Optical: systems and elements – Optical modulator – Light wave temporal modulation
Reexamination Certificate
2003-01-31
2004-04-20
Schwartz, Jordan M. (Department: 2873)
Optical: systems and elements
Optical modulator
Light wave temporal modulation
C359S250000, C359S252000
Reexamination Certificate
active
06724513
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to an electro-optic device that may be used in an electro-optic device, such as an active matrix drive liquid crystal device, for example. The invention also relates to an electronic instrument provided with the electro-optic device.
2. Description of Related Art
In the related art, an electro-optic device includes a pair of substrates with an electro-optic material, such as liquid crystal, interposed therebetween, and electrodes that are disposed on each of the two of substrates to apply an electric field to the electro-optic material. The electrodes are used to apply an electric field to the electro-optic material and thereby to appropriately alter a state of the electro-optic material. According to this electro-optic device, when light enters the electro-optic device from, for instance, a light source and a state of the electro-optic material is appropriately altered as mentioned above, the transmittance of the light can be controlled, and thereby image display can be realized.
One type of such an electro-optic device is provided such that, when one of the two substrates is provided with pixel electrodes arranged in matrix as the electrode, thin film transistors (hereinafter “TFT”) connected to each of the pixel electrodes, and scanning lines and data lines that are connected to each of the TFTs and arranged in parallel with a row and column direction, respectively, so-called active-matrix drive can be realized. Thereby, when a voltage applied to the electro-optic material is controlled for each of the pixel electrodes, or for each of the pixels divided by the scanning lines and the data lines, light transmittance can be controlled for each of the pixels.
Furthermore, in order to display a higher quality image, the electro-optic device can be provided with various configurations other than the above. For instance, typically, a storage capacitor that is formed of a pixel potential side capacitance electrode connected to the pixel electrode and the TFT and a fixed potential side capacitance electrode disposed opposite via a dielectric film to the pixel potential side capacitance electrode can be provided. This is used to hold a voltage applied to an electro-optic material for a predetermined period of time.
SUMMARY OF THE INVENTION
However, the following problems are present in the related art electro-optic device. In the electro-optic device as mentioned above, there is a universal demand in that in order to display a brighter image, an area occupied, on the substrate, by the scanning lines and the data lines or the storage capacitors, is made to be smaller, thereby a light transmission region, that is a region where a light that contributes in an actual image display in each of the pixels exits due to transmission or reflection is enlarged, and thereby an open area ratio is enhanced. In addition, in order to attain power saving, higher definition or miniaturization of the electro-optic device is simultaneously demanded. From these points of view, there is a general demand that the various kinds of constituent elements be miniaturized.
It is particularly problematic that to increase the open area ratio, a capacitance line constituting the storage capacitor also has to be miniaturized. When a width of wiring is narrowed to make the capacitance line fine, the resistance of the capacitance line becomes higher, resulting in a larger time constant of the wiring. Thereby, cross-talk or burn-in is caused. In the related art, the pixel potential side capacitance electrode that constitutes the storage capacitor is, in some examples, formed of polysilicon, tungsten silicide (WSi) or the like. However, since these materials are not necessarily low-resistance, the above problem is profoundly problematic.
As mentioned above, when each of the constituent elements is miniaturized and narrowed, sufficient attention has to also be paid to a light incidence on the TFT. That is, because when a light is incident on a channel region of a semiconductor layer that constitutes the TFT, light leakage current is caused, and thereby flicker is generated on an image, resulting in deteriorating the image quality. In particular, when the electro-optic device is used as a light valve in a projection type display device, since a light emitted from a very powerful light source is projected on the light valve, light is even more liable to enter the TFT and to cause a problem.
In the related art, in order to inhibit such light from entering the TFT, the TFT or the like is not formed on one of the two substrates, and a light shielding layer is disposed thereon. However, according to this structure, since a distance between the light shielding layer and the TFT becomes relatively larger, an effective shielding function for an obliquely entering light cannot be expected. In order to address or overcome this, the light shielding layer may be formed to be wider. However, this causes a decrease in the open area ratio. That is, the above-mentioned general demand or problems are almost impossible to address or overcome.
Furthermore, in order to inhibit light from entering the TFT, other than the above, a structure can be provided to utilize the data line as a light shielding layer. However, according to this structure, in order to decrease a signal transmission loss by as small a degree as possible, the data line is generally made of a low resistance material, such as, for instance, aluminum, accordingly the higher light reflectance thereof becomes problematic. This is because it is considered that according to such a structure, light that directly enters a surface on an incidence side of the data line can be certainly shielded, but the light reflected from the data line becomes stray light, or the light reflected from the other surface of the data line becomes stray light, resulting in light reaching the TFT. Even in such a structure, when a width of the data line is made to be wider to enhance a light shielding function, similarly to the above light shielding layer, a decrease in the open area ratio may cause a problem, and in view of the above stray light, the stray light may be contrarily increased, resulting in a rather adverse effect in view of inhibiting the light leakage current from occurring.
The present invention addresses the above and/or other problems, and provides an electro-optic device that, while realizing lower resistance of the capacitance line, or reduction or suppression of a light leakage current in the TFT, can address a general demand, such as enhancing an open area ratio. The invention also provides an electronic instrument provided with the electro-optic device.
In order to address or overcome the above problems, an electro-optic device according to the present invention includes, on a substrate; a scanning line; a data line; a thin film transistor disposed in correspondence with an intersection of the scanning line and the date line; a pixel electrode disposed in correspondence with the thin film transistor; a pixel potential side capacitance electrode that is electrically connected to the pixel electrode and constitutes a storage capacitor; and a capacitance line including a fixed potential side capacitance electrode that is disposed opposite via a dielectric film, to the pixel potential side capacitance electrode and constitutes the storage capacitor. In the above, the capacitance line has a body line portion that extends along the scanning line and a portion that extends along the data line. A width of the portion that extends along the data line in the capacitance line is formed the same as a width of the data line or wider than such a width.
According to the electro-optic device of the present invention, when a scanning signal and an image signal are supplied through the scanning line and the data line to the thin film transistor, a pixel electrode can be active matrix driven. Since a storage capacitor that is formed by oppositely disposing the pixel potential side capacitance electrode and the fixed pote
Oliff & Berridg,e PLC
Schwartz Jordan M.
Seiko Epson Corporation
Stultz Jessica
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