JP2007279434A - Method for manufacturing charged migrating particle, dispersion for electrophoretic display, and electrophoretic display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing charged migrating particles with stabilized quality and excellent production reproducibility, and also to provide a dispersion for an electrophoretic display with stabilized quality, and an electrophoretic display device for displaying a stabilized image. <P>SOLUTION: In the method for manufacturing the charged migrating particles to be used for the electrophoretic display device which has: a pair of substrates; at least one electrode formed on at least one of the substrates; and the dispersion which is interposed between the substrates and which contains the charged migrating particles and a dispersion medium to disperse the charged migrating particles therein, a polymer is fixed to surfaces of the particles by making a functional group X on an end of the molecular chain of the previously polymerized polymer expressed general formula (1) or/and (2), chemically bond to a functional group Y on the surfaces of the particles. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

  As a basic structure of the electrophoretic display device, FIG. 1 shows an example in which the charged electrophoretic particles move horizontally, FIG. 3 shows an example in which the charged electrophoretic particles move vertically, and FIG. 4 shows an electrophoresis made up of charged electrophoretic particles and a dispersion medium. An example in which a microcapsule containing a display dispersion liquid is used will be described. 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 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)

  However, in the conventional charged electrophoretic particles, there may be a difference in electrophoretic characteristics even when the charged electrophoretic particles are produced under the same raw material and under the same production conditions. For example, there are cases where the charge amount varies, there is a difference in migration speed, or there is a difference in the degree of sticking to the electrode. That is, there is a problem that the quality of the charged electrophoretic particles is not stable and the production reproducibility cannot be obtained.

  The present invention has been made in view of such problems of the prior art, and an object of the present invention is to provide a method for producing charged electrophoretic particles having a stable quality. Provided is an electrophoretic display device capable of obtaining a dispersion liquid for electrophoretic display having a stable quality by using the charged electrophoretic particles produced by the production method and displaying a stable image by using the dispersion liquid for electrophoretic display. It is for the purpose.

  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 the method for producing a charged electrophoretic particle used in an electrophoretic display device having a dispersion containing a medium, a molecular chain of a polymer polymer represented by the general formula (1) or / and (2) polymerized in advance This is a method for producing charged electrophoretic particles, wherein the terminal functional group X and the functional group Y on the particle surface are chemically bonded to immobilize the polymer on the particle surface.

R ₁ and R _{3 represent a} hydrogen atom or —CH ₃ .

_{R 2: -C p H 2p +} 1 or _{-C q H 2q N (C r} H 2r + 1) 2 or - indicates a _{(CF 2) t -B - (} CH 2) s. p is an integer from 0 to 30; q is an integer from 1 to 30; and r is an integer from 0 to 30. B represents a hydrogen atom or a fluorine atom, and s and t are integers of 0 or more and 30 or less. However, the hydrogen atom of CH ₂ may be substituted with a fluorine atom or CF ₃ , while the fluorine atom of CF ₂ may be substituted with CF ₃ .

R ₄ represents a hydrogen atom or —C _x H _{2x + 1} , and x is an integer of 0 or more and 30 or less.

  A second invention of the present invention is the production method according to the first invention, wherein the particles are composite particles composed of a plurality of pigment particles or / and a dye and a polymer.

According to a third invention of the present invention, in the first and second inventions, the functional group X and the functional group Y are selected from —COOH group, —NH ₂ group, —OH group, and —NCO group. It is a manufacturing method.

  A fourth invention of the present invention is the production method according to the third invention, wherein the chemical bond is any one of an ester bond, an amide bond, and a urethane bond.

  A fifth invention of the present invention is the production method according to the first, second or third invention, wherein the molecular weight of the polymer is in the range of 1000 to 10,000.

  A sixth invention of the present invention is the production method according to the first or second invention, wherein the thickness of the polymer immobilized on the particle surface is in the range of 1 to 200 nm.

