JP2017054003A - Electrophoretic dispersion liquid, production method of electrophoretic dispersion liquid, electrophoretic sheet, electrophoretic device and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide electrophoretic dispersion liquid in which electrophoretic particles exhibit both of excellent dispersion power and electrophoresis, and a production method for the electrophoretic dispersion liquid capable of producing the electrophoretic dispersion liquid, an electrophoretic sheet with high reliability using the electrophoretic dispersion liquid, an electrophoretic device and an electronic apparatus.SOLUTION: Electrophoretic dispersion liquid of the present invention includes at least one kind of electrophoretic particles 1. The content of sulfur element derived from at least one kind of a block copolymer (particle surface treating agent) 39 used for forming the electrophoretic particles 1 and the dispersion medium is more than 0 ppm and equal to 20 ppm or less in the electrophoretic dispersion liquid.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an electrophoretic dispersion, an electrophoretic dispersion manufacturing method, an electrophoretic sheet, an electrophoretic apparatus, and an electronic apparatus.

  Generally, it is known that when an electric field is applied to a dispersion system in which fine particles are dispersed in a liquid, the fine particles move (migrate) in the liquid by Coulomb force. This phenomenon is called electrophoresis. In recent years, an electrophoretic display device that displays desired information (image) using this electrophoresis has attracted attention as a new display device.

  This electrophoretic display device has characteristics such as a display memory property and a wide viewing angle property in a state where voltage application is stopped, and a high-contrast display with low power consumption.

  In addition, since the electrophoretic display device is a non-light-emitting device, the electrophoretic display device has a feature that it is easier on the eyes than a light-emitting display device such as a cathode ray tube.

  As such an electrophoretic display device, a device in which electrophoretic particles are dispersed in a dispersion medium is provided as an electrophoretic dispersion liquid disposed between a pair of substrates having electrodes.

  In the electrophoretic dispersion liquid having such a configuration, the electrophoretic particles include positively charged particles and negatively charged particles, so that a voltage is applied between a pair of substrates (electrodes). Thus, desired information (image) can be displayed.

  As such electrophoretic particles, generally, those having a coating layer in which a polymer is linked to a substrate particle are used, and such a configuration is provided with such a coating layer (polymer). The electrophoretic particles can be dispersed and charged in the electrophoretic dispersion liquid (see Patent Document 1).

International Publication No. 2013/170932

  In the electrophoretic particles contained in the electrophoretic dispersion liquid as described above, as a technique for generating the polymer by polymerizing monomers, for example, a living radical polymerization method by reversible addition-fragmentation chain transfer polymerization (RAFT) is used. The case where it uses is considered.

  In this reversible addition-fragmentation chain transfer polymerization (RAFT), in addition to the polymerization initiator, a chain transfer agent (RAFT agent) is used. The compound is incorporated. Further, the chain transfer agent usually contains sulfur element in the molecule. From these facts, electrophoretic dispersions containing electrophoretic particles with polymers produced by the reversible addition-fragmentation chain transfer polymerization (RAFT) method are unintentionally mixed with elemental sulfur, and as a result, As a result, there has been a problem that the dispersibility of the electrophoretic particles in the electrophoretic dispersion is not improved to the desired level.

  Accordingly, one of the objects of the present invention is an electrophoretic dispersion in which electrophoretic particles exhibit both excellent dispersibility and electrophoretic properties, and a method for producing an electrophoretic dispersion capable of producing such an electrophoretic dispersion. It is an object of the present invention to provide an electrophoretic sheet, an electrophoretic apparatus, and an electronic apparatus with high reliability using such an electrophoretic dispersion.

Such an object is achieved by the present invention described below.
The electrophoretic dispersion liquid of the present invention is an electrophoretic dispersion liquid containing at least one kind of electrophoretic particles and a dispersion medium,
In the electrophoretic dispersion, the content of sulfur element is more than 0 ppm and not more than 20 ppm.

  Thereby, it can be set as the electrophoresis dispersion liquid provided with the electrophoretic particle which has the outstanding dispersibility and electrophoretic property.

  In the electrophoretic dispersion liquid of the present invention, the sulfur element may be derived from at least one of a particle surface treatment agent used for forming the electrophoretic particles and a dispersant added to the dispersion medium. preferable.

  Since the elemental sulfur is contained in the electrophoretic dispersion liquid from at least one of these, by setting the content of the elemental sulfur in the electrophoretic dispersion liquid to more than 0 ppm and not more than 20 ppm, An electrophoretic dispersion liquid including electrophoretic particles having excellent dispersibility and electrophoretic properties can be obtained.

In the electrophoretic dispersion of the present invention, at least one of the particle surface treatment agent and the dispersant is a polymer produced by using a living radical polymerization method by reversible addition-fragmentation chain transfer polymerization,
The elemental sulfur is preferably derived from a fragment of the chain transfer agent remaining at one end of the polymer.

  Since the elemental sulfur is contained in the electrophoretic dispersion due to the fragment of the chain transfer agent remaining at one end of the polymer, the content of elemental sulfur in the electrophoretic dispersion is more than 0 ppm and not more than 20 ppm. Thus, an electrophoretic dispersion liquid including electrophoretic particles having both excellent dispersibility and electrophoretic properties can be obtained.

  In the electrophoretic dispersion liquid of the present invention, the chain transfer agent is preferably a sulfur compound having at least one functional group of a dithioester group, a trithiocarbamate group, a xanthate group, and a dithiocarbamate group.

  Since such a sulfur compound is used as a chain transfer agent, the fragment of the chain transfer agent remains at one end of the polymer, so that the elemental sulfur is contained in the electrophoretic dispersion.

  In the electrophoretic dispersion of the present invention, the content of the group 8 transition metal element in the electrophoretic dispersion is preferably more than 0 ppm and 2 ppm or less.

  Thereby, it can be set as the electrophoresis dispersion liquid provided with the electrophoretic particle which has the outstanding dispersibility and electrophoretic property.

  In the electrophoretic dispersion of the present invention, the group 8 transition metal element generates at least one of a particle surface treatment agent used for forming the electrophoretic particles and a dispersant added to the dispersion medium. It is preferably derived from the catalyst used in the process.

  A group 8 transition metal element derived from a catalyst used in generating at least one of a particle surface treatment agent used for forming electrophoretic particles and a dispersant added to a dispersion medium is electrophoretic dispersed. It remains in the liquid.

  In the electrophoretic dispersion of the present invention, the group 8 transition metal element is preferably at least one of a fifth periodic element and a sixth periodic element.

  The catalyst comprising the fifth periodic element and the group 8 transition metal element of the sixth periodic element can be used for the production of the particle surface treatment agent and the dispersion medium. Therefore, the dispersibility of the electrophoretic particles can be reliably improved by setting the content of these metal elements in the electrophoretic dispersion to more than 0 ppm and 2 ppm or less.

The method for producing an electrophoretic dispersion of the present invention is a method for producing an electrophoretic dispersion containing at least one kind of electrophoretic particles and a dispersion medium,
A production step of producing a particle surface treatment agent used for forming the electrophoretic particles using a living radical polymerization method by reversible addition-fragmentation chain transfer polymerization,
A removal step of removing elemental sulfur derived from the chain transfer agent used in the reversible addition-fragmentation chain transfer polymerization from the particle surface treatment agent;
A connecting step of connecting the particle surface treatment agent to the surface of the mother particle to obtain the electrophoretic particles;
A dispersion step of dispersing the electrophoretic particles in the dispersion medium to obtain the electrophoretic dispersion having a content of sulfur element derived from the chain transfer agent of more than 0 ppm and not more than 20 ppm. .

  Thereby, an electrophoretic dispersion liquid including electrophoretic particles having both excellent dispersibility and electrophoretic properties can be produced.

The method for producing an electrophoretic dispersion of the present invention is a method for producing an electrophoretic dispersion containing at least one kind of electrophoretic particles and a dispersion medium,
A production step for producing a dispersant added to the dispersion medium using a living radical polymerization method by reversible addition-fragmentation chain transfer polymerization;
A removal step of removing sulfur element derived from the chain transfer agent used in the reversible addition-fragmentation chain transfer polymerization from the dispersant;
A dispersion step of dispersing the electrophoretic particles in the dispersion medium containing the dispersant to obtain the electrophoretic dispersion liquid in which the content of sulfur element derived from the chain transfer agent is more than 0 ppm and not more than 20 ppm. It is characterized by that.

  Thereby, an electrophoretic dispersion liquid including electrophoretic particles having both excellent dispersibility and electrophoretic properties can be produced.

  In the method for producing an electrophoretic dispersion of the present invention, in the removing step, after the particle surface treatment agent or the fragment of the chain transfer agent remaining at one end of the dispersant is separated from the particle surface treatment agent, It is preferable to remove the chain transfer agent fragments.

  Thereby, the fragment | piece of a chain transfer agent can be reliably removed from at least 1 sort (s) of a particle | grain surface treating agent and a dispersion medium.

  In the method for producing an electrophoretic dispersion of the present invention, the removal method of removing the chain transfer agent fragments in the removing step includes a centrifugation method in which the chain transfer agent fragments are centrifuged, and the chain transfer agent fragments. It is preferably at least one of a heating method in which the chain transfer agent is decomposed and vaporized, and an adsorption method in which the chain transfer agent fragments are adsorbed onto the adsorbent.

  According to these methods, the group 8 transition metal element can be removed with an excellent removal rate from at least one of the particle surface treatment agent and the dispersion medium.

The electrophoretic sheet of the present invention comprises a substrate,
And a structure that is provided on the substrate and stores the electrophoretic dispersion of the present invention.
Thereby, an electrophoretic sheet having high performance and reliability can be obtained.

The electrophoretic device of the present invention includes the electrophoretic sheet of the present invention.
Thereby, an electrophoretic device with high performance and reliability can be obtained.

An electronic apparatus according to the present invention includes the electrophoresis apparatus according to the present invention.
Thereby, an electronic device with high performance and reliability can be obtained.

It is a longitudinal cross-sectional view which shows embodiment of the electrophoretic particle contained in the electrophoretic dispersion liquid of this invention. It is a schematic diagram of the block copolymer which the electrophoretic particle shown in FIG. 1 has. It is a flowchart which shows the manufacturing method of the electrophoresis dispersion liquid of this invention. It is a figure which shows typically the longitudinal cross-section of embodiment of an electrophoretic display apparatus. It is a schematic diagram which shows the principle of operation of the electrophoretic display device shown in FIG. It is a schematic diagram which shows the principle of operation of the electrophoretic display device shown in FIG. It is a perspective view which shows embodiment at the time of applying the electronic device of this invention to electronic paper. It is a figure which shows embodiment at the time of applying the electronic device of this invention to a display. It is a figure which shows embodiment at the time of applying the electronic device of this invention to a display.

  Hereinafter, an electrophoretic dispersion, an electrophoretic dispersion manufacturing method, an electrophoretic sheet, an electrophoretic apparatus, and an electronic apparatus according to the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

<Electrophoretic dispersion>
The electrophoretic dispersion liquid contains at least one kind of electrophoretic particles 1 and a dispersion medium (liquid phase dispersion medium). In the electrophoretic dispersion liquid, the electrophoretic particles 1 are dispersed in the dispersion medium. (Suspended).

First, the electrophoretic particles 1 contained in this electrophoretic dispersion will be described.
(Electrophoretic particles)
FIG. 1 is a longitudinal sectional view showing an embodiment of electrophoretic particles contained in the electrophoretic dispersion of the present invention, and FIG. 2 is a schematic diagram of a block copolymer included in the electrophoretic particles shown in FIG.

  As shown in FIG. 1, the electrophoretic particle 1 has a mother particle (particle) 2 and a coating layer 3 provided on the surface of the mother particle 2.

  For the mother particles 2, for example, at least one of pigment particles, resin particles, or composite particles thereof is preferably used. These particles are easy to manufacture.

  Examples of pigments constituting the pigment particles include black pigments such as aniline black, carbon black, and titanium black, white pigments such as titanium dioxide, antimony trioxide, barium sulfate, zinc sulfide, zinc white, and silicon dioxide, monoazo, and disazo. Azo pigments such as polyazo, isoindolinone, yellow lead, yellow iron oxide, cadmium yellow, titanium yellow, antimony and other yellow pigments, quinacridone red, chrome vermillion and other red pigments, phthalocyanine blue, indanthrene blue, and bitumen Blue pigments such as ultramarine blue and cobalt blue, green pigments such as phthalocyanine green, and the like. Among these, one kind or two or more kinds can be used in combination.

