JP4488105B2 - Electro-optical device, driving method of electro-optical device, and electronic apparatus - Google Patents

Description

  The present invention relates to an electro-optical device composed of a plurality of divided cells enclosing a dispersion system containing electrophoretic particles.

  As a non-luminous display device, an electrophoretic display device using an electrophoretic phenomenon is known (see, for example, Patent Document 1). Here, the electrophoresis phenomenon is a phenomenon in which particles are migrated 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).

  Such an electrophoretic display device is configured such that one electrode and the other electrode face each other at a predetermined interval, and a divided cell in which a dispersion system is sealed is disposed therebetween. The electrophoretic display device includes a peripheral circuit for applying an electric field to the dispersion system. First, description will be made with reference to a partial cross-sectional view of the electrophoretic display panel shown in FIG.

  As shown in FIG. 13, 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 counter substrate 200 are bonded to each other so that the electrode formation surfaces face each other with a certain gap therebetween. In this gap, there are provided divided cells 15 that are divided into a predetermined size with respect to the pixels that are display units of the image and that contain the dispersion system 10.

  This dispersion system 10 is obtained by dispersing electrophoretic particles 12 in a dispersion medium 11. An additive such as a surfactant is added to the dispersion medium 11 as necessary. 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 approximately equal to avoid sedimentation of the electrophoretic particles 12 due to gravity.

  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. As a result, it is possible to prevent a phenomenon in which the dispersion of the electrophoretic particles 12 in the dispersion system 10 is biased or a condensation in which a plurality of particles are combined to form a large lump.

  On the surface of the element substrate 100, a display region and a peripheral region provided with a peripheral circuit are provided. In addition to the pixel electrode 104 described above, a thin film transistor (Thin Film Transistor: hereinafter referred to as TFT) that functions as a scanning line, a data line, and a switching element is formed in the display region. On the other hand, a scanning line driving circuit, a data line driving circuit, etc., which will be described later, are formed in the peripheral region of the element substrate 100.

  Next, an operation when a voltage is applied to the pixel electrode 104 will be described. An electric field is generated when a potential difference is applied between the pixel electrode 104 and the common electrode 201. As a result, the charged electrophoretic particles 12 are attracted to one of the electrodes. Here, when the dispersion medium 11 is colored and the electrophoretic particles 12 are composed of colored particles, and a material having transparency is used as the common electrode 201 and the counter substrate 200, the color of the electrophoretic particles 12 or the dispersion medium 11. I can see the color. Thereby, an image can be displayed by controlling the voltage applied to each electrode.

  Next, the principle of gradation display will be described with reference to FIGS. 14 and 15 are cross-sectional views showing the structure of the divided cell 15 in a simplified manner. First, the reset operation of the electrophoretic display device is performed. In this reset operation, the electrophoretic particles 12 are attracted to the pixel electrode 104 side. When the electrophoretic particles 12 charged with positive charges are used, a negative voltage is applied to the pixel electrode 104 based on the voltage of the common electrode 201. In this case, the electrophoretic particles 12 are attracted to the pixel electrode 104 as shown in FIG.

  Next, a positive voltage corresponding to the gradation to be displayed is applied to the pixel electrode 104. Then, as shown in FIG. 15, the electrophoretic particles 12 move to the common electrode 201 side by an electric field. When the potential difference between the two electrodes is reduced to zero after the lapse of a predetermined time, the electric field stops working, and the electrophoretic particles 12 are stopped by 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. The moving distance of the electrophoretic particles 12 is determined according to the applied voltage and the application time. Therefore, if the application time is made constant, the position of the electrophoretic particles 12 in the thickness direction can be controlled by adjusting the applied voltage.

  Light incident from the common electrode 201 side is reflected by the electrophoretic particles 12, and this reflected light is observed through the common electrode 201. Incident light and reflected light are absorbed by the dispersion medium 11, and the degree of 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 particle 12 is determined according to the applied voltage when the application time is constant, desired gradation display can be performed by adjusting the applied voltage.

JP 2002-116734 A (FIG. 2)

  The display method includes binary display in addition to gradation display. In this case, the image is displayed without using the intermediate color. Unlike gradation display, binary display cannot express a subtle color condition like gradation display, but control for display is easy. However, even in such binary display, the electrophoretic particles 12 diffuse in the dispersion medium 11 over time after displaying the image, and the display becomes thin or disappears.

  SUMMARY An advantage of some aspects of the invention is that it provides an electro-optical device, a driving method thereof, and an electronic apparatus that can maintain display for a long period of time.

