JP2007279433A - Dispersion for electrophoretic display, electrophoretic display device, and method for manufacturing dispersion for electrophoretic display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophoretic display device, wherein a stable state of an image is maintained by stabilizing electric charge on charged migrating particles, and also to provide a method for easily manufacturing a dispersion for an electrophoretic display with stabilized electric charge. <P>SOLUTION: In a pair of substrates, an electrode formed on at least one of the substrates, the charged migrating particles which are interposed between the substrates and are to be used for the electrophoretic display device, and the dispersion for the electrophoretic display containing a dispersion medium to disperse the charged migrating particles therein, the dispersion for the electrophoretic display has the charged migrating particles which are composite particles composed of a coloring material and a polymer, and the charge polarity of the coloring material and that of the polymer are identical to each other. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrophoretic display dispersion used in an electrophoretic display device in which display is performed by moving charged electrophoretic particles between electrodes, the electrophoretic display device, and a method for producing the electrophoretic display dispersion. .

  In recent years, with the development of information equipment, the need for low power consumption and thin display devices is increasing, and research and development of display devices that meet these needs are being actively conducted. In particular, liquid crystal display devices are capable of electrically controlling the arrangement of liquid crystal molecules to change the optical characteristics of the liquid crystal, and are actively developed and commercialized as display devices that can meet the above needs.

  Reflective display devices are expected from the viewpoints of low power consumption and reduced burden on the eyes. As one of them, an electrophoretic display device is known in which display is performed when charged electrophoretic particles dispersed in an insulating solvent move between electrodes. For example, Patent Literature 1 and Patent Literature 2 propose an electrophoretic display device.

  The basic structure of the electrophoretic display device is shown in FIGS. 1 and 2 in which the charged electrophoretic particles move horizontally, in FIG. 3 in which the charged electrophoretic particles move in the vertical direction, and in FIG. 4 with the charged electrophoretic particles and the dispersion medium. An example using microcapsules encapsulating a dispersion for electrophoretic display is shown. In each structure, the charged electrophoretic particles are electrophoresed according to the polarity of the charged electrophoretic particles and the polarity of the voltage applied to both electrodes. As a result, these electrophoretic display devices can realize a high contrast display with a reflection type and a viewing angle.

In the electrophoretic display device, controlling the charging of the charged electrophoretic particles brings about high-contrast display performance and display stability. As a proposal of the charged electrophoretic particles used in these electrophoretic display devices, there is Patent Document 3 in which a polymer chain is attached to the surface of a pigment serving as a nucleus. In addition, as a proposal of a dispersion for electrophoretic display used in an electrophoretic display device, Patent Document 4 of a liquid configuration in which a charge control agent is added to a dispersion, or a particle surface having an acidic group (basic group). In this case, there is Patent Document 5 having a liquid configuration in which a resin having a basic group (acidic group) is added to a dispersion.
JP-A-9-185087 (page 2) Japanese Patent No. 2551783 (first page) JP 2002-287178 A (page 3) Japanese translation of PCT publication No. 8-510790 (2nd page) JP 2002-62545 A (second page)

  Conventionally, among charged electrophoretic particles used in electrophoretic display devices, a charge control agent for the charged electrophoretic particles themselves is used to impart charge to or stabilize the charged electrophoretic particles made of a coloring material and a polymer. Or by adding a charge control agent, a charge stabilizer or the like to a dispersion medium for dispersing the charged electrophoretic particles. In any of the methods, since the evaluation relating to charging can be performed only after the dispersion liquid for electrophoretic display is prepared, the development of the charged electrophoretic particles takes time.

  Further, depending on the combination of the coloring material constituting the electrophoretic particles and the high molecular polymer, the charging characteristics may become unstable even when the above method is applied, and a stable image may not be maintained.

  The present invention has been made in view of such problems of the prior art, and stabilizes the charging of the charged electrophoretic particles, and as a result, a dispersion for electrophoretic display capable of maintaining a stable image state. An object of the present invention is to provide an electrophoretic display device.

  It is another object of the present invention to provide a method for easily producing charged electrophoretic particles with stable charge.

