KR20090076776A - Electrode structure for an lcd device - Google Patents

Abstract

An electrode structure for an LCD device is provided to supply an IPS(In-Plane Switching)-LCD device and/or an FFS(Fringe Field Switching)-LCD device having a quick response and an improved viewing angle. Each pixel comprises an electrode structure between a lower substrate and an upper substrate. The electrode structure comprises electrodes(4). Each electrode has a polygon electrode surface and a plurality of electrode edges. The electrodes are arranged so that one electrode edge faces an electrode edge of an adjacent electrode. The electrode edge and the electrode edge of the adjacent electrode fundamentally define a predetermined distance along with the entire electrode edge.

Description

Electrode structure for liquid crystal display device {ELECTRODE STRUCTURE FOR AN LCD DEVICE}

The present invention relates to in-plane switching and fringe field switching liquid crystal displays.

US-6459465 discloses an IPS-LCD device having a pixel electrode and a common electrode formed in a zigzag pattern.

WO-A2-2006 / 118752 discloses an IPS-LCD device comprising a common electrode in the form of a chevron display and a pixel electrode in the form of a chevron display, arranged in an alternating manner to form a multi-domain liquid crystal distribution.

US-6917406 discloses an IPS-LCD device having a comb-shaped common electrode and a comb-shaped pixel electrode. Teeth of these electrodes can be obtained, for example, by longitudinal connection of trapezoids or inverted trapezoids, thus producing those having a toothed structure.

US-7199852 discloses a fringe field switching liquid crystal display (FFS-LCD). The comb-shaped common electrode and the pixel electrode have symmetrical teeth, which have trapezoidal portions extending periodically from both sides thereof. The interlocked portions of the common electrode and the pixel electrode have trapezoidal portions that are half-cycled with respect to each other.

As such, various types of electrodes have been tried to improve the IPS-LCD device.

An object of the present invention is to provide an electrode structure for an LCD device.

In one embodiment, an optional object of the present invention is to improve an IPS-LCD and / or FFS-LCD device.

In one embodiment, an optional object of the present invention is to provide an IPS-LCD and / or FFS-LCD device having an improved viewing angle.

In one embodiment, an optional object of the present invention is to provide an IPS-LCD and / or FFS-LCD device with fast response.

In one embodiment, a liquid crystal display device having pixels is implemented according to a first aspect of the present invention, wherein each pixel includes an upper substrate and a lower substrate having a liquid crystal material therebetween, and each pixel also includes an upper substrate and a lower substrate. An electrode structure is included between the substrates. The electrode structure includes electrodes. Each electrode has a polygonal electrode surface and a plurality of electrode edges. When the electrodes have one electrode edge facing the electrode edge of the adjacent electrode, the electrode edge and the electrode edge of the neighboring electrode define an essentially constant distance along the entire electrode edge.

In another embodiment, an electronic device including the above-described liquid crystal display device is implemented according to the second aspect of the present invention.

Their polygonal surface, their position relative to their power source, and their combination allows for better control of the electric field in an IPS-LCD or FFS-LCD device. In particular, it provides better viewing angle control or better response for FFS-LCD devices within the scope of the present invention.

The electrode surface forms a region provided with a conductive material to form an electrode. This can be formed in a manner well known to those skilled in the art of making electrodes for LCD devices. To that end, techniques known in the chip production art can be used. This will not be described further and will be considered as well known to those skilled in the art.

The LCD device of the present invention can be used in various types of LCD devices, such as transflective, reflective, transmissive displays, TV displays, displays for mobile phones, and similar electronic devices such as PDAs.

The various aspects discussed in this patent can be combined to provide additional advantages. The various aspects disclosed in this description can form the basis of one or more divisional patents.

The present invention will be described in detail in the following embodiments with reference to the drawings.

The following description is a description of the best mode for carrying out the invention. This description is intended to illustrate the general principles of the invention and should not be taken as a limiting element. The scope of the invention is optimally determined by the claims.

The proposed electrode structure of the present invention may be useful for IPS-LCDs and FFS-LCDs.

IPS technology shows an improved viewing angle compared to twisted nematic and vertical aligned technologies. IPS is implemented by a striped inter-digital finger electrode structure on the underlying substrate. No electrode is required on the top substrate. This is illustrated well in FIG. 1.

In Fig. 1, a schematic longitudinal cross section is shown which shows the most general features of the IPS-LCD device.

