Electric lamp and discharge devices – With luminescent solid or liquid material – Vacuum-type tube
Reexamination Certificate
1999-05-13
2003-03-18
Day, Michael H. (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
Vacuum-type tube
C313S518000, C445S058000
Reexamination Certificate
active
06534912
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an active matrix drive fluorescent display device and a method for manufacturing the same, and more particularly, to an active matrix drive type fluorescent display device in which a semiconductor chip having a plurality of anodes individually driven and arranged in a matrix-like manner thereon is fixed on an inner surface of a substrate of an envelope and which is constructed so as to prevent misluminescence of the anodes due to a failure in insulation between, electrodes.
A conventional active matrix drive fluorescent display device typically includes an envelope constructed of a substrate made of an insulating material such as glass or the like and a casing sealedly mounted on an upper surface of the substrate. The substrate is mounted thereon with a silicon wafer of a rectangular shape acting as a semiconductor chip while being positioned in the envelope. The semiconductor chip has luminous sections arranged in a matrix-like manner thereon. The rectangular silicon wafer is made by slicing a purified or high-purity silicon monocrystal of a circular cylindrical shape into a disc-like shape. The disc-like silicon wafer thus formed is provided thereon with a plurality of rectangular elements each having a required structure incorporated therein. Then, the rectangular elements are cut off.
Such a conventional active matrix drive fluorescent display device will be further described with reference to FIG.
4
.
A silicon wafer
100
of a rectangular shape is adhered to a substrate
101
by means of a die bonding paste
102
. The silicon wafer
100
is provided on an upper surface thereof with anodes
105
in a matrix-like manner, each of which includes an anode conductor
103
and a phosphor layer
104
deposited on the anode conductor
103
. The anodes
105
each are provided thereunder with a transistor acting as a switching element. The silicon wafer
100
is provided on the upper surface thereof with a flat control electrode
106
of a lattice-like shape so as to extend between the anodes
105
adjacent to each other. The active matrix drive fluorescent display device also includes filamentary cathodes
107
stretchedly arranged above the silicon wafer
100
so as to act as an electron source while being positioned in an envelope. The cathodes
107
each include a core wire
107
a
made of a material generating heat due to feeding of a current thereto such as tungsten or the like and an electron emitting substance
107
b
deposited around the core wire
107
a
. The electron emitting substances include oxides of alkaline earth metals including Ba and the like.
The active matrix drive fluorescent display device thus constructed is driven in such a manner that any desired one(s) of the anodes
105
arranged on the silicon wafer
100
is selected by means of the switching element and electrons emitted from the filamentary cathodes
107
are impinged on the phosphor layer
104
of the anode
105
selected. The control electrode
106
has a positive potential constantly applied thereto, so that electrons emitted from the cathodes
107
may be diffused or spread by the control electrode
106
, resulting in being uniformly fed to the anodes
105
. Such selective driving of the desired anodes
2
in arranged in a matrix-like manner for luminescence leads to any desired graphic display.
During actual driving of the active matrix drive fluorescent display device, the electron emitting substance
107
b
of each of the cathodes
107
is activated to produce free metal, which tends to adhere to the silicon wafer
100
. For example, in the conventional fluorescent display device described above, the electron emitting substance
107
b
produces free barium (Ba), which tends to adhere to a cut surface
110
of the silicon wafer
100
which is an outer peripheral end surface of the silicon wafer
100
formed by cutting off it from the disc-like silicon monocrystal, as well as to a periphery thereof.
The outer peripheral end surface of the silicon wafer
100
shown in
FIG. 4
constitutes the cut surface
110
of the silicon wafer formed by cutting off it from the disc-like silicon wafer. The cut surface
110
of the silicon wafer
100
is constructed into a laminate structure having the above-described die bonding paste
102
, a p-type layer
100
a
, an n-type layer
100
b
and an insulating film
100
c
upwardly laminated on each other in turn. The p-type layer
100
a
is adhered to the substrate
101
through the die bonding paste
102
, resulting in providing a portion rendered electrically GND or an electrically GND portion. Such adhesion of free Ba to the cut surface
110
as described above keeps the insulating film
100
c
from carrying out is function, resulting in the electrically GDN portion of the cut surface
110
leading to a failure in insulation between the anodes
105
(phosphor layers
104
) and the control electrode
106
.
Such a failure in insulation causes the anodes
105
to be actually unintendedly turned on when the control electrode
106
is kept turned on, even when the anodes
105
are kept turned off, resulting in electrons impinging on the phosphor layers
104
of the anodes
105
, leading to misluminescence of the phosphor layers. Such misluminescence tends to occur at the phosphor layers
104
positioned in proximity to the cut surface
110
of the silicon wafer
100
.
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 an active matrix drive fluorescent display device which is capable of preventing misluminescence of phosphor layers due to a failure in insulation between electrodes owing to adhesion of a conductive material to a cut surface of a silicon wafer arranged in an envelope and formed thereon with luminous sections in a matrix-like manner.
It is another object of the present invention to provide a method for manufacturing an active matrix drive fluorescent display device which is capable of providing an active matrix drive fluorescent display device attaining the above-described object.
In accordance with one aspect of the present invention, an active matrix drive fluorescent display device is provided. The active matrix drive fluorescent display device includes an envelope, a semiconductor chip arranged on an inner surface of the envelope, and a plurality of anodes arranged in a matrix-like manner on the semiconductor chip and individually driven. The anodes each have a phosphor layer deposited thereon. Also, the fluorescent display device includes filamentary cathodes arranged in the envelope so as to be positioned above the semiconductor chip. The semiconductor chip is covered on an end surface thereof with an insulating material.
Also, in accordance with this aspect of the present invention an active matrix drive fluorescent display device is provided. The active matrix drive fluorescent display device includes an envelope including a substrate, a semiconductor chip arranged on an inner surface of the substrate of the envelope, switching elements arranged in a matrix-like manner on the semiconductor chip and selectively driven, anodes each arranged on each of the switching elements and having a phosphor layer deposited thereon, a control electrode arranged on the semiconductor element in a manner to extend between the anodes adjacent to each other, and filamentary cathodes each including an electron emitting layer made of a metal oxide and arranged in the envelope so as to be positioned above the semiconductor chip. The semiconductor chip being covered on a cut surface thereof with an insulating material.
In a preferred embodiment of the present invention, the insulating material is a fine powder of a material selected from the group consisting of Al
2
O
3
, SiO
2
, ZrO
2
and frit glass.
In a preferred embodiment of the present invention, the semiconductor chip is formed at a part of a portion thereof in proximity to an outer edge of an upper surface thereof with an el
Azeta Akihiro
Hirayama Toshihide
Honda Ken-ichi
Mihira Akihiro
Takano Sadao
Day Michael H.
Futaba Corporation
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Santiago Mariceli
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