JP2007316380A - Electro-optical device, method for driving electro-optical device, and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simplify an overdrive circuit relating to techniques of contributing to simplification of an overdrive configuration. <P>SOLUTION: Image data are compared with brightness information data in the last frame by using a lookup table; a gradation voltage is supplied to each pixel in a preselection period based on response compensation data resulting in acceleration of the response of a liquid crystal; and a gradation voltage based on the image data is supplied to each pixel in the main selection period after a correction period shorter than one frame period. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technique that contributes to simplification of a configuration for performing so-called overdrive.

Electro-optical materials, particularly liquid crystals, have a low optical response speed to electrical changes. For this reason, it has been pointed out that an electro-optical device that performs display using an electro-optical change of liquid crystal has poor display characteristics of moving images compared to other display devices such as a CRT. Therefore, a so-called overdrive technique has been proposed in which response compensation is performed on the gradation (voltage) specified by the image data using the lookup table at the gradation specified by the image data one frame before. (See Patent Document 1).

In addition, since this response speed (responsiveness) greatly depends on the temperature, a plurality of lookup tables corresponding to the temperature classification are prepared, while one lookup table corresponding to the detected temperature is selected to overload. A technique for executing a drive has also been proposed (see Patent Document 2).

JP 2001-265298 A JP 2004-133159 A

However, in the configuration using a plurality of look-up tables, the memory capacity required for the look-up tables becomes large and the circuit becomes large. For this reason, there has been a problem that it is difficult to apply to portable devices that require a small change in weight while the temperature changes greatly.

The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide an electro-optical device and a driving circuit that can improve the display characteristics of a moving image by reducing the capacity required for a lookup table. Another object is to provide a driving method and an electronic apparatus.

In order to solve the above problems, an electro-optical device according to the present invention is an electro-optical device having a plurality of pixels, and corresponds to supplied image data and image data one frame before the image data. Image data switching for switching and outputting a look-up table for storing response compensation data, a first pixel signal as gradation data designated by the image data, and a second pixel signal as the response compensation data And the second pixel signal is supplied in a predetermined period in a frame period before a frame period in which the first pixel signal is supplied to the pixel.
According to the present invention, the period during which the second pixel signal to be overdriven is supplied is shorter than one frame, and the second pixel signal is used only to accelerate the response change of the liquid crystal. Since only the first pixel signal to be subsequently supplied is defined, the control accuracy of the overdrive amount may be rough, and the configuration and number of lookup tables can be simplified and reduced.
In addition, the image data switching circuit has two horizontal scanning periods in the frame period.
The first image signal may be output in one selection period divided into two, and the second image signal may be output in the other selection period.
The image data switching circuit may output the second image signal in the other selection period after outputting the first image signal in the one selection period during the frame period. .

The present invention can be conceptualized not only as an electro-optical device but also as a driving method and an electronic apparatus having the electro-optical device.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration of the electro-optical device according to the present embodiment.
As shown in this figure, the electro-optical device 1 includes a liquid crystal display panel 10, a timing control circuit 20, a frame memory 30, a lookup table (LUT) 40, a data signal conversion circuit 50, an image data switching circuit 60, and an image. A data delay circuit 70 is included.

Among these, the liquid crystal display panel 10 is of a peripheral circuit built-in type in which the scanning line driving circuit 130 and the data line driving circuit 140 are arranged around the display area 100 as shown in FIG. In the display area 100, the 480 rows of scanning lines 112 extend in the row (X) direction, and the 640 columns of data lines 114 extend in the column (Y) direction. It is provided while keeping. The pixels 110 are arranged corresponding to the intersections of the scanning lines 112 of 480 rows and the data lines 114 of 640 columns, respectively. Therefore, in this embodiment, the pixels 110 are arranged in a matrix of 480 rows × 640 columns, but the present invention is not limited to this arrangement.

The scanning line driving circuit 130 performs a characteristic operation of the present invention. According to the timing control circuit 20, which will be described later, the scanning signal G1,
G2, G3,..., G480 are supplied, and in detail, as shown in FIG.
2, 3,..., 480th scanning line 112 is sequentially selected every horizontal scanning period (H), and this is selected as the main selection. This is selected as a precursor selection, the H level is applied to the selected scanning line in the second half of each 1H period, the H level is applied to the first selected scanning line in the first half of each 1H period, and otherwise the scanning line The L level is supplied as a scanning signal.

