JP2005352055A - Particle and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem associated with difficulty of obtaining sufficient blackness due to lack of compatibility with a mother member in the case a large amount of an organic dye or a pigment is made to mix with the mother member in relation to conventional black particles. <P>SOLUTION: Particles are characterized by comprising a plurality of metal fine particles which generate a color by absorbing visible light of a specified wavelength and of which the long diameter is equal to or less than the wavelength of the visible light and which are dispersed in the transparent mother member. <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. For example, Patent Literature 1 and Patent Literature 2 propose an electrophoretic display device.

  4 and 5 show examples of the case where the charged electrophoretic particles move horizontally, FIG. 6 shows an example where the charged electrophoretic particles move vertically, and FIG. 7 shows the basic structure of the electrophoretic display device. An example of using a microcapsule encapsulating a dispersion liquid for electrophoretic display is shown. 4 to 6, 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 (for example, the insulating layer 8 in FIG. 4 and the white scattering layer 9 in FIG. 5), or the color of the particle and the dispersion medium (for example, FIG. 6 and FIG. 7 of the color combinations of the dispersion medium 2).

In particular, a combination of black particles and a white member is preferable in order to realize display such as printed matter on paper. For black particles, a method 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)

  However, in the conventional black particles, when a large amount of organic dye or pigment is mixed with the base material, it is difficult to obtain a sufficient blackness from the viewpoint of compatibility with the base material. In addition, when the produced particles are combined with a dispersion medium to form an electrophoretic liquid and a display device is produced, for a while, a change in color such as a dye oozing out from the particle base material may be observed.

  In addition, when an inorganic pigment was used, the compatibility in the process of dispersion in the base material was not excellent, the choice of the dispersant was limited, and the dispersion state of the pigment was not uniform.

  In order to realize high contrast by an electrophoretic display device, electrophoretic particles having strong blackness and no change in color with time are required.

  Then, this invention aims at solving said subject by providing the novel black particle which has not existed before. The object is to solve the color change when used in a display device or the like as well as particles having strong blackness.

  That is, the first invention of the present invention provides particles containing a plurality of metal fine particles in a continuous phase.

  The second invention provides black particles containing metal fine particles having a diameter of 0.1 to 15 nm or less. By making the metal fine particle diameter within this range, it becomes easy to exhibit black.

  A third invention is an electrophoretic particle containing metal fine particles having a diameter of 0.1 to 15 nm or less and exhibiting a black color when the particles are aggregated. A fourth invention is an electrophoretic display liquid comprising such particles and a dispersion medium. A fifth invention is an electrophoretic display device using such particles.

  The particles of the present invention can be applied to a display device that switches states by aggregation and dispersion of particles such as electrophoretic display. By applying to electrophoretic display, the “blackness” of the display is improved.

  According to the present invention, particles in which metal fine particles are dispersed and arranged can be provided. Further, the particles of the present invention are excellent in blackness and durability, and as a result, display with high black-and-white contrast and no deterioration can be performed in an electrophoretic display device.

  Hereinafter, the present invention will be described in detail.

  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. 2 and 3 are schematic cross-sectional views of another example of the present invention. In the figure, 1 is a metal fine particle, and 2 is a particle base material. The particles of the present invention are dispersed in a transparent base material so that the metal fine particles cover at least the entire surface of the particles. As shown in FIG. 2, those in which metal fine particles are dispersed mainly in the vicinity of the surface as shown in FIG. 2, and those in which metal fine particles are mainly distributed on the outermost surface as shown in FIG. .

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

  Metals usually have a metallic luster in the bulk, but when the size of fine particles becomes a so-called nano-size that is less than or equal to the wavelength of visible light, particularly 100 nm or less, the current state of coloring by absorbing electromagnetic waves of a specific wavelength is well known. (For example, “What are ultrafine particles?” By Kiyoshi Kawamura (Maruzen)). This phenomenon has been used for coloring stained glass etc. for a long time. 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. For example, 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 when the diameter increases even if it is spherical, for example. 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 case 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)), it is shown that Ag, Pt, Cu, and the like also become black when the size of the fine particles is less than about a dozen nm.

  The particles of the present invention can exhibit an arbitrary color vividly by selecting the size, shape, and metal species as the metal fine particles 1 and dispersing them in the transparent material of the base material 2 as shown in FIGS. Is possible. 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.

