JP2008158092A - Particle for display device, liquid for electrophoresis display, and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophoresis display device in which a response speed is quick. <P>SOLUTION: Particles for a display device covers a compound having at least one functional group denoted by general formula (1) (herein, Y denotes hydrogen atom or a cyano group) on the surface of non-transmission particles. Liquid for electrophoresis display consisting of the particles for the display device and a scattering medium and the electrophoresis display device arranging the liquid for the electrophoresis display between a set of composite electrode plates are provided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to particles for display devices, electrophoretic display liquids, and display devices, and more particularly to an electrophoretic display device capable of high-contrast display having a metallic luster.

In recent years, with the development of information equipment, the demand for low power consumption, thinning, and flexibility of display devices has increased, and research and development of display devices that meet these demands have been actively conducted. . Among them, a display device that has attracted particular attention is a so-called electronic paper.
Various types of electronic paper have been proposed, and examples include electrophoresis type, twist ball type, storage liquid crystal type, electrochromy type, thermal rewritable type, magnetophoretic type, and toner. Is a bistable display device that is common in that energy such as electric power and magnetic force is required only at the time of switching the display, and energy is not required for maintaining the display.
On the other hand, prints with high design that express subtle interference colors, pearly luster, metallic luster, and the like have been used for advertising display media such as magazines, posters, POPs, and billboards. In particular, since an advertisement display medium is favorably printed so as to attract the viewer's line of sight and interest, not only color display but also printing having a special effect has been adopted. In recent years, by using the above-described bistable display device for advertisement display media such as magazines, posters, POPs, and public notice signs, it is possible to switch advertisement display, such as advertisement printed matter that has been impossible to switch display until now. In addition, it has been proposed that the design property is higher and the viewer's line of sight and interest are drawn strongly (see, for example, Patent Document 1 and Patent Document 2).
However, the color display methods as shown in Patent Document 1 and Patent Document 2 can perform display-switchable color display, but have high design properties, particularly delicate interference colors, pearly luster, and metallic luster. Etc. have problems such as being very difficult to reproduce.
In Patent Document 3, a pigment in which a core material is coated with a metal or a translucent metal oxide, a pigment made of metal flakes, or a pigment in which a metal is dispersed in a resin matrix is used for display technology by electrophoresis. It is disclosed. However, in this case, since the pigment used has anisotropy, the charging characteristics of the particles are not uniform, so the moving performance of the particles during driving is not sufficient, and the contrast as the display performance is sufficient. is not. In addition, the system described is a toner type, which is not sufficient in that the driving voltage is high due to the high specific gravity of the pigment used.

JP 2003-161822 A JP 2000-035598 A JP 2005-165086 A

  Under such circumstances, the object of the present invention is to provide a design having a metallic luster that can be switched to a high display, a high contrast and a good display, and a display performance that does not deteriorate over time. The object is to provide particles for display devices, liquids for electrophoretic display, and display devices.

  As a result of various studies, the present inventors have obtained the above problem by using particles for display devices in which a non-light-transmitting particle surface is coated with a compound having at least one functional group having a specific structure. The present invention has been completed.

That is, the present invention provides the following (1) to (10).
(1) The following general formula (1)

Particles for a display device provided with a coating layer of a compound having at least one functional group represented by
(2) A compound having at least one functional group represented by the general formula (1) is represented by the general formula (2)

[X ¹ is NH or O or S; X ² is N or O or S; X ³ is NH or O or S; R ¹ is a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aromatic group. Substituted or unsubstituted heterocyclic group, formyl group, acyl group, alkoxycarbonyl group or alkenyl group; R ² represents a hydrogen atom, tricyanoethenyl group, substituted or unsubstituted alkyl group, substituted or unsubstituted aromatic group A group, a substituted or unsubstituted heterocyclic group, a formyl group, an acyl group, an alkoxycarbonyl group or an alkenyl group; R ³ and R ⁴ are each independently a hydrogen atom or a substituted or unsubstituted aromatic group; It is an integer of ~ 3]
The particles for display devices according to the above (1), which is a compound represented by:
(3) A compound having at least one functional group represented by the general formula (1) is represented by the following general formula (3)

[A ¹ is a substituted or unsubstituted aromatic group, a substituted or unsubstituted heterocyclic group, a substituted or unsubstituted condensed Hajime Tamaki, a substituted or unsubstituted alicyclic group, a substituted or unsubstituted spiro ring A dendrimer structure having a group, a substituted or unsubstituted biphenyl residue, a fluorene residue or a triphenylamine skeleton as the core; X ⁴ is a substituted or unsubstituted aromatic group or a substituted or unsubstituted heterocyclic group; R ⁵ Is a substituted or unsubstituted aromatic group, a substituted or unsubstituted heterocyclic group, an alkyl group, an alkenyl group, or a cycloalkyl group; n is an integer of 2 or more, and two or more of R ⁵ and X ⁴ are It can be the same or different]
The particles for display devices according to the above (1), which is a compound represented by:
(4) The display device particle according to any one of (1) to (3), wherein the non-light-transmitting particle is a resin particle in which an inorganic pigment and / or an organic pigment is dispersed in a resin matrix,
(5) The display device particle according to any one of (1) to (4), wherein the particle is subjected to a lipophilic surface treatment.
(6) The particles for a display device according to any one of (1) to (5), wherein the average particle diameter of the particles is 1 to 50 μm,
(7) The display device particle according to any one of (1) to (6), wherein the non-light-transmissive particle is a porous body.
(8) The display device particle according to any one of (1) to (7), wherein the surface of the coating layer of the compound is further coated with an organic or inorganic layer,
(9) An electrophoretic display liquid comprising the dispersion medium and the display device particles according to any one of (1) to (8) dispersed in the same dispersion medium, and (10) the electricity according to (9) Provided is an electrophoretic display device in which an electrophoretic display liquid is disposed between a pair of counter electrode plates.

  According to the present invention, it is possible to switch display with metallic luster, high design, high contrast, good display, and display device particles that display performance does not deteriorate over time, An electrophoretic display solution and a display device are provided.

