JP2015207015A - Picture display unit having memory property - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve multiple gradation expression including intermediate color while suppressing uncomfortable "flicker" during screen update process with a simple configuration.SOLUTION: Electrophoretic particles are composed of a plurality of kinds of charged particles having different color and a different threshold voltage to start migration. Voltage application means performs a series of drive operation in which the relative color density of various charged particles is gradually shifted to the relative color density of corresponding intermediate transition state in order of a higher threshold voltage each time when the voltage drive waveform except a last time is applied during update of the screen. At the final application of the voltage drive waveform, the relative color density of the various charged particles is gradually shifted to a desired relative color density to be updated in order of a higher threshold voltage and the screen is updated.

Description

  The present invention relates to an image display device having a memory property driven by an electrophoretic display method, and more particularly to an image display device having a memory property suitable for use in an electronic paper display device such as an electronic book or an electronic newspaper.

  Electronic paper display devices such as electronic books and electronic newspapers have been developed as display devices that can perform the act of “reading” without stress. Since this type of electronic paper display device is required to be thin, lightweight, hard to break, and to have low power consumption, it is desirable that the electronic paper display device be composed of a display element having a memory property. Conventionally known electrophoretic display elements and cholesteric liquid crystals have been known as display elements suitable for such applications. Recently, electrophoretic display elements using two or more kinds of charged particles have attracted attention. . In this specification, the electrophoretic display element is a concept including an element that performs display by moving charged particles such as an electro-powder fluid element.

  First, as an associated technique, an electrophoretic display device of an active matrix driving system for monochrome display will be described. In this electrophoretic display device, a TFT glass substrate on which a thin film transistor (hereinafter also referred to as TFT) as a switching element is formed, an electrophoretic display element film, and a counter substrate are laminated in this order. It is configured. The TFT glass substrate is provided with a large number of TFTs arranged in a matrix, pixel electrodes connected to the TFTs, gate lines for driving the TFTs, and data lines. The electrophoretic display element film is formed by spreading about 40 μm microcapsules in a polymer binder. A solvent is injected into the inside of the microcapsule. In the solvent, two kinds of positively and negatively charged nanoparticles, that is, a white pigment such as a negatively charged titanium oxide particle, and a positively charged carbon particle are included. It is contained in a state where the black pigment such as is dispersed and suspended. In addition, a counter electrode (also referred to as a common electrode) for applying a reference potential is formed on the counter substrate.

  The operation of the electrophoretic display element is performed by applying a voltage corresponding to pixel data between the pixel electrode and the counter electrode to cause the white pigment and the black pigment to migrate up and down. That is, when a positive voltage is applied to the pixel electrode, negatively charged white pigments gather near the pixel electrode side, while positively charged black pigments gather near the counter electrode side. If so, black will be displayed on the screen. On the other hand, when a negative voltage is applied to the pixel electrode, positively charged black pigments gather near the pixel electrode side, while negatively charged white pigments gather around the counter electrode side. White will be displayed. Next, when updating the screen, that is, when switching the image from white display to black display, a positive signal voltage is applied to the pixel electrode, and when switching from black display to white display, a negative signal voltage is applied to the pixel electrode. To do. Next, when maintaining the current image, that is, when maintaining the white display on the next screen or maintaining the black display, the electrophoretic display element has a memory property, so 0 V is applied. It will be good. Thus, in the electrophoretic display element, a signal to be applied is determined by comparing the current screen (previous screen) and the next screen (update screen).

In addition, a color electrophoretic display device has been developed that can perform color display on a pixel-by-pixel basis without impairing the black-and-white color sensation close to paper without a color filter.
For example, Patent Document 1 includes electrophoretic particles of three colors (for example, cyan C, magenta M, and yellow Y) charged to the same polarity, and a white (W) holder for holding the electrophoretic particles. A color electrophoretic display device comprising an electrophoretic layer is described. The electrophoretic particles of the three colors are set so that the threshold voltage (electrophoresis start voltage) for starting migration is different. In the color electrophoretic display device described in Patent Document 1, the voltage of each electrophoretic particle is controlled using the difference in threshold voltage (absolute value), so that white (W) in pixel (cell) units. In addition to black (K), cyan (C), magenta (M), yellow (Y) and secondary colors and tertiary colors of these CMY can be displayed.

  Patent Document 2 discloses a color electrophoretic display device using an electrophoretic display element film in which various microcapsules are laid in layers. The microcapsules include black first charged particles charged to a first polarity, and red (R), green (G), and blue (B) second charged particles R and G charged to a second polarity. , B and a liquid dispersion medium that disperses each particle so as to migrate. Here, the second charged particles R, G, and B are encapsulated in different microcapsules in such a manner that the charge amounts are different from each other, and therefore the threshold voltages for starting migration are different. Even in the color electrophoretic display device described in Patent Document 2, the voltage of each electrophoretic particle is controlled using the difference in threshold voltage (absolute value). RGB secondary colors and tertiary colors can be displayed in units of pixels (cells).

  Patent Document 3 discloses a color electrophoretic display device using electrophoretic particles of four colors obtained by adding black (K) to cyan (C), magenta (M), and yellow (Y).

  Thus, according to the related art described in Patent Documents 1, 2, and 3, color display is possible by having three different threshold values for C, M, and Y (or R, G, and B). It becomes. With reference to FIGS. 32 and 33, the display operation of the color electrophoretic display device described in Patent Document 1 will be described. Hereinafter, the threshold voltages Vth (c), Vth (m), and Vth (y) of the charged particles C, M, and Y are | Vth (c) | <| Vth (m) | <| Vth (y ) | Is set to satisfy the relationship. The applied voltages V1, V2, and V3 are represented by | Vth (c) | <| V3 | <| Vth (m) |, | Vth (m) | <| V2 | <| Vth (y), | Vth (y ) | <| V1 |. 32 and 33 represent hysteresis curves of the charged particles C, M, and Y, and represent the relationship between the threshold voltage and the relative color density. In the same figure, for the sake of simplicity of explanation, until Y, M, and C move from the back surface to the display surface so that the slopes of the respective hysteresis Y, nY, M, nM, C, and nC are constant. The travel times are set to different times.

  In FIG. 32, the first (previous) screen is white (W). When V3 = 10 V is applied in the white display state, cyan electrophoretic particles C move to the display surface side, so that cyan (C) is displayed as the next screen. When V2 = 15 V is applied in the white display state, cyan (magenta) electrophoretic particles C and M move to the display surface side, so that blue (B) is displayed. Further, when V1 = 30 V is applied in the white display state, the cyan, magenta, and yellow electrophoretic particles C, M, and Y move to the display surface side, so that black is displayed. . In addition, when a negative voltage is applied in the white display state, there is no color particle on the display surface side, and thus white (W) remains.

  Next, the previous screen is set to black (K). When −V3 = −10 V is applied in the black display state, cyan electrophoretic particles C move to the back substrate side, and magenta and yellow electrophoretic particles M and Y are displayed on the display surface side. Therefore, red (R) is displayed as the next screen. When −V2 = −15 V is applied in the black display state, cyan and magenta electrophoretic particles C and M move to the back substrate side, and yellow electrophoretic particles are on the display surface side. Since Y remains, it becomes yellow (Y). When −V1 = −30 V is applied in the black display state, all the cyan, magenta, and yellow electrophoretic particles C, M, and Y move to the back substrate side, so that white (W) Display.

In order to display magenta (M), as shown in FIG. 33, V2 = 15 V is applied from the white display, and the cyan and magenta electrophoretic particles C and M are moved to the display surface side. The display color is once set to the blue (B) intermediate transition state. When −V3 = −10V is applied to the intermediate transition state and the cyan electrophoretic particles C are moved to the back side, a magenta (M) color display state is obtained (see Table 12).
In order to display green (G), as shown in FIG. 32, −V2 = −15 V is applied from black display (K), and cyan and magenta electrophoretic particles C and M are displayed on the back side. The display color is once changed to an intermediate transition state of yellow (Y) color. For this intermediate transition state, V3 = 10 V is applied to move the cyan electrophoretic particles C to the display surface side to display green (G) color (see Table 12).

  Thus, when the previous screen is white (W), as shown in Table 12, the primary color states that can be shifted directly are cyan (C), blue (B), and black (K). In contrast, as shown in Table 12, red (R) and yellow (Y) are displayed via the intermediate transition state I of black (K). Further, magenta (M) is displayed through the intermediate transition state I of blue (B), and green (G) is displayed through the intermediate transition states I and II of black (K) and yellow (Y) ( (See Table 12).

Patent No. 4049202 Japanese Patent No. 4385438 JP 2009-47737 A

As described above, in the electrophoretic display device described in Patent Document 1 using the difference in threshold voltage, red (R), green (G), blue (B), cyan (from the ground state) C), magenta (M), yellow (Y), white (W), black (K) primary color screens can be obtained. This also applies to the electrophoretic display devices of Patent Documents 2 to 3.
However, in the configurations described in Patent Documents 1 to 3, when updating from the previous screen to the next screen, the update is performed through an intermediate transition of one or two primary colors (relative color density 1). In addition, there is a disadvantage that unpleasant “flickering” is caused on the screen at the time of updating due to large and rapid fluctuation of the color density.
In addition, it is very complicated to display an arbitrary display color La * b * including intermediate colors and gradation display using the three charged particles C, M, and Y on the same pixel electrode. Therefore, it is difficult to say that the technology has been solved by the techniques described in Patent Documents 1 to 3.

  The present invention has been made in view of the above-described circumstances, and suppresses unpleasant “flickering” in the screen update process, and only each single color (R, G, B, C, M, Y, W, K). In addition, an object of the present invention is to provide an image display device having a memory property that can realize multi-tone expression including intermediate colors with a simple configuration.

In order to solve the above problems, the configuration of the present invention relates to an image display device having a memory property, and a first substrate on which a pixel electrode is formed, a second substrate on which a counter electrode is formed, A display unit having an electrophoretic layer interposed between the first substrate and the second substrate and capable of migrating electrophoretic particles; and when updating a screen, the pixel electrode and the counter electrode By repeatedly applying a predetermined voltage driving waveform a plurality of times for a predetermined period to the electrophoretic particles between, the display state of the display unit from the previous screen via a plurality of intermediate transition states, A voltage applying means for updating the next screen, and the electrophoretic particles have n types (n is a natural number of 2 or more) of charged particles C1, having different colors and threshold voltages for starting migration,. , Ck,..., Cn (1 <k <n, where n = 2, Ck Together consisting deletion), each seed charged particles C1, ..., Ck, ..., Cn, the threshold voltage of the charged particles C1>...> threshold voltage of the charged particle Ck>...> threshold of charged particles Cn The voltage application means satisfies the voltage-related characteristics, and the voltage application means applies the charged particles C1 →,..., Ck →,. Then, a series of driving operations for gradually changing the relative color density of various charged particles to the relative color density of the corresponding intermediate transition state is performed, and the charged particles C1 → ..., → Ck →, ..., → Cn, the relative color densities of various charged particles are sequentially shifted to the desired relative color density to be updated and updated to the next screen in the final transition state. .

  According to the configuration of the present invention, not only each single color (R, G, B, C, M, Y, W, K) but also an arbitrary color (La * b *) including a halftone and a halftone display is displayed. Can be realized with a simple configuration. Also, unpleasant “flickering” in the screen update process can be suppressed.

It is a fragmentary sectional view which shows notionally the structure of the display part which comprises the electronic paper display apparatus which is the 1st reference example of this invention. It is a state explanatory view for explaining the color display principle of the electrophoretic display device (element) constituting the display unit. It is a figure for demonstrating the reference example, and is a wave form diagram which shows the drive voltage waveform applied to the display part (electrophoretic display device) at the time of intermediate color and gradation display drive. It is a wave form diagram which shows the drive voltage waveform applied to the display part. It is a wave form diagram which shows the drive voltage waveform applied to the display part. It is a wave form diagram which shows the drive voltage waveform applied to the display part. It is a wave form diagram which shows the drive voltage waveform applied to the display part. It is a wave form diagram which shows the drive voltage waveform applied to the display part. It is a wave form diagram which shows the drive voltage waveform applied to the display part. It is a wave form diagram which shows the drive voltage waveform applied to the display part. It is a wave form diagram which shows the drive voltage waveform applied to the display part. It is a figure which shows the drive waveform and intermediate transition state which are used by the reference example at the time of screen update. In the reference example, it is an intermediate transition state diagram showing the behavior of the electrophoretic particles when the screen is updated. It is a figure for demonstrating the drive operation in 1st Embodiment of this invention, and is a wave form diagram which shows the drive voltage waveform applied to a display part at the time of intermediate color and gradation display drive. It is a wave form diagram which shows the drive voltage waveform applied to the display part. It is a wave form diagram which shows the drive voltage waveform applied to the display part. It is a wave form diagram which shows the drive voltage waveform applied to the display part. It is a wave form diagram which shows the drive voltage waveform applied to the display part. It is a wave form diagram which shows the drive voltage waveform applied to the display part. It is a figure which shows the drive waveform and intermediate transition state which are used by the 1st Embodiment at the time of a screen update. In the said 1st Embodiment, it is an intermediate transition state figure which shows the behavior of an electrophoretic particle at the time of screen update. It is a block diagram which shows the electric constitution of the electronic paper display apparatus (image display apparatus) which is the 1st embodiment. It is a block diagram which shows the detail of the electronic paper controller which comprises the electronic paper display apparatus. It is a block diagram which shows the detail of the electronic paper control circuit which comprises the electronic paper controller. It is a block diagram which shows the detail of the LUT conversion circuit which comprises the electronic paper controller. It is a figure which shows the drive waveform and intermediate transition state which are used by 2nd Embodiment of this invention at the time of a screen update. In the 2nd reference example of this invention, it is a wave form diagram which shows the drive voltage waveform applied to a display part (electrophoretic display apparatus). In the same 2nd reference example, it is a wave form diagram which shows the drive voltage waveform applied to a display part. In the same 2nd reference example, it is a wave form diagram which shows the drive voltage waveform applied to a display part. It is a figure which shows the drive waveform and intermediate transition state which are used by 3rd Embodiment of this invention at the time of a screen update. In the said 3rd Embodiment, it is an intermediate transition state figure which shows the behavior of an electrophoretic particle at the time of screen update. It is a figure for demonstrating the problem of related technology. It is a figure for demonstrating the problem of related technology.

