KR20080073265A - Fringe field switching mode liquid crystal display device - Google Patents

Abstract

An FFS(Fringe Field Switching) mode LCD(Liquid Crystal Display) is provided to increase an aperture ratio even without a light-shielding film by controlling arrangement of a data line, a transparent common electrode, and a transparent pixel electrode. A gate line(G) and a data line(600) vertically cross each other to define a unit pixel region on a lower substrate. A transparent pixel electrode(800) and a transparent common electrode(400) are disposed within the unit pixel region such that a portion of the transparent common electrode overlaps with the transparent pixel electrode with an insulating layer therebetween. The transparent pixel electrode is disposed on the same layer as the data line. A color filter is formed on an upper substrate correspondingly to the unit pixel region. The transparent common electrode has a plurality of comb teeth, wherein one of the comb teeth is disposed above the data line so that a light-shielding film needs not to be disposed above the data line.

Description

F-S mode liquid crystal display {FRINGE FIELD SWITCHING MODE LIQUID CRYSTAL DISPLAY DEVICE}

The present invention relates to an FFS mode liquid crystal display device, and more particularly, to an FFS mode liquid crystal display device capable of a design having increased transmission and aperture ratio at a minimum cost without special process development.

In general, a FFS mode (Fringe Field Switching Mode; FFS) liquid crystal display has been proposed to improve the low aperture ratio and transmittance of an In-Plane Switching Mode (IPS Mode) liquid crystal display, and a Korean patent application has been proposed. Filed in US Pat. No. 1998-0009243.

The FFS mode liquid crystal display device forms a counter electrode and a pixel electrode with a transparent conductor, and increases the aperture ratio and transmittance as compared to the IPS mode liquid crystal display device, while maintaining a gap 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 gap smaller than the interval, even the liquid crystal molecules existing on the electrodes are 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 transparent common electrode 2 is formed by etching the first transparent conductive film by a first photolithography process. Next, a metal film is 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.

Subsequently, 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. Subsequently, a channel amorphous silicon film and a doped amorphous silicon film are stacked on the gate insulating layer 3, and then the doped amorphous silicon film and the channel amorphous silicon film are etched by a third photolithography process to form an active pattern. (Not shown) is formed. Subsequently, a metal film is deposited on the resultant, and the metal film is etched by a fourth photolithography process to form a source / drain electrode (not shown) and a data line 4.

Next, after forming the passivation layer 5 on the substrate on which the source / drain electrode and the data line 4 are formed, the passivation layer 5 is etched by a fifth photolithography process to expose a predetermined portion of the source electrode. Contact holes (not shown) are formed.

Thereafter, a transparent conductive film is formed on the passivation layer 5, and then the transparent conductive film is etched by the sixth photolithography process to form the pixel electrode 6 connected to the drain electrode through the contact hole. Unexplained 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 that blocks light is typically formed on the upper portion of the data line 4, which reduces the aperture ratio. There was a problem.

However, when the light shielding film 8 is removed, there is a problem in that a contrast ratio (CR) falls due to light leakage, and thus the light shielding film 8 cannot be removed.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the light blocking film formed on an upper portion of a data line by causing the liquid crystal driving near the data line and the liquid crystal driving at the center of the pixel region to be driven in different liquid crystal driving modes. Meanwhile, an object of the present invention is to provide an FFS mode liquid crystal display device capable of preventing light leakage.

Another object of the present invention is to provide an FFS mode liquid crystal display device having an increased aperture ratio at a minimum cost without special process development by adjusting the width, arrangement, and the like of data lines, transparent common electrodes, and transparent pixel electrodes.

In order to achieve the above object, a first aspect of the present invention includes a lower substrate, an upper substrate, and a liquid crystal layer interposed between the substrates, and the lower substrate has gate lines and data formed in directions crossing each other. In the FFS mode liquid crystal display in which each pixel region is defined by lines, and a switching element is disposed at the intersection of the gate line and the data lines, the pixel region is applied to control an amount of light transmission by applying an electric field to the liquid crystal layer. And a transparent common electrode disposed to be spaced apart from the transparent pixel electrode by a predetermined region with an insulating layer interposed therebetween, wherein the transparent common electrode has a predetermined width in a direction substantially parallel to the data line. A plurality of combs and a structure in which the transparent common electrode covers the data line with the insulating layer interposed therebetween A first comb to be formed and a second comb to be adjacent to the first comb and formed at the center of the pixel area, wherein the light shielding film formed on the data line is removed, and the distance between the first and second comb is Provided is an FFS mode liquid crystal display device characterized in that the distance between the combs formed therein is greater.

