KR100854992B1 - Liquid crystal display - Google Patents

Abstract

Within one subframe or within one frame, the magnitudes of the applied voltage of one polarity and the applied voltage of the other polarity and the respective sustain periods are different. The applied voltage of the polarity for displaying dark display is larger in magnitude and shorter than the applied voltage of the polarity for displaying bright display. The magnitude of the applied voltage of one polarity (the polarity for bright display according to the display data) is V1, the sustain period is T1, the magnitude of the applied voltage of the other polarity (the polarity for dark display) is V2 and the sustain period is T2. In this case, the value of (V1 · T1) / (V2 · T2) is in the range of 0.7 to 1.3, more preferably in the range of 0.7 to 1.1.

Liquid crystal display, TFT, subframe, color filter, backlight, liquid crystal material, applied voltage, capacitor, retention period, liquid crystal panel, pixel electrode, common electrode, data driver

Description

Liquid crystal display {LIQUID CRYSTAL DISPLAY}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to an active drive liquid crystal display device using a switching element such as a TFT (Thin Film Transistor).

With the recent development of the so-called information society, electronic devices typified by personal computers, personal digital assistants (PDAs), and the like have become widely used. With the spread of such electronic devices, there is a demand for portable devices that can be used in offices and outdoors, and their miniaturization and weight reduction are desired. As one of means for achieving such an objective, the liquid crystal display device is widely used. The liquid crystal display device is an indispensable technology for not only miniaturization and light weight but also low power consumption of a battery powered portable electronic device.

Liquid crystal displays are roughly classified into reflection type and transmission type. The reflection type reflects the light incident from the front side of the liquid crystal panel on the back side of the liquid crystal panel and visually recognizes the image by the reflected light. The transmission type is transmitted light from a light source (back light) provided on the rear side of the liquid crystal panel. It is a structure which visually recognizes an image. The reflective type is not constant due to the amount of reflected light due to environmental conditions, and thus the visibility is inferior. Therefore, in particular, as a display device such as a personal computer which performs full-color display, color is generally used. A transmissive color liquid crystal display device using a filter is used.

Background Art A color liquid crystal display device has been widely used in active driving using switching elements such as TFTs. Although the display quality of this TFT drive liquid crystal display is relatively high, since the light transmittance of a liquid crystal panel is low about several% in the present state, high brightness backlight is required in order to acquire high screen brightness. For this reason, power consumption by backlight becomes large. In addition, there is a problem that the responsiveness to the electric field of the liquid crystal is low, and the response speed, in particular, the response speed in a halftone. Moreover, since it is a color display using a color filter, one pixel should be comprised with three subpixels, high precision is difficult, and the display color purity is also not enough.

In order to solve such a problem, the present inventors have developed the field-sequential liquid crystal display device (for example, refer nonpatent literature 1, 2, 3 etc.). This field-sequential liquid crystal display device does not require sub-pixels as compared with the liquid crystal display device of the color filter method, and thus it is possible to easily realize a more accurate display and without using a color filter. Since the light emission color of a light source can be used for display as it is, display color purity is also excellent. Moreover, since light utilization efficiency is high, it also has the advantage that power consumption is minimized. However, in order to realize the liquid crystal display device of a field-sequential system, the high speed response (2ms or less) of a liquid crystal is essential.

Therefore, the inventors of the present invention have achieved a high-speed response of 100 to 1000 times as compared with the conventional one, in order to achieve a high-speed response of the liquid crystal display device of the field-sequential method or the liquid crystal display device of the color filter having the excellent advantages as described above. Research and development of driving by switching elements, such as TFT, of liquid crystals, such as ferroelectric liquid crystals which have anticipated spontaneous polarization, are anticipated (for example, refer patent document 1 etc.). In ferroelectric liquid crystals having spontaneous polarization, liquid crystal molecules are arranged substantially parallel to the substrate, and the long axis direction of the liquid crystal molecules changes by voltage application. Then, the liquid crystal panel having the ferroelectric liquid crystal interposed therebetween is sandwiched between two polarizing plates having perpendicular polarization axes, and the transmitted light intensity is changed using birefringence due to the change in the major axis direction of the liquid crystal molecules.

[Patent Document 1] Japanese Unexamined Patent Publication No. 11-119189

[Non-Patent Document 1] Toshiaki Yoshihara et al. (T. Yoshihara, et. Al.): Issued by ILCC 98 P1-074, 1998

[Non-Patent Document 2] T.Yoshihara, et.al., published by AM-LCD'99 Digest of Technical Papers, p.185, 1999

[Non-Patent Document 3] T.Yoshihara, et.al., published by SID'00 Digest of Technical Papers, p. 1176, 2000

Such a field-sequential liquid crystal display device or a color filter liquid crystal display device is required to further lower power consumption and lower cost in use in a battery-powered portable electronic device.

