JP6710936B2 - Electrophoretic display device and driving method thereof - Google Patents

Description

The present invention relates to an electrophoretic display device that performs display by moving charged particles and a driving method thereof.

2. Description of the Related Art Conventionally, as a thin display device, a liquid crystal display device has been widely used for various electronic devices, and in recent years, it has also been used as a large color display for computers, televisions and the like. A plasma display is also used as a large color display for television. However, although the liquid crystal display device and the plasma display are much thinner than the CRT display device, they are still not thin enough for some purposes and cannot be bent. Further, when used as a display of a mobile device, further reduction of power consumption is desired.

Therefore, a display device called an electronic paper using an electrophoretic display element has been developed as a display device that realizes further thinning and low power consumption, and an electronic book, an electronic newspaper, an electronic advertising signboard, and a guidance display board are developed. It has been tried to be used for. A display device (EPD) using this electrophoretic display element is provided with an image display layer in which charged particles are encapsulated between a pair of substrates each having electrodes on opposite surfaces, and electrodes of the pair of substrates. The charged particles are configured to move by electrophoresis according to the polarity of the voltage applied between them for display.

This electrophoretic display device has a memory property because the charged particles do not move even if the drive voltage applied between the electrodes is removed, and thus the electrophoretic display device can maintain the display state even when the drive power is zero. The display period in which this display state is maintained may last from several seconds to several hours, or even several months. Therefore, this electrophoretic display device can be driven with an extremely small amount of electric power, and is promising in the future as a display device for portable devices such as wristwatches and mobile phones that require low power consumption.

The electrophoretic element includes, for example, black particles and white particles as electrophoretic particles. By selectively attracting these two types of particles to the counter electrode side for each pixel, two gradations of black or white can be obtained. Is displayed. In such an electrophoretic display device, an image is displayed by supplying a data potential according to a gradation to be displayed to the pixel electrode provided in each of the plurality of pixels. For example, as a data potential, a positive potential VSH (for example, +15 V) higher than a potential GND (for example, 0 V) of a counter electrode is supplied to a pixel electrode of a pixel for which black is displayed, and a pixel for which white is displayed. An image is displayed by supplying a negative potential -VSH (for example, -15 V) lower than the potential of the counter electrode to the pixel electrode of.

On the other hand, in such an electrophoretic display device, one pixel that functions as a pixel switching element is provided for each of a plurality of pixels arranged in a matrix corresponding to the intersection of a plurality of scanning lines and a plurality of data lines that intersect each other. Active matrix electrophoretic display including a pixel circuit (so-called 1T1C type pixel circuit) including a TFT (Thin Film Transistor) and one capacitor (that is, a storage capacitor) that functions as a memory circuit. There is a device. During operation of such an active matrix driving type electrophoretic display device, a plurality of scanning lines are sequentially selected in each horizontal scanning period, and a pixel corresponding to the selected scanning line is supplied with a data potential via the data line. Supplied.

Since such an electrophoretic display device is used for applications such as electronic books and small display media, further reduction in power consumption is required. Since the electrophoretic display device consumes power only when rewriting, it is important to reduce the rewriting time. Further, in the electrophoretic display device, the electrophoretic particles perform display by moving in the thickness direction of the device, so that the rewriting time tends to be long. In applications such as electronic books, operations such as screen switching are often performed, and the rewriting time is long, which may cause the operator to feel uncomfortable.

In addition, if a voltage is applied for a long time and black or white is applied to the display after applying a driving voltage, the charged particles in the display layer are allowed to flow slightly, resulting in a white or black display density. Tends to change to a gray color, and the contrast of the display gradually decreases, resulting in poor visibility. Since the deterioration of the contrast due to the elapsed time deteriorates the display quality of the display device, improvement is required.

If the driving voltage for rewriting the display is applied to the pixel electrode when the contrast is lowered and the display density of the pixel is changed, the regular black or white density is not displayed, and the display density is varied. There is also the problem of quality deterioration. Such a phenomenon is called an afterimage phenomenon and is one of the problems of the electrophoretic display device.

