JP2012093610A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device which can suppress degradation in an aperture ratio.SOLUTION: A liquid crystal display device 1, in which pixel electrodes 219 and common electrodes 218 are arranged with an interval each other along an X-direction in a plan view, has third electrodes 216 each of which is provided on a first principal plane 21a of a first substrate 21 so as to face the pixel electrode 219 via a third insulator film 217, and each of both ends of which is located between the end of the pixel electrode 219 and the end of the common electrode 218 in a cross-sectional view along the X-direction. An electric potential difference Vapplied between the pixel electrode 219 and the common electrode 218 is equal to or greater than an electric potential difference Vapplied between the common electrode 218 and the third electrode 216. The distance Dbetween the pixel electrode 219 and the common electrode 218 has a length equal to or less than the distance Dbetween common electrode 218 and the third electrode 216.

Description

  The present invention relates to a liquid crystal display device used for various applications such as a television, a mobile phone, a digital camera, a portable game machine, or a portable information terminal.

  The liquid crystal display device includes a first base and a second base that are arranged to face each other, a liquid crystal layer provided between the bases, and a common electrode and a plurality of pixel electrodes provided on the first base (for example, , See Patent Document 1).

  In such a liquid crystal display device, in a plan view, the pixel electrodes and the common electrodes are alternately arranged along a certain direction, and by applying a voltage to the pixel electrodes and the common electrodes, the pixel electrodes An electric field is generated between the liquid crystal layer and the common electrode, and the direction of liquid crystal molecules in the liquid crystal layer is controlled by the electric field.

JP 2001-318381 A

By the way, in such a liquid crystal display device, an electric field passing through the liquid crystal layer 23 so as to bridge between the adjacent pixel electrode 219 and the common electrode 218 as schematically shown by a thick double arrow line in FIG. E ₁ has occurred.

However, since the electric field E ₁ is generated between the pixel electrode and the common electrode located on the same plane, the electric field E ₁ is hardly generated on the pixel electrode 219. Therefore, there is a possibility that the liquid crystal molecules located on the pixel electrode 219 cannot be controlled effectively. As a result, it is difficult for light to pass through the region where the pixel electrode 219 is located, and the aperture ratio of one pixel may be reduced.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a liquid crystal display device capable of suppressing a decrease in the aperture ratio of a pixel.

  The liquid crystal display device of the present invention includes a first substrate having a first main surface, a second substrate having a second main surface opposite to the first main surface of the first substrate, the first substrate, and the first substrate. A liquid crystal layer provided between two substrates, a first electrode provided on the first main surface of the first substrate, and a second electrode provided on the first main surface of the first substrate. The first electrode and the second electrode are arranged along the first direction at a distance from each other in plan view, and are insulated on the first main surface of the first base. It is provided so as to face the first electrode through the film, and both ends thereof are located between the end portion of the first electrode and the end portion of the second electrode in a sectional view along the first direction. A potential difference applied between the first electrode and the second electrode is less than a potential difference applied between the second electrode and the third electrode. Of a size, the distance between the first electrode and the second electrode is characterized in that a distance less in length between the second electrode third electrode.

According to the liquid crystal display device of the present invention, the first substrate is provided on the first main surface of the first base so as to face the first electrode through the insulating film, and both ends are first in the cross-sectional view along the first direction. A third electrode located between an end of the electrode and the end of the second electrode, and a potential difference applied between the first electrode and the second electrode is different between the second electrode and the third electrode; And the distance between the first electrode and the second electrode is not more than the distance between the second electrode and the third electrode, Since the liquid crystal molecules located on the pixel electrode can be effectively controlled, a decrease in the aperture ratio can be suppressed.

It is the top view which showed the liquid crystal display device in the 1st Embodiment of this invention. It is sectional drawing along the II line | wire of FIG. It is the top view which showed the principal part of the liquid crystal panel. It is sectional drawing along the II-II line of FIG. FIG. 5 is an enlarged cross-sectional view showing a relationship among a pixel electrode, a common electrode, and a third electrode in one pixel. It is sectional drawing which showed the principal part of the liquid crystal display device in the 2nd Embodiment of this invention. It is sectional drawing which shows the conventional liquid crystal display device.