1 and 2 show a conventional field sequential liquid crystal display device, in particular, a liquid crystal display of a conventional field sequential method using a liquid crystal material exhibiting a half V-shaped electro-optic response characteristic as shown in FIG. 3. It is a figure which shows the drive sequence of an apparatus. 1 (a) and 2 (a) show the scanning timing of each line of the liquid crystal panel, and FIGS. 1 (b) and 2 (b) show the lighting timings of the red, green and blue colors of the backlight. Indicates.

One frame is divided into three subframes, for example, red light is emitted in the first subframe and green light is emitted in the second subframe as shown in FIGS. 1B and 2B. The blue light is emitted in the third subframe. On the other hand, as shown in Figs. 1A and 2A, the liquid crystal panel is subjected to two write scans of image data in red, green, and blue subframes. In the first data scan, data scanning is performed with a polarity capable of realizing bright display. In the second data scanning, a voltage having a polarity opposite to that of the first data scanning and having substantially the same magnitude is applied. In the example shown in FIG. 2, compared with the example shown in FIG. 1, the time required for one data scan is shortened, and as shown in FIG. 1B, the backlight is not continuously turned on in the subframe. The power consumption is reduced by setting the lighting period of the backlight from the start of the first data scan to the end of the second data scan (Fig. 2 (b)).

4 and 5 show a driving sequence of a conventional color filter type liquid crystal display device, particularly, a conventional color filter type liquid crystal display device using a liquid crystal material exhibiting the half V-shaped electro-optic response characteristic as shown in FIG. 3. It is a figure which shows. 4 (a) and 5 (a) show the scanning timing of each line of the liquid crystal panel, and Figs. 4 (b) and 5 (b) show the lighting timing of the backlight.

As shown in Figs. 4A and 5A, the liquid crystal panel is write-scanned two times of image data in each frame. In the first data write scan, a data write scan is performed with a polarity capable of realizing bright display, and in the second data write scan, a voltage having a polarity opposite to that of the first data write scan and having substantially the same magnitude is applied. do. In the example shown in FIG. 5, compared with the example shown in FIG. 4, the time required for one scan is shortened, and the backlight is not continuously turned on in the frame as shown in FIG. The power consumption is reduced by setting the lighting time between the first data scan start and the second data scan end (FIG. 5B).

In a conventional field-sequential liquid crystal display device or a color filter liquid crystal display device, the magnitude (V1) of the voltage of one polarity and the magnitude (V2) of the other polarity within one subframe or within one frame. Is equivalent. In addition, after a voltage of one (or the other) polarity is applied to the liquid crystal material, and then a period from which the voltage of the other (or one) polarity is subsequently applied to the liquid crystal material, in other words, of the one (or the other) polarity When the period from the timing at which the voltage is applied to the timing at which the voltage of the other (or one) polarity is applied is referred to as a sustain period, the sustain period T1 of the voltage of one polarity in one subframe or in one frame and It is equivalent to the sustain period T2 of the voltage of the other polarity.

Therefore, when the data scanning period is set to one subframe or 50% of one frame (FIGS. 1 and 4), only about half (50%) of the light emission amount of the backlight can be used for display. Further, even when the data scanning period is set to one sub frame or 25% of one frame (FIGS. 2 and 5), only about 2/3 (67%) of the light emission amount of the backlight can be used for display.

Therefore, in order to realize further low power consumption and low cost, improvement of the light utilization efficiency of the backlight is required.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a liquid crystal display device capable of increasing the light utilization efficiency of a backlight and achieving a lower power consumption and a lower cost.

The liquid crystal display device according to the first invention is a liquid crystal display device in which a liquid crystal material is enclosed in a gap formed of a plurality of substrates, and a plurality of voltages having different polarities with respect to the liquid crystal material are applied within a sustain period, wherein the sustain period The magnitude of the voltage of one polarity to be applied to the liquid crystal material is different from the magnitude of the voltage of the other polarity applied thereto, and the period from the application of the voltage of one polarity to the application of the voltage of the other polarity and from the application of the voltage of the other polarity to the The period until the application of voltage of one polarity is different.

In the first invention, the magnitude of the applied voltage of one polarity and the applied voltage of the other polarity and the respective sustain periods are different in one subframe or in one frame. Therefore, the light utilization efficiency of a backlight can be improved.

