JP2003022053A - Device and method for image display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively suppress an image blur by improving the driving system of a hold type image display device. SOLUTION: The image display device is equipped with a display panel 0 which has pixels 11 arranged in matrix, a row driving circuit 21 which is connected to respective rows of pixels 11 and selects the pixels 11, row by row, one after another, and a column driving circuit which writes and holds an image signal in the sequentially selected pixels 11, and displays an image of one field. The row driving circuit 21 selects each row of pixels 11 twice successive in a period allocated to the one field. The column driving circuit 22 after temporarily writing and holding an image signal of black level to a pixel when the pixel is selected first writes and holds the actual image signal when the pixel is selected later.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device and a driving method thereof. More specifically, the present invention relates to a technique for suppressing moving image blur in a hold-type image display device represented by an active matrix liquid crystal display or the like.

[0002]

2. Description of the Related Art A hold type image display device comprises a display panel, a row drive circuit and a column drive circuit. The display panel has pixels arranged in rows and columns. The row driving circuit is connected to each row of pixels and sequentially selects the pixels on a row-by-row basis. The column drive circuit is connected to each column of pixels,
An image signal is written and held in a pixel selected by line-sequential scanning by the row driving circuit described above, and thus an image for one field is displayed. The hold type image display device
The feature is that the image signal is held over one field and the brightness is kept constant.

[0003]

A hold-type image display device represented by an active matrix type liquid crystal display keeps a constant value until a new image signal is written in a pixel, even when the display image dynamically changes. Since the voltage of is held in the pixel, the brightness of the pixel is constant. On the other hand, in a non-hold type image display device represented by a CRT, the luminance of pixels changes in an impulse shape, and this display method is advantageous for moving image characteristics. In the active matrix liquid crystal display, an image signal (data) writing operation is performed line-sequentially, and the basic driving method is to perform this line-sequential scanning once per field. However, this driving method causes so-called motion blur. In the hold type image display device, the brightness of the displayed image is kept substantially constant in principle over one field period of the image signal. Such a hold-type characteristic is associated with the afterimage effect of human vision and causes new image quality deterioration such as motion blur when displaying a moving image.

A technique for suppressing image quality deterioration such as motion blur is disclosed in, for example, Japanese Patent Laid-Open No. 9-325715, and will be briefly described with reference to FIG. As shown in the figure, the direct-view image display device includes a light source lamp 101 that continues to emit light at a constant brightness, a transmissive display panel 102 whose transmittance changes according to a drive signal, a shutter 103, a drive circuit 104, and pulse generation. The circuit 105 is provided. The display panel 102 is, for example, a TFT type liquid crystal display, and converts an electric image signal into image display light while continuing the operation of transmitting light from the light source lamp (backlight) 101 for a certain display period. It is arranged between the light source lamp 101 and the observer. The drive circuit 104 generates a drive signal for driving the display panel 102 according to the image signal and the synchronizing signal which are the input signals of the display panel 102, and outputs the drive signal to the display panel 102. An image is displayed by changing the transmittance of the display panel 102 according to the image signal by the drive signal and modulating the light from the light source lamp 101. The shutter 103 turns on / off the transmission of display light. As the shutter 103, for example, a polymer dispersed liquid crystal device or a ferroelectric liquid crystal device, which is not suitable for gradation display required for television display but can turn on / off light transmission at high speed, can be used. The pulse generation circuit 105 generates a shutter control pulse synchronized with the vertical synchronization of the input synchronization signal, and controls the transmission of display light through the shutter 103 by the shutter control pulse. As a result, the image display light displayed to the observer is modulated by the shutter 103 as well as the display panel 102. By using these shutter control pulses, the image display light displayed to the observer on the hold type display panel shown in FIG.
50% to 20% of the field period with each field
Limited to only time. As a result, the afterimage effect of the observer is blocked and image blur is suppressed.

