KR20020056618A - Liquid Crystal Display Panel for In-Plane Switching - Google Patents

Abstract

PURPOSE: An in-plane switching mode liquid crystal display panel is provided to remove after sticking or smear caused by DC voltage so as to improve picture quality and reliability of an in-plane switching liquid crystal display. CONSTITUTION: An in-plane switching mode liquid crystal display panel includes upper and lower substrates(300,200), a liquid crystal layer(113) interposed between the upper and lower substrates, a gate line and a common line formed on the lower substrate, and a data line(101) formed on the lower substrate, intersecting the gate line to define a pixel region. The liquid crystal display panel further includes a thin film transistor formed on the gate line or on a predetermined portion of the pixel region, a common electrode(109) and a data electrode(108) formed in the pixel region to generate horizontal field, and a transparent conductive layer(112) formed on the upper substrate. The conductive layer is in a floating state.

Description

Liquid Crystal Display Panel for In-Plane Switching

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transverse electric field type liquid crystal display panel. In particular, a transverse electric field type liquid crystal display having improved image quality and reliability by solving a problem of a panel generated by a direct current signal applied between a data electrode and a common electrode in a transverse electric field mode. It is about the panel.

In recent years, a large area has been strongly demanded in a thin film transistor liquid crystal display panel (TFT LCD), which is widely used in portable televisions and notebook computers. However, the above-described TFT LCD has a problem in that contrast ratio is changed depending on the viewing angle. In order to solve this problem, various liquid crystal display panels, such as a twisted nematic liquid crystal display panel equipped with an optical compensation plate, a multi-domain liquid crystal display panel, have been proposed. It is difficult to solve the problem that the contrast ratio decreases and the color changes depending on the viewing angle.

In order to realize a wide viewing angle, a transverse electric field type liquid crystal display panel which controls the arrangement of liquid crystals by an electric field parallel to the substrate has been proposed.

1 and 2 are plan views illustrating a conventional transverse electric field type liquid crystal display panel, and FIG. 2 is a cross-sectional view taken along line AA ′ of FIG. 1. As shown in the figure, the gate wiring 1 and the data wiring 2 are formed on the lower substrate 10 to divide the lower substrate 10 into a plurality of pixel regions. In the drawing, only one pixel region is shown for convenience. The common wiring 3 is arranged in parallel to the gate wiring 1 in the pixel region, and at the intersection of the gate wiring 1 and the data wiring 2, the gate electrode 5, the gate insulating film 12, and the semiconductor layer A thin film transistor composed of 15, source electrode 6, and drain electrode 7 is formed. In the pixel region, the data electrode 8 and the common electrode 9 are formed in parallel with the data wiring 2. The data electrode 8 has a region overlapping with the common wiring 3 and the common electrode 9 to form a storage capacitor. The common electrode 9 is connected to the common wiring 3, and the data electrode 8 is formed on the gate insulating layer 12 to be connected to the drain electrode 7. The passivation layer 13 is formed on the thin film transistor, the data electrode 8, and the gate insulating layer 12.

A light blocking layer (BM) / color filter layer / overcoating layer / alignment layer 21 is formed on the upper substrate 20, and the liquid crystal layer 22 is formed between the two substrates 10 and 20.

Although not shown in the drawings, polarizers for linearly polarizing the transmitted light are provided on the outer surfaces of the two substrates 10 and 20, and an alignment layer is formed on the inner surfaces of the two substrates 10 and 20 so as to contact the liquid crystal layer. The orientation direction of the layer is determined.

When no voltage is applied in the transverse electric field type liquid crystal display panel having the above structure, the liquid crystal molecules in the liquid crystal layer 22 are aligned in accordance with the alignment direction of the alignment layer, but the voltage between the common electrode 9 and the data electrode 8 is increased. When applied, a transverse electric field parallel to the surface of the lower substrate 10 is generated between the common electrode 9 and the data electrode 8 so that the liquid crystal molecules in the liquid crystal layer 22 are switched by the transverse electric field. The common electrode 9 and the data electrode 8 are oriented in a direction substantially perpendicular to the extending direction.

