JP2004004857A - Active matrix type liquid crystal indicator and driving method for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an active matrix type liquid crystal indicator and a driving method for the same, which attain a high display quality and a low power consumption even when adopting a driving method of interlaced scanning for pixel electrodes. <P>SOLUTION: The driving method is provided for the active matrix type liquid crystal indicator provided with a display part 30 having a plurality of pixel electrodes P arranged in a matrix and a scanning driver 32 for interlaced scanning of at least a part of the plurality of pixel electrodes P. At least a part of pixel electrodes P is divided into a plurality of areas in the column direction, and the scanning driver 32 performs interlaced scanning of pixel electrodes in the plurality of areas and pixel electrodes on both sides of boundaries of the plurality of areas in the order from an odd row to an even row in one frame and in the opposite order from an even row to an odd row in the next frame. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an active matrix type (active matrix type) liquid crystal display typified by a TFT (thin film transistor) type liquid crystal display and a driving method thereof, and in particular, a display device of a portable device or the like which requires low power consumption. The present invention relates to an active matrix type liquid crystal display used as a device and a driving method thereof.
[0002]
[Prior art]
FIG. 1 is a conceptual diagram of a liquid crystal display. The liquid crystal display includes an active matrix substrate, a counter substrate, and a liquid crystal layer sandwiched therebetween. On the active matrix substrate, as shown in FIG. 1, a display unit 30 including a plurality of pixel electrodes P arranged in a matrix, and a plurality of rows for applying a scanning signal (gate voltage) to the plurality of pixel electrodes P. An electrode (scanning line or gate electrode) G, a plurality of column electrodes (source electrodes) S for applying a data signal (grayscale voltage) to the plurality of pixel electrodes P, a pixel electrode P, a row electrode G, and a column electrode S , A scan driver (gate driver) 32 for driving the row electrodes G, and a data driver (data driver) 34 for driving the column electrodes S. The common electrode 36 is formed on the counter substrate.
[0003]
The scan driver 32 is controlled by the control unit 38 and receives a gate voltage from the gate voltage generation circuit 40. The data driver 34 is controlled by the control unit 38 and receives a gray scale voltage from the gray scale voltage generation circuit 42. The common electrode 36 is driven by receiving the common electrode voltage Vcom from the common electrode drive circuit 44.
[0004]
When driving the above active matrix type liquid crystal display, generally, the polarity of the voltage applied to the liquid crystal is alternately inverted (this is called “AC driving of the liquid crystal”) so that no DC voltage is applied to the liquid crystal. Have been devised. This is because the liquid crystal has a property that the characteristics are deteriorated when a DC voltage is applied. The most widely used method of AC driving of a liquid crystal in the past is the row inversion method (also called “line inversion method”) shown in FIG. According to this method, the polarity of the voltage applied to the liquid crystal is inverted for each row (scanning line) and for each frame. When the polarity inversion for each row is added to the polarity inversion for each row, the pixel inversion method (also referred to as “dot inversion”) shown in FIG. The pixel inversion method is becoming mainstream especially for driving a large and high-definition display device of XGA type or higher due to its high display quality.
[0005]
FIG. 4 shows an equivalent circuit corresponding to the simplest one pixel P (i, j). The capacitance of the pixel is mainly composed of the pixel electrode and the auxiliary electrode (additional electrode). In FIG. 4, the total capacitance is Cp.
[0006]
FIG. 5 shows the drive timing of each part of the display shown in FIG. 1 and the applied voltage waveform. In FIG. 5, Vsyn and Hsyn represent a vertical synchronization signal and a horizontal synchronization signal, respectively. When the output VG (j) of the scan driver corresponding to the j-th row becomes high potential, the switch element T (i, j) corresponding to the pixel P (i, j) in the j-th row is turned on, and the pixel P (i) , J) are charged by the output S (i) of the data driver at that time. When VG (j) becomes low potential, the switching element T (i, j) is turned off, and the electric charge charged to the pixel P (i, j) continues until T (i, j) is turned on. During the storage, the liquid crystal filled between the pixel electrode and the common electrode is continuously driven. In FIG. 5, the number assigned to the horizontal synchronization signal indicates a horizontal period in which the image signal for the pixel of the row of the number is transmitted. Since the data driver samples and stores the data in the first row and outputs the data in the next horizontal period, the scanning driver in the corresponding row sets the output to a high potential only in the horizontal period during which data is transmitted. One horizontal period later.
[0007]
FIG. 6 shows an equivalent circuit of one data line of the liquid crystal display. Cd and Rd respectively indicate the capacitance and resistance of the data line represented by a lumped constant, Cp indicates the pixel capacitance, and Ron indicates the on-resistance of the switch element. Although the circuit of FIG. 6 becomes a load for one output of the data driver, the pixel capacitance Cp is smaller by two to three orders of magnitude than the data line capacitance Cd, and thus can be ignored as a load of the driver. Therefore, it is sufficient to consider the data line resistance Rd and the data line capacitance Cd as the load of the driver. By the way, the circuit of FIG. 6 exists in a one-to-one correspondence with the output of the data driver, and the entire display is, for example, a VGA type which has a relatively medium resolution at present, if it is a color display. There are 640 × 3 = 1920 lines, and the load of the data driver as a whole becomes considerably large. In a row inversion method or a pixel inversion method in which the output of the data driver needs to be inverted for each scanning line, the power consumption increases because the capacitor Cd is charged and discharged between positive and negative polarities for each output operation. Problem arises.
