KR20120021373A - Fringe-field switching liquid crystal display - Google Patents

Fringe-field switching liquid crystal display Download PDF

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KR20120021373A
KR20120021373A KR1020100073107A KR20100073107A KR20120021373A KR 20120021373 A KR20120021373 A KR 20120021373A KR 1020100073107 A KR1020100073107 A KR 1020100073107A KR 20100073107 A KR20100073107 A KR 20100073107A KR 20120021373 A KR20120021373 A KR 20120021373A
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South Korea
Prior art keywords
liquid crystal
region
area
auxiliary
pixel
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KR1020100073107A
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Korean (ko)
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이승희
하경수
우창우
임영진
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전북대학교산학협력단
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Priority to KR1020100073107A priority Critical patent/KR20120021373A/en
Priority to PCT/KR2010/008694 priority patent/WO2012015111A1/en
Publication of KR20120021373A publication Critical patent/KR20120021373A/en

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    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1343—Electrodes
    • G02F1/134309—Electrodes characterised by their geometrical arrangement
    • G02F1/134363—Electrodes characterised by their geometrical arrangement for applying an electric field parallel to the substrate, i.e. in-plane switching [IPS]

Abstract

The present invention relates to a fringe field switching type liquid crystal display device. In the liquid crystal display device according to the present invention, the unit pixel includes a main region and an auxiliary region, and the main region and the auxiliary region have different directions of a horizontal electric field applied to the liquid crystal with respect to the rubbing direction of the liquid crystal, and the main region and the auxiliary region. Silver has different areas. According to the present invention, while maintaining the characteristics of high optical efficiency and low driving voltage of the FFS mode, it is possible to improve the image quality by minimizing the problem of color shift according to the viewing angle, and also to improve the problem of lowering of transmittance due to the disclination line. The light efficiency can be maximized.

Description

Fringe field switching liquid crystal display device {FRINGE-FIELD SWITCHING LIQUID CRYSTAL DISPLAY}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fringe-field switching (FFS) type liquid crystal display device. In particular, multiple domains are formed in a unit pixel to minimize color shift according to a viewing angle and to eliminate disclination lines. The present invention relates to a liquid crystal display device for minimizing a decrease in transmittance due to lines.

Currently, liquid crystal mode, which is widely used in small and medium-sized liquid crystal display devices such as a monitor, a notebook, and a mobile phone, is a twisted nematic (TN) mode. TN mode has been widely applied to high process yield as well as high light efficiency, but has a disadvantage in that the viewing angle is narrow because the liquid crystal molecules move in the vertical direction when voltage is applied. In-Plane Switching (IPS) and Fringe Field Switching (FFS) modes have been developed to solve the narrow viewing angle problem.

Both modes have a better viewing angle than the TN mode because the liquid crystal molecules rotate in one direction parallel to the substrate. However, in the IPS mode, liquid crystal molecules do not rotate in the upper portion of the electrode, so that the light efficiency is low, the driving voltage is high, and there is a problem such as color shift due to the viewing angle. In order to solve various problems of the IPS mode, the FFS mode has been proposed. In the FFS mode, the common electrode and the pixel electrode form a transparent electrode structure with an insulating layer therebetween, and the horizontal gap between the common electrode and the pixel electrode is maintained. It is formed to be narrower than the gap between the upper and lower substrates so that a strong fringe electric field is formed between the common electrode and the pixel electrode, thereby rotating the liquid crystal molecules on the upper part of the pixel electrode, thereby exhibiting high light efficiency, low voltage driving, and wide viewing angle characteristics. However, despite these advantages, there is still a problem of color shift depending on the viewing angle, so that the image quality is different depending on the viewing angle.

In order to solve the color shift problem, a dual domain pixel structure has been proposed in which the slit designs of the pixel electrodes are differently formed at the upper and lower portions of the unit pixel to form different rotation directions of the liquid crystals at the upper and lower portions.

