Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2001-03-02
2003-11-18
Ton, Toan (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S038000, C349S129000
Reexamination Certificate
active
06650390
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a liquid crystal display panel, in particular, to a multi-domain color liquid crystal display panel having excellent visual characteristics.
Generally, a liquid crystal display (LCD) panel of an active matrix type comprises a TFT substrate unit, an opposite substrate unit opposed to the TFT substrate unit, and a liquid crystal layer disposed between the TFT substrate unit and the opposite substrate unit. The TFT substrate unit includes a thin film transistor and a pixel electrode for each pixel on a transparent substrate. The opposite substrate unit has a color filter layer, a black matrix, and an opposite or common electrode on a transparent substrate.
A twisted nematic type (which will be abbreviated to a TN type) LCD panel is well known as a conventional LCD panel having the above-mentioned structure. The TN type LCD panel includes liquid crystal molecules in the liquid crystal layer and the liquid crystal molecules have twisted orientation. The twisted orientation has a first direction parallel to a predetermined direction on a side of the TFT substrate unit and a second direction perpendicular to the predetermined direction on a side of the opposite substrate unit. That is, the orientation is continuously changed by 90 degrees from the first direction to the second direction between the TFT substrate unit and the opposite substrate unit.
The TN type LCD panel has a first polarizing film having a first transmission axis parallel to the predetermined direction on an outside surface of the TFT substrate unit. Moreover, a second polarizing film having a second transmission axis perpendicular to the predetermined direction on an outside surface of the opposite substrate unit.
With this structure, incident light on the outside of the first polarizing film is linearly polarized when it passes through the first polarizing film. The linear polarized light going into the liquid crystal layer travels to the second polarizing film with rotation of its transmission plane. Accordingly, the linear polarized light has the transmission plane parallel to the second direction on the side of the opposite substrate unit and can pass through the second polarizing film. The rotation of the transmission plane is caused by rotatory polarization and birefringence of the liquid crystal layer.
If voltage is supplied between the pixel electrode and the opposite electrode, the liquid crystal molecules between the pixel electrode and the opposite electrode are rearranged so that their longitudinal axes are perpendicular to both of the transparent substrates. In this state, the linear polarized light going into the liquid crystal layer through the first polarizing film travels to the second polarizing film without the rotation of the transmission plane. Consequently, the linear polarized light has the transmission plane perpendicular to the second direction and can not pass through the second polarizing film.
Thus, the TN type LCD panel controls penetration/obstruction of the light by using change of the state of the liquid crystal layer and thereby it displays characters and/or pictures.
However, the TN type LCD panel has a problem that it has narrow viewing angle and insufficient visual characteristics This is because it uses the birefringence of the liquid crystal layer.
The problem is solved by a vertical aligned type (which will be abbreviated to a VA type) LCD panel. The VA type LCD panel comprises liquid crystal molecules have negative dielectric aeolotropy and orientation perpendicular to both of transparent substrates. The orientation is called homeolotropic orientation.
In the VA type LCD panel, the pixel electrode and the opposite electrode are designed so as to generate an electric field inclined against the initial orientation when voltage is supplied between the pixel electrode and the opposite electrode. The electric field makes the liquid crystal molecules fall down in a direction so that the longitudinal axes of the liquid crystal molecules become parallel to the transparent substrates. Thus, the VA type LCD panel can display the characters and/or the pictures by changing the penetration of the light in the liquid crystal layer.
By dividing each pixel into a plurality of domains, the VA type LCD panel can have a wide viewing angle and excellent visual characteristics. In each domain, the liquid crystal molecules fall down toward a predetermined direction different from that of other domains. Such a VA type LCD panel is called a multi-domain LCD panel.
Several methods are known to form domains in the pixel. For example, the domains can be formed by forming slopes (e.g. projection, cavity, or the like) on the opposite electrode and/or the pixel electrode. Moreover, the domains can be formed by forming at least one slit for the pixel in the opposite electrode and/or the pixel electrode. Furthermore, the domains can be obtained by dividing the pixel electrode and/or the opposite electrode.
To obtain excellent visual characteristics and high displaying quality, it is necessary that boundaries among domains be exactly located at predetermined positions. A difference between the boundaries and the predetermined positions deteriorates the displaying quality because the liquid crystal molecules are discrete at the boundaries.
Recently, the size of LCD panels has become larger and larger. That is, the size of the transparent substrates has become larger. With the enlargement of the size of the substrates, the position difference between them has become larger. Consequently, each pixel cannot be exactly divided into domains. This is observed when the opposite substrate unit is characterized by having slopes and/or slits.
In addition, the position difference between the substrate units causes deterioration of the numerical aperture when the opposite substrate unit has a color filter layer and a black matrix. That is, transmissivity of the LCD panel deteriorates in this case.
SUMMARY OF THE INVENTION
It is therefore an object of this invention to provide a vertical aligned type multi-domain color liquid crystal display panel having excellent visual characteristics.
It is another object of this invention to provide a vertical aligned type multi-domain color liquid crystal display panel having a TFT substrate unit having a color filter, a black matrix, and an orientation control structure on a transparent substrate.
It is still another object of this invention to provide a vertical aligned type multi-domain color liquid crystal display panel capable of suppressing deterioration of displaying quality with enlargement of size.
It is still another object of this invention to provide a vertical aligned type multi-domain color liquid crystal display panel capable of being easily manufactured.
Other objects of this invention will become clear as the description proceeds.
According to an aspect of this invention, a liquid crystal display panel includes a first substrate, a TFT transistor formed on the first substrate, a pixel electrode formed on the first substrate to connect to the TFT transistor, a second substrate opposed to the first substrate, an opposite electrode formed on the second substrate to face to the pixel electrode at a predetermined interval, and a liquid crystal layer disposed between the pixel electrode and the opposite electrode. The liquid crystal display panel comprises a control electrode formed on the first substrate instead of the pixel electrode. An insulation film is formed on the first substrate to cover the control electrode. A floating electrode having a slit at a predetermined position is formed on the insulation film to face the opposite electrode at the predetermined interval.
According to another aspect of this invention, a method is for manufacturing a liquid crystal display panel including a first substrate, a TFT transistor formed on the first substrate, a pixel electrode formed on the first substrate to connect to the TFT transistor, a second substrate opposed to the first substrate, an opposite electrode formed on t
Hirai Yoshihiko
Ishii Toshiya
Kawada Kiyomi
Matsuyama Hiroaki
Okamoto Mamoru
Hayes & Soloway P.C.
NEC LCD Technologies, Inc.
Schechter Andrew
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