JP2005338189A - Microcapsule for electrophoresis display, its manufacturing method and its use - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microcapsule for an electrophoresis display whose contrast reduction can be suppressed even when being left under the condition of high temperature and high humidity for a long time (e.g. at 60°C with 90% RH for 24 hr), to provide its manufacturing method and to provide a sheet for the electrophoresis display using the same. <P>SOLUTION: In the microcapsule for the electrophoresis display formed by encapsulating electrophoretic fine particles and a solvent in a shell body, the whole microcapsule contains ≤150 ppm alkali metal ions. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a microcapsule for an electrophoretic display device in which electrophoretic fine particles and a solvent are encapsulated in a shell, a method for producing the same, and a sheet for an electrophoretic display device using the microcapsule.

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 fine particles are dispersed in a colored solvent. Specifically, the electrophoretic fine particles have a structure in which the dispersion liquid is sealed in a space provided between at least one transparent electrode substrate (film) and a voltage is applied to a predetermined position between the electrode substrates. Has been conventionally known as a device that performs display using an optical density difference that occurs between other positions. For example, it has a wide viewing angle and is long without power supply (continuous supply). It has many excellent characteristics such as time memory and low power consumption.
In recent years, instead of a conventional electrophoretic display device (for example, see Patent Document 1) in which the dispersion liquid is directly enclosed in a space between the counter electrode substrates, a shell body (capsule shell body, wall film) is used. The same applies hereinafter.) Development of an electrophoretic display device (see, for example, Patent Document 2 and Patent Document 3) having a structure in which microcapsules in which the dispersion liquid is sealed are arranged between counter electrode substrates.・ Research has been actively conducted, and compared to the conventional electrophoretic display device, various performances and functions such as long-term stability of display, responsiveness, contrast, and the number of display rewrites can be greatly improved. ing.

In preparing a microcapsule for an electrophoretic display device using the dispersion as a core substance, a microencapsulation technique that can be applied includes a coacervation method (phase separation method) (for example, see Patent Document 4), melting. So-called interfacial deposition methods such as decomposition cooling method and powder bed method, interfacial polymerization method, in-situ method, cured liquid coating (coating) method (orifice method), interfacial reaction method (inorganic chemical reaction method), etc. In particular, the coacervation method is generally suitable because it has advantages such as easy control of the strength and thickness of the shell and the ability to form a multi-layer shell. It is.
When an electrophoretic display device using microcapsules is tried to be applied to various display devices in various fields of application, further improvement in performance such as contrast that greatly affects the sharpness of an image is strongly desired. ing.
Japanese Patent Publication No. 50-15115 Japanese Patent No. 2551783 JP-A 64-86116 U.S. Pat. No. 2,800,547

However, in an electrophoretic display device using a conventional microcapsule, particularly when it is left for a long time (for example, at 60 ° C. and 90% RH for 24 hours) under high temperature and high humidity conditions, the subsequent contrast is remarkably lowered. There was a problem that was recognized.
Therefore, the problem to be solved by the present invention is that even when the electrophoretic display device is left for a long time (for example, at 60 ° C. and 90% RH for 24 hours) under high temperature and high humidity conditions, An object of the present invention is to provide a microcapsule for an electrophoretic display device, a method for producing the same, and a sheet for an electrophoretic display device using the same.

The present inventor has intensively studied to solve the above problems. In the process, paying attention to the presence of alkali metal ions composed of Li ⁺ , Na ⁺ , K ⁺ , Rb ⁺ , Cs ⁺ and Fr ⁺ that can be contained in the microcapsules for electrophoretic display devices, the ions in the entire microcapsules It has been found that the above-described problems can be easily solved if the amount (concentration) of the azobenzene is below a specific value. Alkali metal ions can be contained in the core material (liquid containing electrophoretic fine particles and a solvent) contained in the shell or in the shell itself (particularly in the shell), but once the temperature is high When the shell is in a hygroscopic state, such as when it is left for a long time under humid conditions, the shell that normally functions as a resistor when a constant voltage is applied between both electrodes of the electrophoretic display device The body becomes conductive, and alkali metal ions contained in the entire microcapsule flow into the shell, causing a leakage current. As a result, it is difficult to apply a predetermined voltage, and electrophoretic particles migrate. In addition to the decrease in the characteristics, this current also flows through the microcapsules other than the predetermined position where the voltage is applied, so that a clear display cannot be obtained and sufficient contrast cannot be obtained.

  The present inventor also includes a hydrophobic solvent and electrophoretic fine particles as a method for easily obtaining the above-described microcapsules for electrophoretic display devices in which the amount (concentration) of alkali metal ions is a specific value or less. As a water-soluble surfactant for dispersing the core material in an aqueous medium, a specific compound formed by binding a polyamine or polycarboxylic acid to a nonionic surfactant is used as a water-soluble surfactant. As the water-soluble compound to be added, a water-soluble compound having an epoxy group or an episulfide group is used, and these are further reacted, that is, by reacting the polyamine moiety or polycarboxylic acid moiety with the epoxy group or episulfide group, The method of making a shell form on the surface (droplet surface) was found. In the present specification, the episulfide group represents a functional group in which an oxygen atom in an epoxy group is substituted with a sulfur atom, and may be referred to as a thioepoxy group or an epithio group.

In this method, the specific compound used as the water-soluble surfactant is a raw material compound that contributes to shell formation similarly to the water-soluble compound by the above reaction with the water-soluble compound having an epoxy group or an episulfide group. However, since these are raw material compounds of the shell, it is possible to obtain microcapsules in which the amount of alkali metal ions in the shell that has been included in the shell is sufficiently reduced. it can.
In this method, the raw material compound having an epoxy group or an episulfide group is generally stable in a free state in an aqueous medium, but with respect to a polyamine part or a polycarboxylic acid part of a specific surfactant compound. Has a high reactivity so that it can be easily chemically bonded even at low temperatures, and the polyamine moiety or polycarboxylic acid moiety and the epoxy group or episulfide group have electrostatic attractive properties. In addition to being easily compatible with the core material, the pH adjuster is capable of forming an alkali metal ion with high efficiency and excellent controllability on the surface (droplet surface) of the core material. Etc., or the amount used can be greatly reduced. Alkali metal ions amount it is possible to obtain a sufficiently reduced microcapsules. In this case, at the same time, microcapsules in which the amount of alkali metal ions in the core substance contained in the shell is sufficiently reduced can be obtained.

  Furthermore, in the above method, by adding a specific surfactant compound and a raw material compound having an epoxy group and repeating these reactions, a shell consisting of a plurality of layers is formed on the surface of the core material (the surface of the droplet). It can also be formed. Therefore, it is possible to freely form a shell having a very high strength, a shell having an adhesive surface layer, or the like by appropriately setting conditions. In addition, since the microcapsules obtained by the above method have moderate hydrophilicity due to the physical properties of the shell, they have high stability such as dispersibility in the aqueous medium regardless of the particle diameter. Therefore, there is no aggregation of the microcapsules in each manufacturing process, and the microcapsules can be obtained in a very stable and high yield.

Based on the above findings, the present invention has been completed.
Therefore, the microcapsule for electrophoretic display device according to the present invention is a microcapsule for electrophoretic display device in which electrophoretic fine particles and a solvent are encapsulated in a shell, and the amount of alkali metal ions in the entire microcapsule is small. It is characterized by being 150 ppm or less.
The method for producing a microcapsule for an electrophoretic display device according to the present invention uses a liquid containing a hydrophobic solvent and electrophoretic fine particles as a core substance, and the core substance is dispersed in an aqueous medium containing a water-soluble surfactant. Then, a method for producing a microcapsule for an electrophoretic display device, wherein a shell is formed on the surface of the core material by adding a water-soluble compound to the aqueous medium, and the water-soluble surfactant is used as the water-soluble surfactant. The following general formula (1):
R ¹ — (CH ₂ —CH ₂ —O—) _n —X—R ² (1)
(However, R ¹ represents an aliphatic or aromatic hydrophobic group having 5 to 25 carbon atoms, and R ² represents a polymer group having a polyamine structure or polycarboxylic acid structure having a weight average molecular weight of 300 to 100,000. , N represents an integer of 3 to 85. X is derived from a group capable of reacting with at least one group selected from the group consisting of an amino group, an imino group and a carboxyl group, and represents a group formed after the reaction. Represented, but may or may not be present.)
And a compound (B) having an epoxy group or an episulfide group as the water-soluble compound, and reacting the compound (A) with the compound (B) to form the shell body. Is formed.

  The sheet for electrophoretic display devices according to the present invention comprises the microcapsules for electrophoretic display devices according to the present invention and a binder resin.

  According to the present invention, even when the electrophoretic display device is left for a long time (for example, at 60 ° C. and 90% RH for 24 hours) under high-temperature and high-humidity conditions, the subsequent reduction in contrast can be suppressed. It is possible to provide a microcapsule for an electrophoretic display device, a method for producing the same, and a sheet for an electrophoretic display device using the microcapsule.

