Liquid crystal cells – elements and systems – Particular excitation of liquid crystal – Electrical excitation of liquid crystal
Reexamination Certificate
2001-03-06
2004-06-15
Chowdhury, Tarifur R. (Department: 2871)
Liquid crystal cells, elements and systems
Particular excitation of liquid crystal
Electrical excitation of liquid crystal
C349S150000, C349S152000, C324S701000, C345S088000, C345S904000
Reexamination Certificate
active
06750926
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to liquid crystal display devices and, more particularly, to liquid crystal display devices of the thin-film transistor type with test procedures made easier for inspection of functional operabilities of thin-film transistors and connection failures at scan line lead lines and/or signal line leads. This invention also relates to a method for manufacturing the same.
2. Description of the Related Art
Liquid crystal display devices are widely employed as high-precision color display devices for use in notebook computers and display monitor units.
Currently available liquid crystal display devices include those of the simple matrix type using a liquid crystal panel with a liquid crystal layer interposed between a pair of substrate having inside surfaces on which parallel electrodes are formed in a manner that these cross over each other, and the ones of the active matrix type using a liquid crystal display element (referred to also as liquid crystal panel hereinafter) having switching elements for selection in units of pixels on one of a pair of substrates.
Active-matrix liquid crystal display devices include a liquid crystal display device of the so-called longitudinal electric field scheme such as twisted nematic (TN) scheme (generally called TN type active-matrix liquid crystal display device) using a liquid crystal panel with a group of pixel selection electrodes formed on a respective one of a pair of upper and lower substrates, and a liquid crystal display device of the so-called lateral electric field scheme (generally known as IPS type liquid crystal display device) using a liquid crystal panel with such pixel selection electrode group formed on only one of a pair of upper and lower substrates.
Typically a liquid crystal panel making up the former Tn type active-matrix liquid crystal display device is such that liquid crystals are aligned to twist by 90° within an interior space of a pair of substrates (two substrates consisting of a first substrate (lower substrate) and second substrate (upper substrate)), wherein two polarization plates are multilayered on outside surfaces of the upper and lower substrates of such liquid crystal panel respectively, with absorption axis directions being disposed in a cross polarization or “crossed Nicol” fashion and also with light entrance side absorption axes being in parallel or at right angles to a rubbing direction.
In the TN type active-matrix liquid crystal display device thus arranged, incident light becomes linearly polarized light at an incidence side polarization plate upon application of no voltages. This linear polarized light travels along twisting of a liquid crystal layer and if the penetration axis of a light output side polarization plate is identical to the azimuth angle of the linear polarized light then all rays of the linear polarized light are permitted to go outwardly resulting in establishment of a white display (what is called the “normally open mode”).
In voltage application events a unit vector's direction (director) indicating the average orientation direction of axes of liquid crystal molecules constituting the liquid crystal layer becomes perpendicular to substrate surfaces while the azimuth angle of incidence side linear polarized light is kept unchanged, thus resulting in coincidence with the absorption axis of the light output side polarization plate to thereby obtain a black display (see “Basics and Applications of Liquid Crystals,” issued by Industry Research Association. 1991).
On the other hand, in an IPS type liquid crystal display device with pixel selection electrodes and electrode leads formed on only one of a pair of substrates for permitting switching of its liquid crystal layer in a specified direction extending in parallel to substrate surfaces through voltage application between neighboring electrodes (between a pixel electrode and counter electrode) on this substrate, polarization plates are so disposed as to to provide the black display when no voltages are applied thereto (so called the “normally close mode”).
The IPS type liquid crystal display device's liquid crystal layer exhibits homogeneous alignment or orientation parallel to the substrate surfaces in the initial state. Simultaneously the director of the liquid crystal layer in a plane parallel to the substrates is parallel or slightly angled to the electrode lead direction upon application of no voltages, causing the direction of the director of the liquid crystal layer in voltage application events to shift toward a direction perpendicular to the electrode lead direction upon application of a voltage thereto. When the liquid crystal layer's director direction is tilted toward the electrode lead direction by 450° in comparison with the director direction when no voltage are applied thereto, the liquid crystal layer upon application of the voltage causes the azimuth angle of polarized light to rotate 90° as in {fraction (
1
/
2
)} wavelength plates resulting in coincidence between the light output side polarization plate's transmission axis and the polarized light's azimuth angle thus providing a white display.
This IPS type liquid crystal display device has its feature that changes in color phase and contrast stay less even at viewing angles thus enabling achievement of wide view-field angles (see Japanese Patent Laid-Open No. 505247/1993).
A major approach to attain full color image visualization of the respective types of liquid crystal display devices stated supra is to employ a color filter scheme. This is for realization by subdividing a pixel corresponding to a single dot of color display into three portions and disposing color filters of the three primary color—e.g. red (R), green (G), and blue (B)—at such unit pixels respectively.
Although the present invention is applicable to the several types of liquid crystal display devices stated above, its outline will be explained below with a TN type active-matrix liquid crystal display device being as an example.
As previously stated, in a liquid crystal element (liquid crystal panel) making up the TN type active-matrix liquid crystal display device (referred to simply as active-matrix liquid crystal display device hereinafter for brevity purposes), there are formed on a liquid crystal layer side surface of one substrate of two transparent dielectric substrates typically made of glass plates mutually opposed with a liquid crystal layer interposed therebetween a group of scanning signal lines (referred to as gate lines hereinafter) extending in its “x” direction and being parallel disposed in “y” direction and a group of drain lines (video signal lines) isolated from this gate line group and extending in the y direction while being parallel disposed in the x direction.
A respective one of regions surrounded by these gate line group and drain line group becomes a pixel region in which a thin-film transistor (TFT) for use as an active element (switching element) and a transparent pixel electrode are formed by way of example.
When a scan signal is supplied to a gate line, the thin-film transistor turns on causing a video signal coming from a drain line to be supplied to the pixel electrode via this turned-on thin-film transistor.
Additionally each drain line of the drain line group and each gate line of the gate line group are extended up to the periphery of a substrate to constitute external terminals respectively, to which video drive circuits and gate scan drive circuits—namely a plurality of drive IC chips (semiconductor integrated circuits as will be referred to simply as drive ICs or ICs hereinafter) making up these circuits—are connected respectively, which are separately mounted at the substrate periphery. In other words a plurality of tape carrier packages (TCPs) with these respective drive ICs mounted thereon are externally bonded to peripheral portions of the substrate.
However, since such substrate is designed so that TCPs with drive ICs mounted are extern
Miyata Kazushi
Niwa Susumu
Ohgiichi Kimitoshi
Ootsu Ryouichi
Tsuruoka Shinichi
Chowdhury Tarifur R.
Duong Thoi V.
LandOfFree
Liquid crystal display device and manufacturing method thereof does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Liquid crystal display device and manufacturing method thereof, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Liquid crystal display device and manufacturing method thereof will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3365060