Patent Application
20070046622
1. Technical Field
The present invention relates to an electrophoretic device driving method, an electrophoretic device, and an electronic apparatus and an electronic watch that include the electrophoretic device.
2. Related Art
A phenomenon (electrophoretic phenomenon) is known in which the application of an electric field to a dispersed system including electrophoretic particles dispersed in a solution causes the electrophoretic particles to migrate due to the Coulomb force. Electrophoretic display devices utilizing such a phenomenon have been developed.
In such electrophoretic display devices, when a display state is maintained for a long period of time, electrophoretic particles may become adhered to an electrode or the like. Thus, the particles may move slowly when rewriting is performed, and a residual image may be generated. For example, when an electrophoretic display device is used for an electronic watch, a plurality of units of display, such as a month display, a date display, an hour display, a minute display, and a second display, are provided in a display region. Such units of display have greatly different rewrite intervals. For the month display and the date display, the same display is maintained for a long period of time. More specifically, for the month display, the same display is maintained for about 720 hours. For the date display, the same display is maintained for 24 hours. Thus, this circumstance is likely to generate residual images when the display is rewritten.
Generation of such residual images can be reduced, for example, by repeatedly performing display refreshing operations at short intervals, by applying a high voltage when rewriting is performed, or by applying a voltage for a long period of time when rewriting is performed. In addition, as a method for solving such problems, JP-A-2004-325489 discloses a method for applying a high-frequency voltage to a common electrode.
However, in a case where generation of residual images is reduced by applying a high voltage or applying a voltage for a long period of time when rewriting is performed, if a plurality of units of display having different rewrite intervals is provided in a display region of an electronic watch or the like, an unnecessary amount of voltage is consumed even for a unit of display, such as a minute display or a second display, which has a short rewrite interval and which is less likely to generate a residual image. In addition, if display refreshing operations are performed at the same interval for all the units of display, display refreshing operations are often performed unnecessarily for a unit of display, such as a month display or a date display, which has a long rewrite interval. Thus, increased electric power is consumed. In addition, if the method for applying a high-frequency voltage is adopted, a driving circuit becomes complicated, and power loss due to parasitic resistance of the wiring is increased.
An advantage of the invention is that it provides an electrophoretic display device driving method for reducing the generation of a residual image while preventing unnecessary consumption of electric power.
A driving method according to a first aspect of the invention for driving an electrophoretic device including a display region including a plurality of electrophoretic elements each including a dispersed system that includes electrophoretic particles and that is disposed between a common electrode and a pixel electrode, a driver that drives the electrophoretic elements by applying voltages to the electrophoretic elements, and a controller that controls the driver, wherein two or more units of display rewritten at different rewrite intervals are provided in the display region, includes controlling, by the controller, the driver to apply a higher voltage to an electrophoretic element included in a unit of display having a longer rewrite interval when an image is rewritten.
With this arrangement, by applying a higher voltage to an electrophoretic element included in a unit of display, such as a month display or a date display of an electronic watch or the like, which has a longer rewrite interval and which is likely to generate a residual image, the generation of a residual image can be reduced. In contrast, for a unit of display, such as a minute display or a second display, which has a shorter rewrite interval, unnecessary power consumption can be avoided. In addition, since applying a higher voltage causes electrophoretic particles to be deposited on an electrode more densely, a unit of display having a long rewrite interval can achieve excellent display for a long period of time.
A driving method according to a second aspect of the invention for driving an electrophoretic device including a display region including a plurality of electrophoretic elements each including a dispersed system that includes electrophoretic particles and that is disposed between a common electrode and a pixel electrode, a driver that drives the electrophoretic elements by applying voltages to the electrophoretic elements, and a controller that controls the driver, wherein two or more units of display rewritten at different rewrite intervals are provided in the display region, includes controlling, by the controller, the driver to apply a voltage to an electrophoretic element included in a unit of display having a longer rewrite interval for a longer period of time when an image is rewritten.
