JP5148819B2 - Liquid crystal display element - Google Patents

Description

  The present invention relates to a liquid crystal display element, and more particularly to a structure of a liquid crystal display element constituting an FFS (Fringe Field Switching) mode liquid crystal display device.

  In recent years, in the field of flat panel display (FPD), a liquid crystal display (LCD), a plasma display (PDP), a field emission display (FED), a vacuum fluorescent display (VFD) and the like have been actively researched. Currently, liquid crystal display devices (hereinafter referred to as “LCD”) are in the spotlight because of mass production technology, ease of driving means and high image quality. An LCD is a device that displays information on a screen using the refractive index anisotropy of liquid crystal.

  LCDs that are driven in various modes such as a TN (twisted nematic) mode, an STN (super twisted nematic) mode, and an IPS (in-plane switching) mode have been developed. Among these, the IPS mode is a mode in which liquid crystal molecules are always switched to be horizontal with respect to the substrate of the liquid crystal panel, and is switched by using a horizontal electric field in the horizontal direction with respect to the substrate. . Therefore, it is known that the liquid crystal molecules do not stand up obliquely and the change in optical characteristics depending on the viewing angle is small, so that a wider viewing angle can be obtained than in the TN mode or STN mode.

  In recent years, an FFS mode, which is a mode in which switching is performed using a horizontal electric field in the horizontal direction with respect to a substrate, has been developed as in the IPS mode. The FFS mode LCD includes a pixel electrode and a common electrode made of transparent electrodes, and forms a fringe field by making the distance between the pixel electrode and the common electrode narrower than the cell gap between the upper and lower substrates of the liquid crystal panel. Since the liquid crystal molecules of the liquid crystal layer are operated by the electric field generated in the fringe field, it is known that the aperture ratio and the transmittance are higher than those of the IPS mode LCD (see, for example, Patent Document 1).

  An FFS mode or IPS mode LCD has a complicated structure because a pixel electrode, a common electrode, a gate line, a data line, a thin film transistor (hereinafter referred to as “TFT”), and the like are formed over one substrate. . Therefore, a pixel defect may occur due to a short circuit between the pixel electrode and the data line, a short circuit between the gate electrode and the drain electrode of the TFT portion, a short circuit between the source electrode and the drain electrode, or the like. This pixel defect is a bright spot pixel defect whose luminance is higher than that of a normal pixel in a normally black type LCD which is generally widely used in FFS mode or IPS mode LCDs. The occurrence of such bright spot pixel defects significantly deteriorates the display quality.

As a method for preventing the display quality from being deteriorated due to the bright spot pixel defect, there is a repair process in which the bright spot pixel is changed to a dark spot pixel to make the pixel defect inconspicuous (dark spot). This repair process is generally a process in which the drain electrode corresponding to the unit pixel region in question is cut with a laser, and the pixel electrode in the unit pixel region is electrically floated. For example, in order to simplify the repair process in the IPS mode LCD, a structure having a repair line has been proposed (see, for example, Patent Document 2).
JP 2005-107535 A JP 2005-62276 A

  Below, the repair process in FFS mode LCD is demonstrated.

  First, the structure of a conventional FFS mode LCD will be described with reference to FIGS. FIG. 4 is a front view showing a structure of a unit pixel in a conventional FFS mode LCD, and FIG. 5 is a cross-sectional view taken along line IV-IV ′ of FIG.

  In the unit pixel region of the conventional FFS mode LCD shown in FIG. 4, a TFT 74 is disposed at a portion where the gate line 62 and the data line 64 intersect, and a pixel electrode 66 is disposed so as to be connected to the TFT 74. That is, the TFT 74 includes a gate electrode 78, a source electrode 92, and a drain electrode 88. The gate electrode 78 is connected to the gate line 62, the source electrode 92 is connected to the data line 64, and the drain electrode 88 is connected to the pixel electrode 66. Connected to. The common line 68 arranged in parallel with the gate line 62 has a role of supplying a common voltage to the common electrode. A horizontal electric field is formed by the voltage difference between the common electrode and the pixel electrode 66 to drive the orientation of liquid crystal molecules (not shown) in the liquid crystal layer sandwiched between the upper and lower substrates.

