Electric lamp and discharge devices – With luminescent solid or liquid material – Vacuum-type tube
Reexamination Certificate
1998-03-17
2001-01-09
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
Vacuum-type tube
C313S292000, C313S309000, C313S336000, C313S351000, C313S496000
Reexamination Certificate
active
06172454
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to displays, and more particularly to processes for forming spacers in a field emission display (FED).
Referring to
FIG. 1
, in a typical FED (a type of flat panel display), a cathode
21
has a substrate
11
of single crystal silicon or glass. Conductive layers
12
, such as doped polysilicon or aluminum, are formed on substrate
11
. Conical emitters
13
are constructed on conductive layers
12
. Surrounding emitters
13
are a dielectric layer
14
and a conductive extraction grid
15
formed over dielectric layer
14
. When a voltage differential from a power source
20
is applied between conductive layers
12
and grid
15
, electrons
17
bombard pixels
22
of a phosphor coated faceplate (anode)
24
. Faceplate
24
has a transparent dielectric layer
16
, preferably glass, a transparent conductive layer
26
, preferably indium tin oxide (ITO), a black matrix grille (not shown) formed over conductive layer
26
and defining regions, and phosphor coating over regions defined by the grille.
Cathode
21
may be formed on a backplate or it can be spaced from a separate backplate. In either event, cathode
21
and faceplate
24
are spaced very close together in a vacuum sealed package. In operation, there is a potential difference on the order of 1000 volts between conductive layers
12
and
26
. Electrical breakdown must be prevented in the FED, while the spacing between the plates must be maintained at a desired thinness for high image resolution.
A small area display, such as one inch (2.5 cm) diagonal, may not require additional supports or spacers between faceplate
24
and cathode
21
because glass substrate
16
in faceplate
24
can support the atmospheric load. For a larger display area, such as a display with a thirty inch (75 cm) diagonal, several tons of atmospheric force will be exerted on the faceplate, thus making spacers important if the faceplate is to be thin and lightweight.
SUMMARY OF THE INVENTION
The present invention includes methods for forming spacers in a display device using chemical vapor deposition (CVD), and methods for forming spacers with different shapes and configurations. According to this method, spacers are grown on a substrate by directing an energy source to provide energy at a desired location to produce a solid from a gaseous vapors. In preferred embodiments, the spacers are formed with strength-enhancing configurations and shapes, such as I-shaped or T-shaped cross-sections in a plane perpendicular to the substrate, or X-shaped cross-sections in a plane parallel to the substrate. The spacers can be made accurately with different heights so that the spacers in the center of the device can be made longer than those at one or both sets of parallel edges such that the faceplate of the display bows outwardly slightly so that external pressure is more evenly distributed if the device is hit by impact. The substrate with the spacers formed thereon is then processed to form a first plate that is then assembled with a parallel second plate and vacuum sealed close together.
The present invention also includes a display, preferably a field emission display, that has a number of spacers between a cathode and a faceplate/anode vacuum-sealed together in parallel in a package. The spacers can have cross-sectional profiles, such as a T-shaped or I-shaped, or X-shaped cross-sections to enhance strength.
The present invention provides a method for forming spacers accurately, in desired locations, with materials and configurations that are stronger than known spacers, such as bonded glass spacers. The spacers in the display are less susceptible to breaking due to shear forces from handling, and can avoid the need for bonding, polishing, and/or planarizing. Other features and advantages will become apparent from the following detailed description, drawings, and claims.
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Hale and Dorr LLP
Haynes Mack
Micro)n Technology, Inc.
Patel Nimeshkumar D.
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