JP2008070445A - Overdrive compensation method for shortening response time of passive matrix liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable a liquid crystal display device to smoothly display a dynamic screen by shortening liquid crystal response time with respect to amplitude selection drive (APT) of a passive matrix liquid crystal display device such as a twisted alignment (TN) mode and a supertwisted alignment (STN) mode without using a liquid crystal material for high speed response. <P>SOLUTION: An overdrive compensation method includes a step in which N pieces of frames of data electrode image data are assembled into a super frame, frame data newly incorporated in data input and previous frame data are compared with each other, and when the newly incorporated data is different from the previous data, an overdrive voltage which is higher than the high voltage of a conventional drive or lower than the low voltage of it to frames from the i-th to the j-th ones out of respective super frames is provided. Wherein, 2≤N, 1≤i, j≤N, and the overdrive voltage is equal to or more than 0 V and less than the maximum voltage of liquid crystal drive. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention is a driving technique for a passive matrix type liquid crystal display device, and in particular, for an amplitude selection drive (APT) of a passive matrix type liquid crystal display device (LCD), a dynamic screen is used by utilizing an overdrive compensation technique. It will make the broadcast even smoother.

In recent years, liquid crystal display devices are gradually replacing CRTs due to the light and thin characteristics of liquid crystal display devices and less power consumption than conventional CRT display devices.

Liquid crystal flat display devices are classified into two types according to the drive display method: passive matrix type (Passive Matrix-LCD; PM-LCD) and active matrix type (Active Matrix-LCD; AM-LCD). In the PM-LCD drive system, transparent ITO (Indium Tin Oxide) electrodes on the panel (X) direction are installed on the upper and lower glass plates, respectively, and the row (Y) direction is on the other panel. When electrodes are installed and the two panels are bonded together (filled with liquid crystal in the middle), the upper and lower panels form grid-like parts that cross the electrodes, that is, display panel pixels (Pixels). By providing a driving voltage and controlling the bipolar potential difference of the pixel, the liquid crystal in the pixel is rotated.

In the AM-LCD drive system, a switch element and a storage signal auxiliary capacitor are installed at each pixel position point on the panel, and each pixel drive is controlled independently by the element on the pixel. AM-LCD has a thin film transistor (TFT) element installed on a panel, and is also called TFT-LCD.

FIG. 1 is a schematic structural view of a passive matrix display device (m × n). Both the twisted array type (TN) and the super twisted array type (STN) are both PM-LCD products. Originally, the non-linear element has no operation to control the liquid crystal pixels, so each pixel 1 has a horizontal common (Common ) It is formed by the overlapping area of the electrode 2 search line and the data (Segment) electrode 3 search line perpendicular to the electrode 2 search line.

The basic operation principle of PM-LCD is the lightning effect generated by the rms value (RMS) applied with voltage using liquid crystal material, and the response time of liquid crystal material must be longer than the scan cycle of driving impulse, If the scan frequency (Frame rate) is 60 Hz, the time interval selected by each horizontal scan line (common electrode 2) is 16.67 ms, and the required response time of the liquid crystal material is generally 200 ms. This is a necessary condition for the rms value (RMS) response of the liquid crystal.

However, when the conventional amplitude selective drive (APT) method is used to display a dynamic screen, the response time of the liquid crystal material is too slow. This causes a serious Flicker phenomenon on the screen, and at the same time the screen contrast is greatly reduced.

In order to solve the above-described drawbacks and eliminate such drawbacks, the present invention is directed to an amplitude selective drive (APT) of a passive matrix liquid crystal display device such as a twist arrangement type (TN) and a super twist arrangement type (STN). It is to shorten the liquid crystal response time and enable a liquid crystal display device to smoothly display a dynamic screen without using a liquid crystal material that reacts quickly.

In order to achieve the above object, the present invention provides an overdrive compensation method for reducing the response time of a passive matrix type liquid crystal display device. The drive method used in the conventional passive matrix type liquid crystal display devices (twisted array type and super twisted array type) is amplitude selection drive (APT), and N frames in the data electrode image data are super-framed. ) And the dynamic screen is judged behind the bus (Bus) for inputting data, and the newly entered frame data and the previous frame data are compared with each other. If the newly entered data is different from the previous data, , Display a dynamic screen, and then provide the i th frame to the j th frame of each superframe with an overdrive voltage that is higher or lower than the high voltage or low voltage of the conventional drive, of which 2 ≦ N, When 1 ≦ i and j ≦ N, the overdrive voltage is greater than 0V and equal to It is smaller than a large voltage and equal. Thus, the liquid crystal between the common electrode and the data electrode achieves or approaches the given high voltage target brightness in a shorter time.

The present invention searches for different overdrive voltage values supplied by different screens using a table lookup operation (LUT) circuit using a table lookup method, and then outputs the corresponding overdrive output voltage values. The output voltage value sent out and sent out accurately outputs the overdrive voltage according to the data electrode, and is used in conventional passive matrix type liquid crystal display devices (twist arrangement type and super twist arrangement type) in this way. Thus, the response time required for the amplitude selection drive (APT) can be shortened effectively, and a serious double image phenomenon at the time of dynamic screen broadcasting can be greatly reduced.

Although the detailed content and technical description regarding the present invention will be described in detail based on examples, it should be understood that the examples are merely illustrative and should not be construed as implementation limitations in the present invention.

  FIG. 2 is a driving waveform schematic diagram of the first row n-column pixel of the conventional passive matrix type liquid crystal display device. The drive method used in the conventional passive matrix type liquid crystal display device (twist arrangement type and super twist arrangement type) is the amplitude selection drive (APT), and the synchronization timing signal Vs, common signal COM1, data signal SEGn (first row n) In the conventional driving method, the equivalent high voltage V2 or the equivalent low voltage V6 is supplied to the data electrodes of every frame by the reference voltage V4.

  FIG. 3 is a schematic diagram of driving waveforms of the first row n column pixels of the passive matrix type liquid crystal display device of the present invention. Examples of patented technology according to the present invention are as follows. One super-frame is assembled into four frames, N = 4, and behind the data input bus, it passes through the screen determination circuit 11 to determine the dynamic screen. (FIG. 4), the circuit compares the newly entered frame data and the previous frame data with each other, and if it is determined that the newly entered data and the previous data are different, a dynamic screen is displayed, and the screen judgment circuit 11 is elastic. The overdrive voltage V ′ higher than the high voltage V2 (or low voltage V6) of the conventional drive (or lower than the ground potential GND) for the i-th frame to the j-th frame of each superframe. Of which 1 ≦ i, j ≦ 4 and 0 ≦ V ′ ≦ the maximum voltage of the liquid crystal drive. FIG. 3 shows an example where i = 2 and j = 3. Of course, each of the superframes has an overdrive voltage V ′ higher than the conventional high voltage V2 (or low voltage V6) (or lower than the ground potential GND), or of each superframe. The i th frame to the j th frame are the overdrive voltage V ′ (eg, i = 1, j = 4). Thus, the liquid crystal between the common electrode 2 and the data electrode 3 can achieve or approximate the target luminance of the supplied high voltage in a shorter time.

  The basic operation principle of the amplitude selection drive (APT) used in the conventional passive matrix type liquid crystal display device (twist arrangement type and super twist arrangement type) is that the rms value (a value applied with a liquid crystal material) ( (RMS) is an electro-optic effect, and even if the overdrive voltage compensation method of the present invention passes the rms value (RMS), there is no significant flicker phenomenon and the screen contrast is enhanced.

  Further, according to the present invention, for the different values of the overdrive voltage V ′ provided by different screens, the current frame data newly entered by the screen judgment circuit 11 and the internal (or external) of the drive IC prior to that. If the dynamic screen is displayed differently compared with the frame data stored before the storage device 111 provided in the storage device 111), the table lookup operation (LUT) circuit 112 uses a table lookup. After searching, the output voltage value of the corresponding overdrive is sent out. The table lookup calculation creates a new overdrive voltage V 'numerical table with the matrix to be pulled, matches non-linear and complicated calculations and summarizes them with constants, and eliminates complicated calculations in the entire calculation process. To improve the image processing efficiency of image quality. Further, the output voltage numerical value sent out can accurately output the overdrive voltage V ′ corresponding to the data electrode 3. Thus, the drive method used in the conventional passive matrix type liquid crystal display device (twisted array type and super twisted array type) effectively reduces the response time that is the amplitude selective drive (APT), and a significant double in the dynamic screen. The appearance of the image phenomenon can be greatly reduced.

  The main spirit of the present invention is that the concept of the over driving compensation method in which the large active matrix thin film transistor liquid crystal display (TFT LCD) improves the dynamic screen response time is the twist type liquid crystal and the super twist type. Applied to (TN / STN) passive matrix liquid crystal display devices, in addition, the basic operation principle of amplitude selective drive (APT) is the electro-optic effect that generates rms value (RMS) by applying voltage using liquid crystal material Therefore, even if the overdrive voltage compensation method of the present invention passes the rms value (RMS), it does not cause a serious Flicker phenomenon.

The above description is only a preferred embodiment of the present invention, and does not limit the scope of the present invention. Accordingly, the scope of the patent application according to the present invention and the contents of the description of the invention are simplified. All such equivalent modifications or corrections are equally intended to be included within the scope of the present patent.

It is a structure schematic of a passive matrix type liquid crystal display device (m × n). It is a drive waveform schematic diagram of the conventional passive matrix type liquid crystal display device first row n column pixel. FIG. 3 is a schematic diagram of driving waveforms of the first-row n-column pixels of the passive matrix type liquid crystal display device of the present invention. It is a table look-up calculation quadrangle schematic diagram of the overdrive circuit of the present invention. It is a table look-up calculation quadrangle schematic diagram of the overdrive circuit of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pixel 11 Screen judgment circuit 111 Storage apparatus 112 Table lookup arithmetic circuit 2 Common electrode 3 Data electrode

Claims (2)

An overdrive compensation method for reducing the response time of a passive matrix type liquid crystal display device which is an amplitude selection drive used in a conventional passive matrix type liquid crystal display device,
The N frames in the data electrode image data are assembled into a super frame, and during data input, the newly entered frame data and the previous frame data are compared with each other. If the newly entered data differs from the previous data, Including the step of providing an overdrive voltage higher or lower than the high voltage or low voltage of the conventional drive to the i-th frame to the j-th frame of the superframe, with 2 ≦ N, 1 ≦ i, and j ≦ N An overdrive compensation method for shortening a response time of a passive matrix type liquid crystal display device, wherein the overdrive voltage is greater than 0 V, equal to and less than a maximum voltage for liquid crystal drive. 2. The method according to claim 1, further comprising the step of sending a different screen to a different overdrive voltage value after searching for the overdrive voltage value using a table lookup method by a table lookup operation circuit. An overdrive compensation method for reducing the response time of the passive matrix liquid crystal display device described.

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