TWI395178B - Writing apparatus for an rewritable display medium - Google Patents

Description

Rewritable display medium writing device

The invention relates to a writing device for a rewritable display medium, in particular to a writing device with a pixel gray scale feedback mechanism for performing a write operation of a rewritable display medium.

Flat Panel Display is widely used in computer screens, mobile phones, personal digital assistants (PDAs), flat-panel TVs and other electronic products because of its slimness, power saving and low radiation. In recent years, display manufacturers have developed electrophoretic display devices (also known as electronic paper) to further provide a lighter, thinner, more portable and portable display. FIG. 1 is a schematic structural view of a conventional electrophoretic display device. As shown in FIG. 1, the electrophoretic display device 100 includes a gate driving circuit 110, a data driving circuit 120, a plurality of thin film transistors 130, and a plurality of electrophoresis capacitors 140. The gate drive circuit 110 is used to provide a plurality of gate signals, and the data drive circuit 120 is used to provide a plurality of data signals. Each electrophoresis capacitor 140 includes an electrophoretic medium and a plurality of charged particles suspended in the electrophoretic medium, wherein the color of the plurality of electric particles is different from the color of the electrophoretic medium. The thin film transistor 130 controls the writing operation of the data signal according to the gate signal, and changes the floating position of the plurality of charged particles in the electrophoretic medium according to the voltage difference between the two ends of the electrophoretic medium, thereby being between the plurality of charged particles and the electrophoretic medium. The color contrast is used to show the desired gray scale.

However, since both the gate driving circuit 110 and the data driving circuit 120 are integrated in the electrophoretic display device 100, the cost is high and high softness cannot be provided, that is, it is quite limited in application. Further, if the electrophoretic display device 100 is deformed, the image displayed thereon is also distorted, thereby reducing the display accuracy.

According to an embodiment of the invention, a writing device is disclosed for performing a writing operation on a rewritable display medium. Such a writing device includes a driving unit, a pixel array unit, a light emitting unit, and a light sensing unit. The drive unit is used to provide complex data signals and complex gate signals. The pixel array unit is electrically connected to the driving unit to receive the plurality of data signals and the plurality of gate signals for writing the plurality of data signals to the rewritable display medium according to the plurality of gate signals. The pixel array unit includes a plurality of pixel units, each pixel unit including a pixel transistor and a pixel electrode. The pixel transistor includes a first end, a second end and a gate terminal, wherein the first end is electrically connected to the driving unit to receive the corresponding data signal, and the gate terminal is electrically connected to the driving unit to receive the corresponding gate signal. The pixel electrode is electrically connected to the second end of the pixel transistor. The illumination unit is used to provide a light source that illuminates the rewritable display medium through the pixel array unit. The light sensing component is disposed in the pixel unit for sensing the reflected light of the rewritable display medium to generate a light sensing signal. Under the operation of the light emitting unit, the driving unit can be further configured to adjust the corresponding data signal according to the light sensing signal.

According to an embodiment of the invention, a writing device is further provided for performing a writing operation on a rewritable display medium to display a picture. Such a writing device includes a driving unit, a pixel array unit, a light emitting unit, and a plurality of scrolling units. The drive unit is used to provide a complex data signal. The pixel array unit is electrically connected to the driving unit to receive the plurality of data signals, and is used for writing the plurality of data signals into the rewritable display medium to display the picture. The pixel array unit includes a plurality of pixel units, each pixel unit including a pixel electrode and a light sensing element. The pixel electrode is electrically connected to the driving unit to receive the corresponding data signal. The light sensing element is embedded in the pixel electrode for sensing the reflected light of the rewritable display medium to generate a photosensitive signal. The illumination unit is used to provide a light source that illuminates the rewritable display medium through the pixel array unit. The complex scrolling unit is used to drive a rewritable display medium. Under the operation of the light emitting unit, the driving unit can be further configured to adjust the corresponding data signal according to the light sensing signal.

In the following, the rewritable display medium writing device according to the present invention is described in detail with reference to the accompanying drawings, but the embodiments are not intended to limit the scope of the invention.

