Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2002-02-22
2004-02-24
Chowdhury, Tarifur R. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S043000, C349S113000, C349S106000, C349S138000
Reexamination Certificate
active
06697138
ABSTRACT:
This application claims the benefit of Korean Patent Application No. 2001-09027, filed on Feb. 22, 2001 in Korea, 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 transflective liquid crystal (CLC) display device and a method of manufacturing the same.
2. Discussion of the Related Art
Flat panel display devices, which have properties of being thin, and having low weight and low power consumption, have been required as the information age rapidly evolves. The flat panel display device may be classified into two types depending on whether it emits light or not. One is a light-emitting type display device that emits light to display images and the other is a light-receiving display device that uses an external light source to display images. Plasma display panels (PDPs), filed emission display (FED) devices and electro luminescence (EL) display devices are examples of the light-emitting type display devices and liquid crystal displays are an example of the light-receiving type display device. The liquid crystal display device is widely used for notebook computers and desktop monitors, etc. because of its superior resolution, color image display and quality of displayed images.
Generally, the liquid crystal display device has first and second substrates, which are spaced apart and facing each other. Each of the substrates includes an electrode and the electrodes of each substrate are positioned to face each other. A Liquid crystal is interposed between the first substrate and the second substrate. Voltage is applied to the liquid crystal through the electrodes of each substrate, and thus an alignment of the liquid crystal molecules is changed according the applied voltage to display images. Because the liquid crystal display device cannot emit light as described before, it needs an additional light source to display images.
The liquid crystal display device can be classified into two types depending on the type of the light source that is used. One is a transmissive liquid crystal display device and the other is a reflective liquid crystal display device. The transmissive liquid crystal display device displays a color image by irradiating artificial light from a back light, which is positioned behind a liquid crystal panel, to the liquid crystal and then controlling the amount of the light according to the alignment of the liquid crystal. The reflective liquid crystal display device displays a color image by controlling a transmittance of the light according to an alignment of the liquid crystal by reflecting ambient light or artificial light. Because the transmissive liquid crystal display device uses an artificial light source such as the back light, it can display a bright image in dark surroundings but it has a high power consumption. The reflective liquid crystal display device depends on ambient light or an external artificial light source for its light source and accordingly it has lower power consumption than the transmissive liquid crystal display device but it is not suitable for dark surroundings. Accordingly, the transflective liquid crystal display device, which has characteristics of both the transmissive liquid crystal display device and the reflective liquid crystal display device, has been suggested in the field.
FIG. 1
is a cross-sectional view of a conventional transflective liquid crystal display device. As shown in the figure, a pixel electrode
20
is formed on a first substrate
10
, referred to as an array substrate, that has a thin film transistor (not shown), i.e., a switching element. The pixel electrode
20
consists of a transmission electrode
21
and a reflection electrode
22
. A hole is formed in the reflection electrode
22
and the transmission electrode
21
is formed in the hole. The transmission electrode
21
is formed of transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO) that has a relatively high transmittance of light. Whereas, the reflection electrode
22
is formed of material such as aluminum (Al) that has a low electric resistance and a high reflectance.
A second substrate
30
, i.e., referred to as a color filter substrate, is positioned over the first substrate
10
maintaining a certain distance from the first substrate
10
. A color filter
40
, which corresponds to the pixel electrode
20
, is formed beneath the second substrate
30
. The color filter
40
includes sub-color-filters red (R), green (G), and blue (B) and each of the sub-color filters corresponds to each of the pixel electrode
20
. A common electrode
50
is formed beneath the color filter
40
using transparent conductive material. A black matrix (not shown) is positioned between the second substrate
30
and the color filter
40
to protect any leakage of light in an area other than the pixel. A liquid crystal layer
60
is positioned between the common electrode
50
and the pixel electrode
20
.
A first retardation film
71
and a second retardation film
72
are formed on the outer side of the first substrate
10
and the second substrate
30
respectively. The first retardation film
71
and the second retardation film
72
serve to change the polarization state of light. Because the first and second retardation films
71
and
72
have a phase difference of &lgr;/4, the first and second retardation films
71
and
72
change linear polarization into circular polarization and circular polarization into linear polarization. A lower polarizer
81
and an upper polarizer
82
are positioned on outer side of the first retardation film
71
and the second retardation film
72
, respectively. The light transmission axis of the upper polarizer
82
is perpendicular to the light transmission axis of the lower polarizer
81
. A back light
90
is positioned under the lower polarizer
81
and serves as a light source for a transmission mode. The transfective liquid crystal display device is designed on the basis of a reflection mode and thus when a voltage is not applied, the transmittance of the transmission mode is only one-half of the transmittance of the reflection mode. Accordingly, a transflective liquid crystal display device in which the transmittance of the transmission mode is controlled the same as the transmittance of the reflection mode by forming the thickness of a liquid crystal layer of the transmission mode thicker than the thickness of a liquid crystal layer of the reflection mode, has been suggested in the field. The transflective liquid crystal display device is manufactured through a series of process steps like the conventional liquid crystal display device. That is, the manufacturing process for the transflective liquid crystal display device includes a process for producing an array substrate, which includes a plurality of the thin film transistors and pixel electrodes thereon, a process for producing a color filter substrate, which includes the color filter and the common electrode, and a process for producing a liquid crystal cell, which includes such processes as an alignment of the two substrates, an injection of the liquid crystal and sealing and forming the polarizer. The alignment of the array substrate and the color filter substrate is performed as follows. A number of seal patterns are formed on one of the array substrate and the color filter substrate and a number of spacers are dispersed on one of the two substrates to maintain a distance between the two substrates. The two substrates then are aligned in such a way that each of the sub-color filters corresponds to each of the pixel electrode and finally the two substrates are assembled by a pressure hardening of the seal pattern. If a misalignment of the array substrate and the color filter substrate occurs during the alignment process, inferiorities such as a leakage of light may be generated. The width of the black matrix on the second substrate may be f
Ha Kyoung-Su
Yi Jong-Hoon
Birch & Stewart Kolasch & Birch, LLP
Chowdhury Tarifur R.
LG Phillips LCD Co., Ltd.
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