KR100899626B1 - In plane switching mode liquid crystal display device and method of fabricating thereof - Google Patents

Abstract

A method of manufacturing a transverse electric field mode liquid crystal display device according to the present invention includes providing a substrate, forming a gate electrode and a common electrode on the substrate, forming a gate insulating layer and a semiconductor layer on the substrate, Forming a drain electrode and a pixel electrode, laminating a protective layer over the entire substrate, and opening at least one of the common electrode and the pixel electrode.

Transverse electric field mode, insulation layer, charge, trap, open, common electrode, pixel electrode

Description

Transverse electric field mode liquid crystal display device and manufacturing method therefor {IN PLANE SWITCHING MODE LIQUID CRYSTAL DISPLAY DEVICE AND METHOD OF FABRICATING THEREOF}

1A is a cross-sectional view showing the structure of a conventional transverse electric field mode liquid crystal display device.

(B) is sectional drawing along the II 'line | wire of (a).

2 is a cross-sectional view illustrating a structure of a transverse electric field mode liquid crystal display device according to an exemplary embodiment of the present invention.

3 (a) to 3 (c) are graphs showing the relationship between time zone residual DC voltages when DC voltages are applied to and removed from the pixel electrodes.

4 is a view illustrating a method of manufacturing a transverse electric field mode liquid crystal display device shown in FIG.

5 is a cross-sectional view illustrating a structure of a transverse electric field mode liquid crystal display device according to another exemplary embodiment of the present invention.

FIG. 6 is a view showing a method of manufacturing a transverse electric field mode liquid crystal display device shown in FIG. 5; FIG.

7 (a) and 7 (b) are cross-sectional views showing the structure of a transverse electric field mode liquid crystal display device according to still another embodiment of the present invention.

Explanation of symbols on the main parts of the drawings                 

105,205,305,405 Common electrode 107,207,307,407 Pixel electrode

111, 211, 311, 411: gate electrodes 112, 212, 312, 412: semiconductor layer

113,213,313,413 Source electrodes 114,214,314,414 Drain electrodes

122,222,322,422: Gate insulating layer 124,224,324,424: Protective layer

132,232,332,432: Black matrix 134,234,334,434: Color filter layer

140,240,340,440: liquid crystal layer

The present invention relates to a transverse electric field mode liquid crystal display device, and more particularly, to a transverse electric field mode liquid crystal display device and a method of manufacturing the same, which can prevent an afterimage on a screen by removing an insulating layer and opening a pixel electrode and a common electrode. .

Recently, with the development of various portable electronic devices such as mobile phones, PDAs, and notebook computers, there is a growing demand for flat panel display devices for light and thin applications. Such flat panel displays are being actively researched, such as LCD (Liquid Crystal Display), PDP (Plasma Display Panel), FED (Field Emission Display), and VFD (Vacuum Fluorescent Display). Liquid crystal display devices (LCDs) are in the spotlight for reasons of implementation.

Such liquid crystal display devices have various display modes according to the arrangement of liquid crystal molecules. However, TN mode liquid crystal display devices are mainly used due to the advantages of easy monochrome display, fast response speed, and low driving voltage. In such a TN mode liquid crystal display device, liquid crystal molecules aligned horizontally with the substrate are almost perpendicular to the substrate when a voltage is applied. Therefore, there is a problem that the viewing angle is narrowed upon application of voltage due to the refractive anisotropy of the liquid crystal molecules.

In order to solve this viewing angle problem, liquid crystal display devices of various modes having wide viewing angle characteristics have recently been proposed, but among them, the liquid crystal display device of the lateral field mode (In Plane Switching Mode) is applied to actual production. It is produced. The IPS mode liquid crystal display device aligns liquid crystal molecules in a plane by forming at least one pair of electrodes arranged in parallel in a pixel to form a transverse electric field substantially parallel to the substrate.

