JP2013205464A - Liquid crystal display device and manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device that suppresses a burn-in phenomenon even when a simple conversion method for converting input interlace signal directly into a progressive signal is used, and a manufacturing method.SOLUTION: A liquid crystal display device having liquid crystal display elements in a FFS mode arranged in matrix includes: a signal conversion unit 17 that compensates an interlace signal of an image to be input with compensation data to convert into a progressive signal; and a polarity switching unit XD that switches polarity of a pixel voltage generated on the basis of the progressive signal by two-frame unit. Data of previous line of the interlace signal is used as the compensation data.

Description

  The present invention relates to a liquid crystal display device used for a medium and small-sized vehicle-mounted TV and a manufacturing method thereof.

  Liquid crystal display devices are widely used as display devices for personal computers, portable information terminals, televisions, car navigation systems, and the like by taking advantage of features such as light weight, thinness, and low power consumption.

  Conventionally, TN type liquid crystal has been mainstream, but in recent years, wide viewing angle liquid crystal has been widely used, and FFS (Fringe Field Switching) system has been proposed as a representative mode. This is to improve the IPS (InPlane Switching) system driven by a lateral electric field, and to achieve a high aperture ratio and a high transmittance by using an ITO electrode having a two-layer structure (for example, see Patent Document 1). ).

JP 2002-221726 A

By the way, before the spread of liquid crystal, a CRT display was a standard, and the signal form was determined according to this driving method. NTSC signals of TV images are output as interlace signals, and TV cameras made with NTSC in mind are designed to output signals in an interlace format even when used for in-vehicle back monitors.
CRT displays use interlaced drive as standard, while liquid crystal displays use progressive drive. For this reason, when displaying on a liquid crystal display using a signal generated for CRT, IP conversion for converting an interlace signal into a progressive signal must be performed.

If it is a high-priced product such as a large-sized liquid crystal television, one screen of the interlace signal can be stored in the frame memory and output as a progressive signal. However, in a relatively inexpensive model such as an in-vehicle TV, the cost of the frame memory becomes high, so it is difficult to introduce this method. Therefore, a simple conversion method is used in which an input interlace signal is directly converted into a progressive signal and displayed.
However, when this simple conversion method is used and the above-described FFS mode liquid crystal display is used, a strong stickiness that has not been seen in the past has occurred.

  The present invention has been made in view of such circumstances, and even when a simple conversion method for directly converting an input interlace signal into a progressive signal is used, a liquid crystal display device with less stickiness phenomenon and An object is to provide a manufacturing method.

  In order to solve the above-described problems, the present invention provides a signal conversion that complements an interlace signal of an input image with complementary data and converts it into a progressive signal in a liquid crystal display device having FFS mode liquid crystal display elements arranged in a matrix. And a polarity switching unit that switches the polarity of the pixel voltage generated based on the progressive signal in units of two frames, and the complementary data uses data on the previous line of the interlace signal.

  According to another aspect of the present invention, there is provided a liquid crystal display device having FFS mode liquid crystal display elements arranged in a matrix, a signal conversion unit that complements an interlace signal of an input image with complementary data and converts the signal into a progressive signal, and the progressive signal. A polarity switching unit that switches the polarity of the pixel voltage generated based on each frame and switches so that the same polarity is repeated once every n (an integer greater than or equal to 3) frames. The data of the previous line of the interlace signal is used.

  In addition, the present invention provides a liquid crystal display device having FFS mode liquid crystal display elements arranged in a matrix, and includes a signal conversion unit that complements an interlace signal of an input image with complementary data and converts the interlace signal into a progressive signal. When the data of the previous line of the interlace signal is equal to the data of the current line, the conversion unit uses the data of the previous line as complementary data, and the data of the previous line of the interlace signal is different from the data of the current line Uses data representing the intermediate gradation of both data as complementary data.

  Further, the present invention provides a liquid crystal display device having FFS mode liquid crystal display elements arranged in a matrix, a signal conversion unit that complements an interlace signal of an input image with complementary data and converts the interlace signal into a progressive signal, and the interlace signal When the data of the previous line and the data of the current line are different, an edge processing unit that performs edge processing in a direction orthogonal to the line is provided.

  According to another aspect of the present invention, there is provided a method of manufacturing a liquid crystal display device having FFS mode liquid crystal display elements arranged in a matrix, wherein the liquid crystal display device supplements an interlace signal of an input image with complementary data and converts it into a progressive signal. And a polarity switching unit that switches the polarity of the pixel voltage generated based on the progressive signal in units of two frames, and the two flicker patterns used for voltage adjustment of the liquid crystal display element are alternated for each frame. Switch to and display.

