JP2008209690A - Display device, driving method of display device, and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To mitigate a gradation difference which is produced at a boundary between a nondisplay region and a display area because sticking occurrs due to application of a GND voltage to a data line and a common electrode. <P>SOLUTION: A boundary area adjacent to the boundary between the nondisplay area and the display area is set, the GND voltage is applied to both of the common electrode 5 and the data line S with respect to the nondisplay area and the writing of only one time per several frames is performed with respect to pixel electrodes corresponding to display lines of areas except the boundary area, whereby power consumption is reduced. An off-voltage ΔV which makes the same state as nondisplay state is applied between the pixel electrode 2 and the common electrode 5 by only one time per several frames with respect to a display line on the boundary area. The boundary area is reduced in a degree of sticking as compared to other parts of the nondisplay areas, an area where the sticking is mitigated is formed on the boundary area, therefore, the gradation on the boundary area is smoothly changed and, as the result, the gradation difference on the boundary part due to the sticking can be made inconspicuous. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a display device having a partial display function for setting a partial region of a display screen to a display state and other regions to a non-display state, a driving method thereof, and an electronic apparatus including the display device.

Conventionally, for example, in a display panel using TFT, a mode called a partial display function for displaying only a part of the display screen has been used in order to reduce power consumption in a standby screen or the like. Mainly used in mobile applications. In such a partial display function, when the desired area of the display screen is a display area, the other area is a non-display area, the display area is arbitrarily set, and this display area is displayed in full screen It is driven by normal driving having a plurality of gradations similar to the above, or by binary driving that displays only binary values (see, for example, Patent Document 1).

In addition, in an active matrix panel, particularly a display panel having an amorphous silicon TFT element or a polysilicon TFT element, the operation is simplified in a drive circuit corresponding to a non-display area when using this partial display function. For example, the γ amplifier for γ correction is stopped, or the TFT source electrode, common electrode, and gate electrode are fixed to the same voltage such as the ground voltage GND. (For example, refer to Patent Document 2), or to divide a non-display area for each block and write the background display data by shifting the area for each frame (for example, refer to Patent Document 3), or By reducing the number of writes to the non-display area, such as by writing to the non-display area at a rate of once per frame Some proposals have been made to reduce power consumption.
Japanese Patent Laid-Open No. 11-184434 JP 2002-99262 A JP 2002-297105 A

However, as described above, when the driving method is different between the display area and the non-display area,
There is a problem that a difference in density occurs between the non-display area and the display area. This is because writing to the non-display area is performed at a rate of once every plural times, so the period of alternating current is long, or the source electrode and the common electrode are at the same voltage. This is considered to be due to the fact that a voltage component is always applied to the liquid crystal, and that display defects such as image sticking occur due to, for example. In particular, when a partial display is performed for a long time, a noticeable gray level difference appears at the boundary between the display area and the non-display area, and even if the same gradation display is performed on the entire display screen, the brightness appears different. End up.
Accordingly, the present invention has been made paying attention to the above-mentioned conventional unsolved problems, and alleviates the difference in density caused at the boundary between the display area and the non-display area due to partial driving. It is an object of the present invention to provide a display device that can be used, a driving method thereof, and an electronic device including the display device.

In order to solve the above-described problems, a display device of the present invention is a pixel provided corresponding to the intersection of a plurality of scanning lines and a plurality of data lines and connected to the corresponding data line via a switch element. An electrode and a common electrode facing the pixel electrode, and when the switch element is turned on by a selection voltage supplied to the scanning line, a data signal supplied to the data line is the pixel In a display device in which gradation display is performed by writing to an electrode, a partial display function in which a part of the image display area is a display area, the remaining area is a non-display area, and only the display area is in a display state When the partial display function is used, the drive circuit has a ratio of once per a plurality of frames with respect to the scanning lines in the boundary area adjacent to the display area in the non-display area. In addition to supplying the selection voltage, an off-voltage that makes the image display region non-display state is applied between the corresponding pixel electrode and the common electrode, and the region of the non-display region excluding the boundary region is applied. The selection voltage is supplied to the scanning line once every a plurality of frames, and a ground voltage is applied to the corresponding pixel electrode and the common electrode.

Here, during the horizontal scanning period of the non-display area, for example, when a ground voltage is applied to each of the data line and the common electrode, and writing of the data signal to the pixel electrode is performed once every plural frames, The switch element feedthrough causes a voltage difference between the pixel electrode and the common electrode, which may cause burn-in in the non-display area. However, for the scanning lines of the boundary area adjacent to the boundary with the display area, the image display area is set to the non-display state between the pixel electrode and the common electrode at a rate of once per a plurality of frames. Therefore, the burn-in in the boundary region adjacent to the boundary with the display region is reduced as compared with the burn-in in other regions of the non-display region. For this reason, an area in which burn-in is reduced, that is, a boundary area is formed between the display area and the non-display area with burn-in, and when full-screen display is performed with the same gradation, It is possible to reduce a difference in shading caused by image sticking that occurs in the vicinity of the boundary between the display area and the non-display area.