However, the dual domain pixel structure solves the color shift problem according to the viewing angle, but there is a problem in that the transmittance is reduced because a disclination line is formed due to the liquid crystal collision caused by the rotation of the liquid crystal in the upper and lower boundary regions.

Therefore, an object of the present invention is to improve image quality by minimizing color shift according to a viewing angle in an FFS mode.

It is another object of the present invention to minimize the decrease in transmittance due to the disclination line.

The objects of the present invention are not limited to the above-mentioned objects, and other objects and advantages of the present invention which are not mentioned above can be understood by the following description, and will be more clearly understood by the embodiments of the present invention. It will also be appreciated that the objects and advantages of the present invention may be realized by the means and combinations thereof indicated in the claims.

In accordance with this object, the present invention provides a fringe field switching type liquid crystal display device, wherein a unit pixel includes a main region and an auxiliary region, wherein the main region and the auxiliary region are applied to the liquid crystal with respect to the rubbing direction of the liquid crystal. The direction of the horizontal electric field is different, the main area and the auxiliary area is characterized in that the area is different.

In the liquid crystal display device of the fringe field switching method, the unit pixel includes a main region and an auxiliary region, and the slit direction of the pixel electrode with respect to the rubbing direction of the liquid crystal in the main region and the auxiliary region is different. It is another feature that the area of the main area and the auxiliary area is different.

In addition, in the liquid crystal display device of the fringe field switching method, the unit pixel includes a main region and an auxiliary region, and the slit direction of the common electrode with respect to the rubbing direction of the liquid crystal in the main region and the auxiliary region is different. Another feature is that the area of the main area and the auxiliary area are different.

According to the present invention, while maintaining the characteristics of high optical efficiency and low drive voltage of the FFS mode, it is possible to improve the image quality by minimizing the problem of color shift according to the viewing angle, and also to improve the problem of lowering of transmittance due to the disclination line The light efficiency can be maximized.

1 is a plan view illustrating a unit pixel of a conventional FFS mode liquid crystal display device.
2 is a plan view of a structure in which a double domain is formed in a unit pixel in a conventional FFS mode liquid crystal display device.
3 is a plan view illustrating a unit pixel of an FFS mode liquid crystal display device according to a first exemplary embodiment of the present invention.
4 is a plan view illustrating an FFS mode liquid crystal display device according to a second exemplary embodiment of the present invention.
FIG. 5 is a diagram illustrating an arrangement state of initial liquid crystals and an arrangement state of liquid crystal molecules during driving in the liquid crystal display device illustrated in FIG. 4.
6 is a plan view illustrating an FFS mode liquid crystal display device according to a third exemplary embodiment of the present invention.
7 is a plan view illustrating an FFS mode liquid crystal display device according to a fourth embodiment of the present invention.

1 shows a single domain pixel structure of a conventional FFS mode liquid crystal display. In Fig. 1, "R" indicates the rubbing direction of the liquid crystal.

Since the data bus line 101 and the gate bus line 104 are insulated from each other and formed on the lower substrate, the unit pixel space is limited. The common electrode 105 is formed in a planar shape in the limited unit pixel, and the pixel electrode 106 separated through an insulating film (not shown) is formed in a slit pattern. In this case, the source / drain 102 is formed on the gate bus line 104 to form a potential difference with the pixel electrode 106 based on the common electrode 105 to form the thin film transistor 103. The liquid crystal display shown in FIG. 1 is a structure having excellent transmission characteristics but having a color shift problem according to a viewing angle.

FIG. 2 illustrates a liquid crystal display device having a dual domain pixel structure proposed to solve a color shift problem according to a viewing angle of the single domain pixel structure of FIG. 1.

As shown in FIG. 1, the data bus line 201 and the gate bus line 204 are insulated from each other and formed on the lower substrate, thereby defining a unit pixel space. The common electrode 205 is formed in a planar shape in the limited unit pixel, and the pixel electrode 206 separated through an insulating film (not shown) is formed in a slit pattern. In order to generate a potential difference with the pixel electrode 206 based on the common electrode 205, a source / drain 202 is formed in the gate bus line 204 to form a thin film transistor 203.

