JP5891854B2 - Display particle dispersion, image display device, electronic device, display medium, and card medium - Google Patents

Description

The present invention relates to a display particle dispersion used in an image display device capable of multicolor display, and an image display device having the same.
The present invention also relates to an electronic device including an image display device, a display medium, and a card medium.

  Conventionally, as a display technology that can be repeatedly rewritten, a display technology using electrophoresis has been proposed. As such a display technology, for example, a dispersion liquid is sealed between a pair of substrates. There is known an image display device having a configuration in which particles composed of charged particles are dispersed.

  In such an image display device, a voltage corresponding to an image is applied between the substrates to move the charged particles and display the image as the color contrast of the particles (for example, from Patent Document 1). 4). Further, it is known to use composite particles containing pigments such as titanium oxide particles as display white particles (see, for example, Patent Documents 5 and 6).

JP 2004-333589 A JP-A-2005-107146 JP 2005-128141 A JP 2003-005228 A JP 2007-041078 A JP 2007-033630 A

  However, when white display particles having a high white display reflectance are prepared and an image display device that can be displayed by moving the display colored particles is produced, sedimentation of the display white particles occurs. At present, the reflectance of white display is lowered when it is attempted to suppress the precipitation of the white particles for display.

Accordingly, the present invention has been made to solve the above-described problem, and a display particle dispersion having a high white display reflectance and suppressing the precipitation of display white particles, and an image display apparatus including the same. It is an issue to provide.
Moreover, this invention makes it a subject to provide an electronic device provided with this image display apparatus, a display medium, and a card | curd medium.

The above problem is solved by the following means. That is,
<1> A white particle for display containing a white pigment and a resin, wherein the content of the white pigment (mass of the white pigment / (total mass of the white pigment and the resin)) is 30% by mass or more and 90% by mass. White particles for display having a volume average particle size of 100 nm to 500 nm and satisfying the following formula (1):
Display colored particles that move in response to an electric field, two or more types of display colored particles excluding white,
A dispersion medium for dispersing the display colored particles and the display white particles;
It is a particle dispersion for display which has.
Formula (1) 400 ≧ 6 kT / (πd ³ (ρp−ρs) g) ≧ 30
(In formula (1), k represents the Boltzmann coefficient (J · K ⁻¹ ), T represents the absolute temperature 298 (K), and d represents the volume average particle diameter (nm) of the white particles for display. ρp is .ρs showing a specific gravity (g / cm ³⁾ of the display for white particles exhibit specific gravity (g / cm ³⁾ .g showing a gravity acceleration (m / ^{s 2)} of the dispersion medium.)

  <2> The particle dispersion for display according to <1>, wherein the white pigment is titanium oxide.

  <3> A moving speed ratio (moving speed Vw of the white particles for display / moving speed Vc of the colored particles for display) that moves according to the electric field between the white particles for display and the colored particles for display is 0. The particle dispersion for display according to <1> or <2>, which is 2 or less.

  <4> The display particle dispersion according to any one of <1> to <3>, wherein the dispersion medium has a viscosity of 5 mPa · s or less.

  <5> The display particle dispersion according to any one of <1> to <4>, wherein the dispersion medium is silicone oil.

<6> a pair of substrates at least one of which has translucency;
The display particle dispersion according to any one of <1> to <5>, which is sealed between the pair of substrates,
An electric field generating means for applying an electric field having an intensity for moving the display colored particles between the pair of substrates;
It is an image display apparatus provided with.

<7> An electronic device including the image display device according to <6>.
<8> An exhibition medium including the image display device according to <6>.
<9> A card medium including the image display device according to <6>.

According to the present invention, it is possible to provide a display particle dispersion that has a high white display reflectance and suppresses the precipitation of display white particles, and an image display device including the same.
In addition, according to the present invention, it is possible to provide an electronic device, an exhibition medium, and a card medium provided with this image display device.

It is a schematic block diagram of the image display apparatus which concerns on this embodiment. FIG. 4 is a diagram schematically illustrating a relationship between an applied voltage and a moving amount (display density) of display colored particles in the image display apparatus according to the present embodiment. It is explanatory drawing which shows typically the migration aspect of the particle group of the voltage aspect applied between the board | substrates of the image display apparatus which concerns on this embodiment, and the movement aspect of the colored particle for a display.

  Hereinafter, the present invention will be described in detail.

[Particle dispersion for display]
The display particle dispersion of the present invention is a display white particle, a display color particle that moves in response to an electric field, and two or more display color particles excluding white, a display color particle, and a display color And a dispersion medium for dispersing white particles.
The white particles for display are white particles for display containing a white pigment and a resin, and the content of the white pigment (mass of white pigment / (total mass of white pigment and resin)) is 30% by mass or more and 90% by mass or less. The volume average particle size is 100 nm or more and 500 nm or less, and the formula (1) is satisfied.

  Here, by setting the content of the white pigment and the volume average particle diameter of the white particles for display within the above ranges, the white reflectance of the white particles for display is high. On the other hand, when the display white particles satisfy the formula (1), the diffusion due to the Brownian motion of the display white particles and the sedimentation due to its own weight are in an equilibrium state, and apparently become a floating state in the dispersion.

Therefore, in the display particle dispersion of the present invention, in the display white particles containing the white pigment and the resin, the content of the white pigment and the volume average particle diameter of the display white particles are within the above ranges, By satisfying 1), the reflectance of white display is high and the sedimentation of white particles for display can be suppressed.
Further, in the display particle dispersion of the present invention, since the precipitation of the display white particles is suppressed and the dispersion stability is increased, it is considered difficult to prevent the movement of the display colored particles. Also improves.

  Hereinafter, each component of the display particle dispersion of the present invention will be described.

(Colored particles for display)
The display colored particles are two or more types of display colored particles that move in response to an electric field, and are display colored particles excluding white. The colored particles for display are, for example, positively or negatively charged, and move in the dispersion medium when an electric field equal to or higher than a predetermined electric field strength is formed. Further, the two or more kinds of display colored particles are particles having different colors and different charging characteristics. The difference in the charging characteristics indicates that the charging polarity or the charging amount of the particles is different, or that both the charging polarity and the charging amount are different.
The change in display color in the image display device is caused by the movement of the display colored particles in the dispersion medium.

-Composition of colored particles for display-
Examples of the colored particles for display include resin particles, those obtained by fixing a colorant on the surface of these resin particles, and particles containing a colorant in the resin. Other examples of the display colored particles include insulating metal oxide particles (for example, particles such as glass beads, alumina, and titanium oxide), metal colloid particles having a plasmon coloring function, and the like.

~resin~
Examples of the thermoplastic resin used for the colored particles for display include styrenes such as styrene and chlorostyrene; monoolefins such as ethylene, propylene, butylene, and isoprene; vinyl acetate, vinyl propionate, vinyl benzoate, and butyric acid. Vinyl esters such as vinyl; α- such as methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate Methylene aliphatic monocarboxylic acid esters; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl butyl ether; single weight of vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and vinyl isopropenyl ketone Body, or a resin consisting of a copolymer thereof.
Examples of the thermosetting resin used for the colored particles for display include cross-linked copolymers mainly composed of divinylbenzene and cross-linked resins such as cross-linked polymethyl methacrylate, phenol resins, urea resins, melamine resins, polyester resins, and silicones. Examples thereof include resins.

  Typical resins used for display colored particles include, for example, polystyrene resins, styrene-alkyl acrylate copolymers, styrene-alkyl methacrylate copolymers, styrene-acrylonitrile copolymers, and styrene-butadiene copolymers. Styrene-maleic anhydride copolymer, polyethylene resin, polypropylene resin, polyester resin, polyurethane resin, epoxy resin, silicone resin, polyamide resin, modified rosin, paraffin wax and the like.

In particular, as the resin used for the colored particles for display, a resin having a charging group (hereinafter referred to as “polymer having a charging group”) is preferably used in order to give the particles electrification.
The polymer having a charged group is, for example, a polymer having a cationic group or an anionic group. Examples of the cationic group as the charged group include an amine group and a quaternary ammonium group (including salts of these groups), and positively charged polarity is imparted to the particles by the cationic group. On the other hand, examples of the anionic group as a charging group include a carboxyl group, a carboxylate group, a sulfonate group, a sulfonate group, a phosphate group, and a phosphate group. Polarity is imparted.

  Specific examples of the polymer having a charging group include, for example, a homopolymer of a monomer having a charging group, a monomer having a charging group, and another monomer (a monomer having no charging group). And a copolymer.

  Examples of the monomer having a charging group include a monomer having a cationic group (hereinafter referred to as a cationic monomer) and a monomer having an anionic group (hereinafter referred to as an anionic monomer). .

  Examples of the cationic monomer include the following. Specifically, N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dibutylaminoethyl (meth) acrylate, N, N-hydroxyethylaminoethyl (meta) ) Acrylate, N-ethylaminoethyl (meth) acrylate, N-octyl-N-ethylaminoethyl (meth) acrylate, N, N-dihexylaminoethyl (meth) acrylate and other aliphatic amino groups (meth) Acrylates; N-methylacrylamide, N-octylacrylamide, N-phenylmethylacrylamide, N-cyclohexylacrylamide, N-phenylacrylamide, Np-methoxy-phenylacrylamide, N, N-dimethylacrylamide, N, N- Dibutyla (Meth) acrylamides such as chloramide and N-methyl-N-phenylacrylamide; aromatic substituted ethylene monomers having a nitrogen-containing group such as dimethylaminostyrene, diethylaminostyrene, dimethylaminomethylstyrene and dioctylaminostyrene Vinyl-N-ethyl-N-phenylaminoethyl ether, vinyl-N-butyl-N-phenylaminoethyl ether, triethanolamine divinyl ether, vinyl diphenylaminoethyl ether, N-vinylhydroxyethylbenzamide, m-amino Nitrogen-containing vinyl ether monomers such as phenyl vinyl ether; and the like.

