JPH10301510A - Magnetic display device and pen for magnetic display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform erasure from a surface side that a user observes by arranging a magnet at a certain interval on the reverse surface of a magneto-phoretic display sheet on the opposite side from its display surface and holding this magnet so that it is displaced at right angles to the display surface of the magneto-phoretic display sheet. SOLUTION: On the reverse surface side of the magneto-phoretic display sheet 31, an erasure magnet 33 is provided normally at an interval of specific size movably in approaching and leaving directions so that the N pole is positioned on the magneto-phoretic display sheet 31. For erasure, the erasure pen 35 is used which has the magnetism of the S polarity at its tip part. Consequently, the erasure magnet 33 is attracted toward the magneto-phoretic display sheet 31 with the erasure pen 35. Simultaneously, magnetic powder 32 is attracted to the reverse surface side by the erasure magnet 33 and not present on the top surface side, so characters and an image which are displayed are erased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for displaying a character or image by forming a magnetophoretic display sheet by arranging magnetophoretic microcapsules enclosing black magnetic powder and a white emulsion in a plane and applying a magnetic force. The present invention relates to a magnetic display device for performing erasing and a pen for a magnetic display device.

[0002]

2. Description of the Related Art The principle of magnetophoresis is used as a display device which can be easily written and erased in a relatively small conference, or as a display device for advertisement which displays the same content continuously for a certain period of time. Display devices (often called information boards) are used. This magnetophoretic display device has a black magnetic powder (magnetic powder) 1 and a white emulsion (liquid) 2 as shown in FIG.
16 are formed by arranging the magnetophoretic microcapsules 3 having a diameter of about 500 μm in a plane between the top sheet 4 and the back sheet 5 as shown in FIG. Thus, a character or a figure is drawn freehand using a magnet pen 7 having a magnet at the tip, or character / image information is displayed using a built-in magnetic head array 8. That is, when the magnet pen 7 is brought into contact with the surface of the magnetophoresis sheet 6 and moved, the colored powder 1 in the magnetophoresis microcapsule 3 is attracted to the surface side by the magnetic force according to the movement of the magnet pen 7. . On the other hand, at locations other than the locus of the magnetic pen 7, the white emulsion 2 of the magnetophoretic microcapsules 3 is displayed as white because the white emulsion 2 is present on the surface as it is. As a result, the user can draw an arbitrary character / image in contrast with the white color of the white emulsion 2 and the black color of the powder 1 made of magnetic powder. An erasing magnet sheet 9 is provided on the back surface side. The magnetic force of the magnet sheet 9 causes the powder 1
Is sucked to the back side so that only white color can be seen from the front side so that characters and images drawn can be erased.

As an information board for displaying characters and images on the basis of such a principle, for example, Japanese Patent Laid-Open No. 5-3
A proposal such as that described in Japanese Patent No. 41719 is made. FIG. 18 is a schematic diagram showing the structure of the information board 10 described therein, and this structure will be described. First, the magnetophoretic sheet 6 has a seamless belt shape and is held by left and right rollers 11 and 12. One of the rollers 11 always exerts a tensile load by a tension spring 13 to prevent the magnetophoretic sheet 6 from being loosened. The other roller 12 has a belt 14 and a pulley 1
5, a motor 16 is connected to the
The magnetophoretic sheet 6 is provided so as to be rotatable in the direction A in FIG. Further, a magnetic head 17 is provided on the display surface side, so that a magnetic field is generated only at a desired position by applying a current based on a command from a control device (not shown) so that an arbitrary character or image can be displayed. ing. At the time of writing by the magnetic head 17, a plate 18 for improving the writing accuracy is provided on the back side sandwiching the magnetophoretic sheet 6, to prevent wear of the magnetophoretic sheet 6 at times other than writing. To reduce the load on the motor 16,
Avoidance mechanism 19 for moving plate 18 away from magnetophoretic sheet 6
Is provided. Further, long erasing magnets 20 are provided so as to be able to freely contact and separate from the magnetophoretic sheet 6 in proximity to the rollers 11 and 12, and a back plate 21 is provided between these erasing magnets 20. ing. Therefore, by rotating the magnetophoretic sheet 6, it is possible to collectively erase characters and images. On the other hand, on the display surface side, a reading device 25 including an illumination 22, a mirror 23, and a reading unit 24 is provided. As a result, the displayed characters and images can be converted into electrical digital signals and processed.

