JP2009042791A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device capable of reducing point defect and improving transmissivity. <P>SOLUTION: In a structure where an opposite electrode composed of a transparent material and having a rectangular planar pattern, and an interdigital transparent pixel electrode are superposed through an insulating film on one of substrates of one pixel region, the opposite electrode has a cut or a slit so that a source electrode made of an opaque material and transmitting electric potential to a transparent pixel electrode from a thin film transistor, is not overlapped to the opposite electrode. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device in which a pixel electrode and a counter electrode are formed on the liquid crystal surface side of one of the substrates disposed to face each other via liquid crystal.

  In this type of liquid crystal display device, the amount of light transmitted through the region between the pixel electrode and the counter electrode is controlled by driving the liquid crystal to which an electric field generated between the electrodes is applied. It has become.

  Such a liquid crystal display device is known to have excellent so-called wide viewing angle characteristics in which the display does not change even when observed from a direction oblique to the display surface.

  Until now, the pixel electrode and the counter electrode have been formed of a conductive layer that does not transmit light.

  However, in recent years, a counter electrode made of a transparent electrode has been formed over the entire region excluding the periphery of the pixel region, and extends in one direction via an insulating film on the counter electrode and arranged in parallel in a direction intersecting the one direction. The thing of the structure which formed the strip | belt-shaped pixel electrode which consists of the made transparent electrode came to be known.

  In the liquid crystal display device having such a configuration, an electric field in a direction substantially parallel to the substrate is generated between the pixel electrode and the counter electrode, and the wide viewing angle characteristic is still excellent and the aperture ratio is greatly improved. (See the following patent document).

JP-A-11-202356

  However, in such a liquid crystal display device, a counter electrode formed in a region excluding a slight periphery of the pixel region overlaps with a comb-like pixel electrode formed through an insulating film in a large area. When there is a pinhole in the insulating film, a short circuit defect occurs, resulting in a point defect on the display and a problem that the image quality is deteriorated.

  Further, in the pixel region, since the pixel electrode and the thin film transistor to be connected to the pixel electrode are arranged on different insulating films through the insulating film, a contact hole having a large area is required at the connection point. There is a problem that the aperture ratio, that is, the transmittance of the liquid crystal display device is lowered. Furthermore, in the case of a configuration in which a signal is supplied to each counter electrode by a counter electrode wiring made of an opaque metal material with a low electrical efficiency, there is a problem in that the transmittance decreases as the width of the counter electrode wiring is wide. It was.

  Further, the contact hole formation portion has a large step, and when an alignment film is formed on this and rubbing is performed, a region where the liquid crystal alignment is disturbed substantially along the rubbing direction is formed, resulting in a decrease in transmittance. It was.

  The present invention has been made based on such circumstances, and an object of the present invention is to provide a liquid crystal display device in which a short circuit between a pixel electrode and a counter electrode is avoided and image quality is improved.

  Another object of the present invention is to provide a liquid crystal display device with an improved porosity.

  Furthermore, another object of the present invention is to provide a liquid crystal display device that avoids disturbance of liquid crystal alignment around the contact hole.

  In order to solve the above-mentioned problems, the following means are provided.

(1) In the present invention, for example, a plurality of counter electrode signal lines, a plurality of gate signal lines, and a plurality of drain signal lines are formed on the first transparent insulating substrate, and the adjacent gate signal lines and adjacent ones are formed. In a liquid crystal display device having a region surrounded by the drain signal wiring as a pixel region, the pixel region having a thin film transistor, a rectangular transparent counter electrode, and a transparent pixel electrode formed through the counter electrode and an insulating film ,
The counter electrode is connected to the counter electrode of the adjacent pixel region by a connection wiring formed so as to straddle the gate signal wiring formed between the counter electrodes through an insulating film. .

(2) In the liquid crystal display device according to the present invention, for example, on the premise of the configuration of (1), the connection wiring is connected through a through hole formed in an insulating film between the connection wiring and the counter electrode. It is characterized by that.

(3) In the liquid crystal display device according to the present invention, for example, on the premise of the configuration of (2), a connecting member made of the same material as the gate signal wiring is arranged between the connection wiring and the gate signal wiring. Features.

(4) The liquid crystal display device according to the present invention is characterized in that, for example, on the premise of the configuration of (1), a semiconductor layer is formed between the connection wiring and the gate signal wiring.

(5) In the liquid crystal display device according to the present invention, for example, the connection wiring is made of the same material as the pixel electrode.

(6) The liquid crystal display device according to the present invention is premised on the configuration of (1), for example, and the connection wiring is formed in parallel with the drain signal wiring.

(7) The liquid crystal display device according to the present invention is based on, for example, the configuration of (1), and the counter electrode wiring is arranged in parallel with the gate signal wiring.

(8) The liquid crystal display device according to the present invention is based on, for example, the configuration of (1), and the pixel electrode is 3 to 20 degrees clockwise or 3 to 20 counterclockwise with respect to the gate signal wiring. It has a plurality of slits having an angle of degrees.

