Electric lamp and discharge devices – With luminescent solid or liquid material – Vacuum-type tube
Reexamination Certificate
1999-12-13
2003-07-29
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
Vacuum-type tube
C313S309000, C313S336000
Reexamination Certificate
active
06600262
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a field emission type cathode, an electron emitting apparatus and a process for manufacturing the electron emitting apparatus.
2. Description of the Related Art
Various kinds of electron emitting apparatus having a field emission type cathode, e.g. plane type display device, i.e. panel type display device have been proposed. In order to display a bright picture, a cathode ray tube type structure in which an electron beam bombards a fluorescent screen to emit a light is generally adopted.
The plane type display device having this cathode ray tube type structure is such that, for example, as proposed in Patent Gazette of Laying-Open No. Hei 1-173555, a plurality of thermionic emission type cathodes, i.e. filaments are provided opposite to the fluorescent screen and the thermious produced by this cathode and the secondary electrons thereby are directed towards the fluorescent screen to cause the electron beam to excite the fluorescent screen of respective colours depending on a video signal for light emission. In this case, as the size of screen becomes large, such structure is adopted that the filaments are provided in common to a large number of pixels, namely, a large number of fluorescencer trio of red, green and blue forming the fluorescent screen.
Therefore, particularly with the large-sizing of the screen, the layout and construction of the filaments become complicated and besides, the filament itself becomes elongated.
Moreover, in order to make the size of plane type display device small, it has been practiced to make short of an electron gun or make large of a deflection angle of electron for aiming at shortening its depth. With the recent large-sizing of the plane type display device, the development of a thin structure of plane type display device is further desired.
On the other hand, in the conventional plane type display device, such a plane type display device is proposed that employs the field emission type cathode, the so-called cold cathode. An example of such plane type display device structure will be described below with reference to the drawings.
The plane type display device
100
shown in
FIG. 1
is comprised of a body
102
of plane type white colour light emitting display device having a white colour light emitting fluorescent screen
101
and field emission type cathodes K arranged opposite thereto as well as a plane type colour shutter
103
arranged adjacent or opposite to the front face of the screen
101
on its arranged side.
As shown in
FIG. 1
, the display device body
102
is constructed in such a manner that a transparent front panel
104
and a rear panel
105
oppose to each other through a spacer (not shown) holding a predetermined space between both panels
104
and
105
and the peripherys thereof are sealed airtightly by the glass frit, etc. to form a flat space between the panels
104
and
105
.
On the inner surface of the front panel
104
is formed the white colour light emitting screen
101
which is made by applying previously a white colour light emitting fluorescencer entirely, and its surface is coated with a metal-backed layer
106
of aluminum film, etc. as in the ordinary cathode ray tube.
On the other hand, on the inner surface of the rear panel
105
are arranged and mounted in parallel a great number of cathode electrodes
107
which, for example, extend vertically in the shape of belts.
These cathode electrodes
107
are covered with an insulation layer
108
, on which gate electrodes
109
that extend, for example, in the horizontal direction nearly perpendicular to the extension direction of cathode electrodes
107
are arranged in parallel.
At intersections between each electrode
107
and each gate electrode
109
are bored openings
110
, in which conical field emission type cathodes K are formed on the cathodes
107
, respectively.
This field emission type cathode K is made of such materials that electron emission occurs due to the tunnel effect by impressing the electric field, e.g. on the level of 10
6
to 10
7
[v/cm] on molybdenum, tungsten, chromium and so on.
For better understanding the construction of cathode structure including the field emission type cathode K and the gate electrode, etc. forming the prior art plane type display device will be described together with an example of its manufacturing process in reference to manufacturing process diagrams of
FIG. 2
to FIG.
5
.
First of all, as described with
FIG. 1
, the cathode electrodes
107
are formed on the inner surface of the rear panel
105
along one direction, e.g. the vertical scanning direction.
These cathode electrodes
107
are formed into a predetermined pattern, e.g. by evaporating or sputtering a metal layer of chromium, etc. entirely And then etching it selectively by photolithography.
Next, as shown in
FIG. 2
, this patterned cathode electrodes
107
are coated entirely with the insulation layer
108
by sputtering, etc. and further on this layer a metal layer
111
becoming finally the gate electrodes
109
is formed, e.g. by evaporating or sputtering the metals of high melting point such as molybdenum, tungsten, etc.
As shown in
FIG. 3
though not shown, a resist pattern by the photoresist, etc. is formed and using this as a mask the anisotropic etching, e.g. RIE (reactive ion-beam etching) is carried out on the metal layer
111
to form into the predetermined pattern, namely, to form the beltlike gate electrode
109
extending in the horizontal direction perpendicular to the extension of the cathode electrode
107
shown in FIG.
1
. At the same time, at the intersections between the gate electrodes
109
and the cathode electrodes
107
, for example, a plurality of small holes
111
h
are bored, respectively.
Next, though these small holes
111
h
, for example, a chemical etching which exhibits no etching property to the gate electrode
109
, i.e. the metal layer
111
but exhibits the isotropic etching property to the insulation layer
108
is carried out to form cavities
112
having an opening width greater than that of the small holes
111
h
with a depth over a whole thickness of the insulation layer
108
.
In this way, as shown in
FIG. 1
, at the intersections between the cathode electrodes
107
and the gate electrodes
109
are formed the openings
110
including the cavities
112
and the small holes
111
h.
Next, as shown in
FIG. 4
, the gate electrode
109
is covered with a metal layer
113
made of e.g. aluminum, nickel, and so forth by an oblique evaporation. This oblique evaporation is carried out while the rear panel
105
is rotated in its plane to form round holes
114
having a conical inner circumference around the small holes
111
h.
In this case, the evaporation of metal layer
113
is carried out at such a selected angle that the inside of cavities
112
may not be coated through the small holes
111
h.
Subsequently, a field emission type cathode material, namely, a metal having a high melting point and a low work function such as tungsten, molybdenum, etc. is adhered through the round holes
114
on the cathode electrode
107
inside the cavities
112
at right angles to this cathode electrode surface by evaporation, sputtering and so on. In this case, although the evaporation is carried out at right angles, because that cathode material forms such a slant face that follows a slant face of the metal layer
113
around the round holes
114
, when reaching some thickness, the round holes
114
turn into blocked conditions. Consequently, conical dotlike cathodes K each of which has a triangular section are formed on the cathode electrode
107
within each cavity
112
.
Thereafter, as shown in
FIG. 5
, the metal layer
113
and the cathode material formed thereon shown in
FIG. 4
are removed, thereby causing the conical dotlike cathodes K each having a triangular section to be formed inside the opening
110
on the beltform, or stripeform cathode electrodes
107
.
The cathodes K are surrounded by the insu
Iida Koichi
Saito Ichiro
Tachizono Shinichi
Yamagishi Takeshi
Patel Ashok
Rader & Fishman & Grauer, PLLC
Zimmerman Glenn
LandOfFree
Field emission type cathode and electron emitting apparatus... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Field emission type cathode and electron emitting apparatus..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Field emission type cathode and electron emitting apparatus... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3065230