A cholesteric liquid crystal display driving method and device for realizing dynamic video display

Abstract

The application discloses a cholesteric liquid crystal display driving method and device for realizing dynamic video display, and belongs to the technical field of display. The method firstly controls the cooperation of the gate electrode and the source electrode driver to reset the full-screen liquid crystal to the vertical arrangement state as a display reference; then, according to the current frame image data, a specific voltage signal is applied to each pixel to make it selectively remain in the vertical arrangement state or be converted into the planar arrangement state to display the target image; subsequently, the polarity of the common electrode voltage is reversed and a reverse voltage is applied for compensation; finally, the process is recycled to realize image updating. The corresponding device comprises a display panel, a gate electrode driver, a source electrode driver and a timing controller for executing the above method. The method and device of the application break through the refresh rate limitation of the traditional cholesteric liquid crystal bistable switching, realize high-speed dynamic video display, effectively improve the display reliability and service life through polarity compensation, and have low power consumption and strong compatibility.

Description

Technical Field

[0001] This invention relates to the field of display technology, and in particular to a cholesteric liquid crystal display driving method and apparatus for realizing dynamic video display. Background Technology

[0002] Cholesteric liquid crystals, due to their tunable optical properties, are widely used in reflective displays (such as e-books and electronic price tags), and typically exist in three macroscopic states: 1. Homeotropic State (H-state): Liquid crystal molecules are aligned perpendicular to the substrate surface, the helical structure is destroyed, and it is transparent; it needs to be formed under the action of a strong electric field or a 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, with the helical axis perpendicular to the substrate, exhibiting selective reflection; it is naturally present without an external electric field and can reflect specific wavelengths of light to display color; 3. Focal Conic State (FC state): Liquid crystal molecules form a multi-domain focal conic structure with randomly distributed helical axes, exhibiting a scattering state; formed under weak electric fields or mechanical disturbances, appearing milky white and opaque.

[0003] Figure 1 This is a conventional cholesteric LCD single-pixel driving architecture, mainly composed of source lines, gate lines, common terminals, TFT transistors, and pixel electrodes. The source lines are used to send data to the drain of the TFT transistor, and the gate lines control the gate of the TFT transistor to control whether the TFT is on or off. The pixel electrodes are connected to the source of the TFT transistor to receive and store data signals and form an electric field with the common terminal electrode to control the deflection of the liquid crystal. Figure 2 For conventional reflective LCD / e-ink screens, the driving timing of the DC common electrode voltage and source voltage is generally based on the architecture of DC common electrode voltage (DCVcom) + conventional timing controller (Tcon). The driving logic is as follows: first, the screen enters the P state (full white), and then the FC state data voltage is written to the source line through the gate line line by line scanning. After traversing all lines, an additional frame discharge is required to lock the image. The whole process takes more than 20 frames and takes several seconds. The refresh rate is far lower than the 25Hz~30Hz required for video playback. It can only realize static display and cannot be extended to the field of dynamic video.

[0004] In addition, existing solutions lack a targeted polarity compensation mechanism: when liquid crystal molecules are subjected to a single polar electric field for a long time, they are prone to polarization, which leads to abnormalities such as display ghosting and brightness decay, shortening the product's lifespan. At the same time, existing solutions do not clearly define the timing connection between image data processing (such as black and white binarization) and voltage application, which can easily lead to problems such as display ghosting and low contrast, further limiting the application scenarios of cholesteric LCDs. Summary of the Invention

[0005] To address the technical problems existing in the background art, the present invention proposes a cholesteric liquid crystal display driving method and apparatus for realizing dynamic video display.

[0006] This invention proposes a cholesteric liquid crystal display driving method for realizing dynamic video display, comprising 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.

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

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

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

[0010] Preferably, 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.

[0011] Preferably, 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.

[0012] Preferably, 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.

[0013] Preferably, the image data is black and white binarized data; the standard for generating black and white binarized 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 as 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 as black pixels and correspond to a second voltage signal.

[0014] Preferably, 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.

[0015] This invention proposes a cholesteric liquid crystal display driving device for realizing dynamic video display, applied to the cholesteric liquid crystal display driving method for realizing dynamic video display as described in any of the above claims, the device 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.

