Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
2002-11-27
2004-09-14
Tran, Thuy Vinh (Department: 2821)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C313S307000, C313S310000, C313S509000, C313S581000, C313S586000
Reexamination Certificate
active
06791278
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to flat panel displays (FPDs), and more specifically to field emission displays (FEDs). Even more specifically, the present invention relates to the cathode structure of a field emission display (FED).
2. Discussion of the Related Art
A field emission display (FED) is a low power, flat cathode ray tube type display that uses a matrix-addressed cold cathode to produce light from a screen coated with phosphor materials.
FIG. 1
is a cross sectional view of a conventional FED. The FED
100
includes a cathode plate
102
and an anode plate
104
, which opposes the cathode plate
102
. The cathode plate
102
includes a substrate
106
, cathodes or base electrodes
107
printed on the substrate
106
, a first dielectric layer
108
disposed on the substrate
106
and the base electrodes
107
,
109
,
111
, and a gate electrode
114
disposed on the first dielectric layer
108
and several emitter wells
110
formed within the gate electrode
114
and the first dielectric layer
108
, such that the gate electrode
114
and the first dielectric layer
108
circumscribe each emitter well
110
. A conical shaped electron emitter
112
, e.g., a Spindt tip, is deposited within each emitter well
110
. A typical well
110
is approximately 1 &mgr;m in diameter. In order to precisely align the gate electrode
114
with the emitters
112
, the wells
110
are formed by etching or cutting them out of the first dielectric layer
108
and the gate electrode
114
then placing or depositing an emitter
112
within each well
110
.
The anode plate
104
includes a transparent substrate
116
upon which is formed an anode
118
. Various phosphors are formed on the anode
118
and oppose the respective emitters
112
, for example, a red phosphor
120
, a green phosphor
122
and a blue phosphor
124
.
It is important in FEDs that the particle emitting surface of the cathode plate
102
and the opposed anode plate
104
be maintained insulated from one another at a relatively small, but uniform distance from one another throughout the full extent of the display face in order to prevent electrical breakdown between the cathode plate and the anode plate, provide a desired thinness, and to provide uniform resolution and brightness. Additionally, in order to allow free flow of electrons from the cathode plate
102
to the phosphors and to prevent chemical contamination, the cathode plate
102
and the anode plate
104
are sealed within a vacuum, e.g., less than 10
−6
torr. In order to maintain the desired uniform separation between the cathode plate
102
and the anode plate
104
across the dimensions of the FED in the pressure of the vacuum, structurally rigid spacers (not shown) are positioned between the cathode plate
102
and the anode plate
104
.
The FED
100
operates by selectively applying a voltage potential between a respective one or more of the base electrodes
107
,
109
,
111
and the gate electrode
114
, producing an electric field focused to cause a selective emission from the tips of the emitters
112
.
FIG. 2
illustrates an electric field
202
produced, which focuses on the tip of the emitter
112
in order to cause the electron emission
204
. The emitted electrons are accelerated toward and illuminate respective phosphors of the anode
118
by applying a proper potential to the anode
118
containing the selected phosphor.
In another conventional FED illustrated in
FIG. 3
, an FED
300
further includes a second dielectric layer
302
disposed upon the gate electrode
114
and a focusing electrode
304
disposed upon the second dielectric layer
302
. In operation, a potential is also applied to the focusing electrode
304
to collimate the electron emission from respective emitters
112
. Thus, the focusing electrode
304
concentrates the electrons to better illuminate a single phosphor and to reduce the spread of electrons, this spread illustrated in the emission
204
of FIG.
2
.
FIG. 4
illustrates yet another conventional FED design. In this design, the FED
400
, multiple emitters
112
are deposited within wells
110
over each base electrode, e.g., base electrode
107
. In operation, the electron emission from each of the emitters
112
on a given base electrode, e.g., base electrode
107
, are directed toward a single phosphor, e.g., phosphor
120
. Since the emission isn't focused, the phosphor
120
is slightly oversized relative to the base electrode
107
such that only the intended phosphor is illuminated.
FIG. 5
illustrates a cut-away perspective view of the conventional FED
100
of FIG.
4
. As shown, the gate electrode
114
and the first dielectric layer
108
form a grid in which the generally circular-shaped emitter wells
110
are formed. In fabrication, the cathode substrate
106
is screen printed with the base electrodes
107
,
109
,
111
(electrode
107
is illustrated). Next, the first dielectric layer
108
is formed over the substrate
106
and the respective base electrodes
107
,
109
,
111
. A gate electrode layer is applied over the first dielectric layer
108
. The wells
110
and gate electrode
114
are formed by etching the first dielectric layer
108
and the gate electrode layer. The emitters
112
are then deposited into the emitter well
110
.
SUMMARY OF THE INVENTION
The invention provides an electron emitting structure, for example, for use as a cathode plate of a field emission display (FED). According to several embodiments, the electron emitting structure includes base electrodes having active regions configured such that an emitter material, for example, several emitter portions or a continuous emitter material is deposited on each active region. In preferred form, the electron emitting structure produces a substantially uniform electric field across the active region resulting in a substantially straight electron emission, which does not require a separate focusing structure. Furthermore, in preferred form, the electron emitting structure has a low drive voltage and a low capacitance, which improves the refresh rate and resolution and allows the use thereof in large screen FEDs.
In one embodiment, the invention can be characterized as an electron emitting structure comprising a substrate, base electrodes formed on the substrate, and gate electrodes formed above and crossing over the base electrodes. An insulating material is formed on the substrate and the base electrodes that separates the gate electrodes from portions of the base electrodes, the gate electrodes formed on the insulating material. And an electron emitting material is deposited on active regions of the base electrodes, each active region defined as a portion of each base electrode between a respective pair of gate electrodes.
In another embodiment, the invention can be characterized as a method of electron emission comprising the steps of: applying a first potential to a respective one of a plurality of base electrodes formed on a substrate of an electron emitting structure; applying a second potential to each of a pair of gate electrodes crossing over the respective one of the plurality of base electrodes, the pair of gate electrodes each separated from the base electrode by an insulating material formed on a portion of the base electrode and the substrate, the gate electrodes formed on the insulating material; and producing an electric field across an active region of the respective one of the plurality of base electrodes as a result of the applying the first potential and the applying the second potential, the electric field sufficient to cause an electron emission from an electron emitting material located on the active region of the respective one of the plurality of base electrodes, the active region defined as a portion of the base electrode between the pair of gate electrodes.
In a further embodiment, the invention may be characterized as a field emission display including a cathode plate and an anode plate. The cathode plate comprises: a
Barger Jack
Russ Benjamin Edward
Fitch Even Tabin & Flannery
Lebens Thomas F.
Sony Corporation
Tran Thuy Vinh
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