[0008]
As one method for preventing the above increase in power consumption, Japanese Patent Application Laid-Open No. 8-32067 proposes interlaced scanning. "Interlaced scanning" refers to scanning all the odd-numbered (or even-numbered) pixel electrodes first, and then scanning the remaining even-numbered (or odd-numbered) pixel electrodes. In this method, the rows of pixels having the same polarity are sequentially scanned, so that the increase in the power consumption can be suppressed. When scanning of one frame (that is, scanning of both odd and even rows) is completed, a state similar to that in FIG. 2 or FIG. 3 is obtained.
[0009]
[Problems to be solved by the invention]
However, new problems associated with the above-described interlaced scanning include a flicker that cannot be ignored sometimes, a deterioration in the image quality of a moving image having a large motion, and a slight problem caused by the influence of the coupling capacitance between the pixel electrodes between adjacent rows. This is the occurrence of slight horizontal stripes due to the difference in gradation.
[0010]
The present invention has been made in view of the above circumstances, and an object of the present invention is to reduce the image quality such as flicker or the gradation between adjacent rows even when using a driving method of performing interlaced scanning on pixel electrodes. It is an object of the present invention to provide an active matrix type liquid crystal display capable of achieving high display quality and low power consumption without causing horizontal stripes due to the difference between the above and a driving method thereof.
[0011]
[Means for Solving the Problems]
The driving method of the active matrix type liquid crystal display according to the present invention comprises a plurality of pixel electrodes arranged in a matrix, a plurality of row electrodes each providing a scanning signal to the same row of pixel electrodes, and a plurality of pixel electrodes in the same column. A plurality of column electrodes each providing a data signal to the display section, and a plurality of continuous row electrodes in at least a first section of the display section and a second section adjacent to the first section. For a plurality of continuous row electrodes, after sequentially scanning either one of the odd-numbered rows or the even-numbered rows, the other row electrodes of the odd-numbered rows or the even-numbered rows are sequentially scanned in the same direction. A method of driving an active matrix liquid crystal display in which interlaced scanning is performed for each frame, wherein a scanning order of the interlaced scanning performed in each of the first and second areas in a second frame is defined as a first frame. At Serial respectively the odd and even rows of the scanning order of the interlace scanning for the opposite takes place in the first and second zones.
[0012]
The positions of the boundaries of the row electrodes in the first area and the second area are different between the first frame and the second frame.
[0013]
The active matrix type liquid crystal display according to the present invention includes a plurality of pixel electrodes arranged in a matrix, a plurality of row electrodes respectively providing scan signals to the same row of pixel electrodes, and a plurality of pixel electrodes in the same column. A display section provided with a plurality of column electrodes each providing a data signal; a plurality of continuous row electrodes in at least a first section of the display section; and a plurality of continuous row electrodes in a second section adjacent to the first section. For the row electrodes, respectively, after sequentially scanning either one of the odd-numbered rows or the even-numbered rows, the interlaced scanning of sequentially scanning the other row electrodes of the odd-numbered rows or the even-numbered rows in the same direction, An active matrix type liquid crystal display having a scan driver for each frame, wherein the scan driver performs a scan order of the interlaced scan performed in each of the first and second areas in a second frame. The first frame Is adapted to the opposite of the odd and even rows of the scanning order of the interlaced scanning is performed in said first and second zones in arm.
[0014]
The scan driver causes a position of a boundary between row electrodes in the first area and the second area to be different between the first frame and the second frame.
[0015]
The pixel electrodes in the uppermost row and the lowermost row of the display section are covered with a light shielding mask.
[0016]
Black data is displayed on the pixel electrodes in the uppermost row and the lowermost row of the display unit.
[0017]
The driving method of the active matrix type liquid crystal display according to the present invention comprises a plurality of pixel electrodes arranged in a matrix, a plurality of row electrodes each providing a scanning signal to the same row of pixel electrodes, and a plurality of pixel electrodes in the same column. And a display unit provided with a plurality of column electrodes each of which applies a data signal to the display unit, such that three or more areas each having a plurality of continuous row electrodes are adjacent to each other. It is provided side by side, for each of a plurality of continuous row electrodes of each area, after sequentially scanning one of the odd-numbered rows or even-numbered row electrodes, respectively, the other of the odd-numbered rows or even-numbered rows A method of driving an active matrix type liquid crystal display, in which interlaced scanning for sequentially scanning row electrodes in the same direction is performed continuously in the order in which each area is arranged for each frame, wherein each area is arranged in a second frame. Done at The interlaced scanning order of the scanning, to oppose said odd and even rows of the scanning order of the interlaced scanning is performed in each zone in the first frame that.
