JP2010244069A - Method of manufacturing microcapsule for electrophoretic display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide: a microcapsule for an electrophoretic display device capable of achieving high display responsiveness and contrast, etc., even at a low application voltage; a method of manufacturing the same; and the electrophoretic display device using the microcapsule. <P>SOLUTION: The microcapsule for the electrophoretic display device is composed by including liquid for which electrophoretic particulates are dispersed in a solvent in a capsule shell body. The electrophoretic particulate is characterized in that a water contact angle is ≥35°, a dry type electrostatic charge amount is ≥10 μc/g by an absolute amount, and particulate dispersion viscosity is ≤300 mPa s. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a microcapsule for an electrophoretic display device in which a dispersion of electrophoretic fine particles is encapsulated in a capsule shell, and an electrophoretic display device using the same.

An electrophoretic display device is a non-luminous display device that uses the electrophoretic phenomenon of pigment particles in a dispersion in which electrophoretic pigment particles are dispersed in a colored solvent. Specifically, at least one of the electrophoretic display devices is transparent. As a display that has a structure in which the above dispersion is sealed in a space provided between various counter electrode substrates (films), and displays an optical density difference caused by migration of electrophoretic fine particles by an applied voltage between the electrode substrates. Conventionally known (for example, refer to Patent Document 1) and has many excellent characteristics such as wide viewing angle, long-time memory without power supply (continuous supply), low power consumption, and the like. .
In particular, in recent years, not only the dispersion liquid is simply enclosed between the counter electrode substrates, but also microcapsules in which the dispersion liquid is enclosed in a capsule shell that is a wall material are spread between the counter electrode substrates. An electrophoretic display device having an arranged structure (see, for example, Patent Document 2 and Patent Document 3) has been developed, and the long-term stability and responsiveness of display compared to conventional electrophoretic display devices that do not use microcapsules. Various functions such as contrast and the number of times the display can be rewritten can be greatly improved.

Moreover, as a typical method for preparing the microcapsule, a coacervation method, an interfacial polymerization method, an in-situ method, and the like can be mentioned. In these methods, all of the electrophoretic fine particles are nonpolar. The dispersion liquid (ink) dispersed in a solvent is dispersed in an aqueous solvent (polar solvent) so as to have a desired droplet diameter, and the capsule shell is formed on the surface of the droplet (interface between the polar solvent and the nonpolar solvent). To form.
In addition to the various characteristics described above, the electrophoretic display device using such microcapsules is a flexible display device that can be bent thinly like paper and a display device that can be easily made large in area and inexpensive. It has been attracting attention as being very useful in obtaining image data, and is expected to be further developed into the so-called digital paper (electronic paper) field such as paper-like display and rewritable paper. Applications to electronic whiteboards, information boards, announcement boards, electronic newspapers, electronic books, and portable terminals (eg PDAs) are also being proposed.

  When application to various display devices such as the above-mentioned various application fields is attempted, further improvement in performance is strongly desired in various performances such as display response at the time of voltage application and contrast that greatly affects the sharpness of an image. In particular, even when a low voltage is applied, there is a demand for an excellent performance in the above performance.

Japanese Patent Publication No. 50-15115 Japanese Patent No. 2551783 JP-A 64-86116

  Therefore, the problem to be solved by the present invention is to use a microcapsule for an electrophoretic display device capable of realizing a high display response and contrast even at a low applied voltage, a method for manufacturing the microcapsule, and the microcapsule. Another object of the present invention is to provide an electrophoretic display device.

The present inventor has intensively studied to solve the above problems. In that process, it is necessary to first increase the chargeability of the electrophoretic fine particles (increase the dry charge amount) in order to achieve high display response even at a low applied voltage. In order to achieve this, it was considered optimal to introduce many polar groups into the fine particles.
However, when a large number of polar groups are introduced into the fine particles in order to further improve the chargeability, various problems as described later arise due to the above-described microcapsule manufacturing method and various performances as a microcapsule for electrophoretic display devices. Therefore, it was practically impossible to give the electrophoretic fine particles with a charge amount for obtaining sufficient responsiveness.

  That is, when a large number of polar groups are introduced into the electrophoretic fine particles, the hydrophilicity of the fine particles themselves is greatly increased. When the electrophoretic fine particles having an excessively high hydrophilicity are used, the microcapsules are prepared at the time of preparation of the microcapsules. Since a large amount of fine particles migrate to the aqueous solvent side, 1) a sufficient amount of fine particles cannot be present in the dispersion finally sealed in the capsule shell, and display performance such as contrast Only low electrophoretic display devices can be obtained, 2) cause contamination of aqueous solvents that become drainage after preparation, and 3) many fine particles adhere to the outer wall surface of the capsule shell when it is formed. There was a problem. Furthermore, even if the electrophoretic fine particles are free from migration to the aqueous solvent side, 4) the dispersibility in non-polar solvents becomes worse, so that after all, sufficient contrast and response speed can be achieved with a low applied voltage. 5) Many of the electrophoretic fine particles move near the interface with the aqueous solvent, and many fine particles adhere to the inner wall of the capsule shell when the capsule shell is formed. The problem of being trapped inside the shell was recognized.

Among the above-mentioned problems, in particular, when the electrophoretic fine particles adhere to the inner and outer wall surfaces of the capsule shell or when the electrophoretic fine particles are taken into the capsule shell, the opaque capsule Since it becomes a shell, even if the microparticles can be migrated at a sufficiently satisfactory level in the microcapsule, an optical change cannot be recognized, resulting in a significant decrease in contrast.
Therefore, the present inventor believes that the above problem can be easily solved by imparting high chargeability to the electrophoretic fine particles and simultaneously imparting appropriate hydrophobicity and lipophilicity. It was. Specifically, with respect to the above-mentioned electrophoretic fine particles, regarding the chargeability, the absolute amount of the dry charge amount of the fine particles is set to a specific value or more, and the hydrophobicity and lipophilicity are indicative of hydrophobicity. Focusing on the water contact angle of the fine particles as described above, making this to be a specific value or more, viscosity of fine particle dispersion as a lipophilic index (viscosity prepared and measured under specific conditions (detailed later)) It was found that it is important to make this less than a specific value.

And if it is a microcapsule for an electrophoretic display device containing such electrophoretic fine particles as a constituent material, and an electrophoretic display device using the microcapsule, it is confirmed that the above problems can be solved at once, The present invention has been completed.
Furthermore, in order to easily prepare the electrophoretic fine particles described above (and thus easily obtain microcapsules for electrophoretic display devices including the electrophoretic fine particles described above as constituent materials), It has been found that high chargeability is imparted by introducing a functional group, and appropriate hydrophobicity and lipophilicity may be imparted by introducing a long-chain alkyl group. In other words, in addition to imparting chargeability by the chargeable functional group, if hydrophobic and lipophilic properties are imparted by the long-chain alkyl group, only hydrophilicity resulting from the chargeability is achieved without reducing the imparted charge amount as much as possible. It has been found that it is possible to effectively reduce the hydrophobicity and impart appropriate hydrophobicity and lipophilicity. In addition, the introduction of the above-mentioned charging functional group or long-chain alkyl group is performed by surface treatment of the fine particles with a coupling agent or a polymer having a reactive group with the fine particles, and the most efficient and sufficient treatment is performed. I thought it would lead to that. Specifically, 1) a coupling agent or fine particle having a long-chain alkyl group as well as a treatment with a coupling agent having a chargeable functional group or a polymer having a reactive group with fine particles and a chargeable functional group. Treatment with a polymer having a reactive group and a long chain alkyl group, or 2) treatment with a coupling agent having both a chargeable functional group and a long chain alkyl group or the above polymer As a result, it has been found that a desired charge amount can be sufficiently imparted, and appropriate hydrophobicity and lipophilicity can be efficiently imparted while suppressing hydrophilicity. It has also been found that the above-mentioned absolute amount of dry charge, water contact angle and fine particle dispersion viscosity can be easily controlled within a specific range by appropriately adjusting the amount of functional group introduced.

And if it was the manufacturing method of the microcapsule for electrophoretic display devices provided with the preparation process of this electrophoretic fine particle, it confirmed that the said subject could be solved easily and came to complete this invention.
That is, the microcapsules for electrophoretic display devices according to the present invention are:
A microcapsule for an electrophoretic display device in which a liquid in which electrophoretic fine particles are dispersed in a solvent is encapsulated in a capsule shell, wherein the electrophoretic fine particles have a water contact angle of 35 ° or more. The dry charge amount is 10 μc / g or more in absolute amount, and the viscosity of the fine particle dispersion is 300 mPa · s or less.

A method for producing a microcapsule for an electrophoretic display device according to the present invention includes:
A method for producing a microcapsule for an electrophoretic display device, wherein a liquid in which electrophoretic fine particles are dispersed in a solvent is encapsulated in a capsule shell, comprising the following step 1) or 2): To do.
1) A surface of the electrophoretic fine particles is coated with a coupling agent having a chargeable functional group and / or a polymer having a group reactive with the electrophoretic fine particles and a chargeable functional group, and a long-chain alkyl group. A treatment with a coupling agent and / or a polymer having a group reactive with the electrophoretic fine particles and a long-chain alkyl group.

  2) The surface of the electrophoretic fine particles is coated with a coupling agent having a chargeable functional group and a long-chain alkyl group, and / or a group reactive with the electrophoretic fine particles, a chargeable functional group, and a long chain. The process of processing with the polymer which has an alkyl group.

  According to the present invention, a microcapsule for an electrophoretic display device capable of realizing high display responsiveness, contrast and the like even at a low applied voltage, a manufacturing method thereof, and an electrophoretic display device using the microcapsule are provided. provide.

Hereinafter, the microcapsules for electrophoretic display devices according to the present invention, the manufacturing method thereof, and the electrophoretic display devices using the same will be described in detail, but the scope of the present invention is not limited to these descriptions, and the following Other than the examples, the present invention can be modified as appropriate without departing from the spirit of the present invention.
The microcapsules for electrophoretic display devices according to the present invention (hereinafter sometimes referred to as the microcapsules of the present invention) are obtained by dispersing a liquid (dispersed liquid for electrophoretic display devices) in which electrophoretic fine particles are dispersed in a solvent. A microcapsule for an electrophoretic display device encapsulated in a capsule shell, wherein the electrophoretic fine particles have a water contact angle of 35 ° or more and a dry charge amount of 10 μc / g or more in absolute quantity. And the viscosity of the fine particle dispersion is 300 mPa · s or less.

