JP2006010937A - Particles containing metal fine particles, and electrophoretic particles, and electrophoretic liquid, and electrophoretic display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem of the difficulty of obtaining sufficient blackness by the use of conventional black particles, comprising an organic dye or an organic pigment mixed in a base material as a colorant due to the poor compatibility of the colorant with the base material. <P>SOLUTION: In relation to particles and a particle-containing composition used for imaging techniques, such as electrophotography, inkjet, a toner display, and especially in relation to migrating particles used for an electrophoretic display device and a migrating liquid using the migrating particles, particles with a plurality of metal fine particles, exhibiting black color in an assembled state disposed on the surface thereof are provided, in relation to recording/displaying of the black color important for such kinds of imaging technologies. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to particles and particle-containing compositions used in imaging techniques such as electrophotography, ink jet, and toner display, and more particularly to electrophoretic particles used in electrophoretic display devices and electrophoretic liquids using the electrophoretic particles. Furthermore, the present invention relates to black recording / display important for such imaging technology.

  In recent years, with the development of information devices such as PCs and mobile devices and the enhancement of the network environment, display devices for information devices are often used not only in offices but also in homes and outdoors. Also, especially in offices, a huge amount of information obtained via information equipment is output once on paper, and then discarded after a while, and the consumption of paper continues to increase. Yes. At the same time, stress caused by being forced to look at a light-emitting display screen such as a liquid crystal display or CRT for a long time has been pointed out.

  In the modern society, the spread of low power consumption display rewriting devices that prevent environmental destruction due to an increase in paper consumption, have low visibility even when viewed for a long time, and have good visibility and excellent portability. Research and development of new display devices such as electronic paper and paper-like displays are thriving. As the most typical display method, monochrome rewriting by electrophoresis is performed, and visibility such as paper by reflected light can be displayed. Patent Literature 1 and Patent Literature 2 propose an electrophoretic display device.

  3 and 4 show examples of the case where the charged electrophoretic particles move horizontally, FIG. 5 shows an example where the charged electrophoretic particles move vertically, and FIG. 6 shows the basic structure of the electrophoretic display device. An example of using a microcapsule encapsulating a dispersion liquid for electrophoretic display is shown. In FIG. 3-5, the charged electrophoretic particles are encapsulated in a micro container divided by upper and lower substrates and partition walls. 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 reflective display with a high viewing angle.

  In the electrophoretic display device, the display contrast is a combination of the color of the particle and the color of the background member (the insulating layer 8 in FIG. 3, the white scattering layer 9 in FIG. 4), or the particle color and the dispersion medium (the dispersion medium 4 in FIG. 5). ) Color combinations.

In particular, a combination of black particles and a white member is preferable in order to realize a display such as a printed matter on paper. For black particles, a method is used in which an organic dye or pigment is kneaded into a resin, or a black inorganic pigment such as carbon black or titanium black is used.
JP-A-9-185087 (page 2) Japanese Patent No. 2551783 (first page)

  In order to realize high contrast by the electrophoretic display device, it is required that the electrophoretic particles have strong blackness and have no color change with time. However, organic dyes and organic pigments have limited compatibility with the base material, and it has been difficult to add a large amount to the base material to further increase the blackness. In addition, when the prepared particles are combined with a dispersion medium to form an electrophoretic solution and a display device is prepared, the dye may ooze out from the particle base material, and a change in color may be observed.

  The first invention of the present invention provides particles containing a plurality of metal fine particles on the particle surface.

  The second invention provides particles containing metal fine particles immobilized on at least one kind of constituents of the particles by chemical bonds on the particle surface. It can be effectively fixed to the surface by chemical bonding.

  The third invention provides black particles containing metal fine particles having a diameter of 0.1 to 15 nm or less on the particle surface. This range of sizes is suitable for exhibiting a black color.

  A fourth aspect of the invention is an electrophoretic particle that contains metal fine particles having a diameter of 0.1 to 15 nm or less on the particle surface and exhibits a black color when the particles are aggregated. In electrophoretic display devices, black particles are often used.

  A fifth invention is an electrophoretic display liquid comprising such particles and a dispersion medium. The dispersion medium is an insulating liquid that holds the particles therein.

  A sixth invention is an electrophoretic display device using such particles.

  The present invention provides black particles based on another coloring principle, which is different from the conventional method of containing a colorant such as a dye or pigment. Because it is a particle in which metal fine particles are dispersed and arranged, it can enhance the blackness, and at the same time, it does not cause dissolution or decomposition even in an electrophoretic dispersion medium mainly composed of an organic solvent. Decrease can be improved.

