KR20060093616A - Liquid crystal display device for driving field sequence - Google Patents

Abstract

Disclosed is a field sequential driving liquid crystal display device in which a reset voltage is not applied to a liquid crystal. Since the reset voltage V _reset is not applied to the liquid crystal filled in the liquid crystal display panel provided in the field sequential driving LCD, power consumption is reduced and response speed is improved to accurately express gray scales.

LCD, response speed, reset voltage

Description

Liquid Crystal Display Device For Driving Field Sequence

1A is a diagram illustrating a unit pixel of a field sequential driving LCD according to the related art.

1B is a liquid crystal state diagram of a field sequential driving liquid crystal display device according to the prior art.

1C is a timing diagram illustrating a liquid crystal transmittance to which a reset voltage according to the related art is applied.

2 is a block diagram illustrating a field sequential driving liquid crystal display according to an exemplary embodiment of the present invention.

3 is a liquid crystal state diagram of a liquid crystal display panel according to an exemplary embodiment of the present invention.

4 is a timing diagram illustrating liquid crystal transmittance without a reset voltage according to an exemplary embodiment of the present invention.

The present invention relates to a field sequential driving liquid crystal display device, and more particularly, to a field sequential driving liquid crystal display device having a reset section for initializing the liquid crystals before applying the gradation data voltage and not applying the gradation data voltage in the reset section. It is about.

In recent years, with the lightening and thinning of personal computers and TVs, liquid crystal display devices are also required to be lighter and thinner, and according to such requirements, liquid crystal displays (LCDs) instead of cathode ray tubes (CRTs) are required. Flat panel displays are constantly being developed.

A liquid crystal display device applies an electric field to a liquid crystal material having an anisotropic dielectric constant injected between two substrates, and adjusts the intensity of the electric field to adjust the amount of light transmitted from an external light source (backlight) to the substrate. It is a display device which obtains a desired image signal.

Such a liquid crystal display device is typical among portable flat panel displays, and among them, a TFT-LCD using a thin film transistor (TFT) as a switching element is mainly used.

In general, a liquid crystal display device includes a liquid crystal panel composed of liquid crystals injected between upper and lower substrates and upper and lower substrates, a driving circuit for driving the liquid crystal panel, and a backlight for providing white light to the liquid crystal. Such a liquid crystal display device may be divided into two methods, an R, G, and B color filter driving method and a color field sequential driving method, according to a method of displaying a color image.

The liquid crystal display of the color filter driving method is a structure in which one pixel is divided into R, G, and B subpixels, and R, G, and B color filters are arranged in each of the R, G, and B subpixels. (Light) is transmitted to the R, G, and B color filters through the liquid crystal to display the color shape.

In addition, the liquid crystal display device of the color field sequential driving method turns on independent light sources of R, G, and B colors periodically, and applies a color signal corresponding to each pixel in synchronism with the lighting cycle to achieve full color. Get a burn. That is, the liquid crystal display of the color field sequential driving method has a structure in which R, G, and B backlights are arranged in one pixel that is not divided into R, G, and B subpixels, and R, G, and B backlights are used in one pixel. By sequentially displaying the light of R, G, and B primary colors through the liquid crystal, a color shape using the afterimage effect of the eyes is displayed.

Therefore, since the color field sequential driving method requires only 1/3 of the pixels while maintaining the same resolution as the color filter method, it is possible to achieve high integration and to realize the same color reproducibility and high-speed moving picture as the color TV.

Usually, the liquid crystal of a liquid crystal display device is a substance in the intermediate state between a liquid and a crystal. The arrangement method of molecules on the liquid crystal is largely classified into three types.

First, a smectic liquid crystal is a substance in which rod-shaped molecules form a layered structure and the constituent molecules are arranged in parallel with each other. In the plane of the layer there is no regularity in the position of the molecules, but in a direction perpendicular to the plane the positional order of the molecular position is maintained and the entire molecular axis is directed in one direction. The bonds between the molecular layers are relatively weak and have a slippery property. Because of this, smectic liquid crystals exhibit the properties of two-dimensional fluids.

Next, the nematic liquid crystal is a material in which rod-shaped molecules are arranged in parallel with each other, but each molecule is relatively freely movable in the long axis direction and no layered structure exists. Because the orientation of the molecules is almost equal up and down, the polarization is canceled out, indicating no strong dielectric properties.