That is, the liquid crystal molecules oriented in the liquid crystal layer 22 rotate in a state parallel to the substrate along the transverse electric field, thereby controlling the amount of light passing through the liquid crystal layer 22. At this time, since gray scale is driven while the liquid crystal molecules are parallel to the substrate, gray level inversion does not occur in the vertical and horizontal viewing angle directions, and thus the difference in light transmittance according to the viewing angle is reduced. do.

By forming a conductive transparent electrode on the upper substrate side of the liquid crystal display panel, even if the polarization of impurities due to the direct current voltage applied between the data electrode and the common electrode occurs instantaneously, evenly dispersed and forced discharge all over the upper substrate side It is an object of the present invention to provide a transverse electric field type liquid crystal display panel having high image quality and reliability by removing afterimages or stains caused by voltage.

1 is a plan view showing a conventional transverse electric field type liquid crystal display panel

FIG. 2 is a cross-sectional view taken along the line AA ′ of FIG. 1.

3 is a conceptual diagram of FIG. 2, illustrating a mechanism of generating an afterimage or a stain on an upper substrate side of a liquid crystal display panel; FIG.

4 is a plan view of a transverse electric field type liquid crystal display panel according to an embodiment of the present invention.

5 is a cross-sectional view taken along the line A-A 'of FIG.

FIG. 6 is a conceptual diagram of FIG. 5, illustrating a mechanism for preventing afterimage or spots occurring on an upper substrate side of a liquid crystal display panel.

* Explanation of symbols for main parts of the drawings

100: gate wiring 101: data wiring

102 common wiring 103 gate electrode

104: gate insulating film 105: semiconductor layer

106: source electrode 107: drain electrode

108: data electrode 109: common electrode

110: shield

111: material layer composed of light blocking layer, color filter layer and overcoating layer

112: conductive film 113: liquid crystal layer

114: alignment layer 200: lower substrate

300: upper substrate

TFT-LCD (thin film transistor-liquid crystal display) has active TFT attached to each pixel area, so each pixel area can be driven independently and directly supply select and non-selection signals to be applied to the pixel area. .

AC inversion driving method such as data inversion driving method that alternately applies data signal to (+) signal and (-) signal according to gate wiring and data wiring based on one pixel area, Examples include field inversion, line inversion, column inversion, and dot inversion.

As described above, the LCD operates AC, which prevents the deterioration of the liquid crystal due to the application of the DC voltage, and the light transmittance is changed with time due to the variation of the pixel voltage according to the field caused by the DC component among the voltages applied to the liquid crystal. This prevents flicker, which is a changing phenomenon, and prevents afterimage effects in which traces of the original image remain even when the screen is changed because DC charge is applied and residual charge does not disappear for a long time due to one electrode. In addition, the afterimage effect may occur even when charge is trapped in the insulating film used as the protective film or depending on the type of the alignment film.

Field inversion during the data inversion driving is a method of inverting and applying the polarity of the data signal by alternating the (+) signal and the (-) signal according to the field over the entire TFT-LCD. Capacitive coupling causes negative asymmetry of the pixel voltage, causing flicker in the entire area of the screen. Line inversion is a method of driving a data signal alternately by applying a (+) signal and a (-) signal in accordance with the gate wiring so that the polarities of voltages applied to the pixels of the odd-numbered gate lines and the pixels of the even-numbered gate lines are opposite to each other. Therefore, the flicker generated in the two adjacent pixels in the vertical direction is canceled out to reduce each other. Column inversion causes the flicker generated in two horizontally adjacent pixels to cancel each other out and reduce. The dot inversion causes polarity of pixels adjacent to each other in the horizontal and vertical directions to be reversed so that the flicker generated in the pixels in the horizontal and vertical directions cancels and decreases each other.