The data line driving circuit 140 includes a sampling signal output circuit 142 and a TFT 146 provided for each data line 114. Here, as shown in the figure, the sampling signal output circuit 142 sequentially samples the sampling signals S1 and S2 which are sequentially set to the H level according to the timing control circuit 20 every time one row of the scanning lines 112 is selected. , S3, ..., S640
Are respectively output.

Further, the TFT 146 provided in each column has a data line 114 whose drain corresponds to the column.
The source is commonly connected to the image signal line 171 to which the data signal Vid is supplied, and the sampling signal corresponding to the column is supplied to the gate.

Therefore, when the sampling signals S1, S2, S3,..., S640 are exclusively at the H level in this order over one horizontal scanning period (H) in which the scanning line 112 of a certain row is selected, 1
The TFTs 146 in the second, third,..., 640th columns are turned on in order.

As shown in the figure, the data line driving circuit 140 supplies each pixel in the selected row corresponding to the data signal Vid in accordance with the timing control circuit 20 every time the scanning line 112 is selected. A pixel signal is generated and output to the data line 114.

The configuration of the pixel 110 will be described with reference to FIG. FIG. 3 is a diagram illustrating an electrical configuration of the pixel 110. The i row and the (i + 1) row adjacent to the i row, the j column, and the 1 column are adjacent to the i row.
A configuration of a total of 4 pixels of 2 × 2 corresponding to the intersection with the (j + 1) column adjacent on the right side of the column is shown.

Note that i and (i + 1) are symbols for generally indicating the row in which the pixels 110 are arranged, and are integers of 1 to 480, respectively. Further, j and (j + 1) are symbols for generally indicating the columns in which the pixels 110 are arranged, and are integers of 1 to 640, respectively.

As shown in FIG. 3, each pixel 110 includes an n-channel thin film transistor (thin fil
m transistor: hereinafter simply abbreviated as “TFT”) 116 and a liquid crystal capacitor 120. Since each pixel 110 has the same configuration, the pixel 110 in the i-th row and j-th column will be described as a representative example. In the pixel 110 in the i-th row and j-th column, the gate of the TFT 116 is connected to the i-th scanning line 112. On the other hand, its source is connected to the data line 114 in the j-th column, and its drain is connected to the pixel electrode 118 which is one end of the liquid crystal capacitor 120. In addition, the liquid crystal capacity 120
The other end is a common electrode 108 common to all the pixels 110, and a voltage LCcom constant in time is applied thereto.

Although not specifically shown, the liquid crystal display panel 10 has a configuration in which a pair of substrates of an element substrate and a counter substrate are bonded together with a certain gap (cell thickness) and liquid crystal is sandwiched in the gap. Yes. Of these, the element substrate includes a scanning line 112, a data line 114, and a TFT.
116 and the pixel electrode 118 are formed, while the common electrode 108 is formed on the counter substrate, and these electrode forming surfaces are bonded to each other so as to face each other. Therefore, the liquid crystal capacitor 120 has a configuration in which the liquid crystal 105 is sandwiched between the pixel electrode 118 and the common electrode 108.

In the present embodiment, for convenience of explanation, if the effective voltage value held in the liquid crystal capacitor 120 is close to zero, the transmittance of light passing through the liquid crystal capacitor is maximized to display white, while the effective voltage value is As the value increases, the amount of transmitted light decreases, and finally a normally white mode in which the black display with the minimum transmittance is set.

In this pixel 110, an H level selection voltage is applied to the scanning line 112, and the TFT 11
6 is turned on (conducted), and a voltage corresponding to the gradation (brightness) is applied to the pixel electrode 118 via the data line 114 and the on-state TFT 116, so that the liquid crystal capacitor 120 has a gradation. It is possible to hold the effective voltage value according to the above.

When the scanning line 112 becomes an L level non-selection voltage, the TFT 116 is turned off (non-conducting).
However, since the off-resistance at this time is not ideal infinity, the liquid crystal capacitance 120
The charge accumulated in the leaks not a little. In order to reduce the influence of this leakage, a storage capacitor 109 is formed for each pixel. One end of the storage capacitor 109 is connected to the pixel electrode 118 (
The other end is connected to the capacitor line 10 over all pixels.
7 is commonly connected. The capacitor line 107 has a constant temporal potential, for example, a ground potential G.
held at nd.

