JP2006018125A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that when scanning electrodes of later scanning is likely to have black pixels, a user considers the electrodes as a flicker at the time of display update and has unpleasant feeling, since update is performed by successively scanning the scanning electrodes from an end toward the other end of a liquid crystal panel after overall erasure of data is performed in a conventional method. <P>SOLUTION: In a liquid crystal display having a liquid crystal panel wherein a first substrate having a plurality of scanning electrodes and a second substrate having a plurality of signal electrodes are disposed opposite to each other via a liquid crystal material having bistability, the scanning electrodes and the signal electrodes are disposed in a matrix shape and pixels are formed at intersection parts of the scanning electrodes and the signal electrodes and having a fixed scanning order when information is written in the liquid crystal panel, a new scanning order different from the predetermined scanning order of the scanning electrodes is determined according to information of a screen to be displayed and scanning is performed based on the determination. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid crystal display device. Specifically, the present invention relates to a liquid crystal display device using a liquid crystal material having bistability.

  The liquid crystal element having bistability takes either the first stable state or the second stable state in response to the applied electric field. In addition, when an electric field is not applied, the state is maintained and memory performance is obtained, which is effective for a product that requires low power consumption and a high-resolution product in which it is difficult to maintain a predetermined frame frequency.

  Switching between the first stable state and the second stable state in the bistable liquid crystal element is performed by, for example, applying the product of the pulse time width (pulse width) and the voltage value when a rectangular pulse is applied. Occurs when the value is greater than or equal to the threshold.

  Next, display rewriting in a bistable liquid crystal element will be described. In the liquid crystal panel having the liquid crystal element, a first substrate having a plurality of scanning electrodes and a second substrate having a plurality of signal electrodes are arranged to face each other with a liquid crystal material having bistability, Pixels are formed at intersections where signal electrodes are arranged in a matrix.

  The display rewriting in the liquid crystal element will be described with reference to FIGS. In FIG. 2, five scan electrodes and five signal electrodes are taken as an example, and a first substrate having scan electrodes and a second substrate having signal electrodes are omitted.

In FIG. 2, 201 is a first scan electrode, 202 is a second scan electrode, 203 is a third scan electrode, 204 is a fourth scan electrode, 205 is a fifth scan electrode, and 211 is a first scan electrode. , 212 is a second signal electrode, 213 is a third signal electrode, 214 is a fourth signal electrode, and 215 is a fifth signal electrode.
The intersection between the scan electrode and the signal electrode is a pixel. It is assumed that white is displayed in the first stable state and black is displayed in the second stable state. It should be noted that the pixels indicated by diagonal lines are black and the other pixels are white. G1 and G2 are pixels, where G1 is a black pixel and G2 is a white pixel.

FIG. 9 is a diagram illustrating voltage waveforms applied to the scan electrodes, signal electrodes, and pixels. The horizontal axis indicates time, and the vertical axis indicates voltage. L1 is a waveform applied to the first scan electrode 201, L2 is a waveform applied to the second scan electrode 202, L3 is a waveform applied to the third scan electrode 203, and L4 is a fourth scan electrode 204. , L5 is a waveform applied to the fifth scan electrode 205, C1 is a waveform applied to the first signal electrode 211, and C3 is a waveform applied to the third signal electrode 213. is there. P1 and P2 correspond to the pixel G1 and the pixel G2 shown in FIG. 2, respectively, and indicate combined waveforms of the scanning electrode and the signal electrode applied to the pixel. T _1A is the erase period of the first scan electrode 201, T _1B is the write period of the first scan electrode 201, T _3A is the erase period of the third scan electrode 203, and T _3B is the write period of the third scan electrode 203. It is a period.

Since the liquid crystal element having bistability has a memory property, when rewriting a display screen, after erasing all the pixels on the scan electrode to white for each scan electrode, to the pixel to be blackened. The operation is to perform writing. As shown in FIG. 9, the first scan electrode 201 erases all the pixels on the scan electrode in the erase period T _1A of the first scan electrode 201,
Writing is performed in the writing period T _1B of the first scan electrode 201. Similarly, the third scan electrode 203 performs writing in the write period T _3B of the third scan electrode 203 after erasing all pixels on the scan electrode in the erase period T _3A of the third scan electrode 203. .

  As described above, both the erasing period and the writing period are required for all the scan electrodes, and there is a problem that a long time is required for display update. Therefore, in order to solve this problem, a method of simultaneously erasing all scan electrodes has been proposed (see, for example, Patent Document 1).

FIG. 10 is a diagram for explaining a driving method of the liquid crystal element disclosed in Patent Document 1. In FIG. T _E is the all-pixel erasing time, T _1W is the writing period of the first scan electrode 201, and T _3W is the writing period of the third scan electrode 203. In FIG. 10, the same symbols are assigned to the same elements as in FIG.
As shown in FIG. 10, by providing all the pixels erasing time T _E, since the white bulk erasure of all the pixels on all the scanning electrodes, writing period T _1W of the first scan electrode _201, the third scan Writing is performed during the writing period T _{3 W} of the electrode 203.
Actually, for all the pixels, scanning electrodes are selected in the order of the first scanning electrode 201 to the fifth scanning electrode 205, and writing to the pixels to be made black is performed. As described above, since the plurality of scanning electrodes are simultaneously erased to be white, the entire rewriting time is shortened, and the problem that a long time is required for display updating has been improved.

JP 61-140924 (page 4-6, FIG. 5)

However, the prior art disclosed in Patent Document 1 has a problem that the screen flickers depending on display data of the screen to be displayed. That is, if there is display data with many black pixels at the bottom of the screen, the user will feel flicker when rewriting it. The reason is that pixels on a plurality of scan electrodes are once whitened, so that it takes a long time for the pixels on the scan electrodes that are in the second half of the scanning order to be white regardless of the color to be displayed. It is.
The display shown in FIG. 2 will be described as an example. Although the pixels on the fifth scan electrode 205 are all black, the display is performed while the pixels on the first to fourth scan electrodes are being rewritten. White that is different from the color to be displayed continues to be displayed. For this reason, even when pixels are correctly written in the writing period of the fifth scan electrode 205, the user feels as flickering at the time of display update, and often feels uncomfortable.
In the display example shown in FIG. 2, there are five scan electrodes and five signal electrodes. However, in the case of an actual liquid crystal panel, the number of electrodes is larger, so this problem is an important problem to be solved. It was.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid crystal display device in which the rewriting time at the time of display update is not prolonged and the flicker at the time of display update is reduced.

  In order to achieve the above object, the present invention adopts the following structure.

A first substrate having a plurality of scanning electrodes and a second substrate having a plurality of signal electrodes are arranged to face each other with a liquid crystal material having bistability, and the scanning electrodes and the signal electrodes are arranged in a matrix. In a liquid crystal display device having a liquid crystal panel in which pixels are formed at the intersection of the scanning electrode and the signal electrode, and having a certain scanning order when writing information to the liquid crystal panel, according to the information on the screen to be displayed A new scanning order different from the preset scanning order of the scanning electrodes is determined, and scanning is performed based on the determination.

  A first substrate having a plurality of scanning electrodes and a second substrate having a plurality of signal electrodes are arranged to face each other with a liquid crystal material having bistability, and the scanning electrodes and the signal electrodes are arranged in a matrix. In a liquid crystal display device having a liquid crystal panel in which pixels are formed at intersections between the scan electrode and the signal electrode and having a certain scanning order when writing information to the liquid crystal panel, the liquid crystal display device needs to be rewritten. Batch erase means for collectively bringing the pixels into the first stable state, and rewrite scanning determination for determining a new scanning order different from the scanning order of the scanning electrodes set in advance according to information on the screen to be displayed And rewriting means for bringing the target pixel on the scan electrode determined by the rewrite scanning determining means into a second stable state.

  The rewrite scan determining means selects a scan electrode having many pixels in the second stable state.

  A flag corresponding to a plurality of scan electrodes is provided, and the flag is set when writing to the corresponding scan electrode is performed.

  The rewrite scan determining means selects a scan electrode to be scanned from the scan electrodes corresponding to the set flag, and clears the flag corresponding to the selected scan electrode.

  It is characterized in that scan electrodes in different display states before and after rewriting are determined, and scan electrodes in different display states are rewritten.

  The liquid crystal material having bistability is a ferroelectric liquid crystal.

In the liquid crystal display device of the present invention, when updating the display, the scanning order is determined in accordance with the information on the screen to be displayed, and in particular, scanning is performed from the scanning electrode having many pixels that are different in color from the collectively erased color. There is a big feature that is not in the past.
By adopting such a configuration, the time required for the display update does not become longer, and the user does not recognize the flicker at the time of the display update, so that the user does not feel uncomfortable.

The liquid crystal display device of the present invention newly determines and displays a scanning order different from the scanning order of scanning electrodes set in advance according to information on the screen to be displayed.
The scan order of the scan electrodes set in advance is, for example, the order of scan electrode numbers (numbers indicating the order of scan electrodes sequentially assigned from one end of the liquid crystal panel), and a newly determined scan order. Is, for example, a scanning order based on the result of selecting a scanning electrode having a large number of black pixels on the scanning electrode. In this case, information on the screen to be displayed is information on the number of black pixels on the scanning electrode.

  Hereinafter, a liquid crystal display device according to an embodiment of the present invention will be described with reference to the drawings.

[Description of structure: Fig. 1]
FIG. 1 is a block diagram showing a liquid crystal display device of the present invention. As shown in FIG. 1, a liquid crystal display device according to an embodiment of the present invention includes a control unit 101, a liquid crystal panel 102, a rewrite determination unit 103, a batch erasure unit 104, a rewrite scan determination unit 105, a rewrite unit 106, a video memory 107, The modified scanning line storage means 108 is provided.

The control unit 101 controls the entire liquid crystal display device of the present invention, and writes display data to the video memory 107 and issues a display update command to the batch erasing unit 104 and the rewriting unit 106.
In the embodiment of the present invention, the information on the screen to be displayed is the display data itself, and the display data is data representing the content displayed on the liquid crystal panel 102. That is, the bit data in the display data corresponds to each pixel on the liquid crystal panel 102.

  In the liquid crystal panel 102, a first substrate having a plurality of scanning electrodes and a second substrate having a plurality of signal electrodes are arranged to face each other through a bistable liquid crystal material such as a ferroelectric liquid crystal. The electrodes are arranged in a matrix, and pixels are formed at the intersections between the scanning electrodes and the signal electrodes.

  Each bit of the display data stored in the video memory 107 and the pixel of the liquid crystal panel 102 have a one-to-one correspondence. When the bit value is “1”, the corresponding pixel is displayed in black and the bit value is “0”. In this case, the corresponding pixel is displayed in white.

  The rewrite determination unit 103 calculates the scan electrode corresponding to the display data to be updated when the control unit 101 writes to the video memory 107, and stores the scan line number in which the display data is updated in the changed scan line storage unit 108. To do. The scanning line number is an electrode number assigned to the scanning electrode, for example, a number indicating the order of the scanning electrodes sequentially assigned from one end of the liquid crystal panel.

  The batch erasure unit 104 reads the scan electrode whose display data is updated from the changed scan line storage unit 108 according to the display update command from the control unit 101, and erases all pixels on the corresponding scan electrode of the liquid crystal panel 102, that is, A voltage that is white in the first stable state is applied.

  The rewrite scan determination unit 105 reads the scan electrode whose display data has been updated from the changed scan line storage unit 108, and reads the display data of the corresponding scan electrode from the video memory 107, and scans with the largest number of pixels that should be black. The electrode is calculated and output to the rewriting means 106. Also, the calculated scanning line number in the changed scanning line storage means 108 is cleared.

  The rewriting unit 106 is activated by the control unit 101 after the batch erasing unit 104 has finished processing. The display data corresponding to the scan electrode calculated by the rewrite scan determining means 105 is read from the video memory 107, and the pixel to be black on the corresponding scan electrode of the liquid crystal panel 102 is in the black state which is the second stable state. Apply a voltage.

  The video memory 107 is composed of a rewritable memory such as a RAM (Random Access Memory) for storing display data, and writing from the control means 101 and reading from the rewrite scanning verification means 105 and rewrite means 106 are performed.

  In the changed scanning line storage unit 108, the rewrite determination unit 103 stores the scanning line number in which the display data in the video memory 107 is updated.

[Description of operation: FIGS. 2 to 8]
Next, the operation of the liquid crystal display device according to the embodiment of the present invention will be described with reference to FIGS. The liquid crystal display device of the present invention is characterized in that the order of the scanning electrodes to be scanned is determined from the information on the screen to be displayed, and scanning is performed in accordance with this. In the present embodiment, the number of black pixels on the scanning electrode is used as the screen information to be displayed. The scanning is performed first from the scanning electrode having many black pixels.

2 to 7 are schematic diagrams showing display states on the liquid crystal panel 102. FIG. 2 to 7, the first substrate having a plurality of scanning electrodes and the second substrate having a plurality of signal electrodes are omitted for easy understanding of the drawings.
FIG. 8 is a drive waveform diagram according to the embodiment of the present invention. Here, it is assumed that the liquid crystal display device according to the embodiment of the present invention includes five scanning electrodes and five signal electrodes. A liquid crystal material having bistability changes from white to black when a voltage of +1.5 V ₀ or more is applied, and changes from black to white when a voltage of −1.5 V ₀ or less is applied. When a voltage between −1.5V ₀ and + 1.5V ₀ is applied, the stable state is maintained and the color of the pixel does not change. In addition, in FIG. 2 to FIG. 7, pixels indicated by diagonal lines indicate black, and other pixels indicate white. The operation when updating to the display state shown in FIG. 2 will be described below. Note that FIG. 2 is also used when explaining the prior art, and since explanations of symbols and the like have already been made, a detailed explanation is omitted.

In FIG. 8, waveforms indicated by L1 to L5 indicate waveforms applied from the first scan electrode 201 to the fifth scan electrode 205, and C1 and C3 are the first signal electrode 211 and the third signal, respectively. The waveform applied to the electrode 213 is shown. P1 and P2 correspond to the pixel G1 and the pixel G2 shown in FIG. 2, respectively, and indicate combined waveforms of the scanning electrode and the signal electrode applied to the pixel. T _E is the erase period, _{T 5} from _{T 1} are each write period of the first scan electrode 201 from the fifth scan electrode 205.

First, writing from the control unit 101 to the video memory 107 is completed, and all pixels on all five scanning electrodes of the liquid crystal panel 102 are turned white by a batch erase command from the control unit 101 to the batch erase unit 104. A voltage is applied (erasing period T _E ). After voltage application by the collective erasing means 104, all pixels as shown in FIG.

Next, the rewrite scanning determination means 105 reads the display data in the video memory 107 and determines the scanning electrode with the largest number of black pixels. In the example of FIG. 2, this is the fifth scan electrode 205. Then, the rewriting means 106 applies a drive waveform indicated by the “T ₅ ” period in FIG. 8 to perform writing to the pixel on the fifth scan electrode 205. After voltage application by the rewrite means 106, a display state as shown in FIG. 4 is obtained.

Further, the rewrite scan determining unit 105 determines the scan electrode with the most black pixels next to the fifth scan electrode 205. In the example of FIG. 2, this is the fourth scanning electrode 204. Then, the rewriting means 106 applies a drive waveform indicated by the “T ₄ ” period in FIG. 8 to perform writing to the pixel on the fourth scan electrode 204. After voltage application by the rewrite means 106, a display state as shown in FIG. 5 is obtained.

Further, the rewrite scanning determination unit 105 determines the scanning electrode with the most black pixels next to the fourth scanning electrode 204. In the example of FIG. 2, this is the first scan electrode 201. Then, the rewrite means 106 applies a drive waveform indicated by the “T ₁ ” period in FIG. 8 to perform writing to the pixel on the first scan electrode 201. After the voltage is applied by the rewriting means 106, the display state is as shown in FIG.

Further, the rewrite scanning determination unit 105 determines the scanning electrode with the most black pixels next to the first scanning electrode 201. In the example of FIG. 2, it is the third scanning electrode 203. And
The rewrite means 106 applies a drive waveform indicated by the “T ₃ ” period in FIG. 8 to perform writing to the pixel on the third scan electrode. After the voltage is applied by the rewriting means 106, the display state is as shown in FIG. At this point, the target display state has already been achieved.

Further, the rewrite scanning determination unit 105 determines the scanning electrode with the most black pixels next to the third scanning electrode 203. In the example of FIG. 2, the scan of the second scan electrode 202 is calculated. However, since there is no black pixel on the scan electrode, there is no problem even if scanning is not performed. In the embodiment of the present invention, a drive waveform indicated by the “T ₂ ” period in FIG. 8 is applied. ing.

  In the description of the operation of the liquid crystal display device according to the embodiments of the present invention so far, the rewrite scanning determining means 105 has a flag corresponding to each scanning electrode, and the batch erasing means 104 has all the five scanning electrodes on all. After the pixel is white, a flag corresponding to the selected scan electrode is set. Then, the scanning order is determined by selecting the scanning electrode having the largest number of black pixels from the scanning electrodes corresponding to the unset flag.

  Here, the flag is a mark for indicating whether or not a certain state is established. For example, it is a concept that expresses a state with two states of “set” and “clear”. Actually, the state is held in a rewritable storage device such as SRAM (Static Random Access Memory), and the subsequent processing is performed based on the state.

  By the way, the rewrite scanning determination unit 105 selects the scanning electrode with the largest number of black pixels on the scanning electrode. If the number of pixels that become black by chance is the same, these scanning electrodes have the same in advance. Writing is performed in the order of scanning line numbers.

