JP2015184366A - Particle for display, particle dispersion for display, display medium, and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide particles for display capable of suppressing generation of reverse polarity particles and agglomeration, and a display medium including the particles for display.SOLUTION: The particles for display includes a polymer containing a basic functional group in a range of 0.1 mass% or more and 5 mass% or less with respect to the polymer total mass and at least one selected from the group consisting of a sulfonic acid ion, nitrate ion, sulfate ion, phosphate ion and halide ion in a range of 20 ppm or more and 70 ppm or less. The display medium comprises a display particle group including the particles for display and a dispersion medium for dispersing the display particle group.

Description

  The present invention relates to display particles, a display particle dispersion, a display medium, and a display device.

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

For example, Patent Document 1 discloses the surface of colored particles containing a polymer compound having an amino group and a colorant for the purpose of obtaining image display particles in which the change in charge amount with time is suppressed. Disclosed is a particle for image display treated with a quaternary ammonium salt.
Further, Patent Document 2 discloses an electrophoretic particle having an acidic group on at least the particle surface for the purpose of realizing a high-speed response even under low voltage driving conditions. Electrophoretic particles having a structure in which a salt is formed with a compound having the above are disclosed.

JP 2009-192740 A JP-A-2005-300969

  The subject of this invention is providing the particle | grains for a display which suppresses generation | occurrence | production of aggregation with generation | occurrence | production of the particle | grains of reverse polarity.

  The above problem is solved by the following means.

The invention according to claim 1
A group comprising a basic functional group in the range of 0.1% by mass to 5% by mass with respect to the total mass of the polymer, and comprising a sulfonate ion, a nitrate ion, a sulfate ion, a phosphate ion, and a halide ion A display particle comprising a polymer containing at least one selected from 20 ppm to 100 ppm.

The invention according to claim 2
At least one inorganic acid ion selected from the group consisting of sulfonate ion, nitrate ion, sulfate ion, phosphate ion and halide ion in a solvent having a swelling degree with respect to the swelling degree in water of 1.2 or more The display particles according to claim 1, wherein the display particles are treated with an acid containing an organic acid ion.

The invention according to claim 3
The display particle according to claim 1, wherein the halide ion is a chloride ion.

The invention according to claim 4
The display particle according to any one of claims 1 to 3, wherein the basic functional group is an amino group.

The invention according to claim 5
A particle group containing the display particles according to any one of claims 1 to 4,
A dispersion medium for dispersing the particle group;
A particle dispersion for display.

The invention according to claim 6
A pair of substrates, at least one of which is translucent,
A particle group encapsulated between the pair of substrates and containing the display particles according to any one of claims 1 to 4,
A dispersion medium enclosed between the pair of substrates and for dispersing the particle group;
A display medium.

The invention according to claim 7 provides:
A display medium according to claim 6;
Electric field forming means for forming an electric field between the pair of substrates;
A display device comprising:

The invention according to claim 8 provides:
A pair of electrodes, at least one of which is translucent,
A group of particles encapsulated between the pair of electrodes and including the display particles according to any one of claims 1 to 4,
A dispersion medium enclosed between the pair of electrodes and for dispersing the particle group;
A display medium.

The invention according to claim 9 is:
A display medium according to claim 8;
Electric field forming means for forming an electric field between the pair of electrodes;
A display device comprising:

  According to the invention of claim 1, 2, 3, or 4, the polymer containing a basic functional group in the range of 0.1% by mass or more and 5% by mass or less with respect to the total mass of the polymer contains the ions. Compared to the case where the content is not included in the above range, display particles are provided that suppress the generation of aggregation as well as the generation of particles having opposite polarity.

According to the invention of claim 5, the polymer containing a basic functional group in the range of 0.1% by mass or more and 5% by mass or less with respect to the total mass of the polymer contains the ions in the above range. Compared to the case where no display particles are applied, a display particle dispersion liquid that suppresses the occurrence of agglomeration as well as the generation of reverse polarity particles in the display particles is provided.
According to the invention which concerns on Claim 6, 7, 8, or 9, the polymer which contains a basic functional group in the range of 0.1 mass% or more and 5 mass% or less with respect to the polymer total mass has the said ion. A display medium or a display device that suppresses the occurrence of agglomeration as well as the generation of reverse polarity particles in the display particles as compared with the case where display particles not included in the above-described content is applied.

It is a schematic block diagram of the display apparatus which concerns on this embodiment. It is explanatory drawing which shows typically the movement aspect of a particle group when a voltage is applied between the board | substrates of the display medium of the display apparatus which concerns on this embodiment. It is a schematic diagram for demonstrating the drive method of the display apparatus (display medium) which concerns on this embodiment.

  Hereinafter, the present invention will be described in detail.

<Display particles, display particle dispersion>
The display particles according to the present embodiment contain a basic functional group in a range of 0.1% by mass to 5% by mass with respect to the total mass of the polymer, and sulfonate ions, nitrate ions, sulfate ions, At least one selected from the group consisting of phosphate ions and halide ions (hereinafter, these ions are also referred to as “specific anions” or “specific anions derived from inorganic acids or organic acids”) in the range of 20 ppm to 100 ppm. Including the polymer (hereinafter also referred to as “specific polymer”). In addition, content of the specific anion derived from an inorganic acid or an organic acid is content of all the specific anions contained in a polymer.

  In the display particles according to the present embodiment, the occurrence of aggregation is suppressed along with the generation of particles having opposite polarity. The reason is not clear, but is presumed to be due to the following reasons.

First, display particles including a polymer having a basic functional group typified by an amino group, a quaternary ammonium group, and the like are particles that are easily positively charged due to the presence of the basic functional group. For example, as shown in the following (a), the amino group maintains the state of> N ⁺ -to maintain the positive chargeability of the display particles, but the positively charged amino group is electrically charged. It is considered that the positive chargeability is lowered by canceling out automatically.
On the other hand, for example, the amino group exhibits the state shown in (b) above and is positively charged due to the presence of an inorganic acid or an organic acid typified by hydrochloric acid or the like. For this reason, it is considered that the polymer having a basic functional group contains an anion derived from an inorganic acid or an organic acid, so that the positive chargeability of the amino group can be easily maintained. And it is thought that the polymer with many specific anions derived from an inorganic acid or an organic acid contains many positively charged amino groups represented by the above (c).

  Thus, it is considered that when the polymer having a basic functional group contains a large amount of a specific anion derived from an inorganic acid or an organic acid, the positive chargeability of the display particles is enhanced.

Here, in order to include a specific anion derived from an inorganic acid or an organic acid in the polymer of the display particles, a method of treating the surface of the display particles with an inorganic acid or an organic acid (neutralization treatment) is employed. . Since this treatment is performed in an aqueous solution of an inorganic acid or an organic acid, the aqueous solution hardly penetrates into the display particles. By this treatment, the specific anion derived from the inorganic acid or organic acid contained in the polymer of the display particle is present only in the polymer of the particle surface layer portion, and is considered to contribute to the positive charging of the basic functional group.
For this reason, in order to suppress generation | occurrence | production of the particle | grains of reverse polarity, in order to raise the positive charge property of the display particle, it is necessary to increase content of an amino group excessively as the polymer of the display particle as a whole.

  However, if the content of the specific anion derived from an inorganic acid or an organic acid is excessively increased as a whole polymer of the display particles, aggregation of the display particles is likely to occur. This is presumably because when the content of the specific anion derived from the inorganic acid or organic acid is excessively increased, the polymers of the display particles are easily entangled with each other.

