JP2008033343A - Method of driving liquid crystal display device - Google Patents

Method of driving liquid crystal display device Download PDF

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JP2008033343A
JP2008033343A JP2007216240A JP2007216240A JP2008033343A JP 2008033343 A JP2008033343 A JP 2008033343A JP 2007216240 A JP2007216240 A JP 2007216240A JP 2007216240 A JP2007216240 A JP 2007216240A JP 2008033343 A JP2008033343 A JP 2008033343A
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liquid crystal
pixel
crystal cell
display device
display
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Keiichi Betsui
Tetsuya Makino
Toshiaki Yoshihara
圭一 別井
敏明 吉原
哲也 牧野
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Fujitsu Ltd
富士通株式会社
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Abstract

There is provided a driving method of a liquid crystal display device which can suppress a driving voltage of a liquid crystal material to be low and can use a liquid crystal material having a large spontaneous polarization.
A ferroelectric liquid crystal material having spontaneous polarization is provided between two opposing substrates, and a pixel electrode corresponding to a liquid crystal cell 44 and a switching TFT 41 connected thereto are provided on the inner surface of one substrate. In addition, a capacitor 45 for accumulating charges in the pixel electrode is connected. The scan time of each of the first scan for displaying on each pixel of the liquid crystal cell 44 and the second scan for erasing the display is set to 10 μs or less, and the capacitance (C S ) of the capacitor 45 is set. The ratio of the liquid crystal cell 44 to the capacity (C LC ) is set to 0.2 ≦ C S / C LC ≦ 5.
[Selection] Figure 8

Description

  The present invention relates to a driving method of a liquid crystal display device that displays an image by on / off driving of a switching element.

  With the progress of the so-called information society in recent years, electronic devices represented by personal computers, PDAs (Personal Digital Assistants) and the like have been widely used. Furthermore, with the spread of such electronic devices, there is a demand for portable devices that can be used both in offices and outdoors, and there is a demand for reduction in size and weight. As one of means for achieving such an object, a liquid crystal display device has been widely used. A liquid crystal display device is an indispensable technology for reducing power consumption of a battery-driven portable electronic device as well as reducing the size and weight.

  By the way, liquid crystal display devices are roughly classified into a reflection type and a transmission type. The reflective liquid crystal display device is configured to reflect light incident from the front surface of the liquid crystal panel on the back surface of the liquid crystal panel and visually recognize the image, and the transmissive type is a light source (backlight) provided on the back surface of the liquid crystal panel. The image is visually recognized by the transmitted light from (). The reflective type is inferior in visibility because the amount of reflected light is not constant depending on environmental conditions. In particular, a transmissive liquid crystal display device is generally used as a display device such as a personal computer for performing multi-color or full-color display.

  On the other hand, current color liquid crystal display devices are generally classified into STN (Super Twisted Nematic) type and TFT-TN (Thin Film Transistor-Twisted Nematic) type in terms of the liquid crystal material used. Although the STN type is relatively inexpensive to manufacture, there is a problem that it is not suitable for displaying moving images because crosstalk is likely to occur and the response speed is relatively slow. On the other hand, the display quality of the TFT-TN type is higher than that of the STN type, but since the light transmittance of the liquid crystal panel is currently only about 4%, a high-luminance backlight is required. For this reason, the TFT-TN type has a problem in use when carrying a battery power supply due to an increase in power consumption by the backlight. In addition, since color display is performed using a color filter, one pixel must be composed of three sub-pixels corresponding to red, green, and blue, and it is difficult to achieve high definition, and the display color purity is not sufficient. There is also.

  In order to solve such problems, the present inventors have developed a field sequential type liquid crystal display device. This field-sequential liquid crystal display device does not require sub-pixels as compared with a color filter-type liquid crystal display device, so that it is possible to easily realize a display with higher accuracy and without using a color filter. In addition, since the emission color of the light source can be used as it is for display, the display color purity is excellent. Furthermore, since the light utilization efficiency is high, there is an advantage that less power consumption is required. However, in order to realize a field-sequential liquid crystal display device, high-speed response of liquid crystal is essential. Therefore, the present inventors have established a field-sequential type liquid crystal display device or a color filter type liquid crystal display device having excellent advantages as described above in order to increase the response speed by 100 to 1000 as compared with the prior art. We are researching and developing driving with switching elements such as TFTs (Thin Film Transistors) of liquid crystals such as ferroelectric liquid crystals having spontaneous polarization that can be expected to have double the high-speed response.