The electro-optical device according to the present invention includes a plurality of scanning lines, a plurality of data lines intersecting with the scanning lines, a switching element formed corresponding to the intersection of the scanning lines and the data line, and the switching element A pixel electrode electrically connected to the pixel electrode, a common electrode facing the pixel electrode, a dispersion system including electrophoretic particles disposed between the common electrode and the pixel electrode, the scanning line, An electro-optical device having a driving unit that drives the data line and a control unit that controls the driving unit, wherein the control unit performs a writing operation and a holding operation, and the writing operation includes a plurality of writing operations. The holding operation is performed in a state where the common electrode and the pixel electrode are at different potentials after the writing operation. Characterized in that it comprises an operation to open the switching element.
The electro-optical device according to the present invention includes a plurality of scanning lines, a plurality of data lines intersecting with the scanning lines, a switching element formed corresponding to the intersection of the scanning lines and the data line, and the switching element A pixel electrode electrically connected to the pixel electrode, a common electrode facing the pixel electrode, a dispersion system including electrophoretic particles disposed between the common electrode and the pixel electrode, the scanning line, An electro-optical device having a driving unit that drives the data line and a control unit that controls the driving unit, wherein the control unit performs a writing operation and a holding operation, and the writing operation includes a plurality of writing operations. And a holding operation including an operation of applying a predetermined voltage to the data line after the writing operation. To.
The electro-optical device according to the present invention includes a plurality of scanning lines, a plurality of data lines intersecting with the scanning lines, a switching element formed corresponding to the intersection of the scanning lines and the data line, and the switching element A pixel electrode electrically connected to the pixel electrode, a common electrode facing the pixel electrode, a dispersion system including electrophoretic particles disposed between the common electrode and the pixel electrode, the scanning line, An electro-optical device having a driving unit that drives the data line and a control unit that controls the driving unit, wherein the control unit performs a writing operation and a holding operation, and the writing operation includes a plurality of writing operations. Including an operation of applying a potential based on image data to the pixel electrode in each of the fields, wherein the holding operation reduces a leakage current of the switching element to the scanning line after the writing operation. Characterized in that it comprises the operation of applying the order of voltage.
In the electro-optical device, the switching element is a transistor having a source terminal, a gate terminal, and a drain terminal, the source terminal is electrically connected to the data line, and the gate terminal is electrically connected to the scanning line. It is preferable that the drain terminal is electrically connected to the pixel electrode.
The electro-optical device is capable of gradation display and binary display, and when the binary display is executed, the control unit preferably executes the holding operation.
The driving method of the electro-optical device according to the invention includes a plurality of scanning lines, a plurality of data lines intersecting the scanning lines, a switching element formed corresponding to the intersection of the scanning lines and the data lines, A pixel electrode electrically connected to the switching element; a common electrode facing the pixel electrode; and a dispersion system containing electrophoretic particles disposed between the common electrode and the pixel electrode. A driving method for an electro-optical device having a writing step in which a potential based on image data is applied to the pixel electrode in each of a plurality of fields, and the common electrode and the pixel electrode are different after the writing step A step of opening the switching element in a potential state.
The driving method of the electro-optical device according to the invention includes a plurality of scanning lines, a plurality of data lines intersecting the scanning lines, a switching element formed corresponding to the intersection of the scanning lines and the data lines, A pixel electrode electrically connected to the switching element; a common electrode facing the pixel electrode; and a dispersion system containing electrophoretic particles disposed between the common electrode and the pixel electrode. A method for driving an electro-optical device comprising: a writing step of applying a potential based on image data to each of the pixel electrodes in each of a plurality of fields; and a step of applying a predetermined voltage to the data line after the writing step It is characterized by having.
The driving method of the electro-optical device according to the invention includes a plurality of scanning lines, a plurality of data lines intersecting the scanning lines, a switching element formed corresponding to the intersection of the scanning lines and the data lines, A pixel electrode electrically connected to the switching element; a common electrode facing the pixel electrode; and a dispersion system containing electrophoretic particles disposed between the common electrode and the pixel electrode. And a writing step of applying a potential based on image data to the pixel electrode in each of a plurality of fields, and a leakage current of the switching element in the scanning line after the writing step. And a step of applying a voltage for reducing the voltage.
In the driving method of the electro-optical device, the switching element is a transistor having a source terminal, a gate terminal, and a drain terminal, the source terminal is electrically connected to the data line, and the gate terminal is connected to the scanning line. It is preferable that the drain terminal is electrically connected to the pixel electrode.
The electro-optical device is capable of gradation display and binary display, and when the binary display is executed, the control unit preferably executes the holding operation.
Another aspect of the electro-optical device of the present invention includes a common electrode, a pixel electrode facing the common electrode, and a switching element connected to the pixel electrode, and the gap is between the common electrode and the pixel electrode. A driving unit that includes a dispersion system containing electrophoretic 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 The control means executes a charge maintaining process for maintaining at least part of the accumulated charge based on the first writing instruction until the second writing instruction.

  According to this, the electric field is maintained by the charge accumulated in the pixel electrode. As a result, the electrophoretic particles maintain a spatial state generated based on the first writing instruction. In a normal writing operation, the charge accumulated in the pixel electrode is extracted, so that the electrophoretic particles maintain a spatial state due to the viscosity of the dispersion system, but the image disappears due to the diffusion of the electrophoretic particles. Therefore, in the present invention, even if the viscosity of the dispersion system is lowered, an image can be displayed over a long period of time using an electric field.

  In the electro-optical device, in the charge maintaining process, after the writing process based on the first writing instruction is finished, the control unit maintains the common electrode and the pixel electrode at different potentials. The switching element is opened.

  According to this, the electric charge accumulated in the pixel electrode can be held, and the spatial state of the electrophoretic particles can be maintained.

