KR100804119B1 - Liquid crystal display device - Google Patents

Abstract

The present invention applies a voltage according to desired image data to a ferroelectric liquid crystal having spontaneous polarization at a predetermined period to perform display image rewriting (period A), and then to apply all voltages applied to the ferroelectric liquid crystal. It removes (timing C) and maintains the display image before the removal (time period B). The gate selection period (voltage application time to the ferroelectric liquid crystal) t ₂ immediately before the voltage application is stopped is made longer than the gate selection period (voltage application time to the ferroelectric liquid crystal) t ₁ in normal display. . By lengthening the voltage application time to the ferroelectric liquid crystal, the liquid crystal sufficiently responds in the gate selection period, thereby achieving high memory characteristics.

Spontaneous polarization, ferroelectric liquid crystal, voltage application time, gate selection period.

Description

Liquid crystal display {LIQUID CRYSTAL DISPLAY DEVICE}

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 type liquid crystal display device having a memory display function using a liquid crystal having spontaneous polarization.

With the recent development of the so-called information society, electronic devices represented by personal computers, PDAs (Persona Digital Assistants), 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, a liquid crystal display device is widely used. The liquid crystal display device is an indispensable technology not only for miniaturization and weight reduction but also for lowering power consumption of a battery powered portable electronic device.

The liquid crystal display device is classified into a reflection type and a transmission type if it is largely classified. The reflection type reflects light incident from the front surface of the liquid crystal panel on the rear surface of the liquid crystal panel and visually recognizes the image by the reflected light. The transmission type includes a light source (backlight) provided on the rear surface of the liquid crystal panel. (back light) is a configuration that visually recognizes an image with transmitted light. Since the reflection type is not constant and the visibility is inferior due to environmental conditions, in particular, as a display device such as a personal computer that performs multi-color or full-color display, a transmissive color liquid crystal display device using a color film is generally used. have.

TN (Twisted Nematic) type using switching elements, such as TFT (Thin Film Transistor), is widely used for a color liquid crystal display device. This TFT-driven TN type liquid crystal display has a higher display quality than the STN (Super Twisted Nematic) type, but the light transmittance of the liquid crystal panel is lower by several percent in the current state, so a high brightness backlight is required to obtain high screen brightness. Done. For this reason, power consumption by a backlight becomes large. Moreover, since it is a color display using a color filter, one pixel must be comprised with three subpixels, high definition is difficult, and the purity of the display color is also not enough.

In order to solve such a problem, the present inventors have developed a field sequential liquid crystal display device (for example, Toshiaki Yoshihara, et al .: I.C.C.). 98 (ILCC 98) P1-074 Published in 1998, Toshiaki Yoshihara, et.al .: AM-LCD'99 Digest of Technical Papers, 185 published in 1999, T.Yoshihara, et.al .: SID'00 Digest of Technical Papers, published on page 1176 (2000). This field sequential liquid crystal display device does not require a subpixel as compared to the color filter liquid crystal display device, so that a higher precision display can be easily realized and a color filter is not used. Since the light emission color of a light source can be used for display as it is, it is excellent also in display color purity. In addition, since the light utilization efficiency is high, it also has the advantage that the power consumption is reduced. However, in order to realize a field sequential liquid crystal display device, high-speed response (less than or equal to 2 Hz) of liquid crystal is essential.

Therefore, the inventors of the present invention have a high speed of 100 to 1000 times as compared with the conventional one in order to achieve a high speed response of the field-sequential liquid crystal display device or the color filter liquid crystal display device having the excellent advantages as described above. Research and development are being conducted by switching elements such as ferroelectric liquid crystal TFTs with spontaneous polarization that can expect a response (for example, Japanese Patent Laid-Open No. 11-119189). In the ferroelectric liquid crystal, the longitudinal direction of the liquid crystal molecules is changed by a tilt angle by applying a voltage. The liquid crystal panel into which the ferroelectric liquid crystal is inserted is sandwiched between two polarizing plates having perpendicular polarization axes, and the transmitted light intensity is changed by using birefringence due to the change in the longitudinal direction of the liquid crystal molecules.

As described above, the field sequential liquid crystal display device has a higher light utilization efficiency and a lower power consumption than the color filter liquid crystal display device. Reduction is required. The demand for such reduction in power consumption is the same in the color filter type liquid crystal display device.

Here, the display function, especially the memory display function, in the liquid crystal display device using the ferroelectric liquid crystal etc. which have spontaneous polarization is demonstrated. In such a liquid crystal display device, there is a normal display function of applying a voltage to the liquid crystal to perform display image rewriting at a predetermined cycle, and a memory display function of stopping the application of the voltage to the liquid crystal to hold the display image before the pause. Since the memory display function removes all voltages applied to the liquid crystal by a switching element such as a TFT, and almost maintains the display state immediately before removing the applied voltage, image display becomes possible without applying a voltage to the liquid crystal material. Therefore, considerable reduction of power consumption can be achieved. Therefore, the present invention can also be applied to a portable device, and in particular, the effect of reducing power consumption increases with respect to a mobile device having a large number of still images.

Hereinafter, the memory function of the ferroelectric liquid crystal having spontaneous polarization will be described. An example of the measurement results when the voltage is applied to the liquid crystal panel, then the application is stopped to remove the voltage, and the voltage value applied to measure the transmittance at the time of voltage application and the transmittance at 60 seconds after the voltage is applied is changed. 1 is shown. In Fig. 1, the measurement results are obtained by taking the voltage V applied to the horizontal axis and the transmittance% in the vertical axis, ○-○ represents the transmittance upon application of voltage, and Δ-Δ represents the transmittance after 60 seconds of voltage removal. . Even after removing the applied voltage, the corresponding characteristic of the applied voltage and the transmittance did not change, and even when the voltage applied to the liquid crystal panel was removed, it was found that the transmittance according to the display state at the time of applying the voltage was maintained. In addition, the black display (transmittance: approximately 0%, applied voltage: approximately OV) maintains the display state without change in voltage application and voltage application.

Moreover, the measurement result at the time of measuring the temporal change of the transmittance | permeability after removing a voltage with respect to a liquid crystal panel is shown in FIG. As shown to Fig.2 (a), the pulse waveform voltage of 5V and 100 Hz was applied to the liquid crystal panel, and the transmittance | permeability was measured over time. In FIG.2 (b), the transmittance | permeability measured by taking time on the horizontal axis and the transmittance | permeability (arbitrary unit) on the vertical axis | shaft is shown. It is understood that the transmittance rapidly increases at the moment of applying the voltage, and then gradually decays thereafter, but after the voltage removal 100 kHz, no decay is observed and the constant transmittance is continuously maintained.