Fig. 2 is a cross-sectional view showing the writing device of the first embodiment of the present invention. As shown in FIG. 2, the writing device 210 is used to perform a writing operation on the rewritable display medium 280, wherein the rewritable display medium 280 is a display medium based on a voltage driving mode, such as an electrophoretic display device (Electrophoretic Display) ; EPD), Liquid Powder Display (LPD), and Cholesteric Liquid Crystal Display (Ch-LCD). For convenience of explanation, an electrophoretic display device is exemplified as a rewritable display medium 280 having a plurality of charged particles 281, an electrophoretic medium 282, a transparent substrate 284, and an opposite substrate 283. The writing device 210 includes a pixel array unit 220, a light emitting unit 230, a common electrode 240, a driving unit 250, and a plurality of light sensing elements 223. The driving unit 250 is configured to convert the plurality of image input signals into a plurality of data signals. In addition, the driving unit 250 is additionally used to provide the common voltage Vcom and the complex gate signal. The common electrode 240 is electrically connected to the driving unit 250 for receiving the common voltage Vcom. The pixel array unit 220 is electrically connected to the driving unit 250 for receiving the plurality of data signals and the plurality of gate signals for writing the plurality of data signals to the rewritable display medium 280 according to the common gate voltage of the common electrode 240 and the common voltage Vcom. To display the picture. The illumination unit 230 is operative to provide a light source required to perform a pixel gray scale feedback procedure in the write operation of the rewritable display medium 280.

The pixel array unit 220 includes a plurality of pixel units 225 and an array substrate 224. The complex pixel unit 225 is disposed on the array substrate 224. Each pixel unit 225 includes a pixel transistor 221 and a pixel electrode 222. The pixel transistor 221 is a Thin Film Transistor or a Field Effect Transistor. The pixel transistor 221 is configured to feed the corresponding data signal to the pixel electrode 222 according to the corresponding gate signal, and the writing operation of the rewritable display medium 280 is performed according to the common voltage Vcom of the common electrode 240. Each of the light sensing elements 223 is corresponding to the pixel unit 225 for sensing the light emitted by the light emitting unit 230 to illuminate the rewritable display medium 280 to generate a light sensing signal, and the driving unit 250 is further configured to adjust the corresponding data according to the light sensing signal. Signal.

Fig. 3 is a circuit diagram showing the structure of the writing device shown in Fig. 2. As shown in FIG. 3, in the circuit configuration of the writing device 210, the complex gate line 226 is used to transmit the plurality of gate signals provided by the driving unit 250, and the plurality of data lines 227 are used to transmit the driving unit 250. Multiple data signals. Each pixel transistor 221 includes a first end, a second end, and a gate terminal, wherein the first end is electrically connected to the corresponding data line 227 to receive the corresponding data signal, and the gate terminal is electrically connected to the corresponding gate line 226 to receive the corresponding gate. The second signal is electrically connected to the corresponding pixel electrode 222.

The driving unit 250 includes a data driving circuit 251, a gate driving circuit 252, a feedback processing circuit 253, and a memory 258. The gate drive circuit 252 is electrically coupled to the plurality of gate lines 226 for providing a plurality of gate signals to the plurality of gate lines 226. The data driving circuit 251 is electrically connected to the plurality of data lines 227 for converting the plurality of image input signals into the plurality of data signals and feeding them to the plurality of data lines 227. The feedback processing circuit 253 is electrically connected to the data driving circuit 251 and the plurality of optical sensing elements 223 for providing a plurality of feedback signals to the data driving circuit 251 according to the plurality of photosensitive signals generated by the plurality of optical sensing elements 223, and the data driving circuit 251 is further Adjust the complex data signal according to the complex feedback signal. That is, the data driving circuit 251 can cooperate with the feedback processing circuit 253 to provide a pixel gray scale feedback mechanism for compensating for write errors caused by uneven gaps between the rewritable display medium 280 and the writing device 210, or to compensate Write errors due to factors such as variations in component characteristics, temperature changes, etc. The memory 258 is a nonvolatile memory (NVM) or a volatile memory. The memory 258 is electrically connected to the data driving circuit 251 and the plurality of light sensing elements 223 for storing the plurality of photosensitive signals generated by the plurality of light sensing elements 223, and the data driving circuit 251 can be additionally used to store the plurality of photosensitive signals stored in the memory 258. The signal is converted into a complex data signal and fed to the pixel array unit 220. In other words, the writing device 210 can provide a screen copy function of a rewritable display medium (or a plain paper) to another rewritable display medium. Note that in the writing device 210 that does not include the screen reproduction function, the memory 258 can be omitted.

As can be seen from the above, the rewritable display medium 280 does not contain any writing mechanism, thereby reducing cost and providing high softness, making it more flexible in application. In addition, even if the rewritable display medium 280 is deformed, each pixel area of the picture to be written is defined by the corresponding pixel unit 225 of the pixel array unit 220 of the writing device 210, and the feedback processing circuit 253 is The pixel gray scale feedback mechanism provided by the data driving circuit 251 can compensate for the writing error caused by the uneven gap between the rewritable display medium 280 and the writing device 210, or compensate for the writing error caused by other factors, so The written picture has high display accuracy.

Fig. 4 is a cross-sectional view showing the writing device of the second embodiment of the present invention. As shown in FIG. 4, the writing device 310 is used to perform a writing operation on the rewritable display medium 380. The rewritable display medium 380 having the electrophoretic display device as an embodiment has a plurality of charged particles 381 and an electrophoretic medium 382. The transparent substrate 384, the counter substrate 383, and the common electrode 388. When the write operation of the rewritable display medium 380 is performed, the common electrode 388 is electrically connected to the writing device 310 to receive the common voltage Vcom, and the common electrode 388 does not need to be electrically connected to the writing device 310. . The writing device 310 includes a pixel array unit 320, a light emitting unit 330, a driving unit 350, and a plurality of light sensing elements 323. Please note that since the rewritable display medium 380 already includes the common electrode 388, the writing device 310 does not need to include the common electrode, and the driving unit 350 feeds the common voltage Vcom to the rewritable display during the writing operation. The common electrode 388 of the medium 380. The structure and function of the pixel array unit 320, the light-emitting unit 330, the light-sensing element 323, and the driving unit 350 are similar to those of the pixel array unit 220, the light-emitting unit 230, and the light-sensing element shown in FIGS. 2 and 3. 223 and the driving unit 250 will not be described again.

Figure 5 is a cross-sectional view showing a writing device of a third embodiment of the present invention. As shown in FIG. 5, the writing device 510 is used to perform a writing operation on the rewritable display medium 580. The rewritable display medium 580 having the electrophoretic display device as an embodiment has a plurality of charged particles 581 and an electrophoretic medium 582. The transparent substrate 584 and the opposite substrate 583. The writing device 510 includes a printing unit 515, a common electrode 540, an erasing unit 570, and a plurality of scrolling units 595. The printing unit 515 includes a pixel array unit 520, a light emitting unit 530, and a driving unit 550. The plurality of scroll units 595 include a plurality of rollers and/or a plurality of rollers. The driving unit 550 is configured to convert the complex image input signal into a plurality of data signals. In addition, the driving unit 550 is additionally used to provide the common voltage Vcom. The common electrode 540 may be a drum electrode electrically connected to the driving unit 550 to receive the common voltage Vcom. The pixel array unit 520 is electrically connected to the driving unit 550 to receive the complex data signal for cooperating with the common voltage Vcom of the common electrode 540, and sequentially writing the plurality of data signals into the rewritable display medium in at least one column of the write mode. 580 to display the picture. That is, in the process of the complex scrolling unit 595 driving the rewritable display medium 580, the pixel array unit 520 sequentially writes the plurality of data signals into the rewritable display medium 580 in a write mode of at least one column at a time. Display the screen. The illumination unit 530 is for providing a light source required to perform a pixel gray scale feedback procedure in the write operation of the rewritable display medium 580.

The erasing unit 570 is disposed on one side of the printing unit 515 for erasing a previous picture of the rewritable display medium 580, that is, erasing the column to be written before the printing unit 515 performs each column writing operation. The data signal of the previous screen is used to speed up the efficiency of writing operations. The erase unit 570 includes an erase voltage supply unit 572 and two erase electrodes 575, wherein the erase electrode 575 may be a drum electrode. The erase voltage supply unit 572 is for providing an erase voltage required to erase a previous picture of the rewritable display medium 580. The erase electrode 575 is electrically connected to the erase voltage supply unit 572 for receiving the erase voltage to perform an erase operation on the rewritable display medium 580. In another embodiment, the erase unit 570 includes only the erase voltage supply unit 572 and the single erase electrode 575, and the erase voltage supply unit 572 has the erase electrode function. Please note that the printing unit 515 can have the erase operation function, that is, the erasing unit 570 can be omitted to save the cost of the writing device 510.