Next, the cholesteric liquid crystal forms a layered structure like the smectic liquid crystal, but the molecules of the long axis have an equilibrium arrangement similar to that of the nematic liquid crystal in the plane. The arrangement orientation of the molecular axis is slightly shifted between adjacent layers, and the entire liquid crystal has a helical structure. That is, the cholesteric liquid crystal exhibits optical properties such as linearity, selective light scattering, and circular polarization dichroism by the spiral structure.

1A is a diagram illustrating a unit pixel of a field sequential driving LCD according to the related art.

Referring to FIG. 1A, a unit pixel 100 of a field sequential driving liquid crystal display device includes a thin film transistor T1 and a thin film transistor T1 having a source electrode and a gate electrode connected to a data line D _m and a scan line S _n , respectively, and the thin film transistor T1. The liquid crystal cell C _LC is connected between the drain electrode and the common voltage V _com , and the storage capacitor C _st is connected to the drain electrode of the thin film transistor T1.

That is, when the thin film transistor T1 is turned on because a scan signal is applied to the scan line S _n , the data voltage V _data supplied to the data line Dm is converted to each pixel electrode through the thin film transistor T1. (Not shown). Thus, an electric field corresponding to the difference between the pixel voltage V _P and the common voltage V _com applied to the pixel electrode is applied to the liquid crystal cell C _LC to transmit light with a transmittance corresponding to the intensity of the electric field. In this case, since the pixel voltage V _P must be maintained for one frame or one field, the storage capacitor C _st is It is used auxiliary to maintain the pixel voltage V _P applied to the pixel electrode.

1B is a liquid crystal state diagram of a field sequential driving liquid crystal display device according to the prior art.

Referring to FIG. 1B, the field sequential driving LCD includes a liquid crystal display panel, and the liquid crystal 110 is filled in the liquid crystal display panel.

The liquid crystal 110 is a material having both crystal and liquid properties, and the liquid crystal 110 of the liquid crystal display panel is mostly a thermotropic LC. The liquid crystal 110 is filled between the first alignment layer 120, which is an upper substrate, and the second alignment layer 130, which is a lower substrate facing the upper substrate.

In detail, when the initial voltage V _reset is applied to the liquid crystal 110, the liquid crystal 110 is in a state in which the light transmittance is substantially 100 (white) (hereinafter, referred to as a “vertical array structure”). Has Subsequently, when the initial voltage V _reset is applied to the liquid crystal 110, the liquid crystal 110 has a light transmittance of 0 (black) in a vertically arranged structure (hereinafter, referred to as a 'horizontal arrangement'). Is converted to). In addition, when the gray scale data voltage V _data is applied to the liquid crystal 110, the liquid crystal 110 has a predetermined direction so that a pretilt angle having a slope θ is formed in a horizontal array structure. Accordingly, the liquid crystal 110 is twisted and uniformly arranged due to the gray data voltage V _data being applied thereto.

That is, when the initial voltage V _reset is applied to the liquid crystal 110 before the gray data voltage V _data for gray scale representation is applied, remind Liquid crystal 110 remind The high tilt state of the vertical array structure is changed to the low tilt state of the horizontal array structure.

Accordingly, the liquid crystal 110 receives the initial voltage V _reset and is converted from a normally white arrangement to a normally black arrangement.

For this reason, the line diameter square θ of the liquid crystal 110 is changed at the same time as the gradation data voltage V _data is changed.

Here, the wire blind spot affects the reaction time, contrast ratio, and foreground line of the liquid crystal 110, and the wire blind spot measurement method includes a capacitance method, a magnetic null method, and a crystal rotation. Crystal rotation method.

1C is a timing diagram showing a liquid crystal transmittance to which a reset voltage is applied according to the prior art.

Referring to FIG. 1C, the R, G, and B LEDs are sequentially turned on and off during one frame formed of transmittances T and R, G, and B subframes according to the grayscale data voltage V _data .

The field sequential driving liquid crystal display shows a transmittance T according to the reset voltage V _reset and the gradation data voltage V _data applied to the liquid crystal, and one frame includes an R subframe and a G subframe according to the application of the gradation data voltage V _data . And a B subframe.

