JP2009192740A - Particle for image display, particle dispersion for image display, display medium, and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide particles for image display, which are suppressive in the variation with time of charging amount, and to provide a particle dispersion for image display using the particles for image display, a display medium, and a display device. <P>SOLUTION: The particles for image display are characterized in that surfaces of colored particles containing a polymer compound having an amino group and a coloring agent are subjected to a quaternary ammonium production treatment. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

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

  Conventionally, a display technique using electrophoresis has been proposed as a display medium that can be rewritten repeatedly.

As such a display technique, for example, a display medium having a configuration in which a dispersion liquid is sealed between a pair of substrates and a group of charged particles is dispersed in the dispersion liquid is known.
In such a display medium, by applying a voltage according to an image between the substrates, the charged particles are moved to display the image as the color contrast of the particles (for example, Patent Documents 1 to 4). reference).

In addition, in a display technique using electrophoresis, a display device is disclosed in which a charge control agent is added to particles in order to control the chargeability of the particles.
Specifically, for example, Patent Document 5 includes a quaternary ammonium compound for imparting positive charge to charged particles in a display device using a dispersion medium containing charged particles and a surfactant. Are disclosed. In Patent Document 6, in order to improve the zeta potential of charged particles, charged particles contain a pigment, a resin compound, and a charge adjusting agent having a solubility in a solvent of 5% by mass or less. It is disclosed.

Patent Document 7 discloses that in order to improve the zeta potential of the charged particles, the surface of the charged particles forms a salt with either an acidic group or a crown ether compound.
Patent Document 8 discloses a polymer having a glass transition temperature of −80 ° C. to 25 ° C. (for example, having a carboxyl group) in order to develop the dispersibility and chargeability of charged particles without adding a charge adjusting agent. Polymers, polymers having quaternary amino groups, etc.) that are physically adsorbed on the pigment surface are disclosed.

JP 2004-333589 A JP-A-2005-107146 JP 2005-128141 A JP 2003-005228 A Japanese Patent Laid-Open No. 11-119704 JP 2004-279732 A JP-A-2005-352424 JP 2005-259170 A

  It is an object of the present invention to provide image display particles in which a change in charge amount with time is suppressed, an image display particle dispersion using the image display particles, a display medium, and a display device.

  The above problem is solved by the following means. That is,

The invention according to claim 1
A particle for image display, wherein the surface of a colored particle containing a polymer compound having an amino group and a colorant is subjected to a quaternary ammonium treatment.

The invention according to claim 2
A group of particles that move in response to an electric field, and a dispersion medium that disperses the group of particles,
The particle group has a first particle composed of the image display particle according to claim 1, and is an image display particle dispersion.

The invention according to claim 3
3. The particle dispersion for image display according to claim 2, wherein the particle group further includes second particles containing a polymer compound having an acid group salt and a colorant.

The invention according to claim 4
4. The particle dispersion for image display according to claim 3, wherein the salt of the acid group includes at least one selected from a carboxylate, a sulfonate, a phosphate, and a boron-based quaternary salt. It is a liquid.

The invention according to claim 5
5. The image display particle dispersion according to claim 3, wherein the volume average primary particle size of the second particles is a particle size capable of moving through a gap between the image display particles. 6. .

The invention according to claim 6
A pair of substrates, at least one of which is translucent,
The particle dispersion for image display according to any one of claims 2 to 5, which is sealed between the pair of substrates.
A display medium characterized by comprising:

The invention according to claim 7 provides:
A pair of substrates, at least one of which is translucent,
A group of particles enclosed between the pair of substrates,
The particle group includes the image display particle according to claim 1.

The invention according to claim 8 provides:
A pair of electrodes, at least one of which is translucent,
The dispersion liquid for image display according to any one of claims 2 to 5, which is held between the pair of electrodes,
A display medium characterized by comprising:

The invention according to claim 9 is:
A display medium according to claim 6 or 7, and
Voltage applying means for applying a voltage between the pair of substrates of the display medium;
Is a display device.

The invention according to claim 10 is:
A display medium according to claim 8;
Voltage applying means for applying a voltage between the pair of electrodes of the display medium;
Is a display device.

  According to the first aspect of the invention, there is an effect that a change with time of the charge amount of the image display particles is suppressed.

  According to the second aspect of the invention, there is an effect that a change with time of the charge amount of the image display particles is suppressed.

  According to the invention of claim 3, even if the system includes particles having different charge polarities, the effect of suppressing the change in the charge amount of the image display particles with time is exhibited.

  According to the fourth aspect of the present invention, even a system including particles having different charge polarities has an effect that the change in the charge amount of the image display particles over time is suppressed.

  According to the fifth aspect of the invention, by applying to the display medium, the background color is displayed by the first particles, the display by the second particles is performed, and an image in which color mixing is suppressed is displayed. There is an effect.

  According to the invention of claim 6, there is an effect that the change over time in the charge amount of the image display particles is suppressed, and the image display property and the image display response can be obtained stably.

  According to the seventh aspect of the present invention, there is an effect that the change over time in the charge amount of the image display particles is suppressed, and the image display property and the image display response can be obtained stably.

  According to the eighth aspect of the present invention, there is an effect that the change over time in the charge amount of the image display particles is suppressed, and the image display property and the image display response can be obtained stably.

  According to the ninth aspect of the present invention, there is an effect that the change with time of the charge amount of the image display particles is suppressed, and the image display property and the image display response can be stably obtained.

  According to the tenth aspect of the present invention, there is an effect that the change over time in the charge amount of the image display particles is suppressed, and the image display property and the image display response can be stably obtained.

  Hereinafter, embodiments of the present invention will be described.

[Image display particles]
The image display particles of this embodiment are characterized in that the surface of colored particles containing a polymer compound having an amino group and a colorant is subjected to a quaternary ammonium treatment.
When the image display particles of the present embodiment have the above-described configuration, a change with time in the charge amount of the image display particles is suppressed. The reason is not clear, but is estimated as follows, for example.

Examples of the positively charged particles include those obtained by adding a quaternary ammonium compound to the particles as a charge control agent. In such particles, the charge amount of the particles is controlled by controlling the addition amount of the quaternary ammonium compound.
However, in the case of particles to which a charge control agent has been added in this way, it is considered that the charge control agent added with use for a long time may gradually desorb, and the charge amount of the particles may change with time. When the charge amount of particles used in electrophoretic display media changes, the drive voltage (threshold voltage) for displaying images and the migration speed of particles change, and good display characteristics cannot be obtained. There is.

On the other hand, since the image display particles of the present embodiment have the above-described configuration, the amino group contained in the resin exposed on the surface of the colored particles is subjected to quaternary ammonium treatment, and the particles are positively charged in the dispersion. That is, since the surface of the particle itself is charge-controlled, unlike the case where the charge control agent is used as described above, the charge-controlled part is not easily detached from the particle, and the change in the charge amount with time is suppressed. It is guessed.
When the image display particles of the present embodiment are used in an electrophoretic display medium or the like, the change in the charge amount of the particles over time is suppressed, so the drive voltage (threshold voltage) for displaying images and the migration speed of the particles Becomes stable, and display characteristics such as particle responsiveness and image display property are improved.

  Moreover, since the image display particles of the present embodiment have the above-described configuration, the detachment of the pigment (colorant) is also suppressed. Therefore, for example, a more stable image display can be performed as compared with a form in which pigment particles are encapsulated with a polymer compound having a quaternary ammonium group.

<Colored particles>
Hereinafter, the colored particles will be described. The colored particles contain a resin and a colorant, and may contain other components as necessary.

-resin-
The resin contains at least a polymer compound having an amino group.
Examples of the “monomer having an amino group” used in the synthesis of the polymer compound having an amino group include, for example, (meth) acrylates having an aliphatic amino group, aromatic substituted ethylene-based monomers having a nitrogen-containing group Body, nitrogen-containing vinyl ether monomers, nitrogen-containing heterocyclic compounds and the like.

  Specific examples of (meth) acrylates having an aliphatic amino group include N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, and N, N-dibutylamino. Ethyl (meth) acrylate, N, N-hydroxyethylaminoethyl (meth) acrylate, N-ethylaminoethyl (meth) acrylate, N-octyl-N-ethylaminoethyl (meth) acrylate, N, N-dihexylaminoethyl (Meth) acrylate etc. are mentioned.

  Specific examples of the aromatic substituted ethylene monomer having a nitrogen-containing group include dimethylaminostyrene, diethylaminostyrene, dimethylaminomethylstyrene, dioctylaminostyrene and the like.

  Specific examples of the nitrogen-containing vinyl ether monomers include vinyl-N-ethyl-N-phenylaminoethyl ether, vinyl-N-butyl-N-phenylaminoethyl ether, triethanolamine divinyl ether, vinyl Examples thereof include diphenylaminoethyl ether and m-aminophenyl vinyl ether.

  Specific examples of the nitrogen-containing heterocyclic compounds include pyrroles such as N-vinylpyrrole, pyrrolines such as N-vinyl-2-pyrroline and N-vinyl-3-pyrroline, and N-vinylpyrrolidine. Pyrrolidines such as vinylpyrrolidine amino ether, N-vinyl-2-pyrrolidone, imidazoles such as N-vinyl-2-methylimidazole, imidazolines such as N-vinylimidazoline, indoles such as N-vinylindole, N -Indolines such as vinylindoline, carbazoles such as N-vinylcarbazole, 3,6-dibromo-N-vinylcarbazole, pyridines such as 2-vinylpyridine, 4-vinylpyridine, 2-methyl-5-vinylpyrazine, (Meth) acrylic piperidine, N-vinyl piperidone, N-vinyl piperazine, etc. Peridines, quinolines such as 2-vinylquinoline and 4-vinylquinoline, pyrazoles such as N-vinylpyrazole and N-vinylpyrazoline, oxazoles such as 2-vinyloxazole, 4-vinyloxazine, morpholinoethyl (meth) acrylate Etc.

  Among the monomers having an amino group, (meth) acrylates having an aliphatic amino group are preferable. Further, among these, specifically, N, N-dimethylaminoethyl (meth) acrylate and N, N-diethylaminoethyl (meth) acrylate are preferable, and N, N-diethylaminoethyl (meth) acrylate is more preferable.

  The polymer compound having an amino group may be one using one or more of the above “monomers having an amino group”, and “others” in addition to the “monomer having an amino group”. It is also possible to use a copolymer using both of the “monomers”.