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 neighboring transparent common electrode, preferably formed on the same layer as the data line or the insulating layer. A transparent pixel electrode disposed between the gaps is provided.

In addition, one end of the transparent pixel electrode may be disposed between a first comb of the transparent common electrode covering the data line and a second comb adjacent to each other, and one end of the transparent pixel electrode may be disposed between the first and the second combs. More preferably, the second comb is further adjacent to the first comb, and more preferably, one end of the transparent pixel electrode is positioned at the center between the first and second combs.

In addition, when the lowest point of the light transmittance of both pixel areas is included in the width of the data line with respect to the data line, the upper portion of the data line can be effectively shielded even if the light blocking film on the data line does not exist.

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

Preferably, the transparent common electrode can reduce the overall resistance when the pixel areas are connected to each other to apply the same voltage.

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 and the second comb and a third comb neighboring toward the center of the pixel area is It is configured to be smaller than or equal to the distance between the upper and lower substrates.

A second aspect of the present invention includes a lower substrate, an upper substrate, and a liquid crystal layer interposed between the substrates, and each pixel region is formed in the lower substrate by gate lines and data lines which are formed to cross each other. In the FFS mode liquid crystal display device in which a switching element is disposed at the intersection of the gate line and the data line, a transparent pixel electrode is provided in the pixel region to apply an electric field to the liquid crystal layer to control light transmission amount; And a transparent common electrode spaced apart from the transparent pixel electrode so as to overlap a predetermined region with an insulating layer interposed therebetween, wherein the transparent common electrode has a predetermined width in a direction parallel to the data line and includes a plurality of combs. At least one of the four comb teeth is formed to have a structure to insulate a part or all of the data line, the data line The light blocking film is removed from the upper portion of the data line by driving in the liquid crystal driving mode of the first mode in the region including the and driving in the liquid crystal driving mode of the second mode in the central region of the pixel region. An FFS mode liquid crystal display device is characterized in that a vertical electric field component is larger than that of one mode.

For descriptions of each mode, reference may be made to the contents disclosed in US Patent Nos. 5,914,762, 5,886,762, and 6,233,034, previously filed and registered by the applicant. For example, in the FFS mode, the distance between each comb 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 IPS mode, the distance between each comb of the transparent electrode is It is generally formed larger than the distance between the upper substrate and the lower substrate. In another example, in the FFS mode, the width of each comb of the transparent electrode is greater than or equal to the distance between the combs, whereas in the IPS mode, the width of each comb of the transparent electrode is the comb of the transparent electrode. It is common to form less than or equal to the distance between.

However, only the FFS mode and the IPS mode have been described above. For example, if the concept of substantially driving the liquid crystal using a transverse electric field is included, any conceptual definition may be additionally included.

On the other hand, by adjusting the voltage applied to the transparent pixel electrode and the transparent common electrode and the arrangement relationship of each electrode, the transmittance is significantly reduced in the data line and its adjacent area, so that the light shielding film on the upper part can be removed, It can be induced not to occur.

According to the FFS mode liquid crystal display device of the present invention as described above, even if the light-shielding film formed on the upper data line of the light-shielding film that serves to block the light can be removed, the light leakage phenomenon or the declining phenomenon can be prevented. It works.

In addition, the present invention has an effect that the aperture ratio can be increased at a minimum cost without special process development by adjusting the width, arrangement, and the like 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, embodiments of the present invention illustrated below may be modified in many different 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 more completely explain the present invention to those skilled in the art.

