KR100994232B1 - Liquid crystal display of in-plane-switching mode and method of driving the same - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-plane switching mode liquid crystal display device and a driving method thereof, wherein the liquid crystal display device is formed on an upper substrate and has a first ferroelectric property having spontaneous polarization in the same direction as an electric field of a first polarity. Liquid crystal layer; A second ferroelectric liquid crystal layer formed on the lower substrate facing the upper substrate and having spontaneous polarization in the same direction as an electric field of a second polarity; A nematic liquid crystal layer sandwiched between the first ferroelectric liquid crystal layer and the second ferroelectric liquid crystal layer; And first and second electrodes formed on each of the upper substrate and the lower substrate to apply an electric field to the first and second ferroelectric liquid crystal layers. The first ferroelectric liquid crystal layer reacts only with the electric field of the second polarity to induce in-plane driving of the nematic liquid crystal layer, and the second ferroelectric liquid crystal layer reacts only with the electric field of the first polarity of the nematic liquid crystal layer. Induces in-plane drive. An electric field whose polarity is reversed is applied to the first and second ferroelectric liquid crystal layers and the nematic liquid crystal layer in a dot inversion manner through the first and second electrodes so that polarities applied to neighboring liquid crystal cells are opposite to each other. do.

Description

Liquid crystal display device and its driving method in in-plane switching mode {LIQUID CRYSTAL DISPLAY OF IN-PLANE-SWITCHING MODE AND METHOD OF DRIVING THE SAME}             

1 is a cross-sectional view schematically showing a liquid crystal display panel of a conventional in-plane switching mode.

2 is a block diagram illustrating an LCD in an in-plane switching mode according to the present invention.

FIG. 3 is a cross-sectional view illustrating the liquid crystal display of the in-plane switching mode shown in FIG. 2.

FIG. 4 is a cross-sectional view illustrating another embodiment of the in-plane switching mode liquid crystal display shown in FIG. 2.

5A through 5D are cross-sectional views illustrating a method of manufacturing a liquid crystal display panel in an in-plane switching mode illustrated in FIG. 3.

FIG. 6 is a diagram illustrating a ferroelectric liquid crystal stabilized in a monostable state in the phase transition process of FIGS. 5A to 5D.

7A through 7D are cross-sectional views illustrating a method of manufacturing a liquid crystal display device in an in-plane switching mode illustrated in FIG. 4.                 

FIG. 8 is a diagram illustrating a ferroelectric liquid crystal stabilized in a monostable state in the phase transition process of FIGS. 7A to 7D.

9A and 9B are detailed views illustrating the operation of the in-plane switching mode of the ferroelectric liquid crystal and the nematic liquid crystal shown in FIG. 3.

10 is a diagram illustrating a case in which a liquid crystal panel into which a ferroelectric liquid crystal layer of a half V switching mode is injected is driven in a dot inversion method.

FIG. 11 is a diagram illustrating a case in which a liquid crystal panel in which a nematic liquid crystal layer is injected between the ferroelectric liquid crystal layers of a half V switching mode is driven in a dot inversion manner as illustrated in FIG. 3 or 4.

12A and 12B are diagrams illustrating light transmittances of the liquid crystal panel illustrated in FIGS. 10 and 11 driven in a dot inversion scheme.

13A and 13B are views illustrating viewing angles of a conventional twisted nematic mode liquid crystal panel and an in-plane switching mode liquid crystal panel according to the present invention.

14A and 14B are diagrams illustrating gradation inversion of a liquid crystal panel of a conventional twisted nematic mode.

15 is a diagram illustrating color coordinates of an in-plane switching mode liquid crystal display according to the present invention.

         <Explanation of symbols for main parts of the drawings>

11, 19: polarizing plates 12, 18, 21, 31, 51: substrate                 

13, 17, 23, 33, 53: alignment layer 15, 16, 22, 32, 52: electrode

24, 34, 54: ferroelectric liquid crystal layer 50: nematic liquid crystal layer

61: timing controller 62: data driver

63: gate driver 64: liquid crystal panel

65: common voltage generator 100: top plate

110: bottom plate

The present invention relates to a liquid crystal display device, and more particularly, to an in-plane switching mode liquid crystal display device and a driving method thereof capable of improving image quality.

The liquid crystal display device displays an image by controlling an electric field applied to the liquid crystal cell to modulate the light incident on the liquid crystal cell. The liquid crystal injected into the liquid crystal display is an intermediate state between a liquid and a solid having both fluidity and elasticity.

