Multi-compartment getter-containing flat-panel device

Information

  • Patent Grant
  • 6194830
  • Patent Number
    6,194,830
  • Date Filed
    Thursday, February 25, 1999
    25 years ago
  • Date Issued
    Tuesday, February 27, 2001
    23 years ago
Abstract
A getter (74) is situated in an auxiliary compartment (72) of a hollow structure (40-46 and 76) having a larger main compartment (70). The auxiliary compartment is situated outside the main compartment and is connected to the main compartment so that the two compartments reach largely the same steady-state compartment pressure. The getter is activated by directing light energy locally through part of the hollow structure and onto the getter. The light energy is typically furnished by a laser beam (60). The getter, typically of the non-evaporable type, is usually inserted as a single piece of gettering material into the auxiliary compartment. The getter normally can be activated/re-activated multiple times in this manner, typically during sealing of different parts of the structure together.
Description




FIELD OF USE




This invention relates to gettering—i.e., the collection and removal, or effective removal, of small amounts of gases from an environment typically at a pressure below room pressure. In particular, this invention relates to techniques for activating getters used in structures such as flat-panel devices, and to structures designed to house the getters.




BACKGROUND




A flat-panel device contains a pair of generally flat plates connected together through an intermediate mechanism. The two plates are typically rectangular in shape. The thickness of the relatively flat structure formed by the two plates and the intermediate connecting mechanism is small compared to the diagonal length of either plate.




When used for displaying information, a flat-panel device is typically referred to as a flat-panel display. The two plates in a flat-panel display are commonly termed the faceplate (or frontplate) and the baseplate (or backplate). The faceplate, which provides the viewing surface, is part of a faceplate structure containing one or more layers formed over the faceplate. The baseplate is similarly part of a baseplate structure containing one or more layers formed over the baseplate. The faceplate structure and the baseplate structure are sealed together, typically through an outer wall.




A flat-panel display utilizes various mechanisms such as cathode rays (electrons), plasmas, and liquid crystals to display information on the faceplate. In a flat-panel cathode-ray tube (“CRT”) display, electron-emissive elements are typically provided over the interior surface of the baseplate. When the electron-emissive elements are appropriately excited, they emit electrons that strike phosphors situated over the interior surface of the faceplate which consists of transparent material such as glass. The phosphors then emit light visible on the exterior surface of the faceplate. By appropriately controlling the electron flow, a suitable image is displayed on the faceplate.




Electron emission in a flat-panel CRT display needs to occur in a highly evacuated environment for the display to operate properly and to avoid rapid degradation in performance. The enclosure formed by the faceplate structure, the baseplate structure, and the outer wall is thus fabricated in such a manner as to be at a high vacuum, typically a pressure of 10


−7


torr or less for a flat-panel CRT display of the field-emission type. Any degradation of the vacuum can lead to various problems such as non-uniform brightness of the display caused by contaminant gases that degrade the electron-emissive elements. The contaminant gases can, for example, come from the phosphors. Degradation of the electron-emissive elements also reduces the working life of the display. It is thus imperative that a flat-panel CRT display be hermetically sealed, that a high vacuum be provided in the hermetically sealed (airtight) enclosure, and that the high vacuum be maintained thereafter.




A field-emission flat-panel CRT display, commonly referred to as a field-emission display (“FED”), is conventionally sealed in air and then evacuated through tubulation provided on the display.

FIG. 1

illustrates how one such conventional FED appears after the sealing and evacuation steps are completed. The FED in

FIG. 1

is formed with baseplate structure


10


, faceplate structure


11


, outer wall


12


, and multiple spacer walls


13


. The FED is evacuated through pump-out tube


14


, now closed, provided at opening


15


in baseplate structure


10


.




Getter


16


, typically consisting of barium, is commonly provided along the inside of tube


14


for collecting contaminant gases present in the sealed enclosure. This enables a high vacuum to be maintained in the FED during its lifetime. Getter


16


is of the evaporable (or flashable) type in that the barium is evaporatively deposited on the inside of tube


14


.




Getter


16


typically performs in a satisfactory manner. However, tube


14


protrudes far out of the FED. Accordingly, the FED must be handled very carefully to avoid breaking getter-containing tube


14


and destroying the FED. It is thus desirable to eliminate tube


14


. In so doing, the location for getter


16


along the inside of tube


14


is also eliminated.




Simply forming an evaporable barium getter at a location along the interior surface of baseplate structure


10


or/and faceplate structure


11


is unattractive. Specifically, a getter typically needs a substantial amount of surface area to perform the gas collection function. However, it is normally important that the active-to-overall area ratio—i.e., the ratio of active display area to the overall interior surface area of the baseplate (or faceplate) structure—be quite high in an FED. Because an evaporable barium getter is formed by evaporative deposition, a substantial amount of inactive area along the interior surface of the baseplate structure or/and the faceplate structure would normally have to be allocated for a barium getter, thereby significantly reducing the active-to-overall area ratio. In addition, the active components of the FED could easily become contaminated during the getter deposition process. Some of the active FED components could become short circuited.




A non-evaporable getter is an alternative to an evaporable getter. A non-evaporable getter typically consists of a pre-fabricated unit. As a result, the likelihood of damaging the components of an FED during the installation of a non-evaporable getter into the FED is considerably lower than with an evaporable getter. While a non-evaporable getter does require substantial surface area, the pre-fabricated nature of a non-evaporable getter generally allows it to be placed closer to the actual display elements than an evaporable getter.




Non-evaporable getters are manufactured in various geometries.

FIGS. 2



a


and


2




b


(collectively “FIG.


2


”) illustrate the basic geometries for two conventional non-evaporable getters manufactured by SAES Getters. See Borghi, “St121 and St122 Porous Coating Getters,” SAES Getters, Jul. 27, 1994, pages 1-13. The getter in

FIG. 2



a


consists of metal wire


18


A covered by coating


19


A of gettering material. The getter in

FIG. 2



b


consists of metal strip


18


B covered by coating


19


B of gettering material. A porous mixture of titanium and a zirconium-containing alloy typically forms the gettering material in these two non-evaporable getters.




Upon being placed in a highly evacuated environment, each of the getters in

FIG. 2

is activated by raising the temperature of getter coating


19


A or


19


B to a suitably high value, typically 500° C., for a suitably long activation time, typically 10 min. At constant activation time, the getter performance can be increased by raising the activation temperature. For the getters of

FIG. 2

, the activation temperature can be as high as 900-950° C. above which the getters may be permanently damaged. Alternatively, as the activation temperature is increased, equivalent performance can be achieved at reduced activation time. The opposite occurs as the activation temperature is lowered to as little as 350° C. below which the gettering performance of the getters in

FIG. 2

is significantly curtailed.




A getter typically consists of a porous mixture of particles that sorb gases which contact the outer surfaces of the particles. When the non-evaporable getters of

FIG. 2

are activated in a high vacuum environment, sorbed gases present on the outer surfaces of the getter particles diffuse into the bulk of the getter particles, leaving their outer surfaces free to sorb more gases. The amount of gas which can be accumulated in the bulk of getter particles that are accessible to the gases is typically much more than the maximum amount of gas that the getter can sorb on the outer surfaces of the accessible particles. When the accessible outer getter surface is filled or partially filled with sorbed gases, the getter can be re-activated in a high vacuum environment to transfer the gases on the accessible outer surface to the bulk of the getter particles and again leave the accessible outer surface free to sorb more gases. Re-activation can typically be performed a relatively large number of times.




Borghi mentions three ways of activating the getters of

FIG. 2

under high vacuum conditions: (a) resistive heating, (b) RF heating, and (c) indirect heating. Resistive heating is performed by passing current through metallic conductor


18


A or


18


B to raise the temperature of getter coating


19


A or


19


B to the activation temperature. The current and accompanying power are relatively high during the activation process, facts that must be taken into account in utilizing resistive heating to activate the getters. Borghi also mentions that the getters can be activated during bake-out treatments of the vacuum devices that contain the getters.




Wallace et al, U.S. Pat. No. 5,453,659, discloses a getter arrangement for an FED in which the gettering material is distributed across the active area of the faceplate structure. As shown in

FIG. 3.1

, the faceplate structure in Wallace et al contains transparent substrate


20


, thin electrically insulating layer


21


, electrically conductive anode regions


22


, and phosphor regions


23


. Electrically insulating material


24


of greater thickness than anode regions


22


is situated in the spaces between regions


22


. Gettering material


25


is situated on insulating material


24


and is spaced apart from phosphor regions


23


. Wallace et al indicates that getter material


25


can be barium or a zirconium—vanadium—iron alloy.




Getter material


25


in Wallace is initially activated during assembly of the FED under high vacuum conditions at 300° C. Wallace et al also provides circuitry, including electrical conductors connected to getter material


25


, for re-activating getter material


25


.




The getter arrangement of Wallace et al appears relatively efficient in terms of area usage. However, getter material


25


is relatively complex in shape and requires manufacturing steps that could be unduly expensive. The necessity to maintain space between getter material


25


and phosphor regions


23


raises reliability concerns. The provision of circuitry to re-activate getter material


25


raises further reliability concerns and also further increases the fabrication cost. It would be desirable to have a simple technique for activating/re-activating a getter, especially one of relatively simple design, in a flat-panel device without raising the reliability concerns of Wallace et al, without incurring high getter installation costs, and without using an awkward getter-containing attachment such as the pump-out tubulation commonly used with evaporable getters in FEDs.




Pepi, U.S. Pat. No. 5,519,284, discloses a composite getter/pump-out arrangement that overcomes much of the awkwardness present in the conventional getter/pump-out arrangement of FIG.


1


.

FIG. 3.2



a


shows Pepi's getter/pump-out arrangement in which plate


25


of a flat display screen, such as an FED, has pump-out aperture


26


. Pump-out tube


27


overlies aperture


26


and is bonded to the exterior surface of plate


25


. Pump-out tube


27


has constricted portion


27


A which broadens into circular cylindrical portion


27


B having concave wall


27


C. A group of getters


28


lie on the exterior surface of plate


25


below concave wall


27


C. Pepi specifies that getters


28


may consist of cylindrical bars or strips. Pepi also discloses that the gettering material may be evaporatively deposited onto broadened tube portion


27


B.




Pepi's flat display screen is pumped out through tube


27


. Subsequently, tube


27


is closed at constricted portion


27


A as shown in

FIG. 3.2



b.


The closure operation is performed in such a way that the remainder


27


D of constricted portion


27


A lies below the highest part of broadened tube portion


27


B.




Pepi's getter/pump-out arrangement enables getters


28


to be located in a pump-out tube which, after tube closure, does not protrude far from the flat display screen. This should reduce the likelihood of damaging the display compared to the getter/pump-out arrangement of FIG.


1


. However, closing tube


27


appears to involve heating constricted portion


27


A along a location very close to concave wall


27


C. Undesired stresses may be produced in concave portion


27


C, thereby forming a weak point in the display. Also, when getter material is evaporatively deposited onto broadened tube portion


27


B (including concave wall


27


C), some of the evaporated getter material may pass through pump-out aperture


26


and contaminate the active display elements. It would be desirable to have a simple FED getter arrangement that overcomes the disadvantages of Pepi's arrangement and is suitable for a non-evaporable getter.





