JP4911942B2 - Electrophoretic particle purification method, particle dispersion using the same, and image display medium / device - Google Patents

Description

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

  Conventionally, a CRT or a liquid crystal display is used as a terminal for displaying so-called images such as characters, still images, and moving images. They can display and rewrite digital data instantly, but it is difficult to always carry the device around, and it has many drawbacks such as eye fatigue when working for a long time and display when turning off the power. is there. On the other hand, when a character or a still image is distributed or stored as a document, it is recorded on a paper medium by a printer. This paper medium is widely used as a so-called hard copy. Hard copy is easier to read than display, less fatigue, and can be read freely. Furthermore, it has the characteristics that it is lightweight and can be carried freely. However, the hard copy is discarded and recycled after it is used. However, since the recycling requires a lot of labor and cost, there remains a problem in terms of resource saving.

There is a great need for a rewritable paper-like display medium that has the advantages of both the above display and hard copy. So far, polymer-dispersed liquid crystals, bistable cholesteric liquid crystals, electrochromic devices, electrophoretic devices The display medium using the above has been attracting attention as a display medium that is reflective and can display bright and has a memory property. Among them, those using an electrophoretic element are excellent in terms of display quality and power consumption during display operation. For example, Patent Document 1 (Japanese Patent Laid-Open No. 5-173194), Patent Document 2 (Japanese Patent No. 2612472). ) And the like. In an electrophoretic display medium, a dispersion liquid in which a plurality of electrophoretic particles having a color different from the color of a dispersion medium is dispersed in a colored dispersion medium is sealed between a pair of transparent electrodes. In this case, the electrophoretic particles (also simply referred to as electrophoretic particles) are charged on the surface in the dispersion medium, and when a voltage opposite to the electrophoretic particle charge is applied to one of the transparent electrodes, the electrophoretic particles migrate. The particles are deposited there, and the color of the migrating particles is observed. When a voltage having the same direction as the charge of the migrating particles is applied, the migrating particles move to the opposite side, so the color of the dispersion medium is observed. As a result, display can be performed.
The electrophoretic particles are required to have optical properties such as white and coloring relating to the display / non-display state, and good charging performance to move quickly in response to an external electric field. That is, all particles of the same type must be charged to the same polarity and move in the same direction with respect to the electric field. Particles charged in reverse polarity or particles that are poorly charged and do not respond to an electric field hinder excellent display characteristics, and cause deterioration in visibility of the display medium, such as a reduction in contrast.
As means for removing impurities, purification by liquid chromatography has been disclosed in Patent Document 3 (Patent No. 2996029), and purification by removal of water by drying under reduced pressure has been disclosed in Patent Document 4 (Japanese Patent Laid-Open No. 2001-188267). Although disclosed, it is not necessarily a separation by electrical means, and therefore, particles having uniform electrophoretic performance are not necessarily obtained.

JP-A-5-173194 Japanese Patent No. 2612472 Japanese Patent No. 2996029 JP 2001-188267 A

  An object of the present invention is to provide an image display medium and an apparatus having excellent display contrast between white display and colored display by solving the above-mentioned problems in electrophoretic display and removing electrophoretic particles having abnormal charging performance. There is to do.

In principle, particles used for electrophoretic display migrate along the electric field direction when a voltage is applied between two electrodes in a nonpolar solvent, and are electrodeposited on one of the electrodes. At this time, some particles are actually charged to the opposite polarity for some reason, and when voltage is applied, they migrate in the opposite direction to most of the particles, or the voltage is applied because they are hardly charged. Nor does it migrate along the electric field. These particles are so-called impurities as electrophoretic particles, and impair the display quality of electrophoretic display. Therefore, it is desirable to remove these impurities by electrical means.
Therefore, paying attention to the phenomenon that particles that migrate normally are electrodeposited on one electrode when a voltage is applied, a DC voltage is actually applied between the two electrodes immersed in the particle dispersion in a nonpolar solvent, and the one electrode is electrically charged. When only the attached particles were collected to prepare a particle dispersion for electrophoretic display, it was found that the display contrast was greatly improved and the display quality was improved.
The present invention is based on the above findings.