  An embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 schematically shows an example of the particles of the present invention in cross section. In the figure, 1 is a metal fine particle, and 2 is a particle base material. The particles of the present invention are those in which metal fine particles are dispersed and arranged so that the metal fine particles cover almost the entire surface of the particles.

  Here, the coloring phenomenon of the metal fine particles will be described.

  Metals usually exhibit a metallic luster in the bulk, but when the size of the fine particles becomes nano-sized, it is well known that the state of coloring by absorbing electromagnetic waves of a specific wavelength (for example, “What are ultrafine particles? Something "by Kawamura Kiyoshi (Maruzen). This phenomenon has been used for coloring stained glass etc. for a long time, and it is characterized by a clear color with no turbidity due to absorption and transmission of natural light and high coloring efficiency, and it is also exposed to direct sunlight. It has excellent coloring characteristics that it hardly fades even when left for a long time.

  The color of the nano-sized fine metal particles is greatly affected mainly by the material, shape and size of the metal. Au is famous for a red Au colloid having an absorption peak in the vicinity of 530 nm, and Ag is famous for a yellow Ag colloid having an absorption peak in the vicinity of 420 nm. Moreover, even if the metal fine particles are made of the same Ag, J.P. J. et al. According to Mock et al. (J. Chem. Phys., Vol. 116, No. 15, 15 April 2002), the absorption peak gradually shifts to the longer wavelength side as the diameter increases even if it is spherical. It has been observed that the absorption peak changes even when the color changes depending on the size and the cross-sectional shape of the particle is different, such as a circle, pentagon, or triangle. It has been shown that color changes are possible.

  Furthermore, it is known that metal fine particles are “blackened” regardless of the material in the state of ultrafine particles of 10 nm or less, particularly about 1 nm (for example, “Introduction to Ultrafine Particle Technology” by Noboru Ichinose et al. (Ohm) )). Compared to black materials such as camphor black (carbon black) and lacquer, it is known that it has a large light absorption and excellent blackness (for example, Kazuyoshi Ito: Vacuum 16p.163 (1973) or Ito Kazuki: Metal 45.7, p.65 (1975)). P.P. According to Taneja et al. (Phys. Rev. B65, 245412 (2002)), Ag, Pt, Cu and the like are also blackened when the size of the fine particles is less than about 10 nm.

  As described above, the particles of the present invention are selected as metal fine particles 1 having an arbitrary size, shape, and metal type, and are arranged on the particle surface as shown in FIG. Any color can be presented vividly. In particular, when it is intended to exhibit a blackness, it can be realized by dispersing the metal fine particles 1 of about 15 nm or less in the base material 2. For this purpose, metal fine particles such as Ag, Cu, Pt, etc. are preferably used in addition to Au that is markedly “blackened”. Moreover, it is not necessary to be a single metal species, and a mixture other than two species may be used. In addition to this, metal fine particles exhibiting black with the above-mentioned size are preferably used.

  The present invention provides fine particles in which metal fine particles are encapsulated and dispersed, and provides new particles that can be colored clearly and efficiently, and in particular, new black particles that have strong blackness and excellent durability.

  In addition, the present invention has a feature that the selectivity can be expanded with respect to the type of solvent to be uniformly dispersed by using metal fine particles. Thereby, as will be described later, a step of bonding metal fine particles to the particle surface by a chemical method can be easily performed.

  Metal fine particles include chemical methods such as physical methods such as vapor deposition in gas, sputtering, and metal vapor synthesis, chemical liquid phase methods such as colloidal methods, alkoxide methods, and uniform precipitation methods, and pyrolysis methods of organometallic compounds. Various production methods such as a chemical vapor phase method are known.

  In general, the physical method generally evaporates to form nuclei and grows, and at the same time, an organic solvent is appropriately attached to obtain fine metal particles coated with a desired material. Further, in a liquid phase method, for example, a colloid method, a noble metal salt is reduced in alcohol under reducing conditions, and metal fine particles coated with a polymer are precipitated in a colloidal form. Unlike pigments and dyes that have restrictions on compounds that are preferably used as dispersants, such as carbon fine particles, it is possible to cover them with hydrophobic or hydrophilic surface adsorbents by appropriately selecting the production method. Uniform dispersion in both aqueous and aqueous solvents is possible.