In the liquid crystal display device according to the second aspect of the invention, the magnitude of the voltage of the other polarity for dark display is greater than the magnitude of the voltage of the one polarity for bright display, from the application of the voltage of the other polarity to the application of the voltage of the one polarity. The period of is shorter than the period from the voltage application of the one polarity to the voltage application of the other polarity.

In the second aspect of the invention, the applied voltage of the polarity for displaying the dark display has a larger size and the holding period shorter than the applied voltage of the polarity for displaying the bright display. Therefore, in the lighting period of the backlight, the period of dark display which can be regarded as black display, that is, the lighting period of the backlight not contributing to the display can be shortened, so that the light utilization efficiency of the backlight is further improved.

The liquid crystal display device according to the third aspect of the invention is characterized in that V1 · T1 ≒ V2 · T2.

V1: magnitude of voltage of one polarity

T1: period from application of voltage of one polarity to application of voltage of the other polarity

V2: magnitude of the voltage of the other polarity

T2: period from application of the voltage of the other polarity to application of the voltage of the one polarity

In the third aspect of the invention, when the magnitude of the applied voltage of one polarity is V1, the sustain period is T1, the magnitude of the applied voltage of the other polarity is V2, and the sustain period is T2, V1, T1 and V2, T2 are approximately Make it equal. Therefore, since the electric charge deflection can be suppressed when the voltage of one polarity is applied and when the voltage of the other polarity is applied, residual image display can be prevented.

The liquid crystal display device according to the fourth aspect of the invention is characterized in that 0.7 ≦ (V1 · T1) / (V2 · T2) ≦ 1.3.

V1: magnitude of voltage of one polarity

T1: period from application of voltage of one polarity to application of voltage of the other polarity

V2: magnitude of the voltage of the other polarity

T2: period from application of the voltage of the other polarity to application of the voltage of the one polarity

In the fourth aspect of the invention, when the magnitude of the applied voltage of one polarity is V1, the sustain period is T1, the magnitude of the applied voltage of the other polarity is V2, and the sustain period is T2, then (V1 · T1) / (V2 · The value of T2) is set in the range of 0.7 to 1.3. Therefore, since the electric charge bias at the time of applying the voltage of one polarity and the application of the voltage of the other polarity becomes small, the afterimage of a display can be suppressed.

The liquid crystal display device according to the fifth aspect of the invention is characterized in that 0.9 ≦ (V1 · T1) / (V2 · T2) ≦ 1.1.

V1: magnitude of voltage of one polarity

T1: period from application of voltage of one polarity to application of voltage of the other polarity

V2: magnitude of the voltage of the other polarity

T2: period from application of the voltage of the other polarity to application of the voltage of the one polarity

In the fifth aspect of the invention, when the magnitude of the applied voltage of one polarity is V1, the sustain period is T1, the magnitude of the applied voltage of the other polarity is V2, and the sustain period is T2, then (V1 · T1) / (V2 · The value of T2) is in the range of 0.9 to 1.1. Therefore, the afterimage of a display can be further suppressed.

The liquid crystal display device according to the sixth invention is characterized in that the liquid crystal material is a liquid crystal material having spontaneous polarization.

In the sixth invention, the liquid crystal material exhibits spontaneous polarization. Since the liquid crystal material having spontaneous polarization is used, high-speed response is possible, high moving display characteristics can be obtained, and display in a field-sequential manner can be performed. In particular, by using a ferroelectric liquid crystal material having a small spontaneous polarization value, driving by a switching element such as a TFT becomes easy.

A liquid crystal display device according to a seventh aspect of the invention is characterized by performing color display in a field-sequential manner.

In the liquid crystal display device of the seventh aspect of the invention, color display is performed in a field-sequential manner in which a plurality of colors of light are switched over time. Therefore, color display with high definition, high color purity, and high speed response is possible.

The liquid crystal display device according to the eighth invention is characterized by performing color display by a color filter method.

In the liquid crystal display device of the eighth invention, color display is performed by a color filter method using a color filter. Therefore, color display can be performed easily.

Effects of the Invention

In the liquid crystal display device of the present invention, since the magnitude of the applied voltage of one polarity and the applied voltage of the other polarity and the respective sustain periods are varied within one subframe or within one frame, the light utilization efficiency of the backlight is different. As a result, it is possible to realize low power consumption and low cost.

BRIEF DESCRIPTION OF THE DRAWINGS The figure which shows an example of the drive sequence of the liquid crystal display device of a conventional field-sequential system.

Fig. 2 is a diagram showing another example of a drive sequence of a liquid crystal display device of a conventional color filter method.

3 is a diagram showing an electro-optical response characteristic (half V-shaped characteristic) of a liquid crystal material.

