JP2005283744A - Display medium and full-color display method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a full-color display method capable of performing full-color display and erasing on a low-cost display medium with good response speed and image stability during storage.
A holding layer 4 made of a heat-meltable material is formed between a base 2 made of a nonmagnetic material and a protective layer 4, and the holding layer 4 has a hue different from each other and has a polarity and a magnetic property. By preparing a display medium 1 in which four different kinds of colored particles 5K, 5C, 5M, and 5Y are dispersed and applying a magnetic field and an electric field to the colored particles 5K, 5C, 5M, and 5Y while heating the display medium 1, The colored particles 5K, 5C, 5M, and 5Y are selectively moved to the display surface side to perform full color display.
[Selection] Figure 3

Description

  The present invention relates to a display medium and a full-color display method that can be rewritten and erased by heat, a magnetic field, and electrostatic force.

As a rewritable, compact (portable) color display device such as electronic paper or paper-like display, it has a recording medium in which microcapsules or cells (display elements) enclosing liquid, white particles, and black particles are formed in layers. A display device that combines a color filter with a device that selectively attracts a display element with magnetic or electrostatic force has been developed.
For example, in a twisting ball display, charged beads divided into two colors are dispersed between two transparent plastic sheets filled with oil, and when a voltage is applied to the surface of the plastic sheet, the charged beads Is configured to rotate so that the side of a certain color faces the viewer and then stops. This display can maintain the image display as it is displayed, and can be viewed with reflected light. Moreover, since it is electrically written and erased, it is possible to quickly rewrite part or all of the image. There is.
A microcapsule-type electropermanent display is a type of electrophoresis system, in which two types of microparticles in which two types of particles, black particles (for example, carbon black) and white particles (for example, titanium oxide) charged negatively and positively are encapsulated, are encapsulated. In this method, capsules are prepared, and an electric field is applied to these microcapsules from outside to move the particles in the microcapsules and collect them on the front side or collect them on the bottom side to change the color seen on the front side. The moved microcapsules remain displayed even after the power is turned off.

  According to the above display method, black and white display or monocolor display using color particles can be performed, but full color display cannot be performed. Therefore, in order to perform full color display, a color filter is required. A color filter divides one pixel into three regions and arranges a set of red, green, and blue stripes. By controlling the microcapsules under red, green, and blue, they are white, black, and gray. Full color can be realized. When a color filter is used, an active display device can be configured. However, an active type display device has several hundred or more scanning lines, and a voltage is applied to each cell through a thin film active element provided at each intersection of dot-matrix wirings. It is manufactured by a manufacturing process, the yield is reduced on a large screen, the cost is high, and it is difficult to put it into practical use as a passive display element.

Therefore, it has been studied to perform full color display without using a color filter. For example, in Patent Document 1, one of two colored charged particles encapsulated in a capsule made of a hollow spherical transparent resin is colored in any one of four colors obtained by adding black to three primary colors in an additive color mixture. The direction of the control electric field for each pixel and the recording medium in which four types of microcapsules in which charged particles with different mirror image forces are encapsulated are formed in layers and electrodes provided so as to sandwich the recording medium By applying a control electric field of varying intensity, the charged particles of each color are selectively perpetually displayed on the display surface using the difference in mirror image force, and a full color image is displayed and recorded on the recording medium. Is described. According to this electrophoretic display device, each microcapsule can be displayed in a color image by controlling the electric field of each microcapsule without being individually positioned in a predetermined manner, so that the cost can be reduced. .
In Patent Document 2, a recording layer is provided on a support, and a plurality of fine void members having voids are arranged in the recording layer. White magnetic particles are placed at room temperature inside the fine void members, respectively. A magnetic field is applied to the recording layer of the display medium that is dispersed in a heat-fusible organic compound colored in an arbitrary color that indicates a solid phase state in FIG. It is described that an image is displayed by selectively moving particles. According to this display device, there is an advantage that the color tone is clear, high-resolution full-color display can be performed, and sharp and clear image display can be erased.