  An seventh aspect of the present invention is an electrophoretic display comprising: charged electrophoretic particles obtained by the production method according to the first to sixth aspects; a dispersion medium for dispersing the charged electrophoretic particles; and a charge stabilizer. Dispersion liquid.

  An eighth invention of the present invention is an electrophoretic display device comprising the dispersion liquid for electrophoretic display according to the seventh invention.

  As described above, according to the present invention, the functional group X at the molecular chain terminal of the polymer polymer represented by the general formula (1) or / and (2) polymerized in advance and the functional group on the particle surface The quality of the charged electrophoretic particles can be stabilized by applying a method for producing charged electrophoretic particles, in which Y is chemically bonded to fix the polymer on the particle surface. Also provided are a dispersion for electrophoretic display having a stable quality by using charged electrophoretic particles produced by the production method, and an electrophoretic display device capable of displaying a stable image by using the dispersion for electrophoretic display. be able to.

  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. FIG. 1 is a schematic diagram showing an example of the configuration of an electrophoretic display device according to the present invention, and FIG. 3 is a schematic diagram showing another example of the configuration of the 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. , 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 FIGS. 1 and 2 will be described as an example.

  As shown in FIG. 1, an electrophoretic display device according to the present invention includes a plurality of charged electrophoretic particles and a dispersion medium in which these charged electrophoretic particles are dispersed, and moves the charged electrophoretic particles by applying a voltage. The image is displayed on the basis of the display.

  In the method for producing charged electrophoretic particles of the present invention, it is essential that the polymer represented by the general formula (1) or / and (2) is polymerized in advance before the step of immobilizing on the particle surface. It is. When the step of polymerizing the polymer of the present invention and the step of immobilizing the polymer of the present invention on the particles are performed simultaneously in the same system, the general formula (1) or / and (2) of the present invention Variations occur in the composition, molecular weight, or amount immobilized on the particle surface of the high molecular polymer represented, and control becomes impossible. As a result, the composition and thickness of the coating layer of the polymer polymer immobilized on the particle surface varies among individual particles, and the quality of the particles is deteriorated and the production reproducibility is also deteriorated. Due to particle quality degradation and production reproducibility deterioration, it becomes difficult to control the charge amount, migration speed, or degree of sticking to the electrode, and stable reproducibility with good reproducibility cannot be obtained.

  The high molecular polymer fixed on the particle surface of the present invention is represented by the general formula (1) or / and the general formula (2). As long as the high molecular polymer is within the range represented by the general formula (1) and the general formula (2), even if the high molecular polymer is composed of two or more monomers, A molecular copolymer may be sufficient, or the high molecular copolymer of General formula (1) and General formula (2) may be sufficient. The polymer copolymer may be a random copolymer or a block copolymer.

  In the present invention, the following effects (1) and (2) can be obtained by immobilizing the polymer represented by the general formula (1) or / and the general formula (2) on the particle surface.

(1) Problems that the main component material constituting the particles present on the surface of the particles before immobilization of the polymer and the pigment or / and dye as the colorant affect the driving of the particles (for example, other than electrodes and electrodes) (2) Charging to particles, stabilization of charging, good dispersibility in dispersion medium, or suppression of sticking to inner walls other than electrodes or electrodes The effect (2) can be precisely controlled by selecting the structure of the general formulas (1) and (2). For example, when (R ₁ , R ₂ ) in the general formula (1) is changed to (—CH ₃ or —H, —CH ₃ ), the ζ potential of the particles is positively charged, and (−CH ₃ or —H, -C ₁₂ H ₂₅ ), the ζ potential of the particles shows a high positive charge, and the particles are dispersed away from each other and do not stick to the electrode or the inner wall other than the electrode. Alternatively, when (R ₁ , R ₂ ) in the general formula (1) is changed to (—CH ₃ , —C ₄ H ₉ ) or (—CH ₃ , —CH ₂₂ H ₄₅ ), the particles aggregate with each other. When (R ₁ , R ₂ ) in the general formula (1) is set to (—CH ₃ , —CH ₂ CH ₂ CF ₃ ), the ζ potential of the particles exhibits a high negative charge, and the particles aggregate together. . Further, when (R ₃ , R ₄ ) in the general formula (2) is changed to (CH ₃ or -H, CH ₃ ), the ζ potential of the particles shows a high positive charge.