That is, the said subject is solved by (1)-(8) of this invention.
(1) “Two electrode substrates are immersed in a particle dispersion in which electrophoretic particles are dispersed in a nonpolar solvent, and a DC voltage is applied between these electrodes to electrodeposit the particles on one electrode substrate. And then collecting only the electrodeposited particles after the electrophoretic particle purification method ”
(2) “The method for purifying electrophoretic particles according to (1) above, wherein the recovered particles are further redispersed in a nonpolar solvent, and the steps of applying the voltage and recovering the particles are repeated a plurality of times. "
(3) “Purification of electrophoretic particles according to (1) or (2) above, wherein after applying the voltage, a DC voltage of opposite polarity is further applied between the two electrodes” Method"
(4) The item (1), wherein the electrode is immersed in a nonpolar solvent and ultrasonic waves are applied when the electrodeposited particles are collected or redispersed in a nonpolar solvent. Thru | or the refinement | purification method of the electrophoretic particle in any one of (3) "
(5) "Electrophoretic particles obtained by the purification method according to any one of (1) to (4)"
(6) “Electrophoretic particle dispersion characterized in that at least the electrophoretic particles according to item (5) are dispersed in a nonpolar solvent”
(7) “At least one of the electrophoretic particles according to the item (6) is dispersed in a nonpolar solvent between two substrates, at least one of which is disposed at a desired interval and is light transmissive. An image display medium comprising a dispersion and performing a display operation by electrophoresis of the particles by applying a voltage between the two substrates "
(8) “Image display device comprising the image display medium according to item (7) as a constituent element”

According to the first aspect of the present invention, two electrode substrates are immersed in a particle dispersion in which electrophoretic particles are dispersed in a nonpolar solvent, and a DC voltage is applied between the electrodes to apply the one electrode substrate. After electrodepositing the particles, only the electrodeposited particles are collected, so that electrophoretic particles having the same charge polarity can be obtained . After applying the voltage, a direct current having a reverse polarity between the two electrodes is obtained. By applying a voltage, particles having strong adhesion to the electrode substrate and not suitable for electrophoretic display are removed, so that electrophoretic particles having higher purity and uniform charge polarity can be obtained.
According to the invention of claim 2, since the recovered particles are further redispersed in a nonpolar solvent, and the voltage application and particle recovery steps are repeated a plurality of times, electrophoresis with higher purity and uniform charge polarity is achieved. Particles can be obtained.
According to the invention of claim 3 , when the electrodeposited particles are collected or redispersed in a nonpolar solvent, the electrode is immersed in the nonpolar solvent and subjected to ultrasonic vibration. Since the particles are easily dispersed in the nonpolar solvent, the time required for purification is shortened.
In addition , by dispersing the electrophoretic particles obtained by the above-described purification method in a nonpolar solvent, a particle dispersion liquid in which particles having the same charge polarity are dispersed is obtained, so that the electrophoretic characteristics suitable for electrophoretic display are excellent. particle dispersion is obtained, the image display medium and image display device, the inclusion of this particle dispersion, it is possible to provide an image display medium and an image display apparatus having excellent display contrast.

A first embodiment of the present invention will be described with reference to FIG.
In FIG. 1, an electrophoretic particle dispersion (2) before purification is placed in a container (1), and a pair of electrodes (3A) and (3B) are immersed therein. The concentration of the particles in the electrophoretic particle dispersion liquid (2) is not particularly limited, but it is desirable that the concentration is too low so that the particle recovery efficiency is poor, but on the other hand, the concentration is not set so that the particles do not aggregate. A concentration range of about 1 to 50% by weight is appropriate. When a DC voltage is applied from the power source (4) between the pair of electrodes (3A) and (3B), particles migrate along the electric field between the electrodes. For example, when the electrophoretic particles are positively charged, when a voltage is applied so that the electrode (3A) becomes +, the particles migrate toward the electrode (3B) and eventually electrodeposit on the electrode (3B).
The applied voltage is preferably such that the electric field strength between the two electrodes is 10 ⁴ to 10 ⁶ V / m. If the electric field strength is too low, the particles are difficult to migrate because the particles are difficult to migrate. On the other hand, if the electric field strength is too high, the particles are strongly electrodeposited on the electrode, making recovery difficult. Purified electrophoretic particles can be obtained by taking out the electrode (3B) on which the particles are electrodeposited in this way and collecting the electrodeposited particles. As a recovery method, the electrode substrate on which the particles are electrodeposited is taken out, and the solvent is evaporated by heating or decompression to collect the remaining solid particles.