[0018]
The active matrix type liquid crystal display according to the present invention includes a plurality of pixel electrodes arranged in a matrix, a plurality of row electrodes respectively providing scan signals to the same row of pixel electrodes, and a plurality of pixel electrodes in the same column. A display unit provided with a plurality of column electrodes each providing a data signal, and at least three areas each having a plurality of continuous row electrodes are provided so as to be adjacent to each other; After sequentially scanning one of the odd-numbered rows or the even-numbered rows, the other row electrodes of the odd-numbered rows or the even-numbered rows in the same direction are sequentially scanned with respect to the plurality of continuous row electrodes of the respective sections. An active matrix type liquid crystal display having a scanning driver for performing interlaced scanning for scanning in order, in which each area is lined up for each frame, in succession, in the second frame. Each of the above The scanning order of the interlaced scanning, respectively carried out in frequency, which is the the odd and even rows of the scanning order of the interlaced scanning is performed in each zone in the first frame to be reversed.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
As a countermeasure against flicker and image quality deterioration due to the above-described interlaced scanning, a method has been proposed in which the display unit is divided into a plurality of sections in the column direction and interlaced scanning is completed for each area. Japanese Patent Application No. Hei 10-161199). With this method, power consumption can be reliably reduced, and flickering and image quality deterioration of a moving image having large motion can be suppressed. However, the gradation is slightly different between the odd-numbered rows and the even-numbered rows, and the phenomenon that slight horizontal stripes are generated every other row still remains, and a new problem occurs in that the boundary of each area occurs.
[0020]
The reason why the above problem occurs will be described below. In the following description, the polarity of the pixels in the same row will be described in a row inversion mode in which the polarity is the same. However, in the pixel inversion mode, only the polarity is inverted for each column, and the content of the description can be applied as it is. The description of the pixel inversion mode is omitted.
[0021]
<About horizontal stripes every other line>
FIGS. 7A to 7D show the state transition of the voltage polarity when the pixel electrode is skipped and scanned. FIG. 7A shows a state immediately before a new frame starts. At this time, the voltage polarity of each pixel is in a row inversion state. By scanning only the odd-numbered rows from here, the voltage polarities of the pixels in the odd-numbered rows are inverted, and the state shifts to the state shown in FIG. Next, by scanning the even-numbered rows, the voltage polarities of the pixels in the even-numbered rows are inverted, and the state shifts to the state shown in FIG. The state in FIG. 7C is a state in which scanning of one frame is completed. In the next frame, the state shifts to the state of FIG. 7A via the state of FIG. 7D in the same manner (however, the polarity is reversed).
[0022]
FIG. 8 shows four (that is, over four rows) pixel electrodes P adjacent in the column direction (TFT switch elements are omitted). Since a scanning line (gate line) exists between the pixel electrodes P and the sides in the scanning line direction are parallel, a coupling capacitance Cpp exists between adjacent pixel electrodes. The charge is held in the coupling capacitance Cpp by the voltage difference V between the two adjacent pixel electrodes, and the magnitude of the charge is a function of the voltage difference V, and is 0 when V = 0, and V (Where V ≧ 0). Since the dielectric constant of the liquid crystal changes depending on the alignment state, the coupling capacitance Cpp itself is also a function of the voltage difference V.
[0023]
FIGS. 9A and 9B respectively show the case where charge is generated in the coupling capacitance Cpp and the case where charge is not generated in the coupling capacitance Cpp (that is, all four pixel electrodes shown in FIG. 8 are at the same potential). 4 shows an equivalent circuit of four pixel electrodes. It is assumed that the same data is written on the entire screen. Note that “writing data” means charging a pixel electrode with a voltage corresponding to data (the same applies hereinafter).
[0024]
When transitioning from the state of FIG. 7A to the state of FIG. 7B and transitioning from the state of FIG. 7C to the state of FIG. 7D, charges due to the coupling capacitance Cpp appear. The state changes from the existing state to the disappearing state. For simplicity, the effect between pixels in two adjacent rows will be described with reference to FIGS. When the pixels in the odd rows are written while the switch elements A in the even rows are open, the moving state of the electric charges is from FIG. 10A to FIG. 10B or from FIG. 10C to FIG. ). Since the switch element A in the even-numbered row remains open, the electric charge of −q or + q captured by the capacitance Cpp moves to the pixel electrode in the even-numbered row due to the disappearance of the voltage difference between both ends of the capacitance Cpp. The charge of the pixel electrode increases to-(Q + q) or (Q + q). That is, writing data to the pixels in one row (odd-numbered row) acts to increase the voltage of the pixels in the adjacent row (even-numbered row). Strictly speaking, due to the slight potential difference generated here, a small amount of charge remains between the capacitors A and B between the capacitors A and B, but can be ignored because it is extremely small with respect to the original charge q. Note that “deeper voltage” means that the potential difference between the pixel electrode and the common electrode becomes larger (the same applies hereinafter).
[0025]
In addition, in FIGS. 10A and 10C, the charges of the pixels in the odd-numbered rows are Qq and − (Qq), respectively, as will be apparent from the following description of FIG. This is the result of the influence of the transition from the state of FIG. 7D to the state of FIG. 7A or the state of FIG. 7B to the state of FIG. . Since the adjacent row is an even row in the above case, a voltage is applied to the even row deeper than the original gradation.
[0026]
When the state of FIG. 7B is changed from the state of FIG. 7B to the state of FIG. 7C or the state of FIG. 7D is changed to the state of FIG. ) From the state of FIG. 11 (c) or FIG. 11 (d) to the state of FIG. 11 (a). The appearance of a voltage difference between adjacent rows causes the electric charge of the pixel electrode to move to the capacitance Cpp, and acts to lower the voltage for the pixels in the adjacent row. “The voltage becomes shallow” means that the potential difference between the pixel electrode and the common electrode becomes small (the same applies hereinafter). In this case, the adjacent row is an odd-numbered row, so that the voltage of the odd-numbered row becomes shallower than the original gradation.