Fig. 4 is a diagram showing an example of a drive sequence of a liquid crystal display device of a conventional color filter method.

Fig. 5 is a diagram showing another example of the drive sequence of the liquid crystal display device of the conventional color filter method.

Fig. 6 is a diagram showing an example of a drive sequence of a liquid crystal display device of a field-sequential system of the present invention.

Fig. 7 is a diagram showing an example of a drive sequence of a liquid crystal display device of a color filter method of the present invention.

8 is a graph showing observation results of the presence or absence of afterimage occurrence.

9 is a graph showing observation results of the presence or absence of afterimage occurrence.

10 is a chart showing observation results of the presence or absence of afterimage occurrence.

11 is a block diagram showing a circuit configuration of a liquid crystal display device according to the first embodiment (field sequential method).

12 is a schematic sectional view of a liquid crystal panel and a backlight of the liquid crystal display device according to the first embodiment;

It is a schematic diagram which shows the structural example of the whole liquid crystal display device which concerns on 1st Embodiment.

Fig. 14 is a block diagram showing a circuit configuration of a liquid crystal display device according to the second embodiment (color filter method).

15 is a schematic cross-sectional view of a liquid crystal panel and a backlight of the liquid crystal display device according to the second embodiment.

It is a schematic diagram which shows the structural example of the whole liquid crystal display device which concerns on 2nd Embodiment.

Fig. 17 is a diagram showing another example (Example 4) of a drive sequence of a liquid crystal display device of a color filter method of the present invention.

Explanation of the sign

2 glass substrates 3 common electrodes

4 glass substrate 13 liquid crystal layer

21 LCD panel 22 backlight

31 Control signal generator circuit 32 Data driver

33 Scan Driver 34 Voltage Reference Circuit

40 pixel electrode 41 TFT

42 signal line 43 scan line

50 drive 60 color filter

The present invention will be specifically described with reference to the drawings showing the embodiments thereof. In addition, this invention is not limited to the following embodiment.

First, the outline | summary of this invention is demonstrated using the drive sequence shown to FIG. 6, FIG. 6 shows an example of a drive sequence of the liquid crystal display device of the field-sequential method of the present invention, and FIG. 7 shows an example of a drive sequence of the liquid crystal display device of the color filter method of the present invention.

In the present invention, as shown in Figs. 6 and 7, the magnitudes are different and the respective sustain periods are different at the applied voltage of one polarity and the applied voltage of the other polarity. That is, in Figs. 6 and 7, the magnitude V1 of the applied voltage according to the display data differs from the magnitude V2 of the applied voltage for substantially black display (│V1│ ≠ │ V2│), and also in the display data. A sustain period T1 after applying the voltage according to the method and until applying the voltage for substantially black display, and a sustain period for applying the voltage according to the display data after applying the voltage for substantially displaying black T2 is different (T1 ≠ T2). In addition, since the potential of the liquid crystal in this sustain period is affected by the response of the liquid crystal or the like, it is not necessarily constant.

For example, when the data scanning period is set to one subframe or 25% of one frame (FIGS. 6 and 7), about 3/4 (75%) of the light emission amount of the backlight can be used for display. Compared with the conventional example, it is possible to improve the light utilization efficiency of the backlight. In this invention, since the light utilization efficiency of a backlight can be improved in this way, when it is the same screen brightness | luminance, it is possible to reduce power consumption. In addition, when the screen brightness is the same as the power consumption, the number of installation of light sources such as LEDs (Light Emitting Diodes) can be reduced, resulting in low ghosting.

The applied voltage V2 (9V in the example of FIG. 6) at the polarity for performing dark display (the second data scan) and the applied voltage V1 at the polarity (first data scan) for performing the bright display according to the image data (Fig. It is made larger than 3V in the example of 6, and the former sustain period T2 (1.4 ms in the example of FIG. 6) is made shorter than the latter sustain period T1 (4.2 ms in the example of FIG. 6). This makes it possible to shorten the period of the dark display which can be regarded as black display in the lighting period of the backlight, that is, the lighting period of the backlight not contributing to the display, thereby further improving the light utilization efficiency of the backlight. It can increase, and further reduction of power consumption and cost can be attained.

The multiplication value V1 · T1 (12.6 in the example of FIG. 6) of V1 and T1 is made equal to the multiplication value V2 · T2 (12.6 in the example of FIG. 6) of V2 and T2. This makes it possible to control the deflection of the electric charges when the voltage of one polarity is applied and when the voltage of the other polarity is applied, so that afterimage display can be prevented.

The value of (V1 · T1) / (V2 · T2) is preferably in the range of 0.7 to 1.3, and more preferably in the range of 0.9 to 1.1. This reason is demonstrated below.

