Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1999-04-13
2002-06-25
Sikes, William L. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S151000, C349S152000
Reexamination Certificate
active
06411359
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to liquid crystal display devices and, more particularly, to a liquid crystal display device including a flexible circuit which is provided along one of short sides of a liquid crystal display element formed by sandwiching a liquid crystal layer with a first substrate having active elements formed thereon and a second substrate having a common electrode formed thereon and which is connected at one end thereof to an interface circuit board to supply a driving signal voltage for display to said active elements and a driving IC chip which is mounted such that it connected to extraction lines of the active elements at output terminals thereof and to a conductive layer portion of said flexible board at input terminals thereof.
2. Description of the Related Art
Liquid crystal display devices arc widely used as display devices capable of high definition color display for use in notebook type computers and display monitors.
Known liquid crystal display devices include liquid crystal display devices of the passive matrix type utilizing a liquid crystal panel sandwiched by a pair of substrates formed with parallel electrodes which are formed on the respective inner surfaces so as to cross each other and of the active matrix type utilizing a liquid crystal display element having switching elements for selection in pixels on one of a pair of substrates (hereinafter also referred to as liquid crystal panel).
Active matrix type liquid crystal display devices include the so-called vertical field type liquid crystal display devices, represented by the twisted nematic (TN) system, utilizing a liquid crystal panel having a group of electrodes for pixel selection formed on each of a pair of upper and lower substrates (generally referred to as TN system active matrix type liquid crystal display devices) and the so-called horizontal field type liquid crystal display devices utilizing a liquid crystal panel having a group of electrodes for pixel selection formed on only one of a pair of upper and lower substrates (generally referred to as IPS system liquid crystal display device).
In a liquid crystal panel forming a part of the former TN system active matrix type liquid crystal display device, liquid crystal is oriented at al twist of 90° within a pair of substrates (two sheets consisting of a first substrate (lower substrate) and a second substrate (upper substrate)), and two polarizing plates are formed on outer surfaces of the upper and lower substrates of the liquid crystal panel which are in the crossed Nicols configuration in the directions of absorption axes thereof and whose absorption axis at the entrance side is in parallel with or orthogonal to the rubbing direction.
In such a TN system active matrix type liquid crystal display device, incident light is tuned into linearly polarized light by the entrance side polarizing plate when no voltage is applied; the linearly polarized light propagates along the twist of the liquid crystal layer; and, when the transmission axis of the exit side polarizing plate coincides with the azimuth angle of said linearly polarized light, the linearly polarized light is entirely emitted to show white display (the so-called normally open mode).
When a voltage is applied, the direction of a unit vector (director) indicating an average direction of orientation of the molecular axes of the liquid crystal forming the liquid crystal layer is in a direction perpendicular to the plane of the substrates. The azimuth angle of the linearly polarized light at the entrance side is thus unchanged and therefore coincides with the absorption axis of the exit side polarizing plate, which results in black display (see Principles and Applications of Liquid Crystal issued by Institute for Industrial Research, 1991).
In an IPS system liquid crystal display in which a group of electrodes for pixel selection and a group of electrode wirings are formed only on one of a pair of substrates and in which a voltage is applied between adjoining electrodes on said substrate (between a pixel electrode and a counter electrode) to switch the liquid crystal layer in a direction parallel with the plane of the substrates, polarizing plates are provided to show black display when no voltage is applied (the so-called normally closed mode).
The liquid crystal layer of an IPS system liquid crystal display device is in a homogeneous orientation in parallel with the plane of the substrates in the initial state. The director of the liquid crystal layer is in parallel with or at some angle to the direction of the electrode wiring in a plane parallel with the substrates when no voltage is applied. During the application of a voltage, the direction of the director of the liquid crystal layer moves to the direction perpendicular to the direction of the electrode wiring as the voltage is applied. When the direction of the director of the liquid crystal layer is inclined toward the direction of the electrode wiring at 45° from the direction of the director under no application voltage, the liquid crystal layer under the application voltage causes the azimuth angle of the polarized light to rotate at 90° as if it is a ½ wavelength plate. As a result, the transmission axis of the exit side polarizing plate and the azimuth angle of the polarized light coincide with each other to show white display.
The IPS system liquid crystal display device is characterized in that it has less variation of hues and contrast associated with the field angle to allow a wider field angle (see Japanese unexamined patent publication No. H5-505247).
Color filter systems are the main stream of attempts to make full-color versions of the various liquid crystal display devices described above. This is achieved by separating a pixel corresponding to one dot in a color display into three parts and by providing color filters corresponding to three respective primary colors, e.g., red (R), green (G) and blue (B), at respective unit pixels.
While the present invention can be applied to the various liquid crystal display devices described above, it will now be briefly described with reference to a TN system active matrix type liquid crystal display device as an example.
As described above, in a liquid crystal display element (liquid crystal panel) forming apart of a TN system active matrix type liquid crystal display device (hereinafter simply referred to as active matrix type liquid crystal display device for simplicity), there is formed a group of gate lines which extend in an x-direction in parallel with a y-direction and a group of drain lines which are insulated from the group of gate lines and which extend in the y-direction in parallel with the x-direction, on the surface toward a liquid crystal layer, of one of two transparent insulated substrates made of glass or the like provided in a face-to-face relationship with each other with the liquid crystal layer interposed therebetween.
Each of regions surrounded by the group of gate lines and the group of drain lines serves as a pixel region and, for example, a thin film transistor (TFT) and a transparent pixel electrode are formed in such a pixel region as active elements (switching elements).
When a scan signal is supplied to a gate line, the thin film transistor is turned on, and an image signal from the drain line is supplied to the pixel electrode through the thin film transistor which has been turned on.
Each gate line among the group of gate lines, not to mention each drain line among the group of drain lines, is also extended to the periphery of the substrate to form an external terminal, and an image driving circuit and a gate scan driving circuit connected to each of the external terminals, i.e., a plurality of driving IC chips (semiconductor integrated circuits which are hereinafter also, simply referred to as driving ICs or ICs) forming the sane arc externally mounted on the periphery of the substrate. That is, a plurality of tape carrier packages (TCPs) carrying those driving ICs are
Hasegawa Kaoru
Kobayashi Kengo
Toriyama Yoshio
Yarita Katsuhiko
Antonelli Terry Stout & Kraus LLP
Hitachi , Ltd.
Qi Mike
Sikes William L.
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