JP2007121677A - Display medium and display element, and image display method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display medium and a display element, and an image display method that can realize high resolution and contrast, while employing the technique of magnetophoresis method. <P>SOLUTION: The display medium has a display layer 6, having display particles 2 in the inside, comprising a carbon structure containing magnetic particles and a dispersing agent 4 dispersing the display particles 2. The display element comprises the display medium 10, formed by arranging a pair of substrates 12 and 14, at least one of which has light transmissivity facing each other and arranging the display layer 6 in the gap between the pair of substrates 12 and 14, and a magnetic field imparting means for display of applying a magnetic field in image pattern to one of the surfaces of the display medium. Furthermore, disclosed is the image display method for making an image written to the display medium 10 and displayed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a rewritable marking technology capable of easily writing, displaying and erasing an image, and more specifically, writing, displaying and erasing can be easily performed by applying a magnetic force to magnetic particles. The present invention relates to a magnetophoretic display medium, a display element, and an image display method.

There are high expectations for rewritable marking technology as a hard copy technology that replaces paper, for reasons such as the preservation of the global environment such as forest resource protection and the improvement of the office environment such as space saving.
As a rewritable marking technology, particles have been moved by an electric field or a magnetic field in addition to the use of liquid crystal and advanced technologies such as organic electroluminescence (organic EL) as a display technology for various electronic papers and flexible displays. Various simple methods for displaying an image by causing the image to be displayed have been proposed.

  Honeycomb core having a large number of hexagonal cells between a transparent or translucent drawing face plate (substrate) and a face material facing the drawing as a magnetophoretic technique for displaying an image by moving magnetic particles by a magnetic field And a magnetic drawing plate in which a plastic dispersion liquid containing magnetic particles is enclosed in each of the cells. In the magnetic drawing board, the tip of the pen magnet is brought into contact with the drawing surface, for example, a magnetic field is acted on the plastic dispersion liquid to float the magnetic particles on the drawing surface, and the difference in contrast between the dispersion medium and the magnetic particles. By displaying a picture or character on the drawing surface and moving the eraser bar under the substrate, the magnetic particles are applied uniformly from the back side, so that the floating magnetic particles are settled again to erase the picture or character. Is.

  In the magnetophoretic display medium, magnetic particles having a relatively large diameter of several tens of μm are used, and it is difficult to improve resolution and contrast. In order to improve the contrast, the magnetic particles are also colored, but when the magnetic particles repeat migration, the paint used for coloring peels off and becomes a contaminant, and the display portion becomes unclear. There was also a problem of end.

  The problem of resolution and contrast is not a big problem if it is used as a toy, for example. However, for example, it is necessary to improve performance when pursuing practicality as a display medium or display element such as electronic paper. It is a hurdle, and dramatically improving it is an important improvement point for realizing a display medium or display element having practicality. That is, in order to establish as a rewritable marking technology that replaces paper, it is an indispensable solution to improve the resolution and contrast of magnetophoretic display media and display elements.

JP 2000-231348 A

  Therefore, an object of the present invention is to provide a display medium and a display element, and an image display method that can realize high resolution and contrast while employing a magnetophoretic technique.

The above object is achieved by the present invention described below. That is, the present invention
<1> A display medium comprising display particles comprising a carbon structure containing magnetic particles, and a display layer having therein a dispersing agent for dispersing the display particles.
<2> The display medium according to <1>, wherein the carbon structure is a carbon nanotube.

<3> The display medium according to <2>, wherein the carbon nanotube is a single-walled carbon nanotube.
<4> The display medium according to claim 2, wherein the display particles are in a state where the magnetic particles are attached to the carbon nanotubes.

<5> The display medium according to <1>, wherein the magnetic particles have a particle size of 50 μm or less.
<6> The display according to <1>, wherein the carbon nanotube produced using the magnetic particle as a catalyst is used as the display particle as it is without separating the magnetic particle used. It is a medium.

<7> The display medium according to <1>, wherein a pair of substrates, at least one of which is light transmissive, are disposed to face each other, and the display layer is disposed in a gap between the pair of substrates. .
<8> The display medium according to <7>, wherein a spacer for dividing the display layer into a plurality when viewed from above is disposed while maintaining a gap between the pair of substrates.

  <9> A pair of substrates, at least one of which is light transmissive, are arranged to face each other, display particles made of a carbon structure containing magnetic particles in a gap between the pair of substrates, and a dispersant that disperses the display particles. A display element comprising: a display medium provided with an internal display layer; and a display magnetic field applying unit that applies an image-like magnetic field to any surface of the display medium. .

<10> The item <9>, wherein the display magnetic field applying unit in the display medium includes an erasing magnetic field applying unit that uniformly applies a magnetic field to the back surface of the front surface to which the magnetic field is applied. Display element.
<11> The display element according to <9>, wherein the carbon structure is a carbon nanotube.

<12> The display element according to <11>, wherein the carbon nanotube is a single-walled carbon nanotube.
<13> The display element according to <11>, wherein the display particles are in a state where the magnetic particles are attached to the carbon nanotubes.

<14> The display element according to <9>, wherein the magnetic particles have a particle size of 50 μm or less.
<15> The display according to <9>, wherein the carbon nanotube produced using the magnetic particle as a catalyst is used as the display particle as it is without separating the magnetic particle used. It is an element.

<16> The display element according to <9>, wherein spacers are provided to partition the display layer into a plurality when viewed from above, while maintaining a gap between the pair of substrates.
<17> The display element according to <9>, wherein the display magnetic field applying unit is a magnetic head that scans a surface of the display medium.

<18> By applying an image-like magnetic field from the display surface side to the display medium according to <1>, the display particles are unevenly distributed on the display surface side and displayed in black only at the portion to which the magnetic field is applied. An image display method characterized by this.
<19> Prior to applying a magnetic field to the image, the display particles are preliminarily unevenly distributed on the back surface side by uniformly applying a magnetic field to the back surface side of the display surface <18 > Is an image display method described in the above.

  <20> For the display medium according to <1>, the display particles are unevenly distributed in advance on the display surface side by applying a magnetic field uniformly on the display surface side. The image display method is characterized in that a magnetic field is applied in an image-like manner from the back side so that the portion to which the magnetic field is applied is displayed in the color of the dispersant.

According to the present invention, it is possible to provide a magnetophoretic display medium and display element that can realize high resolution and contrast, and an image display method.
In particular, by using carbon nanotubes as the carbon structure and diverting the catalyst used in the production of the carbon nanotubes as magnetic particles, it is possible to produce a display medium or display element very simply, and rewritable markings that replace paper. As a technique, an image display method for displaying an image using the display medium has extremely high potential and practicality.

Hereinafter, the display medium, display element, and image display method of the present invention will be described in detail.
[Display medium]
The display medium of the present invention is characterized by comprising display particles comprising a carbon structure containing magnetic particles, and a display layer having therein a dispersing agent for dispersing the display particles.
FIG. 1 is a schematic cross-sectional view of a display medium that is an example of the present invention. In the drawing, the end of the display medium 10 is shown in an enlarged state.