  As other monomers, specifically, for example, methyl acrylate, ethyl acrylate, n-butyl acrylate, iso-butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, tetrahydrofurfuryl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, lauryl methacrylate, mel vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, iso-butyl vinyl ether, n-butyl vinyl ether, styrene, α-methyl styrene, acrylonitrile , Methacrylonitrile, vinyl acetate, vinyl chloride, vinylidene chloride, vinyl fluoride, vinyl Fluoride, ethylene, propylene, isoprene, chloroprene, butadiene, and the like.

  When the polymer compound having an amino group is a copolymer of “a monomer having an amino group” and “another monomer”, the “monomer having an amino group” with respect to the whole monomer Is preferably 0.01 mol% or more and 100 mol% or less, more preferably 0.5 mol% or more and 80 mol% or less, and further preferably 1 mol% or more and 50 mol% or less.

The resin may contain another polymer compound in addition to the polymer compound having an amino group.
Specific examples of the other polymer compounds include polymer compounds obtained by polymerizing the above-mentioned other monomers alone or in combination.

―Colorant―
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 given. 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 48: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 57: 1, C.I. I. Pigment yellow 97, C.I. Blue 15: 1, C.I. I. Pigment Blue 15: 3, etc. can be exemplified as typical ones.

―Other ingredients―
(Charge control agent)
The colored particles may contain a charge control agent as necessary.
Examples of the charge control agent include known ones used for toner materials for electrophotography. Specifically, for example, cetylpyridyl chloride, BONTRON P-51, BONTRON P-53, BONTRON E-84, BONTRON E -81 (above, manufactured by Orient Chemical Industry Co., Ltd.), quaternary ammonium salts, salicylic acid metal complexes, phenol condensates, tetraphenyl compounds, metal oxide particles, metal oxide particles surface-treated with various coupling agents Etc.

(Magnetic material)
The inside and the surface of the colored particles may contain a magnetic material as 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 can 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 appropriately selected, for example, coloring the magnetic powder opaque with a pigment or the like, but it is preferable to use a light interference thin film, for example. 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 selectively reflects the wavelength of light by optical interference in the thin film. It is.

<Method for producing colored particles>
As a method for preparing the colored particles, any conventionally known particle production method may be used.
For example, as described in JP-A-7-325434, after weighing a resin, a colorant, and the like to a predetermined mixing ratio, heating and melting the resin, adding a pigment, mixing, dispersing, and cooling A method of preparing particles using a pulverizer such as a jet mill, a hammer mill, or a turbo mill can be used.
Further, the particles may be prepared by a polymerization method such as suspension polymerization, emulsion polymerization or dispersion polymerization, coacervation, melt dispersion, or emulsion aggregation.

  Furthermore, when the resin can be plasticized, the resin and the colorant are heated and melted in a dispersion medium using, for example, a meteor mixer, a kneader, etc., and the temperature dependence of the solvent solubility of the resin is used to form a molten mixture. A method of producing particles by cooling with stirring and solidifying / precipitating can be used. In this case, it is desirable that the heating and melting temperature is a temperature at which the dispersion medium does not boil and is lower than the decomposition point of either the resin or the colorant.

The above raw materials are put into a suitable container equipped with granular media for dispersion and kneading, for example, a heated vibration mill such as an attritor or a heated ball mill, and the container is placed in a preferred temperature range, for example, 80 A method of dispersing and kneading at a temperature of from 0 ° C. to 160 ° C. can be used.
As granular media, steels such as stainless steel and carbon steel, alumina, zirconia, silica and the like are preferably used.

  In order to produce particles by this method, a raw material that has been sufficiently fluidized is dispersed in a container with granular media, and then the dispersion medium is cooled to precipitate a resin containing a colorant from the dispersion medium. The granular media generates a shear and / or impact to reduce the particle size while maintaining the motion state during and after cooling.

  The dispersion medium used for producing the colored particles is not particularly limited as long as it is a liquid in which a resin and a colorant are dispersed.

<Quaternary ammonium treatment of colored particles>
The quaternary ammonium treatment of the colored particles is performed as follows.
Specifically, for example, a method in which the colored particles obtained as described above are dispersed in a dispersion medium, a quaternizing agent is added, and the like is heated.

  Specific examples of the quaternizing agent include halides such as methyl chloride, methyl bromide, methyl iodide, ethyl bromide, propyl bromide, butyl bromide, dodecyl bromide, benzyl bromide; And alkyl sulfates such as sulfuric acid and diethylsulfuric acid; alkyl p-toluenesulfonates such as methyl p-toluenesulfonate and ethyl p-toluenesulfonate; and the like. Among these, butyl bromide and dodecyl bromide are more preferable.

  The dispersion medium used for the quaternary ammonium conversion treatment of the colored particles is not particularly limited as long as it is a liquid that disperses the colored particles, and examples thereof include a dispersion medium used for an image display particle dispersion described later.

Specifically, the addition amount of the quaternizing agent is preferably, for example, a ratio of 0.1 mol or more and 5 mol or less with respect to 1 mol of the amino group contained in the resin.
Specifically, the heating temperature in the quaternary ammonium treatment is preferably, for example, 30 ° C. or higher and 120 ° C. or lower.
Furthermore, specifically, the heating time in the quaternary ammonium treatment is preferably, for example, 1 hour or more and 10 hours or less.

<Other processing>
The image display particles may be obtained by further externally adding the surface of particles prepared by subjecting colored particles to quaternary ammonium conversion, if necessary.
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, and environment dependency of the particles, they can be surface-treated with a coupling agent or silicone oil.
The color of the external additive is preferably transparent so as not to affect the color of the particles.

  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). Coupling agents, titanium-based coupling agents, epoxy silane coupling agents, acrylic silane coupling agents, etc., silicone oils include amino-modified silicone oil, dimethyl silicone oil, alkyl-modified silicone oil, α-methylsulfone-modified silicone oil, Examples thereof include methylphenyl silicone oil, chlorophenyl silicone oil, and fluorine-modified silicone oil. These are selected according to the desired resistance of the external additive.

Among such external additives, well-known hydrophobic silica and hydrophobic titanium oxide are preferable, and in particular, TiO (OH) ₂ described in JP-A-10-3177 and a silane compound such as a silane coupling agent. The titanium compound obtained by the reaction with is suitable.
As the silane compound, any of chlorosilane, alkoxysilane, silazane, and a special silylating agent can be used.

This titanium compound is produced by reacting TiO (OH) ₂ produced in a wet process with a silane compound or silicone oil and drying. Since it does not pass through the firing step of several hundred degrees, a strong bond between Ti is not formed, there is no aggregation, and the particles are almost primary particles. Furthermore, since the silane compound or silicone oil reacts directly with TiO (OH) ₂ , the amount of silane compound or silicone oil treated can be increased, and the charging characteristics can be controlled by adjusting the amount of silane compound treated. The charging ability that can be imparted and can be imparted can be significantly improved over that of conventional titanium oxide.

The volume average primary particle size of the external additive is preferably 5 nm or more and 100 nm or less, and more preferably 10 nm or more and 50 nm or less, but is not limited thereto.
The addition amount of the external additive is appropriately adjusted based on the balance between the particle size of the image display particles before the external addition and the particle size of the external additive. If the amount of the external additive added is too large, a part of the external additive is liberated from the surface of the particles, and this may adhere to the surface of other particles and the desired charging characteristics may not be obtained. In general, the addition amount of the external additive is preferably 0.01 parts by mass or more and 3 parts by mass or less, more preferably 0.05 parts by mass or more, with respect to 100 parts by mass of the image display particles before external addition. 1 part by mass or less.

  As a method of adding the external additive to the particle surface, a method of driving the external additive into the particle surface with impact force, a method of heating the particle surface and firmly fixing the external additive to the particle surface, or the like is desirable. By using these methods, it is possible to prevent the external additive from being released from the particles, and the external additive of different polarity to strongly aggregate and form an aggregate of the external additive that is difficult to dissociate in an electric field. As a result, image quality deterioration is prevented.

<Physical properties of particles for image display>
The volume average primary particle size of the image display particles is preferably 0.05 μm or more and 50 μm or less, and more preferably 0.1 or more and 30 μm or less.

The charge amount of the image display particles is desirably 1 × 10 ⁻⁷ (1E-7) C / m ² or more and 1 × 10 ⁻⁴ (1E-4) C / m ² or less per unit area of the particle surface. The charge amount of the image display particles depends on the kind and addition amount of the monomer having an amino group used for adjusting the colored particles, the kind and addition amount of the quaternizing agent used for the quaternary ammonium treatment of the colored particles, and the like. Can be controlled.

  The glass transition temperature of the resin contained in the image display particles is preferably 25 ° C. or higher, more preferably 40 ° C. or higher, from the viewpoint that the image display property and the image display responsiveness do not change even when the environmental temperature changes. More preferably, it is not lower than ° C.

  The glass transition temperature was determined by measuring using a differential scanning calorimeter (manufactured by Shimadzu Corporation: DSC-50) under conditions of a heating rate of 3 ° C./min. The glass transition temperature is the temperature at the intersection of the extension line of the base line and the rising line in the endothermic part.

[Particle dispersion for image display]
The particle dispersion for image display according to the present embodiment includes a particle group that moves according to an electric field and a dispersion medium that disperses the particle group, and may include other components as necessary.

<Particle group>
The particle group has the image display particles (first particles) of the above embodiment. You may further contain particles other than the 1st particle as needed. The particles other than the first particles are preferably second particles containing a polymer having a salt of an acid group and a pigment, and other particles (first particles and second particles). Particles other than particles) may be included.
Hereinafter, the second particles will be described.

-Second particle-
The second particles include a resin and a colorant, and may include other components as necessary. The resin includes at least a polymer compound having an acid group salt.
When the second particle has the above-described configuration, it is charged to the negative pole opposite to that of the first particle. Therefore, the direction in which the particles move due to the electric field is reversed between the first particles and the second particles. Therefore, when the particle dispersion for image display is applied to the display medium, the background color is displayed by one of the particles. At the same time, display by the other particle is performed, and an image in which color mixing is suppressed is displayed.

  Specific examples of the “acid group salt” include carboxylate, sulfonate, phosphate, and boron-based quaternary salt. Examples of the salt structure include a salt with a metal alkali and a salt with an amine.

