiting region
7
at a surface thereof, an insulating layer
5
formed on the substrate
9
, a gate electrode
2
formed on the insulating layer
5
, and a plurality of emitter cones
6
formed at a surface of the substrate
9
in an gate opening formed throughout the gate electrode
2
and the insulating layer
5
. A plurality of trenches is formed throughout the insulating layer
5
and further into a certain depth of the substrate
9
. Each of the trenches is filled with an electrical insulator
8
. The trenches filled with the electrical insulator
8
define the current-flow limiting region
7
.
Japanese Unexamined Patent Publication No.
6-176686
has suggested a field emission cold cathode including a current limiting device comprised of a transistor. Specifically, the suggested field emission cold cathode is comprised of an emitter array, a power-feeding line for feeding electric power to emitters, and a field effect transistor located between the emitter array and the power-feeding line, and having a source region, a gate electrode, and a drain region.
Japanese Unexamined Patent Publication No. 10-50205 has suggested a field emission cold cathode comprising a semiconductor substrate, a plurality of electrically conductive regions formed in the substrate, a plurality of pillar-shaped cathodes each formed on each of the electrically conductive regions, and electrodes each formed on each of the electrically conductive regions with an insulating layer sandwiched therebetween, and each formed with an opening around each of the cathodes. Each of the cathodes includes an upper layer and a lower layer which have electrical conductivities different from each other to thereby establish pn-junction therebetween. The upper layer of each of the cathodes is electrically isolated from the electrically conductive regions.
Japanese Unexamined Patent Publication No. 10-64407 has suggested a field emission cold cathode including an emitter having a sharpened summit and electrically connected to a cathode electrode, a gate electrode having an opening around the emitter, and a pinch-off resistance having saturated current characteristic and located between the emitter and the cathode electrode.
Japanese Unexamined Patent Publication No. 10-21820 has suggested a field emission cold cathode including a silicon substrate having electrically insulating regions, a resistive layer formed on the electrically insulating regions, an insulating layer formed on the resistive layer, a gate conductive layer formed on the insulating layer, and a plurality of conical cathodes each located in an opening formed throughout the gate conductive layer and the insulating layer above the electrically insulating regions.
As is obvious, a function of limiting a current flow for preventing destruction of a cathode from abnormal discharge is provided to either a gate electrode or an electrically conductive substrate to which an emitter cone is connected. The function of limiting a current flow may be provided by addition of either a resistor or a transistor to a field emission cold cathode.
However, if the function of limiting a current flow is provided by addition of a resistor to a field emission cold cathode, the resultant field emission cold cathode would be accompanied with a problem that it is impossible to drive the field emission cold cathode with high frequency. Furthermore, there would be caused a problem that the number of emitter cones per a unit area would be reduced, if a current limiting device is formed in a gate electrode.
The reason is as follows. When the function of limiting a current flow is provided by addition of a resistor to a field emission cold cathode, it would be possible to arrange a resistor in the vicinity of an emitter cone, as illustrated in
FIGS. 2A and 2B
, for instance. In such an arrangement, the function of limiting a current flow would start operating immediately after discharge has started. However, if a flow of discharge current is to be limited only by means of a resistor, a resistor would have to have a great resistanc

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