JP5646388B2 - Composition for forming spherical particles, spherical particles using the composition, and electronic paper using the spherical particles - Google Patents

Description

  The present invention relates to electronic paper that can stably maintain a display state for a long time, spherical particles used in the electronic paper, and a composition used in the spherical particles.

In recent years, there has been a demand for a thin display device, and as one of them, an electronic paper of a system using minute spherical particles having different colors for each hemisphere, that is, a so-called twist ball has been developed.
As this twist ball type electronic paper, for example, in Patent Document 1, twist balls are sealed one by one in capsules filled with silicone oil, and the capsules are dispersed in a resin layer and held on one plane. A form of electronic paper has been proposed.
In such an electronic paper, a desired image is displayed by applying electricity according to a desired display object and rotating a twisting ball.

JP 2007-183575 A

However, ordinary electronic paper applies electricity when displaying desired characters and images, and then holds the display image in a charge-free state without applying electricity. There is a problem that the twist ball gradually rotates and the display image becomes unclear.
In short, the conventionally proposed electronic paper cannot hold and display a clear image for a long time, and there is a demand for the development of an electronic paper that can continue to display a desired image clearly for a long time. Currently.
Accordingly, an object of the present invention is to provide an electronic paper, a spherical particle for the electronic paper, and a composition for the spherical particle, which can be clearly maintained for a long time even when displayed characters and images are free of charge.

The inventors of the present invention have studied the idea that the above problem can be solved by reducing the specific gravity difference between two colors of spherical particles colored in different colors. As a result of further diligent examination, it was found that a difference in specific gravity was generated even in the hemisphere of spherical particles colored with different colors, and the gravity center of the particles was biased. As a result of studying the cause, it was found that the composition itself and pigment settling during production were the cause. As a result of further studies based on this finding, it was found that pigment precipitation can be eliminated by blending an inorganic thixotropic agent into a composition for forming spherical particles. That is, the pigment moves in the medium during the transfer in the microchannel, so that the uniform state is maintained, and the thixotropy is maintained so that the pigment does not settle after the droplets are formed. It was found that the difference in specific gravity and the deviation of the center of gravity were eliminated, and the present invention was completed.
That is, the present invention provides the following composition for forming spherical particles, spherical particles using the composition, and electronic paper using the spherical particles.
1. A composition for forming spherical particles having a different color for each hemisphere and charged in a dipole state, comprising a (meth) acrylate monomer and an inorganic thixotropic agent And a composition.
2. 2. The composition according to 1, wherein the inorganic thixotropic agent is finely divided silica.
3. 2. The composition according to 1, wherein 1 to 30 parts by weight of an inorganic thixotropic agent is blended with 100 parts by weight of the (meth) acrylic acid ester monomer.
4). 2. The composition according to 1, wherein one hemisphere constitutes white and the other hemisphere constitutes any color except white.
5. Spherical particles formed using the composition according to 1 and having a different color for each hemisphere and charged in a dipole state.
6). 6. The spherical particle according to 5, which is formed using a microchannel method.
7). A film formed of a pair of supports and the spherical particles according to 5 or 6 positioned between the pair of supports, and a film positioned on at least a user's side of the pair of supports transmits visible light. Electronic paper that is a light-transmitting support.

  The composition for spherical particles and the spherical particles for electronic paper of the present invention can provide electronic paper in which characters and images to be displayed are kept clear for a long time even in a charge-free state. The electronic paper of the present invention In this case, displayed characters and images are kept clear for a long time even in a charge-free state.

FIG. 1 is a perspective view showing an embodiment of the spherical particles of the present invention formed by the composition of the present invention. FIG. 2 is a cross-sectional view schematically showing one embodiment of the electronic paper of the present invention formed using the spherical particles shown in FIG.

DESCRIPTION OF SYMBOLS 1 Electronic paper 10,10 'support body (substrate electrode and transparent electrode), 20 spherical particle, 21 white hemispherical part, 22 colored hemispherical part, 30 particle holding member, 40 silicone oil layer

Hereinafter, the present invention will be described in detail with reference to the drawings.
As shown in FIG. 1, the spherical particles 20 of the present embodiment formed using the composition of the present invention have different colors for each hemisphere and are charged in a dipole state. In this embodiment, as shown in FIG. 1, it consists of a white hemisphere portion 21 and a colored hemisphere portion 22 (black in this embodiment).
The size of the spherical particles of the present embodiment and the aspect of being charged to a dipole state are the same as the spherical particles used in ordinary electronic paper.