In this example, an image is output based on an instruction from a computer or the like, but it is also possible to perform handwriting input by using a pen having a magnet at the tip.

As an erasing method, Japanese Patent Publication No. Sho 57-4
There is also a proposal described in US Pat. In this method, the magnets on the front side attract magnets having a larger magnetic force than the magnets on the back side provided on the back side, and move them integrally to perform erasing.

[0006]

In the prior art shown in FIG. 18, a long magnet for erasing is provided on the back side, and the erasing is performed collectively, so that the user can select an arbitrary position. There is a problem that it is impossible to locally erase characters and images. Further, in the technology described in Japanese Patent Publication No. 57-46439, it is possible to partially erase characters, but characters and images are also erased until a character or the like reaches a target position where the characters are to be erased. There is a problem.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and enables erasing from the front side to be observed by a user. It is an object of the present invention to provide a magnetic display device capable of surely erasing every corner, that is, a so-called information board.

[0008]

According to the first aspect of the present invention,
In a magnetic display device for displaying and erasing characters and images by applying a magnetic force to a magnetophoretic display sheet on which magnetophoretic elements are arranged, a predetermined interval is provided on the back surface opposite to the display surface of the magnetophoretic display sheet. Magnets are arranged at a distance, and the magnet is held so as to be displaced in a direction perpendicular to the display surface of the magnetophoretic display sheet. Therefore, it is possible to draw the magnets arranged from the front side to the back side of the magnetophoretic display sheet, thereby locally erasing characters and images at an arbitrary position from the front side.

According to a second aspect of the present invention, a plurality of magnets arranged on the back surface of the magnetophoretic display sheet are arranged in a two-dimensional array and vibrated at an amplitude corresponding to the entire array or locally at an array pitch. With this configuration, it is possible to finely erase data on the entire display surface, and it is possible to eliminate portions that cannot be erased.

According to a third aspect of the present invention, an electromagnet is formed by a magnetic core serving as a pen tip and a coil wound around the magnetic core, and the direction of current flow to the coil is switched to perform writing during writing. A current switching section is provided for inverting the magnetic pole at the tip of the magnetic core between the time of erasure. Therefore, it is possible to provide a pen that can be used for both writing and erasing.

According to a fourth aspect of the present invention, there is provided a switch for switching between energization and non-energization of the coil depending on whether the magnetic core is in contact with the magnetophoretic display sheet. Therefore, since the magnetic force is lost when the pen retracts during erasing, it is possible to prevent erroneous writing when leaving the magnetophoretic display sheet.

According to a fifth aspect of the present invention, there is provided a magnetic display device for displaying and erasing characters and images by applying a magnetic force to a magnetophoretic display sheet on which magnetophoretic elements are arranged, wherein a display surface of the magnetophoretic display sheet is provided. A large number of protrusions made of a magnetic material are arranged on the reverse side opposite to the display surface at a certain interval in a range of substantially the same size as the display surface. Therefore, characters and images drawn can be erased only by bringing the magnet close to the display surface side of the magnetophoretic display sheet.

According to a sixth aspect of the present invention, the projection is formed of a soft magnetic material. Therefore, the written character / image does not become thin with time or erased.

According to a seventh aspect of the present invention, a vibration means for vibrating the projection is provided. Therefore, written characters and images can be erased without gaps.

According to an eighth aspect of the present invention, the projection is formed of an elastic material. Therefore, written characters and images can be erased without gaps with a structure that is less expensive than when the vibration means is provided.