  Examples of the resin material constituting the resin particles include acrylic resin, urethane resin, urea resin, epoxy resin, polystyrene, polyester, and the like, and one or more of these are combined. Can be used.

  The composite particles include, for example, those coated by coating the surface of pigment particles with a resin material, coated by coating the surface of resin particles with a pigment, and pigment and resin material. Examples thereof include particles composed of a mixture mixed at an appropriate composition ratio.

  In addition, the color of the electrophoretic particles 1 can be set to a desired color by appropriately selecting the types of pigment particles, resin particles, and composite particles used as the mother particles 2.

  Furthermore, by these selections, the positive chargeability or negative chargeability of the mother particle 2 and the charge amount can be set as unique to the mother particle 2.

  The mother particle 2 needs to have (expose) a first functional group that can be bonded (reacted) with a second functional group included in the bonding portion 31 of the block copolymer 39 described later. is there. However, some types of pigment particles, resin particles, and composite particles may not have a functional group. In this case, functional groups such as acid treatment, base treatment, UV treatment, ozone treatment, and plasma treatment are introduced in advance. The first functional group is introduced on the surface of the mother particle 2 by the treatment.

  In addition, the combination of the first functional group provided on the surface of the mother particle 2 and the second functional group provided in the bonding portion 31 of the block copolymer 39 is not particularly limited as long as it can be reacted and connected to each other. Are, for example, combinations of isocyanate groups with hydroxyl groups or amino groups, combinations of epoxy groups, glycidyl groups or oxetane groups with carboxyl groups, amino groups, thiol groups, hydroxyl groups or imidazole groups, amino groups with Cl, Br, I Combinations of such halogen groups, combinations of alkoxysilyl groups and hydroxyl groups or alkoxysilyl groups, and the like are mentioned. Among them, combinations in which the first functional group is a hydroxyl group and the second functional group is an alkoxysilyl group are mentioned. preferable.

  The mother particle 2 and the monomer M2 that are in this combination can be prepared relatively easily, and the monomer M2 (a block copolymer described later) can be firmly connected to the surface of the mother particle 2. Preferably used.

  Therefore, hereinafter, a combination in which the first functional group provided on the surface of the mother particle 2 is a hydroxyl group and the second functional group provided in the monomer M2 is an alkoxysilyl group will be described as an example.

  At least a part of the surface of the mother particle 2 (substantially the whole in the illustrated configuration) is covered with the coating layer 3.

  The coating layer 3 has a structure including a plurality of block copolymers 39 (hereinafter also simply referred to as “polymer 39”) (see FIG. 2).

  The block copolymer 39 includes a dispersion part 32 and a bonding part 31 connected to the dispersion part 32, and the dispersion part 32 includes a first monomer M1 (hereinafter simply referred to as a first monomer M1 having a part (group) contributing to dispersibility in the dispersion medium). "Also referred to as" monomer M1 ") is formed by polymerization, and includes a plurality of units derived from the monomer M1 (constituent units, hereinafter also referred to as dispersion units). The bonding portion 31 is formed by polymerization of the second monomer M2 having an alkoxysilyl group (second functional group) that is reactive with the hydroxyl group (first functional group) on the surface of the mother particle, and the monomer M2 Includes a plurality of units derived from (hereinafter also referred to as binding units). In the bonding portion 31, the mother particle 2 and the block copolymer 39 are chemically bonded by the reaction between the hydroxyl group and the functional group.

  In this embodiment, the block copolymer 39 constitutes a particle surface treatment agent used for forming the electrophoretic particles 1.

  Hereinafter, the dispersion part 32 and the coupling part 31 constituting the block copolymer 39 will be described.

  The dispersion portion 32 is provided on the surface of the mother particle 2 in the coating layer 3 in order to impart dispersibility to the electrophoretic particles 1 in the electrophoresis dispersion liquid.

  The dispersion portion 32 is formed by polymerizing a plurality of monomers M1 having a side chain part that contributes to dispersibility in the dispersion medium after polymerization in the electrophoretic dispersion liquid, and is derived from the monomer M1. Multiple units are connected.

  The monomer M1 is a pendant monofunctional monomer that includes one polymerizable group so that it can be polymerized by living radical polymerization (radical polymerization), and further includes a portion that becomes a nonionic side chain after polymerization.

  As this monomer M1, in this embodiment, a silicone macromonomer represented by the following general formula (I) having dimethylpolysiloxane as a nonionic side chain and (meth) acryloyl group as a polymerization group is used. It is done.

［式中、Ｒ^１は水素原子またはメチル基、Ｒ^２は水素原子または炭素数１〜４のアルキル基、Ｒ^３は、炭素数１〜６までのアルキル基およびエチレンオキサイドまたはプロピレンオキサイドのエーテル基のうちの１種を含む構造、ｎは０以上の整数を表す。］

[Wherein, R ¹ is a hydrogen atom or a methyl group, R ² is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ³ is an alkyl group having 1 to 6 carbon atoms and an ether group of ethylene oxide or propylene oxide. The structure containing 1 type of these, n represents an integer greater than or equal to 0. ]

  By using a silicone macromonomer having such a nonionic side chain as the monomer M1, the dispersion part 32 formed by living radical polymerization is used as a dispersion medium contained in an electrophoretic dispersion described later. In contrast, it shows excellent affinity. Therefore, in the electrophoretic dispersion liquid, the electrophoretic particles 1 including the dispersion portion 32 are dispersed with excellent dispersibility without aggregation. Moreover, since the monomers M1 can be polymerized with excellent reactivity by using the monomer M1 having a (meth) acryloyl group as a polymerization group, the dispersion part 32 can be easily obtained.

  The weight average molecular weight of the silicone macromonomer represented by the above general formula (I) as the monomer M1 is preferably about 1,000 to 50,000, and more preferably about 3,000 to 30,000. Is more preferable, and is more preferably about 5,000 or more and 20,000 or less. Thereby, the electrophoretic particle 1 provided with the dispersion part 32 obtained by polymerizing the monomer M1 can be dispersed in the dispersion medium with more excellent dispersibility.

  Moreover, the weight average molecular weight of the dispersion part 32 is not particularly limited, but is preferably 8,000 or more and 50,000 or less, and more preferably 10,000 or more and 35,000 or less. Thereby, the dispersibility in the electrophoresis dispersion liquid of the electrophoretic particle 1 can be made more excellent.

  Furthermore, in one polymer, the number of dispersion units contained in the dispersion part 32 is preferably 1 or more and 20 or less, and more preferably 2 or more and 10 or less. Thereby, the dispersibility in the electrophoresis dispersion liquid of the electrophoretic particle 1 can be provided reliably.

  Further, the molecular weight distribution of the dispersing portion 32 is preferably 1.2 or less, more preferably 1.1 or less, and further preferably 1.05 or less.

  Here, the molecular weight distribution of the dispersion part 32 represents the ratio (Mw / Mn) of the number average molecular weight (Mn) of the dispersion part 32 and the weight average molecular weight (Mw) of the dispersion part 32. It can be said that the dispersion part 32 exposed in the plurality of electrophoretic particles 1 has a substantially uniform length because the distribution is within the above range. Therefore, each electrophoretic particle 1 exhibits a uniform dispersibility in the electrophoretic dispersion. Such a number average molecular weight (Mn) and a weight average molecular weight (Mw) can be measured as a polystyrene equivalent molecular weight by using, for example, a gel permeation chromatography (GPC) method.

  Furthermore, in the dispersion part 32, it is preferable that the molecular weight of the dispersion unit on the base end part side connected to the coupling part 31 is smaller than the molecular weight of the dispersion unit on the tip part side. More specifically, the molecular weight of the side chain provided in the monomer M1 serving as the precursor of the dispersion unit located on the base end side is equal to that of the side chain provided in the monomer M1 serving as the precursor of the dispersion unit located on the tip side. The molecular weight is preferably smaller. Thereby, the dispersibility of the electrophoretic particles 1 in the electrophoretic dispersion liquid can be further improved, and the dispersion portion 32 can be bonded to the surface of the base particle 2 with high density.

  Such a change in the molecular weight of the side chain may increase continuously from the base end side toward the tip end side, or increase stepwise from the base end side toward the tip end side. It may be.

  The coupling portion 31 is coupled to the surface of the mother particle 2 in the coating layer 3 included in the electrophoretic particle 1, thereby coupling the polymer 39 to the mother particle 2.

  In the present embodiment, the bonding portion 31 is formed by polymerization of a plurality of second monomers M2 having a second functional group that can form a covalent bond by reacting with the hydroxyl group provided on the surface of the mother particle 2. A plurality of bond units (structural units) derived from the monomer M2 are connected.

  Thus, the dispersibility of the electrophoretic particles 1 can be further improved by using the polymer 39 including the binding portions 31 each having a plurality of binding units each having a functional group. That is, the polymer 39 includes not only a plurality of functional groups but also a plurality of functional groups concentrated on the bonding portion 31. Furthermore, since the coupling | bond part 31 has several coupling | bonding units connected, the site | part which can react with the mother particle 2 is large compared with the case where there is only one coupling unit. Therefore, the polymer 39 can be reliably bonded to the surface of the mother particle 2 at the bonding portion 31 formed by the polymerization of the plurality of monomers M2.

  In the present embodiment, as described above, the surface of the base particle 2 has a hydroxyl group, and the functional group that the monomer M2 has is an alkoxysilyl group. By using such a combination of a hydroxyl group and an alkoxysilyl group, the reaction between them exhibits excellent reactivity, so that the bonding to the surface of the mother particle 2 at the bonding portion 31 can be more reliably formed. Can do.

  Such a monomer M2 includes one alkoxysilyl group represented by the following general formula (II) as a functional group, and further includes one polymerizable group so that it can be polymerized by living radical polymerization.

［式中、Ｒは、それぞれ、独立して、炭素数１〜４のアルキル基、ｎは１〜３の整数を表す。］

[In formula, R represents a C1-C4 alkyl group each independently, and n represents the integer of 1-3. ]

  By using the monomer M2 having such a configuration, it is possible to obtain the bonding part 31 in which the monomer M2 is polymerized by living radical polymerization, and the bonding part 31 formed by living radical polymerization is It exhibits excellent reactivity with respect to the hydroxyl group located on the surface.

  Moreover, as one polymeric group which the monomer M2 has, what contains a carbon-carbon double bond like a vinyl group, a styryl group, and a (meth) acryloyl group is mentioned, for example.

  Examples of such a monomer M2 include a vinyl monomer, a vinyl ester monomer, a vinylamide monomer, a (meth) acrylic monomer, and a (meth) acrylic each having one alkoxysilyl group represented by the general formula (II). Examples include ester monomers, (meth) acrylamide monomers, and styryl monomers. More specifically, 3- (meth) acryloxypropyltriethoxy (methoxy) silane, vinyltriethoxy (methoxy) silane, 4-vinylbutyltri Silane-containing monosilanes containing silicon atoms such as ethoxy (methoxy) silane, 8-vinyloctyltriethoxy (methoxy) silane, 10-methacryloyloxydecyltriethoxy (methoxy) silane, 10-acryloyloxydecyltriethoxy (methoxy) silane Chromatography and the like, can be used in combination of one or more of them.

  Further, in one polymer, the number of bonding units included in the bonding portion 31 is preferably 2 or more and 10 or less, and more preferably 3 or more and 6 or less. If the upper limit is exceeded, the binding part 31 has a lower affinity for the dispersion medium than the dispersion part 32, so that depending on the type of the monomer M2, the dispersibility of the electrophoretic particles 1 may be reduced or partially bound. There is a risk of reaction between the parts 31. On the other hand, if the amount is less than the lower limit, depending on the type of the monomer M2, the bond with the mother particle 2 cannot be sufficiently progressed, and the dispersibility of the electrophoretic particles 1 may decrease due to this. is there.

