JP2008286855A - Display medium and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display medium and a display device with which a halftone is easily adjusted. <P>SOLUTION: The display device is provided with a display medium and a means to impart an electric field to the display medium. The display medium is equipped with: a display substrate having a light transmitting property; a rear substrate placed opposite to the display substrate holding a gap in between; a dispersion medium sealed between the display substrate and the rear substrate; a first particle group which is dispersed in the dispersion medium and migrates therein in accordance with an electric field formed between the substrates; and a porous structural body which is arranged between the display substrate and the rear substrate, has a plurality of pores through which the first particle group pass, has optical reflection characteristics different from those of the first particle group, and has light transmittance getting higher as going closer from the rear substrate side to the display substrate side. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a display medium and a display device.

Conventionally, display media using colored particles are known as display media that can be rewritten repeatedly.
The image display medium includes, for example, a pair of substrates and a group of particles sealed between the substrates so as to be movable between the substrates in accordance with an electric field formed between the pair of substrates. Further, a gap member for partitioning the substrates into a plurality of cells may be provided between the substrates for the purpose of preventing the particles from being biased to a specific region in the substrates.

  The particle group enclosed between the pair of substrates is a single type of particle group colored in a specific color, or a plurality of types of particle groups having different colors and different electric field strengths required for movement, etc. There is.

  In this technique, in order to obtain a higher contrast, a technique is known in which a member having an optical reflection characteristic different from that of colored particles is arranged between substrates (see, for example, Patent Document 1 and Patent Document 2).

  According to the technique of Patent Document 1, a plurality of spherical bodies having a diameter substantially the same as the distance between the substrates and a color different from that of the moving particle bodies and having the same diameter are disposed between the pair of substrates. It is arranged so as to occupy 50% or more of the volume between them, and the display is performed by the change in the spatial distribution state of the moving particle body caused by the moving particle body moving between the plurality of spherical bodies and moving between the substrates. Yes. That is, the moving particle body is shielded by a plurality of spherical bodies, and the moving particle body is positioned between the substrate located on the upstream side in the observation direction and the plurality of spherical bodies, or the substrate located on the downstream side in the observation direction and the plurality of The display color is changed depending on whether the moving particle body is positioned between the spherical body.

According to the technique of Patent Document 2, an electrophoretic colored particle and a porous layer made of a colored silicon elastomer having optical reflection characteristics different from that of the electrophoretic colored particle are disposed between a pair of substrates. The display color is changed by moving the electrophoretic colored particles through the holes.
JP 2006-071909 A JP 2002-244163 A JP 2005-156808 A

  It is an object of the present invention to provide a display medium and a display device that can easily adjust halftones.

The above problem is solved by the following means. That is,
The invention according to claim 1 is a display substrate having light transparency;
A rear substrate disposed opposite to the display substrate with a gap; a dispersion medium sealed between the display substrate and the rear substrate; and dispersed between the dispersion medium and formed between the substrates. A first particle group that moves in the dispersion medium according to the applied electric field, and a plurality of holes that are disposed between the display substrate and the back substrate, and through which the first particle group passes. And a porous structure having an optical reflection characteristic different from that of the first particle group and having a higher light transmittance as it approaches the display substrate side from the back substrate side. It is.

  The invention according to claim 2 is the display medium according to claim 1, wherein the porous structure has a stepwise increase in light transmittance from the back substrate side toward the display substrate side. is there.

  The invention according to claim 3 is the display medium according to claim 1, wherein the porous structure has a light transmittance continuously increasing from the back substrate side toward the display substrate side. is there.

  In the invention according to claim 4, the porous structure includes a plurality of layers having different light transmittances, and a layer having a high light transmittance is laminated from the back substrate side toward the display substrate side. The display medium according to claim 1.

  The invention according to claim 5 is the display medium according to claim 4, wherein the porous structure includes three or more layers having different light transmission properties.

  The invention according to claim 6 is the display medium according to any one of claims 1 to 5, wherein the porous structure is an aggregate of second particles.

  The invention according to claim 7 is the display medium according to any one of claims 1 to 6, wherein the porous structure is a nonwoven fabric.

  The invention according to claim 8 is sealed between a display substrate having light transparency, a back substrate disposed to face the display substrate with a gap, and between the display substrate and the back substrate. A dispersion medium, a first particle group dispersed in the dispersion medium and moving in the dispersion medium according to an electric field formed between the substrates, and the display substrate and the back substrate are disposed between the substrates. The first particle group has a plurality of holes through which the first particle group passes and has an optical reflection characteristic different from that of the first particle group, and the light transmittance becomes closer to the display substrate side from the back substrate side. A display device comprising: a display medium including a high porous structure; and an electric field applying unit that applies an electric field to the display medium.

  According to the present invention, there is an effect that it is possible to provide a display medium and a display device in which halftone adjustment is easy.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the display device 10 according to the present embodiment includes a display medium 12 and an electric field applying device 14.

  The display medium 12 includes a display substrate 16 that serves as an image display surface, a rear substrate 18 that faces the display substrate 16 with a gap, and holds the substrates at a predetermined interval, and between the display substrate 16 and the rear substrate 18. Are divided into a plurality of cells, a dispersion medium 38 enclosed in each cell, a first particle group 28 dispersed in the dispersion medium 38, and a space between the display substrate 16 and the back substrate 18 ( That is, the porous structure 26 filled in the cell) is included.

  The cell indicates a region surrounded by the display substrate 16, the back substrate 18, and the gap member 20. In this cell, the dispersion medium 38 is sealed, and the porous structure 26 is filled with no gap as described above. The first particle group 28 is composed of a plurality of particles, and is dispersed in the dispersion medium 38. Although the details of the porous structure 26 will be described later, each particle constituting the first particle group 28 passes through the interior of the porous structure 26 from at least one side of the display substrate 16 and the back substrate 18 to the other side. And a hole that moves from the substrate on the other side to the substrate on the one side.

  That is, the first particle group 28 moves between the display substrate 16 and the back substrate 18 through the holes of the porous structure 26 according to the electric field strength formed in the cell.

  In addition, the gap member 20 is provided so as to correspond to each pixel when an image is displayed on the display medium 12, and cells are formed so as to correspond to each pixel, whereby the display medium 12 can be displayed for each pixel. It can be configured to be possible.

  In the present embodiment, in order to simplify the description, the present embodiment will be described using a diagram focusing on one cell.

  The display substrate 16 is configured by stacking display electrodes 32 on a support substrate 30. The back substrate 18 is configured by laminating a back electrode 36 on a support substrate 34.

  The display substrate 16 or both the display substrate 16 and the back substrate 18 has a light transmittance of 80% or more, preferably 90% or more in the visible light region (within 400 nm to 700 nm).

  Examples of the support substrate 30 and the support substrate 34 include glass and plastics such as polycarbonate resin, acrylic resin, polyimide resin, polyester resin, epoxy resin, polyether sulfone resin, and preferably polyethylene terephthalate (PRT). ), Polyethylene naphthalate (PEN), and polypropylene.

  For the back electrode 36 and the display electrode 32, oxides such as indium, tin, cadmium and antimony, composite oxides such as ITO, metals such as gold, silver, copper and nickel, organic materials such as polypyrrole and polythiophene are used. To do. These can be used as a single layer film, a mixed film, or a composite film, and can be formed by vapor deposition, sputtering, coating, or the like. Further, the thickness is usually in the range of 100 to 2000 mm according to the vapor deposition method and the sputtering method. The back electrode 36 and the display electrode 32 may be formed in a desired pattern, for example, a matrix shape or a stripe shape that enables passive matrix driving by a conventionally known means such as etching of a conventional liquid crystal display element or a printed circuit board. it can.

  The display substrate 16 may have a configuration in which the display electrodes 32 are embedded in the support substrate 30. Further, the back substrate 18 may have a configuration in which the back electrode 36 is embedded in the support substrate 34. In this case, since the materials of the support substrate 30 and the support substrate 34 may affect the electrical characteristics, magnetic characteristics, and fluidity of each particle of the first particle group 28, each of the first particle group 28 Select according to the composition of the particles.

  The display electrode 32 and the back electrode 36 are connected to the electric field applying device 14 so as to exchange signals. The electric field applying device 14 forms an electric field between the display electrode 32 and the back electrode 36 (that is, between the display substrate 16 and the back substrate 18) by applying a voltage to the display electrode 32 and the back electrode 36. It is a device for doing. The electric field applying device 14 may be any device as long as it can apply a voltage to the display electrode 32 and the back electrode 36 at a predetermined voltage value for a predetermined voltage application time.

  In the display medium 12 (see FIG. 1), in order to enable active matrix driving, the support substrate 30 and the support substrate 34 may include a TFT (thin film transistor) for each pixel. The TFTs are preferably formed not on the display substrate but on the back substrate 18 because wiring can be easily laminated and components can be easily mounted.

  If the display medium 12 is a simple matrix drive, the configuration of the display device 10 to be described later in detail with the display medium 12 can be simplified. If the active matrix drive using TFTs is used, the simple matrix drive is used. The display speed can be increased compared to.

  Here, in order to prevent the display electrode 32 and the back electrode 36 from being damaged and the occurrence of leakage between the electrodes causing the fixation of each particle of the first particle group 28, the display electrode 32 and the back electrode 36 are necessary. A surface layer as a dielectric film is preferably formed on each.

  Materials for forming this surface layer include polycarbonate, polyester, polystyrene, polyimide, epoxy, polyisocyanate, polyamide, polyvinyl alcohol, polybutadiene, polymethyl methacrylate, copolymer nylon, ultraviolet curable acrylic resin, thermosetting fluororesin, and silane. A coupling agent or the like can be used.

  The gap member 20 is formed so as not to impair the light transmittance in the visible region of the display substrate 16 and is formed of a thermoplastic resin, a thermosetting resin, an electron beam curable resin, a photocurable resin, rubber, metal, or the like. Can do.

The gap member 20 may be integrated with either the display substrate 16 or the back substrate 18. In this case, it can be manufactured by performing an etching process for etching the support substrate 30 or the support substrate 34, a laser processing process, a press processing process or a printing process using a previously manufactured mold.
In this case, the gap member 20 can be fabricated on either the display substrate 16 side, the back substrate 18 side, or both.

  The gap member 20 may be colored or colorless, but is preferably achromatic or colorless and transparent so as not to adversely affect the display image displayed on the display medium 12, in which case, for example, polystyrene, polyester or acrylic A transparent resin such as can be used.

The dispersion medium 38 in which the first particle group 28 is dispersed is preferably a high resistance liquid. Here, “high resistance” indicates that the volume resistivity is 10 ¹⁰ Ω · cm or more, preferably 10 ¹² Ω · cm or more.

  Specific examples of the high resistance liquid include hexane, cyclohexane, toluene, xylene, decane, hexadecane, kerosene, paraffin, isoparaffin, silicone oil, dichloroethylene, trichloroethylene, perchloroethylene, high-purity petroleum, ethylene glycol, and alcohols. , Ethers, esters, dimethylformamide, dimethylacetamide, dimethylsulfoxide, N-methylpyrrolidone, 2-pyrrolidone, N-methylformamide, acetonitrile, tetrahydrofuran, propylene carbonate, ethylene carbonate, benzine, diisopropylnaphthalene, olive oil, isopropanol, trichloro Trifluoroethane, tetrachloroethane, dibromotetrafluoroethane, etc. and mixtures thereof are preferred. It can be used for.