As shown in FIG. 13, in the ferroelectric liquid crystal, the major axis direction of the liquid crystal molecules changes by 2θ by voltage application. A liquid crystal panel in which a ferroelectric liquid crystal is sandwiched between a pair of substrates is sandwiched between two polarizing plates whose polarization axes are orthogonal to each other, and transmitted light is utilized by utilizing birefringence due to a change in the major axis direction of liquid crystal molecules. Change the intensity. When a ferroelectric liquid crystal is driven by a switching element such as a TFT, spontaneous polarization switching occurs according to the amount of charge injected (accumulated) into the pixel via the switching element, and the transmitted light intensity changes. To do.
JP 11-119189 A

  By the way, in a conventional liquid crystal display device in which a liquid crystal such as a ferroelectric liquid crystal having a spontaneous polarization is driven by a switching element such as a TFT, the magnitude of the spontaneous polarization per unit area is Ps, and the electrode area of each pixel Is 2Ps · A (the total charge amount of the reversal current associated with the complete reversal of the spontaneous polarization) is equal to or less than the charge amount Q injected into each pixel via the switching element. That is, the liquid crystal material, the pixel electrode, the TFT, and the like are designed so as to satisfy the condition of 2Ps · A ≦ Q.

Conventionally, since the maximum transmitted light intensity is obtained by completely reversing the spontaneous polarization under the condition of 2Ps · A ≦ Q as described above, the liquid crystal capacity is not large at a low driving voltage of 7 V or less. The spontaneous polarization size Ps that satisfies the condition is reduced to 8 nC / cm 2 or less, and Ps cannot be increased so much that the responsiveness is delayed. Accordingly, there is a demand for an increase in the magnitude of spontaneous polarization in terms of responsiveness, particularly responsiveness at low temperatures. Due to the relationship between responsiveness and selectable liquid crystal material, when a liquid crystal material having a large spontaneous polarization is used, there is a problem that Q must be increased and the drive voltage becomes high.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a driving method of a liquid crystal display device which can suppress a driving voltage of a liquid crystal material to be low and can use a liquid crystal material having a large spontaneous polarization. To do.

  The driving method of the liquid crystal display device according to the present invention includes two polarizing plates disposed opposite to each other, a liquid crystal cell sandwiched between the polarizing plates, a light source, and a light source disposed on the back side of the liquid crystal cell. A backlight having a light emitting region for guiding red, green, and blue light emitted from the liquid crystal cell, a pixel electrode corresponding to a pixel of the liquid crystal cell, a switching element connected to the pixel electrode, and a pixel electrode A driving method of a liquid crystal display device including a capacitor for accumulating electric charge, wherein the switching element corresponding to the pixel is set in a period of each display period corresponding to red, green, and blue data of each pixel. In addition to on / off driving, the backlight emits red, green, and blue light in a time-sharing manner during each display period in synchronization with the on / off driving of the switching element, and the backlight is red, green, and blue. Time division of light During each period of light emission, a first scan for performing display on each pixel of the liquid crystal cell and a second scan for erasing the display are performed in this order, and the first scan is performed. The scanning time of each of the scanning and the second scanning is set to 10 μs or less, and the ratio of the capacitance of the capacitor to the capacitance of the liquid crystal cell is set to 0.2 or more and 5 or less.

The inventors of the present invention have studied in detail the driving of a liquid crystal material having spontaneous polarization by a switching element such as a TFT, and as a result, when the switching element is turned on and a data voltage based on display data is applied, it is stored in the pixel. The present inventors have found that the drive voltage can be reduced by increasing the amount of charge that is generated. Therefore, by providing a capacitor for accumulating charges in addition to the capacity of the liquid crystal cell for each pixel, it is possible to store more charges than when there is no capacitor even at a low driving voltage. Reduction is possible. Then, by setting the ratio (C S / C LC : capacitance ratio) of the capacitance (C S ) of the capacitor to the capacitance (C LC ) of the liquid crystal cell to 0.2 or more, an effect of greatly reducing the driving voltage can be obtained. Can do. As the capacitance ratio C S / C LC increases, the drive voltage reduction effect increases. However, when the capacitance ratio C S / C LC exceeds 5, the drive voltage reduction effect is saturated. Also, increasing the capacitance ratio C S / C LC is not preferable from the viewpoint of the driving capability of a switching element such as a TFT. Accordingly, the capacity ratio C S / C LC is preferably 0.2 to 5.

