JP2004271719A - Driving method of liquid crystal display, and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driving method of a liquid crystal display and the liquid crystal display for maximizing a moving image quality improvement effect and for preventing flicker by setting simple inversion and an image display system in a driving system for repeating image display and black display in the case of displaying a moving image. <P>SOLUTION: In the driving method of the liquid crystal display having a pixel region surrounded by scanning lines and signal lines, polarity of voltage to be impressed to the pixel region is inverted by every two frames and it comprises a process for inverting scanning line of the even-th lines in the even-th frames and for inverting scanning lines of the odd-th lines in the odd-th frames or a process for inverting the scanning lines of the even-th lines in the odd-th frames and for inverting the scanning lines of the odd-th lines in the even-th frames. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a driving method of a liquid crystal display device and a liquid crystal display device, and more particularly to a driving method for displaying a moving image.
[Prior art]
A conventional liquid crystal display device inputs and drives image data and control signals. A general liquid crystal display device has a drawback that when a moving image is displayed, the image is blurred due to the slow response of the liquid crystal and the driving method for holding the display image for one frame period. In addition, in a normal inversion driving method for each frame, when a signal such as an interlace signal, which repeats a black image, is input, a DC component is applied to the liquid crystal, and the liquid crystal is deteriorated.
[0003]
In order to improve the above-described disadvantages of the liquid crystal display device, a method of blinking a backlight and a method of performing image display and black display during one frame period have been considered. Further, a method of inserting black display for each frame and a method of inserting black for each scanning line such as interlace driving are disclosed (for example, see Patent Document 1).
[0004]
[Patent Document 1]
JP 2001-42282 A (page 4-5, FIGS. 1-4)
[0005]
[Problems to be solved by the invention]
Japanese Patent Application Laid-Open No. H11-163873 discloses a method in which red, green, and blue pixels are converted to data in order to eliminate a feeling of afterimage in a driving method in which image display and black display are repeated for each frame and distortion of an image due to a problem in liquid crystal operation. Black display and image display are repeated with three lines or every other line in a checkered pattern, the polarity of the voltage applied to the liquid crystal is inverted every 2n frames (n = 1, 2, 3,...), And the signal line And the like are disclosed. However, if the polarity is inverted every 2n frames, an in-plane non-uniformity of the optimal common electrode potential occurs, and flicker is visually recognized at a change in polarity. Further, at present, source drive ICs generally manufactured are generally inverted every other line, and this method cannot be used in a general source drive IC. Further, in the method of displaying black and data every other scanning line, in a method of inserting black for every one scanning line as in the case of interlace driving, flickering occurs depending on the position where black is inserted.
[0006]
Accordingly, the present invention has been made to solve the above-described problem, and in the case of performing moving image display, a conventional source driving IC is used in a driving method in which image display and black display are repeated, and a simple polarity is used. Provided are a method of driving a liquid crystal display device and a liquid crystal display device that maximize the effect of improving moving image quality and prevent flicker by setting an inversion and an image display method. In addition, the present invention provides a liquid crystal application voltage polarity inversion method that suppresses power consumption even in normal driving in which black is not inserted.
[0007]
[Means for Solving the Problems]
A method for driving a liquid crystal display device of the present invention includes a plurality of scanning lines formed on a substrate, a plurality of signal lines intersecting the scanning lines, and a pixel region surrounded by the scanning lines and the signal lines. In the method for driving a liquid crystal display device, the polarity of the voltage applied to the pixel region is inverted every two frames, the scanning lines in the even rows are inverted in the even frames, and the scanning lines in the odd rows are odd. The method is characterized by including a step of inverting in a frame or a step of inverting an even-numbered scanning line in an odd-numbered frame and inverting an odd-numbered scanning line in an even-numbered frame.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a driving device of a liquid crystal display device according to the present embodiment will be described with reference to the drawings.
[0009]
Embodiment 1 FIG.
