Patent Grant
9087487
This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2013-040795 filed Mar. 1, 2013.
(i) Technical Field
The present invention relates to a driving device of an image display medium, an image display apparatus, and a non-transitory computer-readable medium storing a driving program.
(ii) Related Art
Recently, an image display medium using colored particles has been known as a rewritable image display medium having a memory property. Such an image display medium includes, for example, a pair of substrates and plural types of particle groups enclosed between the substrates so as to migrate between the substrates with an applied electric field and having different colors and charging characteristics.
In such an image display medium, a voltage corresponding to an image is applied to across a pair of substrate to cause particles to migrate and the image is displayed using the contrast of particles having different colors. Even after the image is displayed and the application of the voltage is stopped, the particles continue to be attached to the substrates with a van der Waals force or an image force and thus the display of the image is maintained.
According to an aspect of the present invention, there is provided a driving device of an image display medium including: an electric field applying unit that applies an electric field between a pair of substrates, at least one of which has a light-transmitting property, of an image display medium including first particles of which a first start voltage for starting migration and a first end voltage for ending the migration vary depending on a variation in external environment and second particles of which a second start voltage for starting migration and a second end voltage for ending the migration vary depending on the variation in external environment and displaying an image on the basis of image information, the first particles and the second particles being enclosed between the pair of substrates; an external environment acquiring unit that acquires external environment information; an information storage unit that stores information of an initial driving electric field for applying an adhesive force, the absolute value of which satisfies the first start voltage<the first end voltage<the second start voltage<the second end voltage, to the first particles and the second particles depending on the external environment information and information of a writing electric field to be applied to the respective particles on the basis of the external environment information and a color to be displayed; and a controller that controls the electric field applying unit so as to apply an electric field between the pair of substrates on the basis of the color to be displayed and the information of the writing electric field stored in the information storage unit after applying the initial driving electric field between the pair of substrates on the basis of the external environment information and the information of the initial driving electric field stored in the information storage unit.
Exemplary embodiments of the present invention will be described in detail based on the following figures, wherein:
Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. Elements having like operational functions will be referenced by like reference numerals in the overall drawings and description thereof may not be repeated. For the purpose of simple explanation, the exemplary embodiments will be described with reference to the drawings appropriately showing a single cell.
It is assumed that cyan colored particles and magenta colored particles are used as colored particles in the exemplary embodiments. The cyan colored particles are referred to as cyan particles C, the magenta colored particles are referred to as magenta particles M, and the particles and the particle groups are referenced by the same reference signs (numerals).
The image display medium 10 includes a pair of substrates in which a display substrate 1 having a light-transmitting property and serving as an image display plane and a rear substrate 2 serving as a non-display plane are disposed to oppose each other with a gap therebetween.
Spacer members 5 are provided which maintain the substrates 1 and 2 at a fixed gap and which partition the space between the substrates into plural cells.
The cell represents a region surrounded with the rear substrate 2 having the rear electrode 4 disposed thereon, the display substrate 1 having the display electrode 3 disposed thereon, and the spacer members 5. A dispersion medium 6 including, for example, an insulating liquid and a first particle group 11, a second particle group 12, and a white particle group 13 dispersed in the dispersion medium 6 are enclosed in the cell.
The first particle group 11 and the second particle group 12 have different threshold characteristics for migration depending on the color and the electric field and have characteristics in which the first particle group 11 and the second particle group 12 independently migrate by applying a voltage equal to or larger than a predetermined threshold voltage between the pair of electrodes 3 and 4. On the other hand, the white particle group 13 is a particle group which has a smaller amount of electric charge than those of the first particle group 11 and the second particle group 12 and which does not migrate to any electrode even when a voltage for causing any one of the first particle group 11 and the second particle group 12 to migrate to any one electrode is applied between the electrodes.
White other than the colors of the electrophoretic particles may be displayed by mixing colorants into the dispersion medium.
The driving device 20 (the voltage applying unit 30 and the controller 40) applies a voltage based on a color to be displayed between the display electrode 3 and the rear electrode 4 of the image display medium 10 so as to cause the particle groups 11 and 12 to migrate and to attract the particle groups to any one of the display substrate 1 and the rear substrate 2 depending on the charged polarities thereof.
The voltage applying unit 30 is electrically connected to the display electrode 3 and the rear electrode 4. The voltage applying unit 30 is connected to the controller 40 so as to transmit and receive signals thereto and therefrom.
The controller 40 is constructed, for example, as a computer 40 as shown in
The voltage applying unit 30 is a voltage application device used to apply a voltage to the display electrode 3 and the rear electrode 4 and applies a voltage corresponding to the control of the controller 40 to the display electrode 3 and the rear electrode 4.
In this exemplary embodiment, for example, it is assumed that the rear electrode 4 is grounded and a voltage is applied to the display electrode 3.