FIG. 3.3

illustrates the FED of Wiemann et al, U.S. Pat. No. 5,545,946, in which gated electron emitters


30


are provided in substrate


31


situated between backplane


32


and a faceplate structure consisting of faceplate


33


, anode layer


34


, and cathodoluminescent material layer


35


. Electrons emitted from gated emitters


30


enter substrate apertures


31


A and then move through interspace apertures


36


A in electrically insulating layer


36


to strike cathodoluminescent material


35


. Spacers


37


maintain a fixed spacing between electron emitters


30


and thin gettering layer


38


overlying backplane


32


. Getter


38


, which appears to be maintained at negative potential relative to anode layer


34


, collects contaminant gases present in apertures


36


A and


31


A and the evacuated region between substrate


31


and getter


38


.




By having gettering layer


38


situated on a different level than emitter-containing substrate


30


or the faceplate structure, the FED of Wiemann et al achieves a high active-to-overall area ratio. This is advantageous. However, it is not clear how getter


38


is activated or whether it can be reactivated. Furthermore, the presence of getter


38


and accompanying spacers


37


causes the overall thickness of the FED to be significantly increased, an undesirable result. In an FED containing a getter, it would be desirable to achieve a high active-to-overall area ratio without having the presence of the getter cause a significant increase in the overall FED thickness.




GENERAL DISCLOSURE OF THE INVENTION




The present invention employs local energy transfer to activate a getter situated in an auxiliary compartment of a hollow structure, such as a flat-panel device, having a larger main compartment. The auxiliary compartment is situated outside the main compartment and is connected pressure-wise to the main compartment so that the two compartments reach largely equal steady-state compartment pressures. In accordance with the invention, light energy is directed locally through a portion of a hollow structure and onto the getter to activate the getter and enable it to collect gases. The term “local” or “locally” as used here in describing an energy transfer means that the energy is directed selectively to certain material largely intended to receive the energy without being significantly transferred to nearby material not intended to receive the energy.




The local energy transfer is typically performed by directing a laser beam onto the getter. By activating the getter with a laser, the getter can be of relatively simple configuration. For example, a getter activated according to the present invention preferably consists of a single piece of gettering material, typically of the non-evaporable type, inserted into the auxiliary compartment of the hollow structure before the activation step. The invention thus avoids the reliability concerns and high manufacturing costs commonly associated with complex getter designs such as that of Wallace et al.




The hollow structure typically contains a first plate structure, a second plate structure, and an outer wall that extends between the plate structures to form the main compartment. Active display elements, such as electron-emissive elements and light-emissive elements that emit light upon being struck by electrons emitted from the electron-emissive elements, are usually provided in the plate structures. The hollow structure preferably further includes an auxiliary wall that contacts the first plate structure and extends away from the first plate structure and main compartment to form the auxiliary compartment. Control circuitry is typically provided over the first plate structure outside the main compartment to the side of the auxiliary compartment.




When arranged in the preceding way, the getter-containing auxiliary compartment does protrude away from the main compartment. However, the amount of protrusion is normally small compared to what occurs in the prior art FED of FIG.


1


. In particular, the auxiliary compartment normally does not extend substantially further away from the first plate structure than the control circuitry provided over the first plate structure. Consequently, the amount of additional care that must be exercised in handling the present hollow structure to avoid damaging the auxiliary compartment and control circuitry is not significantly greater than the amount of additional handling care that must be exercised to avoid damaging just the control circuitry. Contrary to what occurs with getter-containing tube


14


in the prior art FED of

FIG. 1

, the presence of the getter-containing auxiliary compartment here does not significantly raise the level of necessary handling care.




For the case in which the hollow structure is a flat-panel display, arranging the display in the preceding way so that the getter-containing auxiliary compartment at least partially overlies the first plate structure leads to a high active-to-overall area ratio while simultaneously permitting the getter to be made relatively large. This is highly beneficial. Since the auxiliary compartment does not extend significantly further away from the first plate structure than the control circuitry that overlies the first plate structure, the overall thickness of the display depends on the thickness of the control circuitry. The presence of the auxiliary compartment does not lead to any significant increase in the overall display thickness beyond that mandated by the control circuitry. Consequently, the so-configured display makes extremely efficient usage of the total volumetric space typically available for the display.




The getter-activation process is normally performed by passing the laser beam through transparent material of the auxiliary wall used in forming the getter-containing auxiliary compartment. The getter is activated upon being raised to a temperature of 300-950° C., preferably 700-900° C., by the laser beam. Although the getter itself is raised to a highly elevated temperature, the energy transfer that occurs during the activation process normally does not cause any significant heating of the auxiliary wall, the plate structures, or the outer wall.




In particular, very little of the light energy of the impinging laser beam is absorbed directly by transparent auxiliary-wall material through which the laser beam passes. When the laser beam is scanned only once across each part of the getter, only a small part of the getter is at high temperature at any time so that radiation-produced secondary heating is very small. The absence of significant heating of the auxiliary wall, the plate structures, and the outer wall in the invention is a large advantage over a resistively heated getter where a conductor that carries current for activating the getter would likely have to pass through a wall and where the energy transfer that arises from the attendant ohmic heating of the conductor could readily lead to melting of parts of the wall due to the high current needed to activate the getter.




The pressure in the hollow structure during the laser-based getter-activation step of the invention is generally below room pressure. The pressure is typically at a high vacuum level of 10


−2


torr or less. Accordingly, the present getter-activation technique is suitable for applications, such as flat-panel CRT displays, where a high vacuum is needed. Nonetheless, the getter-activation technique of the invention can be employed in devices, such as plasma displays or plasma-addressed liquid-crystal displays, where the internal pressure exceeds 10


−2


torr, typically due to the presence of inert gas. In either case, the getter chemically sorbs gases present in the hollow structure, including gases that move from the main compartment to the auxiliary compartment.




The invention also provides highly advantageous structures for a flat-panel device having a main compartment and a getter-containing auxiliary compartment. The main compartment in the present flat-panel device is formed with a first plate structure, a second plate structure, and a generally annular outer wall that extends between the plate structures.




In one embodiment of the present flat-panel device, the auxiliary compartment is formed with an auxiliary wall that contacts the first plate structure outside the main compartment, extends away from the first plate structure and the main compartment, bends back towards the second plate structure, and contacts the second plate structure outside the main compartment. The auxiliary compartment is connected to the main compartment so that the two compartments reach largely equal steady-state compartment pressures. The getter is situated in the auxiliary compartment.




The preceding multi-compartment structure in which both plate structures are utilized in forming the auxiliary compartment is somewhat more complex than a multi-compartment structure in which only one of two plate structures that form a main compartment with an intervening outer wall is employed in forming an adjoining auxiliary compartment. However, interconnection of the two compartments in the multi-compartment structure of the invention can be made through one or more openings in the outer wall. There is no need to make the interconnection through one of the plate structures as would normally be necessary in the simpler structure where only one of the plate structures is utilized in forming the auxiliary compartment. The present multi-compartment structure thereby avoids structural weakness that could occur due to openings provided through one of the plate structures.




In another embodiment of the present flat-panel device, the outer wall has an interior wall surface that faces the main compartment. A cavity, which serves as the auxiliary compartment, extends from the interior wall surface partially through the outer wall. The getter is situated at least partially in the cavity. Configuring the flat-panel device in this way facilitates device manufacture since there is no need to provide openings through a wall of the main compartment in order to connect the getter-containing cavity to the main compartment. Situating the getter-containing cavity in the outer wall permits the outer wall to be made sufficiently thick to achieve hermetic sealing of the device without having the getter overlie the internal area of the main compartment, thereby reducing the overall size of the flat-panel device.




In short, the present invention furnishes useful structures for housing a getter in a flat-panel device, as well as a simple technique for activating a getter placed in a flat-panel device, especially a flat-panel display of the CRT type where a high vacuum is needed to achieve high display performance. Importantly, the getter can have a very simple configuration—e.g., a single piece of non-evaporable gettering material. Installation and activation of the getter can be performed in an inexpensive manner. The likelihood of damaging the hollow structure due to energy transfer during the activation process is very low in the invention. The getter can be made quite large without significantly increasing the overall device thickness or the overall device area. The invention thus provides a large advance over the prior art.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a cross-sectional view of a conventional flat-panel CRT display having pump-out tubulation that contains an evaporable getter.





FIGS. 2



a


and


2




b


are cross-sectional views of conventional non-evaporable getters.





FIG. 3.1

is a cross-sectional view of a getter-containing faceplate structure of a prior art flat-panel CRT display.





FIGS. 3.2



a


and


3


.


2




b


are cross-sectional views of the getter/pump-out arrangement in a conventional flat display screen respectively before and after closure of pump-out tubulation.





FIG. 3.3

is a cross-sectional view of a conventional flat-panel CRT display in which a gettering layer lies on a backplane spaced apart from a substrate containing electron emitters.





FIGS. 4



a


-


4




h


are cross-sectional side views representing steps in laser activating a getter of a flat-panel display.





FIGS. 5



a


and


5




b


are respective cross-sectional plan views of the faceplate structure and overlying components in

FIGS. 4



a


and


4




b


. The cross sections of

FIGS. 5



a


and


5




b


are taken respectively through planes


5




a





5




a


and


5




b





5




b


in

FIGS. 4



a


and


4




b


. The cross sections of

FIGS. 4



a


and


4




b


are respectively taken through planes


4




a





4




a


and


4




b





4




b


in

FIGS. 5



a


and


5




b.







FIG. 6

is another cross-sectional side view of the faceplate structure and overlying components in

FIGS. 4



b


and


5




b


. The cross section of

FIG. 6

is taken through plane


6





6


in

FIGS. 4



b


and


5




b


. The cross sections of

FIGS. 4



b


and


5




b


are respectively taken through planes


4




b





4




b


and


5




b





5




b


in FIG.


6


.





FIGS. 7



a


and


7




b


are cross-sectional side views of a flat-panel CRT display having a main compartment and a smaller auxiliary compartment that contains a non-evaporable getter suitable for being laser activated according to the invention. The cross section of

FIG. 7



a


is taken through plane


7




a





7




a


in

FIG. 7



b


. The cross section of

FIG. 7



b


is taken through plane


7




b





7




b


in

FIG. 7



a.







FIG. 8

is a cross-sectional plan view of the flat-panel CRT display in

FIGS. 7



a


and


7




b


. The cross section of

FIG. 8

is taken through plane


8





8


in FIGS.


7




a


and


7




b


. The cross sections of

FIGS. 7



a


and


7




b


are taken respectively through planes


7




a





7




a


and


7




b





7




b


in FIG.


8


.





FIGS. 9



a


and


9




b


are cross-sectional side views, corresponding to the view of

FIG. 7



b


, that depict laser activation of the getter in the flat-panel CRT display of

FIGS. 7



a


,


7




b


, and


8


in accordance with the invention.





FIG. 10

is a cross-sectional side view, corresponding to the view of

FIG. 7



a


, that depicts control circuitry provided on the display of

FIGS. 7



a


,


7




b


, and


8


.





FIGS. 11



a


and


11




b


are cross-sectional side views, corresponding to the view of

FIG. 7



b


, that depict how the display of

FIGS. 7



a


,


7




b


, and


8


appears respectively before and after closure of pump-out tubulation provided on the display according to the invention.