When driving the electrophoretic display device, it is called DC unbalance that the time integration of the voltage does not match on the plus side and the minus side. However, if the driving is continued in the DC unbalanced state, the display characteristics and reliability will be deteriorated. It has turned out to fall. Specifically, it is said that a decrease in contrast, a decrease in adhesion of electrodes, and the like will occur. It is important for the drive to be DC balanced, because performance deteriorates if it is driven for a long time in a DC unbalanced state.

In order to realize high-speed rewriting, Patent Document 1 proposes a method of rewriting only the first few pulses and omitting the remaining steps when a rewriting signal is input before the completion of writing. When the above method is used, the writing time can be shortened when rewriting continuously, and the waiting time of the user can be shortened. However, since no consideration is given to the DC balance, there is no description of a measure against the problem that the performance is deteriorated when the driving is performed for a long period of time or the contrast is decreased with the passage of time.

On the other hand, in Patent Document 2, gradation display is performed while maintaining DC balance. According to the method of Patent Document 2, by using a plurality of drive pulses, reproducibility of gradation display is ensured and DC balance is achieved at the same time. However, there is no description of measures for shortening the writing time and reducing the contrast over time.

In addition, Patent Document 3 describes a method of improving rewriting reproducibility in a portion where the contrast is deteriorated with time and relaxing a DC component due to DC imbalance. However, there is no description of measures for shortening the writing time.
As described above, demands for high-speed rewriting, contrast maintenance, and long-term driving are becoming strict, and performance is insufficient with the configurations of Patent Documents 1, 2, and 3.

Japanese Patent Laid-Open No. 2012-3006 JP, 2010-217283, A JP, 2012-32489, A

The present invention has been made in view of the above problems, and it is possible to perform rewriting in a short time, ensure DC balance, and perform electrophoretic display with high contrast. An object is to provide an apparatus and a driving method thereof.

One aspect of the present invention for solving the above problems is a display device having a memory property in which charged particles are enclosed between a pair of substrates each having electrodes on opposite surfaces, and display is performed by movement of the charged particles. A drive circuit that applies a voltage to the charged particles and a controller that outputs a signal to the drive circuit. When the drive circuit detects a signal from the controller, it applies a pulse group and then does not apply a pulse. through downtime application, application time than the pulse group rather short, performs waveform applied process of applying a correction pulse reserved for DC balance between pulse groups, after starting the waveform application treatment, a correction pulse Before a new signal is detected, the rest of the pause time is canceled, the correction pulse is applied as soon as possible after the application of the pulse group is completed, and the waveform application processing according to the new signal is newly added. It is a display device to start .

The rest time may be 0.1 s or more.

The application time of the correction pulse may be 1 ms or more and 300 ms or less.

Another aspect of the present invention is a driving method performed by each unit of a display device having a memory property in which charged particles are enclosed between a pair of substrates each having electrodes on opposite surfaces, and movement of the charged particles causes display. The controller outputs a signal to the drive circuit that applies a voltage to the charged particles, and when the drive circuit detects the signal from the controller, after applying the pulse group, a pause time during which no pulse is applied is applied. after, the application time than the pulse group rather short, performs waveform applied process of applying a correction pulse reserved for DC balance between the pulse groups, the driving circuit, after starting the waveform application treatment, applying a correction pulse Before a new signal is detected, the rest of the pause time is canceled , the correction pulse is applied as soon as possible after the application of the pulse group is completed, and the waveform application processing according to the new signal is newly added. It is a driving method to start.

According to the present invention, it is possible to provide an electrophoretic display device and a driving method capable of performing rewriting in a short time, ensuring DC balance, and performing display with high contrast.

1 is a plan view of an electrophoretic display device according to an embodiment of the present invention. An equivalent circuit diagram of a pixel of an electrophoretic display device according to an embodiment of the present invention. Sectional drawing of the display part of the electrophoretic display device which concerns on one Embodiment of this invention. FIG. 3 is a diagram showing drive waveforms of an electrophoretic display device according to an embodiment of the present invention. FIG. 3 is a diagram showing drive waveforms of an electrophoretic display device according to an embodiment of the present invention. FIG. 3 is a diagram showing drive waveforms of an electrophoretic display device according to an embodiment of the present invention. FIG. 3 is a diagram showing drive waveforms of an electrophoretic display device according to an embodiment of the present invention. FIG. 3 is a diagram showing drive waveforms of an electrophoretic display device according to an embodiment of the present invention. FIG. 3 is a diagram showing drive waveforms of an electrophoretic display device according to an embodiment of the present invention. FIG. 3 is a diagram showing drive waveforms of an electrophoretic display device according to an embodiment of the present invention.

