JP5785371B2 - Electrophoretic display device driving method, electrophoretic display device, electrophoretic display device control circuit, and electronic apparatus - Google Patents

Description

  The present invention relates to a method for driving an electrophoretic display device, an electrophoretic display device driven by the driving method, a control circuit for the electrophoretic display device, and an electronic device including the electrophoretic display device.

  With this type of driving method, the quality of the image displayed on the electrophoretic display device can be improved. For example, Patent Document 1 describes a driving method for instructing setting of a reference driving voltage to a data line driving voltage power supply based on a conversion table between temperature and reference driving voltage stored in advance.

  Further, as an electrophoretic display device driven by this type of driving method, a device has been proposed in which each pixel unit includes a capacitor as a storage capacitor, and an electrophoretic element is driven by charges stored in the capacitor. . In this type of electrophoretic display device, an image displayed on the electrophoretic display device is often rewritten by writing a plurality of times.

Japanese Patent No. 4196615

  The electric resistance of the electrophoretic material constituting the electrophoretic element varies depending on the temperature. Then, the time constant changes and the speed of the potential difference drop (that is, the voltage drop) across the storage capacitor changes. Specifically, the electrical resistance of the electrophoretic material is lowered at a high temperature, the time constant is shortened, and the voltage drop is accelerated. On the other hand, at low temperatures, the electrical resistance of the electrophoretic material becomes high, the time constant becomes long, and the voltage drop becomes slow.

  In the above-mentioned Patent Document 1, no consideration is given to the voltage drop of the storage capacitor. Then, at a high temperature, for example, there is a technical problem that a period during which a voltage is applied to a storage capacitor or the like may be long (that is, an image rewriting period may be long). On the other hand, at a low temperature, there is a technical problem that electric power may be excessively consumed because the storage capacitor is recharged even though the voltage of the storage capacitor hardly decreases.

  The present invention has been made in view of the above problems, for example. An electrophoretic display device driving method, an electrophoretic display device, and an electrophoretic display capable of suppressing a voltage drop of a storage capacitor within a predetermined range regardless of temperature. An object is to propose a control circuit for a display device and an electronic device.

  In order to solve the above problems, a driving method for an electrophoretic display device according to the present invention includes a plurality of pixels respectively defined corresponding to a plurality of scanning lines and a plurality of data lines that intersect with each other. Each of the plurality of pixels is disposed between the pixel electrode and the counter electrode, the pixel electrode and the counter electrode disposed to face each other. And an electrophoretic element including electrophoretic particles, and a storage capacitor that is electrically connected to the pixel electrode and temporarily holds an image signal supplied to the pixel electrode. When the detected environmental temperature is the first temperature, one frame period, which is a period in which each of the plurality of scanning lines is selected once, is defined as a first time, and the detected environment is detected. The temperature is Higher than first temperature to a second temperature, the 1-frame period, and a short second time than the first time.

  According to the driving method of the electrophoretic display device of the present invention, the electrophoretic display device driven by the driving method corresponds to the intersection of the plurality of scanning lines and the plurality of data lines provided to intersect each other. The display unit includes a plurality of pixels each defined, and temperature detection means that detects an environmental temperature, for example, a temperature sensor. Each of the plurality of pixels is electrically connected to the pixel electrode and the counter electrode disposed opposite to each other, the electrophoretic element including the electrophoretic particles disposed between the pixel electrode and the counter electrode, and the pixel electrode. And a holding capacitor for temporarily holding an image signal supplied to the pixel electrode.

  Here, during the operation of the electrophoretic display device, a charge is stored in a storage capacitor (that is, a capacitor), and the electrophoretic element is driven by the stored charge, so that the display unit supports an image signal. The displayed image is displayed. The image displayed on the display unit is rewritten by writing a plurality of times.

  In the driving method, when the detected environmental temperature is the first temperature, one frame period, which is a period in which each of the plurality of scanning lines is selected once, is set as the first time. On the other hand, when the detected environmental temperature is the second temperature higher than the first temperature, one frame period is set to a second time shorter than the first time.