In the following, first, the microcapsules of the present invention will be described, and subsequently, a production method for obtaining the microcapsules will be described including its characteristic items.
The microcapsule of the present invention is a microcapsule for an electrophoretic display device in which a dispersion for an electrophoretic display device in which electrophoretic fine particles are dispersed in a solvent is encapsulated in a capsule shell. As the electrophoretic fine particles, those having a dry charge amount (absolute amount), a water contact angle, and a fine particle dispersion viscosity satisfy a specific range are used. That is, it is important to specifically have the following characteristics (i) and (ii) in chargeability, hydrophobicity and lipophilicity.

(I) Regarding chargeability (and thus hydrophilicity), the dry charge amount of the electrophoretic fine particles used is 10 μc / g or more in absolute amount, preferably 15 μc / g or more, more preferably 20 μc / g or more, More preferably, it is 25 μc / g or more. If the absolute amount of the dry charge amount is less than the above range, the electrophoretic properties are lowered, and there is a risk that contrast sufficient for lowering the voltage (lowering applied voltage) may not be obtained. The absolute amount of the dry charge amount may be a positive (+) charge amount or a negative (−) charge amount, and is not particularly limited, and may be appropriately selected as necessary. Good.
Specifically, the dry charge amount of the electrophoretic fine particles is measured using a blow-off charge amount measuring device (manufactured by Toshiba Chemical Corporation). The measurement sample is prepared by sufficiently mixing 0.1 g of electrophoretic fine particles and 10 g of iron powder (product name: DSP-128, manufactured by Dowa Iron Powder Co., Ltd.).

(Ii) The hydrophobicity and hydrophilicity are as follows.
Regarding hydrophobicity, the water contact angle of the electrophoretic fine particles used is 35 ° or more, preferably 40 ° or more, more preferably 45 ° or more, and further preferably 50 ° or more. If the water contact angle is less than the above range, the electrophoretic fine particles may migrate to an aqueous medium or adhere to the capsule shell at the time of microcapsule production.
Specifically, the water contact angle of the electrophoretic fine particles is measured by press-molding the electrophoretic fine particles to form a disk-shaped compact having a smooth surface, and 1.2 μmL of water droplets are placed on the surface of the compact. The angle between the surface of the molded body and the surface of the water droplet and the angle inside the water droplet is measured as the water contact angle. In the preparation of the molded body, additives other than the electrophoretic fine particles are not used, and press molding is performed at room temperature.

The range of the water contact angle described above is a range that needs to be satisfied at least when the water droplet is brought into contact with the molded body in the measurement, but 30 seconds elapse from the time when the water droplet is brought into contact. It is more preferable that it is satisfied, more preferably until 60 seconds elapse, and particularly preferably until 90 seconds elapse.
On the other hand, in the stage after the time when the water droplet is brought into contact, even when it falls below the range of the water contact angle described above, when 30 seconds have passed since the time when the water droplet was brought into contact with the molded body, The water contact angle is preferably 20 ° or more, more preferably 30 ° or more, and further preferably 35 ° or more. If the water contact angle after 30 seconds elapses below 20 °, the migration of the electrophoretic fine particles to the aqueous medium becomes excessive during the production of the microcapsules, and the above-described problem may become prominent.

  Regarding the lipophilicity, the viscosity of the electrophoretic fine particles used is preferably 300 mPa · s or less, more preferably 250 mPa · s or less, further preferably 200 mPa · s or less, and particularly preferably 180 mPa · s or less. is there. When the viscosity of the fine particle dispersion exceeds 300 mPa · s, the affinity of the electrophoretic fine particles with the solvent is deteriorated and the dispersibility is lowered. As a result, the viscosity of the electrophoretic fine particle dispersion becomes high in the obtained microcapsules. For this reason, the display responsiveness is lowered, and sufficient contrast may not be obtained. The viscosity of the fine particle dispersion does not mean the viscosity of the dispersion for an electrophoretic display device contained in the capsule shell in the microcapsule of the present invention, but the specific preparation shown in the examples described later. And the viscosity value measured for the dispersion prepared under the measurement conditions.

In the microcapsule of the present invention, as the electrophoretic fine particles, those subjected to surface treatment with a specific coupling agent and / or a specific polymer are preferably used. Electrophoretic fine particles are surface-treated with this specific coupling agent and / or specific polymer, so that the above-mentioned chargeability (dry charge amount), hydrophobicity (water contact angle) and lipophilicity (fine particle dispersion) (Viscosity) is preferable. Specifically, as the electrophoretic fine particles, electrophoretic fine particles having a charging functional group and a long-chain alkyl group on the surface thereof are preferable.
Specifically, as the surface treatment with the specific coupling agent and / or the specific polymer, at least one surface treatment selected from the group consisting of the following a), b) and c) can be employed.

a) Surface treatment (a-1) with a coupling agent having a chargeable functional group and / or a polymer having a chargeable functional group and a group reactive with the electrophoretic fine particles, and a long-chain alkyl group Surface treatment (a-2) with a polymer having a coupling agent and / or a group having reactivity with the electrophoretic fine particles and a long-chain alkyl group.
b) Surface treatment with a coupling agent having a chargeable functional group and a long-chain alkyl group.
c) Surface treatment with a polymer having a group reactive with the electrophoretic fine particles, a chargeable functional group, and a long-chain alkyl group.
In a), the order of the surface treatment (a-1) and the surface treatment (a-2) is not particularly limited, and either may be performed first or the surface treatment (a It is more preferable to perform surface treatment (a-2) after performing -1) from the viewpoint that efficient surface treatment can be performed efficiently. In addition, as the coupling agent or polymer in the above a), the coupling agent or polymer in b) or c) can be substituted. That is, for example, in a), a coupling agent having a charging functional group and a coupling agent having a charging functional group and a long-chain alkyl group are used in combination to have a charging functional group. This means that a coupling agent and a coupling agent having a long-chain alkyl group may be used in combination.

  The form of the surface treatment with the specific coupling agent and / or the specific polymer is preferably the surface treatment according to a) or the surface treatment according to b) and / or c). A treatment with a functional group-containing coupling agent, a polymer having a reactive group with the electrophoretic fine particles, and a polymer having a long-chain alkyl group is considered to be particularly preferable. Treatment with a coupling agent and a coupling agent having a long-chain alkyl group, followed by treatment with a coupling agent having a chargeable functional group and a long-chain alkyl group is preferred. If it is the process in the said form, charging property, hydrophilic property, and lipophilicity can be more efficiently provided to electrophoretic fine particles.

Examples of the specific coupling agent include a coupling agent having a charging functional group, a coupling agent having a long-chain alkyl group, and a coupling agent having a charging functional group and a long-chain alkyl group.
Examples of the coupling agent having a chargeable functional group include 3-aminopropyltriethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-ureidopropyltriethoxysilane, 3-ureidopropyltrimethoxysilane, and 3-amino. Propyltrimethoxysilane, 3-aminopropyl-tris (2-methoxy-ethoxy-ethoxy) silane, N-methyl-3-aminopropyltrimethoxysilane, N-aminoethyl-3-aminopropyl-trimethoxysilane, diaminosilane N-aminoethyl-3-aminopropylmethyldimethoxysilane, triaminopropyl-trimethoxysilane, 3-chloropropyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-cyanopropyltriethoxysilane, vinylto Chlorosilane, vinyltriethoxysilane, vinyltrimethoxysilane, vinyltri (2-methoxyethoxy) silane, hexamethyldisilazane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyl Trimethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, methyltri (methacryloyloxyethoxy) silane, methyltri (glycidyloxy) silane, 3-glycidoxypropyldimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltri Methoxysilane, 3-methacryloxypropyltrimethoxysilane, γ- (2-aminoethyl) aminopropylmethyldimethoxysilane, N-β (N-vinylbenzylaminoethyl) -γ-amino Propyltrimethoxysilane hydrochloride, octadecyldimethyl [3- (trimethoxysilyl) propyl] ammonium chloride, γ-chloropropylmethyldichlorosilane, trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, methyldichlorosilane, dimethylchlorosilane, dimethylvinyl Chlorosilane, methylvinyldichlorosilane, methylchlorodisilane, triphenylchlorosilane, methyldiphenylchlorosilane, diphenyldichlorosilane, methylphenyldichlorosilane, phenyltrichlorosilane, chloromethyldimethylchlorosilane hexamethyldisilazane, isopropyltri (n-aminoethyl-amino) Ethyl) titanate, tetraisopropyl bis (dioctyl phosphite) titanate, Tiger octyl bis (ditridecylphosphite) titanate, tetra (2,2-diallyl-1-butyl) bis (ditridecyl) phosphite titanate, etc. trifluoropropyl trimethoxysilane. These may be used alone or in combination of two or more.

  Examples of the coupling agent having a long-chain alkyl group include propyltrimethoxysilane, butyltrimethoxysilane, hexyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, hexadecyltrimethoxysilane, octadecyltrimethoxysilane, Propyl dodecyltrichlorosilane, butyltrichlorosilane, hexyltrichlorosilane, decyltrichlorosilane, dodecyltrichlorosilane, hexadecyltrichlorosilane, octadecyltrichlorosilane, isopropyltriisostearoyl titanate, isopropyltrioctanoyl titanate, acetoalkoxyaluminum diisopropylate, etc. Among them, decyltrimethoxysilane, dodecyltrimethoxysilane, hexadecyl Rutrimethoxysilane, octadecyltrimethoxysilane, propyldodecyltrichlorosilane, decyltrichlorosilane, dodecyltrichlorosilane, hexadecyltrichlorosilane, octadecyltrichlorosilane, isopropyltriisostearoyl titanate, isopropyltrioctanoyl titanate, acetoalkoxyaluminum diisopropylate, etc. Is preferred. These may be used alone or in combination of two or more.

