KR101430695B1 - Electrophoresis particle having low specific gravity, preparation method of electrophoresis particle, and electrophoresis display device - Google Patents

Abstract

The present invention relates to an electrophoretic particle capable of realizing a fast reaction rate with a low specific gravity and relatively high content of inorganic particles to realize an excellent contrast ratio or a color embedding force, a method for producing the electrophoretic particle, Lt; RTI ID = 0.0 > electrophoretic display device. ≪ / RTI >

Description

TECHNICAL FIELD [0001] The present invention relates to an electrophoretic particle having a low specific gravity, a method for producing electrophoretic particles, and an electrophoretic display device using the electrophoretic particle, an electrophoretic particle,

The present invention relates to electrophoretic particles having a low specific gravity, a method for producing electrophoretic particles, and an electrophoretic display device. More specifically, it is possible to realize a high reaction rate with a low specific gravity, and it is possible to achieve a high contrast ratio or a color tone ratio by relatively increasing the content of inorganic particles An electrophoretic particle, a method for producing the electrophoretic particle, and an electrophoretic display device including the electrophoretic particle.

The present invention is derived from the research conducted as part of the industrial technology development project of the Ministry of Knowledge Economy [Project Number: 10033294, Research Project Name: Development of new material for information display element of industrial material chemical process part, research title: Low voltage / long life Development of electronic ink material].

Electronic paper (Electronic Paper, Digital Paper) is also called E-paper. It can be carried conveniently like a paper book, paper newspaper or paper magazine, can be taken out easily whenever necessary, .

Such an electronic paper can take the form of an electrophoretic display, which not only has the advantage of being flexible and bendable, but also has a much lower production cost compared to conventional flat displays and requires a separate backlight Energy efficiency is also far ahead. Such an electronic paper is very clear, has a wide viewing angle, and can have a memory function that does not completely disappear even if there is no power supply.

Due to these great advantages, electronic paper is used in a wide range of fields, such as electronic books with paper-like surfaces and moving illustrations, self-updating newspapers, reusable paper displays for mobile phones, disposable TV screens and electronic wallpaper And has a huge potential market. Electrophoresis, liquid crystal, toner (QR-LPD), and MEMS are examples of electronic paper. Among them, electrophoresis is based on electrophoresis of charged pigment particles suspended in a dielectric solvent. When a voltage difference is applied between electrodes facing each other, the electrophoresis method moves to an electrode having a polarity opposite to that of charged pigment particles by attraction, Or brightness.

Of these electrophoretic displays, the most commercialized approaches are microcapsule electrophoretic displays and microcup electrophoretic displays, which use particles as a color display element. A microcapsule type electrophoretic display is a display device in which a dispersion containing charged particles and a fluid is microencapsulated and disposed between opposing electrodes. The microcup electrophoretic display has a concave A subunit is formed, and a charged particle or a charged particle slurry is sealed in the subunit.

On the other hand, since inorganic particles generally have a relatively large specific gravity, electrophoretic particles were prepared by mixing inorganic particles with polymers having a low specific gravity or by coating a polymer having a low specific gravity. Or a method of lowering the specific gravity of the entire charged particle slurry by using a solvent or the like.

However, it has not been easy to raise the particle moving speed depending on the voltage because there is a certain limit in appropriately lowering the true specific gravity of the charged particles by the previously known methods. Inorganic particles It was difficult to increase the content of the particles so that there was a certain limit in improving the color reproduction power or the control ratio of the display device.

An object of the present invention is to provide an electrophoretic particle capable of realizing a fast reaction rate with a low specific gravity and relatively increasing the content of inorganic particles to realize an excellent control ratio or a color tone ratio.

The present invention also provides a method of producing the electrophoretic particles.

The present invention also provides an electrophoretic display device comprising the electrophoretic particles.

The present invention relates to a process for producing a compound represented by the general formula (1) or (2), which comprises reacting an alkyl group having 2 to 30 carbon atoms, an alkenyl group having 2 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, an alkylaryl group having 7 to 30 carbon atoms, an arylalkyl group having 7 to 30 carbon atoms, An acrylate-based repeating unit substituted with at least one functional group selected from the group consisting of an alkyl group, an amide group in which an alkyl group having 1 to 20 carbon atoms is substituted or unsubstituted, and an alkoxycarbonyl group having 1 to 20 carbon atoms, or a polymer containing a vinyl- ; And white or colored inorganic particles bonded to the surface of the core part, wherein the electrophoretic particles have an average particle diameter of 0.1 to 300 μm and a true specific gravity value of 1.50 or less.

Further, the present invention provides a method for producing a color filter comprising: dispersing white or colored inorganic particles in a solvent; And a solvent in which the white or colored inorganic particles are dispersed are added an alkyl group having 2 to 30 carbon atoms, an alkenyl group having 2 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, an alkylaryl group having 7 to 30 carbon atoms, At least one functional group-substituted acrylate monomer selected from the group consisting of an arylalkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 4 to 20 carbon atoms, an amide group having a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms and an alkoxycarbonyl group having 1 to 20 carbon atoms Or a vinyl monomer and a polymerization initiator, and emulsifying the mixture; And polymerizing the emulsified solution at 10 to 120 ° C for 1 to 50 hours.