FIG. 1 is a view showing the structure of a conventional IPS mode liquid crystal display device, in which FIG. 1 (a) is a plan view and FIG. 1 (b) is a sectional view taken along line II ′ of FIG. 1 (a). As shown in FIG. 1A, the pixels of the liquid crystal panel 1 are defined by gate lines 3 and data lines 4 arranged vertically and horizontally. Although only the (n, m) th pixels are shown in the drawing, the actual liquid crystal panel 1 has N (> n) and M (> m) gate lines 3 and data lines 4, respectively. Are arranged so as to form N × M pixels over the entire liquid crystal panel 1. The thin film transistor 10 is formed at the intersection of the gate line 3 and the data line 4 in the pixel. The thin film transistor 10 includes a gate electrode 11 to which a scan signal is applied from the gate line 3, and a semiconductor layer formed on the gate electrode 11 and activated as a scan signal is applied to form a channel layer. And a source electrode 13 and a drain electrode 14 formed on the semiconductor layer 12 and to which an image signal is applied through the data line 4. Is authorized.

In the pixel, a plurality of common electrodes 5 and a pixel electrode 7 are arranged substantially parallel to the data line 4. In addition, a common line 16 connected to the common electrode 5 is disposed in the middle of the pixel, and a pixel electrode line 18 connected to the pixel electrode 7 is disposed on the common line 16. It overlaps with the common line 16. Storage capacitance is formed in the transverse electric field mode liquid crystal display by overlapping the common line 16 and the pixel electrode line 18.

As described above, in the configured IPS mode liquid crystal display device, the liquid crystal molecules are oriented substantially in parallel with the common electrode 5 and the pixel electrode 7. When the thin film transistor 10 is operated to apply a signal to the pixel electrode 7, a transverse electric field substantially parallel to the liquid crystal panel 1 is generated between the common electrode 5 and the pixel electrode 7. Since the liquid crystal molecules rotate on the same plane along the transverse electric field, gray level inversion due to the refractive anisotropy of the liquid crystal molecules can be prevented.

The conventional IPS mode liquid crystal display device having the above structure will be described in more detail with reference to the cross-sectional view of FIG.

As shown in FIG. 1B, a gate electrode 11 is formed on the first substrate 20, and a gate insulating layer 22 is stacked over the entire first substrate 20. The semiconductor layer 12 is formed on the gate insulating layer 22, and the source electrode 13 and the drain electrode 14 are formed thereon. In addition, a passivation layer 24 is formed on the entire first substrate 20.

In addition, a plurality of common electrodes 5 are formed on the first substrate 20, and a pixel electrode 7 and a data line 4 are formed on the gate insulating layer 22 to form the common electrode 5. A transverse electric field is generated between the pixel electrodes 7.

The black matrix 32 and the color filter layer 34 are formed on the second substrate 30. The black matrix 32 is to prevent light leakage into an area where the liquid crystal molecules do not operate. As shown in the drawing, the black matrix 32 is formed between the region of the thin film transistor 10 and between the pixel and the pixel (ie, the gate line and the data line). Area). The color filter layer 34 is composed of R (Red), B (Blue), and G (Green) to realize actual colors.

The liquid crystal layer 40 is formed between the first substrate 20 and the second substrate 30 to complete the liquid crystal panel 1.

As described above, in the conventional IPS mode liquid crystal display device, an insulating layer (protective layer / gate insulating layer or protective layer) is formed on the common electrode 5 and the pixel electrode 7 forming the transverse electric field. Therefore, when a signal is applied to the pixel electrode 7, a transverse electric field is formed via the insulating layer. However, when the transverse electric field is formed, charges are trapped in an insulating layer (particularly, an interface) located on the transverse electric field path, and the trap of the electric charges is generated in the liquid crystal display device. This causes a residual image on the screen, and as a result, the display quality of the liquid crystal display device is reduced.

 SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and the transverse electric field can be prevented from generating an afterimage on the screen by opening the common electrode and the pixel electrode to minimize the charge trapped in the insulating layer between the common electrode and the pixel electrode. An object of the present invention is to provide a mode liquid crystal display device.

Another object of the present invention is to provide a transverse electric field mode liquid crystal display device which can minimize power consumption by opening the common electrode and the pixel electrode to remove the additional capacitance between the common electrode and the pixel electrode.

In order to achieve the above object, the transverse electric field mode liquid crystal display device according to the present invention includes a plurality of gate lines and data lines defining a plurality of pixels, a driving element formed in each pixel, and a transverse electric field substantially parallel in the pixel. It generates and consists of at least a pair of electrodes opened to the outside.