With this arrangement, by applying a voltage to an electrophoretic element included in a unit of display that has a longer rewrite interval and that is likely to generate a residual image for a longer period of time, the generation of a residual image can be reduced. In contrast, for a unit of display, such as a minute display or a second display, which has a shorter rewrite interval, unnecessary power consumption can be avoided. In addition, since applying a voltage for a longer period of time causes electrophoretic particles to be deposited on an electrode more densely, a unit of display having a long rewrite interval can achieve excellent display for a long period of time.
In addition, in the driving method for driving the electrophoretic device, the voltage may be applied to the electrophoretic element included in the unit of display having the longer rewrite interval for the longer period of time by dividing the voltage into a plurality of pulses and by applying an increased number of pulses to the electrophoretic element. With this arrangement, voltages can be applied to electrophoretic elements for different periods of time using a simple circuit.
In addition, applying a higher voltage to an electrophoretic element included in a unit of display having a longer rewrite interval for a longer period of time is also within the scope of the invention.
A driving method according to a third aspect of the invention for driving an electrophoretic device including a display region including a plurality of electrophoretic elements each including a dispersed system that includes electrophoretic particles and that is disposed between a common electrode and a pixel electrode, a driver that drives the electrophoretic elements by applying voltages to the electrophoretic elements, and a controller that controls the driver, wherein two or more units of display rewritten at different rewrite intervals are provided in the display region, includes controlling, by the controller, the driver to apply a voltage only to an electrophoretic element included in a unit of display having a rewrite interval that is longer than a predetermined period of time and to perform a display refreshing operation for the unit of display.
Here, the “display refreshing operation” means regularly or irregularly applying a voltage based on image data in order to stabilize or maintain a distribution state of electrophoretic particles distributed so as to display a desired image by application of a voltage. Thus, the “display refreshing operation” is different from a known “refreshing operation” constituted by data deletion and writing performed in a liquid crystal display device. Data deletion is not necessarily performed in the “display refreshing operation” in this aspect of the invention.
With this arrangement, by performing a display refreshing operation only for a unit of display having a rewrite interval that is longer than a predetermined period of time and being likely to generate a residual image, the generation of a residual image can be reduced. A constant display refreshing interval may be set for all the units of display having rewrite intervals longer than the predetermined period of time. Alternatively, display refreshing operations may be performed at different intervals depending on the units of display. In contrast, for a unit of display, such as a minute display or a second display, which has a shorter rewrite interval, unnecessary power consumption can be prevented without performing a refreshing operation.
In the driving method for driving the electrophoretic device, the display refreshing operation may be repeatedly performed, and the display refreshing operation may be performed at an interval that is shorter than a period of time in which the display holding performance of the dispersed system is reduced to an unacceptable level. With this arrangement, the display performance can always be maintained within an acceptable range. By setting a display refreshing interval to be slightly shorter than a period of time in which the display holding performance of the dispersed system is reduced to an unacceptable level, the number of refreshing times can be reduced to a minimum. Thus, unnecessary power consumption can be avoided.
In the driving method for driving the electrophoretic device, the display refreshing operation may be repeatedly performed. In each display refreshing operation, a sufficiently high voltage may be applied such that the display holding performance of the dispersed system is not reduced to an unacceptable level before the next display refreshing operation is performed. With this arrangement, the display performance can always be maintained within an acceptable range. By setting a voltage to be applied to a minimum within the range in which the display performance is not reduced to an unacceptable level before the next display refreshing operation is performed, unnecessary power consumption can be avoided.
In the driving method for driving the electrophoretic device, the display refreshing operation may be repeatedly performed. In each display refreshing operation, a voltage may be applied for a sufficiently long period of time such that the display holding performance of the dispersed system is not reduced to an unacceptable level before the next display refreshing operation is performed. With this arrangement, the display performance can always be maintained within an acceptable range. By applying a voltage for the minimum period of time within the range in which the display performance is not reduced to an unacceptable level before the next display refreshing operation is performed, unnecessary power consumption can be avoided.