Moreover, water (so-called pure water) can also be used as the dispersion medium 38 by removing impurities so as to have the following volume resistance value. The volume resistance value can be 10 ³ Ωcm or more, preferably 10 ¹⁰ Ωcm or more, and more preferably 10 ¹² Ωcm or more.

  In addition, to the high resistance liquid, an acid, an alkali, a salt, a dispersion stabilizer, a stabilizer for anti-oxidation or ultraviolet absorption, an antibacterial agent, an antiseptic, and the like can be added as necessary. It is preferable to add so that it may become the range of the specific volume resistance value shown above.

  For high resistance liquids, anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, fluorosurfactants, silicone surfactants, metal soaps as charge control agents , Alkyl phosphate esters, succinimides and the like can be added.

  More specific examples of the ionic and nonionic surfactants are as follows. Nonionic activators include polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, And fatty acid alkylolamide. Examples of the anionic surfactant include alkylbenzene sulfonate, alkylphenyl sulfonate, alkyl naphthalene sulfonate, higher fatty acid salt, sulfate of higher fatty acid ester, sulfonic acid of higher fatty acid ester, and the like. Examples of the cationic surfactant include primary to tertiary amine salts and quaternary ammonium salts. These charge control agents are preferably 0.01% by weight or more and 20% by weight or less, and particularly preferably 0.05% by weight or more and 10% by weight or less, based on the solid content of the particles. If it is less than 0.01% by weight, the desired charge control effect is insufficient, and if it exceeds 20% by weight, an excessive increase in the conductivity of the developer is caused.

  The first particle group 28 is preferably dispersed in a polymer resin as the dispersion medium 38. The polymer resin is preferably a polymer gel, a network polymer, or the like.

  As this polymer resin, agarose, agaropectin, amylose, sodium alginate, propylene glycol ester of alginate, isolikenan, insulin, ethylcellulose, ethylhydroxyethylcellulose, curdlan, casein, carrageenan, carboxymethylcellulose, carboxymethyl starch, callose, agar, chitin , Chitosan, silk fibroin, gar gum, quince seed, crown gall polysaccharide, glycogen, glucomannan, keratan sulfate, keratin protein, collagen, cellulose acetate, gellan gum, schizophyllan, gelatin, elephant palm mannan, tunisin, dextran, dermatan sulfate, starch , Tragacanth gum, nigeran, hyaluronic acid, hydroxyethyl cellulose, hydroxy In addition to polymer gels derived from natural polymers such as propylcellulose, pustulan, funolan, decomposed xyloglucan, pectin, porphyran, methylcellulose, methyl starch, laminaran, lichenan, lentinan, locust bean gum, etc. Includes almost all polymer gels.

  In addition, polymers containing functional groups of alcohol, ketone, ether, ester, and amide in the repeating unit are exemplified. For example, polyvinyl alcohol, poly (meth) acrylamide and derivatives thereof, polyvinyl pyrrolidone, polyethylene oxide, and the like. Mention may be made of copolymers containing molecules.

  Among these, gelatin, polyvinyl alcohol, poly (meth) acrylamide and the like are preferably used from the viewpoints of production stability, electrophoretic characteristics and the like.

  These polymer resins are preferably used as the dispersion medium 38 together with the high resistance liquid.

  The first particle group 28 includes glass beads, alumina as particles having a property of being charged to either positive or negative polarity so that the first particle group 28 can move in the dispersion medium 38 along the electric field gradient direction when placed in an electric field. , Metal oxide particles such as titanium oxide, thermoplastic or thermosetting resin particles, those in which a colorant is fixed on the surface of these resin particles, particles containing a colorant in a thermoplastic or thermosetting resin, In addition, particles having a characteristic of coloring in a state dispersed in the dispersion medium 38 can be used.

  Examples of the thermoplastic resin used for the production of the first particle group 28 include styrenes such as styrene and chlorostyrene, monoolefins such as ethylene, propylene, butylene, and isoprene, vinyl acetate, vinyl propionate, vinyl benzoate, Α- such as vinyl esters such as vinyl butyrate, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate Homopolymers of methylene aliphatic monocarboxylic acid esters, vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl butyl ether, and vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and vinyl isopropenyl ketone It can be exemplified a copolymer.

  Moreover, as thermosetting resin used for manufacture of the 1st particle group 28, crosslinked resin, such as crosslinked copolymer and crosslinked polymethylmethacrylate which have divinylbenzene as a main component, phenol resin, urea resin, melamine resin , Polyester resin, silicone resin and the like. Particularly representative binder resins include polystyrene, styrene-alkyl acrylate copolymer, styrene-alkyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer. Examples thereof include a polymer, polyethylene, polypropylene, polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, and paraffin wax.

As the colorant, organic or inorganic pigments, oil-soluble dyes and the like can be used. Magnetic powder such as magnetite and ferrite, carbon black, titanium oxide, magnesium oxide, zinc oxide, phthalocyanine copper-based cyan colorant, Known colorants such as azo yellow color materials, azo magenta color materials, quinacridone magenta color materials, red color materials, green color materials, and blue color materials can be listed. Specifically, aniline blue, calcoil blue, chrome yellow, ultramarine blue, duPont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, lamp black, rose bengal, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 57: 1, C.I. I. Pigment yellow 97, C.I. Blue 15: 1, C.I. I. Pigment Blue 15: 3, etc. can be exemplified as typical ones.
Also, porous sponge-like particles or hollow particles enclosing air can be used as white particles.

  The resin of the first particle group 28 may be mixed with a charge control agent as necessary. As the charge control agent, known materials used for toner materials for electrophotography can be used. For example, cetylpyridyl chloride, BONTRON P-51, BONTRON P-53, BONTRON E-84, BONTRON E-81 (above, Quaternary ammonium salts such as Orient Chemical Industry Co., Ltd., salicylic acid metal complexes, phenol condensates, tetraphenyl compounds, metal oxide particles, and metal oxide particles surface-treated with various coupling agents. .

A magnetic material may be mixed in the inside or the surface of the first particle group 28 as necessary. As the magnetic material, a color-coated inorganic magnetic material or organic magnetic material is used as necessary. Further, a transparent magnetic material, in particular, a transparent organic magnetic material does not hinder the color development of the color pigment, and the specific gravity is smaller than that of the inorganic magnetic material, and is more desirable.
As the colored magnetic powder, for example, a small-diameter colored magnetic powder described in JP-A-2003-131420 can be used. A material provided with magnetic particles serving as nuclei and a colored layer laminated on the surface of the magnetic particles is used. The colored layer may be selected such that the magnetic powder is opaquely colored with a pigment or the like, but it is preferable to use, for example, a light interference thin film. This optical interference thin film is a thin material having a thickness equivalent to the wavelength of light made of achromatic material such as SiO ₂ or TiO ₂ , and reflects light in a wavelength selective manner by optical interference in the thin film. is there.

  An external additive may be attached to the surface of the first particle group 28 as necessary. The color of the external additive is preferably transparent so as not to affect the color of the particles.

  As the external additive, inorganic particles such as metal oxides such as silicon oxide (silica), titanium oxide, and alumina are used. In order to adjust the chargeability, fluidity, environment dependency, etc. of the inorganic particles, they can be surface-treated with a coupling agent or silicone oil.

  Coupling agents include positively chargeable ones such as aminosilane coupling agents, aminotitanium coupling agents, nitrile coupling agents, and silanes that do not contain nitrogen atoms (consisting of atoms other than nitrogen). There are negatively charged ones such as coupling agents, titanium-based coupling agents, epoxy silane coupling agents, and acrylic silane coupling agents. Silicone oil includes positively charged ones such as amino-modified silicone oil, dimethyl silicone oil, alkyl-modified silicone oil, α-methylsulfone-modified silicone oil, methylphenyl silicone oil, chlorophenyl silicone oil, and fluorine-modified silicone. Examples include negatively chargeable oils. These are selected according to the desired resistance of the external additive.

Of the above external additives, well-known hydrophobic silica and hydrophobic titanium oxide are preferable. In particular, the reaction of TiO (OH) ₂ described in JP-A-10-3177 with a silane compound such as a silane coupling agent. The titanium compound obtained in (1) is preferred. As the silane compound, any of chlorosilane, alkoxysilane, silazane, and a special silylating agent can be used. This titanium compound is produced by reacting TiO (OH) ₂ produced in a wet process with a silane compound or silicone oil and drying it. Since it does not pass through the firing step of several hundred degrees, a strong bond between Ti is not formed, there is no aggregation, and the particles are in the state of primary particles. Furthermore, since the silane compound or silicone oil reacts directly with TiO (OH) ₂ , the amount of silane compound or silicone oil treated can be increased, and the charging characteristics can be controlled by adjusting the amount of silane compound treated. The charging ability that can be imparted and can be imparted can be significantly improved over that of conventional titanium oxide.

  The volume average primary particle diameter of the external additive is generally in the range of 5 nm to 100 nm, and preferably in the range of 10 nm to 50 nm, but is not limited thereto.

  The blending ratio of the external additive and the first particle group 28 is adjusted based on the balance between the volume average primary particle size of the first particle group 28 and the volume average primary particle size of the external additive. If the amount of the external additive added is too large, a part of the external additive is liberated from the particle surface and adheres to the surface of the other particle, so that desired charging characteristics cannot be obtained. In general, the amount of the external additive is in the range of 0.01 to 3 parts by weight, more preferably in the range of 0.05 to 1 part by weight with respect to 100 parts by weight of the particles. It is.

  When an external additive is added to the surface of the first particle group 28, the external additive is applied to the surface of the first particle group 28 with an impact force, or the surface of the first particle group 28 is heated to add the external additive. It is desirable to firmly fix the agent on the particle surface. As a result, the external additive is released from the first particle group 28, and the external additive having a different polarity is strongly aggregated to prevent formation of an aggregate of the external additive that is difficult to dissociate with an electric field. As a result, image quality deterioration is prevented.

As a method for creating the first particle group 28, any conventionally known method may be used. For example, as described in JP-A-7-325434, a resin, a pigment, and a charge control agent are weighed so as to have a predetermined mixing ratio, and after the resin is heated and melted, the pigment is added, mixed, dispersed, and cooled. Then, a method of preparing particles using a pulverizer such as a jet mill, a hammer mill, a turbo mill, etc., and then dispersing the obtained particles in a dispersion medium can be used. Also, particles containing a charge control agent are prepared by polymerization methods such as suspension polymerization, emulsion polymerization, dispersion polymerization, coacervation, melt dispersion, emulsion aggregation, and then dispersed in a dispersion medium. A particle dispersion may be prepared. Furthermore, the resin, colorant, charge control agent and dispersion medium can be plasticized, the dispersion medium does not boil, and is at a temperature lower than the decomposition point of the resin, charge control agent and / or colorant. There is a method using an appropriate apparatus capable of dispersing and kneading the raw materials. Specifically, the pigment, the resin, and the charge control agent are heated and melted in a dispersion medium using a meteor mixer, a kneader, etc., and the temperature dependence of the solvent solubility of the resin is used to cool the molten mixture while stirring. The first particle group 28 can be formed by solidification / precipitation.
Furthermore, the raw materials described above are put into a suitable container equipped with a granular medium for dispersion and kneading, such as a heated vibration mill such as an attritor, a heated ball mill, etc. A method of dispersing and kneading within the range of 80 ° C. or higher and 160 ° C. or lower can be used. As the granular medium, steel such as stainless steel and carbon steel, alumina, zirconia, silica and the like are preferably used. In order to create the first particle group 28 by this method, the raw material previously made into a fluid state is further dispersed in a container with a granular medium, and then the dispersion medium is cooled to precipitate a resin containing a colorant from the dispersion medium. Let While the granular medium continues to be in motion during and after cooling, shear and / or impact is generated to reduce the volume average primary particle size.