Further, the present invention provides a liquid crystal display comprising two substrates facing each other; An electrophoresis unit formed between the two substrates; And the electrophoretic particles positioned in the electrophoretic part.

Hereinafter, electrophoretic particles, a method for producing electrophoretic particles, and an electrophoretic display device according to a specific embodiment of the present invention will be described in detail.

The term " electrophoretic particles " as used herein means particles capable of having a constant charging property and capable of expressing color or lightness by moving to an electrode that is oppositely charged by an attractive force between electrodes to which a specific voltage is applied.

According to one embodiment of the present invention, there is provided a compound represented by the general formula (1), wherein the alkyl group having 2 to 30 carbon atoms, the alkenyl group having 2 to 30 carbon atoms, the aryl group having 6 to 30 carbon atoms, the alkylaryl group having 7 to 30 carbon atoms, An amide group in which an alkyl group having 1 to 20 carbon atoms is substituted or unsubstituted, and an alkoxycarbonyl group having 1 to 20 carbon atoms, or a vinyl-based repeating unit substituted with at least one functional group selected from the group consisting of A core portion including a polymer including the polymer; And white or colored inorganic particles bonded to the surface of the core portion, wherein the electrophoretic particles have an average particle diameter of 0.1 to 300 μm and a true specific gravity value of 1.50 or less.

The inventors of the present invention have been continuously studying the development of electrophoretic particles and have found out that the present inventors have made intensive studies on the development of electrophoretic particles, Has a low specific gravity and can be dispersed very stably in a solvent and can be used in an electrophoretic display to realize a fast response speed with respect to an applied voltage and to exhibit a high contrast ratio or color reproduction capability The test was confirmed and the invention was completed.

Particularly, as shown in the production method described later, the polymer obtained by using the acrylate monomer or vinyl monomer into which the specific functional group is introduced can secure a constant molecular structure due to the chain of the introduced functional groups, Accordingly, it can have a relatively low specific gravity as compared with previously known other polymers. Such a polymer can be distinguished from previous particles in which voids or pores are formed in the interior of the particle in that a constant space is formed within the molecular structure. Accordingly, even when the electrophoretic particles are used at a relatively high ratio, the specific gravity of the slurry contained in the electrophoretic portion is not greatly increased, so that the driving characteristics can be maintained at a constant level.

In addition, in the electrophoretic particles, since most of the inorganic particles are distributed along the surface of the electrophoretic particles, the concentration of the inorganic particles is increased in the same volume, so that an improved whiteness or a control ratio can be realized. In addition, the electrophoretic particles can float on the flow medium even when the power supply to the electrophoretic display device is stopped due to a low specific gravity, so that the electrophoretic particles can maintain white for a certain period of time after the power supply is stopped.

The electrophoretic particles may have a low specific gravity value, for example, a true specific gravity of 1.60 g / cm ³ or less, preferably 0.8 to 1.5 g / cm ³ . Specifically, the true specific gravity refers to a specific gravity value of the material itself, not an apparent specific gravity, and specifically, a specific gravity value of the material itself reflecting the intergranular porosity or pore in the particle, ≪ / RTI >

Previously, the specific gravity modifier or halogen-based solvent used for lowering the specific gravity of the electrophoretic particle slurry has been considered to be a cause of deterioration of the characteristics of the electrical double layer formed on the electrophoretic particle surface and the electrophoretic characteristics of the particles themselves However, since the electrophoretic particles have the above-mentioned true true specific gravity value, the specific gravity of the electrophoretic particle slurry can be lowered without using the former specific gravity adjusting agent or halogen-based solvent.

The electrophoretic particles may have an average particle size of 0.1 to 300 μm, preferably 0.2 to 200 μm. The average particle diameter of the electrophoretic particles can be measured using an apparatus such as an SEM or a size analyzer.

)에 대한 표준 편차(δ)의 비율로서, 하기 일반식1과 같이 나타낼 수 있다. The electrophoretic particle may have an electric potential distribution of -200 to 200 V, and the coefficient of variation of the electric potential distribution may be 20% or less, preferably 15% or less. Since the white or colored inorganic particles are uniformly distributed along the surface of the electrophoretic particle, the potential distribution of each electrophoretic particle may be relatively narrow. The Coefficient of Variation (CV) of the potential distribution is the potential average of the charged particles

) To the standard deviation (?) With respect to the standard deviation (?).

[Formula 1]

This coefficient of variation can represent the dislocation distribution of a certain group, and the lower the value, the narrower the distribution or the range of distribution.

On the other hand, the polymer included in the core part may include a repeating unit represented by the following formula (1) or (2).

[Chemical Formula 1]

(2)

Wherein R ₁ is an alkyl group having 2 to 30 carbon atoms, an alkenyl group having 2 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, an alkylaryl group having 7 to 30 carbon atoms, an arylalkyl group having 7 to 30 carbon atoms , A cycloalkyl group having 4 to 20 carbon atoms, an amide group having a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, and an alkoxycarbonyl group having 1 to 20 carbon atoms, and R ₂ may each be hydrogen or an alkyl group having 1 to 3 carbon atoms .

