JP2010271638A - Electrophoretic particle, electrophoretic particle dispersion liquid, image display medium, and image display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide electrophoretic particles giving a display color, which is not influenced by the color of a dispersion medium or colors of other particles even when combined with a colored dispersion medium or particles of colors other than white. <P>SOLUTION: There are provided electrophoretic particles 13a having organic molecules that absorb visible light in a predetermined wavelength region adsorbed to surfaces of white particles. In the electrophoretic particles 13a, polymer chains may be chemically bonded to surfaces of white particles. An image display medium excellent in visibility is manufactured by dispersing the electrophoretic particles 13a in a nonpolar solvent 13b and interposing the medium between two conductive layers 11, 12. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electrophoretic particle, an electrophoretic particle dispersion, an image display medium, and an image display device.

  Conventionally, a CRT or a liquid crystal display has been used as a terminal for displaying so-called images such as characters, still images, and moving images. These can instantly display and rewrite digital data, but are difficult to carry. In addition, there are problems such as eye fatigue due to long-time work and inability to display with the power off.

  On the other hand, when a character or a still image is distributed or stored, it is recorded on a paper medium using a printer. This paper medium is widely used as a so-called hard copy. Since hard copy makes it easier to see characters and still images than CRT or liquid crystal display, eyes are hard to get tired. Hard copies can be read freely. Furthermore, hard copies are lightweight and can be carried around. On the other hand, hard copies are recycled after being used, but there is a problem that much labor and cost are required for recycling.

  As an image display medium having the advantages of both a display and a hard copy, an image display medium using a polymer dispersed liquid crystal, a bistable cholesteric liquid crystal, an electrochromic element, an electrophoretic element, or the like is known. . These image display media are attracting attention because they can be brightly displayed in a reflective display type and have a memory property.

  Among the above image display media, for example, image display media using electrophoretic elements disclosed in Patent Documents 1 and 2 are excellent in terms of display quality and power consumption during display operation. Such an image display medium includes a pair of transparent electrodes A and B, and a dispersion liquid in which a plurality of electrophoretic particles having a color different from the color of the dispersion medium are dispersed in a colored dispersion medium. The dispersion liquid is sealed between the transparent electrodes A and B. At this time, since the electrophoretic particles are charged in the dispersion medium, the electrophoretic particles can be moved by applying an electric field between the transparent electrodes A and B. For example, when a negative voltage is applied to the transparent electrode A, positively charged electrophoretic particles move to the transparent electrode A side, so that the color of the electrophoretic particles is observed on the transparent electrode A side. On the contrary, when a positive voltage is applied to the transparent electrode A, the positively charged electrophoretic particles move to the transparent electrode B side, so that the color of the dispersion medium is observed on the transparent electrode A side. Thus, various displays can be performed by changing the voltage applied to the transparent electrode.

  Further, Patent Document 3 discloses that white or colored display is performed by using colored particles having a charging polarity different from that of white particles instead of the colored dispersion medium, and similarly changing the voltage applied to the transparent electrode. ing.

  Here, whether using the colored dispersion medium or using colored particles, white has been used exclusively as a pair of colors. In these cases, at the time of colored display, the white particles move to the non-viewing-side substrate side, and a colored dispersion medium or colored particle layer exists on the viewing-side transparent substrate side. External light is incident from the transparent substrate on the viewing side, and the wavelength component of a specific visible light region is absorbed by the colored dispersion medium or colored particle layer, and the remaining wavelength component is diffusely reflected by the white particle layer on the non-viewing side. It is visually recognized as a color. That is, the white particle layer functions as a diffuse reflection layer.

  However, in the case of switching between two colors that do not use white, there is nothing that functions as the diffuse reflection layer described above, so when one color is displayed, it is inevitably influenced by the color existing on the non-viewing side. In reality, there is a problem that the target color cannot be displayed due to color mixture.

  In view of the above-described problems of the prior art, the present invention provides an electrophoretic particle whose display color is not affected by the color of the dispersion medium or the color of other particles even when combined with a colored dispersion medium or particles other than white. An object is to provide an electrophoretic particle dispersion having electrophoretic particles, an image display medium having the electrophoretic particle dispersion, and an image display apparatus having the image display medium.