  Further, the scanning time of each of the first scanning for performing display on the liquid crystal cell and the second scanning for erasing the display is made so that the light transmittance of the liquid crystal material is hardly changed when the switching element is off. Set. The scanning time is specifically 10 μs or less, and the light transmittance of the liquid crystal material hardly changes if the data voltage is the same during the scanning time or less. Therefore, stable halftone display is possible.

  In the driving method of the liquid crystal display device of the present invention, the scanning time of each of the first scanning for displaying and the second scanning for erasing the display is set to 10 μs or less, and the capacitance of the additional capacitor is set. Since the ratio of the liquid crystal cell to the capacity of the liquid crystal cell is set to 0.2 or more and 5 or less, it is possible to realize driving of a liquid crystal substance having spontaneous polarization at a low voltage.

  Hereinafter, the present invention will be described in detail with reference to the drawings showing embodiments thereof. Note that the present invention is not limited to the following embodiments.

First, experimental results of TFT drive evaluation characteristics of a liquid crystal display panel (FLC panel) of a ferroelectric liquid crystal material using an FET switch performed by the present inventors will be described. FIG. 1 is a diagram showing the configuration of this experimental system. A capacitor (capacitance C s ) is connected in parallel with the FLC panel (consisting of one liquid crystal cell) to be evaluated, and a voltage is applied to the liquid crystal cell and the capacitor via the FET switch, so that the liquid crystal cell for light from the backlight The transmitted light was detected with a photomultiplier tube.

Note that the liquid crystal cell to be evaluated was manufactured as follows. After the glass substrate having the electrode (area: 1.77 cm 2 ) was washed, polyimide was applied and baked at 200 ° C. for 1 hour to form a polyimide film of about 200 mm, and then the surface of the polyimide film was covered with rayon. A blank panel is created by rubbing with a cloth made from two glass substrates and holding a gap with a silica spacer with an average particle diameter of 1.6 μm. A ferroelectric liquid crystal material is enclosed in the blank panel. did. The magnitude of spontaneous polarization (Ps) of the encapsulated ferroelectric liquid crystal material was 5.4 nC / cm 2 , 8.0 nC / cm 2 , and 12.8 nC / cm 2 .

Then, by varying the capacitance of the capacitor (storage capacitance C S), while changing the storage capacitor C S capacity ratio C S / C LC with respect to the liquid crystal capacitance C LC in the range of 0 to 12, the size of the storage capacitance C S The transmitted light intensity and the driving voltage were measured. The liquid crystal capacitance C LC is a value at a measurement frequency of 10 kHz because it depends on the frequency. The reason for setting the measurement frequency to 10 kHz is to eliminate the influence of the spontaneous polarization value on the liquid crystal capacitance.

  The gate selection period of the FET was fixed at 5 μs. When the gate selection period was 10 μs, the light transmittance of the liquid crystal cell when the gate was turned off was almost the same as that when the gate selection period was 5 μs. When the gate selection period is set to 10 μs or less, the light transmittance of the liquid crystal cell at the gate-off time hardly changes in any selection period.

FIG. 2 shows the relationship between the voltage and the transmitted light intensity (one of the applied voltages) at five capacitance ratios C S / C LC when using a liquid crystal cell formed using a material with Ps = 12.8 nC / cm 2. It is a graph which shows the polarity (only at the time of + application). It can be seen from FIG. 2 that the voltage-light transmittance characteristic shifts to the low voltage side as the value of C S / C LC increases.

FIG. 3 is a graph showing the relationship between the capacity ratio C S / C LC and the drive voltage. The drive voltage decreases as the value of C S / C LC increases, but it can be seen from FIG. 3 that when the value is greater than 5, the effect of reducing the drive voltage is reduced.