An electrophoretic device according to a fourth aspect of the invention includes a display region including a plurality of electrophoretic elements each including a dispersed system that includes electrophoretic particles and that is disposed between a common electrode and a pixel electrode, a driver that drives the electrophoretic elements by applying voltages to the electrophoretic elements, and a controller that controls the driver. Two or more units of display rewritten at different rewrite intervals are provided in the display region. When rewriting is performed, the controller controls the driver to apply a higher voltage to an electrophoretic element included in a unit of display having a longer rewrite interval.
With this arrangement, by applying a higher voltage to an electrophoretic element included in a unit of display, such as a month display or a date display of an electronic watch or the like, which has a longer rewrite interval and which is likely to generate a residual image, the generation of a residual image can be reduced. In contrast, for a unit of display, such as a minute display or a second display, which has a shorter rewrite interval, unnecessary power consumption can be avoided. In addition, since applying a higher voltage causes electrophoretic particles to be deposited on an electrode more densely, excellent display can be achieved for a long period of time.
An electrophoretic device according to a fifth aspect of the invention includes a display region including a plurality of electrophoretic elements each including a dispersed system that includes electrophoretic particles and that is disposed between a common electrode and a pixel electrode, a driver that drives the electrophoretic elements by applying voltages to the electrophoretic elements, and a controller that controls the driver. Two or more units of display rewritten at different rewrite intervals are provided in the display region. When rewriting is performed, the controller controls the driver to apply a voltage to an electrophoretic element included in a unit of display having a longer rewrite interval for a longer period of time.
With this arrangement, by applying a voltage to an electrophoretic element included in a unit of display that has a longer rewrite interval and that is likely to generate a residual image for a longer period of time, the generation of a residual image can be reduced. In contrast, for a unit of display, such as a minute display or a second display, which has a shorter rewrite interval, unnecessary power consumption can be avoided. In addition, since applying a voltage for a longer period of time causes electrophoretic particles to be deposited on an electrode more densely; excellent display can be achieved for a long period of time.
In addition, when a voltage is applied for a longer period of time, the width of a driving pulse (voltage application time) may be set to be larger (longer). Alternatively, a driving pulse may be divided into a plurality of pulses and an increased number of pulses may be applied, so that the total voltage application time can be increased.
In addition, a device controlled such that a higher voltage is applied to an electrophoretic element included in a unit of display having a longer rewrite interval for a longer period of time is also within the scope of the invention.
An electrophoretic device according to a sixth aspect of the invention includes a display region including a plurality of electrophoretic elements each including a dispersed system that includes electrophoretic particles and that is disposed between a common electrode and a pixel electrode, a driver that drives the electrophoretic elements by applying voltages to the electrophoretic elements, and a controller that controls the driver. Two or more units of display rewritten at different rewrite intervals are provided in the display region, and the controller controls the driver to apply a voltage only to an electrophoretic element included in a unit of display having a rewrite interval that is longer than a predetermined period of time and to perform a display refreshing operation for the unit of display.
Here, the “display refreshing operation” means regularly or irregularly applying a voltage based on image data in order to stabilize or maintain a distribution state of electrophoretic particles distributed so as to display a desired image by application of a voltage. Thus, the “display refreshing operation” is different from a known “refreshing operation” constituted by data deletion and writing performed in a liquid crystal display device. Data deletion is not necessarily performed in the “display refreshing operation” in this aspect of the invention.
With this arrangement, by performing a display refreshing operation only for a unit of display having a rewrite interval that is longer than a predetermined period of time and being likely to generate a residual image, the generation of a residual image can be reduced. A constant display refreshing interval may be set for all the units of display having rewrite intervals longer than the predetermined period of time. Alternatively, display refreshing operations may be performed at different intervals depending on the units of display. In contrast, for a unit of display, such as a minute display or a second display, which has a shorter rewrite interval, unnecessary power consumption can be prevented without performing a refreshing operation.