From the above, it can be seen that the ferroelectric liquid crystal has a memory function, and even when the applied voltage is removed, the liquid crystal molecules continue to maintain the previous state without shifting from the stable position before the voltage application removal to another stable position. have. Therefore, in the liquid crystal display device using the ferroelectric liquid crystal having such a memory function, the applied voltage corresponding to the display information for one screen is given once, until the applied voltage corresponding to the display information on the next screen is applied. Even if the voltage is not continuously applied, the constant display according to the applied voltage can be maintained continuously. Therefore, the screen display can be maintained without applying a voltage, and power consumption can be reduced according to the need for no application.

SUMMARY OF THE INVENTION An object of the present invention is to be made in view of such circumstances, and to provide a liquid crystal display device capable of reducing power consumption.

Another object of the present invention is to provide a liquid crystal display device capable of sufficiently responding to liquid crystal and realizing high memory performance.

Still another object of the present invention is to provide a liquid crystal display device capable of realizing high memory performance in a wide temperature range.

In the liquid crystal display device according to the first invention, a liquid crystal material is enclosed in a gap formed by at least two substrates, and voltage application is selected to control light transmittance by the liquid crystal material corresponding to each pixel. And a switching element for non-selective control, wherein the first display device performs image display by applying a voltage to the liquid crystal material through the switching element, and stops applying voltage to the liquid crystal material through the switching element. A liquid crystal display device having a second display function for maintaining a display state immediately before the application of voltage is stopped, wherein the selection period of the switching element immediately before the application of the voltage is paused to execute the second display function. It is characterized by being longer than the selection period of the switching element in one display function.

In the liquid crystal display device of the first aspect of the invention, the selection period of the switching element (voltage application time to the liquid crystal material) by data write scanning for performing memory display immediately before the voltage application is stopped is selected period of the switching element in the normal display. It is made longer than (voltage application time to liquid crystal substance). When performing the memory display, the liquid crystal responds sufficiently in the selection period by lengthening the selection period of the switching element (time to turn on the gate when the switching element is TFT) and extending the voltage application time to the liquid crystal material. High memory performance is achieved. In particular, when the responsiveness of the liquid crystal deteriorates in a low temperature environment, sufficient memory performance cannot be exhibited in the selection period of the switching element during normal display, but sufficient memory performance is achieved even at low temperatures by lengthening the selection period to increase the voltage application time. Can be exercised.

In the liquid crystal display device according to the fourth aspect of the invention, a liquid crystal material is enclosed in a gap formed by at least two substrates, and voltage selection is selected / non-selected to control light transmittance by the liquid crystal material corresponding to each pixel. A switching element for controlling is provided, the first display function of performing image display by applying a voltage to the liquid crystal material through the switching element, and applying voltage to the liquid crystal material through the switching element while stopping the voltage application. A liquid crystal display device having a second display function for holding a display state just before stopping the display, wherein the non-selection period of the switching element immediately before the application of the voltage is paused to execute the second display function is performed in the first display. And longer than the non-selection period of the switching element in function.

In the liquid crystal display device of the fourth aspect of the invention, the non-selection period (time to turn off the gate when the switching element is a TFT) of the switching element by the data write scan for performing memory display immediately before the voltage application is stopped in the normal display. Is longer than the non-selection period (gate off time) of the switching element by the data write scan. By performing a memory display, by lengthening the non-selection period (gate off time) of a switching element, and lengthening time which a liquid crystal material can respond to an electric field, a liquid crystal responds sufficiently in a non-selection period, and high memory property is achieved. In particular, when the responsiveness of the liquid crystal deteriorates in a low temperature environment, sufficient memory performance cannot be exhibited in the non-selection period of the switching element during normal display. However, the memory performance is sufficient even at low temperatures by increasing the voltage application time by extending the non-selection period. Can exert.

In the first invention, the liquid crystal display according to the second invention is configured to display all pixels as black before resuming application of the voltage to the liquid crystal material in order to return the second display function to the first display function. It is characterized by.

In the fourth invention, the liquid crystal display according to the fifth aspect of the present invention is configured to display all the pixels in black before resuming application of the voltage to the liquid crystal material in order to return the second display function to the first display function. It is characterized by.

In the liquid crystal display device of the second invention or the fifth invention, when the voltage application to the liquid crystal material is resumed, the display of all the pixels is first made black, and then the voltage corresponding to the display data is applied to the liquid crystal material. Therefore, a black base display is always obtained after application restarts, and a clear display can be obtained. If the display of all pixels is not made black at the time of restarting voltage application, a defect occurs. For example, in a state where no voltage is applied, if the held display is a display other than black, in particular, a white display, a white base display is obtained at the start of voltage application, and a desired display cannot be obtained.

In the liquid crystal display device according to the third aspect of the invention, in the second aspect of the invention, the selection period of the switching element when the display of all the pixels is made black is longer than the selection period of the switching element in the first display function. It is done.

In the liquid crystal display device according to the sixth invention, in the fifth invention, the non-selection period of the switching element when the display of all the pixels is all black display is longer than the non-selection period of the switching element in the normal display function. It features.

In the liquid crystal display device of the third invention or the sixth invention, when the display of all the pixels is all black display at the time of restarting voltage application, the selection period of the switching element (voltage application time to the liquid crystal material) by black data write scanning or The non-selection period (gate off time) of the switching element by black data write scanning is selected for the switching element (voltage application time to liquid crystal quality) at the time of normal display or the non-selection period (gate off) at the time of normal display. Time). Therefore, the entire pixel is surely displayed in black.

In the liquid crystal display device according to the seventh invention, a liquid crystal material is enclosed in a gap formed by at least two substrates, and voltage selection is selected / non-selected to control light transmittance by the liquid crystal material corresponding to each pixel. A switching element for controlling is provided, and has a first display function of performing image display by applying a voltage to the liquid crystal material through the switching element, and applying voltage to the liquid crystal material through the switching element while stopping the voltage application. A liquid crystal display device having a second display function for holding a display state just before stopping the display, wherein the selection period of the switching element immediately before the application of the voltage is paused to execute the second display function is the first display function. In order to execute the first display method and the second display function longer than the selection period of the switching element in Characterized in that one to the selection period of the switching element immediately prior to the tissue paper applied to the switch the second driving method equivalent to the selection period of the switching element in the first display function to perform an image display.

In the liquid crystal display device of the seventh invention, the selection period of the switching element (voltage application time to the liquid crystal material) by the data write scan for performing memory display immediately before the voltage application is stopped is the selection period of the switching element in the normal display. The first driving method longer than the (voltage application time to the liquid crystal material) and the selection period (voltage application time to the liquid crystal material) of the switching element by data write scan for performing memory display immediately before the voltage application is stopped Usually, the second driving method that is equivalent to the selection period (voltage application time to the liquid crystal material) of the switching element in the display is switched.

