JP2005352423A - Electrophoretic particles, electrophoretic display dispersion, and electrophoretic display device - Google Patents

Abstract

（式中、Ｒ₁ は水素原子またはメチル基を示す。Ｒ₂ は−（ＣＨ₂ ）_x −（ＣＦ₂ ）_y −Ｂを示す。Ｂは水素原子またはフッ素原子を示す。ｘ、ｙは０〜３０の整数を示す。但し、ＣＨ₂ の水素原子はフッ素原子またはＣＦ₃で置換されてもよく、ＣＦ₂ のフッ素原子はＣＦ₃ で置換されていてもよい。）
【選択図】 図１PROBLEM TO BE SOLVED: To provide charged electrophoretic particles that migrate between electrodes without adhering to a partition wall and perform stable migration even at a high temperature, and an electrophoretic display device using the same.
A charged electrophoretic particle obtained by coating the surface of a particle with a polymer composed of a structural unit represented by the following general formula (1), and an electrophoretic display device using the same.
[Chemical 1]

(In the formula, R ₁ represents a hydrogen atom or a methyl group. R ₂ represents — (CH ₂ ) _x — (CF ₂ ) _y —B. B represents a hydrogen atom or a fluorine atom. _X and y are 0. Represents an integer of ˜30, provided that the hydrogen atom of CH ₂ may be substituted with a fluorine atom or CF ₃ , and the fluorine atom of CF ₂ may be substituted with CF ₃ .
[Selection] Figure 1

Description

  The present invention relates to a charged electrophoretic particle, an electrophoretic display device in which display is performed as the charged electrophoretic particle moves 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.

  As a basic structure of an electrophoretic display device, there are an example in which charged electrophoretic particles move horizontally to a substrate, and an example in which charged electrophoretic particles move vertically between substrates. In these examples, the charged electrophoretic particles are encapsulated in a micro container divided by upper and lower substrates and a partition wall. In addition, there is an example using a microcapsule in which an electrophoretic display dispersion liquid composed of charged electrophoretic particles and a dispersion medium is encapsulated. 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 charged electrophoretic particles that migrate between electrodes without adhering to a partition wall, and perform stable migration even at high temperatures.
The present invention also provides an electrophoretic display device having a stable display quality using the above-mentioned charged electrophoretic particles and an electrophoretic display dispersion used therefor.

  That is, the first invention of the present invention is a charged electrophoretic particle characterized in that the surface of the particle is coated with a polymer composed of a structural unit represented by the following general formula (1).

(In the formula, R ₁ represents a hydrogen atom or a methyl group. R ₂ represents — (CH ₂ ) _x — (CF ₂ ) _y —B. B represents a hydrogen atom or a fluorine atom. _X and y are 0. Represents an integer of ˜30, provided that the hydrogen atom of CH ₂ may be substituted with a fluorine atom or CF ₃ , and the fluorine atom of CF ₂ may be substituted with CF ₃ .

  According to a second aspect of the present invention, the particle surface is coated with a copolymer composed of the structural unit represented by the general formula (1) and the structural unit represented by the following general formula (2). It is a characteristic electrophoretic particle.

(In the formula, R ₃ represents a hydrogen atom or a methyl group. R ₄ represents a hydrogen atom or an alkyl group having 1 to 25 carbon atoms.)

  According to a third aspect of the present invention, there is provided a dispersion for electrophoretic display, comprising the above-described charged electrophoretic particles and a dispersion medium for dispersing the charged electrophoretic particles.

  A fourth invention of the present invention comprises a pair of substrates, at least one electrode formed on at least one of the substrates, and the electrophoretic display dispersion liquid sandwiched between the substrates. An electrophoretic display device.

The present invention can provide charged electrophoretic particles that migrate between electrodes without adhering to the partition walls, and can stably migrate even at high temperatures.
In addition, the present invention can provide an electrophoretic display device having stable display quality using the above-described charged electrophoretic particles and a dispersion for electrophoretic display used therefor.

