JP2007079301A - Method for driving electrophoretic display element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for an electrophoretic display element, in which display is not changed during rewriting, the picture quality of the first line is made to be equal to that of the final line even after completing picture writing and a picture can be quickly switched within a rewriting period of about 0.1 to 1 sec which is the response time of the electrophoretic display element in an OSC group TFT whose ON/OFF ratio is lower than that of a-Si. <P>SOLUTION: After performing initial picture wriring n times, picture quality-held writing is suitably performed at a suitable interval 25 (22). In image storing writing, each pulse of 50 msec is sent at an interval of 5 sec. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for driving an electrophoretic display element for driving an electro-optical device composed of a plurality of divided cells in which a dispersion containing electrophoretic particles is enclosed.

  An electrophoretic phenomenon in which the charged particles move by Coulomb force by applying an electric field to a dispersion material in which charged electrophoretic fine particles are dispersed in a dispersion medium. An electrophoretic display device is known.

  The following are known as techniques relating to such an electrophoretic display device.

  For example, Patent Document 1 discloses an electro-optical device having a driving method related to gradation, a driving method of the electro-optical device, and an electronic apparatus. Further, Patent Document 2 discloses an electrophoretic display device related to improvement in color contrast.

  An electrophoretic display device such as an electrophoretic display element or an electrophoretic display panel using an electrophoretic phenomenon has a configuration in which a dispersion material is sealed between opposed electrodes. A driving circuit such as a thin film transistor (TFT) is connected to the counter electrode corresponding to each pixel, and the driving circuit is connected to an external circuit.

Many of the conventional methods use TFTs made of amorphous silicon (a-Si), and SiO ₂ having high insulating properties is used as a substrate. Therefore, an on / off ratio of 10 ⁸ or more can be obtained, an on-current capacity necessary for writing can be set sufficiently, and an off-current can be minimized. Therefore, it was virtually impossible for the off current to flow into the electrophoretic display element pixel and change the display.

  By the way, in recent years, development of MOS-FETs using organic semiconductor materials (OSC materials) using ink-jet technology that is much simpler and more productive than photolithography and film formation using a vacuum apparatus has been promoted.

OSC has lower mobility than a-Si and cannot take a large on / off ratio. However, there is a possibility that it can be used for application to e-books and the like that perform still image display by an electrophoretic display element that is practically used even for relatively slow writing.
JP 2004-085606 A JP 2004-35775 A

  However, since the OSC has a TFT on / off ratio that is not large compared to a-Si, the written image changes in a relatively short time. This is related to the fact that the off current cannot be completely narrowed together with the fact that the on current cannot be obtained due to the low mobility.

  For example, when the number of rewrite scans per screen is 640 lines as in a VGA (video graphics array), there is only one rewrite opportunity for 640 times for one line. Therefore, if a sufficiently large ratio cannot be obtained with respect to this 640, the display may change during rewriting.

  For this reason, although it is not enough to rewrite the entire screen, it is necessary to perform appropriate rewriting at an appropriate time in order to maintain the display screen. In particular, in the case of rewriting a display element having a very large voltage-charge characteristic (VC characteristic) hysteresis in a rewrite cycle, such as an electrophoretic display element, it is necessary to send a large charge for full rewriting.

Since the current required to hold the display once rewritten does not have to be very large, a driving method that fully considers the drop is required. Therefore, there is a need for a display image holding method in the case where the on / off ratio cannot be sufficiently obtained (−10 ⁵ ), such as a TFT made of an organic semiconductor (OSC).

  Moreover, even if charges are sufficiently sent between the electrodes of the electrophoretic display element, it usually takes about 0.5 to 1 second until the display state of the electrophoretic display element is sufficiently achieved. In other words, there is a large difference between the time taken for charging itself and the time taken until the display is actually completed. Waiting for writing one line at a time and displaying it will take several hundreds of seconds for VGA, which is unacceptable.

  Further, when writing slowly, there is a possibility that the display quality of the first line and the last line of the screen are different. Further, it is not preferable to write slowly from the viewpoint of shortening the writing time and saving the writing power consumption.

  In the techniques described in Patent Document 1 and Patent Document 2, there is no disclosure or mention regarding a display image holding method.

