JP2006113438A - Electrophoresis display device, and charge floating particle and fluid dispersion for electrophoresis display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide charged electrophoresis particles which migrate fast between electrodes from right after voltage application without sticking on the wall in a very small container and fluid dispersion for electrophoresis display, and to provide an electrophoresis display device having stabler display quality. <P>SOLUTION: The electrophoresis display device having a couple of substrates, the electrodes, and the fluid dispersion containing charged electrophoresis particles and a dispersion medium dispersing the charged electrophoretic particles is characterized in that the charged electrophoresis particles have surfaces coated with a macromolecular copolymer expressed by formulas (1) and (2) and having a weight ratio of 3:97 to 40:60 of structure units and the dispersion medium contains rosin ester or rosin derivatives. In the formulas, R<SB>1</SB>is a hydrogen atom or methyl group, R<SB>2</SB>a hydrogen atom or -C<SB>x</SB>H<SB>2x+1</SB>(x: an integer of 0 to 30), R<SB>3</SB>a hydrogen atom or methyl group, and R<SB>4</SB>a hydrogen atom or -C<SB>y</SB>H<SB>2y+1</SB>(y: an integer of 1 to 20). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

  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 FIGS. 1 to 3, the charged electrophoretic particles are encapsulated in a micro container divided by upper and lower substrates and a partition wall. In FIG. 4, the charged electrophoretic particles are encapsulated in a micro container separated by micro capsules. In either case, 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 electrophoresis of the charged electrophoretic particles brings about high-contrast display performance and display stability. There are Patent Documents 3 to 5 as proposals of the charged electrophoretic particles used in these electrophoretic display devices.
JP-A-9-185087 (page 2) Japanese Patent No. 2551783 (first page) JP-A-4-166918 (first page) JP-A-5-173193 (2nd page) JP 2002-287178 A (second page)

  The present invention provides an electrophoretic particle that rapidly migrates between electrodes without adhering to a wall in a micro container, and as a result, an electrophoretic display device having a stable display quality and a dispersion for electrophoretic display used therefor Is intended to provide.

  That is, according to the first aspect of the present invention, a pair of substrates, at least one electrode formed on at least one of the substrates, a charged electrophoretic particle and a dispersion that disperses the charged electrophoretic particle sandwiched between the substrates. In an electrophoretic display device having a dispersion liquid containing a medium, a polymer copolymer having a weight ratio of structural units represented by general formula (1) and general formula (2) in the range of 3:97 to 40:60 An electrophoretic display device comprising charged electrophoretic particles whose surfaces are coated with coalesced particles, wherein the dispersion medium contains a rosin ester or a rosin derivative.

Ｒ₁：水素原子またはメチル基
Ｒ₂：水素原子または−Ｃ_ｘＨ_２ｘ＋１
（ｘは０〜３０の整数）
Ｒ₃：水素原子かメチル基
Ｒ₄：水素原子または−Ｃ_ｙＨ_２ｙ＋１
（ｙは１〜20の整数）

R ₁ : hydrogen atom or methyl group R ₂ : hydrogen atom or -C _x H _{2x + 1}
(X is an integer from 0 to 30)
R _3: a hydrogen atom or a methyl group R _4: a hydrogen atom or _-C y _{H 2y + 1}
(Y is an integer from 1 to 20)

  The second invention is the electrophoretic display device according to the first invention, characterized in that the thickness of the polymer copolymer covering the particle surface is 1 nm or more and 200 nm or less.

  A third invention is the electrophoretic display device according to the second invention, wherein the polymer copolymer has a thickness covering the particle surface of 3 nm or more and 50 nm or less.

  A fourth invention is the electrophoretic display device according to the first or second invention, wherein the dispersion medium contains a styrene-butadiene copolymer.

  The fifth invention is characterized in that the particles whose particle surfaces are coated with the polymer copolymer are a plurality of pigment particles or / and composite particles composed of a dye and a polymer. 4. The electrophoretic display device according to the invention.

  A sixth invention is a charged electrophoretic particle used in the electrophoretic display device according to the first, second, fourth or fifth invention.

  The seventh invention is an electrophoretic display dispersion used in the electrophoretic display device according to the first, second, fourth or fifth invention.