In the above formula (1) or (2), R ₁ is preferably an alkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 10 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, or an alkyl group having 1 to 20 carbon atoms, And R < _{2 >} may each be hydrogen or a methyl group.

Further, the polymer contained in the core portion has, in addition to the repeating unit represented by the above formula (1) or (2), for general acrylate-based repeating unit, or a vinyl-based repeating units (e. G., In the Chemical Formula 1 or 2, R ₁ each Hydrogen or methyl). ≪ / RTI >

On the other hand, the core portion may further include a polyfunctional acrylate-based or vinyl-based repeating unit. The 'multifunctional acrylate repeating unit or multifunctional vinyl-based repeating unit' means a repeating unit derived from a polyfunctional acrylate monomer or a polyfunctional vinyl monomer which can be further used in the production of the electrophoretic particles . Such a polyfunctional acrylate-based or vinyl-based repeating unit is chemically bonded to the main chain containing an acrylate-based repeating unit or a vinyl-based repeating unit substituted with the above-mentioned specific functional group, so that the polymer contained in the core- Structure or a cross-linking structure, and to realize better mechanical properties and solvent resistance.

 The polyfunctional acrylate repeating unit or polyfunctional vinyl repeating unit is preferably used in an amount of 1 to 50 parts by weight based on 100 parts by weight of the total of the acrylate repeating units and vinyl repeating units substituted with specific functional groups contained in the polymer, Preferably 3 to 35 parts by weight. If the content of the polyfunctional acrylate-based repeating unit or the polyfunctional vinyl-based repeating unit is too large, it may be difficult to achieve a low specific gravity due to a decrease in the free space inside the polymer. Due to the existence of the polyfunctional compound, . If the content of the polyfunctional acrylate repeating unit or polyfunctional vinyl repeating unit is too small, the cross-linking structure of the polymer may not be properly formed, and the effect of improving the solvent resistance may be insignificant.

The polyfunctional acrylate-based repeating unit may be, for example, trimethylolmethane tetraacrylate, trimethylolmethane triacrylate, trimethylolbutane triacrylate or ethylene glycol dimethacrylate, Acrylate (Ethylene Glycol Dimethacrylate) and the like. The polyfunctional vinyl-based repeating unit may be a repeating unit derived from divinyl benzene or the like.

In addition, the core portion may further include a crosslinking agent. The crosslinking agent may react with the acrylate monomer or the vinyl monomer substituted with the specific functional group during the preparation of the electrophoretic particle, or react with the polyfunctional acrylate monomer or the polyfunctional vinyl monomer selectively applied, Structure can be formed. Accordingly, the cross-linking agent may be in a state of being bonded to an acrylate-based monomer or a vinyl-based monomer substituted with a specific functional group in the polymer included in the core portion, or in a state of being combined with the polyfunctional acrylate-based monomer or the polyfunctional vinyl- Lt; / RTI >

The crosslinking agent may be used in an amount of 0.1 to 30 parts by weight, preferably 1 to 20 parts by weight, based on 100 parts by weight of the total of the acrylate-based repeating units and the vinyl-based repeating units substituted with specific functional groups contained in the polymer. If the content of the crosslinking agent is too large, it is not easy to control the reaction heat generated in the production process, and it may be difficult to achieve a low specific gravity by reducing the free space inside the polymer. If the content of the crosslinking agent is too small, the crosslinking structure of the polymer may not be properly formed, and the effect of improving the solvent resistance may be insignificant.

As the crosslinking agent, a compound containing two or more unsaturated carbon atoms can be used. For example, 1,2-ethanediol diacrylate, 1,3-propanediol diacrylate, 1,3-butanediol diacrylate, , 4-butanediol diacrylate, 1,5-pentanediol diacrylate, 1,6-hexanediol diacrylate, divinylbenzene, ethylene glycol diacrylate, propylene glycol diacrylate, butylene glycol diacrylate , Triethylene glycol diacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, polybutylene glycol diacrylate, allyl acrylate, 1,2-ethanediol dimethacrylate, 1,3-propanediol Dimethacrylate, 1,3-butanediol dimethacrylate, 1,4-butanediol dimethacrylate, 1,5-pentanediol dimethacrylate, 1,6-hexanediol dimethacrylate, ethylene Recolled dimethacrylate, propylene glycol dimethacrylate, butylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, triethylene glycol methacrylate , Polybutylene glycol dimethacrylate, allyl methacrylate, diallyl maleate, or a mixture thereof.

In addition, the core portion may further include a small amount of a dispersion stabilizer. Such a dispersion stabilizer is added to a solvent in which inorganic particles or the like are dispersed during the production of the electrophoretic particles to enable stable dispersion of the respective components, and it is possible to prevent aggregation of the respective components in the emulsification step described later, It is possible to minimize the occurrence of polymerization aggregates that may occur in the step. However, since such a dispersion stabilizer is removed through a cleaning step or the like during the production of the electrophoretic particles, the dispersion stabilizer may exist in a small amount in the core portion.

On the other hand, the white or colored inorganic particles are inorganic particles bonded to the surface of the core portion. As shown in the manufacturing method described later, after the inorganic particles are dispersed in a certain solvent, the precursor of the polymer contained in the core portion And may be bonded to the surface of the core part through an emulsion polymerization process.

