KR101469853B1 - Fringe field switching mode liquid crystal display device - Google Patents

Abstract

The present invention relates to an FFS mode liquid crystal display, and more particularly, to an FFS mode liquid crystal display device, in which a transparent pixel electrode is formed in a pixel region and a transparent pixel electrode is overlapped with the transparent pixel electrode, And the transparent common electrode includes a plurality of combs having a predetermined width in a direction substantially parallel to the data line, and the transparent common electrode covers the data line with the insulating layer sandwiched therebetween And a second comb formed adjacent to the first comb and formed at the center of the pixel region, wherein a light shielding film formed on the data line is removed, and the first comb and the second comb Is larger than the distance between the comb teeth formed inside the pixel.

FFS mode, liquid crystal display, transparent pixel electrode, transparent common electrode

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a liquid crystal display (LCD)

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an FFS-mode liquid crystal display, and more particularly, to an FFS-mode liquid crystal display capable of designing transmission and aperture ratio at a minimum cost without special process development.

2. Description of the Related Art In general, a FFS mode liquid crystal display device has been proposed to improve the aperture ratio and transmittance of an IPS mode liquid crystal display device. 1998-0009243.

Such an FFS mode liquid crystal display device has a counter electrode and a pixel electrode formed of a transparent conductor so as to increase the aperture ratio and transmittance as compared with the IPS mode liquid crystal display device and to set the interval between the counter electrode and the pixel electrode between the upper and lower glass substrates By forming the fringe field between the common electrode and the pixel electrode by forming the fringe field narrower than the interval, all of the liquid crystal molecules existing above the electrodes are also operated to obtain a more improved transmittance.

1 is a cross-sectional view illustrating a conventional FFS mode liquid crystal display device.

Referring to FIG. 1, first, a transparent conductive film is formed on an upper portion of a lower substrate 1, and then a first transparent conductive film is etched by a first photolithography process to form a transparent common electrode 2. A metal film is then formed on the lower substrate 1 on which the transparent common electrode 2 is formed, and then a gate electrode (not shown) is formed by a second photolithography process.

Then, a gate insulating film 3 is deposited on the entire surface of the lower substrate 1 including the transparent common electrode 2 and the gate electrode. Then, an amorphous silicon film for channel and a doped amorphous silicon film are stacked on the gate insulating film 3, and then the doped amorphous silicon film and the amorphous silicon film for channel are etched by a third photolithography process to form an active pattern (Not shown). Subsequently, a metal film is deposited on the resultant product, and then a metal film is etched by a fourth photolithography process to form source / drain electrodes (not shown) and a data line 4.

After the protective film 5 is formed on the substrate on which the source / drain electrodes and the data lines 4 are formed, the protective film 5 is etched by a fifth photolithography process so that the source electrode is partially exposed Thereby forming a contact hole (not shown).

Thereafter, a transparent conductive film is formed on the protective film 5, and then the transparent conductive film is etched by a sixth photolithography process to form a pixel electrode 6 connected to the drain electrode through the contact hole. Reference numeral 7 denotes an upper substrate, and reference numeral 8 denotes a light shielding film.

However, in the case of the FFS mode liquid crystal display having the above structure, as shown in FIG. 1, a light shielding film 8 for blocking light is usually formed on the data line 4, .

However, when the light shielding film 8 is removed, there is a problem that CR (Contrast Ratio) is lowered due to the light leakage phenomenon, so that the light shielding film 8 can not be removed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a liquid crystal display device and a liquid crystal display device which are capable of driving liquid crystal driving in the vicinity of a data line and liquid crystal driving in a center of a pixel region, The present invention also provides an FFS mode liquid crystal display device capable of preventing a light leakage phenomenon.

It is another object of the present invention to provide an FFS mode liquid crystal display device in which the aperture ratio is increased at a minimum cost without special process development by controlling the width, arrangement relationship, etc. of the data lines, the transparent common electrodes, and the transparent pixel electrodes.