According to a ninth aspect of the present invention, there is provided a magnetic display device for displaying and erasing characters and images by applying a magnetic force to a magnetophoretic display sheet on which magnetophoretic elements are arranged. A damper layer formed of a plate-like gas with a constant thickness in a range of substantially the same size as the display surface on the back side opposite to the above, and a plate-like magnet is provided by being laminated on this damper layer. It is. Therefore, it is possible to draw the magnets arranged from the front side to the back side of the magnetophoretic display sheet, thereby locally erasing characters and images at an arbitrary position from the front side.

According to a tenth aspect of the present invention, there is provided a magnetic display device for displaying and erasing characters and images by applying a magnetic force to a magnetophoretic display sheet on which magnetophoretic elements are arranged. A flat plate-like magnet is arranged on the reverse side of the opposite side at a certain interval in a range of substantially the same size as the display surface, and the periphery of the magnetophoretic display sheet is held by an elastic member. Therefore, not only the central portion of the magnetophoretic display sheet but also the peripheral portion can be easily erased.

[0018]

FIG. 1 shows a first embodiment of the present invention.
4 through FIG. First, FIG. 1 is a schematic diagram showing the principle of writing and erasing in the present embodiment, where (A) shows a state at the time of writing and (B) shows a state at the time of erasing. The magnetophoretic display sheet 31 has magnetic powder in a state of being encapsulated in microcapsules, as in the conventional magnetophoretic display device. However, in the present embodiment, for simplification of the description, the magnetic powder is formed in the sheet body. FIG. 3 shows that the magnetic powder 32 directly migrates. On the back surface of the magnetophoretic display sheet 31, the erasing magnet 3 is usually kept at a predetermined distance from the erasing magnet 3.
Numeral 3 is provided movably in a direction in which the N pole is positioned on the magnetophoretic display sheet 31 and approaches or separates from each other.

First, at the time of writing, as shown in FIG. 1 (A), for example, a writing pen 34 whose tip has N-pole magnetism is used. Thereby, the erasing magnet 33 is separated from the magnetophoretic display sheet 31 by the magnetic force, and the internal magnetic powder 32 moves to the display surface side. Thus, by moving the writing pen 34, the magnetic powder 32 can be attracted to the front side of the magnetophoretic display sheet 31 to form characters and images.

Next, at the time of erasing, as shown in FIG. 1B, an erasing pen 35 having a magnetic pole having an S pole at the tip is used. As a result, the erasing magnet 33 is drawn toward the magnetophoretic display sheet 31 by the erasing pen 35.
Since the magnetic powder 32 is attracted to the back side by the erase magnet 33 and does not exist on the display surface side, the displayed characters and images are erased.

FIG. 2 shows an example of a magnetic display device based on such a principle.
The erasing magnet sheet 36 is provided. The erasing magnet sheet 36 is configured such that the erasing magnets 33 held by a holding member 37 having elasticity such as rubber are two-dimensionally arranged at regular intervals. The erasing magnet sheet 36 is set at a position separated from the magnetophoretic display sheet 31 by a predetermined distance in an initial state.

Therefore, when the writing pen 34 is used,
Characters and images can be written as in the case shown in FIG. 1A, but when erasing written characters, etc.,
An erasing pen 35 is used as shown in FIG. Thereby, the erasing is performed according to the principle shown in FIG. 1B, but the movement of the erasing magnet 33 in the direction of arrow A is caused by the holding member 37.
Is carried out by deforming. By moving the erasing pen 35 in the direction of the arrow B, characters and the like in the moving range are erased. After the erasing pen 35 has passed or at a position separated from the magnetophoretic display sheet 31, the erasing magnet 33
Due to the restoring force of the holding member 37,
It returns to the original position separated from 1.

FIG. 3 shows a modification of the erase magnet sheet 36. That is, the erasing magnet sheet 36 in this case has the erasing magnet 33 held by the hard holding member 37, and the erasing magnet 33 moves in the direction of the arrow A in the hole 38 formed in the holding member 37. It is freely held, and the opening is closed by a cover 39. The writing and erasing operations are exactly the same as those shown in FIG.