The pixel array unit 520 includes a complex pixel unit 525. Each pixel unit 525 includes a pixel electrode 522 and a light sensing element 523. The pixel electrode 222 is configured to receive a corresponding data signal, and the writing operation of the rewritable display medium 580 is performed in accordance with the common voltage Vcom of the common electrode 540. The light sensing element 523 is embedded in the pixel electrode 222 for sensing the light emitted by the light emitting unit 530 to illuminate the rewritable display medium 580 to generate a light sensing signal, and the driving unit 550 is further configured to adjust the corresponding data signal according to the light sensing signal. .

Fig. 6 is a circuit diagram showing the structure of the printing unit shown in Fig. 5. As shown in FIG. 6, in the circuit configuration of the printing unit 515, the plurality of data lines 527 are used to transmit the complex data signals supplied from the driving unit 550 to the plurality of pixel electrodes 522. Please note that in the embodiment of FIG. 6, the pixel array unit 520 includes only one column of pixel units 525, so the pixel array unit 520 sequentially writes the complex data signals to the rewritable in a write mode of one column at a time. The medium 580 is displayed to display a picture. In another embodiment, the pixel array unit 520 can include a plurality of column pixel units 525, so the pixel array unit 520 sequentially writes the complex data signals into the rewritable display medium in the write mode of each complex column. 580 to display the picture. The driving unit 550 includes a data driving circuit 551, a feedback processing circuit 553, and a memory 558. The data driving circuit 551 is electrically connected to the plurality of data lines 527 for converting the plurality of image input signals into the plurality of data signals and feeding them to the plurality of data lines 527. The feedback processing circuit 553 is electrically connected to the data driving circuit 551 and the plurality of optical sensing elements 523 for providing a plurality of feedback signals to the data driving circuit 551 according to the plurality of photosensitive signals generated by the plurality of optical sensing elements 523, and the data driving circuit 551 is further Adjust the complex data signal according to the complex feedback signal. That is, the data driving circuit 551 can cooperate with the feedback processing circuit 553 to provide a pixel gray scale feedback mechanism for compensating for write errors caused by uneven gaps between the rewritable display medium 580 and the printing unit 515, or to compensate Write errors due to factors such as variations in component characteristics, temperature changes, etc. Memory 558 is a non-volatile memory or a volatile memory. The memory 558 is electrically connected to the data driving circuit 551 and the plurality of light sensing elements 523 for storing the plurality of light sensing signals generated by the plurality of light sensing elements 523, and the data driving circuit 551 can be additionally used to store the plurality of photosensitive signals stored in the memory 558. The signal is converted into a complex data signal and fed to the pixel array unit 520. In other words, the writing device 510 can provide a remake of the rewritable display medium (or a plain paper) to another rewritable display medium. Note that in the writing device 510 that does not include the screen reproduction function, the memory 558 can be omitted.

As can be seen from the above, the rewritable display medium 580 does not contain any writing mechanism, thereby reducing cost and providing high softness, making it more flexible in application. In addition, even if the rewritable display medium 580 is deformed, each pixel area of the picture to be written is defined by the corresponding pixel unit 525 of the pixel array unit 520 of the writing device 510, and the feedback processing circuit 553 and The pixel gray scale feedback mechanism provided by the data driving circuit 551 can compensate for the writing error caused by the uneven gap between the rewritable display medium 580 and the printing unit 515, or compensate for the writing error caused by other factors, so The written picture has high display accuracy.

Figure 7 is a cross-sectional view showing a writing device of a fourth embodiment of the present invention. As shown in FIG. 7, the writing device 610 is used to perform a writing operation on the rewritable display medium 680. The rewritable display medium 680 having the electrophoretic display device as an embodiment has a plurality of charged particles 681 and an electrophoretic medium 682. The transparent substrate 684, the opposite substrate 683, and the common electrode 688. When the write operation of the rewritable display medium 680 is performed, the common electrode 688 is electrically connected to the writing device 610 to receive the common voltage Vcom, and the common electrode 688 does not need to be electrically connected to the writing device 610. . The writing device 610 includes a printing unit 615, an erasing unit 570, and a plurality of scrolling units 695, wherein the structure and function of the erasing unit 570 operate as described above. The plurality of scrolling units 695 include a plurality of rollers and/or a plurality of rollers. The printing unit 615 includes a pixel array unit 620, a light emitting unit 630, and a driving unit 650. Please note that since the rewritable display medium 680 already includes the common electrode 688, the writing device 610 does not need to include the common electrode, and the other side of the rewritable display medium 680 corresponding to the printing unit 615 is set to scroll. Unit 695. The driving unit 650 is configured to feed the common voltage Vcom to the common electrode 688 of the rewritable display medium 680 during the writing process of the rewritable display medium 680. The structure and function of the pixel array unit 620, the light-emitting unit 630, and the driving unit 650 are similar to those of the pixel array unit 520, the light-emitting unit 530, and the driving unit 550 shown in FIG.

In summary, by using the writing device of the present invention to perform a write operation, the rewritable display medium does not need to have any built-in writing mechanism, thereby significantly reducing the cost of the rewritable display medium and providing high The rewritable display medium of softness makes it more flexible in application. In addition, even if the rewritable display medium is deformed, each pixel area of the picture to be written is defined by the corresponding pixel unit of the pixel array unit of the writing device of the present invention, and the feedback processing of the writing device of the present invention is performed. The pixel gray scale feedback mechanism provided by the circuit and the data driving circuit can compensate the writing error caused by the uneven gap between the rewritable display medium and the writing device, or compensate the writing error caused by other factors, so it is written The incoming image has a high display accuracy.

While the present invention has been described above by way of example, it is not intended to limit the invention, and the invention may be modified and modified without departing from the spirit and scope of the invention. Therefore, the scope of the invention is defined by the scope of the appended claims.

100. . . Electrophoretic display device

110, 252. . . Gate drive circuit

120, 251, 551. . . Data drive circuit

130. . . Thin film transistor

140. . . Electrophoresis capacitor

210, 310, 510, 610. . . Write device

220, 320, 520, 620. . . Pixel array unit

221. . . Pixel crystal

222, 522. . . Pixel electrode

223, 323, 523. . . Light sensing element

224. . . Array substrate

225, 525. . . Pixel unit

226. . . Gate line

227, 527. . . Data line

230, 330, 530, 630. . . Light unit

240, 388, 540, 688. . . Common electrode

250, 350, 550, 650. . . Drive unit

253, 553. . . Feedback processing circuit

258, 558. . . Memory

280, 380, 580, 680. . . Rewritable display medium

281, 381, 581, 681. . . Charged particle

282, 382, 582, 682. . . Electrophoretic medium

283, 383, 583, 683. . . Counter substrate

284, 384, 584, 684. . . Transparent substrate

515, 615. . . Print unit

570. . . Erase unit

572. . . Erase voltage supply unit

575. . . Erase electrode

595, 695. . . Rolling unit

Vcom. . . Shared voltage

FIG. 1 is a schematic structural view of a conventional electrophoretic display device.

Fig. 2 is a cross-sectional view showing the writing device of the first embodiment of the present invention.

Fig. 3 is a circuit diagram showing the structure of the writing device shown in Fig. 2.

Fig. 4 is a cross-sectional view showing the writing device of the second embodiment of the present invention.

Figure 5 is a cross-sectional view showing a writing device of a third embodiment of the present invention.

Fig. 6 is a circuit diagram showing the structure of the printing unit shown in Fig. 5.

Figure 7 is a cross-sectional view showing a writing device of a fourth embodiment of the present invention.

210. . . Write device

220. . . Pixel array unit

221. . . Pixel crystal

222. . . Pixel electrode

223. . . Light sensing element

224. . . Array substrate

225. . . Pixel unit

230. . . Light unit

240. . . Common electrode

250. . . Drive unit

280. . . Rewritable display medium

281. . . Charged particle

282. . . Electrophoretic medium

283. . . Counter substrate

284. . . Transparent substrate

Vcom. . . Shared voltage

Claims (17)

