JP2013171143A - Electro-optic device control method, electro-optic device control unit, electro-optic device and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To optimally display intermediate gradation in an electro-optic device.SOLUTION: In a control method of an electro-optic device (1), a control process for shifting a pixel (20) to a first intermediate optical state includes: a first control process (phase A) for supplying a first voltage pulse (-VSH) to a pixel electrode (21) up to a first limit optical state; a second control process (phase B) for supplying, after the first control process, a second voltage pulse (VSH) having a reverse polarity with regard to a first voltage pulse to the pixel electrode, up to the first intermediate optical state or an intermediate optical state closer to a second limit optical state than the first intermediate optical state; and a third control process (phase C) for supplying, after the second control process, a third pulse (-VSH) of the same polarity as the first voltage pulse to the pixel electrode up to the first intermediate optical state, if a pixel is in the intermediate optical state closer to the second limit optical state than the first intermediate optical state.

Description

  The present invention relates to a control method for an electro-optical device such as an electrophoretic display device, a control device for the electro-optical device, an electro-optical device, and an electronic device.

  As an example of this type of electro-optical device, a voltage is applied between a pixel electrode and an opposing electrode that are opposed to each other with an electrophoretic element including electrophoretic particles interposed therebetween, and electrophoretic particles such as black particles and white particles are moved. Thus, there is an electrophoretic display device that displays an image on a display unit. The electrophoretic element is composed of, for example, a plurality of microcapsules each including a plurality of electrophoretic particles, and is fixed between the pixel electrode and the counter electrode by an adhesive made of resin or the like. The counter electrode is sometimes called a common electrode.

  In such an electrophoretic display device, for example, white can be displayed by applying a voltage that moves white particles to the display surface side, and black by applying a voltage that moves black particles to the display surface side. Can be displayed. Further, by adjusting the period during which each voltage corresponding to white and black described above is applied, it is possible to display white and black intermediate gradations (that is, gray) (for example, Patent Documents). 1 to 3).

US Patent Application Publication No. 2005/0001812 US Patent Application Publication No. 2005/0280626 International Publication No. 2005/101363

  When displaying an intermediate gradation, each particle may be moved to an intermediate position when white and black are displayed. However, such control is not easy. For example, if the position of each particle varies, the displayed gradation may also vary. In particular, when a plurality of intermediate gradations are displayed, the above-described variation on the display image has a great influence.

  On the other hand, for example, when changing the gradation from light gray (that is, gray near white) to dark gray (that is, gray near black), white or black is once displayed from the state where light gray is displayed. If each particle is moved to a position where it is moved and then moved to a position where dark gray is displayed, the positions of the particles for each pixel can be aligned, and an intermediate gradation can be displayed suitably. .

  However, according to the study by the present inventors, when changing the gradation from the white or black display state to another gradation, the change rate of the gradation with respect to the period during which the voltage is applied is constant. It has been found that this is not possible. Specifically, the gradation change immediately after the start of rewriting is large, but the gradation change tends to decrease as the opposite gradation is approached.

  For this reason, for example, when trying to display gray near white from a state where white is displayed, there is a possibility that a gray closer to black than the gray to be displayed may be displayed even if only one pulse of voltage is applied. is there. That is, since the change rate of the gradation immediately after rewriting is too large, it is very difficult to display an intermediate gradation that is close to the rewriting start gradation.

  As described above, the conventional techniques including the above-described patent documents have a technical problem that it is difficult to display a desired intermediate gradation because the gradation change rate is not constant. .

  The present invention has been made in view of the above-described problems, for example, and a control method for an electro-optical device, a control device for the electro-optical device, an electro-optical device, and an electronic apparatus capable of displaying intermediate gradations suitably. It is an issue to provide.

  In order to solve the above problems, a control method for an electro-optical device according to the present invention is provided corresponding to the intersection of a plurality of scanning lines and a plurality of data lines intersecting each other, and between a pixel electrode and a counter electrode facing each other. A plurality of pixels each having an electro-optic material, wherein the pixels are a first limit optical state, a second limit optical state, and a plurality of pixels between the first limit optical state and the second limit optical state; A display unit capable of taking an intermediate optical state, and a voltage pulse corresponding to the image data is applied to the pixel electrode of each of the plurality of pixels in a plurality of frames in order to display an image corresponding to the image data on the display unit. A control method for controlling an electro-optical device provided with a drive unit that supplies a period of time, wherein a control step when shifting the pixel to a first intermediate optical state is performed on the pixel electrode with respect to the first electrode. The ultimate light A first control step for supplying a first voltage pulse until a state is reached, and after the first control step, the pixel electrode is moved from the first intermediate optical state or the first intermediate optical state. A second control step of supplying a second voltage pulse having a polarity opposite to that of the first voltage pulse until reaching an intermediate optical state close to the second limit optical state, and after the second control step, If the pixel is in an intermediate optical state that is closer to the second extreme optical state than the first intermediate optical state, the first voltage is applied to the pixel electrode until the first intermediate optical state is reached. And a third control step for supplying a third pulse having the same polarity as the pulse.