An external environment acquiring unit 22 that acquires external environment information of the image display medium 10 is connected to the controller 40. The external environment acquiring unit 22 acquires external environment information as a factor for changing threshold characteristics of the particles enclosed between the pair of substrates of the image display medium 10. In this exemplary embodiment, for example, the external environment acquiring unit detects the environmental temperature of the image display medium 10 and outputs the detection result to the controller 40. That is, the external environment acquiring unit 22 is connected to the I/O 40E and the detection result is output to the controller 40. Light may be acquired as the external environment information and may be converted into a temperature.
As shown in
Therefore, the magenta particles M on the side of the rear substrate 2 start migration to the display substrate 1 by applying an electric field intensity of +VML or more between the substrates, and all the magenta particles M migrate to the display substrate 1 by applying an electric field intensity of +VMH or more between the substrates. The magenta particles M on the side of the display substrate 1 start migration to the rear substrate 2 by applying an electric field intensity of −VML or less between the substrates, and all the magenta particles M migrate to the rear substrate 2 by applying an electric field intensity of −VMH or less between the substrates.
The electric field intensity (threshold electric field intensity) at which the cyan particles C on the side of the rear substrate 2 start migration to the display substrate 1 is VCL, and the electric field intensity (threshold electric field intensity) at which all the cyan particles C end the migration to the display substrate 1 is VCH. The electric field intensity (threshold electric field intensity) at which the cyan particles C on the side of the display substrate 1 start migration to the rear substrate 2 is −VCL, and the electric field intensity (threshold electric field intensity) at which all the cyan particles C end the migration to the rear substrate 2 is −VCH.
Therefore, the cyan particles C on the side of the rear substrate 2 start migration to the display substrate 1 by applying an electric field intensity of +VCL or more, and all the cyan particles C migrate to the display substrate 1 by applying an electric field intensity of +VCH or more between the substrates. The cyan particles C on the side of the display substrate 1 start migration to the rear substrate 2 by applying an electric field intensity of −VCL or less, and all the cyan particles C migrate to the rear substrate 2 by applying an electric field intensity of −VCH or less between the substrates.
In this exemplary embodiment, it is assumed that the threshold characteristics of the magenta particles M and the cyan particles C are set in advance so as not to overlap with each other at a predetermined environmental temperature (for example, 20° C.) and the particles are able to be driven independently.
In the image display medium 10 having this configuration, since the display characteristics of the particles vary depending on a variation in external environment of the image display medium 10, the display characteristics needs to be corrected. As in this exemplary embodiment, when plural types of particles are used, the variation characteristic differs depending on the types of the particles and thus the same correction should not be performed on all the particles.
In the image display medium 10, for example, as shown in
When the environmental temperature is changed to 60° C., color mixture (hereinafter, also referred to as crosstalk) occurs as shown in
Therefore, in this exemplary embodiment, the external environment information detected by the external environment acquiring unit 22 is acquired and corrections different depending on the particles are performed on the basis of the acquired external environment information. At this time, when the acquired external environment information represents an external environment causing the crosstalk, the controller 40 performs a control of changing the threshold characteristics. Details of the method of changing the threshold characteristics will be described later.
In this exemplary embodiment, the threshold characteristics for each temperature of the particles are shown in
In this exemplary embodiment, as indicated by mark x in
Here, when color mixture occurs depending on the environmental temperature, the method of changing the threshold characteristics, which is performed by the controller 40, will be described below.
The relationship between the electric field intensity and the driving time of particles (migration time of particles) is the same as shown in
As shown in
Therefore, in this exemplary embodiment, by causing the controller 40 to control the driving energy of the initial driving voltage for forming an initial state, the threshold characteristic of the particles can be changed. Accordingly, the controller 40 changes the threshold characteristics to prevent crosstalk by changing the driving energy of the initial driving voltage when color mixture occurs on the basis of the image information and the external environment information (environmental temperature in this exemplary embodiment). Here, the initial state means a state where an electric field (equal to or more than VMH or equal to or less than −VMH in
Specifically, the table (table representing occurrence of color mixture for each environmental temperature and each display density) shown in
That is, in this exemplary embodiment, information of an initial driving electric field for applying an adhesive force, the absolute value of which satisfies the relational condition of migration start voltage of cyan particles C<migration end voltage of cyan particles C<migration start voltage of magenta particles M<migration end voltage of magenta particles M, to particles and information of a writing electric field to be applied to the particles on the basis of the external environment information and the color to be displayed are stored in the nonvolatile memory 40D or the like in advance, the initial driving electric field is applied between a pair of substrates on the basis of the stored information of the initial driving electric field and the external environment information, and an electric field is applied between the pair of substrates on the basis of the color to be displayed and the stored information of the writing electric field.
The control process flow which is performed by the CPU 40A of the controller 40 will be described below with reference to the flowchart shown in
In step S10, image information of an image to be displayed on the image display medium 10 is acquired from an external device not shown, for example, via the I/O 40E.
In step S12, the external environment information on the particle characteristics of the image display medium 10 is acquired from the external environment acquiring unit 22. For example, the environmental temperature around the image display medium 10 or environment information (for example, environment information in which a rise in temperature can be supposed from the intensity of light applied to the image display medium 10, the application time, and the like) in which the environmental temperature can be supposed are detected by the external environment acquiring unit 22 and the detection result is acquired through the I/O 40E.
In step S14, it is determined whether the density represented by the image information of a pixel of interest corresponds to the density causing crosstalk in the acquired external environment information (environmental temperature in this exemplary embodiment). That is, it is determined whether the density of the particles represented by the image information corresponding to the acquired environment information is a density causing color mixture using the table shown in
In step S16, the threshold characteristic is changed by changing the driving energy for forming the initial state and then the process flow goes to step S18. Regarding the change of the driving energy, the driving energy for forming the initial state is changed, for example, by determining driving energy as the threshold characteristic not causing color mixture for each density causing color mixture in the table shown in
In step S18, the driving voltage for each particle group depending on the external environment is calculated. That is, the driving voltage corrected to correspond to the variation in threshold characteristic different for each particle group is calculated depending on the environmental temperature. For example, a correction coefficient or the like is calculated using a predetermined table or function for calculating the amount of correction corresponding to ΔVC2 or ΔVM2 in
In step S20, an image displaying process is performed and then a series of processes ends. In the image displaying process, all particles are made to migrate to one substrate to form an initial state by applying a voltage for forming the initial state, and a gray scale corresponding to the image information is displayed by performing a control so as to apply a voltage for causing the particles to migrate on the basis of the image information from the formed initial state. By applying the driving voltage for each particle group corresponding to the external environment calculated in step S18 at the time of displaying the gray scale corresponding to the image information, correction varying by the particle groups is performed depending on the environmental variation. When there is no change in threshold characteristic at the time of forming the initial state, the voltage of predetermined driving energy is applied between the substrates. When there is a change in threshold characteristic, the voltage of driving energy corresponding to the changed threshold characteristic is applied between the substrates to change the threshold characteristic. As a result, it is possible to prevent color mixture corresponding to the environmental variation.
In this way, in this exemplary embodiment, even when the threshold characteristic of a particle group is changed differently depending on the environmental variation, the density of an image to be displayed is displayed by calculating the driving voltage with an amount of correction varying depending on the particle group and applying the calculated driving voltage between the substrates. When the threshold characteristic of a particle group varies depending on the environmental variation and crosstalk occurs, the driving energy for forming the initial state is controlled to change the threshold characteristic. Accordingly, it is possible to prevent occurrence of crosstalk.
In the exemplary embodiment, the state (a state where there is no crosstalk) where the threshold characteristics of the particle groups do not overlap with each other does not mean only the state where threshold characteristics do not perfectly overlap with each other, but includes an overlap state to such an extent that color mixture cannot be sensed with a human eye. That is, the voltage at which particles start migration or the voltage at which all the particles end the migration in the above-mentioned exemplary embodiment (VCL, VCH, VML, or VMH) means a voltage at which particles substantially start migration or a voltage at which all the particles substantially end the migration, but does not mean a voltage at which a first particle of the particles starts migration or a voltage at which all the particles perfectly end the migration.
The above-mentioned exemplary embodiment mentions an example where the driving energy is changed to change the threshold characteristics of the particles by fixing the voltage value and changing the voltage application time, but the threshold characteristics of the particles may be changed by fixing the voltage application time and changing the voltage value. Alternatively, both the voltage value and the voltage application time may be changed. The driving energy may be changed by changing the number of applications of a voltage.
Since the variation in threshold characteristic differs depending on the particle type or the temperature, the threshold characteristics of cyan and magenta may get apart from each other in some cases. In this case, the adhesive force is reduced within a range in which the threshold characteristics of cyan and magenta do not crosstalk with each other. That is, when the migration end voltage in the threshold characteristic of the particles on one side and the migration start voltage in the threshold characteristic of the particles on the other side get apart from each other by a predetermined value or more, the driving energy may be changed to reduce the adhesive force so that the migration end voltage in the threshold characteristic of the particles on one side and the migration start voltage in the threshold characteristic of the particles on the other side are within a predetermined range in which crosstalk does not occur. When the adhesive force is reduced, the electric field required for driving may be small and it is thus possible to expect to shorten the time required for displaying an image.
The above-mentioned exemplary embodiment mentions an example where the particle groups include two types of magenta particles M and cyan particles C, but the colors of the particle groups are not limited to the example. The number of types of particles may be three or more. For example, the particle groups may include three types of magenta particles M, cyan particles C, and yellow particles Y, may include four types of white particles W in addition thereto, or may further include other colored particles.
The processes in the controller 40 according to the above-mentioned exemplary embodiment may be performed by hardware or may be performed by executing a software program. The program may be distributed in a state where it is stored in various storage mediums.
The foregoing description of the exemplary embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013-040795 | Mar 2013 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 20070018945 | Machida et al. | Jan 2007 | A1 |
| 20080117165 | Machida et al. | May 2008 | A1 |
| Number | Date | Country |
|---|---|---|
| A-2007-033707 | Feb 2007 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20140247258 A1 | Sep 2014 | US |
