JP2004094168A - Electro-optical device, method for driving electro-optical device and electronic appliance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electro-optical device capable of maintaining display quality while attaining low voltage and low power consumption, a method for driving the electro-optical device and an electronic appliance. <P>SOLUTION: A common electrode voltage is set to be V<SB>coml</SB>by using a counter electrode modulation circuit. The same voltage with a voltage for writing black pixels is used as V<SB>coml</SB>. The V<SB>coml</SB>is applied to retention capacitance via a common electrode and a counter line. Subsequently, a writing operation is performed. In such a case, only white pixels are written. With respect to black pixels, on the other hand, the voltages of a pixel electrode is coincident with that of the common electrode and, therefore, the writing is not performed. After the writing of white pixels are completed, the voltage of a counter electrode is changed. Therein, the common electrode voltage is set to be V<SB>comh</SB>. Then, the writing is performed. In such a case, only black pixels are written. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electro-optical device including a plurality of divided cells enclosing a dispersion system containing electrophoretic particles.
[0002]
[Prior art]
An electrophoretic display device utilizing an electrophoretic phenomenon is known as a non-light emitting display device. Here, the electrophoretic phenomenon is a phenomenon in which particles move by Coulomb force when an electric field is applied to a dispersion system in which fine particles (electrophoretic particles) are dispersed in a liquid (dispersion medium).
[0003]
In such an electrophoretic display device, one electrode and the other electrode are opposed to each other at a predetermined interval, and a divided cell in which a dispersion system is sealed is arranged between the electrodes. The electrophoretic display device includes a peripheral circuit for applying an electric field to the dispersion system. First, a description will be given with reference to a partial cross-sectional view of the electrophoretic display panel shown in FIG.
[0004]
As shown in FIG. 10, the electrophoretic display panel includes an element substrate 100 such as a semiconductor on which pixel electrodes 104 and the like are formed, and a counter substrate 200 on which a planar common electrode 201 and the like are formed. The element substrate 100 and the opposing substrate 200 are bonded to each other so that the respective electrode forming surfaces face each other with a constant gap. In this gap, a divided cell 15 which is divided into a predetermined size for a pixel which is a display unit of an image and includes the dispersion system 10 is provided. In the present embodiment, the divided cells 15 are realized by microcapsules.
[0005]
This dispersion system 10 is obtained by dispersing electrophoretic particles 12 in a dispersion medium 11. The dispersion medium 11 may be colored with a dye, but a plurality of types of electrophoretic particles 12 corresponding to a pigment may be used. For example, as the electrophoretic particles 12, black electrophoretic particles 12b having negative charges and white electrophoretic particles 12w having positive charges are used. An additive such as a surfactant is added to the dispersion medium 11 as needed. In the dispersion system 10, the specific gravity of the dispersion medium 11 and the specific gravity of the electrophoretic particles 12 are set to be substantially equal to avoid sedimentation of the electrophoretic particles 12 due to gravity.
[0006]
As described above, in the dispersion system 10, the region where the electrophoretic particles 12 can migrate is limited to the inside of the divided cell 15. Thereby, it is possible to prevent a phenomenon that the dispersion of the electrophoretic particles 12 in the dispersion system 10 is biased, and to prevent aggregation in which a plurality of particles are combined to form a large lump.
[0007]
On the surface of the element substrate 100, a display area and a peripheral area where peripheral circuits are provided are provided. In the display area, in addition to the above-described pixel electrode 104, a scanning line, a data line, and a thin film transistor (hereinafter, referred to as a TFT) functioning as a switching element described later are formed. On the other hand, in a peripheral region of the element substrate 100, a scanning line driving circuit, a data line driving circuit, and the like, which will be described later, are formed.
[0008]
Next, an operation when a voltage is applied to the pixel electrode 104 will be described. When a potential difference is applied between the pixel electrode 104 and the common electrode 201, the charged electrophoretic particles 12 are attracted to one of the electrodes depending on the direction of the electric field. Here, when the electrophoretic particles 12 are formed of colored particles, and a transparent material is used for the common electrode 201 and the opposing substrate 200, the color of the electrophoretic particles 12 attracted to the opposing substrate 200 side can be seen. Become. Therefore, an image can be displayed by controlling the voltage applied to each electrode.