Generally, when a moving image is displayed on a liquid crystal display, blurring due to the response speed of the liquid crystal itself is a problem.
At the same time, there is blurring due to the data being held when the brightness changes. To eliminate this,
An impulse-like response, such as a change in the brightness of a CRT, may be used. Therefore, in the above-described conventional technique, the backlight is flickered to create a luminance change similar to that of a CRT. However, when the backlight flickers, the brightness of all pixels may change at the same time on the same screen even though the change in brightness originally has a time difference between rows according to scanning, which may cause a problem. . Further, as a means for suppressing the blur of the moving image, a method of increasing the scanning speed and interpolating the process of the luminance change to make an impulse shape can be considered, but the operation becomes complicated both in the row drive circuit and the column drive circuit. , The circuit complexity increases due to the interpolation process. In addition, there is a new problem of deterioration in moving image quality due to the interpolation process itself.

[0006]

SUMMARY OF THE INVENTION In view of the above problems of the prior art, it is an object of the present invention to improve the drive system of a hold type image display device and effectively suppress motion blur. The following measures have been taken to achieve this purpose. That is, a display panel having pixels arranged in a matrix, connected to each row of pixels, a row drive circuit for sequentially selecting pixels in row units, and connected to each column of pixels,
In an image display device that includes a column drive circuit that writes and holds an image signal in sequentially selected pixels, and in which an image display device that displays an image for one field, the row drive circuit is configured to Each row is selected twice before and after, and the column driving circuit once writes and holds the image signal of the black level in the pixel at the previously selected time point, and then writes and holds the actual image signal at the later selected time point. It is characterized by

Preferably, the column driving circuit operates in a normally black mode, outputs an image signal whose polarity is inverted around 0 V to each column of the pixel each time each row of the pixel is selected, and At the time point previously selected, the 0 V image signal corresponding to the black level is once written. Furthermore,
The column driving circuit may maintain the image signal at 0V for a predetermined time when the image signal crosses 0V due to polarity inversion, and may write the pixel signal in the pixel. The display panel has a laminated structure in which plasma cells having row-shaped discharge channels and liquid crystal cells having column-shaped signal electrodes are stacked.
A pixel is formed at the intersection of the discharge channel and the signal electrode.

According to the present invention, in a method of driving a hold type image display device such as an active matrix liquid crystal display, when a moving image is displayed, before holding a true image signal (display data) in each pixel, Black data is once held. As a result, it is possible to weaken the integration effect (afterimage effect) of human vision that occurs when observing a moving image, and thus suppress blurring of a moving image.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic diagram showing a basic configuration of an image display device according to the present invention. As shown in the figure, the image display device comprises a display panel 0, a row drive circuit 21, and a column drive circuit 22. The display panel 0 has pixels 11 arranged in a matrix. The row drive circuit 21 is
The pixels 11 are connected to each row via the scanning line X, and the pixels 11 are sequentially selected in row units. Column drive circuit 22
Is connected to each column of the pixels 11 via a signal line Y, writes and holds an image signal (display data) in the pixels 11 selected by line-sequential scanning, and thus displays an image for one field. . A specific example of the image display device having such a configuration is an active matrix liquid crystal display. In particular, a liquid crystal display using a TFT as an active element has a structure in which a pixel electrode is connected to an intersection of a scanning line X and a signal line Y via a thin film transistor (TFT). Another example of the hold-type image display device is a plasma addressed liquid crystal display. This plasma addressed liquid crystal display has a laminated structure in which a plasma cell and a liquid crystal cell are stacked. The discharge channel formed on the plasma cell side functions as the scanning line X, and the signal electrode formed on the liquid crystal cell side functions as the signal line Y.
A pixel is defined at the intersection of the two.

