JP2004157450A - Electro-optical device and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electro-optical device for easily controlling data writing control. <P>SOLUTION: A data signal Dj supplied within an on-duration of a TFT 16 is held in a holding capacitance 17 in a unit circuit 31a. An amplifier 18 inputs the data signal Dj held in the holding capacitance 17, and applies a pixel voltage with a voltage value based on the data signal Dj to one of pixel electrodes 15 grasping a distribution system 23. Accordingly, the pixel voltage applied to one of the pixel electrodes 15 is kept approximately constant. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electro-optical device and an electronic device, and more particularly, to an electro-optical device having a dispersion system containing electrophoretic particles and an electronic device mounted with the electro-optical device.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an electrophoretic display device using an electrophoretic phenomenon has been known as a non-light emitting display device (see, for example, Patent Document 1). The electrophoresis phenomenon refers to a phenomenon in which, when an electric field is applied to a dispersion system in which fine particles (electrophoretic particles) are dispersed in a liquid (dispersion medium), the fine particles migrate due to Coulomb force.
[0003]
Here, a schematic configuration of the electrophoretic display device will be briefly described.
The electrophoretic display device is configured such that one electrode and the other electrode are opposed to each other at a predetermined interval, and a large number of dispersion systems as pixels, which are display units of an image, are arranged in a matrix therebetween. Then, the electrophoretic display device includes a peripheral circuit for applying an electric field to these dispersion systems.
[0004]
FIG. 10 is a sectional view of a main part of a display panel showing a dispersion system corresponding to one pixel.
In the dispersion system 61 serving as a pixel, a partition 66 is formed between an element substrate 63 provided with a pixel electrode 62 and the like and an opposing substrate 65 provided with a common electrode 64 and the like, and is formed by the electrodes 62 and 64 and the partition 66. A liquid (dispersion medium) 68 in which electrophoretic particles 67 are dispersed is filled in the space to be formed. As the common electrode 64 and the counter substrate 65, a material having a light transmitting property is used. Here, for example, when the binary display is realized, the dispersion medium 68 is dyed black, and white particles such as titanium oxide are used as the electrophoretic particles 67. Then, the electrophoretic particles 67 are charged so as to have either positive or negative charge.
[0005]
In such a display panel, a thin film transistor (hereinafter, referred to as a TFT) functioning as a scanning line, a data line, and a switching element is formed on the element substrate 63 in addition to the above-described pixel electrode 62 (FIG. 10). This is omitted).
[0006]
FIG. 11 is an explanatory diagram illustrating an equivalent circuit corresponding to the one pixel.
That is, the scanning lines 71 and the data lines 72 are provided on the element substrate 63 of the display panel along directions orthogonal to each other, and the TFTs 73 are provided corresponding to intersections thereof. The TFT 73 has a gate electrode connected to the scanning line 71, a source electrode connected to the data line 72, and a drain electrode connected to one pixel electrode 62 sandwiching the dispersion system 61. Note that a predetermined common voltage Vcom (for example, a ground voltage) is applied to the other common electrode 64 sandwiching the dispersion system 61.
[0007]
In such a configuration, the scanning line 71 is activated by a scanning line signal supplied from a scanning line driving circuit (not shown), and the TFT 73 is turned on during this active period. When a data line signal is supplied from a data line driving circuit (not shown) via the data line 72 and the turned-on TFT 73, a voltage is applied to the pixel electrode 62.
[0008]
Next, an operation when a voltage is applied to the pixel electrode 62 will be described.
When a potential difference is applied between the pixel electrode 62 and the common electrode 64, the electrophoretic particles 67 are attracted to one of the pixel electrode 62 and the common electrode 64 by Coulomb force. At this time, when the electrophoretic particles 67 are drawn to the transparent common electrode 64 side, the light incident from the common electrode 64 is reflected by the electrophoretic particles 67, and the color (white) of the electrophoretic particles 67 becomes visible. . On the other hand, when the electrophoretic particles 67 are attracted to the pixel electrode 62 side, the above-described incident light and reflected light are absorbed by the dispersion medium 68, and the color (black) stained by the dispersion medium 68 becomes visible. That is, the electrophoretic display device forms an image by individually controlling the movement position of the electrophoretic particles 67 of the dispersion system 61 for each of the large number of dispersion systems 61 arranged in a matrix on the display panel.