[0027]
As described above, when a potential having the same polarity as the voltage of the electrode is written to an electrode adjacent to a certain electrode, the voltage of the electrode becomes deep. Voltage becomes shallower. For this reason, in the case of a normally black display, the odd-numbered rows are thinner than the original gradations, and the even-numbered rows are darker, so that a slight gradation difference occurs between the even-numbered rows and the odd-numbered rows. It will be observed as thin horizontal stripes every other line.
[0028]
FIG. 12 shows the driving waveforms when the display includes eight rows of pixel electrodes and scanning lines. In the following, for the sake of simplicity, it is assumed that the display has eight scanning lines unless otherwise specified. Although the number of scanning lines of an actual display is much larger, for example, 726, the principle of driving is exactly the same. In FIG. 12, VP (i, 3) and VP (i, 4) represent the potentials of the pixel electrodes in the third and fourth rows, respectively. Show.
[0029]
As described above, when a potential having the same polarity as that of the voltage of the electrode is written to an electrode adjacent to a certain electrode, the voltage of the electrode becomes deeper, while when a voltage of the opposite polarity is written, the voltage of the electrode becomes higher. Becomes shallower. This is reflected in the waveform shown in FIG. That is, VP (i, 3), which is an odd row, changes so that the voltage becomes shallower in successive frames, and PV (i, 4), which is an even row, changes so that the voltage becomes deeper. ing.
[0030]
Note that other factors, such as a pull-in voltage when the gate is turned off, also exist as a factor that causes the potential of the pixel to fluctuate. Similar). In addition, the fluctuation of the potential is extremely exaggerated for visual recognition. Although the actual level of the potential fluctuation depends on the characteristics of the display and cannot be unconditionally determined, it is, for example, about 1% of the pixel electrode potential with respect to the common electrode.
[0031]
<About the boundaries of the area>
Hereinafter, a description will be given of a cause of the occurrence of the boundary of the area in the method of dividing the display unit into a plurality of areas in the column direction and performing interlaced scanning for each area.
[0032]
When the screen of the display is divided into a plurality of areas in the column direction and interlaced scanning is performed in each area in order to prevent flickering (flicker) due to interlaced scanning and deterioration of moving image quality, the above-mentioned every other row is used. In addition to the light horizontal stripes, boundaries of areas appearing on the screen by a luminance pattern different from the horizontal stripes are generated.
[0033]
For example, as shown in FIG. 13, four lines are made into one area (areas 1 and 2) for a display having eight lines of pixel electrodes, and interlaced scanning is performed in the order of odd two lines to even two lines. The voltage fluctuation of each line in this case is shown in FIGS. The above-mentioned phenomenon (when a potential having the same polarity as the voltage of the electrode is written to an electrode adjacent to a certain electrode, the voltage of that electrode becomes deep, and when a voltage of the opposite polarity is written, the voltage of that electrode becomes shallow. Accordingly, the voltages of the respective pixel electrodes at the time points (i) and (q) at which the writing of the pixels of all the lines is completed are as follows based on the voltage due to the writing charge ± Q.
[0034]
Line 1: The voltage is shallow by the charge q due to the influence of line 2.
Line 2: Reference voltage
Line 3: The voltage is reduced by the charge of 2q due to the influence of the lines 2 and 4.
Line 4: Due to the influence of line 5, the voltage becomes shallower by charge q.
Line 5: Due to the influence of line 6, the voltage becomes shallower by charge q.
Line 6: Reference voltage
Line 7: The voltage is reduced by the charge of 2q due to the influence of lines 6 and 8.
Line 8: Reference voltage
The voltages appearing in the writing process up to states (i) and (q) have the same tendency as described above in that the charge is shallow and deep. That is, lines 2, 6 and 8 are deep, lines 1, 4 and 5 are shallow, and lines 3 and 7 are even shallower.
[0035]
Considering the voltage difference between the above lines as a display of a normally black display, [display of (i)] shown in FIG. 14B and [display of (q)] shown in FIG. 14D The display is displayed, and in addition to the horizontal stripes every other line, a light and light (4th and 5th lines) pattern appears as a boundary (if only horizontal stripes are present, the 4th and 5th lines become dark and light patterns).
[0036]
The above description has been given of the case where data is first written to the odd-numbered rows of pixels, and then the data is written to the even-numbered rows of pixels. However, this also occurs when the even-numbered rows are written first and the odd-numbered rows are written later. Since the cause of the problem is the same, the description is omitted.
[0037]
The present invention prevents display deterioration of an image based on the coupling capacitance between adjacent pixels on the same column as described above even when performing interlaced scanning of the entire screen or a part of the screen in order to reduce power consumption. This is intended to realize a high-quality display without horizontal stripes and area boundaries.
[0038]
<Basic concept of the present invention>
As discussed above, when all or part of the screen is interlacedly scanned in a certain field, when the voltage polarity of the pixels in the adjacent row changes from a different state to the same state, writing is performed in the previous field. The voltage of the shifted pixel changes to be deeper. When the voltage polarity of the pixels in the adjacent row changes from the same state to a different state, the voltage of the pixel written in the previous field changes so as to be shallow.
