JP2010191278A - Method for driving liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for driving a liquid crystal display device, by which bias of charge is prevented by suppressing color breaks. <P>SOLUTION: In the method for driving a liquid crystal display device in which a backlight is divided into 2n (n is an integer from 2 to 4) regions in a scanning direction, a write period, a common electrode voltage change period, a liquid crystal response period, and a lighting period are provided in each sub-frame, and a voltage applied to a common electrode is changed from a reference value in the common electrode period so that a voltage which resets a driven state of ferroelectric liquid crystal is applied to the ferroelectric liquid crystal, and two optional regions out of the 2n regions form one group, and write periods are provided in order for each color per region in regions of each group, and write periods are provided in order for each of a plurality of colors per group in 2n regions. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for driving a liquid crystal display device by a field sequential method using a ferroelectric liquid crystal.

  Liquid crystal display devices are widely used in applications ranging from large displays to portable information terminals because of their thinness and low power consumption, and their development is actively underway. To date, liquid crystal display devices have been developed and put to practical use, such as TN mode, STN multiplex drive, and active matrix drive using thin layer transistors (TFTs) for TN, but these use nematic liquid crystals. In addition, the response speed of the liquid crystal material is as slow as several ms to several tens of ms, and it cannot be said that it is sufficiently compatible with moving image display.

Ferroelectric liquid crystal (FLC) is a liquid crystal suitable for high-speed devices because its response speed is as short as μs order. Ferroelectric liquid crystals proposed by Clark and Lagerwol are widely known as bistable ones having two stable states when no voltage is applied (the upper part of FIG. 12), but for switching in two states of light and dark. Although it has limited memory characteristics, it has a problem that gradation display cannot be performed.
Therefore, in recent years, the state of the liquid crystal layer when no voltage is applied is stabilized in one state (hereinafter referred to as “monostable”). It has been noted that gradation display is possible by continuously changing the slope of the light intensity and modulating the transmitted light intensity by analog modulation (see Non-Patent Document 1, lower part of FIG. 12).

  In recent years, color liquid crystal display devices have been actively developed. As a method for realizing color display, there are generally a color filter method and a field sequential method. In the color filter system, a white light source is used as a backlight, and color display is realized by attaching R, G, B micro color filters to each pixel. On the other hand, the field-sequential method switches the backlight to, for example, R, G, B, R, G, B, etc., and opens and closes the black and white shutter of the ferroelectric liquid crystal in synchronization with it, and the afterimage effect of the retina Thus, the colors are mixed temporally to realize color display. In this field sequential method, color display is possible with one pixel, and it is not necessary to use a color filter with low transmittance, so that bright and high-definition color display is possible, and low power consumption and low cost can be realized. It is useful in.

  Since the field sequential method divides one pixel in time, in order to obtain good moving image display characteristics, the liquid crystal as a black and white shutter needs to have high-speed response. If a ferroelectric liquid crystal is used, this problem can be solved. As described above, the ferroelectric liquid crystal used in this case is preferably one that exhibits monostableness in order to enable gradation display by analog modulation and realize high-definition color display as described above. In addition, the ferroelectric liquid crystal exhibiting monostability includes a liquid crystal that responds to voltages of both positive and negative polarities and exhibits V shaped switching characteristics (lower right in FIG. 12), and has either positive or negative polarity. Some of them respond to voltage only and show half-V shaped switching characteristics (lower left in FIG. 12). In particular, when a ferroelectric liquid crystal is driven using a switching element such as a thin film transistor (TFT) element, the one having a half V-shaped switching characteristic is particularly preferable because the influence of reversal current due to spontaneous polarization is small. .

  However, in a liquid crystal display device using a ferroelectric liquid crystal exhibiting a half V-shaped switching characteristic, the ferroelectric liquid crystal responds only to a voltage of either positive or negative polarity. There is a risk that it will be biased and will not operate normally.

  Therefore, a driving method has been proposed in which voltage is applied to the liquid crystal by simultaneously selecting a plurality of pixel electrodes during the erasing process, and the light source is turned on only after data writing scanning to all the pixel electrodes (see, for example, Patent Document 1). ). In this driving method, during the erasing process, voltage application to the liquid crystal by simultaneous selection of a plurality of pixel electrodes is performed a plurality of times, thereby canceling the charge bias.

  On the other hand, in the field sequential method, since light sources of multiple colors are sequentially turned on, when a fast moving video is displayed, a phenomenon in which colors appear to be separated, a so-called color break occurs, and the image quality is significantly reduced. There's a problem. In order to solve this problem, the lighting times of the light sources of a plurality of colors may be shortened.

  In the driving method of Patent Document 1, since the time required for erasing can be reduced, it is considered that the intervals between the lighting periods of the light sources of a plurality of colors can be shortened. However, if the time for applying the reverse polarity voltage during the erasing process is too short, the charge balance becomes poor, and the responsiveness of the ferroelectric liquid crystal gradually decreases. In addition, if the time for applying the reverse polarity voltage during the erasing process is long, it is difficult to shorten the interval between the lighting periods of the light sources of a plurality of colors.

  Further, in the liquid crystal display device, as a method of reducing outline blurring when displaying a moving image, a method of dividing a display area into a plurality of parts and sequentially turning on a light source for each light emission divided area corresponding to the plurality of divided display areas Has been proposed (see, for example, Patent Document 2).

  When sequentially turning on the light source for each light-emitting divided area and writing the RGB three-color image data one by one in all the divided display areas, the red image data is sequentially written in all the divided display areas, and then all The green image data is sequentially written in the divided display areas, and the blue image data is sequentially written in all the divided display areas. In this case, it is difficult to shorten the interval between the lighting periods of the light sources of a plurality of colors.

JP 2003-5153 A JP 2004-62134 A

NONAKA, T., LI, J., OGAWA, A., HORNUNG, B., SCHMIDT, W., WINGEN, R., and DUBAL, H., 1999, Liq. Cryst., 26, 1599.

  The present invention has been made in view of the above circumstances, and a main object of the present invention is to provide a driving method of a liquid crystal display device capable of suppressing color breaks and preventing charge bias.

  To achieve the above object, according to the present invention, the backlight is divided into 2n (n is an integer of 2 to 4) areas in the scanning direction, and the backlight is provided with a light source of a plurality of colors for each of the areas. A method of driving a liquid crystal display device using a ferroelectric liquid crystal exhibiting monostability and exhibiting half V-shaped switching characteristics, wherein a plurality of the one region is included in each subframe. A voltage is sequentially applied to the gate lines to turn on the plurality of switching elements in order, and a writing period in which a voltage having the first polarity is applied to the plurality of source lines and after the writing period, A common electrode voltage change period in which the voltage applied to the common electrode is changed from a reference value so that a voltage that resets the driving state of the dielectric liquid crystal is applied, and after the common electrode voltage change period, The liquid crystal response period for returning the voltage applied to the reference value to wait for the ferroelectric liquid crystal to respond and the lighting period for turning on the light source of one color provided in the area after the liquid crystal response period are provided. Then, any two of the above 2n areas are set as one set, and a writing period is alternately provided for each area in each set of areas, and a plurality of colors are set for each set in the 2n areas. Provided is a method for driving a liquid crystal display device, in which writing periods are sequentially provided.

  According to the present invention, any two regions out of 2n regions are set as one set, and a writing period is sequentially provided for each region in each set region, and 2n regions are provided for each set. Since writing periods are sequentially provided for each of a plurality of colors, the interval between the lighting periods of the light sources of the plurality of colors can be shortened, and a color break can be suppressed. In addition, by providing a common electrode voltage change period between the writing period and the liquid crystal response period in one region, the voltage applied to the common electrode also changes in another region, and the ferroelectricity is changed in one frame. Since a voltage for resetting the driving state of the ferroelectric liquid crystal is applied to the liquid crystal a plurality of times, it is possible to prevent the charge from being biased.

  In the above invention, after the lighting period, a voltage is simultaneously applied to the plurality of gate lines in the region to simultaneously turn on the plurality of switching elements, and simultaneously to the plurality of source lines with respect to the first polarity. It has an erasing period in which either a second polarity voltage of reverse polarity or a zero voltage is applied, and the common electrode voltage change period of one region is provided within the erasing period of a region other than this region It is preferable. This is because a voltage that resets the driving state of the ferroelectric liquid crystal can be applied to the ferroelectric liquid crystal with a larger value, and the balance of charges can be efficiently achieved.

  In the present invention, it is preferable that the time during which the voltage is simultaneously applied to the plurality of gate lines in the erasing period is longer than the time required for the response of the ferroelectric liquid crystal. This is because the charge amount of each pixel can be equalized by turning on the gate line longer than the response time of the ferroelectric liquid crystal in the erasing period. Thereby, it is possible to prevent the charge balance from deteriorating and the response of the ferroelectric liquid crystal from being lowered.

  Further, in the present invention, the scanning order in the writing period of the previous subframe and the scanning order in the writing period of the next subframe may be reversed. This is because the time during which a voltage is applied between the electrodes of the pixels along each gate line can be averaged.

  In the present invention, when the writing period of a certain area overlaps with the lighting period of the area adjacent to the area, the writing period of the certain area is adjacent to the area. You may scan from the said gate line located in the opposite side to the side in which the area | region to provide is provided. This is because light leakage can be prevented.

  Furthermore, in the present invention, it is preferable that the two arbitrary regions are not adjacent to each other. This is because light leakage can be prevented.