The FFS mode liquid crystal display device includes a lower substrate, an upper substrate, and a liquid crystal layer inserted into the substrates, each pixel region being defined by gate lines and data lines formed in cross directions. A switching element is disposed at an intersection of the gate line and the data line, and a transparent pixel electrode, a transparent pixel electrode, and an insulating layer are interposed between the transparent pixel electrode and the pixel layer in order to adjust a light transmission amount by applying a voltage to the liquid crystal layer. It is provided with a transparent common electrode spaced apart from each other and overlapping a predetermined area.

FIG. 2A is a plan view of a portion of a pixel region formed in accordance with a manufacturing process in 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 situation in which each layer is formed step by step. 3 are cross-sectional views taken along line II ′ of FIG. 2, and FIG. 4 is a cross-sectional view taken along line II-II ′ of FIG. 2.

Referring to FIGS. 2A through 2E, 3, and 4, in the lower substrate 100, a gate line G made of an opaque metal and a data line 600 are arranged to vertically intersect to form a unit pixel. In the unit pixel area, the transparent common electrode 800 and the transparent pixel electrode 400 are disposed under the insulating layer 700. The transparent pixel electrode 400 is formed on the same layer as the data line 600 in the form of a plate, for example. The transparent common electrode 800 is formed in a form having a plurality of combs by patterning the transparent conductive layer deposited on the insulating layer 700 and overlaps a predetermined region with the transparent pixel electrode 400.

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

On the other hand, the upper substrate is provided with a color filter (not shown) indicating the color of the screen corresponding to each of the pixel areas formed on the lower substrate 100, the light shielding film is formed on the upper portion of the data line 600, unlike the prior art It doesn't work. In addition, according to the related art, the transparent common electrode 800 is not formed on the data line 600, but in the exemplary embodiment of the present invention, the transparent common electrode 800 is formed on the data line 600.

Next, the 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, 3, and 4.

2A through 2E, 3, and 4, the gate line G including the gate electrode 200 is formed on the lower substrate 100. That is, the gate line G including the gate electrode 200 is formed on the lower substrate 100 portion of the TFT (T) formation part by depositing and patterning an opaque metal film on the lower substrate 100. Form.

Then, after the gate insulating film 300 is deposited on the entire upper substrate 100 to cover the gate line G including the gate electrode 200, the transparent conductive layer is deposited on the gate insulating film 300, and The plate-type transparent pixel electrode 400 is formed to be disposed in each pixel region through patterning.

Next, the a-Si film and the n + a-Si film are sequentially deposited on the substrate resultant and then patterned to form an active pattern 500 on the gate insulating film 200 on the gate electrode 200.

Thereafter, a metal film for source / drain is deposited and then patterned to form a data line 600 including the source / drain electrodes 600a and 600b, and through this, a thin film transistor TFT ( Constitute T). In this case, the drain electrode 600b is formed to be electrically connected to the pixel electrode 400.

Subsequently, after the insulating layer 700, for example, of SiNx material, is coated on the resultant structure in which the thin film transistor T is formed, a transparent common electrode 800 having a comb shape is formed to overlap at least a portion of the transparent pixel electrode 400. Form. Subsequently, although not illustrated, an alignment layer is coated on the top of the substrate resultant on which the common electrode 800 is formed to complete the fabrication of the array substrate.

Meanwhile, a color filter is selectively formed on the upper substrate, and an alignment layer is formed on the upper substrate. The upper substrate and the lower substrate 100 are bonded to each other under the interposition of the liquid crystal layer to complete the manufacture of the FFS mode liquid crystal display device according to the exemplary embodiment of the present invention. Of course, it is preferable to attach a polarizing plate to the outer side surface of each board | substrate after bonding a board | substrate.

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

The transparent common electrode 800 includes 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 the data line 600. The light shielding film applied in the related art may be removed from the upper portion of the data line 600 by forming a structure covering the entirety.

That is, by disposing the first comb teeth C ₁ on the data line 600, it is possible to reduce disclination and increase light transmittance. In this case, it is effective to form the width L ₁ of the first comb C _{1 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.

