CN109298571B

CN109298571B - Liquid crystal display device and driving method

Info

Publication number: CN109298571B
Application number: CN201811273955.9A
Authority: CN
Inventors: 钟德镇; 苏子芳; 沈家军
Original assignee: InfoVision Optoelectronics Kunshan Co Ltd
Current assignee: InfoVision Optoelectronics Kunshan Co Ltd
Priority date: 2018-10-30
Filing date: 2018-10-30
Publication date: 2021-07-13
Anticipated expiration: 2038-10-30
Also published as: CN109298571A

Abstract

A liquid crystal display device and a driving method thereof, the liquid crystal display device comprises a first substrate, a second substrate and a liquid crystal layer arranged between the first substrate and the second substrate, a common electrode is arranged on the first substrate, a first alignment film is arranged on the first substrate close to the liquid crystal layer and has a first alignment direction, a second alignment film is arranged on the second substrate close to the liquid crystal layer and has a second alignment direction, the first alignment direction is vertical to the second alignment direction, the liquid crystal layer adopts positive liquid crystal molecules, a first electrode and a second electrode which are arranged on the same layer and are mutually insulated are also arranged on the first substrate, the first electrode comprises a plurality of first electrode strips which are electrically connected together, the second electrode comprises a plurality of second electrode strips which are electrically connected together, and the plurality of first electrode strips and the plurality of second electrode strips are mutually parallel, spaced and alternately arranged, each first electrode bar and each second electrode bar respectively cover one row or one column of pixel units.

Description

Liquid crystal display device and driving method

Technical Field

The present invention relates to the field of liquid crystal display technologies, and in particular, to a liquid crystal display device and a driving method thereof.

Background

A Liquid Crystal Display (LCD) has advantages of good picture quality, small size, light weight, low driving voltage, low power consumption, no radiation, and relatively low manufacturing cost, and is dominant in the field of flat panel displays.

The current display device gradually develops towards the direction of wide viewing angle, and no matter the application of mobile phone terminal, desktop display or notebook computer, besides the requirement of wide viewing angle, in many occasions, the display device is also required to have the function of switching between wide viewing angle and narrow viewing angle.

At present, there are several ways to switch between a wide viewing angle and a narrow viewing angle of a liquid crystal display device.

The first is realized by attaching a shutter shielding film on the display screen, and when peep prevention is needed, the view angle can be reduced by shielding the screen by the shutter shielding film. However, this method requires additional preparation of the louver films, which causes great inconvenience to users, and one louver film can only realize one viewing angle, and once the louver films are attached, the viewing angle is fixed, which can only realize the narrow viewing angle mode.

The second is to arrange a dual light source backlight system in the lcd device for adjusting the viewing angle of the lcd device, the dual light source backlight system is composed of two stacked light guide plates combined with an inverse prism sheet, the top light guide plate (LGP-T) combined with the inverse prism sheet changes the direction of the light so that the light is limited in a relatively narrow angular range, thereby realizing the narrow viewing angle of the lcd device, while the bottom light guide plate (LGP-B) combined with the inverse prism sheet functions to realize the wide viewing angle of the lcd device. However, such a dual-light source backlight system increases the thickness and cost of the liquid crystal display device, and is not suitable for the trend of thinning the liquid crystal display device.

Disclosure of Invention

The invention aims to provide a liquid crystal display device and a driving method thereof, which can realize wide and narrow visual angle switching in different occasions and overcome the defects of the conventional visual angle switching mode.

The invention provides a liquid crystal display device, comprising a first substrate, a second substrate arranged opposite to the first substrate and a liquid crystal layer arranged between the first substrate and the second substrate, wherein a common electrode is arranged on the first substrate, a plurality of pixel units are limited and formed on the second substrate by scanning lines and data lines, a pixel electrode is arranged in each pixel unit, a first alignment film is arranged on the first substrate and close to the liquid crystal layer, the first alignment film has a first alignment direction, a second alignment film is arranged on the second substrate and close to the liquid crystal layer, the second alignment film has a second alignment direction, the first alignment direction is vertical to the second alignment direction, the liquid crystal layer adopts positive liquid crystal molecules, the liquid crystal display device is characterized in that a first electrode and a second electrode which are arranged on the same layer and are mutually insulated are also arranged on the first substrate, the first electrode comprises a plurality of first electrode strips which are electrically connected together, the second electrode comprises a plurality of second electrode strips which are electrically connected together, the plurality of first electrode strips and the plurality of second electrode strips are mutually parallel, spaced and alternately arranged, and each first electrode strip and each second electrode strip respectively cover one row or one column of pixel units.