Examples of the coupling agent having a charging functional group and a long-chain alkyl group include octadecyldimethyl-3- (trimethoxylyl) propylammonium chloride, dodecafluorooctyltrichlorosilane, isopropyltridodecylbenzenesulfonyl titanate, isopropyl (dioctyl). Sulfate) titanate, and the like. Among them, octadecyldimethyl-3- (trimethoxylyl) propylammonium chloride, dodecafluorooctyltrichlorosilane and the like are preferable. These may be used alone or in combination of two or more.
About the said specific coupling agent, it is preferable that it is at least 1 sort (s) chosen from the group which consists of a silane coupling agent, a titanate coupling agent, and an aluminum coupling agent, for example.

Examples of the specific polymer include a polymer having a group reactive with electrophoretic fine particles and a chargeable functional group, a polymer having a group reactive with electrophoretic fine particles and a long-chain alkyl group, and electricity. Examples thereof include a polymer having a reactive group, a chargeable functional group, and a long-chain alkyl group.
In the specific polymer, the group having reactivity with the electrophoretic fine particles (hereinafter referred to as a reactive group) includes a group consisting of an epoxy group, a thioepoxy group, an alkylamide group, an aziridine group, an oxazoline group and an isocyanate group. At least one selected from the above is preferably used, but as the reactive group, a group excellent in reactivity can be appropriately selected depending on the type of electrophoretic fine particles used. Among these, when the electrophoretic fine particles are titanium oxide particles, the reactive group is particularly preferably an isocyanate group. In the surface treatment with the specific polymer, the affinity between the reactive group and the surface of the electrophoretic fine particle, the chemical bond between the reactive group and the surface of the electrophoretic fine particle, or the like is used.

  The structure and the like of the specific polymer are not particularly limited, but are preferably those that can be dissolved in a solvent used in the dispersion for electrophoretic display devices. Moreover, as said specific polymer, it is preferable to use a thing with a weight average molecular weight Mw of 3,000-100,000, More preferably, it is 3,000-50,000, More preferably, it is 3,000-30,000. Particularly preferred is 3,000 to 20,000, and most preferred is 3,000 to 10,000. When the weight average molecular weight Mw exceeds 100,000, the viscosity of the dispersion liquid for electrophoretic display device contained in the capsule shell is excessively increased, the display response is lowered, and sufficient contrast cannot be obtained. There is a fear. On the other hand, when the weight average molecular weight Mw is less than 3,000, sufficient chargeability or lipophilicity may not be obtained.

  Hereinafter, the polymerizable monomer that can be used in preparing the specific polymer will be described with specific examples. In obtaining the specific polymer, the specific polymer needs to have a predetermined group, that is, a reactive group, a chargeable functional group, and a long-chain alkyl group. It is preferable to use a polymerizable monomer having the above group as an essential component. Specifically, in the polymerizable monomer component to be used, it is preferable that a polymerizable monomer having a reactive group, a polymerizable monomer having a chargeable functional group, and a polymerizable monomer having a long-chain alkyl group are essential. . In addition, for example, instead of using a polymerizable monomer having a reactive group and a polymerizable monomer having a long-chain alkyl group, a polymerizable monomer having both a reactive group and a long-chain alkyl group can be used. Instead of using two or three polymerizable monomers having different predetermined groups, a polymerizable monomer having two or three of the predetermined groups in the same molecule can also be used.

If necessary, the specific polymer may be prepared by introducing the predetermined group into an arbitrary polymer.
Examples of the polymerizable monomer having a reactive group include the following formulas (1) to (5):

Aziridine group-containing polymerizable monomer represented by the formula: 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-vinyl-4- Ethyl-2-oxazoline, 2-vinyl-5-ethyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-methyl-2 -Oxazoline group-containing polymerizability such as oxazoline, 2-isopropenyl-4-ethyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, 2-isopropenyl-4,5-dimethyl-2-oxazoline Monomer; acrylic acid amide, methacrylic acid amide; N-hydroxymethylacrylamide, N-hydroxyethyl Kurylamide, N-hydroxybutylacrylamide, N-hydroxyisobutylacrylamide, N-hydroxy-2-ethylhexylacrylamide, N-hydroxycyclohexylacrylamide, N-hydroxymethylmethacrylamide, N-hydroxyethylmethacrylamide, N-hydroxybutylmethacrylamide, N-hydroxyalkylamide group-containing polymerizable monomers such as N-hydroxyisobutyl methacrylamide, N-hydroxy-2-ethylhexyl methacrylamide, N-hydroxycyclohexyl methacrylamide; the following formulas (6) to (9):

Epoxy group-containing polymerizable monomers represented by the following formulas (10) to (13):

A thioepoxy group-containing polymerizable monomer represented by the following formulas (14) to (16):

And the like. These may be used alone or in combination of two or more.
Examples of the polymerizable monomer having a charging functional group include chlorostyrene, styrene sulfonic acid, acrylic acid, trifluoroethylene acrylate, nitrile acrylate, methacrylic acid, trifluoroethylene methacrylate, nitrile methacrylate, and glycidyl acrylate. Glycidyl methacrylate, tertiary butylaminoethyl methacrylate, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, chlorohydroxypropyl acrylate, chlorohydroxypropyl methacrylate, trichloroethyl acrylate, and trichloroethyl methacrylate These may be used alone or in combination of two or more.

  Examples of the monomer having a long-chain alkyl group include pentyl acrylate, isopentyl acrylate, neopentyl acrylate, hexyl acrylate, octyl acrylate, decyl acrylate, undecyl acrylate, dodecyl acrylate, lauryl acrylate, and acrylic acid. Stearyl, hexadecyl acrylate, heptadecyl acrylate, nonadecyl acrylate, aralkyl acrylate, behenyl acrylate, heptacil acrylate, nonacyl acrylate, doteracyl acrylate, pentyl methacrylate, isopentyl methacrylate, neopentyl methacrylate, hexyl methacrylate, Octyl methacrylate, decyl methacrylate, undecyl methacrylate, dodecyl methacrylate, lauryl methacrylate, stearyl methacrylate, Examples include hexadecyl crylate, heptadecyl methacrylate, nonadecyl methacrylate, aralkyl methacrylate, behenyl methacrylate, heptacil methacrylate, nonacyl methacrylate, and doteracyl methacrylate. These may be used alone or in combination of two or more. May be.

By copolymerizing a monomer component containing at least the monomer having the reactive group and the monomer having the chargeable functional group and / or the monomer having a long-chain alkyl group, the chargeable functional group and / or the long-chain alkyl group is copolymerized. And a specific polymer having a reactive group can be easily obtained.
In obtaining a specific polymer, the blending ratio of various polymerizable monomers having the above-mentioned predetermined group is not particularly limited. However, the electrophoretic fine particles to be surface-treated have desired chargeability and hydrophobic / lipophilic properties. It is preferable to set as appropriate so that a desired reactivity with the surface of the electrophoretic fine particles can be obtained.

  In the preparation of the specific polymer, other polymerizable monomers can be used as necessary in addition to the polymerizable monomers having the predetermined groups listed above. Examples of other monomers include styrene, o-methyl styrene, m-methyl styrene, p-methyl styrene, α-methyl styrene, p-methoxy styrene, p-tert-butyl styrene, p-phenyl styrene, o-chloro. Styrene monomers such as styrene, m-chlorostyrene, p-chlorostyrene; ethylene, propylene, butylene, vinyl chloride, methyl acrylate, ethyl acrylate, n-butyl acrylate, propyl acrylate, isobutyl acrylate, methacrylic acid Examples thereof include methyl, ethyl methacrylate, n-butyl methacrylate, propyl methacrylate, and isobutyl methacrylate. These may be used alone or in combination of two or more.

In the case of using the above other polymerizable monomers, the mixing ratio is not particularly limited, but in consideration of the mixing ratio of the various monomers having the predetermined group described above, the charging obtained by the various monomers having the predetermined group is used. And can be used within the range where the effect of imparting hydrophobicity and hydrophobicity / lipophilicity is not significantly hindered.
The said specific polymer can be obtained by superposing | polymerizing using the monomer component which makes the polymerizable monomer which has the said predetermined group essential. The polymerization method is not particularly limited, and for example, a solution polymerization method, a precipitation polymerization method, a bulk polymerization method, a suspension polymerization method, an emulsion polymerization method and the like can be appropriately selected and employed. And solution polymerization methods are preferred.

  When a polymerization method using a solvent such as the above solution polymerization is adopted, the solvent that can be used is not particularly limited, but for example, aromatic hydrocarbon solvents such as benzene, toluene, xylene, and ethylbenzene; heptane, octane, n -Aliphatic hydrocarbon solvents such as hexane, n-pentane and 2,2,4-trimethylpentane; Alicyclic hydrocarbon solvents such as cyclohexane and methylcyclohexane; Diethyl ether, dibutyl ether, methylbutyl ether Ether solvents such as: solvents of ethylene glycol dialkyl ethers such as dimethoxyethane; organic solvents such as cyclic ether solvents such as THF (tetrahydrofuran) and dioxane; Preparation of dispersion for electrophoretic display Preferably either be used solvent, the solvent used actually in steel 該調 is particularly preferred.

The type of the polymerization reaction is not particularly limited, and preferred examples include anionic polymerization, cationic polymerization, coordination polymerization, and immortal polymerization. Among them, anionic polymerization can be obtained with high reproducibility because a highly pure one can be easily obtained industrially, and since the handling of the reaction initiator is easy and the molecular weight is relatively easy to adjust, More preferred.
Moreover, at the time of the said superposition | polymerization, a conventional general purpose polymerization initiator, antioxidant, solubilizer, etc. can also be added and used as needed.
As the polymerization initiator, a commonly used oil-soluble peroxide-based or azo-based initiator can be used. For example, benzoyl peroxide, lauroyl peroxide, octanoyl peroxide, orthochlorobenzoyl peroxide, orthomethoxybenzoyl peroxide, Peroxide initiators such as methyl ethyl ketone peroxide, diisopropyl peroxydicarbonate, cumene hydroperoxide, cyclohexanone peroxide, t-butyl hydroperoxide, diisopropylbenzene hydroperoxide, and 2,2′-azobisisobuty Ronitrile, 2,2′-azobis- (2,4-dimethylvaleronitrile), 2,2′-azobis- (2,3-dimethylbutyronitrile), 2,2′-azobis (2-methylbutyro) Nitrile), 2,2′-azobis (2-i Propylbutyronitrile), 1,1-azobis- (cyclohexane-1-carbonitrile), 2,2′-azobis- (4-methoxy-2,4-dimethylvaleronitrile), 4,4-azobis-4- Examples include azo initiators such as cyanovaleric acid, 2- (carbamoylazo) isobutyronitrile, dimethyl-2,2′-azobisisobutyrate. These polymerization initiators are preferably used in an amount of 0.01 to 20% by weight, more preferably 0.1 to 10% by weight, based on the total amount of polymerizable monomer used (polymerizable monomer component).