The composition of the present invention, which is a characteristic part of the present invention, will be described.
The composition of the present invention is a composition for forming spherical particles such as the spherical particles of the embodiment shown in FIG. 1, and comprises a (meth) acrylic acid ester monomer and an inorganic thixotropic agent. It is characterized by that. The composition of the present invention is not particularly limited in color, and can be used for either a white hemisphere portion or a colored hemisphere portion, but is particularly preferably used as a composition constituting the white hemisphere portion.
Hereinafter, the composition of the present invention as a composition constituting the white hemisphere portion will be described. In the present specification, (meth) acryl means acryl or methacryl, and (meth) acrylate means acrylate or methacrylate.

<(Meth) acrylic acid ester monomer>
The (meth) acrylic acid ester monomer used in the present invention (hereinafter sometimes simply referred to as “monomer”) is a component that is polymerized to constitute the resin component of the spherical particles. Methyl acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, alkyl acrylates such as octyl (meth) acrylate, cycloalkyl (meth) acrylates such as cyclohexyl (meth) acrylate, acrylic Examples include esters of (meth) acrylic acid such as isobornyl acid and bicyclic alcohols, (meth) acrylic acid aryl esters such as phenyl (meth) acrylate, benzyl (meth) acrylate, and the like. It can be used alone or in combination of two or more.

<Functional group-containing monomer>
In order to improve the dispersibility of the pigment and various colorants described later in the monomer, or to adjust the dielectric constant of each hemisphere constituting the spherical particles, the composition of the present invention has at least one kind. A functional group; for example, a monomer having a carboxyl group, an amide group, an amino group, a hydroxyl group, an epoxy group, or a nitrile group in the molecule can be used in combination.

  Examples of monomers having a carboxyl group in the molecule are unsaturated carboxylic acids; (meth) acrylic acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, maleic acid, fumaric acid, isocrotonic acid, norbornene dicarboxylic acid Acid, bicyclo [2,2,1] hept-2-ene-5,6-dicarboxylic acid and the like, and maleic anhydride, itaconic anhydride, citraconic anhydride, tetrahydrophthalic anhydride as derivatives thereof , Bicyclo [2,2,1] hept-2-ene-5,6-dicarboxylic acid anhydride, acid halide.

  Examples of monomers having an amide group in the molecule are amide group-containing vinyl monomers; (meth) acrylamide, N-methylol (meth) acrylamide, N-methoxyethyl (meth) acrylamide, N-butoxymethyl ( (Meth) acrylamide, N, N-dimethyl (meth) acrylamide, (Meth) acrylamide derivatives such as N, N-dimethylaminopropyl (meth) acrylamide, N-methyl (meth) acrylamide, and N-methylol (meth) Examples include (meth) acrylamides such as acrylamide and diacetone (meth) acrylamide, 6-aminohexyl succinimide, and 2-aminoethyl succinimide.

  Examples of monomers having an amino group in the molecule are amino group-containing vinyl monomers; aminoethyl (meth) acrylate, propylaminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, ( Alkyl ester derivatives of (meth) acrylic acid such as aminopropyl methacrylate, phenylaminoethyl (meth) acrylate, cyclohexylaminoethyl (meth) acrylate, vinylamines such as N-vinyldiethylamine and N-acetylvinylamine Examples thereof include allylamine derivatives such as allylic derivatives, allylamine, (meth) acrylamine, N-methyl (meth) acrylamine, and aminostyrenes such as p-aminostyrene.

  Examples of monomers having a hydroxyl group in the molecule are: (meth) acrylic acid-2-hydroxyethyl, (meth) acrylic acid-2-hydroxypropyl, monoester of (meth) acrylic acid and polypropylene glycol or polyethylene glycol And adducts of lactones and 2-hydroxyethyl (meth) acrylate.

  Examples of monomers having an epoxy group in the molecule: glycidyl (meth) acrylate, mono and diglycidyl esters of maleic acid, mono and diglycidyl esters of fumaric acid, mono and diglycidyl esters of crotonic acid, tetrahydrophthalic acid Mono and diglycidyl esters of itaconic acid, mono and diglycidyl esters of itaconic acid, mono and diglycidyl esters of butenetricarboxylic acid, mono and diglycidyl esters of citraconic acid, mono and glycidyl esters of allyl succinic acid, and the like Examples include esters and alkyl glycidyl esters of p-styrene carboxylic acid.

Examples of the monomer having a nitrile group in the molecule include (meth) acrylonitrile and allyl nitrile.
In the present invention, such functional group-containing monomers can be used singly or in combination of two or more.
In the case of using these functional group-containing monomers, the blending amount is preferably 1 to 90 parts by weight, and more preferably 5 to 50 parts by weight with respect to 100 parts by weight of the monomer.