  As described above, according to the present invention, the surface of particles is made of a polymer copolymer in which the weight ratio of the structural units represented by the general formulas (1) and (2) is in the range of 3:97 to 40:60. And the electrophoretic particles coated with rosin ester or rosin derivative in the dispersion medium in which the charged electrophoretic particles are dispersed, thereby causing problems that the uncoated particle surface has on driving, for example, adhesion to a wall or poor charging For electrophoretic display in which particles are migrated quickly immediately after voltage application because of the addition of high charge to charged electrophoretic particles, stabilization of charge, and good dispersibility in dispersion media. A dispersion can be provided.

  As a result, the electrophoretic display device using the electrophoretic display dispersion can maintain a stable image state immediately after voltage application.

  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. 1 to 4 are schematic views showing an example of the configuration of an electrophoretic display device according to the present invention.

  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. Or what was comprised so that it might move along 3b was meant. 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.

  On the other hand, the electrophoretic display device of FIG. 2 has a configuration in which the first electrode 4 a is disposed inside the partition wall 5. By using the first electrode 4a as a common electrode and applying a voltage to the second electrode 4b corresponding to each pixel (for example, the pixel 8 and the pixel 9), the charged electrophoretic particles are collected on the side surface of the partition wall 5 (FIG. 2 (a )), Or arranged on the second electrode (FIG. 2B) for display.

  In the electrophoretic display device according to the present invention, as shown in FIGS. 1 to 3, a plurality of charged electrophoretic particles 1 and a dispersion medium 2 in which these charged electrophoretic particles 1 are dispersed are separated by upper and lower substrates and partition walls. 1 to 3 are shown in FIG. 1 to 3 for convenience, and an image is displayed based on applying the voltage to move the charged electrophoretic particles 1. It is configured to

  The electrophoretic display device of the present invention is a polymer copolymer in which the weight ratio of the structural units represented by the general formula (1) and the general formula (2) is in the range of 3:97 to 40:60. And the dispersion medium contains a rosin ester or a rosin derivative.

Ｒ₁：水素原子またはメチル基
Ｒ₂：水素原子または−Ｃ_ｘＨ_２ｘ＋１
（ｘは０〜３０の整数）
Ｒ₃：水素原子かメチル基
Ｒ₄：水素原子または−Ｃ_ｙＨ_２ｙ＋１
（ｙは１〜20の整数）

R ₁ : hydrogen atom or methyl group R ₂ : hydrogen atom or -C _x H _{2x + 1}
(X is an integer from 0 to 30)
R _3: a hydrogen atom or a methyl group R _4: a hydrogen atom or _-C y _{H 2y + 1}
(Y is an integer from 1 to 20)

In the present invention, the polymer copolymer comprising the structural units represented by the general formulas (1) and (2) is not particularly limited within the scope of the present invention. Specifically, the general formula of R _1, R ₂ of (1) combining in (R _1, R ₂₎ (-CH ₃ or H, H), (- CH ₃ or H, _-CH 3), ( -CH ₃ or _H, -C _{2 H 5),} or (-CH ₃ or H, -C ₃ H ₇₎ can be mentioned. In the combination of R ₃ and R _{4 in} the general formula (2) (R ₃ and R ₄ ), (—CH ₃ or H, CH ₃ ), (—CH ₃ or H, C ₈ H ₁₇ ), ( -CH ₃ or _{H, -C 10 H 21),} (- CH 3 or H, -C ₁₂ H _25),
Or (—CH ₃ or H, —C ₁₈ H ₃₇ ). Further, two or more different structural units may be combined within the general formulas (1) and (2).

  In the polymer copolymer of the present invention, the structural unit represented by the general formula (1) expresses a high charge amount, while the structural unit represented by the general formula (2) is applied to the electrode and the insulating layer. There is an effect of suppressing sticking.

  In the polymer copolymer of the present invention, the weight ratio of the structural units represented by the general formula (1) and the general formula (2) is in the range of 3:97 to 40:60, more preferably the weight ratio is 5. : It is the range of 95-30: 70. By charging the particle surface with a polymer copolymer in which the weight ratio of the structural units represented by the general formula (1) and the general formula (2) of the present invention is within the range of the present invention, Can be increased to increase the display response speed, and can be prevented from sticking to the electrodes and the insulating layer which are walls in the micro container. When the weight ratio of the structural unit of the general formula (1) is less than 3, the charge amount of the charged electrophoretic particles is insufficient, while when the weight ratio of the structural unit of the general formula (2) is less than 60. In addition, it becomes impossible to suppress sticking to the electrode and the insulating layer.

