TW563081B - Driving method for thin film transistor liquid crystal display - Google Patents

Abstract

The present invention relates to a driving method for thin film transistor liquid crystal display (TFT-LCD) by applying AC or DC signals on the common electrode of the storage capacitor for each pixel of the TFT substrate or on the opposite electrode of the liquid crystal during video-blanking periods. The applied AC or DC signals will cause a pre-added voltage in the liquid crystal of each pixel. Since the optical behavior of liquid crystal molecules is dependent on the root mean square value of the total applied voltage, the voltage for driving all the pixels can be decreased by using the pre-added voltage applied at each pixel. In particular, the threshold value of driving voltage can be considerably decreased; thereby a data driver IC with lower voltage can be employed, which leads to cost down.

Description

563081 V. Description of the invention (1) Technology. The present invention relates to a driving method of a thin film transistor liquid crystal display. This method uses an AC or DC signal to input a video signal during the neutral period (vide〇Bianking), thereby reducing the application. Driving voltage at all pixels. In the conventional thin film transistor liquid crystal display of the invention, the pre-tilt angle of the liquid crystal molecules is based on the alignment film (AHgnment)

Layer) 'Brushing into a slanted surface, so that when no voltage is applied to the liquid crystal molecules covered on it, it is aligned in the same direction due to its A1 ignment characteristics, with a preliminary The inclination angle, so that all the liquid crystal molecules can quickly rotate in the same direction after the driving voltage is applied, thus changing the transmittance. When a driving voltage is applied to a pixel, a cross-over voltage will appear on the LCD's liquid crystal capacitor. See FIG. 5 for the mean square. In the second liquid crystal display, the relationship between the root voltage VLC⑽s > and the light transmittance of the pixel in the liquid crystal capacitor of a pixel is shown. As shown in the figure, when one image shows a certain brightness, the mean square of the voltage across the liquid crystal capacitor is between, and it can hardly make a significant value of the light transmittance of the liquid crystal. The reason is that When the root-mean-square value of the trans-pressure is less than%, it is almost impossible to make the arrangement direction significant for the molecules. Once the root-mean-square value of the liquid 1 pressure is exceeded, the arrangement of the liquid crystal molecules should be It will change rapidly with the increase of the root mean square value of the voltage. According to the above ^