In addition, as the first particle group 28 used in the present embodiment, a particle group having a characteristic of coloring in a state of being dispersed in the dispersion medium 38 may be used.
This “colors when dispersed in a dispersion medium” means that the first particle group 28 is dispersed in the dispersion medium and the dispersion liquid in which the first particle group 28 is dispersed is visually observed. It means to exhibit a hue that can be observed. Note that the observation of the hue in this case means that the dispersion is observed within a range of about 10 μm or more and 1 cm or less with respect to the viewing direction. The hue can be varied by changing the shape, volume average primary particle diameter, etc. of the first particle group 28, and the material constituting the first particle group 28.

As the first particle group 28 that develops color in a dispersed state, organic pigments, inorganic pigments, colored glass, colorants such as dyes, resin particles containing these colorants, metal particles, and the like can be used. If necessary, the surface of these particles subjected to surface treatment with a silane coupling agent or the like can be used. For example, particles composed of a PMMA (polymethyl methacrylate) resin in which black carbon produced by a suspension polymerization method is dispersed can be used.
As organic pigments, inorganic pigments, and dyes used as colorants, known pigments can be used. Examples of organic pigments include azo pigments, polycondensed azo pigments, metal complex azo pigments, and flavanthrone pigments. Benzimidazolone pigments, phthalocyanine pigments, quinacridone pigments, anthraquinone pigments, anthrapyridine pigments, pyranthrone pigments, dioxazine pigments, perylene pigments, perinone pigments, isoindolinone pigments, quinophthalone pigments, Examples of inorganic pigments include zinc white, titanium oxide, zinc oxide, zirconium oxide, antimony white, carbon black, iron black, titanium boride, bengara, mapico yellow, lead. Tan, Cadmium Yellow, Zinc Sulfide, Litopo , Barium sulfide, cadmium selenide, barium sulfate, lead chromate, lead sulfate, barium carbonate, calcium carbonate, lead white, alumina white and the like. Examples of dyes include nigrosine dyes, phthalocyanine dyes, and azo dyes. And dyes, anthraquinone dyes, quinophthalone dyes, methine dyes, and the like.

  The resin particles containing the colorant are, for example, a known dry production method such as kneading and pulverizing resin solids in which the colorant is dispersed, or in a dispersion liquid in which raw materials such as the colorant and the resin are dispersed. What was produced by the well-known wet manufacturing method which granulates and obtains a resin particle can be utilized.

As the first particle group 28 that develops color in a dispersed state, metal particles can also be used. If necessary, the surface of the particles can be used with a silane coupling agent or the like. In addition, as a metal particle, the metal particle containing a noble metal is especially preferable.
The metal particles used as the first particle group 28 have a plasmon coloring function, and the particles themselves have the property of coloring.
Plasmon color development of metal particles is caused by electron plasma oscillation and is due to a color development mechanism called plasmon absorption. Color development due to this plasmon absorption is said to be because free electrons in the metal are shaken by the photoelectric field, electric charges appear on the particle surface, and nonlinear polarization occurs. The coloring by the metal particles has high saturation and light transmittance, and is excellent in durability. The color development by the metal particles is observed in so-called nanoparticles having a volume average primary particle size of about several nanometers to several tens of nanometers. In addition, from the viewpoint of vividness of the hue, it is more advantageous as the metal particles have a narrower volume average primary particle size distribution. Therefore, the volume average primary particle size of the metal particles is preferably in the range of 1 nm to 100 nm, and preferably in the range of 5 nm to 50 nm.

  The metal particles can be colored in various colors depending on the type of metal contained in the particles, the shape of the particles, and the volume average primary particle size. Therefore, various hues including RGB coloring can be obtained by using metal particles in which these are controlled. Therefore, color display is possible if a display medium is produced using a dispersion liquid in which metal particles having a plasmon coloring function are dispersed in a dispersion medium, and each color of metal particles corresponding to R, G, and B is dispersed. If the liquid is used, an RGB display medium can be manufactured.

  The volume average primary particle size of the metal particles for exhibiting RGB colors of R, G, and B depends on the metal used, the preparation conditions of the particles, the shape, etc., and can not be particularly limited. For example, in the case of colloidal gold particles, as the volume average primary particle size increases, R color development, G color development, and B color development tend to be exhibited.

  As a measuring method of the volume average primary particle size in the present embodiment, the particles are observed by SEM or TEM, and the average particle size obtained from the area of 10 particles based on the obtained SEM image or TEM image. Obtained as a value.

  As the metal contained in the metal particles, known noble metals such as gold, silver, ruthenium, rhodium, palladium, osmium, iridium and platinum are preferable, and gold and / or silver are particularly preferable. Moreover, metals (for example, copper) other than noble metals can be used. Further, the metal particles may contain two or more kinds of metals.

Moreover, in order to control the charging property of the first particle group 28, the surface of the first particle group 28 can be subjected to surface treatment (hydrophilic treatment or hydrophobic treatment) as necessary.
Examples of the surface treatment method include a chemical treatment method using a surface treatment agent such as a silane coupling agent and a physical treatment method for modifying the surface by applying some physical stimulus to the surface of the first particle group 28. In the present invention, it is preferable to use a chemical treatment method.
The usable surface treatment agent can be selected in consideration of the affinity with the material constituting the particle main body of the first particle group 28. For example, for the hydrophobic treatment, a silane compound or a silicone compound is used. Fatty acids can be used.

Here, as the silane compound used for the hydrophobic treatment, a known silane coupling agent having a molecular structure including a reactive portion that reacts with the main body of the first particle group 28 and a hydrophobic portion can be used.
Specifically, Octadecyltrimethoxysilane, Phenethyltrimethoxysilane, Aminopropyltriethoxysilane, 3-Aminopropyltrimethoxysilane, Metacryloxytrimethoxysilane, Methoxytrimethylsilane, 3-Aminopropyldiethoxymethylsilane, N- (-2 Aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-Aminoethyl) be exemplified -3-aminopropylmethyldimethoxysilane, etc. Can do.

Examples of the silicone compound used for the hydrophobic treatment include methylpolysiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentanesiloxane, methylcyclopolysiloxane, and methylhydrogenpolysiloxane.
Fatty acids used for hydrophobic treatment include lauric acid, myristic acid, stearic acid, oleic acid, linoleic acid, linoleic acid, hydroxy fatty acid, caproic acid, caprylic acid, palmitic acid, behenic acid, palmitoleic acid, erucic acid, Examples thereof include alkali metal salts such as sodium salt and potassium salt, alkaline earth metal salts such as magnesium salt and calcium salt, esters and the like.

A plurality of first particle groups 28 are dispersed in a dispersion medium 38 between the display substrate 16 and the back substrate 18, and between the display electrode 32 and the back electrode 36 (that is, between the display substrate 16 and the back substrate 18). A voltage exceeding a voltage range determined in advance according to the first particle group 28 is applied between the display substrate 16 and the back substrate 18 (between the back substrate 18 and the back substrate 18). It moves in the dispersion medium 38 by forming an electric field.
The change in display color in the display medium 12 is caused by the movement of the plurality of first particle groups 28 in the dispersion medium 38 in the dispersion medium 38.

The first particle group 28 has a voltage range necessary for moving between the display substrate 16 and the back substrate 18 (in the dispersion medium 38). That is, in the first particle group 28, the display density does not change even when the voltage and the voltage application time are further increased from the start of movement and the voltage necessary for the start of movement of the particles until the display density is saturated. Voltage range.
The voltage indicates a voltage applied between the display substrate 16 and the back substrate 18.

  The display density when the "display density is saturated" is the display electrode of the display medium 12 while measuring the density of the display medium 12 on the display substrate 16 side with a densitometer (measured with X-Rite 404A manufactured by X-Rite). A voltage is applied to 32 and the back electrode 36, and this voltage is gradually changed in the direction of increasing the concentration (the applied voltage value is increased or decreased), so that the concentration change per unit voltage is saturated, and Even if the voltage and the voltage application time are increased in the state, the concentration does not change, and the concentration is shown when the concentration is saturated.

  That is, when a voltage outside the voltage range is applied between the display substrate 16 and the back substrate 18, no change appears in the display density of the display medium 12, and the voltage within the voltage range is When applied between the rear substrate 18 and the first particle group 28, a change appears in the display density of the display medium 12.

  In this “change in the display density of the display medium 12” state, a voltage is applied to the display electrode 32 and the back electrode 36 of the display medium 12, and the voltage value is continuously changed from 0 V to display the display medium 12. The change in density is evaluated by visual observation, and represents a state in which the change appears. In this evaluation, the state in which the display density has changed is that the density of the display substrate 16 is measured with a densitometer (X-Rite 404A, manufactured by X-Rite). This represents a state where the amount of change was 0.1 or more.

  In order to adjust the voltage range of the first particle group 28, the average charge amount of the particles constituting the first particle group 28, the flow resistance to the dispersion medium on the surface of each particle, the average magnetic amount (magnetization strength) ), The volume average primary particle diameter of the particles, and the shape factor of the particles may be adjusted.

  The first particle group 28 does not have the voltage range necessary for moving the particles as described above, and may move regardless of the voltage applied. However, as described above, the voltage range is a desirable mode because the display image has a memory property and can store an image without consuming power.

  In the present embodiment, the case where only the first particle group 28, that is, one color particle is enclosed in the display medium 12 will be described. However, the present invention is not limited to such a form, and the colors are different from each other. Multiple types of particles may be encapsulated. In this case, adjustment may be made in advance so that the voltage ranges described above are different for each color particle group. In this way, by applying a voltage in a specific voltage range between the substrates, the particles to be moved can be selectively moved between the substrates, and multicolor display using a plurality of color particle groups is possible. It becomes.

  Specifically, the adjustment of the average charge amount of each particle constituting the first particle group 28 is specifically performed by the kind and amount of the charge control agent blended in the resin, the kind and amount of the polymer chain bonded to the particle surface, The type and amount of external additives added to or embedded in the particle surface, the type and amount of surfactant, polymer chain or coupling agent applied to the particle surface, the specific surface area of the particle (volume average primary particle size or particle size) This is possible by adjusting the shape factor.

In addition, the adjustment of the average magnetic amount of each first particle group 28 can be specifically performed by various methods for imparting magnetism to the particles.
For example, like a conventional electrophotographic magnetic toner, a magnetic material such as powdered magnetite is mixed with a resin to produce particles, or a magnetic material and a monomer are dispersed and polymerized to produce particles. be able to. Further, the magnetic material is deposited in the pores of the porous particles. Or the method of coat | covering a magnetic body is also known. For example, particles are produced by polymerizing active sites on the surface of the magnetic material and wrapping the magnetic material with resin, or by depositing resin dissolved on the surface of the magnetic material and producing particles wrapping the magnetic material with resin. Or A light, transparent or colored organic magnetic material can also be used as the magnetic material. The average magnetic amount of the first particle group 28 can be adjusted by adjusting the type and amount of the magnetic material to be used.