[0009]
Next, the principle of gradation display will be described. First, a reset operation of the electrophoretic display device is performed. In this reset operation, the electrophoretic particles 12 are moved to one of the electrodes. When a negative voltage is applied to the pixel electrode 104 based on the voltage of the common electrode 201, the positively charged white electrophoretic particles 12 w are attracted to the pixel electrode 104 and the negatively charged black electrophoretic particles 12 b are attracted to the common electrode 201.
[0010]
Next, a voltage having a polarity corresponding to the gradation to be displayed is applied to the pixel electrode 104. Then, the electrophoretic particles 12 move between both electrodes due to the electric field. When the potential difference between the two electrodes is reduced to zero after a lapse of a predetermined time, the electric field stops working, and the electrophoretic particles 12 stop due to the viscous resistance of the dispersion medium 11. In this case, the moving speed of the electrophoretic particles 12 is determined according to the electric field strength, that is, the applied voltage. Then, the moving distance of the electrophoretic particles 12 is determined according to the applied voltage and the applied time. Therefore, if the application time is fixed, the position of the electrophoretic particles 12 in the thickness direction can be controlled by adjusting the applied voltage.
[0011]
Light incident from the common electrode 201 side is reflected by the electrophoretic particles 12, and the reflected light passes through the common electrode 201 and is observed. The incident light and the reflected light are absorbed by the dispersion medium 11, and the degree of the absorption is proportional to the optical path length. Therefore, when observed from the common electrode 201, the gradation can be determined by the position of the electrophoretic particles 12. As described above, since the position of the electrophoretic particles 12 is determined according to the applied voltage when the application time is fixed, a desired gradation display can be performed by adjusting the applied voltage.
[0012]
[Problems to be solved by the invention]
By the way, in order to change the display state, it is necessary to cause the electrophoretic particles 12 to migrate to one electrode against the viscous resistance of the dispersion medium 11. This requires a relatively high drive voltage. If the driving voltage is too low, the electrophoretic particles 12 will remain on the electrode surface, causing a reduction in display quality. However, if the driving voltage is generally increased, it is not possible to reduce the voltage and the power consumption.
[0013]
SUMMARY An advantage of some aspects of the invention is to provide an electro-optical device capable of maintaining display quality while increasing voltage and reducing power consumption, a driving method thereof, and an electronic apparatus. It is in.
[0014]
[Means for Solving the Problems]
The electro-optical device according to the aspect of the invention includes a common electrode, a pixel electrode facing the common electrode, and a switching element connected to the pixel electrode, and includes electrophoretic particles between the common electrode and the pixel electrode. A driving unit for moving the electrophoretic particles using an electric field generated by the electric charge accumulated in the common electrode or the pixel electrode, and a control unit for controlling the driving unit. An optical device, wherein the control means applies a first opposing voltage to the common electrode to perform a reset processing of a first polarity, and thereafter applies a second opposing voltage to write the data of a second polarity. To perform the import process.
[0015]
According to this, when performing the reset and the write processing, it is possible to use the opposite voltages having different polarities suitable for the reset and the write processing. Therefore, by using the first and second counter voltages, the voltages required for the reset and write processes can be effectively used. Therefore, lower voltage and lower power consumption can be achieved.
[0016]
In the electro-optical device, the driving unit applies a first signal voltage and a second signal to the switching element to move the electrophoretic particles, and the first signal voltage is The second signal voltage matches the second counter voltage, and the second signal voltage matches the first counter voltage.
[0017]
According to this, it is possible to further effectively use the voltage required for the reset and write processing, and it is possible to achieve lower voltage and lower power consumption.
In this electro-optical device, the switching element is connected to one end of a storage capacitor, and the other end of the storage capacitor is connected to the common electrode.
[0018]
According to this, the voltage required for the reset to the storage capacitor and the writing process can also be effectively used.
In this electro-optical device, the control unit applies a predetermined voltage to all of the pixel electrodes to execute a reset operation before executing the writing processing of the second polarity.
[0019]
According to this, the initial state of the electrophoretic particles can be achieved by the reset operation, so that a gray scale display using halftone can be realized.
A driving method of an electro-optical device according to the present invention includes a common electrode, a pixel electrode facing the common electrode, and a switching element connected to the pixel electrode, wherein an electric voltage is applied between the common electrode and the pixel electrode. A driving unit that includes a dispersion system containing migrating particles, and that moves the electrophoretic particles using an electric field generated by electric charges accumulated in the common electrode or the pixel electrode; and a control unit that controls the driving unit. Wherein the control means applies a first opposing voltage to the common electrode to perform a reset process of a first polarity, and then applies a second opposing voltage. To perform the write processing of the second polarity.