The operation of the image display device shown in FIG. 1 will be described with reference to FIG. The row driving circuit 21 selects each row of the pixels 11 twice before and after in a period assigned to one field. Specifically, the row drive circuit 21 is configured to scan each scan line X.
The scanning signals are sequentially output to 1, X2 and X3 to select the corresponding pixel row. At that time, each scan signal waveform contains two pulses in one field,
The pixel rows are selected twice before and after at the timing Tb and the timing Tp. On the other hand, the column driving circuit 22 once writes and holds the black level image signal in the pixel at the previously selected time point Tb, and then writes and holds the actual image signal at the later selected time point Tp. As shown in the figure, when driving a liquid crystal display, the column drive circuit 22 outputs an image signal waveform whose polarity is inverted for each scanning line and also for each field for the same pixel to each signal line Y. The so-called AC drive is performed. The column drive circuit 22 sends an image signal (display data) to each signal line Y, and the row drive circuit 21 writes and holds the display data in the pixel row of the corresponding scanning line. Normally, the row driving circuit 21 performs line-sequential scanning once per field.
On the other hand, in the present invention, as shown in the figure, the data corresponding to the black display is temporarily held at least before one horizontal period at the timing Tb. Next, a pulse is generated at timing Tp to hold the true display data. As described above, the row driving circuit 21 sequentially performs two-line sequential scanning in one field to write black display data first and then write true display data. As a result, the luminance change of the CRT is approximated to the impulse, thereby suppressing the moving image blur.

FIG. 3 is a detailed diagram of the timing chart shown in FIG. As described above, the image signal has an AC waveform, and the polarity is inverted around 0V. A liquid crystal display that is driven by an alternating current has a normally white mode and a normally black mode. The normally white mode displays white when 0V is applied. On the other hand, in the normally black mode, black display is performed by applying 0V. The illustrated example is a normally black mode, and the data corresponding to black display has a potential level near 0 V of the image signal waveform.
As shown in the figure, a pulse is generated in the scanning signal waveform at the first timing Tb, and the corresponding pixel row is selected. At this time, the 0V level of the image signal waveform is written in the pixel, so that black display is performed. Then, a pulse is generated again at the timing Tp when one horizontal period or more has elapsed, and the same pixel row is selected. At this time, the true image data assigned to the pixel is written. As described above, the column driving circuit (data driver) outputs an image signal whose polarity is inverted around 0 V to each column of the pixel every time each row of the pixel is selected, and at the time when the pixel is first selected. Then, the 0 V image signal corresponding to the black level is once written. On the other hand, the row driving circuit (scan driver) outputs scanning signal waveforms so that the rows are selected twice by shifting the time. In general, the scan driver includes a shift register, which sequentially transfers start pulses and outputs selection pulses. Normally, the scan driver has a structure in which a start pulse is input at the head of one field and this is transferred by a shift register. Therefore, the scanning signal waveform shown in FIG. 3 can be created by a simple process of adding one start pulse, and the moving image characteristics can be improved without making a significant change from the conventional row drive circuit. Is. Of course, the column driving circuit (data driver) may output an AC image signal waveform as usual, and uses a potential near 0 V to write black data. The first selection pulse may be output at the timing when the image signal waveform crosses 0V. This timing is represented by Tb in the waveform diagram of FIG.

FIG. 4 is a waveform diagram showing changes in the luminance of the pixels. The image signal waveform is shown at the top of the figure. 1
V represents one vertical scanning period. This is the portion where the potential level marked with a circle in the image signal waveform is sampled and held. The first circle represents the black level, and the second circle represents the actual display level. Similar scanning is repeated in the next vertical scanning period. The second stage of FIG. 4 shows the scanning signal waveform, and selection pulses are generated at timings Tb and Tp separated by 1H (one horizontal scanning period) or more. The third row in the figure represents the potential change of the pixel. Here, the solid line represents the potential change when the first and second selections are made according to the present invention, and the dotted line represents the potential change when the selection is made once in one field as in the conventional case. The bottom of the figure shows the actual change in luminance according to the change in pixel potential. The solid line shows the luminance change in the case of the present invention, and the dotted line shows the luminance change in the conventional case.

As described above, the potential level marked with a circle in the image signal waveform is written in the pixel. According to the present invention, when a voltage near 0 V is written at the timing Tb before writing the data to be actually displayed, the brightness of the pixel once decreases toward the black level. After that, the data to be actually displayed is written at timing Tp, and the luminance response occurs. By carrying out such a drive, a hold-type luminance change shown by a dotted line in the conventional drive, but an impulse-like luminance change similar to a CRT is obtained as shown by a solid line.