The twisted nematic mode (TN mode) is driven by a vertical electric field method and is the most commonly used liquid crystal mode in liquid crystal displays. However, the twisted nematic mode has an advantage that the aperture ratio is relatively wide, but since the refractive index of the liquid crystal felt by the observer is significantly different according to the viewing angle, it is difficult to implement the wide viewing angle and the response speed of the liquid crystal is slow.                         

In the horizontal electric field method, an in-plane switching mode (IPS) that forms an electric field between electrodes formed on the same substrate and drives liquid crystal molecules with the electric field is typical.

1 is a cross-sectional view showing a liquid crystal display device of a conventional in-plane switching mode.

Referring to FIG. 1, a liquid crystal display of a conventional in-plane switching mode includes upper and lower substrates 12 and 18 bonded by reality; Upper and lower polarizers 11 and 19 are disposed on the back and upper substrates 12 and 18, respectively.

The color filter, the black matrix, and the like are formed on the upper substrate 12. The pixel electrode 16 and the common electrode 15 are formed side by side on the lower substrate 18, and the electric field 20 in the horizontal direction is formed by the voltage difference applied between the electrodes 15 and 16. By the horizontal electric field 20, the liquid crystal molecules 14 rotate in the plane direction of the substrate to modulate the polarization component of the light passing through the liquid crystal layer.

The upper and lower polarizing plates 11 and 19 have light transmission axes perpendicular to each other. That is, when the light passing through the liquid crystal layer changes its linearly polarized light by the liquid crystal layer, the light passes through the upper polarizer 11 and moves toward the viewer. On the other hand, if the polarization component of light passing through the liquid crystal layer does not change when passing through the liquid crystal layer, it cannot pass through the upper polarizing plate 11.

As described above, the in-plane switching mode illustrated in FIG. 1 is advantageous in implementing a wide viewing angle because the change in refractive index of the liquid crystal felt by the observer is not severe according to the viewing angle. However, in the in-plane switching mode, since the electric field applied to the liquid crystal molecules 14 is bent on the pixel electrode 16 and the common electrode 15, light switching is not normally performed on the electrodes 15 and 16. There is a disadvantage that the opening ratio is low.

The present invention provides an in-plane switching mode liquid crystal display device and a driving method thereof capable of improving image quality.

The liquid crystal display of the present invention comprises: a first ferroelectric liquid crystal layer formed on the upper substrate and having spontaneous polarization in the same direction as the electric field of the first polarity; A second ferroelectric liquid crystal layer formed on the lower substrate facing the upper substrate and having spontaneous polarization in the same direction as an electric field of a second polarity; A nematic liquid crystal layer sandwiched between the first ferroelectric liquid crystal layer and the second ferroelectric liquid crystal layer; And first and second electrodes formed on each of the upper substrate and the lower substrate to apply an electric field to the first and second ferroelectric liquid crystal layers. The first ferroelectric liquid crystal layer reacts only with the electric field of the second polarity to induce in-plane driving of the nematic liquid crystal layer, and the second ferroelectric liquid crystal layer reacts only with the electric field of the first polarity of the nematic liquid crystal layer. Induces in-plane drive. An electric field whose polarity is reversed is applied to the first and second ferroelectric liquid crystal layers and the nematic liquid crystal layer in a dot inversion manner through the first and second electrodes so that polarities applied to neighboring liquid crystal cells are opposite to each other. do.
Each of the first and second ferroelectric liquid crystal layers operates in a half V switching mode.
The liquid crystal display device includes a first alignment layer formed on the upper substrate; A second alignment layer formed on the lower substrate is further provided.
At least one of the first and second alignment layers is any one of a polar medium and a nonpolar medium.
The spontaneous polarization of the first ferroelectric liquid crystal layer is directed toward the first alignment layer, and the spontaneous polarization of the second ferroelectric liquid crystal layer is directed toward the second alignment layer.
The spontaneous polarization of the first ferroelectric liquid crystal layer is directed toward the second alignment layer, and the spontaneous polarization of the second ferroelectric liquid crystal layer is directed toward the first alignment layer.
The method of driving the liquid crystal display device includes forming a first ferroelectric liquid crystal layer having spontaneous polarization in the same direction as an electric field of a first polarity on an upper substrate; Forming a second ferroelectric liquid crystal layer formed on a lower substrate facing the upper substrate and having a spontaneous polarization in the same direction as an electric field of a second polarity; Forming first and second electrodes formed on each of the upper substrate and the lower substrate to apply an electric field to the first and second ferroelectric liquid crystal layers; Forming a nematic liquid crystal layer sandwiched between the first ferroelectric liquid crystal layer and the second ferroelectric liquid crystal layer; And applying an electric field whose polarity is inverted in a dot inversion manner to the first and second ferroelectric liquid crystal layers and the nematic liquid crystal layer such that polarities applied to neighboring liquid crystal cells are opposite to each other.
Other objects and features of the present invention in addition to the above object will be apparent through the description of the embodiments with reference to the accompanying drawings.