  An electro-optical device controlled by the control method for an electro-optical device according to the present invention includes a display unit having a plurality of pixels arranged in a matrix corresponding to intersections of a plurality of scanning lines and a plurality of data lines. ing. The display unit includes an electro-optical material between the pixel electrode and the counter electrode facing each other. In addition, the plurality of pixels in the display unit have a first limit optical state, a second limit optical state, and a plurality of intermediate optical states between the first limit optical state and the second limit optical state. Is possible.

  Here, the “ultimate optical state” is an optical state realized by sufficiently applying a predetermined voltage to the electro-optical material in the display unit. However, the “extreme optical state” according to the present invention not only means a state in which the optical state does not change at all even when a predetermined voltage is applied, but for example, a plurality of pixels simultaneously enter the extreme optical state. This is a broad concept including an optical state in which the optical state of each pixel can be aligned to such an extent that variations in the optical state between pixels described later can be reduced. Specifically, for example, when the electro-optical material is configured as an electrophoretic element including white particles and black particles, white or black that is displayed when the white particles are sufficiently attracted to the display surface side. The optical state when displaying black that is displayed by sufficiently attracting the particles to the display surface side corresponds to the “extreme optical state” according to the present invention.

  The “intermediate optical state” means an intermediate optical state between the first extreme optical state and the second extreme optical state. For example, the above-described optical state when displaying white and black is the extreme optical state. In the case of the state, the optical state when displaying gray corresponds. The “intermediate optical state” is, for example, by adjusting a period for applying a voltage for changing the optical state to the first extreme optical state or a voltage for changing the optical state to the second extreme optical state. Realized. More specifically, for example, the gray of the intermediate optical state is displayed by moving the positions of white particles and black particles included in the electrophoretic element to an intermediate position when displaying white and black. Can do.

  In the display unit according to the present invention, each pixel can have a plurality of intermediate optical states such as light gray and dark gray. Such a plurality of intermediate optical states can be displayed by adjusting the position of each particle between the pixel electrode and the counter electrode. Specifically, by setting white particles to an intermediate position relatively close to the display surface side (or black particles to an intermediate position relatively far from the display surface side), light gray can be displayed. The dark gray color can be displayed by setting the particles at an intermediate position relatively far from the display surface side (or by setting the black particles at an intermediate position relatively close to the display surface side).

  The display unit described above is controlled by the drive unit to display an image corresponding to the image data. Specifically, during the operation of the electro-optical device according to the present invention, a voltage pulse corresponding to image data is supplied to each pixel electrode of the plurality of pixels by the driving unit. As a result, a voltage corresponding to the image data is applied to each pixel, and an image corresponding to the image data is displayed on the display unit.

  Note that the supply of the voltage pulse to each pixel by the driving unit is performed over a plurality of frame periods. In other words, the voltage is applied to the pixels of the display portion a plurality of times in units of frame periods. Specifically, during one frame period, a plurality of scanning lines are selected once in a predetermined order, and a voltage pulse is applied to a pixel electrode in a pixel corresponding to the selected scanning line. Supplied through. Here, the “frame period” is a period set in advance as a period for selecting a plurality of scanning lines once in a predetermined order. That is, in each of a plurality of consecutive frame periods, control for supplying a voltage pulse to the pixel electrode in each of the plurality of pixels is performed once, whereby an image corresponding to the image data is displayed on the display unit.

  According to the control method of the electro-optical device according to the present invention, when the pixel is shifted to the first intermediate optical state, the first control step, the second control step, and the third control step are sequentially performed. Here, the “first intermediate optical state” is an intermediate optical state targeted in image rewriting, and is any one of a plurality of intermediate optical states that can be taken by the pixels of the display unit. Is set.

  In the first control step, a voltage (for example, white) corresponding to the first extreme optical state (for example, white) is applied to a pixel (hereinafter, referred to as “rewritten pixel” as appropriate) that should take the first intermediate optical state in the display unit. For example, −15V) is applied. Thereby, the rewritten pixel is in the first limit optical state. Thus, before the rewritten pixel is set to the first intermediate optical state, the optical state in the plurality of pixels can be made uniform by temporarily setting the ultimate optical state. Specifically, for example, the positions of the particles included in the electrophoretic element can be aligned. Therefore, when the rewritten pixel is shifted to the intermediate optical state, it is possible to prevent noise or the like from being generated in the displayed image due to variation in the optical state between the plurality of pixels. In addition, when the optical state before rewriting is already the first limit optical state, the first control step can be omitted.

  In the second control step, a voltage (for example, +15 V) corresponding to the second extreme optical state (for example, black) is applied to the rewritten pixel. That is, in the second control process, a voltage having a polarity opposite to that of the first control process is applied. Thereby, the optical state in the rewritten pixel is brought close to the first intermediate optical state. Here, in particular, the optical state of the rewritten pixel after the second control step is the first intermediate optical state or an optical state closer to the second limit optical state than the first intermediate optical state. In other words, the optical state of the rewritten pixel after the second control step is not an optical state closer to the first limit optical state than the first intermediate optical state. If the optical state of the rewritten pixel is changed to the first intermediate optical state by the second control step, the third control step described later can be omitted.