  The electrophoretic particle of the present invention is an electrophoretic particle used in an image display device that performs a display operation by electrophoresis of particles caused by applying a voltage between electrodes, and has a specific wavelength range on the surface of white particles. Organic molecules that absorb visible light are adsorbed.

  In the electrophoretic particles, the white particles are preferably composed mainly of a metal oxide.

  In the electrophoretic particle, it is preferable that a polymer chain is further chemically bonded to the surface of the white particle. In this case, it is more preferable that the polymer chain has a polysiloxane structure.

  The electrophoretic particle dispersion of the present invention may be one in which at least the above electrophoretic particles are dispersed in a nonpolar solvent, or at least two or more types of electrophoretic particles having different colors and charging polarities are nonpolar. It may be dispersed in a solvent.

  The image display medium of the present invention is an image display medium provided with an electrophoretic particle dispersion between two conductive layers, wherein the electrophoretic particle dispersion is the electrophoretic particle dispersion, and the two At least one of the two conductive layers is light transmissive.

  The image display apparatus of the present invention includes the above-described image display medium and means for supplying power to the image display medium.

  In the electrophoretic particle of the present invention, organic molecules that absorb visible light in a specific wavelength range are adsorbed on the surface of the white particle, so that light of a specific wavelength is absorbed, but the remaining light that is not absorbed is transmitted through the white particle. Diffuse reflection without Therefore, in the electrophoretic particle dispersion containing the electrophoretic particles, the display color is not affected by the color of the dispersion medium or the color of other particles even when combined with a colored dispersion medium or particles other than white. Therefore, in an image display medium provided with the electrophoretic particle dispersion and an image display apparatus having the image display medium, visibility can be improved and excellent display performance can be obtained.

It is a figure which shows an example of the image display medium of this invention. It is a figure which shows the other example of the image display medium of this invention. It is a figure which shows an example of the image display apparatus of this invention.

  Next, modes for carrying out the present invention will be described with reference to the drawings as appropriate. In the first embodiment of the present invention, in electrophoretic particles used for image display in which a display operation is performed by electrophoretic particles generated by applying a voltage between electrodes, at least the particles are identified on the surface of white particles. Organic molecules that transmit visible light in the wavelength range are adsorbed. “Organic molecules that transmit visible light in a specific wavelength range” refer to what are generally called dyes. By the presence of these dye molecules on the surface of white particles, the particles exhibit a color attributable to the dye and the dye does not absorb. Since the light is scattered by the white particles without passing through, the particles on the non-viewing side or the color of the coloring solvent do not appear.

  It is desirable that the organic molecule has a basic skeleton of a color material as a chemical structure and also has a group for adsorbing to particles. Examples of the basic skeleton include phthalocyanine, triphenylmethane, cyanine, riboflavin, coumarin, ruthenium complex, and xanthene. Examples of the adsorbing group include a carboxyl group, a sulfo group, a phosphonyl group, and a thiocyano group. Specific compounds include, for example, tetrasulfonic acid phthalocyanine zinc complex, tetrasulfonic acid phthalocyanine aluminum complex, tetrasulfonic acid phthalocyanine silicon complex, fluorescein, eosin Y, phloxine B, tetrabromophenol blue, riboflavin-5-phosphate, and the like. Can be mentioned.

  The method for adsorbing the organic molecules on the white particles is not particularly limited. For example, the organic molecules can be dissolved in a soluble solvent such as water and the white particles can be dispersed therein. Adsorb to white particles.

  The electrophoretic particles of the present invention preferably have a particle size of, for example, 100 nm or more and 1 μm or less. When the particle diameter exceeds 1 μm, the dispersion stability in the nonpolar solvent is lowered and the liquid is liable to settle, which may adversely affect the display memory property of the display medium of the present invention. Further, when the particle size is 100 nm or less, Mie scattering of white particles cannot be expected, and the white particles hardly function as light scattering particles.

