Electric lamp and discharge devices – With luminescent solid or liquid material – Vacuum-type tube
Reexamination Certificate
2000-02-17
2002-08-20
O'Shea, Sandra (Department: 2875)
Electric lamp and discharge devices
With luminescent solid or liquid material
Vacuum-type tube
C313S496000, C313S497000
Reexamination Certificate
active
06437503
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an electron emission device with an improved emission-widening characteristic, and relates to a method of driving the electron emission device.
BACKGROUND OF THE INVENTION
Electron emission devices have functions of capturing electrons emitted from emitter by anode electrode and recognizing it as electrical signal, or enabling fluorescent part on anode electrode to emit light by electronic excitation in capturing electrons and recognizing it as optical signal. Application examples to recognize the electrical signal are amplifiers generally called vacuum tube, oscillators etc. On the other hand, application examples to recognize the optical signal are cathode-ray tubes, fluorescent display tubes, a flat-type display called FED (field emission display) etc.
As an example of the conventional electron emission devices, FED is explained below.
FIG. 1
is a cross sectional view illustrating one picture element in a conventional FED. Shown is a structure that electrons are emitted to excite red fluorescent part to emit light. Here, a picture element means a minimum unit when an image displayed by the FED is space-divided. In FED that a color picture is displayed by a display system of optical three primary colors, i.e. R(red), G(green) and B(blue), one of the colors, e.g. R(red), is called a picture element.
As shown in
FIG. 1
, SiO
2
film of about 1 &mgr;m thick, as insulation, film
2
, is deposited on substrate
1
by sputtering, aluminum film of about 200 nm thick, as gate electrode
3
, is deposited on the insulation film
2
, a tubular gate hole
4
is formed penetrating the gate electrode
3
and insulation film
2
. Emitter
5
is formed with cathode material deposited on the substrate
1
at the bottom of the gate hole
4
. Also, anode electrode
6
is disposed around
5
mm above the substrate
1
. Fluorescent material
7
with red fluorescent property is coated on part of the anode electrode
6
located just over the gate hole
4
.
A voltage of about 5.1 kV is applied to the anode electrode
6
and the fluorescent part 7.0 V is applied to the emitter
5
of cathode material, and about 100 V is applied to the gate electrode
3
. By thus applying the voltages, equipotential surface
8
is formed. Here, the distance, between the anode electrode
6
and the gate electrode
3
is 5 mm, and the voltage is 5000 V. So, electric field between the both electrodes
6
and
3
is given by:
5000/5 [V/mm]=1 [kV/mm].
On the other hand, the distance between the gate electrode
3
and the emitter
5
is 1 &mgr;m (10
−3
[mm]), and the voltage is 100 V. So, the electric field between the both electrodes
3
and
5
, gate and emitter is given by:
100/10
−3
[V/mm]=
100 [kV/mm].
Thus, the value of electric field between gate and emitter is 100 timer, the value of electric field between the anode electrode
6
and the gate electrode
3
. Therefore, at the inside of the gate hole
4
and its vicinity, the center of the gate hole
4
floats on the equipotential surface
8
to function as a circular hole lens. In this circular hole lens, in the vicinity of the center axis of the gate hole
4
, electric field applied to the emitter
5
is weakened. In other words, the circular halt lens has power to diverge electrons, and electrons being emitted from positions off the center axis (convergence axis) are thus provided with electron tracks being curved in the direction of getting away from the axis (in the widening direction) Here, “power” of the circular hole lens means energy, which is owned by the equipotential surface
8
composing the circular hole lens, to diverge or converge electrons.
The phenomenon that the electron emission tracks are curved by the circular hole lens effect is detailed below. In
FIG. 1
the emitter
5
is divided into small regions, and electron tracks emitted from the respective regions are shown. Since the gate hole
4
has an axially symmetrical shape, the emitter
5
deposited at the bottom of the gate hole
4
is divided into three regions from the near side of axis to the far side of axis. The regions sectioned by concentric circles like an archery target are called a, b and c from the center. Region a is a region that includes the axis.
9
is electron emitted from region a,
10
is electron emitted from region b, and
11
is electron emitted from region c. The respective electrons
9
,
10
and
11
are widened outside in the order of regions a, b and c.
However, in the above electron emission device, there is a problem that electrons
9
,
10
an
11
omitted are diverged in the direction of getting away from the axis while they travel to the anode electrode
6
. Since in FED the picture elements are arrayed being divided finely, when elections are diverged, there occurs a problem that electron arrives at fluorescent part
7
of the neighboring picture element, not fluorescent part
7
of its own picture element. If electron arrives at fluorescent part
7
of a different color's picture element, then a different color is created. Also, if electron arrives at fluorescent part
7
of a neighboring same-color's picture element, then a failure in space revolution occurs.
FIG. 2
is a graph shaving an operation characteristic of the conventional electron emission device in FIG.
1
. Shown in
FIG. 2
is the relationship between cathode applied electric field and amount of emission current. The cathode applied electric field shown in the graph is applied to the emitter
5
deposited at the bottom of the gate hole
4
. Herein, the value of electric field at the mean height (in 1 &mgr;m insulation film structure, a height of 0.5 &mgr;m) of gate hole is used as a value of cathode applied electric field.
When the cathode applied electric field increases gradually, electric field (threshold electric field) where emission current starts flowing appears. A maximum value in a necessary amount of emission current is called a maximum amount of current, and cathode applied electric field required to get that amount of current is called maximum electric field. To display an image in analogue system by FED, according to input signal, it is necessary to apply arbitrary electric field between the threshold electric field and the maximum electric field to get a desired brightness of fluorescent light. In pulse width drive system, a desired brightness of fluorescent light can be obtained by controlling the time of applying a certain electric field e.g., maximum electric field.
If there is a limit to the emission(or emission electron)-widening characteristic, the electron emission device only has to be driven according to the emission characteristic in FIG.
2
. However, in fact, the emission may be, widened greater than the limit due to the circular hole lens effect. The bigger the difference of electric field at the opening of gate hole (phenomenon (
1
)) or the farther, the emission position of electron deviated from the axis (phenomenon (
2
)), the more significantly the widening phenomenon of electron due to the circular hole lens effect occurs.
FIG. 3
is a graph showing the phenomenon (
1
) when the difference of electric field at the opening of gate hole is big when the cathode applied electric field is increased while keeping the voltage of the anode electrode
6
constant, there occur phenomena such as (
1
′) the distortion of equipotential surface increases and (
2
′) the velocity at the opening of gate hole increases. By the phenomena (
1
′) and (
2
′)) the range of emission widening when arriving at the anode electrode
6
is further extended.
As “length D” to represent the widening range above-mentioned in
FIG. 3
, the, range indicated by arrow D in
FIG. 1
is used. In order to increase the cathode applied electric field, the potential of gate electrode is increased. That there occurs the problem that electron plunges into the neighboring fluorescent part means the widening range “D” is already exceeding the limi
Truong Bao Q.
Young & Thompson
LandOfFree
Electron emission device with picture element array does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electron emission device with picture element array, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electron emission device with picture element array will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2962544