  In this electro-optical device, the switching element is a transistor having a source terminal, a gate terminal, and a drain terminal, and the charge maintaining process is performed after the write process based on the first write instruction is finished, Further applies a predetermined voltage to the source terminal.

  According to this, the leakage current of the switching element can be reduced, and the charge accumulated in the pixel electrode can be held for a longer time.

  In the electro-optical device, the charge maintaining process ends the writing process based on the first writing instruction, and after a predetermined period, the control unit applies a voltage to at least one of the common electrode or the pixel electrode. A rewrite process for applying is further executed.

  According to this, charge lost due to leakage or the like can be compensated, and the spatial state of the electrophoretic particles can be maintained.

  In the electro-optical device, the control unit periodically executes the rewriting process.

  According to this, charge lost due to leakage or the like can be compensated, and the spatial state of the electrophoretic particles can be maintained.

  In this electro-optical device, the switching element is a transistor having a source terminal, a gate terminal, and a drain terminal, and the charge maintaining process is performed after the write process based on the first write instruction is finished, Applies a voltage for reducing the leakage current of the transistor to the gate terminal.

  According to this, the charge lost due to leakage or the like can be reduced. Therefore, the spatial state of the electrophoretic particles can be maintained using the electric field generated by the accumulated charges.

  In this electro-optical device, the electro-optical device can perform gradation display and binary display, and when executing the binary display, the control unit executes the charge maintaining process.

  According to this, the electro-optical device can provide gradation display and binary display. That is, in the case of gradation display, the spatial state of the electrophoretic particles is maintained by extracting the charge accumulated in the pixel electrode, and in the case of binary display, the electric field generated by the accumulated charge is used. The spatial state of the electrophoretic particles can be maintained.

  In this electro-optical device driving method, a common electrode, a pixel electrode opposed to the common electrode, and a switching element connected to the pixel electrode, and an electrophoretic particle between the common electrode and the pixel electrode A driving unit 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. In the driving method of the electro-optical device, the control unit performs a charge maintaining process for maintaining at least a part of the charges accumulated based on the first writing instruction until the second writing instruction.

  According to this, the electric field is maintained by the charge accumulated in the pixel electrode. As a result, the electrophoretic particles maintain a spatial state generated based on the first writing instruction. In a normal writing operation, the charge accumulated in the pixel electrode is extracted, so that the electrophoretic particles maintain a spatial state due to the viscosity of the dispersion system, but the image disappears due to the diffusion of the electrophoretic particles. Therefore, in the present invention, even if the viscosity of the dispersion system is lowered, an image can be displayed over a long period of time using an electric field.

  In the driving method of the electro-optical device, in the charge maintaining process, the control unit maintains the common electrode and the pixel electrode at different potentials after completing the writing process based on the first writing instruction. In the state, the switching element is opened.

  According to this, the electric charge accumulated in the pixel electrode can be held, and the spatial state of the electrophoretic particles can be maintained.

  In the driving method of the electro-optical device, the switching element is a transistor having a source terminal, a gate terminal, and a drain terminal, and the charge maintaining process is performed after finishing the writing process based on the first writing instruction. The control means further applies a predetermined voltage to the source terminal.

  According to this, the leakage current of the switching element can be reduced, and the charge accumulated in the pixel electrode can be held for a longer time.

  In the driving method of the electro-optical device, the charge maintaining process ends the writing process based on the first writing instruction, and after a predetermined period has elapsed, the control unit performs at least the common electrode or the pixel electrode. A rewriting process for applying a voltage to one side is further executed.

  According to this, charge lost due to leakage or the like can be compensated, and the spatial state of the electrophoretic particles can be maintained.

  In the driving method of the electro-optical device, the control unit periodically executes the rewriting process.

  According to this, charge lost due to leakage or the like can be compensated, and the spatial state of the electrophoretic particles can be maintained.

  In the driving method of the electro-optical device, the switching element is a transistor having a source terminal, a gate terminal, and a drain terminal, and the charge maintaining process is performed after finishing the writing process based on the first writing instruction. The control means applies a voltage for reducing a leakage current of the transistor to the gate terminal.

  According to this, the charge lost due to leakage or the like can be reduced. Therefore, the spatial state of the electrophoretic particles can be maintained using the electric field generated by the accumulated charges.

  In the driving method of the electro-optical device, the electro-optical device can perform gradation display and binary display. When the binary display is performed, the control unit performs the charge maintaining process.

  According to this, the electro-optical device can provide gradation display and binary display. That is, in the case of gradation display, the spatial state of the electrophoretic particles is maintained by extracting the charge accumulated in the pixel electrode, and in the case of binary display, the electric field generated by the accumulated charge is used. The spatial state of the electrophoretic particles can be maintained.

  An electronic apparatus according to the present invention has the electro-optical device according to any one of claims 1 to 7 mounted thereon.

  According to this, the electronic device can achieve both low power consumption and sufficient display quality.

The block circuit diagram which shows the circuit structure of the electrophoresis apparatus for describing 1st Embodiment. Explanatory drawing of the whole schematic structure of an electrophoretic display device. 4 is a timing chart showing output data of an image signal processing circuit. The flowchart at the time of writing operation | movement / holding | maintenance operation | movement. A timing chart at the time of writing operation / holding operation. Explanatory drawing of the display density intensity | strength of an electrophoretic display apparatus. The flowchart at the time of the write-in operation | movement and holding | maintenance operation for describing 2nd Embodiment. A timing chart at the time of writing operation / holding operation. FIG. 10 is a flowchart at the time of a writing operation / holding operation for explaining a third embodiment. A timing chart at the time of writing operation / holding operation. FIG. 14 is a perspective view of an electronic book as an example of an electronic apparatus. 1 is a perspective view of a mobile phone as an example of an electronic device. The fragmentary sectional view of an electrophoretic display device. Sectional drawing which simplified and showed the structure of the division | segmentation cell. Sectional drawing which simplified and showed the structure of the division | segmentation cell.

(First 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 in this embodiment includes an electrophoretic display panel and a peripheral circuit.

  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 its peripheral region are provided. In this figure, a driving circuit in the peripheral region is integrated assuming an element with high mobility (such as low-temperature polysilicon), but the present invention can of course be applied to an element with low mobility (such as amorphous silicon). The driving circuit in that case is composed of an element with high mobility (such as single crystal silicon), and the electrophoretic display panel A, the data line driving circuit 140, and the scanning line driving circuit 130 are separate components. The electrophoretic display panel A of this example is composed of a plurality of pixels, and the electrical elements constituting the pixels include a TFT 103 as a switching element and a pixel electrode 104 connected thereto. In the peripheral region of the element substrate 100, a scanning line driving circuit 130 and a data line driving circuit 140 as driving means are formed.

  FIG. 2 shows an overall schematic configuration of the electrophoretic display device 20 to which the present invention is applied. Control signals and image signals are provided from the controller 300 to the scanning line driving circuit 130 and the data line driving circuit 140. In the present embodiment, an interface unit 500 is further provided and connected to the controller 300. Here, the controller 300 receives a signal through the interface unit 500, converts it into an image signal in accordance with a driving cycle, and outputs the converted signal to each driving circuit (130, 140). Function.

  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 them to the data line driving circuit 140. The reset data Drest is output during a predetermined period before the image data D is output. The reset data Drest is used to attract the electrophoretic particles 12 that migrate in the dispersion system 10 to one electrode side and initialize the spatial state thereof. Further, the image data D is generated by performing a correction process on the image signal according to the electrical characteristics of the electrophoretic display panel A. Hereinafter, it is assumed that the dispersion medium 11 of the dispersion system 10 is colored black, and the electrophoretic particles 12 are white particles such as titanium oxide and are positively charged.

  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.

  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, and a plurality of data lines 102 are formed in parallel along the Y direction perpendicular to the X direction. Has been. Each pixel is arranged in a matrix corresponding to the intersection of the scanning line 101 and the data line 102. At each of these intersections, the gate terminal of the TFT 103 is connected to the scanning line 101, while its source terminal is connected to the data line 102. Further, the drain terminal of the TFT 103 is connected to the pixel electrode 104.

  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 electrode 104 connected to the TFT 103 of the i-th scanning line 101. On the other hand, the common electrode voltage Vcom is applied to the common electrode 201 of the counter substrate 200 from a power supply circuit (not shown). Thereby, 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 and a color corresponding to the image data D is displayed for each pixel.

(Drive circuit)
Next, a driving circuit for driving the scanning lines 101 and the data lines 102 will be described.

  First, the scanning line driving circuit 130 has a shift register, and generates scanning line signals Y1 to Ym based on a signal from the timing generator. The scanning line signals Y1 to Ym are output to each scanning line 101, and the active period is sequentially shifted.

  The data line driving circuit 140 includes a shift register, a latch circuit, and a D / A converter. The data line driving circuit 140 generates data line signals X1 to Xn based on the supplied image data D and supplies the data line signals X1 to Xn to each data line 102.

(Operation of electrophoretic display device)
Next, the operation of the electrophoretic display device will be described with reference to FIG. FIG. 3 is a timing chart showing output data of the image signal processing circuit of the controller 300.

  First, when the power of the electrophoretic display device is switched from the off state to the on state at time t0, driving 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 writing 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 an image, and a reset operation and a writing operation are performed as in the period from time t1 to time t3.

(1) Reset operation At a time t1 when a predetermined period has elapsed after the power is turned on and the circuit operation is stable, the image signal processing circuit stores the reset data Drest in one field (in the case of an electrophoretic element having a slow response speed). Output over a period of (field). In the reset period Tr, the electrophoretic particles 12 are attracted toward the pixel electrode 104, and the spatial state thereof is initialized. The data line driving circuit 140 outputs a reset voltage Vrest corresponding to the data value of the reset data Drest to each data line 102. At the same time, the scanning line driving circuit 130 sequentially selects each scanning line 101, whereby a voltage is supplied to the pixel electrode 104, and the reset voltage Vrest is applied between all the pixel electrodes 104 and the common electrode 201. .

(2) Write Operation and Holding Operation Next, when time t2 is reached, writing is started. 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). In the present embodiment, assuming that binary display is performed, a voltage corresponding to the color to be displayed is written in each pixel electrode 104 to complete one image.

  The operation will be described below with reference to FIGS. FIG. 4 is an operation flow after starting the writing operation. FIG. 5 is a timing chart of the electrophoretic display device 20 in the writing operation / holding operation. One frame of this embodiment is composed of n fields. That is, it is assumed that one image is completed by writing data n times to the 1 to m scanning lines 101. Here, the writing operation in the pixels in the i-th row (i-th scanning line) and the j-th column (j-th data line) will be described, but the same writing is performed in other pixels. In the following description, a pixel in i row and j column is represented as Pij, a voltage to be displayed on the pixel Pij is represented as Vij, and a display density of the pixel Pij is represented as Iij.

  As shown in FIG. 4, first, the controller 300 starts a write operation (S1-1). In this case, the scanning line driving circuit 130 sequentially generates the scanning line signals Y1 to Ym. Thereby, each scanning line 101 becomes active. The i-th scanning line 101 is activated by the scanning line signal Yi. At this time, when the data line signal Xj supplied to the j-th data line 102 is output, charges corresponding to the pixel voltage Vij are accumulated between the common electrode 201 and the pixel electrode 104. This results in a pixel voltage Vij as shown in field 1 of FIG. Since this charge leaks over time, the pixel voltage Vij tends to decrease.

  Next, the behavior of the electrophoretic particles 12 in the pixel Pij will be described. Since the above-described reset operation is performed before the writing operation, the electrophoretic particles 12 of the pixel Pij are attracted toward the pixel electrode 104 at this time. At this time, when the pixel voltage Vij is applied to the pixel electrode 104, an electric field is applied from the pixel electrode 104 toward the common electrode 201, and the electrophoretic particles 12 start to migrate.

  Here, the display density Iij in the pixel Pij in the i row and j column is determined by the average amount of movement of the electrophoretic particles in the pixel Pij. Since the electrophoretic particles 12 in this example are white and the dispersion medium 11 is black, the closer the electrophoretic particles 12 are to the common electrode 201, the higher the display density Iij of the pixel Pij. The display density Iij in this case is shown in FIG. As shown in FIG. 6, the display density Iij gradually increases from time T1.

  In the next field (here, field 2), a voltage is further applied to the remaining voltage as shown in FIG. The electrophoretic particles 12 move in the dispersion medium 11 under the influence of the electric field due to the pixel voltage Vij.

  Then, at Tn in the field n, the electrophoretic particles 12 migrate to a predetermined position. In the case of binary display, it is attached to the pixel electrode 104 side or the common electrode 201 side. As a result, the display density Iij becomes a constant value from time Tn as shown in the figure. Then, the writing operation is finished.

  Next, high impedance processing as charge maintenance processing is executed (S1-2). Specifically, the charges accumulated in the common electrode 201 and the pixel electrode 104 are left without being extracted. Here, a voltage for turning off the TFT 103 is applied to the scanning line 101. In addition to the TFT 103, a dedicated transistor may be provided in series with the TFT 103. In this case, a high-impedance process may be performed by connecting a dedicated gate line to the dedicated transistor and supplying an off voltage at a time. As a result, the electric field is maintained in the dispersion medium 11 of each pixel by the remaining charge. And the electrophoretic particle 12 holds the position of the state attracted to each electrode by this electric field.

  Next, a holding period Th from time t3 to time t4 shown in FIG. 4 is a period for holding an image written in the immediately preceding writing period Tw.

  Here, the controller 300 waits for a new writing instruction (S1-3). A new writing instruction is input via the interface unit 500. When a new writing instruction is received (in the case of “Yes” in step (S1-3)), the above-described reset operation is executed (S1-4). On the other hand, when there is no new writing instruction (in the case of “No”), these steps are repeated until the power is turned off (S1-5).

  As described above, according to the present embodiment, the following effects can be obtained.

  In the above embodiment, the electric field is maintained between the pixel electrode 104 and the common electrode 201 due to the charge remaining after the high impedance processing. Therefore, the electrophoretic particles 12 can maintain a spatial state at time t3, that is, a state of sticking to each electrode side, and display an image over the holding period Th.

  In the above embodiment, as the high impedance process, the charges accumulated in the common electrode 201 and the pixel electrode 104 are left without being extracted. For this reason, an image can be efficiently held in binary display.

(Second Embodiment)
Hereinafter, a second embodiment of an electrophoretic display device as an electro-optical device embodying the present invention will be described with reference to FIGS. Note that the second embodiment has a configuration in which only the writing operation / holding operation of the first embodiment is changed, and thus detailed description of the same parts is omitted.

  In the timing chart shown in FIG. 3, when the time t2 is reached, the controller 300 starts writing. In the writing period Tw, the image signal processing circuit outputs the image data D over one frame period. Also in this embodiment, assuming that binary display is performed, a pixel voltage corresponding to a color to be displayed is written to each pixel electrode 104, and one image is completed.

  The operation will be described below with reference to FIGS. FIG. 7 is an operation flow after starting the writing operation. FIG. 8 is a timing chart in the writing operation / holding operation. One frame of this embodiment is composed of n fields.

  As shown in FIG. 7, first, the controller 300 starts a write operation (S2-1). In this operation, as in the first embodiment, the scanning line driving circuit 130 sequentially generates the scanning line signals Y1 to Ym. Thereby, each scanning line 101 becomes active. The i-th scanning line 101 is activated by the scanning line signal Yi. At this time, when the data line signal Xj supplied to the jth data line 102 is output, the charge corresponding to the pixel voltage Vij is accumulated between the common electrode 201 and the pixel electrode 104. This results in a pixel voltage Vij as shown in field 1 of FIG.

  In the next field (here, field 2), a voltage is further applied to the remaining voltage as shown in FIG. The electrophoretic particles 12 move in the dispersion medium 11 under the influence of the electric field due to the pixel voltage Vij.

  Then, in Tn of the field n, the electrophoretic particles 12 move to a predetermined position. In the case of binary display, it is attached to the pixel electrode 104 side or the common electrode 201 side. As a result, the display density Iij becomes a constant value from the time Tn. Then, the writing operation is finished.

  Next, as in the first embodiment, high impedance processing is executed (S2-2). Specifically, the charges accumulated in the common electrode 201 and the pixel electrode 104 are left without being extracted. As a result, the electric field is maintained in the dispersion medium 11 of each pixel by the remaining charge. And the electrophoretic particle 12 holds the position of the state attracted to each electrode by this electric field.

  Next, the holding period Th is entered, and the image written in the immediately preceding writing period Tw is held. Here, the controller 300 waits for a new writing instruction (S2-3). A new writing instruction is input via the interface unit 500. When a new write instruction is received (in the case of “Yes” in step (S2-3)), a reset operation is executed (S2-4).

  On the other hand, when there is no new writing instruction (in the case of “No”), the controller 300 measures the time from the end time of the last writing process (S2-5). When a predetermined time has elapsed from this time (in the case of “Yes” in step (S2-5)), a refresh process as a rewrite process is performed (S2-6). In this process, the data written in the field n is written again.

  These steps are repeated until the power is turned off (S2-7).

  Therefore, according to the second embodiment, in addition to the features described in the first embodiment, an electric field is maintained between the pixel electrode 104 and the common electrode 201 by the charge remaining by the high impedance processing. . Furthermore, the refreshing process allows the electrophoretic particles 12 to maintain a spatial state at time t3, that is, a state of sticking to each electrode side, and display a still image over the holding period Th.

(Third embodiment)
Hereinafter, a third embodiment of an electrophoretic display device as an electro-optical device embodying the present invention will be described with reference to FIGS. Since the third embodiment has a configuration in which only the writing operation / holding operation of the first embodiment is changed, detailed description of similar parts is omitted.

  In the timing chart shown in FIG. 3, when the time t2 is reached, the controller 300 starts writing. In the writing period Tw, the image signal processing circuit outputs the image data D over one frame period. Also in this embodiment, assuming that binary display is performed, a pixel voltage corresponding to a color to be displayed is written to each pixel electrode 104, and one image is completed. Here, it is assumed that the dispersion system 10 used in the electrophoretic display device 20 has a high specific gravity of the white electrophoretic particles 12. In this case, the relaxation time from white to gray is shorter than the relaxation time from black to gray, and it is difficult to maintain white.

  Hereinafter, the operation will be described with reference to FIGS. FIG. 9 is an operation flow after starting the writing operation. FIG. 10 is a timing chart of the electrophoretic display device in the writing operation / holding operation. One frame of this embodiment is composed of n fields.

  As shown in FIG. 9, first, the controller 300 starts a write operation (S3-1). In this operation, as in the first embodiment, the scanning line driving circuit 130 sequentially generates the scanning line signals Y1 to Ym. Thereby, each scanning line 101 becomes active. The i-th scanning line 101 is activated by the scanning line signal Yi. In this case, when the data line signal Xj supplied to the jth data line 102 is output, the charge corresponding to the pixel voltage Vij is accumulated between the common electrode 201 and the pixel electrode 104. As a result, a pixel voltage Vij indicated by T1 in field 1 of FIG. 10 is generated.

  In the next field (here, field 2), a voltage is further applied to the remaining voltage as shown in FIG. The electrophoretic particles 12 move in the dispersion medium 11 under the influence of the electric field due to the pixel voltage Vij.

  Then, in Tn of the field n, the electrophoretic particles 12 move to a predetermined position. In the case of binary display, it is attached to the pixel electrode 104 side or the common electrode 201 side. As a result, the display density Iij becomes a constant value from the time Tn. Then, the writing operation is finished.

  Next, the controller 300 applies a predetermined voltage to a part or all of the data line 102 connected to the source terminal of the TFT 103 as a charge maintaining process (S3-2). When applying the voltages of some of the data lines 102, only a portion where the display color is to be retained is selected and a predetermined voltage is applied. In this embodiment, a voltage for maintaining a display color (white in this embodiment) having a short relaxation time is applied as the predetermined voltage applied to the data line 102. Specifically, a voltage close to the voltage applied to the pixel electrode 104 displaying white is applied.

  Next, the holding period Th is entered, and the image written in the immediately preceding writing period Tw is held. Here, the controller 300 waits for a new writing instruction (S3-3). When a new write instruction is received (in the case of “Yes” in step (S3-3)), a reset operation is executed (S3-4). On the other hand, when there is no new writing instruction (in the case of “No”), these steps are repeated until the power is turned off (S3-5).

  Therefore, according to the third embodiment, in addition to the features described in the first embodiment, a predetermined voltage is applied to a part or all of the data line 102 after the end of the write operation. In the present embodiment, as the predetermined voltage applied to the data line 102, a voltage close to the voltage applied to the display color pixel electrode 104 having a short relaxation time is used. For this reason, the potential difference between the source and the drain of the TFT 103 regarding the display color that is difficult to hold is reduced, and the leakage amount of the TFT 103 can be reduced. Therefore, the charge between the pixel electrode 104 of the display color that is difficult to hold and the common electrode 201 is maintained longer. As a result, due to this charge, the electrophoretic particles 12 can maintain the spatial state at the end of the writing operation, that is, the state where the electrophoretic particles 12 are attached to the electrode side, thereby extending the holding time of the display color that is difficult to hold. be able to. On the other hand, a display color having a long relaxation time due to the specific gravity of the dispersion medium 11 is originally retained by the viscosity of the dispersion medium 11 even if the retention effect due to the residual charge is reduced. Accordingly, relaxation (graying) of both display colors can be suppressed, and an image can be displayed for a longer period.

(Fourth embodiment)
Next, electronic devices using the electrophoretic display device as the electro-optical device described in the first to third embodiments will be described.

(1) Electronic book First, an example in which an electrophoretic display device is applied to an electronic book will be described. FIG. 11 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.

  When the user presses the power switch 1002 and a CD-ROM is inserted 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. The second button 1004 is pressed to advance the page, and the first button 1003 is pressed to return the page.

  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 display image. Therefore, only when the display screen is updated, the electrophoretic display panel 1001 is driven by applying a voltage to the drive circuit. As a result, power consumption can be significantly reduced as compared with the liquid crystal display device.

  Further, since the display image of the electrophoretic display panel 1001 is displayed by the electrophoretic particles 12, the display screen does not shine. Therefore, the electronic book 1000 can display the same as a printed matter, and has an advantage of less eye fatigue even when read for a long time.

(2) Mobile phone Further, an example in which the electrophoretic display device is applied to a mobile phone will be described. FIG. 12 is a perspective view showing the configuration of this mobile phone. In the figure, a mobile phone 1300 includes an electrophoretic display panel 1308 in addition to a plurality of operation buttons 1302, as well as an earpiece 1304 and a mouthpiece 1306. In the liquid crystal display device, a polarizing plate is necessary, and thus the display screen is dark. However, the electrophoretic display panel 1308 does not require a polarizing plate. Therefore, the mobile phone 1300 can display a bright and easy-to-see screen.

  In addition to the electronic device described with reference to FIGS. 11 to 12, the electronic device includes 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. Equipment etc. are mentioned. 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 effects as those of the above-described embodiment are exhibited. 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. And it is possible to reduce the power consumption significantly. As a result, each device can realize both low power consumption and sufficient display quality.

  In addition, you may change the said embodiment into the following aspects.

  In the above embodiment, in the high impedance process as the charge maintenance process, the charges accumulated in the common electrode 201 and the pixel electrode 104 are left without being extracted. In the third embodiment, a predetermined voltage is applied to part or all of the data line 102 to reduce the potential difference between the source and the drain, and to reduce the leakage amount of the TFT 103. Instead of or in addition to this, reduction of residual charges due to leakage of the TFT 103 may be prevented. Specifically, during the holding operation, a gate voltage that minimizes the leakage current of the TFT 103 may be continuously applied to each scanning line 101. As a result, the charges accumulated in the common electrode 201 and the pixel electrode 104 can be held for a long time, and the image can be maintained for a long time.

  In the above embodiment, the write operation is completed in n fields, but the 1-field write operation may be completed. In this case, the refresh operation in the second embodiment applies the data line signal Xj having a low voltage during the write operation. This makes it possible to maintain an image for a long time while reducing power consumption.

  In the above-described embodiment, the binary display electrophoretic display device has been described. In addition to this, the present invention may be applied to an electrophoretic display device capable of gradation display. In this case, the electrophoretic display device is provided with a gradation display mode and a binary display mode. When the binary display mode is selected, the writing operation / holding operation of the present invention is executed. As a result, while realizing gradation display, it is possible to maintain a long image while reducing power consumption in binary display.

  In the above embodiment, the electrophoretic display panel A for monochrome display has been described. Instead, this is an electrophoretic display panel A capable of color display. In this case, three types corresponding to red, green, and blue are used as the dispersion system 10 so that each pixel can display one of the primary colors (RGB). That is, while the electrophoretic particles 12 that reflect the display color are used, the dispersion medium 11 that corresponds to the color that absorbs the display color (complementary color in the above example) is used. Also in this case, it is possible to provide an electrophoretic display device capable of color display that can maintain the distribution of the electrophoretic particles 12 in the dispersion system 10 over a long period of time by performing the charge maintaining process.

  As described above in detail, according to the present invention, it is possible to drive the electro-optical device to display a desired image while achieving both low power consumption and sufficient display quality.