Next, preferred structures of the polymer represented by the general formula (1) and / or the general formula (2) of the present invention will be given. In the polymer the polymer represented by general formula (1) of the present invention, R _1, the R ₂ combinations (R _1, R ₂₎ is preferably selected from the following group.

Group: (- CH ₃ or _{-H, -CH 3), (-} CH 3 or _{-H, -C 4 H 9),} (- CH 3 or _{-H, C 8 H 17) (} - CH 3 or -H _{, CH 10 H 21), (} - CH 3 or _{-H, -C 12 H 25),} (- CH 3 or _{-H, CH 18 H 37),} (- CH 3 or -H, CH ₂₂ H _25), (-CH ₃ or _{-H, -C 2 H 4 NH 2} ), (- CH 3 or _{-H, -C 2 H 4 N (} CH 3) 2), (- CH 3 or -H, -CH ₂ - CF _3), (- CH ₃ or _{-H, -CH 2 CH 2 - (} CF 2) 6 -F).

Is represented by the general formula (1), and in the high molecular copolymer consisting of two or more monomers, a combination of _{R 1, R 2 (R 1} , R 2) is, (- CH ₃ or -H, - CH ₃ ) and (—CH ₃ or —H 2, —C ₁₂ H ₂₅ ) polymer copolymer, (—CH ₃ or —H ₂ , —C ₂ H ₄ N (CH ₃ ) ₂ ) and (—CH _{2 3} or -H, polymeric copolymer is _{-C 12 H 25), (-} CH 3 or -H, -CH ₃₎ as well as (-CH ₃ or -H, polymeric co is CH ₁₈ H ₃₇₎ It is preferably a polymer or a high molecular copolymer which is (—CH ₃ or —H, —C ₂ H ₄ N (CH ₃ ) ₂ ) and (—CH ₃ or —H, CH ₁₈ H ₃₇ ). .

In the polymer represented by the general formula (2), in the combination of R ₃ and R _{4 in} the general formula (2) (R ₃ , R ₄ ), (—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 ) is preferred.

  The functional group X at the molecular chain end of the polymer of the present invention is chemically bonded to the functional group Y present on the particle surface. As a result, the polymer polymer immobilized on the particle surface can control the electrophoretic characteristics of the particles without dissolving in the dispersion medium even at a high temperature of 80 ° C. When the polymer is introduced without being chemically bonded to the particle surface, the polymer may be dissolved in the dispersion medium and the electrophoretic characteristics may change over time.

The functional group X and functional group Y of the present invention are not particularly limited as long as they can be chemically bonded, but may be selected from —COOH group, —NH ₂ group, —OH group, and —NCO group from the viewpoint of easy handling. preferable.

  The chemical bond generated by the reaction of the functional group X and the functional group Y of the present invention is preferably an ester bond, an amide bond or a urethane bond from the viewpoint of a strong bond.

  In the present invention, the functional group X at the molecular chain end of the polymer represented by the general formula (1) or / and (2) and the functional group Y on the particle surface are chemically bonded to form the polymer. Can be carried out by a known chemical reaction, and the reaction conditions can be appropriately selected depending on the combination of the functional group X and the functional group Y. For example, when the combination of the functional group X and the functional group Y is —COOH group and —OH group, the functional group X and the functional group Y can be fixed by an ester bond by dehydration reaction, and the combination of the functional group X and the functional group Y is —NCO group and — In the case of a COOH group, it can be immobilized with an amide bond.