Hereinafter, the present invention will be described in detail. However, the scope of the present invention is not limited to these descriptions, and modifications other than the following examples can be made as appropriate without departing from the spirit of the present invention.
[Microcapsules for electrophoretic display devices]
As described above, the microcapsules for electrophoretic display devices according to the present invention (hereinafter referred to as the microcapsules of the present invention) include electrophoretic fine particles and a solvent contained in a shell (capsule shell, wall film). In detail, the microcapsule is a microcapsule in which a liquid (dispersion) in which electrophoretic fine particles are dispersed in a solvent is encapsulated in a shell as a core substance. In the entire microcapsule, Li ⁺ , It is important that the amount (concentration) of alkali metal ions composed of Na ⁺ , K ⁺ , Rb ⁺ , Cs ⁺ , and Fr ⁺ is 150 ppm or less. The amount of alkali metal ions is preferably 120 ppm or less, and more preferably 100 ppm or less. When the alkali metal ion amount exceeds 150 ppm, the electrophoretic display device using the microcapsule is left in a high temperature and high humidity condition for a long time (for example, at 60 ° C. and 90% RH for 24 hours). Contrast may be significantly reduced.

In particular, it is preferable to reduce the amount of Na ⁺ (sodium ion) because it is possible to further enhance the effect of suppressing the decrease in contrast. Specifically, it is preferably 100 ppm or less in the shell, Preferably it is 80 ppm or less, More preferably, it is 60 ppm, Most preferably, it is 50 ppm or less.
The amount of alkali metal ions in the entire microcapsule (including both individual amounts and total amounts of various alkali metal ions) is a value measured by the method described in the examples described later.
The shell in the microcapsule of the present invention is not limited. For example, a shell formed from a conventionally known shell raw material that can be used for microcapsule production is preferable. A shell formed by carrying out the “manufacturing method of display device microcapsules” is particularly preferable because it can more easily satisfy the above-mentioned range of the amount of alkali metal ions. In addition, as a conventionally known shell material, for example, when using a coacervation method, a compound having an isoelectric point such as gelatin and a cationic compound such as polyethyleneimine, gum arabic, carboxymethylcellulose, styrene- Combinations with maleic acid copolymers and anionic substances such as polyacrylic acid are preferred. In the case of using the in-situ polymerization method, a melamine-formalin resin (melamine-formalin prepolymer), a radical polymerizable monomer, and the like are preferable. In the case of using an interfacial polymerization method, a combination of a hydrophilic monomer such as polyamine, glycol and polyhydric phenol and a hydrophobic monomer such as polybasic acid halide, bishaloformer and polyisocyanate is preferable, and polyamide, Shell bodies such as epoxy resin, polyurethane and polyurea are formed.

A polyamine or the like can be further added to the shell raw material, and a microcapsule having a 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 shell raw material 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 ) Aliphatic polyamine amine epoxy compound adducts such as polyamine / alkylene (C ₂ -C ₁₈ ) oxide adducts, aromatic polyamines 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 dispersion liquid (liquid in which electrophoretic fine particles are dispersed in a solvent) contained in the shell will be described below with specific examples.
In general, the electrophoretic display includes a method of displaying the contrast between the color of the solvent in the dispersion and the color of the electrophoretic fine particles, and the contrast of the colors of at least two types of electrophoretic fine particles in the dispersion. There is a way to display.
The solvent used in the dispersion is not particularly limited as long as it is a solvent that has been generally used in dispersions for electrophoretic display devices. In detail, it is substantially insoluble in water (hydrophobic). It is sufficient that it does not interact to the extent that the formed shell body and its function are impaired. For example, 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, Preferred examples include aliphatic hydrocarbons such as cyclohexane, n-hexane, kerosene, and paraffinic hydrocarbons. Among them, long-chain alkylbenzenes such as dodecylbenzene and hexylbenzene, phenylxylylethane, and the like have boiling points and It is more preferable because it has a high flash point and almost no toxicity. These solvents may be used alone or in combination of two or more.
When the solvent is colored, it is preferable that the solvent is colored to such an extent that a sufficient contrast is obtained with respect to the color of the electrophoretic fine particles (for example, white for titanium oxide fine particles).

  When the solvent is colored, the dye used for coloring is not 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.

The electrophoretic fine particles used in the dispersion liquid may be any electrophoretic pigment particle, that is, a colored particle having a positive or negative polarity in the dispersion liquid. Specific examples include titanium oxide and the like. White particles, black particles such as carbon black and titanium black, and the like, and other particles as described below may be used. These may be used alone or in combination of two or more.
In the case of using titanium oxide fine particles, the type of titanium oxide is not limited as long as it is generally used as a white pigment, and may be a rutile type or anatase type. In view of the above, it is preferable that the rutile type has a low photoactivity, and further, titanium oxide subjected to Si treatment, Al treatment, Si—Al treatment, Zn—Al treatment or the like for reducing the photoactivity. 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.
Examples of the other particles include, but are not limited to, for example, white particles other than the above titanium oxide, inorganic pigments such as barium sulfate, zinc oxide, and zinc white; yellow particles, yellow iron oxide, cadmium yellow Inorganic pigments such as titanium yellow, chrome yellow and yellow lead, insoluble azo compounds such as first yellow, condensed azo compounds such as chromophthal yellow, azo complex salts such as benzimidazolone azo yellow, flavans yellow, etc. Organic pigments such as condensed polycycles, Hansa yellow, naphthol yellow, nitro compounds, and pigment yellow; in the case of orange, inorganic pigments such as molybdate orange, azo complex salts such as benzimidazolone azo orange, and belinone orange Organic pigments such as condensed polycycles such as red; Inorganic pigments such as cadmium red, dye lakes such as madre lake, soluble azo compounds such as lake red, insoluble azo compounds such as naphthol red, condensed azo compounds such as chromophthalscar red, thioindigo Bordeaux, etc. Condensed polycycles, quinacridone pigments such as Shinkasha Red Y and Hosta Palm Red, organic pigments such as azo pigments such as permanent red and first slow red; in the case of purple ones, inorganic pigments such as manganese violet, and rhodamine Organic pigments such as dyed lakes such as lakes, condensed polycycles such as dioxazine violet; inorganic pigments such as bitumen, ultramarine blue, cobalt blue and cerulean blue, phthalocyanines such as phthalocyanine blue, Indanthrenes such as Dunslen Blue, Organic pigments such as Lucari blue; for green ones, inorganic pigments such as emerald green, chrome green, chromium oxide and viridian, azo complex salts such as nickel azo yellow, nitroso compounds such as pigment green and naphthol green, phthalocyanine green Preferred examples of organic pigments such as phthalocyanines such as phthalocyanines; inorganic pigments such as iron black other than carbon black and titanium black, and organic pigments such as aniline black; These may be used alone or in combination of two or more.

Although the particle diameter of the electrophoretic fine particles is not limited, 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 with 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 dispersion liquid may contain other components as necessary in addition to the solvent and the electrophoretic fine particles described above, but the type and the like are not 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 limited.

  The dispersing agent is not particularly limited as long as it is a conventionally known dispersing agent capable of assisting dispersion of particles in a solvent, and examples thereof include an anionic surfactant and a cationic surfactant that are soluble in the dispersion. Agents, amphoteric surfactants, nonionic surfactants, fluorosurfactants, sorbitan fatty acid ester surfactants such as sorbitan sesquioleate, dispersants such as block polymers and graft polymers, and various coupling agents Are preferable, and these may be used alone or in combination of two or more. Among the above-mentioned dispersants, the coupling agent is more preferable because the dispersion stability is improved when a charge is applied. When the fine particles are treated with a coupling agent, a coating layer of the coupling agent is formed on the surface of the fine particles.

  Examples of the coupling agent include (i) a silane coupling agent, (ii) a titanate coupling agent, (iii) an aluminum coupling agent, (iv) a coupling agent having a vinyl group, (v) amino A coupling agent having at least one group selected from a group, a quaternary ammonium salt, a carboxyl group and a phosphate group, (vi) a coupling agent having an amino group or a glycidyl group at the terminal, (vii) an organodisilazane, etc. More preferably, it is a titanate coupling agent and an aluminum-based coupling agent, more preferably the above-mentioned various coupling agents having a long chain alkyl group, particularly preferably. Titanate coupling agents that also have long-chain alkyl groups and aluminum-based cups that also have long-chain alkyl groups It is a ring agent. The above coupling agents may be used alone or in combination of two or more.