1 is a diagram schematically showing a circuit configuration of a liquid crystal display device. 1 is a cross-sectional view illustrating a pixel structure of an FFS type liquid crystal display element used in a liquid crystal display device according to an embodiment of the present invention. 1 is a plan view showing a pixel structure of an FFS type liquid crystal display element used in a liquid crystal display device according to an embodiment of the present invention. The schematic diagram which shows the equivalent circuit between the two electrodes of the display element of FFS mode. The schematic diagram which shows the equivalent circuit between two electrodes of the display element of TN mode and VA mode. The conceptual diagram which shows the conversion method of the drive signal of a liquid crystal display. The figure which shows transition of the voltage applied to each display element. The figure which shows the generation | occurrence | production state of burning. The figure explaining the method of switching a polarity at 30 Hz. The figure explaining the effect at the time of switching polarity at 30 Hz. The figure which shows the form of the variation of polarity switching shown in FIG. The figure explaining the cause of flickering generation. The figure which shows the result of having investigated the flicker phenomenon. FIG. 6 is a diagram illustrating a driving method according to a second embodiment. The figure which represents the polarity of each display pixel in 1 frame on XY plane, and also shows transition of the time of the polarity. The figure explaining the drive method of the variation of 2nd Embodiment. The figure which represents the polarity of each display pixel in 1 frame on XY plane, and also shows transition of the time of the polarity. The figure explaining the drive method of the variation of 2nd Embodiment. The figure which represents the polarity of each display pixel in 1 frame on XY plane, and also shows transition of the time of the polarity. The figure which shows an evaluation pattern. The figure which shows two types of flicker patterns. 6A and 6B illustrate a method for easily switching flicker patterns. The conceptual diagram which shows the conversion method of the drive signal of the liquid crystal display of 3rd Embodiment. The figure which shows transition of the voltage applied to each display element. The figure which shows the condition of stickiness in the conventional drive method and the drive method which added the edge process.

[First Embodiment]
FIG. 1 is a diagram schematically showing a circuit configuration of a liquid crystal display device.
The liquid crystal display device includes a liquid crystal display panel DP, a backlight BL that illuminates the display panel DP, a display panel DP, and a display control circuit CNT that controls the backlight BL.

  The liquid crystal display panel DP has a structure in which a liquid crystal layer 3 is sandwiched between an array substrate 1 and a counter substrate 2 which are a pair of electrode substrates.

The display control circuit CNT controls the transmittance of the liquid crystal display panel DP by the liquid crystal driving voltage applied from the array substrate 1 and the counter substrate 2 to the liquid crystal layer 3. The transition from the spray alignment to the bend alignment is obtained by applying a relatively large electric field to the liquid crystal in a predetermined initialization process performed by the display control circuit CNT when the power is turned on.
In the array substrate 1, a plurality of pixel electrodes PE are arranged in a substantially matrix shape. In addition, a plurality of gate lines Y (Y1 to Ym) are arranged along the rows of the plurality of pixel electrodes PE, and a plurality of source lines X (X1 to Xn) are arranged along the columns of the plurality of pixel electrodes PE. .

  A plurality of pixel switching elements W are arranged in the vicinity of the intersection position of the gate line Y and the source line X. Each pixel switching element W is formed of a thin film transistor in which a gate is connected to the gate line Y and a source-drain path is connected between the source line X and the pixel electrode PE, and corresponds to when driven through the corresponding gate line Y. Conduction is established between the source line X and the corresponding pixel electrode PE.

  Each of the pixel electrodes PE and the common electrode CE is made of a transparent electrode material such as ITO, for example, and is a part of the liquid crystal layer 3 controlled to a liquid crystal molecular arrangement corresponding to the electric field from the pixel electrode PE and the common electrode CE. A liquid crystal pixel PX is configured together with the pixel region.

The display control circuit CNT includes a gate driver YD, a source driver XD, a backlight driving unit LD, a driving voltage generation circuit 4, and a controller circuit 5.
The gate driver YD sequentially drives the plurality of gate lines Y1 to Ym so that the plurality of switching elements W are conducted in units of rows. The source driver XD outputs the pixel voltage Vs to the plurality of source lines X1 to Xn in a period in which the switching elements W in each row are turned on by driving the corresponding gate line Y. The backlight driver LD drives the backlight BL. The driving voltage generation circuit 4 generates a driving voltage for the display panel DP. The controller circuit 5 controls the gate driver YD, the source driver XD, and the backlight driver LD.

  The driving voltage generation circuit 4 includes a gradation reference voltage generation circuit 7 that generates a predetermined number of gradation reference voltages VREF used by the source driver XD, and a common voltage generation that generates a common voltage Vcom applied to the counter electrode CT. Circuit 8 is included.