As shown in FIG. 1, in this example, the display medium 10 is a product in which a display layer 6 is arranged in a gap between a transparent substrate (substrate) 12 and a counter substrate (substrate) 14. The display layer 6 is in a state in which cells C1, C2,... Formed by being divided into a plurality of parts by a spacer 8 when viewed from the plane (in the direction of arrow A) are two-dimensionally arranged. Each cell C1, C2... Is filled with display particles 2 and a dispersant 4 for dispersing them.
Hereinafter, detailed aspects of the constituent elements of the display medium of the present invention will be described with reference to FIG.

<Display particles>
In the present invention, the display particles 2 are made of a carbon structure containing magnetic particles.
(Carbon structure)
Specifically, the carbon structure in the present invention is a carbon nanotube and fullerene.

:carbon nanotube:
In general, a carbon nanotube refers to a carbon hexagonal graphene sheet in which a tube is formed parallel to the axis of the tube. Carbon nanotubes are further classified, and those having a single graphene sheet are called single-walled carbon nanotubes, while those composed of multiple graphene sheets are called multi-walled carbon nanotubes. The structure of carbon nanotubes to be obtained is determined to some extent by the synthesis method and conditions.

  The carbon nanotube used in the present invention may be a single-walled carbon nanotube or a multi-walled carbon nanotube having two or more graphene sheets. Which carbon nanotube is used or whether both are mixed may be appropriately selected depending on the use of the carbon nanotube thin film to be formed or considering the cost. However, as will be described later, it is preferable to use single-walled carbon nanotubes from the viewpoint of production suitability.

  Also, carbon nanohorns (horn-type ones whose diameter is continuously expanded from one end to the other end), carbon nanocoils (coil having a spiral shape as a whole), which are variants of single-walled carbon nanotubes Type), carbon nanobeads (with a tube in the center, which has a shape that penetrates spherical beads made of amorphous carbon, etc.), cup-stacked carbon nanotubes, carbon nanohorns, and carbon whose outer periphery is covered with amorphous carbon Nanotubes and the like that are not strictly tube-shaped can also be used as carbon nanotubes in the present invention.

  Furthermore, carbon nanotubes in which some substance is encapsulated in carbon nanotubes, such as metal-encapsulated carbon nanotubes in which metal or the like is encapsulated in carbon nanotubes, fullerenes or peapod carbon nanotubes in which metal-encapsulated fullerene is encapsulated in carbon nanotubes, are also present. In the invention, it can be used as a carbon nanotube.

  As described above, in the present invention, any type of carbon nanotubes such as general carbon nanotubes, variants thereof, carbon nanotubes with various modifications, and the like can be used without any problem. Therefore, “carbon nanotubes” in the present invention are all included in the concept.

  The synthesis of these carbon nanotubes can be performed by any conventionally known arc discharge method, laser ablation method, or CVD method, and is not limited in the present invention. Among these, the arc discharge method in a magnetic field is preferable from the viewpoint that a high-purity carbon nanotube can be synthesized.

  The diameter of the carbon nanotube used is preferably 0.3 nm or more and 100 nm or less. When the diameter of the carbon nanotube exceeds the range, synthesis is difficult, which is not preferable in terms of cost. A more preferable upper limit of the diameter of the carbon nanotube is 30 nm or less.

  On the other hand, the lower limit of the diameter of the carbon nanotube is generally about 0.3 nm in view of its structure, but if it is too thin, it may not be preferable because the yield at the time of synthesis may be low. More preferably, it is more preferably 10 nm or more.

  The length of the carbon nanotube used is preferably 0.1 μm or more and 100 μm or less. If the length of the carbon nanotube is out of the range, synthesis is difficult, or a special method is required for synthesis, which is not preferable in terms of cost. The upper limit of the carbon nanotube length is more preferably 10 μm or less, and the lower limit is more preferably 1 μm or more.

  When the purity of the carbon nanotubes to be used is not high, it is desirable to purify the carbon nanotubes in advance and increase the purity before preparing a mixed solution described later (purification step). There is no restriction | limiting in particular in the purification method of a carbon nanotube, Any conventionally well-known method is employable. However, as described later, when the catalyst used in the production is diverted as magnetic particles as it is, it is desired to purify the catalyst so as not to remove the catalyst.

In the present invention, carbon nanotubes having a functional group can also be used. Specific examples of functional groups that can be added to such carbon nanotubes include hydrophilic functional groups such as —COOH, —NH ₂ , —OH, and —CHO, —COOR (R is a hydrocarbon), and —SiR. ₃ Hydrophobic functional groups such as (R is a hydrocarbon).
As a method for introducing these functional groups, a known method may be used. For example, the functional groups can be introduced into the carbon nanotubes by the method described in JP-T-2002-503204.

: Fullerene:
In general, fullerene refers to a molecule in which carbon hexagonal meshes are arranged and bonded in a spherical shape (soccer ball shape), and is called a soccer ball molecule. C ₆₀ having 60 carbon atoms is famous, but the fullerene that can be used in the present invention is not particularly limited, and any known fullerenes or derivatives thereof can be used.

Specifically, the fullerene usable in the present invention is selected from the group consisting of C ₃₂ , C ₅₀ , C ₅₈ , C ₆₀ , C ₇₀ , C ₇₆ , C ₇₈ , C ₈₂ , C ₈₄ , C ₉₀ , and C _96. Any one or more thereof, or derivatives thereof. In addition, a cage-like carbon nanocapsule made of multiple layers of graphite can be mentioned as a kind of fullerene. Specific examples of the derivatives include fullerene dimers such as notanofullerene, fullerene epoxide, and azaheterofullerene, or fullerene multimers to which they are further bonded. Among these fullerenes, C ₆₀ and C ₇₀ (particularly C ₆₀ ) are preferable from the viewpoint of stability.

(Magnetic particles)
A magnetic particle refers to a particle that can have magnetism (property attracted to a magnet), and generally may be any particle that exhibits ferromagnetism. Examples thereof include oxide magnetic materials such as black magnetite, γ-hematite, chromium dioxide, and ferrite, alloys such as iron, cobalt, nickel, and gadolinium, or particles of a single metallic magnetic material thereof.

  As for the particle size of the magnetic particles, as far as display is concerned, the smaller one is advantageous in that the image quality is good, and it is preferably 50 μm or less, more preferably 10 μm or less. Moreover, when diverting the magnetic particle used as a catalyst when manufacturing the carbon nanotube as a carbon structure as mentioned later, it is more preferred that it is 1 micrometer or less. The lower limit of the particle size of the magnetic particles is not particularly limited, but is generally 10 nm or more.

