Electric lamp or space discharge component or device manufacturi – Process – With assembly or disassembly
Reexamination Certificate
2000-01-18
2001-12-25
Ramsey, Kenneth J. (Department: 2879)
Electric lamp or space discharge component or device manufacturi
Process
With assembly or disassembly
C430S314000, C430S319000
Reexamination Certificate
active
06332820
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for manufacturing a planar display device using the field electron emitting phenomenon.
2. Description of the Related Art
FIG. 1
is a perspective view showing a part of the cross section of a planar display device using the field electron emitting phenomenon having a typical configuration.
The planar display device
15
is constituted so that a first and second substrates
1
and
2
each comprising a glass substrate are facing each other through a reinforcement spacer
3
by keeping a certain interval from each other. Peripheries of these faced substrates
1
and
2
are airtightly sealed by, for example, a glass frit through an insulating outer-peripheral frame
14
made of ceramic or the like. An airtight flat space is formed between the both substrates
1
and
2
, an electron emitting portion
4
is formed at the side of first substrate
1
, and a fluorescent screen
5
is formed at the side of second substrate
2
.
On the first substrate
1
, for example, a plurality of first striped electrodes (so-called cathode electrodes)
11
and a plurality of second electrodes (so-called gate electrodes for taking out electrons)
12
are arranged in parallel in the direction to be intersected each other (e.g. to be intersected perpendicularly to each other) and intersections are electrically insulated from each other through an insulating layer
7
.
Moreover, a field-emitting type cathode
4
is constituted correspondingly to each of the intersections between the first and second electrodes
11
and
12
. These field-emitting type cathodes
4
respectively have a cold cathode configuration in which, an opening
8
passing through the insulating layer
7
and the upper second electrode
12
is formed at the intersection between the first and second electrodes
11
and
12
as shown in
FIGS. 2A and 2B
, and an electron emitting portion (so-called emitter)
9
is formed on the lower first electrode
11
in the opening
8
. In this case, a plurality of electron emitting portions
9
are arranged for each pixel (for each sub-pixel because phosphors R, G, and B serving as three sub-pixels constitute one pixel in the case of a color fluorescent screen).
A metal back layer
6
made of a thin film conductive layer is formed on the fluorescent screen
5
at the second substrate
2
side and a high acceleration voltage is applied to the metal back layer
6
.
Moreover, because a required voltage is applied between selected electrodes of the first and second electrodes
11
and
12
, electrons are taken out from the electron emitting portions
9
of the field-emitting type cathodes
4
arranged at the intersections and accelerated by the above acceleration voltage, to pass through the metal back layer
6
, and to impact the fluorescent screen
5
, and thereby, the screen
5
is made to fluoresce, and a fluorescent display such as an image display is realized.
The above field-emitting type cathode is formed by the film forming process including spin coating, printing, vacuum evaporation, sputtering, and CVD (chemical vapor deposition) and the so-called photolithography process including etching using a photoresist mask and lift-off.
FIGS. 3 and 4
show the steps of manufacturing a field-emitting type cathode according to a prior art.
First, as shown in
FIG. 3A
, a striped first electrode
11
is formed on one plane of a first substrate
1
, an electron emitting portion
9
is formed at the intersection with a second electrode
12
on the first electrode
11
through the lift-off method or selective etching, thereafter an insulating layer
7
is formed on the entire surface, and moreover a striped second electrode
12
intersecting with the first electrode
11
is formed on the insulating layer
7
.
Then, a positive-type photoresist layer
17
is formed on the entire surface including the second electrode
12
and only the photoresist layer
17
at a portion corresponding to an electron emitting portion
9
is selectively exposed by applying ultraviolet radiation
19
through a photomask
18
. Reference numeral
17
a
denotes a portion to be exposed and
17
b
denotes a portion to be unexposed. In this step, the position of the photomask
18
is adjusted on the basis of a previously-formed reference marker so that the center of the electron emitting portion
9
coincides with the center of the opening of the second electrode
12
to be thereafter formed.
Then, as shown in
FIG. 3B
, development is performed to remove the exposed portion
17
a
of the photoresist layer
17
and form the photoresist layer
17
on which an opening
20
is formed.
Then, as shown in
FIG. 4A
, the opening
8
is formed with selective etching by using the photoresist layer
17
as a mask so that the electron emitting portion
9
is exposed with the openings passing through the second electrode
12
and the insulating layer
7
below the second electrode
12
.
Then, as shown in
FIG. 4B
, the photoresist layer
17
is removed to obtain the field-emitting type cathode
4
constituted by forming the electron emitting portion
9
in the opening
8
formed at the intersection between the first electrode
11
and the second electrode
12
.
In the case of the above conventional method for manufacturing the field-emitting type cathode
4
, a substrate
1
is deformed due to a film stress generated when the insulating layer
7
is formed through sputtering and CVD in the steps of
FIG. 3A
or a relative positional shift is produced between the opening-forming photomask
18
and the position of the electron emitting portion
9
due to expansion and contraction of the substrate
1
caused by heat treatment of glass paste relating to printing when forming the insulating layer
7
. Therefore, as shown in
FIG. 4B
, when a positional shift is finally produced between the opening
8
of the second electrode
12
and the electron emitting portion
9
, problems occur that the number of electrons to be emitted fluctuates and irregular display appears.
On the other hand, when decreasing the distance between the electron emitting portion
9
and the second electrode
12
, an electron emitting voltage tends to become lower. When the electron emitting voltage lowers, a display circuit becomes inexpensive and a display device at a low power consumption is realized. Therefore, very fine patterning is requested.
However, most exposure systems for manufacturing a large planar display device of 20 inches type or more use the so-called proximity exposure in which the photomask
18
is exposed by separating it from the photoresist layer
17
by considering the damage of the photomask
18
. Because the proximity exposure is of a method to form a gap between the photomask
18
and the photoresist layer
17
, it is a problem that a deformed substrate cannot be corrected and thereby, a positional shift occurs.
Moreover, because a gap is present between the photomask
18
and the photoresist layer
17
, a disadvantage occurs that a very fine pattern cannot be obtained.
In the field of manufacturing of a semiconductor device such as an LSI, a projection system is used as an exposure device for realizing very fine photolithography. However, the projection system is not realistic because an exposure system is very expensive and an exposure system for a planar display device of
20
inches type or larger is restricted in its optical system.
By applying the self-alignment method to the alignment between the opening
8
of the second electrode
12
and the electron emitting portion
9
, the problem of positional shift due to deformation or expansion and contraction of a substrate, which generates when forming the insulating layer
7
, is solved. Moreover, because the number of photomasks and the number of position adjusting steps for exposure are decreased by the self-alignment method, an inexpensive planar display device can be manufactured.
As an example of manufacturing a field-emitting type cathode using the self-alignment method, the spin vacuum-evaporati
Inoue Kouji
Shimamura Toshiki
Kananen Ronald P.
Rader & Fishman & Grauer, PLLC
Ramsey Kenneth J.
Sony Corporation
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