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Hereinafter, exemplary embodiments of the present invention will be described with reference to FIGS. 2 to 15.                     

2 is a block diagram illustrating an LCD in an in-plane switching mode according to the present invention.

Referring to FIG. 2, in the in-plane switching mode liquid crystal display according to the present invention, a liquid crystal panel 64 in which a nematic liquid crystal is sandwiched between ferroelectric liquid crystal layers and a data line D of the liquid crystal panel 64 are driven. A data driver 62 for controlling the data driver 62, a gate driver 63 for driving the gate line G of the liquid crystal panel 64, and a timing controller 61 for controlling the data driver 62 and the gate driver 63. And a common voltage generator 65 for supplying a common voltage Vcom to the common electrode of the liquid crystal panel 64.

The timing controller 61 supplies the pixel data signals R, G, and B data input from the outside to the data driver 62. In addition, the timing controller 61 controls the gate control signal GDC and data for controlling each of the gate driver 63 and the data driver 62 in response to control signals H, V, DE, and CLK input from the outside. Generate a control signal DDC.

The gate control signals GDC include a gate start pulse GSP, a gate shift clock signal GSC, a gate output enable signal GOE, and the like. The data control signals DDC include a source start pulse SSP, a source shift clock signal SSC, a source output enable signal SOE, a polarity control signal POL, and the like.

The gate driver 63 sequentially supplies the gate high voltage VGH to the gate lines G1 to Gm in response to the gate control signals GDC from the timing controller 61. Accordingly, the gate driver 63 causes the thin film transistor TFT connected to the gate lines G1 to Gm to be driven in units of the gate line GL.                     

The data driver 62 outputs one horizontal line of pixel signals for each horizontal period H1, H2, ... in response to the data control signals DDC from the timing controller 61. Supplies). In particular, the data driver 62 converts the digital pixel data R, G, and B from the timing controller 61 into an analog pixel signal using a gamma voltage from a gamma voltage generator (not shown). .

As shown in FIG. 3, the liquid crystal panel 64 includes an upper plate 100 and a lower plate 110 bonded by a real material, and first and second ferroelectric liquid crystal layers formed on the upper plate 100 and the lower plate 110. 24 and 34 and nematic liquid crystals 50 injected between the first and second ferroelectric liquid crystal layers 24 and 34.

The upper plate 46 includes a common electrode to which the upper substrate 21, a color filter for implementing colors, a black matrix for preventing light leakage, and a common voltage Vcom generated by the common voltage generator 65 are applied. 22) and an upper alignment film 23 applied for the orientation of the first ferroelectric liquid crystal molecules 24 thereon.

The lower plate 48 is connected to data lines to which data signals are supplied, gate lines to which gate signals are supplied, thin film transistors for switching liquid crystal cells at intersections of the data lines and gate lines, and thin film transistors. A pixel electrode 32 for driving the liquid crystal cell, and a lower alignment film 33 coated for the alignment of the second ferroelectric liquid crystal molecules 34 thereon.

On the light incidence surface of the lower substrate 31 and the light emission surface of the upper substrate 21, polarizing plates (not shown) each having a light transmission axis perpendicular to each other are attached.                     

The first and second ferroelectric liquid crystal layers 24 and 34 operate in a half V switching mode and have different spontaneous polarization directions.

For example, when the first ferroelectric liquid crystal layer 24 has the same spontaneous polarization direction as that of the negative electric field direction as shown in FIG. 3, the second ferroelectric liquid crystal layer 34 has the same spontaneous polarization as the positive electric field direction. Direction. At this time, the first ferroelectric liquid crystal layer 24 is driven in-plane while the spontaneous polarization direction of the first ferroelectric liquid crystal 24 is changed in the same direction as the positive electric field direction in response to the positive electric field, and the second ferroelectric liquid crystal layer 34 In response to the negative electric field, the spontaneous polarization direction of the second ferroelectric liquid crystal 34 is changed in the same direction as the negative electric field direction, thereby being driven in-plane.

