Liquid crystal cells – elements and systems – Particular excitation of liquid crystal – Electrical excitation of liquid crystal
Reexamination Certificate
2001-05-17
2004-06-15
Parker, Kenneth (Department: 2871)
Liquid crystal cells, elements and systems
Particular excitation of liquid crystal
Electrical excitation of liquid crystal
C349S148000, C349S151000
Reexamination Certificate
active
06750924
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to an electro-optical device in which a conductive layer different from other conductive layers constituting scanning lines and data lines is used in a peripheral circuit to improve design versatility in the peripheral circuit, a method for making the same, and an electronic apparatus using the electro-optical device as a display section.
2. Description of Related Art
In electro-optical devices, such as in liquid crystal devices that display using liquid crystal as an electro-optical material, the liquid crystal is disposed between a pair of substrates. Among these, for example, an active-matrix liquid crystal device for driving pixel electrodes by three-terminal switching elements has the following configuration. That is, in this liquid crystal device, a plurality of scanning lines and a plurality of data lines are provided so as to cross each other on one substrate, and each of these crossings is provided with a combination of a three-terminal switching element, such as a thin film transistor (hereinafter referred to as TFT), and a pixel electrode. In this device, the TFT turns on to supply an image signal, applied to the corresponding data line, to the pixel electrode when the scanning signal supplied to the scanning line corresponding to the crossing is an active level. The other substrate is provided with transparent counter electrode which opposes the pixel electrodes.
Driving circuits which drive these scanning lines and data lines generally include at least a scanning line driving circuit, a data line driving circuit, and a sampling circuit. Among these, the scanning line driving circuit supplies scanning signals at a predetermined time interval, whereas the data line driving circuit supplies sampling signals at a predetermined time interval. The sampling circuit supplies image signals supplied by a sampling switch, which is provided to each data line via an image signal line, to the corresponding data line in response to the sampling signals.
Moreover, a peripheral-circuit-built-in-type electro-optical device provided with these driving circuits in the peripheries of a region (display region) of a pixel electrode array is developed. In such an electro-optical device, active elements constituting the driving circuits and switching elements connected to the pixel electrodes are formed by a common process, in consideration of efficiency of the production process. For example, in the above liquid crystal device, elements constituting the driving circuits are TFTs which are formed by the same process as the switching elements connected to the pixel electrodes. Such peripheral-circuit-built-in-type electro-optical devices are advantageous for miniaturization and reduction in overall cost of the device, compared with electro-optical devices provided with external driving circuits.
Recently, higher definition arrays, for example, an extended graphics array (XGA: 1024×768 dots), a super extended graphics array (SXGA: 1365×1024 dots), and an ultra extended graphics array (UXGA: 1600×1200 dots), have been required for all displays including electro-optical devices
SUMMARY OF THE INVENTION
To achieve a higher definition array along with miniaturization of the device requires a technology to significantly reduce the array pitch of the semiconductor devices and the array pitch of the data lines. Since the scanning line driving circuit supplies scanning signals to each scanning line, a unit circuit (latch circuit) constituting a portion of the scanning line driving circuit must be contained within the array pitch between the scanning lines. Since the data line driving circuit sequentially supplies sampling signals to sampling switches provided to data lines, a unit circuit constituting a portion of the data line driving circuit must be contained within the array pitch or an integral multiple thereof. However, to achieve a higher definition array and miniaturization of the peripheral-circuit-built-in-type electro-optical device it is difficult to design the device so as to form the unit circuits in the scanning line driving circuit and the data line driving circuit within extremely limited spaces.
The present invention is completed in view of the above circumstances and has an object to provide an electro-optical device that enables improved design versatility in peripheral circuits. In order to achieve the above object, an electro-optical device according to a first aspect of the present invention comprises a plurality of scanning lines and a plurality of data lines, a combination of a switching element and a pixel electrode provided that correspond to each crossing between the scanning lines and the data lines, a conductive interlayer for electrically connecting the corresponding switching element and the corresponding pixel electrode, and a peripheral circuit containing leads which comprise the same layer as the conductive layer constituting the conductive interlayer and driving the switching element.
According to this configuration, the conductive interlayer is used for connecting each switching element and each pixel electrode in the region of the array of the pixel electrodes (the display region), and leads composed of the same conductive layer as the conductive interlayer are also used in the peripheral circuit. In other words, the conductive interlayer used in the display region is also used as parts of the leads in the peripheral circuit. Since a novel lead layer is provided in the peripheral circuit, design versatility is improved.
In this embodiment, the conductive interlayer is preferably connected to an electrode of the switching element via a first contact hole provided corresponding to the electrode, whereas the pixel electrode is connected to the switching element via a second contact hole. In this configuration, the electrode of the switching electrode is connected to the conductive interlayer via the first contact hole, whereas the pixel electrode is connected to the conductive interlayer via the second contact hole. Since the conductive interlayer functions as a barrier film when the pixel electrode is connected to the other end of the switching element, defects occurring when the contact holes have long distances can be reduced.
In this embodiment, each pixel electrode is preferably provided with a storage capacitor of which one end is connected to the pixel electrode and the other end is commonly connected, and the conductive interlayer functions as a part of an electrode constituting the storage capacitor. According to this configuration, the retention of the voltage in the pixel electrode is improved by the storage capacitor in which the conductive interlayer functions as a part of an electrode constituting the storage capacitor.
In this embodiment, the conductive interlayer may have a light-shading effect, part of the light which pass through or is reflected by the pixel electrodes being regulated by the conductive interlayers. According to this configuration, an exclusive shading film can be omitted at least in the region defined by the conductive interlayer among the light transmission or reflection regions. Thus, the configuration can be simplified.
For achieving the above object, an electro-optical device in accordance with a second aspect of the present invention comprises first, second, and third conductive layers, formed in that order, the third conductive layer having resistance which is lower than that of the first conductive layer, a plurality of scanning lines comprising the first conductive layer, a plurality of data lines comprising the third conductive layer and formed so as to cross the plurality of scanning lines, a combination of a switching element and a pixel electrode provided corresponding to each crossing between the scanning lines and the data lines, a conductive interlayer for electrically connecting the switching element and the corresponding pixel electrode, and a peripheral circuit which is provided with leads comprising the first, seco
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