JP2011075999A - Electrophoretic display device, method of driving the same, and electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct the driving voltage with high accuracy according to the temperature of an electrophoretic element and also achieve cost reduction and miniaturization of the device in an electrophoretic display device. <P>SOLUTION: This electrophoretic display device includes: a pair of first substrate (28) and a second substrate (29); the electrophoretic element (23) held between the first and second substrates; a pixel electrode (21) provided in each pixel on the first substrate; a common electrode (22) provided opposite to the pixel electrode on the second substrate; pixel circuits (24, 25, 110) provided in every pixel on the first substrate and electrically connected to the pixel electrodes; and correction means (221, 222) for detecting a leak current in the off state of at least one transistor constituting the pixel circuit, and correcting the driving voltage to be applied between the pixel electrode and the common electrode according to image data to a voltage suitable for the temperature of the electrophoretic element estimated based on the leak current. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electrophoretic display device, a driving method thereof, and a technical field related to an electronic apparatus.

  In this type of electrophoretic display device, in each of a plurality of pixels arranged in a display region, a driving voltage is applied to an electrophoretic element sandwiched between a pixel electrode and a common electrode according to a gradation to be displayed. Thus, an image is displayed. In such an electrophoretic display device, an optical characteristic (for example, light reflectance) of the electrophoretic element changes depending on the temperature. Therefore, a temperature sensor such as a thermistor is provided, and the electrophoretic display device corresponds to the temperature detected by the temperature sensor. A technique for changing (or correcting) the driving voltage applied to the electrophoretic element is known.

  For example, Patent Document 1 discloses a technique in an active matrix liquid crystal display device in which a transistor for detecting a leakage current due to light when a pixel transistor is off is disposed in the vicinity of an effective pixel region. For example, Patent Document 2 discloses a technique for forming a semiconductor element for detecting the temperature of a liquid crystal material in a liquid crystal panel in a liquid crystal display device.

JP 2005-31164 A JP 2000-338518 A

  However, according to the technique of providing the temperature sensor as described above, (i) the manufacturing cost increases because the temperature sensor is provided, or (ii) it is difficult to provide the temperature sensor in the vicinity of the electrophoretic element. For this reason, there is a technical problem that it may be difficult to accurately detect the temperature of the electrophoretic element.

  The present invention has been made in view of the above-described problems, for example, and can correct the drive voltage with high accuracy according to the temperature of the electrophoretic element, and can reduce the cost and size of the apparatus. It is an object of the present invention to provide a possible electrophoretic display device, a driving method thereof, and an electronic apparatus including the electrophoretic display device.

  In order to solve the above problems, an electrophoretic display device of the present invention is an electrophoretic display device having a display region in which a plurality of pixels are arranged, and includes a pair of first and second substrates, and the first and first substrates. An electrophoretic element sandwiched between two substrates, a pixel electrode provided for each pixel on the first substrate, a common electrode provided on the second substrate so as to face the pixel electrode, A pixel circuit provided for each pixel on the first substrate and electrically connected to the pixel electrode; and a leakage current when at least one transistor constituting the pixel circuit is turned off; And correction means for correcting a drive voltage to be applied between the common electrodes in accordance with image data to a voltage suitable for the temperature of the electrophoretic element estimated based on the leakage current.

  According to the electrophoretic display device of the present invention, during the operation, the electrophoretic display device is sandwiched between the pixel electrode provided for each pixel on the first substrate and the common electrode provided for the plurality of pixels on the second substrate. When an electrophoretic element is applied with a driving voltage corresponding to image data, an image is displayed in a display area in which a plurality of pixels are arranged. More specifically, an image potential based on image data is supplied to the pixel electrode via the pixel circuit, and a predetermined potential is supplied to the common electrode. As a result, a driving voltage corresponding to the image data is applied between the pixel electrode and the common electrode. For example, an electrophoretic element that is a microcapsule includes, as electrophoretic particles, for example, a plurality of negatively charged white particles and a plurality of positively charged black particles. Depending on the driving voltage applied between the pixel electrode and the common electrode, one of the negatively charged white particles and the positively charged black particles moves (ie, migrates) to the pixel electrode side. When the other moves to the common electrode side, an image is displayed on the second substrate side on which the common electrode is provided. The electrophoretic element is fixed between the first and second substrates with, for example, a resin binder or adhesive.

  The pixel circuit, for example, is configured to be able to hold a pixel switching transistor or an image signal that is electrically connected between the pixel switching transistor and the pixel electrode and supplied via the pixel switching transistor. The memory circuit is configured to include at least one transistor. The memory circuit is configured as, for example, an SRAM (Static Random Access Memory) or the like, and includes a plurality of transistors.

  In the present invention, in particular, a leakage current when at least one transistor constituting the pixel circuit is turned off is detected, and a driving voltage to be applied according to image data between the pixel electrode and the common electrode is estimated based on the leakage current. Correction means for correcting to a value suitable for the temperature of the electrophoretic element. For example, the correcting means is a driving IC (Integrated Circuit) that supplies a driving voltage to be applied between the pixel electrode and the common electrode to an electrophoretic display panel in which the electrophoretic element is sandwiched between the first and second substrates. As part of Here, since the pixel circuit is provided for each pixel in the display region on the first substrate, the temperature of at least one transistor constituting the pixel circuit is provided in the display region between the first and second substrates. It can be considered that the temperature of the electrophoretic element is almost the same or practically the same. Therefore, by detecting the leakage current when the at least one transistor constituting the pixel circuit is turned off by the correcting means, the temperature of the electrophoretic element can be estimated with high accuracy based on the detected leakage current. . Further, the correction means corrects the drive voltage to be applied between the pixel electrode and the common electrode to a voltage suitable for the temperature of the electrophoretic element estimated based on the leak current. In other words, the correcting means estimates the temperature of the electrophoretic element based on the detected leakage current, and sets the driving voltage so that a driving voltage suitable for the estimated temperature of the electrophoretic element is applied to the electrophoretic element. to correct. For example, the correction means has a table in which a plurality of voltages determined in advance experimentally or by simulation or the like as appropriate drive voltages with respect to the temperature of the electrophoretic element are defined, and from among the plurality of voltages, A voltage suitable for the temperature of the electrophoretic element estimated based on the leakage current is selected. Therefore, the driving voltage can be corrected with high accuracy according to the temperature of the electrophoretic element by the correcting means. Therefore, high-quality display can be performed. In addition, according to the present invention, the temperature of the electrophoretic element can be estimated by detecting the leakage current when the at least one transistor constituting the pixel circuit is turned off by the correcting unit. There is no need to provide a new temperature sensor (that is, separately from the pixel circuit) for detecting the temperature of the electrophoretic element on one substrate, and the electrophoretic display device can be reduced in cost and size. it can. In other words, according to the present invention, the leakage current when the at least one transistor constituting the pixel circuit is turned off is used as a temperature sensor for detecting the temperature of the electrophoretic element. There is no need to newly provide a sensor in the electrophoretic display device, and the electrophoretic display device can be reduced in cost and size.

  As described above, according to the electrophoretic display device of the present invention, the drive voltage can be corrected with high accuracy according to the temperature of the electrophoretic element, and high-quality display can be performed. Furthermore, the cost and size of the device can be reduced.

  In one aspect of the electrophoretic display device of the present invention, the pixel circuit is electrically connected between a pixel switching transistor, the pixel electrode, and the pixel switching transistor, and is supplied via the pixel switching transistor. A memory circuit capable of holding an image signal, and the correction means detects, as the leakage current, a leakage current when at least one transistor constituting the memory circuit is off.

  According to this aspect, for example, the leakage current when the at least one transistor constituting the memory circuit configured as an SRAM or the like and including a plurality of transistors is turned off is detected by the correction unit. Here, for example, in the case where the memory circuit is configured as an SRAM, a high potential power supply potential for holding an image signal is supplied to the plurality of memory circuits provided for each of the plurality of pixels. And a low potential power supply line to which a low potential power supply potential lower than the high potential power supply potential is supplied are commonly electrically connected. For this reason, all leakage currents when at least one transistor constituting each of the plurality of memory circuits is turned off flow into the low-potential power line. Therefore, the leakage current when at least one transistor in each of the plurality of memory circuits is off can be detected by the correction means as the sum of them in the low-potential power line, so that the temperature of the electrophoretic element can be estimated with high accuracy. can do. Accordingly, the drive voltage can be corrected with high accuracy according to the temperature of the electrophoretic element by the correcting means.