  That is, the first invention of the present invention is a charged electrophoretic particle and a charged electrophoretic particle used in an electrophoretic display device sandwiched between a pair of substrates, an electrode formed on at least one of the substrates, and the substrate. In the dispersion liquid for electrophoretic display containing a dispersion medium for dispersing the electrophoretic particles, the charged electrophoretic particles are composite particles made of a coloring material and a polymer, and the charging polarity of the coloring material and the polymer is the same. The dispersion liquid for electrophoretic display is characterized by the above.

  A second invention is the dispersion liquid for electrophoretic display according to the first invention, wherein the coloring material is a plurality of inorganic pigments.

  A third invention is an electrophoretic display device comprising the electrophoretic display dispersion according to the third and fourth inventions.

  A fourth invention is a dispersion medium for dispersing charged electrophoretic particles and the charged electrophoretic particles used in an electrophoretic display device sandwiched between the pair of substrates, at least one of the substrates, and the substrate. A method for producing a dispersion for electrophoretic display, comprising the step of making the charged polarity of the coloring material and the high molecular weight polymer constituting the electrophoretic particles the same. is there.

  As described above, according to the present invention, the charged electrophoretic particles in which the charging materials of the coloring material and the high molecular weight polymer constituting the charged electrophoretic particles are selected to have the same charge are stabilized. It is possible to provide a dispersion for electrophoretic display and an electrophoretic display device capable of maintaining the above. Further, it is possible to provide a production method capable of easily selecting a constituent material when producing charged electrophoretic particles having a stable charge. Further, it is possible to provide a method for easily producing a dispersion for electrophoretic display in which charging is stable.

  Hereinafter, the present invention will be described in detail.

  An embodiment of the present invention will be described with reference to FIGS. Note that these drawings are diagrams showing the configuration of the electrophoretic display device and the configuration of the charged electrophoretic particles according to the present invention, but an example is schematically shown for convenience.

  First, an electrophoretic display device will be described with reference to FIGS.

  The present invention can be applied to an electrophoretic display device (see FIG. 1) in which the charged electrophoretic particles 1 move horizontally, and also to an electrophoretic display device (see FIG. 3) in which the charged electrophoretic particles 1 move vertically. Here, in the horizontal movement type, as shown in FIG. 1, both the first electrode 4a and the second electrode 4b are arranged along one of the substrates 3a or 3b, and the charged electrophoretic particles 1 are disposed on the substrate 3a. , 3b, it is configured to move along. On the other hand, in the vertical movement type, as shown in FIG. 3, the first electrode 4a and the second electrode 4b are arranged on separate substrates so as to sandwich the dispersion medium 2, and the charged electrophoretic particles 1 are disposed on the substrate 3a. , 3b, it is configured to move in the vertical direction (normal direction). It is assumed that the charged electrophoretic particles illustrated in FIGS. 1 and 3 are positively charged.

  Hereinafter, the horizontal movement type electrophoretic display device of FIG. 1 will be described as an example.

  As shown in FIG. 1, the electrophoretic display device according to the present invention includes a dispersion liquid 10 containing a plurality of charged electrophoretic particles 1 and a dispersion medium 2 in which these charged electrophoretic particles 1 are dispersed, and a voltage is applied. An image is displayed based on applying and moving the charged electrophoretic particles 1.

  The electrophoretic display device of the present invention uses a dispersion liquid for electrophoretic display containing charged electrophoretic particles 1 and a dispersion medium 2 in which the charged electrophoretic particles 1 are dispersed.

  The charged electrophoretic particle according to the present invention is a composite particle in which the charged electrophoretic particle is composed of a coloring material and a polymer, and the charging polarity of each of the coloring material and the polymer is the same. .

  The charged electrophoretic particles of the present invention are composite particles composed of a coloring material and a high molecular polymer that essentially determine the color of the charged electrophoretic particles themselves, and the charged polarity of each of the colored material and the high molecular polymer is the same. In this case, charging is stabilized. If the charge polarities are not the same, even if a charge control agent or charge stabilizer is added to the dispersion, the charge of the particles becomes very unstable, and the charge polarities are mixed or the charge changes over time. cause.

  In the present invention, the charged polarity can be confirmed by dispersing the coloring material constituting the charged electrophoretic particles alone in the dispersion liquid for electrophoretic display used when performing electrophoretic display, or by independently using the polymer. The dispersion material is dispersed, and the dispersion liquid is electrophoresed to confirm the charged polarity of the coloring material and the polymer. The polarity measurement method is not limited as long as it can confirm the charging polarity of each of the coloring material and the high molecular polymer. For example, ζ potential measurement or confirmation by electrophoresis in an actual electrophoretic display device Is mentioned.