  As the nonpolar solvent used in the present invention, a known solvent having a low dielectric constant and high electrical insulation can be used. Examples of such organic solvents include paraffinic hydrocarbons such as pentane, hexane, heptane, octane, nonane, decane and dodecane, isoparaffinic hydrocarbons such as isohexane, isooctane and isododecane, alkyl naphthenic hydrocarbons such as liquid paraffin, and benzene. Aromatic hydrocarbons such as toluene, xylene, alkylbenzene and solvent naphtha, silicone oils such as dimethyl silicone oil, phenylmethyl silicone oil, dialkyl silicone oil, alkylphenyl silicone oil, cyclic polydialkylsiloxane or cyclic polyalkylphenylsiloxane It is done.

  As the white particles, solid particles of metal oxides such as silicon dioxide, aluminum oxide, and titanium oxide can be used. As black colored particles, for example, carbon black, aniline black, furnace black, lamp black and the like can be used. Examples of cyan colored particles include phthalocyanine blue, methylene blue, Victoria blue, methyl violet, aniline blue, and ultramarine blue. As magenta colored particles, for example, rhodamine 6G lake, dimethylquinacridone, watching red, rose bengal, rhodamine B, alizarin lake and the like can be used. As yellow colored particles, for example, chrome yellow, benzidine yellow, Hansa yellow, naphthol yellow, molybdenum orange, quinoline yellow, tartrazine and the like can be used. These colored particles preferably have a particle size range of about 50 nm to 2 μm.

  Further, when dispersing the particles in a nonpolar solvent, a particle dispersant may be used. A particle dispersant is a compound that is soluble in a solvent in a particle dispersion and adsorbs to the particle when it is present, and prevents aggregation between particles due to electrostatic repulsion or the steric effect of the dispersant molecule. It is. In the non-aqueous solvent, the particles are stably dispersed, and a particle dispersion having good dispersibility can be obtained. As the particle dispersant that can be used in the embodiment of the present invention, among the surfactants used as known particle dispersants, those that are soluble in a nonpolar solvent can be used, and preferably a polymeric dispersant. It is. In addition, it is desirable to wash and remove the particle dispersant with a solvent when collecting the particles.

  In the second embodiment of the present invention, the voltage application and particle recovery steps are repeated a plurality of times. That is, the particles recovered from the electrode on which the particles are electrodeposited are dispersed again in a nonpolar solvent, and the above-described voltage application step is repeated again. By repeating this operation, the purity of the migrating particles is increased, and the display characteristics are further improved.

  In the third embodiment of the present invention, after applying the voltage, a DC voltage having a reverse polarity is further applied between the two electrodes. That is, for example, in the first embodiment of the present invention, when the electrophoretic particles are positively charged, first, when a voltage is applied so that the electrode (3A) becomes +, the particles migrate toward the electrode (3B), and eventually Electrodeposit on the electrode (3B). Next, when a voltage is applied so that the electrode (3A) becomes −, the particles electrodeposited on the electrode (3B) migrate toward the electrode (3A) and eventually electrodeposit on the electrode (3A). By performing such an operation, the adhesion force to the electrode substrate is large, and once it is electrodeposited on the electrode substrate, particles that are not suitable for electrophoretic display that do not leave the electrode again even under an electric field in the opposite direction can be removed. it can.

  In the method for purifying electrophoretic particles according to the fourth embodiment of the present invention, when the electrodeposited particles are collected or redispersed in a nonpolar solvent, the electrode is immersed in the nonpolar solvent, and an ultrasonic wave is obtained. Add vibration. Thereby, since the particles electrodeposited on the electrode are easily dispersed in the nonpolar solvent, the time required for collecting the particles is shortened. As a means for applying ultrasonic vibration, it may be added directly to the electrode or may be added to a container in which the electrode is immersed.