The initial arrangement of the liquid crystal has a vertical array structure through which R, G, and B light sources radiated from the backlight unit of the field sequential driving liquid crystal display are transmitted.

First, when the reset voltage V _reset is applied during the time period T _R 'in the R subframe, the R transmittance T _R is initialized and the liquid crystal is normally arranged in a vertically aligned white array structure. Is converted to.

Subsequently, as the R gray data voltage V _data , _R is applied, a predetermined R transmittance T _R is decreased during the R rising time t _Rr (Red rising time) and R correction time t _RC (Red compensation time). Is generated. The R light source also emits R color light during the R subframe.

Here, the sum of the R rising time t _Rr (Red rising time) and the R compensation time t _RC (Red compensation time) is equal to the time t _{R at} which the R gray data voltage is applied.

Next, when a reset voltage V _reset is applied during a time period t _G 'in the G subframe, the G transmittance T _G is initialized and the liquid crystal is normally arranged in a vertically aligned white array structure. Is converted to.

Subsequently, as the G gray data voltage V _data , _G is applied, a predetermined G transmittance T _G is decreased during the G rising time t _Rr (Green rising time) and G correction time t _GC (Green compensation time). Is generated. The G light source also emits G color light during the G subframe.

Here, the sum of the G rising time t _Rr (Green rising time) and the G compensation time t _RC (Green compensation time) is equal to the time t _{G when the} G gray data voltage is applied.

Next, when a reset voltage V _reset is applied during a time t _B ', which is a reset period, in the G subframe, the red transmittance T _B is initialized and the liquid crystal is normally arranged in a vertically arranged white structure. Is converted to.

Subsequently, as the B gray data voltage V _data , _B is applied, a predetermined B transmittance T _B is decreased during the B rising time t _Br (Blue rising time) and B correction time t _BC (Blue compensation time). Is generated. The B light source also emits B color light during the B subframe.

Here, the sum of the B rising time t _Br (Blue rising time) and the B compensation time t _BC (Blue compensation time) is equal to the time t _{B when the} B gray data voltage is applied.

Therefore, if a predetermined reset voltage R _reset is applied to the liquid crystal having the vertical array structure before the gray scale data voltage is applied, the liquid crystal is changed to the horizontal array structure. That is, the liquid crystal is changed from the normally white state to the normally black state due to the application of the reset voltage R _reset .

Problems associated with the conventional field sequential driving liquid crystal display device related to the present invention and solved by the present invention are as follows.

The liquid crystal of the field sequential driving liquid crystal display has a reset voltage V _reset before receiving the respective R, G, and B grayscale data voltages. Once authorized It is changed from normally white with normal array structure to normally black. That is, the liquid crystal has a problem in that power consumption is high and response speed is low due to the reset voltage V _reset applied, thereby limiting gray scale expression.

SUMMARY OF THE INVENTION An object of the present invention is to provide a field sequential driving liquid crystal display device in which the initial arrangement of the liquid crystal forms a horizontal array structure, and thus does not apply the reset voltage V _reset in the reset period.

A liquid crystal display panel formed of pixels including liquid crystal filled between an upper substrate and a lower substrate opposite to the upper substrate, and configured to display a predetermined image according to the arrangement of the liquid crystals; A backlight unit irradiating R, G, and B light sources to the liquid crystal display panel; A scan driver generating a scan signal on the liquid crystal display panel; And a data driver outputting a gray data voltage to the liquid crystal display panel according to the scan signal, wherein the liquid crystal has negative dielectric anisotropy, and the pretilt angle is substantially reduced when the gray data voltage is not applied. 0 °, the pretilt angle is proportional to the gradation data voltage.

Hereinafter, described in detail with reference to the accompanying drawings of the present invention.

2 is a block diagram schematically illustrating a field sequential driving liquid crystal display according to an exemplary embodiment of the present invention.

Referring to FIG. 2, the field sequential driving LCD includes a data driver 200, a scan driver 210, a liquid crystal display panel 220, and a backlight unit 230.

The data driver 200 outputs each of the R, G, and B grayscale data voltages to a plurality of data lines of the liquid crystal display panel 220. In addition, the scan driver 210 generates a scan signal and transmits the scan signal to a plurality of scan lines of the liquid crystal display panel 220.