  In the present invention, the backlight is divided into 2n (n is an integer of 2 to 4) areas in the scanning direction, and a plurality of color light sources are provided for each of the areas, a plurality of gate lines, and a plurality of sources. Lines, a plurality of switching elements connected to the gate lines and source lines and arranged for each pixel, a plurality of pixel electrodes connected to the switching elements and arranged for each pixel, and opposed to the pixel electrodes A common electrode disposed at a position, a ferroelectric liquid crystal disposed between the pixel electrode and the common electrode, a gate driver connected to the plurality of gate lines to apply a scanning signal, and the plurality of source lines. A liquid crystal panel having a source driver for applying an image signal, and a driving method for the liquid crystal display device connected to the gate driver, the source driver, and the backlight. Thus to provide a liquid crystal display device characterized by having a control unit for driving the liquid crystal display device.

  Since the liquid crystal display device of the present invention is driven by the above-described driving method of the liquid crystal display device, it is possible to prevent a bias in charge and suppress a color break.

  In the present invention, any two regions out of 2n regions obtained by dividing the backlight in the scanning direction are set as one set, and a writing period is sequentially provided for each region in each set region. Since the writing period is sequentially provided for each set in each region, a color break can be suppressed. In addition, since the common electrode voltage change period is provided, there is an effect that it is possible to prevent the charge from being biased.

It is a schematic diagram which shows the behavior of a liquid crystal molecule. It is the graph which showed the change of the transmittance | permeability with respect to the applied voltage of a ferroelectric liquid crystal. It is a schematic diagram which shows an example of the circuit diagram of the liquid crystal display device of this invention. 4 is a timing chart illustrating an example of a driving method of the liquid crystal display device of the present invention. It is a timing chart which shows the other example of the drive method of the liquid crystal display device of this invention. It is a timing chart which shows the other example of the drive method of the liquid crystal display device of this invention. It is a timing chart which shows the other example of the drive method of the liquid crystal display device of this invention. It is a timing chart which shows the other example of the drive method of the liquid crystal display device of this invention. It is a timing chart which shows the other example of the drive method of the liquid crystal display device of this invention. It is a schematic diagram which shows 2n area | regions. It is a schematic perspective view which shows an example of the liquid crystal display device of this invention. It is the graph which showed the change of the transmittance | permeability with respect to the applied voltage of a ferroelectric liquid crystal.

  Hereinafter, the driving method and the liquid crystal display device of the liquid crystal display device of the present invention will be described in detail.

A. Driving method of liquid crystal display device In the driving method of the liquid crystal display device of the present invention, the backlight is divided into 2n (n is an integer of 2 to 4) areas in the scanning direction, and the backlight has a plurality of colors in each area. And a liquid crystal display device using a ferroelectric liquid crystal that exhibits monostability and exhibits a half-V-shaped switching characteristic. A voltage is sequentially applied to a plurality of gate lines in each region to turn on the plurality of switching elements in order, and a ferroelectric layer is applied with a first polarity voltage to the plurality of source lines, and after the writing period, the ferroelectric A common electrode voltage change period in which the voltage applied to the common electrode is changed from a reference value so that a voltage that resets the driving state of the ferroelectric liquid crystal is applied to the conductive liquid crystal, and the common electrode voltage change After a period, the voltage applied to the common electrode is returned to the reference value, and a liquid crystal response period for waiting for the ferroelectric liquid crystal to respond, and after the liquid crystal response period, one color light source provided in the region is turned on. A lighting period is set, and any two of the 2n areas are set as one set, and a writing period is alternately provided for each area in each set of areas. Thus, a plurality of colors are provided in order for each set in order.

The ferroelectric liquid crystal used in the present invention exhibits monostability and half V-shaped switching characteristics.
“Showing monostability” means a state in which the state of the ferroelectric liquid crystal when no voltage is applied is stabilized in one state. As illustrated in FIG. 1, the ferroelectric liquid crystal rotates along a cone ridge line in which the liquid crystal molecules 1 are inclined from the layer normal z and have a bottom surface perpendicular to the layer normal z. In such a cone, the tilt angle of the liquid crystal molecules 1 with respect to the layer normal z is referred to as a tilt angle θ. Thus, the liquid crystal molecules 1 can operate on the cone between two states inclined by a tilt angle ± θ with respect to the layer normal z. Specifically, showing monostability means a state where the liquid crystal molecules 1 are stabilized in any one state on the cone when no voltage is applied.

In the present invention, a ferroelectric liquid crystal exhibiting a half-V shaped switching characteristic in which liquid crystal molecules operate only when a positive or negative voltage as illustrated in FIG. 2 is applied. Used. Using a ferroelectric liquid crystal exhibiting such a half V-shaped switching characteristic, it is possible to take a sufficiently long opening time as a black and white shutter, thereby making it possible to display each color that is temporally switched brighter. A liquid crystal display device with bright color display can be realized.
The “half V-shaped switching characteristic” refers to an electro-optical characteristic in which the light transmittance with respect to an applied voltage is asymmetric.

The driving method of the liquid crystal display device of the present invention will be described with reference to the drawings.
FIG. 3 is a circuit diagram of the liquid crystal display device. The circuit illustrated in FIG. 3 includes j rows of gate lines G ₁ , G ₂ ,... G _j and k columns of source lines S ₁ , S _{2 ,.} , J row gate lines G ₁ , G ₂ ,... G _j , and k column source lines S ₁ , S _{2 ,.} . These gate lines _{G 1, G 2, ... G} j and a source line _{S 1,} S 2, ... in each pixel in the vicinity of each intersection of _{S k,} gate lines _{G 1, G 2, ... G} j and Switching elements 4 are arranged in a state of being connected to the source lines S ₁ , S ₂ ,... S _k , and pixel electrodes 5 are connected to the respective switching elements 4.

  The gate driver applies a voltage to the gate line (supplying a scanning signal), and the source driver applies a positive or negative voltage to the source line (supplying an image signal). At this time, an image signal corresponding to one unit color among a plurality of unit colors for displaying an arbitrary color by mixed color is supplied to the source line. As a result, the gate driver sequentially applies voltages to the plurality of gate lines to sequentially turn on the plurality of switching elements in units of gate lines, and the source driver applies positive or negative voltage to the plurality of source lines. The ferroelectric liquid crystal is driven by applying a positive or negative voltage to the ferroelectric liquid crystal through the switching element and the pixel electrode. That is, a voltage corresponding to the image signal is applied between the pixel electrode and the common electrode of the pixel along each gate line, and image data is written to each pixel along the gate line, and the response of the ferroelectric liquid crystal to this Depending on the degree, the light transmittance of each pixel is controlled.

  FIG. 4 is a timing chart showing an example of a method for driving a liquid crystal display device by a field sequential method using the circuit diagram shown in FIG. As the ferroelectric liquid crystal, a liquid crystal molecule that operates only when a positive voltage is applied as illustrated in FIG. 2B is used.

In FIG. 4, Scan schematically shows a state in which m rows of gate lines G ₁ , G ₂ ,... G _m in each region are scanned, and the LED indicates the lighting timing of the light source (RGB three-color light source). It is shown. In addition, a period in which one full-color still image is displayed is 1 frame F, and a period in which one RGB still image is displayed is a subframe SF _R , SF _G , SF _B.

FIG. 5 is a timing chart in regions A ₁ and A ₃ shown in FIG. In FIG. 5, Scan schematically shows a state in which m rows of gate lines are sequentially scanned, V _p indicates a change in the voltage applied to the pixel electrode along the first row of gate lines, and V _com Indicates a change in the voltage applied to the common electrode, V _p -V _com indicates a change in the voltage applied to the ferroelectric liquid crystal, and LED indicates the lighting timing of the light source (RGB three-color light source). Is. In addition, a period in which one full-color still image is displayed is one frame F, and a period in which one RGB still image is displayed is subframes SF _R , SF _G , and SF _B.

As shown in FIG. 3, j rows of gate lines G ₁ , G ₂ ,... G _j are divided into _four regions A _{1 to} A ₄ for each m rows. A color light source is provided. That is, the backlight is divided into _four areas A _{1 to} A ₄ in the scanning direction, and the backlight is provided with light sources of a plurality of colors for each area. In the four areas A _{1 to} A ₄ , any two areas are set as one set. In FIG. 4, the areas A ₁ and A ₃ are set as a first set, and the areas A ₂ and A ₄ are set as a second set. A writing period is sequentially provided for each region in each set of regions, and a plurality of colors are sequentially provided for each set in 2n regions.

First, in the first set of regions _{A 1,} in subframe SF _R, gate lines _G 1 m rows by the gate driver _2, G 2, ... by applying a voltage in the order of the m-th row from the first row to _{G m} a plurality of switching elements 4 as well as on the order in the gate line basis, the source lines S ₁ k columns by the source driver _3, S 2, _... applies a positive voltage to S _k, the switching element 4 and the pixel electrode 5 The ferroelectric liquid crystal is driven by applying a positive voltage to the ferroelectric liquid crystal via the. In this manner, voltages are sequentially applied to a plurality of gate lines in one region to turn on the plurality of switching elements in order, and the first polarity is applied to the plurality of source lines (in FIG. 4, positive polarity is assumed). period for applying a voltage is a write period T _a.