An electrophoretic display device 1 and a driving method thereof according to an embodiment of the present invention will be described below with reference to the drawings. In the present embodiment, the active matrix drive type electrophoretic display device 1 will be described as an example, but a passive type, a segment type, or the like may be used.

FIG. 1 is a plan view of the periphery of the display unit of the electrophoretic display device 1.

In FIG. 1, an electrophoretic display device 1 is an active matrix drive type electrophoretic display device, and includes a display unit 2, a controller 10, a scanning line drive circuit 60, a data line drive circuit 70, and a common potential supply circuit. 100 and. The controller 10 is connected to the display unit 2 via a flexible cable 14, and the controller 10 has a CPU 11, a memory 12, and the like.

FIG. 2 is an equivalent circuit diagram showing an electrical configuration of the pixel 20 of the electrophoretic display device 1. In FIG. 2, the pixel 20 includes a pixel switching transistor 24, a pixel electrode 21, a counter electrode 22, an electrophoretic element 23, and a storage capacitor 27.

FIG. 2 shows an example of the pixel 20 in the i-th row and the j-th column. In the display unit 2, pixels 20 for m rows×n columns are arranged in a matrix (two-dimensionally planar), and m scanning lines 40 (Y1, Y2,..., Yi,..., Ym) are formed. , N data lines 50 (X1, X2,..., Xj,..., Xn) are provided so as to intersect with each other. Specifically, the m scanning lines 40 extend in the row direction (ie, the X direction in FIG. 2), and the n data lines 50 extend in the column direction (ie, the Y direction in FIG. 2). Each is extended. The pixels 20 are arranged corresponding to the intersections of the m scanning lines 40 and the n data lines 50.

The controller 10 controls the operations of the data line driving circuit 70 and the common potential supply circuit 100 by using the scanning line driving circuit 60, the CPU 11, the memory 12, and the like. The controller 10 supplies timing signals such as a clock signal and a start pulse to each circuit.

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

Under the control of the controller 10, the data line driving circuit 70 supplies the data lines 50 (X1, X2,..., Xn) with a data potential (a potential difference for moving charged particles of the electrophoretic element 23 described later). The data potential is either a reference potential GND (for example, 0V), a high potential VSH (for example, +15V), or a low potential −VSH (for example, −15V).

The common potential supply circuit 100 supplies the common potential Vcom (in this embodiment, the same potential as the reference potential GND) to the common potential line 90. The common potential Vcom is a range in which a voltage is not substantially generated between the counter electrode 22 (see FIG. 2) supplied with the common potential Vcom and the pixel electrode 21 (see FIG. 2) supplied with the reference potential GND. The potential may be different from the reference potential GND. For example, the common potential Vcom may be set to a value different from the reference potential GND supplied to the pixel electrode 21 in consideration of the variation in the potential of the pixel electrode 21 due to feedthrough, and even in this case, In this specification, it is assumed that the common potential Vcom and the reference potential GND are the same.

Here, the term "feedthrough" refers to when the supply of the scan signal to the scan line 40 is completed and the supply of the scan signal to the scan line 40 is completed after the potential is supplied to the pixel electrode 21 through the data line 50 (for example, This is a phenomenon in which the potential of the pixel electrode 21 fluctuates due to the parasitic capacitance between the pixel electrode 21 and the scanning line 40 (for example, when the potential of the scanning line 40 decreases) (for example, the potential decreases as the potential of the scanning line 40 decreases). The common potential Vcom may be set to a value slightly lower than the reference potential GND supplied to the pixel electrode 21 on the assumption that the potential of the pixel electrode 21 will decrease due to feedthrough. It is considered that the potential Vcom and the reference potential GND are the same potential.

