KR20120039924A - Liquid crystal display panel - Google Patents

Abstract

PURPOSE: A liquid crystal display panel is provided to minimize a liquid crystal area which generates reverse twist and simultaneously maximize liquid crystal molecules which move in a fringe electric field direction. CONSTITUTION: A conductive plate comprises a common electrode(110), a pixel electrode(150), and a data electrode(130). The edge of the pixel electrode is bent. A liquid crystal layer(300) is formed between a substrate and the conductive plate. The conductive plate comprises a common electrode, a first insulating film, a data electrode, a second insulating film, and a pixel electrode. The pixel electrode is formed on the second insulating film.

Description

Liquid Crystal Display Panel

The present invention relates to a liquid crystal display panel.

In general, the CRT (or CRT: Cathode Ray Tube) has been the most used display device for displaying image information on the screen, which is inconvenient to use because it is bulky and heavy compared to the display area. .

In addition, with the development of the electronics industry, display devices, which have been limitedly used for TV CRTs, have been widely used in personal computers, notebooks, wireless terminals, automobile dashboards, electronic displays, and the like, and transmit large amounts of image information with the development of information and communication technology. As it becomes possible, the importance of next-generation display devices that can process and implement them is increasing.

Such next-generation display devices should be able to realize light and small, high brightness, large screen, low power consumption, and low price, and one of them has recently attracted attention.

The liquid crystal display (LCD) has excellent display resolution than other flat panel display devices and exhibits a response speed that is higher than that of a CRT when implementing a moving image.

In general, the driving principle of the liquid crystal display device uses the optical anisotropy and polarization of the liquid crystal.

Since the liquid crystal has a long structure, it has a directionality in the arrangement of molecules, and the direction of the molecular arrangement can be controlled by artificially applying an electric field to the liquid crystal.

When the molecular alignment direction of the liquid crystal is arbitrarily adjusted, the molecular arrangement of the liquid crystal is changed, and light polarized by optical anisotropy may be arbitrarily modulated to express image information.

Currently, an active matrix liquid crystal display device (AM-LCD: below Active Matrix LCD, abbreviated as liquid crystal display device) in which a thin film transistor and pixel electrodes connected to the thin film transistor are arranged in a matrix manner has the best resolution and video performance. It is attracting attention.

The liquid crystal display includes a color filter substrate on which a common electrode is formed, an array substrate on which a pixel electrode is formed, and a liquid crystal filled between two substrates. The liquid crystal display is one of active matrix liquid crystal display devices that are mainly used and are twisted nematic (TN). nematic) type liquid crystal display device. The twisted nematic method is a method of driving the liquid crystal director by installing electrodes on two substrates, arranging the liquid crystal directors to be twisted by 90 °, and then applying a voltage to the electrodes.

However, the TN (twisted nematic mode) liquid crystal display has a big disadvantage that the viewing angle is narrow.

Recently, researches on liquid crystal displays employing a variety of new methods have been actively conducted to solve the narrow viewing angle problem. In this scheme, an in-plane switching (IPS) using a transverse electric field is used. mode and Fringe Field Switching mode (FFS) have been developed. In particular, the fringe field switching mode has a wide field of view and has a high transmittance characteristic unlike the transverse electric field mode.

In the fringe field switching mode liquid crystal display, the common electrode and the pixel electrode are formed of a transparent conductor, and the gap between the common electrode and the pixel electrode is formed to be narrower than the gap between the upper and lower substrates, and the fringe field is formed on the common electrode and the pixel electrode. By forming a fringe filed, all liquid crystal molecules present on the electrodes are operated.

This invention solves the subject which can improve a pixel aperture ratio and liquid crystal efficiency.

The present invention,

A substrate;

A conductive plate including a common electrode, a bent pixel electrode, and a data electrode;

A liquid crystal display panel including a liquid crystal layer formed between the substrate and the conductive plate is provided.

The conductive plate may include a common electrode formed on the substrate; A first insulating film covering the common electrode and formed on the substrate; A data electrode formed on the first insulating film; A second insulating film covering the data electrode and formed in the first insulating film; And a pixel electrode formed on the second insulating film and having an edge bent.

The common electrode is composed of one metal plate, and the pixel electrode is composed of a plurality of metal stripes.

The metal stripes may have a horizontal structure arranged along the X axis direction of the common electrode or a vertical structure arranged along the Y axis direction of the common electrode.

In addition, the metal stripes are arranged with a slit angle inclined about 60 to 87 degrees with respect to the X or Y axis of the common electrode.

