Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2001-11-01
2004-10-05
Weiss, Howard (Department: 2814)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C257S059000, C257S072000
Reexamination Certificate
active
06801279
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a reflection type liquid crystal display and a method for manufacturing the same, and more specifically, to a reflection type liquid crystal display having a plurality of aligned micro lens and a method for manufacturing the same.
2. Description of the Related Art
In an information-oriented society these days, the role of an electronic display is becoming more important. All kinds of electronic displays are widely used in various industrial fields. As techniques of the electronic display field are continuously developed, various electronic displays having new functions are provided corresponding to diverse requirements of the information society.
Generally, electronic display device is an apparatus for visually transmitting information to a person. That is, an electronic display device can be defined as an electronic apparatus, which converts an electrical information signal output from various electronic equipment into a visually recognizable optical information signal. Also, it may be defined as an electronic apparatus serving as a bridge for connecting the person and the electronic equipment.
These electronic displays are classified into an emissive display in which the optical information signal is displayed by a light-emitting method, and a non-emissive display in which the signal is displayed by an optical modulation method such as light-reflecting, dispersing and interference phenomena, etc. As the emissive display called an active display, for example, there are a CRT (Cathode Ray Tube), a PDP (Plasma display panel), an LED (Light emitting diode) and an ELD (Eelectroluminescesnt Display), etc. The non-emissive display is called a passive display, an LCD (Liquid Crystal Display) and an EPID (Eelectrophoretic Image Display), etc fall in that category.
The CRT has been used in an image display such as a television receiver and a monitor, etc., over the longest period of time. The CRT has the biggest market share because of its high displaying quality and low price, but also has many disadvantages such as heavy weight, large volume and high power consumption.
Meanwhile, as various kinds of electronic devices are small in size and lighter in weight and use lower voltage and less power in driving the electronic devices due to rapid advancement of semiconductor technologies, demands have been increased for a flat panel type display being slimmer and lighter property as well as lower driving voltage and consuming less power.
Among flat panel type displays, the LCD is much slimmer and lighter than any other displays and it requires lower driving voltage and less power consumption. Also, the LCD has the displaying quality similar to the CRT. Therefore, the LCD is widely used in various electronic devices. Further, since the LCD can be manufactured relatively easily, its application area becomes wider.
The LCD is classified into a transmissive type LCD, which displays an image using an external light source and a reflection type LCD, which displays the image using ambient lights instead of the external light source.
The reflection type LCD has an advantage because it consumes less power and shows an excellent display at outdoor compared to the projection type LCD. Further, the reflection type LCD is thin and light because an additional light source such as backlight device is not required.
However, the current reflection type LCD shows darker image than its competition and fails to show a high resolution and multicolor images. Therefore, the reflection type LCDs are restrictively used for a product that requires a simple pattern display, such as, numbers or simple characters.
To use a reflection type LCD for various electronic displays, a high resolution and a multicolor display together with an enhanced reflection luminance are necessary. In addition, a proper brightness, rapid response time and higher contrast are necessary.
In current reflection type LCDs, two technologies are combined to enhance the brightness. One is enhancing the reflection efficiency of the reflective electrode, and the other is achieving an ultra high aperture ratio.
There is disclosed a method for enhancing the reflection efficiency by forming bumps to a reflective electrode in U.S. Pat. No. 5,610,741 (issued to Naofumi Kimur) entitled “Reflection type liquid crystal display device with bumps on the reflector.”
FIG. 1
is a partial plan view of the reflection type LCD device provided in the '741 U.S. patent and
FIG. 2
is a sectional view of the reflection type LCD device of FIG.
1
.
Referring to FIG.
1
and
FIG. 2
, the reflection type LCD device has a first substrate
10
, a second substrate
15
disposed facing the first substrate
10
and a liquid crystal layer
20
interposed between the first substrate
10
and the second substrate
15
.
The first substrate
10
includes a first insulating substrate
30
on which a plurality of gate bus wirings
25
are formed. Gate electrodes
35
branch off from the gate bus wirings
25
. Additionally a plurality of source bus wirings
40
are provided so as to cross the gate bus wirings
25
. The source bus wirings are insulated from the plurality of gate bus wirings
25
by means of an insulating layer. Source electrodes
45
branch off from the source bus wirings
40
.
Reflective electrodes
50
are formed between the first substrate
10
and the liquid crystal layer
20
and are disposed in a plurality of rectangular regions formed by crossing the plurality of gate bus wirings
25
and the plurality of source bus wirings
40
.
The reflective electrode
50
is connected with thin film transistor (TFT)
55
formed on the first substrate
10
. The TFT
55
serves as a switching device with the gate bus wiring
25
and the source bus wiring
40
.
A plurality of dents
70
and
71
are provided on the surface of the reflective electrode
50
, making the surface rugged.
The plurality of dents
70
and
71
are irregularly arranged on the entire surface. The reflective electrode
60
and a drain electrode of the TFT device
55
are connected to each other through a contact hole
65
.
The gate bus wiring
25
and the gate electrode
35
are formed on the first insulating substrate
30
made of, for example, glass by depositing tantalum (Ta) film using a sputtering method and patterning the deposited Ta film using a photolithography method.
Next, the gate insulating film
75
is formed to cover the gate bus wiring
25
and the gate electrode
35
. The gate insulating film
75
is formed, for example, to a thickness of 4000 Å by depositing a SiNx film through a plasma CVD (Chemical Vapor Deposition) method.
A semiconductor layer
80
of amorphous silicon (a-Si) is formed on the gate insulating film
75
over the gate electrode
35
. Contact layers
85
and
90
of n+ type impurity-doped a-Si layer are formed on the semiconductor layer
80
.
Subsequently, molybdenum (Mo) film is formed on the first insulating substrate
30
to cover the resultant structure formed in the above-mentioned manner and then the Mo film is patterned to form a source bus wiring
40
, a source electrode
45
and a drain electrode
60
. In such a manner, TFT
55
is manufactured.
On the entire surface of the insulating substrate
30
in which the TFT device
55
was formed are formed an organic insulating film
95
and a reflective electrode
50
each having a rugged surface.
FIGS. 3A
,
3
B and
3
C are sectional views showing the steps of forming the organic insulating film and the reflective electrode in the device shown in FIG.
2
.
Referring to
FIG. 3A
, a resist film
100
is formed on the surface of the first insulating substrate
30
to cover the TFT device
55
by a spin coating method. After that, the resist film
100
is pre-baked.
Next, a mask
110
where a light transmitting region
105
and a light shielding region
106
are formed in a predetermined pattern is arranged over the applied resist film
100
and exposure and development treatments are carried out. Thereby, bumps
Choi Bang-Sil
Jang Yong-Kyu
Kim Jae-Hyun
Uh Kee-Han
McGuireWoods LLP
Samsung Electronics Co,. Ltd.
Weiss Howard
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