[0039]
In view of this situation, in order to eliminate the horizontal stripes in every other row, the present invention makes the voltage of a row of pixels low in one frame and the voltage of the next frame increases in the next frame. . As a result, the change in the voltage of the pixel is canceled in the consecutive frames, and a uniform voltage is applied to the pixel as an effective value. More specifically, in a part where interlaced scanning is performed, in a certain frame, when scanning is performed in the first scanning order in which scanning of odd-numbered pixel electrodes is performed after scanning of odd-numbered pixel electrodes in a certain frame, In the frame, scanning is performed in a second scanning order in which scanning of odd-numbered pixel electrodes is performed after scanning of even-numbered pixel electrodes in the opposite order to the first scanning order. That is, the first scanning order and the second scanning order are alternated for each frame, thereby eliminating horizontal stripes every other row.
[0040]
On the other hand, the cause of the appearance of the area boundary is that the writing order between two lines (odd and even lines) sandwiching the boundary is opposite to the writing order in the area before and after the boundary. As can be seen from FIG. 13, the order of writing in the area before and after the boundary is odd → even, but the upper and lower lines (fourth and fifth lines) sandwiching the boundary are even → odd. For this reason, after writing the fourth line of the area 1, the opposite voltage is written to the fifth line, so that the voltage of the fourth line becomes shallower. By reversing the writing order, the boundary pattern, which should be the same as the pattern (horizontal stripe) before and after the boundary, becomes a different pattern, and the boundary of the area appears. As shown in [display of (i)] in FIG. 14B and [display of (q)] in FIG. 14D, the lines above and below the boundary, which should be originally shaded, are shaded. Note that the cause of this shading is the same as that of horizontal stripes.
[0041]
From the above considerations, it can be seen that the boundary can be erased by performing scanning so that the writing order is not reversed at the boundary. Specifically, description will be made with reference to FIGS. FIGS. 15A and 15B are schematic diagrams of the display unit 30 (FIG. 1) showing one row of pixels as one line. These figures show the order of scanning over two frames (frame (a) and frame (b)). The numbers written on the left end are the numbers of the pixel rows counted in order from the top of the screen, and the numbers shown in circles indicate the order of scanning. As shown in FIG. 15A, the line above the boundary (fifth line) is the first field in the area, and the line below the boundary (sixth line) is the second field in the area. The boundary can be eliminated by scanning as follows. For example, when the upper line scans as an odd group in the first field of area 1, the lower line scans as an even group in the second field of area 2. Alternatively, as shown in FIG. 15B, when the upper line (fourth line) is scanned as an even group in the first field of the area 1, the lower line (fifth line) is scanned in the second field of the area 2 To perform scanning as an odd group.
[0042]
Even if the boundaries are erased by the method shown in FIG. 15, horizontal stripes remain, so another frame without boundaries that cancels out the respective voltage fluctuations is prepared, and by scanning the two frames continuously, the horizontal stripes are also removed. A display without borders becomes possible. More specifically, scanning for eliminating the above-described boundary is performed, and frames in which the scanning order (the first scanning order and the second scanning order described above) are reversed are continued. For example, the frame of FIG. 15A and the frame of FIG. 15B are continuously scanned.
[0043]
Even when scanning is performed to eliminate horizontal stripes and boundaries as described above, the uppermost row and the lowermost row of pixels of a screen having no adjacent row on one side have a higher gradation than the other rows. FIGS. 16A, 16B, 17A and 17B show the movement of the electric charges when the driving shown in FIGS. 15A and 15B is performed. At the time when the writing of all the lines is completed, by adding the charges of (i) in FIG. 16B and (i) in FIG. 17B, the second line to the seventh line become + 2q, but the first line and the eighth line The line is + q. Thus, when the frame of FIG. 15A and the frame of FIG. 15B are alternately and continuously scanned, it can be understood that the first line and the eighth line have a higher gradation than the other lines.
[0044]
In response to the above-mentioned phenomenon, masks are applied to the upper and lower rows of the display unit so that these rows become invisible, thereby realizing a screen having no gradation difference over the entire surface. For example, in the case of a VGA, a display section of 482 lines is prepared, and masks are applied to both upper and lower lines, whereby a uniform screen of 480 lines can be obtained.
(1st Embodiment)
Hereinafter, a first embodiment of a method of driving an active matrix type liquid crystal display according to the present invention will be described in detail. The active matrix type liquid crystal display of the present invention has a configuration basically similar to the configuration shown in FIG. 1, and a description thereof will be omitted.
[0045]
A method of driving the active matrix type liquid crystal display of the present embodiment will be described with reference to FIGS. First, in the frame of (a), the first, third and fifth odd lines of the first area (area 1) are scanned (first field, first area, first field), and then the even numbers of the second and fourth lines are scanned. Scan the row (first frame, first area, second field). Next, the odd-numbered row of the seventh row in the section 2 is scanned (first field, second section, first field), and then the sixth and eighth rows of the even-numbered row are scanned (first frame, second section, second field). . Conversely, in the next frame (b), the even rows of the second and fourth rows are scanned first (first field, first field of the second frame), and then the odd rows of the first and third rows are scanned. (Second frame, first area, second field). The even and sixth rows of the next area (area 2) are scanned (first field of the second area in the second frame), and then the fifth and seventh rows of the odd number are scanned (second frame of the second frame). Area second field).