  In the present invention, the weight average molecular weight of the polymer copolymer composed of the structural units represented by the general formulas (1) and (2) is preferably 1000 to 100,000.

  The thickness of the polymer copolymer of the present invention covering the particle surface is preferably 1 nm to 200 nm, more preferably 3 nm to 50 nm. When the coating thickness is less than 1 nm, the surface of the uncoated particle as a base may be affected. When the coating thickness exceeds 200 nm, depending on the polymer copolymer to be selected, the polarity of the coated electrophoretic particles increases and aggregates in the dispersion medium, or the color of the electrophoretic particles themselves decreases. It is not preferable.

  In the present invention, a method for coating charged electrophoretic particles with a polymer copolymer comprising the structural units represented by the general formulas (1) and (2) is a known coating method depending on the surface of the particles before coating. Can be selected. Specifically, using uncoated particles as seed particles, a method of seed polymerizing the monomer of the polymer copolymer of the present invention, a method of graft polymerizing the polymer copolymer of the present invention on the particle surface, a coupling agent A method of coating the particle surface with the polymer copolymer of the present invention via a coupling group by the method, or a method of coating the particle surface with a solution obtained by dissolving the polymer copolymer of the present invention in a solvent and removing the solvent Etc.

  As particles constituting the charged electrophoretic particles 1 of the present invention before being coated with the polymer copolymer of the present invention (hereinafter abbreviated as uncoated particles), particles made of an inorganic pigment can 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 Ritopon Orange, Molybdate Orange, Bengala, Red Tan, Silver Zhu, Cadmium Red, Cadmium Ritopon Red, Brown Iron Oxide, Zinc Iron Chrome Brown , Chromium green, chromium oxide, viridian, cobalt green, cobalt chrome green, titanium cobalt green, bitumen, cobalt blue, ultramarine, 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, titanium black, aluminum powder, copper powder, lead powder, bell powder, zinc powder, etc. Is mentioned. These inorganic pigment particles can be used alone or in combination of two or more as required.

  Further, as the uncoated particles, particles made of an organic pigment can 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, resol red, bon lake red, lake red, brilliant carmine, Bordeaux 10B, naphthol red, quinacridone Magenta, condensed azo red, naphthol carmine, perylene scar red, condensed azo scar red, Nido imidazolone 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. If necessary, these organic pigment particles can be used alone or in combination of two or more.

  The aforementioned inorganic pigment and organic pigment can be formed into particles by a known method such as pulverization and granulation.

  In the present invention, the particles whose particle surfaces are coated with the polymer copolymer (uncoated particles) are preferably a plurality of pigment particles or / and composite particles composed of a dye and a polymer.

  The polymer used in the composite particles is not particularly limited as long as it is insoluble in the dispersion medium, but polyester, polymethacrylate, polyacrylate, polymethyl methacrylate, polymethyl acrylate, polyethyl methacrylate, polyethyl acrylate , Polyacrylonitrile, polystyrene, divinylbenzene resin, polyurea, nylon, urethane resin, melamine resin, tetrafluoroethylene resin, phenol resin, phenol novolac epoxy resin, cresol novolac epoxy resin, cycloaliphatic epoxy resin, glycidyl ester And high molecular polymers such as epoxy resins and polymethacrylic acid esters.

  Examples of the pigment particles used for the composite particles include the above-described inorganic pigment particles and organic pigment particles. If necessary, these pigment particles can be used alone or in combination of two or more. In order to adjust the coloring degree of the composite particles, the composite particles may contain a plurality of pigment particles. The size of the pigment particles used for the composite particles is preferably 0.005 μm or more and 1 μm or less in consideration of the average particle diameter of the charged electrophoretic particles.