  The present invention has been made in view of the above problems, and in an OSC TFT having a lower on / off ratio than a-Si, the display is not changed during rewriting, and screen writing is completed. Electrophoretic display that can change the screen quickly without changing the image quality of the first line and the final line at the time, and the rewriting time is about 0.5 to 1 second, which is the response time of the electrophoretic display element. It is an object to provide a method for driving an element.

  According to the first aspect of the present invention, the drain or source electrode of the thin film transistor fabricated for each pixel is used as a data line for sending display contents in the sub-scanning direction, and the gate of the thin film transistor is written in one of the scanning directions. A selection line for selecting display, the data lines and the selection lines are arranged in a matrix connected vertically and horizontally by an extraction electrode to an external circuit, and a pixel electrode and a common electrode constitute a pixel having a capacitance therebetween In the method of driving an electrophoretic display element that is arranged on two substrates and drives an electrophoretic display element in which a microcapsule encapsulating an electrophoretic dispersion material is inserted between the electrodes, the method differs from the previous screen. When displaying the contents, data for one screen is repeatedly written in a time shorter than the time required for rewriting one screen. It is characterized in.

  According to a second aspect of the present invention, in the method for driving an electrophoretic display element according to the first aspect, writing is performed by intermittent scanning after multiple writing necessary for writing data for one screen. .

  According to a third aspect of the present invention, in the electrophoretic display element driving method according to the second aspect, the writing by the intermittent scanning is performed once.

  According to a fourth aspect of the present invention, in the method for driving an electrophoretic display element according to the second aspect, the intermittent scanning is written a plurality of times.

  According to a fifth aspect of the present invention, in the method for driving an electrophoretic display element according to the third or fourth aspect, the writing is performed by the intermittent scanning while changing the scanning speed.

  According to a sixth aspect of the present invention, in the method for driving an electrophoretic display element according to any one of the second to fifth aspects, the method includes a step of changing an intermittent period necessary for writing data for one screen. It is characterized by.

  According to a seventh aspect of the present invention, in the method for driving an electrophoretic display element according to any one of the first to sixth aspects, the method includes a step of changing a scanning speed for one screen.

  According to an eighth aspect of the present invention, in the method for driving an electrophoretic display element according to any one of the first to seventh aspects, the method includes the step of setting the number of times to scan one screen.

  According to a ninth aspect of the present invention, in the method for driving an electrophoretic display element according to any one of the second to eighth aspects, the confirmation of the intermittent drive time and the confirmation of the presence / absence of rewrite data are performed in the same processing step. It is characterized in that it is performed in

  According to the present invention, in the electrophoretic display element, the display does not change during rewriting, the image quality of the first line and the last line does not differ even when the screen writing is completed, and the rewriting time is displayed in the electrophoretic display. The screen can be quickly switched in a time of about 0.5 to 1 second, which is the response time of the element.

<First Embodiment>
Hereinafter, the present invention will be described with reference to embodiments. First, a first embodiment of the present invention will be described.

<Schematic configuration of electrophoretic display element>
FIG. 1 is a side view of a general electrophoretic display element 1. The electrophoretic display element 1 includes a substrate 2, a pixel electrode 3, a microcapsule 4, a transparent electrode 5, and a transparent substrate 6.

  On the substrate 2, pixel electrodes 3 individually formed corresponding to each pixel are disposed, and microcapsules 4 are disposed thereon. A transparent substrate 6 on which a transparent electrode 5 as a common electrode is formed is disposed at a position facing the pixel electrode 3 with the microcapsule 4 interposed therebetween. The user observes the display of the electrophoretic display element 1 from the transparent substrate 6 side.

  A dispersion material is enclosed in the microcapsule 4, and two types of electrophoretic particles charged positively and negatively are dispersed in the dispersion medium. Further, in the dispersion medium, an appropriate dispersion material is added corresponding to each charged particle to prevent precipitation of the charged particle and separation from the dispersion medium.

  Further, the electrophoretic dispersion medium is enclosed in the microcapsule 4 and disposed between the electrodes 3 and 5 by making these microcapsules 4 sufficiently smaller than the pixel size to prevent the charged particles from being biased. This is to have a role.

<Circuit configuration of electrophoretic display element>
Next, the circuit configuration of the electrophoretic display element 1 will be described with reference to FIG. 2A and 2B show a matrix circuit of the electrophoretic display element 1. FIG. 2A shows a circuit of one pixel, and FIG. 2B shows a row / column direction of the circuit. This matrix circuit is provided corresponding to the pixel electrode 3 on the substrate 2.