As the magnetic particles used in the present invention, the catalyst used in the production of carbon nanotubes can be diverted.
Elements that can be used as a catalyst for carbon nanotubes include B, Si, S, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ge, Se, Sr, Y, Zr, and Nb. , Mo, Ru, Rh, Pd, Sb, Hf, Ta, W, Re, Os, Ir, Pt, Au, Th, U, La, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, Tm , Lu and the like. The particle diameter of these catalysts is preferably in the range of 10 nm to 1 μm, and more preferably in the range of 20 nm to 100 nm.
These catalysts are used in particular when producing single-walled carbon nanotubes.

  Display particles comprising carbon structures containing magnetic particles by using a substance containing Fe, Co, Ni, Gd exhibiting ferromagnetism as a catalyst in the production of carbon nanotubes, and diverting the obtained carbon nanotubes together with the catalyst Can be produced easily, which is very advantageous in manufacturing.

  The method of using the catalyst in the production of carbon nanotubes differs depending on the production method, but any production method may be used according to a conventionally known method. For example, in the case of the arc discharge method, it may be mixed in a carbon electrode such as graphite. By using magnetic particles as a catalyst in the production of carbon nanotubes, “display particles made of carbon structures containing magnetic particles (specifically, carbon nanotubes)” (display particles 2), which is an essential component of the present invention, can be easily obtained. Can get to.

  When carbon nanotubes are produced using a catalyst, a product having a structure in which carbon nanotubes are elongated from metal particles (magnetic particles) as a catalyst is mainly obtained, and this is composed of a carbon structure containing magnetic particles. It can be used as it is as “display particles”. In this case, since the carbon of the carbon nanotube and the magnetic particles as the catalyst are chemically bonded at the time of synthesis, the carbon nanotube is hardly peeled off from the magnetic particles, and the display particles 2 as a whole are extremely robust.

  Thus, in addition to the state in which the magnetic particles are the starting point of carbon nanotube growth and both are chemically stable, the state in which the magnetic particles are encapsulated in the carbon nanotubes, van der Waals force, etc. A state in which the two adhere to each other only by physical force, a state in which one or a plurality of carbon nanotubes are entangled so as to be wound around the magnetic particle, etc. are seen. The particles can be used as they are.

  However, in practice, in addition to carbon nanotubes (mainly single-walled carbon nanotubes), nonmagnetic amorphous carbon or the like that does not contain magnetic particles is included, and therefore it is preferable to perform an operation for removing them. For example, the synthesized carbon nanotubes are taken out into a petri dish, the magnet is brought into contact with the bottom of the petri dish, and the carbon nanotubes containing magnetic particles (catalyst) are attached to the bottom of the petri dish by magnetic force, and the components that have not adhered to the magnet (such as amorphous carbon) And a purification method such as leaving only the carbon nanotubes bonded to the magnetic particles in the petri dish. This purification method is an extremely efficient and simple method, and is preferable in that only carbon nanotubes containing magnetic particles can be selectively obtained.

Furthermore, in the metal-encapsulated carbon nanotubes described above, desired magnetic particles may be encapsulated and used as “display particles”. Alternatively, peapod carbon nanotubes in which fullerenes containing desired magnetic particles are encapsulated in carbon nanotubes may be used as “display particles”.
As a method of encapsulating magnetic particles, fullerenes, and fullerene derivatives in carbon nanotubes, a conventionally known method may be employed (for example, a general method described in “Introduction to Material Science of Carbon Nanotubes” by Saihachi Hachihen (Corona)). Is described.)

  When fullerene is used as the carbon structure, desired magnetic particles (atom or a plurality of atoms) may be included and used as “display particles”. As a method of encapsulating magnetic particles in fullerene, a conventionally known method, for example, the method described in “New phase of nanocarbon materials-accelerating full-scale practical use-” supervised by Hissunori Shinohara (CMC Publishing) etc. is adopted. can do.

  By these methods, the metal element or the plurality of atoms that can be included are Ca, Sc, Ti, Sr, Y, Zr, Ba, Hf, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho. , Er, Tm, Yb, Lu, Th, Pa, U, Np, Pu, Am, and the like. On the other hand, fullerene cannot encapsulate magnetic materials such as Fe, Ni, and Co, but carbon nanocapsules can stably encapsulate them, and these can also be used as “display particles”. These can be synthesized in the same manner as the metal-encapsulated fullerene described above. Since the synthesis method is the same as that of the metal-encapsulated fullerene, these are also a kind of metal-encapsulated fullerene.

<Dispersant>
In the present invention, the dispersant (reference numeral 4) is a liquid or a solid (particulate) enclosed in the display layer 6 (and further in the cells C1 and C2) in order to disperse the display particles 2. The dispersant 4 is required to have a function of freely moving the display particles 2 by the action of a magnetic field, and is required to have physical properties such as non-magnetic and a hue other than black. As long as it has, the material to be used is not particularly limited. In addition, the dispersant 4 has a high stability, a carbon structure and magnetic particles, a material that dissolves the transparent substrate 12, the counter substrate 14, and the spacer 8, and does not impair these functions. It is desirable that

Suitable materials for the liquid dispersant (hereinafter sometimes referred to as “dispersion medium”) include polar dispersion media such as water and glycols, and nonpolar dispersion media such as alcohols, organic solvents, and oils. A material used as a dispersion medium in various fields can be used without any problem.
In the case of a liquid dispersant, one having a certain degree of viscosity may be used as long as the display particles 2 can be freely moved. In that respect, the “liquid” referred to in the present invention is a concept including a gel-like object.

  In order to obtain a dispersion medium having a certain degree of viscosity, a fine particle thickener can be added. Examples of the fine particle thickener include silicate fine particles such as anhydrous silicic acid, hydrous aluminum silicate, hydrous calcium silicate, silica, clay, kaolin, bennite, diatomaceous earth, alumina, ultrafine calcium carbonate, Fine active calcium carbonate, heavy calcium carbonate, barium sulfate, hydrous basic magnesium carbonate and the like can be mentioned.

Since carbon structures such as carbon nanotubes and fullerenes are black, it is desirable to color the dispersion medium in an appropriate color in order to make the hue different from these. In order to obtain a high contrast with the black carbon structure, it is particularly advantageous to color white.
In order to color the dispersion medium, a known colorant (various dyes and pigments) may be appropriately dissolved or dispersed. In order to obtain a suitable white color, for example, titanium oxide particles may be used as a colorant and dispersed to form a colloidal solution. The concentration of the colorant in the dispersion medium is not particularly limited, and may be a desired concentration as long as various functions are not impaired.

  As a material suitable as a solid (particulate) dispersant (hereinafter sometimes referred to as “dispersed particles”), polymer particles such as polyvinyl alcohol (PVA), polystyrene (PS), polycarbonate (PC), Alternatively, various materials that are solid at room temperature, such as metal oxide particles such as titanium oxide, silica, and tin oxide, can be used without problems.

  When a high-definition image is to be obtained, it is desirable that the diameter of the dispersed particles be small to some extent. Specifically, it is preferably 1 mm or less, more preferably 1 to 300 μm, and more preferably 10 to 100 μm. Further preferred. At this time, if the display particles 6 and the dispersant 4 are filled in the display layer 6 (and also in the cells C1 and C2) using the dispersed particles having a very small particle size as the dispersant 4, the dispersant 4 becomes Although there is a concern that the movement of the display particles 2 may be restricted, the display particles 2 are not completely filled in the display layer 6 (and further in the cells C1 and C2), and are filled with a margin so that the display particles 2 Movement by a magnetic field can be secured. Therefore, in such a case, it is desirable to appropriately adjust the filling rate in the display layer 6 (and also in the cells C1 and C2).

  As in the case of the dispersion medium, it is desirable to use or color a material having a hue different from black in the case of the dispersed particles. However, if a coating film is formed by applying a paint when coloring, the coating film may fall off due to use and cause display defects. It is desirable to color by mixing in addition to. The colorant that can be used is not particularly limited, and a known colorant can be used according to the purpose. In the case of dispersed particles, as in the case of the dispersion medium, in order to obtain high contrast, it is particularly advantageous to use white dispersed particles or color white.

  The mixing ratio of the dispersant 4 and the display particles 2 varies depending on the materials used, the hue, the filling rate, the thickness of the display layer 6 (or cells C1, C2), etc. As the amount of the display particles 2, at least the upper or lower substrate (12, 14) surface of the display layer 6 (or cells C1, C2) can be uniformly coated, and a black color having a minimum desired density is uneven. It may be the amount that is present without any loss.

<Transparent substrate and counter substrate>
The material of the pair of substrates of the transparent substrate 12 and the counter substrate 14 is not particularly limited, except that at least the transparent substrate 12 on the display side is required to be transparent, and any substrate material that can be used as a substrate is used. be able to. However, since it is desired not to affect the magnetic field applied for writing or erasing, it is desirable to use at least a non-magnetic material.

  As the substrate material, any material having shape retaining properties such as glass, quartz, various resin materials (for example, acrylic, polyethylene, polypropylene, polycarbonate, vinyl chloride, etc.), various ceramic materials (macol, machinable ceramics, etc.) Can also be used.

  The thickness of the substrate is such that a magnetic field applied for writing or erasing can sufficiently act on the internal display layer 6 and the transparent substrate 12 does not affect the display image. There is no particular limitation, and the thickness may be determined as appropriate according to the material to be used, taking into consideration both the thickness sufficient to ensure the shape retention and strength desired for the display medium 10 and the demand for thinning. Specifically, it is selected from a range of about 100 μm to 1 mm, although it varies depending on the material used.

  As described above, as the pair of substrates, at least one of them may be transparent, but both may be transparent substrates. When both are transparent substrates, any surface can be used as a display surface. In that case, the negative image is displayed on the other side of the image on one side.

<Spacer>
In the present invention, the spacer (symbol 8) is a member having a function of dividing the display layer 6 into cells C1, C2,... While maintaining a gap between the transparent substrate 12 and the counter substrate. By providing the spacer 8, a predetermined gap between the transparent substrate 12 and the counter substrate 14 is maintained, and shape retention and strength desired for the display medium 10 can be ensured. Further, by dividing the display layer 6 into cells C1, C2,..., The display particles 2 and the dispersant 4 are separated for each cell, so that the bias of the display medium 10 as a whole is prevented and the image display function is secured. Is done. Further, by dividing the display layer 6 into cells C1, C2,..., It becomes possible to cope with digital writing / display.

The material of the spacer 8 is not particularly limited, but it is desirable to use at least a nonmagnetic material like the substrate. As the spacer material, those exemplified in the substrate can be preferably used as well. In order to minimize the influence on the display image, it is desirable to use a transparent material. However, in some cases, the color can be ignored by sufficiently thinning the spacer.
The material of the substrate and the material of the spacer 8 may be the same or different. However, if the material is the same as that of either the transparent substrate 12 or the counter substrate 14, it can be integrally molded. From the viewpoint of production suitability, it is preferable.

The spacer 8 is desirably as thin as possible so as not to affect the fineness of the display image. Of course, the rigidity required in order to maintain the gap between the transparent substrate 12 and the counter substrate 14 to ensure the shape retention and strength desired for the display medium 10 and the function of fractionating each cell. In addition, the thin film is preferably as thin as possible within a range in which the rigidity can be secured.
The specific thickness of the spacer 8 varies depending on the material used, but when a high-definition display image is to be obtained, it is preferably selected from the range of about 1 μm to 1 mm. More preferably, it is selected from a range of about 5 mm.

[Display element]
In the display element of the present invention, a pair of substrates, at least one of which is light-transmitting, are arranged to face each other, and display particles made of a carbon structure containing magnetic particles are dispersed in the gap between the pair of substrates, and the display particles are dispersed A display medium having a display layer having a dispersing agent to be disposed therein, and a display magnetic field applying unit that applies an image-like magnetic field to any surface of the display medium. Is. That is, the display element of the present invention includes the above-described display element of the present invention and display magnetic field applying means as essential components.

FIG. 2 is a drawing showing a display element which is an example of the present invention, and FIG. 2 (a) is a schematic sectional view thereof. In the figure, an example of a display element capable of writing and displaying an image on the display medium 10 of the present invention described with reference to FIG. 1 is shown. Moreover, FIG.2 (b) is the top view seen from the transparent substrate 12 side of the display element shown to Fig.2 (a). As shown in FIG. 2A, the display medium 10 is a thing in which a total of 121 cells are arranged two-dimensionally, eleven vertically and horizontally.
As shown in FIG. 2, the display element of this example has a magnetic head (display magnetic field applying means) 16 on the display surface side (transparent substrate 12 side) of the display medium 10 and a back surface side (transparent substrate) of the display medium 10. Elongated magnets (erase magnetic field applying means) 18 are respectively provided on the (12 side).

  The magnetic head 16 is provided to apply a magnetic field toward the display surface of the display medium 10 and applies a magnetic field like an image while scanning in the horizontal direction (arrow B direction). When the scanning of the row is completed, it moves to the next row, and a magnetic field is applied like an image while scanning in the horizontal direction. When all the rows (11 rows in the figure) have been scanned, the magnetic head 16 moves to the home position (for example, the area outside the display medium 10 on the left side from the position where the magnetic head 16 is located in FIG. 2B). Return and wait until the next image writing. Or, for example, like a commercially available ink jet printer, the magnetic head 16 can be moved only in the horizontal direction, and the display medium 10 itself can move by one line after the magnetic head 16 scans one line. It does not matter.

In this way, an image is written and displayed. The principle of image writing / display will be described in detail in [Image Display Method] in the next section.
In this example, the magnetic head 16 is exemplified as the display magnetic field applying means, but the present invention is not limited to this. For example, a bar magnet or the like that generates a magnetic field at the end may be used. When such a bar magnet is used as a display magnetic field applying unit, this is regarded as a pen and an image (characters) is displayed on the display surface of the display medium 10 by hand. , Pictures, graphics, etc.), a handwritten image can be written and displayed on the display surface of the display medium 10.

  The long magnet 18 is provided so as to cause a magnetic field to act on the back surface of the display medium 10 among the surfaces in the longitudinal direction, and is configured to be movable in the lateral direction (arrow C direction). The image once written by the magnetic head 16 is erased by moving the long magnet 18 in the horizontal direction and uniformly applying a magnetic field to the entire back surface of the display medium 10.

  After erasing the entire surface of the display medium 10, the long magnet 18 returns to the home position (for example, the place where the long magnet 18 is positioned in FIG. 2B) and waits for the next image erasure. The home position is provided on both the left and right sides, moving in one direction in one erasing operation, waiting in the other home position, moving in one direction again in the next erasing operation, and returning to the original home position. It doesn't matter.

In this way, the image once written is erased. The principle of image erasure will also be described in detail in [Image Display Method] in the next section.
This erasing operation may be performed not for the purpose of erasing but for the purpose of initializing the display medium 10 prior to image writing in order to prevent noise in the display image.

  In this example, the long magnet 18 is exemplified as the erasing magnetic field applying means, but the present invention is not limited to this. For example, a flat magnet that can apply a magnetic field to the entire back surface of the display medium 10 at a time is used so that it is retracted when writing or displaying an image and is opposed to the back surface of the display medium 10 when erasing. It doesn't matter. Alternatively, a bar magnet described as a modification of the display magnetic field applying unit may be used to scan the entire back surface of the display medium 10 during erasing.

  In addition, a planar electromagnet is made to face the back surface of the display medium 10, and the erase operation is controlled by turning on / off the power, or a planar magnet having a size that does not reach the entire back surface of the display medium 10 is used. Various configurations such as a configuration in which this is moved to the entire surface and erased can be exemplified. In any case, as the erasing magnetic field applying means, any configuration may be used as long as the magnetic field can be uniformly applied to the entire back surface of the display medium 10.

  Of course, in the present invention, the erasing magnetic field applying means is not an essential configuration, and this is the case when a permanent image is desired. Further, only when it is necessary to erase, an optional magnet may be separately prepared and a magnetic field may be applied to the entire back surface of the display medium 10 uniformly.

[Image display method]
The image display method of the present invention applies an image-like magnetic field from the display surface side to the display medium of the present invention described above so that the display particles are unevenly distributed on the display surface side only at the site to which the magnetic field is applied. It is characterized by being displayed in black.

  Hereinafter, the display medium shown in FIG. 1 and the display element shown in FIG. 2 will be taken as examples, and the image display method of the present invention will be described focusing on only two cells in the display medium. In this example, a colloidal solution of titanium oxide was used as the dispersant 4. Therefore, the color of the dispersant is white.

FIG. 3A is a schematic cross-sectional view for explaining the image display method of the present invention showing a state in which writing is performed on the display medium shown in FIG. In the figure, lines drawn so as to be emitted radially from the magnetic head 16 are part of the lines of magnetic force.
The magnetic head 16 generates a magnetic field at a position facing the cell C2. This magnetic field acts on the display particles 2 including magnetic particles, and in the cell C2, the display particles 2 are attracted to the transparent substrate 12 side and are unevenly distributed on the display side. Although not shown, the magnetic head 16 scanned in the direction of the arrow B does not generate a magnetic field at a position facing the cell C1, and the display particles 2 are unevenly distributed on the counter substrate 14 side in the cell C1. It does n’t move.

  FIG. 3B is a schematic cross-sectional view showing the state of the display medium 10 after the writing operation is performed as described above. As shown in FIG. 3B, the display particles 2 are unevenly distributed on the counter substrate 14 side in the cell C1 and on the transparent substrate 12 side in the cell C2. Therefore, when viewed from the display surface side (transparent substrate 12 side), the cell C1 is in a white state of the dispersant 4, and the cell C2 is in a black state of the display particles 2 derived from the carbon structure. In this way, white / black is digitally selected for each cell, and a black image is formed on a white background on the entire display surface of the display medium 10.

  If the magnetic head 16 is sufficiently smaller than the cells C1 and C2, white / black is not selected for each cell, but the on / off of the magnetic field is partially controlled in one cell to display particles. It is also possible to perform so-called analog writing in which 2 is partially moved to the transparent substrate 12 side or is left unevenly distributed on the counter substrate 14 side.

  As described above, according to the present invention, the particle size of the carbon structure (carbon nanotube or fullerene) used as the display particle 2 is very small. Therefore, in the case of analog writing, the particle size of the display particle 2 remains as it is. Of course, since the resolution is directly related to the resolution, even in the case of digital writing, each cell can be made extremely fine, so that the resolution of the display image is increased. For the same reason, the boundary portion of the image display portion becomes very sharp.

According to the present invention, since the particle size of the carbon structure used as the display particles 2 is very small and light, the speed at the time of magnetophoresis is high (the display speed is fast), and the driving force may be small. Therefore, it is advantageous in terms of energy cost.
In addition, since the particle size of the carbon structure used as the display particles 2 is very small and light, electrostatic force, van der Waals force, etc. act effectively, and the uneven distribution of the display particles 2 is maintained by these forces, and once formed. Images are held for a long time.

Furthermore, since the color of the display particle 2 is derived from the carbon structure (carbon nanotube or fullerene) and is completely black, the contrast can be easily increased by combining with a dispersing agent such as using a white dispersing agent. .
In addition, since the carbon structure used as the display medium 10 itself and the display particles 2 is light, and the display layer 6 can be thinned, the overall weight can be reduced.

  In addition, when the carbon nanotubes produced using the magnetic particles as the catalyst are used as the display particles 2 without being separated, the carbon particles of the carbon nanotubes are produced at the time of carbon nanotube production. Since many of the catalyst magnetic particles are chemically bonded, the carbon nanotubes are unlikely to be peeled off from the magnetic particles, and there is little fear of contaminating the display layer 6.

  In addition, in the case of magnetic particles such as ferrite coated, there is a concern that the coating film may be peeled off and the particles themselves may be oxidized. However, carbon nanotubes and fullerenes, which are carbon structures, are not oxidized. Even if not, it exhibits almost completely black color, and further, since the catalyst surface forms a solid solution with carbon, the magnetic particles are not oxidized, so the color of the display particles 2 itself does not change. In order to use magnetic particles such as ferrite that are oxidized as a display material without coating, a protective layer or a colored layer is required as described in Patent Document 1, but a carbon structure is displayed. In the present invention used as a material, these layers are of course unnecessary.

  In the above example, the description has been made on the assumption that the counter substrate 14 is not transparent. However, when the transparent substrate 12 is made of the same material as that of the transparent substrate 12 and used as a display medium for both front and back display, the above display is performed. As can be seen from FIG. 3B, the image viewed from the back side (opposite substrate 14 side) with respect to the surface is black of the display particles 2 in which the cell C1 is derived from the carbon structure, and the cell C2 is the dispersant 4. It becomes the state which exhibited white. That is, a black image is formed on a white background on the display surface side (transparent substrate 12 side), and a white image is formed on a black background on the back surface side (counter substrate 14 side). Both have a positive / negative relationship.