In addition, the method of manufacturing a transverse electric field mode liquid crystal display device according to the present invention includes the steps of providing a substrate, forming a gate electrode and a common electrode on the substrate, forming a gate insulating layer and a semiconductor layer on the substrate; Forming a source / drain electrode and a pixel electrode; laminating a protective layer over the entire substrate; and opening at least one of the common electrode and the pixel electrode.

The pixel electrode is formed by etching a portion of the semiconductor layer to form an open region, and then forming a metal layer in the open region. The pixel electrode may be formed by laminating a metal on a semiconductor layer and then etching the metal.

The common electrode and the pixel electrode may be opened by etching the protective layer on the common electrode and the pixel electrode, and may be opened by etching the gate insulating layer on the common electrode after etching the protective layer on the common electrode and the pixel electrode. It may be.

The present invention provides an IPS mode liquid crystal display device capable of applying a uniform transverse electric field to the liquid crystal layer. In particular, the present invention provides an IPS mode liquid crystal display device capable of removing an afterimage. To this end, in the present invention, the common electrode and the pixel electrode are opened to prevent the charge from trapping the insulating layer and the DC voltage remaining in the insulating layer when generating the transverse electric field. On the other hand, since the insulating layer forms an additional capacitance between the common electrode and the pixel electrode, a high voltage must be applied to the pixel electrode in order to drive the liquid crystal molecules, whereas in the IPS mode liquid crystal display device of the present invention, there is no insulating layer. Even when a signal of is applied, liquid crystal molecules are driven smoothly. Therefore, the IPS mode liquid crystal display device of the present invention can reduce power consumption as compared to the conventional IPS mode liquid crystal display device.

Hereinafter, with reference to the accompanying drawings will be described in detail the present invention.

2 is a view showing the structure of an IPS mode liquid crystal display device according to the present invention. As shown in the figure, a thin film transistor, a plurality of common electrodes 105 and a pixel electrode 107 are formed on the first substrate 120 made of a transparent material such as glass. The thin film transistor includes a gate electrode 111 formed on the first substrate 120, a gate insulating layer 122 formed on the gate electrode, a semiconductor layer 112 formed on the gate insulating layer 122, and the semiconductor layer. The source electrode 113 and the drain electrode 114 are formed on the (112), the protective layer 124 is formed on the thin film transistor.

The common electrode 105 is formed on the first substrate 120, and the gate insulating layer 122 is stacked thereon. The pixel electrode 107 is formed on the gate insulating layer 122.

The protective layer 124 is formed only on the thin film transistor, and is not formed in other areas. Therefore, only the gate insulating layer 122 is stacked on the common electrode 105, and the insulating layer is not stacked on the pixel electrode 107. That is, the pixel electrode 107 is open. Although not shown in the drawing, an alignment layer for aligning the liquid crystal molecules is formed on the pixel electrode 107, the gate insulating layer 122, and the protective layer 124, but the alignment layer may be a common electrode ( The transverse electric field between 105 and the pixel electrode 107 is not significantly influenced. In the above description, the expression 'open' has this meaning. That is, it means that no layer affecting the transverse electric field exists on the pixel electrode 107. Thus, the expression 'open' as used in the description and claims of the present specification is to affect the transverse electric field on the common electrode 105 and the pixel electrode 107 (or trap the charge when the image signal is applied or to the common electrode. Means that no insulating layer is formed between the pixel electrode and the pixel electrode.

On the other hand, the second substrate 130 is formed with a black matrix 132 for preventing light leakage into the non-display area and a color filter layer 134 for realizing an image on an actual screen. The liquid crystal layer 140 is formed between the 120 and the second substrate 130. Although not shown in the drawing, an overcoat layer may be formed on the color filter layer 134 to improve the flatness of the second substrate 130.

As described above, in the IPS mode liquid crystal display device of the present invention, the protective layer 124 is formed only on the thin film transistor and is not formed on the common electrode 105 and the pixel electrode 107. Therefore, when the voltage is applied to the pixel electrode 107, the amount of charge trapped in the insulating layer between the common electrode 105 and the pixel electrode 107 can be minimized, and as a result, an afterimage on the screen can be prevented. It becomes possible.

