Electro-responsive particles, method for producing the same, and electrophoretic medium

Abstract

To provide an electric field responsive particle, its manufacturing method, and a medium for electrophoresis containing the electric field responsive particle.SOLUTION: The electric field responsive particles include carbon black, a first polymer including a functional group having a positive charge, and a linking group linking the carbon black and the first polymer. The linking group has an ester group, and the electroactive particles are positively charged in the liquid medium.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to electroresponsive particles, a method for producing the same, and an electrophoretic medium. [Background technology]

[0002] There has been a great deal of interest in preventing shoulder hacking, an attack that involves peeping from behind the operation panel of industrial equipment such as bank ATMs (Automatic Teller Machines). In recent years, the widespread use of portable devices such as laptops, smartphones, and tablets has led to an increasing demand for measures to prevent peeping from the perspective of privacy protection.

[0003] To date, several anti-spying technologies have been developed, based on viewing angle restriction technology. For example, a new method involves designing the LCD display itself, placing a switchable liquid crystal layer on top of the main LCD panel. This method allows the switchable liquid crystal layer to be switched on and off, but does not necessarily provide high shielding. On the other hand, a relatively inexpensive product is a film with light-blocking sections arranged in a microlouver pattern. This film provides excellent shielding, but it must be removed when shielding is not required. This allows the shielding function to be switched on and off, and is therefore expected to realize a privacy filter with excellent shielding.

[0004] Carbon black has excellent light-shielding properties, heat resistance, and a black color, so it is expected to be used as electrophoretic particles in privacy filters. However, carbon black alone is electrically neutral, making it difficult to demonstrate electric field responsiveness.

[0005] Carbon black dispersions play an important role in realizing privacy filters that can be switched on and off and have excellent light-blocking properties. However, carbon black dispersions have the problem that carbon black has a high tendency to aggregate and does not necessarily have high dispersion stability in various solvents. Furthermore, to impart electrophoretic properties to carbon black, the amount of charge introduced must be increased. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] Advances in Polymer Technology, 2021, 1-11 [Non-patent document 2] Journal of Materials Chemistry A, 2014,2, 16039-16050 Summary of the Invention [Problem to be solved by the invention]

[0007] As methods for introducing polymer chains onto the surface of carbon black, for example, Non-Patent Document 1 reports a method in which carbon black is coated with polydopamine and then atom transfer radical polymerization is performed, and Non-Patent Document 2 reports a method in which the carbon black surface is oxidized and then atom transfer radical polymerization is performed. However, these methods do not allow for evaluation of the electric field responsiveness of carbon black.

[0008] Thus, there is a demand for carbon black that is responsive to an electric field.

[0009] In addition to privacy filters, there is also a demand for electro-responsive particles using carbon black in devices such as electronic paper.

[0010] The present disclosure has been made in view of the above-mentioned problems, and aims to provide electroresponsive particles, a method for producing the same, and an electrophoretic medium containing the electroresponsive particles. [Means for solving the problem]

[0011] The electroactive particles according to the first embodiment of the present disclosure include: Carbon black and a first polymer comprising a functional group having a positive charge; a linking group connecting the carbon black and the first polymer; An electroactive particle comprising: the linking group has an ester group, The electroactive particles become positively charged in a liquid medium.

[0012] The electroactive particles according to the second embodiment of the present disclosure include: Carbon black and a first polymer comprising a functional group having a positive charge; a linking group connecting the carbon black and the first polymer; a second polymer layered on the first polymer and including a negatively charged functional group; An electroactive particle comprising: the linking group has an ester group, the second polymer is electrostatically adsorbed to the first polymer; The electroactive particles become negatively charged in a liquid medium.

[0013] The electroactive particles according to the third embodiment of the present disclosure include: Carbon black and a first polymer comprising a functional group having a positive charge; a linking group connecting the carbon black and the first polymer; a second polymer layered on the first polymer and including a negatively charged functional group; a third polymer layered on the second polymer and including a positively charged functional group; An electroactive particle comprising: the linking group has an ester group, the second polymer is electrostatically adsorbed to the first polymer; the third polymer is electrostatically adsorbed to the second polymer; The electroactive particles become positively charged in a liquid medium.

[0014] A method for producing electroresponsive particles according to a fourth embodiment of the present disclosure includes: A method for producing electroactive particles according to a first embodiment, comprising: a polymerization initiating group forming step of converting carboxy groups present on the surface of the carbon black into polymerization initiating groups having an ester group; a first polymer synthesis step of synthesizing a first polymer including a positively charged functional group by allowing a polymerization reaction initiated by the polymerization initiation group to proceed; Includes.

[0015] A method for producing electroresponsive particles according to a fifth embodiment of the present disclosure includes: A method for producing electroactive particles according to a second embodiment, comprising: a polymerization initiating group forming step of converting carboxy groups present on the surface of the carbon black into polymerization initiating groups having an ester group; a first polymer synthesis step of synthesizing a first polymer including a positively charged functional group by allowing a polymerization reaction initiated by the polymerization initiation group to proceed; an adsorption step of electrostatically adsorbing a second polymer including a negatively charged functional group onto the first polymer; Includes.

[0016] A method for producing electroresponsive particles according to a sixth embodiment of the present disclosure includes: A method for producing electroactive particles according to a third embodiment, comprising: a polymerization initiating group forming step of converting carboxy groups present on the surface of the carbon black into polymerization initiating groups having an ester group; a first polymer synthesis step of synthesizing a first polymer including a positively charged functional group by allowing a polymerization reaction initiated by the polymerization initiation group to proceed; an adsorption step 1 in which a second polymer including a negatively charged functional group is electrostatically adsorbed onto the first polymer; an adsorption step 2 in which a third polymer including a positively charged functional group is electrostatically adsorbed onto the second polymer; Includes.

[0017] An electrophoretic medium according to a seventh embodiment of the present disclosure comprises: Electroactive particles according to any one of the first to third embodiments; a solvent in which the electroactive particles are dispersed. [Effects of the Invention]

[0018] According to the present disclosure, it is possible to provide electroresponsive particles, a method for producing the same, and an electrophoretic medium containing the electroresponsive particles. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a diagram schematically illustrating the structure of an electroresponsive particle according to a first embodiment. [Figure 2] 1 is a diagram schematically illustrating the surface of an electroresponsive particle according to Embodiment 1. FIG. [Figure 3] FIG. 10 is a diagram schematically illustrating the structure of an electroresponsive particle according to a second embodiment. [Figure 4] FIG. 10 is a diagram schematically illustrating the surface of an electroresponsive particle according to a second embodiment. [Figure 5] FIG. 10 is a diagram schematically illustrating the structure of an electroresponsive particle according to a third embodiment. [Figure 6] FIG. 10 is a diagram schematically illustrating the surface of an electroresponsive particle according to a third embodiment. [Figure 7] FIG. 1 is a diagram schematically illustrating the structure of an active louver using an electrophoretic medium containing electroresponsive particles. [Figure 8]FIG. 1 is a diagram schematically illustrating the structure of an active louver using an electrophoretic medium containing electroresponsive particles. [Figure 9] 1 shows the electrophoresis experiment of electroactive particles, where (A1) shows the initial state, and (A2) to (A6) show the states after a predetermined time has passed. [Figure 10] 1 shows the electrophoresis experiment of electroactive particles, where (B1) shows the initial state, and (B2) to (B9) show the states after a predetermined time has passed. [Figure 11] 1 shows the electrophoresis experiment of electroactive particles, where (C1) is the initial state, and (C2) to (C9) are the states after a predetermined time has passed. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, electroresponsive particles and a method for producing the same according to the present embodiment, as well as an electrophoretic medium containing the electroresponsive particles, will be described with reference to the drawings.

[0021] [Embodiment 1] 1, an electroactive particle 10 according to this embodiment includes a core material 11 and a first layer 12 provided on the core material 11. As will be described later, the core material 11 is carbon black, and the first layer 12 is composed of a first polymer 13. Although FIG. 1 illustrates an example in which the cross-sectional shape of the electro-responsive particles 10 is circular, the shape of the electro-responsive particles 10 of this embodiment is arbitrary.