  The coloring material constituting the charged electrophoretic particles of the present invention is not particularly limited as long as it is the same as the charge polarity of the high molecular polymer constituting the charged electrophoretic particles. For example, an inorganic pigment and / or an organic pigment can be used as the coloring material.

  The type of inorganic pigment is determined according to the display method of the electrophoretic display device to be used. Specifically, lead white, zinc white, lithopone, titanium dioxide, zinc sulfide, antimony oxide, calcium carbonate, kaolin, mica , Barium sulfate, gloss white, alumina white, talc, silica, calcium silicate, cadmium yellow, cadmium lipoton yellow, yellow iron oxide, titanium yellow, titanium barium yellow, cadmium orange, cadmium lipoton orange, molybdate orange, bengara , Lead red, silver vermilion, cadmium red, cadmium lipoton red, amber, brown iron oxide, zinc iron chrome brown, chrome green, chromium oxide, viridian, cobalt green, cobalt chrome green, titanium cobalt green, bituminous, cobalt blueー, ultramarine blue, cerulean blue, cobalt aluminum chrome blue, cobalt violet, mineral violet, carbon black, iron black, manganese ferrite black, cobalt ferrite black, copper chrome black, copper chrome manganese black, black low-order titanium oxide, aluminum powder, Examples include copper powder, lead powder, bell powder, and zinc powder. These inorganic pigments can be used alone or in combination of two or more as required. These inorganic pigments can be controlled in particle size and shape by known methods such as pulverization and granulation.

  The type of organic pigment is determined according to the display method of the electrophoretic display device to be used. Specifically, fast yellow, disazo yellow, condensed azo yellow, anthrapyrimidine yellow, isoindoline yellow, copper azomethine yellow, Quinophthaloin Yellow, Benzimidazolone Yellow, Nickel Dioxime Yellow, Monoazo Yellow Lake, Dinitroaniline Orange, Pyrazolone Orange, Perinone Orange, Naphthol Red, Toluidine Red, Permanent Carmine, Brilliant Fast Scarlet, Pyrazolone Red, Rhodamine 6G Lake, Permanent red, risor red, bon lake red, lake red, brilliant carmine, Bordeaux 10B, naphthol red, quinacridone magenta, shrunk Azo red, naphthol carmine, perylene car red, condensed azo scar red, benzimidazolone carmine, anthraquinonyl red, perylene red, perylene maroon, quinacridone maroon, quinacridone scarred, quinacridone red, diketopyrrolopyrrole red, benzimidazolone brown Phthalocyanine green, Victoria blue lake, phthalocyanine blue, fast sky blue, alkali blue toner, indanthrone blue, rhodamine B lake, methyl violet lake, dioxazine violet, naphthol violet and the like. These organic pigments can be used alone or in combination of two or more as required.

  Furthermore, as other coloring materials, commercially available colored fine particles can also be used, and specifically, Epocolor (registered trademark) (manufactured by Nippon Shokubai Co., Ltd., FP series) can be mentioned.

  The above-mentioned inorganic pigment and organic pigment, or commercially available colored fine particles can be subjected to particle size control by a known method such as pulverization / granulation, classification, etc. to constitute the charged electrophoretic particles of the present invention.

  The average particle diameter of the coloring material is preferably 0.005 μm to 0.5 μm, and more preferably 0.005 μm to 0.1 μm. When the thickness is less than 0.005 μm, handling is extremely lowered, and when it exceeds 0.5 μm, the particle size of the charged electrophoretic particles is too large. The particle shape of the inorganic pigment may be spherical or non-spherical.

  In order to control the color density, the electrophoretic particles of the present invention preferably contain a plurality of inorganic pigments and / or organic pigments. When an inorganic pigment and / or an organic pigment is contained alone, it is difficult to control the color density of the charged electrophoretic particles. A plurality represents two or more.