FIGS. 12



a


and


12




b


are cross-sectional side views of a flat-panel CRT display configured in accordance with the invention so as to have a main compartment and a smaller auxiliary compartment that contains a getter suitable for being laser activated according to the invention. The cross section of

FIG. 12



a


is taken through plane


12




a





12




a


in

FIG. 12



b


. The cross section of

FIG. 12



b


is taken through plane


12




b





12




b


in

FIG. 12



a.







FIG. 13

is a cross-sectional plan view of the flat-panel CRT display of

FIGS. 12



a


and


12




b


. The cross section of

FIG. 13

is taken through plane


13





13


in

FIGS. 12



a


and


12




b


. The cross sections of

FIGS. 12



a


and


12




b


are taken respectively through planes


12




a





12




a


and


12




b





12




b


in FIG.


13


.





FIGS. 14



a


and


14




b


are perspective views that depict the assembly of a two-part implementation, in accordance with the invention, of the auxiliary wall of the auxiliary compartment in the flat-panel display of

FIGS. 12



a


,


12




b


, and


13


.





FIGS. 15



a


and


15




b


are cross-sectional side views, corresponding to the view of

FIG. 12



b


, that depict laser activation of the getter in the flat-panel CRT display of

FIGS. 12



a


,


12




b


, and


13


in accordance with the invention.





FIG. 16

is a cross-sectional side view, corresponding to the view of

FIG. 12



a


, that depicts control circuitry provided on the display of

FIGS. 12



a


,


12




b


, and


13


in accordance with the invention.





FIGS. 17



a


and


17




b


are cross-sectional side views, corresponding to the view of

FIG. 12



b


, that depict how the display of

FIGS. 12



a


,


12




b


, and


13


appears respectively before and after closure of pump-out tubulation provided on the display according to the invention.





FIGS. 18



a


and


18




b


are cross-sectional side views of another flat-panel CRT display configured in accordance with the invention so as to have a main compartment and a smaller auxiliary compartment that contains a getter suitable for being laser activated according to the invention. The cross section of

FIG. 18



a


is taken through plane


18




a





18




a


in

FIG. 18



b


. The cross section of

FIG. 18



b


is taken through plane


18




b





18




b


in

FIG. 18



a.







FIG. 19

is a perspective view of a portion of the outer wall in the flat-panel CRT display of

FIGS. 18



a


and


18




b.













Like reference symbols are employed in the drawings and in the description of the preferred embodiments to represent the same, or very similar, item or items.




DESCRIPTION OF THE PREFERRED EMBODIMENTS





FIGS. 4



a


-


4




h


(collectively “FIG.


4


”) illustrate how a non-evaporable getter of a flat-panel display is laser activated during the assembly, including the hermetic sealing, of the display. Side views are generally presented in FIG.


4


.

FIGS. 5



a


and


5




b


(collectively “FIG.


5


”) depict top views of the faceplate structure and the overlying components of the flat-panel display at the stages respectively shown in

FIGS. 4



a


and


4




b


.

FIG. 6

illustrates a side view of the faceplate structure and overlying components at the stage shown in

FIG. 4



b


but in a plane perpendicular to the plane of

FIG. 4



b.






As used herein, the “exterior” surface of a faceplate structure in a flat-panel display is the surface on which the display's image is visible to a viewer. The opposite side of the faceplate structure is referred to as its “interior” surface even though part of the interior surface of the faceplate structure is normally outside the enclosure formed by sealing the faceplate structure to a baseplate structure through an outer wall. Likewise, the surface of the baseplate structure situated opposite the interior surface of the faceplate structure is referred to as the “interior” surface of the baseplate structure even though part of the interior surface of the baseplate structure is normally outside the sealed enclosure formed with the two plate structures and the outer wall. The side of the baseplate structure opposite to its interior surface is referred to as the “exterior” surface of the baseplate structure.




With the foregoing in mind, the components of the flat-panel display assembled according to the process of

FIG. 4

include a baseplate structure


40


, a faceplate structure


42


, an outer wall


44


, and a group of spacer walls


46


. Baseplate structure


40


and faceplate structure


42


are generally rectangular in shape. The internal constituency of plate structures


40


and


42


is not shown. However, baseplate structure


40


consists of a baseplate and one or more layers formed over the interior surface of the baseplate. Faceplate structure


42


consists of a transparent faceplate and one or more layers formed over the interior surface of the faceplate. Outer wall


44


consists of four sub-walls arranged in a rectangle. Spacer walls


46


, which extend across active display area


48


as indicated in

FIG. 5



a


, maintain a constant spacing between plate structures


40


and


42


in the sealed display and provide strength to the display.




A flat-panel display assembled according to the process of

FIG. 4

can be anyone of a number of different types of high-vacuum flat-panel displays such as CRT displays and vacuum fluorescent displays as well as any one of a number of reduced-pressure flat-panel displays such as plasma displays and plasma-addressed liquid-crystal displays. In a flat-panel CRT display that operates according to field-emission principles, baseplate structure


40


contains a two-dimensional array of picture elements (“pixels”) of electron-emissive elements provided over the baseplate. The electron-emissive elements form a field-emission cathode.




In particular, baseplate structure


40


in a field-emission display (again, “FED”) typically has a group of emitter row electrodes that extend across the baseplate in a row direction. An inter-electrode dielectric layer overlays the emitter electrodes and contacts the baseplate in the space between the emitter electrodes. At each pixel location in baseplate structure


40


, a large number of openings extend through the inter-electrode dielectric layer down to a corresponding one of the emitter electrodes. Electron-emissive elements, typically in the shape of cones or filaments, are situated in each opening in the inter-electrode dielectric.




A patterned gate layer is situated on the inter-electrode dielectric. Each electron-emissive element is exposed through a corresponding opening in the gate layer. A group of column electrodes, either created from the patterned gate layer or from a separate column-electrode layer that contacts the gate layer, extend over the inter-electrode dielectric in a column direction perpendicular to the row direction. The emission of electrons from the pixel at the intersection of each row electrode and each column electrode is controlled by applying appropriate voltages to the row and column electrodes.




Faceplate structure


42


in the FED contains a two-dimensional array of phosphor pixels formed over the interior surface of the transparent faceplate. An anode, or collector electrode, is situated adjacent to the phosphors in structure


42


. The anode may be situated over the phosphors, and thus is separated from the faceplate by the phosphors. In this case, the anode typically consists of a thin layer of electrically conductive light-reflective material, such as aluminum, through which the emitted electrons can readily pass to strike the phosphors. The light-reflective layer increases the display brightness by redirecting some of the rear-directed light back towards the faceplate. U.S. Pat. Nos. 5,424,605 and 5,477,105 describe examples of FEDs having faceplate structure


42


arranged in the preceding manner. Alternatively, the anode can be formed with a thin layer of electrically conductive transparent material, such as indium tin oxide, situated between the faceplate and the phosphors.




When the FED is arranged in either of the preceding ways, application of appropriate voltages to the row and column electrodes in baseplate structure


40


causes electrons to be extracted from the electron-emissive elements at selected pixels. The anode, to which a suitably high voltage is applied, draws the extracted electrons towards phosphors in corresponding pixels of faceplate structure


42


. As the electrons strike the phosphors, they emit light visible on the exterior surface of the faceplate to form a desired image. For color operation, each phosphor pixel contains three phosphor sub-pixels that respectively emit blue, red, and green light upon being struck by electrons emitted from electron-emissive elements in three corresponding sub-pixels formed over the baseplate.




Baseplate structure


40


is to be hermetically sealed to faceplate structure


42


through outer wall


44


. At the stage shown in

FIGS. 4



a


and


5




a,


outer wall


44


has been sealed (or joined) to faceplate structure


42


. Outer wall


44


typically consists of frit arranged in a rectangular annulus. Spacer walls


44


are mounted on the interior surface of faceplate structure


42


within outer wall


44


. Spacer walls


46


are normally taller than outer wall


44


. The hermetic sealing of composite structure


42


/


44


/


46


to structure


40


is to occur along (a) an annular rectangular sealing area formed by the upper edge


44


S of outer wall


44


and (b) an annular rectangular sealing area


40


S along the interior surface of baseplate structure


40


.




Baseplate structure


40


is transparent along at least part of, normally the large majority of, sealing area


40


S and the area where light energy for getter activation is to pass. Opaque electrically conductive (normally metal) lines in baseplate structure


40


typically cross sealing area


40


S. Where such crossings occur, these opaque lines are sufficiently thin that they do not significantly impact the local transfer of light energy through structure


40


.




A getter structure consisting of a non-evaporable getter strip


50


and a pair of thermally (and electrically) insulating getter supports


52


is installed over the interior surface of faceplate structure


42


within outer wall


44


. See

FIGS. 4



b


,


5




b


, and


6


. As shown in

FIG. 5



b,


getter structure


50


/


52


is situated outside active display area


48


. Getter supports


52


are bonded to faceplate structure


42


. The ends of non-evaporable getter strip


50


are situated in slot-shaped cavities located partway up the height of supports


52


. The slots are slightly narrower than the width of supports


52


. The slots are also slightly bigger than the getter width and thickness at the ends of getter strip


50


so as to allow room for thermal expansion.




With getter structure


50


/


52


so arranged, non-evaporable getter


50


is spaced apart from faceplate structure


42


, outer wall


44


, and spacer walls


46


. Also, when baseplate structure


40


is bonded to faceplate structure


42


through outer wall


44


, getter


50


will also be spaced apart from baseplate structure


40


. This enables both the top and bottom surfaces of getter strip


50


, along with its side edges, to provide gas collection action. Since getter supports


52


are thermal (and electrical) insulators, getter


50


is thermally (and electrically) insulated from faceplate structure


42


, outer wall


44


, and spacer walls


46


and will be thermally (and electrically) insulated from baseplate structure


40


.




Non-evaporable getter


50


is typically configured internally as shown in

FIG. 2



b


. Interior strip


18


B usually consists of nichrome or nickel. Getter coating


19


B consists of a porous mixture of titanium and either a gettering alloy of zirconium and aluminum or a gettering alloy of zirconium, vanadium, and iron. For example, getter


50


is typically a getter strip akin to the St121 or St122 getter strip available from SAES Getters. The thickness of interior strip


18


B is 0.02-0.1 mm, while the total getter thickness is 0.1-0.5 mm The getter width is in the vicinity of 2 mm.




The outside surface of getter


50


is normally chosen so as to be sufficiently large to provide adequate gettering capacity for the entire flat-panel display. If, however, the outside surface of getter


50


is insufficient to achieve the requisite gettering capacity in the space available for getter


50


in that part of the display, one or more additional getter structures configured similarly to getter structure


50


/


52


can be provided elsewhere over the interior surface of faceplate structure


42


. For example, another such getter structure can be provided on the opposite side of active area


48


from where getter structure


50


/


52


is located. If there are advantages to small getter structures or limitations on fabricating large getter structures, one or more getter structures configured similarly to getter structure


50


can also be provided next to getter structure


50


/


52


.




Getter supports


52


are normally slightly shorter than outer wall


44


. Except for the slots that receive getter


50


, supports


52


are generally rectangular solids. Supports


52


are typically formed by a suitable molding process. Pieces of suitable support material could also be machined to produce supports


52


.




