Liquid crystal cells – elements and systems – Particular excitation of liquid crystal – Electrical excitation of liquid crystal
Reexamination Certificate
1998-12-21
2002-08-13
Sikes, William L. (Department: 2871)
Liquid crystal cells, elements and systems
Particular excitation of liquid crystal
Electrical excitation of liquid crystal
C349S044000, C349S110000, C349S152000
Reexamination Certificate
active
06433841
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an active matrix driven or passive matrix driven electro-optical apparatus such as a liquid crystal apparatus based on thin-film transistor driving or thin-film diode driving, a manufacturing method thereof, and an electronic device using the same.
2. Description of Related Art
A liquid. crystal apparatus typically includes an electro-optical apparatus, a pair of alignment films that are rubbed in prescribed directions and provided on a pixel electrode and an opposing electrode between a pair of substrates, and an electro-optical material such as liquid crystal held between the alignment films. An electric field is applied to the electro-optical material from both electrodes. As a result, the alignment condition of the electro-optical material changes and a display is provided within an image display area.
Therefore, if a convex or concave portion caused by a difference in the total film thickness between an area comprising wiring lines (such as data lines, scanning lines and capacitor lines), driving circuits for driving pixels and the like such as thin-film transistor driving circuits (TFT) and thin-film diode elements (TFD) is left as it is up to a face (alignment film) in contact with the electro-optical material, then, defective alignment (disclination) may occur in the electro-optical material in response to the extent of convex or concave, which may lead to deterioration of the image for each pixel. More specifically, when an alignment film having an aperture area formed on the convex or concave face is rubbed, variations may occur in the alignment regulating ability on the alignment film surface in response to the extent of convex or concave. This may cause defective alignment of the electro-optical material and change the display contrast. Upon defective alignment of the electro-optical material for a normally white mode in which non-application of voltage onto the electro-optical material results in white display, a white dropout may occur at the position of defective alignment, which leads to a decrease in contrast which in turn leads to a decrease in fineness. In order to uniformly rub the alignment film over the entire substrate, a prescribed constant distance is maintained between the alignment films. To avoid this inconvenience, it is very important to flatten a pixel portion positioned within the image display area.
On the other hand, an electro-optical material may be sealed in a space surrounded by a sealing material between both substrates having wiring lines and driving circuits to form an electro-optical material layer. The sealing material may be an adhesive comprising a photosetting resin or a thermosetting resin for bonding both substrates around them. Particularly in a small-capacity electro-optical apparatus, the gap between the substrates may be controlled using a sealing material mixed with a bead-shaped or fiber-shaped gap material having an outside diameter of several &mgr;m. In the sealed area (i.e., area bonded by the sealing material), outgoing wire lines of the scanning and data lines are arranged from the image display area to the peripheral areas. This produces a step depending upon the presence or absence of the connecting lines. Such a step makes it difficult to gap control using the gap filler and stress concentration by the gap filler may cause breakage of lines or cause a short circuit. It is therefore very important to flatter the sealed area.
SUMMARY OF THE INVENTION
In order to flatten the above-described pixel portion for one or a plurality of interlayer insulating films provided to insulate individual thin films composing a thin-film transistor or individual thin films composing various wiring lines, the thickness of a non-aperture area of each pixel may be smaller than the thickness of an aperture area thereof. Or, it may be necessary to flatten the upper surface of the interlayer insulating film closest to the electro-optical material using a CMP (Chemical Mechanial Polishing) operation or to form a SOG (Spin On Glass) film using a spin coating operation.
Also for flattening the sealed area as described above, the thickness of the portion having connecting lines formed thereon may be smaller than the thickness having no connecting line thereon. Or, the upper surface of the interlayer insulating film closest to the sealed area may be flattered by forming an SOG using a CMP operation or spin coating.
At all events, therefore, there are posed problems of more complicated manufacturing steps, a lower yield and a high cost.
In order to prevent flicker or a cross-talk even with a low duty ratio upon supplying image signals to each pixel electrode in an electro-optical apparatus of this type, a storage capacitor may be provided for imparting a prescribed capacity to each pixel electrode. The total film thickness in the non-aperture area may be increased by an amount corresponding to the storage capacitor electrode and the capacitor lines composing the same. This may result in an increase in step in the pixel section. When such a storage capacitor is incorporated in an area under the data lines or along the scanning lines, thickness in this portion may increase causing production of a large step. For example, when incorporating a storage capacitor in the area under the data lines, the thickness may increase compared to that of the pixel section not having them by an amount corresponding to the thickness of the storage capacitor (i.e., total thickness of the first storage capacitor electrode, the insulating film and the second storage capacitor electrode) and the data line thickness. This may result in a step of about 10,000 Å. Thus, flattening applied for offsetting the step in the image display area may be difficult and expensive.
In an electro-optical apparatus having each pixel provided with a thin-film transistor, a light shielding film may be provided under the thin-film transistor (on the TFT array substrate side) with a view to prevent optical leakage caused by a feedback light from the back of the projected light having transmitted through the electro-optical apparatus incoming into a channel area of the thin-film transistor particularly in a use such as a projector. Thus, the total thickness in the non-aperture area having a TFT formed thereon becomes larger by an amount corresponding to the light shielding film. This results in a larger step. In this case, the flatten applied for offsetting the step in the image display area may be difficult and expensive.
The present invention may provide an electro-optical apparatus which can reduce the step caused by the presence of various wiring lines and elements in the image display area by using a relatively simple configuration, a manufacturing method thereof, and an electronic device using the same.
An electro-optical apparatus may be provided to reduce the step caused by the presence of various wiring lines in the sealed area by the use of a relatively simple configuration, a manufacturing method thereof, and an electronic device using the same.
An object of the present invention may be to provide an electro-optical apparatus that permits efficient flattening of the pixel section by the utilization of the configuration in which a light shielding film is provided under the TFT and features of the manufacturing steps, a manufacturing method thereof, and an electronic device using the same.
An object of the invention may be to provide an electro-optical apparatus having a large storage capacitor in which defective alignment of liquid crystal may be reduced as far as possible. A manufacturing method and a electronic device using the same may also be provided.
An object of the present invention may be to provide an electro-optical apparatus which permits reduction of defective wiring under the sealed area and accurate control of the gap between substrates. A manufacturing method and an electronic device using the same may also be provided.
An electro-optical apparatus may include a first substrat
Murade Masao
Yoneyama Ryoichi
Ngo Julie
Oliff & Berridg,e PLC
Seiko Epson Corporation
Sikes William L.
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