  In the third control step, a voltage corresponding to the first limit optical state is applied again to the rewritten pixel that is in an optical state closer to the second limit optical state than to the first intermediate optical state. As a result, the optical state of the rewritten pixel is brought close to the first limit optical state. That is, it can be brought close to the first intermediate optical state. Note that the voltage applied in the third control step may be the same value as the voltage applied in the first control step, or may be a different value. That is, the voltage applied in the first control step and the voltage applied in the third control step may have different values as long as they have the same polarity.

  In particular, according to research conducted by the present inventors, when the optical state is changed from the first extreme optical state to another optical state, the rate of change of the optical state with respect to the period during which the voltage is applied is always constant. It has been found that this is not possible. Specifically, the change in the optical state immediately after the start of rewriting from the first limit optical state to the second limit optical state direction is large, but the change in the optical state becomes smaller as the second limit optical state is approached. It tends to go. Such characteristics are the same for rewriting from the second limit optical state, and the change in the optical state immediately after the start of rewrite from the second limit optical state toward the first limit optical state is large. However, the change in the optical state tends to be smaller as the first extreme optical state is approached.

  For this reason, for example, when trying to display a light gray near white from a state where white is displayed, even if a voltage is applied only for one frame period, a gray closer to black than the gray to be displayed may be displayed. There is. That is, since the change rate of the optical state immediately after the start of rewriting is too large, it may become very difficult to display an intermediate optical state close to the optical state at the start of rewriting.

  However, in the present invention, as described above, rewriting from the first limit optical state to the first intermediate optical state after the first control step is divided into two steps, the second control step and the third control step. Done. Therefore, the optical state of the rewritten pixel is changed to the first intermediate optical state by rewriting from the first extreme optical state having a relatively high change rate of the optical state to the second extreme optical state (ie, the second control step). Even if the optical state is closer to the second limit optical state, the optical state is finely adjusted by rewriting in the first limit optical state direction (that is, the third control step) with a relatively low change rate of the optical state. Can be done. Therefore, an optical state closer to the first intermediate optical state can be realized.

  As described above, according to the control method of the electro-optical device according to the present invention, the image rewriting is performed in the first control step, the second control step, and the third control step, so that a plurality of pixels can be rewritten. The desired intermediate optical state can be suitably realized while preventing variations in the optical state. As a result, a high quality image can be displayed.

  In one aspect of the control method of the electro-optical device according to the invention, the first intermediate optical state is an optical state closer to the first limit optical state than the second limit optical state.

  According to this aspect, the optical state of the rewritten pixel is set to the optical state closer to the first intermediate optical state in the first control step. Therefore, compared with the case where the optical state of the rewritten pixel is the optical state far from the intermediate optical state to be displayed in the first control step, the image can be rewritten efficiently.

  In this aspect, in particular, since the optical state of the rewritten pixel is set to the optical state closer to the first intermediate optical state in the first control step, only the second control step (that is, the third control step is performed). It is difficult to set the optical state of the rewritten pixel to the first intermediate optical state. That is, since the change rate of the optical state immediately after the start of rewriting is large, the optical state of the rewritten pixel becomes closer to the second extreme optical state than the first intermediate optical state even when a voltage is applied for one frame period. There is a fear.

  However, in this aspect, as described above, the optical state of the rewritten pixel is finely adjusted in the first limit optical state direction by the third control step. Therefore, it is possible to suitably realize the first intermediate optical state.

  In another aspect of the method for controlling an electro-optical device according to the present invention, the first intermediate optical state is an optical state closer to the second limit optical state than the first limit optical state.

  According to this aspect, the optical state of the rewritten pixel is set to an optical state far from the first intermediate optical state in the first control step. Here, in particular, the display unit of the electro-optical device has a characteristic that the change rate of the optical state immediately after the start of rewriting is large as described above. For this reason, if the optical state of the rewritten pixel is changed to the optical state close to the first intermediate optical state in the first control step, only the second control step (that is, without performing the third control step). It is difficult to set the optical state of the rewritten pixel to the first intermediate optical state. That is, since the change rate of the optical state immediately after the start of rewriting is large, the optical state of the rewritten pixel becomes closer to the second extreme optical state than the first intermediate optical state even when a voltage is applied for one frame period. There is a fear.

  However, in this aspect, the optical state of the rewritten pixel is set to the optical state farther from the first intermediate optical state in the first control step. Therefore, the possibility that the first intermediate optical state can be realized only by the second control step without performing the third control step is increased, and the image can be efficiently rewritten.

  Even if the first intermediate optical state cannot be achieved only by the second control step, the optical state of the rewritten pixel is finely adjusted in the first extreme optical state direction by the third control step. Therefore, it is possible to reliably realize the first intermediate optical state.