  Further, the present invention has an advantage that the selectivity can be expanded with respect to the type of solvent to be uniformly dispersed by using metal fine particles.

  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 microparticles, for example, if the production method is appropriately selected, it can be covered with either hydrophobic or hydrophilic surface adsorbents. 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.

Although the manufacturing method of the particle | grains of this invention will not be specifically limited if the particle | grains typically shown in cross section in FIGS. 1-3 are formed, A typical method is mentioned below.
1. A solution composition in which metal fine particles are previously dispersed in a solvent and base material particles made of a transparent material such as a resin are prepared. The fine metal particles are sufficiently mixed and agitated and uniformly dispersed in the softened or melted base material by the heat-melt mixing method. At this time, the solvent in which the metal fine particles are dispersed is preferably selected from those having good compatibility with the particle base material. After sufficient mixing, the desired particles are formed by pulverization.
2. A solution composition (1) in which fine metal particles adsorbed with a dispersion material are dispersed in a solvent in advance and a solution composition (2) in which a polymerizable monomer is dispersed as a base material of the particles are prepared, and (1) and ( After mixing 2), suspension polymerization is carried out. For (1) and (2), it is preferable to select the same type of solvent or a solvent compatible with each other. Further, at this time, it is preferable that the same kind of alkyl group is arranged in the dispersing material to be adsorbed on the metal fine particles and the particle matrix of the polymerizable monomer because the compatibility of the metal fine particles and the polymerizable monomer in the mixed solution is good. Here, as an example of the same kind of alkyl group in the dispersing agent and the polymerizable monomer, for example, acrylic acid ester, methacrylic acid ester, styrene and the like as the polymerizable monomer, and as a dispersing agent, 2-propanoic acid, 2-mercaptomethyl ester, 2-propenic acid, 2-methyl-, mercaptomethyl ester, 2-propenic acid, 2-methyl-, 2-mercaptomethyl ester, etc. are preferably used.
3. While the base material particles made of a transparent material such as resin are stirred in the gas phase, metal fine particles are sprayed and sprayed onto the particle surface. If necessary, it is also effective to treat the base material particles in a softened state by heating the gas phase bath. At this time, it is also preferable to use a technique in which the metal fine particles to be sprayed are dispersed in a volatile solvent in advance.

  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. When it is less than 0.1 μm, handling is reduced, and when it exceeds 7 μm, the display resolution is reduced. 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 a 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 (Harima Kasei), pencel, ester gum, superester (all of which are Arakawa Chemical Industries) 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, styrene-butadiene copolymer is preferable. For example, commercially available materials include E-SBR, S-SBR (manufactured by JSR Corporation), NIPOL1052, NIPOL1712, NIPOL NS112, NIPOL NS116, NIPOL1006, NIPOL1009 (Nippon Zeon Corporation) )), Toughden, 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 (Showa Shell Japan), IP Solvent 1016, 1620, 2028, 2835 (Idemitsu Petrochemical), Nisseki Isozoru 200, 300, 400 (both manufactured by Nippon Petrochemicals) 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. 5, 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 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. 5, 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. 6), 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 charge control agents and offset preventive agents (release agents). 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 the charge control agent for controlling negative charge 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 metal alkylsalicylate chelate. 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.

Example 1
A solution composition in which the surface of Au nanoparticles having an average particle diameter of 1 nm is treated with thiol and dispersed in a toluene solvent is prepared. The Au content was about 20 parts by weight. On the other hand, polystyrene particles having an average particle diameter of 10 μm are prepared. The polystyrene particle and Au nanoparticle dispersion solution composition is placed in a stirred superheated container, and the temperature is gradually increased from 50 ° C. to 100 ° C. while rotating the container, and kept for 1 hour, and then pulverized by a jet mill (manufactured by Hosokawa). As a result, black particles having an average particle diameter of 5 μm were obtained.

  When the cross section of the particle was observed with a scanning electron microscope (hereinafter SEM), the metal fine particles were uniformly dispersed throughout the particle as shown in FIG.