  Moreover, the number of the coupling | bonding units contained in the coupling | bond part 31 can be calculated | required by the analysis using general purpose analyzers, such as a NMR spectrum, IR spectrum, elemental analysis, and gel permeation chromatography (GPC). In addition, in the polymer 39, since the coupling | bond part 31 and the dispersion | distribution part 32 are high molecular polymers, both have a certain molecular weight distribution. Therefore, the results of the analysis as described above do not always apply to all the polymers 39, but the reactivity of the polymer 39 and the mother particles 2 is at least as long as the number of binding units obtained by the above method is 2-8. And the dispersibility and the electrophoretic property (chargeability) of the electrophoretic particles 1 can be made compatible.

  In this embodiment, such a polymer 39 is obtained by a production method using a living radical polymerization method by reversible addition-fragmentation chain transfer polymerization (RAFT) described later. By using reversible addition-fragmentation chain transfer polymerization (RAFT), a relatively uniform polymer can be obtained. Therefore, if 2 to 10 molar equivalents of the monomer M2 are added to the chain transfer agent and polymerized, the number of bonding units in the bonding portion 31 can be within the above range. When the addition rate of the monomer M2 is 100% or less, the polymerization reaction may be performed with the addition amount of the monomer M2 being 2 to 10 molar equivalents or more in consideration.

  In addition, after producing | generating the dispersion | distribution part 32, when producing | generating a coupling | bond part, the dispersion | distribution part 32 acts as a chain transfer agent. In this case, for example, the weight average molecular weight and the number average molecular weight of the polymer constituting the dispersion portion 32 may be obtained by using the GPC method, and the addition amount of the monomer M2 may be determined based on this.

  As a result, the electrophoretic particles 1 can be made to have a configuration including the polymer 39 so that the effect can be reliably exerted, and the electrophoretic particles 1 have excellent dispersibility in the electrophoretic dispersion liquid.

  In the electrophoretic dispersion liquid, the electrophoretic particles 1 having the above-described configuration are dispersed (suspended) in a dispersion medium (liquid phase dispersion medium).

(Dispersion medium)
As this dispersion medium, in this embodiment, a material mainly composed of silicone oil is used. Silicone oil is used as a dispersion medium because it exhibits excellent affinity for the dispersion part 32 formed by living radical polymerization using the above-described silicone macromonomer as the monomer M1.

  Thereby, since the aggregation suppressing effect of the electrophoretic particles 1 is increased, it is possible to suppress deterioration of the display performance of the electrophoretic display device 920 illustrated in FIG. 4 with time. Silicone oil has the advantage that it has excellent weather resistance and has high safety because it does not have an unsaturated bond.

  Furthermore, the silicone oil (dispersion medium) preferably has a kinematic viscosity at room temperature (25 ° C.) of 5 cs or less, more preferably 2 cs or more and 4 cs or less. Even if the viscosity of the silicone oil (dispersion medium) is within such a range, if the electrophoretic particle 1 is provided with the dispersion part 32 formed by living radical polymerization using a silicone macromonomer as the monomer M1, the dispersion medium It can be dispersed with excellent dispersibility.

  As the silicone oil, those having a relative dielectric constant of 1.5 or more and 3 or less are preferably used, and those having a dielectric constant of 1.7 or more and 2.8 or less are more preferably used. Such a silicone oil is excellent in the dispersibility of the electrophoretic particles 1 and also has good electrical insulation. This contributes to the realization of an electrophoretic display device 920 that consumes less power and can display with high contrast. The value of the dielectric constant is a value measured at 50 Hz, and is a value measured for a dispersion medium having a water content of 50 ppm or less and a temperature of 25 ° C.

  In addition, in the dispersion medium, charge control comprising particles of electrolyte, surfactant (anionic or cationic), metal soap, resin material, rubber material, oils, varnish, compound, etc., if necessary. You may make it add various additives, such as an agent, a lubricant, a stabilizer, and various dyes.

  In the electrophoretic dispersion as described above, a dispersion medium mainly composed of silicone oil, and a dispersion portion 32 formed using the silicone macromonomer represented by the general formula (I) as the monomer M1; However, since both are siloxane compounds, they exhibit excellent affinity. Therefore, it is expected that the electrophoretic particles 1 exhibit excellent dispersibility in the electrophoretic dispersion liquid due to the interaction between the dispersion portion 32 and the dispersion medium included in the polymer 39 (particle surface treatment agent).

  However, even if the combination of the dispersion medium and the dispersion portion 32 has an excellent affinity, the dispersibility of the electrophoretic particles in the electrophoretic dispersion liquid is as high as the target. It has been found that does not improve.

  Here, as will be described in detail later, the polymer 39 is produced by using a dithioester group, a trithiocarbamate, or the like in the case of using a reversible addition-fragmentation chain transfer polymerization (RAFT) method among the living radical polymerization methods. A sulfur compound having a functional group such as a group, a xanthate group or a dithiocarbamate group is preferably used as a chain transfer agent (RAFT agent). In this case, a fragment of the used chain transfer agent (RAFT agent residue) remains at one end of the produced polymer 39. Due to this, in the electrophoretic dispersion liquid, when the electrophoretic display device 920 described later is used or when the electrophoretic display device 920 is manufactured, the electrophoretic dispersion liquid is heated and light is applied to the electrophoretic dispersion liquid. The dithiocarboxylic acid derived from the chain transfer agent leaks, and as a result, impurities such as acid are mixed in the electrophoretic dispersion. Therefore, the electrophoretic particles 1 are aggregated, and the electrophoretic particles 1 are attached to the electrodes 93 and 94 of the electrophoretic display device 920. Finally, the electrophoretic particles in the electrophoretic dispersion liquid It has been clarified by examination of the present inventor that the dispersibility is adversely affected.

  Further, the inventors have further studied to eliminate the adverse effect by setting the content of sulfur element derived from the dithiocarboxylic acid (chain transfer agent) to more than 0 ppm and not more than 20 ppm in the electrophoretic dispersion. In other words, the present inventors have found that the electrophoretic particles 1 can be migrated in a state where the dispersibility of the electrophoretic particles 1 is improved without causing a decrease in contrast or deterioration over time, and the present invention has been completed. It was.

  In addition, the sulfur element derived from dithiocarboxylic acid (chain transfer agent) is not limited to the case where the polymer 39 is generated using a reversible addition-fragmentation chain transfer polymerization (RAFT) method, and a dispersant is added to the dispersion medium. Even when this dispersant (polymer) is produced using a reversible addition-fragmentation chain transfer polymerization (RAFT) method, it may be mixed into the electrophoretic dispersion. Therefore, when at least one of the polymer 39 and the dispersing agent produced by using the reversible addition-fragmentation chain transfer polymerization (RAFT) method is contained in the electrophoretic dispersion, the present invention is applied to perform electrophoresis. By setting the content of elemental sulfur in the dispersion to more than 0 ppm and not more than 20 ppm, the dispersibility of the electrophoretic particles in the electrophoretic dispersion can be improved.

  Examples of the dispersant produced by using the reversible addition-fragmentation chain transfer polymerization (RAFT) method include a dispersion unit 32 provided in the block copolymer 39 and a third monomer having an ionic group as the coupling unit 31 among the coupling unit 31. M3 (hereinafter, also simply referred to as “monomer M3”) is formed by polymerization, and a polar part including a plurality of units derived from monomer M3 is used.

  This polar part is formed by polymerizing a plurality of monomers M3 having a side chain part that contributes to the chargeability into the dispersion medium after polymerization in the electrophoretic dispersion, and is a charging unit derived from the monomer M3. Are connected.

  The monomer M3 is a pendant monofunctional monomer that has one polymerization group so that it can be polymerized by living radical polymerization (radical polymerization), and further has a site that becomes an ionic side chain after polymerization.

  Examples of the ionic side chain include those having an anionic group such as a carboxy group, a sulfonic acid group, and a phosphoric acid group, and those having a cationic group such as an amino group. Examples of the monomer M3 having a chain include ionic monomers represented by the following general formula (V).

［式中、Ｒ^１は水素原子またはメチル基、Ｒ^２およびＲ^３は、それぞれ独立して、炭素数１〜６のアルキル基を表す。］

[Wherein, R ¹ represents a hydrogen atom or a methyl group, and R ² and R ³ each independently represents an alkyl group having 1 to 6 carbon atoms. ]

  Further, the content of elemental sulfur in the electrophoretic dispersion liquid may be more than 0 ppm and 20 ppm or less, but is preferably 0.01 ppm or more and 10 ppm or less, and more preferably 0.01 ppm or more and 5 ppm or less. By setting the content of elemental sulfur within the above range, the dispersibility of the electrophoretic particles can be improved more reliably. In addition, it takes a long time to make the content 0 ppm, that is, to completely eliminate the sulfur element in the electrophoretic dispersion. On the other hand, the working time spent in the removal process can be shortened by setting the content to 0.01 ppm. Therefore, it is possible to provide an electrophoretic dispersion liquid that exhibits both excellent dispersibility and electrophoretic properties and at a reduced production cost.

  In addition, although measurement of content in the electrophoretic dispersion liquid of elemental sulfur is not particularly limited, for example, it can be performed using an inductively coupled plasma mass spectrometry (ICP-MS) method.

  Furthermore, the silicone macromonomer represented by the above general formula (I) used for forming the dispersion part 32 included in the polymer 39 usually proceeds with a hydrosilylation reaction as shown in the following reaction formula (i) to form a polymer. It is generated by making it. As described above, the reaction system includes a catalyst including a group 8 transition metal element such as Pt, and as a result, the group 8 transition metal element such as Pt remains in the electrophoretic dispersion liquid. To do. It is the present invention that the remaining group 8 transition metal element also induces aggregation of the electrophoretic particles 1 and further adhesion of the electrophoretic particles 1 to the electrodes 93 and 94 included in the electrophoretic display device 920. The content of the group 8 transition metal element derived from this catalyst is preferably more than 0 ppm and 2 ppm or less. Thereby, the adverse effect can be eliminated, that is, the electrophoretic particles 1 can be migrated in a state in which the dispersibility of the electrophoretic particles 1 is improved without causing a decrease in contrast or deterioration with time.

［式中、Ｒ^１は水素原子またはメチル基、Ｒ^２は水素原子または炭素数１〜４のアルキル基、Ｒ^３は、炭素数１〜６までのアルキル基およびエチレンオキサイドまたはプロピレンオキサイドのエーテル基のうちの１種を含む構造、Ｒ^４は、Ｒ^３のＳｉ側の末端からメチレン基を除いた構造、ｎは０以上の整数を表す。］

[Wherein, R ¹ is a hydrogen atom or a methyl group, R ² is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ³ is an alkyl group having 1 to 6 carbon atoms and an ether group of ethylene oxide or propylene oxide. R ⁴ is a structure including one of the above, R ⁴ is a structure obtained by removing a methylene group from the Si-side end of R ³ , and n is an integer of 0 or more. ]

  In addition, since the catalyst provided with the group 8 transition metal element such as Pt is used to produce the silicone macromonomer (siloxane compound) represented by the general formula (I), the dispersion portion 32 and the binding portion are used. In addition to the electrophoretic dispersion liquid that includes the electrophoretic particles 1 having the polymer 39 including 31, it may be included in the electrophoretic dispersion liquid that includes the dispersing agent including the dispersion portion 32 and the polar portion. Therefore, when at least one of the electrophoretic particles 1 and the dispersing agent is contained in the electrophoretic dispersion, the content of the group 8 transition metal element in the electrophoretic dispersion is set to more than 0 ppm and 2 ppm or less. Is preferred. Thereby, the dispersibility of the electrophoretic particles in the electrophoretic dispersion liquid can be reliably improved.

  Further, the group 8 transition metal element is not limited to Pt, and may be at least one of the fifth periodic element and the sixth periodic element. A catalyst comprising a Group 8 transition metal element of the fifth periodic element and the sixth periodic element can also be used for the production of the silicone macromonomer (siloxane compound) represented by the general formula (I). Therefore, these metal elements may be contained in the electrophoretic dispersion liquid. However, as the catalyst, a catalyst containing at least one of Ru, Rh and Pd in addition to Pt is preferably used for producing the siloxane compound. Therefore, the dispersibility of the electrophoretic particles can be reliably improved by setting the content of these metal elements in the electrophoretic dispersion to more than 0 ppm and 2 ppm or less. The catalyst containing at least one of Pt, Ru, Rh and Pd is not particularly limited. For example, Pt, Pd, chloroplatinic acid, Wilkinson catalyst represented by the following formula (B1), Examples include Trost catalyst represented by B2) and those represented by the following formula (B3).

