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  Liquid crystal display device, display device and manufacturing method thereofUSPTO Application #: 20060187371Title: Liquid crystal display device, display device and manufacturing method thereof Abstract: Image display device having an electrode forming layer which includes a plurality of gate lines, a plurality of drain lines, a plurality of switching elements and the a plurality of pixel electrodes, and having reference electrode layer between the electrode forming layer and a substrate where the electrode forming layer formed thereon, and the reference electrode layer and the electrode forming layer are insulated by insulating layer. (end of abstract) Agent: Reed Smith LLP - Falls Church, VA, US Inventors: Yoshiaki Nakayoshi, Kazuhiko Yanagawa USPTO Applicaton #: 20060187371 - Class: 349038000 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20060187371. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application is a Divisional of U.S. Ser. No. 11/211,574 filed Aug. 26, 2005, which is a Divisional of U.S. Ser. No. 10/237,911 filed Sep. 10, 2002. Priority is claimed based on U.S. Ser. No. 11/211,574 filed Aug. 26, 2005, which claims priority to U.S. Ser. No. 10/237,911 filed Sep. 10, 2002, which claims priority to Japanese Patent Application No. 2001-317147 filed on Oct. 15, 2001, and which is hereby incorporated by reference. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to a liquid crystal display device, and more particularly to an active matrix type liquid crystal display device which can reduce holding capacity for holding lighting of pixels for a given time and feeding resistance thereof thus enhancing numerical aperture. [0004] 2. Description of the Related Art [0005] An active matrix type liquid crystal display device generally adopts a system in which liquid crystal is sandwiched between a pair of substrates which face each other in an opposed manner and pixels are selected by pixel electrodes which are driven by a large number of switching elements represented by thin film transistors formed on one of the above-mentioned pair of substrates. One type of the liquid crystal display device adopting such a system is a so-called vertical field type in which on the other substrate (second substrate) which faces one substrate (first substrate) of the above-mentioned pair of substrates, color filters and common electrodes are formed or the color filters are also formed on the first substrate. [0006] As another system, there exists a so-called IPS system in which counter electrodes which correspond to the common electrodes are formed on the above-mentioned first substrate side. Also with respect to this system, there has been known a system which forms color filters on either the first substrate side or the second substrate side. [0007] The vertical field type liquid crystal display device includes a plurality of gate lines which extend in the first direction (usually horizontal scanning direction) and are arranged parallel to each other and a plurality of drain lines which extend in the second direction which crosses the gate lines (usually vertical scanning direction) and are arranged parallel to each other. The liquid crystal display device further includes switching elements such as thin film transistors or the like in the vicinity of respective crossing portions of the gate lines and drain lines and pixel electrodes which are driven by the switching elements. [0008] In this vertical field type liquid crystal display device, the common electrodes are formed on the second substrate such that the common electrodes face the pixel electrodes in an opposed manner, an electric field is generated between the common electrodes and the selected pixel electrodes in the direction which approximately crosses a surface of the substrate at a right angle, and lighting of the pixels is performed by changing the orientation of liquid crystal molecules sandwiched between the pixel electrode and the common electrodes. [0009] On the other hand, in the IPS type liquid crystal display device, gate lines, drain lines, and switching elements similar to those of the vertical field type liquid crystal display device are formed on an inner surface of the above-mentioned first substrate, comb-shaped pixel electrodes are formed on the same substrate, and counter electrodes are formed close to the pixel electrodes on the same substrate. Then, an electric field is generated between the selected pixel electrodes and the counter electrodes in the direction approximately parallel to a surface of the substrate, and lighting of the pixels is performed by changing the orientation direction of liquid crystal molecules arranged between the pixel electrodes and the counter electrodes. As a liquid crystal display device which has developed this type, there exists a liquid crystal display device which adopts a matted electrode as the counter electrodes and forms comb-shaped pixel electrodes as a layer above or below the counter electrodes. [0010] In both of the above-mentioned type liquid crystal display devices, the charge storing capacity for holding the lighting time of `the pixels which are lit due to selection at a given value (hereinafter, simply referred to as "holding capacity") is formed in regions where the pixel electrodes and the gate lines are overlapped or regions where other electrode lines which are formed such that the other electrode lines transverse the pixel electrode forming region and the pixel electrodes, and feeding paths for storing charge in the holding capacity is formed of either the gate lines or the above-mentioned electrode lines. SUMMARY OF INVENTION [0011] In this manner, one electrode which forms the holding capacity is a linear electrode and the feeding is limited to one direction (extending direction of the electrode) and hence, the feeding resistance is large. Further, corresponding to the increase of the distance between the electrode and a feeding end, the voltage drop is remarkably increased so that there arises a case that the required charge cannot be fed. Further, since the above-mentioned gate line usually crosses the drain line, a crossing capacity is increased. As a result, this has been one of causes which make the rapid driving of liquid crystal display device difficult. As a countermeasure to cope with such a problem, there has been proposed a liquid crystal display device which uses the above-mentioned other electrode line. However, when the holding capacity is formed in the pixel electrode forming region, numerical aperture is reduced as a matter of course. [0012] Further, along with the demand for high definition, the size of pixels per one pixel is reduced so that there has been a task that it is difficult to form the sufficient holding capacity. [0013] Further, although it is effective to reduce the size of the holding capacity to enhance the numerical aperture, this brings about the reduction of the holding capacity. That is, there has been a task that there exists a trade-off relationship between the enhancement of numerical aperture and the assurance of holding capacity. [0014] Accordingly, it is an object of the present invention to provide an active matrix liquid crystal display device which can reduce resistance of feeding electrodes which constitute holding capacities. It is another object of the present invention to provide a rapid driving active matrix type liquid crystal display device having high brightness by obviating the reduction of numerical aperture of pixels. [0015] It is still another object of the present invention to realize an active matrix type liquid crystal display device which can satisfy both of the assurance of holding capacity and the enhancement of numerical aperture simultaneously. [0016] Other objects and advantages of the present invention will be apparent from the explanation made hereinafter. [0017] The typical constitution of the present invention lies in that on a switching element forming substrate of the liquid crystal display device, a transparent conductive layer (reference layer) having a large area which covers at least a major portion or a whole area of a pixel electrode forming region is formed, and switching elements (active elements), other electrodes and lines are formed over the transparent conductive layer by way of an insulation layer. Due to such a constitution, the feeding resistance with respect to the holding capacity can be largely reduced. Further, a trade-off between the enhancement of numerical aperture and the increase of holding capacity can be eliminated. Representative constitutions of the present invention are described hereinafter. (1): [0018] In a liquid crystal display device in which liquid crystal is sandwiched between a first substrate and a second substrate which face each other in an opposed manner, and at least a plurality of gate lines which extend in the first direction and are arranged parallel to each other, a plurality of drain lines which extend in the second direction which crosses the gate lines and are arranged parallel to each other, a plurality of switching elements which are arranged at crossing portions of the gate lines and the drain lines, and pixel electrodes which are driven by the switching elements are formed on an inner surface of the first substrate, [0019] having an electrode forming layer which include the gate lines, the drain lines, the switching elements and the pixel electrodes, [0020] having a reference electrode layer arranged between the first substrate and the electrode forming layer with first insulation layer between the reference electrode layer and the electrode forming layer, and Continue reading... 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