Next, the voltage applied to the common electrode is changed so that a voltage that resets the driving state of the ferroelectric liquid crystal is applied to the ferroelectric liquid crystal. Specifically, since the driving state of the ferroelectric liquid crystal is reset when a negative voltage is applied as shown in FIG. 2B, V _p −V _com is negative as shown in FIG. The voltage V _com applied to the common electrode is changed from the reference value so as to be (−). That is, V _com is set to the positive (+) side. In this way, after the writing period, the common electrode is applied such that a voltage that resets the driving state of the ferroelectric liquid crystal (a negative voltage in FIG. 4) is applied to the ferroelectric liquid crystal. period for changing the voltage applied from the reference value is a common electrode voltage change period T _b.
By changing the voltage applied to the common electrode as described above, a voltage that resets the driving state of the ferroelectric liquid crystal is applied to the ferroelectric liquid crystal. That is, the driving state of the ferroelectric liquid crystal is reset.

Next, the voltage applied to the common electrode is returned to the reference value, and a liquid crystal response period T _c for waiting for the ferroelectric liquid crystal to respond is provided as a time for almost completing the response of the ferroelectric liquid crystal.

Next, after the ferroelectric liquid crystal is driven, the red light R is irradiated from the red light source for a predetermined time so that the red image is recognized. Thus, the period during which the light source is turned on after the liquid crystal response period is the lighting period _Td .

Then, even in the sub-frame SF _G and SF _B, similarly to the sub-frame SF _R, performs write, the common electrode voltage changes, the liquid crystal response and lighting. Then, it is a non-selection period T _h.

Further, in the first set of regions A _3, in the same manner as area A _1, the writing, the common electrode voltage changes, liquid crystal response, lighting, writing, common electrode voltage changes, liquid crystal response, lighting, writing, common electrode voltage changes, The liquid crystal responds and lights up and is subsequently deselected.

In the first set of regions _A 1, _{A 3,} following the writing period _{T a} of the sub-frame SF _R region _{A 1,} the writing period _{T a} of the sub-frame SF _R region _{A 3} is provided. Moreover, following the writing period _{T a} of the sub-frame SF _R region _{A 3,} the writing period _{T a} of the sub-frame SF _G region _{A 1} is provided. That is, the write period, region subframe _{A 1} SF writing period _{R T a,} the writing period _{T a} of the sub-frame SF _R region _{A 3,} the area _{A 1} of the sub-frame SF writing period of _{G T a,} the area A writing period of ₃ subframes SF _{G T a,} the writing period _{T a} of the sub-frame SF _B regions _{a 1,} are provided in the order of writing period _{T a} of the sub-frame SF _B area _{a 3.}
Thus, in each set of areas, red image data is first written in each area in turn, then green image data is written in each area in order, and finally blue image data is written in each area in order. That is, the writing period is provided in order for each color in each set of regions.

Further, in the second set area A ₂ , similarly to the first set area A ₁ , writing, common electrode voltage change, liquid crystal response, lighting, writing, common electrode voltage change, liquid crystal response, lighting, writing, common Electrode voltage change, liquid crystal response and lighting are performed, and then unselected.
Further, in the second group A ₄ , similarly to the first group A ₁ , writing, common electrode voltage change, liquid crystal response, lighting, writing, common electrode voltage change, liquid crystal response, lighting, writing, common Electrode voltage change, liquid crystal response and lighting are performed, and then unselected.

In the second set of regions _A 2, _{A 4,} similarly to the first set of regions _A 1, _{A 3,} writing period, the area _{A 2} of the sub-frame SF _R writing period _{T a,} the sub-frame region _{A 4} SF writing period _{R T a,} the writing period _{T a} of the sub-frame SF _G regions _{a 2,} area writing period _{T a} of the sub-frame SF _G of _{a 4,} the writing period of the sub-frame SF _B region _{a 2 T} a, It is provided in order of the writing period _{T a} of the sub-frame SF _B area _{a 4.}

Furthermore, a first set of regions _{A 3} in the second set of regions _{A 2,} following the writing period _{T a} of the sub-frame SF _B area _{A 3,} sub-frame regions _{A 2} SF writing period _{R T a} Is provided. Also, a second set of regions _{A 4} in the first set of regions _{A 1} and, following the writing period _{T a} of the sub-frame SF _B area _{A 4,} subframe areas _{A 1} SF writing period _{R T a} Is provided. That is, the write period, region subframe _{A 1} SF writing period _{R T a,} the writing period _{T a} of the sub-frame SF _R region _{A 3,} the area _{A 1} of the sub-frame SF writing period of _{G T a,} the area A ₃ subframe SF _G write period T _a , area A ₁ subframe SF _B write period T _a , area A ₃ subframe SF _B write period T _a , area A ₂ subframe SF _R write period _{T a,} the writing period of the sub-frame SF _R region _{a 4 T a,} the writing period _{T a} of the sub-frame SF _G area _{a 2,} the region _{a 4} subframes SF _G writing period _{T a,} the area _{a 2} writing period of the sub-frame SF _{B T a,} it is repeatedly arranged in the order of writing period _{T a} of the sub-frame SF _B area _{a 4.}
In this way, the three color image data are sequentially written in the first set of areas, and then the three color image data are sequentially written in the second set of areas. That is, the writing period is provided in order of plural colors for each group in 2n areas.

  In one area, a series of driving (writing, common electrode voltage change, liquid crystal response, lighting, writing, common electrode voltage change, liquid crystal response, lighting, writing, common electrode voltage change, liquid crystal response, lighting and non-selection) This is repeated while changing the color RGB of the light emitted from the light source and the image to be displayed. In one set of areas, image data is written for each color. Then, in 2n areas, image data is written in three colors of RGB for each set. By repeating such a series of driving operations, images of different colors can be visually mixed and recognized as a full color image.

According to the present invention, an arbitrary two regions are set as one set, and a writing period is alternately provided for each region in each set of regions, and a writing period is provided for each group in a plurality of colors in 2n regions. Are provided in order, the intervals of the lighting periods of the light sources of the plurality of colors can be shortened, and color breaks can be suppressed. For example, in FIG. 4, in any of the areas A _{1 to} A ₄ , the interval between the lighting period T _d of the red R light source and the lighting period T _d of the green G light source, and the lighting period T of the green G light source. it is possible to shorten the distance between the lighting period T _d of the light source of the _d and blue B.

  On the other hand, for example, when writing periods are sequentially provided for each color in 2n areas, when writing image data of RGB three colors, red image data is sequentially written in 2n areas, and then 2n Since the green image data is sequentially written in this area, and then the blue image data is sequentially written in the 2n areas, it is difficult to shorten the intervals of the lighting periods of the three color light sources.

  In the present invention, any two areas are set as one set, and a writing period is sequentially provided for each area in each set area, and a plurality of colors are sequentially set for each group in 2n areas. Therefore, when writing RGB three-color image data, red image data is sequentially written in a certain set of areas, then green image data is sequentially written in that set of areas, and then in that set of areas. Blue image data is sequentially written, and red image data is sequentially written in the next set of areas. Therefore, it is possible to shorten the interval between the lighting periods of the light sources of a plurality of colors. Therefore, in the present invention, color break can be suppressed.

  Further, according to the present invention, the common electrode voltage change period in which the voltage applied to the common electrode is changed from the reference value so that a voltage that resets the driving state of the ferroelectric liquid crystal is applied to the ferroelectric liquid crystal. Therefore, a voltage that resets the driving state of the ferroelectric liquid crystal is applied to the ferroelectric liquid crystal during the common electrode voltage change period. After completion of the writing period, the driving state of the ferroelectric liquid crystal (the degree of modulation of the liquid crystal) differs according to the scanning order. However, by changing the voltage applied to the common electrode as described above, the common state after the writing period is changed. The driving state of the ferroelectric liquid crystal can be reset during the electrode voltage change period. Thereby, the difference in brightness depending on the scanning order can be eliminated.

Usually, since the common electrode is common to all regions, while the common electrode voltage change period is provided in one region, the common electrode voltage change period is similarly provided in other regions. . For example, as shown in FIG. 4, a common electrode voltage change period (hereinafter also referred to as a first common electrode voltage change period) T _b is provided between the writing period _Ta and the liquid crystal response period T _c in the region A ₁ . during are other areas a _2, a _3, a ₄ also similarly common electrode voltage change period (hereinafter, also referred to as a second common electrode voltage change period.) T _e is provided. That is, a common electrode voltage change period is provided a plurality of times in one frame. As described above, in the present invention, by providing the common electrode voltage change period a plurality of times in one frame, it is possible to prevent the charge from being biased.

  In this specification, the common electrode voltage change period provided between the writing period and the liquid crystal response period is referred to as a first electrode voltage change period, and the other common electrode voltage change period is referred to as a second electrode voltage change period. Sometimes it is.

Here, a common electrode voltage change period is provided between the writing period and the liquid crystal response period. However, since only the voltage applied to the common electrode is changed, the written image data does not change. . In the present invention, since the liquid crystal response period is provided as the time when the response of the ferroelectric liquid crystal is almost completed after the common electrode voltage change period, the written image data is changed by changing the voltage applied to the common electrode. It will not be affected.
Further, the writing period and the second common electrode voltage change period may overlap in one region, but as described above, only the voltage applied to the common electrode is changed in the second common electrode voltage change period. Therefore, the written image data is not affected.