On the other hand, the content of the basic functional group contained in the polymer of the display particles is reduced to a range of 0.1% by mass to 5% by mass with respect to the total mass of the polymer. Thereby, aggregation of display particles is suppressed. In this state, the content of the specific anion derived from the inorganic acid or organic acid contained in the polymer of the display particles is increased to a range of 20 ppm to 100 ppm. That is, a specific anion derived from an inorganic acid or an organic acid is present even inside the display particles, and the basic functional group present in the particles is also positively charged. This increases the positive chargeability of the particles as a whole and suppresses the generation of particles with reverse polarity.
That is, the display particles containing a specific polymer mean particles having a small amount of basic functional groups but a larger amount of positively charged basic functional groups than in the past.

  From the above, it is presumed that the display particles according to the present embodiment suppress the occurrence of aggregation together with the generation of particles having opposite polarity.

  In addition, since the display particles according to the present embodiment have a positive chargeability as a whole, the image maintainability (hereinafter also referred to as “memory property”) is improved. Further, by reducing the content of the basic functional group of the polymer, it is possible to suppress an excessive increase in the threshold value (threshold value at which the display particles start to move according to the electric field) accompanying the increase in the charge amount of the display particles. Furthermore, by reducing the content of the basic functional group of the polymer, deterioration of the continuous drive characteristics (deterioration of responsiveness and expansion of color difference) of the display particles can be suppressed.

  Hereinafter, the configuration of the display particles according to the present embodiment will be described.

  The polymer (specific polymer) included in the display particles according to the present embodiment has a basic functional group. Hereinafter, the basic functional group is also referred to as a basic functional group.

The specific polymer contains a basic functional group in a range of 0.1% by mass to 5% by mass with respect to the total mass of the polymer. By setting the content of the basic functional group within the above range, the occurrence of aggregation is suppressed. In addition, it is easy to suppress an excessive increase in the threshold and deterioration of the continuous drive characteristics of the display particles.
The content of the basic functional group is 0.2% by mass or more and 4% by mass or less from the viewpoints of suppressing the occurrence of aggregation, suppressing excessive increase of the threshold value, and suppressing deterioration of the continuous driving characteristics of the display particles. Preferably, it is 0.2 mass% or more and 3 mass% or less.

In addition, content of a basic functional group is the value measured by the method shown next.
Basic functional groups were measured by fluorescent X-ray elemental analysis. First, cellulose tablets containing various concentrations of functional groups are prepared, and calibration curves for the concentration and fluorescent X-ray intensity of elements derived from the functional groups are prepared. Next, a cellulose tablet of a sample to be obtained is prepared, and the content of the functional group is calculated from the fluorescent X-ray intensity derived from the functional group and a calibration curve.

The basic functional group is a functional group that positively charges the display particles, and examples thereof include an amino group and a quaternary ammonium group. The amino group may be a primary amino group or a secondary amino group.
The basic functional group is preferably an amino group.
The specific polymer may have only one type of basic functional group, or two or more types may be mixed.

The specific polymer is selected from the group consisting of sulfonate ion (SO ₃ ⁻ ), nitrate ion (NO ₃ ⁻ ), sulfate ion (SO ₄ ²⁻ ), phosphate ion (PO ₄ ³⁻ ), and halide ion. At least one kind of anion (specific anion) is contained in the range of 20 ppm to 100 ppm. The specific anion is an anion derived from an inorganic acid or an organic acid and, as described above, is considered to play a role of maintaining the positive chargeability of the basic functional group.

By setting the content of the specific anion in the specific polymer within the above range, the generation of particles having reverse polarity is suppressed. In addition, the memory properties of the display particles are likely to increase.
The specific anion content in the specific polymer is preferably 30 ppm or more and 70 ppm or less from the viewpoint of suppressing the generation of particles with reverse polarity and improving the memory property.

  The specific anion content in the specific polymer is a value measured by the following method. First, 0.02 parts by mass of display particles are suspended in 5 parts by mass of purified water and ultrasonically dispersed for 30 minutes. Thereafter, the display particles are filtered, the filtrate is measured by ion chromatography, and the concentration of the specific anion is measured.

Examples of the halide ions include fluoride ions (F ⁻ ), chloride ions (Cl ⁻ ), bromide ions (Br ⁻ ), iodide ions (I ⁻ ), and the like.
Among the above, the specific anion is preferably a halide ion, and more preferably a chloride ion.

  The specific polymer may contain only one kind of sulfonate ion, nitrate ion, sulfate ion, phosphate ion and halide ion, or may contain two or more kinds. .

  The specific polymer is, for example, a basic functional group-containing polymer including a basic functional group-containing structural unit derived from a polymerizable compound having a basic functional group, or a basic functional group-containing copolymer, an inorganic acid or Examples thereof include polymers formed by the action of organic acids. As the inorganic acid or organic acid, at least one kind of inorganic acid and organic acid containing sulfonate ion, nitrate ion, sulfate ion, phosphate ion or halide ion may be used.

Examples of the polymerizable compound having a basic functional group include aminoethyl acrylate, N, N-dimethylaminoethyl acrylate, N, N-diethylaminoethyl acrylate, N, N-dimethylaminoethyl methacrylate, N, N-diethylamino. Examples include amino group-containing or substituted amino group-containing monomers such as ethyl methacrylate.
Of these, N, N-diethylaminoethyl methacrylate is preferred.

The basic functional group-containing copolymer may have two or more types of basic functional group-containing structural units different from each other in the polymerizable compound having a basic functional group, and the basic functional group-containing structural unit. And other structural units derived from other polymerizable compounds.
A basic functional group-containing copolymer having a basic functional group-containing constitutional unit and another constitutional unit is one having a basic functional group-containing constitutional unit and another constitutional unit independently. Or it may have two types.

Examples of other polymerizable compounds constituting other structural units that can be contained in the basic functional group-containing copolymer include (meth) acrylic acid, methacrylate, acrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert. -Butyl methacrylate, 2-ethylhexyl methacrylate, isodecyl methacrylate, n-lauryl methacrylate, tridecyl methacrylate, n-stearyl methacrylate, butoxydiethylene glycol methacrylate, methoxypolyethylene glycol methacrylate, methoxypolyethylene glycol methacrylate, cyclohexyl methacrylate, tetrahydrofurfuryl methacrylate, benzyl Methacrylate, phenoxyethyl methacrylate, isobornyl meta Relate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxybutyl methacrylate and the like.
Of these, methacrylic acid is preferred.

The other polymerizable compound is preferably a polyfunctional polymerizable compound containing two or more polymerizable groups. For example, ethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate, 1,4-butanediol. Examples include diacrylate, 2,2-dimethyl-1,3-propanediol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,10-decanediol diacrylate, 1,1,1-trimethylolpropane trimethacrylate, and the like. It is done.
As the polyfunctional polymerizable compound, ethylene glycol dimethacrylate is preferred.

  The specific polymer may be a compound obtained by reacting a base compound with a thermoplastic resin or a thermosetting resin to introduce a basic functional group and causing an inorganic acid or an organic acid to act.

The following resin is mentioned as a thermoplastic resin or a thermosetting resin.
Thermoplastic resins include styrenes such as styrene and chlorostyrene, monoolefins such as ethylene, propylene, butylene and isoprene, vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate and vinyl butyrate, methyl acrylate, acrylic Α-methylene aliphatic monocarboxylic acid esters such as ethyl acetate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate, vinyl methyl ether And vinyl ethers such as vinyl ethyl ether and vinyl butyl ether, and homopolymers or copolymers of vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and vinyl isopropenyl ketone.

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

The display particles according to the present embodiment may further contain a colorant.
The colorant may be included in the display particles as an external additive of the specific polymer, or may be included in the specific polymer.

