FR2870947A1 - In-plane switching LCD for e.g. television, has thin film transistor placed at left/right side of pixel area based on pixel columns, using column inversion technique, and gate lines arranged parallel to common and pixel electrodes - Google Patents

Abstract

The display has gate lines (42) and data lines (44) crossing each other to define pixel areas (P1-P4). A thin film transistor is placed at left or right side of the pixel area according to pixel columns, using a column inversion technique. A pixel electrode (48) is arranged in an alternating pattern with a common electrode (46). The gate lines are arranged parallel to the common and pixel electrodes. An independent claim is also included for a method of driving an in-plane switching liquid crystal display.

Description

LIQUID CRYSTAL DISPLAY AND CONTROL METHOD

  The present invention relates to a liquid crystal display with coplanar switching technology (so-called IPS for In Plane Switching in English) and a control method thereof. More particularly, the present invention relates to a liquid crystal display with IPS technology and a control method thereof that can provide a better aperture ratio and lower power consumption.

  The demands in terms of flat panel displays (thin, small and light), which can be used in a television and in various portable electronic devices such as a mobile phone, PDA (PDA) ) and a laptop, have recently increased. Various display devices, such as a liquid crystal display (LCD), a plasma display (PDD), a field emission display (FED), and a vacuum fluorescent display (VFD), have been actively studied. for use as a flat panel display device.

  Among them, the thin, small and lightweight LCD is highlighted as the flat panel display device, since it can provide a high resolution image and low power consumption.

  The LCD includes a liquid crystal panel for displaying an image, and a control unit for applying a control signal to the liquid crystal panel. The liquid crystal panel includes first and second substrates joined to each other, and a liquid crystal layer injected between the first and second substrates.

  Generally, the first substrate (or thin film transistor substrate) comprises a plurality of grid lines arranged to be spaced apart from each other by a predetermined interval in one direction, a plurality of data lines arranged to be respectively perpendicular to the grid lines, a plurality of pixel electrodes arranged in matrix form in respective pixel areas defined by grid lines and data lines, and a plurality of thin film transistors activated by grid line signals to thereby transfer the signals from the data lines to the respective pixel electrodes.

  The second substrate (or color filter substrate) comprises a black-bottomed matrix layer for intercepting light from portions other than pixel areas, a R / VB color filter layer for reproducing the HIRSCH6. PATENTS \ Patents \ 23900 \ 23906. doc-30 May 2005 - 1/14 color, and a common electrode for reproducing an image. In the IFS-technology LCD, the common electrode is formed on the first substrate.

  The first and second substrates are assembled one on the other. Next, liquid crystals are injected between the first and second assembled substrates.

  Meanwhile, the LCD is controlled by means of the properties of optical anisotropy and polarizability of the liquid crystals.

  The liquid crystals have a fine and long structure and therefore have directionality in a molecular arrangement. The molecular arrangement direction of the liquid crystal can be artificially controlled by applying an electric field to the liquid crystal.

  Therefore, if the direction of arrangement of the liquid crystal is arbitrarily changed, the arrangement of the liquid crystal molecules is changed and the polarized light due to the optical anisotropy is arbitrarily modulated. In this way, information relating to the image is expressed.

  The LCD has different display modes based on the arrangement of liquid crystal molecules. Among them, a helical nematic LCD is widely used because it can easily display black / white and has a fast reaction speed and a low control voltage. In the twisted nematic LCD, when a voltage is applied, the liquid crystal molecules aligned parallel to a substrate are aligned substantially perpendicular to the substrate. Therefore, when a voltage is applied, the angle of view is narrow due to the refractive anisotropy.

  In order to solve this problem, different modes having wide angle of view features have been proposed. Among them, an LCD with IPS (In-plane switching) technology has been developed.

  When a voltage is applied, the IPS-based LCD forms a horizontal electric field on the plane and aligns the liquid crystal molecules on the plane, thereby improving the viewing angle characteristic.

  Figure 1 is a sectional view of an IPS technology LCD of the related art.

  In FIG. 1, a pixel electrode 12 and a common electrode 13 are formed on the same plane on a lower substrate 11.

  The lower substrate 11 is connected to an upper substrate 15 with a pre-determined space therebetween. A liquid crystal layer 14 is formed between the lower substrate 11 and the upper substrate 15. The liquid crystal layer 14 operates with a horizontal electric field formed between the pixel electrode 12 and the common electrode 13 on the lower electrode 11.

