Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2002-09-26
2004-01-27
Ton, Toan (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S064000, C349S043000, C349S106000, C349S044000
Reexamination Certificate
active
06683667
ABSTRACT:
This application claims the benefit of Korean Patent Application No. 2001-87595, filed on Dec. 28, 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 a LCD device having a scattering layer and a fabricating method thereof.
2. Discussion of the Related Art
Flat panel display (FPD) devices having a small size, lightweight, and low power consumption have been a subject of recent research in the advent of the information age. FPD devices may be classified into two types depending on whether the device emits or receives light. One type is a light-emitting type display device that emits light to display images, and the other type is a light-receiving type display device that uses an external light source to display images. Plasma display panels (PDPs), field emission display (FED) devices, and electroluminescent (EL) devices are examples of the light-emitting type display devices. Liquid crystal display (LCD) devices are examples of the light-receiving type display device. Among many kinds of FPD devices, LCD devices are widely used for notebook computers and desktop monitors because of their excellent characteristics of resolution, color display and display quality.
Generally, LCD devices include an upper substrate and a lower substrate facing each other with liquid crystal molecules interposed therebetween. Each substrate has an electrode on the inner surface thereof. An electric field is generated by applying a voltage to the electrodes, thereby driving the liquid crystal molecules to display images in accordance with the light transmittance.
Since LCD devices do not emit light, an additional light source is necessary. Accordingly, LCD devices display images by disposing a backlight at a backside thereof and transmitting light from the backlight. Here, electric field-generating electrodes of LCD devices are usually made of a transparent conductive material and the two substrates are usually transparent. This kind of LCD device is referred to as a transmission type LCD device or a transmissive LCD device. Even though a transmissive LCD device can display bright images under a dark environment due to an artificial light source such as a backlight, the transmissive LCD device has a disadvantage of high power consumption due to the backlight.
To remedy this disadvantage, a reflective (or reflection type) LCD device is suggested. The reflective LCD device displays images by reflecting external natural or artificial light, thereby having a low power consumption compared with the transmissive LCD device. In the reflective LCD device, a lower electric field-generating electrode is made of a conductive material having high reflectance and an upper electric field-generating electrode is made of a transparent conductive material so that external light can be transmitted through the upper electric field-generating electrode.
FIG. 1
is a schematic cross-sectional view of a related art reflective LCD device. In
FIG. 1
, first and second substrates
11
and
21
are spaced apart from each other. A gate electrode
12
and a gate line (not shown) are formed on an inner surface of the first substrate
11
and a gate insulating layer
13
is formed on the gate electrode
12
. An active layer
14
, an ohmic contact layer
15
a
and
15
b,
and source and drain electrodes
16
b
and
16
c
are sequentially formed on the gate insulating layer
13
over the gate electrode
12
and constitutes a thin film transistor (TFT) “T” with the gate electrode
12
. A data line
16
a
of the same material as the source and drain electrodes
16
b
and
16
c
is also formed on the gate insulating layer
13
and connected to the source electrode
16
b.
The data line
16
a
crosses the gate line (not shown), thereby defining a pixel region. Next, a passivation layer
17
of an organic material is formed on the data line
16
a,
and the source and drain electrodes
16
b
and
16
c.
The passivation layer
17
covers the TFT “T” and has a contact hole
17
a
exposing the drain electrode
16
c.
A pixel electrode
18
is formed on the passivation layer
17
at the pixel region and connected to the drain electrode
16
c
through the contact hole
17
a.
Here, the pixel electrode
18
of a conductive material such as metal covers the TFT “T” and overlaps the data line
16
a
to improve an aperture ratio. Further, the passivation layer
17
is made of an organic material having a low dielectric constant to prevent signal interference between the pixel electrode
18
and the data line
16
a.
A black matrix
22
is formed on an inner surface of the second substrate
21
. A color filter layer
23
a,
23
b
and
23
c
having red, green and blue colors are formed on the black matrix
22
. A common electrode
24
of a transparent conductive material is formed on the color filter layer
23
a,
23
b
and
23
c.
Here, one color of the color filter layer
23
a,
23
b
and
23
c
corresponds the pixel electrode
18
and the black matrix covers an edge of the pixel electrode
18
. Since the pixel electrode
18
of an opaque material covers the TFT “T”, the black matrix
22
can overlap only the edge of the pixel electrode
18
.
A liquid crystal layer
30
is interposed between the pixel electrode
18
and the common electrode
24
. Further, orientation films (not shown) that determine an initial alignment state of liquid crystal molecules are formed on the pixel electrode
18
and the common electrode
24
, respectively.
As mentioned above, the reflective LCD device displays images by reflecting an incident light at the pixel electrode of a high reflective material. Therefore, the reflective LCD device can operate for a longer time without exchanging a battery because power consumption is reduced.
Since the related art reflective electrode has a flat surface, light is reflected as if the reflective electrode is a mirror. This phenomenon is referred to as a mirror reflection. Therefore, the brightness is higher only along any reflection direction depending on Snell's Law of Refraction. When incident light is reflected on a reflective display according to a position of a light source, the brightness is low along a normal direction of an LCD device. Another phenomenon that occurs is the light glare effect. This happens when a high-intensity external light source is reflected on a liquid crystal display panel. The displayed image is poor due to the glare that occurs as viewed by an observer due to the reflection of light. To increase the brightness along the normal direction and decrease the light glare effect on an LCD device, a reflective electrode of an uneven shape and a front scattering film are suggested.
FIG. 2
is a schematic cross-sectional view of a related art reflective LCD device using a front scattering film. In
FIG. 2
, a front scattering film
40
is disposed on an outer surface of a second substrate
21
. However, an image blurring phenomenon due to back scattering at the front scattering film
40
degrades a display efficiency of the reflective LCD device.
FIG. 3
is a schematic cross-sectional view of a related art reflective LCD device using a reflective plate of an uneven shape. In
FIG. 3
, a surface of a pixel electrode
18
that is a reflective plate has an uneven shape by forming a passivation layer
17
that has an uneven surface. Accordingly, a brightness along a normal direction of the reflective LCD device increases by changing a reflection angle of light.
A slanting angle of the uneven shape may be about 10° so that light can be reflected along the normal direction of the reflective LCD device. However, a process of forming the uneven shape is a complicated process and has a low repeatability. The uneven shape of the passivation layer is initially formed to have a square shape. Subsequently, the passivation layer is cured to form a round shape. Uniform curing of the entire area of the passivation layer is d
Jin Hyun-Suk
Kang Won-Seok
LG. Philips LCD Co. Ltd.
McKenna Long & Aldridge LLP
Ton Toan
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