Furthermore, each first electrode strip and each second electrode strip extend along the horizontal direction and respectively cover one row of pixel units; or each first electrode strip and each second electrode strip extend along the vertical direction and respectively cover one column of pixel units.

Further, each of the first electrode bars and each of the second electrode bars are formed as patterned comb-shaped electrodes at positions corresponding to each of the pixel units.

Furthermore, the included angle between the electrode strips of the comb-shaped electrode and the horizontal direction is 0-45 degrees, the first alignment direction is along the vertical direction, and the second alignment direction is along the horizontal direction; or the included angle between the electrode strips of the comb-shaped electrode and the vertical direction is 0-45 degrees, the first alignment direction is along the horizontal direction, and the second alignment direction is along the vertical direction.

Further, each pixel unit comprises a first area and a second area, each first electrode strip and each second electrode strip are formed into a patterned first comb-shaped electrode at a position corresponding to the first area of each pixel unit, each first electrode strip and each second electrode strip are formed into a patterned second comb-shaped electrode at a position corresponding to the second area of each pixel unit, the electrode strips of the first comb-shaped electrode form an included angle of 0-45 degrees with the horizontal direction, the electrode strips of the second comb-shaped electrode form an included angle of 0-45 degrees with the vertical direction, the first alignment direction is along the vertical direction, and the second alignment direction is along the horizontal direction.

Further, a first insulating layer is disposed between the common electrode and the first and second electrodes, and the first and second electrodes are closer to the liquid crystal layer than the common electrode.

Furthermore, a third electrode is disposed on the second substrate, a second insulating layer is disposed between the pixel electrode and the third electrode, the third electrode is closer to the liquid crystal layer than the pixel electrode, the third electrode is formed in a patterned comb-like structure at a position corresponding to each pixel unit, and the third electrode is electrically connected to the common electrode.

The present invention also provides a driving method for driving the above liquid crystal display device, the driving method comprising:

under a wide view angle mode, applying a direct current common voltage to the common electrode, and respectively applying voltages which are the same as or similar to the common electrode to the first electrode and the second electrode, so that the voltage differences between the first electrode and the common electrode and between the second electrode and the common electrode are smaller than a preset value;

in the narrow viewing angle mode, a dc common voltage is applied to the common electrode, a first ac voltage biased up and down around the dc common voltage is applied to the first electrode, and a second ac voltage biased up and down around the dc common voltage is applied to the second electrode, so that the voltage differences between the first electrode and the common electrode and between the second electrode and the common electrode are both greater than a predetermined value, and' the polarity of the first ac voltage is opposite to the polarity of the data voltage applied to the pixel unit covered by the first electrode, and the polarity of the second ac voltage is opposite to the polarity of the data voltage applied to the pixel unit covered by the second electrode.

Further, in the wide viewing angle mode, the voltage difference between the first electrode and the common electrode and between the second electrode and the common electrode is between 0V and 0.5V; in the narrow viewing angle mode, the voltage difference between the first electrode and the common electrode and between the second electrode and the common electrode is between 3V and 7V.

Further, the polarity of the first alternating voltage is opposite to that of the second alternating voltage, the polarities of the first alternating voltage and the second alternating voltage are both inverted once per frame, the liquid crystal display device is in row inversion driving when each first electrode bar and each second electrode bar respectively covers one row of pixel units, and the liquid crystal display device is in column inversion driving when each first electrode bar and each second electrode bar respectively covers one column of pixel units.

According to the liquid crystal display device and the driving method provided by the invention, the common electrode, the first electrode and the second electrode are arranged on the first substrate, and the liquid crystal display device can be controlled to switch between a wide visual angle and a narrow visual angle by controlling the voltage applied to the first electrode and the second electrode, so that the wide and narrow visual angles can be switched under the conditions that a shielding film is not needed, the thickness of a product is not increased basically, and the manufacturing cost is not increased.

Drawings

Fig. 1 is a schematic cross-sectional view of a liquid crystal display device according to a first embodiment of the present invention.

Fig. 2 is a schematic circuit diagram of the liquid crystal display device in fig. 1.

Fig. 3 is a schematic plan view of the first electrode and the second electrode in fig. 2.

FIG. 4 is a second schematic circuit diagram of the LCD device of FIG. 1.