Hereinafter, the present invention will be described in detail.
The display device particle of the present invention is characterized in that a coating layer of a compound having at least one functional group represented by the general formula (1) is provided on the surface of the non-light-transmitting particle.
The “non-light transmissive particles” in the display device particles of the present invention include inorganic pigment particles and organic pigment particles themselves as well as resin particles made of an organic material in which they are dispersed in a resin matrix.
Examples of inorganic pigment particles include titanium dioxide, zinc sulfide, calcium carbonate, silica, calcium silicate, white lead, zinc white, zinc white, lithopone, antimony oxide, kaolin, mica, barium sulfate, gloss white, alumina white, talc, cadmium. Yellow, cadmium lipotone yellow, yellow iron oxide, titanium yellow, titanium barium yellow, cadmium orange, cadmium lipoton orange, molybdate orange, bengara, red lead, silver vermilion, cadmium red, cadmium lipoton red, amber, brown iron oxide , Zinc iron, chrome brown, chrome green, chromium oxide, viridian, cobalt green, cobalt chrome green, titanium cobalt green, bitumen, cobalt blue, ultramarine, cerulean blue, cobalt aluminum chrome Blue, cobalt violet, mineral violet, carbon black, iron black, manganese ferrite black, cobalt ferrite black, copper chrome black, copper chrome manganese black, black low-order titanium oxide, aluminum powder, copper powder, lead powder, tin powder, zinc The particle | grains which consist of at least 1 sort (s) chosen from powder | flour etc. are mentioned.
In order to develop sufficient contrast, it is preferable to use particles such as titanium dioxide and zinc oxide from the viewpoint of non-light transmission and high light scattering effect.

Organic pigment particles include, for example, fast yellow, disazo yellow, condensed azo yellow, anthrapyrimidine yellow, isoindoline yellow, copper azomethine yellow, quinophthaloin yellow, benzimidazolone yellow, nickel dioxime yellow, monoazo yellow lake, dinitro Aniline Orange, Pyrazolone Orange, Perinone Orange, Naphthol Red, Toluidine Red, Permanent Carmine, Brilliant Fast Scarlet, Pyrazolone Red, Rhodamine 6G Lake, Permanent Red, Resol Red, Bon Lake Red, Lake Red, Priliant Carmine, Bordeaux 10B, Naphthol Red, Quinacridone Magenta, Condensed Azo Red, Naphthol Carmine, Berylens Carred, Condensed Zoskar Red, Benzimidazolone Carmine, Anthraquinonyl Red, Perylene Red, Perylene Maroon, Quinacridone Maroon, Quinacridone Scarred, Quinacridone Red, Diketopyrrolopyrrole Red, Benzimidazolone Brown, Phthalocyanine Green, Victoria Blue Lake, Phthalocyanine Blue, Fast Examples thereof include particles composed of at least one selected from sky blue, alkali blue toner, indanthrone blue, rhodamine B lake, methyl violet lake, dioxazine violet, naphthol violet, and the like.
These pigments can be appropriately selected from the viewpoint of adjusting the color tone, such as phthalocyanine blue for obtaining a desired bright color, for example, a blue bright color, and azo red for obtaining a red bright color. .
Depending on the purpose, one or more inorganic pigments and organic pigments can be blended and used.

The pigment particles can be used after being subjected to the lipophilic surface treatment described later, or may be used as particles dispersed in a resin matrix insoluble in a dispersion medium described later.
Further, the pigment particles may be used as particles in a state in which a lipophilic surface treatment is performed and the pigment particles are dispersed in a resin matrix insoluble in a dispersion medium.
Examples of the resin insoluble in the dispersion medium include highly crosslinked acrylic resins (crosslinked polymethyl methacrylate, crosslinked styrene-acrylic resin, etc.). These resins may be produced by a wet production method such as an emulsion polymerization method or a suspension polymerization method, or may be produced by a conventional pulverization classification method. The particles obtained by the wet manufacturing method become spherical particles, and the particles obtained by the pulverization classification method become amorphous particles.
Further, heat treatment may be performed in order to make the spherical particles and irregular particles obtained by these production methods uniform in shape. Examples of the method for aligning the particle size distribution include a method of adjusting the granulation conditions in the above-described wet manufacturing method and classifying the particles once obtained.
When adjusting the granulation conditions in the wet manufacturing method, adjust the stirring speed when dispersing the oil phase in which the materials constituting the particles for display devices are dispersed in the aqueous phase, or use a surfactant. In this case, the particle size distribution of the particles can be controlled by adjusting the concentration.
In addition, as a method for classifying particles, for example, various vibrating sieves, ultrasonic sieves, pneumatic sieves, and wet sieves, a method using a rotor rotary classifier using the principle of centrifugal force, a wind classifier, etc. However, it is not limited to these. These can be adjusted to a desired particle size distribution either alone or in combination. In particular, when adjusting precisely, it is preferable to use a wet sieve. In the case of using a classifier, for example, in a rotary classifier, components on the fine powder side / coarse powder side can be selectively removed from the particles before classification by controlling the rotation speed. Moreover, as a sieve, it is preferable to use a nylon sieve at the point that the distribution of opening is narrow and a high yield can be obtained.
The shape of the particles for display device is desirably close to a true sphere. In the case of a particle close to a true sphere, the contact between the particles is almost a point contact, and the contact between the particle and the counter electrode plate described later is also a point contact, and between the particles and between the particle and the counter electrode plate surface. The adhesion force based on the van der Waals force becomes smaller. Moreover, it becomes easy to control the charge density on the particle surface. Therefore, even if the surface between the counter electrode plates is a derivative, it is considered that particles charged by the electric field can move smoothly between the counter electrode plates.

Examples of the resin insoluble in the dispersion medium include, in addition to the above highly crosslinked acrylic resins, phenolic resins, melamine resins, thermosetting resins such as urea-formalin resins, polyolefin resins such as polyethylene and polypropylene, and polytetrafluoroethylene resins. Examples thereof include a fluorine resin, a polyoxymethylene resin such as polyacetal, an epoxy resin, a urethane resin, a silicone resin, and a polyester resin.
The content of the pigment particles is usually 0 to 50%, preferably 5 to 30% on a mass basis in the total amount of the resin insoluble in the dispersion medium.
By adding the resin, the surface of the pigment particles is smoothed, the shape of the particles is made close to a true sphere, and the surface properties of the particles can be easily controlled, and the display properties are improved.
The average particle diameter of the non-light-transmitting particles is usually 0.1 to 50 μm, preferably 0.5 to 30 μm, and more preferably 1 to 20 μm. By setting the average particle diameter to 1 μm or more, it is possible to prevent the dispersion system from becoming unstable due to the influence of diffusion due to the Brownian motion of the fine particles, the display characteristics being lowered, and the tendency of aggregation to become strong. On the other hand, when the average particle size is 50 μm or less, fine particles are likely to settle, and display memory properties and dispersion stability are prevented from deteriorating.
The non-light-transmitting particles are preferably porous bodies having voids inside, and by making the particles porous, the apparent specific gravity can be reduced, and the particles move smoothly between the counter electrode plates. And the response speed of the display device can be increased.
In order to make the non-light-transmitting particles porous, a method such as a fusion method is used in the dry method, a relaxation coagulation method, or a spinodal decomposition type phase separation method is used in the sintering method or the wet method.