  Preferred examples of the cationic monomer include nitrogen-containing heterocyclic compounds, among which pyrroles such as N-vinylpyrrole; N-vinyl-2-pyrroline, N-vinyl-3-pyrroline, etc. Pyrrolines; pyrrolidines such as N-vinylpyrrolidine, vinylpyrrolidine aminoether, N-vinyl-2-pyrrolidone; imidazoles such as N-vinyl-2-methylimidazole; imidazolines such as N-vinylimidazoline Indoles such as N-vinylindole; indolines such as N-vinylindoline; carbazoles such as N-vinylcarbazole and 3,6-dibromo-N-vinylcarbazole; 2-vinylpyridine, 4- Pyridines such as vinylpyridine and 2-methyl-5-vinylpyrazine; (meth) acrylic piperidine, N- Piperidines such as vinylpiperidone and N-vinylpiperazine, quinolines such as 2-vinylquinoline and 4-vinylquinoline; pyrazoles such as N-vinylpyrazole and N-vinylpyrazoline, oxazoles such as 2-vinyloxazole; 4 -Oxazines such as vinyl oxazine and morpholinoethyl (meth) acrylate;

On the other hand, examples of the anionic monomer include a carboxylic acid monomer, a sulfonic acid monomer, and a phosphoric acid monomer.
Examples of the carboxylic acid monomer include (meth) acrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, anhydrides thereof, monoalkyl esters thereof, carboxyethyl vinyl ether, and carboxypropyl vinyl ether. Examples thereof include vinyl ethers having a carboxyl group and salts thereof.
Examples of the sulfonic acid monomer include styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 3-sulfopropyl (meth) acyclic acid ester, bis- (3-sulfopropyl) -itaconic acid ester, and the like. The salt is mentioned. Moreover, as a sulfonic acid monomer, the sulfuric monoester of 2-hydroxyethyl (meth) acrylic acid and its salt are also mentioned.
Examples of phosphoric acid monomers include vinylphosphonic acid, vinyl phosphate, acid phosphoxyethyl (meth) acrylate, acid phosphoxypropyl (meth) acrylate, bis (methacryloxyethyl) phosphate, diphenyl-2-methacryloyloxyethyl phosphate, diphenyl Examples include 2-acryloyloxyethyl phosphate, dibutyl-2-methacryloyloxyethyl phosphate, dibutyl-2-acryloyloxyethyl phosphate, dioctyl-2- (meth) acryloyloxyethyl phosphate, and the like.

Examples of other monomers include water-soluble monomers (for example, monomers having a hydroxyl group). Specific examples include hydroxyethyl (meth) acrylate and hydroxybutyl (meth) acrylate. , Monomers having ethylene oxide units (for example, (meth) acrylates of alkyloxyoligoethylene glycol such as tetraethylene glycol monomethyl ether (meth) acrylate, (meth) acrylates of one end of polyethylene glycol), (meth) acrylic acid and salts thereof , Maleic acid, (meth) acrylamide-2-methylpropanesulfonic acid and its salt, vinylsulfonic acid and its salt. Examples include vinyl pyrrolidone.
Examples of other monomers include other well-known nonionic monomers.

  “(Meth) acryl” is a notation for both “acryl and methacryl”. “(Meth) acrylo” is a notation for both “acrylo and methacrylo”, and “(meth) acrylate” is a notation for both “acrylate and methacrylate”.

~ Colorant ~
Examples of the colorant used for the display colored particles include organic or inorganic pigments and oil-soluble dyes.
Examples of the colorant include magnetic powder such as magnetite and ferrite, carbon black, titanium oxide, magnesium oxide, zinc oxide, phthalocyanine copper-based cyan color material, azo-based yellow color material, azo-based magenta color material, and quinacridone-based magenta color. Known colorants such as materials, red color materials, green color materials, and blue color materials can be used.
Specific examples of the colorant include aniline blue, calcoyl 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 122C. I. Pigment red 57: 1, C.I. I. Pigment yellow 97, C.I. Blue 15: 1, C.I. I. Pigment Blue 15: 3 is a typical example.

  As content of a coloring agent, 10 mass% or more and 99 mass% or less are good with respect to resin which comprises the colored particle for a display, for example, Preferably they are 30 mass% or more and 99 mass% or less.

~ Other ingredients ~
The colored particles for display may contain a charge control agent as required. Examples of the charge control agent include known ones used for toner materials for electrophotography. For example, cetylpyridyl chloride, BONTRON P-51, BONTRON P-53, BONTRONE-84, BONTRON E-81 (orientated above) Quaternary ammonium salts such as those manufactured by Chemical Industry Co., Ltd., salicylic acid metal complexes, phenol condensates, tetraphenyl compounds, metal oxide particles, and metal oxide particles surface-treated with various coupling agents.

If necessary, an external additive may be attached to the surface of the display colored particles. The color of the external additive is preferably transparent so as not to affect the color of the colored particles for display.
Examples of the external additive include inorganic particles such as metal oxides such as silicon oxide (silica), titanium oxide, and alumina. The external additives may be surface-treated with a coupling agent or silicone oil in order to adjust the chargeability, fluidity, environment dependency, etc. of the colored particles for display.
Coupling agents include aminosilane coupling agents, aminotitanium coupling agents, nitrile coupling agents and other positively chargeable ones, and silanes that do not contain nitrogen atoms (consisting of atoms other than nitrogen). Examples include negatively chargeable ones such as coupling agents, titanium-based coupling agents, epoxy silane coupling agents, and acrylic silane coupling agents.
Silicone oils include positively chargeable ones such as amino-modified silicone oils, dimethyl silicone oils, alkyl-modified silicone oils, α-methylsulfone-modified silicone oils, methylphenyl silicone oils, chlorophenyl silicone oils, fluorine-modified silicone oils, etc. Negatively chargeable ones.
These coupling agents and silicone oils are selected according to the desired resistance of the external additive.

  The primary particles of the external additive are, for example, preferably from 1 nm to 100 nm, and preferably from 5 nm to 50 nm, but are not limited thereto.

The external addition amount of the external additive is, for example, preferably 0.01 parts by mass or more and 3 parts by mass or less, and preferably 0.05 parts by mass or more and 1 part by mass or less with respect to 100 parts by mass of the display colored particles. It is.
The external addition amount of the external additive is preferably adjusted based on the balance between the particle diameter of the colored particles for display and the particle diameter of the external additive. When the amount of the external additive is within the above range, at least a part of the external additive is released from the surface of the display colored particles, and this adheres to the surface of the other display colored particles, so that desired charging characteristics are obtained. This is advantageous in that it is easily prevented from being obtained.

  The external additive may be added to any one of a plurality of types of display coloring particles, or may be externally added to a plurality of types or all types of display coloring particles. When an external additive is added to the surface of all display colored particles, the external additive is applied to the surface of the display colored particle with an impact force, or the surface of the display colored particle is heated to color the external additive for display. It is preferable to firmly adhere to the particle surface. Thereby, the external additive is released from the colored particles for display, and the external additive of different polarity is firmly aggregated to prevent formation of an aggregate of the external additive that is difficult to dissociate with an electric field, As a result, it is advantageous in that image quality deterioration is easily prevented.

-Characteristics of colored particles for display-
The volume average particle diameter of the colored particles for display is, for example, preferably from 0.05 μm to 20 μm, and preferably from 0.1 μm to 1 μm. In addition, the magnitude | size of the colored particle for a display does not have a restriction | limiting in particular, A preferable range can be determined according to a use.

The concentration of the colored particles for display is not particularly limited as long as a desired display color can be obtained. For example, the concentration is preferably 0.01% by mass or more and 50% by mass or less.
The concentration of the colored particles for display is preferably within the above range as the concentration in the display particle dispersion in a state of being enclosed between a pair of substrates of the image display device. It is also effective to adjust the concentration of the display colored particles by the distance between the pair of substrates of the image display device. In order to obtain a desired hue, the particle concentration decreases as the distance between the pair of substrates of the image display device increases, and the particle concentration increases as the distance decreases.

-Manufacturing method of colored particles for display-
As a method for producing the colored particles for display, any conventionally known method may be used. Specifically, the method shown below is mentioned, for example.
1) As described in JP-A-7-325434, the resin, the pigment and, if necessary, the charge control agent are weighed to the desired mixing ratio, the resin is heated and melted, and then the pigment is added and mixed A method for producing colored particles for display by using a pulverizer such as a jet mill, a hammer mill, or a turbo mill after being dispersed and cooled.
2) A method for producing colored particles for display by polymerization methods such as suspension polymerization, emulsion polymerization, and dispersion polymerization, coacervation, melt dispersion, and emulsion aggregation methods.
3) When the resin has plasticity, the dispersion medium does not boil, and the resin, the colorant, and the dispersion are at a temperature lower than the decomposition point of at least one of the resin, the colorant, and if necessary, the charge control agent. A method for producing particles by dispersing and kneading the medium and, if necessary, the raw material of the charge control agent (specifically, the colored particles for display include, for example, a resin, a colorant, a meteor mixer, a kneader, etc. If necessary, the charge control agent is heated and melted in a dispersion medium, and the temperature dependence of the solvent solubility of the resin is used to cool the molten mixture with stirring, to solidify / precipitate, and to give colored particles for display. Manufacturing method).
4) 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 ° C. A method of producing particles by dispersing and kneading at 160 ° C. or lower.
As the granular media, for example, steel such as stainless steel and carbon steel, alumina, zirconia, silica and the like are desirably used. In order to produce colored particles for display by a method using granular media, the raw material previously fluidized is further dispersed in the container by granular media, and then the dispersion medium is cooled to contain the colorant from the dispersion medium. It is better to precipitate the resin. It is preferable that the granular media generate shear and / or impact while maintaining the motion state during and after cooling, and reduce the particle size of the resulting colored particles for display.

(White particles for display)
The white particles for display are particles satisfying the formula (1), the white display reflectance is high, and from the viewpoint of suppressing the precipitation of the white particles for display, the formula (1-2) is preferable, and more preferably ( It is a particle satisfying 1-3).

Formula (1) 400 ≧ 6 kT / (πd ³ (ρp−ρs) g) ≧ 30
Formula (1-2) 200 ≧ 6 kT / (πd ³ (ρp−ρs) g) ≧ 40
Formula (1-3) 100 ≧ 6 kT / (πd ³ (ρp−ρs) g) ≧ 40
(In the formulas (1) to (1-3), k represents a Boltzmann coefficient (J · K ⁻¹ ), T represents an absolute temperature 298 (K), and d represents a volume average particle diameter of white particles for display ( .ρp showing a nm) is .ρs showing a specific gravity (g / cm ³⁾ of the display white particles exhibit specific gravity of the dispersion medium (g / cm ³⁾ shows the .g is a gravitational acceleration (m / ^{s 2).} )

In the formula (1), when “6 kT / (πd ³ (ρp−ρs) g)” is set to 30 or more, the settling of the white particles for display can be suppressed. On the other hand, when set to 400 or less, the settling of the display white particles is suppressed. Meanwhile, the white reflectance of the display white particles can be increased.

