JP2011209447A - Non-electrostatic colored resin particle, silicone oil dispersion thereof, electrophoretic display device, and method for manufacturing non-electrostatic colored resin particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide non-migrating non-electrostatic colored resin particles which do not inhibit electrophoresis of colored migrating particles.SOLUTION: The non-electrostatic colored resin particles have a silicone chain, and a product of a reaction between a carboxyl group and an amino group on surfaces, wherein the carboxyl group is a group originating from positively charged colored resin particles and the amino group is a group originating from an amino-group-containing compound, and exhibit a measured value of electrostatic charge of 10 nC/cmor less when placed between ITO electrodes forming parallel flat plates with a distance between electrodes of 50 μm and with an applied voltage of 100 V during 60 s, in a state of being dispersed in a silicone oil having dynamic viscosity of 100 centistokes or less and with solid concentration of 10 wt.%.

Description

  The present invention relates to non-charged colored resin particles, a silicone oil dispersion thereof, an electrophoretic display device, and a method for producing non-charged colored resin particles. More specifically, the present invention relates to non-charged colored resin particles that stably exhibit non-charging properties, a silicone oil dispersion thereof, an electrophoretic display device, and a method for producing non-charged colored resin particles.

  In recent years, attention has been paid to an image display device using electrophoresis of colored resin particles exhibiting charging properties. This device has features that are not found in conventional display devices, such as having a viewing angle as wide as ordinary printed matter, low power consumption, and memory characteristics that display information does not disappear even when the power is turned off. It is expected to spread as an inexpensive display device.

  Here, an example in which the colored resin particles are used as an image display element of an image display device will be introduced. Display in which colored resin particles exhibiting positive and / or negative chargeability as an image display element are dispersed in a dispersion medium between two electrode substrates that are arranged to face each other with a spacer interposed therebetween. A liquid crystal is sealed to form a display panel. By applying an electric field between the two electrode substrates of the display panel, colored resin particles exhibiting charging properties can be electrophoresed to obtain a display.

Recently, attempts have been made to make such an image display device display in multiple colors.
As a conventional technique related to such multicolor display, a method using a dispersion medium colored by dissolving a dye or the like is known (see Patent Document 1). In Patent Document 1, when colored particles that exhibit electrophoretic properties by application of a voltage (hereinafter, colored electrophoretic particles) are arranged on a transparent electrode substrate serving as a display surface, dispersion media having different color tones are formed in the gaps between the colored particles. When mixed in, color mixing occurs, and there is a problem that a desired color display is not performed.

  As a technique for solving the problem of Patent Document 1, by dispersing resin particles (hereinafter referred to as non-electrophoretic particles) that do not show electrophoresis due to voltage application and have a large refractive index difference from the solvent in a nonpolar solvent, A method using a dispersion medium is known (see Patent Document 2). In Patent Document 2, when the colored migrating particles are moved onto the electrode substrate opposite to the display surface to display the color developed by the non-migrating particles, the non-migrating particles are not concealed and are therefore arranged on the opposite electrode. There was a problem that the color of the colored migrating particles could be seen from the display surface.

  As a technique for solving the problem of Patent Document 2, white particles are obtained by dispersing non-electrophoretic particles in which a resin particle having a large difference in refractive index from a solvent is uniformly coated with titanium oxide as a colorant and being uncharged in the solvent. There is known a method using a dispersion medium (see Patent Document 3).

Japanese Patent No. 2551783 JP 2001-188269 A JP 2008-122468 A

In view of the results of Patent Document 3, the inventors conducted a similar experiment with increasing the amount of non-electrophoretic particles described in Example 2 of Patent Document 3 in order to further enhance the color developed by the non-electrophoretic particles. As a result, it was found that the viscosity of the entire display liquid increases and the moving speed of the colored migrating particles by electrophoresis becomes slow. In addition, attempts were made to eliminate the above problems by increasing the proportion of the colorant in the non-electrophoretic particles, but it was found that the charge amount of the non-electrophoretic particles was increased and the electrophoresis of the colored electrophoretic particles was hindered. The present invention solves the above-described problems, and an object of the present invention is to provide non-electrophoretic non-charged colored resin particles that do not hinder electrophoresis of colored electrophoretic particles.

  As a result of intensive studies, the inventors of the present invention once produced positively charged colored resin particles having a silicone chain and a carboxyl group on the surface, and then converted the carboxyl group of the positively charged colored resin particles to the amino group-containing compound amino acid. The present invention was achieved by surprisingly finding that stable non-charged colored resin particles can be obtained by reacting with a group.

Thus, according to the present invention, a group having a silicone chain and a reaction product of a carboxyl group and an amino group on the surface, the carboxyl group is derived from positively charged colored resin particles, and the amino group is derived from an amino group-containing compound. And a voltage of 10 V is applied between ITO electrodes, which are parallel flat plates with a distance between electrodes of 50 μm, in a state where the solid content is dispersed in a silicone oil having a dynamic viscosity of 100 centistokes or less at a solid concentration of 10 wt% for 60 seconds. There is provided non-chargeable colored resin particles characterized by showing a measured charge amount of 10 nC / cm ² or less when applied.

  Further, according to the present invention, there is provided a method for producing the above-mentioned non-chargeable colored resin particles, wherein the carboxyl group of the positively-charged colored resin particles having a silicone chain and a carboxyl group on the surface is substituted with the amino group of the amino group-containing compound. There is provided a method for producing non-charged colored resin particles, which is reacted to obtain non-charged colored resin particles.