In the liquid crystal display according to the eighth invention, a liquid crystal material is enclosed in a gap formed by at least two substrates, and voltage selection is selected / non-selected to control light transmittance by the liquid crystal material corresponding to each pixel. A switching element for controlling is provided, the first display function of performing image display by applying a voltage to the liquid crystal material through the switching element, and applying voltage to the liquid crystal material through the switching element while stopping the voltage application. A liquid crystal display device having a second display function for holding a display state just before stopping the display, wherein the non-selection period of the switching element immediately before the application of the voltage is paused to execute the second display function is performed in the first display. To execute the first driving method longer than the non-selection period of the switching element in the function, and the second display function. The non-selection period of the switching element immediately before the voltage application is stopped is switched so that the image display is performed by switching the second driving method that is equivalent to the non-selection period of the switching element in the first display function.

In the liquid crystal display device of the eighth aspect of the invention, the non-selection period (gate off time) of the switching element by data write scanning for performing memory display immediately before the application of the voltage is stopped is performed. The non-selection period (gate off time) of the switching element due to the first driving method longer than the off time) and the data write scan for performing the memory display immediately before the voltage application is stopped, the non-selection of the switching element in the normal display. The second driving method equivalent to the period (gate off time) is switched.

In the liquid crystal display device of the seventh invention or the eighth invention, when high memory performance cannot be exhibited in the selection period or the non-selection period of the switching element equivalent to that of normal display, the first driving method is switched to realize high memory performance. When high memory performance can be exhibited even during the selection period or the non-selection period of the switching element equivalent to that of normal display, the second drive system is switched to realize the reduction of power consumption.

In the seventh or eighth invention, the liquid crystal display according to the ninth invention includes measuring means for measuring the temperature of the liquid crystal material and switching between the first driving method and the second driving method according to the measurement result of the measuring means. It is characterized by including a means for controlling.

In the liquid crystal display device of the ninth invention, switching between the first driving method and the second driving method is controlled in accordance with the temperature of the liquid crystal material. Therefore, in the case of a low temperature environment, switching to the first driving method is realized reliably in high memory. In addition, in a high temperature environment where there is no need to switch to the first driving method, the second driving method is executed to reduce power consumption.

INDUSTRIAL APPLICABILITY The present invention is also applicable to a liquid crystal display device of a color filter system using a color filter, as well as a liquid crystal display device of a field sequential method of switching a plurality of colors of light over time. In the former field-sequential liquid crystal display device, color display with high precision, high color purity, and high speed response is possible, and in the latter color filter system liquid crystal display device, color display can be easily performed.

In addition, the present invention can be applied to any of a transmissive liquid crystal display device, a reflective liquid crystal display device, or a transflective liquid crystal display device. In the case of the transmissive type, the memory display can reduce the power consumption, but the semi-transmissive or reflective type can further reduce the power consumption.

In the liquid crystal display device of the present invention, it is preferable to use a monostable or bistable ferroelectric liquid crystal, in particular a bistable ferroelectric liquid crystal. By using such liquid crystal, stable memory display becomes possible.

In the liquid crystal display device of the present invention, it is preferable to have a mechanism for stopping the application of voltage to the liquid crystal material at a desired timing. By having such a mechanism, the stable memory display becomes possible also in the liquid crystal display device which displays by line scanning. In particular, in the case of a liquid crystal display device using ferroelectric liquid crystal using a switching element, a half V-shaped electro-optic response characteristic (a high transmittance when a voltage of one polarity is applied and a voltage of the other polarity) When is applied, the liquid crystal has a characteristic of exhibiting a low transmittance of a degree that can be regarded as black display. For this reason, in each subframe (in the case of the field sequential method) or in each frame (in the case of the color filter method), data writing scan is performed two or more times by the voltage of one polarity and the voltage of the other polarity. In the case of the field sequential method, it is preferable to make the polarity of the voltage in each write scan equal to all the pixels. In the case of the color filter system, it is not necessary to write scan all the pixels at the voltage of the same polarity, but when performing memory display, it is preferable to perform the write scan at the voltage of the same polarity. Then, the memory scanning is stabilized by stopping the voltage application to the liquid crystal material at a desired timing before the write scanning by the voltage of the polarity capable of realizing high transmittance is finished and the write scanning by the next voltage of the other polarity starts. To realize.

In the liquid crystal display device of the present invention, it is preferable to vary the intensity of the light source for display depending on the display form. That is, at the time of memory display, the output intensity of light sources, such as a backlight, is made low compared with the case of normal display. In the case of using a liquid crystal material having a half V-shaped electro-optical response characteristic, a transmittance of about twice as high as that in the normal display can be obtained in the memory display. Therefore, at the time of memory display, even if the output intensity of a light source is reduced, the brightness equivalent to normal display can be implement | achieved and power consumption can be reduced. Thus, by making the output intensity of a light source changeable according to a display form, fine adjustment of display brightness is attained and it becomes possible to suppress unnecessary power consumption by a light source.

In the liquid crystal display device of the present invention, the voltage corresponding to the image to be displayed after the voltage pause is applied to the liquid crystal material immediately before the voltage is applied to the liquid crystal material. Therefore, it is possible to reliably write memory display data different from the normal display data, and the desired memory display can be realized.

1 is a graph showing an example of transmittances when voltage is applied and when voltage is not applied.

2 is a graph showing a pulse voltage application example and a temporal change in transmittance thereof.

Fig. 3 is a diagram for explaining the similar TFT driving of the liquid crystal panel for evaluation.

4 is a graph showing the relationship between memory rate and temperature.

5 is a graph showing a relationship between a memory rate and a gate selection period.

6 is a graph showing a relationship between a memory rate and a gate non-selection period.

7 is a schematic cross-sectional view of a liquid crystal panel and a backlight of the liquid crystal display device according to the first and third embodiments.

8 is a schematic diagram showing an example of the entire configuration of a liquid crystal display device according to the first and third embodiments.

9 is a graph showing the electro-optical response characteristics of ferroelectric liquid crystals.

Fig. 10 is a diagram showing a driving sequence of the liquid crystal display device according to the first and third embodiments.

Fig. 11 is a diagram showing a driving sequence of the liquid crystal display device according to the first and second embodiments.

12 is a view for explaining a change in transmittance of a black base.

13 is a view for explaining a change in transmittance of a white base.

14 is a schematic sectional view of a liquid crystal panel and a backlight of the liquid crystal display device according to the second and fourth embodiments.