[0046]
Next, the state transition of the polarity of the pixel voltage in the above scanning will be described with reference to FIGS. 16A and 16B and FIGS. 17A and 17B. In the first field, the first area, and the first field, the voltages of the pixels in the first, third, and fifth rows change from positive to negative. Therefore, the pixels in the adjacent rows (second, fourth, and sixth rows) have the same potential from the different polarity to the same potential with respect to the pixels in the first, third, and fifth rows. The voltages of the pixels in rows 4, 4 and 6 become deeper (actually, the potential that has become shallower returns). In the first field, first area, second field, the pixel voltages of the second and fourth rows change from negative to positive. Therefore, since the pixels in the adjacent rows (first, third and fifth rows) have different polarities from the same potential having the same polarity, the voltages of the first, third and fifth rows written in the previous field become shallower. Similarly, in the first field of the second area of the first frame, since the transition is to the same polarity, the potentials of the sixth and eighth rows written in the previous frame become deeper (actually, the potential that became shallower becomes the original). In the second field of the second area of the first frame, since the transition is to the opposite polarity, the pixel potentials of the fifth and seventh rows become shallower.
[0047]
In the first field of the first area of the second frame, since the potentials of the pixels in the adjacent rows transition to the same polarity, the first, third and fifth rows written in the previous frame become deeper (actually, shallower). In the second field, the first field and the second field of the second frame, the potentials of the pixels in the adjacent rows transition to the opposite polarities, so that the pixel potentials in the second and fourth rows become shallower. In the second field, second area, first field, the potentials of the pixels in the adjacent rows transition to the same polarity, so the fifth and seventh rows written in the previous frame become deeper (actually, they became shallower). In the second field of the second frame, in the second field, the potentials of the pixels in the adjacent rows transition to the opposite polarities, so that the pixel potentials in the fourth, sixth, and eighth rows become shallower.
[0048]
By scanning two frames alternately and continuously in this manner, the influence on the gradation in the odd and even rows is the same, and horizontal stripes and boundaries do not occur. However, since the uppermost and lowermost rows are affected only by the lower line or the upper line, the influence on the gradation is deeper than the other lines, and the gradation is darker.
[0049]
FIG. 18 shows a waveform of the above driving. Both the odd-numbered pixel P (i, 3) and the even-numbered pixel P (i, 4) are set so that the potentials (VP (i, 3) and VP (i, 4)) in the negative time period become shallower. Fluctuating. For this reason, the influence on the gradation in the odd-numbered and even-numbered rows is the same, and horizontal stripes do not occur.
[0050]
However, in the present embodiment, since the driving times of the positive polarity and the negative polarity are different as shown in FIG. 18, a small amount of DC is applied as an average value. But that is not immediately a problem at the practical level. Even if a direct current as an average value is applied, a slight voltage does not lead to irreversible destruction of the liquid crystal. For example, there is a problem that an afterimage is likely to occur, but it is sufficient if there is no problem from a practical level. In this sense, this embodiment has a sufficient level of practicality depending on the purpose of use of the display.
[0051]
In the above description, a case where all screens display the same gradation is described for easy understanding. When the gradation of the pixels in the adjacent row is different, the charge always remains in the coupling capacitance Cpp. However, the movement of the charge is caused by the same mechanism, and the difference is slightly different from the original gradation. It is. Also in the following description, a case where all screens display the same gradation will be described.
(Second embodiment)
Hereinafter, a second embodiment of the driving method of the active matrix type liquid crystal display according to the present invention will be described. In this embodiment, the scanning order of the first frame and the second frame is the same as that of the first embodiment, and the third frame and the fourth frame are the scanning order opposite to that of the first frame and the second frame. To That is, in the third frame, the even-numbered rows are scanned first and then in the fourth frame, and in the fourth frame, the odd-numbered rows are scanned first and the even-numbered rows are scanned later. The scanning order of such four consecutive frames is shown in FIGS.
[0052]
FIG. 20 shows waveforms of the above driving. As shown in FIG. 20, the positive polarity portion (T) of the voltage VP (i, 3) of the pixel P (i, 3) in the third row ₁ (+), T ₂ (+)) And the negative polarity part (T ₁ (-), T ₂ The effective value of (−)) is the positive part (T) of the voltage VP (i, 4) of the pixel P (i, 4) in the fourth row. ₁ (+), T ₂ (+)) And the negative polarity part (T ₁ (-), T ₂ (−)) Becomes substantially equal to the effective value. Therefore, the effective values (alternating current) are almost the same, no difference in gradation occurs, and no horizontal stripes and boundaries occur.
[0053]
Note that the write timing of adjacent rows between frames differs between rows as shown in FIG. 20, so that the area of the shallow portion of the voltage is slightly different between rows and the effective value differs. However, since this difference is about several q in the four frames, it can be considered that the effective values between rows are almost the same. For example, in the case of the driving shown in FIG. 20, the difference in the effective charge value between the pixels in the third row and the pixels in the fourth row is 2q in four frames. Here, q indicates the amount of charge that moves under the influence of the adjacent electrode. When this scanning is performed by VGA, the charge difference between the pixels in the third and fourth rows is 2q in about 2000 horizontal times, and the charge difference in four frames is a very small value.