Fig. 5 is a schematic plan view of the first electrode and the second electrode in fig. 4.

Fig. 6a-6b are schematic views of a single pixel region of the liquid crystal display device of fig. 1.

FIGS. 7a-7b are second schematic diagrams of a single pixel region of the LCD device of FIG. 1.

FIGS. 8a-8b are third schematic diagrams illustrating a single pixel region of the LCD device of FIG. 1.

FIGS. 9a-9b are schematic diagrams illustrating the liquid crystal display device of FIG. 1 being deflected in a wide viewing angle mode.

FIGS. 10a-10b are schematic diagrams illustrating the deflection of the LCD device of FIG. 1 in a narrow viewing angle mode.

Fig. 11 is a schematic diagram of driving waveforms in the case of the liquid crystal display device adopting the architecture shown in fig. 2.

Fig. 12 is a schematic diagram of driving waveforms in the case of the liquid crystal display device adopting the architecture shown in fig. 4.

FIG. 13 is a schematic cross-sectional view of a liquid crystal display device according to a second embodiment of the present invention.

Detailed Description

To further illustrate the technical means and effects of the present invention adopted to achieve the predetermined objects, the following detailed description of the embodiments, structures, features and effects of the present invention will be made with reference to the accompanying drawings and examples.

Fig. 1 is a schematic cross-sectional view of a liquid crystal display device according to a first embodiment of the invention, and referring to fig. 1, the liquid crystal display device includes a first substrate 20, a second substrate 30 disposed opposite to the first substrate 20, and a liquid crystal layer 40 disposed between the first substrate 20 and the second substrate 30. The first substrate 20 is, for example, a color filter substrate, and the second substrate 30 is, for example, a thin film transistor array substrate.

The first substrate 20 is provided with a color resist layer 21, a black matrix 22, a common electrode 23(common electrode), a first insulating layer 26, a first electrode 24, a second electrode 25, and a first alignment film 28 on a side facing the liquid crystal layer 40. The color-resisting layer 21 includes color-resisting material of R, G, B three colors, and the black matrix 22 is located between sub-pixels of R, G, B three colors, so that adjacent sub-pixels are spaced apart from each other by the black matrix 22, thereby preventing light leakage. The common electrode 23 is disposed on the color resist layer 21 and the black matrix 22, and the common electrode 23 may have a full-surface structure.

Referring to fig. 2 to 5, the first electrode 24 and the second electrode 25 are located on the same layer and insulated from each other, and the first electrode 24 and the second electrode 25 can be formed by etching and patterning the same conductive layer. The first electrode 24 includes a plurality of first electrode stripes 24a electrically connected together, the second electrode 25 includes a plurality of second electrode stripes 25a electrically connected together, the plurality of first electrode stripes 24a and the plurality of second electrode stripes 25a are spaced in parallel and alternately arranged, and each first electrode stripe 24a and each second electrode stripe 25a respectively cover one row or one column of pixel units P.

As shown in fig. 2 and 3, each of the first electrode stripes 24a and each of the second electrode stripes 25a extend in the horizontal direction and respectively cover one row of pixel cells P, for example, each of the first electrode stripes 24a respectively covers pixel cells P located in an odd-numbered row (

row

1, 3, 5 …), and each of the second electrode stripes 25a respectively covers pixel cells P located in an even-numbered row (row 2, 4, 6 …).

Alternatively, as shown in fig. 4 and 5, each of the first electrode stripes 24a and each of the second electrode stripes 25a extend in the vertical direction and respectively cover one column of the pixel cells P, for example, each of the first electrode stripes 24a respectively covers the pixel cells P located in the odd columns (1 st, 3 rd, 5 … th columns), and each of the second electrode stripes 25a respectively covers the pixel cells P located in the even columns (2 nd, 4 th, 6 … th columns).

Further, the first electrode 24 further includes a first conductive strip 24b perpendicular to and electrically connected to the plurality of first electrode strips 24a, such that the plurality of first electrode strips 24a are electrically connected together by the first conductive strip 24 b; the second electrode 25 further includes a second conductive strip 25b perpendicular to and electrically connected to the plurality of second electrode strips 25a, such that the plurality of second electrode strips 25a are electrically connected together by the second conductive strip 25 b. The first electrode 24 and the second electrode 25 are fitted to each other as if two combs are inserted into each other.

In the present embodiment, the first insulating layer 26 is provided between the common electrode 23 and the first and

second electrodes

24 and 25, and the first and

second electrodes

24 and 25 are closer to the liquid crystal layer 40 than the common electrode 23.