  In addition, the catalyst provided with the group 8 transition metal element used for the production | generation of the silicone macromonomer represented by the said general formula (I) is contained in the electrophoretic dispersion liquid in the state which maintained the form of the catalyst. Alternatively, it may exist in a state in which at least one of a complex and a salt different from the form of the catalyst is formed. Thus, even if a group 8 transition metal element is contained in the electrophoresis dispersion liquid in any state, the content of the group 8 transition metal element in the electrophoresis dispersion liquid is set to more than 0 ppm and 2 ppm or less. Thus, the dispersibility of the electrophoretic particles can be reliably improved.

  The content of the group 8 transition metal element in the electrophoretic dispersion is preferably more than 0 ppm and 2 ppm or less, more preferably 0.01 ppm or more and 1.0 ppm or less, and more preferably 0.01 ppm or more and 0.0. More preferably, it is 5 ppm or less. By setting the content of the group 8 transition metal element within the above range, the dispersibility of the electrophoretic particles can be more reliably improved. It takes a long time to make the content 0 ppm, that is, to completely eliminate the content of the group 8 transition metal element in the electrophoretic dispersion. On the other hand, the working time spent in the removal process can be shortened by setting the content to 0.01 ppm. Therefore, it is possible to provide an electrophoretic dispersion liquid that exhibits both excellent dispersibility and electrophoretic properties and at a reduced production cost.

  The electrophoretic particles 1 in which the polymer 39 having the bonding part 31 and the dispersion part 32 as described above are connected to the surface of the base particle 2 at the bonding part 31 are dispersed in silicone oil as a dispersion medium, and An electrophoretic dispersion liquid in which the content of elemental sulfur is more than 0 ppm and not more than 20 ppm can be produced, for example, as follows.

(Method for producing electrophoretic dispersion)
FIG. 3 is a flowchart showing a method for producing an electrophoretic dispersion of the present invention.

  In the method for producing an electrophoretic dispersion liquid having the above-described configuration, a generation step (S1) for generating a plurality of block copolymers 39 (particle surface treatment agents) in which the dispersion portion 32 and the binding portion 31 are connected, and sulfur from the block copolymer 39 is produced. The block copolymer 39 is converted into the mother particle 2 by the removal step (S2) for removing the element, and the reaction between the first functional group of the mother particle 2 and the second functional group of the second monomer M2. A connecting step (S3) for obtaining the electrophoretic particles 1 by forming the covering layer 3 by linking, and a dispersing step (S4) for dispersing the obtained electrophoretic particles 1 in a dispersion medium to obtain an electrophoretic dispersion liquid; have.

  In the production process, the case where the block copolymer 39 is produced by a living radical polymerization method using reversible addition-fragmentation chain transfer polymerization (RAFT) will be described. Furthermore, the block copolymer 39 is obtained by polymerizing the first monomer M1. After forming the dispersed portion 32, the coupling portion 31 in which the second monomer M2 having the second functional group is polymerized may be formed, or the dispersion portion 32 may be formed after the coupling portion 31 is formed. Here, the case where the coupling portion 31 is formed after the dispersion portion 32 is formed will be described.

Hereinafter, each process is explained in full detail.
[1] First, a plurality of block copolymers 39 (particle surface treatment agents) in which the dispersion portion 32 and the bonding portion 31 are connected are generated by a living radical polymerization method using reversible addition-fragmentation chain transfer polymerization (RAFT) ( Production step; S1).

  [1-1] First, the dispersion part 32 in which the first monomer M1 is polymerized is formed by a living radical polymerization method using reversible addition-fragmentation chain transfer polymerization (RAFT).

  As this living polymerization method, living radical polymerization, living cation polymerization, living anion polymerization and the like are generally known, and among them, living radical polymerization is preferably used. By using living radical polymerization, a reaction solution generated in the reaction system can be easily used, and the monomer M1 can be polymerized with good controllability of the reaction.

  Living radical polymerization methods include atom transfer radical polymerization (ATRP), radical polymerization via nitroxide (NMP), radical polymerization using organic tellurium (TERP), and reversible addition-fragmentation chain transfer polymerization (RAFT). Among these, reversible addition-fragmentation chain transfer polymerization (RAFT) is preferably used. According to reversible addition-fragmentation chain transfer polymerization (RAFT), polymerization at the time of polymerization of the monomer M1 can be easily advanced. Moreover, when the molecular weight distribution in the dispersion part 32 is 1.2 or less, it can be easily set within this range.

  For the above reasons, the living radical polymerization method using reversible addition-fragmentation chain transfer polymerization (RAFT) is preferably used for the production of the block copolymer 39. In this case, as described above, the electrophoretic particles comprising the block copolymer 39 are prepared as follows. In the present embodiment, the case where the block copolymer 39 is generated by a living radical polymerization method using reversible addition-fragmentation chain transfer polymerization (RAFT) will be described because the electrophoretic dispersion liquid contains elemental sulfur.

  The polymerization initiator (radical polymerization initiator) used in the reversible addition-fragmentation chain transfer polymerization (RAFT) is not particularly limited. For example, 2,2′-azobisisobutyronitrile (AIBN), 2,2 '-Azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis (2,4-dimethylvaleronitrile), dimethyl 2,2'-azobis (2-methylpropionate), 1 , 1'-azobis (cyclohexane-1-carbonitrile), 2,2'-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride, 2,2'-azobis [2- (2- Azoline initiators such as imidazolin-2-yl) propane, and persulfates such as potassium persulfate and ammonium persulfate.

  For reversible addition-fragmentation chain transfer polymerization (RAFT), a chain transfer agent (RAFT agent) is used in addition to the polymerization initiator. The chain transfer agent is not particularly limited, and examples thereof include a sulfur compound having at least one functional group of a dithioester group, a trithiocarbamate group, a xanthate group, a dithiocarbamate group, and the like.

  Specifically, examples of the chain transfer agent include compounds represented by the following chemical formulas (1) to (7), and one or more of them can be used in combination. These compounds are preferably used because they are relatively easily available and the reaction can be easily controlled.

  Among these, the chain transfer agent is preferably 2-cyano-2-propylbenzodithioate represented by the above chemical formula (6). Thereby, control of reaction can be performed more easily.

  Furthermore, when using reversible addition-fragmentation chain transfer polymerization (RAFT), the ratio of the monomer M1, the polymerization initiator, and the chain transfer agent takes into consideration the degree of polymerization of the dispersion 32 to be formed and the reactivity of the compound such as the monomer M1. These molar ratios are preferably monomer: polymerization initiator: chain transfer agent = 500 to 5: 5 to 0.25: 1. Thereby, the length (polymerization degree) of the dispersion part 32 obtained by superposing | polymerizing the monomer M1 can be set to an appropriate magnitude | size.

  Examples of the solvent for preparing a solution for polymerizing the monomer M1 by reversible addition-fragmentation chain transfer polymerization (RAFT) include water, alcohols such as methanol, ethanol and butanol, hexane, octane, benzene and toluene. And hydrocarbons such as xylene, ethers such as diethyl ether and tetrahydrofuran, esters such as ethyl acetate and butyl acetate, and halogenated aromatic hydrocarbons such as chlorobenzene and o-dichlorobenzene. It can be used alone or as a mixed solvent.

  The solution (reaction solution) is preferably subjected to deoxygenation treatment before starting the polymerization reaction. Examples of the deoxidation treatment include substitution after vacuum degassing with an inert gas such as argon gas and nitrogen gas, purge treatment, and the like.

  In the polymerization reaction of the monomer M1, the monomer polymerization reaction can be performed more quickly and reliably by heating (heating) the temperature of the solution to a predetermined temperature.

  The heating temperature varies slightly depending on the type of the monomer M1 and the like, and is not particularly limited, but is preferably about 30 to 100 ° C. The heating time (reaction time) is preferably about 3 to 48 hours when the heating temperature is in the above range.

  When reversible addition-fragmentation chain transfer polymerization (RAFT) is used, a fragment (thiocarbonylthio group) of the chain transfer agent used is present at one end (front end) of the dispersion portion 32. And the dispersion | distribution part 32 provided with this fragment | piece acts as a chain transfer agent in reaction which superpose | polymerizes the coupling | bond part 31 by the dispersion | distribution part 32 in the following process [1-2].

  In the present embodiment, a silicone macromonomer represented by the general formula (I) is used as the first monomer M1, and the silicone macromonomer (monomer M1) is a catalyst including a group 8 transition metal element. It produces | generates by advancing the said Reaction formula (i) used. As a result, the group 8 transition metal element derived from this catalyst remains in the dispersion portion 32 formed by polymerizing the first monomer M1.

  [1-2] Next, the coupling portion 31 in which the second monomer M2 having the second functional group having reactivity with the first functional group included in the mother particle 2 is polymerized so as to be coupled to the dispersion portion 32 is polymerized. Form.

  As a result, a polymer 39 composed of a block copolymer in which the dispersion part 32 and the bonding part 31 are connected is generated.

  In addition, prior to the formation of the bonding portion 31 using the monomer M2 in this step [1-2], if necessary, the unreacted monomer M1 and solvent used in the step [1-1], polymerization start An impurity such as an agent may be removed and a purification process (removal process) for isolating and purifying the dispersion part 32 may be performed. Thereby, the obtained polymer 39 becomes more uniform and high in purity. The purification treatment is not particularly limited, and examples thereof include a column chromatography method, a recrystallization method, a reprecipitation method, and the like, and one or more of them can be combined.

  As described above, when reversible addition-fragmentation chain transfer polymerization (RAFT) is used, a fragment of the used chain transfer agent is present at one end of the dispersion portion 32. For this reason, the coupling part 31 having such a configuration prepares a solution containing the dispersion part 32 obtained by completing the step [1-1], the monomer M2, and the polymerization initiator, and in this solution It is formed by performing living polymerization again.

  The polymer 39 obtained through this process uses 2,2′-azobisisobutyronitrile (AIBN) as a polymerization initiator and 2 represented by the above chemical formula (6) as a chain transfer agent. When -cyano-2-propylbenzodithioate is used, it is represented by the following chemical formula (VI), and there is a fragment of the used chain transfer agent (RAFT agent residue) at one end, and elemental sulfur is included. . In addition, RAFT agent residue represents the group which consists of a sulfur element etc. which are located in the terminal side rather than the monomer M2 in the polymer 39 represented by following Chemical formula (VI).

［式中、ｎ、ｍは、それぞれ独立して、１以上の整数を表す。］

[Wherein, n and m each independently represents an integer of 1 or more. ]

  Moreover, as a solvent used for this process, the thing similar to what was quoted by the said process [1-1] can be used, and the conditions at the time of superposing | polymerizing the monomer M2 in a solution are the said process [1]. It can be made to be the same as that mentioned as the conditions for polymerizing the monomer M1 in the solution in [1].

  [2] Next, the elemental sulfur derived from the chain transfer agent used in producing the block copolymer 39 is removed from the block copolymer 39 (removal step; S2).

  This removal of the elemental sulfur is carried out in the subsequent step [4], when the electrophoretic particles 1 are dispersed in a dispersion medium to obtain an electrophoretic dispersion, the content of the elemental sulfur in the electrophoretic dispersion is more than 0 ppm and not more than 20 ppm. Implement so that it becomes.

  Furthermore, it is preferable to remove the group 8 transition metal element derived from the catalyst used in producing the silicone macromonomer (monomer M1) when removing this sulfur element. In this case, the group 8 transition metal element is removed so that the content of the group 8 transition metal element in the electrophoretic dispersion is more than 0 ppm and 2 ppm or less.

  [2-1] First, a fragment of the chain transfer agent present at one end of the bonding portion 31 provided in the block copolymer 39 is released (released).

  The detachment of this fragment is because the block copolymer 39 exhibits solubility in an organic solvent, and therefore, the solution of the block copolymer 39 dissolved in the organic solvent was mentioned in the step [1-1]. It can be carried out by adding an excessive polymerization initiator.

  For example, when the polymer 39 is represented by the chemical formula (VI) and 2,2′-azobisisobutyronitrile (AIBN) is used as the polymerization initiator, the reaction represented by the following reaction formula (ii) is performed. By proceeding, the fragment of the chain transfer agent can be released.

