JP2007033610A - Liquid crystal display element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display element capable of suppressing image roughness and unevenness of display. <P>SOLUTION: A CS wiring line 13 divides a pixel area into four subpixels and surrounds them. A pixel electrode 11 is formed corresponding to each of the subpixel. A voltage is applied to produce a vertical electric field of 5V between a common electrode 18 and a pixel electrode 11. Further, a horizontal electric field is produced between the pixel electrode 11 and wiring line 13. With the vertical and horizontal electric fields, liquid crystal molecules in the four subpixels are aligned around the center 26 of a vortex like being attracted to the CS wiring line 13. Consequently, the center position of the vortex becomes stable and the image roughness and unevenness of display can be suppressed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid crystal display element, and more particularly to a vertical alignment type liquid crystal display element.

  As a liquid crystal display, a TFT (Thin Film Transistor) liquid crystal panel is widely used. In a TFT liquid crystal panel, a parallel alignment liquid crystal material typified by a TN type or a vertical alignment liquid crystal material typified by a VA (Vertical Alignment) type is used (for example, Patent Document 1).

As shown in the plan view of FIG. 8A and the cross-sectional view along AA ′ in FIG. 8B, the conventional vertical alignment type TFT liquid crystal display element has a pixel on one of a pair of glass substrates. An electrode is formed, and a common electrode facing the pixel electrode is formed on the other glass substrate. A liquid crystal display element is formed by the opposing portion of the pixel electrode and the common electrode, the liquid crystal between them, and a pair of retardation plates and a polarizing plate disposed therebetween. In addition, a compensation capacitor (CS) wiring is formed so as to form a compensation capacitor that is insulated from the pixel electrode and that partly faces the edge of the pixel electrode and is connected in parallel to the pixel capacitor. This CS wiring is maintained at the same potential as the common electrode.
JP 2003-29284 A

  In the above-described liquid crystal display element, in a non-electric field state where no voltage is applied between the pixel electrode and the common electrode, the liquid crystal molecules are aligned so that their long axes are perpendicular to the glass substrate, as shown in FIG. ing. On the other hand, for example, when a voltage of 5 V is applied between the pixel electrode and the common electrode, that is, when the voltage is ON, as shown in FIG. 10, a vertical electric field of 5 V between the common electrode and the pixel electrode is generated. In addition, a horizontal electric field of 5 V is applied between the pixel electrode and the CS wiring. For this reason, the center of the vortex is formed in the plurality of liquid crystal molecules, and the liquid crystal molecules are arranged horizontally so that the center of the vortex is pulled in the direction of the CS wiring. The center of this vortex appears as a black dot on the display.

  The position of the center of the vortex is not fixed due to the design element (size, shape, etc.) of the pixel and the variation of the lateral electric field, and varies from pixel to pixel. Therefore, this variation has been a cause of roughness and unevenness in the display of the liquid crystal display element.

  The present invention has been made in view of the above circumstances, and an object thereof is to realize a liquid crystal display element capable of suppressing roughness and unevenness at the time of display.

In order to achieve the above object, a liquid crystal display element according to the first aspect of the present invention provides:
One substrate provided with a first electrode;
A second substrate provided with at least one second electrode disposed opposite to the first electrode at a predetermined interval and forming each pixel region by a region facing the first electrode; ,
A vertical alignment film formed on each of the inner surfaces of the first and second electrodes facing each other;
A liquid crystal layer sealed between the substrates and having negative dielectric anisotropy;
A liquid crystal display element comprising:
Further comprising a dividing means for dividing the pixel region into a plurality of micro-alignment regions;
The liquid crystal molecules in the liquid crystal layer are aligned with a predetermined position as the alignment center for each of the micro-alignment regions according to the voltage between the first electrode and the second electrode.
It is characterized by that.

The dividing means includes
The pixel region is divided into a plurality of micro-alignment regions and arranged so as to surround each micro-alignment region, and for forming a compensation capacitor between the second electrode and the second electrode. It is preferable to include a compensation capacitor electrode.

