Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1995-08-14
2001-06-19
Mengistu, Amare (Department: 2673)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C313S495000, C313S496000
Reexamination Certificate
active
06249266
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a fluorescent display device and a process for manufacturing the same, and more particularly to a fluorescent display device having a planar cathode incorporated therein and a process for manufacturing the same.
In general, a fluorescent display device includes a box-line envelope of which an interior is evacuated to a high vacuum. The envelope is provided therein with a cathode acting as an electron source, a control electrode, and an anode having a phosphor deposited thereon so as to serve as a luminous display section. In the conventional fluorescent display device thus constructed, electrons emitted from the cathode are caused to selectively impinge on the phosphor while being controlled by the control electrode, so that the phosphor is selectively excited, resulting in a desired luminous display being carried out.
Recently, a planar cathode such as a field emission cathode (hereinafter referred to as “FEC”) has been often used as a cathode for the fluorescent display device in place of a filamentary cathode. A typical spindt-type FEC includes an insulating layer and a gate electrode which are laminatedly formed on a cathode conductor of a cathode substrate. The insulating layer and gate electrode each are formed with a number of holes extending to the cathode conductor. The holes each are provided therein with an emitter of a conical shape in a manner to be positioned on the cathode conductor. Then, application of a voltage of a suitable level to each of the emitters and the gate electrode causes electrons to be emitted from the emitter.
The planar cathode such as an FEC or the like permits emission of electrons therefrom to be directly controlled by means of a voltage applied thereto. Thus, when the planar cathode is used as an electron source for the fluorescent display device, it is required that the cathode substrate on which the planar cathode is provided is arranged in proximity to the anode substrate on which the phosphor layer is deposited, to thereby prevent electron beams from spreading before they reach the anode. Also, when the phosphor is deposited in a strip-like or dot-like manner on the anode, it is required to align the phosphor layer of the anode with the cathode. This permits only control of the planar cathode to directly control a luminous display of the anode.
The conventional fluorescent display device includes a getter which is arranged so as to absorb residual gas thereon, to thereby permit the envelope to be evacuated to a high vacuum. Unfortunately, in order to accomplish this purpose, it is required to maintain, in the envelope, a space for arranging the getter. Thus, the conventional fluorescent display device, as shown in
FIG. 6
, is typically constructed in such a manner that an envelope
101
and a cathode substrate
100
are provided separate from each other, resulting in an interval between an anode
103
and a cathode
104
being adjusted depending on a thickness of the cathode substrate
100
. Also, alignment between the anode
103
and the cathode
104
is carried out by previously positioning the cathode substrate
101
on one of front and rear plate members constituting the envelope
101
and then positioning the cathode substrate
100
with respect to the other plate member on which the anode
103
is formed.
In the conventional fluorescent display device thus constructed, the envelope
101
is formed by assembling the plate members by means of a sealing agent or material such as low-melting frit glass deposited on each of the plate members, fixing the plate members to each other by vertically applying a pressure thereto while interposedly holding them by means of a clip or the like, and subjecting the plate members to a heat treatment or calcination to melt the sealing material, resulting in the plate members being integrally connected to each other.
Thus, the envelope
101
is pressurized by the clip or the like which interposedly holds it, so that profile irregularity of side plates
102
of the envelope
101
causes misregistration between the plate members to occur during assembling of the envelope
101
, resulting in alignment between the anode
103
and the cathode
104
in a horizontal direction being rendered highly difficult. Concurrently, profile irregularity of the side plates
102
requires to provide the interval between the anode
103
and the cathode
104
with allowance, thus, it is impossible to position the front and rear plate members in close proximity to each other and with high precision.
Further, in the conventional fluorescent display device, the envelope
101
is typically made of a glass plate. Also, the cathode plate
100
is often made of Si in the case that a drive circuit for the cathode
103
is formed on the cathode substrate
100
. In this instance, when the fluorescent display device is so constructed that the cathode substrate
100
is mounted on one of the front and rear plate members of the envelope
101
in such a manner as conventionally employed in the art, a different in thermal expansion coefficient between the cathode substrate
100
and the plate member causes damage to either the cathode substrate
100
or the plate member of the envelope
101
during the heat treatment.
Furthermore, the conventional fluorescent display device is so constructed that the cathode substrate
100
on which the cathode
104
is arranged is formed separate from the envelope
101
on which the anode
103
is arranged. Such construction renders connection between each of electrode elements of the cathode
104
and a lead wire extending through a sealed section of the envelope
101
substantially hard. The connection is conventionally carried out by means of wire bondings
105
. Unfortunately, this causes a disadvantage of failing to arrange the anode
103
and cathode
104
in proximity to each other because it is required to prevent a loop of a wire from contacting with each of the electrode elements.
SUMMARY OF THE INVENTION
The present invention has been made in view of the foregoing disadvantage of the prior art.
Accordingly, it is an object of the present invention to provide a fluorescent display device including a planar cathode which is capable of accomplishing alignment between the cathode and an anode in a horizontal direction with high precision.
It is another object of the present invention to provide a fluorescent display device including a planar cathode which is capable of arranging the cathode and an anode with respect to each other while decreasing an interval therebetween as desired.
It is a further object of the present invention to provide a fluorescent display device including a planar cathode which is capable of facilitating connection of wirings to the cathode.
It is still another object of the present invention to provide a process for manufacturing a fluorescent display device which is capable of manufacturing a fluorescent display device effectively accomplishing the above-described objects.
In accordance with one aspect of the present invention, a fluorescent display device is provided. The fluorescent display device includes an envelope formed by integrally attaching an substrate and a casing to each other through a sealing layer, an anode formed on the anode substrate in the envelope and having a phosphor layer deposited thereon, support members fixed on the sealing layer, a cathode substrate supported in the envelope by means of the support members in a manner to face the anode at a predetermined interval defined therebetween, a planar cathode formed on the cathode substrate, and lead wires arranged so as to extend through the sealing layer into the envelope and connected to the cathode substrate.
In a preferred embodiment of the present invention, the cathode substrate is formed of a material different in thermal expansion coefficient from a material for the casing.
In a preferred embodiment of the present invention, the planar cathode comprises an FEC.
In a preferred embodiment of the present invention, the fluorescent display
Kishino Takao
Nakata Hisashi
Futaba Denshi Kogyo K.K.
Mengistu Amare
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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