  The matrix circuit includes a TFT 7, a capacitor 8, a data line 9, and a signal line 10.

  A TFT (thin film transistor) 7 is manufactured for each pixel, and a drain electrode or a source electrode of the TFT 7 is connected to a data line 9 for sending display contents in the sub-scanning direction, and a gate electrode of the TFT 7 is 1 in the scanning direction. It is connected to a selection line 10 for selecting one writing. The electrode on the side not connected to the data line 9 among the source electrode or the drain electrode is connected to the pixel electrode 3.

  The pixel electrode 3 forms a capacitor 8 with the transparent electrode 5 disposed opposite to the pixel electrode 3. The transparent counter electrode 5 is shown as a ground 11. The direction of the electric field in the capacitor 8 is determined according to the direction of the electric charge stored in the capacitor 8, and the charged particles move in accordance with the direction of the electric field.

  K rows of data lines 9 in the scanning direction (row numbers = 1, 2,..., K−1, K) and L columns of selection lines 10 in the sub scanning direction (column numbers = 1, 2,... , L-1, L) are provided in a matrix as shown in (b), and the ends thereof are drawn out to an external circuit.

<Data write signal>
Next, with reference to FIG. 3, an electrical signal for writing data for one screen will be described. FIG. 3 shows signals of the electrophoretic display element 1 having the number of pixels of K rows and L columns.

  Note that “H” and “L” in the pulse signal in the figure indicate that either of two voltage levels such as ± 15 volts can be taken. In the selection lines 16 to 18 in FIG. 3, “H” represents active (TFT 7 by OSC is active). The same applies to 13 to 15 representing data lines, and any one of signals “H” and “L” suitable for the image to be displayed is transmitted.

  Reference numeral 12 denotes a state in which the most typical frame is written many times and a signal in which intermittent writing is performed. 12 shows a state in which a write signal 131 for one frame is sent n times, and a write signal 132 in units of one frame is sent to the electrophoretic display element 1 after completion of frame writing by multiple writing.

  Reference numerals 13 to 15 indicate details of the data signal of the portion that transmits the data signal for one frame. In addition, 16 to 18 indicate signals sent to the column signal lines at this time.

  In order to obtain data for one screen, writing for several L times of the selection line 10 is performed, and the data of the row data 1 to K rows are simultaneously transmitted as a display signal in the one time. Therefore, in order to send a signal to all the pixels, it is only necessary to send the data for one column to all the column data to the row data line group and send the selection signal H only to the column for which the column data is to be displayed. By repeating this L times, data is sent to all pixels.

  In this way, 13 to 15 row data (1 to K) are sent one by one, and in synchronization with this, one corresponding line is selected from 16 to 18 column data (1 to L), and this is converted to L By repeating the process once, writing of data for one screen is completed. Hereinafter, this is referred to as “writing of data for one screen”. Note that the n-time multiple writing means that the writing operation for the K rows × L columns is performed n times.

  In the general data writing 12 for one screen shown in FIG. 3, the display can be held by sequentially scanning one screen and turning off the TFT 7. However, an OSC or the like that does not have a large on / off ratio has a large leak, and thus a display holding operation is required.

  Therefore, multiple writing is repeated n times at the first writing, and after completion, the selection signal and the data signal are stopped, and intermittent writing is appropriately performed to maintain display quality.

<Intermittent writing>
The intermittent writing operation will be described with reference to FIG. FIG. 4 is a timing chart showing the intermittent write operation.

  Multiple writing is performed on the electrophoretic display element 1 having a slow rewriting speed by using a TFT made of OSC having such a size that a sufficiently high electrical response speed can be obtained. At this time, the data is not completely written line by line, but is written by scanning multiple times at a speed sufficiently faster than the response speed of the electrophoretic display element 1 (usually 0.5 to 1 second). Thereby, it is possible to display such that the entire screen appears slowly.

  The screen data is written n times before the writing of the row data column of FIG. 4, that is, one screen is completed.

  In FIG. 4, one pulse represents writing for one frame (writing is performed n times for rewriting one screen). After performing n times of screen data writings 21 and 23, image quality holding writings 22 and 24 are performed one pulse at a time in an intermittent cycle with the same pulse width as one pulse of writings 21 and 23 and an appropriate interval 25.