However, the voltage variation caused by the capacitive coupling between the gate and the source / drain is corrected by the voltage applied to the common electrode. However, since the liquid crystal capacitance is a function of the data voltage, it cannot be corrected for the data voltage in all cases. The case where a direct current component exists exists.

In addition, an inversion of the polarity of the data signal does not occur clearly, and thus a case where a direct current component exists.

This problem becomes more serious in an In-Plane Switching (IPS) mode in which a liquid crystal is driven by an electric field between a counter electrode, that is, a data electrode and a common electrode, arranged horizontally.

In general, the IPS mode does not apply an electric field to the upper substrate side in order not to affect the horizontal electric field, and does not form a conductor film connecting the entire upper substrate side.

As described above, when a DC voltage is applied because an inversion voltage is not applied accurately between the opposite electrodes, impurity ions of the alignment layer or the liquid crystal are polarized around the counter electrode formed on the lower substrate side. For example, when a positive DC voltage is applied between the counter electrodes, anions are polarized around the counter electrodes, and thus cations are polarized with counter ions on the upper substrate side. This is shown schematically in FIG. 3. FIG. 3 is a conceptual diagram of FIG. 2 illustrating an afterimage or a stain generation mechanism occurring on an upper substrate side of a liquid crystal display panel.

At this time, the ions polarized around the electrode on the lower substrate side can be reset by the newly inverted voltage applied between the counter electrodes at every moment, but the ions polarized around the electrode on the upper substrate side do not have a conductor that can be a dispersion path of the ions. It is not possible to remove polarized ions by applying a special forcing voltage to the upper substrate side.

Therefore, when the voltage applied between the counter electrodes is kept in a predetermined pattern for a long time, a slightly different amount of voltage is applied to the upper substrate side by the impurity ions of the alignment film or the liquid crystal according to the intensity of the signal applied between the counter electrodes to form an afterimage. They may be expressed or appear as additional stains. That is, when a large amount of DC voltage applied between the counter electrodes is applied, a large amount of DC voltage is applied to the upper substrate side, and a small amount of DC voltage is applied to the upper substrate side when the DC voltage applied between the opposing electrodes is applied a small amount of voltage. This is applied, which leaves behind images and stains.

That is, in the IPS mode of the TFT-LCD according to the related art described above, since there is only an insulator and no conductor at the upper substrate side, when a DC voltage is applied during driving, charges due to the DC voltage may be discharged or dispersed. The pass is disadvantageous than the twisted nematic (TN) mode, which causes charge to accumulate with a constant potential and remain as an afterimage or stain.

Therefore, the present invention has been made to solve the above problems, and by forming a transparent electrode having conductivity on the upper substrate side of the liquid crystal display panel, even if a polarization phenomenon due to the application of DC voltage occurs instantaneously evenly throughout the upper substrate side It is an object of the present invention to provide a transverse electric field type liquid crystal display panel having high image quality and reliability by removing afterimages or stains caused by DC voltage by dispersive and forced discharge.

Features of the transverse electric field type liquid crystal display panel according to the present invention for achieving the above object is an upper substrate and a lower substrate; A liquid crystal layer interposed between the upper substrate and the lower substrate; A gate wiring and a common wiring formed on the lower substrate; A data line arranged to intersect the gate line to define a pixel area; A thin film transistor formed on any one of the upper portion of the gate wiring and a predetermined region of the pixel region; A common electrode and a data electrode formed in the pixel area to generate a transverse electric field; It is configured to include a conductive film formed on the inner surface of the upper substrate.

Another aspect of the transverse electric field type liquid crystal display panel according to the present invention for achieving the above object is an upper substrate and a lower substrate; A liquid crystal layer interposed between the upper substrate and the lower substrate; A gate wiring line and a common wiring line formed side by side on the lower substrate; A data line formed to intersect the gate line to define a pixel area; A thin film transistor formed on any one of the upper portion of the gate wiring and a predetermined region of the pixel region; A data electrode formed in the pixel region and receiving a data signal voltage from the thin film transistor; A common electrode formed in the pixel region and generating a transverse electric field together with the data electrode; It is configured to include a conductive film formed on the inner surface of the upper substrate to pass the charge (pass).

