JP2010145615A - Display medium, display element, and display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display medium, a display element and a display apparatus in which the displayed image can be retained favorably compared with the case where non-flocculated particles are used as electrophoresing particles. <P>SOLUTION: In the display element 12, flocculated particles 28 comprising positive electrode particles 28A having charging characteristics of a positive polarity, and negative electrode particles 28B having charging characteristics of a negative polarity are used as electrophoresing particles in a dispersion medium 14. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a display medium, a display element, and a display device.

  Conventionally, display media using colored particles are known as display media that can be rewritten repeatedly. The display medium includes, for example, a pair of substrates and a group of particles sealed between the substrates so as to be movable between the substrates in accordance with an electric field formed between the pair of substrates.

  In a display medium based on electrophoresis, an image is displayed by moving encapsulated particles by applying a voltage between a pair of substrates. That is, by applying a voltage between the substrates to move the particle group to be moved according to the color of the image to be displayed, the particle group to be moved is placed on either side of the pair of substrates. The image corresponding to the color of the image to be displayed is displayed.

For example, in Patent Document 1, a microcapsule including a positively charged sphere and a negatively charged sphere is disposed between substrates, and an electric field is formed between the substrates, so that one color sphere is microscopic. It has been proposed to move to the surface of the capsule and cause a color change.
JP 2001-500192 A

  An object of the present invention is to provide a display medium, a display element, and a display device in which a displayed image is favorably retained as compared with a case where non-aggregated particles are used as electrophoretic particles.

The above problem is solved by the following means. That is,
The invention according to claim 1 is characterized in that at least one of them has a light-transmitting property, a pair of substrates arranged with a gap, a dispersion medium sealed between the pair of substrates, dispersed in the dispersion medium, A first aggregated particle that moves in the dispersion medium in accordance with an electric field formed between a pair of substrates, is an aggregate of positive electrode particles and negative electrode particles, and has positive or negative electrode charging characteristics; A display medium provided.

  The invention according to claim 2 is the display medium according to claim 1, wherein the positive electrode particles and the negative electrode particles constituting the first aggregated particles have the same color.

  The invention according to claim 3 is provided with second particles that are dispersed in the dispersion medium, exhibit charging characteristics having a polarity opposite to that of the first aggregated particles, and have a color different from that of the first aggregated particles. The display medium according to claim 2.

  The invention according to claim 4 is the display medium according to claim 3, wherein the second particles are aggregates of positive electrode particles and negative electrode particles.

  According to a fifth aspect of the present invention, the absolute value A of the charge amount per one particle having a polarity opposite to that of the second particle out of the positive electrode particle and the negative electrode particle constituting the first aggregated particle. And the absolute value B of the charge amount per particle having the same polarity as the second particle among the positive electrode particles and the negative electrode particles constituting the first aggregated particles, and the second The display medium according to claim 3 or 4, wherein the relationship between the absolute value C of the charge amount per particle and the relationship of A> B> C is satisfied.

  According to a sixth aspect of the present invention, in the first agglomerated particles, among the positive electrode particles and the negative electrode particles constituting the first agglomerated particles, charging of particles having the same polarity as the second particles is performed. A sum D of absolute values of the amount and of the positive particles and the negative particles constituting the first aggregated particles of the first aggregated particles, the particles having the opposite polarity to the second particles. The relationship between the absolute value E of the charge amount and the relationship D <E, and the second particles among the positive electrode particles and the negative electrode particles constituting the first aggregated particles And the absolute value A of the charge amount per particle having a polarity opposite to that of the first particle, and the positive electrode particle and the negative electrode particle constituting the first agglomerated particle, the particle 1 having the same polarity as the second particle. The relationship between the absolute value B of the charge amount per unit and the absolute value C of the charge amount per unit of the second particles is B> > The display medium of claim 3 or claim 4, characterized in that the relation C.

  In the invention according to claim 7, at least one has translucency, a pair of substrates arranged with a gap, a dispersion medium enclosed between the pair of substrates, dispersed in the dispersion medium, A first aggregated particle that moves in the dispersion medium in accordance with an electric field formed between a pair of substrates, is an aggregate of positive electrode particles and negative electrode particles, and has positive or negative electrode charging characteristics; A display element comprising: a display medium provided; and an electrode for forming an electric field between the pair of substrates of the display medium.

According to an eighth aspect of the present invention, at least one of the pair of substrates having translucency and disposed with a gap, a dispersion medium sealed between the pair of substrates, dispersed in the dispersion medium, A first aggregated particle that moves in the dispersion medium in accordance with an electric field formed between a pair of substrates, is an aggregate of positive electrode particles and negative electrode particles, and has positive or negative electrode charging characteristics; A display device comprising: a display medium provided; an electrode for forming an electric field between the pair of substrates of the display medium; and a voltage applying device for applying a voltage to the electrode.

  According to the first aspect of the present invention, there is an effect that the displayed image is favorably retained as compared with the case where non-aggregated particles are used as the electrophoretic particles.

  According to the invention concerning Claim 2, compared with the case where the particle | grains which comprise aggregated particle are made into a different color, there exists an effect that the fall of color reproducibility is suppressed.

  According to the third aspect of the present invention, there is an effect that a decrease in color reproducibility is suppressed as compared with the case where non-aggregated particles are used as the electrophoretic particles.

  According to the invention which concerns on Claim 4, compared with the case where at least one of 1st particle | grains and 2nd particle | grains is made into a non-aggregated particle, there exists an effect that the displayed image is hold | maintained suitably.

  According to the invention concerning Claim 5, compared with the case where it does not have the structure of this invention, there exists an effect that the aggregated particle by which the charge amount and the polarity were adjusted easily is adjusted.

  According to the invention concerning Claim 6, compared with the case where it does not have the structure of this invention, there exists an effect that the aggregated particle in which the charge amount and the polarity were adjusted easily is adjusted.

  According to the invention concerning Claim 7, compared with the case where it does not have the structure of this invention, there exists an effect that the aggregated particle in which the charge amount and the polarity were adjusted easily is adjusted.

  According to the invention concerning Claim 8, compared with the case where non-aggregated particles are used as the electrophoretic particles, there is an effect that the displayed image is suitably held.

  According to the ninth aspect of the invention, there is an effect that the displayed image is favorably retained as compared with the case where non-aggregated particles are used as the electrophoretic particles.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol may be provided to the member which an effect | action and function bear the same function through all the drawings, and the overlapping description may be abbreviate | omitted.

(First embodiment)
In the present embodiment, as shown in FIG. 1, the display device 10 includes a display element 12, a voltage application unit 16 that applies a voltage to the display element 12, and a control unit 18.

  The display element 12 includes a display substrate 20 that serves as an image display surface, a rear substrate 22 that faces the display substrate 20 with a gap, and holds the substrates at a predetermined interval, and between the display substrate 20 and the rear substrate 22. And a reflecting member 26 having optical reflection characteristics different from those of the aggregated particles 28 and having holes through which the aggregated particles 28 pass.

Although the details will be described later, the agglomerated particles 28 are agglomerates in which two types of particles having oppositely charged characteristics are electrostatically combined, and these two types of particles are dispersed in the dispersion medium 14. Behave as one without being. The agglomerated particles 28 have a positive or negative charge characteristic as a whole when the aggregate is formed by electrostatically combining two kinds of particles having oppositely charged characteristics as described above. Yes.
Therefore, the agglomerated particles 28 dispersed in the dispersion medium 14 pass between the display substrate 20 and the back substrate 22 according to the electric field formed between the display substrate 20 and the back substrate 22. Move through the hole.

In the present embodiment, the display substrate 20 has a configuration in which a surface electrode 32 and a surface layer 34 are sequentially stacked on a support substrate 30. The back substrate 22 has a structure in which a back electrode 38 and a surface layer 34 are sequentially laminated on a support substrate 36.
In the present embodiment, the case where the back substrate 22 includes the back electrode 38 and the display substrate 20 includes the surface electrode 32 will be described. However, the back electrode 38 and the surface electrode 32 are described. May be provided separately from the display element 12.
In the present embodiment, when the back electrode 38 and the surface electrode 32 are provided separately from the display element 12, that is, the back electrode 38 and the surface electrode 32 in the display element 12 are not included. The component will be described as the display medium 13.

The display device 10 corresponds to the display device of the present invention, and the display element 12 corresponds to the display device of the present invention. The display medium 13 described later corresponds to the display medium of the present invention.
Furthermore, the display substrate 20 and the back substrate 22 correspond to a pair of substrates of the display medium of the present invention, and the dispersion medium 14 corresponds to the dispersion medium of the display medium of the present invention. Furthermore, the aggregated particles 28 correspond to the first particle group of the display medium of the present invention. The voltage application unit 16 corresponds to the voltage application device of the display device of the present invention.

  Of the display substrate 20 and the back substrate 22, at least the display substrate 20 has translucency. Here, translucency and transparency in this embodiment indicate that the visible light transmittance is 60% or more.

  Examples of the support substrate 30 and the support substrate 36 include glass and plastics such as polyethylene terephthalate resin, polycarbonate resin, acrylic resin, polyimide resin, polyester resin, epoxy resin, and polyethersulfone resin.

  For the surface electrode 32 and the back electrode 38, oxides such as indium, tin, cadmium and antimony, composite oxides such as ITO, metals such as gold, silver, copper and nickel, organic materials such as polypyrrole and polythiophene are used. Is done. These are used as a single layer film, a mixed film or a composite film, and are formed by vapor deposition, sputtering, coating, or the like. Moreover, the thickness is normally 100 to 2000 mm according to the vapor deposition method and the sputtering method. The back electrode 38 and the surface electrode 32 are formed by a conventionally known means such as etching of a conventional liquid crystal display medium or a printed board.

  The surface electrode 32 may be embedded in the support substrate 30. Further, the back electrode 38 may be embedded in the support substrate 36.

  When the surface electrode 32 and the back electrode 38 are formed on the support substrate 30 and the support substrate 36, respectively, the surface layer 34 and the surface layer 40 are damaged on the surface electrode 32 and the back electrode 38, and each aggregated particle 28 In order to prevent the occurrence of leaks between the electrodes that cause the particles to adhere to each other, it is desirable to form a dielectric film on each of the surface electrode 32 and the back electrode 38.

  As materials for forming the surface layer 34 and the surface layer 40, polycarbonate, polyester, polystyrene, polyimide, epoxy, polyisocyanate, polyamide, polyvinyl alcohol, polybutadiene, polymethyl methacrylate, copolymerized nylon, ultraviolet curable acrylic resin, fluorine Resin or the like is used.

  In addition to the materials described above as materials constituting the surface layer 34 and the surface layer 40, a material containing a charge transport substance in this material is also used.

  Examples of the charge transport material include a hydrazone compound, a stilbene compound, a pyrazoline compound, and an arylamine compound that are hole transport materials. Further, a fluorenone compound, a diphenoquinone derivative, a pyran compound, zinc oxide, or the like, which is an electron transport material, can also be used. Furthermore, a self-supporting resin having a charge transporting property is used.

  Specific examples thereof include polyvinyl carbazole and polycarbonate obtained by polymerization of a specific dihydroxyarylamine and bischloroformate described in US Pat. No. 4,806,443.

  The gap member 24 that holds the gap between the display substrate 20 and the back substrate 22 is formed so as not to impair the translucency of the display substrate 20, and is made of a thermoplastic resin, a thermosetting resin, an electron beam curable resin, It is made of photo-curing resin, rubber, metal or the like.

  The gap member 24 may be integrated with either the display substrate 20 or the back substrate 22. In this case, the support substrate 36 or the support substrate 44 is manufactured by performing etching processing, laser processing processing, press processing processing, printing processing, or the like using a previously manufactured mold. In this case, the gap member 24 is formed on either the display substrate 20 side, the back substrate 22 side, or both.

  The gap member 24 may be colored or colorless, but is preferably colorless and transparent so as not to adversely affect the display image displayed on the display element 12, and in this case, for example, transparent such as polystyrene, polyester, or acrylic Resin or the like is used.

