Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1999-11-03
2002-10-15
Parker, Kenneth (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
Reexamination Certificate
active
06466286
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present-invention relates to a reflectance-type liquid crystal display apparatus, and more particularly, to a reflecting substrate of a reflectance-type liquid crystal display apparatus.
2. Description of the Related Art
A liquid crystal display (LCD) apparatus has been widely used as a display for a portable television and a notebook computer. Liquid crystal display apparatuses are classified into two types. One type of LCD apparatus is a transmitting-type which uses a backlight as a light source, and the other type of LCD apparatus is a reflectance-type liquid crystal display device using an external light source such as sunlight and an indoor lamp for the required light source.
It is hard to decrease the weight, the volume, the cost and the power consumption of the transmitting-type LCD because of the need to include the backlight. Accordingly, a lot of research and product development have been focused on improving the reflectance-type LCD.
Conventionally, the reflectance-type LCD uses a reflecting substrate having an uneven reflecting surface to enlarge the viewing angle range of the user.
FIG. 1
is a sectional view showing a conventional reflectance-type LCD
10
, which includes a substrate
1
, a gate electrode
5
, a gate bus line (not illustrated), a gate pad electrode
9
, a cladding electrode
6
, a gate insulating layer
2
, a semiconductor layer
4
, ohmic contact layers
7
, a source electrode
3
, a drain electrode
8
, a passivation layer
12
, an uneven insulating layer
13
, and a reflecting electrode
11
.
The cladding electrode
6
is formed on the gate electrode
5
, the gate bus line, and the gate pad electrode
9
which are provided on the substrate
1
. The gate electrode
5
, the gate bus line, and the gate pad electrode
9
are generally made of Al, which is not expensive and has a high conductivity. However, Al has a very low heat-resistance, and thereby hillocks are generated on the Al metal layer during a heat-treatment process.
The cladding electrode
6
having a highly heat-resistant metal such as Cr and Mo is formed on the electrodes of Al to prevent the hillocks. However, in this case, the manufacturing cost is increased and the manufacturing process is complicated because of need to form the cladding electrode
6
.
The reflecting electrode
11
is generally made of Al having a high reflectance and a high conductivity. However, the reflecting electrode
11
must also be heat-treated and therefore also will likely have the hillock problem.
An Al alloy including the highly heat-resistant metal can be used for the reflecting electrode to prevent hillocks. However, the reflecting electrode made of Al alloy has low conductivity and low reflectance.
SUMMARY OF THE INVENTION
To overcome the problems described above, preferred embodiments of the present invention provide a reflecting substrate of a reflectance-type liquid crystal display apparatus, wherein hillocks are prevented from occuring on a reflecting electrode and a gate electrode, and the manufacturing process is simple.
According to a preferred embodiment of the present invention, a reflectance-type liquid crystal display apparatus includes a substrate, a gate electrode, a gate bus line, and a gate pad electrode which are provided on the substrate and made of aluminum neodymium, an insulating layer on the gate electrode and the gate bus line, and a reflecting electrode on the insulating layer, the reflecting electrode being made of aluminum neodymium.
Preferred embodiments of the present invention preferably are such that the gate electrode, the gate bus line, the gate pad electrode, and the reflecting electrode are formed of aluminum neodymium(AlNd).
The gate electrode, the gate bus line, and the pad electrode made of AlNd according to preferred embodiments of the present invention have a high conductivity as well as having a structure which prevents the occurrence of hillocks. The manufacturing process using AlNd for the electrodes is simple and has a low manufacturing cost in comparison with the prior art which requires the process of forming the cladding electrode to prevent hillocks.
The reflecting electrode made of AlNd according to preferred embodiments of the present invention has a high reflectance and a high conductivity while also being arranged to prevent the hillock problem.
Other features, advantages and elements of the present invention will be described in more detail below with reference to the attached drawings.
REFERENCES:
patent: 5514909 (1996-05-01), Yamamoto et al.
patent: 5526149 (1996-06-01), Kanbe et al.
patent: 5691782 (1997-11-01), Nishikawa et al.
patent: 5811835 (1998-09-01), Seiki et al.
patent: 5903326 (1999-05-01), Lee
patent: 6154264 (2000-11-01), Koide et al.
patent: 11-258 (1999-09-01), None
Takayama et al, Low resistivity AI-RE (RE=La, Pr, Nd) alloy thin films with high thermal stability for thin film tranistro interconnects), J Vac Sci Technol B 14(5), 1996.*
Onishi et al, “Effects of Nd content in AI thin films on hillock formation” J Vac Sci Technol B 15(4), 1997.
Birch & Stewart Kolasch & Birch, LLP
LG. Philips LCD Co. Ltd.
Parker Kenneth
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