JP2007175945A - Rewritable printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To lengthen the life of a display medium by preventing an erasing speed from decreasing and eliminating a coagulation phenomenon. <P>SOLUTION: In the rewritable printer 1-1, an erasing head 31 is composed of a conductive charged roller 311 to apply voltage by contacting a rewritable paper 100 and a transfer roller 312 arranged oppositely to the charged roller 311 and pinching and transferring the rewritable paper 100, and the diameter R<SB>1</SB>of the charged roller 311 is made relatively larger than the diameter R<SB>2</SB>of the transfer roller 312. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electric field display type rewritable printer that rewrites a display medium by electric field action.

  For example, as a rewritable electric field display type rewritable printer, the following patent document discloses an electronic paper printer. This printer includes a drawing head for drawing a display pattern on an electrophoretic electronic paper, an erasing head for erasing a display pattern drawn on the electronic paper, a driving mechanism for rotating the drawing head and the erasing head, and an electronic paper. And a transport mechanism for transporting. The drawing head is composed of a pair of drums that are rotatably supported, and the erasing head is also composed of a pair of drums that are also rotatably supported. The diameter of the drum of the drawing head and the diameter of the drum of the erasing head Are all set identically.

  On the other hand, electrophoretic electronic paper is configured by applying an electronic ink layer in which a plurality of microcapsules are dispersed in a transparent binder onto paper. The microcapsule is filled with a liquid colored in blue, and white charged particles having a negative charge are dispersed in the liquid.

  When the display pattern of the electronic paper is rewritten by the printer, the drawing mechanism and the drum of the erasing head are both driven to rotate by the driving mechanism, and the electronic paper is conveyed by the conveying mechanism and passed through the erasing head and the drawing head in this order. At this time, the erasing head applies a positive voltage from the drum to the electronic ink layer of the electronic paper passing between the drums, and draws the negatively charged white charged particles dispersed in the microcapsules, so that the color of the charged particles is displayed on the display surface. The white color is displayed and erased. On the other hand, in the drawing head, a negative voltage is applied from the drum to the electronic ink layer of the electronic paper passing between the drums, and the negatively charged white charged particles dispersed in the microcapsules are repelled, thereby causing a liquid on the display surface. The display pattern is drawn by displaying the color blue.

JP 2000-127478 A

  A conventional rewritable printer, like the above-described electronic paper printer, writes after erasure when rewriting on a display medium, and therefore cannot be accurately rewritten if erasure is incomplete. Depending on the display medium, if the time for applying the voltage at the time of erasing is short, the charged particles cannot move and characters or images to be erased remain, so it takes time to secure enough time to apply the voltage. This has led to a decrease in the erasing speed, which has become a factor of delaying the time required for rewriting.

  On the other hand, in order to prevent a decrease in erasing speed, a method of increasing the voltage applied at the time of erasing can be considered. However, when a high voltage is applied, a phenomenon in which charged particles stick to each other to form larger particles, a so-called aggregation phenomenon, may occur. When this agglomeration phenomenon occurs, the charged particles do not move even when a voltage is applied, and thus erasing and writing cannot be performed. For this reason, there is a problem that the number of rewrites to the display medium is reduced, that is, the life of the display medium is shortened.

  Note that such problems are not limited to the exemplified microcapsule type electrophoretic display medium, but horizontal or vertical electrophoretic methods, particle rotation methods using spherical twisting balls or cylindrical twisting balls, or charged toners or electronic powders. The same can occur in other electric field display type display media such as a particle movement type by fluid.

  The present invention has been made in order to solve the above-described problem. In an electric field display type rewritable printer that rewrites a display medium by an electric field effect, the length of the display medium is prevented by preventing a decrease in erasing speed and eliminating an agglomeration phenomenon. An object of the present invention is to provide a rewritable printer capable of extending the service life.