  Further, the gap member 24 may be in the form of particles. In this case, glass particles are also used in addition to transparent resin particles such as polystyrene, polyester or acrylic.

The dispersion medium 14 is preferably an insulating liquid. Here, “insulating” indicates that the volume resistivity is 10 ¹¹ Ωcm or more. The same applies hereinafter.

  Specific examples of the insulating liquid include hexane, cyclohexane, toluene, xylene, decane, hexadecane, kerosene, paraffin, isoparaffin, silicone oil, dichloroethylene, trichloroethylene, perchloroethylene, high-purity petroleum, ethylene glycol, and alcohols. , Ethers, esters, dimethylformamide, dimethylacetamide, dimethylsulfoxide, N-methylpyrrolidone, 2-pyrrolidone, N-methylformamide, acetonitrile, tetrahydrofuran, propylene carbonate, ethylene carbonate, benzine, diisopropylnaphthalene, olive oil, isopropanol, trichloro Trifluoroethane, tetrachloroethane, dibromotetrafluoroethane, etc. and mixtures thereof are preferred. They are used to.

Further, water (so-called pure water) is also suitably used as the dispersion medium 14 by removing impurities so that the following volume resistance value is obtained. The volume resistance value is preferably 10 ³ Ωcm or more, more preferably 10 ⁷ Ωcm or more and 10 ¹⁹ Ωcm or less, and further preferably 10 ¹⁰ Ωcm or more and 10 ¹⁹ Ωcm or less. By setting the volume resistance value in this range, it is possible to more effectively apply an electric field to the particle group, and the generation of bubbles due to the electrolysis of the liquid due to the electrode reaction is suppressed, The electrophoretic properties of the agglomerated particles 28 are not impaired and contribute to excellent repeated stability.

The insulating liquid is added with acid, alkali, salt, dispersion stabilizer, stabilizer for anti-oxidation or UV absorption, antibacterial agent, preservative, etc. as necessary. It is desirable to add so that it may become the range of the specific volume resistance value shown. The aggregated particles 28 enclosed in the display element 12 are desirably dispersed in a polymer resin as the dispersion medium 14. This polymer resin may be a polymer gel, a polymer, or the like.
Further, a known colorant may be mixed in the dispersion medium 14. When the colorant is mixed with the dispersion medium 14, a color different from the colors of the reflective member 26 and the aggregated particles 28 on the display element 12 is displayed.

In the dispersion medium 14, the aggregated particles 28 move. Therefore, if the viscosity of the dispersion medium 14 is equal to or higher than a predetermined value, the dispersion of the adhesion force to the back substrate 22 and the display substrate 20 is large. It is also preferable to adjust the viscosity.
The viscosity of the dispersion medium 14 is in the range of 0.1 mPa · s or more and 100 mPa · s or less in an environment of a temperature of 20 ° C. from the viewpoint of the moving speed of the aggregated particles 28, that is, the display speed. -It is desirable that it is s or more and 50 mPa * s or less, and it is still more desirable that they are 0.1 mPa * s or more and 20 mPa * s or less.

  The viscosity of the dispersion medium 14 can be adjusted by adjusting the molecular weight, structure, composition, and the like of the dispersion medium. In addition, the Tokyo Keiki B-8L type | mold viscosity meter is used for the measurement of this viscosity.

  The reflecting member 26 has optical reflection characteristics different from those of the aggregated particles 28 and has holes through which the aggregated particles 28 pass.

  The holes provided in the reflecting member 26 are at least holes extending in the direction of the electric field gradient formed in the display element 12. In the present embodiment, the surface electrode 32 and the back electrode 38 form the display substrate 20. The holes are at least formed in the electric field gradient direction formed between the rear substrate 22 and the substrate, that is, the direction in which the display substrate 20 and the rear substrate 22 face each other. The holes of the reflecting member 26 are configured such that at least particles constituting the agglomerated particles 28 move from one of the display substrate 20 and the back substrate 22 to the other substrate side through the holes. ing.

  The reflection member 26 has “an optical reflection characteristic different from that of the aggregated particles 28” means that the dispersion medium 14 in which a plurality of aggregated particles 28 are dispersed and the reflection member 26 in which the dispersion medium 14 is permeated into the holes. This means that there is a difference that can distinguish the difference between the two in terms of hue, brightness, freshness, and the like.

  The reflecting member 26 preferably has a function of shielding the aggregated particles 28. Here, “concealment” in the present embodiment means a case where the transmittance is 50% or less with respect to visible light.

  For this reason, when the aggregated particles 28 are closer to the display substrate 20 than the reflecting member 26, the color of the aggregated particles 28 is different. When the aggregated particles 28 are closer to the rear substrate 22 than the reflecting member 26, the color of the reflecting member 26 is increased. Is displayed on the display element 12.

The color of the reflecting member 26 is preferably white because the display can be performed with a white background, the whiteness is preferably 30% or more, and particularly preferably 40% or more.
The whiteness is a measure of whiteness, and is specifically a value measured using a Hunter whiteness meter or an X-rite colorimeter according to the method described in JIS-P8123.

  As described above, the shape of the reflecting member 26 is not particularly limited as long as it has holes through which the aggregated particles 28 move and has optical reflection characteristics different from the aggregated particles 28. Titanium oxide, zinc oxide Such as inorganic material particles composed of materials such as, and organic material particles composed of materials such as methyl methacrylate resin, styrene acrylic resin, silicone resin, and polytetrafluoroethylene resin. Alternatively, a resin sheet or a non-woven fabric may be used.

  The reflective member 26 is sealed between the substrates by, for example, an ink jet method. When the reflecting member 26 is fixed, for example, after the reflecting member 26 is sealed, the particle gap is maintained by heating (and pressing if necessary) to melt the particle group surface layer of the reflecting member 26. To be done.

  As described above, the aggregated particles 28 are aggregates in which two types of particles having charging characteristics of opposite polarities are electrostatically combined, and these two types of particles are dispersed in the dispersion medium 14. It behaves as one without it. Further, when the aggregated particles 28 are aggregates in which two types of particles having oppositely charged characteristics are electrostatically combined as described above, the aggregated particles 28 as a whole have a positive or negative charge characteristic. is doing. In the present embodiment, the charging characteristics indicate the charging polarity of the particles.

  For example, as shown in FIG. 2, the agglomerated particles 28 are configured to include one or more positive electrode particles 28A having positive electrode charging characteristics and one or more negative electrode particles 28B having negative electrode charging characteristics. These are electrostatically coupled. Each aggregated particle 28 dispersed in the dispersion medium 14 has a ratio between the positive electrode particles 28A and the negative electrode particles 28B constituting each aggregated particle 28 and these ratios, even after repeated display on the display element 12. It exists stably to the extent that there is no change in the configuration such as the number of.

  In the example shown in FIG. 2, the agglomerated particles 28 have one positive electrode particle 28A having a positive electrode charging characteristic, a negative electrode charging characteristic, and the same charge amount as the absolute value of the charge amount of the positive electrode particle 28A. The negative electrode particles 28B are composed of two pieces. For this reason, the aggregated particles 28 are in a state of exhibiting the negative electrode charging characteristics.

  The charge amount of each of the positive electrode particles 28A and the negative electrode particles 28B constituting the aggregated particles 28, and the number and ratio of the positive electrode particles 28A and the negative electrode particles 28B included in the aggregated particles 28 are determined by the positive electrode particles 28A and the negative electrode particles 28B. It is determined according to the electrostatic bonding force generated between the particles, and even when repeated display is performed in the dispersion medium 14, it is stable to the extent that there is no change in the particle configuration between the aggregated particles 28. Any configuration exists. For this reason, it is not restricted to the form aggregated by the one-to-two relationship (one positive electrode particle 28A and two negative electrode particles 28B) which are demonstrated by this Embodiment.

  Note that the size of the positive electrode particles 28A and the negative electrode particles 28B constituting the aggregated particles 28 may be the same or different for each polarity particle.

  The color of the positive electrode particles 28A and the negative electrode particles 28B constituting the aggregated particles 28 may be a combination in which the color when the aggregated particles 28 are different from the color of the reflecting member 26, and may be the same color. Although different colors may be used, the same color is desirable from the viewpoint of increasing the color purity of display.

  In addition, about the manufacturing method of this aggregated particle 28, it is demonstrated collectively at the end of description of each embodiment mentioned later.

  In order to fix the display substrate 20 and the back substrate 22 through the gap member 24, fixing means such as a combination of bolts and nuts, a clamp, a clip, and a frame for fixing the substrate can be used. In addition, fixing means such as an adhesive, heat melting, and ultrasonic bonding are also used.

  The display element 12 is a bulletin board capable of storing and rewriting images, a circulation version, an electronic blackboard, an advertisement, a signboard, a flashing sign, an electronic paper, an electronic newspaper, an electronic book, and a document sheet shared with a copier / printer. used.

  Specifically, the display of a desired image on the display element 12 is realized by configuring the display element 12 in the display device 10.

  For example, as shown in FIG. 1, the display device 10 includes the display element 12 and the writing device 17 described above. The writing device 17 includes a voltage application unit 16 and a control unit 18.

  The voltage application unit 16 is electrically connected to the front electrode 32 and the back electrode 38. The voltage application unit 16 is connected to the control unit 18 so as to be able to exchange signals.

The control unit 18 stores in advance various programs such as a CPU (Central Processing Unit) that controls the operation of the entire apparatus, a RAM (Random Access Memory) that temporarily stores various data, and a control program that controls the entire apparatus. And a ROM (Read Only Memory).
The voltage application unit 16 is a voltage application device for applying a voltage to the surface electrode 32 and the back electrode 38, and applies a voltage according to the control of the control unit 18 between the surface electrode 32 and the back electrode 38.

  When a voltage for forming an electric field for causing the aggregated particles 28 to move to the display substrate 20 side is applied from the voltage application unit 16 to the front electrode 32 and the back electrode 38 by the control of the control unit 18. The agglomerated particles 28 are electrophoresed to the display substrate 20 side.

  As shown in FIG. 3, when the particles constituting the aggregated particles 28 that have been electrophoresed on the display substrate 20 reach the opposing surface of the back substrate 22 of the display substrate 20, the particles deform into a shape along the opposing surface. This is because the positive electrode particles 28A and the negative electrode particles 28B constituting the agglomerated particles 28 are in an electrostatically coupled state, so that the impact when reaching the opposing surface, the display substrate 20 and the back substrate 22 This is considered to be easily deformed by the force of pressing on the display substrate 20 side by the electric field formed between the substrates.

  In addition, under the control of the control unit 18, a voltage is applied from the voltage application unit 16 to the surface electrode 32 and the back electrode 38 to form an electric field for causing the aggregated particles 28 to move to the back substrate 22 side between the substrates. Then, the aggregated particles 28 are electrophoresed to the back substrate 22 side.

  The agglomerated particles 28 that have reached the surface of the back substrate 22 facing the display substrate 20 are deformed into a shape along the surface of the opposite surface in the same manner as when reaching the display substrate 20.

  As described above, in the display element 12 of the present embodiment, the aggregated particles 28 composed of the positive electrode particles 28A having the positive electrode charging characteristics and the negative electrode particles 28B having the negative electrode charging polarity are used as the dispersion medium. 14 is used as a particle to be electrophoresed. For this reason, the aggregated particles 28 that have reached the facing surface of one of the display substrate 20 and the back substrate 22 and the other are deformed into a shape along the facing surface.

  On the other hand, as shown in FIG. 4 showing an example of the conventional configuration, even if the particles 29 configured as a single particle having the same average particle diameter as the aggregated particles 28 reach the facing surface, this particle Since 29 remains spherical and is not composed of a plurality of particles combined by electrostatic force like the aggregated particles 28, it is considered that the degree of deformation is lower than that of the aggregated particles 28.

