KR20020002651A - Multi-domain vertical aligned - fringe field switching mode lcd improved electric-field - Google Patents

Abstract

PURPOSE: A multi-domain VA-FFS LCD(Vertical Aligned Fringe Field Switching mode Liquid Crystal Display) is provided to improve an electric field by feeding power including an electrode to an upper panel of a VA-FFS LCD, and to obtain a large viewing angle, a fast response period and high transmissivity by adopting perpendicular rib structure of a pixel substrate. CONSTITUTION: A multi-domain VA-FFS LCD includes an upper panel and a lower panel. The lower panel consists of a common electrode(30), a common electrode line(30c) for feeding power to the common electrode, a rib pattern type pixel electrode(32), a TFT(Thin Film Transistor,34) for driving the pixel electrode, a gate bus line(36) feeding power to a channel(34g) of the TFT, and a data bus line(38) feeding power to a source(34s) of the TFT. A drain(34d) of the TFT is connected to the pixel electrode to control the driving of the LCD. For multi-domain structure, the pixel electrode includes a domain X unit(32X) and a domain Y unit(32Y). A quadruple domain is formed by the domain X unit and the domain Y unit of the pixel electrode. Herein, the domain means the direction of LC molecules in an LC layer when the LC layer in the center is operated according to the direction of ribs. The upper panel has an auxiliary electrode of ITO(Indium Tin Oxide). The auxiliary electrode improves the operating characteristics as well as transmissivity by enhancing an electric field of an LCD.

Description

MULTI-DOMAIN VERTICAL ALIGNED-FRINGE FIELD SWITCHING MODE LCD IMPROVED ELECTRIC-FIELD}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film transistor liquid crystal display (TFT-LCD), which is a type of display device, and more particularly, to improve transmittance and operation characteristics. A multi-domain vertical alignment-fringe field switching (hereinafter referred to as "VA-FFS") mode liquid crystal display (hereinafter referred to as "LCD").

Display devices, which are of interest as a field of the future electronics industry, started from the initial cathode ray tube (CRT), but have a new concept device according to the needs and needs of light and small, which reduces the volume, weight and power consumption. Among these display devices, liquid crystal displays (LCDs) are being actively researched due to many advantages of reviving such demands.

The liquid crystal display starts from an initial twist nematic (TN) mode in which the liquid crystal is twisted, and includes an in-plane switching (IPS) mode, a vertically aligned (VA) mode, and a fringe field switching (FFS) mode. It has been developed in recent years, and its production is being further advanced by incorporating semiconductor technologies such as thin film transistors (hereinafter referred to as TFTs).

1 is a cross-sectional view of a conventional FFS mode LCD device. Hereinafter, an operation of the FFS mode LCD device will be described with reference to FIG. 1.

As shown, in the FFS mode LCD device, the pixel electrode 12 and the common electrode 14 are positioned on the glass substrate 10 of the lower plate, and the liquid crystal layer 16 is present between the glass substrate 18 of the upper plate. do. There are a plurality of liquid crystal molecules 16a in the liquid crystal layer 16. In FIG. 1, some liquid crystals are schematically illustrated for the purpose of operation.

The conventional FFS mode LCD device shown in Fig. 1 is manufactured so that liquid crystals are arranged in a horizontal direction. Therefore, the liquid crystal molecules 16a are held in one direction before the voltage is applied to the two electrodes 12 and 14. However, once the voltage is applied as shown by the arrow, each of the liquid crystal molecules is the pixel electrode 12 and the common electrode 14. The direction is slightly changed according to the distance of. Therefore, the light passing through the glass substrate 18 of the upper plate is rotated little by little through the twisted liquid crystal layer 16, and finally passes through the glass substrate 10 of the lower plate. As a result, the pixels of the LCD device are uniformly arranged in a planar shape and a screen is generated according to the driving of the electrodes included in each pixel.

However, the FFS mode LCD device is excellent in terms of wide viewing angle and light efficiency, but also has a problem in realizing a video due to a slow response time. There is a VA-FFS mode LCD device that simultaneously adopts orientation and fringe field.

However, the aforementioned conventional LCD devices have many problems.

VA mode LCD device uses multi-mode to solve the problem of viewing angle, but it is fundamentally difficult to prevent transmittance deterioration, and not only the driving is not stable, such as the formation of disclination line, There is still a problem in light efficiency and operation characteristics. In addition, the FFS mode LCD device is excellent in terms of wide viewing angle and light efficiency, but also has a problem in implementing a video due to a slow response time. In addition, the VA-FFS mode LCD device, which combines the advantages of the VA mode LCD device with the FFS mode LCD device, has not only a difference in transmittance depending on the structure of the electrode, but also a decrease in transmittance due to a disclination line. There is a problem.

