KR20100066233A - Fringe field switching mode liquid crystal display device and manufacturing method thereof - Google Patents

Abstract

PURPOSE: A fringe field switching mode liquid crystal display device and a manufacturing method thereof are provided to prevent light leakage in right/left viewing angles. CONSTITUTION: A reflecting structure(300) is formed using a material of a data line(150) in an electrically independent form on a gate line(120). The reflecting structure includes an area divided into two around the gate line. In an upper plate corresponding to a pixel area, a light shielding layer(205) is formed. A transparent pixel electrode(170) is separated from a transparent common electrode(110) with an inter-layer insulating layer.

Description

F s mode liquid crystal display device and manufacturing method therefor {FRINGE FIELD SWITCHING MODE LIQUID CRYSTAL DISPLAY DEVICE AND MANUFACTURING METHOD THEREOF}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an invention for blocking light leakage in an open region between a reflecting plate and a data line in a non-opening region, and a reflecting plate and a TFT in a transmissive type FPS mode liquid crystal display.

In general, a liquid crystal display device includes an array substrate (lower substrate) on which a liquid crystal driving thin film transistor (TFT) is formed, an upper substrate on which a color filter and a black matrix are formed, and liquid crystal encapsulated between two substrates. Is done. The array substrate on which the thin film transistor is formed is largely divided into portions in which metal electrodes such as data lines and gate lines are formed and openings in which metal electrodes are not formed, and light from the backlight does not pass through the openings of the metal electrodes.

1 illustrates a planar structure of one pixel area in a general liquid crystal display device. Referring to FIG. 1, a gate electrode 11 and a data line 12 are arranged to intersect with each other on an array substrate, and a pixel electrode is formed in a pixel region defined by the gate line 11 and the data line 12. 13 is formed, and a thin film transistor 14 connected to the pixel electrode 13 is formed at a portion where the gate line 11 and the data line 12 cross each other. In the liquid crystal display device, an opening, that is, a portion except the pixel electrode 13 is blocked by the light blocking film 15 formed on the upper substrate as shown in FIG. 2.

3 illustrates a cross-sectional structure of one pixel of the liquid crystal display. When the light shielding film 15 is formed on the upper substrate 20, as shown in FIG. 3, the light shielding film is considered in consideration of a bonding margin between the lower substrate 10 and the upper substrate 20, and light leakage between peripheral pixels. It should be formed wider than the array line to be covered by. This is because, if the bonding margin is not secured, when the bonding occurs between the two substrates, the light shielding film may not completely cover the metal line.

Meanwhile, the FFS mode liquid crystal display is proposed to improve the low aperture ratio and transmittance of the In-Plane Switching Mode (IPS mode) liquid crystal display.

In the FFS mode liquid crystal display, the common electrode and the pixel electrode are formed of a transparent conductor, thereby increasing the aperture ratio and the transmittance compared with the IPS mode liquid crystal display. In addition, the fringe field is formed between the common electrode and the pixel electrode by forming the gap between the common electrode and the pixel electrode smaller than the gap between the upper and lower glass substrates, so that all liquid crystal molecules on the electrodes are also present. Operation to obtain improved transmittance. Prior arts for FFS mode liquid crystal displays are disclosed, for example, in US Pat. Nos. 6,608,1,6226118 and the like, filed and registered by the present applicant.

The conventional FFS mode liquid crystal display device includes a lower substrate including a plurality of pixels including a transparent pixel electrode, a transparent common electrode, and a thin film transistor (TFT), corresponding to red (R), green (G), and blue ( The upper filter substrate includes a color filter and a black matrix formed by alternately arranging the color filter patterns of B). The transparent pixel electrode generates a transparent common electrode and an electric field to control light transmittance with a liquid crystal interposed between the lower substrate and the upper substrate.

