Electric lamp and discharge devices – With luminescent solid or liquid material – Vacuum-type tube
Reexamination Certificate
2001-09-18
2004-03-23
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
Vacuum-type tube
C313S496000, C313S497000, C313S271000, C313S272000
Reexamination Certificate
active
06710536
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a display device such as a fluorescent display device using a cathode filament; and, more particularly to a cathode filament serving as an electron source for the display device.
BACKGROUND OF THE INVENTION
FIGS. 10A and 10B
show schematic internal structures of conventional display devices
800
and
850
, respectively. Referring to
FIG. 10A
, the display device
800
includes a glass substrate
81
, a filament
84
, a filament support
82
and an anchor
83
for the filament
84
. While one end of the filament
84
is fixed to a support member
821
of the filament support
82
, the other end of the filament
84
is fixed to a support member
831
of the anchor
83
. The height of the filament support
82
and that of the anchor
83
define the height (i.e., a distance between the substrate
81
and top end thereof) of the filament
84
(e.g., see, Japanese utility model laid open publication No. 61-7856).
The support member
831
of the anchor
83
is formed as a plate spring structure. A preset tension force is applied to the filament
84
to prevent the filament from hanging down due to the thermal expansion thereof. Accordingly, the plate spring structure of the support member
831
should be fabricated so that a uniform tension force is applied to the filament
84
. Further, the support member
831
should be fabricated with high precision since the support member
831
should fixedly support the filament
84
and maintain the height of the filament
84
at a preset level. The anchor
83
is of a complex structure, requiring a fabrication with high accuracy, and therefore, its fabrication is not easy and the cost thereof is expensive. In addition, it is not easy to make the anchor
83
of a small size, thereby rendering the fabrication of a thin and small display device difficult.
FIG. 10B
illustrates a schematic internal structure of a conventional display devices
850
which does not use an anchor. Like reference numerals represent like parts in
FIGS. 10A and 10B
.
Referring to
FIG. 10B
, the display device
850
includes a glass substrate
81
, a left filament support
82
, a right filament support
82
′ and a filament having a coiled portion
842
and a linear portion
841
. The filament supports
82
and
82
′ are fixed at a left and right end portion on top of the substrate
81
, respectively. While the left end of the coiled portion
842
is fixed at a support member
821
of the left filament support
82
, the right end of the linear portion
841
is fixed at a support member
821
′ of the right filament support
82
′. The coiled portion
842
applies a tension force on the linear portion
841
, thereby functioning similar to the anchor
83
in the device
800
shown in
FIG. 10A
(e.g., see, Japanese utility model laid open publication No. 61-7856).
The device
850
solves the problem of the anchor
83
as shown in
FIG. 10A
but entails another problem in that a temperature of the coiled portion
842
becomes higher than that of the linear portion
841
during the operation of the display device
850
. Namely, for example, during normal turning-on period of the display device
850
, the temperature of the coiled portion
842
reaches to about 800° C. while that of the linear portion
841
approaches to about 600° C. Under this condition, the coiled portion
842
emits red light to thereby prevent a normal display operation thereof.
In a manufacturing process of a conventional display device, in order to activate the filament, a flushing is performed at a high voltage. During the flushing, the temperature of the coiled portion
842
reaches to about 1500° C. to 2000° C. while that of the linear portion
841
reaches to 1000° C. As a result, electron emitting source material, e.g., a carbonate, coated on the coiled portion
842
is decomposed and flies around thereby contaminate fluorescent material deposited on an anode. This prevents the display device from operating normally.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a simple and inexpensive display device of high display quality by employing a filament free from above-mentioned problems, i.e., display quality degradation due to red light emission from the coiled portion and contamination of fluorescent material deposited on the anode due to flight of carbonate of a coiled portion, originated from an excessively high temperature of the coiled portion of the filament.
The display device of the present invention overcomes the above-mentioned problems of the conventional display device by adopting a cathode filament having a coiled portion and a linear portion and applying a tension force with the coiled portion and providing electrons only to the linear portion of the filament.
In accordance with a preferred embodiment of the present invention, there is provided a display device including: a cathode filament containing a coiled portion and a linear portion thereof; and a power feeding member, wherein an end of the coiled portion is fixed either to a substrate made of an insulating material or to an insulated support, the power feeding member being installed to contact with the linear portion of the cathode filament.
In accordance with another preferred embodiment of the present invention, there is provided a display device including: a cathode filament containing a coiled portion and a linear portion thereof; and a power feeding wiring for feeding power to the cathode filament, wherein an end of the coiled portion is fixed on either the power feeding wiring or a support member fixed on the power feeding wiring, the coiled portion being insulated.
In accordance with yet another preferred embodiment of the present invention, there is provided a display device including: an anode substrate; a back substrate having either a transparent conductor film or a control electrode formed thereon; a cathode filament installed between the anode substrate and the back substrate, the cathode filament having a coiled portion and a linear portion thereof; and a plurality of spacers fixed to either the transparent conductor film or the control electrode of the back substrate, wherein an end of the coiled portion is fixed either on an insulated support fixed on one of the anode substrate and the back substrate or on one of the anode substrate and the back substrate, a power feeding member being installed to contact with the linear portion of the cathode filament and the substrate on which the end of the coiled portion is fixed being made of insulating material.
In accordance with still yet another preferred embodiment of the present invention, there is provided a display device including: an anode substrate; a back substrate having either a transparent conductor film or a control electrode formed thereon; a cathode filament installed between the anode substrate and the back substrate, the cathode filament having a coiled portion and a linear portion thereof; and a plurality of spacers fixed to either the transparent conductor film or the control electrode of the back substrate, wherein an end of the coiled portion is fixed on either a support member fixed on a power feeding wiring of the cathode filament or the power feeding wiring, the coiled portion being insulated.
REFERENCES:
patent: 3780326 (1973-12-01), Raago
patent: 4047074 (1977-09-01), Kishino et al.
patent: 4338542 (1982-07-01), Takanashi et al.
patent: 5134338 (1992-07-01), Shiratori et al.
patent: 5179317 (1993-01-01), Watanabe et al.
patent: 5708326 (1998-01-01), Mizohata et al.
patent: 6441543 (2002-08-01), Yaniv et al.
patent: 6509693 (2003-01-01), Yonezawa et al.
Ishikawa Kazuyoshi
Kogo Katsutoshi
Ogawa Yukio
Yonezawa Yoshihisa
Yoshimura Satoshi
Bacon & Thomas PLLC
Futaba Denshi Kogyo Kabushiki Kaisha
Patel Nimeshkumar D.
Perry Anthony
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