According to an aspect of the present invention, there is provided a liquid crystal display device including a lower substrate, an upper substrate, and a liquid crystal layer sandwiched between the substrates, wherein gate lines and data In the FFS mode liquid crystal display device in which each pixel region is defined by lines and a switching device is disposed at an intersection of the gate line and the data lines, in order to control the light transmission amount by applying an electric field to the liquid crystal layer, And a transparent common electrode which is disposed so as to be spaced apart from the transparent pixel electrode so as to overlap with the predetermined area with the insulating layer interposed therebetween, wherein the transparent common electrode has a predetermined width in a direction substantially parallel to the data line And a transparent common electrode covering the data line with the insulating layer interposed therebetween, A first comb and a second comb formed adjacent to the first comb and formed at the center of the pixel area, wherein a light shielding film formed on the data line is removed, and a distance between the first comb and the second comb is Wherein the distance between the comb teeth is larger than the distance between the comb teeth formed inside the FFS mode liquid crystal display.

Preferably, the width of the first comb of the transparent common electrode covering the data line is wider than the width of the second comb of the adjacent transparent common electrode, and is preferably formed in the same layer as the data line, And a transparent pixel electrode is disposed.

Preferably, one end of the transparent pixel electrode is disposed between a first comb and a second comb adjacent to the transparent common electrode covering the data line, and one end of the transparent pixel electrode is connected to the first and second transparent comb electrodes, More preferably, the first comb teeth are closer to the first comb teeth, and one end of the transparent pixel electrode is located at the center between the first comb tooth and the second comb tooth.

In addition, if all of the lowest points of the light transmittance of both pixel regions are included in the width of the data line based on the data line, the upper portion of the data line can be effectively shielded even if the light blocking film is not present on the data line.

The transparent pixel electrode may have a plate shape or a comb shape.

Preferably, the transparent common electrode has a structure in which the pixel regions are connected to each other and the same voltage is applied, so that the total resistance can be reduced.

Preferably, the distance between the first and second comb teeth is greater than or equal to the distance between the upper and lower substrates, and the distance between the second comb tooth and the second comb tooth and the third comb tooth neighboring toward the center of the pixel area is The distance between the upper and lower substrates is equal to or smaller than the distance between the upper and lower substrates.

A second aspect of the present invention is a liquid crystal display device including a lower substrate, an upper substrate, and a liquid crystal layer sandwiched between the substrates, wherein gate lines and data lines formed in a direction crossing the lower substrate, And a switching element is disposed at an intersection of the gate line and the data line. In order to control the amount of light transmitted through the liquid crystal layer by applying an electric field to the liquid crystal layer, a transparent pixel electrode, And a transparent common electrode spaced apart from the transparent pixel electrode so as to overlap the transparent pixel electrode with an insulating layer interposed therebetween, wherein the transparent common electrode has a predetermined width in a direction parallel to the data line and has a plurality of combs, At least one of the comb teeth is formed so as to cover part or all of the data line in an insulated manner, The second mode is driven by the liquid crystal driving mode of the first mode and the second mode is driven by the liquid crystal driving mode of the second mode in the central region of the pixel region, 1 mode, the vertical electric field component is larger than that of the first mode.

A description of each mode can be found in U.S. Patent Nos. 5,914,762, 5,886,762, and 6,233,034, both of which are incorporated herein by reference. For example, in the FFS mode, the distance between the comb teeth of the transparent electrode is formed to be smaller than or equal to the distance between the upper substrate and the lower substrate, whereas in the case of the IPS mode, the distance between the comb teeth of the transparent electrode is Is generally larger than the distance between the upper substrate and the lower substrate. As another example, in the case of the FFS mode, the width of each of the combs of the transparent electrode is equal to or greater than the distance between the combs, whereas in the case of the IPS mode, As shown in FIG.

However, only the FFS mode and the IPS mode have been described above, and any concept definition can be further added if the concept of substantially driving the liquid crystal using the transverse electric field is included.