  The high molecular polymer constituting the charged electrophoretic particles is not particularly limited as long as the charged polarity of the coloring material constituting the charged electrophoretic particles is the same. In addition, materials that can be combined with coloring materials with good adhesion and are insoluble in the dispersion medium are preferably used. For example, polyester polymers, polystyrene polymers, poly (meth) acrylate polymers, styrene (meth) acrylates. High molecular polymers such as a copolymer, a polycarbonate polymer, a polyarylate polymer, a polyacrylonitrile, a polyurea polymer, a nylon polymer, a urethane polymer, and a melamine polymer are exemplified. Two or more kinds of these polymer polymers may be used. Among these, a polystyrene polymer, a poly (meth) acrylate polymer, or a styrene (meth) acrylate copolymer is preferable in terms of excellent dispersibility in a dispersion medium. Furthermore, the polymer can be used after being subjected to a crosslinking treatment for the purpose of insolubilization in the dispersion medium.

  Examples of the method for producing the charged electrophoretic particles of the present invention include a method in which the coloring material is dispersed in a high molecular weight monomer having the same charging polarity as that of the coloring material, and polymerization is performed. Known methods such as polymerization, dispersion polymerization, suspension polymerization and seed polymerization can be applied.

  As another method for producing the charged electrophoretic particles, the coloring material is dispersed in a solution in which a high molecular polymer having the same charging polarity as the coloring material is dissolved in a good solvent, and then the solvent is removed. There is a precipitation granulation method in which particles are produced by changing the solubility of a high molecular polymer by substituting a solvent with a poor solvent or by lowering the temperature. Alternatively, there can be mentioned a method in which the coloring material and the polymer are melt-kneaded and then the kneaded product is pulverized and granulated.

  The average particle diameter of the charged electrophoretic particles of the present invention is in the range of 0.1 μm to 7 μm, and preferably in the range of 0.1 μm to 3 μm. When it is less than 0.1 μm, handling is reduced, and when it exceeds 7 μm, the display resolution is reduced. In the electrophoretic particles 1 of the present invention, the average particle diameter can be controlled within the range of the present invention by a known method such as dry classification or wet classification, if necessary.

  The charged electrophoretic particles of the present invention can be dyed with a dye as necessary in order to adjust the degree of coloring, but it is preferable that the charging of the charged electrophoretic particles is not affected.

  In the present invention, the dispersion medium for dispersing the charged electrophoretic particles may contain a charge control agent. The charge control agent is not particularly limited as long as it is soluble in the dispersion medium. For example, cobalt naphthenate, zirconium naphthenate, copper naphthenate, iron naphthenate, lead naphthenate, manganese naphthenate, zinc naphthenate, etc. Metal soaps such as naphthenic acid metal soaps, cobalt octenoate, zirconium octenoate, iron octenoate, lead octenoate, nickel octenoate, manganese octenoate, zinc octenoate, etc., metal soaps such as stearic acid metal soap , Known ones such as polyaminopolybuterosuccinimide and lecithin. When the charge control agent is not contained, the charged electrophoretic particles may not be charged or the charge may become unstable, and as a result, electrophoresis may not occur or electrophoresis may become unstable. Among these charge control agents, metal soap is preferable. The content of the charge control agent is appropriately determined depending on the type, but is preferably in the range of 0.0001 to 5 parts by weight, more preferably 0.001 to 1 part by weight with respect to 100 parts by weight of the dispersion medium.

  The dispersion medium of the present invention can contain a rosin ester or a rosin derivative as a charge stabilizer. The rosin ester or rosin derivative is not particularly limited as long as it is soluble in a dispersion medium. For example, gum rosin, wood rosin, tall oil rosin, rosin modified maleic acid, rosin modified pentaerythritol, rosin glycerin ester, partially hydrogenated rosin methyl ester Partially hydrogenated rosin glycerin ester, partially hydrogenated rosin triethylene glycol ester, fully hydrogenated rosin pentaerythritol ester, maleic acid modified rosin ester, fumaric acid modified rosin ester, acrylic acid modified rosin ester, maleic acid modified rosin pentaerythritol ester , Fumaric acid modified rosin pentaerythritol ester, acrylic acid modified rosin glycerin ester, maleic acid modified rosin glycerin ester, fumaric acid modified logistic Glycerol esters, such as acrylic acid-modified rosin glycerin ester.