3 (a) to 3 (c) are graphs showing the relationship between the conventional IPS mode liquid crystal display device and the time zone residual DC voltage when the DC voltage applied to the pixel electrode is removed in the IPS mode liquid crystal display device according to the present invention. to be. At this time, Figure 3 (a) is a graph of removing the DC voltage after applying a DC voltage of 10V for 30 minutes and Figure 3 (b) is a case of removing the DC voltage after applying a DC voltage of 5V 30 minutes 3 (c) is a graph when the DC voltage is removed after applying a DC voltage of 1V for 10 minutes.

As shown in FIG. 3 (a), in the conventional IPS mode liquid crystal display device in which a protective layer is formed on the pixel electrode immediately after removing the DC voltage of 10 V applied for 30 minutes, a DC voltage of about 0.8 V remains in the insulating layer. On the other hand, in the IPS mode liquid crystal display device of the present invention, only a DC voltage of about 0.28V remains in the insulating layer. In addition, in the conventional IPS mode liquid crystal display device, the DC voltage remaining slightly decreases with time, and a DC voltage of about 0.7 V remains after 30 minutes. As it decreases, the residual DC voltage decreases significantly, and after 30 minutes, only a DC voltage of about 0.03V remains. As described above, the residual DC in the IPS mode liquid crystal display device of the present invention without the pixel electrode and the common electrode as compared to the residual DC voltage in the conventional IPS mode liquid crystal display device in which a protective layer is stacked on the pixel electrode and the common electrode. It can be seen that the voltage is greatly reduced.

As shown in FIGS. 3 (b) and 3 (c), the above-described phenomenon is applied when the DC voltage of 5V is applied to the IPS mode liquid crystal display device for 30 minutes and the DC voltage of 1V is applied for 10 minutes. Even when it appears the same. Therefore, since the protective layer 124 is not formed on the pixel electrode, the DC voltage remaining in the insulating layer can be greatly reduced, and as a result, the afterimage on the screen can be prevented.

The IPS mode liquid crystal display device having the above structure can be manufactured by removing the protective layer 124 on the pixel electrode 107. The IPS mode liquid crystal display device is fabricated in FIGS. 4 (a) to 4 (e). The method is shown.

First, as shown in FIG. 4A, a Cu, Mo, Ta, Cr, Ti, Al, or Al alloy is deposited on a transparent first substrate 120 such as glass by evaporation or sputtering. After forming a single or a plurality of metal layers made of a metal such as, and etching with an etchant (etchant) to form a gate electrode 111 and a common electrode 105. In this case, the gate electrode 111 and the common electrode 105 may be formed of different materials by different processes. However, the gate electrode 111 and the common electrode 105 may be formed of the same materials by the same process as described above.

Subsequently, as shown in FIG. 4B, the gate insulating layer 122 is formed over the entire first substrate 120, and then the semiconductor layer 112 is stacked thereon. The gate insulating layer 122 and the semiconductor layer 112 are formed by a chemical vapor deposition (CVD) method. For example, the gate insulating layer 122 is made of SiOx or SiNx and the semiconductor layer is made of a-Si. . Thereafter, a portion of the semiconductor layer 112 is etched to form an open region 123 in which the gate insulating layer 122 is opened to the outside.

Thereafter, as illustrated in FIG. 4C, a metal such as Cr, Mo, Ta, Cu, Ti, Al, or Al alloy is stacked and etched on the semiconductor layer 112 to etch the source electrode 113 and the drain electrode ( 114). In this case, the pixel electrode 107 and the data line 104 are formed in the open region 123 of the semiconductor layer 112. As described above, the pixel electrode 107 is formed by the same process as the source electrode 113 and the drain electrode 114 of the thin film transistor, but may be formed by another process.

Subsequently, as shown in FIG. 4D, after the protective layer 124 is stacked over the entire first substrate 120, the protective layer 124 and the semiconductor layer 112 are removed to remove the pixel electrode. Open 107.

As illustrated in FIG. 4E, the black matrix 132 and the color filter layer 134 are formed on the second substrate 130, and the first substrate 120 and the second substrate 130 are formed on the second substrate 130. The IPS mode liquid crystal display device of the present invention is completed by bonding and forming the liquid crystal layer 140 therebetween.