  In the aspect in which the pixel circuit includes a pixel switching transistor and a memory circuit, the correction unit may detect a leakage current when the pixel switching transistor is off as the leakage current.

  In this case, in addition to the transistors constituting the memory circuit, the leakage current when the pixel switching transistor is off is detected by the correcting means. Therefore, the amount of leakage current detected by the correction means can be increased compared to the case where only the leakage current when at least one transistor constituting the memory circuit is detected, for example. The temperature of the element can be estimated with higher accuracy. Therefore, the drive voltage can be corrected with higher accuracy according to the temperature of the electrophoretic element by the correction means.

  In the aspect in which the above-described pixel circuit includes a pixel switching transistor and a memory circuit, the pixel circuit can select any of the first and second control lines in accordance with an output signal based on the image signal output from the memory circuit. The correction means detects a leakage current when the at least one transistor constituting the switching circuit is turned off as the leakage current.

  In this case, a switch circuit is provided between the memory circuit and the pixel electrode. The switch circuit electrically connects one of the first and second control lines for supplying different potentials to the pixel electrode in accordance with an output signal output from the memory circuit based on the image signal. More specifically, the switch circuit includes, for example, a plurality of transistors, and a control line electrically connected to the pixel electrode is supplied with a first pixel potential according to an output from the memory circuit. Switching is performed between a first control line and a second control line that supplies a second pixel potential different from the first potential. As a result, the pixel electrode electrically connected to the first control line is supplied with the first pixel potential via the first control line, and the pixel electrically connected to the second control line. A second pixel potential is supplied to the electrode through the second control line.

  In particular, the leakage current when the at least one transistor constituting the switch circuit is turned off is detected by the correcting means. Therefore, the temperature of the electrophoretic element can be estimated with high accuracy by the correcting means, and the drive voltage can be corrected with high accuracy according to the temperature of the electrophoretic element.

  In another aspect of the electrophoretic display device of the present invention, the correction means applies a predetermined voltage to the electrophoretic element, detects an element current flowing through the electrophoretic element, and determines the driving voltage as the element current. And a voltage suitable for the temperature of the electrophoretic element estimated based on the leakage current.

  According to this aspect, the correction unit detects the element current flowing through the electrophoretic element in addition to the leakage current when the at least one transistor constituting the pixel circuit is off. Here, since the element current flows through the electrophoretic element, its temperature characteristic almost or completely coincides with the temperature characteristic of the electrophoretic element in practice. Therefore, by detecting the element current flowing through the electrophoretic element in addition to the leakage current when the at least one transistor constituting the pixel circuit is turned off by the correction unit, the correction means detects the element current based on the detected leakage current and element current. The temperature of the electrophoretic element can be estimated with high accuracy. Therefore, it becomes possible to correct the driving voltage with higher accuracy according to the temperature of the electrophoretic element by the correcting means.

  In the aspect in which the correction unit detects the element current, the correction unit may apply the predetermined voltage to the electrophoretic element by generating a potential difference between the adjacent pixel electrodes.

  In this case, an element current can be generated in the electrophoretic element by a potential difference between adjacent pixel electrodes, and the element current can be detected reliably. Therefore, the temperature of the electrophoretic element can be estimated with higher accuracy.

  In the aspect in which the correction unit measures the element current, the correction unit may apply the predetermined voltage to the electrophoretic element by generating a potential difference between the pixel electrode and the common electrode.

  In this case, an element current can be generated in the electrophoretic element due to a potential difference between the pixel electrode and the common electrode, and the element current can be reliably detected. Therefore, the temperature of the electrophoretic element can be estimated with higher accuracy.

  In the aspect in which the correction unit measures the element current, the correction unit applies the predetermined voltage to the electrophoretic element at different timings to each of a plurality of divided regions obtained by dividing the display region. The element current may be detected for each of the divided regions.

  In this case, the temperature of the electrophoretic element can be estimated for each divided region. Therefore, the drive voltage can be corrected more appropriately by the correction means in accordance with the temperature estimated for each divided region.

  In order to solve the above problems, a driving method of an electrophoretic display device according to the present invention is an electrophoretic display device having a display region in which a plurality of pixels are arranged, and includes a pair of first and second substrates, An electrophoretic element sandwiched between a first substrate and a second substrate; a pixel electrode provided for each pixel on the first substrate; and a pixel electrode provided on the second substrate so as to face the pixel electrode. An electrophoretic display device driving method for driving an electrophoretic display device comprising a common electrode and a pixel circuit provided for each pixel on the first substrate and electrically connected to the pixel electrode. A detection step of detecting a leakage current when at least one transistor constituting the pixel circuit is turned off, and a drive voltage to be applied according to image data between the pixel electrode and the common electrode based on the leakage current Estimated That corrects the voltage suitable for the temperature of the electrophoretic element and a correction step.

  According to the driving method of the electrophoretic display device of the invention, the leakage current when the at least one transistor constituting the pixel circuit is turned off is detected by the detection step. Therefore, the temperature of the electrophoretic element can be estimated with high accuracy based on the leakage current. Furthermore, the drive voltage to be applied according to the image data between the pixel electrode and the common electrode is corrected to a voltage suitable for the temperature of the electrophoretic element estimated based on the leak current detected in the detection process. to correct. Therefore, the drive voltage can be corrected with high accuracy according to the temperature of the electrophoretic element. Therefore, high-quality display can be performed.

  Various aspects similar to the various aspects related to the electrophoretic display device of the present invention described above can be applied as appropriate to the driving method of the electrophoretic display device according to the present invention.

  In order to solve the above problems, an electronic apparatus of the present invention includes the above-described electrophoretic display device of the present invention (including various aspects thereof).

  According to the electronic apparatus of the present invention, since the electrophoretic display device of the present invention described above is provided, high-quality display can be performed, for example, wristwatch, electronic paper, electronic notebook, mobile phone, mobile phone, etc. Various electronic devices such as audio equipment can be realized.

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

It is a block diagram which shows the whole structure of the electrophoretic display panel which concerns on 1st Embodiment. FIG. 3 is an equivalent circuit diagram illustrating an electrical configuration of a pixel according to the first embodiment. It is a fragmentary sectional view in the display field of the electrophoretic display panel concerning a 1st embodiment. It is a schematic diagram which shows the structure of a microcapsule. It is a block diagram which shows the structure of the drive circuit of the electrophoretic display device which concerns on 1st Embodiment. It is a block diagram which shows the structure of the temperature detection circuit which concerns on 1st Embodiment. It is a block diagram for demonstrating the correction | amendment operation | movement of the drive voltage by the drive circuit of the electrophoretic display device which concerns on 1st Embodiment. It is a block diagram for demonstrating the correction | amendment operation | movement of the drive voltage by the drive circuit of the electrophoretic display device which concerns on 2nd Embodiment. It is a block diagram for demonstrating the correction | amendment operation | movement of the drive voltage by the drive circuit of the electrophoretic display device which concerns on 3rd Embodiment. It is a block diagram for demonstrating the correction | amendment operation | movement of the drive voltage by the drive circuit of the electrophoretic display device which concerns on 4th Embodiment. It is a schematic diagram which shows an example of the display image in the display area at the time of the drive voltage correction | amendment operation | movement by the drive circuit of the electrophoretic display apparatus which concerns on 4th Embodiment. It is a schematic diagram which shows an example of the display image in the display area at the time of the drive voltage correction | amendment operation | movement by the drive circuit of the electrophoretic display apparatus which concerns on the modification of 4th Embodiment. It is a schematic diagram for demonstrating the state of the mutually adjacent pixel of the division area which all the pixels display the mutually same gradation at the time of the drive voltage correction | amendment operation | movement based on the modification of 4th Embodiment. It is a block diagram for demonstrating the correction | amendment operation | movement of the drive voltage by the drive circuit of the electrophoretic display device which concerns on 5th Embodiment. It is a perspective view which shows the structure of the electronic paper which is 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 which is an example of the electronic device to which the electrophoretic display apparatus is applied.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, an active matrix driving type electrophoretic display device, which is an example of the electrophoretic display device of the present invention, is taken as an example.

<First Embodiment>
The electrophoretic display device according to the first embodiment will be described with reference to FIGS.

  First, the overall configuration of the electrophoretic display panel provided in the electrophoretic display device according to the present embodiment will be described with reference to FIGS. 1 and 2.

  FIG. 1 is a block diagram showing the overall configuration of the electrophoretic display panel according to this embodiment.