The distance D ₁ between the first comb C ₁ and the neighboring second comb C ₂ of the transparent common electrode 800 is greater than or equal to the distance D ₂ between the combs formed inside the pixel. 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 distance greater than or equal to the distance between the second comb C ₂ and the third comb C ₃ adjacent to the pixel area.

Due to this structure, the electric field generated in the region B including the data line 600 has a smaller vertical electric field component than the electric field generated in the central region A of the pixel region, and the regions A and B are The liquid crystal is driven in different liquid crystal driving modes. According to such a structure, an opaque region is formed on the data line 600, so that a light shielding effect can be obtained even if the light shielding film applied in the prior art is removed from the data line 600.

Meanwhile, although the transparent pixel electrode 300 is illustrated in a plate shape in FIG. 2, the shape of the comb teeth may be of course.

In addition, referring to FIG. 5, the transparent common electrode 800 formed of a plurality of combs covers an entire portion except for a region where a thin film transistor TFT (see FIGS. 2A and 3) is formed and does not have a separate wiring. Each pixel region has a structure 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 E of the transparent pixel electrode 400 is preferably positioned at a central portion between the first comb C ₁ and the second comb C ₂ , more preferably, the first comb C ₁ and the first comb C ₁ . More preferably, the second comb C ₂ is further adjacent to the first comb C ₁ .

FIG. 6 illustrates light transmittance that changes according to a point where one end E of the transparent pixel electrode 400 is positioned between the first comb C ₁ and the second comb C ₂ . A diagram of simulation results for comparison.

2 to 6, a central portion between one end E of the transparent pixel electrode 400 is disposed between the first comb C ₁ on the data line 600 and the second comb C ₂ adjacent thereto. While the light emitting device exhibits a light transmittance of 33% when disposed on the substrate, when one end E of the transparent pixel electrode 400 is disposed closer to the second comb teeth C ₂ than the first comb teeth C ₁ , When the one end E of the transparent pixel electrode 400 is disposed adjacent to the first comb C ₁ , it has a light transmittance of 30.81%, and one end E of the transparent pixel electrode 400. ) Is extended to the first comb (C ₁ ), it shows a light transmittance of 31.23%.

However, in the case where one end E of the transparent pixel electrode 400 extends to the first comb C ₁ , the light transmittance is high, but an opaque region is not properly formed on the data line. It cannot be removed.

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

Therefore, one end E of the transparent pixel electrode 400 is present between the first comb teeth C ₁ and the second comb teeth C ₂ , but is further adjacent to the first comb teeth C ₁ , and is transparent. More preferably, one end E of the pixel electrode 400 is positioned at the center of the first comb teeth C ₁ and the second comb teeth C ₂ .

On the other hand, the white bar portion on each figure represents the ends of the first and second comb teeth (C ₁ , C ₂ ) of the transparent common electrode 800, the red bar portion is one end ( E) is shown.

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

In order to remove the light blocking film on the data line 600 and to form an opaque region efficiently on the data line 600, the lowest points (X, Y) of the left and right light transmittances of the data line 600 are respectively defined. All are configured to be included in the width (L ₃ of FIG. 4) of the data line 600.

Although a preferred embodiment of the FFS mode liquid crystal display device according to the present invention has been described above, the present invention is not limited thereto, and the present invention is not limited thereto, and various modifications are made within the scope of the claims and the detailed description of the invention and the accompanying drawings. It is possible and this also belongs to the present invention.

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

2A to 2E are plan views illustrating a situation in which a portion of a pixel area is formed in each layer in a lower substrate of an FFS mode liquid crystal display according to an exemplary embodiment of the present invention.

3 is a cross-sectional view taken along line II ′ of FIG. 2A.

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

FIG. 5 is a plan view showing only a partial layer in FIG. 2A.

FIG. 6 is a diagram illustrating a simulation result for comparing light transmittances that vary according to a point where one end of a transparent pixel electrode is positioned in an exemplary embodiment of the present invention.

FIG. 7 is a graph showing the lowest points of the light transmittances on both sides of the data line in one embodiment of the present invention.

