Vapor phase low molecular weight lubricants

Details Vapor phase low molecular weight lubricants Vapor phase low molecular weight lubricants

1999-12-20

2001-06-26

McAvoy, Ellen M. (Department: 1764)

Solid anti-friction devices, materials therefor, lubricant or se

Lubricants or separants for moving solid surfaces and...

Organic oxygen compound

C508S583000, C134S031000, C134S037000, C359S290000, C359S291000, C359S224200, C359S572000

Reexamination Certificate

active

06251842

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to micro machine devices and a method for creating these devices. More particularly, the present invention relates to micro machine devices which have moveable elements which engage a different element wherein the point of engagement may have a tendency to stick or adhere. The present invention relates to lubricants which prevent, or reduce this tendency.
BACKGROUND OF THE INVENTION
There have been recent developments in the miniaturation of various electro-mechanical devices also known as micro machines. From this push to miniaturize, the field of diffraction gratings or now commonly referred to as grating light valves has emerged. An example of a GLV is disclosed in U.S. Pat. No. 5,311,360 which is incorporated in its entirety herein by reference. According to the teachings of the '360 patent, a diffraction grating is formed of a multiple mirrored-ribbon structure such as shown in
FIG. 1. A
pattern of a plurality of deformable ribbon structures
100
are formed in a spaced relationship over a substrate
102
. Both the ribbons and the substrate between the ribbons are coated with a light reflective material
104
such as an aluminum film. The height difference that is designed between the surface of the reflective material
104
on the ribbons
100
and those on the substrate
102
is &lgr;/2 when the ribbons are in a relaxed, up state. If light at a wavelength &lgr; impinges on this structure perpendicularly to the surface of the substrate
102
, the reflected light from the surface of the ribbons
100
will be in phase with the reflected light from the substrate
102
. This is because the light which strikes the substrate travels &lgr;/2 further than the light striking the ribbons and then returns &lgr;/2, for a total of one complete wavelength &lgr;. Thus, the structure appears as a flat mirror when a beam of light having a wavelength of &lgr; impinges thereon.
By applying appropriate voltages to the ribbons
100
and the substrate
102
, the ribbons
100
can be made to bend toward and contact the substrate
102
as shown in FIG.
2
. The thickness of the ribbons is designed to be &lgr;/4. If light at a wavelength &lgr; impinges on this structure perpendicularly to the surface of the substrate
102
, the reflected light from the surface of the ribbons
100
will be completely out of phase with the reflected light from the substrate
102
. This will cause interference between the light from the ribbons and light from the substrate and thus, the structure will diffract the light. Because of the diffraction, the reflected light will come from the surface of the structure at an angle &THgr; from perpendicular.
In formulating a display device, one very important criteria is the contrast ratio between a dark pixel and a lighted pixel. The best way to provide a relatively large contrast ratio is to ensure that a dark pixel has no light. One technique for forming a display device using the structure described above, is to have a source of light configured to provide light with a wavelength &lgr; which impinges the surface of the structure from the perpendicular. A light collection device, e.g., optical lenses, can be positioned to collect light at the angle &THgr;. If the ribbons for one pixel are in the up position, all the light will be reflected back to the source and the collection device will receive none of the light. That pixel will appear black. If the ribbons for the pixel are in the down position, the light will be diffracted to the collection device and the pixel will appear bright.
Experimentation has shown that the turn-on and turn-off voltages for GLV ribbons exhibit hysteresis.
FIG. 3
shows a brightness versus voltage graph for the GLV. The vertical axis represents brightness and the horizontal axis represent voltage. It will be understood by those of ordinary skill in the art that if diffracted light is collected, when the GLV ribbon is up and at rest, that the minimum of light is collected. When the GLV ribbon is down, the maximum of light is collected. In the case where the ribbon is able to move downwardly by exactly &lgr;/4 of the wavelength of the anticipated light source, then the light collected in the down position with the ribbon firmly against the substrate is truly at a maximum.
Upon initial use, the GLV remains in a substantially up position while at rest, thereby diffracting no light. To operate the GLV, a voltage is applied across the ribbon
100
(
FIG. 1
) and the underlying substrate
102
. As the voltage is increased, almost no change is evident until a switching voltage V
2
is reached. Upon reaching the switching voltage V
2
, the ribbon snaps fully down into contact with the substrate. Further increasing the voltage will have negligible effect on the optical characteristics of the GLV as the ribbon
100
is fully down against the substrate
102
. Though the ribbon is under tension as a result of being in the down position, as the voltage is reduced the ribbon does not lift off the substrate until a voltage V
1
is reached. The voltage V
1
is lower than the voltage V
2
. This initial idealized operating characteristic is shown by the solid line curve
106
in FIG.
3
.
The inventors discovered that the GLV devices exhibited aging. It was learned that operating the GLV over an extended period of time caused the release voltage to rise toward the switching voltage V
2
. Additionally, the amount of diffracted light available for collection also decreased as the release voltage increased. Experience led the inventors to realize that the GLV devices were fully aged after about one hour of continuously switching the GLV between the up and relaxed state to the down and tensioned state. These experiments were run at 10,000 Hz. Though those previous inventions worked as intended, this change in release voltage and the degradation of the diffracted light made such GLV devices unsuitable as commercial production products.
FIG. 4
shows an actual graph for the amount of light versus voltage for a control GLV device operated in an ambient atmosphere. A series of five curve traces are shown,
108
,
110
,
112
,
114
and
116
. Each of the traces is taken at a different point during the aging cycle, trace
108
being recorded first in time, and then each successive trace recorded at a later point in the aging cycle.
FIG. 4
shows the voltage applied both positively and negatively. What the traces of
FIG. 4
show is that after the ribbon
100
(
FIG. 1
) is forced into the down position against the substrate
102
at a voltage V
2
, reducing the applied voltage will cause the amount of the collected diffracted light to diminish until the release voltage V
1
is reached. This phenomenon is likely reached as the edges of the ribbon
100
begin to rise. However, as long as at least a portion of the ribbon
100
remains in contact with the substrate
102
, a significant portion of the light is diffracted and hence available for collection.
It is apparent from
FIG. 4
that each recorded successive trace
110
,
112
,
114
and
116
shows that the release voltage V
1
continues to rise and concurrently the amount of collected diffracted light decreases.
FIG. 5
is a corresponding graph to FIG.
4
and shows the switching voltage V
2
and the release voltage V
1
during the aging process. The voltage levels are shown on the vertical axis and time is shown in the horizontal axis.
FIG. 5
shows that the switching voltage V
2
remains fairly stable during the aging process. However,
FIG. 5
also shows that the release voltage V
1
rises during the aging cycle.
Analysis of GLVs after the completion of the aging cycle shows that structures build between the ribbon surface and the underlying substrate.
FIG. 6
schematically shows that structures can develop on the bottom of a ribbon
120
while the substrate
122
remains relatively unchanged.
FIG. 7
schematically shows that structures can develop on the top of the substrate
124
while the bottom of a ribbon
126
remains relatively unchanged.
FIG. 8
sc

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