  The weight average molecular weight of the polymer immobilized on the particle surface of the present invention is preferably from 1,000 to 200,000, more preferably from 1,000 to 10,000. When the weight average molecular weight is less than 1000, the amount of charge imparted to the particles is insufficient, and when the weight average molecular weight exceeds 200,000, the viscosity of the high molecular polymer increases, and the immobilization reaction on the particle surface is not allowed. It becomes uniform.

  The polymer of the present invention can be synthesized by a known polymerization method. The method for introducing the functional group X at the end of the molecular chain into the polymer can be carried out by a known method. For example, it is introduced by adding a polymerization terminator having the functional group X at the time of polymerizing the polymer. Can do.

As the polymer of the present invention, a commercially available polymer can be used. For example, Actflow UMB1001 in which an OH group is introduced at the end of the molecular chain [R ₁ , R _{2 of the} general formula (1)] ) = (− H, −C ₄ H ₉ )], UME1001 [(R ₁ , R ₂ ) in general formula (1) = (− H, −C ₂ H ₅ )], UMM1001 [in general formula (1) (R ₁ , R ₂ ) = (— H, —CH ₃ )] (both Soken Chemical Co., Ltd.), CBL3098 having a COOH group introduced at the end of the molecular chain [(R ₁ , R in general formula (1) _{2) = (- H, -C} 12 H 25)], CBB3098 [ general formula _{(1) (R 1, R} 2) = (- H, -C 4 H 9)] ( both manufactured by Soken Chemical & Engineering Co., ) Can be used.

As the particles that can be used in the present invention, particles made of an inorganic pigment can be used. The black pigment is not particularly limited as long as it does not dissolve in the dispersion medium. Specifically, carbon black, black low-order titanium oxide, titanium black, and titanium dioxide (TiO ₂ ) as the white pigment are preferable. Used. If necessary, inorganic pigment particles can be used alone or in combination of two or more.

  In addition, as the particles that can be used in the present invention, particles made of an organic pigment can be used. Although it will not specifically limit if it does not melt | dissolve in a dispersion medium, For example, fast yellow, phthalocyanine blue, etc. are mentioned. If necessary, organic pigment particles can be used alone or in combination of two or more.

  When the inorganic pigment and the organic pigment are used in the particles of the present invention, the functional group Y can be introduced on the pigment surface by a known method, for example, by a coupling agent. Alternatively, hydrophilic groups such as —OH groups and —COOH groups can be introduced by irradiating the pigment surface with UV.

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

  Furthermore, as the particles of the present invention, a plurality of pigment particles or / and composite particles composed of a dye and a polymer can be used. In particular, since the functional group Y of the present invention can be easily introduced into a polymer constituting the composite particle, the composite particle is preferably used in the present invention.

  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 High molecular polymers such as epoxy resins and polymethacrylic acid esters are exemplified.

  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, Varifast (registered trademark) Red, Varifast (registered trademark) Yellow, Oplas (registered trademark) Red, Oil Scarlet, Varifast (registered trademark) Black 3810, Orient Oil Black (manufactured by Orient Chemical Co., Ltd.), Oil Blue V, Oil Green, Bright, Green, Sudan IV, Sudan III (manufactured by Daiwa Kako), Sumiplast (registered trademark) Blue, Sumip ast (registered trademark) Red HFG, Sumiplast (registered trademark) Red HF4G, Sumiplast (registered trademark) Yellow, Whitefloor B, Sumikaron Brilliant Blue, Sumikaron Violet (registered trademark of Sumitomo Chemical Co., Ltd.), Macro Japan Corporation], Micros Blue, Micros Green [Ciba Geigy Japan], Kayacryl Black, Kaylon Polyester Blue, Kayalon Poly Red [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.

  In the present invention, as a method for introducing the functional group Y into the surface of a plurality of pigment particles or / and a composite particle composed of a dye and a polymer, the functional group Y is added to the monomer of the polymer constituting the composite particle. Examples thereof include a method of using a compound having a functional group Y, a method of introducing a functional group Y onto the surface of a composite particle with a coupling agent, a method of introducing a hydrophilic property by UV irradiation on the surface of the composite particle, and the like.