Alternatively, when the first ferroelectric liquid crystal layer 24 has the same spontaneous polarization direction as the positive electric field direction as shown in FIG. 4, the second ferroelectric liquid crystal layer 34 has the same spontaneous polarization direction as the negative electric field direction. do. At this time, the first ferroelectric liquid crystal layer 24 is driven in-plane while the spontaneous polarization direction of the first ferroelectric liquid crystal 24 is changed in the same direction as the negative electric field direction in response to the negative electric field, and the second ferroelectric liquid crystal layer 34 ) Is driven in-plane in response to the positive electric field while the spontaneous polarization direction of the second ferroelectric liquid crystal is changed to the same direction as the positive electric field direction.

The nematic liquid crystal layer 50 has a switching angle of 90 degrees and forms an interface with the first and second ferroelectric liquid crystal layers 24 and 34. The nematic liquid crystal layer 50 induces in-plane driving by any one of the first and second ferroelectric liquid crystal layers 24 and 34 which are driven in-plane while the spontaneous polarization direction is changed to the same direction as the electric field direction.                     

5A through 5D are steps of a method of manufacturing a liquid crystal display device in an in-plane switching mode according to the present invention. Here, the upper and lower plates shown in FIG. 3 are manufactured by the manufacturing method shown in FIGS. 5A to 5D.

First, as shown in FIG. 5A, an electrode 52 and a polar alignment layer 53 are formed on the substrate 51. The electrode 52 is formed of a transparent conductive material such as indium tin oxide (Indium-Tin-Oxide). Since the polar alignment layer 53 has an electrical negativity like polyamic acid, the polar alignment layer 53 is made of an organic alignment material having electrical polarity and capable of liquid crystal alignment. The polar alignment film 53 is subjected to a rubbing treatment to set the alignment direction of the ferroelectric liquid crystal molecules.

Subsequently, as shown in FIG. 5B, a mixture of ferroelectric liquid crystals and an organic solvent is uniformly applied in a state in which the substrate 51 is exposed to a non-polar medium having almost no electrical polarity, and then the substrate 51 is coated. The temperature is raised to a temperature between 140 ° C. and 160 ° C. to vaporize the organic solvent. As a result, an isotropic ferroelectric liquid crystal layer 54 is formed on the substrate 51. Here, the nonpolar medium may be selected as an air or nitrogen (N ₂ ) atmosphere as an example.

Then, the temperature of the substrate 51 is lowered to a phase transition temperature between 110 ° C. and 85 ° C. to cause the isotropic ferroelectric liquid crystal layer 54 to be phase shifted into the nematic phase N * as shown in FIG. 5C. In order to phase-transfer the nematic ferroelectric liquid crystal layer 54 of the nematic phase N * to the smear C phase Sm C * as shown in FIG. 5D, the temperature of the substrate 51 is changed to a phase transition temperature between 80 ° C and 50 ° C. Lower. At this time, spontaneous polarization Ps is expressed in the liquid crystal molecules of the ferroelectric liquid crystal layer 54 as shown in FIG. 6 during the phase transition to the smear C phase Sm C *, and the spontaneous polarization Ps Direction is directed toward the polar alignment layer 53. That is, the liquid crystal molecules of the ferroelectric liquid crystal layer 54 are phase-shifted to the smear C phase (Sm C *), and the direction of the spontaneous polarization Ps is constantly arranged in a monostable state without an external electric field.

7A to 7D illustrate a method of manufacturing a liquid crystal display device in an in-plane switching mode according to another exemplary embodiment of the present invention. Here, the upper and lower plates shown in FIG. 4 are manufactured by the manufacturing method shown in FIGS. 7A to 7D.

First, as shown in FIG. 7A, the electrode 52 and the alignment layer 53 are formed on the substrate 51. The electrode 52 is made of a transparent conductive material such as indium tin oxide. The alignment layer 53 is made of an organic alignment material such as polyamic acid or polyimide and is rubbed to set the alignment direction of the ferroelectric liquid crystal molecules.