The magnetic particles for color image display can be produced by various methods. For example, magnetic particles having a predetermined hue can be obtained by using an organic magnetic material that is a transparent or translucent material. However, since the magnetic particles have a low magnetic force, a color image with a low density is formed and the manufacturing cost increases. Therefore, the current magnetic particles for color images generally use a wet chemical reaction. It is manufactured. For example, Patent Document 3 discloses a method in which a powder is dispersed in a metal alkoxide solution and the metal alkoxide is hydrolyzed to form a metal oxide film on the powder surface. It is described that the powder dispersion is heated after the reaction. Further, in Patent Document 4, when an encapsulated magnetic toner comprising a core material mainly composed of magnetic particles and a shell material covering the core material is manufactured, the shell material is formed of a layer of an inorganic metal compound having a high refractive index. The formation by precipitation reaction is described.
Has been described.
JP 2000-322007 A (page 4-9, FIGS. 3 and 4) JP 2003-322882 A (page 3-6, FIG. 3-7) JP-A-10-67503 (page 3-5) JP-A-6-102696 (page 2-3)

However, since the display device described in Patent Document 1 uses a microcapsule in which a liquid dispersion medium in which charged particles are permanently dispersed is used, a low-viscosity dispersion medium is used to increase the response speed. The image stability during storage is lowered, whereas when a dispersion medium having a high viscosity is used, the image during storage is stabilized, but the response speed is lowered. In addition, the display device described in Patent Document 2 is mainly composed of three types of hot-melt organic compounds that show a solid state at room temperature in which white magnetic particles are dispersed and show a fluid state when heated to room temperature or higher. Since the microcapsules in which the core material is encapsulated are used, the stability of the image during storage is reduced when a low-viscosity dispersion medium is used to increase the response speed, similar to that described in Patent Document 1. On the other hand, when a high-viscosity dispersion medium is used, the image during storage is stabilized, but there is a drawback that the response speed is lowered.
Further, the toner described in Patent Document 3 uses a difference in refractive index of each metal oxide film, and thus has a problem that particles with high brightness cannot be obtained. Furthermore, since the toner described in Patent Document 4 forms a shell substance by a wet chemical reaction, there is a problem that the usable materials are limited and the manufacturing cost may increase.

  An object of the present invention is to provide a full-color display method capable of performing full-color display and erasure on a low-cost display medium with good response speed and image stability during storage.

  In order to achieve the above object, the display medium of the present invention is different in hue between a base made of a non-magnetic material and a heat-meltable material formed on the base and has at least one of charging polarity and magnetism. And a holding layer in which four different kinds of colored particles are dispersed.

  In order to achieve the above object, the full-color display method of the present invention has a holding layer made of a heat-meltable material formed on a substrate made of a nonmagnetic material, and the holding layer has a different hue and charging. Either of the colored particles is prepared by preparing a display medium in which four kinds of colored particles different in at least one of polarity and magnetism are dispersed, and applying an electric field and a magnetic field to the colored particles while heating the holding layer. One type is moved to the display surface side of the display medium.

  In the present invention, the colored particles are preferably composed of two types of magnetic particles having different charging polarities and two types of nonmagnetic particles having different charging polarities.

  According to the display medium and the full-color display method of the present invention, a magnetic field and an electric field according to the characteristics are applied to a plurality of types of colored particles having different magnetic and charged polarities dispersed inside the display medium while heating the display medium. Therefore, the largest driving force can be given to any one kind of colored particles. As a result, it is possible to selectively move one type of colored particles to a specific side (display surface side) of the display medium. After the heating is stopped, the temperature of the holding layer is lowered and the fluidity is lost, so that the moved colored particles are fixed there. Thus, full-color display with high response speed and high image stability during storage can be performed.

  According to the present invention, full-color display can be performed using a passive display medium, so that the cost of the display medium can be reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. 1 is a cross-sectional view schematically showing a display medium used in the present invention, FIG. 2 is a cross-sectional view schematically showing colored particles, and FIG. 3 is a schematic view of a display medium for explaining the display method of the present invention. FIG.