As described above, the reason why a coupling agent having a long-chain alkyl group is preferable is that it has an effect of increasing the dispersion stability of the electrophoretic fine particles because the affinity is increased by a long-chain alkylbenzene, which is a highly safe solvent. Is high.
In preparing the above dispersion, the method for dispersing the electrophoretic fine particles in the solvent may be any known dispersion method, and is not limited. For example, the electrical component that is the raw material component in the ultrasonic bath is used. A method in which electrophoretic fine particles, a solvent, a coupling agent, and the like are charged and ultrasonically dispersed while stirring, a method in which dispersion is performed using an apparatus having a dispersing ability such as a paint shaker, a ball mill, a sand grind mill, a solvent in a V blender, etc. In addition, a dry method in which the coupling agent is sprayed with dry air or nitrogen gas while forcibly stirring the fine particles, a wet method in which the fine particles are appropriately dispersed in a solvent and a slurry is added, and a wet method in which the coupling agent is added in advance. Preferable examples include a spraying method in which the coupling agent is sprayed while vigorously stirring the solvent and the fine particles.

Although the shape of the microcapsule of the present invention is not limited, it is preferably a particulate shape such as a true sphere.
Although the particle diameter (volume average particle diameter) of the microcapsule of the present invention is not limited, it is preferably 5 to 300 μm, more preferably 10 to 200 μm, and still 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 coefficient of variation of the particle size (volume average particle size) of the microcapsules of the present invention is preferably 30% or less, more preferably 25% or less, and even more preferably 20% or less. If the coefficient of variation exceeds 30%, the abundance of those having effective particle diameters as microcapsules for electrophoretic display devices is lowered, and there is a possibility that a large number of microcapsules need to be used.
The particle size of the microcapsule of the present invention and its coefficient of variation (that is, the sharpness of the particle size distribution) greatly depend on the particle size and particle size distribution of the dispersion dispersed in the aqueous medium during preparation. Therefore, microcapsules having a desired particle diameter and coefficient of variation can be obtained by appropriately controlling the dispersion conditions.

Although the thickness of the shell of the microcapsule of the present invention is not limited, it is preferably 0.1 to 5 μm in a wet state, more preferably 0.1 to 4 μm, and further preferably 0.1 to 3 μm. is there. If the thickness of the shell is less than 0.1 μm, sufficient strength as the shell may not be obtained. If the thickness exceeds 5 μm, the transparency is lowered and the contrast is lowered. There is a possibility that the flexibility of the resin is lowered and the adhesion to an electrode film or the like is insufficient.
As the method for producing the microcapsule of the present invention, an electrophoretic display device microcapsule having the above-described characteristics can be easily obtained. Is particularly preferred. Further, the method for producing the microcapsules of the present invention is not limited to this, and a conventionally known production method including a microencapsulation step, for example, a coacervation method (phase separation method), a submerged drying method, So-called interfacial deposition methods such as melt decomposition cooling method, spray drying method, pan coating method, air suspension coating method and powder bed method, interfacial polymerization method, in-situ polymerization method, submerged cured film (coating) method ( A manufacturing method using a so-called interfacial reaction method such as an orifice method) or an interfacial reaction method (inorganic chemical reaction method) can also be preferably employed. In this case, for example, an electrophoretic display device obtained through a microencapsulation step The microcapsules for use in an aqueous medium include a step (A) of stirring in the presence of an ion exchange resin to remove (desalinate) ionic substances, It is preferable to reduce Chi ion amount (alkali metal ion content).

The microcapsules of the present invention are microcapsules for electrophoretic display devices, and can be used for all display devices that can be used and applied by electrophoretic display devices. For example, in addition to a normal electrophoretic display panel, a flexible display device that can be bent thinly like paper, a display device that can be easily made large and inexpensive, a paper-like display, a rewritable paper, or the like Examples include digital paper (electronic paper), display devices such as IC cards and IC tags, electronic whiteboards, guide boards, notice boards, electronic newspapers, electronic books, and portable terminals (for example, PDAs).
[Method for producing microcapsules for electrophoretic display device]
As described above, the method for producing the microcapsules for electrophoretic display devices according to the present invention (hereinafter referred to as the production method of the present invention) includes a liquid containing a hydrophobic solvent and electrophoretic fine particles (specifically, hydrophobic A liquid in which electrophoretic fine particles are dispersed in a hydrophobic solvent (hydrophobic dispersion liquid) is used as a core substance, and the core substance is dispersed in an aqueous medium containing a water-soluble surfactant, and then the aqueous medium is dissolved in water. When the shell compound is formed on the surface of the core material by adding a functional compound, the above-mentioned compound (A) is used as the water-soluble surfactant, and the above-mentioned compound (B) is used as the water-soluble compound. It is important to form a shell by reacting the compound (A) with the compound (B). That is, in the present invention, not only the compound (B) that is a water-soluble compound but also the compound (A) that is a water-soluble surfactant is a raw material compound for the shell.

It can be said that the production method of the present invention is a production method of microcapsules for electrophoretic display devices classified into a so-called coacervation method (phase separation method).
Hereinafter, a general manufacturing method of microcapsules for electrophoretic display devices in carrying out the present invention will be described, and features of the manufacturing method of the present invention will also be described in detail. In the practice of the present invention, techniques, conditions, and the like other than those shown below can be appropriately used techniques, conditions, and the like that can be normally employed in the method for producing microcapsules for electrophoretic display devices by the coacervation method.
In the production method of the present invention, first, a hydrophobic dispersion as a core material (which becomes a core material) is dispersed in an aqueous medium containing a specific water-soluble surfactant.

The aqueous medium that can be used in the production method of the present invention is not limited. For example, water or a mixed liquid of a hydrophilic organic solvent and water can be used. In the case where a hydrophilic organic solvent and water are used in combination, the water content is preferably 95 to 70% by weight, more preferably 95 to 80% by weight.
Examples of the hydrophilic organic solvent include, but are not limited to, alcohols such as methanol, ethanol, isopropyl alcohol, n-propyl alcohol, and allyl alcohol; ethylene glycol, propylene glycol, butylene glycol, hexylene glycol, and pentanediol. Glycols such as hexanediol, heptanediol, dipropylene glycol; ketones such as acetone, methyl ethyl ketone, methyl propyl ketone; esters such as methyl formate, ethyl formate, methyl acetate, methyl acetoacetate; diethylene glycol monomethyl ether, diethylene glycol mono Ethyl ether, diethylene glycol dimethyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, Ethers such as propylene glycol monomethyl ether; and the like preferably. These may be used alone or in combination of two or more.

In the production method of the present invention, in addition to the water and the hydrophilic organic solvent described above, another solvent may be used in combination with the aqueous medium. Examples of the other solvent include hexane, cyclopentane, pentane, isopentane, octane, benzene, toluene, xylene, ethylbenzene, aminyl squalene, petroleum ether, terpene, castor oil, soybean oil, paraffin, and keronine. It is done. When the other solvent is used in combination, the amount used is preferably 30% by weight or less, more preferably 25% by weight or less, and still more preferably based on the above-described hydrophilic organic solvent or an aqueous medium composed of water. Is 20% by weight or less.
The hydrophobic dispersion that can be used in the production method of the present invention is not limited, but the above description of the “dispersion” in the microcapsules of the present invention can be similarly applied.

In the production method of the present invention, the amount of the hydrophobic dispersion as the core substance dispersed in the aqueous medium is not limited, but for example, it is preferable to use 5 to 70 parts by weight with respect to 100 parts by weight of the aqueous medium. The amount is preferably 10 to 65 parts by weight. If the amount is less than 5 parts by weight, the reaction between the compound (A) and the compound (B) takes a long time because the concentration is low, and the target shell may not be formed. There is a risk of reducing efficiency. On the other hand, when the amount exceeds 70 parts by weight, the droplets of the hydrophobic dispersion liquid may aggregate or coalesce (unify), and may become a reverse suspension, making it impossible to produce microcapsules.
In the production method of the present invention, as described above, as the specific water-soluble surfactant, the following general formula (1):
R ¹ — (CH ₂ —CH ₂ —O—) _n —X—R ² (1)
(However, R ¹ represents an aliphatic or aromatic hydrophobic group having 5 to 25 carbon atoms, and R ² represents a polymer group having a polyamine structure or polycarboxylic acid structure having a weight average molecular weight of 300 to 100,000. , N represents an integer of 3 to 85. X is derived from a group capable of reacting with at least one group selected from the group consisting of an amino group, an imino group and a carboxyl group, and represents a group formed after the bonding. Represented, but may or may not be present.)
The compound (A) represented by the formula is used. By using the compound (A), the above-described problems of the present invention can be easily solved.

In the general formula (1), R ¹ represents an aliphatic or aromatic hydrophobic group having 5 to 25 carbon atoms, and specifically includes a pentyl group, hexyl group, heptyl group, octyl group, decyl group. Group, dodecyl group, octadecyl group, behenyl group and other aliphatic hydrocarbon groups, phenyl group, benzyl group, tolyl group, xylyl group, biphenyl group, p-terphenyl group, indenyl group, naphthyl group and indenyl-naphthyl group An aromatic hydrocarbon group such as, but not limited to.
The hydrophobic group represented by R ¹ has 5 to 25 carbon atoms, preferably 5 to 18 carbon atoms. If the number of carbon atoms is less than 5, the compound (A) may not exhibit sufficient surface activity, and if it exceeds 25, the hydrophobicity becomes too high and the solubility of the compound (A) in water decreases. There is a risk.