[0022] As shown schematically in Figure 2, the first polymer 13 constituting the first layer 12 is a polymer containing positively charged functional groups 14. Because the first polymer 13 contains the positively charged functional groups 14, the first layer 12 located at the outermost layer of the electroactive particles 10 is positively charged as a whole in a liquid medium, and the electric charge of the electroactive particles 10 becomes positive. This allows the electroactive particles 10 to have the property of responding to an electric field in a liquid medium. In this embodiment, electroactive particles refer to particles that migrate to one of the electrodes when a voltage is applied. As will be described later, by utilizing this property, the dispersed and aggregated states of electroactive particles in a liquid medium can be controlled by turning on and off the application of a voltage. Between the core material 11 and the first polymer 13, there is a linking group 15 that connects them. One end of the linking group 15 is covalently bonded to the core material 11, and the other end of the linking group 15 is covalently bonded to the first polymer 13. In this way, the first polymer 13 is chemically bonded to the core material 11 via the linking group 15, so that the electroresponsive particles 10 are less likely to undergo charge separation (detachment of charged components).

[0023] (Core 11) In this embodiment, carbon black is used as the core material 11. Carbon black is made of fine carbon particles. The carbon black may have any shape. Carbon black generally has a spherical particle as its smallest unit, and is known to have a complex structure formed by the adhesion of several particles. The shape of the carbon black is not limited to the spherical shape shown in this embodiment; the structure may also be oval or polygonal. Carboxy groups are present on the surface of the carbon black. As will be described later, the electroresponsive particles 10 of this embodiment can be efficiently produced by converting these carboxy groups into polymerization initiator groups.

[0024] (First Polymer 13) In this embodiment, the first polymer 13 constituting the first layer 12 is a polymer containing a positively charged functional group 14 (in the present disclosure, the positively charged functional group contained in the first polymer may be referred to as a "functional group A"). The electroactive particle 10 may contain one type of first polymer 13, or two or more types.

[0025] Examples of the functional group A include an ammonium group, a pyridinium group, a sulfonium group, and a phosphonium group. Among these, an ammonium group is preferred, and a quaternary ammonium group is more preferred, because a positively charged first layer 12 is more likely to be formed. The functional group A may interact with a counter ion to form a salt. Examples of the counter ion include a fluoride ion, a chloride ion, a bromide ion, an iodide ion, a tetrafluoroborate ion, a hexafluorophosphate ion, and a methyl sulfate ion.

[0026] The first polymer 13 may be a polymer having a repeating unit represented by the following formula (I) (hereinafter, sometimes referred to as "repeating unit (1)"). In the present disclosure, some hydrogen atoms may be omitted in chemical formulas.

[0027] [ka]

[0028] In formula (I), R 1 represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and R 2 represents a group containing functional group A.

[0029] R in formula (I) 1 Examples of the alkyl group having 1 to 5 carbon atoms represented by the formula (I) include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, and a t-butyl group. R 1 is preferably a hydrogen atom, a methyl group or an ethyl group.

[0030] R in formula (I) 2 Examples of the group containing the functional group A represented by the following formula (II) and the group represented by the following formula (III) are given.

[0031] [ka]

[0032] In formula (II), R 3 ~R 5 R each independently represents a hydrogen atom or an unsubstituted or substituted hydrocarbon group having 1 to 10 carbon atoms. 3 ~R 5 Two of the R may be bonded to each other to form a ring. 6 represents a divalent hydrocarbon group having 2 to 10 carbon atoms. A1 represents a bond to the polymer main chain. R 3 ~R 5 The unsubstituted or substituted hydrocarbon group represented by the formula (I) has 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms. R 3 ~R 5 Examples of the unsubstituted hydrocarbon group represented by the formula include alkyl groups such as methyl, ethyl, n-propyl, and isopropyl; aralkyl groups such as benzyl; and aryl groups such as phenyl and naphthyl. R 3 ~R 5 Examples of the substituent contained in the hydrocarbon group having a substituent represented by the formula: include a hydroxyl group; an alkoxy group such as a methoxy group or an ethoxy group; and a halogen atom such as a fluorine atom, a chlorine atom or a bromine atom. R 6 Examples of the divalent hydrocarbon group having 2 to 10 carbon atoms represented by the formula include an ethylene group, a 1,2-propylene group, a trimethylene group, and a tetramethylene group.

[0033] [ka]

[0034] In formula (III), R 7 represents a hydrogen atom or an unsubstituted or substituted hydrocarbon group having 1 to 10 carbon atoms. A2 represents a bond to the polymer main chain. R 7 The unsubstituted or substituted hydrocarbon group represented by the formula (I) has 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms. R 7Examples of the unsubstituted hydrocarbon group represented by the formula include alkyl groups such as methyl, ethyl, n-propyl, and isopropyl; aralkyl groups such as benzyl; and aryl groups such as phenyl and naphthyl. R 7 Examples of the substituent contained in the hydrocarbon group having a substituent represented by the formula: include a hydroxyl group; an alkoxy group such as a methoxy group or an ethoxy group; and a halogen atom such as a fluorine atom, a chlorine atom or a bromine atom.

[0035] Preferred repeating units (1) of the first polymer 13 include repeating units represented by the following formulae (Ia) to (Id): In these repeating units, Me represents a methyl group, and Et represents an ethyl group.

[0036] [ka]

[0037] The first polymer 13 may contain one type of repeating unit (1), or may contain two or more types.

[0038] The first polymer 13 may contain a repeating unit other than the repeating unit (1) (hereinafter, this may be referred to as "repeating unit (2)"). By introducing the repeating unit (2) into the first polymer 13, it may be possible to adjust the amount of surface charge of the electroresponsive particles 10.

[0039] Examples of the repeating unit (2) include a repeating unit derived from a polyfunctional monomer (a monomer having two or more polymerizable groups) and a repeating unit derived from a monofunctional monomer (a monomer having one polymerizable group) (excluding the repeating unit (1)). Examples of polyfunctional monomers include ester compounds of polyhydric alcohols and (meth)acrylic acid, such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, and dipentaerythritol hexa(meth)acrylate, as well as divinylbenzene. Examples of monofunctional monomers that provide the repeating unit (2) include methyl (meth)acrylate, ethyl (meth)acrylate, and styrene. In the present disclosure, (meth)acrylate means acrylate or methacrylate.

[0040] The content of the repeating unit (1) is preferably 70 to 100 mol %, more preferably 80 to 100 mol %, and even more preferably 90 to 100 mol %, of the total amount of the repeating unit (1) and the repeating unit (2).

[0041] The degree of polymerization of the first polymer 13 is preferably 10-1,000, and more preferably 20-500. When the degree of polymerization of the first polymer 13 is within the above range, it becomes easier to obtain electroactive particles 10 that contain a large number of functional groups A and have a sufficient positive charge.

[0042] The first polymer 13 can be efficiently synthesized by a living radical polymerization reaction such as an atom transfer radical polymerization reaction, as will be described later. For example, a first polymer 13 obtained by atom transfer radical polymerization reaction and having only the repeating unit (1) as the repeating unit is represented by the following formula (IV).

[0043] [ka]

[0044] In formula (IV), X represents a halogen atom such as a chlorine atom or a bromine atom, RU(1) represents the repeating unit (1), A3 represents a bond to the linking group 15, and m represents the degree of polymerization.

[0045] The amount of the first polymer 13 contained in the electroactive particles 10 is not particularly limited, but for example, the amount of the first polymer 13 is preferably 5% by weight or more, more preferably 10% by weight or more, and even more preferably 15% by weight or more, relative to the weight of the carbon black. As the amount of the first polymer 13 contained in the electroactive particles 10 increases, the electroactive particles 10 contain more functional groups A and have a sufficient positive charge. Such electroactive particles 10 have excellent electric field responsiveness. There is no particular upper limit to the amount of the first polymer 13, but it is, for example, 25% by weight or less relative to the weight of the carbon black. The amount of the first polymer 13 can be determined, for example, by thermal gravimetric analysis (TGA).

