Electric lamp and discharge devices – Cathode ray tube – Ray generating or control
Reexamination Certificate
1998-08-31
2001-04-03
Day, Michael H. (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Ray generating or control
C313S479000, C313S4770HC
Reexamination Certificate
active
06211611
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a cathode-ray tube used as a receiving set of television, a computer display, and so on.
BACKGROUND OF THE INVENTION
In a general cathode-ray tube, a high resistivity film is provided at the midpoint of a feed line from an anode provided for a funnel to an anode of an electron gun in order to lower the maximum instantaneous current at sparking inside a bulb, and to prevent the current from damaging the electron circuit connected to the electron gun, or the like. More specifically, as shown in
FIG. 7
, a conventional cathode-ray tube comprises a bulb
6
comprising a panel
2
having a phosphor
1
provided on the inner surface and a funnel
5
having conductive films
4
a
,
4
b
, and
4
c
provided on the inner wall
3
, an electron gun
7
housed in a neck portion
5
a
of the funnel
5
, and springs
10
having contact portions
9
to electrically connect the conductive film
4
a
on the funnel inner wall
3
with a final electrode
8
. Numeral
24
indicates an anode terminal which applies high voltage to the final electrode
8
of the electron gun
7
through the conductive films
4
a
,
4
b
, and
4
c.
The specific resistance value of the conductive film
4
a
at the neck portion
5
a
is set to be 0.1-1 &OHgr;cm, the specific resistance value of the conductive film
4
b
at the cone portion
5
b
is set to be no more than 0.1 &OHgr;cm, and the specific resistance value of the conductive film
4
c
between the conductive film
4
a
at the neck portion
5
a
and the conductive film
4
b
at the cone portion
5
b
is set to be 1-10 &OHgr;cm respectively. The contact portions
9
of the springs
10
to contact with the conductive film
4
a
at the neck portion
5
a
are made of a metallic material having high conductivity, such as stainless steel. The above-mentioned construction lowers the maximum instantaneous current generated at a discharge inside the bulb
6
, and protects the circuit parts of a TV set from malfunction or breakage (Tokkai Sho 59-171439).
In such a cathode-ray tube, however, the conductive films (
4
a
,
4
b
,
4
c
) made of different materials are respectively formed on the funnel inner wall
3
, so the cathode-ray tube has problems in connection, such as conductivity failures at the junction A between the conductive films
4
a
and
4
c
, and the junction B between the conductive films
4
b
and
4
c
, and stripping of the coating film. Another problem is the complicated production process since the different kinds of conductive films (
4
a
,
4
b
,
4
c
) are respectively formed in a wide range at predetermined regions having different shapes on the inner wall
3
of the funnel
5
.
SUMMARY OF THE INVENTION
The object of this invention is to provide a cathode-ray tube that solves the problems in connecting different kinds of conductive films at the junctions and that simplifies the production process.
A cathode-ray tube of this invention comprises a bulb having a panel provided with a phosphor on the inner surface and a funnel having a conductive film provided on the inner wall, an electron gun housed in the neck portion of the funnel, and a spring that is provided for the final electrode of the electron gun and has a contact portion to electrically connect the conductive film on the funnel inner wall with the final electrode, in which the spring has a part with a specific resistance value greater than that of the conductive film that contacts with the contact portion at the mid-point of the conductive path between the conductive film and the final electrode.
As a result, only one kind of conductive film is applied to the funnel inner wall, which resolves the problem of the conventional cathode-ray tube, that is, the problem in the junction of different kinds of conductive films, and the production process can be simplified. Moreover, the maximum instantaneous current at a discharge inside the bulb can be lowered since the part in the spring composing the conductive path at a discharge has a specific resistance value greater than that of the conductive film that contacts with the contact portion. Therefore, malfunction and breakage of the circuit parts of a TV set can be prevented.
It is preferable that the portion housing a getter is formed between the phosphor on the inner surface of the panel and the final electrode of the electron gun.
This preferable constitution allows a getter flash, and thus, the vacuum level inside the bulb can be improved. Moreover, the entire specific resistance value of the conductive path will not be lowered at a discharge even if the getter adheres to the conductive film on the funnel inner wall at the getter flash so that the specific resistance value of the conductive film is lowered, since the part in the spring has the specific resistance value greater than that of the conductive film that contacts with the contact portion. Therefore, the maximum instantaneous current generated at a discharge inside the bulb can be maintained at a low value even after the getter flash.
REFERENCES:
patent: 3882348 (1975-05-01), Paridaens
patent: 4255689 (1981-03-01), Fischman et al.
patent: 55-1010 (1980-01-01), None
patent: 55-151754 (1980-11-01), None
patent: 59-171439 (1984-09-01), None
patent: 61-131341 (1986-06-01), None
T.A. Giorgi, Getters and Gettering, Japan J. Appl. Phys. Suppl. 2, Pt. 1 pp. 53-60, 1974 (No Month).
Ohmae Hideharu
Taguchi Yuji
Day Michael H.
Matsushita Electronics Corporation
Merchant & Gould P.C.
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