Further, at the time of erasing, the erasing magnet sheet 36 formed of a rigid body is reciprocally oscillated by using an actuator or the like in a plane parallel to the surface of the magnetophoretic display sheet 31 using an actuator or the like. The entire display surface of the sheet 31 can be completely erased.

FIG. 4 shows a magnetic display pen 40. The magnetic display device pen 40 has a housing 41 in which a magnetic core 42 serving as a pen tip is provided with a spring 4.
The coil 44 is wound around the magnetic core 42 by being slidably urged in the protruding direction by 3. A battery 46 is connected to the coil 44 via a switch unit 45. Although a detailed description of the structure is omitted, a current switching unit 47 that switches the direction of a current flowing through the coil 44 is provided at an end of the magnetic display device pen 40.

Therefore, in the free state, as shown in FIG. 4A, the switch 45 is in the OFF state,
4 is not energized, the magnetic core 42 is not magnetized, but when the tip of the magnetic core 42 is pressed against the magnetophoretic display sheet 31 as shown in FIG. As described above, the switch unit 45 is turned ON, whereby the magnetic core 42 is magnetized. The direction of the current flowing through the coil 44 is switched by the current switching unit 47 depending on the polarity of an erasing magnet (not shown).
By switching the polarity of the tip portion 2 to N pole or S pole, writing or erasing can be switched.

In particular, when the magnetic core 42 is separated from the magnetophoretic display sheet 31, the switch 45 is turned off before the magnetic cores 42 are separated from each other, so that the magnetic core 42 loses its magnetic force, thereby being drawn to the back side. The disadvantage that the magnetic powder 32 is attracted by the magnetic force and moves to the surface side can be eliminated. That is, it is possible to eliminate the occurrence of erasing errors. Another effect of the switch 45 is that the coil 44 is not energized except at the time of writing or erasing, so that power can be saved and the life of the battery 46 can be extended. is there.

FIGS. 5 to 1 show a second embodiment of the present invention.
1 will be described. The same parts as those in the above-described embodiment are denoted by the same reference numerals, and description thereof is omitted (the same applies hereinafter). In the present embodiment, as shown in FIG. 5, a protrusion 48 made of a magnetic material is arranged on the entire back surface of the magnetophoretic display sheet 31. These projections 48 are provided on the magnetophoretic display sheet 31.
Holes are formed in a non-magnetic material such as polycarbonate, for example, having a size similar to that of polycarbonate, and a magnetic material having a protruding shape is fixed to these holes by press-fitting or bonding, and arranged at a predetermined pitch. Then, as shown in FIG. 6, the projections 48 are arranged on the back surface of the magnetophoretic display sheet 31.
Is a state where characters and images have been written in advance with a writing pen or the like. Then, as shown in FIG. 6B, when the erasing magnet 33 is approached, the lines of magnetic force concentrate on the protrusions 48, and the magnetic powder 32 is drawn to the periphery of the protrusions 48 on the back surface of the magnetophoretic display sheet 31. As a result, the written character / image is partially erased. The principle that the lines of magnetic force concentrate on the protrusion 48 in this way is shown in FIG.

The protrusion 48 may be a magnetic material that is strongly magnetized, but if the magnetization remains, the magnetic powder 32 is attracted over time to thin or erase the written characters and images. I do it. Therefore, if a soft magnetic material is used as the magnetic material constituting the protrusion 48,
Characters and images are not faded or erased over time. Here, the soft magnetic material refers to a magnetic material having a very large magnetization and a small residual magnetization and a small coercive force even when a small external magnetic field is applied thereto, among the mirror magnetic materials.