[0046] (linking group 15) In this embodiment, the linking group 15 is a group that connects the core material 11 and the first polymer 13. The linking group 15 has an ester group. Usually, a carboxy group is present on the surface of the core material 11 (carbon black), and by utilizing this carboxy group, the ester group can be efficiently generated. As will be described later, when producing the electro-responsive particles 10, the carboxy groups present on the surface of the carbon black are converted into polymerization initiating groups containing halogen atoms, and then when the first polymer 13 is synthesized using these polymerization initiating groups as a starting point, the group with the structure obtained by removing the halogen atom from the polymerization initiating group becomes the linking group 15. Since the electroactive particles 10 have the linking groups 15, the first polymer 13 is chemically fixed to the surface of the core material 11. Therefore, the electroactive particles 10 are less likely to experience charge separation.

[0047] Examples of the linking group 15 include groups represented by the following formula (V).

[0048] [ka]

[0049] In formula (V), R 8 , R 9 each independently represents a hydrogen atom or an unsubstituted or substituted hydrocarbon group having 1 to 10 carbon atoms; R 10 represents a divalent hydrocarbon group having 2 to 10 carbon atoms. n represents an integer of 1 to 5. When n is 2 or more, multiple R 10 A4 represents a bond to the carbon black surface, and A5 represents a bond to the first polymer 13.

[0050] R 8 , R 9 The unsubstituted or substituted hydrocarbon group represented by the formula (I) has 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms. R 8 , R 9 Examples of the unsubstituted hydrocarbon group represented by the formula include alkyl groups such as methyl, ethyl, n-propyl, and isopropyl; aralkyl groups such as benzyl; and aryl groups such as phenyl and naphthyl. R 8 , R 9 Examples of the substituent contained in the hydrocarbon group having a substituent represented by the formula: include a hydroxyl group; an alkoxy group such as a methoxy group or an ethoxy group; and a halogen atom such as a fluorine atom, a chlorine atom or a bromine atom. R 10 Examples of the divalent hydrocarbon group having 2 to 10 carbon atoms represented by the formula include an ethylene group, a 1,2-propylene group, a trimethylene group, and a tetramethylene group. n is an integer of 1 to 5, preferably 1 or 2, and more preferably 1.

[0051] A preferred example of the linking group 15 is a group represented by the following formula (Va): In this repeating unit, Me represents a methyl group, and A4 and A5 have the same meanings as above.

[0052] [ka]

[0053] (Electroresponsive particles 10) The electroactive particles 10 according to this embodiment are positively charged in a liquid medium and exhibit electroactive properties. For example, when a voltage is applied to the electroactive particles 10 dispersed in a liquid medium, the particles 10 move toward the negative electrode and aggregate.

[0054] The average particle size of the electro-responsive particles 10 is preferably 10 μm or less, more preferably 1 μm or less, even more preferably 500 nm or less, and particularly preferably 100 nm or less. Electro-responsive particles 10 with an average particle size of 10 μm or less have excellent dispersion stability in a liquid medium. Furthermore, the average particle size of the electro-responsive particles 10 is preferably 1 nm or more, more preferably 5 nm or more, and even more preferably 10 nm or more. Electro-responsive particles 10 with an average particle size of 1 nm or more have excellent productivity. The polydispersity index (PDI) of the electroactive particles 10 is preferably 0.3 or less. The polydispersity index (PDI) is an index that indicates the spread of particle size distribution. A dispersion (electrophoretic medium) of electroactive particles 10 with a small polydispersity index (PDI) contains electroactive particles 10 that exhibit approximately the same electric field responsiveness, and is therefore suitable for use as the electrophoretic medium for high-performance active louvers. The average particle size and polydispersity index of the electroactive particles 10 are measured in a liquid medium by dynamic light scattering. An example of a dynamic light scattering measurement device is the nanoSAQLA (manufactured by Otsuka Electronics Co., Ltd.), which is equipped with a semiconductor laser (70 mW) as a light source and a photocounting avalanche photodiode (APD) as a detector.

[0055] The electroresponsive particles 10 preferably have a CV (Coefficient of Variation) value of 40% or less, more preferably 35% or less, even more preferably 25% or less, and particularly preferably 10% or less. The CV value is the coefficient of variation obtained by dividing the standard deviation based on the scattering intensity distribution in a dynamic light scattering method by the average particle diameter and multiplying the result by 100. A dispersion of electroresponsive particles 10 with a CV value of 40% or less has excellent light-blocking properties in a dispersed state and is resistant to aggregation.

[0056] The zeta potential of the electroactive particles 10 is preferably 5 mV or more, more preferably 10 mV or more. There is no particular upper limit to the zeta potential of the electroactive particles 10, but it is usually 20 mV or less. Electroactive particles 10 with a zeta potential of 5 mV or more have sufficient electroactive properties.

[0057] (Method for manufacturing electroresponsive particles 10) The method for producing the electroactive particles 10 is not particularly limited. The electroactive particles 10 can be produced efficiently by utilizing carboxy groups on the surface of the carbon black. The carboxy groups may be those originally present on the surface of the carbon black, or may be newly generated on the surface of the carbon black through an oxidation reaction. The oxidation reaction can be carried out using a known method. For example, carboxy groups can be formed on the surface of the carbon black by oxidizing the surface of the carbon black using sulfuric acid and potassium permanganate.

[0058] In one example of a method for producing the electroresponsive particles 10, first, the carboxy groups present on the surface of the carbon black are converted into polymerization initiating groups having an ester group (hereinafter, the "polymerization initiating groups having an ester group" may be referred to as polymerization initiating groups Y). The method for converting the carboxy groups present on the carbon black surface into polymerization initiating groups Y is not particularly limited. For example, the carboxy groups present on the carbon black surface can be converted into acyl chloride groups (—COCl), and then the acyl chloride groups can be reacted with hydroxyl groups to form polymerization initiating groups Y on the carbon black surface.

[0059] For example, when an atom transfer radical polymerization reaction is used to synthesize the first polymer 13, the carboxyl groups present on the surface of the carbon black can be converted into polymerization initiation groups Y by carrying out the reaction shown in the following scheme.

[0060] [ka]

[0061] In the above scheme, R 8 ~R 10 , n, and A4 have the same meanings as above. X represents a halogen atom. Examples of the halogen atom include a chlorine atom and a bromine atom.

[0062] After the carboxy groups present on the surface of the carbon black are converted into polymerization initiation groups Y, a polymerization reaction is carried out starting from the polymerization initiation groups Y formed on the surface of the carbon black, and a first polymer 13 is synthesized. The degree of polymerization of the first polymer 13 can be efficiently determined by using a polymerization initiation group-containing compound that is not bonded to carbon black (hereinafter referred to as "polymerization initiation group-containing compound F"). For example, the polymerization initiation group-containing compound F is a compound represented by the following formula (wherein R 8 ~R 10 , X, and n have the same meanings as above.) and the first polymer 13 is synthesized in a state where the polymerization initiation group-containing compound F is present in the reaction system.

[0063] [ka]

[0064] In this case, a polymerization reaction initiated by the polymerization initiating group Y formed on the surface of the carbon black and a polymerization reaction initiated by the polymerization initiating group of the polymerization initiating group-containing compound F proceed simultaneously in the reaction system. Therefore, the degree of polymerization of the first polymer 13 can be determined by examining the degree of polymerization of the polymer generated from the polymerization initiating group-containing compound F using techniques such as gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR).

[0065] The polymerization reaction initiated by the polymerization initiating group Y is preferably a living radical polymerization reaction. Examples of living radical polymerization reactions include nitroxide-mediated radical polymerization (NMP), atom transfer radical polymerization (ATRP), reversible addition fragmentation chain transfer polymerization (RAFT), etc. Among these, atom transfer radical polymerization is preferred because it is relatively easy to control the degree of polymerization of the first polymer 13.