The liquid crystal layer 140 may be formed by a vacuum liquid crystal injection method for injecting liquid crystal between the first substrate 120 and the second substrate 140 bonded in a vacuum state, and the liquid crystal dropping method has recently been spotlighted ( liquid crystal dispensing method), ie, dropping liquid crystal directly on the first substrate 120 or the second substrate 130 and then bonding the first substrate 120 and the second substrate 130 to the substrates 120 and 130. It may be formed by a method that spreads uniformly throughout.

5 is a view showing the structure of an IPS mode liquid crystal display device according to another embodiment of the present invention.

As shown in the figure, the IPS mode liquid crystal display device of this embodiment has a structure substantially similar to that of the IPS mode liquid crystal display device shown in FIG. That is, since the protective layer 224 is not formed on the pixel electrode and the common electrode, the pixel electrode 207 is open, and only the gate insulating layer 222 is formed on the common electrode 205. Therefore, it is possible to reduce the trap of charge by the insulating layer, that is, the residual DC voltage. At this time, the structural difference from the IPS mode liquid crystal display shown in Fig. 2 is only in the pixel electrode. That is, in the IPS mode liquid crystal display device shown in FIG. 2, only a pixel electrode made of metal is formed on the gate insulating layer, whereas in the present embodiment, the pixel electrode is composed of a metal layer 207 and a semiconductor layer 208. It is.

Substantially, the IPS mode liquid crystal display device shown in FIG. 2 and the IPS mode liquid crystal display device of this embodiment have the same function, and the effect is almost similar. Nevertheless, the structure is different as described above according to the difference in the manufacturing method of the IPS liquid crystal display device, look at the manufacturing method of the present embodiment is as follows.

FIG. 6 is a view illustrating a method of manufacturing the IPS mode liquid crystal display device shown in FIG. 5.                     

First, as shown in FIG. 6 (a), a single or plurality of gate electrodes 211 and a common electrode 105 are formed on a transparent first substrate 220 such as glass, and then shown in FIG. 6 (b). As illustrated, the gate insulating layer 222 is formed over the entire first substrate 220 using the CVD method, and then the semiconductor layer 212 is stacked thereon.

Subsequently, as illustrated in FIG. 6C, a source electrode 213, a drain electrode 214, and a pixel electrode 207 are formed on the semiconductor layer 212. In this case, the data line 204 is also formed at the same time as the pixel electrode 207.

Thereafter, as shown in FIG. 6 (d), after the protective layer 224 is stacked over the entire first substrate 220, the protective layer 224 in a region other than the thin film transistor region is removed, and the thin film transistor region and The semiconductor layer 212 in the region except for the lower portion of the pixel electrode 207 is removed.

Subsequently, as shown in FIG. 6E, after forming the black matrix 232 and the color filter layer 234 on the second substrate 230, the first substrate 220 and the second substrate 230 are formed. By bonding and forming the liquid crystal layer 240 therebetween, the IPS mode liquid crystal display device of the present invention is completed.

As described above, in the IPS mode liquid crystal display device of the present invention, since the protective layer is formed only in the thin film transistor region, the pixel electrode is opened to the outside. Therefore, only the gate insulating layer exists between the pixel electrode and the common electrode, and as a result, the trap of charges by the insulating layer can be greatly reduced, thereby preventing the afterimage on the screen.

Meanwhile, in the IPS mode liquid crystal display device of the present invention, not only the pixel electrode but also the common electrode can be opened to the outside. Considering the object of the present invention that the charge trap of the insulating layer formed between the pixel electrode and the common electrode is reduced, the IPS mode liquid crystal display device having the structure of opening the pixel electrode and the common electrode at the same time as described above is more efficient to remove the afterimage. will be.

An IPS mode liquid crystal display device having such a structure is shown in Figs. 7 (a) and 7 (b). As shown in the figure, the protective layers 324 and 424 are stacked only in the thin film transistor region and are not stacked in the pixel region (where the pixel electrodes 307 and 407 and the common electrodes 305 and 405 are formed). In addition, gate insulating layers 322 and 422 are not formed on the common electrodes 305 and 405.

At this time, Figure 7 (a) and Figure 7 (b) has a slightly different structure. That is, in the structure of FIG. 7A, the gate insulating layer 322 in other regions except for the gate insulating layer 322 under the pixel electrode 307 is removed, whereas in the structure of FIG. Only the gate insulating layer 422 on the common electrode 405 is removed.