FIG. 1A is a block diagram of the liquid crystal display device according to the present embodiment, and FIG. 1B is a circuit configuration diagram for applying a voltage to a liquid crystal layer of the liquid crystal display device. In the figure, a plurality of scanning lines 1 and signal lines 2 are arranged on a matrix, and have a pixel region 3 (hereinafter, referred to as a pixel) in an enclosed region. The scanning line 1 is connected to a scanning line driving IC 4, and the signal line 2 is connected to a signal line driving IC 5 (source driving IC). Each IC operates by scanning from a control circuit 6. The polarity of the voltage applied to the liquid crystal 7 can be switched by scanning input to the signal line driving IC 5, and generally available signal line driving ICs are set so that the polarity of the signal lines 2 is inverted one by one. Have been. In the liquid crystal display device, a TFT 9 connected to the scanning lines 1 and the signal lines 2 is formed on a TFT array substrate of a pair of substrates opposing each other and a counter substrate (not shown). On the other hand, a common electrode 8 is formed on the counter substrate. A voltage is applied to the liquid crystal 7 between the transparent pixel electrode 10 disposed in the pixel 3 and the common electrode 8, and the brightness of the liquid crystal display device is adjusted by the voltage difference between the two electrodes.
[0010]
Next, FIG. 5 shows changes in the applied voltage applied to the liquid crystal. 5A and 5B show the case of normally black, and FIGS. 5C and 5D show the case of normally white. As described above, when the driving method in which black display and image display are repeated for each frame is employed, attention is paid to the pixel, and the liquid crystal application voltage in the case where the existing driving method in which the polarity is inverted every other frame is used. The change must be positive image display → negative black display → positive image display → negative black display or negative image display → positive black display → negative image display → positive black display. As the DC component continues to be applied to the liquid crystal, the polarity is biased to positive or negative. For this reason, an image or stickiness is caused to cause liquid crystal deterioration. In order to solve this, it is necessary to make the number of frames in which the polarity of the liquid crystal applied voltage is switched a multiple of 2 to cancel the polarities.
[0011]
As described above, the brightness of the pixel 3 is controlled by the absolute value of the voltage between the pixel electrode 10 and the common electrode 8. For example, in a normally white mode liquid crystal drive, the light transmittance changes depending on the voltage difference between the pixel electrode and the common electrode. Therefore, the brightness of the pixel changes as the voltage difference increases. As shown in FIG. 6, for example, at the optimum common electrode potential 11, there is no potential difference between the liquid crystal applied voltage 13 of the positive polarity and the applied voltage 14 of the negative polarity, and the ideal liquid crystal applied voltage has no change in brightness. . However, when the optimum common electrode potential 11 is shifted to the negative side and is the actual common electrode potential 15, for example, the positive applied voltage 16 is large, the negative applied voltage 17 is small, and the brightness changes. . As described above, even when an image is displayed at the same gradation due to a change in the common electrode potential (in-plane non-uniformity), the case where an image is displayed with a positive polarity and the case where an image is displayed with a negative polarity are different. The brightness changes.
[0012]
The image visually recognized by the retina is at the time of image display. As described above, if the driving method of inverting the liquid crystal applied voltage polarity by a multiple of 2 is adopted, the image display will be every 2n frames at a certain pixel, but the same floor will be displayed. Even when an image is displayed in a tonality, if there is a voltage difference, the brightness when displaying an image with positive polarity and the brightness when displaying an image with negative polarity change every 2n frames. In the conventional driving method in which the frame in which the black display is not inserted and the polarity of the voltage applied to the liquid crystal is changed to 1 is changed at a frame frequency of about 60 Hz, the change is hardly visually recognized. In the case of the system, since light and dark at a maximum of about 30 Hz (two frames) are continuous, it is easy to be visually recognized. When the number of frames in which the polarity of the liquid crystal application voltage is changed becomes large, the change interval becomes large, and light and dark are visually recognized and flicker easily occurs. Therefore, the optimal number of frames in which the polarity of the liquid crystal application voltage is changed is two.
[0013]
For this reason, the polarity of the liquid crystal applied voltage is inverted every two frames. In order to further prevent flicker, even-numbered scanning lines are inverted in even-numbered frames, and odd-numbered scanning lines are inverted in odd-numbered frames, as shown in FIG. Alternatively, as shown in FIG. 4, the polarity of the liquid crystal applied voltage may be inverted every two frames, the even-numbered scanning lines may be inverted in odd-numbered frames, and the odd-numbered scanning lines may be inverted in even-numbered frames.