  In FIG. 1, an electrophoretic display panel 1 according to this embodiment has a display region 3a in which pixels 20 of m rows × n columns are arranged in a matrix (two-dimensional plane). In the display area 3a, m scanning lines 40 (that is, scanning lines Y1, Y2,..., Ym) and n data lines 50 (that is, data lines X1, X2,..., Xn) intersect each other. It is provided to do. 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 electrophoretic display panel 1 includes a scanning line driving circuit 60 and a data line driving circuit 70.

  The scanning line driving circuit 60 sequentially supplies a scanning signal in a pulse manner to each of the scanning lines Y1, Y2,..., Ym based on the timing signal. The data line driving circuit 70 supplies image signals to the data lines X1, X2,..., Xn based on the timing signal. The image signal takes a binary level of a high potential level (hereinafter referred to as “high level”, for example, 5 V) or a low potential level (hereinafter referred to as “low level”, for example, 0 V).

  Here, each pixel 20 is electrically connected to a high potential power line 91, a low potential power line 92, a common potential line 93, a first control line 94, and a second control line 95. The high potential power supply line 91, the low potential power supply line 92, the common potential line 93, the first control line 94, and the second control line 95 are typically in the row direction (X direction) as shown in FIG. Each pixel column composed of the pixels 20 arranged along the line is wired in common to the pixels 20 belonging to the pixel column.

  FIG. 2 is an equivalent circuit diagram illustrating the electrical configuration of the pixel.

  In FIG. 2, the pixel 20 includes a pixel switching transistor 24, a memory circuit 25, a switch circuit 110, a pixel electrode 21, a common electrode 22, and an electrophoretic element 23. The pixel switching transistor 24, the memory circuit 25, and the switch circuit 110 constitute an example of the “pixel circuit” according to the present invention.

  The pixel switching transistor 24 is configured by an N-type transistor as an example. The pixel switching transistor 24 has its gate electrically connected to the scanning line 40, its source electrically connected to the data line 50, and its drain electrically connected to the input terminal N 1 of the memory circuit 25. It is connected to the. The pixel switching transistor 24 is configured to pulse the image signal supplied from the data line driving circuit 70 (see FIG. 1) via the data line 50 via the scanning line 40 from the scanning line driving circuit 60 (see FIG. 1). Is output to the input terminal N1 of the memory circuit 25 at a timing corresponding to the scanning signal supplied to the memory circuit 25.

  The memory circuit 25 includes inverter circuits 25a and 25b, and is configured as an SRAM.

  The inverter circuits 25a and 25b have a loop structure in which the other output terminal is electrically connected to the input terminals of each other. That is, the input terminal of the inverter circuit 25a and the output terminal of the inverter circuit 25b are electrically connected to each other, and the input terminal of the inverter circuit 25b and the output terminal of the inverter circuit 25a are electrically connected to each other. The input terminal of the inverter circuit 25a is configured as the input terminal N1 of the memory circuit 25, and the output terminal of the inverter circuit 25a is configured as the output terminal N2 of the memory circuit 25.

  The inverter circuit 25a has an N-type transistor 25a1 and a P-type transistor 25a2. The gates of the N-type transistor 25 a 1 and the P-type transistor 25 a 2 are electrically connected to the input terminal N 1 of the memory circuit 25. The source of the N-type transistor 25a1 is electrically connected to a low potential power supply line 92 to which a low potential power supply potential Vss is supplied. The source of the P-type transistor 25a2 is electrically connected to a high potential power supply line 91 to which a high potential power supply potential Vdd is supplied. The drains of the N-type transistor 25 a 1 and the P-type transistor 25 a 2 are electrically connected to the output terminal N 2 of the memory circuit 25.

  The inverter circuit 25b has an N-type transistor 25b1 and a P-type transistor 25b2. The gates of the N-type transistor 25 b 1 and the P-type transistor 25 b 2 are electrically connected to the output terminal N 2 of the memory circuit 25. The source of the N-type transistor 25b1 is electrically connected to a low potential power supply line 92 to which a low potential power supply potential Vss is supplied. The source of the P-type transistor 25b2 is electrically connected to a high potential power supply line 91 to which a high potential power supply potential Vdd is supplied. The drains of the N-type transistor 25 b 1 and the P-type transistor 25 b 2 are electrically connected to the input terminal N 1 of the memory circuit 25.

  When a high level image signal is input to the input terminal N1, the memory circuit 25 outputs a low potential power supply potential Vss from the output terminal N2, and when a low level image signal is input to the input terminal N1. The high potential power supply potential Vdd is output from the output terminal N2. That is, the memory circuit 25 outputs the low potential power supply potential Vss or the high potential power supply potential Vdd depending on whether the input image signal is at a high level or a low level. In other words, the memory circuit 25 is configured to be able to store the input image signal as the low potential power supply potential Vss or the high potential power supply potential Vdd.

  The switch circuit 110 includes a first transmission gate 111 and a second transmission gate 112.

  The first transmission gate 111 includes a P-type transistor 111p and an N-type transistor 111n. The sources of the P-type transistor 111p and the N-type transistor 111n are electrically connected to the first control line 94. The drains of the P-type transistor 111p and the N-type transistor 111n are electrically connected to the pixel electrode 21. The gate of the P-type transistor 111p is electrically connected to the input terminal N1 of the memory circuit 25, and the gate of the N-type transistor 111n is electrically connected to the output terminal N2 of the memory circuit 25.

  The second transmission gate 112 includes a P-type transistor 112p and an N-type transistor 112n. The sources of the P-type transistor 112p and the N-type transistor 112n are electrically connected to the second control line 95. The drains of the P-type transistor 112p and the N-type transistor 112n are electrically connected to the pixel electrode 21. The gate of the P-type transistor 112p is electrically connected to the output terminal N2 of the memory circuit 25, and the gate of the N-type transistor 112n is electrically connected to the input terminal N1 of the memory circuit 25.

  The switch circuit 110 selectively selects one of the first control line 94 and the second control line 95 in accordance with the image signal input to the memory circuit 25, and selects one of the control lines. The control line is electrically connected to the pixel electrode 21.

  Specifically, when a high-level image signal is input to the input terminal N1 of the memory circuit 25, the low-potential power supply potential Vss is output from the memory circuit 25 to the gates of the N-type transistor 111n and the P-type transistor 112p. Since the high potential power supply potential Vdd is output to the gates of the P-type transistor 111p and the N-type transistor 112n, only the P-type transistor 112p and the N-type transistor 112n constituting the second transmission gate 112 are turned on. The P-type transistor 111p and the N-type transistor 111n constituting one transmission gate 111 are turned off. On the other hand, when a low-level image signal is input to the input terminal N1 of the memory circuit 25, the high potential power supply potential Vdd is output from the memory circuit 25 to the gates of the N-type transistor 111n and the P-type transistor 112p, and the P-type By outputting the low-potential power supply potential Vss to the gates of the transistor 111p and the N-type transistor 112n, only the P-type transistor 111p and the N-type transistor 111n constituting the first transmission gate 111 are turned on, and the second transmission The P-type transistor 112p and the N-type transistor 112n constituting the gate 112 are turned off. That is, when a high-level image signal is input to the input terminal N1 of the memory circuit 25, only the second transmission gate 112 is turned on, while a low-level image signal is input to the input terminal N1 of the memory circuit 25. Is input, only the first transmission gate 111 is turned on.

  Each pixel electrode 21 of the plurality of pixels 20 is electrically connected to the first control line 94 or the second control line 95 that is alternatively selected according to the image signal by the switch circuit 110. At that time, the pixel electrode 21 of each of the plurality of pixels 20 is supplied with the first potential S1 or the second potential S2 as a pixel potential according to the on / off state of the switch 94s or 95s, or is in a high impedance state. Is done.

  More specifically, for the pixel 20 to which the low-level image signal is supplied, only the first transmission gate 111 is turned on, and the pixel electrode 21 of the pixel 20 is electrically connected to the first control line 94. The first potential S1 is supplied in accordance with the on / off state of the switch 94s, or a high impedance state is established. On the other hand, for the pixel 20 to which the high-level image signal is supplied, only the second transmission gate 112 is turned on, and the pixel electrode 21 of the pixel 20 is electrically connected to the second control line 95, The second potential S2 is supplied according to the on / off state of the switch 95s, or the high impedance state is set.

  The pixel electrode 21 is disposed so as to face the common electrode 22 through the electrophoretic element 23. The common electrode 22 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.