The white inorganic particles may include at least one compound selected from the group consisting of titanium oxide, magnesium oxide, zinc oxide, calcium oxide and zirconium oxide.

The colored inorganic particles may be a metal compound of iron oxide, CrCu or Carbon Balck or a metal compound of phthalocyanine blue, phthalocyanine green, diarylide yellow, diarylide AAOT yellow, and quinacridone, Azo, rhodamine, perylene pigment series or colored pigment compounds of Hansa yellow G particles. However, examples of the compound that can be included in the colored inorganic particles are not limited thereto, and any compound known to be used for coloring the charged particles may be used without limitation. The average particle size of the inorganic particles is not particularly limited, but may be in the range of 100 nm to 100 μm in order to be easily applied to an electrophoretic display.

The amount of the white or colored inorganic particles bound to the surface of the core portion may be 5 to 50 wt%, preferably 15 to 40 wt%, of the entire charged particles. If the amount of the inorganic particles is too small, the electrophoretic particles may not have sufficient chargeability, and if it is too large, the specific gravity may be greatly increased and the stability or electrophoresis characteristics of the electrophoretic slurry may be deteriorated, The amount of inorganic particles not bonded to the sub-surface can be greatly increased.

The electrophoretic particles may further include a protective layer formed on the core. Such a protective layer can prevent swelling of the core portion and improve the solvent resistance or mechanical properties. The protective layer may be formed by adding a silicone compound or an acrylic monomer substituted with a fluorine group to a first slurry containing inorganic particles, a solvent, a dispersion stabilizer and the like, and then adding a monomer for forming a core part And then emulsion polymerization is carried out. Also, the protective layer may be formed by coating a surface of inorganic particles with a fluorine-based compound or a silicon-based compound.

According to another embodiment of the present invention, there is provided a process for producing a white inorganic pigment, comprising: dispersing white or colored inorganic particles in a solvent; And a solvent in which the white or colored inorganic particles are dispersed are added an alkyl group having 2 to 30 carbon atoms, an alkenyl group having 2 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, an alkylaryl group having 7 to 30 carbon atoms, At least one functional group-substituted acrylate monomer selected from the group consisting of an arylalkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 4 to 20 carbon atoms, an amide group having a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms and an alkoxycarbonyl group having 1 to 20 carbon atoms Or a vinyl monomer and a polymerization initiator, and emulsifying the mixture; And a step of polymerizing the emulsified solution at 10 to 120 ° C for 1 to 50 hours.

As described above, according to the method for producing electrophoretic particles, a core portion including a polymer containing an acrylate-based repeating unit or a vinyl-based repeating unit into which a specific functional group has been introduced, and a white charged particle May be provided. Such electrophoretic particles have a low specific gravity, can be dispersed very stably in a solvent, are used in electrophoretic display, exhibit a fast response speed to an applied voltage, and can exhibit a high contrast ratio or color reproduction power.

As described above, the electrophoretic particles obtained by the above production method can have a low specific gravity value, for example, a true specific gravity of 1.60 g / cm ³ or less, preferably 0.8 to 1.5 g / cm ³ . In addition, the electrophoretic particles may have an average particle diameter of 0.1 to 300 μm, preferably 1 to 200 μm. The electrophoretic particle may have an electric potential distribution of -200 to 200 V, and the coefficient of variation of the electric potential distribution may be 20% or less, preferably 15% or less. The details of the electrophoretic particle are as described above.

The step of dispersing the white charged particles in a solvent may be carried out by a conventional stirring or mixing method at room temperature, for example, at 10 to 40 ° C. The solvent is preferably a water-soluble solvent, and specifically, distilled water, supernatant, alcohol solvents, or a mixture thereof may be used.

In the step of adding and emulsifying an acrylate monomer or a vinyl monomer substituted with a specific functional group and a polymerization initiator into a solvent in which the white or colored inorganic particles are dispersed, a droplet having a predetermined particle size distribution .

The method and apparatus that can be used in the emulsification step are not limited and can be appropriately adjusted in consideration of the size and physical properties of the electrophoretic particle to be produced and can be performed at room temperature using a conventional homogenizer or a stirrer . For example, the emulsifying step may be performed at a temperature of 10 to 40 DEG C using a homomixer at a speed of 100 to 10,000 rpm for 1 minute to 2 hours.

After the droplets having the desired particle size distribution are formed through the emulsification step, the emulsion solution is polymerized at 10 to 120 ° C for 1 to 50 hours to obtain electrophoretic particles. At this time, the polymerization reaction may be performed in a nitrogen atmosphere, and it is preferable that the stirring speed of the electrophoretic particles to be produced does not sink, for example, a speed of 50 to 500 rpm is maintained. In the above-mentioned polymerization reaction, except for the above-mentioned contents, the apparatus and method used in the commonly used homogenization suspension polymerization method can be used without any limitation.

Specific examples of the acrylate monomers or vinyl monomers substituted with the specific functional groups include monomers represented by the following formulas (3) and (4).