Subsequently, as shown in FIG. 7B, the substrate 51 is exposed to a medium having a higher electrical negative (or higher polarity), for example, water (H ₂ O) or oxygen (O ₂ ) than the alignment layer 53. In this state, a mixture of the ferroelectric liquid crystal and the organic solvent is uniformly applied, and the temperature of the substrate 51 is raised to a temperature between 140 ° C. and 160 ° C. to vaporize the organic solvent. As a result, an isotropic ferroelectric liquid crystal layer 54 is formed on the substrate 51.

In order to phase-transfer the isotropic ferroelectric liquid crystal layer 54 to the nematic phase N *, as shown in FIG. 7C, the temperature of the substrate 51 is lowered to a phase transition temperature between 110 ° C and 85 ° C. And in order to phase-transfer the nematic ferroelectric liquid crystal layer 54 of the nematic phase (N *) of FIG. 7C to the smear C phase (Sm C *) as shown in FIG. 7D, the temperature of the board | substrate 51 is 80 degreeC-50 Lower to phase transition temperature between ° C. At this time, as shown in FIG. 8, the spontaneous polarization Ps is expressed in the liquid crystal molecules of the ferroelectric liquid crystal layer 54 during the phase transition to the smear C phase (Sm C *), and the direction of the spontaneous polarization Ps is shown. It is directed toward the opposite polar medium of the alignment film 53. This is because the electrical negativeness of the polar medium on the opposite side is larger than that of the alignment film 53. That is, the liquid crystal molecules of the ferroelectric liquid crystal layer 54 are phase shifted to the smear C phase (Sm C *), and the direction of the spontaneous polarization Ps is uniformly arranged in a monostable state without an external electric field.

9A and 9B are cross-sectional views illustrating a method of driving a liquid crystal display according to the present invention. For example, as shown in FIG. 2, an external electric field (E (+)) having a positive polarity and a negative polarity is applied to a ferroelectric liquid crystal molecule of a half-v switching mode oriented in a direction coinciding with the negative electric field (E (−)). It shows a change in the arrangement of the ferroelectric liquid crystal molecules in the half V switching mode when E (−)) is applied.

When a positive electric field is applied to the liquid crystal panel having the first and second ferroelectric liquid crystals 24 and 34 and the nematic liquid crystal, as shown in FIG. 9A, the spontaneous polarization direction of the first ferroelectric liquid crystal 24 is the positive electric field. It drives in the in-plane direction while changing in the same direction as the direction, and induces in-plane driving of the nematic liquid crystal adjacent thereto. In addition, the second ferroelectric liquid crystal 34 having the same spontaneous polarization direction as the positive electric field direction is maintained in an initial state without reacting to an electric field. At this time, since the nematic liquid crystal 50 is in-plane switched by the first ferroelectric liquid crystal 24, the nematic liquid crystal 50 is twisted in the vertical direction.

In addition, when a negative electric field is applied to the liquid crystal panels having the first and second ferroelectric liquid crystals 24 and 34 and the nematic liquid crystal, as shown in FIG. 9B, the spontaneous polarization direction of the second ferroelectric liquid crystal 34 is negative. It drives in the in-plane direction while changing in the same direction as the polar electric field direction, and induces in-plane driving of the nematic liquid crystal 50 adjacent thereto. In addition, the first ferroelectric liquid crystal 24 having the same spontaneous polarization direction as that of the negative electric field is maintained in an initial state without reacting to an electric field. At this time, since the nematic liquid crystal 50 is in-plane switched by the second ferroelectric liquid crystal 34, the nematic liquid crystal 50 is twisted in the vertical direction.

In the in-plane switching mode liquid crystal display device, not only a wide viewing angle is realized by in-plane driving of the nematic liquid crystal 50 but also an electric field is applied to the liquid crystal 50 in a vertical electric field manner to minimize the decrease in the aperture ratio. Furthermore, since the nematic liquid crystal 50 rotates rapidly by the ferroelectric liquid crystals 24 and 34, the response speed of the nematic liquid crystal 50 may be improved.

FIG. 10 is a diagram illustrating a case in which a liquid crystal panel into which a ferroelectric liquid crystal layer of a half V switching mode is injected is driven in a dot inversion manner, and FIG. 11 is a ferroelectric liquid crystal of a half V switching mode as illustrated in FIG. 3 or 4. It is a figure which shows the case where the liquid crystal panel in which the nematic liquid crystal layer was injected between layers was driven by the dot inversion system.

