Electric lamp and discharge devices – With gas or vapor – Electrode composition
Reexamination Certificate
1997-07-15
2001-04-10
O'Shea, Sandra (Department: 2875)
Electric lamp and discharge devices
With gas or vapor
Electrode composition
C313S311000, C313S310000, C252S512000, C361S222000, C361S230000, C250S324000, C096S079000
Reexamination Certificate
active
06215248
ABSTRACT:
TECHNICAL FIELD
Static elimination is an important activity in the production of advanced technologies such as ultra large scale integrated circuits, magnetorestrictive recording heads, and so on. The generation of particulate matter by corona in static eliminators, however, competes with the equally important need to establish environments that are free from particles and impurities. Since metallic impurities cause fatal damage to these advanced technologies, it is desirable to suppress those contaminants to the lowest possible level.
BACKGROUND ART
It is well known that when metallic ion emitters are subjected to corona discharges in room air, they show signs of deterioration within a few hours and the generation of fine particles. This is known for needle tips, copper, stainless steel, aluminum, and titanium emitters. Corrosion is found in areas under the discharge or subjected to the active gaseous species NO
X
. NO
3
ions are found on all the above materials, whether the emitters had positive or negative polarity. Also, ozone-related corrosion is dependent on relative humidity and on the condensation nuclei density.
Silicon and silicon dioxide emitter electrodes experience significantly lower corrosion than metals in the presence of corona discharges. It is also known that by purging the emitter electrodes with dry air, NH
4
NO
3
can be reduced as either an airborne contaminant or deposit on the emitters.
Surface reactions lead to the formation of compounds that change the mechanical structure of the emitters. At the same time, those reactions lead to the generation of particles from the electrodes or contribute to the formation of particles in the gas phase.
Silicon is known to undergo thermal oxidation, plasma oxidation, oxidation by ion bombardment and implantation, and similar forms of nitridation.
Prior art includes U.S. Pat. Nos. 5,447,763; 5,047,892; 5,057,966; 4,967,608; 3,789,278; 3,813,549; 4,110,614; 4,837,658; 5,539,205; 5,596,478; 5,116,583; and Japanese patent 7-70348. None of these, nor of many technical papers in the field teach or suggest the present invention.
DISCLOSURE OF THE INVENTION
REFERENCES:
patent: 4381927 (1983-05-01), Noll
patent: 5057966 (1991-10-01), Sakata et al.
patent: 5447763 (1995-09-01), Gehlke
Day Michael
Illinois Tool Works Inc.
O'Shea Sandra
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