Example 1.
FIG. 2 is a diagram showing an equivalent circuit of the liquid crystal display panel according to the first embodiment of the present invention together with an external circuit of the liquid crystal display panel.

  In FIG. 2, scanning signals (voltage signals) are sequentially supplied by the vertical scanning circuit V to the gate signal lines GL extending in the x direction and arranged in parallel in the y direction.

  The thin film transistor TFT in each pixel region arranged along the gate signal line GL to which the scanning signal is supplied is turned on by the scanning signal.

  In accordance with this timing, a video signal is supplied from the video signal driving circuit H to each drain signal line DL. Each drain signal line DL extends in the y direction in the drawing and is arranged in parallel in the x direction. This video signal is applied to the pixel electrode PX via the thin film transistor in each pixel region.

  In each pixel region, a counter voltage is applied to the counter electrode CT formed together with the pixel electrode PX via the counter voltage signal line CL, and an electric field is generated between these electrodes. ing. Each of the pixel electrode PX and the counter electrode CT is applied with the video information voltage from the drain signal line DL to the pixel electrode PX while the thin film transistor TFT is turned on at the timing when the gate signal line GL is applied with the on voltage. The counter voltage signal line CL connected to the power source is propagated to the counter electrode CT in each pixel region, thereby functioning to apply a voltage to the liquid crystal capacitor. The pixel electrode PX and the counter electrode CT are formed on the first transparent substrate SUB1 on which the thin film transistor TFT is formed. The pixel electrode PX and the counter electrode CT are the sum of the two capacitances of the storage capacitor element Cstg formed with an insulating film sandwiched between the pixel electrode PX and the counter electrode CT and the electric field between the pixel electrode PX and the counter electrode CT. Configure capacity. The liquid crystal mode of the present invention is characterized in that the area where the counter electrode CT and the pixel electrode PX are stacked with an insulating film interposed therebetween is large, so that the storage capacitor element Cstg of one pixel has a large value.

  The light transmittance of the liquid crystal LC is controlled by an electric field having a component parallel to the transparent substrate SUB1.

  In the drawing, the reference numerals R, G, and B shown in each pixel region indicate that a red filter, a green filter, and a blue filter are formed in each pixel region, respectively.

  In the above, one pixel region is a region surrounded by the adjacent drain signal line DL and the adjacent gate signal line GL, and the thin film transistor TFT, the pixel electrode PX, and the counter electrode CT are formed in the region as described above. Has been.

  On the other hand, the counter voltage signal line CL is a first transparent substrate SUB1, which is a horizontal wiring arranged in parallel with the gate signal line GL, and is collected outside the pixel region and connected to an external power source.

  FIG. 1 is a configuration diagram in a pixel region of a liquid crystal display device (panel) according to the present invention, and is a plan view as viewed from the liquid crystal side of one transparent substrate among transparent substrates arranged to face each other through liquid crystal. is there.

  3 is a sectional view taken along line I (a) -I (b) in FIG. 1, FIG. 5 is a sectional view taken along line II (a) -II (b), and FIG. 5 is taken along line III (a) -III (b). A cross-sectional view is shown in FIG. 6, and a cross-sectional view taken along line IV (a) -IV (b) is shown in FIG. FIG. 4 is a plan view schematically showing the operation of the liquid crystal molecules in the liquid crystal mode when the voltage is on and off.

  First, in FIG. 1, gate signal lines GL extending in the x direction and arranged in parallel in the y direction are, for example, molybdenum (Mo), aluminum (Al), molybdenum (Mo) from the first transparent substrate side. The three-layer laminated film is formed. The gate signal line GL forms a rectangular area with a drain signal line DL described later, and the area constitutes a pixel area.

  In this pixel region, a counter electrode CT that generates an electric field with a pixel electrode PX, which will be described later, is formed, and this counter electrode CT is formed in almost the entire center except for a slight periphery of the pixel region, For example, the transparent conductor is made of ITO (Indium-Tin-Oxide). The counter electrode CT has a notch, which will be described later.

  The counter electrode CT is connected to the counter voltage signal line CL arranged in parallel with the gate signal line GL near the center of the adjacent gate signal line GL. The counter voltage signal line CL is formed integrally with the counter electrode CT in the region (each pixel region arranged along the gate signal line GL).

  The counter voltage signal line CL is formed of an opaque material made of, for example, a three-layer laminated film of molybdenum (Mo), aluminum (Al), and molybdenum (Mo).

  Further, as described above, by using the same material for the counter voltage signal line CL as that for the gate signal line GL, they can be formed in the same process, and an increase in the number of manufacturing steps can be avoided.

  Here, the counter voltage signal line CL is not limited to the above-mentioned three-layer film, but for example, a single-layer film of Cr, Ti, Mo, or a two-layer film or a three-layer film of these and a material containing Al Needless to say, it may be formed by the following.

  However, in this case, it is effective to position the counter voltage signal line CL in an upper layer with respect to the counter electrode CT. However, the selective etching solution (for example, HBr) of the ITO film constituting the counter electrode CT easily dissolves Al.

