Electric lamp and discharge devices – With luminescent solid or liquid material – Vacuum-type tube
Reexamination Certificate
2003-05-22
2004-09-21
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
Vacuum-type tube
C313S496000, C313S313000
Reexamination Certificate
active
06794813
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electron source, an image forming apparatus, and a manufacture method for an electron source.
2. Related Background Art
Many types of apparatus are known in which a number of electron emitting devices and wirings connected to the devices are disposed on a substrate to form a plane type electron source and an electron beam is emitted from a desired electron emitting device to display an image. For example, the publication of U.S. Pat. No. 5,942,849 (Neil Alexander Cade) discloses an apparatus in which electron emission from a field emitter chip is controlled by two grid electrodes (wirings) crossing each other at a right angle. In this apparatus, an electron emitting device is disposed at a cross point between the wirings. Another structure is also known in which an electron emitting device is disposed near at the wiring cross point in an area of the substrate where the wiring is not formed. The present applicant has already proposed an apparatus having such a structure. For example, this apparatus is disclosed in the publication of U.S. Pat. No. 5,654,607.
Electron emitting devices are roughly classified into thermal electron emitting devices and cold cathode electron emitting devices. As cold cathode electron emitting devices, a field emission type (hereinafter called an “FE type”), a metal/insulator/metal type (hereinafter called an “MIM type”), surface conduction electron emitting devices and the like are known.
Examples of the FE type are those disclosed in “Field emission” by W. P. Dyke & W. W. Dolan, Advance in Electron Physics, 8, 89 (1956), “Physical Properties of thin-film field emission cathodes with molybdenium cones” by C. A. Spindt, J. Appl. Phys., 47, 5284 (1976) and the like.
Examples of the MIM type are those disclosed in “Operation of Tunnel-Emission Devices” by C. A. Mead, J. Appl. Phys., 32, 646 (1961) and the like.
Examples of the surface conduction type electron emitting device are those disclosed by M. I. Elinson in Recio Electron Phys., 10, 1290 (1965) and the like.
Surface conduction electron emitting devices utilize the phenomenon that electron emission occurs when current is flowed through a thin film having a small area formed on an insulating substrate in parallel to the film plane.
Reports on surface conduction electron emitting devices show those using SnO
2
thin films by Elinson or the like, those using Au thin films (“Thin Solid Films” by G. Dittmer, 9, 317 (1972)), those using In
2
O
3
/SnO
2
thin films (by M. Hartwell and C. G. Fonstad in “IEEE Trans. ED Conf., 519 (1975)), those using carbon thin films (“Vacuum” by Hisashi ARAKI, et. al., Vol. 26, No. 1, p. 22 (1983)), and the like.
As a typical example of these surface conduction electron emitting devices, the device structure by M. Hartwell is schematically shown in FIG.
19
. On a substrate
401
, an electroconductive film
404
having an H-character shaped pattern and made of a sputtered metal oxide thin film is formed. An electron emitting region
405
shown by hatching in
FIG. 19
is formed by an operation called an energization forming operation to be described later. A device electrode distance L shown in
FIG. 19
is set to 0.5 to 1 mm and W′ is set to 0.1 mm.
Generally, prior to electron emission of the surface conduction electron forming device, the electroconductive film
404
is subjected to the operation called an energization forming operation to form the electron emitting region
405
. With the energization forming operation, a voltage is applied between opposite ends of the electroconductive film
404
to locally destruct, deform, or decompose the electroconductive film
404
and change the structure thereof to thereby form the electron emitting region
405
having an electrically high resistance. Fissures
1
are partially formed in the electron emitting region
405
of the electroconductive film
404
. Electrons are emitted nearly from these fissures.
Since the surface conduction electron emitting device has a simple structure, it has the advantage that a number of devices can be arranged in a large area. Various applications utilizing such characteristics have been studied. For example, applications to a charged beam source, an image forming apparatus such as a display apparatus and the like are known.
One example of an electron source having a number of surface conduction electron emitting devices is an electron source (e.g., publications of JP-A-64-031332, JP-A-1-283749, JP-A-2-257552 and the like) in which a number of rows are disposed (in a lattice type) and both ends (two device electrodes) of each of surface conduction electron emitting devices disposed in parallel are connected by wirings (common wires).
Surface conduction electron emitting devices can be used for a flat apparatus, particularly a display apparatus similar to liquid display apparatus which is of a self light emission type requiring no back light. Such a display apparatus is disclosed in the publication of U.S. Pat. No. 5,066,883 in which an electron source having a number of surface conduction electron emitting devices is combined with a fluorescent member which emits visual light when an electron beam is applied from the electron source.
The present applicant has also disclosed an example of an image displaying apparatus in the publication of JP-A-6-342636 in which an electron source with surface conduction electron emitting devices having a wiring pattern whose outline structure is schematically shown in FIG.
20
. In
FIG. 20
, a plurality of surface conduction electron emitting devices are connected in a matrix shape by upper wirings
73
and lower wirings
72
.
FIG. 21A
is a plan view showing the structure of a surface conduction electron emitting device, and
FIG. 21B
is a cross sectional view of the surface conduction electron emitting device taken along line
21
B—
21
B shown in FIG.
21
A. The surface conduction electron emitting device has: a pair of electrodes
202
and
203
formed on an insulating substrate
201
; an electroconductive thin film
204
made of fine particles and electrically connected to the electrodes
202
and
203
; and an electron emitting region
205
formed partially in the electroconductive thin film
204
for emitting electrons. In this surface conduction electron emitting device, a distance between the pair of electrodes
202
and
203
is set to several ten thousand nm to several hundred &mgr;m, and the length of the device electrode is set to several &mgr;m to several hundred &mgr;m by taking into consideration the resistance of the device electrode and the electron emission characteristics. The thickness of the device electrode is set in a range from several thousand nm to several &mgr;m in order to retain the electrical connection to the electroconductive film
204
. For example, the electrodes
202
and
203
are formed by photolithography techniques. The thickness of the electroconductive film
204
is set properly by taking into consideration the step coverage to the electrodes
202
and
203
, the resistance between the device electrodes, the energization forming conditions and the like. The thickness of the electroconductive film
204
is preferably set in a range from several ten nm to several ten thousand nm, or more preferably in a range from 100 nm to 5000 nm. The sheet resistance Rs of the electroconductive film is preferably set to 10
2
to 10
7
&OHgr;/□. Rs is given by R=Rs(l/w) where R is a resistance of a thin film having a thickness t, a width w and a length l as measured in the longitudinal direction. If the thickness t and a resistivity &rgr; are Constance, then Rs=&rgr;/t.
FIG. 22
is a schematic diagram showing an example of the structure of an image display apparatus using an electron source with a plurality of surface conduction electron forming devices wired in a matrix format, as disclosed in the above-cited publication of JP-A-6-342636. A rear plate
81
, an outer frame
82
and a face plate
86
are adhered togeth
Ono Takeo
Sugeno Toru
Guharay Karabi
Patel Nimeshkumar D.
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