  The “second temperature” is set, for example, as an environmental temperature at which the contrast of the image displayed on the display unit starts to decrease beyond an allowable range.

  According to the inventor's research, the following matters have been found. That is, the electrical resistance of the electrophoretic material constituting the electrophoretic element varies depending on the temperature. As a result, the time constant changes depending on the temperature, and the voltage drop speed of the storage capacitor changes. For this reason, if no measures are taken and the image displayed on the display unit is always rewritten by writing a fixed number of times, the voltage drop is relatively fast at a relatively high environmental temperature. May be longer. On the other hand, when the environmental temperature is relatively low, the voltage drop is relatively slow, so that the storage capacitor is recharged relatively frequently, which may result in excessive power consumption.

  However, in the present invention, as described above, when the detected environmental temperature is the first temperature, one frame period is the first time, and the detected environmental temperature is the second temperature higher than the first temperature. In some cases, one frame period is a second time shorter than the first time. In other words, in the present invention, when the environmental temperature becomes the second temperature higher than the first temperature, one frame period is set to the second time shorter than the first time (in other words, the refresh rate increases). .

  At the second temperature, which is a relatively high temperature, the one-frame period is a relatively short second time corresponding to the voltage drop of the storage capacitor being relatively fast, so the storage capacitor is recharged relatively frequently, Accordingly, the voltage drop of the storage capacitor can be suppressed. On the other hand, at the first temperature, which is relatively low, one frame period is a relatively long first time corresponding to the voltage drop of the storage capacitor being relatively slow, so that the number of times the storage capacitor is charged is suppressed, Therefore, power consumption can be suppressed.

  In order to solve the above problems, an electrophoretic display device of the present invention is a display comprising a plurality of pixels respectively defined corresponding to the intersection of a plurality of scanning lines and a plurality of data lines provided to intersect each other. Each of the plurality of pixels is disposed between the pixel electrode and the counter electrode, and is disposed between the pixel electrode and the counter electrode. An electrophoretic element including electrophoretic particles; and a storage capacitor that is electrically connected to the pixel electrode and temporarily holds an image signal supplied to the pixel electrode, the detected ambient temperature being a first In the case of the temperature, a first frame period is a period in which each of the plurality of scanning lines is selected once, and the detected ambient temperature is a second temperature higher than the first temperature. In the case of The beam duration, further comprising a drive means for a short second time than the first time.

  According to the electrophoretic display device of the present invention, similarly to the above-described electrophoretic display device of the present invention, the voltage drop of the storage capacitor can be suppressed to a predetermined range regardless of the temperature.

  In order to solve the above problems, the control circuit of the electrophoretic display device according to the present invention includes a plurality of pixels respectively defined corresponding to a plurality of scanning lines and a plurality of data lines that intersect with each other. Each of the plurality of pixels is disposed between the pixel electrode and the counter electrode, the pixel electrode and the counter electrode disposed to face each other. A control circuit for an electrophoretic display device, comprising: an electrophoretic element including electrophoretic particles; and a storage capacitor that is electrically connected to the pixel electrode and temporarily holds an image signal supplied to the pixel electrode. When the detected environmental temperature is the first temperature, a signal indicating that one frame period, which is a period in which each of the plurality of scanning lines is selected once, is set as the first time. Output Environment temperature, if it is the first temperature second temperature higher than the one frame period, and outputs a signal indicating that a shorter second time than the first time.

  According to the control circuit of the electrophoretic display device of the present invention, similarly to the electrophoretic display device of the present invention described above, the voltage drop of the storage capacitor can be suppressed to a predetermined range regardless of the temperature.

  In order to solve the above problems, an electronic apparatus according to the present invention includes the above-described electrophoretic display device according to the present invention.

  According to the electronic apparatus of the present invention, since the electrophoretic display device of the present invention described above is provided, the voltage drop of the storage capacitor can be suppressed to a predetermined range regardless of the temperature. As a result, for example, since a reduction in contrast can be suppressed, various electronic devices that can display high-quality images, such as wristwatches, electronic paper, electronic notebooks, mobile phones, and portable audio devices, can be realized.