In the general formula (1), “— (CH ₂ —CH ₂ —O—) _n ” is a polymer group having a polyether structure (polyethylene oxide structure), and the structural unit “CH ₂ —CH ₂ — Although it is important that the number n of “O—” is 3 to 85, the above n is preferably 5 to 60, more preferably 5 to 50. When n is less than 3, although depending on the balance with the hydrophobic group, the solubility in an aqueous medium may not be sufficiently exhibited and the water may become insoluble. When it exceeds 85, the solubility in an aqueous medium may be increased. Even if it becomes too high, even if it reacts with the compound (B), it does not precipitate as an insoluble substance, and there is a possibility that the shell is not sufficiently formed.
In the general formula (1), X is derived from a group capable of reacting (binding reaction) with at least one group selected from the group consisting of an amino group, an imino group, and a carboxyl group, and the reaction (binding reaction). Although the group formed later is represented, it may or may not be present in the general formula (1). Here, the amino group, imino group and carboxyl group are specifically the amino group and imino group which can be present in a polymer having a polyamine structure, and the carboxyl group which can be present in a polymer having a polycarboxylic acid structure. As the group capable of reacting with at least one group selected from the group consisting of these groups, a group represented by X ² in the following general formula (3) can be exemplified. Specific examples of the group represented by X include “—CH ₂ —CH ₂ —S—” derived from a group represented by the following structural formula (b) and “—NH” derived from an isocyanate group. —CO— ”,“ —CO—NH—CH ₂ —CH ₂ — ”derived from an oxazoline group,“ —CH (OH) — ”derived from an aldehyde group,“ —CO— ”derived from a carboxyl group. ”,“ —NH— ”derived from an amino group,“ ═N— ”derived from an imino group, and the like.

In the general formula (1), R ² represents a polymer group having a polyamine structure or a polycarboxylic acid structure having a weight average molecular weight of 300 to 100,000, and the weight average molecular weight is preferably 300 to 50, 000. When the weight average molecular weight is less than 300, precipitation of insoluble matter is slow even when reacted with the compound (B), and it may take a long time to form a shell or a high strength shell may not be obtained. When the amount exceeds 100,000, the viscosity of the entire reaction system may increase rapidly due to the reaction with the compound (B), and stirring may become difficult. It becomes difficult to control the droplet size, and for example, there is a possibility that the droplet size becomes too small.

  The polymer group having a polyamine structure is not limited, but a polymer group having a polyamine structure containing a primary amino group and / or a secondary amino group, such as polyethyleneimine, polyamine, polyetheramine, polyvinyl At least selected from the group consisting of amine, modified polyvinylamine, polyalkylamine, polyamide, polyamine epichlorohydrin, polydialkylaminoalkyl vinyl ether, polydialkylaminoalkyl (meth) acrylate, polyallylamine, polyethyleneimine grafted polyamidoamine and protonated polyamidoamine Examples thereof include a polymer group having one type of structure.

The polymer group having a polycarboxylic acid structure is not limited, but acrylic acid, methacrylic acid, α-hydroxyacrylic acid, crotonic acid, phthalic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, aconitic acid and Examples thereof include a polymer group having a structure of a water-soluble polycarboxylic acid obtained by polymerization of a monomer component containing 30 mol% or more of an unsaturated carboxylic acid such as vinyl acetate.
The method for preparing the compound (A) represented by the general formula (1) is not limited, but for example, the following general formula (2) or the following general formula ( The method obtained by dripping the compound represented by 3) and making it react is preferable.

^{_{R 1 - (CH 2 -CH 2}} -O-) n-1 -X 1 (2)
(However, ^{X 1} is represented by the following structural formula (a):

Represents a group represented by )
R ¹ — (CH ₂ —CH ₂ —O—) _n —X ² (3)
(Where X ² is the following structural formula (b):

Or any one selected from the group consisting of an isocyanate group, an oxazoline group, an aldehyde group, a carboxyl group, an amino group and an imino group. That is, X ² represents a group capable of reacting (binding reaction) with at least one group selected from the group consisting of an amino group, an imino group, and a carboxyl group. )
When the compound represented by the general formula (2) is used in the preparation of the compound (A), the group represented by X does not exist in the general formula (1). On the other hand, when the compound represented by the general formula (3) is used, a group represented by X is present in the general formula (1).

Although it does not limit as reaction temperature at the time of making it react, when using polyamine, 10-90 ° C is preferred, more preferably it is 15-80 ° C, and when using polycarboxylic acid, it is 20-20. 100 degreeC is preferable, More preferably, it is 20-90 degreeC. Moreover, although reaction time is not limited, 0.5 to 5 hours are preferable, More preferably, it is 1 to 5 hours.
In the production method of the present invention, the compound (A) used as the water-soluble surfactant may be dissolved or dispersed in the aqueous medium before the hydrophobic dispersion is dispersed in the aqueous medium. It may be dissolved at the same time or after being dispersed, and is not limited.

  In the production method of the present invention, the compounding ratio of the compound (A) is preferably 1 to 30% by weight, more preferably 3 to 25% by weight, based on the hydrophobic dispersion dispersed in the aqueous medium. More preferably, it is 5 to 25% by weight. When the compounding ratio of the compound (A) is less than 1% by weight, the dispersion state of the hydrophobic dispersion cannot be maintained sufficiently stably, and droplets of the hydrophobic dispersion are aggregated or fused ( ) On the other hand, if it exceeds 30% by weight, the viscosity of the entire reaction system may increase rapidly due to the reaction with the compound (B), and stirring may become difficult. It becomes difficult to control the particle size, and for example, the particle size may be too small.

  In the production method of the present invention, the method for dispersing the hydrophobic dispersion in the aqueous medium is not limited, but a generally known dispersion method may be employed. For example, a mixture containing an aqueous medium, a hydrophobic dispersion, and a water-soluble surfactant is mechanically treated using a disper, a homomixer (manufactured by Special Machinery Co., Ltd.) and a homogenizer (manufactured by Nippon Seiki Co., Ltd.). Method of dispersing by vigorous stirring; the above mixture is mixed into a static tube mixer (Noritake static mixer (manufactured by Noritake Company Limited), Sruzer mixer (manufactured by Sumitomo Heavy Industries, Ltd.), Sakea mixer (( (Manufactured by Sakura Seisakusho Co., Ltd.), TK / ROSS / LPD mixer (manufactured by Special Machinery Co., Ltd.), etc.); a hydrophobic dispersion in an aqueous medium containing a water-soluble surfactant. A method of passing and dispersing regulated pores such as a membrane (shirasu porous glass) and a microchannel emulsification device (Eptec Corp.); And the like properly.

In the production method of the present invention, a shell is formed on the surface of the droplet of the hydrophobic dispersion by adding a specific water-soluble compound to the aqueous medium after the dispersion of the hydrophobic dispersion. .
As the specific water-soluble compound, a compound (B) having an epoxy group or an episulfide group is used. By using the compound (A) and the compound (B) in combination, the above-described problems of the present invention can be easily solved. In addition, as an epoxy group in a compound (B), group represented by the said Structural formula (a), and following Structural formula (c):

A group represented by formula (b) is preferably exemplified, and examples of the episulfide group in the compound (B) include a group represented by the structural formula (b) and the following structural formula (d):

The group etc. which are represented by these are mentioned preferably.
Although it does not limit as said compound (B) which has the said epoxy group, The water-soluble epoxy compound which has two or more epoxy groups in 1 molecule is preferable, for example, sorbitol polyglycidyl ester, solovitane polyglycidyl ester, ( Poly) glycerol polyglycidyl ester, pentaerythritol polyglycidyl ester, triglycidyl tris (2-hydroxyethyl) isocyanurate, trimethylolpropane polyglycidyl ester, neopentyl glycol diglycidyl ester, ethylene, polyethylene glycol diglycidyl ester, propylene, polypropylene Examples include glycol diglycidyl ester and adipic acid diglycidyl ester. These may be used alone or in combination of two or more.

The compound (B) having an episulfide group is not limited, but is preferably a water-soluble episulfide compound having two or more episulfide groups in one molecule, such as sorbitol polythioglycidyl ester, (poly) glycerol polythiol. Examples thereof include glycidyl ester, trithioglycidyl tris (2-hydroxyethyl) isocyanurate, propylene glycol dithioglycidyl ester, polypropylene glycol dithioglycidyl ester, and adipic acid dithioglycidyl ester. These may be used alone or in combination of two or more.
The compound (B) has a solubility in water of preferably 30% by weight or more, more preferably 40% by weight or more, and still more preferably 50% by weight or more. When the dissolution rate of compound (B) in water satisfies the above range, the reaction with compound (A) is performed uniformly and rapidly, and the formation of the shell is uniformly and quickly performed. Excellent effects such as good controllability such as strength can be obtained. On the other hand, when the dissolution rate is less than 30% by weight, the reaction with the compound (A) becomes non-uniform, and the formation of shells may be made non-uniform. In the present invention, the solubility of compound (B) in water is a value determined by the method described in Examples described later.