The second substrate 30 is provided with a scan line 31, a data line 32, a Thin Film Transistor (TFT)33, a pixel electrode 35, and a second alignment film 38 on a side (i.e., an inner side) facing the liquid crystal layer 40.

The second substrate 30 is defined by a plurality of scan lines 31 and a plurality of data lines 32 which are insulated from each other and crossed to form a plurality of pixel units P distributed in an array, a pixel electrode 35 is arranged in each pixel unit P, and the pixel electrode 35 in each pixel unit P is connected with the corresponding scan line 31 and data line 32 through a thin film transistor 33.

The first alignment film 28 and the second alignment film 38 are disposed adjacent to the liquid crystal layer 40, the first alignment film 28 has a first alignment direction X1, the second alignment film 38 has a second alignment direction X2, and the first alignment direction X1 is perpendicular to the second alignment direction X2. Specifically, the alignment operation of the first alignment film 28 and the second alignment film 38 may be performed by rubbing alignment, photo-alignment, or the like.

The liquid crystal molecules in the liquid crystal layer 40 close to the first substrate 20 are aligned along the first alignment direction X1, the liquid crystal molecules close to the second substrate 30 are aligned along the second alignment direction X2, and the liquid crystal molecules are aligned in a 90 ° twisted posture between the upper and

lower substrates

20 and 30 because the first alignment direction X1 is perpendicular to the second alignment direction X2, as shown in fig. 1.

Further, as shown in fig. 3 and 5, each of the first electrode stripes 24a and each of the second electrode stripes 25a are formed as patterned electrodes, specifically comb-shaped electrodes (i.e., having slits S) in the present embodiment, at positions corresponding to each of the pixel units P. In other embodiments, the patterned electrode may be an electrode with other hollow patterns.

Fig. 6a is a schematic plan view illustrating a single pixel region on a first substrate, fig. 6b is a schematic plan view illustrating a single pixel region on a second substrate, please refer to fig. 6a and fig. 6b, in one embodiment, an included angle θ 1 between the electrode strips of the comb-shaped electrode and the horizontal direction may be 0 ° to 45 °, for example, 7 °, the first alignment direction X1 is along the vertical direction, the second alignment direction X2 is along the horizontal direction, and in this case, the liquid crystal display device may implement a switching display of a wide viewing angle and a narrow viewing angle in the left-right direction, that is, a display of a wide viewing angle or a display of a narrow viewing angle in the left-right direction. In this embodiment, an included angle θ 1 between the electrode strips of the comb-shaped electrode and the horizontal direction may be 0 to 45 °, and light leakage in the left and right directions at a large viewing angle may be formed in the narrow viewing angle display, but the narrow viewing angle effect is affected by an increase in the angle θ 1 and a decrease in the degree of light leakage at a large viewing angle in the left and right directions, and therefore, the included angle θ 1 is preferably 7 °.

Fig. 7a is a schematic plan view illustrating a single pixel region on a first substrate, and fig. 7b is a schematic plan view illustrating a single pixel region on a second substrate, please refer to fig. 7a and fig. 7b, in another embodiment, an included angle θ 2 between the electrode strips of the comb-shaped electrode and the vertical direction may be 0 ° to 45 °, for example, 7 °, the first alignment direction X1 is along the horizontal direction, and the second alignment direction X2 is along the vertical direction, in which case the liquid crystal display device may implement a switching display of a wide viewing angle and a narrow viewing angle in the up-down direction, that is, a wide viewing angle display or a narrow viewing angle display in the up-down direction. In this embodiment, an included angle θ 2 between the electrode strips of the comb-shaped electrode and the vertical direction may be 0 to 45 °, and light leakage in the up-and-down direction at a large viewing angle may be formed in a narrow viewing angle display, but the angle θ 2 is increased, and the degree of light leakage at the large viewing angle in the vertical direction is reduced, which affects the narrow viewing angle effect, so preferably, the included angle θ 2 is 7 °.