[0014]
Further, in the driving method for inserting black, flicker can be further prevented by setting the frame frequency to 100 Hz or more.
[0015]
FIG. 2 illustrates an example of a driving method of the liquid crystal display device in this embodiment. In the figure, + and-indicate the polarity of the voltage applied to the pixel. In the positive polarity of the sign (+), a plus voltage is applied to the common electrode voltage, and in the negative polarity of the sign (-), a minus voltage is applied. In addition, the pixels that perform black display are hatched, and the other pixels indicate that image display is performed.
[0016]
The polarity of the voltage applied to the pixel is inverted every two frames, the scanning lines in the even rows are inverted in the even frames, and the odd frames are inverted in the odd frames. Further, since the polarity inversion on one scanning line uses the standard signal line driving IC 5, the polarity is inverted for each signal line and the polarity is inverted for every two scanning lines in the vertical direction. With such a driving method, flicker is further less noticeable, and crosstalk in the horizontal and vertical directions is less likely to occur.
[0017]
In addition, in the case of a driving method of inserting a black display, the display of pixels is visually recognized as dark and dark, and it is easy to cause flicker. You can also. With such a configuration, black display can be inserted without making a major change from the existing liquid crystal display. The arrangement for scattering the black display most precisely has a checkered pattern as shown in FIG. As a result, the change in brightness in units of several pixels is smoothed (sprinkled), and flicker can be prevented in the eyes.
[0018]
However, even when an image is displayed using this checkered pattern and the inversion method described in the first embodiment is used, a display problem may occur. Focusing on a certain scanning line, when black display is inserted every other odd number of signal lines on the same scanning line, the pixel displaying an image on that scanning line has a positive or negative polarity. The ratio becomes larger than that of the opposite polarity, and the phenomenon that the scanning line is bright or dark occurs due to the shift of the common electrode potential as described above. Therefore, when a checkered black display as shown in FIG. 7 is inserted, light and dark lines every two scanning lines are visible.
[0019]
In order to prevent such light and dark streaks every two scanning lines, it is desirable that the black display be inserted on the same scanning line for each even signal line as shown in FIG. It is preferable that every two lines can be formed most densely. The black display may be inserted between the scanning lines in any number of cycles. However, it is preferable to insert every other black line. As shown in FIG. 2, in the image display, a black display is inserted every two pixels, and the insertion place is switched every scanning line. Further, this frame is characterized by being replaced every other frame.
[0020]
Furthermore, in recent years, every other scanning line of NTSC or the like is skipped (also referred to as interlaced scanning) on a liquid crystal display device, and the scanning line is divided into two (field) scans to complete one image in two fields. In many cases, data obtained by performing interlace-progressive conversion (IP conversion) of interlace scanning drive, which is a system, is displayed. Depending on the IP conversion system, particularly in a still image, a pixel that repeats image display and black display every other frame occurs. In some cases, by using this method, the applied voltage polarity bias is automatically canceled, so that deterioration of the liquid crystal can be prevented.
[0021]
In the liquid crystal display device using the driving method according to the first embodiment, in the display method in which black display and image display are repeated every other frame, the polarity inversion method as described above is used by using a readily available source driving IC. By using, the deterioration of the liquid crystal due to the bias of the polarity of the voltage applied to the liquid crystal can be prevented, the flicker of the displayed image can be minimized, and the image quality of the moving image can be improved. Further, flicker can be prevented by disposing the black display spatially without inserting the black display over the entire surface.
[0022]
Further, the polarity inversion method according to the first embodiment can be used even in a driving method in which black display is not inserted. At this time, basically, every two scanning lines and the polarity of pixels are switched every two frames. The number of times that the polarity of the voltage applied to the switch is switched is reduced, and power consumption can be reduced.
Embodiment 2 FIG.