As the colorant, organic or inorganic pigments, oil-soluble dyes, etc. can be used, magnetic powders such as magnetite and ferrite, carbon black, titanium oxide, magnesium oxide, zinc oxide, phthalocyanine copper-based cyan colorant, Known colorants such as an azo yellow color material, an azo magenta color material, a quinacridone magenta color material, a red color material, a green color material, and a blue color material can be used. Specifically, aniline blue, calcoil blue, chrome yellow, ultramarine blue, duPont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, lamp black, rose bengal, C.I. I. Pigment red 254, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 57: 1, C.I. I. Pigment yellow 97, C.I. I. Pigment blue 15: 1, C.I. I. Pigment Blue 15: 3 etc. are exemplified as typical ones.
“CI pigment red” is also simply referred to as “PR”, “CI pigment yellow” is simply referred to as “PY”, and “CI pigment blue” is also simply referred to as “PB”. For example, “CI Pigment Red 254” is represented as “PR254”.
These may be used in combination with a plurality of color materials.
Among the above, the colorant is preferably a pigment such as carbon black or PR254.

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

A magnetic material may be mixed in the inside and the surface of the display particles according to the present embodiment, if necessary. As the magnetic material, a color-coated inorganic magnetic material or organic magnetic material is used as necessary. Further, a transparent magnetic material, in particular, a transparent organic magnetic material does not hinder the color development of the color pigment, and the specific gravity is smaller than that of the inorganic magnetic material, and is more desirable.
As the colored magnetic powder, for example, a small-diameter colored magnetic powder described in JP-A-2003-131420 may be used. A material provided with magnetic particles serving as nuclei and a colored layer laminated on the surface of the magnetic particles is used. The colored layer may be selected by coloring the magnetic powder opaque with a pigment or the like, but it is desirable to use, for example, a light interference thin film. This optical interference thin film is a thin film having a thickness equivalent to the wavelength of light made of an achromatic material such as SiO ₂ or TiO ₂ , and reflects light in a wavelength selective manner by optical interference in the thin film. is there.

  An external additive may be attached to the surface of the display particles according to the present embodiment, if necessary. The color of the external additive is desirably transparent so as not to affect the color of the display particles according to the present embodiment.

  As the external additive, inorganic particles such as metal oxides such as silicon oxide (silica), titanium oxide, and alumina are used. In order to adjust the charging property, fluidity, environment dependency, and the like of the display particles according to this embodiment, they may be surface-treated with a coupling agent or silicone oil.

  Coupling agents include positively chargeable ones such as aminosilane coupling agents, aminotitanium coupling agents, nitrile coupling agents, and silanes that do not contain nitrogen atoms (consisting of atoms other than nitrogen). There are negatively charged ones such as coupling agents, titanium-based coupling agents, epoxy silane coupling agents, and acrylic silane coupling agents. Silicone oil includes positively charged ones such as amino-modified silicone oil, dimethyl silicone oil, alkyl-modified silicone oil, α-methylsulfone-modified silicone oil, methylphenyl silicone oil, chlorophenyl silicone oil, and fluorine-modified silicone. Examples include negatively chargeable oils. These are selected according to the desired resistance of the external additive.

Next, the characteristics of the display particles according to this embodiment will be described.
The volume average particle diameter of the display particles according to the present embodiment is preferably 0.3 μm or more and 10 μm or less, more preferably 1 μm or more and 10 μm or less, and more preferably 3 μm or more and 8 μm or less from the viewpoint of driveability of the display particles. More preferably it is.
The display particles according to the present embodiment preferably have a narrow particle size distribution from the viewpoint of balancing the driveability of the display particles. Specifically, the CV value (Coefficient of Variation) is preferably 20% or more and 30% or less, more preferably 20% or more and 28% or less, and further preferably 20% or more and 25% or less. The CV value of the display particles is represented by the following formula.
CV value [%] = (σ / D) × 100
However, (sigma) represents a standard deviation and D represents a volume average particle diameter.

The display particles according to this embodiment are preferably particles having a volume average particle size of 0.3 μm or more and 10 μm or less and a CV value of 20% to 30%, particularly from the viewpoint of image display properties. .
The volume average particle diameter and the CV value of the display particles are values measured with a Horiba LA-300, a laser light scattering / diffraction particle size measuring device manufactured by Horiba, Ltd.

The display particles according to this embodiment preferably have a degree of swelling in methanol of 1.1 to 2.0 with respect to the degree of swelling in water.
Here, the degree of swelling means that the radius of the display particles is measured under an optical microscope when the display particles are put in water and methanol for 1 minute at room temperature (25 ° C.). It is a value calculated from
Swelling degree = (radius of display particles in methanol) ³ / (radius of display particles in water) ³
The display particles are excellent in memory properties because the swelling degree in methanol with respect to the swelling degree in water is 1.1 or more and 2.0 or less. If the display particles easily swell in methanol, it is considered that anions are easily released from the particles.
The swelling degree of the display particles in methanol with respect to the swelling degree in water is more preferably 1.4 or more and 2.0 or less, and further preferably 1.5 or more and 2.0 or less.

Next, a method for producing display particles according to the present embodiment will be described.
As a method for producing the display particles according to the present embodiment, for example, after a specific polymer is synthesized in advance and the specific polymer is heated and melted, a pigment is added and mixed, dispersed, and cooled as necessary. , Particles may be prepared using a pulverizer such as a jet mill, a hammer mill, or a turbo mill.
The display particles may be prepared by a polymerization method such as suspension polymerization, emulsion polymerization, dispersion polymerization, or coacervation, melt dispersion, or emulsion aggregation.

Among these, it is preferable to produce particles containing a specific polymer by a polymerization reaction using a polymerizable compound having a basic functional group, another polymerizable compound, or the like.
Specifically, for example, a polymerization step for obtaining particles containing a polymer having a basic functional group in the above range with respect to the total mass of the polymer using at least a polymerizable compound having a basic functional group is obtained. Particles containing a polymer having a basic functional group are selected from at least one inorganic acid ion or organic compound selected from the group consisting of a specific anion (sulfonate ion, nitrate ion, sulfate ion, phosphate ion and halide ion). And a neutralization step of obtaining particles containing a polymer containing a specific anion in the above range by neutralization with an acid containing an acid ion).
The “polymer having a basic functional group” refers to the aforementioned basic functional group-containing polymer or basic functional group-containing copolymer.

In the polymerization step, a polymerizable compound having one or two basic functional groups, or a polymerizable compound having one or two basic functional groups and one or two other polymerizable compounds Using the compound, particles containing a basic functional group-containing polymer or basic functional group-containing copolymer as a polymer having a basic functional group are obtained.
The details of the polymerizable compound having a basic functional group and other polymerizable compounds are as described above.

  In the polymerization step, in addition to the polymerizable compound having a basic functional group and other polymerizable compounds, a polymerization reaction may be performed using a colorant, a polymerization initiator, and the like. Further, emulsion polymerization may be carried out by further using a solvent such as water and saline, a surfactant and the like in combination. By obtaining a basic functional group-containing polymer or basic functional group-containing copolymer by emulsion polymerization, it is easy to control the volume average particle size of the basic functional group-containing polymer or basic functional group-containing copolymer. . When a basic functional group-containing polymer or basic functional group-containing copolymer is obtained by emulsion polymerization, the basic functional group-containing polymer or basic functional group-containing copolymer is contained as particles in the emulsion. .

  In the neutralization step, the particles containing the polymer having a basic functional group are neutralized with an acid containing a specific anion.

  Here, in order to contain the specific anion in the above range in the polymer of the obtained display particles, the neutralization step is performed in a solvent having a swelling degree of 1.2 or more with respect to the swelling degree in water. It is preferable to neutralize particles containing a polymer having a basic functional group with an acid containing. Specifically, for example, in the neutralization step, the display particles were swollen with the solvent by a neutralization treatment liquid containing a solvent having a degree of swelling of 1.2 or more compared with water and an acid containing a specific anion. It is preferable to neutralize the display particles in the state. That is, the display particles are preferably treated with an acid containing a specific anion in a solvent having a swelling degree of 1.2 or more with respect to the swelling degree in water.

  When the particles are neutralized in a solvent having a degree of swelling of 1.2 or more with respect to the degree of swelling in water, an acid containing a specific anion penetrates into the inside of the particles and is neutralized. Thereby, the specific anion can be contained in the above range even in the display particles including a polymer having a small content of basic functional groups.

The swelling degree of the display particles in the solvent used in the neutralization treatment is preferably 1.2 or more with respect to the swelling degree of the display particles in water, but is 1.4 or more and 2.0 or less. More preferably, it is 1.5 or more and 2.0 or less.
Examples of such a solvent include methanol, ethanol, acetone, isopropanol, tetrahydrofuran and the like. Of these, methanol is preferable as the solvent.
Here, the degree of swelling means the radius of the display particles when the display particles are put in water and a solvent used in the neutralization treatment for 1 minute at room temperature (25 ° C.) under an optical microscope. It is a value calculated by the following formula. The degree of swelling is the average value of 50 display particles.
Swelling degree = (radius of display particles in solvent) ³ / (radius of display particles in water) ³

  In the neutralization step, the concentration and amount of the acid are not particularly limited, and the content of the specific anion in the polymer of the obtained display particles may be in the above range.

Next, a display particle dispersion using display particles will be described.
A display particle dispersion using display particles (display particle dispersion according to the present embodiment) includes a particle group including display particles and a dispersion medium for dispersing the particle group.
The display particle dispersion may contain other display particles (electrophoretic particles) as a particle group. In addition, acids, alkalis, salts, dispersants, dispersion stabilizers, stabilizers for the purpose of preventing oxidation or UV absorption, antibacterial agents, preservatives, etc. may be added to the display particle dispersion as necessary. May be.

  Various dispersion media used for display media are applied as the dispersion medium, but a low dielectric solvent (for example, a dielectric constant of 5.0 or less, preferably 3.0 or less) may be selected. The dispersion medium may use a solvent other than the low dielectric solvent, but preferably contains 50% by volume or more of the low dielectric solvent. In addition, the dielectric constant of the low dielectric solvent is obtained by a dielectric constant meter (manufactured by Nippon Luft).

Examples of the low dielectric solvent include petroleum-derived high-boiling solvents such as paraffinic hydrocarbon solvents, silicone oils, and fluorinated liquids, which should be selected according to the type of copolymer that is a component of the coating layer. Is good.
Specifically, for example, when applying a copolymer containing a polymerization component having a silicone chain as the polymerization component, it is preferable to select silicone oil as the dispersion medium. Moreover, when applying the copolymer containing the polymerization component which has an alkyl chain as a polymerization component, it is good to select a paraffinic hydrocarbon solvent as a dispersion medium. Of course, it is not limited to this.

  Specific examples of the silicone oil include silicone oils in which a hydrocarbon group is bonded to a siloxane bond (for example, dimethyl silicone oil, diethyl silicone oil, methyl ethyl silicone oil, methyl phenyl silicone oil, diphenyl silicone oil, etc.). Of these, dimethyl silicone is particularly desirable.

  Examples of the paraffinic hydrocarbon solvent include normal paraffinic hydrocarbons and isoparaffinic hydrocarbons having 20 or more carbon atoms (boiling point of 80 ° C. or higher), but it is desirable to use isoparaffins for reasons such as safety and volatility. . Specifically, shell sol 71 (manufactured by Shell Petroleum), Isopar O, Isopar H, Isopar K, Isopar L, Isopar G, Isopar M (manufactured by Exxon), IP Solvent (manufactured by Idemitsu Petrochemical) and the like can be mentioned.

  Charge control agents include ionic or nonionic surfactants, block or graft copolymers composed of a lipophilic part and a hydrophilic part, polymers such as cyclic, star-like or dendritic polymers (dendrimers) A compound having a chain skeleton, a metal complex of salicylic acid, a metal complex of catechol, a metal-containing bisazo dye, a tetraphenylborate derivative, a polymerizable silicone macromer (manufactured by JNC Corporation: Silaplane) and an anionic monomer or a cationic polymer A copolymer etc. are mentioned.

  The display particle dispersion according to this embodiment may be encapsulated by a capsule wall. That is, the capsule particles may contain display particles, a dispersion medium, and other additives as necessary.

The display particle dispersion liquid (and its display particles) according to this embodiment is used for an electrophoretic display medium (including an electrophoretic light control medium (light control element)). In addition, as an electrophoretic display medium, a method of moving a particle group in a direction opposite to a known electrode (substrate) surface, and a method of moving in a direction along the electrode (substrate) surface (a so-called in-plane). Type element), or a hybrid element combining these.
In the display particle dispersion according to the present embodiment, color display can be realized by mixing and using a plurality of types of particles having different colors and charging polarities as migrating particles that move in response to an electric field.

<Display medium, display device>
FIG. 1 is a schematic configuration diagram illustrating a display device according to the present embodiment.
The display device 10 according to the present embodiment has a form in which the particle group including the display particles according to the present embodiment is applied as the colored particle group 34 in the display medium 12.
Specifically, the colored particle group 34 includes a cyan cyan particle group 34C and a red red particle group 34R having a larger particle diameter than the cyan particle group 34C and the same charging polarity as the cyan particle group 34C. is there.
In the colored particle group 34, the small particle colored particle group of the display particle dispersion according to the present embodiment is applied as the cyan particle group 34C, and the large particle colored particle group is applied as the red particle group 34R. .

  As shown in FIG. 1, the display device 10 according to the present embodiment includes, for example, a display medium 12, a voltage application unit 16 (an example of an electric field generation unit), and a control unit 18.

(Display medium)
As shown in FIG. 1, the display medium 12 holds, for example, a display substrate 20 that is a display surface, a back substrate 22 that faces the display substrate 20 with a gap, and a distance between these substrates at a target interval. The gap member 24 divides the display substrate 20 and the back substrate 22 into a plurality of cells.
Here, the cell refers to a region surrounded by the display substrate 20, the back substrate 22, and the gap member 24. In this cell, a colored particle group 34, a white particle group 36, and a dispersion medium 50 for dispersing these particle groups are enclosed. The colored particle group 34 and the white particle group 36 are dispersed in the dispersion medium 50, and the colored particle group 34 moves between the display substrate 20 and the back substrate 22 in accordance with the electric field strength formed in the cell.

It is to be noted that the gap member 24 is provided so as to correspond to each pixel when an image is displayed on the display medium 12, and cells are formed so as to correspond to each pixel, whereby the display medium 12 displays the color for each pixel. May be configured to be realized.
A plurality of types of colored particle groups 34 having different colors are dispersed in the dispersion medium 50 of the display medium 12. The plurality of types of colored particle groups 34 are particles that are electrophoresed between the substrates, and the absolute value of the voltage required to move in accordance with the electric field is different for each color particle group.

-Display board, rear board-
The display substrate 20 has a configuration in which, for example, a display electrode 40 and a surface layer 42 are sequentially stacked on a support substrate 38. The back substrate 22 has a configuration in which, for example, a back electrode 46 and a surface layer 48 are sequentially laminated on a support substrate 44.

  Examples of the material of the support substrate 38 and the support substrate 44 include glass and resin, for example, polycarbonate resin, acrylic resin, polyimide resin, polyester resin, epoxy resin, and polyethersulfone resin.

  Examples of the material of the display electrode 40 and the back electrode 46 include oxides such as indium, tin, cadmium, and antimony, composite oxides such as ITO, metals such as gold, silver, copper, and nickel, and organics such as polypyrrole and polythiophene. Materials and the like. The display electrode 40 and the back electrode 46 may be any of these single layer films, mixed films, or composite films, and are formed by, for example, a vapor deposition method, a sputtering method, a coating method, or the like.

The film thickness of the display electrode 40 and the back electrode 46 is adjusted so as to obtain a desired conductivity, but is generally, for example, 10 nm or more and 1 μm or less.
The back electrode 46 and the display electrode 40 are formed in a desired pattern, for example, a matrix shape or a stripe shape that realizes passive matrix driving by a conventionally known means such as etching of a conventional liquid crystal display element or a printed board.

  The display electrode 40 may be embedded in the support substrate 38, for example. Similarly, the back electrode 46 may be embedded in the support substrate 44, for example. Each of the back electrode 46 and the display electrode 40 may be separated from the display substrate 20 and the back substrate 22 and disposed outside the display medium 12.

In the above description, the case where the electrodes (the display electrode 40 and the back electrode 46) are provided on both the display substrate 20 and the back substrate 22 has been described. However, the electrodes may be provided on only one of them.
In order to realize active matrix driving, the support substrate 38 and the support substrate 44 are, for example, TFT (Thin Film Transistor), TFD (Thin Film Diode), MIM (Metal-Insulator-Metal) element, varistor or the like for each pixel. An active element may be provided. The active elements are preferably formed not on the display substrate 20 but on the back substrate 22 because wiring can be easily laminated and components can be easily mounted.

When the display electrode 40 and the back electrode 46 are formed on the support substrate 38 and the support substrate 44, respectively, the electrodes between the electrodes that cause breakage of the display electrode 40 and the back electrode 46 and adhesion of the particles of the colored particle group 34 are caused. In order to suppress the occurrence of leakage, it is desirable to form the surface layer 42 and the surface layer 48 as dielectric films on the display electrode 40 and the back electrode 46, respectively, as necessary.
In the present embodiment, the case where the surface layers (each of the surface layer 42 and the surface layer 48) are provided on both the opposing surfaces of the display substrate 20 and the back substrate 22 will be described. However, the display substrate 20 and the back substrate 22 are described. The structure provided only in either one of these opposing surfaces may be sufficient. Further, these may be different materials.

  Examples of the material of the surface layer 42 and the surface layer 48 include polyolefins such as polyethylene and polypropylene, polycarbonate, polyester, polystyrene, polyimide, polyurethane, polyamide, polymethyl methacrylate, copolymer nylon, epoxy resin, ultraviolet curable acrylic resin, A silicone resin, a fluororesin, etc. are mentioned.

As the material of the surface layer 42 and the surface layer 48, when the dispersion medium 50 is silicone oil, for example, a polymer compound having a silicone chain is preferably used from the viewpoint of preventing the particles from sticking.
Examples of the polymer compound having a silicone chain include a copolymer containing the following structural unit (A) and the following structural unit (B).

In the structural units (A) and (B), X represents a group containing a silicone chain.
Ra ¹ represents a hydrogen atom or a methyl group.
Ra ² represents a hydrogen atom, a methyl group, or a halogen atom (for example, a chlorine atom).
Rb ² represents a hydrogen atom, an alkyl group, an alkenyl group, a cyano group, an aromatic group, a heterocyclic group, or —C (═O) —O—Rc ² (where Rc ² represents an alkyl group, a hydroxyalkyl group, polyoxyethylene alkyl group _{(- (C x H 2x -O} ) n -H [x, n = 1 or more integer), amino group, monoalkylamino group or dialkylamino group).
n1 and n2 represent mol% of each structural unit with respect to the entire copolymer, and represent 0 <n1 <50 and 0 <n2 <80. n represents a natural number of 1 or more and 3 or less.

In the structural unit (A), the group containing a silicone chain represented by X is, for example, a group containing a linear or branched silicone chain (a siloxane chain in which two or more Si—O bonds are linked), Preferably, it includes a dimethylsiloxane chain in which two or more dimethylsiloxane structures (—Si (CH ₃ ) ₂ —O—) are connected, and a part thereof (part of —CH ₃ ) may be substituted. It is a group. Specific examples of the group containing a silicone chain represented by X include a group represented by the following structural formula (X1) or (X2).

In Structural Formulas (X1) and (X2), R ¹ represents a hydroxyl group, a hydrogen atom, or an alkyl group having 1 to 10 carbon atoms. n represents an integer of 1 to 10.

  Specifically, as a monomer constituting the structural unit (A) in a polymer compound having a silicone chain, for example, a dimethyl silicone monomer having a (meth) acrylate group at one end (for example, manufactured by JNC Corporation) : Silaplane: FM-0711, FM-0721, FM-0725, etc., Shin-Etsu Chemical Co., Ltd .: X-22-174DX, X-22-2426, X-22-2475, etc.). Among these, silaplanes: FM-0711, FM-0721, FM-0725, etc. are desirable.

  Examples of monomers constituting the structural unit (B) include (meth) acrylonitrile, (meth) acrylic acid alkyl esters such as methyl methacrylate and butyl methacrylate, (meth) acrylamide, ethylene, propylene, butadiene, and isoprene. , Isobutylene, N-dialkyl-substituted (meth) acrylamide, styrene, vinyl carbazole, styrene, styrene derivatives, polyethylene glycol mono (meth) acrylate, vinyl chloride, vinylidene chloride, isoprene, butadiene, vinyl pyrrolidone, hydroxyethyl (meth) acrylate, And hydroxybutyl (meth) acrylate. In these notations, the description such as “(meth) acrylate” is an expression including both “acrylate” and “methacrylate”.

  The polymer compound having a silicone chain may contain a crosslinking unit in addition to the structural units (A) and (B). Examples of the crosslinking unit include monomers containing an epoxy group, an oxazoline group, an isocyanate group, and the like.

  The weight average molecular weight of the polymer compound having a silicone chain is preferably from 100 to 1,000,000, more preferably from 400 to 1,000,000. The weight average molecular weight is measured by a static light scattering method or size exclusion column chromatography, and the numerical values described in this specification are measured by the method.

  The thickness of the surface layer (surface layer 42, surface layer 48) composed of a polymer compound having a silicone chain is, for example, preferably 0.001 μm to 10 μm, and more preferably 0.01 μm to 1 μm.

As the material for the surface layer 42 and the surface layer 48, in addition to the above-described insulating material, an insulating material containing a charge transporting substance may be used. Inclusion of a charge transport material improves particle chargeability by injecting particles into the particle, and when the charge amount of the particle becomes extremely large, the charge of the particle is leaked and the charge amount of the particle is stabilized. An effect is obtained.
Examples of charge transport materials include hole transport materials such as hydrazone compounds, stilbene compounds, pyrazoline compounds, and arylamine compounds, electron transport materials such as fluorenone compounds, diphenoquinone derivatives, pyran compounds, and zinc oxide, and polyvinylcarbazole. Examples thereof include resins having charge transport properties such as

-Gap member-
The gap member 24 is a member for holding a gap between the display substrate 20 and the back substrate 22 and is formed so as not to impair the transparency of the display substrate 20, for example, a thermoplastic resin, a thermosetting resin, an electronic It is formed of a wire curable resin, a photo curable resin, rubber, metal or the like.
The gap member 24 includes a cell type and a particle type. Examples of the cellular shape include a net or a sheet having holes formed in a matrix shape by etching or laser processing.
The gap member 24 may be integrated with any one of the display substrate 20 and the back substrate 22, and the support substrate 38 or the support substrate 44 is etched, laser processed, or using a prefabricated mold, By the printing or the like, the support substrate 38 or the support substrate 44 having the cell pattern of the target size, and the gap member 24 are manufactured. In this case, the gap member 24 can be fabricated on either the display substrate 20 side, the back substrate 22 side, or both. The gap member 24 may be colored, but is preferably colorless and transparent so as not to adversely affect the display image displayed on the display medium 12.
The wall surface of the gap member 24 may be provided with a surface layer having the same composition as the surface layer 42 and the surface layer 48.

(Voltage application part)
The voltage application unit 16 is electrically connected to the display electrode 40 and the back electrode 46, for example. In the present embodiment, a case where both the display electrode 40 and the back electrode 46 are electrically connected to the voltage application unit 16 will be described. However, one of the display electrode 40 and the back electrode 46 is grounded. The other may be connected to the voltage application unit 16.
The voltage application unit 16 is, for example, a voltage application device for applying a voltage to the display electrode 40 and the back electrode 46, and applies a voltage according to the control of the control unit 18 between the display electrode 40 and the back electrode 46.

(Control part)
For example, the control unit 18 is connected to the voltage application unit 16 so as to exchange signals.
Although not shown, the control unit 18 includes a CPU (Central Processing Unit) that controls the operation of the entire apparatus, a RAM (Random Access Memory) that temporarily stores various data, and a control program and processing routine that control the entire apparatus. The microcomputer includes a ROM (Read Only Memory) in which various programs including the program shown are stored in advance.

(Driving method)
In the display device 10 according to the present embodiment, the display medium 12 displays different colors by changing the applied voltage (V) applied between the display substrate 20 and the back substrate 22.
In the display medium 12, by moving according to the electric field formed between the display substrate 20 and the back substrate 22, the color corresponding to each pixel of the image data for each cell corresponding to each pixel of the display medium 12 Is displayed.

  Here, in the display medium 12, as shown in FIG. 2, the colored particle group 34 has a voltage required for moving the colored particle group 34 according to the electric field when the colored particle group 34 is electrophoresed between the substrates. Absolute values are different. The colored particle group 34 for each color has a voltage range necessary for moving the colored particle group 34 for each color, and the voltage range is different. In other words, the absolute value of the voltage has the voltage range, and the voltage range is different for each color of the colored particle group 34.

  Hereinafter, a driving method of the display device 10 (display medium 12) according to the present embodiment (hereinafter referred to as “driving method of the present embodiment”) will be described. In the following description, the polarity of the applied voltage indicates the voltage polarity applied to the back electrode 46 of the back substrate 22.

In the driving method according to this embodiment, as shown in FIG. 1, as the colored particle group 34 enclosed in the same cell of the display medium 12, two cyan cyan particle groups 34 </ b> C and two red red particle groups 34 </ b> R are used. This is a driving method of a mode in which colored colored particle groups 34 are enclosed.
However, the cyan particle group 34C and the red red particle group 34R are all positively charged particles.

Here, in the driving method according to the present embodiment, the absolute value of the voltage (movement start voltage) when each of the two color particle groups of the cyan particle group 34C and the red red particle group 34R starts to move is set to cyan. In the following description, the color cyan particle group 34C is | Vtc |, and the red color red particle group 34R is | Vtr |.
Further, the cyan cyan particle group as an absolute value of the maximum voltage for moving almost all of the two color particle groups of the cyan cyan particle group 34C and the red red particle group 34R of the colored particle group 34 of each color. In the following description, it is assumed that 34C is | Vdc | and the red red particle group 34R is | Vdr |.

Further, the absolute values of Vtr, -Vtr, Vdr, -Vdr, Vtc, -Vtc, Vdc, and -Vdc are described as having a relationship of | Vtr | <| Vdr | <| Vtc | <| Vdc |.
Specifically, as shown in FIG. 2, for example, the colored particle groups 34 are all charged to the same polarity, and the absolute value of the voltage range necessary to move the red particle group 34R | Vtr ≦ Vr ≦ Vdr | ( Absolute value of the value between Vtr and Vdr) and the absolute value of the voltage range necessary to move the cyan particle group 34C | Vtc ≦ Vc ≦ Vdc | (the absolute value of the value between Vtc and Vdc) It is set to be large without overlapping in this order.

  Further, in order to independently drive the colored particle groups 34 of the respective colors, the absolute value | Vdr | of the maximum voltage for moving almost all the red particle groups 34R is in the voltage range necessary for moving the cyan particle group 34C. It is set smaller than the absolute value | Vtc ≦ Vc ≦ Vdc | (the absolute value of the value between Vtc and Vdc).

  That is, in the driving method according to this embodiment, the color particle groups 34 of each color are driven independently by setting the voltage ranges necessary for moving the color particle groups 34 of each color so as not to overlap. Yes.

The “voltage range necessary for moving the colored particle group 34” means the voltage necessary for the particle to start moving and the change in display density even if the voltage and voltage application time are further increased from the start of movement. Indicates a voltage range until the display density is saturated.
The “maximum voltage necessary for moving almost all the colored particle groups 34” means that even if the voltage and voltage application time are further increased from the start of the above movement, the display density does not change and the display density is saturated. Indicates the voltage to be used.
Further, “almost all” means that the characteristics of some of the colored particle groups 34 are different so that the characteristics of some of the colored particle groups 34 do not contribute to the display characteristics. That is, even if the voltage and the voltage application time are further increased from the start of the movement described above, the display density does not change and the display density is saturated.
In addition, “display density” is measured between the display surface side and the back side while measuring the color density on the display surface side with a reflection densitometer of optical density (Optical Density = 0D) of X-rite. Apply a voltage and gradually change this voltage in the direction of increasing the measured concentration (increase or decrease the applied voltage) to saturate the concentration change per unit voltage, and in that state, adjust the voltage and voltage application time. Even when the density is increased, the density does not change, and the density is shown when the density is saturated.

  In the driving method according to the present embodiment, the voltage applied between the substrates is gradually increased by applying a voltage from 0 V between the display substrate 20 and the back substrate 22 to increase the voltage value of the applied voltage. If it exceeds + Vtr, the display density starts to change due to the movement of the red particle group 34R in the display medium 12. Further, when the voltage value is increased and the voltage applied between the substrates becomes + Vdr, the change in display density due to the movement of the red particle group 34R in the display medium 12 stops.

  Further, when the voltage value is increased and the voltage applied between the display substrate 20 and the back substrate 22 exceeds + Vtc, a change in display density due to the movement of the cyan particle group 34C starts to appear in the display medium 12. When the voltage value is further increased and the voltage applied between the display substrate 20 and the back substrate 22 becomes + Vdc, the change in display density due to the movement of the cyan particle group 34C in the display medium 12 stops.

  On the other hand, if the negative voltage from 0V is applied between the display substrate 20 and the back substrate 22 to gradually increase the absolute value of the voltage and the absolute value of the voltage −Vtr applied between the substrates is exceeded. In the display medium 12, the display density starts to change due to the movement of the red particle group 34R between the substrates. Further, when the absolute value of the voltage value is increased and the voltage applied between the display substrate 20 and the rear substrate 22 becomes −Vdr or more, the change in display density due to the movement of the red particle group 34 </ b> R in the display medium 12. Stop.

  Further, when the negative voltage is applied by increasing the absolute value of the voltage value and the voltage applied between the display substrate 20 and the rear substrate 22 exceeds the absolute value of −Vtc, cyan is generated in the display medium 12. A change in display density due to the movement of the particle group 34C begins to appear. When the absolute value of the voltage value is further increased and the voltage applied between the display substrate 20 and the rear substrate 22 becomes −Vdc, the change in display density due to the movement of the cyan particle group 34C in the display medium 12 stops. .

That is, in the driving method according to the present embodiment, as shown in FIG. 2, a voltage that causes the voltage applied between the substrates to be within the range of −Vtr to Vtr (voltage range | Vtr | or less) is the display substrate 20. And the back substrate 22 are applied between the colored particles 34 (the red particles 34R and the cyan particles 34C) to such a degree that the display density of the display medium 12 changes. It can be said that it has not occurred.
When a voltage equal to or higher than the absolute value of the voltage + Vtr and the voltage −Vtr is applied between the substrates, a change occurs in the display density of the display medium 12 with respect to the red particle group 34 </ b> R of the two color particle groups 34. The display density starts to change for the first time when a certain amount of particle movement occurs, and when a voltage equal to or higher than the absolute value | Vdr | of the voltage −Vdr and the voltage Vdr is applied, the display density per unit voltage does not change.

Further, when a voltage is applied between the display substrate 20 and the back substrate 22 so that the voltage applied between the substrates is within a range of −Vtc to Vtc (voltage range | Vtc | or less), It can be said that the movement of the particles of the cyan particle group 34C to the extent that the display density of the display medium 12 changes does not occur.
Then, when a voltage higher than the absolute value of the voltage + Vtc and the voltage −Vtc is applied between the substrates, the movement of particles that causes a change in the display density of the display medium 12 begins to occur in the cyan particle group 34C. When the display density per voltage starts to change and a voltage equal to or higher than the absolute value | Vdc | of the voltage −Vdc and the voltage Vdc is applied, the display density does not change.

  Next, the driving method according to this embodiment will be specifically described with reference to FIG.

  First, a voltage −Vdc is applied between the display substrate 20 and the back substrate 22. Thus, all of the cyan particle group 34C and the red particle group 34R are positioned on the back substrate 22 side, and are displayed in white (W) display (see FIG. 3A).

Next, when the voltage + Vdc is applied in the state of FIG. 3A, all of the cyan particle group 34C and the red particle group 34R move to the display substrate 20 side and display black (K) (FIG. 3). (See (B)).
When the voltage + Vtc is applied in the state of FIG. 3A, the red particle group 34R moves to the display substrate 20 side, but the cyan particle group 34C remains as it is and displays red (R) (FIG. 3 ( C)).
When the voltage exceeds + Vtc and less than + Vdc, a part of the cyan particle group 34C moves, so that a halftone is obtained.

Next, when the voltage −Vdc is applied in the state of FIG. 3B, the cyan particle group 34C and the red particle group 34R move to the back substrate 22 side, and as a result, white (W) display is obtained (FIG. 3). 3 (D)).
When the voltage −Vdr is applied in the state of FIG. 3B, the cyan particle group 34C remains on the display substrate 20 side, and the red particle group 34R moves to the back substrate 22 side, resulting in cyan ( C) is displayed (see FIG. 3E).
On the other hand, when the voltage −Vdr is applied in the state of FIG. 3C, the cyan particle group 34C remains on the back substrate 22 side, and the red particle group 34R moves to the back substrate 22 side, resulting in white (W) is displayed (see FIG. 3F).
When the voltage exceeds -Vtr and is less than -Vdr, a part of the red particle group 34R moves, so that a halftone is obtained.

  As described above, in the driving method according to the present embodiment, each particle is selectively moved by applying a voltage corresponding to the particle group in order from each colored particle group 34 having a high movement start voltage. Thus, the intended color display is realized.

  In the display medium 12 and the display device 10 according to the present embodiment, the display electrode 40 is provided on the display substrate 20, the back electrode 46 is provided on the back substrate 22, and a voltage is applied between the electrodes (that is, between the substrates). Although the embodiment has been described in which the particle group 34 is moved and displayed between the substrates, the present invention is not limited to this. For example, the display electrode 40 is provided on the display substrate 20, while the electrode is provided on the gap member, The particle group 34 may be moved between the display substrate 20 and the gap member and displayed.

In addition, in the display medium 12 and the display device 10 according to the above-described embodiment, the mode in which two types (two colors) of particle groups are applied as the colored particle group 34 has been described. There may be a form in which three or more types (three colors) of particle groups are applied with different combinations of threshold voltages (voltages at which the migrating particles start migrating) having the same charging polarity.
Specifically, for example, as the particle group 34, a positively chargeable first particle group, a negatively chargeable second particle group, and a positively chargeable particle having a threshold voltage different from those of the first particle group, The form which applied the 3rd particle group with a big diameter is mentioned.

<Electronic devices equipped with a display device>
The display device according to the present embodiment is, for example, an electronic device, an exhibition medium, a card medium, etc. that can store and rewrite images (specifically, for example, an electronic bulletin board, an electronic circulation version, an electronic blackboard, an electronic advertisement, Electronic signs, flashing signs, electronic paper, electronic newspapers, electronic books, electronic document sheets shared with copiers and printers, portable computers, tablet computers, mobile phones, smart cards, signature equipment, watches, shelf labels, flash drives, etc.) Prepared for.

  Hereinafter, the present invention will be described more specifically with reference to examples. In the following, “part” is based on mass unless otherwise specified.

<Example 1>
(Preparation of red particles A)
40.0 parts of methyl methacrylate, 2.0 parts of 2- (diethylamino) ethyl methacrylate as a polymerizable compound having a basic functional group, red pigment as a colorant [Pigment Red 254 (PR254) manufactured by Dainippon Seika Kogyo Co., Ltd.] 4.5 parts were mixed, and ball milling was performed for 2 hours using zirconia balls having a diameter of 10 mm to prepare a dispersion A-1.
Next, 40 parts of calcium carbonate and 60 parts of water were mixed and pulverized in the same manner as above to prepare a calcium carbonate dispersion A-2. Next, 6.0 parts of calcium carbonate dispersion A-2 and 90 parts of 20% saline were mixed, and then stirred with an emulsifier to prepare a mixed liquid A-3.

  30 g of dispersion A-1, ethylene glycol dimethacrylate (manufactured by Wako Pure Chemical Industries, Ltd.) 0.9 part, 2,2′-azobis (2-methylpropionic acid) dimethyl (polymerization initiator, Wako Pure Chemical) V-601) manufactured by Kogyo Co., Ltd. was sufficiently mixed with 0.3 part, and deaerated with an ultrasonic machine for 10 minutes. This was added to the mixed solution A-3 and emulsified with an emulsifier for 2 minutes. Next, this emulsified liquid was put into a flask, 160 parts of 20% saline was added, vacuum deaeration was sufficiently performed, and the mixture was sealed with nitrogen gas. Next, it was reacted at 65 ° C. for 3 hours to prepare particles.

Next, after cooling the prepared particles, the particles were filtered, the obtained particle powder was dispersed in ion-exchanged water, calcium carbonate was decomposed with 30 parts of 3.0 mol / L hydrochloric acid, and filtered. Next, the obtained particle powder was dispersed in a hydrochloric acid methanol solution (hydrochloric acid) having an acid concentration of 3.0 mol / L in which hydrochloric acid was added to methanol, neutralized, and then filtered. Thereafter, the particles were washed with sufficient distilled water, passed through a nylon sieve having openings of 15 μm and 5 μm, and the particle sizes were made uniform. As a result of measuring the volume average particle size and CV value of red particles in the aqueous dispersion (Horiba LA-300: Laser Light Scattering / Diffraction Particle Size Measuring Device, manufactured by Horiba Ltd.), the volume average particle size of the red particles is 10 μm. And the CV value was 22%.
The red particles were washed with 210 parts by mass of methanol, filtered, and then heat-dried to produce particles A-1.