The dividing means includes
It is preferable to include the second electrode formed with a step portion on the surface so as to divide the pixel region into a plurality of micro alignment regions and surround each micro alignment region.

The dividing means includes
A plurality of recesses formed on the other substrate between the second electrode and the other substrate and corresponding to each of the plurality of micro alignment regions so as to divide the pixel region into a plurality of micro alignment regions. It is preferable that the insulating film formed including

The dividing means includes
The pixel region is divided into a plurality of micro-alignment regions and is configured to have a stepped portion on the surface so as to surround each micro-alignment region, and the pixel region and other pixel regions are insulated around the pixel region It is preferable to include a pad insulating film.

  ADVANTAGE OF THE INVENTION According to this invention, the liquid crystal display element which can suppress the roughness and nonuniformity at the time of a display is realizable.

  Hereinafter, a liquid crystal display device according to an embodiment of the present invention will be described with reference to the drawings.

(Embodiment 1)
The liquid crystal display element 1 according to the present embodiment includes a CF side glass arranged facing each other as shown in a plan view in FIG. 1A and a cross-sectional view along AA ′ in FIG. A substrate 3 and a TFT side glass substrate 2 are provided, and a liquid crystal 21 exhibiting negative dielectric anisotropy is sealed between the two substrates.

  On the inner surface of the TFT side glass substrate 2, a pixel electrode 11, a drain wiring 12, a CS wiring 13, a gate wiring 14, an insulating film 15, and a pad insulating film 16 are formed. On the other hand, a black mask 17, a common electrode 18, and a CF (color filter) 19 are formed under the inner surface of the CF side glass substrate 3.

  The pixel electrode 11 is a transparent electrode made of an ITO film containing indium oxide as a main component, etc., is provided with a convex portion, and demarcates a pixel region by a region facing the common electrode 18.

  The drain wiring 12 is composed of an aluminum wiring or the like formed so as to extend in the column direction for each pixel column. The drain wiring 12 is connected to the drain electrode of the TFT element in the same pixel column, and supplies the image signal from the column driver to the pixel electrode 11 via the TFT element that is turned on.

  The CS wiring 13 is composed of aluminum wiring or the like. The CS wiring 13 is formed around the pixel electrode 11 so as to overlap the pixel electrode 11, and is maintained at the same potential as the common electrode 18. The CS wiring 13 is formed so as to surround the pixel electrode 11 so that four subpixels are formed in one pixel.

  The gate wiring 14 is composed of an aluminum wiring formed so as to extend in the row direction for each pixel. The gate wiring 14 is connected to the gate electrode of the TFT element in the corresponding pixel row, supplies a gate signal (pulse) to the TFT element, and controls on / off of the TFT element.

  The insulating film 15 is an insulating film formed on a glass substrate on which the CS wiring 13 and the gate wiring 14 are formed, and is made of, for example, a silicon nitride film. The insulating film 15 electrically isolates a gate electrode (corresponding pixel row) (not shown) of the TFT element from a semiconductor layer (channel layer) and source / drain regions facing the gate electrode. The source region of each TFT element is connected to the corresponding pixel electrode, and the drain region is connected to the corresponding drain wiring.

  The pad insulating film 16 is an insulating film formed on the drain wiring 12 between the pixel electrode 11 and the pixel electrode of the adjacent pixel, and is composed of a silicon nitride film or the like.

  The black mask 17 is a light shielding film composed of an aluminum film or the like, and is formed on the CF side glass substrate 3 between adjacent CFs 19 or in a portion facing the TFT element.

  The common electrode 18 is an electrode formed so as to face the plurality of pixel electrodes 11 in common. The common electrode 18 is formed from a transparent conductive material such as an ITO film.

  The CF 19 is a color filter corresponding to three color elements formed by applying a color resist solution made of an acrylic resin, pattern exposure, and development. The CF 19 is formed so as to face the pixel electrode 11.