  As the “monomer having an acid group salt” used for the synthesis of a polymer compound having an acid group salt, for example, a “monomer having an acid group” which is made into a salt with an alkali metal or the like can be used. Can be mentioned. Specific examples of the “monomer having an acid group” include a carboxylic acid monomer, a sulfonic acid monomer, a phosphoric acid monomer, and a boron monomer.

  Specific examples of the carboxylic acid monomer include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, and citraconic acid.

  Specific examples of the sulfonic acid monomer include styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 3-sulfopropyl (meth) click acid ester, and bis- (3-sulfopropyl). -Itaconic acid ester etc. are mentioned.

  Specific examples of the phosphoric acid monomer include vinylphosphonic acid, vinyl phosphate, acid phosphooxyethyl (meth) acrylate, acid phosphoxypropyl (meth) acrylate, bis (methacryloxyethyl) phosphate, and diphenyl- 2-methacryloyloxyethyl phosphate, diphenyl-2-acryloyloxyethyl phosphate, dibutyl-2-methacryloyloxyethyl phosphate, dibutyl-2-acryloyloxyethyl phosphate, dioctyl-2- (meth) acryloyloxyethyl phosphate Etc.

  Specifically, as the boron-based monomer, tetraphenylboron having a polymerizable substituent such as vinyl group or (meth) acrylate group on any phenyl group, amines and salt compounds are preferable. In particular, tetraphenylborons, amines and salt compounds having an electron withdrawing group such as a fluorine-substituted alkyl group such as a trifluoromethyl group on the phenyl group are preferred. Further, as a tetraphenylboron salt, a salt with a quaternary ammonium compound is desirable from the viewpoint of a high charge amount and charge stability.

The “polymer compound having an acid group salt” may be one using one or more of the “monomer having an acid group salt” or the above “having the above acid group salt”. A copolymer using “other monomers” in addition to “monomer” may be used.
As the “other monomer”, specifically, for example, the same “other monomer” used for the synthesis of the “polymer compound having an amino group” described above can be used.
The “polymer having an acid group salt” is synthesized by polymerizing the above “monomer having an acid group” (and “other monomers” if necessary) and then subjecting it to a salt treatment. You can also

  When the polymer compound having an acid group salt is a copolymer of a “monomer having an acid group salt” and an “other monomer”, the “acid group salt” for the entire monomer The ratio of the “monomer having” is preferably 0.1 mol% or more and 100 mol% or less, more preferably 0.5 mol% or more and 80 mol% or less, and further preferably 1 mol% or more and 50 mol% or less.

The resin contained in the second particles may contain other polymer compound in addition to the polymer compound having an acid group salt.
Specific examples of the other polymer compound include “other polymer compounds” used for the resin contained in the image display particles of the above embodiment.

As the colorant contained in the second particles, the same colorants as those contained in the image display particles of the above embodiment can be used.
The second particles may contain a charge control agent, a magnetic material, and the like as other components, similarly to the image display particles of the above embodiment.

As a manufacturing method of the second particle, the same manufacturing method as the manufacturing method of the colored particle of the above embodiment can be used.
Further, the second particles may be subjected to an external addition process, similarly to the image display particles of the above embodiment.

The volume average primary particle size of the second particles is preferably 20 nm or more and 10 μm or less.
The volume average primary particle size of the second particles is desirably a particle size that can move through the gaps of the first particles. Specifically, the volume average primary particle size of the second particles is preferably 1/10 or less, more preferably 1/20 or less, of the volume average primary particle size of the first particles. As a result, when the image display particle dispersion is applied to the display medium, the second particles can move well in the gaps between the first particles without clogging, and the image display response is excellent. In addition, since the background color is displayed by the first particles having a large particle diameter and the display is performed by the second particles having a small particle diameter, an image in which color mixing is suppressed is displayed.

<Dispersion medium>
The dispersion medium is not particularly limited as long as it disperses the particle group, but is preferably a high resistance liquid. Here, “high resistance” indicates that the volume resistivity is 10 ⁷ Ω · cm or more, preferably 10 ¹⁰ Ω · cm or more, more preferably 10 ¹² Ω · cm or more.

  Specific examples of high-resistance liquids include hexane, cyclohexane, toluene, xylene, decane, hexadecane, kerosene, paraffin, isoparaffin, silicone oil, dichloroethylene, trichloroethylene, perchloroethylene, high-purity petroleum, benzine, diisopropylnaphthalene, and olive oil. , Trichlorotrifluoroethane, tetrachloroethane, dibromotetrafluoroethane, and the like, and mixtures thereof can be suitably used.

  In addition, to the high-resistance liquid, an acid, an alkali, a salt, a dispersion stabilizer, a stabilizer, an antibacterial agent, a preservative, and the like can be added for the purpose of preventing oxidation or absorbing ultraviolet rays. It is preferable to add so that it may become the range of the specific volume resistance value shown by.

  For high resistance liquids, anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, fluorosurfactants, silicone surfactants, metal soaps as charge control agents , Alkyl phosphate esters, succinimides and the like can be added.

  More specific examples of the ionic and nonionic surfactants are as follows. Nonionic activators include polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, And fatty acid alkylolamide. Examples of the anionic surfactant include alkylbenzene sulfonate, alkylphenyl sulfonate, alkyl naphthalene sulfonate, higher fatty acid salt, sulfate of higher fatty acid ester, sulfonic acid of higher fatty acid ester, and the like. Examples of the cationic surfactant include primary to tertiary amine salts and quaternary ammonium salts. These charge control agents are preferably 0.01% by mass or more and 20% by mass or less, and particularly preferably 0.05 to 10% by mass with respect to the solid content of the particles. If it is less than 0.01% by mass, the desired charge control effect is insufficient, and if it exceeds 20% by mass, an excessive increase in conductivity of the dispersion is caused.

  As the dispersion medium, among the high resistance liquids, those containing at least one of silicone oil and paraffinic hydrocarbon solvent are preferable.

    Specific examples of the silicone oil include dimethyl silicone oil, diethyl silicone oil, methyl ethyl silicone oil, methyl phenyl silicone oil, diphenyl silicone oil, fluorine-modified silicone oil, and epoxy-modified silicone oil in which a hydrocarbon group is bonded to a siloxane bond. And alcohol-modified silicone oil. Among these, dimethyl silicone is particularly desirable from the viewpoints of high safety, chemical stability, long-term reliability, and high resistivity.

  The viscosity of the silicone oil is desirably 0.1 mPa · s or more and 20 mPa · s or less, and more desirably 0.1 mPa · s or more and 2 mPa · s or less in an environment at a temperature of 20 ° C. By setting the viscosity within the above range, the moving speed of particles, that is, the display speed can be improved. In addition, Tokyo Keiki B-8L type | mold viscosity meter is used for the measurement of this viscosity.

  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). For reasons of safety and volatility, use isoparaffins. Is preferred. Specifically, Shell Sol 71 (manufactured by Shell Petroleum), Isopar O, Isopar H, Isopar K, Isopar L, Isopar G, Isopar M (Isopar is a trade name of Exxon), IP Solvent (manufactured by Idemitsu Petrochemical), etc. Can be mentioned.

<Other ingredients>
In addition, an acid, alkali, salt, a dispersion stabilizer, a stabilizer for the purpose of preventing oxidation or ultraviolet absorption, an antibacterial agent, an antiseptic, and the like may be added to the image display particle dispersion as necessary. However, it is preferable to add so that it may become the range of the specific volume resistance value shown above.
In the particle dispersion, an anionic surfactant, a cationic surfactant, an amphoteric surfactant, a nonionic surfactant, a fluorosurfactant, a silicone surfactant, a metal soap as a charge control agent , Alkyl phosphate esters, succinimides and the like can be added.
It has ionic and nonionic surfactants, block or graft copolymers consisting of lipophilic and hydrophilic parts, and also has a polymer chain skeleton such as cyclic, star-like, and dendritic polymers (dendrimers). Further, compounds selected from metal complexes of salicylic acid, metal complexes of catechol, metal-containing bisazo dyes, tetraphenylborate derivatives and the like can be used.

  More specific examples of the ionic and nonionic surfactants are as follows. Nonionic activators include polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, And fatty acid alkylolamide. Examples of the anionic surfactant include alkylbenzene sulfonate, alkylphenyl sulfonate, alkyl naphthalene sulfonate, higher fatty acid salt, sulfate of higher fatty acid ester, sulfonic acid of higher fatty acid ester, and the like. Examples of the cationic surfactant include primary to tertiary amine salts and quaternary ammonium salts. These charge control agents are preferably 0.01% by mass or more and 20% by mass or less, particularly preferably 0.05% by mass or more and 10% by mass or less, based on the solid content of the particles. This is because if it is less than 0.01% by mass, the desired charge control effect is insufficient, and if it exceeds 20% by mass, the conductivity of the particle dispersion is excessively increased, making it difficult to use.

[Display medium, display device]
<First Embodiment>
The particle dispersion for image formation according to the above-described embodiment is used as a particle dispersion of particle groups in an electrophoretic display medium. Since this particle dispersion suppresses the change in the charging characteristics of the dispersed particles, it can be applied particularly to each field using a dispersion for dispersing charged particles. Hereinafter, a display medium and a display device using the image forming particle dispersion of the present embodiment will be described.

  The display medium according to the present embodiment includes a pair of substrates, at least one of which has translucency, and the particle dispersion for image display according to the above-described embodiment sealed between the pair of substrates. To do.

The display device according to the present embodiment includes the display medium according to the present embodiment and voltage applying means for applying a voltage between the substrates of the display medium.
Hereinafter, description will be given based on the drawings.

  FIG. 1 is a schematic configuration diagram illustrating an image display apparatus according to the first embodiment. FIG. 1 is a diagram showing an example of red display.

  As shown in FIG. 1, the image display device 10 (display device) according to the first embodiment moves the colored particles 32 (first colored particles 32A, second colored particles 32B, and third colored particles 32C) described later. And an image display medium 12 (display medium) for displaying an image and a control unit 42 for controlling driving of the voltage application unit 40.

