JP2012145601A - Display medium and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent occurrence of color mixture when displaying gradation.SOLUTION: A display medium 100 comprises: a display substrate 1 having light transmissivity; a back substrate 2 arranged opposite the display substrate 1 with a clearance between them; a dispersant 6 filled in an inter-substrate between the display substrate 1 and back substrate 2; first electrophoresis particles 11 dispersed in the dispersant 6 and detached from either one of the display substrate 1 and back substrate 2 and moved to the other substrate by being charged to a positive or negative polarity and applying a first voltage to the inter-substrate; and second electrophoresis particles 12 dispersed in the dispersant 6 and detached from either one of the display substrate 1 and back substrate 2 and moved to the other substrate by being different from the first electrophoresis migration particles 11 in color and charging polarity and applying a second voltage, which is smaller in absolute value than the first voltage, to the inter-substrate. The first electrophoresis particles 11 and second electrophoresis particles 12 are dissociated from each other by applying a third voltage smaller in absolute value than the first voltage.

Description

  The present invention relates to a display medium and a display device.

  In Patent Document 1, at least one of a pair of light-transmitting substrates, a liquid sealed between the substrates, dispersed in the liquid, charged with opposite polarities, move according to an electric field. Therefore, there is disclosed an image display medium including two kinds of colored particles having different absolute values of voltages necessary for the above and different colors.

JP 2008-185641 A

  In the present invention, when gradation display is performed, a voltage necessary for dissociating an aggregate of a plurality of types of particles charged to different polarities is the voltage of a particle having a higher voltage necessary for separation from a substrate. It is an object of the present invention to provide a display medium and a display device that can prevent color mixing from occurring when compared with a higher case.

  According to a first aspect of the present invention, there is provided a display medium having a light-transmitting property, a back substrate disposed to face the display substrate with a gap, and a substrate between the display substrate and the back substrate. An encapsulated dispersion medium, dispersed in the dispersion medium, positively or negatively charged, and peeled from one of the display substrate and the back substrate by applying a first voltage between the substrates. The first particles moving to the other substrate, dispersed in the dispersion medium, differing in color and charging polarity from the first particles, and having an absolute voltage value higher than the first voltage between the substrates. A second particle that is peeled off from one of the display substrate and the back substrate when a second voltage having a small value is applied, and moves to the other substrate, and the first particle and The second particles are formed on the display substrate and the back substrate. In a state of moving to one substrate side, a third voltage having a smaller absolute value than the first voltage is applied between the substrates, whereby the first particle and the second voltage are applied. Dissociate from the other particles.

  According to a second aspect of the present invention, when the first particles and the second particles are moving to one of the display substrate and the back substrate, the absolute value of the voltage value is the first value. Is applied between the substrates, the first particles move to the display substrate side and the second particles move to the back substrate side, and then the first particles The first voltage corresponding to the display concentration of particles is applied between the substrates, so that the first particles corresponding to the display concentration of the first particles remain on the display substrate side and the other The first particles move to the back substrate side and the second particles move to the display substrate side.

  According to a third aspect of the present invention, when the first particles and the second particles are moving to one of the display substrate and the back substrate, the absolute value of the voltage value is the first value. Is applied between the substrates, the first particles move to the back substrate side, the second particles move to the display substrate side, and then the first particles. By applying the first voltage according to the display density between the substrates, the first particles according to the display density of the first particles move to the display substrate side, and the other The first particles remain on the back substrate side and the second particles move to the back substrate side.

  According to a fourth aspect of the present invention, there is provided a display medium having a translucent display substrate, a back substrate disposed to face the display substrate with a gap, and a substrate between the display substrate and the back substrate. An encapsulated dispersion medium, dispersed in the dispersion medium, positively or negatively charged, and peeled from one of the display substrate and the back substrate by applying a first voltage between the substrates. The first particles moving to the other substrate, dispersed in the dispersion medium, differing in color and charging polarity from the first particles, and having an absolute voltage value higher than the first voltage between the substrates. Second particles that are peeled off from one of the display substrate and the back substrate and applied to the other substrate by applying a second voltage having a small value, are dispersed in the dispersion medium, and The first particles and the second particles are different in color and before When a third voltage having a smaller absolute value than the second voltage is applied between the substrates, the third substrate peels from one of the display substrate and the rear substrate and moves to the other substrate. 3 particles, and in a state where the first particles and the second particles are moving to one of the display substrate and the back substrate, the voltage value is higher than the first voltage. When the fourth voltage having a small absolute value is applied between the substrates, the first particles and the second particles are dissociated, and the first particles have a polarity different from that of the third particles. Alternatively, in the state where the second particles and the third particles are moving to one of the display substrate and the back substrate, the absolute value of the voltage value is higher than the second voltage. The absolute value of the voltage value is smaller than the fourth voltage. By voltage of 5 is applied between the substrate and the third particles and the third particles and the first polarity different particles or the second particles is dissociated.

  According to a fifth aspect of the present invention, when the first particles and the second particles are moving to one of the display substrate and the back substrate, the absolute value of the voltage value is the first value. Is applied between the substrates, the first particles move to the display substrate side and the second particles move to the back substrate side, and then the first particles The first voltage corresponding to the display concentration of particles is applied between the substrates, so that the first particles corresponding to the display concentration of the first particles remain on the display substrate side and the other The first particles move to the back substrate side and the second particles move to the display substrate side.

  According to a sixth aspect of the present invention, the first particle or the second particle having a polarity different from that of the third particle and the third particle are one of the display substrate and the back substrate. In the state where the first particles and the second particles are moving toward the display substrate, the second voltage corresponding to the display concentration of the second particles is By being applied, the second particles corresponding to the display concentration of the second particles remain on the display substrate side and the other second particles move to the back substrate side, and the third The particles have moved to the display substrate side or the back substrate side.

  According to a seventh aspect of the present invention, the absolute value of the voltage value is the first value when the first particles and the second particles are moving to one of the display substrate and the back substrate. Is applied between the substrates, the first particles move to the back substrate side, the second particles move to the display substrate side, and then the first particles. By applying the first voltage according to the display density between the substrates, the first particles according to the display density of the first particles move to the display substrate side, and the other The first particles remain on the back substrate side and the second particles move to the back substrate side.

  According to an eighth aspect of the present invention, the first particle or the second particle having a polarity different from that of the third particle and the third particle are one of the display substrate and the back substrate. In the state where the first particles and the second particles are moving to the back substrate side, the second voltage corresponding to the display concentration of the second particles is By being applied, the second particles according to the display concentration of the second particles move to the display substrate side and the other second particles move to the back substrate side, and the second particles move to the back substrate side. 3 particles are moved to the display substrate side or the back substrate side.

  A display device according to a ninth aspect of the present invention is a voltage application that applies a voltage according to image information between the display medium according to any one of the first to eighth aspects and the substrate of the display medium. Means.

  According to the first to ninth aspects of the present invention, in the case of gradation display, the voltage necessary for the separation of the aggregate of a plurality of types of particles charged to different polarities is the voltage necessary for peeling from the substrate. As compared with the case where the voltage of the higher particle is higher than the voltage, the color mixing can be prevented from occurring.

It is the schematic which shows the display apparatus which concerns on 1st Embodiment. It is a figure which shows the voltage application characteristic of each migrating particle which concerns on 1st Embodiment. It is the schematic which shows the behavior of the electrophoretic particle according to the voltage application in the display apparatus which concerns on 1st Embodiment. It is the schematic which shows the behavior of the electrophoretic particle according to the voltage application in the display apparatus which concerns on 1st Embodiment. It is the schematic which shows the behavior of the electrophoretic particle according to the voltage application in the display apparatus which concerns on 1st Embodiment. It is the schematic which shows the behavior of the electrophoretic particle according to the voltage application in the display apparatus which concerns on 1st Embodiment. It is a figure which shows the voltage application characteristic of each migrating particle which concerns on 2nd Embodiment. It is the schematic which shows the behavior of the electrophoretic particle according to the voltage application in the display apparatus which concerns on 2nd Embodiment. It is the schematic which shows the behavior of the electrophoretic particle according to the voltage application in the display apparatus which concerns on 2nd Embodiment. It is the schematic which shows the behavior of the electrophoretic particle according to the voltage application in the display apparatus which concerns on 2nd Embodiment. It is the schematic which shows the behavior of the electrophoretic particle according to the voltage application in the display apparatus which concerns on 2nd Embodiment. It is a figure which shows the voltage application characteristic of each migrating particle which concerns on 3rd Embodiment. It is the schematic which shows the behavior of the electrophoretic particle according to the voltage application in the display apparatus which concerns on 3rd Embodiment. It is the schematic which shows the behavior of the electrophoretic particle according to the voltage application in the display apparatus which concerns on 3rd Embodiment. It is the schematic which shows the behavior of the electrophoretic particle according to the voltage application in the display apparatus which concerns on 3rd Embodiment. It is the schematic which shows the behavior of the electrophoretic particle according to the voltage application in the display apparatus which concerns on 3rd Embodiment. It is a figure which shows the relationship between the threshold voltage of the magenta particle | grains M, and the maximum value of the aggregation dissociation voltage of CM particle | grains.