On the other hand, a liquid crystal display (LCD) can be generally classified into two types: a transmissive liquid crystal display using a backlight and a reflective liquid crystal display using natural light as a light source. The transmissive liquid crystal display uses a backlight as a light source, so a bright image can be realized even in a dark environment. However, the use of the backlight has high power consumption and poor readability in the outdoors. The reflective liquid crystal display does not use a backlight. Because it uses the natural light of the surrounding environment, the power consumption is small and can be used outdoors, but the disadvantage is that it is impossible to use when the surrounding environment is dark.

The paper "A Novel Outdoor Readability of Portable TFT-LCD with AFFS" published by the present applicant to solve the problems of the conventional transmissive and reflective liquid crystal display device (KH Lee et. Al., SID 06, 2006, p1079), an AFFS (Advanced FFS) mode liquid crystal display which is a transmissive FFS mode liquid crystal display having improved readability both indoors and outdoors has been proposed.

In such an improved FFS mode liquid crystal display, no light shielding film is formed except a portion where a gate line and a data line cross each other. This is because when the light shielding film is formed on the gate line and the data line, the aperture ratio is reduced. For example, in Application Nos. 10-2007-0112655 and 10-2007-0009158 filed by the present applicant, instead of forming a light shielding film on the data line and the gate line, a technique of forming a reflector in an electrically independent form, etc. Is disclosed.

However, in the liquid crystal display device having such a structure, the reflective plate and the light shielding film should play a role of preventing light leakage, so that the reflective plate and the light shielding film overlap with each other more than the bonding margin. In this case, the liquid crystal display having such a structure expands the reflection area as much as possible in order to maximize visibility in the outdoors, but secures the reflection area in a region that is not related to the conventional aperture ratio, that is, the non-opening area, and provides an overlap area between the reflection plate and the light shielding film. Minimizing within the bonding margin is a design that can enhance the screen quality.

However, even when the pixel design within the bonding margin is secured to secure the reflective region, the overlap region between the light shielding film and the reflecting plate is changed during panel pressure according to the shape and size of the panel. The wider the panel and the larger the size, the smaller the overlap area between the light blocking film and the reflector plate during panel pressure. As the overlap area is reduced, light leakage of the panel occurs at the left and right viewing angles.

4 is a cross-sectional view for explaining the misalignment of a substrate before and after panel pressure. As can be seen in FIG. 4A, the light leakage phenomenon does not occur because the light shielding film 15 and the reflecting plate 17 are not distorted before the panel pressure. However, as can be seen in FIG. 4B, after panel acupressure is distorted, the light blocking film 15 and the reflecting plate 17 are distorted, and thus light leakage of the non-opening region can be observed at the left and right viewing angles.

5 is a photograph measuring that distortion occurs after panel pressure in a conventional liquid crystal display. As can be seen in FIG. 5, the distance from the end of the light shielding film to the center of the reflector was 8.050286 μm (yellow line) before panel acupressure, but 12.26710 μm (yellow line) after panel acupressure (b). You can check it. That is, it can be seen that after the panel acupressure (b), the arrangement of the light shielding film and the reflecting plate is about 4 μm (L).

The present invention has been invented in view of the above, and is an FFS mode liquid crystal display device that can improve screen quality by suppressing light leakage at left and right viewing angles during panel pressure without changing the manufacturing process significantly. And its manufacturing method.

One aspect of the present invention for achieving the above object includes a lower substrate, an upper substrate and a liquid crystal layer interposed between the substrates, the lower substrate in the gate line and the data lines formed in the direction crossing each other In the FFS mode liquid crystal display device in which each pixel region is defined and a switching element is disposed at an intersection portion of the gate line and the data line, the FFS mode liquid crystal display device has an electrically independent form using a material of the data line on the gate line. A reflective structure having a region separated into two regions based on the gate line, a region corresponding to the gate line is removed, and a light transmission film formed on the upper substrate, and an electric field is applied to the liquid crystal layer to reduce light transmission. In order to control, the pixel area is spaced apart with an insulating layer on top of the transparent common electrode. And a transparent pixel electrode protruding from the end of the transparent pixel electrode to the gate line and interposed between the light blocking film and the reflective structure, wherein the transparent pixel electrode extends to an end of the reflective structure, A liquid crystal display device electrically separated from a transparent pixel electrode is provided.