As shown, the slit of the pixel electrode 206 is formed to be inclined in a direction opposite to the rubbing direction R in the upper and lower portions. Through the slit design of the upper and lower parts, when voltage is applied between the pixel electrode 206 and the common electrode 205, the directions of the liquid crystals in the upper and lower parts of the pixel are different from each other. As described above, the liquid crystal display shown in FIG. 2 solves the color shift problem according to the viewing angle through the liquid crystal director having the compensation structure during driving. However, in the dual domain pixel structure of FIG. 2, the slit direction of the pixel electrode 206 is Since the angle formed with respect to the rubbing direction R is symmetrical, and the area of the upper region and the lower region is the same, the liquid crystals in the upper region and the lower region have different rotational directions and the same magnitude of force. Thus, a disclination line is formed due to the liquid crystal collision due to the rotation of the liquid crystal in the boundary region.

That is, in the case of the FFS mode liquid crystal display device that is initially horizontally aligned, the optical axis of the liquid crystal coincides with one axis of the orthogonal polarizing plate, and the general transmittance formula is shown in Equation (1).

Figure pat00001

Where T is the transmittance, T 0 is the transmittance to the reference light, Φ is the angle between the optical axis of the liquid crystal molecules and the transmission axis of the polarizer, Δn is the refractive index anisotropy, d is the thickness of the liquid crystal layer, and λ is the wavelength of the incident light. Point to.

In the FFS mode, the transmission axis of one of the crossed polarizers coincides with the rubbing direction of the lower substrate. Since Φ is 0 °, light cannot be transmitted by the transmittance formula. As the voltage is applied, the liquid crystal director rotates by the fringe field, and Φ is not 0 °, thereby allowing light to pass through. In the FFS mode, the size of phi of the liquid crystal director is different depending on the direction in which the slits are formed and the rubbing direction. When the slits and rubbing directions formed during the actual process are formed differently for each region, Φ at the same voltage is formed differently for each region, and thus the electrical and optical characteristics are different for each position. When? Is formed in different directions in the same pixel, the color shift problem according to the viewing angle of the liquid crystal display device in the viewing angle direction is minimized. However, when liquid crystals having different? Are formed in the same pixel, a disclination line is formed due to the collision of liquid crystals, thereby causing a problem of a decrease in transmittance.

Hereinafter, embodiments of the present invention will be described with reference to FIGS. 3 to 7.

3 illustrates a unit pixel of a liquid crystal display device according to a first embodiment of the present invention. As shown, the gate bus line 304 and the data bus line 301 are formed to be connected to the lower substrate while being insulated from each other, thereby limiting the unit pixel space. The data bus line 301 may be formed in a straight shape or bent in accordance with the shape of the common electrode 305. In the limited unit pixel, the common electrode 305 is formed to have a planar shape or a pattern, and the pixel electrode 306 separated through an insulating film (not shown) is formed to have a slit pattern. In this case, in order to generate a potential difference between the common electrode 305 and the pixel electrode 306, a source / drain 302 is formed in the gate bus line 304 to form a thin film transistor 303. The formation positions of the common electrode 305 and the pixel electrode 306 may be reversed.

When the liquid crystal having positive dielectric anisotropy is used in the present embodiment, a liquid crystal layer sandwiched between the upper and lower substrates of transparent glass or polymer material is formed to a thickness of 5 μm or less. In the structure shown in FIG. 3, when the slits are patterned on the pixel electrode 306, the slits are formed at different angles by dividing the auxiliary region S and the main region M for each pixel position. The angle θ 'formed between the slit direction of the pixel electrode 306 and the rubbing direction R of the liquid crystal in the S region, and the angle formed between the slit direction of the pixel electrode 306 and the rubbing direction R of the liquid crystal in the M region ( (theta) is formed between 3 degrees and 40 degrees, and it is preferable that (theta) 'is formed larger than (theta). Further, the widths w 'and w of the pixel electrodes 306 in the S and M regions are 7 µm or less, and the lengths of the slits 1' and 1 between the pixel electrodes 306 are 10 µm or less.