Returning to FIG. 1, the timing control circuit 20 controls each unit in synchronization with a vertical synchronization signal Vsync, a horizontal synchronization signal Hsync, and a clock signal Dclk supplied from an upper circuit (not shown).

In this embodiment, the image data Cd is digital data that designates the gradation of the pixel 110 with 8 bits. In one vertical scanning period (F) defined by the vertical synchronization signal Vsync, the image data Cd is 480 rows 640 from 1 row 1 column. The horizontal synchronization signal Hs is supplied corresponding to the pixels up to the column.
In one horizontal scanning period (H) defined by ync, one pixel corresponding to one row is supplied, and one pixel is supplied for each dot clock Dclk.

Here, the timing control circuit 20 controls the scanning line driving circuit 130 so that the scanning line 112 in the row corresponding to the supplied data signal Vid is pioneered or selected.

The image data Cd supplied from the upper circuit is for designating the gradation (equal voltage) of the pixel, but does not process the image data Cd at all and corresponds to the gradation designated by the image data Cd. In the configuration in which the voltage is directly applied to the pixel 110 (pixel electrode 118), the moving image display characteristics are deteriorated due to the low response of the liquid crystal.

Therefore, in this embodiment, the image data Cd is compared with the brightness information data Pd one frame before by using the lookup table 40, and as a result, the voltage compensated image data for accelerating the response of the liquid crystal. (Response compensation data) A gradation (voltage) based on Od is supplied to each pixel during the precursor selection period, and after a time shorter than one frame period (hereinafter referred to as a correction period), based on the image data Cd. A gradation (voltage) is supplied to each pixel during the main selection period, and the liquid crystal display panel 1
The configuration is such that 0 is driven. Note that the data signal V based on the image data Cd during this selection period.
In order to output id, it is necessary to delay and output the image data Cd by the correction period.
This delaying circuit is the image data delay circuit 70, and the delayed output signal is delayed image data Cdd.

In this embodiment, a frame means that all the pixels 110 constituting one screen are sequentially selected and scanned, and a frame period is a period required to scan all the pixels 110, that is, One vertical scanning period (F).

Further, the response compensation data Od need not be highly accurate data, for example, image data C
If d is brighter than the image data Pd one frame before, the response compensation data Od may be white data, and if dark, it may be black data.

The frame memory 30 stores the brightness feature of the image data Cd and reads the brightness feature data Pd according to the timing control circuit 20. Specifically, the brightness of the image data Cd supplied from the upper circuit is stored in the frame memory 30, and the brightness characteristic data stored before one vertical scanning period is read and output as Pd. is there.

The brightness characteristic of the image data Cd may be, for example, the upper 1 or 2 bits of the digital image data Cd. Alternatively, the entire numerical value range of the image data is sectioned, and digitally corresponding to each section assignment. The numerical value represented may be sufficient.

The look-up table 40 is a two-dimensional conversion table that performs response compensation on the gradation specified by the image data Cd according to the value specified by the brightness feature data Pd, and outputs the result as image data Od. Specifically, for example, in this embodiment, the look-up table 40, in this embodiment, if the image data Cd is simply brighter than the gradation indicated by the brightness feature data data Pd, white data If it is dark, black data is output.

In the precursor selection period, pixel data Vid obtained by converting the response compensation data by the data signal conversion circuit 50 is supplied to each pixel.

That is, when a certain pixel changes brightly, during the period from the pioneer selection period to the next main selection period,
Apply a “white” pixel voltage to the pixel and accelerate the liquid crystal to respond faster to the brighter,
On the other hand, when the pixel changes darkly, the pixel has “
Apply "black" pixel voltage and accelerate the liquid crystal to respond faster to the darker.

The image data Cd is, for example, 8 bits. However, since the frame memory 30 only needs to store brightness information, it may be 1 or 2 bits per pixel. Lookup table 4
The brightness characteristic data Pd output by 0 is also a total of four values obtained by adding binary information of “white” and “black” as described above, or adding “bright gradation” and “dark gradation” thereto. Coarse information can be used.

The data signal conversion circuit 50 corresponds to the image data Od read from the lookup table 40 corresponding to the pioneer selection period (the first half of one horizontal selection period) and the main drive selection period (the second half of one horizontal selection period). Then, the image data Cd is supplied to the data line driving circuit 140, and each pixel 11
Applied to 0 (pixel electrode 118).