Moreover, according to this invention, the silicone oil dispersion obtained by disperse | distributing said non-chargeable colored resin particle in silicone oil is provided.
Furthermore, according to this invention, the electrophoretic display device obtained using said silicone oil dispersion is provided.

  Since the non-charged colored resin particles according to the present invention have a stable non-charge property, when used in an electrophoretic display device, a desired color display can be realized without hindering the movement of the colored electrophoretic particles. Can do.

  In addition, when the amino group-containing compound is a compound selected from an aliphatic amine or an amino group-containing silicone compound, non-charged colored resin particles having a more stable non-charge property can be obtained.

  Further, when the amino group of the amino group-containing compound is contained in an amount of 0.2 to 1.5 molar equivalents relative to 1 molar equivalent of the positively chargeable colored resin particles, the nonchargeable colored resin particles having further stable non-chargeability. Can be obtained.

In addition, the silicone chain is a structural unit according to the following:
(R is a C1-4 alkyl group or phenyl group, and n is an integer.)
When it has, it can obtain the non-chargeable colored resin particle which has the more stable non-charge property.

  Further, when the non-charged colored resin particles contain 20% by weight to 90% by weight of titanium oxide as a colorant, the non-charged colored resin particles have stable non-chargeability even if the content of the colorant is high. Can be obtained.

  In addition, the method for producing non-charged colored resin particles according to the present invention makes it possible to produce non-charged colored resin particles having stable non-charge properties. When the non-charged colored resin particles obtained by this manufacturing method are used in an electrophoretic display device, a desired color display can be realized without disturbing the movement of the colored electrophoretic particles.

  The electrophoretic display device using the silicone oil dispersion obtained by dispersing the non-charged colored resin particles according to the present invention in silicone oil can prevent an undesired color from being displayed.

It is the schematic of the apparatus for evaluating the charge amount of the colored resin particle obtained in the Example and comparative example of this invention.

The non-charged colored resin particles according to the present invention (hereinafter also referred to as non-charged particles) have a silicone chain and a reaction product of a carboxyl group and an amino group on the surface. The carboxyl group is derived from positively charged colored resin particles (hereinafter also referred to as positively charged particles), and the amino group is a group derived from an amino group-containing compound. Further, the non-charged colored resin particles are dispersed between the ITO electrodes that are parallel flat plates with a distance between the electrodes of 50 μm in a state where the dynamic viscosity is dispersed in a silicone oil having a dynamic viscosity of 100 centistokes or less at a solid content concentration of 10 wt%. When a voltage of 10 V is applied for 60 seconds, a measured charge amount of 10 nC / cm ² or less is shown.
In the present invention, “non-chargeable” refers to a substance that does not show any positive or negative reaction in the polarity evaluation method and has the above-mentioned measured charge amount. The polarity evaluation method and the charge amount measurement method will be described in Examples.

Examples of the silicone chain present on the surface of the positively chargeable colored resin particles include those having an organosiloxane structure represented by the following formula.
(R is a C1-4 alkyl group or phenyl group, and n is an integer.)
Examples of the alkyl group include methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl, and tert-butyl. The phenyl group may be substituted with a C1-4 alkyl group.

  The non-charged colored resin particles are, for example, positively charged colored resin particles (positively charged colored resin particles) having a carboxyl group obtained by a known method such as suspension polymerization, emulsion polymerization, and dispersion polymerization. It is obtained by reacting the containing compound.

(1) Method for Producing Positively Charged Colored Resin Particles An example of a method for producing positively chargeable colored resin particles by a dispersion polymerization method will be described below, but the present invention is not limited to this production method.

Positively charged colored resin particles can be obtained by copolymerizing a vinyl monomer and a dispersant by dispersion polymerization.
Here, although the positively charged colored resin particles have a carboxyl group, the carboxyl group may be derived from a vinyl monomer having a carboxyl group contained in a vinyl monomer copolymerized with a dispersant. , May be derived from a vinyl monomer having a carboxyl group contained in the monomer mixture when forming the dispersant.

(Dispersant)
Examples of the dispersant used in the dispersion polymerization for introducing the silicone chain into the positively charged colored resin particles include a copolymer of a silicone macromonomer, a vinyl monomer, and α-methylstyrene dimer. As the silicone macromonomer, various compounds having a polymerizable unsaturated group at one end and having a silicone unit (organosiloxane unit such as dimethylpolysiloxane unit) can be used.

Examples of the silicone macromonomer include those having a structure represented by the following formula.
(R ₁ is a hydrogen atom or a methyl group, R ₂ is an alkylene group of C2-4, R ₃ are the same or different C1~4 alkyl group or a phenyl group, n is an integer.)

Specific examples of the structure represented by the above formula include α-butyl-ω- (3-methacryloxypropyl) polydimethylsiloxane.
The molecular weight of the silicone macromonomer is preferably in the range of a number average molecular weight of 500 to 40000, more preferably 1000 to 20000. Two or more types of silicone macromonomers may be mixed and used. N in the above formula is an integer that can give this number average molecular weight.

  The vinyl monomer for the dispersant may be the same as or different from the vinyl monomer for producing the positively charged colored resin particles. The vinyl monomer for the dispersant and / or positively charged colored resin particles will be described below.