In the electrophoretic device, the display refreshing operation may be repeatedly performed, and the display refreshing operation may be performed at an interval that is shorter than a period of time in which the display holding performance of the dispersed system is reduced to an unacceptable level. With this arrangement, the display performance can always be maintained within an acceptable range. By setting a display refreshing interval to be slightly shorter than a period of time in which the display holding performance of the dispersed system is reduced to an unacceptable level, the number of refreshing times can be reduced to a minimum. Thus, unnecessary power consumption can be avoided.
In the electrophoretic device, the display refreshing operation may be repeatedly performed. In each display refreshing operation, a sufficiently high voltage may be applied such that the display holding performance of the dispersed system is not reduced to an unacceptable level before the next display refreshing operation is performed. With this arrangement, the display performance can always be maintained within an acceptable range. By setting a voltage to be applied to a minimum within the range in which the display performance is not reduced to an unacceptable level before the next display refreshing operation is performed, unnecessary power consumption can be avoided.
In the electrophoretic device, the display refreshing operation may be repeatedly performed. In each display refreshing operation, a voltage may be applied for a sufficiently long period of time such that the display holding performance of the dispersed system is not reduced to an unacceptable level before the next display refreshing operation is performed. With this arrangement, the display performance can always be maintained within an acceptable range. By applying a voltage for the minimum period of time within the range in which the display performance is not reduced to an unacceptable level before the next display refreshing operation is performed, unnecessary power consumption can be avoided.
An electronic apparatus according to an aspect of the invention includes the foregoing electrophoretic device as a display section. The “electronic apparatus” may be any apparatus including a display section adopting display using an electrophoretic material. The “electronic apparatus” may be a display apparatus, a television apparatus, electronic paper, a watch, an electronic calculator, a cellular phone, a portable information terminal, or the like. In addition, although deviating from the concept of an “apparatus”, for example, the “electronic apparatus” may be flexible paper or film, an object belonging to a fixed property, such as a wall surface, to which such paper or film is attached, or an object belonging to a moving body, such as a vehicle, a flying vehicle, or a ship.
An electronic watch according to an aspect of the invention includes the foregoing electrophoretic device as a display section, and the two or more units of display are selected from a group including a month display, a date display, an hour display, a minute display, and a second display. Even if such an electronic watch has units of display having largely different rewrite intervals, the generation of a residual image can be efficiently reduced without wasting electric power.
The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements.
Embodiments of the invention will be described.
The controller 21 controls the scanning line driving circuit 23 and the data line driving circuit 24. The controller 21 includes an image signal processing circuit, a timing generator, and the like, which are not shown in
The display region 16 includes a plurality of data lines disposed in parallel in an X direction, a plurality of scanning lines disposed in parallel in a Y direction, and a plurality of pixel circuits disposed at the intersections of the data lines and the scanning lines. An electrophoretic element contained in each of the pixel circuits performs image display.
The scanning line driving circuit 23 is connected to each of the scanning lines in the display region 16. The scanning line driving circuit 23 selects one of the scanning lines and supplies a predetermined scanning line signal Y1, Y2, . . . , or Ym to the selected scanning line. The scanning line signals Y1, Y2, . . . , and Ym are signals for sequentially shifting an active period (H-level period). The scanning line signals Y1, Y2, . . . , and Ym output to the corresponding scanning lines cause pixel circuits connected to the scanning lines to be turned on sequentially.
The data line driving circuit 24 is connected to each of the data lines in the display region 16. The data line driving circuit 24 supplies a data signal X1, X2, . . . , or Xn to a pixel circuit selected by the scanning line driving circuit 23.