A writing device for performing a writing operation on a rewritable display medium, the writing device comprising: a driving unit for providing a plurality of data signals and a plurality of gate signals; a pixel array unit electrically connected The driving unit receives the data signals and the gate signals for writing the data signals to the rewritable display medium according to the gate signals, wherein the pixel array unit comprises a plurality of pixel units, each The pixel unit includes a first pixel, a second terminal, and a gate terminal, wherein the first terminal is electrically connected to the driving unit to receive the data signal corresponding to one of the data signals. The gate is electrically connected to the driving unit to receive one of the gate signals corresponding to the gate signal; and a pixel electrode electrically connected to the second end of the pixel transistor; a light emitting unit is configured to provide a a light source that illuminates the rewritable display medium through the pixel array unit; and a light sensing element disposed in the pixel unit for sensing reflected light of the rewritable display medium Generating a signal the photoreceptor, wherein the drive unit is further used to adjust the basis of the data signals corresponding to the photosensitive signal. The writing device of claim 1, wherein the driving unit is further configured to provide a common voltage, the writing device further comprising: a common electrode electrically connected to the driving unit to receive the common voltage. The writing device of claim 1, wherein the rewritable display medium comprises a common electrode, and the driving unit is further configured to provide a common voltage to be fed to the common electrode of the rewritable display medium. The writing device of claim 1, wherein the driving unit comprises: a gate driving circuit electrically connected to the pixel array unit for providing the gate signals; and a data driving circuit electrically connected to the gate a pixel array unit for converting a plurality of image input signals into the data signals; and a feedback processing circuit electrically connected to the data driving circuit and the light sensing element for providing a feedback signal according to the light sensing signal And entering the data driving circuit; wherein the data driving circuit adjusts the corresponding data signal according to the feedback signal. The writing device of claim 4, wherein the driving unit further comprises: a memory electrically connected to the data driving circuit and the light sensing element for storing the photosensitive signal; wherein the memory system is a non-volatile Sexual memory or a volatile memory. The writing device of claim 5, wherein the data driving circuit is further configured to convert the plurality of photosensitive signals stored in the memory into the data elements to be fed to the pixel array unit, so as to The copy display medium performs a write operation. A writing device for performing a writing operation on a rewritable display medium to display a picture, the writing device comprising: a driving unit for providing a plurality of data signals; a pixel array unit electrically connected to the The driving unit receives the data signals for writing the data signals to the rewritable display medium, and displaying the picture according to the picture, the pixel array unit comprises a plurality of pixel units, each pixel unit comprising: a pixel electrode electrically connected to the driving unit to receive a data signal corresponding to one of the data signals; and a light sensing element embedded in the pixel electrode for sensing the reflected light of the rewritable display medium to generate a light sensing unit; a light emitting unit for providing a light source, the light source is irradiated to the rewritable display medium through the pixel array unit; and a plurality of scrolling units for driving the rewritable display medium; wherein the driving The unit is further configured to adjust the corresponding data signal according to the light sensing signal. The writing device of claim 7, wherein the driving unit is further configured to provide a common voltage, the writing device further comprising: a common electrode electrically connected to the driving unit to receive the common voltage. The writing device of claim 8, wherein the common electrode is a drum electrode. The writing device of claim 7, wherein the rewritable display medium comprises a common electrode, and the driving unit is further configured to provide a common voltage to be fed to the common electrode of the rewritable display medium. The writing device of claim 7, wherein the driving unit comprises: a data driving circuit electrically connected to the pixel array unit for converting the plurality of image input signals into the data signals; and a feedback processing circuit And electrically connected to the data driving circuit and the light sensing component for feeding a feedback signal to the data driving circuit according to the light sensing signal; wherein the data driving circuit adjusts the corresponding data signal according to the feedback signal. The writing device of claim 11, wherein the driving unit further comprises: a memory electrically connected to the data driving circuit and the light sensing element for storing the photosensitive signal; wherein the memory system is a non-volatile Sexual memory or a volatile memory. The writing device of claim 12, wherein the data driving circuit is further configured to convert the plurality of photosensitive signals stored in the memory into the data elements to be fed to the pixel array unit, so as to The copy display medium performs a write operation. The writing device of claim 7, further comprising: an erasing unit disposed on one side of the pixel array unit for erasing a previous picture of the rewritable display medium. The writing device of claim 14, wherein the erasing unit comprises: an erasing voltage providing unit for providing at least one erasing voltage required for erasing a picture before the rewritable display medium; and at least one erasing The electrode is electrically connected to the erase voltage supply unit for receiving the at least one erase voltage. The writing device of claim 15, wherein the at least one erasing electrode is a drum electrode. The writing device of claim 7, wherein the rolling units comprise a plurality of rollers and/or a plurality of rollers.