*** Explanation of symbols on the main parts of the drawing ***

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 (21)

A lower substrate, an upper substrate, and a liquid crystal layer interposed between the substrates, wherein each pixel region is defined by gate lines and data lines formed in a direction crossing each other. And a switching element disposed at an intersection of data lines. In order to control an amount of light transmission by applying an electric field to the liquid crystal layer, the pixel region includes a transparent pixel electrode and a transparent common electrode disposed to be spaced apart from the transparent pixel electrode by a predetermined region with an insulating layer interposed therebetween. The transparent common electrode has a plurality of combs having a predetermined width in a direction substantially parallel to the data line, The transparent common electrode includes a first comb formed in a structure covering the data line and a second comb formed adjacent to the first comb and formed at a central portion of the pixel region, thereby removing the light blocking film formed on the data line. The distance between the first and second comb teeth is greater than the distance between the comb teeth formed in the pixel area. The method of claim 1, 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. The method of claim 1, And the transparent pixel electrode is disposed on the same layer as the data line. The method of claim 1, And the transparent pixel electrode is disposed with the data line and the insulating layer interposed therebetween. The method of claim 1, And an end portion of the transparent pixel electrode is disposed between a first comb of the transparent common electrode covering the data line and a neighboring second comb. The method of claim 5, wherein One end of the transparent pixel electrode may be further adjacent to the first comb among the first and second combs. The method of claim 5, wherein One end of the transparent pixel electrode is positioned in the center portion between the first and second comb teeth. The method of claim 1, And a lowest point of the light transmittance of the outer portions of both pixel regions with respect to the data line is included in the width of the data line. The method of claim 1, And the transparent pixel electrode has a plate shape or a comb tooth shape. The method of claim 1, The transparent common electrode of the FFS mode liquid crystal display, characterized in that each pixel region is connected to each other to apply the same voltage. The method of claim 1, The distance between the first and second comb teeth is greater than the distance between the upper and lower substrates, and the distance between the second comb teeth and the second comb teeth and the neighboring third comb teeth toward the pixel area is the distance between the upper and lower substrates. FFS mode liquid crystal display device, characterized in that less than or equal. The method of claim 1, The width of the first comb of the transparent common electrode is greater than or equal to the width of the data line FFS mode liquid crystal display device. The method of claim 1, The width of the second comb is formed to be less than or equal to the distance between the first and second comb, greater than or equal to the distance between the second comb and the second comb and the neighboring third comb toward the pixel area. An FFS mode liquid crystal display device. A lower substrate, an upper substrate, and a liquid crystal layer interposed between the substrates, wherein each pixel region is defined by gate lines and data lines formed in a direction crossing each other. And a switching element disposed at an intersection of data lines. In order to control an amount of light transmission by applying an electric field to the liquid crystal layer, the pixel region includes a transparent pixel electrode and a transparent common electrode disposed to be spaced apart from the transparent pixel electrode by a predetermined region with an insulating layer interposed therebetween. The transparent common electrode has a predetermined width in a direction parallel to the data line and includes a plurality of combs. At least one of the plurality of comb teeth is formed in a structure that covers a portion or all of the data line insulated, In the region including the data line, the light-shielding film is removed on the data line by driving in the liquid crystal driving mode of the first mode and driving in the liquid crystal driving mode of the second mode in the central region of the pixel region. And the second mode has a larger vertical electric field component than the first mode. The method of claim 14, A first comb of the transparent common electrode is provided to cover at least part or all of the data line, and the second comb of the transparent common electrode adjacent to the first comb is provided in the pixel area Mode liquid crystal display device. The method of claim 15, One end of the transparent pixel electrode is positioned between the first and second comb teeth of the transparent common electrode. The method of claim 15, And one end of the transparent pixel electrode is further adjacent to the first comb. The method of claim 15, One end of the transparent pixel electrode is positioned in the center between the first and second comb teeth, the FFS mode liquid crystal display device. The method of claim 14, And the transparent pixel electrode has a plate shape or a comb tooth shape. The method of claim 14, The transparent common electrode of the FFS mode liquid crystal display, characterized in that each pixel region is connected to each other to apply the same voltage. The method of claim 14, And a lowest point of the light transmittance of the outer portions of both pixel regions with respect to the data line is included in the width of the data line.

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