If getter strip


50


is so long that it is likely to bend and touch baseplate structure


40


or faceplate structure


42


due to the influence of gravity or/and other forces, one or more additional thermally (and electrically) insulating supports are provided along getter


50


to prevent it from touching structure


40


or


42


. One part of each additional getter support lies between baseplate structure


42


and getter


50


, while another part of each additional support overlies getter


50


so as to ensure that it is spaced apart from baseplate structure


40


. Because the presence of additional getter supports occupies getter area, the number of additional getter supports is preferably kept as low as reasonable.




Using a suitable alignment system (not shown), structures


40


and


42


/


44


/


46


/


50


/


52


are positioned relative to one another in the manner shown in

FIG. 4



c.






This entails aligning sealing areas


40


S and


44


S (vertically in

FIG. 4



c


) and bringing the interior surface of baseplate structure


40


into contact with the upper edges of spacer walls


46


. Because getter supports


52


are shorter than outer wall


44


and thus are shorter than spacer walls


46


, baseplate structure


40


is spaced vertically apart from supports


52


. The alignment is done optically in a non-vacuum environment, normally at room pressure, with alignment marks provided on plate structures


40


and


42


for aligning them, thereby causing sealing areas


40


S and


44


S to be aligned. Plate structures


40


and


42


and outer wall


44


now form a hollow structure having a cavity in which spacer walls


46


and getter structure


50


/


52


are situated. Spacer walls


46


are sufficiently taller than outer wall


44


that a gap


54


extends between sealing areas


44


S and


40


S.




With structures


40


and


42


/


44


/


46


/


50


/


52


situated in the alignment system, a tacking operation is performed to hold structure


40


in a fixed position relative to structure


42


/


44


/


46


/


50


/


52


. Techniques for performing the tacking operation and the subsequent gap-jumping final sealing operation are described in Cho et al, U.S. patent application Ser. No. 08/766,477, filed Dec. 12, 1996, now U.S. Pat. No. 6,109,994 the contents of which are incorporated by reference to the extent not repeated herein.




In the process of

FIG. 4

, the tacking operation is typically performed with a laser (unshown) that tacks structure


40


to structure


42


/


44


/


46


/


50


/


52


at several locations along aligned sealing areas


40


S and


44


S. See

FIG. 4



c


. The tacking operation causes portions


44


A of outer wall


44


to protrude upward and become firmly bonded to baseplate structure


40


. The tacking operation can alternatively be performed with separate tack posts situated outside outer wall


44


and tacked to plate structures


40


and


42


with suitable glue.




The tacked/partially sealed flat-panel display is removed from the alignment system and placed in a vacuum chamber


56


, as shown in

FIG. 4



d


, for laser activating getter


50


and performing other operations to complete the hermetic seal. Vacuum chamber


56


is pumped from room pressure down to a high vacuum at a pressure no greater than 10


−2


torr, typically 10


−6


torr or lower.




A laser


58


that produces a laser beam


60


is located outside vacuum chamber


56


. Laser


58


is arranged so that laser beam


60


can pass through a transparent window


56


W of chamber


56


and then through transparent material of baseplate structure


40


so as to impinge on getter


50


. Window


56


W typically consists of quartz.




The transparent material of baseplate structure


40


normally consists of glass. Laser beam


60


has a major wavelength at which the glass does not significantly absorb light energy. For example, when the transparent material of baseplate structure


40


consists of Schott D263 glass, the wavelength of laser beam


60


is in the approximate range of 0.3-2.5 μm across which Schott D263 glass strongly transmits light. As used here in connection with light transmission, “strongly” means at least 90% transmission. Consequently, very little of the thermal energy of laser beam


60


is transferred directly to baseplate structure


40


when laser beam


60


passes through the transparent material of structure


40


. Nor is substantially any of the thermal energy of laser beam


60


normally transferred directly to faceplate structure


42


, outer wall


44


, or any of spacer walls


46


.




Laser


58


can be implemented with anyone of a number of different types of lasers such as a semiconductor diode laser, a carbon dioxide laser (with the beam offset by 90°), an ultraviolet laser, or a neodymium YAG laser. For example, laser


58


is typically a diode laser such as the Optopower OPCA 015-810-FCPS continuous-wave integrated fiber-coupled diode laser module whose beam wavelength is approximately 0.85 μm. The laser power is typically 2-5 w. The width of getter strip


50


is typically no more than the diameter of laser beam


60


. For a 2-mm width of getter


50


, the diameter of beam


60


is typically 3 mm.




With the tacked structure at room temperature and with the pressure in chamber


56


at the high vacuum level, laser beam


60


is optionally scanned along the length of getter


50


to raise its temperature to a sufficient value to activate getter


50


. The activation temperature is in the range of 300-950° C. More particularly, the activation temperature is 700-900° C., typically 800° C.




A single scan along the length of getter strip


50


is normally sufficient to activate all the gettering material of getter


50


as long as the diameter of laser beam


60


is at least the width of getter


50


. If the diameter of beam


60


is so small compared to the width of getter strip


50


that some of the gettering material is likely not to be activated during a single laser scan, beam


60


can be scanned two or more times along different laterally separated paths that extend along the length of getter


50


.




When laser


58


is operated in the preceding manner, each part of getter strip


50


is subjected directly to laser beam


60


only once. While the part of getter


50


immediately subjected to beam


60


is raised to a high temperature in activating that part of getter


50


, the temperature of the activated part of getter


50


drops rapidly after beam


60


passes on. Consequently, only a small part of getter


50


is at a high temperature at any time. Secondary heating of components


40


-


46


by way of radiation from getter


50


is thus very small.




Using a heating element (not shown), the flat-panel display is raised to a bias temperature of 200-350° C., typically 300° C. The temperature ramp-up is usually performed in an approximately linear manner at a ramp-up rate in the vicinity of 3-5° C./min.




The components of the partially sealed flat-panel display outgas during the temperature ramp-up and during the subsequent “soak” time at the bias temperature prior to display sealing. The gases, typically undesirable, that were trapped in the display structure enter the unoccupied part of vacuum chamber


56


, causing its pressure to rise slightly. To remove these gases from the enclosure that will be produced when baseplate structure


40


is fully sealed to composite structure


42


/


44


/


46


/


50


/


52


, the vacuum pumping of chamber


56


is continued during the sealing operation in chamber


56


. If activated, getter strip


50


assists in collecting undesired gases during the temperature ramp-up and subsequent soak.




A laser


62


that produces a laser beam


64


is located outside vacuum chamber


56


as shown in

FIG. 4



e


. Laser


62


may be the same as laser


58


depending on the factors such as the desired power level and beam diameter. Laser


62


is arranged so that beam


64


can pass through chamber window


56


W and through transparent material of baseplate structure


40


along sealing area


40


S.




With the pressure of vacuum chamber


54


at the high vacuum level and with the flat-panel display at the bias temperature, laser beam


64


is moved in such a way as to substantially fully traverse aligned sealing areas


40


S and


44


S.

FIG. 4



e


illustrates how the flat-panel display appears at an intermediate point during the traversal of beam


64


along sealing areas


40


S and


44


S. If desired, beam


64


can skip tack portions


44


A. As laser beam


64


traverses sealing areas


40


S and


44


S, light energy is transferred through baseplate structure


40


and locally to upper material of outer wall


44


along gap


54


. The local energy transfer causes the material of outer wall


44


subjected to the light energy to melt and jump gap


54


. The melted wall material along sealing area


44


S hardens after beam


64


passes.




Getter strip


50


may be activated during the gap-jumping sealing operation using laser


58


in the manner described above. If getter


50


was activated prior to the final gap-jumping seal, this activation constitutes a re-activation. Also, if getter activation is performed during this step, laser


62


is normally a different laser from laser


58


.




Gap


54


progressively closes during the sealing operation with laser


62


. As gap


54


closes, the gases present in the enclosure being formed by the sealing of outer wall


44


to baseplate structure


40


escape from the enclosure through the progressively decreasing remainder of gap


54


. Full closure of gap


54


occurs when beam


64


completes the rectangular traversal of sealing areas


40


S and


44


S.




Further contaminant gases are normally introduced into the unoccupied part of vacuum chamber


56


as a result of the display sealing process. Some of these gases will be present in the now-sealed compartment (cavity) formed by plate structures


40


and


42


and outer wall


44


. Because the flat-panel display is sealed, the gases in sealed enclosure


40


/


42


/


44


cannot be removed by further vacuum pumping of chamber


56


.




If getter strip


50


was activated prior to or/and during the final sealing operation (after pumping chamber


56


down to the desired vacuum level), getter


50


collected some of the gases present in sealed enclosure


40


/


42


/


44


. However, in so doing, some of the gas-collection capability of getter


50


was used up.




In any case, after completing the display sealing step and while the sealed flat-panel display is approximately at the bias temperature, laser


58


is normally employed to activate getter


50


in the manner described above.

FIG. 4



f


illustrates the bias-temperature getter-activation step. If getter


50


was previously activated, this activation constitutes a re-activation.




The temperature of the sealed flat-panel display is subsequently returned to room temperature according to a cool-down thermal cycle that is controlled so as to avoid having the instantaneous cool-down rate exceed a selected value in the range of 3-5° C./min. The term “room temperature” here means the external (usually indoor) atmospheric temperature, typically in the vicinity of 20-25°C. Inasmuch as the natural cool-down rate at the beginning of the thermal cool-down cycle normally exceeds 3-5° C./min., heat is applied during the initial part of the cycle to maintain the cool-down rate at approximately the selected value in the range of 3-5° C./min. The heating is progressively decreased until a temperature is reached at which the natural cool-down rate is approximately the selected value, after which the flat-panel display is typically permitted to cool down naturally at a rate that progressively decreases to zero. Alternatively, a forced cool down can be employed during this part of the cool-down cycle to speed up the cool down.




During the cool-down period, getter


50


can be activated/re-activated one or more times using laser


58


in the above-described manner to remove contaminant gases not previously collected and/or contaminant gases released during the sealing operation and cool down. The pressure in vacuum chamber


56


is subsequently raised to room pressure, and the fully sealed flat-panel display is removed from chamber


56


. The term “room pressure” here means the external atmospheric pressure, normally in the vicinity of 1 atm. depending on the altitude. Alternatively, the chamber pressure can be raised to room pressure before cooling the sealed display down to room temperature. In either case,

FIG. 4



g


illustrates the resulting structure. Item


44


B in the sealed flat-panel display indicates the sealed shape of outer wall


44


.




Part of the gettering-capability of getter strip


50


is used up in collecting gases present in enclosure


40


/


42


/


44


after it is sealed and the flat-panel display is brought down to room temperature. Accordingly, getter


50


is re-activated after the temperature ramp-down is completed and the sealed flat-panel display is approximately at room temperature. The re-activation is performed with a laser


66


having a laser beam


68


as indicated in

FIG. 4



g.






The getter re-activation can be performed while the sealed flat-panel display is in vacuum chamber


56


or after removing the display from chamber


56


. If the getter re-activation is done while the flat-panel display is in chamber


56


, laser


66


is normally the same as laser


58


. In this case, the re-activation is performed in the manner described above for activating (or re-activating) getter


50


.




