High-resolution field emission display

Details High-resolution field emission display High-resolution field emission display

2001-05-31

2004-02-10

Clinger, James (Department: 2673)

Electric lamp and discharge devices: systems

Plural power supplies

Plural cathode and/or anode load device

C313S497000

Reexamination Certificate

active

06690116

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a high-resolution field emission display. More particularly, it relates to a high-resolution field emission display for applying a field emission device (or a field emission array) being an electron source element to a flat panel display device.
BACKGROUND OF THE INVENTION
Field emission display devices are manufactured by making a vacuum-packaging between a lower plate having field emitter arrays and a upper plate having phosphors positioned within a small distance, e.g., 2 mm from the lower plate. The field emission display device generates cathode luminescence by colliding electrons emitted from field emitters of the lower plate against phosphors of the upper plate, thereby achieving an image display. Recently, the field emission display devices have been widely developed as a flat panel display substituting for conventional cathode ray tube (CRT).
The field emitter serving the most important function of the lower plate of the field emission display device has different electron emission efficiency according to the structure, emitter material, and emitter shape. At present, there are two kinds of field emission elements, those are, diode type device comprised of a cathode (or emitter) and an anode, and triode type device comprised of a cathode, a gate and an anode. Several materials such as metal, silicon, diamond, diamond-like carbon, or carbon nanotube have been used as the emitter material. In general, metal and silicon are used for the triode type device, and diamond-like carbon or carbon nanotube are used for the diode type structure. The diode type field emitter has a disadvantage in the control characteristic of the electron emission and high voltage driving characteristic, as compared to the triode type field emitter. But, the manufacturing process of the diode type field emitter is relatively easier than that of the triode type field emitter, so that large-sized devices can be easily manufactured.
In the meantime, field emission display device is classified into simple matrix panel type and active matrix panel type, according to the pixel arrangement of the lower plate in a matrix format. The simple matrix field emission display forms each pixel with a field emitter array only, whereas the active matrix field emission display forms each dot pixel with a field emitter array and a semiconductor device (mainly, a transistor) controlling the field emission current of the field emitter array.
FIGS. 1-3
are cross-sectional views illustrating one dot pixel of a conventional field emission display device.
FIG. 1
is a cross-sectional view illustrating a dot pixel structure of a simple matrix field emission display device consisting of a conventional triode type field emitter array.
Referring to
FIG. 1
, the conventional field emission display device includes a lower plate and a upper plate facing to each other, wherein the lower plate and the upper plate are vacuum-packaged. The lower plate includes a glass substrate
101
, a cathode electrode
102
made of metal deposited on the glass substrate
101
, a resistance layer
103
made of doped amorphous silicon on the cathode electrode
102
, a cone-type field emission tip
104
made of a metal (mainly, molybdenum), which is partially deposited on the resistance layer
103
, and a gate insulation layer
105
and a gate electrode
106
which are used to apply electric field to the field emission tip
104
. The upper plate includes a glass substrate
121
, a transparent electrode
122
formed on the glass substrate
121
, a red, green, or blue phosphor
123
partially formed on the transparent electrode
122
.
The field emission display of
FIG. 1
has an advantage of inducing reliable field emission at a relatively low voltage (generally, 80 V), but the field emission display has a limitation in manufacturing field emission tips in large-sized plate and requires a high field emission voltage.
FIG. 2
is a cross-sectional view illustrating a dot pixel structure of a simple matrix field emission display device comprised of a conventional diode type field emission element.
Referring to
FIG. 2
, a conventional field emission display device includes a lower plate and a upper plate facing to each other, wherein the lower plate and the upper plate are vacuum-packaged. The lower plate includes a glass substrate
201
, a cathode electrode
202
made of metal deposited on the glass substrate
201
, a resistance layer
203
made of doped amorphous silicon on the cathode electrode
202
, and a diode type field emission film
204
made of carbon nanotube, which is partially formed on the resistance layer
203
. The upper plate includes a glass substrate
221
, a transparent electrode
222
formed on the glass substrate
221
, a red, green, or blue phosphor
223
partially formed on the transparent electrode
222
.
The field emission display device of
FIG. 2
has a simple structure and facilitates the fabrication process, but the field emission display device requires a high field emission voltage and has unstable field emission characteristic and relating low an uniformity and reliability.
FIG. 3
is a cross-sectional view illustrating a dot pixel structure of an active matrix field emission display device comprised of a conventional diode type field emission element and a polycrystalline silicon thin film transistor (TFT).
Referring to
FIG. 3
, a conventional field emission display device includes a lower plate and a upper plate facing to each other, wherein the lower plate and the upper plate are vacuum-packaged. The lower plate includes a glass substrate
301
; a TFT's channel
302
made of undoped polycrystalline silicon; TFT's source
303
and drain
304
made of doped polycrystalline silicon on both sides of the TFT's channel
302
; a gate insulation layer
305
made of silicon oxide (SiO
2
) layer, which is deposited on the channel
302
, the source
303
and the drain
304
of TFT; a first gate
306
which is formed on some parts of the gate insulation layer
305
to vertically overlap with some portions of the TFT's source
303
and the TFT's channel
302
, and not overlap with the TFT's drain
304
; a passivation insulation layer
307
made of a silicon oxide layer, which is formed on the first gate
306
; a second gate
308
which is formed on some portions of the passivation insulation layer
307
to vertically overlap with some parts of the TFT's channel
302
and the TFT's drain
304
; and a diode type field emission film
309
formed of carbon nanotube, which is formed to be electrically connected to the TFT's drain
304
by partially removing the gate insulation layer
305
and the passivation insulation layer
307
that are formed on the TFT's drain
304
. The upper plate includes a glass substrate
321
, a transparent electrode
322
formed on the glass substrate
321
, a red, green, or blue phosphor
323
partially formed on the transparent electrode
322
.
The field emission display device of
FIG. 3
can remarkably restrict the cross-talk a display signal because each dot pixel is electrically isolated by a polycrystalline silicon thin film transistor. In addition, since the field emission current is controlled by the polycrystalline silicon thin film transistor, the field emission display device can be driven at a low voltage and can achieve very stable electron emission characteristic. However, the field emission display of
FIG. 3
has a difficulty in manufacturing a large-sized field emission display device because a process for making a polycrystalline silicon thin film transistor should be added to the manufacturing process of the field emission display device of
FIG. 3
, and therefore the production cost becomes very expensive.
In the meantime, conventional field emission displays shown in
FIGS. 1-3
have a difficulty in manufacturing a high-resolution display device, because spreading of electron beam occurs when the electron beam emitted from the field emission element is applied on the phosphor. Accordi

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