  For this reason, in the display element 12 of the present embodiment, as shown in FIG. 4, the particles 29 composed of single particles that are non-aggregated particles are either one of the display substrate 20 and the back substrate 22. The aggregated particles 28 are present in a region closer to the interface between the opposing surface and the dispersion medium 14 than when the opposing surface is reached. For this reason, the density of particles in the vicinity of the electrode is larger in the aggregated particles 28 than in the particles 29, and the dispersion medium 14 in the region closer to the interface between the facing surface and the dispersion medium 14 uses the particles 29. Compared to the case, the case where the aggregated particles 28 are used is more efficiently excluded from the region, or the volume of the dispersion medium 14 existing between the particles is less when the aggregated particles 28 are used.

  Therefore, when the aggregated particles 28 are used as the particles to be electrophoresed, it can be said that the displayed image is preferably retained as compared with the case where the particles to be electrophoresed are configured as a single particle 29.

Further, since the aggregated particles 28 are composed of the positive electrode particles 28A having the positive electrode charging characteristics and the negative electrode particles 28B having the negative electrode charging characteristics, the aggregated particles 28 gather on the surface of the display substrate 20 facing the back substrate 22. It is considered that the electrostatic repulsive force between the adjacent aggregated particles 28 is smaller than that when the aggregated particles 28 are configured as a single particle.
For this reason, when the aggregated particles 28 are used as the electrophoretic particles, it can be said that the displayed image is retained as compared with the case where the electrophoretic particles are configured as the single particles 29.

(Second Embodiment)
In the first embodiment, the case where the aggregated particles 28 are dispersed in the dispersion medium 14 as the electrophoretic particles in the display element 12 has been described. However, in the present embodiment, the dispersion medium 14 includes Next, the case where the aggregated particles 28 and the particles 42 (see FIG. 5) that are different in color and charged with opposite polarity are dispersed will be described.

  Hereinafter, parts having the same configurations and functions as those of the display device 10 and the display element 12 described in the first embodiment are given the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 5, the display device 10 according to the present embodiment includes a display element 12 </ b> A, a voltage application unit 16 that applies a voltage to the display element 12 </ b> A, and a control unit 18.

  The display element 12 </ b> A includes a display substrate 20, a back substrate 22, a gap member 24, aggregated particles 28, and particles 42. In addition, although the case where the display element 12A of this Embodiment is a structure which does not include the reflection member 26 is demonstrated, the structure by which the reflection member 26 was provided similarly to the display element 12 demonstrated in 1st Embodiment. It may be.

  The display substrate 20 has a configuration in which a surface electrode 32 and a surface layer 34 are sequentially stacked on a support substrate 30. The back substrate 22 has a structure in which a back electrode 38 and a surface layer 34 are sequentially laminated on a support substrate 36. In the present embodiment, a component of the display element 12A that does not include the surface electrode 32 on the display substrate 20 and does not include the back electrode 38 on the back substrate 22 is referred to as a display medium 13A.

  As described above, the display element 12A of the present embodiment has a configuration in which the particles 42 are dispersed in the dispersion medium 14 together with the aggregated particles 28 described in the first embodiment.

  As described in the first embodiment, the agglomerated particles 28 are agglomerates in which two types of particles having charging characteristics of opposite polarities are electrostatically combined, and these two types of particles are used as a dispersion medium. 14 behave as one unit without being dispersed. Further, the aggregated particles 28 as a whole have a positive or negative charge characteristic.

  In the present embodiment, the two types of particles (positive electrode particle 28A and negative electrode particle 28B) constituting the aggregated particle 28 are the same color particles, that is, particles having the same optical reflection characteristics.

  On the other hand, the particles 42 dispersed in the dispersion medium 14 have a charging property having a reverse polarity with respect to the aggregated particles 28. The particle 42 is composed of a single particle. The particles 42 are adjusted in advance so as to have a color different from that of the aggregated particles 28, that is, have different optical reflection characteristics. Specifically, the particles 42 have a different color from the aggregated particles 28.

  Assuming that the particles 42 are particles exhibiting positive electrode charging characteristics as shown in FIG. 6, the negative electrode particles 28 </ b> B having a polarity opposite to that of the particles 42 among the positive electrode particles 28 </ b> A and the negative electrode particles 28 </ b> B constituting the aggregated particles 28. The charge amount is adjusted so as to form aggregates with the positive electrode particles 28A preferentially compared with the particles 42, and to exist stably (without being dispersed) in the dispersion medium 14 as the formed aggregates. Has been.

  Similarly, when the particle 42 is a particle exhibiting the charging characteristics of the negative electrode, the positive electrode particle 28A having a polarity opposite to that of the particle 42 among the positive electrode particle 28A and the negative electrode particle 28B constituting the aggregated particle 28 is the particle 42. The charge amount is adjusted so that the negative electrode particles 28B and aggregates are preferentially formed, and the aggregates thus formed are present stably (without being dispersed) in the dispersion medium 14.

  The amount of charge and polarity of each particle (positive electrode particle 28A, negative electrode particle 28B, particle 42) are adjusted by adjusting the amount and type of magnetic component added in the manufacturing method of positive electrode particle 28A, negative electrode particle 28B, and particle 42 described later. , And is adjusted depending on the material constituting each particle.

  In the dispersion medium 14, the method of adjusting the charge amount so that the positive electrode particles 28 </ b> A and the negative electrode particles 28 </ b> B preferentially form aggregates compared to the particles 42 has, for example, one of the following two relationships. Thus, the charge amount of each particle may be adjusted in advance.

  Specifically, the absolute value of the charge amount per one type of particles showing the charging characteristics opposite in polarity to the particles 42 among the positive electrode particles 28A and the negative electrode particles 28B constituting the aggregated particles 28 is It is larger than the absolute value of the charge amount per particle of the kind (the same polarity as the particle 42) and the absolute value of the charge amount per particle of the second particle, and the other kind (the same polarity as the particle 42). What is necessary is just to adjust beforehand that the absolute value of the charge amount per particle of the particle is larger than the absolute value of the charge amount per particle 42.

  For example, as shown in FIG. 6, it is assumed that the particles 42 are charged to the positive electrode, the charge amount of the positive electrode particles 28A constituting the aggregated particles 28 is + M (positive electrode), and the charge amount of the negative electrode particles 28B is −M (negative electrode). ) And the charge amount of the particles 42 is + C (positive electrode), the relationship between these charge amounts may be adjusted in advance so as to satisfy the relationship | -M |> | + M |> | + C |.

  Further, for example, assuming that the particles 42 are charged on the negative electrode, the charge amount of the positive electrode particles 28A constituting the aggregated particles 28 is + M (positive electrode), the charge amount of the negative electrode particles 28B is −M (negative electrode), and the particles 42 If the charge amount is + C (positive electrode), the relationship between these charge amounts may be adjusted in advance so as to satisfy the relationship | + M |> | −M |> | −C |.

As another method, specifically, charging is performed per one type of particles having the same polarity as the particles 42 among the positive particles 28A and the negative particles 28B constituting the aggregated particles 28. The absolute value of the amount is smaller than the sum of the absolute values of the charge amount of the other type (the polarity opposite to that of the particles 42) of the aggregated particles 28;
The absolute value of the charge amount per one type of particles having the same polarity as the particles 42 among the positive electrode particles 28A and the negative electrode particles 28B constituting the aggregated particles 28 is the other type (particles). The absolute value of the charge amount per particle having a polarity opposite to that of the particle 42 and the absolute value of the charge amount per particle 42 may be adjusted in advance.

  For example, as shown in FIG. 8, it is assumed that the particles 42 are charged to the positive electrode, the charge amount of the positive electrode particles 28A constituting the aggregated particles 28 is + M (positive electrode), and the charge amount of the negative electrode particles 28B is −M (negative electrode). ) And the charge amount of the particles 42 is + C (positive electrode). Assume that the aggregated particles 28 are aggregates of one positive electrode particle 28A and n negative electrode particles 28B (n = 2 in FIG. 8). In this case, the relationship between these charge amounts satisfies the relationship of | + M |> | −M |> | + C | and satisfies the relationship of (| −M | × n)> | + M | in advance. Adjust it.

  As described above, the charge amount of the positive electrode particles 28A and the negative electrode particles 28B constituting the aggregated particles 28 dispersed in the dispersion medium 14 and the charge amount and polarity of the particles 42 are adjusted. Of the two types of positive electrode particles 28A and negative electrode particles 28B, one type of particle having the same polarity as the particle 42 is preferentially compared with the other type of particles (with a polarity opposite to that of the particle 42). Aggregates are formed and exist stably in the dispersion medium 14 (without being dispersed) as aggregates formed.

  In the display element 12A of the present embodiment, similarly to the display element 12 described in the first embodiment, the control unit 18 controls the aggregated particles from the voltage application unit 16 to the surface electrode 32 and the back electrode 38. When a voltage is applied to form an electric field for causing the electrophores 28 to move toward the display substrate 20 between the substrates, the aggregated particles 28 are electrophoresed to the display substrate 20 side and are charged with a polarity opposite to that of the aggregated particles 28. The particles 42 having electrophorese to the back substrate 22 side.

  As shown in FIG. 7, when the particles constituting the aggregated particles 28 that have been electrophoresed on the display substrate 20 reach the facing surface of the back substrate 22 of the display substrate 20, they are deformed along the facing surface. This is because the positive electrode particles 28A and the negative electrode particles 28B constituting the agglomerated particles 28 are in an electrostatically coupled state, so that the impact when reaching the opposing surface, the display substrate 20 and the back substrate 22 This is considered to be easily deformed by the force of pressing on the display substrate 20 side by the electric field formed between the substrates. For this reason, it can be said that the displayed image is favorably retained as compared with the case where the aggregated particles 28 are configured as single particles.

  Further, the positive electrode particles 28A and the negative electrode particles 28B constituting the aggregated particles 28 form aggregates with the other type of particles (opposite the polarity of the particles 42) preferentially as compared with the particles 42, and the aggregates thus formed are formed. It exists stably (without being dispersed) in the dispersion medium 14 as a collection. Therefore, compared to the case where two kinds of particles having different colors and polarities are used as the particles to be electrophoresed, between the particles of different colors (between the aggregated particles 28 and the particles 42 in the present embodiment), It is considered that the attracting action is suppressed, and the occurrence of color mixing due to aggregation of particles of different colors is suppressed.

  In addition, under the control of the control unit 18, a voltage is applied from the voltage application unit 16 to the surface electrode 32 and the back electrode 38 to form an electric field for causing the aggregated particles 28 to move to the back substrate 22 side between the substrates. Then, the aggregated particles 28 are electrophoresed to the back substrate 22 side, and the particles 42 are electrophoresed to the display substrate 20 side.

  When the particles constituting the aggregated particles 28 that have been electrophoresed on the back substrate 22 reach the facing surface of the display substrate 20 of the back substrate 22, the particles deform into a shape along the facing surface. This is because the positive electrode particles 28A and the negative electrode particles 28B constituting the agglomerated particles 28 are in an electrostatically coupled state, so that the impact when reaching the opposing surface, the display substrate 20 and the back substrate 22 This is considered to be easily deformed by the force of pressing on the back substrate 22 side by the electric field formed between the substrates. For this reason, it can be said that the displayed image is favorably retained as compared with the case where the electrophoretic particles are configured as single particles.

  Further, the positive electrode particles 28A and the negative electrode particles 28B constituting the aggregated particles 28 form aggregates with the other type of particles (opposite the polarity of the particles 42) preferentially as compared with the particles 42, and the aggregates thus formed are formed. It exists stably (without being dispersed) in the dispersion medium 14 as a collection. Therefore, compared to the case where two kinds of particles having different colors and polarities are used as the particles to be electrophoresed, between the particles of different colors (between the aggregated particles 28 and the particles 42 in the present embodiment), It is considered that the attracting action is suppressed, and the occurrence of color mixing due to aggregation of particles of different colors is suppressed.

  In the present embodiment, as the particles to be electrophoresed, the aggregated particles 28 and the particles 42 that are different in color from the aggregated particles 28 and are charged with the opposite polarity are dispersed in the dispersion medium 14. Although the case has been described, both the aggregated particles 28 and the particles 42 may be aggregates composed of two types of particles having charging characteristics of opposite polarities.