  Embodiments of the present invention will be described below with reference to the drawings. Members having the same functions and functions are given the same reference numbers throughout the drawings, and redundant descriptions may be omitted. In addition, in order to simplify the description, the present embodiment will be described with reference to a diagram that focuses on one cell as appropriate.

  Further, cyan particles are denoted by cyan particles C, magenta particles are denoted by magenta particles M, yellow particles are denoted by yellow particles Y, and each particle and its particle group are indicated by the same symbol (symbol).

<First Embodiment>

  FIG. 1A schematically shows a display device according to the first embodiment. The display device 100 includes a display medium 10 and a drive device 20 that drives the display medium 10. The driving device 20 controls the voltage application unit 30 that applies a voltage between the display-side electrode 3 and the back-side electrode 4 of the display medium 10 and the voltage application unit 30 according to image information of an image to be displayed on the display medium 10. And a control unit 40.

  In the display medium 10, a translucent display substrate 1 serving as an image display surface and a back substrate 2 serving as a non-display surface are disposed to face each other with a gap.

  A gap member 5 is provided that holds the substrates 1 and 2 at a predetermined interval and partitions the substrates into a plurality of cells.

  The cell indicates a region surrounded by the back substrate 2 provided with the back side electrode 4, the display substrate 1 provided with the display side electrode 3, and the gap member 5. In the cell, a dispersion medium 6 made of, 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.

  The first particle group 11 and the second particle group 12 are different in color and charging polarity, and by applying a voltage equal to or higher than a predetermined threshold voltage between the pair of electrodes 3 and 4, Each of the two particle groups 12 has a characteristic of migrating alone. On the other hand, the white particle group 13 has a smaller charge amount than the first particle group 11 and the second particle group 12, and the voltage at which the first particle group 11 and the second particle group 12 move to one of the electrode sides is the electrode. A particle group that does not move to any electrode side even when applied between them.

  In addition, you may display white different from the color of electrophoretic particle by mixing a coloring agent with a dispersion medium.

  The drive device 20 (the voltage application unit 30 and the control unit 40) migrates the particle groups 11 and 12 by applying a voltage corresponding to the color displayed between the display side electrode 3 and the back side electrode 4 of the display medium 10. Then, it is attracted to either the display substrate 1 or the back substrate 2 according to the respective charging polarities.

  The voltage application unit 30 is electrically connected to the display side electrode 3 and the back side electrode 4, respectively. Further, the voltage application unit 30 is connected to the control unit 40 so as to exchange signals.

  As shown in FIG. 1B, the control unit 40 is configured as a computer 40, for example. The computer 40 includes a CPU (Central Processing Unit) 40A, a ROM (Read Only Memory) 40B, a RAM (Random Access Memory) 40C, a non-volatile memory 40D, and an input / output interface (I / O) 40E via a bus 40F. The voltage application unit 30 is connected to the I / O 40E. In this case, a program for causing the computer 40 to execute processing for instructing the voltage application unit 30 to apply a voltage necessary for displaying each color is written in, for example, the nonvolatile memory 40D, and this is read and executed by the CPU 40A. The program may be provided by a recording medium such as a CD-ROM.

  The voltage application unit 30 is a voltage application device for applying a voltage to the display side electrode 3 and the back side electrode 4, and applies a voltage according to the control of the control unit 40 to the display side electrode 3 and the back side electrode 4. .

  In the present embodiment, a case where the display-side electrode 3 is grounded and a voltage is applied to the back-side electrode 4 will be described as an example.

  FIG. 2 shows the characteristics of the applied voltage necessary to move the cyan particles C and magenta particles M to the display substrate 1 side and the back substrate 2 side in the display device 100 according to the present embodiment. In FIG. 2, the applied voltage characteristic of cyan particles C is represented by characteristic 50C, and the applied voltage characteristic of magenta particles M is represented by characteristic 50M.

  FIG. 2 shows the relationship between the pulse voltage applied to the surface side electrode 3 with the display side electrode 3 as the ground (0 V) and the display density by each particle group.

  As shown in FIG. 2, the movement start voltage (threshold voltage) at which the magenta particles M on the back substrate 2 side start moving to the display substrate 1 side is −Vm, and the magenta particles M on the display substrate 1 side are on the back substrate 2 side. The movement start voltage (threshold voltage) at which the movement starts is + Vm. Therefore, by applying a voltage of −Vm or less, the magenta particles on the back substrate 2 side move to the display substrate 1 side, and by applying a voltage of + Vm or more, the magenta particles M on the display substrate 1 side are moved to the back substrate 2 side. Move to.

  The amount of particles that move the magenta particles M on the back substrate 2 side to the display substrate 1 side is controlled by the pulse width (application time) when the voltage values of the applied voltages are the same (pulses), for example. Width modulation). For example, when the voltage value to be applied is set to a predetermined voltage smaller than −Vm, the amount of magenta particles M to be moved to the display substrate 1 side increases as the pulse width becomes longer. Thereby, the gradation display of the magenta particles M is controlled. The same applies to the amount of particles when the magenta particles M on the display substrate 1 side are moved to the back substrate 2 side.

  Further, the movement start voltage (threshold voltage) at which the cyan particles C on the back substrate 2 side start to move toward the display substrate 1 side is + Vc, and the movement start at which the cyan particles C on the display substrate 1 side start to move toward the back substrate 2 side. The voltage is -Vc. Accordingly, the cyan particles C on the rear substrate 2 side move to the display substrate 1 side by applying a voltage of + Vc or higher, and the cyan particles C on the display substrate 1 side of the rear substrate 2 move by applying a voltage of −Vc or lower. Move to the side.

  As shown in FIG. 2, | Vm | (first voltage)> | Vc | (second voltage).

  The amount of particles for moving the cyan particles C on the back substrate 2 side to the display substrate 1 side and the amount of particles for moving the cyan particles C on the display substrate 1 side to the back substrate 2 side are the same as in the case of the magenta particles M described above. For example, when the voltage values of the applied voltages are the same, the pulse width is controlled.

  Note that the pulse width of the voltage to be applied may be the same, and the amount of moving particles may be controlled by changing the voltage value to control gradation display (voltage modulation). For example, when controlling the amount of particles that move the magenta particles M on the back substrate 2 side to the display substrate 1 side, the pulse width of the applied voltage is the same and the voltage value is set to an arbitrary voltage value of −Vm or less. The magenta particles M having a particle amount corresponding to the voltage value can be moved to the display substrate 1 side.

  Hereinafter, as an example, a case where the amount of particles moving is controlled by voltage modulation will be described.

  Next, display of each color will be described. The display side electrode 3 is set to the ground (0V). Further, it is assumed that the magenta particles M and the cyan particles C are enclosed between the substrates in the same amount.

  3 to 6 schematically show an example of the behavior of magenta particles M and cyan particles C in response to voltage application in the display medium according to the first embodiment. 3 to 6, the white particles 13, the dispersion medium 6, the gap member 5, and the like are omitted.

  In the present embodiment, the first particles 11 are negatively charged electrophoretic particles (magenta particles M) having a magenta color, and the second particles 12 are positively charged electrophoretic particles (cyan particles) having a cyan color. Although the case of C) will be described, the present invention is not limited to this. The color and charging polarity of each particle may be set as appropriate. In addition, the value of the voltage to be applied in the following description is also an example, and is not limited thereto, and may be set as appropriate according to the charging polarity of each particle, the responsiveness, the distance between the electrodes, and the like.

  As shown in FIG. 3A, a voltage value smaller than −Vm at the back side electrode 4 and a voltage value necessary for attaching all the magenta particles M on the back substrate 2 side to the display substrate 1 side. When the voltage V1 is applied with a predetermined pulse width, all negatively charged magenta particles M migrate to the display substrate 1 side and positively charged cyan particles C migrate to the back substrate 2 side and adhere to the entire surface of each substrate. It becomes a state. As a result, a magenta color is displayed.

