Electric lamp and discharge devices – With luminescent solid or liquid material – Vacuum-type tube
Reexamination Certificate
1998-03-20
2004-01-13
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
Vacuum-type tube
C313S495000, C313S310000, C315S169100
Reexamination Certificate
active
06677706
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an electron emission apparatus comprising electron-emitting devices, an image-forming apparatus and a voltage application apparatus for applying a voltage between electrodes.
2. Related Background Art
Known electron emission apparatus include image-forming apparatus such as an electron-beam display panel realized by arranging in parallel an electron source substrate carrying thereon a large number of cold cathode electron-emitting devices, a metal back or transparent electrode for accelerating electrons emitted from the electron-emitting devices and an anode substrate provided with a fluorescent body and evacuating the inside. An image-forming apparatus comprising field emission type electron-emitting devices is described in I. Brodie, “Advanced technology: flat cold-cathode CRT's”, Information Display, 1/89, 17 (1989). An image-forming apparatus comprising surface conduction electron-emitting devices is disclosed in U.S. Pat. No. 5,066,883. A plane type electron-beam display panel can be made lightweight and have a large display screen as compared with currently popular cathode ray tubes (CRTs) and can provide brighter and higher quality images than any other plane type display panels such as plane type display panels using liquid crystals, plasma displays and electroluminescent displays.
FIG. 17
of the accompanying drawings schematically illustrates an electron-beam display panel as an example of an image-forming apparatus comprising electron-emitting devices. Referring to
FIG. 17
, there is shown a vacuum envelope
48
comprising a rear plate
31
operating as electron source substrate, a face plate
47
operating as anode substrate, an outer frame
42
, a glass substrate
41
supporting the rear plate. The vacuum envelope
48
contains therein electron-emitting devices
34
, wiring electrodes
32
(scan electrodes) and
33
(signal electrodes) connected to the respective device electrodes. Otherwise, there is shown a glass substrate
46
of the face plate
47
, a transparent electrode (anode)
44
and a fluorescent body (fluorescent film)
45
. The scan electrodes
32
and the signal electrodes
33
are arranged rectangularly relative to each other to produce a wiring matrix.
The display panel displays an image when selected ones of the electron-emitting devices
34
located at the crossings of the matrix are driven to emit electrons by sequentially applying a given voltage to the scan electrodes
32
and the signal electrodes
33
and the fluorescent body
45
is irradiated with emitted electrons to produce bright spots at locations corresponding to the activated respective electron-emitting devices. A High voltage Hv is applied to the transparent electrode
44
in order to give it a high electric potential relative to the electron-emitting devices
34
and accelerate the emitted electrons so that the bright spots may emit light actively. The voltage applied to the transparent electrode
44
is between several hundred volts to several tens of kilovolts depending on the performance of the fluorescent body. Therefore, the rear plate
31
and the face plate
46
are separated from each other normally by a distance between a hundred micrometers and several millimeters in order to prevent dielectric breakdown of a vacuum (electric discharges) from occurring due to the applied voltage.
While a transparent electrode is used as an acceleration electrode in the above arrangement, alternatively the fluorescent body
45
may be formed directly on the glass substrate
46
and a metal back may be arranged thereon so that a high voltage may be applied to the latter in order to accelerate electrons.
FIGS. 18A and 18B
of the accompanying drawings schematically illustrate two possible arrangements of fluorescent film that can be used for an electron-beam display panel. While the fluorescent film comprises only a single fluorescent body if the display panel is used for showing black and white pictures, it needs to comprise for displaying color pictures black conductive members
91
and fluorescent bodies
92
, of which the former are referred to as black stripes (
FIG. 18A
) or a black matrix (
FIG. 18B
) depending on the arrangement of the fluorescent bodies. Black stripes or a black matrix are arranged for a color display panel in order to make mixing of the fluorescent bodies
92
of the three different primary colors less discriminable and weaken the adverse effect of reducing the contrast of displayed images of reflected external light by blackening the surrounding areas. While graphite is normally used as a principal ingredient of the black stripes, other conductive material having low light transmissivity and reflectivity may alternatively be used.
A precipitation or printing technique can be suitably used for applying a fluorescent material on the glass substrate regardless of black and white or color display. The metal back is provided in order to enhance the luminance of the display panel by causing the rays of light emitted from the fluorescent bodies and directed to the inside of the envelope to be mirror-reflected toward the face plate
47
, to use it as an electrode for applying an accelerating voltage to electron beams and to protect the fluorescent bodies against damages that may be caused when negative ions generated inside the envelope collide with them. It is prepared by smoothing the inner surface of the fluorescent film (in an operation normally called “filming”) and depositing an Al film thereon after forming the fluorescent film.
A transparent electrode (not shown) may be formed on the face plate
47
facing the outer surface of the fluorescent film
45
(the side facing the glass substrate
46
) in order to raise the conductiveness of the fluorescent film
45
.
Care should be taken to accurately align each of color fluorescent bodies and the corresponding electron-emitting device for a color display.
When a plane type image-forming apparatus using electron beams is made to have a large display screen, structural members called spacers may be required to protect the envelope against the pressure difference between the internal vacuum and the external atmospheric pressure. When spacers are used, they can become electrically charged as some electrons emitted from the electron source at locations near the spacers and/or cations ionized by electrons collide with the spacers directly or after being reflected by the face plate. When the spacers are strongly charged, electrons emitted from the electron source can be deflected to show respective swerved trajectories and get to the target fluorescent bodies at improper spots to display a distorted image having an uneven brightness distribution.
Techniques for solving the problem of electrically charged spacers by causing a small electric current to flow through the spacers have been proposed (see, inter alia, Japanese Patent Applications Laid-Open Nos. 57-118355 and 61-124031). According to one of such techniques, an electrically highly resistive film is formed-on the surface of each insulating spacer to make a slight electric current flow therethrough.
Meanwhile, in an image-forming apparatus of the type under consideration comprising an oppositely disposed positive electrode such as a metal back or a transparent electrode, a high voltage is advantageously applied thereto in order to accelerate electrons emitted from cold cathode electron-emitting devices of the electron source so that the fluorescent bodies are made to emit light to a maximum extent. Additionally, the distance separating the opposite electrode from the electron source should be minimized to display images with an enhanced degree of resolution because otherwise the electron beams emitted from the electron source can be dispersed before they get to the target electrode depending on the type of the electron-emitting devices of the electron source.
Then, a strong electric field is produced between the opposite electrode and the electron source due to the high voltage to giv
Hara Toshitami
Miyazaki Kazuya
Yamano Akihiko
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Guharay Karabi
Patel Nimeshkumar D.
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