If the post cool-down re-activation is done after removing the flat-panel display from vacuum chamber


56


, laser


66


is normally a separate laser arranged so that laser beam


68


passes through transparent glass of baseplate structure


40


and impinges on getter


50


. As with laser beam


60


, laser beam


68


has a wavelength at which the glass strongly transmits light. No significant heating of any of components


40


-


46


occurs during the re-activation. When laser


66


is a separate laser from laser


58


, the re-activation of laser


66


is performed in substantially the same way as, and at very similar conditions to, the activation/re-activation with laser


58


.





FIG. 4



h


illustrates how the flat-panel display appears after the post cool-down re-activation of getter


50


is complete. The sealed display with activated getter


50


is ready for the addition of external circuitry and/or incorporation into a television, video monitor, or other such image-presentation apparatus.




In the final flat-panel display of

FIG. 4



h


, the combination of plate structures


40


and


42


and outer wall


44


forms a compartment (or chamber) that houses non-evaporable getter


50


, including getter supports


52


. Alternatively, a non-evaporable getter activated by a laser beam in accordance with the teachings of the invention can be situated in an auxiliary compartment that adjoins the main compartment formed with components


40


-


44


. The getter-containing auxiliary compartment is typically connected to the main compartment by way of one or more openings through components


40


-


44


so that the two compartments reach substantially equal steady-state compartment pressures. Due to the random movement of gas molecules, gases present in the main compartment move into the auxiliary compartment and are sorbed by the getter.




Such a multi-compartment flat-panel display is preferably configured so that the getter-containing auxiliary chamber does not protrude so far from the main chamber as to require substantial additional handling care in order to avoid damaging the auxiliary compartment and destroying the display. In particular, the non-evaporable getter typically overlies, or largely overlies, the exterior surface of baseplate structure


40


and is housed in an auxiliary compartment which overlies part of the exterior surface of baseplate structure


40


. The vertical dimension—i.e., the dimension in the direction perpendicular to the exterior surface of baseplate structure


40


—of the auxiliary compartment is then preferably chosen so that it does not vertically extend significantly further away from baseplate structure


40


than circuitry, provided over the exterior surface of structure


40


to the side of the getter-containing auxiliary compartments, for controlling image-producing elements in the flat-panel display. Consequently, the presence of the auxiliary compartment does not significantly increase the amount of care that must be exerted in handling the display beyond the amount of handling care already needed due to the presence of the control circuitry.




With the getter being situated outside the main compartment in such a manner so as to overlie, or largely overlie, the main compartment, the getter does not cause the internal area of the main compartment to be significantly increased. Consequently, a flat-panel device arranged in this way has a high active-to-overall area ratio. Since the getter-containing auxiliary compartment is configured so as to not extend significantly further away from the main compartment than the control circuitry overlying the main compartment to the side of the auxiliary compartment, the overall thickness of the display depends on the thickness (or height) of the control circuitry. The presence of the auxiliary compartment does not lead to any significant increase in the overall thickness of a flat-panel display so configured.





FIGS. 7



a


and


7




b


(collectively “FIG.


7


”) illustrate an embodiment of such a two-compartment flat-panel display having a main compartment


70


and a smaller auxiliary compartment


72


that houses a non-evaporable getter strip


74


suitable for being laser activated according to the invention.

FIG. 8

presents a top view of the flat-panel display in FIG.


7


. The top view of

FIG. 8

is taken through auxiliary compartment


72


.




As indicated in

FIG. 7

, main compartment


70


is formed with plate structures


40


and


42


and outer wall


44


. Baseplate structure


40


in

FIG. 7

is provided with electron-emissive elements in the manner described above. Similarly, faceplate structure


42


is provided with light-emissive elements as described above. Spacer walls


46


are present in main compartment


70


and extend between plate structures


40


and


42


so as to maintain a constant spacing between structures


40


and


42


and provide strength to the display. Spacer walls


46


run generally perpendicular to the length of getter strip


74


.




Auxiliary compartment


72


overlies main compartment


70


above part of the exterior surface of baseplate structure


40


. Auxiliary compartment


72


is formed with baseplate structure


40


and a five-sided transparent auxiliary wall


76


consisting of a relatively flat rectangular top portion


76


T and four relatively flat rectangular lateral portions


76


L arranged in a rectangular annulus. Top auxiliary wall portion


76


T extends generally parallel to baseplate structure


40


. Lateral auxiliary wall portions


76


L extend generally perpendicular to both top wall portion


76


T and baseplate structure


40


. The top edges of lateral wall portions


76


L merge into the edges of top wall portion


76


T. The bottom edges of lateral wall portions


76


L are hermetically bonded to baseplate structure


40


along its exterior surface by way of sealing material


78


, typically frit or indium.




Auxiliary wall


76


preferably consists of a unitary piece of glass. As such, auxiliary wall


76


is typically created by a molding, glass-blowing, etching or machining process. The corners of auxiliary wall


76


may be rounded. Alternatively, auxiliary wall portions


76


L and


76


T can be made separately and subsequently joined together.




Auxiliary compartment


72


is connected to main compartment


70


by way of a group of openings


80


extending through baseplate structure


40


.

FIGS. 7



b


and


8


illustrate four such inter-compartment openings


80


.




As indicated in

FIG. 8

, openings


80


can be circular as viewed from the top.




Getter strip


74


is typically configured and constituted the same as getter strip


50


described above. A pair of getter supports


82


are located in auxiliary compartment


72


and are bonded to baseplate structure


40


along its exterior surface. Getter supports


82


thermally (and electrically) insulate getter


74


from auxiliary wall


76


, baseplate structure


40


, and the other components of the flat-panel display. Getter supports


82


are typically configured and constituted similar to getter supports


52


described above. The ends of getter strip


74


are situated in slot-shaped cavities located partway up the height of getter supports


82


.




The flat-panel display of

FIGS. 7 and 8

can be assembled in various ways. In a typically assembly sequence that begins with inter-compartment openings


80


provided through baseplate structure


40


, plate structures


40


and


42


are hermetically sealed together through outer wall


44


according to a suitable technique. Getter structure


74


/


82


is then positioned appropriately over baseplate structure


40


after which getter supports


82


are bonded to structure


40


along its exterior surface. Auxiliary wall


76


is positioned over getter structure


74


/


82


and hermetically bonded to baseplate structure


40


.




Instead of bonding getter supports


82


to baseplate structure


40


, the flat-panel display of

FIGS. 7 and 8

can be modified by bonding getter supports


82


to auxiliary wall


76


, preferably the inside of top portion


76


T. The combination of getter supports


82


, getter strip


74


, and auxiliary wall


76


can then be pre-fabricated as a unit to be later mounted over baseplate structure


40


. Although inter-compartment openings


80


are typically provided through baseplate structure


40


before bonding auxiliary wall


76


, by itself or as part of a pre-fabricated unit with getter structure


74


/


82


, to baseplate structure


40


, openings


80


can be created through structure


40


after bonding wall


76


to structure


40


.




Getter strip


74


is activated with a laser beam in substantially the same manner as described above in connection with

FIGS. 4



d


,


4




f


, and


4




g


except that the laser beam passes through transparent material of top auxiliary wall portion


76


T rather than transparent material of baseplate structure


40


. The pressure in auxiliary compartment


72


during the getter-activation step is at a high vacuum level no greater than 10


−2


torr, typically 10


−6


torr or less. The getter-activation temperature with the laser beam again is 300-950° C., preferably 700-900° C. As in the process of

FIG. 4

, very little heating of any of the display components, except for getter


74


, occurs during the getter-activation process.





FIG. 9



a


depicts how getter strip


74


is activated with laser beam


60


produced by laser


58


while the flat-panel display of

FIGS. 7 and 8

is in vacuum chamber


56


.




After the initial getter activation, one or more re-activation steps may be performed with the same laser or a different one.

FIG. 9



b


depicts how getter


74


is activated/re-activated with laser beam


68


produced by laser


66


after the flat-panel display of

FIGS. 7 and 8

is removed from vacuum chamber


56


. Upon being activated/re-activated, getter


74


sorbs gases (i.e., gas molecules or atoms) that come in contact with getter


74


, including gases produced during high-temperature operations by outgassing in compartments


70


and


72


.




The laser-initiated gap jumping technique described above for the process of

FIG. 4

can be employed in hermetically sealing plate structures


40


and


42


together through outer wall


44


in the flat-panel display of

FIGS. 7 and 8

. The sequence of getter activation, gap-jump sealing, and getter re-activation steps for the flat-panel display of

FIGS. 7 and 8

is the same as that described above for the process of

FIG. 4

except that directing a laser beam to produce gap jumping is not performed through any part of baseplate structure


40


covered by getter structure


74


/


82


, and is typically not performed through any portion of baseplate structure


40


covered by auxiliary wall


76


. The difficulty created by having getter structure


74


/


82


or auxiliary wall


76


cover area which is to be hermetically sealed by gap jumping, as occurs with part of aligned sealing areas


40


S and


44


S in the particular configuration of the flat-panel display shown in

FIGS. 7 and 8

, can be overcome by moving auxiliary compartment


72


slightly so that none of it overlies outer wall


44


. Alternatively, gap jumping can be employed to seal faceplate structure


42


to outer wall


44


after sealing baseplate structure


40


to outer wall


44


and after bonding auxiliary wall


76


to baseplate structure


40


.




Control circuitry is normally provided on the exterior surface of baseplate structure


40


to the side of auxiliary compartment


72


as shown in FIG.


10


. The control circuitry typically consists of circuitry elements


84


interconnected by way of electrically conductive traces (not shown) provided on a printed circuit board


86


attached to baseplate structure


40


. In order to minimize high temperatures that control circuitry


84


/


86


could be subjected to during sealing and bonding operations, control circuitry


84


/


86


is normally mounted on the flat-panel display after sealing plate structures


40


and


42


to outer wall


44


and after bonding auxiliary wall


76


to baseplate structure


40


.

FIG. 10

illustrates that auxiliary wall


76


extends to roughly the same height above baseplate structure


40


as control circuitry


84


/


86


. In any case, auxiliary wall


76


does not extend significantly further above baseplate structure


40


than control circuitry


84


/


86


.




Instead of hermetically sealing the flat-panel display of

FIGS. 7 and 8

by a process that involves laser-initiated gap jumping at in a high vacuum environment, the hermetic sealing of plate structures


40


and


42


together through outer wall


44


can be performed at a pressure close to room pressure in a suitable neutral (i.e., non-reactive) environment, after which the pressure in the sealed display is reduced to a high vacuum level by pumping gas out of the display through a suitable port provided on the display, preferably a pump-out port that does not protrude out awkwardly from the display.

FIG. 11



a


presents a variation of the flat-panel display of

FIGS. 7 and 8

in which a glass pump-out tube


88


is connected to auxiliary compartment


72


through an opening


90


in one of lateral auxiliary wall portions


76


L to form a port for evacuating the display in accordance with the invention. Pump-out tube


88


extends laterally over a part of baseplate structure


40


not covered by control circuitry


84


/


86


.