As shown in FIG. 10, if a liquid crystal display device in which a ferroelectric liquid crystal cell of a half-v switching mode is arranged in a matrix form is uniformly electric field aligned with a negative electric field and the liquid crystal display device is driven in a dot inversion manner, the ferroelectric liquid crystal Since the cell transmits light only in the positive electric field, ferroelectric liquid crystal cells transmit light one by one. That is, the radix liquid crystal cells in the odd horizontal lines and the even ferroelectric liquid crystal cells in the even horizontal lines transmit light in response to the positive electric field (+) in the odd frame and emit light in response to the negative electric field (-) in the even frame. Block it. The even-numbered liquid crystal cells in the odd horizontal line and the odd-numbered ferroelectric liquid crystal cells in the even horizontal line block light in response to the negative electric field (-) in the odd frame and transmit light in response to the positive electric field (+) in the even frame. Let's do it. At this time, as shown in FIG. 12A, only one odd liquid crystal cell is applied with data of 60 Hz, that is, an odd frame period (1Fr, 3Fr, 5Fr) to which an electric field whose polarity is reversed is applied and a positive electric field is applied. It transmits light. Therefore, when the ferroelectric liquid crystal cell of the half switching mode is uniformly electric field-oriented and inversion driven over the entire panel, the viewer perceives light periodically every frame period, so that the brightness of the display image is reduced and flickers.

On the other hand, as shown in FIG. 11, if the liquid crystal display device in which the nematic liquid crystal layer is sandwiched between the first and second ferroelectric liquid crystal layers of the half-v switching mode is driven in a dot inversion manner, the first and second ferroelectric liquid crystals are driven. One of the layers is in-plane switched in the positive electric field and the other is in-plane switched in the negative electric field. For example, the first ferroelectric liquid crystal layer is in-plane switched in the positive electric field, and the second ferroelectric liquid crystal layer is in-plane switched in the negative electric field.

That is, the radix liquid crystal cells in the odd horizontal lines and the even ferroelectric liquid crystal cells in the even horizontal lines transmit light in response to the positive electric field (+) in the radix frame and in response to the negative electric field (-) in the even frame. Penetrates. The even liquid crystal cells of the odd horizontal lines and the odd ferroelectric liquid crystal cells of the even horizontal lines transmit light in response to the negative electric field (-) in the odd frame and transmit light in response to the positive electric field (+) in the even frame. Let's do it. In this case, as shown in FIG. 12B, the data of 60 Hz, that is, the odd frame periods (1Fr, 3Fr, 5Fr) to which an electric field whose polarity is inverted is applied and a positive electric field is applied to any one liquid crystal cell as shown in FIG. Light is transmitted in the excellent frame periods 2Fr, 4Fr, and 6Fr to which a negative electric field is applied. Therefore, even when the ferroelectric liquid crystal cell of the half switching mode is uniformly field-oriented and inversion driven over the entire panel, the viewer perceives light every frame period, thereby improving the brightness of the display image.

13A and 13B are views illustrating viewing angle characteristics of a conventional twisted nematic mode liquid crystal display and an in-plane switching mode liquid crystal display according to the present invention. 13A and 13B, the azimuth angles of 90 degrees, 270 degrees, 180 degrees, and 0 degrees respectively represent up / down / left / right viewing angles, and the concentric circles represent inclination angles inclined at an azimuth angle from the display surface.

As shown in FIG. 13A, the liquid crystal display of the conventional twisted nematic mode can obtain contrast 100 at an inclination angle of 10 degrees of 45 degrees, 135 degrees, 225 degrees, and 315 degrees, and contrasts 0 to 10 at an inclination angle of 50 degrees or more. You can get it. That is, the liquid crystal display of the conventional twisted nematic mode has a relatively narrow viewing angle for obtaining high contrast.

In addition, in the liquid crystal display of the conventional twisted nematic mode, the luminance according to the viewing angle in the up / down / left / right directions should be increased according to the applied voltage, but a gray level inversion phenomenon occurs in which the luminance decreases as the voltage increases. . For example, as shown in FIG. 14A, the brightness of the 0 gray level increases more than the 95 gray level near about 50 degrees in the left / right direction. In addition, as shown in FIG. 14B, the brightness of the 255 gray level decreases from the 223 gray level and the brightness of the 191 gray level decreases from the 63 gray level near about 20-30 degrees in the up / down direction.

As shown in FIG. 13B, the in-plane switching mode liquid crystal display according to the present invention can obtain contrast 100 at an inclination angle of 40 degrees of 45 degrees, 135 degrees, 225 degrees, and 315 degrees of azimuth, and obtain a contrast of 10 at 70 degrees of inclination. Can be. And the viewing angle characteristic is symmetric up / down / left / right, so the range of up / down / left / right viewing angle is wide. That is, the liquid crystal display device of the in-plane switching mode according to the present invention has a relatively wide viewing angle attaining high contrast compared to the liquid crystal display device of the conventional twisted nematic mode. In addition, since the color coordinates of the liquid crystal display of the in-plane switching mode according to the present invention are located adjacent to the coordinates of the standard white light ([x, y] = [0.329,0.333]) as shown in FIG. 15, white balance adjustment is easy. Do.

As described above, the liquid crystal display and the driving method of the in-plane switching mode according to the present invention, the first ferroelectric liquid crystal layer and the second ferroelectric liquid crystal layer formed on each of the upper and lower substrates in response to the electric field of different polarities, respectively In-plane driving of the liquid crystal molecules of the tick-based liquid crystal layer can be induced. As such, regardless of the polarity of the voltage applied to the liquid crystal display according to the present invention by the first and second ferroelectric liquid crystal layers respectively reacting to electric fields of different polarities, the liquid crystal display may implement an image in every frame. .

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (12)

A first ferroelectric liquid crystal layer formed on the upper substrate and having spontaneous polarization in the same direction as the electric field of the first polarity; A second ferroelectric liquid crystal layer formed on the lower substrate facing the upper substrate and having spontaneous polarization in the same direction as an electric field of a second polarity; A nematic liquid crystal layer sandwiched between the first ferroelectric liquid crystal layer and the second ferroelectric liquid crystal layer; And First and second electrodes formed on each of the upper substrate and the lower substrate to apply an electric field to the first and second ferroelectric liquid crystal layers; The first ferroelectric liquid crystal layer reacts only with the electric field of the second polarity to induce in-plane driving of the nematic liquid crystal layer, and the second ferroelectric liquid crystal layer reacts only with the electric field of the first polarity of the nematic liquid crystal layer. Induces in-plane drive, An electric field whose polarity is reversed is applied to the first and second ferroelectric liquid crystal layers and the nematic liquid crystal layer in a dot inversion manner through the first and second electrodes so that polarities applied to neighboring liquid crystal cells are opposite to each other. In-plane switching mode liquid crystal display device characterized in that. The method of claim 1, And each of the first and second ferroelectric liquid crystal layers operates in a half V switching mode. The method of claim 1, A first alignment layer formed on the upper substrate; And a second alignment layer formed on the lower substrate. The method of claim 3, wherein At least one of the first and second alignment layers is any one of a polar medium and a non-polar medium, the liquid crystal display of the in-plane switching mode. The method of claim 3, wherein The spontaneous polarization of the first ferroelectric liquid crystal layer is directed toward the first alignment layer, and the spontaneous polarization of the second ferroelectric liquid crystal layer is directed toward the second alignment layer. delete The method of claim 3, wherein The spontaneous polarization of the first ferroelectric liquid crystal layer is directed toward the second alignment layer, and the spontaneous polarization of the second ferroelectric liquid crystal layer is directed toward the first alignment layer. delete Forming a first ferroelectric liquid crystal layer having spontaneous polarization in the same direction as the electric field of the first polarity on the upper substrate; Forming a second ferroelectric liquid crystal layer formed on a lower substrate facing the upper substrate and having a spontaneous polarization in the same direction as an electric field of a second polarity; Forming first and second electrodes formed on each of the upper substrate and the lower substrate to apply an electric field to the first and second ferroelectric liquid crystal layers; Forming a nematic liquid crystal layer sandwiched between the first ferroelectric liquid crystal layer and the second ferroelectric liquid crystal layer; And Applying an electric field whose polarity is reversed in a dot inversion manner to the first and second ferroelectric liquid crystal layers and the nematic liquid crystal layer so that polarities applied to neighboring liquid crystal cells are opposite to each other; The first ferroelectric liquid crystal layer reacts only with the electric field of the second polarity to induce in-plane driving of the nematic liquid crystal layer, and the second ferroelectric liquid crystal layer reacts only with the electric field of the first polarity of the nematic liquid crystal layer. A driving method of an in-plane switching mode liquid crystal display device, characterized by inducing in-plane driving. delete delete delete

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