  The volume average primary particle size of the first particle group 28 is specifically adjusted when the particles are produced. When the particles are prepared by a polymerization method, the amount of the dispersing agent, the dispersion conditions, the heating conditions, etc., and when the particles are prepared by kneading and pulverizing classification, the classification conditions, etc. In this case, the size, rotation time, rotation speed, etc. of the steel balls used in the ball mill can be adjusted. It is not limited to the above.

  The shape factor of the first particle group 28 can be adjusted by, for example, dissolving a polymer in a solvent described in JP-A-10-10775, mixing a colorant, and in the presence of an inorganic dispersant. In the so-called suspension polymerization method in which the particles are dispersed and dispersed in an aqueous medium, a non-polymerizable organic solvent compatible with the monomer is added, suspension polymerization is performed, and particles are produced, removed, and dried. A method for selecting a drying method for removing the organic solvent is preferably used. As this drying method, a lyophilization method is preferably exemplified, and in this lyophilization method, it is preferably performed in the range of −10 ° C. to −200 ° C., more preferably −30 ° C. to −180 ° C. The freeze-drying method is performed at a pressure of about 40 Pa or less, but is preferably performed at 13 Pa or less. Also, the particle shape can be controlled by a method of agglomerating and coalescing small particles described in JP-A-2000-292971, and increasing the particles to a desired volume average primary particle size.

  The content (% by weight) of the first particle group 28 with respect to the total mass in the cell is not particularly limited as long as it is a concentration at which a desired hue can be obtained, and the cell thickness (that is, the display substrate 16). The content is adjusted according to the distance between the substrate and the back substrate 18). That is, in order to obtain a desired hue, the content rate decreases as the cell becomes thicker, and the content rate increases as the cell becomes thinner. Generally, it is 0.01 wt% or more and 50 wt% or less.

  The size of the cell in the display medium 12 is not particularly limited, but in order to prevent display density unevenness due to deviation in the display surface of the first particle group 28, the display substrate 16 of the display medium 12 is usually used. The length in the plate surface direction is about 10 μm or more and 1 mm or less.

  The porous structure 26 in the display medium 12 of the present embodiment has a hole through which each particle constituting the first particle group 28 moves, and has an optical reflection characteristic different from that of the first particle group 28. And a porous structure having high light transmittance from the back substrate 18 side toward the display substrate 16 side.

  The holes provided in the porous structure 26 are at least holes extending in the direction of the electric field gradient formed in the display medium 12. In this embodiment, the display substrate 32 and the back electrode 36 are used for the display substrate. 16 is a hole formed at least in the direction of the electric field gradient formed between the display substrate 16 and the back substrate 18, that is, in the direction in which the display substrate 16 and the back substrate 18 face each other. In the holes of the porous structure 26, at least particles constituting the first particle group 28 move from one of the display substrate 16 and the back substrate 18 to the other substrate side through the holes. It is structured in size.

The porous structure 26 “has an optical reflection characteristic different from that of the first particle group 28” means that the dispersion medium 38 in which only the first particle group 28 is dispersed and the dispersion medium 38 in the pores. This means that there is a difference in which the difference between the two can be discriminated in hue, brightness, saturation, and the like when the porous structure 26 infiltrated with is visually observed.
Therefore, when the first particle group 28 is closer to the display substrate 16 than the porous structure 26, the color of the first particle group 28 is different from that of the porous structure 26. If it is on the 18th side, the color of the porous structure 26 is displayed on the display medium 12.

The thickness of the porous structure 26 is desirably at least equal to or larger than the volume average primary particle size of the particles constituting the first particle group 28. Since the first particle group 28 existing on the back substrate 18 side of the porous structure 26 may be observed from the hole portion of the porous structure 26, the thickness of the porous structure 26 is the first It is more desirable that the volume average primary particle size of the particle group 28 is 3 times or more.
Specifically, the thickness of the porous structure 26 includes the distance between the display substrate 16 and the back substrate 18, the form of the porous structure 26, the porosity of the porous structure 26, and the first particles. Although it depends on the particle diameter of the group 28, the content of the first particle group 28, etc., it is preferably 10 μm or more and 1000 μm or less, and more preferably 10 μm or more and 100 μm or less.
If the thickness of the porous structure 26 is less than 10 μm, the first particle group 28 may not be sufficiently concealed, and there may be a problem that sufficient color developability cannot be obtained, and if the thickness exceeds 1000 μm. There is a problem that the distance between the electrodes becomes large and a high driving voltage is required.

  The refractive index can be measured by using a laser measuring instrument, and for particles by the Becke line method, the immersion method, the method of measuring attenuation for each wavelength, the method of measuring the critical angle of refraction, and the like.

  As the form of the porous structure 26, as described above, each of the particles constituting the first particle group 28 has a hole for movement, and has an optical reflection characteristic different from that of the first particle group 28. It is not particularly limited as long as it has a characteristic of being a porous structure having a high light transmittance from the back substrate 18 side to the display substrate 16 side (details will be described later), and materials such as titanium oxide and zinc oxide Particulate members (hereinafter referred to as second particles 27) such as inorganic material particles composed of organic material particles composed of materials such as methyl methacrylate resin, styrene acrylic resin, silicone resin, polytetrafluoroethylene resin, and the like. May be used, or a resin sheet, a nonwoven fabric, or the like may be used.

  In the case where the porous structure 26 is configured as an aggregate of the second particles 27, the volume average primary particle size of the second particles 27 is not particularly limited. When the porous structure 26 made of an aggregate is disposed in the region between the display substrate 16 and the back substrate 18, the first particle group 28 can pass through the gap between the adjacent second particles 27. It is desirable to have a volume average primary particle size.

  For this reason, the volume average primary particle size of the second particles 27 is desirably 10 times or more of the volume average primary particle size of the first particle group 28, and desirably 25 times or more. If the volume average primary particle size of the second particles 27 is less than 10 times the volume average primary particle size of the first particle group 28, the gaps between the plurality of second particles 27 constituting the porous structure 26 ( It may be difficult for the first particle group 28 to pass through the holes. The upper limit of the volume average primary particle size of the second particles 27 is not particularly limited, but in order to sufficiently conceal the first particle group 28, the second particles 27 are porous with a plurality of layers laminated. Since the structure 26 is preferably configured, the upper limit of the volume average primary particle size of the second particles 27 is preferably less than ½ times the distance between the display substrate 16 and the back substrate 18.

  In the present embodiment, the volume average primary particle size of the first particle group 28 and the second particle 27 is determined by observing each of the first particle group 28 and the second particle 27 with SEM or TEM. Based on the obtained SEM image or TEM image, the average particle size was determined from the area of 10 particles. In addition, when the 1st particle group 28 and the 2nd particle | grains 27 are comprised from the multiple types of particle | grains from which a volume average particle diameter differs, each kind of particle | grain is each about the average particle diameter of all the kinds of particles. The average value of the particle size obtained from the area in the same manner as described above for 10 particles was obtained, and the average value was obtained by dividing the sum of the average values of all types by the number of types of particles, and the volume average primary particle size did.

  Further, when the porous structure 26 is composed of a resin sheet or nonwoven fabric, examples of the material constituting the resin sheet or nonwoven fabric include polyethylene, polystyrene, polyester, polyacryl, polypropylene, and polytetrafluoro. A fluorinated resin such as ethylene (PTFE) can be used. In particular, polypropylene and PTFE-based resins can be preferably applied because they are easily charged by corona treatment. What is necessary is just to comprise as the aggregate | assembly of the fiber which consists of these materials, when comprising the porous structure 26 with a nonwoven fabric.

  The porosity of the porous structure 26 is preferably 50% or more and 80% or less for the reason that both the passage performance through which the first particle group 28 passes and the high color developability of the display medium 12 are achieved. .

Further, the average pore diameter of the pores of the porous structure 26 is not particularly limited as long as the particles constituting the first particle group 28 can pass through, but the average pore diameter of the pores of the porous structure 26 is the first pore diameter. The volume average primary particle size of one particle group 28 is preferably in the range of 1.2 to 10 times, more preferably in the range of 2 to 5 times.
When the average pore size of the pores of the porous structure 26 is less than 1.2 times the volume average primary particle size of the first particle group 28, each particle constituting the first particle group 28 passes through the pore. In some cases, it may be difficult to move, and if it exceeds 10 times, the particles constituting the first particle group 28 may not be sufficiently concealed, and there may be a problem that color developability and contrast are lowered.

Further, when the porous structure 26 is made of a nonwoven fabric, the density of the fibers constituting the nonwoven fabric has a gap through which the particle groups constituting the first particle group 28 can pass, and the first structure For the reason that the particle group constituting the particle group 28 is sufficiently concealed and the physical strength is maintained, the fiber basis weight is preferably in the range of 10 g / m ^{2 to} 70 g / m ² , and 20 g / m ^{2 to} 50 g / m. A range of ² or less is better.

  The diameter of the fibers constituting the nonwoven fabric is in the range of 0.1 μm to 20 μm, and preferably in the range of 0.1 μm to 3 μm, to ensure a sufficient surface area and physical strength. To preferred.

  As described above, the porous structure 26 in the display medium 12 of the present embodiment is a porous structure having a high light transmittance from the back substrate 18 side toward the display substrate 16 side.

Here, the “light transmittance of the porous structure 26” in the present embodiment is the visible light region (only the dispersion medium 38 is filled between the display substrate 16 and the back substrate 18 of the display medium 12). The transmitted light intensity in the range from 400 nm to 700 nm is T ₁ , and the porous structure 26 to be measured is immersed in the dispersion medium 38 between the display substrate 16 and the back substrate 18 of the display medium 13 (porous) When the transmitted light intensity in the visible light region (within 400 nm or more and 700 nm or less) when filled with the dispersion medium 38 in the pores of the porous structure 26 is T ₂ , it is expressed by the following formula.
Light transmittance of porous structure 26 = T ₂ / T ₁ × 100 (%)

  Here, the light transmittance was measured using a USB2000 manufactured by Ocean Optics.

The light transmittance of the porous structure 26 may be adjusted so as to increase continuously from the back substrate 18 side toward the display substrate 16 side, or adjusted so as to increase stepwise. Also good.
Smooth gradation display is possible when the light transmittance is continuously adjusted to be high, and accurate gradation display is possible when the light transmittance is adjusted to be gradually increased. It becomes.

  The light transmittance of the entire region of the porous structure 26 is preferably 10% or less, and more preferably 5% or less.

  Furthermore, the light transmittance per unit thickness of the region having the lowest light transmittance of the porous structure 26, that is, the region closest to the back substrate 18 in the entire region of the porous structure 26. Is the light transmittance per unit thickness of the region having the highest light transmittance of the porous structure 26, that is, the region closest to the display substrate 16 in the entire region of the porous structure 26. It is preferable that the light transmittance per unit thickness in the region having the lowest light transmittance of the porous structure 26 is preferably 70% or less, and the light transmittance of the light transmittance of the porous structure 26 is the highest. More preferably, it is 50% or less of the light transmittance per unit thickness of the region having a high rate.

  By adjusting the light transmittance of the region having the highest light transmittance in the entire region of the porous structure 26 within the above range and adjusting the light transmittance of the region having the lowest light transmittance within the above range, As will be described in detail later, in the display medium 12, the first particle group 28 passes from the back substrate 18 side to the display substrate 16 side or from the display substrate 16 side to the back substrate 18 side through the holes in the porous structure 26. By moving, it is possible to easily display a color having a density (intermediate gradation) corresponding to this movement. When the first particle group 28 is positioned between the porous structure 26 and the back substrate 18, the color of the first particle group 28 is porous when viewed from the display substrate 16 side. The structure 26 is shielded by the region having the lowest light transmittance, and the color of the porous structure 26 can be presented.

