Cholesteric liquid crystal display driving method and device for realizing dynamic video display

Abstract

The invention discloses a cholesteric liquid crystal display driving method and a cholesteric liquid crystal display driving device for realizing dynamic video display, and belongs to the technical field of display. The method comprises the following steps: firstly, controlling a grid electrode and a source electrode driver to cooperatively work, and resetting a full-screen liquid crystal to a vertical arrangement state as a display reference; then applying a specific voltage signal to each pixel according to the current frame image data, so that the pixels are selectively kept in a vertical arrangement state or converted into a plane arrangement state to display a target image; then common electrode voltage polarity inversion is carried out, reverse voltage is applied for compensation, and finally the process is cycled to achieve image updating. The corresponding device comprises a display panel, a gate driver, a source driver and a time schedule controller for executing the method. According to the method and device, the refresh rate limitation of traditional cholesteric liquid crystal bistable switching is broken through, high-speed dynamic video display is achieved, meanwhile, the display reliability is effectively improved through polarity compensation, the service life is effectively prolonged through polarity compensation, and low power consumption and high compatibility are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of display technology, and in particular to a cholesteric liquid crystal display driving method and device for realizing dynamic video display. BACKGROUND

[0002] Cholesteric liquid crystal is widely used in reflective display field (such as electronic book, electronic price tag) due to its adjustable optical properties. There are three typical macroscopic states: 1. Homeotropic state (H state): liquid crystal molecules are arranged vertically to the substrate surface, the helical structure is destroyed, and the state is transparent; it is formed under the action of strong electric field or vertical alignment layer, and the color of the substrate bottom layer can be transmitted; 2. Planar state (P state): liquid crystal molecules are arranged parallel to the substrate, the helical axis is perpendicular to the substrate, and the state is selectively reflective; it is naturally presented without external electric field, and specific wavelength light can be reflected to show color; 3. Focal conic state (FC state): liquid crystal molecules form a multi-domain focal conic structure, the helical axis is randomly distributed, and the state is scattering; it is formed under weak electric field or mechanical disturbance, and appears milky white and opaque.

[0003] Figure 1 It is a conventional cholesteric LCD single-pixel driving architecture, mainly including source line, gate line, common terminal, TFT transistor and pixel electrode. The source line is used to send data to the drain of the TFT transistor, the gate line is used to control the gate of the TFT transistor to control the TFT to open or close the pixel electrode connected to the source of the TFT transistor, and the pixel electrode is used to receive and save data signals and form an electric field with the common terminal electrode to control the deflection of the liquid crystal. Figure 2 It is a conventional reflective LCD / ink screen direct current common voltage and source voltage driving timing. The existing cholesteric LCD driving scheme generally adopts a direct current common electrode voltage (DCVcom) + conventional timing controller (Tcon) architecture, and the driving logic is as follows: first, make the screen enter the P state (full white), then write the FC state data voltage to the source line through the gate line by row scanning, and after traversing all the rows, additional frame discharge is required to lock the picture. The whole process requires more than 20 frames, and the total time consumption is several seconds. The refresh frequency is far lower than the required 25Hz~30Hz for video playing, and only static display can be realized, which cannot be expanded to the dynamic video field.

[0004] In addition, the existing scheme lacks a targeted polarity compensation mechanism: liquid crystal molecules are prone to polarization when subjected to a single polarity electric field for a long time, leading to display residual images, brightness decay and other abnormalities, shortening the service life of the product; at the same time, the timing connection of the image data processing (such as black and white binary) and the voltage application in the existing scheme is not clearly defined, which is prone to display lag, low contrast and other problems, further limiting the application scenarios of cholesteric LCD. SUMMARY

[0005] To solve the technical problems in the background art, the present application proposes a cholesteric liquid crystal display driving method and device for realizing dynamic video display.