<Multifunctional monomer>
In the composition of the present invention, a bifunctional or higher polyfunctional monomer may be blended and reacted with the monomer.
Examples of the bifunctional or higher polyfunctional monomer include (poly) alkylene glycol di (meth) acrylates, tri (meth) acrylates, and tetra (meth) acrylates. .
Specific examples thereof include ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, neopentyl glycol Di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, 1,1,1-trishydroxymethylethane di (meth) acrylate, 1,1,1-trishydroxymethylethanetri (Meth) acrylate, 1,1,1-trishydroxymethylpropane tri (meth) acrylate, N-methylol (meth) acrylamide, 1,9-nonanediol di (meth) acrylate 2-butyl-2-ethyl-1,3-propanediol di (meth) acrylate.

  The bifunctional or higher polyfunctional monomer is used for introducing a crosslinked structure into the resin. Although the cross-linked structure is not essential, the spherical particles have a cross-linked structure, so that in the electronic paper of the present invention, even if the insulating liquid such as silicone oil and the spherical particles of the present invention come into contact, the spherical particles are insulated. The spherical particles can be stably suspended in the insulating liquid without being swollen by the conductive liquid.

  In addition, when such a polyfunctional monomer is used, the blending amount is usually preferably 10 to 90 parts by weight in a total amount of 100 parts by weight with the above monomers.

<Inorganic-based thixotropic agent>
As the thixotropic agent, there are an organic type and an inorganic type. In the present invention, an inorganic thixotropic agent is used. Organic thixotropic products (for example, polyvinyl alcohol and urea urethane) are less likely to form an O / W or W / O state in a microchannel in which a fluid medium flows when manufactured by the microchannel method. There are problems such as manufacturing problems, and the color separation of the two colors on the surface of the spherical particles tends to be unclear.
Examples of the inorganic thixotropic agent include finely divided silica, metal fine particles, calcium carbonate powder, mica powder and the like, and can be used alone or in combination of two or more. In the present invention, finely divided silica is preferable in that pigment sedimentation can be eliminated without impairing whiteness on the white side. Hydrophilic silica (such as “AEROSIL” series R200 manufactured by Nippon Aerosil Co., Ltd.) can also be used, but the liquid medium is colored especially in the microchannel in which the fluid medium flows when manufactured by the microchannel method. Hydrophobic silica can be preferably used in that it does not dissolve the continuous phase, forms an O / W or W / O state, and the colored continuous phase becomes more stable and spherical.
Examples of hydrophobic silica include “AEROSIL” series (RY50, R504, R711, R812, R972, etc.) manufactured by Nippon Aerosil Co., Ltd., “NIPSIL” series (SS50A, SS50F, SS70, SS178, etc.) manufactured by Tosoh Silica Corporation, Tokuyama. “Retro Seal” series (MT-10, MT-10C, DM-10, DM-10C, HM-20L, PM-20L, KS-20S, etc.) manufactured by FUJI SILICIA CHEMICAL CO., LTD. Commercial products such as series (100, 200, etc.) can be used.

  The blending ratio of the (meth) acrylic acid ester monomer to the inorganic thixotropic agent is 1 to 30 weights of the inorganic thixotropic agent with respect to 100 parts by weight of the (meth) acrylic acid ester monomer. It is preferable to mix partly in terms of suppressing the precipitation of the pigment and increasing the dispersion stability of the pigment, and it is more preferable to add 1 to 20 parts by weight.

<White pigment>
Examples of white pigments include titanium oxide, zinc oxide, zinc sulfide, calcium carbonate, barium sulfate, and alumina white. Among these, titanium oxide can be preferably used.

In the present invention, it is also possible to use a white pigment that has been subjected to conductive treatment instead of or in combination with the above-described white pigment. By using a conductive white pigment, a region occupying one hemisphere when prepared into spherical particles exhibits conductivity and a high dielectric constant. Therefore, a potential difference is generated between one hemisphere and the other hemisphere, and the rotational property of the spherical particles when charged is improved.
The conductive white pigment is obtained, for example, by treating a white pigment with a conductive material of either antimony oxide / tin oxide or indium oxide / tin dioxide to impart conductivity.

  Specifically, the treatment is an operation of coating or impregnating with a conductive material using a spherical white pigment (for example, titanium dioxide) as a core. When the white pigment is titanium dioxide, the titanium dioxide may be rutile or anatase. The coating or impregnation can be performed by mixing a white pigment with a conductive material in a wet or dry manner. The conductive white pigment thus obtained is also commercially available. For example, a conductive white pigment commercially available under the trade name “ET-500W” (manufactured by Ishihara Sangyo Co., Ltd.) can be used.

  In the present invention, the amount of the white pigment and the covering material (or impregnating material) constituting the conductive white pigment can be appropriately set, but the weight ratio of the white pigment and the covering material (or impregnating material) (white) The pigment: coating material (or impregnating material) is usually set in the range of 95: 5 to 70:30, preferably 90:10 to 80:20. By using a covering material or an impregnating material within the above range, good conductivity can be imparted to the white pigment.