[0020]
According to this, when performing the reset and the write processing, it is possible to use the opposite voltages having different polarities suitable for the reset and the write processing. Therefore, by using the first and second counter voltages, the voltages required for the reset and write processes can be effectively used. Therefore, lower voltage and lower power consumption can be achieved.
[0021]
In this method of driving an electro-optical device, the driving unit applies a first signal voltage and a second signal to the switching element to move the electrophoretic particles, and The voltage matches the second opposing voltage, and the second signal voltage matches the first opposing voltage.
[0022]
According to this, it is possible to further effectively use the voltage required for the reset and write processing, and it is possible to achieve lower voltage and lower power consumption.
In this method of driving an electro-optical device, the switching element is connected to one end of a storage capacitor, and the other end of the storage capacitor is connected to the common electrode.
[0023]
According to this, the voltage required for the reset to the storage capacitor and the writing process can also be effectively used.
In the driving method of the electro-optical device, the control unit performs a reset operation by applying a predetermined voltage to all the pixel electrodes before executing the writing processing of the second polarity.
[0024]
According to this, the initial state of the electrophoretic particles can be achieved by the reset operation, so that a gray scale display using halftone can be realized.
An electronic apparatus according to the present invention has the electro-optical device according to any one of claims 1 to 4 mounted thereon.
[0025]
According to this, the electronic device can achieve both low power consumption and sufficient display quality.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
(1st Embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. An electrophoretic display device as an electro-optical device according to the present embodiment includes an electrophoretic display panel and peripheral circuits.
[0027]
FIG. 1 is a block diagram showing an electrical configuration of the electrophoretic display device. On the surface of the element substrate 100, an electrophoretic display panel A and a peripheral area thereof are provided. In this figure, a drive circuit in a peripheral region is integrated assuming a device having a high mobility (such as low-temperature polysilicon). However, the present invention can be applied to a device having a low mobility (such as amorphous silicon). In that case, the driving circuit is formed of an element having high mobility (such as single crystal silicon), and the electrophoretic display panel A and the data line driving circuit 140 and the scanning line driving circuit 130 are separate components. The electrophoretic display panel A of this example includes a plurality of pixels, and the pixels include a TFT 103 as a switching element described later and a pixel electrode 104 connected to the TFT 103. On the other hand, a scanning line driving circuit 130 and a data line driving circuit 140 are formed in a peripheral region of the element substrate 100.
[0028]
A controller 300 is provided in a peripheral circuit of the electrophoretic display device. The controller 300 includes an image signal processing circuit and a timing generator. Here, the image signal processing circuit generates reset data Drest and image data D and inputs the data to the data line driving circuit 140. The reset data Drest is output during a predetermined period before outputting the image data D. The reset data Drest is used to attract the electrophoretic particles 12 migrating in the dispersion system 10 to the pixel electrode 104 or the common electrode 201, and to initialize a spatial state.
[0029]
The timing generator generates various timing signals for controlling the scanning line driving circuit 130 and the data line driving circuit 140 when the reset data Drest and the image data D are output from the image signal processing circuit.
[0030]
On the electrophoretic display panel A of the element substrate 100, a plurality of scanning lines 101 are formed in parallel along the X direction. Also, a plurality of data lines 102 are formed in parallel along the Y direction orthogonal to this. Each pixel is arranged in a matrix corresponding to the intersection of the scanning line 101 and the data line 102.
[0031]
The structure of this pixel will be described with reference to FIG. This pixel includes a TFT 103, a pixel electrode 104, and a storage capacitor 110. The gate terminal of the TFT 103 is connected to the scanning line 101, while the source terminal of the TFT 103 is connected to the data line 102. Further, the drain terminal of the TFT 103 is connected to the pixel electrode 104 and the storage capacitor 110.
[0032]
By the way, since the pixel is configured such that the dispersion system 10 is sandwiched between the pixel electrode 104 and the common electrode 201, the pixel capacitance 111 according to the electrode area, the distance between the electrodes, and the dielectric constant of the dispersion system 10 is set. Is formed. The other side of the storage capacitor 110 is connected to the opposite line 106. Then, the common electrode 201 and the opposing line 106 are connected to the opposing electrode modulation circuit 150 shown in FIG. For simplification of wiring, a method in which the opposing line 106 is connected to a gate line in the preceding stage may be used. However, since the voltage is disturbed at the time of switching the opposite voltage described later, the present invention can be applied to the case where the response of the electrophoretic particles is slower than one field period. In other words, it can be used when writing is performed by accumulation of a plurality of fields, the electrophoretic particles respond, and disturbance at the time of switching one field is absorbed as an error.