FIG. 4 is a diagram showing the timing of the signal of the scanning line 112 and the data signal Vid.
The cross hatched portion of Vid in the figure corresponds to the precursor selection period of each row, and indicates that the voltage Vid supplied to the pixel corresponding to each column of the row is based on the response correction data Od. The portion without hatching corresponds to the main selection period of each row, and indicates that the voltage Vid supplied to the pixel corresponding to each column of the row is based on the delayed image data Cdd. The image data switching circuit 60 performs switching between the response correction data Od and the delayed image data Cdd.

In this embodiment, 2H is set between the precursor selection period and the main selection period of each row. However, the present invention is not limited to this, and may be set to about 10 to 20H, for example. Since the optimum set value depends on the electro-optical characteristics of the liquid crystal, it may be obtained experimentally, for example.

Although not particularly shown in the present embodiment, a row inversion method in which the polarity of the data signal is inverted for each scanning line is used, but the surface in which the polarity of the data signal is inverted for each frame scanning line. (Frame) inversion method, column inversion, and dot inversion may be used.

Next, the operation of the electro-optical device 1 according to this embodiment will be described. This electro-optical device 1
Is to compensate for the low response of liquid crystal by overdrive.
This is the application timing of the overdrive voltage.

First, FIG. 5 is a schematic diagram showing timing for applying an overdrive voltage to a pixel.
For comparison, FIG. 6A shows the pixel voltage when overdrive is not performed, FIG. 6B shows the pixel voltage when overdrive according to the prior art is performed, and FIG. FIG. 6 shows one pixel voltage when the form of overdrive is performed. Note that the polarity of the pixel voltage is generally inverted every time writing is performed, but the absolute value of the pixel voltage is shown for the sake of simplicity.

When overdrive is not performed, as shown in FIG. 5A, when the display gradation changes and the pixel voltage (absolute value) changes, the pixel voltage corresponding to the changed display gradation Continues to be applied (upward hatching).

Next, in the case of performing overdrive according to the prior art, as shown in FIG. 5B, when the display gradation changes and the pixel voltage (absolute value) changes, only one frame period after the change occurs. A compensated voltage (indicated by cross-hatching) is superimposed on the pixel voltage corresponding to the display gradation, followed by 2
After the frame, the pixel voltage corresponding to the display gradation after the change continues to be applied.

In the case of the present embodiment, as shown in FIG. 5C, when the display gradation changes and the voltage (absolute value) of the pixel changes, a large compensation voltage (cross) for a predetermined period before the change. The pixel voltage corresponding to the display gradation after the change continues to be applied after one frame thereafter.

Therefore, in the case of the overdrive of the prior art shown in FIG. 5B, the correction voltage is superimposed during one frame period, and if there is too much correction voltage, a jump (overshoot) occurs in the response. If a pseudo contour is generated in the display and the amount is small, display blur cannot be eliminated.

Therefore, the correction voltage to be superimposed must be appropriately controlled, but in the case of the present embodiment shown in FIG. 5C, a large compensation voltage is applied before the change of the pixel voltage due to the display gradation change. To do. This large compensation voltage contributes to accelerating the electro-optic response of the liquid crystal and speeds up the optical response. On the other hand, since the period during which this large compensation voltage is applied is short, it does not contribute to human perception of light and darkness, and only the pixel voltage on which the correction voltage for one frame and thereafter is not superimposed contributes. In other words, the brightness is defined by this voltage.

According to this embodiment, even if the compensation voltage of this embodiment is a little too high, overshoot does not occur. Therefore, it is possible to set the compensation voltage somewhat larger, and the response at low temperature Speed can also be improved.

As described above, the rough compensation voltage is applied before the change of the pixel voltage due to the change in the display gradation, so that the response compensation with the coarse accuracy is made in time, and the look-up table 4
The number of zeros and the circuit scale can be reduced, and it is not necessary to prepare a plurality of lookup tables for each temperature. Further, the number of bits of the memory corresponding to each pixel of the frame memory 30 can be reduced.

In the above-described embodiment, the pixel signals corresponding to the pixels in the first column to the 480th column located on the scanning line are sequentially supplied so-called dot sequential driving. However, the scanning signal corresponding to one scanning line 112 is used. When the signal becomes H level, data signals may be supplied to all the data lines 114 at once, so-called line-sequential driving may be used. The data signal is multiplied by n (n is an integer of 2 or more) times on the time axis. A configuration may be used in which the expansion and the so-called phase expansion (also referred to as serial-parallel conversion) driving supplied to the n image signal lines are used together.

