Electric lamp and discharge devices – Discharge devices having a thermionic or emissive cathode
Reexamination Certificate
2000-12-21
2004-05-18
Wong, Don (Department: 2821)
Electric lamp and discharge devices
Discharge devices having a thermionic or emissive cathode
C315S169100
Reexamination Certificate
active
06737792
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a field emission cathode, an electron emission device and an electron emission device manufacturing method.
2. Description of the Related Art
Various types of flat display devices each having a field emission cathode, i.e., panel display devices, have been proposed. To realize bright picture display, a cathode-ray tube configuration for impacting an electron beam on a fluorescent screen serving as a picture formation surface to thereby emit light is normally adopted.
In a conventional flat display device having a cathode-ray tube configuration, as proposed in Japanese laid-open patent publication No. 1-173555, for example, a plurality of thermionic emission cathodes, i.e., filaments are provided to face a fluorescent screen, thermions generated from the cathodes and secondary electrons resultant from the thermions are directed toward the fluorescent screen to thereby excite and emit the fluorescent screen having colors according to a video signal using an electron beam. In this case, as a display screen becomes larger in size, a constitution in which common filaments are provided for many pixels, i.e., many red, green and blue fluorescent trios forming a fluorescent screen, is adopted.
Therefore, as the display screen becomes larger in size,it becomes complicated to arrange and assemble the filaments. Further, with a view of making a flat display device of cathode-ray tube configuration smaller in size, the depth of the device is made shorter by shortening an electron gun and increasing the deviation angle of electrons. However, since the display screen of a flat display device is increasingly made larger in size, the development of thinner, flat display devices is further desired.
In light of the above respects, a flat display device employing field emission cathodes or so-called cold cathodes has been proposed for the conventional flat display device. In case of the electron emission device having cold cathodes, the selection of a cathode material and a method of forming the cold cathodes constitute important factors in the determination of device performance. The conventional field emission cathode employs high melting point metal such as Mo, Ni and W, or Si for the material of an emitter which emits electrons.
Further, there is proposed a so-called Spindt type electron emission section constituting a flat display device having a conventional structure.
The structure of one example of a conventional flat display device
100
will be described with reference to the drawing.
FIG. 14
is a schematic perspective view of a flat display device
100
having a conventional structure.
The flat display device
100
has a fluorescent screen
101
, a flat white light emission display device main body
102
having field emission cathodes K arranged to face the fluorescent screen
101
, and a flat color shutter
103
arranged to contact with or face the front surface at which the fluorescent screen
101
is arranged.
As shown in
FIG. 14
, the display device main body
102
has a light transmission front panel
104
and a back panel
105
facing each other through a spacer (not shown) for holding the panels
104
and
105
at a predetermined distance therebetween, the peripheral portions thereof are airtight sealed by a glass frit or the like, and a flat space is formed between the panels
104
and
105
.
An anode metal layer
160
and a fluorescent screen
101
having a white light emission fluorescent materral bonded on the entire surface are formed on the inner surface of the front panel
104
. A metallized layer
106
such as an Al film is bonded on the resultant surface as in the case of an ordinary cathode-ray tube.
On the other hand, many cathode electrodes
107
extending perpendicularly in, for example, a band manner are arranged in parallel and bonded on the inner surface of the back panel
105
.
An insulating film
108
is bonded on the cathode electrodes
107
and gate electrodes
109
extending in a direction almost orthogonal to the extension direction of the cathode electrodes
107
, e.g., in a horizontal direction, are arranged in parallel.
Opening holes
110
are perforated at crossings at which the cathode electrodes
107
and the gate electrodes
109
cross one another. Conical field emission cathodes K are bonded and formed on the cathode electrodes
107
in each opening hole
110
.
The field emission cathodes K are formed by using high melting point metal such as Mo, W or Cr, or Si. The cathodes K are of conical shape with a tip end thereof having a radius of curvature of several tens of nanometers and directed toward the gate electrode side.
If a positive voltage of several tens of volts is applied to the gate electrodes relative to the cathode electrodes, a electric field of, for example, about 10
6
to 10
7
V/cm is applied to the conical tip end portions and electrons are emitted therefrom by a tunnel effect.
The emitted electrons are allowed to impact on the fluorescent screen
101
formed on the anode electrodes facing the cathodes K at a distance of 0.2 mm to 1 mm therebetween, thereby obtaining fluorescence emission.
One pixel of the flat display device
100
consists of several tens to several thousands of Spindt-type electron emission sections. To structure a display having 1024×768×(RGB) pixels of XGA class which is the standard class of a computer display, for example, 100 million to 100 billion electron emission sections are required.
The constitution of a cathode structure including the field emission cathodes K, the gate electrodes and the like constituting the flat display device
100
having the conventional structure will be described with reference to the manufacturing step views shown in
FIGS. 15
to
18
, together with one example of a manufacturing method to facilitate understanding the cathode structure.
First, as already described above with reference to
FIG. 14
, cathode electrodes
107
are formed on the inner surface of the back panel
105
in one direction, e.g., in a perpendicular scan direction.
Each cathode electrode
107
is formed into a predetermined pattern by, for example, forming a metal layer such as a Cr layer on an entire surface by deposition, sputtering or the like and then selectively etching the metal layer by photolithography.
Next, as shown in
FIG. 15
, an insulating layer
108
is bonded on the entire surfaces of the cathode electrodes
107
thus patterned by sputtering or the like. Further, metal
111
such as high melting point metal of Mo or W, finally constituting gate electrodes
109
, is formed on the insulating layer
108
by deposition, sputtering or the like.
Next, as shown in
FIG. 16
, a resist pattern (not shown) made by a photoresist or the like is formed and the metal film
111
is subjected to anisotropic etching, e.g., RIE (reactive ion etching) using the resist pattern as a mask, thereby forming band-shaped cathode electrodes
109
into a predetermined pattern, i.e., in a horizontal direction orthogonal to the extension direction of the cathode electrodes
107
shown in FIG.
14
. In addition, a plurality of small holes
111
h
, for example, are formed in portions where the gate electrodes
109
cross the cathode electrodes
107
.
Next, through these holes
111
h
, etching, e.g., chemical etching by which the gate electrodes
109
, i.e., the metal layer
111
is not etched and the insulating layer
108
is isotropically etched, is performed to thereby form opening holes
112
each having a larger width than the width of a small hole
111
h
and having a depth corresponding to the entire thickness of the insulating layer
108
.
In this way, as shown in
FIG. 14
, the opening holes
110
each consisting of the opening hole
112
and the small hole
111
h
are formed at crossings at which the cathode electrodes
107
and the gate electrodes
109
cross one another.
Next, as shown in
FIG. 17
, a metal layer
113
made of, for example, Al, Ni or the like is bonded on the gate electrodes
109
by oblique dep
Inoue Kouji
Saito Ichiro
Tachizono Shinichi
Yamagishi Takeshi
Kananen Ronald P.
Rader & Fishman & Grauer, PLLC
Sony Corporation
Tran Chuc
Wong Don
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