Such structural differences are due to the manufacturing method. In the case of the IPS mode liquid crystal display device having the structure shown in FIG. 7A, after forming the pixel electrode 307 on the gate insulating layer 322, the gate insulating layer 322 is etched and removed. In the case of the IPS mode liquid crystal display device having the structure shown in FIG. 1, the pixel electrode 407 is formed after etching the gate insulating layer 422 on the common electrode 405. However, despite the structural difference due to the difference in the method, the IPS mode liquid crystal display device shown in FIGS. 7A and 7B can obtain the same effect.                     

As described above, in the IPS mode liquid crystal display device of the present invention, after the pixel electrode and the common electrode are opened, the afterimage generation due to the charge trap on the insulating layer can be prevented. However, the present invention is not limited to the IPS mode liquid crystal display device having a specific structure. Although only four block IPS mode liquid crystal display devices in which two pixel electrodes and three common electrodes are formed in the pixel to form four light transmission regions are shown in the drawing, the present invention is similar to two or six blocks. It will be applicable to IPS mode liquid crystal display of all possible blocks.

As described above, in the IPS mode liquid crystal display device of the present invention, after the pixel electrode and the common electrode are opened to minimize the charge trapped in the insulating layer when generating the transverse electric field (minimizing the residual DC voltage), an afterimage occurs on the screen. Can be prevented. Therefore, the IPS mode liquid crystal display device having improved quality can be obtained.

In addition, since the insulating layers on the pixel electrode and the common electrode are removed, the additional capacitance generated between the pixel electrode and the common electrode can be removed. Therefore, it is possible to smoothly drive the liquid crystal molecules even at a low voltage, and as a result, it is possible to minimize the power consumption of the IPS mode liquid crystal display device.

Claims (14)

A plurality of gate lines and data lines defining a plurality of pixels; A gate electrode formed on each pixel, a gate insulating layer formed over the substrate on which the gate electrode is formed, a semiconductor layer formed on the gate insulating layer, a source electrode and a drain electrode formed on the semiconductor layer; Thin film transistor; A protective layer formed on the substrate on which the thin film transistor is formed; And Each of which is formed of a pair of common electrodes and pixel electrodes formed on the substrate and the gate insulating layer in the pixel to generate a transverse electric field substantially parallel to the substrate, And a protective layer over the common electrode and the pixel electrode and a gate insulating layer disposed over the common electrode. delete delete delete The transverse electric field mode liquid crystal display device of claim 1, wherein a semiconductor layer is disposed under the pixel electrode. Providing a substrate; Forming a gate electrode and a common electrode on the substrate; Forming a gate insulating layer and a semiconductor layer on the substrate; Forming a source / drain electrode and a pixel electrode; Depositing a protective layer over the substrate; And And opening at least one of the common electrode and the pixel electrode. The method of claim 6, wherein the forming of the pixel electrode comprises: Etching a portion of the semiconductor layer to form an open region; And Stacking and etching metal on the semiconductor layer to form a metal layer in the open region. The method of claim 6, wherein the forming of the pixel electrode comprises: Depositing a metal on the semiconductor layer; And And etching the metal to form a metal layer on the semiconductor layer. The method of claim 6, wherein the opening of the common electrode and the pixel electrode comprises etching a protective layer on the common electrode and the pixel electrode. The method of claim 6, wherein the opening of the common electrode and the pixel electrode comprises: Etching the passivation layer over the common electrode and the pixel electrode; And A method of manufacturing a transverse electric field mode liquid crystal display device, comprising the step of etching a gate insulating layer on a common electrode. Providing a substrate; Forming a gate electrode and a common electrode on the substrate; Stacking an insulating layer on the substrate and etching the gate insulating layer on the common electrode; Forming a semiconductor layer on the insulating layer; Forming a source / drain electrode and a pixel electrode; Depositing a protective layer over the substrate; And And forming a protective layer on the common electrode and the pixel electrode. The method of claim 11, wherein the forming of the pixel electrode comprises: Etching a portion of the semiconductor layer to form an open region; And Stacking and etching metal on the semiconductor layer to form a metal layer in the open region. The method of claim 11, wherein the forming of the pixel electrode comprises: Depositing a metal on the semiconductor layer; And And etching the metal to form a metal layer on the semiconductor layer. delete

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