  In this case, as shown in FIG. 9, the aggregated particles 28 are composed of the positive electrode particles 28A and the negative electrode particles 28B, and are composed of the positive electrode particles 42A and the negative electrode particles 42B. The agglomerated particles 42 having different particle sizes may be dispersed in the dispersion medium 14 as electrophoretic particles.

  As shown in FIG. 9, the agglomerated particles 42 include one or a plurality of positive electrode particles 42A having a positive electrode charging characteristic, one or a plurality of negative electrode particles 42B having a negative electrode charging characteristic, And these are electrostatically coupled. Each aggregated particle 42 dispersed in the dispersion medium 14 has a ratio between the positive electrode particle 42A and the negative electrode particle 42B constituting each aggregated particle 42 and these ratios, even after the display is repeatedly performed on the display element 12A. It exists stably to the extent that there is no change in the configuration such as the number of.

  Then, the positive electrode particles 42A and the negative electrode particles 42B constituting the agglomerated particles 42 are aggregated together to form an agglomerate, and the formed agglomerates are formed in the same manner as the positive electrode particles 28A and the negative electrode particles 28B that constitute the agglomerated particles 28. The charge amount may be adjusted in advance so as to be present stably (without being dispersed) in the dispersion medium 14 as an aggregate.

  As described above, as the two types of electrophoretic particles having different polarities dispersed in the dispersion medium 14, the aggregated particles 28 and the aggregated particles 42 having different colors and polarities are used for the aggregated particles 28. When any of the aggregated particles 28 and the aggregated particles 42 is electrophoresed to the display substrate 20 side or the back substrate 22 side, the aggregated particles are formed on the opposing surfaces of the display substrate 20 and the back substrate 22. Each of 28 and the agglomerated particles 42 is deformed into a shape along the facing surface. For this reason, it can be said that the displayed image is preferably held as compared with the case where either one or both of the aggregated particles 28 and the aggregated particles 42 are configured as single particles.

Further, the positive electrode particles 28A and the negative electrode particles 28B constituting the aggregated particles 28 exist stably (without being dispersed) in the dispersion medium 14 as aggregates. Further, the positive electrode particles 42A and the negative electrode particles 42B constituting the aggregated particles 42 are present stably (without being dispersed) in the dispersion medium 14 as aggregates.
For this reason, compared with the case where two types of single particles having different colors and polarities are used as the particles to be electrophoresed, the particles attract each other between the particles of different colors, that is, between the aggregated particles 28 and the aggregated particles 42. It is considered that color mixing due to aggregation of particles of different colors is suppressed.

(Production method of particles)
In the first embodiment and the second embodiment, the positive particles 28A and the negative particles 28B constituting the aggregated particles 28 used as the electrophoretic particles, the particles 42, and the aggregated particles composed of the particles 42 as aggregates The respective adjustment methods of the positive electrode particles 42A and the negative electrode particles 42B constituting 42 will be described.

  Examples of the positive electrode particles 28A, the negative electrode particles 28B, the particles 42, the positive electrode particles 42A, and the negative electrode particles 42B (hereinafter collectively referred to as “particles”) include glass beads, alumina, and titanium oxide. Insulating metal oxide particles such as thermoplastic or thermosetting resin particles, those having a colorant fixed on the surface of these resin particles, particles containing a colorant in a thermoplastic or thermosetting resin, etc. Is mentioned.

  Examples of the thermoplastic resin used in the production of particles include styrenes such as styrene and chlorostyrene, monoolefins such as ethylene, propylene, butylene, and isoprene, vinyls such as vinyl acetate, vinyl propionate, vinyl benzoate, and vinyl butyrate. Α-methylene aliphatic monocarboxylic acid such as ester, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate Homopolymers or copolymers of vinyl ethers such as acid esters, vinyl methyl ether, vinyl ethyl ether, vinyl butyl ether, vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, vinyl isopropenyl ketone It is exemplified.

  In addition, as thermosetting resins used for the production of particles, crosslinked resins mainly composed of divinylbenzene and crosslinked resins such as crosslinked polymethyl methacrylate, phenol resins, urea resins, melamine resins, polyester resins, silicones Examples thereof include resins. Particularly representative binder resins include polystyrene, styrene-alkyl acrylate copolymer, styrene-alkyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer. Examples of the polymer include polyethylene, polypropylene, polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, and paraffin wax.

  As the colorant, organic or inorganic pigments, oil-soluble dyes, etc. can be used, magnetic powders such as magnetite and ferrite, carbon black, titanium oxide, magnesium oxide, zinc oxide, phthalocyanine copper-based cyan colorant, Known colorants such as an azo yellow color material, an azo magenta color material, a quinacridone magenta color material, a red color material, a green color material, and a blue color material can be used. Specifically, aniline blue, calcoil blue, chrome yellow, ultramarine blue, DuPont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, lamp black, rose bengal, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 57: 1, C.I. I. Pigment yellow 97, C.I. Blue 15: 1, C.I. I. Pigment Blue 15: 3, etc. are exemplified as typical examples.

  The particle resin may be mixed with a charge control agent, if necessary. As the charge control agent, known materials used for toner materials for electrophotography are used. For example, cetylpyridyl chloride, BONTRON P-51, BONTRON P-53, BONTRON E-84, BONTRON E-81 (above, Quaternary ammonium salts such as Orient Chemical Industry Co., Ltd., salicylic acid metal complexes, phenol condensates, tetraphenyl compounds, metal oxide particles, and metal oxide particles surface-treated with various coupling agents.

  An external additive may be attached to the surface of the particles as necessary. The color of the external additive is desirably transparent so as not to affect the color of the particles. As the external additive, inorganic particles such as metal oxides such as silicon oxide (silica), titanium oxide, and alumina are used. In order to adjust the charging property, fluidity, and environment dependency of the particles, they may be surface-treated with a coupling agent or silicone oil.

  Any conventionally known method may be used as a method for producing the particles. For example, as described in JP-A-7-325434, a resin, a pigment, and a charge control agent are weighed to a predetermined mixing ratio, and after the resin is heated and melted, the pigment is added, mixed, dispersed, and cooled. After that, a method is used in which particles are prepared using a pulverizer such as a jet mill, a hammer mill, a turbo mill, and the obtained particles are then dispersed in a dispersion medium. Also, particles containing a charge control agent are prepared by polymerization methods such as suspension polymerization, emulsion polymerization, dispersion polymerization, coacervation, melt dispersion, emulsion aggregation, and then dispersed in a dispersion medium. A particle dispersion medium may be produced. Furthermore, the resin, the colorant, the charge control agent and the dispersion medium can be plasticized, the dispersion medium does not boil, and the temperature is lower than the decomposition point of the resin, the charge control agent and / or the colorant. There is a method using an appropriate apparatus capable of dispersing and kneading the raw materials. Specifically, the pigment, the resin, and the charge control agent are heated and melted in a dispersion medium with a meteor mixer, a kneader, etc., and the molten mixture is cooled with stirring using the temperature dependence of the solvent solubility of the resin. Solidify / precipitate to produce particles.

  Furthermore, the raw materials described above are put into a suitable container equipped with granular media for dispersion and kneading, such as a heated vibration mill such as an attritor or a heated ball mill, and the container is placed in a desired temperature range, for example 80 A method of dispersing and kneading at a temperature of from 0 ° C. to 160 ° C. is used. As granular media, steels such as stainless steel and carbon steel, alumina, zirconia, silica and the like are desirably used. In order to produce particles by this method, the raw material that has been previously fluidized is further dispersed in a container by means of granular media, and then the dispersion medium is cooled to precipitate a resin containing a colorant from the dispersion medium. The granular media generates a shear and / or impact to reduce the particle size while maintaining a motion state during and after cooling.

  Using each of the particles (positive electrode particles 28A, negative electrode particles 28B, particles 42, positive electrode particles 42A, and negative electrode particles 42B), the aggregated particles 28 and the aggregates used in the first and second embodiments are used. The charge amount and polarity of the particles 42 are easily adjusted, for example, by adjusting the charge control agent contained in the particles, the amount of magnetic material added, the type of material used, and the like.

  As a method for forming the aggregated particles 28 and the aggregated particles 42 using each of these particles, as described above, in the aggregated particles 28, the desired positive electrode particles 28 </ b> A and the negative electrode particles 28 </ b> B have the same dispersion medium. The charge amount may be adjusted so as to form an aggregate in preference to other particles (for example, the particles 42 and the aggregated particles 42) that are planned to be included in 14 or included therein. Similarly, the desired positive electrode particle 42A and negative electrode particle 42B form aggregates in preference to the other particles (for example, the aggregated particles 28) contained in the same dispersion medium 14. The charge amount may be adjusted so as to achieve this.

  When configured as a display medium in the dispersion medium 14, aggregated particles 28 of the positive electrode particles 28 </ b> A and the negative electrode particles 28 </ b> B in the same cell (region surrounded by the display substrate 20, the back substrate 22, and the gap member 24). In addition, when the aggregated particles 28 and the particles 42 are used as electrophoretic particles by dispersing the particles 42 that are single particles, one of the two methods described in the second embodiment is used. The charge amount of each particle may be adjusted in advance so as to have a relationship, and the aggregated particles 28 and the particles 42 may be dispersed in the dispersion medium 14 in the same cell.

For example, as shown in FIG. 10, the positive electrode particles 28 </ b> A and the negative electrode particles 28 </ b> B are prepared as particles constituting the particles 42 charged to the positive electrode and the aggregated particles 28 having a color different from that of the particles 42.
Assuming that particles charged to the negative electrode are used as the particles 42, the charge amount of the positive electrode particles 28A constituting the aggregated particles 28 is + M (positive electrode), the charge amount of the negative electrode particles 28B is −M (negative electrode), When the amount is + C (positive electrode), the charge amount may be adjusted in advance at the time of producing each particle so that the relationship between the charge amounts satisfies the relationship | -M |> | + M |> | + C |.

  And the particle | grains 42 and the negative electrode particle | grains 28B of the opposite polarity to this particle | grain 42 are disperse | distributed in the dispersion medium 14, as shown in FIG. 10, and positive electrode particle | grains 28A are added here. In the dispersion medium 14 in which the particles 42 and the negative electrode particles 28 </ b> B are dispersed, a pair of electrodes 50 and 52 are provided at an interval, and the electrodes 50 and 52 are interposed between the electrodes 50 and 52. And positive and negative voltages are applied alternately. Specifically, a process of applying a voltage with the electrode 50 side as a positive electrode, the electrode 52 side as a negative electrode, and then applying a voltage with the electrode 50 side as a negative electrode and the electrode 52 side as a positive electrode is defined as one step. Repeat several times (ie apply AC voltage). As a result, an electric field that causes the negative electrode particles 28 </ b> B, the positive electrode particles 28 </ b> A, and the particles 42 to reciprocate between the electrodes 50 and 52 is formed in the dispersion medium 14.

  By this treatment, among the negative electrode particles 28B, the positive electrode particles 28A, and the particles 42 dispersed in the dispersion medium 14, the positive electrode particles 28A and the negative electrode particles 28B are preferentially electrostatically bonded and bonded. The number of particles grows to such an extent that it is difficult to incorporate other positive electrode particles 28A or negative electrode particles 28B into the aggregate (see FIG. 11). As a result, even if a voltage is further applied to the dispersion medium 14, the ratio of the positive electrode particles 28A and the negative electrode particles 28B constituting each aggregated particle 28 and the number and the like thereof are stably present to the extent that there is no change. It is assumed that

  Through the above steps, the particles 42 and the aggregated particles 28 of the positive electrode particles 28A and the negative electrode particles 28B are dispersed in the dispersion medium 14, and the aggregated particles 28 are adjusted.

