Large area spacer-less field emissive display package

Details Large area spacer-less field emissive display package Large area spacer-less field emissive display package

1998-06-10

2001-03-06

Patel, Ashok (Department: 2875)

Electric lamp and discharge devices

With luminescent solid or liquid material

Vacuum-type tube

C313S292000, C313S309000, C313S252000, C313S249000

Reexamination Certificate

active

06198214

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to packaging and design of anode, cathode and support plates in a field emissive display.
BACKGROUND OF THE INVENTION
FIG. 1
shows the cross-section of a typical FED
10
assembly; Plates
12
and
15
represent the cathode and anode plates, respectively. A glass spacer frame
13
is bonded to the anode and cathode plates via a frit seal
14
. A hole in the cathode provides pump down, which is achieved through the exhaust tube
11
. This tube
11
also serves as a cavity for an evaporable getter (not shown).
The interior space
16
within the FED should be evacuated of gas through the exhaust tube
11
in order for the FED to work properly. As the interior space
16
is evacuated, the pressure on the interior walls of plates
12
and
15
is vastly reduced in comparison to the pressure on the exterior walls of these plates.
FIG. 2
shows what may happen when the pressure in the interior space
16
decreases to the levels required for proper operation of the FED. Under the atmospheric pressure, both the anode and the cathode plates,
15
and
12
, tend to bend inward because there is no pressure within the FED to oppose the pressure being applied from outside the FED. This results in destructive compression and tension forces being applied to the frit seal
14
. The inner portions of the frit seal
14
are compressed, and the outer portions of the frit seal are placed in tension. It is easy to understand that the larger the glass span of plates
12
and
15
, the greater the compressive and tension forces that may be applied to the frit
14
. For a given glass thickness n and seal width w, there is a maximum force which can be applied without tearing the seal
14
and cracking the plates
12
and
15
. As the pixel pitch decreases (higher resolution) and the viewing area gets larger (higher information content), the pressure exerted on the anode and cathode plates, due to atmospheric pressure, becomes very high and presents a challenge to the manufacture of large area FEDs with a gap between the plates
12
and
15
.
Thicker glass or stronger materials can be used for plates
12
and
15
, but they do not really provide a scalable solution. While the seal width w can also be increased to spread the load and improve shear resistance, the required width often is in conflict with FED applications that require small peripheral widths of the frit seal
14
. In addition, the increase in frit seal width requires larger glass plates
12
and
15
, but does not increase the actual viewing area of the FED. Other display technologies, such as liquid crystal displays, do not suffer from this drawback of increased seal width.
One method of reducing the stress on the frit seals
14
is to use internal spacers within the interior space
16
. Spacers are essentially insulative structures that form a bridge between the cathode plate
12
and the anode plate
15
within the interior space
16
. The spacers can be used to keep a constant separation between the cathode and anode plates across the dimensions of these plates. This approach allows for the use of thin glass plates, similar to those used in the LCD technology, for the cathode
12
and anode
15
plates.
The presence of these spacers within the interior space
16
means that there can be no pixels where there are spacers. Thus, the inclusion of internal spacers may affect display resolution. In addition, this approach may preclude the use of high voltage phosphors, considered to be the best fit for the FED technology, because of the chance that the spacers will provide a path for flashovers between the cathode and anode plates
12
and
15
. Further, the high voltage operation necessitates a large space between the plates
12
and
15
, which means a large spacer, thus resulting in spacer-created dark regions.
Another method for reducing frit seal stress is to use thick glass plates for the cathode and anode plates,
12
and
15
, to compensate for the unbalanced pressure forces on the plates. This approach is presently being used for displays smaller than 3″ in diagonal. Larger displays require a thicker glass but also an increase in the width w of the perimeter seal. This increase places limitations on the display's ability to be used in applications where border area is at a premium (for example, in avionics displays). In addition, the weight increase is likely to result in a non-competitive package, even when compared to conventional CRTs. Even the use of stronger materials, such as glass ceramics, may not remove the need for a wider frit seal in order to reduce the point shear force.
With reference to
FIG. 3
, a third method of reducing frit seal stress has been to use a 3-piece FED
10
assembly including a rear piece
17
in the shape of a shrunken funnel to reduce the stress on the seal
14
between the spacer frame
13
and the cathode plate
12
. This approach may strengthen the assembly by providing a rear piece
17
that does not deflect under pressure as much as a flat plate. The addition of the rear piece
17
, however, results in a non-flat panel, making the display more bulky.
The rear piece
17
may provide another benefit by providing a location for getter material in the FED. The operation of an FED may be highly dependent on the maintenance of a gas free vacuum between cathode and anode plates,
12
and
15
. Getter material within the FED is useful in capturing gas that is inside the FED. The inclusion of a rear piece
17
results in the formation of an additional wall within the FED on which getter material may be located. The advantage of using a rear piece to house getter material, however, is counter balanced by the bulkiness of the overall FED with a shrunken funnel shaped rear piece.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to provide a means for reducing the deflection of an FED cathode plate as a result of the FED being evacuated.
It is another object of the present invention to provide a means for reducing the stress on the seal between an FED cathode plate and other elements of the FED.
It is a further object of the present invention to provide a means for stiffening an FED cathode plate.
It is still another object of the present invention to provide an FED with a space behind the cathode plate for containing getter material.
Additional objects and advantages of the invention are set forth, in part, in the description which follows and, in part, will be apparent to one of ordinary skill in the art from the description and/or from the practice of the invention.
SUMMARY OF THE INVENTION
In response to the foregoing challenge, Applicants have developed an innovative, economical field emissive display having a cathode plate sealed to an anode plate along a periphery of the cathode plate; at least one field emissive device provided on an upper side of the cathode plate inside of the periphery; and comprising a support plate in contact with a lower side of the cathode plate at at least one point inside the cathode plate periphery.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed. The accompanying drawings, which are incorporated herein by reference, and which constitute a part of this specification, illustrate certain embodiments of the invention, and together with the detailed description serve to explain the principles of the present invention.


REFERENCES:
patent: 5210462 (1993-05-01), Konishi
patent: 5385499 (1995-01-01), Ogawa et al.
patent: 5503582 (1996-04-01), Cathey, Jr. et al.
patent: 5522751 (1996-06-01), Taylor et al.
patent: 5525861 (1996-06-01), Banno et al.
patent: 5562517 (1996-10-01), Taylor et al.
patent: 5603649 (1997-02-01), Zimmerman
patent: 5844360 (1998-12-01), Jeong et al.
patent: 5910705 (1999-06-01), Banno et al.

Affiliated with

Also associated with

Rating

Large area spacer-less field emissive display package does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Large area spacer-less field emissive display package, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Large area spacer-less field emissive display package will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2536134