If the adjustment of the voltage applied to the transparent pixel electrode and the transparent common electrode and the arrangement relationship of the electrodes are adjusted, the transmissivity of the data line and its adjacent region is remarkably reduced so that the upper shielding film can be removed, So that it can be prevented from occurring.

As described above, according to the FFS mode liquid crystal display of the present invention, it is possible to prevent light leakage or discoloration phenomenon even when the light shielding film formed on the data line of the light shielding film, It is effective.

Further, the present invention has the effect of increasing the aperture ratio at a minimum cost without special process development by adjusting the width, arrangement relation, etc. of the data line, the transparent common electrode, and the transparent pixel electrode.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the following embodiments of the present invention may be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below. The embodiments of the present invention are provided to enable those skilled in the art to more fully understand the present invention.

The FFS mode liquid crystal display device includes a lower substrate, an upper substrate, and a liquid crystal layer interposed in the substrates. Each pixel region is defined by gate lines and data lines formed in a direction crossing the lower substrate A switching element is disposed at an intersection of the gate line and the data line and a transparent pixel electrode is formed in the pixel region and a transparent pixel electrode is formed between the transparent pixel electrode and the insulating layer in order to control the light transmission amount by applying a voltage to the liquid crystal layer. And a transparent common electrode which is spaced apart and overlapped with a predetermined region.

2A is a plan view of a part of a pixel region of a lower substrate of an FFS mode liquid crystal display according to an exemplary embodiment of the present invention, and FIGS. 2B to 2E illustrate a state in which layers are formed step by step, 3 is a cross-sectional view taken along a line I-I 'in Fig. 2, and Fig. 4 is a cross-sectional view taken along a line II-II' in Fig.

Referring to FIGS. 2A to 2E, 3 and 4, a unit pixel is formed by arranging the gate line G and the data line 600, which are made of opaque metal, vertically crossing each other on the lower substrate 100, A transparent common electrode 800 and a transparent pixel electrode 400 are disposed under the insulating layer 700 in the unit pixel region. The transparent pixel electrode 400 is formed in the same layer as the data line 600, And the transparent common electrode 800 is provided in a form having a plurality of combs by patterning the transparent conductive layer deposited on the insulating layer 700 and overlapped with the transparent pixel electrode 400 in a predetermined region.

An active pattern 500 in which an a-Si film and an n + a-Si film are sequentially deposited under the gate insulating film 300 and source / drain electrodes 600a and 600b are sequentially formed on the gate electrode 200 in the gate line G To form a thin film transistor TFT (T). The drain electrode 600b is electrically connected to the transparent pixel electrode 400 and a data signal is applied to the unit pixel.

A color filter (not shown) is provided on the upper substrate to correspond to each of the pixel regions formed on the lower substrate 100, and a light shielding film is formed on the data line 600 It does not. According to the related art, the transparent common electrode 800 is not formed on the data line 600, but a transparent common electrode 800 is formed on the data line 600 in an embodiment of the present invention.

Next, a manufacturing method of the FFS mode liquid crystal display device of the present invention will be described in detail with reference to FIGS. 2A to 2E, FIG. 3, and FIG.

Referring to FIGS. 2A to 2E, 3 and 4, a gate line G including a gate electrode 200 is formed on a lower substrate 100. That is, the gate line G including the gate electrode 200 is formed on the lower substrate 100 portion of the thin film transistor (TFT) forming portion through the deposition and patterning of the opaque metal film on the lower substrate 100 .

Then, a gate insulating layer 300 is deposited on the entire upper surface of the lower substrate 100 to cover the gate line G including the gate electrode 200, and then a transparent conductive layer is deposited on the gate insulating layer 300, A plate-shaped transparent pixel electrode 400 is formed to be disposed in each pixel region through patterning.

Next, the active pattern 500 is formed on the gate insulating film 200 on the gate electrode 200 by patterning the a-Si film and the n + a-Si film in this order on the resultant substrate.