Although various signals are input to and output from the controller 10, the scanning line drive circuit 60, the data line drive circuit 70, and the common potential supply circuit 100, the description of those not particularly related to the present embodiment will be omitted. ..

Since the controller 10 has the memory 12, information indicating the number of times the correction pulse described below is applied, the time, and the number of times the application of the correction pulse is planned but not actually applied, the time, etc. is collected from the data line driving circuit 70. Then, the degree and tendency of the DC imbalance is determined based on these values, and when the degree becomes a certain value or more, the data line driving circuit 70 outputs an output signal of a reset pulse described later. It is possible to issue As an example, add one internal memory (counter) when the + correction pulse is applied, decrement the internal memory by 1 when the-correction pulse is applied, and decrease the internal memory by 5 when the internal memory exceeds 5. Reset pulse (application time is 5 times the correction pulse) is applied to decrease the memory value by 5. When the internal memory exceeds -5, the + side reset pulse (application time is 5 times the correction pulse) is applied, Operations such as adding 5 memory values are possible. By applying the reset pulse as described above, the DC imbalance is periodically eliminated.

The pixel switching transistor 24 is composed of, for example, an N-type transistor. The pixel switching transistor 24 has its gate electrically connected to the scanning line 40, its source electrically connected to the data line 50, and its drain electrically connected to the pixel electrode 21 and the storage capacitor 27. It is connected to the. The pixel switching transistor 24 timings the data potential supplied from the data line driving circuit 70 via the data line 50 in accordance with the scanning signal pulse-wise supplied from the scanning line driving circuit 60 via the scanning line 40. Then, it outputs to the pixel electrode 21 and the storage capacitor 27.

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

The counter electrode 22 is electrically connected to the common potential line 90 to which the common potential Vcom is supplied.

The electrophoretic element 23 is composed of a plurality of microcapsules 80 each containing electrophoretic particles which are a plurality of charged particles having different colors and polarities.

The storage capacitor 27 is composed of a pair of electrodes that are arranged to face each other with a dielectric film interposed therebetween, one electrode being electrically connected to the pixel electrode 21 and the pixel switching transistor 24, and the other electrode being the common potential line 90. Electrically connected to. The storage capacitor 27 allows the data potential to be maintained for a fixed period.

Next, a specific configuration of the display unit 2 of the electrophoretic display device 1 will be described with reference to FIG.

FIG. 3 is a partial cross-sectional view of the display unit 2 of the electrophoretic display device 1 according to this embodiment.

The pixel 20 is configured such that the microcapsules 80 are sandwiched between the TFT substrate 28 and the counter substrate 29. It should be noted that the present embodiment will be described on the assumption that an image is displayed on the counter substrate 29 side.

The TFT substrate 28 is a substrate made of, for example, glass or plastic. Although not shown here, the pixel switching transistor 24, the storage capacitor 27, the scanning line 40, the data line 50, the common potential line 90 and the like are formed on the TFT substrate 28. A laminated structure is formed. A plurality of pixel electrodes 21 are provided in a matrix on the upper layer side of this laminated structure.

The counter substrate 29 is a transparent substrate made of, for example, glass or plastic. On the surface of the counter substrate 29 facing the TFT substrate 28, the counter electrode 22 is formed in a solid shape so as to face the plurality of pixel electrodes 21. The counter electrode 22 is formed of a transparent conductive material such as magnesium silver (MgAg), indium tin oxide (ITO), indium zinc oxide (IZO).

The electrophoretic element 23 is composed of a plurality of microcapsules 80 each containing electrophoretic particles, and is fixed between the TFT substrate 28 and the counter substrate 29 by a binder 30 and an adhesive layer 31 made of, for example, resin or the like. .. In the present embodiment, in the display unit 2, in the manufacturing process, the electrophoretic sheet in which the electrophoretic element 23 is previously fixed to the counter substrate 29 side with the binder 30 is formed, and the separately manufactured pixel electrode 21 and the like are formed. The TFT substrate 28 side is bonded to the adhesive layer 31.

The microcapsule 80 is sandwiched between the pixel electrode 21 and the counter electrode 22, and one or a plurality of microcapsules 80 are arranged in one pixel 20 (in other words, for one pixel electrode 21 ).