  In order to solve the above problems, a control device for an electro-optical device according to the present invention is provided corresponding to the intersection of a plurality of scanning lines and a plurality of data lines intersecting each other, and between a pixel electrode and a counter electrode facing each other. A plurality of pixels each having an electro-optic material, wherein the pixels are a first limit optical state, a second limit optical state, and a plurality of pixels between the first limit optical state and the second limit optical state; A display unit capable of taking an intermediate optical state, and a voltage pulse corresponding to the image data is applied to the pixel electrode of each of the plurality of pixels in a plurality of frames in order to display an image corresponding to the image data on the display unit. A control unit that controls an electro-optical device including a driving unit that supplies the pixel in a period, and the first limit optical unit is configured with respect to the pixel electrode when the pixel is shifted to a first intermediate optical state. To the state First control means for supplying a first voltage pulse, and after the first voltage pulse is supplied by the first control means, the first intermediate optical state or the Second control means for supplying a second voltage pulse having a polarity opposite to that of the first voltage pulse until reaching an intermediate optical state closer to the second extreme optical state than the first intermediate optical state; 2 When the second voltage pulse is supplied by the control means and the pixel is in an intermediate optical state that is closer to the second extreme optical state than the first intermediate optical state, And third control means for supplying a third pulse having the same polarity as the first voltage pulse until the first intermediate optical state is reached.

  According to the control device for an electro-optical device according to the present invention, in the electro-optical device, similarly to the above-described control method for the electro-optical device according to the present invention, while preventing variations in the optical state among a plurality of pixels, A desired intermediate optical state can be suitably realized. As a result, a high quality image can be displayed.

  The electro-optical device control apparatus according to the present invention can also adopt various aspects similar to the various aspects of the electro-optical device control method according to the present invention described above.

  In order to solve the above problems, an electro-optical device according to the present invention includes the above-described electro-optical device control device according to the present invention (including various aspects thereof).

  According to the electro-optical device according to the present invention, since the electro-optical device control device according to the present invention described above is provided, a desired intermediate optical state can be suitably obtained while preventing variations in the optical state among a plurality of pixels. Can be realized. As a result, a high quality image can be displayed.

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

  The electronic apparatus according to the present invention includes the above-described electro-optical device according to the present invention, so that a high-quality image can be displayed, for example, a wristwatch, electronic paper, an electronic notebook, a mobile phone, and a portable device. Various electronic devices such as audio devices can be realized.

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

1 is a block diagram illustrating an overall configuration of an electrophoretic display device according to an embodiment. It is a block diagram which shows the structure of the display part periphery of the electrophoretic display device which concerns on embodiment. It is an equivalent circuit diagram which shows the electrical structure of the pixel which concerns on embodiment. It is a fragmentary sectional view of the display part of the electrophoretic display device concerning an embodiment. It is a flowchart which shows the control method of the electrophoretic display device which concerns on embodiment. It is a graph which shows the change of the gradation at the time of rewriting from white to black. It is a graph which shows the change of the gradation at the time of rewriting from black to white. It is a conceptual diagram which shows the voltage application method in the case of displaying the intermediate gradation of level 4. It is a conceptual diagram which shows the voltage application method in the case of trying to display the intermediate gradation of level 6 only by phase A and phase B. FIG. It is a conceptual diagram which shows the voltage application method in the case of displaying the intermediate gray level 6 using the phase C. It is a conceptual diagram which shows the voltage application method in the case of displaying the intermediate gradation of level 1. FIG. It is a conceptual diagram which shows the voltage application method in the case of displaying the intermediate gradation of level 2. FIG. It is a conceptual diagram which shows the voltage application method in the case of displaying the intermediate | middle gradation of level 3. FIG. It is a conceptual diagram which shows the voltage application method in the case of displaying the intermediate | middle gradation of level 5. FIG. It is a perspective view which shows the structure of the electronic paper which is an example of the electronic device to which the electro-optical device 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 electro-optical apparatus is applied.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<Electro-optical device>
The electro-optical device according to this embodiment will be described with reference to FIGS. In the following embodiments, an active matrix driving type electrophoretic display device will be described as an example of the electro-optical device according to the invention.

  First, the overall configuration of the electrophoretic display device according to the present embodiment will be described with reference to FIGS. 1 to 3.

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

  In FIG. 1, an electrophoretic display device 1 according to this embodiment includes a display unit 3, a ROM 4, a RAM 5, a controller 10, and a CPU 100.

  The display unit 3 includes a display element having a memory property, and is a display device that maintains a display state even when writing is not performed. Note that the memory property refers to a property of maintaining a display state even when no voltage is applied when a predetermined display state is achieved by application of voltage, and is also referred to as bistability. A specific configuration of the display unit will be described in detail later.

  The ROM 4 is means for storing data used during operation of the electrophoretic display device. The ROM 4 stores, for example, a drive voltage waveform table for realizing a target display state in each pixel. The drive voltage waveform table will be described in detail later. The ROM 4 can be replaced with a rewritable storage means such as a RAM.

  The RAM 5 is a means for storing data used during the operation of the electrophoretic display device, like the ROM 4 described above. The RAM 5 stores, for example, data indicating the display state before the rewriting operation and data indicating the display state after the rewriting. The RAM 5 includes, for example, a VRAM that functions as a frame buffer, and stores frame image data based on the control of the CPU 100.