Hereinafter, the present invention will be described in detail.
An embodiment of the present invention will be described with reference to FIGS. 1 to 4 are schematic views showing an example of the configuration of the electrophoretic display device according to the present invention. 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.

  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 different 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). Note that the charged electrophoretic particles exemplified in FIGS. 1 and 3 are charged positively.

  On the other hand, the electrophoretic display device of FIG. 2 shows 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 (see FIG. )), 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

  Examples of the charged electrophoretic particles of the present invention include particles obtained by coating the surface of the particles with a polymer composed of a structural unit represented by the following general formula (1).

(In the formula, R ₁ represents a hydrogen atom or a methyl group. R ₂ represents — (CH ₂ ) _x — (CF ₂ ) _y —B. B represents a hydrogen atom or a fluorine atom. _X and y are 0. Represents an integer of ˜30, provided that the hydrogen atom of CH ₂ may be substituted with a fluorine atom or CF ₃ , and the fluorine atom of CF ₂ may be substituted with CF ₃ .

In the present invention, the polymer comprising the structural unit represented by the general formula (1) is not particularly limited within this range. Specifically, the combination of R ₁ and R ₂ is shown in Table 1 and Table 1 below. The structural unit represented by 2 is mentioned. Moreover, the polymer selected from the structural unit represented by General formula (1) can also be selected from two or more types of structural units represented by General formula (1).

In the present invention, the weight average molecular weight of the polymer composed of the structural unit represented by the general formula (1) is preferably 1,000 to 2,000,000, more preferably 2,000 to 500,000.
In the present invention, the charge amount of the charged electrophoretic particles is increased by coating the particle surface with a polymer composed of the structural unit represented by the general formula (1).

In addition, since the polymer has high solvent resistance to the dispersion medium, the charged electrophoretic particles whose particle surfaces are coated with the polymer do not chemically change even at high temperatures, and can stably migrate at high temperatures.
As will be described later, by adding a rosin ester or a rosin derivative to the dispersion medium in which the charged electrophoretic particles are dispersed, adhesion to a wall, change with time of driving, and the like can be reduced.

  The partition wall is an essential component for preventing particle movement between pixels in the horizontal movement type electrophoretic display device, and the electrode and the insulating layer provided on the partition wall are configured by covering the surface with the coating material of the present invention. Sticking to can be suppressed. Alternatively, even in an electrophoretic display element in which charged electrophoretic particles are enclosed in a micro container such as a microcapsule, sticking to the inner wall of the micro container can be prevented.

  The electrophoretic display device using the electrophoretic display device immediately after voltage application is provided with the function of improving and stabilizing the chargeability of the charged electrophoretic particles, good dispersibility in the dispersion medium, or suppressing adhesion to the wall of the micro container. Therefore, the particles migrate quickly and can maintain a stable image state. In addition, it has excellent durability at high temperatures.

  Further, the charged electrophoretic particles of the present invention are particles in which the surface of the particles is coated with a copolymer composed of the structural unit represented by the general formula (1) and the structural unit represented by the following general formula (2). Is mentioned.

(In the formula, R ₃ represents a hydrogen atom or a methyl group. R ₄ represents a hydrogen atom or an alkyl group having 1 to 25 carbon atoms.)
Specific examples of the structural unit represented by the general formula (2) of the present invention include structural units in which the combination of R ₃ and R ₄ is represented by the following Table 3.

  The content ratio of the structural unit represented by the general formula (1) and the structural unit represented by the general formula (2) is represented by the structural unit represented by the general formula (1) and the general formula (2). % By weight of the structural unit (meaning the weight percentage of the monomer of each structural unit) is 99% by weight: 1% by weight to 10% by weight: 90% by weight, preferably 97% by weight: 3% by weight to 30% by weight : 70% by weight is desirable.

In addition, examples of the form of the copolymer include a block copolymer and a random copolymer.
The copolymer has a weight average molecular weight of preferably 1,000 to 2,000,000, more preferably 2,000 to 500,000.

