JP2009086564A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device that reduces the deterioration of image quality while reducing the heat generation of a driver IC. <P>SOLUTION: The liquid crystal display device has a liquid crystal display panel having a liquid crystal material sealed between a pair of substrates, and a control circuit board for providing display control of the liquid crystal display panel. The control circuit board has a tone correction means for comparing input tone data to be written to one of a plurality of pixel electrodes input from outside the display device with input tone data written to a pixel electrode in the preceding stage of the one pixel electrode on a video signal line connected with the one pixel electrode via a TFT element, and correcting the input tone data to be written to the one pixel electrode according to information on one or more of the tone difference between the two input tone data, and the ambient temperature and the position on the liquid crystal display panel of the pixel electrode. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device, and more particularly to a technique effective when applied to an active matrix TFT liquid crystal display device.

  2. Description of the Related Art Conventionally, there is an active matrix type TFT liquid crystal display device (hereinafter simply referred to as a TFT liquid crystal display device) as a display device used for a monitor of a television or a personal computer.

  The TFT liquid crystal display device is a display device having a liquid crystal display panel in which liquid crystal is sealed between two substrates. At this time, one of the two substrates is generally called a TFT substrate. For example, a plurality of scanning signal lines and a plurality of video signals are formed on the surface of an insulating substrate such as a glass substrate. A line, a plurality of TFT elements (active elements), a plurality of pixel electrodes, and the like are formed. The other of the two substrates is generally called a counter substrate. For example, a light-shielding film that divides the display region into regions for each pixel on the surface of an insulating substrate such as a glass substrate. And color filters are formed. Note that the counter electrode that drives the liquid crystal in a pair with the pixel electrode may be formed on the TFT substrate side or may be formed on the counter substrate side.

  In the liquid crystal display panel, a display area for displaying images and images is set as a set of a plurality of pixels, and each pixel has a TFT element and a pixel electrode connected to the source of the TFT element. At this time, each TFT element has a drain connected to the video signal line and a gate connected to the scanning signal line. In the present specification, regarding the source and drain of the TFT element, the one connected to the pixel electrode is referred to as the source, and the one connected to the video signal line is referred to as the drain. The one connected to the electrode may be called a drain, and the one connected to the video signal line may be called a source. In an actual liquid crystal display panel, the relationship between the source and drain of the TFT element is sequentially switched depending on the relationship between the potential of the video signal applied to the video signal line and the potential of the counter electrode.

  In the conventional liquid crystal display panel, a plurality of pixel electrodes arranged along the extending direction of the video signal line between two adjacent video signal lines are connected to each pixel electrode, for example. It is connected to one of the two adjacent video signal lines via a TFT element. At this time, in the conventional general liquid crystal display panel, the drains of the TFT elements connected to the pixel electrodes are all connected to the same video signal line of the two video signal lines. .

  Further, in a recent liquid crystal display panel, for example, a TFT element in which a drain is connected to one of the two adjacent video signal lines between two adjacent video signal lines. There is a liquid crystal display panel in which TFT elements whose drains are connected to the other video signal line are alternately arranged along the extending direction of the video signal line (see, for example, Patent Document 1). In such a liquid crystal display panel, a plurality of pixel electrodes arranged along the extending direction of the video signal lines between two adjacent video signal lines are, for example, the two pixel electrodes via TFT elements. Pixel electrodes connected to one of the adjacent video signal lines and pixel electrodes connected to the other video signal line alternately along the extending direction of the video signal line Are lined up.

  In addition, when the liquid crystal display panel of Patent Document 1 is viewed, for example, for each column of a plurality of pixel electrodes arranged in the extending direction of the scanning signal line, each pixel electrode is arranged on the right side of the pixel electrode. The column connected to the video signal line and the column connected to the video signal line in which each pixel electrode is arranged on the left side of the pixel electrode are alternately arranged. That is, a pixel electrode on the right side of the video signal line and a pixel electrode on the left side of the video signal line are alternately connected to one video signal line. Therefore, the pixel arrangement in the liquid crystal display panel of Patent Document 1 is sometimes referred to as, for example, a staggered arrangement.

  In addition, among the conventional TFT liquid crystal display devices, the liquid crystal display device having the configuration described in Patent Document 1 (staggered arrangement), for example, has two video signal lines when applied to each video signal line. Add so that the relationship of the polarity of the video signal applied to the adjacent video signal line is opposite. That is, when the potential of the video signal applied to one of the two adjacent video signal lines is higher than the potential of the counter electrode, the potential of the video signal line applied to the other video signal line is opposite. It is lower than the potential of the electrode. Further, the polarity of the video signal applied to one video signal line is switched every frame period, for example, and is added to the next frame period when the potential of the video signal applied in a certain frame period is higher than the potential of the counter electrode. The potential of the video signal line is lower than the potential of the counter electrode.

That is, the liquid crystal display device of Patent Document 1 can drive a liquid crystal display panel by a driving method called dot inversion driving by adding a video signal corresponding to a driving method called column-by-column inversion driving. Therefore, there is an advantage that the amount of heat generated by the driver IC that generates the video signal (gradation voltage) can be reduced, and malfunction and failure due to heat can be reduced.
Japanese Patent Laid-Open No. 10-90712

  By the way, in TFT liquid crystal display devices such as liquid crystal televisions, in recent years, a high refresh rate has been advanced in order to suppress flickering of the screen or improve the display performance of moving images.

  However, in the conventional TFT liquid crystal display device, as the refresh rate increases, for example, a video signal (grayscale voltage) applied to the video signal line via the TFT element (active element) is applied to the pixel electrode. When writing to the recording medium, there is a problem that insufficient writing occurs and the image quality deteriorates.

  Among the conventional TFT liquid crystal display devices, the liquid crystal display device disclosed in Patent Document 1 has an advantage that the amount of heat generated by the driver IC can be reduced as described above. On the other hand, for example, a phenomenon called a horizontal stripe occurs. There is a problem that the image quality is easily deteriorated by the horizontal stripe.

  An object of the present invention is, for example, to provide a technique capable of reducing the amount of heat generated by a driver IC of a liquid crystal display device and reducing image quality deterioration.

  The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

  The outline of typical inventions among the inventions disclosed in the present application will be described as follows.

  (1) A liquid crystal display panel in which a liquid crystal material is sealed between a pair of substrates, and a control circuit substrate that performs display control of the liquid crystal display panel, and one of the pair of substrates is an insulating substrate A plurality of scanning signal lines, a plurality of video signal lines, a plurality of TFT elements, and a plurality of pixel electrodes connected to the sources of the TFT elements, In addition, a plurality of pixel electrodes arranged along the extending direction of the video signal line between two adjacent video signal lines are connected to the two adjacent video signal lines via TFT elements. Pixel electrodes connected to one of the video signal lines and pixel electrodes connected to the other of the two adjacent video signal lines via the TFT element alternately It is a liquid crystal display device arranged side by side, The control circuit board Input gradation data to be written to each pixel electrode input from outside the display device, input gradation data to be written to one pixel electrode of the plurality of pixel electrodes, and the one pixel electrode via a TFT element And the input gradation data written to the pixel electrode in the preceding stage of the one pixel electrode in the connected video signal line, and based on the gradation difference between the two input gradation data, the one pixel A liquid crystal display device having gradation correction means for correcting input gradation data written to an electrode.

(2) In the liquid crystal display device according to (1), the gradation correction unit is configured such that the gradation number of the input gradation data to be written to the one pixel electrode is K _n , and the input gradation data to be written to the previous pixel electrode. Is a liquid crystal that corrects the number of gradations of gradation data to be written to the one pixel electrode to K _n ′ represented by the following equation 1, where K _n−1 is the number of gradations and C _n is the correction coefficient. Display device.
K _n ′ = int {(K _n−1 −K _n ) × C} + K _n (Expression 1)

(3) In the liquid crystal display device of (2), the correction coefficient C is a first correction coefficient represented by a function of the difference in the number of gradations of the two input gradation data K _n−1 -K _n. α, a second correction coefficient β expressed as a function of the temperature around the one pixel electrode, a video signal line connected to the TFT element connected to the one pixel electrode, and the TFT element A third correction coefficient γ ₁ expressed as a function of the distance from the signal input terminal of the connected scanning signal line, a scanning signal line to which the TFT element connected to the one pixel electrode is connected; Liquid crystal represented by a product of any one or two or more of the fourth correction coefficients γ ₂ represented by a function of the distance from the signal input end of the video signal line to which the TFT element is connected. Display device.

(4) In the liquid crystal display device according to (3), the first correction coefficient α is obtained when the difference K _n−1 −K _n between the two input gradation data is negative. A positive value, a negative value when the difference in the number of gradations K _n−1 −K _n of the two input gradation data is a positive value, and the two input gradation data A liquid crystal display device in which the absolute value of the correction coefficient α is larger as the absolute value of the gradation number difference K _n−1 −K _n is larger.