In this case, the protruding transparent pixel electrode has two protrusions extending to the end of the reflective structure, one end of each side of each protrusion of the transparent pixel electrode is located between the end of the light shielding film and the end of the reflective structure, the other end of the side It is preferably located between the end of the reflective structure and the data line. The common electrode and the pixel electrode are made of ITO.

Another aspect of the present invention for achieving the above object is, by a gate line and a data line including a lower substrate, an upper substrate and a liquid crystal layer interposed between the substrates and formed in a direction crossing each other on the lower substrate; A method for manufacturing a FFS mode liquid crystal display device in which each pixel region is defined and a switching element is disposed at an intersection of the lines, the method comprising: a gate line, a gate insulating film, a data line, a transparent common electrode, an insulating layer, And forming the transparent pixel electrodes in sequence, wherein in the forming of the data line, an electrically independent reflective structure is formed on the gate line by using a material of the data line, and the transparent pixel electrode is formed. In the step, the insulating layer is interposed between the transparent common electrode and the pixel region. And forming a light shielding film, a color filter, and an overcoat in sequence on the upper substrate, wherein the forming the light shielding film is formed by removing the light shielding film in a region corresponding to the gate line. The transparent pixel electrode is protruded to the gate line and interposed between the light blocking layer and the reflective structure, and the transparent pixel electrode extends to the end of the reflective structure and is electrically separated from the transparent pixel electrode of an adjacent pixel region. A method of manufacturing a liquid crystal display device is provided.

In this case, the protruding transparent pixel electrode has two protrusions extending to the end of the reflective structure, one end of each side of each protrusion of the transparent pixel electrode is located between the end of the light shielding film and the end of the reflective structure, the other end of the side It is preferably located between the end of the reflective structure and the data line. The common electrode and the pixel electrode are made of ITO.

As described above, according to the present invention, by forming the protruding pixel electrode between the light blocking film and the reflective structure in the liquid crystal display device, it is possible to prevent the generation of light leakage at the left and right viewing angles by converting the vertical field of the non-opening region into a horizontal field.

Therefore, there is an effect that can increase the yield of the panel and improve the pixel quality through a relatively simple process change without significantly changing the manufacturing process.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the following embodiments are provided to those skilled in the art to fully understand the present invention, and may be modified in various forms, and the scope of the present invention is limited to the embodiments described below. It doesn't happen.

The liquid crystal display according to the exemplary embodiment of the present invention includes a lower substrate, an upper substrate, and a liquid crystal layer interposed between the lower substrate and the upper substrate, and the lower substrate is formed in a direction crossing each other to apply a voltage to the liquid crystal layer. Each pixel region is defined by the electrodes. 6 is a plan view of a pixel area formed on a lower substrate of a liquid crystal display according to an exemplary embodiment of the present invention. 7A to 7C are cross-sectional views taken along the lines II ′, II-II ′, and III-III ′ of FIG. 6, respectively.

6 and 7A to 7C, the FFS mode liquid crystal display according to the present exemplary embodiment is arranged such that the gate line 120 and the data line 150 intersect on the lower substrate 100 and the gate line 120 crosses the gate line 120. A thin film transistor (TFT), which is a switching element, is disposed at the intersection of the data line 150 and the data line 150. In the unit pixel region defined by the gate line 120 and the data line 150, the transparent pixel electrode 170 having a plurality of slits formed at a predetermined angle with the transparent common electrode 110 and the gate line 120 is formed. The interlayer insulating layer 160 is disposed to be spaced apart from the transparent common electrode 110. 6 illustrates a case where the transparent common electrode 110 is manufactured in a plate shape as an example, but the transparent common electrode 110 may also be configured to have a plurality of slits. The gate insulating layer 130 is provided between the gate line 120 and the active layer 140.