  In the present invention, the charged electrophoretic particles in the dispersion medium are further coated with the above-mentioned copolymer by coating the surface of the particles with the particles coated with the polymer consisting only of the structural unit represented by the general formula (1). The dispersibility of can be increased.

  The particles constituting the electrophoretic particles of the present invention and coated with the polymer or copolymer of the present invention include at least one selected from inorganic pigment particles, organic pigment particles, pigments and dyes, and polymers Colored polymer particles composed of a polymer can be used.

  Specific examples of inorganic pigment particles include lead white, zinc white, lithopone, titanium dioxide, zinc sulfide, antimony oxide, calcium carbonate, kaolin, mica, barium sulfate, gloss white, alumina white, talc, silica, and silicic acid. Calcium, cadmium yellow, cadmium lithopone yellow, yellow iron oxide, titanium yellow, titanium barium yellow, cadmium orange, cadmium lithopone orange, molybdate orange, bengara, red lead, silver vermilion, cadmium red, cadmium lithopone red, brown oxide Iron, zinc iron chrome brown, chrome 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. are mentioned. These inorganic pigment particles can be used alone or in combination of two or more as required.

  Specific examples of organic pigment particles include fast yellow, disazo yellow, condensed azo yellow, anthrapyrimidine yellow, isoindoline yellow, copper azomethine yellow, quinophthaloin yellow, benzimidazolone yellow, nickel dioxime yellow, and monoazo yellow. Lake, dinitroaniline orange, pyrazolone orange, perinone orange, naphthol red, toluidine red, permanent carmine, brilliant fast scarlet, pyrazolone red, rhodamine 6G rake, permanent red, risor red, bon lake red, lake red, brilliant carmine, bordeaux 10B, naphthol red, quinacridone magenta, condensed azo red, naphthol carmine, perylene scar red, Combined azoscar red, benzimidazolone carmine, anthraquinonyl red, perylene red, perylene maroon, quinacridone maroon, quinacridone scarred, quinacridone red, diketopyrrolopyrrole red, benzimidazolone brown, phthalocyanine green, victoria blue lake, phthalocyanine Blue, fast sky blue, alkali blue toner, indanthrone blue, rhodamine B lake, methyl violet lake, dioxazine violet, naphthol violet and the like. If necessary, these organic pigment particles can be used alone or in combination of two or more.

The aforementioned inorganic pigment particles and organic pigment particles can be formed into particles by a known method such as pulverization and granulation of the pigment.
As the colored polymer particles, particles composed of at least one selected from pigments and dyes and a high molecular weight polymer can be used.

  The polymer used for the colored polymer particles is not particularly limited as long as it is insoluble in the dispersion medium. For example, 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 polymers such as epoxy resins and polymethacrylates.

  Examples of the pigment used in the colored polymer particles include the above-described inorganic pigment particles and organic pigment particles. If necessary, these pigments can be used alone or in combination of two or more. In order to adjust the coloring degree of the colored polymer particles, the colored polymer particles may contain a plurality of pigments. The average particle diameter of the pigment particles used for the colored polymer 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 colored polymer particles is not particularly limited as long as the polymer can be dyed and does not elute in the dispersion medium. For example, azo dyes, anthraquinone dyes, azine dyes are used. And dyes, phthalocyanine dyes, and triphenylmethane dyes. Specifically, Valifast Red, Valifast Yellow, Oplas Red, Oil Scarlet, Variast Black 3810, Orient Oil Black (manufactured by Orient Chemical Industry Co., Ltd.), Oil Blue V, Oil Green, BridS, Daiwa Kako Co., Ltd., Sumiplast Blue, Sumiplast Red HFG, Sumiplast Red HF4G, Sumiplast Yellow, Whitefloor B, Sumikaron Brilliant Blue, Sumikaron Viol, Sumikaron Violet lue, Microris Green (manufactured by Ciba Geigy Japan), Kayacryl Black, Kayalon Polyester Blue, Kayalon Polyester Red (manufactured by Nippon Kayaku Co., Ltd.).