In the display device described above, a plurality of scanning lines belong to the boundary region, and the driving circuit includes the pixel electrode corresponding to the scanning line close to the boundary among the plurality of scanning lines of the boundary region and the common. The frequency of applying the off voltage to the electrode is increased.
For this reason, image sticking is eased near the boundary between the display area and the non-display area, and the image sticking degree changes relatively smoothly between the display area and the non-display area. , Can be less noticeable.
In the display device described above, the off voltage is set to a value corresponding to a feedthrough voltage of the switch element.
Thereby, the image sticking caused by the feedthrough voltage can be mitigated accurately.

The display device driving method according to the present invention includes a pixel electrode provided corresponding to the intersection of a plurality of scanning lines and a plurality of data lines, and connected to the corresponding data line via a switch element; A common electrode facing the pixel electrode, and a data signal supplied to the data line is written to the pixel electrode when the switch element is turned on by a selection voltage supplied to the scan line. In the display device driving method in which gradation display is performed, a partial display function in which a part of the image display area is a display area, the remaining area is a non-display area, and only the display area is in a display state And when the partial display function is used, the selection voltage is supplied at a rate of once per a plurality of frames with respect to the scanning line of the boundary area adjacent to the display area in the non-display area. A plurality of frames are applied to a scanning line in a region excluding the boundary region in the non-display region by applying an off voltage that makes the image display region non-display state between the corresponding pixel electrode and the common electrode. The selection voltage is supplied at a rate of once, and a ground voltage is applied to the corresponding pixel electrode and the common electrode.

For this reason, the selection voltage is supplied at a rate of once per a plurality of frames to the scanning lines in the non-display area, and the ground voltage is applied to the corresponding pixel electrode and the common electrode, whereby the switching element feedthrough causes the pixel. Even if a voltage difference occurs between the electrode and the common electrode, and there is a possibility that burn-in may occur in the non-display area, the scan line of the boundary area adjacent to the boundary with the display area in the non-display area In this case, an off-voltage that sets the image display area to the non-display state is applied between the pixel electrode and the common electrode at a rate of once per a plurality of frames, so that the boundary between the non-display area and the display area is applied. The burn-in in the adjacent boundary area is alleviated as compared with the burn-in in other areas of the non-display area. In other words, an area where the burn-in is reduced, that is, a boundary area is formed between the display area and the non-display area where the burn-in occurs, and the display is performed when full-screen display is performed with the same gradation. Which occurs near the boundary between the region and the non-display region,
The difference in shading caused by image sticking can be reduced.
In addition, an electronic apparatus according to the present invention includes the display device according to any one of claims 1 to 3.
Accordingly, an electronic apparatus including a display device in which the difference in density at the boundary between the display area and the non-display area is not noticeable can be easily obtained.

Embodiments of the present invention will be described below.
FIG. 1 is a configuration diagram showing an example of a liquid crystal display device 100 to which the present invention is applied.
In FIG. 1, reference numeral 1 is a liquid crystal panel, reference numeral 10 is a liquid crystal driving circuit for driving the liquid crystal panel 1, reference numeral 20 is a control circuit for controlling the liquid crystal driving circuit 10, and reference numeral 50 is a voltage applied to the liquid crystal panel 1 and the liquid crystal driving circuit 10. This is a liquid crystal driving power supply circuit to be supplied. The liquid crystal driving circuit 10, the control circuit 20, and the liquid crystal driving power supply circuit 50 correspond to the driving circuit.

The liquid crystal panel 1 is the same as a known liquid crystal panel, and is arranged such that a plurality of scanning lines G and a plurality of data lines S are substantially orthogonal to each other, and corresponds to each intersection of the scanning lines G and the data lines S. Thus, the pixel electrode 2 is provided. That is, the source of the TFT 3 as a switching element is connected to each data line S, and the drain of the TFT 3 is the pixel electrode 2 and the storage capacitor 4.
The same common electrode voltage Vcom as that of the common electrode 5 is applied to the other end.

The gate of the TFT 3 is connected to the scanning line G. When the TFT 3 is turned on by the selection voltage of the scanning line G, the data line S and the pixel electrode 2 are turned on, and the voltage between the pixel electrode 2 and the common electrode 5 is turned on. Due to the difference, the orientation state of a liquid crystal layer (not shown) formed between the substrate on which the pixel electrode 2 is formed and the substrate on which the common electrode 5 is formed is changed, and the pixel electrode 2 and the common electrode 5 are also changed.
The voltage difference between them is maintained by the storage capacity 4.

The common electrode 5 is arranged along the scanning line G, for example, so that the common electrode voltage Vcom can be individually set.
The liquid crystal driving circuit 10 includes a scanning line driving circuit 30 and a data line driving circuit 40. The scanning line driving circuit 30 supplies a selection voltage to the scanning line G in a predetermined order. For example, when a selection voltage is supplied to a certain scanning line G, all the TFTs 3 connected to the scanning line G are turned on, and writing is performed on all the pixel electrodes 2 corresponding to the scanning line G.