  Figs. 2A and 2B illustrate a change of the liquid crystal when a voltage is applied or not in the LCD with IPS technology.

  HIRSCH6 \\ \ PATENTS 'Patent \ 23900 \ 23906. doc - May 30, 2005 - 2/14 As can be seen in Figure 2A, no phase change of the liquid crystal 14 occurs in the deactivated state, that is to say when no horizontal electric field n ' is applied to the pixel electrode 12 or the common electrode 13. For example, the liquid crystals are twisted at 45 relative to a horizontal direction of the pixel electrode 12 and the common electrode 13.

  As can be seen in FIG. 2B, a phase change of the liquid crystal layer occurs in the activated state, i.e. when a horizontal electric field is applied to the pixel electrode 12 or in the common electrode 13. In comparison with the deactivated state of FIG. 2A, the twist angle is about 10 45 and the twist direction of the liquid crystal coincides with the horizontal direction of the pixel electrode 12 and the common electrode 13.

  As described above, the IPS technology LCD has the pixel electrode and the common electrode on the same plane.

  The LCD with IPS technology has the advantage of having a wide angle of view.

  Thus, when the LCD is viewed from the front, the viewing angle is 70 in the up / down / right / left directions.

  In addition, in comparison with a conventional LCD, the manufacturing process is simple and the movement of colors according to the angle of view is light.

  However, since the common electrode and the pixel electrode are formed on the same plane, the transmission rate and the aperture ratio are reduced.

  Figure 3 is a top view of an IPS technology LCD of the related art.

  In Fig. 3, a plurality of grid lines 32 are arranged at regular intervals in one direction. Several lines of data 35 are arranged at regular intervals in a direction perpendicular to the grid lines 32 so as to define pixel areas P on a transparent lower substrate 31.

  A common line 39 is arranged parallel to the grid lines 32 in the pixel area P. A thin film transistor T is formed at each pixel area P defined by the crossing of the grid line 32 and the line of the grid. data 35.

  Here, the thin film transistor T comprises a gate electrode 32a protruding from the gate line 32, a gate insulating layer (not shown) formed on a front of the lower substrate 31, an active layer 34 formed on the gate insulating layer disposed at an upper portion of the gate electrode 32a, a source electrode 35a protruding from the data line 35, and a drain electrode 35b spaced from the source electrode 35a according to a predetermined distance.

  Several pixel electrodes 38 are formed parallel to the data line 35 in the pixel area P. A terminal of the pixel electrode 38 is formed by a plurality of pixel electrodes 38. connected to the drain electrode 35b of the thin film transistor T. In addition, several of the common electrodes 39a protruding from the common line 39 are formed in the pixel area P. A protective electrode 36 is formed between the common electrodes 39a adjacent to the data line 35 so as to prevent any distortion of an electric field.

  More specifically, when a scanning signal is applied to the thin film transistor T through the gate line, the thin film transistor T is activated so that an image signal is transmitted to the electrode. of pixels 38 through the data line 35. Next, an electric field is formed between the common electrode 39a and the pixel electrode 38 in a substantially horizontal direction relative to the substrate. The molecules of the liquid crystals rotate in the direction of the electric field.

  However, when the image signal is transmitted to the pixel electrode 38, the electric field is formed not only between the common electrode 39a and the pixel electrode 38, but also between the pixel electrode 38 and the data line 35.

  At this time, the electric field between the pixel electrode 38 and the data line distorts the entire horizontal electric field within the pixel. Consequently, the molecules of the liquid crystals are not arranged completely horizontally with respect to the substrate. Thus, crosstalk occurs in a vertical direction.

  The change of the electric field causes the rotation of the liquid crystals, so that the color tone is changed. In order to prevent this problem, a protective electrode 36 for shielding the electric field is formed between the data line 35 and the common electrode 39a, and between the data line 35 and the pixel electrode 38.

  For the formation of the protective electrode 36, a width of the common electrode 39a must be 10 m or more.

  Therefore, since the width of the common electrode is enlarged due to the formation of the protective electrode, the opening ratio of the pixel area is reduced.

  Accordingly, the present invention relates to an IPS-based liquid crystal display and a control method thereof, which substantially eliminate one or more problems related to the limitations and disadvantages of the related art.

