Electric lamp and discharge devices – With luminescent solid or liquid material – Vacuum-type tube
Reexamination Certificate
2002-11-22
2004-10-05
Lee, Wilson (Department: 2821)
Electric lamp and discharge devices
With luminescent solid or liquid material
Vacuum-type tube
C313S308000, C313S309000, C313S497000
Reexamination Certificate
active
06800995
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image display device that utilizes electron beams such as a field emission display (FED).
2. Related Background Art
Up to now, image display devices such as a CRT (Cathode Ray Tube) have been required to be larger in size, and researches for this purpose have been actively conducted. In addition, as the image display devices have been required to be larger in size, it has become an important subject to make the devices thin, light-weight and low in costs. However, since a CRT deflects electrons accelerated with a high voltage by a deflection electrode to excite phosphors on a faceplate, when it is attempted to increase a size of the CRT, a larger depth is required in principle. Therefore, it is difficult to make the device thin and light-weight. Thus, as an image display device that can solve the above-mentioned problem, the inventors have been studying an image display device that uses surface conduction electron-emitting devices as electron beam sources.
The inventors have been attempting, for example, applications of a multi-electron beam source shown in FIG.
13
.
FIG. 13
is a perspective view showing a display panel of a conventional image display device with a part thereof cut away.
As shown in
FIG. 13
, the conventional multi-electron beam source is constituted by surface conduction electron-emitting devices
4001
that are wired in a passive matrix shape in areas surrounded by column direction wirings
4002
and row direction wirings
4003
. In addition,
FIG. 13
also shows a structure of a cathode ray tube using this multi-electron beam source. This structure consists of an outer container bottom (which may also be referred to as “rear plate”)
4004
provided with the multi-electron beam source
4001
, a sidewall (which may also be referred to as “support frame” or “outer container frame”)
4005
and a faceplate
4006
provided with a phosphor layer
4007
and a metal back
4008
. In addition, phosphors that are excited and caused to emit light by electron beams and a black matrix for controlling reflection of external light to prevent color mixing of the phosphors are provided in the phosphor layer
4007
on the faceplate
4006
. In addition, a high voltage is applied to the phosphor layer
4007
and the metal back
4008
from a high voltage introducing terminal Hv. The phosphor layer
4007
and the metal back
4008
form an anode electrode.
The image display device as described above applies a high voltage (which may also be referred to as “acceleration voltage” or “anode voltage”) to the metal back
4008
that is a part of the anode electrode, generates an electric field between the rear plate
4004
and the face plate
4006
, accelerates electrons emitted from the electron beam sources
4001
, and excites and causes the phosphors to emit light, thereby forming an image. Here, since a luminance of the image display device depends largely on an acceleration voltage, it is necessary to increase the acceleration voltage in order to realize a high luminance. In addition, in order to realize thinning of the image display device, a thickness of the image display panel should be reduced. For this purpose, a distance between the rear plate
4004
and the faceplate
4006
should be reduced. Consequently, a relatively high electric field is generated between the rear plate
4004
and the faceplate
4006
.
However, the above-mentioned image display device has problems as described below.
FIG. 14
is a view schematically showing a section of the display panel of the image display device shown in FIG.
13
. The above-mentioned image display device includes the rear plate
4004
having the electron beam sources
4001
and the faceplate
4006
provided with the anode electrode
4101
consisting of the metal back or a not-shown black matrix. An acceleration voltage Va is applied to the anode electrode
4101
. Here, the anode electrode
4101
is insulated by a vacuum gap between the faceplate
4006
and the rear plate
4004
and creeping on surfaces of members such as the faceplate
4006
and the rear plate
4004
.
A dimension of the vacuum gap regulates a depth of the display panel, and creeping distances of the faceplate
4006
and the rear plate
4004
regulate an area and a width of a region other than an image display region (which may be referred to as “frame region”). Both the depths of the display panel and the frame region are preferably smaller. However, when dimensions of them decrease, even if the same voltage is applied to the anode electrode
4101
, a field intensity that is a value found by dividing the voltage by the distance increases. Thus, a probability of break down increases. When break down occurs, it is also likely that an image quality of the image display device is extremely deteriorated. This is a significant problem for improvement of reliability of the image display device.
In particular, the rear plate
4004
and the faceplate
4006
are generally formed of a glass member in many cases. Since a dielectric voltage of a dielectric body surface such as glass is extremely inferior to that of the vacuum air gap, it is very important to increase the dielectric voltage of a glass surface part.
FIG. 15
is a schematic sectional view of another conventional display panel described in EP1117124 (Japanese Patent Application Laid-Open No. 2001-250494).
As in the conventional another display panel shown in
FIG. 15
, a potential regulating electrode (which may also be referred to as “guard electrode”)
5102
, which is regulated to a potential lower than an anode potential, may be formed on the same member surface on which the anode electrode
5101
is formed for the purpose of regulating a potential distribution and limiting a region on which an electric field is applied on the surfaces of the rear plate
5004
and the faceplate
5006
. This is because, if a structure is present in a region other than an image display region and an electric field is applied to that part, concentration of an electric field occurs depending on a shape of the structure, which leads to a possibility of causing break down. By forming the potential regulating electrode
5102
as described above and regulating it to a potential lower than an anode potential, it is possible to relax an electric field applied to the outside of the potential regulation electrode
5102
.
Note that the structures of the electron beam source
5001
, the row direction wiring and the column direction wiring (both of which are not shown) are the same as those in the display panel shown in FIG.
13
.
However, with the structure having an electrode regulated to a potential lower than an anode potential on the same member surface as a region regulated to the anode potential as described above, an electric field on the outside of a potential regulating electrode (region receding away from an anode electrode) can be weakened. Thus, designing in the region on the outside of the potential regulating electrode becomes easy. However, on the other hand, if the distance between the potential regulating electrode
5102
and the anode electrode
5101
is reduced too much in order to reduce dimensions of regions other than the image display region, a field intensity between the anode electrode and the potential regulating electrode increases and break down occurs in that part.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide an image display device in which a dielectric breakdown voltage is increased while reducing a depth and a frame region of the image display device.
In order to attain the above-mentioned object, according to the present invention, there is provided an image display device comprising:
a rear plate having an electron beam source; and
a face plate having an anode electrode regulated to an electron accelerating potential and a first potential regulating member, which is arranged apart from the anode electrode and is regulated to a potential lower than that of the anode electrode, on
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Lee Wilson
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