  DESCRIPTION OF SYMBOLS A ... Electrophoretic display panel, 10 ... Dispersion system, 11 ... Dispersion medium, 12 ... Electrophoretic particle, 15 ... Divided cell, 20 ... Electrophoretic display device as electro-optical device, 100 ... Element substrate, 103 ... As switching element TFT, 104 ... pixel electrode, 130 ... scanning line drive circuit, 140 ... data line drive circuit as drive means, 201 ... common electrode, 300 ... controller as control means, 500 ... interface unit, Y1-Ym ... scan line , X1 to Xn: data lines.

Claims (11)

  A plurality of scan lines;
  A plurality of data lines intersecting the scan lines;
  A switching element formed corresponding to the intersection of the scan line and the data line;
  A pixel electrode electrically connected to the switching element;
  A common electrode facing the pixel electrode;
  A dispersion system containing electrophoretic particles disposed between the common electrode and the pixel electrode;
  Driving means for driving the scanning lines and the data lines;
  An electro-optical device having control means for controlling the driving means,
  The control means performs a writing operation and a holding operation,
  The writing operation includes an operation of applying a potential based on image data to the pixel electrode in each of a plurality of fields,
  The holding operation includes an operation of opening the switching element after the writing operation and the common electrode and the pixel electrode are in different potential states.   A plurality of scan lines;
  A plurality of data lines intersecting the scan lines;
  A switching element formed corresponding to the intersection of the scan line and the data line;
  A pixel electrode electrically connected to the switching element;
  A common electrode facing the pixel electrode;
  A dispersion system containing electrophoretic particles disposed between the common electrode and the pixel electrode;
  Driving means for driving the scanning lines and the data lines;
  An electro-optical device having control means for controlling the driving means,
  The control means performs a writing operation and a holding operation,
  The writing operation includes an operation of applying a potential based on image data to the pixel electrode in each of a plurality of fields,
  The holding operation includes an operation of applying a predetermined voltage to the data line after the writing operation.   A plurality of scan lines;
  A plurality of data lines intersecting the scan lines;
  A switching element formed corresponding to the intersection of the scan line and the data line;
  A pixel electrode electrically connected to the switching element;
  A common electrode facing the pixel electrode;
  A dispersion system containing electrophoretic particles disposed between the common electrode and the pixel electrode;
  Driving means for driving the scanning lines and the data lines;
  An electro-optical device having control means for controlling the driving means,
  The control means performs a writing operation and a holding operation,
  The writing operation includes an operation of applying a potential based on image data to the pixel electrode in each of a plurality of fields,
  The holding operation includes an operation of applying a voltage for reducing a leakage current of the switching element to the scanning line after the writing operation.   The switching element is a transistor having a source terminal, a gate terminal, and a drain terminal,
  The source terminal is electrically connected to the data line;
  The gate terminal is electrically connected to the scan line;
  The electro-optical device according to claim 1, wherein the drain terminal is electrically connected to the pixel electrode.   The electro-optical device is capable of gradation display and binary display,
  The electro-optical device according to claim 1, wherein the control unit performs the holding operation when the binary display is performed.   An electronic apparatus comprising the electro-optical device according to any one of claims 1 to 5.   A plurality of scan lines;
  A plurality of data lines intersecting the scan lines;
  A switching element formed corresponding to the intersection of the scan line and the data line;
  A pixel electrode electrically connected to the switching element;
  A common electrode facing the pixel electrode;
  A method of driving an electro-optical device having a dispersion system including electrophoretic particles disposed between the common electrode and the pixel electrode,
  A writing step of applying a potential based on image data to the pixel electrode in each of a plurality of fields;
  And a step of opening the switching element after the writing step in a state where the common electrode and the pixel electrode are at different potentials.   A plurality of scan lines;
  A plurality of data lines intersecting the scan lines;
  A switching element formed corresponding to the intersection of the scan line and the data line;
  A pixel electrode electrically connected to the switching element;
  A common electrode facing the pixel electrode;
  A method of driving an electro-optical device having a dispersion system including electrophoretic particles disposed between the common electrode and the pixel electrode,
  A writing step of applying a potential based on image data to the pixel electrode in each of a plurality of fields;
  And a step of applying a predetermined voltage to the data line after the writing step.   A plurality of scan lines;
  A plurality of data lines intersecting the scan lines;
  A switching element formed corresponding to the intersection of the scan line and the data line;
  A pixel electrode electrically connected to the switching element;
  A common electrode facing the pixel electrode;
  A method of driving an electro-optical device having a dispersion system including electrophoretic particles disposed between the common electrode and the pixel electrode,
  A writing step of applying a potential based on image data to the pixel electrode in each of a plurality of fields;
  An electro-optical device driving method comprising: applying a voltage for reducing a leakage current of the switching element to the scanning line after the writing step.   The switching element is a transistor having a source terminal, a gate terminal, and a drain terminal,
  The source terminal is electrically connected to the data line;
  The gate terminal is electrically connected to the scan line;
  The method of driving an electro-optical device according to claim 7, wherein the drain terminal is electrically connected to the pixel electrode.   The electro-optical device is capable of gradation display and binary display,
  The method of driving an electro-optical device according to claim 7, wherein the control unit performs the holding operation when the binary display is performed.

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