[0023]
In the second embodiment, a description will be given of a driving method that repeats image display and black display and that maximizes a moving image improvement effect. In general, a liquid crystal display device performs a hold-type drive in which an image is displayed continuously for a certain period of time in order to display the image continuously. For this reason, the previous screen is burned into the eyes and remains until the next screen is displayed, and the images appear to overlap. Due to such a phenomenon, the outline of an image looks blurred when displaying a moving image. In order to solve this problem, the light emitted from the liquid crystal display device uses an impulse method, such as a CRT, in which pixels emit light with high luminance at the moment of scanning as much as possible. So that it does not blur.
[0024]
The impulse method in the liquid crystal display will be described. For example, in the display method in which the image display and the black display are reversed, the image display is displayed for one frame, and after being held, the black image is displayed for one frame. In this state, the image is held for one frame period during which the image is displayed, so that the impulse period during which the image is displayed is 50%. For example, when the frame frequency is 60 Hz, the hold period during which an image integrated on the eyes is displayed is about 17 ms. For example, even when liquid crystal having an infinitely fast response speed is used, the image is compared with normal driving. Bleeding is similar.
[0025]
Therefore, a liquid crystal having a faster response speed from non-black display to black display than the response speed from black display to non-black display is used. With the structure using such a liquid crystal, the time during which an image is displayed is shortened, so that the image hold period can be shortened. For this reason, the image does not overlap with the immediately preceding image, and when displaying a moving image, blurring of the image is eliminated and display quality can be improved. However, at a frame frequency of 60 Hz, the brightness of an image may be visually recognized. Therefore, it is desirable to drive at a frame frequency of at least 100 Hz or more. The time required for displaying one frame of image display and one frame of black display is, for example, about 17 ms in the case of 60 Hz, however, the response speed from non-black display to black display is not black to black display. Since the liquid crystal is faster than the response speed to the display, the image hold time can be set short. Preferably, the sum of the time during which the image display is displayed for one frame and the time when the black display is displayed for one frame, that is, the frame period for inverting from image display to black display and the frame period for inverting from black display to image display When the sum is 20 ms or less, blurring in displaying a moving image is eliminated, and display quality can be improved. The polarity at this time can further prevent flicker by using the driving method described in the first embodiment.
[0026]
This driving method can be realized by installing a known frame memory or the like in the display device.
[0027]
Also, in the interlaced driving and the driving method using a pattern for inserting a black display at the time of displaying an image as in the first embodiment, the response speed of the gray scale display from black to gray scale is changed from black to black. If a liquid crystal faster than the response speed to the gradation display other than the above is used, the effect of improving the moving image quality is increased.
[0028]
Also, in the interlace driving shown in FIG. 8, when liquid crystal having an infinitely high response speed is used as described above, black and image display are repeated when viewed from each pixel. Since it is held during the frame period, there is a possibility that the effect of improving the image quality of the moving image cannot be expected much. Therefore, when a liquid crystal having a high response speed to black is used from a gradation display other than black, a display as shown in FIG. 9 is obtained, and the image display period integrated in the eyes is shortened, and the effect of improving the moving image quality is increased. . Further, in the normal driving using the liquid crystal having a finite response speed, when the image in the frame is switched, a double image in which the previous image and the new image are overlapped is displayed. Since the display is reset to the black display, only a new image is displayed each time, so that the image does not become blurred and the effect of improving the moving image quality is increased.
[0029]
In the second embodiment, the image hold period can be shortened by using a liquid crystal whose response speed from non-black display to black display is faster than response speed from black display to non-black display. it can. For this reason, the image does not overlap with the immediately preceding image, bleeding in displaying a moving image is eliminated, and display quality can be improved.
[0030]
Further, by setting the frame frequency faster or by setting the sum of one frame period of black display or image display, the image hold period can be shortened. In this case, bleeding is eliminated, and display quality can be improved.
Embodiment 3 FIG.
[0031]
In the driving method of the liquid crystal display device described in Embodiments 1 and 2 as described above, the shorter the image display time is, the larger the effect of improving the moving image quality is. However, since the black display is inserted, the luminance is reduced. May be done. In order to solve this problem, a method is used in which light emitted to a pixel displaying black is reflected inside the liquid crystal display device and reused for a pixel displaying an image.