IPS-LCD devices often have a liquid crystal material layer 3 provided between two substrate layers 1, 2 made of glass or transparent polymer material. Usually, there is an upper transparent substrate 1 and a lower transparent substrate 2. An electrode 4 for switching, ie changing the orientation of the liquid crystal in the liquid crystal material 3, is essentially planar on or near one of the substrate layers 1, 2 and on one of the substrate layers 1, 2. Is provided. Usually this electrode 4 is arranged like an interdigital finger electrode in order to provide a separate electrode having mutually different voltages. Usually, these finger electrodes alternately have different potentials or at different voltages. This is illustrated in FIG. 1, where the first group of finger electrodes 4 (1) are at a first voltage level and the second group of finger electrodes 4 (2) are at a second voltage level. The first voltage level may be lower than the second voltage level, so as shown to generate an electric field induced from the first group of finger electrodes 4 (1) to the second group of finger electrodes 4 (2). do. This electric field mainly has electric field lines parallel to the substrate layer 2.

The (nematic) liquid crystal material 3 is usually aligned in a plane between the two substrate layers 1, 2 using a polymer alignment layer. In general, a cross linear polarizer is often located on the substrate layer, whereby one of the linear polarizers is in the rubbing direction of the liquid crystal material to provide a dark state when no voltage is applied to the finger electrode 4. Have an aligned optical polarization axis. If no electric field is generated between the inter-digital finger electrodes 4 (1) and 4 (2) in the pixel, the pixel in the liquid crystal material is distorted (twisted). This results in a phase transition of light entering the device in the lower substrate layer 2 and the pixels appear bright.

Other features of such an IPS-LCD device are well known to those skilled in the art, and further description thereof will be omitted.

One disadvantage of the IPS technique is that the electric field in the region directly above the electrode 4 is very weak, which means that the liquid crystal material 3 is weakly distorted in this region and thus the transmittance in this region is low.

Therefore, a new technique called Fringing Field Switching (FFS) has recently been developed, which is similar to IPS but with improved transmission over the electrodes. The FFS structure has an additional common electrode under the finger structure, which will be described in more detail with reference to FIG. 2.

Figure 2 shows a schematic longitudinal cross section showing the most general features of the FFS-LC device.

This FFS-LCD device is the same as the IPS-LCD device but is provided with a common electrode 6 on the surface of the substrate, usually the lower substrate 2. An insulating layer 5 is provided over the common electrode 6 to electrically separate the common electrode 6 from the electrode 4. The electrode 4 is called a "pixel electrode", and the pixel electrode has essentially the same potential. In practice, the insulating layer 5 usually covers the entire lower substrate 2.

In an FFS LCD, an electric field is applied between the pixel electrode 4 and the common electrode 4. This creates a fringing field (eg FIG. 2) and the area above the electrode 4 is distorted. FFS technology has the advantage of improved light transmittance compared to IPS technology. However, it requires an additional lithography process.

Again, other features of this FFS-LCD device are well known to those skilled in the art, and thus further detailed description thereof will be omitted.

The electrodes 4 in known devices can have different shapes and designs. The most common shape is as shown in Figures 3-5. In FIG. 3, the electrode is comb-shaped, and two comb-shaped electrodes, which may correspond to electrodes 4 (1) and 4 (2) of FIG. 1, are provided in teeth. That is, each tooth of the electrode 4 (1) is located between adjacent ones of the other electrode 4 (2). Thus, the structure shown in FIG. 3 can be applied to the IPS technique shown in FIG. However, this may equally well apply to the FFS technique of FIG. In such FFS embodiments, one of the comb-shaped electrodes may be the common electrode 6 and the other may be the pixel electrode 4.

In Fig. 4 another design of the electrode structure is shown, wherein the teeth of the electrodes 4 (1), 4 (2) (or 4, 6) have a chevron display structure. The chevron display structure is essentially constant in mutual distance between two opposite electrodes 4 (1), 4 (2) (or 4, 6) facing each other.

In Figure 5, the teeth have a zigzag (or "snake") shape. Again, the structure is essentially constant in the mutual distance between two opposite electrodes 4 (1), 4 (2) (or 4, 6) facing each other.

Therefore, various types of electrodes have been tried and many forms have been explored to create an ideal electrostatic field for liquid crystal alignment.

It has been found that electrode structures with polygonal surfaces provide a suitable electric field to support fast response times or improved viewing angles. 6-11, an example of an electrode having a polygonal surface according to the present invention is shown. Also in these embodiments, the electrode surfaces are arranged in a tiled fashion. Suitable designs have equilateral hexagons.

FIG. 6 shows an embodiment of an FFS structure with one pixel with a square common electrode 6 with an insulating layer 5 on top, the polygonal pixel electrode 4 of the invention having a hexagonal surface. 6 shows seven such polygonal pixel electrodes 4. However, the pixels may actually have more pixel electrodes 4, for example around ten. This pixel electrode 4 is arranged in a tile manner, as mentioned. Further, this hexagon is equilateral in this embodiment and has a constant space. In addition, they have the same spacing. In this embodiment, the hexagon is coupled to the common power supply V via an electrode lead 8 providing a voltage V1. The power source V may be a display driver.