  In order to achieve the above object, the present invention is an electric field display type rewritable printer that rewrites a display medium by an electric field effect, and a display surface of the display medium is applied by applying a voltage in contact with the display medium. And an erasing head for erasing the written display, and the erasing head includes means for expanding a contact area with the display surface of the display medium.

  As means for enlarging the contact area, the following configuration can be considered.

  (1) The erasing head includes a conductive charging roller that is in contact with the display surface of the display medium, and a conveying roller that is disposed opposite to the charging roller and conveys the display medium, and conveys the diameter of the charging roller. Set relatively larger than the roller diameter of the roller.

  (2) The erasing head includes a conductive charging roller that is in contact with the display surface of the display medium, and a conveying roller that is disposed opposite to the charging roller and conveys the display medium. The charging roller is made of a soft elastic material. Constitute. In this configuration, a charging roller in which a conductive material is kneaded with a rubber roller can be used. The charging roller preferably has a rubber hardness of 60 degrees or less as defined in JIS-K6253.

  (3) The erasing head is transported in contact with the display surface of the display medium, the conductive charging roller that applies a voltage by rotating the conductive belt, and the display medium is conveyed opposite to the charging roller. And a conveying roller to be configured.

  (4) The erasing head is opened along a conductive belt that contacts the display surface of the display medium, a conductive charging roller that applies a voltage by rotating the conductive belt, and a conveyance direction of the conductive belt. And a suction mechanism for sucking air from the suction hole to the inside of the belt.

  Here, in the configurations of (3) and (4), the conductive belt is a rubber belt in which a conductive material is kneaded, a conductive belt is bonded to the entire surface of the rubber belt, or a metal is applied to the entire surface of the rubber belt. A laminate of foils can be used.

  In the rewritable printer of the present invention, as the electric field display method, an electrophoretic method using any of microcapsule electrophoresis, horizontal electrophoresis, and vertical electrophoresis, or a particle rotation method using a spherical twist ball or a cylindrical twist ball Alternatively, it can be applied to a particle movement method using charged toner or an electronic powder fluid.

  According to the rewritable printer of the present invention, by providing means for increasing the contact area between the erasing head and the display surface of the display medium, there is no need to apply a high voltage to increase the erasing speed as in the prior art, In addition, the voltage application time is shortened. For this reason, the load applied to the display medium at the time of erasing can be reduced. Thereby, the aggregation phenomenon of the fine particles constituting the electric field display layer does not occur in the display medium, and it is possible to prevent the decrease in the number of rewrites of the display medium and to realize a long life.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

(1) First Embodiment FIG. 1 is a side view showing an overall configuration of a rewritable printer according to a first embodiment, FIG. 2 is a cross-sectional view showing an example of a display medium that can be used in the printer, and FIG. It is explanatory drawing which shows the state at the time of erasing and writing.

  As shown in FIG. 1, the rewritable printer 1-1 according to the present embodiment is an electric field display type printer capable of erasing and writing on the display medium 100 by electric field action, that is, rewriting. The rewritable printer 1-1 includes a paper feeding unit 2, an erasing unit 3, a writing unit 4, and a paper discharge unit 5.

(Display medium)
A display medium 100 shown in FIG. 2 is a rewritable paper of a microcapsule type electrophoresis system. This rewritable paper 100 is configured by including an electric field display layer 120 on the surface of a sheet-like substrate 110 made of paper or resin as shown in FIG. 1A, and the surface of the electric field display layer 120 can be rewritten. The display surface P is displayed. The electric field display layer 120 is made of electronic ink in which an aqueous solution containing a large number of microcapsules 130 is mixed in a transparent resin binder 140, and the electronic ink is uniformly coated on the substrate 110. Each microcapsule 130 is filled with a transparent insulating liquid 132 inside a hollow spherical diaphragm 131 as shown in FIG. 5A, and the insulating liquid 132 has a white fine particle having a negative charge. 133 and the black fine particles 134 having a positive charge are dispersed in an electrophoretic manner. The color of the fine particles is not limited to white and black, but may be other colors with high contrast.