  The controller 10 controls the display operation of the display unit 3 using the data stored in the ROM 4 and RAM 5 described above. The controller 10 controls the display unit 3 by outputting an image signal indicating an image to be displayed on the display unit 3 and other various signals (for example, a clock signal).

  The CPU 100 is a processor that controls the operation of the electrophoretic display device 1, and reads and writes data by executing a program stored in advance. For example, when rewriting an image, the CPU 100 stores image data to be displayed on the display unit 3 in the VRAM.

  FIG. 2 is a block diagram showing a configuration around the display unit of the electrophoretic display device according to the present embodiment.

  In FIG. 2, the electrophoretic display device 1 according to the present embodiment is an active matrix drive type electrophoretic display device, and includes a display unit 3, a controller 10, a scanning line driving circuit 60, a data line driving circuit 70, and the like. And a common potential supply circuit 220.

  In the display unit 3, m rows × n columns of pixels 20 are arranged in a matrix (in a 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 controller 10 controls operations of the scanning line driving circuit 60, the data line driving circuit 70, and the common potential supply circuit 220. For example, the controller 10 supplies timing signals such as a clock signal and a start pulse to each circuit.

  The scanning line driving circuit 60 sequentially supplies a scanning signal in a pulsed manner to each of the scanning lines Y1, Y2,..., Ym during a predetermined frame period under the control of the controller 10.

  The data line driving circuit 70 supplies a data potential to the data lines X1, X2,..., Xn under the control of the controller 10. The data potential is any one of a reference potential GND (for example, 0 volt), a high potential VSH (for example, +15 volt), or a low potential -VSH (for example, -15 volt).

  The common potential supply circuit 220 supplies a common potential Vcom (in this embodiment, the same potential as the reference potential GND) to the common potential line 93. Note that the common potential Vcom is a potential different from the reference potential GND within a range in which no voltage is substantially generated between the counter electrode 22 supplied with the common potential Vcom and the pixel electrode 21 supplied with the reference potential GND. It may be. For example, the common potential Vcom may be a value different from the reference potential GND supplied to the pixel electrode 21 in consideration of fluctuations in the potential of the pixel electrode 21 due to feedthrough. In this specification, it is assumed that the common potential Vcom and the reference potential GND are the same.

  Here, the feed-through means that when the scanning signal is supplied to the scanning line 40 after the scanning signal is supplied to the scanning line 40 and the potential is supplied to the pixel electrode 21 via the data line 50 (for example, This refers to a phenomenon in which the potential of the pixel electrode 21 fluctuates due to parasitic capacitance with the scanning line 40 (for example, decreases with a decrease in the potential of the scanning line 40). The common potential Vcom may have a value slightly lower than the reference potential GND supplied to the pixel electrode 21 on the assumption that the potential of the pixel electrode 21 is lowered by feedthrough in advance. The potential Vcom and the reference potential GND are considered to be the same potential.

  Note that various signals are input to and output from the controller 10, the scanning line driving circuit 60, the data line driving circuit 70, and the common potential supply circuit 220, but descriptions of those that are not particularly related to the present embodiment are omitted. .

  FIG. 3 is an equivalent circuit diagram showing an electrical configuration of the pixel 20 according to the present embodiment.

  In FIG. 3, the pixel 20 includes a pixel switching transistor 24, a pixel electrode 21, a counter 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 data potential supplied from the data line driving circuit 70 (see FIG. 2) via the data line 50 via the scanning line 40 from the scanning line driving circuit 60 (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.

  A data potential is supplied to the pixel electrode 21 from the data line driving circuit 70 via the data line 50 and the pixel switching transistor 24. The pixel electrode 21 is disposed so as to face the counter electrode 22 via the electrophoretic element 23.

  The counter 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.

  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 storage capacitor 27 can maintain the data potential for a certain period.

  Next, a specific configuration of the display unit of the electrophoretic display device according to the present embodiment will be described with reference to FIG.

  FIG. 4 is a partial cross-sectional view of the display unit 3 of the electrophoretic display device 1 according to the present embodiment.

  In FIG. 4, the display unit 3 is configured such that the 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 a substrate made of, for example, glass or plastic. Although not shown here, the pixel switching transistor 24, the storage capacitor 27, the scanning line 40, the data line 50, the common potential line 93, and the like described above with reference to FIG. 2 are formed on the element substrate 28. A laminated structure 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 counter electrode 22 is formed in a solid shape so as to face the plurality of pixel electrodes 21. The counter electrode 22 is made of a transparent conductive material such as magnesium silver (MgAg), indium / tin oxide (ITO), indium / zinc oxide (IZO).

  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 device 1 according to this embodiment, in the manufacturing process, an electrophoretic sheet in which the electrophoretic element 23 is previously fixed to the counter substrate 29 side by the binder 30 is separately manufactured, such as the pixel electrode 21. It is constituted by being bonded by an adhesive layer 31 to the element substrate 28 side on which is formed.

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

  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, gum arabic, and gelatin. .

  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, cycloaliphatic 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 counter 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.

  In FIG. 4, when a voltage is applied between the pixel electrode 21 and the counter electrode 22 so that the potential of the counter electrode 22 is relatively high, the positively charged black particles 83 are caused by Coulomb force. While attracted to the pixel electrode 21 side in the microcapsule 80, the negatively charged white particles 82 are attracted to the counter 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 counter electrode 22 side) in the microcapsule 80, and the color of the white particles 82 (that is, white) is displayed on the display surface of the display unit 3. Will be displayed. Conversely, when a voltage is applied between the pixel electrode 21 and the counter 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 counter electrode 22 side by Coulomb force. As a result, the black particles 83 are collected on the display surface side of the microcapsule 80, and the color of the black particles 83 (that is, black) is displayed on the display surface of the display unit 3.

  In addition, 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, the operation at the time of image rewriting in the electrophoretic display device according to the present embodiment will be described with reference to FIG. Hereinafter, for convenience of description, the operation at the time of rewriting will be described by focusing on one pixel to be rewritten. Each process shown below is typically performed by the controller 10, but may be performed by other than the controller 10.

  FIG. 5 is a flowchart showing a control method of the electrophoretic display device according to this embodiment.

  In FIG. 5, during the operation of the electrophoretic display device according to the present embodiment, when an instruction is given to rewrite an image (step S01: YES), the gradation after rewriting (hereinafter referred to as “target gradation” as appropriate). Is referred to as intermediate gradation (step S02). Note that the gradation here is an example of the “optical state” of the present invention, and can be rephrased as, for example, brightness or reflectance. The target gradation is an example of the “first optical state” in the present invention.

  If it is determined that the target gradation is not an intermediate gradation (step S02: NO), a phase X for setting the gradation to white or black is set (step S03). Since the processing in phase X is general, detailed description thereof is omitted here.

  On the other hand, when it is determined that the target gradation is an intermediate gradation (step S02: YES), it is determined whether or not white is currently displayed (that is, before rewriting) in the pixel to be rewritten (ie, before rewriting) ( Step S04).

  If it is determined that white is not displayed in the pixel to be rewritten (step S04: NO), a phase A for setting the gradation displayed on the pixel to white is set (step S05). Phase A is set as a period during which the drive voltage -VSH corresponding to white is applied for a long time until the gray level displayed so far becomes white. If it is determined that white is displayed in the pixel to be rewritten (step S04: YES), step S05 for setting phase A is omitted.

  According to the phase A, it is possible to align the positions of the white particles 82 and the black particles 83 having variations in each pixel by displaying white before realizing the intermediate gradation that is the target gradation. . Therefore, when displaying the intermediate gradation, it is possible to prevent the displayed gradation from being varied due to the variation in the particle position in each pixel. Phase A is an example of the “first control step” in the present invention.

  Subsequently, in phase B, which is a period following phase A, it is determined whether or not the target gradation can be realized (step S06). If it is determined that the target gradation can be realized in phase B (step S07: YES), phase B for realizing the target gradation is set (step S07).

  Phase B is a period in which a drive voltage VSH corresponding to black (that is, a potential opposite to that of phase A) is applied to the pixel to be rewritten, and phase B is a relatively short period (that is, the display floor). By setting the period to a level where the tone does not reach black, it is possible to realize gray, which is an intermediate gradation between white and black. Here, in particular, the electrophoretic display device 1 according to the present embodiment can display a plurality of intermediate gradations by adjusting the phase B period. That is, it is possible to display light gray close to white, dark gray close to black, and the like. Phase B is an example of the “second control step” in the present invention.

  According to the present inventors' research, when the gradation is changed from white to an intermediate gradation, the target gradation may not be realized only by Phase B due to the characteristics of the electrophoretic element 23. It has been found that it can exist. Hereinafter, gradations that can be realized only by Phase B and gradations that cannot be realized only by Phase B will be described with reference to FIGS.

  In the following description, the electrophoretic display device 1 according to this embodiment will be described by taking as an example a case in which eight levels of gradation can be displayed. Here, the gradation corresponding to black is level 0, the gradation corresponding to white is level 7, and the intermediate gradation between black and white is indicated by level 1 to level 6, respectively.

  FIG. 6 is a graph showing a change in gradation when rewriting from white to black.

  In FIG. 6, when the image is rewritten from white to black, the change in gradation with respect to the period during which the voltage is applied is large immediately after the start of rewriting, but tends to decrease as the opposite gradation is approached. That is, the gradation changes greatly in the black direction at the time when the gradation is close to white, but the gradation becomes difficult to change as it approaches black.

  FIG. 7 is a graph showing a change in gradation when rewriting from black to white.

  In FIG. 7, when the image is rewritten from black to white, the change in gradation with respect to the period during which the voltage is applied is large immediately after the start of rewriting, but tends to decrease as the opposite gradation is approached. That is, the gradation changes greatly in the white direction at the time when the gradation is close to black, but the gradation becomes difficult to change as it approaches white.

  FIG. 8 is a conceptual diagram showing a voltage application method in the case of displaying level 4 intermediate gradation.