  The vinyl monomer having a carboxyl group is not particularly limited as long as it can be polymerized, but (meth) acrylic acid, 2- (meth) acryloyloxyethyl succinic acid, 2- (meta) ) Acrylic acid such as acryloyloxyethyl phthalic acid and 2- (meth) acryloyloxyethyl hexahydrophthalic acid, carboxylic acid-containing esters of methacrylic acid, maleic acid, fumaric acid and the like. Only one vinyl monomer may be used, or two or more vinyl monomers may be used in combination. Here, “(meth) acrylic acid” means acrylic acid or methacrylic acid.

  The added amount of the vinyl monomer having a carboxyl group is a polymerizable monomer composition 100 in which a dispersant used for dispersion polymerization for producing positively charged colored resin particles, a vinyl monomer, and a colorant are mixed. 1 to 30 weight% is preferable in weight%. More preferably, it is 2 to 20% by weight. When the content is less than 1% by weight, the true density of the non-charged colored resin particles produced by polymerization increases, and the sedimentation rate of the non-charged colored resin particles in the dispersion medium increases, resulting in sedimentation and aggregation. There is. On the other hand, if it exceeds 30% by weight, the amount of the amino group-containing compound necessary for obtaining the non-charge property becomes excessive, and it takes a lot of time for washing to remove the excess amino group-containing compound, and the production efficiency May decrease.

In addition, various vinyl monomers that are widely used in addition to the above may be used as long as the effects of the present invention are not hindered.
Examples of such vinyl monomers include styrene, o-methyl styrene, m-methyl styrene, p-methyl styrene, p-ethyl styrene, 2,4-dimethyl styrene, pn-butyl styrene, p-tert. -Butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, n-methoxy styrene, p-phenyl styrene, p -Styrene and derivatives thereof such as chlorostyrene and 3,4-dichlorostyrene, vinyl halides such as vinyl chloride, vinylidene chloride, vinyl bromide and vinyl fluoride, vinyl acetate, vinyl propionate, vinyl benzoate, butyric acid Vinyl esters such as vinyl, methyl (meth) acrylate, ethyl (meth) acrylate, (meth) N-butyl crylate, isobutyl (meth) acrylate, propyl (meth) acrylate, n-octyl (meth) acrylate, dodecyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (meth) acrylic acid Stearyl, isostearyl (meth) acrylate, 2-chloroethyl acrylate, phenyl (meth) acrylate, methyl α-chloroacrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, methacrylic acid Isobutyl, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, methacrylate Α-methylene aliphatic monocarboxylic acid esters such as diethylaminoethyl acrylate, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, methacryl Acrylic acid or methacrylic acid derivatives such as 2-hydroxypropyl acid, vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether, vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, methyl isopropenyl ketone, N-vinyl Examples thereof include N-vinyl compounds such as pyrrole, N-vinylcarbazole, N-vinylindole, and N-vinylpyrrolidone, and vinyl naphthalene salts. These various vinyl monomers can be used singly or in combination of two or more, as long as the effects of the present invention are not impaired.

  Furthermore, a compound having two or more polymerizable double bonds may be added as a vinyl monomer. Such a compound also serves as a crosslinking agent. Examples of the crosslinking agent include aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene and derivatives thereof, and diethylenic carboxylic acids such as ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol triacrylate, and trimethylolpropane triacrylate. Examples thereof include divinyl compounds such as esters, N, N-divinylaniline, divinyl ether and divinyl sulfite, and compounds containing three or more vinyl groups. These can be used alone or in combination of two or more.

  The amount of vinyl monomer used for the dispersant is preferably 2 to 50 parts by weight with respect to 100 parts by weight of the silicone macromonomer for dispersant. More preferably, it is 5 to 25 parts by weight. When the amount is less than 2 parts by weight, the affinity with the non-charged colored resin particles is deteriorated, so that it is difficult to chemically bond, and as a result, the dispersion stability of the non-charged colored resin particles may be deteriorated. On the other hand, when the amount exceeds 50 parts by weight, the affinity with the nonpolar solvent is deteriorated and the dispersion stability of the non-charged colored resin particles may be deteriorated.

The α-methylstyrene dimer for the dispersant is an addition cleavage type chain transfer agent having a structure represented by the following formula.

  Copolymerization of α-methylstyrene dimer, silicone macromonomer and vinyl monomer yields a polymerizable copolymer (living copolymer) with a controlled molecular weight and a reactive double bond at the end. It is done.

  The amount of α-methylstyrene dimer used varies depending on the number average molecular weight of the dispersant, but is generally 0.1 to 10 parts by weight with respect to 100 parts by weight of the silicone macromonomer for the dispersant. If it is less than 0.1 part by weight, the resulting dispersant may have too many number average molecular weights. On the other hand, when the amount exceeds 10 parts by weight, it is difficult to control the molecular weight with α-methylstyrene dimer, the number average molecular weight cannot be lowered, and the effect seen in addition may not be obtained.

  By conducting dispersion polymerization of the dispersant and vinyl monomer, positively charged coloring in which silicone chains derived from silicone macromonomer are chemically immobilized on the surface while preventing aggregation due to coalescence of particles during polymerization Resin particles can be obtained. As a result, non-chargeable colored resin particles having a particle size of submicron or less and excellent in dispersion stability in silicone oil can be obtained.

  Although the molecular weight of a dispersing agent is not specifically limited, It is preferable that it is the range of the number average molecular weight 2000-50000.