  As a method for producing colored polymer particles, a method of performing emulsion polymerization, dispersion polymerization, suspension polymerization, or seed polymerization by adding a pigment or a dye in the polymerization process of the polymer (including when the monomer is charged), a polymer, A method of dyeing the particles themselves with a dye, a method of melt-kneading and pulverizing a pigment with a polymer, adding a pigment or dye to a solution in which the polymer is dissolved in a solvent, then removing the solvent, and lowering the temperature of the solution, Or it can carry out by well-known methods, such as the method of performing reprecipitation using a poor solvent, and depositing and granulating a colored polymer particle. The polymer or dye constituting the colored polymer particles can also be used after being subjected to a crosslinking treatment or an immobilization treatment for the purpose of insolubilization in the dispersion medium. Furthermore, pigment particles and dyes can be mixed and used according to the degree of coloring of the colored polymer particles.

  As the 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 exemplified, but are not particularly limited.

  The charged electrophoretic particles of the present invention coat the above particles with the polymer or the copolymer, and the thickness of the polymer or copolymer covering the particle surface is 1 nm or more and 200 nm or less, and further 3 nm to 50 nm. The following is preferable. If the coating thickness is within this range, it is sufficient to conceal the influence of the surface of the underlying particles, and the color of the underlying particles is maintained. Depending on the structure of the polymer to be selected, the polarity of the charged electrophoretic particles increases, but if it is within this thickness range, it does not aggregate in the dispersion medium.

  In the present invention, the method of coating particles with a polymer composed of the structural unit represented by the general formula (1) or a copolymer composed of the structural unit represented by the general formulas (1) and (2) is as follows. A known coating method can be selected depending on the kind of particles before coating. Specifically, using a particle as a seed particle, seed polymerization of a polymer or copolymer monomer, a method of graft polymerizing a polymer or copolymer on the particle surface, via a coupling group by a coupling agent Examples thereof include a method of coating the particle surface with a polymer or copolymer, a method of coating the particle surface with a solution in which the polymer is dissolved in a solvent, and removing the solvent.

  The average particle size of the charged electrophoretic particles of the present invention is in the range of 0.1 μm to 7 μm, preferably 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. The charged electrophoretic particles of the present invention can be controlled to have an average particle size within the range of the present invention by a known method such as dry classification or wet classification, if necessary.

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 for electrophoretic display of the present invention contains the above-mentioned charged electrophoretic particles and a dispersion medium for dispersing the charged electrophoretic particles.

  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 include solvents, halogenated hydrocarbon solvents such as chloroform, trichloroethylene, tetrachloroethylene, dichloromethane, trichlorotrifluoroethylene, and ethyl bromide, 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 Isosol 200, 300, 400 (all Nippon Petrochemical). 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.

  The dispersion medium in the present invention preferably contains a rosin ester or a rosin derivative in order to stabilize the charging of the charged electrophoretic particles. 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 a rosin ester or a rosin derivative is contained in the dispersion medium, charging of the charged electrophoretic particles is stabilized, and changes such as reversal of the charging polarity and no particle electrophoresis can be eliminated. 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 in the present invention may contain a charge control agent in order to impart charge to the charged electrophoretic particles or to assist charging. The charge control agent is not particularly limited as long as it is soluble in the dispersion medium. 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, for example, OLOA 1200, OLOA 4375H, or OLOA 5274 (Olonite Japan Co., Ltd.), lecithin, etc. Among these, the electrophoretic particles of the present invention are included. Points to increase charging and particle dispersion Polybutene succinimide in that is preferred.

  Furthermore, the dispersion medium in 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.