  For example, in the case of obtaining a solution composition in which metal fine particles having a particle diameter of several nanometers are uniformly dispersed in a desired solvent, the metal fine particles of Au are converted into a non-aqueous organic solvent such as toluene using the above-described physical method. It is known that a monodispersed solution composition can be prepared, while it is also known that a monodispersed solution composition of the same Au metal fine particles in an aqueous solvent such as ethanol + water can be prepared.

  Among the preferred production methods described later, the metal fine particle solution composition to be used is preferably one of the above production methods.

  Next, the suitable manufacturing method of the particle | grains of this invention is demonstrated.

  The method for producing the particles of the present invention is not particularly limited as long as the particles schematically shown in cross section in FIG. 1 are formed, but a preferred production method using the conceptual diagram of FIG. 2 below. Will be explained.

  Among the above-described methods for producing fine metal particles, a solution composition (not shown) in which the fine metal particles 1 having the surface modifying molecules R2 bonded to the surface is dispersed in a solvent by an appropriately selected technique is prepared. On the other hand, a material in which the functional group R1 is arranged on the surface of the particle base material 2 is prepared.

  The metal fine particles 1 having the surface modifying molecule R2 and the particle base material 2 having a functional group on the surface are reacted in a solution in the presence of a catalyst to produce the bonded particles 13.

  When mixing the particle base material 2 with the solution composition in which the metal fine particles 1 are dispersed, it is preferable to combine those having good compatibility with the surface functional groups R1 of the base material particles.

  Or the method of preparing the solution composition which disperse | distributed the particle | grain base material 2 in another solvent previously, and mixing with the solution composition in which the metal microparticle 1 was disperse | distributed after that is also preferably used. In that case, it is preferable to combine the solution compositions before mixing that have good compatibility with each other.

  It is also preferable to add a catalyst for promoting the reaction between the surface modifying molecule R2 of the metal fine particle and the surface functional group R1 of the particle base material 2 as appropriate.

  Although details for producing the binding particles 13 of the present invention are not particularly limited, an imide compound is preferably used as a surface modification molecule of the metal fine particles 1. In particular, it is known that Au is easily surface-modified with an imide group or a thiol group, and thereby can be easily dispersed uniformly in a solution.

  One particle base material 2 is preferably prepared by polymerizing an acrylic acid monomer and having a carboxyl group disposed on the surface of the particle base material because it is easy to create.

  Two types of metal fine particles, surface-modified with an imide compound, dispersed in an aqueous solution and one obtained by polymerizing an acrylic acid monomer and dispersing a particle matrix having carboxyl groups on the surface in an aqueous solution are prepared. The solutions are mixed and a catalyst such as thionyl chloride is added and reacted as appropriate to obtain the bonded particles 13 and a solution composition in which the bonded particles 13 are dispersed.

  In addition to those mentioned above, the polymer used for the particle matrix is polyester, polymethacrylate, polyacrylate, polymethyl methacrylate, polymethyl acrylate, polyethyl methacrylate, polyethyl acrylate, polyacrylonitrile, polystyrene, divinyl. Benzene resin, polyurea, nylon, urethane resin, melamine resin, tetrafluoroethylene resin, phenol resin, phenol novolac epoxy resin, cresol novolac epoxy resin, cyclic aliphatic epoxy resin, glycidyl ester epoxy resin, polymethacrylate And the like.

  The size of the particles of the present invention can be appropriately adjusted according to the purpose.

  As an example, when used as electrophoretic particles, it is preferably used in an average particle size range of 0.1 μm to 7 μm. Preferably, it can be made into the range of 0.1 micrometer-3 micrometers or less. Particles in this range are preferred because they maintain the resolution required for the display device and maintain ease of handling in production. In order to use the particles of the present invention as electrophoretic particles, the average particle diameter may be controlled within the range of the present invention by a known method such as dry classification or wet classification, if necessary.

  The dispersion medium when the particles of the present invention are used as electrophoretic particles may contain a rosin ester or a rosin derivative in order to stabilize the charging of the charged electrophoretic particles. The rosin ester or rosin derivative to be used is not particularly limited as long as it is soluble in the dispersion medium. For example, gum syrup, wood rosin, tall oil rosin, rosin modified maleic acid, rosin modified pentaerythritol, rosin glycerin ester, partially hydrogenated rosin methyl Esters, partially hydrogenated rosin glycerin esters, partially hydrogenated rosin triethylene glycol esters, fully hydrogenated rosin pentaerythritol esters, maleic acid modified rosin esters, fumaric acid modified rosin esters, acrylic acid modified rosin esters, maleic acid modified rosin pentaerythritol Esters, fumaric acid modified rosin pentaerythritol ester, acrylic acid modified rosin glycerin ester, maleic acid modified rosin glycerin ester, fumaric acid modified Jin glycerol esters, acrylic acid-modified rosin glycerin ester. Specifically, for example, neotol (manufactured by Harima Chemicals Co., Ltd.), pencel, ester gum, superester (all manufactured by Arakawa Chemical Co., Ltd.) can be mentioned. If the rosin ester or rosin derivative is not contained in the dispersion medium, the charged electrophoretic particles may not be stably charged, and the polarity of the charge may be reversed or the particles may not migrate. 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.