  The controller circuit 5 includes a control circuit 10, a vertical timing control circuit 11, a horizontal timing control circuit 12, a frame circuit 17, and a backlight control circuit 14.

The control circuit 10 generates a new synchronization signal SYNC (VSYNC, DE) based on the synchronization signal SYNC ′ input from the external signal source SS, and generates a signal for controlling the operation of each part of the display control circuit CNT.
The vertical timing control circuit 11 generates a control signal CTY for the gate driver YD and the like based on the synchronization signal SYNC (VSYNC, DE) input from the control circuit 10. The horizontal timing control circuit 12 generates a control signal CTX for the source driver XD based on the synchronization signal SYNC (VSYNC, DE) input from the control circuit 10.

  The image data conversion circuit 17 simply supplements the image data DI input from the external signal source SS by the interlace method (details will be described later) to generate a progressive signal, and outputs it to the source driver XD at a predetermined timing. The backlight control circuit 14 controls the backlight driver LD based on the control signal CTY output from the vertical timing control circuit 11.

  The image data DI is updated every frame period (vertical scanning period V). The control signal CTY is supplied to the gate driver YD, and the control signal CTX is supplied to the source driver XD together with the pixel data DO obtained from the image data conversion circuit 17. The control signal CTY is used to cause the gate driver YD to sequentially drive the plurality of gate lines Y as described above, and the control signal CTX is obtained for each liquid crystal pixel PX of the image data conversion circuit 17 and output in series. The pixel data DO is assigned to a plurality of source lines X and used to cause the source driver XD to perform an operation for designating the output polarity.

The gate driver YD is configured using, for example, a shift register circuit in order to select the gate line Y.
The source driver XD refers to a predetermined number of gradation reference voltages VREF supplied from the gradation reference voltage generation circuit 7 and converts the pixel data DO into pixel voltages Vs, respectively, and in parallel with the plurality of source lines X1 to Xn. Output to.

  The pixel voltage Vs is a voltage applied to the pixel electrode PE with reference to the common voltage Vcom of the common electrode CE. For example, the polarity is inverted with respect to the common voltage Vcom so as to perform dot inversion driving, line inversion driving, and frame inversion driving. . This polarity inversion is executed by the source driver XD based on an instruction from the control circuit 10.

FIG. 2 is a cross-sectional view showing a pixel structure of an FFS type liquid crystal display element used in the liquid crystal display device according to the embodiment of the present invention.
In the FFS type liquid crystal display device, a first ITO (Indium Tin Oxide) electrode 24 is formed on a transparent array substrate 1, and a second ITO electrode 26 having a slit is formed on the upper surface thereof via an insulating film 25. doing. A liquid crystal layer 3 is sandwiched between the array substrate 1 and the counter substrate 2 thus configured.

FIG. 3 is a plan view showing a pixel structure of an FFS type liquid crystal display element used in the liquid crystal display device according to the embodiment of the present invention.
The second ITO electrode 26 has a structure in which electrodes are alternately arranged by a plurality of slits provided in parallel. On the other hand, the first ITO electrode 24 has a flat plate structure.

  When a voltage is applied between the first and second ITO electrodes, an electric field corresponding to the slit electrode interval is generated, and the liquid crystal molecules of the liquid crystal layer 3 rotate. Thereby, the transmittance of the liquid crystal can be changed.

In this pixel structure, since the electric field concentrates on the electrode edge, the transmittance is controlled by using a fringe electric field, which is called FFS (Fringe Field Switching).
In FIG. 2, the first ITO electrode 24 is the common electrode CE, and the second ITO electrode 26 is the pixel electrode PE. However, the present invention is not limited to this. The first ITO electrode 24 may be the pixel electrode PE, and the second ITO electrode 26 may be the common electrode CE.

  Next, the cause of the stickiness that occurs in the FFS mode liquid crystal display will be described.

FIG. 4 is a schematic diagram showing an equivalent circuit between two electrodes of a display element in the FFS mode. As described above, not only the liquid crystal layer 3 to be driven but also the insulating film 25 such as a nitride film (SiN film) or an HRC planarizing film is arranged in series between the first and second ITO electrodes. Yes.
Therefore, if the applied voltage includes a DC component, the insulating film 25 is polarized by the DC component. Thereafter, even when the DC component is not applied, the polarization of the insulating film 25 does not disappear instantaneously. The presence of polarization by the insulating film 25 is considered to cause a sticking phenomenon in which the previous display pattern remains. In addition, since a strong fringe electric field is used, electric field concentration occurs locally, and stickiness is more likely to occur.