  In addition, when the aggregated particles 28 are formed in the dispersion medium 14, the dispersion is performed in order to prevent the cathode particles 28 </ b> A or the anode particles 28 </ b> B that have not been taken in as the aggregated particles 28 from remaining in the dispersion medium 14. The addition amount of the particles 42, the negative electrode particles 28B and the positive electrode particles 28A added to the medium 14, and the charge amounts of the respective particles 42, the negative electrode particles 28B and the positive electrode particles 28A are expressed by the above formula (| −M |> | + M |> |). Adjustment may be made within a range satisfying the relationship of + C |).

  In the case where the particles 42 charged to the negative electrode are used as the particles 42, for example, it is assumed that the particles 42 are charged to the negative electrode, the charge amount of the positive electrode particles 28A constituting the aggregated particles 28 is + M (positive electrode), When the charge amount of the particle 28B is −M (negative electrode) and the charge amount of the particle 42 is + C (positive electrode), the relationship between these charge amounts is expressed by the above formula (| −M |> | + M |> | + C |). In the same manner, except that particles whose charge amount and polarity are adjusted in advance so as to satisfy the above formula (| + M |> | −M |> | −C |) are used, the negative electrode is charged in the dispersion medium 14. The dispersed state of the particles 42 and the aggregated particles 28 charged on the positive electrode may be adjusted.

Further, for example, the absolute value of the charge amount per one type of particles having the same polarity as that of the particles 42 among the positive electrode particles 28A and the negative electrode particles 28B constituting the aggregated particles 28 is the aggregated particle. Smaller than the sum of absolute values of the charge amount of the other type in 28,
The absolute value of the charge amount per one type of particles having the same polarity as the particles 42 among the positive electrode particles 28A and the negative electrode particles 28B constituting the aggregated particles 28 is the other type of particles. The dispersion medium 14 in which the agglomerated particles 28 and the particles 42 are dispersed is adjusted in advance so that the absolute value of the charge amount per particle and the absolute value of the charge amount per particle 42 are larger. Also good.

In this case, for example, as shown in FIG. 12, it is assumed that the particle 42 is charged to the positive electrode, the charge amount of the positive particle 28A constituting the aggregated particle 28 is + M (positive electrode), and the charge amount of the negative electrode particle 28B. Is −M (negative electrode), and the charge amount of the particles 42 is + C (positive electrode). Further, the aggregated particles 28 are adjusted so as to be aggregates of one positive electrode particle 28A and n negative electrode particles 28B.
In this case, the relationship between these charge amounts satisfies the relationship of | + M |> | −M |> | + C | and satisfies the relationship of (| −M | × n)> | + M | The charge amount of each particle (particle 42, positive electrode particle 28A, and negative electrode particle 28B) is adjusted in advance.

  And the particle | grains 42 and the negative electrode particle | grains 28B of reverse polarity to this particle | grain 42 are disperse | distributed in the dispersion medium 14, as shown in FIG. 12, and positive electrode particle | grains 28A are added here. In the dispersion medium 14 in which the particles 42 and the negative electrode particles 28 </ b> B are dispersed, a pair of electrodes 50 and 52 are provided at an interval, and the electrodes 50 and 52 are interposed between the electrodes 50 and 52. And positive and negative voltages are applied alternately. Specifically, a process of applying a voltage with the electrode 50 side as a positive electrode, the electrode 52 side as a negative electrode, and then applying a voltage with the electrode 50 side as a negative electrode and the electrode 52 side as a positive electrode is defined as one step. Repeat several times. As a result, an electric field that causes the negative electrode particles 28 </ b> B, the positive electrode particles 28 </ b> A, and the particles 42 to reciprocate between the electrodes 50 and 52 is formed in the dispersion medium 14.

  By this treatment, among the negative electrode particles 28B, the positive electrode particles 28A, and the particles 42 dispersed in the dispersion medium 14, the positive electrode particles 28A and the negative electrode particles 28B are preferentially electrostatically bonded and bonded. The number of particles grows to such an extent that it is difficult to incorporate other positive electrode particles 28A or negative electrode particles 28B into the aggregate (see FIG. 13). As a result, even when a voltage is further applied to the dispersion medium 14, the ratio (1 to n) of the positive electrode particles 28A and the negative electrode particles 28B constituting each aggregated particle 28, the number of these, and the like are not changed. In a stable state.

  Through the above steps, the particles 42 and the aggregated particles 28 of the positive electrode particles 28A and the negative electrode particles 28B are dispersed in the dispersion medium 14, and the aggregated particles 28 are adjusted.

  As shown in FIGS. 1 and 2, when only the aggregated particles 28 are dispersed as the electrophoretic particles in the dispersion medium 14, for example, the dispersion medium is dispersed in the dispersion medium 14. 14, the above-described AC electric field is formed, so that it is more electrostatic when two types of particles having different polarities are aggregated than when particles (positive electrode particles 28A, negative electrode particles 28B) are present alone. The positive electrode particles 28 </ b> A and the negative electrode particles 28 </ b> B may be used so as to be in a stable state. The electrostatic stable state may be adjusted, for example, by the charge amount, charge amount ratio, average particle size, addition amount, and addition amount ratio of the positive electrode particles 28A and the negative electrode particles 28B.

  Similarly to the above, even if the positive electrode particles 28A and the negative electrode particles 28B are dispersed in the dispersion medium 14, an AC electric field is formed in the dispersion medium 14, and a voltage is applied to the dispersion medium 14. The formation of the alternating electric field may be continued until the ratio of the positive electrode particles 28A and the negative electrode particles 28B constituting each aggregated particle 28, the number thereof, and the like are stably present to the extent that there is no change. Thus, the aggregated particles 28 of the positive electrode particles 28A and the negative electrode particles 28B may be adjusted.

  Further, as shown in FIG. 9, in order to adjust the dispersed state of the aggregated particles 28 charged on the positive electrode and the aggregated particles 42 charged on the negative electrode in the dispersion medium 14, for example, the dispersion medium 14 First, the aggregated particles 28 of the positive electrode particles 28A and the negative electrode particles 28B are adjusted using the above method. Further, the aggregated particles 42 of the positive electrode particles 42 </ b> A and the negative electrode particles 42 </ b> B are adjusted in the separately prepared dispersion medium 14 using the above method. Then, the charge amount and polarity of each particle (the positive electrode particle 28A, the negative electrode particle 28B, the positive electrode particle 42A, and the negative electrode particle 42B) are set in advance so that the polarities of the aggregated particles 28 and the aggregated particles 42 to be adjusted are opposite to each other. If the charge amount is adjusted in advance so that each of the aggregated particles 28 and the aggregated particles 42 is formed as each of the aggregated particles 28 and the aggregated particles 42 so that each of the aggregated particles 28 and the aggregated particles 42 is present as a stable aggregate without mixing. Good.

  Then, by mixing the adjusted aggregated particles 28 and aggregated particles 42, the state where the aggregated particles 28 and aggregated particles 42 having opposite polarities and different colors are dispersed in the dispersion medium 14 can be adjusted. Good.

  In order to confirm the operation of the above embodiment, the following tests were performed. In the following examples, “part” and “%” represent “part by mass” and “% by mass”, respectively.

(Example A1)
―Adjustment of aggregated particles―
As electrophoretic particles, aggregated particles of cyan particles A charged on the positive electrode, magenta particles B charged on the positive electrode, and cyan particles C charged on the negative electrode were prepared. Although details are shown below, the ratio of the absolute value of the charge amount per particle of these particles was cyan particle A: magenta particle B: cyan particle C = 3: 1: 2. In addition, the aggregated particles prepared in Example A1 consist of cyan particles A charged on the positive electrode, magenta particles B charged on the positive electrode, and cyan particles C charged on the negative electrode in a mass ratio of 1: 4: 5. And mixed.

-Adjustment of cyan particle C-
--Preparation of reactive silicone polymer C--
Silaplane FM-0711 (manufactured by Chisso) which is a silicone monomer: 95 parts by mass and 5 parts by mass of glycidyl dimethacrylate are mixed with 100 parts by mass of silicone oil (KF-96L-2CS, manufactured by Shin-Etsu Silicone), and a polymerization initiator. Azobisvaleronitrile (manufactured by Wako Pure Chemical Co., Ltd .: V-65) was added in an amount of 0.2 parts by weight, and polymerization was carried out at 55 ° C. for 10 hours to give a reactive silicone polymer C having an epoxy group (reactivity) Dispersant) was prepared. The weight average molecular weight was 800,000. And the 3 mass% silicone oil solution of the reactive silicone polymer C was prepared.

--Preparation of particle dispersion for display--
Next, a 10% by mass aqueous solution of polymethacrylic acid (manufactured by Wako Pure Chemical Industries, Ltd .: weight average molecular weight 50,000) as a polymer having a charged group was prepared. Next, 1 part by mass of a water-dispersed pigment solution made by Ciba (Unisperse cyan color: pigment concentration 26% by mass), 3 parts by mass of the 10% by mass aqueous solution of polymethacrylic acid and a stoichiometric amount for neutralizing the same. Triethylamine is mixed, and this mixed solution is mixed with 10 parts by mass of the 3% by mass silicone resin of the above reactive silicone polymer C. The mixture is stirred with an ultrasonic crusher (UH-600S manufactured by SMT Co., Ltd.) A suspension was prepared by dispersing and emulsifying an aqueous solution containing a polymer having high molecular weight and a pigment in silicone oil.

  Next, the suspension was decompressed (2 KPa) and heated (70 ° C.) for 1 hour to remove moisture, and cyan colored particles containing a polymer having a charged group and a pigment were dispersed in silicone oil. A silicone oil dispersion was obtained. Further, this dispersion was heated at 100 ° C. for 3 hours to cause the reactive silicone polymer C to react with and bind to the surface of the colored particles. In this state, the unbonded reactive silicone polymer C coexists in the solution, and an epoxy polymerization catalyst is used to form a polymer gel layer using the unbonded reactive silicone polymer. And 0.2 g of triethylamine was added and heated at 100 ° C. for 3 hours. After the reaction, the particles were settled using a centrifugal separator and purified by repeating washing with silicone oil.

  Further, the concentration was adjusted with silicone oil to prepare a 5 mass% cyan particle C dispersion (cyan).

It was 380 nm as a result of measuring the volume average particle diameter of the display particles of the produced display particle dispersion (Holiba LA-300: laser light scattering / diffraction particle size measuring device).
After a part of the display particles of the display particle dispersion was centrifuged and settled, methanol was added to dissolve and wash the colored particles, and the residue was optically analyzed. As a result, a polymer gel was produced. From the amount, it was found that the polymer gel layer was formed at 30% by mass with respect to the colored particles.
The charging polarity of the display particles in this display particle dispersion was negatively charged as a result of enclosing the dispersion between two electrode substrates and applying a DC voltage to evaluate the migration direction.

When the charge amount of the adjusted cyan particle C was determined by measuring the electrophoretic current value and converting it by the number of particles, the average charge amount per particle was −1.0 × 10 ⁻⁷ (C / Piece).

-Adjustment of cyan particle A-
For the cyan particle C charged with the negative electrode and having an average particle size of 380 nm and an average charge amount per particle of 1 × 10 ⁻⁷ (C / piece), the absolute value of the charge amount is 3 A cyan particle A which shows an absolute value of the charge amount of 2 times and which is charged on the positive electrode was prepared.

  As a polymer having a charged group, a copolymer (weight average molecular weight 60,000) having a mass ratio of N-vinylpyrrolidone and N, N-diethylaminoethyl methacrylate of 8/2 was synthesized by ordinary radical solution polymerization. Further, this resin was added with an equimolar amount or more of ethyl iodide with respect to the amino group in isopropanol, and heated at 80 ° C. for 1 hour to quaternize the amino group and purified again as a solid.

  As a method for adjusting the cyan particles A, a 5 mass% cyan color particle A dispersion (cyan color) was prepared using the same method as the cyan particles A except that the present resin was used as the charging resin for the cyan particles C. Produced.

