Electric lamp and discharge devices – With luminescent solid or liquid material – Vacuum-type tube
Reexamination Certificate
1999-08-24
2002-06-18
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
Vacuum-type tube
C313S496000, C313S318120, C313S558000
Reexamination Certificate
active
06407500
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a vacuum envelope effective to various devices where field emission elements, each emitting electrons in an electric field, are arranged within the vacuum envelope. Particularly, the present invention relates to an electrode leading structure in a vacuum envelope for photoelectric conversion elements or displays employing field emission devices (FEDs) being flat-emission-type cold cathode ray tubes fabricated by the semiconductor micro-processing technology.
The Spindt-type field emission cathodes (FECs) are now in the practical stage as field emission elements fabricated by fully using the semiconductor technology and are well employed for displays.
FIG. 7
schematically illustrates the configuration of a Spindt-type cathode field emission cathode. This perspective view shows a field emission cathode manufactured using the semiconductor micro-processing technology.
Referring to
FIG. 7
, a cathode k is vapor-deposited on the substrate S. Cone emitters E are formed on the surface of the cathode K. A gate GT is formed over the cathode K via the insulating layer of a silicon dioxide (SiO2). The cone emitters E are respectively formed within holes opened in the gate GT. The tips of the cone emitters E are respectively viewed from the openings of the gate GT.
The micro-processing technology is employed to fabricate the cone emitters E arranged with pitches of less than 10 microns. Field emission cathodes of several ten thousands to several hundred thousands can be formed on a single substrate S.
Since the space between the gate GT and a cone emitter E can be set to the order of sub-microns, the emitter E field-emits electrons with several ten volts Vgk applied between the gate GT and the cathode K.
The anode A is spaced from the gate GT by a predetermined distance. The anode A can attract electrons emitted from the emitter E with the anode voltage Va applied. A fluorescent substance (not shown) coated over the anode A is excited by the accelerated electrons so that the display becomes a glow state.
With the photoelectric conversion layer film stacked over the anode A, the anode current depends on the light amount externally applied. An image pickup can detect the anode current.
In the conventional field emission display shown in
FIG. 7
, the space between the gate GT and the anode A is the order of several hundred micrometers. Such a field emission device allows a very thin vacuum envelope to be fabricated.
FIG. 8
is a cross sectional view partially illustrating the main portion of the flat vacuum envelope.
Referring to
FIG. 8
, a first glass substrate
11
has a field emission portion
11
a
formed of emitters E and the gate GT. A second glass substrate
12
has an anode
12
a
which has a laminated layer of a fluorescent display substance and a transparent electrode acting as a conductive metal-back layer. A side wall portion
13
surrounds the space between the first glass substrate
11
and the second substrate
12
to maintain a vacuum state. Normally, the side wall portion
13
is constructed slightly larger to define a getter room. The end portions of the side wall portion are joined with the first glass substrate and the second glass substrate using the fritted glass
14
so that the inside thereof is maintained in a vacuum state.
Numeral
13
a
represents an exhaust hole attached to evacuate the vacuum envelope to a vacuum state. The exhaust tube
13
b
externally attached to the exhaust hole
13
a
is used to evacuate the inside the vacuum envelope. The vacuum envelope is fabricated by sealing the exhaust tube
13
a.
The side wall section
13
has a hole
13
c
through which the lead
15
passes to be in contact with the anode
12
a.
With the lead
15
penetrating the hole
13
c
, the side wall portion
13
is securely fixed with the crystallized glass
13
d
while the spring member
15
a
formed at the front end of the lead
15
is resiliently contacted to the anode
12
a
. Thus, a relatively high voltage can be applied to the anode
12
a.
A relatively-low drive voltage applied to the field mission portion
11
a
on which the emitters E and the gate GT are formed can be externally applied via a great number of transparent conductive films printed on the first glass substrate
11
(not shown).
According to the flat vacuum envelope mentioned above, the lead
15
is in direct contact with the anode
12
a
and is drawn outside thereof, so that the contact between the anode
12
a
and the lead
15
becomes unstable. This causes a frequent contact failure or a self-discharge occurs when a high voltage of, for instance, several kilovolts is applied to the anode.
Particularly, the conductivity between the front end of the lead
15
and the anode
12
a
is achieved with the contact pressure of the spring member
15
a
of the front end after the sealing of the side wall portion
13
. However, the conductivity may be impaired because of impact during fabrication or mechanical shock after fabrication. This results in poor manufacturing yields and poor product reliability.
SUMMARY OF THE INVENTION
The present invention is made to solve the above-mentioned problems.
Moreover, the objective of the invention is to provide a flat vacuum envelope where an anode electrode can be connected to the high-voltage supplying electrode with high reliability.
The objective of the present invention is achieved by an electrode structure within a flat vacuum envelope comprising a first glass substrate on which field emission cathodes are arranged on a surface thereof; a second glass substrate on which an anode electrode to attract electrons emitted from the field emission cathodes, the second glass substrate being confronted with the first glass substrate, a space between the first glass substrate and the second glass substrate being maintained in a vacuum state; a connection electrode plate placed on the anode electrode and acting as a conductive metal plate; and a lead connected to the connection electrode plate and externally extended through the first glass substrate or the vacuum envelope.
REFERENCES:
patent: 5965978 (1999-10-01), Kishino et al.
patent: 6084344 (2000-07-01), Kishino et al.
patent: 6114804 (2000-09-01), Kawase et al.
patent: 4-163833 (1992-06-01), None
patent: 10-31433 (1998-02-01), None
Kagawa Yoshitaka
Tsuburaya Kazuhiko
Futaba Corporation
Guharay Karabi
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Patel Nimeshkumar D.
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