Fig. 15 is a schematic diagram showing an overall configuration example of a liquid crystal display device according to the second and fourth embodiments.

Fig. 16 is a diagram showing a driving sequence of the liquid crystal display device according to the second and fourth embodiments.

Fig. 17 shows driving sequences of the liquid crystal display device according to the third and fourth embodiments.

18 is a schematic diagram showing an example of the entire configuration of a liquid crystal display device according to the fifth and sixth embodiments.

Fig. 19 is a diagram showing a drive sequence which can be switched to the liquid crystal display device according to the fifth and sixth embodiments.

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

First, the optimum value of the length of the gate on time (selection period of the switching element) or the gate off time (non-selection period of the switching element) immediately before memory display, which is a feature of the present invention, will be described.

After washing two glass substrates having a transparent electrode having a diameter of 15 mm, a polyimide film of about 200 kPa was formed on each transparent electrode by applying polyimide and firing at 200 ° C for 1 hour. The surface of this polyimide film was rubbed with a rayon cloth, and two glass substrates were overlapped so that rubbing directions could be parallel to each other, and the blank panel which produced the gap with the spacer made from silica with an average particle diameter of 1.6 micrometers was produced. . A ferroelectric liquid crystal material (e.g., a material disclosed in A. Mochizuki, et.al .: Ferroelectrics, 133, 353 (1991)) containing a naphthalene-based liquid crystal as a main component was enclosed in this blank panel to prepare a liquid crystal panel for evaluation. . The size of the spontaneous polarization of the enclosed ferroelectric liquid crystal material was 6 nC / cm 2.

And the memory ratio of the produced liquid crystal panel was evaluated by the evaluation apparatus as shown in FIG. Specifically, pseudo TFT driving is applied to the produced liquid crystal panel (consisting of one liquid crystal cell) by applying a voltage from the outside by FET switching, and the light transmitted by the photoliquid crystal panel from the backlight is transferred to the photomultiplier tube. The memory ratio of the liquid crystal panel was evaluated by detecting at. The memory rate was defined as the ratio of the transmittance at the time of voltage application (transmittance in the gate-off period) and the transmittance 60 seconds after the voltage was removed.

FIG. 4 shows the relationship between the memory rate and the temperature when the gate selection period (gate on) is set to 5 mA / line, the gate non-selection period (gate off) is set to 2.8 mA, and the applied voltage is + 5V. The reason why the gate selection period is 5 ms / line is that a short gate selection period of 5 to 10 ms / line or less is appropriate to realize stable halftone display in TFT driving of ferroelectric liquid crystals, and the gate selection period is 5 to 10 ms. This is because fast screen rewriting and stable halftone display can be realized by setting in a short time of less than / line. That is, because the gate selection period in the normal display of the liquid crystal display device using the ferroelectric liquid crystal of TFT drive is 5-10 kV / line or less.

The reason why the gate non-selection period (gate off) is set to 2.8 ms is that the sub frame time of each of the R and GB colors in the field sequential method is 1/180 s or less, and two data write scans are performed in a 1/180 s time. This is because the gate-off period of each line in each write scan is 1 / 360s, that is, 2.8 ms. That is, the gate non-selection period in the normal display of the liquid crystal display device using the ferroelectric liquid crystal of TFT driving in the field sequential method is 2.8 ms or less. In the color filter system, the gate non-selection period in the normal display is 8.3 ms or less.

The results of Fig. 4 show that the memory ratio of 50% to 80% is high in the temperature range of 20 ° C to 40 ° C. However, when the temperature falls below l5 ° C, the memory rate drops rapidly and memory display cannot be performed. have.

Next, in various temperature environments, the change in the memory rate was measured while changing the gate selection period (gate on). The measurement result is shown in FIG. 5 shows that by increasing the gate selection period, a high memory rate can be realized and a high memory rate can be achieved even at a low temperature of -20 ° C. This is because by increasing the gate selection period, the responsiveness of the liquid crystal becomes higher in the gate selection period, and the responsiveness deterioration of the liquid crystal due to the low temperature can be compensated.

From the above, it can be seen that by making the gate selection period longer than 5 to 10 kHz / line in normal display, a high memory rate can be realized in a wide temperature range, and stable memory display is enabled. When performing the memory display, the gate selection period can always be longer than 5 to 10 ms / line at the time of normal display irrespective of the temperature. From Figs. It is understood that the gate selection period can be made longer than 5 to 10 ms / line at the time of normal display only when the temperature is set to 20 degrees C or less.

In addition, in various temperature environments, the change in the memory rate was measured while changing the gate non-selection period (gate off). The measurement result is shown in FIG. 6 shows that by increasing the gate non-selection period, a high memory rate can be realized, and a high memory rate can be realized even at a low temperature of -20 ° C. This is because by increasing the gate non-selection period, the responsiveness of the liquid crystal in the gate non-selection period is increased, and the response degradation of the liquid crystal due to the low temperature can be compensated.

From the above, it can be seen that by making the gate non-selection period longer than 2.8 s in normal display, a high memory rate can be realized in a wide temperature range, and stable memory display is enabled. When performing memory display, the gate non-selection period can always be longer than 2.8 kPa in normal display, regardless of the temperature. From Figs. It is understood that the gate non-selection period can be made longer than 2.8 s in normal display only at 20 ° C or lower.

First, when performing the memory display, examples in which the high memory ratio can be reliably realized by making the gate selection period (voltage application period to the liquid crystal) longer than normal display will be described as the first and second embodiments.

(First embodiment)

FIG. 7 is a schematic cross-sectional view of the liquid crystal panel 1 and the backlight 30 of the liquid crystal display device according to the first embodiment, and FIG. 8 is a schematic diagram showing an example of the overall configuration of the liquid crystal display device. The first embodiment is a liquid crystal display device which performs color display in the color filter method.

As shown in FIG. 7 and FIG. 8, the liquid crystal panel 1 has a polarizing film 2, a common electrode 3 and a color filter arranged in a matrix form from an upper layer (surface) side to a lower layer (back side) side ( The glass substrate 5 which has 4), the glass substrate 7 which has the pixel electrode 6 arranged in matrix form, and the polarizing film 8 are laminated | stacked in this order, and are comprised.

A driver 20 having a data driver, a scan driver (not shown), or the like is connected between the common electrode 3 and the pixel electrode 6. The data driver is connected to the TFT 21 via the signal line 22, and the scan driver is connected to the TFT 21 via the scan line 23. The TFT 21 is controlled on / off by the scan driver. In addition, the individual pixel electrodes 6 are controlled on / off by the TFT 21. Therefore, the intensity of each pixel transmitted light is controlled by the signals from the data driver given through the signal line 22 and the TFT 21.