In FIG. 1, reference numeral 1 denotes a display medium, which can take various forms such as a card, a sheet, and a film, and is a holding layer formed between a substrate 2 and a protective layer 3 as a rewritable recording layer. 4. Inside the holding layer 4, there are three kinds of colored particles that can be subtractively mixed with cyan, magenta, and yellow, which are the three primary colors of light, the magnetic colored particles 5C, the nonmagnetic colored particles 5M and 5Y, and the magnetic properties of black. The colored particles 5K are dispersed.
The base 2 is a flexible member formed of a non-magnetic material, for example, engineering plastics such as polyethylene terephthalate, polycarbonate, and polyester, paper, metal materials such as aluminum alloy and austenitic stainless steel. And is selected according to the required properties (rigidity, concealment, etc.) according to the application.
The protective layer 3 is formed of a non-magnetic material having optical transparency so that the retaining layer 4 is protected and the hue of the colored particles can be visually recognized from the outside. Examples of such materials include acrylic resins and engineering plastics (polyethylene terephthalate, polycarbonate, polyester, polytetrafluoroethylene, polymethyl methacrylate, etc.).
The holding layer 4 is solid at normal temperature, but can be heat-melted when heated to a relatively low temperature (60 to 90 ° C.), for example, waxes such as paraffin wax (natural wax or synthetic wax may be used). ). Therefore, the colored particles filled in the holding layer 3 can move in any direction by heating and melting the holding layer 3.

  For example, the colored particles have the following particle structure. As shown in FIG. 2A, the magnetic colored particle 5C is a positively charged magnetic particle having a core particle 6 made of a magnetic material, a concealing layer 7 covering the surface, and a colored layer 8 covering the surface. . The core particle 6 is a magnetic fine particle composed of a metal element exhibiting ferromagnetism such as Fe, Ni, Co, or an oxide thereof, or a particle obtained by dispersing the magnetic fine particle in a thermoplastic resin. It has an average particle size of 5-15 μm. Since the core particle 6 usually has a brown or black hue, the masking layer 7 is a layer in which a white pigment is dispersed in a binder resin in order to mask the hue. The colored layer 8 is a layer in which a colorant 9 and a charge control agent 10 imparting positive charge characteristics are dispersed in a binder resin.

  As shown in FIG. 2 (b), the magnetic colored particles 5K are negatively charged magnetic particles in which a coloring agent 9, a charge control agent 10 for imparting negative charging characteristics, and magnetic fine particles 11 are dispersed in a binder resin. is there. As shown in FIG. 2C, the nonmagnetic colored particles 5Y are positively charged nonmagnetic particles in which a colorant 9 and a charge control agent 10 imparting a positive charging property are dispersed in a binder resin. As shown in FIG. 2D, the non-magnetic colored particles 5M are non-magnetic particles having a negative charging polarity in which a coloring agent 9 and a charge control agent 10 imparting a negative charging property are dispersed in a binder resin.

  The colored particles can be made of the following materials, for example. As the binder resin, for example, a vinyl resin such as a styrene resin or an olefin resin, or a known toner resin such as an epoxy resin or a polyester resin can be used. Titanium oxide can be used as the white pigment, but since anatase type particles are easily yellowed, rutile type particles are preferred. As other colorants, inorganic or organic pigments or dyes corresponding to a desired hue can be used. Red pigments include inorganic pigments such as cadmium red and cadmium mercury red, organic pigments such as quinacridone maroon medium red and pigment scarlet blueish red, and yellow pigments such as chrome yellow, ceramic yellow, zinc chromate yellow, and cadmium sulfide yellow. Inorganic pigments, nickel azo green yellow (organic pigments), green pigments such as inorganic pigments such as chrome oxide green and chrome green, organic pigments such as chromium oxide dull green and phthalocyanine green, and ultramarine as blue pigments Inorganic pigments such as blue and cobalt aluminate blue or organic pigments such as phthalocyanine blue and indanthrene blue can be used.