[Embodiment 1]
The liquid crystal display device 1 according to the first embodiment of the present invention will be described. The liquid crystal display device 1 of the present example is a so-called lateral electric field method in which an electric field is generated between a pixel electrode provided on one of a pair of substrates and a common electrode to control the direction of liquid crystal molecules in the liquid crystal layer. Is adopted.

As shown in FIGS. 1 and 2, the liquid crystal display device 1 includes a display region A _D and the liquid crystal panel 2 with a non-display area A _O positioned outside the display area A _D, the liquid crystal panel 2 display area A A light source device 3 that emits light to _D , a first polarizing plate 4 that is disposed outside the liquid crystal panel 2, and a second polarizing plate 5 that is disposed to face the first polarizing plate 4 with the liquid crystal panel 2 interposed therebetween. And.

  The liquid crystal panel 2 includes a first base 21, a second base 22 disposed opposite to the first base 21, a liquid crystal layer 23 positioned between the first base 21 and the second base 22, and a liquid crystal layer 23. A seal member 24 is provided between the first base 21 and the second base 22 so as to surround the first base 21 and the second base 22.

Further, on the first main surface 21 a of the first base 21, a plurality of gate wirings 211 and a first insulating film 212 provided from the gate wiring 211 to the first base 21 so as to cover the plurality of gate wirings 211. And a plurality of source wirings 213 provided in the first insulating film 212 so as to intersect the gate wiring 211.
And a thin film transistor 214 located in the vicinity of the intersection region of the gate wiring 211 and the source wiring 213
A second insulating film 215 provided from the source wiring 213 to the first insulating film 212 so as to cover the source wiring 213, a third electrode 216 provided on the second insulating film 215, and the third electrode 216 A third insulating film 217 provided from the third electrode 216 to the second insulating film 215 so as to cover, a common electrode 218 as a second electrode provided on the third insulating film 217, and a third insulating film 217 A plurality of pixel electrodes 219 are provided as the provided first electrodes.

  The first base 21 is made of a light-transmitting material such as glass or plastic. Here, translucency means having transparency to visible light.

The gate wiring 211 has a function of applying a voltage supplied from a power source to the thin film transistor 214. As shown in FIG. 3, the gate wiring 211 extends in the X direction. The plurality of gate wirings 211 are arranged on the first main surface 21a of the first base 21 along the Y direction. The gate wiring 211 is formed of a conductive material, for example, aluminum, molybdenum, titanium, neodymium, chromium, copper, or an alloy containing these.

The first insulating film 212 has a function of electrically insulating the gate wiring 211 and the source wiring 213. The first insulating film 212 is provided on the first main surface 21 a of the first base 21 so as to cover the gate wiring 211. The first insulating film 212 is formed of an insulating material, for example, silicon nitride or silicon oxide.

  The source wiring 213 has a function of applying a signal voltage supplied from a power source to the pixel electrode 219 through the thin film transistor 214. As shown in FIG. 3, the source wiring 213 extends in the Y direction. The plurality of source lines 213 are arranged in the first insulating film 212 along the X direction. The material of the source wiring 213 may be formed of the same material as that of the gate wiring 211.

The thin film transistor 214 includes a semiconductor layer 214a such as amorphous silicon or polysilicon, and a source electrode 214b provided on the semiconductor layer 214a and connected to the source wiring 213.
And a drain electrode 214c provided on the semiconductor layer 214a and connected to the pixel electrode 219. In the thin film transistor 214, the resistance of the semiconductor layer 214a in the source electrode 214b and the drain electrode 214c changes in accordance with the voltage applied to the semiconductor layer 214a in the gate wiring 211 via the gate wiring 211, whereby the pixel electrode The voltage applied to 219 is controlled.

The second insulating film 215 has a function of electrically insulating the source wiring 213 and the common electrode 218.
The second insulating film 215 is provided on the first insulating film 212 so as to cover the source wiring 213. The second insulating film 215 may be formed of the same material as the first insulating film 212.

The third insulating film 217 has a function of electrically insulating the third electrode 216 and the pixel electrode 219. As shown in FIG. 4, the third insulating film 217 is provided on the second insulating film 215 so as to cover the third electrode. The third insulating film 217 may be formed using the same material as the first insulating film 212.