  The effect | action and other gain of this invention are clarified from the form for implementing demonstrated below.

1 is a block diagram illustrating an overall configuration of an electrophoretic display device according to an embodiment of the present invention. It is a block diagram which shows the structure of the display part of the electrophoretic display device which concerns on embodiment of this invention. 2 is an equivalent circuit diagram illustrating an electrical configuration of a pixel according to an embodiment of the present invention. FIG. 3 is a flowchart showing a main part of a method for driving an electrophoretic display device according to an embodiment of the present invention. It is an example of the table which prescribes | regulates the relationship between temperature, a frame rate, and the frequency | count of a flame | frame. It is a characteristic view which shows an example of the time change of the voltage of a storage capacity for every temperature. It is a perspective view which shows the structure of the electronic paper as an example of the electronic device to which the electrophoretic display apparatus is applied. It is a perspective view which shows the structure of the electronic notebook as another example of the electronic device to which an electrophoretic display apparatus is applied.

  Hereinafter, embodiments of an electrophoretic display device according to the present invention and an electronic apparatus including the electrophoretic display device will be described with reference to the drawings.

<Electrophoretic display device>
(Configuration of electrophoretic display device)
An electrophoretic display device according to an embodiment of the present invention will be described with reference to FIGS. In the following drawings, the scale of each layer / member is different for each layer / member to have a size recognizable on the drawing.

  First, the overall configuration of the electrophoretic display device according to the present embodiment will be described with reference to FIG. FIG. 1 is a block diagram showing the overall configuration of the electrophoretic display device according to this embodiment.

  In FIG. 1, the electrophoretic display device 1 includes a display unit 3, a control circuit 10, a temperature sensor 111, a display body drive circuit 130, and a display body power supply circuit 200. The display unit 3 and the control circuit 10 may be configured to be separable from each other.

  The temperature sensor 111 as an example of the “temperature detection means” according to the present invention detects the environmental temperature. Here, the temperature sensor 111 is arrange | positioned at the center of the back surface of the display part 3 (namely, panel), for example. Note that the position of the temperature sensor 111 is not limited to the center of the back surface of the display unit 3, but for example, the temperature of the environment such as the edge of the back surface of the display unit 3 or the part of the display frame that is not always touched by the user's hand. As long as the position is detectable (in other words, without being affected by the user's body temperature), it may be placed anywhere. Further, the temperature sensor 111 is not limited to one, and a plurality of temperature sensors 111 may be provided.

  A signal indicating the environmental temperature output from the temperature sensor 111 is converted into a digital value by an ADC (Analog Digital Converter) 112, and the converted value is stored in a RAM (Random Access Memory) 113.

  As an example of “driving means” according to the present invention, the control circuit 10 includes a CPU (Central Processing Unit) 101, a display drive circuit 102, a flash ROM (Read Only Memory) 103, and a RAM 104. .

  Here, the flash ROM 103 stores image data transferred from, for example, a personal computer. The RAM 104 temporarily holds image data to be drawn next time on the display unit 3. The display body drive control circuit 102 is based on, for example, the image data stored in the RAM 104, the environmental temperature stored in the RAM 113, and the like acquired via the CPU 101, and the display body power supply circuit 200 and the display body drive circuit. 130 is controlled to rewrite the image displayed on the display unit 3.

  The display body driving circuit 130 includes a scanning line driving circuit 131, a data line driving circuit 132, and a common potential supply circuit 133, which will be described later.

  Next, the display unit 3 of the electrophoretic display device 1 will be described with reference to FIG. FIG. 2 is a block diagram showing the configuration of the display unit of the electrophoretic display device according to this embodiment. In FIG. 2, for the convenience of explanation, among the members shown in FIG. 1, members that are not directly related are not shown.