FIG. 6 is a timing chart showing an example of a method of driving a liquid crystal display device by a field sequential method using the circuit diagram shown in FIG. As the ferroelectric liquid crystal, a liquid crystal molecule that operates only when a positive voltage is applied as illustrated in FIG. 2B is used. Moreover, the symbols in FIG. 6 are the same as the symbols in FIG.
FIG. 7 is a timing chart in regions A ₁ and A ₃ shown in FIG. The symbols in FIG. 7 are the same as the symbols in FIG.

First, in the first set of regions _{A 1,} in subframe SF _R frame _{F 1,} the gate lines _G 1 m _rows, G 2, ... by applying a voltage in the order of the m-th row from the first row to _{G m} The plurality of switching elements 4 are sequentially turned on in units of gate lines, and a positive voltage is applied to the _k source lines S ₁ , S ₂ ,... A ferroelectric liquid crystal is driven by applying a positive voltage to the dielectric liquid crystal (writing period T _a ). Then, after the writing period T _a, it provided a common electrode voltage change period T _b for varying the voltage applied to the common electrode. Then, after the common electrode voltage change period T _b, it provided a liquid crystal response period T _c as the ferroelectric liquid crystal response time (rise time). Next, after the ferroelectric liquid crystal is driven, the red light R is emitted from the red light source for a predetermined time so that the red image is recognized (lighting period T _d ). Then, the gate lines _{G 1,} G 2 of the m rows, ... with simultaneously on a plurality of the switching elements 4 and simultaneously applying a voltage to the _{G m,} the source lines _S 1 of k _columns, S 2, ... _{S k} simultaneously A zero voltage is applied to reset the driving state of the liquid crystal (erasing period T _f ).

Next, in the sub-frame SF _G, as with the sub-frame SF _R, write, the common electrode voltage changes, liquid crystal response, lighting and erasing. Next, performed in the sub-frame SF _B, similarly to the sub-frame SF _R, write, the common electrode voltage changes, liquid crystal response, lighting and erasing. Then, it is a non-selection period T _h.

In the first group A ₃ , similarly to the area A ₁ , writing, common electrode voltage change, liquid crystal response, lighting, erasing, writing, common electrode voltage change, liquid crystal response, lighting, erasing, writing, common The electrode voltage change, liquid crystal response, lighting and erasing are performed, and it is not selected.

Further, in the second group A ₂ , similarly to the area A ₁ , writing, common electrode voltage change, liquid crystal response, lighting, erasing, writing, common electrode voltage changing, liquid crystal response, lighting, erasing, writing, common The electrode voltage change, liquid crystal response, lighting and erasing are performed, and it is not selected.
Furthermore, even the second set of regions A _4, in the same manner as area A _1, the writing, the common electrode voltage changes, liquid crystal response, lighting, erase, write, the common electrode voltage changes, liquid crystal response, lighting, erase, write, common The electrode voltage change, liquid crystal response, lighting and erasing are performed, and it is not selected.

  In one area, a series of driving (writing, common electrode voltage change, liquid crystal response, lighting, erasing, writing, common electrode voltage change, liquid crystal response, lighting, erasing, writing, common electrode voltage change, liquid crystal response, lighting, Erasing and non-selection) are repeated while changing the color RGB of light emitted from the light source and the image to be displayed. In one set of areas, image data is written for each color. Then, in 2n areas, image data is written in three colors of RGB for each set. By repeating such a series of driving operations, images of different colors can be visually mixed and recognized as a full color image.

  In the present invention, after the lighting period, a plurality of switching elements are simultaneously turned on by simultaneously applying a voltage to a plurality of gate lines in one region, and a second polarity voltage or a zero voltage is simultaneously applied to a plurality of source lines. It is preferable to have an erasing period in which any of the above is applied. Since the driving state of the ferroelectric liquid crystal in each pixel is simultaneously reset in the erasing period, it does not take time to erase the image data written in each pixel in the writing period. Since the erasing period can be shortened in this way, even when the erasing period is provided, the interval between the lighting periods of the light sources of a plurality of colors can be shortened. In addition, there is an erasing period after the lighting period, and the driving state of the ferroelectric liquid crystal in each pixel is reset all at once, so that the fluctuation of the image display in the next subframe due to the image display in the previous subframe is completely eliminated. Therefore, it is possible to realize gradation display with good reproducibility.

In the case of having an erasing period, the first common electrode voltage change period of one region is provided in an erasing period of a region other than this region.
In the common electrode voltage change period, the voltage applied to the common electrode is changed so that a voltage that resets the driving state of the ferroelectric liquid crystal is applied to the ferroelectric liquid crystal. Specifically, since the driving state of the ferroelectric liquid crystal is reset when a negative voltage is applied as shown in FIG. 2B, V _p −V _com is negative as shown in FIG. The voltage V _com applied to the common electrode is changed from the reference value so as to be (−). That is, V _com is set to the positive (+) side. When the voltage applied to the common electrode is changed in this way, a voltage that resets the driving state of the ferroelectric liquid crystal is applied to the ferroelectric liquid crystal.
Further, the voltage applied to the source line is set so that a voltage that resets the driving state of the ferroelectric liquid crystal is applied to the ferroelectric liquid crystal even during the erasing period.
Therefore, since the first common electrode voltage change period in one region overlaps with the erasing period in another region, the voltage for resetting the driving state of the ferroelectric liquid crystal to the ferroelectric liquid crystal is set to a larger value. Can be applied. For example, in FIG. 7, in the erasing period T _f of the subframe SF _R in the region A ₁ , the voltage V _p −V _com applied to the ferroelectric liquid crystal can be set to a larger negative (−) value. As a result, it is possible to prevent the charge from being biased.

  Hereinafter, each period in the driving method of the liquid crystal display device of the present invention and the ferroelectric liquid crystal used in the present invention will be described in detail.

1. Write period In the driving method of the liquid crystal display device of the present invention, in each subframe, voltages are sequentially applied to a plurality of gate lines in one region to sequentially turn on a plurality of switching elements, and to a plurality of source lines. A writing period for applying a voltage of the first polarity is provided.

  A voltage is sequentially applied to the gate lines row by row (a scanning signal is sequentially supplied) to set a selected state. That is, a plurality of gate lines in one region are scanned line-sequentially. A voltage having a first polarity (positive polarity or negative polarity) is applied to the source line (image signal is supplied). As a result, a voltage corresponding to the image signal is applied between the pixel electrode and the common electrode of each pixel along the gate line, that is, a voltage corresponding to the difference between the pixel electrode and the common electrode is applied to the ferroelectric liquid crystal. The image data is written to each pixel along the gate line. In each pixel, the ferroelectric liquid crystal responds according to the potential difference between the pixel electrode and the common electrode. The light transmittance of each pixel is controlled by the degree of response of the ferroelectric liquid crystal.

  The first polarity voltage may be either positive or negative voltage.

The order of scanning in the writing period is not particularly limited.
For example, the scanning order in the writing period of the previous subframe and the scanning order in the writing period of the next subframe may be reversed. In the example shown in FIG. 8, in the region _{A 1,} first, in the previous frame _{F 1,} at sub-frame SF _R, m-th row, the (m-1) row, the m-2 line, ..., the first row A voltage is sequentially applied to the gate line. Next, in the subframe SF _G , a voltage is applied to the gate lines in the order of the first row, the second row, the third row,. Subsequently, in the subframe SF _B , a voltage is applied to the gate lines in the order of the m-th row, the m−1th row, the m−2th row,. Then, in the next frame F _2, at subframe SF _R, first row, second row, third row, ..., a voltage is applied to the gate line in the order of the m-th row. Then, although not shown, at the sub-frame SF _G of the next frame F _2, the m-th row, the (m-1) row, the m-2 line, ..., a voltage is applied to the gate line in the order of the first row. Subsequently, although not shown, in the next frame F ₂ of the sub-frame SF _B, the first row, second row, third row, ..., a voltage is applied to the gate line in the order of the m-th row. In such a driving method, the time during which a voltage is applied between the pixel electrode and the common electrode of the pixel along each gate line can be averaged.

In addition, for example, when the writing period of a certain region overlaps with the lighting period of a region adjacent to the region, the region adjacent to the region is changed in the writing period of the certain region. You may scan from the said gate line located in the opposite side to the side provided. In the example shown in FIG. 9, for example, for each write period T _a region A _3, and a lighting period T _c of the writing period T _a and the area A ₂ of the sub-frame SF _B sub-frame SF _R region A ₃ duplicate and, in the writing period T _a of the sub-frame SF _R region a _3, the m-th row, the (m-1) row, the m-2 line, ..., and scan the gate lines in the order of the first row Yes. That is, in the writing period in the region A _3, is scanning from the gate line located on the side opposite to the side where the area A ₂ that is adjacent to the region A ₃ is provided. Also, region and lighting period T _c of the sub-frame SF _R writing period of the sub-frame SF _G of A ₃ T _a and the area A ₄ is duplicated, the writing period of the sub-frame SF _B region A ₃ T _a and the area A a lighting period T _c of the _fourth sub-frame SF _G are duplicated, the sub-frame SF _G area a _3, in each writing period T _a of SF _B, the first row, second row, third row, ..., the gate lines are scanned in the order of the m-th row. That is, in the writing period in the region A _3, is scanning from the gate line located on the side opposite to the side where the area A ₄ which are adjacent to the region A ₃ is provided. As a result, it is possible to prevent light leakage from occurring in the area A ₃ where writing scanning is performed while the light source is lit in the adjacent areas A ₂ and A ₄ .
In this way, when the writing period of a certain region overlaps with the lighting period of a region adjacent to this region, a region adjacent to this region is provided in the writing period of a certain region. In the case of scanning from the gate line located on the opposite side to the side where the light is present, light leakage can be prevented.