That is, the scan signal of the scan driver 210 of the liquid crystal display panel 220 such that the R, G, B grayscale data voltages output from the data driver 200 are displayed on the liquid crystal display panel 220. It is input to a plurality of scan lines.

The liquid crystal display panel 220 includes a liquid crystal in which the R, G, and B gray scale voltages are received and displayed, and the initial state is normally arranged in black. In addition, the liquid crystal display panel 220 is formed of pixels with liquid crystal and displays a predetermined image according to the arrangement state of the liquid crystal.

The liquid crystal is formed of a TN (Twist Nematic) module having a pretilt angle according to the R, G, and B gray voltages, and a vertical alignment mode is applied to the liquid crystal array.

The backlight unit includes an RLED 231, a GLED 232, and a B LED 233, wherein each of the R, G, B LEDs 231, 232, 233 generates the R, G, B light sources. The R, G, and B light sources sequentially transmit R, G, and B color light to the liquid crystal display panel 220.

3 is a liquid crystal state diagram of a liquid crystal display panel according to an embodiment of the present invention.

Referring to FIG. 3, the liquid crystal 240 of the liquid crystal display panel is a material having both properties of crystal and liquid, and a liquid crystal material having an initial state of normally black is applied.

That is, the liquid crystal 240 is a material in which the vertical alignment layer and the dielectric anisotropy are negative (-), and the liquid crystal 240 has a form in which the array structure is uniformly arranged in the vertical direction or the horizontal direction using a vertical alignment mode. . The liquid crystal 240 is filled between the first alignment layer 250, which is an upper substrate, and the second alignment layer 260, which is a lower substrate facing the upper substrate.

Here, the dielectric anisotropy refers to a property in which a dielectric constant in a direction perpendicular to the long axis and the long axis of the liquid crystal 240 is different, and has a dielectric constant within a range of -4.9 to -5.1.

In addition, the liquid crystal 240 has a birefringence of 11.0% to 12.1% at 460nm to 630nm, which is a wavelength range of visible light, and the liquid crystal 240 reflects a state in which a uniform molecular arrangement is changed by external force. It has an elastic modulus that is a normalized value. Here, the elastic modulus is in the range of 10 to 18.

Subsequently, when the gray scale data voltage V _data is applied to the liquid crystal 240, the liquid crystal 240 has a pretilt angle θ ′ and a liquid crystal module state of twist nematic (TN). Accordingly, the liquid crystal line 240 is also changed by the gradation data voltage V _data . In other words, when the grayscale data voltage is not applied, the pretilt angle θ 'is substantially 0 ° and the pretilt angle θ' is proportional to the grayscale data voltage.

4 is a timing diagram illustrating liquid crystal transmittance without a reset voltage according to an exemplary embodiment of the present invention.

Referring to FIG. 4, one frame formed of transmittance T and R, G, and B subframes according to respective R, G, and B gray data voltages V _data , _R , V _data , _G , V _data , and _B While the R, G, and B LEDs show an on / off state that flashes the colored light sequentially. In addition, the R, G, B gray-scale data voltage (V _{data, R,} V _{data, G,} V _{data, B)} is applied to the liquid crystal assuming R, G, B that are applied in order of.

Here, when the R, G, and B gray data voltages V _data , _R , V _data , _G , V _data and _B are applied to the liquid crystal, the liquid crystal twists and exhibits a transmittance T, which is a value through which a light source is transmitted.

Specifically, the initial arrangement of the liquid crystal has a horizontal arrangement structure that blocks the transmission of the R, G, and B light sources emitted from the backlight unit of the field sequential driving liquid crystal display according to the vertical alignment mode. The R, G and B light sources emit respective R color light, G color light and B color light during the periods of the R subframe, the G subframe and the B subframe.

First, the R subframe has a predetermined R transmittance T _R due to the application of the R gray data voltages V _data and _R during the R rising time t _Rr (Red rising time) and R correction time t _Rc (Red compensation time). That is, the RLED provided in the backlight unit receives the R gray data voltages V _data and _R to generate an R light source and transmits the R light source to the liquid crystal display panel of the field sequential driving liquid crystal display. The R transmittance T _R is initialized because the R gray data voltage V _data , _R is not applied during the R falling time t _Rf (Red falling time).

