Electric lamp and discharge devices – With luminescent solid or liquid material – Vacuum-type tube
Reexamination Certificate
2001-03-30
2004-11-02
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
Vacuum-type tube
C313S495000, C313S553000
Reexamination Certificate
active
06812636
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 display CRT display typically consists of 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 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
contains faceplate
32
coupled to backplate
24
of 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 light-emissive 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 when struck by electrons. Hence, some of the so-emitted light travels backward toward the interior of the display. Layer
38
reflects some of that rear-directed light forward to increase the intensity of the image. In addition, layer
38
functions as the display's anode for attracting electrons toward light-emitting device
22
.
The electrons emitted by regions
26
pass through light-reflective layer
38
before striking light-emissive regions
34
. In so doing, the electrons lose some energy. The image intensity increase resulting from the light-reflective nature of layer
38
at least partially compensates for any image intensity decrease caused by this electron energy loss. Nonetheless, it would be desirable to further improve the image intensity in a light-emitting device whose anode overlies the device's light-emitting regions.
Each light-emitting region in a light-emitting device such as that of
FIG. 1
normally consists of light-emissive particles formed with phosphor material. The constituents of the phosphor particles commonly include elements such as sulfur or/and oxygen. When the light-emissive particles are struck by electrons, some of the sulfur or/and oxygen is commonly released in gaseous form into the interior of the display. The so-released gases can contaminate the display and cause it to degrade.
Petersen et al (“Peterson”), U.S. Pat. No. 5,844,361, addresses the problem of outgassing from phosphor particles in a light-emitting device of a flat-panel CRT display by chemically treating the outer particle surfaces in a way intended to reduce undesired outgassing.
FIGS. 2 and 3
depict two examples of Petersen's approach in which light-emissive regions overlie transparent substrate
40
. Each light-emissive region consists of a layer of phosphor particles
42
.
A coating
44
fully surrounds each phosphor particle
42
in the example of FIG.
2
. Coatings
44
can alter the surface chemistry of particles
42
in such a way that they are more thermodynamically resistant to outgassing. Alternatively, coatings
44
can simply be impervious encapsulants that substantially prevent any contaminant gases produced by particles
42
from entering the display's interior. In either case, coatings
44
are provided on particles
42
before they are deposited over substrate
40
. The display's anode is formed with aluminum layer
46
provided above composite particles
42
/
44
.
In the example of
FIG. 3
, coatings
48
of stable oxide are provided on particles
42
after they are deposited on substrate
40
. Each coating
48
conformally covers an upper portion of the outer surface of one particle
42
. Coatings
48
, typically formed by chemical vapor deposition of silane, disiloxane, or tetra-ethyl-orthosilicate, are more thermodynamically resistant to outgassing than are particles
42
. Petersen indicates that the display's anode in the example of
FIG. 3
can be formed with a conductive layer analogous to aluminum layer
46
.
Providing phosphor particles
42
with full coatings
44
before particles
42
are deposited on substrate
40
in the example of
FIG. 2
raises concerns that coatings
44
may be damaged during the deposition of particles
42
. Also, full coatings
44
may detrimentally affect the formation of the light-emissive regions by absorbing radiation typically utilized in defining the light-emissive regions. Petersen avoids this difficulty with the example of
FIG. 3
where partial coatings
48
are deposited on particles
42
after they are deposited on substrate
40
. However, Petersen only discloses that coatings
48
may consist of oxide. Petersen does not deal with improving the image intensity.
GENERAL DISCLOSURE OF THE INVENTION
The present invention furnishes a light-emitting device in which a light-emissive region formed with a plurality of light-emissive particles overlies light-transmissive material of a plate. 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 strike the light-emissive region, causing it to emit light.
The light-emissive particles in light-emissive region of the present light-emitting device are provided with coatings that perform various functions. In some cases, the particle coatings enable the intensity of light that travels generally in the forward direction to be enhanced, especially when the light-emitting device contains a light-reflective layer situated over the coatings. Alternatively or additionally, the particle coatings may cause the optical contrast to be enhanced between two such light-emissive regions when one of the light-emissive regions is turned on (emitting light) and the other is turned off (not emitting light). The coatings may getter contaminant gases. The coatings also typically reduce damaging effects that occur as the result of electrons striking the light-emissive particles.
Depending on the function or functions to be performed by the particle-coating material, each light-emissive particle may have two or more of the present coatings. In any event, each coating covers only part of the outer surface of the underlying particle in such a way as to be spaced apart from where that particle is closest to the plate. By configuring the coatings in this way, the coatings can be provided over the particles after they are provided over the plate, thereby avoiding difficulties that arise when light-emissive particles are provided with coatings before the particles are provided over a plate.
The light-emissive particles normally emit light in substantially all directions. Part of the emitted light travels generally forward, including partially sideways, toward the plate and passes through it. Part of the emitted light travels generally ba
Fahlen Theodore S.
Kajiwara Kazuo
Kato Haruo
Pan Lawrence S.
Pearson Roger A.
Candescent Technologies Corporation
Guharay Karabi
Meetin Ronald J.
Patel Ashok
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