It was 380 nm as a result of measuring the volume average particle diameter of the display particles of the produced display particle dispersion (Holiba LA-300: laser light scattering / diffraction particle size measuring device).
After a part of the display particles of the display particle dispersion was centrifuged and settled, methanol was added to dissolve and wash the colored particles, and the residue was optically analyzed. As a result, a polymer gel was produced. From the amount, it was found that the polymer gel layer was formed at 30% by mass with respect to the colored particles.
The charging polarity of the display particles in this display particle dispersion was positively charged as a result of encapsulating the dispersion between two electrode substrates and applying a DC voltage to evaluate the migration direction.

When the charge amount of the adjusted cyan particle C was determined by measuring the electrophoretic current value and converting it by the number of particles, the average charge amount per particle was 1.6 × 10 ⁻⁷ (C / ).

-Adjustment of magenta particle B-
-Preparation of polymer with charged group-
A 9/1 copolymer (weight average molecular weight 60,000) in weight ratio of N-vinylpyrrolidone and N, N-diethylaminoethyl methacrylate was synthesized by ordinary radical solution polymerization. Furthermore, in this isopropanol solution of the copolymer (polymer), an equimolar amount or more of ethyl iodide is added to the amino group of the copolymer (polymer) and heated at 80 ° C. for 1 hour. The copolymer was purified after quaternization of the amino group. This was a polymer having a charged group.

  5% by mass of magenta particle B dispersion in the same manner as cyan particle C, except that Ciba water-dispersed pigment solution (Unisperse / magenta color: pigment concentration of 16% by mass) was used together with the polymer having the charged group. Was made.

It was 350 nm as a result of measuring the volume average particle diameter of the produced magenta particles B (Holiba LA-300: laser light scattering / diffraction particle size measuring device).
Further, the charged polarity of the prepared magenta particles B was positively charged as a result of evaluating the migration direction by enclosing the dispersion liquid between two electrode substrates and applying a DC voltage.
The charge amount of the adjusted magenta particle B was determined by measuring the electrophoretic current value and converting it by the number of particles. As a result, the average charge amount per particle was 0.5 × 10 ⁻⁷ (C / ).

  Therefore, the ratio of the absolute value of the charge amount per particle of each of the adjusted cyan particles A (positive electrode), magenta particles B (positive electrode), and cyan particles C (negative electrode) is as follows: cyan particle A: magenta Particle B: Cyan particle C = 3: 1: 2.

-Adjustment of reflection member-
As the reflecting member, the following titanium oxide-containing particles (average particle diameter: 14 μm) were prepared.

-Preparation of dispersion AA-
The following components were mixed and ball milling was performed for 20 hours with 10 mmφ zirconia balls to prepare dispersion AA.
<Composition>
・ Cyclohexyl methacrylate: 53 parts by mass. Titanium oxide 1 (white pigment) (primary particle size 0.3 μm, Type CR63: manufactured by Ishihara Sangyo Co., Ltd.): 45 parts by mass. Cyclohexane: 5 parts by mass.

-Preparation of charcoal dispersion AB-
The following components were mixed, and finely pulverized with a ball mill in the same manner as above to prepare a charcoal dispersion AB.
<Composition>
-Calcium carbonate: 40 parts by mass-Water: 60 parts by mass

-Preparation of mixture AC-
The following components were mixed, degassed with an ultrasonic machine for 10 minutes, and then stirred with an emulsifier to prepare a mixed liquid AC.
<Composition>
-2% by mass aqueous serogen solution (2% by mass aqueous solution of serogen 5A manufactured by Daiichi Pharmaceutical Co., Ltd.)
Charcoal cal dispersion AB: 8.5g
・ 20% saline: 50 g

  35 g of dispersion AA, 1 g of divinylbenzene, and polymerization initiator AIBN: 0.35 g were weighed and mixed well, and deaeration was performed for 10 minutes with an ultrasonic machine. This was added to the mixed solution AC and emulsified with an emulsifier. Next, this emulsified liquid was put into a bottle, put into a silicone bottle, used with an injection needle, sufficiently degassed under reduced pressure, and sealed with nitrogen gas. Next, it was reacted at 65 ° C. for 15 hours to prepare particles. After cooling, cyclohexane was removed from the dispersion with a freeze dryer at −35 ° C. and 0.1 Pa for 2 days. The obtained particle powder was dispersed in ion-exchanged water, calcium carbonate was decomposed with hydrochloric acid water, and filtered. Thereafter, it was washed with sufficient distilled water, and passed through a nylon sieve having openings of 14 μm and 25 μm to make the particle sizes uniform. This was dried to obtain a group of white particles having an average particle diameter of 14.5 μm. This was made into the reflective member which consists of a some white particle.

  A display element shown in FIG. 1 was produced using the produced cyan particles A, magenta particles B, cyan particles C, and a reflecting member.

-Fabrication of display elements-
As the display substrate, a transparent conductive ITO supporting substrate of 70 mm × 50 mm × 1.1 mm (thickness) was used. Further, as the back substrate, a transparent conductive ITO supporting substrate of 70 mm × 50 mm × 1.1 mm (thickness) was used. The ITO electrodes provided on these substrates were so-called solid electrodes provided over the entire region in the surface direction of the substrate.

  Next, a gap member was provided on the back substrate and formed to have a height of 100 μm.

  The gap member was formed by applying an epoxy resin (SU-8 manufactured by MicroChem Corp.) to the back substrate 22 and then performing exposure and wet etching. The gap member had a size of 20 mm × 20 mm, a height of 10 μm, and a width of 2 mm.

  The cyan particle A dispersion, the magenta particle B dispersion, and the cyan particle C dispersion adjusted as described above are mixed at a 1: 4: 4 ratio, and the adjusted white particles as the reflecting member are mixed with dimethyl. Silicone oil (a dispersion obtained by adding 10% by mass of KF-96L 2cs made by Shin-Etsu Silicone Co., Ltd. to 100% by mass is filled on the back substrate on which the above-mentioned gap member is formed. Each partitioned area) was filled with a dispersion of mixed particles.

  The reflecting member is a mixture of the white particles adjusted as the reflecting member in the above ratio, so that the aggregated particles adjusted in the subsequent process can pass along the direction orthogonal to the opposing direction of the display substrate and the back substrate. The white particles as the reflecting member were arranged with a small gap, and the distance between the reflecting member and the display substrate and the back substrate was set in the cell so as to be substantially equal.

  In this cell in which the cyan particle A dispersion, the magenta particle B dispersion, and the cyan particle C dispersion are dispersed, ITO electrodes are immersed facing each other at intervals of 1 mm, and a rectangular wave AC voltage of ± 300 V and 0.1 Hz. Was applied for 10 minutes. As a result, it was confirmed that aggregated particles in which cyan particles A, magenta particles B, and cyan particles C dispersed in a dispersion medium (silicone oil) were almost all aggregated were produced. Aggregation of all particles was confirmed by the absence of particles migrating on the display surface when a reverse voltage was applied. The color of the aggregated particles was cyan and was charged on the positive electrode.

  Further, the display substrate was placed on the gap member, and the periphery was sealed and fixed with an ultraviolet curable adhesive (manufactured by Norland), and then irradiated with ultraviolet rays. Thus, a display element was produced.

(Evaluation)
When a voltage of 12 V was applied to both electrodes for 60 seconds so that the electrode on the display substrate side of the display element produced in Example A1 was a negative electrode and the electrode on the back substrate side was a positive electrode, the cyan color in the display element was The movement of the aggregated particles to the display substrate side was confirmed.
Then, immediately after applying a voltage of 12 V to both electrodes for 60 seconds so that the electrode on the display substrate side becomes a negative electrode and the electrode on the back substrate side becomes a positive electrode, and after 24 hours have passed since the voltage application was released. In both cases, the concentration is measured with a densitometer (X-Rite 404A, manufactured by X-Rite) at 10 points including the end and center of the entire area of the surface of the display substrate. Mean values were compared. As a result, the decrease in the average concentration value was 3% or less immediately after voltage application and after 24 hours.

(Example A2)
―Adjustment of aggregated particles―
As electrophoretic particles, aggregated particles of magenta particles D charged on the positive electrode, magenta particles E charged on the positive electrode, and magenta particles F charged on the negative electrode were prepared. Although details are shown below, the ratio of the absolute value of the charge amount per particle of these particles was magenta particle D: magenta particle E: magenta particle F = 3: 1: 2. In addition, the aggregated particles prepared in Example A2 have a weight ratio of 1: 4: 2 between magenta particles D charged on the positive electrode, magenta particles E charged on the positive electrode, and magenta particles F charged on the negative electrode. And mixed.

-Adjustment of magenta particle D-
-Fabrication of polymers with charged groups-
A copolymer (weight average molecular weight 60,000) having a mass ratio of N-vinylpyrrolidone and N, N-diethylaminoethyl methacrylate of 7/3 was synthesized by ordinary radical solution polymerization. Furthermore, in this isopropanol solution of the copolymer (polymer), an equimolar amount or more of ethyl iodide is added to the amino group of the copolymer (polymer) and heated at 80 ° C. for 1 hour. The copolymer was purified after quaternization of the amino group. This was a polymer having a charged group.

  5% by mass of magenta particle D dispersion in the same manner as cyan particle C, except that Ciba water-dispersed pigment solution (Unisperse / magenta color: pigment concentration: 16% by mass) was used together with the polymer having the charged group. Was made.

It was 350 nm as a result of measuring the volume average particle diameter of the produced magenta particle D (Holiba LA-300: laser light scattering / diffraction particle size measuring device).
Further, the charged polarity of the prepared magenta particles B was positively charged as a result of evaluating the migration direction by enclosing the dispersion liquid between two electrode substrates and applying a DC voltage.
When the charge amount of the adjusted magenta particle D was determined by measuring the electrophoretic current value and converting it by the number of particles, the average charge amount per particle was 2.1 × 10 ⁻⁷ (C / Piece).

-Adjustment of magenta particle E-
A 5% by mass magenta particle E dispersion was prepared in the same manner as the magenta particle D, except that the mass ratio of N-vinylpyrrolidone and N, N-diethylaminoethyl methacrylate was 9/1 in the production of the magenta particle D. Was made.

It was 350 nm as a result of measuring the volume average particle diameter of the produced magenta particle E (Holiba LA-300: laser light scattering / diffraction particle size measuring device).
Further, the charged polarity of the adjusted magenta particle E was positively charged as a result of enclosing the dispersion liquid between two electrode substrates and applying a DC voltage to evaluate the migration direction.
When the charge amount of the adjusted magenta particle E was determined by measuring the electrophoretic current value and converting it by the number of particles, the average charge amount per particle was 0.5 × 10 ⁻⁷ (C / Piece).

-Adjustment of magenta particle F-
--Preparation of reactive silicone polymer A--
First, Silaplane FM-0711 (manufactured by Chisso), which is a silicone monomer, is mixed with 95 parts by mass and 5 parts by mass of glycidyl methacrylate with 100 parts by mass of dimethyl silicone oil (KF-96L 2cs, manufactured by Shin-Etsu Silicone). Reactive silicone polymer having an epoxy group by adding 0.5 part by mass of azobisvaleronitrile (manufactured by Wako Pure Chemicals: V-65) as a polymerization initiator and performing polymerization at 55 ° C. for 10 hours. A (reactive dispersant) was prepared. The weight average molecular weight was 800,000. And the 3 mass% silicone oil solution of the reactive silicone type polymer A was prepared by diluting with dimethyl silicone oil (KF-96L 2cs by Shin-Etsu Silicone Co., Ltd.).

--Preparation of particle dispersion for display--
Next, a commercially available product (manufactured by Wako Pure Chemical Industries, Ltd.) as a polymer having a charging group was prepared as a 10% by mass aqueous solution of polymethacrylic acid (weight average molecular weight 50,000). Next, 3 parts by mass of the polymethacrylic acid 10% by mass aqueous solution and 0.36 parts by mass of triethylamine were mixed with 1 part by mass of Ciba water-dispersed pigment solution (Unisperse / magenta color: pigment concentration 16% by mass). The solution is mixed with 10 parts by mass of a 3% by mass silicone oil solution of the above reactive silicone polymer A, and this is stirred for 10 minutes with an ultrasonic crusher (UH-600S manufactured by SMT Co., Ltd.). In addition, a suspension was prepared by dispersing and emulsifying an aqueous solution containing the pigment and the pigment in silicone oil.