Furthermore, the particle diameter of the white pigment and / or the conductive white pigment is usually 0.10 to 5 μm, preferably 0.10 to 0.5 μm. The powder resistivity of the conductive white pigment is usually 1 to 100 Ωcm, preferably 1 to 30 Ωcm.
The amount of the white pigment and / or conductive white pigment in the composition of the present invention is preferably 1 to 50 parts by weight with respect to 100 parts by weight of the monomer, from the viewpoint that the specific gravity difference between the two colors can be reduced. 1 to 20 parts by weight is more preferable.

<Polymerization initiator>
The composition of the present invention preferably contains a known thermal polymerization initiator or photopolymerization initiator.
Examples of the thermal polymerization initiator include peroxyesters, organic peroxides, organic hydroperoxides, organic peroxyketals, and azo compounds.
Examples of peroxyesters include: tert-hexyl peroxypivalate, tert-butyl peroxyneodecanate, tert-butyl peroxybenzoate, tert-hexylperoxy-2-ethylhexanoate, hexyl peroxyneo Examples include decanate, cumylperoxyneodecanate, and 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate.
Examples of the organic peroxides include: dicumyl peroxide, di-tert-butyl peroxide, tert-butyl cumyl peroxide, dilauroyl peroxide, dibenzoyl peroxide, diacetyl peroxide, didecanoyl peroxide, di- Examples thereof include isononyl peroxide and 2-methylpentanoyl peroxide.
Examples of organic hydroperoxides include: tert-butyl hydroperoxide, cumyl hydroperoxide, 2,5-dimethyl-2,5-dihydroperoxyhexane, p-methane hydroperoxide, diisopropylbenzene A hydroperoxide is mentioned.
Examples of organic peroxyketals include: 1,1-bis (tert-hexylperoxy) -3,3,5-trimethylcyclohexane, 1,1-bis (tert-hexylperoxy) cyclohexane, , 1-bis (tert-butylperoxy) 3,3,5-trimethylcyclohexane.
Examples of the azo compounds include: 2,2′-azobisisobutyronitrile, 2,2′-azobis-2,4-dimethylvaleronitrile, 2,2′-azobiscyclohexylnitrile, 1,1 ′ -Azobis (cyclohexane-1-carbonitrile), 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile, dimethyl-2,2'-azobisisobutyrate.

Examples of the photopolymerization initiator include conventionally known acetophenones; for example, acetophenone, 2,2-diethoxyacetophenone, p-dimethylaminoacetophenone, methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2- Hydroxy-2-cyclohexylacetophenone and ketones; for example, benzophenone, 2-chlorobenzophenone, p, p'-dichlorobenzophenone, p, p'-bisdiethylaminobenzophenone, N, N'-tetramethyl-4,4'- Diaminobenzophenone (Michler ketone), 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone, and benzoin ethers; for example, benzoin, benzoin methyl ether, benzoin ethyl ether, In isopropyl ether, benzoin isobutyl ether, benzyl methyl ketal, benzoyl benzoate, alpha-acyloxime esters, and thioxanthones.
These polymerization initiators can be used alone or in combination of two or more.

  The blending amount of these polymerization initiators is preferably 0.01 to 5 parts by weight, more preferably 0.5 to 2 parts by weight, per 100 parts by weight of the monomer.

<Other ingredients>
In addition, the composition of the present invention includes a UV sensitizer, a charge control agent, a pigment dispersant, a heat stabilizer, a conductive agent, an antiseptic, a surface tension adjusting agent, an antifoaming agent, a rust preventive, an antioxidant, Other components such as a near-infrared absorber, an ultraviolet absorber, a fluorescent agent, and a fluorescent brightening agent can be blended without departing from the spirit of the present invention.

  The UV sensitizer is used in order to exert the effect of the photopolymerization initiator more strongly. Examples thereof include n-butylamine, triethylamine, and tri-n-butylphosphine.

  The charge control agent is contained in the background hue and / or an arbitrary colored phase other than the background color, thereby adjusting the charging characteristics of the substantially hemispheres of the obtained spherical particles, and the spherical shape when a voltage is applied. Used to improve particle rotation performance. Examples of charge control agents include styrene acrylic polymers, calixarene derivatives, hindered amines, azine compounds, salicylic acid metal complexes, phenol condensates, lecithin, pararosarinin, nigrosine dyes, alkoxylated amines, alkylamides. , Phosphorus and tungsten simple substances and compounds, molybdate chelate pigments, fluorine-based activator, hydrophobic silica, metal salt of monoazo dye, sulfonylamine of copper phthalocyanine, oil black, metal salt of naphthenate, benzyltributylammonium-4-hydroxy And quaternary ammonium salts such as naphthalene-1-sulfonate. The charge control agent may also serve as a colorant, and the colorant may also serve as a charge control agent.

  The charge control agent is preferably used in an amount of 0.05 to 5 parts by weight, more preferably 0.5 to 2 parts by weight, based on 100 parts by weight of the monomer.

<Material for forming hemispherical parts other than white>
The composition of the present invention can also be used for forming a colored hemispherical portion, but in the colored hemispherical portion, a styrene monomer, vinyl monomer, or other monomer can be used instead of the above monomer ( Hereinafter, these and the above monomers are collectively referred to as “colored hemispherical monomers”).

  Examples of styrenic monomers are: styrene, methyl styrene, dimethyl styrene, trimethyl styrene, ethyl styrene, diethyl styrene, triethyl styrene, propyl styrene, butyl styrene, hexyl styrene, heptyl styrene, octyl styrene, fluorostyrene, chlorostyrene, bromo Examples include styrene, dibromostyrene, chloromethylstyrene, nitrostyrene, acetylstyrene, methoxystyrene, α-methylstyrene, vinyltoluene, and sodium p-styrenesulfonate.

  Examples of vinyl monomers are: vinyl acetate, vinyl propionate, vinyl n-butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caproate, vinyl persate, vinyl laurate, vinyl stearate, vinyl benzoate, p -T-butyl vinyl benzoate and vinyl salicylate are mentioned.

  Examples of other monomers include: vinylidene chloride, vinyl chlorohexanecarboxylate, β- (meth) acryloyloxyethyl hydrogen phthalate, perfluoroethylene, perfluoropropylene, vinylidene fluoride, vinyltrimethoxysilane, vinyltriethoxysilane Is mentioned.

<Colorant>
Instead of the white pigment and / or the conductive white pigment, various colorants can be used in the composition constituting other colored hemispherical portions depending on the desired color.
Examples of the colorant include achromatic dyes, achromatic pigments, chromatic dyes, and chromatic pigments.

In particular,
If it is a black colorant, Olesolol Fast Black, BONJET BLACK CW-1, Solvent Black 27Cr (trivalent) containing 5%, Pigment Black 7, Carbon Black, Black Pearls 430, Bengala, Ultramarine Blue, etc.
If it is a red colorant, VALIFAST
Contains RED 3306, Olesolol Fast RED BL, Solvent RED 8Cr (trivalent) 5.8%, Permanent Carmain
FBB02-JP, solvent red, etc.
If it is a blue colorant, Kayaset Blue, Solvent Blue 35, Cyanine Blue, Solvent Blue, etc.
If it is a yellow colorant, VALIFAST
YELLOW 4120, Oil Yellow 129, Solvent
Yellow 16, Solvent Yellow 33, Disperse
Yellow 54, PV Fast Yellow H2G lemon color ... Piast Yellow 8005, Permanent Yellow DHG, Lionol Yellow 1212B, Shimla First Yellow 4400, Pigment Yellow 12, etc.
Oil if it is a green colorant
Green 502, Opias Green 502, Solvent Green 3, Solvent Green, etc.
If it is a magenta colorant, VALIFAST
PINK 2310N, Plast RED D-54, Plast RED 8355, Plast RED 8360, Plast Vioiet 8850, Disperse
Violet 28, Solvent RED 149, Solvent
RED 49, Solvent RED 52, Solvent
Contains RED 218Cr (trivalent) 4%, Pigment Red 57: 1, Lionol Red 6B-4290G, Irgarite Rubin 4BL, Fastgen Super Magenta RH,
If it is a cyan colorant, VALIFAST
BLUE 2610, VALIFAST BLUE 2606, Oil
Contains BLUE 650, Plast BLUE 8580, Plast BLUE 8540, Oil BLUE 5511, Solvent Blue 70 Cu 4%, Lionol Blue 7027, Fastgen Blue BB, Chromophthal Blue 4GNP,
If it's an orange colorant, Oil
Orange 201, VALIFAST ORANGE 3210, Solvent Orange 70, Kayaset Orange G, Solvent Orange, Lummogen F Orange, etc.
Examples of the brown colorant include VALIFAST BROWN 2402, Solvent Yellow 116, Kayase Flavine FG, and the like.

  In addition, for example, dyes and thermosensitive dyes usually used in writing recording liquids such as clarine, perylene, dicyanopinyl, azo, quinophthalone, aminopyrazole, methine, dicyanoimidazole, indoaniline, phthalocyanine Leuco dyes used as recording paper or temperature sensitive colorants, rhodamine B stearate (red 215), tetrachlorotetrabromofluoresene (red 218), tetrabromofluorescene (red 223), sudan III (red 225), dibromofluorescein (orange 201), diiodo fluorescein (orange 206), fluorescein (yellow 201), quinizarin green SS (green 202), azurin purple SS (purple 201) , Medicinal scarlet (red 501), oil red XO Tar dyes used in cosmetics such as Red 505), Orange SS (Orange 403), Yellow AB (Yellow 404), Yellow OB (Yellow 405), Sudan Blue B (Blue 403) are also listed above. It can be mentioned as a colorant.