  (5) In the liquid crystal display device according to (3), the second correction coefficient β is determined when the temperature around the one pixel electrode is higher than the specific temperature with a predetermined specific temperature as a boundary. Is a constant value regardless of the temperature difference from the specific temperature, and is a negative value when the temperature around the one pixel electrode is lower than the specific temperature, and the specific temperature and A liquid crystal display device in which the absolute value of the correction coefficient β is larger as the temperature difference is larger.

(6) In the liquid crystal display device of (3), the third correction coefficient γ ₁ is connected to a TFT element connected to the one pixel electrode with a predetermined distance as a boundary. When the distance between the video signal line and the signal input end of the scanning signal line to which the TFT element is connected is shorter than the specific distance, it is a constant value regardless of the difference from the specific distance, When the distance between the video signal line connected to the TFT element connected to one pixel electrode and the signal input end of the scanning signal line connected to the TFT element is longer than the specific distance, A liquid crystal display device that has a negative value and a larger absolute value of the third correction coefficient γ ₁ as a difference from the specific distance is larger.

  (7) In the liquid crystal display device of (6), the specific distance is a distance between a video signal line arranged at a position closest to the signal input end of the scanning signal line and a signal input end of the scanning signal line. Shorter liquid crystal display.

(8) In the liquid crystal display device of (3), the fourth correction coefficient γ ₂ is connected to a TFT element connected to the one pixel electrode with a predetermined distance as a boundary. When the distance between the scanning signal line and the signal input end of the video signal line to which the TFT element is connected is shorter than the specific distance, it is a constant value regardless of the difference from the specific distance, When the distance between the scanning signal line connected to the TFT element connected to one pixel electrode and the signal input end of the video signal line connected to the TFT element is longer than the specific distance, A liquid crystal display device having a negative value and a larger absolute value of the fourth correction coefficient γ ₂ as the difference from the specific distance is larger.

  (9) In the liquid crystal display device according to (8), the specific distance is a distance between a scanning signal line disposed at a position closest to a signal input end of the video signal line and a signal input end of the video signal line. Shorter liquid crystal display.

  According to the liquid crystal display device of the present invention, the amount of heat generated by the driver IC can be reduced, and image quality deterioration due to the occurrence of a phenomenon called a horizontal stripe can be reduced.

Hereinafter, the present invention will be described in detail together with embodiments (examples) with reference to the drawings.
In all the drawings for explaining the embodiments, parts having the same function are given the same reference numerals and their repeated explanation is omitted.

FIG. 1A to FIG. 1E are schematic views for explaining a configuration example of a TFT liquid crystal display device according to the present invention.
FIG. 1A is a schematic block diagram showing an example of a schematic configuration of a TFT liquid crystal display device according to the present invention. FIG. 1B is a schematic circuit diagram showing an example of a schematic configuration of a display area in the liquid crystal display panel shown in FIG. FIG. 1C is a schematic diagram showing a configuration example of input gradation data input to the TFT liquid crystal display device. FIG. 1D is a schematic diagram illustrating a configuration example of output gradation data obtained by rearranging input gradation data. FIG. 1E is a schematic diagram showing an example of a method for driving the liquid crystal display panel shown in FIG.

  A TFT liquid crystal display device according to the present invention includes, for example, a liquid crystal display panel 1 having a plurality of scanning signal lines GL and a plurality of video signal lines DL, a data driver 2, as shown in FIG. It has a gate driver 3 and a control circuit board 4.

  Although omitted in FIG. 1A, the TFT liquid crystal display device includes several circuit components in addition to the liquid crystal display panel 1, the data driver 2, the gate driver 3, and the control circuit board 4. Needless to say, for example, when the TFT liquid crystal display device is a transmissive or transflective type, it has a light source called a backlight unit.

  The liquid crystal display panel 1 is a display panel in which a liquid crystal material is sealed between a TFT substrate and a counter substrate. The display area DA of the liquid crystal display panel 1 is set as a set of pixels arranged in a matrix, and one pixel is, for example, two adjacent scanning signal lines GL and two adjacent pixels. This corresponds to the size of the area surrounded by the video signal line DL. At this time, for example, as shown in FIG. 1B, each pixel includes a TFT element Tr that is an active element (sometimes referred to as a switching element) and a pixel electrode PX connected to the source of the TFT element Tr. And have.

  The drain of each TFT element Tr is connected to one of the two video signal lines DL adjacent to each other across the pixel electrode connected to the source of the TFT element Tr. The gate of each TFT element is connected to one scanning signal line GL of two adjacent scanning signal lines GL across the pixel electrode PX connected to the source of the TFT element Tr. Yes. In other words, the pixel electrode PX disposed between two adjacent video signal lines DL is connected to one of the two adjacent video signal lines DL via the TFT element Tr. is doing.

  At this time, the pixel electrode PX includes a liquid crystal material LC sealed between the TFT substrate and the counter substrate, and a pixel capacitor (also referred to as a liquid crystal capacitor) together with the counter electrode CT provided on the TFT substrate or the counter substrate. Is forming.

  Further, in the liquid crystal display panel 1 of the TFT liquid crystal display device according to the present invention, a plurality of pixel electrodes arranged along the extending direction of the video signal lines DL between two adjacent video signal lines DL are The pixel electrode PX connected to one video signal line DL of the two adjacent video signal lines DL via the TFT element Tr and the other video signal line DL via the TFT element. The pixel electrodes PX are alternately arranged along the extending direction of the video signal lines DL.

  Further, when the liquid crystal display panel 1 is viewed, for example, for each column of a plurality of pixel electrodes PX arranged in the extending direction of the scanning signal line GL, each pixel electrode PX is disposed on the left side of the pixel electrode PX. The column connected to the video signal line DL and the column connected to the video signal line DL in which each pixel electrode PX is arranged on the right side of the pixel electrode PX are alternately arranged. That is, the pixel electrode PX on the right side of the video signal line DL and the pixel electrode PX on the left side of the video signal line DL are alternately connected to one video signal line DL. For this reason, the pixel arrangement as shown in FIG. 1B is sometimes called, for example, a staggered arrangement.

  In the conventional general TFT liquid crystal display device, when a plurality of pixel electrodes PX arranged in the extending direction of the video signal line DL are connected to a common video signal line DL, the display area DA is displayed. When the number of pixels in the horizontal direction is M pixels (M is an arbitrary natural number), there are M video signal lines DL to which video signals are actually added. In the case of a TFT liquid crystal display device corresponding to color display, one dot (or one pixel) of an image or an image is composed of a plurality of sub-pixels. For example, in the case of an RGB color TFT liquid crystal display device One dot of video or image is constituted by three sub-pixels arranged in the extending direction of the scanning signal line GL. Therefore, in the RGB color TFT liquid crystal display device, when the horizontal direction of the display area DA is M dots, the number of video signal lines DL to which video signals are actually applied is 3M.

  On the other hand, in the TFT liquid crystal display device according to the present invention, when the number of pixels in the horizontal direction of the display area DA is M, the number of video signal lines DL to which video signals are actually added is M + 1. In the RGB color TFT liquid crystal display device, when the horizontal direction of the display area DA is M dots, the number of video signal lines DL to which video signals are actually added is 3M + 1.

  When displaying an image or an image on the TFT liquid crystal display device according to the present invention, first, input signals such as an input gradation data group Kin, a control signal CS, and a power supply voltage V inputted from the outside of the TFT liquid crystal display device are displayed. And received by the control circuit board 4. For example, the control circuit board 4 converts the input gradation data Kin into the output gradation data Kout, and transmits the output gradation data Kout, the data driver control signal CS1, the power supply voltage V1, and the like to the data driver 2 for gate driver control. The signal CS2, the power supply voltage V2, and the like are transmitted to the gate driver 3.

The input gradation data Kin has a configuration as shown in FIG. In FIG. 1C, HL _n (n = 1, 2, 3, 4, 5) represents a column of gradation data for the pixel electrodes of the pixels arranged in the extending direction of the scanning signal line GL. BL _m (m = 1, 2, 3, 4, 5) represents a block of gradation data _{Kn, m} for each pixel electrode. When the display gradation of each pixel is 256 gradations, one gradation data _{Kn, m} block is 8 bits.

In the case of a conventional general TFT liquid crystal display device, the gradation data K _{n, m} of the block BL _m of each column HL _n is input to a common video signal line DL _m , so When the number of pixels in the horizontal direction is M pixels (M is an arbitrary natural number), the gradation data of one column HL _n is composed of M blocks. Further, in a color TFT liquid crystal display device of the RGB system, if the lateral direction of the display area DA of the M dot, the gradation data of one column HL _n is composed of 3M block.

On the other hand, in the case of the TFT liquid crystal display device according to the present invention, one video signal line DL _m includes, for example, gradation data K _{n, m} of the block BL _{m in} the column HL _n where n is an odd number _, and n is an even number. It is necessary to alternately input the gradation data K _{n, m + 1} of the block BL _{m + 1} of the column HL _n . Therefore, in the TFT liquid crystal display device according to the present invention, the input gradation data Kin is converted into, for example, output gradation data Kout configured as shown in FIG. Incidentally, gradation data _{K n, m} in FIG. 1 (d) is made to coincide with the gradation data _{K n, m} in FIG. 1 (c).

At this time, the gradation data for one column HL _n in the output gradation data Kout is composed of M + 1 blocks (in the case of a color TFT liquid crystal display device of the RGB system 3M + 1 block).

Incidentally, gradation data KD of blocks BL ₁ of the first column HL _n n is an even number of such rows HL _2, column HL ₄ in FIG. 1 (d) is a gray-scale data of the dummy, for example, 0 gradation Gradation data, or the same gradation data as the block BL _{1 of the} previous column HL _n−1 . Although not shown, the last block BL _{M + 1} (or BL _{3M + 1} ) of the column HL _n where n is an odd number such as the column HL ₁ , the column HL ₃ , and the column HL ₅ is also set as dummy gradation data.

  The output gradation data Kout created (converted) in the control circuit board 4 is transmitted to the data driver 2. The control circuit board 4 and the data driver 2 are connected via, for example, a flexible printed wiring board or another circuit board, and the output gradation data Kout passes through the flexible printed wiring board or the other circuit board. And input to the data driver 2.

The data driver 2 generates a video signal (grayscale voltage signal) to be written to each pixel electrode PX based on the grayscale data Kn _{, m} of the output grayscale data Kout configured as shown in FIG. . Then, the generated video signal is applied to each video signal line DL in synchronization with the scanning signal input from the gate driver 3 to each scanning signal line GL.

  At this time, the video signal applied from the data driver 2 to each video signal line DL has, for example, the polarity of the video signal applied to two adjacent video signal lines in one frame period as shown in FIG. One is always positive (+) and the other is always negative (-). The polarity of the video signal represents the relationship between the potential of the video signal written to the pixel electrode PX from the video signal line DL via the TFT element Tr and the potential of the counter electrode CT. The case where the potential is higher than the potential of the counter electrode CT is called positive polarity, and the case where the potential of the pixel electrode PX is lower than the potential of the counter electrode CT is called negative polarity.

At this time, regarding the pixel electrode PX arranged between two video signal lines DL (for example, DL _m−1 and DL _m ), the positive (+) pixel electrode PX and the negative (−) pixel electrode PX. Pixel electrodes PX are alternately arranged. In addition, when looking at the pixel electrode PX aligned between two scanning signal lines GL (for example, GL _n and GL _{n + 1} ), the positive (+) pixel electrode PX and the negative (−) pixel electrode PX Are lined up alternately.

  In addition, when the polarity of the video signal applied to each video signal line DL in a certain frame period is as shown in FIG. 1E, the polarity of the video signal applied to each video signal line DL in the next frame period. Is switched between positive polarity (+) and negative polarity (−). Further, the polarity of the video signal applied to each video signal line DL in the next frame period has a relationship as shown in FIG.

  That is, in the TFT liquid crystal display device according to the present invention, the data driver 2 generates a video signal corresponding to a driving method called column-inversion and applies it to each video signal line DL. It can be driven by a so-called driving method. Therefore, the processing load on the data driver 2 is reduced, and the amount of heat generated by the data driver 2 can be reduced.

  However, in the conventional driving method in the TFT liquid crystal display device according to the present invention, when it is driven at a high refresh rate (for example, 120 Hz), a phenomenon called a horizontal stripe tends to occur. The phenomenon called the horizontal stripe, for example, appears that the luminance and chromaticity of even-numbered horizontal lines (pixel columns) and odd-numbered horizontal lines differ from the luminance and chromaticity specified by the video signal. It is a phenomenon.

  There are various causes for the occurrence of the horizontal stripes in the TFT liquid crystal display device according to the present invention. In particular, the difference between the gradation voltages of the two pixel electrodes, the temperature of each pixel, and the video signal line or scanning signal of each pixel. The inventors of the present application have found that the distance from the signal input end of the line is greatly related to the generation of the horizontal stripe. In view of this, the following describes a tendency and a method for reducing the horizontal stripes for each of the main factors causing the horizontal stripes.

FIG. 2A and FIG. 2B are schematic diagrams for explaining the first cause of the occurrence of lateral stripes in the TFT liquid crystal display device according to the present invention.
FIG. 2A is a schematic circuit diagram showing an example of the gradation of each pixel in the TFT liquid crystal display device according to the present invention. FIG. 2B is a schematic waveform diagram showing an example of the gradation voltage written to the two pixel electrodes PX1 and PX2 shown in FIG.

When the TFT liquid crystal display device according to the present invention is a general RGB color TFT liquid crystal display device, two adjacent video signal lines DL (for example, DL _m−1 and the like) shown in FIG. (DL _m ) and two adjacent scanning signal lines GL (for example, GL _n and GL _{n + 1} ), one pixel corresponding to a region is a sub-pixel and is aligned in the extending direction of the scanning signal line GL. The three sub-pixels constitute one dot of the video or image.

Further, in the case of a general RGB color TFT liquid crystal display device, a pixel located between two adjacent video signal lines DL (for example, DL _m−1 and DL _m ) shown in FIG. The sub-pixels having the electrode PX are all the same color and are any one of R (red), G (green), and B (blue). Further, the sub-pixel having the pixel electrode PX between two adjacent scanning signal lines GL (for example, GL _n and GL _{n + 1} ) is, for example, a red sub-pixel, a green sub-pixel, and a blue sub-pixel. However, they are repeatedly arranged in this order.

In the RGB color TFT liquid crystal display device, in explaining the first cause of horizontal stripes, the relationship between the color of each sub-pixel and the number of gradations of gradation voltage written to the pixel electrode PX. However, a case where the relationship is as shown in FIG. In FIG. 2A, R _u is a column of red sub-pixels, G _u−1 and G _u are columns of green sub-pixels, and B _u−1 and B _u are columns of blue sub-pixels. The numerical value shown for each pixel electrode PX is the display gradation of each pixel in the input gradation data Kin. That is, in the example shown in FIG. 2A, each dot is displayed in a color obtained by adding 100 gradations of red, 100 gradations of green, and 250 gradations of blue.

At this time, in FIG. 2A, the output gradation data Kout shown in FIG. 1D is respectively applied to the pixel electrode PX between two adjacent scanning signal lines GL _n−1 and GL _n . Among them, the gradation data K _{n, m} of the column HL _n is written. Similarly, in FIG. 2A, the pixel electrodes PX between two adjacent scanning signal lines GL _n and GL _{n + 1} are respectively connected to the output gradation data Kout shown in FIG. The gradation data K _{n + 1, m} of the column HL _{n + 1} is written. Further, the pixel electrode PX between _two adjacent scanning signal lines GL _{n + 1} and GL _{n + 2} has a gray level of the column HL _{n + 2 in} the output gray level data Kout shown in FIG. Data K _{n + 2, m} is written.

In the RGB color TFT liquid crystal display device, when the display as shown in FIG. 2A is performed, for example, a video signal line DL passing between two adjacent sub-pixel columns B _u−1 and R _{u. In m} , for example, as shown in the upper side of FIG. 2B, a video signal of voltage V ₂₅₀ corresponding to 250 gray levels in blue for writing to the pixel electrode PX in the column B _u−1 , the video signal voltage _{V 100,} which corresponds to 100 gradations in the red for writing to a pixel electrode PX in the R _u is applied a video signal DATA _m to alternating. Note that, in DATA _m of the waveform diagram shown on the upper side of FIG. 2B, the three sections S _n , S _{n + 1} , and S _{n + 2} are respectively the columns HL of the output gradation data shown in FIG. _This is a section where a video signal based on the gradation data of the corresponding block in _n , HL _{n + 1} and HL _{n + 2} is added.

In this case, paying attention to the pixel electrodes PX1 shown in FIG. 2 (a), the waveform of the scanning signal Vg when the video signal of the voltage _{V 100,} which corresponds to 100 gradations of red is written, the waveform of the common voltage Vcom, and The relationship between the waveform of the voltage Vpx of the pixel electrode PX1 and the waveform of the video signal DATA _m applied to the video signal line DL _m is, for example, as shown on the upper side of FIG. That is, the voltage Vpx of the pixel electrode PX1 is immediately after the scanning signal line _{GL n + 1} of the scanning signal Vg is turned on, for example, the voltage of the video signal to be written in front of the pixel electrode PX3 pixel electrode PX1 in the video signal line DL _m V rapidly rises due to the effect of _250, the video signal of the original voltage V ₁₀₀ from its state is written. As a result, the potential difference ΔV1 between the gradation voltage for the pixel electrode PX1 in the video signal DATA _m and the voltage actually written to the pixel electrode PX1 at the time when the falling edge of the scanning signal Vg starts is small.

On the other hand, the video signal line DL _{m + 1} passing between two adjacent sub-pixel columns R _u and G _u includes, for example, a pixel electrode in the column R _u as shown in the lower side of FIG. 100 and the video signal voltage _{V 100,} which corresponds to the gray scale, the video signal and the alternating voltage _{V 100,} which corresponds to 100 gradations in the green for writing to a pixel electrode PX in the column _{G u} in the red to write to PX The video signal DATA _{m + 1} to be replaced with is added. Note that in DATA _{m + 1} in the waveform diagram shown in the lower side of FIG. 2B, the three sections S _{n + 1} , S _{n + 2} , and S _{n + 3} are columns of output gradation data shown in FIG. 2A, respectively. This is a section to which video signals based on the gradation data of the corresponding block in HL _{n + 1} , HL _{n + 2} and column HL _{n + 3} (not shown) are added.

In this case, paying attention to the pixel electrode PX2 shown in FIG. 2 (a), the waveform of the scanning signal Vg when the video signal of the voltage _{V 100,} which corresponds to 100 gradations of red is written, the waveform of the common voltage Vcom, and The relationship between the waveform of the voltage Vpx of the pixel electrode PX2 and the waveform of the video signal DATA _{m + 1} applied to the video signal line DL _{m + 1} is, for example, as shown on the lower side of FIG. . That is, the voltage Vpx of the pixel electrode PX2 is equal to the voltage V of the video signal written to the pixel electrode PX4 in the preceding stage of the pixel electrode PX2 in the video signal line DL _{m + 1} , for example, immediately after the scanning signal Vg of the scanning signal line GL _{n + 2} is turned on. slowly rise due to the effect of _100, the video signal of the original voltage V ₁₀₀ from its state is written. As a result, the potential difference ΔV2 between the gradation voltage for the pixel electrode PX2 in the video signal DATA _{m + 1} and the voltage actually written to the pixel electrode PX2 at the time when the falling edge of the scanning signal Vg starts is the difference in the video signal DATA _m . This is larger than the potential difference ΔV1 between the gradation voltage for the pixel electrode PX1 and the voltage actually written to the pixel electrode PX1.

Two pixel electrodes PX1, PX2 are the pixel electrodes in the column _{R u} of the same sub-pixel, the voltage _{V 100,} which corresponds to 100 gradation is to be written in the red would otherwise. However, in practice, as shown in FIG. 2 (b), the potential difference between the actually written voltage to the gradation voltage _{V 100} and the pixel electrode PX1 in the video signal DATA _m are applied to the video signal line DL _m and [Delta] V1, different sizes of the potential difference ΔV2 between the actually written voltage to the gradation voltage _{V 100} and the pixel electrode PX2 in the video signal DATA _{m + 1} are applied to the video signal line _{DL m + 1.} That is, the pixel electrodes PX1 are connected to the video signal line DL _m via the TFT element, and the pixel electrodes PX2 are connected to the video signal line DL m _{+ 1} via the TFT element, a deficiency of insufficient writing are different .

  Therefore, in the conventional TFT liquid crystal display device, the gradation (luminance) of the pixel having the pixel electrode PX1 and the gradation (luminance) of the pixel having the pixel electrode PX2 are different from each other, and a phenomenon called a horizontal stripe occurs. There was a problem that the image quality deteriorated.

Note that the number of gradations of each pixel electrode shown in FIG. 2A is an example of a combination in which a phenomenon called a horizontal stripe is easily noticeable, and a phenomenon called a horizontal stripe occurs even in other combinations of gradation numbers. To do. Also, in FIG. 2A, pixel electrodes in a plurality of sub-pixel columns responsible for display of the same color, for example, pixel electrodes in a sub-pixel column B _u-1 and pixels in a sub-pixel column B _u. Although the case where all the electrodes have the same number of gradations is taken as an example, even if the number of gradations of the pixel electrodes in each column is an arbitrary combination, a phenomenon called a horizontal stripe occurs. Further, in FIG. 2 (a), the plurality of pixel electrodes in the column of the same sub-pixel, for example, the pixel electrodes in the column R _u of the sub-pixel, a case where all the same number of tones as an example However, even if the number of gradations of each pixel electrode is an arbitrary combination, a phenomenon called a horizontal stripe occurs.

  In order to prevent the occurrence of horizontal stripes due to such a cause, for example, the gradation of the video signal written to the pixel electrode PX1 is lowered, and the insufficient writing amount of the pixel electrode PX1 is made closer to the insufficient writing amount ΔV of the pixel electrode PX2. That's fine.

FIG. 3A and FIG. 3B are schematic views for explaining the principle of the driving method of the TFT liquid crystal display device according to the first embodiment of the present invention.
FIG. 3A is a schematic circuit diagram illustrating an example of a driving method of the liquid crystal display device according to the first embodiment. FIG. 3B is a schematic waveform diagram showing an example of gradation voltages written to the two pixel electrodes PX1 and PX2 shown in FIG.

  The first cause of the phenomenon called horizontal stripes in the TFT liquid crystal display device according to the present invention is the pixel electrode PX1 as in the example shown in FIGS. 2 (a) and 2 (b), for example. That is, the difference between the writing insufficient amount ΔV1 of the gradation voltage written to the pixel and the writing insufficient amount ΔV2 of the gradation voltage written to the pixel electrode PX2 becomes large.

That is, when the display as shown in FIG. 2A is performed, an insufficient writing amount ΔV1 of the gradation voltage written to the pixel electrode PX1 and an insufficient writing amount ΔV2 of the gradation voltage written to the pixel electrode PX2. If the difference between and becomes smaller, it is considered that the occurrence of horizontal stripes can be reduced (not noticeable). In order to reduce the difference between the writing insufficient amount ΔV1 of the gradation voltage written to the pixel electrode PX1 and the writing insufficient amount ΔV2 of the gradation voltage written to the pixel electrode PX2, for example, in the video signal line DL _m The gradation of the video signal written to the pixel electrode PX1 may be corrected based on the gradation difference between the video signal for the pixel electrode PX3 in the previous stage of the pixel electrode PX1 and the video signal for the pixel electrode PX1.

In the driving method of the liquid crystal display device according to the first embodiment, when the display as shown in FIG. 2A is performed, the gradation data for the pixel electrode PX1 in the output gradation data Kout is changed to, for example, FIG. As shown in FIG. 5, the video signal generated based on the corrected output gradation data Kout is written to the pixel electrode PX1 after correcting from 100 gradations to 98 gradations. In this way, the pixel electrode PX1, and the scanning signal Vg waveform, the waveform of the common voltage Vcom, and the waveform of the voltage Vpx of a pixel electrode PX1 of when the video signal of the voltage _{V 98} corresponding to the 98 gray scale of the red is written, The relationship with the waveform of the video signal DATA _{m applied to} the video signal line DL _m is, for example, the relationship shown on the upper side of FIG.

At this time, the potential difference [Delta] V1 (i.e. insufficient writing amount) of the gradation voltages in the voltage Vpx and the video signal DATA _m written into the pixel electrodes PX1, when allowed to write the video signal voltage _{V 98} corresponding to 98 gradation Is the potential difference. Therefore, the potential difference ΔV1 ′ between the video signal at the voltage V ₁₀₀ corresponding to the 100 gradation shown by the dotted line in FIG. 3B and the voltage Vpx written to the pixel electrode PX1 with the 98 gradation video signal is: It becomes larger than the potential difference ΔV1 shown in FIG.

At this time, if the gradation of the video signal written to the pixel electrode PX2 is not corrected and remains at 100 gradations, for example, the waveform of the gradation voltage Vpx written to the pixel electrode PX2 is as shown in FIG. potential difference between the waveform shown in the lower side is the same waveform, the voltage Vpx written to the gradation voltage _{V 100} and the pixel electrode PX2 in the video signal DATA _{m + 1} waveform, i.e. FIG. 2 (b) shown in the lower side of the Is the same as the potential difference Δ2 shown in FIG.

Therefore, in the driving method of the TFT liquid crystal display device according to the first embodiment, the potential difference ΔV1 ′ between the gradation voltage of the video signal DATA _m at the time when the falling edge of the scanning signal Vg starts and the voltage actually written to the pixel electrode PX1. And the difference (ΔV2−ΔV1 ′) between the gradation voltage of the video signal DATA _{m + 1 and} the voltage actually written to the pixel electrode PX2 (ΔV2−ΔV1 ′) at the time when the falling edge of the scanning signal Vg starts. Smaller than. For this reason, the difference between the gradation (luminance) of the pixel having the pixel electrode PX1 and the gradation (luminance) of the pixel having the pixel electrode PX2 is reduced, and deterioration of image quality due to the occurrence of a phenomenon called a horizontal stripe can be avoided.

FIG. 4A to FIG. 4C are schematic diagrams for explaining one specific example of the gradation data correction method in the TFT liquid crystal display device of the first embodiment.
FIG. 4A is a schematic graph showing an example of the relationship between the gradation difference between two gradation data to be compared and the level of horizontal stripes. FIG. 4B shows an example of the relationship between the gradation difference between the two gradation data to be compared and the correction coefficient, and the relationship between the gradation difference between the two gradation data to be compared and the level of the horizontal stripe after correction. It is a schematic graph figure to show. FIG. 4C is a schematic graph showing an example of the relationship between the applied potential to the liquid crystal and the gradation in a general TFT liquid crystal display device.

In the conventional TFT liquid crystal display device, a gradation number K _n of the video signal to be written to a single pixel electrode, the same video signal line and said certain one pixel electrode and the front of said certain one pixel electrode A gradation difference ΔK (= K _n−1 −K _n ) with respect to the number of gradations K _n−1 of the video signal written to the pixel electrode, and a horizontal stripe in the pixel having the one pixel electrode at the gradation difference ΔK The relationship with the level SLV is, for example, a profile P1 indicated by a solid line in FIG. The graph shown in FIG. 4A shows a profile P1 in which the gradation difference ΔK is −255 to 255.

  As described above, in the conventional TFT liquid crystal display device, when the gradation difference ΔK is a negative value, the gradation of the video signal written to the one pixel electrode is lower than the gradation in the input gradation data. Thus, when the gradation difference ΔK is a positive value, the gradation of the video signal written to the one pixel electrode is higher than the gradation in the input gradation data.

  Further, in the profile P1 shown in FIG. 4A, the horizontal stripe level SLV with the gradation number ΔK in the vicinity of −180 to −120 is remarkably low, and the horizontal stripe level SLV with the gradation number ΔK in the vicinity of 120 to 180 is extremely high. It has become. This is because, in this region (halftone), a change in pixel gradation (luminance) becomes sensitive to a change in potential difference. The reason why the luminance change is sensitive to the potential change in the halftone will be briefly described with reference to a graph showing an example of the relationship between the applied potential V to the liquid crystal and the gradation K shown in FIG. According to the graph shown in FIG. 4C, in the halftone range from 64 gradations (K = 64) to 192 gradations (K = 192), the low gradation side (K <63) and the high gradation side. It can be seen that the change in the gradation K is larger than the change in the applied potential V (that is, the slope of the graph is larger) than (K> 193). From this, it can be said that the luminance change is sensitive to the change in the potential V in the halftone.

Therefore, the gradation number K _n is halftone, and if the absolute value of the gray level difference ΔK is large, for example, as shown in FIG. 4 (b), the absolute value of the lateral stripe level SLV is large It is considered to be.

  Note that the relationship between the gradation K and the applied potential V as shown in FIG. 4C depends on the electro-optical characteristics of the liquid crystal material. Examples of the characteristics of the liquid crystal material depending on the elastic constant include dielectric constant, dielectric anisotropy, and pretilt angle.

When the gradation difference ΔK of the video signal written to the two pixel electrodes and the horizontal stripe level SLV have the relationship as shown in FIG. 4A, in order to reduce the horizontal stripe level SLV, for example, FIG. The gradation data K _n for one pixel electrode may be corrected to the gradation data K _n ′ by the following formula 2 using the correction coefficient α given by the function f (ΔK) as shown in FIG.
K _n ′ = int {(K _n−1 −K _n ) × α} + K _n (Expression 2)

In the above formula 2, int {(K _n−1 −K _n ) × α} means that only the integer part of (K _n−1 −K _n ) × α is taken.

  As shown in FIG. 4B, the function f (ΔK) is corrected when the gradation difference ΔK is a negative value, and the correction coefficient α is a positive value, and when the gradation difference ΔK is a positive value. This is a function with a negative coefficient α. The function f (ΔK) is a function that increases the absolute value of the correction coefficient α as the gradation difference ΔK increases.

The driving method for a TFT liquid crystal display device of Example 1, when applied at the time of the display as shown in FIG. 2 (a), the gradation data K _n to the pixel electrode PX1 is 100 gradations, the pixel electrode PX1 The gradation data Kn _-1 for the previous pixel electrode PX4 is 250 gradations. For this reason, when Expression 2 is used, the gradation data K _n ′ for the pixel electrode PX1 is expressed by Expression 3 below.
K _n ′ = int {150 × α} +100 (Expression 3)

The correction coefficient α in Equation 3 is a negative value from the function f (ΔK) shown in FIG. 4B, and K _n ′ in Equation 3 is a value smaller than 100 (K _n ′ <100). . Therefore, when a video signal (gradation voltage) generated based on the gradation data K _n ′ is written to the pixel electrode PX1, for example, as shown in FIGS. 3A and 3B, the pixel electrode PX1 The difference between the insufficient writing amount Δ1 ′ and the insufficient writing amount Δ2 of the pixel electrode PX2 becomes small, and the horizontal stripes are less noticeable.

  That is, when the driving method of the liquid crystal display device of Example 1 is applied, as shown in FIG. 4B, the horizontal stripe level SLV is changed from the profile P1 to the profile P1 ′, and the horizontal stripe level SLV is reduced as a whole. . Therefore, it is possible to reduce image quality degradation due to horizontal stripes.

  FIG. 5 is a schematic block diagram illustrating a configuration example of a correction circuit that realizes the driving method of the TFT liquid crystal display device according to the first embodiment.

  In order to realize the driving method of the TFT liquid crystal display device according to the first embodiment, for example, the correction circuit 401 having the configuration shown in FIG. 4A is provided on the control circuit board 4 shown in FIG. May be provided. The correction circuit 401 includes, for example, a gradation data rearranging unit 401a, a line memory 401c, and a gradation correcting unit 401b.

  The input gradation data Kin input to the TFT liquid crystal display device (control circuit board 4) has a format as shown in FIG. 1C, for example. Therefore, first, the gradation data rearranging means 401 rearranges (converts) the input gradation data Kin into, for example, output gradation data Kout having a configuration as shown in FIG.

Output gradation data Kout rearranged by the gray-scale data rearranging section 401a, for each column HL _n, are transferred to the tone correction unit 401b and the line memory 401c. Tone correction unit 401b compares the gradation data of each block BL _m column HL _n, of each block BL _m column _{HL n-1} held in the line memory 401c and tone data, for example, Using the gradation difference ΔK, the correction coefficient α = f (ΔK) as shown in FIG. 4B, and Expression 2, the gradation data of each block BL _{m in} the column HL _n is corrected. Thereafter, the corrected output gradation data Kout ′ is transferred to the data driver 2 to generate a video signal (gradation voltage signal) to be applied to each video signal line DL, and is controlled by the control circuit board 4 or the like, for example. In addition to applying a video signal to each video signal line DL based on a certain timing (clock signal), and sequentially turning on the scanning signal applied to each scanning signal line GL, the video or image for one frame period is liquid crystal It is displayed on the display panel 1.

  As described above, according to the TFT liquid crystal display device and the driving method thereof according to the first embodiment, the horizontal streak depending on the gradation difference ΔK of the gradation data for the two pixels is reduced, and the image quality of the TFT liquid crystal display device is deteriorated. Can be prevented.

  The correction coefficient α is not limited to the function f (ΔK) shown in FIG. 4B, but may be obtained using another function g (ΔK).

  A correction circuit 401 illustrated in FIG. 5 is an example of a circuit configuration for realizing the driving method according to the first embodiment. That is, if the gradation of the video signal written to each pixel electrode PX can be corrected by the method described with reference to FIGS. 3 (a), 3 (b), and 4 (b), Of course, it may be the structure of.

FIGS. 6A and 6B are schematic diagrams for explaining one specific example of the gradation data correction method in the TFT liquid crystal display device according to the second embodiment of the present invention.
FIG. 6A is a schematic graph showing an example of the relationship between the temperature of the pixel electrode and its surroundings and the level of the horizontal stripe. FIG. 6B is a schematic graph showing an example of the relationship between the pixel electrode and its surrounding temperature and the correction coefficient, and the relationship between the pixel electrode and its surrounding temperature and the corrected horizontal stripe level.

  In the first embodiment, the configuration and driving method of the TFT liquid crystal display device that reduces the horizontal streak depending on the gradation difference ΔK of the gradation data for the two pixels has been described. However, other causes for the occurrence of horizontal stripes in the conventional TFT liquid crystal display device include, for example, the temperature of the liquid crystal display panel.

  The relationship between the temperature Temp of the liquid crystal display panel 1 and the horizontal stripe level SLV in the conventional TFT liquid crystal display device is represented by, for example, a profile P2 shown in FIG.

Incidentally, in FIG. 6 (a), as an example of the profile P2, tone data (gradation _number) for the two pixels _{K n-1, K n respectively, K n-1 = 250,} K n = 100 in In this case, the relationship between the temperature Temp around the two pixels and the horizontal stripe level SLV is shown.

  Further, the horizontal streak level SLV on the vertical axis in the graph shown in FIG. 6A is a horizontal streak level that depends only on the temperature change in the vicinity of the two pixels, and corresponds to the gradation difference ΔK described in the first embodiment. This is the transverse muscle level from which the dependent components are removed.

  That is, in the conventional TFT liquid crystal display device, when the temperature of the liquid crystal display panel 1 is changed while displaying a specific image or image, the horizontal stripe level SLV is substantially 0 at room temperature (20 ° C. to 30 ° C.) or higher. Even if it is (zero), as the temperature is lowered, the transverse stripe level SLV is gradually increased as the temperature is lowered.

When the temperature Temp of the liquid crystal display panel 1 and the horizontal stripe level SLV have a relationship as shown in FIG. 6A, in order to reduce the horizontal stripe level SLV depending on this temperature, for example, as shown in FIG. The gradation data K _n for one pixel electrode may be corrected to the gradation data K _n ′ by the following formula 4 using the correction coefficient β given by the correct function f (Temp).
K _n ′ = int {(K _n−1 −K _n ) × β} + K _n (Expression 4)

In the above equation 4, int {(K _n−1 −K _n ) × β} means that only the integer part of (K _n−1 −K _n ) × β is taken.

  As shown in FIG. 6B, the function f (Temp) has a correction coefficient β of 0 (zero) when the temperature is higher than a specific temperature, and when the temperature is lower than the specific temperature. This is a function in which the correction coefficient β is a negative value. The function f (Temp) is a function in which the absolute value of the correction coefficient β increases as the difference between the temperature of the liquid crystal display panel and the specific temperature increases.

  The specific temperature is, for example, a constant value at a temperature at which the horizontal stripe level changes from 0 (zero) to a positive value in the profile P2 shown in FIG. 6A, in other words, a value at a temperature higher than room temperature. And the temperature at the intersection (contact point) between the profile component whose value at a temperature lower than room temperature changes.

The driving method for a TFT liquid crystal display device of Example 2, when applied at the time of the display as shown in FIG. 2 (a), the gradation data K _n to the pixel electrode PX1 is 100 gradations, the pixel electrode PX1 The gradation data Kn _-1 for the previous pixel electrode PX4 is 250 gradations. For this reason, when Expression 4 is used, the gradation data K _n ′ for the pixel electrode PX1 is expressed by Expression 5 below.
K _n ′ = int {150 × β} +100 (Expression 5)

The correction coefficient β in the above formula 5 is always a value of 0 or less (β ≦ 0) in the function f (Temp) as shown in FIG. 6B, for example. Therefore, K _n ′ in the above formula 5 is 100 A smaller value (K _n ′ ≦ 100) is obtained. Therefore, when a video signal (gradation voltage) generated based on the gradation data K _n ′ is written to the pixel electrode PX1, for example, when used in an environment where the temperature is below freezing (0 degree or less), the horizontal stripes are conspicuous. It becomes difficult.

  That is, when the driving method of the liquid crystal display device according to the second embodiment is applied, as shown in FIG. 6B, the horizontal stripe level SLV depending on the temperature changes from the profile P2 to the profile P2 ′, and the horizontal stripe level as a whole. SLV decreases. Therefore, it is possible to reduce image quality degradation due to the horizontal stripes depending on temperature.

  By the way, in a large-screen TFT liquid crystal display device such as a liquid crystal television, the temperature at each point (each pixel) in the display area DA of the liquid crystal display panel 1 is non-uniform and exhibits a specific temperature distribution. Therefore, when the driving method as in the second embodiment is applied, the temperature Temp is not the temperature of the liquid crystal display panel 1, but the temperature of the pixel (pixel electrode) to be corrected and the surrounding temperature. However, it is difficult to measure the temperature of each pixel. Therefore, when the driving method as in the second embodiment is applied, the temperature of a specific location in the TFT liquid crystal display device is measured, and the temperature Temp of the pixel to be corrected and its surroundings are estimated from the temperature.

FIG. 7A and FIG. 7B are schematic views showing a configuration example of a TFT liquid crystal display device that realizes the driving method of the second embodiment.
FIG. 7A is a schematic block diagram illustrating a configuration example of a correction circuit that realizes the driving method of the TFT liquid crystal display device according to the second embodiment. FIG. 7B is a schematic diagram illustrating an example of an installation position of the temperature sensor.

  In order to realize the driving method of the TFT liquid crystal display device according to the second embodiment, for example, a correction circuit 401 having a configuration as shown in FIG. 7A is provided on the control circuit board 4 shown in FIG. May be provided. The correction circuit 401 includes, for example, a gradation data rearranging unit 401a, a line memory 401c, a gradation correcting unit 401b, and a temperature estimating unit 401d. The temperature estimation unit 401d is connected to the temperature sensor 5 installed in the TFT liquid crystal display device, and estimates the temperature of each pixel in the display area DA of the liquid crystal display panel 1 based on the temperature detected by the temperature sensor 5. For example, as shown in FIG. 7B, the temperature sensor 5 is provided on the circuit board 7 among the flexible printed wiring board 6 that connects the control circuit board 4 and the data driver 2 and the other circuit board 7.

  The input gradation data Kin input to the TFT liquid crystal display device (control circuit board 4) has a format as shown in FIG. 1C, for example. Therefore, first, the gradation data rearranging means 401 rearranges (converts) the input gradation data Kin into, for example, output gradation data Kout having a configuration as shown in FIG.

The output gradation data Kout rearranged by the gradation data rearranging means 401a is transferred to the gradation correction means 401b and the line memory 401c for each column HLn. Tone correction unit 401b compares the gradation data of each block BL _m column HL _n, of each block BL _m column _{HL n-1} held in the line memory 401c and tone data, for example, Using the temperature Temp estimated by the temperature estimating means 401d, the correction coefficient β = f (Temp) as shown in FIG. 6B, and the equation 4, the gradation data of each block BL _{m in} the column HL _n is corrected. To do. Thereafter, the corrected output gradation data Kout ′ is transferred to the data driver 2 to generate a video signal (gradation voltage signal) to be applied to each video signal line DL, and is controlled by the control circuit board 4 or the like, for example. In addition to applying a video signal to each video signal line DL based on a certain timing (clock signal), and sequentially turning on the scanning signal applied to each scanning signal line GL, the video or image for one frame period is liquid crystal It is displayed on the display panel 1.

  As described above, according to the TFT liquid crystal display device and the driving method thereof according to the second embodiment, horizontal stripes depending on the temperature of the liquid crystal display panel can be reduced, and deterioration of the image quality of the TFT liquid crystal display device can be prevented.

  The correction coefficient β is not limited to the function f (Temp) shown in FIG. 6B, but may be obtained using another function g (Temp).

  Further, the correction circuit 401 illustrated in FIG. 7A is an example of a circuit configuration for realizing the driving method according to the second embodiment. That is, as long as the gradation of the video signal written to each pixel electrode PX can be corrected by the method described with reference to FIG. Furthermore, the temperature sensor 5 is not limited to the position shown in FIG. 7B, and may be installed at an arbitrary position.

FIGS. 8A to 8E are schematic diagrams for explaining one specific example of the gradation data correction method in the TFT liquid crystal display device according to the third embodiment of the present invention.
FIG. 8A is a schematic graph showing an example of the relationship between the distance from the input end of the video signal line to the pixel and the level of the horizontal stripe. FIG. 8B shows an example of the relationship between the distance from the input end of the video signal line to the pixel and the correction coefficient, and the relationship between the distance from the input end of the video signal line to the pixel and the level of the corrected horizontal stripe. It is a schematic graph figure to show. FIG. 8C is a schematic graph showing an example of the relationship between the distance from the input end of the scanning signal line to the pixel and the level of the horizontal stripe. FIG. 8D shows an example of the relationship between the distance from the input end of the scanning signal line to the pixel and the correction coefficient, and the relationship between the distance from the input end of the scanning signal line to the pixel and the level of the corrected horizontal stripe. It is a schematic graph figure to show. FIG. 8E is a schematic diagram for explaining a modification of the correction method according to the third embodiment.

  In the first embodiment, a configuration and a driving method of a TFT liquid crystal display device that reduces horizontal stripes depending on the magnitude of the gradation difference ΔK of the gradation data for two pixels will be described. In the second embodiment, a liquid crystal display panel (each The configuration and driving method of the TFT liquid crystal display device that reduces the horizontal streak depending on the temperature Temp of the pixel) have been described. However, other causes of horizontal stripes in the conventional TFT liquid crystal display device include, for example, the distance between the signal input end of the video signal line and the pixel and the distance between the signal input end of the scanning signal line and the pixel. ing.

In the conventional TFT liquid crystal display device, the relationship between the distance between the signal input end of the video signal line DL and the pixel and the horizontal stripe level SLV is represented by, for example, a profile P3 shown in FIG. In FIG. 8A, the horizontal axis indicates the number n of the scanning signal line GL _n to which the gate of the TFT element of each pixel is connected, not the actual distance between the signal input end of the video signal line DL and the pixel. I have to. The number n of the scanning signal line GL _n is set so that the scanning signal line closest to the signal input end of the video signal line DL is 1, and the number increases as the distance from the signal input end of the video signal line DL increases.

Further, in FIG. 8 (a), as an example of a profile P3, tone data (gradation _number) for the two pixels _{K n-1, K n respectively, K n-1 = 250,} K n = 100 in In this case, the relationship between the distance from the signal input end of the video signal line of the two pixels and the horizontal stripe level SLV is shown.

  In addition, the horizontal streak level SLV on the vertical axis in the graph shown in FIG. 8A is a horizontal streak level that depends only on the change in the distance from the signal input end of the video signal line of the two pixels. The horizontal streak level is obtained by removing the component that depends on the explained gradation difference ΔK and the component that depends on the temperature Temp explained in the second embodiment.

  That is, in the conventional TFT liquid crystal display device, when a horizontal stripe level of each pixel arranged along the extending direction of the video signal line is examined while displaying a specific video or image, the signal input end of the video signal line As the distance increases, the transverse muscle level SLV gradually increases.

When the distance from the signal input end of the video signal line and the horizontal stripe level SLV have the relationship as shown in FIG. 8A, in order to reduce the horizontal stripe level SLV depending on this distance, for example, FIG. The gradation data K _n for one pixel electrode may be corrected to gradation data K _n ′ by the following equation 6 using the correction coefficient γ ₁ given by the function f (n) as shown in FIG.
K _n ′ = int {(K _n−1 −K _n ) × γ ₁ } + K _n (Expression 6)

In the above equation 6, int {(K _n−1 −K _n ) × γ ₁ } means that only the integer part of (K _n−1 −K _n ) × γ ₁ is taken.

The function f (n) is always a negative value as shown in FIG. 8B, and the absolute value of the correction coefficient γ ₁ increases as n increases.

The driving method for a TFT liquid crystal display device of Example 3, when applied at the time of the display as shown in FIG. 2 (a), the gradation data K _n to the pixel electrode PX1 is 100 gradations, the pixel electrode PX1 The gradation data Kn _-1 for the previous pixel electrode PX4 is 250 gradations. Therefore, when Expression 5 is used, the gradation data K _n ′ for the pixel electrode PX1 is expressed by Expression 7 below.
K _n ′ = int {150 × γ ₁ } +100 (Expression 7)

Correction coefficient gamma ₁ in the above equation 7, for example, from a function f (n) as shown in FIG. 8 (b) is always negative value _{(γ 1 <0), K} n ' is in the formula 7 The value is smaller than 100 (K _n ′ <100). Therefore, when a video signal (gradation voltage) generated based on the gradation data K _n ′ is written to the pixel electrode PX1, for example, even if the distance from the signal input end of the video signal line DL is long, the horizontal stripes are not noticeable. Become.

  That is, when the driving method of the liquid crystal display device of Example 3 is applied, as shown in FIG. 8B, the horizontal stripe level SLV depending on the distance from the signal input end of the video signal line is changed from the profile P3 to the profile P3 ′. The transverse muscle level SLV is reduced as a whole. Therefore, it is possible to reduce image quality degradation due to horizontal stripes depending on the distance from the signal input end of the video signal line.

Further, in the conventional TFT liquid crystal display device, the relationship between the distance between the signal input end of the scanning signal line GL and the pixel and the level SLV of the horizontal stripe is represented by, for example, a profile P4 shown in FIG. . In FIG. 8C, the horizontal axis represents the number m of the video signal line DL _m to which the drain of the TFT element of each pixel is connected, not the actual distance between the signal input end of the video signal line DL and the pixel. I have to. Further, the number m of the video signal line DL _m, the closest video signal line to the signal input terminal of the scan signal lines GL and the 1, wearing such number increases as the distance to the signal input terminal of the scan signal lines GL.

Further, in FIG. 8 (c), as an example of a profile P4, tone data (gradation _number) for the two pixels _{K n-1, K n respectively, K n-1 = 250,} K n = 100 in In this case, the relationship between the distance from the signal input end of the scanning signal line of the two pixels and the horizontal stripe level SLV is shown.

  The horizontal streak level SLV on the vertical axis in the graph shown in FIG. 8C is a horizontal streak level that depends only on the change in distance from the signal input end of the scanning signal line of the two pixels. The horizontal streak level is obtained by removing the component that depends on the explained gradation difference ΔK and the component that depends on the temperature Temp explained in the second embodiment.

  That is, in the conventional TFT liquid crystal display device, when the horizontal stripe level of each pixel arranged along the extending direction of the scanning signal line is examined while displaying a specific image or image, the signal input end of the scanning signal line As the distance increases, the transverse muscle level SLV gradually increases.

When the distance from the signal input end of the scanning signal line and the horizontal stripe level SLV have the relationship as shown in FIG. 8C, in order to reduce the horizontal stripe level SLV depending on this distance, for example, FIG. The gradation data K _n for the one pixel electrode may be corrected to the gradation data K _n ′ by the following formula 8 using the correction coefficient γ ₂ given by the function f (m) as shown in FIG.
K _n ′ = int {(K _n−1 −K _n ) × γ ₂ } + K _n (Expression 8)

In the above formula 8, int {(K _n−1 −K _n ) × γ ₂ } means that only the integer part of (K _n−1 −K _n ) × γ ₂ is taken.

As shown in FIG. 8D, the function f (m) is always a negative value, and the absolute value of the correction coefficient γ ₂ decreases as m increases.

The driving method for a TFT liquid crystal display device of Example 3, when applied at the time of the display as shown in FIG. 2 (a), the gradation data K _n to the pixel electrode PX1 is 100 gradations, the pixel electrode PX1 The gradation data Kn _-1 for the previous pixel electrode PX4 is 250 gradations. For this reason, when Expression 8 is used, the gradation data K _n ′ for the pixel electrode PX1 is expressed by Expression 9 below.
K _n ′ = int {150 × γ ₂ } +100 (Equation 9)

Correction coefficient gamma ₂ in the above equation 9, for example, since the function f (m) as shown in FIG. 8 (d) is always negative value _{(γ 2 <0), K} n ' is in the formula 9 The value is smaller than 100 (K _n ′ <100). Therefore, when a video signal (gradation voltage) generated based on the gradation data K _n ′ is written to the pixel electrode PX1, for example, even if the distance from the signal input end of the scanning signal line GL is long, it depends on the distance. The horizontal stripes that become visible are less noticeable.

  That is, when the driving method of the liquid crystal display device of Example 3 is applied, as shown in FIG. 8D, the horizontal stripe level SLV depending on the distance from the signal input end of the scanning signal line changes from the profile P4 to the profile P4 ′. The transverse muscle level SLV is reduced as a whole. Therefore, it is possible to reduce deterioration in image quality due to horizontal stripes depending on the distance from the signal input end of the scanning signal line.

When the TFT liquid crystal display device is driven by the correction method as in the third embodiment, a correction circuit 401 as shown in FIG. Then, the gradation correction unit 401b may correct the gradation data K _n of each pixel to K _n ′ based on, for example, Expression 6 and Expression 8 above.

  As described above, according to the TFT liquid crystal display device of Embodiment 3 and the driving method thereof, the horizontal stripes depending on the distance from the signal input end of the video signal line and the distance from the signal input end of the scanning signal line can be reduced. Degradation of the image quality of the TFT liquid crystal display device can be prevented.

The correction coefficient γ ₁ is not limited to the function f (n) shown in FIG. 8B, but may be obtained using another function g (n). As another function g (n), for example, as shown in FIG. 8 (e), the scanning signal line GL _x having the number x which is a specific distance from the signal input end of the video signal line is used as a boundary. The pixels closer to the signal input end of the video signal line than the scanning signal line GL _x have a constant value regardless of the distance, and the distance from the signal input end of the video signal line is smaller than the scanning signal line GL _x . include the functions such as the absolute value of the correction coefficient gamma ₁ increases as larger the distance for even larger pixels. Similarly, the correction coefficient γ ₂ is not limited to the function f (m) shown in FIG. 8D, but may be obtained using another function g (m).

  The present invention has been specifically described above based on the above-described embodiments. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention. is there.

For example, in the first embodiment, the gradation data is corrected using only the correction coefficient α given by the function f (ΔK) of the gradation difference ΔK. In the second embodiment, the gradation data is corrected using only the correction coefficient β given by the temperature function f (Temp). In the third embodiment, tone data is corrected using only correction coefficients γ ₁ and γ ₂ given by functions f (n) and f (m) of distance from the signal input end.