The structure of the electrode lead 9 may be as shown in FIG. 6. However, alternatively, it is possible to connect one hexagonal pixel electrode 4 to the power supply V and to connect the hexagons to each other using electrode leads. The electrode lead structure can depend on the desired fringing field. The electrode lead 9 may be made of a transparent material such as ITO so that light transmission through the electrode lead 9 is not blocked.

A characteristic of the tile structure as shown is that the mutual distance between adjacent tiles along the all edges of the pixel electrodes 4 facing the adjacent pixel electrode is essentially constant. That is, each electrode 4 has a polygonal electrode surface and a plurality of electrode edges. The electrodes 4 are arranged such that when an electrode edge faces an electrode edge of an adjacent electrode, that electrode edge and the electrode edge of the adjacent electrode define an essentially constant distance along the entire electrode edge. Although this distance has the same value over the entire pixel surface, this is not essential. This feature can be applied to other polygons. This feature helps to form some form of fringing field between adjacent pixel electrodes 4 towards the common electrode 6 which supports excellent viewing angle action.

In FIG. 7, a further embodiment of the pixel electrode structure of FIG. 6 is shown. Again, the polygonal pixel electrode 4 has a hexagonal outer edge. Again, the polygonal pixel electrode 4 is connected to a power supply V providing a voltage V1 through the electrode lead 9. Again, the power supply V may be a display driver. However, in contrast to FIG. 6, the hexagonal pixel electrode 4 has an opening 7. This opening 7 can be made by removing the corresponding part of the pixel electrode 4, or optionally not making that part. In this embodiment, the opening 7 also has a hexagonal shape. Therefore, the opening 7 in the electrode surface of this embodiment has the same shape as the pixel electrode 4. The opening 7 can be formed in the center of the electrode surface. The opening 7 can have a different shape, such as a circle, square, rectangle, or other polygon.

The opening 7 provides additional space where a fringing field between the pixel electrode 4 and the common electrode 6 is generated. This increases the transmission capacity of light entering the device in the substrate layer 2 (eg FIGS. 1 and 2).

8 also shows an FFS structure. In FIG. 8, electrodes 4 of the same shape as in FIG. 6 are depicted. In the present embodiment, however, different pixel electrodes 4 (1), 4 (2) are connected to different voltages: the first group of electrodes 4 (1) is an electrode lead (V1) providing a voltage V1. 9 (1) is connected to the power supply V (1), and the second group of electrodes 4 (2) is further powered via an electrode lead 9 (2) providing a different voltage V2. Is connected to (V (2)). The power supplies V (1) and V (2) may be display drivers. This structure allows for a change in the direction of the electric field lines of the fringing field in the pixels on more local foundations, thus freeing the effect on the viewing angle of the pixels. In addition, such electrode structures may affect other electro-optic behavior of the pixel, such as response time.

8 shows another power supply V (1), V (2) through pixel electrodes 4 (1), 4 (2), which should have different potentials, through different electrode leads 9 (1), 9 (2). Optionally, the pixel electrode 4 (1) is connected to a power supply V (1) and the pixel electrodes 4 (1) and 4 (2) are coupled to each other so as to be capacitive therebetween. A device is provided and a pixel electrode 4 (2) having a lower potential than the pixel electrode 4 (1) is provided, of course, in this embodiment, the coupling between the voltages V1 and V2 is fixed and the viewing angle is fixed. Less freedom of change

In Figure 9, the embodiments of Figures 7 and 8 are combined. Pixel electrodes 4 (1), 4 (2) having openings 7 are provided. The voltage V1 is maintained at the pixel electrode 4 (1) provided with the opening 7, and the voltage V2 is maintained at the pixel electrode 4 (2). Like the device of FIG. 7, the device of FIG. 9 has more space for the electric field lines between the pixel electrodes 4 (1), 4 (2) and the common electrode 6 so that light transmission capacitance through the pixel is achieved. This is improved.

The present invention can also be applied to an IPS-LCD structure. In Fig. 10, the pixel having the electrode structure of the present invention is shown in the IPS-LCD structure. In this embodiment, several electrodes are held at different voltages V1, V2, V3 provided by three different power sources V (1), V (2), V (3), which may be display devices. In this embodiment, no common electrode is necessary. Therefore, it is possible to create other fringing fields and ways of affecting them. In this way, it is possible to finish further influence on the viewing angle in this type of LCD device.