Fig. 8a illustrates a schematic plan view of a single pixel region on the first substrate, and fig. 8b illustrates a schematic plan view of a single pixel region on the second substrate, please refer to fig. 8a and 8b, in yet another embodiment, each pixel cell P includes a first region P1 and a second region P2, each first electrode strip 24a and each second electrode strip 25a are formed as a patterned first comb-shaped electrode at a position corresponding to the first region P1 of each pixel cell P, each first electrode strip 24a and each second electrode strip 25a are formed as a patterned second comb-shaped electrode at a position corresponding to the second region P2 of each pixel cell P, and the electrode strips of the first comb-shaped electrode and the electrode strips of the second comb-shaped electrode have different extending directions. Specifically, an included angle θ 1 between the electrode strips of the first comb-shaped electrode and the horizontal direction may be 0 ° to 45 °, for example, 7 °; the included angle θ 2 between the electrode strips of the second comb-shaped electrode and the vertical direction may be 0 ° to 45 °, for example, 7 °. The first alignment direction X1 is along the vertical direction, and the second alignment direction X2 is along the horizontal direction, so that the liquid crystal display device can realize the switching display of the wide viewing angle and the narrow viewing angle in the left-right direction and the up-down direction.

Each pixel electrode 35 is preferably a planar electrode, that is, each pixel electrode 35 is a one-piece planar structure without a slit.

In the liquid crystal display device, the common electrode 23 and the pixel electrode 35 are formed on the upper and

lower substrates

20 and 30, respectively, and liquid crystal molecules are Twisted at 90 ° between the upper and

lower substrates

20 and 30, and a normally white mode (normal white) is performed when no voltage is applied, that is, the liquid crystal display device adopts a Twisted Nematic (TN) configuration.

It should be understood that in the present embodiment, only the film layer structures related to the present embodiment are illustrated on the first substrate 20 and the second substrate 30, and the film layer structures not related to the present embodiment are omitted.

The liquid crystal layer 40 uses positive liquid crystal molecules, that is, liquid crystal molecules having positive dielectric anisotropy. In an initial state (i.e., a state where no voltage is applied to the liquid crystal display device), the positive liquid crystal molecules in the liquid crystal layer 40 assume a lying posture substantially parallel to the

substrates

20, 30, i.e., the long axis direction of the positive liquid crystal molecules is substantially parallel to the surfaces of the

substrates

20, 30. In practical applications, the positive liquid crystal molecules in the liquid crystal layer 40 and the

substrates

20 and 30 may have a small initial pretilt angle, so as to increase the response speed of the liquid crystal molecules during deflection. The initial pretilt may range less than 10 degrees.

The first electrode 24 and the second electrode 25 are used to control the liquid crystal display device to perform viewing angle switching, and the liquid crystal display device can realize switching between a wide viewing angle mode and a narrow viewing angle mode by controlling voltages applied to the first electrode 24 and the second electrode 25.

Wide view angle mode: referring to fig. 9a and 9b, during wide viewing angle display, a DC common voltage DC Vcom (for example, 0V) is applied to the common electrode 23, and voltages identical to or similar to the common electrode 23 are respectively applied to the first electrode 24 and the second electrode 25, so that voltage differences between the first electrode 24 and the common electrode 23 and between the second electrode 25 and the common electrode 23 are both smaller than a predetermined value (for example, smaller than 0.5V), that is, there is no voltage difference or a small voltage difference between the first electrode 24 and the common electrode 23 and between the second electrode 25 and the common electrode 23, and at this time, the liquid crystal display device realizes normal wide viewing angle display.

In the wide viewing angle mode, when no data voltage is applied to the pixel electrode 35, the voltage difference between the pixel electrode 35 and the common electrode 23 is zero, the liquid crystal molecules maintain an initial twisted posture between the first substrate 20 and the second substrate 30, the light emitted from the lower polarizer can pass through the upper polarizer, and the liquid crystal display device is in a white state as shown in fig. 9 a; when a data voltage is applied to the pixel electrode 35, a voltage difference between the pixel electrode 35 and the common electrode 23 is greater than zero, a vertical electric field is generated between the pixel electrode 35 and the common electrode 23, the liquid crystal molecules tilt under the action of the vertical electric field, when the voltage difference reaches a certain value, the liquid crystal molecules tilting at a certain angle can prevent light emitted from the lower polarizing plate from penetrating through the upper polarizing plate, and the liquid crystal display device is in a black state as shown in fig. 9 b; by adjusting the magnitude of the data voltage applied to the pixel electrode 35, the liquid crystal display device can display different gray scales.

In the wide viewing angle mode, the voltage difference between the first electrode 24 and the common electrode 23 and between the second electrode 25 and the common electrode 23 may be between 0V and 0.5V. Preferably, the same voltage as that of the common electrode 23 is applied to both the first electrode 24 and the second electrode 25, so that the voltage difference between the first electrode 24 and the common electrode 23 and between the second electrode 25 and the common electrode 23 are both zero, and a good wide viewing angle display effect can be achieved.