  The liquid crystal 21 has negative dielectric anisotropy and is sealed between the TFT side glass substrate 2 and the CF side glass substrate 3. The liquid crystal 21 is aligned so as to be perpendicular to both substrates when there is no electric field (when no voltage is applied).

The lower retardation plate 23 and the lower polarizing plate 22 are disposed on the outer surface of the TFT side glass substrate 2, and the upper retardation plate 24 and the upper polarizing plate 25 are disposed on the outer surface of the CF side glass substrate 3. As shown in FIG. 2, the upper polarizing plate 25 and the lower polarizing plate 22 are arranged so that optical axes such as a transmission axis and an absorption axis thereof are orthogonal (crossed Nicols).
The upper retardation plate 24 and the lower retardation plate 23 adjust the phase difference so that light passing through the lower polarizing plate 22 and entering the liquid crystal cell can pass through the upper polarizing plate 25 arranged in crossed Nicols. . As shown in FIG. 2, the upper retardation plate 24 and the lower retardation plate 23 are arranged so that their slow axes are orthogonal to each other.

Next, the behavior of the liquid crystal in the pixel having the above structure will be described.
In a state where no voltage is applied between the pixel electrode 11 and the common electrode 18 (no electric field state), the pixel electrode 11, the CS wiring 13, and the common electrode 18 are at the same potential. The molecular long axis of the liquid crystal 21 remains aligned perpendicular to the TFT side glass substrate 2 and the CF side glass substrate 3.

  On the other hand, when a voltage is applied between the pixel electrode 11 and the common electrode 18 and the CS wiring 13, a vertical electric field of 5V is generated between the pixel electrode 11 and the common electrode 18, as shown in FIG. Further, a lateral electric field is generated between the peripheral edge of the pixel electrode 11 and the CS wiring 13. For this reason, the liquid crystal molecules in the periphery of the pixel are arranged horizontally so as to be pulled by the CS wiring 13 around the center 26 of the vortex. As described above, since the pixel is divided into four subpixels by the CS wiring 13, four vortex centers 26 can be formed in one pixel.

As described above, a subpixel having four sides surrounded by the CS wiring 13 and the pixel electrode 11 is formed.
In the divided sub-pixels, the liquid crystal molecules are aligned so as to be pulled by the surrounding CS wiring 13, so that the position of the center of the generated vortex is stable. Therefore, since the position of the black spot generated during display is stabilized, it is possible to suppress roughness and unevenness on the display.

  Next, a liquid crystal display element capable of further determining the center position of the vortex will be described.

(Embodiment 2)
The liquid crystal display element 1 according to the present embodiment has a structure as shown in a plan view in FIG. 5A and a cross-sectional view along AA ′ in FIG. The liquid crystal display element 1 of the present embodiment is different from the liquid crystal display element 1 of the first embodiment in that a hole 27 is formed in the insulating film 15 at the center of each subpixel. The pad insulating film 16 is formed with a convex portion so as to surround the pixel region.

  In a state where no voltage is applied between the pixel electrode 11 and the common electrode 18 (no electric field), the liquid crystal 21 remains vertically aligned as shown in FIG. On the other hand, when a voltage is applied between the pixel electrode 11 and the common electrode 18, as shown in FIG. 7, the liquid crystal molecules of the liquid crystal 21 are pulled by the CS wiring 13 around the hole 27, and the pad They are arranged horizontally so as to be supported by the insulating film 16.

As described above, in the liquid crystal display element 1 according to the present embodiment, the hole 27 is formed in the insulating film 15, and the pad insulating film 16 is formed with a convex portion.
The holes 27 can create liquid crystal molecules that maintain a vertical alignment state even when a voltage is applied to the liquid crystal 21.
Further, by providing a high pad insulating film 16, a concavo-convex shape is formed, the periphery of the subpixel defined by the CS wiring 13 can be highlighted, and the vortices in the subpixel oriented so as to be pulled by the CS wiring 13. The center position of can be determined more reliably.
Accordingly, display roughness and unevenness can be reduced.

  In addition, this invention is not limited to the example shown by the said embodiment, A various deformation | transformation and application are possible.