  These dyes can be used alone or in admixture of two or more, and various direct dyes, acid dyes, basic dyes, azoic dyes, reactive dyes, fluorescent dyes and fluorescent dyes as necessary. It is possible to disperse in a brightener, and further in the above (meth) acrylic monomer.

  Furthermore, if necessary, titanium white, zinc sulfide, zinc oxide, alumina white, calcium carbonate, etc. can be used as a white pigment having no conductivity.

  In the present invention, the total amount of the colorant contained in the colored other hemisphere portion is usually 0.1 to 50 parts by weight, preferably 100 parts by weight of the total amount of the colored hemisphere monomers used, Is 2 to 40 parts by weight. Moreover, when represented by a volume fraction, it is preferably 1 to 20%.

  About components other than these, the component similar to the composition of the above-mentioned this invention can be mix | blended with the same compounding quantity.

<Method for producing spherical particles>
The spherical particles of the present invention can be produced using a known microchannel method.
As the microchannel method, a method described in JP 2010-145598 A can be used.
Briefly described below, the microchannel method used in the present invention is a two-phase separation of a raw material adjustment liquid containing the composition of the present invention and a raw material adjustment liquid containing a composition that forms a colored hemispherical portion. The colored continuous phase is transferred and sequentially or intermittently discharged into the microchannel in which the fluid medium flows. Since the colored continuous phase and the fluid medium are in an insoluble relationship in which they form an O / W or W / O state with each other, the discharged colored continuous phase passes through the second microchannel. While flowing, it becomes spherical particles by interfacial tension. This colored continuous phase contains a resin or its monomer, and the resin or its monomer is polymerized and cured by UV irradiation and / or heating when the colored continuous phase is discharged and spheroidized. Thus, a cured resin body is usually formed, and spherical particles are prepared in which individual spherical particles are roughly divided into two different colors in appearance.

  In this method, when the channel width of the microchannel is extremely fine, such as about several hundreds of μm, the fluid (colored continuous phase) flowing therethrough is dominant in viscosity, so the Reynolds number is about 1000 or less and the flow is laminar. Tend to be. The same is true even if the colored continuous phase is split into two colors, and the colored continuous phase split into two colors tends to be transported in a nearly laminar flow state, so it can be easily used as a continuous phase in which the two colors are not mixed. Can be transported.

  The speed at which the colored continuous phase is transferred depends on the viscosity, surface tension, density, liquidity (polar group), etc. of the colored continuous phase, but is preferably a flow rate of normal flow F1 = 0.01 to 10 ml / hr. Is a flow rate of 0.01 to 5 ml / hr.

  The flow F2 of the fluid medium is not particularly limited as long as the discharged colored continuous phase is spheroidized while flowing. Usually, the flow F2 is a flow rate of 1 to 100 ml / hr, preferably 1 to 50 ml / hr. The flow rate of

  The flow ratio represented by F2 / F1 indicates the liquidity such as the production amount of spherical particles to be produced, the average particle size and particle monodispersity, the fluid viscosity, density, and surface tension of the colored continuous phase and fluid medium. It can be set as appropriate in consideration.

  The colored continuous phase discharged into the microchannel is formed into spherical particles during discharge, dispersion, and transfer while being separated into two colors, and the resin or monomer in the discharged colored continuous phase is subjected to UV irradiation and / or heating. Polymerized and cured. Since the spherical shape of the discharged colored continuous phase after spheroidization is stable, this polymerization curing does not necessarily occur when the colored continuous phase does not completely polymerize and cure while flowing in the microchannel. Can be appropriately performed under UV irradiation and / or heating in a separate container which is a spherical particle recovery tank.

The irradiation amount when irradiating UV is usually 300 to 1500 mJ / cm ² , the heating temperature when heating is usually 60 to 100 ° C., and the heating time is 20 to 120 minutes.

<Fluid medium>
As described above, the fluid medium used in the microchannel method has a relationship of O / W or W / O with the colored continuous phase. In other words, the colored continuous phase is not dissolved in the fluid medium, and the colored continuous phase is colored continuously. Since the phase becomes spherical, the colored continuous phase can be freely deformed in this fluid medium.