  The image display medium 12 includes a translucent display substrate 18 serving as an image display surface, and a back substrate 28 disposed opposite to the display substrate 18 with a predetermined interval. It should be noted that a gap member that partitions the substrate between the display substrate 18 and the back substrate 28 into a plurality of cells may be included. In this case, the cell refers to a region surrounded by the display substrate 18, the back substrate 28, and the gap member. Further, the gap member may be provided so as to correspond to each pixel when an image is displayed on the image display medium 12, or may be provided so as to include a plurality of pixels, or a plurality of pixels within one pixel. You may make it provide so that it may divide | segment into a cell. In addition to the above, the cell can be formed by holding a capsule in which a dispersion medium is enclosed in a substrate. In this case, the substrate need not be a pair but may be one.

  Between the display substrate 18 and the back substrate 28, a dispersion liquid 24 (particle dispersion liquid for image formation) containing a light-transmitting dispersion medium is sealed, and colored particles 32 (particles) contained in the dispersion liquid 24 are enclosed. The group) is composed of three types of colored particles 32 (first colored particles 32A, second colored particles 32B, and third colored particles 32C). Each colored particle 32 moves according to the electric field strength formed between the substrates. The translucency means that the visible light transmittance is 70% or more, preferably 90% or more.

  The display substrate 18 has a configuration in which the surface electrode 16 and the surface layer 17 are sequentially stacked on the support substrate 14, and the back substrate 28 has a configuration in which the back electrode 22 and the surface layer 20 are sequentially stacked on the support substrate 26. It has become. In the present embodiment, the surface layer 17 and the surface layer 20 are used. However, only one of the surface layer 17 and the surface layer 20 may be used, or neither of them may be used.

  Examples of the support substrates 14 and 26 include glass and plastics such as polycarbonate resin, acrylic resin, polyimide resin, polyester resin, epoxy resin, and polyethersulfone resin.

  The surface electrode 16 and the back electrode 22 are made of oxides such as indium, tin, cadmium and antimony, composite oxides such as ITO, metals such as gold, silver, copper and nickel, organic materials such as polypyrrole and polythiophene, etc. can do. These can be formed by a single layer film, a composite film, or a composite film and a vapor deposition method, a sputtering method, a coating method, or the like. The thickness is usually 100 to 2000 angstroms according to the vapor deposition method and the sputtering method. The front electrode 16 and the back electrode 22 can be formed in a desired pattern by a conventionally known means such as etching of a conventional liquid crystal display element or a printed circuit board. For example, any segment shape or passive matrix drive is possible. Can be formed in a stripe shape or the like.

  The front electrode 16 may be embedded in the support substrate 14, and similarly, the back electrode 22 may be embedded in the support substrate 26. In this case, since the material of the support substrates 14 and 26 may affect the electrical characteristics, magnetic characteristics, and fluidity of the colored particles 32, it is necessary to select them according to the composition of each particle.

  Further, each of the front electrode 16 and the rear electrode 22 may be separated from the display substrate 18 and the rear substrate 28 and disposed outside the image display medium 12. In the present embodiment, a case will be described in which electrodes (surface electrode 16 and back electrode 22) are provided on both the display substrate 18 and the back substrate 28, but they may be provided on only one of them.

  In order to enable active matrix driving, the support substrates 14 and 26 may be provided with TFTs (thin film transistors) for each pixel. In this case, it is preferable to form the TFT on the back substrate 28 instead of the display substrate 18 because wiring can be easily laminated and components can be easily mounted.

  If the image display medium 12 is driven in a simple matrix, the configuration of the image display device 10 can be simplified. If the active matrix drive using TFTs is used, the display speed is increased as compared with the simple matrix drive. Can do.

  Further, when the surface electrode 16 and the back electrode 22 are respectively formed on the support substrates 14 and 26, the surface electrode 16 and the back electrode 22 are damaged, or leakage between the electrodes that causes the colored particles 32 to be fixed occurs. In order to prevent this, it is preferable to form a surface layer as a dielectric film on the surface electrode 16 and the back electrode 22 as necessary. As a material for forming this surface layer, polycarbonate, polyester, polystyrene, polyimide, epoxy, polyisocyanate, polyamide, polyvinyl alcohol, polybutadiene, polymethyl methacrylate, copolymer nylon, ultraviolet curable acrylic resin, fluorine resin, etc. are applied. Can do.

  As a material constituting the dielectric film, in addition to the above-mentioned materials, a material containing a charge transport substance in this material can be used. Examples of the charge transport material include a hydrazone compound, a stilbene compound, a pyrazoline compound, and an arylamine compound that are hole transport materials. Further, a fluorenone compound, a diphenoquinone derivative, a pyran compound, zinc oxide, or the like, which is an electron transport material, can also be used. Furthermore, a self-supporting resin having a charge transporting property can also be used. Specific examples thereof include polyvinyl carbazole and polycarbonate obtained by polymerization of a specific dihydroxyarylamine and bischloroformate described in US Pat. No. 4,806,443. Further, the surface layer as the dielectric film may affect the charging characteristics and fluidity of each colored particle 32, and therefore needs to be selected according to the composition of each colored particle 32.

  Further, since the display substrate 18 constituting the image display medium 12 needs to have a light-transmitting property as described above, a material having a light-transmitting property among the above materials is used.

  When the gap member is provided, it can be formed of a thermoplastic resin, a thermosetting resin, an electron beam curable resin, a photocurable resin, rubber, metal, or the like. The gap member may be integrated with either the display substrate 18 or the back substrate 28. In this case, it can be manufactured by an etching process for etching either one of the support substrates 14 and 26, a laser processing process, a press processing process using a previously manufactured mold, or the like. Alternatively, it can be manufactured by using a printing method, an inkjet method, or the like. The gap member can be produced on at least one of the display substrate 18 side or the back substrate 28 side. The gap member may be colored or colorless, but is preferably achromatic or colorless and transparent so as not to adversely affect the display image displayed on the image display medium 12, and in that case, for example, polystyrene Transparent resins such as polyester and acrylic can be used.

As described above, the colored particles 32 include the first colored particles 32A, the second colored particles 32B, and the third colored particles 32C. In the present embodiment, the second colored particles 32B correspond to the first particles (image display particles) in the above embodiment, and the third colored particles 32C correspond to the second particles in the above embodiment. The third colored particles 32C have a volume average primary particle size that can move through the gap between the first colored particles 32A and the second colored particles 32B.
In the present embodiment, three types of particles have the above-described configuration. However, the present invention is not limited to this configuration as long as the first particles (image display particles) in the above-described embodiment are included. Specifically, for example, the first colored particles 32A may be the second particles in the above embodiment, or the particles may be one type (only the second colored particles 32B) or four or more types.

  The first colored particles 32 </ b> A and the second colored particles 32 </ b> B may have a filling amount such that one layer is arranged between the display substrate 18 and the back substrate 28. It is preferable because of its property. In this case, when the size of the first colored particles 32A and the second colored particles 32B is increased, the distance between the substrates is increased, the display drive voltage is increased, and the display switching speed is decreased. The size of the second colored particles 32B is preferably 50 μm or less, and more preferably 30 μm or less.

  The first colored particles 32A and the second colored particles 32B of the present embodiment are moved to different substrate sides when an electric field is applied by applying a predetermined specific level of voltage between the substrates for a predetermined time. In this embodiment, the first colored particles 32A are negatively charged and the second colored particles 32B are positively charged. Even if the first colored particles 32A are not charged, the colored particles of the first colored particles 32A can be moved to the opposite substrate side by the movement of the second colored particles 32B. There can be various forms.

  The first colored particles 32A and the second colored particles 32B have a volume filling rate of 10% to 60% when the space in the cell is set to 100% in order to secure the movement between the substrates and the display density. Preferably, it is 30 to 50%. When the first colored particles 32A and the second colored particles 32B are in an aggregated state (a state in which an electric field is applied between the substrates and moved in the direction of each substrate), the third colored particles 32C are described above. As described above, it is possible to pass between the first colored particles 32A and the second colored particles 32B.

  The colored particles 32 are colored in different colors. In the present embodiment, the first colored particles 32A are colored white, the second colored particles 32B are colored black, and the third colored particles 32C are It is colored red.

  On the other hand, the surface electrode 16 and the back electrode 22 are respectively connected to the voltage application unit 40, and an electric field is formed between the substrates by applying a voltage to the surface electrode 16 and the back electrode 22 by the voltage application unit 40. .

  The voltage application unit 40 is connected to the control unit 42. The control unit 42 includes, for example, a CPU, a ROM, a RAM, a hard disk, and the like, and the CPU loads the image display medium 12 according to a program stored in an image recording unit (not shown) such as a ROM or a hard disk. The thing controlled so that an image display may be performed is mentioned. Specifically, for example, the control unit 42 controls the voltage application unit 40 according to the display image stored in the image storage unit to apply a voltage between the substrates (between the display substrate 18 and the back substrate 28). By doing so, each colored particle 32 moves according to the voltage, and an image is displayed.

  Each colored particle 32 maintains its state when a voltage is applied, even after the application of the voltage between the substrates is stopped, by an adhesive force such as van der Waals force or mirror image force.

  FIG. 2 is a diagram for explaining an applied voltage necessary for moving each colored particle 32 in the image display apparatus according to the first embodiment of the present invention.

  In the present embodiment, the charging characteristics of the respective colored particles 32 are different, and the voltage range necessary for displaying the color of each colored particle 32 by moving each colored particle 32 to the desired substrate side is shown in FIG. As shown. FIG. 2 shows the display density characteristics of the colored particles 32 when the back electrode 22 is ground (0 V) and a desired pulse voltage is applied to the surface electrode 16. The display density is applied by applying a pulse voltage between the display surface side and the back surface side, and gradually changing the pulse voltage stepwise (increasing or decreasing the applied voltage). The optical density (Optical Density = 0D) was measured with a reflection densitometer (X-Rite404) manufactured by X-rite. For white, in FIG. 2, the case where white particles are moving toward the display substrate is shown as having a high concentration.

  In the present embodiment, the adhesion between the colored particles 32 and the surface layer 17 of the display substrate 18, and between the colored particles 32, depending on the difference between the charge amount and the particle size (volume average primary particle size) of the colored particles 32. A difference was provided in the adhesion force, and a difference was provided in the movement start voltage of the first colored particles 32A and the second colored particles 32B and the third colored particles 32C.

  The display density characteristic of each colored particle 32 may be controlled by the difference in adhesion as described above, or may be controlled by the difference in mobility of each colored particle 32. However, since at least the white particles of the first colored particles 32A and the second colored particles 32B are not transparent, the third colored particles 32C do not contribute to the display density unless they move to the display substrate side than the white particles. When the mobility of the three colored particles 32C is small, it moves only slightly when a low voltage pulse voltage is applied, so it does not contribute to the display density at all. When a certain voltage is exceeded, the white particles move to the display substrate side and display It contributes to the density and has the display characteristics as shown in FIG. Similarly, the first colored particles 32A and the second colored particles 32B do not contribute to the display density until the black particles move to the display substrate side rather than the white particles, so that the display characteristics as shown in FIG. 2 are obtained. .

  In the present embodiment, the first colored particles 32A are negatively charged, the second colored particles 32B are positively charged, the third colored particles 32C are negatively charged, and the first colored particles 32A and the second colored particles are charged. The voltage range required to display the color of each colored particle by moving 32B is | V2 ≦ V ≦ V1 | (absolute value between V2 and V1), and the third colored particle 32C is moved. The voltage range necessary for displaying the color of the third colored particles is set to | V4 ≦ V ≦ V3 | (absolute value between V4 and V3). Here, | V4 | = 0V may be used, but it is preferable that | V |> 0V in consideration of the memory property of display.

  Next, an example of drive control of the image display apparatus 10 according to the first embodiment of the present invention configured as described above will be described. In the following description, in order to simplify the description, it is assumed that the back electrode 22 is ground (0 V) and a voltage is applied to the front electrode 16.

  First, when the voltage application unit 40 applies the applied voltage V (V1) between the front electrode 16 and the back electrode 22 under the control of the control unit 42, the negatively charged first colored particles 32A move to the display substrate 18 side, The positively charged second colored particles 32B move to the back substrate 28 side. Further, the negatively charged third colored particles 32C pass through the gap between the first colored particles 32A and the second colored particles 32B and move to the display substrate 18 side, so that the state shown in FIG. The red color of the particle 32C is displayed.

  Further, from the state shown in FIG. 3A, the voltage application unit 40 applies the applied voltage V (−V3) between the front electrode 16 and the back electrode 22 under the control of the control unit 42, whereby the third colored particles Only 32C moves to the back substrate 28 side and enters the state shown in FIG. 3B, and the white color of the first colored particles 32A is displayed.

  On the other hand, when the voltage application unit 40 applies the applied voltage V (−V1) between the front electrode 16 and the back electrode 22 under the control of the control unit 42, the negatively charged first colored particles 32A move to the back substrate 28 side. Then, the positively charged second colored particles 32B move to the display substrate 18 side. Further, the negatively charged third colored particles 32C pass through the gap between the first colored particles 32A and the second colored particles 32B and move to the back substrate 28 side, resulting in the state shown in FIG. The black color of the particles 32B is displayed.

  That is, in the present embodiment, among the three types of colored particles, the two types of colored particles, the first colored particles 32A and the second colored particles 32B, have a larger particle size than the other one type of the third colored particles 32C. The gap between the two colored particles of the first colored particle 32A and the second colored particle 32B is made small enough to allow the other one third colored particle 32C to move, and the voltage range for moving the colored particles is different. I am doing so. Accordingly, even if the third colored particles 32C that are in contact with or close to the first colored particles 32A and the second colored particles 32B are driven, the first colored particles 32A and the second colored particles 32B are third colored due to the mass difference between them. Less susceptible to the movement of the particles 32C. Further, the friction between the first colored particles 32A and the second colored particles 32B is obtained by setting the first colored particles 32A and the second colored particles 32B to a certain volume filling rate (30 to 60% in this embodiment). Thus, since the first colored particles 32A and the second colored particles 32B are difficult to move, they are not affected by the movement of the third colored particles 32C.

  Therefore, it is difficult to move, that is, a color in which color mixing is suppressed by first driving the first colored particles 32A and the second colored particles 32B having a large voltage range for moving the colored particles and then moving the third colored particles 32C. Display is performed.

  Further, if one of the first colored particles 32A and the second colored particles 32B is charged, the desired one can be moved to the display substrate 18 side. However, in the present embodiment, the charged particles have opposite polarities. The desired one is more reliably moved to the display substrate 18 side.

  In the present embodiment, the first colored particles 32A are white, the second colored particles 32B are black, and the third colored particles 32C are red. However, the present invention is not limited to this. Colored ones may be applied. For example, the first colored particles 32A colored white, the second colored particles 32B colored cyan, and the third colored particles 32C colored red may be applied. In this case, FIG. 3A is displayed in red, FIG. 3B is displayed in white, and FIG. 3C is displayed in cyan. Further, from the state shown in FIG. When the voltage application unit 40 applies the applied voltage V (−V4) between the front electrode 16 and the back electrode 22 under the control of 42, only the third colored particles 32C move to the display substrate 18 side, and FIG. Since the second colored particles 32B and the third colored particles 32C are in a complementary color relationship, black is displayed, and four colors of white, black, red, and cyan can be displayed. Further, in this case, in order to display black with the red color of the third colored particle 32C and the cyan color of the second colored particle 32B, the third colored particle 32C has a translucency enough to display a secondary color. It is preferable to apply.

  In the present embodiment, the voltage range in which the display is performed by moving the first colored particles 32A and the second colored particles 32B is larger than the voltage range in which the display is performed by moving the third colored particles 32C. On the contrary, the voltage range in which the display is performed by moving the third colored particles 32C may be larger than the voltage range in which the display is performed by moving the first colored particles 32A and the second colored particles 32B. . However, in this case, the third colored particles 32C previously moved to the desired substrate side may be disturbed by the movement of the first colored particles 32A and the second colored particles 32B having a large particle diameter. It is more preferable that the voltage range for displaying by moving the colored particles 32A and the second colored particles 32B is larger than the voltage range for displaying by moving the third colored particles 32C.

Second Embodiment
Subsequently, a display medium and a display device according to the second embodiment will be described.
The display medium according to the present embodiment includes a pair of substrates, at least one of which has translucency, and a particle group enclosed between the pair of substrates. The particle group is the image display particle in the above embodiment. Including.

FIG. 4 shows a display medium and a display device according to the second embodiment.
The image forming apparatus 112 (display device) according to the present embodiment includes a voltage applying unit 201 as shown in FIG. In the image display medium 110, a spacer 204, red particles 118, and white particles 120 are enclosed between a display substrate 114 on the image display side and a non-display substrate 116 (back substrate) facing the display substrate 114. It has been configured. The display substrate 114 and the non-display substrate 116 are provided with a transparent electrode 205 as will be described later. However, the transparent electrode 205 of the non-display substrate 116 is grounded, and the transparent electrode 205 of the display substrate 114 is a voltage applying unit. 201 is connected.

Next, details of the image display medium 110 will be described.
For the display substrate 114 and the non-display substrate 116 constituting the outside of the image display medium 110, for example, a 7059 glass substrate with a transparent electrode ITO of 50 × 50 × 1.1 mm is used. The inner surface in contact with the particles of the glass substrate is coated with polycarbonate resin (PC-Z) 206 to a thickness of 5 μm. A central portion of a 40 × 40 × 0.3 mm silicon rubber plate (spacer 204) is cut into a 15 × 15 mm square to form a space, and this silicon rubber plate is placed on the non-display substrate 116.
For example, titanium oxide-containing white particles 120 having a volume average particle diameter of 20 μm and red particles 118 having a volume average particle diameter of 20 μm, for example, are mixed at a mass ratio of 2: 1, and about 15 mg of the mixed particles are mixed with the silicon. Shake it through the screen into the space cut into the square of the rubber plate.
Thereafter, the display substrate 114 is brought into intimate contact with the silicon rubber plate, the two substrates are pressed and held with a double clip, and the silicon rubber plate and the two substrates are brought into intimate contact to form the image display medium 110.

  In this embodiment, the image display particles in the above embodiment are used as the red particles 118, and other particles are used as the white particles. However, the present invention is not limited to this, and the image display particles in the above embodiments are used as the white particles 120. May be used. In the present embodiment, two types of particles are used. However, the present invention is not limited to this as long as the image display particles in the above embodiment are used, and only one type or three or more types may be used.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples. In addition, unless otherwise indicated, a part shows a mass part.

  Hereinafter, embodiments of the present invention will be described in detail.

<Measurement method>
-Measurement of volume average primary particle size of particles-
The volume average primary particle diameter of the particles was measured using a Coulter Multisizer-II type (manufactured by Beckman Coulter, Inc.) with an aperture diameter of 50 μm. At this time, the measurement is performed after the particles are dispersed in an electrolyte aqueous solution (Isoton aqueous solution, manufactured by Beckman Coulter, Inc.) and dispersed by ultrasonic waves for 30 seconds or more.

  As a measuring method, 0.5 to 50 mg of a measurement sample is added to 2 ml of a 5% aqueous solution of a surfactant, preferably sodium alkylbenzenesulfonate as a dispersant, and this is added to 100 to 150 ml of the electrolytic solution. The electrolytic solution in which the measurement sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for about 1 minute, and the particle size distribution of the particles is measured. The number of particles to be measured is 50,000.

  For the measured particle size distribution, a cumulative distribution is drawn from the smaller diameter side with respect to the divided particle size range (channel), and the particle size at which 50% is accumulated is defined as the volume average primary particle size.

-Measurement of glass transition temperature of resin contained in particles-
The glass transition temperature was measured according to JIS 7121-1987 using a differential scanning calorimeter (DSC-50 manufactured by Shimadzu Corporation). The melting point of a mixture of indium and zinc was used for temperature correction of the detection part of this apparatus, and the heat of fusion of indium was used for correction of heat quantity.

The particles were put in an aluminum pan as they were, and an aluminum pan containing particles and an empty aluminum pan for control were set, and measurement was performed at a heating rate of 10 ° C./min.
The glass transition temperature was defined as the temperature at the intersection of the extension line of the base line and the rising line in the endothermic part of the DSC curve obtained by the measurement.

<Preparation of particle A-1 (large yellow particle)>
-Preparation of dispersion A-1A-
The following components were mixed and ball milling was performed for 20 hours with 10 mmφ zirconia balls to prepare dispersion A-1A.
・ Methyl methacrylate 53 mass parts ・ Methyl methacrylate 2- (diethylamino) ethyl 0.3 mass part ・ Yellow pigment (FY7416: manufactured by Sanyo Color Co., Ltd.) 1.5 mass parts

-Preparation of dispersion A-1B (calcium carbonate dispersion A-1B)-
The following components were mixed and finely pulverized with a ball mill in the same manner as described above to prepare a calcium carbonate dispersion A-1B.
・ 40 parts by weight of calcium carbonate ・ 60 parts by weight of water

-Preparation of liquid mixture A-1C-
The following components were mixed, degassed with an ultrasonic machine for 10 minutes, and then stirred with an emulsifier to prepare a mixed solution A-1C.
・ Calcium carbonate dispersion A-1B 60g
・ 20% saline 4g

-Preparation of colored particles-
Dispersion A-1A: 20 g, ethylene glycol dimethacrylate: 0.6 g, polymerization initiator V601 (Dimethyl 2,2′-azobis (2-methylpropionate): Wako Pure Chemical Industries, Ltd.): 0.2 g The mixture was thoroughly mixed and deaerated with an ultrasonic machine for 10 minutes. This was added to the mixed solution A-1C and emulsified with an emulsifier. Next, this emulsified liquid was put into a flask, and a silicone soot was added thereto. Using an injection needle, vacuum deaeration was sufficiently performed and sealed with nitrogen gas. Next, it was reacted at 65 ° C. for 15 hours to prepare particles.
After cooling, the particles were filtered, and the obtained particle powder was dispersed in ion-exchanged water, and calcium carbonate was decomposed with hydrochloric acid water, followed by filtration.
Thereafter, it was washed with sufficient distilled water, and passed through a nylon sieve having openings of 15 μm and 10 μm, so that the particle sizes were made uniform. The obtained particles had a volume average primary particle size of 13 μm.

-Quaternary ammonium treatment-
The obtained particles were dispersed in 1 cSt silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd., KF96-1cs), and dodecyl bromide (quaternizing agent) was used, such as 2- (diethylamino) ethyl methacrylate used for the preparation of the particles. Molar amount was added and heated at 90 ° C. for 6 hours.
After cooling, the dispersion was washed with a large amount of silicone oil and dried under reduced pressure to obtain yellow particles. This was designated as Particle A-1 (large yellow particles). The glass transition temperature of the resin contained in the particles A-1 was 145 ° C.

<Preparation of Particle A-2 (Large Yellow Particle for Comparative Example)>
-Preparation of dispersion A-2A-
The following components were mixed and ball milling was performed for 20 hours with 10 mmφ zirconia balls to prepare dispersion A-2A.
-53 parts by weight of methyl methacrylate-0.3 parts by weight of 2- (diethylamino) ethyl methacrylate-1.5 parts by weight of yellow pigment (FY7416: manufactured by Sanyo Dye Company)-Charge control agent (Bontron P-51: Orient Chemical Co., Ltd.) 0.5 parts by mass)

-Preparation of dispersion A-2B (calcium carbonate dispersion A-2B)-
The following components were mixed and finely pulverized with a ball mill in the same manner as described above to prepare calcium carbonate dispersion A-2B.
・ 40 parts by weight of calcium carbonate ・ 60 parts by weight of water

-Preparation of liquid mixture A-2C-
The following components were mixed, degassed with an ultrasonic machine for 10 minutes, and then stirred with an emulsifier to prepare a mixed solution A-2C.
・ Calcium carbonate dispersion A-2B 60g
・ 20% saline 4g

-Preparation of colored particles-
Dispersion A-2A: 20 g, ethylene glycol dimethacrylate: 0.6 g, polymerization initiator V601 (Dimethyl 2,2′-azobis (2-methylpropionate): Wako Pure Chemical Industries, Ltd.): 0.2 g The mixture was thoroughly mixed and deaerated with an ultrasonic machine for 10 minutes. This was added to the mixed solution A-2C and emulsified with an emulsifier. Next, this emulsified liquid was put into a flask, and a silicone soot was added thereto. Using an injection needle, vacuum deaeration was sufficiently performed and sealed with nitrogen gas. Next, it was reacted at 65 ° C. for 15 hours to prepare particles.
After cooling, the particles were filtered, and the obtained particle powder was dispersed in ion-exchanged water, and calcium carbonate was decomposed with hydrochloric acid water, followed by filtration.
Thereafter, it was washed with sufficient distilled water, and passed through a nylon sieve having openings of 15 μm and 10 μm, so that the particle sizes were made uniform. The obtained particles had a volume average primary particle size of 13 μm. This was designated as Particle A-2 (large yellow particle for comparative example). The glass transition temperature of the resin contained in the particles A-2 was 145 ° C.

<Preparation of particles A-3 (large yellow particles for comparison)>
-Preparation of polymer A-3A-
Weigh 30 g of methyl methacrylate, 0.3 g of 2- (diethylamino) ethyl methacrylate, 0.4 g of polymerization initiator V65 (2,2′-Azobis (2,4-dimethylvaleronitile)), 150 ml of tetrahydrofuran, and mix well. Degassing was carried out for 10 minutes with a sonicator, and the mixture was put into a flask, poured into a silicone flask and allowed to react for 15 hours at 50 ° C. After that, the mixture was slowly added to 600 ml of methanol with stirring, and the supernatant was decanted. The polymer remaining was dried at 40 ° C. under vacuum to obtain polymer A-3A.

-Preparation of colored particle particles A-3C-
After 2 g of polymer A-3A was dissolved in 30 ml of tetrahydrofuran, 2 g of yellow pigment (FY7416: manufactured by Sanyo Color Co., Ltd.) was added, dispersed for 10 minutes with an ultrasonic machine, and then allowed to stand overnight at room temperature for yellow. Polymer A-3A was adsorbed on the pigment. This dispersion is put into a centrifuge tube, centrifuged at 8000 rpm for 10 minutes, the supernatant is removed by decantation, the remaining precipitate is dried at 40 ° C. under vacuum, and a particle A-3 having a volume average primary particle size of 13 μm. (Large yellow particles for comparative example). The glass transition temperature of the resin contained in the particles A-3 was 145 ° C.

<Preparation of particles A-4 (large yellow particles)>
-Preparation of dispersion A-4A-
The following components were mixed, and ball milling was performed for 20 hours with 10 mmφ zirconia balls to prepare dispersion A-4A.
-53 parts by weight of methyl methacrylate-3.0 parts by weight of 2- (diethylamino) ethyl methacrylate-Yellow pigment (FY7416: manufactured by Sanyo Dye) 1.5 parts by weight

-Preparation of dispersion A-4B (calcium carbonate dispersion A-4B)-
The following components were mixed, and finely pulverized with a ball mill in the same manner as described above to prepare a calcium carbonate dispersion A-4B.
・ 40 parts by weight of calcium carbonate ・ 60 parts by weight of water

-Preparation of liquid mixture A-4C-
The following components were mixed, degassed with an ultrasonic machine for 10 minutes, and then stirred with an emulsifier to prepare a mixed solution A-4C.
・ Calcium carbonate dispersion A-4B 60g
・ 20% saline 4g

-Adjustment of colored particles-
Dispersion A-4A: 20 g, ethylene glycol dimethacrylate: 0.6 g, polymerization initiator V601 (Dimethyl 2,2′-azobis (2-methylpropionate)): 0.2 g is weighed, mixed well, and ultrasonicated The machine was degassed for 10 minutes. This was added to the mixed solution A-4C and emulsified with an emulsifier. Next, this emulsified liquid was put into a flask, and a silicone soot was added thereto. Using an injection needle, vacuum deaeration was sufficiently performed and sealed with nitrogen gas. Next, it was reacted at 65 ° C. for 15 hours to prepare particles.
After cooling, the particles were filtered, and the obtained particle powder was dispersed in ion-exchanged water, and calcium carbonate was decomposed with hydrochloric acid water, followed by filtration.
Thereafter, it was washed with sufficient distilled water, and passed through a nylon sieve having openings of 15 μm and 10 μm, so that the particle sizes were made uniform. The obtained particles had a volume average primary particle size of 13 μm.

-Quaternary ammonium treatment-
The obtained particles were dispersed in 1 cSt silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd., KF96-1cs), and dodecyl bromide (quaternizing agent) was used, such as 2- (diethylamino) ethyl methacrylate used for the preparation of the particles. Molar amount was added and heated at 90 ° C. for 6 hours.
After cooling, the dispersion was washed with a large amount of silicone oil and dried under reduced pressure to obtain yellow particles. This was designated as Particle A-4 (large yellow particles). The glass transition temperature of the resin contained in the particles A-4 was 145 ° C.

<Preparation of particles A-5 (large yellow particles)>
-Preparation of dispersion A-5A-
The following components were mixed and ball milling was performed for 20 hours with 10 mmφ zirconia balls to prepare dispersion A-5A.
・ Methyl methacrylate 53 mass parts ・ Methyl methacrylate 2- (diethylamino) ethyl 15 mass parts ・ Yellow pigment (FY7416: manufactured by Sanyo Color Co., Ltd.) 1.5 mass parts

-Preparation of dispersion A-5B (calcium carbonate dispersion A-5B)-
The following components were mixed and finely pulverized with a ball mill in the same manner as described above to prepare calcium carbonate dispersion A-5B.
・ 40 parts by weight of calcium carbonate ・ 60 parts by weight of water

-Preparation of liquid mixture A-5C-
The following components were mixed, degassed with an ultrasonic machine for 10 minutes, and then stirred with an emulsifier to prepare a mixed solution A-5C.
・ Calcium carbonate dispersion A-5B 60g
・ 20% saline 4g

-Adjustment of colored particles-
Dispersion A-5A: 20 g, ethylene glycol dimethacrylate: 0.6 g, polymerization initiator V601 (Dimethyl 2,2′-azobis (2-methylpropionate)): 0.2 g, weighed, mixed well, and super Deaeration was performed for 10 minutes with a sonicator. This was added to the mixed solution A-5C and emulsified with an emulsifier. Next, this emulsified liquid was put into a flask, and a silicone soot was added thereto. Using an injection needle, vacuum deaeration was sufficiently performed and sealed with nitrogen gas. Next, it was reacted at 65 ° C. for 15 hours to prepare particles.
After cooling, the particles were filtered, and the obtained particle powder was dispersed in ion-exchanged water, and calcium carbonate was decomposed with hydrochloric acid water, followed by filtration.
Thereafter, it was washed with sufficient distilled water, and passed through a nylon sieve having openings of 15 μm and 10 μm, so that the particle sizes were made uniform. The obtained particles had a volume average primary particle size of 13 μm.

-Quaternary ammonium treatment-
The obtained particles were dispersed in 1 cSt silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd., KF96-1cs), and dodecyl bromide (quaternizing agent) was equimolar with 2- (diethylamino) ethyl methacrylate used for particle preparation. The amount was added and heated at 90 ° C. for 6 hours.
After cooling, the dispersion was washed with a large amount of silicone oil and dried under reduced pressure to obtain yellow particles. This was designated as Particle A-5 (large yellow particles). The glass transition temperature of the resin contained in the particles A-5 was 145 ° C.

<Preparation of particles A-6 (large yellow particles)>
-Preparation of dispersion A-6A-
The following components were mixed, and ball milling was performed for 20 hours with 10 mmφ zirconia balls to prepare dispersion A-6A.
・ Methyl methacrylate 53 parts by mass ・ 2- (dimethylamino) ethyl methacrylate (0.3 parts by mass) ・ Yellow pigment (FY7416: Sanyo Dye Co., Ltd.) 1.5 parts by mass

-Preparation of dispersion A-6B (calcium carbonate dispersion A-6B)-
The following components were mixed, and finely pulverized with a ball mill in the same manner as described above to prepare calcium carbonate dispersion A-6B.
・ 40 parts by weight of calcium carbonate ・ 60 parts by weight of water

-Preparation of liquid mixture A-6C-
The following components were mixed, degassed with an ultrasonic machine for 10 minutes, and then stirred with an emulsifier to prepare a mixed solution A-6C.
・ Calcium carbonate dispersion A-6B 60g
・ 20% saline 4g

-Adjustment of colored particles-
Dispersion A-6A: 20 g, ethylene glycol dimethacrylate: 0.6 g, polymerization initiator V601 (Dimethyl 2,2′-azobis (2-methylpropionate)): 0.2 g, weighed, mixed thoroughly, and super Deaeration was performed for 10 minutes with a sonicator. This was added to the mixed solution A-6C and emulsified with an emulsifier. Next, this emulsified liquid was put into a flask, and a silicone soot was added thereto. Using an injection needle, vacuum deaeration was sufficiently performed and sealed with nitrogen gas. Next, it was reacted at 65 ° C. for 15 hours to prepare particles.
After cooling, the particles were filtered, and the obtained particle powder was dispersed in ion-exchanged water, and calcium carbonate was decomposed with hydrochloric acid water, followed by filtration.
Thereafter, it was washed with sufficient distilled water, and passed through a nylon sieve having openings of 15 μm and 10 μm, so that the particle sizes were made uniform. The obtained particles had a volume average primary particle size of 13 μm.

-Quaternary ammonium treatment-
The obtained particles were dispersed in 1 cSt silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd., KF96-1cs), and dodecyl bromide (quaternizing agent) was mixed with 2- (dimethylamino) ethyl methacrylate used for particle preparation. An equimolar amount was added and heated at 90 ° C. for 6 hours.
After cooling, the dispersion was washed with a large amount of silicone oil and dried under reduced pressure to obtain yellow particles. This was designated as Particle A-6 (large yellow particles). The glass transition temperature of the resin contained in the particles A-6 was 145 ° C.

<Preparation of particles A-7 (large yellow particles)>
-Preparation of dispersion A-7A-
The following components were mixed and ball milling was performed for 20 hours with 10 mmΦ zirconia balls to prepare dispersion A-7A.
・ Methyl methacrylate 53 mass parts ・ Methyl methacrylate 2- (diethylamino) ethyl 0.3 mass part ・ Yellow pigment (FY7416: manufactured by Sanyo Color Co., Ltd.) 1.5 mass parts

-Preparation of dispersion A-7B (calcium carbonate dispersion A-7B)-
The following components were mixed, and finely pulverized with a ball mill in the same manner as described above to prepare a calcium carbonate dispersion A-7B.
・ 40 parts by weight of calcium carbonate ・ 60 parts by weight of water

-Preparation of liquid mixture A-7C-
The following components were mixed, degassed with an ultrasonic machine for 10 minutes, and then stirred with an emulsifier to prepare a mixed solution A-7C.
・ Calcium carbonate dispersion A-7B 60g
・ 20% saline 4g

-Adjustment of colored particles-
Dispersion A-7A: 20 g, ethylene glycol dimethacrylate: 0.6 g, polymerization initiator V601 (Dimethyl 2,2′-azobis (2-methylpropionate)): 0.2 g, weighed, mixed thoroughly, and super Deaeration was performed for 10 minutes with a sonicator. This was added to the mixed solution A-7C and emulsified with an emulsifier. Next, this emulsified liquid was put into a flask, and a silicone soot was added thereto. Using an injection needle, vacuum deaeration was sufficiently performed and sealed with nitrogen gas. Next, it was reacted at 65 ° C. for 15 hours to prepare particles.
After cooling, the particles were filtered, and the obtained particle powder was dispersed in ion-exchanged water, and calcium carbonate was decomposed with hydrochloric acid water, followed by filtration.
Thereafter, it was washed with sufficient distilled water, and passed through a nylon sieve having openings of 15 μm and 10 μm, so that the particle sizes were made uniform. The obtained particles had a volume average primary particle size of 13 μm.

-Quaternary ammonium treatment-
The obtained particles were dispersed in 1 cSt silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd., KF96-1cs), and butyl bromide (quaternizing agent) was mixed with 2- (diethylamino) ethyl methacrylate used for the preparation of the particles. Molar amount was added and heated at 90 ° C. for 6 hours.
After cooling, the dispersion was washed with a large amount of silicone oil and dried under reduced pressure to obtain yellow particles. This was designated as Particle A-7 (large yellow particles). The glass transition temperature of the resin contained in the particles A-7 was 145 ° C.

<Preparation of particles B-1 (large white particles)>
-Preparation of dispersion B-1A-
The following components were mixed and ball milling was performed for 20 hours with 10 mmφ zirconia balls to prepare dispersion B-1A.
-53 parts by mass of cyclohexyl methacrylate-Titanium oxide 1 (white pigment) (primary particle size 0.3 µm, Type CR63: manufactured by Ishihara Sangyo Co., Ltd.) 45 parts by mass-5 parts by mass of cyclohexane

-Preparation of dispersion B-1B (calcium carbonate dispersion B-1B)-
The following components were mixed and finely pulverized with a ball mill in the same manner as described above to prepare a calcium carbonate dispersion B-1B.
・ 40 parts by weight of calcium carbonate ・ 60 parts by weight of water

-Preparation of liquid mixture B-1C-
The following components were mixed, degassed with an ultrasonic machine for 10 minutes, and then stirred with an emulsifier to prepare a mixed solution B-1C.
・ 2% Serogen (Daiichi Kogyo Seiyaku Co., Ltd.) 4.3g
・ 8.5 g of calcium carbonate dispersion B-1B
・ 20% saline 50g

Dispersion B-1A: 35 g, divinylbenzene: 1 g, polymerization initiator AIBN (azobisisobutyronitrile): 0.35 g were weighed and mixed thoroughly, and deaerated with an ultrasonic machine for 10 minutes. This was added to the mixed solution B-1C and emulsified with an emulsifier. Next, this emulsified liquid was put into a bottle, put into a silicone bottle, used with an injection needle, sufficiently degassed under reduced pressure, and sealed with nitrogen gas. Next, it was reacted at 65 ° C. for 15 hours to prepare particles.
After cooling, cyclohexane was removed by placing this dispersion in a freeze dryer at −35 ° C. and 0.1 Pa for 2 days. The obtained particle powder was dispersed in ion-exchanged water, calcium carbonate was decomposed with hydrochloric acid water, and filtered.
Thereafter, it was washed with sufficient distilled water, and passed through a nylon sieve having openings of 15 μm and 10 μm, so that the particle sizes were made uniform. This was dried to obtain white particles having a volume average primary particle size of 13 μm. This was designated as Particle B-1 (large white particles).

<Preparation of particles B-2 (large white particles)>
-Preparation of dispersion B-2A-
The following components were mixed, and ball milling was performed for 20 hours with 10 mmφ zirconia balls to prepare dispersion B-2A.
-38 parts by mass of cyclohexyl methacrylate-1: 1 chloride of methacrylic acid and trihexylamine (monomer having acid group salt) 7 parts by mass-Titanium oxide 1 (white pigment) (primary particle size 0.3 μm , Taipei CR63: manufactured by Ishihara Sangyo Co., Ltd.) 45 parts by mass / cyclohexane 5 parts by mass

-Preparation of dispersion B-2B (calcium carbonate dispersion B-2B)-
The following components were mixed and finely pulverized with a ball mill in the same manner as described above to prepare a calcium carbonate dispersion B-2B.
・ 40 parts by weight of calcium carbonate ・ 60 parts by weight of water

-Preparation of liquid mixture B-2C-
The following components were mixed, degassed with an ultrasonic machine for 10 minutes, and then stirred with an emulsifier to prepare a mixed solution B-2C.
・ 2% Serogen (Daiichi Kogyo Seiyaku Co., Ltd.) 4.3g
・ 8.5 g of calcium carbonate dispersion B-2B
・ 20% saline 50g

Dispersion B-2A: 35 g, divinylbenzene: 1 g, and polymerization initiator AIBN (azobisisobutyronitrile): 0.35 g were weighed and mixed thoroughly, and deaerated with an ultrasonic machine for 10 minutes. This was added to the mixed solution B-2C and emulsified with an emulsifier. Next, this emulsified liquid was put into a bottle, put into a silicone bottle, used with an injection needle, sufficiently degassed under reduced pressure, and sealed with nitrogen gas. Next, it was reacted at 65 ° C. for 15 hours to prepare particles.
After cooling, cyclohexane was removed by placing this dispersion in a freeze dryer at −35 ° C. and 0.1 Pa for 2 days. The obtained particle powder was dispersed in ion-exchanged water, calcium carbonate was decomposed with hydrochloric acid water, and filtered.
Thereafter, it was washed with sufficient distilled water, and passed through a nylon sieve having openings of 15 μm and 10 μm, so that the particle sizes were made uniform. This was dried to obtain white particles having a volume average primary particle size of 13 μm. This was designated as Particle B-2 (large white particles).