  Furthermore, in the dispersion medium of the present invention, a polymer resin soluble in the dispersion medium can be used as a dispersion stabilizer. Specific examples include polybutadiene, polyisoprene, polyisobutylene, polybutene, styrene butadiene copolymer, styrene isoprene copolymer, styrene maleic anhydride copolymer, norbornene resin, and polyethylene wax. Among them, a styrene butadiene copolymer is preferable. For example, commercially available materials include E-SBR, S-SBR (manufactured by JSR Corporation), NIPOL (registered trademark) 1502, NIPOL (registered trademark) 1712, NIPOL (registered trademark). NS112, NIPOL (registered trademark) NS116, NIPOL (registered trademark) 1006, NIPOL (registered trademark) 1009 (manufactured by Zeon Corporation), Tuffden (registered trademark), Tuffprene (registered trademark), Asaprene (registered trademark) ( Asahi Kasei Co., Ltd.) and Sumitomo SBR (Sumitomo Chemical Co., Ltd.) can be used.

  In the present invention, the above components contained in the dispersion medium can be used alone or in combination of two or more. In addition, in the dispersion medium of the present invention, an anionic surfactant, a cationic surfactant, an amphoteric surfactant, a nonionic surfactant, and a fluorosurfactant that are soluble in the dispersion medium as necessary. You may contain, These may be used individually or in mixture of 2 or more types.

  As the dispersion medium for dispersing the charged electrophoretic particles of the present invention, a highly insulating organic solvent having low conductivity is used. Specifically, aliphatic hydrocarbon solvents such as aromatic hydrocarbon solvents such as benzene, ethylbenzene, dodecylbenzene, toluene, xylene and naphthenic hydrocarbons, paraffinic hydrocarbon solvents such as hexane, cyclohexane and kerosene, and isoparaffinic hydrocarbon solvents. Examples include hydrogen solvents, halogenated hydrocarbon solvents such as chloroform, trichloroethylene, tetrachloroethylene, dichloromethane, trichlorotrifluoroethylene, and ethyl bromide, or silicon oil, high-purity petroleum, etc. Among them, aliphatic hydrocarbon solvents are preferably used. Specifically, Isopar (registered trademark) G, H, M, L, P, V (all manufactured by Exxon Chemical Co., Ltd.), Shellsol (registered trademark) (Showa Shell Japan), IP solvent 1016, 1620, 2028, 2835 Idemitsu Petrochemical), Nisseki ISOSOL 200, 300 and 400 (both manufactured by Nippon Petrochemicals) and the like. These can be used alone or in admixture of two or more.

  The dispersion medium used in the present invention can be colored in a different color from the particles in accordance with the display method of the electrophoretic display device used. The colorant is not particularly limited as long as it is an oil-soluble dye that can be dissolved in a dispersion medium.

  In the present invention, two or more types of charged electrophoretic particles having different particle diameters, particle components, coloring, etc. may be used in accordance with the display method of the electrophoretic display device.

  The dispersion liquid for electrophoretic display of the present invention can be used by being included in a microcapsule 10 as shown in FIG. Examples of the microcapsule encapsulation method include ordinary methods such as an in-situ method, an interfacial polymerization method, and a coacervation method.

  Microcapsule wall materials include polyurethane, polyurea, polyurea-polyurethane, urea-formaldehyde resin, melamine-formaldehyde resin, polyamide, polyester, polysulfonamide, polycarbonate, polysulfinate, epoxy, polyacrylate, polymethacrylic acid Examples include esters, polyvinyl acetate, polyvinyl alcohol, and gelatin.

  The size of the microcapsule used in the electrophoretic display device of the present invention is in the range of 1 μm to 500 μm, and preferably in the range of 20 μm to 100 μm.

  The charged electrophoretic particles of the present invention can be used in an arbitrary weight ratio with respect to the dispersion, but preferably in the range of 0.1 to 20 parts by weight with respect to 100 parts by weight of the dispersion medium. .

  The present invention is a method for producing a dispersion for electrophoretic display in which the charge polarity of the coloring material constituting the electrophoretic particles and the high molecular polymer is the same, and the dispersion for electrophoretic display having a stable charge is easily produced. How to do it.

  Next, the electrophoretic display device will be described with reference to FIGS.