In addition, the width of the metal stripes and the distance between adjacent metal stripes are 2um-90um.

In addition, the edges of the metal stripes are bent with a slit angle of 45 to 90 degrees.

The common electrode and the pixel electrode are made of transparent electrode oxide.

In addition, the liquid crystal layer covers the pixel electrode and is formed on the second insulating layer.

In addition, a cover substrate is positioned on the liquid crystal layer, and a polarizing plate is positioned on the substrate on which the common electrode is formed and the cover substrate.

Since the liquid crystal display panel according to the present invention has a pixel electrode region in which the pixel electrode is bent at the edge, the liquid crystal region causing a reverse twist by the common electrode for driving the FFS-LCD and the fringe electric field generated when the voltage is applied to the pixel electrode. With this minimized, liquid crystal molecules moving in the direction of the fringe electric field can be maximized.

Therefore, the liquid crystal display panel according to the present invention can improve the pixel aperture ratio and liquid crystal efficiency, solve the problem of wide viewing angle transmittance, and enable the development of high efficiency LCD, and realize the low voltage, high speed response LCD while maintaining the dynamic stability of liquid crystal molecules. There is also a possible effect.

1 is a conceptual cross-sectional view for explaining a pixel area of a liquid crystal display panel according to the present invention.
2 is a conceptual plan view illustrating a pixel area of a liquid crystal display panel according to the present invention.
3 is a conceptual cross-sectional view for explaining a pixel region of a comparative example of the present invention.
4 is a transmittance characteristic diagram of a comparative example of the present invention;
5 is a transmittance characteristic diagram of a liquid crystal display panel of the present invention.
6 is a direction profile graph of liquid crystal molecules of a liquid crystal display panel of the present invention.
7 is a direction profile graph of liquid crystal molecules of a comparative example of the present invention.
8 is a graph measuring voltage and transmittance of a liquid crystal display panel and a comparative example of the present invention.
9 is a conceptual plan view illustrating another example of a pixel area of a liquid crystal display panel according to the present invention.

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

1 is a conceptual cross-sectional view for describing a pixel area of a liquid crystal display panel according to the present invention, and FIG. 2 is a conceptual plan view for explaining a pixel area of a liquid crystal display panel according to the present invention.

The liquid crystal display panel according to the present invention includes a substrate 100; A conductive plate including a common electrode 110, a pixel electrode 150 having a bent edge, and a data electrode 130; It is configured to include a liquid crystal layer 300 formed between the substrate 100 and the conductive plate.

That is, as shown in FIG. 1, the conductive plate may include a common electrode 110 formed on the substrate 100; A first insulating film 120 covering the common electrode 110 and formed on the substrate 100; A data electrode 130 formed on the first insulating layer 120; A second insulating film 140 covering the data electrode 130 and formed on the first insulating film 120; The pixel electrode 150 is formed on the second insulating layer 140 and has curved edges.

In this case, the common electrode 110 has a plate shape and is composed of one metal plate.

The liquid crystal layer 300 covers the pixel electrode 150 and is formed on the second insulating layer 140.

In addition, the first insulating layer 120 is for insulating between the common electrode 110 and the data electrode 130.

In addition, the second insulating layer 140 serves as a passivation layer to insulate the data electrode 130 and the pixel electrode 150.

In addition, the pixel electrode 150 is formed at an overlapping position corresponding to the common electrode 110, and the data electrode 130 is not overlapped with the pixel electrode 150 and the common electrode 110. not.

In addition, the pixel electrode 150 and the common electrode 110 may be formed of a transparent electrode oxide such as indium tin oxide (ITO).

In addition, the rubbing direction of the liquid crystal layer 300 may be the same as the field direction.

In addition, the pixel electrode 150 may have a slit form and may be formed of a plurality of metal stripes.

At this time, as shown in FIG. 2, the width L of the metal stripe W of the pixel electrode 150 and the distance L between adjacent metal stripes may be about 2 μm to about 90 μm.

Here, when the width L of the metal stripe and the distance L between adjacent metal stripes are outside the numerical range, driving characteristics may deteriorate and driving of the liquid crystal display panel may be difficult.

In addition, the width W of the metal stripe preferably has a smaller value than the distance L between adjacent metal stripes.

In addition, the metal stripes of the pixel electrode 150 are formed along the X-axis direction of the common electrode 110 and have a slit angle ΘA inclined by about 60 to 87 degrees with respect to the X axis of the common electrode 110. Can be arranged with

In addition, edges of the metal stripes of the pixel electrode 150 are bent.