  Each voltage driving waveform is obtained by causing the charged particles C1, ..., Ck, ..., Cn to migrate a predetermined distance in the thickness direction of the electrophoretic layer. | First voltage | (| first voltage |> charged particle C1 For the remainder of the time, 0 V is applied to stop the migration, while when there is no need for migration, a first voltage application period in which 0 V is applied; Next, the charged particles Ck,..., Cn are migrated by a predetermined distance in the layer thickness direction. | Kth voltage | (threshold voltage of charged particle Ck-1> | kth voltage |> charged particle Ck (Threshold voltage) is applied, and for the remainder of the time, 0V is applied to stop the migration. On the other hand, when migration is not necessary, the kth voltage application period in which 0V is applied, To move only the charged particles Cn by a predetermined distance in the layer thickness direction | nth voltage | (charged particles) n-1 threshold voltage> | nth voltage |> charged particle Cn threshold voltage) is applied, and 0 V for stopping the migration is applied for the remaining time, while migration is not necessary. And the nth voltage application period for applying 0 V, thereby realizing the configuration of the present invention.

  In addition, each voltage driving waveform is obtained by causing the charged particles C1, ..., Ck, ..., Cn to migrate in the thickness direction of the electrophoretic layer by a predetermined distance | first voltage | (| first voltage |> charging The threshold voltage of the particle C1) is applied for a predetermined number of subframes, and 0V is applied to stop the migration for the remaining subframes, while 0V is applied when the migration is not necessary. First sub-frame group period,..., Next, the charged particles Ck,..., Cn are migrated by a predetermined distance in the layer thickness direction. Threshold voltage> | kth voltage |> threshold voltage of charged particle Ck) is applied for a period of a predetermined number of subframes, and 0 V for stopping migration is applied for the period of the remaining subframes, When there is no need for electrophoresis, the kth subframe group to which 0V is applied Finally, only the charged particles Cn migrate in the layer thickness direction for a predetermined distance | nth voltage | (threshold voltage of charged particles Cn−1> | nth voltage |> Threshold voltage of charged particles Cn) is applied for a period of a predetermined number of subframes, and 0 V for stopping migration is applied for the period of the remaining subframes. The configuration of the present invention is also realized by having an n-th subframe group period for applying.

Reference example 1

First, an embodiment of the invention according to the earlier application of the applicant will be described as a first reference example with reference to the drawings.
FIG. 1 is a partial cross-sectional view conceptually showing the structure of a display unit constituting an electronic paper display device (image display device) which is a first reference example of the present invention.

The display unit 1 includes an electrophoretic display device (element) 2 having a memory property and performing color display by active matrix driving. The electrophoretic display device 2 includes a TFT glass substrate 3, a counter substrate 4, and a TFT glass substrate. 3 and the electrophoretic layer 5 enclosed between the counter substrate 4 and the counter substrate 4.
The TFT glass substrate 3 is provided with TFTs 6 as switching elements arranged in a matrix, pixel electrodes 7 connected to the TFTs 6, gate lines (not shown), and data lines.

  The electrophoretic layer 5 has a thickness of about 10 to 100 μm, and includes a dispersion medium D and nanoparticles (C), magenta (M), and yellow (Y) that are nanoparticles dispersed in the dispersion medium. The electrophoretic particles C, M, and Y and the white holding body H that holds the electrophoretic particles C, M, and Y, for example, having a particle diameter of about 10 to 100 μm are filled (the same applies to the following embodiments). is there). In the first reference example, the electrophoretic layer 5 has a layer thickness of about 10 to 100 μm. The electrophoretic particles C, M, and Y of the three colors are charged in the same polarity (positive polarity in the first reference example) in a state of being dispersed in the dispersion medium D, but the charge amount setting value is Since they are different from each other, the absolute value of the threshold voltage (electrophoresis start voltage) for separating from the surface of the holding body H and starting migration in the dispersion medium is different. Here, it is preferable that the holding body H is larger than the electrophoretic particles C, M, and Y and is charged with a polarity opposite to that of the electrophoretic particles C, M, and Y, but is not limited thereto. Not.

  Further, the counter substrate 4 is provided with a counter electrode 8 for applying a reference potential, and supplied with a COM voltage for determining the reference potential of the electrophoretic display devices 2. The operation of the color electrophoretic display device is performed by applying a voltage corresponding to the pixel data between the pixel electrode 7 and the counter electrode 8 to generate electrophoretic particles (hereinafter also referred to as charged particles) C of three colors (CMY). M and Y are moved from the TFT glass substrate 3 side to the counter substrate 4 side or from the counter substrate 4 side to the TFT glass substrate 3 side. In the first reference example, the counter electrode 2 side is the display surface (the same applies to the following embodiments).

  Next, the color display principle of the electrophoretic display device 2 according to the first reference example will be described with reference to FIGS. In the first reference example, the threshold voltages Vth (c), Vth (m), and Vth (y) of the three types of electrophoretic particles C, M, and Y in the figure are | Vth (c) | < It is set to satisfy the relationship | Vth (m) | <| Vth (y) |. Further, voltages V1, V2, and V3 applied between the pixel electrode 7 and the counter electrode 8 are referred to as | Vth (c) | <| V3 | <| Vth (m) |, | Vth (m) | <| V2 | <| Vth (y) and | Vth (y) | <| V1 | are set to satisfy the relationship. Here, the threshold voltage refers to a voltage (electrophoresis start voltage) at which the corresponding charged particles start to move when the absolute value of the applied voltage is equal to or greater than the absolute value of the threshold voltage.

  As will be understood from FIG. 2, first, the behavior of the electrophoretic particles C will be described. When the voltage becomes equal to or higher than the threshold voltage Vth (c), the electrophoretic particles C are separated from the TFT glass substrate 3 side. 4 side, the display density of cyan becomes darker, and becomes saturated before the voltage reaches the voltage Vth (m). In this state, when a negative voltage is applied and the voltage falls below −Vth (c), which is the threshold voltage, the electrophoretic particles C move from the counter substrate 4 side to the TFT glass substrate 3 side, and cyan The display density of the color becomes lighter and the cyan display density becomes the lowest before the voltage reaches −Vth (m). Similarly, in the electrophoretic particle M, the display density increases (or decreases) when the voltage is equal to or higher than the threshold voltage Vth (m) (or lower than −Vth (m)), and in the electrophoretic particle Y, the voltage is increased. The display density increases (or decreases) at a threshold voltage Vth (y) or higher (or −Vth (y) or lower).

  Next, a TFT driving method of the color electrophoretic display device (element) according to the first reference example will be described. In the TFT drive of the electrophoretic display device 2 as well as the liquid crystal display device, a gate signal is applied to the gate line, the shift operation is performed for each line, and the data line is written to the pixel electrode through the TFT of the switching element. Is done. The time when all lines are written is defined as one frame, and one frame is scanned at, for example, 60 Hz (16.6 msec cycle). In general, in a liquid crystal display device, the entire image is switched in one frame. On the other hand, the electrophoretic display device 2 has a slower response speed than the liquid crystal, and a plurality of frame periods (hereinafter referred to as a subframe period in the electrophoretic display element, and a screen update composed of a plurality of subframe periods). The screen cannot be switched unless the voltage is continuously applied during the period of the screen update period). For this reason, the electrophoretic display device employs pulse width modulation driving (hereinafter also referred to as PWM driving) in which a constant voltage is continuously applied during a plurality of subframe periods. Then, gradation display is performed by applying a predetermined voltage V1 (V2 or V3) of a predetermined number of subframes. In the following description, in order to represent an arbitrary display color (for example, La * b * system, XYZ system, and RGB system), the relative color density of the CMY system is the same as the colors of the three electrophoretic particles C, M, and Y. This will be explained in terms of conversion.

Drive operation <Case where drive waveform is applied once>
In the first reference example, in order to display the display state NEXT (hereinafter, also referred to as the next screen or the update screen) after the image update from the previous display state CURRENT (hereinafter also referred to as the previous screen or the current screen), it will be described later. By passing through the intermediate transition states WK → I-1 → I-2, a systematic and simple driving method including intermediate color / gradation display is realized. A predetermined image is updated by driving over a plurality of subframes. The drive period over a plurality of subframes includes a reset period for transitioning to a white (W) or black (K) ground state, and a first subframe group that applies a voltage of V1, 0, or −V1 [V]. A period (first voltage application period), a second subframe group period (second voltage application period) in which a voltage of V2, 0, or −V2 [V] is applied, and V3, 0, or −V3 It consists of a third subframe group period (third voltage application period) in which a voltage of [V] is applied. The first to third voltage application periods are collectively referred to as a set period.

Specifically, when the display information of the pixels of the image to be displayed (next screen NEXT to be updated) is represented by the relative color density (CMY) of the charged particles C, M, and Y by (Rc, Rm, Ry). ,
(1) The first sub-frame group period is a period during which a transition from a white (W) or black (K) ground state to a first intermediate transition state I-1 in which the relative color density of the charged particles Y is Ry. ,
(2) The second subframe group period is a period of transition from the first intermediate transition state I-1 to the second intermediate transition state I-2 in which the Y concentration is Ry and the M concentration is Rm.
(3) The third subframe group period is a period during which the second intermediate transition state I-2 transitions to the final display state NEXT.

Here, the relative color density Rx (x = c, m, y) takes a relative color density of 0 to 1, and Rx = 0 is a state where no X particles (charged particles C, M, Y) are present on the surface. Rx = 1 represents a state in which all X particles have moved to the surface. Therefore, (CMY) = (0, 0, 0) represents white (W) display, and (CMY) = (1, 1, 1) represents black (K) display.
Table 1 shows specific drive voltage data in which each gradation of the CMY three colors is three gradations. For simplicity, the charged particles C, M, and Y have the charge amount Q set as | Qc |> | Qm |> | Qy |, and the threshold voltage at which the particles start moving is | Vth ( c) | <| Vth (m) | <| Vth (y) |. However, by changing the weight and size of the particles, the moving speed (mobility) with respect to the same applied voltage is increased. , M, and Y are set to be the same.

  As shown in Table 1, the driving voltage is set to | V1 | = 30V in the first subframe group period, | V2 | = 15V in the second subframe group period, and in the third subframe group period. | V3 | = 10 V (note that the drive voltage can be set to an arbitrary value if necessary).

  Furthermore, the time Δt for each charged particle C, M, Y to move from the back surface to the display surface is, in a simple model, inversely proportional to the applied voltage V above the threshold voltage, and V × Δt = constant. Become. Therefore, in the first reference example, the time for the charged particles C to move from the back surface to the front surface (or from the front surface to the back surface) is 0.2 sec at | V | = 30 V, 0.4 sec at | V | = 15 V, | V | = 10 V and 0.6 sec. The time for the charged particles M to move from the back surface to the front surface (or from the front surface to the back surface) is set to 0.2 sec at | V | = 30 V and 0.4 sec at | V | = 15 V. The time for the charged particles Y to move from the back surface to the front surface (or from the front surface to the back surface) is set to 0.2 sec at | V | = 30V. In consideration of these relationships, in this first reference example, one subframe period is 100 msec, 14 subframes (the reset voltage application period is 2 subframes, the first subframe group period is 2 subframes, The subframe group period is 4 subframes and the third subframe group period is 6 subframes) to form a screen update period (in addition, if the next screen is a still image, a later-described termination 0V application subframe is also included. And the screen update period is 15 subframes).

A specific driving operation (driving method) of the first reference example will be described with reference to Table 1.
The first column represents the relative color density (CMY) of the target update display state. The second column represents the applied voltage during the reset period and the relative color density of the ground state after the reset is completed. The reset period is composed of two subframes Ra and Rb in the driving of the first reference example, and a possible applied voltage is −30V. The third column represents the applied voltage of the first subframe group period and the relative color density of the first intermediate transition state I-1 after the period. The first subframe group period is composed of two subframes 1a and 1b, and possible applied voltages are + 30V and 0V. The reason for the 2 subframes is that the charged particle response time at 30 V is 0.2 sec. In other words, in one subframe period, the time required for the particles in the applied voltage 30 V to move about half way between the layers. This is because it is 0.1 sec corresponding to. The fourth column represents the applied voltage of the second subframe group period and the relative color density of the second intermediate transition state I-2 after the period.

  The second subframe group period is composed of four subframes 2a, 2b, 2c, and 2d, and possible applied voltages are + 15V, 0V, and -15V. The reason why 4 subframes are used is that the response time of charged particles at 15 V is 0.4 sec. In other words, during one subframe period, particles in the applied voltage of 15 V can move about ¼ between layers. This is because it is 0.1 sec corresponding to the required time. The fifth column represents the applied voltage of the third subframe group period and the relative color density of the last updated display state NEXT after the period. The third subframe group period is composed of six subframes 3a, 3b, 3c, 3d, 3d, and 3f, and possible applied voltages are + 10V, 0V, and -10V. The reason for setting 6 subframes is that the response time of particles at 10 V is 0.6 sec and the period of 1 subframe is 0.1 sec. In the reset period, V1 = -30V is applied for two frames, and the charged particles C, M, and Y are moved and concentrated on the opposite side of the display surface to obtain a white (W) display that is a ground state.

First, the transition state of the screen from the previous screen to the final transition state that is the update screen will be described for each reset period and subframe group period.
In the reset period, V1 = -30V is applied for two frames, and the charged particles C, M, and Y are moved and concentrated on the opposite side of the display surface to obtain a white (W) display that is a ground state.
In the first subframe group period, when the relative color density (Y) is 0, the applied voltage is 0 V, and the relative color density (Y) is 0.5, corresponding to the relative color density of the charged particles Y. Applies an applied voltage of 30 V for only one subframe. When the relative color density (Y) is 1, the applied voltage of 30 V is applied for two subframes. As a result, the ground state W changes to the first intermediate transition state (CMY) = (Ry, Ry, Ry) (Ry is 3 gradations, Ry = 0, 0.5, 1).

  In the second subframe group period, MY, which is the difference in relative color density between the target charged particle M and charged particle Y, is calculated, and a predetermined number of −15V or 15V is applied. For example, when the relative color density (Y) = 0.5 and the relative color density (M) = 0, since the relative color density difference (MY) = − 0.5, −15V is divided into two subframes. Then, the charged particles M and C are moved to the opposite side of the display surface to lower the gradation by one. When the relative color density (Y) = 0.5 and the relative color density (M) = 0.5, 0 V is applied. When the relative color density (Y) = 0.5 and the relative color density (M) = 1, in order to increase the gradation by one, 15 V is applied for two subframes, and the charged particles M, C on the display surface side are applied. Increase. As described above, the first intermediate transition state I-1: (CMY) = (Ry, Ry, Ry) to the second intermediate transition state I-2: (CMY) = (Rm, Rm, Ry) (Rm is 3 It is a gradation and transitions to Rm = 0, 0.5, 1).