  The common electrode 218 has a function of generating an electric field between the pixel electrode 219 and a voltage applied from a power source. The common electrode 218 is provided on the third insulating film 217. As shown in FIG. 3, the common electrode 218 is provided so as to surround the pixel electrode 219. Further, as shown in FIG. 4, the common electrode 218 is disposed on both sides of the pixel electrode 219 in the X direction.

In the liquid crystal display device 1, the width of the common electrode 218 in the X direction is set to 2 to 5 μm. The thickness of the common electrode 218 is set to 0.03 to 0.1 μm.

The common electrode 218 is formed of a material having translucency and conductivity, for example, ITO (Indium Tin Oxide), IZO (Indium Zinc Oxide), ATO (Antimony Tin Oxide), AZO (Al-Doped Zinc Oxide), oxidation, and the like. It is formed of tin, zinc oxide, or a conductive polymer.

The pixel electrode 219 has a function of generating an electric field with the common electrode 218 by a voltage applied from a power source. The plurality of pixel electrodes 219 are provided on the third insulating film 217. Further, when viewed in plan, the plurality of pixel electrodes 219 are arranged along the X direction and the Y direction. The pixel electrodes 219 and the common electrodes 218 are alternately arranged along the X direction. The pixel electrode 219 may be formed of the same material as the common electrode 218.

In the liquid crystal display device 1, the width of the pixel electrode 219 in the X direction is set to 2 to 5 μm. The thickness of the pixel electrode 219 is set to 0.03 to 0.1 μm.

The third electrode 216 has a function of generating an electric field between the pixel electrode 219 and a voltage applied from a power source. The third electrode 216 is provided on the second insulating film 217 so as to face the pixel electrode 219 with the third insulating film 217 interposed therebetween. As shown in FIG. 4, the third electrode 216 has both ends located between the end portion of the pixel electrode 219 and the end portion of the common electrode 218.

In the liquid crystal display device 1, the width of the third electrode 216 in the X direction is set to 4 to 7 μm. The thickness of the third electrode 219 is set to 0.03 to 0.1 μm.

  As described above, the third electrode 216 includes the overlapping region 216 a that overlaps the pixel electrode 219 and the non-overlapping region 216 b that does not overlap the pixel electrode 219 and the common electrode 218.

The third electrode 216 has a non-overlapping region 216 b that does not overlap the pixel electrode 219. As a result, as shown in FIG. 4, the electric field generated between the third electrode 216 and the pixel electrode 219 passes through the liquid crystal layer 23 located on the pixel electrode 219. The direction of the liquid crystal molecules of the liquid crystal layer 23 positioned can be controlled. Therefore, an area on the pixel electrode 219 can be effectively used as a display area, and a decrease in aperture ratio in one pixel can be reduced.

Further, the non-overlapping region 216 b of the third electrode 216 does not overlap the common electrode 218. That is,
The third electrode 216 does not overlap the common electrode 218. Accordingly, it is possible to suppress a decrease in light transmittance in the pixel due to the common electrode 218 and the third electrode 216 overlapping. Therefore, the luminance in the pixel can be ensured.

As shown in FIG. 4, the third electrode 216 has an overlapping region 219 a that overlaps with the pixel electrode 219. As a result, an auxiliary capacitance can be formed between the pixel electrode 219 and the third electrode 216, and it is not necessary to provide an additional auxiliary capacitance line, thereby reducing the complexity of the structure of the liquid crystal display device 1.

Further, in the liquid crystal display device 1, the third electrode 216 includes the overlapping region 216a and the non-overlapping region 216b.
Are integrated. Therefore, compared to the case where the overlapping region 219a and the non-overlapping region 216b are provided separately, when the pixel electrode 219 is formed by patterning in the formation region of the third electrode 216, even if a slight shift occurs in the X direction. The size of the overlapping region 216a and the non-overlapping region 216b of the third electrode 216 can be ensured.

