Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1999-08-03
2001-11-27
Sikes, William L. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S139000, C349S138000
Reexamination Certificate
active
06323927
ABSTRACT:
This application claims the benefit of Korean Application No. 10152/1996 filed on Apr. 4, 1996, which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display, and more particularly to an IPS(In-Plane Switching) liquid crystal display that is large in area and exhibits a wide viewing angle.
Conventional TFT LCDs (thin film transistor liquid crystal display) have a drawback known as a viewing angle dependency, that is, the contrast ratio is changed according to the viewing angle. This has made it difficult to apply the technology to a large size display.
To solve this problem, various liquid crystal displays have been proposed, such as a retardation attaching TNLCD (twisted nematic liquid crystal display) and a multi-domain liquid crystal display. These LCDs still have other technical problems such as complicated production-process and shifting color tones.
2. Discussion of the Related Art
Recently, an IPS LCD has been introduced to obtain a wide viewing angle. This technology is discussed in JAPAN DISPLAY 92, p547, Japanese patent application No. 7-36058, Japanese patent application No. 7-225538, and ASIA DISPLAY 95, p707. As shown in
FIG. 1
a
and
FIG. 1
c
, in the liquid crystal layer
12
the molecules are aligned at a 45° angle. The principal transmittance axis of a polarizer
9
attached to the first substrate
1
is the same direction as the alignment direction of the liquid crystal
12
, and the principal transmittance direction of an analyzer
10
attached to the second substrate
5
is perpendicular to the alignment direction of the liquid crystal layer
12
. A pair of electrodes
2
,
3
is formed on the first substrate
1
.
In
FIG. 1
b
and
FIG. 1
d
, when the voltage is applied between two electrodes, a horizontal electric field is created. Therefore, the transmittance is controlled by causing the liquid crystal molecules to be rotated to be parallel with the electric field. When the rotation angle of the liquid crystal molecules is 45° in the normally black mode, the retardation value(&Dgr;nd) is about &lgr;/2(0.21-0.36 &mgr;m) for a maximum transmittance.
In conventional IPS LCDs as described above, the transmittance is controlled by birefringence, and a retardation film is necessary to compensate for the viewing angle which increases the manufacturing cost.
In addition, a viewing angle inverted area appears in the central portion of the outer lines of the display.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a liquid crystal display that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is an IPS mode liquid crystal display having a wide viewing angle and improved picture quality.
Another object of the present invention is an IPS mode liquid crystal display that can be fabricated at low cost by using a low voltage driving IC and by eliminating the need for a retardation film.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the liquid crystal display device of the present invention includes a first substrate having a first surface and a second surface, a first alignment layer formed on the second surface of the first substrate, a second substrate having a first surface and a second surface, a second alignment layer formed on the second surface of the second substrate, a molecular liquid crystal layer between the second surface of the first substrate and the second surface of the second substrate, a pair of electrodes formed in parallel on the second surface of the first substrate, a polarizer formed on the first surface of the first substrate and having a transmittance axis, and an analyzer formed on the second surface of the second substrate and having a transmittance axis.
A liquid crystal display device comprises a first substrate; a transistor formed over the first substrate, the transistor including a gate electrode, a source electrode and a drain electrode; a data line formed over the first substrate, the data line being connected to the source electrode; a common electrode formed over the first substrate, the common electrode including a plurality of spaced apart parallel common projections formed in a first direction; a data electrode formedover the first substrate and connected to the drain electrode, the date electrode including a plurality of spaced apart parallel data portions formed in a second direction and interleaved between the common projections, the first direction being parallel to the second direction; an insulating layer formed over the common projections and under the data portions; and a gate line formed over the first substrate, the gate line being connected to the gate electrode.
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LG Philips LCD Co., Ltd.
Long Aldridge & Norman LLP
Sikes William L.
Ton Toan
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