  Next, a specific configuration of the electrophoretic display panel according to the present embodiment will be described with reference to FIGS. 3 and 4.

  FIG. 3 is a partial cross-sectional view of the display area of the electrophoretic display panel according to this embodiment.

  In FIG. 3, the electrophoretic display panel 1 is configured such that an electrophoretic element 23 is sandwiched between an element substrate 28 and a counter substrate 29. In the present embodiment, description will be made on the assumption that an image is displayed on the counter substrate 29 side. The element substrate 28 is an example of a “first substrate” according to the present invention, and the counter substrate 29 is an example of a “second substrate” according to the present invention.

  The element substrate 28 is a substrate made of, for example, glass or plastic. Although not shown here on the element substrate 28, the pixel switching transistor 24, the memory circuit 25, the switch circuit 110, the scanning line 40, the data line 50, and the high potential power supply line 91 described above with reference to FIG. 2. A laminated structure in which the low potential power supply line 92, the common potential line 93, the first control line 94, the second control line 95, and the like are formed is formed. A plurality of pixel electrodes 21 are provided in a matrix on the upper layer side of the stacked structure.

  The counter substrate 29 is a transparent substrate made of, for example, glass or plastic. On the surface of the counter substrate 29 facing the element substrate 28, the common electrode 22 is formed in a solid shape so as to face the plurality of pixel electrodes 9a. The common electrode 22 is formed of a transparent conductive material such as magnesium silver (MgAg), indium / tin oxide (ITO), indium / zinc oxide (IZO), or the like.

  The electrophoretic element 23 is composed of a plurality of microcapsules 80 each including electrophoretic particles, and is fixed between the element substrate 28 and the counter substrate 29 by a binder 30 and an adhesive layer 31 made of, for example, resin. . In the electrophoretic display panel 1 according to this embodiment, in the manufacturing process, an electrophoretic sheet in which the electrophoretic element 23 is fixed to the counter substrate 29 side in advance by the binder 30 is separately manufactured. It is bonded to the element substrate 28 side where is formed by an adhesive layer 31.

  One or a plurality of microcapsules 80 are sandwiched between the pixel electrode 21 and the common electrode 22 and arranged in one pixel 20 (in other words, with respect to one pixel electrode 21).

  FIG. 4 is a schematic diagram showing the configuration of the microcapsule. In addition, in FIG. 4, the cross section of the microcapsule is shown typically.

  In FIG. 4, the microcapsule 80 is formed by enclosing a dispersion medium 81, a plurality of white particles 82, and a plurality of black particles 83 inside a coating 85. The microcapsule 80 is formed in a spherical shape having a particle size of about 50 μm, for example.

  The coating 85 functions as an outer shell of the microcapsule 80 and is formed of a translucent polymer resin such as acrylic resin such as polymethyl methacrylate and polyethyl methacrylate, urea resin, and gum arabic.

  The dispersion medium 81 is a medium for dispersing the white particles 82 and the black particles 83 in the microcapsules 80 (in other words, in the coating 85). Examples of the dispersion medium 81 include water, alcohol solvents such as methanol, ethanol, isopropanol, butanol, octanol, and methyl cellosolve, various esters such as ethyl acetate and butyl acetate, and ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone. , Aliphatic hydrocarbons such as pentane, hexane and octane, alicyclic hydrocarbons such as cyclohexane and methylcyclohexane, benzene, toluene, xylene, hexylbenzene, hebutylbenzene, octylbenzene, nonylbenzene, decylbenzene, undecyl Aromatic hydrocarbons such as benzenes with long chain alkyl groups such as benzene, dodecylbenzene, tridecylbenzene, tetradecylbenzene, etc., halo such as methylene chloride, chloroform, carbon tetrachloride, 1,2-dichloroethane, etc. Emissions of hydrocarbons, carboxylate or other oils may be used singly or as a mixture. In addition, a surfactant may be added to the dispersion medium 81.

  The white particles 82 are particles (polymer or colloid) made of a white pigment such as titanium dioxide, zinc white (zinc oxide), and antimony trioxide, and are negatively charged, for example.

  The black particles 83 are particles (polymer or colloid) made of a black pigment such as aniline black or carbon black, and are positively charged, for example.

  For this reason, the white particles 82 and the black particles 83 can move in the dispersion medium 81 by the electric field generated by the potential difference between the pixel electrode 21 and the common electrode 22.

  These pigments include electrolytes, surfactants, metal soaps, resins, rubbers, oils, varnishes, charge control agents composed of particles such as compounds, titanium-based coupling agents, aluminum-based coupling agents, silanes as necessary. A dispersant such as a system coupling agent, a lubricant, a stabilizer, and the like can be added.

  3 and FIG. 4, when a voltage is applied between the pixel electrode 21 and the common electrode 22 so that the potential of the common electrode 22 is relatively high, the positively charged black particles 83 are While being attracted to the pixel electrode 21 side in the microcapsule 80 by the Coulomb force, the negatively charged white particles 82 are attracted to the common electrode 22 side in the microcapsule 80 by the Coulomb force. As a result, the white particles 82 gather on the display surface side (that is, the common electrode 22 side) in the microcapsule 80, so that the color of the white particles 82 (that is, white) can be displayed in the display region 3a. Conversely, when a voltage is applied between the pixel electrode 21 and the common electrode 22 so that the potential of the pixel electrode 21 becomes relatively high, the negatively charged white particles 82 are generated by the Coulomb force. While attracted to the electrode 21 side, the positively charged black particles 83 are attracted to the common electrode 22 side by Coulomb force. As a result, the black particles 83 gather on the display surface side of the microcapsule 80, whereby the color of the black particles 83 (that is, black) can be displayed in the display area 3a.

  Depending on the distribution state of the white particles 82 and the black particles 83 between the pixel electrode 21 and the common electrode 22, it is also possible to display gray such as light gray, gray, dark gray and the like, which is an intermediate gradation between white and black. is there. Moreover, red, green, blue, etc. can be displayed by replacing the pigment used for the white particle 82 and the black particle 83 with pigments, such as red, green, and blue, for example.

  Next, a driving circuit for driving the electrophoretic display panel 1 described above will be described with reference to FIGS. The driving circuit described below may be built in the electrophoretic display panel 1 together with the scanning line driving circuit 60, the data line driving circuit 70, or the like. For example, the driving circuit may be provided outside the panel as an external circuit. You may make it mount in the electrophoresis display panel 1. FIG. Further, at least one of the scanning line driving circuit 60 and the data line driving circuit 70 may be provided as an external circuit and mounted on the electrophoretic display panel 1.

  FIG. 5 is a block diagram schematically showing a configuration of a drive circuit for driving the electrophoretic display panel according to the present embodiment.

  In FIG. 5, the electrophoretic display device according to the present embodiment includes the electrophoretic display panel 1 described above with reference to FIGS. 1 to 4 and a drive circuit 200.

  The drive circuit 200 includes a controller 290, a power supply circuit 210, and a drive voltage control unit 220, and is configured as a drive IC.

  The controller 290 controls the operation of the electrophoretic display panel 1 and controls the operations of the scanning line driving circuit 60 and the data line driving circuit 70 (see FIG. 1), the power supply circuit 210, and the driving voltage control unit 220.

  The power supply circuit 210 is configured to be able to supply various power sources for driving the electrophoretic display panel 1. The power supply circuit 210 supplies the high potential power supply line 91 with the high potential power supply potential Vdd, the low potential power supply line 92 with the low potential power supply potential Vss, the common potential line 93 with the common potential Vcom, A first potential S1 is supplied to the control line 94, and a second potential S2 is supplied to the second control line 95, respectively. The power supply circuit 210 also supplies power for driving the scanning line driving circuit 60, the data line driving circuit 70, and the like.

  The drive voltage controller 220 controls the drive voltage to be applied between the pixel electrode 21 and the common electrode 22 according to the image data.

  Particularly in the present embodiment, the drive voltage control unit 220 includes a temperature detection circuit 221 and a drive voltage parameter table 222. The temperature detection circuit 221 and the drive voltage parameter table 222 constitute an example of the “correction unit” according to the present invention.

  FIG. 6 is a block diagram showing a configuration of the temperature detection circuit according to the present embodiment.

  In FIG. 6, the temperature detection circuit 221 has a current detection circuit 221a and a signal processing circuit 221b.