  The rewritable marking technology is established by erasing the image once written and preparing for the next writing. The image formed by the image display method of the present invention described above can be erased by the erasing method described with reference to FIG. Here, FIG. 4 is a schematic cross-sectional view showing a state in which an image written on the display medium is erased by the image display method described in FIG. 3, and FIG. 4 (b) represents a state in which the erasing operation has slightly advanced. In the drawing, lines drawn so as to be emitted radially from the long magnet 18 are part of the lines of magnetic force.

  When the long magnet 18 moves in the direction of arrow C due to the start of the erasing operation, a magnetic field acts from the back side (opposite substrate 14 side) of the display surface of the display medium 10, and FIGS. 4 (a) to 4 (b). As time elapses, a magnetic field is uniformly applied to the cells C1 and C2. Therefore, in the cell C1, since the display particles 2 are already unevenly distributed on the counter substrate 14 side, they do not move as they are, but in the cell C2 in which the display particles 2 are unevenly distributed on the transparent substrate 12 side, the display is performed. The particles 2 are attracted to the counter substrate 14 side and are unevenly distributed on the back surface side of the display surface.

  By the movement of the long magnet 18 in the arrow C direction, a magnetic field is sequentially applied to each cell, and the display particles 2 in a state of being unevenly distributed on the transparent substrate 12 side are attracted to the counter substrate 14 side. When a magnetic field is applied, all the display particles 2 are attracted to the counter substrate 14 side and the display image is erased.

  This erasing operation is performed not only for the purpose of erasing but also for the purpose of initializing the display medium 10 before the image is written, and the display particles 2 are unevenly distributed in advance on the back surface side (opposite substrate 14 side) of the display surface. It is also a preferable aspect to keep. If, for example, a part of the display particles 2 has moved to the display surface side before writing, it will be a stain (noise) on the display image. In this case, it is possible to form a high-definition and high-contrast image without such contamination.

  Of course, even if the display particles 2 are not completely unevenly distributed on the back surface side of the display surface, for example, even if they are present in a dispersed state in the display layer 6, the display surface after writing as long as it is not unevenly distributed on the display surface Since sufficient contrast is obtained with the uneven distribution state, the erase operation for initialization is not an essential configuration.

By the way, contrary to the display element of the example shown in FIG. 2, the display magnetic field applying means is arranged on the back side of the display surface, the erasing magnetic field applying means is arranged on the display surface side, and an image is displayed on the display medium 10. It is also possible to write. FIG. 5 is a schematic cross-sectional view of a display element of a modification example having such a configuration. The plan view is omitted.
As shown in FIG. 5, the display element of the modification has a long magnet (erase magnetic field applying means) 18 ′ on the display surface side (transparent substrate 12 side) of the display medium 10, and the back surface side of the display medium 10 ( Magnetic heads (display magnetic field applying means) 16 ′ are provided on the transparent substrate 12 side.

  The long magnet 18 ′ is provided so as to apply a magnetic field toward the display surface of the display medium 10 among the surfaces in the longitudinal direction, and is configured to be movable in the lateral direction (arrow C ′ direction). On the other hand, the magnetic head 16 ′ is provided to apply a magnetic field toward the back surface of the display medium 10, and applies a magnetic field like an image while scanning in the horizontal direction (arrow B ′ direction).

In order to write an image with the display element of the modification, a so-called erasing operation for initialization (hereinafter, simply referred to as “initialization operation”) is an essential configuration.
An image display method according to a modification of the present invention in which an image is written on the display element shown in FIG. 5 will be described with reference to FIGS.

  6A and 6B are schematic cross-sectional views for explaining the initialization operation performed before actually writing an image. FIG. 6A is a diagram immediately after the start of the initialization operation, and FIG. 6B is the initialization operation. Indicates a slightly advanced state. In the drawing, lines drawn so as to be emitted radially from the long magnet 18 'are part of the lines of magnetic force.

When the long magnet 18 'arranged on the display surface side moves in the direction of arrow C by the start of the initialization operation, the display particles 2 in the dispersed state or the unevenly distributed state are as shown in FIG. 6B. All are attracted to the display surface side (transparent substrate 12 side) and are unevenly distributed.
FIG. 7A is a schematic cross-sectional view for explaining an image display method of a modified example showing a state in which writing is performed using the display element shown in FIG. In the figure, lines drawn so as to be emitted radially from the magnetic head 16 'are part of the lines of magnetic force.

  The magnetic head 16 'generates a magnetic field at a position facing the cell C2. This magnetic field acts on the display particles 2 including magnetic particles, and is attracted to the counter substrate 14 side in the cell C2 and is unevenly distributed on the back surface side of the display surface. Although not shown, the magnetic head 16 ′ scanned in the direction of the arrow B ′ does not generate a magnetic field at a position facing the cell C1, and the display particles 2 are unevenly distributed on the transparent substrate 12 side in the cell C1. It does not move as it is.

FIG. 7B is a schematic cross-sectional view showing the state of the display medium 10 after the writing operation is performed as described above. As shown in FIG. 7B, the display particles 2 are unevenly distributed on the transparent substrate 12 side in the cell C1 and on the counter substrate 14 side in the cell C2. Therefore, when viewed from the display surface side (transparent substrate 12 side), the cell C1 is in the state of black of the display particles 2 derived from the carbon structure, and the cell C2 is in the state of white of the dispersant 4. In this way, white / black is digitally selected for each cell, and a white image is formed on a black background on the entire display surface of the display medium 10. Note that analog writing is also possible, as in the example of FIG. 3 using the display element of FIG.
Thereafter, if the erase operation is performed in the same manner as the initialization operation, it is possible to prepare for the next writing, and it can be seen that even in the case of the present modification, it is practical as a rewritable marking technique.

  As described above, the display medium, the display element, and the image display method of the present invention have been described with specific examples. However, the present invention is not limited to these specific examples, and various modifications and improvements can be made according to conventionally known knowledge. Can be added. Of course, as long as the configuration of the present invention is provided, it goes without saying that various modifications and improvements are included in the scope of the present invention.

Next, the present invention will be described more specifically by giving examples of the display medium of the present invention having a simple configuration. Of course, the present invention is not limited to the following examples.
<Example 1>
FIG. 8 is a schematic cross-sectional view of a display medium manufactured in this example. The display medium has a structure in which a slide glass 22 is bonded to an opening of a rectangular flat container 24 made of a fluororesin. A gap is formed between the flat container 24 and the slide glass 22, and this constitutes the display layer 26. That is, the slide glass 22 corresponds to the transparent substrate according to the present invention, and the bottom of the flat container 24 corresponds to the counter substrate.