  In FIG. 2, the display unit 3 includes m rows × n columns of pixels 20 arranged in a matrix (two-dimensional plane). The display unit 3 includes m scanning lines 40 (that is, scanning lines Y1, Y2,..., Ym) and n data lines 50 (that is, data lines X1, X2,..., Xn). It is provided so as to cross each other. Specifically, the m scanning lines 40 extend in the row direction (that is, the X direction), and the n data lines 50 extend in the column direction (that is, the Y direction). The pixels 20 are arranged corresponding to the intersections of the m scanning lines 40 and the n data lines 50.

  The control circuit 10 controls operations of the scanning line driving circuit 131, the data line driving circuit 132, and the common potential supply circuit 133. For example, the control circuit 10 supplies timing signals such as a clock signal and a start pulse to each circuit.

  Based on the timing signal supplied from the control circuit 10, the scanning line driving circuit 131 sequentially supplies a scanning signal in a pulse manner to each of the scanning lines Y1, Y2,. The data line driving circuit 132 supplies image signals to the data lines X1, X2,..., Xn based on the timing signal supplied from the control circuit 10. The common potential supply circuit 133 supplies the common potential Vcom to the common potential line 93.

  Various signals are input / output to / from the control circuit 10, the scanning line driving circuit 131, the data line driving circuit 132, and the common potential supply circuit 133, but descriptions of those that are not particularly related to the present embodiment are omitted. To do.

  Next, the basic configuration of the pixel 20 of the electrophoretic display device 1 will be described with reference to FIG. FIG. 3 is an equivalent circuit diagram showing an electrical configuration of the pixel according to the present embodiment.

  In FIG. 3, the pixel 20 includes a pixel switching transistor 24, a pixel electrode 21, a common electrode 22, an electrophoretic element 23, and a storage capacitor 27.

  The pixel switching transistor 24 is composed of, for example, an N-type transistor. The pixel switching transistor 24 has a gate electrically connected to the scanning line 40, a source electrically connected to the data line 50, and a drain electrically connected to the pixel electrode 21 and the storage capacitor 27. It is connected to the.

  The pixel switching transistor 24 is configured to pulse the image signal supplied from the data line driving circuit 132 (see FIG. 2) via the data line 50 via the scanning line 40 from the scanning line driving circuit 131 (see FIG. 2). Are output to the pixel electrode 21 and the storage capacitor 27 at a timing corresponding to the scanning signal supplied to the pixel.

  An image signal is supplied to the pixel electrode 21 from the data line driving circuit 132 via the data line 50 and the pixel switching transistor 24. The pixel electrode 21 is disposed so as to face the common electrode 22 through the electrophoretic element 23.

  The common electrode 22 as an example of the “counter electrode” according to the present invention is electrically connected to a common potential line 93 to which a common potential Vcom is supplied.

  The electrophoretic element 23 is composed of a plurality of microcapsules each containing electrophoretic particles.

  The storage capacitor 27 is composed of a pair of electrodes arranged opposite to each other with a dielectric film therebetween, one electrode is electrically connected to the pixel electrode 21 and the pixel switching transistor 24, and the other electrode is a common potential line 93. Is electrically connected. The image signal can be maintained for a certain period by the holding capacitor 27.

(Driving method of electrophoretic display device)
Next, a driving method of the electrophoretic display device 1 configured as described above will be described with reference to FIGS.

  A driving method of the electrophoretic display device 1 when the image displayed on the display unit 3 is rewritten will be described with reference to the flowchart of FIG. FIG. 4 is a flowchart showing a main part of the driving method of the electrophoretic display device according to this embodiment.

  In FIG. 4, first, when the screen rewriting button 121 (see FIG. 1) is pressed by the user, the CPU 101 in the control circuit 10 acquires the environmental temperature measured by the temperature sensor 111 stored in the RAM 113. (Step S101).

  Next, the CPU 101 rewrites the current image with reference to a table (see FIG. 5) that defines the relationship between the acquired environmental temperature and the temperature, the frame rate, and the number of frames stored in the ROM 103, for example. The frame rate is determined (step S102). FIG. 5 is an example of a table that defines the relationship between temperature, frame rate, and number of frames.