  In the third subframe group period, CM, which is the difference between the relative color densities of the charged particles C and the charged particles M having a target relative density, is calculated, and a predetermined number of −10V or 10V is applied. For example, when M = 0.5 and the relative color density (C) = 0, the color density difference (C−M) = − 0.5, so −10 V is applied for 3 subframe periods to display the charged particles C. Move to the opposite side of the surface to lower the gradation by one. When the relative color density (M) = 0.5 and the relative color density (C) = 0.5, 0 V is applied. When the relative color density (M) = 0.5 and the relative color density (C) = 1, in order to increase one gradation, 10 V is applied for 3 subframes to increase the charged particles C on the display surface side.

Thus, the final display state NEXT: (CMY) = (Rc, Rm, Ry) (Rc is the third floor) from the second intermediate transition state I-2: (CMY) = (Rm, Rm, Ry) Key, and can transition to Rc = 0, 0.5, 1).
3 to 11 show specific drive waveforms based on Table 1. FIG.
For example, with reference to the drive waveform shown in FIG. 12 extracted from FIG. 8B, the intermediate color / gradation display realizing the display state (CMY) = (0.5, 1, 0.5) will be described. .
First, in order to erase the previous display state (current screen) CURRENT, -30V is applied to the reset period for 2 subframes (0.2 sec), and the white ground state W: (CMY) = (0 , 0, 0). Next, by applying + 30V for 1 subframe period and 0V for 1 subframe period in the first subframe group period, the first intermediate transition state I-1: (CMY) = (0 .5, 0.5, 0.5). In the next second subframe group period, +15 V is applied for 2 subframe periods and 0 V is applied for 2 subframe periods, so that the second intermediate transition state I-2: (CMY) = (1 , 1, 0.5). In the next third subframe group period, −10 V is applied for 3 subframe periods, and 0 V is applied for 3 subframe periods, and the update display state NEXT: (CMY) = (0.5, 1.. 0, 0.5).

  FIG. 13 shows intermediate transition states of the charged particles C, M, and Y that respond to the drive waveform of FIG. After completion of the reset period, the charged particles C, M, and Y move to the TFT glass substrate 3 side, and only the white holding body is visible from the counter substrate 4 side, so that the display state W is changed. In the next first subframe group period, all of the charged particles C, M, and Y move from the TFT glass substrate 3 side to the middle of the TFT glass substrate 3 and the counter substrate 4, so that the first intermediate transition state I-1 is reached. Transition. Then, in the second sub-frame group period, while Y remains in the middle, the charged particles C and M move to the display surface side and transition to the second intermediate transition state I-2. In the third subframe group period, the charged particles M remain on the surface, and only the charged particles C transition to the middle, so that it is possible to transition to a predetermined update display state NEXT.

By the way, for example, when the target display state is NEXT: (CMY) = (1.0, 1.0, 0.5), the first intermediate transition state I-1: (CMY) = (0. 5, 0.5, 0.5), I-2: (1.0, 1.0, 0.5), and (I-2) is the final display state NEXT. And the intermediate transition state I-2 is not necessary. When the target display state is NEXT: (CMY) = (0.5, 0.5, 0.5), the first intermediate transition state I-1: (CMY) = (0.5, 0.5, 0.5), which is the final display state NEXT, the second and third subframe group periods can be omitted, and the intermediate transition states I-1 and I-2 are not necessary.
When NEXT: (CMY) = (0, 0, 0), the final display state NEXT can be realized only by the reset period. Therefore, when the ground state, the intermediate transition state I-1 or the intermediate transition state I-2 coincides with the final display state NEXT, the subsequent subframe period may be omitted.

  In the above description, the case where the charged particles C, M, and Y have the same mobility has been described. However, when the mobility is different, in the first intermediate transition state I-1, the relative color density of the charged particle Y is set to (Y ) = Ry, the relative color densities of the charged particles C and M are different from Ry. In the second intermediate transition state I-2, the relative color density of the charged particles Y can be controlled to (Y) = Ry and the relative color density of the charged particles M can be controlled to (M) = Rm. The concentration is different from Rm. Therefore, the relative color density of the first intermediate transition state I-1 is (CMY) = (X, X, Ry) (X: arbitrary, X ≠ Ry), and the relative color of the second intermediate transition state I-2. The concentration can be generalized as (CMY) = (X, Rm, Ry) (X: arbitrary X ≠ Rm).

  In the above description, it is assumed that the moving time of the charged particles C, M, and Y differs from the back side to the display surface side according to the applied voltage. , V3 = 10V and t3 = 0.6 sec. When the mobility of the charged particles C, M, Y is the same, generalizing this, the subframe periods t1, t2, t3 of each subframe group period are If the applied voltages in each subframe group period are V1, V2, and V3, Vi · ti = constant (i = 1, 2, 3) is set. When the unit subframe time is constant, if the number of subframes in each period is ni, Vi · ni = constant (n = 1, 2, 3). Alternatively, the number of subframes in each period may be constant, and the unit subframe time in each period may be different in each period.

Although the case where the ground state after reset is set to white (W) has been described above, a drive waveform can be created with the same idea even when the ground state is set to black (K).
Further, in the subframe group period for setting the relative color density of CMY of the intermediate transition to “0” and “1”, the applied voltage of the subframe group is saturated and the relative color density is saturated to “0”. Needless to say, if it is “1”, an extra applied voltage may be applied.
In the above description, C, M, and Y have three gradations. Needless to say, the same driving can be performed with two gradations or multiple gradations of three gradations or more.

As described above, according to the configuration of the first reference example, not only each single color (R, G, B, C, M, Y, W, K) but also multi-tone expression including intermediate colors can be simplified. It can be realized by configuration.
However, the luminance and color variation in the intermediate transition state are very large, and the technical problem of preventing “flickering” has not been solved. For example, in order to transition to the final display state NEXT: (CMY) = (0, 1, 0), the transition to the first intermediate transition state I-1: (CMY) = (0, 0, 0) Next, the state transits to the second intermediate transition state I-2: (CMY) = (1, 1, 0), and finally transits to NEXT: (CMY) = (0, 1, 0). That is, in order to set the final color as magenta, the previous screen is once erased to display the ground state WK and the first intermediate transition state I-1 in white (W), and then the second intermediate transition state I. -2 is displayed in blue (B) with a relative color density of 1, and finally becomes magenta. Therefore, according to the first reference example, similarly to the configurations described in Patent Documents 1 to 3, when updating from the previous screen to the next screen, an intermediate transition of one or two primary colors (relative color density 1) is performed. Therefore, it is impossible to avoid the disadvantage that unpleasant “flickering” occurs on the screen at the time of updating due to the brightness and color density fluctuating greatly and rapidly in the updating process.

Embodiment 1

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Unless otherwise specified, the configuration of the electronic paper display device according to the first embodiment of the present invention is the same as the configuration of the first reference example of the present invention described above. When necessary in the description of the following embodiment, the drawings and tables used in the description of the first reference example are referred to.

Drive operation <Case of repeated application of unit drive waveform>
In the first embodiment of the present invention, the subframe frequency is increased, and the drive waveform shown in Table 1 (hereinafter referred to as a unit drive waveform, also referred to as a basic waveform) is repeated, so that the final display is started from the ground state WK. A smooth transition to state NEXT is realized.
That is, in this embodiment, when the screen is updated, for example, when the final display state is NEXT: (CMY) = (1, 0, 1), the ground state (0, 0, 0) is changed to (0, 0, 0). ) →…… → (0.25, 0, 0.25) →…… → (0.5, 0, 0.5) →…… → (0.75, 0, 0.75) →…… → It is configured to make a smooth transition to (1, 0, 1).

  Tables 2-1 to 2-5 show specific drive voltage data consisting of five levels, in which each gradation of the three colors CMY is three gradations used in the first embodiment. . First, Table 2-1 shows the driving voltage in the reset period and the ground state WK after application. Table 2-2 shows the drive voltage during the first drive voltage application period and the intermediate transition state I1-3 after the application, and Table 2-3 shows the drive voltage during the second drive voltage application period and after the application. Intermediate transition state I2-3, Table 2-4 shows the drive voltage during the third drive voltage application period and intermediate transition state I3-3 after the application, and Table 2-5 shows the fourth time The drive voltage during the drive voltage application period and the final display state NEXT after application are shown.

  Here, one subframe period is set to 25 msec at 4 × speed, and 12 subframes (the first subframe group period is 2 subframes, the second subframe group period is 4 subframes, the third subframe group period) The final display state NEXT is realized by repeating the unit drive waveform composed of 6 subframes) 4 times. Note that a period in which the unit drive waveform is repeatedly applied is referred to as a set period.

With reference to Table 2-1 to Table 2-5, a specific driving operation (driving method) of this embodiment will be described.
In Table 2-1, the first column represents the relative color density (CMY) of the target update display state. The second column represents the applied voltage during the reset period and the relative color density of the ground state after the reset period. In the driving according to this embodiment, the reset period is composed of eight subframes Ra to Rh, and a possible applied voltage is −30V.

  In Table 2-2, the first column represents the intermediate transition state after application of the reset period, and the second column represents the first application period of the unit drive waveform, and is composed of 12 subframes. Yes. The applied voltage and intermediate transition states I1-1, I1-2, and I1-3 to be applied in each subframe period are shown. The unit drive waveform includes a first voltage application period in which V1, 0, −V1 [V] is applied, a second voltage application period in which V2, 0, −V2 [V] is applied, and V3, 0, −. It is comprised from the 3rd voltage application period which applies V3 [V]. The first subframe group period is composed of two subframes W1-1a and W1-1b, and possible applied voltages are + 30V and 0V. The second subframe group period is composed of four subframes 2a, 2b, 2c, and 2d, and possible applied voltages are + 15V, 0V, and -15V. The third subframe group period is composed of six subframes 3a, 3b, 3c, 3d, 3d, and 3f, and possible applied voltages are + 10V, 0V, and -10V.

Similarly, Table 2-3 shows the applied voltage and intermediate transition state of each subframe group in the second application period of the unit drive waveform, and Table 2-4 shows each of the application period in the third application period of the unit drive waveform. The applied voltage and intermediate transition state of the subframe group are shown, and Table 2-5 shows the applied voltage and intermediate transition state of each subframe group in the fourth application period of the unit drive waveform.
14 to 19 show specific voltage driving waveforms based on Tables 2-1 to 2-5. For example, when an applied waveform for transition to the final transition state NEXT: (CMY) = (0, 1, 0) is extracted from FIG. 16A, it is as shown in FIG. By explaining the display state of the intermediate transition, the luminance and color variation in the intermediate transition of the relative color density will be described. FIG. 21 shows the states of the charged particles C, M, and Y in the intermediate transition display state in each period.
Here, in order to simplify the explanation, the charged particles C, M, and Y linearly increase or decrease in relative color density depending on the application period until they reach the counter substrate or TFT substrate surface side, Assume that the relative color density is saturated when reached. First, in the reset period, a transition is made from the previous screen state to the reset state W: (CMY) = (0, 0, 0). At this time, all of the charged particles C, M, and Y have moved to the TFT substrate side.

  Next, with reference to FIG. 20 (Table 2-2) and FIG. 21, the operation in the first application period of the unit drive waveform will be described. In the first subframe group period from the reset state W: (CMY) = (0, 0, 0), I1-1: (0, 0, 0) remains unchanged because no voltage is applied. Next, in the second subframe group period, 15 V is applied for 4 subframes, that is, 100 msec. When the moving time from the TFT substrate to the counter substrate is 15 V, it is assumed that each particle is 0.4 sec. Therefore, when 15 V and 100 msec are applied, the C particle and the M particle move by a distance of ¼. For this reason, it changes to display state I1-2: (0.25,0.25,0). Next, in the third subframe group period, −10 V is applied for 6 subframes, that is, 150 msec. Thereby, the C particles once moved are returned to the TFT substrate side again. As a result, the state transits to the display state I1-3: (0, 0.25, 0).

Next, the operation in the second application period of the unit drive waveform will be described. In the first subframe group period from I1-3: (CMY) = (0, 0.25, 0), no voltage is applied, so I2-1: (0, 0.25, 0) remains. Next, in the second subframe group period, 15 V is applied for 4 subframes, that is, 100 msec. When the moving time from the TFT substrate to the counter substrate is 15 V, it is assumed that each particle is 0.4 sec. Therefore, when 15 V and 100 msec are applied, the C particle and the M particle move by a distance of ¼. In the first unit drive waveform application period, the M particles have moved by a distance of 1/4 of the distance between the TFT and the counter substrate, and have further moved by a quarter, and have just moved to the center of the TFT-counter substrate. On the other hand, since the C particles are returned to the TFT substrate side after the first unit driving waveform application period, they move by ¼ of the distance between the TFT and the counter substrate by this application. Therefore, the state transits to the display state I2-2: (0.25, 0.5, 0). Next, in the third subframe group period, −10 V is applied for 6 subframes, that is, 150 msec. Thereby, the C particles once moved are returned to the TFT substrate side again. As a result, the display state transitions to I2-3: (0, 0.5, 0).
The same operation is repeated in the third and fourth unit drive waveform applications, and after the third unit drive waveform application, I3-2: (0, 0.75, 0) is obtained, and the fourth unit drive waveform application is performed. Later, a transition is made to the final display state NEXT: (0, 1, 0).

  As described above, in the driving operation according to the present embodiment, the previous screen is reset to the white ground state after the reset period, and after the first application period of the unit drive waveform (CMY) = (0, 0. 25, 0) to the intermediate transition state (CMY) = (0, 0.5, 0) after the end of the second application period, and (CMY) = (0, 0.75, after the end of the third application period. 0), after the fourth application period, the state transits to the final display state NEXT: (CMY) = (0, 1, 0). In each unit drive waveform application period, the variation is only C particles, and the variation in C concentration is suppressed within ΔC = ± 0.25. For this reason, the transition from the previous screen to the update screen, once the previous screen is reset to a white state, the magenta color gradually increases from white, even though there are some brightness and color variations. The final target display state, magenta color, will be reached. That is, by adopting the above driving method, it is possible to realize predetermined intermediate color / gradation display while suppressing unpleasant “flickering” in the screen update process.

In this embodiment, as described above, the unit drive waveform is repeated four times. However, if the unit drive waveform is repeated four or more times by further increasing the subframe frequency, the color variation (for example, intermediate transition) (for example, , ΔC, ΔM, ΔY) can be further reduced, and “flicker” can be suppressed accordingly.
Further, after the drive period of each unit drive waveform is completed, 0V is applied for several subframes, so that (0, 0.25, 0), (0, 0.5, 0), (0, 0.75, Since the intermediate transition state in which the color of 0)... Is close to the final display state can be emphasized, the “flickering” of the screen can be further alleviated.