Then, a metal film for source / drain is deposited and patterned to form a data line 600 including the source / drain electrodes 600a and 600b, thereby forming a thin film transistor TFT T). At this time, the drain electrode 600b is formed to be electrically connected to the pixel electrode 400.

Subsequently, an insulating layer 700 made of, for example, SiNx is coated on the resultant structure in which the thin film transistor T is formed, and then a transparent common electrode 800 having a comb-like shape is formed so as to overlap at least a part with the transparent pixel electrode 400 . Thereafter, although not shown, an alignment film is applied to the top of the resultant substrate on which the common electrode 800 is formed to complete the fabrication of the array substrate.

On the other hand, a color filter is selectively formed on the upper substrate, and an alignment film is formed thereon. The upper substrate 100 and the lower substrate 100 are bonded together under a liquid crystal layer, thereby completing the fabrication of an FFS mode liquid crystal display device according to an embodiment of the present invention. Of course, it is preferable to attach the polarizing plate to the outer surface of each substrate after the substrate is bonded.

Hereinafter, one embodiment of the present invention will be described in more detail with reference to FIGS. 4 and 5. FIG.

The transparent common electrode 800 has a plurality of combs having a predetermined width in a direction substantially parallel to the data line 600 and the first comb C ₁ of the transparent common electrode 800 is connected to the data line 600, And the light shielding film applied in the prior art can be removed at the upper portion of the data line 600.

That is, by disposing the first comb C ₁ on the data line 600, it is possible to reduce the disclination and increase the light transmittance. In this case, it is effective that the width L ₁ of the first comb C ₁ is formed to be greater than or equal to the width L _{3 of} the data line 600 to cover the entire data line 600 to be.

A second comb (C _2), the distance (D ₁₎ is formed equal to or greater than the distance (D ₂₎ between the teeth formed in the pixel between the neighboring with the first comb (C ₁₎ of the transparent common electrode 800 do.

Further, the second comb (C ₂₎ a width of (L ₂₎ has a first comb (C ₁₎ and the second comb (C ₂₎ distance equal to less than or (D ₁₎ between the second teeth (C ₂₎ And a third comb tooth (C ₃ ) adjacent to the second comb tooth (C ₂ ) toward the pixel area.

By this structure, the electric field generated in the area B including the data line 600 has a smaller vertical electric field component than the electric field generated in the central area A of the pixel area, and the area A and the area B The liquid crystal is driven in different liquid crystal driving modes. According to this structure, a light-shielding effect can be obtained even if a light-shielding film applied in the prior art is removed from the upper portion of the data line 600 by forming an opaque region above the data line 600.

Although the transparent pixel electrode 300 is shown in a plate shape in FIG. 2, it is needless to say that the transparent pixel electrode 300 may have a comb shape or the like.

5, the transparent common electrode 800 formed of a plurality of combs covers an entire portion excluding a region where the thin film transistor TFT (T (see FIG. 2A and FIG. 3) is formed) And each pixel region is electrically connected to each other.

One end E of the transparent pixel electrode 400 is disposed between the first comb C ₁ of the transparent common electrode 800 covering the data line 600 and the second comb C ₂ adjacent thereto, one end of the transparent pixel electrode (400) (E) includes a first comb (C ₁₎ and a second comb, and preferably located in the central part between the (C _2), more preferably the first comb (C ₁₎ and It is more preferable that the second comb teeth C ₂ are closer to the first comb teeth C ₁ .

6 is a graph showing the relationship between the light transmittance of the transparent pixel electrode 400 according to the position where one end E of the transparent pixel electrode 400 is located between the first comb C ₁ and the second comb C ₂ And a simulation result for comparison.

2 to 6, one end E of the transparent pixel electrode 400 is connected to the center of a central portion between the first comb C ₁ on the data line 600 and the second comb C ₂ adjacent thereto, Whereas when one end E of the transparent pixel electrode 400 is disposed closer to the second comb C ₂ than the first comb C ₁ is 24% A light transmittance of 30.81% is obtained when one end E of the transparent pixel electrode 400 is disposed adjacent to the first comb C ₁ and a light transmittance of 30.81% is observed at one end E of the transparent pixel electrode 400 ) Is extended to the first comb (C ₁ ), the light transmittance is 31.23%.

However, in the above example, when one end E of the transparent pixel electrode 400 extends to the first comb C ₁ , the light transmittance is high but the impermeable region is not properly formed on the data line, It can not be removed.

In FIG. 6, a graph drawn on top of the arrangement structure of the transparent pixel electrode 400, the first comb (C ₁ ), and the second comb (C ₂ ) is a graph showing the light transmittance.

Therefore, it is preferable that one end E of the transparent pixel electrode 400 is present between the first comb C ₁ and the second comb C ₂ and is further adjacent to the first comb C ₁ , It is more preferable that one end E of the pixel electrode 400 is located at the center of the first comb C ₁ and the second comb C ₂ .

On the other hand, the white bar portion on each picture represents the end portion of the first and second combs C ₁ and C ₂ of the transparent common electrode 800, and the red bar portion represents the end portion of the transparent pixel electrode 400 E).

7 is a graph showing the lowest points of light transmittance on both sides of the data line 600. Referring to FIG. 7, the lowest point of the left light transmittance is indicated by X with respect to the data line 600, and the right light transmittance is indicated by Y with respect to the data line.

In order to remove the light shielding film on the data line 600 and efficiently form the non-transmissive region on the data line 600, the minimum points (X, Y) of the left and right light transmittance Are all included in the width of the data line 600 (L _{3 in} FIG. 4).

Although the preferred embodiments of the FFS-mode liquid crystal display device according to the present invention have been described, the present invention is not limited thereto, and various modifications and changes may be made within the scope of the claims, And this also belongs to the present invention.

1 is a cross-sectional view illustrating a conventional FFS mode liquid crystal display device.

FIGS. 2A to 2E are plan views illustrating a state in which a portion of a pixel region in a lower substrate of an FFS mode liquid crystal display according to an embodiment of the present invention is formed in accordance with a manufacturing process.

3 is a cross-sectional view taken along a line I-I 'in FIG. 2A.

4 is a cross-sectional view taken along the line II-II 'of FIG. 2A.

FIG. 5 is a plan view showing only some layers in FIG. 2A.

6 is a simulation result chart for comparing the light transmittance varying according to the point where one end of the transparent pixel electrode is located in one embodiment of the present invention.

Fig. 7 is a graph showing the lowest points of light transmission on both sides of a data line in an embodiment of the present invention. Fig.

*** Description of the main parts of drawings ***

100: lower substrate, 200: gate electrode,

300: gate insulating film, 400: transparent pixel electrode,

500: active pattern, 600: data line,

600a, 600b: source / drain electrode, 700: insulating layer,

800: transparent common electrode

Claims (29)

And a liquid crystal layer interposed between the substrates, wherein the pixel regions are defined by gate lines and data lines formed in a direction crossing the lower substrate, And a switching element disposed at an intersection of the data lines, the FFS mode liquid crystal display comprising: A transparent pixel electrode in the pixel region and a transparent common electrode spaced apart from the transparent pixel electrode so as to overlap the transparent pixel electrode with an insulating layer interposed therebetween in order to adjust the light transmittance by applying an electric field to the liquid crystal layer, Wherein the transparent common electrode has a plurality of combs having a predetermined width in a direction substantially parallel to the data line, Wherein the transparent common electrode includes a first comb formed to cover the data line and a second comb adjacent to the first comb and formed at the center of the pixel region, Wherein the transparent pixel electrode has a shape including at least one comb having a predetermined width in a direction substantially parallel to the data line in the pixel region, and one end of the transparent pixel electrode closest to the data line is a A first comb and a second comb, the first comb and the second comb being located at a central portion between the first comb and the second comb, The comb teeth of the transparent pixel electrode are arranged such that the width thereof is greater than or equal to the distance between the comb teeth of the transparent common electrode and corresponds to the area between the comb teeth of the transparent common electrode, Wherein a distance between the first comb and the second comb is larger than a distance between combs formed in the pixel region. The method according to claim 1, And the width of the first comb of the transparent common electrode covering the data line is wider than the width of the second comb of the neighboring transparent common electrode. The method according to claim 1, And the transparent pixel electrode is disposed on the same layer as the data line. The method according to claim 1, And the transparent common electrode is disposed between the data line and the insulating layer. The method according to claim 1, And the width of the first comb may be greater than or equal to the width of the data line. The method according to claim 1, Wherein the first comb is formed to cover a part or all of the data lines. delete delete delete The method according to claim 1, Wherein a lowest point of light transmittance of an outer portion of both pixel regions with respect to the data line is included within a width of the data line. delete delete delete The method according to claim 1, Wherein the transparent common electrode is a structure in which the pixel regions are connected to each other and the same voltage is applied thereto. The method according to claim 1, Wherein a distance between the first comb and the second comb is larger than a distance between the upper substrate and the lower substrate. The method according to claim 1, Wherein a width of the second comb is smaller than or equal to a distance between the first comb and the second comb. The method according to claim 1, Wherein the transparent common electrode further comprises a third comb and a third comb neighboring the second comb and the pixel region. 18. The method of claim 17, Wherein the distance between the first comb and the second comb is larger than the distance between the upper substrate and the lower substrate and the distance between the second comb and the third comb is smaller than or equal to the distance between the upper and lower substrates. The FFS mode liquid crystal display device. 18. The method of claim 17, Wherein a width of the second comb is formed to be smaller than or equal to a distance between the first comb and the second comb and is formed to be equal to or greater than a distance between the second comb and the third comb, Display device. And a liquid crystal layer interposed between the substrates, wherein the pixel regions are defined by gate lines and data lines formed in a direction crossing the lower substrate, And a switching element disposed at an intersection of the data lines, the FFS mode liquid crystal display comprising: A transparent pixel electrode in the pixel region and a transparent common electrode spaced apart from the transparent pixel electrode so as to overlap the transparent pixel electrode with an insulating layer interposed therebetween in order to adjust the light transmittance by applying an electric field to the liquid crystal layer, Wherein the transparent common electrode has a predetermined width in a direction substantially parallel to the data line and has a plurality of combs, Wherein the liquid crystal display device is driven in a liquid crystal driving mode of a first mode in an area including the data line and in a liquid crystal driving mode of a second mode in the pixel area, Wherein the transparent common electrode includes a first comb formed to cover the data line and a second comb adjacent to the first comb and formed at the center of the pixel region, Wherein the transparent pixel electrode has a shape including at least one comb having a predetermined width in a direction substantially parallel to the data line in the pixel region and one end of the transparent pixel electrode closest to the data line is a A first comb and a second comb, The comb teeth of the transparent pixel electrode are arranged such that the width thereof is greater than or equal to the distance between the comb teeth of the transparent common electrode and corresponds to the area between the comb teeth of the transparent common electrode, Wherein the second mode has a larger vertical electric field component than the first mode. 21. The method of claim 20, Wherein the first comb is formed to cover a part or all of the data lines. 21. The method of claim 20, And one end of the transparent pixel electrode is adjacent to the first comb. 21. The method of claim 20, And one end of the transparent pixel electrode is located at a center between the first comb and the second comb. delete delete delete delete 21. The method of claim 20, Wherein the transparent common electrode is a structure in which the pixel regions are connected to each other and the same voltage is applied thereto. 21. The method of claim 20, Wherein a lowest point of light transmittance of an outer portion of both pixel regions with respect to the data line is included within a width of the data line.

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