  The current detection circuit 221a is electrically connected to the low potential power supply line 92, and is configured to detect a current flowing through the low potential power supply line 92. Specifically, the current detection circuit 221a includes an operational amplifier 310, resistors 321 and 322, and a shunt resistor 323. One input terminal (that is, + input terminal) of the operational amplifier 310 is electrically connected to the low potential power line 92 and the shunt resistor 323. The other input terminal (that is, −input terminal) of the operational amplifier 310 is electrically connected to the resistors 321 and 322. The output terminal of the operational amplifier 310 is electrically connected to the signal processing circuit 221b. The other end side different from the one end side electrically connected to the operational amplifier 310 of the resistor 321 is electrically connected to a ground potential (or a ground (GND) potential). The other end side of the resistor 322 that is different from the one end side that is electrically connected to the operational amplifier 310 is electrically connected to the output end of the operational amplifier 310. The other end side of the shunt resistor 323 different from the one end side electrically connected to the operational amplifier 310 is electrically connected to the ground potential. The current detection circuit 221a amplifies the potential generated when the current Iout input from the low potential power supply line 92 flows through the shunt resistor 323 by the operational amplifier 310, and outputs it as the potential Vout to the signal processing circuit 221b. Here, assuming that the resistance values of the resistors 321 and 322 and the shunt resistor 323 are R1, R2, and Rs, respectively, the potential Vout is expressed by the following equation (1).

Vout = Iout × Rs × (1 + R2 / R1) (1)
The signal processing circuit 221b has a driving voltage (in other words, a potential level of the pixel potential, that is, a first potential supplied to the pixel electrode 21 as a pixel potential among a plurality of voltages defined in advance in a driving voltage parameter table 222 described later. Are selected in accordance with the potential Vout input from the current detection circuit 221a.

  In FIG. 5, the drive voltage parameter table 222 defines a plurality of voltages (specifically, a plurality of voltage waveforms) determined in advance experimentally or by simulation or the like as appropriate drive voltages with respect to the temperature of the electrophoretic element 23. The table is

  Next, a drive voltage correction operation by the drive circuit 200 configured as described above will be described with reference to FIG. 7 in addition to FIGS.

  FIG. 7 is a block diagram for explaining a drive voltage correction operation by the drive circuit of the electrophoretic display device according to the present embodiment.

  In FIG. 7, when correcting the drive voltage, the drive circuit 200 first detects, for example, a leakage current Iout1 when the transistors 25a1 and 25b2 constituting the memory circuit 25 are turned off by the current detection circuit 221a. More specifically, first, by supplying a low level (L) image signal to the memory circuit 25 of each pixel 20, the transistors 25a1 and 25b2 are turned off, and the transistors 25a2 and 25b1 are turned on. (ON) state. As a result, a leakage current Iout1 flowing through the transistors 25a1 and 25b2 that are turned off is generated from the high potential power supply line 91 side toward the low potential power supply line 92 side. The drive circuit 200 detects the leak current Iout1 generated in this way by the current detection circuit 221a. Specifically, the current detection circuit 221a detects the leak current Iout1 using the potential generated by the leak current Iout1 flowing through the shunt resistor 323 (see FIG. 6) as a potential amplified by the operational amplifier 310.

  Next, the drive circuit 200 corrects the drive voltage to a voltage suitable for the temperature of the electrophoretic element 23 estimated based on the leak current Iout1 detected by the current detection circuit 221a. Specifically, the drive circuit 200 estimates the electric power estimated based on the detected leakage current Iout1 from a plurality of voltages defined in the drive voltage parameter table 222 as appropriate drive voltages with respect to the temperature of the electrophoretic element 23. A voltage suitable for the temperature of the electrophoretic element 23 is selected by the signal processing circuit 221b.

  Here, since the memory circuit 25 is provided for each pixel 20 in the display area 3a on the element substrate 28 (see FIG. 3), the transistors 25a1 and 25b2 (and the transistors 25a2 and 25b1) constituting the memory circuit 25 are provided. The temperature can be considered to be almost or completely the same as the temperature of the electrophoretic element 23 provided in the display area 3 a between the element substrate 28 and the counter substrate 29. Therefore, the current detection circuit 221a detects the leakage current Iout1 when the transistors 25a1 and 25b2 (or the transistors 25a2 and 25b1) constituting the memory circuit 25 are turned off, and electrophoresis is performed based on the detected leakage current Iout1. The temperature of the element 23 can be estimated with high accuracy. Accordingly, the signal processing circuit 221b selects a voltage suitable for the temperature of the electrophoretic element 23 estimated based on the leakage current Iout1 from the plurality of voltages defined in the drive voltage parameter table 222, thereby The drive voltage can be corrected with high accuracy according to the temperature of the electrophoretic element 23. Therefore, according to the electrophoretic display device according to this embodiment, high-quality display can be performed.

  In addition, according to the electrophoretic display device according to the present embodiment, the drive circuit 200 detects the leakage current Iout when the transistors constituting the memory circuit 25 provided in each pixel 20 are turned off, thereby performing electrophoresis. Since the temperature of the element 23 can be estimated, for example, there is no need to newly provide a temperature sensor for detecting the temperature of the electrophoretic element 23 on the element substrate 28, and the cost of the electrophoretic display device can be reduced. And size reduction can be achieved. In other words, according to the electrophoretic display device according to this embodiment, the leakage current Iout1 when the transistors 25a1 and 25b2 (or the transistors 25a2 and 25b1) constituting the memory circuit 25 are turned off is detected, and the temperature of the electrophoretic element 23 is detected. Therefore, it is not necessary to newly provide a temperature sensor such as a thermistor in the electrophoretic display device, and the electrophoretic display device can be reduced in cost and size. .

  Particularly in the present embodiment, the high potential power supply line 91 and the low potential power supply line 92 are electrically connected in common to the plurality of memory circuits 25 provided for each of the plurality of pixels 20. For this reason, all of the leakage currents Iout when the transistors 25a1 and 25b2 (or transistors 25a2 and 25b1) constituting each of the plurality of memory circuits 25 are turned off flow into the low-potential power line 92. Therefore, the leakage current Iout1 in each of the plurality of memory circuits 25 can be detected by the current detection circuit 221a as a sum of them in the low-potential power line 92, so that the temperature of the electrophoretic element 23 can be estimated with high accuracy. Can do.

  As described above, according to the electrophoretic display device according to the present embodiment, the driving voltage can be corrected with high accuracy in accordance with the temperature of the electrophoretic element 23, and high-quality display can be performed. . Furthermore, the cost and size of the device can be reduced.

Second Embodiment
An electrophoretic display device according to a second embodiment will be described with reference to FIG.

  FIG. 8 is a block diagram for explaining a drive voltage correction operation by the drive circuit of the electrophoretic display device according to the second embodiment. In FIG. 8, the same components as those in the first embodiment shown in FIGS. 1 to 7 are denoted by the same reference numerals, and description thereof will be omitted as appropriate. This also applies to FIGS. 9 to 14.

  In FIG. 8, the electrophoretic display device according to the second embodiment includes the current detection circuit 221a2 and the signal processing circuit 221b2 in place of the current detection circuit 221a and the signal processing circuit 221b according to the first embodiment. Unlike the electrophoretic display device according to the first embodiment, the other configuration is substantially the same as the electrophoretic display device according to the first embodiment described above.

  In FIG. 8, the current detection circuit 221 a 2 is electrically connected to the second control line 95 and configured to be able to detect a current flowing through the second control line 95. The current detection circuit 221a2 is configured in substantially the same manner as the current detection circuit 221a in the first embodiment described above with reference to FIG. 6, but the second input instead of the low-potential power supply line 92 is connected to the + input terminal of the operational amplifier 310. Is different from the current detection circuit 221a in the first embodiment in that the control line 95 is electrically connected.

  The signal processing circuit 221b2 selects a drive voltage from a plurality of voltages defined in advance in the drive voltage parameter table 222 according to the potential Vout input from the current detection circuit 221a2.

  In FIG. 8, when correcting the drive voltage, the drive circuit 200 first detects a leakage current Iout2 when the transistors 112p and 112n constituting the switch circuit 110 are turned off by the current detection circuit 221a2. More specifically, first, when a low level (L) image signal is supplied to the memory circuit 25 of each pixel 20, the transistors 111p and 111n constituting the first transmission gate 111 of the switch circuit 110 are turned on. The transistors 112p and 112n constituting the second transmission gate 112 of the switch circuit 110 are turned on (ON). At this time, a high level potential is supplied from the power supply circuit 210 to the first control line 94 as the first potential S1. As a result, a leakage current Iout2 that flows through the transistors 112p and 112n turned off from the first control line 94 side toward the second control line 95 side is generated. The drive circuit 200 detects the leak current Iout2 generated in this way by the current detection circuit 221a2. Specifically, the current detection circuit 221a2 detects the leakage current Iout2 using the potential generated by the leakage current Iout2 flowing through the shunt resistor 323 (see FIG. 6) as a potential amplified by the operational amplifier 310.