(Paper Feeder)
In the rewritable printer 1-1 shown in FIG. 1, a paper feed tray 21 is provided in the paper feed unit 2, and a plurality of rewritable papers 100, 100,. Stacked up and stacked. The rewritable papers 100 stacked on the paper feed tray 21 are sequentially sent out from the uppermost paper by the rotational force of the paper feed roller 22 and are conveyed one by one to the subsequent erasing unit 3.

(Erase part)
A contact type erasing head 31 is installed in the erasing unit 3, and an electric field is applied by the erasing head 31 to erase the display on the rewritable paper 100. The erasing head 31 is characterized in that it includes means for increasing the contact area with the display surface P of the rewritable paper 100. The erasing head 31 according to the present embodiment includes a conductive charging roller 311 that contacts the rewritable paper 100 and applies a voltage, and a conveying roller 312 that is disposed opposite to the charging roller 311 and conveys the rewritable paper 100 while sandwiching it. Configured.

  The charging roller 311 is made of a metal roller that is rotatably supported. Pixel electrodes arranged in a matrix are provided on the outer peripheral surface of the roller, and a negative voltage is supplied from the electrode portion 313 to the pixel electrode of the target portion. As a result, a negative charge can be charged. The transport roller 312 is also a metal roller, and rotates reversely to the charging roller 311 to transport the rewritable paper 100 to the writing unit 4 at the subsequent stage.

  Since both the charging roller 311 and the conveying roller 312 are made of metal, the charged charge remains even after erasing. If dirt such as dust adheres to the outer peripheral surface of the roller due to this residual charge, the voltage cannot be applied with an accurate pixel pattern, and erasure failure may occur. Therefore, a ground 314 common to the charging roller 311 and the conveying roller 312 is provided to remove residual charges. The ground 314 may be provided individually for each roller.

As a means for enlarging the contact area between the display surface P of the erasing head 31 and the rewritable paper 100 in this embodiment, relatively large roller diameter R ₁ of the charging roller 311 than the roller diameter R ₂ of the conveying roller 312 It is set. The contact area between them by contact width (nip width) W widens the rewritable paper 100 when the roller diameter R ₁ is set larger the charging roller 311 is enlarged. Roller diameter R ₁ of the charging roller 311 is preferably larger as possible, are set to a proper value in relation to the printer size. For example, in the case of a 20 mm diameter roller, the nip width W is about 1 mm, and in the case of a roller having the same rubber hardness and a diameter of 40 mm, the nip width W is about 1.5 mm. That is, when the diameter of the roller is doubled, the nip width W is increased by about 1.5 times.

  When a negative voltage is supplied to the pixel electrode of the charging roller 311 to charge the surface of the electric field display layer 120 with a negative charge, the positively charged white fine particles 133 become negative in the microcapsule 130 as shown in FIG. It is attracted and electrophoresed in the insulating liquid 132 and moves to the surface side of the electric field display layer 120. On the other hand, the negatively charged black fine particles 134 are repelled by negative charges, and migrate in the insulating liquid 132 and move to the back side of the electric field display layer 120. That is, in the microcapsule 130 to which the negative voltage is applied, the white fine particles 133 gather on the display surface P side and appear white. Therefore, when a negative voltage is applied with a pixel pattern corresponding to the character or image to be erased, the applied portion of the microcapsule 130 appears white and the written character or image can be erased.

By the present embodiment has been set to a large roller diameter R ₁ of the charging roller 311, it is possible to secure a large contact area between the erase head 31 and the field display layer 120. For this reason, a region where a voltage can be applied at the same timing is expanded, and as a result, the speed of erasing the display of the electric field display layer 120 can be increased.