Pump-out tube


88


has a constricted portion


88


A close to the location at which tube


88


meets one of lateral auxiliary wall portions


76


L. Constricted tube portion


88


A is employed for closing pump-out port


88


by heating portion


88


A with a suitable heating element situated close to portion


88


A after the display has been pumped out through part


88


to a high vacuum level no greater than 10


−2


torr, again typically 10


−6


torr or less. The pressure differential across constricted tube portion


88


A (i.e., the difference between the high outside pressure in the neutral environment and the very low pressure in the pumped-down display) causes portion


88


A to collapse and become closed when it is suitably heated. The heating to close tube portion


88


A could also be performed with a laser.




As indicated in

FIG. 11



a


, pump-out tube


88


extends laterally away from auxiliary compartment


72


and thus does not overlie compartment


72


. Consequently, the heating of constricted portion


88


A to close tube


88


is not likely to result in heat transfer that could generate significant stress in auxiliary wall


76


and thereby create weak points in the flat-panel display.





FIG. 11



b


depicts how the flat-panel display of

FIG. 11



a


appears after pump-out port


88


is closed. Item


88


B in

FIG. 11



b


is the closed remainder of the pump-out tube


88


. Inasmuch as closed pump-out portion


88


B extends laterally away from auxiliary compartment


72


, closed portion


88


B does not extend significantly higher above baseplate structure


40


than auxiliary wall


76


. Furthermore, closed pump-out portion


88


B normally does not extend laterally beyond the outer perimeter of baseplate structure


40


. As a result, the incorporation of closed pump-out portion


88


B into the sealed flat-panel display does not necessitate any significant amount of additional handling care to avoid damaging the display.




Hermetic room-pressure sealing of plate structures


40


and


42


together through outer wall


44


in a neutral environment, typically dry nitrogen or an inert gas such as argon, at approximately room pressure is performed at an elevated sealing temperature, typically 300° C., for the flat-panel display of

FIG. 11



a


. The hermetic bonding of auxiliary wall


76


to baseplate structure


40


, which can be done at various times relative to the steps involved in hermetically sealing plate structures


40


and


42


and outer wall


44


, is likewise performed in a neutral environment, again typically dry nitrogen or an inert gas such as argon, at approximately room pressure and at elevated temperature.




After these sealing and bonding operations are complete, a bake operation is normally performed on the flat-panel display of

FIG. 11



a


in order to outgas further gases, such as gases released during the sealing and bonding operations, that might cause damage to the display during normal operation. The bake is typically done for 1-2 hrs. at 150-300° C., typically 200° C.




The display of

FIG. 11



a


is subsequently evacuated with a suitable vacuum pump (not shown) connected directly to pump-out port


88


. When the requisite vacuum level is reached, pump-out tube


88


is thermally closed at constricted portion


88


A to produce the sealed display of

FIG. 11



b


. The display evacuation and tube closure steps are typically performed after the display is cooled to room temperature, but can be done while the display is at the bake temperature or during cool down.




Non-evaporable getter


74


is laser activated after pump-out port


88


is closed. At the minimum, activation of getter


74


with laser beam


68


of

FIG. 9



b


is performed after the flat-panel display is cooled to room temperature. If pump-out port


88


is closed while the display is at elevated temperature, getter


74


can be activated with laser beam


60


or


68


of

FIG. 9



a


or


9




b


one or more times during the period that the display is at elevated temperature and/or is being cooled down to room temperature. The getter activation after cool down is then a re-activation.





FIGS. 12



a


and


12




b


(collectively “FIG.


12


”) illustrate, in accordance with the invention, an embodiment of a two-compartment flat-panel display having an auxiliary compartment


92


that houses a non-evaporable getter strip


94


suitable for being laser activated according to the invention. Getter strip


92


, situated outside main compartment


70


in the two-compartment flat-panel display of

FIG. 12

, is of somewhat more complex shape than auxiliary compartment


72


in display of

FIGS. 7 and 8

but avoids any loss of strength due to openings through baseplate structure


40


. Aside from this difference, the two-compartment display of

FIGS. 12 and 13

achieves substantially all the advantages of the two-compartment display of

FIGS. 7 and 8

, particularly a high active-to-overall area ratio.

FIG. 13

presents a top view of the flat-panel display in FIG.


12


. The top view of

FIG. 13

is taken through a portion of auxiliary compartment


92


above baseplate structure


40


.




Main compartment


70


in the flat-panel display of

FIGS. 12 and 13

is formed with plate structures


40


and


42


and outer wall


44


in the same manner as in the display of

FIGS. 7 and 8

. However, baseplate structure


40


is slightly shorter at the left-hand edge in the display of

FIGS. 12 and 13

, while faceplate structure


42


is slightly longer at the left-hand edge in the display of

FIGS. 12 and 13

. Plate structures


40


and


42


in the display of

FIGS. 12 and 13

respectively contain electron-emissive elements and light-emissive elements as described above. Spacer walls


46


run perpendicular to the length of getter strip


94


.




Auxiliary compartment


92


overlies larger main compartment


70


above part of the exterior surface of baseplate structure


40


and extends beyond main compartment


70


so as to overlie a portion of the interior surface of faceplate structure


42


. Auxiliary compartment


92


is formed with baseplate structure


40


, faceplate structure


42


, and a five-sided transparent auxiliary wall consisting of a relatively flat rectangular top portion


96


T and four relatively flat lateral portions


96


L


1


,


96


L


2


,


96


L


3


, and


96


L


4


(collectively “


96


L”) arranged in a rectangular annulus. Top auxiliary wall portion


96


T extends generally parallel to baseplate structure


40


. Lateral auxiliary wall portions


96


L extend generally perpendicular to top wall portion


96


T and plate structures


40


and


42


. The top edges of lateral wall portions


96


L merge into top wall portion


96


T.




Opposing lateral auxiliary wall portions


96


L


1


and


96


L


2


are rectangular in shape. The bottom edge of lateral wall portion


96


L


1


is hermetically bonded to baseplate structure


40


along its exterior surface. The bottom edge of lateral wall portion


96


L


2


is hermetically bonded to faceplate structure


42


along its interior surface at a location not overlapped by baseplate structure


40


.




Each of opposing lateral auxiliary wall portions


96


L


3


and


96


L


4


is in the shape of a rectangle with a rectangular portion of one corner removed. The bottom edge of each of lateral wall portions


96


L


3


and


96


L


4


has an upper edge portion, a side edge portion, and a lower edge portion respectively bonded to the exterior surface of baseplate structure


40


, the outside surface of outer wall


44


, and the interior surface of faceplate structure


42


. The bonding of auxiliary lateral wall portions


96


L to components


40


-


44


is done with sealing material


98


, typically frit.




Auxiliary wall portions


96


L and


96


T (collectively “


96


”) typically consist of a unitary piece of glass. As with auxiliary wall


76


, auxiliary wall


96


is normally created by a molding, glass-blowing, etching, or machining process. Likewise, the corners of auxiliary wall


96


may be rounded. Alternatively, auxiliary wall portions


96


L and


96


T can be made separately and subsequently joined together.





FIGS. 14



a


and


14




b


(collectively “FIG.


14


”) illustrate a method of fabricating auxiliary wall


96


as a two-part component. As shown in

FIG. 14



a


, the two components of auxiliary wall


96


are a five-sided upper wall section


96


A and a three-sided lower wall section


96


B. Upper auxiliary wall section


96


A consists of top wall portion


96


T that merges into an annular four-sided wall portion consisting of equal-height wall portions


96


L


1


,


96


L


2


U,


96


L


3


U and


96


L


4


U whose composite upper edge merges into the perimeter edge of top wall portion


96


T. Lower auxiliary wall section


96


B consists of equal-height wall portions


96


L


2


L,


96


L


3


L, and


96


L


4


L that form a partially annular wall. Each of wall sections


96


A and


96


B in

FIG. 14



a


is typically formed by molding, glass blowing, etching, or machining.




The lower edge of upper wall section


96


A is joined to the upper edge of lower wall section


96


B by bonding material


96


J as depicted in

FIG. 14



b


. The bonding step is performed in such a way that wall portions


96


L


2


U and


96


L


2


L are joined together to form wall portion


96


L


2


, wall portions


96


L


3


U and


96


L


3


L are joined together to form wall portion


96


L


3


, and wall portions


96


L


4


U and


96


L


4


L are joined together to form wall portion


96


L


4


. Although fabrication of auxiliary compartment


92


in the manner shown in

FIG. 14

requires that the flat-panel display of

FIGS. 12 and 13

have an extra seal (bonding material


96


J), assembling auxiliary wall


96


from wall sections


96


A and


96


B in the indicated way facilitates manufacture of wall


96


.




Auxiliary compartment


92


is connected to main compartment


70


by way of one or more openings


100


through one sub-wall of outer wall


44


. One such inter-compartment opening


100


is depicted in

FIGS. 12 and 13

. Inter-compartment opening


100


in

FIGS. 12 and 13

extends the full height of outer wall


44


and thereby forms a gap in otherwise annular wall


44


. By interconnecting compartments


70


and


92


by way of one or more openings through outer wall


44


, there is no need to interconnect compartments


70


and


92


by way of one or more openings through baseplate structure


40


. Weak points that might arise in a flat-panel display due to the presence of openings through baseplate structure


40


are avoided in the display of

FIGS. 12 and 13

.




As with getter strip


74


in the display of

FIGS. 7 and 8

, getter strip


94


is typically configured and constituted the same as getter strip


50


described above. A pair of getter supports


102


are located in auxiliary compartment


92


above baseplate structure


40


and are bonded to structure


40


along its exterior surface. Getter supports


102


may extend laterally slightly beyond the perimeter of baseplate structure


40


as depicted in the example of

FIG. 12



a


. Getter supports


102


thermally (and electrically) insulate getter


90


from auxiliary wall


92


, plate structures


40


and


42


, and the other display components. As with getter supports


82


in the display of

FIGS. 7 and 8

, getter supports


102


are typically configured and constituted similar to getter supports


52


. The ends of getter strip


94


are situated in slots located partway up getter supports


102


. Getter


94


is thus spaced apart from plate structures


40


and


42


and walls


44


and


96


.




The flat-panel display of

FIGS. 12 and 13

can be assembled in various ways, typically in a similar manner to the display of

FIGS. 7 and 8

. In one assembly sequence that begins with inter-compartment opening


100


present in outer wall


44


, plate structures


40


and


42


are hermetically sealed together through outer wall


44


according to a suitable technique. The laser-initiated gap jumping technique described above can be utilized in the hermetic sealing of components


40


-


44


. Getter structure


94


/


102


is positioned over baseplate structure


40


after which getter supports


102


are bonded to structure


40


. Finally, auxiliary wall


96


is positioned over getter structure


94


/


102


and is hermetically bonded to plate structures


40


and


42


.




Similar to what is done in the flat-panel display of

FIGS. 7 and 8

, the flat-panel display of

FIGS. 12 and 13

can be modified by bonding getter supports


102


to auxiliary chamber


96


, likewise preferably the inside of top wall portion


96


T, rather than to baseplate structure


40


. The combination of getter supports


82


, getter


94


, and auxiliary wall


96


can then be pre-fabricated as a unit to be mounted on baseplate structure


40


.




