Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
2003-01-21
2004-06-08
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C345S075200
Reexamination Certificate
active
06747416
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) and grating light valves (GLVs). 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 side cut-away (cross sectional) view of a conventional FED. The FED
100
includes a cathode plate
102
and an anode plate
104
(or face plate), which opposes the cathode plate
102
. The cathode plate
102
includes a cathode substrate
106
, cathode electrodes (cathode electrode
107
is illustrated) printed on the substrate
106
, a dielectric layer
108
disposed on the cathode substrate
106
and the cathode electrode
107
, and a gate electrode
114
disposed on the dielectric layer
108
and several emitter wells
110
formed within the gate electrode
114
and the dielectric layer
108
. An electron emitter
112
is deposited within each emitter well
110
, the emitters
112
shaped as conical electron emitters, e.g., Spindt tips.
The anode plate
104
includes a transparent substrate
116
(face plate or display face) upon which is formed various phosphors (e.g., red, green and blue) that oppose the electron emitters
112
, for example, a red phosphor
120
is illustrated. A thin metallic anode
118
is formed over the phosphors, e.g., phosphor
120
.
It is important that 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. In order to maintain a 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 the cathode electrode
107
and the gate electrode
114
, producing an electric field
122
focused to cause a selective electron emission
124
from the tips of the electron emitters
112
. The emitted electrons are accelerated toward and illuminate the phosphor
120
of the anode
118
by applying a proper potential to the anode
118
. The anode potential must be high enough that the electrons penetrate through the anode
118
to illuminate the phosphors. One problem with known FEDs is that a high electric field is necessary to drive the device. Thus, designers use a very high drive voltage or use sub-micron spacing between the cathode electrode
107
and the gate electrode
114
, which may lead to crosstalk and increases the cost of the FED.
A grating light valve (GLV) is micromachined diffraction grating that acts as a spatial light modulator (SLM) to vary how light is reflected from each of multiple deflecting ribbon-like structures and are commonly used projection elements. A conventional GLV
10
, such as described in U.S. Pat. No. 5,311,360, issued May 10, 1994 to Bloom et al., entitled METHOD AND APPARATUS FOR MODULATING A LIGHT BEAM, is illustrated in
FIGS. 2
,
3
and
4
. A pattern of deformable elements
18
(typically ribbons) are formed in a spaced relationship over a substrate
16
having an electrode
24
formed on the base of the substrate
16
. The elements
18
and the substrate
16
are coated with a reflective material
22
. In
FIG. 3
, the grating
10
is shown in a non-diffracting state with no voltage applied between the electrode
24
of the substrate
16
and the individual elements
18
, and with a lightwave
26
incident upon it. The height difference between the reflective material
22
on the elements
18
and on the substrate
16
is designed to be &lgr;/2 of the incident lightwave
26
when the deformable elements
18
are in a relaxed state (FIG.
3
), such that light reflected from the elements
18
and from the substrate
16
add in phase and the grating
10
acts to reflect the incident lightwave
26
as a flat mirror.
However, as illustrated in
FIG. 4
, when a voltage is applied between the elements
18
and the electrode
24
of the substrate
16
, the electrostatic forces pull the elements
18
down onto the substrate
16
, with the result that the distance between the top of the elements
18
and the top of the substrate
16
is now &lgr;/4 of the incident lightwave
26
. Thus, the total path length difference for the light reflected from the elements
18
and from the substrate
16
is now &lgr;/2 of the incident lightwave and the reflections interfere destructively, causing the light to be diffracted, indicated as
28
. By using this grating
10
in combination with a system, for detecting the reflected light, which has a numerical aperture sized to detect one order of diffracted light from the grating, the grating
10
can used to be modulate the reflected light with high contrast in order to create a projection display.
Typically, the elements
18
are formed by depositing a layer of conducting material over an insulating layer
11
formed on a substrate, then etching away the elements
18
and portions of the insulating layer
11
such that the remaining portions of the conducting material form the elements
18
. However, the entire conducting layer is not etched away, in order to form a frame
20
that the elements
18
are tensioned between and which is supported above the substrate
16
by the remaining portions of the insulating layer
11
.
SUMMARY OF THE INVENTION
The invention provides an electron emitting structure that uses a field emission display (FED)-like cathode in combination with deflecting electrodes or deflecting ribbons, such as used in grating light valves (GLVS) to produce various electron emitting structures. In a preferred form, the electron emitting structure is used as a cathode plate of an FED, which advantageously, provides lower drive voltages in order to provide an electric field sufficient to produce an electron emission without requiring sub-micron spacing between electrodes.
In one embodiment, the invention can be characterized as an electron emitting structure comprising a substrate having base electrodes and gate electrodes coupled thereto, an insulating material separating and electrically insulating the base electrodes and the gate electrodes, and an electron emitting material deposited on active regions of the base electrodes. Upon applying a voltage potential difference between a respective base electrode and a respective gate electrode, a portion of one of the respective base electrode and the respective gate electrode deflects through electrostatic force positioning the portion of the one of the respective base electrode and the respective gate electrode relative to another one of the respective base electrode and the respective gate electrode such that an electric field is produced at a respective active region sufficient to cause an electron emission from a respective electron emitting material deposited on the respective active region.
In another embodiment, the invention can be characterized as a method of electron emission comprising the steps of: applying a voltage potential difference between a base electrode and a gate electrode of an electron emitting structure, the base electrode electrically insulated from the gate electrode; deflecting, as a result of the applying step, a portion of one of the base electrode and the gate el
Barger Jack
Guillou Jean-Pierre
Russ Benjamin Edward
Wang James Qian
A Minh Dieu
Fitch Even Tabin & Flannery
Lebens Thomas F.
Wong Don
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