Narrow view angle mode: referring to fig. 10a and 10b, in the narrow viewing angle display, a DC common voltage DC Vcom (for example, 0V) is applied to the common electrode 23, a first ac voltage V1 biased up and down with the DC common voltage DC Vcom as the center is applied to the first electrode 24, a second ac voltage V2 biased up and down with the DC common voltage DC Vcom as the center is applied to the second electrode 25, so that the voltage differences between the first electrode 24 and the common electrode 23 and between the second electrode 25 and the common electrode 23 are both greater than a predetermined value (for example, greater than 3V), that is, a large voltage difference exists between the first electrode 24 and the common electrode 23 and between the second electrode 25 and the common electrode 23, a strong horizontal electric field is formed in the region of the first substrate 20 close to the liquid crystal layer 40, and the polarity of the first ac voltage V1 is opposite to the polarity of the data voltage applied to the pixel P covered by the first electrode 24, the polarity of the second ac voltage V2 is opposite to the polarity of the data voltage applied to the pixel unit P covered by the second electrode 25, so that the voltage difference between the first electrode 24 and the pixel electrode 35 and between the second electrode 25 and the pixel electrode 35 can be increased, a stronger vertical electric field can be further formed between the first substrate 20 and the second substrate 30, liquid crystal molecules are deflected under the combined action of the horizontal electric field and the vertical electric field, and a light leakage phenomenon occurs at a large viewing angle of a screen, the contrast is reduced, and the viewing angle is reduced, so that the liquid crystal display device realizes narrow viewing angle display.

In the narrow viewing angle mode, when no data voltage is applied to the pixel electrode 35, the voltage difference between the pixel electrode 35 and the common electrode 23 is zero, the liquid crystal molecules at the positions corresponding to the first electrode 24 and the second electrode 25 tilt at a certain angle, the liquid crystal molecules in the remaining area still maintain the initial twisted posture, and the liquid crystal display device is in a white state as shown in fig. 10 a; when a data voltage is applied to the pixel electrode 35, a voltage difference between the pixel electrode 35 and the common electrode 23 is greater than zero, and at this time, a vertical electric field is generated between the pixel electrode 35 and the common electrode 23, so that the electric field in the vertical direction is enhanced, the tilt angle of the liquid crystal molecules in the whole area is increased, and the liquid crystal display device is in a black state, as shown in fig. 10 b; by adjusting the magnitude of the data voltage applied to the pixel electrode 35, the liquid crystal display device can display different gray scales.

In the narrow viewing angle mode, the voltage difference between the first electrode 24 and the common electrode 23 and between the second electrode 25 and the common electrode 23 may be between 3V and 7V. For example, the voltage difference between the first electrode 24 and the common electrode 23 and between the second electrode 25 and the common electrode 23 may be 6V, and a good narrow viewing angle display effect may be achieved.

Referring to fig. 11 and 12, in the narrow viewing angle mode, the polarity of the first ac voltage V1 is opposite to the polarity of the second ac voltage V2, and the polarities of the first ac voltage V1 and the second ac voltage V2 are inverted once per frame.

As shown in fig. 11, in the narrow viewing angle mode, when the liquid crystal display device of the architecture shown in fig. 2 is employed, each of the first electrode bars 24a and each of the second electrode bars 25a respectively cover one row of the pixel cells P, at which time the liquid crystal display device adopts the row inversion driving. In the nth frame, the polarity of the first ac voltage V1 is negative, and the polarity of the data voltage applied to each row of pixel cells P covered by each first electrode bar 24a is positive; in the (N + 1) th frame, the first ac voltage V1 is converted to a positive polarity, and at this time, the data voltage applied to each row of pixel cells P covered by each first electrode bar 24a is converted to a negative polarity. Therefore, the polarity of the first ac voltage V1 is opposite to the polarity of the data voltage applied to each row of pixel cells P covered by the first electrode 24, so that the voltage difference between the first electrode 24 and the pixel electrode 35 can be increased. Similarly, the polarity of the second ac voltage V2 is just opposite to the polarity of the data voltage applied to each row of pixel units P covered by the second electrode 25, so that the voltage difference between the second electrode 25 and the pixel electrode 35 can be increased, thereby facilitating a stronger vertical electric field to be formed between the first substrate 20 and the second substrate 30 in the narrow viewing angle mode, and enhancing the narrow viewing angle display effect.