  In the embodiment of the present invention, writing is performed after all the pixels are set to white as batch erasure, but when all pixels are set to black and then writing to white is performed, the color on the scanning electrode is white. Needless to say, the scan electrode having the largest number of pixels is selected. Further, the rewrite scanning determination unit 105 selects the one having the largest number of black pixels on the scanning electrode, but the selection of the scanning electrode is not limited to the number of black pixels. For example, instead of simply the number of black pixels, a scan electrode having a large number of continuous black pixels may be selected, or may be determined from both the number of black pixels and the number of continuous pixels.

  As is clear from the above description, when the display is updated, the liquid crystal display device of the present invention displays the number of black pixels on the scan electrode or the state in which the pixels are continuous. This is used as information to newly determine the scanning order. In particular, there is a large feature that does not exist in the past when scanning from a scan electrode that has many pixels that differ in color from the batch erased color, and this configuration allows the user to recognize flicker when updating the display. There will be no discomfort.

  The liquid crystal display device of the present invention is effective for a liquid crystal panel using a bistability liquid crystal element that does not need to apply a voltage to a scan electrode or a signal electrode except during display update. Therefore, the present invention can be applied to small information devices with limited power consumption. More specifically, it is suitable for a liquid crystal display device used for a portable information device such as a wristwatch or a battery-less IC card except when updating the display.

It is a block diagram which shows the liquid crystal display device in embodiment of this invention. It is a schematic diagram of the display state of the liquid crystal display device explaining embodiment of this invention and a prior art. It is a schematic diagram which shows the display state in the liquid crystal display device in embodiment of this invention. It is a schematic diagram which shows the display state in the liquid crystal display device in embodiment of this invention. It is a schematic diagram which shows the display state in the liquid crystal display device in embodiment of this invention. It is a schematic diagram which shows the display state in the liquid crystal display device in embodiment of this invention. It is a schematic diagram which shows the display state in the liquid crystal display device in embodiment of this invention. It is a figure explaining the drive waveform in the liquid crystal display device in embodiment of this invention. It is a figure explaining the drive waveform in the liquid crystal display device of a prior art. It is a figure explaining the drive waveform in the liquid crystal display device of a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Control means 102 Liquid crystal panel 103 Rewriting determination means 104 Collective erasure means 105 Rewriting scanning determination means 106 Rewriting means 107 Video memory 108 Change scanning line storage means 201 1st scanning electrode 202 2nd scanning electrode 203 3rd scanning electrode 204 4th scan electrode 205 5th scan electrode 211 1st signal electrode 212 2nd signal electrode 213 3rd signal electrode 214 4th signal electrode 215 5th signal electrode

Claims (7)

A first substrate having a plurality of scanning electrodes and a second substrate having a plurality of signal electrodes are arranged to face each other with a liquid crystal material having bistability, and the scanning electrodes and the signal electrodes are arranged in a matrix. In a liquid crystal display device having a liquid crystal panel having pixels formed at intersections of the scanning electrodes and the signal electrodes, and having a certain scanning order when information is written to the liquid crystal panel,
A liquid crystal display device, wherein a new scanning order different from a preset scanning order of scanning electrodes is determined according to information on a screen to be displayed, and scanning is performed based on the determination. A first substrate having a plurality of scanning electrodes and a second substrate having a plurality of signal electrodes are arranged to face each other with a liquid crystal material having bistability, and the scanning electrodes and the signal electrodes are arranged in a matrix. In a liquid crystal display device having a liquid crystal panel having pixels formed at intersections of the scanning electrodes and the signal electrodes, and having a certain scanning order when information is written to the liquid crystal panel,
Batch erasing means for collectively bringing the pixels on the plurality of scan electrodes that require rewriting into a first stable state;
Rewrite scanning determination means for determining a new scanning order different from the scanning order of scanning electrodes set in advance according to information on a screen to be displayed;
Rewriting means for bringing the target pixel on the scanning electrode determined by the rewriting scanning determining means into a second stable state.   3. The liquid crystal display device according to claim 2, wherein the rewrite scanning determination unit selects the scanning electrode having a large number of the pixels in a second stable state.   4. The liquid crystal according to claim 2, wherein a flag corresponding to the plurality of scan electrodes is provided, and the flag is set when writing to the corresponding scan electrode is performed. Display device.   The rewrite scanning determination unit selects the scanning electrode to be scanned from the scanning electrodes corresponding to the set flag, and clears the flag corresponding to the selected scanning electrode. The liquid crystal display device according to claim 4.   6. The liquid crystal display device according to claim 1, wherein the scanning electrodes that are in different display states before and after rewriting are determined, and the scanning electrodes that have different display states are rewritten. 7. The liquid crystal display device according to claim 1, wherein the liquid crystal material having bistability is a ferroelectric liquid crystal.

Images