  When the particles of the present invention are used as electrophoretic particles, a charge control material may be contained in order to impart charge to the electrophoretic particles or to assist charging. The charge control material is not particularly limited as long as it is soluble in the dispersion medium. For example, cobalt naphthenate, zirconium naphthenate, copper naphthenate, iron naphthenate, lead naphthenate, manganese naphthenate, and zinc naphthenate are used. Metal soap, cobalt octoate, zirconium octoate, iron octoate, lead octoate, nickel octoate, manganese octoate, zinc octoate metal soap, stearic acid metal soap, etc., polyaminopolybuteruccinic acid Well-known things, such as an imide and a lecithin, are mentioned.

  In addition, when the particles of the present invention are used as electrophoretic particles, a polymer resin that is soluble in a dispersion medium may be contained as a dispersion stabilizer for charged electrophoretic particles or an adhesion inhibitor to walls. Specific examples include polybutadiene, polyisoprene, polybutene, styrene butadiene copolymer, styrene isoprene copolymer, styrene maleic anhydride copolymer, norbornene resin, and polyethylene wax. Among them, a styrene butadiene copolymer is preferable. For example, commercially available materials include E-SBR, S-SBR (manufactured by JSR Corporation), NIPOL 1052, NIPOL 1712, NIPOL NS112, NIPOL NS116, NIPOL 1006, and NIPOL 1009 ( Nippon Zeon Co., Ltd.), Tuffden, Tuffprene, Asaprene (Asahi Kasei Co., Ltd.), Sumitomo SBR (Sumitomo Chemical Co., Ltd.) can be used.

  These dispersion stabilizers and adhesion inhibitors can be used alone or in admixture of two or more. Moreover, you may contain the anionic surfactant soluble in a dispersion medium as needed, and these may be used individually or in mixture of 2 or more types.

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

  Furthermore, if necessary, the dispersion medium can be colored in a different color from the particles. 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 liquid for electrophoretic display of the present invention can be used by being encapsulated in a microcapsule 12, 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.

  For the substrates 5a and 5b, polymer films such as polyethylene terephthalate (PET), polyethersulfone (PES), polyimide (PI), polyethylene naphthalate (PEN), polycarbonate (PC), inorganic materials such as glass and quartz, Alternatively, a stainless steel substrate having an insulating layer on 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 5a 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, thermoreversible elastomer resin, or the like may be formed on the surface of the substrate 5a in contact with the dispersion.

  The electrodes 6a and 6b 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, it is preferable to form an insulating layer 8 on the surfaces of the electrodes 6a and 6b. When an insulating layer is formed, charge injection from the electrodes 6a and 6b to the charged electrophoretic particles 1 can be prevented. The material used for the insulating layer 8 is preferably a thin film that is difficult to form pinholes. Specific examples include a highly transparent polyimide resin, polyester resin, polyacrylate resin, polymethacrylate resin, polycarbonate resin, polyarylate resin, novolac resin, and epoxy resin.

  Further, a polymer resin may be used for the partition wall 7, and in the case of the electrophoretic display device of FIG. 4, the partition wall is formed on the electrode 6a. Examples of the material used include polyimide resin, polyester resin, polyacrylate resin, polymethacrylate resin, polycarbonate resin, polyacrylate resin, novolac resin, and epoxy resin.

  The partition 7 can be formed by applying a photosensitive resin layer and then performing exposure and wet development, a method of forming by a printing method, a method of adhering to the substrate after forming the partition, 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 manufactured by Nihon Magdermit Co., Ltd.).

  Further, the region where one of the first electrode 6a and the second electrode 6b is disposed is colored the same as the charged electrophoretic particle 1, and the region where the other electrode is disposed is colored differently. can do. For example, in the case of the apparatus of FIG. 4, the first electrode 4a itself may be colored black, or a colored insulating layer may be arranged so as to overlap the electrode.