When the scanning line G is selected by the scanning line driving circuit 30, the data line driving circuit 40 supplies an image signal to each data line S and sequentially writes the image data to the pixel electrode 2 through the TFT 3 in the on state. . Here, the data line driving circuit 40 uses the common electrode voltage Vcom of the common electrode 5 as a reference voltage, and positive writing for supplying an image signal to the data line S at a voltage higher than the reference voltage, and lower than the reference voltage. The negative polarity writing for supplying the image signal to the data line S by the voltage is alternately performed. The data line driving circuit 40 is driven by, for example, an H line inversion driving method in which positive polarity writing and negative polarity writing are alternately performed for each horizontal line using an AC voltage in order to prevent liquid crystal burn-in. .

The control circuit 20 includes a display control unit 21 and an image data conversion unit 22.
Based on a display switching signal input from a host device (not shown), the display control unit 21 is a full display mode in which the entire screen is a display area, or a part of the entire screen is a display area and the remaining areas are not displayed. One of the partial (partial) display modes as an area is selected, and the selected display mode is output as a mode signal to the scanning line driving circuit 30, the data line driving circuit 40, and the liquid crystal driving power supply circuit 50. Further, a control signal for adjusting the operation timing among the scanning line driving circuit 30, the data line driving circuit 40, and the liquid crystal driving power supply circuit 50 is output to these circuits.
The image data conversion unit 22 converts the image signal input from the host device in accordance with positive polarity writing or negative polarity writing, and outputs this to the data line driving circuit 40.

FIG. 2 is a block diagram of the power supply circuit 50 for driving the liquid crystal.
The liquid crystal driving power supply circuit 50 supplies voltages to the scanning line driving circuit 30, the data line driving circuit 40, and the liquid crystal panel 1, respectively.
The voltages supplied to the scanning line driving circuit 30 by the liquid crystal driving power supply circuit 50 include a TFT on voltage that is a voltage for turning on the TFT 3, a TFT off voltage that turns off the TFT 3, and a scanning line driving circuit. There are an analog voltage and analog GND for driving 30 analog units, a digital voltage for driving the digital unit of the scanning line driving circuit 30, and a digital GND.

The voltages supplied from the liquid crystal driving power supply circuit 50 to the data line driving circuit 40 include a positive writing voltage used during positive writing, a negative writing voltage used during negative writing, and an analog of the data line driving circuit 40. Voltage and analog GND
And a digital voltage and a digital GND for driving the digital part of the data line driving circuit 40.

Further, as the voltage supplied to the liquid crystal panel 1 by the liquid crystal driving power supply circuit 50, a common electrode voltage Vcom, a pouch period voltage set to a high impedance or an arbitrary voltage used as a voltage of the common electrode 5 in the pouch period, and In the partial display mode, the common electrode 5 for the display line in the area excluding the preset boundary area adjacent to the boundary between the non-display area and the display area
And GND (ground voltage) used as a supply voltage to the data line S, and the like.

The common electrode voltage Vcom takes a binary value and is a voltage whose polarity is inverted in synchronization with switching between the positive write voltage and the negative write voltage from the data line driving circuit 40. The common electrode voltage Vcom is a voltage that is lower than the reference voltage that is the center of amplitude of the positive polarity write voltage and the negative polarity write voltage by the data line driving circuit 40 by a preset offset voltage equivalent to the feedthrough voltage of the TFT 3. The binary value is taken as the center. This offset voltage is set to a voltage value in which the display state is equivalent to the non-display state, that is, about the same level as black display or white display when this offset voltage is applied between the pixel electrode 2 and the common electrode 5. The

The above liquid crystal display device 100 operates as follows in the full-screen display mode.
First, the scanning line driving circuit 30 supplies the TFT on-voltage supplied from the liquid crystal driving power supply circuit 50 as a selection voltage to the scanning line G in a line-sequential manner, so that the TF corresponding to the predetermined scanning line G is supplied.
Select all T3. Then, after supplying the TFT on-voltage, after a predetermined time has elapsed, the scanning line G
The TFT off voltage is supplied to the TFT 3 to cancel the selection of the TFT 3.

In synchronization with the selection of the TFT 3, the data line driving circuit 40 supplies an image signal to each data line S. As a result, an image signal is supplied to all the pixel electrodes 2 selected by the scanning line driving circuit 30, and image data is written into the pixel electrodes 2.
Further, since the liquid crystal driving power supply circuit 50 is in the full-screen display mode, the common electrode voltage Vcom having a polarity corresponding to the polarity of the image signal is supplied to the common electrode 5 corresponding to each scanning line G.

When image data is written to the pixel electrode 2, a driving voltage is applied to the liquid crystal due to a voltage difference between the pixel electrode 2 and the common electrode 5. Therefore, by changing the voltage level of the image signal, the alignment state and order of the liquid crystal can be changed, and gradation display by light modulation of each pixel can be performed.
On the other hand, the liquid crystal display device 100 operates as follows in the partial display mode.