  For substrates 3a and 3b, polymer films such as polyethylene terephthalate (PET), polyethersulfone (PES), polyimide (PI), polyethylene naphthalate (PEN), polycarbonate (PC), etc., inorganic materials such as glass and quartz A stainless steel substrate having an insulating layer on the material or the surface can be used. Note that a material having a high visible light transmittance, such as a transparent polymer film or glass, may be used for the substrate 3a on the viewer side. Further, a polymer material having a rubber hardness in the range of 10 or more and 90 or less, specifically silicon resin, natural rubber, thermoplastic elastomer resin, or the like may be formed on the surface of the substrate 3a in contact with the dispersion.

  The electrodes 4a and 4b are not particularly limited as long as they are conductive materials that can be patterned, and examples thereof include indium tin oxide (ITO), aluminum, titanium, and copper.

  Furthermore, an insulating layer 6 may be formed on the surfaces of the electrodes 4a and 4b. When the insulating layer is formed, charge injection from the electrodes 4a and 4b to the charged electrophoretic particles 1 can be prevented. The material used for the insulating layer 6 is preferably a thin film that is difficult to form pinholes. Specific examples include a highly transparent polyimide resin, polyester resin, polyacrylate resin, polymethacrylate resin, polycarbonate resin, polyarylate resin, novolac resin, and epoxy resin.

  In addition, a polymer resin may be used for the partition wall 5, and in the case of the electrophoretic display device of FIG. 2, the partition wall 5 is formed on the electrode 4a. Examples of the material used for the partition include polyimide resin, polyester resin, polyacrylate resin, polymethacrylate resin, polycarbonate resin, polyarylate resin, novolac resin, and epoxy resin.

  As a method of forming the partition wall 5, a method of performing exposure and wet development after applying a photosensitive resin layer, a method of forming by a printing method, a method of bonding to a substrate after forming the partition wall, a light-transmitting substrate surface The method of forming by a mold can be mentioned. Specific examples of the material include a photosensitive epoxy resin (SU8 Nippon Magder Mid Co., Ltd.).

  Further, the region where either one of the first electrode 4a and the second electrode 4b is arranged has the same color as the charged electrophoretic particle 1, and the region where the other electrode is arranged has a different color. Can be colored. For example, in the case of the apparatus of FIG. 2, the first electrode 4a itself may be colored black, or a colored insulating layer may be arranged so as to overlap the electrode.

  In the case of the vertical movement type shown in FIG. 3, the dispersion medium 2 for dispersing the charged electrophoretic particles can be colored in a color different from that of the particles 1. These enable two-color display. However, the display device as a whole can perform color display by displaying different colors with a plurality of adjacent pixels.

  Hereinafter, the electrophoretic display device shown in FIG. 2 will be described.

  The average particle size of the particles of the present invention is determined from a particle size distribution measuring device (Model 9320-X100 manufactured by Microtrack). The charge polarity and charge amount in the present invention are determined from a ζ electrometer (Zeta PALS manufactured by Brookhaven). Further, the charged polarity of the coloring material and the high molecular polymer constituting the charged electrophoretic particles in the present invention can be confirmed by analyzing the coloring material and the high molecular polymer in the dispersion liquid for electrophoretic display used for electrophoretic display. Are dispersed independently and the ζ potential of the dispersion is used.

  The size of one pixel was 100 μm × 100 μm, and the number of pixels was 200 × 200. In FIG. 2, two pixels (pixels 8 and 9) are shown for convenience. The substrate 3b is made of non-alkali glass having a thickness of 1.1 mm, and aluminum is deposited on the surface thereof to a thickness of 100 nm to dispose the second electrode 4b. A polyurethane resin layer whitened by mixing fine titanium oxide particles was disposed as the white scattering layer 7 on the second electrode 4b. A partition wall 5 made of photosensitive epoxy resin SU8 (Nippon Magdermid) having a width of 5 μm and a height of 18 μm (the total height of the partition wall 5 and the first electrode 4a in FIG. 2) is arranged at the boundary of the pixel. Further, as shown in FIG. 2, a first electrode 4a in which Ti is deposited in a range of 5 μm in width and 5 μm in height at the bottom of the partition wall 5 is disposed. Then, the insulating transparent resin layer 6 made of polyacrylate resin (Optomer SS6699, manufactured by JSR Corporation) is formed on the partition wall 5 including the first electrode 4a and the second electrode. Thereafter, a heat-fusible adhesive layer is formed on the upper surface of the partition wall 5 (bonding surface with the substrate 3a).