  The compound (B) preferably has a weight average molecular weight of 300 to 100,000, more preferably 300 to 75,000, and still more preferably 300 to 50,000. When the weight average molecular weight of the compound (B) satisfies the above range, excellent effects such as easy control of the thickness and strength of the shell can be obtained. When the weight average molecular weight is less than 300, it is difficult to obtain a shell having sufficient strength, and it becomes difficult to control the reactivity with the compound (A), thereby making it difficult to form a uniform shell. There is. On the other hand, if it exceeds 100,000, the viscosity of the entire reaction system may increase rapidly due to the reaction with the compound (A), and stirring may become difficult. It becomes difficult to control the particle size, and for example, the particle size may be too small.

The amount of the compound (B) added is not limited, but is preferably 0.1 to 10 parts by weight, more preferably 0.5 to 5 parts by weight, based on 1 part by weight of the compound (A). More preferably, it is 0.5-3 weight part. By adjusting the amount of compound (B) added, the thickness of the shell formed can be easily controlled. If the amount of the compound (B) added is less than 0.1 part by weight, a sufficient amount of shell may not be formed. If the amount exceeds 10 parts by weight, the component composition of the shell will be greatly biased. The shell strength may be reduced.
The method for adding the compound (B) to the aqueous medium is not limited, and may be batch addition or sequential addition (continuous addition and / or intermittent addition).

In the production method of the present invention, the added compound (B) is reacted with the aforementioned compound (A) to form a shell on the surface of the droplet of the hydrophobic dispersion. Specifically, the epoxy group of the compound (B) is reacted with the polyamine moiety (amino group, imino group, etc.) or the polycarboxylic acid moiety (carboxyl group, etc.) of the compound (A) to thereby react the compound (A) with the compound. The insoluble reactant derived from (B) is deposited on the surface of the droplet of the hydrophobic dispersion to form a shell.
The reaction temperature between the compound (A) and the compound (B) is not limited, but when the compound (A) is a compound in which R ^{2 in the} general formula (1) is a polymer group having a polyamine structure, When 25 to 75 ° C is preferable, more preferably 30 to 75 ° C, and a compound in which R ^{2 in the} general formula (1) is a polymer group having a polycarboxylic acid structure is used as the compound (A), 40-95 degreeC is preferable, More preferably, it is 45-90 degreeC. Moreover, although reaction time is not limited, 3 to 24 hours are preferable, More preferably, it is 3 to 12 hours.

In the reaction of the compound (A) and the compound (B), an aging period may be further provided. The temperature at the time of aging is not limited, but is preferably the same as the reaction temperature, and the aging time is not limited, but is preferably 1 to 5 hours, more preferably 1 to 3 hours.
In the production method of the present invention, a crosslinking agent can be added to the aqueous medium after dispersing the hydrophobic dispersion in addition to the compound (B). By adding and using a cross-linking agent, the strength of the formed shell can be further increased, and it is effective that the shell collapses or is damaged during the isolation and cleaning processes after microencapsulation. Can be suppressed. The timing of the addition of the crosslinking agent may be before the reaction of the compound (A) and the compound (B), such as addition with the compound (B), or the compound (A) and the compound ( It may be during or after the reaction with B) and is not limited.

  Examples of the crosslinking agent include, but are not limited to, sodium diethyldithiocarbamate, diethylammonium diethyldithiocarbamate, dithiosuccinic acid, and dithiocarbonate. These may be used alone or in combination of two or more. Moreover, although the usage-amount of the said crosslinking agent is not limited, For example, it is preferable to set it as 0.1-30 weight part with respect to 100 weight part of compounds (B), More preferably, 0.3-20 weight part Parts, more preferably 0.5 to 15 parts by weight. When the amount of the crosslinking agent used is less than 0.1 parts by weight, it takes a long time to form the shell, and it may be difficult to control the thickness and strength of the shell, and 30 parts by weight If it exceeds, the reaction with the epoxy group or episulfide group in the compound (B) becomes excessive, which may hinder the reaction between the compound (A) and the compound (B).

In the production method of the present invention, as described above, the microcapsules for forming a shell on the droplet surface of the hydrophobic dispersion liquid by the reaction between the compound (A) and the compound (B) are used. A preparation liquid containing the capsule and the aqueous medium is obtained.
In the production method of the present invention, if necessary, the compound (A) is further added to the preparation liquid of the microcapsules for electrophoretic display device, and the compound (B) is further added, and the same reaction as described above is performed. In this way, a shell can be further formed on the shell once formed, and as a result, a microcapsule for an electrophoretic display device in which a shell having a plurality of layers is formed. Is obtained. The microcapsules for electrophoretic display devices in which a shell composed of a plurality of layers is formed, for example, can further improve the physical properties obtained with a single-layer shell and are different between the inside and the outside of the shell. Physical properties can also be expressed. Specifically, there is obtained an effect that physical properties such as adhesiveness, high hydrophilicity, and flexibility can be easily introduced while having the original performance of the shell.

In the production method of the present invention, the microcapsules for electrophoretic display devices are prepared by the microencapsulation process by the reaction of the compound (A) and the compound (B) described above, and then the microcapsules are simply used as necessary. May be separated. For example, after the preparation of the microcapsules for electrophoretic display devices, the microcapsules can be separated and isolated from the aqueous medium by suction filtration or natural filtration.
After the isolation, the microcapsules may be classified in order to obtain microcapsules for electrophoretic display devices with a sharper particle size distribution.
For the classification, for example, a wet classification method (wet classification) is preferably adopted. Wet classification is a method of classifying microcapsules for electrophoretic display devices with respect to a prepared liquid obtained by microencapsulation. Since classification is performed on the prepared solution, wet classification is performed. Specifically, the prepared solution is diluted as it is or diluted with an arbitrary aqueous medium, etc., and classified so that the microcapsules for electrophoretic display devices in the prepared solution have a desired particle size and particle size distribution. This is a classification method. 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 for electrophoretic display devices having a relatively large particle size, the sieve type can be used effectively.

In addition, in order to remove impurities and improve product quality, it is also preferable to perform an operation of washing the obtained microcapsules for electrophoretic display devices.
[Electrophoresis display sheet]
The sheet for electrophoretic display devices (display sheet) according to the present invention is a sheet comprising the microcapsules of the present invention and a binder resin. Specifically, for example, the microcapsules of the present invention arranged so as to be planar as a whole are preferably sheets having a layer fixed with a binder resin so that the arrangement can be maintained. By using the microcapsules of the present invention as the microcapsules in the display sheet, the above-described problems of the present invention can be easily solved.

  The binder resin is not limited, but various organic binder resins are preferably exemplified. For example, acrylic resin, polyester resin, fluororesin, alkyd resin, amino resin, vinyl resin, epoxy resin , Polyamide resin, polyurethane resin, unsaturated polyester resin, phenol resin, polyolefin resin, silicone resin, acrylic silicone resin, xylene resin, ketone resin, rosin modified maleic resin, liquid polybutadiene and Synthetic resin binders such as coumarone resin; natural or synthetic rubber binders such as ethylene-propylene copolymer rubber, polybutadiene rubber, styrene-butadiene rubber and acrylonitrile-butadiene copolymer rubber; shellac, rosin (pine resin), esthetic Natural resin binders such as gum, hardened rosin, decolorized shellac and white shellac; thermoplastic or thermosetting polymer binders such as cellulose nitrate, cellulose acetate butyrate, cellulose acetate, ethylcellulose, hydroxypropylmethylcellulose and hydroxyethylcellulose; etc. Can be mentioned. The synthetic resin binder may be a plastic (thermoplastic) binder, or curable (thermosetting, ultraviolet curable, electron beam curable) such as acrylic, methacrylic or epoxy. It may be a moisture curable binder. These organic binders may be used alone or in combination of two or more, and are not limited.

The form of the binder is not limited, and examples include a solvent-soluble type, a water-soluble type, an emulsion type, and a dispersion type (any solvent such as water / organic solvent).
Examples of water-soluble binders include water-soluble alkyd resins, water-soluble acrylic-modified alkyd resins, water-soluble oil-free alkyd resins (water-soluble polyester resins), water-soluble acrylic resins, water-soluble epoxy ester resins, and water-soluble melamine resins. Can be mentioned.
For example, as an emulsion type binder, (meth) alkyl acrylate copolymer dispersion, vinyl acetate resin emulsion, vinyl acetate copolymer resin emulsion, ethylene-vinyl acetate copolymer resin emulsion, acrylate (co) polymer resin emulsion, Examples thereof include styrene-acrylic acid ester (co) polymer resin emulsion, epoxy resin emulsion, urethane resin emulsion, acrylic-silicone emulsion, and fluororesin emulsion.

  The display sheet of the present invention may be a sheet composed only of the microcapsules and the binder resin of the present invention, or may include other components or components in addition to the microcapsules and the binder resin of the present invention. There is no limitation. As the latter display sheet, for example, a layer containing the microcapsules of the present invention and a binder resin is formed on a film-like or sheet-like substrate, or after the formation, the layer is interposed. A display sheet or the like in which another film-like base material is further disposed (the layer is laminated by a film-like base material), and the layer and the base material are integrated. A display sheet is preferable. The latter form is preferable in that the production method is easy and the microcapsules of the present invention can be produced while easily retaining the characteristics.

  Since the display sheet of the present invention is a display sheet for an electrophoretic display device, in the case where the display sheet is also provided with a film-like base material (in the case of the latter display sheet described above), generally, the base material is conductive. A film is used. Specific examples of the conductive film include an electrode film that can be used as an electrode of an electrophoretic display device. For example, the conductive film may be a non-transparent electrode film or a transparent electrode film (for example, a PET film with ITO). Although not limited, a transparent electrode film is preferable. In particular, as described above, a layer containing the microcapsules of the present invention and a binder resin is laminated with two opposing electrode films. In this case, it is necessary that at least one of the electrode films is transparent.

  The method for producing the display sheet of the present invention is not limited, but generally, as described in detail below, the microcapsules of the present invention and a binder resin are mixed to form a paint, and the paint is formed into a film or A method of applying to the surface of the sheet-like substrate and drying is preferably employed. When obtaining a display sheet in which the layer containing the microcapsule and binder resin of the present invention and the base material are integrated, it may be handled as it is after the drying, but when it is obtained as a display sheet of only the layer It is sufficient to isolate (peel off) only the layer from the substrate after the drying. Moreover, when obtaining the display sheet by which the said layer is laminated | stacked by the said base material, what is necessary is just to arrange | position and laminate | stack a base material further on the coated surface after the said drying.

The concentration of the microcapsules in the coating is not limited, but is preferably 30 to 70% by weight, more preferably 30 to 60% by weight, and still more preferably 30 to 55% by weight. When the microcapsule concentration is within the above range, for example, a substrate in which the microcapsules of the present invention are densely arranged on a substrate (electrode film or the like) can be obtained, and the display sheet of the present invention is electrophoresed. When used in a display device, excellent product quality (display quality) can be exhibited.
The viscosity of the paint is preferably 500 to 5000 mPa · s, more preferably 800 to 4000 mPa · s, and still more preferably 800 to 3000 mPa · s. If the viscosity of the paint is in the above range, the microcapsules of the present invention can be easily disposed on the substrate (electrode film or the like) without gaps, and the microcapsules of the present invention are densely packed. The coating film (coating layer) can be finished.

In addition to the microcapsules and the binder resin of the present invention, the coating material may contain other components as necessary. As said other component, a viscosity modifier, a leveling agent, an antifoamer, etc. are mentioned, for example. The blending ratio of the other components can be appropriately set within a range that does not hinder the effects of the present invention.
The method of applying the coating material to the substrate is not limited, and for example, a method of applying the coating material to each substrate using an applicator, a blade coater, or the like, or a multi-coater or the like may be used. It may be a method of continuously coating on a substrate using a continuous coating machine, and can be appropriately selected as necessary.

The drying method after the coating is not limited, and known drying techniques and drying conditions can be employed.
The thickness of the display sheet of the present invention is not limited because there is a balance with the particle size of the microcapsule to be used. However, when only the thickness of the layer including the microcapsule and the binder resin is considered, for example, 10 It is preferable that it is -250 micrometers, More preferably, it is 10-180 micrometers, More preferably, it is 10-100 micrometers. When the thickness is less than 10 μm, when the display sheet of the present invention is used in an electrophoretic display device, a sufficient display density cannot be obtained in the display portion, and there is a risk that it cannot be clearly distinguished from other non-display portions. If the display sheet of the present invention is used in an electrophoretic display device, it is activated to fully exhibit the electrophoretic characteristics of the electrophoretic fine particles in the dispersion encapsulated in the microcapsule. It is necessary to increase the voltage, which may be inferior in economic efficiency. In addition, when using the said film-like or sheet-like base material, the thickness of this base material is not limited and several tens of micrometers to several mm are preferable.

In the case of obtaining the above-described laminated display sheet as the display sheet of the present invention, a known laminating technique and lamination conditions can be adopted as the laminating method.
When the display sheet of the present invention is the laminated display sheet described above, in order to obtain an electrophoretic display device that can stably exhibit excellent display quality, generally, the microcapsule of the present invention is used. It is preferably one that is sufficiently adhered to both electrode films (one that has a large contact area). If the adhesiveness between the two electrode films is low, the responsiveness 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 lamination. In addition, regarding the microcapsules to be used, it is possible to further enhance the ease of adhesion to the electrode film by appropriately setting the content ratio of the components constituting the shell and increasing the flexibility and adhesiveness. In that case, sufficient adhesiveness can be obtained even in a state in which various conditions such as temperature and pressure at the time of lamination are moderately moderated.

  Similarly to the above, in the case of a laminated display sheet, the clearance between the opposing electrode films is not limited, but is preferably 10 to 250 μm, more preferably 10 to 180 μm, still more preferably 10 to 10 μm. 100 μm. When the clearance is less than 10 μm, when the display sheet of the present invention is used in an electrophoretic display device, a sufficient display density cannot be obtained in the display portion, and there is a risk that it cannot be clearly distinguished from other non-display portions. If the display sheet of the present invention is used in an electrophoretic display device, it is activated to fully exhibit the electrophoretic characteristics of the electrophoretic fine particles in the dispersion encapsulated in the microcapsule. It is necessary to increase the voltage, which may be inferior in economic efficiency.

[Electrophoretic display device]
An electrophoretic display device can be manufactured using the display sheet of the present invention. For example, among the display sheets of the present invention, an electrophoretic display device including a display sheet in which a layer containing microcapsules and a binder resin is laminated with two opposing electrode films can be preferably exemplified. If the display sheet of this invention is used, the subject of this invention mentioned above can be solved easily.
In the electrophoretic display device, as various constituent parts (for example, a drive circuit and a power supply circuit) other than the display sheet, constituent parts used in a conventionally known electrophoretic display apparatus can be employed.

The required display operation in the electrophoretic display device is that a controlled voltage is applied between the opposing electrode films (for example, a voltage is applied only to a portion where a desired image is to be displayed), and the electrophoretic fine particles in the microcapsule. This can be done by changing the orientation position.
The display sheet of the present invention is a sheet for an electrophoretic display device, but can also be used for the same use as a known display sheet using microcapsules such as non-carbon paper or a pressure measurement film.

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these. Hereinafter, for the sake of convenience, “liter” may be simply referred to as “L”. In addition, “wt%” may be described as “wt%”.
Measurement methods in Examples and Comparative Examples are shown below.
<Average particle size of microcapsules>
The volume average particle size of the microcapsules was measured using a laser diffraction / scattering particle size distribution measuring device (product name: LA-910, manufactured by Horiba, Ltd.).
<Solubility in water>
In a 300 mL beaker, 25.0 g of a sample compound (for example, an epoxy compound such as compound (B)) is precisely weighed, 225 g of water is added, and the sample compound is dissolved by vigorously stirring for 1 hour with a magnetic stirrer. Thereafter, the mixture was allowed to stand for 1 hour, and the undissolved sample compound (oil) precipitated at the bottom of the beaker was extracted, placed in a 10 mL (or 5 mL) graduated cylinder, and allowed to stand for another 30 minutes. The liquid volume (mL) is read to the first decimal place, and the value is substituted into the following formula to calculate the dissolution rate (%) of the sample compound in water.

Dissolution rate in water (%) = 100− (A / 21) × 100
(However, A represents the liquid volume (mL) of the read sample compound.)
<Amount of alkali metal ions>
The outline of the measuring method of the amount of alkali metal ions is shown in the following 1-3.
1. 1 g of microcapsules is placed in 20 g of ultrapure water and subjected to ultrasonic irradiation for 45 minutes using an ultrasonic cleaner (180 W, 42 kHz).
2. The liquid after ultrasonic irradiation is filtered with a filter having an aperture of 0.45 μm.
3. The amount of alkali metal ions in the filtrate is measured using an ICP emission analyzer.

Specifically, in a 50 mL plastic container (product name: PP vial PV-7, manufactured by Reciprocal Chemical Glass Co., Ltd.), together with 20 g of ultrapure water, 1 g of microcapsules dried in advance was precisely weighed and put. Using an ultrasonic cleaner (product name: Bronson 5510, manufactured by Yamato Kagaku Co., Ltd., output: 180 W, frequency: 45 kHz), ultrasonic irradiation was performed for 45 minutes to perform alkali metal ion extraction operation.
After ultrasonic irradiation, the liquid in the container was filtered with a filter (product name: GL Chromatodisc 13I, Kurashiki Boseki Co., Ltd., opening: 0.45 μm), and the amount of alkali metal ions in the filtrate that passed through the filter (Ppm) was measured using an ICP emission spectrometer (product name: Inductively Coupled Plasma Atomic Emission Spectrometer, manufactured by Seiko Denshi Kogyo Co., Ltd.).

The amount of alkali metal ions (ppm) in the entire microcapsule is multiplied by the amount of alkali metal ions (ppm) in the filtrate multiplied by the microcapsule dilution factor (20 times (20 g of ultrapure water / 1 g of microcapsules)). It was calculated as a value.
<Contrast>
The reflectivity of white display and blue display (or black display) when a DC voltage of 15 V is applied between the electrodes of the electrophoretic display device for 0.4 seconds, respectively, is measured with a Macbeth spectrophotometer (product name: SpectroEye, GretagMacbeth). The contrast (reflectance ratio) was determined by the following formula. In addition, the reflectance of white display and blue display (or black display) is measured separately by switching and applying the poles, and each reflectance is a value measured for one entire surface of the electrophoretic display device.

Contrast = (Reflectance of white display) / (Reflectance of blue display (or black display))
[Synthesis Example 1-1]
A 300 mL separable flask is initially charged with 14.5 g of polyethyleneimine (product name: Epomin SP006 (Mw = 600), manufactured by Nippon Shokubai Co., Ltd.) and 43.5 g of water, and then prepared in advance under stirring. 97.2 g of a 25 wt% aqueous solution of the epoxy compound (lauryl polyoxyethylene (n = 22) glycidyl ester, water solubility: 100%) was added dropwise over 10 minutes.
The dropping is performed while maintaining the liquid temperature in the flask at 25 ° C. or lower, and stirring is continued for 30 minutes after the dropping is completed. Thereafter, the temperature is raised to 70 ° C., kept at the same temperature for 2 hours, and then cooled to room temperature. A compound (A1) having a dispersion content of 25 wt% solid content was obtained.

[Synthesis Example 1-2]
In Synthesis Example 1-1, a 25 wt% aqueous solution of an epoxy compound (lauryl polyoxyethylene (n = 44) glycidyl ester, solubility in water: 100%) prepared in advance after stirring was initially stirred. A compound (A2) having a solid content of 25 wt% having dispersibility was obtained in the same manner as in Synthesis Example 1-1 except that 4 g was dropped over 10 minutes.
[Synthesis Example 1-3]
Into the same flask as in Synthesis Example 1-1, 14.5 g of polyethyleneimine (product name: P-1000 (Mw = 70,000), manufactured by Nippon Shokubai Co., Ltd.) and 43.5 g of water were initially charged. Under stirring, 130.4 g of a 25 wt% aqueous solution of an epoxy compound (lauryl polyoxyethylene (n = 44) glycidyl ester, water solubility: 100%) prepared in advance was added dropwise over 10 minutes.

Thereafter, in the same manner as in Synthesis Example 1-1, a compound (A3) having a solid content of 25 wt% having a dispersion performance was obtained.
[Synthesis Example 1-4]
In a 500 mL separable flask, 93.7 g of polyacrylic acid aqueous solution (product name: Aquaric HL-415 (Mw = 10,000, resin concentration: 45 wt%), manufactured by Nippon Shokubai Co., Ltd.) and 281.1 g of water were added. After initial charging, 20 g of a 25 wt% aqueous solution of an epoxy compound (phenol polyoxyethylene (n = 5) glycidyl ester, water solubility: 100%) prepared in advance was added dropwise over 10 minutes with stirring. did.

The dropping is performed while maintaining the liquid temperature in the flask at 25 ° C. or lower, and stirring is continued for 30 minutes after the dropping is completed. Thereafter, the temperature is raised to 70 ° C., kept at the same temperature for 2 hours, and then cooled to room temperature. A compound (A4) having a solid content of 25 wt% and having dispersion performance was obtained.
[Synthesis Example 2-1]
In a 300 mL four-necked flask, 100 g of titanium oxide (product name: Taipei CR-97, manufactured by Ishihara Sangyo Co., Ltd.), 100 g of n-hexane and octadecyltrichlorosilane (product name: LS6495, manufactured by Shin-Etsu Chemical Co., Ltd.) are charged. While stirring and mixing, the flask was placed in an ultrasonic bath at 55 ° C. (a bath where ultrasonic waves were generated by an ultrasonic homogenizer (product name: BRANSON 5210, manufactured by Yamato)), and a coupling agent was used while performing ultrasonic dispersion. The treatment was performed for 2 hours.

This dispersion is transferred to a sedimentation tube for centrifugation, and subjected to sedimentation at 10000 G for 15 minutes using a centrifuge (product name: high-speed cooling centrifuge GRX-220, manufactured by Tommy), and then the supernatant of the sedimentation tube is removed. Thus, surface-treated titanium oxide (p1) was obtained.
82 g of dodecylbenzene was charged with 11.5 g of titanium oxide (p1) and 1.5 g of anthraquinone blue dye, and subjected to dispersion treatment for 2 hours in the above-described ultrasonic bath to obtain a dispersion liquid (1) for electrophoretic display devices. .
[Synthesis Example 2-2]
A 200 mL beaker was charged with 5 g of carbon black (product name: MA100, manufactured by Mitsubishi Chemical Corporation) and 172.5 g of methyl methacrylate, and subjected to a dispersion treatment with an ultrasonic homogenizer (product name: BRANSON 5210, manufactured by Yamato Corporation). 3.5 g of azobisbutyronitrile was added and dissolved to obtain a monomer composition.

An aqueous solution in which 2.5 g of an anionic surfactant (product name: Haitenol NO8) was dissolved in 750 g of water was prepared in advance, and the entire amount of the monomer composition was added thereto, and a high-speed stirring emulsifier (product name: The mixture was dispersed using Clearmix CLM-0.8S (M Technique Co., Ltd.) to obtain a suspension of the monomer composition.
The suspension was heated to 75 ° C. and held for 5 hours to carry out a polymerization reaction to obtain a dispersion of black fine particles. The particle diameter (volume average particle diameter) of the black fine particles was measured using a laser diffraction / scattering particle size distribution analyzer (product name: LA-910, manufactured by Horiba, Ltd.) and found to be 0.8 μm. The dispersion was filtered, washed and dried to obtain black fine particles (p2).

In 85.6 g of dodecylbenzene, 3.1 g of black fine particles (p2) and 11.5 g of titanium oxide (p1) obtained in Synthesis Example 2-1 were charged, and the ultrasonic bath used in Synthesis Example 2-1 was used for 2 hours. The dispersion process was performed and the dispersion liquid (2) for electrophoretic display devices was obtained.
[Example 1]
A 500 mL flat bottom separable flask is charged with 40 g of compound (A1) and 60 g of water, and 95 g of dispersion liquid (1) for electrophoretic display device is stirred with a disper (product name: ROBOMICS, manufactured by Tokushu Kika Kogyo Co., Ltd.). After that, the stirring speed was gradually increased, and stirring was performed at 800 rpm for 5 minutes to obtain a suspension.

While maintaining this suspension at 30 ° C., with stirring, polyglycerol polyglycidyl ester (product name: Denacol EX521, manufactured by Nagase ChemteX Corporation, water solubility: 100) as an epoxy compound (compound (B)) %) A total amount of 10 g of an aqueous solution dissolved in 80 g of water was added dropwise over 10 minutes, and an aqueous solution of 2 g of sodium diethylthiocarbamate trihydrate dissolved in 100 g of water was added dropwise over 10 minutes. Thereafter, the temperature of the suspension was raised to 70 ° C. over 60 minutes, and kept at that temperature for 1 hour for aging.
After aging, the mixture was cooled to room temperature to obtain a dispersion of microcapsules (m1) for electrophoretic display devices. The volume average particle diameter of the microcapsules (m1) for electrophoretic display devices was 65.0 μm.

This dispersion was classified by passing through a mesh having an aperture of 80 μm and 30 μm to obtain a paste (solid content: 63 wt%) of microcapsules (m1) for electrophoretic display devices having a particle size of 30 to 80 μm.
This paste was dried in a hot air dryer at 50 ° C. for 24 hours to obtain only the microcapsules (m1) for electrophoretic display devices. By the method described above, the alkali in the entire microcapsules (m1) for electrophoretic display devices was obtained. The amount of metal ions was measured. The results are shown in Table 1.
Next, 2.1 g of an alkali-soluble acrylic resin emulsion (product name: WR503A, manufactured by Nippon Shokubai Co., Ltd., resin content: 30 wt%) was diluted with water so that the solid content was 5 wt%, and 25 wt% was added thereto. A solution of the above alkali-soluble acrylic resin was prepared by adding 0.2 g of aqueous ammonia. 12.8 g of this resin solution was added to 10 g of the paste and mixed for 10 minutes with a mixer (product name: Awatori Netaro AR-100, manufactured by Sinky Corporation) to obtain a coating solution.

This coating solution was applied to a PET film with ITO with an applicator and then dried at 90 ° C. for 10 minutes to obtain an electrophoretic display device sheet (1).
Another PET film with ITO was laminated and laminated on the coated surface of the sheet (s1) for electrophoretic display device to produce an electrophoretic display device (d1) having a counter electrode.
The electrophoretic display device (d1) was left in a constant temperature and humidity room at 20 ° C. and 50% RH for one day, and the contrast (A) was measured under the same temperature and humidity environment.
Next, the electrophoretic display device (d1) is placed in a constant temperature and humidity chamber (product name: constant temperature and humidity chamber PL-ZF-P2, manufactured by Daiken Riken Chemical Co., Ltd.) at 60 ° C. and 90% RH for 24 hours. After (humidity test), the sample was left in a constant temperature and humidity room at 20 ° C. and 50% RH for 1 hour, and the contrast (B) was measured under the same temperature and humidity environment.

Table 1 shows the measurement results of contrast (A) before the moisture resistance test and contrast (B) after the moisture resistance test.
[Example 2]
In Example 1, the compound (A2) was used in place of the compound (A1), and 100.2 g of the dispersion liquid for electrophoretic display device (2) was used instead of 95 g of the dispersion liquid for electrophoretic display device (1). Produced a dispersion of microcapsules (m2) for electrophoretic display devices in the same manner as in Example 1. The volume average particle diameter of the microcapsules (m2) for electrophoretic display devices was 68.0 μm.

This dispersion was classified by passing through a mesh having an aperture of 80 μm and 30 μm to obtain a paste (solid content: 55 wt%) of an electrophoretic display device microcapsule (m2) having a particle size of 30 to 80 μm.
Using this paste, the amount of alkali metal ions in the entire microcapsule (m2) for electrophoretic display device was measured in the same manner as in Example 1. The results are shown in Table 1.
Next, a coating solution was obtained in the same manner as in Example 1 except that the amount of the paste added to the acrylic resin solution was 11.5 g.
Thereafter, in the same manner as in Example 1, an electrophoretic display device sheet (s2) was obtained, and an electrophoretic display device (d2) was produced.

For the electrophoretic display device (d2), the contrast (A) before the moisture resistance test and the contrast (B) after the moisture resistance test were measured in the same manner as in Example 1. The results are shown in Table 1.
Example 3
A dispersion liquid of microcapsules (m3) for electrophoretic display devices was obtained in the same manner as in Example 1, except that the compound (A3) was used instead of the compound (A1). The volume average particle diameter of the microcapsules (m3) for electrophoretic display devices was 71.0 μm.
This dispersion was classified by passing through a mesh having an aperture size of 80 μm and 30 μm to obtain a paste (solid content: 66.5 wt%) of microcapsules (m3) for electrophoretic display devices having a particle size of 30 to 80 μm.

Using this paste, the amount of alkali metal ions in the entire microcapsule (m3) for electrophoretic display devices was measured in the same manner as in Example 1. The results are shown in Table 1.
Next, a coating solution was obtained in the same manner as in Example 1 except that the amount of the paste added to the acrylic resin solution was 9.5 g.
Thereafter, in the same manner as in Example 1, an electrophoretic display device sheet (s3) was obtained, and an electrophoretic display device (d3) was produced.
For the electrophoretic display device (d3), the contrast (A) before the moisture resistance test and the contrast (B) after the moisture resistance test were measured in the same manner as in Example 1. The results are shown in Table 1.

Example 4
A dispersion liquid of microcapsules (m4) for electrophoretic display devices was obtained in the same manner as in Example 1, except that the compound (A4) was used instead of the compound (A1). The volume average particle diameter of the microcapsules (m4) for electrophoretic display devices was 66.0 μm.
This dispersion was classified by passing through a mesh having an aperture size of 80 μm and 30 μm to obtain a paste (solid content: 57.8 wt%) of microcapsules (m4) for electrophoretic display devices having a particle size of 30 to 80 μm.
Using this paste, the amount of alkali metal ions in the entire microcapsule (m4) for electrophoretic display devices was measured in the same manner as in Example 1. The results are shown in Table 1.

Next, a coating solution was obtained in the same manner as in Example 1 except that the amount of the paste added to the acrylic resin solution was 10.9 g.
Thereafter, in the same manner as in Example 1, an electrophoretic display device sheet (s4) was obtained, and an electrophoretic display device (d4) was produced.
For the electrophoretic display device (d4), the contrast (A) before the moisture resistance test and the contrast (B) after the moisture resistance test were measured in the same manner as in Example 1. The results are shown in Table 1.
[Comparative Example 1]
In a 500 mL flat bottom separable flask, 60 g of water, 6 g of gum arabic and 6 g of gelatin were charged and dissolved.

While maintaining this solution at 43 ° C., 95 g of the dispersion for electrophoretic display device (1) heated to 50 ° C. was added under stirring by a disper (product name: ROBOMICS, manufactured by Tokushu Kika Kogyo Co., Ltd.) Thereafter, the stirring speed was gradually increased, and stirring was performed at 1200 rpm for 30 minutes to obtain a suspension. The stirring speed was gradually lowered while adding 300 mL of warm water at 43 ° C. to this suspension.
Under stirring that can keep the whole suspension in a uniform state with a vertical stirring blade, about 11 mL of a 10 wt% acetic acid aqueous solution was quantitatively added over 22 minutes to adjust the pH to 4.0, and then cooled to 10 ° C.
After maintaining the suspension in a cooled state for 2 hours, 3 mL of 37 wt% formalin aqueous solution was added, and 22 mL of 10 wt% Na ₂ CO ₃ aqueous solution was added quantitatively over 25 minutes.

Furthermore, the temperature of the suspension was returned to room temperature and aged for 20 hours to obtain a dispersion of microcapsules (cm1) for electrophoretic display devices. The volume average particle diameter of the microcapsules (cm1) for electrophoretic display devices was 51.1 μm.
This dispersion was classified by passing through a mesh having an aperture of 80 μm and 30 μm to obtain a paste (solid content: 57 wt%) of an electrophoretic display device microcapsule (cm1) having a particle size of 30 to 80 μm.
Using this paste, the amount of alkali metal ions in the entire microcapsules (cm1) for electrophoretic display devices was measured in the same manner as in Example 1. The results are shown in Table 1.

Next, a coating solution was obtained in the same manner as in Example 1 except that the amount of the paste added to the acrylic resin solution was 11.1 g.
Thereafter, in the same manner as in Example 1, an electrophoretic display device sheet (cs1) was obtained, and an electrophoretic display device (cd1) was produced.
For the electrophoretic display device (cd1), the contrast (A) before the moisture resistance test and the contrast (B) after the moisture resistance test were measured in the same manner as in Example 1. The results are shown in Table 1.

The microcapsule of the present invention and the microcapsule of the present invention are, for example, display devices such as ordinary electrophoretic display panels, so-called digital papers (electronic papers) such as paper-like displays and rewritable papers, IC cards, IC tags, etc. It can be suitably used for various electrophoretic display devices such as an electronic whiteboard, a guide board, a notice board, an electronic newspaper, an electronic book, and a portable terminal (eg, PDA).
The production method of the present invention is suitable as a method for easily obtaining the microcapsules of the present invention.

Claims (4)

  A microcapsule for an electrophoretic display device in which electrophoretic fine particles and a solvent are encapsulated in a shell, wherein the amount of alkali metal ions in the entire microcapsule is 150 ppm or less. Micro capsule. A liquid containing a hydrophobic solvent and electrophoretic fine particles is used as a core substance, the core substance is dispersed in an aqueous medium containing a water-soluble surfactant, and then a water-soluble compound is added to the aqueous medium. A method of manufacturing a microcapsule for an electrophoretic display device, wherein a shell is formed on the surface of the core substance,
As the water-soluble surfactant, the following general formula (1):
R ¹ — (CH ₂ —CH ₂ —O—) _n —X—R ² (1)
(However, R ¹ represents an aliphatic or aromatic hydrophobic group having 5 to 25 carbon atoms, and R ² represents a polymer group having a polyamine structure or polycarboxylic acid structure having a weight average molecular weight of 300 to 100,000. , N represents an integer of 3 to 85. X is derived from a group capable of reacting with at least one group selected from the group consisting of an amino group, an imino group and a carboxyl group, and represents a group formed after the reaction. Represented, but may or may not be present.)
And using the compound (B) having an epoxy group or an episulfide group as the water-soluble compound,
The shell is formed by reacting the compound (A) with the compound (B).
A method for producing a microcapsule for an electrophoretic display device.   An electrophoretic display device sheet comprising the microcapsule according to claim 1 and a binder resin.   The sheet for electrophoretic display devices according to claim 3, wherein a layer containing the microcapsules and the binder resin is formed on a conductive film.