Examples of the fluid medium include a polyvinyl alcohol aqueous solution, a carboxymethyl cellulose aqueous solution, and a hydroxymethyl cellulose aqueous solution in which polyvinyl alcohol is dissolved in ion exchange water. Since the colored continuous phase is often an oily phase (O phase), the fluid medium is preferably an aqueous phase (W phase).
<Spherical particles>
For example, the spherical particles of the present invention produced by the above-described method have an average particle diameter in the range of usually 30 to 200 μm, preferably 70 to 150 μm on a volume basis. Spherical particles having an average particle diameter in this range are likely to rotate when a voltage is applied. In addition, the variation in the particle diameter is usually 20% or less, preferably 5% or less, and more preferably 3% or less, when the uniformity is expressed as a Cv value. In the case of producing spherical particles by the microchannel method, the average particle diameter of the obtained spherical particles can be adjusted by limiting the discharge amount, the nozzle, the resin viscosity, and the like.

Next, the electronic paper of the present invention will be described with reference to FIG.
The electronic paper of this embodiment shown in FIG. 2 is located between a pair of supports 10, 10 ′ and a pair of the supports 10, 10 ′, and has a different color for each hemisphere and is charged in a dipole state. And a large number of spherical particles 20. Each spherical particle 20 is disposed so as to be positioned substantially in one plane in the transparent resin 30.
Moreover, in this embodiment, a pair of support body 10 and 10 'are the support bodies 10 which are located in the visual recognition surface side which a user visually recognizes, and the transparent support body (transparent electrode) which permeate | transmits visible light, and is opposite. The support 10 'located on the side is an electrode substrate that is not transparent.
The spherical particles 20 are included in the silicone oil layer 40 and are rotatable due to the presence of the silicone oil 40.
Further, although not particularly illustrated, the periphery of each support is hermetically sealed with a frame, and the configuration of the entire electronic paper can employ the same configuration as that of a known electronic paper without any particular limitation.

In the electronic paper 1 of the present embodiment, similarly to normal electronic paper, electricity is applied to a support that is an electrode according to predetermined information so that the hemisphere of a predetermined color is positioned on the viewing surface A side. It can be used by rotating and displaying desired characters and images.
And since the electronic paper 1 of this embodiment is formed using the spherical particle | grains formed using the above-mentioned composition, after forming a desired image by applying an electric charge, it is a charge free state Even if it becomes, the spherical particles do not rotate, and an image displayed for a long time can be held.

  The electronic paper of this embodiment can be manufactured according to a conventional method.

  The electronic paper of the present invention is not limited to the above-described example, and various changes can be made without departing from the spirit of the present invention.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited to these at all.
[Example 1]
The composition for white hemispheres in spherical particles was prepared by blending the (meth) acrylic acid ester monomers shown in Table 1, other monomers, inorganic thixotropic substances and white pigments in the amounts shown in Table 1.

In addition, 40 parts by weight of trimethylolpropane triacrylate (TMPTA) as a cross-linking agent and 0% of quaternary ammonium salt (benzyltributylammonium-4-hydroxynaphthalene-1-sulfonate) as a charge control agent were added to the obtained composition. .5 parts by weight was added to obtain a raw material adjustment liquid A.
Separately, 40 parts by weight of methyl methacrylate (MMA) as a monomer and 6 parts by weight of carbon black as a pigment were blended to prepare a composition for black hemispheres in spherical particles.
80 parts by weight of TMPTA as a crosslinking agent and 1 part by weight of a salicylic acid-based metal complex (Orient Chemical Industries, trade name: BONTRON E-84) as a charge control agent were added to the obtained composition to prepare a raw material adjusting solution B was obtained.
Using the obtained raw material adjustment liquids A and B, the flowable medium was a polyvinyl alcohol aqueous solution, the flow rate was 100 ml / hr, the polymerization method was UV irradiation, and the same as the example of JP 2010-145598 A The spherical particles shown in FIG. 1 were prepared using a microchannel apparatus.
As shown in FIG. 1, it was visually confirmed whether or not the obtained particles were color-divided for each hemisphere, and the case where they were separated was marked with ◯, and the case where they were not separated was marked with x (two-color droplet generation).
The rotational properties of the obtained spherical particles were measured. Further, contrast (CR) and contrast change rate (CR change rate) were measured. The results are shown in Table 1.

(Rotation of particles)
The electronic paper shown in FIG. 2 was produced using the obtained spherical particles, and voltage was applied to the obtained electronic paper so that a potential difference of 100 V was generated between the electrodes, thereby unifying the direction of the two-color particles. The dichroic particles were inverted by reversing the method of applying a voltage between the electrodes. At that time, the time until rotating particles could not be confirmed was measured. The confirmation size was set within about 1 mm square, and evaluation was performed with an average value at N = 5.

