Electric lamp and discharge devices – With electrical shield or static charge distribution means
Reexamination Certificate
2002-04-19
2004-03-30
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
With electrical shield or static charge distribution means
C313S309000, C313S351000, C313S495000
Reexamination Certificate
active
06713947
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a display device which utilizes an emission of electrons into a vacuum, and more particularly, to a display device which can enhance the display characteristics by implementing electron emitting sources enabling the stable control of an electron emission quantity and a method of manufacturing the display device.
As a display device which exhibits the high brightness and the high definition, color cathode ray tubes have been widely used conventionally. However, along with the recent request for the higher quality of images of information processing equipment or television broadcasting, the demand for planar displays (panel displays) which are light in weight and require a small space while exhibiting the high brightness and the high definition has been increasing.
As typical examples, liquid crystal display devices, plasma display devices and the like have been put into practice. Further, particularly, as display devices which can realize the higher brightness, it is expected that various kinds of panel-type display devices including a display device which utilizes an emission of electrons from electron emitting sources into a vacuum (hereinafter, referred to as “an electron emission type display device” or “a field emission type display device”) and an organic EL display which is characterized by low power consumption will be commercialized.
Among such panel type display devices, as the above-mentioned field emission type display device, a display device having an electron emission structure which was invented by C. A. Spindt et al (for example, see U.S. Pat. No. 3,453,478, Japanese Laid-open Patent Publication 21305/2000), a display device having an electron emission structure of a metal-insulator-metal (MIM) type, a display device having an electron emission structure which utilizes an electron emission phenomenon based on a quantum theory tunneling effect (also referred to as “surface conduction type electron emitting source, see Japanese Laid-open Patent Publication 21305/2000), and a display device which utilizes an electron emission phenomenon having a diamond film, a graphite film and carbon nanotubes and the like have been known.
FIG. 10
is a schematic view for explaining the fundamental constitution of a field emission type display device. In the drawing, CNT indicates carbon nanotubes mounted on a cathode K and A indicates an anode, wherein a fluorescent material PH is formed on an inner surface of the anode A. By applying a voltage Vs between a control electrode G disposed in the vicinity of the cathode K and the cathode K, electrons e are emitted from the carbon nanotubes CNT, while by applying a high voltage Eb between the cathode K and the anode A, the electrons are accelerated and are made to impinge on the fluorescent material PH so that the fluorescent material PH is excited whereby irradiating colored light L which depends on the composition of the fluorescent material PH.
Then, by controlling an electron emission quantity (including turning on and off of emission) in response to the modulated voltage Vs given to the control electrode G disposed in the vicinity of the cathode K, the magnitude (brightness) of the colored light L can be controlled. Here, by providing a focusing electrode F of a given potential between the control electrode G and the anode A so as to focus the electrons e on the fluorescent material PH, the utilization efficiency of the electrons which excite the fluorescent material PH can be enhanced.
FIG.
11
A and
FIG. 11B
are schematic views showing one constitutional example of a known field emission type display device, wherein
FIG. 11A
is an exploded perspective view and
FIG. 11B
is a cross-sectional view of the display device after assembling. In this field emission type display device, a face panel
2
having anodes and fluorescent material layers on an inner surface thereof and a rear panel
1
on which field emission type electron emitting sources and control electrodes are formed are arranged to face each other in an opposed manner, a sealing frame
5
is interposed between inner peripheries of these panels so as to seal a space between them, and the inside which is defined by the face panel
2
, the rear panel
1
and the sealing frame
5
is reduced to a low pressure (including a vacuum) lower than an external atmospheric pressure or is evacuated (referred to as “vacuum” hereinafter).
As shown in
FIG. 11A
, in this field emission type display device, the rear panel
1
having a substrate
11
preferably made of glass, alumina or the like and the electron emitting sources and the face panel
2
having a substrate
21
made of a light transmitting material such as glass and fluorescent materials are arranged to face each other in an opposed manner.
The sealing frame
5
made of glass or the like is arranged between the rear panel
1
and the face panel
2
. This sealing frame
5
is sealed to the rear panel
1
and the face panel
2
respectively using frit glass or the like.
The electron emitting sources and the control electrodes which are not shown in the drawings are formed on the inner surface of the substrate
11
which constitutes the rear panel
1
. Cathode terminals
70
which are pulled out from cathodes constituting the electron emitting sources and control electrode terminals
50
which are pulled out from the control electrodes being disposed by way of an insulation layer
16
with respect to the cathodes are provided to a periphery of the rear panel
1
. Further, the anodes and the fluorescent materials not shown in the drawings are formed on an inner surface of the substrate
21
which constitutes the face panel
2
.
In the drawing, a dotted line
51
depicted on an upper surface of the substrate
11
of the rear panel
1
indicates positions where the outer periphery of the sealing frame
5
is brought into contact with the upper surface of the substrate
11
. An exhaust pipe
6
is provided to the outside of a display region of the rear panel
1
and to the inside of the sealing frame
5
, and the inside which is surrounded by respective main surfaces of the rear panel
1
, the face panel
2
and the sealing frame
5
is evacuated to a vacuum of 10
−5
to 10
−7
Torr, for example, by discharging air from the inside.
The carbon nanotubes (CNT) are extremely fine needle-like carbon compound (in a strict sense, molecules formed by binding carbon atoms in a net form and a columnar form) and are used as electron emitting sources when they are arranged on the cathode wires.
In mounting the carbon nanotubes on the cathode wires, a method which coats and bakes a paste in which carbon nanotubes are mixed, a method which exposes end portions of carbon nanotubes in an electric field space by coating a paste in which nickel is mixed as conductive fillers to carbon nanotubes and baking and polishing, or a method which coats a silver paste in which carbon nanotubes are mixed and bakes such silver paste or the like has been adopted.
However, it has been difficult to firmly fix the carbon nanotubes to the cathode wires and to arrange the carbon nanotubes such that end peripheries of the carbon nanotubes which constitute electron emitting portions are efficiently exposed in the inside of the vacuum. When only the paste formed of the carbon nanotubes is used, the electric resistance between carbon nanotubes which constitute needle-like crystals is large and hence, the carbon nanotubes exhibits the small electron emission ability compared to a case the paste is baked with the conductive fillers made of nickel or the like.
When the paste containing nickel (Ni) or the like is used, it is necessary to remove nickel particles exposed on an uppermost surface by polishing. The polishing of such ultra-fine particles is difficult and hence, the method is not suitable for the mass production. Further, the carbon nanotubes which are exposed to the electric field space are substantially formed of only portions which are protruded from a polished surface so that the
Hirasawa Shigemi
Kawasaki Hiroshi
Kijima Yuuichi
Hitachi , Ltd.
Milbank, Tweed, Hadley & McCoy LLP
Patel Ashok
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