  FIG. 5 is a schematic diagram showing an equivalent circuit between two electrodes of a conventional TN mode and VA mode display element. Most of the space between the two electrodes (PE, CE) is the liquid crystal layer 3. As a result, a sticking phenomenon due to the presence of polarization does not occur, and therefore, there is no problem even if some DC component is included in the applied voltage.

  From the above study, it can be seen that the burning phenomenon can be alleviated by reducing the DC component of the voltage applied to the display element in the FFS mode. In the present embodiment, a driving method capable of reducing the applied DC component is proposed.

Next, a signal driving method in the liquid crystal display will be described.
The TV signal adopts a signal form that takes into account the former CRT (Cathode Ray Tube), that is, an interlace signal. The signal form is also applied to the liquid crystal display as it is. Therefore, it is necessary to convert and use the interlace signal in the liquid crystal display.

FIG. 6 is a conceptual diagram showing a method for converting a driving signal of a liquid crystal display.
FIG. 6A is a diagram schematically showing an image to be displayed. In this figure, 480 pixels are shown in the vertical direction and 1 pixel is shown in the horizontal direction. As an image, a pattern is assumed in which the first line is white, the second to fourth lines are black, and the fifth to sixth lines are white.

FIG. 6B is a diagram illustrating signals written by interlaced driving. Each column in the horizontal direction in this figure represents an image in which one pixel is written in accordance with the time transition.
In interlaced driving, half of the 480 scanning lines constituting the entire screen are divided into odd lines and even lines, and 240 lines are sent. Therefore, the data is input to the liquid crystal display in a state where data is missing.
The video signal of odd lines (1, 3, 5,...) Is transmitted to column 1 in FIG. 6B, and the video of even lines (2, 4, 6,...) Is transmitted to column 2. It is shown that a signal is transmitted. Also, column 3 and column 4 indicate that video signals are divided and transmitted in the same manner as column 1 and column 2, respectively.

Here, since the liquid crystal display has 480 scanning lines, the 240 signals must be converted into 480 signals. This conversion is called IP conversion or interlace / progressive conversion.
In a large-sized liquid crystal display, it is possible to temporarily store the transmitted interlace signal in a memory and configure it as data for one screen, and then send it out sequentially. However, for example, in-vehicle liquid crystal displays, the cost for realizing such a configuration is high. For this reason, the above-described method cannot be easily introduced in a device that places importance on cost.

In order to solve such a problem, a simple IP conversion function is employed. In this method, a memory for one line is provided, and missing data is complemented with the same data as the previous line.
FIG. 6C shows a result of complementing the video by the simple IP conversion function. The first video is inserted in the second row of row 1 and the third video is inserted in the fourth row. In addition, the second video is inserted in the third row of column 2 and the fourth video is inserted in the fifth. In this way, the signal is complemented without greatly reducing the resolution.

  By the way, in the liquid crystal display, when a DC voltage is continuously applied, a display defect occurs. Therefore, AC driving is performed to switch the polarity of the voltage applied for each frame. However, it has been clarified that there is a case where a large DC voltage is applied to the display element when simple IP conversion is performed.

FIG. 7 is a diagram showing the transition of the voltage applied to each display element. This voltage transition is a diagram created based on the video signal shown in FIG.
In the first line, the signal changes from white voltage (5V) → white voltage (−5V) → white voltage (5V) → white voltage (−5V). In this signal, both the positive polarity and the negative polarity have large amplitudes, but on average, 0 V and DC components are not applied.
In the second line, the signal changes from white voltage (5V) → black voltage (0V) → white voltage (5V) → white voltage (0V). In this signal, the positive polarity has a large amplitude and the negative polarity has a small amplitude, which corresponds to the application of a DC component of about 2.5 V on average.
In the third line, the signal changes from black voltage (0) → black voltage (−0V) → black voltage (0V) → black voltage (−0V). In this signal, both the positive polarity and the negative polarity have small amplitudes, and on average, 0 V and DC components are not applied.

Therefore, in the case where the display element blinks for each frame (change in luminance of the image), for example, when driving with 5 V amplitude, DC of up to 2.5 V may be applied.
As described above, the FFS type liquid crystal display is easy to stick when a DC voltage is applied. Therefore, when a large DC voltage is applied by such a simple IP conversion, the intensity of the FFS type liquid crystal display is strong even for a display of about 1 minute. Will occur.

  FIG. 8 is a diagram illustrating a state in which stickiness occurs. Intensity sticking occurs at the portion where the luminance of the image changes in the vertical direction of the screen, and the residual pattern is displayed as a horizontal line pattern.