In the polymerization for obtaining the specific polymer, the other reaction conditions such as the reaction temperature and the reaction time can be carried out by employing the polymerization conditions that are usually performed, and can be appropriately set to carry out the polymerization reaction.
Among the specific coupling agent and the specific polymer, a coupling agent having a charging functional group, a coupling agent having a charging functional group and a long-chain alkyl group, a group having reactivity with electrophoretic fine particles, and In a polymer having a chargeable functional group, and a polymer having a group reactive with electrophoretic fine particles, a chargeable functional group, and a long-chain alkyl group, the chargeable functional group is, for example, an amino group or an amide. It is preferably at least one selected from the group consisting of a group, a quaternary ammonium group, a carboxyl group, a glycidyl group, a sulfone group, a nitrile group, a fluorine group and a phosphoric acid group. If the chargeable functional groups in a specific coupling agent or specific polymer are those listed above, the electrophoretic fine particles can be imparted with good chargeability and the electrophoretic properties can be efficiently increased.

  Among the specific coupling agent and the specific polymer, a coupling agent having a long-chain alkyl group, a coupling agent having a chargeable functional group and a long-chain alkyl group, a group having reactivity with electrophoretic fine particles, In a polymer having a long chain alkyl group, and a polymer having a group reactive with electrophoretic fine particles, a chargeable functional group, and a long chain alkyl group, the long chain alkyl group has, for example, 8 or more carbon atoms. It is preferably at least one selected from the group consisting of alkyl groups, more preferably at least one selected from the group consisting of alkyl groups having 8 or more carbon atoms, which essentially requires an alkyl group having 10 or more carbon atoms. More preferably, it is at least one selected from the group consisting of alkyl groups having 10 or more carbon atoms. If the long-chain alkyl group in a specific coupling agent or a specific polymer is listed above, the electrophoretic fine particles can be efficiently hydrophobized, and the water contact angle of the fine particles can be made 35 ° or more. In addition, the electrophoretic fine particles can be efficiently oleophilic, and thus the fine particle dispersion viscosity of the fine particles can be reduced to 300 mPa · s or less. Problems such as adhesion to the capsule shell can be easily avoided, and the dispersibility in the solvent can also be increased efficiently.

By the treatment with the above-described specific coupling agent or specific polymer, the electrophoretic fine particles are imparted with chargeability from the chargeable functional group (and thus imparted hydrophilicity), and from the long-chain alkyl group. Will be given hydrophobicity and lipophilicity.
The method for producing a microcapsule for an electrophoretic display device according to the present invention includes a step of treating the surface of the electrophoretic fine particle to be used with the specific coupling agent and / or the specific polymer described above. However, in general, for example, a production method including a dispersion step and a microencapsulation step described in detail below can be preferably employed.
The dispersion step is a step of dispersing electrophoretic fine particles in a solvent. The dispersion liquid obtained by this step is finally the liquid encapsulated in the microcapsules for electrophoretic display devices. In the dispersion step, the electrophoretic fine particles are once dispersed in the solvent, but in the stage after the final encapsulation in the microcapsules, the dispersion state exactly the same as that during the dispersion is not maintained. Alternatively, the dispersed state may not be temporarily maintained, and there is no particular limitation, but it is preferable to maintain the dispersed state in the dispersing step.

The solvent is not particularly limited as long as it is conventionally used as a dispersion liquid for electrophoretic display devices, and a highly insulating organic solvent is preferable.
Examples of the highly insulating organic solvent include aromatic hydrocarbons such as o-, m- or p-xylene, toluene, benzene, dodecylbenzene, hexylbenzene, phenylxylylethane, and naphthenic hydrocarbons; Aliphatic hydrocarbons such as hexane, n-hexane, kerosene, and paraffinic hydrocarbons; various esters such as ethyl acetate and butyl acetate; ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; methanol, ethanol, isopropanol, Alcohol solvents such as octanol and methyl cellosolve; chlorobutane, chloroform, trichloroethylene, trichlorofluoroethylene, trichloroethane, carbon tetrachloride, cyclohexyl chloride, chlorobenzene, 1,1,2,2-tetrachloroethylene, Halogenated hydrocarbons such as chlorofluoroethane, ethyl tetrafluoride dibromide, ethane bromide, ethane tetrafluoride difluoride, methylene iodide, triiodosilane, methyl iodide; carbon disulfide; Single or a mixture thereof is preferably mentioned. Among them, long-chain alkylbenzenes such as dodecylbenzene and hexylbenzene, phenylxylylethane, and the like are more preferable because they have a high boiling point, a flash point, and almost no toxicity. These solvents may be used alone or in combination of two or more.

The amount of the solvent used is preferably 40 to 95% by weight, more preferably 50 to 92% by weight, and still more preferably 60 to 90% by weight, based on the entire dispersion. When the amount used is less than 40% by weight, the viscosity of the dispersion is increased and the electrophoretic properties of the electrophoretic fine particles are reduced. When it exceeds 95% by weight, the concentration of the electrophoretic fine particles is low. It becomes low, and sufficient contrast cannot be obtained.
The solvent is preferably colorless and transparent, and may be colored as necessary.
When the solvent is colored, the dye used for coloring is not particularly limited, but oil-soluble dyes are preferable, and azo dyes and anthraquinone dyes are more preferable from the viewpoint of ease of use. Specifically, as yellow dyes, azo compounds such as Oil Yellow 3G (manufactured by Orient Chemical Co.) are used, and as orange dyes, azo compounds such as First Orange G (manufactured by BASF) are used as blue dyes. Anthraquinones such as Macrolex Blue RR (manufactured by Bayer) are used as the dye, anthraquinones such as Sumiplast Green G (manufactured by Sumitomo Chemical) are used as the green dye, and oil is used as the brown dye. Azo compounds such as Brown GR (manufactured by Orient Chemical Co., Ltd.) are red dyes, and azo compounds such as Oil Red 5303 (manufactured by Arimoto Chemical Co., Ltd.) and Oil Red 5B (manufactured by Orient Chemical Co., Ltd.) are purple. As the dye, anthraquinones such as Oil Violet # 730 (manufactured by Orient Chemical Co., Ltd.) are used. As the black dye, Sudan Black X6 is used. And (BASF Corp.) azo compounds such as mixtures of anthraquinone MACROLEX Blue FR (manufactured by Bayer AG) and azo Oil Red XO (manufactured by Tho Chemical Co.), is preferred. These dyes may be used alone or in combination of two or more.

It is preferable to use 0.1-10 weight part of said dye with respect to 100 weight part of solvent normally, More preferably, it is 0.5-10 weight part, More preferably, it is 1-10 weight part. When the amount of the dye used is less than 0.1 part by weight, the coloring power is insufficient and sufficient contrast with the electrophoretic fine particles cannot be obtained, and when it exceeds 10 parts by weight, the cost is more than necessary. Will lead to up.
The electrophoretic fine particles may be pigment particles having electrophoretic properties, that is, colored particles having a positive or negative polarity in the dispersion.
As described above, the production method of the present invention includes a step of treating the surface of the electrophoretic fine particles with a specific coupling agent and / or a specific polymer, and obtained by this surface treatment step. The electrophoretic fine particles are used in the dispersion step or the like, and finally the microcapsules for electrophoretic display device of the present invention are obtained.

In the surface treatment step, electrophoretic fine particles are obtained in which the value of the water contact angle and the value of the fine particle dispersion together with the dry charge amount (absolute amount) satisfy the specific ranges described above.
Regarding the treatment of the surface of the electrophoretic fine particles with the specific coupling agent and / or the specific polymer in the surface treatment step, specifically, description of the electrophoretic fine particles used for the microcapsules of the present invention. The same as described above with reference to the surface treatments a), b) and c). Therefore, as the form of the surface treatment, at least one surface treatment selected from the group consisting of a), b) and c) can be adopted, but the surface treatment by a), b) and / or Or a surface treatment by c), and in particular, a treatment with a coupling agent having a chargeable functional group, and a polymer having a group reactive with the electrophoretic fine particles and a long-chain alkyl group. Particularly preferred, next preferred is treatment with a coupling agent having a charging functional group and a coupling agent having a long chain alkyl group, and next preferred is a charging functional group and a long chain alkyl group. It is the process by the coupling agent which has this.

  In the above surface treatment step, the total amount of treatment with a specific coupling agent and a specific polymer (specifically, not the amount used for the surface treatment but the amount used as a result of adhering / bonding to the surface of the fine particles as a result) ) Is preferably 0.5 to 5% by weight with respect to the weight of the electrophoretic fine particles after the surface treatment, more preferably 0.5 to 4.5% by weight, and still more preferably 0.5 to 4.0% by weight. If the total treatment amount is below the above range, it is difficult to obtain the surface treatment effect of the electrophoretic fine particles, and there is a possibility that sufficient electrophoretic properties may not be obtained, and sufficient hydrophobization / hydrophilicity cannot be achieved. Sometimes, the electrophoretic fine particles may migrate to the aqueous medium or adhere to the capsule shell. On the other hand, when the total treatment amount exceeds the above range, the surface treatment effect according to the amount used is difficult to obtain and the cost is high, and the viscosity is low when electrophoretic fine particles are dispersed in a solvent. May become too high, resulting in trouble with electrophoretic properties and poor handling. The treatment amount when the surface treatment is performed with the specific coupling agent and / or the specific polymer is obtained by measuring the weight of the fine particles after the treatment and the weight loss when the treated fine particles are heated and fired. In addition, it can be obtained by a method of calculating the weight ratio of the latter to the former (so-called thermal analysis). Even when either one of the specific coupling agent and the specific polymer is used or when the specific coupling agent is used in combination, it can be similarly determined by the method described above.