Page 5 V. Description of the invention (2) One can define VR in Figure 5 as the critical voltage. As described above, in the conventional thin film transistor liquid crystal display, the pretilt angle of the liquid crystal molecules is completely controlled by the inclined surface of the alignment film on the TO surface. To obtain a high inclination angle, and the alignment film with the same inclined surface, It is very difficult to make it, so the above-mentioned threshold voltage must exist. When the cross voltage of the liquid crystal cell changes from 0 to the threshold voltage Vr, there is almost no significant effect on the pixel. Therefore, if the threshold voltage% can be reduced, then Z drop: plus: the driving voltage outside the pixel, And effectively reduce the image into a single image; the column contains a plurality of pressure, the overall manufacturing cost image = ::::: low the sum of the additional driving electric invention summary dry i Π 'proposed by the present invention-a thin film transistor liquid crystal The display voltage is equal to the power of the image-free signal (K1 ... t〇r): the storage capacitance of each pixel on the two bases is a voltage signal, which is reduced by the injection of the eight-way electrode or the counter electrode of the liquid crystal.丄 == A voltage is generated in advance on the liquid crystal of the pixel, which reduces the threshold voltage of the driving voltage. In particular, the drive voltage of the integrated circuit (Data f) can be greatly driven. Therefore, lower voltage data can be used to avoid each pixel. rveF. We can keep the leakage current (TFT Leakage) connected to various flea and transistors, the method is, the pixel electrode potential of the transistor source as far as possible and the voltage signal in the film ^ image signal period, respectively The positive and negative phases, the storage capacitance of each pixel on the transistor substrate, a total of five, the description of the invention (3) The electrification and the potential of the liquid crystal electrode are as constant as possible. The effect of the counter electrode can be positive and negative voltage signals. The pixels cancel each other to maintain the voltage signal of each pixel on the substrate of the pixel electrode potential body. The two DC signals need to be close to zero to avoid affecting its characteristics. The connection method of the LCD drive gate Scanning line. The same method is used to generate a voltage value of the storage capacitor's common current signal or the direct current of multiple liquid crystals without pixels on the opposite side of the line or liquid crystal. The above-mentioned counter electrode 液晶 of the liquid crystal injection electrode f is injected into the thin film transistor, and the average value of the signal during the gap period is a direct current voltage when the signal is a direct current signal. The thin film transistor of the present invention is 〇r 〇n The storage capacitor is connected to the adjacent one, and the adjacent scanning number is used, so that the liquid crystal of each pixel Detailed description of the drum-best embodiment FIG. 1 is a schematic diagram showing the working principle of a thin film transistor liquid crystal display according to the present invention. # Mainly includes: a pixel array u, a scanning line driving circuit 13 and a signal line driving circuit 12. The pixel array n includes a plurality of pixels. The driving method of a mother pixel is as follows: & is the scan line of the < column, and when the scan line is at a high potential, the plurality of transistors on the scan line are turned on (ON ) State, at this time, the potentials of the signal lines such as D !, D2, d3 ~ Dn will be written into the source of the transistors (that is, the pixel electrode), so that a voltage across the liquid crystal capacitor (cLC) appears when scanning When line 01 returns to the low potential state, the corresponding transistor is turned off. Then the next scan line h goes high, repeating the driver in the next stage. 563081 V. Description of the invention (4) where 'Pi is the common electrode of the storage capacitor of each pixel on the thin film transistor substrate, and P2 is the opposite electrode of the liquid crystal, which is generally the IT0 electrode on the color filter 3 substrate. . Cst is the storage capacitor and ° c is the liquid crystal capacitor. LC " Fig. 2 is a schematic diagram showing a comparison of a driving voltage method of a thin film transistor liquid crystal display used in the present invention with a conventional driving voltage method. In order to facilitate the description, Pi and & electrodes using a conventional driving voltage method are denoted by PlA and 4, respectively, and P1 and Dz electrodes using a driving voltage method of the present invention are denoted by P1B and PZB, respectively. The conventional driving voltage mode_general system "connects P1A and L together and drives with DC voltage, as shown in Figure 2 PZA, where VP1A = Vm. On the other hand, the driving mode of the present invention ... The LCD LCD has an image signal period 21, the driving voltage method of P2B is consistent with the conventional technology. However, in the thin film transistor. The display device has no image signal interval 22, which can be exchanged directly with D and P, respectively. Signal, this AC or DC signal is generated on its liquid crystal capacitor for each ^ effect-the voltage value is added to the voltage written by the data signal line of this pixel, and the electricity appearing on the liquid capacitor is It is the sum of the applied voltage and the written voltage. The schematic diagram of the working principle of the thin film transistor liquid crystal display of the present invention by Beco "Line" is the main difference between the 15 dynamic voltages and the storage capacitor C. . The first and the first; the embodiment, such as the first scanning line, the lamp of each pixel stores f the next scanning line. Example Draw line G2, the pixel capacitor CsT of each pixel on scan line g2 is connected to the stray storage capacitor CST of the second scan pixel and connected to the third scan 563081 V. Description of the invention (5) Draw line g3, the rest are similar. This connection method is called storage capacitor on gate. The storage capacitance of each pixel on a certain scanning line is connected to the previous or next scanning line. In the embodiment of the present invention, a storage capacitor is used to connect to the next scanning line ^. FIG. 4 is a schematic diagram showing a comparison of a driving voltage method of a storage capacitor on gate and a conventional driving voltage method of a thin film transistor liquid crystal display of the present invention. For the convenience of explanation, the A and & electrodes using the driving voltage method of% ° are represented by 'and dagger respectively; while the G2 and 5 electrodes using the driving voltage method of the present invention are expressed by & and the heart watch, respectively No. The conventional driving voltage method uses a DC voltage Vf ^ to drive the counter electrode dagger, as shown in FIG. 4. As for the common electrode of CST, it is connected to the next scanning line & therefore, the signal on it is the same as the signal appearing on the next one, as shown in Figure 4 '. On the other hand, the electric method of the present invention is in the period during which the thin film transistor liquid crystal display has an image signal. The dynamic voltage method is consistent with the conventional technique. However, in the gap period of the thin film transistor liquid crystal LCD without image signal 22, the present invention adopts the method of Storage 2 =, Gate, and injects AC or straight two numbers at 'and b, respectively. This AC or DC signal will The effect brought by one pixel is to generate a voltage value on its liquid crystal capacitor, which will not be repeated here. ♦ = Exceeding the method of Storage Capacitor on Gate, g warranty = In the thin film transistor liquid crystal display, there is no image signal gap period 1 ^ The potential on the next scanning line will not cause the corresponding film of the scanning line The transistor is turned on. The voltage signal of P1B and the core in FIG. 2 or g2B and ρ2B in FIG.