  [2-2] Next, the chain transfer agent fragments are removed from the solution of the block copolymer 39 from which the chain transfer agent fragments are released. That is, the elemental sulfur derived from the chain transfer agent is removed from the block copolymer 39.

  In the present specification, the fragment of the chain transfer agent includes a decomposition product of the chain transfer agent fragment, and further a product produced from the fragment of the chain transfer agent (or the decomposition product). I will do it.

  The removal of the fragment (elemental sulfur) of the chain transfer agent is performed in the subsequent step [4] when the electrophoretic particles 1 are dispersed in a dispersion medium to obtain an electrophoretic dispersion liquid. It implements so that content may become more than 0 ppm and 20 ppm or less.

  Furthermore, it is preferable to remove the group 8 transition metal element derived from the catalyst used in producing the silicone macromonomer (monomer M1) when removing the chain transfer agent fragment.

  The removal method for removing the fragment of the chain transfer agent is not particularly limited, and examples thereof include a centrifugal separation method, a heating method, an adsorption method extraction method, and the like, and one or more of these are used in combination. be able to. According to these methods, the fragments of the chain transfer agent can be removed from the block copolymer 39 with an excellent removal rate.

  Here, the centrifugal separation method is a method of separating and removing the chain transfer agent fragments by centrifuging the solution of the block copolymer 39 containing the chain transfer agent fragments.

  In the heating method, the solution of the block copolymer 39 containing the fragment of the chain transfer agent is heated to decompose the fragment of the chain transfer agent, and further, the decomposition product of the obtained fragment of the chain transfer agent is vaporized. It is a method of removing.

  The adsorption method is a method of removing the chain transfer agent by adsorbing a fragment of the chain transfer agent on an adsorbent such as silica gel, alumina or activated carbon. In addition, as a method for adsorbing the chain transfer agent fragments to the adsorbent, the adsorbent is dispersed in the solution of the block copolymer 39 to bring the chain transfer agent fragments into contact with the adsorbent, and the adsorbent is filled. In addition, a method of bringing a chain transfer agent fragment into contact with the adsorbent by allowing the solution of the block copolymer 39 to pass through the column is preferable, but the latter method is preferable. According to the latter method, the contact opportunity between the adsorbent and the fragment of the chain transfer agent can be increased, so that the removal of the fragment of the chain transfer agent can be carried out more efficiently.

  In addition, when removing the group 8 transition metal element derived from the catalyst, the removal is performed simultaneously with the removal of the fragment of the chain transfer agent after the production of the block copolymer 39 as in this step [2]. It may be carried out alone after the production of the silicone macromonomer (first monomer M1) represented by the general formula (I), or alone after the dispersion of the first monomer M1 to produce the dispersion part 32. You may go.

  Further, the removal of the chain transfer agent fragments is not limited to the removal from the block copolymer 39 (particle surface treatment agent), but the dispersion medium contains a dispersant, which is a reversible addition-fragmentation chain transfer polymerization (RAFT). In the case of a polymer produced by a living radical polymerization method using a chain, it is preferable to remove the chain transfer agent fragment after the production of the dispersant. Thereby, in the post-process [4], when the electrophoretic particles 1 are dispersed in a dispersion medium containing a dispersant to obtain an electrophoretic dispersion, the content of the elemental sulfur in the electrophoretic dispersion is more reliably determined. It can be set within the range of more than 0 ppm and 2 ppm or less.

  [3] Next, the first functional group included in the mother particle 2 and the plurality of second functional groups included in the bonding portion 31 are reacted to form a chemical bond between them. The block copolymer 39 (particle surface treatment agent) is connected to the surface of the base particle 2 to form the coating layer 3 (connection step; S3).

  Thereby, the electrophoretic particle 1 in which at least a part of the mother particle 2 is coated with the coating layer 3 is obtained.

Examples of such processes include the dry method and wet method shown below.
<< dry method >>
In the dry method, first, the polymer 39 and the mother particle 2 are mixed in a suitable solvent to prepare a solution. In addition, in order to accelerate | stimulate hydrolysis of the alkoxy silyl group (2nd functional group) with which the polymer 39 is provided in a solution, you may add a trace amount of water, an acid, and a base as needed. Moreover, you may perform a heating, light irradiation, etc. as needed.

  At this time, the volume of the solvent is preferably about 1% by volume or more and about 20% by volume or less, and more preferably about 5% by volume or more and about 10% by volume or less with respect to the volume of the mother particles 2. Thereby, since the contact opportunity of the polymer 39 with respect to the mother particle 2 can be increased, the bonding portion 31 can be more reliably bonded to the surface of the mother particle 2.

  Next, dispersion by ultrasonic irradiation, stirring using a ball mill, bead mill, or the like is performed to adsorb the polymer 39 to the surface of the base particle 2 with high efficiency, and then the solvent is removed.

  Subsequently, the powder obtained by removing the solvent is preferably heated at 100 ° C. to 200 ° C. for 1 hour or more to decompose the alkoxysilyl group (second functional group), thereby generating the mother particles. Electrophoretic particles 1 are obtained by forming a chemical bond with a hydroxyl group (first functional group) exposed on the surface of 2.

Next, the polymer is washed several times in the solvent again using a centrifuge, thereby removing the excess polymer 39 adsorbed on the surface of the mother particle 2 without forming a chemical bond.
Through the above-described steps, purified electrophoretic particles 1 can be obtained.

<< Wet method >>
In the wet method, first, the polymer 39 and the mother particles 2 are mixed in a suitable solvent to prepare a solution. In addition, in order to accelerate | stimulate hydrolysis of the alkoxy silyl group (2nd functional group) with which the polymer 39 is provided in a solution, you may add a trace amount of water, an acid, and a base as needed. Moreover, you may perform a heating, light irradiation, etc. as needed.

  At this time, the volume of the solvent is preferably about 1% by volume or more and about 20% by volume or less, and more preferably about 5% by volume or more and about 10% by volume or less with respect to the volume of the mother particles 2. Thereby, since the contact opportunity of the polymer 39 with respect to the mother particle 2 can be increased, the bonding portion 31 can be more reliably bonded to the surface of the mother particle 2.

  Next, dispersion by ultrasonic irradiation, stirring using a ball mill, a bead mill, or the like is performed so that the polymer 39 is adsorbed on the surfaces of the mother particles 2 with high efficiency. By decomposing the alkoxysilyl group (second functional group) by heating at 200 ° C. for 1 hour or longer, a chemical bond is formed with the hydroxyl group (first functional group) exposed on the surface of the mother particle 2. Thus, electrophoretic particles 1 are obtained.

Next, the polymer is washed several times in the solvent again using a centrifuge, thereby removing the excess polymer 39 adsorbed on the surface of the mother particle 2 without forming a chemical bond.
Through the above-described steps, purified electrophoretic particles 1 can be obtained.

  Depending on the type of monomer M1 constituting the polymer 39, when the electrophoretic particles 1 are dried, they may not be dispersed in the dispersion solvent. In such a case, it is preferable to carry out the solvent replacement method in which the reaction solvent is gradually replaced with the dispersion solvent during the washing operation (without passing through the drying step).

  In addition, as a solvent used for this process, the thing similar to what was quoted by the said process [1-1] can be used, and the silicone oil quoted as a dispersion liquid with which an electrophoretic dispersion liquid is equipped can be used. .

  [4] Next, an electrophoretic dispersion liquid is obtained by dispersing the obtained electrophoretic particles 1 in a dispersion medium (dispersing step; S4).

  As the dispersion medium, in the present embodiment, a material mainly composed of the above-described silicone oil is used.

  At this time, in the step [2], the elemental sulfur derived from the chain transfer agent used in producing the block copolymer 39 is removed from the block copolymer 39. Therefore, since the content of elemental sulfur in the electrophoretic dispersion obtained in this step [4] can be more than 0 ppm and 20 ppm or less, the electrophoretic particles 1 have both excellent dispersibility and electrophoretic properties. An electrophoretic dispersion liquid can be obtained.

  The method for dispersing the electrophoretic particles 1 in the dispersion medium is not particularly limited, and examples thereof include a paint shaker method, a ball mill method, a media mill method, an ultrasonic dispersion method, a stirring dispersion method, and the like. It can carry out combining 1 type (s) or 2 or more types.

  In the case where the dispersion medium contains a dispersant, and this dispersant is a polymer produced by a living radical polymerization method using reversible addition-fragmentation chain transfer polymerization (RAFT), after the production of this dispersant. The removal of elemental sulfur has been carried out. Therefore, also in this case, the content of elemental sulfur in the electrophoretic dispersion obtained in this step [4] can be more than 0 ppm and not more than 20 ppm.

  Through the above-described steps, the electrophoretic particle 1 in which the polymer 39 having the coupling part 31 and the dispersion part 32 is connected to the surface of the base particle 2 at the coupling part 31 is converted into the silicone oil as the dispersion medium. An electrophoretic dispersion liquid is produced which is dispersed and the content of elemental sulfur is more than 0 ppm and not more than 20 ppm. Therefore, in this electrophoretic dispersion, the electrophoretic particles exhibit both excellent dispersibility and electrophoretic properties.

  In the present embodiment, the block copolymer 39 is produced using a reversible addition-fragmentation chain transfer polymerization (RAFT) method, and after the production of the block copolymer 39, the elemental sulfur is removed by removing the elemental sulfur. Although the case where the amount is set within the range of more than 0 ppm and not more than 20 ppm has been described, for example, the element contains sulfur element derived from the sulfur-containing compound used when forming pigment particles or resin particles constituting the mother particle 2 It is possible that In this electrophoretic dispersion liquid, even when sulfur element forms thiol or the like, it is considered that the dispersibility of the electrophoretic particles is adversely affected. Therefore, from this point of view, inclusion of elemental sulfur in the electrophoretic dispersion liquid It is presumed that it is useful to set the amount to more than 0 ppm and not more than 20 ppm. Therefore, the electrophoretic dispersion liquid of the present invention can be applied to an electrophoretic dispersion liquid containing electrophoretic particles provided with such a particle surface treatment agent.

<Electrophoretic display device>
Next, an electrophoretic display device (the electrophoretic device of the present invention) to which the electrophoretic sheet of the present invention is applied will be described.

  FIG. 4 is a diagram schematically illustrating a longitudinal section of an embodiment of the electrophoretic display device, and FIGS. 5 and 6 are schematic diagrams illustrating an operation principle of the electrophoretic display device illustrated in FIG. 4. In the following description, for convenience of explanation, the upper side in FIGS. 4 to 6 will be described as “upper” and the lower side as “lower”.

  The electrophoretic display device 920 shown in FIG. 4 includes an electrophoretic display sheet (front plane) 921, a circuit board (back plane) 922, an adhesive layer 981 that joins the electrophoretic display sheet 921 and the circuit board 922, A sealing portion 97 that hermetically seals a gap between the electrophoretic display sheet 921 and the circuit board 922 is provided.

  An electrophoretic display sheet (electrophoretic sheet of the present invention) 921 includes a substrate 912 including a flat base 92 and a second electrode 94 provided on the lower surface of the base 92, and a lower surface (one surface) of the substrate 912. ) And a display layer 9400 composed of partition walls 940 formed in a matrix and an electrophoretic dispersion liquid 910.

  On the other hand, the circuit board 922 includes a counter substrate 911 including a flat base 91 and a plurality of first electrodes 93 provided on the upper surface of the base 91, and the counter substrate 911 (base 91), for example. A circuit (not shown) including a switching element such as a TFT and a drive IC (not shown) for driving the switching element are included.

Hereinafter, the structure of each part is demonstrated sequentially.
The base portion 91 and the base portion 92 are each composed of a sheet-like (flat plate) member, and have a function of supporting and protecting each member disposed between them.

  Each of the bases 91 and 92 may be either flexible or hard, but preferably has flexibility. By using the flexible base portions 91 and 92, a flexible electrophoretic display device 920, that is, an electrophoretic display device 920 useful for constructing, for example, electronic paper can be obtained.

  Moreover, when each base part (base material layer) 91 and 92 shall have flexibility, it is preferable to respectively comprise these with resin material.

  The average thicknesses of the bases 91 and 92 are appropriately set depending on the constituent material, application, and the like, and are not particularly limited, but are preferably about 20 to 500 μm, and more preferably about 25 to 250 μm. .