[0033]
In such an electrophoretic display panel A, when a certain scanning line signal Yi becomes active, the TFT 103 of the i-th scanning line 101 is turned on. Therefore, the data line signals X1, X2,..., Xn are supplied to the pixel electrodes 104 connected to the TFTs 103 of the i-th scanning line 101. On the other hand, the common electrode 201 of the counter substrate 200 is applied with a common electrode voltage Vcom as a counter voltage from the counter electrode modulation circuit 150. As a result, a potential difference is generated between the pixel electrode 104 and the common electrode 201, and the electrophoretic particles 12 in the dispersion system 10 migrate to display a gradation or a binary level corresponding to the image data D for each pixel. .
[0034]
(Drive circuit)
Next, a driving circuit for driving the scanning lines 101 and the data lines 102 will be described.
[0035]
First, the scanning line driving circuit 130 has a shift register, and generates scanning line signals Y1 to Ym based on a clock signal from a timing generator. As a result, the scanning line signals Y1 to Ym in which the active period (H level period) is sequentially shifted are generated and output to the respective scanning lines 101.
[0036]
Next, the driving operation will be described with reference to FIGS. FIG. 3 is a block diagram of the data line driving circuit 140. As shown in the figure, the data line driving circuit 140 includes an X shift register 141, a bus BUS to which 6-bit image data D is supplied, switches SW1 to SWn, a first latch 142, a second latch 143, a selection circuit 144, A D / A converter 145 is provided. FIG. 4 is a timing chart of the scanning line driving circuit 130 and the data line driving circuit 140.
[0037]
First, the X shift register 141 sequentially shifts the X transfer start pulse DX according to the X clock XCK and the inverted X clock XCKB to sequentially generate the sampling pulses SR1, SR2,..., SRn shown in FIG. ing.
[0038]
Next, the bus BUS is connected to each latch of the first latch 142 via the switches SW1 to SWn, and the control input terminals of the switches SW1 to SWn are supplied with sampling pulses SR1, SR2,. It is supposed to be. One switch SWj has a set of six switches SWj corresponding to 6-bit image data D. Therefore, the image data D is simultaneously taken into the first latch 142 in synchronization with the sampling pulses SR1, SR2,..., SRn.
[0039]
Next, the first latch 142 latches the image data D supplied from the switches SW1 to SWn and outputs them as dot-sequential image data Da1 to Dan. The second latch 143 latches the dot sequential image data Da1 to Dan of the first latch 142 by a latch pulse. Here, the latch pulse is a signal that becomes active every horizontal scanning period. Therefore, the second latch 143 generates line-sequential image data Db1 to Dbn from dot-sequential image data Da1 to Dan.
[0040]
Next, the selection circuit 144 is supplied with the common voltage data Dcom generated by the image signal processing circuit and the unbiased timing signal Cb generated by the timing generator. Here, the common voltage data Dcom is data indicating a voltage value supplied to the common electrode 201. Further, the no-bias timing signal Cb is a signal that becomes active (H level) during a period from one half of one horizontal scanning period to the end thereof as shown in FIG. The selection circuit 144 selects the common voltage data Dcom while the non-bias timing signal Cb is active, and selects the line-sequential image data Db1 to Dbn during the inactive period while the non-bias timing signal Cb is inactive. Output. This figure shows a high-speed electrophoretic display element which is completed in one selection period. In the case of a low-speed electrophoretic display element which is completed in n fields, the state during the selection period is to output only D from 1 to n-1 fields, and select Dcom for the last n fields. Will be. The signal of Cb is "L" from 1 to n-1 fields and "H" in n fields.
[0041]
The D / A converter 145 converts the 6-bit data Dc1 to Dcn from a digital signal to an analog signal to generate data line signals X1 to Xn, respectively, and supplies these to the data lines 102.
[0042]
(Operation of electrophoretic display device)
Next, the operation of the electrophoretic display device will be described with reference to FIG. FIG. 5 is a timing chart showing output data of the image signal processing circuit.
[0043]
First, at time t0, when the power of the electrophoretic display device is switched from the off state to the on state, drive power is supplied to the image signal processing circuit, the timing generator, and the electrophoretic display panel A. Hereinafter, the reset operation (t1 to t2), the write operation (t2 to t3), and the holding operation (t3 to t4) will be described in this order. Further, a period from time t4 to time t5 to time t6 is a period for rewriting the image, and the reset operation and the writing operation are performed similarly to the period from time t1 to time t3.