Example 2
2-Propenic acid, mercaptomethyl ester CH2 = CHCOOCH2-SH and LiB (C2H5) 3H are added to THF (tetrahydrafuran) added with HAuCl4 (chloroauric acid), and the Au surface has an acrylate group A solution composition having a surface coated with a thiol compound and dispersed therein is prepared, centrifuged in ethanol, and then Au particles are redispersed in a toluene solvent. On the other hand, a solution is prepared by dissolving the acrylate monomer CH2 = CH-COOR in toluene. Two types of solutions were mixed, AIBN (manufactured by Otsuka Chemical Co., Ltd.) was added as a trace amount of polymerization initiator, and polymerization was performed while stirring to prepare fine particles. Particles of about 2 μm to 50 μm were prepared.

  Thereafter, particles prepared by drying the solution were taken out and pulverized with a jet mill to obtain black particles having an average particle diameter of about 5 μm.

  When the cross section of the particle was observed with an SEM, the metal fine particles were uniformly dispersed in the entire particle as shown in FIG. 1, and there were slightly diluted regions of metal fine particles inside the particle as shown in FIG. There was something that was made.

Example 3
In the same manner as in Example 1, a solution composition in which the surface of Au fine particles having an average particle diameter of 1 nm is subjected to thiol treatment and dispersed in a toluene solvent is prepared. On the other hand, styrene particles having an average particle diameter of 5 μm are prepared. Styrene particles are charged into a gas phase stirring tank, and the whole tank is kept at about 60 ° C., and nitrogen is refluxed from below to keep the particles stirred. The Au fine particle dispersion is sprayed from the spray nozzle into the tank at a high speed.

  After finishing spraying on the styrene particles, stirring in the gas phase was continued for about 30 minutes, and then cooled to recover black particles.

  When the cross section of the particle was observed with an SEM, a state in which metal fine particles covered the entire surface of the particle as shown in FIG. 3 was observed. When a large number of particles were observed, there were some particles in which not only the surface of the particles as shown in FIG.

Example 4
A solution composition is prepared in which the surface of Au fine particles having an average particle diameter of 20 nm is thiol-treated and dispersed in a toluene solution. Thereafter, after mixing with styrene particles by the heat-melt blending method in the same procedure as in Example 1, red particles having an average particle diameter of 5 μm were obtained by pulverization.

Example 5
100 parts by weight of Isopar H (Exxon) which is an aliphatic hydrocarbon solvent as a dispersion medium, 2.5 parts by weight of Neotol 125H (Harima Kasei Co., Ltd.) as a 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.

Example 6
The electrophoretic display device shown in FIG. 5 was prepared using the electrophoretic dispersion prepared in Example 5.

  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. 5A 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 surfaces 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. 5B 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.

Example 7
The electrophoretic display device produced in Example 6 was left in the vicinity of an indoor window for 1 month. The electrophoretic display device was irradiated with sunlight through the daytime window glass.

  When a voltage was applied to the display device in the same manner as in Example 6, 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 those immediately after production in Example 5 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 cross-sectional schematic diagram which shows another example of the particle | grains which carried out dispersion | distribution inclusion of the metal microparticles | fine-particles of this invention. It is a cross-sectional schematic diagram which shows another example of the particle | grains which carried out dispersion | distribution inclusion of the metal microparticles | fine-particles 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. FIG. 5 is still another schematic cross-sectional view showing the structure of the electrophoretic display device according to the present 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 microparticle 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

Claims (6)

  A particle obtained by dispersing a plurality of fine metal particles having a major axis that absorbs visible light having a specific wavelength and has a major axis shorter than or equal to the visible light wavelength in a transparent base material.   The particle according to claim 1, wherein the metal fine particle has a major axis of 15 nm or less and exhibits a black color.   An electrophoretic display device comprising the particles according to claim 1, a liquid that holds the particles, and a container that encloses the liquid.   The method for producing particles according to claim 1 or 2, wherein at least a solution composition in which metal fine particles are dispersed and base material particles are heated and melt-blended in the same container to produce particles. Manufacturing method.   3. The method for producing particles according to claim 1, wherein the solution composition in which the metal fine particles are dispersed and the solution composition in which the polymerizable monomer that is the base material of the particles is mixed are mixed and then suspension polymerization is performed. The manufacturing method of the particle | grain which creates particle | grains by this.   3. The method for producing particles according to claim 1 or 2, wherein particles are prepared by jetting and stirring in a gas phase a metal composition or a solution composition in which metal particles are dispersed in a base material particle. Particle production method.

Images