[0009]
[Patent Document 1]
JP-A-2002-116734
[0010]
[Problems to be solved by the invention]
By the way, in the dispersion system 61, the dispersion medium 68 has a certain viscosity in order to maintain the display state of an image, and the movement of the electrophoretic particles 67 that migrate the dispersion system 61 against the viscous resistance is slow (that is, Reaction rate is slow). On the other hand, the time during which the TFT 73 is turned on by the activation of the scanning line 71 (access time) is extremely short.
[0011]
Therefore, the time (reaction time) for the electrophoretic particles 67 to migrate through the dispersion system 61 becomes longer than the access time, and the electrophoretic particles 67 start to migrate substantially after the access time has elapsed. That is, a charge corresponding to the voltage (pixel voltage) supplied to the pixel electrode 62 during the ON time of the TFT 73 is accumulated between the two electrodes 62 and 64, and the electrophoretic particles 67 are affected by the electric field thereby. Starts to migrate the dispersion system 61.
[0012]
Therefore, the conventional electrophoretic display has the following problems. FIG. 12 is an explanatory diagram showing a transition of a pixel voltage in one field in a writing operation, for example. One field is a period in which each scan line is driven to write data once, and in a writing period (one frame), one image is formed by writing data n times.
[0013]
In the figure, an initial voltage V0 as a write voltage is supplied to a pixel electrode 62 corresponding to a pixel in an i-th row (i-th scanning line) and a j-th column (j-th data line), and an access time elapses. Then, at time t1, the electrophoretic particles 67 start to migrate. At this time, the potential difference between the pixel electrode 62 and the common electrode 64 gradually decreases as the electrophoretic particles 67 migrate. As a result, the pixel voltage Vij gradually decreases from the initial voltage V0, and becomes the value of the voltage V1 when one field is completed.
[0014]
On the other hand, the reflection brightness Iij of the pixel gradually increases as the electrophoretic particles 67 migrate under the influence of the electric field generated between the electrodes 62 and 64. However, the reflection brightness Iij does not reach the value corresponding to the initial voltage V0 given as the writing voltage at the time when one field is completed due to the drop of the pixel voltage Vij, and the reflection brightness Iij corresponds to the voltage V1. The value becomes the reflection lightness I1.
[0015]
As described above, conventionally, since the pixel voltage Vij applied to the pixel electrode 62 decreases with time, data cannot be written at a specified voltage, thereby deteriorating display quality and writing. There has been a problem that the operation becomes longer.
[0016]
SUMMARY An advantage of some aspects of the invention is to provide an electro-optical device and an electronic apparatus that can easily perform data writing control.
[0017]
[Means for Solving the Problems]
The electro-optical device according to the present invention is an electro-optical device having a dispersion system containing electrophoretic particles sandwiched between a first electrode and a second electrode facing the first electrode, wherein the electrophoretic particles A switching element that supplies a predetermined data signal for controlling the moving position of the signal, a signal holding unit that holds the data signal supplied via the switching element, and a data holding unit that holds the data signal. Application voltage control means for applying a corresponding voltage to the first electrode.
[0018]
According to this, the applied voltage control means controls the voltage applied to the first electrode to a substantially constant value even after the switching element is turned off, based on the data signal held in the signal holding means. Therefore, a decrease in the potential of the first electrode due to the migration of the electrophoretic particles is prevented. Thus, the voltage applied to the first electrode can be easily controlled to the specified voltage, and thus the data write control during the reset operation and the write operation can be easily performed.
[0019]
Further, the electro-optical device according to the present invention includes a plurality of scanning lines, a plurality of data lines, and unit circuits provided respectively corresponding to intersections of the plurality of scanning lines and the plurality of data lines. An electro-optical device including a dispersion system containing electrophoretic particles sandwiched between a first electrode and a second electrode opposed to the first electrode in the unit circuit, wherein the unit circuit is A scanning element to be turned on when a scanning line to be selected is selected, and a switching element for supplying a predetermined data signal supplied from a corresponding data line when the scanning line is in the conductive state, and holding the data signal supplied via the switching element. A signal holding unit; and an applied voltage control unit that applies a voltage corresponding to the data signal held by the signal holding unit to the first electrode.