  In the first embodiment, as a countermeasure against tightness, a method is adopted in which two frames are grouped to have the same polarity. For example, if a 60 Hz interlace signal is input, the polarity is switched at 30 Hz.

  FIG. 9 is a diagram for explaining a method of switching the polarity at 30 Hz. In this figure, 480 pixels are shown in the vertical direction and 1 pixel is shown in the horizontal direction. In the horizontal direction, the time transition of the polarity at which the one pixel is switched for each frame is shown.

Looking at the polarity of frame 1 in the vertical direction, the polarity of the first scanning line is “+”, the polarity of the second scanning line is “−”, the polarity of the third scanning line is “+”,... Inverted. Next, in frame 2, the polarity is the same as in frame 1 and has not changed.
In frame 3, the polarity is changed opposite to that in frame 2. In frame 4, the polarity is the same as in frame 3 and does not change.

FIG. 10 is a diagram for explaining the effect when the polarity is switched at 30 Hz.
FIG. 10A is a diagram showing a result of complementing video by the simplified IP conversion function shown in FIG. FIG. 10B is a diagram showing the transition of the voltage applied to each display element by the method of switching the polarity at 60 Hz shown in FIG. FIG.10 (c) is a figure which shows transition of the voltage applied to each display element by the method of switching polarity at 30 Hz.

According to the driving method of FIG. 10C, in the first line, the signal changes from white voltage (5V) → white voltage (5V) → white voltage (−5V) → white voltage (−5V). In this signal, both the positive polarity and the negative polarity have large amplitudes, but on average, 0 V and DC components are not applied.
In the second line, the signal changes from white voltage (5V) → black voltage (0V) → white voltage (−5V) → white voltage (0V). In this signal, both the positive polarity and the negative polarity have large amplitudes, but on average, 0 V and DC components are not applied. Therefore, the phenomenon in which a DC component of about 2.5 V on average is applied by the 60 Hz drive of FIG.
In the third line, the signal changes from black voltage (0) → black voltage (0V) → black voltage (−0V) → black voltage (−0V). In this signal, both the positive polarity and the negative polarity have small amplitudes, and on average, 0 V and DC components are not applied.

Next, variations of the above-described polarity switching will be described.
The polarity switching described above was executed every 30 Hz, that is, every two screens. However, it is not necessary to switch the polarity every two screens. Since tightness is not a phenomenon that occurs instantaneously, polarity switching (alternating current) should be performed within a few seconds or less. For example, it is also effective to switch the direction in which the voltage is applied by a switching method in which the same polarity is continued once every several frames to several tens of frames.

FIG. 11 is a diagram showing a variation of the polarity switching shown in FIG.
In FIG. 11, the same polarity is continued once every four frames. From frame 1 to frame 3, the polarity of the drive signal is switched for each frame. The frame 4 is driven with the same polarity as the frame 3. From frame 5 to frame 7, the polarity of the drive signal is switched for each frame. The frame 8 is driven with the same polarity as the frame 7.

[Second Embodiment]
The second embodiment relates to a driving method for solving the flickering problem as well as solving the burning problem described in the first embodiment. Accordingly, the same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

FIG. 12 is a diagram for explaining the cause of flickering. FIG. 12A shows the transition of the transmitted light amount when the polarity is switched at 60 Hz, and FIG. 12B shows the transition of the transmitted light amount when the polarity is switched at 30 Hz.
As shown in FIGS. 12A and 12B, the luminance decreases immediately after switching to a different polarity, and then increases to the original luminance. However, as shown in FIG. 12B, when switching to the same polarity, no decrease in luminance is observed.

  In general, flicker is recognized when the frequency of change in luminance is below about 50 Hz. Therefore, flicker may be recognized when the period of switching to the same polarity shown in the first embodiment is longer than 1/50 second.

  Note that the decrease in luminance at the time of polarity switching was not remarkable in the TN mode or VA mode, but was a phenomenon peculiar to the FFS mode. This is presumed to be because the FFS type liquid crystal display element has an insulating film, so that the voltage applied by the insulating film during polarity switching is absorbed, and as a result, the luminance is lowered.

FIG. 13 is a diagram showing the results of investigating the flicker phenomenon.
FIG. 13A is a diagram illustrating a transition of the amount of transmitted light when the polarity conversion of the drive signal is performed at 60 Hz. At this time, no flicker was recognized.

  FIG. 13B is a diagram showing the transition of the amount of transmitted light and the like when the polarity conversion of the drive signal is performed at 30 Hz. At this time, flicker was recognized. In the diagram showing the change in polarity, the latter half of the case of switching to the same polarity is shown circled. Since the luminance changes with this timing as a period, it is considered that the flicker was observed as 30 Hz.

