Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
1999-07-26
2001-04-17
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C445S024000, C445S025000
Reexamination Certificate
active
06218783
ABSTRACT:
TECHNICAL FIELD
The present claimed invention relates to the field of flat panel displays. More specifically, the present claimed invention relates to a coating material for a spacer structure of a flat panel display.
BACKGROUND ART
In some flat panel displays, a backplate is commonly separated from a faceplate using a spacer structure. In high voltage applications, for example, the backplate and the faceplate are separated by spacer structures having a height of approximately 1-2 millimeters. For purposes of the present application, high voltage refers to an anode to cathode potential greater than 1 kilovolt. In one embodiment, the spacer structure is comprised of several strips or individual wall structures each having a width of about 50 microns. The strips are arranged in parallel horizontal rows with each strip extending across the width of the flat panel display. The spacing of the rows of strips depends upon the strength of the backplate and the faceplate and the strips. Because of this, it is desirable that the strips be extremely strong. The spacer structure must meet a number of intense physical requirements. A detailed description of spacer structures is found in commonly-owned co-pending U.S. patent application Ser. No. 08/683,789 by Spindt et al. entitled “Spacer Structure for Flat Panel Display and Method for Operating Same”. The Spindt et al. application was filed Jul. 18, 1996, and is incorporated herein by reference as background material.
In a typical flat panel display, the spacer structure must comply with a long list of characteristics and properties. More specifically, the spacer structure must be strong enough to withstand the atmospheric forces which compress the backplate and faceplate towards each other (In a diagonal 10-inch flat panel display, the spacer structure must be able to withstand as much as a ton of compressing force). Additionally, each of the rows of strips in the spacer structure must be equal in height, so that the rows of strips accurately fit between respective rows of pixels. Furthermore, each of the rows of strips in the spacer structure must be very flat to insure that the spacer structure provides uniform support across the interior surfaces of the backplate and the faceplate. The spacer structure must also have a coefficient of thermal expansion (CTE) which closely matches that of the backplate and faceplate to which the spacer structure is attached (For purposes of the present application, a closely matching CTE means that the CTE of the spacer structure is within approximately 10 percent of the CTE of the faceplate and the backplate to which the spacer structure is attached). The temperature coefficient of resistance (TCR) of the spacer structure must also be low. An acceptable spacer structure must meet all of the above-described physical requirements and must be inexpensive to manufacture with a high yield. Besides the physical requirements set forth above, the conventional spacer structure must also meet several electrical property requirements. Specifically, a spacer structure must have specific resistance and secondary emission characteristics, and have a high resistance to high voltage breakdown.
In conventional prior art spacer structures, an insulating material such as alumina is covered with a coating. In such prior art spacer structures, the insulating material has a very high sheet resistance, while the coating has a lower sheet resistance. Other prior art approaches utilize a spacer structure in which both the insulating material and the overlying coating have a very high sheet resistance.
Thus, due to the large number of stringent physical requirements on the bulk of the spacer structure (i.e., high strength, precise resistivity, low TCR, precise CTE, accurate mechanical dimensions etc.) it is desirable to separate out the additional requirements on the properties of the surface. Hence, a need exists for a spacer structure which meets the above-described physical and electrical property requirements without dramatically complicating and/or increasing the cost of the spacer structure manufacturing process.
DISCLOSURE OF THE INVENTION
The present invention eliminates the requirement for a spacer material to meet specific secondary emission characteristics in addition to meeting requirements such as, for example, high strength, precise resistivity, low TCR, precise CTE, accurate mechanical dimensions and the like. The present invention further achieves a spacer structure which meets the above-described physical, electrical, and emission property requirements without dramatically complicating and/or increasing the cost of the spacer structure manufacturing process. The present invention achieves the above accomplishments with a coating material which is applied to a spacer body. In addition, the present invention achieves the above accomplishments without stringent CTE, TCR, resistivity, or uniformity requirements on the coating. The present invention also points out advantages of having a spacer body which is resistive, and a spacer coating which has a sheet resistance which is higher than that of the spacer body.
Specifically, in one embodiment, the present invention provides a coating material having specific resistivity, thickness, and secondary emission characteristics. The coating material of the present embodiment is especially well-adapted for coating a spacer structure of a flat panel display. In this embodiment, the coating material is characterized by.
a sheet resistance, &rgr;
sc
, and an area resistance, r, wherein &rgr;
sc
and r are approximately defined by:
&rgr;
sc
>100(&rgr;
sw
) and r<&rgr;
sw
(l
2
/8).
In the present embodiment, &rgr;
sw
is the sheet resistance of a spacer structure to which the coating material is adapted to be applied, and l is the height of the spacer structure to which the coating material is adapted to be applied. The bulk sheet resistance &rgr;
sw
is defined here as the resistance of the structure divided by the height and multiplied by the perimeter. In the present embodiment, the sheet resistance, &rgr;
sw
of said spacer has a value of approximately 10
10
to 10
13
&OHgr;/□. By having a coating material with such characteristics, the present invention eliminates the need to place rigorous secondary emission characteristic requirements on the bulk material comprising the spacer structure in a flat panel display.
In order to avoid stringent requirements on the value or the uniformity of the coating, the sheet resistance, &rgr;
sc
, it is desirable to have its value be high compared to &rgr;
sw
, that is:
&rgr;
sc
>approximately 100(&rgr;
sw
)
As in the previous embodiment, &rgr;
sw
is the sheet resistance of the spacer structure to which the coating material is adapted to be applied. Additionally, the coating material of the present embodiment has an area resistance, r, wherein r is defined as:
&Dgr;V
cc
/j
c
&Dgr;V
cc
, of the present embodiment is the voltage across the thickness of the coating at a charging current j
c
where the &Dgr;V
cc
used to characterize r for a typical HV display is in the range of approximately 1-20 volts. In this embodiment, j
c
is defined as:
∫j
inc
(E)(1−&dgr;(E))dE.
In the above relationship, j
inc
(E) is the electron current density, as a function of incident energy E, incident to the coating material; and &dgr; is the secondary emission ratio of the coating material as a function of the energy E of electrons incident on the coating material. &Dgr;V
cc
and j
c
could be measured by sample currents and energy shifts in peaks using, for example, Auger electron or photoelectron spectroscopy. As in the previous embodiment, by having a coating material with such characteristics, the present invention eliminates the need to place rigorous requirements on secondary emission characteristics of the material comprising the spacer structure of a flat panel display. It also allows for tailoring the resistivity and other properties of the spacer without strict requirements on &dgr;, and tailoring of the coating withou
Hopple George B.
Spindt Christopher J.
Candescent Technologies Corporation
Tran Thuy Vinh
Wagner , Murabito & Hao LLP
Wong Don
LandOfFree
High voltage compatible spacer coating does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with High voltage compatible spacer coating, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and High voltage compatible spacer coating will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2494042