Static molds – Container-type molding device – Adjustable – forming different size or shaped product
Reexamination Certificate
2002-06-24
2004-03-16
Ton, Toan (Department: 2871)
Static molds
Container-type molding device
Adjustable, forming different size or shaped product
C349S153000, C349S156000, C349S190000, C349S106000
Reexamination Certificate
active
06705584
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device which is provided with spacers having novel constitution for securing a fixed distance or gap between a pair of substrates which seals liquid crystal therebetween.
2. Description of the Related Art
A liquid crystal display device has been popularly used as a display device for a notebook type computer or a computer monitor which is capable of providing a high-definition color display. This type of liquid crystal display device is substantially configured such that liquid crystal is filled in a gap formed between a pair of substrates which are opposite to one another, wherein at least one of the substrates is made of transparent glass or the like.
A liquid crystal display device is roughly classified into a type which performs lighting and extinguishing of light of given pixels by selectively applying a voltage to respective electrodes for forming pixels formed on a pair of substrates (simple-matrix type liquid crystal display device) and a type which performs lighting and extinguishing of light of given pixels by controlling several types of electrodes and switching elements for selecting pixels formed on either one or both of the above-mentioned substrates (active-matrix type liquid crystal display device).
Typically, the active-matrix type liquid crystal display device employs thin film diodes (TFDs) or thin film transistors (TFTs) as the switching elements formed on one substrate. Particularly, because of its characteristics of being thin and light-weighted and capable of exhibiting high image quality comparable to image quality of a cathode ray tube, the liquid crystal display device using the thin film transistors has been popularly used as a display terminal monitor or the like of various types of OA equipments.
A display method of this active-matrix type liquid crystal display device is roughly classified into following two methods. One display method is a method in which a liquid crystal composition is sandwiched between two sheets of substrates on which transparent electrodes are respectively formed, the liquid crystal composition is operated by voltages applied to the transparent electrodes, and display is performed by modulating light incident on the liquid crystal layer after passing through the transparent electrodes (so-called vertical electric field method or TN method). Products which have been popularly commercialized adopt this method.
Further, another method is a method in which liquid crystal composition is operated due to an electric field formed substantially parallel to a substrate surface between two electrodes constituted on the same substrate, and display is performed by modulating light incident on the liquid crystal composition layer through a gap formed between these two electrodes (IPS or lateral electric field method).
In the liquid crystal display device, it is necessary to maintain a gap formed between a pair of substrates which sandwich liquid crystal therebetween, that is, to maintain a cell gap to a given value. As means for maintaining such a gap, fine beads (bead spacers) made of glass or resin have been popularly used in the past. Since these bead spacers are scattered on a surface of one substrate using spray means or the like before laminating respective substrates, these bead spacers are distributed also in pixel regions. Accordingly, there has been a problem that a transmitting light or a reflecting light passes through bead spacers and generates a so-called leaking of light thus degrading contrast.
To overcome such a problem derived from the bead spacers, there has been proposed a method in which spacers are provided by fixedly forming columnar members at portions avoiding pixel regions with respect to the above-mentioned lateral electric field method (for example, Japanese Laid-open Patent Publication 48636/1998). These spacers are referred to as columnar spacers, wherein the spacers are formed in a columnar shape by laminating color filters of a plural colors and a light shielding layer, or the spacers are formed in a columnar shape by laminating end portions of color filters, or the spacers are formed on a color filter substrate side where wiring and electrodes are not present using a photolithography technique which forms the spacers by exposure/etching using a photosensitive resist.
SUMMARY OF THE INVENTION
However, since the TN (Twisted Nematic) type liquid crystal display device is provided with a common electrode at a color filter substrate side, the order of forming the common electrodes and the columnar spacers is limited. Over the color filters of the color filter substrate, a transparent protective film (overcoat) may also be formed to level the unevenness. In the conventional color filter substrate having such a constitution, the columnar spacers are formed on the transparent protective film using a photosensitive resist and, thereafter, the columnar spacers and the transparent protective film are covered with the common electrode, and an orientation film is further formed on the common electrode. Such a color filter substrate is disclosed in Japanese Laid-open Patent Publication 84394/1999, for example. On the other hand, with respect to the color filter substrate which forms the columnar spacers by laminating color layers (color filter layers), the common electrode is formed such that the common electrode covers the columnar spacers after the columnar spacers are formed.
However, with respect to the TN type liquid crystal display device, as mentioned above, when the color filter substrate which covers the columnar spacers with the common electrode after the columnar spacers are formed and a so-called thin film transistor substrate on which thin film transistors and pixel electrodes which are connected to the thin film transistors are formed for respective pixels are laminated to each other, the common electrode which is formed on upper portions of columnar spacers are projected toward a main surface of the thin film transistor substrate from a main surface of the color filter substrate. Accordingly, a conductive film which constitutes the common electrode above the main surface of the color filter substrate and electrode layers such as wiring layers or the above-mentioned pixel electrodes which are formed above the main surface of the thin film transistor substrate are brought into contact with each other thus generating short-circuit whereby the product failure such as defective pixels or the like are brought about. In the above-mentioned Japanese Laid-open Patent Publication 84394/1999, although an insulation film is provided to prevent the short-circuit, steps for forming the insulation layer become necessary.
Usually, it is considered that the adhesiveness between the common electrode formed of ITO (Indium Tin Oxide) and the columnar spacers formed of resin material is not favorable. Accordingly, the columnar spacers are moved or turned down in a cell gap adjustment step so that a given cell gap can not be secured or the columnar spacers are projected into the pixel regions thus generating leaking of light. Further, since the common electrode is selectively formed on a display area of the color filter substrate, it is difficult to maintain the gap between two substrates to a fixed value in the display area, in a periphery thereof and in a sealing region. Further, with only the provision of the columnar spacers formed in the display area, in laminating two substrates, when only a sealing material is applied to a sealing portion, that is, peripheral portions of two substrates, since a pressing force is not uniformly applied to the display area and the peripheral portion at the time of adjusting the cell gap, it is difficult to perform the uniform gap adjustment with respect to the gap between the two substrates. These constitute conventional problems to be solved.
On the other hand, Japanese Laid-open Patent Publication 21902/2001 discloses a
Hamamoto Tatsuo
Hiroshima Minoru
Yamada Hironobu
Juan Carlos A. Marquez, Esq.
Qi Mike
Ton Toan
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