FIG. 3 is a diagram showing a display screen of the liquid crystal panel 1 in the partial display mode.
In the partial display mode, the display screen 70 is divided into a display area 71 for displaying an image and a non-display area 72 provided across the display area 71. In the display area 71, for example, the remaining battery level and time are displayed, and nothing is displayed in the non-display area 72. That is, in the non-display area 72, white is displayed in the case of normally white, and black is displayed in the case of normally black.

In such a partial display mode, the scanning line driving circuit 30 uses the TFT on voltage supplied from the liquid crystal driving power supply 50 as a selection voltage, and this selection is performed for each scanning frame G corresponding to the display area. The voltage is sequentially supplied, and the selection voltage is supplied to the scanning line G corresponding to the non-display area with a lower frequency than in the display area. For example, the selection voltage is supplied once every three frames.

In synchronization with the selection of the TFT 3, the data line driving circuit 40 supplies an image signal to each data line S. When a scanning line G corresponding to the display area is selected, an image signal for the display area is supplied. When the scanning line G corresponding to the non-display area is selected, the GND voltage is supplied as an image signal for the non-display area.
As a result, the image signal for the display area or the image signal for the non-display area is supplied to the pixel electrode 2 selected by the scanning line driving circuit 30, and the image data is written to the pixel electrode 2.
In the full display mode, the liquid crystal driving power supply circuit 50 applies a common electrode voltage Vcom whose polarity is inverted in synchronization with the image signal supplied to the data line S to the common electrode 5 as shown in FIG. Supply.

Further, in the partial display mode, as shown in FIG. 5, when the scanning line G corresponding to the display area is selected, the image signal supplied to the data line S is synchronized as in the full display mode. Thus, the common electrode voltage Vcom whose polarity is inverted is supplied to the common electrode 5. When the scanning line G corresponding to the non-display area is selected, if the scanning line G does not belong to the boundary area adjacent to the boundary with the display area in the non-display area, the GND voltage is applied to the common electrode 5. And the common electrode voltage Vcom having a polarity corresponding to the polarity of the common electrode voltage Vcom to the common electrode 5 corresponding to the scanning line G in the adjacent display region is supplied to the common electrode 5. To do.

4 and 5, the horizontal axis represents time, and the vertical axis represents the output timing of the selection signal to each scanning line. In addition, together with the output timing of the selection signal to the scanning line G1,
The output timing of the image signal and the voltage applied to the common electrode when each scanning line is selected are described. VS is a vertical synchronization signal VSYNC indicating the start of one frame. A broken line represents a potential during the pouch period, and is set to high impedance or an arbitrary potential.

Next, the operation of the present invention will be described based on the flowcharts of FIGS. 6 and 7 showing an example of the processing procedure of the display control unit 21 of the control circuit 20.
When the full-screen display mode is instructed by using the mode signal from the host device, the display control unit 21 executes the process in the full-screen display mode of FIG. 6 and first sets the total number of display lines (step S1). For example, the number of display lines when displaying an image in the entire screen area of the liquid crystal panel 1 stored in a predetermined storage area, that is, the number of scanning lines, is read and set as the total number of display lines. Further, the full display mode is notified to the scanning line driving circuit 30, the data line driving circuit 40, and the liquid crystal driving power supply circuit 50 as a mode signal.

Next, the process proceeds to step S2, and after setting the line counter to the initial value zero, step S2
Then, the control signal for instructing the selection of the scanning line corresponding to the count value of the line counter is output to the scanning line driving circuit 30. In addition, a control signal for instructing supply of an image signal to the pixel electrode 2 connected to the scanning line corresponding to the counter value is output to the data line driving circuit 40. Also,
The liquid crystal driving power supply circuit 50 is instructed to supply the common electrode 5 with the common electrode voltage Vcom whose polarity changes in accordance with the writing polarity of the image signal by the data line driving circuit 40.
As a result, the first scanning line G1 is selected, image data is written to the pixel electrode 2 connected thereto, and the alignment state of the liquid crystal is changed according to the voltage difference between the pixel electrode 2 and the common electrode 5. Change.

Subsequently, the line counter is incremented by “1” (step S4). If the count value does not reach the total number of display lines, it is determined that the writing of one frame is not completed, and the process returns from step S5 to step S3. Instructing the output of the selection signal, the writing of the image signal, and the application of the common electrode voltage Vcom to the scanning line corresponding to the count value, the writing to the pixel electrode 2 connected to the second scanning line is performed. This process is repeated, and when the count value reaches the total number of display lines, it is determined that the writing of one frame has been completed. Then, after returning to step S2 and setting the line counter to the initial value zero, writing in the next frame is performed.

As a result, as shown in FIG. 4, all the scanning lines (G1 to G10 in the case of FIG. 4) are sequentially selected, and the image data corresponding to the selected scanning line is written into the pixel electrode 2. By performing this process for each frame, image data is written to the pixel electrode 2 corresponding to each scanning line for each frame, and the display image is updated.
From this state, when the display mode is switched and the partial display mode is instructed as a mode signal from the host device, the processing in the partial display mode of FIG. 7 is executed. First, the total number of display lines, which is the total number of scan lines when displaying in the entire screen area, stored in a predetermined storage area, and the scan line corresponding to the start position of the display area in the partial display mode are specified. The start line PS and the end line PE for specifying the scanning line corresponding to the end position of the display area, the writing cycle RF indicating how many frames are written to the non-display area, and the display lines included in the boundary area, that is, The display line number BD representing the number of scanning lines is read (step S1).
1).
Next, the frame counter is set as an initial value to the write cycle “RF” (step S12), and the line counter is set to the initial value zero (step S13).