  In order to satisfy the formula (1) for the display white particles, for example, the volume average particle diameter of the display white particles, the specific gravity of the display white particles (that is, the white pigment and the resin constituting the particles), This is realized by adjusting the specific gravity of the dispersion medium.

-Composition of white particles for display-
The display white particles include a white pigment and a resin. Specifically, the display white particles have a configuration in which the surface of the pigment is coated with a resin, for example.

  There is no restriction | limiting in particular as resin, For example, resin used by the colored particle for a display is mentioned. However, in order to make the moving speed of the display white particles sufficiently slow or not to move substantially in response to the electric field, it is preferable to use a resin with a reduced amount of charged groups.

Examples of the white pigment include arbitrary white pigments such as zinc oxide, basic lead carbonate, basic lead sulfate, ritbon, zinc sulfide, titanium oxide, zirconia oxide, antimony oxide, and barium sulfate.
Among these, as the white pigment, titanium oxide and zirconia oxide are preferable, and titanium oxide is most preferable from the viewpoint of achieving both high reflectance of display white particles and suppression of sedimentation.
Here, the titanium oxide particles may be latent images formed by any method such as a sulfuric acid method, a chlorine method, and a gas phase method. The crystal system of titanium oxide may be an anatase type, a rutile type, or a pulgite type crystal system, but the rutile type is preferred. The titanium oxide particles preferably contain aluminum oxide, aluminum hydroxide, silicon oxide or the like from the viewpoint of suppressing photocatalytic properties.

The volume average particle diameter of the white pigment is, for example, preferably from 1 nm to 500 nm, preferably from 10 nm to 200 nm, and more preferably from 20 nm to 150 nm.
When the volume average particle diameter of the white pigment is in the above range, it is advantageous in that sedimentation is easily suppressed while increasing the white reflectance of the white particles for display.

The content of white pigment (mass of white pigment / (total mass of white pigment and resin)) is 30% by mass to 90% by mass, preferably 40% by mass to 70% by mass, and more preferably 40% by mass to 60% by mass. The mass% or less is more preferable.
The white reflectance of the white particles for display can be increased by setting the content of the white pigment to 30% by mass or more, while the white reflectance of the white particles for display is increased by setting the content to 90% by mass or less. However, sedimentation is suppressed.

-Characteristics of white particles for display-
The volume average particle diameter of the display white particles is 100 nm or more and 500 nm or less, and preferably 150 nm or more and 300 nm or less.
By setting the volume average particle size of the white particles for display to 100 nm or more, the white reflectance of the white particles for display can be increased. On the other hand, by setting the volume average particle size to 500 nm or less, the white reflectance of the white particles for display is increased. However, sedimentation is suppressed.

Specific gravity of the display white particles, for example, well, is preferably from 2.4 g / cm ³ or more 3.6 g / cm ³ or less 2.1 g / cm ³ or more 4.3 g / cm ^3, 2.4 g / Cm ³ or more and 3.3 g / cm ³ or less is more preferable.
Setting the specific gravity of the display white particles in the above range is advantageous in that the white reflectance of the display white particles is increased and sedimentation is easily suppressed.

From the viewpoint of obtaining a good display contrast due to the colored particles for display, the white particles for display have a charge characteristic of opposite polarity to that of the colored particles for display, or have a low charge amount and display a moving speed that moves according to electrolysis. It is preferable that the particles be sufficiently lower than the colored particles for display, and in particular, the particles should not substantially move in response to the electric field. Specifically, the white particles for display have an electric field with the colored particles for display. The moving speed ratio (moving speed Vw of display white particles / moving speed Vc of colored particles for display) is preferably 0.2 or less, preferably 0.1 or less, more preferably 0. .05 or less.
When the moving speed ratio is in the above range, it is advantageous in that a good display contrast due to the colored particles for display is easily realized. Further, it is advantageous in that a decrease in display response due to the movement of the display colored particles being hindered by the movement of the display white particles is easily suppressed.
In addition, the moving speed of each particle | grain is the value measured by the method measured using the cell for a measurement mentioned later.

  Note that the moving speed ratio of the white particles for display and the colored particles for display moving according to the electric field is the same as the moving speed of the white particles for display and the display for both particles dispersed in the display particle dispersion. It is a ratio with the moving speed of the particles having the slowest moving speed among the colored particles.

The concentration of the white particles for display (concentration in the display particle dispersion in a state enclosed between a pair of substrates of the image display device) is preferably, for example, 1% by volume to 50% by volume, and preferably Is 2% by volume or more and 30% by volume or less.
When the concentration of the white particles for display is within the above range, the increase in the viscosity of the dispersion medium due to the dispersion of the white particles for display is suppressed while increasing the reflectance of white display, and the decrease in display responsiveness due to the colored particles for display is easily suppressed. This is advantageous.
The concentration of the white particles for display is preferably in the above range as the concentration in the display particle dispersion in a state of being enclosed between a pair of substrates of the image display device. It is also effective to adjust the concentration of the display white particles by the distance between the pair of substrates of the image display device. In order to obtain a desired hue, the particle concentration decreases as the distance between the pair of substrates of the image display device increases, and the particle concentration increases as the distance decreases.

-Manufacturing method of white particles for display-
The display white particles can be produced by a method similar to the production method of the display colored particles.

(Dispersion medium)
The dispersion medium is preferably an insulating liquid. Here, “insulating” indicates that the volume resistivity value is 10 ¹¹ Ωcm or more.
Specific examples of the insulating liquid include hexane, cyclohexane, toluene, xylene, decane, hexadecane, kerosene, paraffin, isoparaffin, silicone oil, high-purity petroleum, ethylene glycol, alcohols, ethers, esters, dimethylformamide. , Dimethylacetamide, dimethylsulfoxide, 1-methyl-2-pyrrolidone, N-methylformamide, acetonitrile, tetrahydrofuran, propylene carbonate, ethylene carbonate, benzine, diisopropylnaphthalene, olive oil, trichlorotrifluoroethane, tetrachloroethane, dibromotetrafluoroethane, etc. Moreover, a mixture thereof is preferably mentioned.

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

-Additive of dispersion medium-
If necessary, the dispersion medium may contain acid, alkali, salt, dispersion stabilizer, stabilizer for anti-oxidation, ultraviolet absorption, antibacterial agent, preservative, etc. It is preferable to add so that it may become the range of the specific volume specific resistance value.

For dispersion media, anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, fluorosurfactants, silicone surfactants, metal soaps, alkyl phosphates as charge control agents Esters and succinimides may be added and used.
Examples of these surfactants include the following.

-Nonionic surfactant-
-Polyoxyalkylene alkylphenol ethers such as polyoxyethylene nonylphenol ether and polyoxyethylene octylphenyl ether.
Polyoxyalkylene ethers such as polyoxyethylene cetyl ether and polyoxypropylene ether.
-Glycols such as monool type polyoxyalkylene glycol, diol type polyoxyalkylene glycol, and triol type polyoxyalkylene glycol.
-Alkyl alcohol ethers such as primary linear alcohol ethoxylates such as octylphenol ethoxylate and secondary linear alcohol ethoxylates.
Polyoxyalkylene alkyl esters such as polyoxyethylene lauryl ester.
Sorbitan fatty acid esters such as sorbitan monolaurate, sorbitan dilaurate and sorbitan sesquipalmitate.
-Polyoxyethylene sorbitan esters such as polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan dilaurate, polyoxyethylene sorbitan sesquilaurate, and the like.
Fatty acid esters such as saturated fatty acid stearyl ester, unsaturated fatty acid stearyl ester, and stearic acid polyethylene glycol ester.
-Fatty acids such as stearic acid and oleic acid, and amidated compounds of these fatty acids. Polyoxyethylene alkylamines, higher fatty acid monoethanolamides, higher fatty acid diethanolamides, amide compounds, and alkanolamides.

~ Anionic surfactant ~
-Carboxylic acid salts such as polycarboxylic acid type polymer activators and rosin soaps. Castor oil sulfate ester salt, sulfate ester salt of lauryl alcohol, sulfate ester amine salt of lauryl alcohol, sulfate sulfate amine salt of lauryl alcohol ether, sulfate ester amine salt of lauryl alcohol ether, lauryl alcohol ether Sulfate Na salt, sulfate amine salt of synthetic higher alcohol ether, sulfate ester Na salt of synthetic higher alcohol ether, alkyl polyether sulfate amine salt, alkyl polyether sulfate Na salt, natural alcohol EO (ethylene oxide) addition system sulfuric acid Ester amine salt, natural alcohol EO (ethylene oxide) addition system sulfate ester Na salt, synthetic alcohol EO (ethylene oxide) addition system sulfate ester amine salt, synthetic alcohol EO (ethylene oxide) addition system sulfate ester Na salt, alkylphenol EO (ethylene oxide) addition system sulfate ester amine salt, alkylphenol EO (ethylene oxide) addition system sulfate ester Na salt, polyoxyethylene nonylphenyl ether sulfate amine salt, polyoxyethylene Sulfate esters such as nonylphenyl ether sulfate Na salt, polyoxyethylene polycyclic phenyl ether sulfate amine salt, and polyoxyethylene polycyclic phenyl ether sulfate Na salt.
・ Various alkyl allyl sulfonic acid amine salts, various alkyl allyl sulfonic acid Na salts, naphthalene sulfonic acid amine salts, naphthalene sulfonic acid Na salts, various alkyl benzene sulfonic acid amine salts, various alkyl benzene sulfonic acid Na salts, naphthalene sulfonic acid condensates, naphthalene Sulfonic acid salts such as sulfonic acid formalin condensate.
Polyoxyalkylene sulfonates such as polyoxyethylene nonyl phenyl ether sulfonate amine salt and polyoxyethylene nonyl phenyl ether sulfonate sodium salt.

-Cationic surfactant-
-Alkyltrimethylamine-based quaternary ammonium salts. Quaternary ammonium salts such as tetramethylamine salts and tetrabutylamine salts. Acetates represented by (RNH ₃ ) (CH ₃ COO) [R = stearyl, cetyl, lauryl, oleyl, dodecyl, palm, soybean, beef tallow, etc.] Benzylamine quaternary ammonium salts such as lauryldimethylbenzylammonium salt (halogen / amine salt, etc.), stearyldimethylbenzylammonium salt (halogen / amine salt, etc.), dodecyldimethylbenzylammonium salt (halogen / amine salt, etc.).
・ R (CH ₃ ) N (C ₂ H ₄ O) _m H (C ₂ H ₄ O) _n × X [R = stearyl, cetyl, lauryl, oleyl, dodecyl, palm, soybean, beef tallow / X = halogen Polyoxyalkylene-based quaternary ammonium salts represented by amines and the like].