In addition, regarding the treatment with the specific coupling agent and / or the specific polymer, the introduction amount of the charging functional group and the introduction amount of the long chain alkyl group are not particularly limited. The quantity ratio may be appropriately set so that the dry charge amount, the water contact angle, and the fine particle dispersion viscosity are within the specific ranges.
The method for surface-treating the electrophoretic fine particles with the specific coupling agent is not particularly limited. For example, (i) dry method: a cup whose concentration is appropriately adjusted to the electrophoretic fine particles being stirred. (Ii) Wet method: a method in which electrophoretic fine particles are dispersed in a solvent to form a slurry, and a coupling agent is added to the slurry, and (iii) a spray method: electricity. A method of spraying a coupling agent on electrophoretic fine particles in a high temperature state when preparing the electrophoretic fine particles is exemplified. Further, various treatment conditions with a specific coupling agent are not particularly limited, and the treatment conditions that are usually employed may be selected as appropriate. Among these, for the dry method, a V-type mixer or a hensiyl mixer is used. It is preferable that the electrophoretic fine particles are mixed well by using, etc., the coupling agent is uniformly attached to each fine particle, and further, a drying heat treatment is performed after spraying. As for the wet method, the electrophoretic fine particles are dispersed in a single particle in a solvent and treated, or the electrophoretic fine particle slurry is heated during or after the addition of the coupling agent, Preferably, the slurry is dried and heat-treated after the coupling agent is added.

The method for surface-treating the electrophoretic fine particles with the specific polymer is not particularly limited. For example, the methods (i) to (iii) that can be adopted when the surface treatment is performed with a specific coupling agent; A similar method can be employed.
In addition, the various treatment conditions with the specific polymer are not particularly limited, and the treatment conditions that are usually employed may be selected as appropriate. Especially, for the dry method, a V-type mixer or a Hensyl mixer is used. It is preferable that the electrophoretic fine particles are mixed well, the polymer is uniformly adhered to each fine particle, and further, a dry heat treatment is performed after spraying. As for the wet method, electrophoretic fine particles are dispersed in a single particle in a solvent and treated, or a slurry of electrophoretic fine particles is heat-treated during or after the addition of the polymer. It is preferable to evaporate and dry the slurry after the addition of heat treatment.

The type of electrophoretic fine particles is not particularly limited. Specifically, white particles such as titanium oxide and black particles such as carbon black and titanium black are preferably used, and will be described later. Other particles may also be used. These may be used alone or in combination of two or more.
In the case of using fine particles of titanium oxide, the type of titanium oxide is not particularly limited as long as it is generally used as a white pigment, and may be a rutile type or anatase type. In view of fading, etc., it is preferable that the rutile type has a low photoactivity, and is further subjected to Si treatment, Al treatment, Si—Al treatment, Zn—Al treatment or the like for reducing the photoactivity. Titanium oxide is more preferable.

As the electrophoretic fine particles, particles other than the titanium oxide fine particles, carbon black, and titanium black may be used in combination, or other particles may be used instead of titanium oxide or the like. The other particles are preferably pigment particles as with the titanium oxide fine particles. Further, the other particles are not necessarily required to have electrophoretic properties like the titanium oxide fine particles and the like, and if necessary, the electrophoretic properties may be imparted by any conventionally known method.
The other particles are not particularly limited. Specifically, for example, white particles other than the above titanium oxide, inorganic pigments such as barium sulfate, zinc oxide, and zinc white; yellow Inorganic pigments such as yellow iron oxide, cadmium yellow, titanium yellow, chrome yellow and chrome lead, insoluble azo compounds such as first yellow, condensed azo compounds such as chromophthal yellow, benzimidazolone azo yellow, etc. Azo complex salts, condensed polycycles such as flavans yellow, organic pigments such as hansa yellow, naphthol yellow, nitro compounds and pigment yellow; in the case of orange, inorganic pigments such as molybdate orange, Organic pigments such as azo complex salts such as orange and condensed polycycles such as belinone orange; red In the system, inorganic pigments such as Bengala and cadmium red, dyed lakes such as Madareki, soluble azo compounds such as lake red, insoluble azo compounds such as naphthol red, condensed azo compounds such as chromophthalscar red , Condensed polycycles such as thioindigo bordeaux, quinacridone pigments such as Shinkashiya Red Y and Hosta Palm Red, organic pigments such as azo pigments such as permanent red and first slow red; Inorganic pigments, dye lakes such as rhodamine lakes, organic pigments such as condensed polycycles such as dioxazine violet; blue pigments such as inorganic pigments such as bitumen, ultramarine, cobalt blue and cerulean blue, and phthalocyanine blue Phthalocyanines such as Indanthrene Organic pigments such as alkaline blue; organic pigments such as alkaline blue; inorganic pigments such as emerald green, chrome green, chromium oxide and viridian; azo complex salts such as nickel azo yellow; pigment green and naphthol Organic pigments such as nitroso compounds such as green, phthalocyanines such as phthalocyanine green; black pigments other than the above carbon black and titanium black, inorganic pigments such as iron black, and organic pigments such as aniline black; Preferably mentioned. These may be used alone or in combination of two or more.

The particle diameter of the electrophoretic fine particles is not particularly limited, but the volume average particle diameter is preferably 0.1 to 5 μm, more preferably 0.2 to 3 μm. When the particle diameter (volume average particle diameter) is less than 0.1 μm, sufficient concealability cannot be obtained in the display portion of the electrophoretic display device, and the coloring degree is lowered, and an electrophoretic display device having high contrast is obtained. If it exceeds 5 μm, it may be necessary to increase the coloring degree of the particles more than necessary (increase the pigment concentration), and the smooth electrophoretic characteristics of the fine particles may be deteriorated. .
The concentration of the electrophoretic fine particles in the dispersion is preferably 5 to 60% by weight, more preferably 5 to 50% by weight, and even more preferably 5 to 40% by weight. When the concentration of the electrophoretic fine particles is less than 5% by weight, the display portion of the electrophoretic display device does not exhibit sufficient coloring and concealment by the electrophoretic fine particles, so that sufficient contrast cannot be obtained and the display is clear. If the amount exceeds 60% by weight, the viscosity during the dispersion process will be high and the load on the dispersion device will be too great, and high energy will be applied to the display part of the electrophoretic display device. If applied, the electrophoretic fine particles may be agglomerated, and the response speed (display response) of the electrophoretic fine particles at a portion where voltage is applied may be reduced.

In the dispersion step, the obtained dispersion liquid may contain some other component as required in addition to the solvent and the electrophoretic fine particles, but the kind thereof is not particularly limited. As said other component, a dispersing agent etc. are mentioned, for example. The dispersant may be contained before or after the electrophoretic fine particles are dispersed in the solvent, and is not particularly limited.
The dispersant is not particularly limited, but generally, any dispersant that can be used to assist dispersion of particles in a solvent may be used. Specifically, for example, the dispersant can be dissolved in a dispersion. Anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, fluorosurfactants, sorbitan fatty acid ester surfactants such as sorbitan sesquioleate, block polymers and graft polymers And the like, and various coupling agents, and the like may be preferably used. These may be used alone or in combination of two or more.

  In the dispersion step, the method for dispersing the electrophoretic fine particles in the solvent is not particularly limited, but any method that is usually used for dispersing desired particles in any solvent may be used. Specifically, for example, a raw material component such as titanium oxide fine particles, a solvent and a coupling agent are charged into an ultrasonic bath, and ultrasonic dispersion is performed while stirring, or dispersion such as paint shaker, ball mill, sand grind mill, etc. A method of dispersing using a machine, a dry method of spraying the coupling agent with dry air or nitrogen gas while forcibly stirring the solvent and fine particles with a V blender, etc. Preferable examples include a wet method in which a coupling agent is added and a spray method in which a coupling agent is sprayed while vigorously stirring a preheated solvent and fine particles.

The microencapsulation step is a step of encapsulating the dispersion of electrophoretic fine particles obtained in the dispersion step with a shell (capsule shell) in the presence of an aqueous medium. By this step, a preparation liquid containing microcapsules (microcapsules for electrophoretic display devices) prepared by microencapsulation and an aqueous medium is obtained.
The method of encapsulating is not particularly limited, and may be appropriately selected and employed from methods generally known as microencapsulation methods. Specifically, for example, a coacervation method (phase separation) Method), melting decomposition cooling method, and powder bed method, so-called interfacial deposition method, interfacial polymerization method, in-situ method, submerged cured film (coating) method (orifice method) and interfacial reaction method (inorganic) And so-called interfacial reaction methods such as a chemical reaction method). Among these, a coacervation method (phase separation method), an in-situ method, an interfacial polymerization method, and a melt decomposition cooling method are more preferable. According to these various production methods, microencapsulation is performed in the presence of an aqueous medium, and a preparation liquid containing microcapsules and an aqueous medium is obtained.

Although it does not specifically limit as an aqueous medium which can be used in the said various manufacturing methods, Specifically, for example, the liquid mixture of water and hydrophilic solvents (alcohol, ketone, ester, glycol etc.), Water-soluble polymers (PVA (polyvinyl alcohol), CMC (carboxymethylcellulose), gelatin, gum arabic, etc.) in water, surfactants in water (anionic surfactants, cationic surfactants, nonions) Or the like, or a solution in which these aqueous media are combined can be used.
The amount of the dispersion obtained in the dispersion step to be dispersed in the aqueous medium is not particularly limited. Specifically, 20 to 200 parts by weight of the dispersion is used with respect to 100 parts by weight of the aqueous medium. Is more preferable, and 30 to 150 parts by weight is more preferable. If the amount is less than 20 parts by weight, the microcapsules have a wide particle size distribution, which may lead to a reduction in production efficiency. If the amount exceeds 200 parts by weight, the suspension may become a reverse suspension and the microcapsules may not be manufactured.