Other objects, features and advantages of the present invention will become apparent from the detailed description of the embodiments with reference to the accompanying drawings.

A preferred embodiment of the transverse electric field type liquid crystal display panel according to the present invention will be described with reference to the accompanying drawings.

4 is a plan view of a transverse electric field type liquid crystal display panel according to an embodiment of the present invention, and FIG. 5 is a cross-sectional view taken along line AA ′ of FIG. 4.

As shown in the drawing, the gate wiring 100 and the data wiring 101 are formed on the lower substrate 200 to divide the lower substrate 200 into a plurality of pixel regions. In the drawing, only one pixel region is shown for convenience.

The common wiring 102 is arranged in parallel to the gate wiring 100 in the pixel area, and the intersection of the gate wiring 100 and the data wiring 101 to be formed later, that is, the predetermined area or the gate wiring 100 of the pixel area. The gate electrode 103 is formed on the upper portion, and the common electrode 109 is formed together to be connected to the common wiring 102 and the common wiring 102.

A gate insulating film 104 is formed on the entire surface including the gate electrode 103 and the common electrode 109 so that the gate electrode 103, the gate insulating film 104, the semiconductor layer 105, and the source electrode 106 are formed. A thin film transistor composed of the drain electrode 107 is formed.

The data wiring 101 is formed together to be connected to the source electrode 106, and is connected to the drain electrode 107 and is parallel to the common electrode 109 on the gate insulating film 104 in the pixel region. 108 are formed together.

The data electrode 108 has a region overlapping with the common wiring 102 and the common electrode 109 to form a storage capacitor. That is, the common wiring 102 forms a capacitor together with the data electrode 101 with the gate insulating film 104 interposed therebetween, so that the data applied to the data electrode 101 while the gate signal voltage (scan signal voltage) is not applied. Maintain signal voltage.

The passivation layer 110 is formed on the thin film transistor, the data electrode 108 and the gate insulating layer 104.

In addition, the conductive layer 112 is formed on the upper substrate 300 by using a material layer 111 including a light blocking layer (BM) / color filter layer / overcoating layer and a transparent electrode such as indium tin oxide (ITO). The liquid crystal layer 113 is formed between the two substrates 200 and 300.

Although not shown in the drawings, polarizers for linearly polarizing the transmitted light are provided on the outer surfaces of the two substrates 200 and 300, and the alignment layer 114 is disposed on the inner surface of the upper substrate 300 to contact the liquid crystal layer 113. It is formed to determine the alignment direction of the liquid crystal layer 113. The alignment layer may be further formed on the lower substrate 200.

FIG. 6 is a view conceptually illustrating FIG. 5, and illustrates a mechanism for preventing afterimages and stains occurring on the upper substrate 300 of the liquid crystal display panel.

When a transverse electric field is applied between the common electrode 109 and the data electrode 108, due to an imbalance between the opposite electrodes of the data electrode 108, that is, the inversion voltage of the common electrode 109 and the data electrode 108. Even if a DC voltage is applied, the remaining components will be spread over the entire upper substrate 300 side or a considerably wider range by the conductive film 112 formed on the upper substrate 300 side. It can prevent occurrence.

In this case, the conductive film 112 on the upper substrate 300 side is floated without applying an electric field at all, thereby distorting the horizontal electric field on the lower substrate 200 side, that is, the transverse electric field.

The transverse electric field type liquid crystal display panel according to the present invention as described above has the following effects.

When a lateral electric field is applied to the common electrode and the data electrode, a direct current voltage is applied between the data electrode and the common electrode so that a polarization phenomenon due to an alignment film or impurity ions occurs on the upper substrate side of the panel. By immediately dispersing and forcibly distributing the entire upper substrate side to remove the afterimage or stains caused by the DC voltage it can implement a transverse electric field type liquid crystal display panel with high image quality and reliability.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments, but should be defined by the claims.