[0066] Examples of transition metal complexes used in atom transfer radical polymerization reactions include complexes containing a transition metal such as ruthenium, iron, nickel, or copper as a central metal and 2,2'-bipyridine, N,N,N',N",N"-pentamethyldiethylenetriamine, tris(2-pyridylmethyl)amine, tris[2-(N,N-dimethylamino)ethyl]amine, or derivatives thereof as a ligand.

[0067] The first polymer 13 can be synthesized by a method of performing a polymerization reaction using a monomer containing a functional group A, or a method of performing a polymerization reaction using a monomer containing a functional group that can be converted into functional group A by a chemical reaction (hereinafter, sometimes referred to as "functional group A'"), and then converting functional group A' into functional group A. In either method, the monomers can be used alone or in combination of two or more.

[0068] Furthermore, as described above, when synthesizing the first polymer 13, in addition to the monomer containing the functional group A or the monomer containing the functional group A', a polyfunctional monomer such as ethylene glycol di(meth)acrylate or a monofunctional monomer such as methyl (meth)acrylate may be used in combination.

[0069] When a polymerization reaction is carried out using a monomer containing a functional group A, examples of the monomer containing the functional group A include N,N-dimethyl-N-alkyl-N-2-(meth)acryloyloxyethylammonium bromide, N,N-diethyl-N-alkyl-N-2-(meth)acryloyloxyethylammonium bromide, N-alkyl-vinylpyridinium chloride, (meth)acryloyloxyphenyldimethylsulfonium methylsulfate, and (4-vinylbenzyl)trialkylphosphonium chloride.

[0070] When a polymerization reaction is carried out using a monomer containing a functional group A', examples of the monomer containing the functional group A' include (meth)acrylate monomers such as 2-(N,N-dimethylamino)ethyl (meth)acrylate, 2-(N,N-diethylamino)ethyl (meth)acrylate, 3-(N,N-dimethylamino)propyl (meth)acrylate, 3-(N,N-diethylamino)propyl (meth)acrylate, and 2-aminoethyl (meth)acrylate, as well as vinylpyridine.

[0071] A method using an alkyl halide can be used as a method for converting the functional group A' to the functional group A. Specifically, the functional group A' such as an amino group can be converted to the functional group A such as an ammonium group using an alkyl halide. Examples of alkyl halides include chloromethane, bromomethane, iodomethane, chloroethane, bromoethane, iodoethane, chloropropane, bromopropane, iodopropane, chlorobutane, bromobutane, and iodobutane. Among these, alkyl halides having 1 to 2 carbon atoms are preferred, and iodomethane is more preferred, since they can efficiently convert functional group A' to functional group A.

[0072] Among these, the method of synthesizing the first polymer 13 is preferably a method of synthesizing a polymer containing an amino group using a monomer containing an amino group, and then converting the amino group to an ammonium group, and more preferably a method of synthesizing a polymer containing a tertiary amino group using a monomer containing a tertiary amino group, and then converting the tertiary amino group to a quaternary ammonium group.

[0073] As a solvent for the polymerization reaction and the reaction for converting the functional group A' to the functional group A, a solvent that does not adversely affect the reaction, disperses carbon black, and dissolves components other than carbon black is preferably used. The solvent can be appropriately selected from among water; alcoholic solvents such as methanol; ketone solvents such as acetone; ester solvents such as ethyl acetate; ether solvents such as tetrahydrofuran; amide solvents such as N,N-dimethylformamide; and aromatic solvents such as toluene, depending on the purpose.

[0074] [Embodiment 2] The electro-responsive particle 20 according to this embodiment will be described with reference to Figures 3 and 4. The electro-responsive particle 20 according to embodiment 2 differs from the electro-responsive particle 10 according to embodiment 1 in that it includes a second layer 21. The same reference numerals are used to designate parts common to embodiment 1, and detailed description thereof will be omitted.

[0075] 3, the electroactive particle 20 comprises a core material 11, a first layer 12 provided on the core material 11, and a second layer 21 laminated on the first layer 12. As described above, the core material 11 is carbon black, and the first layer 12 is composed of a first polymer 13 containing a functional group A. Furthermore, as will be described later, the second layer 21 is composed of a second polymer 22. As shown schematically in Fig. 4, the second polymer 22 constituting the second layer 21 is a polymer containing negatively charged functional groups 23. Because the second polymer 22 contains the negatively charged functional groups 23, the second layer 21 located at the outermost layer of the electroactive particles 20 is negatively charged as a whole in a liquid medium, and the electric charge of the electroactive particles 20 becomes negative. This allows the electroactive particles 20 to have the property of responding to an electric field in a liquid medium.

[0076] The amount of the first polymer 13 contained in the electroresponsive particles 20 is not particularly limited, but for example, the amount of the first polymer 13 is preferably 5% by weight or more, more preferably 10% by weight or more, and even more preferably 15% by weight or more, relative to the weight of the carbon black. The amount of the first polymer 13 is preferably 25% by weight or less, more preferably 20% by weight or less, relative to the weight of the carbon black. In the electroactive particles 20, the first polymer 13 having the functional group A interacts with the second polymer 22 through an affinity. Furthermore, the electroactive particles 20 are particles that migrate toward the positive electrode when a voltage is applied. The amount of the first polymer 13 in the electroactive particles 20 is preferably determined in consideration of the balance between these factors.

[0077] (Second Polymer 22) In this embodiment, the second polymer 22 constituting the second layer 21 is a polymer containing a negatively charged functional group 23 (in the present disclosure, the negatively charged functional group contained in the second polymer may be referred to as a "functional group B"). The electroresponsive particles 20 may contain one type of second polymer 22, or two or more types. As described above, since the second polymer 22 is a polymer having the functional group B, electrostatic interaction occurs between the second polymer 22 and the first polymer 13 having the functional group A. Furthermore, affinity interactions such as hydrogen bonding may occur. These affinity interactions contribute to the stabilization of the second layer 21.

[0078] Examples of the functional group B include a carboxylate group, a sulfate group, a sulfonate group, a phosphate group, and a phosphonate group. Among these, a sulfonate group is preferred because it is more likely to form a negatively charged second layer 21. The functional group B may interact with a counter ion to form a salt. Examples of the counter ion include ammonium ions, sodium ions, and potassium ions. In the present disclosure, protonated groups (those that form acids) are also included in the functional group B in the description of the manufacturing process of the electro-responsive particles 20.

[0079] The second polymer 22 may be a polymer having a repeating unit derived from a monomer having the functional group B. Examples of the monomer having the functional group B include (meth)acrylic acid, styrenesulfonic acid, 2-(meth)acrylamide-2-methylpropanesulfonic acid, 3-{(meth)acryloyloxy}propionic acid, and 3-(meth)acryloyloxypropylphosphonic acid.

[0080] As the second polymer 22, a homopolymer of a monomer having the functional group B, or a copolymer using a monomer having the functional group B may be used. Among these, the second polymer 22 is preferably a homopolymer of a monomer having the functional group B, and more preferably polystyrene sulfonic acid, because it is easy to make the electric charge of the electroactive particles 20 negative.

[0081] The degree of polymerization of the second polymer 22 is preferably 10-1,000, and more preferably 20-500.

[0082] The amount of the second polymer 22 contained in the electroactive particles 20 is not particularly limited, but for example, the amount of the second polymer 22 is preferably 10% by weight or more, more preferably 15% by weight or more, and even more preferably 20% by weight or more, relative to the weight of the carbon black. As the amount of the second polymer 22 contained in the electroactive particles 20 increases, the electroactive particles 20 contain more functional groups B and have a sufficient negative charge. Such electroactive particles 20 have excellent electric field responsiveness. There is no particular upper limit to the amount of the second polymer 22, but it is, for example, 30% by weight or less relative to the weight of the carbon black. The amount of the second polymer 22 can be determined, for example, by thermal gravimetric analysis (TGA).