Accordingly, an object of the present invention for solving the above problems is to include an electrode on the upper plate of the VA-FFS mode LCD device to apply electric power to improve the electric field, and to make the multi-domain, The structure provides a multi-domain vertical aligned fringe field switching mode liquid crystal display device with an improved electric field that can realize a wide viewing angle, a fast response period, and a high transmittance. There is.

1 is a cross-sectional view of a conventional FFS mode LCD device.

2 is a view for explaining the operation of the multi-domain VA-FFS mode LCD device with improved electric field according to an embodiment of the present invention.

3 is a structural diagram of a lower plate of the LCD device shown in FIG.

4 is a view showing a measurement result of the operation and transmittance of the liquid crystal when a voltage is applied to the LCD device of the present invention shown in FIG.

5 is a view for explaining the operation of the multi-domain VA-FFS mode LCD device with improved electric field according to another embodiment of the present invention.

6 is a structural diagram of a lower plate of the LCD device according to another embodiment shown in FIG.

(Explanation of symbols for the main parts of the drawing)

12, 32: pixel electrode 14, 30: common electrode

16, 21: liquid crystal layer

20: top plate 22: bottom plate

32X, 32Y: domain portion of pixel electrode 34: thin film transistor

The multi-domain vertical alignment-fringe field switching mode liquid crystal display device having an improved electric field according to the present invention is a liquid crystal display device in which a plurality of liquid crystal pixels are arranged to form an image.

A first electrode for controlling the operation of the liquid crystal material; A second electrode positioned near the first electrode and having a gap not greater than the thickness of the liquid crystal material, the second electrode including at least two collections of ribs formed perpendicularly and perpendicularly to the directions of the liquid crystal pixels arranged; A control element having a predetermined thickness for controlling the operation of the second electrode; A lower plate including the first electrode and / or the second electrode, the lower plate being manufactured to control the progress of light passing through the liquid crystal material; A liquid crystal layer disposed on the lower plate and arranged such that a predetermined axis of the liquid crystal material is substantially perpendicular to the lower plate; An auxiliary electrode to which a predetermined potential associated with the first and / or second electrode is applied so as to have a good transmittance of the liquid crystal display; And a top plate positioned above the liquid crystal layer to include the auxiliary electrode and arranged in a predetermined direction to assist the operation of the liquid crystal layer to control the progress of light incident on the liquid crystal display.

The multi-domain vertical alignment-fringe field switching mode liquid crystal display device which improves another electric field of the present invention is a liquid crystal display device in which a plurality of liquid crystal pixels are arranged to form an image.

A first electrode for controlling the operation of the liquid crystal material; A second electrode located near the first electrode and having a gap not greater than the thickness of the liquid crystal material, the second electrode including at least two collections of oblique lines in the direction of the arranged liquid crystal pixels; A control element having a predetermined thickness for controlling the operation of the second electrode; A lower plate including the first electrode and / or the second electrode, the lower plate being manufactured to control the progress of light passing through the liquid crystal material; A liquid crystal layer disposed on the lower plate and arranged such that a predetermined axis of the liquid crystal material is substantially perpendicular to the lower plate; An auxiliary electrode to which a predetermined potential associated with the first and / or second electrode is applied so as to have a good transmittance of the liquid crystal display; And a top plate positioned above the liquid crystal layer to include the auxiliary electrode and arranged in a predetermined direction to assist the operation of the liquid crystal layer to control the progress of light incident on the liquid crystal display.

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

2 is a view for explaining the operation of the multi-domain VA-FFS mode LCD device with an improved electric field according to an embodiment of the present invention, Figure 3 is a structural diagram of the lower plate of the LCD device shown in Figure 2, Figure 4 FIG. 2 is a view showing the results of measuring the operation and transmittance of the liquid crystal when a voltage is applied to the LCD device of the present invention shown in FIG. 2.

As shown in Figs. 2 and 4, the multi-domain VA-FFS mode LCD device with improved electric field according to the present invention includes a top plate 20 and a bottom plate 22. As shown in the cross-sectional view, the liquid crystal layer 21 between the upper plate 20 and the lower plate 22 is located.