  FIG. 13C is a diagram showing a transition of the amount of transmitted light and the like when the polarity conversion of the drive signal is performed once every five frames. Even in this case, flicker was recognized. In the diagram showing the change in polarity, the latter half of the case of switching to the same polarity is shown circled. Since the luminance changes at this timing, it is considered that it was observed as flushing.

FIG. 14 is a diagram for explaining a driving method according to the second embodiment.
The reason why flicker occurs in the above-described driving method is that the luminance of all the pixels increases at a time. Therefore, flicker can be reduced by dispersing the change in luminance temporally and spatially.

FIG. 14A shows the polarity when the polarity is switched at 30 Hz in the 2H1V inversion driving method.
Since it is 2H inversion driving, the polarity is switched every two scans. For example, the first, second, third, fourth,... Scanning lines are driven to have the same polarity. Normally, the polarity is switched every frame, but in this method, the polarity is switched at 30 Hz, so the polarity is switched every two frames. For this reason, the polarities of the second and third frames are the same, and the polarities of the fourth and fifth frames are the same.

  Here, the latter half of the case of switching to the same polarity is shown circled. Since the luminance changes at the timing when the circle is added, the luminance changes at 30 Hz, and flicker occurs.

FIG. 14B shows the polarity when the polarity is switched at 30 Hz and further shifted by 1H in the 2H1V inversion driving method.
In FIG. 14B, for example, in FIG. 14A, the polarity is displayed by shifting the frame position by one side (to the right) every other row. As a result, the timing at which the luminance changes is dispersed, and flickering can be prevented.

This driving method will be described in detail.
In FIG. 14B, the horizontal axis is time, and the polarity of each display pixel in one frame is not shown. FIG. 15 is a diagram showing the polarity of each display pixel in one frame on the XY plane, and further showing the transition of the polarity over time.

FIG. 15A corresponds to frame 1 in FIG. 14B, and the leftmost column in FIG. 15A is described in frame 1 in FIG. 14B.
FIG. 15B corresponds to the frame 2 in FIG. 14B, and the leftmost column in FIG. 15B is described in the frame 2 in FIG. 14B.
FIG. 15C corresponds to the frame 3 in FIG. 14B, and the leftmost column in FIG. 15C is described in the frame 3 in FIG. 14B.
FIG. 15D corresponds to the frame 4 in FIG. 14B, and the leftmost column in FIG. 15D is described in the frame 4 in FIG. 14B.

  Each frame in FIG. 15 represents 2H1V dot inversion driving. Therefore, the polarity alternately changes in units of two pixels in the Y direction, and alternately changes in units of one pixel in the X direction. The positions of high luminance pixels marked with circles are different for each of the frames (a) to (d). In this way, by using the 2H1V inversion drive, the high-luminance pixel is shifted downward (or upward) by one line in the next frame, so that each pixel can flicker while being driven at 30 Hz.

  The driving method described above is not limited to 2H inversion driving.

FIG. 16 is a diagram for explaining a variation driving method of the second embodiment.
FIG. 16A shows the polarity when the polarity is switched at 30 Hz in the 1H1V inversion driving method.
Since it is 1H inversion driving, the polarity is switched every scanning. The polarity is switched every frame, but in this method, the polarity is switched at 30 Hz, so the polarity is switched every two frames. For this reason, the polarities of the second and third frames are the same, and the polarities of the fourth and fifth frames are the same.

  Here, the latter half of the case of switching to the same polarity is shown circled. Since the luminance changes with the period indicated by the circle as a cycle, a luminance change of 30 Hz occurs and flicker occurs.

FIG. 16B shows the polarity when the polarity is switched at 30 Hz and further shifted by 1H in the 1H1V inversion driving method.
In FIG. 16B, for example, the polarity is displayed by shifting the position of the frame one horizontal (to the right) every other row in FIG. 16A. As a result, the timing at which the luminance changes is dispersed, and flickering can be prevented.

This driving method will be described in detail.
In FIG. 16B, the horizontal axis is time, and the polarity of each display pixel in one frame is not shown. FIG. 17 is a diagram showing the polarity of each display pixel in one frame on the XY plane, and further showing the transition of the polarity over time.
Each frame in FIG. 17 represents 1H1V dot inversion driving. Accordingly, the polarity alternately changes in units of one pixel in the Y direction, and alternately changes in units of one pixel in the X direction. The positions of high luminance pixels marked with circles are different for each of the frames (a) to (d). In this way, by using the 1H1V inversion drive and shifting the high-luminance pixel downward (or upward) by one line in the next frame, each pixel can flicker while being driven at 30 Hz.

FIG. 18 is a diagram illustrating a variation driving method according to the second embodiment.
FIG. 18A shows the polarity when the polarity is switched at 30 Hz in the 3H1V inversion driving method.
Since it is 3H inversion driving, the polarity is switched every three scans. For example, the second, third and fourth scanning lines are driven so as to have the same polarity. Normally, the polarity is switched every frame, but in this method, the polarity is switched at 30 Hz, so the polarity is switched every two frames. For this reason, the polarities of the second and third frames are the same, and the polarities of the fourth and fifth frames are the same.

  Here, the latter half of the case of switching to the same polarity is shown circled. Since the luminance changes with the period indicated by the circle as a cycle, a luminance change of 30 Hz occurs and flicker occurs.

FIG. 18B shows the polarity when the polarity is switched at 30 Hz and further shifted by 1H in the 3H1V inversion driving method.
In FIG. 18B, for example, in FIG. 18A, the polarity is displayed by shifting the frame position by one side (rightward) every other row. As a result, the timing at which the luminance changes is dispersed, and flickering can be prevented.

This driving method will be described in detail.
In FIG. 18B, the horizontal axis is time, and the polarity of each display pixel in one frame is not shown. FIG. 19 is a diagram showing the polarity of each display pixel in one frame on the XY plane, and further showing the transition of the polarity over time.

  Each frame in FIG. 19 represents 3H1V dot inversion driving. Accordingly, the polarity alternately changes in units of 3 pixels in the Y direction and alternately changes in units of 1 pixel in the X direction. The positions of high luminance pixels marked with circles are different for each of the frames (a) to (d). In this way, by using the 3H1V inversion drive and shifting the high-luminance pixel downward (or upward) by one line in the next frame, each pixel can flicker while being driven at 30 Hz.

  The second embodiment has been described above. In any of the driving methods described here, the polarity is shifted in time every other line from the base driving method. In the second embodiment, every other line is shifted in the gate line direction (horizontal direction), but it may be shifted in the source line direction (vertical direction) or random. Anyway, it is important to disperse the portions where the luminance changes temporally and spatially.

In addition, there is a flicker pattern setting problem to be considered when adopting the method of changing the polarity switching pattern with time described in the second embodiment.
The flicker pattern is a pattern generally used for DC adjustment of liquid crystal. In the case of normal 1H1V dot inversion driving, a staggered pattern shown in FIG. 20 is used as an evaluation pattern. Using this evaluation pattern, only pixels with one display polarity are turned on instantaneously to make flickering obvious, thereby adjusting DC, in particular, Vcom voltage.

  However, in this embodiment, this polarity pattern is switched over time. Therefore, as shown in FIG. 21, it is necessary to prepare two types of flicker patterns and switch the patterns alternately for each frame.

FIG. 22 is a diagram for explaining a method of simply switching the flicker pattern.
This method uses a data interpolation function by interlace driving.
When the pattern of FIG. 22A is interlaced, data is thinned out and transmitted, and the complement is automatically executed by the above-described IP conversion.

In FIG. 22B, the data of the first, third, fifth,... Scanning lines are transmitted. The second, fourth, sixth,... Data is complemented by copying the previous line data (first, third, fifth,...) Using a line memory.
In FIG. 22C, the second, fourth, sixth,... Data of the scanning lines are transmitted. The third, fifth, seventh,... Data is complemented by copying the data in the previous line (second, fourth, sixth,...) Using a line memory.
FIGS. 22D and 22E differ only in the polarities of FIGS. 22A and 22B, respectively, and the data complementing operation is the same.

  In this way, a desired pattern can be switched and displayed by using the data complementing function by interlace driving. Therefore, when 2H inversion driving is used, such flicker matching can be easily realized. Considering this point, 2H inversion driving is the optimum driving method.

[Third embodiment]
In each of the embodiments described above, measures against interlacing and tightness due to low frequency have been described. In the third embodiment, the tightness is prevented by changing the IP conversion method.
Originally, interlacing and tightness are caused by complementing a missing data portion with data of the previous line during IP conversion. At this time, a noticeable stickiness occurs in a portion where data with the previous line changes. Therefore, when the line memory is held for several lines and data changes, the tightness is considerably improved by replacing the complementary data with halftone data.

FIG. 23 is a conceptual diagram showing a driving signal conversion method for the liquid crystal display according to the third embodiment.
Since FIG. 23 (a) and FIG. 23 (b) have already been described, description thereof will be omitted.
In the conversion method of the third embodiment, a plurality of line memories are provided, and when the data changes in the vertical direction in the figure, the missing data is supplemented with the intermediate gradation data.