[0083] (Electroresponsive particles 20) The electroactive particles 20 according to this embodiment are negatively charged in a liquid medium and exhibit electroactive properties. For example, when a voltage is applied to the electroactive particles 20 dispersed in a liquid medium, the particles 20 move toward the positive electrode and aggregate.

[0084] The average particle size of the electroactive particles 20 is preferably 10 μm or less, more preferably 1 μm or less, even more preferably 500 nm or less, and particularly preferably 100 nm or less. The average particle size of the electroactive particles 20 is preferably 1 nm or more, more preferably 5 nm or more, and even more preferably 10 nm or more. The polydispersity index (PDI) of the electroactive particles 20 is preferably 0.3 or less. The CV value of the electroactive particles 20 is preferably 40% or less, more preferably 35% or less, even more preferably 25% or less, and particularly preferably 10% or less. The zeta potential of the electroactive particles 20 is preferably −20 mV or less, more preferably −40 mV or less.

[0085] In the electroactive particles 20, the first polymer 13 is chemically fixed to the surface of the core material 11. There is an electrostatic interaction between the second polymer 22 and the first polymer 13, and an affinity interaction such as a hydrogen bond may also occur. For this reason, the electroactive particles 20 are less likely to experience charge separation.

[0086] (Method for manufacturing electroresponsive particles 20) There is no particular limitation on the method for producing the electroactive particles 20. For example, after producing the electroactive particles 10 by the above-described method, the second polymer 22 is electrostatically adsorbed onto the first polymer 13 constituting the first layer 12 of the electroactive particles 10, thereby enabling the electroactive particles 20 to be produced efficiently.

[0087] Specifically, a dispersion of the electroresponsive particles 10 and a solution of the second polymer 22 are mixed and stirred to bring the electroresponsive particles 10 into contact with the second polymer 22, thereby producing the electroresponsive particles 20. The solvent constituting the dispersion of the electroactive particles 10 and the solution of the second polymer 22 is not particularly limited as long as it can disperse the electroactive particles 10 and dissolve the second polymer 22 . Examples of the solvent include water; alcohol solvents such as methanol; ketone solvents such as acetone; ester solvents such as ethyl acetate; ether solvents such as tetrahydrofuran; amide solvents such as N,N-dimethylformamide; and aromatic solvents such as toluene.

[0088] Furthermore, as long as the first polymer 13 and the second polymer 22 have a sufficient affinity interaction, particles other than the electroactive particles 10 can be used as production intermediates for the electroactive particles 20. Examples of particles other than the electroactive particles 10 include particles that contain carbon black and the first polymer and have a negative zeta potential. By using particles containing carbon black and a first polymer and having a negative zeta potential as a production intermediate for electro-responsive particles 20, it becomes easier to obtain electro-responsive particles 20 having a large absolute negative zeta potential.

[0089] [Embodiment 3] The electro-responsive particle 30 according to this embodiment will be described with reference to Figures 5 and 6. The electro-responsive particle 30 according to embodiment 3 differs from the electro-responsive particle 20 according to embodiment 2 in that it includes a third layer 31. The same reference numerals are used to designate parts common to embodiments 1 and 2, and detailed descriptions thereof will be omitted.

[0090] 5, the electroactive particle 30 comprises a core material 11, a first layer 12 provided on the core material 11, a second layer 21 laminated on the first layer 12, and a third layer 31 laminated on the second layer 21. As described above, the core material 11 is carbon black, the first layer 12 is composed of a first polymer 13 containing a functional group A, and the second layer 21 is composed of a second polymer 22 containing a functional group B. Furthermore, as will be described later, the third layer 31 is composed of a third polymer 32. As shown schematically in Fig. 6, the third polymer 32 constituting the third layer 31 is a polymer containing positively charged functional groups 33. Since the third polymer 32 contains the positively charged functional groups 33, the third layer 31 located at the outermost layer of the electroactive particles 30 is positively charged as a whole in a liquid medium, and the electric charge of the electroactive particles 30 becomes positive. As a result, the electroactive particles 30 have the property of responding to an electric field in a liquid medium.

[0091] The amount of the first polymer 13 contained in the electroresponsive particles 30 is not particularly limited, but for example, the amount of the first polymer 13 is preferably 5% by weight or more, more preferably 10% by weight or more, and even more preferably 15% by weight or more, relative to the weight of the carbon black. The amount of the first polymer 13 is preferably 25% by weight or less, more preferably 20% by weight or less, relative to the weight of the carbon black. The amount of the second polymer 22 contained in the electroresponsive particles 30 is not particularly limited, but for example, the amount of the second polymer 22 is preferably 10% by weight or more, more preferably 15% by weight or more, and even more preferably 20% by weight or more, relative to the weight of the carbon black. The amount of the second polymer 22 is preferably 30% by weight or less, more preferably 25% by weight or less, relative to the weight of the carbon black. In the electroactive particle 30, the first polymer 13 having the functional group A and the second polymer 22 having the functional group B affect the interlayer interaction and the charge of the entire particle. Therefore, it is preferable to determine the amount of the first polymer 13 and the amount of the second polymer 22 in the electroactive particle 30 in consideration of the balance between these factors.

[0092] (Third Polymer 32) In this embodiment, the third polymer 32 constituting the third layer 31 is a polymer containing a positively charged functional group 33 (in the present disclosure, the positively charged functional group contained in the third polymer may be referred to as a "functional group C"). The electroresponsive particles 30 may contain one type of third polymer 32 or two or more types. As described above, the third polymer 32 is a polymer having the functional group C, and therefore electrostatic interaction occurs between the third polymer 32 and the second polymer 22 having the functional group B. Furthermore, affinity interactions such as hydrogen bonding may occur. These affinity interactions contribute to the stabilization of the third layer 31.

[0093] Examples of the functional group C include an ammonium group, a pyridinium group, a sulfonium group, and a phosphonium group. Among these, an ammonium group is preferred, and a quaternary ammonium group is more preferred, because a positively charged third layer 31 is more likely to be formed. The functional group C may interact with a counter ion to form a salt. Examples of the counter ion include a fluoride ion, a chloride ion, a bromide ion, an iodide ion, a tetrafluoroborate ion, a hexafluorophosphate ion, and a methyl sulfate ion.

[0094] The third polymer 32 may be a polymer having a repeating unit derived from a monomer having a functional group C. Examples of the monomer having the functional group C include allylamine, diallyldimethylammonium chloride, and vinylbenzyltrimethylammonium chloride.

[0095] The third polymer 32 may be a homopolymer of a monomer having the functional group C, or a copolymer using a monomer having the functional group C. Among these, a homopolymer of a monomer having the functional group C is preferred as the third polymer 32, since it is easy to make the overall charge of the electroactive particles 30 positive. Examples of the third polymer 32 include polyallylamine hydrochloride (PAH), poly(diallyldimethylammonium chloride) (PDADMAC), poly(vinylbenzyltrimethylammonium chloride), cationic polyethyleneimine, and polyamidine.

[0096] The degree of polymerization of the third polymer 32 is preferably 10-1,000, and more preferably 20-500.

[0097] The amount of the third polymer 32 contained in the electroactive particles 30 is not particularly limited, but for example, the amount of the third polymer 32 is preferably 10% by weight or more, more preferably 15% by weight or more, and even more preferably 20% by weight or more, relative to the weight of the carbon black. As the amount of the third polymer 32 contained in the electroactive particles 30 increases, the electroactive particles 30 contain more functional groups C and have a sufficient positive charge. Such electroactive particles 30 have excellent electric field response. There is no particular upper limit to the amount of the third polymer 32, but it is, for example, 30% by weight or less relative to the weight of the carbon black. The amount of the third polymer 32 can be determined, for example, by thermal gravimetric analysis (TGA).

[0098] (Electroresponsive particles 30) The electroactive particles 30 according to this embodiment are positively charged in a liquid medium and exhibit electroactive properties. For example, when a voltage is applied to the electroactive particles 30 dispersed in a liquid medium, the particles 30 move toward the negative electrode and aggregate.