The microcapsule 80 is formed by enclosing a dispersion medium, a plurality of white particles, and a plurality of black particles inside a coating film. The microcapsule 80 is formed in a spherical shape having a particle size of about 50 μm, for example.

The coating functions as an outer shell of the microcapsule 80, and is formed of a translucent polymer resin such as an acrylic resin such as polymethylmethacrylate or polyethylmethacrylate, a urea resin, gum arabic, or gelatin.

The dispersion medium is a medium that disperses white particles and black particles in the microcapsules 80 (in other words, in the coating film). As the dispersion medium, water, methanol, ethanol, alcohol solvents such as isopropanol, butanol, octanol, methyl cellosolve, ethyl acetate, various esters such as butyl acetate, acetone, methyl ethyl ketone, ketones such as methyl isobutyl ketone, Aliphatic hydrocarbons such as pentane, hexane and octane, alicyclic hydrocarbons such as cyclohexane and methylcyclohexane, benzene, toluene, xylene, hexylbenzene, butylbenzene, octylbenzene, nonylbenzene, decylbenzene and undecylbenzene. , Dodecylbenzene, tridecylbenzene, tetradecylbenzene, and other aromatic hydrocarbons such as benzene having a long-chain alkyl group, methylene chloride, chloroform, carbon tetrachloride, halogenated hydrocarbons such as 1,2-dichloroethane, and carvone. Acid salts and other oils can be used alone or as a mixture. A surfactant may be added to the dispersion medium.

The white particles are particles (polymer or colloid) made of white pigment such as titanium dioxide, zinc oxide (zinc oxide), and antimony trioxide, and are negatively charged, for example.

The black particles are particles (polymer or colloid) composed of black pigments such as aniline black and carbon black, and are positively charged, for example.

Therefore, the white particles and the black particles can move in the dispersion medium by the electric field generated by the potential difference between the pixel electrode 21 and the counter electrode 22.

These pigments include, if necessary, electrolytes, surfactants, metal soaps, resins, rubbers, oils, varnishes, charge control agents composed of particles such as compounds, titanium coupling agents, aluminum coupling agents, silanes. A dispersant such as a system coupling agent, a lubricant, a stabilizer and the like can be added.

When a voltage is applied between the pixel electrode 21 and the counter electrode 22 so that the potential of the counter electrode 22 becomes relatively high, the positively charged black particles are generated in the microcapsules 80 by the Coulomb force. While being attracted to the pixel electrode 21 side, the negatively charged white particles are attracted to the counter electrode 22 side in the microcapsule 80 by the Coulomb force. As a result, white particles gather on the display surface side (that is, the counter electrode 22 side) in the microcapsule 80, and the color of the white particles (that is, white) is displayed on the display surface of the display unit 2. The Rukoto. On the contrary, when a voltage is applied between the pixel electrode 21 and the counter electrode 22 so that the potential of the pixel electrode 21 is relatively high, the negatively charged white particles are generated by the Coulomb force. While being attracted to the 21 side, the positively charged black particles are attracted to the counter electrode 22 side by the Coulomb force. As a result, black particles gather on the display surface side of the microcapsules 80, and the color of the black particles (that is, black) is displayed on the display surface of the display unit 2.

By replacing the pigments used for the white particles and black particles with pigments of red, green, blue, etc., red, green, blue, etc. can be displayed.

The above is the configuration for the active matrix type black and white display using the TFT, but within the scope of the present invention, it is possible to appropriately change the display method such as the passive type/segment type display and the multi-color gradation display. ..

Reference example 1 of the drive waveform of the present invention is shown below. 4 and 5 show drive waveforms supplied from the data line drive circuit 70. FIG. 4 shows an example of black and white binary display, where V11 is a waveform for overwriting white in white display, V12 is a waveform for writing white in black display, and V13 is for writing black in white display. A waveform V14 is a waveform overwriting black when displaying black. Both waveforms show the waveforms of the waveform drive processing performed when the data line drive circuit 70 detects at the time t0 according to the signal output from the controller 10.