  In the fifth embodiment of the present invention, the electrophoretic particles are particles obtained by the purification method according to the first to fourth embodiments of the present invention. Since the electric particles purified by electrodeposition have the same charge polarity, when applied to electrophoretic display, all particles migrate in the same direction with respect to the applied voltage, thereby obtaining a display medium with excellent display contrast. be able to.

  In the sixth embodiment of the present invention, the electrophoretic particle dispersion liquid is obtained by dispersing at least the electrophoretic particles in the fifth embodiment of the present invention in a nonpolar solvent. In order to control the dispersibility of the dispersed particles, a dispersant or the like may be added to the nonpolar solvent as necessary. The weight ratio of the solid content in the particle dispersion is appropriately set so as to obtain a desired concentration of color, but about 0.1 to 25% by weight is appropriate. These components are added to a nonpolar solvent and mixed and dispersed to obtain a particle dispersion. In this case, a known dispersing means such as a homogenizer, a ball mill, a sand mill, or an attritor may be used as the dispersing means.

A seventh embodiment of the present invention will be described with reference to FIG.
In FIG. 2, (5) and (6) are conductive layers, at least one of which is light transmissive. As the conductive layer, a metal such as Al, Ag, Ni, Cu or the like, or a transparent conductor such as ITO, SnO ₂ , ZnO: Al or the like formed into a thin film by a sputtering method, a vacuum deposition method, a CVD method, a coating method, Or what mixed and apply | coated the electrically conductive agent with the solvent or the synthetic resin binder is used. Conductive agents include cationic polyelectrolytes such as polymethylbenzyltrimethyl chloride and polyallylpolymethylammonium chloride, anionic polyelectrolytes such as polystyrene sulfonate and polyacrylate, and electronically conductive zinc oxide and tin oxide. Indium oxide fine powder or the like is used. The conductive layer itself may be thick enough to have a self-holding function, or the conductive layer may be provided on a substrate having a self-holding function (not shown), which can be preferably used in either case. In addition, the conductive layers (5) and (6) may be layers having anisotropic conductivity, or layers having pattern-like or multi-dot segments with conductive portions penetrating in the thickness direction. May be. In any case, if the power supply electrode is contacted to a part of the conductive layers (5) and (6), an electric field can be generated between the conductive layers (5) and (6). Can move reliably. In order to perform the display, voltage applying means between the conductive layers (5) and (6) may be prepared, which is convenient.

  In FIG. 2, (7) is a microcapsule. However, the microcapsule is not an essential requirement, and a particle dispersion described later may be enclosed in a cell provided with fine partition walls by photolithography or the like. In any case, it is preferable to divide the two electrodes by a large number of fine cells because it can prevent the deviation of particles and the aggregation of particles due to gravity. A known method such as a coacervation method or a phase separation method can be used as a method for producing the microcapsules, and is not particularly limited. (8) is a purified white particle. The weight ratio of the solid content in the particle dispersion is appropriately set so as to obtain a desired concentration of color, but about 0.1 to 25% by weight is appropriate. These components are added to a nonpolar solvent and mixed and dispersed to obtain a particle dispersion. In this case, a known dispersing means such as a homogenizer, a ball mill, a sand mill, or an attritor may be used as the dispersing means.

In FIG. 2, (9) is a colored dispersion medium, and the nonpolar organic solvent is colored in a color different from the color of the white particles. In order to control the dispersibility of the dispersed particles, a dispersant or the like may be added to the colored dispersion medium as necessary.
Examples of the dye used include oil-soluble dyes that are soluble in the dispersion medium, and dyes that are classified as Solvent dye in the Color Index are preferably used. These dyes include azo dyes, anthraquinone dyes, phthalocyanine dyes, and triallylmethane dyes. These oil-based dyes include, 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), Fast 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), Oil Black (HBB, 860, BS), Bali First Yellow (1101, 1105, 3108, 4120), Bali First ole Di (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), Vari First Black (1802, 1807, 3804, 3810, 3820, 3830) are typical examples, as long as they are not contrary to the object of the present invention. Oil-based dyes or oil-soluble dyes other than the dyes described herein may be used.

  In FIG. 2, (10) is an adhesive support layer, which holds the microcapsules between the conductive layers (5) and (6). Although any known material that adheres to the conductive layer can be used for the adhesive support layer (10), it is preferably transparent and excellent in electrical insulation. A solvent-free curable material is particularly preferable. Examples of such a material include a photocurable epoxy resin, a urethane resin, and an acrylic resin.

Another seventh embodiment of the present invention will be described with reference to FIG.
In FIG. 3, (8A) and (8B) are purified white or colored particles, and (8A) and (8B) have different colors and charged polarities. In FIG. 3, (11) is a dispersion medium, and being colorless and transparent is preferable because it does not adversely affect the contrast of the image based on the color difference between white or colored particles (8A) and (8B). In order to control the dispersibility of the dispersed particles, a dispersant or the like may be added to the dispersion medium (11) as necessary. Examples of white particles constituting the particle dispersion include the white particles. Examples of the colored particles include known electrophoretic particles other than white. In FIG. 3, (5) and (6) are conductive layers, at least one of which is light transmissive. The above materials can be used for the conductive layer. An electric field can be generated between the conductive layers (5) and (6) by contacting the power supply electrode with a part of the conductive layers (5) and (6), and the two kinds of particles (8A) and (8B) ) Can move reliably and in the opposite directions. In order to perform the display, voltage applying means between the conductive layers (5) and (6) may be prepared, which is convenient.

  In order to manufacture the image display medium in the present embodiment, a mixture obtained by mixing the particle dispersion-containing microcapsules obtained above and an adhesive serving as an adhesive support layer is applied to an electrode substrate, and the counter electrode substrate is bonded to the electrode substrate. . As a coating method, a known coating film forming method such as blade, wire bar, dipping, spin coating or the like can be used, and it is not particularly limited. An image display medium can be easily manufactured by these steps.

An eighth embodiment of the present invention will be described with reference to FIG.
As shown in FIG. 4, the image display device (12) of the present invention includes an image display medium (13), and includes a drive circuit, an arithmetic circuit, an internal memory, a power source and the like (not shown). The electrodes in the display medium form a dot matrix and display an image as a whole by displaying ON a specified dot. In FIG. 4, (14) is a housing, and (15) is information input means.

The invention is explained in more detail by means of examples. However, the present invention is not limited to the following examples. The parts used in the following examples are all parts by weight.
Example 1
(Purification of electrophoretic particles)
Titanium oxide (Ishihara Sangyo TIPAQUE CR-90 average primary particle size 280 nm) 1 in a dispersion medium in which 0.1 part of an oil-soluble pigment dispersant (Abyssia Solsperse 17000) is dissolved in 100 parts of an isoparaffinic hydrocarbon solvent (Exxon Chemical Isopar H) Parts were dispersed. This dispersion was put in a container, and two metal electrodes were immersed so as to face each other at 1 mm intervals, and a DC voltage of 50 V was applied between both electrodes for 10 minutes. After the voltage application was completed, the titanium oxide electrodeposited on one electrode was washed off with a solvent and centrifuged three times to dry, thereby obtaining purified particles.

(Production and operation of image display medium)
A solution prepared by dissolving 10 parts of urea, 1 part of resorcinol and 10 parts of ethylene-maleic anhydride copolymer in 290 parts of water was adjusted to pH 3.5 with an aqueous sodium hydroxide solution. Separately, 30 parts of an isoparaffin hydrocarbon solvent (Exxon Chemical Isopar H) dye (Bayer Macrolex Blue RR) saturated solution and ultrasonically dispersed with 6 parts of the fine particles and 0.03 part of zirconium octoate are dispersed into particles. The dispersion was added to the aqueous solution, 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 microcapsules were collected by suction filtration, washing with water and drying.
The microcapsules obtained above were dispersed in an ultraviolet curable epoxy resin (trade name: ThreeBond 3121) and applied on a glass substrate with an ITO electrode with a wire bar. Next, the coating film was sandwiched with another ITO electrode so that the distance between the electrodes was 100 μm, and then cured by irradiation with ultraviolet rays.
When −100 V was applied to the upper ITO electrode, the white fine particles were quickly electrodeposited on the upper electrode side, and looked white when viewed from the upper substrate surface. Next, when +100 V was applied to the upper electrode, the white fine particles moved to the lower electrode side, and when viewed from the upper substrate side, the coloring state due to the color of the dye was clearly seen. The white reflectance during white display (the ratio of the reflected light amount to the white incident light amount) was 35%.