-Amphoteric surfactant-
-Various betaine surfactants.

The content of these charge control agents is, for example, preferably 0.01% by mass or more, preferably 20% by mass or less, more preferably 0.05% by mass or more and 10% by mass or less, based on the total solid content of the particles. It is.
When the content of the charge control agent is 0.01% by mass or more, it is advantageous in that the desired charge control effect is sufficiently exhibited, and when it is 20% by mass or less, an excessive increase in conductivity of the dispersion medium is achieved. Is advantageous in that it is easily suppressed.

  The dispersion medium may be added with a polymer. The polymer is preferably a polymer gel or a polymer.

-Dispersion medium characteristics-
The specific gravity of the dispersion medium, for example, in an environment of temperature 25 ℃, 0.6g / cm ³ or more 1.2 g / cm ³ or less is that good, 0.7 g / cm ³ or more 1.1 g / cm ³ or less Is preferable, and 0.7 g / cm ³ or more and 1.0 g / cm ³ or less is more preferable.
Setting the specific gravity of the display white particles in the above range is advantageous in that the precipitation of the display white particles is easily suppressed.

The viscosity of the dispersion medium is, for example, preferably from 0.1 mPa · s to 100 mPa · s, preferably from 0.1 mPa · s to 50 mPa · s in an environment of a temperature of 20 ° C. More preferably, it is s or more and 20 mPa · s or less.
In particular, the viscosity of the dispersion medium is preferably 5 mPa · s or less. When the viscosity of the dispersion medium is 5 mPa · s or less, the display responsiveness of the colored particles for display is improved, and even when the viscosity is 5 mPa · s or less, the white particles for display have the above characteristics, so that the sedimentation is suppressed. It is advantageous in that it becomes easy.
The viscosity of the dispersion medium can be adjusted, for example, by adjusting the molecular weight, structure, composition, etc. of the dispersion medium.

(Other aspects of particle dispersion for display)
The display dispersion of the present invention may be enclosed by a capsule wall. That is, the capsule particles may contain display white particles, display colored particles, and a dispersion medium.

As the main material constituting the capsule wall, gelatin, formalin resin and urethane resin can be preferably used, but gelatin is most preferable.
Gelatin includes so-called alkali-treated gelatin with treatment with lime in the process of induction from collagen, so-called acid-treated gelatin with treatment with hydrochloric acid, oxygen-treated gelatin with treatment with hydrolase, etc., contained in gelatin molecules Examples of treated and modified amino group, imino group, hydroxyl group or carboxyl group as a functional group with a reagent having one group capable of reacting with them, such as phthalated gelatin, succinylated gelatin, trimethrylated gelatin, etc. Examples of so-called gelatin derivatives and modified gelatin include those commonly used in the art described in JP-A-62-215272, page 222, lower left column, line 6 to page 225, upper left column.

Examples of the crosslinking agent used when a polymer electrolyte such as gelatin is used for the capsule wall include glyoxal, glutaraldehyde, succinaldehyde, and dicarboxylic acid (for example, oxalic acid, succinic acid, fumaric acid, maleic acid). , Malic acid, glutaric acid, adipic acid, 2,3-O-isopropylidene tartaric acid, etc.), diacid chlorides (eg succinyl chloride, fumaryl chloride, glutaryl chloride, adipoyl chloride etc.), tricarboxylic acids (eg Citric acid, 1,2,3-propanetricarboxylic acid, hemimellitic acid, trimellitic acid, trimesic acid and the like).
As the crosslinking agent, for example, JP 2005-522313 describes the use of a crosslinking reaction by an enzyme (such as transglutaminase), and an enzyme that causes such a crosslinking reaction is also mentioned.
Examples of the crosslinking agent include epoxy resins, 2-hydroxyalkylamides, tetramethoxymethyl glyceryl, polyaziridine, polycarbodiimide, isocyanates, blocked isocyanates, drying oils (described in JP 2009-531532 A). For example, triglycerides, glycerol epoxy esters, fatty acid triesters, etc.), aliphatic amines, phenols, polyisocyanates, amines, urea, carboxylic acids, alcohols, polyethers, urea formaldehyde, melamines, Examples include aldehydes and salts of polyvalent anions.
The crosslinking agent may be used in combination with a catalyst that promotes the crosslinking reaction. Examples of the catalyst include alcohols, phenols, weak acids, amines, metal salts, urethanes described in JP-T-2009-531532. Chelates, organometallic materials, photoinitiators, free radical initiators, onium salts of strong acids.

  Whether the crosslinking agent and / or the catalyst thereof are added to the aqueous phase and used or whether the crosslinking agent and / or its catalyst are added to the internal oil phase to cause the crosslinking reaction in the organic solvent can be appropriately selected.

  Here, examples of the emulsifying and dispersing apparatus used in the emulsifying and dispersing step for forming the capsule wall include ordinary emulsifying means such as a high-speed stirrer (dissolver), a homogenizer, and an in-line mixer, and in particular, a microreactor or a micromixer. Is preferably used.

  The normal emulsification means has a region where shear force necessary for emulsification is limited to the vicinity of the emulsifying blade, so the shearing force becomes uneven near the emulsifying blade, and the particle size distribution of the dispersed droplets There was a problem of widening. Ultrasonic dispersers are used in laboratories or small-scale industrial production scales, but in production systems that demand high productivity, there are issues in controlling production volume, cost, and particle size distribution. Remains.

  In this regard, Japanese Patent No. 2630501 discloses an emulsification method using a so-called cylindrical mill as an emulsification method for solving the problem of particle size distribution caused by using the emulsification means as described above. This emulsification method is an emulsification method in which an inner cylinder is rotated in a fixed outer cylinder, and an emulsion is obtained by passing a mixture of a dispersion medium and a dispersion into a gap between the inner cylinder and the outer cylinder. Is supplied from the side of one end of the outer cylinder from the tangential direction along the circumference so that a uniform shear force is applied over the length of the inner cylinder while the mixture moves while rotating through the gap between the inner and outer cylinders. And fully emulsified. According to this emulsification method, an emulsified liquid having an extremely narrow particle size distribution can be obtained, but the size of the droplet particle size obtained by this method depends on the size of the gap between the inner cylinder and the outer cylinder. It is difficult to obtain emulsified particles having a particle size below a certain limit, and the particle size of droplets obtained by this method is usually about 10 μm, and it is difficult to obtain droplets with a particle size of several μm or less. It is.

In contrast, so-called microreactors have been used in the fields of fine chemicals, biochemicals, etc., and have recently been greatly developed (W. Ehrfeld, V. Hessel, H. Lowe, " Microreactor ", 1Ed. (2000), WILEY-VCH).
A microreactor is a general term for reaction devices having a plurality of microscale flow paths (channels). For example, two types of liquids contact each other as extremely thin liquid films while passing through different flow paths. In the meantime, mass transfer takes place through the interface of the layers and a reaction takes place.
The microreactor is used not only for a chemical reaction but also for mixing or separating two or more liquids. In particular, a microreactor used for mixing is called a micromixer, which forms liquid films of different liquids to be mixed in a laminated structure, and mixes them by passing through narrow passages. An emulsified dispersion can be prepared by using an oil phase liquid and an aqueous phase liquid. WO 00/62913 proposes a disperser (micromixer) that performs dispersion using such a microreactor. This disperser is divided into spatially divided liquid layers (liquid films) by separately passing the liquid flows of liquid A and liquid B through micro-scale flow paths (channels), and then divided. In this method, the liquid A or the liquid B is dispersed into fine droplets by combining the liquid flow and passing through a narrow passage, and at that time, droplet formation is promoted using a mechanical oscillator.

  Techniques for producing capsule walls by emulsification and dispersion using a microreactor or micromixer having such a microchannel are described in detail in JP-A Nos. 2002-282678 and 2002-282679, and the present invention uses this technique. It is good to do.

[Image display device]
In the image display device according to the present embodiment, at least one of the pair of translucent substrates, the display particle dispersion encapsulated between the pair of substrates, and the display colored particles are moved between the pair of substrates. And an electric field generating means for applying an electric field having a strength to be generated.
The display particle dispersion according to the present embodiment is applied as the display particle dispersion.

The image display apparatus according to this embodiment will be described below with reference to the drawings.
FIG. 1 is a schematic configuration diagram illustrating an image display apparatus according to an embodiment of the present invention.
The image display device 10 according to the present embodiment uses the display particle dispersion according to the present embodiment as a particle dispersion including the colored particle group 34, the white particle group 36, and the dispersion medium 50 of the display medium 12. Is a form to apply. In other words, a group of display colored particles is applied as the colored particle group 34, and display white particles are applied as the white particle group 36.

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

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

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

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

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

  As materials for the front electrode 40 and the back electrode 46, 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. Is mentioned. The front electrode 40 and the back electrode 46 may be any of these single layer films, mixed films, or composite films, and are formed by, for example, vapor deposition, sputtering, coating, or the like.

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

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

In the above description, the case where both the display substrate 20 and the back substrate 22 are provided with the electrodes (the front electrode 40 and the back electrode 46) has been described.
In order to enable active matrix driving, the support substrate 38 and the support substrate 44 are provided with active elements such as TFT (Thin Film Transistor), TFD (Thin Film Diode), MIM (Metal-Insulator-Metal) element, and varistor for each pixel. May be provided. The active elements are preferably formed not on the display substrate 20 but on the back substrate 22 because wiring can be easily stacked and components can be easily mounted.

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

  Materials for the surface layer 42 and the surface layer 48 include polyolefins such as polyethylene and polypropylene, polycarbonate, polyester, polystyrene, polyimide, polyurethane, polyamide, polymethyl methacrylate, copolymer nylon, epoxy resin, ultraviolet curable acrylic resin, and silicone resin. And fluororesin.

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

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

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

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

  In the polymer compound having a silicone chain, as a monomer constituting the structural unit (A), specifically, for example, a dimethyl silicone monomer having a (meth) acrylate group at one end (for example, manufactured by Chisso: Sila) Plane: FM-0711, FM-0721, FM-0725, etc., Shin-Etsu Chemical Co., Ltd .: X-22-174DX, X-22-2426, X-22-2475, etc.). Among these, silaplane: FM-0711, FM-0721, FM-0725, etc. are preferable.

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

  The polymer compound having a silicone chain may contain a crosslinking unit in addition to the structural units (A) and (B). As the crosslinking unit, for example, a monomer containing an epoxy group, an oxazoline group, an isocyanate group, or the like can be used.

