Electric lamp and discharge devices – Discharge devices having a multipointed or serrated edge...
Reexamination Certificate
2000-03-29
2002-09-24
Patel, Vip (Department: 2879)
Electric lamp and discharge devices
Discharge devices having a multipointed or serrated edge...
C313S495000, C313S336000, C313S351000
Reexamination Certificate
active
06455989
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an electron emission source typically suitable for an ultrathin display, a production method thereof, and a display using the electron emission source.
Conventionally, there has been proposed an ultrathin display of a type in which a panel-like electron emission source is provided inside a fluorescent screen of the display and a number of microchips made from an electron emission material are formed in each of pixel regions of the electron emission source, wherein the fluorescent screen is made luminous by exciting the microchips in the corresponding pixel regions in response to specific electric signals.
The electron emission source of this type includes a plurality of strip-like cathode electrode lines (first electrodes); a plurality of strip-like gate electrode lines (second electrodes) formed on the cathode electrode lines in such a manner as to intersect the cathode electrode lines; and the microchips disposed in an intersection region (corresponding to one pixel of the display) located between each of the cathode electrode lines and each of the gate electrode lines.
The configuration of the prior art electron emission source will be more concretely described with reference to
FIG. 1. A
plurality of strip-like cathode electrode lines
103
are formed on a lower substrate
101
made from typically a glass material; an insulating layer
104
is formed on the cathode electrode lines
103
excluding connection ends
103
a
thereof; and a plurality of strip-like gate electrode lines
105
are disposed on the insulating layer
104
in such a manner as to intersect the cathode electrode lines
103
. The connection ends
103
a
of the cathode electrode lines
103
and connection ends
105
a
of the gat e electrode lines
105
are connected to a control means
109
.
A number of fine holes
17
are formed in an intersection region between each of the cathode electrode lines
103
and each of the gate electrode lines
105
. The fine holes
17
pass through the gate electrode line
105
and the insulating layer
104
and reach the surface of the cathode electrode line
103
. A microchip
106
is provided in each of the fine holes
17
in such a manner as to project from the bottom of the fine hole
17
.
The microchips
106
are each formed into an approximately conical shape by using an electron emission material such as molybdenum, and are disposed on the cathode electrode lines
103
. The height of the leading end of the conical body of each microchip
106
is substantially the same as the height of the film surface of the gate electrode line
105
. In this way, a number of the microchips
106
are provided in the intersection region between each of the cathode electrode lines
103
and each of the gate electrode lines
105
, and the intersection region forms a pixel region which corresponds to one pixel of the display.
The electron emission source, designated by reference numeral
100
in
FIG. 1
, is operated by selecting a desired one of the cathode electrode lines
103
and a desired one of the gate electrode lines
105
and applying a specific voltage therebetween by the control means
109
, to apply the specific voltage to the microchips
106
in the corresponding pixel region, thereby allowing electrons to be emitted from the leading ends of the microchips
106
on the basis of the tunnel effect. In the case of using the microchips
106
made from molybdenum, the specific voltage applied to each microchip
106
is set at such a value as to obtain the strength of an electric field near the leading end of the conical body of the microchip
106
in a range of about 10
8
to about 10
10
V/m.
When the electron emission source
100
shown in
FIG. 1
is used for a display, a transparent upper substrate (not shown) is assembled to the electron emission source
100
in such a manner as to be disposed on the gate electrode lines
105
with a gap put therebetween. Strip-like anode electrode lines are formed on the under face of the upper substrate and phosphor stripes are formed on the anode electrode lines. The anode electrode lines are made from a transparent conductive material such as ITO (Indium Tin Oxide). Connection ends of the anode electrode lines are connected to the control means
109
. A space between the upper substrate and the lower substrate
101
is configured as a high vacuum region.
Such a display is operated such that electrons emitted from the microchips
106
in a desired pixel region by exciting the pixel region are accelerated by a voltage applied between the corresponding cathode electrode line
103
and anode electrode line, passing through the vacuum region between the gate electrode lines
105
and the anode electrode lines, and reach the corresponding phosphor stripe. When the electrons are thus made incident on the phosphor stripe, visual light is emitted from an electron-incident portion of the phosphor stripe and is observed through the transparent anode electrode line and upper substrate.
The above-described prior art electron emission source has the following problems:
At first, it is difficult to uniformly produce the microchips
106
, particularly, the leading ends thereof without occurrence of differences in size and/or shape therebetween. If there occur differences in size between the microchips
106
, the amount of electrons emitted from the microchips
106
, that is, the amount of a current flowing the microchips
106
differs for each pixel. As a result, luminous spots formed on the upper substrate of the display become non-uniform, thereby degrading the image quality.
At second, gas remaining in the high vacuum region between the lower substrate
101
and the upper substrate is ionized to sputter the microchips
106
, so that the shapes of the leading ends of the microchips
106
tend to be easily deteriorated with an elapsed time, thereby reducing the amount of a current flowing in the microchips
106
.
At third, since the flying direction of electrons emitted from the microchips
106
is extended by about ±30° with respect to the direction perpendicular to the cathode plane, the luminous region of the phosphor screen composed of the phosphor stripes is enlarged. This is disadvantageous in terms of high-definition of the display.
At fourth, the prior art electron emission source has a problem in its production steps. The microchips
106
are generally formed by vapor-depositing a refractory metal such as molybdenum in vacuum with a lift-off spacer left on the gate electrode lines
105
. To be more specific, the conical microchips
106
are formed in self-alignment by reversely making use of the poor step-coverage which is the characteristic of the vacuum vapor-deposition process, and then the refractory metal such as molybdenum deposited on the lift-off spacer is removed by a lift-off process. At this time, metal pieces peeled by lift-off enter in each fine hole, to cause short-circuit between the microchip
106
and the gate electrode line
105
, thereby causing short-circuit between the cathode electrode line
103
and the gate electrode line
105
. As a result, there arises a problem in degrading the production yield.
To solve the above-described problems, an electron emission source of a type using electron emission planes has been disclosed in Japanese Patent Laid-open No. Hei 8-55564. According to this prior art technique, since the electron emission planes are used in place of the microchips, it is possible to avoid the above-described problems associated with the microchips.
Such a technique, however, has another problem that since the distance between the cathode electrode lines
103
and the gate electrode lines
105
of a display according to this technique is longer than that in the case of using the microchips
106
, a high voltage is required to be applied between the electrode lines
103
and
105
in order to ensure a sufficient amount of a current for obtaining a high brightness, thereby bringing a possibility of occurrence of electric breakdown.
SUMMARY O
Nakada Satoshi
Negishi Eisuke
Kananen, Esq. Ronald P.
Patel Vip
Rader & Fishman & Grauer, PLLC
Sony Corporation
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