  The porous structure 26 may be composed of a single layer as long as it satisfies the above characteristics, but a plurality of layers having different light transmittances are arranged in the opposing direction of the back substrate 18 and the display substrate 16. A stacked structure may be used.

  By forming the porous structure 26 from a plurality of layers, an effect of enabling accurate gradation display can be obtained.

  When the porous structure 26 is composed of a plurality of layers, it is preferable that three or more layers having different light transmittances are stacked. In order to reliably block the color due to the first particle group 28, the layer present on the back substrate 18 side is the layer having the lowest light transmittance, and the first particle group 28 is on the display substrate 16 side. In order to increase the concentration of the first particle group, the layer present on the side of the display substrate 16 is the layer having the highest light transmittance as much as possible, and from the layer on the back substrate 18 side to the display substrate 16. Each layer may be adjusted such that the light transmittance increases continuously or stepwise toward the side layer.

  The porous structure 26 has a structure in which three or more layers having different light transmittances are stacked so that the light transmittance increases from the back substrate 18 side toward the display substrate 16 side. Compared to the case where the body 26 has a configuration in which two layers having different light transmittances are stacked, the intermediate gradation can be expressed in multiple values.

As described above, the light transmittance of the porous structure 26 is adjusted so as to increase from the back substrate 18 side toward the display substrate 16 side. A porous structure that exists in each region from the back substrate 18 side to the display substrate 16 side within the above-described range in terms of the porosity of the structure 26, the aperture ratio of the holes, the average pore diameter, and the constituent materials, etc. It can be adjusted by adjusting 26.
Moreover, when the porous structure 26 is a nonwoven fabric, the light transmittance can be adjusted by further adjusting the density (fiber basis weight), fiber diameter, and the like of the nonwoven fabric.

  Specifically, the light transmittance of the porous structure 26 increases as the porosity increases. Similarly, the light transmittance of the porous structure 26 increases as the aperture ratio and the average pore diameter of the pores increase. Moreover, when the porous structure 26 is comprised with a nonwoven fabric, the light transmittance of the porous structure 26 becomes high, so that the density of the fiber of a nonwoven fabric becomes low.

  Further, by further selecting a material constituting the porous structure 26 as appropriate or adjusting the content of a colorant or the like as a material that affects the light transmittance, the porous structure 26 The light transmittance of the porous structure 26 can be adjusted so that the light transmittance of 26 increases from the back substrate 18 side toward the display substrate 16 side. Further, the light transmittance can be further adjusted by combining the porous structure 26 with a plurality of layers and adjusting the thickness of each layer.

  Specifically, the refractive index of the material constituting the porous structure is selected so that the difference from the refractive index of the solvent is small on the display substrate 16 side and large on the back substrate side 18, or the size of the colorant is increased. By selecting the size to be small on the display substrate 16 side and large on the back substrate side 18, or by selecting the colorant content ratio to be small on the display substrate 16 side and large on the back substrate side 18. The light transmittance of the porous structure 26 is adjusted.

  In FIG. 1, as an example, a case where the porous structure 26 of the display medium 12 of the present embodiment is configured by a plurality of layers, and each layer is configured as an aggregate of second particles 27. Indicated.

  In the case of the example shown in FIG. 1, the porous structure 26 is porous in which the light transmittance is different from the back substrate 18 side toward the display substrate 16 side in the facing direction of the back substrate 18 and the display substrate 16. A porous structure 26 in which three layers of a porous structure 26C, a porous structure 26B, and a porous structure 26A are stacked is provided.

  The light transmittance of the porous structure 26B laminated on the porous structure 26C is higher than the light transmittance of the porous structure 26C, and the light of the porous structure 26A laminated on the porous structure 26B. The transmittance is adjusted to be higher than that of the porous structure 26B.

  In the example illustrated in FIG. 1, the case where the porous structure 26 includes three layers has been described. However, as described above, the porous structure 26 may include two layers. As shown in the display medium 13 shown, there may be four layers, or five or more layers.

  Moreover, in the example shown in FIG. 1, although each layer of the porous structure 26 which consists of multiple layers has shown the case where it is comprised as the aggregate | assembly of the 2nd particle | grains 27, each layer is from a nonwoven fabric or a resin sheet. It may be configured. For example, like the porous structure 29 of the display medium 15 shown in FIG. 3, each layer is formed of a nonwoven fabric, and layers with high transmittance are stacked in order from the back substrate 18 side to the display substrate 16 side. Alternatively, the nonwoven fabric 29C, the nonwoven fabric 29B, and the nonwoven fabric 29A may be laminated in order.

  The display device 11 including the display medium 13 illustrated in FIG. 2 and the display device 17 including the display medium 15 illustrated in FIG. 3 are different from the display device 10 including the display medium 12 illustrated in FIG. Since the structure is the same except that the structure 26 is different, the same reference numerals are given to the same parts, and detailed description thereof is omitted.

  In addition, the porous structure 26 composed of a plurality of layers is formed by laminating one or more layers selected from a layer made of nonwoven fabric, a layer made of a resin sheet, and a layer made of the second particles 27. It may be.

Although the manufacturing method of the display medium 12 is not specifically limited, For example, it can produce by the following processes.
First, a rear substrate 18 and a display substrate 16 are prepared as a pair of substrates. As these substrates, electrodes may be provided in advance. Subsequently, the gap member 20 is formed on the surface of either the back substrate 18 or the display substrate 16 (for example, the back substrate 18).
Next, when the porous structure 26 is composed of a plurality of layers in the region (cell) delimited by the gap member 20 of the back substrate 18, the layer having the lowest light transmittance (porous structure In order from 26C), the porous structure 26C, the porous structure 26B having a higher light transmittance than the porous structure 26C, and the porous structure 26A having a higher light transmittance than the porous structure 26B are stacked, The porous structure 26 is disposed.
Next, the porous structure 26 disposed in each cell is filled with the dispersion medium 38 in which the first particle group 28 is dispersed up to the height of the gap member 20, and the back substrate 18 and the display substrate 16 are spaced from each other. The display medium 12 is manufactured by bonding through the member 20.

  When the porous structure 26 is composed of a plurality of layers, the layers may be simply laminated, or the layers may be heat-sealed after being laminated.

  In addition, in order to fix the display substrate 16 and the rear substrate 18 to each other via the gap member 20, a fixing means such as a combination of bolts and nuts, a clamp, a clip, and a frame for fixing the substrate can be used. Also, fixing means such as an adhesive, heat melting, and ultrasonic bonding can be used.

  The display medium 12 configured in this way is shared with bulletin boards, circular editions, electronic blackboards, advertisements, signboards, blinking signs, electronic paper, electronic newspapers, electronic books, and copiers / printers that can store and rewrite images. It can be used for document sheets that can be used.

Next, the display device 10 according to the present embodiment will be described.
As described above, the display device 10 according to the present embodiment includes the display medium 12 and the electric field applying device 14.

  The electric field applying device 14 is connected to the display electrode 32 and the back electrode 36 of the display medium 12 so that a voltage can be applied.

  In such a display device 10, for example, as shown in FIG. 4A, the first particle group 28 dispersed in the display medium 12 is present on the back substrate 18 side from the porous structure 26. The color of the porous structure 26 is presented when viewed from the display substrate 16 side.

  In FIG. 4, as an example, the color of the porous structure 26 is white, the color of the first particle group 28 is black, and the light transmittance of the porous structure 26 is the porous structure. The body 26C, the porous structure 26B, and the porous structure 26A are adjusted so as to increase in this order. In the present embodiment, the electric field applying device 14 applies a voltage having a constant voltage value between the display electrode 32 and the back electrode 36 of the display substrate 16 and adjusts the voltage application time of this voltage value. Thus, the display density of the display medium 12 is adjusted.

As shown in FIG. 4A, between the display electrode 32 and the back electrode 36 of the display medium 12 in a state where the first particle group 28 exists on the back substrate 18 side from the porous structure 26, When a voltage for forming an electric field gradient in which the first particle group 28 moves toward the display substrate 16 from the electric field applying device 14 is applied and the electric field gradient is formed between the substrates, the first particle group 28 starts to move toward the display substrate 16 (see FIG. 4B).
At this time, since the light transmittance of the porous structure 26 increases from the back substrate 18 side toward the display substrate 16 side, the display density of the display medium 12 is increased as the first particle group 28 moves. Changes begin to occur.

  Furthermore, when the voltage application between the display electrode 32 and the back electrode 36 is continued from the electric field applying device 14, the first particle group 28 further moves toward the display substrate 16 as the voltage application time elapses. Move (see FIG. 4C). Since the porous structure 26 is a member having a higher light transmittance as it approaches the display substrate 16 side, the porous structure 26 is moved by the movement of the first particle group 28 toward the display substrate 16 side. The hiding power of the first particle group 28 is weakened, and the display density of the display medium 12 is increased.

  Further, voltage application from the electric field applying device 14 to the display electrode 32 and the back electrode 36 is continued, and the first particle group 28 is positioned on the display substrate 16 side from the porous structure 26. The color of the first particle group 28 is displayed at the maximum density that can be expressed by the first particle group 28 enclosed in each cell (see FIG. 4D).

  On the other hand, between the display electrode 32 and the back electrode 36 of the display medium 12 in the state where the first particle group 28 shown in FIG. When a voltage for forming an electric field gradient in which the first particle group 28 moves from the display substrate 16 side to the rear substrate 18 side is applied from the electric field applying device 14, and the electric field gradient is formed between the substrates, The first particle group 28 starts to move toward the back substrate 18 side. Then, by continuing this voltage application, the first particle group 28 moves from the display substrate 16 side to the back substrate 18 as the voltage application time increases.

  At this time, since the porous structure 26 of the display medium 12 has a high light transmittance from the back substrate 18 side to the display substrate 16 side, the first particle group 28 from the display substrate 16 side to the back substrate 18 side. The display density of the display medium 12 gradually decreases with the movement to (see FIGS. 4D, 4C, 4B, and 4A).

  Here, for example, as shown in FIG. 4A, the display electrode 32 and the back electrode 36 of the display medium 12 in a state where the first particle group 28 is present on the back substrate 18 side from the porous structure 26. When a voltage having a predetermined voltage value for forming an electric field gradient in which the first particle group 28 moves from the electric field applying device 14 to the display substrate 16 side is applied, the application starts (time T0). ) Is the concentration a. Then, when time T1 seconds have elapsed from the start of application of the voltage of the voltage value, the first particle group 28 in the display medium 12 exists in the layer of the porous structure 26C as shown in FIG. 4B. The density in the current state is a density b higher than the density a. Further, when the time T2 seconds (T1 <T2) has elapsed from the start of voltage application of the voltage value, the first particle group 28 in the display medium 12 has a porous structure as shown in FIG. The density in the state existing in the layer of the body 26B is a density c higher than the density b. Further, when the time T3 seconds (T2 <T3) has elapsed from the voltage application time of the voltage value, the first particle group 28 in the display medium 12 is porous as shown in FIG. The structure 26A exists on the display substrate 16 side with respect to the layer of the structure 26A, and the density in this state is a density d higher than the density c.