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

  The thickness of the surface layer (surface layer 42, surface layer 48, and surface layer 25) composed of a polymer compound having a silicone chain is, for example, preferably 0.001 μm to 10 μm, and preferably 0.01 μm to 1 μm. is there.

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

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

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

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

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

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

  In the present embodiment, as the colored particle group 34 enclosed in the same cell of the display medium 12, as shown in FIG. 1, a magenta magenta particle group 34M, a cyan cyan particle group 34C, and The description will be made assuming that the three colored particles 34 of the yellow yellow particle group 34Y are enclosed.

  The magenta magenta particle group 34M, the cyan cyan particle group 34C, and the yellow color yellow particle group 34Y are used as the absolute value of the voltage when the three color particle groups start moving. It is assumed that 34M is | Vtm |, the cyan cyan particle group 34C is | Vtc |, and the yellow yellow particle group 34Y is | Vty |. Further, the maximum voltage for moving almost all of the three color particle groups of the magenta particle group 34M, the cyan cyan particle group 34C, and the yellow yellow particle group 34Y of the colored particle group 34 of each color is set. As absolute values, it is assumed that the magenta magenta particle group 34M is | Vdm |, the cyan cyan particle group 34C is | Vdc |, and the yellow yellow particle group 34Y is | Vdy |.

The absolute values of Vtc, -Vtc, Vdc, -Vdc, Vtm, -Vtm, Vdm, -Vdm, Vty, -Vty, Vdy, and -Vdy described below are | Vtc | <| Vdc | <| Vtm | In the following description, it is assumed that the relationship is <| Vdm | <| Vty | <| Vdy |.
Specifically, as shown in FIG. 2, for example, all the colored particle groups 34 are charged to the same polarity, and the absolute value of the voltage range necessary to move the cyan particle group 34C | Vtc ≦ Vc ≦ Vdc | ( Absolute value of a value between Vtc and Vdc), absolute value of voltage range necessary to move the magenta particle group 34M | Vtm ≦ Vm ≦ Vdm | (absolute value of a value between Vtm and Vdm), and yellow The absolute value of the voltage range necessary to move the particle group 34M | Vty ≦ Vy ≦ Vdy | (the absolute value of the value between Vty and Vdy) is set so as to increase without overlapping in this order. ing.

  Further, in order to independently drive the colored particle groups 34 of the respective colors, the absolute value | Vdc | of the maximum voltage for moving almost all of the cyan particle groups 34M is within the voltage range necessary for moving the magenta particle group 34M. Absolute value | Vtm ≦ Vm ≦ Vdm | (absolute value between Vtm and Vdm), and absolute value of voltage range necessary to move yellow particle group 34M | Vty ≦ Vy ≦ Vdy | (Vty to Vdy) Is set to be smaller than the absolute value). Further, the absolute value | Vdm | of the maximum voltage for moving almost all of the magenta particle group 34M is equal to the absolute value | Vty ≦ Vy ≦ Vdy | (Vty to Vdy) of the voltage range necessary for moving the yellow particle group 34M. Is set to be smaller than the absolute value).

That is, in this embodiment, the color particle groups 34 of each color are driven independently by setting the voltage ranges necessary for moving the color particle groups 34 of each color so as not to overlap.
The “voltage range necessary for moving the colored particle group 34” means the voltage necessary for the particle to start moving and the change in display density even if the voltage and voltage application time are further increased from the start of movement. Indicates a voltage range until the display density is saturated.
The “maximum voltage necessary for moving almost all the colored particle groups 34” means that even if the voltage and voltage application time are further increased from the start of the above movement, the display density does not change and the display density is saturated. Indicates the voltage to be used.

  Further, “almost all” means that the characteristics of some of the colored particle groups 34 are different so that the characteristics of some of the colored particle groups 34 do not contribute to the display characteristics. That is, even if the voltage and the voltage application time are further increased from the start of the movement described above, the display density does not change and the display density is saturated.

In addition, “display density” is measured between the display surface side and the back side while measuring the color density on the display surface side with a reflection densitometer of optical density (Optical Density = 0D) of X-rite. Apply a voltage and gradually change this voltage in the direction of increasing the measured concentration (increase or decrease the applied voltage) to saturate the concentration change per unit voltage, and in that state, adjust the voltage and voltage application time. Even when the density is increased, the density does not change, and the density is shown when the density is saturated.
In the display medium 12 according to this embodiment, the voltage applied between the substrates is gradually increased by applying a voltage from 0 V between the front substrate 20 and the rear substrate 22 to increase the voltage value of the applied voltage. When the value exceeds + Vtc, the display density starts to change due to the movement of the cyan particle group 34C in the display medium 12. Further, when the voltage value is increased and the voltage applied between the substrates becomes + Vdc, the change in display density due to the movement of the cyan particle group 34 in the display medium 12 stops.

  Further, when the voltage value is increased and the voltage applied between the front substrate 20 and the rear substrate 22 exceeds + Vtm, a change in display density due to the movement of the magenta particle group 34M starts to appear in the display medium 12. When the voltage value is further increased and the voltage applied between the front substrate 20 and the rear substrate 22 becomes + Vdm, the change in display density due to the movement of the magenta particle group 34M in the display medium 12 stops.

Further, when the voltage value is increased and the voltage applied between the substrates exceeds + Vty, a change in display density due to the movement of the yellow particle group 34Y starts to appear in the display medium 12. When the voltage value is further increased and the voltage applied between the substrates becomes + Vdy, the change in display density due to the movement of the yellow particle group 34Y in the display medium 12 stops.
On the other hand, if the negative electrode voltage is applied from 0 V to the substrate between the front substrate 20 and the rear substrate 22 to gradually increase the absolute value of the voltage, and the absolute value of the voltage −Vtc applied between the substrates is exceeded. In the display medium 12, the display density starts to change due to the movement of the yellow particle group 34C between the substrates. Further, when the absolute value of the voltage value is increased and the voltage applied between the front substrate 20 and the rear substrate 22 becomes −Vdc or more, the display density changes due to the movement of the cyan particle group 34C in the display medium 12. Stop.

  Further, when the negative voltage is applied by increasing the absolute value of the voltage value and the voltage applied between the front substrate 20 and the rear substrate 22 exceeds the absolute value of −Vtm, the display medium 12 displays magenta. A change in display density due to the movement of the particle group 34M begins to appear. When the absolute value of the voltage value is further increased and the voltage applied between the front substrate 20 and the rear substrate 22 becomes −Vdm, the change in display density due to the movement of the magenta particle group 34M in the display medium 12 stops. .

  Further, when the negative voltage is applied by increasing the absolute value of the voltage value, and the voltage applied between the front substrate 20 and the rear substrate 22 exceeds the absolute value of −Vty, the display medium 12 displays yellow. Changes in the display density begin to appear due to the movement of the particle group 34Y. When the absolute value of the voltage value is further increased and the voltage applied between the substrates becomes −Vdy, the change in display density due to the movement of the yellow particle group 34 </ b> C in the display medium 12 stops.

  That is, in the present embodiment, as shown in FIG. 2, the voltage applied between the substrates is in the range of −Vtc to Vtc (voltage range | Vtc | or less). Are applied between the substrates, the movement of the particles of the colored particle group 34 (the cyan particle group 34C, the magenta particle group 34M, and the yellow particle group 34Y) to the extent that the display density of the display medium 12 changes. Is not occurring. When a voltage equal to or higher than the absolute value of the voltage + Vtc and the voltage −Vtc is applied between the substrates, a change occurs in the display density of the display medium 12 for the cyan particle group 34 </ b> C among the three color particle groups 34. The display density starts to change for a certain degree of particle movement, and when a voltage equal to or higher than the absolute value | Vdc | of the voltage −Vdc and the voltage Vdc is applied, the display density per unit voltage does not change.

  Further, when a voltage is applied between the front substrate 20 and the rear substrate 22 such that the voltage applied between the substrates is in the range of −Vtm to Vtm (voltage range | Vtm | or less), It can be said that the movement of the particles of the magenta particle group 34M and the yellow particle group 34Y to the extent that the display density of the display medium 12 changes does not occur. When a voltage higher than the absolute value of the voltage + Vtm and the voltage −Vtm is applied between the substrates, the display density of the display medium 12 is changed for the magenta particle group 34M and the magenta particle group 34M of the yellow particle group 34Y. The display density per unit voltage starts to change to the extent that particles are generated, and when the voltage −Vdm and voltage Vdm absolute value | Vdm | or more are applied, the display density changes. Disappear.

  Further, when a voltage is applied between the front substrate 20 and the rear substrate 22 so that the voltage applied between the substrates is within a range of −Vty to Vty (voltage range | Vty | or less), the display is performed. It can be said that the movement of the particles of the yellow particle group 34Y to the extent that the display density of the medium 12 changes does not occur. When a voltage higher than the absolute value of the voltage + Vty and the voltage −Vty is applied between the substrates, the yellow particle group 34Y starts to move and display a particle that causes a change in the display density of the display medium 12. When the density starts to change and a voltage equal to or higher than the absolute value | Vdy | of the voltage −Vdy and the voltage Vdy is applied, the display density does not change.

  Next, a driving method for displaying an image on the display medium 12 in the image display apparatus 10 according to the present embodiment will be described with reference to FIG.

  First, a voltage −Vdy is applied between the display substrate 20 and the back substrate 22. Thereby, all of the magenta particle group 34M, the cyan particle group 34C, and the yellow particle group 34Y are positioned on the back substrate 22 side (see FIG. 3A).

  Next, it is selected whether the yellow particle group 34Y having the highest movement start voltage is moved or left as it is. When the voltage + Vdy is applied, all of the magenta particle group 34M, the cyan particle group 34C, and the yellow particle group 34Y move to the display substrate 20 side and display black (K) (see FIG. 3B). On the other hand, when the voltage + Vty is applied, the magenta particle group 34M and the cyan particle group 34C move to the display substrate 20 side, but the yellow particle group 34Y remains as it is and is displayed in blue (B) (FIG. 3C )reference). When the voltage is greater than or equal to + Vty and less than or equal to + Vdy, a part of the yellow particle group 34Y moves, so that a halftone can be obtained.

  Next, it is selected whether the magenta particle group 34M having the second highest movement start voltage is moved or left as it is. When the voltage −Vdm is applied, the magenta particle group 34M moves to the back substrate 22 side, while when the voltage −Vtm is applied, the magenta particle group 34M remains on the display substrate 20 side. The cyan particles 34C whose movement start voltage is lower than the magenta particles 34M move to the back substrate 22 side in any case. On the other hand, the yellow particles 34Y whose movement start voltage is higher than the magenta particles 34M maintain the previous state in any case. When the voltage is −Vtm or more and −Vdm or less, a part of the magenta particle group 34M moves, so that a halftone can be obtained.