After cleaning the TFT substrate having the pixel electrode (640 × 480 pixels, 3.2 inches diagonal) and the glass substrate having the common electrode, polyimide was applied and baked at 200 ° C. for 1 hour, thereby obtaining approximately 200 kPa of polyimide. A film was formed. In addition, the polyimide film is rubbed with a rayon cloth, and these two substrates are superposed so that the rubbing directions are parallel to each other, and the superimposition of the polyimide films is superposed in a state of maintaining a gap with a spacer made of silica having an average particle diameter of 1.6 µm. To make an empty panel. A monostable ferroelectric liquid crystal material (manufactured by Clarit Japan: R2301) exhibiting a half V-shaped electro-optic response characteristic was enclosed in this hollow panel. The magnitude of the spontaneous polarization of the enclosed liquid crystal material was 6nC / cm <^2> . After sealing, a 3 V DC voltage was applied between the cholesteric phase and the chiral smectic C phase to realize a uniform liquid crystal alignment state (orientation treatment). ). The produced panel was sandwiched between two polarizing films in a cross nicol state to form a liquid crystal panel, so that the panel was in a dark state when no voltage was applied.

In accordance with the driving sequence as shown in FIG. 6 while superimposing the liquid crystal panel thus produced and the backlight capable of monochromatic surface emission switching of red, green, and blue, and varying V1, V2, T1, and T2, White check checkerboard marking was performed for 2 hours to observe whether or not an afterimage occurred. The observation result is shown to FIG. 8, FIG. 9, and FIG. 8 to 10, when (circle) is not recognized, (triangle | delta) is a case where afterimage is recognized a little but there is no problem practically, (x) has shown the case where a residual image is recognized and there is a problem.

It is understood from the results of Figs. 8 to 10 that the afterimage can be suppressed by setting the value of (V1 · T1) / (V2 · T2) in the range of 0.7 to 1.3. Moreover, it turns out that it is more preferable that the range of this value is 0.9-1.1.

(1st embodiment)

FIG. 11 is a block diagram showing a circuit configuration of a liquid crystal display device according to a first embodiment of the present invention, FIG. 12 is a schematic cross-sectional view of a liquid crystal panel and a backlight, and FIG. 13 shows a structural example of the entire liquid crystal display device. It is a schematic diagram. 1st Embodiment is a liquid crystal display device which performs color display by a field-sequential system.

In FIG. 11, 21 and 22 show the liquid crystal panel and the backlight which the cross-sectional structure is shown in FIG. As shown in FIG. 12, the backlight 22 includes an LED array 7, a light guide, and a light diffusion plate 6. As shown in FIG. 12, FIG. 13, the liquid crystal panel 21 is a polarizing film 1, the glass substrate 2, the common electrode 3, and the glass substrate from the upper layer (surface) side to the lower layer (back surface) side. (4) and the polarizing film 5 are laminated | stacked in this order, Comprising: The pixel electrode 40, 40 ... arrange | positioned in matrix form is formed in the surface on the common electrode 3 side of the glass substrate 4, have.

The driver 50 which consists of the data driver 32, the scan driver 33, etc. is connected between these common electrodes 3 and the pixel electrodes 40, 40 .... 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 scan line 43. The TFT 41 is controlled on / off by the scan driver 33. Further, the individual pixel electrodes 40, 40... Are connected to the TFT 41. Therefore, the transmitted light intensity of each pixel is controlled by the signal (data voltage) from the data driver 32 provided through the signal line 42 and the TFT 41.

The alignment film 12 is disposed on the top surface of the pixel electrodes 40, 40... On the glass substrate 4, and the alignment film 11 is disposed on the bottom surface of the common electrode 3, respectively. The material is filled to form the liquid crystal layer 13. In addition, 14 is a spacer for maintaining the layer thickness of the liquid crystal layer 13.

The backlight 22 is located on the lower layer (back side) side of the liquid crystal panel 21, and the LED array 7 is directed to the end face of the light guide and the light diffusion plate 6 constituting the light emitting region. It is provided. The LED array 7 has one or a plurality of LEDs each having three primary colors, that is, red, green, and blue light emitting diode elements, as one chip, on a surface facing the light guide and the light diffusion plate 6. In each of the subframes of red, green, and blue, the red, green, and blue LED elements are turned on. The light guide and the light diffusion plate 6 function as light emitting regions by guiding the light from each LED of the LED array 7 to the entire surface thereof and simultaneously diffusing it to the upper surface.

The liquid crystal panel 21 and the backlight 22 capable of time division emission of red, green and blue are superimposed. The lighting timing and emission color of the backlight 22 are controlled in synchronization with data scanning based on the display data on the liquid crystal panel 21.

