Electric lamp and discharge devices – Discharge devices having a multipointed or serrated edge...
Reexamination Certificate
2001-12-11
2004-08-10
Cariaso, Alan (Department: 2875)
Electric lamp and discharge devices
Discharge devices having a multipointed or serrated edge...
C313S311000, C313S497000, C313S336000, C313S351000
Reexamination Certificate
active
06774548
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a field emission display (FED) and, more particularly, to a carbon nanotube field emission display (CNT-FED).
2. Description of the Related Art
Filed emission display (FED), having competitiveness in the panel display market, is a high-voltage display with a triode structure consisting of anode, cathode and gate electrode to achieve high illumination by applying a high voltage and a low current. FED has advantages of light weight and thin profile, like liquid crystal display (LCD), and advantages of high brightness and self luminescence, like cathode ray tube (CRT). In conventional FED processing, fluorescent material is formed on an anode substrate, an electron-emitting source with a discharge tip is formed on a cathode substrate, and a gate electrode is formed to surround the discharge tip. Thus, applying a high electric field generated from the gate electrode, electrons are released from the discharge tip and then the electrons are accelerated by applied high voltage to strike the fluorescent material, resulting in emitted cathode fluorescence. With regard to the fabrication of the electron-emitting source, molybdenum (Mo) metal is employed to form a micro-tip shape, despite attendant problems of complex process, expensive equipment cost and low throughput.
Recently, carbon nanotube (CNT) materials, having high mechanical strength and great electrical performance, have been used to form the electron-emitting source of FED. Since simple and low cost technologies, such as screen printing, chemical vapor deposition (CVD) and coating, are applied to coat/grow carbon nanotubes within an electron-emitting area, the product, CNT-FED, has high throughput and may be formed as a large-size display.
FIG. 1
is a sectional diagram showing a primitive CNT-FED
10
. The CNT-FED
10
has a cathode substrate
12
, an anode substrate
14
over and parallel to the cathode substrate
12
, a spacer
16
disposed in the vacuum space between the two substrates
12
and
14
for maintaining a predetermined vertical distance and resisting atmosphere pressure. The anode substrate
14
has a glass substrate
18
, a plurality of fluorescent layers
20
patterned on predetermined regions of the glass substrate
18
, and planarized Al film
22
formed on the exposed regions of the glass substrate
18
. The first purpose of the Al film
22
is to serve as a conductive layer of the anode substrate
14
, the second purpose is to serve as a reflective layer of the fluorescent layer
20
, and the third purpose is to serve as a protective layer for protecting the fluorescent layer
20
from ion bombardment and electric-filed attraction. The cathode substrate
12
has a glass substrate
24
, a plurality of cathode layers
26
patterned on predetermined regions of the glass substrate
24
, a plurality of CNT structures
34
grown on each electron-emitting area of the cathode layer
26
, an insulating layer
28
formed on peripheral region of the glass substrate
24
, and a net-shaped metal layer
32
glued on the insulating layer
28
by frit. In addition, each opening
32
a
of the net-shaped metal layer
32
corresponds to each electron-emitting area of the cathode layer
26
, thus the metal material of the net-shaped metal layer
32
surrounding the cathode layer
26
serves as a gate electrode
32
b.
However, the CNT-FED
10
has disadvantages. First, edge effect is found at the outer carbon nanotubes that surround the electron-emitting area, thus each fluorescent layer
20
emits a comparatively brighter light at periphery and a comparatively darker light at the center. This causes non-uniform luminescence and decreases luminescent property of the CNT-FED
10
. Second, since only the edge of the net-shaped metal layer
32
is glued to the insulating layer
28
that is formed on the peripheral region of the cathode substrate
12
, most of the gate electrodes
32
b
are suspended over the cathode substrate
12
. As the size of the net-shaped metal layer
32
is increased, the center area of the net-shaped metal layer
32
easily droops and become uneven. This causes electrons to bombard the gate electrode
32
and forms non-uniform electric fields, which may vibrate the gate electrode
32
or even peel the net-shaped metal layer
32
. Third, when removing organic materials at high temperature, preferably at 450~500° C., part of the Al film
22
may be oxidized to become aluminum oxide, resulting in a decreased conductivity of the Al film
22
. This leads to an accumulation of charges when electrons are emitted to bombard the anode substrate
14
. Also, when the charges are accumulated to reach a critical amount, an arc phenomenon is formed in order to deplete the accumulated charges, and thus the brightness on the anode substrate
14
is burned out. Moreover, the accumulated charges may generate a repellent electric field that makes the subsequently emitted electrons unable to bombard the anode substrate
14
. This decreases the electron quantities that bombard the anode substrate
14
and degrades the brightness that is emitted from the fluorescent layer
20
. Fourth, no matter whether the electron-emitting source employs a metal tip or the CNT structure
34
, a divergent phenomenon of the electrons is always found to cause cross-talk on the anode substrate
14
. Furthermore, as the amount of emitted electrons is greater, the excessive electrons directly bombard the anode substrate
14
to generate a spark. Thus, a novel structure of the CNT-FED and an improved process of forming the same to solve the aforementioned problems are called for.
SUMMARY OF THE INVENTION
The present invention provides a CNT-FED with a novel cathode substrate and a novel anode substrate to solve the problems caused by prior art.
The carbon nanotube (CNT) field emission display has a cathode substrate having a cathode layer patterned on a glass substrate. The surface of the cathode layer is defined as a plurality of electron-emitting areas apart from each other, and a plurality of CNT structures is grown on the plurality of electron-emitting areas respectively.
A method of forming a cathode substrate comprises: providing a glass substrate on which a plurality of cathode layers are patterned; forming a plurality of ribs in each space between adjacent cathode layers, wherein the rib protrudes from the top of the cathode layer to reach a predetermined height; printing to form a net-shaped gate electrode layer on the plurality of ribs; and performing high-temperature baking.
The CNT-FED has an anode substrate with a plurality of fluorescent layers patterned on a glass substrate. A planarized Al film covers the fluorescent layers, and a metal sheet covers the Al film. The metal sheet has a plurality of openings, wherein the openings are corresponding to the fluorescent layers respectively.
The CNT-FED has a cathode substrate with a plurality of cathode layers patterned on a glass substrate, wherein each cathode layer has an electron-emitting area on which a CNT structure is formed. A plurality of ribs fills each space between adjacent cathode layers and each rib protrudes from the top of the cathode layer to reach a predetermined height. A net-shaped gate electrode layer is formed on the plurality of ribs, and a metal cap covers the gate electrode layer. The metal cap has a plurality of apertures, wherein the plurality of apertures is corresponding to the electron-emitting areas respectively.
Accordingly, it is a principle object of the invention to provide the metal sheet to prevent arc phenomenon.
It is another object of the invention to protect the gate electrode layer from vibrating and peeling.
Yet another object of the invention is to increase the luminescent uniformity and luminescent efficiency of the CNT-FED.
It is a further object of the invention to provide the metal cap to avoid cross-talk on the anode substrate.
Still another object of the invention is to provide the apertures on the metal cap to limit the emitting space of the direct
Chen Lai-Cheng
Fran Yui-Shin
Cariaso Alan
Delta Optoelectronics, Inc.
Dong Dalei
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