  As the charge control agent, a charge control substance that imparts positive or negative charge is used. Examples of positive charge control substances include nigrosine bases and derivatives thereof, quaternary ammonium salts, naphthenic acid or higher fatty acid salts, alkoxylated amines, alkylamides, triphenylmethane dyes, and these positive-polarity substances in the side chain. Oligomer or polymer, quaternary pyridinium, metal salts of higher fatty acids can be used. As the negative charge control substance, a metal-containing (Cr or Fe) azo complex dye, salicylic acid or its derivative chromium-zinc-aluminum-boron complex may be used. However, these charge control substances have a difference in solubility between the coating resin and the dispersion medium (for example, ethylene oxide), and use a material having high solubility in the coating resin or a material having high affinity when dispersed in the coating resin. It is desirable to do.

The colored particles can be produced by the following process. For example, the magnetic colored particles 5C are produced by a phase separation method using a non-aqueous emulsion. That is, the colored particles 5C are desirably prepared by a phase separation method using a non-aqueous emulsion in order to cover the surface of the core particles with a concealing layer. Phase separation is defined as the separation of a homogeneous mixture of two or more components into two or more phases according to equilibrium conditions (temperature, pressure, concentration, etc.). This is called a phase separation method using a non-aqueous emulsion because phase separation is performed after dispersing core particles made of a magnetic material and a binder resin in which a white pigment is dispersed in a solvent other than water. That is, according to the present invention, a mixture of core particles made of a magnetic material, a binder resin in which a white pigment is dispersed, and a dispersion medium incompatible with this resin is prepared, and this is mixed with a kneader or a mixer. By kneading while heating at a temperature lower than the softening point, core particles made of a magnetic material are dispersed in a binder resin to obtain white particles in which the core particles are covered with a concealing layer. When the heating temperature of the above mixture is low, it is not dispersed in the fine particles, and when it is high, thermal decomposition of the binder resin tends to occur. Therefore, it is desirable to set the heating temperature to be 10-30 ° C. lower than the softening point of the binder resin. The kneaded product is put into hot water and stirred to dissolve the dispersion medium, and then the white particles are separated by, for example, a centrifuge. Next, the white particles are washed (for example, washed with water and washed with alcohol) and dried. Then, the white particles are put into a mixer together with a colorant, a charge control agent, a binder resin and a solvent, and heated and mixed to form the surface of the core particles. A colored layer is formed. As a dispersion medium that is not compatible with a binder resin (for example, a thermoplastic resin), a solvent that does not substantially swell or dissolve the resin can be used. That is, a solvent having an SP value far from the solubility parameter {SP value (MJ / m ³ ) ^1/2 } of the resin may be selected. Specific examples of the solvent include polyethylene oxide, ethylene glycol (SP value: 29.1), propylene glycol, and polyvinyl alcohol. The SP value of the resin is, for example, polystyrene: 18.7, polypropylene 16.6, epoxy: about 22.5, polyamide: 27.8, PTFE: 12.7. The amount of the solvent used is preferably in the range of 200 to 300 parts by mass with respect to 100 parts by mass of the resin.

  The non-magnetic colored particles 5M and 5Y are mixed with a binder resin, a colorant and a charge control agent, heated and kneaded with a kneader, etc., coarsely and finely pulverized, classified to a predetermined particle size, and then fluidized as necessary. It is produced by adding and mixing agents. The magnetic colored particles 5K are produced by mixing a binder resin, a colorant, a charge control agent, and magnetic fine particles, then heat-kneading with a kneader or the like, coarsely pulverizing and finely pulverizing, and then classifying to a predetermined particle size. Each of the colored particles 5C, 5M, 5Y, and 5K preferably has a mass average particle diameter of 10 to 20 μm.

  The colored particles are dispersed inside the resin material forming the holding layer 4, and then the resin material is applied to the surface of the base 2 and then covered with the protective layer 3, thereby coloring the inside of the holding layer 4. A display medium 1 in which particles are dispersed and enclosed is obtained.