  Next, the drive circuit 200 corrects the drive voltage to a voltage suitable for the temperature of the electrophoretic element 23 estimated based on the leak current Iout2 detected by the current detection circuit 221a2. Specifically, the drive circuit 200 estimates the electric power estimated based on the detected leakage current Iout2 from a plurality of voltages defined in the drive voltage parameter table 222 as appropriate drive voltages with respect to the temperature of the electrophoretic element 23. A voltage suitable for the temperature of the electrophoretic element 23 is selected by the signal processing circuit 221b2.

  Here, since the switch circuit 110 is provided for each pixel 20 in the display region 3a on the element substrate 28 (see FIG. 3), the transistors 112p and 112n (and the transistors 111p and 111n) constituting the switch circuit 110 are provided. The temperature can be considered to be almost or completely the same as the temperature of the electrophoretic element 23 provided in the display area 3 a between the element substrate 28 and the counter substrate 29. Therefore, the current detection circuit 221a2 detects the leakage current Iout2 when the transistors 112p and 112n (or the transistors 111p and 111n) included in the switch circuit 110 are off, so that electrophoresis is performed based on the detected leakage current Iout2. The temperature of the element 23 can be estimated with high accuracy. Therefore, the signal processing circuit 221b2 selects a voltage suitable for the temperature of the electrophoretic element 23 estimated based on the leakage current Iout2 from the plurality of voltages defined in the drive voltage parameter table 222, thereby The drive voltage can be corrected with high accuracy according to the temperature of the electrophoretic element 23. Therefore, according to the electrophoretic display device according to this embodiment, high-quality display can be performed.

  The current detection circuit 221a2 is configured to detect both the leakage current Iout1 of the memory circuit 25 and the leakage current Iout2 of the switch circuit 110, and the signal processing circuit 221b2 includes a plurality of voltages defined in the drive voltage parameter table 222. A voltage suitable for the temperature of the electrophoretic element 23 estimated based on the leakage currents Iout1 and Iout2 may be selected by the signal processing circuit 221b2. Also in this case, the driving voltage can be corrected with high accuracy according to the temperature of the electrophoretic element 23.

<Third Embodiment>
An electrophoretic display device according to a third embodiment will be described with reference to FIG.

  FIG. 9 is a block diagram for explaining a drive voltage correction operation by the drive circuit of the electrophoretic display device according to the third embodiment.

  In FIG. 9, the electrophoretic display device according to the third embodiment includes the current detection circuit 221a3 and the signal processing circuit 221b3 in place of the current detection circuit 221a and the signal processing circuit 221b in the first embodiment. Unlike the electrophoretic display device according to the first embodiment, the other configuration is substantially the same as the electrophoretic display device according to the first embodiment described above.

  In FIG. 9, the current detection circuit 221a3 is configured to be electrically connectable to the low potential power supply line 92 and the data line 50, and is configured to be able to detect a current flowing through the low potential power supply line 92 and the data line 50. The current detection circuit 221a3 is configured in substantially the same manner as the current detection circuit 221a in the first embodiment described above with reference to FIG. 6, but the data line in addition to the low potential power supply line 92 is connected to the + input terminal of the operational amplifier 310. 50 differs from the current detection circuit 221a in the first embodiment in that it is configured to be electrically connectable.

  The signal processing circuit 221b3 selects a drive voltage from a plurality of voltages defined in advance in the drive voltage parameter table 222 according to the potential Vout input from the current detection circuit 221a3.

  In FIG. 9, when the driving circuit 200 corrects the driving voltage, first, the leakage current Iout1 when the transistors 25a2 and 25b1 constituting the memory circuit 25 are turned off and the leakage current when the pixel switching transistor 24 is turned off. Iout3 is detected by the current detection circuit 221a3. More specifically, first, a high level (H) image signal is supplied to the memory circuit 25 of each pixel 20 via the data line 50, whereby the transistors 25a2 and 25b1 are turned off. The transistors 25a1 and 25b2 are turned on. As a result, a leakage current Iout1 flowing through the transistors 25a1 and 25b2 that are turned off from the high potential power supply line 91 side toward the low potential power supply line 92 side is generated. On the other hand, after the high-level image signal is supplied to the memory circuit 25 via the data line 50, the pixel switching transistor 24 is turned off and the data line 50 is set to the low level (L) by the drive circuit 200. Potential. As a result, a leak current Iout3 flowing through the pixel switching transistor 24 that is turned off from the memory circuit 25 side holding the high-level image signal toward the data line 50 side is generated. The drive circuit 200 detects the leak currents Iout1 and Iout3 generated in this way by the current detection circuit 221a3. Specifically, the current detection circuit 221a3 detects the sum of the leakage currents Iout1 and Iout3 using the potential generated by the leakage currents Iout1 and Iout3 flowing through the shunt resistor 323 (see FIG. 6) as the potential amplified by the operational amplifier 310.

  Next, the drive circuit 200 corrects the drive voltage to a voltage suitable for the temperature of the electrophoretic element 23 estimated based on the leakage currents Iout1 and Iout3 detected by the current detection circuit 221a3. Specifically, the drive circuit 200 is estimated based on the detected leakage currents Iout1 and Iout3 from a plurality of voltages defined in the drive voltage parameter table 222 as appropriate drive voltages with respect to the temperature of the electrophoretic element 23. The voltage suitable for the temperature of the electrophoretic element 23 is selected by the signal processing circuit 221b3.

  According to the present embodiment, since the leak current Iout3 of the pixel switching transistor 24 is detected in addition to the leak current Iout1 of the memory circuit 25, for example, as in the first embodiment described above, the leak current Iout1 of the memory circuit 25 is detected. Compared with the case where only the current is detected, the amount of leakage current to be detected can be increased. Therefore, the temperature of the electrophoretic element 23 can be estimated with higher accuracy, and the drive voltage can be corrected with higher accuracy according to the temperature of the electrophoretic element 23. Since the pixel switching transistor 24 is provided for each pixel 20 in the display region 3a on the element substrate 28 (see FIG. 3), the temperature of the pixel switching transistor 24 is between the element substrate 28 and the counter substrate 29. It can be considered that the temperature of the electrophoretic element 23 provided in the display area 3a in FIG.

<Fourth embodiment>
An electrophoretic display device according to a fourth embodiment will be described with reference to FIGS. 10 and 11.

  FIG. 10 is a block diagram for explaining a drive voltage correction operation by the drive circuit of the electrophoretic display device according to the fourth embodiment.

  In FIG. 10, the electrophoretic display device according to the fourth embodiment includes the current detection circuit 221a4 and the signal processing circuit 221b4 in place of the current detection circuit 221a and the signal processing circuit 221b in the first embodiment. Unlike the electrophoretic display device according to the first embodiment, the other configuration is substantially the same as the electrophoretic display device according to the first embodiment described above.

  In FIG. 10, the current detection circuit 221 a 4 is electrically connected to the second control line 95 and configured to be able to detect a current flowing through the second control line 95. The current detection circuit 221a4 is configured in substantially the same manner as the current detection circuit 221a in the first embodiment described above with reference to FIG. 6, but the second input instead of the low-potential power supply line 92 is connected to the + input terminal of the operational amplifier 310. Is different from the current detection circuit 221a in the first embodiment in that the control line 95 is electrically connected.

  The signal processing circuit 221b4 selects a drive voltage from a plurality of voltages defined in advance in the drive voltage parameter table 222 according to the potential Vout input from the current detection circuit 221a4.

  10, when the drive circuit 200 corrects the drive voltage, the potentials of the pixel electrodes 21 of the adjacent pixels 20 are different from each other, and the common electrode 22 is in a high impedance (Hi-Z) state. Thus, the electrophoretic display panel 1 is driven.

  FIG. 11 is a schematic diagram illustrating an example of a display image in the display region during the drive voltage correction operation by the drive circuit of the electrophoretic display device according to the present embodiment.

  That is, as shown in FIG. 11, when correcting the driving voltage, the driving circuit 200 displays different gray levels in the pixels 20 adjacent to each other (in other words, black is displayed in the display area 3a. The electrophoretic display panel 1 is driven so that the pixels 20B to be displayed and the pixels 20W to display white are alternately arranged) and the common electrode 22 is in a high impedance state.