As shown in FIG. 3, the lower plate 22 of one pixel of the LCD device of FIG. 2 includes a common electrode 30, a common electrode line 30c for applying power to the common electrode 30, Applying power to the pixel electrode 32 having a striated pattern shape, a thin film transistor 34 for driving the pixel electrode 32, and a channel 34g of the TFT 34. A gate bus line 36 and a data bus line 38 for applying power to the source 34s of the TFT 34. Then, the other pole drain 34d of the TFT 34 is connected to the pixel electrode 32 to control the driving of the present LCD device. In addition, the pixel electrode 32 includes the domain X portion 32X of the pixel electrode and the domain Y portion 32Y of the pixel electrode for the multi-domain which is a large feature of the present invention.

In general, in the VA-FFS mode LCD device, the width of the liquid crystal layer, that is, the width of the upper plate (FIGS. 2 and 4 and 20) and the lower plate (FIGS. 3, 30) and the pixel electrode (Figs. 3, 32) is made larger than the interval (length), the long axis of each liquid crystal before applying power to the LCD device of the present invention, as in the VA mode, that is, the vertical alignment means Orient to align perpendicular to the top and bottom plates 20 and 22 of the device.

As described above, in the LCD device, which is one type of display device, the characteristics of the viewing angle are important. That is, the LCD device has a difference in image quality, color, and the like, depending on the angle of view of the LCD device due to refractive index anisotropy, which is an optical characteristic of liquid crystal. To compensate for this, the liquid crystals affected by the electric fields of the electrodes must be formed in multiple directions. For this purpose, in the present invention, the rod-shaped pixel electrode 32 shown in FIG. There is a characteristic to be divided so as to be perpendicular to each other. The liquid crystal layer 21 in the center operates in accordance with the directions of the rods. The liquid crystals in which the operation is completed are referred to as domains. In the present embodiment, the domain X portion 32X and the domain Y portion ( 32Y) form a total of four domains.

In addition, the direction of the two domain portions 32X and 32Y of the pixel electrodes perpendicular to each other, the direction of rubbing (arrow R1) shown in FIG. 2, the direction of the upper plate deflection plate (arrow P1), and the direction of the lower plate deflection plate ( Taking into account the arrow A1), determine the maximum operating characteristics such as transmittance. The rubbing process can be made larger than 0 ° and smaller than 90 ° with respect to the top plate, but takes about 45 ° to maximize efficiency. In addition, the upper plate 20 and the lower plate 22 includes a deflection plate, which maintains 45 ° and 135 ° of the direction of the electrode to obtain the largest transmittance.

In addition, the top plate 20 includes an auxiliary electrode 20p made of indium thin oxide (ITO) material, as shown in the cross-sectional view of FIG. 4. The auxiliary electrode 20p improves the electric field of the liquid crystal display device, thereby improving operation characteristics including high transmittance.

In addition, by applying a vertical fragrance to the upper plate 20 and the lower plate 22, the long axis of the liquid crystal injected into the intermediate liquid crystal layer 21 is vertically arranged. In addition, the liquid crystal to which the dopant of about 1% was added is used for the liquid crystal layer 21 to have a chiral pitch of 70-100 micrometers. A chiral pitch means a twisted period of the liquid crystal layer 21 when the twisted liquid crystal operates in a twisted form, and a dopant is a twist of the liquid crystal when a voltage is applied to the LCD device. It is an additive to make warping easier.

The multi-domain VA-FFS mode LCD device of the present invention having such structural characteristics operates the TFT 34 by applying power to the gate bus line 36 and the data bus line 38, and drains the TFT 34. By activating 34d) and applying power to the pixel electrode 32, an electric field is formed between the common electrode 30 and the pixel electrode 32. FIG. In addition, by applying the same voltage as the common electrode 30 to the auxiliary electrode 20p of the upper plate 20 shown in FIG. 4, the central liquid crystal layer 21 is interposed between the common electrode 30 and the pixel electrode 32 and the pixel. It is possible to operate under the influence of the double electric field between the electrode 32 and the auxiliary electrode (20p).

After applying the voltage, the liquid crystals start to lie down under the influence of the formed electric field (Figs. 4 and 21f). Finally, the rubbing effect of the top plate and the rubbing effect of the electric field are combined to provide the electric field. The liquid crystals of the liquid crystal layer 21 form quadruple domains. And light is transmitted by the liquid crystals twisted along this electric field.