V11 will be described as an example. The first write pulse group P1 has a waveform that drives a general electrophoretic element 23. In the case of overwriting from white to white, white writing is performed by applying the first write pulse group P1. After that, writing is not performed during the pause time T0. The pause time T0 is a time between the first write pulse group P1 and a correction pulse P2, which will be described later, and is a time during which no voltage is applied. In the electrophoretic display device 1, since the brightness change immediately after writing due to kickback or the like is the largest, correction of the application time shorter than that of the first write pulse group P1 is performed after the rest time T0 elapses and the change in display is completed. By applying the pulse P2 and slightly writing white, the brightness of white is changed to a high value again. The correction pulse P2 is a waveform that is applied after the pause time T0 to improve the display contrast. The above also applies to V12, V13, and V14. By applying the correction pulse P2 after the pause time T0, white is displayed whiter and black is displayed blacker. T1 is the application time of P1, and T2 is the application time of P2.

Next, an example in which a new overwrite signal is detected before the end of the overwrite process will be described. When a new overwrite signal is detected after the application of the first write pulse group P1 (after the elapse of T1), the current overwrite process is stopped and the new overwrite process is immediately executed. Specifically, a new first write pulse group P1 is applied without applying the correction pulse P2. As a result, the image changes as the screen is input. The correction pulse P2 is not applied to the image before the change, but there is no problem because the image is rewritten. Then, after T0 has elapsed, the correction pulse P2 is applied, and at V11, white is held in a whiter state. As described above, it is possible to quickly rewrite when the rewriting is performed by the input person, and high contrast display is possible when rewriting is not continuously performed. When a new overwrite signal is detected during the application of the first write pulse group P1, the new overwrite processing is executed after the completion of the application of the first write pulse group P1.

During the above rewriting, it is important to maintain DC balance within the first write pulse group P1. In the example of FIG. 4, DC balance of V11 and V14 is ensured within the first write pulse group P1. Regarding V12 and V13, since black→white and white→black are rewritten, the same number of pixels are always applied (if white→black is not written, black does not become black, so black→white writing occurs. No). Therefore, it is sufficient that V12 and V13 have a total DC balance secured. In this reference example 1, DC imbalance is slightly generated every time the correction pulse P2 is applied, but the DC imbalance is eliminated by applying the reset pulse described below.

FIG. 5 shows a waveform when a reset pulse is applied. In the example of FIG. 5, the reset pulse P3 is applied immediately before the application of the first write pulse group P1. The reset pulse P3 is a waveform that is applied so as to cancel the DC imbalance so far, based on the information on the number of times the correction pulse is applied, the time, the number of times the correction pulse is not applied, and the time stored in the memory 12. For example, in the case of setting the reset pulse to be applied after the plus side correction pulse P2 is applied five times, it is possible to apply the reset pulse P3 having an application time that is five times as long as the correction pulse P2. The same applies to the case where the write waveforms are V12, V13, and V14, and the DC balance can be maintained.

The application time T1 of the first write pulse group P1 is not particularly limited, but is preferably 10 ms or more and 20 s or less, and more preferably 100 ms or more and 1 s or less. If it is less than 10 ms, writing tends to be insufficient, and if it exceeds 20 s, rewriting takes too much time. On the other hand, the rest time T0 is preferably 0.1 s or more. When T0 is less than 0.1 s, the movement of the electrophoretic element is not settled down, and even if the correction pulse is applied, the flow continues, so that the effect of applying the correction pulse is small.

The application time T2 of the correction pulse P2 is preferably 1 ms or more and 300 ms or less. Furthermore, 10 ms or more and 100 ms or less are more preferable. When T2 is less than 1 ms, the application time is too short, and it is difficult to obtain the effect of improving the contrast. When it exceeds 300 ms, DC imbalance is promoted, resulting in a decrease in reliability.

It is desirable that the application time T3 of the reset pulse P3 be appropriately selected so that the correction pulse can be canceled efficiently. Specifically, it is preferable to be about 2 to 20 times the correction pulse application time T2. When the reset pulse application time T3 is shortened, the frequency of applying the reset pulse P3 increases, and when the reset pulse application time T3 is lengthened, the rewriting time itself increases. Therefore, it is desirable to determine the DC unbalanced state and the application of the display device.