In Fig. 11, 31 is a control signal generation circuit for inputting a synchronization signal SYN from a personal computer to generate various control signals CS for display. The pixel data PD is output from the image memory section 30 to the data driver 32. Based on the pixel data PD and the control signal CS for changing the polarity of the applied voltage, a voltage is applied to the liquid crystal panel 21 through the data driver 32.

The control signal CS is output from the control signal generator 31 to the reference voltage generator 34, the data driver 32, the scan driver 33 and the backlight control circuit 35, respectively. The reference voltage generator 34 generates the 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 applies a signal (data voltage) to the signal line 42 of the pixel electrode 40 on the basis of the pixel data PD from the image memory unit 30 and the control signal CS from the control signal generation circuit 31. ) 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. In addition, the backlight control circuit 35 applies a driving voltage to the backlight 22 to emit red light, green light, and blue light from the backlight 22, respectively.

Next, the operation of the liquid crystal display device will be described. The pixel data PD for display is input from the personal computer to the image memory unit 30, and the image memory unit 30 stores the pixel data PD once, and then outputs the control signal CS output from the control signal generation circuit 31. Is received, this pixel data PD is outputted. The control signal CS generated by the control signal generating circuit 31 is provided to the data driver 32, the scan driver 33, the reference voltage generating circuit 34, and the backlight control circuit 35. When the reference voltage generating circuit 34 receives the control signal CS, the reference voltage generating circuit 34 generates the 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. do.

When the data driver 32 receives the control signal CS, the data driver 32 applies a signal (data voltage) to the signal line 42 of the pixel electrode 40 based on the pixel data PD output from the image memory unit 30. Output When the scan driver 33 receives the control signal CS, the scan driver 33 sequentially scans the scan line 43 of the pixel electrode 40 line by line. The TFT 41 is driven in accordance with the signal (data voltage) from the data driver 32 and the scan of the scan driver 33, and a voltage is applied to the pixel electrode 40 to control the transmitted light intensity of the pixel. When the backlight control circuit 35 receives the control signal CS, the backlight control circuit 35 applies a driving voltage to the backlight 22 to provide red, green, and blue colors of the LED array 7 of the backlight 22. The LED element is time-divided to emit light, and red light, green light, and blue light are sequentially emitted over time. Thus, color display is performed by synchronizing the lighting control of the backlight 22 (LED array 7) which emits incident light to the liquid crystal panel 21, and the data scanning of the liquid crystal panel 21 several times. Doing.

Hereinafter, specific examples will be described.

Example 1

After cleaning the TFT substrate having the pixel electrodes 40, 40... (Pixel number 640 x 480, 3.2 inches diagonal) and the glass substrate 2 having the common electrode 3, polyimide was applied to apply the film at 200 캜. By baking for 1 hour, about 200 kV of polyimide films were formed as the alignment films 11 and 12. In addition, the alignment films 11 and 12 are rubbed with a rayon cloth, and these two substrates are superposed so that the rubbing directions are parallel, and they are superimposed on the silica spacer 14 having an average particle diameter of 1.6 mu m between them in a state where the fin is kept. An empty panel was produced. Between the alignment films 11 and 12 of this hollow panel, a ferroelectric liquid crystal material having a naphthalene-based liquid crystal exhibiting half V-shaped electro-optic response characteristics as shown in FIG. 3 as a main component (for example, A. Mochizuki, et. al .: Ferroelectrics, 133, 353 (a material disclosed in 1991) was encapsulated to form a liquid crystal layer 13. The magnitude of the spontaneous polarization of the enclosed ferroelectric liquid crystal material was 10 nC / cm ² . The produced panel was sandwiched between two polarizing films 1 and 5 in a cross nicol state to form a liquid crystal panel 21, and when the major axis direction of the ferroelectric liquid crystal molecules was directed to one side, the panel was in a dark state.

The liquid crystal panel 21 thus fabricated and the backlight 22 using the LED array 7 capable of monochromatic surface emission switching of red, green, and blue as a light source are superimposed, and the driving sequence as shown in FIG. Therefore, color display by the field sequential system was performed. Specifically, V1 = 3V, V2 = 9V, T1 = 4.2 ms, and T2 = 1.4 ms. Therefore, it was (V1 * T1) / (V2 * T2) = 1.

As a result, high precision, high speed response, and high color purity display could be realized simultaneously. No afterimage of the sign was seen.