The multi-domain VA-FFS mode LCD device according to an embodiment of the present invention exhibits good operating characteristics with high permeability and wide viewing angle, as shown in the transmittance measurement results shown in the upper portion of FIG. 4.

As described above, in addition to the pixel electrode in which the domain portion illustrated in FIG. 2 is perpendicular to each other, various changes may be made to the shape of the lower electrode. Hereinafter, another embodiment will be described with reference to the drawings.

5 is a view for explaining the operation of the multi-domain VA-FFS mode LCD device with improved electric field according to another embodiment of the present invention, Figure 6 is a lower plate of the LCD device according to another embodiment shown in FIG. It is a structural diagram.

As shown in FIG. 6, the LCD device, which is another embodiment of the present invention, is rotated by about 45 ° in the direction of the two domain portions 62X and 62Y of the pixel electrode 62, unlike the embodiment described above. As shown in Fig. 5, the rubbing direction (arrow R2), the direction of the upper plate deflection plate (arrow P2), and the direction of the lower plate deflection plate (arrow A2) are also produced in the state of being rotated by 45 degrees from the above-described embodiment.

In another embodiment of the present invention manufactured as described above, the interval between the upper plate (FIGS. 5, 50) and the lower plate (FIGS. 5, 52) in order to satisfy the FFS condition is the interval between the common electrode 60 and the pixel electrode 62 It is made narrower. The two electrodes are oriented at an angle of about 45 ° with respect to the gate bus line 66 and the data bus line 68, but in this embodiment, quadruple domains are formed to improve the viewing angle of the LCD device.

In addition, when the TFT 64 is operated by the gate bus line 66 and the data bus line 68, the TFT drain 64d is activated to apply power to the pixel electrode 62. Therefore, a liquid crystal is operated by forming a double electric field between the common electrode 60 and the pixel electrode 62 and between the pixel electrode 62 and the upper plate 50. Liquid crystals whose efficiency of operation is increased by the double electric field are finally laid down in the direction of the electric field and form quadruple domains, and thus light passing through the upper plate 50 is transmitted to the lower plate 52. And, many of these pixels are arranged in a horizontal line to form an image. Other operating characteristics and measurement results of this embodiment are the same as the above-described embodiment.

In addition, based on the principles of the invention described above, the LCD device of the present invention can be manufactured to form multiple domains of four or more domains. That is, a plurality of pixel electrodes of the embodiments described with reference to FIGS. 2 to 4 are doubled, three times, four times, etc. as necessary, and the embodiments described with reference to FIGS. By fabrication, multiple domains of four or more can be formed. In this case, the multi-domain LCD device generally considers the angle of dividing the array angle of the pixel electrode in half, and sets the angle according to the concept of the present invention to show the maximum operating characteristics.

In addition, the VA-FFS mode LCD device in which the electric field is improved in the present invention can properly compensate for the black state of the liquid crystal in accordance with the viewing angle by attaching a phase compensation film. In addition, the liquid crystal display device of the present invention does not require a rubbing process of the lower plate, there is an advantage that can use the process of the existing FFS mode LCD device as it is.

As described above, the multi-domain VA-FFS mode LCD device having an improved electric field according to the present invention changes the arrangement of pixel electrodes on the lower plate to form multiple domains, and the upper plate includes electrodes having a common electrode and an equipotential. It is included to improve the electric field to improve the operation characteristics of the liquid crystal. In addition, the conventional FFS mode LCD device process can be used as it is, as well as a side effect of reducing the process time by a simple rubbing process. Therefore, the VA-FFS mode LCD device with improved electric field has the effect of realizing high quality image with high transmittance, wide viewing angle and improved operation characteristics.

Claims (16)