[0020]
According to this, in each unit circuit, the applied voltage control means sets the voltage applied to the first electrode to a substantially constant value even after the switching element is turned off, based on the data signal held in the signal holding means. Control. Therefore, a decrease in the potential of the first electrode due to the migration of the electrophoretic particles is prevented. As a result, in each unit circuit provided corresponding to each pixel, the voltage applied to the first electrode can be easily controlled to a specified voltage. Control can be easily performed.
[0021]
In this electro-optical device, the voltage applied to the first electrode can be held for one frame period required to determine the moving position of the electrophoretic particles. According to this, the voltage applied to the first electrode can be held for one frame period during the reset operation or the write operation, so that the data write control during the reset operation and the write operation can be easily performed. It can be carried out.
[0022]
In this electro-optical device, the data signal held in the signal holding unit via the switching element includes a voltage having a positive polarity with respect to a voltage applied to the second electrode and a voltage applied to the second electrode. A voltage having the same voltage value or a voltage having a negative polarity with respect to the voltage applied to the second electrode.
[0023]
According to this, the reset voltage applied to the first electrode during the reset period is maintained at a substantially constant value, and the write voltage applied to the first electrode during the write period is maintained at a substantially constant value. You.
[0024]
In this electro-optical device, the signal holding unit is configured by a storage capacitor, and the applied voltage control unit is configured by an amplifier driven based on a voltage held by the storage capacitor.
[0025]
According to this, the data signal supplied via the switching element controlled to the conductive state is temporarily held in the storage capacitor, and the first electrode is supplied to the first electrode by an amplifier driven based on the voltage held by the storage capacitor. A voltage corresponding to the data signal is applied at a substantially constant value.
[0026]
An electronic apparatus according to the present invention has the electro-optical device according to any one of claims 1 to 5 mounted thereon.
According to this, image display with high display quality can be realized.
[0027]
BEST MODE FOR CARRYING OUT THE INVENTION
(First embodiment)
Hereinafter, a first embodiment of an electrophoretic display device as an electro-optical device embodying the present invention will be described with reference to FIGS.
[0028]
FIG. 1 is an exploded perspective view of a main part showing an electrophoretic display panel.
The electrophoretic display device includes an electrophoretic display panel (hereinafter, display panel) 11, which has an element substrate 12 and a counter substrate 13. The element substrate 12 is made of a material such as glass or a semiconductor, and a grid-like partition wall 14 is formed on the element substrate 12.
[0029]
More specifically, the display panel 11 has a display area Z1 and a peripheral area Z2 surrounding the display area Z1. Then, on the element substrate 12 corresponding to the display area Z1, a grid-shaped partition wall 14 is formed. The data lines X1 to Xn (see FIG. 3) are formed between the lower surface of the partition wall 14 extending in the X direction and the element substrate 12 in the partition wall 14 formed in a grid pattern. Further, in the partition wall 14 formed in a grid pattern, scanning lines Y1 to Ym (see FIG. 3) are formed between the lower surface of the partition wall 14 extending in the Y direction and the element substrate 12, respectively. The portions where the data lines X1 to Xn and the scanning lines Y1 to Ym intersect at right angles are electrically insulated by an insulating layer (not shown).
[0030]
Further, on the element substrate 12 in each space surrounded by the grid-shaped partition walls 14, a pixel electrode 15 (refer to FIG. 2) as a first electrode, a thin film transistor (hereinafter, referred to as a TFT) 16 as a switching element, A storage capacitor 17 as a means and an amplifier 18 as an applied voltage control means (each shown in FIG. 3) are formed.
[0031]
As shown in FIG. 2, a liquid (dispersion medium) 22 in which electrophoretic particles 21 are dispersed is filled in each space surrounded by the grid-shaped partition walls 14. In this embodiment, the dispersion medium 22 is dyed black with a dye. On the other hand, the electrophoretic particles 21 are white particles in the present embodiment, and are made of, for example, titanium oxide, and are charged with a positive charge. In the present embodiment, the dispersion medium 22 in which the electrophoretic particles 21 are dispersed is referred to as a dispersion system 23.
[0032]
The liquid black may be colored by dispersing black particles. Further, in the present embodiment, the dispersion system 23 is divided by the partition walls 14, but may be a microcapsule type dispersion system in which each space is formed by microcapsules.