Through this structure, a two-domain structure having different electrical and optical characteristics is formed in the unit pixel, thereby minimizing the color shift problem according to the viewing angle. In addition, when the angle formed between the slit direction of the pixel electrode 306 in the M region having a large area ratio and the rubbing direction R of the liquid crystal is reduced, the light efficiency can be improved. In addition, the auxiliary area S and the main area M have different areas, and angles θ 'and θ formed between the slit direction of the pixel electrode 306 and the rubbing direction R of the liquid crystal are different in each area. Therefore, since the rotational force applied to the liquid crystal in each region during driving is opposite in direction and different in magnitude, the liquid crystal collision is weakened compared to the case where the magnitude of the force in the liquid crystal collision is the same, thereby minimizing the disclination line. This improves the overall transmittance.

4 illustrates a liquid crystal display device according to a second embodiment of the present invention. As shown, slits of the pixel electrodes 406 are symmetrically formed between pixels adjacent in the column direction (or the rubbing direction of the liquid crystal). As shown, in the upper pixel, the main region M is formed at the upper portion and the auxiliary region S is formed in the lower pixel. In the lower pixel, the auxiliary region S is formed at the upper portion and the main region M is formed in the lower pixel. Is formed.

The gate bus line 404 and the data bus line 401 are formed on the lower substrate while being insulated from each other to define a unit pixel space. The data bus line 401 is formed in a straight form in this embodiment, but may be formed in a bent form according to the shape of the common electrode 405. In a limited unit pixel, the common electrode 405 is formed to have a planar shape or a pattern, and the pixel electrode 406 separated through an insulating film (not shown) is formed to have a slit pattern. In addition, a source / drain 402 is formed on the gate bus line 404 to form a potential difference between the common electrode 405 and the pixel electrode 406 to form a thin film transistor 403.

FIG. 5 is a diagram illustrating an arrangement state of initial liquid crystals and an arrangement state of liquid crystal molecules during driving in the liquid crystal display device illustrated in FIG. 4. In FIG. 5, θ is an angle in which the slit direction of the pixel electrode 406 forms the rubbing direction R in the main region, and θ 'is an angle in which the slit direction of the pixel electrode 406 forms the rubbing direction R in the auxiliary region. Point to. In the state in which the driving voltage is not applied, the liquid crystal molecules are arranged in the rubbing direction R in the main region M and the auxiliary region S in the same manner. However, when the driving voltage is applied, the liquid crystal molecules rotate in a direction perpendicular to the slit as shown in the drawing. Since the slit directions of the main region M and the auxiliary region S are different, the arrangement direction of the liquid crystal molecules is also the main region M. ) And in the auxiliary region S.

6 shows a liquid crystal display device according to a third embodiment of the present invention. As illustrated, the common electrode 605 is patterned along the direction of the slit, and the data bus line 601 is also formed to have a structure that is bent in the same direction as the common electrode 605. Through such a structure, higher light efficiency and wide aperture ratio can be obtained. The gate bus line 604, the pixel electrode 606, the source / drain 602, and the thin film transistor 603 are formed in the same manner as in FIG. 4.

7 shows a liquid crystal display device according to a fourth embodiment of the present invention. In the present embodiment, the positions at which the common electrode 705 and the pixel electrode 706 are formed are opposite to those of FIG. 4. The data bus line 701, the source / drain 702, the thin film transistor 703, and the gate bus line 704 are formed in the same manner as in FIG. 4.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the spirit of the present invention for those skilled in the art to which the present invention pertains. It is not limited by.

