Active solid-state devices (e.g. – transistors – solid-state diode – Non-single crystal – or recrystallized – semiconductor... – Field effect device in non-single crystal – or...
Reexamination Certificate
2001-03-26
2003-03-04
Ho, Hoai (Department: 2818)
Active solid-state devices (e.g., transistors, solid-state diode
Non-single crystal, or recrystallized, semiconductor...
Field effect device in non-single crystal, or...
C257S059000, C438S048000, C438S128000, C438S149000
Reexamination Certificate
active
06528822
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to an electro-optical device in which a difference in surface level in the connection terminal-formed region is minimized, to a method for fabricating the same, and to an electronic apparatus using the electro-optical device as a display unit.
2. Description of Related Art
In general, in an electro-optical device, for example, in a liquid crystal device which performs a predetermined display using a liquid crystal as an electro-optical material, the liquid crystal is sandwiched between a pair of substrates. As one of such a liquid crystal device, for example, an active matrix liquid crystal device, in which a pixel electrode is driven by a three terminal switching element, has the structure described below. That is, one substrate of a pair of substrates constituting such a liquid crystal device is provided with a plurality of scanning lines and a plurality of data lines intersecting with each other. At each intersection thereof, a three-terminal switching element, such as a TFT (Thin Film Transistor), and a pixel electrode are formed as a set, and peripheral circuits for driving the individual scanning lines and data lines are provided in the periphery of the region (display region) in which these pixel electrodes are formed. The other substrate is provided with a transparent counter electrode facing the pixel electrodes. Additionally, an alignment layer, which has been subjected to rubbing treatment so that the long axis directions of the liquid crystal molecules are continuously twisted, for example, by approximately 90 degrees, between the two substrates, is provided on the inner surface of each substrate. A polarizer corresponding to the alignment direction is provided on the outer surface of each substrate.
Herein, image signals are usually supplied via image signal lines, and are sampled to the individual data lines by sampling switches with appropriate timing. The switching element provided at the intersection between each scanning line and each data line is turned on when a scanning signal applied to the corresponding scanning line is at an active level, so that the image signal sampled to the corresponding data line is supplied to the pixel electrode. The counter electrode provided on the counter substrate is maintained at a predetermined electric potential.
In such a structure, when the scanning signal supplied to each scanning line and the sampling signal for controlling the sampling switch are supplied with appropriate timing by the peripheral circuits, an effective voltage corresponding to the image signal is applied, pixel by pixel, to a liquid crystal capacitor composed of the pixel electrode, the counter electrode, and the liquid crystal sandwiched between both electrodes.
At this stage, light passing between the pixel electrode and the counter electrode is optically rotated by approximately 90 degrees along the twist of the liquid crystal molecules if the voltage difference between both electrodes is zero. As the voltage difference is increased, since the liquid crystal molecules are inclined in the electric field direction, the optical activity thereof disappears. Therefore, for example, in a transmissive electro-optical device, when polarizers in which the polarization axes are orthogonal to each other corresponding to the rubbing directions are disposed on the incident side and on the back side of the device, if the voltage difference between both electrodes is zero, light is transmitted, while as the voltage difference between both electrodes is increased, light is blocked. Therefore, by controlling the voltage applied to the pixel electrode for each pixel, a predetermined display is enabled.
In the rubbing treatment, usually, by rotating a buffing cloth wound around a roller, the surface of an organic film, such as a polyimide, is rubbed in a predetermined direction (rubbing direction). By the rubbing treatment, it is believed that the polymer backbone of the organic film is drawn in the rubbing direction and the liquid crystal molecules are aligned in the drawing direction.
SUMMARY OF THE INVENTION
However, a difference in level of approximately 500 nm to 1,000 nm occurs in the underlying surface on which the alignment layer is formed, in particular, in the underlying surface of one substrate provided with pixel electrodes, switching elements, scanning lines, data lines, and peripheral circuits, due to the presence or absence of various types of wiring, various elements, and contact holes. Even if an alignment layer is formed on the underlying surface having such a difference in level, a difference in level also occurs in the surface of the alignment layer. Moreover, if such an alignment layer is subjected to rubbing treatment, since the tips of fibers implanted in the buffing cloth become disordered due to the difference in level, the surface of the substrate is rubbed nonuniformly. If a liquid crystal is filled and sealed between the substrates in which rubbing treatment has been performed nonuniformly, display unevenness occurs, presumably because the liquid crystal molecules are not aligned in a predetermined direction. Specifically, striped display unevenness may occur, resulting in a decrease in display quality.
Objects of the present invention are to at least provide an electro-optical device in which a difference in level in the surface of the substrate is minimized, and thus inconvenience in display resulting from nonuniform rubbing treatment is prevented, to provide a method for fabricating the same, and to provide an electronic apparatus using the same.
The present inventors had believed that the difference in level which degrades the display quality most is a difference in level caused by connection terminals for inputting various signals from external circuits and wiring extending from the connection terminals.
This will be described in more detail. Since pixel electrodes and switching elements connected thereto are provided corresponding to the individual intersections between scanning lines and data lines, the pitch of the array thereof depends on the pitch of the array of the scanning lines and data lines. Moreover, since peripheral circuits including sampling switches are provided corresponding to the scanning lines and the data lines, the pitch of the array of the elements constituting the peripheral circuits also depends on the pitch of the array of the scanning lines and data lines. Therefore, since display unevenness due to the differences in level of such elements and wiring occurs at the same pitch as that of the array of pixels or at an integral multiple thereof, these are believed to be not conspicuous in view of display.
In contrast, in view of decreasing the length of wiring extending from the connection terminals and in view of maintaining the symmetry of the overall device, the connection terminals are disposed close to the sampling switches and a data line drive circuit for driving the data lines, and are arrayed in the extending direction of the scanning lines (i.e., in a direction orthogonal to the extending direction of the data lines), and also in view of facilitating the connection to the exterior, the connection terminals are formed at a much larger pitch than that of the array of the scanning lines and data lines, i.e., are formed independently of the pitch of the array of scanning lines and data lines. Therefore, display unevenness due to the difference in level of the connection terminals and wiring leading to the connection terminals is believed to be highly conspicuous.
(1) Accordingly, in one exemplary aspect of the present invention, an electro-optical device includes a substrate composed of a plurality of layers, an insulating film formed on the outer surface of the substrate, connection terminals for inputting image signals formed at substantially the same level of the insulating film, and wiring connected to the connection terminals.
In such a structure, it is possible to minimize a difference in level between the surface of each
Ho Hoai
Huynh Andy
Oliff & Berridge PLC.
Seiko Epson Corporation
LandOfFree
Electro-optical device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electro-optical device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electro-optical device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3013900