  The display medium shown in FIG. 1 can be a passive type display medium. For example, full color image display can be performed as shown in FIG. When the display medium 1 is heated and the holding layer 4 made of, for example, wax is melted, a magnetic head (not shown) provided on the back surface of the display medium 1 is applied with a magnetic field H, thereby magnetic colored particles 5C. And 5K move to the back side of the display medium 1. Simultaneously with the application of the magnetic field, a DC voltage is applied to electrodes (not shown) provided on both surfaces of the display medium 1 so that the surface of the display medium 1 is negative and the back surface of the display medium 1 is positive (or zero potential). By providing such a potential difference, both the positively charged magnetic colored particles 5C and the nonmagnetic colored particles 5Y tend to move to the surface side of the display medium 1. Here, instead of making the back surface of the display medium 1 positive, the base 2 made of a conductive material may be grounded. However, since the magnetic colored particles 5C also have a force to move to the back side due to the magnetic field, the driving force is offset and the combined driving force is relatively small. Since only the force that moves to the surface side by the electric field acts on the nonmagnetic colored particles 5Y, the driving force to the largest surface side among the four kinds of colored particles is given. In this way, the yellow nonmagnetic colored particles 5Y move to the side closest to the display surface, and the magenta nonmagnetic colored particles 5M wrap around the lower side (see FIG. 3A). When the heating is stopped and the holding layer 4 is cooled and solidified again, this particle arrangement is fixed. According to this particle arrangement, yellow non-magnetic colored particles 5Y are visually recognized from the display surface side, so that yellow is displayed. Further, when the display medium 1 is heated to melt the holding layer 4, the magnetic colored particles 5 </ b> C and 5 </ b> K are formed by forming a magnetic field H with a magnetic head (not shown) provided on the back surface of the display medium 1. It moves to the back surface of the display medium 1 as described above. Simultaneously with the formation of the magnetic field, a direct current voltage is applied to electrodes (not shown) provided on both surfaces of the display medium 1 so that the surface of the display medium 1 is positive and the potential of the back surface of the display medium 1 is zero. By providing, the magenta magnetic colored particles 5M move to the side closest to the display surface, and the yellow magnetic colored particles 5Y wrap around the lower side (see FIG. 3B). That is, according to this particle arrangement, the magenta colored particles are visually recognized from the display surface, so that magenta is displayed.

  Next, the magnetic colored particles 5K and 5C are formed by forming a magnetic field H with a magnetic head (not shown) provided on the surface of the display medium 1 in a state where the display medium 1 is heated and the holding layer 3 is melted. Moves to the surface side of the display medium. Simultaneously with the formation of the magnetic field, a DC voltage is applied to electrodes (not shown) provided on both surfaces of the display medium 1, and an electric field is applied so that the surface of the display medium 1 is positive and the back surface of the display medium 1 is negative. By doing (providing a potential difference), the black magnetic colored particles 5K move to the side closest to the display surface, and toward the back surface of the display medium 1, cyan magnetic colored particles 5C, magenta non-magnetic colored particles 5M, yellow Are arranged in the order of the non-magnetic colored particles 5Y (see FIG. 3C). That is, according to this particle arrangement, since black colored particles are visually recognized from the display surface, black is displayed. Further, by applying a magnetic field H by a magnetic head (not shown) provided on the surface of the display medium 1 in a state where the display medium 1 is heated to melt the holding layer 3 (waxes), the magnetic colored particles 5C are applied. And 5K move to the surface side of the display medium 1 as described above. Simultaneously with the application of the magnetic field, a DC voltage is applied to electrodes (not shown) provided on both surfaces of the display medium 1, and the potential difference is set so that the surface of the display medium 1 is negative and the back surface of the display medium 1 is positive. By providing, the cyan magnetic colored particles 5C move to the side closest to the display surface, and toward the back surface of the display medium 1, black magnetic colored particles 5K, yellow nonmagnetic colored particles 5Y, and magenta nonmagnetic colored particles. They are arranged in the order of 5M (see FIG. 3D). That is, according to this particle arrangement, cyan colored particles are visually recognized from the display surface, so that cyan is displayed. Thus, by switching the direction of the magnetic field and potential gradient applied to the display medium, it becomes possible to selectively move any of the four types of colored particles to the display surface, and display and erase desired colors. It can be carried out.