The size of the gap between the flat container 24 and the slide glass 22 is 20 mm × 20 mm × 1 mm. In the gap constituting the display layer 26, a titanium oxide colloid solution (manufactured by nano corp., NTS-20: 10 mass% aqueous solution of titanium oxide particles having a particle size of 20 to 30 nm) is added to 15 ml of single-walled carbon nanotubes (MTR Ltd.). Made by magnet, refined with magnet, carbon nanotube average diameter about 30 nm, average length about 1 μm, catalyst was Co particles, number average particle diameter 20 nm.) 1 mg dispersed was enclosed.
The display medium of the present embodiment having the above configuration is suitable for analog image writing because the display surface is not divided into cells.

  As shown in FIG. 8, while holding the display medium of the present embodiment vertically, a neodymium magnet (Nd—Fe—B) is brought closer to the half region of the entire display surface from the slide glass 22 side to A black display with nanotubes and a white display with dispersion were formed. Even when the neodymium magnet was moved away from the display medium, the formed display image was maintained as it was without disappearing.

When the boundary portion between the white display and the black display of the obtained display image was visually confirmed, it was exactly in a straight line.
The contrast ratio of white display and black display of the obtained display image was compared using a spectral densitometer (manufactured by X-Rite). Assuming that the white display is 0, the black display is 0.7.
Furthermore, although it was left as it was for one week, no change appeared in the displayed image, and the contrast ratio was maintained.

<Example 2>
Similar to Example 1, a display medium having the structure shown in FIG. 8 was produced. However, the following points have been changed.

(1) As the flat container 24, a ceramic product that can be machined is used.
(2) The dimension of the space between the flat container 24 and the slide glass 22 was 20 mm × 20 mm × 5 mm.
(3) A mixture of 50 mg of polyvinyl alcohol (PVA) particles (particle size: 1 mm) and 1 mg of single-walled carbon nanotubes (same as above) was sealed in the gaps constituting the display layer.

In the same manner as in Example 1, a display image was formed by a neodymium magnet so that a half area of the entire display surface of the display medium was black display by carbon nanotubes and the rest was white display by a dispersant. Even when the neodymium magnet was moved away from the display medium, the formed display image was maintained as it was without disappearing.
When the boundary portion between the white display and the black display of the obtained display image was visually confirmed, it was exactly in a straight line. From this result, it was found that even when the dispersant was solid, the display particles (carbon nanotubes) migrated by magnetic force and can be displayed.

The contrast ratio of white display and black display of the obtained display image was compared using a spectral densitometer (manufactured by X-Rite). Assuming that the white display is 0, the black display is 0.9. Since the dispersant is solid particles, it is considered that the whiteness is increased due to irregular reflection, and the contrast ratio is improved.
Furthermore, although it was left as it was for one week, no change appeared in the displayed image, and the contrast ratio was maintained.

<Example 3>
In Example 1, except that the voids constituting the display layer 26 were filled with a mixture of 200 mg of SiO ₂ particles (particle size: 10 to 30 nm) and 1 mg of single-walled carbon nanotubes (same as above). In the same manner as in Example 1, a display medium having the structure shown in FIG. 8 was produced.

In the same manner as in Example 1, a display image was formed by a neodymium magnet so that a half area of the entire display surface of the display medium was black display by carbon nanotubes and the rest was white display by a dispersant. Even when the neodymium magnet was moved away from the display medium, the formed display image was maintained as it was without disappearing.
When the boundary portion between the white display and the black display of the obtained display image was visually confirmed, it was exactly in a straight line. From this result, it was found that even when the dispersant is as large as the display particles (carbon nanotubes), the display particles migrate by magnetic force and can be displayed.

The contrast ratio of white display and black display of the obtained display image was compared using a spectral densitometer (manufactured by X-Rite). Assuming that the white display is 0, the black display is 0.9. Since the dispersant is solid particles, it is considered that the whiteness is increased due to irregular reflection, and the contrast ratio is improved.
Furthermore, although it was left as it was for one week, no change appeared in the displayed image, and the contrast ratio was maintained.

<Example 4>
In Example 1, 1 mg of nickel (Ni) -encapsulated fullerene (carbon nanocapsule) produced by the following method was used as display particles, and this was dispersed in the same dispersion (titanium oxide colloid solution 15 ml) as in Example 1. A display medium having the structure shown in FIG. 8 was produced in the same manner as in Example 1 except that was enclosed in the voids constituting the display layer 26.

(Production of nickel-encapsulated fullerene)
Ni-encapsulated fullerene was synthesized by the following method.
A 1 mmφ hole was drilled in a carbon rod (15 mmφ), and Ni particles (particle size 100 μm) were filled therein, and this was used as an electrode for arc discharge in vacuum to synthesize. Black traps attached to the wall of the vacuum chamber were collected and purified with a magnet in the same manner as for single-walled carbon nanotubes. When the wrinkle attracted to the magnet was observed with a scanning transmission electron microscope, it was confirmed that a metal element was present in the carbon nanocapsule.

  Furthermore, Ni was detected by elemental analysis (SEM-EDX) of the soot, and it was confirmed that Ni-containing carbon nanocapsules could be synthesized. Since the Ni-encapsulated carbon nanocapsule is encapsulated in a cage in which Ni atoms are made of carbon, it can be considered as a kind of metal-encapsulated fullerene.

In the same manner as in Example 1, a display image was formed by a neodymium magnet so that a half area of the entire display surface of the display medium was black display by Ni-encapsulated fullerene and the rest was white display by a dispersant. Even when the neodymium magnet was moved away from the display medium, the formed display image was maintained as it was without disappearing.
When the boundary portion between the white display and the black display of the obtained display image was visually confirmed, it was exactly in a straight line. From this result, it was found that display particles can be displayed not only with carbon nanotubes but also with metal-encapsulated fullerenes.

The contrast ratio of white display and black display of the obtained display image was compared using a spectral densitometer (manufactured by X-Rite). Assuming that the white display is 0, the black display is 0.7.
Furthermore, although it was left as it was for one week, no change appeared in the displayed image, and the contrast ratio was maintained.

<Example 5>
FIG. 9 is a schematic cross-sectional view of a display medium manufactured in this example. The display medium has a structure in which four rectangular flat containers 34 made of a fluororesin are juxtaposed in the lateral direction and connected, and a slide glass 32 is bonded so as to cover the entire opening. A space is formed between each flat container 34 and the slide glass 32, and this constitutes the display layer 36. That is, the slide glass 32 corresponds to the transparent substrate according to the present invention, and the bottom of the flat container 34 corresponds to the counter substrate.

The space | interval of each space | gap between the flat container 34 and the slide glass 32 is about 1 mm, ie, it has the structure partitioned off with the fluororesin of 1 mm in width. The size of each gap is 10 mm × 10 mm × 1 mm. As in Example 1, the voids constituting the display layer 36 were each sealed with 1 mg of single-walled carbon nanotubes dispersed in 15 ml of a titanium oxide colloid solution.
The display medium of the present embodiment having the above configuration is suitable for digital image writing in which the display surface is divided into cells.