  In the case of the vertical movement type (FIG. 5), 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, by displaying different colors on a plurality of adjacent pixels, the entire display device can be displayed in color.

  Next, a method of using the fine particles of the present invention as a colored ink for an ink jet printer will be described.

  When the fine particles of the present invention are used in ink for an ink jet printer, the fine particles produced by the above-described production method may be dispersed in a suitable medium. At that time, a dispersion stabilizer is preferably used. The particle diameter in the case of using for ink is not particularly limited, but 0.005 to 5 μm, preferably about 0.1 to 1 μm is appropriate.

  Next, a method of using the fine particles of the present invention as a toner for a copying machine will be described.

  When the fine particles of the present invention are used as toner for a copying machine, the fine particles produced by the above-described production method are further mixed with various toners such as a charge control agent and an anti-offset agent (release agent). It is preferably used by containing an additive. As the resin constituting the fine particles, among the materials described above, a styrene resin used as a fixing resin in a conventional toner is more preferably used.

  More specifically, examples of the styrene monomer used in the styrene resin, particularly the styrene-acrylic copolymer, include vinyl toluene, α-methyl styrene and the like in addition to styrene. Examples of the acrylic monomer include acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, phenyl acrylate, methyl methacrylate, hexyl methacrylate, Examples include 2-ethylhexyl methacrylate, ethyl β-hydroxyacrylate, propyl γ-hydroxyacrylate, and the like.

  The charge control agent is applied to control the frictional charging of the toner, and there are a charge control agent and a charge control agent.

  As the charge control agent for controlling positive charge, for example, basic dyes, aminopyridines, pyrimidine compounds, polyamino compounds, aminosilane compounds, fillers surface-treated with the above compounds, oil-soluble dyes and the like are preferably used.

  Examples of charge control agents for controlling negative charges include oil-soluble dyes such as oil black, bontron, and spiron black, charge control resins such as styrene-styrene sulfonic acid copolymer, and carboxyls such as alkyl salicylic acid metal chelates. Examples thereof include compounds containing a group, metal complex dyes, fatty acid metal soaps, resin acid soaps, and naphthenic acid metal salts.

  The charge control agent may be used in a proportion of 0.1 to 10 parts by weight, preferably 0.5 to 8 parts by weight with respect to 100 parts by weight of the resin.

  Examples of the offset inhibitor include aliphatic hydrocarbons, aliphatic metal salts, higher fatty acids, fatty acid esters, silicone oil, various waxes, and the like. In particular, an aliphatic hydrocarbon having a weight average molecular weight of about 1000 to 10,000 is preferable.

  When the particles of the present invention are used as a toner, the particle size of the toner is 0.1 to 30 μm, preferably about 1 μm to 10 μm, and can be used as a toner for small particle size fine printing.

  It is also preferable to apply a known surface treatment agent such as inorganic fine particles such as hydrophobic silica fine powder or a fluororesin to the surface of the toner to improve the fluidity.

  Hereinafter, the present invention will be described based on examples.

  A solution composition is prepared in which acetamide is adsorbed on the surface of Au fine particles having an average particle diameter of 1 nm and dispersed in an aqueous solution. The Au fine particles in the solution are 30 parts by weight, and the color of the solution is dark black red. On the other hand, another solution composition is prepared in which a particle matrix of an acrylate copolymer is dispersed in an aqueous solvent. To the solution composition in which the particle matrix is dispersed, the black-red metal fine particle dispersion is added little by little with stirring. Thereafter, a small amount of thionyl chloride was added, and stirring was continued for about 3 hours for reaction.

  When the solution thus obtained was dropped onto a glass substrate and sprinkled with an optical microscope, a large number of particles having transparent acrylic particles whose surface was changed to black were observed.

  An Au fine particle surface having an average particle diameter of 20 nm is prepared by adsorbing acetamide and dispersing it in an aqueous solution in the same procedure as in Example 1. The Au fine particles in the solution are 30 parts by weight, and the color of the solution is dark black red. Another solution composition in which the same acrylic ester copolymer particle base material as in Example 1 is dispersed in an aqueous solvent is prepared. To the solution composition in which the particle matrix is dispersed, the black-red metal fine particle dispersion is added little by little with stirring. Thereafter, a small amount of thionyl chloride was added, and stirring was continued for about 3 hours for reaction.

  The solution thus obtained was dropped on a glass substrate and observed with an optical microscope. As a result, many particles in which the surface of transparent acrylic particles was changed to red were observed.