  A first electrode 93 and a second electrode 94 that form a layer (film shape) are provided on the surface of the bases 91 and 92 on the partition wall 940 side, that is, on the upper surface of the base 91 and the lower surface of the base 92, respectively. Yes.

  When a voltage is applied between the first electrode 93 and the second electrode 94, an electric field is generated between them, and this electric field acts on the electrophoretic particles 95.

  In the present embodiment, the second electrode 94 is a common electrode, the first electrode 93 is an individual electrode (pixel electrode connected to a switching element) divided in a matrix (matrix), A portion where the two electrodes 94 overlap with one first electrode 93 constitutes one pixel.

  The constituent materials of the electrodes 93 and 94 are not particularly limited as long as they are substantially conductive.

  The average thicknesses of the electrodes 93 and 94 are appropriately set depending on the constituent materials and applications, and are not particularly limited, but are preferably about 0.05 to 10 μm, and about 0.05 to 5 μm. Is more preferable.

  Of the base portions 91 and 92 and the electrodes 93 and 94, the base portion and the electrodes (in the present embodiment, the base portion 92 and the second electrode 94) disposed on the display surface side each have light transmittance. In other words, substantially transparent (colorless transparent, colored transparent or translucent).

  In the electrophoretic display sheet 921, a display layer 9400 is provided in contact with the lower surface of the second electrode 94.

  The display layer 9400 is configured such that an electrophoretic dispersion liquid (the above-described electrophoretic dispersion liquid of the present invention) 910 is contained (enclosed) in a plurality of pixel spaces 9401 defined by partition walls 940.

  The partition 940 is formed between the counter substrate 911 and the substrate 912 so as to be divided in a matrix.

  Examples of the constituent material of the partition wall 940 include various resins such as thermoplastic resins such as acrylic resins, urethane resins, and olefin resins, epoxy resins, melamine resins, and thermosetting resins such as phenol resins. A material etc. are mentioned, Among these, it can use combining 1 type (s) or 2 or more types.

  In this embodiment, the partition wall 940 is bonded to the second electrode 94 via the adhesive layer 982, and thereby the partition wall 940 is fixed to the substrate 912.

  In this embodiment, the electrophoretic dispersion liquid 910 accommodated in the pixel space 9401 is dispersed (suspended) in the dispersion medium 96, in which two types of colored particles 95b and white particles 95a (at least one type of electrophoretic particle 1) are dispersed. The electrophoretic dispersion liquid of the present invention described above is applied.

  In such an electrophoretic display device 920, when a voltage is applied between the first electrode 93 and the second electrode 94, colored particles 95b and white particles 95a (electrophoretic particles) are generated according to the electric field generated therebetween. 1) Electrophoresis toward one of the electrodes.

  In the present embodiment, white particles 95a having a positive charge are used, and negative particles are used as colored particles (black particles) 95b. That is, the electrophoretic particle 1 in which the mother particle 2 is positively (positively) charged is used as the white particle 95a, and the electrophoretic particle 1 in which the mother particle 2 is negatively (negatively) charged as the colored particle 95b. Is used.

  When such electrophoretic particles 1 are used, if the first electrode 93 is set to a negative potential, the colored particles 95b move to the second electrode 94 side as shown in FIG. Gather at 94. On the other hand, the white particles 95 a move to the first electrode 93 side and gather at the first electrode 93. For this reason, when the electrophoretic display device 920 is viewed from above (display surface side), the color of the colored particles 95b can be seen, that is, black can be seen.

  On the other hand, when the first electrode 93 is set to a positive potential, the colored particles 95b move to the first electrode 93 side and gather on the first electrode 93 as shown in FIG. On the other hand, the white particles 95 a move to the second electrode 94 side and gather at the second electrode 94. For this reason, when the electrophoretic display device 920 is viewed from above (the display surface side), the color of the white particles 95a can be seen, that is, white can be seen.

  In such a configuration, the electrophoretic display device is appropriately set by appropriately setting the charge amount of the white particles 95a and the colored particles 95b (electrophoretic particles 1), the polarity of the electrodes 93 or 94, the potential difference between the electrodes 93 and 94, and the like. On the display surface side of 920, desired information (image) is displayed according to the combination of the colors of the white particles 95a and the colored particles 95b, the number of particles gathered at the electrodes 93 and 94, and the like.

  Moreover, it is preferable that the specific gravity of the electrophoretic particles 1 is set to be approximately equal to the specific gravity of the dispersion medium 96. Thereby, even after the application of the voltage between the electrodes 93 and 94 is stopped, the electrophoretic particles 1 can stay in a certain position in the dispersion medium 96 for a long time. That is, information displayed on the electrophoretic display device 920 is held for a long time.

  The average particle diameter of the electrophoretic particles 1 is preferably about 0.1 to 10 μm, and more preferably about 0.1 to 7.5 μm. By setting the average particle size of the electrophoretic particles 1 within the above range, aggregation of the electrophoretic particles 1 and sedimentation in the dispersion medium 96 can be reliably prevented. As a result, the display of the electrophoretic display device 920 is displayed. The deterioration of quality can be suitably prevented.

  In the present embodiment, the electrophoretic display sheet 921 and the circuit board 922 are bonded via the adhesive layer 981. Thereby, the electrophoretic display sheet 921 and the circuit board 922 can be more reliably fixed.

  The average thickness of the adhesive layer 981 is not particularly limited, but is preferably about 1 to 30 μm, and more preferably about 5 to 20 μm.

  A sealing portion 97 is provided between the base portion 91 and the base portion 92 and along the edges thereof. With the sealing portion 97, the electrodes 93 and 94, the display layer 9400, and the adhesive layer 981 are hermetically sealed. Accordingly, it is possible to prevent moisture from entering the electrophoretic display device 920 and more reliably prevent the display performance of the electrophoretic display device 920 from deteriorating.

  As the constituent material of the sealing portion 97, the same materials as those described above as the constituent material of the partition wall 940 can be used.

<Electronic equipment>
Next, the electronic apparatus of the present invention will be described.

The electronic apparatus of the present invention includes the electrophoretic display device 920 as described above.
<< Electronic Paper >>
First, an embodiment when the electronic apparatus of the present invention is applied to electronic paper will be described.

  FIG. 7 is a perspective view showing an embodiment when the electronic apparatus of the present invention is applied to electronic paper.

  An electronic paper 600 shown in FIG. 7 includes a main body 601 composed of a rewritable sheet having the same texture and flexibility as paper, and a display unit 602.

  In such an electronic paper 600, the display unit 602 includes the electrophoretic display device 920 as described above.

<< Display >>
Next, an embodiment when the electronic apparatus of the present invention is applied to a display will be described.

  8 and 9 are diagrams showing an embodiment when the electronic apparatus of the present invention is applied to a display. 8 is a sectional view, and FIG. 9 is a plan view.

  A display (display device) 800 shown in FIGS. 8 and 9 includes a main body 801 and an electronic paper 600 that is detachably attached to the main body 801.

  The main body 801 is provided with an insertion port 805 into which the electronic paper 600 can be inserted on the side (right side in FIG. 8), and two pairs of conveying rollers 802a and 802b are provided therein. When the electronic paper 600 is inserted into the main body 801 through the insertion port 805, the electronic paper 600 is installed in the main body 801 in a state of being sandwiched between the pair of conveyance rollers 802a and 802b.

  Further, a rectangular hole 803 is formed on the display surface side (the front side in FIG. 9) of the main body 801, and a transparent glass plate 804 is fitted in the hole 803. Thereby, the electronic paper 600 installed in the main body 801 can be viewed from the outside of the main body 801. That is, in the display 800, the display surface is configured by visually recognizing the electronic paper 600 installed in the main body 801 on the transparent glass plate 804.

  Further, a terminal portion 806 is provided at the leading end portion (left side in FIG. 8) of the electronic paper 600 in the insertion direction, and the terminal is provided inside the main body portion 801 with the electronic paper 600 installed on the main body portion 801. A socket 807 to which the unit 806 is connected is provided. A controller 808 and an operation unit 809 are electrically connected to the socket 807.

  In such a display 800, the electronic paper 600 is detachably installed on the main body 801, and can be carried and used while being detached from the main body 801.

  Further, in such a display 800, the electronic paper 600 includes the electrophoretic display device 920 as described above.

  Note that the electronic apparatus of the present invention is not limited to the application to the above, and for example, a television, a viewfinder type, a monitor direct view type video tape recorder, a car navigation device, a pager, an electronic notebook, a calculator, an electronic Examples include newspapers, word processors, personal computers, workstations, videophones, POS terminals, and devices equipped with touch panels. The electrophoretic display device 920 can be applied to the display units of these various electronic devices. is there.

  The electrophoretic dispersion, the electrophoretic dispersion manufacturing method, the electrophoretic sheet, the electrophoretic apparatus, and the electronic apparatus according to the present invention have been described based on the illustrated embodiments, but the present invention is not limited thereto. Instead, the configuration of each unit can be replaced with any configuration having a similar function. In addition, any other component may be added to the present invention.

  Furthermore, in the method for producing an electrophoretic dispersion of the present invention, one or two or more optional steps may be added.

Next, specific examples of the present invention will be described.
1. Examination of elemental sulfur in electrophoretic dispersion [Example 1A]
1-1. Synthesis of Dispersed Monomer A terminal hydroxyl group silicone having a molecular weight of 16,000 (“Silane Plain FM-0426” manufactured by JNC): 500 g was added to the flask, and after nitrogen substitution, 150 mL of THF was added, and 15 g of methacryloyl chloride was added to 150 mL of THF. What was dissolved was dropped, and the reaction was carried out by stirring at room temperature for 3 hours. The resulting reaction solution was purified with a silica gel column using a mixed solvent of hexane and chloroform as a developing solvent, thereby removing impurities containing a Group 8 transition metal element and isolating a silicone macromonomer.

1-2. Polymerization of dispersion and bonding part To 100 g of the silicone macromonomer obtained above, 6.2 g of 2-cyano-2-propylbenzodithioate and 600 mg of azobisisobutyronitrile were added to the flask, and the system was replaced with nitrogen. After the replacement, 100 mL of ethyl acetate was further added, and then heated and stirred at 75 ° C. for 1 hour, and then 3-methacryloxypropyltriethoxysilane (manufactured by Shin-Etsu Silicone, “KBE-503”): 7.2 g was added, Furthermore, it superposed | polymerized by heating and stirring at 75 degreeC for 3 hours. The reaction was terminated by cooling the mixture to room temperature to obtain a block copolymer.

1-3. Removal of elemental sulfur To the solution containing the block copolymer obtained above, azobisisobutyronitrile: 600 mg was further added, the system was purged with nitrogen, and then heated and stirred at 80 ° C. for 2 hours. The reaction for releasing the fragment of the chain transfer agent remaining at one end of was proceeded. Thereafter, the resulting reaction solution was purified with a silica gel column using a mixed solvent of hexane and chloroform as a developing solvent, thereby removing the chain transfer agent fragment and isolating the block copolymer.

1-4. Preparation of Electrophoretic Dispersion Into a flask, 10 g of the block copolymer obtained above and titania particles (“CR90” manufactured by Ishihara Sangyo Co., Ltd.): 60 g were added to silicone oil (“KF-96-20cs” manufactured by Shin-Etsu Chemical Co., Ltd.). In addition, after ultrasonication for 1 hour, the block copolymer was bonded to the particles by heating and stirring at 180 ° C. for 4 hours to obtain electrophoretic particles. From the solution after the reaction, the unreacted block copolymer was removed, and the silicone oil (dispersion medium) was replaced with “KF-96-2cs” manufactured by Shin-Etsu Chemical Co., thereby obtaining a white electrophoretic dispersion. In addition, IPC-MS (inductively coupled plasma mass spectrometer, manufactured by SII Corporation) in a solution after adding 2 mL of hydrofluoric acid to 0.4 g electrophoresis dispersion and making it into a solution by performing microwave decomposition at 190 ° C. The content of elemental sulfur measured using “SPS3000”) was 10 ppm.

  Further, a black electrophoretic dispersion was obtained in the same manner as described above except that 60 g of titanium black particles (“SC13-MT” manufactured by Mitsubishi Materials Corporation) were used instead of titania particles. The content of elemental sulfur in the solution measured by IPC-MS using the dispersion was also 10 ppm.