In the liquid crystal display device in which a plurality of liquid crystal pixels are arranged to form an image, A first electrode for controlling the operation of the liquid crystal material; A second electrode positioned near the first electrode and having a spacing not greater than the thickness of the liquid crystal material, the second electrode including at least two collections of ribs formed perpendicularly and perpendicularly to the direction of the arranged liquid crystal pixels; A control element having a predetermined thickness for controlling the operation of the second electrode; A lower plate including the first electrode and / or the second electrode, the lower plate being manufactured to control the progress of light passing through the liquid crystal material; A liquid crystal layer disposed on the lower plate and arranged such that a predetermined axis of the liquid crystal material is substantially perpendicular to the lower plate; An auxiliary electrode to which a predetermined potential associated with the first and / or second electrode is applied so as to have a good transmittance of the liquid crystal display; And, Located on the liquid crystal layer and including the auxiliary electrode and arranged in a predetermined direction to assist the operation of the liquid crystal layer, characterized in that it comprises a top plate for controlling the progress of light incident on the liquid crystal display device, Multi-domain vertical alignment-fringe field switching mode liquid crystal display with improved electric field. The method of claim 1, wherein the second electrode The multi-domain vertical alignment-fringe field switching mode liquid crystal display device of claim 1, further comprising a first vowel formed vertically in the direction of the liquid crystal pixels and a second vowel formed horizontally. The method of claim 1, wherein the liquid crystal layer A multi-domain vertical alignment-fringed field switching mode liquid crystal display device, characterized in that the rubbing to be within about 45 degrees with the top plate. The method of claim 1, wherein the liquid crystal layer A multi-domain vertical alignment-fringed field switching mode liquid crystal display device characterized by comprising a negative liquid crystal having a dielectric anisotropy of -15 to -3. The method of claim 1, wherein the liquid crystal layer A multi-domain vertical alignment-fringed field switching mode liquid crystal display device, characterized in that it consists of a positive liquid crystal having a dielectric anisotropy of 3 to 15. The method of claim 1, wherein the liquid crystal layer A multi-domain vertical alignment-fringed field switching mode liquid crystal display device having an improved electric field, wherein a predetermined dopant is added to have a chiral pitch of 70 to 100 [μm]. The method of claim 1, wherein the upper and lower plates A multi-domain vertical alignment-fringed field switching mode liquid crystal display device having an electric field enhanced, characterized by having an interval of 2 to 10 [탆]. The method of claim 1, wherein the upper and / or lower plate is An electric field-enhanced multi-domain vertical alignment-fringed field switching mode liquid crystal display further comprising at least one or more phase compensation films for improving the viewing angle. In the liquid crystal display device in which a plurality of liquid crystal pixels are arranged to form an image, A first electrode for controlling the operation of the liquid crystal material; A second electrode located near the first electrode and having a gap not greater than the thickness of the liquid crystal material, the second electrode including at least two collections of oblique lines in the direction of the arranged liquid crystal pixels; A control element having a predetermined thickness for controlling the operation of the second electrode; A lower plate including the first electrode and / or the second electrode, the lower plate being manufactured to control the progress of light passing through the liquid crystal material; A liquid crystal layer disposed on the lower plate and arranged such that a predetermined axis of the liquid crystal material is substantially perpendicular to the lower plate; An auxiliary electrode to which a predetermined potential associated with the first and / or second electrode is applied so as to have a good transmittance of the liquid crystal display; And, Located on the liquid crystal layer and including the auxiliary electrode and arranged in a predetermined direction to assist the operation of the liquid crystal layer, characterized in that it comprises a top plate for controlling the progress of light incident on the liquid crystal display device, Multi-domain vertical alignment-fringe field switching mode liquid crystal display with improved electric field. The method of claim 9, wherein the second electrode A multi-domain vertical alignment with an improved electric field, characterized in that it comprises a first vowel collection formed in an oblique direction to the directions of the liquid crystal pixels and a second vowel collection formed in another diagonal direction perpendicular to the first vowel collection. -Fringe field switching mode LCD. The method of claim 9, wherein the liquid crystal layer A multi-domain vertical alignment-fringed field switching mode liquid crystal display device, characterized in that the rubbing to be within about 45 degrees with the top plate. The method of claim 9, wherein the liquid crystal layer A multi-domain vertical alignment-fringed field switching mode liquid crystal display device characterized by comprising a negative liquid crystal having a dielectric anisotropy of -15 to -3. The method of claim 9, wherein the liquid crystal layer A multi-domain vertical alignment-fringed field switching mode liquid crystal display device, characterized in that it consists of a positive liquid crystal having a dielectric anisotropy of 3 to 15. The method of claim 9, wherein the liquid crystal layer A multi-domain vertical alignment-fringed field switching mode liquid crystal display device having an improved electric field, wherein a predetermined dopant is added to have a chiral pitch of 70 to 100 [μm]. The method of claim 9, wherein the top and bottom plate is A multi-domain vertical alignment-fringed field switching mode liquid crystal display device having an electric field enhanced, characterized by having an interval of 2 to 10 [탆]. The method of claim 9, wherein the top and / or bottom plate is An electric field-enhanced multi-domain vertical alignment-fringed field switching mode liquid crystal display further comprising at least one or more phase compensation films for improving the viewing angle.