On the other hand, the common bus line 122 is arranged parallel to the gate line 120 at the pixel edge portion spaced apart from the gate line 120, and the common bus line 122 is electrically connected to the transparent common electrode 110. It is connected to continuously apply a common signal to the transparent common electrode (110).

An upper substrate 200 is formed on the lower substrate 100 by a predetermined distance, and the lower substrate 100 includes a light blocking film 205, a color filter (not shown), and an overcoat 220. ) And a liquid crystal layer (not shown) including a plurality of liquid crystal molecules are interposed therebetween.

As shown in FIG. 7C, the light blocking film is removed and the reflective structure 300 is formed in the upper region of the gate line 120 in a manner to improve outdoor readability by improving internal reflectance. The reflective structure 300 is formed to cover the gate line 120. The reflective structure 300 is manufactured in an electrically independent form using the material of the data line 150. Preferably, a curved shape is formed in the reflective structure 300 using the material of the active layer. In FIG. 6, the reflective structure is shown only in the gate line at the bottom of the drawing for convenience of illustration, but it is apparent that the reflective structure is formed on all the gate lines of the liquid crystal display.

The curved shape of the reflective structure 300 forms active layer patterns 145 by forming a plurality of separated closed curve patterns, such as circles and ellipses, using the active layer material, to form the active layer patterns 145. The pattern 155 of the data line has a curved shape to increase the internal reflection by the curved shape. Accordingly, outdoor readability may be significantly improved by allowing the data line pattern 155, which is the reflective structure 300, to have a bent portion without forming a light blocking film on the gate line 120.

In detail, the reflective structure 300 is formed independently of each other, and is formed of two regions separated by the gate line 120. Since the gate line 120 may be made of an opaque metal, the reflective structure 300 may be formed as a separated region while exposing the gate line 120 based on the gate line 120. On the other hand, the light shielding film 205 formed on the switching element is implemented in such a manner as to cover the reflective structure 300 in a predetermined area to secure a process margin.

Hereinafter, a manufacturing method of the liquid crystal display device according to the present embodiment will be described with reference to FIGS. 6 and 7A to 7C.

First, a transparent conductive layer is deposited on the lower substrate 100 and patterned to form a transparent common electrode 110. In addition, after the opaque metal is deposited on the transparent common electrode 110, the gate line 120 is formed on one side of the transparent common electrode 110 through patterning, and the structure covers a portion of the transparent common electrode 110. A common bus line 122 is formed (see FIG. 7B).

Next, the gate insulating layer 130 is deposited on the entire surface of the lower substrate 100 on which the patterned transparent common electrode 110, the gate line 120, and the common bus line 122 are formed. The active layer 140 is formed by patterning the a-Si layer and the n + a-Si layer on the upper gate insulating layer 130.

In addition, after the metal layer is deposited on the entire surface of the lower substrate on which the active layer 140 is patterned, the data line 150, the source-drain electrode 152, and the reflective structure 300 are formed through patterning, and the data line 150 is formed. The interlayer insulating layer 160 is deposited on the lower substrate 100 on which the source and drain electrodes 152 are formed.

Next, after forming the contact hole CN to expose a portion of the source-drain electrode 152, a transparent conductive layer is deposited on the interlayer insulating layer 160. In this case, the transparent conductive layer is patterned to connect the source-drain electrode 152 and the transparent pixel electrode 170 through the contact hole CN to form a transparent pixel electrode 170 having a slit shape. The transparent common electrode 110 and the transparent pixel electrode 170 are formed of a transparent conductive layer such as indium tin oxide (ITO).

Meanwhile, the light blocking film 205 is formed on the upper substrate 200 corresponding to the pixel region. According to the present embodiment, only the upper substrate 200 corresponding to the TFT is provided with the light blocking film.

Hereinafter, embodiments of the present invention will be described in more detail with reference to FIGS. 8 and 9. FIG. 8 is an enlarged plan view of a portion of a light blocking film and a reflective structure in a pixel area of the liquid crystal display illustrated in FIG. 6. FIG. 9 is a cross-sectional view taken along the line VV ′ of FIG. 8, and illustrates only the light blocking film 205, the reflective structure 300, and the pixel electrode 170 for convenience of description.