  As shown in FIG. 9, a neodymium magnet (Nd—Fe—B) is brought close to the two ends of the four cells from the slide glass 32 side while the display medium of the present embodiment is held vertically. A black display with carbon nanotubes was formed. Even when the neodymium magnet was moved away from the display medium, the formed display image was maintained as it was without disappearing.

When the black display of the obtained display image was confirmed visually, the entire cell surface was black.
Next, a neodymium magnet was brought closer from one end, the flat container 34 side, and the displayed black display was erased. When visually observed, the cells at both ends returned to the white display of titanium oxide. Furthermore, a black display by carbon nanotubes was formed by bringing a neodymium magnet close to the center two cells from the slide glass 32 side. Even when the neodymium magnet was moved away from the display medium, the formed display image was maintained as it was without disappearing.

From the above results, it was confirmed that so-called digital display was possible when divided into cells.
Furthermore, although it was left as it was for one week, no change appeared in the displayed image, and the contrast ratio was maintained.

<Comparative Example 1>
In Example 2, Example 2 except that the gap constituting the display layer 26 was filled with the same titanium oxide colloidal solution as in Example 1: 15 ml of ferrite particles (particle size 50 μm) dispersed in 15 mg. In the same manner, a display medium having the structure shown in FIG. 8 was produced.

  In the same manner as in Example 1, a display image was formed by a neodymium magnet so that a half area of the entire display surface of the display medium was black display by carbon nanotubes and the rest was white display by dispersion. When the neodymium magnet was separated from the display medium, a part of the ferrite particles dropped off, and the formed display image was slightly thinned.

When the boundary portion between the white display and the black display of the obtained display image was visually confirmed, the ferrite particles were confirmed and became rough and jagged.
The contrast ratio of white display and black display of the obtained display image was compared using a spectral densitometer (manufactured by X-Rite). Assuming that the white display is 0, the black display is 0.6.
Further, it was left as it was, but after 3 days, the ferrite particles were oxidized and turned from black to brown.

  As described above, the display medium according to the present invention can be easily manufactured and has a wide range from low cost to high resolution and high contrast to simple use of handwriting to high-definition image writing with a magnetic head. Applications are expected and it is extremely useful as a rewritable marking technology.

It is a schematic cross section of a display medium which is an example of the present invention. It is drawing showing the display element which is an example of this invention which writes an image in the display medium of FIG. 1, (a) is a schematic cross section, (b) is a top view. FIG. 3 is a schematic cross-sectional view for explaining an image display method according to an example of the present invention in which an image is written by the display element of FIG. 2, and (a) shows a state in which writing is performed on the display medium shown in FIG. 1. , (B) shows the state of the display medium after the writing operation. 4A and 4B are schematic cross-sectional views showing a state in which an image written on a display medium is erased by the image display method described in FIG. It represents the advanced state. It is drawing which represents the display element which is another example (modification) of this invention which writes an image in the display medium of FIG. 1, (a) is a schematic cross section, (b) is a top view. FIG. 6 is a schematic cross-sectional view for explaining an initialization operation performed prior to image writing in an image display method according to a modified example of the present invention in which an image is written by the display element of FIG. 5, and FIG. Immediately after the start, (b) represents a state in which the initialization operation has slightly advanced. FIG. 6 is a schematic cross-sectional view for explaining an image writing operation in an image display method according to a modified example of the present invention, in which an image is written by the display element of FIG. 5, and (a) shows writing on the display medium shown in FIG. 5. (B) shows the state of the display medium after the writing operation. 3 is a schematic cross-sectional view of display media manufactured in Examples 1 to 4 and Comparative Example 1. FIG. 6 is a schematic cross-sectional view of a display medium manufactured in Example 5. FIG.

Explanation of symbols

  2: display particles, 4: dispersant, 6, 26, 36: display layer, 8: spacer, 10: display medium, 12: transparent substrate (substrate having optical transparency), 14: counter substrate (substrate), 16 : Magnetic head (display magnetic field applying means), 18: long magnet (erasing magnetic field applying means), 22, 32: slide glass (light-transmitting substrate), 24, 34: flat container (substrate), C1 , C2: Cell

Claims (20)

A display medium comprising: display particles comprising a carbon structure containing magnetic particles; and a display layer having therein a dispersant for dispersing the display particles. The display medium according to claim 1, wherein the carbon structure is a carbon nanotube. The display medium according to claim 2, wherein the carbon nanotube is a single-walled carbon nanotube. The display medium according to claim 2, wherein the display particles are in a state in which the magnetic particles are attached to the carbon nanotubes. The display medium according to claim 1, wherein the magnetic particles have a particle size of 50 μm or less. The display medium according to claim 1, wherein the display medium is obtained by using carbon nanotubes produced using magnetic particles as a catalyst as they are as the display particles without separating the magnetic particles used. The display medium according to claim 1, wherein a pair of substrates, at least one of which is light transmissive, are arranged to face each other, and the display layer is arranged in a gap between the pair of substrates. The display medium according to claim 7, wherein a spacer for dividing the display layer into a plurality when viewed from above is disposed while maintaining a gap between the pair of substrates. A pair of substrates, at least one of which is light transmissive, are arranged to face each other, and a display particle made of a carbon structure containing magnetic particles and a dispersant for dispersing the display particles are provided in the gap between the pair of substrates. A display element comprising: a display medium on which a display layer is disposed; and a display magnetic field applying unit that applies a magnetic field like an image to any surface of the display medium. 10. The display element according to claim 9, wherein the display magnetic field applying unit in the display medium includes an erasing magnetic field applying unit that uniformly applies a magnetic field to the back surface of the front surface to which the magnetic field is applied. . The display device according to claim 9, wherein the carbon structure is a carbon nanotube. The display device according to claim 11, wherein the carbon nanotube is a single-walled carbon nanotube. The display element according to claim 11, wherein the display particles are in a state where the magnetic particles are attached to the carbon nanotubes. The display element according to claim 9, wherein a particle diameter of the magnetic particles is 50 μm or less. The display element according to claim 9, wherein the display element is obtained by using carbon nanotubes produced using magnetic particles as a catalyst as they are as the display particles without separating the magnetic particles used. The display element according to claim 9, wherein a spacer for dividing the display layer into a plurality when viewed from above is disposed while maintaining a gap between the pair of substrates. The display element according to claim 9, wherein the display magnetic field applying unit is a magnetic head that scans a surface of the display medium. By applying an image-like magnetic field from the display surface side to the display medium according to claim 1, only the portion to which the magnetic field is applied causes the display particles to be unevenly distributed on the display surface side and displayed in black. Image display method. 19. The display particles according to claim 18, wherein the display particles are unevenly distributed in advance on the back surface side by uniformly applying a magnetic field to the entire back surface side of the display surface prior to applying the image-like magnetic field. Image display method. By applying a magnetic field uniformly to the display surface side to the display medium according to claim 1, the display particles are preliminarily unevenly distributed on the display surface side, and then from the back side of the display surface. An image display method, wherein an image-like magnetic field is applied to display a portion to which a magnetic field is applied in the color of the dispersant.

Images