Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2003-01-27
2004-08-03
Ton, Toan (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S139000
Reexamination Certificate
active
06771345
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a liquid crystal display (LCD) that has a high aperture ratio (HAR), and more particularly, to a pixel electrode structure for the LCD with HAR.
2. Description of the Related Art
As resolutions of liquid crystal display (LCD) increase, aperture ratio of the LCD becomes more and more insufficient. Recently, color filter on array (COA) technology, has been developed to provide a LCD of high aperture ratio. In the HAR process, the color filter process is integrated with the TFT array process on the same glass substrate, thus the aperture ratio of the TFT-LCD device is increased to effectively improve brightness of the panel, and the step of attachment/alignment between a color filter substrate and a TFT array substrate is omitted to improve yield and decrease process costs. Moreover, in the HAR process, an overlapping portion is formed between a transparent pixel electrode and a data line to decrease the required area of a black matrix (BM) layer, resulting in a higher aperture ratio in the TFT-LCD device.
FIG. 1
is a top view showing an electrode structure in a pixel of a conventional TFT-LCD device formed using a HAR process.
FIG. 2
is a sectional diagram along line
1
—
1
of
FIG. 1
showing the rotating orientations of liquid crystal molecules in the conventional TFT-LCD device using a HAR process.
The conventional TFT-LCD device comprises a plurality of traversing gate lines
12
and data lines
14
extending lengthwise to define a plurality of pixels
10
in a matrix, each pixel
10
comprising a pixel electrode
16
and a TFT. Using one data line
14
as the boundary, a first pixel
10
A is covered by a first pixel electrode
16
A, and a second pixel
10
B is covered by a second pixel electrode
16
B. Also, the periphery of the first pixel electrode
16
A overlaps one side portion of the data line
14
, the periphery of the second pixel electrode
16
A overlaps another side portion of the data line
14
, and a predetermined distance is kept to space the first pixel electrode
16
A from the second pixel electrode
16
B over the data line
14
. Further, an arrow P indicates a light-polarization planar direction on a polarizer, a light-entry direction.
During a HAR process on a TFT array glass substrate
17
, a first metal layer is patterned as the gate lines
12
, and then an insulating layer
15
is deposited to cover the gate lines
12
and the glass substrate
17
. Next, processes corresponding to TFT are performed on a predetermined area of the gate line
12
, and a second metal layer is patterned as the data lines
14
. Next, a transparent conductive layer is patterned as the first pixel electrode
16
A and the second pixel electrode
16
B.
In a case using TN-type (twisted nematic type) LCD, when an extra voltage exceeds a critical value, the liquid crystal molecules
18
originally parallel to the alignment film are rotated to become perpendicular to the alignment layer in accordance with the magnitude of the lengthwise electric field. However, a transverse electric field is generated between the periphery of the first pixel electrode
16
A and the periphery of the second pixel electrode
16
B, thus the inclined directions of the liquid crystal molecules
18
I and
18
II near the periphery of the pixel electrodes
16
A and
16
B are influenced by the lengthwise and transverse electric field. Also, when an included angle between the arrow P (a light-polarization planar direction on a polarizer) and the long-axis direction of the liquid crystal molecule
18
I is 45°, an ellipsoidal polarized light caused by birefringence effect may pass an analyzer perpendicular to the polarizer to result in light leakage. With regard to the rotating orientation of the liquid crystal molecules
18
II over the sidewall of the data line
14
, however, a Mura phenomenon occurs, manifesting as non-uniform color difference, to form a light leakage area L.
In another attempt to solve the above-described problems, the width of the data line
14
is increased to shield the light leakage area L, but this decreases the aperture ratio of the TFT-LCD device.
SUMMARY OF THE INVENTION
Accordingly, an object of the invention is to provide a pixel electrode structure in an L CD to increase the aperture ratio and eliminate Mura phenomenon near the overlapping portion between the pixel electrode and the data line.
To achieve these and other aims, the invention provides a pixel electrode structure of a liquid crystal display with a high aperture ratio. A first substrate and a second substrate are disposed parallel to each other, such that an internal space is formed between the interior surface of the first substrate and the interior surface of the second substrate. A liquid crystal layer is formed in the internal space. At least one polarizer is formed on the exterior surface of the first substrate or the exterior surface of the substrate. A plurality of parallel gate lines is transversely formed on the interior surface of the first substrate. A plurality of data lines parallel and extends lengthwise on the interior surface of the first substrate. A plurality of pixels is defined by the gate lines and the data lines in a matrix, in which each pixel comprises at least one TFT formed on the interior surface of the first substrate and near the intersection of the gate line and the data line, a common electrode on the interior surface of the second substrate, covering the pixel, and a pixel electrode on the interior surface of the first substrate, covering the pixel.
In one preferred embodiment, no two adjacent pixel electrodes are connected to each other. Each pixel electrode comprises a first-lengthwise periphery that overlaps a first-adjacent data line to form a first overlapping portion, and a second-lengthwise periphery that overlaps a second-adjacent data line to form a second overlapping portion. The first-lengthwise periphery and the second-lengthwise periphery have an identical triangle-wave profile and are symmetrical to each other. The triangle-wave profile is formed by connecting a plurality of right-angled and equilateral triangles.
In another preferred embodiment, no two adjacent pixel electrodes are connected to each other. Each pixel electrode comprises a first-lengthwise periphery that overlaps a first-adjacent data line to form a first overlapping portion, and a second-lengthwise periphery that overlaps a second-adjacent data line to form a second overlapping portion. The first-lengthwise periphery and the second-lengthwise periphery have an identical square-wave profile, and the square-wave profile is formed by connecting a square protrusion and a square indentation in sequence. The square protrusion of the first-lengthwise periphery corresponds in position to the square indentation of the second-lengthwise periphery, and the square indentation of the first-lengthwise periphery corresponds in position to the square protrusion of the second-lengthwise periphery.
REFERENCES:
patent: 5745207 (1998-04-01), Asada et al.
patent: 6411357 (2002-06-01), Ting et al.
patent: 6522379 (2003-02-01), Ishihara et al.
Liu Hsiang-Lung
Wu Hsu-Ho
Hannstar Display Corp.
Thomas Kayden Horstemeyer & Risley
Ton Toan
LandOfFree
Pixel electrode structure for a liquid crystal display with... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Pixel electrode structure for a liquid crystal display with..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Pixel electrode structure for a liquid crystal display with... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3359779