  FIG. 23C shows the result of complementing the video by this method. Intermediate tone (gray) images are inserted in the second and fourth lines of row 1. In the sixth line, since the data does not change in the vertical direction, the fifth data (white) is inserted. In addition, intermediate gray (gray) images are inserted in the first and fifth lines of column 2. In the third line, since the data does not change in the vertical direction, the second line (black) is inserted.

FIG. 24 is a diagram showing the transition of the voltage applied to each display element. This voltage transition is a diagram created based on the video signal shown in FIG.
Conventionally, in the second case where the stickiness has occurred, the signal changes in the order of gray voltage (2.5 V) → black voltage (0 V) → gray voltage (2.5 V) → white voltage (0 V). On average, it is about 1.25 V, which can halve the conventional DC component.

Note that as a variation of the complementary processing of the third embodiment, signal processing (“edge processing”) that detects an “edge” in the vertical direction and relaxes a change in the signal at the edge portion may be performed. Since this “edge processing” has an effect of “blurring” an interlace signal, it can be expected to have an effect of preventing interlacing and tightness.
Further, the complement processing of the third embodiment may be performed, and this edge processing may be executed at a later stage.
FIG. 25 is a diagram showing a sticking situation between the conventional driving method and the driving method to which edge processing is added. In the driving method to which edge processing was added, no stickiness was observed.

Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage.
Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

  DESCRIPTION OF SYMBOLS 1 ... Array substrate, 2 ... Opposite substrate, 3 ... Liquid crystal layer, 4 ... Drive voltage generation circuit, 5 ... Controller circuit, 7 ... Tone reference voltage generation circuit, 10 ... Control circuit, 14 ... Backlight control circuit, 17 ... Image data conversion circuit, 24 ... first ITO electrode, 25 ... insulating film, 26 ... second ITO electrode, YD ... gate driver, DI ... image data, DO ... pixel data, XD ... source driver, PE ... pixel Electrode, CE ... Common electrode, PX ... Liquid crystal pixel, DP ... Display panel, BL ... Back light, CNT ... Display control circuit, X ... Source line, Y ... Gate line, W ... Switching element.

Claims (8)

In a liquid crystal display device having FFS mode liquid crystal display elements arranged in a matrix,
A signal converter that complements the interlaced signal of the input image with complementary data and converts it to a progressive signal;
A polarity switching unit that switches the polarity of the pixel voltage generated based on the progressive signal in units of two frames;
The liquid crystal display device according to claim 1, wherein the complementary data uses data of the previous line of the interlace signal.   The frame in which the polarity switching unit switches the polarity of the pixel voltage to be written to the liquid crystal display element of the even line and the frame to switch the polarity of the pixel voltage to be written to the liquid crystal display element of the odd line are different. 1. A liquid crystal display device according to 1.   The liquid crystal display device according to claim 1, wherein the polarity switching unit switches the polarity of the pixel voltage by a 2H inversion driving method. In a liquid crystal display device having FFS mode liquid crystal display elements arranged in a matrix,
A signal converter that complements the interlaced signal of the input image with complementary data and converts it to a progressive signal;
A polarity switching unit that switches the polarity of the pixel voltage generated based on the progressive signal every frame, and further switches the polarity so that the same polarity is repeated once every n (an integer of 3 or more) frames,
The liquid crystal display device according to claim 1, wherein the complementary data uses data of the previous line of the interlace signal. In a liquid crystal display device having FFS mode liquid crystal display elements arranged in a matrix,
It has a signal converter that complements the interlace signal of the input image with complementary data and converts it to a progressive signal,
The signal converter is
When the data of the previous line of the interlace signal and the data of the current line are equal, the data of the previous line is used as complementary data,
2. A liquid crystal display device according to claim 1, wherein when the data of the previous line of the interlace signal is different from the data of the current line, data representing a gray level intermediate between both data is used as complementary data. In a liquid crystal display device having FFS mode liquid crystal display elements arranged in a matrix,
A signal converter that complements the interlaced signal of the input image with complementary data and converts it to a progressive signal;
An edge processing unit that performs edge processing in a direction orthogonal to the line when the data of the previous line of the interlace signal is different from the data of the current line. In a method for manufacturing a liquid crystal display device having FFS mode liquid crystal display elements arranged in a matrix,
The liquid crystal display device includes a signal converter that complements an interlace signal of an input image with complementary data and converts the signal into a progressive signal, and polarity switching that switches the polarity of a pixel voltage generated based on the progressive signal in units of two frames. With
A method for manufacturing a liquid crystal display device, wherein two flicker patterns used for voltage adjustment of the liquid crystal display element are alternately switched and displayed for each frame.   The manufacturing method according to claim 7, wherein the image input to the signal conversion unit is one of the two flicker patterns.

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