  As the charged particles used in the present invention, commercially available particles can be used within the scope of the present invention. For example, Micropearl (registered trademark) (manufactured by Sekisui Chemical Co., Ltd.), NATCO (registered trademark) spacer particles (manufactured by NATCO), Epocolor (registered trademark) particles (manufactured by Nippon Shokubai Chemical Industry Co., Ltd.), Chemisnow (registered trademark) (manufactured by Soken Chemical Co., Ltd.), Tospearl (registered trademark) (manufactured by GE Toshiba Silicone Co., Ltd.), Techpolymer (registered trademark) (Sekisui Plastics), etc. It is not something.

  Furthermore, the average particle size of the electrophoretic particles 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 thickness of the polymer immobilized on the particle surface of the present invention is preferably in the range of 3 nm to 200 nm, more preferably in the range of 3 nm to 50 nm. When the thickness of the polymer is less than 3 nm, the electrophoretic characteristics may not be controlled. If it exceeds 200 nm, the color of the particles may be light.

  In addition, the present invention is characterized by a dispersion for electrophoretic display, which contains charged electrophoretic particles obtained by the production method of the present invention and a dispersion medium for dispersing the charged electrophoretic particles.

  Furthermore, the present invention is characterized by an electrophoretic display device comprising the electrophoretic display dispersion.

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

  A charge stabilizer can be added to the dispersion medium of the present invention in order to stabilize the charge of the charged electrophoretic particles of the present invention. The charge stabilizer is not particularly limited as long as it is soluble in the dispersion medium, and examples thereof include rosin ester or rosin derivative. Specifically, gum rosin, wood rosin, tall oil rosin, rosin modified maleic acid, rosin modified pentaerythritol. Rosin glycerol 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 Phosphorus esters, fumaric acid-modified rosin glycerin esters, acrylic acid-modified rosin glycerin ester. Specific examples include Neotol (registered trademark) (Harima Kasei), Pencel (registered trademark), ester gum, and superester (all of which are Arakawa Chemical Industries). The charge stabilizer can be contained in the range of 0.01 to 5 parts by weight, preferably 0.05 to 3 parts by weight, based on 100 parts by weight of the dispersion medium.

  The dispersion medium of the present invention may contain a charge control agent in order to impart charge to the electrophoretic particles or assist the charge. 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 soaps such as metal soaps, cobalt octoate, zirconium octoate, iron octoate, lead octoate, nickel octoate, manganese octoate, zinc octoate octanoate metal soap, stearic acid metal soap, polyaminopolypropyl Well-known things, such as tersuccinimide and a lecithin, are mentioned.

  Furthermore, the dispersion medium 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, isoprene butadiene 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. 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 for dispersing the charged electrophoretic particles 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 (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 ( Light 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 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. 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 material used for the electrodes 4a and 4b is not particularly limited as long as it is a conductive material that can be patterned. 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 can be 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. 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, an embodiment will be described using the electrophoretic display device shown in FIG.

  The average particle diameter of the particles of the present invention and the thickness at which the uncoated particles are covered with the polymer are determined from the average of 20 samples using a transmission electron microscope.

As the particles used in the examples and comparative examples, the following three types are used.
(1) Particle A:
Polymerized particles obtained by suspension polymerization of 75 parts by weight of methyl methacrylate, 10 parts by weight of 2-hydroxypropyl methacrylate and 15 parts by weight of carbon black (CB, average particle size 0.02 μm). 5 μm. There are —OH groups on the surface of the particles.
(2) Particle B:
Particles obtained by dyeing polymer copolymer particles consisting of 50 parts by weight of styrene and 50 parts by weight of methacrylic acid in black with the dye Varifast (registered trademark) Black 3810, Orient Oil Black (manufactured by Orient Chemical Industry Co., Ltd.). The particle size is 1.5 μm. There are —COOH groups on the surface of the particles.
(3) Particle C:
Polymerized particles obtained by suspension polymerization of 65 parts by weight of styrene, 20 parts by weight of allyl methacrylate, and 15 parts by weight of carbon black (CB, average particle size 0.02 μm), and the average particle size is 2.5 μm. Further, the particle surface allyl group _{(CH2 = CH-CH 2 -} ) are present.