In the first embodiment, the entire first to third subframe groups are repeated as unit drive waveforms. However, in the target update display state, unnecessary subframe groups need to be omitted and applied. Only the first to third subframe groups having the same may be repeated.
In addition, in the subframe group period in which the relative color density of CMY at the intermediate transition is set to “0” and “1”, the applied voltage of the subframe group is saturated and the relative color density is saturated and “0”. Needless to say, if “1” is set, an extra applied voltage may be applied. In addition, the driving period can be shortened by reducing the application period of 0V. Furthermore, the number of subframes in each period may be constant, and the unit subframe time in each period may be different in each period. In the above description, the ground state after reset is described as white (W). However, a drive waveform can be created with the same idea even when the ground state is black (K). Further, for each final display state, the driving period can be shortened by selecting the ground state as white or black so that the intermediate transition state I-1 or I-2 matches the final display state NEXT. It is. Furthermore, although C, M, and Y have three gradations in the above, it goes without saying that the same driving can be performed with two gradations or multiple gradations of three gradations or more. In the above description, the case of three particles of C, M, and Y has been described. However, three RGB colors may be used instead of three CMY colors, and the same driving method can be applied to three or more colors such as four CMYK colors and six CMYRGB colors. .

Generation of Lookup Table Next, a method for generating and converting a lookup table (LookUp Table, hereinafter also referred to as LUT) for realizing the drive waveforms of FIGS. 14 to 19 will be described. As can be seen from Table 1, a constant voltage is applied during the reset period (Ra to Rh) regardless of the target update display state (CMY). Thereafter, the drive waveform as a base is applied four times. Therefore, as shown in Table 3, the LUT group R_WF (Table 3 (a)) for the reset period and the LUT group B_WF (Table 3 (b)) for the unit drive waveform are prepared as shown in Table 3, and subframes are prepared. A desired drive waveform can be expressed by selecting a predetermined LUT from the L_WF and B_WF LUT groups each time.

  That is, since the same applied voltage is repeated for 8 subframes during the reset period, it is sufficient to prepare one R_WF that is an LUT of m rows and 1 column, and the unit drive waveform that is repeated four times is composed of 12 subframes. Therefore, it is sufficient to prepare 12 subframes of m rows and 1 column LUTs. The LUTs for 12 subframes for the unit drive waveform are set as a unit drive waveform LUT group B_WFn (n = 1 to 12). Note that n means the nth LUT that defines the applied voltage in the nth subframe period in the reset period or unit drive waveform application period. The index representing the line number m is represented by a 6-bit binary number, the upper 2 bits are Y gradations, m [4: 5] = [00], [01], [10], M [2: 3] = [00], [01], [10], where the 2nd order bit is M gradation, and m [0: 1] = [00] where the lower 2 bits are C gradation , [01], [10].

  The matrix element in each row represents a driver data signal to be supplied to a data driver (described later) of the electronic paper display device when transitioning to the gradation data of the pixel on the update screen in each subframe. Here, the driver data signal takes a value of [000], [001], [010], [011], [100], [101], [110], [111] in a 3-bit binary number. When [000] is input, the data driver outputs 0V, and similarly [001] = 10V, [010] = 15V, [011] = 30V, [000] = 0V, [101] = −. 10V, [110] =-15V, and [111] =-30V are output. In the above configuration, Tables 3 (a) and 3 (b) show LUT groups for realizing the drive waveforms in Tables 2-1 to 2-5.

  For example, when the display state NEXT: (CMY) = (0, 1, 0), the relative color density (C) = [00], (M) = [10], (Y) = [00], so the LUT The line number m is m = [001000]. At this time, from Table 2, the driving waveform is applied with −30 V for 8 subframes of the reset period, so the corresponding element data of the reset LUT group R_LUT is R_WF1 [001000] = [111]. Further, in the first voltage application period during the unit drive waveform application period, 0 V is applied for two subframes, so that B_WFn [001000] = [000] (n = 1, 2). Next, in the second voltage application period during application of the unit drive waveform, 15 V for 4 subframes is applied, so that B_WFn [001000] = [010] (n = 3, 4, 5, 6). Further, since −10 V for 6 subframes is applied in the third voltage application period during the unit drive waveform application, B_WFn [001000] = [101] (n = 7, 8, 9, 10, 11, 12) Become. The correspondence relationship between other drive waveforms and each element of the lookup table is the same.

Circuit Configuration Next, the circuit configuration of this embodiment will be described.
FIG. 22 is a block diagram showing the electrical configuration of the electronic paper display device (image display device) according to the first embodiment of the present invention, and FIG. 23 shows the details of the electronic paper controller constituting the electronic paper display device. FIG. 24 is a block diagram showing details of an electronic paper control circuit constituting the electronic paper controller, and FIG. 25 is a block diagram showing details of an LUT conversion circuit constituting the electronic paper controller. .

  This electronic paper display device is an image display device that is driven based on the drive waveform of this embodiment as described above, and as shown in FIG. 23, an electronic paper unit 9 capable of color display, an electronic paper, and the like. It consists of a module substrate 10. The electronic paper unit 9 includes a display unit (electronic paper) 1 including an electrophoretic display device 2 having a memory property and capable of color display, and a driver (voltage applying unit) that drives the display unit 1. Yes. This driver includes a gate driver 11 that performs a shift register operation and a multi-value output data driver 12.

  The electronic paper module substrate 10 includes an electronic paper controller 13 that drives the electronic paper unit 9, a graphic memory 14 that constitutes a frame buffer, and a CPU that controls each part of the apparatus and provides image data to the electronic paper controller 13. A (central processing unit) 15, a main memory 16 such as a ROM and a RAM, a storage device (storage) 17 for storing various image data and various programs, and a data transmission / reception unit 18 including a wireless LAN and the like are provided.

The electronic paper controller 13 uses the LUT groups R_WFn and B_WFn (n is 1 to 15) shown in Table 3 to implement voltage control means for realizing the drive waveforms at the time of screen update shown in FIGS. Specifically, as shown in FIG. 23, the display power supply circuit 19, the electronic paper control circuit 20, the data reading circuit 21, and the LUT conversion circuit 22 are included.
The data readout circuit 21 reads out RGB data representing the color gradation of the pixel of the updated image (next screen NEXT) written in the graphic memory 14 by the CPU 15 and once converts it into arbitrary display color data La * b *. This is a circuit that converts the data into corresponding CMY relative color density data and transmits it to the LUT conversion circuit 22. The converted CMY relative color density data is represented by an 8-bit binary number, the upper 2 bits are [00], the next 2 bits are Y (yellow color) gradations, [00], [01], [10] is taken, [00], [01], [10] are taken for the next 2 bits in M (magenta color) gradation, and [00], [10] are taken in the lower 2 bits in C (cyan color) gradation 01] and [10]. However, the relative color density data corresponding to the CMY gradations is not limited to the above, and different data may be used as long as a one-to-one correspondence relationship is obtained. The CPU 15 may store the converted CMY relative color density data in the graphic memory 14 instead of the RGB data.

The display power supply circuit 19 receives the power supply output request signal REQV transmitted from the electronic paper control circuit 20, supplies a plurality of reference voltages VDR to the drivers 11 and 12 of the electronic paper unit 9, and the reference potential of the electronic paper unit 9. Is a circuit for supplying a COM voltage VCOM to be applied to the counter electrode (common electrode) 8 that determines
As shown in FIG. 24, the electronic paper control circuit 20 includes a driver control signal generation circuit 23, a subframe counter 24, and an LUT generation circuit 25. When the driver control signal generation circuit 23 receives a screen update command REFL from the CPU 15, the driver control signal generation circuit 23 outputs a driver control signal CTL to the gate driver 11 and the data driver 12 of the electronic paper unit 9, and at each clock (for each pixel). A tone data read request signal REQP is output to the data read circuit 21. Further, the power supply output request signal REQV is output to the display power supply circuit 19.

The subframe counter 24 receives the screen update command REFL from the CPU 15 and starts counting subframes. The subframe counter 24 counts up the subframes by the number of frames necessary for the screen update. The subframe number NUB indicating that the current driving process is the nth subframe is output.
The LUT generation circuit 25 reads the reset LUT group R_WFn and the unit drive waveform LUT group B_WFn shown in Table 3 stored in the non-volatile memory, generates an LUT corresponding to the subframe number, and converts the LUT as LUT data. Output to the circuit 22.
For example, in the subframe W2a-a in Table 2, since the second application of the base unit drive waveform is the second in the second subframe group, the WF4 of the corresponding unit drive waveform LUT group in Table 3 is It is read out and output to the LUT conversion circuit as LUT data.

  The LUT conversion circuit 22 includes a conversion circuit 26 and a driver data generation circuit 27 as shown in FIG. The conversion circuit 26 deletes the upper 2 bits of the 8-bit CMY relative color density data transmitted from the data reading circuit 21, converts it into the LUT matrix row number m, and outputs it to the driver data generation circuit 27. The driver data generation circuit 27 refers to the LUT data output from the electronic paper control circuit 20 and uses the LUT matrix element corresponding to the LUT matrix row number m output from the conversion circuit 26 as driver data DAT. To the drivers 11 and 12 of the unit 9. In this way, the electronic paper controller 13 outputs the driver data DAT for realizing the drive waveforms shown in FIGS.

  In the first embodiment, when a predetermined display state NEXT: (Rc, Rm, Ry) is realized at the time of screen update, the subframe frequency is increased N times (N is a natural number of 2 or more), and unit basic Since the waveform is repeated N times, a predetermined intermediate color / gradation display can be realized while suppressing an unpleasant “flicker” in the screen update process.

Embodiment 2

Next, a second embodiment of the present invention will be described. In the first embodiment, the subframe frequency is increased in order to prevent unpleasant “flickering” in the screen update process. However, increasing the subframe frequency has limitations due to increased power consumption during driving and panel driving capability. For example, if the repetition is 4 times, the subframe period is 25 msec. However, if the repetition is 10 times, the subframe period is 10 msec, which is close to the limit of the writing ability of the TFT.
Therefore, in the second embodiment, the subframe frequency is relaxed by combining a plurality of types of unit drive waveforms and repeating them.
In the second embodiment, the circuit configuration, the corresponding LUT generation method, and the like are substantially the same as those in the first embodiment described above, and thus the description thereof is omitted or simplified.

Creation of Unit Drive Waveform First, a method for creating a unit drive waveform as a base for relaxing the drive frequency will be described. As can be seen from the drive waveforms in Tables 2-1 to 2-5, in order to realize the final display state NEXT: (CMY) = (Rc, Rm, Ry), the final transition state NEXT: (CMY) = (1, 0, 0.5), when V1 = 30V is applied only to W1-1a, and the final transition state NEXT: (CMY) = (1, 0, 1), W1-1a, W1- V1 = 30V may be applied to both 1b. Similarly, there is a case where V2 = 15V (or −V2 = −15V) is applied to W1-2a / W1-2b and a case where it is applied to all W1-2a / W1-2b / W1-2c / W1-2d. Further, when V3 = 10V (−V3 = −10V) is applied only to W1-3a / W1-3b / W1-3c, and W1-3a / W1-3b / W1-3c / W1-3d / W1-3e / W1-3f may be applied to all. Consider stopping the application of the voltage V1 (V2, V3) to only a part of this.

As an example, creation of a unit drive waveform for displaying the final transition state NEXT: (CMY) = (1, 0, 0.5) will be described with reference to Tables 4-1 to 4-5.
Tables 4-1 to 4-5 show specific drive voltage data in which the gradations of the three colors CMY used in the second embodiment are three gradations. Here, Table 4-1 shows the driving voltage in the reset period and the ground state after application. Table 4-2 shows the drive voltage and the intermediate transition state after application in the first application period of the unit drive waveform A, and Table 4-3 shows the drive in the first application period of the unit drive waveform B. The voltage and the intermediate transition state after application are shown. Table 4-4 shows the drive voltage and the intermediate transition state after application in the second application period of the unit drive waveform A, and Table 4-5 shows the drive in the second application period of the unit drive waveform B. The voltage and the final display state after application are shown. Here, the point that one subframe period is set to 25 msec, which is four times the drive waveform before improvement in which “flickering” appears, is the same as in the first embodiment.

  In Table 2 used in the first embodiment, the drive waveforms for displaying the final transition state NEXT: (CMY) = (1, 0, 0.5) are W1-1a = 30V and W1-1b = 0V. However, in the unit drive waveform A of this embodiment, W1-1b is set to the same voltage as W1-1a, and is corrected to W1-1a = W1-1b = 30V. In Table 2, W1-2a = W1-2b = -15V and W1-2c = W1-2d = 0V, but in the unit drive waveform A of this embodiment, W1-2c / W1-2d is set to W1- The voltage is the same as 2a / W1-2b, and W1-2a = W1-2b = W1-2c = W1-2d = -15V. In Table 2, since W1-3a (b, c, d, e, f) = 10 V and the voltages in the first half and the second half are the same, no correction is necessary. By applying the voltage of the unit drive waveform A, as shown in Table 4-2, transition is made to the intermediate transition state IA1-3: (CMY) = (0.25, 0, 0.25).

  Next, in a period corresponding to the second application period of the unit drive waveform shown in Table 2-3, by applying a unit drive waveform B different from the unit drive waveform A, as shown in Table 4-3 The transition is made to the intermediate transition state IB1-3: (CMY) = (0.5, 0, 0.25) after the end of the second application period of the unit drive waveform. For this purpose, W2-1a (b) = 0V, W2-2a (b, c, d) = 0V, and W2-3a (b, c, d, e, f) = 10V may be applied. Thereby, the transition to the intermediate transition state I2-3: (CMY) = (0.5, 0, 0.25) becomes possible. By repeating the application of the unit drive waveform A and the application of the unit drive waveform B again, the transition to the final display state NEXT: (CMY) = (1, 0, 0.5) becomes possible. Tables 4-1 to 4-5 show driving waveforms for the final display state of all three gradations. In Tables 4-1 to 4-5, the subframe frequencies are the same as those in Tables 2-1 to 2-5, but W1-1a and W1-1b are the same voltage, W1-2a and W1-2b (c , D,) are the same voltage, and W1-3a and W1-3b (c, d, e, f) are the same voltage, so the subframe frequency is halved (the reset period is four subframes, each of the drive waveforms A, B). The voltage application period can be 6 subframes). Table 5 shows the drive waveform used in the second embodiment with the subframe frequency halved. FIG. 26 shows drive waveforms and intermediate transition states used in the second embodiment when transitioning to NEXT: (CMY) = (0, 1, 0.5).