  Next, this suspension was reduced in pressure (2 KPa) and heated (70 ° C.) for 1 hour to remove moisture, and a silicone oil in which magenta particles containing a polymer having a charged group and a pigment were dispersed in silicone oil. An oil dispersion was obtained. Further, this dispersion was heated at 100 ° C. for 3 hours to cause the reactive silicone polymer A (non-crosslinked product) to react with and bind to the surface of the colored particles.

  Next, 0.2 parts by mass of triethylamine as an epoxy polymerization catalyst (crosslinking agent) is added to the silicone oil dispersion after reacting the reactive silicone polymer A with the colored particle surface, and then at 100 ° C. for 3 hours. Heating was performed to crosslink the unreacted reactive silicone polymer A remaining in the dispersion and coexisting. Thereby, a silicone polymer gel was formed, and a polymer gel layer formed thereby covered the colored particles. In this state, the unbonded silicone-based reactive dispersant C coexists in the solution, and an epoxy polymerization catalyst is used to form a polymer gel layer using the unbonded reactive silicone dispersant. Triethylamine 0.2g was added and it heated at 100 degreeC / 3 hours.

  After the reaction, the particles were settled using a centrifugal separator and purified by repeating washing with silicone oil. Further, the concentration was adjusted with silicone oil to prepare a 5 mass% magenta particle F dispersion.

It was 400 nm as a result of measuring the volume average particle diameter of the magenta particle F in the produced magenta particle F dispersion (Holiba LA-300: laser light scattering / diffraction particle size measuring device).
The charging polarity of the magenta particles F of the display particles was negatively charged as a result of enclosing the dispersion liquid between two electrode substrates and applying a DC voltage to evaluate the migration direction.
The adjusted charge quantity of the magenta particles F, measured electrophoretic current, was determined by converting it in particle number, average charge amount per one particle, -1.0 × 10 ^-7 ( C / piece).

  Therefore, the ratio of the absolute value of the charge amount per particle of the adjusted magenta particle D (positive electrode), magenta particle E (positive electrode), and magenta particle F (negative electrode) is magenta particle D: magenta. Particle E: Magenta particle F = 1: 4: 2.

  Using the magenta particle D, the magenta particle E, the magenta particle F, and the reflection member prepared in Example A1, the display element shown in FIG. 1 was manufactured.

-Fabrication of display elements-
As the display substrate, a transparent conductive ITO supporting substrate of 70 mm × 50 mm × 1.1 mm (thickness) was used. Further, as the back substrate, a transparent conductive ITO supporting substrate of 70 mm × 50 mm × 1.1 mm (thickness) was used. The ITO electrodes provided on these substrates were so-called solid electrodes provided over the entire region in the surface direction of the substrate.

  Next, a gap member was provided on the back substrate and formed to have a height of 100 μm.

  The gap member was formed by applying an epoxy resin (SU-8 manufactured by MicroChem Corp.) to the back substrate 22 and then performing exposure and wet etching. The gap member had a size of 20 mm × 20 mm, a height of 10 μm, and a width of 2 mm.

  The magenta particle D dispersion, the magenta particle E dispersion, and the magenta particle F dispersion prepared as described above are mixed at a 1: 4: 2 ratio, and the adjusted white particles as the reflecting member are mixed. A dispersion liquid in which 10% by mass of dimethyl silicone oil (KF-96L 2cs- manufactured by Shin-Etsu Silicone Co., Ltd.) is added to 100% by mass is filled on the back substrate on which the above-mentioned gap members are formed. Each region partitioned by the member was filled with a dispersion of mixed particles in the same manner as in Example A1.

  In this cell in which magenta particles D, magenta particles E, and magenta particles F are dispersed, ITO electrodes are immersed oppositely at 1 mm intervals, and a rectangular wave AC voltage of ± 300 V and 0.1 Hz is applied for 10 minutes. . As a result, it was confirmed that aggregated particles in which cyan particles D, magenta particles E, and cyan particles F dispersed in a dispersion medium (silicone oil) were almost totally aggregated were produced. Aggregation of all particles was confirmed by the absence of particles migrating on the display surface when a reverse voltage was applied. The color of the aggregated particles was magenta and charged on the positive electrode.

  Further, the display substrate was placed on the gap member, and the periphery was sealed and fixed with an ultraviolet curable adhesive (manufactured by Norland), and then irradiated with ultraviolet rays. Thus, a display element was produced.

(Evaluation)
When a voltage of 12 V was applied to both electrodes for 60 seconds so that the electrode on the display substrate side of the display element produced in Example A2 was a negative electrode and the electrode on the back substrate side was a positive electrode, the cyan color in the display element was The movement of the aggregated particles to the display substrate side was confirmed. Then, immediately after applying a voltage of 12 V to both electrodes for 60 seconds so that the electrode on the display substrate side becomes a negative electrode and the electrode on the back substrate side becomes a positive electrode, and after 24 hours have passed since the voltage application was released. In both cases, the concentration is measured with a densitometer (X-Rite 404A, manufactured by X-Rite) at 10 points including the end and center of the entire area of the surface of the display substrate. Mean values were compared. As a result, the decrease in the average concentration value was 3% or less immediately after voltage application and after 24 hours.

(Comparative Example A1)
In Comparative Example A1, only cyan particles A and magenta particles B out of cyan particles A, magenta particles B, and cyan particles C prepared in Example A1 were used, and these were mixed at a weight ratio of 1: 4. A display element was manufactured and evaluated in the same manner as in Example A1.

  Specifically, in the manufacture of the display element of Example A1, “cyan particle A dispersion, magenta particle B dispersion, and cyan particle C dispersion 1: 4: 4 filled in each cell in Example A1. The white particles as the reflective member adjusted as described above were changed to dimethyl silicone oil (a dispersion obtained by adding 10% by mass of KF-96L 2cs manufactured by Shin-Etsu Silicone Co., Ltd. to 100% by mass). The cyan particle A dispersion liquid and the magenta particle B dispersion liquid were mixed at a ratio of 1: 4, and the white particles as the reflecting member prepared in Example A1 were mixed with dimethyl silicone oil (KF-96L 2cs manufactured by Shin-Etsu Silicone Co., Ltd.). Each cell was filled with the dispersion by the same method as in Example A1 except that the dispersion was changed to “dispersion with 10% by mass added to 100% by mass”.

Next, ITO electrodes were immersed in the cells in which the cyan particles A and magenta particles B were dispersed so as to face each other at intervals of 1 mm, and a rectangular wave AC voltage of ± 300 V and 0.1 Hz was applied for 10 minutes.
However, the agglomeration of cyan particles A and magenta particles B did not occur, and no agglomerated particles were produced. It was confirmed that each particle was present as it was in the dispersion medium as it was.

(Evaluation)
When a voltage of 12 V was applied to both electrodes for 60 seconds so that the electrode on the display substrate side of the display element produced in Comparative Example A1 was a negative electrode and the electrode on the back substrate side was a positive electrode, the cyan particles in the display element were Both A and magenta particles B were confirmed to move toward the display substrate.
Then, immediately after applying a voltage of 12 V to both electrodes for 60 seconds so that the electrode on the display substrate side becomes a negative electrode and the electrode on the back substrate side becomes a positive electrode, and after 24 hours have passed since the voltage application was released. In both cases, the concentration is measured with a densitometer (X-Rite 404A, manufactured by X-Rite) at 10 points including the end and center of the entire area of the surface of the display substrate. Mean values were compared. As a result, the decrease in the average concentration value was 80% or more immediately after voltage application and after 24 hours.

(About the evaluation result about Example A1, A2, and comparative example A1)
As shown in Examples A1 and A2, when the particles to be electrophoresed are aggregated particles composed of positive electrode particles and negative electrode particles, Comparative Example A1 in which a single particle is used as the electrophoretic particles is used. In comparison, the result that the change in the average concentration value was small immediately after the particles or aggregated particles were moved to the display substrate side and after 24 hours had elapsed was obtained. For this reason, in Example A1 and A2, the result that the image was hold | maintained suitably compared with comparative example A1 was obtained.

(Example B1)
―Adjustment of aggregated particles―
As electrophoretic particles, agglomerated particles of magenta particles G charged on the negative electrode, cyan particles H charged on the positive electrode, and magenta particles I charged on the positive electrode were prepared.
Although the details are shown below, the relationship between the absolute values of the charge amount per particle of these particles shows the relationship of magenta particle G> magenta particle I> cyan particle H.
The ratio was magenta particles G: magenta particles I: cyan particles H = 10: 5: 3. In Example B1, the mass of the magenta particles G charged on the negative electrode, the cyan particles H charged on the positive electrode, and the magenta particles I charged on the positive electrode are 1: 4: 1 in the dispersion medium. The mixture was used in a% ratio.

-Adjustment of the magenta particles G charged on the negative electrode-
As the magenta particles G, the magenta particles F adjusted as described above (negatively charged −1.0 × 10 ⁻⁷ (C / particle) volume average particle diameter 400 nm) were used.

-Adjustment of magenta particles I charged on the positive electrode-
As the magenta particles I, the magenta particles E (positively charged 0.5 × 10 ⁻⁷ (C / piece) volume average particle diameter 350 nm) prepared as described above were used.

-Adjustment of cyan particles H charged on the positive electrode-
As the cyan particles H, a copolymer having a mass ratio of N-vinylpyrrolidone and N, N-diethylaminoethyl methacrylate of 9.5 / 0.5 in the above-prepared cyan particles A was prepared. Except for the above, cyan particles H were prepared by the same method as cyan particles A. The charge amount of the adjusted cyan particles H was 0.3 × 10 ⁻⁷ (C / piece), and the volume average particle diameter was 380 nm.

  A display element shown in FIG. 5 was produced using the magenta particles G, cyan particles H, magenta particles I, and the reflective member prepared in Example A1.

-Fabrication of display elements-
As the display substrate, a transparent conductive ITO supporting substrate of 70 mm × 50 mm × 1.1 mm (thickness) was used. Further, as the back substrate, a transparent conductive ITO supporting substrate of 70 mm × 50 mm × 1.1 mm (thickness) was used. The ITO electrodes provided on these substrates were so-called solid electrodes provided over the entire region in the surface direction of the substrate.

  Next, a gap member was provided on the back substrate and formed to have a height of 100 μm.

  The gap member was formed by applying an epoxy resin (SU-8 manufactured by MicroChem Corp.) to the back substrate 22 and then performing exposure and wet etching. The gap member had a size of 20 mm × 20 mm, a height of 10 μm, and a width of 2 mm.

  The magenta particle G dispersion, the magenta particle I dispersion, and the cyan particle H dispersion adjusted as described above are mixed at a volume ratio of 1: 1: 4, and the adjusted white particles as the reflecting member are mixed. Dimethyl silicone oil (a dispersion obtained by adding 10% by mass of KF-96L 2cs made by Shin-Etsu Silicone Co. to 100% by mass on the back substrate on which the above-mentioned gap member is formed is filled in each cell (gap member Each region partitioned by) was filled with a dispersion of mixed particles.

  The reflecting member is a mixture of the white particles adjusted as the reflecting member in the above ratio, so that the aggregated particles adjusted in the subsequent process can pass along the direction orthogonal to the opposing direction of the display substrate and the back substrate. The white particles as the reflecting member were arranged with a small gap, and the distance between the reflecting member and the display substrate and the back substrate was set in the cell so as to be substantially equal.

  In this cell in which magenta particles G, magenta particles I, and cyan particles H are dispersed, ITO electrodes are immersed facing each other at intervals of 1 mm, and a rectangular wave AC voltage of ± 300 V and 0.1 Hz is applied for 10 minutes. . As a result, it was confirmed that aggregated particles in which the magenta particles G and magenta particles I among the magenta particles G, magenta particles I, and cyan particles H dispersed in the dispersion medium (silicone oil) were aggregated were produced. It was done. Confirmation that the aggregates are formed from the particles G and I is that particles derived from the particle I (magenta: positively charged) are not observed on the negative electrode side, and particles derived from the particle H (cyan: positively charged) are This was done by not observing on the positive electrode side. The color of the aggregated particles was magenta and charged on the negative electrode.