  After the initial screen writing is written n times (21), image quality holding writing is appropriately performed at an appropriate interval 25 (22). When the next screen writing command is received, writing with new data is performed n times (23) for rewriting a new screen, and image quality holding writing is intermittently performed again at an appropriate interval 25 (24).

  FIG. 5 is a timing chart showing a state in which the same data for one screen is written at an appropriate intermittent time interval at a speed slower than the same writing speed as the multiple writing after n times of multiple writing on the electrophoretic display panel.

  In FIG. 5, one pulse represents writing for one frame (writing is performed n times for rewriting one screen). After performing n times of screen data writing 31, 33, write signals 32, 34 with the writing width changed intermittently are sent. At this time, adjustment is performed by an appropriate time interval 35 and an appropriate writing time width.

  After the initial screen writing is written n times (31), image quality retention writing is performed as appropriate (32). When the next screen writing command is received, writing with new data is performed n times (33) for new screen rewriting, and image quality holding writing is performed again intermittently (34).

  FIG. 6 is a timing chart showing a state in which the same data for one screen is written m times at an appropriate intermittent time interval at the same writing speed as that for multiple writing after n times of multiple writing on the electrophoretic display panel.

  In FIG. 6, one pulse indicates writing for one frame (writing is performed n times for rewriting one screen). After n times of screen data writing 41, 43, the same pulse width as one pulse at the time of writing 41, 43 intermittently, image quality of m pulses with appropriate m pulses and appropriate intervals 45 Retention writing 42 and 44 is performed.

  After the initial screen writing is written n times (41), image quality retention writing is appropriately performed (42). When the next screen writing command is received, writing with new data is performed n times (43) for rewriting a new screen, and image quality holding writing is performed again intermittently (44).

  As described above, as shown in FIGS. 4 to 6, by performing rewriting (intermittent scanning) at an appropriate interval 25, image quality can be maintained with a small current.

  FIG. 7 shows the relationship between the applied voltage of the electrophoretic display element and the accumulated charge. The horizontal axis indicates the applied voltage, and the vertical axis indicates the amount of charge [pC] injected and stored in the electrophoretic display element. The applied voltage is applied in the range of ± 16 volts. The relationship shown in the figure is that of 1 cycle at 2 Hz, 0.2 Hz, and 0.05 Hz.

  From FIG. 7, when the writing cycle becomes faster than the response time of the electrophoretic display element 1, the necessary amount of charge consumed rapidly per cycle increases and the power consumption increases. It can be seen that the amount of electric charge consumed is reduced when the voltage between the electrodes of the electrophoretic display element 1 is slowly increased.

  By controlling so that the division multiple writing is performed only when the number of times of rewriting is necessary only when the image itself changes, the display quality can be improved as compared with the control of slowly writing the screen corresponding to the selection line 1 and the selection line L. Differences can be reduced. That is, even if the on / off ratio is small, it is possible to prevent a difference in display quality between the first line and the last line. It should be noted that the time required for one scan is preferably a time during which a human does not feel the scan, that is, 1/10 second or less.

  The time required for charging the capacitor 8 between the electrodes 3 and 5 itself can be considerably faster than the time required for the charged particles of the electrophoretic element 1 to move. On the other hand, the movement of the charged particles of the electrophoretic element according to the electric field charged is completed due to the mechanical operation / movement, which is considerably slow. Therefore, in the meantime, other lines on the screen can be scanned and written.

  Also, if the period of the VC characteristic of the electrophoretic element 1 is to be charged in a time that is close to the response speed of the electrophoretic element 1, the area of the hysteresis curve increases and the amount of charge necessary for charging increases, so a large amount of current is consumed. The loss is large because it is necessary to flow (see FIG. 7). On the other hand, when the voltage is slowly increased and charged over 0.5 to 2 times the response speed of the electrophoretic element (about 0.5 to 1 second), not only the area of the hysteresis curve is reduced, The peak of the current that flows is reduced.

  Therefore, if the entire scanning line of the screen is not charged in a short time, but the entire screen is slowly charged at a speed about the response speed of the electrophoretic element, the display screen can be driven with low power.

  Also, there are three rewriting methods as shown in FIGS. 4 to 6 for maintaining the display image quality, and any of these methods can be performed by a slight amount of writing rather than the first n-time multiple writing. Can hold time data. In other words, since the battery has already been charged and only the amount due to slight leakage is corrected, the display screen can be held by driving with a very small current.