Example 2

Monostable ferroelectric liquid crystal material (R2301 manufactured by Clariant Japan) exhibiting half V-shaped electro-optic response characteristics as shown in FIG. 3 between the alignment films 11 and 12 of the blank panel produced in the same manner as in Example 1. Was enclosed to obtain a liquid crystal layer (13). The magnitude of the spontaneous polarization of the enclosed liquid crystal material was 6nC / cm <^2> . After encapsulation, a 3 V DC voltage was applied between the cholesteric phase and the chiral smectic C phase to realize a uniform liquid crystal alignment state (orientation treatment). ). The produced panel was sandwiched between two polarizing films 1 and 5 in a cross nicol state to form a liquid crystal panel 21, and when the voltage was not applied, the panel was made dark.

The liquid crystal panel 21 produced in this way and the backlight 22 similar to Example 1 were overlapped, and color display by the field-sequential system was performed according to the drive sequence as shown in FIG. Specifically, V1 = 4V, V2 = 10V, T1 = 4.2 ms, and T2 = 1.4 ms. Therefore, it was (V1 * T1) / (V2 * T2) = 1.2.

As a result, high precision, high speed response, and high color purity display could be realized simultaneously. No afterimage of the sign was seen.

(2nd embodiment)

14 is a block diagram showing a circuit configuration of a liquid crystal display device according to a second embodiment of the present invention, FIG. 15 is a schematic cross-sectional view of a liquid crystal panel and a backlight, and FIG. 16 is a structural example of the entire liquid crystal display device. It is a schematic diagram. 2nd Embodiment is a liquid crystal display device which performs color display by a color filter system. 14-16, the same code | symbol is attached | subjected to the part same or similar to FIGS. 11-13.

In the common electrode 3, color filters 60, 60, ... of three primary colors R, G, and B are provided. In addition, the backlight 22 is comprised from the white light source 70 provided with the one or several white light source element which emits white light, and the light guide and the light-diffusion plate 6. In such a color filter type liquid crystal display device, color display is performed by selectively transmitting white light emission from the white light source 70 capable of time-divisional light emission of white light through the color filters 60 of a plurality of colors.

Hereinafter, specific examples will be described.

Example 3

TFT substrate having pixel electrodes 40, 40... (Pixel number 320 × 3 (RGB) × 240, 3.5 inches diagonal) and glass substrate 2 having common electrode 3 and color filter 60 cleaned. Thereafter, polyimide was applied and baked at 200 ° C. for 1 hour, thereby forming a film of about 200 kPa as the alignment films 11 and 12. In addition, these alignment films 11 and 12 are rubbed with a rayon cloth, and these two substrates are superposed so that the rubbing directions are parallel, and they overlap each other in the state which kept the gap by the silica spacer 14 of an average particle diameter of 1.6 micrometers. A blank panel was produced. Between the alignment films 11 and 12 of this hollow panel, as shown in FIG. 3, a ferroelectric liquid crystal material having a naphthalene-based liquid crystal exhibiting half V-shaped electro-optic response characteristics as a main component (for example, A. Mochizuki, et. al .: Ferroelectrics, 133, 353 (a material disclosed in 1991)) was sealed to form a liquid crystal layer (13). The magnitude of the spontaneous polarization of the enclosed ferroelectric liquid crystal material was 10 nC / cm ² . The produced panel was sandwiched between two polarizing films 1 and 5 in a cross nicol state to form a liquid crystal panel 21, and when the major axis direction of the ferroelectric liquid crystal molecules was directed to one side, the panel was in a dark state.

The liquid crystal panel 21 thus produced is overlapped with the backlight 22 having the white light source 70 capable of time-divisional emission of white light, and according to the driving sequence as shown in FIG. Color display was performed. Specifically, V1 = 5V, V2 = 7V, T1 = 9.7 ms, and T2 = 6.9 ms. Therefore, it was (V1 * T1) / (V2 * T2) = 1.

As a result, good color display and high-speed response display could be realized, and no afterimage of the display was seen.

Example 4

Monostable ferroelectric liquid crystal material (R2301 manufactured by Clarit Japan) exhibiting half V-shaped electro-optic response characteristics as shown in FIG. 3 between the alignment films 11 and 12 of the blank panel produced in the same manner as in Example 3. Was sealed to obtain the liquid crystal layer (13). The magnitude of the spontaneous polarization of the enclosed liquid crystal material was 6nC / cm <^2> . After encapsulation, a uniform liquid crystal alignment state was realized by applying a DC voltage of 3 V across the transition point of the cholesteric phase to the chiral smectic C phase (orientation treatment). ). The produced panel was sandwiched between two polarizing films 1 and 5 in a cross nicol state to form a liquid crystal panel 21, and when the voltage was not applied, the panel was made dark.