[Example 2A]
In the step of removing elemental sulfur, the addition of azobisisobutyronitrile was performed in the same manner as in Example 1A, except that the time for heating and stirring at 80 ° C. was 1 hour. An electrophoretic dispersion was obtained. In addition, the elemental sulfur measured using IPC-MS in the solution after adding 2 mL of hydrofluoric acid to the white and black 0.4 g electrophoresis dispersion liquid, and making it into a solution by performing microwave decomposition at 190 ° C. Both contents were 19 ppm.

[Comparative Example 1A]
A white and black electrophoretic dispersion of Comparative Example 1A was obtained in the same manner as in Example 1A, except that the sulfur element removal step was omitted. In addition, the elemental sulfur measured using IPC-MS in the solution after adding 2 mL of hydrofluoric acid to the white and black 0.4 g electrophoresis dispersion liquid, and making it into a solution by performing microwave decomposition at 190 ° C. Both contents were 108 ppm.

[Example 1B]
In the polymerization step of the dispersion part and the bond part, instead of 3-methacryloxypropyltriethoxysilane, 5.8 g of N- (2-aminoethyl) aminopropyl methacrylic acid synthesized in-house: Example 1A, except that, in the step of removing elemental sulfur, the time of heating and stirring at 80 ° C. was set to 1 hour after the addition of azobisisobutyronitrile. In the same manner, white and black electrophoretic dispersions of Example 1B were obtained. In addition, the elemental sulfur measured using IPC-MS in the solution after adding 2 mL of hydrofluoric acid to the white and black 0.4 g electrophoresis dispersion liquid, and making it into a solution by performing microwave decomposition at 190 ° C. Both contents were 8 ppm.

[Example 2B]
In the step of removing sulfur, after adding azobisisobutyronitrile, the white and black colors of Example 2B were the same as Example 1B, except that the time for heating and stirring at 80 ° C. was 30 minutes. An electrophoretic dispersion was obtained. In addition, the elemental sulfur measured using IPC-MS in the solution after adding 2 mL of hydrofluoric acid to the white and black 0.4 g electrophoresis dispersion liquid, and making it into a solution by performing microwave decomposition at 190 ° C. Both contents were 15 ppm.

[Comparative Example 1B]
A white and black electrophoretic dispersion liquid of Comparative Example 1B was obtained in the same manner as in Example 1B except that the sulfur element removal step was omitted. In addition, the elemental sulfur measured using IPC-MS in the solution after adding 2 mL of hydrofluoric acid to the white and black 0.4 g electrophoresis dispersion liquid, and making it into a solution by performing microwave decomposition at 190 ° C. Both contents were 61 ppm.

1-5. Evaluation of Electrophoretic Dispersion Liquid Each of the electrophoretic dispersion liquids of Examples and Comparative Examples was evaluated for particle aggregation and electrode adhesion as follows.

<Evaluation of particle aggregation>
That is, the white and black electrophoretic dispersions of each example and each comparative example were each observed at 200 times using a microscope.

  As a result, in the electrophoretic dispersion liquid, no aggregation of the electrophoretic particles is observed, and the electrophoretic particles are evenly spread in the electrophoretic dispersion liquid and no unevenness is observed: ◎, the electrophoretic particle aggregation Although slightly observed, the electrophoretic particles spread almost uniformly in the electrophoretic dispersion and almost no unevenness was observed: ○, obvious aggregation of the electrophoretic particles was observed in the electrophoretic dispersion. If the electrophoretic particles are unevenly distributed in the electrophoretic dispersion liquid and unevenness is observed, it is evaluated as x.

<Electrode adhesion evaluation>
Two ITO vapor-deposited glasses are arranged with a gap of 50 μm, and 15 V between the electrodes is applied between the gaps in the state where both the white and black electrophoretic dispersion liquids of each example and each comparative example are dropped. When applied, the presence or absence of adhesion of the electrophoretic particles to the electrode surface was observed 200 times using a microscope.

As a result, if the electrophoretic particles do not adhere to the electrode surface in the electrophoretic dispersion liquid: ◎, only a small amount of electrophoretic particles adhere to the electrode surface in the electrophoretic dispersion liquid. If the adhesion to the electrode surface is resolved by applying: ○, the adhesion of the electrophoretic particles to the electrode surface is clearly recognized in the electrophoretic dispersion, and the adhesion to the electrode surface is also resolved by applying a voltage. If not: rated as x.
These evaluation results are shown in Table 1.

  As is clear from Table 1, in the electrophoretic dispersion liquid of each example, the aggregation of the electrophoretic particles in the white and black electrophoretic dispersion liquids, and further, the adhesion of the electrophoretic particles to the electrodes are accurately suppressed. As a result, the electrophoretic particles in the electrophoretic dispersion exhibited excellent dispersibility and electrophoretic properties.

  On the other hand, in the electrophoretic dispersion liquid of each comparative example, the electrophoretic particles in the electrophoretic dispersion liquid are caused by the content of elemental sulfur derived from the fragment of the chain transfer agent exceeding 20 ppm. Aggregation between each other and adhesion of electrophoretic particles to the electrode were observed, and as a result, it could not be said to be excellent in dispersibility and electrophoretic properties (particularly dispersibility).

2. Study of group 8 transition metal elements in electrophoretic dispersion [Reference Example 1A]
2-1. Synthesis of Dispersed Monomer A terminal hydroxyl group silicone having a molecular weight of 16,000 (“Silane Plain FM-0426” manufactured by JNC): 500 g was added to the flask, and after nitrogen substitution, 150 mL of THF was added, and 15 g of methacryloyl chloride was added to 150 mL of THF. What was dissolved was dropped, and the reaction was carried out by stirring at room temperature for 3 hours. The resulting reaction solution was purified with a silica gel column using a mixed solvent of hexane and chloroform as a developing solvent, thereby removing impurities containing a Group 8 transition metal element and isolating a silicone macromonomer.

2-2. Polymerization of dispersion and bonding part To 100 g of the silicone macromonomer obtained above, 6.2 g of 2-cyano-2-propylbenzodithioate and 600 mg of azobisisobutyronitrile were added to the flask, and the system was replaced with nitrogen. After the replacement, 100 mL of ethyl acetate was further added, and then heated and stirred at 75 ° C. for 1 hour, and then 3-methacryloxypropyltriethoxysilane (manufactured by Shin-Etsu Silicone, “KBE-503”): 7.2 g was added, Furthermore, it superposed | polymerized by heating and stirring at 75 degreeC for 3 hours. This was cooled to room temperature to complete the reaction, and the solvent was removed to obtain a block copolymer.

2-3. Preparation of Electrophoretic Dispersion Into a flask, 10 g of the block copolymer obtained above and titania particles (“CR90” manufactured by Ishihara Sangyo Co., Ltd.): 60 g were added to silicone oil (“KF-96-20cs” manufactured by Shin-Etsu Chemical Co., Ltd.). In addition, after ultrasonication for 1 hour, the block copolymer was bonded to the particles by heating and stirring at 180 ° C. for 4 hours to obtain electrophoretic particles. From the solution after the reaction, the unreacted block copolymer was removed, and the silicone oil (dispersion medium) was replaced with “KF-96-2cs” manufactured by Shin-Etsu Chemical Co., thereby obtaining a white electrophoretic dispersion. In addition, IPC-MS (inductively coupled plasma mass spectrometer, manufactured by SII Corporation) in a solution after adding 2 mL of hydrofluoric acid to 0.4 g electrophoresis dispersion and making it into a solution by performing microwave decomposition at 190 ° C. The content of group 8 transition metal element (Pt) measured using “SPS3000” was 1 ppm.

  Further, a black electrophoretic dispersion was obtained in the same manner as described above except that 60 g of titanium black particles (“SC13-MT” manufactured by Mitsubishi Materials Corporation) were used instead of titania particles. The content of the group 8 transition metal element (Pt) in the solution measured by IPC-MS using the dispersion was also 1 ppm.

[Reference Example 2A]
The removal of impurities containing a group 8 transition metal element from the obtained reaction solution in the synthesis step of the dispersion portion was performed in place of the above Reference Example 1A except that a centrifuge was used instead of purification using a silica gel column. Similarly, white and black electrophoretic dispersions of Reference Example 2A were obtained. In addition, 8 mL measured using IPC-MS in the solution after adding 2 mL of hydrofluoric acid to the white and black 0.4 g electrophoresis dispersion liquid, and making it into a solution by performing microwave decomposition at 190 ° C. Both transition metal element (Pt) contents were 2 ppm.

[Reference Example 3A]
The white and black electrophoresis of Reference Example 3A was performed in the same manner as in Reference Example 1A, except that the removal of impurities containing a Group 8 transition metal element from the obtained reaction solution in the dispersion step was omitted. A dispersion was obtained. In addition, 8 mL measured using IPC-MS in the solution after adding 2 mL of hydrofluoric acid to the white and black 0.4 g electrophoresis dispersion liquid, and making it into a solution by performing microwave decomposition at 190 ° C. The transition metal element (Pt) content was 3 ppm.

[Reference Example 1B]
In a flask, titania particles (“CR90” manufactured by Ishihara Sangyo Co., Ltd.): 60 g, silicone oil (“KF-96-2cs” manufactured by Shin-Etsu Chemical Co., Ltd.) were added and stirred, and then further a siloxane-based dispersant (manufactured by Shin-Etsu Chemical Co., Ltd.). 1% by weight of “KF-393”) was added to silicone oil (dispersion medium) to obtain a white electrophoretic dispersion. In addition, as a siloxane type dispersing agent, what removed the impurity containing a group 8 transition metal element by refine | purifying previously with the silica gel column which used the mixed solvent of hexane and chloroform as a developing solvent was used. In addition, 2 mL of hydrofluoric acid was added to the 0.4 g electrophoresis dispersion, and the group 8 transition metal element (measured using IPC-MS in the solution after being made into a solution by performing microwave decomposition at 190 ° C. ( The content of Pt) was 1 ppm.

  Further, a black electrophoretic dispersion was obtained in the same manner as described above except that 60 g of titanium black particles (“SC13-MT” manufactured by Mitsubishi Materials Corporation) were used instead of titania particles. The content of the group 8 transition metal element (Pt) in the solution measured by IPC-MS using the dispersion was also 1 ppm.

[Reference Example 2B]
Reference Example 2B is the same as Reference Example 1B except that a centrifuge is used instead of purification using a silica gel column to remove impurities containing a Group 8 transition metal element from a siloxane-based dispersant. White and black electrophoretic dispersions were obtained. In addition, 8 mL measured using IPC-MS in the solution after adding 2 mL of hydrofluoric acid to the white and black 0.4 g electrophoresis dispersion liquid, and making it into a solution by performing microwave decomposition at 190 ° C. Both transition metal element (Pt) contents were 2 ppm.

[Reference Example 3B]
A white and black electrophoretic dispersion liquid of Reference Example 3B was obtained in the same manner as in Reference Example 1B, except that the removal of impurities containing a Group 8 transition metal element from the siloxane-based dispersant was omitted. In addition, 8 mL measured using IPC-MS in the solution after adding 2 mL of hydrofluoric acid to the white and black 0.4 g electrophoresis dispersion liquid, and making it into a solution by performing microwave decomposition at 190 ° C. The transition metal element (Pt) content was 4 ppm.

[Reference Example 1C]
In the step of synthesizing the dispersion portion, a silicone macromonomer obtained by advancing the following reaction formula (ia) using a catalyst containing Pd represented by the above formula (B3) as a catalyst is used. The white and black electrophoretic dispersions of Reference Example 1C were obtained in the same manner as Reference Example 1A, except for the above. The reaction conditions for the hydrosilylation reaction in the following reaction formula (ia) were room temperature, 30 minutes, and a catalyst amount of 0.05 equivalent. Moreover, the 8th group measured using IPC-MS in the solution after adding 2 mL of hydrofluoric acid to the white and black 0.4g electrophoresis dispersion liquid, and making it into a solution by performing a microwave decomposition at 190 degreeC. The content of the transition metal element (Pd) was 1 ppm.