[0054]
The point that the present embodiment is superior to the first embodiment is that, with four frames as one cycle, the time of positive polarity and the time of negative polarity are the same for both the odd-numbered pixels and the even-numbered pixels. It is in the point. Pixel P (i, 3) and pixel P (i, 4) are both T ₁ (+) And T ₂ The time when (+) is added is T ₁ (-) And T ₂ This is because it becomes equal to the time obtained by adding (-). Therefore, it is possible to prevent the occurrence of horizontal stripes without sacrificing the AC driving of the liquid crystal for preventing the application of the DC voltage as an average value. However, also in this case, the phenomenon that the gradation of the uppermost and lowermost row pixels of the display unit is darkened remains. If the time of one frame is 1/60 second, the period of four frames is 1/15 second. However, since the voltage difference in question here is extremely small, this causes flickering. I will not.
(Third embodiment)
The third embodiment of the present invention relates to a method of eliminating horizontal stripes in upper and lower ends of a screen remaining in the first and second embodiments. Note that the method of driving the display is the same as the method of the first or second embodiment, and a description thereof will be omitted.
[0055]
According to the present embodiment, as shown in FIG. 21, the display unit includes the required number of rows (eight rows) plus two rows of pixels. Pixels in both upper and lower rows (first and tenth rows) are covered with the mask 50 and shielded from light. With this configuration, horizontal stripes due to the upper and lower rows of the screen are not visible. The data to be written to the two rows of pixels at the upper and lower ends need not be data to be displayed on the screen, and thus is not particularly defined. As a material of the mask 50, a material having a light shielding effect, such as tantalum, titanium, and aluminum, may be used.
[0056]
Also, instead of using the mask 50, by displaying black data on both upper and lower rows at all times, these rows can be isolated from the portion that actually contributes to display, and the same effect as applying the mask 50 can be obtained. The data displayed in the upper and lower ends of the row may be uniform data, and need not necessarily be black data.
[0057]
In FIG. 21, two rows covered by the mask 50 are added to eight rows of the screen size to make ten rows. However, as described above, the actual number of rows of pixels of the display is much larger. Needless to say, the present invention can be applied to such a case.
[0058]
【The invention's effect】
By dividing the display unit into a plurality of sections in the column direction and performing interlaced scanning for each section, power consumption is reduced, and at the same time, flicker (flicker) and image quality deterioration of a moving image having large motion are suppressed. it can.
[0059]
In addition, according to the present invention, the pixel electrodes in the plurality of areas and the pixel electrodes sandwiching the boundaries of the plurality of areas are scanned after scanning the odd-numbered (or even-numbered) pixel electrodes in a certain frame. In the case of scanning the pixel electrodes of (1) and (2), in the next frame, a driving method is performed in which the pixel electrodes of even-numbered rows (or odd-numbered rows) are scanned and then the pixel electrodes of odd-numbered rows (or even-numbered rows) are scanned. As a result, it is possible to prevent the occurrence of horizontal stripes every other row and the boundary between areas.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram of a liquid crystal display.
FIG. 2 is a diagram showing a polarity distribution and transition of a pixel voltage in a row inversion method;
FIG. 3 is a diagram showing a polarity distribution and transition of a pixel voltage in a pixel inversion method;
FIG. 4 is a simplified equivalent circuit diagram of a TFT and a pixel.
FIG. 5 is a diagram showing a drive timing of a TFT liquid crystal display and a waveform of a pixel voltage.
FIG. 6 is an equivalent circuit diagram of a data line.
FIGS. 7A to 7D are diagrams showing a state transition of the polarity of a pixel voltage during interlaced scanning.
FIG. 8 is a diagram showing continuous pixel electrodes on the same column.
FIGS. 9A and 9B are equivalent circuit diagrams of continuous pixel electrodes on the same column.
10A to 10D are diagrams showing a state change of an equivalent circuit when pixels in odd rows are charged.
11A to 11D are diagrams showing a state change of an equivalent circuit when pixels in an even-numbered row are charged.
FIG. 12 is a diagram showing a driving waveform of a display device when display quality is deteriorated.
FIG. 13 is a diagram showing a scanning order in a case where an area boundary occurs.
FIG. 14A is a diagram showing a state transition of the polarity of a pixel voltage when an area boundary occurs.
FIG. 14B is a continuation of FIG. 14A, showing a state transition of the polarity of the pixel voltage when an area boundary occurs.
FIG. 14C is a continuation of FIG. 14B, showing a state transition of the polarity of the pixel voltage when an area boundary occurs.
FIG. 14D is a continuation of FIG. 14C, showing a state transition of the polarity of the pixel voltage when an area boundary occurs.
FIGS. 15A and 15B are diagrams showing a scanning order when there is no area boundary and no horizontal stripe in one embodiment of the present invention; FIGS.