The compound having at least one functional group represented by the above general formula (1) for coating the non-light-transmitting particle surface has Y as a hydrogen atom or a cyano group. From the viewpoint of crystallinity and glitter, it is preferably a cyano group.

  Specifically, the compound represented by the general formula (2) (1-substituted 2,5-dithienylpyrrole derivative and the like) and the compound represented by the general formula (3) (4-tricyanoethenylphenyl derivative and the like). Is mentioned.

In the general formula (2), X ¹ and X ³ are NH or O or S, and X ² is N or O or S. From the viewpoint of self-assembly stability and π-electron system interaction Therefore, X ¹ and X ³ are preferably S, and X ² is preferably NH, and exhibits a stronger metallic luster.

R ¹ is a hydrogen atom, a substituted or unsubstituted alkyl group (including a cycloalkyl group), a substituted or unsubstituted aromatic group, a formyl group, an acyl group, an alkoxycarbonyl group, and an alkenyl group. The alkyl group constituting R ^1, preferably an alkyl group having 1 to 30 carbon atoms, particularly preferably an alkyl group having 1 to 18 carbon atoms. The alkyl group may be linear, branched or cyclic, and examples of the substituent of the alkyl group include an alkoxy group having 1 to 18 carbon atoms, a phenyl group, a naphthyl group, a benzothienyl group, an indolyl group, and a pyridyl group. Aromatic groups such as phenoxy group, naphthyloxy group, bromine, iodine, chlorine and fluorine are particularly preferred. As the aromatic group, a phenyl group, a naphthyl group, a thienyl group, a benzothienyl group, an indolyl group, a pyridyl group, and the like are preferable. As the substituent of the aromatic group, an alkyl group having 1 to 18 carbon atoms, an alkoxy group having 1 to 18 carbon atoms, a phenoxy group, a naphthyloxy group, bromine, iodine, chlorine, fluorine, a monoalkylamino group, a dialkylamino group , Monoarylamino group, diarylamino group, and thioalkyl group are preferable, and the number of carbon atoms of the alkyl group constituting the thioalkyl group is preferably 1 to 18.
R ¹ is preferably a cyanophenyl group from the viewpoint that the interaction between molecules is further strengthened by the continuous π electron system in the molecule.
R ² represents a hydrogen atom, a tricyanoethenyl group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aromatic group, a substituted or unsubstituted heterocyclic group, a formyl group, an acyl group, an alkoxycarbonyl group, or an alkenyl group. It is.
The substituted or unsubstituted aromatic group means a group derived from a group of compounds having 6 to 30 carbon atoms such as a benzene ring and a naphthalene ring. More specifically, a substituted or unsubstituted phenyl group, biphenyl group, naphthyl group, and the like.
Substituted or unsubstituted heterocyclic groups include pyridine ring, pyrazine ring, pyrimidine ring, pyridazine ring, triazine ring, indoline ring, quinoline ring, acridine ring, carbazole ring, furan ring, thiophene ring, oxazole ring, oxadiene A group derived from a compound group composed of 2 to 30 carbon atoms such as azole ring, benzoxazole ring, thiazole ring, thiadiazole ring, benzothiazole ring, triazole ring, benzotriazole ring, imidazole ring, benzimidazole ring .
R ³ and R ⁴ are each independently a hydrogen atom or a substituted or unsubstituted aromatic group. The substituted or unsubstituted aromatic group means a group derived from a group of compounds having 6 to 30 carbon atoms such as a benzene ring and a naphthalene ring. A substituted or unsubstituted phenyl group, biphenyl group, naphthyl group and the like;

In the compound represented by the general formula (3), the substituted or unsubstituted aromatic group in A ¹ refers to a group derived from a group of compounds having 6 to 30 carbon atoms such as a benzene ring and a naphthalene ring.
More specifically, they are benzylene group, biphenylene group, naphthylene group and the like. Heterocyclic groups are pyridine ring, pyrazine ring, pyrimidine ring, pyridazine ring, triazine ring, indoline ring, quinoline ring, acridine ring, carbazole ring, furan ring, thiophene ring, oxazole ring, oxadiazole ring, benzoxazole A group derived from a group of compounds having 2 to 30 carbon atoms, such as a ring, a thiazole ring, a thiadiazole ring, a benzothiazole ring, a triazole ring, a benzotriazole ring, an imidazole ring, and a benzimidazole ring.
A substituted or unsubstituted condensed polycyclic residue is a group derived from a compound obtained by condensing one or more aromatic rings or heterocyclic rings to the above aromatic group or heterocyclic group, Or an unsubstituted alicyclic group means a group derived from a saturated cyclic carbon compound derivative such as cyclopropane, cyclobutane, cyclopentane, cyclohexane, etc., including those in which a part of the ring is unsaturated, Alternatively, the unsubstituted spiro ring includes a group derived from a compound containing a spiro atom as part of its structure. A substituted or unsubstituted biphenyl residue is a group derived from a compound in which two or more aromatic groups as defined above are bonded by a single bond, and a fluorene residue is a compound having a fluorene ring as part of its structure. A group derived from a triphenylamine residue means a group derived from a compound containing a dendrimer structure having a triphenylamine structure as a core in a part of the structure.
An aromatic group such as a biphenylene group is preferred.
X ¹ is a substituted or unsubstituted aromatic group or a substituted or unsubstituted heterocyclic group, preferably from the viewpoint of enhancing the intermolecular interaction by the π electron system and improving the crystallinity by the stack structure. Is an aromatic group having 6 or more carbon atoms such as a phenylene group.