[Reference Example 2C]
The removal of impurities containing a group 8 transition metal element from the reaction solution obtained in the synthesis step of the dispersion portion was replaced with purification using a silica gel column, except that a centrifuge was used, and the above Reference Example 1C Similarly, white and black electrophoretic dispersions of Reference Example 2C were obtained. In addition, 8 mL measured using IPC-MS in the solution after adding 2 mL of hydrofluoric acid to the white and black 0.4 g electrophoresis dispersion liquid, and making it into a solution by performing microwave decomposition at 190 ° C. The content of the transition metal element (Pd) was 2 ppm.

[Reference Example 3C]
The white and black electrophoresis of Reference Example 3C was performed in the same manner as in Reference Example 1C, except that the removal of impurities containing a Group 8 transition metal element from the obtained reaction solution in the dispersion step was omitted. A dispersion was obtained. In addition, 8 mL measured using IPC-MS in the solution after adding 2 mL of hydrofluoric acid to the white and black 0.4 g electrophoresis dispersion liquid, and making it into a solution by performing microwave decomposition at 190 ° C. The content of the transition metal element (Pd) was 4 ppm.

[Reference Example 1D]
In the step of synthesizing the dispersion, a silicone macromonomer obtained by advancing the reaction formula (ia) using a Trost catalyst containing Ru represented by the above formula (B2) as a catalyst as a silicone macromonomer A white and black electrophoretic dispersion liquid of Reference Example 1D was obtained in the same manner as Reference Example 1A except that it was used. The reaction conditions for the hydrosilylation reaction in the above reaction formula (ia) were room temperature, 1 hour, and a catalyst amount of 0.01 equivalent. Moreover, the 8th group measured using IPC-MS in the solution after adding 2 mL of hydrofluoric acid to the white and black 0.4g electrophoresis dispersion liquid, and making it into a solution by performing a microwave decomposition at 190 degreeC. The content of transition metal element (Ru) was 1 ppm.

[Reference Example 2D]
The removal of impurities including a group 8 transition metal element from the obtained reaction solution in the synthesis step of the dispersion portion was replaced with purification using a silica gel column, except that a centrifuge was used, and the above Reference Example 1D Similarly, white and black electrophoretic dispersions of Reference Example 2D were obtained. In addition, 8 mL measured using IPC-MS in the solution after adding 2 mL of hydrofluoric acid to the white and black 0.4 g electrophoresis dispersion liquid, and making it into a solution by performing microwave decomposition at 190 ° C. The content of transition metal element (Ru) was 2 ppm.

[Reference Example 3D]
The white and black electrophoresis of Reference Example 3D was performed in the same manner as Reference Example 1D, except that the removal of the impurities containing the Group 8 transition metal element from the obtained reaction solution in the dispersion step was omitted. A dispersion was obtained. In addition, 8 mL measured using IPC-MS in the solution after adding 2 mL of hydrofluoric acid to the white and black 0.4 g electrophoresis dispersion liquid, and making it into a solution by performing microwave decomposition at 190 ° C. The content of transition metal element (Ru) was 3 ppm.

[Reference Example 1E]
In the step of synthesizing the dispersion, a silicone macromonomer obtained by advancing the above reaction formula (ia) using a Wilkinson catalyst containing Rh represented by the above formula (B1) as a catalyst is used as a silicone macromonomer. The white and black electrophoretic dispersions of Reference Example 1E were obtained in the same manner as Reference Example 1A, except that they were used. The reaction conditions for the hydrosilylation reaction in the above reaction formula (ia) were room temperature for 2 hours and a catalyst amount of 0.05 equivalent. Moreover, the 8th group measured using IPC-MS in the solution after adding 2 mL of hydrofluoric acid to the white and black 0.4g electrophoresis dispersion liquid, and making it into a solution by performing a microwave decomposition at 190 degreeC. The content of the transition metal element (Rh) was 1 ppm.

[Reference Example 2E]
The removal of impurities containing a group 8 transition metal element from the obtained reaction solution in the synthesis step of the dispersion portion was performed in the same manner as in Reference Example 1E except that a centrifuge was used instead of purification using a silica gel column. Similarly, white and black electrophoretic dispersions of Reference Example 2E were obtained. In addition, 8 mL measured using IPC-MS in the solution after adding 2 mL of hydrofluoric acid to the white and black 0.4 g electrophoresis dispersion liquid, and making it into a solution by performing microwave decomposition at 190 ° C. The content of transition metal element (Rh) was 2 ppm.

[Reference Example 3E]
The white and black electrophoresis of Reference Example 3E was performed in the same manner as Reference Example 1E, except that the removal of impurities containing Group 8 transition metal elements from the obtained reaction solution in the synthesis step of the dispersion portion was omitted. A dispersion was obtained. In addition, 8 mL measured using IPC-MS in the solution after adding 2 mL of hydrofluoric acid to the white and black 0.4 g electrophoresis dispersion liquid, and making it into a solution by performing microwave decomposition at 190 ° C. The content of the transition metal element (Rh) was 4 ppm.

2-4. Evaluation of Electrophoretic Dispersion Liquid Each of the electrophoretic dispersion liquids of each reference example was evaluated for particle aggregation and electrode adhesion as follows.

<Evaluation of particle aggregation>
That is, the white and black electrophoretic dispersions of each reference example were each observed at 200 times using a microscope.

  As a result, in the electrophoretic dispersion liquid, no aggregation of the electrophoretic particles is observed, and the electrophoretic particles are evenly spread in the electrophoretic dispersion liquid and no unevenness is observed: ◎, the electrophoretic particle aggregation Although slightly observed, the electrophoretic particles spread almost uniformly in the electrophoretic dispersion and almost no unevenness was observed: ○, obvious aggregation of the electrophoretic particles was observed in the electrophoretic dispersion. If the electrophoretic particles are unevenly distributed in the electrophoretic dispersion liquid and unevenness is observed, it is evaluated as x.

<Electrode adhesion evaluation>
Two ITO vapor-deposited glasses are arranged with a gap of 50 μm, and between this gap, both white and black electrophoretic dispersions of each reference example are dropped, and 15 V is applied between the electrodes. At this time, the presence or absence of the electrophoretic particles adhering to the electrode surface was observed 200 times using a microscope.

As a result, if the electrophoretic particles do not adhere to the electrode surface in the electrophoretic dispersion liquid: ◎, only a small amount of electrophoretic particles adhere to the electrode surface in the electrophoretic dispersion liquid. If the adhesion to the electrode surface is resolved by applying: ○, the adhesion of the electrophoretic particles to the electrode surface is clearly recognized in the electrophoretic dispersion, and the adhesion to the electrode surface is also resolved by applying a voltage. If not: rated as x.
These evaluation results are shown in Table 2.

  As is clear from Table 2, in the electrophoretic dispersion liquid of each reference example in which the content of the group 8 transition metal element derived from the catalyst is 2 ppm or less, aggregation of the electrophoretic particles in the white and black electrophoretic dispersion liquids In addition, the adhesion of the electrophoretic particles to the electrode was accurately suppressed, whereby the electrophoretic particles showed excellent dispersibility and electrophoretic properties in the electrophoretic dispersion.

  On the other hand, in the electrophoretic dispersion liquid of each reference example in which the content of the group 8 transition metal element derived from the catalyst exceeds 2 ppm, aggregation of the electrophoretic particles in the electrophoretic dispersion liquid, and further to the electrode As a result, adhesion of electrophoretic particles was observed, and as a result, it could not be said that it was excellent in dispersibility and electrophoretic properties (particularly dispersibility).

DESCRIPTION OF SYMBOLS 1 ... Electrophoretic particle, 2 ... Mother particle, 3 ... Coating layer, 31 ... Coupling part, 32 ... Dispersion part, 39 ... Block copolymer, 91 ... Base part, 92 ... Base part, 93 ... 1st electrode, 94 ... 2nd 95 ... electrophoretic particles, 95a ... white particles, 95b ... colored particles, 96 ... dispersion medium, 97 ... sealing part, 600 ... electronic paper, 601 ... main body, 602 ... display unit, 800 ... display, 801 ... Main unit, 802a ... conveying roller pair, 802b ... conveying roller pair, 803 ... hole, 804 ... transparent glass plate, 805 ... insertion port, 806 ... terminal part, 807 ... socket, 808 ... controller, 809 ... operation part, 910 Electrophoretic dispersion liquid, 911 ... Counter substrate, 912 ... Substrate, 920 ... Electrophoretic display device, 921 ... Electrophoretic display sheet, 922 ... Circuit board, 940 ... Partition, 981 ... Adhesive , 982 ... adhesive layer, 9400 ... display layer, 9401 ... pixel space, M1 ... first monomer, M2 ... second monomer

Claims (14)

An electrophoretic dispersion liquid containing at least one type of electrophoretic particles and a dispersion medium,
In the electrophoresis dispersion liquid, the content of sulfur element is more than 0 ppm and not more than 20 ppm.   The electrophoretic dispersion according to claim 1, wherein the elemental sulfur is derived from at least one of a particle surface treatment agent used for forming the electrophoretic particles and a dispersant added to the dispersion medium. At least one of the particle surface treatment agent and the dispersant is a polymer produced using a living radical polymerization method by reversible addition-fragmentation chain transfer polymerization,
The electrophoretic dispersion according to claim 2, wherein the elemental sulfur is derived from a fragment of a chain transfer agent remaining at one end of the polymer.   The electrophoretic dispersion according to claim 3, wherein the chain transfer agent is a sulfur compound having at least one functional group selected from a dithioester group, a trithiocarbamate group, a xanthate group, and a dithiocarbamate group.   5. The electrophoretic dispersion according to claim 1, wherein the content of the group 8 transition metal element in the electrophoretic dispersion is more than 0 ppm and 2 ppm or less.   The Group 8 transition metal element is derived from a particle surface treatment agent used for forming the electrophoretic particles and a catalyst used when generating at least one of a dispersant added to the dispersion medium. The electrophoretic dispersion according to claim 5.   The electrophoretic dispersion according to claim 5 or 6, wherein the group 8 transition metal element is at least one of a fifth periodic element and a sixth periodic element. A method for producing an electrophoretic dispersion liquid comprising at least one type of electrophoretic particles and a dispersion medium,
A production step of producing a particle surface treatment agent used for forming the electrophoretic particles using a living radical polymerization method by reversible addition-fragmentation chain transfer polymerization,
A removal step of removing elemental sulfur derived from the chain transfer agent used in the reversible addition-fragmentation chain transfer polymerization from the particle surface treatment agent;
A connecting step of connecting the particle surface treatment agent to the surface of the mother particle to obtain the electrophoretic particles;
A dispersion step of dispersing the electrophoretic particles in the dispersion medium to obtain the electrophoretic dispersion having a content of sulfur element derived from the chain transfer agent of more than 0 ppm and not more than 20 ppm. A method for producing an electrophoretic dispersion. A method for producing an electrophoretic dispersion liquid comprising at least one type of electrophoretic particles and a dispersion medium,
A production step for producing a dispersant added to the dispersion medium using a living radical polymerization method by reversible addition-fragmentation chain transfer polymerization;
A removal step of removing sulfur element derived from the chain transfer agent used in the reversible addition-fragmentation chain transfer polymerization from the dispersant;
A dispersion step of dispersing the electrophoretic particles in the dispersion medium containing the dispersant to obtain the electrophoretic dispersion liquid in which the content of sulfur element derived from the chain transfer agent is more than 0 ppm and not more than 20 ppm. A method for producing an electrophoretic dispersion liquid.   9. The chain transfer agent fragments are removed after the chain transfer agent fragments remaining at one end of the particle surface treatment agent or the dispersant are separated from the particle surface treatment agent in the removing step. Or the method for producing an electrophoretic dispersion liquid according to 9.   In the removing step, the removal method of removing the chain transfer agent fragments includes a centrifugal separation method of centrifuging the chain transfer agent fragments, a heating method of heating and decomposing and vaporizing the chain transfer agent fragments, and the The method for producing an electrophoretic dispersion according to claim 10, which is at least one of adsorption methods in which a fragment of a chain transfer agent is adsorbed on an adsorbent. A substrate,
An electrophoretic sheet comprising: a structure provided on the substrate and containing the electrophoretic dispersion liquid according to claim 1.   An electrophoretic apparatus comprising the electrophoretic sheet according to claim 12.   An electronic apparatus comprising the electrophoresis apparatus according to claim 13.

Images