The alignment film 9 is disposed on the top surface of the pixel electrode 6 on the glass substrate 7, and the alignment film 10 is disposed on the bottom surface of the common electrode 3, respectively. The liquid crystal, which is a ferroelectric liquid crystal, between the alignment films 9 and 10. The material is filled to form the liquid crystal layer 11. Note that (l2) is a spacer for maintaining the layer thickness of the liquid crystal layer l1.

The backlight 30 is positioned on the lower layer (back) side of the liquid crystal panel 1 and emits white light in a state in which the light guide and the light diffusion plate 31 constituting the light emitting area are directed toward the end surface. An LED array 32 is provided. The LED array 32 has a wide adjustment range of brightness and easy adjustment of brightness. The light guide and the light diffusion plate 3l function as light emitting regions by guiding the white light emitted from each LED of the LED array 32 to the entire surface thereof and simultaneously diffusing it onto the upper surface. In addition, the lighting / non-lighting and luminance of this backlight 30 (LED array 32) are adjusted by the backlight control circuit 33.

Here, the specific example of the liquid crystal display device in 1st Example is demonstrated. After cleaning the TFT substrate having the pixel electrode 6 (640 × 3 (RGB) × 480, 3.2 inches diagonal) and the common electrode substrate having the common electrode 3 and the color filter 4 of RGB, the polyimide Was applied and baked at 200 ° C. for l hour to form a film of about 200 kV of polyimide as the alignment films 9 and 10.

Further, these alignment films 9 and 10 were rubbed with a cloth made of rayon, and a blank panel was produced by superimposing them in a state where a gap was maintained in the spacer 12 made of silica having an average particle diameter of 0.6 mu m. In this blank panel, a ferroelectric liquid crystal material (e.g., A. Mochizuki, et.al.) mainly containing a naphthalene-based liquid crystal exhibiting half-V-shaped electro-optic response characteristics as shown in Fig. 9 during TFT driving. Ferroe Ectrics, l 33,353 (a material disclosed in 1999)) was encapsulated to form a liquid crystal layer 11. The size of the spontaneous polarization of the enclosed ferroelectric liquid crystal material was 6 nC / cm 2.

In the polarizing films 2 and 8 of the produced panel in the cross-Nicol state, a dark state occurs when the longitudinal direction of the ferroelectric liquid crystal molecules of the liquid crystal layer ll is inclined to one side. The liquid crystal panel 1 was sandwiched in between. The liquid crystal panel 1 and the backlight 30 were superimposed so that color display could be performed by the color filter method.

Next, a specific operation example of the first embodiment will be described. 10 and 11 are timing charts showing an example of a drive sequence in the operation example. FIG. 10A shows the scanning timing of each line of the liquid crystal panel 1, and FIG. 10B shows the lighting timing of the backlight 30. FIG. As shown in Fig. 10A, the liquid crystal panel 1 is write-scanned twice of image data in each frame. In the first data write scan, a data write scan is performed at a polarity capable of realizing bright display, and in the second data write scan, a voltage substantially equal in magnitude to opposite polarity to that of the first data write scan is applied. . As a result, dark display can be realized as compared with the first data write scan, and can be regarded as " black display ".

11A is a magnitude of signal voltage applied to the ferroelectric liquid crystal in order to obtain a desired display, FIG. 11B is a gate voltage of the TFT 2l, and FIG. 11C shows a transmittance. It is shown. 11 shows a drive sequence in a selected line. Normal display function (period A) for applying a voltage to the ferroelectric liquid crystal at a predetermined period for rewriting the display image, and a memory display function for stopping the application of voltage to the ferroelectric liquid crystal and holding the display image before the pause (period B )) Can be performed.

After the voltage corresponding to the desired image is applied to the ferroelectric liquid crystal for each line at the timing of the gate-on voltage, the voltage is applied to the liquid crystal panel 1 immediately before the application of the voltage of the last line is finished and the first line is selected. Turn off all voltages (timing C). However, in the write scan immediately before all the voltages are turned off, the voltage (signal voltage D) corresponding to the desired image data to be retained and displayed when no voltage is applied is applied.

In the period in which no voltage is applied (period B), the transmittance is maintained based on the memory function of the ferroelectric liquid crystal, and the display image is maintained in accordance with the voltage (signal voltage D) applied immediately before. After that, in order to display another image, application of voltage to the ferroelectric liquid crystal is resumed (timing E). At this time, after the display of the liquid crystal panel 1 is made all black display, a voltage corresponding to the desired display data is applied. In other words, when the application of voltage to the ferroelectric liquid crystal is resumed, a voltage (signal voltage F) corresponding to black display is first applied.

In the first embodiment, the gate selection period t _l in the data write scan to the normal display is 5 ms / line, and the gate selection period t in the data write scan in the data immediately before the memory display is performed. ₂ ) is set to l00 kHz / line for the purpose of realizing a good memory display up to -10 占 폚 based on the above-described characteristic result (see FIG. 5). At this time, the application time of the signal voltage is also changed in accordance with the gate selection period.

According to the driving sequence shown in FIG. 11, voltage was applied to each line through switching of the TFTs 21, and all voltages applied to the liquid crystal panel 1 were turned off at a desired timing after the end of voltage application of the last line. . And the transmittance | permeability at the time of voltage application and the transmittance | permeability after voltage removal 60 seconds after measuring the voltage applied to the liquid crystal panel 1 were measured. This measurement result showed the same characteristic as FIG. 1, FIG. Accordingly, it can be seen from the drive sequence of FIG. 11 that the transmittance according to the display state at the time of voltage application can be maintained by removing all voltages applied to the liquid crystal panel 1. As a result, it can be seen that the image display can be performed without applying voltage, that is, the memory display function can be reliably performed.

In addition, when the voltage application to the liquid crystal panel 1 is started again, the display of the liquid crystal panel 1 is all black display, and then the voltage corresponding to the display data is applied to the liquid crystal panel 1. As a result, high quality color display including moving picture display can be performed again. Even when the display of the liquid crystal panel 1 is all black display, the gate selection period t ₃ is 100 microseconds / line, and the voltage application time to the liquid crystal is longer than normal display, so that a reliable black display can be realized. Make sure

12 is a view for explaining the change in transmittance of the black base, and the liquid crystal molecules 40 are positioned along the polarization axis as shown in FIG. Therefore, the direction is changed between the position and the position away from the polarization axis (the position of the white display indicated by the broken line). An example of the change in transmittance at this time is shown in FIG. FIG. 13 is a view for explaining the change in transmittance of the white base, and the liquid crystal molecules 40 are positioned away from the polarization axis as shown in FIG. 13 (a) for the first time (the position of the white display indicated by the solid line), and the voltage According to the application, the direction is changed between the position and the position along the polarization axis (the position of the black display indicated by the broken line).