  In FIG. 8, it is assumed that the gradation before rewriting is level 0 (that is, black) and the target gradation is an intermediate gradation of level 4. In this case, first, in the phase A, 15 frames of the drive voltage −VSH corresponding to white is applied to the pixel to be rewritten. As a result, the displayed gradation becomes level 7 (that is, white).

  Subsequently, in phase B, one frame of the drive voltage VSH corresponding to black is applied. As a result, the displayed gradation becomes level 4, and the target gradation is realized.

  FIG. 9 is a conceptual diagram showing a voltage application method in a case where an intermediate gray level 6 is displayed only in phase A and phase B. FIG.

  In FIG. 9, it is assumed that the gradation before rewriting is level 0 (that is, black) and the target gradation is an intermediate gradation of level 6. In this case, first, in the phase A, 15 frames of the drive voltage −VSH corresponding to white is applied to the pixel to be rewritten. As a result, the displayed gradation becomes level 7 (that is, white).

  Subsequently, in phase B, one frame of the drive voltage VSH corresponding to black is applied. However, the display gradation after phase B is level 4 as in the case of FIG. 8, and the target gradation of level 6 is not realized. That is, even when VSH is applied for only one frame, which is the minimum unit of the voltage application period, the gradation changes greatly due to the characteristics of the electrophoretic element 23 and the target gradation cannot be realized. .

  As described above, an intermediate gray level that is relatively far from white, such as level 4, can be realized only by phase B, but an intermediate gray level, such as level 6, that is relatively close to white can be realized only by phase B. It can be difficult.

  Returning to FIG. 5, in the electrophoretic display device 1 according to the present embodiment for the above-described problem, when it is determined that the target gradation cannot be realized only by the phase B (step S07: NO), the target gradation is determined. A phase B for realizing a gradation close to black is set (step S08), and a phase C for setting the gradation after the phase B as a target gradation is set (step S09).

  Here, phase C is an example of the “third control step” of the present invention, and is set to bring the gray level that is closer to black than the target gray level by applying the voltage in phase B closer to the target gray level. It is a period. In phase C, a drive voltage VSH corresponding to white (that is, a voltage having the same polarity as phase A) is applied to the pixel to be rewritten. Hereinafter, a method for realizing the target gradation using this phase C will be described with reference to FIG.

  FIG. 10 is a conceptual diagram showing a voltage application method in the case of displaying a level 6 intermediate gradation using phase C. FIG.

  In FIG. 10, phase C is set as a period in which the gradation that has reached level 4 by phase B (that is, the gradation closer to black than the target gradation) is level 6 that is the target gradation. In phase C, since the drive voltage VSH corresponding to white is applied, the gradation is brought close to white. At this time, as shown in FIG. 7, the change rate of the gradation is smaller than that of the phase B having a relatively high change rate. That is, in phase C, the gradation changes more slowly than in phase B. Therefore, if four frames of the drive voltage VSH are applied in the phase C, the intermediate gray level that was level 4 can be changed to level 6 that is the target gray level.

  As described above, by using Phase C, it is possible to suitably realize a gradation that cannot be realized only by Phase B.

  Returning to FIG. 5, after each phase is set, the drive voltage is actually output for the frame set in each phase, and the image rewriting process in the rewritten pixel is executed (step S <b> 10).

  Note that the above-described processing for setting each phase can be omitted by storing in advance a drive voltage waveform (for example, a waveform as shown in FIG. 10) corresponding to each gradation as a table or the like. Specifically, if the waveform of the drive voltage to be output is set for each combination of the gradation before the rewriting and the target gradation, the image rewriting process is executed simply by selecting the corresponding waveform. be able to.

  Incidentally, gradations other than level 4 and level 6, which have already been exemplified, can be realized by outputting the waveforms shown in FIGS. 11 to 1412, respectively.

  FIGS. 11 to 14 are conceptual diagrams showing voltage application methods in the case of displaying intermediate gray levels of levels 1, 2, 3, and 5, respectively.

  As shown in FIG. 11, the rewriting from the black level 0 to the intermediate gray level 1 involves applying 15 frames of the driving voltage −VSH in the phase A and then applying 6 frames of the driving voltage VSH in the phase B. It is realized with.

  As shown in FIG. 12, the rewriting from the black level 0 to the intermediate gray level 2 involves applying 15 frames of the driving voltage -VSH in the phase A and then applying 4 frames of the driving voltage VSH in the phase B. It is realized with.

  As shown in FIG. 13, the rewriting from the black level 0 to the intermediate gray level 3 involves applying 15 frames of the driving voltage −VSH in the phase A and then applying 2 frames of the driving voltage VSH in the phase B. It is realized with.

  As shown in FIG. 14, the rewriting from the black level 0 to the intermediate gray level 5 is performed by applying 15 frames of the driving voltage -VSH in the phase A and then applying 2 frames of the driving voltage VSH in the phase B. Further, in phase C, the driving voltage -VSH is applied by applying two frames.