  The raw material for the capsule shell is not particularly limited as long as it is the same as the raw material for the capsule shell in a conventionally known microcapsule. For example, when the coacervation method is used, gum arabic and alginic acid are used. Anionic substances such as sodium, styrene-maleic anhydride copolymer, vinyl methyl ether-maleic anhydride copolymer, phthalate ester of starch and polyacrylic acid are preferably used as raw materials. When using the in situ method, melamine-formalin resin (melamine-formalin prepolymer) is preferably used as a raw material. When the interfacial polymerization method is used, hydrophilic monomers such as polyamines, glycols and polyhydric phenols and hydrophobic monomers such as polybasic acid halides, bishaloformales and polyisocyanates are preferably used as raw materials, polyamides, A capsule shell made of epoxy resin, polyurethane, polyurea or the like is used.

A polyvalent amine or the like can be further added to the raw material of these capsule shells, and microcapsules having a capsule shell excellent in heat-resistant storage stability can be obtained. The use amount of the polyvalent amine or the like may be such that the desired shell physical properties resulting from the raw material of the capsule shell are not significantly impaired.
Examples of the polyvalent amine include aliphatic amines such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, 1,3-propylenediamine, and hexamethylenediamine, and poly (1-5) alkylene (C _2- C ₆ ) Epoxy compound adducts of aliphatic polyvalent amines such as polyamine / alkylene (C ₂ -C ₁₈ ) oxide adducts, aromatic polyvalent amines such as phenylenediamine, diaminonaphthalene and xylylenediamine, and fats such as piperazine Preferred examples include cyclic polyvalent amines and heterocyclic diamines such as 3,9-bis-aminopropyl 2,4,8,10-tetraoxaspiro- [5,5] undecane. These may be used alone or in combination of two or more.

The amount of the capsule shell material used is not particularly limited, but specifically, it is preferably 1 to 50 parts by weight, more preferably 5 to 5 parts by weight with respect to 1 part by weight of the electrophoretic fine particle dispersion. 30 parts by weight. If the amount used is outside the above range, the desired capsule shell thickness described later may not be obtained.
In the microencapsulation step, other components can be used as needed in addition to the aqueous medium, the capsule shell material, and the dispersion obtained in the dispersion step.
The shape of the microcapsule obtained in the microencapsulation step is not particularly limited, but it is preferable to appropriately set the conditions so as to obtain a particle shape such as a true sphere.

  The particle diameter of the obtained microcapsules is not particularly limited, but specifically, it is preferable to appropriately set conditions such as the dispersed particle diameter of the dispersion liquid, more preferably 10 to 300 μm. It is 200 μm, and more preferably 15 to 150 μm. If the particle size of the microcapsule is less than 5 μm, there is a possibility that a sufficient display density may not be obtained in the display part when the microcapsule is used in an electrophoretic display device. In addition to the possibility of problems in mechanical strength, when microcapsules are used in electrophoretic display devices, the electrophoretic properties of titanium oxide particles in the dispersion encapsulated in the microcapsules are not fully exhibited, and display is not possible. Therefore, there is a possibility that the start-up voltage will be high.

The thickness of the capsule shell of the microcapsule to be obtained is not particularly limited, but specifically, it is preferable to appropriately set conditions such as the amount of the capsule shell raw material used so as to be 0.1 to 5 μm. More preferably, it is 0.1-4 micrometers, More preferably, it is 0.1-3 micrometers. When the thickness of the capsule shell is less than 0.1 μm, sufficient strength as the capsule shell cannot be obtained, and when it exceeds 5 μm, the transparency is lowered and the contrast is lowered. The flexibility of the microcapsule itself may be reduced, and the adhesion to the electrode film or the like may be insufficient.
In the manufacturing method of the microcapsule of this invention, another process can be provided as needed other than the said various processes. For example, a step of classifying the prepared microcapsules, a step of washing, and the like can be mentioned.

  As the classification step, for example, wet classification (wet classification step) is preferably employed. The wet classification step is a step of subjecting the preparation solution obtained by the microencapsulation step, that is, a preparation solution containing the prepared microcapsules and an aqueous medium, to a process of classifying the microcapsules. Since classification is performed on the prepared solution, wet classification is performed. Specifically, for example, in the step of classifying the prepared liquid as it is or diluted with an arbitrary aqueous medium and classifying the microcapsules in the prepared liquid to have a desired particle size and particle size distribution. is there. The wet classification can be performed by, for example, a method or an apparatus using a method such as a sieve type (filter type), a centrifugal sedimentation type, or a natural sedimentation type. For microcapsules having a relatively large particle size, the sieve type can be used effectively.

The electrophoretic display device according to the present invention is formed by arranging the microcapsules for electrophoretic display devices according to the present invention between at least one transparent electrode film.
By applying a controlled voltage between the counter electrodes of the electrophoretic display device, the dispersion state of the electrophoretic fine particles in the microcapsule is changed, the optical reflection characteristics are changed, and the required display operation is performed. Can be done.
When producing the electrophoretic display device of the present invention, the microcapsules for electrophoretic display device according to the present invention described above are mixed with a binder polymer or the like to form a paint, and then applied to an electrode film. A method of laminating a coated surface on which microcapsules are arranged with an electrode film is preferable. Also, there is a method of laminating a sheet obtained by mixing the microcapsule with a binder polymer or the like, or a sheet obtained by coating on a film-like substrate after the mixing with two opposing electrode films. Can be mentioned. In any method, it is required that at least one of the opposing electrode films is a transparent electrode (for example, a PET film with ITO).

  Usually, in order to obtain an electrophoretic display device having a stable and excellent display quality, it is desired that the microcapsules are in close contact with the electrode film. This is because if the adhesion to the electrode is low, the response of the electrophoretic fine particles may be lowered or the contrast may be lowered. In order to improve this adhesion, for example, it is conceivable to increase the temperature and pressure during the lamination. Furthermore, by selecting the material and physical properties of the capsule shell as a microcapsule as necessary, the adhesion with the electrode film can be further enhanced. In that case, various conditions such as temperature and pressure are used. Can be laminated so as to have excellent adhesion even in a more relaxed state.

In the electrophoretic display device of the present invention, the particle size of the microcapsule used is not particularly limited, but is preferably 30 to 200 μm, more preferably 50 to 150 μm.
In the electrophoretic display device of the present invention, the clearance between the opposing electrode films is not particularly limited, but is preferably 30 to 150 μm, more preferably 30 to 120 μm.

Hereinafter, the present invention will be described more specifically by way of examples. However, the present invention is not limited to these examples. Hereinafter, for convenience, “parts by weight” may be simply referred to as “parts” and “liters” may be simply referred to as “L”. In addition, “wt%” may be described as “wt%”.
Hereinafter, various measurement methods and evaluation methods in the respective examples and comparative examples will be described.
<Measurement of dry charge>
0.1 g of electrophoretic fine particles are sufficiently mixed with 10 g of iron powder (DSP-128, manufactured by Dowa Iron Powder Co., Ltd.) to create a developer, and a blow-off powder charge measuring device (manufactured by Toshiba Chemical Co., Ltd.). ) To measure the dry charge amount of the electrophoretic fine particles.

The measurement conditions were 0.1 g developer, blow nitrogen pressure 1 kgf / cm ² , measurement time 30 seconds, and a 500 mesh SUS wire mesh was used as the mesh.
<Measurement of water contact angle>
About 1 g of electrophoretic fine particles were press-molded at a room temperature into a disk having a diameter of 1 cm at a pressure of 400 kg / cm ² . The water contact angle of the disk was measured with a contact angle meter DCA-VZ type (manufactured by Kyowa Interface Chemical Co., Ltd.). In this contact angle meter, when a 1.2 μmL water droplet is brought into contact with the press-molded disk surface, the angle formed by the disk surface and the water droplet surface, and the angle inside the water droplet is the angle of the water contact angle. As measured.

The water contact angle was measured twice, 0 seconds (immediately after the water droplet was brought into contact with the disk surface in the measurement with the above contact angle meter) and 30 seconds later.
<Measurement of fine particle dispersion viscosity>
In the solvent used for the dispersion for electrophoretic display devices, electrophoretic fine particles are mixed at a blending ratio of 40 wt%, and ultrasonic dispersion is performed for 30 minutes to prepare a fine particle dispersion. The viscosity of this dispersion is Using an E-type viscometer (VISCOMETER TVE-20L, manufactured by Tokimec Co., Ltd.), the measurement was performed under the following conditions.
Temperature: 25 ° C
Rotor: Cone plate type 1 ° 34 '× R24
Rotational speed: 2.5 rpm for 240 mPa · S or less, 1.0 rpm for 600 mPa · S or less
<Measurement of surface treatment with coupling agent and polymer>
Using a Shimadzu thermogravimetric measuring device DTG-50 (manufactured by Shimadzu Corporation), the surface-treated electrophoretic fine particles are heated from 110 ° C. to 500 ° C. at a temperature rising rate of 6 ° C./min. The ratio of weight loss in air (% by weight) was measured. The reduced weight ratio means the weight ratio of the surface treatment amount to the weight of the electrophoretic fine particles before the heat treatment.

<Measurement of particle size>
The particle size (volume average particle size) of the microcapsules was measured with a laser diffraction / scattering particle size distribution analyzer LA-910 (manufactured by Horiba, Ltd.).
<Measurement of transfer amount of titanium oxide into aqueous medium>
The filtrate after filtering the microcapsule dispersion was evaporated to dryness, the solid content was elementally analyzed, and the amount of titanium oxide in the filtrate was measured to determine the amount transferred into the aqueous medium. About evaluation of this transfer amount, it shows with the ratio (transfer rate (wt%)) of the said transfer amount with respect to the total amount of the used titanium oxide.

<Measurement of contrast>
Using a Macbeth spectrophotometer (product name: SpectroEye, manufactured by Gretag Macbeth), the reflectance of blue display and white display is measured, and the ratio of these reflectances (reflectance ratio (contrast) = white reflectance / blue reflectance). (Reflectance).
Reflectance ratio measures the reflectance of the display (for example, blue) when a direct current is applied to the counter electrode of the electrophoretic display device, and then measures the reflectance of the display (for example, white) when the polarity is switched and applied. And a value calculated from both reflectances. Each reflectance is measured for the entire surface of the electrophoretic display device.