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

The electrodes 4a and 4b are not particularly limited as long as they are conductive materials that can be patterned, and examples thereof include indium tin oxide (ITO), aluminum, titanium, and copper.
Furthermore, an insulating layer 6 may be formed on the surfaces of the electrodes 4a and 4b. When the insulating layer is formed, charge injection from the electrodes 4a and 4b to the charged electrophoretic particles 1 can be prevented. The material used for the insulating layer 6 is preferably a thin film that is difficult to form pinholes. Specific examples include a highly transparent polyimide resin, polyester resin, polyacrylate resin, polymethacrylate resin, polycarbonate resin, polyarylate resin, novolac resin, and epoxy resin.

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

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

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

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

Hereinafter, the electrophoretic display device shown in FIG. 2 will be described.
Moreover, the average particle diameter of the particles of the present invention and the thickness at which the uncoated particles are coated with the polymer are determined from the average of 20 samples using a transmission electron microscope.

The following two types are used as uncoated particles in the present invention.
(1) Particle A:
These are colored polymer 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:
Colored polymer particles obtained by dyeing polymer particles made of polystyrene (PS) in black with the dyes Varifast Black 3810 and Orient Oil Black (manufactured by Orient Chemical Co., Ltd.) as a colorant, and having an average particle size of 1.5 μm It is.

Example 1
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 is disposed as the white scattering layer 7 on the second electrode 4b. A partition wall 5 made of a 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, a polymer of a structural unit in which the combination (R ₁ , R ₂ ) of R ₁ and R ₂ in the general formula (1) is represented by (—CH ₃ , —CH ₂ —CF ₃ ) (weight average molecular weight = 100000) ) Is coated on the surface of the particle A with a thickness of 20 nm by a graft polymerization method using trifluoroethyl methacrylate as a monomer to obtain charged electrophoretic particles.

  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 as a styrene-butadiene copolymer Electrophoresis by mixing 0.8 parts by weight of 1205 (manufactured by Asahi Kasei Co., Ltd.) for 24 hours with mixing and stirring, followed by pressure filtration using a 0.2 μm PTFE membrane filter and 3 parts by weight of charged electrophoretic particles. A display dispersion is prepared.

  The thus-prepared dispersion liquid is filled in the partition wall 5, and a polycarbonate film substrate 3a having a thickness of 100 μm is sealed by heat bonding with an adhesive layer on the partition wall to manufacture the electrophoretic display device of the present invention. To do.

In the display device thus manufactured, the first electrode 4a is a common electrode of 0V, and the voltage ± 15V is applied to the second electrode 4b with a rectangular wave having a frequency of 0.25 Hz.
The charged electrophoretic particles are negatively charged immediately after voltage application, and migrate quickly between the electrodes, so that a display with high black and white contrast can be confirmed without adhering to the wall in the container. Further, the display response time for black display is 100 msec. FIG. 2A shows a case where a voltage of −15 V is applied to the second electrode 4b. Since the negatively charged electrophoretic particles gather on the side surfaces of the partition walls 5, the pixels 8 and 9 are observed from the substrate 3a side. Then, the scattering layer 7 is visually recognized and white display is performed. On the other hand, FIG. 2B shows a case where a voltage of +15 V is applied to the second electrode 4b. Since the charged electrophoretic particles spread on the second electrode 4b, when the pixels 8 and 9 are observed from the substrate 3a side, the charged particles are charged. The migrating particles are visually recognized and become black.

  In addition, when the electrophoretic display device of the present example, which was heat-treated at 100 ° C. for 5 hours, was similarly manufactured and its operation was confirmed, there was no change in electrophoretic characteristics and a display with high black and white contrast. Can be confirmed.

Example 2
A structural unit in which (R ₁ , R ₂ ) in the general formula (1) is represented by (—CH ₃ , —CH ₂ —CF ₃ ), and (R ₃ , R ₄ ) in the general formula (2) of the present invention. The surface of the particle B is prepared by using a copolymer in which the structural unit represented by (—CH ₃ , —C ₁₂ H ₂₅ ) is 90:10 by weight and using trifluoroethyl methacrylate and lauryl methacrylate as monomers. The electrophoretic particles are obtained by coating with a graft polymerization method at a thickness of 20 nm.