[0044]
(1) Reset Operation and Write Operation At a time t1 when a predetermined period has elapsed since the power supply was turned on and the circuit operation was stabilized, the image signal processing circuit stores the reset data Drest in one field (electrophoretic element having a slow response speed). Is output over a period of n fields). In the reset period Tr, the electrophoretic particles 12 are drawn toward the pixel electrode 104, and the spatial state is initialized. The data line drive circuit 140 outputs a predetermined voltage (reset voltage Vrest) corresponding to the data value of the reset data Drest to each data line 102. At the same time, when the scanning line driving circuit 130 sequentially selects each scanning line 101, a voltage is supplied to the pixel electrodes 104, and the reset voltage Vrest is applied between all the pixel electrodes 104 and the common electrode 201. . When performing a gray scale display for displaying a halftone, a reset operation is indispensable for all pixels. In the present invention, in the case of binary display in which the display density is saturated, the reset operation can be omitted for a pixel of the same color as the color to be written (black pixel if black).
[0045]
Next, when time t2 is reached, writing starts. In the writing period Tw, the image signal processing circuit outputs the image data D over one field period (n fields in the case of an electrophoretic element having a slow response speed). The gradation voltage V corresponding to the gradation to be displayed is written to each pixel electrode 104, and one display image is completed.
[0046]
Hereinafter, the operation will be described in more detail with reference to FIGS. FIG. 6 is an operation flow of the reset process and the write process. FIG. 7 is a timing chart of the electrophoretic display device in each operation. Here, the reset processing of the reset period Tr corresponds to the steps (S1-1) and (S1-2). The writing process in the writing period Tw corresponds to the steps (S1-3) and (S1-4). In the present embodiment, an example of an electrophoretic element which performs binary display and has a low response speed will be described. One frame is composed of a first-half n-field (Tr) and a second-half n-field (Tw), and each scans n times. That is, it is assumed that one image is completed by performing 2n data scans on the scan lines 101 of 1 to m.
[0047]
Here, the writing operation in the pixel at the i-th row and j-th column (hereinafter, referred to as (i, j)) and the (i + 1) -th row, j-th column (hereinafter, referred to as (i + 1, j)) will be described. The same writing is performed in. In the following description, the voltage applied to the pixel (i, j) is denoted by V1, and the voltage applied to the pixel (i + 1, j) is denoted by V2. Further, as a configuration visible from the common electrode 201 side, a black pixel means a pixel in which the black migrating particles 12b are present on the common electrode 201 side with respect to the white migrating particles 12w. On the other hand, a white pixel means a pixel in which the white electrophoretic particles 12w are closer to the common electrode 201 than the black electrophoretic particles 12b.
[0048]
Prepare for reset operation. First, the potential of the common electrode 201 is set (S1-1). Specifically, the controller 300 instructs the counter electrode modulation circuit 150 to set the counter electrode potential. Here, the common electrode voltage Vcom is set to the first counter voltage (Vcoml). The same voltage as the voltage for writing the black pixel (second signal voltage) is used for Vcoml. Of course, they do not have to be completely the same, but in general, the configuration is simple and preferable. In this case, the common electrode modulation circuit 150 provides Vcoml to the storage capacitor 110 via the common electrode 201 and the common line 106.
[0049]
Next, a reset operation is performed (S1-2). It is assumed that the i-th scanning line 101 becomes active and the first signal voltage (Vcomh) is output to the j-th data line as the data line signal Xj. In this case, charges are accumulated in the storage capacitor 110 and the pixel capacitor 111, and the movement of the electrophoretic particles 12 starts at the pixel (i, j).
[0050]
Next, it is assumed that the (i + 1) -th scanning line 101 becomes active and the second signal voltage (Vcoml) is output to the j-th data line as the data line signal Xj. In this case, since the second signal voltage applied to the (i + 1, j) pixel electrode 104 and the first counter voltage (Vcoml) applied to the common electrode 201 match, no charge is accumulated. No movement of the electrophoretic particles 12 occurs. In this case, when performing the binary display, since the spatial initialization of the electrophoretic particles 12 is not performed, the pixel does not indicate a specific display state but becomes unstable. Of course, it is also possible to initialize this pixel.