  The writing period is appropriately selected according to the type of ferroelectric liquid crystal (the response speed of the ferroelectric liquid crystal), the number of gate lines, and the like. For example, the writing time per gate line can be set to 3 μs to 12 μs.

In the present invention, any two regions out of 2n regions are set as one set, and a writing period is sequentially provided for each region in each set region, and a plurality of sets are provided for each set in 2n regions. Writing periods are provided in order for each color.
In each set of regions, it is only necessary to provide a writing period for each region in order, so that the writing period in each region may or may not be continuous.

For example, a writing period of one color in a region where the writing period of the first color is performed first and a writing period of the color in a region where the writing period of the first color is performed later are continuous even if they are continuous. It does not have to be. In particular, when these writing periods are continuous, the color break can be effectively suppressed. In FIG. 4, for example, in the first set of regions _A 1, _{A 3,} and the writing period _{T a} of the sub-frame SF _R region _{A 1,} the writing period _{T a} of the sub-frame SF _R region _{A 3} are continuously ing. In this case, the intervals between the lighting periods of the light sources of a plurality of colors can be shortened, and the color break can be effectively suppressed.

Further, for example, the first color writing period in the region where the first color writing period is performed later and the second color writing period in the region where the first color writing period is performed first are continuous even if they are continuous. It does not have to be. In particular, when these writing periods are continuous, the color break can be effectively suppressed as described above. In FIG. 4, for example, in the first set of regions _A 1, _{A 3,} and the writing period _{T a} of the sub-frame SF _R region _{A 3,} and the writing period _{T a} of the sub-frame SF _G region _{A 1} is continuously ing. In this case, similarly to the above, the intervals of the lighting periods of the light sources of the plurality of colors can be shortened, and the color break can be effectively suppressed.

Further, in the 2n areas, a plurality of colors are written in order for each set, and a lighting period of a certain area only needs to be provided within a black display period of an area adjacent to the area. The last writing period of one set and the first writing period of the next set may or may not be continuous, and are set as appropriate depending on the arrangement of each region. In particular, when these writing periods are continuous, the color break can be effectively suppressed as described above. For example, in FIG. 4, in the second set area A ₄ and the first set area A ₁ , the write period T _a (second set last write) of the last subframe SF _B of the second set area A _4. the period _{T a),} a first set of regions _{a 1} of the first subframe SF writing period _{R T a} (first set of first writing period _{T a)} are continuous. In this case, similarly to the above, the intervals of the lighting periods of the light sources of the plurality of colors can be shortened, and the color break can be effectively suppressed.

2. Common electrode voltage change period In the driving method of the liquid crystal display device of the present invention, a voltage that resets the driving state of the ferroelectric liquid crystal is applied to the ferroelectric liquid crystal after the writing period in each subframe. And a common electrode voltage change period in which the voltage applied to the common electrode is changed from the reference value.

  If the voltage applied to the common electrode is changed from the reference value so that a voltage that resets the driving state of the ferroelectric liquid crystal is applied to the ferroelectric liquid crystal, the distance between the pixel electrode and the common electrode of all pixels is changed. In addition, a voltage corresponding to the amount of change in the voltage applied to the common electrode is applied.

A voltage that resets the driving state of the ferroelectric liquid crystal is appropriately selected according to the type of the ferroelectric liquid crystal and the like. In the present invention, since a ferroelectric liquid crystal having a half V-shaped switching characteristic is used, a voltage that resets the driving state of the ferroelectric liquid crystal is usually a second polarity voltage or a zero voltage.
The voltage of the second polarity may be a voltage having a polarity opposite to that of the first polarity, and may be a positive voltage or a negative voltage.

  The common electrode voltage change period is appropriately selected according to the type of ferroelectric liquid crystal (response speed of the ferroelectric liquid crystal), the applied voltage in the writing period, and the like. For example, the common electrode voltage change period can be set to about 50 μs to 1000 μs.

  Moreover, the change width of the applied voltage of the common electrode may always be the same or different.

3. Liquid crystal response period In the driving method of the liquid crystal display device of the present invention, after each common electrode voltage change period, the voltage applied to the common electrode is returned to the reference value during each subframe, and the pixel along the gate line scanned last In FIG. 2, a period of time during which the response of the ferroelectric liquid crystal is almost completed has a liquid crystal response period in which the ferroelectric liquid crystal waits for a response.

  The liquid crystal response period is appropriately selected according to the type of ferroelectric liquid crystal (response speed of the ferroelectric liquid crystal), the potential difference between the applied voltage immediately before the writing period and the applied voltage in the writing period, and the like. For example, the liquid crystal response period can be set from 100 μs to 500 μs.

4). Lighting Period The driving method of the liquid crystal display device of the present invention has a lighting period in which a light source of one color provided in one region is lit after each liquid crystal response period in each subframe.

  As the backlight, a light source provided with a plurality of color light sources is used for each area, and is configured to selectively irradiate light of, for example, two or more colors, preferably three to five colors. A backlight is used.

  The lighting period is appropriately selected according to the length of the writing period or the like.

5). Erase period In the driving method of the liquid crystal display device of the present invention, a plurality of switching elements are simultaneously turned on by simultaneously applying voltages to a plurality of gate lines in one region after a lighting period in each subframe. It is preferable to have an erasing period in which either a voltage having a second polarity opposite to the first polarity or a zero voltage is simultaneously applied to the source line.

  A voltage is applied to the gate lines all at once (a scanning signal is supplied) to select the gate line. In addition, a voltage having a second polarity (positive or negative polarity) or zero voltage is applied to the source line (a reset signal is supplied). Thereby, a voltage corresponding to the reset signal is applied between the pixel electrode and the common electrode of all the pixels, and the reset data is written to all the pixels.

Whether to apply the second polarity voltage or the zero voltage is appropriately selected according to the type of the ferroelectric liquid crystal, the applied voltage of the common electrode during the common electrode voltage change period, and the like. When applying the voltage of the second polarity, the magnitude of the voltage applied to the ferroelectric liquid crystal so as to reset the driving state of the ferroelectric liquid crystal can be increased.
Among these, it is preferable to apply the zero voltage after applying the voltage of the second polarity. This is because the response speed (falling) of the ferroelectric liquid crystal can be increased and the operation start positions of the ferroelectric liquid crystal can be aligned.

  The voltage of the second polarity may be a voltage having a polarity opposite to that of the first polarity, and may be a positive voltage or a negative voltage.

The erase period is usually set on the order of μs.
In particular, the time for applying a voltage to a plurality of gate lines at the same time in the erasing period is preferably longer than the time required for the response of the ferroelectric liquid crystal, and more preferably about the time required for the response of the ferroelectric liquid crystal. Is preferred.
When the ferroelectric liquid crystal is operated by applying a voltage during the writing period, the direction of spontaneous polarization is reversed. In each pixel, the charge is reduced by the polarization of the ferroelectric liquid crystal. Then, when the ferroelectric liquid crystal is operated by applying a reverse polarity voltage in the erasing period after the lighting period, the direction of spontaneous polarization is reversed again. In each pixel, as in the writing period, the charge is reduced by the polarization of the ferroelectric liquid crystal. In this way, even when the same voltage is applied, the charge is reduced in the bright display area and the voltage is not sufficiently applied, resulting in a charge bias, and the ferroelectric liquid crystal compared to the other areas. Responsiveness may be reduced.
On the other hand, by setting the time during which voltage is simultaneously applied to a plurality of gate lines in the erasing period to be longer than the time required for the response of the ferroelectric liquid crystal, the ferroelectric liquid crystal operates to change the direction of spontaneous polarization. Even when it is inverted, the charge that compensates for the reduced charge due to the polarization of the ferroelectric liquid crystal is supplied, so that the charge amount can be equalized in all the pixels. As a result, it is possible to prevent the response of the ferroelectric liquid crystal from being lowered.

  In the erase period, when the time for applying a voltage to a plurality of gate lines simultaneously is about the time required for the response of the ferroelectric liquid crystal, the time for applying a voltage to a plurality of gate lines at the same time is ferroelectric. It is appropriately selected according to the type of liquid crystal (response speed of the ferroelectric liquid crystal), the potential difference between the applied voltage during the writing period and the applied voltage during the erasing period, and the like. For example, the time for simultaneously applying the voltage to the plurality of gate lines can be set to 100 μs to 500 μs. On the other hand, when the response time of the ferroelectric liquid crystal is not taken into consideration, the time for simultaneously applying the voltage to the plurality of gate lines can be set to, for example, 6 μs to 8 μs.

6). Black Display Period The liquid crystal display device driving method according to the present invention includes a black display period in which a second polarity voltage or zero voltage is applied to a plurality of source lines after an erase period of the last subframe in one frame. It is preferable to have. By providing the black display period only once after the erasing period of the last subframe in one frame, it is possible to suppress the bias of electric charges and prevent burn-in. This black display period is provided only once in one frame.

  Whether to hold the second polarity voltage or the zero voltage applied is appropriately selected according to the type of the ferroelectric liquid crystal. When the voltage of the second polarity is held while being applied, the magnitude of the voltage applied to the ferroelectric liquid crystal and resetting the driving state of the ferroelectric liquid crystal during the second common electrode voltage change period. The thickness can be increased.

