Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2000-10-10
2003-04-01
Kim, Robert H. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S102000
Reexamination Certificate
active
06542210
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims the priority benefit of Taiwan application serial no. 89118903, filed Sep. 15, 2000.
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to liquid crystal display device. More particularly, the present invention relates to a structure of a liquid crystal display.
2. Description of Related Art
Displaying device is very common in the daily life. Especially, a displaying device cannot be absent in a television set or a computer system, where the displaying device is used to display image to the user. In general, if the displaying device is designed by the cathode-ray tube (CRT) manner, it occupies a large space, causing inconvenient use. For example, a notebook cannot be equipped with a CRT display. In these considerations, a panel displaying device with matrix of pixels is successfully developed. The panel displaying device includes, for example, a liquid crystal display (LCD), or a thin film transistor (TFT) liquid crystal display (TFT-LCD).
For a LCD, particularly to a TFT-LCD, the vision quality for images or words may change from different view direction. If the view angle is too large, the vision quality, such as the illumination contrast ratio, is degraded. A wide view technology is always important to improve the vision quality of the TFT LCD, in which a wide view film is the most efficient way in the wide view technology to improve the vision quality.
FIG. 1A
is a top view, schematically illustrating a relation between the LCD and the view angle.
FIG. 1B
is a side view, schematically illustrating the relation between the view angle and the LCD in
FIG. 1A. A
wide view film
110
is put on a LCD device
100
. The images on the LCD device can be viewed from a left
50
, right
52
, up
56
, and down
54
. The current wide view film
110
allows the image to be viewed by a view angle of 60 degrees, and the contrast ratio (CR) at that angle is about CR=10. The up view angle is about 30 degrees and the lower view angle is about 60 degrees. In this range of view angle, it is still insufficient.
In the LCD, the liquid crystal means a material of which the material structure is between a crystal and a liquid. When the liquid crystal material is applied with an external electric field, the liquid crystal molecules are affected by the electric field and the alignment structure of the liquid crystal molecules are changed. Due to the difference of liquid crystal alignment, the polarization direction of passing light is rotated. By making use of these properties, the liquid crystal material can be used as a displaying device. Since the LCD has various advantages of small weight, small thickness, low driving voltage, small volume, and low power consumption, LCD has wide applications. However, how to improve the vision quality is an essential issue to continuously develop.
The working principle of the LCD is schematically shown in FIG.
2
. In
FIG. 2
, theory of a twisted nematic (TN) LCD is, for example, shown. A liquid crystal layer
108
is confined between a glass plate
106
. A polarizing layer
104
is arranged on the outer side of the glass plate
106
at the both sides, but the polarization direction is vertical to each other. For the left situation in
FIG. 2
, the incident light is polarized into one direction after the light travels the polarizing plate
104
. The polarized incident light then enters the liquid crystal layer
108
. When the liquid crystal layer
108
is not applied with a bias, the liquid crystal molecules are twisted by 90 degrees from one side to the other side. Since the polarizing plates
104
for the two sides have vertical polarization direction, the incident light can pass the lower polarizing plate
104
.
If the liquid crystal layer
108
is applied with bias, such as the right situation in
FIG. 2
, the liquid crystal molecules is changed to a line structure. In this manner, the polarization direction of the incident light does not change. Due to the lower polarizing plate
104
has the 90 degree shift to the upper polarizing plate
104
, the incident light can not pass the lower polarizing plate when the liquid crystal material is applied with bias.
A TFT LCD typically include a TFT matrix to form the image pixel. The TFT's are formed by semiconductor technology to form a TFT matrix with respect to the desired pixel matrix. By controlling the bias produced by the TFT, the bias of TFT can control the TN LCD to decide whether the light can travel through or not. In the foregoing, the working principle of the TFT LCD is described. If the displaying image is a color image, the color effect can also by achieved by control of the applied bias. These technology is well known by the skilled artisans. No further description is made here.
For a LCD, the upper polarizer and the lower polarizer with polarization directions vertical to each other are necessary. However, when the light travels through the polarizer, an additional phase angle usually produces. This causes an optical leakage, and consequently causes the poor contrast ratio at the wide angle. Since the wide view technology is the essential method for the TFT LCD to have better image quality, the wide view quality is the key factor to decide whether the wide view technology is successful or not.
FIG. 3
is a drawing, schematically illustrating a conventional structure of a LCD. In
FIG. 3
, a liquid crystal layer
112
is located at the middle. The arrows on the liquid crystal layer
112
is the rubbing direction of a glass substrate, that is, the aligning direction of the liquid crystal molecules. On both sides of the liquid crystal layer
112
, each side has a wide view (WV) film
110
and a polarizer
104
. The arrow directions on the polarizers
104
are the polarizing directions. As shown in
FIG. 3
, the polarization directions on the polarizers
104
are vertical to each other. The principle directions of the WV films
110
are also vertical to each other.
As the light travels through the upper polarizer
104
, only the light component polarized at 45 degrees can transmit through the upper polarizer
104
. Under proper control of bias on the liquid crystal layer
112
, polarization of the light is rotated to match to the lower polarizer
104
. Then, the light passes. Usually, a polarizer always has additional phase deviation from polarization direction, causing optical leakage, and consequently causing the poor quality of the image.
FIG. 5
also shows a structure of WV device, which is fabricated by a manner known as a TAC less technology. In
FIG. 5
, the WV structure includes a first adhesion layer
200
. On the adhesion layer
200
, it sequentially has a WV film
202
, a first TAC substrate
204
, a second adhesion layer
206
, a second TAC substrate
208
, a PVS polarization base film
210
, a third TAC substrate
212
, and a protection film
214
. This is a conventional WV structure. There is no a retardation phase plate. The PVA polarization base film
210
can also serve as a polarizer with polarization direction.
SUMMARY OF THE INVENTION
The invention provides a structure of LCD, of which a retardation phase plate is included at the front side or back side of the WV film, so as to delay the polarized light transmitting from the polarizer. Thereby, optical leakage is effectively reduced, and the contrast ratio is effectively increased.
The invention provides a structure of LCD, the structure of LCD included a first polarizer with a first polarization direction along a first angle. A first retardation phase plate is located behind the first polarizer. The first retardation phase plate is used to produce a retardation effect. The retardation direction is the same as the first angle. A first WV film is behind the first retardation phase plate. The WV film is operated along a second angle vertical to the first angle. A liquid crystal layer is located behind the WV film
110
. The crystal rubbing direction of the liquid crystal layer is along the second direction. A second WV film i
Au Optronics Corp.
Duong Thoi V
J. C. Patents
LandOfFree
Structure of liquid crystal display does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Structure of liquid crystal display, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Structure of liquid crystal display will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3069744