Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
2002-02-08
2004-07-06
Shankar, Vijay (Department: 2673)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S075200
Reexamination Certificate
active
06760001
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electron source and an image display device. In particular, the present invention relates to a method and apparatus for adjusting a characteristic of an electron source or image display device and a method and apparatus for manufacturing the electron source or image display device.
2. Related Background Art
Electron sources each comprising a plurality of electron emitting devices have been known. Image display apparatuses each comprising a plurality of display devices have also been known. Image display apparatuses have been known which use as display devices electron emitting devices (combined with fluorescent materials that emit light when irradiated with electrons) or electroluminescence devices.
Two types of electron emitting devices, that is, hot-cathode devices and cold-cathode devices have been known. The known cold-cathode devices include, for example, field emitting devices, metal/insulated layer/metal type emitting devices, and surface conduction type emitting devices.
The cold-cathode devices, the surface conduction type electron-emitting devices (hereinafter simply referred to as the “devices”) utilizes the phenomenon in which electrons are emitted by causing current to flow through a small-area thin film and parallel with its surface, the film being formed on a substrate and composed of SnO
2
, Au, In
2
O
3
/SnO
2
, carbon, or the like.
FIG. 15
shows an example of a typical device configuration. In this figure, reference numeral
3001
denotes a substrate, and reference numeral
3004
denotes a conductive thin film composed of a metal oxide and formed by sputtering. The conductive thin film
3004
is formed as an H-shaped plane as shown in the figure. The conductive thin film
3004
is subjected to a process called “forming” to form an electron emitting section
3005
. The interval L in the figure is set between 0.5 and 1 mm, and the interval W therein is set at 0.1 mm. For the convenience of illustration, the electron emitting section
3005
is shown at the center of the conductive thin film
3004
to have a rectangular shape. However, this is schematic and does not faithfully represent the position or shape of the actual electron emitting section.
As described previously, to form an electron emitting section in a surface conduction type emitting device, current is allowed to flow through a conductive thin film to locally destroy, deform, or modify it to form a crack therein (forming process). Subsequently, an activation process can be executed to significantly improve an electron emitting characteristic.
That is, the activation process allows current to flow through the electron emitting section under appropriate conditions, the electron emitting section having been formed by a forming process, so that carbons or carbon compounds deposit in the vicinity of the electron emitting section. For example, in a vacuum atmosphere in which organisms under an appropriate pressure are present and which has a total pressure of 10
−2
to 10
−3
[Pa], by periodically applying pulses having a predetermined voltage, monocrystal graphite, polycrystal graphite, amorphous carbon, or a mixture thereof is deposited in the vicinity of the electron emitting section so as to have a thickness of about 500 Angstrom or less. However, these conditions are only an example and may be properly varied depending on the material or shape of the surface conduction type emitting device.
Such a process enables emitted current to be increased by a factor of 100 or more with the same applied voltage compared to a value measured immediately after forming. Accordingly, even when a multi-electron-source is manufactured which utilizes a large number of surface conduction type emitting devices such as those described above, each device is preferably subjected to the activation process. (After the activation process has been completed, the partial pressure on the organisms in the vacuum atmosphere is desirably reduced. This is called a “stabilizing process”.)
FIG. 16
shows a typical example of the emitted current Ie vs. device applied voltage Vf characteristic and device current If vs. device applied voltage Vf of a surface conduction type electron-emitting device.
The emitted current Ie is significantly smaller than the device current If, and it is thus difficult to illustrate it using the same scale. Further, these characteristics may be varied by varying design parameters such as the size and shape of the devices. Accordingly, the two graphs in the figure are shown in the respective arbitrary units.
The surface conduction type electron-emitting devices have the following three characteristics in connection with the emitted current Ie.
When a voltage equal to or larger than certain magnitude (this will be hereinafter referred to as a “threshold voltage Vth”) is applied to the devices, they rapidly emit the emitted current Ie. On the other hand, with a voltage lower than the threshold voltage Vth, substantially no emitted current Ie is detected. That is, these are nonlinear devices having the definite threshold voltage Vth in connection with the emitted current Ie.
Since the emitted current Ie varies depending on the voltage Vf applied to the devices, the magnitude of the emitted current Ie can be controlled using the voltage Vf.
The current Ie emitted from the devices responds to the voltage Vf applied to the devices, at high speed, so that the amount of charges in electrons emitted from the devices can be controlled on the basis of the period of time for which the voltage Vf is applied.
In addition to the adjustment based on activation, the adjustment of the characteristics of the surface conduction type electron-emitting devices can be achieved by applying a voltage equal to or higher than a certain voltage (threshold voltage Vth) to the devices, that is, applying a characteristic shift voltage that adjusts the characteristics of the devices, as described in Japanese Patent Application Laid-Open No. 10-228867.
Further, since the surface conduction type electron-emitting devices have a simple structure and can be easily manufactured, they are advantageous in that a large number of devices can be formed over a large area. Thus, image forming apparatuses such as image display and recording apparatuses as well as electron beam sources have been researched to which the surface conduction type electron-emitting devices are applied.
The inventors have tested various surface conduction type electron-emitting devices that are composed of different materials, have different structures, and are manufactured using different methods. The inventors have also studied multi-electron-sources (simply referred to as “electron sources”) having a large number of surface conduction type electron-emitting devices arranged therein as well as image display apparatuses to which these electron sources have been applied.
For example, the inventors have tested an electron source based on the electrical wiring method shown in FIG.
17
. In the figure, reference numeral
4001
denotes a schematically illustrated surface conduction type electron-emitting device,
4002
is a row-wise wire, and
4003
is a column-wise wire. In
FIG. 17
, reference numerals
4004
and
4005
denote wiring resistances.
The above described wiring method is called “simple matrix wiring”. For the convenience of illustration, a 6×6 matrix is shown, but the scale of the matrix is not limited to this example.
In an electron source comprising devices connected together using the simple matrix wiring method, an appropriate electric signal is applied to the row-wise wires
4002
and the column-wise wires
4003
. At the same time, a high voltage is applied to an anode (not shown).
For example, to drive arbitrary devices in the matrix, a selected voltage Vs is applied to the terminals of the row-wise wires
4002
for the selected rows, while, at the same time, a non-selected voltage Vns is applied to the terminals of the row-wise wires
4002
for
Kanda Makoto
Oguchi Takahiro
Yamano Akihiko
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Patel Nitin
Shankar Vijay
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