[0033]
A sealing material 24 for sealing the dispersion system 23 filled in each space surrounded by the partition wall 14 is formed on the upper surface of the partition wall 14 formed in a grid pattern. A common electrode 25 as a second electrode is formed on the upper surface of the sealing material 24, and the above-described counter substrate 13 is formed on the upper surface of the common electrode 25. The sealing member 24, the common electrode 25, and the counter substrate 13 are each formed of a material having transparency.
[0034]
In such a display panel 11, a voltage having a positive polarity (hereinafter referred to as a first voltage) with respect to the common voltage Vcom is applied to the pixel electrode 15 in a state where a predetermined common voltage Vcom as a reference is applied to the common electrode 25. When applied, the electrophoretic particles 21 move toward the common electrode 25 due to Coulomb force. Conversely, when a voltage having a negative polarity (hereinafter, a second voltage) is applied to the pixel electrode 15 based on the common voltage Vcom, the electrophoretic particles 21 move toward the pixel electrode 15 due to Coulomb force. When the same voltage as the common voltage Vcom is applied to the pixel electrode 15, the Coulomb force disappears and the electrophoretic particles 21 stop at that position.
[0035]
Accordingly, light incident from the opposing substrate 13 is reflected by the electrophoretic particles 21, and the optical path length of the reflected light passing through the opposing substrate 13 and reaching the eyes corresponds to the position of the electrophoretic particles 21 in the thickness direction. As a result, the degree to which the incident light and the reflected light are absorbed by the dispersion medium 22 is proportional to the optical path length, so that the gray scale recognized by a person is determined by the position of the electrophoretic particles 21. That is, the closer the electrophoretic particles 21 are to the pixel electrode 15, the darker the electrophoretic particles 21 are, and the closer the electrophoretic particles 21 are to the common electrode 25, the whiter the electrophoretic particles 21 become.
[0036]
Next, the electrical configuration of the electrophoretic display device will be described with reference to FIG.
The electrophoretic display device includes a pixel unit 31, a scanning line driving circuit 32, a data line driving circuit 33, and a control circuit 34. The pixel section 31, the scanning line driving circuit 32, and the data line driving circuit 33 are formed on the surface of the element substrate 12 in the display panel 11.
[0037]
The pixel unit 31 has the plurality of data lines X1 to Xn extending along the X direction and the plurality of scanning lines Y1 to Ym extending along the Y direction. The pixel unit 31 has a unit circuit 31a for driving the dispersive system 23 which is a display unit (pixel) of an image corresponding to an intersection of each of the data lines X1 to Xn and each of the scanning lines Y1 to Ym. Is arranged. Each unit circuit 31a has the above-described TFT 16, storage capacitor 17, amplifier 18, and dispersion system 23, respectively.
[0038]
The scanning line driving circuit 32 sequentially selects a plurality of scanning lines Y1 to Ym at a predetermined timing based on various signals from the control circuit 34, outputs scanning signals SC1 to SCm, and outputs the scanning signals SC1 to SCm to each of the scanning lines Y1 to Ym. The connected unit circuits 31a are sequentially driven. Specifically, the scanning line drive circuit 32 scans the scanning signals SC1 to SC1 at a constant cycle during a reset period in which the position of the electrophoretic particles 21 is moved to a reset position described later or a writing period for displaying one image. SCm are sequentially generated and output. On the other hand, the scanning line driving circuit 32 does not output the scanning signals SC1 to SCm during the holding period for maintaining the image formed during the writing period.
[0039]
In this embodiment, the scanning line drive circuit 32 is formed in the peripheral area Z2 (see FIG. 1) of the display panel 11, and is configured by a thin film transistor formed on the element substrate 12 similarly to the TFT 16 described above. Of course, the scanning line drive circuit 32 may be configured as a component separate from the display panel 11 and mounted with an anisotropic conductive film or the like.
[0040]
The data line driving circuit 33 generates and outputs data signals D1 to Dn for each of the data lines X1 to Xn. Specifically, the data line driving circuit 33 is a unit circuit 31a connected to each of the data lines X1 to Xn, and is a unit circuit connected to each of the scanning lines Y1 to Ym selected by the scanning line driving circuit 32. The data signals D1 to Dn are output to 31a.
[0041]
The data line drive circuit 33 outputs data signals D1 to Dn for supplying a reset voltage to each unit circuit 31a during the reset period, and outputs each data signal during the write period, as described later. It outputs data signals D1 to Dn for supplying a write voltage to unit circuit 31a.