  100 parts by weight of Isopar H (Exxon), an aliphatic hydrocarbon solvent as a dispersion medium, 2.5 parts by weight of Neotol 125H (Harima Kasei) as rosin ester, Asaprene 1205 (Asahi Kasei) as a styrene butadiene copolymer (Made by Co., Ltd.) After mixing and stirring 0.8 parts by weight for 24 hours, 10 parts by weight of the black particles prepared in Example 1 were mixed with the liquid filtered under pressure using a 5 μm PTFE membrane filter. A dispersion for electrophoresis of the present invention was prepared.

  The electrophoretic display device shown in FIG. 4 was prepared using the electrophoretic dispersion prepared in Example 3.

  As an element configuration, the size of the pixels 10 and 11 is 100 μm × 100 μm, and the number of pixels is 200 × 200. The substrate 5b is made of alkali-free glass having a thickness of 1.1 mm. The second electrode 6b is arranged by vapor-depositing aluminum with a thickness of 100 nm on the glass surface. A polyurethane resin layer whitened by mixing fine titanium oxide particles is disposed as the white scattering layer 9 on the second electrode 6b. A partition wall 7 having a width of 5 μm and a height of 18 μm is disposed at the boundary of the pixel, and a first electrode 6 a having a width of 5 μm and a height of 5 μm is disposed below the partition wall 7 as shown in FIG. Then, an insulating transparent resin layer 8 made of polyacrylate resin (manufactured by Optomer SS6699 JSR) is formed on the partition wall 7 including the first electrode 6a and the second electrode.

  Thereafter, a heat-fusible adhesive layer is formed on the upper surface of the partition wall 7 (bonding surface with the substrate 5a).

  The electrophoretic dispersion prepared in Example 5 was filled in the partition wall 7, and a polycarbonate film substrate 5a having a thickness of 100 μm was sealed by heat bonding with an adhesive layer on the upper side of the partition wall. A device was made.

  In the display device thus manufactured, the first electrode 6a was a common electrode of 0V, and the voltage ± 15V was applied to the second electrode 6b with a rectangular wave having a frequency of 0.25 Hz.

  The charged electrophoretic particles of the present invention were negatively charged after voltage application and migrated quickly between the electrodes, confirming a display with high black and white contrast. The response speed for black display was 50 ms. FIG. 4A shows a case where a voltage of −15 V is applied to the second electrode 6b, and the negatively charged electrophoretic particles gather on the side face of the partition wall 7, so that the pixels 10 and 11 are observed from the substrate 5a side. The scattering layer 9 is visually recognized and white display is performed. On the other hand, FIG. 4B shows a case where a voltage of +15 V is applied to the second electrode 6b, and the charged electrophoretic particles spread on the second electrode 6b. When the pixels 10 and 11 are observed from the substrate 5a side, the charged electrophoretic particles are visually recognized and a black display is obtained.

  The above-described black display using the electrophoretic particles of the present invention was very excellent in blackness, and the black and white contrast was clear.

  The electrophoretic display device produced in Example 4 was left in the vicinity of an indoor window for 1 month. The electrophoretic display device was irradiated with sunlight through the window glass during the day.

  When a voltage was applied to the display device in the same manner as in Example 4, a display with high black and white contrast was reproduced. Further, when a plurality of pixels were observed under a microscope, no elution of blackness from the electrophoretic particles into the electrophoretic liquid was observed, and the state of the electrophoretic liquid and particles similar to that immediately after the production was confirmed.

It is a cross-sectional schematic diagram which shows an example of the particle | grains which carried out the dispersion | distribution inclusion of the metal fine particle of this invention. It is a conceptual diagram for demonstrating the method of making the metal fine particle couple | bond with the particle | grain base material surface of this invention. It is a cross-sectional schematic diagram which shows the structure of the electrophoretic display device which concerns on this invention. It is another cross-sectional schematic diagram which shows the structure of the electrophoretic display device which concerns on this invention. It is another cross-sectional schematic diagram which shows the structure of the electrophoretic display device which concerns on this invention. It is another cross-sectional schematic diagram which shows the structure of the electrophoretic display device which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Metal fine particle 2 Base material 3 Electrophoretic particle 4 Dispersion medium 5a, 5b Substrate 6a 1st electrode 6b 2nd electrode 7 Partition 8 Insulating layer 9 White scattering layer 10 Pixel 11 Pixel 12 Microcapsule 13 Binding particle

Claims (1)

  Particles characterized in that a plurality of fine metal particles that are black in an aggregated state are arranged on the surface.

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