  The dye used for the composite particles is not particularly limited as long as it can dye a polymer and does not elute in the dispersion medium. For example, azo dyes, anthraquinone dyes, azine dyes are used. Examples include dyes, phthalocyanine dyes, and triphenylmethane dyes. Specifically, Variast Red, Variast Yellow, Oplas Red, Oil Scarlet, Variast Black 3810, Orient Oil Black (manufactured by Orient Chemical Industry Co., Ltd.), Oil Blue V, Oil Green, Bright, Green, Sudan IV, Sudan III (manufactured by Daiwa Chemical Industry Co., Ltd.), Sumiplast Blue, Sumiplast Red HFG, Sumiplast Red HF4G Sumiplast Yellow, Whitefloor B, Sumikaron Brilliant Blue, Sumikaron Violet (manufactured by Sumitomo Chemical Co., Ltd.), Macrolex Red GS (manufactured by Bayer Japan Co., Ltd.), Micros Blue Gee, Micros Blue Co., Ltd. Examples include Kayalon Polyester Red (manufactured by Nippon Kayaku Co., Ltd.).

  As a method for preparing a plurality of pigment particles or / and composite particles composed of a dye and a polymer, emulsion polymerization is performed by adding pigment particles and dyes in the polymerization process of the polymer (including when the monomer is charged). A method of performing dispersion polymerization, suspension polymerization, or seed polymerization, a method of dyeing polymer particles themselves with a dye, a method of melt-kneading and pulverizing pigment particles with a polymer, and using a polymer as a solvent Add pigment particles or dye to the dissolved solution, and then remove the solvent, lower the temperature of the solution, or perform reprecipitation using a poor solvent to precipitate and granulate the composite particles. It can be carried out. Further, the polymer or dye constituting the composite particle can be used after being subjected to a crosslinking treatment or an immobilization treatment for the purpose of insolubilization with respect to the dispersion medium. Furthermore, pigment particles and dyes can be mixed and used according to the coloring degree of the composite particles.

  As uncoated particles used in the present invention, commercially available particles can be used within the scope of the present invention. For example, Micropearl (manufactured by Sekisui Chemical Co., Ltd.), Natoko Spacer Particles (manufactured by Natco Co., Ltd.), Epocolor Particles (manufactured by Nippon Shokubai Chemical Industry Co., Ltd.), Chemisnow (manufactured by Soken Chemical Co., Ltd.), Tospearl ( GE Toshiba Silicone Co., Ltd.), techpolymer (Sekisui Chemicals Co., Ltd.) and the like are mentioned, but not particularly limited.

  Furthermore, the average particle diameter of the electrophoretic particles 1 of the present invention can be 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 dispersion medium 2 of the present invention contains a rosin ester or a rosin derivative in order to stabilize the charging of the charged electrophoretic particles of the present invention. The rosin ester or rosin derivative used is not particularly limited as long as it is soluble in the 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 penta Erythritol ester, fumaric acid modified rosin pentaerythritol ester, acrylic acid modified rosin glycerin ester, maleic acid modified rosin glycerin ester, fumaric acid Sex rosin glycerin esters, acrylic acid-modified rosin glycerin ester. Specifically, for example, neotol (Harima Kasei), pencel, ester gum, superester (all of which are Arakawa Chemical Industries) can be mentioned. When the rosin ester or rosin derivative is not contained in the dispersion medium, the charged electrophoretic particles may not be stably charged, and the charge polarity may be reversed or the particles may not be electrophoresed. The rosin ester or rosin derivative can be contained in the range of 0.01 to 5 parts by weight, preferably 0.05 to 3 parts by weight, with respect to 100 parts by weight of the dispersion medium.

  The dispersion medium 2 of the present invention may contain a charge control agent in order to impart charge to the electrophoretic particles or to assist charging. The charge control agent is not particularly limited as long as it is soluble in the dispersion medium, but, for example, naphthenic acid type of cobalt naphthenate, zirconium naphthenate, copper naphthenate, iron naphthenate, lead naphthenate, manganese naphthenate, zinc naphthenate Metal soap, cobalt octoate, zirconium octoate, iron octoate, lead octoate, nickel octoate, manganese octoate, zinc octoate metal soap such as stearic acid metal soap, polyisobutylene cocoon Examples include polybutene succinimides such as acid imides (specifically, known examples such as OLOA 1200, OLOA 4375H, or OLOA 5274 (Olonite Japan)), and lecithin.