In the electrophoretic element 32, for example, when a low power supply potential Vss (for example, 0 V) is applied to the pixel electrode 43 via a data line and a high power supply potential Vdd (for example, +10 V) is applied as the potential (common potential) Vcom of the common electrode 44, the white electrophoretic particles 46 move toward the common electrode 44 and the black electrophoretic particles 47 move toward the pixel electrode 43. Thus, when viewed from the common electrode 44 (from the bottom of
A specific driving method for driving the electrophoretic device 2 contained in the electronic watch 1 is described next. In the electrophoretic device 2 according to this embodiment, in order to rewrite an image, the controller 21 controls the scanning line driving circuit 23 and the data line driving circuit 24 to apply voltages to the common electrode 44 and the pixel electrode 43 of each of the electrophoretic elements 32. The controller 21 is capable of controlling a voltage to be applied to the electrophoretic element 32 included in each of the month display 11, the date display 12, the hour display 13, the minute display 14, and the second display 15, individually.
Parts (a) to (e) of
As shown in part (a) of
The controller 21 controls the scanning line driving circuit 23 and the data line driving circuit 24 such that a higher voltage is applied to the electrophoretic element 32 included in a unit of display having a longer rewrite interval, such as the month display 11 or the date display 12. That is, the controller 21 controls the scanning line driving circuit 23 and the data line driving circuit 24 such that the relationship between the applied voltages satisfies the condition VM≧VD≧VE≧Vmin≧VS. The size of each of the voltages is not particularly limited as long as the condition VM≧VD≧VH≧Vmin≧VS is satisfied. For example, the relationship between the voltages may be represented by the condition Vm>VD>VH>Vmin>VS. Alternatively, for example, the relationship between the voltages may be represented by the condition VM=VD>VH>Vmin=VS.
Under such control, a high voltage is applied to a unit of display that has a long rewrite interval and that is likely to generate a residual image. Thus, even if electrophoretic particles are adhered to an electrode or the like, the electrophoretic particles can be moved so as to achieve display of the next image without generating a residual image. In addition, since applying a high voltage when rewriting is performed causes electrophoretic particles to be densely deposited on an electrode, excellent display can be maintained over a long period of time even without performing display refreshing. In contrast, a low voltage, which is sufficient for rewriting the display, can be applied to a unit of display, such as the minute display 14 or the second display 15, which does not need to maintain display for a long period of time and which is less likely to cause adhesion of electrophoretic particles. Thus, power consumption can be reduced.
Parts (a) to (e) of
The controller 21 controls the scanning line driving circuit 23 and the data line driving circuit 24 to apply, every single month, a voltage to the month display 11 for an application time VLM, to apply, every single day, a voltage to the date display 12 for an application time VLD, to apply, every single hour, a voltage to the hour display 13 for an application time VLH, to apply, every single minute, a voltage to the minute display 14 for an application time VLmin, and to apply, every single second, a voltage to the second display 15 for an application time VLS.
The controller 21 applies a voltage to the electrophoretic element 32 included in a unit of display, such as the month display 11 or the date display 12, which has a longer rewrite interval, for a longer period of time. That is, the controller 21 controls the voltages to have a relationship satisfying the condition VLM≧VLD≧VLH≧VLmin≧VLS. The size of each of the voltages is not particularly limited as long as the condition VLM≧VLD≧VLH≧VLmin≧VLS is satisfied. For example, the relationship between the voltages may be represented by the condition VLM>VLD>VLH>VLmin≧VLS. Alternatively, for example, the relationship between the voltages may be represented by the condition VLM=VLD>VLH>VLmin=VLS.
Under such control, a voltage is applied to a unit of display that has a longer rewrite interval and that is likely to generate a residual image for a longer period of time. Thus, even if electrophoretic particles are adhered to an electrode or the like, the electrophoretic particles can be moved so as to achieve display of the next image without generating a residual image. In addition, since applying a voltage for a long period of time when rewriting is performed causes electrophoretic particles to be densely deposited on an electrode, excellent display can be maintained over a long period of time even without performing display refreshing. In contrast, a voltage is applied, for a short period of time, to a unit of display, such as the minute display 14 or the second display 15, which does not need to maintain display for a long period of time and which is less likely to cause adhesion of electrophoretic particles. Thus, power consumption can be reduced.