As described above, according to the first reference example, the writing time can be shortened, the display can be maintained in a state where the contrast is high, and the DC balance allows the performance to be deteriorated even if the driving is performed for a long time. A display device and a driving method that can suppress the display device can be provided.

Next, with reference to FIGS. 6 and 7, a reference example 2 of the drive waveform of the present invention will be described. FIG. 6 is a drive waveform of the second reference example. The difference from Reference Example 1 is that a pulse corresponding to the correction pulse P2 is added to the first write pulse group P1 in advance and the application time is T1′ (=T1+T2). In the case of this reference example 2, DC balance is ensured for the entire waveform. Therefore, unlike Reference Example 1, the DC balance is maintained unless the overwrite signal is detected during the waveform application. On the other hand, when the overwrite signal is detected during the overwrite process, when the first write pulse group P1 is applied again as in the first reference example, pulses corresponding to the correction pulse P2 are added to the first write pulse group P1. Since it is included, there is a slight DC imbalance. FIG. 7 shows a waveform when the reset pulse P3 is applied in the case of the second embodiment. Also in the case shown in FIG. 7, the controller 10 determines the frequency/time of the reset pulse P3 based on the information about the number of times the correction pulse is applied, the time and/or the number of times the correction pulse is not applied, and the time stored in the memory 12. ..

FIG. 6 and FIG. 7 are examples of the case where a pulse having the opposite sign to the correction pulse P2 is applied to the first write pulse group P1. It is also possible to create a waveform by a method such as shortening the group P1.

Next, with reference to FIG. 8, a third embodiment of the drive waveform of the present invention will be described. FIG. 8 is a drive waveform of the third embodiment. The waveform V11 is a total DC-balanced waveform including the correction pulse P2. Here, when a new overwrite signal is detected before the correction pulse P2 is applied, the waveform V11 becomes the waveform V11', and the pause time T0 ends (the remaining time) at the moment when the overwrite signal is detected. Is canceled), and the correction pulse P2′ is input as soon as possible after the application of the first write pulse group P1, and thereafter, the waveform drive processing according to the new signal is performed. By using the waveform of the third embodiment, the DC balance can be maintained regardless of the presence or absence of the overwrite signal during the overwrite process. Although FIG. 8 shows the case of the waveform V11, the same applies to the cases of V12, V13, and V14.

Next, with reference to FIG. 9 and FIG. 10, reference example 4 of the drive waveform of the present invention will be described. 9 and 10 show drive waveforms of this reference example 4, which are examples of waveforms of partial rewriting. Since partial rewriting is performed, no voltage is applied in the first write pulse group P1 for white→white (V11) and black→black (V14). FIG. 9 shows a waveform when the correction pulse P2 is applied in the case of the third embodiment. The configuration other than the above is the same as that of the reference example 1. Even in the partial rewriting, since the correction pulse P2 is applied regardless of the rewriting portion and the non-rewriting portion, high contrast display is possible. FIG. 10 shows a case where the reset pulse P3 is applied in the case of the fourth reference example.

As described above, according to the present invention, since the display image is corrected by the correction pulse after the writing is performed by the first writing pulse group, it is possible to perform the display with high contrast. Further, since the correction pulse is shorter than that of the first write pulse group, there is little change in appearance when the correction pulse is applied and flicker can be suppressed, so that it is possible to reduce the burden on the eyes of the device user. Become.

In addition, in a display medium using an electrophoretic element or the like, the contrast generally decreases with time. Although this is called a kickback phenomenon, even if the contrast of the display image is lowered due to the kickback phenomenon or the like, the pause time is provided between the first write pulse group and the correction pulse to make the pause time longer. Since the correction pulse is applied after the elapse, it is possible to improve the contrast of the display image. On the other hand, when the pause time is not provided, the voltage is applied before the operation of the electrophoretic element settles down, so that the effect of improving the contrast cannot be obtained.

Further, when the rest time is 0.1 s or more, it is possible to improve the deterioration of contrast over time and maintain the display in a high contrast state. On the other hand, when the rest time is less than 0.1 seconds, the voltage is applied before the operation of the electrophoretic element settles down, so that the effect of improving the contrast cannot be obtained.

Further, since the application time of the correction pulse is 1 ms or more and 300 ms or less, it is possible to improve the contrast of the display image while suppressing the temporary DC imbalance. When the application time of the correction pulse is less than 1 ms, the time is too short to drive the electrophoretic element and the contrast cannot be improved. If the application time of the correction pulse exceeds 300 ms, the DC imbalance becomes large, which accelerates the deterioration of the display device.

Further, since the first write pulse group has the DC balance waveform or the DC overwrite waveform in the entire overwriting process, the DC balance can be easily maintained and the performance deterioration can be suppressed.

Further, when the overwrite signal is continuously input, rewriting can be performed without waiting for the correction pulse, so that high-speed rewriting is possible.

Further, when the rewriting input is continuously performed, the correction pulse can be immediately input and the new overwriting process can be performed, so that the overwriting process can be performed at high speed. Further, when the drive waveform is DC balanced including the correction pulse, it is possible to always maintain the DC balance.

Further, in either state of overwriting input and not overwriting input, the DC unbalance is periodically canceled out, and the drive can be performed in the DC balanced state.

Further, the reset pulse may be applied before the first pulse group, the correction pulse, and the dwell time, whereby the DC balance is maintained and the correction pulse maintains a high contrast state.

The above-mentioned various pulse waveforms, application timings, etc. are merely examples, and the present invention is not limited to these. If the DC balance is obtained by combining a pulse group in which DC balance is achieved individually or in groups, a pulse for compensation when these application processes are interrupted, and the like, various modifications are possible.

INDUSTRIAL APPLICABILITY The electrophoretic display device of the present invention is useful for electronic books, electronic newspapers, electronic advertisement signs, guide display boards, and the like.

1 Electrophoretic Display Device 2 Display Unit 10 Controller (Drive Device of Electrophoretic Display Device 1)
11 CPU
12 memory 13 communication device 14 flexible cable 20 pixel 21 pixel electrode 22 counter electrode 23 electrophoretic element 24 pixel switching transistor 27 storage capacitor 28 TFT substrate 29 counter substrate 30 binder 31 adhesive layer 40 scanning line 50 data line 60 scanning line driving circuit 70 data line driving circuit 80 microcapsule (electrophoretic display material)
90 common potential line 100 common potential supply circuit P1 first write pulse group P2 correction pulse P3 reset pulse T0 pause time T1 first write pulse group application time T1' correction pulse first write pulse group application time T2 correction pulse Application time T3 Reset pulse application time t0 Overwrite signal detection time

Claims (4)

A display device having a memory property in which charged particles are enclosed between a pair of substrates each having electrodes on opposite surfaces, and display is performed by movement of the charged particles,
A drive circuit for applying a voltage to the charged particles,
A controller for outputting a signal to the drive circuit,
The driving circuit detects a signal from the controller, after applying a pulse group, via a pause time is not performed the application of the pulse, the application time than the pulse group rather short, between the pulse groups performs waveform applied process of applying a correction pulse secured the DC balance,
When a new signal is detected after the waveform application process is started and before the correction pulse is applied, the rest of the pause time is canceled, and the correction pulse is applied as soon as possible after the application of the pulse group is completed. Is applied, and a waveform applying process corresponding to the new signal is newly started,
Display device. The display device according to claim 1 , wherein the pause time is 0.1 s or more. The application time of the correction pulse is 1ms than 300ms or less, the display device according to claim 1 or 2. Charged particles are enclosed between a pair of substrates each having electrodes on opposite surfaces, and a driving method performed by each unit of a display device having a memory property for displaying by movement of the charged particles,
The controller outputs a signal to a drive circuit that applies a voltage to the charged particles,
Wherein the drive circuit has detected a signal from the controller, after applying a pulse group, via a pause time it is not performed the application of the pulse, and the application time than the pulse groups is rather short, between the pulse groups Performs waveform application processing to apply the correction pulse with DC balance secured ,
The drive circuit cancels the rest of the rest time when a new signal is detected after the waveform application process is started and before the correction pulse is applied, and after the application of the pulse group is completed , as much as possible. A driving method in which the correction pulse is promptly applied and a waveform application process corresponding to the new signal is newly started.

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