FIG. 5 is a schematic diagram showing an improved example of the image display device according to the present invention, and shows an image signal waveform output from the column drive circuit. As shown in the figure, in order to make it easier to write the potential level near 0 V, the column drive circuit (data driver) is improved so that the potential of 0 V can be generated while the polarity changes line by line. That is, the column driving circuit keeps the image signal at 0V for a predetermined time when the image signal crosses 0V due to the polarity inversion and writes it in the pixel.

FIG. 6 is a schematic cross-sectional view showing a specific structural example of a display panel incorporated in the image display device according to the present invention. The illustrated example is a so-called plasma addressed liquid crystal panel, which has a flat structure composed of a liquid crystal cell 1, a plasma cell 2 and a common intermediate sheet 3 interposed therebetween. The intermediate sheet 3 is made of ultrathin plate glass or the like and is called a microsheet. The plasma cell 2 is composed of a lower glass substrate 4 bonded to the intermediate sheet 3, and a dischargeable gas is enclosed in the space between the two. Striped discharge electrodes are formed on the inner surface of the lower glass substrate 4. These discharge electrodes function as an anode electrode A and a cathode electrode K, respectively. Since the discharge electrode can be printed on the flat glass substrate 4 by the screen printing method or the like, it is excellent in productivity and workability. A partition 7 is formed so as to divide the anode electrode A and the cathode electrode K into pairs, and a discharge channel X is formed by dividing a gap filled with a dischargeable gas. This partition wall 7 can also be formed by a screen printing method, and its top portion is in contact with one surface side of the intermediate sheet 3. In the discharge channel X surrounded by the pair of barrier ribs 7, plasma discharge is generated between the anode electrode A and the cathode electrode K having opposite polarities. The intermediate sheet 3 and the lower glass substrate 4 are joined to each other by a glass frit or the like.

On the other hand, the liquid crystal cell 1 is constructed by using a transparent upper glass substrate 8. The glass substrate 8 is adhered to the other surface side of the intermediate sheet 3 with a sealing material or the like through a predetermined gap, and a liquid crystal 9 is filled in the gap as an electro-optical substance. A signal electrode Y is formed on the inner surface of the upper glass substrate 8. Matrix-shaped pixels are formed at the intersections of the signal electrodes Y and the discharge channels X.
A color filter 13 is also provided on the inner surface of the glass substrate 8 to assign, for example, RGB three primary colors to each pixel.
The flat panel having such a configuration is a transmissive type, and for example, the plasma cell 2 is located on the incident side and the liquid crystal cell 1 is located on the emitting side. Further, the backlight 12 is the plasma cell 2
It is attached to the side.

In the plasma addressed liquid crystal display panel having such a configuration, the row-shaped discharge channels X for plasma discharge are line-sequentially switched and scanned, and the column-shaped signal electrodes Y on the display cell 1 side are synchronized with this scanning. Display driving is performed by applying an image signal. When plasma discharge is generated in the discharge channel X, the inside becomes almost uniformly at the anode potential, and pixel selection is performed for each row. That is, one discharge channel X corresponds to one scanning line and functions as a sampling switch. When an image signal is applied to each signal electrode while the plasma sampling switch is on, sampling is performed and the gradation (brightness) of the pixel can be controlled. Even after the plasma sampling switch is turned off, the image signal is held in the pixel as it is. The display cell 1 modulates the incident light from the backlight 12 into the emitted light according to the image signal to display an image.

FIG. 7 is a schematic view showing only two pixels cut out. In this figure, two signal electrodes Y1 and Y2 and one cathode electrode K1 are shown to facilitate understanding.
And one discharge channel X1 with one anode electrode A1 is shown. Each pixel 11 has a signal electrode Y
1 or Y2, the liquid crystal 9, the intermediate sheet 3, and the discharge channel X1 have a laminated structure. The discharge channel X1 is connected to substantially the anode potential during plasma discharge. When an image signal is applied to each of the signal electrodes Y1 and Y2 in this state, charges are injected into the liquid crystal 9 and the intermediate sheet 3. On the other hand, when the plasma discharge ends, the discharge channel X1
Becomes a floating potential because it returns to an insulating state, and the injected charges are held in each pixel 11. A so-called sampling hold operation is performed. Therefore, the discharge channel X1 functions as an individual sampling switching element provided in each pixel 11, and is therefore schematically represented by the switching symbol S1. On the other hand, the signal electrode Y1,
The liquid crystal 9 and the intermediate sheet 3 held between Y2 and the discharge channel X1 function as a sampling capacitor. When the sampling switch S1 is turned on by line-sequential scanning, the image signal is written in the sampling capacitor, and each pixel is turned on or off according to the signal voltage level. The signal voltage is held in the sampling capacitor even after the sampling switch S1 is turned off, and the active matrix operation of the display device is performed. The effective voltage actually applied to the liquid crystal 9 is determined by capacity division with the intermediate sheet 3.

