Active solid-state devices (e.g. – transistors – solid-state diode – Thin active physical layer which is – Low workfunction layer for electron emission
Reexamination Certificate
2002-09-20
2004-10-19
Jackson, Jerome (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Thin active physical layer which is
Low workfunction layer for electron emission
C257S010000, C313S306000
Reexamination Certificate
active
06806489
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a field emission display, and more particularly, to a field emission display having a surface electron source made of a carbon-based material and an electron structure to improve the convergence of electron beams emitted from the surface electron source.
2. Description of the Related Art
The first field emission displays (FEDs) used Spindt-type emitters as the source for emitting electrons, in which a low work function metal such as molybdenum, tungsten, and polysilicon is used to form microtips on cathode electrodes. However, Spindt-type emitters are made using conventional semiconductor manufacturing processes that require the use of expensive vacuum equipment. As a result, the overall cost to manufacture the semiconductor is increased and the production of display devices of a large screen size is difficult.
There has been disclosed a surface electron source structure realized by providing a carbon-based material such as carbon nanotubes, graphite, and diamond-like carbon (DLC) as a film covering the cathode electrodes. Since such a surface electron source may be produced by a thick-layer process such as screen printing, the cost of manufacturing the display element is reduced and the manufacture of large screen sizes is simplified.
However, when using the thick-layer process, it is difficult to form the surface electron source within holes of an insulation layer provided to expose the cathode electrodes, and it is difficult to realize a conventional triode structure on the insulation layer. This is because the cathode electrodes and the gate electrodes are easily shorted by the conducting material forming the surface electron source when the surface electron source is printed in holes of the gate electrodes and of the insulation layer.
Therefore, there has been disclosed a structure for an FED, in which gate electrodes for controlling the emission of electrons are arranged on a substrate below cathode electrodes, and an insulation layer is provided between the gate electrodes and the cathode electrodes. U.S. Patent Application Publication No. US2001/0006232 A1 discloses a triode FED of this structure. In such an FED, the structure is simple to thereby make the manufacturing process easy, and the problem of a short occurring between the cathode electrodes and the gate electrodes is eliminated.
However, with this type of FED, except for the anode electrodes for applying a high voltage to accelerate electrons, there are no electrodes involved in the converging of the electron beams emitted from the surface electron source. Accordingly, with reference to
FIG. 13
, when electron beams are emitted from the surface electron source
22
by the electric field formed in the vicinity of the same, the electron beams are spread out while traveling toward the anode electrodes.
As a result, with reference to
FIG. 14
, the electron beams emitted from the surface electron source
22
land not only on desired pixels Pa, but also on adjacent pixels Pb and Pc of another color such that these pixels are illuminated. This reduces overall picture quality by degrading resolution, picture precision, etc.
SUMMARY OF THE INVENTION
The present invention has been made in an effort to solve the above problems.
It is an object of the present invention to provide a field emission display that converges electron beams emitted from a surface electron source such that spreading of the electron beams is minimized to selectively illuminate only desired pixels, thereby improving picture quality.
To achieve the above object, in accordance with an embodiment of the present invention, a field emission display is provided including first and second substrates opposing one another with a predetermined gap therebetween; a plurality of gate electrodes formed on a surface of the first substrate opposing the second substrate, the gate electrodes being formed in a striped pattern; an insulation layer formed on the first substrate covering the gate electrodes; a plurality of cathode electrodes formed on the insulation layer in a striped pattern to perpendicularly intersect the gate electrodes; a plurality of surface electron sources formed along one long side of the cathode electrodes; focusing units provided on the cathode electrodes for controlling emission of electron beams from the surface electron sources; an anode electrode formed on a surface of the second substrate opposing the first substrate; and a plurality of phosphor layers formed on the anode electrode.
According to an embodiment of the present invention, the surface electron sources are made from one or mixture of carbon nanotubes, graphite, diamond, DLC, and C
60
(fullerene).
According to another embodiment of the present invention, the surface electron sources are formed at a predetermined distance and in each of a plurality of pixel regions, which correspond to the intersection of the gate electrodes and cathode electrodes.
According to yet another embodiment of the present invention, the focusing units are converging electrodes that are formed on the cathode electrodes on ends of each of the surface electron sources such that a pair of the converging electrodes is provided for each surface electron source.
According to still yet another embodiment of the present invention, a thickness of the converging electrodes is greater than a thickness of the surface electron sources.
In another embodiment of the present invention, the focusing units are cut portions formed in the cathode electrodes on long sides of the cathode electrodes opposite the long sides on which the surface electron sources are formed, the cut portions decreasing a width of the cathode electrodes.
According to another embodiment of the present invention, the surface electron sources are formed along an entire length of the long sides of the cathode electrodes opposite the long sides in which the cut portions are formed.
According to another embodiment of the present invention, the surface electron sources are formed at predetermined intervals at each pixel region corresponding to areas of intersection between the gate electrodes and the cathode electrodes.
In yet another embodiment of the present invention, the focusing units are extended electrodes, which are extended from a side surface of the cathode electrodes between a bottom surface of the cathode electrodes contacting the insulation layer and an edge portion of the cathode electrodes along which the surface electron sources are formed, the extended electrodes being formed at a predetermined length in a direction perpendicular to a long axis direction of the cathode electrodes and at edges of each pixel region corresponding to areas of intersection between the gate electrodes and the cathode electrodes.
According to another embodiment of the present invention, the length of the extended electrodes is 95% or less a distance between adjacent cathode electrodes.
REFERENCES:
patent: 6445114 (2002-09-01), Kurokawa et al.
patent: 2001/0006232 (2001-07-01), Choi et al.
Ahn Sang-Hyuck
Choi Yong-Soo
Han Ho-Su
Kang Jung-Ho
Jackson Jerome
McGuireWoods LLP
Samsung SDI & Co., Ltd.
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