  The present invention is not limited to the above example, and full color display can be performed by additive color mixing using colored particles of the three primary colors red, green, blue, and black. In the case of additive color mixing, for example, yellow can be displayed by reflecting only red and green.

  The invention is illustrated in more detail by the following examples. In the following description, “part” means “part by mass”.

(Preparation of magnetic colored particles 5C)
Core particles made of a magnetic material were prepared by hydrophobizing the surface of magnetite particles having an average particle size (mass average particle size, the same applies below) with oleic acid. 100 parts of the core particles, 15 parts of a binder resin (styrene-acrylic copolymer having a softening temperature of 140 ° C.) and 25 parts of a white pigment (titanium oxide) were mixed and dispersed using a biaxial kneader. The mixed dispersion was cooled and then coarsely pulverized with a pin mill. The obtained coarsely pulverized powder was subjected to a dispersion treatment using a biaxial kneader together with a matrix resin (polyethylene oxide having a softening temperature of 130 ° C.), and the obtained dispersion was put into hot water. When the binder resin is dissolved in hot water, the particles mainly composed of this resin and titanium oxide have a relatively small specific gravity. Therefore, white particles (average particle size 12 μm, Hunter whiteness of 85) was obtained. 100 parts of these white particles, 1 part of a cyan pigment (Hoechst), 1 part of a positive charge control agent (Copy Blue PR (manufactured by Clariant)), 2 parts of acrylic resin and 5 parts of a solvent (isopropyl alcohol) are 75 ° C. By mixing with a high-speed mixer (with reduced pressure and a solvent trap) heated to 1, magnetic colored particles (hereinafter referred to as cyan particles) in which a cyan pigment was fixed on the surface of white particles were obtained. The triboelectric charge amount measured by this cyan particle blow-off method (using a commercially available iron powder carrier (TB200 manufactured by Toshiba Corporation) as a standard carrier) is +3.5 (mC / kg). The saturation magnetization (σ _s ) measured in a magnetic field of a maximum of 5 KOe by British Industrial Co., Ltd. VSM-III type) was 76 (Am ² / kg).

(Preparation of magnetic colored particles 5K)
75 parts of magnetite (KBC-100SS manufactured by Kanto Denka Kogyo Co., Ltd.) having an average primary particle size of 0.1 μm, 25 parts of polyester resin (softening temperature 150 ° C.), negative charge control agent (T77 manufactured by Hodogaya Chemical Co., Ltd.) 2 Parts were mixed, heated and kneaded with a kneader, cooled and solidified, pulverized with a jet mill, and then classified to prepare magnetic colored particles (hereinafter referred to as black particles) having an average particle size of 15 μm. The triboelectric charge amount of the black particles was −23 (mC / kg).

(Preparation of non-magnetic colored particles 5Y)
Mix 3 parts of yellow pigment (Hoechst), 100 parts of styrene-acrylic copolymer (softening temperature 150 ° C.) and 3 parts of positive charge control agent (201PS manufactured by Fujikura Kasei Co., Ltd.) After cooling and solidifying, pulverizing with a jet mill, and then classifying, non-magnetic particles (hereinafter referred to as yellow particles) having an average particle diameter of 15 μm were produced, and the triboelectric charge amount of these yellow particles was +12 (mC / kg). )Met.

(Preparation of non-magnetic colored particles 5M)
Mix 3 parts of magenta pigment (Hoechst), 100 parts of polyester resin (softening temperature 150 ° C.) and 3 parts of negative charge control agent (Bontron E89 manufactured by Orient Chemical Co., Ltd.) By pulverizing with a jet mill and then classifying, non-magnetic colored particles (hereinafter referred to as magenta particles) having an average particle diameter of 15 μm were produced, and the triboelectric charge amount of the magenta particles was −20 (mC / kg). It was.

(Preparation of display medium)
On a PET film (substrate) having a thickness of 25 μm, a mixture (holding layer) of paraffin wax having a melting point of 70 ° C., a white pigment (titanium oxide) and the above four kinds of colored particles was applied, and a surface having a thickness of 5 μm was applied. A light gray display medium (see FIG. 1) having a thickness of 150 μm was produced by covering with an acrylic resin film (protective layer).

(Display and deletion of full-color images)
A thermal head was provided close to the display medium, and a magnetic head and recording electrodes were provided on both sides of the display medium, and images of each color were displayed under the following conditions.
As a result of applying a magnetic field from the back surface of the display medium by a magnetic head in a state where the paraffin wax is melted by heating in a spot shape at 70 ° C. with a thermal head arranged close to the surface of the display medium, Cyan particles and black particles as particles moved to the back side. At the same time, by providing a potential difference of 400 V so that the display surface side is negative and the back surface is positive by the recording electrodes provided on both surfaces of the display medium, the yellow particles move to the display surface side, and the magenta color particles are slightly back. As a result, the particle arrangement as shown in FIG. 3A was obtained, and yellow was visually displayed.
In the above, the magnetic head is moved to another position, the magnetic field is applied from the back side of the display medium in a state where the display medium is heated in a spot shape under the same conditions as described above, and the display side is +400 V and the back side is zero. By providing such a potential gradient, a particle arrangement as shown in FIG. 3B was obtained, and magenta was visually displayed.
The display medium is heated in a spot shape with a laser beam, and at the same time, a magnetic field is applied from the back surface side of the display medium and a DC electric field is applied so that the display surface side becomes +500 V. ) Was obtained, and a display medium visually displayed in black was obtained. By applying a magnetic field from the display surface side of the display medium and applying a DC electric field so that the display surface side is −500 V, a particle arrangement as shown in FIG. Cyan display was made.
After the state of the above-described particle arrangement appeared, by removing the magnetic field and electric field, an at-random particle arrangement was obtained, and the displayed image could be erased.
From the above, it can be seen that according to the present invention, full-color image display and erasure can be performed by applying a magnetic field and a DC electric field to a predetermined region while heating the display medium.

It is sectional drawing which shows typically the display medium concerning embodiment of this invention. It is sectional drawing which shows typically the colored particle concerning embodiment of this invention, (a) (b) is a figure which shows a magnetic colored particle, (c) (d) is a figure which shows a nonmagnetic colored particle. It is sectional drawing which shows typically the display medium for demonstrating full-color display of this invention.

Explanation of symbols

1: Display medium 2: Substrate 3: Protective layer 4: Retaining layer 5C, 5K: Magnetic colored particles 5M, 5Y: Nonmagnetic colored particles 6: Core particles 7: Concealing layer 8: Colored layer 9: Colorant 10: Charge control Agent 11: Magnetic fine particles

Claims (4)

A base made of a non-magnetic material, and a holding layer in which four types of colored particles having different hues and at least one of charging polarity and magnetic property are dispersed in a material that can be thermally melted formed on the base. A display medium comprising the display medium. The display medium according to claim 1, wherein the colored particles are composed of two kinds of magnetic particles having different charging polarities and two kinds of nonmagnetic particles having different charging polarities. A holding layer made of a heat-meltable material is formed on a non-magnetic material base, and four types of colored particles having different hues and at least one of charging polarity and magnetism are dispersed in the holding layer The display medium is prepared, and by applying an electric field and a magnetic field to the colored particles while heating the holding layer, any one of the colored particles is moved to the display surface side of the display medium. Full color display method. 4. The full color display method according to claim 3, wherein the colored particles are composed of two kinds of magnetic particles having different charging polarities and two kinds of nonmagnetic particles having different charging polarities.

Images