  Specifically, as shown in FIG. 10, when the drive voltage is corrected, the pixel electrode 21 </ b> B of the pixel 20 </ b> B that displays black is in response to the first transmission gate ( The high potential VH is supplied from the first control line 94 as the first potential S1 through the switch circuit 110B in which the TG1) 111 is turned on and the second transmission gate (TG2) 112 is turned off. As a result, the high potential VH is maintained constant. On the other hand, in the pixel electrode 21W of the pixel 20W displaying white, the first transmission gate (TG1) 111 is turned off in response to the high level image signal from the memory circuit 25, and the second transmission gate ( (TG2) The low potential VL is supplied as the second potential S2 from the second control line 95 through the switch circuit 110W in which the 112 is turned on, so that the low potential VL is constant.

  As described above, one of the adjacent pixel electrodes 21 (that is, the pixel electrode 21B) is set to the high potential VL, and the other (that is, the pixel electrode 21W) is set to the low potential VL. An element current Iout4 flowing through the electrophoretic element 23 is generated by the potential difference. The element current Iout4 flows from the pixel electrode 21B side having the high potential VL toward the pixel electrode 21W side having the low potential VL, and then flows into the second control line 95 via the switch circuit 110W. .

  On the other hand, in the switch circuit 110B, as in the second embodiment described above, the leakage current flowing through the transistors 112p and 112n turned off from the first control line 94 side to the second control line 95 side. Iout2B is generated. In the switch circuit 110W, as in the second embodiment described above, the leakage current Iout2W flowing through the transistors 111p and 111n turned off from the first control line 94 side to the second control line 95 side. Will occur. The leak currents Iout2B and Iout2W flow into the second control line 95.

  The drive circuit 200 detects the leak current Iout2 generated in this way by the current detection circuit 221a4. Specifically, the current detection circuit 221a4 includes the leakage currents Iout2B and Iout2W and the elements as potentials obtained by amplifying the potential generated by the leakage of currents Iout2B and Iout2W and the element current Iout4 through the shunt resistor 323 (see FIG. 6) by the operational amplifier 310. The sum total of the current Iout4 is detected.

  Next, the drive circuit 200 corrects the drive voltage to a voltage suitable for the temperature of the electrophoretic element 23 estimated based on the leakage currents Iout2B and Iout2W and the element current Iout4 detected by the current detection circuit 221a4. Specifically, the driving circuit 200 converts the detected leakage currents Iout2B and Iout2W and the element current Iout4 from a plurality of voltages defined as appropriate driving voltages with respect to the temperature of the electrophoretic element 23 in the driving voltage parameter table 222. The signal processing circuit 221b4 selects a voltage suitable for the temperature of the electrophoretic element 23 estimated based on the signal processing circuit 221b4.

  According to this embodiment, in addition to the leakage current Iout2 (that is, leakage currents Iout2B and Iout2W) of the memory circuit 25, the element current Iout4 flowing through the electrophoretic element 23 is detected. Since the element current Iout4 flows through the electrophoretic element 23, its temperature characteristic almost or completely coincides with the temperature characteristic of the electrophoretic element 23 in practice. Therefore, according to this embodiment, the temperature of the electrophoretic element 23 can be estimated with higher accuracy, and the drive voltage can be corrected with higher accuracy according to the temperature of the electrophoretic element 23. .

  Next, a modification of the present embodiment will be described with reference to FIGS.

  FIG. 12 is a schematic diagram illustrating an example of a display image in the display region during the drive voltage correction operation by the drive circuit of the electrophoretic display device according to the modification of the present embodiment.

  As shown in FIG. 12, when the drive circuit 200 corrects the drive voltage, each of the plurality of (four in this embodiment) divided regions 3a1, 3a2, 3a3, and 3a4 formed by dividing the display region 3a is provided. On the other hand, at different timings, different gradations are displayed in adjacent pixels 20 (in other words, pixels 20B displaying black and pixels 20W displaying white are alternately arranged). In addition, the electrophoretic display panel 1 may be driven so that the common electrode 22 is in a high impedance state.

  For example, when correcting the drive voltage, the drive circuit 200 first displays different gradations in the adjacent pixels 20 in one divided region 3a1 among the four divided regions 3a1, 3a2, 3a3, and 3a4. In addition, in the other divided regions 3a2, 3a3, and 3a4, the electrophoretic display panel 1 is driven so that all the pixels 20 display the same gradation and the common electrode 22 is in a high impedance state. To do. As a result, the leakage current Iout2 and the element current Iout4 are generated and flow into the second control line 95 in the same divided region 3a1 as in the above-described embodiment. On the other hand, in the other divided regions 3 a 2, 3 a 3 and 3 a 4, the element current Iout 4 is not generated, but the leakage current Iout 2 of the switch circuit 25 is generated and flows into the second control line 95.

  FIG. 13 is a schematic diagram for explaining a state of pixels adjacent to each other in a divided region where all pixels display the same gradation in a driving voltage correction operation according to a modification of the present embodiment. .

  As shown in FIG. 13, when all the pixels 20 in the other divided areas 3a2, 3a3 and 3a4 display the same gradation (in this modification, when displaying black), the other divided areas 3a2, 3a3 3a4, the pixel electrode 21 has the first transmission gate (TG1) 111 turned on and the second transmission gate (TG2) according to the low-level image signal from the memory circuit 25. The high potential VH is supplied as the first potential S1 from the first control line 94 through the switch circuit 110 in which 112) is turned off, so that the high potential VH is kept constant. At this time, the common electrode 22 is supplied with the low potential VL as the common potential Vcom through the common potential line 93, whereby black is displayed in the other divided regions 3a2, 3a3, and 3a4. High impedance state. Therefore, in this case, the element current Iout4 is not generated in the other divided regions 3a2, 3a3, and 3a4 because the potentials of the adjacent pixel electrodes 21 are the same. On the other hand, a leakage current Iout2 that flows through the second transmission gate 112 that is turned off and that constitutes the switch circuit 25 is generated.

  In FIG. 13, the driving circuit 200 generates a leakage current Iout2 and a device current Iout4 that are generated in one divided region 3a1 and flow into the second control line 95, and are generated in the other divided regions 3a2, 3a3, and 3a4. The leakage current Iout2 flowing into the control line 95 is detected by the current detection circuit 221a4. Specifically, in the current detection circuit 221a4, the leakage current Iout2 and element current Iout4 generated in one divided region 3a1 and the leakage current Iout2 generated in the other divided regions 3a2, 3a2, and 3a3 are shunt resistors 323 (FIG. 6). As a potential amplified by the operational amplifier 310, the leakage current Iout2 and the element current Iout4 generated in one divided region 3a1 and the leakage current Iout2 generated in the other divided regions 3a2, 3a2, and 3a3 Detect the sum.

  Next, the drive circuit 200 displays different gradations in the pixels 20 adjacent to each other in one divided region 3a2 among the four divided regions 3a1, 3a2, 3a3, and 3a4. In 3a3 and 3a4, the electrophoretic display panel 1 is driven so that all the pixels 20 can display the same gradation and the common electrode 22 is in a high impedance state. Then, the drive circuit 200 generates the second control by generating the leakage current Iout2 and the device current Iout4 generated in one divided region 3a2 and flowing into the second control line 95, and in the other divided regions 3a1, 3a3, and 3a4. The leak current Iout2 flowing into the line 95 is detected by the current detection circuit 221a4. By repeating this operation for the divided regions 3a3 and 3a4 in the same manner, the leakage current Iout2 and the element current Iout4 generated in the one divided region 3a3 and 3a4 are detected by the current detection circuit 221a4.

  As described above, in this modification, the element current Iout4 is detected at different timings for each of the divided regions 3a1, 3a2, 3a3, and 3a4. Therefore, the temperature of the electrophoretic element 23 can be estimated for each of the divided regions 3a1, 3a2, 3a3, and 3a4, and the drive voltage can be corrected more appropriately.

<Fifth Embodiment>
An electrophoretic display device according to a fifth embodiment will be described with reference to FIG.

  FIG. 14 is a block diagram for explaining a drive voltage correction operation by the drive circuit of the electrophoretic display device according to the fifth embodiment.

  In FIG. 14, the electrophoretic display device according to the fifth embodiment includes the current detection circuit 221a5 and the signal processing circuit 221b5 in place of the current detection circuit 221a and the signal processing circuit 221b in the first embodiment. Unlike the electrophoretic display device according to the first embodiment, the other configuration is substantially the same as the electrophoretic display device according to the first embodiment described above.