  Further, the conventional FFS mode LCD shown in FIG. 4 has a structure in which a plate-like (solid) common electrode 72 is formed on the entire surface of the liquid crystal panel. By adopting such a structure, it becomes possible to supply the common voltage not only from the common line 68 but also from an arbitrary portion at the end of the common electrode 72, and to reduce the resistance generated by the voltage supply. Can do. Next, the detailed structure of the conventional FFS mode LCD shown in FIG. 4 will be described with reference to FIG.

As shown in FIG. 5, a gate electrode 78 is formed on a substrate 76 made of a transparent insulating material such as glass, and an insulating film 82 (a gate insulating film on the gate electrode 78) is formed thereon. . An a-Si layer 84 and an N ⁺ a-Si layer 86 are sequentially formed on the gate insulating film, and a metal layer is formed on the N ⁺ a-Si layer 86, and the source electrode 92 and the drain are formed by etching. An electrode 88 is formed.

  Further thereon, a passivation layer (protective layer) 94 is formed on the entire surface of the liquid crystal panel, and an insulating layer (or a layer having an insulating layer and a photoacryl layer formed thereon) 96 is formed. A common electrode (ITO) 72 is formed in a plate shape on the entire surface of the liquid crystal panel on the insulating layer 96, and a passivation layer 102 is formed on the common electrode (ITO) 72, and a pixel electrode is connected to the drain electrode 88. 66 is formed.

  In the process of manufacturing a conventional FFS mode LCD, in particular, the gate electrode 78 may have a defect such as an uneven surface. When such a defective gate electrode 78 is short-circuited with the drain electrode 88 and a high voltage, which is a gate voltage, is applied to the pixel electrode 66 connected to the drain electrode 88, a bright pixel is formed.

  Repair processing is performed to darken the bright pixel. When repair processing using a laser is performed in the FFS mode LCD having the structure shown in FIG. 5, the drain electrode 88 is cut by irradiating a laser as indicated by an arrow A or an arrow B. The position indicated by the arrow A or the arrow B indicates a position (hereinafter referred to as “repair point”) where the drain electrode 88 is cut by irradiating a laser in a general repair process.

  When the repair process is performed and the drain electrode 88 is cut, the drain electrode 88 is melted by irradiating a laser, and the common electrode 72 and the gate electrode 78 are short-circuited due to the scattered melt, whereby the gate electrode 78 In some cases, the voltage drops rapidly, and a wide range of display defects centering on the short-circuited location may occur.

  The present invention has been made in view of the above problems, and an object thereof is to provide a liquid crystal display element constituting an FFS mode LCD having a structure capable of easily performing an appropriate repair process.

  In order to solve the above-described problems, the present invention provides a pair of transparent insulating substrates that are arranged to face each other at a predetermined interval through a liquid crystal layer composed of a plurality of liquid crystal molecules, and one of the pair of transparent insulating substrates. A plurality of gate lines and data lines formed in a matrix form so as to limit each unit pixel, a pixel electrode made of a transparent conductor disposed on each unit pixel, and a fringe field together with the pixel electrode A common electrode made of a transparent conductor, a thin film transistor that is arranged at a portion where the gate line and the data line intersect, and includes a gate electrode, a source electrode, and a drain electrode, and a drain An opening is provided in a region on the common electrode corresponding to the repaired portion of the electrode.

  Further, the present invention is formed on one of the pair of transparent insulating substrates and a pair of transparent insulating substrates disposed opposite to each other with a predetermined interval through a liquid crystal layer composed of a plurality of liquid crystal molecules, A plurality of gate lines and data lines arranged in a matrix form so as to limit each unit pixel, a pixel electrode made of a transparent conductor arranged in each unit pixel, and a fringe field formed together with the pixel electrode Corresponding to a region including a drain electrode, including a common electrode made of a transparent conductor, and a thin film transistor including a gate electrode, a source electrode, and a drain electrode arranged at a portion where the gate line and the data line intersect. An opening is provided in a region on the common electrode.

  The present invention has a structure in which an opening is provided in a region on a common electrode corresponding to a drain electrode serving as a general repair point, so that when a laser irradiation is performed in a repair process, the gate electrode and the common electrode It is possible to provide a liquid crystal display element that constitutes an FFS mode LCD that can prevent a short circuit.

  Hereinafter, first and second embodiments to which the present invention is applied will be described with reference to FIGS. FIG. 1 shows a front view of a unit pixel common to the first and second embodiments. 2 and 3 are cross-sectional views taken along the line II-II 'in FIG. 1, and correspond to the first and second embodiments, respectively.