  At this time, the relationship between the voltage application time and the display density is a substantially linear relationship as shown in FIG.

  Thus, according to the display medium 12 of the present embodiment, the porous structure 26 is configured so that the light transmittance increases from the back substrate 18 side toward the display substrate 16 side. Compared to the case where the porous structure 26 does not have the light transmittance characteristics of the porous structure 26 of the display medium 12 of the present embodiment, the concentration change of the display medium 12 due to the movement of the first particle group 28. However, it gradually changes according to the light transmittance distribution of the porous structure 26.

  On the other hand, the light transmittance of the porous structure 26 does not have the characteristics of the display medium 12 of the present embodiment, and the particles constituting the first particle group 28 are displayed through the holes of the porous structure. When changing the color and concentration of the first particle group 28 depending on whether or not it is viewed from the substrate 16 side, is the color of the first particle group 28 visible through the pores of the porous structure? Since the color and density are adjusted by binary adjustment of whether or not, the light transmittance of the porous structure body 26 from the back substrate 18 side to the display substrate 16 side as in the display medium 12 of the present embodiment is increased. It is considered that the change in display density with respect to the voltage application time becomes abrupt as compared with the case where it is configured to be high.

  Therefore, according to the display medium 12 of the present embodiment, the porous structure 26 is configured so that the light transmittance increases from the back substrate 18 side toward the display substrate 16 side. Compared to a display medium having a porous structure that does not have characteristics, the change in display density with respect to the voltage application time becomes gradual, making it easy to display the desired halftone, and making it easy to adjust the halftone There is an effect that the medium 12 and the display device 10 are provided.

  The above embodiment will be described below with reference to examples, but the present invention is not limited to the following examples.

Example 1
A display medium 12 having the configuration shown in FIG. 1 was produced by the following procedure.

  First, prior to the production of the display medium 12, a dispersion medium 38 was prepared and a first particle group 28 was produced.

  As the dispersion medium 38, silicone oil (KF-96, manufactured by Shin-Etsu Chemical Co., Ltd.) was prepared.

-Production of first particle group 28-
-Preparation of dispersion A-
・ Cyclohexyl methacrylate: 53 parts by weight ・ Magenta pigment (Kermin 6B; manufactured by Dainichi Seika Co., Ltd.) 3 parts by weight ・ Charge control agent (COPY CHARGE PSY VP2038; manufactured by Clariant Japan) 2 parts by weight Dispersion A was prepared by ball milling for 20 hours using 10 mm zirconia balls.

-Preparation of dispersion B-
-Calcium carbonate: 40 parts by weight-Water: 60 parts by weight Dispersion B was prepared by finely grinding a mixture of the above components with a ball mill.

-Adjustment of mixture C-
-2% by weight serogen aqueous solution: 4.3 g
・ Dispersion B: 8.5 g
・ 20% by weight saline solution: 50 g
The above components were mixed, degassed with an ultrasonic machine for 10 minutes, and stirred with an emulsifier to prepare mixture C.

-Production of first particle group 28-
35 g of dispersion A, 1 g of divinylbenzene, and polymerization initiator AIBN (2,2′-azobisisobutyronitrile): 0.35 g are sufficiently mixed and deaerated with an ultrasonic machine for 10 minutes. This is put in the mixed solution C and emulsified with an emulsifier.
Next, the obtained emulsified liquid is put into a bottle, siliconized, and using an injection needle, vacuum degassing is sufficiently performed and sealed with nitrogen gas. Next, it was made to react at 60 degreeC for 10 hours, and particle | grains were produced. The obtained fine particle powder was dispersed in ion-exchanged water, calcium carbonate was decomposed with 1N (1N) hydrochloric acid, and filtered. Thereafter, it was washed with sufficient distilled water to have a uniform particle size and dried.

The first particle group 28 was positively charged in the silicone oil used as the dispersion medium 38. Further, the first particle group 28 had a magenta color.
The volume average primary particle size of the first particle group 28 was 0.42 μm.

  In the examples, the volume average primary particle size of the first particle group 28 is a particle obtained by observing the particles with SEM or TEM and obtaining from the area of 10 particles based on the obtained SEM image or TEM image. It calculated | required as an average value of a diameter.

  Subsequently, second particles 27 were produced.

-Production of second particles 27-
-Adjustment of dispersion D-
-Methyl methacrylate monomer: 80 parts by weight-Titanium oxide (manufactured by Ishihara Sangyo Co., Ltd., Taipei CR63): 0.5 part by weight-Hollow particles (manufactured by JSR, SX866 (A)): 3 parts by weight
A mixture of the above components was subjected to ball milling using zirconia balls having a diameter of 10 mm for 20 hours to prepare dispersion D.

-Adjustment of dispersion E-
-Calcium carbonate: 40 parts by weight-Water: 60 parts by weight or more of components were mixed, and the same operation as in dispersion D was performed to prepare dispersion E.

-Adjustment of mixture F-
-Dispersion E: 8.5 parts by weight-20% saline: 50 parts by weight or more of the components were mixed with stirring to prepare a mixture F.

-Production of second particles 27A-
-35 parts by weight of dispersion D-1 part by weight of ethylene glycol dimethacrylate-0.35 parts by weight or more of azoisobutyronitrile are mixed and then emulsified by adding mixture F to obtain emulsion G It was.
The obtained emulsion G was heated to 65 ° C. under a nitrogen stream and stirred for 15 hours to obtain solid particles H. 15 parts by weight of 35% hydrochloric acid was added to the obtained solid particles H and stirred to dissolve calcium carbonate, and then suction filtration and water washing were repeated 5 times to obtain white particles I. The obtained white particles I were classified by sieving to obtain second particles 27A having an average particle size of 13 μm.

-Production of second particles 27B-
Second particles having an average particle diameter of 13 μm were prepared in the same manner as the preparation of the second particles 27A except that the weight of titanium oxide was changed to 5 parts by weight in the preparation of the dispersion D for the preparation of the second particles 27. 27B was obtained.

-Production of second particles 27C-
Second particles having an average particle diameter of 13 μm were prepared in the same manner as the preparation of the second particles 27A except that the weight of titanium oxide was changed to 17 parts by weight in the preparation of the dispersion D for the preparation of the second particles 27. 27C was obtained.

-Production of display medium 12-
First, two transparent substrates made of glass having a size of 50 mm × 50 mm and a thickness of 0.7 mm are prepared, and an ITO film is formed on each side as a transparent electrode (display electrode 32, back electrode 36) by sputtering to a thickness of 50 nm. The display substrate 16 and the back substrate 18 were manufactured by forming a film with a thickness.

  Subsequently, an epoxy resin (SU-8 manufactured by MicroChem Corp.) is applied to the surface of the back substrate 18 on which the back electrode 36 is provided, and then exposure and wet etching are performed to form a back surface on the back substrate 18. A gap member 20 having a height of 50 μm and a width of 2 mm was formed so as to partition the surface of the substrate 18 into 20 mm × 20 mm.

  Next, a porous structure 26 composed of three layers was disposed in a region separated by the gap member 20 on the back substrate 18.

As shown in FIG. 1, the three-layer porous structure 26 has a three-layer structure of a porous structure 26C, a porous structure 26B, and a porous structure 26A.
As the porous structure 26C, an aggregate of the second particles 27C obtained by laminating a plurality of second particles 27C in one layer was used.

  In a region separated by the gap member 20 on the back substrate 18 produced in Example 1, 0.2 mg of a dispersion liquid in which 20% by weight of the second particles 27C are dispersed in the dispersion medium 38 is dropped, and 80 ° C. The porous structure 26C was produced by heating and drying for 30 minutes for fusion.

  Subsequently, 0.2 mg of a dispersion in which 20% by weight of the second particles 27B are dispersed in the dispersion medium 38 is dropped into the above-described region, and similarly heated at 80 ° C. for 30 minutes to perform drying and fusion. A porous structure 26B was produced on top of the porous structure 26C.

  Similarly, a porous structure 26A composed of an aggregate of the second particles 27A was produced on the upper part of the porous structure 26B, and a porous structure 26 having a three-layer structure was produced.

  When the light transmittance of the porous structure 26 was measured with the USB2000 manufactured by Ocean Optics by the above method, the light transmittance of the entire region of the porous structure 26 was 4%. Further, the light transmittances of the porous structure 26C, the porous structure 26B, and the porous structure 26A were measured in the same manner, and were 25%, 32%, and 53%, respectively.

  Thus, in Example 1, the porous structure 26 is composed of a plurality of particle aggregates and a plurality of layers, and the colorant content of the particle aggregates constituting each layer is set. By adjusting, the light transmittance of each layer (porous structure 26A, porous structure 26B, and porous structure 26C) was adjusted.

  Subsequently, a dispersion in which 7% by weight of the adjusted first particle group 28 is dispersed in a region partitioned by the gap member 20 on the display substrate 16 on which the porous structure 26 having a three-layer structure is manufactured. Was filled up to the height of the gap member 20.

  Subsequently, after the display substrate 16 manufactured in Example 1 is overlaid on the back substrate 18 via the gap member 20, the dispersion medium 38 and the surface of the display substrate 16 are brought into close contact with each other so that air is not mixed therein. Was sealed and fixed with an ultraviolet curable adhesive (manufactured by Norland) to produce a display medium 12.

  Using the display medium 12 thus produced, the display medium 12 was observed from the side of the display medium 12 on which the display substrate 16 was provided, and the change in density was confirmed.

First, the electrodes on the display substrate 16 and the electrodes on the rear substrate 18 are applied from the electric field applying device 14 so that the electrode on the display substrate 16 side of the display medium 12 immediately after assembly is positive and the electrode on the rear substrate 18 side is negative. A voltage of 15 V was applied to both electrodes until the display density on the display surface was sufficiently saturated. At this time, white was displayed on the display surface.
Moreover, it was 0.15 when the optical density of magenta of the display medium 12 at this time was measured by X-Rite404 by X-Rite.

  At this time, when the display medium 12 is observed from the rear substrate 18 side, the first particle group 28 is in a state of being arranged on the rear substrate 18 side (the state shown in FIG. 4A).

  Note that “until the display density is sufficiently saturated” means that the display per unit time on the display substrate 16 side when a voltage of 15 V is applied to both the electrodes of the display substrate 16 and the back substrate 18. A state in which the change in density is 0.1 or less is shown.

Next, 15 V is applied to both the electrode of the display substrate 16 and the electrode of the rear substrate 18 so that the electrode on the display substrate 16 side of the display medium 12 becomes negative and the electrode on the rear substrate 18 side becomes positive. The density of the display surface when a voltage was applied for 0.2 seconds was measured in the same manner as described above, and was 0.27.
Subsequently, 15V is applied to both the electrodes of the display substrate 16 and the back substrate 18 so that the electrode on the display substrate 16 side of the display medium 12 becomes negative and the electrode on the back substrate 18 side becomes positive. When the display surface density was measured in the same manner as described above when the voltage was applied for 0.4 seconds, 0.8 seconds, and 1.5 seconds, they were 0.54, 1.16, and 1.63, respectively. .

  In the measurement of the concentration, 10 concentrations were measured in the surface direction of the display substrate 16, and the average value of the measurement results was used as the concentration measurement result.

  The relationship between the elapsed time from the voltage application start in the display medium 12 and the relationship with the density is the relationship shown in FIG. 5, indicating a substantially linear relationship.