Therefore, when the voltage −Vdm is applied in the state of FIG. 3B, the yellow particles 34Y remain on the display substrate 20 side, and the magenta particles 34M and the cyan particles 34C move to the back electrode 22 side. As yellow (Y) display (see FIG. 3D).
When the voltage −Vtm is applied in the state of FIG. 3B, the yellow particles 34Y and the magenta particles 34M remain on the display substrate 20 side, and the cyan particles 34C move to the back electrode 22 side, resulting in red (R) is displayed (see FIG. 3E).
When the voltage −Vdm is applied in the state of FIG. 3C, the yellow particles 34Y remain on the back substrate 22 side, and the magenta particles 34M and cyan particles 34C move to the back electrode 22 side, resulting in white (W) is displayed (see FIG. 3F).
When the voltage −Vtm is applied in the state of FIG. 3C, the yellow particles 34Y remain on the back substrate 22 side, the magenta particles 34M remain on the display substrate 20 side, and the cyan particles 34C remain on the back electrode. As a result, the display is changed to magenta (M) (see FIG. 3G).

  Finally, it is selected whether the cyan particle 34C having the lowest movement start voltage is moved or left as it is. When the voltage + Vdc is applied, the cyan particle group 34C moves to the display substrate 20 side. On the other hand, when the voltage Vtc is applied, the cyan particle group 34C remains on the back substrate 22 side. The magenta particles 34M and the yellow particles 34Y whose movement start voltage is higher than that of the cyan particle group 34C maintain the previous state in any case. Therefore, when the voltage Vtc is applied, the previous display color is maintained. When the voltage is greater than or equal to + Vtc and less than or equal to + Vdc, part of the cyan particle group 34C moves, so that a halftone can be obtained.

Therefore, when the voltage Vdc is applied in the state of FIG. 3D, the cyan particle group 34C moves to the display substrate 20 side, the yellow particles 34Y move to the display substrate 20 side, and the magenta particles 34M move to the back electrode 22 side. As a result, green (G) is displayed (see FIG. 3H).
When the voltage Vdc is applied in the state of FIG. 3E, the cyan particle group 34C moves to the display substrate 20 side, and the yellow particles 34Y and the magenta particles 34M remain on the display substrate 20 side, resulting in black ( K) is displayed (see FIG. 3I).
When the voltage Vdc is applied in the state of FIG. 3F, the cyan particle group 34C moves to the display substrate 20 side, and the yellow particles 34Y remain on the magenta particle 34M back electrode 22 side, resulting in cyan ( C) Display is made (see FIG. 3J).
When the voltage Vdc is applied in the state of FIG. 3G, the cyan particle group 34C moves to the display substrate 20 side, the yellow particles 34Y remain on the back electrode 22 side, and the magenta particles 34M remain on the display substrate 20 side. As a result, blue (B) display is obtained (see FIG. 3K).

  In this way, any color display can be performed by selectively moving desired particles by applying a voltage corresponding to the particle group between the substrates in order from each colored particle group 34 having a high movement start voltage. It becomes.

[Electronic devices equipped with image display devices]
The image display device of the present invention is provided in electronic devices, exhibition media, card media, and the like.
Specifically, the image display device of the present invention includes, for example, an electronic bulletin board capable of storing and rewriting images, an electronic circulation version, an electronic blackboard, an electronic advertisement, an electronic signboard, a flashing sign, electronic paper, an electronic newspaper, and an electronic book. Electronic document sheets that can be shared with copiers and printers, portable computers, tablet computers, mobile phones, smart cards, signature devices, watches, shelf labels, flash drives, etc.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.
In addition, each measuring method in a present Example is as follows.

[Measuring method]
(Measurement of volume average particle diameter of particles)
The volume average 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 (sodium alkylbenzenesulfonate) as a dispersant, and this is added to 100 to 150 ml of an 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 particle size.

(Measurement of pigment content of particles)
Pigment content from (wa-wb / wa) × 100, where wa is the mass after the particle dispersion is dried at 120 ° C. for 1.5 hours, and wb is the mass after burning at 550 ° C. for 1 hour. Asked.

(Measurement of specific gravity of particles)
The specific gravity of the particles was calculated from the content of the pigment contained therein, the specific gravity of the pigment, and the specific gravity of the resin.
The specific gravity of the pigment and resin was measured according to JIS Z8807.

(Measurement of specific gravity of dispersion medium)
The specific gravity of the dispersion medium was measured according to JIS Z8804.

(Measurement of viscosity of dispersion medium)
The viscosity of the dispersion medium was measured using a B-8L viscometer manufactured by Tokyo Keiki (measurement temperature 20 ° C.).

(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.

[Example 1: CRW mixed system]
(Preparation of cyan particles C1)
1) Preparation of core particles-Preparation of dispersed phase-
The following components were mixed while heating at 60 ° C. to prepare a dispersed phase so that the ink solid content concentration was 15% and the pigment concentration after drying was 50%.
-Styrene acrylic polymer X345 (manufactured by Seiko PMC): 7.2 g
-Cyan pigment PB15: 3 aqueous dispersion: 18.8 g
(Emacol SF Blue H524F (manufactured by Sanyo Color Co., Ltd., solid content: 26% by mass))
・ Distilled water: 24.1 g

-Preparation of continuous phase-
The following components were mixed to prepare a continuous phase.
Surfactant KF-6028 (Shin-Etsu Chemical Co., Ltd.): 3.5g
-Silicon oil KF-96-2cs (manufactured by Shin-Etsu Chemical Co., Ltd.): 346.5 g

-Particle preparation-
50 g of the above dispersed phase and 350 g of the above continuous phase were mixed and emulsified for 10 minutes at a rotational speed of 10,000 rpm and a temperature of 30 ° C. using an internal tooth tabletop dispersing machine ROBOMICS (manufactured by Tokushu Kika Kogyo Co., Ltd.). As a result, an emulsified liquid having an emulsified droplet diameter of about 2 μm was obtained. This was dried by a rotary evaporator at a vacuum of 20 mbar and a water bath temperature of 40 ° C. for 18 hours.
The obtained particle suspension was centrifuged at 6,000 rpm for 15 minutes, the supernatant was removed, and the washing step of redispersing with silicone oil KF-96-2CS was repeated three times. In this way, 6 g of core particles were obtained. As a result of SEM image analysis, the average particle size was 0.6 μm.

2) Shell formation (coacervation method)
-Synthesis of shell resin-
The following components were mixed and polymerized at 70 ° C. for 6 hours under nitrogen.
-Silaplane FM-0721 (manufactured by Chisso Corporation): 50g
・ Hydroxyethyl methacrylate (Aldrich): 32g
Monomer AMP-10G containing phenoxy group (manufactured by Shin-Nakamura Chemical Co., Ltd.): 18 g
・ Monomer containing a blocked isocyanate group: 2 g
(Karenz MOI-BP (made by Showa Denko))
・ Isopropyl alcohol (Kanto Chemical Co., Inc.): 200g
-Polymerization initiator AIBN: 0.2g
(2,2′-azobisisobutyronitrile, manufactured by Aldrich)

  The product was purified using cyclohexane as a reprecipitation solvent and dried to obtain a shell resin. 2 g of this shell resin was dissolved in 20 g of t-butanol solvent to prepare a shell resin solution.

-Particle coating with shell resin-
1 g of the core particles was placed in a 200 mL eggplant flask, 15 g of silicon oil KF-96-2cs was added, and the mixture was stirred and dispersed while applying ultrasonic waves. 7.5 g of t-butanol, 22 g of the above shell resin solution, and 12.5 g of silicon oil KF-96-2cs (manufactured by Shin-Etsu Chemical Co., Ltd.) were sequentially added thereto. The input speed was all 2 mL / s. The eggplant flask was connected to a rotary evaporator, and t-butanol was removed at a vacuum of 20 mbar and a water bath temperature of 50 ° C. for 1 hour.

This was further heated in an oil bath with stirring. First, after heating at 100 ° C. for 1 hour to remove residual moisture and residual t-butanol, heating is continued at 130 ° C. for 1.5 hours to remove the blocking group of the blocked isocyanate group, and the shell resin The crosslinking reaction was performed.
After cooling, the obtained particle suspension is centrifuged at 6,000 rpm for 15 minutes, the supernatant is removed, and then re-dispersed using silicone oil KF-96-2cs (manufactured by Shin-Etsu Chemical Co., Ltd.). Was repeated three times. In this way, 0.6 g of cyan particles C1 was obtained.

(Preparation of red particle R1)
-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 (Aldrich): 53g
-2- (Diethylamino) ethyl methacrylate (manufactured by Aldrich): 0.3 g
・ Red pigment Red 3090 (manufactured by Sanyo Color Co., Ltd.): 1.5g

-Preparation of dispersion A-1B-
The following components were mixed, and finely pulverized with a ball mill in the same manner as described above to obtain a calcium carbonate dispersion A-
1B was prepared.
・ Calcium carbonate: 40g
・ Water: 60g

-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: 4g
・ 20% saline solution: 60g

-Preparation of colored particles-
After mixing the following components, deaeration was performed with an ultrasonic machine for 10 minutes.
-Dispersion A-1A: 20 g
-Ethylene glycol dimethacrylate: 0.6 g,
-Polymerization initiator V601: 0.2g
(Dimethyl 2,2′-azobis (2-methylpropionate) manufactured by Wako Pure Chemical Industries, Ltd.)

  This was added to the mixed solution A-1C and emulsified with an emulsifier. Next, this emulsified liquid was put into a flask, 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, 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. After washing with sufficient distilled water, the openings were passed through nylon sieves having a mesh size of 15 μm and 10 μm to make the particle sizes uniform. The obtained particles had a volume average particle size of 13 μm.

-Quaternary ammonium treatment-
The obtained particles are dispersed in silicone oil KF96-1cs (manufactured by Shin-Etsu Chemical Co., Ltd.), and dodecyl bromide (quaternizing agent) is equimolar with 2- (diethylamino) ethyl methacrylate used for particle preparation. In addition, the mixture was heated at 90 ° C. for 6 hours.
After cooling, this dispersion was washed with a large amount of silicone oil and dried under reduced pressure to obtain red particles R1. The glass transition temperature of the resin contained in the particles was 145 ° C.

(Preparation of white particles W1)
1) Preparation of core particles-Preparation of solution A1 (continuous phase)-
The following materials were mixed and a polymer dispersant E1 was synthesized by radical solution polymerization (55 ° C./6 hours).
・ Silaplane FM-0711: 36g
(Made by Chisso, weight average molecular weight Mn = 1,000)
・ Methacrylic acid (manufactured by Aldrich): 0.35 g
・ Silicone oil KF-96-2cs (manufactured by Shin-Etsu Chemical Co., Ltd.): 40g
・ Polymerization initiator V-65 (manufactured by Wako Pure Chemical Industries, Ltd.): 0.06 g
Then, the product was diluted with silicone oil KF-96-2cs (manufactured by Shin-Etsu Chemical Co., Ltd.) so that the polymerization anti-solubility component was 3 g, and a solution A1 (continuous phase) containing the polymer dispersant E1 was prepared. .

-Preparation of solution B1 (dispersed phase)-
Add zirconia beads to a mixture of 10 g of styrene acrylic resin X-1220L (manufactured by Seiko PMC), 10 g of titanium dioxide TTO-55A (manufactured by Ishihara Sangyo Co., Ltd.), and 90 g of distilled water, and disperse with a rocking mill for 1 hour. To disperse phase B1.

-Emulsification and drying process in liquid-
80 g of solution A1 (continuous phase) and 20 g of solution B1 (dispersed phase) were mixed and emulsified at 20,000 rpm for 10 minutes using an omnihomogenizer GLH-115 to prepare an emulsion.
Next, the obtained emulsion is put into an eggplant flask, water is removed by heating and reducing to 65 ° C. and 10 mPa with an evaporator while stirring, and a particle dispersion in which titanium dioxide particles are dispersed in silicone oil is obtained. Obtained. The obtained dispersion was sedimented using centrifugation, the supernatant was removed, and toluene was added to prepare a particle solid content concentration of 20% by mass to obtain a particle toluene dispersion C1.

2) Shelling process-Synthesis of shell resin-
・ Styrene (Wako Pure Chemical Industries, Ltd.): 70g
・ Silaplane FM-0721: 25g
(Made by Chisso, weight average molecular weight Mw = 5000)
・ Methacrylic acid (manufactured by Tokyo Chemical Industry Co., Ltd.): 5g
・ Lauroyl peroxide (manufactured by Aldrich): 1 g
・ Toluene (Kanto Chemical Co., Inc.): 100g
After mixing each material with the said composition and heating at 75 degreeC for 6 hours, it was dripped in isopropyl alcohol (made by Kanto Chemical Co., Inc.), and refine | purified by the reprecipitation method, and white solid was obtained. The obtained resin had a weight average molecular weight and a molecular weight Mw of 30000.

-Particle coating with shell resin-
・ Shell resin: 10g
-Particle toluene dispersion C1 (particle solid content concentration 20% by mass): 50 g
Each material was mixed with the said composition, 200g of silicone oil KF-96L-2cs (made by Shin-Etsu Chemical Co., Ltd.) was dripped at it, and shell resin was deposited. Then, the dispersion liquid of the white particle W1 which consists of a titanium oxide coat | covered with shell resin was obtained by removing toluene using an evaporator under 60 degreeC and 20 mbar.
The volume average particle diameter of the white particles W1 was 250 nm. The titanium oxide content (pigment content) of the white particles W1 was 40% by mass.

(Preparation of white particles W2 to W10)
In the production of the white particles W1, the ratio of the styrene acrylic resin X-1220L (manufactured by Seiko PMC) to be added to the solution B1 (dispersed phase) and titanium dioxide TTO-55A (manufactured by Ishihara Sangyo) is changed according to Table 1. Thus, the titanium oxide content in the white particles was adjusted. Moreover, the volume average particle diameter of the white particles obtained was adjusted by adjusting the rotation speed and dispersion time of the omni homogenizer.
In this way, a dispersion of white particles W2 to W8 was obtained.

(Preparation of white particles W11 to W12)
In the production of the white particles W1, styrene acrylic resin X-1202L (manufactured by Seiko PMC) added to solution B1 (dispersed phase), styrene acrylic resin X-345 (manufactured by Seiko PMC), polyvinylpyrrolidone (Wako Pure Chemical Industries, Ltd.) The dispersion liquid of white particles W11 to W12 was obtained by changing to PVP K30) manufactured by the company.

(Preparation of white particles W13)
In a 500 ml three-neck flask equipped with a reflux condenser, 45 g of 2-vinylnaphthalene (manufactured by Nippon Steel Chemical Co., Ltd.), 45 g of Silaplane FM-0721 (manufactured by Chisso Corporation), silicone oil KF-96L-1cs (Shin-Etsu Chemical Co., Ltd.) 240 g) was added. After raising the temperature to 65 ° C., bubbling with nitrogen gas was performed for 15 minutes, and 2.3 g of lauroyl peroxide (manufactured by Aldrich) was added as an initiator. Polymerization was performed at 65 ° C. for 24 hours under a nitrogen atmosphere.
The obtained particle suspension was centrifuged at 8,000 rpm for 10 minutes, the supernatant was removed, and the washing step was repeated 3 times using silicone oil KF-96-2cs (manufactured by Shin-Etsu Chemical Co., Ltd.). Repeated. Finally, the particle solid content concentration was adjusted to 40% by mass with silicone oil to obtain a dispersion of white particles W13. The volume average particle diameter of the white particles W9 was 398 nm.

(Preparation of display particle dispersions 1 to 13 (CRW mixed particle dispersion))
The cyan particle C1, the red particle R1, and the white particle W1 are weighed and mixed so that the solid content of the cyan particle C1 is 0.1 g, the red particle R1 is 1.3 g, and the white particle W1 is 2.0 g. Silicone oil KF-96L-2cs (manufactured by Shin-Etsu Chemical Co., Ltd.) was added so that the amount became 10 g, and ultrasonic dispersion was performed to prepare a display particle dispersion 1.
Similarly, instead of the white particles W1, white particles W2 to W13 were used to prepare display particle dispersions 2 to 13, respectively.
The viscosity of “silicone oil KF-96L-2cs (manufactured by Shin-Etsu Chemical Co., Ltd.)” corresponding to the dispersion medium was 2 mPa · s.

(Production of evaluation cells 1 to 13)
-Synthesis of polymer compound A-
The following components were polymerized under nitrogen at 70 ° C. for 6 hours.
・ Silaplane FM-0721: 5g
(Made by Chisso, weight average molecular weight Mw = 5000)
・ Phenoxyethylene glycol acrylate: 5g
(NK ester AMP-10G (manufactured by Shin-Nakamura Chemical Co., Ltd.))
・ Hydroxyethyl methacrylate (Wako Pure Chemical Industries, Ltd.): 90g
・ Isopropyl alcohol (IPA): 300 g
AIBN (2,2-azobisisobutylnitrile): 1 g

  The obtained product was purified using hexane as a reprecipitation solvent and dried to obtain polymer compound A.

-Production of evaluation cell-
The polymer compound A was dissolved in IPA (isopropyl alcohol) so that the solid content concentration was 4 wt%. A solution of the polymer compound A is spin-coated on a glass substrate on which ITO (indium tin oxide) having a thickness of 50 nm is formed as an electrode by a sputtering method, and dried at 130 ° C. for 1 hour. A surface layer was formed.

Two ITO substrates with a surface layer thus prepared were prepared and used as a display substrate and a back substrate. Using a Teflon (registered trademark) sheet having a thickness of 50 μm as a spacer, the display substrate was superimposed on the back substrate with the surface layers facing each other, and fixed with clips. An evaluation cell 1 was produced by injecting the display particle dispersion 1 into the empty cell for evaluation thus produced.
Similarly, instead of the display particle dispersion 1, evaluation cells 2 to 13 were prepared using the display particle dispersions 2 to 13, respectively.

The evaluation cells are listed below in Table 1.
In Table 1, the calculation of the “6 kT / (πd ³ (ρp−ρs) g)” value of the general formula (1) is the volume average particle diameter of the white particles applied to each evaluation cell, the specific gravity of the white particles, It calculated from the specific gravity of the silicone oil as a dispersion medium.
Incidentally, the specific gravity of the white particles, and titanium oxide content, specific gravity of 4.26 g / cm ³ of titanium oxide was calculated from the specific gravity of 1.2 g / cm ³ of resin. Further, the specific gravity of silicone oil was calculated as 0.878 g / cm ³ .

(Evaluation of white display reflectance and response time)
Using the fabricated evaluation cell, a potential difference of 15 V was applied between the electrodes for 5 seconds so that the surface electrode was positive. The positively charged cyan particles and the positively charged red particles were the negative electrode, that is, the back electrode. When viewed from the display substrate side, white color is observed. The reflection density at this time was measured with a spectrocolorimeter (X-Rite 939 manufactured by X-Rite) to obtain the reflectance of white display.
Next, a potential difference of 15 V was applied between the electrodes for 5 seconds so that the surface electrode was negative. The dispersed positively charged cyan particles and positively charged red particles moved to the negative electrode, that is, the surface electrode side, and when observed from the display substrate side, black was observed. The reflection density at this time was measured with a spectrocolorimeter (X-Rite 939 manufactured by X-Rite Co., Ltd.) to obtain Dmax. When switching from white display to black display, the state of reflection density changing was measured at each next time, and the time to reach a density of 90% of Dmax was taken as the response time.

(Evaluation of white particle sedimentation)
White particles are weighed to a solid content of 0.5 g, silicone oil KF-96L-2cs (manufactured by Shin-Etsu Chemical Co., Ltd.) is added to a liquid volume of 10 g, and ultrasonically stirred dispersion for sedimentation evaluation. Was prepared. A sedimentation evaluation cell was prepared by changing the display particle dispersion of the evaluation cell to a dispersion for sedimentation evaluation. These cells were placed vertically, and the appearance of white particles settled after standing for 5 days was observed and evaluated.
A: No sedimentation of white particles B: The upper liquid is slightly thinner C: White particles settle and are clearly separated into white and transparent portions

From the results in Table 2, it can be seen that increasing the pigment (titanium oxide) content in the white particles increases the reflectivity but deteriorates the sedimentation stability and response speed. On the other hand,
Further, in the display particle dispersion, the volume average particle size of the white particles and the pigment (titanium oxide) content are within the predetermined ranges, and by satisfying the general formula (1), an excellent high white display reflectance, It can be seen that excellent white particle sedimentation stability is achieved. It can also be seen that a quick display response speed can be realized.
Moreover, even if the viscosity of “silicone oil KF-96L-2cs (manufactured by Shin-Etsu Chemical Co., Ltd.)” corresponding to the dispersion medium is as low as 5 mPa · s or less, excellent sedimentation stability of white particles is realized. I understand that.