FIG. 8 shows an example of a magnetic display pen 40 having a writing magnet 49 at one end thereof.
A thin non-magnetic spacer 50 is fixed to the tip of the writing magnet 49. Also, at the other end,
The erasing magnet 51 is fixed. The state in which writing and erasing are performed using the magnetic display device pen 40 will be described with reference to FIG. FIG. 9A shows a state at the time of writing, and the writing magnet 49 includes a non-magnetic spacer 5.
Since there is 0, the magnetic powder 32 is attracted to the surface of the magnetophoretic display sheet 31 with little influence of the magnetic force on the projection 48 located far away. On the other hand, FIG. 9B shows a state at the time of erasing. Since the erasing magnet 51 is close to the projection 48, it exerts a magnetic force on the projection 48,
The protrusion 48 is magnetized, and the magnetic powder 32 is drawn to the back side where the protrusion 48 is located.

Since the lines of magnetic force have a certain extent, they are erased with a certain extent around the projection. Therefore, it is sufficient to arrange the projections 48 in each area where one projection 48 can be erased.
However, if the interval between the projections 48 is wide, there arises a problem that characters and images written in the interval cannot be erased. As a means for solving this, it is effective to vibrate the protrusion 48 along the surface of the magnetophoretic display sheet 31, as shown in FIG. This allows
Even if the interval between the protrusions 48 is wide, erasing can be performed over the entire surface of the magnetophoretic display sheet 31. As another means, it is effective to form the projection 48 from an elastic material so that the projection 48 swings by moving the erasing magnet 51, and this state is shown in FIG. . In this case, the projection 48 may be made of, for example, an elastic material such as rubber or fiber containing a powdery soft magnetic material.

A third embodiment of the present invention will be described with reference to FIGS. As a configuration of the present embodiment, as shown in FIG. 12, a damper layer 52 is provided along the back surface of the magnetophoretic display sheet 31, and a flat magnet 53 is provided along the back surface of the damper layer 52. is there. As shown in FIG. 13, the damper layer 52 is formed of a gas layer in which a gas such as air is sealed. And FIG.
FIG. 12A shows a state in which the erase pen 54 is brought close to a state in which characters and images have already been written. As shown in FIG. By pressing the part to be bent, the damper layer 52 bends to bring the magnetic powder 32 closer to the magnet 53, thereby moving the magnetic powder 32 to the back surface side. Then, as shown in FIG. 12C, the erasing state continues even when the erasing pen 54 is released.

However, the thickness of the damper layer 52 is normally not affected by the magnetic force generated by the flat magnet 53 disposed on the back surface of the magnetic powder 32. It is set so that 32 migrations are performed.

FIG. 14 shows a modified example of the damper layer 52 in which an elastic body such as a sponge is formed in a plate shape instead of the gas layer. In this case, a collar 55 having a thickness corresponding to the thickness of the damper layer 52 is fixed around the magnet 53, and a frame 56 is fixed to the collar 55. These fixing means are performed by bonding or the like. The magnetophoretic display sheet 31 and the frame 56 are connected via an elastic member 57. Thereby, the peripheral portion of the magnetophoretic display sheet 31 is erased by the pen 54.
Even when pressed, the electrophoretic display sheet 31 is close to the magnet 53, so that an erasable state can be obtained over all corners.

[0035]

According to the first aspect of the present invention, there is provided a magnetic display apparatus for displaying and erasing characters and images by applying a magnetic force to a magnetophoretic display sheet on which magnetophoretic elements are arranged. Magnets are arranged at a fixed interval on the back surface opposite to the display surface, and this magnet is held so as to be displaced in a direction perpendicular to the display surface of the magnetophoretic display sheet, so that the The magnets arranged on the back side can be attracted from the front side, which has the effect that characters and images at arbitrary positions can be locally erased from the front side.

According to a second aspect of the present invention, a plurality of magnets arranged on the back surface of the magnetophoretic display sheet are arranged in a two-dimensional array and vibrated at an amplitude corresponding to the entire array or locally at an array pitch. With such a configuration, it is possible to finely erase the entire display surface, and it is possible to eliminate an unerasable portion.

