Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
2001-11-07
2004-03-09
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C315S169100, C345S079000, C345S076000, C313S310000
Reexamination Certificate
active
06703791
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image display device for displaying an image on a display member by irradiation with electrons emitted from an electron source.
2. Related Background Art
Conventionally, two types of electron-emitting devices electron sources, hot cathode devices and cold cathode devices, are known. Examples of the cold cathode device include a surface conduction electron-emitting device, a field emission (hereinafter referred to as FE) electron-emitting device, a metal/insulating-layer/metal (hereinafter referred to as MIM) electron-emitting device. Application of these devices to, for example, an image display device, an image-forming apparatus such as an image-recording apparatus and a charged beam source has been studied.
In particular, as an application example of a surface conduction electron-emitting device to an image display device, an image display device that combines to use surface conduction electron-emitting devices and phosphors for emitting light by irradiation of electron beams has been studied as disclosed in U.S. Pat. No. 5,066,883 and Japanese Patent Application Laid-open Nos. 2-257551 and 4-28137 filed by the applicant of the present application. The image display device that combines to use surface conduction electron-emitting devices and phosphors is expected to have a property that is more excellent than that of conventional image display devices of other systems. For example, it is more excellent than a liquid crystal display device, which has been widely used in recent years, in that it does not need a back light because it is a self-luminescence type and that it has a wider view angle.
In addition, a method in which a number of FE electron-emitting devices are arranged to be driven is disclosed, for example, in U.S. Pat. No. 4,904,895 by the applicant of the present application. In addition, as an example in which an FE electron-emitting device is applied to an image display device, for example, a flat panel display reported by R. Meyer et al. is known (R. Meyer: “Recent Development on Microtips Display at LETI”, Tech. Digest of 4th Int. Vacuum Microelectronics Conf., Nagahama, pp. 6-9 (1991)).
Among the image display devices using electron-emitting devices as described above, a thin plane type display device is attracting attention as a display device replacing a cathode-ray tube display device because it occupies less space and is light in weight.
FIG. 17
is a perspective view showing an example of a display panel portion forming a plane type image display device, which is shown with a part of the panel cut away in order to show an internal structure.
In the figure, reference numeral
3115
denotes a rear plate,
3116
denotes a side wall and
3117
denotes a face plate. The rear plate
3115
, the side wall
3116
and the face plate
3117
form an envelope (an airtight container) for maintaining a vacuum inside the display panel.
A substrate
3111
is fixed to the rear plate
3115
, and N×M cold cathode devices
3112
are formed on this substrate
3111
(N and M are positive integers equal to or larger than two and are properly set according to the target number of display pixels). In addition, as shown in
FIG. 17
the N×M cold cathode devices
3112
are wired by M lines of row-directional wiring
3113
and N lines of the column-directional wiring
3114
. A portion composed of the substrate
3111
, the cold cathode device
3112
, the row-directional wiring
3113
and the column-directional wiring
3114
is called a multi-electron beam source. In addition, an insulating layer (not shown) is formed between both the wiring at least in parts where the row-directional wiring
3113
and the column-directional wiring
3114
cross each other, whereby electrical insulation is maintained.
A fluorescent film
3118
consisting of a phosphor is formed on the lower surface of the face plate
3117
, and the phosphors of three primary colors of red (R), green (G) and blue (B) (not shown) are arranged. An example of the phosphors is shown in FIG.
14
. Here, a portion surrounded by dotted lines is referred to as a sub-pixel and a portion surrounded by solid lines is referred to as a pixel. One pixel is composed of three sub-pixels consisting of R, G and B. In addition, a black body (not shown) is provided among the above-mentioned phosphors forming the fluorescent film
3118
. Moreover, a metal back
3119
made of Al or the like is formed on the surface on the rear plate
3115
side of the fluorescent film
3118
.
Dx
1
to Dxm, Dy
1
to Dyn and Hv are terminals for electric connection of an airtight structure provided for electrically connecting the display panel and electric circuit (not-shown). Dx
1
to Dxm, Dy
1
to Dyn and Hv are electrically connected to the row-directional wiring
3113
of the multi-electron beam source, the column-directional wiring
3114
of the multi-electron beam source and the metal back
3119
, respectively.
In addition, a vacuum in the order of 133×10
−6
Pa (10
−6
Torr) is maintained inside the above-mentioned airtight container.
FIG. 18
shows a schematic view of an electron beam spot shape and an amount of electron beams when electron beams emitted from a surface conduction electron-emitting device have collided against a phosphor (not shown) on the face plate
3117
.
In the image display device using the above-described display panel, when a voltage is applied to each cold cathode device
3112
through the terminals Dx
1
to Dxm and Dy
1
to Dyn which are arranged outside the container, an electron is emitted from each cold cathode device
3112
. At the same time, a high voltage of several hundreds of V to several kV is applied to the metal back
3119
through the terminal Hv which is arranged outside the container, whereby the emitted electrons are accelerated and caused to collide against the internal surface of the face plate
3117
. Consequently, the phosphors of each color forming the fluorescent film
3118
are excited to emit light and an image is displayed.
It has been found that the above-described display panel of the image display device has the following problems.
In a thin image display device, there is an upper limit to the high voltage that can be applied to a part between a rear plate and a face plate. Thus, it is absolutely necessary to increase the amount of current from electron-emitting devices in order to realize a desired light-emitting luminance, which causes Coulomb degradation of the phosphor. In particular, in the case of an electron emitting device in which emitted electrons have an initial velocity in a direction other than the direction of the electrode from the electron-emitting device toward the face plate as in the surface conduction electron-emitting device as shown in
FIG. 18
, there is a deviation in the current density distribution, which makes the degradation of a phosphor more serious (a horizontal FE of
FIG. 19
(FE provided with both an emitter and a gate on the surface of a substrate) is also a device having the same problem). That is, since an amount of electron applied to one sub-pixel in order to realize desired luminance concentrates in one part within the one sub-pixel, the degradation of the phosphor in that part is aggravated rapidly and, as a result, the life of the phosphor is rendered short.
Thus, we have found that it is effective to disperse and arrange electron-emitting areas of electron-emitting devices (one unit) forming one sub-pixel in a plurality of places in order to eliminate the deviation of the current density distribution and, as a result, prevent progress of partial degradation of the phosphor. If two electron-emitting areas are provided, it becomes possible to reduce the amount of current from one of the electron-emitting areas by fifty percent and the concentration of the current density is improved by approximately fifty percent as long as the luminance thereof are equivalent. Thus, it becomes possible to increase the life of the phosphor so as to be twice a
Canon Kabushiki Kaisha
Dinh Trinh Vo
Fitzpatrick ,Cella, Harper & Scinto
Wong Don
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