The liquid crystal panel 21 produced in this way and the backlight 22 similar to Example 3 were overlapped, and the color display by the color filter system was performed according to the drive sequence as shown in FIG. In the fourth embodiment, three consecutive scans with the applied voltage corresponding to the display data are performed three times in a frame, and then three consecutive scans with the applied voltage for black display are performed. In addition, in Embodiment 4, unlike Embodiments 1 to 3 in which the backlight is turned on in each subframe or each frame from the scan start timing by the voltage of one polarity to the scan end timing by the voltage of the other polarity, in the fourth embodiment, The backlight is turned on from the middle of the first write scan in accordance with the display data in each frame to the middle of the first write scan for black display. The specific numerical value in Example 4 was set to V1 = 4V, V2 = 10V, T1 = 4.2ms, and T2 = 1.4ms. Therefore, it was (V1 * T1) / (V2 * T2) = 1.2.

As a result, good color display and high-speed response display could be realized, and no afterimage of the display was seen.

Moreover, in the above-mentioned example, although the case where the ferroelectric liquid crystal material which shows spontaneous polarization was used was demonstrated as an example, when the other liquid crystal material which shows spontaneous polarization, for example, anti-ferroelectric liquid crystal material is used, or spontaneous polarization is used. Needless to say, even when a nematic liquid crystal material is used that does not exhibit the same effect as in the case of a ferroelectric liquid crystal material when the drive display system is the same.

Moreover, although the transmissive liquid crystal display device was demonstrated, this invention can be similarly applied also to a reflective or semi-transmissive liquid crystal display device. In the case of a reflective or semi-transmissive liquid crystal display device, since the display can be performed without using a light source such as a backlight, power consumption is low.

Claims (8)

In a liquid crystal display device in which a liquid crystal material is enclosed in a gap formed of a plurality of substrates, and a plurality of voltages having different polarities with respect to the liquid crystal material are applied within a sustain period, the liquid crystal material is applied to the liquid crystal material within the sustain period. At the same time, the magnitude of the voltage of one polarity is different from that of the voltage of another polarity, and at the same time, the period from the application of the voltage of one polarity to the application of the voltage of the other polarity and from the application of the voltage of the other polarity The period until the application of voltage is different, It is V1 * T1 * V2 * T2, The liquid crystal display device characterized by the above-mentioned. V1: magnitude of voltage of one polarity T1: period from application of the voltage of one polarity to application of the voltage of the other polarity V2: magnitude of the voltage of the other polarity T2: The period from the application of the voltage of the other polarity to the application of the voltage of the one polarity. delete delete In a liquid crystal display device in which a liquid crystal material is enclosed in a gap formed of a plurality of substrates, and a plurality of voltages having different polarities with respect to the liquid crystal material are applied within a sustain period, the liquid crystal material is applied to the liquid crystal material within the sustain period. At the same time, the magnitude of the voltage of one polarity is different from that of the voltage of another polarity, and at the same time, the period from the application of the voltage of one polarity to the application of the voltage of the other polarity and from the application of the voltage of the other polarity The period until the application of voltage is different, A liquid crystal display device wherein 0.7 ≦ (V1 · T1) / (V2 · T2) ≦ 1.3. V1: magnitude of voltage of one polarity T1: period from application of the voltage of one polarity to application of the voltage of the other polarity V2: magnitude of the voltage of the other polarity T2: The period from the application of the voltage of the other polarity to the application of the voltage of the one polarity. In a liquid crystal display device in which a liquid crystal material is enclosed in a gap formed of a plurality of substrates, and a plurality of voltages having different polarities with respect to the liquid crystal material are applied within a sustain period, the liquid crystal material is applied to the liquid crystal material within the sustain period. At the same time, the magnitude of the voltage of one polarity is different from that of the voltage of another polarity, and at the same time, the period from the application of the voltage of one polarity to the application of the voltage of the other polarity and from the application of the voltage of the other polarity The period until the application of voltage is different, A liquid crystal display device wherein 0.9 ≦ (V1 · T1) / (V2 · T2) ≦ 1.1. V1: magnitude of voltage of one polarity T1: period from application of the voltage of one polarity to application of the voltage of the other polarity V2: magnitude of the voltage of the other polarity T2: The period from the application of the voltage of the other polarity to the application of the voltage of the one polarity. The method according to any one of claims 1, 4, and 5, The liquid crystal material is a liquid crystal material having spontaneous polarization. The method according to any one of claims 1, 4, and 5, A liquid crystal display device characterized by performing color display in a field-sequential manner. The method according to any one of claims 1, 4, and 5, A liquid crystal display device, wherein color display is performed by a color filter method.

Images