Thus, in the second embodiment as well, the unit drive waveform is repeated four times as in the first embodiment, but the subframe frequency is further increased and the unit drive waveform is increased four times or more. If it is repeated, the color variation (for example, ΔC, ΔM, ΔY) of the intermediate transition can be further reduced, and “flickering” can be suppressed accordingly.
Further, after the drive period of each unit drive waveform is completed, 0V is applied for several subframes, so that (0, 0.25, 0), (0, 0.5, 0), (0, 0.75, Since the intermediate transition state in which the color of 0)... Is close to the final display state can be emphasized, the “flickering” of the screen can be further alleviated.

In the second embodiment, the entire first to third subframe groups are repeated as unit drive waveforms. However, in order to obtain a target update display state, unnecessary subframe groups are omitted, Only the first to third subframe groups that need to be applied may be repeated.
In addition, in the subframe group period in which the relative color density of CMY at the intermediate transition is set to “0” and “1”, the applied voltage of the subframe group is saturated and the relative color density is saturated and “0”. Needless to say, if “1” is set, an extra applied voltage may be applied. In addition, the driving period can be shortened by reducing the application period of 0V. Furthermore, the number of subframes in each period may be constant, and the unit subframe time in each period may be different in each period. In the above description, the ground state after reset is described as white (W). However, a drive waveform can be created with the same idea even when the ground state is black (K). Further, for each final display state, the driving period can be shortened by selecting the ground state as white or black so that the intermediate transition state I-1 or I-2 matches the final display state NEXT. It is. Furthermore, although C, M, and Y have three gradations in the above, it goes without saying that the same driving can be performed with two gradations or multiple gradations of three gradations or more. In the above description, the case of three particles of C, M, and Y has been described. However, three RGB colors may be used instead of three CMY colors, and the same driving method can be applied to three or more colors such as four CMYK colors and six CMYRGB colors. .

  Also in the second embodiment, the unit basic waveform is repeated N times, so that it is possible to realize predetermined intermediate color / gradation display while suppressing unpleasant “flickering” in the screen update process. . In addition, in the first embodiment described above, the number of subframes for transitioning to the final display state is 8 subframes in the reset period, 12 subframes in the drive waveform application period, and 4 subframes = 48 subframes. However, in this second embodiment, only half of the 28 subframes are required, and the subframe frequency can be reduced to half, so that the load on the element configuration can be reduced. .

    In the second embodiment, as shown in Tables 4-1 to 4-5, the unit drive waveform A and the unit drive waveform B are alternately repeated twice, and four times as a whole. As can be seen from FIG. 26, the unit drive waveform A and the unit drive waveform B can be combined to be regarded as a single unit drive waveform C. In view of this, the second embodiment can be considered as an example in which the unit drive waveform C is repeated twice (the repetition frequency is half). The finer the intermediate transition color variation (eg, ΔC, ΔM, ΔY), the higher the repetition frequency, and the coarser the intermediate transition color variation, the lower the repetition frequency, and therefore the designer may Thus, the color variation (and hence the repetition frequency) of the intermediate transition can be set.

Reference example 2

Next, a second reference example (the invention according to the original application) of the present invention will be described.
In the first reference example described above, a reset period is provided, the previous screen is erased and the transition to the white ground state is performed, and then the update screen is displayed. In the second reference example, By referring to the previous screen, the update screen is displayed only in the set period without providing a reset period, which is significantly different from that in the first reference example described above.

Drive operation <Case where drive waveform is applied once>
In the electrophoretic display device according to the second reference example, the previous screen CURRENT: (CMY) = (Rc ′, Rm ′, Ry ′) is updated to the next screen NEXT: (CMY) = (Rc, Rm, Ry). In this case, the final display state (updated display state) is realized only through the intermediate transition state I-1 → I-2 without providing a reset period. Here, a driving period over a plurality of subframes includes a first subframe group period (first voltage application period) in which a voltage of V1, 0, −V1 [V] is applied, and V2, 0, −V2 [ Second sub-frame group period (second voltage application period) in which a voltage of V] is applied, and a third sub-frame group period (third voltage in which a voltage of V3, 0, −V3 [V] is applied) Application period).

  The first subframe group period is a period during which the display state CURRENT of the previous screen transitions to the first intermediate transition state I-1 in which the relative color density of the charged particles Y is Ry. The second subframe group period Is a period of transition from the first intermediate transition state I-1 to the second intermediate transition state I-2 in which the Y concentration is Ry and the M concentration is Rm, and the third subframe group period is This is a period of transition from the second intermediate transition state I-2 to the final display state NEXT. Here, the relative color density Rx (x = c, m, y) takes a relative color density of 0 to 1, and Rx = 0 is a state where no X particles (charged particles C, M, Y) are present on the surface. Rx = 1 represents a state in which all X particles have moved to the surface. Therefore, (CMY) = (0, 0, 0) represents white (W) display, and (CMY) = (1, 1, 1) represents black (K) display.

Tables 6-1 to 6-8 show an update screen (from the previous screen (CMY) = (Rc, Rm, Ry)) when the gradation of each of the three colors CMY is set to 3 in the second reference example. A specific drive waveform for displaying (CMY) = (Rc, Rm, Ry) is shown.
Here, in Table 6-1, CURRENT: (0, 0, 0) → NEXT: (Rc, Rm, Ry) (Rx = 0, 0.5, 1 gradation is taken. X = c, The applied voltage and the intermediate transition state for transition to m, y) are described. Similarly, in Table 6-2, an applied voltage and an intermediate transition state for transition from CURRENT: (1, 0, 0) to NEXT: (Rc, Rm, Ry) are described. Table 6-3 describes applied voltages and intermediate transition states for transition from CURRENT: (0, 1, 0) to NEXT: (Rc, Rm, Ry). Table 6-4 describes applied voltages and intermediate transition states for transition from CURRENT: (1, 1, 0) to NEXT: (Rc, Rm, Ry). Table 6-5 describes an applied voltage and an intermediate transition state for transition from CURRENT: (0, 0, 1) to NEXT: (Rc, Rm, Ry). Table 6-6 describes the applied voltage and the intermediate transition state for transition from CURRENT: (1, 0, 1) to NEXT: (Rc, Rm, Ry). Table 6-7 describes applied voltages and intermediate transition states for transition from CURRENT: (0, 1, 1) to NEXT: (Rc, Rm, Ry). Table 6-8 describes applied voltages and intermediate transition states for transition from CURRENT: (1, 1, 1) to NEXT: (Rc, Rm, Ry).

For simplicity, the display state of the previous screen is (CMY) = (0,0,0), (1,0,0), (0,1,0), (1,1,0), (0, 0, 1), (1, 0, 1), (0, 1, 1), (1, 1, 1) only shown in the eight cases, but even if the previous screen is in other halftone / color mixture states With the same idea as shown below, a drive waveform can be created as shown in Table 6-9.
Here, for the sake of simplicity, the charged amount C of each charged particle C, M, Y is set as | Qc |> | Qm |> | Qy |, and the threshold voltage at which the particle starts moving is | Vth. (C) | <| Vth (m) | <| Vth (y) |, but the moving speed (mobility) with respect to the same applied voltage can be changed by changing the weight and size of the particles. C, M, and Y are set to be the same.
As shown in Tables 6-1 to 6-8, the drive voltage is set to | V1 | = 30V in the first subframe group period, and | V2 | = 15V in the second subframe group period. In the third subframe group period, | V3 | = 10 V is set (note that the drive voltage can be set to an arbitrary value as required).

  Furthermore, the time Δt for each charged particle C, M, Y to move from the back surface to the display surface has an inversely proportional relationship with the applied voltage V in a simple model, and is V × Δt = constant above the threshold voltage. Become. In the second reference example, the time for the charged particles C to move from the back surface to the front surface (or from the front surface to the back surface) is 0.2 sec at | V | = 30 V, 0.4 sec at | V | = 15 V, and | V It is set to 0.6 sec at | = 10V. The time for the charged particles M to move from the back surface to the front surface (or from the front surface to the back surface) is set to 0.2 sec at | V | = 30 V and 0.4 sec at | V | = 15 V. The time for the charged particles Y to move from the back surface to the front surface (or from the front surface to the back surface) is set to 0.2 sec at | V | = 30V. In consideration of these relationships, in the second reference example, one subframe period is 100 msec, 12 subframes (the first subframe group period is 2 subframes, the second subframe group period is 4 subframes). The screen update period is set in the third subframe group period is 6 subframes).

    In Tables 6-1 to 6-9, the first column represents the relative color density (CMY) in the target update display state. The second column represents the relative color density of the display state of the previous screen. The third column represents the applied voltage of the first subframe group period and the relative color density of the first intermediate transition state I-1 after the period. The first subframe group period is composed of two subframes 1a and 1b, and possible applied voltages are + 30V, 0V, and -30V. The reason for setting 2 subframes is that the response time of particles at 30 V is 0.2 sec and the 1 subframe period is 0.1 sec. The fourth column represents the applied voltage of the second subframe group period and the relative color density of the second intermediate transition state I-2 after the period.

  The second subframe group period is composed of four subframes 2a, 2b, 2c, and 2d, and possible applied voltages are + 15V, 0V, and -15V. The reason why the number of subframes is 4 is that the response time of particles at 15 V is 0.4 sec and the period of 1 subframe is 0.1 sec. The fifth column represents the applied voltage of the third subframe group period and the relative color density of the last updated display state NEXT after the period. The third subframe group period is composed of six subframes 3a, 3b, 3c, 3d, 3d, and 3f, and possible applied voltages are + 10V, 0V, and −10V. The reason for setting 6 subframes is that the response time of particles at 10 V is 0.6 sec and the period of 1 subframe is 0.1 sec.

Next, as an example, update driving when the display state of the previous screen is (CMY) = (1, 0, 0) will be described with reference to Table 6-2.
In the first subframe group period, since the relative color density Y of the previous screen is 0, the target relative color density (Y) is 0 corresponding to the target relative color density of the charged particles Y. Since it is not necessary to apply an applied voltage, 0 V is applied for two subframes, and the intermediate transition state I-1: (CMY) = (1, 0, 0) maintains the display state of the previous screen. On the other hand, when the target relative color density (Y) is 0.5, an applied voltage of −30 V is applied only for one subframe, and the intermediate transition state I-1: (CMY) = (1 , 0.5, 0.5). When the target relative color density (Y) is 1, an applied voltage of 30 V is applied for two subframes to transition to the intermediate transition state I-1: (CMY) = (1, 1, 1). As a result, the transition from the display state CURRENT: (CMY) = (1, 0, 1) of the previous screen to the first intermediate display state I-1: (CMY) = (X, X, Ry) (X is arbitrary) To do.

  In the second subframe group period, with reference to the relative color density of the charged particles M in the first intermediate transition state I-1, the relative color density of the charged particles M becomes the target relative color density of the charged particles M. A predetermined number of −15V or 15V is applied. For example, when the relative color density Rm ′ of M in the first intermediate transition state I-1 is Rm and the target relative color density of M is Rm, it is necessary to apply a voltage when Rm−Rm ′ = 0. Therefore, 0V is applied for 4 subframes. On the other hand, when Rm−Rm ′ = 0.5, 15V is applied for two subframes, and when Rm−Rm ′ = 1, 15V is applied for four subframes. Conversely, when Rm−Rm ′ = − 0.5, −15V is applied for 2 subframes, and when Rm−Rm ′ = − 1, −15V is applied for 4 subframes. From the above, the first intermediate transition state I-1: (CMY) = (X, X, Ry) to the second intermediate transition state I-2: (CMY) = (X, Rm, Ry) (X is arbitrary) ).

  In the third subframe group period, with reference to the relative color density of the charged particles C in the second intermediate transition state I-2, the relative color density of the charged particles C becomes the target relative color density of the charged particles C. A predetermined number of −10V or 10V is applied. For example, when the relative color density Rc ′ of C in the second intermediate transition state I-2 and the relative color density of target C are Rc, it is necessary to apply a voltage when Rc−Rc ′ = 0. Therefore, 0V is applied for 6 subframes. When Rc−Rc ′ = 0.5, 10 V is applied for 3 subframes. When Rc−Rc ′ = 1, 10 V is applied for 6 subframes. Conversely, when Rc−Rc ′ = − 0.5, −10V is applied for 3 subframes, and when Rc−Rc ′ = − 1, −10V is applied for 6 subframes. As described above, the transition from the second intermediate transition state I-2: (CMY) = (x, Rm, Ry) to the target final display state NEXT: (CMY) = (Rc, Rm, Ry) can be performed. . The same applies to other cases.

  27 to 29 show drive waveforms for transition from the display state CURRENT: (Rc, Rm, Ry) of the previous screen to the target display state NEXT: (0, 1, 0) of the next screen. . As shown in FIG. 27 to FIG. 29, when the display state CURRENT: (x, 0, 0) of the previous screen changes to the display state NEXT: (1, 0, 0) of the next screen, the display state CURRENT of the previous screen. : (1,1,0) → Next screen display state NEXT: When changing to (0,1,0), previous screen display state CURRENT: (0,1,0) → next screen display state NEXT: When transitioning to (0, 1, 0), transition from the previous screen display state CURRENT: (x, x, 1) to the next screen display state NEXT: (0, 1, 0) (x is 0 or 1) In this case, it is understood that the drive waveform to be applied differs depending on the previous screen state, and it is necessary to determine the drive waveform in the final display state of the update screen with reference to the display state of the previous screen.

In summary, during the voltage application period, the first voltage V1 (or V1) or / and 0V voltage is applied to change the color density of the charged particles Y from Ry on the previous screen to Ry ′ on the next screen. Applying the first sub-frame group and the second voltage V2 (or V2) or / and 0V voltage to maintain the color density of the charged particle Y at Ry, the relative color density of the charged particle M is set. Applying the second sub-frame group for transition to the second intermediate transition state to be Rm and the third voltage V3 (or V3) or / and 0V voltage, the color density of the charged particles M and Y is set to Rm. , Ry, and a third subframe group that changes the relative color density of the charged particles C to a final display state of Rc,
V1, V2, and V3 satisfy the relationship (| Vth (c) | <| V3 | <| Vth (m) | <| V2 | <| Vth (y) | <| V1 |).
The applied voltage of each subframe group is determined with reference to the display state of the previous screen and the display state of the update screen.