FIG. 4 shows a capacitance ratio C S / C LC when a liquid crystal cell formed using three kinds of materials with Ps = 5.4, 8.0, 12.8 (nC / cm 2 ) is used. It is a graph which shows the relationship between a voltage ratio. The voltage ratio on the vertical axis indicates the reduction ratio of the drive voltage, and specifically, the ratio of the drive voltage when the capacitor is provided to the drive voltage when the capacitor is not provided. It can be understood from FIG. 4 that the effect of reducing the driving voltage is more remarkable when Ps is increased than when Ps is decreased.

From the results of FIG. 4, it can be seen that, in order to realize a reduction in driving voltage of 10% or more, the capacitance ratio C S / C LC ≧ 0.2 should be set, although it varies slightly depending on the spontaneous polarization value Ps. . However, when the capacitance ratio C S / C LC > 5, it can be seen that the effect of reducing the drive voltage is small as in the result of FIG. Increasing C S / C LC is not preferable because it requires a large storage capacitor C S and a large driving capability for a switching element such as a TFT. Therefore, from the above, the value of the capacity ratio C S / C LC is preferably 0.2 or more and 5 or less.

  Next, specific embodiments of the present invention will be described. FIG. 5 is a block diagram showing a circuit configuration of the liquid crystal display device, FIG. 6 is a schematic cross-sectional view of the liquid crystal panel and the backlight, FIG. 7 is a schematic diagram showing an example of the overall configuration of the liquid crystal display device, and FIG. FIG. 9 is a diagram illustrating an equivalent circuit of the LED array, and FIG. 9 is a diagram illustrating a configuration example of an LED array that is a light source of a backlight.

  As shown in FIGS. 6 and 7, the liquid crystal panel 21 has a polarizing film 1, a glass substrate 2, a common electrode 3, a glass substrate 4, and a polarizing film 5 from the upper layer (front surface) side to the lower layer (back surface) side. A plurality of pixel electrodes 40, 40... Arranged in a matrix are formed on the surface of the glass substrate 4 on the common electrode 3 side.

A plurality of liquid crystal cells 44 arranged in a matrix are formed between the common electrode 3 and the pixel electrodes 40, 40..., And each cell is driven by a data driver 32, a scan driver 33, and the like via a TFT 41 described later. The unit 50 is connected. The data driver 32 is connected to the TFT 41 via the signal line 42, and the scan driver 33 is connected to the TFT 41 via the scanning line 43. The TFT 41 is on / off controlled by the data driver 32 and the scan driver 33. The individual pixel electrodes 40, 40... Are controlled by the TFT 41. Therefore, the transmitted light intensity of each liquid crystal cell is controlled by a signal from the data driver 32 given through the signal line 42 and the TFT 41. As shown in FIG. 8, a capacitor 45 (storage capacitor C S ) is connected to the TFT 41 in parallel with the liquid crystal cell 44 (capacitance C LC ) in order to increase the amount of charge stored in each pixel. . The value of the C S / C LC satisfies 0.2 ≦ C S / C LC ≦ 5. In this embodiment, the combination of the liquid crystal cell 44, the TFT 41, and the capacitor 45 is referred to as a pixel.

  An alignment film 12 is disposed on the upper surface of the pixel electrodes 40, 40... On the glass substrate 4, and an alignment film 11 is disposed on the lower surface of the common electrode 3, and a liquid crystal substance is filled between the alignment films 11 and 12. A liquid crystal layer 13 is formed. Reference numeral 14 denotes a spacer for maintaining the layer thickness of the liquid crystal layer 13.

The liquid crystal panel 21 shown in FIGS. 6 and 7 was specifically manufactured as follows. A TFT substrate and a common electrode 3 having pixel electrodes 40, 40 (number of pixels: 640 × 480, electrode area: 6 × 10 −5 cm, storage capacitance C S : 0.2 pF, diagonal: 3.2 inches) After cleaning the glass substrate 2, the polyimide was applied and baked at 200 ° C. for 1 hour to form about 200 μm polyimide films as the alignment films 11 and 12.

