Electric lamp and discharge devices – With getter
Reexamination Certificate
2001-03-30
2003-10-07
Patel, Vip (Department: 2879)
Electric lamp and discharge devices
With getter
C313S496000, C313S554000
Reexamination Certificate
active
06630786
ABSTRACT:
FIELD OF USE
This invention relates to the configuration and manufacture of light-emitting devices suitable for use in flat-panel displays such as flat-panel cathode-ray tube (“CRT”) displays.
BACKGROUND ART
A flat-panel CRT display is formed with an electron-emitting device and an oppositely situated light-emitting device. The electron-emitting device, or cathode, contains electron-emissive elements that emit electrons across a relatively wide area. An anode in the light-emitting device attracts the electrons toward light-emissive regions distributed across a corresponding area in the light-emitting device. The anode can be located above or below the light-emissive regions. In either case, the light-emissive regions emit light upon being struck by the electrons to produce an image on the display's viewing surface.
FIG. 1
presents a side cross section of part of a conventional flat-panel CRT display such as that described in U.S. Pat. No. 5,859,502 or U.S. Pat. No. 6,049,165. The flat-panel CRT display of
FIG. 1
is formed with electron-emitting device
20
and light-emitting device
22
. Electron-emitting device
20
contains backplate
24
and overlying electron-emissive regions
26
. Electrons emitted by regions
26
travel toward light-emitting device
22
under control of electron-focusing system
28
. Item
30
represents an electron trajectory.
Light-emitting device
22
, a partial plan view of which is shown in
FIG. 2
, contains faceplate
32
coupled to electron-emitting device
20
through an outer wall (not shown) to form a sealed enclosure maintained at a high vacuum. Light-emissive regions
34
overlie faceplate
32
respectively opposite electron-emissive regions
26
. When electrons emitted by regions
26
strike light-emissive regions
34
, the light emitted by regions
34
produces the display's image on the exterior surface (lower surface in
FIG. 1
) of light-emitting device
22
. Contrast-enhancing black matrix
36
laterally surrounds regions
34
.
Light-emitting device
22
also contains light-reflective layer
38
situated over light-emissive regions
34
and black matrix
36
. Regions
34
emit light in all directions. Part of the light thus travels backward toward the interior of the display. Layer
38
reflects some of the rear-directed light forward to increase the intensity of the image.
Light-reflective layer
38
typically consists of aluminum, a silvery white metal which is highly reflective of visible light and a good conductor of electricity. Layer
38
is commonly exposed to air at some point during the display fabrication process. Inasmuch as aluminum is of relatively high chemical reactivity, a native coating (not shown) of aluminum oxide normally forms along the outside surface of layer
38
during the exposure to air. The native aluminum oxide coating is quite thin, typically 1-5 nm in thickness.
Light-reflective layer
38
functions as the display's anode. For this purpose, layer
38
receives a high electrical potential that attracts electrons toward light-emitting device
22
. Because layer
38
is located above light-emissive regions
34
, electrons emitted by regions
26
pass through layer
38
and the overlying native oxide coating before striking light-emissive regions
34
. By having layer
38
located above regions
34
, the display of
FIGS. 1 and 2
avoids the loss in image intensity that occurs in a flat-panel CRT display where light emitted by the light-emitting device must pass through the anode, typically transparent but still partially light-absorbent, before reaching the viewing surface.
A disadvantage of the conventional display of
FIGS. 1 and 2
is that the electrons emitted by regions
26
lose some energy when they pass through light-reflective layer
38
and the overlying native oxide coating. Also, instead of passing through layer
38
and the oxide coating, some of the electrons emitted by regions
26
(a) scatter backward off layer
38
or/and the oxide coating or (b) cause layer
38
or/and the oxide coating to emit secondary electrons. Some of the backscattered and secondary electrons strike the interior of the display at such locations as to cause the image to be degraded. In addition, the native oxide coating along light-reflective layer
38
forms part of the interior surface of the display of
FIGS. 1 and 2
. Contaminants, such as oxygen and other chemically reactive gaseous species, commonly adhere to the oxide coating. As electrons (both primary and secondary) strike the oxide coating, these contaminants can be released into the display's interior and cause damage.
Washington, “Color Display Using the Channel Multiplier CRT”,
Procs. SID,
1998, pages 23-31, discloses a flat channel multiplier CRT display in which a carbon coating is applied to a light-reflective aluminum layer situated over the interior surface of the display's fluorescent screen. Electrons pass through the carbon coating before passing through the aluminum layer to strike the screen. Washington reports that the carbon coating reduces both the number and energy of backscattered electrons. Although Washington is of interest, Washington presents a narrow solution to the electron backscattering problem and does not deal generally with electron backscattering, secondary electron mission, and display contamination problems that occur as electrons impinge on a light-reflective layer such as layer
38
in the conventional display of
FIGS. 1 and 2
.
It is desirable to reduce the loss in electron energy that occurs when electrons pass through a light-reflective layer in a flat-panel CRT display before striking light-emissive regions in the display's light-emitting device. It is also desirable to have a general methodology for reducing electron backscattering and secondary electron emission that occur as electrons emitted by the display's electron-emitting device impinge on the light-reflective layer. Furthermore, it is desirable to reduce the amount of contaminants released into the interior of the display as electrons impinge on the light-reflective layer.
GENERAL DISCLOSURE OF THE INVENTION
The present invention furnishes a light-emitting device containing a plate, a light-emissive region overlying the plate where the plate is generally transmissive of visible light, and a light-reflective layer extending over the light-emissive region. The light-emitting device of the invention is suitable for use in a flat-panel display, especially a flat-panel CRT display in which an electron-emitting device is situated opposite the light-emitting device. The electron-emitting device emits electrons which pass through the light-reflective layer and strike the light-emissive region, causing it to emit light.
Compared to a conventional light-emitting device having an aluminum light-reflective layer covered with a native coating of aluminum oxide and situated in generally the same relative location as the light-reflective layer in the light-emitting device of the invention, the present light-emitting device is configured to achieve one or more of the following characteristics: (1) reduced electron energy loss as electrons pass through the light-reflective layer, (2) gettering in the immediate vicinity of the light-reflective layer for reducing the amount of damage caused by contaminants, especially contaminants released close to the light-reflective layer, (3) reduced electron backscattering as electrons impinge on the light-reflective layer from above the light-emitting device, (4) reduced secondary electron emission as electrons impinge on the light-reflective layer from above the light-emitting device, and (5) reduced chemical reactivity along the light-reflective layer.
In a first aspect of the invention, the light-reflective layer contains non-aluminum metal consisting of at least one of lithium, beryllium, boron, sodium, and magnesium. The energy lost by an electron in passing through a layer depends on the number of protons that the electron effectively encounters (interacts with) during its passage through the lay
Cummings William J.
Dunphy James C.
Fahlen Theodore S.
Hopple George B.
Pan Lawrence S.
Candescent Technologies Corporation
Meetin Ronald J.
Patel Vip
Quarterman Kevin
LandOfFree
Light-emitting device having light-reflective layer formed... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Light-emitting device having light-reflective layer formed..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Light-emitting device having light-reflective layer formed... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3120730