  As described above, according to the electrophoretic display device according to the present embodiment, it is possible to appropriately display a desired intermediate gradation while preventing a variation in gradation among a plurality of pixels. Therefore, a high quality image can be displayed.

  In the above embodiment, the case where the gradation is set to white in phase A has been described, but the gradation may be set to black in phase A. That is, when displaying an intermediate gradation, the target gradation may be realized by Phase B or Phase C after the gradation is first changed to black in Phase A. In this case, the drive voltage VSH corresponding to black is applied in the phase A, the drive voltage −VSH corresponding to white is applied in the phase B, and the drive voltage VSH corresponding to black is applied in the phase C.

  In addition, the gradation realized in phase A may be selected from white and black. That is, the gradation realized in Phase A is not fixed to white or black, but may be selected as appropriate from either white or black according to the gradation before rewriting or the target gradation. . In this way, it is possible to display the intermediate gradation more efficiently.

  In the above embodiment, the white particles 82 are negatively charged and the black particles 83 are positively charged. However, the white particles 82 are positively charged and the black particles 83 are negatively charged. May be. Further, the electrophoretic element 23 is not limited to the configuration having the microcapsules 80, and may be a configuration in which the electrophoretic dispersion medium and the electrophoretic particles are included in a space partitioned by the partition walls. Further, the electro-optical device having the electrophoretic element 23 has been described as an example, but the present invention is not limited to this. The electro-optical device may be, for example, an electro-optical device using an electronic powder fluid.

<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 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 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.

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

  The present invention is not limited to the above-described embodiments, and can be appropriately changed without departing from the spirit or idea of the invention that can be read from the claims and the entire specification, and an electro-optical device with such a change. The control method, electro-optical device control device, electro-optical device, and electronic apparatus are also included in the technical scope of the present invention.

  DESCRIPTION OF SYMBOLS 3 ... Display part, 4 ... ROM, 5 ... RAM, 10 ... Controller, 20 ... Pixel, 21 ... Pixel electrode, 22 ... Counter electrode, 24 ... Pixel switching transistor, 28 ... Element substrate, 29 ... Counter substrate, 40 ... Scan line 50... Data line 60. Scan line drive circuit 70 70 Data line drive circuit 82. White particle 83 83 Black particle 100 CPU 220 Common potential supply circuit

Claims (6)

A plurality of pixels provided corresponding to the intersection of a plurality of scanning lines and a plurality of data lines intersecting each other, each having a pixel electrode facing each other and an electro-optic material between the counter electrodes, A display unit capable of taking a plurality of intermediate optical states between the first limit optical state and the second limit optical state, and the display unit according to image data A control method for controlling an electro-optical device including a driving unit that supplies a voltage pulse corresponding to the image data to each of the pixel electrodes of each of the plurality of pixels in a plurality of frame periods in order to display a captured image. There,
A control step in transitioning the pixel to the first intermediate optical state,
A first control step of supplying a first voltage pulse to the pixel electrode until the first limit optical state is reached;
After the first control step, the first intermediate optical state or the intermediate optical state closer to the second limit optical state than the first intermediate optical state is reached with respect to the pixel electrode. A second control step of supplying a second voltage pulse having a polarity opposite to that of the first voltage pulse;
After the second control step, when the pixel is in an intermediate optical state that is closer to the second limit optical state than the first intermediate optical state, the first intermediate optical state with respect to the pixel electrode And a third control step of supplying a third pulse having the same polarity as that of the first voltage pulse.   2. The method of controlling an electro-optical device according to claim 1, wherein the first intermediate optical state is an optical state closer to the first limit optical state than the second limit optical state.   2. The method of controlling an electro-optical device according to claim 1, wherein the first intermediate optical state is an optical state closer to the second limit optical state than the first limit optical state. A plurality of pixels provided corresponding to the intersection of a plurality of scanning lines and a plurality of data lines intersecting each other, each having a pixel electrode facing each other and an electro-optic material between the counter electrodes, A display unit capable of taking a plurality of intermediate optical states between the first limit optical state and the second limit optical state, and the display unit according to image data A control unit that controls an electro-optical device including a drive unit that supplies a voltage pulse corresponding to the image data to each pixel electrode of each of the plurality of pixels in a plurality of frame periods in order to display a captured image. There,
In transitioning the pixel to the first intermediate optical state,
First control means for supplying a first voltage pulse to the pixel electrode until the first limit optical state is reached;
After the first voltage pulse is supplied by the first control unit, the first intermediate optical state or the second extreme optical state is set to the pixel electrode rather than the first intermediate optical state or the first intermediate optical state. Second control means for supplying a second voltage pulse having a polarity opposite to that of the first voltage pulse until a near intermediate optical state is reached;
After the second voltage pulse is supplied by the second control means, when the pixel is in an intermediate optical state that is closer to the second extreme optical state than the first intermediate optical state, On the other hand, a control device for an electro-optical device, comprising: third control means for supplying a third pulse having the same polarity as the first voltage pulse until the first intermediate optical state is reached.   An electro-optical device comprising the control device for an electro-optical device according to claim 4.   An electronic apparatus comprising the electro-optical device according to claim 5.