  Furthermore, it is effective to interpose a refractory metal such as Ti, Cr, Mo, Ta, and W at least on the contact surface of the counter voltage signal line CL with the counter electrode CT. However, the ITO constituting the counter electrode CT oxidizes Al in the counter voltage signal line CL to generate a high resistance layer.

  For this reason, as an example, when forming the counter voltage signal line CL made of Al or a material containing Al, it is preferable to have a multilayer structure in which the refractory metal is the first layer.

  An insulating film GI made of, for example, SiN is formed on the upper surface of the transparent substrate on which the counter electrode CT, the counter voltage signal line CL, and the gate signal line GL are formed.

  This insulating film GI functions as an interlayer insulating film for the counter voltage signal line CL and the gate signal line GL with respect to a drain signal line DL described later, and as a gate insulating film in a region where a thin film transistor TFT described later is formed. In a region where a capacitance element Cstg, which will be described later, is formed, it has a function as a dielectric film.

  A thin film transistor TFT is formed so as to overlap a part of the gate signal line GL (lower left in the figure), and a semiconductor layer AS made of, for example, a-Si is formed on the insulating film GI in this part.

  By forming the drain electrode SD1 and the source electrode SD2 on the upper surface of the semiconductor layer AS, an inverted staggered MIS transistor having a part of the gate signal line GL as a gate electrode is formed. The drain electrode SD1 and the source electrode SD2 are formed simultaneously with the drain signal line DL.

  That is, drain signal lines DL extending in the y direction and arranged in parallel in the x direction in FIG. 1 are formed, and a part of the drain signal lines DL extends to the surface of the semiconductor layer AS of the thin film transistor TFT. Thus, the drain electrode SD1 of the thin film transistor TFT is configured.

  Further, when the drain signal line DL is formed, a source electrode SD2 is formed, and the source electrode SD1 extends into the pixel region and a contact hole CN for connecting to a pixel electrode PX, which will be described later, is also integrated. To be formed.

  As shown in FIG. 5, a contact layer d0 doped with, for example, an n-type impurity is formed at the interface of the semiconductor layer AS with the source electrode SD2 and the drain electrode SD1.

  In this contact layer d0, an n-type impurity doped layer is formed over the entire surface of the semiconductor layer AS, and after the source electrode SD2 and the drain electrode SD1 are formed, the semiconductor exposed from these electrodes using the electrodes as a mask. The n-type impurity doping layer on the surface of the layer AS is formed by etching.

  A protective film PAS made of, for example, SiN is formed on the surface of the transparent substrate on which the thin film transistor TFT is thus formed so as to cover the thin film transistor TFT. This is to avoid direct contact of the thin film transistor TFT with the liquid crystal LC.

  Further, the pixel electrode PX is formed on the upper surface of the protective film PAS by a transparent conductive film made of, for example, ITO (Indium-Tin-Oxide).

  The pixel electrodes PX are overlapped on the formation region of the counter electrode CT, have an angle of about 10 degrees with respect to the x direction in the drawing, extend at equal intervals, and both ends thereof are respectively The same material layers extending in the y direction are connected to each other.

  Incidentally, in this embodiment, the distance L between adjacent pixel electrodes PX is set in the range of 3 to 10 μm, for example, and the width W is set in the range of 2 to 6 μm, for example.

  In this case, the same material layer at the lower end of each pixel electrode PX is connected to the contact portion of the source electrode SD2 of the thin film transistor TFT through a contact hole formed in the protective film PAS, and the same material layer at the upper end. The material layer is formed so as to overlap with the counter electrode CT.

  When configured in this manner, a capacitive element Cstg having a dielectric film that is a stacked film of the gate insulating film GI and the protective film PAS is formed in the overlapping portion between the counter electrode CT and each pixel electrode PX. Yes.

  The capacitive element Cstg stores the video signal in the pixel electrode PX for a relatively long time even after the thin film transistor TFT is turned off after the video signal from the drain signal line DL is applied to the pixel electrode PX via the thin film transistor TFT. It is provided for such purposes.

  Here, the capacitance of the capacitive element Cstg is proportional to the overlapping area of the counter electrode CT and each pixel electrode PX, and the area becomes relatively large. The dielectric film has a laminated structure of the insulating film GI and the protective film PAS.

  Needless to say, the protective film PAS is not limited to SiN, and may be formed of, for example, a synthetic resin. In this case, since it forms by application | coating, there exists an effect that manufacture is easy even when forming the film thickness large.

  An alignment film ORI1 is formed on the surface of the transparent substrate SUB1 on which the pixel electrode PX and the counter electrode CT are formed in this manner so as to cover the pixel electrode PX and the counter electrode CT. This alignment film ORI1 is a film that is in direct contact with the liquid crystal LC and determines the initial alignment direction of the liquid crystal LC.

  In the above-described embodiments, description has been made using ITO as the transparent conductive film, but it goes without saying that the same effect can be obtained by using, for example, IZO (Indium-Zinc-Oxide).