<Evaluation of display responsiveness>
A DC voltage of 30 V is applied between the electrodes of the electrophoretic display device, and the applied electrodes are alternately switched, and the display responsiveness of “blue / white” display is determined by the naked eye and the microscope (product name: power scope KH-2700, ( And manufactured under the following criteria.
A: Blue and white display are instantaneously switched, and the display response is very good.
◯: Sufficient display response is recognized with the naked eye.
Δ: Slightly delayed display response
X: The display response is slow and the switching between blue and white is unclear.

Example 1
100 mL of methanol was weighed into a 300 mL separable flask, and then 0.5 g of aminopropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) as a coupling agent having a chargeable functional group was mixed to obtain a uniform solution. Thereafter, the pH was adjusted to 10 with aqueous ammonia.
To this solution was added 50 g of titanium oxide (titanium oxide fine particles) (product name: Taipei CR-90, manufactured by Ishihara Sangyo Co., Ltd.), and ultrasonic dispersion treatment was performed at 50 ° C. for 60 minutes while stirring with a saddle type blade. Thereafter, 1.5 g of isopropyl triisostearoyl titanate (product name: Preneact KR-TTS, manufactured by Ajinomoto Co., Inc.) as a coupling agent having a long-chain alkyl group is further added, and the dispersion treatment is performed for 60 minutes. Thus, titanium oxide was surface-treated to obtain a dispersion.

Titanium oxide was recovered from this dispersion by centrifugation and dried at 120 ° C. to obtain titanium oxide (1).
The dry charge amount, water contact angle and fine particle dispersion viscosity of this titanium oxide (1) were measured, and the measurement results are shown in Table 1.
In addition, about titanium oxide (1), it was confirmed that it has a chargeable functional group by the measurement of a dry-type charge amount, and it was confirmed that it has a long-chain alkyl group by the measurement of a water contact angle.
14 g of this titanium oxide (1) is added to 130 g of dodecylbenzene and subjected to ultrasonic dispersion treatment for 30 minutes, and then 2 g of an anthraquinone blue oil dye (product name: Oil Blue F, manufactured by Chuo Synthetic Chemical Co., Ltd.) is added. To obtain a dispersion liquid for electrophoretic display (1).

Disperse (product name: ROBOMICS, special machine) 105 g of dispersion liquid for electrophoretic display (1) in an aqueous solution prepared by dissolving 5.5 g of gum arabic and 5.5 g of gelatin in 60 g of water in advance. (Manufactured by Kagaku Kogyo Co., Ltd.) The mixture was added with stirring, the stirring speed was gradually increased, and stirring was performed at 1050 rpm for 30 minutes to obtain a suspension.
After stirring for 30 minutes, while adding 300 mL of hot water of 43 ° C. to this suspension, the stirring speed was gradually decreased to 500 rpm, and further 0.75 mL of 10% NaCO ₃ was added and held for 30 minutes.
To the liquid held for 30 minutes, 11 mL of 10% acetic acid solution was quantitatively added over 25 minutes, and then cooled to 10 ° C. or lower.

After maintaining for 2 hours in the cooled state, 3 mL of 37% formalin aqueous solution was quantitatively added over 30 seconds, and 10 mL of NaCO ₃ was further quantitatively added over 25 minutes.
Thereafter, the mixture is returned to room temperature with stirring and aged for 20 hours to obtain a dispersion of microcapsules (1) in which the dispersion liquid for electrophoretic display (1) is encapsulated in a capsule shell. ) Was prepared. As a result of measuring the particle size of the microcapsule (1), the volume average particle size was 78 μm.
The dispersion of the microcapsule (1) was filtered to obtain a paste having a solid content of 52% microcapsule (1). The amount of titanium oxide in the filtrate was measured, and the rate of transfer to the aqueous medium was determined to be 0%.

Next, 9.6 g of this microcapsule (1) paste, 1.3 g of an acrylic emulsion (solid content 38%) as a binder and 2.8 g of water were uniformly mixed to prepare a coating solution.
This coating solution was applied to a PET film with ITO (transparent electrode) with an applicator having a gap of 100 μm and then dried to obtain a coated sheet of microcapsules (1). An electrophoretic display device (1) was produced by laminating a PET film with ITO (transparent electrode) on this sheet so as to be a facing electrode.
About the produced electrophoretic display device (1), a direct-current voltage of 30 V is applied between both electrodes, the contrast at this time is measured, and the electrophoretic stability of titanium oxide is measured with the naked eye and a microscope (product name: power Scope KH-2700 (manufactured by Hyrocks Co., Ltd.). As a result, the contrast shows a sufficiently large value (5.5), and the display response is white on the negative electrode side and blue on the positive electrode side, and the display response is very good (◎) and stable. The display was confirmed.

In addition, even when the application of the voltage was stopped, the display was maintained for one week or more, and it was confirmed that the display had stable memory properties (long-term display maintenance property, display memory property).
Furthermore, with respect to the electrophoretic display device (1), when the polarity of the voltage to be applied is alternately inverted at a frequency of 1 Hz and the display is repeated, the display is stable even after 10,000 times of inversion. The contrast between white and blue was clear.
-Example 2-
In Example 1, instead of 0.5 g of aminopropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) and 1.5 g of isopropyl triisostearoyl titanate (product name: Preneact KR-TTS, manufactured by Ajinomoto Co., Inc.), charging In the same manner as in Example 1 except that 0.5 g of dimethyloctadecyltrimethoxylylammonium chloride (manufactured by Shin-Etsu Chemical Co., Ltd.) was used as a coupling agent having both a functional group and a long-chain alkyl group, Surface-treated titanium oxide (2), microcapsules (2) and electrophoretic display device (2) were obtained. Various measurements and evaluations similar to those in Example 1 were performed, and the results are shown in Table 1.

In addition, about titanium oxide (2), it was confirmed by the method similar to Example 1 that it has both a chargeable functional group and a long-chain alkyl group.
The average volume particle diameter of the microcapsules (2) was 48 μm.
For the electrophoretic display device (2), a direct current voltage of 30 V is applied between the electrodes, the contrast at this time is measured, and the electrophoretic stability of titanium oxide is visually and microscopically (product name: power scope KH -2700, manufactured by Hylox Corporation). As a result, the contrast shows a sufficiently large value (4.7), and the display responsiveness is displayed with white on the negative electrode side and blue on the positive electrode side, and the display responsiveness is very good (◯) stable. The display was confirmed.

In addition, even when the application of the voltage was stopped, the display was maintained for one week or more, and it was confirmed that the display had stable memory properties (long-term display maintenance property, display memory property).
Furthermore, with respect to the electrophoretic display device (2), when the polarity of the applied voltage is alternately reversed at a frequency of 1 Hz and the display is repeated, the display is stable even after 10,000 times of reversal. The contrast between white and blue was clear.
-Example 3-
In Example 2, except that the amount of dimethyloctadecyltrimethoxylylammonium chloride (manufactured by Shin-Etsu Chemical Co., Ltd.) was changed from 0.5 g to 2.5 g, surface-treated titanium oxide ( 3) A microcapsule (3) and an electrophoretic display device (3) were obtained. Various measurements and evaluations similar to those in Example 1 were performed, and the results are shown in Table 1.

In addition, about titanium oxide (3), it was confirmed by the method similar to Example 1 that it has both a charging functional group and a long-chain alkyl group.
The average volume particle diameter of the microcapsules (3) was 93 μm.
Regarding the electrophoretic display device (3), a direct current voltage of 30 V is applied between the electrodes, the contrast at this time is measured, and the electrophoretic stability of titanium oxide is measured with the naked eye and a microscope (product name: power scope KH). -2700, manufactured by Hylox Corporation). As a result, the contrast shows a sufficiently large value (3.4), and the display responsiveness is displayed with white on the negative electrode side and blue on the positive electrode side, and the display responsiveness is very good (◯) stable. The display was confirmed.

In addition, even when the application of the voltage was stopped, the display was maintained for one week or more, and it was confirmed that the display had stable memory properties (long-term display maintenance property, display memory property).
Furthermore, with respect to the electrophoretic display device (3), when the polarity of the applied voltage is alternately inverted at a frequency of 1 Hz and the display is repeated, the test is repeated, and the display is stable even after 10,000 inversions. The contrast between white and blue was clear.
Example 4
100 mL of methanol was weighed into a 300 mL separable flask, and then 0.5 g of aminopropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) as a coupling agent having a chargeable functional group was mixed to obtain a uniform solution. Thereafter, the pH was adjusted to 10 with aqueous ammonia.

To this solution is added 50 g of titanium oxide (titanium oxide fine particles) (product name: Taipei CR-90, manufactured by Ishihara Sangyo Co., Ltd.), and ultrasonic dispersion treatment is performed at 50 ° C. for 60 minutes while stirring with a saddle type blade. Thus, titanium oxide was surface-treated to obtain a dispersion. Titanium oxide was recovered from this dispersion by centrifugation, and the recovered titanium oxide was dried at 120 ° C.
A polymer having an isocyanate group as a reactive group with titanium oxide and a lauryl group as a long-chain alkyl group prepared in advance from the recovered and dried titanium oxide (polymerizable monomer component used as a raw material) Composition ratio (weight): “cyclohexyl methacrylate / lauryl methacrylate / isocyanate ethyl methacrylate / = 6/3/1”, weight average molecular weight Mw: 13,000) The titanium oxide was surface-treated by carrying out ultrasonic dispersion treatment at 50 ° C. for 60 minutes while stirring at a temperature to obtain a dispersion. Titanium oxide was recovered from this dispersion by centrifugation and dried at 120 ° C. to obtain titanium oxide (4).

Thereafter, in the same manner as after obtaining titanium oxide (1) in Example 1, microcapsules (4) and electrophoretic display devices (4) were obtained. Various measurements and evaluations similar to those in Example 1 were performed, and the results are shown in Table 1.
In addition, about titanium oxide (4), it was confirmed by the method similar to Example 1 that it has both a charging functional group and a long-chain alkyl group.
The average volume particle diameter of the microcapsules (4) was 120 μm.
Regarding the electrophoretic display device (4), a direct current voltage of 30 V was applied between both electrodes, the contrast at this time was measured, and the electrophoretic stability of titanium oxide was visually and microscopically (product name: power scope KH -2700, manufactured by Hylox Corporation). As a result, the contrast showed a sufficiently large value (5.2), and the display response was white on the negative electrode side and blue on the positive electrode side, and the display response was very good (◎) and stable. The display was confirmed.

