Liquid crystal cells – elements and systems – Particular excitation of liquid crystal – Electrical excitation of liquid crystal
Reexamination Certificate
2001-08-22
2004-10-12
Niebling, John F. (Department: 2812)
Liquid crystal cells, elements and systems
Particular excitation of liquid crystal
Electrical excitation of liquid crystal
C349S141000, C349S122000
Reexamination Certificate
active
06803974
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to liquid crystal display devices and also relates for example to liquid crystal display devices of the active matrix type.
2. Background Art
An active-matrix liquid crystal display device is typically arranged so that a region surrounded by gate signal lines extending in the x direction and being parallel-provided in the y direction and drain signal lines extending in the y direction and being parallel-provided in the x direction on a liquid crystal-side surface of one transparent substrate of respective transparent substrates that are disposed to oppose each other with a layer of liquid crystal material interposed between them is for use as a pixel region, the device comprising in this pixel region a thin-film transistor as driven by supplement of a scan signal from one-side gate signal line and a pixel electrode to which an image signal from one-side drain signal line is supplied via this thin-film transistor.
And although it is arranged so that the liquid crystal's optical transmissivity is controlled by an electric field which is created between this pixel electrode and an opposite or “counter” electrode, there is known the one that the counter electrode is formed on the transparent substrate side with the pixel electrode being formed therein.
In brief, the pixel electrode and counter electrode are designed to have a comb-shaped pattern, for example, with respective ones biting each other, wherein an electric field having components extending in parallel to the transparent substrate of those electric fields created between them is used to drive liquid crystal molecules (this is called the lateral electric field scheme).
Here, the pixel electrode and counter electrode are covered by a protective film for preventing a dielectric film functioning as a gate insulation film of the thin-film transistor and the thin-film transistor from coming into direct contact with the liquid crystal; thus, they will not be brought into direct contact with the liquid crystal.
SUMMARY OF THE INVENTION
However, it has been affirmed that the liquid crystal display device thus arranged in this way suffers from risks of occurrence of stain-like display defects in its display region plane (region surface consisting of an ensemble of pixel regions), which can progress in some cases.
And, the cause of this display defect generation has been investigated to reveal the fact that holes or cracks or the like take place at a protective film or else thus causing a leak current to be derived between signal lines or the like as exposed thereby via liquid crystals leading to generation of electrochemical reaction whereby the liquid crystal's ion species density locally gets higher resulting in a likewise decrease in liquid crystal support rate.
One remedy for this is to make the protective film be formed of a thick film; however, in cases where more than one contact hole for connection between a pixel electrode and thin-film transistor is formed in such protective film, this contact hole will be formed to have a larger size, which in turn serves as a serious bar to successful achievement of the required miniaturization or downsizing.
The present invention was made based on such circumstance and its primary objective is to provide a liquid crystal display device capable of precluding generation of the above-noted stain-like display defects.
A brief summary of a representative one of the inventions as disclosed in this application for patent will be explained below.
The liquid crystal display device in accordance with the instant invention is one comprising, in a liquid crystal side pixel region of one substrate of respective substrates as disposed to oppose each other with a layer of liquid crystal material interposed therebetween, a thin-film transistor which is driven by a scan signal from a gate signal line; a pixel electrode to which an image signal from a drain signal is supplied via this thin-film transistor; a protective film formed to also cover the thin-film transistor and the pixel electrode; and a resin film formed on or over an upper surface of this protective film.
The liquid crystal display device arranged in this way comes to have an arrangement that even when scars and/or cracks occur at the protective turn, such scars and/cracks are cured by the resin film.
Owing to this, it will no longer happen that those signal lines or the like underlying the protective film are exposed to the liquid crystal side; thus, it will hardly happen that a leak current is generated through the liquid crystal resulting in a local increase in the liquid crystal's ion species density due to creation of electrochemical reaction, which in turn leads to a decrease in liquid crystal support rate.
Due to this, it becomes possible to suppress unwanted generation of stain-like display defects.
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Office action from Korean Patent Office dated Oct. 27, 2003.
Ishii Masahiro
Kamoshida Kenta
A. Marquez, Esq. Juan Carlos
Fisher Esq. Stanley P.
Hitachi , Ltd.
Kennedy Jennifer M.
Niebling John F.
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