  In FIG. 14, the current detection circuit 221 a 5 is configured to be electrically connectable to the common potential line 93 and configured to be able to detect a current flowing through the common potential line 93. The current detection circuit 221a5 is configured in substantially the same manner as the current detection circuit 221a in the first embodiment described above with reference to FIG. 6, but the second input instead of the low-potential power line 92 is added to the + input terminal of the operational amplifier 310. The control line 95 and the common potential line 93 are configured to be electrically connectable with each other, and are different from the current detection circuit 221a in the first embodiment.

  The signal processing circuit 221b5 selects a drive voltage from a plurality of voltages defined in advance in the drive voltage parameter table 222 according to the potential Vout input from the current detection circuit 221a5.

  In FIG. 14, when the drive circuit 200 corrects the drive voltage, the same gradation is displayed in all the pixels 20 in the display area 3 a (in other words, for example, an all black image ( Or the electrophoretic display panel 1 is driven so that the common electrode 22 is at a low potential VL.

  Specifically, at the time of correcting the driving voltage, the pixel electrode 21 of each pixel 20 is turned on in response to the first transmission gate (TG1) 111 being turned on in accordance with the low-level image signal from the memory circuit 25. The high potential VH is supplied as the first potential S1 from the first control line 94 via the switch circuit 110 in which the second transmission gate (TG2) 112 is turned off. Is done. On the other hand, the common electrode 22 is supplied with the low potential VL as the common potential Vcom through the common potential line 93.

  As described above, when the pixel electrode 21 is set to the high potential VH and the common electrode 22 is set to the low potential VL, the element current Iout5 flowing through the electrophoretic element 23 is generated by the potential difference between the pixel electrode 21 and the common electrode 22. . The element current Iout5 flows through the electrophoretic element 23 from the pixel electrode 21 side at the high potential VL toward the common electrode 22 side at the low potential VL, and flows into the common potential line 93.

  On the other hand, in the switch circuit 110, as in the second embodiment described above, the second transmission gate 112 (ie, the second transmission gate 112 (ie, the second control gate 95) is turned off from the first control line 94 side toward the second control line 95 side. , A leakage current Iout2 flowing through the transistors 112p and 112n) turned off is generated. The leak current Iout2 flows into the second control line 95.

  The drive circuit 200 detects the element current Iout5 and the leak current Iout2 generated in this way by the current detection circuit 221a5. Specifically, the current detection circuit 221a5 uses the sum of the element current Iout5 and the leakage current Iout2 as a potential amplified by the operational amplifier 310 by the potential generated by the element current Iout5 and the leakage current Iout2 flowing through the shunt resistor 323 (see FIG. 6). Is detected.

  Next, the drive circuit 200 corrects the drive voltage to a voltage suitable for the temperature of the electrophoretic element 23 estimated based on the leakage current Iout2 and the element current Iout5 detected by the current detection circuit 221a5. Specifically, the drive circuit 200 is based on the detected leak current Iout2 and element current Iout5 from among a plurality of voltages defined as appropriate drive voltages for the temperature of the electrophoretic element 23 in the drive voltage parameter table 222. A voltage suitable for the estimated temperature of the electrophoretic element 23 is selected by the signal processing circuit 221b5.

  According to this embodiment, in addition to the leakage current Iout2 of the memory circuit 25, the element current Iout5 flowing through the electrophoretic element 23 is detected. Since the element current Iout5 flows through the electrophoretic element 23, the temperature characteristic thereof almost or completely coincides with the temperature characteristic of the electrophoretic element 23 in practice. Therefore, according to this embodiment, the temperature of the electrophoretic element 23 can be estimated with higher accuracy, and the drive voltage can be corrected with higher accuracy according to the temperature of the electrophoretic element 23. .

<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. 15 is a perspective view illustrating a configuration of the electronic paper 1400.

  As illustrated in FIG. 15, the electronic paper 1400 includes the electrophoretic display device 1 according to the above-described embodiment as a display unit 1401. The electronic paper 1400 has flexibility, and includes a main body 1402 formed of a rewritable sheet having the same texture and flexibility as conventional paper.

  FIG. 16 is a perspective view showing the configuration of the electronic notebook 1500.

  As shown in FIG. 16, an electronic notebook 1500 is obtained by bundling a plurality of electronic papers 1400 shown in FIG. 15 and sandwiching them between covers 1501. The cover 1501 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 1400 and the electronic notebook 1500 described above include the electrophoretic display device according to the above-described embodiment, high-quality image display can be performed.

  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. The apparatus, the driving method of the electrophoretic display device, and the electronic apparatus provided with the electrophoretic display device are also included in the technical scope of the present invention.

  DESCRIPTION OF SYMBOLS 21 ... Pixel electrode, 22 ... Common electrode, 23 ... Electrophoretic element, 24 ... Pixel switching transistor, 25 ... Memory circuit, 25a1, 25a2, 25b1, 25b2 ... Transistor, 28 ... Element substrate, 29 ... Opposite substrate, 60 ... Scanning line drive circuit, 70 ... Data line drive circuit, 80 ... Microcapsule, 94, 95 ... Control line, 110 ... Switch circuit, 111, 112 ... Transmission gate, 111p, 111n, 112p, 112n ... Transistor, 200 ... Drive circuit , 210... Power supply circuit, 220... Drive voltage controller, 290.

Claims (10)

An electrophoretic display device having a display area in which a plurality of pixels are arranged,
A pair of first and second substrates;
An electrophoretic element sandwiched between the first and second substrates;
A pixel electrode provided for each of the pixels on the first substrate;
A common electrode provided on the second substrate so as to face the pixel electrode;
A pixel circuit provided for each pixel on the first substrate and electrically connected to the pixel electrode;
A leakage current when at least one transistor constituting the pixel circuit is turned off is detected, and a driving voltage to be applied according to image data between the pixel electrode and the common electrode is estimated based on the leakage current. An electrophoretic display device comprising: correction means for correcting to a voltage suitable for the temperature of the electrophoretic element. The pixel circuit includes:
A pixel switching transistor;
A memory circuit electrically connected between the pixel electrode and the pixel switching transistor and capable of holding an image signal supplied via the pixel switching transistor;
The electrophoretic display device according to claim 1, wherein the correction unit detects a leakage current when at least one transistor included in the memory circuit is turned off as the leakage current.   The electrophoretic display device according to claim 2, wherein the correction unit detects a leak current when the pixel switching transistor is off as the leak current. The pixel circuit includes a switch circuit that electrically connects one of the first and second control lines to the pixel electrode in response to an output signal based on the image signal output from the memory circuit.
The electrophoretic display device according to claim 2, wherein the correction unit detects, as the leakage current, a leakage current when at least one transistor constituting the switch circuit is off.   The correction means applies a predetermined voltage to the electrophoretic element, detects an element current flowing through the electrophoretic element, and estimates the driving voltage based on the element current and the leakage current. The electrophoretic display device according to claim 1, wherein the voltage is corrected to a voltage suitable for the temperature of the element.   The electrophoretic display device according to claim 5, wherein the correcting unit applies the predetermined voltage to the electrophoretic element by generating a potential difference between the adjacent pixel electrodes.   The electrophoretic display device according to claim 5, wherein the correcting unit applies the predetermined voltage to the electrophoretic element by generating a potential difference between the pixel electrode and the common electrode.   The correction means applies the predetermined voltage to the electrophoretic element at different timings to each of a plurality of divided areas obtained by dividing the display area, and detects the element current for each divided area. The electrophoretic display device according to claim 5, wherein the electrophoretic display device is a display device. An electrophoretic display device having a display area in which a plurality of pixels are arranged, a pair of first and second substrates, an electrophoretic element sandwiched between the first and second substrates, and the first substrate A pixel electrode provided for each pixel; a common electrode provided on the second substrate so as to face the pixel electrode; and a pixel electrode provided on the first substrate for each pixel. An electrophoretic display device driving method for driving an electrophoretic display device comprising a pixel circuit electrically connected to
A detection step of detecting a leakage current when the at least one transistor constituting the pixel circuit is off;
And a correction step of correcting a drive voltage to be applied according to image data between the pixel electrode and the common electrode to a voltage suitable for the temperature of the electrophoretic element estimated based on the leak current. A method for driving an electrophoretic display device.   An electronic apparatus comprising the electrophoretic display device according to claim 1.