[0051]
Next, the behavior of the electrophoretic particles 12 in the pixel (i, j) will be described in detail. Since the above-described reset operation has been performed, the electrophoretic particles 12 of the pixels in the matrix (i, j) are in the initial state. Here, it is assumed that the display is white. At this time, when a negative voltage is applied to the pixel electrode 104 with respect to the common electrode 201, an electric field is generated, and the electrophoretic particles 12 start moving. The black migrating particles 12b having a negative charge move from the common electrode 201 to the pixel electrode 104, and the white migrating particles 12w having a positive charge move from the pixel electrode 104 to the common electrode 201, and the pixel becomes white. Here, the display density at the pixels of the matrix (i, j) is determined by the average moving amount of the electrophoretic particles in the pixels. Hereinafter, n scans required for displaying white pixels are performed. FIG. 7 shows only the scanning of the first field, but the scanning is similarly performed in the second and subsequent fields.
[0052]
Next, preparation for the write operation will be described. First, the potential of the counter electrode is changed (S1-3). Specifically, the controller 300 instructs the counter electrode modulation circuit 150 to change the counter electrode potential. Here, the common electrode voltage Vcom is set to the second counter voltage (Vcomh). As Vcomh, the same voltage as the voltage (first signal voltage) for writing a white pixel is used. In this case, the common electrode modulation circuit 150 provides Vcomh to the storage capacitor 110 via the common electrode 201 and the common line 106.
[0053]
Next, a write operation is performed (S1-4). When the i-th scanning line 101 becomes active, the first signal voltage (Vcomh) is output to the j-th data line as the data line signal Xj. In this case, since the first signal voltage applied to the (i, j) pixel electrode 104 matches the second counter voltage (Vcomh) applied to the common electrode 201, no charge is accumulated. No movement of the electrophoretic particles 12 occurs. Therefore, the white display is maintained.
[0054]
On the other hand, when the (i + 1) -th scanning line 101 becomes active, the second signal voltage (Vcoml) is output to the j-th data line as the data line signal Xj. In this case, charges are accumulated in the storage capacitor 110 and the pixel capacitor 111, and the movement of the electrophoretic particles 12 starts at the pixel (i + 1, j).
[0055]
Hereinafter, n scans required for displaying black pixels are performed. Also in this case, the electrophoretic particles 12 migrate as in the case of the reset processing of the white pixel, and a display density is generated. As described above, when the second counter voltage (Vcomh) is set as the common electrode voltage Vcom, the movement of the electrophoretic particles 12 of only the black pixels is performed. The binary display can be displayed in this manner.
[0056]
If gradation display is performed instead of binary, the following procedure must be added. Each pixel has a storage capacitor 110 and a pixel capacitor 111. Therefore, even if the TFT 103 is turned off and the supply of charges to the pixel electrode 104 is stopped, the charge is accumulated in the pixel capacitance, and a constant electric field is continuously generated between the two electrodes. Become. As long as the electric field is applied, the black migrating particles 12b and the white migrating particles 12w continue to migrate. In order to obtain an intermediate concentration, it is necessary to stop the generation of the electric field. That is, a step of removing the electric charge accumulated in the pixel capacitance is required. In this step, the common electrode voltage Vcom is applied to the pixel electrode 104.
[0057]
The pixel electrode 104 and the common electrode 201 have the same potential. Here, assuming that the viscosity resistance of the dispersion medium 11 is large to some extent, the electrophoretic particles 12 stop the electrophoresis at the time when the external force stops acting. As a result, the display density takes an arbitrary intermediate density. As described above, such a mechanism requires initialization.
[0058]
(2) Holding Operation Next, the holding period Th from time t3 to time t4 shown in FIG. 5 is a period for holding the image written in the immediately preceding writing period Tw, and its length can be set arbitrarily. . In this period, the image signal processing circuit stops operating, and no electric field is generated between the pixel electrode 104 and the common electrode 201. The electrophoretic particles 12 do not move without an electric field, and maintain the spatial state at the time t3. Therefore, during the holding period Th, a still image is displayed.
[0059]
As described above, according to the present embodiment, the following effects can be obtained.