[0032]
As shown in FIG. 10, an optical film 20 for generating a phase difference is provided on a color filter substrate 19 in order to polarize and reuse light emitted from the backlight 22 and passing through the liquid crystal cell 18 during black display. Insert. A cholesteric liquid crystal layer 21 capable of selectively reflecting light converted into polarized light is further provided thereon. The cholesteric liquid crystal layer 21 can selectively reflect left circularly polarized light.
Light emitted from the backlight becomes linearly polarized light by the polarizing plate 24. In the black display state, light passes through the liquid crystal cell 18 in the same polarization state, but in the white display state, the polarization state is linearly polarized light twisted by 90 degrees. Light transmitted through the liquid crystal panel 19 enters the optical film 20. In the optical film 20, a phase difference of λ / 4 is generated so that the linearly polarized light becomes circularly polarized light. However, in the black display state and the white display state, the angles of the linearly polarized light are different by 90 degrees, so that they become left circularly polarized light and right circularly polarized light, respectively. . Since the cholesteric liquid crystal layer 21 can selectively reflect the left circularly polarized light, the light is reflected in the black display state. The reflected light passes through the optical film 20, is converted into linearly polarized light, returns to the backlight light source, and can be guided (reused) to the pixel area (image display). In the white display state, the light passes through the cholesteric liquid crystal layer 21 in a polarized state and exits from the display surface.
[0033]
Although an example has been described above, in the black display state, a structure in which light passing through the liquid crystal cell is reflected into the liquid crystal cell and reused for image display can be variously changed.
[0034]
By adopting Embodiment Mode 3, light is reflected in a black display state, and the reflected light is further converted into linearly polarized light through an optical film, returned to a liquid crystal cell and further to a backlight light source, and reused. Becomes possible.
[0035]
In Embodiments 1 to 3, an active matrix type liquid crystal display device has been described. However, the present invention can be applied to a passive type liquid crystal display device.
【The invention's effect】
As described above, the driving method of the liquid crystal display device of the present invention includes a plurality of scanning lines formed on a substrate, a plurality of signal lines that intersect the scanning lines, and the scanning lines and the signal lines. In a method for driving a liquid crystal display device having an enclosed pixel region, the polarity of the voltage applied to the pixel region is inverted every two frames, and the scanning lines in the even lines are inverted in the even frames, and the odd lines are inverted. The scanning line of the row is inverted in the odd frame, or the scanning line of the even line is inverted in the odd frame, and the scanning line in the odd line is inverted in the even frame. In a display method in which black display and image display are repeated every frame, using a readily available source drive IC and using the above-described polarity inversion method prevents the deterioration of the liquid crystal due to the bias in the polarity of the liquid crystal applied voltage. It is possible, It is possible to suppress the flicker of the shown image to a minimum, it is possible to improve the image quality of the moving image.
[Brief description of the drawings]
FIG. 1A is a block diagram illustrating the present embodiment, and FIG. 1B is a circuit configuration diagram illustrating the present embodiment.
FIG. 2 illustrates an example of a method for driving a liquid crystal display device in this embodiment.
FIG. 3 illustrates an example of a method for driving a liquid crystal display device in this embodiment.
FIG. 4 illustrates an example of a method for driving a liquid crystal display device in this embodiment.
FIG. 5 is a diagram showing a change in an applied voltage applied to the liquid crystal of the liquid crystal display device according to the present embodiment.
FIG. 6 is a diagram showing a change in an applied voltage applied to the liquid crystal of the liquid crystal display device according to the present embodiment.
FIG. 7 illustrates an example of a method for driving a liquid crystal display device in this embodiment.
FIG. 8 illustrates an example of a method for driving a liquid crystal display device in this embodiment.
FIG. 9 illustrates an example of a method for driving a liquid crystal display device in this embodiment.
FIG. 10 is an example of a liquid crystal display device in this embodiment.