[0099] The average particle size of the electroactive particles 30 is preferably 10 μm or less, more preferably 1 μm or less, even more preferably 500 nm or less, and particularly preferably 100 nm or less. The average particle size of the electroactive particles 30 is preferably 1 nm or more, more preferably 5 nm or more, and even more preferably 10 nm or more. The polydispersity index (PDI) of the electroactive particles 30 is preferably 0.3 or less. The CV value of the electro-responsive particles 30 is preferably 40% or less, more preferably 35% or less, even more preferably 25% or less, and particularly preferably 10% or less. The zeta potential of the electroactive particles 30 is preferably 5 mV or more, and more preferably 10 mV or more.

[0100] In the electroactive particles 30, the first polymer 13 is chemically fixed to the surface of the core material 11. An electrostatic interaction occurs between the second polymer 22 and the first polymer 13, and an affinity interaction such as a hydrogen bond may occur. Furthermore, an electrostatic interaction occurs between the third polymer 32 and the second polymer 22, and an affinity interaction such as a hydrogen bond may occur. Therefore, the electroactive particles 30 are less likely to experience charge separation.

[0101] (Method for manufacturing electroresponsive particles 30) There is no particular limitation on the method for producing the electroactive particles 30. For example, after producing the electroactive particles 20 by the above-described method, the third polymer 32 is electrostatically adsorbed to the second polymer 22 constituting the second layer 21 of the electroactive particles 20, thereby enabling the electroactive particles 30 to be produced efficiently.

[0102] Specifically, a dispersion of the electroresponsive particles 20 and a solution of the third polymer 32 are mixed and stirred to bring the electroresponsive particles 20 into contact with the third polymer 32, thereby producing the electroresponsive particles 30. The solvent constituting the dispersion of the electroactive particles 20 and the solution of the third polymer 32 is not particularly limited as long as it can disperse the electroactive particles 20 and dissolve the third polymer 32 . Examples of the solvent include the same solvents as those exemplified in the method for producing the electroactive particles 20.

[0103] [Electrophoretic medium] The electrophoretic medium of the present disclosure includes the electroresponsive particles of any one of Embodiments 1 to 3 and a solvent in which the electroresponsive particles are dispersed. In the electrophoretic medium of the present disclosure, the dispersion state and aggregation state of the electroresponsive particles can be controlled by turning on and off the application of a voltage, and therefore the light-blocking and light-shielding properties of the electrophoretic medium can be changed by turning on and off the application of a voltage.

[0104] For example, the electroactive particles of Embodiments 1 and 3 have a positive charge on their surfaces, while the electroactive particles of Embodiment 2 have a negative charge on their surfaces. Therefore, when no voltage is applied, the electroactive particles tend to maintain a dispersed state due to electrostatic repulsion between the electroactive particles. When a voltage is applied in this state, the electroactive particles of Embodiments 1 and 3 move toward the negative electrode and become aggregated, while the electroactive particles of Embodiment 2 move toward the positive electrode and become aggregated.

[0105] When used as an electrophoretic medium such as an active louver, the particle diameter of the electroresponsive particles is preferably 10 nm to 10 μm, more preferably 20 nm to 5 μm. Within this range, dispersibility and light-blocking and shielding properties tend to be compatible.

[0106] The concentration of the electroactive particles is, for example, 0.01 to 20% by weight, preferably 2 to 10% by weight, and more preferably 3 to 5% by weight.

[0107] The solvent constituting the electrophoretic medium is a liquid that disperses the electroactive particles. The solvent is not particularly limited as long as it disperses the electroactive particles.

[0108] Examples of the solvent include ester-based solvents such as ethyl acetate; ether-based solvents such as diethyl ether; ketone-based solvents such as acetone; alcohol-based solvents such as methanol; amide-based solvents such as N,N-dimethylformamide; glycol-based solvents such as ethylene glycol; isoparaffin-based solvents such as isooctane; aromatic hydrocarbon-based solvents such as methylnaphthalene, ethylbiphenyl, diphenylethane, ethyl benzoate, and benzyl acetate; and halogenated hydrocarbon-based solvents such as dibromopropane. These solvents can be used alone or in combination of two or more.

[0109] The solvent is preferably an organic solvent having a boiling point of 80° C. or higher. By using an organic solvent having a boiling point of 80° C. or higher, volatilization of the solvent can be prevented in the process of producing the electrophoretic medium and in the process of introducing the electrophoretic medium into the electrophoretic cell. Furthermore, the solvent is preferably an isoparaffin-based solvent having a boiling point of 80° C. or higher. When the solvent is an isoparaffin-based solvent, the insulating properties in the electrophoretic cell are improved.

[0110] Examples of isoparaffinic solvents include NAS-3, NAS-4, and NAS-5 (all manufactured by NOF Corporation); Isopar C, Isopar D, Isopar E, Isopar F, Isopar G, Isopar H, Isopar K, Isopar L, Isopar M, and Isopar V (all manufactured by ExxonMobil Corporation); IP Solvent 1016 and IP Clean LX (all manufactured by Idemitsu Kosan Co., Ltd.); Isozol (manufactured by Eneos Corporation); and Marukasol R (manufactured by Maruzen Petrochemical Co., Ltd.).

[0111] The electrophoretic medium may contain a surfactant, which may improve the dispersibility of the electroresponsive particles. The surfactant is preferably a nonionic surfactant, such as sorbitan trioleate (Span 85). The amount of the surfactant is not particularly limited, but is, for example, 1 to 15% by weight based on the solvent.

[0112] The electrophoretic medium may further contain additives such as lubricants, stabilizers, dyes, and the like. The amounts of these additives are not particularly limited and can be determined appropriately depending on the purpose of use.

[0113] The dispersion state and aggregation state of the electroresponsive particles constituting the electrophoretic medium of the present disclosure are controlled by turning on and off the application of a voltage. Therefore, the light-blocking or shielding properties of the electrophoretic medium change depending on whether the voltage is turned on or off. Because of these properties, the electrophoretic medium of the present disclosure is suitable for use as an electrophoretic medium for active louvers and the like that exhibit light-blocking or shielding properties.

[0114] 7 and 8 show an example of an active louver using the electrophoretic medium of the present disclosure. The active louver 40 includes a first electrode 41, a second electrode 42 facing the first electrode 41, a transparent / opaque switching section 43 disposed between the first electrode 41 and the second electrode 42, a first substrate 44, and a second substrate 45. The transparent / opaque switching sections 43 are arranged in a blade-like pattern on a micrometer scale. A transparent section 46 is disposed adjacent to the transparent / opaque switching section 43. The first electrode 41 is disposed on one surface of the first substrate 44, and the second electrode 42 is disposed on one surface of the second substrate 45. The first electrode 41, the second electrode 42, the first substrate 44, and the second substrate 45 are all translucent. The first electrode 41 and / or the second electrode 42 may be patterned to correspond to the transparent / opaque switching section 43. When the second electrode 42 is patterned, the second electrode 42 may be non-transparent. The electrophoretic medium 47 of this embodiment is provided in the transmission / shield switching section 43. The active louver 40 is provided on a display (not shown) such as a liquid crystal panel, an organic EL panel, or a micro LED panel. In the case of a liquid crystal panel, the active louver 40 can also be provided between the liquid crystal panel and the backlight.

[0115] The electrophoretic medium 47 includes a solvent 48 and electroactive particles 49 dispersed in the solvent. The electrophoretic medium 47 may further include a surfactant to improve the dispersibility of the electroactive particles 49 in the solvent 48. It is assumed that the electroactive particles 49 are negatively charged particles.

[0116] When no voltage is applied between the first electrode 41 and the second electrode 42, in other words, when the blocking function is on, the electroactive particles 49 are dispersed in the solvent 48, as shown in Fig. 7. Therefore, part of the light cannot pass through the transmission / blocking switching unit 43 provided with the electrophoresis medium 47, and part of the light can be blocked. On the other hand, when a voltage is applied between the first electrode 41 and the second electrode 42, in other words, when the blocking function is turned off, the electroactive particles 49 aggregate near the electrode to which a positive voltage is applied (first electrode 41 in FIG. 8), as shown in Fig. 8. When the electroactive particles 49 aggregate on one of the electrodes, light can pass through the light transmission / light blocking switching part 43. In this way, the active louver 40 allows the shielding function to be turned on and off, realizing a privacy filter.