Further, a voltage of 15V is applied to both the electrode of the display substrate 16 and the electrode of the rear substrate 18 so that the electrode on the display substrate 16 side of the display medium 12 becomes positive and the electrode on the rear substrate 18 side becomes negative. Is applied until the display density on the display surface is sufficiently saturated, and then a voltage of 15 V is applied again so that the electrode on the display substrate 16 side of the display medium 12 becomes negative and the electrode on the rear substrate 18 side becomes positive. In the same manner as described above, the process of measuring the concentration at the time of voltage application after 0.2 seconds, 0.4 seconds, 0.8 seconds, and 1.5 seconds was repeated 20 times. A diagram showing the relationship between the elapsed time from the start of voltage application and the concentration was created, and the variation in the diagram between each number of measurements was confirmed. The maximum and minimum concentration measurement results for the same voltage application time The difference from the value is the density difference It was .04.
From this, in order to obtain the target concentration, the relationship between the voltage application time and the concentration of each display medium 12 is measured in advance, and the voltage of the voltage application time based on the measurement result is applied. It can be said that the concentration can be easily presented.

(Example 2)
In the first embodiment, as shown in FIG. 1, the display medium 12 in which the porous structure 26 is configured as an aggregate of a plurality of second particles 27 is manufactured. However, in the second embodiment, the porous medium 26 is porous. The case where the structure 26 is comprised from the nonwoven fabric is demonstrated.

  In Example 2, a display medium was produced in the same manner as in Example 1 except that a porous structure 29 made of a nonwoven fabric was used instead of the porous structure 26 used in Example 1.

  In Example 2, a porous structure 29 having a configuration in which three layers of nonwoven fabrics were laminated was used as the porous structure.

  As shown in FIG. 3, the porous structure 29 has a three-layer structure of a nonwoven fabric 29C, a nonwoven fabric 29B, and a nonwoven fabric 29A, and each layer is formed of a nonwoven fabric and disposed on the display substrate 16. These non-woven fabrics were laminated so that the light transmittance was higher as the thickness was higher.

Specifically, as the nonwoven fabric 29A, Japan Gore-Tex, PTFE (Ishihara Sangyo CR60, containing 5%) was prepared. This nonwoven fabric 29A had an average pore diameter of 3 μm, a fiber diameter of 100 nm, and a thickness of 15 μm.
Moreover, when the light transmittance of the nonwoven fabric 29A was measured by USB2000 manufactured by Ocean Optics by the above method, it was 50%.

  As the nonwoven fabric 29B, PTFE (Ishihara Sangyo CR60, containing 20%) manufactured by Japan Gore-Tex was prepared. This nonwoven fabric 29B had an average pore diameter of 3 μm, a fiber diameter of 100 nm, and a thickness of 15 μm. Moreover, when the light transmittance of the non-woven fabric 29B was measured by USB2000 manufactured by Ocean Optics by the above method, it was 20%.

  As nonwoven fabric 29C, Japan Gore-Tex, PTFE (Ishihara Sangyo CR60, containing 30%) was prepared. This nonwoven fabric 29C had an average pore diameter of 3 μm, a fiber diameter of 100 nm, and a thickness of 15 μm. Moreover, when the light transmittance of the nonwoven fabric 29C was measured by USB2000 made by Ocean Optics by the above method, it was 7%.

  Thus, in the present Example 2, the light transmission rate was adjusted by setting the porous structure 29 to the structure which laminated | stacked the nonwoven fabric, and adjusting the content rate of the coloring agent of the nonwoven fabric which comprises each layer.

  Note that the nonwoven fabric 29A, the nonwoven fabric 29B, and the nonwoven fabric 29C constituting the porous structure 29 each had a white color.

  Using the non-woven fabric 29A, non-woven fabric 29B, and non-woven fabric 29C prepared in the second embodiment, the non-woven fabric 29C is formed on the back substrate 18 in the region separated by the gap member 20 on the back substrate 18 manufactured in the first embodiment. The porous structure 29 (thickness: 45 μm) was arranged by sequentially laminating the nonwoven fabric 29B and the nonwoven fabric 29A.

When the light transmittance of the porous structure 29 was measured by USB2000 manufactured by Ocean Optics by the above method, the light transmittance of the entire region of the porous structure 29 was 3%.
Subsequently, after the first particle group 28 prepared in the above Example 1 was dispersed in a silicone oil as a dispersion medium 38 at a content of 7% by weight up to the height of the gap member 20, Example 1 was used. A display medium 15 was produced in the same manner as described above.

  Using the display medium 15 thus manufactured, the display medium 15 was observed from the side of the display medium 15 on which the display substrate 16 was provided, and the change in density was confirmed in the same manner as in Example 1.

First, 15 V is applied to both the electrode of the display substrate 16 and the electrode of the back substrate 18 so that the electrode on the display substrate 16 side of the display medium 15 immediately after assembly is positive and the electrode on the back substrate 18 side is negative. Was applied until the display density on the display surface was sufficiently saturated. At this time, white was displayed on the display surface.
Further, the concentration of the display medium 15 at this time was 0.15 when measured by X-Rite 404 manufactured by X-Rite.

  At this time, when the display medium 15 is observed from the back substrate 18 side, the first particle group 28 is in a state of being arranged on the back substrate 18 side.

  Next, 15 V is applied to both the electrode of the display substrate 16 and the electrode of the rear substrate 18 so that the electrode on the display substrate 16 side of the display medium 15 becomes negative and the electrode on the rear substrate 18 side becomes positive. The density of the display surface when a voltage was applied for 0.2 seconds was measured in the same manner as described above, and was 0.25.

  Subsequently, 15 V is applied to both the electrode of the display substrate 16 and the electrode of the rear substrate 18 so that the electrode on the display substrate 16 side of the display medium 15 becomes negative and the electrode on the rear substrate 18 side becomes positive. When the display surface density was measured in the same manner as described above when the voltage was applied for 0.4 seconds, 0.8 seconds, and 1.5 seconds, they were 0.47, 1.09, and 1.62, respectively. .

  The relationship between the elapsed time from the voltage application start in the display medium 15 and the relationship with the density is the relationship shown in FIG. 6, indicating a substantially linear relationship.

Further, a voltage of 15 V is applied to both the electrodes of the display substrate 16 and the back substrate 18 so that the electrode on the display substrate 16 side of the display medium 15 becomes positive and the electrode on the back substrate 18 side becomes negative. Is applied until the display density on the display surface is sufficiently saturated, and then a voltage of 15 V is applied again so that the electrode on the display substrate 16 side of the display medium 13 becomes negative and the electrode on the back substrate 18 side becomes positive. In the same manner as described above, the process of measuring the concentration at the time of voltage application after 0.2 seconds, 0.4 seconds, 0.8 seconds, and 1.5 seconds was repeated 20 times. A diagram showing the relationship between the elapsed time from the start of voltage application and the concentration was created, and the variation in the diagram between each number of measurements was confirmed. The maximum and minimum concentration measurement results for the same voltage application time The difference from the value is the density difference It was .05.
From this, in order to obtain the target concentration, the relationship between the voltage application time and the concentration of the display medium 15 is measured in advance, and if the voltage of the voltage application time based on the measurement result is applied, the target concentration is obtained. It can be said that can be presented easily.

(Comparative Example 1)
The display medium in Comparative Example 1 was produced by the following procedure.

  In the first embodiment, the light transmittance is different from each other in the region defined by the gap member 20 on the rear substrate 18 adjusted in the first embodiment, and the light transmittance is higher as the display substrate 16 side is approached. A display medium in which the porous structure 26 composed of the three layers (porous structure 26C, porous structure 26B, and porous structure 26A) laminated as described above was prepared. In the case where only the porous structure 26C is disposed therein, that is, a display medium in which the porous structure is disposed in which the light transmittance is substantially constant in the direction in which the rear substrate 18 and the display substrate 16 face each other is manufactured.

  As the porous structure 26C, the porous structure 26C produced in Example 1 was used.

  Except for using the porous structure 26C instead of the porous structure 26 (a laminated body of the porous structure 26C, the porous structure 26B, and the porous structure 26A) used in Example 1 above. A display medium 42 (see FIG. 7) was produced in the same manner as in Example 1.

  Using the display medium 42 thus manufactured, the display medium 42 was observed from the side of the display medium 42 where the display substrate 16 was provided, and the change in density was confirmed.

First, 15 V is applied to both the electrode of the display substrate 16 and the electrode of the rear substrate 18 so that the electrode on the display substrate 16 side of the display medium 42 immediately after assembly is positive and the electrode on the rear substrate 18 side is negative. This voltage was applied from the electric field applying device 14 until the display density on the display surface was sufficiently saturated. At this time, white was displayed on the display surface.
Moreover, it was 0.20 when the density | concentration of the display medium 42 at this time was measured by X-Rite404 by X-Rite.

  At this time, when the display medium 42 is observed from the rear substrate 18 side, the first particle group 28 is in a state of being disposed on the rear substrate 18 side (the state shown in FIG. 7A).

Next, 15 V is applied to both the electrode of the display substrate 16 and the electrode of the rear substrate 18 so that the electrode on the display substrate 16 side of the display medium 42 becomes negative and the electrode on the rear substrate 18 side becomes positive. When the density of the display surface when a voltage was applied for 0.2 seconds was measured in the same manner as described above, it was 0.30 (see FIG. 7B).
Subsequently, 15V is applied to both the electrode of the display substrate 16 and the electrode of the rear substrate 18 so that the electrode on the display substrate 16 side of the display medium 42 becomes negative and the electrode on the rear substrate 18 side becomes positive. When the density of the display surface was measured in the same manner as described above when the voltage was applied for 0.4 seconds, 0.8 seconds, and 1.5 seconds, they were 1.00, 1.45, and 1.56, respectively. (See FIGS. 7C and 7D).

  The relationship between the elapsed time from the start of voltage application in the display medium 42 and the relationship with the density is the relationship shown in FIG. 8, indicating a relationship of a quadratic curve.

  In addition, in the display media manufactured in Example 1 and Example 2, a change in density was observed from the start of voltage application, and the concentration changed as the voltage application time increased. In the display medium manufactured in Comparative Example 1, The concentration change did not occur until 100 milliseconds after the start of voltage application, and the concentration change per unit time abruptly compared with Example 1 and Example 2 after several hundred milliseconds.

  This is because the display medium 42 manufactured in Comparative Example 1 enables concentration display by the first particle group 28 depending on whether or not the first particle group 28 is in a position shielded by the porous structure. As shown in FIGS. 7B to 7C, no change in concentration occurs at the same time as the voltage application is started, and as shown in FIGS. 7B to 7C, particles having a fast moving speed are transferred from the display substrate 16 side. It is considered that the concentration starts to change due to the observation, and the concentration changes due to variations in the moving speed of the particles constituting the first particle group 28.

  On the other hand, in the display medium 12 and the display medium 13 produced in Example 1 and Example 2, when the first particle group 28 starts to move from the back substrate 18 side to the display substrate 16 side, the porous structure 26 is configured such that the light transmittance increases from the back substrate 18 side toward the display substrate 16 side. Therefore, the closer the first particle group 28 is to the display substrate 16 side, the more the porous structure 26 becomes. It is considered that the concealing effect of the color of the first particle group 28 is reduced, and the density gradually changes.