  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, the combination (R ₁ , R ₂ ) of R ₁ and R ₂ in the general formula (1) is represented by (—H ₂ , —C ₁₂ H ₂₅ ), and the functional group X at the molecular chain end is —COOH. A high molecular weight polymer (weight average molecular weight = 3000, product name Actflow CBL3098 (manufactured by Soken Chemical Co., Ltd.)) is chemically bonded to —OH, which is a surface functional group of the particle A, under a dehydration catalyst, and immobilized on the particle surface. Thus, charged electrophoretic particles D are obtained. Further, charged electrophoretic particles D are prepared five times under the same conditions.

  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 , Asaprene (registered trademark) 1205 (Asahi Kasei Co., Ltd.) 0.8 parts by weight 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. The electrophoretic display dispersion is prepared by mixing the charged electrophoretic particles D.

  Using the electrophoretic particles D prepared every 5 times, the electrophoretic display dispersion was prepared so that the particle concentration was 0.01% by weight, and a zeta potential measuring device (Zeta PALS manufactured by Brookhaven) was prepared. ) To measure the zeta potential.

  The coating thickness of the charged electrophoretic particles prepared 5 times in total is in the range of 27 to 30 nm, and the zeta potential is in the range of 52 to 56 mV.

  Next, the dispersion liquid for electrophoretic display having a particle concentration of 5% by weight is filled in the partition wall 5, and a polycarbonate film substrate 3a having a thickness of 100 μm is heated and bonded by an adhesive layer on the partition wall, and sealed. The electrophoretic display device of the present invention is manufactured.

  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.

  In any of the charged electrophoretic particles from the first to the fifth production, display with high black-and-white contrast without being charged to the positive polarity immediately after voltage application and migrating between the electrodes quickly and adhering to the electrode or the inner wall other than the electrode. Can be confirmed. FIG. 2A shows a 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. 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.

Combination of R _1, R ₂ in the general formula (1) (R _1, R ₂₎ is (-H, _-C 2 _{H 5)} is represented by, and high functional group X of the chain ends is -OH A molecular polymer (weight average molecular weight = 3000, product name Actflow UME1001 (manufactured by Soken Chemical Co., Ltd.)) is chemically bonded to -COOH, which is a surface functional group of particle B, under a dehydration catalyst, and immobilized on the particle surface. Charged electrophoretic particles E are obtained. Further, charged electrophoretic particles E are produced 5 times under the same conditions.

  Using the charged electrophoretic particles E prepared every 5 times, the electrophoretic display dispersion is prepared so that the particle concentration becomes 0.01% by weight, and the zeta potential is measured with a zeta potential measuring device. .

  The coating thickness of the charged electrophoretic particles prepared 5 times in total is in the range of 28 to 31 nm, and the zeta potential is in the range of 20 to 23 mV.

  Next, in the same manner as in Example 1, a dispersion liquid for electrophoretic display with a charged electrophoretic particle concentration of 5 wt% is prepared, and an electrophoretic display device is manufactured.

  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.

  In any of the charged electrophoretic particles from the first to the fifth production, display with high black-and-white contrast without being charged to the positive polarity immediately after voltage application and migrating between the electrodes quickly and adhering to the electrode or the inner wall other than the electrode. Can be confirmed.

(Comparative Example 1)
In the same manner as in Example 1, an electrophoretic display dispersion containing particles A is prepared. Next, an electrophoretic display device is manufactured by the same method as in Example 1. When a voltage is applied to the manufactured display device under the same conditions as in Example 1, the charged electrophoretic particles migrate slowly between the electrodes, and after 3 hours of migration, adhere to the electrodes and do not migrate.

(Comparative Example 2)
The combination of R ₁ and R ₂ in the general formula (1) (R ₁ , R ₂ ) is the same as the polymer polymer monomer (lauryl acrylate) represented by (—H, —C ₁₂ H ₂₅ ) and the particle C By carrying out polymerization in the system, charged electrophoretic particles F in which lauryl acrylate is graft-polymerized from an allyl group (CH ₂ ═CH—CH ₂ —) present on the surface of the particle C are obtained. The surface of the charged electrophoretic particles F is coated with the polymer. Further, charged electrophoretic particles F are prepared 5 times under the same conditions.

  The electrophoretic display dispersion is prepared using the charged electrophoretic particles F at each production time so that the particle concentration becomes 0.01% by weight, and the zeta potential is measured with a zeta potential measuring device.

  The coating thickness of the charged electrophoretic particles produced 5 times in total is in the range of 14 nm to 30 nm, the zeta potential is in the range of 20 to 43 mV, and the quality variation is large.

  Next, in the same manner as in Example 1, a dispersion liquid for electrophoretic display with a charged electrophoretic particle concentration of 5 wt% is prepared, and an electrophoretic display device is manufactured.

  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.

  Except for the 2nd and 4th charged electrophoretic particles, the particles are charged positively immediately after voltage application and migrate quickly between the electrodes, and do not adhere to the walls of the electrodes or the inner wall other than the electrodes. A high contrast display can be confirmed. However, in the second and fourth preparation particles, there were particles sticking to the electrode or the inner wall other than the electrode, and the dispersion of the particle migration characteristics was large. Thus, in Comparative Example 2, the production reproducibility of the particles is low, and the quality variation is large.

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 (8)

Electrophoresis having 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 electrophoretic particles sandwiched between the substrates In the method for producing the charged electrophoretic particles used in the display device, the functional group X at the molecular chain end of the polymer polymer represented by the general formula (1) or / and (2) polymerized in advance, A method for producing charged electrophoretic particles, wherein the functional group Y is chemically bonded to immobilize the polymer on the particle surface.

R ₁ and R _{3 represent a} hydrogen atom or —CH ₃ .
_{R 2: -C p H 2p +} 1 or _{-C q H 2q N (C r} H 2r + 1) 2 or - indicates a _{(CF 2) t -B - (} CH 2) s. p is an integer from 0 to 30; q is an integer from 1 to 30; and r is an integer from 0 to 30. B represents a hydrogen atom or a fluorine atom, and s and t are integers of 0 or more and 30 or less. However, the hydrogen atom of CH ₂ may be substituted with a fluorine atom or CF ₃ , while the fluorine atom of CF ₂ may be substituted with CF ₃ .
R ₄ represents a hydrogen atom or —C _x H _{2x + 1} , and x is an integer of 0 or more and 30 or less.   2. The production method according to claim 1, wherein the charged particles are a plurality of pigment particles or / and composite particles composed of a dye and a polymer. The production method according to claim 1, wherein the functional group X and the functional group Y are selected from a —COOH group, a —NH ₂ group, a —OH group, and a —NCO group.   The method according to claim 3, wherein the chemical bond is any one of an ester bond, an amide bond, and a urethane bond.   4. The production method according to claim 1, wherein a molecular weight of the high molecular polymer having a functional group X at a terminal is in a range of 1000 or more and 10,000 or less.   The manufacturing method according to claim 1 or 2, wherein the thickness of the polymer immobilized on the particle surface is in the range of 3 nm to 200 nm.   A dispersion for electrophoretic display, comprising: charged electrophoretic particles obtained by the production method according to claim 1; and a dispersion medium for dispersing the charged electrophoretic particles.   An electrophoretic display device comprising the electrophoretic display dispersion according to claim 7.

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