[0006] The cholesteric liquid crystal display driving method for realizing dynamic video display proposed by the present application comprises the following steps: S1, obtaining an initialization instruction, controlling the gate driver to turn on all pixels row by row, and applying a first voltage signal to all pixels through the source driver, so that the full-screen cholesteric liquid crystal is converted into a vertical arrangement state; S2, obtaining image data of the current video frame, controlling the gate driver to turn on the pixels row by row, and controlling the source driver to apply a second voltage signal or a third voltage signal to each pixel according to the image data, so that the liquid crystal of each pixel is selected to remain in a vertical arrangement state or is converted into a planar arrangement state, to display a target image; S3, controlling the polarity of the alternating common electrode voltage to reverse, and again controlling the source driver to apply a fourth voltage signal or a fifth voltage signal with a polarity opposite to the second voltage signal or the third voltage signal to each pixel according to the image data, to perform polarity compensation on the liquid crystal molecules; S4, obtaining image data of the next frame of video, and repeating steps S2 and S3 to realize dynamic image updating.

[0007] Preferably, the first voltage signal is a voltage signal with a polarity opposite to that of the alternating common electrode voltage and an equal amplitude.

[0008] Preferably, the alternating common electrode voltage is a square wave, a sine wave or a trapezoidal wave.

[0009] Preferably, the frequency of the alternating common electrode voltage is 50Hz to 60Hz.

[0010] Preferably, the second voltage signal is a voltage signal with the same polarity as the alternating common electrode voltage and an equal amplitude, for keeping the liquid crystal molecules of the corresponding pixel in a vertical arrangement state.

[0011] Preferably, the third voltage signal is a voltage signal with a polarity opposite to that of the alternating common electrode voltage and an equal amplitude, for converting the liquid crystal molecules of the corresponding pixel from a vertical arrangement state to a planar arrangement state.

[0012] Preferably, in steps S1 and S2, when the gate driver is controlled to turn on the pixels row by row, the turn-on time of a single gate line is configured to ensure that the corresponding pixel can sufficiently receive the corresponding voltage signal.

[0013] Preferably, the image data is black-and-white binary data, and the generation standard of the black-and-white binary data is that the video frame grayscale data input from outside is processed, pixels with a grayscale value greater than a set grayscale value threshold are determined as white pixels and correspond to the third voltage signal, and pixels with a grayscale value less than or equal to the set grayscale value threshold are determined as black pixels and correspond to the second voltage signal.

[0014] Preferably, in step S2, the operation of “controlling the gate driver to turn on the pixels row by row, and controlling the source driver to apply the second voltage signal or the third voltage signal to each pixel according to the image data” specifically includes that when the gate line is turned on row by row, the third voltage signal is synchronously output to the source line corresponding to the white pixel in the current row, and the second voltage signal is synchronously output to the source line corresponding to the black pixel in the current row, so that all the pixels in a row are synchronously completed to apply the voltage and then enter the scanning of the next row.

[0015] The application provides a cholesteric liquid crystal display driving device for realizing dynamic video display, which is applied to the cholesteric liquid crystal display driving method for realizing dynamic video display. The display panel comprises a plurality of cholesteric liquid crystal pixels arranged in a matrix. The gate driver is connected to a plurality of gate lines and is used for selecting the pixels row by row. The source driver is connected to a plurality of data lines and is used for applying a data voltage signal to the selected pixels. The timing controller is electrically connected to the gate driver and the source driver and is configured to perform the following operations: The gate driver and the source driver are controlled to apply a first voltage signal to all the pixels to make all the liquid crystals on the full screen enter a vertical arrangement state. Image data is acquired, and the gate driver and the source driver are controlled to apply a second voltage signal or a third voltage signal to each pixel according to the image data to display a target image. The polarity of the alternating common electrode voltage is reversed, and a voltage signal with opposite polarity is applied again according to the image data for compensation. The above process is repeated to realize dynamic image updating.