In Fig. 11, another structure of the polygonal electrode surface for the IPS-LCD device is shown. Again, no common electrode is needed. In this embodiment of the polygonal electrode, the electrodes are fitted in such a way that they are filled with square pixels. In this embodiment, two electrodes 4 (3) having triangular surfaces are coupled to two electrodes 41 (1), 4 (2) having an isosceles trapezoidal surface, which have substantially constant spacing. Thus, again, the feature of the tile structure as shown in FIG. It is essentially constant along all edges of I). In addition, these surfaces are positioned to create square fields or pixels. In this embodiment, different voltages V1, V2, V3 are applied to the electrode surfaces. Thus, electrode 4 (1) is connected to power source V (1), electrode 4 (2) is connected to power source V (2), and electrode 4 (3) is connected to power source Is connected to (V (3)). The power supplies may be display drivers. Again, this makes it possible to vary the other in-plan fields along the edges of their surfaces to further influence the viewing angle in the LCD device of this embodiment type.

11 shows different power sources V (1), V (2), and V (3) through electrodes 4 (1), 4 (2), and 4 (3) that must have different potentials. It shows an embodiment connected to). Optionally, only electrode 4 (1) is connected to power source V (1) and between electrodes 4 (1) and 4 (3) as well as between electrodes 4 (1) and 4 (2). Capacitive elements are provided by their capacitive coupling between and provide an electrode 4 (2) having a lower potential than the electrode 4 (1). Of course, in this embodiment, the power sources V (1) are provided. There is a fixed coupling between), V (2) and between the power sources V (1), V (3), and there is less freedom of changing the viewing angle.

The basic structure of FIG. 11 can also be applied to the FFS structure. That is, the common electrode 6 may be applied below the pixel electrodes 4 (1), 4 (2), 4 (3), and in use, the fringing field may be, for example, as described above with reference to FIG. Similarly, the pixel electrodes 4 are formed between the pixel electrodes 4 (1), 4 (2), and 4 (3) and the common electrode 6.

Next, the pixel electrodes 4 (1), 4 (2), and 4 (3) may have the same voltage (that is, V (1)). However, it may optionally be connected to other power sources V (1), V (2), and V (3) as shown in FIG. As another example, as described above with reference to FIG. 11, only the pixel electrode 4 (1) is connected to the power supply V (1) and the other pixel electrodes 4 (2), 4 (3) are pixels. Capacitively coupled to electrode 4 (1).

In addition, in such an FFS embodiment, the pixel electrodes 4 (1), 4 (2), and 4 (3) may be provided with holes 7 such as the holes 7 shown in FIGS. 7 and 9. have.

The device of the present invention can be used in various LCD displays, such as transflective, reflective, transmissive, TV, mobile telephone or PDA displays.

Although the present invention has been described with reference to examples, this description is not to be construed as limiting. Various modifications to the embodiments of the invention as well as other embodiments will be possible with reference to the description of the invention. Therefore, the appended claims will cover any variations or embodiments as falling within the true scope of the present invention and its legal equivalents.

1 is a schematic cross-sectional view of an IPS-LCD device showing the most general features of this type of device;

2 is a schematic cross-sectional view of an FFS-LCD device showing the most general features of this type of device;

3 is a schematic representation of a typical FFS electrode structure;

4 is a schematic representation of another general FFS electrode structure;

5 is a schematic representation of another general FFS electrode structure;

6 is a plan view of an electrode structure according to an embodiment of the present invention;

7 is a plan view of another electrode structure according to an embodiment of the present invention;

8 is a plan view of another electrode structure according to an embodiment of the present invention;

9 is a plan view showing a combination of the electrode structures of FIGS. 7 and 8;

10 is a plan view of the electrode structure of FIG. 6 with variable potential;

11 shows another electrode structure.

Claims (9)

In a liquid crystal display device having pixels, each pixel includes a lower substrate and an upper substrate having a liquid crystal material therebetween, each pixel also including an electrode structure between the lower substrate and the upper substrate, wherein the electrode structure is Electrodes, each electrode having a polygonal electrode surface and a plurality of electrode edges, the electrodes arranged so that one electrode edge faces an electrode edge of an adjacent electrode and the electrode edge and the electrode edge of the adjacent electrode Is an essentially constant distance along the entire electrode edge. The method of claim 1, And the liquid crystal display device is an in-plane switching device. The method of claim 1, The liquid crystal display device is a fringe field switching device, characterized in that the liquid crystal display device. The method of claim 3, wherein And the electrode has an opening. The method of claim 1, And the electrodes have essentially the same polygonal electrode surface. The method of claim 1, Wherein each electrode has a polygon selected from a group of polygons including triangles, trapezoids, and hexagons. The method of claim 1, And the electrodes are coupled to power sources such that the electrodes have different potentials. An electronic device comprising the liquid crystal display device according to claim 1. The method of claim 8, Wherein said electronic device is one of a transflective type, a reflective type, a transmissive type, a TV, a mobile telephone, and a PDA display.

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