As shown in fig. 12, in the narrow viewing angle mode, when the liquid crystal display device of the architecture shown in fig. 4 is employed, each of the first electrode bars 24a and each of the second electrode bars 25a respectively cover one column of the pixel cells P, at which time the liquid crystal display device adopts the column inversion driving. In the nth frame, the polarity of the first ac voltage V1 is negative, and the polarity of the data voltage applied to each row of pixel cells P covered by each first electrode bar 24a is positive; in the (N + 1) th frame, the first ac voltage V1 is converted to a positive polarity, and at this time, the data voltage applied to each column of pixel cells P covered by each first electrode stripe 24a is converted to a negative polarity. Therefore, the polarity of the first ac voltage V1 is opposite to the polarity of the data voltage applied to each column of pixel cells P covered by the first electrode 24, so that the voltage difference between the first electrode 24 and the pixel electrode 35 can be increased. Similarly, the polarity of the second ac voltage V2 is just opposite to the polarity of the data voltage applied to each column of pixel units P covered by the second electrode 25, so that the voltage difference between the second electrode 25 and the pixel electrode 35 can be increased, thereby facilitating a stronger vertical electric field to be formed between the first substrate 20 and the second substrate 30 in the narrow viewing angle mode, and enhancing the narrow viewing angle display effect.

In the narrow viewing angle mode, the first ac voltage signal V1 and the second ac voltage signal V2 may have the same type of waveform, such as square waves.

Fig. 13 is a schematic cross-sectional view of a liquid crystal display device in a second embodiment of the present invention, please refer to fig. 13, the main difference between this embodiment and the first embodiment is that a third electrode 36 is further disposed on the second substrate 30, a second insulating layer 37 is disposed between the pixel electrode 35 and the third electrode 36, the third electrode 36 is closer to the liquid crystal layer 40 than the pixel electrode 35, the third electrode 36 is formed in a patterned comb-like structure at a position corresponding to each pixel unit P, the third electrode 36 is electrically connected to the common electrode 23, for example, in a peripheral non-display region, the third electrode 36 may be in conductive communication with the common electrode 23 via a conductive paste (not shown), namely, the same DC common voltage DC Vcom as the common electrode 23 is always applied to the third electrode 36, therefore, the electric field can be further enhanced on the basis of the framework of the first embodiment, and the narrow-view display effect is improved. For other structures and operation principles of the present embodiment, reference may be made to the first embodiment, which is not described herein again.

Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A liquid crystal display device comprises a first substrate (20), a second substrate (30) arranged opposite to the first substrate (20), and a liquid crystal layer (40) arranged between the first substrate (20) and the second substrate (30), wherein a common electrode (23) is arranged on the first substrate (20), a plurality of pixel units (P) are formed on the second substrate (30) and limited by scanning lines (31) and data lines (32), a pixel electrode (35) is arranged in each pixel unit (P), a first alignment film (28) is arranged on the first substrate (20) and close to the liquid crystal layer (40), the first alignment film (28) has a first alignment direction (X1), a second alignment film (38) is arranged on the second substrate (30) and close to the liquid crystal layer (40), the second alignment film (38) has a second alignment direction (X2), and the first alignment direction (X1) is perpendicular to the second alignment direction (X2), the liquid crystal layer (40) adopts positive liquid crystal molecules, and is characterized in that a first electrode (24) and a second electrode (25) which are positioned on the same layer and are insulated from each other are further arranged on the first substrate (20), the first electrode (24) comprises a plurality of first electrode strips (24a) which are electrically connected together, the second electrode (25) comprises a plurality of second electrode strips (25a) which are electrically connected together, the plurality of first electrode strips (24a) and the plurality of second electrode strips (25a) are mutually parallel, spaced and alternately arranged, each first electrode strip (24a) and each second electrode strip (25a) respectively cover one row or one column of pixel units (P), the first electrode (24) is used for applying a first alternating current voltage (V1) with the opposite polarity of the data voltage applied to the pixel units (P) covered by the first electrode (24) in a narrow viewing angle mode, the second electrode (25) is used for applying a second alternating voltage (V2) with the polarity opposite to that of the data voltage applied on the pixel unit (P) covered by the second electrode (25) in the narrow viewing angle mode.

2. A liquid crystal display device according to claim 1, characterized in that each first electrode stripe (24a) and each second electrode stripe (25a) extends in the horizontal direction and covers one row of pixel cells (P), respectively; or, each first electrode bar (24a) and each second electrode bar (25a) extend along the vertical direction and respectively cover one column of pixel units (P).