Here, the sum of the R rising time t _Rr (Red rising time) and the R falling time t _RC (Red compensation time) is the R gray scale response time t _R.

Next, the G subframe has a predetermined G transmittance T _G due to the application of the G gray data voltage V _data and _G during the G rising time t _Gr (Green rising time) and the G compensation time t _GC (Green compensation time). That is, the GLED included in the backlight unit receives the G gray data voltages V _data and _G to generate a G light source and transmits the G light source to the liquid crystal display panel of the field sequential driving LCD. In addition, the G transmittance T _G is initialized because the G gray data voltage V _data , _G is not applied during the G falling time t _Gf (Green falling time).

Here, the sum of the G rising time t _Gr (Green rising time) and the G falling time t _GC (Green compensation time) is the G gray scale response time t _G.

Next, the B subframe has a predetermined B transmittance T _B due to the application of the B gray scale data voltages V _data and _B during the B rising time t _Br (Blue rising time) and the B compensation time t _BC (Blue compensation time). That is, the BLED included in the backlight unit receives the B gray data voltages V _data and _B to generate a B light source and transmits the B light source to the liquid crystal display panel of the field sequential driving liquid crystal display. In addition, the B transmittance T _B is initialized because the B gray data voltage V _data , _B is not applied during the B falling time t _Rf (Blue falling time).

Here, the sum of the B rising time t _Br (Red rising time) and the B falling time t _Bc (Blue compensation time) is the B gray scale response time t _B.

Therefore, the liquid crystal having the initial horizontal array structure is uniformly arranged to form the pretilt angle θ 'by the respective R, G, and B gray data voltages.

The liquid crystal having the initial horizontal array structure according to the embodiment of the present invention can obtain the response speed from the transmittance due to the application of the respective R, G, B gray voltages.

The response speed is a time value obtained by adding the rising time and the polling time, and the liquid crystal having the initial horizontal arrangement has a response speed within a range of 3.6 ms to 3.7 ms according to the respective R, G, and B gray data voltages. Have

Although the above has been described with reference to the preferred embodiment of the present invention, those skilled in the art will be variously modified and modified within the scope of the present invention without departing from the spirit and scope of the present invention described in the claims below. It will be appreciated that it can be changed.

According to the present invention described above, the field sequential driving liquid crystal display device does not apply the reset voltage V _reset to the liquid crystal filled in the liquid crystal display panel provided in the field sequential driving liquid crystal display device, thereby reducing power consumption and improving response speed. Improves the effect of gradation.

Claims (8)

A liquid crystal display panel formed of pixels including liquid crystal filled between an upper substrate and a lower substrate opposite to the upper substrate, and configured to display a predetermined image according to the arrangement of the liquid crystals; A backlight unit irradiating R, G, and B light sources to the liquid crystal display panel; A scan driver generating a scan signal on the liquid crystal display panel; And A data driver for outputting a gray scale data voltage to the liquid crystal display panel according to the scan signal, The liquid crystal has negative dielectric anisotropy, and the pretilt angle is substantially 0 ° when the grayscale data voltage is not applied. And the pretilt angle is proportional to the gradation data voltage. 2. The field sequential driving liquid crystal display device according to claim 1, wherein the liquid crystal has a response speed in a range of 3.6 ms to 3.7 ms. The field sequential driving liquid crystal display device according to claim 1, wherein the dielectric anisotropy has a dielectric constant in a range of -4.9 to -5.1. The liquid crystal display of claim 1, wherein the initial arrangement of the liquid crystals has a horizontal arrangement that blocks the R, G, and B light sources from being transmitted from the backlight unit. The liquid crystal display of claim 1, wherein the liquid crystal has a wavelength band within a range of 460 nm to 630 nm. 6. The field sequential driving liquid crystal display device according to claim 5, wherein the liquid crystal has a birefringence within a range of 11.0% to 12.1% within a range having the wavelength band. The field sequential driving liquid crystal display device according to claim 1, wherein the liquid crystal has an elastic modulus within a range of 10 to 18. The liquid crystal display of claim 1, wherein the gray level data voltage is a voltage for arranging the liquid crystal having an initial horizontal array structure at a pretilt angle.

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