In the target update display state, unnecessary subframe groups can be omitted, and driving can be performed using only the first to third subframe groups that need to be applied.
Further, there are drive waveforms different from those in Table 6 in which the intermediate transition state is the same, and it goes without saying that the drive waveforms are also included in this embodiment. For example, in the subframe group period for setting the relative color density of CMY in the intermediate transition to “0” or “1”, the applied color of the subframe group is saturated and the relative color density becomes “0” even if it is excessive. If it is “1”, an extra applied voltage may be applied. In addition, the driving period can be shortened by reducing the application period of 0V. Furthermore, the number of subframes in each period may be constant, and the unit subframe time in each period may be different in each period.
In the above description, C, M, and Y have three gradations. Needless to say, the same driving can be performed with two gradations or multiple gradations of three gradations or more. Furthermore, the previous screen may be displayed once in two gradations, and then the next screen may be displayed using the drive waveforms shown in Table 6. In addition, as described above, in the case of three particles of C, M, and Y, this driving method may be applied to three or more RGB colors instead of three CMY colors, or three or more colors such as four CMYK colors or six CMYRGB colors. it can.

The LUT generation method is the same as that of the first embodiment. The generation method used in the second reference example does not require the reset period LUTR_LUT, but the LUT according to the display state of the previous screen. If a plurality of groups are required and the previous screen has 3 gradations, 27 LUT groups Bk_LUTn (n = 1... 12) are required for k = 1... 27, and the previous screen has 2 gradations. 8 are required.
The circuit configuration for driving the above is the same as that of the first embodiment, with the following differences. The image data stored in the graphic memory requires both the RGB data of the pixels of the previous screen and the RGB data of the update screen, and the data reading circuit needs to read both data. Further, the LUT generation circuit needs to read the LUT group Bk_LUTn corresponding to the RGB data of the pixels on the previous screen from the nonvolatile memory and generate the LUT corresponding to the subframe number.

  As described above, according to the configuration of the second reference example, not only each single color (R, G, B, C, M, Y, W, K) but also multi-tone expression including intermediate colors can be simplified. It can be realized by configuration. In addition, since there is no reset period, the screen update time can be shortened.

Embodiment 3

Next explained is the third embodiment of the invention.
The third embodiment is characterized in that a driving method based on repeated application of unit driving waveforms is used in connection with the improvement of the second reference example described above.
That is, in the third embodiment, the subframe frequency is increased, and the drive waveforms shown in Tables 6-1 to 6-9 are repeated, so that a smooth transition from the previous screen state CURRENT to the final display state NEXT is performed. Realized. Here, the generation of the unit drive waveform can be created in the same manner as described for the drive operation (drive method) by repeatedly applying the basic waveform in the first embodiment, but it is very complicated if applied as it is. is there.

  This is because in the first embodiment, since the transition from the ground state in the same direction, for example, the transition from (0, 0, 0) to (1, 0, 1), each charged particle C, M, Y Each moved in the same direction (in this case, the display surface side) or not. Further, when it is intended to enable a smooth transition by repeating the unit drive waveform with respect to the drive method by applying the drive waveform once used in the second reference example, each charged particle C, M, Y may have a moving direction that is not constant. For example, in the transition of (0, 1, 1) → (1, 1, 0), the C particles move to the display surface side, the Y particles move to the TFT substrate side, and the M particles remain on the display surface side. For this reason, when −30 V is applied, it is assumed that the C particles do not move because of the ground state “0” in the unit drive waveform, but when applying a plurality of unit drive waveforms, for example, the first time Since the C particles are not in the ground state after the waveform is applied, the C particles are moved by the application of −30 V in the second waveform application period. This is an operation that is not originally assumed, and thus a deviation occurs. .

In order to correct (correct) this shift, a corrected (corrected) second subframe group period in which the second voltage V2 / −V2 is further applied, and a corrected third subframe group in which the third voltage V3 / −V3 is further applied. It is necessary to correct the particle motion by inserting a period between the repetitions of the unit drive waveform and applying a modified drive waveform.
In the following example, one subframe period is 25 msec at 4 × speed, and 12 subframes of a unit drive waveform (the first subframe group period is 2 subframes, the second subframe group period is 4 subframes, 3 subframe group periods of 6 subframes) are repeated 4 times, and 10 subframes of modified waveform (modified 2 subframe 4 subframes, modified 3rd subframe group period 6 subframes) are inserted between them. Thus, the final display state NEXT is realized.

  In order to simplify the description, a drive waveform for direct transition from the previous screen to the update screen will be described with reference to Tables 7-1 to 7-8 for each of the two gradations of CMY. In Table 7-1, when the display state of the previous screen is CURRENT: (CMY) = (0, 0, 0), the next screen state is NEXT: (CMY) = (Rc, Rm, Ry) (Rc, Rm, Ry is a drive waveform for transition to 0 or 1), and (a), (b), (c), and (d) in the table are inserted between four unit drive waveforms and each unit drive waveform. The drive waveforms for four times when the three corrected waveforms are repeated are sequentially shown.

  Similarly, Table 7-2 transitions from CURRENT: (CMY) = (1, 0, 0) to NEXT: (CMY) = (Rc, Rm, Ry) (Rc, Rm, Ry is 0 or 1). The drive waveforms for four times are sequentially shown. Table 7-3 shows that CURRENT: (CMY) = (0,1,0) = NEXT: (CMY) = (Rc, Rm, Ry) (Rc, Rm, Ry is 0 or 1) The drive waveforms for the times are shown sequentially. Table 7-4 shows a transition from CURRENT: (CMY) = (1, 1, 0) to NEXT: (CMY) = (Rc, Rm, Ry) (Rc, Rm, Ry is 0 or 1). The four drive waveforms are sequentially shown. Table 7-5 shows CURRENT: (CMY) = (0, 0, 1) = NEXT: (CMY) = (Rc, Rm, Ry) (Rc, Rm, Ry is 0 or 1) The drive waveforms for the times are shown sequentially. Table 7-6 shows CURRENT: (CMY) = (1, 0, 1) => NEXT: (CMY) = (Rc, Rm, Ry) (Rc, Rm, Ry is 0 or 1) The drive waveforms for the times are shown sequentially. Table 7-7 shows a transition from CURRENT: (CMY) = (0, 1, 1) to NEXT: (CMY) = (Rc, Rm, Ry) (Rc, Rm, Ry is 0 or 1). The four drive waveforms are sequentially shown. Further, Table 7-8 shows that CURRENT: (CMY) = (1,1,1) ⇒NEXT: (CMY) = (Rc, Rm, Ry) (Rc, Rm, Ry is 0 or 1). The four drive waveforms are sequentially shown.

The transition from CURRENT: (0, 0, 0) to NEXT: (Rc, Rm, Ry) shown in Table 7-1 is a transition from the ground state as in the first embodiment, and the modified drive waveform Is not necessary, so the description is omitted. Next, a specific driving method for the transition from CURRENT: (1, 0, 0) to NEXT: (Rc, Rm, Ry) will be described with reference to Table 7-2. First, the transition of CURRENT: (1, 0, 0) → NEXT: (Rc, Rm, 0) will be described. In this case, since there is no movement of Y particles, only movement of C particles and M particles is considered.
In the case of CURRENT: (1, 0, 0) → NEXT: (0, 0, 0), CURRENT: (1, 0, 0) → NEXT: (1, 0, 0), the relative color density of M particles is “0” → “0” stays on the TFT substrate side, and C particles move from “1” → “0” or “1” to the TFT substrate side or move to the display surface side. And the moving direction of the M particles are the same, and it is not necessary to apply the correction driving waveform, and it is not necessary to apply a voltage during the correction driving period, and 0 V may be applied. In CURRENT: (1, 0, 0) → NEXT: (1, 1, 0), the relative color density of the M particles changes from “0” to “1”, and the M particles move to the display surface side. Since the C particles remain on the display surface side from “1” to “1”, the moving directions of the C particles and the M particles are the same, and no correction drive waveform needs to be applied, and 0 V may be applied for the correction drive period. .

  Next, in the case of CURRENT: (1, 0, 0) → NEXT: (0, 1, 0), the relative color density of the M particles transitions from “0” to “1”, and the M particles are on the display surface side. Move to. The relative color density of the C particles changes from “1” to “0”, and the C particles move to the TFT substrate side opposite to the display surface. That is, the moving directions of C particles and M particles are opposite. For this reason, for example, in a driving method in which a transition to the update display state is performed with a single driving waveform, when the M particle transitions from “0” to “1” by applying +15 V, the C particle is “1” → “1”. In the driving method in which the movement of the C particles is not assumed as it is and the transition to the update display state is performed by repeatedly applying the unit driving waveform, the C particles are in the ground state after the first unit driving waveform is applied. Since the transition is from “1”, the C particles move due to the application of +15 V in the second subframe group period during the second repetitive unit drive waveform application. For this reason, transition to the update display state cannot be made by repeating the unit drive waveform. In order to prevent this, −10 V is applied for 6 subframes before the second unit drive waveform application, and the movement of C particles in the application of −15 V4 subframes in the second subframe group period is corrected. There is a need.

Next, the transition of CURRENT: (1, 0, 0) → NEXT: (Rc, Rm, 1) will be described. In the case of this event, the relative color density of the Y particles changes from “0” to “1”, and thus moves to the display surface side. Since the transition from “0” to “0” or “1” for the M particles, the Y particles and the moving direction change depending on whether they move to the display surface side or stay on the TFT substrate side in the same manner as the Y particles. It is the same, and it is not necessary to apply the modified driving waveform, so the applied voltage in the modified second subframe group period is 0 V. For C particles, CURRENT: (1, 0, 0) → NEXT: In the case of (1, Rm, 1), since the C particles do not move, it is not necessary to apply the corrected driving waveform, and the waveform application in the corrected third subframe may be 0 V. On the other hand, CURRENT: (1, 0, In the case of 0) → NEXT: (0, Rm, 1), the Y particles move to the display surface side, whereas the C particles move to the TFT substrate side, and the moving direction is opposite. In the drive method that transitions to the update display state with a single drive waveform When the Y particle moves from “0” to “1” with the application of the unit drive waveform first subframe group period +30 V, the movement of the C particle is not assumed. After the first unit driving waveform is applied, the C particles move from the ground state “1”. Therefore, when the second unit driving waveform is applied, the C particles are applied by applying +30 V in the first subframe group period. In order to prevent this, -10V is applied for 6 subframes before the second unit drive waveform application, and the movement of C particles in the first subframe group period of 30V and 2 subframes is applied. It needs to be corrected.
In this case, the applied voltage is set to 0 V when the transition to the final screen state can be made without applying the applied voltage during the modified subframe group period. However, for example, in the transition from (0, 1, 1) to (0, 1, 0), even if -15V is applied during the modified third subframe group period of the modified drive waveform, the final screen state of the C particles is Since it remains in the ground state of “0”, there is no problem.

Next, a specific driving method for the transition from CURRENT: (1, 0, 0) to NEXT: (Rc, Rm, Ry) will be described with reference to Table 7-3. The transition of CURRENT: (0, 1, 0) → NEXT: (Rc, Rm, 0) is the same as that shown in Table 7-2. CURRENT: (0, 1, 0) → NEXT: (0, 0, 0), CURRENT: (0, 1, 0) → NEXT: (0, 1, 0), CURRENT: (0, 1, 0) → NEXT: (1, 1, 0) applies the modified drive waveform CURRENT: (0, 1, 0) → NEXT: (1, 0, 0) requires that a corrected waveform for applying −10 V for 6 subframes be inserted between the unit drive waveforms. .
On the other hand, for the transition of CURRENT: (0, 1, 0) → NEXT: (Rc, Rm, 1), CURRENT: (0, 1, 0) → NEXT: (0, 1, 1), CURRENT : When transitioning from (0, 1, 0) to NEXT: (1, 1, 1), the M particle does not move, and the C particle moves in the same direction as the Y particle or does not move Therefore, it is not necessary to apply a corrected driving waveform.
In the transition from CURRENT: (0, 1, 0) to NEXT: (0, 0, 1), the C particles remain in the ground state, but the M particles and the Y particles need to move in opposite directions. is there. In order to correct the movement of the M particles, it is necessary to apply −15 V for 4 subframes in the corrected second subframe group at the time of applying the corrected waveform. Before and after this, the C particles do not move from the ground state. It is not necessary to apply voltage in the 3 subframe group.

  In the case of CURRENT: (0,1,0) → NEXT: (1,0,1), the C and Y particles move in the same direction, while the M and Y particles need to move in opposite directions. . First, in order to correct the movement of the M particles moving in the opposite direction, it is necessary to apply −15 V to 4 subframes in the corrected second subframe group when applying the correction waveform. Before and after this, the C particles move in the same direction as the M particles. However, the C particle needs to move in the same direction as the Y particle, the movement in the same direction as the M particle needs to be canceled, and the modified third subframe is to cancel the application of −15V, 4 subframes. Further application of 10 V and 6 subframes is required for the group period.

Next, a specific driving method for the transition from CURRENT: (1, 1, 0) to NEXT: (Rc, Rm, Ry) will be described with reference to Table 7-4. For CURRENT: (1, 1, 0) → NEXT: (Rc, Rm, 0), the Y particles do not move, and either the C particles or the M particles do not move or move in the same direction. There is no need to apply a waveform.
For the transition from CURRENT: (1, 1, 0) to NEXT: (Rc, Rm, 1), the transition from CURRENT: (1, 1, 0) to NEXT: (1, 1, 1) Since only Y particles move, there is no need to apply a modified drive waveform. At the transition from CURRENT: (1, 1, 0) to NEXT: (0, 1, 1), the M particles do not move, and the C particles and Y particles move in opposite directions. At the time of application, it is necessary to apply −10 V, 6 subframes in the modified third subframe group period. At the transition from CURRENT: (1, 1, 0) to NEXT: (0, 0, 1), C particles and M particles move in the same direction, and C, M particles, and Y particles move in opposite directions. Therefore, when applying the corrected drive waveform, it is necessary to apply −15 V and 4 subframes in the corrected second subframe group period.
At the transition from CURRENT: (1,1,0) → NEXT: (0,1,1), M and Y particles move in opposite directions, and C and Y particles move in the same direction. To do. For this reason, at the time of applying the corrected drive waveform, -15V and 4 subframes are applied during the corrected second subframe group period. Then, in order to cancel the influence of the voltage application on the C particles in the modified second subframe group period, 10 V, 6 subframes are applied in the modified third subframe group period. Since the cases of Tables 7-5 to 7-8 are the same as described above, the description thereof will be omitted.