Furthermore, in the embodiment, a normally white mode in which white is displayed in a state in which no voltage is applied is used. However, a normally black mode in which black is displayed in a state in which no voltage is applied may be used. Alternatively, color display may be performed by forming one dot with three pixels of R (red), G (green), and B (blue). The display region 100 is not limited to the transmissive type, and may be a reflective type or a semi-transmissive / semi-reflective type intermediate between the two.

The present invention is not limited to liquid crystals, and can be applied to all configurations in which display is performed using an electro-optical material having a low optical response speed with respect to an electrical change.

Next, an electronic apparatus having the electro-optical device 1 according to the above-described embodiment will be described. FIG. 6 is a diagram illustrating a configuration of a mobile phone 1200 using the electro-optical device 1 according to the embodiment.
As shown in this figure, a cellular phone 1200 includes the electro-optical device 1 described above, together with a plurality of operation buttons 1202, an earpiece 1204 and a mouthpiece 1206.
Note that components of the electro-optical device 1 other than the display area 100 are the mobile phone 12.
Because it is built in 00, it does not appear as an appearance.

As an electronic apparatus to which the electro-optical device 1 is applied, in addition to the mobile phone shown in FIG. 6, a digital still camera, a notebook computer, a liquid crystal television, a viewfinder type (or a monitor direct view type) video recorder. , Car navigation devices, pagers, electronic notebooks, calculators, word processors, workstations, videophones, POS terminals, devices equipped with touch panels, and the like. Needless to say, the above-described electro-optical device 1 is applicable as a display device of these various electronic devices.

1 is a block diagram illustrating a configuration of an electro-optical device according to an embodiment of the invention. FIG. 3 is a diagram illustrating a configuration of a liquid crystal display panel in the electro-optical device. 2 is a diagram showing a configuration of a pixel in the liquid crystal display panel. FIG. FIG. 6 is a diagram for explaining the operation of the electro-optical device. The schematic diagram which shows the timing which applies an overdrive voltage to a pixel. 6 is a diagram showing a mobile phone as an example of an electronic apparatus to which the electro-optical device is applied. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electro-optical device, 10 ... Liquid crystal display panel, 20 ... Timing control circuit, 30 ... Frame memory, 40 ... Look-up table, 50 ... Data signal conversion circuit, 60 ... Data switching circuit, 70 ... Image data delay circuit, 100 DESCRIPTION OF SYMBOLS Display area 112 Scan line 114 Data line 116 TFT Electrode 120 Liquid crystal capacitor 130 Scan line drive circuit 140 Data line drive circuit 1200 Mobile phone

Claims (7)

An electro-optical device having a plurality of pixels,
A lookup table for storing response compensation data corresponding to the supplied image data and image data one frame before the image data;
An image data switching circuit for switching and outputting a first pixel signal as gradation data designated by the image data and a second pixel signal as the response compensation data;
Have
The electro-optical device, wherein the second pixel signal is supplied in a predetermined period in a frame period before a frame period in which the first pixel signal is supplied to the pixel. The image data switching circuit
In one selection period obtained by dividing one horizontal scanning period into two in the frame period,
The electro-optical device according to claim 1, wherein the first image signal is output, and the second image signal is output in the other selection period. The image data switching circuit
3. The electricity according to claim 2, wherein, during the frame period, after the first image signal is output in the one selection period, the second image signal is output in the other selection period. Optical device. An electro-optical device driving method comprising: a plurality of pixels; supplied image data; and a look-up table that generates response compensation data corresponding to image data one frame before the image data. ,
Switching and outputting a first pixel signal as gradation data specified by the image data and a second pixel signal as the response compensation data;
The method of driving an electro-optical device, wherein the second pixel signal is supplied in a predetermined period in a frame period before a frame period in which the first pixel signal is supplied to the pixel. In one selection period obtained by dividing one horizontal scanning period into two in the frame period,
5. The method of driving an electro-optical device according to claim 4, wherein the first image signal is output, and the second image signal is output in the other selection period. 6. The electricity according to claim 5, wherein, during the frame period, the second image signal is output in the other selection period after the first image signal is output in the one selection period. Driving method of optical device. An electronic apparatus comprising the electro-optical device according to claim 1.

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