[0016] The cholesteric liquid crystal display driving method and apparatus proposed in this invention for realizing dynamic video display effectively overcomes the technical bottleneck of existing cholesteric liquid crystal displays, which rely on bistable transitions, resulting in limited refresh rates and an inability to achieve dynamic video display. By using a driving logic with vertical alignment as the core display state, stable dynamic video playback can be achieved. Simultaneously, through a reverse voltage compensation design, the polarization effect caused by liquid crystal molecules being subjected to a single polar electric field for a long time can be effectively counteracted, avoiding abnormalities such as image retention and brightness decay, ensuring display stability and extending product lifespan. Key voltage parameters can be flexibly adjusted according to different cholesteric liquid crystal characteristics to adapt to various application scenarios, further expanding the application scope of cholesteric liquid crystal display technology. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a conventional cholesteric LCD single-pixel driving architecture. Figure 2 This is a schematic diagram of the driving timing of the DC common voltage and source voltage for a conventional reflective LCD / e-ink screen. Figure 3 This is a schematic diagram of the driving timing of one embodiment of the cholesteric liquid crystal display driving method for realizing dynamic video display proposed in this invention; Figure 4 This is a schematic diagram illustrating the workflow of a cholesteric liquid crystal display driving method for realizing dynamic video display proposed in this invention. Detailed Implementation

[0018] Reference Figures 1-4 The present invention proposes a cholesteric liquid crystal display driving method for realizing dynamic video display, comprising 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.

[0019] S2. Obtain 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 kept in a vertical alignment state or converted to a planar alignment state to display the target image.

[0020] In this embodiment, 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.

[0021] In this embodiment, 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.

[0022] In this embodiment, 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.

[0023] In this embodiment, the image data is black and white binarized data; the standard for generating black and white binarized 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.

[0024] In this embodiment, 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, the third voltage signal is output to the source line corresponding to the white pixel in the current row and the 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.

[0025] Specifically, the image data is black and white binary data. When writing data for the current video frame, white pixels are displayed, and the source voltage output has the same polarity as the AC common voltage. At this time, the voltage difference is 0, maintaining the white display in step S1. When displaying black pixels, the source voltage output has the opposite polarity to the AC common voltage. At this time, the voltage difference is 2A (which allows the cholesteric phase LC to enter the H state). Entering the H state, i.e., the transmission state, allows the black ink under the bottom layer to be transmitted, displaying black.

[0026] 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.

[0027] Specifically, after the forward scan is completed, the AC common electrode voltage and the source voltage output waveform are reversed, and the image is scanned again to complete polarity compensation and prevent cholesteric phase LCD polarization from causing the product to be unusable for a long time.

[0028] Specifically, the purpose of reverse scanning is to compensate for the polarity of the liquid crystal. That is, the forward AC common electrode voltage is 17.5V and the source voltage is -17.5V to enter the H state for blackening. Reverse scanning means that the AC common electrode voltage is -17.5V and the source voltage is +17.5V. Liquid crystal cannot be subjected to an electric field in one direction for a long time, otherwise it will become polarized. It needs to be driven by two electric fields, one positive and one negative, alternately to prevent polarization.

[0029] S4. Obtain the image data of the next frame of video, and repeat steps S2 and S3 to achieve dynamic image updates.

[0030] Specifically, based on TFT characteristics, for example: charging takes about 30µs, and with an FHD display resolution, there are 1080 lines; one frame takes 32.5ms, and the image is updated every frame, so 1 / 32.5ms = 30 frames per second. Since it does not need to enter a bistable state, the refresh rate can reach 25Hz~30Hz. The refresh rate is related to the TFT characteristics. If it is an oxide TFT or a faster LTPS device, the refresh rate will be higher. It is calculated based on the charging speed.

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

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

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

[0034] Reference Figures 1-4 The present invention proposes 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 as described in any of the above claims. The device includes: The display panel includes multiple cholesteric liquid crystal pixels arranged in a matrix. Gate driver, connected to multiple gate lines, is used for row-by-row pixel selection; 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: Control the gate driver and source driver to apply a first voltage signal to all pixels so that the full-screen liquid crystal enters a vertical alignment state; The system acquires image data and controls the gate driver and source driver 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 with the opposite polarity is applied again based on the image data for compensation. Repeat the above process to achieve dynamic image updates.

[0035] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

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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