  HIRSCH6 \\ \ PATENTS \ Patent \ 23900 \ 23906. It is an advantage of the present invention to provide an IPS-based liquid crystal display and control method thereof that can improve an aperture ratio by arranging a pixel electrode. , a common electrode, and a line of grids being substantially parallel to each other and inclined at a predetermined angle, and which can reduce power consumption by using a column inversion method in rows of pixels.

  Other advantages and features of the invention are set forth in part in the description which follows, and will be partly apparent to those skilled in the art when examining the following, or can be learned during the implementation. practice of the invention. The objectives and other advantages of the invention can be realized by the structure particularly indicated in the written description and the claims, as well as in the accompanying drawings.

  In order to realize these and other advantages, and in accordance with the object of the invention, described in detail herein, an IPS-based liquid crystal display comprises: a plurality of grid lines and a plurality of lines intersecting data to define a plurality of pixel areas; a thin film transistor formed at a cross of the grid and data lines; a pair of common lines facing each other and substantially parallel to the data lines in the pixel area; a common electrode integrally formed with the common lines, the common electrode being inclined at a predetermined angle; a pair of pixel electrode lines overlapping the common lines; and an integrally formed pixel electrode with the pixel electrode lines, the pixel electrode being inclined substantially parallel to the common electrode, the pixel electrode being arranged in an alternating pattern with the common electrode, wherein the grid lines are formed substantially parallel to the common electrode and the pixel electrode.

  According to another aspect of the present invention there is provided a method of driving an IPS-based liquid crystal display, the method comprising: sequentially applying a data signal on the data lines; and sequentially applying a scan signal on the grid lines, wherein voltages having a different polarity are alternately applied to the pixel areas of a liquid crystal panel.

  It should be understood that the foregoing general description and the following detailed description of the present invention are given as explanatory examples and are intended to provide another explanation of the present invention.

  The accompanying drawings, which are included to provide a better understanding of the invention and which are incorporated in and constitute a part of this application, are incorporated herein by reference. doc May 2005 - 5/14 illustrate embodiments of the invention and, with the description, serve to explain the principle of the invention.

  In the drawings: Fig. 1 is a schematic sectional view of a general IPS technology LCD; Figs. 2A and 2B are views illustrating a change in liquid crystal when an IPS-enabled LCD is turned on or off; Figure 3 is a top view of an IPS technology LCD of the related art; Figure 4 is a schematic top view of an IPS technology LCD 10 according to the present invention; Fig. 5 is an enlarged top view of a region of a pixel area shown in Fig. 4 (surrounded by a circle); and Fig. 6 is a view illustrating a case in which a row of pixels of an IPS-based LCD of the invention is controlled when a signal is applied to the row of pixels.

  Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numerals are used throughout the drawings to denote like or similar parts.

  FIG. 4 is a schematic top view of an IPS-based LCD according to the present invention, and FIG. 5 is an enlarged top view of a region of a pixel area (surrounded by a circle) illustrated in FIG. figure 4.

  In FIGS. 4 and 5, in order to define the pixel areas in an IPS technology LCD of the present invention, a plurality of vertical data lines 44 are spaced from each other at a predetermined interval, and a plurality of grid lines 42 are arranged by being inclined at a predetermined angle with respect to the data lines 44.

  A thin film transistor "T" is formed in the respective pixel areas P1 to P4 defined by the crossings of the data lines 44 and the gate lines 42. The thin film transistor may be disposed on the left or the right of the pixel area, according to the pixel columns.

  Thus, the source electrodes 45A connected to a data line 44 are alternately provided in the left and right pixel areas with respect to the data line 44.

  In addition, a common line 51 and a pixel electrode line 52 are arranged substantially parallel to the data line 44 at a location near the data line 44 in the pixel area. The common line 51 and the PATENT / Patent 23909. doc ruai 2005 - 6/14 pixel electrode line 52 are formed to have a width of about 8 m or less.

  In addition, the common line 51 and the pixel electrode line 52 overlap and thus form a storage capacity in each pixel area.

  The first and second electrodes protrude from the common line 51 and the pixel electrode line 52, and are arranged substantially parallel to the grid line 42. The first electrode and the second electrode respectively correspond to a common electrode. 46 and a pixel electrode 48.

  The common electrode 46 and the pixel electrode 48 may be inclined upward or downward with respect to a horizontal center line of the pixel area, whereby an enlarged viewing angle can be achieved.

  In addition, the gate line 42 is arranged substantially parallel to the common electrode 46 and the pixel electrode 48, whereby an opening ratio is improved.