[0016] In the present application, the cholesteric liquid crystal display driving method and device for realizing dynamic video display effectively break through the technical bottleneck that the refresh speed of the existing cholesteric liquid crystal display is limited due to the dependence on bistable conversion and dynamic video display cannot be realized. Through the driving logic taking the vertical alignment state as the core display state, stable dynamic video playback can be realized. At the same time, with the aid of the reverse voltage compensation design, the polarization effect generated by the long-term bearing of the single polarity electric field of the liquid crystal molecules can be effectively offset, and abnormalities such as display ghosting and brightness attenuation can be avoided, so as to ensure the display stability and prolong the service life of the product. The key voltage parameters can be flexibly adjusted according to different cholesteric liquid crystal characteristics, and various application scenarios can be adapted, so that the application range of the cholesteric liquid crystal display technology is further expanded. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 It is a schematic diagram of a conventional cholesteric LCD single-pixel driving architecture. Figure 2 It is a schematic diagram of a conventional reflective LCD / ink screen direct current common electrode voltage and source electrode voltage driving timing. Figure 3 It is a driving timing schematic diagram of one embodiment of the cholesteric liquid crystal display driving method for realizing dynamic video display proposed in the present application. Figure 4 It is a working flow schematic diagram of the cholesteric liquid crystal display driving method for realizing dynamic video display proposed in the present application. DETAILED DESCRIPTION

[0018] REFERENCE Figures 1-4 The cholesteric liquid crystal display driving method for realizing dynamic video display proposed in the present application comprises the following steps: S1, an initialization instruction is obtained, a gate driver is controlled to turn on all pixels row by row, and a source driver is controlled to apply a first voltage signal to all pixels, so that the full-screen cholesteric liquid crystal is converted into a vertical alignment state.

[0019] S2, image data of a current video frame is obtained, the gate driver is controlled to turn on the pixels row by row, and the source driver is controlled to apply a second voltage signal or a third voltage signal to each pixel according to the image data, so that the liquid crystal of each pixel is selected to remain in the vertical alignment state or is converted into a planar alignment state, to display a target image.

[0020] In the present embodiment, the second voltage signal is a voltage signal with the same polarity and equal amplitude as the alternating common electrode voltage, which is used to make the liquid crystal molecules of the corresponding pixel remain in the vertical alignment state.

[0021] In the present embodiment, the third voltage signal is a voltage signal with opposite polarity and equal amplitude to the alternating common electrode voltage, which is used to make the liquid crystal molecules of the corresponding pixel convert from the vertical alignment state to the planar alignment state.

[0022] In the embodiment, in steps S1 and S2, when the gate driver is controlled to open the pixels row by row, the opening time of a single gate line is configured to ensure that the corresponding pixel can sufficiently receive the corresponding voltage signal.

[0023] In the embodiment, the image data is black-and-white binary data; the generation standard of the black-and-white binary data is that the video frame grayscale data input from outside is processed, the pixel with a grayscale value greater than a set grayscale value threshold is determined as a white pixel and corresponds to the third voltage signal, and the pixel with a grayscale value less than or equal to the set grayscale value threshold is determined as a black pixel and corresponds to the second voltage signal.

[0024] In the embodiment, in step S2, “controlling the gate driver to open the pixels row by row, and controlling the source driver to apply the second voltage signal or the third voltage signal to each pixel according to the image data” specifically means that when the gate line is opened row by row, the third voltage signal is synchronously output to the source line corresponding to the white pixel in the current row, and the second voltage signal is synchronously output to the source line corresponding to the black pixel in the current row, to ensure that all the pixels in a row are synchronously completed with voltage application before entering the next row scanning.

[0025] Specifically, the image data is black-and-white binary data, when the current video frame is writing data, the pixel displaying white, the polarity of the source voltage output is consistent with that of the alternating common voltage, at this time, the voltage difference is 0, maintaining the white display of step S1. When the pixel displaying black, the polarity of the source voltage output is opposite to that of the alternating common voltage, at this time, the voltage difference is 2A (which can make the cholesteric LC enter the H state), at this time, the H state, i.e., the transmission state, can transmit the black ink of the bottom layer, displaying black.