101, 201, 301, 401, 601, 701: data bus lines
102, 202, 302, 402, 602, 702: source / drain
103, 203, 303, 403, 603, 703: thin film transistor (TFT)
104, 204, 304, 404, 604, 704: gate busline
105, 205, 305, 405, 605, 705: common electrode
106, 206, 306, 406, 606, 706: pixel electrode

Claims (12)

In the fringe field switching type liquid crystal display device,
The unit pixel has a main area and an auxiliary area.
The main region and the auxiliary region are different in the direction of the horizontal electric field applied to the liquid crystal relative to the rubbing direction of the liquid crystal,
And an area of the main area and the auxiliary area is different.
The method of claim 1,
And the unit pixel is symmetrical with an adjacent unit pixel.
The method of claim 2,
And the unit pixel is symmetrical with adjacent unit pixels in a column direction.
The method according to claim 1 or 2,
And an angle formed between the rubbing direction of the liquid crystal and the slit direction is smaller in the main region than in the auxiliary region.
The method according to claim 1 or 2,
And the slit direction of the pixel electrode relative to the rubbing direction of the liquid crystal is different in the main region and the auxiliary region.
The method of claim 5, wherein
The common electrode of the unit pixel is patterned along the slit direction of the pixel electrode.
The method of claim 5, wherein
And a data bus line for the unit pixel is patterned along the slit direction of the pixel electrode.
The method according to claim 1 or 2,
And a slit direction of the common electrode with respect to the rubbing direction of the liquid crystal is different in the main region and the auxiliary region.
The method of claim 8,
And the pixel electrode of the unit pixel is patterned along the slit direction of the common electrode.
In the fringe field switching type liquid crystal display device,
The unit pixel has a main area and an auxiliary area.
The slit direction of the pixel electrode with respect to the rubbing direction of the liquid crystal is different in the main region and the auxiliary region,
And an area of the main area and the auxiliary area is different.
In the fringe field switching type liquid crystal display device,
The unit pixel has a main area and an auxiliary area.
The slit direction of the common electrode with respect to the rubbing direction of the liquid crystal is different in the main region and the auxiliary region,
And an area of the main area and the auxiliary area is different.
The method according to claim 9 or 10,
And the unit pixel is symmetrical with adjacent unit pixels in a column direction.
KR1020100073107A 2010-07-29 2010-07-29 Fringe-field switching liquid crystal display KR20120021373A (en)

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KR20140005717A (en) * 2012-07-06 2014-01-15 엘지디스플레이 주식회사 Fringe field switching mode liquid crystal display device
US9952466B2 (en) 2014-12-08 2018-04-24 Samsung Display Co., Ltd. Liquid crystal display device having branch electrodes

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CN104407476B (en) * 2014-12-23 2017-11-14 厦门天马微电子有限公司 A kind of array base palte, display panel and display device
CN107908315B (en) * 2015-12-07 2021-01-01 上海天马微电子有限公司 Display panel

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KR100687322B1 (en) * 1999-06-25 2007-02-27 비오이 하이디스 테크놀로지 주식회사 LCD having high aperture ratio and high transmittance ratio
KR100527084B1 (en) * 2000-12-05 2005-11-09 비오이 하이디스 테크놀로지 주식회사 Ffs liquid crystal display device
KR100850380B1 (en) * 2002-09-03 2008-08-04 비오이 하이디스 테크놀로지 주식회사 Horizontal electric field mode liquid crystal display device
KR100827459B1 (en) * 2006-04-11 2008-05-06 비오이 하이디스 테크놀로지 주식회사 In Plane Field Mode Liquid Crystal Display
JP5477523B2 (en) * 2006-06-15 2014-04-23 三国電子有限会社 Low cost large screen wide viewing angle fast response liquid crystal display
KR20100118235A (en) * 2009-04-28 2010-11-05 전북대학교산학협력단 Fringe field switching liquid crystal display

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20140005717A (en) * 2012-07-06 2014-01-15 엘지디스플레이 주식회사 Fringe field switching mode liquid crystal display device
US9952466B2 (en) 2014-12-08 2018-04-24 Samsung Display Co., Ltd. Liquid crystal display device having branch electrodes

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