[0019]

As described above, according to the present invention, the black level is once written in the pixel within one field, and then the actual display level is written. This allows CR
An impulse-like response is obtained like the brightness change of T. By adopting this driving method, the present invention realizes a pseudo CRT-like luminance change in a hold-type device such as a liquid crystal, thereby improving moving image characteristics. In terms of circuit configuration, it is possible to improve the moving image characteristics without making a great change from the conventional drive circuit.

[Brief description of drawings]

FIG. 1 is a block diagram showing a basic configuration of an image display device according to the present invention.

FIG. 2 is a waveform diagram for explaining the operation of the image display device shown in FIG.

FIG. 3 is a waveform diagram for explaining the operation of the image display device shown in FIG.

FIG. 4 is a waveform diagram for explaining the operation of the image display device shown in FIG.

5 is a waveform diagram provided for explaining the operation of the image display device shown in FIG.

6 is a cross-sectional view showing an example of a display panel included in the image display device shown in FIG.

FIG. 7 is a schematic diagram for explaining the operation of the display panel shown in FIG.

FIG. 8 is a schematic diagram showing an example of a conventional image display device.

[Explanation of symbols]

0 ... Display panel, 11 ... Pixel, 21 ... Row drive circuit, 22 ... Column drive circuit

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G09G 3/20 624 G09G 3/20 624A 641 641R 660 660V F term (reference) 2H089 HA36 QA06 TA09 TA18 2H093 NA16 NA31 NA41 NA51 NA71 NC22 NC23 NC34 ND49 5C006 AA01 AC23 AF44 AF46 BB16 BB18 BC03 BC12 FA29 5C080 AA10 BB05 DD03 EE19 EE28 FF11 JJ02 JJ04 JJ06

Claims (5)

[Claims] 1. A display panel having pixels arranged in a matrix, a row driving circuit connected to each row of pixels, sequentially selecting pixels on a row-by-row basis, and connected to each column of pixels. In an image display device that includes a column drive circuit that writes and holds an image signal in sequentially selected pixels, and in which an image display device for displaying an image for one field is provided, the row drive circuit is configured such that each row of pixels is in a period assigned to one field. And the column drive circuit writes and holds the black level image signal in the pixel once at the previously selected time and then writes and holds the actual image signal at the later selected time. An image display device characterized by. 2. The column driving circuit operates in a normally black mode, and outputs an image signal whose polarity is inverted around 0V to each column of the pixel each time each row of the pixel is selected, and the pixel first The image display device according to claim 1, wherein an image signal of 0 V corresponding to the black level is once written at the time of being selected. 3. The image display according to claim 2, wherein the column driving circuit maintains the image signal at 0V for a predetermined time when the image signal crosses 0V due to polarity inversion and writes the image signal in a pixel. apparatus. 4. The display panel has a laminated structure in which plasma cells having row-shaped discharge channels and liquid crystal cells having column-shaped signal electrodes are stacked, and the discharge channels intersect the signal electrodes. The image display device according to claim 1, wherein a pixel is constituted by a portion. 5. A row driving procedure for sequentially selecting pixels on a row-by-row basis for driving a display panel having pixels arranged in a matrix, and a column driving procedure for writing and holding an image signal in the sequentially selected pixels. In the image display method for displaying an image for one field, the row driving procedure selects each row of pixels twice in the period assigned to one field, and the column driving procedure first. An image display method, wherein a black level image signal is once written and held in a pixel at a selected time point, and then an actual image signal is written and held at a later selected time point.