[0026] S3, controlling the polarity of the alternating common electrode voltage to be reversed, and again controlling the source driver to apply a fourth voltage signal or a fifth voltage signal with a polarity opposite to that of the second voltage signal or the third voltage signal to each pixel according to the image data, to perform polarity compensation on the liquid crystal molecules.

[0027] Specifically, after the forward scanning is completed, the alternating common electrode voltage is opposite to the source voltage output waveform, which is scanned once for this frame, to complete the polarity compensation and prevent the polarization of the cholesteric LCD from causing the product to be unable to be used for a long time.

[0028] Specifically, the purpose of the reverse scanning is to perform polarity compensation on the liquid crystal, i.e., the forward alternating common electrode voltage is 17.5V, and the source voltage is -17.5V to enter the H state to brush black, and the reverse scanning is that the alternating common electrode voltage is -17.5V, and the source voltage is +17.5V; the liquid crystal cannot be applied with a single electric field direction for a long time, and will be polarized, and needs to be driven alternately by a positive and a negative electric field to prevent polarization.

[0029] S4, obtaining the image data of the next frame of video, and repeatedly performing steps S2 and S3 to realize dynamic image updating.

[0030] Specifically, according to the TFT characteristics, for example: charging requires about 30us, according to the display resolution FHD, there are 1080 rows; the time of a frame is 32.5ms, the picture is updated every frame, 1 / 32.5ms=30 frame speed, since it is not necessary to enter the bistable state, the refresh speed can reach 25hz~30hz, the refresh speed is related to the TFT characteristics, if it is oxide TFT, or more block LTPS as a device, the refresh speed will be higher, which is calculated according to the charging speed.

[0031] In the embodiment, the first voltage signal is a voltage signal with the same amplitude and opposite polarity of the alternating common electrode voltage.

[0032] In the embodiment, the alternating common electrode voltage is a square wave, a sine wave or a trapezoidal wave.

[0033] In the embodiment, the frequency of the alternating common electrode voltage is 50Hz to 60Hz.

[0034] With reference to Figures 1-4 The application provides a cholesteric liquid crystal display driving device for realizing dynamic video display, which is applied to the cholesteric liquid crystal display driving method for realizing dynamic video display. The display panel comprises a plurality of cholesteric liquid crystal pixels arranged in a matrix. The gate driver is connected to the plurality of gate lines and is configured to select the pixels row by row. The source driver is connected to the plurality of data lines and is configured to apply a data voltage signal to the selected pixels. The timing controller is electrically connected to the gate driver and the source driver and is configured to perform the following operations: The timing controller controls the gate driver and the source driver to apply a first voltage signal to all the pixels so that the liquid crystals on the full screen enter a vertical arrangement state. The timing controller acquires image data and controls the gate driver and the source driver to apply a second voltage signal or a third voltage signal to each pixel according to the image data so as to display a target image. The timing controller controls the polarity of the alternating common electrode voltage to be reversed and applies a voltage signal with opposite polarity according to the image data again to compensate. The above process is repeated to realize dynamic image update.

[0035] The above description is only the preferred embodiment of the application, and the protection scope of the application is not limited to this. Any person skilled in the art can make equivalent replacement or change according to the technical solution and the inventive concept of the application within the technical range disclosed by the application, which should be covered by the protection scope of the application.

Claims

1. A method for driving a cholesteric liquid crystal display to achieve dynamic video display, characterized in that, Includes the following steps: S1. Obtain initialization instructions, control the gate driver to turn on all pixels row by row, and apply the first voltage signal to all pixels through the source driver to convert the full-screen cholesteric liquid crystal into a vertical alignment state; S2. Acquire the image data of the current video frame, control the gate driver to turn on the pixels line by line, and control the source driver to apply a second voltage signal or a third voltage signal to each pixel according to the image data, so that the liquid crystal of each pixel is either kept in a vertical alignment state or converted to a planar alignment state to display the target image. S3. Control the polarity reversal of the AC common electrode voltage, and again control the source driver to apply a fourth voltage signal or a fifth voltage signal with the opposite polarity to the second voltage signal or the third voltage signal to each pixel according to the image data, so as to perform polarity compensation on the liquid crystal molecules. S4. Obtain the image data of the next frame of video, and repeat steps S2 and S3 to achieve dynamic image updates.

2. The cholesteric liquid crystal display driving method for realizing dynamic video display according to claim 1, characterized in that, The first voltage signal is a voltage signal with the opposite polarity and the same amplitude as the AC common electrode voltage.

3. The cholesteric liquid crystal display driving method for realizing dynamic video display according to claim 2, characterized in that, The AC common electrode voltage is a square wave, a sine wave, or a trapezoidal wave.

4. The cholesteric liquid crystal display driving method for realizing dynamic video display according to claim 3, characterized in that, The frequency of the AC common electrode voltage is 50Hz to 60Hz.

5. The cholesteric liquid crystal display driving method for realizing dynamic video display according to claim 1, characterized in that, The second voltage signal is a voltage signal with the same polarity and amplitude as the AC common electrode voltage, used to keep the liquid crystal molecules of the corresponding pixel in a vertical alignment state.

6. The cholesteric liquid crystal display driving method for realizing dynamic video display according to claim 1, characterized in that, The third voltage signal is a voltage signal with opposite polarity and equal amplitude to the AC common electrode voltage, used to convert the liquid crystal molecules of the corresponding pixel from a vertically aligned state to a planarly aligned state.

7. The cholesteric liquid crystal display driving method for realizing dynamic video display according to claim 1, characterized in that, In steps S1 and S2, when the gate driver turns on the pixels row by row, the turn-on time of a single gate line is configured to ensure that the corresponding pixel can fully receive the corresponding voltage signal.

8. The cholesteric liquid crystal display driving method for realizing dynamic video display according to claim 1, characterized in that, The image data is black and white binary data; the standard for generating black and white binary data is as follows: the grayscale data of the externally input video frame is processed, and pixels with grayscale values ​​greater than a set grayscale value threshold are determined to be white pixels and correspond to a third voltage signal, while pixels with grayscale values ​​less than or equal to the set grayscale value threshold are determined to be black pixels and correspond to a second voltage signal.

9. The cholesteric liquid crystal display driving method for realizing dynamic video display according to claim 8, characterized in that, In step S2, "controlling the gate driver to turn on the pixels row by row, and controlling the source driver to apply a second voltage signal or a third voltage signal to each pixel according to the image data" specifically means: when the gate line is turned on row by row, a third voltage signal is output to the source line corresponding to the white pixel in the current row and a second voltage signal is output to the source line corresponding to the black pixel in the current row, so as to ensure that all pixels in a row complete the voltage application synchronously before entering the next row scan.

10. A cholesteric liquid crystal display driving device for realizing dynamic video display, characterized in that, The apparatus is applied to the cholesteric liquid crystal display driving method for realizing dynamic video display as described in any one of claims 1-9, the apparatus comprising: The display panel includes multiple cholesteric liquid crystal pixels arranged in a matrix. A gate driver, connected to multiple gate lines, is used to select the pixels row by row; The source driver, connected to multiple data lines, is used to apply a data voltage signal to the selected pixel; A timing controller, electrically connected to the gate driver and the source driver, is configured to perform the following operations: The gate driver and source driver are controlled to apply a first voltage signal to all pixels so that the full-screen liquid crystal enters a vertical alignment state; Image data is acquired, and the gate driver and source driver are controlled to apply a second voltage signal or a third voltage signal to each pixel according to the image data in order to display the target image; The polarity of the AC common electrode voltage is reversed, and a voltage signal of opposite polarity is applied again according to the image data for compensation. Repeat the above process to achieve dynamic image updates.

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