  Furthermore, the dispersion medium 2 of the present invention may contain a polymer resin that is soluble in the dispersion medium as a dispersion stabilizer for charged electrophoretic particles or an adhesion inhibitor to the wall. 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, and for example, commercially available materials include E-SBR, S-SBR (manufactured by JSR Corporation), NIPOL 1502, NIPOL 1712, NIPOL NS112, NIPOL NS116, NIPOL 1006, NIPOL 1009 ( Nippon Zeon Co., Ltd.), Tuffden, Tuffprene, Asaprene (Asahi Kasei Co., Ltd.), Sumitomo SBR (Sumitomo Chemical Co., Ltd.) can be used.

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

  As the dispersion medium 2 for dispersing the charged electrophoretic particles 1 of the present invention, a highly insulating organic solvent having low conductivity is used. Specifically, aromatic hydrocarbon solvents such as benzene, ethylbenzene, dodecylbenzene, toluene, xylene, naphthenic hydrocarbons, hexane, cyclohexane, kerosene, paraffinic hydrocarbon solvents and aliphatic hydrocarbons of isoparaffinic hydrocarbon solvents Examples of the solvent include halogenated hydrocarbon solvents such as chloroform, trichloroethylene, tetrachloroethylene, dichloromethane, trichlorotrifluoroethylene, and ethyl bromide, or silicon oil and high-purity petroleum. Among them, aliphatic hydrocarbon solvents are preferably used. Specifically, Isopar G, H, M, L, P, V (all manufactured by Exxon Chemical Co., Ltd.), Shellsol (Showa Shell Japan), IP Solvent 1016, 1620, 2028, 2835 (Idemitsu Petrochemical), Nisseki Eye Tetrazole 200, 300, 400 (all manufactured by Nippon Petrochemicals) and the like. These can be used alone or in admixture of two or more.

  The dispersion medium 2 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.

  Further, in the present invention, two or more types of charged electrophoretic particles 1 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 about 1 to 500 μm, preferably about 20 to 100 μm.

  The charged electrophoretic particles 1 of the present invention can be used in an arbitrary weight ratio with respect to the dispersion medium 2, but preferably in the range of 0.1 to 20 parts by weight with respect to 100 parts by weight of the dispersion medium. It is.

  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. For the substrate 3a on the viewer side, a material having a high visible light transmittance, such as a transparent polymer film or glass, may be used. 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.

  Further, 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 is formed on the electrode 4a. Examples of the material to be used 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 the 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 (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 diameter of the particles of the present invention and the thickness at which the uncoated particles were coated with the polymer copolymer were determined from the average of 20 samples using a transmission electron microscope.

The following two types were used as uncoated particles in the present invention.
(1) Particle A:
Polymerized particles consisting of 85 parts by weight of polymethyl methacrylate (PMMA) and 15 parts by weight of carbon black (CB, average particle size 0.02 μm), and the average particle size is 1.5 μm.
(2) Particle B:
Polymerized particles made of polystyrene (PS), and particles dyed in black by the dye Varifast Black 3810 and Orient Oil Black [manufactured by Orient Chemical Industry Co., Ltd.] as the colorant of the particles. 5 μm.

Example 1
The size of one pixel is 100 μm × 100 μm, and the number of pixels is 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 with a thickness of 100 nm to dispose the second electrode 4b. A polyurethane resin layer whitened by mixing fine titanium oxide particles is disposed as the white scattering layer 7 on the second electrode 4b. A partition wall 5 having a width of 5 μm and a height of 18 μm is disposed at the boundary of the pixel, and a first electrode 4a having a width of 5 μm and a height of 5 μm is disposed below the partition wall 5 as shown in FIG. Then, the insulating transparent resin layer 6 made of polyacrylate resin (manufactured by Optomer SS6699 JSR) is formed on the partition wall 5 including the first electrode 4a and the second electrode. Thereafter, a heat-fusible adhesive layer was formed on the upper surface of the partition wall 5 (bonding surface with the substrate 3a).

The combination of (R ₁ , R ₂ ) in the general formula (1) of the present invention is represented by (—CH ₃ , —H), and (R ₃ , R _{4 in} the general formula (2) of the present invention. ) Is a polymer copolymer in which the structural unit represented by (—CH ₃ , —C ₁₈ H ₃₇ ) has a weight ratio of 20:80, and the surface of the particle A is coated with a graft polymerization method at a thickness of 20 nm. The inventive electrophoretic particles were obtained.