  FIG. 30 is a diagram showing a driving waveform and an intermediate transition state at the time of transition from CURRENT: (1, 0, 0) to NEXT: (0, 0, 1) in the third embodiment at the time of screen update. FIG. 31 is an intermediate transition state diagram showing the behavior of the electrophoretic particles at that time. 30 and 31, CURRENT: (1, 0, 0) → I1: (0.75, 0, 0.25) → I1 ′: (0.5, 0, 0.25) → I2 : (0.5, 0, 0.5) → I2 ′: (0.25, 0, 0.5) → I3: (0.25, 0, 0.75) → I3 ′: (0, 0, 0.75) → NEXT: (0, 0, 1).

Thus, in order to enable direct transition without resetting the previous screen when transitioning from the current screen to the next screen, in this embodiment, the unit drive waveform is Are configured to apply different modified drive waveforms.
The corrected driving waveform is composed of a subframe group period in which the second voltage V2 (or V2) is applied for a predetermined number of subframes, and then V3 (or V3) is applied for a predetermined number of subframes. In the modified subframe group period in which the second voltage is applied, the voltage is applied when the Y particles that move only at the first voltage and the M particles that move at the first and second voltages move in opposite directions during the transition. In the modified subframe group period in which the third voltage is applied, the Y particles that move only at the first voltage or the M particles that move at the first and second voltages, Voltage application is required when the C particles that move with voltage move in the opposite direction.

As described above, in the third embodiment as well, the unit drive waveform is repeated four times as in the first embodiment, but the subframe frequency is further increased and the unit drive waveform is increased four times or more. If it is repeated, the color variation (for example, ΔC, ΔM, ΔY) of the intermediate transition can be further reduced, and “flickering” can be suppressed accordingly.
Further, after the drive period of each unit drive waveform is completed, 0V is applied for several subframes, so that (0, 0.25, 0), (0, 0.5, 0), (0, 0.75, Since the intermediate transition state in which the color of 0)... Is close to the final display state can be emphasized, the “flickering” of the screen can be further alleviated.

In the target update display state, unnecessary subframe groups may be omitted, and driving may be performed using only the first to third subframe groups that need to be applied.
Further, there are unit drive waveforms in which the intermediate transition state is the same, and it goes without saying that the drive waveforms are also included in this embodiment. For example, in the subframe group period for setting the relative color density of CMY in the intermediate transition to “0” or “1”, the applied color of the subframe group is saturated and the relative color density becomes “0” even if it is excessive. If it is “1”, an extra applied voltage may be applied. In addition, the driving period can be shortened by reducing the application period of 0V. Furthermore, the number of subframes in each period may be constant, and the unit subframe time in each period may be different in each period. In the above description, C, M, and Y have three gradations. Needless to say, the same driving can be performed with two gradations or multiple gradations of three gradations or more. Furthermore, it is also possible to display the previous screen once in two gradations, and then display the next screen using the drive waveforms shown in Table 6. In the above description, the case of three particles of C, M, and Y has been described. However, three RGB colors may be used instead of three CMY colors, and the same driving method can be applied to three or more colors such as four CMYK colors and six CMYRGB colors. .

  Thus, according to the third embodiment, the update period of the screen update can be shortened because there is no reset period as compared with the first embodiment. In addition, since the display of the ground state can be omitted, a natural screen transition without any sense of incongruity can be achieved with less luminance and color variation in the intermediate transition state.

Reference example 3

Next, a third reference example (the invention according to the original application) of the present invention will be described.
This third reference example is different from the first to third embodiments described above in that the three-color electrophoretic particles are eliminated and the two-color electrophoretic particles are used.
That is, in the third reference example, cyan (C) electrophoretic particles, red (R) electrophoretic particles, and white holders, which are complementary to each other, are used to obtain red (R), Cyan (C), black (K), white (W), and their intermediate colors and gradations are displayed.

Drive operation <Reset period and drive waveform applied once>
In this embodiment, updating from the previous screen to the next screen is performed by first resetting the screen to the white (W) or black (K) ground state WK and then applying the corresponding drive waveform once. . The period region of the drive waveform used in this embodiment includes a reset period for transitioning to the white (W) or black (K) ground state WK and a voltage V1, 0, −V1 [V] applied. 1 sub-frame group period (first voltage application period) and a second sub-frame group period (second voltage application period) in which a voltage of V2, 0, −V2 [V] is applied. .
Specifically, when the relative color density (CR) of the charged particles C and R, which is display information for each pixel of the next screen NEXT to be updated, is represented by (Rc, Rr), the first subframe group period Is a period of transition from the ground state of white (W) or black (K) to the intermediate transition state I-1 in which the relative color density of the charged particles R is Rr, and the second subframe group period is an intermediate transition This is a period of transition from state I-1 to the final display state (update screen).

Here, the relative color density Rx (x = c, r) takes a relative color density of 0 to 1, Rx = 0 represents a state in which there are no X particles (charged particles C, R) on the surface, and Rx = 1. Represents a state in which all the X particles have moved to the surface.
Table 8 shows specific drive voltage data when the gradations of the two colors C and R are three gradations (0, 0.5, 1). Further, for the sake of simplicity, the charged particles C and R have a threshold voltage at which the charged particles start moving when the charge amount Q is set to | Qc |> | Qr | is | Vth (c) | <| Vth (r) |.

As shown in Table 8, the drive voltage is set to | V1 | = 30V or 0V in the first subframe group period, and is set to | V2 | = 15V or 0V in the second subframe group period. .
Furthermore, the time Δt for each charged particle C, R to move from the back surface to the display surface is equal to or higher than the threshold voltage and is inversely proportional to the applied voltage V in a simple model, and V × Δt = constant. Is the same as in the first embodiment. In this embodiment, one subframe period is set to 100 msec, and the screen update period is 8 subframes (the reset voltage application period is 2 subframes, the first subframe group period is 2 subframes, the second subframe is The frame group period is composed of 4 subframes).

Next, a specific driving operation (driving method) according to this embodiment will be described with reference to Table 8.
In Table 8, the first column represents the relative color density (CR) in the target updated display state. The second column represents the applied voltage during the reset period and the relative color density of the ground state after the reset period. In the third reference example, the reset period is composed of two subframes Ra and Rb, and a possible applied voltage is −30V. The third column represents the applied voltage of the first subframe group period and the relative color density of the intermediate transition state I-1 after the period. The first subframe group period is composed of two subframes 1a and 1b, and possible applied voltages are + 30V and 0V. The reason for setting 2 subframes is that the response time of particles at 30 V is 0.2 sec and the 1 subframe period is 0.1 sec. The fourth column represents the applied voltage of the second subframe group period and the relative color density of the final display state NEXT after the period. The second subframe group period is composed of four subframes 2a, 2b, 2c, and 2d, and possible applied voltages are + 15V, 0V, and -15V. The reason why the number of subframes is 4 is that the response time of particles at 15 V is 0.4 sec and the period of 1 subframe is 0.1 sec.

First, in the reset period, V1 = −30 V is applied over two subframes, and the charged particles C and R are moved and concentrated on the back side opposite to the display surface to obtain a white (W) display which is a ground state. In the next first subframe group period, when the relative color density (R) is 0 corresponding to the relative color density of the charged particles R, an applied voltage of 0 V is applied for two subframes, and the relative color density is set. When (Y) is 0.5, an applied voltage of 30 V is applied for one subframe and an applied voltage of 0 V is applied for one subframe. When the relative color density (R) is 1, the applied voltage of 30 V is applied for two subframes. Apply for minutes. As a result, the transition from the ground state W to the intermediate transition state I-1: (CR) = (Rr, Rr) (Rr is 3 gradations, Ry = 0, 0.5, 1).
Similarly, in the next second subframe group period, a predetermined number of −15V or 15V is applied from the intermediate transition state I-1: (CR) = (Rr, Rr), and the final display state NEXT: (CR) = (Rc, Rr) For example, when the difference between the relative color density Rr of the charged particles R in the intermediate transition state I-1 and the relative color density Rc of the charged particles in the final display state NEXT is (Rr−Rc) = − 0.5, −15V is set. Two subframes are applied. Similarly, when (Rr−Rc) = 1, 0.5, 0, −1, a predetermined number of −15V / 15V is applied. By such a driving operation, the intermediate display state I-1: (CR) = (Rr, Rr) to the final display state NEXT: (CR) = (Rc, Rr) (Rc, r = 0, 0.5, 1 Transition to 3 gradations).

Embodiment 4

Drive operation <case with reset period, unit drive waveform repeated 4 times>
Next explained is the fourth embodiment of the invention.
In this embodiment, the update from the previous screen to the next screen is performed by first resetting the screen to the white (W) or black (K) ground state WK, and then repeatedly applying the corresponding unit drive waveform a plurality of times. Done.
Table 9 shows specific drive voltage data for realizing an update screen of two colors (C, R) and three gradations according to the fourth embodiment. Specifically, this embodiment shows specific drive voltage data when a reset period is provided and thereafter a unit drive waveform is repeatedly applied four times.
First, Table 9 (a) shows the driving voltage in the reset period and the ground state WK after application, and Table 9 (b) shows the driving voltage in the first driving voltage application period and the intermediate transition state I1- after application. Table 9 (c) shows the drive voltage during the second drive voltage application period and the intermediate transition state I2-2 after the application, and Table 9 (d) shows the drive during the third drive voltage application period. The voltage and the intermediate transition state I3-2 after application are shown, and Table 9 (e) shows the drive voltage in the fourth drive voltage application period and the final display state NEXT after application.

Reference example 4

Drive operation <case of no reset period, drive waveform applied once>
Next, a fourth reference example (the invention according to the original application) of the present invention will be described.
In the fourth reference example, the update from the previous screen to the next screen is performed by applying the drive waveform once without providing a reset, as shown in Tables 10-1 and 10-2.

Embodiment 5

Drive operation <reset period, unit drive waveform applied multiple times>
Next explained is the fifth embodiment of the invention.
In the fifth embodiment, the update from the previous screen to the next screen is performed by applying the unit drive waveform a plurality of times without providing a reset, as shown in Table 11.
As an example of the driving method by repeatedly applying the unit driving waveform four times, Table 11 shows that when the display state of the previous screen is (CR) = (0, 1), any (CR) = (Rc, Rr) (Rc , R = 0, 0.5, 1 (three gradation display).

The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and even if there is a design change or the like without departing from the gist of the present invention. Included in the invention.
For example, in each of the above-described embodiments, an electrophoretic display element composed of electrophoretic particles of three colors of cyan C, magenta M, and yellow Y and a white holder is used, but cyan C, magenta M, and yellow Y are used. Instead of the electrophoretic particles, red R, green G, and blue B electrophoretic particles may be used. Alternatively, a microcapsule in which colored particles are encapsulated without using the holding body may be used. In short, three or more different colored particles (for example, four-color particles of C, M, Y, K, R, G, B, and W, and six-color particles of C, M, Y, R, G, and B). If an electrophoretic display element having a different threshold voltage is applied to the present invention, it is possible to display not only each single color display but also any color (La * b *) including intermediate colors and halftone displays with a simple configuration. realizable.

The generalized configuration of the present invention, which is encompassed by n types (n is a natural number of 2 or more) of electrophoretic particles, is as follows. That is,
A first substrate on which switching elements and pixel electrodes are arranged in a matrix, a second substrate on which a counter electrode is formed, and the first substrate and the second substrate are sandwiched between the first substrate and the second substrate. A display unit comprising an electrophoretic layer containing electrophoretic particles; and at the time of screen update, applying a predetermined voltage to the electrophoretic particles between the pixel electrode and the counter electrode for a predetermined period, An image display device having a memory function, comprising: voltage application means for updating a display state of a display unit from a current screen to a next screen having a predetermined color density,
The electrophoretic particles are n kinds (n is a natural number of 2 or more) of charged particles Cn,..., Ck,..., C1 (k = 2 to 2) having different colors and threshold voltages for starting migration. n-1) and each charged particle Cn,..., Ck,..., C1 is a threshold voltage of charged particle Cn | Vth (Cn) | | Vth (Ck) | <... << threshold voltage C1 of charged particles Cn | Vth (c1) |
The first voltage V1 (or -V1), or / and the second voltage V2 (or -V2), or / and ..., the nth voltage Vn (or -Vn), or / and 0V are applied to a predetermined subframe. It is characterized by comprising a basic waveform application period in which one or more basic drive waveforms to be applied several times are applied a plurality of times. Note that V1,..., Vk,..., Vn are | Vth (cn) | <| Vn | <| Vth (c (n-1)) |, ..., | Vth (ck) | <| Vk. | <| Vth (c (k−1)) |,..., | Vth (c1) | <| V1 |

The basic waveform includes first applying a first voltage V1 (or V1) for a predetermined number of subframes, ..., applying a kth voltage Vk (or Vk) for a predetermined number of subframes, ... Finally, the n-th voltage Vn (or Vn) is divided into subframe group periods in which a predetermined number of subframes are applied.
Here, when the first and second embodiments are generalized, the application period further includes a reset period in which the current screen is reset to a ground state, and in each intermediate transition state after the application of each basic waveform The relative color density information of each charged particle is characterized by being between the relative color density information in the ground state and the relative color density information in the update display state.

