Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1997-11-20
2004-07-13
Ton, Toan (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S043000, C438S030000
Reexamination Certificate
active
06762813
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor device having an insulated gate structure using a crystalline silicon film disposed on an insulating substrate of glass, quartz or the like, for example, a thin film transistor (TFT), a thin film diode (TFD), and a thin film integrated circuit using the thin film elements, especially a thin film integrated circuit for a passive matrix type liquid crystal display device and a thin film integrated circuit for an active matrix type liquid crystal display device, and also relates to a method of manufacturing the same.
2. Description of the Related Art
In recent years, there has been vigorously carried out studies on an active matrix type liquid crystal display device in which thin film transistors are formed in a matrix form on an insulating substrate of glass, quartz or the like, and the TFTs are used as switching elements.
Also, an attention has been paid to an active matrix type liquid crystal display device in which an active matrix circuit (also called a pixel circuit or pixel matrix circuit) and a peripheral drive circuit (also called a driver circuit) are integrated on the same insulating substrate. This structure is called a peripheral drive circuit integration type.
A conventional active matrix type liquid crystal display device uses transparent electrodes in which electrodes for driving a liquid crystal layer are formed on two substrates faced to each other. A liquid crystal is sealed between the two substrates, and the direction of an electric field applied to the liquid crystal is made substantially perpendicular to the surface of the substrate. The liquid crystal device is realized by changing the intensity of the electric field so that the direction of orientation of liquid crystal molecules generally having a rod shape are changed so as to be parallel to the substrate or perpendicular to the substrate. Generally, in this case, since light is made to be modulated by using an optical anisotropy as one of features of the liquid crystal material, a polarizing plate is disposed in the device so that incident light is made linearly polarized light.
However, in the liquid crystal electro-optical device having such an operation method, there is observed such a phenomenon that although the state of display is normal when the display surface is seen from the direction perpendicular thereto, the display is dark and becomes blurred when the display surface is seen from the direction at an angle thereto, and further, color is changed when the display is colored.
In order to solve such a problem, there is a method (IPS mode) in which the direction of an electric field applied to a liquid crystal layer is made parallel to the surface of a substrate.
In such an electro-optical device, since switching is carried out while a longitudinal axis of a liquid crystal molecule is kept parallel to the substrates, the change of optical characteristics of the liquid crystal due to an angle of visual field is small.
Thus, leak of light, lowering of contrast and the like due to the angle of visual field are smaller than a conventional TN or STN system.
There is known a structure of an electrode of this IPS mode as shown in
FIG. 17
in which a comb-shaped electrode is formed on one substrate.
However, there is a problem that when the comb-shaped electrode is used, a wiring pattern is made minute and complicated in a pixel element, so that productivity becomes inferior.
Also, since the shape of the electrode is complicated, an electric field applied to a liquid crystal layer becomes complicated.
Further, light is shaded by the comb-shaped electrode, so that an effective area (opening rate) through which light can passes, becomes extremely low. Thus, only a dark display can be realized, and it can not be put into practical use.
SUMMARY OF THE INVENTION
The present invention has been made to overcome the above described problems, and an object of the invention is therefore to provide a liquid crystal display device of peripheral drive circuit integration type which has high contrast even if a transparent electrode is not provided, can be manufactured through simple steps, can be mass-produced, has a large opening rate, and is bright. Another object thereof is to provide a method of manufacturing the same.
In order to solve the above problems, according to the present invention, the following means are adopted.
According to a first aspect of the present invention, as shown in
FIG. 1
, a liquid crystal display device is characterized by comprising: a pair of substrates, at least one thereof being transparent; a liquid crystal layer placed between the pair of substrates; a plurality of pixels arranged in a matrix form on one thereof; a pixel electrode
108
and common electrodes
110
and
111
existing in the same layer; and common lines
103
and
104
existing in a layer different from the common electrodes through an insulating layer and being connected to the common electrodes through contact holes, an electric field being applied between the pixel electrode and the common electrodes substantially parallel to the surface of the substrate so as to control the state of orientation of liquid crystal molecules so that light can be modulated.
In the above structure, the liquid crystal display device is an active matrix type liquid crystal display device in which a thin film transistor is disposed for each of the pixels, and the thin film transistor includes a pixel electrode
108
, gate lines
102
and
105
connected to a scanning line, and source lines
106
and
107
connected to a signal line.
In the above structure, the liquid crystal display device is a passive matrix type liquid crystal display device driven in a passive manner.
In the liquid crystal display device, the common electrodes
110
and
111
, and the pixel electrode
108
are parallel to each other, exist in the same layer as shown in
FIG. 2
, and are made of the same material and by the same steps.
In the liquid crystal display device, the common electrodes and the pixel electrode are made of aluminum, metal mainly containing aluminum, silicon, or a laminated layer of titanium and aluminum.
In the liquid crystal display device, the common lines
103
and
104
and the gate lines
102
and
105
exist in the same layer as shown in
FIG. 2
, and are made of the same material and by the same steps.
According to a second aspect of the present invention, as shown in
FIG. 3
, a liquid crystal display device is characterized by comprising: a pair of substrates, at least one thereof being transparent; a liquid crystal layer placed between the pair of substrates; a plurality of pixels arranged in a matrix form on one thereof; a pixel electrode
108
and common electrodes
110
and
111
existing in the same layer; a common line existing in a layer different from the common electrodes through an insulating layer and being connected to the common electrodes through contact holes; and a flattened film
230
disposed on the common electrodes and the pixel electrode, an electric field being applied between the pixel electrode and the common electrodes substantially parallel to the surface of the substrate so as to control the state of orientation of liquid crystal molecules, so that light can be modulated.
In the liquid crystal display device, the flattened film
230
disposed on the common electrodes and the pixel electrode is formed of an organic material film made of polyimide or the like, an inorganic material film made of silicon nitride, silicon oxide or the like, or a laminated film thereof.
Also, as shown in
FIG. 1
, a liquid crystal display device is characterized by comprising: a pair of substrates, at least one thereof being transparent; a liquid crystal layer placed between the pair of substrates; a plurality of pixels arranged in a matrix form on one thereof; and a pixel electrode
108
placed between a pair of common electrodes
110
and
111
in one pixel, an electric field being applied between the pixel electrode and the
Hirakata Yoshiharu
Kuwabara Hideaki
Otsuka Kenji
Yamazaki Shunpei
Zhang Hongyong
Duong Tai
Fish & Richardson P.C.
Semiconductor Energy Laboratory Co,. Ltd.
Ton Toan
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