When the application of voltage is resumed, after all of the display of the liquid crystal panel 1 is made black, when the voltage according to the desired display data is applied, the display is necessarily black based, as shown in FIG. 12, to obtain a clear display. Can be. In contrast, when the voltage application is resumed, a defect occurs when the display of the liquid crystal panel 1 is not entirely black. For example, if the display held in the voltage-free state is a display other than black, in particular, a white display, when the voltage is started, a white base display is shown as shown in Fig. 13, and a desired display cannot be obtained.

Next, the brightness adjustment of the backlight 30 will be considered. In the normal application of the display voltage (period A in FIG. 11), positive and negative voltages are alternately applied to the liquid crystal. In the case of a ferroelectric liquid crystal having an electro-optic response characteristic having a half V shape, light is transmitted only when a voltage of one polarity is applied. Therefore, when the ratio applied at the positive voltage and the negative voltage is l: 1, the average brightness is light. It is about half at the time of transmission. On the other hand, the brightness is always constant when no voltage is applied. Therefore, the time when no voltage is applied may be brighter than when voltage is applied.

In order to solve such a problem, in the first embodiment, the brightness of the backlight 30 when no voltage is applied is reduced to about 70% in normal display in synchronization with the removal of the applied voltage, and the brightness is adjusted. This does not reduce the screen brightness. Since the brightness reduction of this backlight 30 is related to the reduction of power consumption, it is significant. In addition, the luminance of the backlight 30 when no voltage is applied may be arbitrary, and in order to further reduce power consumption when no voltage is applied, the luminance of the backlight 30 may be reduced to about 70% or less. Of course. After resuming the voltage application, the brightness of the backlight 30 is returned to its original state.

By the above, the same image display can be realized at the time of voltage application and at the time of no voltage application. The specific power consumption at the time of voltage application was 2.5W. In addition, the specific power consumption when no voltage was applied was 1.3 W, which was a low power consumption.

(Second embodiment)

FIG. 14 is a schematic sectional view of the liquid crystal panel 1 and the backlight 30 of the liquid crystal display device according to the second embodiment, and FIG. 15 is a schematic view showing an example of the entire configuration of the liquid crystal display device. The second embodiment is a liquid crystal display device which performs color display in the field sequential method. In FIG. 14, FIG. 15, the same code | symbol is attached | subjected to the part same or similar to FIG.

There is no color filter in this liquid crystal panel 1 as can be seen in the first embodiment (Figs. 7 and 8). In addition, the backlight 30 is located on the lower layer (back side) side of the liquid crystal panel 1, and the LED array 42 is provided in a state of facing the cross section of the light guide and the light diffusion plate 31 constituting the light emitting region. The LED array 42 has 10 light LEDs each having three primary colors, i.e., red, green, and blue LED elements, each of which has one chip on the surface facing the light guide and the light diffusion plate 3l. . In each of the subframes of red, green, and blue, the LED elements of red, green, and blue are turned on. The light guide and the light diffusion plate 31 function as light emitting regions by guiding the light from each LED of the LED array 42 to the entire surface thereof and simultaneously diffusing it to the upper surface.

The liquid crystal panel 1 overlaps the backlight 30 capable of time-division light emission of red, green, and blue. The emission color, lighting timing and luminance of the backlight 30 are controlled by the backlight control circuit 35 in synchronization with data write scanning based on the display data for the liquid crystal panel 1.

A specific example of the liquid crystal display device in the second embodiment will be described. After cleaning the TFT substrate having the pixel electrode 6 (640 × 480, 3.2 inches diagonal) and the common electrode substrate having the common electrode 3, polyimide was applied and baked at 200 ° C. for 1 hour, thereby reducing The polyimide film was formed into a film as alignment films 9 and 10. Furthermore, these alignment films 9 and 10 were rubbed with a cloth made of rayon, and a blank panel was produced by superimposing the gaps in the spacer 12 made of silica with an average particle diameter of 1.6 μm between them. In this blank panel, a ferroelectric liquid crystal material mainly containing a naphthalene-based liquid crystal exhibiting half-V-shaped electro-optic response characteristics as shown in Fig. 9 during TFT driving (for example, A. Mochizuki, et.al .: Ferroelectrics, 133, 353 (the material disclosed in l991)) was sealed to obtain a liquid crystal layer 1l. The size of the spontaneous polarization of the enclosed ferroelectric liquid crystal material was 6 nC / cm 2.

The produced panel is sandwiched between two polarizing films 2 and 8 in a cross nicol state so as to be in a dark state when the longitudinal direction of the ferroelectric liquid crystal molecules of the liquid crystal layer 11 is inclined to one side, and sandwiched therebetween. (1). This liquid crystal panel 1 and the backlight 30 were overlapped, and color display was performed by the field sequential system.

Next, a specific operation example of the second embodiment will be described. 16 and 10 are timing charts showing an example of a drive sequence in the operation example.

FIG. 16A shows the scanning timing of each line of the liquid crystal panel 1, and FIG. 16B shows the lighting timing of the red, green, and blue colors of the backlight 30. FIG. One frame is divided into three subframes, for example, as shown in FIG. 16B, red is emitted in the first subframe, green is emitted in the second subframe, and blue is emitted in the third subframe. Emit light. On the other hand, as shown in Fig. 16A, the liquid crystal panel 1 is subjected to two write scans of image data in subframes of each color of red, green, and blue. In the first data write scan, a data write scan is performed at a polarity for realizing bright display. In the second data write scan, a voltage substantially equal in magnitude to the opposite of the first data write scan is applied. As a result, dark display can be realized as compared with the first data write scan, and can be regarded as " black display ".

In addition, since the drive sequence shown in FIG. 10 is the same as that of 1st Embodiment, the detailed description is abbreviate | omitted.

As in the first embodiment, a voltage is applied to the liquid crystal for each line through switching of the TFTs 21, and all voltages applied to the liquid crystal panel 1 are turned off at a desired timing after the end of voltage application of the last line. do. However, the data write scan immediately before all the voltages are turned off is a write scan of desired monochrome display data to be displayed when no voltage is applied.

