Optical: systems and elements – Optical modulator – Light wave temporal modulation
Reexamination Certificate
2003-01-30
2004-12-07
Schwartz, Jordan M. (Department: 2873)
Optical: systems and elements
Optical modulator
Light wave temporal modulation
C359S315000, C359S354000
Reexamination Certificate
active
06829070
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to an electro-optic device and an electronic device. In particular, the invention relates to an electro-optic device utilizing columnar spacers to keep the interval of a clearance sandwiched by two substrates at a predetermined value, and an electronic device that incorporates such an electro-optic device.
2. Description of Related Art
Electro-optic devices, such as liquid crystal display device, are typically configured by sealing liquid crystals between two substrates formed with electrodes, wiring lines and elements. Such an electro-optic device is generally provided with spacers between the two substrates to keep the interval of the clearance sandwiched between the two substrates constant (about three to five micrometers, for example) throughout the substrate surfaces. In other words, the interval is a thickness of a layer formed of liquid crystals (hereinafter “cell gap”). The reason why the cell gap has to be kept constant is that the display characteristics, such as the light transmittance, the contrast ratio and the response speed are adversely affected if the cell gap is not kept constant, and display unevenness is likely to be generated in a bad or the worst case.
More specifically, spacers can be used that have a fine, approximately spherical shape, for example. Many such fine, approximately spherical spacers are uniformly scattered in the liquid crystals between two substrates in the case of direct view (large) liquid crystal display devices, such as a liquid crystal television and a monitor. On the other hand, in the case of small liquid crystal display devices to zoom a light bulb of a projector, the spacers are sometimes used in the form to be mixed in a sealing material to bond two substrates.
In addition, as another example of the spacers, those having a so-called columnar shape (hereafter “columnar spacer”) can also be used (which are disclosed in JP-A-2000-66181). This is an example of spacers for use in the form that columnar members made of suitable organic materials stand together in large numbers at a proper interval on a substrate, which support two substrates by bearing force of the columns in the axial direction to keep the cell gap between the substrates constant. The proper interval is traditionally an extent that a single columnar spacer exists for a few to few tens of pixels, for example. In this connection, even in the case of using such columnar spacers, the approximately spherical spacers mixed in the sealing material (hereafter, the spacers in the sealing material are “gap materials”) can be combined. Accordingly, the requirement to keep the cell gap constant can be satisfied better throughout the substrate surface.
Furthermore, the accuracy in the case of keeping the interval between the substrates constant is varied according to the difference in the twisted angle of liquid crystal molecules configuring the layer made of liquid crystals between the two substrates. For example, the requirement is about ±0.1 &mgr;m or less in the TN (Twisted Nematic) type that the twisted angle is 90 degrees, whereas the requirement is about ±0.3 &mgr;m or less in the STN (Super Twisted Nematic) type that the twisted angle is about 260 degrees.
SUMMARY OF THE INVENTION
However, the related art spacers are subject to the following problem. More specifically, the above liquid crystal display devices need to inject liquid crystals between two substrates, and thus a liquid crystal inlet to communicate the clearance sandwiched between the two substrates with the exterior is disposed. However, the existence of the liquid crystal inlet makes it difficult to keep the cell gap constant.
These circumstances will be described more specifically. First, the manufacture of the liquid crystal display device is largely performed as follows. The necessary features, such as electrodes, wiring lines and elements, are formed over both two substrates beforehand. Then, the sealing material mixed with the gap materials is coated around the circumference of at least one of the two substrates (sealing material coating process). Subsequently, the two substrates are bonded to each other (panel alignment process). Finally, liquid crystals are introduced into the clearance through the liquid crystal inlet by vacuuming.
In such a manufacturing processes, first, the sealing material cannot be coated over the portion to be the liquid crystal inlet in the sealing material coating process. This is because, when the sealing material is coated over the portion, liquid crystals cannot be introduced. In addition, the panel alignment process as a proper pressure is typically applied to two substrates.
Accordingly, the portion where the liquid crystal inlet exists has the cell gap that is smaller than that in the other portions. As described above, this is because two substrates are bonded as a proper pressure is utilized in the panel alignment process. Thus, the sealing material or gap materials in the sealing material generate a predetermined reaction to the substrates coming closer to each other as resisting the pressure. However, the sealing material and the gap materials are not in the portion where the liquid crystal inlet exists.
Here, even though the columnar spacers exist as the spacers between two substrates, the above problem cannot be eliminated. This is because the pressure in the panel alignment process is considerably great, and thus the reaction generated by the columnar spacers does not become equal to the reaction generated by the sealing material and the gap materials. This is more apparent by considering that the columnar spacers support the substrates by the bearing force of the columns in the axial direction as described above, that is, they support the substrate surfaces by so-called ‘points’, whereas the sealing material supports the substrate surfaces by surfaces, although the sealing material is only coated around the circumference of the substrates.
The invention may address the above and/or other problems. The invention provides an electro-optic device capable of keeping the cell gap constant throughout the substrate surfaces and even in of the liquid crystal inlet. The invention also provides an electronic device that incorporates such an electro-optic device.
In order to address or solve the above problem, a first electro-optic device of the invention has a pair of substrates formed to sandwich an electro-optic material, an inlet to communicate a clearance sandwiched by the pair of the substrates with the exterior, and a plurality of columnar spacers scattered within the surfaces of the pair of the substrates facing each other. The columnar spacers are disposed more densely in the vicinity of the inlet, and more sparsely beyond the vicinity of the inlet within the surfaces.
According to the first electro-optic device of the invention, first, the columnar keep the clearance sandwiched between the pair of the substrates at a predetermined thickness. In addition, an electro-optic material, such as liquid crystal, can be introduced from outside of the clearance to the clearance through the inlet. Then, the portion where the inlet exists is generally weaker in strength than other portions because of the formation of the port. Therefore, in the panel alignment process where a pair of substrates is bonded to each other, the portion where the inlet exists is more crushable than the other portions, and thus the cell gap becomes smaller.
Here, particularly in the invention, a plurality of the columnar spacers is disposed between a pair of substrates so as to be scattered within the surfaces in parallel to the pair of the substrates, and the columnar spacers are disposed more densely in the vicinity of the inlet and more sparsely beyond the vicinity of the inlet within the surfaces. Therefore, the reaction caused by the columnar spacers in the vicinity of the inlet becomes greater than that in the other locations. Accordingly, even though a considerably great pressure is applied in bondi
Schwartz Jordan M.
Seiko Epson Corporation
Stultz Jessica
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