[0117] In terms of visibility and power consumption, it is desirable for the active louver 40 to have a high transmittance of light emitted by the display, regardless of whether it is in the on state shown in FIG. 7 or the off state shown in FIG. 8. Therefore, it is desirable for the volume (width) of the transmission / shield switching section 43, which houses the electrophoretic medium 47, to be smaller than the volume (width) of the transmission section 46 adjacent to the transmission / shield switching section 43. The width w of the transmission / shield switching section 43 is set to, for example, 5 to 20 μm. Furthermore, to narrow the angular range through which light passes during narrow viewing, it is desirable for the transmission / shield switching section 43 to be high, i.e., to have a large height / width aspect ratio. Compared to electronic paper, in terms of aspect ratio, it is desirable for electronic paper to have a large aperture ratio (equivalent to width) of the pixel housing the electrophoretic medium as a display element. Therefore, a large aspect ratio (height / width) is not necessarily required for electronic paper; a lower aspect ratio (height / width) is actually desirable from the perspective of achieving a thinner display. Due to these differences, privacy filters (active louvers) need to move over narrower distances in the left and right directions and longer distances in the up and down directions, so they require more sensitive electric field response. The electroactive particles 10, 20, and 30 of this embodiment can be advantageously used as electrophoretic particles for privacy filters because the absolute value of the zeta potential can be easily increased. [Example]

[0118] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not intended to be limited to the following examples.

[0119] [Calculation of the degree of polymerization of the amino group-containing polymer] In Production Examples 1 to 3, the degree of polymerization of the amino group-containing polymer was calculated based on the molecular weight of the polymer derived from 2-hydroxyethyl 2-bromopropionate measured by nuclear magnetic resonance (NMR) spectroscopy. The conditions for measuring the degree of polymerization by nuclear magnetic resonance spectroscopy are as follows. Sample: Supernatant obtained by centrifuging after atom transfer radical polymerization reaction Measurement equipment: Bruker DPX400NMR (Bruker Japan Co., Ltd.) Measurement method: The sample was dried, and the polymer derived from 2-hydroxyethyl 2-bromopropionate was dissolved in deuterated chloroform. The degree of polymerization was determined from the integrals of the resonance peaks characteristic of 2-hydroxyethyl 2-bromopropionate and 2-(N,N-dimethylamino)ethyl (meth)acrylate.

[0120] [Production Example 1] Production of particles containing carbon black and first polymer (degree of polymerization of first polymer: 25) (1) Production of carbon black having polymerization initiating groups on its surface (polymerization initiating group-containing CB) 1 g of carbon black and 20 mL of tetrahydrofuran (THF) were added to a recovery flask. While stirring the contents of the flask, 9.83 g of thionyl chloride was added at 25°C and stirred for 1 hour. After the reaction was completed, the THF was removed under reduced pressure, and the contents of the flask were further heated under reduced pressure to remove the remaining thionyl chloride.

[0121] After the thionyl chloride was removed, THF was added to the flask, and then 1.54 g of 2-hydroxyethyl 2-bromopropionate was added, and the contents of the flask were stirred for 24 hours at 25° C. The reaction solution was centrifuged, and the solid matter was washed with pure water. This procedure was repeated three times to obtain CB containing a polymerization initiating group.

[0122] (2) Preparation of carbon black having a first polymer on its surface (first polymer-containing CB) 15 mL of THF was added to a recovery flask, and 0.98 g of 2-(N,N-dimethylamino)ethyl methacrylate, 13.5 mg of N,N,N',N",N"-pentamethyldiethylenetriamine, and 30.7 mg of 2-hydroxyethyl 2-bromopropionate were dissolved therein. Next, 200 mg of the polymerization initiating group-containing CB obtained in the above step was added to the flask. Dissolved oxygen was removed by freeze-degassing. Under a nitrogen atmosphere, 11.2 mg of copper bromide was added, and the contents of the flask were then stirred at 25°C for 24 hours to carry out an atom transfer radical polymerization reaction. The reaction solution was exposed to air, centrifuged, and the solid matter was washed with pure water. This procedure was repeated three times to obtain carbon black having an amino group-containing polymer on its surface (amino group-containing CB). Analysis of the polymer derived from 2-hydroxyethyl 2-bromopropionate in the solution revealed that the degree of polymerization of the amino group-containing polymer was 25.

[0123] 60 mL of water and 30 mg of the amino-containing CB obtained in the above step were added to a recovery flask, and the contents of the flask were stirred to disperse the amino-containing CB. Next, 4.56 g of iodomethane was added to the flask, and the contents of the flask were stirred at 25°C for 72 hours to convert the dimethylamino groups in the amino-containing CB to trimethylammonium groups. The reaction solution was centrifuged (14,500 rpm), and the solids were washed with pure water three times to obtain particles containing carbon black and the first polymer (first polymer degree of polymerization: 25).

[0124] [Production Example 2] Production of particles containing carbon black and first polymer (first polymer polymerization degree 100) Particles containing carbon black and a first polymer (degree of polymerization of the first polymer: 100) were obtained in the same manner as in Production Example 1, except that the amount of N,N,N',N",N"-pentamethyldiethylenetriamine was changed to 54 mg and the amount of copper bromide was changed to 44.8 mg.

[0125] [Production Example 3] Production of particles containing carbon black and first polymer (first polymer polymerization degree 700) Particles containing carbon black and a first polymer (degree of polymerization of the first polymer: 700) were obtained in the same manner as in Production Example 1, except that the amount of 2-(N,N-dimethylamino)ethyl methacrylate in Production Example 1 was changed to 2.46 g.

[0126] Example 1: Production of electroactive particles 20 (particles containing carbon black, a first polymer, and a second polymer) with a first polymer having a degree of polymerization of 25 A solution obtained by dissolving 153 mg of sodium polystyrene sulfonate in 15 mL of pure water was added dropwise to the aqueous dispersion of particles containing carbon black and the first polymer obtained in Production Example 1, and the mixture was stirred for 1 hour. The reaction solution was centrifuged (14,500 rpm), and the solid content was washed with pure water. This procedure was repeated three times to obtain electro-responsive particles 20 in which the degree of polymerization of the first polymer was 25.

[0127] Example 2: Production of electroactive particles 20 (particles containing carbon black, a first polymer, and a second polymer) with a first polymer having a degree of polymerization of 100 Electro-responsive particles 20 in which the degree of polymerization of the first polymer was 100 were obtained in the same manner as in Example 1, except that in Example 1, particles containing carbon black and a first polymer obtained in Production Example 2 were used instead of the particles containing carbon black and a first polymer obtained in Production Example 1.

[0128] Example 3: Production of electroactive particles 20 (particles containing carbon black, a first polymer, and a second polymer) with a first polymer having a degree of polymerization of 700 Electro-responsive particles 20 having a degree of polymerization of the first polymer of 700 were obtained in the same manner as in Example 1, except that in Example 1, particles containing carbon black and a first polymer obtained in Production Example 3 were used instead of the particles containing carbon black and a first polymer obtained in Production Example 1.