According to a third aspect of the present invention, an electromagnet is formed by a magnetic core serving as a pen tip and a coil wound around the magnetic core, and the direction of current flow to the coil is switched to perform writing during writing. Since the current switching unit for reversing the magnetic pole at the tip of the magnetic core at the time of erasing is provided, it is possible to provide a pen that can be used for both writing and erasing.

According to a fourth aspect of the present invention, a switch is provided for switching between energization and non-energization of the coil depending on whether or not the magnetic core is in contact with the magnetophoretic display sheet. Has no magnetic force, and thus has the effect of preventing erroneous writing when leaving the magnetophoretic display sheet.

According to a fifth aspect of the present invention, there is provided a magnetic display device for displaying and erasing characters and images by applying a magnetic force to a magnetophoretic display sheet on which magnetophoretic elements are arranged, wherein a display surface of the magnetophoretic display sheet is provided. Since a large number of protrusions made of a magnetic material are arranged in a range of substantially the same size as the display surface at a predetermined interval on the back surface opposite to the above, the magnet is brought closer to the display surface side of the magnetophoretic display sheet. This has the effect that the characters and images drawn can be erased only by using the mouse.

According to the sixth aspect of the present invention, since the projections are formed of a soft magnetic material, the written characters and images do not become thin or erased over time. Have.

According to the seventh aspect of the present invention, since the vibrating means for vibrating the protruding portion is provided, there is an effect that written characters and images can be erased without gaps.

According to the eighth aspect of the present invention, since the protrusions are formed of an elastic material, the written characters and images can be erased without gaps with a less expensive structure than when the vibration means is provided. Having.

According to a ninth aspect of the present invention, there is provided a magnetic display device for displaying and erasing characters and images by applying a magnetic force to a magnetophoretic display sheet on which magnetophoretic elements are arranged, wherein a display surface of the magnetophoretic display sheet is provided. Since a damper layer formed of a plate-like gas with a constant thickness was provided in a range of substantially the same size as the display surface on the reverse side of the back side, and a plate-like magnet was provided by being laminated on this damper layer. In addition, it is possible to attract magnets arranged from the front side to the back side of the magnetophoretic display sheet, thereby providing an effect that characters and images at arbitrary positions can be locally erased from the front side.

According to a tenth aspect of the present invention, there is provided a magnetic display device for displaying and erasing characters and images by applying a magnetic force to a magnetophoretic display sheet on which magnetophoretic elements are arranged. A flat plate-like magnet was arranged in a range of substantially the same size as the display surface at a predetermined interval on the back surface opposite to the above, and the periphery of the magnetophoretic display sheet was held by an elastic member, This has an effect that not only the central portion of the display sheet but also the peripheral portion can be easily erased.

[Brief description of the drawings]

FIGS. 1A and 1B show the principle of the first embodiment of the present invention, in which FIG. 1A is a schematic diagram showing a state at the time of writing, and FIG. 1B is a schematic diagram showing a state at the time of erasing.

FIG. 2 is a longitudinal sectional side view of a state where the erasing magnet is formed in a sheet shape by being held by a holding member made of an elastic member.

FIG. 3 is a longitudinal sectional side view showing a state where the erasing magnet is held by a rigid holding member and is formed in a sheet shape.

4A and 4B show a pen for a magnetic display device, in which FIG. 4A is a longitudinal side view in a state not in contact with a magnetophoretic display sheet, and FIG. 4B is a longitudinal side view in a state in contact with the magnetophoretic display sheet; FIG.

FIG. 5 is a perspective view showing a second embodiment of the present invention.

6A and 6B are vertical side views of the structure, FIG. 6A is a vertical side view in a display state, and FIG. 6B is a vertical side view at the time of erasing;

7A is a side view showing the state of the magnetic force lines, and FIG. 7A is a side view showing the magnetic force lines of the erasing magnet in a state where no protrusion exists.
(B) is a side view showing the magnetic lines of force of the erasing magnet in the state where the protrusion exists.

FIG. 8 is a front view of a magnetic display pen.

FIG. 9 is a vertical sectional side view showing a state in which writing and erasing are performed using a magnetic display pen, where (A) shows a writing state and (B) shows an erasing state. .