Furthermore, these alignment films 11 and 12 were rubbed with a cloth made of rayon and overlapped with a gap held between them by a silica spacer 14 having an average particle diameter of 1.6 μm to produce an empty panel. A ferroelectric liquid crystal substance having a spontaneous polarization magnitude of 12.8 nC / cm 2 containing naphthalene liquid crystal as a main component was sealed between the alignment films 11 and 12 of the empty panel to form a liquid crystal layer 13. At this time, the liquid crystal capacitance C LC was 0.23 pF. Therefore, the capacity ratio C S / C LC was 0.87. The produced panel was sandwiched between two polarizing films 1 and 5 in a crossed Nicol state so that the ferroelectric liquid crystal molecules of the liquid crystal layer 13 were in a dark state when tilted to one side to obtain a liquid crystal panel 21.

  FIG. 10 shows the measurement result of measuring the transmitted light intensity by applying a voltage to each liquid crystal cell 44 and capacitor 45 of the liquid crystal panel 21 thus manufactured through switching of the TFT 41. It can be seen that driving is possible at a voltage as low as 5V.

  The backlight 22 is located on the lower layer (rear) side of the liquid crystal panel 21, and the LED array 7 is provided in a state where the backlight 22 faces the end face of the light guide and light diffusion plate 6 constituting the light emitting region. As shown in FIG. 9, the LED array 7 emits three primary colors, that is, red (R), green (G), and blue (B), on the surface facing the light guide and light diffusion plate 6. The LEDs are arranged sequentially and repeatedly. Then, red, green, and blue LEDs are caused to emit light in each of the red, green, and blue subframes in the field sequential method, which will be described later. The light guide and light diffusing plate 6 functions as a light emitting region by guiding light emitted from each LED of the LED array 7 to its entire surface and diffusing it to the upper surface.

  In FIG. 5, reference numeral 30 denotes an image memory unit which receives display data DD from an external personal computer, for example, and stores the input display data DD, and 31 also receives a synchronization signal SYN from the personal computer to control the display data DD. It is a control signal generation circuit that generates a signal CS and a data inversion control signal DCS. The pixel data PD is output from the image memory unit 30, and the data inversion control signal DCS is output from the control signal generation circuit 31 to the data inversion circuit 36. The data inversion circuit 36 generates inverse pixel data #PD obtained by inverting the input pixel data PD in accordance with the data inversion control signal DCS.

  A control signal CS is output from the control signal generation circuit 31 to the reference voltage generation circuit 34, the data driver 32, the scan driver 33, and the backlight control circuit 35, respectively. The reference voltage generation circuit 34 generates reference voltages VR1 and VR2, and outputs the generated reference voltage VR1 to the data driver 32 and the reference voltage VR2 to the scan driver 33, respectively. The data driver 32 outputs a signal to the signal line 42 of the pixel electrode 40 based on the pixel data PD or the inverse pixel data #PD received from the image memory unit 30 via the data inversion circuit 36. In synchronization with the output of this signal, the scan driver 33 sequentially scans the scanning lines 43 of the pixel electrodes 40 line by line. The backlight control circuit 35 applies drive voltage to the backlight 22 and causes the LEDs of the red, green, and blue colors included in the LED array 7 of the backlight 22 to emit light in a time-sharing manner.

  Next, the operation of the liquid crystal display device will be described. Display data DD for each color of red, green and blue to be displayed by the liquid crystal panel 21 is given to the image memory unit 30 from a personal computer. The image memory unit 30 temporarily stores the display data DD, and then outputs pixel data PD, which is data for each pixel, when the control signal CS output from the control signal generation circuit 31 is received. When the image data DD is supplied to the image memory unit 30, the control signal generation circuit 31 is supplied with the synchronization signal SYN, and the control signal generation circuit 31 receives the control signal CS and the data inversion control signal DCS when the synchronization signal SYN is input. Is generated and output. The pixel data PD output from the image memory unit 30 is given to the data inversion circuit 36.

  The data inversion circuit 36 passes the pixel data PD as it is when the data inversion control signal DCS output from the control signal generation circuit 31 is at L level, while the inverse pixel data # when the data inversion control signal DCS is at H level. Generate and output PD. Therefore, the control signal generation circuit 31 sets the data inversion control signal DCS to the L level during the data write scan, and sets the data inversion control signal DCS to the H level during the data erase scan.