  Next, 100 parts by weight of Isopar H (produced by Exxon), an aliphatic hydrocarbon solvent, as a dispersion medium, 2.5 parts by weight of Neotol 125H (produced by Harima Chemical Co., Ltd.) as a rosin ester, Asaprene 1205 as a styrene-butadiene copolymer Mixing and stirring 0.8 parts by weight (Asahi Kasei Co., Ltd.) for 24 hours, and then mixing 3 parts by weight of the charged electrophoretic particles of the present invention into a solution filtered under pressure using a 0.2 μm PTFE membrane filter. Thus, a dispersion for electrophoretic display of the present invention was prepared.

  The thus-prepared dispersion liquid is filled in the partition walls 5, and a polycarbonate film substrate 3a having a thickness of 100 μm is heat-bonded and sealed with an adhesive layer on the partition walls, and the electrophoretic display device of the present invention (FIG. 2) was produced.

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

  The charged electrophoretic particles of the present invention were positively charged immediately after voltage application, and migrated quickly between the electrodes, and a display with high black and white contrast could be confirmed without adhering to the wall in the container. The display response time when displaying black was 70 msec. 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 surface of the partition wall 5, the pixels 8 and 9 are observed from the substrate 3a side. 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, the pixels 8 and 9 are observed from the substrate 3a side. The charged electrophoretic particles are visually recognized and become black.

(Example 2)
A structural unit in which (R ₁ , R ₂ ) in the general formula (1) of the present invention is represented by (—CH ₃ , —H) and (R ₃ , R ₄ ) in the general formula (2) of the present invention are A polymer copolymer in which the weight ratio of the structural unit represented by (—CH ₃ , —C ₁₈ H ₃₇ ) is 5:95, and the surface of the particle A is coated with a graft polymerization method at a thickness of 30 nm. Charged electrophoretic particles. Next, an electrophoretic display device was produced under the same conditions as in Example 1 except that the styrene-butadiene copolymer was removed from the dispersion medium, and the display evaluation was performed. As a result, the charged electrophoretic particles in Example 2 were immediately after voltage application. From the first to the positive polarity, the electrodes quickly migrated, and a display with high black and white contrast could be confirmed without adhering to the wall in the container. The display response time when displaying black was 80 msec.

(Example 3)
A structural unit in which (R ₁ , R ₂ ) in the general formula (1) of the present invention is represented by (—CH ₃ , —H) and (R ₃ , R ₄ ) in the general formula (2) of the present invention are A polymer copolymer in which the weight ratio of structural units represented by (—CH ₃ , —C ₁₈ H ₃₇ ) is 35:65, and the surface of the particle A is coated with a graft polymerization method at a thickness of 20 nm. Charged electrophoretic particles. Other than that, an electrophoretic display device was produced under the same conditions as in Example 1, and display evaluation was performed. As a result, the charged electrophoretic particles in Example 3 were charged positively immediately after voltage application, and were quickly As a result, it was possible to confirm a display with high black and white contrast without adhering to the wall in the container. The display response time when displaying black was 70 msec.

Example 4
A structural unit in which (R ₁ , R ₂ ) in the general formula (1) of the present invention is represented by (—CH ₃ , —H) and (R ₃ , R ₄ ) in the general formula (2) of the present invention are A polymer copolymer in which the weight ratio of structural units represented by (—CH ₃ , —C ₁₂ H ₂₅ ) is 20:80, and the surface of particle B is coated with a graft polymerization method at a thickness of 20 nm. Charged electrophoretic particles. Other than that, an electrophoretic display device was produced under the same conditions as in Example 1, and display evaluation was performed. As a result, the charged electrophoretic particles in Example 3 were charged positively immediately after voltage application, and were quickly As a result, it was possible to confirm a display with high black and white contrast without adhering to the wall in the container. The display response time when displaying black was 80 msec.

(Example 5)
A structural unit in which (R ₁ , R ₂ ) in the general formula (1) of the present invention is represented by (—H, —CH ₃ ) and (R ₃ , R ₄ ) in the general formula (2) of the present invention are A polymer copolymer in which the weight ratio of structural units represented by (—CH ₃ , —C ₁₂ H ₂₅ ) is 20:80, and the surface of the particle B is coated with a graft polymerization method at a thickness of 100 nm. Charged electrophoretic particles. Other than that, an electrophoretic display device was produced under the same conditions as in Example 1, and display evaluation was performed. As a result, the charged electrophoretic particles in Example 3 were charged positively immediately after voltage application, and were quickly As a result, it was possible to confirm a display with high black and white contrast without adhering to the wall in the container. The display response time when displaying black was 70 msec.

(Comparative Example 1)
An electrophoretic display dispersion of the present invention was prepared from the particles B under the same conditions as in Example 1, and an electrophoretic display device of the present invention was manufactured in the same manner as in Example 1. When a voltage was applied to the produced display device under the same conditions as in Example 1, the charged electrophoretic particles of the present invention had bipolar particles and migrated irregularly between the electrodes. Furthermore, after 3 hours of migration, the sample stuck to the electrode and no longer migrated.

(Comparative Example 2)
On the surface of the particle A, a polymer weight having polystearyl methacrylate ((R ₁ , R ₂ ) of the structural unit represented by the general formula (2) of the present invention is (—CH ₃ , —C ₁₈ H ₃₇ )) The mixture) was introduced by graft polymerization to obtain charged electrophoretic particles. The formation thickness of the polymer polymer graft chain was 30 nm. Next, an electrophoretic display dispersion was prepared from the charged electrophoretic particles by the same method as in Example 1, and an electrophoretic display device was manufactured by the same method as in Example 1.

  When a voltage was applied to the display device thus manufactured under the same conditions as in Example 1, the charged electrophoretic particles of the present invention were charged and migrated positively immediately after the voltage application, and displayed with a high monochrome contrast. Although confirmed, the display response time when displaying black was 120 msec.

(Comparative Example 3)
A structural unit in which (R ₁ , R ₂ ) in the general formula (1) of the present invention is represented by (—CH ₃ , —H) and (R ₃ , R ₄ ) in the general formula (2) of the present invention are A polymer copolymer in which the weight ratio of structural units represented by (—CH ₃ , —C ₁₂ H ₂₅ ) is 50:50, and the surface of the particle A is coated with a graft polymerization method at a thickness of 20 nm. Charged electrophoretic particles.

  Next, an electrophoretic display dispersion was produced from the charged electrophoretic particles under the same conditions as in Example 1, and an electrophoretic display device was produced in the same manner as in Example 1.

  When a voltage was applied to the display device thus produced under the same conditions as in Example 1, the charged electrophoretic particles of the present invention adhered to the wall in the micro container immediately after the voltage application and did not peel off.

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 the schematic which shows the other example of the structure of the electrophoretic display apparatus 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 (7)

Electrophoresis comprising a pair of substrates, at least one electrode formed on at least one of the substrates, and a dispersion containing charged electrophoretic particles and a dispersion medium for dispersing the charged electrophoretic particles sandwiched between the substrates In a display device, charged electrophoresis in which the surface of particles is coated with a polymer copolymer in which the weight ratio of the structural units represented by the general formula (1) and the general formula (2) is in the range of 3:97 to 40:60. An electrophoretic display device comprising particles and containing a rosin ester or a rosin derivative in the dispersion medium.

R ₁ : hydrogen atom or methyl group R ₂ : hydrogen atom or -C _x H _{2x + 1}
(X is an integer from 0 to 30)
R _3: a hydrogen atom or a methyl group R _4: a hydrogen atom or _-C y _{H 2y + 1}
(Y is an integer from 1 to 20)   2. The electrophoretic display device according to claim 1, wherein the polymer copolymer has a thickness covering the particle surface of 1 nm to 200 nm.   The electrophoretic display device according to claim 2, wherein the polymer polymer or the polymer copolymer has a thickness covering the particle surface of 3 nm to 50 nm.   The electrophoretic display device according to claim 1, wherein the dispersion medium contains a styrene-butadiene copolymer.   The particle whose surface is coated with the polymer copolymer is a plurality of pigment particles or / and composite particles composed of a dye and a polymer. Electrophoretic display device.   Charged electrophoretic particles used in the electrophoretic display device according to claim 1, 2, 4 or 5.   An electrophoretic display dispersion used in the electrophoretic display device according to claim 1, 2, 4 or 5.

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