Coating processes – Electrical product produced
Reexamination Certificate
2002-06-28
2004-11-09
Talbot, Brian K. (Department: 1762)
Coating processes
Electrical product produced
C427S162000, C427S168000, C445S009000, C445S024000
Reexamination Certificate
active
06815002
ABSTRACT:
This application claims the benefit of Korean Patent Application No. P2002-15967, filed on Mar. 25, 2002, which is hereby incorporated by reference for all purposes as if fully set forth herein.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of dispensing liquid crystal. More particularly, the present invention relates to a method of dispensing liquid crystal from N liquid crystal dispensing devices onto M panel locations (where M>N) such that the amount of liquid crystal dispensed from each of the N liquid crystal dispensing devices over time is substantially the same.
2. Discussion of the Related Art
Portable electric devices, such as mobile phones, personal digital assistants (PDA), and notebook computers, often require thin, lightweight, and efficient flat panel displays. There are various types of flat panel displays, including liquid crystal displays (LCD), plasma display panels (PDP), field emission displays (FED), and vacuum fluorescent displays (VFD). Of these, LCDs have the advantages of being widely available, easy to use, and superior image quality.
The LCD displays information based on the refractive anisotropy of liquid crystal. As shown in
FIG. 1
, an LCD
1
comprises a lower substrate
5
, an upper substrate
3
, and a liquid crystal layer
7
that is disposed between the lower substrate
5
and the upper substrate
3
. The lower substrate
5
includes an array of driving devices and a plurality of pixels (not shown). The individual driving devices are usually thin film transistors (TFT) located at each pixel. The upper substrate
3
includes color filters for producing color. Furthermore, a pixel electrode and a common electrode are respectively formed on the lower substrate
5
and on the upper substrate
3
. Alignment layers are formed on the lower substrate
5
and on the upper substrate
3
. The alignment layers are used to uniformly align the liquid crystal layer
7
.
The lower substrate
5
and the upper substrate
3
are attached using a sealing material
9
. In operation, the liquid crystal molecules are initially oriented by the alignment layers, and then reoriented by the driving device according to video information so as to control the light transmitted through the liquid crystal layer to produce an image.
The fabrication of an LCD device requires the forming of driving devices on the lower substrate
5
, the forming of the color filters on the upper substrate
3
, and performing a cell process (described subsequently). Those processes will be described with reference to FIG.
2
.
Initially, in step S
101
, a plurality of perpendicularly crossing gate lines and data lines are formed on the lower substrate
5
, thereby defining pixel areas between the gate and data lines. A thin film transistor that is connected to a gate line and to a data line is formed in each pixel area. Also, a pixel electrode that is connected to the thin film transistor is formed in each pixel area. This enables driving the liquid crystal layer according to signals applied through the thin film transistor.
In step S
104
, R (Red), G (Green), and B (Blue) color filter layers (for reproducing color) and a common electrode are formed on the upper substrate
3
. Then, in steps S
102
and S
105
, alignment layers are formed on the lower substrate
5
and on the upper substrate
3
. The alignment layers are rubbed to induce surface anchoring (establishing a pretilt angle and an alignment direction) for the liquid crystal molecules. Thereafter, in step S
103
, spacers for maintaining a constant, uniform cell gap is dispersed onto the lower substrate
5
.
Then, in steps S
106
and S
107
, a sealing material is applied onto outer portions such that the resulting seal has a liquid crystal injection opening. That opening is used to inject liquid crystal. The upper substrate
3
and the lower substrate
5
are then attached together by compressing the sealing material.
While the foregoing has described forming a single panel area, in practice it is economically beneficial to form a plurality of unit panel areas. To this end, the lower substrate
5
and the upper substrate
3
are large glass substrates that contain a plurality of unit panel areas, each having a driving device array or a color filter array surrounded by sealant having a liquid crystal injection opening. To isolate the individual unit panels, in step S
108
the assembled glass substrates are cut into individual unit panels. Thereafter, in step S
109
liquid crystal is injected into the individual unit panels by way of liquid crystal injection openings, which are then sealed. Finally, in step S
110
the individual unit panels are tested.
As described above, liquid crystal is injected through a liquid crystal injection opening. Injection of the liquid crystal is usually pressure induced.
FIG. 3
shows a device for injecting liquid crystal. As shown, a container
12
that contains liquid crystal, and a plurality of individual unit panels
1
are placed in a vacuum chamber
10
such that the individual unit panels
1
are located above the container
12
. The vacuum chamber
10
is connected to a vacuum pump that produces a predetermined vacuum. A liquid crystal display panel moving device (not shown) moves the individual unit panels
1
into contact with the liquid crystal
14
such that each injection opening
16
is in the liquid crystal
14
.
When the vacuum within the chamber
10
is increased by inflowing nitrogen gas (N
2
) the liquid crystal
14
is injected into the individual unit panels
1
through the liquid crystal injection openings
16
. After the liquid crystal
14
entirely fills the individual unit panels
1
, the liquid crystal injection opening
16
of each individual unit panel
1
is sealed by a sealing material.
While generally successful, there are problems with pressure injecting liquid crystal
14
. First, the time required for the liquid crystal
14
to inject into the individual unit panels
1
is rather long. Generally, the gap between the driving device array substrate and the color filter substrate is very narrow, on the order of micrometers. Thus, only a very small amount of liquid crystal
14
is injected into per unit time. For example, it takes about 8 hours to inject liquid crystal
14
into an individual 15-inch unit panel
1
. This decreases fabrication efficiency.
Second, liquid crystal
14
consumption is excessive. Only a small amount of liquid crystal
14
in the container
12
is actually injected into the individual unit panels
1
. Since liquid crystal
14
exposed to air or to certain other gases can be contaminated by chemical reaction the remaining liquid crystal
14
should be discarded. This increases liquid crystal fabrication costs.
Therefore, a method of disposing liquid crystal between substrates using a plurality of liquid crystal dispensing devices would be beneficial. Even more beneficial would be a method of using N liquid crystal dispensing devices to disposing liquid crystal on M substrate locations, wherein M>N, such that the amount of liquid crystal dispensed from each of the N liquid crystal dispensing devices over time is substantially the same.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to provide a method for dispensing liquid crystal that enables increased efficiency and reduced liquid crystal consumption by applying liquid crystal from a plurality of liquid crystal dispensing devices onto a plurality of liquid crystal panels that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
Another advantage of the present invention is to provide a method of dispensing liquid crystal from N liquid crystal dispensing devices onto M panel areas, wherein M>N, such that each liquid crystal dispensing device applies substantially the same amount of liquid crystal over time. This beneficially reduces refilling, cleaning, and set-up problems associated with refilling liquid crystal into the liquid crystal containers.
Additional feat
Kweon Hyug-Jin
Son Hae-Joon
LG. Philips LCD Co. Ltd.
McKenna Long & Aldridge LLP
Talbot Brian K.
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