Since the counter value of the frame counter is set to “RF”, step S13
From a to step S14, the scanning line to be selected next is determined from the count value of the line counter, the display area start line PS, the end line PE, and the boundary display line number BD in the partial display mode. It is determined whether the boundary display line is included in a preset boundary region. As the boundary area, an area adjacent to the boundary with the display area in the non-display area is set, and the number of display lines included in the boundary area is set as the boundary display line number BD. In this determination, the count value of the line counter is changed from the start line PS to the boundary display line number B.
It is determined whether the value is between the value obtained by subtracting D and the start line PS, or between the end line PE and the value obtained by adding the boundary display line number BD to the end line PE. If any of these conditions is satisfied, it is determined that the boundary display line.

In the case of FIG. 3, since the first line is a non-display area and not a boundary display line, the process proceeds from step S14 to step S16 to determine whether or not it belongs to the display area. That is, it is determined whether or not the count value of the line counter is a value between the start line PS and the end line PE. In this case, since the first line is not a display area, step S16 is performed.
From step S18, it is determined whether the counter value of the frame counter coincides with the write cycle RF. In this case, the counter value of the frame counter is “RF”. A control signal instructing selection of the scanning line corresponding to the value is output to the scanning line driving circuit 30. Further, as the image signal for the pixel electrode 2 connected to the scanning line corresponding to the counter value and the applied voltage to the common electrode 5, a control signal for instructing application of the GND voltage is used as the data line driving circuit 40 and the liquid crystal driving power supply circuit. Output to 50.

Subsequently, the line counter is updated by “1” (step S21). Since the count value has not reached the total number of display lines, writing of one frame has not been completed.
2 returns to step S13a. Since the second scanning line G2 is a non-display area, is not a boundary display line, and does not belong to the display area, the process proceeds from step S13a to step S19 via steps S14, S16, and S18. A control signal instructing selection of the scanning line corresponding to the counter value is output to the scanning line driving circuit 30. Further, the image signal to the pixel electrode 2 connected to the scanning line corresponding to the counter value and the control signal for instructing the application of the GND voltage as the applied voltage to the common electrode 5 are sent to the data line driving circuit 40 and the liquid crystal driving power supply circuit. Output to 50.

As a result, as shown in FIG. 5, both the common electrode 5 and the data line S corresponding to the first and second scanning lines G1 and G2 become the GND voltage, and this is written to the pixel electrode 2 corresponding to the scanning line G1. Since both the common electrode 5 and the pixel electrode 2 are at the GND voltage, the liquid crystal layer is in an alignment state when no voltage is applied, that is, in a non-display state of white display or black display.
Thus, by controlling the data line S and the common electrode 5 to the GND voltage and stopping the driving of an amplifier (not shown) for applying a predetermined voltage to the data line S and the common electrode 5, power consumption is reduced. We are trying to reduce it.

Subsequently, the line counter is updated by “1” (step S21). Assuming that the third scanning line G3 belongs to the non-display area and is a boundary display line, step S1.
The process proceeds from step 3a to step S15 via step S14. Then, a control signal instructing selection of the third scanning line G3 is output to the scanning line driving circuit 30, and the scanning line G3 is output.
Is directed to the data line driving circuit 40 and the liquid crystal driving power supply circuit 50. That is, in the case of a normally black type liquid crystal display device, the image signal and the common electrode 5 are set to a display state equivalent to the case of performing black display in the case of a normally white type liquid crystal display device and performing white display. Instructs the application of voltage to. Specifically, the common electrode voltage V having a polarity determined according to the polarity of the common electrode voltage Vcom when writing to the pixel electrode 2 corresponding to the scanning line G4 which is the scanning line of the adjacent display region.
com is instructed to the power supply circuit 50 for driving the liquid crystal. In the case of FIG. 5, the scanning line G4
Since the polarity of the common electrode voltage Vcom when writing to the pixel electrode 2 corresponding to is high, the common electrode 5 corresponding to the scanning line G3 has a low level common electrode voltage Vco.
m will be applied.

For the data line driving circuit 40, the voltage difference from the common electrode voltage Vcom corresponds to an offset voltage corresponding to the feedthrough voltage, and the alignment state of the liquid crystal by applying the off voltage ΔV is: An instruction is given to apply a voltage that can be opposite to the orientation of the liquid crystal by feedthrough as an image signal.
As a result, as shown in part A of FIG. 5, a low-level common electrode voltage Vcom is applied to the common electrode 5. Further, the amplitude center of the common electrode voltage Vcom and the data line driving circuit 4
Since the amplitude center of the positive polarity write voltage and the negative polarity write voltage by 0 is shifted by an offset voltage corresponding to the feedthrough voltage, for example, when the GND voltage is applied to the data line S, the scan line G3 is selected in this state. Since the voltage is supplied, the off-voltage ΔV is applied between the pixel electrode 2 and the common electrode 5 corresponding to the scanning line G3, and the liquid crystal layer according to the voltage difference between the pixel electrode 2 and the common electrode 5 The orientation state changes, and black display or white display is performed in a state equivalent to the non-display state.