  In the second embodiment of the present invention, in the electrophoretic particles of the first embodiment of the present invention, it is preferable that the white particles are mainly composed of a metal oxide, and the white particles are metal-oxidized. More preferably, it consists of a product. Metal oxides generally have a high refractive index, and the difference in refractive index from the dispersion medium is large, so that the light scattering effect is high. Accordingly, the whiteness is also increased. The metal oxide that can be used in this embodiment is not particularly limited. For example, metal oxides such as silicon dioxide, aluminum oxide, and titanium oxide can be used.

  In the third embodiment of the present invention, in the electrophoretic particles of the first to second embodiments of the present invention, it is preferable that a polymer chain is further chemically bonded to the surface of the white particles. In order to obtain particles having such a form, a method of grafting a polymer onto the surface of white particles can be mentioned. In this case, a polymerizable functional group may be formed on the surface of the white particles, and a monomer may be added to cause a polymerization reaction, and a known method can be applied.

  When a polymer is grafted on the surface of the metal oxide, it is preferable to surface-treat the metal oxide with a coupling agent having a polymerizable functional group. For example, a vinyl group can be formed on the surface of the metal oxide by reacting a silane coupling agent having a vinyl group such as 3- (trimethoxysilyl) propyl methacrylate with the metal oxide. Examples of monomers to be polymerized include 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, vinyl Laurate, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, phenyl (meth) acrylate, styrene, vinyltoluene, Vinyl acetate, divinylbenzene, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol tri (meth) acrylate, butane Di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tri (meth) acrylate, tetramethylolmethane tetra (meth) acrylate, dipropylene glycol di ( Monomers having a vinyl group such as (meth) acrylate, trimethylolhexane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, 1,3-dibutylene glycol di (meth) acrylate, trimethylolethane tri (meth) acrylate And two or more of them may be used in combination. By grafting a polymer on the surface of the metal oxide, electrophoretic particles excellent in dispersion stability in a nonpolar solvent can be obtained.

  In the fourth embodiment of the present invention, in the electrophoretic particles of the first to third embodiments of the present invention, the polymer chain preferably has a polysiloxane structure. In order to form these polymer chains, the general formula (I);

(In the formula, R ₁ is a hydrogen atom or a methyl group, R ₂ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, n is a natural number, and x is an integer of 1 to 3. .)
The polymerization reaction may be performed in the same manner as in the third embodiment of the present invention using the monomer represented by The polysiloxane moiety of this monomer (silicone macromer having a (meth) acryloyloxy group at one end) is a nonpolar solvent preferably used in the electrophoretic particle dispersion of the present invention, particularly aliphatic hydrocarbons, silicone oils, etc. Has excellent affinity. The polysiloxane moiety incorporated in the polymer forms a comb structure in which many side chains are bonded to the main chain. Electrophoretic particles having such a polymer with a polysiloxane moiety incorporated on the surface thereof have a comb-like structure that is compatible with a nonpolar solvent, resulting in steric hindrance (a hindrance to interatomic attractive force). Excellent dispersion stability.

  The monomer of the general formula (I) may be a compound having a single molecular weight, but is usually produced as a mixture having a molecular weight distribution. Although the molecular weight of the monomer of general formula (I) is not specifically limited, It is preferable that a number average molecular weight is 500-50000. When the number average molecular weight is less than 500, the effect of dispersion stability cannot be obtained, and when it exceeds 50,000, the polymerization reaction hardly occurs.

Commercially available products can be used as the monomer of the general formula (I). For example, R ₁ in the general formula (I) is a methyl group, x = 3, and a monomer having a number average molecular weight of 1000, 5000, 10000, for example, Silaplane FM-0711, FM-0721, FM-0725 (trade name ; Manufactured by Chisso Corporation) can be used. Further, as other examples of commercially available monomers of the general formula (I), for example, X-22-174DX, X-24-8201, X-22-2426 (above, trade names; manufactured by Shin-Etsu Chemical Co., Ltd.) are listed. be able to.