In the present invention, in the FFS mode liquid crystal display, horizontal fields are forcibly formed by using pixel electrodes in order to prevent light leakage in an overlapping area between the light blocking film and the reflective structure. Using this method, the existing reflector area can be maintained without reduction, and external visibility can be maintained.

Referring to FIG. 8, an end of the transparent pixel electrode 170 protrudes to the gate line 120. However, since the reflective structure 300 preferably includes a region separated into two regions based on the gate line 120, the protruding transparent pixel electrode 170 extends to the end of the reflective structure 300. desirable. However, the protruding transparent pixel electrode 170 should be electrically separated from the protruding transparent pixel electrode of the adjacent pixel region. As shown in FIG. 8, the protruding transparent pixel electrode 170 preferably has two protruding portions.

9, the protruding transparent pixel electrode 170 is interposed between the light blocking film 205 and the reflective structure 300, and one end of the side surface of the protruding transparent pixel electrode 170 is formed at an end of the light blocking film 205. The other end portion of the protruding transparent pixel electrode 170 may be disposed between the ends of the reflective structure 300, and may be positioned between the end of the reflective structure 300 and the data line 150. The protruding transparent pixel electrode 170 is interposed between the light blocking film 205 and the reflective structure 300 over the entire pixel area of the liquid crystal display to prevent light leakage when the substrate is twisted.

The protruding pixel electrode 170 converts the vertical field of the corresponding area into a horizontal field. As shown in FIG. 10A, in the liquid crystal display according to the related art, when there is no protruding pixel electrode, the vertical field is stronger than the horizontal field due to the potential formation between the gate line and the common line. However, in the FFS mode LCD having horizontal rubbing, since light leakage occurs when the horizontal field is generated, the non-opening area must be blocked by a light blocking film or a reflective structure.

In FIG. 8, the protruding pixel electrode 170 has an extended end of the pixel electrode, and a signal of the pixel electrode is applied thereto. In the L0 state of the pixel (please explain what it means in Korean), there is always a field between the protruding pixel electrode 170 and the data line 150 so that there is always a field, which makes the horizontal field strong. Even when the protruding pixel electrode 170 is formed between the light blocking film 205 and the reflective structure 300, the vertical field still exists, but the vertical field may be weakened in contrast to the case where there is no existing protruding pixel electrode. . Although there may be a horizontal field between the reflective structure and the data line without the protruding pixel electrode, the field formed by the reflective structure is weak because the reflective structure is a floating electrode without an artificial signal.

10A and 10B are diagrams for describing field changes caused by the protruding pixel electrode 170. 10A is a liquid crystal director simulation of a pixel structure of a conventional FFS mode liquid crystal display at L0 of a pixel. Referring to this, as shown by the arrow, in the non-opening region, the liquid crystal directors can see that a vertical field is formed between the gate line 120, the common line 122, and the pixel electrode 170. Although there is a horizontal field with the data line 150, the vertical field is stronger.

10B is a liquid crystal director simulation of the pixel structure of the FFS mode liquid crystal display device according to the present invention at L0 of the pixel. As indicated by the arrow, it can be seen that the vertical field has been converted to the horizontal field with respect to the gate line 120 around the protruding pixel electrode 170. In addition, it can be seen that the strength of the strong vertical field around the existing data line 150 is reduced.

11A and 11B illustrate optical simulation results of pixels of a liquid crystal display. As shown in FIG. 11A, in the conventional FFS mode liquid crystal display, light leakage may occur at left and right viewing angles when distortion occurs during panel pressure. On the other hand, as shown in FIG. 11B, in the FFS mode LCD according to the present invention, since the protruding pixel electrode 170 is disposed between the reflective structure 300 and the light blocking film 205, light leakage around the reflective structure 300 is caused. It can be seen that the occurrence is significantly reduced. Therefore, even if distortion occurs after panel pressure, light leakage can be prevented at the left and right viewing angles.