Getter strip


94


is activated with a laser beam in way described above for getter strip


74


in the display of

FIGS. 7 and 8

, and thus in substantially the same manner described above in connection with

FIGS. 4



d


,


4




f


, and


4




g


except that the laser beam passes through transparent material of top auxiliary wall portion


96


T rather than through baseplate structure


40


. The temperature and pressure parameters for activating getter


94


with the laser beam are the same as for laser activating getter


74


. When gap jumping is employed in hermetically sealing the flat-panel display of

FIGS. 12 and 13

, the gap jumping is typically modified in the way described above for the display of

FIGS. 7 and 8

. That is, gap jumping is typically performed along the faceplate-structure-to-outer-wall interface rather than the baseplate-structure-to-outer-wall interface.





FIG. 15



a


depicts how getter strip


94


is activated with laser beam


60


when the flat-panel display of

FIGS. 12 and 13

is in vacuum chamber


56


. After initially activating getter


94


, one or more re-activation steps may be performed with the same laser or a different one.

FIG. 15



b


depicts how getter strip


94


is activated/re-activated with laser beam


68


after the display of

FIGS. 12 and 13

is removed from chamber


56


. Upon being activated/re-activated, getter


94


sorbs gases that come into contact with getter


94


, including gases produced during high-temperature operations by outgassing in compartments


70


and


92


.




Control circuitry, again consisting of circuitry elements


84


interconnected by way of electrically conductive traces on printed circuit board


86


attached to the exterior surface of baseplate structure


40


, is provided on the flat-panel display of

FIGS. 12 and 13

to the side of auxiliary compartment


92


as shown in FIG.


16


. To avoid subjecting control circuitry


84


/


86


to the high temperatures involved in sealing/bonding components


40


-


46


, and


96


together, control circuitry


84


/


86


is normally mounted on the display after sealing plate structures


40


and


42


to outer wall


44


and after bonding auxiliary wall


96


to components


40


-


44


. Auxiliary wall


96


typically extends to roughly the same height above baseplate structure


40


as control circuitry


84


/


86


and, in any event, does not extend significantly further above structure


40


than control circuitry


84


/


86


.




Similar to the display of

FIGS. 7 and 8

, the hermetic sealing of plate structures


40


and


42


together through outer wall


44


in the of

FIGS. 12 and 13

can be done at a pressure close to room pressure in a suitable neutral (again, non-reactive) environment after which the display is internally pumped down to a vacuum pressure level through a suitable port provided on the display, likewise preferably a pump-out port that does not protrude out awkwardly so as to create significant display handling problems.

FIG. 17



a


presents a variation of the flat-panel display of

FIGS. 12 and 12

in which a glass pump-out tube


104


is connected to auxiliary compartment


92


through an opening


106


in lateral auxiliary wall portion


96


L


4


to form a port for evacuating the display in accordance with the invention. As with pump-out tube


88


applied in

FIG. 11



a


to the display of

FIGS. 7 and 8

, pump-out tube


104


applied in

FIG. 17



a


to the display

FIGS. 12 and 13

extends laterally over part of baseplate structure


40


not covered by control circuitry


84


/


86


.




Pump-out port


104


has a constricted portion


104


A close to where port


104


meets lateral wall portion


96


L


4


. Constricted port portion


104


A is utilized for closing port


104


by heating constricted portion


104


A with an appropriate heating element situated close to portion


104


A. A laser could also be used to close tube


104


at portion


104


A. Similar to what occurs with pump-out tube


88


in

FIG. 11



a


,

FIG. 17



a


shows that pump-out tube


104


extends laterally away from auxiliary compartment


92


and thus does not overlie compartment


92


. Accordingly, heat transfer that could generate significant stresses in auxiliary wall


96


and create weak points in the display is not likely to occur from the heating of constricted portion


104


A to close port


104


.





FIG. 17



b


illustrates the flat-panel display of

FIG. 17



a


after port closure. Item


104


B in

FIG. 17



b


is the closed remainder of pump-out port


104


. Closed pump-out portion


104


B does not extend significantly higher above baseplate structure


40


than auxiliary wall


96


. Nor does pump-out tube remainder


104


B normally extend laterally beyond the perimeter of baseplate structure


40


. The incorporation of remaining pump-out portion


104


S into the sealed flat-panel display of

FIGS. 12 and 13

therefore does not significantly increase the degree of handling care that must be employed to avoid damaging the display.




The hermetic sealing of the display of

FIG. 17



a


in a neutral environment approximately at room-pressure is performed in the way described above for the display of

FIG. 11



a


. The same applies to the auxiliary-compartment bonding operation. When these operations are completed, the display of

FIG. 17



a


is baked as described above for the display of

FIG. 11



a


and then evacuated after which pump-out port


104


is closed at constricted portion


104


A to produce the sealed display of

FIG. 17



b


. The laser activation/re-activation of getter


94


in the display of

FIG. 17



b


after port closure is performed at the same stages that getter


74


is activated in the sealed display of

FIG. 11



a.







FIGS. 18



a


and


18




b


(collectively “FIG.


18


”) illustrate, in accordance with the invention, an embodiment of a two-compartment flat-panel display having an annular outer wall


110


through which a cavity partially extends to form an auxiliary compartment


112


next to main compartment


70


. Auxiliary compartment


112


houses a non-evaporable getter


114


suitable for being laser activated according to the invention. Main compartment


70


, which again contains spacer walls


46


, is here formed with baseplate structure


40


, faceplate structure


42


, and intervening outer wall


110


.

FIG. 19

presents a perspective view of a portion of outer wall


110


having auxiliary compartment


112


.




Outer wall


110


consists of a (relatively) tall portion


110


A, a short upper portion


110


B, a short intermediate portion


110


C, and a short lower portion


110


D. Tall outer-wall portion


110


A occupies three sides of the outer wall perimeter and contacts both of plate structures


40


and


42


. Short outer-wall portions


110


B and


110


D are rectangular layers that respectively contact plate structures


40


and


42


along the fourth side of the outer wall perimeter. Outer-wall portions


110


A,


110


B, and


110


D typically consist of frit. Portions


110


B and


110


D could also be formed with epoxy. The material of outer-wall portion


110


B is normally transparent to light in certain wavelength bands.




Short intermediate outer-wall portion


110


C is a hollow five-sided transparent structure having a top side, a bottom side, a pair of opposing lateral sides (or ends) that merge with the top and bottom sides, and a central third lateral side that merges with the other four sides. The top and bottom sides of intermediate portion


110


C respectively contact upper outer-wall portion


110


B and lower outer-wall portion


110


D. The ends of intermediate portion


110


C contact the insides of the ends of tall lateral-wall portion


110


A. The ends of portion


110


C can be eliminated if the remainder of portion


110


C is strong enough to maintain the requisite spacing between plate structures


40


and


42


along portion


110


C. The hollow part of intermediate portion


110


C forms the cavity of auxiliary compartment


112


. Intermediate portion


110


C consists of transparent material, typically a unitary piece of glass formed by a molding, glass-blowing, etching, or machining process.




Getter strip


114


is typically configured and constituted the same as getter strip


50


. A pair of getter supports


116


situated in auxiliary compartment


112


thermally (and electrically) insulate getter


114


from intermediate outer-wall portion


110


C and the other components of the flat-panel display. Getter supports


116


are bonded to the top of the lower side of intermediate portion


110


C. Getter supports


116


are typically configured and constituted the same as getter supports


52


. The ends of getter strip


114


are situated in-slots partway up getter supports


116


so that getter


114


is spaced apart from intermediate portion


110


C and the other display components.




Assembly of the flat-panel display in

FIGS. 18 and 19

is initiated by inserting getter structure


114


/


116


into auxiliary compartment


112


, bonding getter supports


116


to the top of intermediate outer-wall portion


110


C, placing outer-wall portions


110


B and


110


D respectively over the top and bottom sides of intermediate portion


110


C, and placing composite wall structure


110


B/


110


C/


110


D between the sides of the ends of three-sided tall outer-wall portion


110


A situated on one of plate structures


40


and


42


, typically baseplate structure


40


. These initial steps can be performed in various orders. After completing the initial assembly steps, plate structures


40


and


42


are hermetically sealed together through outer wall


110


, during which intermediate portion


110


C becomes hermetically sealed to outer-wall portions


110


B and


110


D.




Laser-initiated gap jumping can be employed in hermetically sealing plate structures


40


and


42


together through outer wall


110


in substantially the same way as described above for the process of FIG.


4


. Getter


114


is then typically activated/re-activated during the hermetic sealing process at the same stages as in the process of FIG.


4


. The only notable difference is that, instead of having the laser beam pass through a transparent generally central portion of baseplate structure


40


, the laser beam passes either from the side through the central side of intermediate outer-wall portion


110


C or from the top through a transparent portion of baseplate structure


40


near its perimeter, through short upper outer-wall portion


110


B, and then through the top side of intermediate outer-wall portion


110


C. When the laser beam passes through the side of intermediate outer-wall portion


110


C, getter strip


114


is typically slanted to facilitate local heat transfer from the laser beam to getter


114


.




Subject to the difference in how the laser beam enters the flat-panel display to activate getter


114


and to the fact that the display of

FIGS. 18 and 19

is a two-compartment structure rather than the one-compartment structure of

FIG. 4

, the views shown in

FIGS. 4



f


and


4




g


closely represent how getter


114


is laser activated before and after removal of the display from vacuum chamber


56


, with getter


114


being substituted for getter


50


in

FIGS. 4



f


and


4




g


. During the laser activation/re-activation of getter


114


, very little heat is transferred to any of the display components other than getter


114


.




Alternatively, the flat-panel display of

FIGS. 18 and 19

can be provided with a pump-out port (not shown). Hermetic sealing of plate structures


40


and


42


together through outer wall


110


is then performed at approximately room pressure in a suitable neutral environment, again typically dry nitrogen or argon. The display is subsequently pumped down to a vacuum pressure level through the pump-out port, and the port is closed. Getter


114


is now laser activated at least once in the manner described above. Laser activation of getter


114


is, at the minimum, performed after cooling the display down to room temperature. Laser activation of getter


114


can be performed while the display is at the sealing temperature and/or during cool down.




While the invention has been described with reference to particular embodiments, this description is solely for the purpose of illustration and is not to be construed as limiting the scope of the invention claimed below. For example, a getter akin to getter strip


74


,


94


, or


114


can be situated in an auxiliary compartment of a reduced-pressure flat-panel device such as a plasma display or a plasma-addressed liquid-crystal display having a main compartment in which a plasma is formed during display operation. The auxiliary and main compartments are connected together so that the pressures in the two compartments substantially reach a common pressure between room pressure and a high vacuum due to the presence of inert gas in the two compartments. The inert gas is typically xenon, neon, helium, krypton, or/and argon. The pressure in the auxiliary and main compartments of the reduced-pressure device is at least 1 torr, typically 5 torr to 0.5 atm.




The getter situated in the auxiliary compartment of the reduced-pressure device is laser activated in the manner described above. The getter sorbs non-inert gases in the compartments but does not sorb inert gases. Consequently, the presence of the inert gas in the compartments does not cause a significant part of the gettering capability to be expended. The plasma which is created in the main compartment and whose ions invariably enter the auxiliary compartment is created from the inert gas. The getter likewise does not collect ions of the inert gas.




Outer wall


44


can be formed with a rectangular annular non-frit portion sandwiched between a pair of rectangular annular frit layers. Non-evaporable getter strips


50


,


74


,


94


, and


114


can be formed with materials other than a porous combination of titanium and a vanadium-containing alloy. Each of getters


50


,


74


,


94


, and


114


can have shapes other than a strip.