[0042]
In this embodiment, the data line drive circuit 33 is formed in the peripheral region Z2 (see FIG. 1) of the display panel 11, and is formed of a thin film transistor formed on the element substrate 12 in the same manner as the TFT 16 described above. Of course, the data line drive circuit 33 may be configured as a component separate from the display panel 11 and mounted with an anisotropic conductive film or the like.
[0043]
A control circuit 34 that controls the scanning line driving circuit 32 and the data line driving circuit 33 receives an input image signal VID and a basic clock CLK from an external device (not shown). The control circuit 34 generates reset data Drest and image data D based on the input image signal VID, and outputs the data to the data line driving circuit 33. As described later, the reset data Drest is output in a predetermined period before outputting the image data D.
[0044]
Further, the control circuit 34 outputs the data line side control clock signal CLKX for determining the timing of outputting each of the data signals D1 to Dn corresponding to the reset data Drest and the image data D based on the basic clock CLK. Output to the drive circuit 33. Further, the control circuit 34 outputs a scan line side control clock signal CLKY to the scan line drive circuit 32 for determining the timing of outputting each of the scan signals SC1 to SCm based on the basic clock CLK. .
[0045]
Next, the structure of the unit circuit 31a will be described in detail with reference to FIG. Note that, for convenience of explanation, FIG. 7 shows only the unit circuit 31a corresponding to the pixel on the i-th row (i-th scanning line Yi) and j-th column (j-th data line Xj).
[0046]
As described above, the unit circuit 31a includes the TFT 16, the storage capacitor 17, the amplifier 18, and the dispersion system 23. The TFT 16 of the unit circuit 31a is an N-channel transistor whose gate electrode is connected to a corresponding one of the scanning lines Yi extending in the Y direction, and whose source electrode is a corresponding one of the data lines extending in the X direction. Xj. Further, the drain electrode of the TFT 16 of the unit circuit 31 a is connected to one electrode of the storage capacitor 17 and to the input terminal of the amplifier 18. The other electrode of the storage capacitor 17 is grounded.
[0047]
The output terminal of the amplifier 18 is connected to one pixel electrode 15 that sandwiches the dispersion system 23. Then, as described above, the common voltage Vcom is applied to the other common electrode 25 sandwiching the dispersion system 23 of the unit circuit 31a.
[0048]
Therefore, when the scanning signal SCi supplied to the scanning line Yi becomes active and the TFT 16 is turned on, the data signal Dj supplied to the data line Xj is held in the storage capacitor 17 via the turned-on TFT 16. Then, the amplifier 18 is driven by the voltage stored in the storage capacitor 17.
[0049]
The amplifier 18 is a general analog buffer circuit, and the amplifier 18 is supplied with a power supply voltage Vcc. Then, the amplifier 18 outputs the power supply voltage Vcc as a voltage having a value corresponding to the data signal Dj held by the holding capacitor 17. That is, the voltage stored in the storage capacitor 17 is input to the amplifier 18, and a voltage having a value corresponding to the input voltage is applied from the amplifier 18 to the pixel electrode 15.
[0050]
Thus, in each unit circuit 31a, even after the scanning signal SCi becomes inactive and the TFT 16 is turned off, the amplifier 18 is driven by the voltage held in the holding capacitor 17. Therefore, the potential of the pixel electrode 15 does not drop due to the electrophoretic particles 21 migrating in the dispersion medium 22. That is, the potential difference between the pixel electrode 15 and the common electrode 25 sandwiching the dispersion system 23 does not change and is kept substantially constant.
[0051]
Next, the operation of the electrophoretic display device configured as described above will be described.
Now, a case where one image is displayed on the display panel 11 based on the input image signal VID will be described. As shown in FIG. 5, the control circuit 34 performs a reset operation in a reset period T1, a write operation in a write period T2, and a hold operation in a hold period T3 based on the input image signal VID. It is to be noted that, for the sake of explanation, although omitted here, when one image is displayed and then the image is rewritten, the reset operation, the write operation, and the holding operation are performed in the same manner.
[0052]
[Reset operation]
When the control circuit 34 receives the input image signal VID, it first performs a reset operation. The reset operation is performed to attract the electrophoretic particles 21 migrating the dispersion system 23 to one electrode side (the pixel electrode 15 side in the present embodiment) and to initialize the spatial state.