  The control signal CS generated by the control signal generation circuit 31 is supplied to the data driver 32, the scan driver 33, the reference voltage generation circuit 34, and the backlight control circuit 35. When receiving the control signal CS, the reference voltage generation circuit 34 generates reference voltages VR1 and VR2, and outputs the generated reference voltage VR1 to the data driver 32 and the reference voltage VR2 to the scan driver 33, respectively.

  When the data driver 32 receives the control signal CS, the data driver 32 applies the signal line 42 of the pixel electrode 40 based on the pixel data PD or the inverse pixel data #PD output from the image memory unit 30 via the data inversion circuit 36. In response, a signal is output. When receiving the control signal CS, the scan driver 33 sequentially scans the scanning lines 43 of the pixel electrodes 40 line by line. The TFT 41 is driven in accordance with the output of the signal from the data driver 32 and the scan of the scan driver 33, the voltage is applied to the pixel electrode 40, and the transmitted light intensity of the pixel is controlled.

  When receiving the control signal CS, the backlight control circuit 35 applies a drive voltage to the backlight 22 to time-divide the red, green, and blue LEDs of the LED array 7 of the backlight 22. Each emits light.

  Display control in this liquid crystal display device is performed according to a field sequential time chart shown in FIG. 11A shows the light emission timing of each color LED of the backlight 22, FIG. 11B shows the scanning timing of each line of the liquid crystal panel 21, and FIG. 11C shows the color development state of the liquid crystal panel 21, respectively.

  Then, the period of one frame is divided into three subframes, and red, green, and blue LEDs are sequentially emitted in each of the first to third subframes as shown in FIG. . Color display is performed by switching each pixel of the liquid crystal panel 21 in units of lines in synchronization with the sequential light emission of each color.

  On the other hand, as shown in FIG. 11B, the liquid crystal panel 21 is scanned twice during the sub-frames of red, green, and blue. However, the start timing of the first scan (data write scan) (timing to the first line) coincides with the start timing of each subframe, and the end timing of the second scan (data erase scan) (final) The timing is adjusted so that (timing to line) coincides with the end timing of each subframe. In the present invention, the light transmission rate of the liquid crystal cell when the gate selection period of the TFT 41 is set to 10 μs or less, preferably 5 μs or less and the gate of the TFT 41 is off is equivalent to the TFT 41 corresponding to the scanning time of one line. Almost no change is made according to the gate selection period.

  In the data writing scan, a voltage corresponding to the pixel data PD is supplied to each pixel of the liquid crystal panel 21 to adjust the transmittance. This enables full color display. In the data erasing scan, a voltage having substantially the same voltage and reverse polarity as that in the data writing scan is supplied to each pixel of the liquid crystal panel 21, and the display of each pixel of the liquid crystal panel 21 is erased to the liquid crystal cell. Is prevented from being applied.

  As described above, as a result of performing field sequential color display by the driving method of the liquid crystal display device of the present invention, it was possible to realize bright and high-quality display with excellent color purity.

(Comparative example)
A ferroelectric liquid crystal material having a spontaneous polarization of 12.8 nC / cm 2 is encapsulated in an empty panel manufactured in the same manner as in the above-described embodiment except that no capacitor for charge storage is provided. The panel was sandwiched between two polarizing films in a crossed Nicol state so that when the ferroelectric liquid crystal molecules were tilted to one side, the liquid crystal panel as a comparative example was produced. The capacity of the liquid crystal cell of the liquid crystal panel as this comparative example was 0.23 pF, as in the above-described embodiment. Of course, since no capacitor is provided, the capacitance ratio C S / C LC is zero.

  FIG. 12 shows the measurement result of measuring the transmitted light intensity by applying a voltage to each liquid crystal cell of the liquid crystal panel as a comparative example manufactured in this way through switching of the TFT. It can be seen that a drive voltage as high as 9V is necessary.

  In the above-described example, the ferroelectric liquid crystal is used as the liquid crystal substance having spontaneous polarization. However, the anti-ferroelectric liquid crystal, particularly the V-shaped voltage-light transmittance characteristic (positive in a state where the same amount of transmitted light is obtained). Of course, the same effect can be obtained even when an antiferroelectric liquid crystal having a voltage and a negative voltage is used.