Comparative Example 1
(Production and operation of image display medium)
An image display medium was prepared in the same manner as in Example 1 except that titanium oxide that had not been subjected to a purification operation was used as white migrating particles, and the display was switched by applying a voltage. The coloration due to the color of the dye was equivalent but was not clear due to the titanium oxide migrating to the opposite polarity.

Example 2
(Purification of electrophoretic particles)
Dispersion liquid in which 0.2 parts of carbon black (Mitsubishi Chemical MA100 average diameter 1 μm) and 0.8 parts of polyethylene were melt-kneaded by heating and finely pulverized as black particles in 100 parts of silicone oil (Shin-Etsu Chemical KF96L-1cs) Was immersed in two metal electrodes facing each other at 1 mm intervals, and a DC voltage of 50 V was applied between both electrodes for 10 minutes. After the voltage application was completed, the polarity of the voltage was reversed and a DC voltage of 50 V was applied again between the electrodes for 10 minutes. After the voltage application was completed, one electrode electrodeposited with a large amount of black particles was immersed in 100 parts of new silicone oil and subjected to ultrasonic vibration for 5 minutes. The above operation was repeated once again on the obtained particle dispersion, and finally black particles were collected by centrifugation and drying.

(Production and operation of image display medium)
An image display medium was prepared in the same manner as in Example 1 except that 1 part of the black particles and 6 parts of white particles purified in Example 1 were added to 30 parts of silicone oil and ultrasonically dispersed. .
When -100 V was applied to the upper ITO electrode of this image display medium, the white fine particles were quickly electrodeposited on the upper electrode side, while the black particles moved to the lower electrode side and looked white when viewed from the upper substrate surface. Next, when +100 V was applied to the upper electrode, the white fine particles moved to the lower electrode side, while the black particles moved to the upper electrode side, and looked black when viewed from the upper substrate side. The white reflectance during white display was 40%.

Comparative Example 2
(Production and operation of image display medium)
An image display medium was prepared in the same manner as in Example 2 except that white particles and black particles that were not refined were used, and the display was switched by applying a voltage. The white reflectance was 25%. The whiteness was clearly low.

It is a schematic diagram of the apparatus which embodies the purification method of the electrophoretic particle which is one embodiment of the present invention. It is sectional drawing of the image display medium which shows one embodiment of this invention. It is sectional drawing of the image display medium which shows other one Embodiment of this invention. It is a schematic diagram of an image display device showing an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Container 2 Particle dispersion liquid 3A, 3B Electrode 4 Power supply 5 Conductive layer 6 Conductive layer 7 Microcapsule 8 White particle 8A, 8B White thru | or colored particle 9 Colored dispersion medium 10 Adhesive support layer 11 Dispersion medium 12 Image display apparatus 13 Image display medium 14 Housing 15 Information input means

Claims (3)

After immersing two electrode substrates in a particle dispersion in which particles having electrophoretic properties are dispersed in a nonpolar solvent and applying a DC voltage between these electrode substrates, the particles are electrodeposited on one electrode substrate. Further, after applying a DC voltage of opposite polarity between the two electrode substrates, causing the particles electrodeposited on the one electrode substrate to migrate and electrodepositing on the other electrode substrate, only the electrodeposited particles A method for purifying electrophoretic particles, comprising collecting 2. The method for purifying electrophoretic particles according to claim 1, wherein the recovered particles are further redispersed in a nonpolar solvent, and the steps of applying the voltage and recovering the particles are repeated a plurality of times. 3. Electrophoresis according to claim 1 or 2, wherein the electrode is immersed in a nonpolar solvent and ultrasonic waves are applied when the electrodeposited particles are collected or redispersed in a nonpolar solvent. Particle purification method.

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