  In Fig. 5, the thin film transistor comprises a gate electrode (not shown) extending from the gate line 42, a semiconductor layer (not shown) formed on the gate electrode, a source electrode 45A formed on the semiconductor layer and extending from the data line 44, and a drain electrode 45B. A scan signal is applied to the gate electrode, and the semiconductor layer is activated by the scan signal to thereby form a channel layer. An image signal is applied to the source electrode 45A.

  The common electrode 46 and the pixel electrode 48 are arranged to tilt at a predetermined angle to a horizontal direction substantially perpendicular to the data line 44, and the gate line 42 is arranged substantially parallel to the common electrode 46 and the pixel electrode 48. Here, the tilt angle is less than about 45.

  When the common electrode 46, the pixel electrode 48 and the gate line 42 are arranged to tilt as above, the liquid crystal can be aligned horizontally (00).

  Since the direction of an electric field generated between the data line 44 and the neighboring common electrode 46 is identical to the alignment direction of the liquid crystal, no distortion is generated due to an electric field generated by the data line 44.

  Therefore, an aperture ratio of the pixel area can be improved since a separate protective electrode and a black-bottomed matrix for shielding an undesired electric field are unnecessary.

  HIRSCH6 \\ \ PATENTS \ Patent \ 23900 \ 23906. In addition, when the grid line 42 is not perpendicular to the data line 44 but is arranged to be inclined at a predetermined angle to the horizontal direction, the ratio of The aperture can be improved because the gap between the grid line 42 and the neighboring pixel electrode 48 can be maintained at a constant value (e.g., about 10 m).

  When the pixel electrode 48 and the common electrode 46 are arranged to be inclined and the grid line 42 is arranged horizontally, a gap between the grid line 42 and the pixel electrode 48 is not maintained steadily.

  Therefore, a region in which the above range is greater than about 10 gm exists in a pixel area. Since this undesirable region can not be used as a region for efficiently transmitting light, the aperture ratio is reduced.

  However, the gate line 42 is arranged substantially parallel to the pixel electrode 48 and the common electrode 46 in the present invention. Thus, a gap between the grid line 42 and the pixel electrode 48 is maintained steadily. Therefore, since a region in which the above range is greater than about 10 m does not exist in a pixel area, the aperture ratio can be improved.

  Here, the above range is not limited to about 10 m, but may vary depending on the size and image resolution of a liquid crystal panel.

  In addition, since the gate line 42 is symmetrically inclined with respect to the front gate line 42, an opening region of the pixel area can be further enlarged.

  At the same time, the common electrode 46 is connected to the common line 51 arranged near the neighboring pixel, and the pixel electrode 48 is connected to the pixel electrode line 52 overlapping the common line 51.

  The common line 51 and the pixel electrode line 52 overlap to thereby form a storage capacitor 50 for use as a storage electrode.

  The storage capacitor 50 is used to improve the retention property of a voltage applied to the liquid crystals and the reproducing stability of the gradation, and to reduce flicker and recurring image.

  Fig. 6 is a view illustrating a row of pixels of an IPS-based LCD of the invention control when a signal is applied to the row of pixels.

  In FIG. 6, a thin-film transistor formed at a portion in which the grid line and the data line intersect, can be arranged on the left or right side of a pixel area according to the columns of FIG. pixels.

  In detail, since the thin-film transistor can be arranged on the left or right side of a corresponding pixel area according to the columns. of pixels, each thin-film transistor receives a signal according to the polarity applied thereto.

  When data signals are sequentially applied to the first and second data lines in a column inversion method, a data signal is applied to each pixel area connected to a source electrode of the first line. data (see the pixel structure in Figure 4).

  Since two data lines can apply data signals respectively to the pixel areas formed along a zigzag column, the pixel areas corresponding to a vertical direction of the data lines are alternately turned on / off.

  A disabled pixel area is activated by a data signal provided by the neighboring data line.

  Therefore, as shown in Fig. 6, pixel areas controlled by a column inversion method are driven as with a point inversion method.

  When data signals are sequentially applied to two data lines and on / off signals are sequentially applied to the grid lines, a voltage greater than that of a common electrode is applied to a pixel area. connected to the first data line, and a voltage lower than that of the common electrode is applied to a neighboring pixel area P2 since no data signal is applied thereto.

  Similarly, when an on / off control signal is applied to the next grid line, a voltage lower than that of the common electrode is applied to pixel area P2 since no data signal is applied thereto, and a voltage higher than that of the common electrode is applied to pixel area P4 since a data signal is applied thereto.