(CR and CR change rate)
The electronic paper shown in FIG. 2 was produced using the obtained spherical particles, and voltage was applied to the obtained electronic paper so that a potential difference of 100 V was generated between the electrodes, thereby unifying the direction of the two-color particles. The dichroic particles were inverted by reversing the method of applying a voltage between the electrodes. The electronic paper was allowed to stand horizontally, and then a voltage of 100 V was applied, and the reflectance was measured with a color difference meter immediately after stopping the application and after leaving for 12 hours.
Then, the contrast was calculated from the obtained reflectance, and the change rate of the contrast immediately after stopping and after standing for 12 hours was also calculated. Table 1 shows the initial CR and CR change rate. The measurement used a 4 cm square test piece.

[Examples 2 to 4]
The composition, raw material adjustment liquids A and B, spherical shape as in Example 1 except that the (meth) acrylic acid ester monomer, other monomers, inorganic thixotropic substance, and white pigment were mixed in the amounts shown in Table 1. Each particle was prepared, and the rotational property, CR, and CR change rate of the particle were measured. The results are shown in Table 1.
[Comparative Examples 1-3]
The composition, raw material adjustment liquids A and B, spherical shape as in Example 1 except that the (meth) acrylic acid ester monomer, other monomers, inorganic thixotropic substance, and white pigment were mixed in the amounts shown in Table 1. Each particle was prepared, and the rotational property, CR and CR change rate of the particle were measured. The results are shown in Table 1.

MMA ... Methyl methacrylate BMA ... Butyl methacrylate TMPTA ... Trimethylolpropane triacrylate EGDMA ... Ethylene glycol dimethacrylate R711 ... Nippon Aerosil's hydrophobic silica R972 ... Nippon Aerosil's Hydrophobic silica R812: Hydrophobic silica R200 manufactured by Nippon Aerosil Co., Ltd. Hydrophilic silica PVA manufactured by Nippon Aerosil Co., Ltd. Polyvinyl alcohol CR-50-2 Titanium white manufactured by Ishihara Sangyo Co., Ltd.

As is clear from the results shown in Table 1, the electronic papers of Examples 1 to 4 using the composition of the present invention have a small CR change rate, and a desired image can be retained for a long time even in a charge-free state. I understand.
On the other hand, when the white pigment concentration is high as in Comparative Example 1, although the initial CR shows a high value, the CR change rate is high and a desired image is not held for a long time. Further, when only the white pigment concentration is reduced for the purpose of eliminating the specific gravity difference between black and white as in Comparative Example 2, the CR change rate can be reduced, but the initial CR becomes low. Further, when the organic thixotropic agent was added as in Comparative Example 3, two-color droplets with clear color separation were not generated, and the rotational properties of the particles were poor. This is thought to be because the O / W or W / O state became difficult to form in the microchannel in which the fluid medium flows, and the color separation of the two colors on the surface of the spherical particles became unclear. It is done.

  The electronic paper of the present invention formed using the composition of the present invention and spherical particles is useful as various thin display devices.

Claims (9)

Spherical particles formed using a composition for forming spherical particles that are different in color for each hemisphere and charged in a dipole state,
The composition is
(Meth) acrylic acid ester monomers,
Ri Na and a finely divided silica as inorganic thixotropic material,
A spherical particle formed using a microchannel method .
Spherical particles formed using a composition for forming spherical particles that are different in color for each hemisphere and charged in a dipole state,
The composition includes a (meth) acrylic acid ester monomer,
Of the two hemispheres, the hemisphere having the higher specific gravity of the composition constituting the hemisphere contains finely divided silica as an inorganic thixotropic agent.
Spherical particles characterized by that.
Of the two hemispheres, the hemisphere having the lower specific gravity of the composition constituting the hemisphere does not contain an inorganic thixotropic agent.
The spherical particles according to claim 2, wherein:
The hemisphere having the higher specific gravity of the composition constituting the hemisphere is the hemisphere in which pigment sedimentation occurs unless the inorganic far-modifying additive is included.
The spherical particles according to claim 2, wherein:
The hemisphere having the higher specific gravity of the composition constituting the hemisphere is a white hemisphere.
The spherical particles according to claim 2, wherein:
The fine powder silica is hydrophobic silica
3. The spherical particle according to claim 1 or 2, wherein
The composition further comprises a charge control agent,
The inorganic far modified modifier is a component added separately from the charge control agent.
The spherical particle according to claim 1 or 2.
The amount of the inorganic thixotropic agent added is as follows:
For 100 parts by weight of the (meth) acrylic acid ester monomer,
The spherical particles according to claim 1 or 2 , wherein the inorganic thixotropic substance is 1 to 30 parts by weight.
A pair of supports;
The spherical particles according to any one of claims 1 to 8 located between the pair of supports,
An electronic paper in which a film located on at least a side visually recognized by the user of the pair of supports is a light transmissive support that transmits visible light.