<Preparation of particles B-3 (small white particles)>
-Preparation of dispersion B-3A-
The following components were mixed, and ball milling with 10 mmφ zirconia balls was performed for 20 hours to prepare dispersion B-3A.
-38 parts by mass of cyclohexyl methacrylate-1: 1 salt compound of methacrylic acid and trihexylamine (monomer having acid group salt) 7 parts by mass-Titanium oxide 1 (white pigment) (primary particle size 0.3 μm , Taipei CR63: manufactured by Ishihara Sangyo Co., Ltd.) 45 parts by mass / cyclohexane 5 parts by mass

-Preparation of dispersion B-3B (calcium carbonate dispersion B-3B)-
The following components were mixed, and finely pulverized with a ball mill in the same manner as described above to prepare a calcium carbonate dispersion B-3B.
・ 40 parts by weight of calcium carbonate ・ 60 parts by weight of water

-Preparation of liquid mixture B-3C-
The following components were mixed, degassed with an ultrasonic machine for 10 minutes, and then stirred with an emulsifier to prepare a mixed solution B-3C.
・ 2% Serogen (Daiichi Kogyo Seiyaku Co., Ltd.) 4.3g
・ 8.5g of calcium carbonate dispersion B-3B
・ 20% saline 50g

Dispersion B-3A: 35 g, divinylbenzene: 1 g, and polymerization initiator AIBN (azobisisobutyronitrile): 0.35 g were weighed and mixed thoroughly, and deaerated with an ultrasonic machine for 10 minutes. This was added to the mixed solution B-3C and emulsified with an emulsifier. Next, this emulsified liquid was put into a bottle, put into a silicone bottle, used with an injection needle, sufficiently degassed under reduced pressure, and sealed with nitrogen gas. Next, it was reacted at 65 ° C. for 15 hours to prepare particles.
After cooling, cyclohexane was removed by placing this dispersion in a freeze dryer at −35 ° C. and 0.1 Pa for 2 days. The obtained particle powder was dispersed in ion-exchanged water, calcium carbonate was decomposed with hydrochloric acid water, and filtered.
Thereafter, it was washed with sufficient distilled water, and sieved through nylon sieves having openings of 5 μm and 3 μm to make the particle sizes uniform. This was dried to obtain white particles having a volume average primary particle size of 4 μm. This was designated as Particle B-3 (small white particles).

[Example A]
<Example A-1>
A 1 mm thick glass substrate in which a transparent conductive film (ITO film) is formed with a thickness of 100 nm on one side of the substrate by a sputtering method, a pair of the glass substrates are arranged to face each other via a spacer, and has a space of 100 μm thickness. A cell was produced.

  After injecting large yellow particles (particles A-1) and 1cSt silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd., KF96-1cs) prepared in the space, electrophoresis is performed by sealing both glass plates with an epoxy resin adhesive. A display medium was produced. In addition, the volume filling rate of the whole particle (particle A-1) with respect to the volume of the space was 20%.

A voltage with a peak value of 100 V is applied between the opposing ITO surfaces of the produced electrophoretic display medium by a rectangular wave of 1 Hz, and the value of the electrophoretic current at that time is measured. From the particle group concentration, particles per gram are measured. The charge amount of (Particle A-1) was calculated to be 3.6 × 10 ⁻⁶ (C / g).

The sample was left in an environment of 25 ° C. and 40% RH for 30 days, and after 1 day, 5 days, 6 days, 13 days, and 30 days, measurement was performed with the same rectangular wave, and the charge amount of the particles was calculated. The results are shown in Table 1.

<Example A-2 to Example A-5>
The charge amount of the particles was measured in the same manner as in Example A-1, except that the particles A-4 to A-7 were used instead of the particles A-1. The results are shown in Table 1.

<Comparative Example A-1 to Comparative Example A-2>
The charge amount of the particles was measured in the same manner as in Example A-1, except that the particles A-2 to A-3 were used instead of the particles A-1. The results are shown in Table 1.

  From the above results, it can be seen that in Example A-1 to Example A-5, changes with time in the charge amount of the particles are suppressed as compared with Comparative Example A-1 to Comparative Example A-2.

[Example B]
<Example B-1>
A 1 mm thick glass substrate in which a transparent conductive film (ITO film) is formed with a thickness of 50 nm on one side of the substrate by a sputtering method, a pair of the glass substrates are arranged to face each other via a spacer, and has a space of 100 μm thickness. A cell was produced.

  After injecting large yellow particles (particles A-1) and large white particles (particles B-1) prepared in the space and 1 cSt silicone oil (KF96-1cs, manufactured by Shin-Etsu Chemical Co., Ltd.), both glass plates are epoxy resin An electrophoretic display medium was produced by sealing with a system adhesive. The mass ratio of the injected particles A-1 and B-1 was 2: 3, and the volume filling rate of the entire particles (particle A-1 and particle B-1) with respect to the volume of the space was 20%. .

When a voltage having a peak value of 100 V was applied between the opposing ITO surfaces of the produced electrophoretic display medium with a rectangular wave of 1 Hz, a white-yellow color change was observed.
Further, the value of the electrophoretic current at that time was measured, and the charge amount of the particles (particles A-1 and B-1) per gram was calculated from the particle group concentration, and found to be 3.5 × 10 ^−6. (C / g).

After being left in an environment of 25 ° C. and 40% RH for 30 days, the current value of the display medium was measured with the same rectangular wave, and the charge amount of the particles was calculated to be 3.45 × 10 ⁻⁶ (C / g). There was no change in the initial charge amount.
Further, even after being left for 30 days, a white-yellow color change was observed, and no deterioration was observed in the color change.

<Example B-2 to Example B-4, Comparative Example B-1 to Comparative Example B-2>
Measurement was performed in the same manner as in Example B-1 except that the yellow particles and white particles listed in Table 2 were used. The results (charge amount and color change of yellow particles) are also shown in Table 2.
The evaluation criteria for color change are as follows, and a practically acceptable range is G1 to G3.
G1: White / yellow color change was clearly observed G2: White / yellow color change was not complete, but acceptable in practical use.
G3: Mixed color was clearly confirmed in the color change of white to yellow.

  From the above results, in Example B-1 to Example B-4, the change in the charge amount of the particles with time is suppressed and the deterioration of the color change is suppressed as compared with Comparative Example B-1 to Comparative Example B-2. You can see that.

[Example C]
<Example C-1>
A 1 mm thick glass substrate in which a transparent conductive film (ITO film) is formed with a thickness of 50 nm on one side of the substrate by a sputtering method, a pair of the glass substrates are arranged to face each other via a spacer, and has a space of 100 μm thickness. A cell was produced.

  After injecting large yellow particles (particle A-1) and large white particles (particle B-1) prepared in the space, an electrophoretic display medium is produced by sealing both glass plates with an epoxy resin adhesive. did. The mass ratio of the injected particles A-1 and particles B-1 was 2: 3, and the volume filling rate of the entire particles (particles A-1 and particles B-1) with respect to the volume of the space was 30%. .

When a voltage with a peak value of 150 V was applied between the opposing ITO surfaces of the produced electrophoretic display medium with a rectangular wave of 1 Hz, a white-yellow color change was observed.
Moreover, when the value of the electrophoretic current at that time was measured and the charge amount of particles (particles A-1 and B-1) per gram was calculated from the particle group concentration, 4.7 × 10 ^{−6 was obtained.} (C / g).

After being left in an environment of 25 ° C. and 40% RH for 30 days, the current value of the display medium was measured with the same rectangular wave, and the charge amount of the particles was calculated to be 4.7 × 10 ⁻⁶ (C / g). There was no change in the initial charge amount.
Further, even after being left for 30 days, a white-yellow color change was observed, and no deterioration was observed in the color change.

<Example C-2, Comparative Example C-1>
Measurement was performed in the same manner as in Example C-1 except that the yellow particles and white particles listed in Table 3 were used. The results (charge amount and color change of yellow particles) are also shown in Table 3.
The color change evaluation criteria are the same as in the above (Example B).

  From the above results, it can be seen that in Example C-1 to Example C-2, the change in the charge amount of the particles with time is suppressed and the deterioration of the color change is suppressed as compared with Comparative Example C-1. .

1 is a schematic configuration diagram illustrating a display device according to a first embodiment of the present invention. It is a figure for demonstrating the applied voltage required in order to move each colored particle in the display apparatus which concerns on 1st Embodiment of this invention. It is a figure for demonstrating the drive control of the display apparatus which concerns on 1st Embodiment of this invention, and is a state transition diagram to each color display. It is explanatory drawing. It is a schematic block diagram which shows the display apparatus which concerns on 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image display apparatus 12 Image display medium 16 Surface electrode 18 Display substrate 22 Back electrode 24 Dispersion liquid 28 Back substrate 32 Colored particle 32A 1st colored particle 32B 2nd colored particle 32C 3rd colored particle 40 Voltage application part 42 Control part 110 Image Display medium 112 Image forming apparatus 114 Display substrate 116 Non-display substrate 118 Red particles 120 White particles 201 Voltage application means

Claims (10)

  A particle for image display, wherein the surface of a colored particle containing a polymer compound having an amino group and a colorant is subjected to a quaternary ammonium treatment. A group of particles that move in response to an electric field, and a dispersion medium that disperses the group of particles,
2. The particle dispersion for image display, wherein the particle group includes first particles composed of the image display particles according to claim 1.   The particle dispersion for image display according to claim 2, wherein the particle group further includes second particles containing a polymer compound having an acid group salt and a colorant.   4. The particle dispersion for image display according to claim 3, wherein the salt of the acid group includes at least one selected from a carboxylate, a sulfonate, a phosphate, and a boron-based quaternary salt. liquid.   5. The image display particle dispersion according to claim 3, wherein the volume average primary particle size of the second particles is a particle size capable of moving through a gap between the image display particles. 6. A pair of substrates, at least one of which is translucent,
The particle dispersion for image display according to any one of claims 2 to 5, which is sealed between the pair of substrates.
A display medium comprising: A pair of substrates, at least one of which is translucent,
A group of particles enclosed between the pair of substrates,
The display medium according to claim 1, wherein the particle group includes the image display particles according to claim 1. A pair of electrodes, at least one of which is translucent,
The dispersion liquid for image display according to any one of claims 2 to 5, which is held between the pair of electrodes,
A display medium comprising: A display medium according to claim 6 or 7, and
Voltage applying means for applying a voltage between the pair of substrates of the display medium;
A display device comprising: A display medium according to claim 8;
Voltage applying means for applying a voltage between the pair of electrodes of the display medium;
A display device comprising:

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