  95 parts of Silaplane FM-0711 (linear silicone monomer, manufactured by JNC Corporation), 2 parts of glycidyl methacrylate and 3 parts of methyl methacrylate are mixed with 300 parts of isopropyl alcohol, and azobisisobutyronitrile ( 1 part of a polymerization initiator (AIBN manufactured by Aldrich) was dissolved and polymerized under nitrogen at 70 ° C. for 6 hours. Thereafter, 300 parts of dimethyl silicone oil (KF-96L-2CS, manufactured by Shin-Etsu Chemical Co., Ltd.) was added, and then isopropyl alcohol was removed under reduced pressure to obtain a linear silicone polymer. This linear silicone polymer is referred to as surface treating agent B-1.

Next, the following surface treatment was performed on the particles A-1.
Particle A-1 (2 parts), surface treating agent B-1 (25 parts), and triethylamine (0.01 part) were mixed and stirred at a temperature of 100 ° C. for 1 hour. Thereafter, the solvent was removed by centrifugal sedimentation, followed by drying under reduced pressure to obtain display particles (red particles A) in which a silicone polymer was bonded and adhered to the surface of the particles A-1.

(Preparation of display particle dispersion)
Weigh out so that red particle A is 1.3 g in solid content, add silicone oil KF-96L-2cs (manufactured by Shin-Etsu Chemical Co., Ltd.) so that the amount of liquid is 10 g, and ultrasonically agitate to display particles Dispersion 1 was prepared. The viscosity of “silicone oil KF-96L-2cs (manufactured by Shin-Etsu Chemical Co., Ltd.)” corresponding to the dispersion medium was 2 mPa · s.

<Examples 2-5, Comparative Examples 1-4>
According to Table 1, in the production of red particles A of Example 1, 1) type and number of colorants, and 2) a polymerizable compound having a basic functional group (denoted as “basic group-containing polymerizable compound” in Table 1) ) Type and number of copies, 3) Red particles were produced in the same manner as the red particles of Example 1 except that the type of solution used for the neutralization treatment was changed.
A display particle dispersion was prepared in the same manner as in Example 1 using the obtained red particles.

<Evaluation>
[Various measurements]
Regarding the red particles obtained in each example, 1) basic functional group content (indicated as “basic group content” in Table 1), 2) anion content, 3) swelling of display particles in water The degree of swelling of the display particles in the solvent used in the neutralization treatment with respect to the degree (indicated simply as “swelling degree” in Table 1) was measured according to the method described above. The results are shown in Table 1.

[Production and evaluation of device samples]
After adjusting each of the display particle dispersions obtained in each example so that the solid content of the particles is 10% by mass, between a pair of glass substrates on which indium tin oxide (ITO) electrodes are formed (a pair of glass An element sample having a display area of 1 cm × 1 cm was fabricated by enclosing in a cell having a 50 μm spacer (gap member) interposed between the substrates. The following evaluation was performed using the element sample.

(Ratio of reverse polarity particles)
Using the element sample, the ratio of the reverse polarity particles was determined as follows.
Using an optical microscope with a short focal length, the number of particles moved to the substrate side to which a voltage of +30 V having the same polarity as the charging of the particles was applied was counted in the field of view. This is A. On the other hand, similarly, using an optical microscope having a short focal length, the number of particles moved to the substrate side to which a voltage of −30 V having a polarity opposite to that of charging of the particles was applied was counted in the visual field. Let this be B pieces. And the ratio of reverse polarity particle | grains was computed as A / (A + B).

(Occurrence of aggregated particles)
Using the device sample, the occurrence of aggregated particles was examined as follows.
The device samples were observed and evaluated by counting the number of agglomerates which were aggregates of particles.
The evaluation criteria are as follows.
A: No aggregate B: 1 or more and 2 or less aggregates C: 3 or more and less than 10 aggregates D: 10 or more aggregates

(Continuous drive performance)
Using the element sample, data for each hour of the current flowing through the element sample was measured while applying a triangular wave of plus / minus 30V, 0.1 Hz to 0.5 Hz. When the red particle threshold is exceeded, red particles start to move and current starts to be observed, and when all red particles finish moving, the current associated with particle movement is not observed, so the current data has a peak shape. It becomes. Then, the charge amount (nC / cm ² ) per display unit area of the red particles [denoted as “initial charge amount” in Table 1] was measured by the integrated value of this peak.
Next, using the element sample, the operation of moving the cyan particles between the glass substrate on the display side and the glass substrate on the back side was performed 500 times by changing the polarity of the voltage applied to both electrodes.
Thereafter, the charge amount (nC / cm ² ) per unit display area of the red particles [expressed as “charge amount after continuous driving” in Table 1] was measured for the element sample in the same manner as described above.

(Memory)
An element sample was used, voltage was applied to both electrodes, and red particles were moved to the glass substrate on the display side. After the application of the voltage was stopped, the rate at which the red particles dropped in 10 minutes (the rate at which they were detached from the display-side glass substrate) was measured.

From the above results, it can be seen that in this example, the occurrence of agglomeration is suppressed as well as the generation of particles of opposite polarity as compared with the comparative example.
Further, it can be seen that the present example is excellent in continuous drive characteristics and memory characteristics.

Details of abbreviations and the like in Table 1 are as follows.
PR254: Red pigment [Pigment Red 254 (PR254) manufactured by Dainippon Seika Kogyo Co., Ltd.]
DEAEMA: 2- (diethylamino) ethyl methacrylate

10 display device 12 display medium 16 voltage application unit 18 control unit 20 display substrate 22 back substrate 24 gap members 34, 34C, 34R colored particle group 36 white particle group 38 support substrate 40 display electrode 42 surface layer 44 support substrate 46 back electrode 48 Surface layer 50 Dispersion medium

Claims (9)

  A group comprising a basic functional group in the range of 0.1% by mass to 5% by mass with respect to the total mass of the polymer, and comprising a sulfonate ion, a nitrate ion, a sulfate ion, a phosphate ion, and a halide ion A display particle comprising a polymer containing at least one selected from 20 ppm to 100 ppm.   At least one inorganic acid ion selected from the group consisting of sulfonate ion, nitrate ion, sulfate ion, phosphate ion and halide ion in a solvent having a swelling degree with respect to the swelling degree in water of 1.2 or more The display particles according to claim 1, wherein the display particles are treated with an acid containing an organic acid ion.   The display particle according to claim 1, wherein the halide ion is a chloride ion.   The display particle according to any one of claims 1 to 3, wherein the basic functional group is an amino group. A particle group containing the display particles according to any one of claims 1 to 4,
A dispersion medium for dispersing the particle group;
A particle dispersion for display. A pair of substrates, at least one of which is translucent,
A particle group encapsulated between the pair of substrates and containing the display particles according to any one of claims 1 to 4,
A dispersion medium enclosed between the pair of substrates and for dispersing the particle group;
A display medium. A display medium according to claim 6;
Electric field forming means for forming an electric field between the pair of substrates;
A display device comprising: A pair of electrodes, at least one of which is translucent,
A group of particles encapsulated between the pair of electrodes and including the display particles according to any one of claims 1 to 4,
A dispersion medium enclosed between the pair of electrodes and for dispersing the particle group;
A display medium. A display medium according to claim 8;
Electric field forming means for forming an electric field between the pair of electrodes;
A display device comprising: