Web fabrication of devices

Details Web fabrication of devices Web fabrication of devices

2001-08-17

2004-01-27

Chowdhury, Tarifur R. (Department: 2871)

Liquid crystal cells, elements and systems

Particular excitation of liquid crystal

Electrical excitation of liquid crystal

C349S042000, C349S187000, C438S034000, C438S110000

Reexamination Certificate

active

06683663

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to the field of fabricating electronic assemblies such as display panels.
DESCRIPTION OF RELATED ART
Electronic assemblies such as display panels. Display panels may be comprised of active matrix or passive matrix panels are widely used. Active matrix panels and passive matrix panels may be either transmissive or reflective. Transmissive displays include polysilicon thin-film transistor (TFT) displays, and high-resolution polysilicon displays. Reflective displays typically comprise single crystal silicon integrated circuit substrates that have reflective pixels.
Liquid crystals, electroluminescent (EL) materials, organic light emitting diodes (OLEDs), up and downconverting phosphor (U/DCP), electrophoretic (EP) materials, or light emitting diodes (LEDs) may be used in fabricating flat-panel display panels. Each of these is known in the art and is discussed briefly below.
Liquid crystal displays (LCDs) may have an active-matrix backplane in which thin-film transistors are co-located with LCD pixels. Flat-panel displays employing LCDs generally include five different components or layers: a White or sequential Red, Green, Blue light source, a first polarizing filter, that is mounted on one side of a circuit panel on which the TFTs are arrayed to form pixels, a filter plate containing at least three primary colors arranged into pixels, and a second polarizing filter. A volume between the circuit panel and the filter plate is filled with a liquid crystal material. This material will rotate the polarized light when an electric field is applied between the circuit panel and a transparent ground electrode affixed to the filter plate or a cover glass. Thus, when a particular pixel of the display is turned on, the liquid crystal material rotates polarized light being transmitted through the material so that it will pass through the second polarizing filter. Some liquid crystal materials, however, require no polarizers.
LCDs may also have a passive matrix backplane. A passive matrix backplane typically includes two planes of strip electrodes that sandwich the liquid crystal material. However, passive matrices generally provide a lower quality display compared to active matrices. Liquid crystal material includes, but is not limited to, twisted nematic (TN), Super TN, double STN, and ferroelectric. U/DCP and EP displays are formed in a similar fashion except the active medium is different (e.g., upconverting gas, downconverting gas, electrophoretic materials).
EL displays have one or more pixels that are energized by an alternating current (AC) that must be provided to each pixel by row and column interconnects. EL displays generally provide a low brightness output because passive circuitry for exciting pixel phosphors typically operates at a pixel excitation frequency that is low relative to the luminance decay time of the phosphor material. However, an active matrix allows the use of higher frequency AC excitation in order to obtain brighter electroluminescence in the pixel phosphor
LED displays are also used in flat-panel displays. LEDs emit light when energized. OLEDs operate like the LEDs except OLEDs use organic material in the formation of the diode.
Regardless of the type of active medium used, displays are generally comprised of at least a substrate and a backplane. The backplane forms the electrical interconnection of the display and typically comprises electrodes, capacitors, and transistors in at least some embodiments of a backplane.
FIGS. 1A-1D
illustrate a variety of displays that formed on a rigid substrate are known in the art.
FIG. 1A
illustrates a rigid display device in which the active matrix display backplane
10
is coupled to a rigid substrate
12
. Typically, the active matrix display backplane is also rigid.
FIG. 1B
shows another rigid display. There, the active matrix display backplane
10
is coupled to a rigid substrate
12
(e.g., glass). Also shown is a plurality of blocks
14
. These blocks may be fabricated separately and then deposited into holes on substrate
12
by a process known as fluidic self assembly; an example of this process is described in U.S. Pat. No. 5,545,291. These blocks may each contain driver circuitry (e.g., MOSFET and capacitor) for driving a pixel electrode. The active matrix backplane includes transparent pixel electrodes and row/column interconnects (not shown) to electrically interconnect blocks
14
. Plurality of blocks
14
are coupled to active matrix display backplane
10
and rigid substrate
12
.
FIG. 1C
illustrates reflective display
16
coupled to rigid substrate
12
.
FIG. 1D
illustrates a reflective display
16
coupled to rigid substrate
12
. Plurality of blocks
14
is coupled to reflective display
16
and to rigid substrate
12
.
Given the brief description of some electronic assemblies such as displays, the discussion now turns to the placement of elements onto rigid substrate
12
. Placing elements, such as pixel drivers, on a rigid substrate is well known. Prior techniques may be generally divided into two types: deterministic methods or random methods. Deterministic methods, such as “pick and place”, use a human or an arm of a robot to pick each element and place it into its corresponding location in a different substrate. Pick and place methods generally place devices one at a time and are generally not applicable to very small or numerous elements such as those needed for large arrays, such as an active matrix liquid crystal display.
Random placement techniques are more effective and result in high yields if the elements to be placed have the right shape. U.S. Pat. No. 5,545,291 describes a method that uses random placement. In this method, microstructures are assembled onto a different substrate through fluid transport. This is sometimes referred to as fluidic self-assembly (FSA). Using this technique, various blocks, each containing a functional component, may be fabricated on one substrate and then separated from that substrate and assembled onto a separate rigid substrate through FSA. The blocks that are deposited onto receptor regions of a substrate may include any of a number of different functional components, such as LEDs, pixel drivers, sensors, etc. An example of a particular type of block and its functional component is described in co-pending U.S. patent application Ser. No. 09/251,220 entitled “Functionally Symmetric Integrated Circuit Die” which was filed Feb. 16, 1999 by the inventor John Stephen Smith. This application is hereby incorporated herein by reference.
As noted above,
FIGS. 1B and 1D
illustrate substrate
12
with blocks
14
formed in rigid substrate
12
. Blocks
14
may be deposited through an FSA process. In the FSA process, a slurry containing blocks
14
is deposited over the rigid substrate
12
and blocks
14
rest in corresponding openings in substrate
12
.
FIG. 2
illustrates a cross-sectional view of block
14
and circuit element
18
on the top surface of block
14
. Generally, blocks
14
have a trapezoidal cross-section where the top of block
14
is wider than the bottom of block
14
.
FIG. 3
illustrates a cross-sectional view of blocks
14
in recessed regions of rigid substrate
12
. Between block
14
and rigid substrate
12
is eutetic layer
13
.
FIG. 4
illustrates a cross-sectional view of rigid substrate
12
coupled to a rigid display backplane
30
with plurality of blocks
14
between rigid display backplane
30
and substrate
12
. Plurality of blocks
14
are functionally part of display backplane
30
and are deposited onto receptor regions of substrate
12
. Each block
14
drives at least one transparent pixel electrode. The electrode pixel is fabricated over a transistor that is fabricated in block
14
.
FIG. 5
illustrates a top view of a portion of an array in an active matrix display backplane. Control line rows
31
and
32
in this device are coupled to gate electrodes along row and control line columns
34
and
35
are coupled to data drivers that supply pixel voltages

Affiliated with

Also associated with

Rating

Web fabrication of devices does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Web fabrication of devices, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Web fabrication of devices will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3200630