As shown in FIG. 5, in the liquid crystal display device 1, the distance D ₃ between the pixel electrode 219 and the third electrode 216 is set smaller than the distance D ₄ between the gaps of the liquid crystal layer 23. If the distance D ₃ between the pixel electrode 219 and the third electrode 216 is set to be larger than the gap distance D ₄ between the liquid crystal layers 23, an electric field generated between the pixel electrode 219 and the third electrode 216. In some cases, E ₂ does not reach the liquid crystal molecules located in the vicinity of the second major surface 22a of the second substrate 22, and the liquid crystal molecules cannot be sufficiently controlled. On the other hand, if the distance D ₃ between the pixel electrode 219 and the third electrode 216 is made smaller than the gap distance D ₄ between the liquid crystal layers 23, the liquid crystal layer 23 is located near the second main surface 22 a of the second substrate 22. A sufficient electric field can be applied to the liquid crystal molecules.

The distance D ₃ refers to the shortest distance between the pixel electrode 219 and the third electrode 216, in this example, the distance between the surface and the surface of the third electrode 216 of the pixel electrode 219. The distance D ₄ refers to the shortest distance between the pixel electrode 219 and the second substrate 22, in this embodiment, an alignment film provided on the surface and a second substrate 22 of the pixel electrode 219 (not shown) Is the distance between

Here, in the liquid crystal display device 1, relationship between the gap distance D ₄ of the distance D ₃ and the liquid crystal layer 23 between the pixel electrode 219 and the third electrode 216 is set to D ₃ ≦ 0.3D _4.

As shown in FIG. 5, in the liquid crystal display device 1, the thickness H ₃ of the third electrode 216 is set smaller than the thickness H ₂ of the pixel electrode 219 and the thickness H ₃ of the common electrode 218. Since the third electrode 216 has an overlapping region 216a that overlaps the pixel electrode 219, the light transmittance in the overlapping region 216a is likely to decrease. Therefore, in the liquid crystal display device 1, by setting smaller to than the thickness H ₃ of the third electrode 216 in a thickness of H ₂ thicknesses H ₁ and the common electrode 218 of the pixel electrode 219 can be reduced decrease of the transmittance of the light .

Further, in the liquid crystal display device 1, the potential difference V ₂ between the third electrode 216 and the common electrode 218 is set to be smaller than or equal to the potential difference V ₁ between the pixel electrode 219 and the common electrode 218. Yes. In the liquid crystal display device 1, for example, the potential difference _{V 2} is the 0 to 5V, the potential difference _{V 1} is is set to 5V. The potential difference V is the absolute value of the potential difference between the electrodes.

In addition, as shown in FIG. 5, the third electrode 216, the distance D ₁ of the between the common electrode 218 and pixel electrode 219, the distance D ₂ less in length between the common electrode 218 and the third electrode 216 Is set.

The distance D ₁ refers to the shortest distance between the pixel electrode 219 and the common electrode 219, in this example, the distance between the end of the common electrode 218 and the edge of the pixel electrode 219. The distance _{D 2,} the common electrode 218
Is the shortest distance between the end of the common electrode 219 and the end of the third electrode 216 in this example.

In the liquid crystal display device 1, the distance D ₁ between the pixel electrode 219 and the common electrode 216 is set to ₃ to 8 μm, and the distance D ₂ between the common electrode 218 and the third electrode 216 is set to 5 to 10 μm. .

Thus, by setting the potential difference V and the distance D between the electrodes, the electric field generated between the common electrode 218 and the third electrode 216 is changed to the electric field E generated between the pixel electrode 219 and the common electrode 218. ₁ , the magnitude of the electric field E ₁ generated between the pixel electrode 219 and the common electrode 218 can be suppressed from being reduced.

In addition, when the third electrode 216 and the common electrode 218 are set to the same potential, no electric field is generated between the third electrode 216 and the common electrode 218, and therefore, the electric field E ₁ between the pixel electrode 219 and the common electrode 218 is not generated. Can be further suppressed. In order to make the third electrode 216 and the common electrode 218 have the same potential, for example, the third electrode 216 and the common electrode 218 may be connected by a contact hole or the like.

On the second substrate 22, as shown in FIG. 4, a light shielding pattern 221 for shielding light and a color filter 222 arranged so as to be adjacent to the light shielding pattern 221 are provided.

  The second base 22 has a function of supporting the member. The first base 22 has a second main surface 22a on which the above members are provided. The second substrate 22 may be the same as the first substrate 21.