  For example, in the first embodiment, pixel division by the CS wiring 13 and pixel division by the pixel electrode 11 are performed, and in the second embodiment, pixel division by the hole 27 of the insulating film 15 and the convex portion of the pad insulating film 16 is performed. An example of a liquid crystal display element has been described. However, these may be used alone or in combination.

  In the above embodiment, the vertical alignment liquid crystal display device using the liquid crystal having negative dielectric anisotropy has been described. However, the present invention is applicable to any active matrix liquid crystal display device. Therefore, a liquid crystal having positive dielectric anisotropy can also be used.

  In the above-described embodiment, the pixel electrode 11 and the pad insulating film 16 are configured to have a convex portion. However, the pixel electrode 11 and the pad insulating film 16 may be configured to have a step on the surface, for example, a concave portion. It may be a thing.

It is a figure which shows the structure of the liquid crystal display element which concerns on Embodiment 1 of this invention. It is a figure for demonstrating the optical design of the liquid crystal display element which concerns on this embodiment. It is a figure which shows the mode in the voltage non-application state of the liquid crystal display element of FIG. It is a figure which shows the mode in the voltage application state of the liquid crystal display element of FIG. It is a figure which shows the structure of the liquid crystal display element which concerns on Embodiment 2 of this invention. It is a figure which shows the mode in the voltage non-application state of the liquid crystal display element of FIG. It is a figure which shows the mode in the voltage application state of the liquid crystal display element of FIG. It is a figure which shows the structure of the conventional liquid crystal display element. It is a figure which shows the mode in the voltage non-application state of the liquid crystal display element of FIG. It is a figure which shows the mode in the voltage application state of the liquid crystal display element of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display element, 2 ... TFT side glass substrate, 3 ... CF side glass substrate, 11 ... Pixel electrode, 12 ... Drain wiring, 13 ... CS wiring, 14 ... Gate wiring, 15 ... insulating film, 16 ... pad insulating film, 17 ... black mask, 18 ... common electrode, 19 ... CF, 21 ... liquid crystal, 22 ... bottom Side polarizing plate, 23 ... lower retardation plate, 24 ... upper retardation plate, 25 ... upper polarizing plate.

Claims (5)

One substrate provided with a first electrode;
A second substrate provided with at least one second electrode disposed opposite to the first electrode at a predetermined interval and forming each pixel region by a region facing the first electrode; ,
A vertical alignment film formed on each of the inner surfaces of the first and second electrodes facing each other;
A liquid crystal layer sealed between the substrates and having negative dielectric anisotropy;
A liquid crystal display element comprising:
Further comprising a dividing means for dividing the pixel region into a plurality of micro-alignment regions;
The liquid crystal molecules in the liquid crystal layer are aligned with a predetermined position as the alignment center for each of the micro-alignment regions according to the voltage between the first electrode and the second electrode.
The liquid crystal display element characterized by the above-mentioned. The dividing means includes
The pixel region is divided into a plurality of micro-alignment regions and arranged so as to surround each micro-alignment region, and for forming a compensation capacitor between the second electrode and the second electrode. Including compensation capacitance electrode,
The liquid crystal display element according to claim 1. The dividing means includes
Including the second electrode formed with a stepped portion on the surface so as to divide the pixel region into a plurality of micro-alignment regions and surround each micro-alignment region;
The liquid crystal display element according to claim 1 or 2. The dividing means includes
A plurality of recesses formed on the other substrate between the second electrode and the other substrate and corresponding to each of the plurality of micro alignment regions so as to divide the pixel region into a plurality of micro alignment regions. Including an insulating film formed with
The liquid crystal display element according to claim 1, wherein the liquid crystal display element is a liquid crystal display element. The dividing means includes
The pixel region is divided into a plurality of micro-alignment regions and is configured to have a stepped portion on the surface so as to surround each micro-alignment region, and the pixel region and other pixel regions are insulated around the pixel region Including pad insulation film for
The liquid crystal display element according to claim 1, wherein the liquid crystal display element is a liquid crystal display element.

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