  From the state of FIG. 3A (magenta display), as shown in FIG. 3B, the back side electrode 4 has a voltage value greater than + Vm and all the magenta particles M on the display substrate 1 side are transferred to the back substrate. When the voltage of the voltage value + V1 necessary for attaching all the cyan particles C on the rear substrate 2 side to the display substrate 1 side is applied with a predetermined pulse width, the positively charged cyan particles C are attached to the second substrate 2 side. The negatively charged magenta particles M migrate to the back substrate 2 side and adhere to the entire surface of each substrate. As a result, a cyan color is displayed.

  From the state of FIG. 3B (cyan display), as shown in FIG. 3C, the back side electrode 4 has a voltage value smaller than −Vc and larger than −Vm, and cyan particles on the display substrate 1 side. Among the C, cyan particles C having a particle amount corresponding to the gradation to be displayed are left on the display substrate 1 side, and other cyan particles C (cyan particles C to be peeled off from the display substrate 1) are moved to the back substrate 2 side. When a voltage having a voltage value −V2 necessary for this is applied with a predetermined pulse width, cyan particles C having an amount of particles to be peeled according to the gradation migrate to the back substrate 2 side and adhere to the back substrate 2 side. It becomes a state. FIG. 3C shows a case where the number of cyan particles C moving to the back substrate 2 decreases in the order of the left side, the center, and the right side. That is, the pulse width of the applied voltage becomes shorter in the order of left side, center, and right side in FIG.

  From the state of FIG. 4A (same as FIG. 3A) (magenta display), as shown in FIG. 4B, the back-side electrode 4 has a voltage value greater than + Vm and the display substrate 1 side. Among the magenta particles M, the magenta particles M having a particle amount corresponding to the gradation to be displayed are left on the display substrate 1 side, and other magenta particles M (magenta particles M to be peeled off from the display substrate 1) are on the rear substrate 2 side. When a voltage of the voltage value + V1 necessary to move to the surface is applied with a predetermined pulse width, magenta particles M having an amount of particles to be separated according to the gradation migrate to the back substrate 2 side and move to the back substrate 2 side. At the same time, the cyan particles C migrate to the display substrate 1 side and adhere to the display substrate 1.

  Then, from the state of FIG. 4B, as shown in FIG. 4C, the back side electrode 4 has a voltage value smaller than −Vc and larger than −Vm, and the cyan particles C on the display substrate 1 side. Of these, cyan particles C having a particle amount corresponding to the gradation to be displayed are left on the display substrate 1 side, and other cyan particles C (cyan particles C to be peeled off from the display substrate 1) are attached to the back substrate 2 side. When a voltage having a necessary voltage value −V2 is applied with a predetermined pulse width, cyan particles C having an amount of particles to be peeled according to the gradation migrate to the back substrate 2 side and adhere to the back substrate 2 side. Become.

  FIG. 4C shows a case where the number of cyan particles C moving to the back substrate 2 side decreases in the order of the left side, the center, and the right side, as in FIG. 3C. That is, the voltage value of the applied voltage decreases in the order of the left side, the center, and the right side in FIG.

  FIGS. 5 and 6 are also the same as FIG. 4. To the rear substrate 2 side when shifting from the state shown in FIG. 5A to the state shown in FIG. 5B and from FIG. 6A to FIG. The only difference is the amount of the moving magenta particles M.

  Here, in the states of FIGS. 4B, 5B, and 6B, the magenta particles M and the cyan particles C are attached to the display substrate 1 side, and the cyan particles C charged to different polarities. The magenta particles M are electrostatically aggregated. Even when the voltage −V2 is applied to move only the cyan particles C to the back substrate 2 side from this state, the magenta particles M of different polarity and the aggregated cyan particles C cannot be moved or should not move originally. In some cases, the magenta particles M move to the rear substrate 2 while being aggregated with the cyan particles C.

  In order to prevent this, the adhesive force of the magenta particles M to the substrate needs to be stronger than the cohesive force of the CM particles.

  Therefore, in the display medium 100 according to the present embodiment, for example, the magenta particles M are moved to the display substrate 1 side, and the cyan particles C are moved to the rear substrate 2 side, and then a part of the magenta particles M is rear surface substrate 2. By moving the cyan particles C to the display substrate 1 side and moving the magenta particles M and the cyan particles C to the display substrate 1 side, the threshold voltage | Vm | 1), a voltage | VA | (third voltage) whose absolute value is smaller than the voltage value is applied, so that the aggregates of cyan particles C and magenta particles M are dissociated. The characteristics of the substrate surface are controlled. 4B, FIG. 5B, and FIG. 6B, when a voltage having a voltage value −V2 that is smaller than −Vc and larger than −Vm is applied, only the cyan particles C are exposed to the rear substrate 2. Move to the side.

  In this embodiment, the case where the magenta particle M is negatively charged and the cyan particle C is positively charged has been described, but the magenta particle M is positively charged and the cyan particle C is negatively charged. Good. In this case, the movement of each particle is the reverse of the above.

Second Embodiment

  Next, a second embodiment of the present invention will be described. In the present embodiment, a display medium having three types of electrophoretic particles will be described.

  The display medium according to the present embodiment has positively charged cyan particles C, negatively charged magenta particles M, and larger diameters than the cyan particles C and magenta particles M as electrophoretic particles in the dispersion medium. In this configuration, the charged yellow particles Y are dispersed. Since the drive device 20 is the same as that of the first embodiment, description thereof is omitted.

  FIG. 7 shows the characteristics of the applied voltage necessary to move the cyan particles C, magenta particles M, and yellow particles Y to the display substrate 1 side and the back substrate 2 side in the display device 100 according to the present embodiment. . In FIG. 7, the applied voltage characteristic of the cyan particle C is represented by a characteristic 50C, the applied voltage characteristic of the magenta particle M is represented by a characteristic 50M, and the applied voltage characteristic of the yellow particle Y is represented by 50Y.

  FIG. 7 shows the relationship between the pulse voltage applied to the surface-side electrode 3 with the display-side electrode 3 as ground (0 V) and the display density of each particle group.

  The applied voltage characteristics of the cyan particles C and the magenta particles M are the same as those in the first embodiment, and thus description thereof will be omitted. The applied voltage characteristics 50Y of the yellow particles Y will be described.

  As shown in FIG. 7, the movement start voltage (threshold voltage) at which the yellow particles Y on the back substrate 2 side start moving to the display substrate 1 side is −Vy, and the yellow particles Y on the display substrate 1 side are on the back substrate 2 side. The movement start voltage (threshold voltage) at which the movement starts is + Vy. Therefore, the yellow particles Y on the back substrate 2 side move to the display substrate 1 side by applying a voltage of −Vy or less, and the yellow particles Y on the display substrate 1 side of the back substrate 2 are applied by applying a voltage of + Vy or more. Move to the side. As shown in FIG. 7, | Vm | (first voltage)> | Vc | (second voltage)> | Vy | (third voltage).

  The amount of particles that move the yellow particles Y on the back substrate 2 side to the display substrate 1 side is controlled by the pulse width (pulse width modulation), for example, when the applied voltage value is the same. For example, when the voltage value of the applied voltage is set to a predetermined voltage smaller than −Vy, the amount of yellow particles Y moved to the display substrate 1 side increases as the pulse width becomes longer. Thereby, the gradation display of the yellow particles Y is controlled. The same applies to the amount of particles when the yellow particles Y on the display substrate 1 side are moved to the back substrate 2 side.

  Note that the pulse width of the voltage to be applied may be the same, and the amount of moving particles may be controlled by changing the voltage value to control gradation display (voltage modulation). For example, when controlling the amount of particles that move the yellow particles Y on the back substrate 2 side to the display substrate 1 side, the pulse width of the applied voltage is the same, and the voltage value is set to an arbitrary voltage value of −Vy or less. The yellow particles Y having a particle amount corresponding to the voltage value can be moved to the display substrate 1 side.

  Hereinafter, as an example, a case where the amount of particles moving is controlled by voltage modulation will be described.

  Next, display of each color will be described. The display side electrode 3 is set to the ground (0V).

  8 to 11 schematically show an example of the behavior of magenta particles M, cyan particles C, and yellow particles Y in response to voltage application in the display medium according to the second embodiment. 8 to 11, the white particles 13, the dispersion medium 6, the gap member 5, and the like are omitted.