  In the fifth embodiment of the present invention, it is preferable that the electrophoretic particle dispersion liquid is obtained by dispersing at least the electrophoretic particles of the first to fourth embodiments of the present invention in a nonpolar solvent. In general, the dispersion medium used for the electrophoretic particle dispersion is preferably a nonpolar solvent having high electrical insulation. The nonpolar solvent is not particularly limited. For example, paraffinic hydrocarbons such as pentane, hexane, heptane, octane, nonane, decane and dodecane, isoparaffinic hydrocarbons such as isohexane, isooctane and isododecane, and alkyl naphthenes such as liquid paraffin. Hydrocarbons, aromatic hydrocarbons such as benzene, toluene, xylene, alkylbenzene, solvent naphtha, dimethyl silicone oil, phenylmethyl silicone oil, dialkyl silicone oil, alkylphenyl silicone oil, cyclic polydialkylsiloxane, cyclic polyalkylphenylsiloxane, etc. And silicone oil.

  The dispersion medium can be colored in a different color from the electrophoretic particles. By dispersing the electrophoretic particles of the present embodiment in a colored dispersion medium having a different color from that of the electrophoretic particles, the color of the particles when the particles are on the viewing side substrate side, and the color of the particles and the dispersion medium when the particles are on the non-viewing side It is possible to present a color mixture of the following colors. For example, when yellow organic molecules are adsorbed on white particles and the dispersion medium is colored blue, yellow is displayed when the particles are on the viewing side of the substrate, and black is displayed when the particles are on the non-viewing side. .

  As the dye used for coloring the nonpolar solvent, a dye soluble in the nonpolar solvent can be used, and a dye classified as Solvent dye in the Color Index is preferable. Such dyes are not particularly limited, but azo dyes, anthraquinone dyes, phthalocyanine dyes, and triallylmethane dyes are preferable. Specifically, for example, spirit black (SB, SSBB, AB), nigrosine base (SA, SAP, SAPL, EE, EEL, EX, EXBP, EB), oil yellow (105, 107, 129, 3G, GGS), oil orange (201, PS, PR), first orange, oil red (5B, RR, OG), Oil Scarlet, Oil Pink 312, Oil Violet # 730, Macrolex Blue RR, Sumiplast Green G, Oil Brown (GR, 416), Sudan Black X60, Oil Green (502, BG), Oil Blue ( 613, 2N, BOS), O Le Black (HBB, 860, BS), Bali First Yellow (1101, 1105, 3108, 4120), Bali First Orange (3209, 3210), Bali First Red (1306, 1355, 2303, 3304, 3306, 3320), Bali First Pink 2310N, Bali First Brown (2402, 3405), Bali First Blue (3405, 1501, 1603, 1605, 1607, 2606, 2610), Bali First Violet (1701, 1702), Bali First Black (1802, 1807, 3804) , 3810, 3820, 3830).

  In the electrophoretic particle dispersion liquid of the present invention, the content of the electrophoretic particles can be appropriately adjusted so that a desired concentration of color can be obtained, but about 1 to 50% by weight is preferable. In addition, in order to control the dispersibility of the electrophoretic particles, the electrophoretic particle dispersion may contain a dispersant or the like as necessary. Although it does not specifically limit as a dispersing agent, The polymeric pigment dispersing agent melt | dissolved in a nonpolar solvent is preferable.

  The electrophoretic particle dispersion of the present invention can be obtained by adding and dispersing electrophoretic particles and, if necessary, a dispersing agent or the like in a nonpolar solvent. As a means for mixing and dispersing, for example, known means such as a homogenizer, a ball mill, a sand mill, and an attritor can be used.