  The black display period is appropriately selected according to the length of the writing period, the lighting period, and the like. Usually, the black display period is set in the order of ms, and can be set to, for example, 1 ms to 3 ms.

  In the present invention, in one area, the non-selection period is from the end of the last subframe erasure period to the start of the next frame in the previous frame. Since the light source is not turned on during this non-selection period, basically, no matter how the liquid crystal is driven, the image display is not affected. A black display period can be provided in this non-selection period.

7). Zero voltage reset period In the driving method of the liquid crystal display device of the present invention, after a black display period, a plurality of switching elements are simultaneously turned on by simultaneously applying a voltage to a plurality of gate lines in one region, and a plurality of source lines May have a zero voltage reset period in which a zero voltage is applied simultaneously.
For example, when a zero voltage is applied during the erasing period, the operation start position of the ferroelectric liquid crystal can be aligned by providing a zero voltage reset period after the black display period. In particular, it is possible to align the liquid crystal operation start positions immediately before the writing period of each subframe.
In addition, for example, when a voltage having the second polarity is applied in the erasing period, a response speed of the ferroelectric liquid crystal is obtained in the writing period of the first subframe by providing a zero voltage reset period after the black display period. This is because (rise) can be accelerated, and the response time (liquid crystal response period) of the ferroelectric liquid crystal can be shortened.

  This zero voltage reset period is provided immediately after the black display period and immediately before the next frame.

  The zero voltage reset period is usually set on the order of μs or ms.

  Either the black display period or the zero voltage reset period may be long or short. For example, when the scanning order in the writing period of the previous subframe and the scanning order in the writing period of the next subframe are the same, the black display period is longer than the zero voltage reset period and relatively Longer is preferred. In this case, a line having a fast scanning order is applied with a voltage having the same polarity for a relatively long time as compared with a line having a slow scanning order, so that the black display period is preferably relatively long. On the other hand, for example, when the scanning order in the writing period of the previous subframe and the scanning order in the writing period of the next subframe are reversed, the black display period may be longer or shorter than the zero voltage reset period. Also good. In this case, since the time during which the voltage is applied is averaged between the line with the earlier scanning order and the line with the later scanning order, the black display period may be relatively short.

  In addition, when a voltage of the second polarity is applied in the erasing period and the zero voltage reset period is longer than the black display period, the voltage is simultaneously applied to the plurality of gate lines immediately before the next frame. The plurality of switching elements may be simultaneously turned on by applying the voltage, and a second polarity voltage may be simultaneously applied to the plurality of source lines. This makes it possible to align the operation start positions of the ferroelectric liquid crystals immediately before the writing period of each subframe.

  When the zero voltage reset period is shorter than the black display period, the zero voltage reset period can be set at, for example, 50 μs to 300 μs.

  In addition, the time for applying the zero voltage to the plurality of gate lines at the same time in the zero voltage reset period is preferably longer than the time required for the response of the ferroelectric liquid crystal, and especially the time required for the response of the ferroelectric liquid crystal. Preferably there is. In the zero voltage reset period, the ferroelectric liquid crystal operates and the direction of spontaneous polarization is reversed by making the time for applying the zero voltage to multiple gate lines simultaneously longer than the time required for the response of the ferroelectric liquid crystal. In some cases, charges that compensate for the reduced charge due to the polarization of the ferroelectric liquid crystal are supplied, so that the charge amount can be equalized in all pixels. As a result, it is possible to prevent the response of the ferroelectric liquid crystal from being lowered.

  In the zero voltage reset period, when the time for applying the voltage to the plurality of gate lines at the same time is about the time required for the response of the ferroelectric liquid crystal, the time for applying the zero voltage to the plurality of gate lines at the same time is: For example, it can be set at 100 μs to 200 μs.

8). Other Periods In the present invention, as illustrated in FIG. 9, a subframe SF _W for displaying other colors such as white or yellow (Y), green (G), magenta (M) is provided. Also good.
In the example shown in FIG. 9, after writing the three primary colors of RGB for each set in all areas A _{1 to} A ₄ , the RGB three-color light sources are simultaneously turned on to obtain white light, and all areas A _{1 are written.} It is written order for white in to a _4. In the subframe SF _W , as in the subframes SF _R , SF _G , SF _B , the writing period T _a ′, the common electrode voltage change period T _b ′, the liquid crystal response period T _c ′, the lighting period T _d ′, and An erasing period T _f ′ is provided.

  When displaying white, the white image data is the smallest signal among the original RGB image data, and the RGB image data is converted from the original RGB signal to the white signal. The signal value can be subtracted. For example, when the original RGB image data is (R, G, B) = (125, 100, 220), the minimum signal 100 is a white signal, and 100 is subtracted from the original RGB signal Can be (R, G, B, W) = (25, 0, 120, 100).

  Since a color break does not occur in the white display, the writing of the white image data can be started after the writing of RGB for each group is completed in all regions. When white is displayed, W may be written after the writing of RGB is completed for each group in all areas as described above, or RGBW may be written for each group in all areas.

9. Ferroelectric liquid crystal The ferroelectric liquid crystal used in the present invention exhibits monostability and half V-shaped switching characteristics.

The ferroelectric liquid crystal is not particularly limited as long as it exhibits a chiral smectic C phase (SmC ^* ). For example, the phase sequence changes in phase with a nematic phase (N) -cholesteric phase (Ch) -chiral smectic C phase (SmC ^* ) in the temperature lowering process, or a nematic phase (N) -chiral smectic C phase (SmC ^* ). , Nematic phase (N) -smectic A phase (SmA) -chiral smectic C phase (SmC ^* ), phase change, nematic phase (N) -cholesteric phase (Ch) -smectic A phase (SmA ) -Chiral smectic C phase (SmC ^* ) and the like.

  Such a ferroelectric liquid crystal can be variously selected from generally known liquid crystal materials according to required characteristics.

In particular, a liquid crystal material that exhibits an SmC ^* phase from the Ch phase without passing through the SmA phase is suitable as a material that exhibits a half V-shaped switching characteristic. Specifically, “R2301” manufactured by AZ Electronic Materials may be mentioned.

In addition, as the liquid crystal material that passes through the SmA phase, a material that expresses the SmC ^* phase from the Ch phase through the SmA phase is preferable because of a wide range of material selection. In this case, a single liquid crystal material exhibiting an SmC ^* phase can be used, but a non-chiral liquid crystal (hereinafter sometimes referred to as a host liquid crystal) having a low viscosity and easily exhibiting an SmC phase is used. By adding a small amount of an optically active substance that does not show large spontaneous polarization and an appropriate helical pitch, the liquid crystal material showing the phase sequence as described above has low viscosity and can realize faster response. preferable.

The host liquid crystal is preferably a material exhibiting an SmC phase in a wide temperature range, and can be used without particular limitation as long as it is generally known as a host liquid crystal of a ferroelectric liquid crystal. For example, the general formula:
^{Ra-Q 1 -X 1 - (} Q 2 -Y 1) m -Q 3 -Rb
(In the formula, Ra and Rb are each a linear or branched alkyl group, alkoxy group, alkoxycarbonyl group, alkanoyloxy group or alkoxycarbonyloxy group, and Q ¹ , Q ² and Q ³ are each 1 , 4-phenylene group, 1,4-cyclohexylene group, pyridine-2,5-diyl group, pyrazine-2,5-diyl group, pyridazine-3,6-diyl group, 1,3-dioxane-2,5 -Diyl group, and these groups may have a substituent such as a halogen atom, a hydroxyl group, and a cyano group, and X ¹ and Y ¹ are each —COO—, —OCO—, —CH ₂ O— , —OCH ₂ —, —CH ₂ CH ₂ —, —C≡C—, or a single bond, and m is 0 or 1.). As the host liquid crystal, the above compounds can be used alone or in combination of two or more.

The optically active substance added to the host liquid crystal is not particularly limited as long as it is a material having a large spontaneous polarization and the ability to induce an appropriate helical pitch, and is generally added to a liquid crystal composition exhibiting an SmC phase. Any known material can be used. In particular, a material that can induce large spontaneous polarization with a small addition amount is preferable. Examples of such an optically active substance include the following general formula:
^{Rc-Q 1 -Za-Q 2} -Zb-Q 3 -Zc-Rd
(In the formula, Q ¹ , Q ² and Q ³ represent the same meaning as in the above general formula, and Za, Zb and Zc are —COO—, —OCO—, —CH ₂ O—, —OCH ₂ —, —CH _{2, respectively.} CH ₂ —, —C≡C—, —CH═N—, —N═N—, —N (→ O) ═N—, —C (═O) S— or a single bond, and Rc is asymmetric. A linear or branched alkyl group which may have a carbon atom, an alkoxy group, an alkoxycarbonyl group, an alkanoyloxy group or an alkoxycarbonyloxy group, wherein Rd is a linear or branched group having an asymmetric carbon atom; And an alkyl group, an alkoxy group, an alkoxycarbonyl group, an alkanoyloxy group or an alkoxycarbonyloxy group, and Rc and Rd may be substituted with a halogen atom, a cyano group or a hydroxyl group. Can be used. As the optically active substance, the above compounds may be used alone or in combination of two or more.

  Specific examples of the ferroelectric liquid crystal passing through the SmA phase include “FELIXM4851-100” manufactured by AZ Electronic Materials.