In the above embodiment, first, the common electrode voltage Vcom is set to Vcoml, and writing for resetting white pixels is performed. After the writing of the white pixel is completed, the common electrode voltage Vcom is changed to Vcomh, and the writing of the black pixel is performed. In the electrophoretic display device, the spatial distribution of the electrophoretic particles 12 that has been written once can be maintained by viscous resistance of the dispersion medium 11, so that the spatial distribution of other electrophoretic particles 12 can be written. Utilizing this property, the voltage required for the write operation can be effectively used based on the common electrode voltage Vcom. Therefore, it is possible to lower the voltage as a whole while maintaining the voltage required for the writing operation, and to achieve lower power consumption. In particular, by making the first signal voltage and the second opposing voltage and the second signal voltage and the first opposing voltage coincide with each other as in the above-described embodiment, the voltage required for each writing can be made more effective. And the configuration of the power supply circuit can be simplified.
[0060]
In the above embodiment, one end of the storage capacitor 110 is connected to the drain terminal of the TFT 103, and the other end is connected to the counter electrode modulation circuit 150 via the counter line 106. Therefore, the writing process is also performed on the storage capacitor 110 based on the common electrode voltage Vcom, so that the writing voltage can be effectively used.
[0061]
(Second embodiment)
Next, an application of an electronic apparatus equipped with the electrophoretic display device as the electro-optical device described in the first embodiment will be described.
[0062]
(1) Electronic Book First, an example in which the electrophoretic display device is applied to an electronic book will be described. FIG. 8 is a perspective view showing the electronic book. In the figure, an electronic book 1000 includes an electrophoretic display panel 1001, a power switch 1002, a first button 1003, a second button 1004, and a CD-ROM slot 1005.
[0063]
When the user presses the power switch 1002 and inserts the CD-ROM into the CD-ROM slot 1005, the contents of the CD-ROM are read, and a menu is displayed on the electrophoretic display panel 1001. When the user operates the first button 1003 and the second button 1004 to select a desired book, the first page is displayed on the electrophoretic display panel 1001. To advance the page, the second button 1004 is pressed, and to return the page, the first button 1003 is pressed.
[0064]
In the electronic book 1000, after displaying the contents of the book, the display screen is updated only when the first button 1003 and the second button 1004 are operated. As described above, the electrophoretic particles 12 do not migrate unless an electric field is applied. In other words, no power supply is required to maintain the displayed image. Therefore, the voltage is applied to the drive circuit to drive the electrophoretic display panel 1001 only when the display screen is updated. As a result, power consumption can be significantly reduced as compared with the liquid crystal display device.
[0065]
Further, since the display image of the electrophoretic display panel 1001 is displayed by the electrophoretic particles 12 which are pigment particles, the display screen does not shine. Therefore, the electronic book 1000 can display the same as a printed matter, and there is an advantage that reading the book for a long time causes less eye fatigue.
[0066]
(2) Mobile Phone An example in which the electrophoretic display device is applied to a mobile phone will be described. FIG. 9 is a perspective view showing the configuration of the mobile phone. In the figure, a mobile phone 1300 includes an electrophoretic display panel 1308 in addition to a plurality of operation buttons 1302, an earpiece 1304, a mouthpiece 1306, and the like. In the liquid crystal display device, a polarizing plate is required, and the display screen is darkened, but the electrophoretic display panel 1308 does not require a polarizing plate. Therefore, the mobile phone 1300 can display a bright and easy-to-view screen.
[0067]
In addition, as the electronic device, in addition to the description with reference to FIGS. 8 and 9, a personal computer, an outdoor sign, a car navigation device, an electronic notebook, a calculator, a word processor, a workstation, a POS terminal, and a touch panel are provided. Equipment and the like. The electro-optical device of each embodiment can be applied to these various electronic devices. Even when the electrophoretic display device is applied to these devices, the same effect as in the above-described embodiment is exerted. Since a backlight required for a transmissive / semi-transmissive liquid crystal display device is not required, each electronic device can be reduced in size and weight. Then, it is possible to significantly reduce the power consumption. As a result, each device can achieve both low power consumption and sufficient display quality.
[0068]
The above embodiment may be changed to the following modes.
In the above embodiment, the description has been made assuming the electrophoretic display device of the binary display. Instead, the present invention may be applied to an electrophoretic display device for gradation display. In this case, it is necessary to perform a reset operation for all pixels, but a higher quality display can be performed.
[0069]
In the above embodiment, one end of the storage capacitor 110 is connected to the drain terminal of the TFT 103, and the other end is connected to the counter electrode modulation circuit 150 via the counter line 106. Alternatively, the other end of the storage capacitor 110 may be connected to the adjacent scanning line 101. This also allows the voltage for writing to be used effectively.