In order to apply a voltage for a longer period of time, the width of a driving pulse may be changed, as shown in part (a) to (e) of
In addition, applying a higher voltage to a unit of display having a longer rewrite interval for a longer period of time is also within the scope of the invention.
In the electronic watch 1 according to another embodiment of the invention, the controller 21 applies a voltage only to an electrophoretic element included in a unit of display having a rewrite interval that is longer than a predetermined period of time and performs display refreshing for the unit of display regularly or irregularly. For example, if the predetermined period of time is set to twelve hours, display refreshing is performed only for the month display 11 and the date display 12. A single display refreshing operation may be performed. Alternatively, display refreshing operations may be repeatedly performed. In addition, display refreshing operations may be performed for the month display 11 and the date display 12 at the same time. Alternatively, display refreshing operations may be performed for the month display 11 and the date display 12 at different timings.
When display refreshing operations are repeatedly performed, the display refreshing operations can be performed at an interval that is determined in consideration of the display holding performance of an electrophoretic dispersed system used and a desired display quality (acceptable quality). More specifically, the display refreshing operations can be performed at an interval that is shorter than a period of time in which the display holding performance of the electrophoretic dispersed system included in the electronic watch 1 is reduced to an unacceptable level. For example, when the display holding performance of the electrophoretic dispersed system included in the electronic watch 1 is represented by a contrast relative value shown in
In addition, as described above, when a display refreshing interval is determined by calculating a period of time in which the display holding performance is reduced to an unacceptable level, it is desirable that the display refreshing interval be set to be slightly shorter than the calculated period of time. If the display refreshing operations are performed at an interval that is slightly shorter than the calculated period of time, the display performance can always be maintained within an acceptable range, and at the same time, the number of display refreshing operations can be reduced to a minimum. Thus, unnecessary power consumption can be prevented.
Generally, the display holding performance of an electrophoretic dispersed system changes with the passage of time. Thus, a display refreshing interval may be determined in consideration of a change in the display holding performance. Such a configuration can be realized by, for example, the controller 21 processing display holding performance information, acquiring from the display holding performance information a period of time in which the display holding performance is reduced to an unacceptable level, determining a display refreshing interval based on the acquired period of time, and applying voltages to an electrophoretic element at the determined interval.
In contrast, a constant display refreshing interval may be set, irrespective of the deterioration speed of the display holding performance of a dispersed system, and a high voltage may be applied or a voltage may be applied for a long period of time so that the display holding performance is not reduced to an unacceptable level before the next refreshing operation is performed. For example, if a refreshing operation is performed every hour, a voltage large enough for maintaining display for an hour can be applied. In this case, if the voltage to be applied is set to a value that exactly offsets the reduction of the performance in an hour or a value that largely offsets the reduction of the performance in an hour, the display holding performance can always be maintained within an acceptable range, and unnecessary power consumption can be avoided. In addition, in this case, a change in the display holding performance of the dispersed system with the passage of time can be considered.
For electrophoretic devices and electrophoretic device driving methods according to the embodiments of the invention, the electronic watch 1 has been described by way of example. However, the electrophoretic devices and the electrophoretic device driving methods according to the embodiments of the invention are not necessarily limited to the electronic watch 1. For example, the electrophoretic devices and the electrophoretic device driving methods according to the embodiments of the invention can also be applied to an electronic apparatus having clock display or the like, such as a display having different rewrite intervals.
The invention is not limited to the foregoing embodiments. Various changes can be made to the invention without departing from the scope of the invention. For example, although an active-matrix structure has been explained as a circuit structure of an electrophoretic device, the electrophoretic device does not necessarily have such a circuit structure. For example, a driving method according to any of the foregoing embodiments can be applied to an electrophoretic device having a passive-matrix circuit structure or an electrophoretic device having a so-called segment-direct drive circuit structure in which a controller individually applies a driving voltage to each pixel electrode.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-250830 | Aug 2005 | JP | national |