Page 9 (1) 563081 V. Description of the invention (6) The effective driving voltage vG generated is calculated as follows ...

The pre-added root mean square voltage (VRMS) is calculated as

Therefore, the voltage signals of 4 or gzb and dagger are applied to all boxes ^ a + 丄》 each suppression / "^ ^ (2)

In the above formula, τ is the period during which there is no image signal, and the voltage signal / main input period, TFRAME is updated for each image frame (v 丨 de〇 J

Refresh Frame). For = thin film transistor leakage problem, you can make the pixel's electricity (H H ί transistor potential) as far as possible, I can ί; Ϊ:: f Clc and storage capacitor Cst capacitance value ratio Relations, Yu; Guang; P09, respectively, inject positive and negative signals into the electrodes P1B and /, and P: injected in the embodiment of Figure 2 and Figure 4; reduce the wave time: 'easy sine wave and other waveforms, To

And P2B or G2B and P2B each have a change in symmetry, which may cause the delay of each element of the "face" element of p1B to be different. However, the electrodes P1B and L or (^ and? The long-term average detection is 2B. 彳 ° can also be a direct slave signal, and the average time) is close to zero. During the gap period of several gap periods with no image signal, add positive electricity = as in the first If there is no picture signal in the picture frame and no picture signal gap n ^ DC signal, a negative voltage DC signal can be added between the picture frames.

Page 10 563081 V. Description of the invention (7) It is worth noting that the driving method of the thin film transistor liquid crystal display according to the present invention can also be applied to an IPS (In Plane Switching) type without a counter electrode having a color filter. LCD display, in this case no image # 5 Tiger's air-during period 'by the common electrode of each pixel (Common

Electrode) or an adjacent known trace (in the case of the Common Electrode on Gate) injected AC signal or DC signal can also achieve the same effect. The transmissivity of the crystal capacitor Cu is again the same as the change in the root mean square added to it. The invention of the driver's accumulated voltage #Refer to Figure 5 for the voltage across the liquid crystal and the liquid crystal on the liquid crystal. The brightness voltage displayed by the circuit of the present invention is based on the brightness of the pixel. Liquid root mean square value (VLC⑽S). Since the tilt angle of the son of the liquid crystal is related, and the root-mean-square voltage of the tilt angle of the liquid crystal molecules is related, the light transmittance of the liquid crystal is determined by the rms value of the sum, and within 0 to%, it is almost impossible to make the liquid crystal produce a significant By adding the above-mentioned pre-applied voltage, the transmission rate can reduce the driving voltage that data needs to provide to the pixel, especially the drive (equivalent to Vr in FIG. 5) can be greatly reduced. The invention provides a thin film thief

It can reduce the driving voltage of thin film transistor liquid crystal display :: d ”device ’s driving voltage, especially the driving voltage can be greatly reduced. :: II on the pixel uses lower voltage data to drive the β boundary voltage. So, y

The righteous benedictor integrated circuit 0 — integrated circuit with A A A voltage, its cost is lower, and S, the lower the overall cost of the LCD. -Be sure to reduce the thin-film electricity generation

Page 11 563081 V. Description of the invention (8) Only for easy explanation of the technical content of the present invention, and not to limit the present invention to this embodiment in a narrow sense, without exceeding the spirit of the present invention and the scope of patent application below, Various changes can be implemented.