Next, an electrophoretic display dispersion is prepared from the charged electrophoretic particles by the same method as in Example 1, and an electrophoretic display device is manufactured by the same method as in Example 1.
In the display device thus manufactured, the first electrode 4a is a common electrode of 0V, and the voltage ± 15V is applied to the second electrode 4b with a rectangular wave having a frequency of 0.25 Hz.

  The charged electrophoretic particles are negatively charged immediately after voltage application, and migrate quickly between the electrodes, so that a display with high black and white contrast can be confirmed without adhering to the wall in the container. Further, the display response time for black display is 100 msec.

  In addition, when the electrophoretic display device of the present example, which was heat-treated at 100 ° C. for 5 hours, was similarly manufactured and its operation was confirmed, there was no change in electrophoretic characteristics and a display with high black and white contrast. I can confirm.

Example 3
In the polymer of the general formula (1) of the present invention, (R ₁ , R ₂ ) is a polymer composed of structural units represented by (—CH ₃ , —CH ₂ CH ₂ — (CF ₂ ) ₆ —F). The surface of is coated with a graft polymerization method at a thickness of 15 nm to obtain charged electrophoretic particles.

  Next, an electrophoretic display dispersion is prepared from the charged electrophoretic particles by the same method as in Example 1, an electrophoretic display device is manufactured by the same method as in Example 1, and a voltage is applied under the same conditions as in Example 1. To do.

  The charged electrophoretic particles are negatively charged immediately after voltage application, and migrate quickly between the electrodes, and display with high black and white contrast can be confirmed without adhering to the walls in the container. Further, the display response time when displaying black is 100 msec.

  In addition, when the electrophoretic display device of the present example, which was heat-treated at 100 ° C. for 5 hours, was similarly manufactured and its operation was confirmed, there was no change in electrophoretic characteristics and a display with high black and white contrast. Can be confirmed.

Example 4
A structural unit in which (R ₁ , R ₂ ) in general formula (1) is represented by (—CH ₃ , — (CF ₂ ) ₄ —H) and (R ₃ , R ₄ ) in general formula (2) are A structural unit represented by (—CH ₃ , —C ₁₈ H ₃₇ ) is a copolymer having a weight ratio of 60:40, and the surface of the particle A is coated with a graft polymerization method at a thickness of 15 nm to form charged electrophoretic particles. obtain.

  Next, an electrophoretic display dispersion is prepared from the charged electrophoretic particles by the same method as in Example 1, an electrophoretic display device is manufactured by the same method as in Example 1, and a voltage is applied under the same conditions as in Example 1. To do.

  The charged electrophoretic particles are negatively charged immediately after voltage application, and migrate quickly between the electrodes, and display with high black and white contrast can be confirmed without adhering to the walls in the container. Further, the display response time for black display is 100 msec.

  In addition, when the electrophoretic display device of the present example, which was heat-treated at 100 ° C. for 5 hours, was similarly manufactured and its operation was confirmed, there was no change in electrophoretic characteristics and a display with high black and white contrast. Can be confirmed.

Example 5
A structural unit in which (R ₁ , R ₂ ) in the general formula (1) is represented by (—CH ₃ , —CH ₂ —CF ₃ ) and (R ₃ , R ₄ ) in the general formula (2) are (— A structural unit represented by CH ₃ , —C ₁₂ H ₂₅ ) is a copolymer having a weight ratio of 90:10, and the surface of the particle B is coated with a graft polymerization method at a thickness of 20 nm to obtain charged electrophoretic particles.