Getter supports


52


,


82


,


102


, and


116


likewise can have different shapes than described above, providing that they thermally (and electrically) insulate getters


50


,


74


,


94


, and


114


from the other display components. Getter supports


116


can be bonded to the top or central portion of intermediate outer-wall portion


110


C, rather than to the bottom of intermediate outer-wall portion


110


C, prior to the alignment and sealing steps. If getter


74


,


94


, or


114


is likely to bend and touch an undesired surface, one or more additional getter supports can be provided along the length of getter


74


,


94


, or


114


to resist such bending.




Getter


74


can be replaced with two or more getters situated in auxiliary compartment


72


. In like manner, getter


94


can be replaced with two or more getters situated in auxiliary compartment


92


. Multiple getters can be situated in multiple auxiliary compartments located outside main compartment


70


.




Each of two or more of the sub-walls of outer wall


110


in the display of

FIGS. 18 and 19

can be provided with getter


114


, along with getter supports


116


. If the opposing lateral sides of intermediate outer-wall portion


110


C are not sufficient to ensure a substantially constant spacing between plate structures


40


and


42


along composite outer-wall portion


110


B/


110


C/


110


D, one or more spacer supports that extends from lower outer-wall portion


110


D to upper outer-wall portion


110


B can be placed in cavity


112


.




Getter


50


,


74


,


94


, or


114


can be also replaced with a getter of the evaporable type. Although getter supports


52


,


82


,


102


, or


116


are typically eliminated in this case, the gettering material could be evaporatively deposited on material that thermally (and electrically) insulates the evaporable getter from the active display components.




Instead of using gap jumping and/or radiative heating in sealing the flat-panel display, the display can be sealed by local heating with a laser after bringing the top edge of outer wall


44


or


110


substantially into contact with the interior surface of baseplate structure


40


. Outer wall


44


can be joined to baseplate structure


40


after which faceplate structure


42


is sealed to outer wall


44


. Laser


58


and/or laser


62


can be located inside vacuum chamber


56


.




The flat-panel CRT display can employ a thermionic-emission technique rather than a field-emission technique. The invention can be employed to activate getters in flat-panel devices other than displays. Getters situated in hollow structures other than flat-panel devices can be sealed by using the laser activation technique of the invention.




Light energy sources such as a focused lamp having a suitable spectral output can be employed in place of a laser for activating getter


50


,


74


,


94


, or


114


. Furthermore, getter


50


,


74


,


94


, or


114


in a flat-panel CRT display can be activated/re-activated with any energy source that produces a sufficiently strong beam of energy which can be directed locally onto the getter without significantly heating components through which the energy beam is intended to pass before reaching the getter and without having the beam impinge significantly on any other components of the CRT display except for the material through which the beam is intended to pass. Examples include locally directed RF energy, including locally-directed microwave energy which falls near the middle of the RF band. Various modifications and applications may thus be made by those skilled in the art without departing from the true scope and spirit of the invention as defined in the appended claims.



Claims
  • 1. A flat-panel device comprising:a main compartment formed with a first plate structure and a second plate structure situated opposite to, and coupled to, the first plate structure; a plurality of spacer walls extending generally parallel to one another between the plate structures; an auxiliary compartment (a) formed with an auxiliary wall coupled to the first plate structure and (b) connected pressure-wise to the main compartment through a plurality of openings in the first plate structure so that the two compartments reach largely equal steady-state compartment pressures; and a getter situated in the auxiliary compartment, the getter comprising a getter strip extending generally perpendicular to the spacer walls.
  • 2. A device as in claim 1 wherein:the first plate structure is controlled to selectively emit electrons; and the second plate structure emits light to produce an image in response to electrons received from the first plate structure.
  • 3. A device as in claim 1 wherein the main compartment is also formed with a generally annular outer wall through which the plate structures are coupled to each other.
  • 4. A flat-panel device comprising:a main compartment formed with a first plate structure and a second plate structure situated opposite to, and coupled to, the first plate structure; an auxiliary compartment (a) formed with an auxiliary wall coupled to the first plate structure and (b) connected pressure-wise to the main compartment through at least one opening through the first plate structure so that the two compartments reach largely equal steady-state compartment pressures; a getter situated in the auxiliary compartment; and additional component material situated over the first plate structure outside the compartments, the additional component material comprising control circuitry, the auxiliary wall not extending significantly further away from the first plate structure than the additional component material.
  • 5. A device as in claim 4 wherein:the first plate structure is controlled to selectively emit electrons; and the second plate structure emits light to produce an image in response to electrons received from the first plate structure.
  • 6. A device as in claim 4 wherein the main compartment is also formed with a generally annular outer wall through which the plate structures are coupled to each other.
  • 7. A device as in claim 4 wherein the control circuitry and the auxiliary wall extend to approximately the same distance away from the first plate structure.
  • 8. A device as in claim 4 further including a pump-out port connected pressure wise to the auxiliary compartment.
  • 9. A device as in claim 8 wherein the pump-out port extends approximately parallel to the first plate structure.
  • 10. A device as in claim 4 wherein the getter is situated within the auxiliary compartment at a location suitable for being activated by light energy transferred locally through the auxiliary wall.
  • 11. A flat-panel device comprising:a main compartment comprising a first plate structure, a second plate structure, and a generally annular outer wall that extends between the plate structures; an auxiliary compartment situated over the first plate structure outside the main compartment and connected pressure-wise to the main compartment so that the two compartments reach largely equal steady-state compartment pressures; a getter situated in the auxiliary compartment; and control circuitry situated over the first plate structure outside the compartments, the auxiliary compartment not extending significantly further away from the first plate structure than the control circuitry.
  • 12. A device as in claim 11 wherein the compartments are connected together through at least one opening in the first plate structure.
  • 13. A device as in claim 11 wherein the getter is situated within the auxiliary compartment at a location suitable for being activated by light energy transferred locally through a wall of the auxiliary compartment.
  • 14. A device as in claim 11 further including a plurality of spacer walls extending generally parallel to one another between the plate structures and extending generally perpendicular to the getter.
  • 15. A device as in claim 11 further including getter support means for supporting the getter and thermally insulating it from the compartments.
  • 16. A device as in claim 11 wherein the getter comprises a piece of non-evaporable gettering material.
  • 17. A device as in claim 11 further including a pump-out port connected pressure-wise to the auxiliary compartment.
  • 18. A device as in claim 17 wherein the pump-out port extends approximately parallel to the first plate structure.
  • 19. A device as in claim 18 wherein the pump-out port, when closed, does not extend significantly laterally beyond the first plate structure.
  • 20. A device as in claim 11 wherein the compartments, getter, and control circuitry are components of a flat-panel display for which the second plate structure contains a faceplate on which an image produced by the flat-panel display is visible.
  • 21. A device as in claim 20 wherein:the first plate structure contains multiple electron-emissive elements; and the second plate structure contains multiple light-emissive elements that emit light upon being struck by electrons emitted from the electron-emissive elements.
  • 22. A flat-panel device comprising:a main compartment formed with a first plate structure, a second plate structure, and a generally annular outer wall that extends between the plate structures; an auxiliary compartment situated outside the main compartment, the auxiliary compartment formed with an auxiliary wall that contacts the first plate structure outside the main compartment, extends away from the first plate structure and main compartment, bends back towards the second plate structure, and contacts the second plate structure outside the main compartment, the auxiliary compartment connected pressure-wise to the main compartment so that the two compartments reach largely equal steady-state compartment pressures; a getter situated in the auxiliary compartment; and a pump-out port connected directly to the auxiliary compartment, extending approximately parallel to the first plate structure, and, when closed, not extending significantly laterally beyond the first plate structure.
  • 23. A device as in claim 22 wherein the pump-out port, when closed, does not extend significantly further away from the first plate structure than the auxiliary wall.
  • 24. A device as in claim 22 wherein the compartments are connected together through at least one opening in the outer wall.
  • 25. A device as in claim 22 further including control circuitry situated over the first plate structure outside the compartments, the auxiliary wall not extending significantly further away from the first plate structure than the control circuitry.
  • 26. A device as in claim 22 wherein the getter is situated within the auxiliary compartment at a location suitable for being activated by light energy transferred locally through the auxiliary wall.
  • 27. A device as in claim 22 further including a plurality of spacer walls extending generally parallel to one another between the plate structures and extending generally perpendicular to the getter.
  • 28. A device as in claim 22 wherein the plate structures, walls, getter, and pump-out port are components of a flat-panel display for which the second plate structure contains a faceplate on which an image produced by the flat-panel display is visible.
  • 29. A device as in claim 20 wherein:the first plate structure contains multiple electron-emissive elements; and the second plate structure contains multiple light-emissive elements that emit light upon being struck by electrons emitted from the electron-emissive elements.
  • 30. A flat-panel device comprising:a main compartment formed with a first plate structure and a second plate structure situated opposite to, and coupled to, the first plate structure; an auxiliary compartment (a) formed with an auxiliary wall coupled to the first plate structure and (b) connected pressure-wise to the main compartment through at least one opening through the first plate structure so that the two compartments reach largely equal steady-state compartment pressures; a getter situated in the auxiliary compartment; a pump-out port connected pressure-wise to the auxiliary compartment, the pump-out port extending approximately parallel to the first plate structure; and additional component material situated over the first plate structure outside the compartments, the auxiliary wall not extending significantly further away from the first plate structure than the additional component material.
  • 31. A device as in claim 30 wherein:the first plate structure is controlled to selectively emit electrons; and the second plate structure emits light to produce an image in response to electrons received from the first plate structure.
  • 32. A device as in claim 30 wherein the main compartment is also formed with a generally annular outer wall through which the plate structures are coupled to each other.
  • 33. A device as in claim 30 wherein the getter is situated within the auxiliary compartment at a location suitable for being activated by light energy transferred locally through the auxiliary wall.
  • 34. A flat-panel device comprising:a main compartment formed with a first plate structure and a second plate structure situated opposite to, and coupled to, the first plate structure; an auxiliary compartment (a) formed with an auxiliary wall coupled to the first plate structure and (b) connected pressure-wise to the main compartment through at least one opening through the first plate structure so that the two compartments reach largely equal steady-state compartment pressures; a getter situated in the auxiliary compartment at a location suitable for being activated by light energy transformed locally through the auxiliary wall; and additional component material situated over the first plate structure outside the compartments, the auxiliary wall not extending significantly further away from the first plate structure than the additional component material.
  • 35. A device as in claim 34 wherein:the first plate structure is controlled to selectively emit electrons; and the second plate structure emits light to produce an image in response to electrons received from the first plate structure.
  • 36. A device as in claim 34 wherein the main compartment is also formed with a generally annular outer wall through which the plate structures are coupled to each other.
CROSS REFERENCE TO RELATED APPLICATIONS

This is a division of U.S. patent application Ser. No. 08/766,435, filed Dec. 12, 1996, now U.S. Pat. No. 5,977,706 now allowed. This is also related to Pothoven et al U.S. patent application Ser. No. 08/766,688, filed Dec. 12, 1996, now U.S. Pat. No. 6,139,390. To the extent not repeated herein, the contents of Pothoven et al are incorporated by reference.

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