  In the above-described example, color display is performed by a field sequential method using RGB individual light sources, but it is also possible to use a single light source capable of emitting light by switching RGB. Of course, the present invention can be similarly applied to a configuration in which color display is performed using the color filter.

It is a figure which shows the structure of the experimental system of the TFT drive evaluation characteristic of a liquid crystal cell. It is a graph which shows the relationship between the voltage and transmitted light intensity in five types of capacity ratios (C S / C LC ). It is a graph showing the relationship between the volume ratio (C S / C LC) and the driving voltage. Volume ratio in the size of the three spontaneous polarization (C S / C LC) and a graph showing the relationship between the voltage ratio. It is a block diagram which shows the circuit structure of a liquid crystal display device. It is typical sectional drawing of a liquid crystal panel and a backlight. It is a schematic diagram which shows the structural example of the whole liquid crystal display device. It is a figure which shows the equivalent circuit of a liquid crystal panel. It is a figure which shows the structural example of a LED array. It is a graph which shows the relationship between the voltage and transmitted light intensity by embodiment. It is a time chart which shows display control of a liquid crystal display device. It is a graph which shows the relationship between the voltage and transmitted light intensity by a comparative example. It is a figure which shows the alignment state of the liquid crystal molecule in a ferroelectric liquid crystal panel.

Explanation of symbols

1,5 Polarizing film 13 Liquid crystal layer 22 Backlight 21 Liquid crystal panel 40 Pixel electrode 41 TFT
44 Liquid crystal cell 45 Capacitor

Claims (1)

  1. Two polarizing plates disposed opposite to each other, a liquid crystal cell sandwiched between the polarizing plates, a light source and red, green, and blue light emitted from the light source disposed on the back side of the liquid crystal cell. A liquid crystal comprising a backlight having a light emitting region leading to a cell, a pixel electrode corresponding to a pixel of the liquid crystal cell, a switching element connected to the pixel electrode, and a capacitor for accumulating charge in the pixel electrode A driving method of a display device,
    The switching element corresponding to the pixel is turned on / off during the period of each display period corresponding to the red, green, and blue data of each pixel, and each display is synchronized with the on / off drive of the switching element. During the period of the cycle, the backlight red, green, blue light is emitted in a time-sharing manner,
    During each period in which the backlight emits red, green, and blue light in a time-sharing manner, a first scan for displaying on each pixel of the liquid crystal cell and a second for erasing the display Are scanned in this order,
    A scanning time for each of the first scanning and the second scanning is set to 10 μs or less, and a ratio of the capacitance of the capacitor to the capacitance of the liquid crystal cell is set to 0.2 or more and 5 or less. Device driving method.
JP2007216240A 2007-08-22 2007-08-22 Method of driving liquid crystal display device Pending JP2008033343A (en)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0534724A (en) * 1991-07-31 1993-02-12 Mitsubishi Electric Corp Ferroelectric liquid crystal cell
JP2000171838A (en) * 1998-12-02 2000-06-23 Dainippon Ink & Chem Inc Liquid crystal display element and liquid crystal display device using the same
JP2000180827A (en) * 1998-12-11 2000-06-30 Fujitsu Ltd Liquid crystal display device
JP2001051253A (en) * 1999-08-16 2001-02-23 Fujitsu Ltd Liquid crystal display device
JP2003091019A (en) * 2001-09-19 2003-03-28 Fujitsu Ltd Liquid crystal display device

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0534724A (en) * 1991-07-31 1993-02-12 Mitsubishi Electric Corp Ferroelectric liquid crystal cell
JP2000171838A (en) * 1998-12-02 2000-06-23 Dainippon Ink & Chem Inc Liquid crystal display element and liquid crystal display device using the same
JP2000180827A (en) * 1998-12-11 2000-06-30 Fujitsu Ltd Liquid crystal display device
JP2001051253A (en) * 1999-08-16 2001-02-23 Fujitsu Ltd Liquid crystal display device
JP2003091019A (en) * 2001-09-19 2003-03-28 Fujitsu Ltd Liquid crystal display device

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