  Next, 100 parts by weight of Isopar (registered trademark) H (manufactured by Exxon) as an aliphatic hydrocarbon solvent as a dispersion medium, and 2.5 parts by weight of Neotol (registered trademark) 125H (manufactured by Harima Chemical Co., Ltd.) as a rosin ester Then, 0.8 part by weight of Asaprene (registered trademark) 1205 (manufactured by Asahi Kasei Co., Ltd.) as a styrene-butadiene copolymer was mixed and stirred for 24 hours, and then subjected to pressure filtration using a 0.2 μm PTFE membrane filter. create.

  In this liquid A, a yellow pigment (Yellow No. 12, average particle size of 0.3 μm) and a high-molecular polymer powder polymethyl methacrylate (PMMA, average particle size of 5 μm) are dispersed alone. When the ζ potential of each liquid is measured, Yellow No12, which is a coloring material, is +25 mV, and PMMA, which is a polymer, is +30 mV. From the above, polymer particles composed of 15 parts by weight of yellow No. 12 as an organic pigment and 85 parts by weight of polymethyl methacrylate as a polymer are prepared and used as charged electrophoretic particles. The average particle size is 5 μm.

  A more detailed method for producing charged electrophoretic particles is as follows. Yellow No. 12 (1.5 g), AIBN (2,2′-azobisisobutyronitrile) as a polymerization initiator, 0.1 g, and methyl methacrylate monomer, 8.5 g, were charged into a beaker, mixed and stirred, To do. Meanwhile, 120 g of distilled water, 5 g of calcium phosphate, and 0.082 g of sodium dodecyl sulfate are mixed and stirred to obtain a suspension stabilizing solution. Next, the monomer droplets were suspended by treating the reaction solution and the suspension stabilizing solution with a homomixer at 10000 rpm for 15 minutes, and then placed in a 300 ml separable flask. The charged electrophoretic particles of the present invention are obtained by suspension polymerization at a stirring speed of 150 rpm and a reaction time of 7 hours, washing the particles after the completion of polymerization with hydrochloric acid (1/10 N), washing with water, dehydration, drying and classification. Get.

  3 parts by weight of the thus obtained charged electrophoretic particles and liquid A are mixed and stirred for 1 hour to prepare an electrophoretic display dispersion. The dispersion liquid is filled into the partition walls 5, and a polycarbonate film substrate 3a having a thickness of 100 μm is sealed by heating and bonding with an adhesive layer on the partition walls, thereby producing an electrophoretic display device of the present invention.

  In the display device thus manufactured, the first electrode 4a is a common electrode of 0V, and the voltage ± 15V is applied to the second electrode 4b with a rectangular wave having a frequency of 0.25 Hz.

  The charged electrophoretic particles are charged to a negative polarity immediately after voltage application and migrate quickly between the electrodes, and display with a high black-and-white contrast can be confirmed without adhering to the electrodes or inner walls other than the electrodes. Even if it was driven for 24 hours, no change in the charging polarity of the particles was observed.

  FIG. 2A shows the case where a voltage of +15 V is applied to the second electrode 4b. Since the positively charged electrophoretic particles gather on the side surfaces of the partition walls 5, the pixels 8 and 9 are observed from the substrate 3a side. Then, the scattering layer 7 is visually recognized and white display is performed. On the other hand, FIG. 2B shows a case where a voltage of −15 V is applied to the second electrode 4b. Since the charged electrophoretic particles spread on the second electrode 4b, when the pixels 8 and 9 are observed from the substrate 3a side, The charged electrophoretic particles are visually recognized and become black.

  In the same manner as in Example 1, FP1050 (manufactured by Nippon Shokubai Co., Ltd.), which is a blue colored material, ground to an average particle size of 0.3 μm by pulverizing into liquid A, and powder polymethylmethacrylate (high molecular polymer) ( PMMA and an average particle diameter of 5 μm) are dispersed individually. When the ζ potential of each dispersion is measured, FP1050 which is a coloring material is +32 mV, and PMMA which is a polymer is +30 mV. From the above, polymer particles composed of 15 parts by weight of FP1050, which is a coloring material, and 85 parts by weight of polymethyl methacrylate, which is a polymer, are produced in the same manner as in Example 1 and are used as charged electrophoretic particles. The average particle diameter of the charged electrophoretic particles is 4 μm.