  Therefore, according to the present embodiment, it is not necessary to apply a high voltage in order to increase the erasing speed as in the prior art, and the voltage application time is shortened, so that the load applied to the rewritable paper 100 during erasing can be reduced. . Thereby, the agglomeration phenomenon of the fine particles in the microcapsule 120 does not occur, the decrease in the number of rewrites of the rewritable paper 100 can be prevented, and a long life can be realized.

(Writing part)
A non-contact type writing head 41 is installed in the writing unit 4, and writing is performed on the rewritable paper 100 by applying an electric field by the writing head 41. The writing head 41 of the present embodiment includes an ion flow head 411 that applies a voltage to the rewritable paper 100 in a non-contact manner, a transport roller 412 that is disposed opposite to the ion flow head 411 and transports the rewritable paper 100, and an ion flow head 411. And an electrode portion 413 for supplying a voltage. In addition, although the earth | ground 414 common to the ion flow head 411 and the conveyance roller 412 is provided, this earth | ground 414 may be provided in both separately.

  In the writing unit 4, writing is performed by irradiating an ion flow from the ion flow head 411 toward the rewritable paper 100 and applying a positive voltage with a pixel pattern corresponding to a target character or image. When a positive voltage is applied from the ion flow head 411 to the electric field display layer 120, the negatively charged black fine particles 134 are attracted to the positive charge in the microcapsule 130 as shown in FIG. Then, the electric field display layer 120 moves to the surface side. On the other hand, the positively charged white fine particles 133 repel the positive charge, migrate in the insulating liquid 132, and move to the back side of the electric field display layer 120.

  That is, the microcapsules 130 to which the positive voltage is applied are in a state where the black fine particles 134 gather on the display surface P side and appear black. Therefore, when a positive voltage is applied with a pixel pattern corresponding to a character or image to be written, the applied portion of the microcapsule 130 appears black and the desired character or image can be displayed.

(Output section)
A paper discharge roller 52 is provided in the paper discharge unit 5, and the rewritable paper 100 after writing is discharged one by one by the rotational force of the paper discharge roller 52. The discharged rewritable papers 100 are sequentially stacked on the discharge tray 51 and stacked.

(2) Second Embodiment FIG. 4 is a side view showing the overall configuration of a rewritable printer according to a second embodiment. The configurations of the paper feed unit 2, the writing unit 4, and the paper discharge unit 5 in the rewritable printer 1-2 according to the present embodiment are the same as those in the first embodiment, and thus the same reference numerals are given and detailed descriptions thereof are omitted. In the present embodiment, only the configuration of the erasing unit 3 is different as follows.

  A contact-type erasing head 32 is installed in the erasing unit 3 shown in FIG. 4 and includes means for increasing the contact area between the erasing head 32 and the display surface P of the rewritable paper 100. As a specific means, the erasing head 32 of this embodiment is conveyed while holding the rewritable paper 100 in contact with the charging roller 321 and a conductive charging roller 321 that applies a voltage by contacting the rewritable paper 100. And an electrode portion 323 for supplying a voltage to the charging roller 321. The charging roller 321 is made of a soft elastic material.

  As the charging roller 321 made of a soft elastic material, for example, an NBR (nitrile rubber) rubber roller kneaded with a conductive material such as metal powder or carbon black can be used. When the charging roller 321 is made of a soft elastic material, the nip width W with the rewritable paper 100 is widened and the contact area is larger than when a hard material such as metal is used. The standard of the hardness of the charging roller 321 is preferably a rubber hardness of 60 degrees or less as defined in JIS-K6253. Further, when the roller diameter of the charging roller 321 is set large as in the first embodiment in combination with the above configuration, the contact area can be further increased.

  The conveyance roller 322 may be made of a soft elastic material having the same conductivity as that of the charging roller 321, or may be made of a metal material as in the first embodiment. Also in the present embodiment, a ground 324 common to the charging roller 321 and the conveying roller 322 is provided in order to remove residual charges.