(Production method of dispersant)
The dispersant can be obtained by copolymerization, for example, by adding a silicone macromonomer, a vinyl monomer, and α-methylstyrene dimer to a nonpolar solvent and heating with stirring by a known method. . A polymerization initiator may be used for the copolymerization. The polymerization initiator is usually used after being preliminarily dissolved in a vinyl monomer.

  The polymerization initiator is not particularly limited as long as it is a known radical polymerization initiator. For example, azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 2,2′-azobis (2,4-dimethylvaleronitrile), 4,4′-azobis (4-cyano Azo initiators such as valeric acid) and 2,2′-azobis (2-methylpropionamidine); and peroxides such as benzoyl peroxide, halochlorobenzoyl peroxide, lauroyl peroxide and t-butyl perbenzoate. Examples thereof include oxide-based initiators.

  The polymerization initiator is preferably contained in the monomer composition (mixture of silicone macromonomer and vinyl monomer) in an amount of about 0.1 to 5% by weight.

  The reaction temperature and time in the above copolymerization are not particularly limited. For example, the kind and amount of polymerization initiator used and the silicone macromonomer, vinyl monomer and α-methylstyrene dimer used. It can be adjusted in a timely manner depending on reactivity. The reaction temperature is preferably 40 to 120 ° C and the reaction time is preferably 0.5 to 50 hours. More preferably, the reaction temperature is 40 to 80 ° C., and the reaction time is 2 to 25 hours.

  The polymerization atmosphere in the copolymerization may be an air atmosphere or an inert gas atmosphere. However, in order to prevent a delay in polymerization rate and inhibition of polymerization due to oxygen in the atmosphere, it is preferably performed in an inert gas atmosphere. Examples of such an inert gas include nitrogen gas and argon gas, and nitrogen gas is preferable from the viewpoint of economy.

  Here, the dispersant may or may not be separated from the non-polar solvent used after the dispersant is produced. When not separated, a dispersant dispersed or dissolved in a nonpolar solvent can be used as it is for the production of positively charged colored resin particles.

  Non-polar solvents include paraffinic hydrocarbons such as pentane, hexane, heptane, octane, nonane, decane and dodecane, isoparaffinic hydrocarbons such as isohexane, isooctane and isododecane, alkyl naphthenic hydrocarbons such as liquid paraffin, and dimethyl silicone oil. And silicone oils such as phenylmethyl silicone oil, dialkyl silicone oil, alkylphenyl silicone oil, cyclic polydialkylsiloxane, and cyclic polyalkylphenylsiloxane.

  Among these, silicone oils such as dimethyl silicone oil, phenyl methyl silicone oil, dialkyl silicone oil, alkyl phenyl silicone oil, cyclic polydialkyl siloxane or cyclic polyalkyl phenyl siloxane are considered in consideration of the environmental impact such as the working environment. preferable.

  Further, in order to efficiently disperse by ultrasonic waves in the production of the dispersant, the silicone oil used is more preferably an oil having a kinematic viscosity measured by JIS K 2283 of 100 centistokes or less.

  The amount of the nonpolar solvent used for the preparation of the copolymer as a dispersant is preferably 20 to 400 parts by weight with respect to 100 parts by weight of the monomer composition. More preferably, it is 50-200 weight part.

(Production of positively charged colored resin particles)
The production of the positively charged colored resin particles is carried out by adding the above dispersant and vinyl monomer to a nonpolar solvent and mixing them, followed by dispersion polymerization.

  The vinyl monomer used for the production of the positively charged colored resin particles needs to contain a monomer having a carboxyl group when a monomer having a carboxyl group is not used in the production of the dispersant. . When a monomer having a carboxyl group is used in the production of the dispersant, the monomer having a carboxyl group may or may not be included.

As a result, the positively charged colored resin particles have a silicone chain and a carboxyl group, and as a result, it is possible to obtain non-charged colored resin particles having a reaction product of a carboxyl group and an amino group on the surface.
Here, as the vinyl monomer, any of the vinyl monomers described in the column of the dispersant can be used.

  In order to prevent coalescence of the positively charged colored particles during polymerization, the dispersion polymerization is preferably performed under irradiation of ultrasonic waves. Also. You may use together mechanical stirring apparatuses, such as a magnetic stirrer.

  The dispersion polymerization reaction is preferably performed in an inert gas atmosphere for the same reason as in the method for producing the dispersant. A more preferable inert gas atmosphere is a nitrogen gas atmosphere.

  The reaction temperature and time in the above dispersion polymerization are not particularly limited, and can be adjusted as appropriate depending on the type and amount of polymerization initiator used and the amount of vinyl monomer used in the reaction. is there. Preferably, the reaction can be carried out at a reaction temperature of 40 to 120 ° C. and a reaction time of 0.5 to 50 hours. More preferably, the reaction temperature is 40 to 80 ° C., and the reaction time is 2 to 12 hours.

  As the polymerization initiator used for the dispersion polymerization, any of the polymerization initiators described in the column for the manufacturing method of the dispersant can be used.

  As the nonpolar solvent used in the dispersion polymerization for producing positively charged colored resin particles, any of those listed in the column of the dispersant can be used. Moreover, you may use what was used in the manufacturing process of a dispersing agent as it is. The amount of the nonpolar solvent is preferably 400 to 1900 parts by weight with respect to 100 parts by weight of the monomer composition. More preferably, it is 400-900 weight part.

The particle diameter of the positively charged colored resin particles can be controlled by selecting the amount of dispersant used and the vinyl monomer used.
For example, the particle diameter of the resin particles can be reduced by increasing the proportion of the dispersant used relative to the vinyl monomer used. Moreover, the particle diameter of the resin particles can be reduced by selecting and using a vinyl monomer having high affinity for the nonpolar solvent.

A known organic pigment or inorganic pigment can be suitably used for the positively charged colored resin particles.
For example, black pigments include carbon black (CI pigment black 7) such as furnace black, lamp black, acetylene black and channel black, or copper oxide and iron oxide (CI pigment black 11). And organic pigments such as metals such as titanium oxide and aniline black (CI Pigment Black 1). Among these, titanium oxide is preferable from the viewpoint of obtaining a display close to paper by combining uncharged particles and electrophoretic particles having other colors.

  The titanium oxide as the colorant contained in the positively charged colored resin particles is preferably 20 to 90% by weight. More preferably, it is 20 to 60% by weight. When the content of titanium oxide is less than 20% by weight, the color development of white may be deteriorated due to low concealability. On the other hand, if it exceeds 90% by weight, the resin coating may be incomplete and dispersibility in silicone oil may be deteriorated.

Further, examples of the pigment include C.I. I. Pigment Yellow 1, 3, 12, 13, 14, 17, 24, 34, 35, 37, 42 (yellow iron oxide), 53, 55, 74, 81, 83, 95, 97, 98, 100, 101, 104 , 108, 109, 110, 117, 120, 138, 153, C.I. I. Pigment Red 1, 2, 3, 5, 17, 22, 23, 31, 38, 48: 2, 48: 2, 48: 3, 48: 4, 49: 1, 52: 2, 53: 1, 57: 1, 60: 1, 63: 1, 63: 2, 64: 1, 81, 83, 88, 101 (Bengara), 104, 105, 106, 108, 112, 114, 122 (Quinacridone magenta), 123, 146 149, 166, 168, 170, 172, 177, 178, 179, 185, 190, 193, 209, 219, C.I. I. Pigment Blue 1, 2, 15, 15: 1, 15: 2, 15: 3, 15: 4, 15: 6, 16, 17: 1, 56, 60, 63, C.I. I. Pigment Green 1, 4, 7, 8, 10, 17, 18, 36, etc. can also be used.
In addition, a coupling agent or a pigment dispersant can be used when dispersing the pigment.

The pigment can be mixed in the dispersant or the positively charged colored resin particles by being polymerized after being dispersed in a nonpolar solvent by a known method.
The apparatus for dispersing the pigment is not particularly limited, and examples thereof include a media type dispersing apparatus such as a ball mill, an attritor, and a sand mill, a shear type dispersing apparatus such as a homomixer, a homogenizer, and a biomixer, and an ultrasonic dispersing apparatus. It is done.

(2) Production Method of Non-Charging Colored Resin Particles Uncharged colored resin particles can be obtained by reacting the carboxyl group of positively-charged colored resin particles with the amino group of the amino group-containing compound.
Examples of the amino group-containing compound include aliphatic amines such as butylamine, hexylamine, octylamine, stearylamine, dibutylamine and triethylamine, and amino group-containing silicone compounds such as bis (3-aminopropyl) polydiphenylsiloxane.

The addition amount of the amino group-containing compound is preferably 0.2 to 1.5 molar equivalents relative to 1 molar equivalent of the positively charged colored resin particles having a carboxyl group. More preferably, it is 0.3 to 1.0 molar equivalent. If it is less than 0.2 molar equivalent, the charge amount of the non-chargeable colored resin particles obtained may be higher than 10 nC / cm ² . On the other hand, if it exceeds 1.5 molar equivalents, the effect commensurate with the addition cannot be obtained, and it takes a lot of time for washing to remove the excess amino group-containing compound, which may reduce the production efficiency. is there.

  In order to obtain non-chargeable colored resin particles, the method of reacting positively-charged colored resin particles with an amino group-containing compound is not particularly limited as long as it is a known method. For example, an amino group-containing compound is added to a silicone oil dispersion of positively chargeable colored resin particles, and the amino group-containing compound is stirred while being dissolved in silicone oil under heating, and then centrifugal sedimentation is performed using silicone oil. Examples thereof include a method obtained by repeatedly washing.

  The average particle diameter of the non-chargeable colored resin particles is preferably 0.02 to 1.0 μm. More preferably, it is 0.05-0.8 micrometer. When the average particle diameter is less than 0.02 μm, the viscosity of the nonpolar solvent increases during polymerization, and as a result, it may be impossible to produce non-charged colored resin particles having stable average particles. On the other hand, when it exceeds 1.0 μm, dispersion stability in silicone oil may be deteriorated.

  Further, the obtained non-chargeable colored resin particles may be taken out from the nonpolar solvent, or may be used as it is without being taken out. The extracted resin particles can be washed with a nonpolar solvent as necessary. Further, the washed nonpolar colored resin particles may be dispersed again in the nonpolar solvent.

  The non-chargeable colored resin particles of the present invention are excellent in dispersion stability in a non-polar solvent (for example, silicone oil). Further, the content of the colorant is high, and it has a stable non-charging property. Utilizing this property, it can be suitably used as a display element of an image display device utilizing electrophoresis.

  Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto.

  First, an average particle diameter measurement method, an average molecular weight measurement method, a polarity evaluation method, and a charge amount evaluation method will be described.

(Measurement method of average particle size)
The average particle diameter here means a Z average particle diameter measured using a method called a dynamic light scattering method. That is, the silicone oil dispersion of resin particles is irradiated with laser light, and the intensity of scattered light scattered from the resin particles is measured with a time change in units of microseconds. This is a Z average particle size obtained by a cumulant analysis method for calculating an average particle size by applying a scattering intensity distribution caused by the detected resin particles to a normal distribution. This type of average particle diameter can be easily measured with a commercially available measuring device, and in this example and comparative example, “Zeta Sizer Nano ZS” commercially available from Malvern is used for measurement.
The above-mentioned commercially available measuring apparatus is equipped with data analysis software, and the Z average particle diameter can be calculated by automatically analyzing the measurement data.

(Measurement method of average molecular weight)
The measuring method of average molecular weight (Mw) is performed using gel permeation chromatography (GPC). In addition, an average molecular weight means a polystyrene (PS) conversion weight average molecular weight. Specifically, the measurement is performed as follows.
A 50 mg sample is dissolved in 10 ml of tetrahydrofuran (THF), filtered through a non-aqueous 0.45 μm chromatographic disk, and measured using a chromatograph. The chromatographic conditions are as follows.
Liquid chromatograph: manufactured by Tosoh Corporation, trade name “Gel Permeation Chromatograph HLC-8020”
Column: Tosoh Corporation, trade name “TSKgel GMH-XL-L” φ7.8 mm × 30 cm × 2 Column temperature: 40 ° C.
Carrier gas: Tetrahydrofuran (THF)
Carrier gas flow rate: 1 ml / min Injection / pump temperature: 35 ° C
Detection: RI
Injection amount: 100 microliters Standard polystyrene for calibration curve: manufactured by Showa Denko KK, trade name “shodex” weight average molecular weight: 1030000 and manufactured by Tosoh Corporation, weight average molecular weight: 5480000, 3840000, 355000, 102000, 37900, 9100, 2630, 870

(Polarity evaluation method)
The polarity of the colored resin particles in the silicone oil is measured by the following method.
Weigh the colored resin particles into a 20 ml glass bottle and add silicone oil (kinematic viscosity: 2 centistokes, KF-96L-2CS, manufactured by Shin-Etsu Chemical Co., Ltd.) so that the solid content of the colored resin particles is 5% by weight. 10 g, and this is used as a measurement sample.
Next, two flat glass plates coated with indium tin oxide (ITO) on one side, with the coated surface on the inside, a spacer with a copper tape attached between the glass plates, and a parallel plate with an interval of 1 mm between the glass plates Prepare a jig. The jig is immersed in the measurement sample, a voltage of +100 V is applied to the left side of the jig, and the sample is allowed to stand for 10 seconds. After 10 seconds, the jig is lifted from the measurement sample. If particles are attached to the left glass plate, the particle polarity is negative. If particles are attached to the right glass plate, the particle polarity is determined to be positive. To do.

(Evaluation method of charge amount)
Two glass plates (width 25 mm, length 100 mm, thickness 0.7 mm) coated with indium tin oxide (ITO) on one side are prepared. Among them, as shown in FIG. 1, a 50 μm thick silicone film (width 20 mm, length 25 mm) is attached to one coated surface as a spacer. After that, using a parallel plate sandwiched between two glass plates with a spacer in the state where the coating surface is on the inside as a jig, the gap between the two glass plates coated with indium tin oxide (ITO) (width 25 mm) The sample for measurement is infiltrated by capillary action using a syringe to a length of 20 mm and a thickness of 50 μm). Next, both sides of the jig were connected to a measuring device (manufactured by AUTOLAB: PGSTAT128N), and the measurement value obtained by applying a voltage of +10 V for 60 seconds by chronoamperometry & chronocoulometry as a measurement item was divided by the measurement area. This is the charge amount (nC / cm ² ).

(Example 1)
(A-1) Preparation of dispersant In a 300 ml separable flask, 100 parts by weight of silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd .: KF-96L-1CS, kinematic viscosity: 1 centistokes) and 2,2′- as a polymerization initiator in advance 8.0 parts by weight of methyl methacrylate in which 2.0 parts by weight of azo-bis- (2,4-dimethylvaleronitrile) (Nippon Hydrazine Kogyo Co., Ltd., hereinafter ABNV) is dissolved, silicone macromonomer (manufactured by Chisso Corporation: Silaplane) _{FM-0721, R 1 = CH} 3, R 2 = C 3 H 6, R 3 = CH 3, the number average molecular weight 5,850) 90.9 parts by weight of α- methyl styrene dimer (NOF Corporation: Nofiner MSD ) 1.1 parts by weight were added. The mixture was subjected to solution polymerization for 20 hours while stirring at 50 ° C. in a nitrogen atmosphere. Next, the silicone oil was removed at 70 ° C. to obtain a reaction product. The obtained reaction product was a colorless and transparent liquid (hereinafter referred to as a dispersant). As a result of molecular weight measurement by GPC using toluene, the number average molecular weight was 26,800.

(B-1) Preparation of positively charged colored resin particles In a 300 ml glass bead pot containing 500 g of zirconia beads (diameter 1 mm), 95 parts by weight of silicone oil (KF-96L-1CS), 50 parts by weight of a dispersant, a colorant 30 parts by weight of titanium oxide (manufactured by Ishihara Sangyo Co., Ltd .: PT-401M) was added and dispersed by a bead mill at room temperature for 24 hours.
Next, 175 parts by weight of the above solution was transferred to a 300 ml separable flask, 805 parts by weight of silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd .: KF-96L-1CS, kinematic viscosity: 1 centistokes), and lauroyl peroxide (Japan) as a polymerization initiator in advance. Oil and fat company: Parroyl L (hereinafter LPO) 2.5 parts by weight of isostearyl acrylate dissolved 5.0 parts by weight, methacrylic acid 5.0 parts by weight, ethylene glycol dimethacrylate 10 parts by weight were added, under nitrogen atmosphere Dispersion polymerization was performed at 60 ° C. under ultrasonic irradiation for 8 hours.
For ultrasonic irradiation, a 300 ml separable flask was immersed in a cleaning tank (internal dimensions: L230 mm × W180 mm × H110 mm) of an ultrasonic cleaning machine (VELVO-CLEAR: VS-150) with an output of 150 W, and the water in the tank Was carried out while maintaining a constant temperature of 60 ° C.
After the completion of the dispersion polymerization, the resin particles were precipitated and separated by centrifugation, and dispersed again in silicone oil (KF-96L-1CS). This operation was repeated three times, and the resin particles were washed to remove reaction residues such as a polymerization initiator. Thereafter, dispersion was performed in silicone oil (KF-96L-1CS) to obtain a silicone oil dispersion of colored resin particles having a solid content of 10%. The obtained colored resin particles had an average particle diameter in a silicone oil solvent of 228 nm and exhibited a clear positive chargeability. The charge amount was 52 nC / cm ² .

(C-1) Reaction with amino group-containing compound Next, 100 parts by weight of a silicone oil dispersion of positively charged colored resin particles having a solid content of 10% was added to a 300 ml separable flask equipped with a stirrer, a thermometer and a reflux condenser. And 5 parts by weight of stearylamine were added and reacted at 60 ° C. for 4 hours with stirring.
After completion of the reaction, the resin particles were separated by sedimentation by centrifugation and dispersed again in a 1: 1 solvent mixture of ethanol / silicone oil (KF-96L-1CS). After repeating this operation three times, the same washing was further performed with silicone oil (KF-96L-1CS). Thereafter, it is further dispersed in silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd .: KF-96L-2CS, kinematic viscosity: 2 centistokes), and after removing volatile components at 90 ° C. under reduced pressure drying, silicone of colored resin particles having a solid content of 10% is obtained. An oil dispersion was obtained. The obtained colored resin particles had an average particle size in the silicone oil solvent of 232 nm and did not show a clear charge polarity. The charge amount was 2.4 nC / cm ² .

(Example 2)
(A-2) Preparation of Dispersing Agent 100 parts by weight of silicone oil (KF-96L-1CS) in a 300 ml separable flask, 5.0 parts by weight of methacrylic acid in which 2.0 parts by weight of ABNV was previously dissolved as a polymerization initiator, 3.0 parts by weight of methyl acid, 90.9 parts by weight of silicone macromonomer (Silaplane FM-0721) and 1.1 parts by weight of α-methylstyrene dimer (Nofmer MSD) were added and stirred at 50 ° C. in a nitrogen atmosphere. The solution polymerization was carried out for 20 hours. Next, the silicone oil was removed at 70 ° C. The obtained reaction product was a colorless and transparent liquid (hereinafter referred to as a dispersant). As a result of molecular weight measurement by GPC using toluene, the number average molecular weight was 22,700.

(B-2) Preparation of positively chargeable colored resin particles 95 parts by weight of silicone oil (KF-96L-1CS), 50 parts by weight of a dispersant, and a colorant in a 300 ml glass bead pot containing 500 g of zirconia beads (diameter 1 mm) 30 parts by weight of titanium oxide (PT-401M) was added and dispersed by a bead mill at room temperature for 24 hours.
Next, 175 parts by weight of the above solution was transferred to a 300 ml separable flask, 805 parts by weight of silicone oil (KF-96L-1CS), 10 parts by weight of methyl methacrylate in which 2.5 parts by weight of LPO was previously dissolved as a polymerization initiator, ethylene glycol 10 parts by weight of dimethacrylate was added, and dispersion polymerization was performed in a nitrogen atmosphere at 60 ° C. under ultrasonic irradiation for 8 hours in the same manner as in Example 1.
After the completion of the dispersion polymerization, the resin particles were precipitated and separated by centrifugation, and dispersed again in silicone oil (KF-96L-1CS). This operation was repeated three times, and the resin particles were washed to remove reaction residues such as a polymerization initiator. Thereafter, dispersion in silicone oil was performed to obtain a silicone oil dispersion of colored resin particles having a solid content of 10%. The obtained colored resin particles had an average particle size of 212 nm in a silicone oil solvent and exhibited positive chargeability. The charge amount was 46.4 nC / cm ² .

(C-2) Reaction with amino group-containing compound Next, 100 parts by weight of a silicone oil dispersion of positively charged colored resin particles having a solid content of 10% was added to a 300 ml separable flask equipped with a stirrer, a thermometer and a reflux condenser. And 5 parts by weight of stearylamine were added and reacted at 60 ° C. for 4 hours with stirring.
After completion of the reaction, the resin particles were separated by sedimentation by centrifugation and dispersed again in a 1: 1 solvent mixture of ethanol / silicone oil (KF-96L-1CS). After repeating this operation three times, the same washing was further performed with silicone oil (KF-96L-1CS). Thereafter, it was further dispersed in silicone oil (KF-96L-2CS), and volatile components were removed at 90 ° C. under reduced pressure drying, and then a silicone oil dispersion of colored resin particles having a solid content of 10% was obtained. The obtained colored resin particles had an average particle size in the silicone oil solvent of 232 nm and did not show a clear charge polarity. The charge amount was 1.6 nC / cm ² .