Claims (15)

Upper and lower substrates; A liquid crystal layer interposed between the upper substrate and the lower substrate; A gate wiring and a common wiring formed on the lower substrate; A data line arranged to intersect the gate line to define a pixel area; A thin film transistor formed on any one of the upper portion of the gate wiring and a predetermined region of the pixel region; A common electrode and a data electrode formed in the pixel area to generate a transverse electric field; And a conductive film formed on an inner side surface of the upper substrate. The transverse electric field liquid crystal display panel according to claim 1, wherein the conductive film is a transparent conductive film. The transverse electric field type liquid crystal display panel of claim 1, wherein the conductive layer is in a floating state in which an electric field is not applied. The thin film transistor of claim 1, wherein the thin film transistor A gate electrode formed together with the gate wiring; A gate insulating film formed on the entire surface including the gate electrode; And a semiconductor layer and a source / drain electrode sequentially formed in a predetermined region on the gate insulating film. The transverse electric field liquid crystal display panel of claim 1, wherein a color filter layer is formed on the upper substrate. The transverse electric field liquid crystal display panel according to claim 1, wherein polarizers for linearly polarizing light transmitted are provided on outer surfaces of the upper substrate and the lower substrate. The transverse electric field liquid crystal display of claim 1, wherein an alignment layer is formed on at least one of an inner side surface of the upper substrate and an inner side surface of the lower substrate to determine an alignment direction of the liquid crystal layer. panel. Upper and lower substrates; A liquid crystal layer interposed between the upper substrate and the lower substrate; A gate wiring line and a common wiring line formed side by side on the lower substrate; A data line formed to intersect the gate line to define a pixel area; A thin film transistor formed on any one of the upper portion of the gate wiring and a predetermined region of the pixel region; A data electrode formed in the pixel region and receiving a data signal voltage from the thin film transistor; A common electrode formed in the pixel region and generating a transverse electric field together with the data electrode; And a conductive film formed on an inner surface of the upper substrate to pass electric charges. The transverse electric field liquid crystal display panel according to claim 8, wherein the conductive film is a transparent conductive film. The transverse electric field type liquid crystal display panel of claim 8, wherein the conductive layer is in a floating state in which an electric field is not applied. The thin film transistor of claim 8, wherein the thin film transistor is A gate electrode formed together with the gate wiring; A gate insulating film formed on the entire surface including the gate electrode; And a semiconductor layer and a source / drain electrode sequentially formed in a predetermined region on the gate insulating film. The transverse electric field liquid crystal display panel of claim 8, wherein a color filter layer is formed on the upper substrate. The transverse electric field type liquid crystal display panel according to claim 8, wherein polarizers for linearly polarizing light transmitted are provided on outer surfaces of the upper substrate and the lower substrate. The transverse electric field liquid crystal display of claim 8, wherein an alignment layer is formed on at least one of an inner side surface of the upper substrate and an inner side surface of the lower substrate to determine an alignment direction of the liquid crystal layer. panel. Upper and lower substrates; A liquid crystal layer interposed between the upper substrate and the lower substrate; A gate wiring line and a common wiring line formed side by side on the lower substrate; A data line formed to intersect the gate line to define a pixel area; A common electrode connected to the common wiring and formed on the pixel area; A gate electrode connected to the gate line and formed on one of a predetermined region on the pixel area and on the gate line; A gate insulating film formed on the entire surface including the gate electrode and the common electrode; A semiconductor layer formed on a predetermined region of the gate insulating film; A source electrode and a drain electrode formed on the semiconductor layer so as to be connected to the data line; A data electrode connected to the drain electrode to apply a transverse electric field together with the common electrode; And a conductive film formed on an inner surface of the upper substrate to pass charge.