In this case, the edges of the metal stripes of the pixel electrode 150 may have a slit angle θE of 45 to 90 degrees to minimize reverse regions in which liquid crystals are arranged in a direction different from that of an active region. It is preferable to have it bent.

In other words, if the slit angle of the edges of the metal stripes of the pixel electrode 150 is out of the range, the driving characteristics are deteriorated because the reverse area becomes larger.

Therefore, the liquid crystal display panel according to the present invention includes the pixel areas for FFS (Fringe Field Switching) in which the pixel electrode 150 is bent, so that the generation area of the noise electric field near the edge of the pixel electrode 150 is minimized. The liquid crystal molecules in this region are twisted in the same direction ('a' direction) as the liquid crystal molecules in the pixel.

That is, unstable dark disclination lines (DLs) and reverse twisted regions are not generated in one pixel, and the overall behavior of liquid crystal molecules is dynamically maintained.

Therefore, the liquid crystal display panel according to the present invention has a pixel electrode region ('151' in FIG. 2) in which the pixel electrode is bent at the edge, so that the fringe generated when the voltage is applied to the common electrode and the pixel electrode for driving the FFS-LCD. By the electric field, liquid crystal molecules moving in the direction of the fringe electric field can be maximized while the liquid crystal region causing the reverse twist is minimized.

As a result, the liquid crystal display panel according to the present invention can improve the pixel aperture ratio and liquid crystal efficiency, solve the problem of wide viewing angle transmittance, and enable the development of high efficiency LCD, and realize the low voltage, high speed response LCD while maintaining the dynamic stability of liquid crystal molecules. There is also a possible advantage.

On the other hand, the length and width of the bent pixel electrode region ('151' of FIG. 2) formed at the edge of the pixel electrode preferably has a range of about 1um-10um.

Here, the driving characteristics may deteriorate outside this range.

In the present invention, as shown in the pixel region of FIG. 2, the metal stripes of the pixel electrode are horizontal structures arranged along the X-axis direction of the common electrode 110, or as in the pixel region of FIG. It is preferable that it is a vertical structure arranged along the Y-axis direction of.

In addition, referring to FIG. 1, the cover substrate 200 is positioned on the liquid crystal layer 300, the first polarizing plate 310 is positioned on the substrate 100, and the cover substrate 200 is formed on the liquid crystal layer 300. The first polarizer 320 may be located.

Here, the transmission axes of the first and second polarizing plates 310 and 320 are perpendicular to each other.

3 is a conceptual cross-sectional view for explaining a pixel region of a comparative example of the present invention, and FIG. 4 is a transmittance characteristic diagram of the comparative example of the present invention.

In the pixel region of the comparative example, the edge of the pixel electrode 15 is not bent as compared with the pixel region of the liquid crystal display panel of the present invention.

Therefore, the comparative example is a wide viewing angle liquid crystal display panel driven by a fringe electric field, and because the pixel electrode 15 has a slit shape and the common electrode 10 has a plate shape, A noise electric field is generated, which destabilizes the dynamic stability of the liquid crystal.

Such a noise electric field generates a twist behavior (behavior in the 'a' direction) and a reverse twist behavior (behavior in the 'b' direction) in the active region in the pixel.

In the vicinity of the boundary where the reverse twist behavior is reversed to the twist behavior, the liquid crystal molecules are not moved in any direction, and as shown in FIG. 4, they form a dark disclination line (DLs) and are dynamic. You will have a very uneasy state.

In fact, when a driving voltage or higher voltage is applied, unstable liquid crystal molecules penetrate into the pixel electrode in such a region, thereby greatly reducing the transmittance in the panel.

These areas also adversely affect LCD electro-optical properties, such as increased drive voltage and response time in the panel.

That is, in the case of the wide viewing angle FFS-LCD using the lower fringe electric field, a strong noise electric field having a different direction from the inside and the electric field is generated around the edge of the pixel electrode.

Therefore, in the liquid crystal display panel, a reverse twist zone, which is an unstable liquid crystal behavior region, is generated by this electric field, which adversely affects the LCD electro-optical characteristics.

As a result, as described above, the present invention has an edge structure of the bent pixel electrode for minimizing such an area, thereby maximizing liquid crystal molecules moving in the electric field direction while minimizing an area causing reverse twist.