The light shielding pattern 221 is provided on the second main surface 22a of the second base 22 in a lattice shape so as to extend in the X direction and the Y direction. In other words, the light shielding pattern 221 partitions the display area _AD for each pixel. Examples of the material of the light shielding pattern 221 include a resin to which a dye or pigment having a high light shielding ratio (for example, black) is added, or a metal such as chromium.

The color filter 222 has a function of transmitting only a specific wavelength of visible light. A plurality of color filters 222 are provided on the second main surface 22 a of the second base 22. Each color filter 222 has one color of red (R), green (G), and blue (B). The color of the color filter 222 is not limited to the above color, and for example, yellow (Y), white (
It may have a color such as W). Examples of the material of the color filter 222 include a material obtained by adding a dye or a pigment to an acrylic resin.

  The liquid crystal layer 23 is provided between the first base 21 and the second base 22. The liquid crystal layer 23 includes liquid crystal molecules such as a nematic liquid crystal, a cholesteric liquid crystal, or a smectic liquid crystal.

  The seal member 24 has a function of bonding the first base 21 and the second base 22 together. The seal member 24 is provided between the first base 21 and the second base 22 so as to surround the liquid crystal layer 23.

The light source device 3 has a function of emitting light toward the first base 21 and the second base 22 in the display area _AD . The light source device 3 includes a light source 31 and a light guide plate 32. In the light source device 3 in this example, a point light source such as an LED is adopted as the light source 31, but a linear light source such as a cold cathode tube may be adopted.

  The first polarizing plate 4 has a function of selectively transmitting light in a predetermined vibration direction. The first polarizing plate 4 is located outside the first base 21 and the second base 22, and is provided on the opposite side of the second base 22 from the first main surface 22 a.

  The second polarizing plate 5 has a function of selectively transmitting light in a predetermined vibration direction. The second polarizing plate 5 is disposed to face the first polarizing plate 4 with the first base 21 and the second base 22 interposed therebetween.

  In the liquid crystal display device 1, the first electrode is the pixel electrode 219 and the second electrode is the common electrode 218. Instead, the first electrode is the common electrode 218 and the second electrode is the pixel electrode 219. It may be a configuration.

[Embodiment 2]
FIG. 6 is a diagram illustrating an example of a liquid crystal display device 1A according to the second embodiment.

  The difference between the liquid crystal display device 1A and the liquid crystal display device 1 is that, in the liquid crystal display device 1A, the outer periphery of the third electrode 216 is located outside the outer periphery of the pixel electrode 219 in plan view. .

Thereby, in the liquid crystal display device 1A, the orientation of the liquid crystal molecules can be controlled by applying an electric field to the liquid crystal layer 23 located on the pixel electrode 219 in a favorable manner. Thereby, an aperture ratio can further be improved.

1, 1A liquid crystal display device 2 liquid crystal panel
21 First substrate
21a 1st main surface
216 Third electrode
217 Insulating film (third insulating film)
218 Second electrode (Common electrode)
219 First electrode (pixel electrode)
22 Second substrate
22a 2nd main surface
23 Liquid crystal layer

Claims (5)

A first base having a first main surface; a second base having a second main surface opposite to the first main surface of the first base; and the first base and the second base. A liquid crystal layer, a first electrode provided on the first main surface of the first base, and a second electrode provided on the first main surface of the first base;
In plan view, the first electrode and the second electrode are arranged along the first direction with a space therebetween,
The first base is provided on the first main surface of the first base so as to face the first electrode with an insulating film interposed therebetween, and both ends of the first base and the end of the first electrode in a cross-sectional view along the first direction. Having a third electrode positioned between the end of the second electrode;
A potential difference applied between the first electrode and the second electrode is greater than or equal to a potential difference applied between the second electrode and the third electrode;
The liquid crystal display device, wherein a distance between the first electrode and the second electrode is not more than a distance between the second electrode and the third electrode.   The liquid crystal display device according to claim 1, wherein the second electrode is provided on the insulating film.   The liquid crystal display device according to claim 1, wherein a thickness of the third electrode is smaller than thicknesses of the first electrode and the second electrode.   The liquid crystal display device according to claim 1, wherein the third electrode and the second electrode are connected.   5. The liquid crystal display device according to claim 1, wherein an outer periphery of the third electrode is located outside an outer periphery of the first electrode in plan view.

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