1 is a plan view illustrating one pixel area in a general liquid crystal display device.

2 is a plan view illustrating a light shielding film formed on an upper substrate in a general liquid crystal display device.

3 is a cross-sectional view illustrating a cross-sectional structure of one pixel of a general liquid crystal display device.

4A and 4B are cross-sectional views illustrating the distortion of a substrate before and after panel pressure in a conventional liquid crystal display.

5 is a photograph measuring that distortion occurs after panel pressure in a conventional liquid crystal display.

6 is a plan view of a pixel area formed on a lower substrate of a liquid crystal display according to an exemplary embodiment of the present invention.

7A to 7C are cross-sectional views taken along the lines II ′, II-II ′, and III-III ′ of FIG. 6, respectively.

FIG. 8 is an enlarged plan view of a portion of a light blocking film and a reflective structure in a pixel area of the liquid crystal display illustrated in FIG. 6.

FIG. 9 is a cross-sectional view taken along the line VV ′ of FIG. 8.

10A and 10B are views for explaining field changes caused by the protruding pixel electrodes in the liquid crystal display according to the exemplary embodiment of the present invention.

11A and 11B illustrate optical simulation results of pixels of a liquid crystal display.

Claims (6)

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 an intersecting direction on the lower substrate, and the gate lines and the data. In the FFS mode liquid crystal display device in which a switching element is arranged at the intersection of the lines, A reflective structure formed on the gate line in an electrically independent form using a material of the data line, and having a region separated into two regions based on the gate line; A light blocking film formed on the upper substrate by removing a region corresponding to the gate line; In order to control the amount of light transmission by applying an electric field to the liquid crystal layer, the pixel region includes a transparent pixel electrode spaced apart from each other with an insulating layer interposed therebetween, The transparent pixel electrode is protruded to the gate line and interposed between the light blocking layer and the reflective structure, and the transparent pixel electrode extends to the end of the reflective structure and is electrically separated from the transparent pixel electrode of an adjacent pixel region. Liquid crystal display device characterized in that.  The method of claim 1, The protruding transparent pixel electrode has two protrusions extending to the end of the reflective structure, And one end portion of each side of each of the protrusions of the transparent pixel electrode is disposed between the end of the light blocking layer and the end portion of the reflective structure, and the other end portion thereof is positioned between the end of the reflective structure and the data line. The liquid crystal display device according to claim 1, wherein the common electrode and the pixel electrode are formed of ITO. Each pixel region is defined by gate lines and data lines including a lower substrate, an upper substrate, and a liquid crystal layer interposed between the substrates, and the lower substrate has a gate line and data lines intersecting with each other. In the manufacturing method of the FFS mode liquid crystal display device in which an element is arrange | positioned, And sequentially forming a gate line, a gate insulating film, a data line, a transparent common electrode, an insulating layer, and a transparent pixel electrode on the lower substrate. In the forming of the data line, an electrically independent reflective structure is formed on the gate line by using a material of the data line. In the forming of the transparent pixel electrode, the pixel area is formed to be spaced apart from each other with the insulating layer interposed therebetween, Including forming a light shielding film, a color filter, and an overcoat in sequence on the upper substrate, In the forming of the light blocking film, the light blocking film in a region corresponding to the gate line is removed and formed. The transparent pixel electrode is protruded to the gate line and interposed between the light blocking layer and the reflective structure, and the transparent pixel electrode extends to the end of the reflective structure and is electrically separated from the transparent pixel electrode of an adjacent pixel region. Method of manufacturing a liquid crystal display device, characterized in that. The method of claim 4, wherein The protruding transparent pixel electrode has two protrusions extending to the end of the reflective structure, One end side of each of the protrusions of the transparent pixel electrode is positioned between the end of the light blocking film and the end of the reflective structure, the other end side is located between the end of the reflective structure and the data line. . The method of claim 4, wherein the common electrode and the pixel electrode are formed of ITO.

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