  Further, the display substrate was placed on the gap member, and the periphery was sealed and fixed with an ultraviolet curable adhesive (manufactured by Norland), and then irradiated with ultraviolet rays. Thus, a display element in which the agglomerated particles of the magenta particles G and the magenta particles I and the cyan particles H were dispersed in the dispersion medium was manufactured.

(Evaluation)
When a voltage of 12 V was applied to both electrodes for 60 seconds so that the electrode on the display substrate side of the display element produced in Example B1 was a positive electrode and the electrode on the back substrate side was a negative electrode, the aggregated particles in the display element were obtained. Has been confirmed to move toward the display substrate.
Then, immediately after applying a voltage of 12V to both electrodes for 60 seconds so that the electrode on the display substrate side becomes a positive electrode and the electrode on the back substrate side becomes a negative electrode, and after 24 hours have passed since the voltage application was released In both cases, the concentration is measured with a densitometer (X-Rite 404A, manufactured by X-Rite) at 10 points including the end and center of the entire area of the surface of the display substrate. Mean values were compared. As a result, the decrease in the average concentration value was within 5% immediately after voltage application and after 24 hours.

  Next, after applying a voltage of 12V to both electrodes for 5 seconds so that the electrode on the display substrate side becomes a negative electrode and the electrode on the back substrate side becomes a positive electrode, the electrode on the display substrate side becomes the positive electrode and again on the back substrate side. The process of applying a voltage of 12V to both electrodes so that the electrodes become negative is a series of processes, and after 1000 times, both the electrodes on the display substrate side become positive and the electrodes on the back substrate become negative. A voltage of 12 V was applied to the electrodes for 60 seconds to move the aggregated particles to the display substrate side.

For the display element in which the aggregated particles are moved again to the display substrate side after the repeated display, the cyan density is measured at 10 points including the end portion and the central portion of the entire area of the surface substrate surface by a densitometer (X-Rite). X-Rite 404A) and a density average value of 97% were compared with the value before 1000 repetitions. As a result, a color density of 97% was confirmed.
For this reason, good color reproducibility was confirmed even after repeated display.

(Comparative Example B1)
―Particle adjustment―
As the electrophoretic particles, the magenta particles G charged in the negative electrode and the cyan particles H charged in the positive electrode, which were prepared in Example B1, were used.
In Comparative Example B1, magenta particles G charged on the negative electrode and cyan particles H charged on the positive electrode were mixed in a dispersion medium at a weight ratio of 1: 2.

  A display element was produced using the magenta particles G and cyan particles H produced in Example B1 and the reflective member prepared in Example A1.

-Fabrication of display elements-
As the display substrate, a transparent conductive ITO supporting substrate of 70 mm × 50 mm × 1.1 mm (thickness) was used. Further, as the back substrate, a transparent conductive ITO supporting substrate of 70 mm × 50 mm × 1.1 mm (thickness) was used. The ITO electrodes provided on these substrates were so-called solid electrodes provided over the entire region in the surface direction of the substrate.

  Next, a gap member was provided on the back substrate and formed to have a height of 100 μm.

  The gap member was formed by applying an epoxy resin (SU-8 manufactured by MicroChem Corp.) to the back substrate 22 and then performing exposure and wet etching. The gap member had a size of 20 mm × 20 mm, a height of 10 μm, and a width of 2 mm.

  The magenta particle G dispersion liquid and the cyan particle H dispersion liquid prepared as described above were mixed at a volume ratio of 1: 4, and the white particles serving as the adjusted reflective member were mixed with dimethyl silicone oil (manufactured by Shin-Etsu Silicone Co., Ltd.). Each cell (each region partitioned by the gap member) is filled with a dispersion liquid in which 10% by mass of KF-96L 2cs is added to 100% by mass on the back substrate on which the gap member is formed. Was filled with a dispersion of mixed particles.

  The reflecting member is a mixture of the white particles adjusted as the reflecting member in the above ratio, so that the aggregated particles adjusted in the subsequent process can pass along the direction orthogonal to the opposing direction of the display substrate and the back substrate. The white particles as the reflecting member were arranged with a small gap, and the distance between the reflecting member and the display substrate and the back substrate was set in the cell so as to be substantially equal.

  In this cell in which the magenta particles G and cyan particles H are dispersed, ITO electrodes are immersed facing each other at intervals of 1 mm, and a square wave AC voltage of ± 300 V and 0.1 Hz is applied for 10 minutes. However, no agglomerated particles were produced, and some of the magenta particles G and cyan particles H were agglomerated. However, the agglomeration may be canceled by repeated application of an alternating voltage. It could not be said that "particles" were produced.

  Further, the display substrate was placed on the gap member, and the periphery was sealed and fixed with an ultraviolet curable adhesive (manufactured by Norland), and then irradiated with ultraviolet rays. Thereby, a display element in which magenta particles G and cyan particles H were dispersed in a dispersion medium was produced.

(Evaluation)
When a voltage of 12 V was applied to both electrodes for 60 seconds so that the electrode on the display substrate side of the display element produced in Comparative Example B1 was a positive electrode and the electrode on the back substrate side was a negative electrode, the magenta particles G in the display element were Has been confirmed to move toward the display substrate.
Then, immediately after applying a voltage of 12 V to both electrodes for 60 seconds so that the electrode on the display substrate side becomes a positive electrode and the electrode on the back substrate side becomes a negative electrode, and after 24 hours have passed since the voltage application was released. In both cases, the concentration is measured with a densitometer (X-Rite 404A, manufactured by X-Rite) at 10 points including the end and center of the entire area of the surface of the display substrate. Mean values were compared. As a result, the decrease in the average concentration value was 80% or more immediately after voltage application and after 24 hours.

  Next, after applying a voltage of 12V to both electrodes for 5 seconds so that the electrode on the display substrate side becomes a negative electrode and the electrode on the back substrate side becomes a positive electrode, the electrode on the display substrate side becomes the positive electrode and again on the back substrate side. The process of applying a voltage of 12V to both electrodes so that the electrodes become negative is a series of processes, and after 1000 times, both the electrodes on the display substrate side become positive and the electrodes on the back substrate become negative. A voltage of 12 V was applied to the electrodes for 60 seconds to move the aggregated particles to the display substrate side.

For a display element to which a voltage is applied so that the magenta particles G are again moved to the display substrate side after this repeated display, the cyan color density is determined at 10 points including the end and center of the entire area of the surface substrate surface. It was 70% when measured with a densitometer (X-Rite 404A, manufactured by X-Rite) and the concentration average value was compared with the value before 1000 repetitions. It is considered that the color reproducibility was lowered because aggregates of particles G and H were formed during repeated driving.
For this reason, after repeated display, a decrease in color reproducibility was confirmed.

(About the evaluation result about Example B1 and Comparative Example B1)
As shown in Example B1, when the particles to be electrophoresed are composed of aggregated particles composed of positive electrode particles and negative electrode particles, and particles existing as single particles, only single particles are included. Compared to Comparative Example B1 used as electrophoretic particles, the results showed that the change in the average concentration immediately after moving the particles or aggregated particles to the display substrate side and after 24 hours was small. . For this reason, in Example B1, the result that the image was hold | maintained suitably compared with comparative example B1 was obtained.

  Furthermore, as shown in Example B1, when the particles to be electrophoresed are composed of aggregated particles composed of positive electrode particles and negative electrode particles and particles existing as single particles, single particles As compared with Comparative Example B1 using only as the electrophoretic particles, the result that the decrease in color reproducibility was suppressed even after repeated display was obtained.

1 is a schematic configuration diagram of a display medium, a display element, and a display device according to a first embodiment. It is an expansion schematic diagram of the aggregated particle concerning 1st Embodiment. It is the schematic cross section which expanded a part of display substrate concerning a 1st embodiment. It is the schematic cross section which expanded a part of display substrate which concerns on the conventional form. It is an expansion schematic diagram of the aggregated particle concerning 2nd Embodiment. It is an expansion schematic diagram which shows the aggregated particle and particle | grains which are disperse | distributed in the dispersion medium concerning 2nd Embodiment. It is the schematic cross section which expanded a part of display substrate concerning a 2nd embodiment. It is the schematic cross section which expanded a part of display substrate concerning a 2nd embodiment. It is an expansion schematic diagram which shows the aggregated particle and particle | grains which are disperse | distributed in the dispersion medium concerning 2nd Embodiment. It is a schematic diagram which shows the adjustment method of the aggregated particle which concerns on this Embodiment. It is a schematic diagram which shows the adjustment method of the aggregated particle which concerns on this Embodiment. It is a schematic diagram which shows the adjustment method of the aggregated particle which concerns on this Embodiment. It is a schematic diagram which shows the adjustment method of the aggregated particle which concerns on this Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Display apparatus 10A Display apparatus 12 Display element 12A Display element 13 Display medium 13A Display medium 16 Voltage application part 18 Control part 20 Display board 22 Back board 26 Reflective member 28 Aggregated particle 32 Surface electrode 38 Back electrode

Claims (8)

A pair of substrates at least one of which is translucent and disposed with a gap;
A dispersion medium sealed between the pair of substrates;
It is dispersed in the dispersion medium and moves in the dispersion medium according to an electric field formed between the pair of substrates, and is an aggregate of positive electrode particles and negative electrode particles. First agglomerated particles having,
A display medium comprising:   The display medium according to claim 1, wherein the positive electrode particles and the negative electrode particles constituting the first aggregated particles have the same color.   3. A second particle dispersed in the dispersion medium and having a charging property opposite to that of the first aggregated particles and having a color different from that of the first aggregated particles is provided. The display medium described in 1.   The display medium according to claim 3, wherein the second particles are aggregates of positive electrode particles and negative electrode particles. Of the positive electrode particles and the negative electrode particles constituting the first agglomerated particles, the absolute value A of the charge amount per particle having the opposite polarity to the second particles,
Among the positive electrode particles and the negative electrode particles constituting the first agglomerated particles, the absolute value B of the charge amount per particle having the same polarity as the second particle,
An absolute value C of the charge amount per one of the second particles;
The display medium according to claim 3, wherein the relationship of A>B> C. The sum D of the absolute values of the charge amount of the particles having the same polarity as the second particles out of the positive electrode particles and the negative electrode particles constituting the first aggregate particles in the first aggregate particles; ,
In the first aggregated particles, among the positive electrode particles and the negative electrode particles constituting the first aggregated particles, a total E of the absolute values of the charge amounts of the particles having the opposite polarity to the second particles; ,
Indicates a relationship of D <E,
and,
Of the positive electrode particles and the negative electrode particles constituting the first agglomerated particles, the absolute value A of the charge amount per particle having the opposite polarity to the second particles,
Among the positive electrode particles and the negative electrode particles constituting the first agglomerated particles, the absolute value B of the charge amount per particle having the same polarity as the second particle,
An absolute value C of the charge amount per one of the second particles;
The display medium according to claim 3, wherein the relationship of B>A> C. A pair of substrates at least one of which is translucent and disposed with a gap;
A dispersion medium sealed between the pair of substrates;
It is dispersed in the dispersion medium and moves in the dispersion medium according to an electric field formed between the pair of substrates, and is an aggregate of positive electrode particles and negative electrode particles. First agglomerated particles having,
A display medium comprising:
An electrode for forming an electric field between the pair of substrates of the display medium;
A display device comprising: A pair of substrates at least one of which is translucent and disposed with a gap;
A dispersion medium sealed between the pair of substrates;
It is dispersed in the dispersion medium and moves in the dispersion medium according to an electric field formed between the pair of substrates, and is an aggregate of positive electrode particles and negative electrode particles. First agglomerated particles having,
A display medium comprising:
An electrode for forming an electric field between the pair of substrates of the display medium;
A voltage applying device for applying a voltage to the electrode;
A display device comprising:

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