5 is a transmittance characteristic diagram of the liquid crystal display panel of the present invention, Figure 6 is a direction profile graph of the liquid crystal molecules of the liquid crystal display panel of the present invention, Figure 7 is a direction profile graph of the liquid crystal molecules of the comparative example of the present invention.

As shown in FIG. 5, the liquid crystal display panel according to the present invention has the pixel electrode region 151 bent at the edge of the pixel electrode 151, thus generating a noise electric field near the edge of the pixel electrode 150. As the area is minimized, the liquid crystal molecules in this region are twisted in the same direction as the liquid crystal molecules inside the pixel.

Accordingly, it can be seen from FIG. 5 that unstable dark disclination lines (DLs) and reverse twisted regions are not generated in the pixel, and the overall behavior of the liquid crystal molecules is dynamically maintained. Able to know.

6 and 7 are director profile data of liquid crystal molecules near a pixel edge when a driving voltage is applied to the liquid crystal display panel and the comparative example of the present invention, and the liquid crystal display panel of the present invention is shown in FIG. It can be seen that the reverse twist region and the black disclination line do not occur in all of the 'A' region, the 'B' region, and the 'C' region of the pixel electrode 150.

On the other hand, as shown in FIG. 7, in the comparative example, a reverse twist region occurred in the 'B' region and the 'C' region of the pixel electrode 150.

That is, in the liquid crystal display panel of the present invention, the liquid crystal array is stable even at the edge region of the pixel electrode 150, but in the comparative example, the liquid crystal array is unstable at the edge region of the pixel electrode, thereby generating a reverse twisted region.

8 is a graph measuring voltage and transmittance of a liquid crystal display panel and a comparative example of the present invention.

This graph shows the voltage and transmittance curves (C) of the liquid crystal display panel of the present invention having the pixel electrodes with curved areas at the edges, and the voltage and transmittance curves (C) of the comparative example with pixel electrodes with no curved areas at the edges. )to be.

In the comparative example, the transmittance characteristic rapidly deteriorates when a high voltage is applied above the driving voltage, whereas the liquid crystal display panel of the present invention exhibits a stable VT curve characteristic in which the transmittance characteristic does not decrease even when a high voltage is applied above the driving voltage. .

In fact, the edge region of the pixel electrode of the liquid crystal display panel structure of the comparative example has an adverse effect on the electro-optical characteristics of the LCD, such as an increase in driving voltage and a decrease in transmittance, and in order to minimize such an area, a black matrix (BM) It should increase the shading area such as

In this case, the decrease in the LCD aperture ratio due to the portion covered by the black matrix is a factor that directly reduces the transmittance in the panel.

Therefore, the pixel electrode having the bent edge shape as shown in the present invention can minimize the adverse effects on the electro-optic properties, thereby enabling high efficiency and high aperture ratio FFS-LCD.

At the same time, the dynamic characteristics of the unstable liquid crystal near the pixel edges disappear, and low-voltage, high-speed LCD can be realized at the same time.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (10)

A substrate;
A conductive plate including a common electrode, a bent pixel electrode, and a data electrode;
And a liquid crystal layer formed between the substrate and the conductive plate.
The method according to claim 1,
The conductive plate,
A common electrode formed on the substrate;
A first insulating film covering the common electrode and formed on the substrate;
A data electrode formed on the first insulating film;
A second insulating film covering the data electrode and formed in the first insulating film;
And a pixel electrode formed on the second insulating film and having an edge bent.
The method according to claim 2,
The common electrode is composed of one metal plate, and the pixel electrode is composed of a plurality of metal stripes.
The method according to claim 3,
The metal stripes,
Or a horizontal structure arranged along the X-axis direction of the common electrode,
Or a vertical structure arranged along the Y-axis direction of the common electrode.
The method of claim 4,
The metal stripes,
And a slit angle inclined about 60 to 87 degrees with respect to the X or Y axis of the common electrode.
The method according to claim 3,
And a distance between the widths of the metal stripes and the adjacent metal stripes is 2um-90um. The method according to claim 3,
The edges of the metal stripes are bent with a slit angle of 45 to 90 degrees.
The method according to claim 1,
Material of the common electrode and the pixel electrode,
A liquid crystal display panel which is a transparent electrode oxide.
The method according to claim 3,
The liquid crystal layer,
And a liquid crystal display panel covering the pixel electrode and formed in the second insulating film.
The method according to claim 1,
A liquid crystal display panel is disposed on the liquid crystal layer, and a polarizing plate is disposed on the substrate and the substrate on which the common electrode is formed.

Images