Liquid crystal cells – elements and systems – Particular excitation of liquid crystal – Electrical excitation of liquid crystal
Reexamination Certificate
2002-07-25
2004-10-12
Chowdhury, Tarifur R. (Department: 2871)
Liquid crystal cells, elements and systems
Particular excitation of liquid crystal
Electrical excitation of liquid crystal
C349S042000, C349S104000, C349S106000, C349S191000
Reexamination Certificate
active
06803975
ABSTRACT:
The present invention claims the benefit of Korean Patent Application No. 2001-45800, filed in Korea on Jul. 30, 2001, 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 liquid crystal display (LCD) device, and more particularly, to an array substrate having color filters for use in the LCD device and a manufacturing method thereof.
2. Discussion of the Related Art
In general, since flat panel display devices are thin, low weight, and have low power consumption, they are increasingly being used for displays of portable devices. Among the various types of flat panel display devices, liquid crystal display (LCD) devices are widely used for laptop computers and desktop monitors because of their superiority in resolution, color image display, and display quality.
LCD devices use the optical anisotropy and polarization properties of liquid crystal molecules to produce a predetermined image. Liquid crystal molecules have a definite orientation that results from their peculiar characteristics. The specific orientation can be modified by an electric field that is applied across the liquid crystal molecules. In other words, electric fields applied across the liquid crystal molecules can change the orientation of the liquid crystal molecules. Due to optical anisotropy, incident light is refracted according to the orientation of the liquid crystal molecules.
Specifically, the LCD devices have upper and lower substrates with electrodes that are spaced apart and face each other, and a liquid crystal material is interposed therebetween. Accordingly, when a voltage is applied to the liquid crystal material by the electrodes of each substrate, an alignment direction of the liquid crystal molecules is changed in accordance with the applied voltage to display images. By controlling the applied voltage, the LCD device provides various transmittances for rays of light to display image data.
The lower substrate, commonly referred to as an array substrate, includes switching elements, such as thin film transistors (TFTs) and pixel electrodes. The thin films for the TFTs on the lower substrate are usually formed by repetitive photolithography. The upper substrate, commonly referred to as a color filter substrate, usually includes a common electrode and color filters. The color filters have red (R), green (G) and blue (B) sub-color filters that are alternately disposed on the upper substrate. The color filters are formed of organic substances and made by a method, such as pigment dispersion, dyeing process or electrostatic painting.
FIG. 1
is a schematic cross-sectional view showing a pixel of a related art liquid crystal display (LCD) panel. As shown in
FIG. 1
, the related art LCD panel includes a first substrate
11
, a second substrate
21
and a liquid crystal layer
30
. The upper and lower substrates
11
and
21
are spaced apart from each other, and the liquid crystal layer
30
is interposed therebetween. The upper and lower substrates
11
and
21
are often referred to as an array substrate and a color filter substrate, respectively.
A gate electrode
12
is disposed on a front surface of a first substrate
11
, and a gate insulation layer
13
is formed to cover the gate electrode
12
. The gate electrode
12
is made of a conductive material, such as metal, and the gate insulation layer
13
is made of a insulating material, such as silicon nitride (SiN
x
) or silicon oxide (SiO
2
). An active layer
14
that is made of amorphous silicon is disposed on the gate insulation layer
13
, especially over the gate electrode
12
. First and second ohmic contact layers
15
a
and
15
b
, which are made of doped amorphous silicon, are disposed on the active layer
14
. Source and drain electrodes
16
a
and
16
b
are formed on the first and second ohmic contact layers
15
a
and
15
b
, respectively. The source and drain electrodes
16
a
and
16
b
are formed of a conductive material, such as metal. Thus, a thin film transistor (TFT) T on the first substrate
11
includes the gate electrode
12
, the active layer
14
, the ohmic contact layers
15
a
and
15
b
, and the source and drain electrodes
16
a
and
16
b
. Although not shown in
FIG. 1
, the gate electrode
12
is connected to a gate line (not shown), and the data electrode
14
is connected to a data line (not shown). The gate and data lines cross each other so as to define a pixel region. A passivation layer
17
is formed on the gate insulation layer
13
and on the source and drain electrodes
16
a
and
16
b
to cover the TFT T. An organic material, such as benzocyclobutene (BCB), or an inorganic material, such as silicon nitride or silicon oxide, is used for the passivation layer
17
. The passivation layer
17
has a drain contact hole
17
c
therethrough to expose a portion of the drain electrode
16
b
. On the passivation layer
17
, a pixel electrode
18
that is made of a transparent conductive material is formed such that the pixel electrode
18
contacts the drain electrode
16
b
through the drain contact hole
17
c.
Meanwhile, as mentioned before, the second substrate
21
is spaced apart from the first substrate
11
over the TFT T. On the rear surface of the second substrate
21
, a black matrix
22
is disposed in a position corresponding to the TFT T of the first substrate
11
. Although it is not clearly shown in
FIG. 1
, the black matrix
22
is actually formed on the whole surface of the second substrate
21
and has an opening that corresponds to the pixel electrode
18
of the first substrate
11
. The black matrix
22
prevents light leakage in the LCD panel except for a portion for the pixel electrode
18
. The black matrix
22
protects the TFT T from the light such that the black matrix
22
prevents the occurrence of photo current in the TFT T. Color filters
23
a
and
23
b
are formed on the rear surface of the second substrate
21
to cover the black matrix
22
. Each of the color filters
23
a
and
23
b
has one of the red, green and blue colors. The red, green and blue color filters are alternately arranged on the second substrate
21
, and each of the red, green and blue color filters corresponds to one pixel region where the pixel electrode
18
is located. A common electrode
24
that is made of a transparent conductive material is disposed on the color filters
23
a
and
23
b
all over the second substrate
21
. The liquid crystal layer
30
is interposed between the first and second substrates
11
and
21
, specifically between the pixel electrode
18
and the common electrode
24
.
In the conventional LCD panel mentioned above, the pixel electrode has a one-to-one correspondence with one of the color filters. Namely, after forming the array substrate and the color filter substrate, respectively, the color filter substrate having the color filters is arranged over the array substrate in order to let one pixel electrode correspond to one color filter. However, when arranging the second substrate to the first substrate or vice versa, misalignment can occur between the first substrate and the second substrate, thereby causing malfunction such as light leakage in the LCD panel. To overcome this problem, the black matrix on the second substrate is enlarged. However, in this case of enlarging the black matrix, the aperture ratio of the liquid crystal panel is lessened.
Therefore, the color filters are formed on the array substrate (i.e., the first substrate) to prevent misalignment between the first substrate and the second substrate, thereby reducing the black matrix size and increasing the aperture ratio of the LCD panel. When the color filters are formed between the substrate and the TFT (i.e., beneath the TFT), it is referred to as a Thin film transistor On Color filter (TOC) structure. At this time, only the black matrix and common electrode are formed on the second substrate without the color filters.
As mentioned hereinbefore, the array substrate includes many t
Kim Woong-Kwon
Park Seung-Ryul
Chowdhury Tarifur R.
LG. Phillips LCD CO., Ltd.
McKenna Long & Aldridge LLP
LandOfFree
Liquid crystal display panel and manufacturing method thereof does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Liquid crystal display panel and manufacturing method thereof, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Liquid crystal display panel and manufacturing method thereof will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3304402