[0070]
In the above embodiment, the electrophoretic display device for monochrome display has been described. This electrophoretic display panel A can perform full-color display. In this case, in order to allow each pixel to display one of the primary colors (RGB), three types of dispersion systems 10 corresponding to red, green, and blue are used. That is, the electrophoretic particles 12 that reflect the display color are used, while the dispersion medium 11 that corresponds to the color that absorbs the display color (complementary color in the above-described example) is used. Also in this case, the distribution of the electrophoretic particles 12 in the dispersion system 10 can be controlled by the intensity of the applied electric field, and an electrophoretic display device capable of color display can be provided.
[0071]
【The invention's effect】
As described in detail above, according to the present invention, it is possible to drive the electro-optical device to reduce the voltage and the power consumption, and to provide a desired image with higher display quality. In addition, cost reduction of the driver IC and the like can be achieved by lowering the voltage.
[Brief description of the drawings]
FIG. 1 is a block circuit diagram showing a circuit configuration of an electrophoresis apparatus for explaining a first embodiment.
FIG. 2 is an equivalent circuit of one pixel.
FIG. 3 is a block diagram of a data line driving circuit of the device.
FIG. 4 is a timing chart of a scanning line driving circuit and a data line driving circuit.
FIG. 5 is a timing chart showing output data of an image signal processing circuit.
FIG. 6 is a processing flowchart at the time of a writing operation.
FIG. 7 is a timing chart in a write operation.
FIG. 8 is an external perspective view of an electronic book as an example of an electronic apparatus.
FIG. 9 is an external perspective view of a mobile phone as an example of an electronic apparatus.
FIG. 10 is a partial cross-sectional view of an electrophoretic display device.
[Explanation of symbols]
A Electrophoretic display panel 10 Dispersion system 11 Dispersion medium 12 Electrophoretic particles 15 Divided cell 100 Element substrate 103 TFT as switching element
104 pixel electrode 110 storage capacitor 130 scanning line driving circuit 140 data line driving circuit 150 as driving means counter electrode modulation circuit 201 common electrode 300 controllers Y1 to Ym as control means scanning lines X1 to Xn data lines

Claims (9)

A common electrode, a pixel electrode facing the common electrode, and a switching element connected to the pixel electrode, including a dispersion system containing electrophoretic particles between the common electrode and the pixel electrode,
Driving means for moving the electrophoretic particles using an electric field generated by the electric charge accumulated in the common electrode or the pixel electrode,
An electro-optical device having control means for controlling the driving means,
The control means performs a reset process of a first polarity by applying a first counter voltage to the common electrode;
Thereafter, a second opposite voltage is applied to perform the writing processing of the second polarity, and the electro-optical device is characterized in that: The driving unit applies a first signal voltage and a second signal voltage to the switching element to move the electrophoretic particles,
The first signal voltage matches the second counter voltage,
The electro-optical device according to claim 1, wherein the second signal voltage is equal to the first counter voltage. The switching element is connected to one end of a storage capacitor,
The electro-optical device according to claim 1, wherein the other end of the storage capacitor is connected to the common electrode. 4. The method according to claim 1, wherein the control unit performs a reset operation by applying a predetermined voltage to all of the pixel electrodes before executing the second polarity writing process. The electro-optical device according to claim 1. A common electrode, a pixel electrode facing the common electrode, and a switching element connected to the pixel electrode, including a dispersion system containing electrophoretic particles between the common electrode and the pixel electrode,
Driving means for moving the electrophoretic particles using an electric field generated by the electric charge accumulated in the common electrode or the pixel electrode,
A driving unit for controlling the driving unit, and a driving method of the electro-optical device having:
The control means performs a reset process of a first polarity by applying a first counter voltage to the common electrode;
Thereafter, a writing process of a second polarity is performed by applying a second counter voltage, and the driving method of the electro-optical device is characterized in that the method of driving the electro-optical device is performed. The driving unit applies a first signal voltage and a second signal voltage to the switching element to move the electrophoretic particles,
The first signal voltage matches the second counter voltage,
The method according to claim 5, wherein the second signal voltage is equal to the first counter voltage. The switching element is connected to one end of a storage capacitor,
7. The method according to claim 5, wherein the other end of the storage capacitor is connected to the common electrode. 8. The method according to claim 5, wherein the control unit performs a reset operation by applying a predetermined voltage to all of the pixel electrodes before executing the writing processing of the second polarity. A method for driving an electro-optical device according to any one of the preceding claims. An electronic apparatus comprising the electro-optical device according to claim 1.

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