<First embodiment>
FIG. 1 is a front view showing the structure of a unit pixel in the first embodiment. In the unit pixel region of the FFS mode LCD to which the present invention shown in FIG. 1 is applied, a TFT 12 is disposed at a portion where the gate line 2 and the data line 4 intersect, and a pixel electrode 6 is disposed so as to be connected to the TFT 12. ing. The TFT 12 includes a gate electrode, a source electrode, and a drain electrode. The structure of the TFT 12 is the same as that of the TFT 74 shown in FIGS. Further, since a plate-like (solid) common electrode 8 is formed on the entire surface of the liquid crystal panel and a common voltage can be supplied from an arbitrary portion of the end of the common electrode 8, a common line is required. It has a structure that does not.

  Further, in the structure of the unit pixel of the FFS mode LCD to which the present invention is applied, a portion that clearly differs from the conventional FFS mode LCD is a portion in which the repair opening 14 is provided. Next, the repair opening 14 will be described in detail with reference to FIG.

FIG. 2 is a cross-sectional view taken along line II-II ′ of FIG. As shown in FIG. 2, a gate electrode 18 is formed on a substrate 16 made of a transparent insulating material such as glass, and an insulating film 22 (a gate insulating film on the gate electrode 18) is formed thereon. . An a-Si layer 24 and an N ⁺ a-Si layer 26 are sequentially formed on the gate insulating film, and a metal layer is formed on the N ⁺ a-Si layer 26, and the source electrode 32 and the drain are formed by etching. Electrode 28 is formed.

  Further, a passivation layer (protective layer) 34 is formed on the entire surface of the liquid crystal panel, and an insulating layer (or a layer having a structure in which an insulating layer and photoacryl is formed thereon) 36 is formed. A common electrode (ITO) 8 is formed in a plate shape on the entire surface of the liquid crystal panel on the insulating layer 36, and a passivation layer 42 is formed on the common electrode (ITO) 8, and the pixel electrode is connected to the drain electrode 28. 6 is formed.

  Here, a first repair region 46 is provided in a region on the plate-like common electrode 8 corresponding to the drain electrode 28. The first repair region 46 has a structure in which the plate-like common electrode 8 is removed, and corresponds to the repair opening 14 shown in FIG.

  And in order to manufacture the liquid crystal panel which has the 1st repair area | region 46 in each pixel unit, when exposing in the photolithography process performed after apply | coating ITO which is a constituent material of the common electrode 8 on the insulating layer 36, A mask having a shape provided with the repair opening 14 may be used.

  Thus, the structure provided with the repair opening 14 prevents the common electrode 8 and the gate electrode 18 from being short-circuited when the laser irradiation in the repair process is performed as indicated by the arrow C or the arrow D. Can do. However, an arrow C or an arrow D indicates a general repair point. The repair location is a repair point portion after the repair process is performed.

  As described above, according to the first embodiment of the present invention, the repair opening 14 is provided on the plate-like common electrode 8 in the first repair region 46 corresponding to the drain electrode 28 serving as a general repair point. Thus, it is possible to prevent a short circuit between the common electrode 8 and the gate electrode 18 due to laser irradiation in the repair process. Further, the repair opening 14 is provided at a position where the opening of the pixel electrode 6 is not affected, so that the aperture ratio is not changed.

<Second embodiment>
The unit pixel of the FFS mode LCD in this embodiment has a structure in which another common electrode is provided on the plate-like common electrode of the first embodiment and two layers of common electrodes are provided. However, portions common to the first embodiment are denoted by the same reference numerals in the drawing and description thereof is omitted.

  FIG. 3 is a cross-sectional view showing the structure of the unit pixel in this embodiment. As shown in FIG. 3, a second-layer common electrode 48 (second common electrode) is formed on the plate-like common electrode 8 (first common electrode). However, a contact hole is provided in the passivation layer 42 formed on the plate-like common electrode 8, and the plate-like common electrode 8 and the second-layer common electrode 48 are electrically connected. Such a contact hole is provided at an appropriate position in each unit pixel region. In addition, by forming the common electrodes 8 and 48 in a two-layer structure in this way, it is possible to reduce the resistance caused by the voltage supply.

  The first repair region 46 is provided on the plate-like common electrode 8 as in the first embodiment, and the second repair region 52 is provided on the second layer common electrode 48. The second repair region 52 has a structure in which the second-layer common electrode 48 is removed, and corresponds to the repair opening 14 shown in FIG. 1 in the same manner as the first repair region 46.

  In addition, in order to manufacture a liquid crystal panel having the first repair region 46 and the second repair region 52 in each unit pixel, as in the case of the first embodiment, the plate-like common electrode 8 or the second layer A mask having a shape including the repair opening 14 may be used in exposure performed in a photolithography process performed after ITO, which is a constituent material of the common electrode 48, is applied on the insulating layer 36 or the passivation layer 42.

  As described above, the first repair region 46 and the second repair region 52 are respectively formed on the plate-like common electrode 8 and the second-layer common electrode 48 in regions corresponding to the drain electrode 28 serving as a general repair point. A repair opening 14 is provided at the top. With the structure having the repair opening 14, when the laser irradiation in the repair process is performed at a position indicated by an arrow C or an arrow D corresponding to a general repair point, the plate-like common electrode 8 or the second layer A short circuit between the common electrode 48 of the eye and the gate electrode 18 can be prevented.

  As described above, according to the second embodiment of the present invention, the first and second repair regions corresponding to the drain electrode 28 serving as a general repair point even if the structure includes the two layers of the common electrodes 8 and 48. In 46 and 52, by providing the repair opening 14 in each of the common electrodes 8 and 48, a short circuit between the common electrodes 8 and 48 and the gate electrode 18 due to laser irradiation in the repair process can be prevented. As in the first embodiment, the repair opening 14 is provided at a position that does not affect the opening of the pixel electrode 6, so that the aperture ratio is not changed.

It is a top view which shows the structure of the unit pixel to which this invention is applied. It is sectional drawing which shows the structure of the unit pixel in 1st Example. It is sectional drawing which shows the structure of the unit pixel in 2nd Example. It is a top view which shows the structure of the conventional unit pixel. FIG. 5 is a cross-sectional view taken along line IV-IV ′ shown in FIG. 4.

Explanation of symbols

2 Gate line 4 Source line 18 Gate electrode 28 Drain electrode 32 Source electrode 6 Pixel electrode 8 Plate-like (solid) common electrode 12 TFT
14 repair opening 46 first repair region 48 second layer common electrode 52 second repair region

Claims (3)

A pair of transparent insulating substrates disposed opposite to each other at a predetermined interval through a liquid crystal layer composed of a plurality of liquid crystal molecules;
A plurality of gate lines and data lines formed on one of the pair of transparent insulating substrates and arranged in a matrix so as to limit each unit pixel;
A thin film transistor disposed at a portion where the gate line and the data line intersect, and including a gate electrode, a source electrode, and a drain electrode;
An insulating layer formed on the entire surface of the liquid crystal panel on the thin film transistor;
A first common electrode formed in a flat plate shape on the entire surface of the substrate on which the data line and the gate line are disposed on the insulating layer, and made of a transparent conductor;
A passivation layer formed on the entire surface of the liquid crystal panel on the common electrode;
Each unit pixel on the passivation layer is disposed so as to form a fringe field together with the common electrode, and includes a pixel electrode made of a transparent conductor,
A liquid crystal display element, wherein an opening is provided in the common electrode region on the drain electrode corresponding to a repair location.
A pair of transparent insulating substrates disposed opposite to each other at a predetermined interval through a liquid crystal layer composed of a plurality of liquid crystal molecules;
A plurality of gate lines and data lines formed on one of the pair of transparent insulating substrates and arranged in a matrix so as to limit each unit pixel;
A thin film transistor disposed at a portion where the gate line and the data line intersect, and including a gate electrode, a source electrode, and a drain electrode;
An insulating layer formed on the entire surface of the liquid crystal panel on the thin film transistor;
A first common electrode formed in a flat plate shape on the entire surface of the substrate on which the data line and the gate line are disposed on the insulating layer, and made of a transparent conductor;
A passivation layer formed on the entire surface of the liquid crystal panel on the common electrode;
Each unit pixel on the passivation layer is disposed so as to form a fringe field together with the common electrode, and includes a pixel electrode made of a transparent conductor,
A liquid crystal display element, wherein an opening is provided in the common electrode on the drain electrode.
Are arranged to sandwich an insulating layer on the previous SL first common electrode is connected to the first common electrode through a contact hole insulating layer has, further comprising a second common electrode formed of a transparent conductor The liquid crystal display element according to claim 1 or 2.

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