R ¹ is an unsubstituted aromatic group, a heterocyclic group, an alkyl group, an alkenyl group or a cycloalkyl group, but from the viewpoint of strengthening the intermolecular interaction by the π electron system and structuring the crystallinity by the stack structure. An aromatic group such as a phenyl group or a naphthyl group is preferable.
n is an integer of 2 or more, and generally represents an integer of 2 to 100. Two or more R ¹ may be the same or different from each other, and two or more X ¹ may be the same or different from each other.
The substituents in A ¹ , X ¹ and R ¹ are an alkyl group which may have a substituent, a cycloalkyl group which may have a substituent, an alkenyl group which may have a substituent, and a substituent. An aryl group that may have a substituent, a heterocyclic group that may have a substituent, an alkoxy group that may have a substituent, an alkylthio group that may have a substituent, and a substituent. Good aryloxy group, arylthio group which may have a substituent, alkenyloxy group which may have a substituent, acyloxy group, alkoxycarbonyl group, carbamoyl group, acylamino group, amino which may have a substituent Group, acyl group, sulfonamido group, cyano group, nitro group, halogen atom, silyl group, carboxyl group, phosphoryl group, phosphonyl group, sulfonyl group, sulfonic acid group, hydroxy group, thiol group, Examples thereof include, but are not limited to, a droxamic acid group, and a plurality of one type of groups or one or a plurality of two or more types of substituents may be included. Further, substituents may be bonded to form a ring, and a salt may be formed with an alkali metal, alkaline earth metal, quaternary ammonium or the like depending on the application.
As the compound represented by the general formula (2) or (3), each of various compounds may be used alone, or at least one of the respective compounds may be used in combination of two or more.

  Specific examples of the compound represented by the general formula (2) include the following formula (4):

The compound represented by these is mentioned.
In addition, many specific examples of the compound represented by the general formula (2) are disclosed in JP-A No. 2001-353882, and these are also included in the compound represented by the general formula (2).

  Specific examples of the compound represented by the general formula (3) include the following formula (5) or (6)

The compound represented by these is mentioned.
In addition, many specific examples of the compound represented by the general formula (3) are disclosed in JP-A-2004-315545 [Formulas (1) to (32)], and these are also represented by the general formula (3). Included in the compound.

Together with the compound having at least one functional group represented by the general formula (1), a charge control agent and a resistance adjusting agent can be mixed and used as necessary.
Known charge control agents can be used, for example, quaternary ammonium salts such as cetylpyridyl chloride, P-51, P-53 [manufactured by Orient Chemical Co., Ltd.], salicylic acid metal complexes, phenolic Examples include condensates, tetraphenyl compounds, calixarene compounds, metal oxide fine particles, or metal oxide fine particles that are surface-treated with various coupling agents. The charge control agent is preferably colorless or has a low coloring power.
The addition amount is preferably in the range of 0.1 to 10% by mass in the total amount with the compound having at least one functional group represented by the general formula (1), and 0.5 to 5% by mass The range of is more preferable.
As the resistance adjuster, an inorganic fine powder having a resistance value of 1 × 10 ⁶ Ωcm or less can be used. For example, fine particles coated with tin oxide, titanium oxide, zinc oxide, iron oxide, various conductive oxides ( For example, tin oxide-coated titanium oxide and the like. The resistance adjuster is preferably colorless or has a low coloring power. The addition amount is preferably in a range that does not interfere with the color of the particles for display devices colored by the colored fine particles. Specifically, the compound has at least one functional group represented by the general formula (1). Is preferably in the range of 0.1% by mass to 10% by mass.

The coating amount of the compound having at least one functional group represented by the general formula (1) is usually 0.5 to 100%, preferably 5 to 50% on a mass basis with respect to the non-light-transmitting particles. is there. By setting it to 0.5% or more, it is possible to ensure a sufficient thickness of the compound film. By setting it to 100% or less, the uniformity of the coating can be ensured.
The coating of the compound having at least one functional group represented by the general formula (1) on the surface of the non-light-transmitting particles is performed by using various organic compounds having at least one functional group represented by the general formula (1). It is carried out by dissolving in a solvent, adding particles therein and dispersing sufficiently using ultrasonic waves or the like, and then heating under reduced pressure as necessary to evaporate the solvent.
The organic solvent to be used is appropriately selected depending on the compound having at least one functional group represented by the above general formula (1) to be used. Alcohols such as ethanol, esters such as ethyl acetate, ethyl ether Ethers such as, ketones such as methyl ethyl ketone, aromatic hydrocarbons such as xylene, aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane, and terpenes.

Regardless of whether or not the non-light-transmitting particles contain a resin insoluble in the dispersion medium, the non-light-transmitting particles are subjected to a lipophilic surface treatment with the resin and the functional group represented by the general formula (1). This is preferable from the viewpoint of ensuring adhesion with the coating of at least one compound.
Examples of the lipophilic surface treatment agent include a coupling agent, a pigment derivative, and a lipophilic surfactant, and the use of a coupling agent is particularly desirable from the viewpoint of dispersibility and fluidity. Examples of coupling agents that can be used include silane coupling agents, titanate coupling agents, aluminum coupling agents, zirconium coupling agents, zircoaluminate coupling agents, chromium coupling agents, and Includes a fluorine-based coupling agent.
Examples of these various coupling agents include, but are not limited to, the following.
Examples of titanate coupling agents include isopropyl triisostearoyl titanate. Examples of aluminum coupling agents include acetoalkoxyaluminum diisopropylate. Examples of silane coupling agents include 3-aminopropyltriethoxy. Silanes, zirconium-based coupling agents, for example, zirconium butyrate, etc., zircoaluminate-based coupling agents, for example, tetrapropylzircoaluminate, etc., chromium-based coupling agents, for example, chromium methacrylate and chromium chloride Examples of the fluorine-based coupling agent such as a complex of trifluoropropyltrimethoxysilane include trifluoropropyltrimethoxysilane.
About each said coupling agent, besides using each individually (1 type), it is also possible to mix and use a plurality (two or more types) of coupling agents, and also to use a plurality of coupling agents. It is also possible to perform processing step by step. Further, among the various coupling agents described above, in particular, when a titanate coupling agent, an aluminum coupling agent, or a silane coupling agent is used, it is desirable from the point of showing further excellent effects.

Particles subjected to lipophilic surface treatment (non-light-transmitting particles) are commercially available and can be used as they are.
Specifically, ITT-2 TiO ₂ CR-50 (manufactured by Nikko Chemicals, titanium oxide particles having a surface treated with a titanium coupling agent, average particle size of about 0.4 μm), ITT-7 TiO ₂ TTO-S— 3 [manufactured by Nikko Chemicals Co., Ltd., fine particle titanium oxide whose surface was treated with a titanium coupling agent, average particle size of about 0.05 to 0.1 μm], KR-380 [manufactured by Titanium Industry Co., Ltd., surface oleophilic Titanium oxide particles treated with a surface treatment agent, average particle size of about 0.5 μm], KR-270 [manufactured by Titanium Industry Co., Ltd., titanium oxide whose surface was treated with a lipophilic surface treatment agent, average particle size of about 0.4 μm ], Taipei CR-50 [Ishihara Sangyo Co., Ltd., titanium oxide particles having a hydrophilic surface, average particle size of about 0.4 μm] coupling agent (for example, aluminum coupling agent, silane coupling agent) Such as treated particles.

In addition, the display device particles of the present invention, whether or not containing a resin, are further organic or inorganic on the surface of the coating layer of the compound having at least one functional group represented by the general formula (1). It is preferred that the layer is coated. By coating with an organic layer or an inorganic layer, migration of a compound having at least one functional group represented by the general formula (1) to a dispersion medium or the like can be suppressed, and also from the viewpoint of charge control and the like. Depending on the purpose, an organic or inorganic layer is introduced. Further, by further covering the organic or inorganic layer, aggregation between particles can be prevented.
The material for forming the organic or inorganic layer is not particularly limited, and various surfactants, resins, surface coating agents, silica, alumina, fine particle titanium oxide, metal oxides, organic / inorganic hybrid materials, etc. Is mentioned.
These materials preferably have sufficient light transmittance in consideration of not affecting the metallic luster. Further, the coating layer surface of the non-light-transmitting particles is coated using a dry method or a wet method, and in some cases, a vacuum process.

Along with the above display device particles, the present invention also provides an electrophoretic display liquid comprising a dispersion medium and the display device particles dispersed therein.
Hereinafter, the electrophoretic display liquid of the present invention will be described.
The electrophoretic display liquid of the present invention is obtained by dispersing the display device particles in a dispersion medium.
As the dispersion medium to be used, for example, various types used in conventional electrophoretic display can be used. A dispersion medium having a low dielectric constant such as paraffin having 5 or more carbon atoms such as dodecane, isoparaffin, xylene, tetrachloroethylene, silicone oil, and terpene compound is used. Above all, dodecane, isoparaffin, and terpene can be used from the viewpoint of further improving white reflectance in display devices, maintaining stable quality over a long period of time, and reducing the impact on the human body and environmental impact. Compounds are preferred.
These can be used alone or as a mixture. As other dispersion media that can be used, for example, various types of media conventionally used for electrophoretic display can be used.
Specifically, examples of the aromatic hydrocarbon include benzene, alkylbenzene derivatives such as toluene, ethylbenzesi, and dodecylbenzene, phenylxylylethane, 1,1-ditolylethane, 1,2-ditolylethane, 1,2-bis ( Diarylalkane derivatives such as 3,4-dimethylphenylethane (BDMF), alkylnaphthalene derivatives such as diisopropylnaphthalene, alkylbiphenyl derivatives such as monoisopropylbiphenyl, isopropylbiphenyl, isoamylbiphenyl, and terphenyl hydrogenated at various ratios Derivatives, triallyldimethane derivatives such as dibenzyltoluene, benzylnaphthalene derivatives, phenylene oxide derivatives, diallylalkylene derivatives, allylindane derivatives, polychlorinated biphenyl derivatives, naphthenic carbonization Arsenide, and the like.
In addition, aliphatic hydrocarbons such as hexane, cyclohexane, kerosene, isopar, paraffin hydrocarbons, halogenated hydrocarbons such as chloroform, trichloroethylene, tetrachloroethylene, trifluoroethylene, tetrafluoroethylene, dichloromethane, ethyl bromide, phosphorus Phosphate esters such as tricresyl acid, trioctyl phosphate, octeldiphenyl phosphate, tricyclohexyl phosphate, dibutyl phthalate, dioctyl phthalate, dilauryl phthalate, dicyclohexyl phthalate, butyl oleate, Diethylene glycol dibenzoate, dioctyl sebacate, dibutyl sebacate, dioctel adipate, trioctyl trimellitic acid, acetyl triethyl citrate, octyl maleate, male Phosphate, dibutyl acid esters such as ethyl acetate, chlorinated paraffin, N, N-dibutyl-2-butoxy-5-but-tertiary octyl aniline, and the like, but is not limited thereto.

The content of these dispersion media is appropriately determined depending on the type of non-light-transmitting particles coated with a compound having at least one functional group represented by the general formula (1). It is preferable that it is 25-85 mass% in a liquid whole quantity, More preferably, it is 30-60 mass%. By setting the content of the dispersion medium to 25% by mass or more, the viscosity of the liquid is prevented from increasing and the response speed is reduced. On the other hand, by setting it to 85% by mass or less, sufficient contrast is displayed. Can do.
Dispersion media include hydroxyethyl lauryl amine, polyethylene glycol stearyl amine, polyethylene glycol lauryl amine, polyethylene glycol diolyl amine, polyethylene glycol alkyl (tallow) amine, polyoxyethylene alkyl (tallow) propylene diamine, polyethylene glycol alkyl (deer) Alkyl polyether amines such as amines and polyethylene glycol alkyl (coconut) amines can also be added as charge control agents.
In order to prevent aggregation between the particles, the dispersion is further added with a dispersant such as a nonionic surfactant, an anionic surfactant, a cationic surfactant, an amphoteric surfactant, and a polymer surfactant. Can be added.
Nonionic surfactants include, for example, sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan dilaurate, sorbitan dipalmitate, sorbitan distearate, sorbitan sesquilaurate, sorbitan sesquipalmitate, sorbitan sesquiskites. As sorbitan fatty acid esters such as stearate, sorbitan monooleate, sorbitan dioleate, sorbitan sesquioleate, sorbitan trioleate, anionic surfactants, for example, special fatty acid soap, cationic surfactant, for _{example, R-N (CH 3)} 3X alkyl trimethylamine system [R = stearyl, cetyl, lauryl, oleyl, dodecyl, coconut, soybean, tallow, etc. / X is halogen, amine, etc.] represented by Examples of quaternary ammonium salts and amphoteric surfactants include various betaine surfactants. Examples of anionic polymer surfactants include styrene-maleic anhydride copolymers and cationic polymer surfactants. Examples of the activator include polyethyleneimine and nonionic polymer type surfactants such as polyvinyl alcohol.
These dispersants can be used alone or in combination of two or more, and the content thereof is appropriately determined depending on the fine particles and solvent type used. 0.01 to 50.0% by mass, and more preferably 1 to 30% by mass.
By setting the content of the dispersant to 0.01% by mass or less, sufficient dispersion stability of the dispersion can be ensured. On the other hand, by setting the content to 50% by mass or less, the conductivity of the dispersion can be increased. The display characteristics are prevented from being adversely affected by increasing the viscosity of the dispersion system.

Furthermore, the present invention also provides a display device in which the display liquid is disposed between a pair of counter electrode plates.
In the display device of the present invention, it is necessary that at least one of the pair of counter electrode plates is transparent. By applying a voltage to the counter electrode plate, it is possible to obtain a density contrast between the positively charged particles and the negatively charged particles in the dispersion, and display characters and figures. It becomes possible to do.

The electrode plate used may be a conductive plate or a conductive surface of an insulating support, and may be crystalline or amorphous. Good. Examples of the conductive electrode plate in which the electrode plate itself is conductive include metals such as aluminum, stainless steel, nickel, chromium, and alloy crystals thereof, and semiconductors such as Si, GaAs, GaP, GaN, SiC, and ZnO. .
Examples of the insulating support include a polymer film, glass, quartz, and ceramic. Conductive treatment of the insulating support is performed by vapor deposition, sputtering, ion plating, using the metal or gold, silver, copper, etc. mentioned in the specific example of the conductive electrode plate in which the electrode plate itself is conductive. It can be performed by film formation. The thickness of the conductive thin film is about 0.01 to 0.5 μm, preferably about 0.05 to 0.3 μm.
As the transparent conductive electrode plate, a conductive electrode plate in which a transparent electrode is formed on one side of an insulating transparent support, or a transparent support having its own conductivity is used. Examples of the transparent support having its own conductivity include transparent conductive materials such as ITO (Indium-Tin Oxide), zinc oxide, tin oxide, lead oxide, indium oxide, and copper iodide.
Insulating transparent supports include transparent inorganic materials such as glass, quartz, sapphire, MgO, LiF, and CaF ₂ , and transparent organic polymer films such as fluororesin, polyester, polycarbonate, polyethylene, and polyethylene terephthalate Alternatively, a plate-like body can be used.
As a transparent electrode provided on one side of the transparent support, a transparent conductive material such as ITO, zinc oxide, tin oxide, lead oxide, indium oxide, copper iodide is used, and by a method such as vapor deposition, ion plating, sputtering, etc. A formed one or a thin one made of metal such as Al, Ni, Au or the like so as to be translucent by vapor deposition or sputtering is used.
The thickness of the insulating transparent support is usually 1 to 500 μm, preferably 10 to 200 μm.
In the electrophoretic display device of the present invention, a film-like sheet having a large number of cells containing an electrophoretic display liquid can be sandwiched between the counter electrodes. This film-like sheet can be produced by processing and forming fine cells on a thin film sheet by applying various UV laser processing techniques, photoetching methods, and various printing methods.

Hereinafter, a manufacturing process and the like of the electrophoretic display device of the present invention will be described with reference to schematic views.
FIG. 1 is a schematic view showing a cross section of the display device of the present invention in a state where a device display liquid is not sealed, and 10 and 15 are a pair of counter electrode plates. A pair of counter electrode plates 10 and 15 are separated by a spacer 20.
FIG. 2 is an enlarged view of the dotted line display portion in FIG. 1, but shows a state where the spacer is not bonded to the transparent electrode on the front surface, and shows a state where an arbitrary constant distance is maintained. . In the case where the counter electrode has flexibility, the state of being bonded in this way is preferable, but in the case of a hard substrate such as glass, it may be bonded.
FIG. 3 is a perspective view showing a spacer, and FIGS. 4 and 5 are schematic views showing the shape of an opening for forming a spacer cell. The shape of the opening includes a circle, a rectangle (rectangle, square), a hexagon, and the like, but a square and a hexagon are preferable from the viewpoint of securing a high aperture ratio and maintaining the uniformity of display.
6 [(a) to (d)] are schematic views showing a manufacturing process of the display device of the present invention.
First, a pair of counter electrode plates (a front electrode 10 and a back electrode 15) is prepared, and a spacer 20 is placed on the electrode plate of the back electrode 15 [(a) to (b)]. A barrier wall 30 to the outside is attached to the four side edges of the electrode plate, and the edge of the back electrode 15 and the barrier wall 30 are bonded [(c)]. Next, after injecting an electrophoretic display liquid used as a display element and disposing the front electrode 10, the front electrode 10 and the blocking wall 30 are bonded [(d)] to produce a display device.
FIG. 7 [(a) to (g)] shows a schematic diagram of a step of manufacturing a display device by combining a step by photolithography which is an example of a method of manufacturing the spacer 20 and a counter electrode plate.
In this method, a photosensitive material 40 for forming a spacer is formed on one electrode so as to have a predetermined film thickness using a liquid resist or a dry film resist [(a) to (b)]. Next, after placing the pattern forming photomask 50 [(c)], a pattern is formed [(d)] on the target spacer through a step of exposing and removing unnecessary portions. Furthermore, after forming an adhesive layer on the spacer [(e)], injecting the electrophoretic display liquid, disposing the counter electrode and adhering to the spacer [(f) to (g)] Make it.

  EXAMPLES Next, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited at all by these examples.