  Next, 100 parts by weight of Isopar H (Exxon), which is an aliphatic hydrocarbon solvent, is used as a dispersion medium, 2.5 parts by weight of Superester A115 (Arakawa Chemical Industries, Ltd.) is used as a rosin ester, and OLOA 1200 (Olonite Japan ( Co., Ltd.) 1 part by weight was mixed and stirred for 24 hours, and then mixed with 3 μ parts by weight of the above-mentioned charged electrophoretic particles in a liquid filtered under pressure using a 0.2 μm PTFE membrane filter. Make a liquid.

An electrophoretic display device is produced in the same manner as in Example 1 by using the dispersion liquid for electrophoretic display in the same manner as in Example 1.
In the electrophoretic display device, the first electrode 4a is a common electrode of 0V, and a voltage ± 15V is applied to the second electrode 4b as a rectangular wave having a frequency of 0.25 Hz.

  The charged electrophoretic particles are negatively charged immediately after voltage application, and migrate quickly between the electrodes, so that a display with high black and white contrast can be confirmed without adhering to the wall in the container. Further, the display response time for black display is 60 msec.

  In addition, when the electrophoretic display device of the present example, which was heat-treated at 100 ° C. for 5 hours, was similarly manufactured and its operation was confirmed, there was no change in electrophoretic characteristics and a display with high black and white contrast. 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 have a small charge amount and migrate slowly between the electrodes, and after 3 hours of migration, the charged electrophoretic particles are stuck to the electrodes and do not migrate.

  Further, when the electrophoretic display device of this comparative example heat-treated at 100 ° C. for 5 hours was used to produce an electrophoretic display device in the same manner and check the operation, the particles aggregated from the beginning of the electrophoretic migration. Defects are observed.

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 (9)

Charged electrophoretic particles for use in an electrophoretic display element, wherein the surface is coated with a polymer composed of a structural unit represented by the following general formula (1).

(In the formula, R ₁ represents a hydrogen atom or a methyl group. R ₂ represents — (CH ₂ ) _x — (CF ₂ ) _y —B. B represents a hydrogen atom or a fluorine atom. _X and y are 0. Represents an integer of ˜30, provided that the hydrogen atom of CH ₂ may be substituted with a fluorine atom or CF ₃ , and the fluorine atom of CF ₂ may be substituted with CF ₃ . A charged electrophoretic particle used in an electrophoretic display element, the surface of which is coated with a copolymer comprising a structural unit represented by the following general formula (1) and a structural unit represented by the following general formula (2): Charged electrophoretic particles characterized in that

(In the formula, R ₁ represents a hydrogen atom or a methyl group. R ₂ represents — (CH ₂ ) _x — (CF ₂ ) _y —B. B represents a hydrogen atom or a fluorine atom. _X and y are 0. Represents an integer of ˜30, provided that the hydrogen atom of CH ₂ may be substituted with a fluorine atom or CF ₃ , and the fluorine atom of CF ₂ may be substituted with CF ₃ .

(In the formula, R ₃ represents a hydrogen atom or a methyl group. R ₄ represents a hydrogen atom or an alkyl group having 1 to 25 carbon atoms.)   3. The charged electrophoretic particle according to claim 1, wherein a thickness of the polymer or copolymer covering a particle surface is 1 nm or more and 200 nm or less.   The charged electrophoretic particle according to any one of claims 1 to 3, wherein the particle is an inorganic pigment particle or an organic pigment particle.   The charged electrophoretic particle according to any one of claims 1 to 3, wherein the particle comprises a colored polymer particle comprising at least one selected from a pigment and a dye and a polymer.   6. Electrophoresis in which the charged electrophoretic particles according to claim 1 and a dispersion medium containing rosin ester or a rosin derivative and dispersing the charged electrophoretic particles are held in a container surrounded by a wall surface. Display device.   The electrophoretic display device according to claim 6, wherein the dispersion medium contains a styrene-butadiene copolymer.   The electrophoretic display device according to claim 6 or 7, wherein the charged electrophoretic particles and the dispersion liquid are encapsulated in a microcapsule.   The electrophoretic display device according to claim 6, wherein an insulating layer is provided on the wall surface.

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