  The thus configured first transparent substrate SUB1 is referred to as a TFT substrate, and the second transparent substrate SUB2 disposed opposite to the TFT substrate via the liquid crystal LC is referred to as a filter substrate.

  As shown in FIG. 3 or FIG. 6 to FIG. 7, the filter substrate is formed with a black matrix BM on the liquid crystal side so as to define each pixel region. A filter FIL is formed over the opening that determines the pixel region.

  An overcoat film OC made of, for example, a resin film is formed so as to cover the black matrix BM and the filter FIL, and an alignment film ORI2 is formed on the upper surface of the overcoat film.

  The above are the schematic plane and cross-sectional configurations of the first embodiment. Next, the operation of the present liquid crystal mode will be described with reference to FIGS. In this embodiment, a so-called positive type nematic liquid crystal in which the liquid crystal molecules are aligned in the major axis direction of the electric field is used as the liquid crystal. When the liquid crystal display is turned on and off, it shows a behavior with normally-black voltage-transmittance characteristics that transitions to a black state with no electric field and to a white state when a voltage is applied.

  FIG. 3 is a cross-sectional view on a two-dot broken line connecting the lines I (a) to I (b) in FIG. 1. . In the in-plane display mode (that is, the pixel electrode PX and the counter electrode CT are provided on the first transparent substrate SUB1 side), the electric lines of force (E in FIG. 3) from the comb-like pixel electrode PX enter the liquid crystal LC. The applied lines of electric force pass through the liquid crystal LC, pass through the protective film PAS and the gate insulating film GI in the gap between the comb teeth, and reach the counter electrode CT formed on the entire surface in a substantially square shape in the pixel region. In FIG. 3, the liquid crystal molecule LC1 on the left hand side with respect to the central counter voltage signal line CL (that is, the region under the counter voltage signal line CL running in the lateral direction in the pixel region of FIG. 1) is formed on the first substrate SUB1. The liquid crystal molecule LC2 rotates counterclockwise in the region on the right side of FIG.

  The optical operation will be described with reference to the schematic plan view of FIG. The counter voltage signal line CL is arranged in the central region of one pixel in the horizontal direction. In the upper region, the comb-like pixel electrode PX extends so as to have an inclination of about 10 degrees in the clockwise direction with respect to the counter voltage signal line CL, while in the lower region, the pixel electrode PX The counter voltage signal line CL is arranged so as to extend in the direction of about 10 degrees counterclockwise. The polarization axis of the polarizing plate of the first substrate SUB1 is arranged in a direction parallel to the extending direction of the counter voltage signal line CL, and the polarizing axis of the polarizing plate on the second substrate SUB2 side is arranged in the vertical direction. It is a polarization axis arrangement. The rubbing direction for controlling the direction of the liquid crystal molecules at the interface between the alignment films (ORL1 and ORL2) is processed in parallel on the upper and lower substrate sides (parallel to the extending direction of the counter voltage signal line CL and the gate signal line GL).

  When the voltage applied to the liquid crystal is absent or small, the major axes of the liquid crystal molecules LC1 and LC2 are aligned in the extending direction of the counter voltage signal line CL. The pixel electrode PX in the upper region has an inclination of 10 degrees in the clockwise direction. On the other hand, the direction of the electric force line E from the pixel electrode PX shown in the cross section of FIG. 3 through the liquid crystal to the counter electrode CT is perpendicular to the pixel electrode PX, that is, the counter voltage signal line CL is 110 degrees clockwise. With an angle of The liquid crystal molecules LC1 follow this and rotate in the electric field direction, that is, counterclockwise, and the transmittance becomes maximum when the major axis rotates in the direction of 45 degrees with the polarization axis of the polarizing plate. The liquid crystal molecules in the lower region are arranged in a vertically symmetrical manner with respect to the counter voltage signal line CL with respect to the pixel electrode PX. In this embodiment, since the liquid crystal molecules of one pixel are divided into two regions, clockwise and counterclockwise as described above, the viewing angle of the screen does not invert from any direction, and the color change does not occur. A small wide viewing angle can be displayed. In addition, since the pixel electrode PX and the counter electrode CT are made of transparent ITO and a sufficient electric field is applied to the liquid crystal LC, a bright image can be displayed through almost the entire pixel region inside the black matrix BM.

  Next, the characteristics of the present embodiment having a pixel structure with an increased aperture ratio or transmittance, and having a good image quality in which point defects are unlikely to occur at that time will be described in detail.

  The largest cause of decreasing the aperture ratio is the ratio of the area occupied by the source electrode SD2 and the drain electrode SD1 in addition to the gate signal line GL, the drain signal line DL, or the counter voltage signal line CL formed of an opaque metal material. It will be bigger. In particular, when it is necessary to connect the source electrode SD2 formed on the gate insulating film GI and the pixel electrode PX formed on the protective film PAS by the contact hole CN as in the present embodiment, the area near the contact hole CN The area of the source electrode SD1 increases according to the thickness of the protective film PAS, and the aperture ratio decreases.

  In addition to the pattern design of the thin film transistor TFT, the transmittance may be substantially reduced. The biggest factor is when the alignment film for controlling the interface of the liquid crystal molecules is not rubbed well. In particular, the contact hole CN having a large step is not sufficiently rubbed in the vicinity of the hole, and a region in which the shadow-like liquid crystal molecules are not controlled spreads several times the area of the contact hole in the shadowed portion in the rubbing direction. This phenomenon is not only a simple reduction in transmittance, but also a liquid crystal molecule control disorder, so it looks like an image with a reduced response speed. In order to eliminate this disturbance at least in the influence of the response speed, it is necessary to shield the light with an opaque material such as the black matrix BM or the wiring on the first substrate SUB1, but the aperture ratio may be lowered. .

  The structure in which the countermeasure is taken is shown below with reference to the drawings. In order to avoid a decrease in the aperture ratio, if the source electrode SD2 of the contact hole CN extends from the thin film transistor TFT on the counter voltage signal line CL, which is a non-transparent area, and overlaps the thin film transistor TFT, the transmittance loss is reduced. Will not increase. However, in this case, there arises a new problem that the number of point defects increases.

  In the liquid crystal display mode of this embodiment, as described above, the transparent counter electrode CT is arranged in a rectangular shape in the pixel, the gate insulating film GI and the protective film PAS are stacked on the top, and the transparent pixel electrode PX is formed on the top. Deploy. The laminated area of both electrodes ranges from 20 to 30% of one pixel region, which is a large value compared to other liquid crystal modes. If there is a pinhole in the insulating film, a short circuit will occur and a point defect on the screen will result. In order to prevent this to the minimum, this embodiment uses a gate insulating film GI and a protective film PAS, which are two insulating films having different processes, as a laminated film, even when there is a pinhole in one film. This is a redundant structure that maintains this insulating property.

  However, as described above, in order to improve the transmittance, the source electrode SD2 of the contact hole CN may be formed on the counter voltage signal line CL as shown in FIG. Therefore, when the source electrode SD2 is simply extended from the drain electrode SD1 of the thin film transistor TFT as shown in FIG. 1, the source electrode SD1 extends on the single-layer gate insulating film GI on the counter electrode CT. It is self-evident that the redundancy for short circuit failure is lost.

  In this embodiment, first, as can be seen from the plan view of FIG. 1, the counter electrode CT below the region where the source electrode SD1 extends is cut into a slit shape. As a result, the lower counter electrode CT and the source electrode SD1 do not cause a short circuit defect. As can be seen from the cross-sectional structure of FIG. 5, the source electrode SD1 overlaps the single layer portion of the gate insulating film GI for the first time in the portion overlapping the counter voltage signal line CL. Thereby, even when the transmittance is improved, the occurrence of point defects can be prevented and a good image quality can be obtained.

  On the other hand, the pixel electrode PX disposed on the protective film PAS so as to cross the source electrode SD1 overlaps with the single-layer protective film PAS in a large area, but the pixel electrode PX and the source electrode SD1 are given the same image potential. Therefore, even if a physical short-circuit occurs, no point defect occurs. Therefore, the pixel electrode PX can be laid out in the same manner as the upper region in FIG. 1 of the counter voltage signal line CL in which the counter electrode CT has no slit. This suppresses a decrease in aperture ratio due to the provision of the slit. The slit of the counter electrode is set wider than the source electrode SD1 formed with the minimum processing size as shown in FIG. 6 in consideration of misalignment in the photo process of each layer.

  On the other hand, the liquid crystal alignment due to the rubbing of the contact hole CN is also improved as follows to improve the transmittance. As described with reference to FIG. 4, the rubbing direction is defined in parallel to the gate signal line GL and the counter voltage signal line CL. Therefore, the rubbing shadow liquid crystal molecules several times the contact hole CN diameter are generated along the counter voltage signal line CL. As can be seen from the plan view of FIG. 1, the counter voltage signal line CL extends in the rubbing direction of the contact hole CN to shield the light source on the first transparent substrate SUB1 side.

  With the structure of the above embodiment, it is possible to provide a liquid crystal display device with good image quality that has a high transmittance and is bright and has few point defects due to short-circuit defects between the pixel electrode PX and the counter electrode CT.

Example 2
FIG. 9 is a diagram showing an equivalent circuit of the liquid crystal display panel according to the second embodiment of the present invention together with an external circuit of the liquid crystal display panel.

  In FIG. 9, scanning signals (voltage signals) are sequentially supplied by the vertical scanning circuit V to the gate signal lines GL extending in the x direction and arranged in parallel in the y direction.

  The thin film transistor TFT in each pixel region arranged along the gate signal line GL to which the scanning signal is supplied is turned on by the scanning signal.

  In accordance with this timing, a video signal is supplied from the video signal drive circuit H to each drain signal line DL, and this video signal is applied to the pixel electrode PX via the thin film transistor in each pixel region. It has become so.

  In each pixel region, a counter voltage is applied to the counter electrode CT formed together with the pixel electrode PX via the counter voltage signal line CL, and an electric field is generated between them. Each of the pixel electrode PX and the counter electrode CT is connected to an external power supply that applies the video information voltage from the drain signal line DL to the pixel electrode PX when the thin film transistor TFT is turned on at the timing when the gate signal line GL is applied with the on voltage. The connected counter voltage signal line CL is propagated to the counter electrode CT in each pixel region and functions to apply a voltage to the liquid crystal capacitor. The pixel electrode PX and the counter electrode CT are formed on the first transparent substrate SUB1 on which the thin film transistor TFT is formed. The pixel electrode PX and the counter electrode CT are the sum of the two capacitances of the storage capacitor element Cstg formed with an insulating film sandwiched between the pixel electrode PX and the counter electrode CT and the electric field between the pixel electrode PX and the counter electrode CT. Configure capacity. The liquid crystal mode of the present invention is characterized by a large area in which the counter electrode CT and the pixel electrode PX are stacked with an insulating film interposed therebetween. Therefore, the storage capacitor element Cstg of one pixel has a large value.

  The light transmittance of the liquid crystal LC is controlled by an electric field having a component parallel to the transparent substrate SUB1.

  In the above, one pixel region is a region surrounded by the adjacent drain signal line DL and the adjacent gate signal line GL, and the thin film transistor TFT, the pixel electrode PX, and the counter electrode CT are formed in the region as described above. Has been.

  FIG. 10 shows a timing chart of each signal supplied to the liquid crystal display panel. In the figure, Vgh and Vgl are the high voltage level and low voltage level of the scanning signal supplied to the gate signal line GL, respectively. Indicates the maximum and minimum voltage levels of the video signal supplied to the drain signal line DL, and Vcom indicates the counter voltage signal supplied to the counter voltage signal line CL. The driving is a line-sequential scanning in which a pulse-like driving voltage is applied to each gate signal line GL with respect to the screen scrolling time per cycle, and the drain signal line DL simultaneously sends a video voltage to all the lines. Therefore, the off voltage (Vgl) is applied to the other gate signal lines GL while one gate signal line GL is selected (on). This scanning is performed in order like GL1, GL2. One gate selection time tp is a time obtained by dividing the scroll time of one cycle by the total number of gate signal lines GL.

  On the other hand, the continuous thin film transistor TFT is turned on (period in which Vgh is applied) for one gate signal line GL, and the potential of the pixel electrode PX of each pixel is determined. The liquid crystal is turned on by a voltage difference between this potential and the potential Vcom of the counter electrode CT of the other electrode of the sum of the storage capacitor Cstg and the liquid crystal capacitor Clc which is a capacitor. This difference potential is held until the gate signal line GL is turned on again.

  On the other hand, the counter voltage signal line CL is the first transparent substrate SUB1, and the insulation of the first substrate SUB1 is sandwiched between the gate signal line GL and the lateral wiring arranged in parallel with the gate signal line GL. In other words, they are also connected by vertical wiring that crosses them. Due to the mesh-like wiring, the large voltage amplitude of the gate signal line GL fluctuates through the parasitic capacitance in one pixel even in the center area of the screen far from the external power supply, which makes the voltage of the counter voltage signal line CL unstable. Thus, display defects due to application of DC voltage such as afterimage and flicker to the liquid crystal are remarkably reduced. As a result, the resistance specification of the counter voltage signal line CL that runs parallel to the gate signal line GL is relaxed by the mesh-like connection of the main network, the width on the layout can be narrowed, and the transmittance can be improved. The counter voltage signal line CL running in parallel with the gate signal line GL is connected to the gate signal line GL via a connection line SE disposed on the protective film PAS via an insulating film. The method for connecting the counter electrode CT and the counter voltage signal line CL in one pixel will be described in detail below.

  FIG. 8 is a plan view showing another embodiment of the liquid crystal display device according to the present invention, which is a sectional view taken along line V (a) -V (b) and a sectional view taken along line VI (a) -VI (b). FIG. 11 is a cross-sectional view taken along the line VII (a) -VII (b), which is shown in FIGS. 11, 12, and 13, respectively.

  The configuration of the plan view of FIG. 8 has high transmittance, which is the object of the present invention, and has a small number of point defects due to short-circuit defects between the pixel electrode PX and the counter electrode CT formed with the insulating film interposed therebetween. A good liquid crystal display device is realized.

  First, the source electrode SD2 below the first contact hole CN1 does not overlap the counter electrode CT in plan view. That is, the counter electrode CT has a cutout shape so as not to overlap with the source electrode SD2 formed in the same process as the drain signal line DL. The effect can be understood from the cross-sectional structure of FIG. The source electrode SD2 connected to the semiconductor layer AS of the thin film transistor TFT basically extends over the semiconductor layer AS or the gate insulating film GI continuously formed in the same process. The source electrode SD2 is connected to the ITO pixel electrode through the first contact hole CN1 opened on the protective film PAS. The source electrode SD2 is formed on the gate insulating film GI and the semiconductor layer AS which are continuously formed by a single layer film of the GI on the gate insulating film or a plasma chemical vapor deposition (PCVD) method in the same process. In order to avoid this, there is no counter electrode made of ITO so as to avoid this, and a short-circuit defect does not occur in principle even with a single-layer insulating film that easily generates pinholes.

  FIG. 11 shows a cross-sectional structure of the main transmission part of one pixel. A gate insulating film made of SiN is formed on the transparent counter electrode formed on almost the entire surface of the first transparent substrate SUB1 and the counter voltage signal line CL that feeds the transparent counter electrode along the gate signal line GL. The GI and the protective film PAS are stacked. Although both the gate insulating film GI and the protective film PAS are formed by the PCVD method, each film formation is performed in different processes, and further, a cleaning process for foreign matters or the like is inserted between them, so that there is a pinhole in one film. Even if it exists, it becomes a redundant structure in which a two-layer film does not short-circuit at the same location. As shown in this cross-sectional structure, the pixel electrode PX and the counter electrode CT are all insulated by two layers of insulating films in one pixel region, so that both electrodes are short-circuited and no point defect occurs. As described above, in this embodiment, the source electrode SD2 and the pixel electrode PX, the common electrode CT, and the counter voltage signal line CL to which the pixel potential is supplied from the TFT in one pixel are all two layers of the gate insulating film GI and the protective film PAS. It is possible to provide a liquid crystal display device which is insulated by wiring and has an extremely small short-circuit defect in a region overlapped with these insulating films and is free from point defects.

  Next, a mechanism for increasing the transmittance in this embodiment will be described. In the plan view of one pixel in FIG. 8, the counter voltage signal line CL has a large non-transparent area in the opening region inside the black matrix BM. However, the width of the counter voltage signal line CL of the second embodiment is less than half that of the first embodiment. When the width of the counter voltage signal line CL is narrowed, the wiring delay is increased, a DC voltage is applied to the liquid crystal, and an afterimage and flicker are generated, thereby degrading the image quality.

  In this embodiment, the upper and lower adjacent counter electrodes CT are connected by the lower right or upper right connection wiring SE in the plan view of FIG. 8, so that the image quality does not deteriorate even if the width of the counter voltage signal line CL is narrow and the resistance is high. . First, the structure of this connection arrangement SE is shown, and this shows the effect | action for the transmittance | permeability improvement.

  The connection wiring SE is a wiring that connects the upper and lower counter electrodes CT. As can be seen from the cross-sectional structure of FIG. 13, contact holes CN2 and CN3 are opened in the gate insulating film GI and the protective film PAS on the counter electrode CT arranged in a rectangle in one pixel so as to sandwich the gate signal line GL, Through this, the connection is made by a connection wiring SE made of ITO formed in the same process as the pixel electrode PX.

  Below the contact hole CN is a pad region PAD formed in the same process as the gate signal line GL, which has a larger area than the second contact hole CN2 and the third contact hole CN3. Therefore, the counter voltage signal line CL running in parallel with the gate signal line GL is electrically connected to each other in a repetitive configuration of the counter electrode CT, the pad region PAD, and the connection wiring SE.

  By forming the connection wiring SE, the transmittance is improved as a result. As shown in FIG. 10, the gate signal lines GL are sequentially scanned one by one. When an on voltage is supplied to the gate signal lines GL, the thin film transistor TFT is turned on, and a video voltage is applied to the pixel electrode PX. The On the other hand, at the moment when the gate signal line GL is turned off, the pixel potential is unintentionally lowered due to the coupling effect of the stray capacitance between the gate signal line GL and the pixel electrode PX. At the same time, the counter voltage signal line CL is also shaken, and as a result, the image quality is such that the voltage applied to the liquid crystal is distorted according to the wiring distance from the power source. As a countermeasure, the counter voltage wiring may be thickened to reduce the delay, but the aperture ratio decreases. In this embodiment, as shown in FIG. 8, a rectangular ITO counter electrode CT close to the area of one pixel is formed inside the black matrix BM of one pixel. This is a large area so as to shield all the openings of the first substrate SUB1. Therefore, since ITO is high in specific resistance, it has a large spread in the extending direction of the counter voltage signal line CL, and is effective in reducing resistance. Further, the counter electrode CT that shields the opening region is connected to the entire region of the display device by a connection line SE that straddles the gate signal line GL. Therefore, even if the potential of the counter voltage signal line CL corresponding to the moment when one gate signal line GL is selected and turned off, the charge is replenished through the connection wiring SE and is immediately stabilized.

  The effect of the connection wiring SE as described above is remarkably reduced when the counter voltage signal line CL that runs parallel to the conventional gate signal line GL is a so-called surface wiring. This effect is further enhanced because the area is larger as the counter electrode CT shields the opening region. As a result, the width of the counter voltage signal line CL made of an opaque material can be set very narrow, so that the transmittance can be improved.

  In this embodiment, the influence of the shadow of the contact hole step portion in the rubbing process is reduced as follows, and the transmittance is further improved.

  That is, in this embodiment, the rubbing process is performed in the extending direction of the counter voltage signal line CL or the counter electrode as in the first embodiment.

  As shown in FIG. 8, a black matrix BM is formed in the rubbing direction in all the first to third contact holes CN1, CN2, and CN3. Further, an opaque pad area PAD is provided below the contact holes CN2 and CN3 of the connection wiring SE, and the upper and lower substrates are shielded from light.

  In other words, in the case of a liquid crystal pixel structure in which a rectangular counter electrode CT and a pixel electrode PX are combined so as to sandwich an insulating film, and having a connection wiring SE formed through a contact hole so as to straddle the gate signal line GL The transmittance can be improved if the rubbing direction is substantially perpendicular to the line connecting the adjacent connection lines SE or within an angle of 20 degrees from this.

  Further, the contact holes CN2 and CN3 of the connection wiring SE are approximately 10 clockwise or counterclockwise with respect to the extending direction of the gate signal line GL (more precisely, the polarization axis direction of the polarizing plate of the first substrate SUB1). The pixel electrodes PX are inclined and arranged at an angle of degrees. It is arranged in the space at the end of the rectangular counter electrode CT at that angle, and the factor that reduces the transmittance is eliminated.

It is a top view which shows one Example of the pixel area | region of the liquid crystal display device by this invention. FIG. 2 is an equivalent circuit diagram illustrating an embodiment of a liquid crystal display device according to the present invention. It is sectional drawing in the I (a) -I (b) line | wire of FIG. It is a schematic diagram which shows the polarization behavior of the liquid crystal molecule in a 1st Example. It is sectional drawing in the II (a) -II (b) line | wire of FIG. It is sectional drawing in the III (a) -III (b) line | wire of FIG. It is sectional drawing in the IV (a) -IV (b) line | wire of FIG. It is a top view which shows the other Example in the pixel area | region of the liquid crystal display device by this invention. FIG. 6 is an equivalent circuit diagram showing another embodiment of the liquid crystal display device according to the present invention. It is a timing chart which shows the other Example in the drive of the liquid crystal display device by this invention. It is sectional drawing in the V (a) -V (b) line | wire of FIG. It is sectional drawing in the VI (a) -VI (b) line | wire of FIG. It is sectional drawing in the VII (a) -VII (b) line | wire of FIG.

Explanation of symbols

SUB1 ... 1st transparent substrate, SUB2 ... 2nd transparent substrate, POL1 ... Polarizing plate of 1st transparent substrate, POL2 ... Polarizing plate of 2nd transparent substrate, BM ... Black matrix, FIL ... Color filter, OC ... Overcoat film, ORI1 ... Alignment film of first transparent substrate, ORI2 ... Alignment film of second transparent substrate, LC ... Liquid crystal layer or liquid crystal molecule, GL ... Gate signal line, CL ... Counter voltage signal line, DL ... Drain signal line, CT ... counter electrode, PX ... pixel electrode, TFT ... thin film transistor, AS ... semiconductor layer, SD1 ... drain electrode, SD2 ... source electrode, CN ... contact hole, SE ... connection wiring, PAD ... pad region, GI ... Gate insulating film, PAS ... Protective film

Claims (8)

A plurality of counter electrode signal lines, a plurality of gate signal lines, and a plurality of drain signal lines are formed on the first transparent insulating substrate, and are surrounded by the adjacent gate signal lines and the adjacent drain signal lines In a liquid crystal display device having a pixel region, and a thin film transistor, a rectangular transparent counter electrode, and a transparent pixel electrode formed through the counter electrode and an insulating film in the pixel region,
The counter electrode is connected to the counter electrode of the adjacent pixel region by a connection wiring formed so as to straddle the gate signal wiring formed between the counter electrodes through an insulating film. Liquid crystal display device.   The liquid crystal display device according to claim 1, wherein the connection wiring is connected to the connection wiring through a through hole formed in an insulating film between the counter electrodes.   3. The liquid crystal display device according to claim 2, wherein a connecting member made of the same material as the gate signal wiring is disposed between the connection wiring and the gate signal wiring.   2. The liquid crystal display device according to claim 1, wherein a semiconductor layer is formed between the connection wiring and the gate signal wiring.   2. The liquid crystal display device according to claim 1, wherein the connection wiring is made of the same material as the pixel electrode.   2. The liquid crystal display device according to claim 1, wherein the connection wiring is formed in parallel with the drain signal wiring.   2. The liquid crystal display device according to claim 1, wherein the counter electrode wiring is arranged in parallel with the gate signal wiring.   2. The liquid crystal display according to claim 1, wherein the pixel electrode has a plurality of slits having an angle of 3 to 20 degrees clockwise or 3 to 20 degrees counterclockwise with respect to the gate signal wiring. apparatus.

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