  3 parts by weight of the thus obtained charged electrophoretic particles and liquid A are mixed and stirred for 1 hour to prepare an electrophoretic display dispersion. The dispersion liquid is filled into the partition walls 5, and a polycarbonate film substrate 3a having a thickness of 100 μm is sealed by heating and bonding with an adhesive layer on the partition walls, thereby producing an electrophoretic display device of the present invention.

  In the display device thus manufactured, the first electrode 4a is a common electrode of 0V, and the voltage ± 15V is applied to the second electrode 4b with a rectangular wave having a frequency of 0.25 Hz.

  The charged electrophoretic particles are charged to a negative polarity immediately after voltage application and migrate quickly between the electrodes, and display with a high black-and-white contrast can be confirmed without adhering to the electrodes or inner walls other than the electrodes. Even if it was driven for 24 hours, no change in the charging polarity of the particles was observed.

Comparative Example 1
In the same manner as in Example 1, FP1050 (manufactured by Nippon Shokubai Co., Ltd.), which is a blue coloring material, ground to an average particle size of 0.3 μm by pulverizing into liquid A and powder polystyrene (PS, Each having an average particle diameter of 5 μm) is dispersed alone. When the ζ potential of each dispersion liquid is measured, FP1050 which is a coloring material has a ζ potential of +32 mV, and PS which is a polymer is -15 mV. Next, polymer particles composed of 15 parts by weight of FP1050, which is a coloring material, and 85 parts by weight of polystyrene, which is a polymer, are produced in the same manner as in Example 1 to obtain charged electrophoretic particles. The average particle diameter of the charged electrophoretic particles is 4 μm.

  3 parts by weight of the thus obtained charged electrophoretic particles and liquid A are mixed and stirred for 1 hour to prepare an electrophoretic display dispersion. The dispersion liquid is filled into the partition walls 5, and a polycarbonate film substrate 3a having a thickness of 100 μm is sealed by heating and bonding with an adhesive layer on the partition walls, thereby producing an electrophoretic display device of the present invention.

  In the display device thus manufactured, the first electrode 4a is a common electrode of 0V, and the voltage ± 15V is applied to the second electrode 4b with a rectangular wave having a frequency of 0.25 Hz.

  Immediately after the voltage is applied, the charged polarity of the charged electrophoretic particles is not stable and the bipolar particles migrate between the electrodes, so that the black-and-white contrast of the display is low.

It is the schematic which shows an example of the structure of the electrophoretic display device which concerns on this invention. It is the schematic which shows the other example of the structure of the electrophoretic display apparatus which concerns on this invention. It is the schematic which shows the other example of the structure of the electrophoretic display apparatus which concerns on this invention. It is process drawing which shows the manufacturing method of the electrophoretic display device which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Charged electrophoretic particle 2 Dispersion medium 3a, 3b Substrate 4a 1st electrode 4b 2nd electrode 5 Partition 6 Insulating layer 7 White scattering layer 8 Pixel 9 Pixel 10 Microcapsule

Claims (4)

  Electrophoresis containing a pair of substrates, electrodes formed on at least one of the substrates, and charged electrophoretic particles used in an electrophoretic display device sandwiched between the substrates and a dispersion medium for dispersing the charged electrophoretic particles In the display dispersion, the electrophoretic display, wherein the electrophoretic particles are composite particles composed of a coloring material and a polymer, and the charging polarity of the coloring material and the polymer is the same Dispersion liquid.   The dispersion liquid for electrophoretic display according to claim 1, wherein the coloring material is a plurality of inorganic pigments or organic pigments.   An electrophoretic display device comprising the electrophoretic display dispersion according to claim 1.   Electrophoresis containing a pair of substrates, electrodes formed on at least one of the substrates, and charged electrophoretic particles used in an electrophoretic display device sandwiched between the substrates and a dispersion medium for dispersing the charged electrophoretic particles In the method for producing a display dispersion, a method for producing a dispersion for electrophoretic display, wherein the charged polarity of the coloring material and the high molecular polymer constituting the charged electrophoretic particles are the same.

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