Further, the second reference example (a driving method for applying a driving waveform once without a reset period) is generalized as follows. That is,
A first substrate in which switching elements and pixel electrodes are arranged in a matrix, a second substrate on which a counter electrode is formed, and the first substrate and the second substrate are interposed between the first substrate and the second substrate. A display unit comprising an electrophoretic layer containing electrophoretic particles;
When updating the screen, a predetermined voltage is applied to the electrophoretic particles between the pixel electrode and the counter electrode for a predetermined period, and the display state of the display unit is changed from the current screen to the next screen having a predetermined color density. An image display device having a memory property comprising a voltage application means for updating,
The electrophoretic particles are n types (n is a natural number of 2 or more) of charged particles Cn,..., Ck,..., C1 (k = 2 to n) having different colors and threshold voltages for starting migration. −1) and each charged particle Cn,..., Ck,..., C1 has a threshold voltage | Vth (cn) | <... <a threshold voltage of the charged particle Ck | Vth (ck ) | <... <threshold voltage of charged particle C1 | Vth (c1) |
For each pixel constituting the next screen to be updated, the relative color density information of the charged particles Cn is Rn, ..., the relative color density information of the charged particles Ck is Rk, ..., and the relative color density information of the charged particles C1 is R1. When the predetermined period during which the voltage is applied is
Applying the first voltage V1 (or -V1) or / and 0V voltage and referring to the relative color density of the current screen, the first intermediate transition in which the relative color density of the charged particle C1 is R1 A first voltage application period for transitioning to a state;
By applying a kth voltage Vk (or -Vk) or / and 0V voltage, the relative color density of the charged particle C1 is set to R1, from the k-1th intermediate transition state,..., The charged particle Ck-1. Second to n-1th voltage application periods for sequentially transitioning to the kth intermediate transition state where the relative color density of the charged particles Ck,..., Cn is Rk, while maintaining the relative color density of Rk−1. ,
By applying the nth voltage Vn (or -Vn) or / and 0V voltage, the relative color density of the charged particle C1 is set to R1, from the n-1th intermediate transition state,..., The charged particle Cn-1 And the nth voltage application period in which the relative color density of the charged particles Cn is changed to the final display state in which the relative color density of the charged particles Cn is Rn. The threshold voltage and the voltage applied during each voltage application period are:
| Vth (cn) | <| Vn | <| Vth (c (n−1)) |,
| Vth (ck) | <| Vk | <| Vth (c (k−1)) |,
| Vth (c1) | <| V1 |
It is characterized by satisfying the relational expression of

    Further, when the third embodiment (driving method of applying a drive waveform without a reset period multiple times) is generalized, a modified drive waveform different from the basic drive waveform is applied while the basic drive waveform is applied multiple times. Thus, the transition from the current screen to the next screen can be performed without resetting the previous screen. The modified driving waveform is obtained by applying the second voltage V2 (or V2) for a predetermined number of subframes and then applying the kth voltage Vk (or Vk) (k = 3 to n-1) for a predetermined subframe. It is characterized in that it is divided into subframe group periods in which the number of frames is applied and finally the nth voltage Vn (or Vn) is applied for a predetermined number of subframes.

Further, when the third reference example relating to two particles is generalized, it can be expressed as follows. That is,
A first substrate in which switching elements and pixel electrodes are arranged in a matrix, a second substrate on which a counter electrode is formed, and a gap between the first substrate and the second substrate; Applying a predetermined voltage for a predetermined period to the electrophoretic particles between the pixel electrode and the counter electrode at the time of screen update when the display unit includes an electrophoretic layer containing electrophoretic particles, An image display device having a memory property, comprising: voltage application means for updating a display state of the display unit from a current screen to a next screen having a predetermined color density,
The electrophoretic particles are composed of two kinds of charged particles C and R having different colors and threshold voltages for starting migration, and each C and R has a threshold voltage | Vth ( c) | <threshold voltage of charged particle R | Vth (r) |
When the relative color density of the charged particles C is Rc and the relative color density of the charged particles R is Rr in each pixel constituting the next screen to be updated,
A first sub-frame group that applies a first voltage V1 (or V1) or / and 0V voltage during the predetermined period during which a voltage is applied to change the color density of the charged particles R to Rr;
While the second voltage V2 (or V2) or / and 0V voltage is applied and the color density of the charged particles R is maintained at Rr, the relative color density of the charged particles C is changed to the final display state NEXT where the relative color density is Rc. A second subframe group to be transitioned,
V1 and V2 satisfy the relationship (| Vth (c) | <| V2 | <| Vth (r) | <| V1 |.

Further, the applied voltage of each subframe group may be determined from the display state of the previous screen and the display state of the update screen, or a reset period may be provided to erase the previous screen state.
Further, the first period V1 (or -V1), or / and the second voltage V2 (or -V2), or / and the third voltage V3 (or -V3) during the predetermined period during which the voltage is applied. Or / and / or a drive waveform application period in which one or more unit drive waveforms for applying a predetermined number of subframes to 0 V are applied a plurality of times, thereby making it possible to transition to the final display state NEXT.
In the target update display state, unnecessary subframe groups may be omitted, and driving may be performed using only the first to third subframe groups that need to be applied.
Further, there are drive waveforms different from those in Tables 8 to 11 in which the intermediate transition states are the same, and it goes without saying that the drive waveforms are also included in this embodiment. In addition, the driving period can be shortened by reducing the application period of 0V. Furthermore, the number of subframes in each period may be constant, and the unit subframe time in each period may be different in each period.

The first to fifth embodiments are summarized from the transition state of the charged particles as follows.
<With reset period>
A first substrate on which switching elements and pixel electrodes are arranged in a matrix, a second substrate on which a counter electrode is formed, and the first substrate and the second substrate are sandwiched between the first substrate and the second substrate. A display unit including an electrophoretic layer containing electrophoretic particles; and at the time of screen update, a predetermined voltage is applied to the electrophoretic particles between the pixel electrode and the counter electrode for a predetermined period, An image display device having a memory characteristic, comprising a voltage application means for updating the next screen of the color density of the electrophoretic particles, wherein the electrophoretic particles have two or more kinds of different colors and threshold voltages for starting migration Composed of charged particles of
The screen update period is composed of a reset period in which the previous screen is reset to the ground state and a set period in which the next screen is set. Within the set period, the relative color density of each electrophoretic particle is intermediate between the primary colors. Does not take transition state.

<Without reset period>
A first substrate on which switching elements and pixel electrodes are arranged in a matrix, a second substrate on which a counter electrode is formed, and the first substrate and the second substrate are sandwiched between the first substrate and the second substrate. A display unit including an electrophoretic layer containing electrophoretic particles; and at the time of screen update, a predetermined voltage is applied to the electrophoretic particles between the pixel electrode and the counter electrode for a predetermined period, An image display device having a memory characteristic, comprising a voltage application means for updating the next screen of the color density of the electrophoretic particles, wherein the electrophoretic particles have two or more kinds of different colors and threshold voltages for starting migration Composed of charged particles of
Within the screen update period, the relative color density of each electrophoretic particle does not take the intermediate transition state of the primary color.

  In the above embodiment, a DC cancellation compensation subframe group is further added so that ∫Vdt = 0 throughout the update period, so that an unnecessary DC voltage is not applied to the charged particles, and reliability is deteriorated. It is also possible to prevent this. In this case, the voltage applied in the DC cancellation compensation subframe group has an absolute value set to be equal to or lower than the absolute value of the minimum threshold voltage of the charged particles, and charged particles C, M, Y (or C, It is necessary to prevent all R) from moving.

  In the first to fifth embodiments described above, the voltage signal supplied to the data driver of the electronic paper unit is the three values -Vdd, 0, and Vdd, and the driver reference voltage Vdd is variable for each subframe. A configuration is also possible. According to this configuration, since the electrophoretic display element can be driven even when the data driver cannot output the voltage required for driving at the same time, the driver can be simplified, and thus the cost can be reduced. You can go down.

  Furthermore, when the breakdown voltage of the data driver is lower than the drive voltage of the element, it is possible to realize a drive voltage of a predetermined element by changing the COM voltage for each subframe.

  In the above-described first embodiment, the voltage drive waveform applied a plurality of times has been described with respect to the case where the waveform patterns are composed of the same unit drive waveform, but is not necessarily limited to the same waveform pattern. For example, the combination of the first and second unit voltage drive waveforms in the first embodiment described above is used as the first voltage drive waveform, and the third and fourth unit voltage drive waveforms are left as they are. Also, substantially the same effect as described above can be obtained.

  The present invention can be widely applied to color electronic paper display devices such as electronic books, electronic newspapers, and digital signage.

1 Electronic paper (display unit)
2 Electrophoretic display device (image display device)
3 TFT glass substrate (first substrate)
4 Counter substrate (second substrate)
5 Electrophoresis layer 6 TFT (switching element)
7 Pixel electrode 8 Counter electrode 9 Electronic paper section 13 Electronic paper controller 22 LUT conversion circuit 25 LUT generation circuit C, M, Y Electrophoretic particles

Claims (18)

The first substrate on which the pixel electrode is formed, the second substrate on which the counter electrode is formed, and the electrophoretic particles can be migrated by being interposed between the first substrate and the second substrate. A display portion comprising an electrophoretic layer included in
When the screen is updated, the display state of the display unit is changed from the previous screen by repeatedly applying a predetermined voltage driving waveform a plurality of times for a predetermined period to the electrophoretic particles between the pixel electrode and the counter electrode. And a voltage application means for updating to the next screen via a plurality of intermediate transition states,
The electrophoretic particles are n types (n is a natural number of 2 or more) of charged particles C1,..., Ck,..., Cn (1 <k <n) that have different colors and threshold voltages for starting migration. , provided that, when n = 2, with Ck consists deleted), the seed charged particles C1, ..., Ck, ..., Cn, the threshold voltage of the charged particles C1>...> threshold of charged particles Ck Voltage>...> satisfies the relational characteristics of the threshold voltage of the charged particles Cn, and
The voltage application means, at the time of screen update, every application of the voltage drive waveform excluding the last time,
The charged particles C1 →,... → Ck →,.
A series of driving operations that gradually transition the relative color density of various charged particles to the relative color density of the corresponding intermediate transition state,
When the voltage drive waveform is applied for the last time, the relative color densities of various charged particles are sequentially shifted to the desired relative color density to be updated in the order of the charged particles C1,..., Ck,. An image display device having memory characteristics, wherein the image is updated to the next screen in the final transition state. Each voltage driving waveform is:
The charged particles C1,..., Ck,..., Cn are migrated by a predetermined distance in the thickness direction of the electrophoretic layer | first voltage | (| first voltage |> threshold voltage of the charged particles C1) For the remainder of the time, 0V is applied to stop the migration, while when there is no need for migration, a first voltage application period in which 0V is applied;
……………
Next, the charged particles Ck,..., Cn are migrated by a predetermined distance in the layer thickness direction. | Kth voltage | (threshold voltage of charged particle Ck-1> | kth voltage |> charged particle Ck (Threshold voltage) is applied, and for the remainder of the time, 0V is applied to stop the migration. On the other hand, when migration is not required, the kth voltage application period in which 0V is applied;
……………
Finally, only the charged particles Cn migrate in the layer thickness direction for a predetermined distance | nth voltage | (threshold voltage of charged particles Cn−1> | nth voltage |> threshold of charged particles Cn Voltage is applied, and 0 V for stopping the migration is applied for the remainder of the time, while when no migration is required, an n-th voltage application period for applying 0 V is provided. Item 12. An image display device having memory characteristics according to Item 1. Each voltage driving waveform is:
The charged particles C1,..., Ck,..., Cn are migrated for a predetermined distance in the thickness direction of the electrophoretic layer. Is applied for a period of a predetermined number of subframes, and 0 V for stopping migration is applied for the period of the remaining subframes, while when there is no need for migration, ,
……………
Next, the charged particles Ck,..., Cn are migrated by a predetermined distance in the layer thickness direction. | Kth voltage | (threshold voltage of charged particle Ck-1> | kth voltage |> charged particle Ck Threshold voltage) is applied for a predetermined number of subframes, and 0V is applied to stop the migration for the remaining subframes. On the other hand, when no migration is required, the 0th voltage is applied. Subframe group period;
……………
Finally, only the charged particles Cn migrate in the layer thickness direction for a predetermined distance | nth voltage | (threshold voltage of charged particles Cn−1> | nth voltage |> threshold of charged particles Cn Voltage) is applied for a period of a predetermined number of subframes, and 0V for stopping migration is applied for the period of the remaining subframes. On the other hand, when migration is not necessary, the nth subframe group to which 0V is applied 2. The image display device having memory characteristics according to claim 1, wherein the image display device has a period. The voltage application means, for each voltage drive waveform to be repeatedly applied at the time of screen update,
For the plurality of types of charged particles whose order of magnitude of the threshold voltage is adjacent to each other and whose relative color density to be updated is the same,
The memory property according to claim 1, wherein the relative color density of each charged particle is gradually changed to the relative color density of the corresponding intermediate transition state, thereby updating the next screen which is the final transition state. An image display device.   4. The image display device having memory characteristics according to claim 1, wherein each of the voltage drive waveforms repeatedly applied has the same waveform pattern as a unit drive waveform.   4. The voltage application unit according to claim 1, wherein the voltage application unit resets the previous screen when the screen is updated and places the electrophoretic particles in a ground state, and then applies the voltage driving waveform a plurality of times. An image display device having memory characteristics.   In the process of repeatedly applying the voltage drive waveform, the voltage application means omits the subsequent application of the voltage drive waveform when any intermediate transition state matches the display state of the next screen which is the final display state. 4. The image display device having memory characteristics according to claim 1, 2, or 3.   When the screen is updated, the voltage drive waveform is used when the electrophoretic particles are placed in the ground state and the reset process for transitioning each charged particle in the same direction is omitted and the transition is performed directly from the previous screen. Each charged particle, the transition of any charged particles caused by the reverse movement of any charged particles between each other and the transition of another charged particle that follows. 4. The image display device having memory characteristics according to claim 1, wherein a correction voltage drive waveform for correction is inserted and applied. The electrophoretic layer is sandwiched between a first substrate on which switching elements and pixel electrodes are arranged in a matrix, and a second substrate on which a counter electrode is formed,
2. The memory according to claim 1, wherein the voltage applying unit drives the switching element when the screen is updated, and applies the voltage driving waveform between the pixel signal and the counter electrode in units of pixels. Image display device.   2. The image display device having memory characteristics according to claim 1, wherein holding particles for holding the n kinds of charged particles are contained in the electrophoretic layer.   2. The image having memory characteristics according to claim 1, wherein the n kinds of charged particles are composed of three kinds of charged particles of cyan, magenta and yellow, or three kinds of charged particles of red, green and blue. Display device.   The electrophoretic layer includes three kinds of charged particles of cyan, magenta, and yellow, and white holding particles for holding the three kinds of charged particles. The image display device having memory characteristics according to claim 1.   2. The electrophoretic layer includes three kinds of charged particles of red, green, and blue and black holding particles for holding the three kinds of charged particles. An image display device having the described memory characteristics.   2. The image display device having a memory property according to claim 1, wherein the electrophoretic particles are composed of two kinds of charged particles having a complementary color relationship with each other.   The electrophoretic layer includes two types of charged particles having a complementary color relationship with each other and white or black holding particles for holding the two types of charged particles. Item 12. An image display device having memory characteristics according to Item 1.   A DC cancellation compensation subframe group is further added so that ∫Vdt = 0 over the entire update period, and the voltage applied in the DC cancellation compensation subframe group has an absolute value that is the minimum | 2. The image display device having memory characteristics according to claim 1, wherein the threshold voltage is set to be equal to or lower than |.   The voltage signal supplied to the voltage applying means is set to three values of -Vdd, 0, and Vdd, and the driving reference voltage Vdd is variable for each subframe period. An image display device having memory characteristics.   2. The image display device having memory characteristics according to claim 1, wherein a COM voltage defining a reference potential of the electrophoretic particles applied to the counter electrode is changed every subframe period.

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