[0053]
In this reset operation, the control circuit 34 outputs to the scanning line driving circuit 32 a scanning line side control clock signal CLKY for sequentially selecting each of the scanning lines Y1 to Ym based on the scanning signals SC1 to SCm. The control circuit 34 also includes a reset data Drest and a data line side control for supplying a reset voltage (the above-described second voltage) to the unit circuits 31a on the scanning lines sequentially selected in response to the scanning signals SC1 to SCm. The clock signal CLKX is output to the data line drive circuit 33. The reset data Drest is set in a reset period T1 of one field (an n-field period is required when the response speed of the electrophoretic particles 21 is slow, but the pixel may be accessed only once and thereafter may be omitted). Output across.
[0054]
The scanning line driving circuit 32 sequentially outputs the scanning signals SC1 to SCm based on the scanning line side control clock signal CLKY, and sequentially selects the scanning lines Y1 to Ym. On the other hand, every time the scanning line driving circuit 32 selects one of the scanning lines Y1 to Ym, the data line driving circuit 33 outputs a data signal corresponding to the reset data Drest based on the data line side control clock signal CLKX. D1 to Dn are output to the data lines X1 to Xn, respectively.
[0055]
This causes the electrophoretic particles 21 of the entire dispersion system 23 to be held at the position attracted to the pixel electrode 15 side, so that the display panel 11 is reset to black. When the display panel 11 is reset to black, the control circuit 34 proceeds to the next writing operation.
[0056]
[Write operation and holding operation]
In the writing operation, the control circuit 34 outputs the scanning line side control clock signal CLKY to the scanning line driving circuit 32 for sequentially selecting each of the scanning lines Y1 to Ym based on the scanning signals SC1 to SCm, as described above. Further, the control circuit 34 supplies the write voltage (the first voltage, the second voltage, or the common voltage Vcom described above) to the unit circuits 31a on the sequentially selected scanning lines in response to the scanning signals SC1 to SCm. Data signal D and a data line side control clock signal CLKX to the data line driving circuit 33. This image data D has a writing period T2 of one field (an n-field period is required when the response speed of the electrophoretic particles 21 is slow, but the pixel may be accessed only once and may not be provided thereafter). Is output to
[0057]
Hereinafter, the details of the write operation / hold operation will be described with reference to FIG. Note that the writing period T2 (one frame) of the present embodiment is composed of n fields. That is, it is assumed that one image is completed with a response time of n field periods. Here, the writing operation in the pixel on the i-th row and the j-th column will be described, but the same writing is performed on the other pixels.
[0058]
The scanning line driving circuit 32 sequentially outputs the scanning signals SC1 to SCm based on the scanning line side control clock signal CLKY, and sequentially selects the scanning lines Y1 to Ym. Thus, the i-th scanning line Yi is activated by the scanning signal SCi. At this time, the data line driving circuit 33 outputs a data signal Dj to be supplied to the j-th data line Xj based on the data line side control clock signal CLKX.
[0059]
The data signal Dj is stored in the storage capacitor 17 of the unit circuit 31a corresponding to the pixel in the i-th row and the j-th column, and the amplifier 18 of the unit circuit 31a writes data based on the data signal Dj stored in the storage capacitor 17. A predetermined pixel voltage Vij as an input voltage is supplied to the pixel electrode 15.
[0060]
Next, the behavior of the electrophoretic particles 21 in the pixel at the i-th row and the j-th column will be described.
Since the above-described reset operation is performed before the writing operation, the electrophoretic particles 21 are drawn toward the pixel electrode 15 at the start of the writing operation. Therefore, when the pixel voltage Vij is applied to the pixel electrode 15, an electric field is applied from the pixel electrode 15 to the common electrode 25, and the electrophoretic particles 21 start to migrate.
[0061]
At this time, the reflection brightness Iij at the pixel on the i-th row and the j-th column is determined by the average movement amount of the electrophoretic particles 21 in the pixel. In this embodiment, since the electrophoretic particles 21 are white and the dispersion medium 22 is black, the reflection brightness Iij increases as the electrophoretic particles 21 approach the common electrode 25. FIG. 7 shows the reflection brightness Iij in this case. As shown in the drawing, the reflection brightness Iij gradually increases from time t1.