As in the first embodiment, the gate selection period t ₁ in the data write scan in the normal display is 5 ms / line, and the gate selection period t ₂ in the data write scan immediately before the memory display is performed. Shall be 10O㎲ / line. In addition, when voltage application to the liquid crystal panel 1 is started again, the display of the liquid crystal panel 1 is all black display, and then the voltage corresponding to the display data is applied to the liquid crystal panel 1. Even when the display of the liquid crystal panel 1 with all black display, as the gate selection period (t ₃₎ 1OO㎲ / line, and the voltage application time of the liquid crystal display to be longer than normal. In addition, during the memory display, the brightness of the backlight 30 is reduced as compared with the normal display.

In this way, a high quality display including a moving picture display can be obtained at the time of voltage application, and when the voltage is removed, the backlight 30 is switched to white light, and the luminance is further adjusted to a desired value, whereby monochrome display at low power consumption is achieved. After the voltage application is resumed, a high quality display including a moving picture display can be obtained again. The specific power consumption at the time of moving picture color display to which a voltage was applied was 1.5W. Moreover, the specific power consumption at the time of monochrome display which does not apply a voltage was 0.53W, and was low power consumption.

Next, examples in which the high memory ratio can be reliably realized by making the gate non-selection period (gate off period) longer than normal display when performing memory display will be described as the third and fourth embodiments.

(Third embodiment)

The third embodiment is a liquid crystal display device which performs color display in the color filter method, and since its configuration and manufacturing process are the same as those of the above-described first embodiment (Figs. 7 and 8), the description thereof is omitted.

Next, a specific operation example of the third embodiment will be described. 10 and 17 are timing charts showing an example of a drive sequence in the operation example. The driving sequence in FIG. 10 is the same as that of the first embodiment.

FIG. 17A shows the magnitude of the signal voltage applied to the ferroelectric liquid crystal in order to obtain a desired display, FIG. 17B shows the gate voltage of the TFT 2l, and FIG. 17C shows the transmittance. . 17 shows a drive sequence in a selected line. Normal display function (period A) for applying a voltage to a ferroelectric liquid crystal at a predetermined period for rewriting the display image, and a memory display function for removing the application of voltage to the ferroelectric liquid crystal to hold the display image before removal (period (B) )) Can be performed in the same manner as the drive sequence shown in FIG.

In the third embodiment, the gate selection period in the data write scan in the normal display is 5 ms / line, and the gate non-selection (off) period T ₁ is 8 占 3 ms. The gate non-selection (off) period T ₂ in the data write scan is set to 100 microseconds or more for the purpose of realizing a good memory display up to -10 DEG C based on the above-described characteristic result (see FIG. 6). That is, after 100 mA of the final line voltage is applied, all the voltages applied to the liquid crystal panel 1 are turned off.

According to the driving sequence shown in FIG. 17, voltage was applied to each line through switching of the TFTs 2l, and all voltages applied to the liquid crystal panel 1 were turned off at a desired timing after the end of voltage application of the last line. . And the transmittance | permeability at the time of voltage application and the transmittance | permeability after voltage removal 60 seconds after measuring the voltage applied to the liquid crystal panel 1 were measured. This measurement result showed the same characteristic as FIG. 1, FIG. Therefore, it can be seen from the driving sequence of FIG. 17 that the transmittance according to the display state at the time of voltage application can be maintained by removing all the voltages applied to the liquid crystal panel 1. As a result, it can be seen that image display is possible without performing voltage application, that is, the memory display function can be reliably performed.

Moreover, when starting application of the voltage to the liquid crystal panel 1 again, after making the display of the liquid crystal panel 1 all black display, the voltage according to display data is applied to the liquid crystal panel 1. As a result, high quality color display including moving picture display can be performed again. Even when the display of the liquid crystal panel 1 is entirely black, the gate non-selection (off) period T ₃ is set to l000 ms, longer than the gate non-selection (off) period T _l at the time of normal display, It is possible to realize a certain black display. The reason for doing so is as described in the first embodiment.

Considering the adjustment of the brightness of the backlight 30, also in the third embodiment, similarly to the first embodiment, the case where no voltage is applied may be brighter than when voltage is applied. Thus, in the same manner as in the first embodiment, the brightness of the backlight 30 when no voltage is applied is reduced to about 70% in normal display in synchronization with the removal of the applied voltage, and the brightness is adjusted.

By the above, the same image display can be realized at the time of voltage application and at the time of no voltage application. The specific power consumption at the time of voltage application was 2.4W. In addition, the specific power consumption when no voltage was applied was 1.4 W, which was low power consumption.

(Example 4)

The fourth embodiment is a liquid crystal display device which performs color display in the field sequential method, and since its configuration and manufacturing process are the same as those of the above-described second embodiment (Figs. 14 and 15), the description thereof is omitted.

Next, a specific operation example of the fourth embodiment will be described. 16 and 17 are timing charts showing an example of a drive sequence in the operation example. The drive sequence in FIG. 16 is the same as in the second embodiment, and the drive sequence in FIG. 17 is the same as in the third embodiment. As in the third embodiment, a voltage is applied to the liquid crystal for each line through switching of the TFTs 21, and all voltages applied to the liquid crystal panel 1 are turned off at a desired timing after the end of voltage application of the last line. do. However, the data write scan immediately before turning off all voltages is a desired monochrome display data write scan to be displayed when voltage is not applied.

As in the third embodiment, the gate non-selection period T ₁ in the data write scan in the normal display is 2.8 ms, and the gate non-selection period T ₂ in the data write scan immediately before the memory display is performed. ) Should be over 100,000㎳. Moreover, when starting application of the voltage to the liquid crystal panel 1 again, after making the display of the liquid crystal panel 1 all black display, the voltage according to display data is applied to the liquid crystal panel 1. All black display to the black display of the liquid crystal display panel (1) also, as the gate non-selection period (T ₃₎ 1000㎳ be longer than normal display. In addition, while performing memory display, the brightness of the backlight 30 is reduced as compared with normal display.

In this way, a high quality display including moving picture display can be obtained at the time of voltage application, and when the voltage is removed, the backlight 30 is switched to white light, and the luminance is further adjusted to a desired value, whereby monochrome display at low power consumption is achieved. After the voltage application is resumed, a high quality display including a moving picture display can be obtained again. The specific power consumption at the time of moving picture color display to which a voltage was applied was 1.3W. In addition, the specific power consumption at the time of monochrome display without applying a voltage was 0.51W, which was low power consumption.

(Example 5)

18 is a schematic diagram showing an example of the entire configuration of a liquid crystal display device according to a fifth embodiment. In FIG. 18, the same parts as in FIG. 15 are assigned the same numbers, and their description is omitted.

In FIG. 18, reference numeral 51 denotes a thermometer for measuring the temperature of the liquid crystal panel 1, and the thermometer 51 outputs the measured temperature value to the driver 20. The driving unit 20 has a first driving method and a second driving method, and either driving method of the first driving method and the second driving method is selected according to the temperature measured by the thermometer 51. Specifically, when the temperature is 20 degrees C or less, it can switch to a 1st drive system, and when temperature is higher than 20 degreeC, it can switch to a 2nd drive system.