3. A liquid crystal display device according to claim 1, characterized in that each first electrode strip (24a) and each second electrode strip (25a) is formed as a patterned comb-shaped electrode at a position corresponding to each pixel cell (P).

4. A liquid crystal display device as claimed in claim 3, characterized in that the electrode strips of the comb-shaped electrodes have an angle of 0 ° to 45 ° with the horizontal direction, the first alignment direction (X1) being along the vertical direction, the second alignment direction (X2) being along the horizontal direction; or, the included angle between the electrode strips of the comb-shaped electrode and the vertical direction is 0-45 degrees, the first alignment direction (X1) is along the horizontal direction, and the second alignment direction (X2) is along the vertical direction.

5. The liquid crystal display device according to claim 1, wherein each pixel cell (P) includes a first region (P1) and a second region (P2), each first electrode stripe (24a) and each second electrode stripe (25a) are formed as patterned first comb-shaped electrodes at a position corresponding to the first region (P1) of each pixel cell (P), each first electrode stripe (24a) and each second electrode stripe (25a) are formed as patterned second comb-shaped electrodes at a position corresponding to the second region (P2) of each pixel cell (P), the included angle between the electrode strip of the first comb electrode and the horizontal direction is 0-45 degrees, the included angle between the electrode strip of the second comb electrode and the vertical direction is 0-45 degrees, the first alignment direction (X1) is along the vertical direction, and the second alignment direction (X2) is along the horizontal direction.

6. A liquid crystal display device as claimed in claim 1, characterized in that a first insulating layer (26) is provided between the common electrode (23) and the first and second electrodes (24, 25), the first and second electrodes (24, 25) being closer to the liquid crystal layer (40) than the common electrode (23).

7. A liquid crystal display device as claimed in claim 1, characterized in that a third electrode (36) is further provided on the second substrate (30), a second insulating layer (37) is provided between the pixel electrode (35) and the third electrode (36), the third electrode (36) is closer to the liquid crystal layer (40) than the pixel electrode (35), the third electrode (36) is formed in a patterned comb-like structure at a position corresponding to each pixel unit (P), and the third electrode (36) is electrically connected to the common electrode (23).

8. A driving method for driving the liquid crystal display device according to any one of claims 1 to 7, characterized in that the driving method comprises:

in a wide viewing angle mode, applying a direct current common voltage (DC Vcom) to the common electrode (23), and respectively applying voltages which are the same as or close to the common electrode (23) to the first electrode (24) and the second electrode (25) so that the voltage differences between the first electrode (24) and the common electrode (23) and between the second electrode (25) and the common electrode (23) are smaller than a preset value;

in a narrow viewing angle mode, a DC common voltage (DC Vcom) is applied to the common electrode (23), a first AC voltage (V1) which is biased up and down around the DC common voltage (DC Vcom) is applied to the first electrode (24), a second AC voltage (V2) which is biased up and down around the DC common voltage (DC Vcom) is applied to the second electrode (25), so that the voltage difference between the first electrode (24) and the common electrode (23) and the voltage difference between the second electrode (25) and the common electrode (23) are both larger than a preset value, and the polarity of the first alternating voltage (V1) is opposite to the polarity of the data voltage applied to the pixel cell (P) covered by the first electrode (24), the polarity of the second alternating voltage (V2) is opposite to the polarity of the data voltage applied to the pixel cell (P) covered by the second electrode (25).

9. The driving method according to claim 8, wherein in the wide viewing angle mode, a voltage difference between the first electrode (24) and the common electrode (23) and a voltage difference between the second electrode (25) and the common electrode (23) are between 0V and 0.5V; in the narrow viewing angle mode, the voltage difference between the first electrode (24) and the common electrode (23) and between the second electrode (25) and the common electrode (23) is between 3V and 7V.

10. The driving method according to claim 8, wherein the polarity of the first ac voltage (V1) is opposite to the polarity of the second ac voltage (V2), the polarities of the first ac voltage (V1) and the second ac voltage (V2) are inverted once per frame, the liquid crystal display device is driven by row inversion when each of the first electrode bars (24a) and each of the second electrode bars (25a) respectively covers one row of the pixel cells (P), and the liquid crystal display device is driven by column inversion when each of the first electrode bars (24a) and each of the second electrode bars (25a) respectively covers one column of the pixel cells (P).