  A compound having an arbitrary function may be added to the ferroelectric liquid crystal depending on the function required for the liquid crystal display device. Examples of such a compound include a polymerized polymerizable monomer. By containing a polymer of such a polymerizable monomer in the liquid crystal layer, the alignment of the liquid crystal material is so-called “polymer stabilization”, and a liquid crystal display device excellent in alignment stability can be obtained.

  The polymerizable monomer used in the polymerized polymer of the polymerizable monomer is not particularly limited as long as it is a compound that generates a polymer by a polymerization reaction, and a thermosetting resin monomer that generates a polymerization reaction by heat treatment, and actinic radiation. An actinic radiation curable resin monomer that undergoes a polymerization reaction upon irradiation of can be exemplified. Among these, it is preferable to use an actinic radiation curable resin monomer. When a thermosetting resin monomer is used, it is necessary to perform a heating process in order to cause a polymerization reaction. Therefore, the regular arrangement of the ferroelectric liquid crystal is impaired by such a heating process, There is a risk of inducing a phase transition. On the other hand, when the actinic radiation curable resin monomer is used, there is no such fear, and the alignment of the ferroelectric liquid crystal is hardly harmed by the polymerization reaction.

  Examples of the actinic radiation curable resin monomer include an electron beam curable resin monomer that undergoes a polymerization reaction upon irradiation with an electron beam and a photocurable resin monomer that undergoes a polymerization reaction upon irradiation with light. Among these, it is preferable to use a photocurable resin monomer. It is because a manufacturing process can be simplified by using a photocurable resin monomer.

  The photocurable resin monomer is not particularly limited as long as it causes a polymerization reaction when irradiated with light having a wavelength in the range of 150 nm to 500 nm. Among them, it is preferable to use an ultraviolet curable resin monomer that generates a polymerization reaction when irradiated with light having a wavelength in the range of 250 nm to 450 nm, particularly in the range of 300 nm to 400 nm. This is because it has advantages in terms of the ease of the irradiation apparatus.

  The polymerizable functional group possessed by the ultraviolet curable resin monomer is not particularly limited as long as it causes a polymerization reaction upon irradiation with ultraviolet rays in the above wavelength region. In particular, it is preferable to use an ultraviolet curable resin monomer having an acrylate group.

  Further, the UV curable resin monomer may be a monofunctional monomer having one polymerizable functional group in one molecule, or a polyfunctional having two or more polymerizable functional groups in one molecule. It may be a monomer. Among these, it is preferable to use a polyfunctional monomer. By using a polyfunctional monomer, a stronger polymer network can be formed, so that the intermolecular force and the polymer network at the alignment film interface can be strengthened. Thereby, the disorder of the alignment of the ferroelectric liquid crystal due to the temperature change can be suppressed.

  Among the polyfunctional monomers, bifunctional monomers having a polymerizable functional group at both ends of the molecule are preferably used. By having a polymerizable functional group at both ends of the molecule, it is possible to form a polymer network with a wide interval between polymers, and to prevent a decrease in driving voltage of the ferroelectric liquid crystal due to the inclusion of a polymer of a polymerizable monomer. Because.

  Of the ultraviolet curable resin monomers, it is preferable to use an ultraviolet curable liquid crystal monomer that exhibits liquid crystallinity. The reason why such an ultraviolet curable liquid crystal monomer is preferable is as follows. That is, since the ultraviolet curable liquid crystal monomer exhibits liquid crystallinity, it can be regularly arranged by the alignment regulating force of the alignment film. For this reason, the ultraviolet curable liquid crystal monomer can be fixed while maintaining the regular alignment state by causing a polymerization reaction after the ultraviolet light curable liquid crystal monomer is regularly arranged. By the presence of the polymer having such a regular alignment state, the alignment stability of the ferroelectric liquid crystal can be improved, and excellent heat resistance and impact resistance can be obtained.

  The liquid crystal phase exhibited by the ultraviolet curable liquid crystal monomer is not particularly limited, and examples thereof include an N phase, an SmA phase, and an SmC phase.

  Examples of the ultraviolet curable liquid crystal monomer used in the present invention include compounds represented by the following formulas (1) to (3).

In the above formulas (1) and (2), A, B, D, E and F represent benzene, cyclohexane or pyrimidine, and these may have a substituent such as halogen. A and B, or D and E may be bonded via a bonding group such as an acetylene group, a methylene group, or an ester group. M ¹ and M ² may be any of a hydrogen atom, an alkyl group having 3 to 9 carbon atoms, an alkoxycarbonyl group having 3 to 9 carbon atoms, or a cyano group. Further, the acryloyloxy group at the end of the molecular chain and A or D may be bonded via a bonding group such as an alkylene group having 3 to 6 carbon atoms.

  In the above formula (3), Y is hydrogen, alkyl having 1 to 20 carbons, alkenyl having 1 to 20 carbons, alkyloxy having 1 to 20 carbons, alkyloxycarbonyl having 1 to 20 carbons, It represents formyl, alkylcarbonyl having 1 to 20 carbons, alkylcarbonyloxy having 1 to 20 carbons, halogen, cyano or nitro.

  Among the above, the compounds represented by the following formulas can be exemplified as those suitably used.

  Moreover, the said polymerizable monomer may be used independently and may be used in combination of 2 or more type. When two or more different polymerizable monomers are used, for example, an ultraviolet curable liquid crystal monomer represented by the above formula and another ultraviolet curable resin monomer can be used.

  When an ultraviolet curable liquid crystal monomer is used as the polymerizable monomer, the polymer of the polymerizable monomer is a main chain liquid crystal type polymer in which the main chain exhibits liquid crystallinity by having an atomic group exhibiting liquid crystallinity in the main chain. It may be a side chain liquid crystal polymer in which the side chain exhibits liquid crystallinity by having an atomic group exhibiting liquid crystallinity in the side chain. Especially, it is preferable that the polymer of a polymerizable monomer is a side chain liquid crystal type polymer. This is because the presence of an atomic group exhibiting liquid crystallinity in the side chain increases the degree of freedom of the atomic group, so that the atomic group exhibiting liquid crystallinity is easily aligned. Further, as a result, the alignment stability of the ferroelectric liquid crystal can be improved.

The amount of the polymerized monomer in the liquid crystal layer is not particularly limited as long as the alignment stability of the ferroelectric liquid crystal is within a desired range, but usually 0.5% by mass in the liquid crystal layer. It is preferably within the range of ˜30% by mass, more preferably within the range of 1% by mass to 20% by mass, and even more preferably within the range of 1% by mass to 10% by mass. This is because if it exceeds the above range, the drive voltage may increase or the response speed may decrease. On the other hand, if the amount is less than the above range, the alignment stability of the ferroelectric liquid crystal becomes insufficient, and the heat resistance and impact resistance of the liquid crystal display device may be impaired.
The abundance of the polymerizable monomer polymer in the liquid crystal layer is obtained by washing the monomolecular liquid crystal in the liquid crystal layer with a solvent and then measuring the weight of the remaining polymerizable monomer polymer with an electronic balance. It can be calculated from the remaining amount and the total mass of the liquid crystal layer.

10.2n Regions In the present invention, the backlight is divided into 2n (n is an integer of 2 to 4) regions in the scanning direction. The number of regions is 2n (n is an integer of 2 to 4), specifically, any of 4, 6, or 8. For example, as shown in FIG. 10, the backlight has four regions (A _{1 to} A ₄ ), six regions (A _{1 to} A ₆ ), or eight regions (A _{1 to} A ₈ ) in the scanning direction. It is divided into.

In addition, 2n areas are a set of arbitrary two areas.
The two arbitrary regions are not particularly limited. For example, in the case of the four regions shown in FIG. 10A, A ₁ and A ₂ are the first set, and A ₃ and A ₄ are the second. A ₁ and A ₃ may be a first set, A ₂ and A ₄ may be a second set, A ₁ and A ₄ may be a first set, and A ₂ and A ₃ may be a second set. .
Especially, it is preferable to combine so that arbitrary two area | regions may not adjoin. For example, in the case of the four regions shown in FIG. 10A, it is preferable that A ₁ and A ₃ are a first set and A ₂ and A ₄ are a second set. This is because by combining in this way, a lighting period of a certain area can be provided within a non-selection period of an area adjacent to that area, and light leakage can be prevented. For example, in FIG. 4, areas A ₁ and A ₃ are a first set, areas A ₂ and A ₄ are a second set, and four areas are grouped every other area. Can be provided within a non-selection period of a region adjacent to this region. Then, for example, the lighting period _{T d} of region _{A 2,} is provided on the non-selection period in the period _{T h} of adjacent regions _{A 1} and the area _{A 3,} RGB three color light sources in the area _{A 2} is lit Occasionally, it does not transmit light in the area a ₁ and the area a _3, it is possible to prevent light leakage.

  Further, the combination of any two regions may be the same in all frames or may be different for each frame.

  As the number of sets, for example, two sets of two in the case of four areas, three sets of two in the case of six areas, and four sets of two in the case of eight areas. Is done.

  In the case of full high-definition (FHD), the FHD panel is divided into two upper and lower areas, and data is input using the source driver located on the upper side for the upper area and the source driver located on the lower side for the lower area. can do. As described above, by arranging the source drivers in both the upper and lower two regions, the gate lines can be scanned in parallel.

  The number of gate lines may be plural and may be selected as appropriate. In addition, when the backlight is divided into 2n regions in the scanning direction, the number of gate lines for one region is appropriately selected as described above.

  In the 2n areas, light sources of a plurality of colors are provided for each area.