FIG. 16A is a diagram showing the state transition of the polarity of the pixel voltage when there is no area boundary and no horizontal stripe according to the embodiment of the present invention;
FIG. 16B is a continuation of FIG. 16A, showing a state transition of the polarity of the pixel voltage when there is no area boundary and no horizontal stripes;
FIG. 17A is a diagram showing a state transition of the polarity of a pixel voltage when there is no area boundary and no horizontal stripe according to the embodiment of the present invention;
FIG. 17B is a continuation of FIG. 17A, showing a state transition of the polarity of the pixel voltage when there is no boundary between areas and no horizontal stripes;
FIG. 18 is a diagram showing driving waveforms according to the embodiment of the present invention.
FIGS. 19A to 19D are views showing a scanning order in another embodiment of the present invention.
FIG. 20 is a diagram showing driving waveforms according to another embodiment of the present invention.
FIG. 21 is a diagram showing one embodiment of a display unit according to the present invention.
[Explanation of symbols]
30 Display
32 scan driver (gate driver)
34 Data Driver (Data Driver)
36 common electrode
38 Control unit
40 Gate voltage generation circuit
42 gradation voltage generation circuit
44 Common electrode drive circuit
50 mask

Claims (8)

A plurality of pixel electrodes arranged in a matrix, a plurality of row electrodes each providing a scan signal to the same row of pixel electrodes, and a plurality of column electrodes each providing a data signal to the same column of pixel electrodes are provided. Comprising a display unit provided,
At least one of an odd-numbered row and an even-numbered row with respect to a plurality of continuous row electrodes in at least a first area of the display unit and a plurality of continuous row electrodes in a second area adjacent to the first area. After sequentially scanning the row electrodes, an interlaced scan for sequentially scanning the other row electrodes of the odd-numbered rows or even-numbered rows in the same direction, a driving method of an active matrix type liquid crystal display for each frame,
The scanning order of the interlaced scanning performed in the first and second areas in the second frame, respectively, is an odd-numbered row of the scanning order of the interlaced scanning performed in the first and second areas in the first frame. And a method for driving an active matrix type liquid crystal display in which the even rows are reversed. The method of driving an active matrix type liquid crystal display according to claim 1, wherein the positions of the boundaries of the row electrodes in the first area and the second area are different between the first frame and the second frame. A plurality of pixel electrodes arranged in a matrix, a plurality of row electrodes each providing a scan signal to the same row of pixel electrodes, and a plurality of column electrodes each providing a data signal to the same column of pixel electrodes are provided. A display unit provided,
At least one of an odd-numbered row and an even-numbered row with respect to a plurality of continuous row electrodes in at least a first area of the display unit and a plurality of continuous row electrodes in a second area adjacent to the first area. After scanning the row electrodes in order, the interlaced scanning for sequentially scanning the other row electrodes of the odd or even rows in the same direction is performed by an active matrix type liquid crystal display device having a scan driver for each frame. So,
The scan driver sets the order of the interlaced scanning performed in the first and second areas in a second frame to the interlaced scanning performed in the first and second areas in a first frame. An active matrix type liquid crystal display, wherein odd rows and even rows in the scanning order are reversed. 4. The active matrix type liquid crystal display according to claim 3, wherein the scan driver changes a position of a boundary of a row electrode in the first area and the second area between the first frame and the second frame. 5. 5. The active matrix type liquid crystal display according to claim 3, wherein the pixel electrodes in the uppermost row and the lowermost row of the display unit are covered with a light shielding mask. 5. The active matrix type liquid crystal display according to claim 3, wherein black data is displayed on the pixel electrodes in the uppermost row and the lowermost row of the display unit. A plurality of pixel electrodes arranged in a matrix, a plurality of row electrodes each providing a scan signal to the same row of pixel electrodes, and a plurality of column electrodes each providing a data signal to the same column of pixel electrodes are provided. Comprising a display unit provided,
In the display unit, three or more areas each having a plurality of continuous row electrodes are provided side by side so as to be adjacent to each other,
After sequentially scanning one of the odd-numbered rows or the even-numbered rows with respect to a plurality of continuous row electrodes in each area, the other row electrodes of the odd-numbered rows or even-numbered rows are sequentially aligned in the same direction. A method of driving an active matrix type liquid crystal display that performs interlaced scanning continuously in the order in which each area is arranged for each frame,
Reversing the scanning order of the interlaced scanning performed in each of the sections in the second frame and the odd and even rows in the scanning order of the interlaced scanning performed in each of the sections in the first frame; Driving method of matrix type liquid crystal display. A plurality of pixel electrodes arranged in a matrix, a plurality of row electrodes each providing a scan signal to the same row of pixel electrodes, and a plurality of column electrodes each providing a data signal to the same column of pixel electrodes are provided. A display unit provided, wherein three or more areas each having a plurality of continuous row electrodes are provided so as to be adjacent to each other;
After sequentially scanning one of the odd-numbered rows or the even-numbered rows, the other row electrodes of the odd-numbered rows or the even-numbered rows are sequentially scanned with respect to a plurality of continuous row electrodes of each section in the display unit. An active matrix type liquid crystal display device having a scanning driver for performing interlaced scanning in order in the same direction, and a scanning driver that continuously performs each area in the order in which each area is arranged for each frame,
The scan driver sets the scanning order of the interlaced scanning performed in each of the sections in the second frame to an odd-numbered row and an even-numbered row of the scanning order of the interlaced scanning performed in each of the sections in the first frame. An active matrix type liquid crystal display which is designed to reverse the above.

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