  In the present embodiment, since the charging roller 321 is made of a soft elastic material, when the charging roller 321 is pressed against the rewritable paper 100, it is elastically deformed flexibly according to the surface shape of the paper, and the nip width is increased, and the erasing head A large contact area between 32 and the electric field display layer 120 can be secured. For this reason, a region where a voltage can be applied at the same timing is expanded, and as a result, the speed of erasing the display of the electric field display layer 120 can be increased.

  Therefore, in this embodiment, it is not necessary to apply a high voltage to increase the erasing speed, and the voltage application time is shortened. Therefore, the load applied to the rewritable paper 100 during erasing can be reduced. Thereby, the agglomeration phenomenon of the fine particles in the microcapsule 120 does not occur, the decrease in the number of rewrites of the rewritable paper 100 can be prevented, and a long life can be realized.

(3) Third Embodiment FIG. 5 is a side view showing the overall configuration of a rewritable printer according to a third embodiment. Since the configurations of the paper feed unit 2, the writing unit 4, and the paper discharge unit 5 in the rewritable printer 1-3 according to the present embodiment are the same as those in the first embodiment, the same reference numerals are given and detailed descriptions thereof are omitted. Also in this embodiment, only the configuration of the erasing unit 3 is different as follows.

  The erasing unit 3 shown in FIG. 5 is provided with an erasing head 33, and a contact belt structure is adopted as means for expanding the contact area between the erasing head 33 and the display surface P of the rewritable paper 100. is there. The erasing head 33 according to the present embodiment includes a conductive belt 331 that contacts the rewritable paper 100, a conductive charging roller 332 that rotates the conductive belt 331 to apply a voltage, and a rewritable head that is disposed opposite the charging roller 332. A conveyance roller 333 that sandwiches and conveys the paper 100 and an electrode unit 334 that supplies a voltage to the charging roller 332 are provided.

  The conductive belt 331 is conductive such as metal powder or carbon black to impart conductivity to a synthetic rubber belt such as NBR (nitrile rubber), EPR (ethylene propylene rubber), or EPT (ethylene propylene terpolymer). A kneaded material can be used. Other than this, use the one that is made by laminating and integrating the conductive film on the entire surface of the synthetic rubber belt, or the one that is made by laminating and integrating the metal foil on the whole surface of the synthetic rubber belt. Also good.

  The charging roller 332 and the conveyance roller 333 can be made of a soft elastic material or metal material having conductivity. In this embodiment, a voltage is applied from the electrode portion 334 to the charging roller 332, but a voltage may be applied to the conductive belt 331. In this case, the charging roller 332 does not necessarily have conductivity. Good. Similarly, a conductive belt may be stretched around the transport roller 333. In this embodiment, the ground 335 for removing the residual charge is provided on each of the conductive belt 331 and the transport roller 333. Instead, the ground 335 is common to both the charging roller 332 and the transport roller 333 or independent. It is also possible to provide them.

  In the present embodiment, since the belt structure is employed, the conductive belt 331 contacts the rewritable paper 100 over a wide range in the transport direction, so that a very large contact area between the erasing head 33 and the electric field display layer 120 can be secured. it can. For this reason, a region where a voltage can be applied at the same timing is remarkably widened, and as a result, the speed of erasing the display of the electric field display layer 120 can be significantly increased.

  Therefore, in this embodiment, it is not necessary to apply a high voltage to increase the erasing speed, and the voltage application time is shortened. Therefore, the load applied to the rewritable paper 100 during erasing can be reduced. Thereby, the agglomeration phenomenon of the fine particles in the microcapsule 120 does not occur, the decrease in the number of rewrites of the rewritable paper 100 can be prevented, and a long life can be realized.

(4) Fourth Embodiment FIG. 6 is a side view showing the overall configuration of a rewritable printer according to a fourth embodiment. The configurations of the paper feed unit 2, the writing unit 4, and the paper discharge unit 5 in the rewritable printer 1-4 according to the present embodiment are also the same as those in the first embodiment, and thus the same reference numerals are given and detailed descriptions thereof are omitted. Also in this embodiment, only the configuration of the erasing unit 3 is different as follows.