  In the present embodiment, the case where the display medium includes a negatively charged magenta particle M, a positively charged cyan particle C, and a negatively charged yellow particle Y will be described. However, the present invention is not limited to this. The color and charging polarity of each particle may be set as appropriate. In addition, the value of the voltage to be applied in the following description is also an example, and is not limited thereto, and may be set as appropriate according to the charging polarity of each particle, the responsiveness, the distance between the electrodes, and the like.

  As shown in FIG. 8A, the voltage value of the back side electrode 4 is less than −Vm and is necessary for attaching all the magenta particles M on the back substrate 2 side to the display substrate 1 side. When the voltage V1 is applied with a predetermined pulse width, all negatively charged magenta particles M and all yellow particles Y migrate to the display substrate 1 side, and positively charged cyan particles C migrate to the back substrate 2 side. It will be in the state which adhered to the whole surface of the board | substrate. As a result, a mixed color of magenta and yellow particles Y is displayed.

  From the state of FIG. 8 (A), as shown in FIG. 8 (B), the back side electrode 4 has a voltage value greater than + Vm, and all the magenta particles M and yellow particles Y on the display substrate 1 side are transferred to the back substrate. When the voltage of the voltage value + V1 necessary for attaching all the cyan particles C on the rear substrate 2 side to the display substrate 1 side is applied with a predetermined pulse width, the positively charged cyan particles C are attached to the second substrate 2 side. The negatively charged magenta particles M and yellow particles Y migrate to the rear substrate 2 side and adhere to the entire surface of each substrate on the display substrate 1 side. As a result, a cyan color is displayed.

  From the state of FIG. 8B, as shown in FIG. 8C, the back side electrode 4 has a voltage value smaller than −Vc and larger than −Vm, and is displayed among the cyan particles C on the display substrate 1 side. Necessary for moving cyan particles C (cyan particles C to be peeled off from the display substrate 1) to the back substrate 2 side while leaving the cyan particles C having a particle amount corresponding to the gradation to be processed on the display substrate 1 side. When a voltage having a voltage value of −V2 is applied with a predetermined pulse width, cyan particles C having an amount of particles to be separated according to the gradation migrate to the back substrate 2 side and are attached to the back substrate 2 side. FIG. 8C shows a case where the number of cyan particles C moving to the back substrate 2 side decreases in the order of the left side, the center, and the right side. That is, the pulse width of the applied voltage becomes shorter in the order of left side, center, and right side in FIG.

  8C, from the center state, as shown in FIG. 8D, the back side electrode 4 has a voltage value larger than + Vy and smaller than + Vc, and is displayed among the yellow particles Y on the display substrate 1 side. The voltage necessary to leave the yellow particles Y of the amount corresponding to the power gradation on the display substrate 1 side and move the other yellow particles Y (the yellow particles Y to be peeled from the display substrate 1) to the back substrate 2 side. When a voltage of the value + V3 is applied with a predetermined pulse width, yellow particles Y having an amount of particles to be peeled according to the gradation migrate to the back substrate 2 side and are attached to the back substrate 2 side.

  From the state of FIG. 9A (same as FIG. 8A), as shown in FIG. 9B, the back side electrode 4 has a voltage value greater than + Vm, and the magenta particles M on the display substrate 1 side. The magenta particles M having a particle amount corresponding to the gradation to be displayed are left on the display substrate 1 side, and the other magenta particles M (magenta particles M to be peeled off from the display substrate 1) are moved to the rear substrate 2 side. Is applied at a predetermined pulse width, the magenta particles M having the amount of particles to be peeled off and all the yellow particles Y migrate to the back substrate 2 side according to the gradation and migrate to the back substrate 2 side. At the same time, the cyan particles C migrate to the display substrate 1 side and adhere to the display substrate 1.

  Then, from the state of FIG. 9 (B), as shown in FIG. 9 (C), the voltage applied to the back side electrode 4 is less than −Vc and greater than −Vm, and among the cyan particles C on the display substrate 1 side. Necessary for leaving cyan particles C having a particle amount corresponding to the gradation to be displayed on the display substrate 1 side, and attaching other cyan particles C (cyan particles C to be peeled off from the display substrate 1) to the back substrate 2 side. When a voltage having a negative voltage value −V2 is applied with a predetermined pulse width, cyan particles C having an amount of particles to be separated according to the gradation migrate to the back substrate 2 side and are attached to the back substrate 2 side. .

  FIG. 9C shows a case where the number of cyan particles C moving to the back substrate 2 side decreases in the order of the left side, the center, and the right side as in FIG. 8C. That is, the pulse width of the applied voltage becomes shorter in the order of left side, center, and right side in FIG.

  From the state of FIG. 9 (C), as shown in FIG. 9 (D), a voltage value larger than + Vy and smaller than + Vc is displayed on the back side electrode 4 among the yellow particles Y on the display substrate 1 side. The voltage necessary to leave the yellow particles Y of the amount corresponding to the power gradation on the display substrate 1 side and move the other yellow particles Y (the yellow particles Y to be peeled from the display substrate 1) to the back substrate 2 side. When a voltage of the value + V3 is applied with a predetermined pulse width, yellow particles Y having an amount of particles to be peeled according to the gradation migrate to the back substrate 2 side and are attached to the back substrate 2 side.

  10 and 11 are also the same as FIG. 9, and the back substrate when the state is changed from FIG. 10 (A) to the state of FIG. 11 (B) and from FIG. 11 (A) to the state of FIG. The only difference is the amount of magenta particles M moving to the two sides. 10 and 11, the gradation display of the yellow particles Y is not shown.

  8C, 9C, 10C, and 11C, the cyan and C particles are attached to the display substrate 1 side. In other words, the yellow particles Y and the cyan particles C charged to different polarities are electrostatically aggregated. Even when the voltage + V3 is applied to move only the yellow particles Y to the back substrate 2 side from this state, the cyan particles C of different polarity and the aggregated yellow particles Y cannot be moved, or cyan which should not move originally. The particles C may move to the back substrate 2 while being agglomerated with the yellow particles Y.

  In order to prevent this, the adhesion force of cyan particles C to the substrate is stronger than the aggregation force of CY particles, and the aggregation force of CM particles is equal to the adhesion force of yellow particles Y to the substrate and the aggregation force of CY particles. Need to be stronger.

  Therefore, in the display medium 100 according to the present embodiment, for example, the magenta particles M are moved to the display substrate 1 side, and the cyan particles C are moved to the rear substrate 2 side, and then a part of the magenta particles M is rear surface substrate 2. By moving the cyan particles C to the display substrate 1 side and moving the magenta particles M and the cyan particles C to the display substrate 1 side, the threshold voltage | Vm | The voltage | VA | (fourth voltage) having a smaller absolute value than the voltage 1 is applied to dissociate the aggregates of the cyan particles C and the magenta particles M. After moving to the display substrate 1 side and moving the yellow particles Y to the back substrate 2 side, a part of the cyan particles C is moved to the back substrate 2 side and the yellow particles Y are moved to the display substrate 1 side. Thus, in a state where the cyan particles C and the yellow particles Y are moving toward the display substrate 1, the absolute value of the voltage value is smaller than the threshold voltage | Vc | (second voltage) of the cyan particles C and CM. By applying a voltage | VB | (fifth voltage) having a smaller absolute value than the voltage | VA | at which particle aggregation dissociates, the yellow particles Y and cyan particles C are dissociated. The characteristics of each particle and the characteristics of the substrate surface are controlled. Accordingly, when a voltage of + V3, which is larger than + Vy and smaller than + Vc in the center and right side states of FIGS. 8C, 9C, 10C, and 11C, is applied, Only the yellow particles Y move to the back substrate 2 side.

  In this embodiment, the case where the magenta particle M is negatively charged, the cyan particle C is positively charged, and the yellow particle Y is negatively charged has been described. However, the magenta particle M is positively charged and the cyan particle C C may be negatively charged and the yellow particles Y may be positively charged. In this case, the movement of each particle is the reverse of the above.

<Third Embodiment>

  Next, a third embodiment of the present invention will be described.

  The display medium according to the present embodiment is different from the second embodiment in that the yellow particles Y are positively charged. Since the drive device 20 is the same as that of the first embodiment, description thereof is omitted.

  FIG. 12 shows the characteristics of the applied voltage necessary to move the cyan particles C, magenta particles M, and yellow particles Y to the display substrate 1 side and the back substrate 2 side in the display device 100 according to the present embodiment. . As shown in FIG. 12, only the applied voltage characteristic 50Y of the yellow particles Y is different from the applied voltage characteristic 50Y shown in FIG. 7 described in the second embodiment. Accordingly, the applied voltage characteristics of the cyan particles C and the magenta particles M are the same as those in the first and second embodiments, and thus description thereof will be omitted. The applied voltage characteristics 50Y of the yellow particles Y will be described.

  As shown in FIG. 12, the movement start voltage (threshold voltage) at which the yellow particles Y on the back substrate 2 side start moving to the display substrate 1 side is + Vy, and the yellow particles Y on the display substrate 1 side go to the back substrate 2 side. The movement start voltage (threshold voltage) at which movement starts is −Vy. Accordingly, the yellow particles Y on the back substrate 2 side move to the display substrate 1 side by applying a voltage of + Vy or higher, and the yellow particles Y on the display substrate 1 side are transferred to the back substrate 2 by applying a voltage of −Vy or less. Move to the side.

  The amount of particles that move the yellow particles Y on the back substrate 2 side to the display substrate 1 side is controlled by the pulse width (pulse width modulation), for example, when the applied voltage value is the same. For example, when the voltage value to be applied is a predetermined voltage greater than + Vy, the amount of yellow particles Y to be moved to the display substrate 1 side increases as the pulse width becomes longer. Thereby, the gradation display of the yellow particles Y is controlled. The same applies to the amount of particles when the yellow particles Y on the display substrate 1 side are moved to the back substrate 2 side.

  Note that the pulse width of the voltage to be applied may be the same, and the amount of moving particles may be controlled by changing the voltage value to control gradation display (voltage modulation). For example, when controlling the amount of particles that move the yellow particles Y on the back substrate 2 side to the display substrate 1 side, the pulse width of the applied voltage is the same, and the voltage value is set to an arbitrary voltage value of + Vy or more, The yellow particles Y having a particle amount corresponding to the voltage value can be moved to the display substrate 1 side.

  Hereinafter, as an example, a case where the amount of particles moving is controlled by voltage modulation will be described.

  Next, display of each color will be described. The display side electrode 3 is set to the ground (0V).

  13 to 16 schematically show an example of the behavior of magenta particles M, cyan particles C, and yellow particles Y in response to voltage application in the display medium according to the third embodiment. 13 to 16, the white particles 13, the dispersion medium 6, the gap member 5, and the like are omitted.

  In the present embodiment, the case where the display medium includes a negatively charged magenta particle M, a positively charged cyan particle C, and a positively charged yellow particle Y will be described. However, the present invention is not limited to this. The color and charging polarity of each particle may be set as appropriate. In addition, the value of the voltage to be applied in the following description is also an example, and is not limited thereto, and may be set as appropriate according to the charging polarity of each particle, the responsiveness, the distance between the electrodes, and the like.

  As shown in FIG. 13A, a voltage value smaller than −Vm at the back side electrode 4 and a voltage value necessary for attaching all the magenta particles M on the back substrate 2 side to the display substrate 1 side. When the voltage V1 is applied with a predetermined pulse width, all negatively charged magenta particles M migrate to the display substrate 1 side, and all positively charged cyan particles C and yellow particles Y migrate to the back substrate 2 side. It will be in the state which adhered to the whole surface of the board | substrate. As a result, a magenta color is displayed.

  From the state of FIG. 13 (A), as shown in FIG. 13 (B), all the magenta particles M on the display substrate 1 side having a voltage value larger than + Vm are attached to the back substrate 2 side. In addition, when a voltage of a voltage value + V1 necessary for attaching all the cyan particles C and yellow particles Y on the back substrate 2 side to the display substrate 1 side is applied with a predetermined pulse width, the positively charged cyan particles C are applied. The yellow particles Y migrate to the display substrate 1 side, and the negatively charged magenta particles M migrate to the rear substrate 2 side and are attached to the entire surface of each substrate. As a result, a mixed color of cyan and yellow is displayed.

  From the state of FIG. 13B, as shown in FIG. 13C, the back side electrode 4 has a voltage value smaller than −Vc and larger than −Vm, and is displayed among the cyan particles C on the display substrate 1 side. Necessary for moving cyan particles C (cyan particles C to be peeled off from the display substrate 1) to the back substrate 2 side while leaving the cyan particles C having a particle amount corresponding to the gradation to be processed on the display substrate 1 side. When a voltage having a voltage value of −V2 is applied with a predetermined pulse width, cyan particles C and all yellow particles Y having an amount of particles to be peeled off according to the gradation migrate to the back substrate 2 side and move to the back substrate 2 side. It will be in an attached state. FIG. 13C shows a case where the number of cyan particles C that move to the back substrate 2 side decreases in the order of the left side, the center, and the right side. That is, the pulse width of the applied voltage becomes shorter in the order of left side, center, and right side in FIG.

  From the center state of FIG. 13 (C), as shown in FIG. 13 (D), the back side electrode 4 has a voltage value smaller than −Vy and larger than −Vc, and among the yellow particles Y on the back substrate 2 side. Necessary for moving yellow particles Y of the amount corresponding to the gradation to be displayed on the back substrate 2 side and moving other yellow particles Y (yellow particles Y to be peeled from the back substrate 2) to the display substrate 1 side. When a small voltage value −V3 is applied with a predetermined pulse width, the yellow particles Y having an amount of particles to be peeled according to the gradation migrate to the display substrate 1 side and are attached to the display substrate 1 side.

  From the state of FIG. 14A (same as FIG. 13A), as shown in FIG. 14B, the back-side electrode 4 has a voltage value greater than + Vm and the magenta particles M on the display substrate 1 side. The magenta particles M having a particle amount corresponding to the gradation to be displayed are left on the display substrate 1 side, and the other magenta particles M (magenta particles M to be peeled off from the display substrate 1) are moved to the rear substrate 2 side. When a voltage of the voltage value + V1 necessary for the above is applied with a predetermined pulse width, magenta particles M having an amount of particles to be peeled according to gradation migrate to the back substrate 2 side and adhere to the back substrate 2 side. All the cyan particles C and yellow particles Y migrate to the display substrate 1 side and are attached to the display substrate 1.

  Then, from the state of FIG. 14B, as shown in FIG. 14C, the back side electrode 4 has a voltage value smaller than −Vc and larger than −Vm, and the cyan particles C on the display substrate 1 side. Of these, cyan particles C having a particle amount corresponding to the gradation to be displayed are left on the display substrate 1 side, and other cyan particles C (cyan particles C to be peeled off from the display substrate 1) are attached to the back substrate 2 side. When a voltage of a necessary voltage value −V2 is applied with a predetermined pulse width, all yellow particles Y of the amount of cyan particles C to be peeled off according to the gradation migrate to the back substrate 2 side, and the back substrate 2 side It will be in the state which adhered to.

  FIG. 14C shows a case where the number of cyan particles C moving to the back substrate 2 side decreases in the order of the left side, the center, and the right side, as in FIG. 13C. That is, the pulse width of the applied voltage becomes shorter in the order of left side, center, and right side in FIG.

  From the state of FIG. 14C, as shown in FIG. 14D, the back side electrode 4 has a voltage value smaller than −Vy and larger than −Vc, and is displayed among the yellow particles Y on the back substrate 2 side. Necessary for leaving the yellow particles Y of the amount corresponding to the gradation to be left on the back substrate 2 side and moving other yellow particles Y (the yellow particles Y to be peeled from the back substrate 2) to the display substrate 1 side. When the voltage value −V3 is applied with a predetermined pulse width, the yellow particles Y having an amount of particles to be peeled according to the gradation migrate to the display substrate 1 side and are attached to the display substrate 1 side.

  15 and 16 are also the same as FIG. 14, and the back substrate when shifting from the state of FIG. 15A to the state of FIG. 15B and from the state of FIG. 16A to the state of FIG. The only difference is the amount of magenta particles M moving to the two sides. 15 and 16, the gradation display of the yellow particles Y is omitted.

  Here, in the states of FIGS. 14B, 15B, and 16B, the magenta particles M and the yellow particles Y are attached to the display substrate 1 side, and the yellow particles Y charged with different polarities are used. The magenta particles M are electrostatically aggregated. Even when the voltage −V2 is applied to move only the yellow particles Y and the cyan particles C to the back substrate 2 side from this state, the magenta particles M of different polarity and the aggregated yellow particles Y cannot be moved. The magenta particles M that should not move may move to the back substrate 2 while being agglomerated with the yellow particles Y.

  Similarly, in the states of FIGS. 13C, 14C, and 15C, yellow particles charged with different polarities have magenta particles M and yellow particles Y attached to the back substrate 2 side. Y and magenta particles M are electrostatically aggregated. Even when voltage + V3 is applied to move only the yellow particles Y to the display substrate 1 side from this state, the magenta particles M having different polarity and the aggregated yellow particles Y cannot be moved, or magenta that should not move originally. The particles M may move to the display substrate 1 while being agglomerated with the yellow particles Y.

  In order to prevent this, the adhesion force of cyan particles C to the substrate needs to be stronger than the cohesion force of MY particles, and the cohesion force of CM particles needs to be stronger than the cohesion force of MY particles.

  Therefore, in the display medium 100 according to the present embodiment, for example, the magenta particles M are moved to the display substrate 1 side, and the cyan particles C are moved to the rear substrate 2 side, and then a part of the magenta particles M is rear surface substrate 2. By moving the cyan particles C to the display substrate 1 side and moving the magenta particles M and the cyan particles C to the display substrate 1 side, the threshold voltage | Vm | The voltage | VA | (fourth voltage) having a smaller absolute value than the voltage 1 is applied to dissociate the aggregates of the cyan particles C and the magenta particles M. For example, the magenta particles M After moving to the display substrate 1 side and moving the yellow particles Y to the back substrate 2 side, a part of the magenta particles M is moved to the back substrate 2 side and the yellow particles Y are moved to the display substrate 1 side. As a result, the absolute value of the voltage value is smaller than the threshold voltage | Vc | (second voltage) of the cyan particles C and the CM value in the state where the magenta particles M and the yellow particles Y are moved to the display substrate 1 side. By applying a voltage | VB | (fifth voltage) having a smaller absolute value than the voltage | VA | at which particle aggregation dissociates, the yellow particles Y and the magenta particles M are dissociated. The characteristics of each particle and the characteristics of the substrate surface are controlled. Accordingly, when a voltage value −V2 that is smaller than −Vc and larger than −Vm is applied in the states of FIGS. 14B, 15B, and 16B, only the yellow particles Y and the cyan particles C are back. Move to the substrate 2 side. In addition, when a voltage having a voltage value + V3 larger than + Vy and smaller than + Vc is applied in the states of FIGS. 13C, 14C, and 15C, only the yellow particles Y move to the display substrate 1 side. .

  In this embodiment, the case where the magenta particle M is negatively charged, the cyan particle C is positively charged, and the yellow particle Y is positively charged has been described. However, the magenta particle M is positively charged and the cyan particle C C may be negatively charged and the yellow particles Y may be negatively charged. In this case, the movement of each particle is the reverse of the above.

  Although the display device according to each embodiment has been described above, the present invention is not limited to each of the above embodiments.

  For example, the particle group that does not migrate is not limited to the white particle group, and for example, a black particle group may be used.

(Example)

  Next, examples of the present invention will be described.

  The threshold characteristics of particles include the charge amount of particles, particle diameter, particle size distribution, steric repulsion layer (silicone graft chain length, density), surface energy of substrate surface layer, and functional groups added to base resin of substrate surface layer. Controlled by type and amount, and solid rebound layer.

  Further, the cohesive force between two particles having different polarities is controlled by the charge amount, particle diameter, particle size distribution, and steric repulsion layer (the length and density of the silicone graft chain) of the particles.

  The charging characteristics (charging polarity and charging amount) of the particles are controlled by the type and amount of functional groups (amino group, carboxyl group, sulfonic acid group, etc.) added to the matrix resin of the particles.

  Hereinafter, examples of threshold characteristics of particles, cohesion between two particles having different polarities, and charging characteristics of particles will be described.

<Synthesis of cyan particles C>

  Silaplane FM-0725 (manufactured by Chisso, weight average molecular weight Mw = 10000) as the first silicone monomer (first silicone chain component), 12 parts by mass, Silaplane FM as the second silicone monomer (second silicone chain component) -0721 (manufactured by Chisso Corporation, weight average molecular weight Mw = 5000) 36 parts by mass, diethylaminoethyl methacrylate (DEAEMA, manufactured by Wako Pure Chemical Industries) 20 parts by mass, and other monomers (other copolymerization components) hydroxyethyl methacrylate (other copolymerization components) 32 parts by mass of HEMA (manufactured by Wako Pure Chemical Industries, Ltd.) is mixed with 300 parts by mass of isopropyl alcohol (IPA), and 1 part by mass of AIBN (2,2-azobisisobutylnitrile) is dissolved as a polymerization initiator. At 70 ° C. for 6 hours. The resulting product was purified and dried using hexane as a reprecipitation solvent to obtain silicone polymer A.

  Next, 0.5 g of the above silicone-based polymer A was added to 9 g of isopropyl alcohol (IPA) and dissolved, and 0.5 g of a cyan pigment (Cyanine Blue 4973) made by Sanyo Dye was added, and a 0.5 mmφ zirconia ball was added. And dispersed for 48 hours to obtain a pigment-containing polymer solution.

  3 g of this pigment-containing polymer solution was taken out and heated to 40 ° C., and then 12 g of 2CS silicone oil (KF96, manufactured by Shin-Etsu Chemical Co., Ltd.) was dropped little by little while applying ultrasonic waves. Polymer was deposited on the pigment surface. Thereafter, the solution was heated to 60 ° C. and dried under reduced pressure to evaporate IPA, thereby obtaining cyan particles having a silicone polymer adhered to the pigment surface.

  Thereafter, the particles of the solution are settled with a centrifuge, the supernatant is removed, 5 g of the silicone oil is added, ultrasonic waves are applied, washed, the particles are settled with a centrifuge, and the supernatant is removed. Further, 5 g of the above silicone oil was added to obtain a cyan particle dispersion. The obtained cyan particles had a volume average particle size of 0.3 μm. The charged polarity of the particles in this dispersion was positively charged as a result of enclosing the dispersion between two electrode substrates and applying a DC voltage to evaluate the migration direction.

<Synthesis of magenta particles M>

  Silaplane FM-0725 (manufactured by Chisso Corporation, weight average molecular weight Mw = 10000) as the first silicone monomer (first silicone chain component) 19 parts by mass, Silaplane FM as the second silicone monomer (second silicone chain component) -0721 (manufactured by Chisso Corporation, weight average molecular weight Mw = 5000) 29 parts by mass, methyl methacrylate (MMA, manufactured by Wako Pure Chemical Industries) 9 parts by mass, octafluoropentyl methacrylate (OFPMA, manufactured by Wako Pure Chemical Industries) 5 parts by mass And 38 parts by mass of hydroxyethyl methacrylate (HEMA, manufactured by Wako Pure Chemical Industries, Ltd.) as another monomer (another copolymerization component) are mixed with 300 parts by mass of isopropyl alcohol (IPA), and AIBN (2 , 2-azobisisobutylnitrile) 1 part by mass, dissolved in nitrogen at 70 ° C., 6 hours Polymerization was carried out. The product thus obtained was purified and dried using hexane as a reprecipitation solvent to obtain a silicone polymer B.

  Next, in the synthesis of the cyan particles C, all of the above cyan particles were used except that the silicone polymer B was used instead of the silicone polymer A and a magenta pigment (Pigment Red 3090) was used instead of the cyan pigment. A magenta particle dispersion was obtained in the same manner as in the synthesis of C. The obtained magenta particles had a volume average particle size of 0.4 μm. The charged polarity of the particles in this dispersion was negatively charged as a result of enclosing the dispersion between two electrode substrates and applying a DC voltage to evaluate the migration direction.

  The agglomeration force of CM particles when cyan particles C and magenta particles M aggregate is controlled by the amount of DEAEMA added to cyan particles C, the amount of MMA and OFPMA added to magenta particles M.

Further, the cohesive strength of CM particles can be determined by using the amounts of silicone monomers FM-0725 and FM-0721, or FM-0711 (manufactured by Chisso Corporation, weight average molecular weight Mw = 1000) having different molecular weights instead. Be controlled.

<Preparation of white particles (white particles are used as a light reflecting member)>

  In a 100 ml three-necked flask equipped with a reflux condenser, 5 parts by weight of 2-vinylnaphthalene (manufactured by Nippon Steel Chemical Co., Ltd.), 5 parts by weight of silicone macromer FM-0721 (manufactured by Chisso Corporation), lauroyl peroxide as an initiator 0.3 parts by weight (manufactured by Wako Pure Chemical Industries, Ltd.) and 20 parts by weight of silicone oil KF-96L-1CS (manufactured by Shin-Etsu Chemical Co., Ltd.) were added, and bubbling with nitrogen gas was performed for 15 minutes. Polymerization was carried out at ° C for 24 hours.

  The obtained white particles have a particle diameter of 550 nm, and even when mixed with other colored electrophoretic particle dispersions, they are hardly charged (electrophoresis) and do not affect the display by other colored electrophoretic particles. It was.

<Substrate surface layer>

-Polymer compound A-DEAEMA (amino group) added system

  Silaplane FM-0721 (manufactured by Chisso Corporation, weight average molecular weight Mw = 5000) 40 parts by mass, diethylaminoethyl methacrylate (DEAEMA, manufactured by Wako Pure Chemical Industries) 25 parts by mass, and hydroxyethyl methacrylate (HEMA, manufactured by Wako Pure Chemical Industries, Ltd.) 35 parts by mass is mixed with 300 parts by mass of isopropyl alcohol (IPA), 1 part by mass of AIBN (2,2-azobisisobutylnitrile) is dissolved as a polymerization initiator, and polymerization is performed at 70 ° C. for 6 hours under nitrogen. I did it. The product thus obtained was purified and dried using hexane as a reprecipitation solvent to obtain polymer compound A.

-Polymer compound B-MAA (carboxyl group) added system

  Silaplane FM-0721 (manufactured by Chisso Corporation, weight average molecular weight Mw = 5000) 45 parts by mass, methacrylic acid (MAA, manufactured by Wako Pure Chemical Industries) 10 parts by mass, and hydroxyethyl methacrylate (HEMA, manufactured by Wako Pure Chemical Industries) 45 Part by mass is mixed with 300 parts by mass of isopropyl alcohol (IPA), 1 part by mass of AIBN (2,2-azobisisobutylnitrile) is dissolved as a polymerization initiator, and polymerization is performed at 70 ° C. for 6 hours under nitrogen. It was. The product thus obtained was purified and dried using hexane as a reprecipitation solvent to obtain polymer compound B.

-Polymer compound C-Functional group non-addition system

  50 parts by mass of Silaplane FM-0721 (manufactured by Chisso Corporation, weight average molecular weight Mw = 5000) and 50 parts by mass of hydroxyethyl methacrylate (HEMA, manufactured by Wako Pure Chemical Industries, Ltd.) are mixed with 300 parts by mass of isopropyl alcohol (IPA). As a polymerization initiator, 1 part by mass of AIBN (2,2-azobisisobutylnitrile) was dissolved, and polymerization was performed at 70 ° C. for 6 hours under nitrogen. The product thus obtained was purified using hexane as a reprecipitation solvent and dried to obtain polymer compound C.

-Formation of thin film-Formation of surface layer

  The obtained polymer compound was dissolved in isopropyl alcohol (concentration 4 wt%), a thin film was formed on the ITO substrate with a spin coater, and dried at 120 ° C. for 30 minutes.

  By changing the amount of DEAEMA or MAA in the surface layer, or the amount of silaplane FM-0721, or using a silaplane (FM-0711 or FM-0725) having a different molecular weight, Adhesion is controlled.

  The cyan particles C, magenta particles M, and white particles described above were mixed at the following ratios to prepare a CM2 particle-based mixed solution.

Mixing ratio → C: M: W = 0.8: 1.4: 40 (wt%)

  In the cell using the above mixed liquid and using the above-described polymer compound C as the substrate surface layer (gap between substrates: 50 μm), the characteristics of cyan particles C and magenta particles M were as follows.

Cyan particle C: positively charged, threshold voltage ± 7 [V] (small threshold)

Magenta particle M: negative charge, threshold voltage ± 10 [V] (large threshold)

Aggregation dissociation voltage of CM particles: ± 5 [V] to ± 12 [V] (aggregation dissociation voltage has a range due to variation in particle characteristics)

  Note that the threshold voltage at which the particles peel from the substrate is applied by applying a voltage between a pair of substrates to adhere the particles to one substrate, and then gradually increasing the voltage of the opposite polarity from 0 V. It is obtained by measuring the voltage at which the peeling movement starts from the substrate. Further, whether or not the particles are peeled off from the substrate is determined by measuring a change in display color density.

  Further, the aggregation dissociation voltage at which CM particles, which are aggregates of different polarity cyan particles C and magenta particles M, dissociate is applied to a substrate by applying a voltage between a pair of substrates. Thereafter, the voltage is gradually increased from 0 V, and the voltage at which the aggregate dissociates is measured. At this time, since the particle characteristics vary, the dissociating voltage has a width. Whether or not the aggregate has dissociated is determined by measuring a change in display color density.

  Further, by using the polymer compound A as the substrate surface layer and changing the DEAEMA amount of the polymer compound A from 10 parts by mass to 50 parts by mass, the characteristics of the cyan particles C and the magenta particles M are controlled as follows. did.

C particles: positively charged, threshold voltage ± 3 [V] to ± 6 [V]

M particles: negative charge, threshold voltage ± 11 [V] to ± 15 [V]

Aggregation dissociation voltage of CM particles: ± 5 [V] to ± 12 [V]

(The numerical range is smaller when the DEAEMA amount is smaller)

  Moreover, the characteristic of the said C particle and M particle | grains was controlled as follows by changing the amount of DEAEMA of C particle | grains from 3 mass parts to 30 mass parts.

C particles: positively charged, threshold voltage ± 5 [V] to ± 9 [V]

M particles: negatively charged, threshold voltage ± 8 [V] to ± 14 [V]

Aggregation dissociation voltage of CM particles: ± 3 [V] to ± 6 [V] to ± 7 [V] to ± 14 [V]

(The numerical range is smaller when the DEAEMA amount is smaller)

  As described above, FIG. 17 shows the presence or absence of color mixing when the threshold of cyan particles C and magenta particles M and the cohesive force of CM particles are controlled and gradation driving is performed under each condition.

  As shown in FIG. 17, if the threshold voltage of the magenta particles M is larger than the aggregation dissociation voltage (maximum value) of the CM particles, it was confirmed that no color mixing occurs even when gradation display is performed. It was also confirmed that the threshold voltage of cyan particles C was not particularly limited.

<Synthesis of large-diameter yellow particles Y>

  53 parts by mass of methyl methacrylate, 10 parts by mass of methacrylic acid (MAA, manufactured by Wako Pure Chemical Industries, Ltd.) and 1.5 parts by mass of yellow pigment (FY7416: manufactured by Sanyo Dye Co., Ltd.) are mixed, and zirconia having a diameter of 10 mm is mixed. Ball milling with a ball was performed for 20 hours to prepare dispersion A-1.

  Next, 40 parts by mass of calcium carbonate and 60 parts by mass of water were mixed and finely pulverized with a ball mill in the same manner as above to prepare a calcium carbonate dispersion A-2. Further, 60 g of calcium carbonate dispersion A-2 and 4 g of 20% saline were mixed, degassed with an ultrasonic machine for 10 minutes, and then stirred with an emulsifier to prepare a mixed liquid A-3.

  Dispersion A-1: 20 g, ethylene glycol dimethacrylate: 0.6 g, polymerization initiator V601 (Dimethyl 2, 2′-azobis (2-methylpropionate): Wako Pure Chemical Industries, Ltd.): 0.2 g The mixture was thoroughly mixed and deaerated with an ultrasonic machine for 10 minutes. This was added to the mixed solution A-3 and emulsified with an emulsifier. Next, this emulsified liquid was put into a flask, and a silicone jar was added, and a vacuum needle was sufficiently deaerated using an injection needle and sealed with nitrogen gas. Next, the particles were prepared by reacting at 65 ° C. for 15 hours. After cooling, the particles were filtered, and the obtained particle powder was dispersed in ion-exchanged water, and calcium carbonate was decomposed with hydrochloric acid water, followed by filtration. Thereafter, the particles were washed with sufficient distilled water and passed through a nylon sieve having openings of 15 μm and 10 μm to make the particle sizes uniform. The obtained large-diameter yellow particles Y had a volume average primary particle size of 13 μm.

<Surface treatment of large-diameter yellow particles Y>

  The following surface treatment was performed on the large-diameter yellow particles Y obtained in the above process.

  95 parts by mass of Silaplane FM-0711 (manufactured by Chisso Corporation, weight average molecular weight Mw = 1000), 2 parts by mass of glycidyl methacrylate (GMA, manufactured by Wako Pure Chemical Industries), 3 parts by mass of methyl methacrylate (MMA, manufactured by Wako Pure Chemical Industries, Ltd.) Parts were mixed with 300 parts by mass of isopropyl alcohol (IPA), 1 part by mass of AIBN (2,2-azobisisobutylnitrile) was dissolved as a polymerization initiator, and polymerization was performed at 70 ° C. for 6 hours under nitrogen. . Thereafter, after adding 300 parts by mass of silicone oil having a viscosity of 2CS (manufactured by Shin-Etsu Chemical Co., Ltd .: KF96), IPA was removed under reduced pressure to obtain surface treating agent B-1.

  Thereafter, 2 parts by mass of the obtained large-diameter yellow particles Y, 25 parts by mass of the surface treating agent B-1 and 0.01 parts by mass of triethylamine were mixed and stirred at a temperature of 100 ° C. for 5 hours. Thereafter, the solvent was removed by centrifugal sedimentation, followed by drying under reduced pressure to obtain large-diameter Y particles subjected to surface treatment. The large yellow particles Y obtained were negatively charged.

  The above-mentioned cyan particles C, magenta particles M, yellow particles Y, and white particles were mixed in the following ratio to prepare a CMY 3-particle mixed liquid.

Mixing ratio → C: M: Y: W = 0.8: 1.4: 13: 30 (wt%)

  In the cell using the above mixed liquid and using the above-described polymer compound C as the substrate surface layer (gap between substrates: 50 μm), the characteristics of cyan particles C and magenta particles M were as follows.

C particles: positive charge, threshold voltage ± 7 [V] (in threshold)

M particles: negative charge, threshold voltage ± 10 [V] (large threshold)

Y particle: negative charge, threshold voltage ± 2 [V] (small threshold)

Aggregation dissociation voltage of CM particles: ± 5 [V] to ± 12 [V] (aggregation dissociation voltage has a range due to variation in particle characteristics)

Aggregation dissociation voltage of CY particles: ± 4 [V] to ± 8 [V]

  Further, by changing the amount of DEAEMA or MAA of the substrate surface layer or the amount of silaplane FM-0721, or using a silaplane (FM-0711 or FM-0725) having a different molecular weight, The adhesion of each color particle was controlled.

  Further, by changing the DEAEMA amount of the cyan particles C, the MMA amount and OFPMA amount of the magenta particles M, the MAA amount of the yellow particles, the amount of the silaplane, and the molecular weight, the cyan particles C, the magenta particles M, and the cyan particles C The cohesive strength of the yellow particles Y was controlled.

  As described above, gradation driving was performed by variously changing the adhesion force (threshold value) of the cyan particles C, magenta particles M, and yellow particles Y to the substrate, the cohesion force of the CM particles, and the cohesion force of the CY particles. As a result, when the following relationship was established, good gradation display without color mixture could be performed.

  Threshold voltage of magenta particle M> aggregation dissociation voltage of CM particle> aggregation dissociation voltage of CY particle and threshold voltage of cyan particle C> aggregation dissociation voltage of CY

DESCRIPTION OF SYMBOLS 1 Display substrate 2 Back substrate 3 Display side electrode 4 Back side electrode 5 Gap member 6 Dispersion medium 10 Display medium 11 1st migrating particle (group)
12 Second migrating particles (group)
13 White particles (group)
20 Display medium 30 Voltage application unit 40 Control unit 100 Display device C Cyan particle (group)
M Magenta particles (group)
Y yellow particles (group)

Claims (9)

A translucent display substrate;
A rear substrate disposed opposite to the display substrate with a gap;
A dispersion medium sealed between the display substrate and the back substrate;
Dispersed in the dispersion medium, positively or negatively charged and peeled from one of the display substrate and the back substrate by being applied with a first voltage between the substrates and moved to the other substrate A first particle that
The second voltage dispersed in the dispersion medium, different in color and charging polarity from the first particles, and having a smaller absolute voltage value than the first voltage is applied between the substrates. Second particles that peel from one of the display substrate and the back substrate and move to the other substrate;
Including
In a state where the first particles and the second particles are moving to one of the display substrate and the back substrate,
The display medium in which the first particles and the second particles are dissociated by applying a third voltage having a smaller voltage value than the first voltage between the substrates. The state in which the first particles and the second particles are moving to one of the display substrate and the rear substrate is such that the absolute value of the voltage value is equal to or higher than the first voltage. By being applied in between, the first particles move to the display substrate side and the second particles move to the back substrate side, and then the display according to the display concentration of the first particles. When the first voltage is applied between the substrates, the first particles corresponding to the display concentration of the first particles remain on the display substrate side, and the other first particles remain on the back substrate. The display medium according to claim 1, wherein the second particles move to the display substrate side while moving to the display substrate side. The state in which the first particles and the second particles are moving to one of the display substrate and the rear substrate is such that the absolute value of the voltage value is equal to or higher than the first voltage. By being applied in between, the first particles move to the back substrate side and the second particles move to the display substrate side, and then the first particles according to the display concentration of the first particles. When the voltage of 1 is applied between the substrates, the first particles according to the display concentration of the first particles move to the display substrate side, and the other first particles move to the back substrate. The display medium according to claim 1, wherein the display medium remains on the side and the second particles have moved to the back substrate side. A translucent display substrate;
A rear substrate disposed opposite to the display substrate with a gap;
A dispersion medium sealed between the display substrate and the back substrate;
Dispersed in the dispersion medium, positively or negatively charged and peeled from one of the display substrate and the back substrate by being applied with a first voltage between the substrates and moved to the other substrate A first particle that
The second voltage dispersed in the dispersion medium, different in color and charging polarity from the first particles, and having a smaller absolute voltage value than the first voltage is applied between the substrates. Second particles that peel from one of the display substrate and the back substrate and move to the other substrate;
A third voltage that is dispersed in the dispersion medium, has a color different from that of the first particles and the second particles, and is smaller in absolute value than the second voltage is applied between the substrates. A third particle that peels from one of the display substrate and the back substrate and moves to the other substrate,
Including
In a state where the first particles and the second particles are moving to one of the display substrate and the back substrate,
When a fourth voltage having a smaller absolute value than the first voltage is applied between the substrates, the first particles and the second particles are dissociated,
In the state where the first particle or the second particle having a polarity different from that of the third particle and the third particle are moving to one of the display substrate and the back substrate. ,
A fifth voltage having a smaller absolute value than the second voltage and a smaller absolute value than the fourth voltage is applied between the substrates, whereby the third particles and A display medium in which the first particle or the second particle having a polarity different from that of the third particle is dissociated. The state in which the first particles and the second particles are moving to one of the display substrate and the rear substrate is such that the absolute value of the voltage value is equal to or higher than the first voltage. By being applied in between, the first particles move to the display substrate side and the second particles move to the back substrate side, and then the display according to the display concentration of the first particles. When the first voltage is applied between the substrates, the first particles corresponding to the display concentration of the first particles remain on the display substrate side, and the other first particles remain on the back substrate. The display medium according to claim 4, wherein the second particles move to the display substrate side while moving to the side. The first particle or the second particle having a polarity different from that of the third particle, and the third particle are moving to one of the display substrate and the back substrate. In the state where the first particles and the second particles are moved to the display substrate side, the second voltage corresponding to the display concentration of the second particles is applied, whereby the first particles The second particles corresponding to the display concentration of the second particles remain on the display substrate side, and the other second particles move to the back substrate side, and the third particles are on the display substrate side or The display medium according to claim 5, wherein the display medium is moved to the rear substrate side. The state in which the first particles and the second particles are moving to one of the display substrate and the rear substrate is such that the absolute value of the voltage value is equal to or higher than the first voltage. By being applied in between, the first particles move to the back substrate side and the second particles move to the display substrate side, and then the first particles according to the display concentration of the first particles. When the voltage of 1 is applied between the substrates, the first particles according to the display concentration of the first particles move to the display substrate side, and the other first particles move to the back substrate. The display medium according to claim 4, wherein the display medium remains on the side and the second particles have moved to the back substrate side. The first particle or the second particle having a polarity different from that of the third particle, and the third particle are moving to one of the display substrate and the back substrate. In the state where the first particles and the second particles are moved to the back substrate side, the second voltage corresponding to the display concentration of the second particles is applied, whereby the first particles The second particles according to the display concentration of the second particles move to the display substrate side, the other second particles move to the back substrate side, and the third particles move to the display substrate side. The display medium according to claim 7, wherein the display medium is moved to the back substrate side. The display medium according to any one of claims 1 to 8, and
Voltage applying means for applying a voltage according to image information between the substrates of the display medium;
A display device comprising: