Electric lamp and discharge devices – With support and/or spacing structure for electrode and/or... – Supporting and/or spacing elements
Reexamination Certificate
1998-12-11
2003-09-09
Patel, Vip (Department: 2879)
Electric lamp and discharge devices
With support and/or spacing structure for electrode and/or...
Supporting and/or spacing elements
C313S495000, C445S024000
Reexamination Certificate
active
06617772
ABSTRACT:
FIELD OF USE
This invention relates to flat-panel displays of the cathode-ray tube (“CRT”) type, including the fabrication of flat-panel CRT displays.
BACKGROUND
A flat-panel CRT display basically consists of an electron-emitting component and a light-emitting component. The electron-emitting component, commonly referred to as a cathode, contains electron-emissive regions that emit electrons over a relatively wide area. The emitted electrons are suitably directed towards light-emissive elements distributed over a corresponding area in the light-emitting component. Upon being struck by the electrons, the light-emissive elements emit light that produces an image on the display's viewing surface.
The electron-emitting and light-emitting components are connected together to form a sealed enclosure normally maintained at a pressure much less than 1 atm. The exterior-to-interior pressure differential across the display is typically in the vicinity of 1 atm. In a flat-panel CRT display of significant viewing area, e.g., at least 10 cm
2,
the electron-emitting and light-emitting components are normally incapable of resisting the exterior-to-interior pressure differential on their own. Accordingly, a spacer (or support) system is conventionally provided inside the sealed enclosure to prevent air pressure and other external forces from collapsing the display.
The spacer system typically consists of a group of laterally separated spacers positioned so as to not be directly visible on the viewing surface. The presence of the spacer system can adversely affect the flow of electrons through the display. For example, electrons coming from various sources occasionally strike the spacer system, causing it to become electrically charged. The electric potential field in the vicinity of the spacer system changes. The trajectories of electrons emitted by the electron-emitting device are thereby affected, often leading to degradation in the image produced on the viewing surface.
More particularly, electrons that strike a body, such as a spacer system in a flat-panel display, are conventionally referred to as primary electrons. When the body is struck by primary electrons of high energy, e.g., greater than 100 eV, the body normally emits secondary electrons of relatively low energy. More than one secondary electron is, on the average, typically emitted by the body in response to each high-energy primary electron striking the body. Although electrons are often supplied to the body from one or more other sources, the fact that the number of outgoing (secondary) electrons exceeds the number of incoming (primary) electrons commonly results in a net positive charge building up on the body.
It is desirable to reduce the amount of positive charge buildup on a spacer system in a flat-panel CRT display. Jin et al, U.S. Pat. No. 5,598,056, describes one technique for doing so. In Jin et al, each spacer in the display's spacer system is a pillar consisting of multiple layers that extend laterally relative to the electron-emitting and light-emitting components. The layers in each spacer pillar alternate between an electrically insulating layer and an electrically conductive layer. The insulating layers are recessed with respect to the conductive layers so as to form grooves. When secondary electrons are emitted by the spacers in Jin et al, the grooves trap some of the secondary electrons and prevent them from escaping the spacers. Because fewer secondary electrons escape the spacers than what would occur if the grooves were absent, the amount of positive charge buildup on the spacers is reduced.
The technique employed in Jin et al to reduce positive charge buildup is creative. However, the spacers in Jin et al are relatively complex and pose significant concerns in dimensional tolerance and, therefore, in reliability. Manufacturing the spacers in Jin et al could be problemsome. It is desirable to have a relatively simple technique, including a simple spacer design, for reducing charge buildup on a spacer system of a flat-panel CRT display.
GENERAL DISCLOSURE OF THE INVENTION
The present invention furnishes a flat-panel display in which a spacer situated between a pair of plate structures has a rough face. An image is supplied by one of the plate structures in response to electrons provided from the other plate structure. Somewhat similar to what occurs in Jin et al, the roughness in the face of the present spacer prevents some secondary electrons emitted by the spacer from escaping the spacer. Accordingly, positive charge buildup on the spacer is normally reduced. The image is thereby improved.
In particular, secondary electrons emitted by the present spacer as a result of being struck by primary electrons are, on the average, normally of significantly lower energy than the primary electrons. Due to the roughness in the spacer's face, the lower-energy secondary electrons are more prone to impact the spacer and be captured by it than what would occur if the spacer's face were smooth. The lower-energy secondary electrons captured by the spacer cause relatively little further secondary electron emission from the spacer.
Roughness in the face of a body being struck by primary electrons may sometimes itself cause the body to emit an increased number of secondary electrons, especially when the energy of the primary electrons is quite high. This increase in the secondary electron emission is offset by the number of secondary electrons captured by the body due to its facial roughness. In the present flat-panel display, the primary electron energy, while high, is normally sufficiently low that the roughness in the spacer's face leads to a reduction in the overall number of secondary electrons that escape the spacer.
To the extent that the spacer used in the present flat-panel display has multiple levels of spacer material, the levels typically extend vertically relative to the electron-emitting and light-emitting components rather than laterally as in Jin et al. A spacer with vertically extending spacer-material levels is generally simpler in design, and can be fabricated to high tolerances more easily, than a spacer having laterally extending spacer-material levels. When the present spacer has multiple vertically extending levels of spacer material, reliability concerns associated with the spacer design are considerably less severe than those that arise with the spacer design of Jin et al. When the spacer used in the present display has only a single level of spacer material, the display essentially avoids the reliability concerns that arise in Jin et al. The net result is a substantial improvement over Jin et al.
A flat-panel display that employs the teachings of the invention is generally configured in the following way. The display contains a first plate structure, a second plate structure situated opposite the first plate structure, and a spacer situated between the plate structures. The first plate structure emits electrons. The second plate structure emits light to produce an image upon receiving electrons emitted by the first plate structure. The spacer has a rough face that extends at least partway from either plate structure to the other plate structure.
Primary electrons which strike the spacer include electrons that follow trajectories directly from the first plate structure to the spacer as well as electrons that reflect off the second plate structure after having traveled from the first plate structure to the second plate structure. The reflected electrons are generally referred to as “backscattered” electrons. While the flat-panel display can normally be controlled so that only a small fraction of the electrons emitted by the first plate structure directly strike the spacer, the backscattered electrons travel in a broad distribution of directions as they leave the second plate structure. As a result, electron backscattering off the second plate structure is difficult to control direction-wise.
By inhibiting secondary electrons emitted by the present spacer from escaping the spac
Barton Roger W.
Gopalakrishnan Sudhakar
Hopple George B.
Macaulay John M.
Mackey Bob L.
Candescent Technologies Corporation
Patel Vip
Williams Joseph
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