Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2001-01-25
2004-02-17
Vo, Peter (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S846000, C313S495000, C428S315700
Reexamination Certificate
active
06691404
ABSTRACT:
FIELD OF USE
This invention relates to flat-panel displays of the cathode-ray tube (“CRT”) type, including the manufacture of flat-panel CRT displays. This invention also relates to the constitution and fabrication of structures that can be partially or fully utilized in 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 90 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 variety of structures that are porous, at least along a face of each structure. Each of the porous structures, or a portion of each structure, is typically suitable for use in a spacer of a flat-panel CRT display. The present invention also furnishes techniques for manufacturing such porous-faced structures, including methods for manufacturing flat-panel displays.
A porous-faced spacer constituted according to the invention lies between a pair of plate structures of a flat-panel display. 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 porosity along the face of the spacer creates facial roughness that prevents some secondary electrons emitted by the spacer from escaping the spacer. Accordingly, positive charge buildup on the spacer is reduced. The image is thereby improved.
In one structure configured according to the invention, multiple particle aggregates are bonded together in an open manner to form a solid porous body in which pores extend between the particle aggregates. The pores inhibit secondary electrons emitted by the porous body from escaping the body. Each particle aggregate contains multiple coated particles bonded together. Each of the coated particles is formed with a support particle and a particle coating that overlies at least part of the support particle.
The particle coatings preferably consist of material which, when struck by high-energy primary electrons, emit fewer secondary electrons than the material that forms the support particles. Candidate materials for the particle coatings are oxides and hydroxides of titanium, vanadium, chromium, manganese, iron, germanium, yttrium, zirconium, niobium, molybdenum, tin, cerium, praseodymium, neodymium, europium, and tungsten, including oxide and/or hydroxide of two or more of these metals. The particle coating material may also contain carbon.
Candidate materials for the support particles include a substantial number of oxides and hydroxides of metals, especially transition metals, and metal-like elements. In particular, the oxides and hydroxides of the non-carbon elements in Groups 3b, 4b, 5b, 6b, 7b, 8, 1b, 2b, 3a, and 4a of Periods 2-6 of the Periodic Table, including the lanthanides, are candidates for the support particles. This includes oxide and/or hydroxide of two or more of these non-carbon elements. As an example, when oxide and/or hydroxide of one or more of aluminum, silicon, titanium, chromium, iron, zirconium, cerium, and neodymium is utilized in the support particles, oxide and/or hydroxide of one or more of titanium, chromium, manganese, iron, zirconium, cerium, and neodymium is typically utilized in the particle coatings. The particle coatings are typically of different chemical composition than the support particles.
Various process sequences can be utilized in accordance with the invention to form a solid porous structure that contains multiple aggregates of coated particles. For instance, starting with (separate) aggregates of support particles, the support-particle aggregates can be bonded together in an open manner to form bonded aggregates of the support particles. Particle coatings are then provided over the support particles in the so-bonded aggregates to form the desired porous structure. Alternatively, the particle coatings can be provided over the support particles before or during the bonding of the support-particle aggregates. As another alternative, the particle coatings can be provided over (separate) support particles before or during particle bonding to form aggregates of the coated particles. The coated particle aggregates are then bonded together to form the desired solid porous structure.
When a porous-faced spacer of the present flat
Barton Roger W.
Mackey Bob L.
Nystrom Michael J.
Pan Lawrence S.
Pei Shiyou
Candescent Intellectual Property Services Inc.
Meetin Ronald J.
Nguyen Donghai
Vo Peter
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