  For this reason, in the display medium 12 and the display medium 13 manufactured in Example 1 and Example 2, the first particle group 28 is transferred from the back substrate 18 side to the display substrate 16 side or from the display substrate 16 side to the back substrate 18. As it moves to the side, the concentration changes more slowly than in Comparative Example 1. Therefore, in the display medium and the display device manufactured in Example 1 and Example 2, the adjustment of the voltage application time for displaying the target density is easier than in Comparative Example 1, and the adjustment of the halftone is possible. It can be said that it is easy.

  Further, a voltage of 15 V is applied to both the electrodes of the display substrate 16 and the back substrate 18 so that the electrode on the display substrate 16 side of the display medium 42 is positive and the electrode on the back substrate 18 side is negative. Is applied until the display density on the display surface is sufficiently saturated, and then a voltage of 15 V is applied again so that the electrode on the display substrate 16 side of the display medium 13 becomes negative and the electrode on the back substrate 18 side becomes positive. In the same manner as described above, the process of measuring the concentration at the time of voltage application after 0.2 seconds, 0.4 seconds, 0.8 seconds, and 1.5 seconds was repeated 20 times. A diagram showing the relationship between the elapsed time from the start of voltage application and the concentration was created, and the variation in the diagram between each number of measurements was confirmed. The maximum and minimum concentration measurement results for the same voltage application time The difference from the value is the density difference Is .15, as compared to the measurement results of Example 1 and Example 2, the density difference was 0.10 greater.

  Therefore, in the display medium 42 manufactured in Comparative Example 1, in order to obtain a target concentration, the relationship between the voltage application time and the concentration of each display medium 12 is measured in advance, and the voltage based on the measurement result is measured. It can be said that it is difficult to display the target concentration with high accuracy even when a voltage for an application time is applied.

  Therefore, the display medium manufactured in Example 1 and Example 2 can display the target density with higher accuracy than the display medium manufactured in Comparative Example 1, and can easily adjust the halftone. You can say that.

(Comparative Example 2)
In Comparative Example 1, the case where the porous structure has one layer (a configuration in which particles are arranged in a line in the plane direction) has been described, but in Comparative Example 2, the porous structure has a structure as shown in FIG. A display medium 46 in which a plurality of layers were laminated was produced.

  The display medium in Comparative Example 2 was produced by the following procedure.

  In the first comparative example, a porous structure in which one row of particles is arranged in the surface direction of the display substrate 16 in the region defined by the gap member 20 on the rear substrate 18 adjusted in the first embodiment. Although the display medium 42 is manufactured using the structure 26C, in the present comparative example 2, as shown in FIG. 9, the display medium 46 has a structure in which a plurality of porous structures 26C are laminated. Was made.

  The porous structure 48 in Comparative Example 2 has a porous structure in which three layers of the porous structure 26C prepared in Example 1 and Comparative Example 1 are stacked in the facing direction of the display substrate 16 and the back substrate 18. The light transmittance of this porous structure 48 was 2%.

  A porous structure 48 prepared in Comparative Example 2 was used instead of the porous structure 26 (a laminate of the porous structure 26C, the porous structure 26B, and the porous structure 26A) used in Example 1 above. A display medium 46 (see FIG. 9) was produced in the same manner as in Example 1 except that was used.

  Using the display medium 46 thus produced, the display medium 46 was observed from the side of the display medium 46 where the display substrate 16 was provided, and the change in density was confirmed.

First, 15 V is applied to both the electrode of the display substrate 16 and the electrode of the back substrate 18 so that the electrode on the display substrate 16 side of the display medium 46 immediately after assembly is positive and the electrode on the back substrate 18 side is negative. This voltage was applied from the electric field applying device 14 until the display density on the display surface was sufficiently saturated. At this time, white was displayed on the display surface.
Further, the density of the display medium 46 at this time was 0.13 when measured by X-Rite 404 manufactured by X-Rite.

  At this time, when the display medium 46 is observed from the back substrate 18 side, the first particle group 28 is in a state of being arranged on the back substrate 18 side.

Next, both the electrode of the display substrate 16 and the electrode of the rear substrate 18 are arranged so that the electrode on the display substrate 16 side of the display medium 46 becomes positive and the electrode on the rear substrate 18 side becomes negative.
The density of the display surface when a voltage of 15 V was applied for 0.2 seconds was measured in the same manner as described above, and was 0.17.

  Subsequently, 15V is applied to both the electrodes of the display substrate 16 and the back substrate 18 so that the electrode on the display substrate 16 side of the display medium 12 becomes negative and the electrode on the back substrate 18 side becomes positive. When the display surface density was measured in the same manner as described above when the voltage was applied for 0.4 seconds, 0.8 seconds, and 1.5 seconds, they were 0.22, 0.70, and 1.60, respectively. .

  The relationship between the elapsed time from the start of voltage application in the display medium 46 and the relationship with the density is the relationship shown in FIG. 10, indicating a relationship of a quadratic curve.

  Further, in the display media manufactured in Example 1 and Example 2, a change in concentration was observed from the start of voltage application, and the concentration changed with an increase in voltage application time. In the display medium manufactured in Comparative Example 2, The concentration change did not occur until several hundred milliseconds after the start of voltage application, and after several hundred milliseconds, the concentration change per unit time occurred more rapidly than in Example 1 and Example 2.

  As in Comparative Example 1, in the display medium 46 produced in Comparative Example 2, the first particle group 28 depends on whether or not the first particle group 28 is in a position shielded by the porous structure 48. Therefore, the concentration change does not occur at the same time as the voltage application is started, and the concentration change is caused by observing particles of the first particle group 28 having a high moving speed from the display substrate 16 side. This is considered to be because the concentration has changed due to variations in the moving speed of the particles constituting the first particle group 28.

  On the other hand, in the display medium 12 and the display medium 13 produced in Example 1 and Example 2, when the first particle group 28 starts to move from the back substrate 18 side to the display substrate 16 side, the porous structure 26 is configured such that the light transmittance increases from the back substrate 18 side toward the display substrate 16 side. Therefore, the closer the first particle group 28 is to the display substrate 16 side, the more the porous structure 26 becomes. It is considered that the concealing effect of the color of the first particle group 28 is reduced, and the density gradually changes.

  For this reason, in the display medium 12 and the display medium 13 manufactured in Example 1 and Example 2, the first particle group 28 is transferred from the back substrate 18 side to the display substrate 16 side or from the display substrate 16 side to the back substrate 18. As it moves to the side, the concentration changes more slowly than in Comparative Example 2. Therefore, in the display medium and the display device manufactured in Example 1 and Example 2, the adjustment of the voltage application time for displaying the target density is easier than in Comparative Example 2, and the adjustment of the halftone is possible. It can be said that it is easy.

  Further, a voltage of 15V is applied to both the electrodes of the display substrate 16 and the back substrate 18 so that the electrode on the display substrate 16 side of the display medium 46 becomes positive and the electrode on the back substrate 18 side becomes negative. Is applied until the display density on the display surface is sufficiently saturated, and then a voltage of 15 V is applied again so that the electrode on the display substrate 16 side of the display medium 13 becomes negative and the electrode on the back substrate 18 side becomes +. In the same manner as described above, the process of measuring the concentration at the time of voltage application after 0.2 seconds, 0.4 seconds, 0.8 seconds, and 1.5 seconds was repeated 20 times. A diagram showing the relationship between the elapsed time from the start of voltage application and the concentration was created, and the variation in the diagram between each number of measurements was confirmed. The maximum and minimum concentration measurement results for the same voltage application time The difference from the value is the density difference 0. Is 3, as compared with the measurement results of Example 1 and Example 2, the density difference was 0.08 greater.

  Therefore, in the display medium 46 manufactured in Comparative Example 2, in order to obtain the target concentration, the relationship between the voltage application time and the concentration of each display medium 46 is measured in advance, and the voltage based on the measurement result is measured. It can be said that it is difficult to display the target concentration with high accuracy even when a voltage for an application time is applied.

  Therefore, the display media manufactured in Example 1 and Example 2 can display the target density with higher accuracy than the display media manufactured in Comparative Example 1 and Comparative Example 2, and can easily display intermediate gray levels. It can be said that adjustment is possible.

It is a schematic block diagram which shows an example of the display apparatus which concerns on embodiment of this invention. It is a schematic block diagram which shows an example of the display apparatus which concerns on embodiment of this invention. It is a schematic block diagram which shows an example of the display apparatus which concerns on embodiment of this invention. (A)-(D) In the display medium of the display apparatus shown in FIG. 1 which concerns on embodiment of this invention, it is a transition diagram which shows the state change in which the 1st particle group moves from the back substrate side to the display substrate side. is there. In the display apparatus shown in FIG. 1 which concerns on embodiment of this invention, it is a diagram which shows the relationship between the voltage application time to a display medium, and a density | concentration. FIG. 4 is a diagram showing the relationship between the voltage application time to the display medium and the concentration in the display device shown in FIG. 3 according to the embodiment of the present invention. (A)-(D) In the display medium in the comparative example 1, it is a transition diagram which shows the state change in which the 1st particle group moves from the back substrate side to the display substrate side. It is a diagram which shows the relationship between the voltage application time to a display medium, and a density | concentration in the comparative example 1. FIG. 10 is a schematic diagram showing a display medium manufactured in Comparative Example 2. FIG. It is a diagram which shows the relationship between the voltage application time to a display medium, and a density | concentration in the comparative example 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Display apparatus 12 Display medium 13 Display medium 14 Electric field application apparatus 15 Display medium 16 Display substrate 18 Back substrate 26C Porous structure 26B Porous structure 26A Porous structure 26 Porous structure 27 Second particle 28 1st Non-woven fabric 29B Non-woven fabric 29A Non-woven fabric 29 Porous structure 38 Dispersion medium 42 Display medium 46 Display medium 48 Porous structure

Claims (8)

A display substrate having optical transparency;
A rear substrate disposed facing the display substrate with a gap;
A dispersion medium sealed between the display substrate and the back substrate;
A first group of particles dispersed in the dispersion medium and moving in the dispersion medium in response to an electric field formed between the substrates;
The back substrate is disposed between the display substrate and the back substrate, has a plurality of holes through which the first particle group passes, and has an optical reflection characteristic different from that of the first particle group, A porous structure having a higher light transmittance as it approaches the display substrate side from the side,
A display medium comprising:   The display medium according to claim 1, wherein the porous structure has a light transmittance that increases stepwise from the back substrate side toward the display substrate side.   The display medium according to claim 1, wherein the porous structure has a light transmittance continuously increasing from the back substrate side toward the display substrate side.   The porous structure includes a plurality of layers having different light transmittances, and a layer having a high light transmittance is laminated from the back substrate side toward the display substrate side. The display medium described.   The display medium according to claim 4, wherein the porous structure includes three or more layers having different light transmittances.   The display medium according to claim 1, wherein the porous structure is an aggregate of second particles.   The display medium according to claim 1, wherein the porous structure is a nonwoven fabric. A display substrate having optical transparency, a back substrate disposed opposite to the display substrate with a gap, a dispersion medium sealed between the display substrate and the back substrate, and in the dispersion medium A first particle group that is dispersed in the substrate and moves in the dispersion medium according to an electric field formed between the substrates; and the first particle group that is disposed between the display substrate and the back substrate. A porous structure having a plurality of holes through which the first particle group and an optical reflection characteristic different from that of the first particle group, and having a higher light transmittance as it approaches the display substrate side from the back substrate side, A display medium provided;
An electric field applying means for applying an electric field to the display medium;
A display device comprising: