JP2000035562A - Liquid crystal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal device capable of improving a decrease with elapse of time in a conventional driving margin. SOLUTION: Driving means 102, 103 drive a liquid crystal which maintains a display state at the time of turning off a power supply even after signals are impressed on the electrodes according to display information and the power supply is switched off, and also display information generated by a display information generating part 109 or specific display information are inputted to these driving means 102, 103. Moreover, a control part 105 inputs detection information of a detecting means 106 for detecting power-supply-off to a display information generating part 109, and controls the display information generating part 109 to generate specific display information at the time of turning off the power supply. And, this liquid crystal device is arranged so that the liquid crystal maintains the state according to this specific display information even after the power source supply is turned off, by impressing the signal in accordance with the specific display information on the electrodes at the time of turning off the power supply in this manner for driving the liquid crystal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal device having a liquid crystal element, and more particularly to a liquid crystal device which eliminates a temporal decrease in a driving margin of the liquid crystal element.

[0002]

2. Description of the Related Art Conventionally, as a liquid crystal element used in a liquid crystal device, a type of liquid crystal element which controls transmitted light by using a refractive element anisotropy of a ferroelectric liquid crystal in combination with a deflection element is known as Clark. And Lager Wall (La
gerwall) and JP-A-56-10721.
No. 6 and U.S. Pat. No. 4,367,924.

Here, the ferroelectric liquid crystal exhibits bistability, and such a liquid crystal is generally a chiral smectic C phase (SmC ^* ) or an H phase (SmH ^* ).
^* ) Is used.

In these states, the liquid crystal takes one of a first optically stable state and a second optically stable state in response to an applied electric field, and when no electric field is applied. Since it has the property of maintaining its state, that is, has bistability, and has a quick response to a change in electric field, it is expected to be widely used in fields such as high-speed and storage-type display devices.

On the other hand, as a method of driving the liquid crystal element, a matrix electrode composed of a scanning line and an information line is incorporated, a scanning signal is sequentially applied to the scanning line, and the information line electrode is synchronized with the scanning signal. Multiplexing drive for applying a signal is common.

[0006]

In a conventional liquid crystal device having such a liquid crystal element, for example, as disclosed in Japanese Patent Application Laid-Open No. 3-296713, the liquid crystal element immediately after the power is turned off or thereafter. In order to erase the image information displayed on the screen of the display panel, which is one example, a one-polarity pulse is applied to the scanning lines to erase the display contents. By erasing the display contents in this way, image burn-in on the display panel is prevented.

On the other hand, as the display panel is used, the drive margin, which is an applied voltage width which enables a favorable image display as shown in FIG. 8, is reduced. However, immediately after or after the power is turned off, the display is performed. By erasing the contents, the drive margin is prevented from decreasing over time. In the figure, th indicates a threshold voltage, and CT indicates a crosstalk voltage.

However, erasing the display contents alone is not enough to eliminate the decrease over time. For example, the driving margin after leaving the display panel for 10 hours while erasing the display contents is shown in FIG. As shown in the figure, it has been clarified by a study by the inventor that although the drive margin at the time of erasing can be prevented, the drive margin cannot be recovered.

The present invention has been made to solve such a conventional problem, and an object of the present invention is to provide a liquid crystal device which can improve a conventional drive margin with time. Things.

[0010]

SUMMARY OF THE INVENTION The present invention is a liquid crystal device comprising a liquid crystal for maintaining a display state when the power is turned off even after the power is turned off, and a liquid crystal element having electrodes for driving the liquid crystal. During power-off or sleep, a signal corresponding to specific display information is applied to the electrode to drive the liquid crystal, and the liquid crystal is maintained in a state corresponding to the specific display information after the power-off or during sleep. It is characterized by doing so.

According to another aspect of the present invention, there is provided a liquid crystal device including a liquid crystal for maintaining a display state when the power is turned off even after the power is turned off, and a liquid crystal element having an electrode for driving the liquid crystal. A driving unit that applies a signal to the electrode to drive the liquid crystal, a display information generating unit that selectively generates display information or specific display information input to the driving unit, and a detection unit that detects power-off. And a control unit that inputs a detection signal of the detection unit to the display information generation unit and controls the display information generation unit to generate the specific display information when power is turned off. The liquid crystal is maintained in a corresponding state even after the power is turned off.

According to another aspect of the present invention, there is provided a liquid crystal device including a liquid crystal for maintaining a display state when the power is turned off even after the power is turned off, and a liquid crystal element having an electrode for driving the liquid crystal. A driving unit that applies a signal to the electrode to drive the liquid crystal, a display information generation unit that selectively generates display information or specific display information input to the driving unit, and a detection unit that detects a sleep state. A control unit that inputs a detection signal of the detection unit to the display information generation unit and controls the display information generation unit to generate the specific display information during sleep. The liquid crystal is maintained in the sleep state during the sleep.

Further, the present invention is characterized in that the specific display information is display information for alternately displaying a light / dark state for each pixel or picture element of the liquid crystal element.

Further, according to the present invention, the electrode is a matrix electrode formed by a plurality of scanning lines and information lines, and the specific display information is one or more scanning lines or one or more scanning lines. The display information is a display information for alternately displaying the light / dark state for each information line.

Further, the present invention is characterized in that the liquid crystal is a ferroelectric liquid crystal.

Further, the present invention is characterized in that the liquid crystal is a chiral smectic liquid crystal.

Further, as in the present invention, by applying a signal corresponding to specific display information to the electrodes at the time of power-off or sleep, the display state at power-off or power-down even after power-off is maintained. The liquid crystal that maintains the display state is driven, and the liquid crystal maintains the state corresponding to the specific display information after the power is turned off or during sleep.

Further, as in the present invention, the driving means drives a liquid crystal which maintains a display state when the power is turned off even after the power is turned off, by applying a signal corresponding to the display information to the electrodes and drives the liquid crystal. The display information generated by the display information generation unit or specific display information is input to the means. Further, the control unit inputs the detection information of the detection unit that detects power-off to the display information generation unit, and controls the display information generation unit to generate specific display information when the power is turned off. Then, by applying a signal corresponding to specific display information to the electrode when the power is turned off and driving the liquid crystal, the liquid crystal maintains a state corresponding to the specific display information even after the power is turned off. I do.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a liquid crystal device according to an embodiment of the present invention. In FIG. 1, reference numeral 101 denotes a matrix electrode formed by scanning lines and information lines and a chiral smectic which is an example of a ferroelectric liquid crystal. A display panel having liquid crystal (hereinafter, referred to as liquid crystal); 102, a scanning line driving circuit which is a driving unit for driving a scanning line; 103, an information line driving circuit, which is a driving unit for driving an information line;
Is a drive voltage generation circuit for supplying voltages V1, V2 and Vc to the scanning line drive circuit 102 and supplying voltages V3, V4 and Vc to the information line drive circuit 103.

A control circuit 105 controls the scanning line driving circuit 102, the information line driving circuit 103, and the driving voltage generating circuit 104.
Includes a voltage detection circuit 106 which is a detection unit for detecting interruption of power supply from the power supply 111 due to an OFF operation of the switch 110, a logic control circuit 107, and a logic control voltage power supply 108.

Reference numeral 109 denotes a data generator which is a display information generator for generating image information which is display information to be displayed on the display panel 101. The data generator 109 inputs the image information to the logic control circuit 107. Along with
As will be described later, when the switch 110 is turned off or enters a sleep state, specific image information is input to the logic control circuit 107.

It should be noted that data from a personal computer or the like (not shown) is also input to the liquid crystal device, and image data corresponding to an external input from the personal computer or the like is also input to the data generator 109. The data is input to the logic control circuit 107.

Here, the logic control circuit 107 activates the switching element unit 33 provided in the drive voltage generation circuit 104 to output a ground potential and a switch control signal for outputting a ground potential. 2A comprising a scan selection signal shown in FIG. 2A and a non-selection scan signal shown in FIG. 2B comprising a voltage Vc for an unselected scan line. A scanning line drive control signal and a scanning side Vc control signal for controlling the switching array 21 shown in FIG. 3 to be described later are output.

Further, the logic control circuit 107
An image signal corresponding to the image information from the data generator 109, and a white information signal and a black information signal shown in FIGS. 2C and 2D composed of voltages V3, V4 and Vc are selected based on the image signal. An information line drive control signal for controlling a switching array 22 shown in FIG. 3 to be described later and an information side Vc control signal so as to be output to the information lines are output.

Reference numeral 112 denotes an external input detecting means which is a detecting means for detecting a sleep state. The external input detecting means 112 monitors an external input input from a personal computer (not shown) or the like to the data generating section 109. When an external input is not input for a predetermined period, a sleep signal indicating that no external input is input for a predetermined period, that is, a sleep state, is output to the data generation unit 109. Then, based on the sleep signal, the data generation unit 109 inputs predetermined image information to the logic control circuit 107.

FIG. 3 is a block diagram showing the scanning line driving circuit 102 and the information line driving circuit 103 in detail. Here, as shown in FIG. 2, the scanning line driving circuit 102 includes an address decoder 23 for decoding the scanning line address data of the scanning line driving control signal from the control circuit 105, and the scanning line driving circuit 102 shown in FIG. A scanning line waveform control logic circuit 24 for activating the switching array 21 so as to sequentially output the scanning selection signal and the scanning non-selection signal to the scanning line 1011 as shown in FIG.
It is composed of

Further, the information line driving circuit 103 includes a shift register / latch circuit 25 for converting image information serially input from the control circuit 105 into parallel, and a shift register / latch circuit 25 shown in FIG. An information line waveform logic circuit 26 for generating an information signal (voltage) shown in (d) and activating the switching array 22 so as to output the information signal to the information line 1012 is formed.

In the figure, reference numeral 50 denotes the display panel 1.
01 is a pixel formed at the intersection of each scanning line 1011 and each information line 1012.
One picture element is formed by one pixel.

When the switch 110 shown in FIG. 1 is turned off and this is detected by the voltage detection circuit 106, the control circuit 105 outputs a detection signal to the data generation unit 10.
9 to be sent. Upon receiving the detection signal, the data generator 109 sends specific image information to the logic controller 107. In addition, the data generation unit 109 includes the external input detection unit 1 as described above.
When a sleep signal is input from 12, a specific image information is sent to the logic control unit 107 based on the sleep signal.

The specific image information includes, for example, image information for displaying a so-called checkerboard pattern image in which light and dark states are alternately displayed for each pixel or one picture element, or for each of one or a plurality of scanning lines. This is image information for displaying a stripe image that alternately displays light and dark states for one or more information lines.

When such specific image information is input from the data generation unit 109, the logic control unit 10
7 outputs a scanning line driving control signal and an information line driving control signal corresponding to the image information to the scanning line driving circuit 102 and the information line driving circuit 103. Thereby, the display panel 10
1 displays specific image information, after which the liquid crystal device goes into a completely off state or a sleep state.

As described above, even when the liquid crystal device is completely turned off or in a sleep state, the liquid crystal bistability, in other words, the display when the power is turned off even after the liquid crystal is turned off. The specific image information is maintained by the property of maintaining the state or the property of maintaining the display state even after the sleep state. Then, by maintaining the specific image information, the liquid crystal performs burn-in subdivision, and as a result, the drive margin is recovered as shown in FIG.

Next, a display operation in the liquid crystal device having such a configuration will be described with reference to a flowchart shown in FIG.

During the image display operation, the switch 110 is turned off to stop the image display operation, and when the power is turned off (Y in step 50), the voltage detection circuit 106 detects that the power is off (step 51). , And sends a detection signal to the data generator 109. Then, the data generator 109
Based on this detection signal, specific image information to be displayed when the power is turned off is output to the logic control unit 107 (step 5).
2).

Thereafter, the logic control unit 107 supplies the scanning line driving circuit 102 and the information line driving circuit 103 with the scanning line driving control signal and the information line driving control signal corresponding to the image information.
Output to As a result, the display panel 101 displays the specific image information (step 53), after which the liquid crystal device is completely stopped.

Here, when the specific image information is displayed when the power is turned off, the liquid crystal remains in a state where the specific image, that is, the checkered image or the stripe image is displayed, due to the bistability (memory effect) of the liquid crystal. Will be maintained.
When the liquid crystal maintains the specific image information in this manner, the driving margin is recovered.

On the other hand, until the power is turned off (N in step 50), the external input detecting means 112 monitors the state of the external input. If the external input is not input for a predetermined period (Y in step 55), A sleep signal indicating the sleep state is output to the data generator 109 (step 56).

Then, the data generator 109 outputs specific image information to be displayed during sleep to the logic controller 107 based on the detection signal (step 57).

After that, the logic control unit 107 sends the scanning line driving control signal and the information line driving control signal corresponding to the image information to the scanning line driving circuit 102 and the information line driving circuit 103.
Output to Thus, the display panel 101 displays the specific image information (Step 58). After that, when an external input is input (N in step 55), the liquid crystal device displays an image corresponding to the external input.

Here, when the specific image information is displayed in the sleep mode, the liquid crystal maintains a state where the specific image, that is, the checkered image or the stripe image is displayed, due to the bistability (memory effect) of the liquid crystal. I will be.
When the liquid crystal maintains the specific image information in this manner, the driving margin is recovered.

FIG. 6 shows a drive margin before implementation in the case of displaying a one-pixel checkerboard pattern, one-pixel stripe pattern, and an entire black pattern (REF) in the liquid crystal device according to the present embodiment. FIG. 7 is a diagram comparing drive margins after displaying a specific image and a specific image, and FIG. 7 is a chart showing the evaluation. The display panel 101 used had an image already burned in.

By turning off the power while displaying the image information in this manner, as is clear from FIGS. 6 and 7, it is possible to recover the drive margin even in the burned-in display panel 101. . The same effect was also obtained in the specific pattern display during sleep.

In the above description, the case where the matrix electrode is used as the electrode for driving the liquid crystal has been described. However, the present invention is not limited to this, and the liquid crystal may be driven by a TFT.

[0045]

As described above, according to the present invention, when the power is turned off or in sleep mode, the liquid crystal is driven according to specific display information, and the state according to the specific display information is changed after the power is turned off. , Or by keeping the liquid crystal during sleep,
The drive margin once decreased can be recovered, and the decrease in the drive margin over time can be eliminated.

[Brief description of the drawings]

FIG. 1 is a block diagram of a liquid crystal device according to an embodiment of the present invention.

FIG. 2 is a diagram showing driving waveforms used in the liquid crystal device.

FIG. 3 is a block diagram of a driving circuit of the liquid crystal device.

FIG. 4 is a diagram showing a drive margin recovery state in the liquid crystal device.

FIG. 5 is a flowchart illustrating a display operation in the liquid crystal device.

FIG. 6 is a table showing the results of a drive margin recovery experiment in the liquid crystal device.

FIG. 7 is a table showing evaluation of the drive margin recovery experiment.

FIG. 8 is a conceptual diagram of a driving margin.

FIG. 9 is a diagram showing a drive margin recovery state in a conventional liquid crystal device.

[Explanation of symbols]

 Reference Signs List 101 display panel 1011 scanning line 1012 information line 102 scanning line driving circuit 103 information line driving circuit 104 driving voltage generation circuit 105 control circuit 106 voltage detection circuit 107 logic control circuit 109 data generation unit 112 external input detection circuit

Claims (7)

[Claims] 1. A liquid crystal device comprising a liquid crystal that maintains a display state at the time of power-off even after the power is turned off, and a liquid crystal element having electrodes for driving the liquid crystal, wherein the liquid crystal device includes a liquid crystal device having a specific power-off or sleep mode. The liquid crystal is driven by applying a signal corresponding to display information to the electrode to drive the liquid crystal, and the liquid crystal is maintained in a state corresponding to the specific display information after the power is turned off or during sleep. Liquid crystal device. 2. A liquid crystal device comprising a liquid crystal for maintaining a display state even when the power is turned off even after the power is turned off, and a liquid crystal element having an electrode for driving the liquid crystal, wherein a signal corresponding to display information is transmitted. A driving unit for driving the liquid crystal by applying to the electrodes; a display information generating unit for selectively generating display information or specific display information input to the driving unit; a detection unit for detecting power-off; A control unit that inputs a detection signal of the means to the display information generation unit and controls the display information generation unit to generate the specific display information when power is turned off, and a state according to the specific display information. Wherein the liquid crystal is maintained even after the power is turned off. 3. A liquid crystal device comprising a liquid crystal for maintaining a display state when the power is turned off even after the power is turned off, and a liquid crystal element having an electrode for driving the liquid crystal, wherein a signal corresponding to display information is transmitted to the liquid crystal device. A driving unit that drives the liquid crystal by applying to the electrodes; a display information generation unit that selectively generates display information or specific display information input to the driving unit; a detection unit that detects a sleep state; A control unit for inputting a detection signal of the means to the display information generation unit and controlling the display information generation unit to generate the specific display information during sleep, and a state corresponding to the specific display information. The liquid crystal device, wherein the liquid crystal is maintained during the sleep. 4. The liquid crystal display device according to claim 1, wherein the specific display information is display information for alternately displaying a light and dark state for each pixel or each pixel of the liquid crystal element. Liquid crystal device. 5. The method according to claim 1, wherein the electrode is a matrix electrode formed by a plurality of scanning lines and information lines, and the specific display information is one or a plurality of scanning lines or one or a plurality of information lines. 4. The liquid crystal device according to claim 1, wherein the display information is a display information for alternately displaying a light and dark state every time. 6. The liquid crystal device according to claim 1, wherein the liquid crystal is a ferroelectric liquid crystal. 7. The liquid crystal device according to claim 1, wherein the liquid crystal is a chiral smectic liquid crystal.