  The erasing head 34 shown in FIG. 6 is the same as the third embodiment in that a contact belt structure is adopted, but is characterized in that the conveying roller is eliminated. In this embodiment, the erasing head 34 includes a conductive belt 341 that contacts the rewritable paper 100, a conductive charging roller 342 that applies a voltage by rotating the conductive belt 341, and an electrode that supplies a voltage to the charging roller 342. Part 343. Further, a suction hole 344 is formed in the contact surface of the conductive belt 341 with the rewritable paper 100 along the belt conveyance direction, and a suction mechanism 345 for sucking air into the belt from the suction hole 344 is provided. ing.

  As in the third embodiment, the conductive belt 341 may be a rubber belt kneaded with a conductive material, or a conductive belt or metal foil bonded to the entire surface of the rubber belt. The charging roller 342 can be made of a soft elastic material or metal material having conductivity. In this embodiment, a voltage is applied from the electrode portion 343 to the charging roller 342. However, a voltage may be applied to the conductive belt 341. In this case, the charging roller 342 does not necessarily have conductivity. Good. In this embodiment, the charging roller 342 is provided with the ground 346 for removing the residual charge. However, the conductive belt 341 may be provided instead.

  In the present embodiment, since the belt structure is employed, the conductive belt 341 contacts the rewritable paper 100 over a wide range in the transport direction, so that a very large contact area between the erasing head 34 and the electric field display layer 120 can be secured. it can. For this reason, a region where a voltage can be applied at the same timing is remarkably widened, and as a result, the speed of erasing the display of the electric field display layer 120 can be significantly increased.

  Therefore, in this embodiment, it is not necessary to apply a high voltage to increase the erasing speed, and the voltage application time is shortened. Therefore, the load applied to the rewritable paper 100 during erasing can be reduced. Thereby, the agglomeration phenomenon of the fine particles in the microcapsule 120 does not occur, the decrease in the number of rewrites of the rewritable paper 100 can be prevented, and a long life can be realized.

  Moreover, in this embodiment, the rewritable paper 100 is sucked and held on the conductive belt 341 by sucking air from the suction holes 343 by the suction mechanism 344. For this reason, if the conductive belt 341 is rotationally driven, the rewritable paper 100 can be conveyed to the writing unit 4 at the subsequent stage. Accordingly, there is an advantage that the conveyance roller as shown in FIG. 5 is not required to hold the rewritable paper 100, and the structure inside the printer can be simplified.

  Although the embodiment of the rewritable printer according to the present invention has been described above, the following modifications are possible in the above-described embodiment. For example, the rewritable paper of the microcapsule type electrophoresis system is exemplified as the rewritable display medium. However, the present invention is not limited to this, and the horizontal or vertical electrophoresis system, the particle rotation system using a spherical twist ball or a cylindrical twist ball, or the charged toner The present invention can be similarly applied to other electric field display type rewritable papers such as a particle movement method using an electronic powder fluid. Further, although a non-contact type ion flow head is used as an example of the writing head, a contact type charging roller may be used instead.

1 is a side view showing an overall configuration of a rewritable printer according to a first embodiment of the present invention. FIG. 3 is a cross-sectional view illustrating an example of a display medium that can be used in the printer. Explanatory drawing which shows the state at the time of the erasure | elimination and writing in the display medium. The side view which shows the whole structure of the rewritable printer of 2nd Embodiment by this invention. The side view which shows the whole structure of the rewritable printer of 3rd Embodiment by this invention. The side view which shows the whole structure of the rewritable printer of 4th Embodiment by this invention.

Explanation of symbols

1-1, 1-2, 1-3, 1-4 ... Rewritable printer 2 ... Paper feed unit 21 ... Paper feed tray 22 ... Paper feed roller 3 ... Erase unit 31 ... Erase head (first embodiment)
311 ... charging roller 312 ... conveying rollers 313 ... electrode portion 314 ... ground R 1 _... contact width 32 ... erase head of the roller diameter W ... erase head and rewritable paper roller diameter R 2 _... conveying roller of the charging roller (second embodiment Form)
321 ... Charging roller 322 ... Conveying roller 323 ... Electrode portion 324 ... Earth 33 ... Erasing head (third embodiment)
331: Conductive belt 332 ... Charging roller 333 ... Conveying roller 334 ... Electrode unit 335 ... Earth 34 ... Erasing head (fourth embodiment)
341 ... Conductive belt 342 ... Charging roller 343 ... Electrode part 344 ... Suction hole 345 ... Suction mechanism 346 ... Earth 4 ... Writing part 41 ... Writing head 411 ... Ion flow head 412 ... Conveying roller 413 ... Electrode part 414 ... Earth 5 ... Paper discharge unit 51 ... Paper discharge tray 52 ... Paper discharge roller 100 ... Display medium (rewritable paper)
DESCRIPTION OF SYMBOLS 110 ... Base material 120 ... Electric field display layer 130 ... Microcapsule 131 ... Diaphragm 132 ... Insulating liquid 133 ... White fine particle 134 ... Black fine particle 140 ... Resin binder

Claims (13)

  An electric field display type rewritable printer that rewrites a display medium by an electric field effect, and an erasing head that erases a display written on the display surface of the display medium by applying a voltage in contact with the display medium And a rewritable printer comprising means for enlarging a contact area with the display surface of the display medium in the erasing head.   As means for expanding the contact area, the erasing head includes a conductive charging roller that comes into contact with the display surface of the display medium, and a conveyance roller that is disposed opposite to the charging roller and conveys the display medium. The rewritable printer according to claim 1, wherein a roller diameter of the charging roller is set to be relatively larger than a roller diameter of the conveying roller.   As means for expanding the contact area, the erasing head includes a conductive charging roller that comes into contact with the display surface of the display medium, and a conveyance roller that is disposed opposite to the charging roller and conveys the display medium. The rewritable printer according to claim 1, wherein the charging roller is made of a soft elastic material.   4. The rewritable printer according to claim 3, wherein the charging roller is a rubber roller obtained by kneading a conductive material.   The rewritable printer according to claim 3 or 4, wherein the charging roller has a hardness of 60 degrees or less as defined in JIS-K6253.   As means for enlarging the contact area, the erasing head is opposed to the conductive belt that contacts the display surface of the display medium, the conductive charging roller that rotates the conductive belt to apply a voltage, and the charging roller. The rewritable printer according to claim 1, further comprising a conveyance roller that is arranged and conveys the display medium.   As means for enlarging the contact area, the erasing head includes a conductive belt that contacts the display surface of the display medium, a conductive charging roller that applies a voltage by rotating the conductive belt, and a conductive belt. The rewritable printer according to claim 1, further comprising: a suction mechanism that sucks air from a suction hole opened along a transport direction to the inside of the belt.   The rewritable printer according to claim 6 or 7, wherein the conductive belt is a rubber belt obtained by kneading a conductive material.   The rewritable printer according to claim 6 or 7, wherein the conductive belt is obtained by bonding a conductive film to the entire surface of a rubber belt.   The rewritable printer according to claim 6 or 7, wherein the conductive belt is formed by bonding a metal foil to the entire surface of a rubber belt.   The rewritable printer according to any one of claims 1 to 10, wherein the electric field display method is an electrophoretic method of any one of microcapsule electrophoresis, horizontal electrophoresis, and vertical electrophoresis.   The rewritable printer according to any one of claims 1 to 10, wherein the electric field display method is a particle rotation method using a spherical twist ball or a cylindrical twist ball.   The rewritable printer according to claim 1, wherein the electric field display method is a particle movement method using charged toner or an electronic powder fluid.

Images