[0062]
Here, as described above, the pixel voltage Vij applied to the pixel electrode 15 is supplied from the amplifier 18 driven by the holding voltage of the holding capacitor 17 even after the scanning signal SCi becomes inactive. For this reason, the pixel voltage Vij supplied in the field 1 is kept substantially constant over the period of the field, and at the end of the field 1, the electrophoretic particles 21 move to the position corresponding to the given pixel voltage Vij. Up to the common electrode 25.
[0063]
Then, in the next field (here, field 2), as shown in FIG. 6, a voltage having the same voltage value as the voltage supplied in field 1 described above is continuously applied. At this time, as shown by a two-dot chain line in the figure, the scanning signals SC1 to SCm may be output again to write the same data to the storage capacitor 17, but if the voltage drop due to the leakage current of the storage capacitor 17 is small, This is unnecessary since the voltage written in field 1 is kept substantially constant. Under the influence of the electric field due to the held pixel voltage Vij, the electrophoretic particles 21 migrate the dispersion system 23 to a position closer to the common electrode 25.
[0064]
Thereafter, at time tn of field n, the electrophoretic particles 21 migrate to a predetermined position. That is, in the present embodiment, the electrophoretic particles 21 adhere to the common electrode 25 side. As a result, the reflection brightness Iij becomes a constant value from time tn as shown in FIG. Thus, the writing operation ends.
[0065]
When the writing operation is completed, the control circuit 34 shifts to a holding period T3 for holding one image formed in the immediately preceding writing period T2 until the next new input image signal VIN is input. Holds the display image.
[0066]
Therefore, the above-described electrophoretic display has the following effects.
(1) In the present embodiment, in the unit circuit 31a, the data signal Dj supplied during the ON period of the TFT 16 is stored in the storage capacitor 17. The amplifier 18 is driven based on the voltage stored in the storage capacitor 17, and the amplifier 18 has a substantially constant pixel voltage according to the data signal Dj even after the scanning line Yi becomes inactive and the TFT 16 is turned off. Vij is supplied to the pixel electrode 15. As a result, the pixel voltage Vij is kept substantially constant over n fields (one frame), and a decrease in the pixel voltage Vij due to the migration of the electrophoretic particles 21 is prevented. Therefore, data writing control during a writing operation can be performed extremely easily, and the display quality of an image displayed on the display panel 11 can be improved. In this embodiment, similarly, the data write control at the time of the reset operation can be easily performed.
[0067]
(2) In the present embodiment, since the pixel voltage Vij applied to the pixel electrode 15 can be kept substantially constant, data writing at a specified desired voltage becomes easy. Thus, a good display state can be obtained even when the specific resistance of the dispersion medium 22 is low.
[0068]
(3) In the present embodiment, since the pixel voltage Vij applied to the pixel electrode 15 can be kept substantially constant, the reset period T1 and the writing period T2 can be shortened.
[0069]
(4) Since the unit circuit 31a provided for each pixel includes only the TFT 16, the storage capacitor 17, and the amplifier 18, a very simple and inexpensive circuit configuration can be achieved.
[0070]
(Second embodiment)
Next, application of the electronic apparatus equipped with the electrophoretic display device described in the first embodiment will be described with reference to FIGS.
[0071]
FIG. 8 is a perspective view showing one configuration of a mobile personal computer. In the figure, a personal computer 41 includes a main body 43 having a keyboard 42 and a display unit 44 using the electrophoretic display device. Even in this case, the display unit 44 using the electrophoretic display device has the same effect as the above embodiment. As a result, the personal computer 41 can realize a high-quality image.
[0072]
FIG. 9 is a perspective view showing one configuration of a mobile phone. In the figure, a mobile phone 51 includes a plurality of operation buttons 52, an earpiece 53, a mouthpiece 54, and a display unit 55 using the electrophoretic display device. Even in this case, the display unit 55 using the electrophoretic display device has the same effect as the above embodiment. As a result, the mobile phone 51 can realize a high-quality image.
[0073]
Note that the above embodiments may be implemented with the following modifications.
In the above embodiments, the description has been given of the electrophoretic display device of the binary display. In addition, the present invention may be applied to an electrophoretic display device capable of gradation display. That is, when the above embodiments are applied, writing can be performed at a specified voltage while holding the pixel voltage Vij, so that multi-gradation display can be easily controlled.
[0074]
In the above embodiments, the case where the writing operation is completed in n fields has been described, but the writing operation may be completed in one field (= 1 frame).