However, the horizontal stripes generated in the TFT liquid crystal display device are combined with factors such as the difference ΔK in the number of gradations, the temperature Temp, and the distance from the signal input end. Therefore, of course, the gradation data K _n may be corrected to K _n ′ using the following equation 10 based on the points described in the above embodiments.
K _n ′ = int {(K _n−1 −K _n ) × α × β × γ ₁ × γ ₂ } + K _n (Equation 10)

Of course, the present invention is not limited to this, and two or three of the correction coefficients α, β, γ ₁ and γ ₂ may be selected and corrected.

It is a schematic block diagram which shows an example of schematic structure of the TFT liquid crystal display device concerning this invention. FIG. 2 is a schematic circuit diagram illustrating an example of a schematic configuration of a display area in the liquid crystal display panel illustrated in FIG. It is a schematic diagram which shows one structural example of the input gradation data input into a TFT liquid crystal display device. It is a schematic diagram which shows one structural example of the output gradation data which rearranged the input gradation data. It is a schematic diagram which shows an example of the drive method of the liquid crystal display panel shown to Fig.1 (a). It is a schematic circuit diagram which shows an example of the gradation of each pixel in the TFT liquid crystal display device concerning this invention. FIG. 3 is a schematic waveform diagram showing an example of gradation voltages written to two pixel electrodes PX1 and PX2 shown in FIG. 6 is a schematic circuit diagram illustrating an example of a driving method of the liquid crystal display device of Embodiment 1. FIG. FIG. 4 is a schematic waveform diagram showing an example of gradation voltages written to two pixel electrodes PX1 and PX2 shown in FIG. It is a schematic graph which shows an example of the relationship between the gradation difference of two gradation data to compare, and the level of a horizontal stripe. It is a schematic graph which shows an example of the relationship between the gradation difference of two gradation data to be compared, and a correction coefficient, and the relationship between the gradation difference of two gradation data to be compared, and the level of a horizontal stripe after correction. It is a schematic graph which shows an example of the relationship between the applied potential to the liquid crystal in a general TFT liquid crystal display device, and a gradation. FIG. 3 is a schematic block diagram illustrating a configuration example of a correction circuit that realizes the driving method of the TFT liquid crystal display device according to the first embodiment. It is a schematic graph which shows an example of the relationship between the temperature of a pixel electrode and its periphery, and the level of a horizontal stripe. It is a schematic graph which shows an example of the relationship between the temperature of a pixel electrode and its periphery, and a correction coefficient, and the relationship between the temperature of a pixel electrode and its periphery, and the level of a horizontal stripe after correction | amendment. FIG. 10 is a schematic block diagram illustrating a configuration example of a correction circuit that realizes the driving method of the TFT liquid crystal display device according to the second embodiment. It is a schematic diagram which shows an example of the installation position of a temperature sensor. It is a schematic graph which shows an example of the relationship between the distance from the input end of a video signal line to a pixel, and the level of a horizontal stripe. It is a schematic graph which shows an example of the relationship between the distance from the input end of a video signal line to a pixel, and a correction coefficient, and the relationship between the distance from the input end of a video signal line to a pixel, and the level of a horizontal line after correction. It is a schematic graph which shows an example of the relationship between the distance from the input end of a scanning signal line to a pixel, and the level of a horizontal stripe. It is a schematic graph which shows an example of the relationship between the distance from the input end of a scanning signal line to a pixel, and a correction coefficient, and the relationship between the distance from the input end of a scanning signal line to a pixel, and the level of a horizontal line after correction. FIG. 10 is a schematic diagram for explaining a modification of the correction method according to the third embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display panel 2 ... Data driver 3 ... Gate driver 4 ... Control circuit 401 ... Correction circuit board 401a ... Gradation data rearrangement means 401b ... Gradation correction means 401c ... Line memory 401d ... Temperature estimation means 5 ... Temperature sensor 6 ... flexible printed wiring board 7 ... circuit board _{GL, GL n-1, GL} n, GL n + 1, GL n + 2 ... scanning signal lines _{DL, DL m-2, DL} m-1, DL m, DL m + 1, DL m + 2, DL _{m + 3} ... Video signal line Tr ... TFT element PX, PX1, PX2, PX3, PX4 ... Pixel electrode LC ... Liquid crystal material CT ... Counter electrode

Claims (9)

A liquid crystal display panel in which a liquid crystal material is sealed between a pair of substrates, and a control circuit board that performs display control of the liquid crystal display panel;
One of the pair of substrates is connected to a plurality of scanning signal lines, a plurality of video signal lines, a plurality of TFT elements, and a source of the TFT elements on the surface of the insulating substrate. A plurality of pixel electrodes, and
A plurality of pixel electrodes disposed along the extending direction of the video signal line between two adjacent video signal lines are connected to each other among the two adjacent video signal lines via a TFT element. The pixel electrodes connected to one of the video signal lines and the pixel electrodes connected to the other video signal line of the two adjacent video signal lines through the TFT elements are alternately arranged. A liquid crystal display device,
The control circuit board, for input gradation data written to each pixel electrode input from the outside of the display device,
Input gradation data to be written to one of the plurality of pixel electrodes;
Compare the input grayscale data to be written to the pixel electrode in the previous stage of the one pixel electrode in the video signal line to which the one pixel electrode is connected via the TFT element,
A liquid crystal display device comprising: gradation correction means for correcting input gradation data written to the one pixel electrode based on a gradation difference between the two input gradation data. The gradation correction means sets the number of gradations of input gradation data to be written to the one pixel electrode to K _n , and the number of gradations of input gradation data to be written to the previous pixel electrode to K _n−1 .
When the correction coefficient is C,
2. The liquid crystal display device according to claim 1, wherein the number of gradations of gradation data written to the one pixel electrode is corrected to K _n ′ represented by the following formula 1.
K _n ′ = int {(K _n−1 −K _n ) × C} + K _n (Expression 1) The correction coefficient C is a first correction coefficient α represented by a function of a difference in the number of gradations of the two input gradation data K _n−1 −K _n .
A second correction coefficient β expressed as a function of temperature around the one pixel electrode;
Third correction expressed as a function of the distance between the video signal line connected to the TFT element connected to the one pixel electrode and the signal input end of the scanning signal line connected to the TFT element Coefficient γ ₁ ,
Fourth correction expressed as a function of the distance between the scanning signal line connected to the TFT element connected to the one pixel electrode and the signal input end of the video signal line connected to the TFT element The liquid crystal display device according to claim 2, wherein the liquid crystal display device is represented by any one of the coefficients γ ₂ or a product of two or more. The first correction coefficient α is a positive value when the difference in the number of gradations K _n−1 −K _n between the two input gradation data is a negative value, and the two input gradation data If the difference in the number of gradations K _n-1 −K _n is a positive value, it is a negative value, and
The liquid crystal display device according to claim 3, wherein the absolute value of the correction coefficient α is larger as the absolute value of the difference in the number of gradations K _n−1 −K _n of the two input gradation data is larger. . The second correction coefficient β is constant regardless of a temperature difference from the specific temperature when the temperature around the one pixel electrode is higher than the specific temperature with a predetermined specific temperature as a boundary. Value of
When the temperature around the one pixel electrode is lower than the specific temperature, the absolute value of the correction coefficient β is larger as the temperature difference is a negative value and the temperature difference from the specific temperature is larger. The liquid crystal display device according to claim 3. The third correction coefficient γ ₁ is connected to a video signal line to which the TFT element connected to the one pixel electrode is connected, and the TFT element is connected at a predetermined specific distance. When the distance from the signal input end of the scanning signal line is shorter than the specific distance, it is a constant value regardless of the difference from the specific distance,
When the distance between the video signal line to which the TFT element connected to the one pixel electrode is connected and the signal input end of the scanning signal line to which the TFT element is connected is longer than the specific distance The liquid crystal display device according to claim 3, wherein the absolute value of the third correction coefficient γ ₁ is larger as the difference between the negative distance and the specific distance is larger.   The specific distance is shorter than a distance between a video signal line arranged at a position closest to a signal input end of the scanning signal line and a signal input end of the scanning signal line. Liquid crystal display device. The fourth correction coefficient γ ₂ is connected to the scanning signal line to which the TFT element connected to the one pixel electrode is connected, with the predetermined specific distance as a boundary. When the distance from the signal input end of the video signal line is shorter than the specific distance, it is a constant value regardless of the difference from the specific distance,
When the distance between the scanning signal line connected to the TFT element connected to the one pixel electrode and the signal input end of the video signal line connected to the TFT element is longer than the specific distance The liquid crystal display device according to claim 3, wherein the absolute value of the fourth correction coefficient γ ₂ is larger as the difference between the negative distance and the specific distance is larger.   The said specific distance is shorter than the distance of the scanning signal line arrange | positioned in the position nearest to the signal input end of the said video signal line, and the signal input end of the said video signal line. Liquid crystal display device.

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