  As described above, in the IPS LCD of the invention, the pixel electrode, the common electrode and the gate line are arranged substantially parallel to each other, whereby an opening ratio can be improved.

  In addition, a point inversion method may be implemented using a column inversion method in which a thin film transistor is disposed on a left or right side of a pixel area according to the columns of pixels. whereby the energy consumption can be reduced.

  It will be apparent to those skilled in the art that various modifications and variations can be made within the present invention without departing from the spirit or the spirit of the present invention. doc 30 May 2005 - 9/14 the scope of the invention. Thus, it is intended that the present invention covers the modifications and variations of this invention, provided that they fall within the scope of the appended claims and their equivalents.

  HIRSCH6 \\ \ PATENTS \ Patent \ 23900 \ 23906. doc - May 30, 2005 - 10/14

Claims (17)

  A coplanar switching technology (IPS) liquid crystal display comprising: - a plurality of grid lines (42) and a plurality of data lines (44) intersecting each other to define a plurality of pixel areas; - a thin-film transistor (T) formed at a cross of the data lines and grid lines; a pair of common lines (51) facing each other and being substantially parallel to the data lines in the pixel areas; a common electrode (46) integrally formed with the common lines, the common electrode being inclined at a predetermined angle; a pair of pixel electrode lines (52) overlapping the common lines; and a pixel electrode (48) integrally formed with the pixel electrode lines, the pixel electrode being inclined substantially parallel to the common electrode, the pixel electrode being arranged in an alternating pattern with the common electrode, wherein the grid lines are formed substantially parallel to the common electrode and the pixel electrode.   The display of claim 1, wherein the gate lines are inclined substantially parallel to the common electrode and the pixel electrode, wherein an opening ratio is increased at the intersection of the data lines and the lines. of grids.   The display of claim 1 or 2, wherein the common electrode is inclined upward or downward at a predetermined angle to a horizontal centerline of the pixel areas.   The display according to one of claims 1 to 3, wherein the pixel electrode is inclined upwards or downwards at a predetermined angle with respect to a horizontal centerline of the pixel areas.   The display according to one of claims 1 to 4, wherein a storage capacitor is formed in a region in which the common lines and the pixel electrode lines overlap.   R: \ Patents \ 23900 \ 23906-unit-amendments.doc - 5 September 2005 - 11/3 6. Display according to one of claims 1 to 5, wherein the grid lines, the common electrode and the pixel electrode are arranged to be inclined at the same angle and to be substantially parallel to each other. others in pixel areas.   The display according to one of claims 1 to 6, wherein the grid lines, the common electrode and the pixel electrode are arranged to be inclined at an angle of less than about 45 relative to a horizontal direction. .   8. Display according to one of claims 1 to 7 wherein the common lines are formed to have a width of about 8 m or less.   9. The display according to one of claims 1 to 8, wherein the grid lines and a front grid line are formed so as to extend relative to each other so as to enlarge an area of the grid. opening of each pixel area.   10. Display according to one of claims 1 to 9, wherein the thin film transistor is disposed on a left or right side of the pixel area according to the columns of pixels.   The display of one of claims 1 to 10, wherein the pixel electrodes are spaced from each other by a predetermined interval in the pixel areas.   The display of claim 11, wherein the pixel electrodes are spaced apart from each other by a predetermined interval of about 10 m in the pixel areas.   A method of controlling a coplanar IPS switching crystal liquid crystal display as claimed in any one of claims 1 to 12, comprising: sequentially applying a data signal to data lines; and sequentially applying a scan signal to grid lines, wherein voltages having a different polarity are alternately applied to pixel areas of a liquid crystal panel.   R: \ Patents \ 23 9 0 012 3 90 6-unit-modifevdoc - September 5, 2005 - 12/3 The method of claim 13, wherein the data signal is sequentially applied to the data lines using a column inversion method.   The method of claim 13 or 14, wherein the voltages having a different polarity are alternately applied to the pixel areas using a point inversion method.   The method of claim 13 or 14, wherein the voltages having a different polarity are alternately applied to the pixel areas in a vertical direction.   The method of claim 13 or 14, wherein the voltages having a different polarity are alternately applied to the pixel areas in a horizontal direction.   R: \ Patents \ 23900 \ 23906-unit-amendments.doc - 5 September 2005 - 13/3