Page 12 563081 Brief Description of Drawings Figure 1 is a schematic diagram showing the working principle of a thin film transistor liquid crystal display (TFT LCD) according to the present invention. Fig. 2 shows a comparison diagram of a driving voltage method and a conventional driving voltage method of a thin film transistor liquid crystal display of the present invention. FIG. 3 is a schematic diagram showing a working principle of a thin film transistor liquid crystal display (TFT LCD) according to the present invention using a Storage Capacitor on Gate method. Fig. 4 is a schematic diagram showing a comparison between a driving voltage method and a conventional driving voltage method of the thin film transistor liquid crystal display of the present invention, which adopts the Stoga Capacitor on Gate method. FIG. 5 shows the root-mean-square value of the cross-voltage across a liquid crystal capacitor of a pixel in a thin film transistor liquid crystal display νί (: (KM) and the light transmittance of the pixel. Explanation of symbols 11 to pixel array 12 to signal lines Drive circuit 1 3 to scan line drive circuit 1 4 to pixels 2 1 to thin film transistor with image signal period 22 to thin film transistor without image signal period

Page 13

Claims (1)

563081 VI. Application for Patent Scope 1.-A driving method of thin film transistor liquid crystal display 'Using thin film transistor liquid crystal display in the period of no video signal (vide〇Blanking)' by the storage capacitor of each pixel on the thin film transistor substrate The common electrode of (Storage CaPaci tor) or the counter electrode of liquid crystal is injected with a voltage signal ^, thereby generating a voltage value on the liquid crystal of each pixel, so the driving voltage for driving each pixel can be greatly reduced. The threshold voltage of the voltage, so you can use a lower voltage: Driver Data driver integrated circuit (Data Driver κ). Use the low battery & 2 as the application of the first scope of the patent application_Tai's driving method, in which there is no image signal, said the eight-body liquid crystal display instead of the voltage signal on the thin film transistor base // Do not inject positive and negative phases of the common electrode and the liquid crystal. The source potential of the storage capacitor body of each pixel is kept as constant as possible, so as to make the leakage of the transistor of each pixel. Avoid the thin film transistor of each pixel 3. If the driving method of the second item of the patent application is applied, the common electrode of the storage capacitor of the thin film liquid crystal display and the crystal substrate of the liquid crystal are injected. Pixel's streaming signal. The voltage signal to the electrode is cross 4. The driving method according to item 2 of the patent application range, wherein the common electrode injected into the storage capacitor of the thin film transistor liquid crystal display and the liquid crystal: each pixel on the body substrate The two DC signals have a straight average value close to zero in the voltage signals of the plurality of two electrodes. ", During the empty slot of the video signal 563081 VI. For the driving method of the patent application, the valley system is connected to the positive and negative opposite electrodes of the phase injection, and M is not changed to avoid the driving method of 6 as described above, and the driving method of 7 as stated, and The pair of signals of the liquid crystal are in a plurality of the thin adjacent scanning voltage signals, so that each of the pixels is patented in a μ patent, which is in a non-directional electrode, which is in a non-directional signal-free signal film transistor substrate. For each sketch line, during the period when there is no image signal, the f electric number is at the source potential of the adjacent scan line, the other tc body; this is the leakage of the film transistor. Here, during the period of the video signal of the thin boat hall around item 5, the electric signal of the liquid crystal display is an AC signal. The electric two-body liquid crystal display is displayed between the scanning lines, and the voltage signal of the device is Ji Er / Empty Γ into each scanning line number, the child is born, and the average value between the two DC fields 4 is close to zero. 15th stomach