As shown in Fig. 11, in the first driving scheme, the gate selection period (voltage application time to the liquid crystal material: t ₂ ) immediately before the voltage application is stopped to execute the memory display function is the gate selection period in normal display. It is longer than (the voltage applied to the liquid crystal material, the time _{t l) (t 2> t} l) is driven. As shown in Fig. 19, in the second driving scheme, the gate selection period in which the gate selection period (voltage application time to the liquid crystal material: t ₂ ) immediately before the voltage application is stopped to execute the memory display function is normal display. (T ₂ = t ₁ ) is equivalent to (t voltage application time to the liquid crystal material: t ₁ ).

In the fifth embodiment, when the temperature is 20 ° C. or less, since high memory performance cannot be exhibited in the gate selection period (voltage application time to the liquid crystal material) equivalent to that of normal display, switching to the first driving method results in high memory performance. We aim at realization. On the other hand, when the temperature is higher than 20 ° C., high memory performance can be exhibited even during the gate selection period (voltage application time to the liquid crystal material) equivalent to that of normal display, so that switching to the second driving method is carried out to reduce the power consumption. Promote.

(Example 6)

The entire structural example of the liquid crystal display device according to the sixth embodiment is the same as that of the fifth embodiment (Fig. 18). The thermometer 51 outputs the measured temperature value to the drive unit 20. The driving unit 20 has a first driving method and a second driving method.

As shown in Fig. 17, since the first driving method executes the memory display function, the gate non-selection period (gate off period: T ₂ ) immediately before the voltage application is stopped is applied. Off period: Longer than T _l ) (T ₂ > T _l ). Since the second driving method executes the memory display function as shown in Fig. 19, the gate non-selection period (gate off period: T ₂ ) immediately before the voltage application is stopped is applied. off period: T _l) and equal to (T ₂ = T _l) is driven.

In the sixth embodiment, when the temperature is 20 ° C. or lower, high memory performance cannot be exhibited in the gate non-selection period (gate off period) equivalent to that of normal display, so that switching to the first driving method is achieved to achieve high memory performance. do. On the other hand, when the temperature is higher than 20 ° C, high memory performance can be exhibited even in the gate non-selection period (gate off period) equivalent to that in normal display, so that switching to the second driving method is achieved, thereby reducing power consumption.

In the fifth and sixth embodiments, the liquid crystal display device of the field sequential method has been described as an example, but the liquid crystal display device of the color filter method shown in Figs. Of course, one method can be applied equally.

In addition, although the above-mentioned example demonstrated the transmissive liquid crystal display device, it goes without saying that the present invention can be similarly applied to the reflective or semi-transmissive liquid crystal display device. In the case of the reflective or semi-transmissive liquid crystal display device, since it is possible to display without using a light source such as a backlight, the power consumption can be approached to infinity O by combining with the memory display function.

As described above, in the present invention, the memory display function can be reliably performed in a wide temperature range. In addition, by switching the driving method as necessary, it is possible to achieve both high memory performance and reduced power consumption.

Claims (9)

A liquid crystal material is enclosed in a gap formed by at least two substrates, and a switching element is provided for selecting / non-selecting voltage application to control light transmittance by the liquid crystal material corresponding to each pixel. And a first display function of performing image display by applying a voltage to the liquid crystal material through the switching element, and resting the application of voltage to the liquid crystal material through the switching element and stopping the voltage application. A liquid crystal display device having a second display function for maintaining a display state immediately before the above, wherein the selection period of the switching element immediately before the application of the voltage is stopped to execute the second display function is performed in the first display function. And longer than the selection period of the switching element. The method of claim 1, And all the displays of all pixels are made black before the application of voltage to the liquid crystal material is resumed in order to return the second display function to the first display function. The method of claim 2, And the selection period of the switching element when the display of all the pixels is all black display is longer than the selection period of the switching element in the first display function. A liquid crystal material is enclosed in a gap formed by at least two substrates, and a switching element is provided for selecting / non-selecting voltage application to control light transmittance by the liquid crystal material corresponding to each pixel; A first display function of performing image display by applying a voltage to the liquid crystal material through the switching element, and stopping the application of voltage to the liquid crystal material through the switching element and maintaining the display state just before stopping the voltage application A liquid crystal display device having a second display function, wherein the non-selection period of the switching element immediately before the application of the voltage is paused to execute the second display function is not selected of the switching element in the first display function. A liquid crystal display device characterized by being longer than the period. The method of claim 4, wherein And all display of all pixels to black display before resuming application of voltage to the liquid crystal material in order to return the second display function to the first display function. The method of claim 5, wherein The non-selection period of the switching element when the display of all the pixels is made black display is longer than the non-selection period of the switching element in the first display function. A liquid crystal material is enclosed in a gap formed by at least two substrates, and a switching element is provided for selecting / non-selecting voltage application to control light transmittance by the liquid crystal material corresponding to each pixel; A first display function of performing image display by applying a voltage to the liquid crystal material through the switching element, and stopping the application of voltage to the liquid crystal material through the switching element and maintaining the display state just before stopping the voltage application A liquid crystal display device having a second display function, wherein the selection period of the switching element immediately before the application of the voltage is stopped to execute the second display function is greater than the selection period of the switching element in the first display function. The switch immediately before the voltage application is stopped to perform the first long drive method and the second display function. A liquid crystal display device, characterized in that the selection period of the referred elements by switching the second driving method equivalent to the selection period of the switching element in the first display function to perform an image display. A liquid crystal material is enclosed in a gap formed by at least two substrates, and a switching element is provided for selecting / non-selecting voltage application to control light transmittance by the liquid crystal material corresponding to each pixel; A first display function of performing image display by applying a voltage to the liquid crystal material through the switching element, and stopping the application of voltage to the liquid crystal material through the switching element and maintaining the display state just before stopping the voltage application A liquid crystal display device having a second display function, wherein the non-selection period of the switching element immediately before the application of the voltage is paused to execute the second display function is not selected of the switching element in the first display function. The first driving method longer than the period and the phase immediately before the application of the voltage is stopped to execute the second display function. A liquid crystal display device, characterized in that the non-selection period of the switching element is switched to the second driving method equivalent to the non-selection period of the switching device in the first indication to perform an image display. The method according to claim 7 or 8, And a means for measuring the temperature of the liquid crystal material and means for controlling the switching of the first drive method and the second drive method in accordance with the measurement result of the measurement means.

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