FIG. 10 is a vertical sectional side view showing a state in which a projection is vibrated.

FIG. 11 is a vertical sectional side view showing the operation of a protrusion formed by an elastic member.

FIG. 12 shows a third embodiment of the present invention,
(A) is a longitudinal side view in a state where characters and images are written, (B) is a longitudinal side view at the time of erasing, and (C) is a longitudinal side view in a state where erasing is completed.

FIG. 13 is a partial longitudinal side view showing a configuration of a damper layer.

14A and 14B show another type of a damper layer, in which FIG. 14A is a front view of a magnetic display device, and FIG. 14B is a partial longitudinal side view.

FIG. 15 is a schematic diagram showing the structure of a magnetophoretic microcapsule.

FIG. 16 is a schematic diagram showing a conventional magnetophoretic display device.

FIG. 17 is a perspective view of a conventional magnetophoretic display device.

FIG. 18 is a vertical sectional side view showing an example of a conventional magnetophoretic display device.

[Explanation of symbols]

 31 Magnetophoresis display sheet 32 Magnetophoresis element 33 Magnet 42 Magnetic core 44 Coil 45 Switch part 47 Current switching part 48 Projection part 52 Damper layer 53 Flat magnet 57 Elastic member

Claims (10)

[Claims] 1. A magnetic display device for displaying and erasing characters and images by applying a magnetic force to a magnetophoretic display sheet on which magnetophoretic elements are arranged, wherein a back surface opposite to a display surface of the magnetophoretic display sheet is provided. A magnetic display device, wherein a magnet is arranged at a predetermined interval from the magnetic display device, and the magnet is held so as to be displaced in a direction perpendicular to the display surface of the magnetophoretic display sheet. 2. A method according to claim 1, wherein a plurality of magnets arranged on the back surface of the magnetophoretic display sheet are arranged in a two-dimensional array, and the whole or an array is vibrated locally with an amplitude corresponding to an array pitch. The magnetic display device according to claim 1, wherein 3. An electromagnet is formed by a magnetic core serving as a pen tip and a coil wound on the magnetic core, and the direction of current flow to the coil is switched to change the magnetic current between writing and erasing. A pen for a magnetic display device, comprising a current switching unit for reversing the magnetic pole at the tip of the body core. 4. The pen for a magnetic display device according to claim 3, further comprising a switch for switching between energization and non-energization of the coil depending on whether the magnetic core is in contact with the magnetophoretic display sheet. 5. A magnetic display device for displaying and erasing characters and images by applying a magnetic force to a magnetophoretic display sheet on which magnetophoretic elements are arranged, wherein a back surface opposite to a display surface of the magnetophoretic display sheet is provided. A plurality of protrusions made of a magnetic material are arranged at a predetermined interval in a range of substantially the same size as the display surface. 6. The magnetic display device according to claim 5, wherein the protrusion is formed of a soft magnetic material. 7. The magnetic display device according to claim 5, further comprising vibration means for vibrating the projection. 8. The magnetic display device according to claim 5, wherein the protrusion is formed of an elastic material. 9. A magnetic display device for displaying and erasing characters and images by applying a magnetic force to a magnetophoretic display sheet on which magnetophoretic elements are arranged, wherein a back surface opposite to a display surface of the magnetophoretic display sheet is provided. A magnetic display characterized by providing a damper layer made of a plate-like gas with a constant thickness in a range of substantially the same size as the display surface, and providing a plate-like magnet by being laminated on the damper layer. apparatus. 10. A magnetic display device for displaying and erasing characters and images by applying a magnetic force to a magnetophoretic display sheet on which magnetophoretic elements are arranged, wherein a back surface opposite to a display surface of the magnetophoretic display sheet is provided. A magnetic display device, comprising: a plate-like magnet disposed at a predetermined interval in a range substantially the same size as the display surface; and a peripheral portion of the magnetophoretic display sheet held by an elastic member.