Subsequently, the line counter is updated (step S21). If the fourth line is a display area, the process proceeds from step S13a to step S14 through step S16.
17, the control signal for instructing the selection of the fourth scanning line G4 is sent to the scanning line driving circuit 30.
And instructing the data line driving circuit 40 to output an image signal for the display area to the scanning line G4, and supplying the common electrode voltage Vcom to the data line S according to the polarity of the image signal for liquid crystal driving. The power supply circuit 50 is instructed.

Since the fifth and sixth lines are also display areas, the same processing is performed.
Image data corresponding to this display area is written to the pixel electrodes 2 in the line and the sixth line.
As a result, as shown in FIG. 5, corresponding image data is written to the pixel electrodes 2 of the fourth line, the fifth line, and the sixth line, and the image signal and the polarity of the image signal are changed. The alignment state of the liquid crystal layer is controlled in accordance with the voltage difference with the common electrode voltage Vcom that changes, and a predetermined image is displayed.

Subsequently, assuming that the seventh scanning line G7 is a boundary display line, step S1.
From step 3a to step S14, the process proceeds to step S15. Similarly to the case of the scanning line G3, the scanning line G7 is selected and, for example, a low-level common electrode voltage Vcom is applied as an applied voltage to the common electrode 5, As an image signal, a voltage, for example, a GND voltage, whose voltage difference from the common electrode voltage Vcom is equivalent to the off-voltage ΔV is applied. As a result, as shown in part B of FIG. Is applied with an off-voltage ΔV. Thus, a black display or a white display similar to the non-display state is performed.

Subsequently, since the 8th, 9th, and 10th scanning lines G8 to G10 belong to a region excluding the boundary region of the non-display region, the steps S13a to S14, S16, and S18 are performed. The process proceeds to S19, where the data line S and the common electrode 5
Since the GND voltage is applied to these and the scanning lines G8 to G10 are selected, the GND voltage is applied to both the pixel electrode 2 and the common electrode 5, and the liquid crystal layer is not white or black. Controlled to display state.

Subsequently, when the line counter is updated (step S21), since the counter value reaches the total number of display lines, it is determined that the writing of the first frame is completed. As a result, writing is performed on the pixel electrodes corresponding to all scanning lines, that is, image data is written in the display area, and a voltage difference from the common electrode 5 is present in the boundary area for the non-display area. A voltage that can be the off-voltage ΔV is written, and the GND voltage is written in a region other than the boundary region.
Subsequently, the process proceeds from step S22 to step S23. In this case, since the frame counter is set to the initial value “RF”, the process proceeds to step S25, the frame counter is reset to zero, and then the process returns to step S13.

Then, the writing of the second frame is performed. First, the frame counter is “0” for the scanning lines G1 and G2 of the first line and the second line excluding the boundary area of the non-display area. From step S13a to step S16 and step S18, the process proceeds to step S20. The scanning lines G1 and G2 are not selected, and the data line S and the common electrode 5 are controlled to the GND voltage to be in a non-display state. . The third scanning line G3 is a boundary display line included in the boundary region. However, since the frame counter is “0”, the process proceeds from step S13a to step S16 through step S16 and step S18, and the boundary region is displayed. Similarly to the scanning lines G1 and G2 in the non-display area that does not belong, the scanning line G3 is not selected, and the data line S and the common electrode 5 are controlled to the GND voltage to be in a non-display state.

For the scanning lines G4 to G6 included in the display area from the fourth line to the sixth line, the process proceeds from step S13a to step S16 to step S17, and image data corresponding to each line is written to the pixel electrode 2. A predetermined image display is performed.
Subsequently, the seventh line is a boundary display line, but since the frame counter is “0”, the process proceeds from step S13a to step S20 through steps S16 and S18, and the scanning line G7 is not selected and the data is displayed. The line S and the common electrode 5 are controlled to the GND voltage to be in a non-display state.

Since the 8th to 10th scanning lines G8 to G10 are non-display areas, the process proceeds from step S13a to step S14 through step S14, step S16, and step S18 to the scanning lines G8 to G10. The selection is not performed, and the data line S and the common electrode 5 are controlled to the GND voltage to be in a non-display state.
This completes the writing of the second frame. As a result, data is written only in the display area, and the non-display area is not written regardless of whether or not it is a boundary area.
Subsequently, the frame counter is updated to “1”, the process returns to step S13, and writing of the third frame is performed in the same procedure. When writing of the third frame is completed, the frame counter is updated to “2”. Subsequently, the fourth frame is written.

At this time, the writing cycle RF is set to “2”, and when the counter value “2” of the frame counter matches the writing cycle RF, the scanning line G in the non-display region excluding the boundary region.
For 1 and G2, the process proceeds from step S13a to step S19 through step S14, step S16, and step S18, and the scanning lines G1 and G2 are selected while both the data line S and the common electrode 5 are set to the GND voltage. A GND voltage is written to the pixel electrode 2. For the scanning line G3 that is the boundary display line, the process proceeds from step S13a to step S14 to step S15, and the off voltage ΔV is applied between the pixel electrode 2 and the common electrode 5. The common electrode voltage Vcom on the side is applied, and a voltage value at which the voltage difference from the common electrode voltage Vcom on the high level side can be equivalent to the offset voltage is applied to the data line S.

For the display areas of the scanning lines G4 to G6, the steps S13a to S1 are performed.
4. After passing through step S16, the process proceeds to step S17, where image data corresponding to the scanning lines G4 to G6 is written into the corresponding pixel electrode to perform a predetermined image display. As for the boundary display line G7, as in the case of the scanning line G3, the voltage for applying the OFF voltage ΔV between the pixel electrode 2 and the common electrode 5 is applied to the data line S and the common electrode 5 in the process in step S15. For the scanning lines G8 to G10 in the non-display area that is not the boundary area, the data lines and the common electrode are maintained at the GND voltage without selection of the scanning lines G8 to G10.

As a result, as shown in FIG. 5, in the display areas of the scanning lines G4 to G6, image data is written for each frame and a predetermined image display is performed.
For the scanning lines G1, G2, and G8 to G10 excluding the boundary region, the writing cycle (three frames in the case of FIG. 5) designated by the writing cycle RF with respect to the pixel electrode 2 and the common electrode 5 corresponding thereto. Every time, the GND voltage is applied to both the pixel electrode 2 and the common electrode 5 to maintain the non-display state, and the scanning lines G3 and G7 in the boundary region are applied to the pixel electrode 2 and the common electrode 5 corresponding thereto. Thus, an off voltage ΔV is applied between the pixel electrode 2 and the common electrode 5 at every predetermined writing cycle, and the display state is maintained equivalent to the non-display state.

Here, as described above, both the data line S and the common electrode 5 are connected to the GND in the non-display area.
When the voltage is held and writing to the pixel electrode 2 is performed at each writing cycle, there is a possibility that the liquid crystal layer may be burned by the influence of the feedthrough voltage or the like. However, the boundary display line of the boundary area adjacent to the boundary of the non-display area and the display area, that is, FIG.
In this case, for the scanning lines G3 and G7, an off voltage ΔV is applied between the pixel electrode 2 and the common electrode 5 for each writing cycle.

Therefore, by applying this off voltage ΔV, it is avoided that a DC voltage equivalent to the feedthrough voltage is continuously applied to the liquid crystal layer, and the alignment state of the liquid crystal layer is shifted in the reverse direction. Burn-in is alleviated.
Here, in the non-display area, when burn-in occurs due to the continued application of the GND voltage to both the pixel electrode 2 and the common electrode 5, the charge is accumulated, so that the luminance profile at the dotted line position in FIG. As shown in FIG. 8A, the brightness difference becomes significant between the non-display area and the display area, and even if the same gradation is displayed, the brightness may appear different.

However, since the off voltage ΔV is applied between the pixel electrode 2 and the common electrode 5 corresponding to the scanning line in the boundary region at every writing cycle, the occurrence of burn-in in the boundary region is reduced. Therefore, as shown in FIG. 8B, the luminance changes stepwise between the non-display region and the display region, and visually, the luminance appears to change gently. For this reason, even when the same gradation is displayed, it is possible to avoid a significant difference in luminance at the boundary between the non-display area and the display area.

Further, since the common electrode voltage Vcom on the high level side or the low level side is applied as the voltage applied to the common electrode 5 when the off voltage ΔV is applied, the scanning line in the boundary region is driven at the timing. It is only necessary to apply the common electrode voltage Vcom that is normally used,
Since it can be dealt with by adjusting the output timing of the common electrode voltage Vcom, it can be realized without significant change.

In the above embodiment, the case where one line each of the scanning line G3 and the scanning line G7 is provided as the scanning line of the boundary display line is described. However, the present invention is not limited to this, and non-display adjacent to the display area is performed. A plurality of boundary display lines may be provided for each region. In this case, if the number of scanning lines of the boundary display line is large, the luminance changes in a stepwise manner between the non-display area and the display area, and in some cases, there may be a visual difference in luminance. For this reason, the number of lines with which the luminance changes smoothly may be set as the number of boundary display lines.

In the non-display area, the power consumption can be reduced by applying the GND voltage to the data line S and the common electrode 5 during the scanning period to stop driving the γ amplifier or the like, and reducing the number of scanning line selections. As shown, if the number of scanning lines included in the boundary area, that is, the number of boundary display lines is large,
Since the power consumption increases accordingly, it is desirable to set the number of boundary display lines in consideration of these.

In addition, a plurality of scanning lines for the boundary display line are set, and for example, as shown in FIG. 9, the frequency of applying the OFF voltage ΔV is varied for each one or several scanning lines to change the degree of burn-in. By increasing the frequency of applying the off voltage ΔV to the scanning line closer to the display area and making it difficult for image sticking to occur, the degree of image sticking is changed smoothly, resulting in a brightness between the display area and the non-display area. , It may be changed smoothly.

In the above embodiment, as shown in FIG. 3, the case where the non-display area 72 is formed above and below the display area 71 is described. However, the present invention is not limited to this. The present invention can be applied even when a display area and a non-display area are formed.
Moreover, in the said embodiment, although demonstrated about the liquid crystal display device as an example, you may apply this invention to the organic electroluminescent apparatus which used electro-optical substances other than a liquid crystal, for example.

Next, an electronic apparatus to which the above-described liquid crystal display device 100 is applied will be described.
FIG. 10 is a perspective view showing a configuration of a mobile phone 120 to which the liquid crystal display device 100 is applied.
As shown in FIG. 10, the mobile phone 120 includes the liquid crystal display device 100 described above together with the earpiece 122 and the mouthpiece 123 in addition to the plurality of operation buttons 121. In addition,
In the liquid crystal display device 100, components other than the liquid crystal panel 1 are built in the telephone, so that they do not appear as appearance.

Further, as an electronic device to which the liquid crystal display device 100 is applied, in addition to the mobile phone shown in FIG. 10, a digital still camera, a notebook personal computer, a liquid crystal television, a viewfinder type (or monitor direct view type) video recorder. , A car navigation device, a pager, an electronic notebook, a calculator, a word processor, a workstation, a video phone, a POS terminal, a device equipped with a touch panel, and the like. And it cannot be overemphasized that the liquid crystal display device 100 mentioned above is applicable as a display apparatus of these various electronic devices.

It is a schematic block diagram which shows an example of the liquid crystal display device to which this invention is applied. It is a block diagram of the power supply circuit for a liquid crystal drive. It is a figure which shows an example of the display screen in partial display mode. 6 is a timing chart in a full display mode. It is a timing chart in the partial display mode. It is a flowchart which shows an example of the process sequence in the full display mode of a display control part. It is a flowchart which shows an example of the process sequence in the partial display mode of a display control part. It is an example of the brightness | luminance profile at the time of performing the same gradation display in a full surface display mode. It is a timing chart in the partial display mode which shows the other example of this invention. It is a perspective view which shows the structure of the mobile telephone to which the liquid crystal display device of this invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid crystal panel, 2 Pixel electrode, 3 TFT, 5 Common electrode, 20 Control circuit, 30 Scan line drive circuit, 40 Data line drive circuit, 50 Power supply circuit for liquid crystal drive

Claims (5)

A pixel electrode provided corresponding to the intersection of the plurality of scanning lines and the plurality of data lines and connected to the corresponding data line via a switch element; and a common electrode facing the pixel electrode. When the switch element is turned on by the selection voltage supplied to the scanning line,
In a display device in which a data signal supplied to the data line is written into the pixel electrode and gradation display is performed,
A drive circuit having a partial display function for setting a part of the image display area as a display area, the remaining area as a non-display area, and setting only the display area as a display state,
When using the partial display function, the drive circuit,
The selection voltage is supplied at a rate of once per a plurality of frames with respect to the scanning line of the boundary area adjacent to the display area of the non-display area, and between the corresponding pixel electrode and the common electrode, Apply an off voltage to hide the image display area,
1 in a plurality of frames with respect to the scanning lines in the non-display area excluding the boundary area.
The display device is characterized in that the selection voltage is supplied at a rate of times and a ground voltage is applied to the corresponding pixel electrode and the common electrode. A plurality of scanning lines belong to the boundary region,
The drive circuit increases the frequency with which the off-voltage is applied to the pixel electrode and the common electrode corresponding to a scanning line close to the boundary among a plurality of scanning lines in the boundary region. Item 4. The display device according to Item 1. The display device according to claim 1, wherein the off voltage is set to a value corresponding to a feedthrough voltage of the switch element. A pixel electrode provided corresponding to the intersection of the plurality of scanning lines and the plurality of data lines and connected to the corresponding data line via a switch element; and a common electrode facing the pixel electrode. When the switch element is turned on by the selection voltage supplied to the scanning line,
In a driving method of a display device in which a data signal supplied to the data line is written into the pixel electrode and gradation display is performed,
A partial display function in which a part of the image display area is a display area, the remaining area is a non-display area, and only the display area is in a display state;
When the partial display function is used, the selection voltage is supplied at a rate of once per a plurality of frames to the scanning line of the boundary area adjacent to the display area in the non-display area, and the corresponding display function Applying an off voltage between the pixel electrode and the common electrode to turn off the image display region;
1 in a plurality of frames with respect to the scanning lines in the non-display area excluding the boundary area.
A method for driving a display device, wherein the selection voltage is supplied at a rate of times and a ground voltage is applied to the corresponding pixel electrode and the common electrode. An electronic apparatus comprising the display device according to any one of claims 1 to 3.

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