In addition, even when the application of the voltage was stopped, the display was maintained for one week or more, and it was confirmed that the display had stable memory properties (long-term display maintenance property, display memory property).
Furthermore, with respect to the electrophoretic display device (4), when the polarity of the applied voltage is alternately inverted at a frequency of 1 Hz and the display is repeated, the test is repeated, and the display is stable even after 10,000 inversions. The contrast between white and blue was clear.
-Example 5
In Example 1, instead of aminopropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.), isopropyltris (dioctylpyrophosphate) titanate (product name) as a coupling agent having a chargeable functional group and a long-chain alkyl group : Preneact KR-38S, manufactured by Ajinomoto Co., Inc., and a coupling agent having a long chain alkyl group instead of isopropyl triisostearoyl titanate (Product name: Preneact KR-TTS, manufactured by Ajinomoto Co., Inc.) The surface-treated titanium oxide (5), microcapsule (5), and electrophoretic display device (5) were obtained in the same manner as in Example 1 except that 0.5 g of octadecyltrichlorosilane was used. Various measurements and evaluations similar to those in Example 1 were performed, and the results are shown in Table 1.

In addition, about titanium oxide (5), it was confirmed by the method similar to Example 1 that it has both a chargeable functional group and a long-chain alkyl group.
The average volume particle diameter of the microcapsules (5) was 88 μm.
For the electrophoretic display device (5), a direct current voltage of 30 V is applied between the electrodes, the contrast at this time is measured, and the electrophoretic stability of titanium oxide is visually and microscopically (product name: power scope KH -2700, manufactured by Hylox Corporation). As a result, the contrast shows a sufficiently large value (5.3), and the display responsiveness is white on the negative electrode side and blue on the positive electrode side, and the display responsiveness is very good (◎) and stable. The display was confirmed.

In addition, even when the application of the voltage was stopped, the display was maintained for one week or more, and it was confirmed that the display had stable memory properties (long-term display maintenance property, display memory property).
Furthermore, with respect to the electrophoretic display device (5), when the polarity of the applied voltage is alternately inverted at a frequency of 1 Hz and the display is repeated, the display is stable even after 10,000 times of inversion. The contrast between white and blue was clear.
-Comparative Example 1-
Titanium oxide dispersion was obtained by adding 14 g of titanium oxide (product name: Taipei CR-90, manufactured by Ishihara Sangyo Co., Ltd.) to 130 g of dodecylbenzene solution and carrying out ultrasonic dispersion for 60 minutes.

Thereafter, titanium oxide (c1) was obtained in the same manner as in Example 1, and further microcapsules (c1) and electrophoretic display devices (c1) were obtained. Various measurements and evaluations similar to those in Example 1 were performed, and the results are shown in Table 1. In addition, about the measurement of a water contact angle, the disk which shape | molded the titanium oxide absorbed water too much, and was not measurable.
As for titanium oxide (c1), the presence of the chargeable functional group and the long-chain alkyl group was not confirmed by the same method as in Example 1.
The average volume particle diameter of the microcapsule (c1) was 70 μm.
For the electrophoretic display device (c1), a direct current voltage of 30 V was applied between the electrodes, the contrast at this time was measured, and the electrophoretic stability of titanium oxide was measured with the naked eye and a microscope (product name: Powerscope KH). -2700, manufactured by Hylox Corporation). As a result, the contrast shows a very low value (1.0), and the display responsiveness does not show any migration of titanium oxide even when a voltage is applied between both electrodes, and the change in display can be confirmed. There wasn't. Therefore, display memory properties and repeated tests could not be evaluated.

-Comparative Example 2-
In Example 2, instead of 0.5 g of dimethyloctadecyltrimethoxylylammonium chloride (manufactured by Shin-Etsu Chemical Co., Ltd.), isopropyl tris (dioctyl pyrophosphate) as a coupling agent having a chargeable functional group and a long-chain alkyl group ) Titanium oxide (c2), microcapsule (c2) and electric surface-treated in the same manner as in Example 2 except that 0.5 g of titanate (product name: Preneact KR-38S, manufactured by Ajinomoto Co., Inc.) was used. An electrophoretic display device (c2) was obtained. Various measurements and evaluations similar to those in Example 1 were performed, and the results are shown in Table 1.

In addition, about titanium oxide (c2), it was confirmed by the method similar to Example 1 that it has both a chargeable functional group and a long-chain alkyl group.
The average volume particle diameter of the microcapsules (c2) was 95 μm.
For the electrophoretic display device (c2), a 30 V DC voltage was applied between the electrodes, the contrast at this time was measured, and the electrophoretic stability of the titanium oxide was measured with the naked eye and a microscope (product name: Powerscope KH). -2700, manufactured by Hylox Corporation). As a result, the contrast shows a very low value (1.0), and the display responsiveness does not show any migration of titanium oxide even when a voltage is applied between both electrodes, and the change in display can be confirmed. There wasn't. Therefore, display memory properties and repeated tests could not be evaluated.

-Comparative Example 3-
In Example 1, instead of 1.5 g of isopropyl triisostearoyl titanate (product name: Preneact KR-TTS, manufactured by Ajinomoto Co., Inc.) as a coupling agent having a long chain alkyl group, another long chain alkyl group was used. In the same manner as in Example 1, except that 1.5 g of tetradiacloxymethylbutyl bisditridecyl phosphito titanate (product name: Preneact KR-55, manufactured by Ajinomoto Co., Inc.) was used as the coupling agent. Treated titanium oxide (c3), microcapsules (c3) and electrophoretic display device (c3) were obtained. Various measurements and evaluations similar to those in Example 1 were performed, and the results are shown in Table 1. Incidentally, the viscosity of the fine particle dispersion of titanium oxide (c3) was too high (1200 mPa · s or more) and could not be measured under the conditions described above.

Titanium oxide (c3) was confirmed to have both a chargeable functional group and a long-chain alkyl group by the same method as in Example 1.
The average volume particle diameter of the microcapsule (c3) was 75 μm.
For the electrophoretic display device (c3), a 30 V DC voltage was applied between the electrodes, the contrast at this time was measured, and the electrophoretic stability of titanium oxide was visually and microscopically (product name: Powerscope KH) -2700, manufactured by Hylox Corporation). As a result, the contrast shows a very low value (1.0), and the display responsiveness does not show any migration of titanium oxide even when a voltage is applied between both electrodes, and the change in display can be confirmed. There wasn't. Therefore, display memory properties and repeated tests could not be evaluated.

-Comparative Example 4-
In Example 1, instead of 0.5 g of aminopropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.), aminoethylaminopropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) as a coupling agent having a chargeable functional group was used. ) And octadecyltrichlorosilane as a coupling agent having a long-chain alkyl group instead of 1.5 g of isopropyl triisostearoyl titanate (product name: Preneact KR-TTS, manufactured by Ajinomoto Co., Inc.) A surface-treated titanium oxide (c4), microcapsule (c4), and electrophoretic display device (c4) were obtained in the same manner as in Example 1 except that 7.5 g was used. Various measurements and evaluations similar to those in Example 1 were performed, and the results are shown in Table 1.

In addition, about titanium oxide (c4), it was confirmed by the method similar to Example 1 that it has both a chargeable functional group and a long-chain alkyl group.
The average volume particle diameter of the microcapsule (c4) was 105 μm.
For the electrophoretic display device (c4), a 30 V DC voltage was applied between the electrodes, the contrast at this time was measured, and the electrophoretic stability of titanium oxide was measured with the naked eye and a microscope (product name: Powerscope KH). -2700, manufactured by Hylox Corporation). As a result, a slightly effective value (2.5) was shown for the contrast. As for the display response, although the negative electrode side was displayed in blue and the positive electrode side was displayed in white, the display response was extremely slow (display response was extremely low) (×), but stable display was shown.

In addition, even when the application of the voltage was stopped, the display was maintained for one week or more, and it was confirmed that the display had stable memory properties (long-term display maintenance property, display memory property).
Further, the electrophoretic display device (c4) was repeatedly tested by alternately inverting the polarity of the applied voltage at a frequency of 1 Hz and repeating the display. However, the evaluation of the test was performed because the display response was extremely low. Could not do itself.

INDUSTRIAL APPLICABILITY The present invention can be effectively used when manufacturing microcapsules for electrophoretic display devices that can realize high display responsiveness and contrast even at a low applied voltage.

Claims (5)

A microcapsule for an electrophoretic display device comprising a capsule shell containing a liquid in which electrophoretic fine particles are dispersed in a solvent,
The electrophoretic fine particles have a water contact angle of 35 ° or more, a dry charge amount of 10 μc / g or more in absolute amount, and a fine particle dispersion viscosity of 300 mPa · s or less.
An electrophoretic display device microcapsule characterized by the above.   The microcapsule for electrophoretic display devices according to claim 1, wherein the electrophoretic fine particles have a chargeable functional group and a long-chain alkyl group on a surface thereof. A method for producing a microcapsule for an electrophoretic display device comprising a capsule shell containing a liquid in which electrophoretic fine particles are dispersed in a solvent,
The surface of the electrophoretic fine particles is coated with a coupling agent having a chargeable functional group and / or a polymer having a group reactive with the electrophoretic fine particles and a chargeable functional group, and a cup having a long-chain alkyl group. Treatment with a polymer having a ring agent and / or a group having reactivity with the electrophoretic fine particles and a long-chain alkyl group,
A method for producing a microcapsule for an electrophoretic display device. A method for producing a microcapsule for an electrophoretic display device comprising a capsule shell containing a liquid in which electrophoretic fine particles are dispersed in a solvent,
The surface of the electrophoretic fine particles is coated with a coupling agent having a chargeable functional group and a long chain alkyl group, and / or a group reactive with the electrophoretic fine particles, a chargeable functional group, and a long chain alkyl group. Treating with a polymer having
A method for producing a microcapsule for an electrophoretic display device. An electrophoretic display device, wherein the microcapsules for electrophoretic display devices according to claim 1 or 2 are arranged between at least one transparent electrode film.