[Example 2: YMCW mixed system]
(Preparation of yellow particles Y1)
-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: 53g
-2- (Diethylamino) ethyl methacrylate: 0.3 g
・ Yellow pigment (FY7416: Sanyo Color Co., Ltd.): 1.5g

-Preparation of dispersion A-1B-
The following components were mixed, and finely pulverized with a ball mill in the same manner as described above to obtain a calcium carbonate dispersion A-
1B was prepared.
・ Calcium carbonate: 40g
・ Water: 60g

-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: 4g
・ 20% saline solution: 60g

-Preparation of colored particles-
After mixing the following components, deaeration was performed with an ultrasonic machine for 10 minutes.
-Dispersion A-1A: 20g
・ Ethylene glycol dimethacrylate: 0.6g
-Polymerization initiator V601: 0.2g
(Dimethyl 2,2′-azobis (2-methylpropionate): Wako Pure Chemical Industries, Ltd.)
This was added to the mixed solution A-1C and emulsified with an emulsifier. Next, this emulsified liquid was put into a flask, 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, 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. After washing with sufficient distilled water, the openings were passed through nylon sieves having a mesh size of 15 μm and 10 μm to make the particle sizes uniform. The obtained particles had a volume average particle size of 13 μm.

-Quaternary ammonium treatment-
The obtained particles are dispersed in silicone oil KF96-1cs (manufactured by Shin-Etsu Chemical Co., Ltd.), and dodecyl bromide (quaternizing agent) is equimolar with 2- (diethylamino) ethyl methacrylate used for particle preparation. In addition, the mixture was heated at 90 ° C. for 6 hours.
After cooling, this dispersion was washed with a large amount of silicone oil and dried under reduced pressure to obtain yellow particles Y1. The glass transition temperature of the resin contained in the particles was 145 ° C.

(Preparation of magenta particles M1)
1) Preparation of core particles-Preparation of dispersed phase-
The following components were mixed while heating at 60 ° C. to prepare a dispersed phase so that the ink solid content concentration was 15% and the pigment concentration after drying was 50%.
Styrene acrylic polymer X345 (manufactured by Seiko PMC): 7.2 g
Aqueous dispersion of magenta pigment PR122 Emacol SF Blue H502F (manufactured by Sanyo Dye Co., Ltd., solid content 21 mass%): 20 g
Distilled water: 22.8g

-Preparation of continuous phase-
The following components were mixed to prepare a continuous phase.
Surfactant KF-6028 (Shin-Etsu Chemical Co., Ltd.): 3.5g
-Silicon oil KF-96-2cs (manufactured by Shin-Etsu Chemical Co., Ltd.): 346.5 g

-Particle preparation-
50 g of the above dispersed phase and 350 g of the above continuous phase were mixed and emulsified for 10 minutes at a rotational speed of 10,000 rpm and a temperature of 30 ° C. using an internal tooth tabletop dispersing machine ROBOMICS (manufactured by Tokushu Kika Kogyo Co., Ltd.). As a result, an emulsified liquid having an emulsified droplet diameter of about 2 μm was obtained. This was dried using a rotary evaporator at a vacuum degree of 20 mbar and a water bath temperature of 40 ° C. for 18 hours.
The obtained particle suspension was centrifuged at 6,000 rpm for 15 minutes, the supernatant was removed, and the washing step of redispersing with silicone oil KF-96-2CS was repeated three times. In this way, 6 g of core particles were obtained. As a result of SEM image analysis, the average particle size was 0.6 μm.

2) Shell formation (coacervation method)
-Synthesis of shell resin-
The following components were mixed and polymerized at 70 ° C. for 6 hours under nitrogen.
-Silaplane FM-0721 (manufactured by Chisso Corporation): 50g
・ Hydroxyethyl methacrylate (Aldrich): 32g
・ Methacrylic acid (manufactured by Aldrich): 14g
・ 1H, 1H, 5H-octafluoropentyl methacrylate: 4 g
(Aldrich)
・ Monomer containing a blocked isocyanate group: 2 g
(Karenz MOI-BP (made by Showa Denko))
・ Isopropyl alcohol (Kanto Chemical Co., Inc.): 200g
-Polymerization initiator AIBN: 0.2g
(2,2′-azobis (isobutyronitrile)) (manufactured by Aldrich)
The product was purified using cyclohexane as a reprecipitation solvent and dried to obtain a shell resin. 2 g of this shell resin was dissolved in 20 g of t-butanol solvent to prepare a shell resin solution.

-Particle coating with shell resin-
1 g of the core particles was placed in a 200 mL eggplant flask, 15 g of silicon oil KF-96-2cs was added, and the mixture was stirred and dispersed while applying ultrasonic waves. To this, 7.5 g of t-butanol, 22 g of the above shell resin solution, and 12.5 g of silicon oil KF-96-2cs (manufactured by Shin-Etsu Chemical Co., Ltd.) were sequentially added. The input speed was all 2 mL / s. The eggplant flask was connected to a rotary evaporator, and t-butanol was removed at a vacuum of 20 mbar and a water bath temperature of 50 ° C. for 1 hour.

This was further heated in an oil bath with stirring. First, after heating at 100 ° C. for 1 hour to remove residual moisture and residual t-butanol, heating is continued at 130 ° C. for 1.5 hours to remove the blocking group of the blocked isocyanate group, and the shell resin The crosslinking reaction was performed.
After cooling, the obtained particle suspension was centrifuged at 6,000 rpm for 15 minutes, the supernatant was removed, and the washing step of redispersing with silicone oil KF-96-2CS was repeated three times. In this way, 0.6 g of magenta particles M1 was obtained.

(Preparation of display particle dispersions 2-1 to 2-13 (CRW mixed particle dispersion))
The cyan particles C1, the magenta particles M1, the yellow particles Y1, and the white particles W1 are solid particles of cyan particles C1 of 0.1 g, magenta particles M1 of 0.1 g, yellow particles Y1 of 1.3 g, and white particles W1 of 2 Weigh and mix to 0.0 g, add silicone oil KF-96L-2cs (manufactured by Shin-Etsu Chemical Co., Ltd.) so that the amount of liquid is 10 g, and ultrasonically agitate the display particle dispersion 2-1 Prepared.
Similarly, instead of the white particles W1, white particles W2 to W9 were used to prepare display particle dispersions 2-2 to 2-13, respectively.

(Production and evaluation of evaluation cells)
Evaluation cells were produced in the same manner as in the evaluation cell 1 (Example 1) except that the display particle dispersions 1-2 to 2-13 were used.
And about each obtained evaluation cell, when the white display reflectance and response time were evaluated similarly to Example 1, it has confirmed that the same result was obtained.

[Example 3]
In the white particles W1, according to Table 3, the amount of monomer species was changed to synthesize a shell resin, and the white particles W14 to W17 were obtained in the same manner as the white particles W1 except that this shell resin was used. Furthermore, display particle dispersions 14 to 17 were obtained.
And evaluation cell 14-17 was produced like evaluation cell 1 (1) except having used display particle dispersions 14-17, and the same evaluation as Example 1 was performed.
In the white particles W14 to W17 and the display particle dispersions 14 to 17, the titanium oxide content, the value of “6 kT / (πd ³ (ρp−ρs) g)” in the general formula (1) The same as the display particle dispersion 1.

(Measurement of particle moving speed)
An empty cell for speed measurement in which two opposing electrodes that are horizontally opposed to each other with a spacing of 300 μm are formed on a glass substrate, and each of the display particle dispersions 10 to 13 is sealed therein, thereby preparing a cell for speed measurement. did.
Then, a potential difference of 0.3 V / μm was applied between the counter electrode of the velocity measuring cell to move the particles, and the situation was photographed using an optical microscope with a high-speed camera. The time required for the particle group to move between the counter electrode was measured, and the moving speed was calculated.
Specifically, with the particles to be measured moved to one of the counter electrodes, a potential difference is applied between the counter electrodes, and more than half of the particles move to the other of the counter electrodes at the center between the counter electrodes. The time required for the measurement was measured, and the moving speed of the particles was calculated from the time and the distance between the counter electrodes (300 μm).
The measurement object is cyan particles having a slow moving speed among white particles and colored particles. The moving speed of cyan particles (Vc: μm / sec), the moving speed of white particles (Vw: μm / sec), and The ratio (Vw / Vc) was determined.
For the display particle dispersion 1, the particle moving speed was measured in the same manner.

  From the results of Table 4, it can be seen that the evaluation cell having Vw / Vc of 0.2 or less is more excellent in display response speed.

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

Claims (9)

White particles for display containing a white pigment and a resin, wherein the content of the white pigment (mass of the white pigment / (total mass of the white pigment and the resin)) is 30% by mass or more and 90% by mass or less. White particles for display having a volume average particle diameter of 100 nm to 500 nm and satisfying the following formula (1):
Display colored particles that move in response to an electric field, two or more types of display colored particles excluding white,
A dispersion medium for dispersing the display colored particles and the display white particles;
A particle dispersion for display.
Formula (1) 400 ≧ 6 kT / (πd ³ (ρp−ρs) g) ≧ 30
(In formula (1), k represents the Boltzmann coefficient (J · K ⁻¹ ), T represents the absolute temperature 298 (K), and d represents the volume average particle diameter (nm) of the white particles for display. ρp is .ρs showing a specific gravity (g / cm ³⁾ of the display for white particles exhibit specific gravity (g / cm ³⁾ .g showing a gravity acceleration (m / ^{s 2)} of the dispersion medium.)   The display particle dispersion according to claim 1, wherein the white pigment is titanium oxide.   The moving speed ratio (moving speed Vw of the white particles for display / moving speed Vc of the colored particles for display) that moves according to the electric field between the white particles for display and the colored particles for display is 0.2 or less. The display particle dispersion according to claim 1 or 2.   The particle dispersion for display according to claim 1, wherein the dispersion medium has a viscosity of 5 mPa · s or less.   The display dispersion according to claim 1, wherein the dispersion medium is silicone oil. A pair of substrates, at least one of which is translucent,
The display particle dispersion according to any one of claims 1 to 5, enclosed between the pair of substrates,
An electric field generating means for applying an electric field having an intensity for moving the display colored particles between the pair of substrates;
An image display device comprising:   An electronic apparatus comprising the image display device according to claim 6.   An exhibition medium comprising the image display device according to claim 6.   A card medium comprising the image display device according to claim 6.