<Writing time, number of writing and reflectance>
FIG. 8 shows a change in the writing time (unit: msec) of data for one screen of the electrophoretic display element 1, the number of times of multiple writing, and a change in the reflectivity of the electrophoretic display element 1 with respect thereto (a change from black to white). Is a table showing the arrival rate (unit:%).

  FIG. 8 shows (1) the time required to write one screen for VGA (K × L = 640 × 480), (2) the number of screen writes, and (3) reflectance (black: 12%, white: 65%).

  From the figure, it can be seen that if one screen can be written in 50 milliseconds, the reflectivity reaches 64% by multiple writing about 10 times. Note that the data does not indicate the relationship between the electrical writing time and the reflectivity, and it takes about 0.5 to 1 second to obtain the ultimate reflectivity even if the data is actually written at the time shown here. .

  In order to sufficiently change the screen from black to white, it is necessary to perform multiple writing 100 times when the frame writing time is 20 ms, 10 times when the frame writing time is 50 ms, and twice when the frame writing time is 100 ms. Although it seems that 100 ms rewriting is possible with the total rewriting time per screen, the reflectivity still does not reach 65 when writing is completed.

  In either case, it takes about 0.5 seconds for the final reflectance to reach 65. In the case of the electrophoretic display element used in the experiment, it is appropriate to match the delay of the reflectance ratio of about 0.5 seconds. That is, in this experiment, it can be seen that it is appropriate to rewrite in a time of about 50 msec per screen. In this case, the cycle for sending one set of data in the K column is about 100 μsec. At this time, the selection line is selected, and one screen is completely written at L = 480.

<Decrease in reflectance with time>
FIG. 9 is a table showing the relationship between the leaving time after writing the electrophoretic display element 1 until it becomes white and the decrease in reflectance. Here, a decrease in white reflectance caused by the off-current of the TFT 7 from a sufficiently high reflectance ratio is confirmed in the standing time (unit: seconds).

  From this table, it can be seen that the reflectance decreases with leakage current of the organic TFT or the like as time passes. This represents the time taken for image quality degradation, and is data for determining the time interval of intermittent drive.

  The degree to which the reduction in reflectance is allowed depends on the definition, but the allowable reduction in reflectance here is about 59%. In the result of FIG. 9, 61% is obtained in 5 seconds and 57% in 10 seconds. Therefore, the leaving time corresponding to the allowable decrease in reflectance is about 5 seconds to 10 seconds, and more precisely about 5 seconds. .

The leakage current at this time is probably less than 10 ⁻¹¹ [C]. This is an amount of current that is possible even with a driving time of around 0.1 [μsec] by an organic TFT having a saturation current of 10 ⁻⁷ [A]. Accordingly, if a pulse of 50 msec (≈0.1 [μsec] × 480 lines) is sent once every 5 seconds with a slight margin, almost the initial image quality can be maintained.

<Driving method for multiple writing and image holding>
Next, with reference to FIG. 10, a driving method for multiple writing and image quality maintenance of the electrophoretic display element 1 will be described. FIG. 10 shows a flow of driving for multiple writing and image quality maintenance of the electrophoretic display element 1, and particularly shows a flow of performing n times of multiple writing and subsequent image quality maintenance writing in one time.

  First, the entire screen is initialized (step S1), and data for one screen is written (step S2). Next, it is determined whether or not the number of times of writing is n (step S3). If the number of writings is not n (S3 / No), the process returns to S2 to perform multiple writing.

  If the number of times of writing is n (S3 / Yes), it is determined whether there is next screen data (step S4). If there is next screen data (S4 / Yes), the process returns to S2 to write the next screen data, and the screen is rewritten.

  When there is no next screen data (S4 / No), it is determined whether or not to stop the display operation (step S5). If the display operation is to be stopped (S5 / Yes), the display is initialized and the process is exited (step S8).

  When the display operation is not stopped (S5 / No), it is confirmed whether or not the intermittent time has been reached (step S6). When the intermittent time has come (S6 / Yes), data for one screen is stored to maintain image quality. Write (step S7). In S7, here, the image quality holding data is written only once as shown in FIGS. And it returns to S4 again and the process which confirms the presence or absence of the next screen data is performed.

  FIG. 11 is a flowchart showing another method for driving the multiple writing and image quality maintenance of the electrophoretic display element 1. This flow employs a method of performing n multiple writings and subsequent image quality holding writings m times as shown in FIG.

  First, the entire screen is initialized (step S11), and data for one screen is written (step S12). Next, it is determined whether or not the number of times of writing is n (step S13). If the number of writes is not n (S13 / No), the process returns to S12 to perform multiple writing.

  If the number of times of writing is n (S13 / Yes), it is determined whether there is next screen data (step S14). If there is next screen data (S14 / Yes), the process returns to S2 to write the next screen data, and the screen is rewritten.

  If there is no next screen data (S14 / No), it is determined whether or not to stop the display operation (step S15). If the display operation is to be stopped (S15 / Yes), the display is initialized and the process is exited (step S19).

  If the display operation is not stopped (S15 / No), it is confirmed whether or not the intermittent time has been reached (step S16), and if the intermittent time is reached (S16 / Yes), data for one screen is stored to maintain image quality. Write (step S17). It is determined whether or not the number of times of writing for holding the image is m times (step S18). If the number has not reached m times (S18 / No), the process returns to S17 and the writing process is continued. . When it has reached m times (S18 / Yes), the process returns to S14 again, and processing for confirming the presence or absence of the next screen data is performed.

  In the flow of FIG. 10 and FIG. 11, the confirmation of the presence / absence of the next screen data (rewrite data) and the confirmation of the stop determination are performed in the same processing flow as the confirmation of whether or not the intermittent drive time has been reached. ing. By processing in this way, when there are various requests, except during rewriting to a new screen (this is because the screen has been completely rewritten), data for one screen It is possible to shift to the next operation with a delay of about the writing time.

  Regarding the adjustment of the screen, when there has been a change of multiple writing n times, the process returns to the display initialization of S1 (S11) and resumes. When the intermittent time is changed, the result of changing the intermittent time is reflected after the data for the next one screen is written.

  When the number of writings m times for maintaining image quality is changed to m ′ times, the writing number is changed to m ′ times from the next rewriting. Similarly, when the writing time for maintaining the image quality is changed, it may be reflected from the next timing. These take into account that the intermittent time is as long as several seconds, and the change result may not be reflected smoothly depending on how the change is reflected.

  In the driving method of the electrophoretic display element 1 of the present embodiment, when displaying content different from the previous screen, display data for one screen is repeatedly written in a time shorter than the time required to rewrite one screen. Here, 21 and 23 in FIG. 4, 31 and 33 in FIG. 5, 41 and 43 in FIG. 6, a loop for writing data for one screen in FIG. 10 n times, and a loop for writing data for one screen in FIG. 11 n times With respect to, the display data for one screen is repeatedly written in a time shorter than the time required for rewriting one screen.

  By controlling in this way, the ON / OFF ratio cannot be sufficiently obtained, so that the display cannot be maintained for a sufficiently long time just by turning off the TFT. Since writing scanning is performed for the same display on the regularly displayed screen, the display quality of the screen can be maintained.

  In the driving method of the electrophoretic display element 1 according to the present embodiment, intermittent scanning is performed after multiple writing necessary for writing data for one screen. By controlling in this way, it is possible to reproduce only the deteriorated image quality on the screen on which display writing has been completed by writing for maintaining the image quality. In particular, since the same processing as that for writing data for one screen at the time of multiple writing is performed, the driving hardware of the electrophoretic display element 1 is simplified.

  In this intermittent scanning, a method of performing writing once (FIGS. 4, 5, and 10) or a method of performing writing a plurality of times (FIGS. 6 and 11) can be employed. In addition, a method (FIG. 5) in which the scanning speed necessary for scanning one screen is changed can be adopted.

  Further, in the method for driving the electrophoretic display element 1 of the present embodiment, the “intermittent drive time confirmation step” and the “rewrite data presence / absence confirmation step” are included in the same processing flow.

  Since intermittent drive takes a drive time on the order of several seconds, if a request to rewrite the display screen occurs during the “intermittent drive time confirmation” operation, it is not possible to immediately exit from the intermittent drive confirmation and start rewriting the screen. Thus, the intermittent driving time confirmation step and the rewrite data presence / absence confirmation step are performed in the same processing flow.

  Thereby, when rewriting data of the electrophoretic display element 1 is generated, it is possible to immediately exit from the intermittent driving confirmation and rewrite the display screen.

<Second Embodiment>
A second embodiment of the driving method of the electrophoretic display element 1 of the present invention will be described.

  In the first embodiment, if the period for holding and writing the image quality is fixed and the number of writings and the writing speed are constant, the writing for holding is unnecessarily performed when the performance of the electrophoretic element 1 changes. Driving may occur, or the rewriting amount (number of times) may be insufficient.

  Therefore, in this embodiment, the method for driving the electrophoretic display element 1 according to the first embodiment includes a step of changing an intermittent period necessary for writing data for one screen.

  Accordingly, it is possible to set the image quality retention capability by changing the intermittent period. Further, it is possible to set the image quality retention capability of the electrophoretic display element 1 in both the writing time and the intermittent period.

  In addition, you may make it have the process of changing the scanning speed required in order to scan one screen instead of changing an intermittent period. Also with this configuration, the image quality retention capability of the electrophoretic display element 1 can be set.

<Third Embodiment>
A third embodiment of the present invention will be described. The driving method of the electrophoretic display element 1 according to the present embodiment includes a step of setting the number of scans necessary for scanning one screen in the first and second embodiments.

  Accordingly, the image quality retention capability of the electrophoretic display panel can be set by setting the number of scans of data for one screen using the same writing procedure as that for multiple writing.

<Additional notes>
The above-described embodiment is merely an example of a preferred embodiment of the present invention, and is not intended to limit the embodiment of the present invention. Therefore, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention.

  The present invention relates to various devices having an electronic display such as an electronic book, an electronic screen, an electronic dictionary, and electronic paper, and in particular, a device for displaying a still image such as a line drawing or a document. It can be used for electronic devices with functions.

It is a side view of an electrophoretic display element. It is a figure which shows the circuit structure of an electrophoretic display element. It is a figure for demonstrating the electrical signal at the time of writing the data for 1 screen. It is a timing chart which shows the operation | movement of intermittent writing. It is a timing chart which shows the operation | movement of intermittent writing. It is a timing chart which shows the operation | movement of intermittent writing. It is a table | surface which shows the relationship between the applied voltage of an electrophoretic display element, and the accumulated electric charge. It is a table | surface of the write time of the data for 1 screen, the multiple writing frequency | count, and the arrival rate of the change of the reflectance of an electrophoretic display element. It is a table | surface which shows the relationship between the leaving time of an electrophoretic display element, and the fall of a reflectance. It is a flowchart which shows the drive of multiple writing of an electrophoretic display element and image quality maintenance. It is a flowchart which shows the drive of multiple writing of an electrophoretic display element and image quality maintenance.

Explanation of symbols

1 Electrophoretic display element 7 TFT
9 Data line 10 Selection line

Claims (9)

The drain or source electrode of the thin film transistor manufactured for each pixel is a data line for sending display contents in the sub-scanning direction, and the gate of the thin film transistor is a selection line for selecting one writing display from the scanning direction, On the two substrates, the data lines and the selection lines are arranged in a matrix connected vertically and horizontally by lead electrodes to an external circuit, and the pixel electrode and the common electrode constitute a pixel having a capacitance between them. In an electrophoretic display element driving method for driving an electrophoretic display element that is disposed in a microcapsule in which an electrophoretic dispersion material is sealed between the electrodes,
A method for driving an electrophoretic display element, wherein when displaying contents different from a previous screen, data for one screen is repeatedly written in a time shorter than a time required to rewrite one screen.   2. The method for driving an electrophoretic display element according to claim 1, wherein writing is performed by intermittent scanning after the multiple writing necessary for writing data for one screen.   3. The method for driving an electrophoretic display element according to claim 2, wherein the writing by the intermittent scanning is performed once.   3. The driving method of an electrophoretic display element according to claim 2, wherein the intermittent scanning is performed a plurality of times.   5. The method for driving an electrophoretic display element according to claim 3, wherein writing is performed by the intermittent scanning while changing a scanning speed.   6. The method for driving an electrophoretic display element according to claim 2, further comprising a step of changing an intermittent period necessary for writing data for one screen.   The method for driving an electrophoretic display element according to claim 1, further comprising a step of changing a scanning speed for one screen.   8. The method for driving an electrophoretic display element according to claim 1, further comprising a step of setting the number of times of scanning one screen.   9. The method for driving an electrophoretic display element according to claim 2, wherein confirmation of intermittent drive time and confirmation of presence / absence of rewrite data are performed in the same processing step.

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