[Example 1]
(1-1) Production of display device particles coated with a compound having at least one functional group represented by the above general formula (1) Powder obtained by adjusting the compound represented by the above formula (5) to a particle size of 300 mesh or less In a highly crosslinked polymethyl methacrylate matrix, titanium oxide [ITT-2 TiO ₂ CR-50, manufactured by Nippon Chemicals Co., Ltd.] was added to a solution in which 0.5 part by mass of a material was added and dispersed and dissolved in 50 parts by mass of ethanol. 20% by weight of white resin fine particles having an average particle diameter of about 18 μm was added and sonicated to prepare a dispersion. The dispersion was then dried at 50 ° C. under reduced pressure for 6 hours to evaporate ethanol to produce a solid.
This solid material was put into a hybridization system [NHS-0 type, manufactured by Nara Machinery Co., Ltd.] at room temperature, subjected to mechanochemical dry treatment at 8000 rpm for 5 minutes, and further polyethylene glycol having a molecular weight of 10,000. 3 g was added, and a mechanochemical dry treatment at 12,000 rpm for 5 minutes was performed to produce particles for a display device having a golden gloss. This is designated as “prototype particle 1”. The average particle diameter of the particles was about 18 μm.
The average particle size was measured using a multisizer manufactured by Beckman Coulter (the same applies hereinafter).

(1-2) Preparation of electrophoretic display liquid containing particles for display device 10 parts by mass of “prototype particle 1” prepared in (1-1) above, same titanium oxide as used in (1-1) above 20 parts by mass, polyethylene glycol stearylamine [manufactured by Nippon Oil & Fats Co., Ltd., Naimine S-202] as a charge control agent, 1 part by mass of sorbitan trioleate adjusted to 100 parts by mass with dodecane Was dispersed for 30 minutes with a paint shaker using glass beads to prepare an electrophoretic display liquid containing particles for display devices.

(1-3) Production of electrophoretic display device A glass substrate (thickness 0.7 mm) on which a transparent conductive film (ITO) having a thickness of 180 nm to be an electrode is formed by sputtering and a polyethylene terephthalate film (thickness 100 μm) (PET film) is laser-processed with a grid-like (opening 500 nm × 500 nm, aperture ratio 78%) mesh spacer and placed opposite to each other to enclose the electrophoretic display liquid prepared in (1-2) above Thus, an electrophoretic display device was produced.

(1-4) Evaluation of electrophoretic display device The performance of the electrophoretic display device was evaluated as follows using an electrophoretic drive device (MY-01) manufactured in-house.
It was confirmed that good white / gold color display can be achieved by applying a voltage of +90 V or −90 V through the electrode of the electrophoretic display device produced in (1-3) above to cause the particles to undergo electrophoresis.
Contrast is a value measured using PC-T manufactured by Suga Test Instruments Co., Ltd. The response speed is a value calculated from the time when the contrast ratio is not changed by measuring the contrast ratio while changing the application time.

[Example 2]
(2-1) Production of display device particles coated with a compound having at least one functional group represented by the above general formula (1) Powder obtained by adjusting the compound represented by the above formula (4) to a particle size of 500 mesh or less A mixture was prepared by dry-mixing 20 parts by mass of white resin fine particles having an average particle size of about 6 μm containing 0.5 parts by mass of the glassy material and 20% by mass of titanium oxide as in Example 1 in the highly crosslinked polymethyl methacrylate.
This mixture is put into a hybridization system [manufactured by Nara Machinery Co., Ltd.] at room temperature, subjected to a mechanochemical dry treatment at 3000 rpm for 3 minutes, and further mechanochemical for 7 minutes at 14000 rpm. By performing a dry treatment, particles for a display device coated with a compound having at least one functional group represented by the general formula (1) were produced. This is designated as “prototype particle 2”.
The average particle diameter of the particles was about 6 μm.

(2-2) Preparation of electrophoretic display liquid containing particles for display device A liquid for electrophoretic display was carried out in the same manner as in Example 1 except that “prototype particle 2” prepared in (2-1) above was used. Was made.

(2-3) Production of electrophoretic display device Instead of a mesh spacer obtained by laser processing of PET film, a spacer having a thickness of 50 μm obtained by plain weaving a polyarylate yarn having a fiber diameter of 25 μm to be 130 mesh is used. An electrophoretic display device was produced in the same manner as in Example 1 except that the electrophoretic display liquid prepared in 2-2) was used.

(2-4) Evaluation of electrophoretic display device A white / gold color is produced by applying a voltage of +50 V or −50 V through the electrode of the electrophoretic display device prepared in (2-3) above to cause electrophoresis of particles. It was confirmed that good display was possible.

Example 3
(3-1) Production of display device particles coated with a compound having at least one functional group represented by the general formula (1) 0.5 parts by mass of the compound represented by the formula (6) is 50 masses of xylene. 20 parts by weight of white resin fine particles having an average particle diameter of about 6 μm, containing 20% by mass of titanium oxide similar to that in Example 1 in the same highly crosslinked polymethyl methacrylate as in Example 1 was added to the solution dissolved in the part. Part of the mixture was added and sonicated to prepare a dispersion. The dispersion was then dried at 180 ° C. under reduced pressure for 6 hours to evaporate xylene to produce a solid.
This solid material was put into a hybridization system [manufactured by Nara Machinery Co., Ltd.] at room temperature and subjected to mechanochemical dry treatment at 10000 rpm for 5 minutes, and 3 g of polyethylene glycol having a molecular weight of 20000 was added. A display device particle having at least one functional group represented by the above general formula (1) was prepared by performing a mechanochemical dry treatment at 14000 rpm for 8 minutes. This is designated as “prototype particle 3”.
The average particle diameter of the particles was about 6 μm.

(3-2) Preparation of electrophoretic display liquid containing particles for display device Using 10 parts by mass of “Prototype particle 3” prepared in (3-1) above, adjusting the total amount to 100 parts by mass with isoparaffin. Except that, an electrophoretic display solution containing display device particles was prepared in the same manner as in Example 1.

(3-3) Production of electrophoretic display device By sputtering, a polyethylene terephthalate film (thickness: 100 μm) on which a transparent conductive film (ITO) with a thickness of 180 nm serving as an electrode is formed and a polyarylate yarn having a fiber diameter of 25 μm An electrophoretic display device was produced by enclosing the electrophoretic display liquid prepared in (3-2) above by placing a 50 μm thick spacer plain-woven so as to form a mesh and placing the electrophoretic display liquid prepared in (3-2) above.

(3-4) Evaluation of electrophoretic display device A white / gold color is produced by applying + 50V or −50V voltage through the electrode of the electrophoretic display device prepared in (3-3) above to cause the particles to undergo electrophoresis. It was confirmed that good display was possible.

