Electric lamp and discharge devices – With luminescent solid or liquid material – Vacuum-type tube
Reexamination Certificate
2002-04-09
2004-04-06
Wong, Don (Department: 2821)
Electric lamp and discharge devices
With luminescent solid or liquid material
Vacuum-type tube
C315S169300, C313S495000
Reexamination Certificate
active
06717352
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 enabling the stable control of an electron emission quantity by forming a gap between electron emitting sources and control electrodes which controls the electron emission quantity from the electron emitting sources with high accuracy.
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 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 Patent Laid-open No. 2000-21305), 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 tunnelling effect (also referred to as “surface conduction type electron emitting source, see Japanese Patent Laid-open No. 2000-21305), and a display device which utilizes an electron emission phenomenon having a diamond film, a graphite film and a carbon nanotube and the like have been known.
FIG. 29
is a cross-sectional view for explaining one constitutional example of a known field emission type display device, and
FIG. 30A
to
FIG. 30B
are explanatory views showing constitutional examples of an electron emission source of one pixel and a control electrode which controls an electron emission quantity from the electron emission source. The field emission type display device is constituted such that a sealing frame
300
is interposed and sealed between both inner peripheries of a rear panel
100
which forms field-emission type electron emitting sources
2
a
and control electrodes
4
over an inner surface thereof and a face panel
200
which form anodes
7
and a fluorescent material layer
6
on an inner surface thereof which faces the above-mentioned rear panel
100
, and the inside which is defined by the rear panel
100
, the face panel
200
and the sealing frame
300
is reduced to a pressure lower than an atmospheric pressure of an external field or is evacuated (hereinafter referred to as “vacuum”).
The rear panel
100
includes cathode wires
2
which have electron emitting sources
2
a
and the control electrodes
4
which are formed such that the control electrodes
4
cross the cathode wires
2
by way of an insulation layer
3
on the rear substrate
1
preferably made of glass or alumina or the like. Then, an electron emission quantity (including turning on or off of emission) from the electron emitting sources
2
a
are controlled in response to the potential difference between the cathode wires
2
and the control electrodes
4
.
Further, the face panel
200
includes the anodes
7
and the fluorescent material layer
6
on a face substrate
5
formed of light-transmitting material such as glass. The sealing frame
300
is fixedly secured to the inner peripheries of the rear panel
100
and the face panel
200
using an adhesive such as frit glass. The inside defined by the rear panel
100
, the face panel
200
and the sealing frame
300
is evacuated to a vacuum of 10
−5
to 10
−7
Torr, for example. A gap formed between the rear panel
100
and the face panel
200
is held by gap holding members
9
.
The insulation layer
3
is interposed between the cathode wires
2
formed on the rear panel
100
and the control electrode
4
which cross the cathode wires
2
and an hole (grid hole)
4
a
is formed at each crossing portion of the cathode wire
2
and the control electrode
4
. The hole
4
a
allows electrons emitted from the electron emitting source
2
a
to pass therethrough toward the anode side. On the other hand, the electron emitting source
2
a
is formed on the above-mentioned crossing portion of the cathode wire
2
and the control electrode
4
and an insulation layer
3
is eliminated at a portion which corresponds to the hole
4
a
of the control electrode
4
. The above-mentioned electron emitting sources
2
a
are constituted of carbon nanotubes (CNT), diamond-like carbon (DLC) or other field emission cathode, for example.
Here, as the electron emitting sources
2
a
, light sources which use carbon nanotubes are illustrated. As shown in FIG.
30
A and
FIG. 30B
, the electron emitting source
2
a
is formed right below the hole
4
a
of the control electrode
4
. Although the case in which one electron emitting source
2
a
is formed per one pixel is illustrated in FIG.
30
A and
FIG. 30B
, a plurality of electron emitting sources
2
a
may be formed per one pixel.
FIG.
31
A and
FIG. 31B
are explanatory views corresponding to
FIG. 30A
to
FIG. 30B
which show a display device forming a plurality of electron emitting sources per one pixel. Here, a plurality of holes
4
a
are formed in the control electrode
4
and a plurality of electron emitting sources
2
a
are arranged on a cathode wire
2
corresponding to respective holes
4
a.
Electrons emitted from a rear panel
100
impinge on a fluorescent material layer
6
of an opposing face panel
200
. Light which corresponds to the emitting characteristics of the fluorescent material layer
6
is irradiated to the outside of the face panel
200
and functions as a display device.
As literatures which disclose the conventional technique related to this type of display device, for example, Japanese Patent Laid-open No. 1999-144652, Japanese Patent Laid-open No. 2000-323078 and the like are named.
However, the display devices which have been explained in conjunction with
FIG. 30A
, FIG.
30
B and
FIG. 31A
,
FIG. 31B
have following problems.
FIG. 32
is an enlarged cross-sectional view of one pixel portion for explaining a constitutional example of a rear panel of a conventional field emission type display device. In such a display device of this type, with respect to a rear panel
100
, cathode wires
2
are formed on a rear substrate
1
by a thin film patterning technique, an insulation layer
3
having a given thickness is formed on the cathode wires
2
, and the insulation layer
3
corresponding to pixel portions are removed. Then, control electrodes
4
are formed on the insulation layer
3
by a vapor deposition method or a sputtering method except for holes
4
a.
Since the insulation layer
3
is formed by coating resin material using a screen printing method, it is difficult to make a thickness of the insulation layer
3
uniform. Accordingly, it is impossible to obtain the uniform thickness with no irregularities over the entire surface of the display region. Since the control electrodes
4
are formed along the surface contour of the insulation layer
3
, as emphasized in conjunction with
FIG. 32
, the irregularities are generated with respect to a gap defined between the cathode wires
2
and the control electrodes
4
due to the irregularities of the thickness of the insulation la
Hirasawa Shigemi
Kawasaki Hiroshi
Kijima Yuuichi
Miyata Kenji
Yaguchi Tomio
Hitachi , Ltd.
Vu Jimmy T.
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