Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1999-12-17
2004-04-06
Ton, Toan (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
Reexamination Certificate
active
06717646
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to alignment indicators for a liquid crystal display (LCD). The alignment indicators are used to examine the alignment of the lower and upper substrates of an LCD device when the substrates are assembled together. Generally, the lower substrate is provided with an array of thin film transistors and the upper substrate is provided with a black matrix for a color filter.
2. Discussion of the Related Art
In general, the manufacture of an LCD device involves the steps of providing a lower substrate including an array of thin film transistors (TFTs), providing an upper substrate including a black matrix for defining a color filter, assembling the upper and lower substrates together, injecting liquid crystals between the assembled substrates, attaching a polarizing substrate on the outside surfaces of the assembled substrates, performing module processing, and other steps.
Alignment indicators for an LCD device are used to determine and check the accuracy of alignment between the upper and lower substrates when they are assembled together. Referring to
FIG. 1
, an alignment indicator of an LCD device is defined by providing alignment indicators
3
and
4
usually located at the corner edges of the upper substrate
2
and the lower substrate
1
. The misalignment of the two substrates is indicated by the alignment indicators if the upper and lower alignment indicators overlap with each other or the spacing between the alignment marks are uneven when the upper substrate
2
and the lower substrate
1
are assembled together.
Generally, the alignment indicator
4
, which is made of a substance similar to that of the gate or source/drain electrode, is defined at a corner edge of the lower substrate
1
when a pixel array consisting of TFTs and pixel electrodes are defined. The alignment indicator
3
, which is made of a substance similar to that of a black matrix for defining a color filter, is defined at a corner edge of the upper substrate
2
so that the alignment indicators
4
and
3
are located across from each other when the upper substrate
2
and the lower substrate
1
are assembled together.
FIG. 2
shows alignment indicator
21
of the lower substrate and alignment indicator
22
of the upper substrate of a LCD when the upper substrate
2
and the lower substrate
1
are assembled together. The alignment indicator
21
of the lower substrate has a cross-like shape having a predetermined width. The alignment indicator
22
of the upper substrate has four L-shaped members arranged in such a manner that the alignment indicator
21
can be placed in the middle of the four L-shaped members when the upper and lower substrates
1
and
2
are assembled together, as shown in FIG.
2
.
When the upper and lower substrates are put together, the alignment indicator
21
of the lower substrate is across from the L-shaped members of the alignment indicator
22
of the upper substrate. If the substrates are put together without any misalignment, the alignment indicators
22
and
21
of the upper and lower substrates should not overlap with each other and should have equal spacing between the edges the four L-shaped members of the alignment indicator
22
and the cross shaped figure of alignment indicator
21
, as shown in FIG.
2
.
Unfortunately, the amount of misalignment between the upper and lower substrate as shown by the alignment indicators of the related art can only be guessed at by a visual inspection. Thus, it is very difficult to accurately calculate the misalignment of the upper and lower substrates, which makes it difficult to properly align the subsequent substrates for manufacture of other LCDs in the assembly line.
SUMMARY OF THE INVENTION
To overcome the problems described above, preferred embodiments of the present invention provide alignment indicators for an LCD device that achieves accurate measurement of the misalignment when the upper and lower substrates of a LCD are assembled together so that subsequent LCDs that are to be manufactured have properly aligned lower and upper substrates.
A preferred embodiment of the present invention includes a first substrate, a second substrate, a first alignment indicating member provided on the first substrate, and a second alignment indicating member including a measuring member provided on the second substrate, wherein the first and second alignment indicating members are arranged such that an amount of misalignment can be measured by a position of the measuring member relative to the first alignment indicating member when the first substrate and the second substrate are assembled together.
Another preferred embodiment of the present invention includes a first substrate, a second substrate, a first alignment indicating member on the first substrate, and a second alignment indicating member on the second substrate, the second alignment indicating member including at least one of a plurality of recessed portions having various depths and a plurality of protruded portions having various lengths, wherein the recessed portions and protruded portions are defined at an edge of the second alignment indicating member, and wherein the relative position of the recessed portions and the protruded portions with respect to the first alignment indicating member provides a measurement of an amount of misalignment between the first substrate and the second substrate when the first and second substrates are assembled together.
Therefore, preferred embodiments of the present invention have the advantages of providing alignment indicators that allow for accurate measurement of the misalignment between an upper and lower substrates of a LCD for proper alignment of subsequent LCDs.
REFERENCES:
patent: 5771085 (1998-06-01), Ochi et al.
patent: 5936695 (1999-08-01), Hida et al.
Chung In-Jae
Park Kwang-Seop
Birch & Stewart Kolasch & Birch, LLP
Duong Tai
LG. Philips LCD Co. Ltd.
Ton Toan
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