Liquid crystal cells – elements and systems – Particular excitation of liquid crystal – Electrical excitation of liquid crystal
Reexamination Certificate
1999-07-29
2002-05-21
Ton, Toan (Department: 2871)
Liquid crystal cells, elements and systems
Particular excitation of liquid crystal
Electrical excitation of liquid crystal
C349S138000
Reexamination Certificate
active
06392722
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an active matrix liquid crystal display device and particularly relates to a reflective type liquid crystal display device.
BACKGROUND OF THE INVENTION
In recent years, as such information and communication equipment as portable telephone, PHS (Personal Handy Phone System), PDA (Personal Digital Assistant) and the like springs into wide use, a required infrastructure has been in completion, thereby allowing anyone to access and send out information easily regardless of time and place.
Since such information and communication equipment is used in mobile applications, features such as being thin in size, light in weight and low in power consumption are required of a display system. Nowadays, the liquid crystal display device occupies a central position among such display systems. Among the variety of liquid crystal display devices, a reflective type liquid crystal display device requiring no back light is becoming a main-stream. A typical prior art active matrix reflective type liquid crystal display device is disclosed in Japanese Patent Application Unexamined Publication No. H08-160463.
A description is made on a typical prior art active matrix reflective type liquid crystal display device as follows:
An active matrix reflective type liquid crystal display device has a transparent substrate, many pixel electrodes disposed on the foregoing transparent substrate and non-linear elements to drive respective pixel electrodes.
As the non-linear element is used a thin film diode, a thin film transistor (referred to as TFT hereafter) or the like. These pixel electrodes and non-linear elements are arranged in a two-dimensional matrix pattern.
In the following description, a typical prior art active matrix reflective type liquid crystal display device uses a TFT as the non-linear element.
FIG. 6
shows an opening and a TFT element of a prior art active matrix reflective type liquid crystal display device, and FIG.
6
(
b
) shows a cross-sectional view of the above opening and TFT element and FIG.
6
(
a
) shows a plan view of the opening of FIG.
6
(
b
). In FIG.
6
(
a
), a depiction of a reflective pixel electrode
401
is omitted for easy recognition of the size of the opening.
A gate insulating film
408
is disposed on a glass substrate
410
.
A protective film
403
is disposed on the gate insulating film
408
. An interlayer insulating film
402
is disposed on the protective film
403
. The reflective pixel electrode
401
is disposed on the interlayer insulating film
402
. A TFT element
411
has a drain electrode
405
, a source electrode
406
, a semiconductor layer
407
and a gate electrode
409
.
By way of an opening
404
acting as a contact hole, the reflective pixel electrode
401
and the drain electrode
405
become conductive with each other.
In the structure as described above, the distance between the gate electrode
409
acting as a scanning line electrode and the reflective pixel electrode
401
can be shortened and further the distance between the source electrode
406
acting as a signal line electrode and the reflective pixel electrode
401
can be shortened. At the same time, a short circuit between the reflective pixel electrode
401
and the gate electrode
409
and between the reflective pixel electrode
401
and the source electrode
406
can be prevented from occurring by the interlayer insulating film
402
, thereby allowing the opening ratio to be increased by a large amount when compared with the case where no interlayer insulating film is used.
However, the prior art active matrix reflective type liquid crystal display device as described above has some problems as in the following:
For instance, with the prior art liquid crystal display device, the size of the opening
404
at the protective film
403
measures 6 &mgr;m in the longitudinal length “Xa” and 6 &mgr;m in the lateral length “Ya”. The size of the opening
404
at the interlayer insulating film
402
measures 15 &mgr;m in the longitudinal length “Xb” and 15 &mgr;m in the lateral length “Yb”. In this case, the dimension of the opening
404
at the protective film
403
and the dimension of the opening
404
at the interlayer insulating film
402
are different from each other.
As a result, a step-wise difference in level [“A” in FIG.
6
(
b
)] is formed on the reflective pixel electrode
401
at the boundary of the protective film
403
and the interlayer insulating film
402
. Because of this step-wise difference in level, a break in the reflective pixel electrode
401
is likely to occur. When the break occurs in the reflective pixel electrode
401
, the electrical continuity between the reflective pixel electrode
401
and the TFT element
411
can not be secured, thereby causing the problem of dot defects to the liquid crystal display device.
In addition, with a liquid crystal display device using pixel electrodes that are formed mainly of aluminum, such defects as poor contact, disconnection and the like are caused by the differences in film thickness of the reflective pixel electrodes, having resulted in such problems as a display failure, a reduction in reflectivity and the like
The present invention provides a liquid crystal display device, which enables the prevention of a break in pixel electrodes from occurring and the realization of excellent display characteristics, and provides a video display apparatus and an information processing apparatus using the foregoing liquid crystal display device.
SUMMARY OF THE INVENTION
A display device which employs a liquid crystal material of the present invention comprises:
a transparent substrate;
nonlinear elements, each of which has a plurality of electrodes, disposed on the transparent substrate;
a protective film disposed on each respective nonlinear element of above;
an interlayer insulating film disposed on the protective film; and
a pixel electrode disposed on the interlayer insulating film, in which an opening with the cross-section thereof configured in a V-letter like slanting shape is formed in the protective film and interlayer insulating film, respectively, the openings are exposed to the surface of the nonlinear element, one of the openings is provided with a first end part formed on the protective film and the other is provided with a second end part formed on the interlayer insulating film, the first end part is located outside of the second end part, the pixel electrode is also disposed on the interlayer insulating film of the opening and an electrode out of the plurality of electrodes of the nonlinear element is in contact with the pixel electrode in the opening.
A manufacturing method of display device employed liquid crystal material of the present invention comprising the steps of:
(a) disposing a nonlinear element having a plurality of electrodes an a substrate
(b) disposing a protective film with covering said nonlinear element, in which said protective film has a lower opening, and a first electrode of said plurality of electrodes exposes at said lower opening,
(c) disposing a interlayer insulating film with covering said protective film, in which said interlayer insulating film has an upper opening formed at a place according to said lower opening, and said first electrode exposes at said upper opening, and
(d) disposing a pixel electrode with covering said interlayer insulating film and said first electrode,
wherein said lower opening and said upper opening formed a opening,
said opening has a V-letter like slanting shape,
said opening has a first end part formed on said protective film and a second end part formed on said interlayer insulating film, and
said opening is formed so that said first end part is located outside of said second end part.
According to the above structure, dot defects are prevented from occurring and missing of pixels is prevented, thereby realizing a display device with excellent display characteristics such as a bright display screen and the like. Furthermore, the yield rate of conforming display devices is remarkably impr
Iwai Yoshio
Kato Mieko
Kato Naoki
Sekime Tomoaki
Yamaguchi Hisanori
Kato Mieko
Ton Toan
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