[Explanation of symbols]
1: Scan line 13: Positive liquid crystal applied voltage 2: Signal line 14: Negative liquid crystal applied voltage 3: Pixel area 15: Actual common electrode voltage 4: Scan line drive IC 16: Actual positive liquid crystal applied voltage 5: Signal line drive IC 17: Actual negative liquid crystal applied voltage 6: Control circuit 18: Liquid crystal cell 7: Liquid crystal 19: Color filter substrate 8: Common electrode 20: Optical film 9: TFT 21: Cholesteric liquid crystal layer 10: Pixel electrode 22 : Backlight 11: optimal common electrode potential 23: TFT array substrate 24: polarizing plate

Claims (10)

A plurality of scanning lines formed on the substrate,
A plurality of signal lines intersecting the scanning line;
In a method for driving a liquid crystal display device including a pixel region surrounded by the scanning lines and the signal lines,
A step of inverting the polarity of the voltage applied to the pixel region every two frames, and inverting even-numbered scanning lines in even-numbered frames and inverting odd-numbered scanning lines in odd-numbered frames; The method of driving a liquid crystal display device according to claim 1, further comprising the step of: A plurality of scanning lines formed on the substrate,
A plurality of signal lines intersecting the scanning line;
In a method for driving a liquid crystal display device including a pixel region surrounded by the scanning lines and the signal lines,
In the display of the pixel area, black display and image display are inverted every even number of signal lines, the black display and image display are inverted every scanning line, and the display of the pixel area is inverted every frame. A process of repeatedly displaying
A step of inverting the polarity of the voltage applied to the pixel region every two frames, and inverting even-numbered scanning lines in even-numbered frames and inverting odd-numbered scanning lines in odd-numbered frames; The method of driving a liquid crystal display device according to claim 1, further comprising the step of: 3. The method according to claim 1, further comprising a step of inverting the polarity of the voltage applied to the pixel region for each signal line on the same scanning line and for every two scanning lines on the same signal line. Driving method of a liquid crystal display device. The display of the pixel area is performed by inverting the pixel display and the black display for each frame, and the frame frequency at which the image display and the black display are inverted is 100 Hz or more. 4. The method for driving a liquid crystal display device according to item 3. In the display of the pixel region, the pixel display and the black display are inverted and displayed in one frame, and the sum of the frame period for inverting the image display to the black display and the frame period for inverting the black display to the image display is obtained. 5. The method according to claim 1, wherein the driving time is 20 ms or less. 6. The driving method of a liquid crystal display device according to claim 1, wherein a liquid crystal having a response speed from an image display to a black display is higher than a response speed from a black display to an image display. A plurality of scanning lines formed on the substrate,
A plurality of signal lines intersecting the scanning line;
In a liquid crystal display device including a pixel region surrounded by the scanning lines and the signal lines,
Means for inverting the polarity of the voltage applied to the pixel region every two frames, and inverting even-numbered scanning lines in even-numbered frames and inverting odd-numbered scanning lines in odd-numbered frames, or A liquid crystal display device comprising: means for inverting a scanning line in an odd frame and inverting a scanning line in an odd line in an even frame. A plurality of scanning lines formed on the substrate,
A plurality of signal lines intersecting the scanning line;
In a liquid crystal display device including a pixel region surrounded by the scanning lines and the signal lines,
In the display of the pixel area, black display and image display are inverted every even number of signal lines, the black display and image display are inverted every scanning line, and the display of the pixel area is inverted every frame. Means for repeatedly displaying
The polarity of the voltage applied to the pixel region is inverted every two frames, the even-numbered scanning lines are inverted in even-numbered frames, and the odd-numbered scanning lines are inverted in odd-numbered frames. Means for inverting scanning lines in odd-numbered frames and inverting odd-numbered scanning lines in even-numbered frames. 9. The apparatus according to claim 7, further comprising means for inverting the polarity of the voltage applied to the pixel area for each signal line on the same scanning line and for every two scanning lines on the same signal line. The liquid crystal display device according to the above. 10. The liquid crystal display device according to claim 8, further comprising means for reflecting the light in the pixel region displaying black to the inside of the liquid crystal display device and reusing the light in the pixel region displaying images.

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