  Next, the CPU 101 determines whether or not the determined frame rate is different from the currently set frame rate (that is, at the time of the previous rewriting) (step S103). When it is determined that the determined frame rate is the same as the currently set frame rate (step S103: No), the CPU 101 displays an image displayed on the display unit 3 without changing the frame rate. The display body drive circuit 130 and the display body power supply circuit 200 are controlled via the display body drive control circuit 102 (step S104).

  On the other hand, when it is determined that the determined frame rate is different from the currently set frame rate (that is, when the environmental temperature has changed since the previous rewriting) (step S103: Yes), The CPU 101 updates the frame rate to the frame rate determined in the process of step S102 (step S105), and rewrites the image displayed on the display unit 3 at the updated frame rate. The display body drive circuit 130 and the display body power supply circuit 200 are controlled via the display body drive control circuit 102 (step S104).

  Here, the time change of the potential difference between both ends of the storage capacitor 27 will be described with reference to FIG. FIG. 6 is a characteristic diagram showing an example of the change over time of the voltage of the storage capacitor for each temperature.

  As shown in FIG. 6, when the environmental temperature is relatively high (see dotted line), the frame rate is higher than that at room temperature (see solid line), so the storage capacitor 27 is charged relatively frequently. For this reason, the degree of voltage drop of the storage capacitor 27 can be suppressed to the same level as that at room temperature. As a result, the effective voltage of the storage capacitor 27 can be maintained relatively high, and thus the image displayed on the display unit 3 can be rewritten in a relatively short time.

  On the other hand, when the environmental temperature is relatively low (see the one-dot chain line), since the frame rate is lower than that at room temperature, the holding capacity until the voltage drop of the holding capacity 27 is about the same as that at room temperature, for example. 27 is not charged. As a result, the number of times the storage capacitor 27 is charged can be suppressed, and the power consumption can be suppressed.

<Electronic equipment>
Next, electronic devices to which the above-described electrophoretic display device is applied will be described with reference to FIGS. Below, the case where the electrophoretic display device described above is applied to electronic paper and an electronic notebook is taken as an example.

  FIG. 7 is a perspective view illustrating a configuration of the electronic paper 400.

  As illustrated in FIG. 7, the electronic paper 400 includes the electrophoretic display device according to the above-described embodiment as a display unit 401. The electronic paper 400 has flexibility, and includes a main body 402 made of a rewritable sheet having the same texture and flexibility as conventional paper.

  FIG. 8 is a perspective view showing the configuration of the electronic notebook 500.

  As shown in FIG. 8, an electronic notebook 500 is obtained by bundling a plurality of electronic papers 400 shown in FIG. 7 and sandwiching them between covers 501. The cover 501 includes display data input means (not shown) for inputting display data sent from an external device, for example. Thereby, according to the display data, the display content can be changed or updated while the electronic paper is bundled.

  Since the electronic paper 400 and the electronic notebook 500 described above include the electrophoretic display device according to the above-described embodiment, the voltage drop of the storage capacitor can be suppressed within a predetermined range regardless of the temperature. As a result, for example, since a reduction in contrast can be suppressed, high-quality image display capable of displaying a high-quality image can be performed.

  In addition to these, the electrophoretic display device according to the present embodiment described above can be applied to the display unit of an electronic device such as a wristwatch, a mobile phone, or a portable audio device.

  In the embodiment described above, the environmental temperature is directly detected by the temperature sensor 111. However, for example, the amount of leakage current is detected, and the environmental temperature is indirectly determined based on the detected amount of leakage current. It may be detected. Alternatively, based on the detected variation in the leakage current, the variation in the electrical resistance of the electrophoretic material is estimated, and the image displayed on the display unit 3 is rewritten according to the estimated variation in the electrical resistance. The frame rate may be set or changed.

  The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist or concept of the invention that can be read from the claims and the entire specification, and an electrophoretic display with such a change. An apparatus driving method, an electrophoretic display device, a control circuit for the electrophoretic display device, and an electronic apparatus including the electrophoretic display device are also included in the technical scope of the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Electrophoretic display device, 3 ... Display part, 10 ... Control circuit, 20 ... Pixel, 21 ... Pixel electrode, 22 ... Common electrode, 23 ... Electrophoretic element, 27 ... Retention capacity, 40 ... Scanning line, 50 ... Data Line 111... Temperature sensor 130. Display body drive circuit 200 200 Display body power supply circuit

Claims (6)

Comprising a display unit comprising a respective defined plurality of pixels corresponding to intersections of a plurality of scanning lines and a plurality of data lines provided so as to cross each other, a temperature detecting means for detecting the environmental temperature, and the Each of the plurality of pixels includes a pixel electrode and a counter electrode that are disposed to face each other, an electrophoretic element that is disposed between the pixel electrode and the counter electrode, and includes electrophoretic particles; and A storage capacitor that is connected and temporarily holds an image signal supplied to the pixel electrode, and a method for driving an electrophoretic display device,
Rewriting the image displayed on the display unit by using a plurality of one frame periods each of which is selected once each of the plurality of scanning lines;
If the detected ambient temperature is the first temperature, the storage capacitor is charged at a first frame rate;
When the detected environmental temperature is a second temperature higher than the first temperature , the effective voltage of the storage capacitor can be maintained higher than charging the storage capacitor at the first frame rate. A driving method of an electrophoretic display device, wherein the storage capacitor is charged at a second frame rate shorter than the first frame rate. The method of driving an electrophoretic display device according to claim 1, wherein the longer the detected environmental temperature, the shorter the length of the one frame period. Pre-store a table that defines the relationship between the environmental temperature and the length of the one frame period;
The method for driving an electrophoretic display device according to claim 1, wherein the length of the one frame period is specified based on the detected environmental temperature and the stored table. A display unit composed of a plurality of pixels respectively defined corresponding to the intersection of a plurality of scanning lines and a plurality of data lines provided to intersect each other;
Temperature detecting means for detecting the environmental temperature, and
Each of the plurality of pixels is
A pixel electrode and a counter electrode disposed to face each other;
An electrophoretic element disposed between the pixel electrode and the counter electrode and including electrophoretic particles;
A storage capacitor that is electrically connected to the pixel electrode and temporarily holds an image signal supplied to the pixel electrode, and a plurality of one frame period in which each of the plurality of scanning lines is selected once. And rewriting the image displayed on the display unit, and when the detected environmental temperature is the first temperature, the storage capacitor is charged at a first frame rate, and the detected environmental temperature is When the second temperature is higher than the first temperature, the second temperature shorter than the first frame rate is maintained so that the effective voltage of the storage capacitor can be maintained higher than charging the storage capacitor at the first frame rate. Driving means for charging the holding capacitor at a frame rate of:
An electrophoretic display device comprising: A plurality of scanning lines provided to intersect with each other and a display unit composed of a plurality of pixels respectively defined corresponding to the intersection of the plurality of data lines, and a temperature detection means for detecting an environmental temperature, Each of the pixels includes a pixel electrode and a counter electrode disposed to face each other, an electrophoretic element including electrophoretic particles disposed between the pixel electrode and the counter electrode, and electrically connected to the pixel electrode. A storage capacitor that temporarily holds an image signal supplied to the pixel electrode, and a control circuit for an electrophoretic display device,
Rewriting an image displayed on the display unit using a plurality of one frame periods each of which is selected once for each of the plurality of scanning lines, and when the detected environmental temperature is a first temperature, charging the storage capacitor at a first frame rate, the more the detected ambient temperature, if it is higher than said first temperature second temperature, charging the storage capacitor at the first frame rate Control of an electrophoretic display device, wherein a signal indicating that the storage capacitor is charged at a second frame rate shorter than the first frame rate is output so that the effective voltage of the storage capacitor can be maintained high. circuit.   An electronic apparatus comprising the electrophoretic display device according to claim 4.

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