[0129] (Measurement of particle size of electro-responsive particles) The particle sizes of the particles obtained in Production Examples 1 to 3 and Examples 1 to 3 are shown in Table 1. The measuring equipment and conditions used for measuring the particle sizes are as follows. In Table 1, Dh represents the average particle size, and PDI represents the polydispersity index. Measuring equipment: nanoSAQLA (Otsuka Electronics Co., Ltd.) Measurement temperature: 25℃ Accumulation count: 75 times

[0130] (Zeta potential of electroactive particles) The zeta potentials of the particles obtained in Production Examples 1 to 3 and Examples 1 to 3 are shown in Table 1. The measuring equipment and conditions used for measuring the zeta potential are as follows. Measurement equipment: Zeta potential / particle size measurement system (ELSZ-1000ZSCK, manufactured by Otsuka Electronics Co., Ltd.) Measurement temperature: 25℃

[0131] [Table 1]

[0132] (Electrophoresis of electroresponsive particles) An electrophoretic medium was prepared by adding the electroresponsive particles 20 (first polymer having a degree of polymerization of 100) obtained in Example 2 and sorbitan trioleate (SPAN85) to an isoparaffinic solvent (Isopar G, manufactured by ExxonMobil Corporation) to concentrations of 1 wt % and 5 wt %, respectively. The electrophoretic medium was injected, by capillary action, into a comb-shaped electrode cell having an electrode separation distance of 90 μm (electrodes 1 and 2) and a cell gap of 10 μm.

[0133] Next, a voltage of −30 V was applied to electrode 1 and a voltage of +30 V was applied to electrode 2, and the electrophoretic movement of the electroactive particles 20 between the electrodes (electrodes 1 and 2) was observed under an optical microscope. A photograph taken at that time is shown in FIG. In Figure 9, A1 represents the state before voltage application. A2 represents the state one second after A1, and a voltage of -30 V was applied to electrode 1 and +30 V to electrode 2 between A1 and A2. Application of voltage caused the uniformly dispersed electroactive particles 20 to migrate toward electrode 2. This experiment shows that 3 to 4 seconds after A1, the electroactive particles 20 are almost completely collected at electrode 2.

[0134] Next, voltages of opposite polarities were applied to electrode 1 and electrode 2, and the electrophoretic movement of the electroactive particles 20 between the electrodes (electrode 1 and electrode 2) was observed using an optical microscope. A photograph of this observation is shown in FIG. In Figure 10, B1 is the state before the applied voltage was changed. B2 is the state 0.2 seconds after B1; the applied voltage was changed between B1 and B2, with +30 V applied to electrode 1 and -30 V applied to electrode 2. Because the voltage was reversed, the electroactive particles 20 that had gathered on electrode 2 migrated all at once toward electrode 1. In this experiment, it can be seen that 3 to 4 seconds after B1, the electroactive particles 20 were almost completely gathered on electrode 1.

[0135] Next, voltages with opposite polarities were again applied to electrode 1 and electrode 2, and the electrophoretic movement of the electroactive particles 20 between the electrodes (electrode 1 and electrode 2) was observed with an optical microscope. A photograph taken at that time is shown in FIG. In Figure 11, C1 is the state before the applied voltage was changed. C2 is the state 0.2 seconds after C1; the applied voltage was changed between C1 and C2, with -30 V applied to electrode 1 and +30 V applied to electrode 2. Because the voltage was changed from positive to negative, the electroactive particles 20 that had gathered on electrode 1 migrated all at once toward electrode 2. In this experiment, it can be seen that 3 to 4 seconds after C1, the electroactive particles 20 were almost completely gathered on electrode 2. [Explanation of symbols]

[0136] 10,20,30,49 Electroresponsive particles 11 Core material 12 First Layer 13 First Polymer 14 Positively charged functional groups 15 Linking group 21 Second Layer 22 Second Polymer 23 Negatively charged functional groups 31 Third Layer 32 Third Polymer 33 Positively charged functional groups 40 Active Louver 41 1st electrode 42 2nd electrode 43 Transmittance / light blocking switch 44 First board 45 Second board 46 Transparent part 47 Electrophoresis media 48 Solvents

Claims

1. Carbon black and a first polymer comprising a functional group having a positive charge; a linking group connecting the carbon black and the first polymer; An electroactive particle comprising: the linking group has an ester group, The electroactive particles are electroactive particles that become positively charged in a liquid medium.

2. The electroactive particle according to claim 1 , wherein the positively charged functional group contained in the first polymer is an ammonium group or a salt thereof.

3. The linking group is represented by the following formula (V): 【Chemistry 1】 (R ８ , R ９ each independently represents a hydrogen atom or an unsubstituted or substituted hydrocarbon group having 1 to 10 carbon atoms; R １０ represents a divalent hydrocarbon group having 2 to 10 carbon atoms. n represents an integer of 1 to 5. When n is 2 or more, a plurality of R １０ may be the same or different. A4 represents a bond to the carbon black surface, and A5 represents a bond to the first polymer. The electroresponsive particle according to claim 1 , wherein R 1 is a divalent group represented by the formula:

4. 2. The electroactive particle according to claim 1, wherein the degree of polymerization of the first polymer is 10 to 1,000.

5. Carbon black and a first polymer comprising a functional group having a positive charge; a linking group connecting the carbon black and the first polymer; a second polymer layered on the first polymer and including a negatively charged functional group; An electroactive particle comprising: the linking group has an ester group, the second polymer is electrostatically adsorbed to the first polymer; The electroactive particles are electroactive particles that become negatively charged in a liquid medium.

6. The electroactive particle according to claim 5 , wherein the negatively charged functional group contained in the second polymer is a carboxylate group, a sulfate group, a sulfonate group, a phosphate group, a phosphonate group, or a salt thereof.

7. Carbon black and a first polymer comprising a functional group having a positive charge; a linking group connecting the carbon black and the first polymer; a second polymer layered on the first polymer and including a negatively charged functional group; a third polymer layered on the second polymer and including a positively charged functional group; An electroactive particle comprising: the linking group has an ester group, the second polymer is electrostatically adsorbed to the first polymer; the third polymer is electrostatically adsorbed to the second polymer; The electroactive particles are electroactive particles that become positively charged in a liquid medium.

8. A method for producing electroactive particles according to claim 1, comprising: a polymerization initiating group forming step of converting carboxy groups present on the surface of the carbon black into polymerization initiating groups having an ester group; a first polymer synthesis step of synthesizing a first polymer including a positively charged functional group by allowing a polymerization reaction initiated by the polymerization initiation group to proceed; A method for producing electroresponsive particles, comprising:

9. 9. The method for producing electroresponsive particles according to claim 8, wherein the polymerization initiation group forming step converts carboxy groups present on the surface of the carbon black into acyl chloride groups (—COCl), and then carries out a reaction represented by the following scheme: 【Chemistry 2】 (R ８ , R ９ each independently represents a hydrogen atom or an unsubstituted or substituted hydrocarbon group having 1 to 10 carbon atoms; R １０ represents a divalent hydrocarbon group having 2 to 10 carbon atoms. n represents an integer of 1 to 5. When n is 2 or more, a plurality of R １０ may be the same or different. A4 represents a bond to the carbon black surface, and X represents a halogen atom.

10. 9. The method for producing an electro-responsive particle according to claim 8, wherein the first polymer synthesis step comprises synthesizing a polymer containing an amino group using a monomer containing an amino group, and then converting the amino group into an ammonium group.

11. The method for producing electroresponsive particles according to claim 5, a polymerization initiating group forming step of converting carboxy groups present on the surface of the carbon black into polymerization initiating groups having an ester group; a first polymer synthesis step of synthesizing a first polymer including a positively charged functional group by allowing a polymerization reaction initiated by the polymerization initiation group to proceed; an adsorption step of electrostatically adsorbing a second polymer including a negatively charged functional group onto the first polymer; A method for producing electroresponsive particles, comprising:

12. The method for producing electroactive particles according to claim 7, a polymerization initiating group forming step of converting carboxy groups present on the surface of the carbon black into polymerization initiating groups having an ester group; a first polymer synthesis step of synthesizing a first polymer including a positively charged functional group by allowing a polymerization reaction initiated by the polymerization initiation group to proceed; an adsorption step 1 in which a second polymer including a negatively charged functional group is electrostatically adsorbed onto the first polymer; an adsorption step 2 in which a third polymer including a positively charged functional group is electrostatically adsorbed onto the second polymer; A method for producing electroresponsive particles, comprising:

13. The electroactive particle according to any one of claims 1 to 7, a solvent in which the electroactive particles are dispersed.

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