B. Next, the liquid crystal display device of the present invention will be described.
The liquid crystal display device of the present invention is divided into 2n (n is an integer of 2 to 4) regions in the scanning direction, a backlight having a plurality of color light sources provided in each region, a plurality of gate lines, A plurality of source lines, a plurality of switching elements connected to the gate lines and source lines and arranged for each pixel, a plurality of pixel electrodes connected to the switching elements and arranged for each pixel, and the pixel electrodes A common electrode disposed at a position opposite to the pixel electrode, a ferroelectric liquid crystal disposed between the pixel electrode and the common electrode, a gate driver connected to the plurality of gate lines and applying a scanning signal, and the plurality of the plurality of gate electrodes A liquid crystal panel having a source driver connected to a source line and applying an image signal, and the above-mentioned liquid crystal display device connected to the gate driver, the source driver and the backlight. The driving method is characterized in that it has a control unit for driving the liquid crystal display device.

FIG. 11 is a schematic perspective view showing an example of the liquid crystal display device of the present invention.
As illustrated in FIG. 11, the liquid crystal display device 10 includes a liquid crystal panel 11, a backlight 12 disposed so as to face the liquid crystal panel 11, a gate driver 2 and a source driver 3 of the liquid crystal panel 11, and a backlight. 12 and a control unit 13 connected to 12. In the liquid crystal panel 11, a plurality of gate lines G and a plurality of source lines S and a plurality of switching elements 4 connected to the gate lines G and the source lines S and arranged for each pixel are formed on the base material 7a. A plurality of pixel electrodes 5 connected to the switching element 4 and arranged for each pixel are provided, and a common electrode 6 is provided on the base material 7 b so as to face the pixel electrode 5. In the liquid crystal panel 11, a gate driver 2 connected to a plurality of gate lines G and a source driver 3 connected to a plurality of source lines S are provided.
Further, the backlight 12 is divided into _four regions (A _{1 to} A ₄ ) in the scanning direction as illustrated in FIG. Then, RGB light sources 12R, 12G, and 12B are provided for each region.
Although not shown, a ferroelectric liquid crystal is sandwiched between the pixel electrode and the common electrode.

  The gate line G and the source line S are arranged vertically and horizontally, respectively, and by applying a signal to the gate line G and the source line S, the switching element 4 can be operated to drive the ferroelectric liquid crystal. A portion where the gate line G and the source line S intersect is insulated by an insulating layer (not shown), and the scanning signal of the gate line G and the image signal of the source line S can operate independently. A portion surrounded by the gate line G and the source line S is a pixel which is a minimum unit for driving the liquid crystal display device, and at least one switching element 4 and a pixel electrode 5 are formed in each pixel. Then, by sequentially applying a signal voltage to the gate line and the source line, the switching element of each pixel can be operated.

  The gate driver 2 applies a voltage to the gate line G (applies a scanning signal), and the source driver 3 applies a positive or negative voltage to the source line S (applies an image signal). At this time, an image signal corresponding to one unit color among a plurality of unit colors (RGB in FIG. 11) for displaying an arbitrary color by mixing colors is supplied to the source line S. Accordingly, the gate driver 2 sequentially applies voltages to the plurality of gate lines G to turn on the plurality of switching elements 4 in units of gate lines, and the source driver 3 applies positive or negative polarity to the plurality of source lines S. A voltage is applied, and a positive or negative voltage is applied to the ferroelectric liquid crystal via the switching element 4 and the pixel electrode 5 to drive the ferroelectric liquid crystal. That is, a voltage corresponding to the image signal is applied between the pixel electrode and the common electrode of the pixel along each gate line, and image data is written to each pixel along the gate line, and the response of the ferroelectric liquid crystal to this Depending on the degree, the light transmittance of each pixel is controlled.

  Since the liquid crystal display device of the present invention is driven by the above-described driving method of the liquid crystal display device, it is possible to shorten the interval between lighting periods of a plurality of light sources, and prevent a color break and a bias of charge. Can do.

A general thing can be used for each component of a liquid crystal display device.
Since the liquid crystal and the backlight are described in detail in the above “A. Driving method of liquid crystal display device”, description thereof is omitted here.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

  The following examples illustrate the present invention in more detail.

[Example 1]
The number of scanning lines of full high-definition (FHD): The display method of the upper region in the case where the display of 1080 is divided into two vertically and the respective upper and lower regions are further divided into four (8 divided in total) is shown in FIG. The lower region was driven symmetrically with the upper region.
The number of scanning lines in each area is 1080/2/4 = 135. The gate selection time was 10.3 μsec, and the time required for 135 writing scans (writing period T _a ) was 1.39 msec. Further, 0.25 msec common electrode voltage change period T _b, the liquid crystal response period T _c 0.30msec, was 0.84msec the lighting period T _d.

[Example 2]
FIG. 6 shows a driving method of the upper area when the number of scanning lines of full high-definition (FHD): 1080 display is divided into two parts in the upper and lower directions, and the upper and lower areas are further divided into four parts (8 parts in total). The lower region was driven symmetrically with the upper region.
The number of scanning lines in each area is 1080/2/4 = 135. The gate selection time was 8.0 μsec, and the time required for 135 writing scans (writing period T _a ) was 1.08 msec. Further, 0.26Msec a common electrode voltage change period T _b, the liquid crystal response period T _c 0.33msec, 0.80msec the lighting period T _d, was 0.31msec an erasing period T _f.

[Example 3]
FIG. 9 shows a driving method of the upper region when the number of scanning lines of full high-definition (FHD): 1080 displays is divided into two vertically and the respective upper and lower regions are further divided into four (8 divided in total). The lower region was driven symmetrically with the upper region.
The number of scanning lines in each area is 1080/2/4 = 135. The gate selection time was 6.0 μsec, and the time required for 135 writing scans (writing period T _a ) was 0.81 msec. Further, the common electrode voltage change period T _b of 0.20 msec, the liquid crystal response period T _c of 0.25 msec, the lighting period T _d of 0.60 msec, and a 0.23 msec to erase period T _f.

T _a ... Write period T _b ... Common electrode voltage change period (first common electrode voltage change period)
T _c ... liquid crystal response period T _d ... lighting period T _e ... common electrode voltage change period (second common electrode voltage change period)
T _f ... Erasure period

Claims (7)

The backlight is divided into 2n (n is an integer of 2 to 4) regions in the scanning direction, the backlight is provided with a light source of a plurality of colors for each region, exhibits monostability, and A method for driving a liquid crystal display device using a ferroelectric liquid crystal exhibiting half V-shaped switching characteristics,
During each subframe,
A write period in which a plurality of switching elements are sequentially turned on by sequentially applying a voltage to a plurality of gate lines in the one region, and a voltage having a first polarity is applied to a plurality of source lines;
A common electrode voltage change period in which the voltage applied to the common electrode is changed from a reference value so that a voltage that resets the driving state of the ferroelectric liquid crystal is applied to the ferroelectric liquid crystal after the writing period;
After the common electrode voltage change period, the voltage applied to the common electrode is returned to the reference value, and a liquid crystal response period for waiting for a ferroelectric liquid crystal to respond,
After the liquid crystal response period, a lighting period for turning on one color light source provided in the region,
Arbitrary two areas out of the 2n areas are set as one set, and a writing period is alternately provided for each area in each set area, and a plurality of colors are written for each set in the 2n areas. A method for driving a liquid crystal display device, characterized in that periods are provided in order. After the lighting period, a voltage is simultaneously applied to the plurality of gate lines in the region to simultaneously turn on the plurality of switching elements, and the second polarity having the opposite polarity to the first polarity is simultaneously applied to the plurality of source lines. Having an erasing period of applying either a voltage of zero polarity or zero voltage,
2. The method for driving a liquid crystal display device according to claim 1, wherein the common electrode voltage change period of a certain region is provided within the erasing period of a region other than the region.   3. The liquid crystal display device according to claim 1, wherein a time during which voltage is simultaneously applied to the plurality of gate lines in the erasing period is longer than a time required for a response of the ferroelectric liquid crystal. Driving method.   4. The scanning order in the writing period of the previous subframe and the scanning order in the writing period of the next subframe are opposite to each other. 5. A driving method of a liquid crystal display device.   When the writing period of a certain region overlaps with the lighting period of a region adjacent to the region, a region adjacent to the region is provided in the writing period of the certain region. 4. The method for driving a liquid crystal display device according to claim 1, wherein scanning is performed from the gate line located on the side opposite to the side where the liquid crystal is present.   6. The method for driving a liquid crystal display device according to claim 1, wherein the two arbitrary regions are not adjacent to each other. A backlight that is divided into 2n (n is an integer of 2 to 4) regions in the scanning direction, and a light source of a plurality of colors is provided in each region;
A plurality of gate lines, a plurality of source lines, a plurality of switching elements connected to the gate lines and the source lines and arranged for each pixel, and a plurality of pixels connected to the switching elements and arranged for each pixel An electrode; a common electrode disposed at a position opposite to the pixel electrode; a ferroelectric liquid crystal disposed between the pixel electrode and the common electrode; and a gate connected to the plurality of gate lines to apply a scanning signal. A liquid crystal panel having a driver and a source driver connected to the plurality of source lines and applying an image signal; and
A liquid crystal display comprising: a control unit which is connected to the gate driver, the source driver, and a backlight and drives the liquid crystal display device by the method for driving a liquid crystal display device according to any one of claims 1 to 6. Display device.

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