In the above embodiments, the electrophoretic display device is a monochrome display, but may be applied to a color display. In this case, the display panel 11 has three types of dispersion systems, a dispersion system that performs red display, a dispersion system that performs green display, and a dispersion system that performs blue display.
[0075]
In each of the above embodiments, the reset operation was performed when one image was displayed. However, the reset operation was not performed and the position of the electrophoretic particles 21 of each dispersion system 23 previously displayed as an image is displayed for the next image display. Control may be performed to move the electrophoretic particles 21 to the position.
[0076]
Other examples of the electronic device equipped with the electrophoretic display device described in the second embodiment include an electronic book, an outdoor sign, a car navigation device, an electronic notebook, a calculator, a POS terminal, a device equipped with a touch panel, and the like. Is mentioned. That is, even when the electrophoretic display device is applied to these devices, the same effects as those of the above embodiments can be obtained.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing a main part of a configuration of an electrophoretic display panel according to a first embodiment.
FIG. 2 is a sectional view of a main part of the electrophoretic display panel.
FIG. 3 is an electric circuit diagram showing a schematic electric configuration of the electrophoretic display device.
FIG. 4 is an explanatory diagram showing a unit circuit.
FIG. 5 is a timing chart showing output data of a control circuit.
FIG. 6 is a timing chart at the time of a write operation / hold operation.
FIG. 7 is an explanatory diagram showing changes in pixel voltage and reflection brightness.
FIG. 8 is an external perspective view showing a configuration of a mobile personal computer for describing a second embodiment.
FIG. 9 is an external perspective view showing a configuration of a mobile phone for explaining a second embodiment.
FIG. 10 is a sectional view of a main part for describing a dispersion system.
FIG. 11 is an explanatory diagram showing an equivalent circuit corresponding to one pixel.
FIG. 12 is an explanatory diagram showing a transition of a pixel voltage in the related art.
[Explanation of symbols]
Reference numeral 15 denotes a pixel electrode as a first electrode, 16 denotes a thin film transistor (TFT) as a switching element, 17 denotes a storage capacitor as a signal holding means, 18 an amplifier as an applied voltage control means, 21 denotes electrophoretic particles, and 23 denotes dispersion. System, 25: Common electrode as second electrode, 31a: Unit circuit, Yi, Y1 to Ym: Scan line, Xj, X1 to Xn: Data line, Dj, D1 to Dn: Data signal.

Claims (6)

An electro-optical device having a dispersion system containing electrophoretic particles sandwiched between a first electrode and a second electrode opposed to the first electrode,
A switching element for supplying a predetermined data signal for controlling the movement position of the electrophoretic particles,
Signal holding means for holding the data signal supplied via the switching element,
An electro-optical device comprising: an applied voltage control unit configured to apply a voltage corresponding to the data signal held by the signal holding unit to the first electrode. Multiple scan lines;
Multiple data lines,
A unit circuit provided corresponding to each of the intersections of the plurality of scanning lines and the plurality of data lines,
An electro-optical device comprising a dispersion system containing electrophoretic particles sandwiched between a first electrode and a second electrode opposed to the first electrode, wherein the dispersion system is provided in the unit circuit,
The unit circuit includes:
A switching element that conducts when a corresponding scanning line is selected and supplies a predetermined data signal given from the corresponding data line when in the conducting state;
Signal holding means for holding the data signal supplied via the switching element,
An electro-optical device comprising: an applied voltage control unit configured to apply a voltage corresponding to the data signal held by the signal holding unit to the first electrode. 3. The electro-optical device according to claim 1, wherein a voltage applied to the first electrode can be held for one frame period necessary for determining a moving position of the electrophoretic particles. The data signal held by the signal holding means via the switching element is a voltage having a positive polarity with respect to a voltage applied to the second electrode, and a voltage having the same voltage value as the voltage applied to the second electrode. 4. The electro-optical device according to claim 1, wherein the voltage has a negative polarity based on a voltage applied to the second electrode. 5. 5. The signal holding device according to claim 1, wherein the signal holding device includes a holding capacitor, and the applied voltage control device includes an amplifier that is driven based on a voltage held by the holding capacitor. An electro-optical device according to any one of the preceding claims. An electronic apparatus on which the electro-optical device according to claim 1 is mounted.

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