[Comparative Example 1]
―Preparation of electrophoretic display solution (1) for comparison―
Example 1 (1-) except that 10 parts by mass of silver-coated glass flake [Merck Co., Ltd., Metashine MC2080PS, sphere equivalent average particle diameter 10 μm] was used as “comparative particle 1” instead of “prototype particle 1”. As in 2), a comparative electrophoretic display solution (1) was prepared.

―Production of electrophoretic display device (1) for comparison―
An electrophoretic display device (1) for comparison was produced in the same manner as in Example 1 (1-3) except that the electrophoretic display liquid (1) for comparison was used.

―Evaluation of electrophoretic device (1) for comparison―
It was carried out in the same manner as in Example 1 (1-4) except that the comparative electrophoresis device (1) was used, and it was confirmed that good white / silver color display was not possible.

[Comparative Example 2]
―Preparation of electrophoretic display solution (2) for comparison―
Example 1 except that 10 parts by mass of a copper-colored pearl pigment [Merck, Iriodin 500 Bronze, sphere equivalent average particle diameter 20 μm] was used as “Comparative Particle 2” instead of “Prototype Particle 1” In the same manner as in (1-2), a comparative electrophoretic display solution (2) was prepared.

―Production of comparative electrophoretic display device (2) ―
An electrophoretic display device (2) for comparison was produced in the same manner as in Example 2 (2-3) except that the electrophoretic display liquid (2) for comparison was used.

―Evaluation of electrophoretic device (2) for comparison―
It was carried out in the same manner as in Example 2 (2-4) except that the comparative electrophoretic device (2) was used, and it was confirmed that good white / copper color display was not possible.

[Comparative Example 3]
―Preparation of electrophoretic display solution (3) for comparison―
Example 1 (1) except that 5 parts by mass of a copper powder particle pigment [Ishihara Sangyo Co., Ltd., MD-200, average particle size 0.2 μm] was used as “Comparative Particle 3” instead of “Prototype Particle 1”. As in -2), a comparative electrophoretic display solution (3) was prepared.

―Production of electrophoretic display device (3) for comparison―
An electrophoretic display device (3) for comparison was produced in the same manner as in Example 2 (2-3) except that the electrophoretic display liquid (3) for comparison was used.

―Evaluation of electrophoretic device (3) for comparison―
It was carried out in the same manner as in Example 2 (2-4) except that the comparative electrophoretic device (3) was used, and it was confirmed that good white / copper color display was not possible.
The results obtained in Examples 1 to 3 and Comparative Examples 1 to 3 are summarized in Table 1.

  From the results shown in Table 1, it is clear that the display devices in the examples using the particles for display devices of the present invention are superior in display and contrast of each color and have a very fast response speed as compared with those in the comparative example. It is. In the comparative example, the response speed could not be measured because the contrast value was low.

  A display device using the particles for a display device of the present invention is an electrophoretic display device having a high response speed, and is extremely excellent when applied to an electronic paper or the like.

It is the schematic diagram which showed the cross section of the display device of this invention. It is an enlarged view of the dotted line display part in FIG. It is a perspective view which shows a spacer. It is a schematic diagram which shows one embodiment of the shape of the opening part for forming the cell of a spacer. It is a schematic diagram which shows another embodiment of the shape of the opening part for forming the cell of a spacer. It is a schematic diagram showing a manufacturing process of a display device of the present invention. It is a schematic diagram which shows the process of producing the display device of this invention combining the process by the photolithography which is an example of the production method of a spacer, and a counter electrode plate.

Explanation of symbols

10: Front electrode 15: Back electrode 20: Spacer 30: Separating partition 40: Photosensitive material for spacer formation 50: Photomask for pattern formation

Claims (10)

The following general formula (1)

A particle for a display device provided with a coating layer of a compound having at least one functional group represented by the formula: A compound having at least one functional group represented by the general formula (1) is represented by the general formula (2)

[X ¹ is NH or O or S; X ² is N or O or S; X ³ is NH or O or S; R ¹ is a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aromatic group. Substituted or unsubstituted heterocyclic group, formyl group, acyl group, alkoxycarbonyl group or alkenyl group; R ² represents a hydrogen atom, tricyanoethenyl group, substituted or unsubstituted alkyl group, substituted or unsubstituted aromatic group A group, a substituted or unsubstituted heterocyclic group, a formyl group, an acyl group, an alkoxycarbonyl group or an alkenyl group; R ³ and R ⁴ are each independently a hydrogen atom or a substituted or unsubstituted aromatic group; It is an integer of ~ 3]
The particle | grains for display devices of Claim 1 which are the compounds represented by these. The compound having at least one functional group represented by the general formula (1) is represented by the following general formula (3)

[A ¹ is a substituted or unsubstituted aromatic group, a substituted or unsubstituted heterocyclic group, a substituted or unsubstituted condensed Hajime Tamaki, a substituted or unsubstituted alicyclic group, a substituted or unsubstituted spiro ring A dendrimer structure having a group, a substituted or unsubstituted biphenyl residue, a fluorene residue or a triphenylamine skeleton as the core; X ⁴ is a substituted or unsubstituted aromatic group or a substituted or unsubstituted heterocyclic group; R ⁵ Is a substituted or unsubstituted aromatic group, a substituted or unsubstituted heterocyclic group, an alkyl group, an alkenyl group, or a cycloalkyl group; n is an integer of 2 or more, and two or more of R ⁵ and X ⁴ are It can be the same or different]
The particle | grains for display devices of Claim 1 which are the compounds represented by these.   The display device particles according to claim 1, wherein the non-light-transmitting particles are resin particles obtained by dispersing an inorganic pigment and / or an organic pigment in a resin matrix.   The display device particle according to claim 1, wherein the particle is subjected to a lipophilic surface treatment.   The particles for display device according to claim 1, wherein the particles have an average particle size of 1 to 50 μm.   The display device particle according to claim 1, wherein the non-light-transmitting particle is a porous body.   The particle | grains for display devices in any one of Claims 1-7 by which the organic or inorganic layer is further coat | covered by the coating layer surface of the said compound.   The liquid for electrophoretic displays which consists of the particle | grains for display devices in any one of Claims 1-8 disperse | distributed to the same dispersion medium.   An electrophoretic display device comprising the electrophoretic display liquid according to claim 9 disposed between a pair of counter electrode plates.

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