  In the sixth embodiment of the present invention, at least two types of electrophoretic particles according to the first to fourth embodiments of the present invention in which the electrophoretic particle dispersion has different colors and charging polarities are used as nonpolar solvents. It is dispersed. For example, when two types of electrophoretic particles having different colors and charging polarities are used, as shown in the examples below, each particle has a different color and charging polarity. The color can be switched depending on the side. Moreover, it is possible to exhibit the color of each particle | grain, without mixing each color. Further, for example, when three types of electrophoretic particles having different colors and charging polarities are used, one type of positively charged particles and two types of negatively charged particles, or positively charged particles Can be used in combination with two types of particles and one type of negatively charged particles. In this case, it is possible to express three colors with three different kinds of particles, but two kinds of display ("one color alone" and "mixture of two other colors") using three kinds of particles. It is also possible to do this. In the same manner as described above, the electrophoretic particle dispersion of the present embodiment can be produced using electrophoretic particles of four or more different colors that are positively or negatively charged.

  Although the charged polarity of the electrophoretic particles in this embodiment largely depends on the charged polarity of the white particles themselves, the surface treatment of the white particles can be performed in order to control the polarity more clearly. For example, when the particles themselves are negatively charged metal oxides, the particles can be made positively charged by treating the metal oxide with a silane coupling agent having a basic group. Examples of the silane coupling agent having a basic group include N-2 (aminoethyl) 3-aminopropylmethyldimethoxysilane, N-2 (aminoethyl) 3-aminopropyltrimethoxysilane, and N-2 (amino Ethyl) 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, N-phenyl- Examples include 3-aminopropyltrimethoxysilane.

  In a seventh embodiment of the present invention, an image display medium has the electrophoretic particle dispersion liquid described in the fifth to sixth embodiments of the present invention between two conductive layers, At least one of the two conductive layers is light transmissive. FIG. 1 shows an example of the image display medium of the present invention. The image display medium 10 includes a microcapsule 13 containing the electrophoretic particle dispersion of the present invention and an adhesive support layer 14 between an upper electrode (conductive layer) 11 and a lower electrode (conductive layer) 12. The adhesive support layer 14 holds the microcapsule 13 between the upper electrode 11 and the lower electrode 12. At least one of the upper electrode 11 and the lower electrode 12 is light transmissive, and in the microcapsule 13, the electrophoretic particles 13a according to the first to fourth embodiments of the present invention have a different color. Dispersed in the colored nonpolar solvent 13b.

As the electrodes 11 and 12, for example, a metal such as Al, Ag, Ni, or Cu, or a transparent conductor such as ITO, SnO ₂ , or ZnO: Al is formed into a thin film by a sputtering method, a vacuum evaporation method, a CVD method, a coating method, or the like. The one formed in a shape or the one formed by applying a coating liquid in which a conductive agent is mixed with a solvent, resin, or the like is used. Here, examples of the conductive agent include cationic polymer electrolytes such as polymethylbenzyltrimethyl chloride and polyallylpolymethylammonium chloride, anionic polymer electrolytes such as polystyrene sulfonate and polyacrylate, and zinc oxide. , Tin oxide, indium oxide fine powder, and the like. The upper electrode 11 and the lower electrode 12 may be thick enough to have a self-supporting function, or may be provided on a base (not shown) having a self-supporting function. Further, the upper electrode 11 and the lower electrode 12 may be layers having anisotropic conductivity, or may be layers having pattern-shaped or multi-dot segments with conductive portions penetrating in the thickness direction. Good. At this time, if a power supply electrode is connected to a part of the upper electrode 11 and the lower electrode 12, an electric field can be applied between the upper electrode 11 and the lower electrode 12, so that the electrophoretic particles 13a can be moved. .

  The solid content in the electrophoretic particle dispersion in the microcapsule 13 can be appropriately adjusted so as to obtain a desired color, but is preferably about 0.1 to 25% by weight. The electrophoretic particle dispersion is obtained by adding the electrophoretic particles 13a to the colored nonpolar solvent 13b and mixing and dispersing them. The microcapsule 13 can be prepared using the obtained electrophoretic particle dispersion by using a known method such as a coacervation method or a phase separation method.

  In the present invention, instead of the microcapsule 13, a microcell in which the electrophoretic particle dispersion of the present invention is sealed in a fine cell provided with a partition wall by photolithography or the like may be used. In this way, by separating the two electrodes with fine cells, it is possible to suppress the bias of the electrophoretic particles and the aggregation of the electrophoretic particles due to gravity.

  The adhesive support layer 14 is not particularly limited as long as it is a material that adheres to the upper electrode 11 and the lower electrode 12. However, the adhesive support layer 14 is preferably transparent and excellent in electrical insulation, and a solvent-free curable material is particularly preferable. Examples of such a material include a photo-curable epoxy resin, a urethane resin, and an acrylic resin.

  The image display medium 10 is obtained by applying a mixture obtained by mixing the microcapsule 13 and an adhesive serving as the adhesive support layer 14 to the upper electrode 11 or the lower electrode 12 and bonding the upper electrode 11 and the lower electrode 12 together. Although it does not specifically limit as a coating method, For example, well-known methods, such as a blade, a wire bar, dipping, a spin coat, can be used.

  FIG. 2 shows another example of the image display medium of the present invention. The image display medium 20 is the same as the image display medium 10 except that the microcapsule 23 is used instead of the microcapsule 13. In the microcapsule 23, the electrophoretic particles 23a and 23b are dispersed in the nonpolar solvent 23c. The electrophoretic particles 23a and 23b have different colors and charging polarities. The nonpolar solvent 23c is preferably colorless and transparent because it does not adversely affect the contrast of the image based on the difference in color between the electrophoretic particles 23a and 23b. At this time, if a power supply electrode (not shown) is connected as a means for supplying power to the electrodes 11 and 12, an electric field can be applied between the upper electrode 11 and the lower electrode 12, and thus the electrophoretic particles 23a and 23b. Can be moved in opposite directions.

  An example of the image display apparatus according to the eighth embodiment of the present invention is shown in FIG. The image display device 30 includes an image display medium 10, information input means 31 for inputting image information to the image display medium 10, a housing 32, a drive circuit (not shown), an arithmetic circuit (not shown), and an internal memory (not shown). The image display medium 10 and the information input means 31 are provided with power supply means (not shown) for supplying power. The upper electrode 11 and the lower electrode 12 of the image display medium 10 form a dot matrix and display an image as a whole by displaying ON a designated dot. As the power supply means, internal power such as a battery may be provided, or a power receiving device such as an outlet receiving power from an external power source may be provided. In the image display device 30, the image display medium 20 may be used instead of the image display medium 10.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited to a following example. In the description of Examples and Comparative Examples, “part”, “%” and the like are based on weight unless otherwise specified.

Example 1
A solvent prepared by mixing 93 parts of ethanol and 7 parts of water was placed in a reaction vessel equipped with a stirrer, and the pH was adjusted to 4.5 with glacial acetic acid. Next, 16 parts of 3- (trimethoxysilyl) propyl methacrylate was added and dissolved, and then 100 parts of titanium oxide was added and stirred for 10 minutes. Further, 180 parts of ethanol was added and stirred, and the solid content collected by centrifugation was left standing for a whole day and night, followed by vacuum drying at 70 ° C. for 4 hours to obtain a vinyl group surface-treated titanium oxide.

  In a reaction vessel equipped with a stirrer, a thermometer and a reflux condenser, 100 parts of Silaplane FM-0711 (trade name; manufactured by Chisso Corporation) of methacryloxypropyl-modified silicone was dissolved in 130 parts of toluene. Next, a solution obtained by dissolving 75 parts of the above-mentioned vinyl group surface-treated titanium oxide and 0.5 part of azobisisobutyronitrile was added to 50 parts of toluene, and the mixture was heated and stirred at 70 ° C. for 6 hours in a nitrogen atmosphere. After completion of the reaction, the solid content was washed with toluene by repeated centrifugation, and finally dried in vacuo at 70 ° C. for 4 hours to obtain white electrophoretic particles.

  After 10 parts of the electrophoretic particles were dispersed in 100 parts of a methanol saturated solution of zinc tetraphthalate phthalocyanine complex and allowed to stand for 12 hours, the particles were collected, washed with methanol, and vacuum dried at 50 ° C. to give cyan. Electrophoretic particles were obtained.

  10 parts of the above colored electrophoretic particles are added to 30 parts of a solution obtained by saturating oil red 5B, which is a dye, in an isoparaffin hydrocarbon solvent Isopar G (trade name; manufactured by Exxon Chemical Co., Ltd.), ultrasonically dispersed, and electrophoretic particles. A dispersion was obtained.

  10 parts of urea, 1 part of resorcinol and 10 parts of ethylene-maleic anhydride copolymer were dissolved in 290 parts of water, and then adjusted to pH 3.5 with an aqueous sodium hydroxide solution. Next, an electrophoretic particle dispersion was added, and 25 parts of a formaldehyde solution was further added, followed by heating and stirring at 50 ° C. for 3 hours. After completion of the reaction, the mixture was suction filtered, washed with water, and dried to obtain microcapsules.

  The obtained microcapsules were dispersed in a heat-sealing urethane resin and applied on a glass substrate with an ITO electrode with a wire bar. Next, the coated film was sandwiched between another ITO electrode and laminated to obtain an image display medium.

  When a voltage of +10 V was applied to the upper electrode with reference to the lower electrode, the electrophoretic particles quickly moved to the upper electrode side, and when viewed from the upper electrode side, the color appeared to be cyan due to the electrophoretic particles. Next, when a voltage of −10 V is applied to the upper electrode, the electrophoretic particles quickly move to the lower electrode side, and when viewed from the upper electrode side, the red color resulting from the dye and the cyan color of the electrophoretic particles are combined. It looked black.

(Comparative Example 1)
An image display medium was prepared in the same manner as in Example 1 except that 3 parts of copper phthalocyanine was used as cyan particles and 0.1 part of Solsperse 17000 (trade name; manufactured by Lubrizol) was added as a dispersant for copper phthalocyanine. Obtained.

  When the voltage of + 10V is applied to the upper electrode and the voltage of -10V is applied to the upper electrode with respect to the lower electrode, both the red color caused by the dye and the electrophoretic particles The cyan color mixed and looked black, and the display color could not be switched.

(Example 2)
A solvent prepared by mixing 93 parts of ethanol and 7 parts of water was placed in a reaction vessel equipped with a stirrer, and the pH was adjusted to 4.5 with glacial acetic acid. Next, 16 parts of 3-aminopropyltrimethoxysilane was added and dissolved, and then 100 parts of titanium oxide was added and stirred for 10 minutes. Further, 180 parts of ethanol was added and stirred, and the solid content collected by centrifugation was left standing for a whole day and night, followed by vacuum drying at 70 ° C. for 4 hours to obtain amino group surface-treated titanium oxide.

  Next, a solvent obtained by mixing 93 parts of ethanol and 7 parts of water was placed in a reaction vessel equipped with another stirrer, and the pH was adjusted to 4.5 with glacial acetic acid. Next, 16 parts of 3- (trimethoxysilyl) propyl methacrylate was added and dissolved, and then 100 parts of the amino group surface-treated titanium oxide was added and stirred for 10 minutes. Further, 180 parts of ethanol was added and stirred, and the solid content collected by centrifugation was left standing for a whole day and night, followed by vacuum drying at 70 ° C. for 4 hours to obtain amino group and vinyl group surface-treated titanium oxide.

  In a reaction vessel equipped with a stirrer, a thermometer, and a reflux condenser, 100 parts of lauryl methacrylate was dissolved in 130 parts of toluene. Next, a solution obtained by dissolving 75 parts of the above-mentioned amino group and vinyl group surface-treated titanium oxide and 0.5 part of azobisisobutyronitrile is added to 50 parts of toluene, and the mixture is heated and stirred at 70 ° C. for 6 hours in a nitrogen atmosphere. did. After completion of the reaction, the solid content was washed with toluene by repeated centrifugation, and finally dried in vacuo at 70 ° C. for 4 hours to obtain white positively charged electrophoretic particles.

  After dispersing 10 parts of the above white electrophoretic particles in 100 parts of a saturated solution of eosin Y in methanol and allowing them to stand for 12 hours, the particles were collected, washed with methanol, and vacuum dried at 50 ° C. Charged electrophoretic particles were obtained.

  40 parts of Isopar G (trade name; manufactured by Exxon Chemical Co., Ltd.), 10 parts of the magenta electrophoretic particles and 10 parts of cyan electrophoretic particles of Example 1 and oil-soluble surfactant Solsperse 17000 (trade name; Lubrizol Corporation) (Product made) 0.1 part was added and ultrasonically dispersed to obtain an electrophoretic particle dispersion.

  10 parts of urea, 1 part of resorcinol and 10 parts of ethylene-maleic anhydride copolymer were dissolved in 290 parts of water, and then adjusted to pH 3.5 with an aqueous sodium hydroxide solution. Next, an electrophoretic dispersion was added, and 25 parts of a formaldehyde solution was further added, followed by heating and stirring at 50 ° C. for 3 hours. After completion of the reaction, the mixture was suction filtered, washed with water, and dried to obtain microcapsules.

  The obtained microcapsules were dispersed in a heat-sealing urethane resin and applied on a glass substrate with an ITO electrode with a wire bar. Next, the coated film was sandwiched between another ITO electrode and laminated to obtain an image display medium.

  When a voltage of +10 V is applied to the upper electrode with respect to the lower electrode, cyan electrophoretic particles quickly move to the upper electrode side, and magenta electrophoretic particles quickly move to the lower electrode side. When viewed from the upper electrode side, it looked cyan. Next, when a voltage of −10 V is applied to the upper electrode, the magenta electrophoretic particles quickly move to the upper electrode side, and the cyan electrophoretic particles quickly move to the lower electrode side. Seen from the side, it looked magenta.

(Comparative Example 2)
Except for using 3 parts of quinacridone as magenta electrophoretic particles in Example 2 and adding 0.1 part of Solsperse 17000 (trade name; manufactured by Lubrizol) as a quinacridone dispersant, An image display medium was obtained.

  When a voltage of +10 V is applied to the upper electrode with respect to the lower electrode, cyan electrophoretic particles quickly move to the upper electrode side, and magenta electrophoretic particles quickly move to the lower electrode side. However, it looked cyan when viewed from the upper electrode side. Next, when a voltage of −10 V was applied to the upper electrode, the magenta electrophoretic particles quickly moved to the upper electrode side, and the cyan electrophoretic particles quickly moved to the lower electrode side. When viewed from the electrode side, the magenta and cyan colors are mixed and appear blue, and the magenta color that is the particle color cannot be displayed.

  Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made.

10, 20; Image display medium 11; Upper electrode 12; Lower electrode 13, 23; Microcapsule 13a, 23a, 23b; Electrophoretic particles 13b, 23c; Nonpolar solvent 14; Adhesive support layer 30; Image display device 31; Input means 32;

JP-A-5-173194 Japanese Patent No. 2612472 JP 62-269124 A

Claims (8)

Electrophoretic particles used in an image display device that performs display operation by electrophoresis of particles that occur by applying a voltage between electrodes,
An electrophoretic particle, wherein an organic molecule that absorbs visible light in a specific wavelength region is adsorbed on a surface of a white particle.   The electrophoretic particle according to claim 1, wherein the white particle contains a metal oxide as a main component.   3. The electrophoretic particle according to claim 1, wherein a polymer chain is further chemically bonded to the surface of the white particle.   The electrophoretic particle according to claim 3, wherein the polymer chain has a polysiloxane structure.   An electrophoretic particle dispersion, wherein the electrophoretic particles according to any one of claims 1 to 4 are dispersed in a nonpolar solvent.   5. An electrophoretic particle dispersion liquid, wherein two or more types of electrophoretic particles having different colors and charging polarities described in any one of claims 1 to 4 are dispersed in a nonpolar solvent. An image display medium comprising an electrophoretic particle dispersion between two conductive layers,
7. The image display medium according to claim 5, wherein the electrophoretic particle dispersion is the electrophoretic particle dispersion according to claim 5 or 6, and at least one of the two conductive layers has light transmittance.   An image display device comprising: the image display medium according to claim 7; and means for supplying power to the image display medium.