(Comparative Example 1)
(A-3) Preparation of dispersing agent In a reaction vessel equipped with a stirrer, a thermometer and a reflux condenser, 14 parts by weight of silicone macromonomer (Silaplane FM-0721) and 0.1 part by weight of ABNV as a polymerization initiator were dissolved in advance. A solution prepared by dissolving 6 parts by weight of N, N-dimethylaminoethyl methacrylate (manufactured by Kyoeisha Chemical Co., Ltd .: Light Ester DM) in 180 parts by weight of silicone oil (KF-96L-1CS) is added and heated at 60 ° C. for 6 hours in a nitrogen atmosphere. did. After completion of the reaction, the silicone oil was removed at 70 ° C. under reduced pressure. The resulting solution was uniform and transparent.

(B-3) Addition of reactive group to dispersing agent Next, 1.5 parts by weight of the dispersing agent, titanium oxide (trade name; CR-90) in a reaction vessel equipped with a stirrer, a thermometer and a reflux condenser. (Manufactured by Ishihara Sangyo Co., Ltd.) 30 parts by weight and 150 parts by weight of silicone oil were combined and subjected to ultrasonic irradiation for 1 hour with ice cooling to disperse titanium oxide. After the completion of dispersion, 0.3 part by weight of 4-vinylbenzyl chloride was added and heated at 40 ° C. for 3 hours to modify the surplus amino group of the dispersant adsorbed on titanium oxide into a vinyl group.

(C-3) Preparation of colored resin particles Subsequently, 40 parts by weight of 2-vinylnaphthalene, 30 parts by weight of a silicone macromonomer (Silaplane FM-0721), and 7.5 parts by weight of LPO as an initiator were added, and 65 ° C. For 10 hours. After completion of the reaction, the resin particles were separated by sedimentation by centrifugation and dispersed again in a 1: 1 solvent mixture of ethanol / silicone oil (KF-96L-1CS). After repeating this operation three times, the same washing was further performed with silicone oil (KF-96L-1CS). Thereafter, it was further dispersed in silicone oil (KF-96L-2CS), and volatile components were removed at 90 ° C. under reduced pressure drying, and then a silicone oil dispersion of colored resin particles having a solid content of 10% was obtained. The obtained colored resin particles had an average particle diameter in a silicone oil solvent of 432 nm and did not show a clear charge polarity. However, the charge amount was 26.6 nC / cm ² .

(Comparative Example 2)
The colored resin particles obtained by the production of (b-1) positively chargeable colored resin particles in Example 1 above were referred to as Comparative Example 2.

(Comparative Example 3)
The colored resin particles obtained by the production of (b-2) positively chargeable colored resin particles in Example 2 were used as Comparative Example 3.
The results of Examples 1-2 and Comparative Examples 1-3 are summarized in Table 1.

MMA: Methyl methacrylate ABNV: 2,2′-azo-bis- (2,4-dimethylvaleronitrile)
LPO: Lauroyl peroxide

  From the results of Examples and Comparative Examples, it can be obtained by once producing positively charged colored resin particles and then reacting the carboxyl group in the positively charged colored resin particles with the amino group of the amino group-containing compound. It was found that the resin particles have a low charge amount and a stable non-charging property.

Claims (8)

It has a silicone chain, a reaction product of a carboxyl group and an amino group on the surface, the carboxyl group is derived from positively charged colored resin particles, the amino group is a group derived from an amino group-containing compound, and the dynamic viscosity 10 nC / cm when a voltage of 10 V is applied for 60 seconds between ITO electrodes that are parallel flat plates with a distance between the electrodes of 50 μm in a state where the solid content is dispersed in a silicone oil having a solid content concentration of 10 wt% in a silicone oil of 100 centistokes or less. A non-charged colored resin particle having a measured charge amount of ² or less.   The non-chargeable colored resin particles according to claim 1, wherein the amino group-containing compound is a compound selected from an aliphatic amine or an amino group-containing silicone compound.   The non-chargeable colored resin particles according to claim 1 or 2, wherein the amino group of the amino group-containing compound is contained in an amount of 0.2 to 1.5 molar equivalents relative to 1 molar equivalent of the positively charged colored resin particles. The silicone chain is a structural unit according to the following:
(R is a C1-4 alkyl group or phenyl group, and n is an integer.)
The non-chargeable colored resin particles according to any one of claims 1 to 3.   The non-chargeable colored resin particle according to any one of claims 1 to 4, wherein the non-charged colored resin particle contains 20 wt% to 90 wt% of titanium oxide as a colorant.   It is a manufacturing method of the non-chargeable colored resin particle as described in any one of Claims 1-5, Comprising: The carboxyl group of the positively-charged colored resin particle which has a silicone chain and a carboxyl group on the surface is made of an amino-group containing compound. A method for producing non-charged colored resin particles, comprising reacting with an amino group to obtain non-charged colored resin particles.   A silicone oil dispersion obtained by dispersing the non-chargeable colored resin particles according to claim 1 in silicone oil.   An electrophoretic display device obtained by using the silicone oil dispersion according to claim 7.