(3)

[Chemical Formula 4]

Wherein R ₁ is an alkyl group having 2 to 30 carbon atoms, an alkenyl group having 2 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, an alkylaryl group having 7 to 30 carbon atoms, an arylalkyl group having 7 to 30 carbon atoms , A cycloalkyl group having 4 to 20 carbon atoms, an amide group having a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, and an alkoxycarbonyl group having 1 to 20 carbon atoms, and R ₂ is each hydrogen or a Lt; / RTI >

Preferably, in formula (3) or (4), R ₁ is an alkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 10 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, or an alkyl group having 1 to 20 carbon atoms, And each of R < ₂ > may be hydrogen or a methyl group.

Specific examples of the acrylate monomer substituted with the specific functional group include methyl acrylate, methyl methacrylate, butyl acrylate, butyl methacrylate, urethane acrylate, benzyl methacrylate, cyclohexyl acrylate, dicyclo Pentyl acrylate, norbornyl acrylate, methyl acrylamide, acrylamide or lauryl methacrylate.

In the solvent in which the white or colored inorganic particles are dispersed, an acrylic or vinyl monomer (for example, in the formula (3) or (4), R ₁ is hydrogen or Methyl).

The polymerization initiator may be used without any limitation as far as it is known that it can be used in the polymerization reaction of the acrylate monomer or the vinyl monomer, and preferably an azo initiator, a peroxide initiator or a mixture thereof can be used . The azo-based initiator is a compound capable of initiating polymerization by pyrolysis in the useful phase, and examples thereof include 2,2-azobisisobutyronitrile, 4,4-azobis (4-cyanopentanoic acid) Azobis (2-methylbutyronitrile), and 2,2'-azobis (2,4-dimethylvaleronitrile). The peroxide initiator may be benzoyl peroxide, lauryl peroxide, octanoyl peroxide, dicumyl peroxide, or the like.

The polymerization initiator may be used in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the total amount of the acrylate monomers and vinyl monomers substituted with the specific functional groups. If the amount of the polymerization initiator used is too small, monomers that can not participate in the polymerization reaction may occur in an excess amount. If the amount is too large, there is a problem that the reaction stability is deteriorated due to rapid heat generation in the polymerization process.

On the other hand, a dispersion stabilizer may be further added to the solvent in which the white charged particles are dispersed. Such a dispersion stabilizer is added to a solvent in which white charged particles and the like are dispersed during the production of the electrophoretic particles to allow each component to be stably dispersed. In the emulsification step, It is possible to minimize the occurrence of polymerization aggregates that may occur in the step.

The dispersion stabilizer may be used in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the total amount of the acrylate monomers and vinyl monomers substituted with the specific functional groups. If the amount of the dispersing agent used is too small, there is little effect of improving the stability of each component or minimizing the occurrence of polymerization agglomerates in the emulsification step. If the amount of the dispersing agent is too large, it is easy to remove the dispersion stabilizing agent in the cleaning process of the electrophoretic particles I can not.

Specific examples of such a dispersion stabilizer include polyvinyl pyrrolidone, polyvinyl methyl ether, polyethyleneimine, polymethyl methacrylate acrylic acid copolymer, polyvinyl alcohol, vinyl acetate copolymer, ethyl cellulose, hydroxypropyl cellulose or a mixture thereof .

On the other hand, a polyfunctional acrylic monomer or a polyfunctional vinyl monomer may be further added to the solvent in which the white charged particles are dispersed. When such a polyfunctional acrylic monomer or a polyfunctional vinyl monomer is further added, the polymer contained in the core portion can form a more dense network structure or a crosslinked structure, so that excellent mechanical properties can be obtained, The stability to the solvent or the dispersibility in the solvent can also be improved.

The polyfunctional acrylic monomer or polyfunctional vinyl monomer is used in an amount of 1 to 50 parts by weight, preferably 3 to 35 parts by weight, based on 100 parts by weight of the total amount of the acrylate monomers and vinyl monomers substituted with the specific functional groups . If the amount of the polyfunctional acrylic monomer or the polyfunctional vinyl monomer is too large, it may be difficult to achieve a low specific gravity due to a decrease in the free space inside the polymer, and the specific gravity may be greatly increased due to the presence of the polyfunctional compound . If the amount of the polyfunctional acrylic monomer or the polyfunctional vinyl monomer is too small, the cross-linking structure of the polymer may not be properly formed, and the effect of improving the solvent resistance may be insignificant.

For example, the polyfunctional acrylate monomer may be selected from the group consisting of trimethylolmethane tetraacrylate, trimethylolmethane triacrylate, trimethylolbutane triacrylate or ethylene glycol dimethacrylate Ethylene Glycol Dimethacrylate, etc., and the polyfunctional vinyl-based repeating unit may be divinyl benzene or the like.

Further, a crosslinking agent may be further added to the solvent in which the white charged particles are dispersed. The crosslinking agent may react with the acrylate-based monomer or the vinyl-based monomer substituted with the specific functional group described above, or may react with the polyfunctional acrylate-based monomer or the polyfunctional vinyl-based monomer to form a crosslinked structure. Accordingly, the cross-linking agent may be in a state of being bonded to an acrylate-based monomer or a vinyl-based monomer substituted with a specific functional group in the polymer included in the core portion, or in a state of being combined with the polyfunctional acrylate-based monomer or the polyfunctional vinyl- Lt; / RTI >

The crosslinking agent may be used in an amount of 0.1 to 30 parts by weight, preferably 1 to 20 parts by weight based on 100 parts by weight of the total amount of the acrylate monomer or vinyl monomer substituted with the specific functional group. If the content of the crosslinking agent is too large, it is not easy to control the reaction heat generated in the production process, and it may be difficult to achieve a low specific gravity by reducing the free space inside the polymer. If the content of the crosslinking agent is too small, the crosslinking structure of the polymer may not be properly formed, and the effect of improving the solvent resistance may be insignificant.

As the crosslinking agent, a compound containing two or more unsaturated carbon atoms can be used, and specific examples thereof are as described above.

Details of the white or colored inorganic particles are as described above.

The electrophoretic particle manufacturing method may further include forming a protective layer. Such a protective layer may be formed on the surface of the core portion and may be formed by coating a certain compound on the surface of the white or colored inorganic particles.

Accordingly, the method for preparing the electrophoretic particles may include the steps of: adding a silicone compound or an acrylic monomer substituted with a fluorine group to a solvent in which the white or colored inorganic particles are dispersed; Or coating the surface of the white or colored inorganic particles with a silicon compound or an acrylic compound substituted with a fluorine group.

Examples of the silicone compound that can be used for forming the protective layer include Methicone, Hydrogen Dimethicone Triethoxysilylethyl polydimethylsiloxyethyl dimethicone, Triethoxysilylethyl polydimethylsilylethyl hexyl dimethicone, Acrylates / Tridecyl Acrylate / Triethoxysilylpropyl Methacrylate / Dimethicone Methacrylate Copolymer.

According to another embodiment of the present invention, there is provided a plasma display panel comprising two substrates facing each other; An electrophoresis unit formed between the two substrates; And an electrophoretic display device including the above electrophoretic particles located in the electrophoretic portion.

As described above, electrophoretic particles comprising a core portion containing a polymer containing an acrylate-based repeating unit or a vinyl-based repeating unit to which a specific functional group has been introduced, and white or colored inorganic particles bonded to the surface of the core portion It has a low specific gravity and can be dispersed very stably in the solvent. Accordingly, when the electrophoretic particles are used in an electrophoretic display, a fast response speed can be realized with respect to an applied voltage, and a high contrast ratio or color reproduction capability can be exhibited.

The details of the electrophoretic particle are as described above.

The 'substrate' refers to both sides of the electrophoretic display device including the electrophoresis portion, for example, a substrate surface constituting the upper / lower surface. Such a substrate may be formed on or included in one surface of the substrate, such as various kinds of layers or structures or electrodes for electrophoresis.

Accordingly, the substrate may include a base layer, a conductive base layer, or an electrode layer. The substrate layer can be applied without limitation as long as it can be used as a substrate or a substrate of a display device. For example, a thermoplastic or thermosetting resin may be used, or PET, PAN, PI, or glass may be used . In addition, the conductive base layer may include a conductive material known to be commonly used in a display device, without limitation, for example, CNT, conductive polymer, or the like. At least one of the electrode materials included in both substrates may be a transparent electrode material such as ITO, SnO ₂ , ZnO, or the like. IZO (Indium Zinc Oxide) or the like is preferably used.

The electrophoresis unit refers to a part where the charged particles move to the electrode due to the attraction force when the voltage difference is applied between the substrates facing each other to realize color or light and dark. The electrophoresis part may comprise a flow medium and the electrophoretic particles floating in the flow medium. The ratio of the electrophoretic particles to the flow medium in the electrophoresis part is not particularly limited, but the volume ratio of the electrophoretic particles: flow fluid is, for example, 5:95 to 60:40, preferably 7:93 to 40: Lt; / RTI > As the flowing fluid, a solvent having a viscosity of 20 cP or less may be used. Examples of such flow fluids include hydrocarbons such as decahydronaphthalene (DECALIN), 5-ethylidene-2-norbornene, fatty oils, paraffin oils (Isopar G, Isopar L, Isopar M and the like); Aromatic hydrocarbons such as toluene, xylene, phenyl xylylethane, dodecylbenzene and alkylnaphthalene; Halogenated solvents such as perfluorodecalin, perfluorotoluene, perfluoroxylene, dichlorobenzotrifluoride, 3,4,5-trichlorobenzotrifluoride, chloropentafluoro-benzene, dichlorononene and pentachlorobenzene; Perfluorinated solvents; And low molecular weight halogen solvents containing polymers such as perfluoropolyalkyl ethers.

The shape or structure of the electrophoresis portion is not particularly limited, and may include, for example, a structure of a microcapsule or a microcup. The 'microcup' refers to a cup-shaped recess formed in the electrophoretic display device, and may mean, for example, a space surrounded by two opposing electrodes and a partition formed between the electrodes. The 'microcapsule' means a spherical or elliptical closed container formed in the electrophoretic display device and having a diameter of micrometer (um) unit.

The size and shape of the microcup can be defined by the partition walls formed in the electrophoresis portion and can be appropriately adjusted according to the characteristics and size of the electrophoretic display device to be manufactured. For example, the barrier ribs may have a height of 10 to 500 um and a thickness of 2 to 100 um, and may have various cross-sectional shapes such as a rectangle, a square, and a trapezoid, but the present invention is not limited thereto. In addition, the microcups may have a planar shape such as a circle, a triangle, a rectangle, a rectangle, an ellipse, or various polygons.

The size and the material of the 'microcapsule' can be controlled according to the characteristics of the display to be manufactured. For example, each microcapsule may be spherical or elliptic spherical with a longest particle diameter of 10 to 1,000 μm. The microcapsule may be combined with a binder or an organic solvent to form a electrophoresis unit. The electrophoresis unit of the type known to be usable for a microcapsule electrophoretic display can be used without any limitation Do.

Except for the foregoing, devices, components and methods known to be commonly used in electrophoretic display devices are applicable without limitation to the electrophoretic display device of the present invention.

On the other hand, the electrophoretic display device can exhibit a high control ratio value, for example, a control ratio of 14: 1 (white: black) or more, and realize a short reaction speed, by using the electrophoretic particles.

According to the present invention, there is provided an electrophoretic particle having a low specific gravity and exhibiting a high reaction rate with respect to an applied voltage and exhibiting a high contrast ratio or a color reproduction capability, a method of producing the electrophoretic particle, and an electrophoretic display A device may be provided.

1 is a SEM photograph of the electrophoretic particle of Example 1. Fig.
2 is a SEM photograph of the electrophoretic particle of Example 2. Fig.
3 is a SEM photograph of the electrophoretic particle of Example 3. Fig.
4 is a SEM photograph of the electrophoretic particle of Example 4. Fig.
5 is a SEM photograph of the electrophoretic particle of Example 5. Fig.
6 is a SEM photograph of the electrophoretic particle of Comparative Example 1. Fig.
7 is a SEM photograph of the electrophoretic particle of Comparative Example 2. Fig.
8 is an SEM photograph of the electrophoretic particle of Comparative Example 3. Fig.
Fig. 9 shows the results of evaluating the solvent resistance of the electrophoretic particles of Examples 4 and 5. Fig.
10 shows the stability evaluation results of the slurry containing the electrophoretic particles of Example 3 and Comparative Examples 1 and 3.
FIG. 11 shows an electrophoretic display sample at +15 V voltage application in Experimental Example 5. FIG.
FIG. 12 shows an electrophoretic display sample at -15 V voltage application in Experimental Example 5.

The invention will be described in more detail in the following examples. However, the following examples are illustrative of the present invention, and the present invention is not limited by the following examples.

< Example  1 to 5: Preparation of electrophoretic particles>

Example 1

5 g of polyvinyl alcohol (PVA) as a dispersion stabilizer and 20 g of white charged particles (TiO2, Dupont Co., 200 to 400 nm) were mixed in an ethanol dispersion medium and the mixture was stirred at 6000 rpm for 30 minutes using a homomixer Lt; / RTI &gt; to prepare a primary dispersion solution.

Then, 60 g of methyl methacrylate, 10 g of lauryl methacrylate, 10 g of methacrylic acid, 10 g of ethylene glycol dimethacrylate as a multifunctional acrylate monomer, glycol dimethacrylate) and 1 g of polymerization initiator 2,2'-azobis (2,4-dimethylvaleronitrile) were mixed to prepare a secondary solution.

The primary dispersion solution was added to the secondary dispersion solution to prepare a mixture, which was then homogenized and homogenized at 4000 rpm for 10 minutes using a homogenizer. The resulting emulsion was placed in a reaction tube and reacted at 50 ° C for 6 hours under a nitrogen atmosphere. The temperature was raised to 75 ° C and reacted again for 4 hours. The polymer synthesized by the above reaction was filtered, washed with water and aqueous ethanol solution, and the filtrate was dried in a vacuum oven for one day to obtain electrophoretic particles.

Example  2

Electrophoretic particles were obtained in the same manner as in Example 1, except that 40 g of methyl methacrylate and 30 g of lauryl methacrylate were used.

Example  3

Electrophoretic particles were obtained in the same manner as in Example 1 except that 20 g of methyl methacrylate and 50 g of lauryl methacrylate were used.

Example  4

Electrophoretic particles were obtained in the same manner as in Example 1, except that 0 g of methyl methacrylate and 70 g of lauryl methacrylate were used.

Example  5

5 g of polyvinyl alcohol (PVA) as a dispersion stabilizer, 20 g of white charged particles (TiO2, Dupont, 200 to 400 nm) and 3 g of Methicone were mixed in an ethanol dispersion medium, Was homogenized at 6000 rpm for 30 minutes to prepare a primary dispersion solution.

Then, 70 g of lauryl methacrylate, 10 g of methacrylic acid, 20 g of ethylene glycol dimethacrylate as a multifunctional acrylate monomer, and 20 g of polymerization initiator 2,2'-azobis (2,4-dimethylvaleronitrile) were mixed to prepare a secondary solution.

The primary dispersion solution was added to the secondary dispersion solution to prepare a mixture, which was then homogenized and homogenized at 4000 rpm for 10 minutes using a homogenizer. The resulting emulsion was placed in a reaction tube and reacted at 50 ° C for 6 hours under a nitrogen atmosphere. The temperature was raised to 75 ° C and reacted again for 4 hours. The polymer synthesized by the above reaction was filtered, washed with water and aqueous ethanol solution, and the filtrate was dried in a vacuum oven for one day to obtain electrophoretic particles.

< Comparative Example >

Comparative Example 1

60 g of methyl methacrylate, 10 g of lauryl methacrylate, 10 g of methacrylic acid, and 10 g of a polyfunctional acrylate monomer, ethylene glycol dimethacrylate 20 g of the polymerization initiator, 1 g of 2,2'-azobis (2,4-dimethylvaleronitrile), 5 g of polyvinyl alcohol (PVA) as a dispersion stabilizer and white charged particles (TiO2, Was mixed with an ethanol dispersion medium, and the mixture was homogenized and emulsified at 6000 rpm for 30 minutes using a high-speed stirrer (Homomixer).

The resulting emulsion was placed in a reaction tube and reacted at 50 ° C for 6 hours under a nitrogen atmosphere. The temperature was raised to 75 ° C and reacted again for 4 hours. The polymer synthesized by the above reaction was filtered, washed with water and aqueous ethanol solution, and the filtrate was dried in a vacuum oven for one day to obtain electrophoretic particles.

Comparative Example 2

Electrophoretic particles were obtained in the same manner as in Comparative Example 1, except that 0 g of methyl methacrylate and 70 g of lauryl methacrylate were used.

Comparative Example 3

Electrophoretic particles were obtained in the same manner as in Example 1, except that 10 g of the lauryl methacrylate was not used.

< Experimental Example >

Experimental Example 1 . Observation of morphology and surface of electrophoretic particles

The morphology and surface state of the electrophoretic particles obtained in the above Examples and Comparative Examples were observed using SEM. The concrete results are as shown in Figs. 1 to 5 (Examples 1 to 5) and Figs. 6 to 8 (Comparative Examples 1 to 3).

As shown in FIGS. 1 to 5, it can be seen that most of the TiO ₂ particles are uniformly distributed along the surface of the electrophoretic particles in Examples 1 to 5. Accordingly, the specific gravity of the slurry containing the electrophoretic particles of the example can be relatively lowered and the whiteness can be increased, as shown in the following experimental examples.

On the other hand, as shown in Figs. 6 to 8, it was confirmed that the TiO ₂ particles were not uniformly distributed on the surface of the electrophoretic particles of the comparative example. In Comparative Example 3, not only spherical electrophoretic particles could be formed, but also TiO ₂ particles were distributed in a considerable amount in the broken particles.

Experimental Example 2 . Of electrophoretic particles True weight  And product yield measurement

Product yield and true specific gravity of the electrophoretic particles obtained in the above Examples and Comparative Examples were measured, and the results of the analysis are shown in Table 1.

(1) Product yield measurement: the yield after filtration

(Binary specific gravity: Pycnometer (Micromeritics instrument)

Results of Experimental Example 1 Primary dispersion step
Introduction Amount of usage of lauryl methacrylate (g) yield(%) True weight
[g / cm ^3] Example 1 O 10 88% 1.54 Example 2 O 30 87% 1.40 Example 3 O 50 89% 1.32 Example 4 O 70 88% 1.20 Example 5 O 70 87% 1.20 Comparative Example 1 X 0 85% 1.65 Comparative Example 2 X 10 85% 1.58 Comparative Example 3 O 0 87% 1.60

However, in the above Examples and Comparative Examples, electrophoretic particles having a particle size of 3 to 10 um were prepared.

Experimental Example 3 . Of electrophoretic particles Solvent resistance  Measure

When the increase in the viscosity measured after 8 hours based on the initial viscosity of the tank solution obtained by mixing the electrophoretic particles obtained in Examples 4 and 5 and toluene at a weight ratio of 1: 1 is less than 100%, the solvent resistance is "good" "Poor ". The viscosity was measured by Brookfield's DV II. The measured results are shown in Fig.

As shown in Fig. 5, the electrophoretic particles of Examples 4 and 5 were found to have good solvent resistance. In addition, it was confirmed that the electrophoretic particles obtained in Example 5 had relatively low viscosity as the protective layer was further included, and thus the solvent resistance was improved. The higher the solvent resistance as in Examples 4 and 5, the longer-term stability is improved and the viscosity increase can be suppressed, so that the proportion of the charged particles in the slurry of electrophoretic particles can be greatly increased.

Experimental Example 4 . Electrophoretic particle Slurry  Stability evaluation

The electrophoretic particle slurry was prepared by dispersing the white charged particles and the carbon black particles obtained in Example 3 and Comparative Examples 1 and 3 in a hydrocarbon solvent (Isopar G: Halocarbon = 1: 1 solution) at a ratio of 5: 1 . The electrophoretic particle slurry was stored in a transparent glass bottle for 3 days or longer, and the results are shown in FIG.

As shown in Fig. 10, it was confirmed that when the electrophoretic particles of Example 3 were used three days after the preparation of the slurry, the stability of the slurry was excellent. On the contrary, in the case of using the charged particles of Comparative Examples 1 and 3, precipitation occurred, and it was confirmed that the stability of the slurry was poor. That is, when the specific gravity of the white charged particles and the black charged particles is not appropriate, the stability of the slurry is lowered especially when the black charged particles have a specific gravity lower than that of the white charged particles.

Experimental Example 5 . Performance test of electrophoretic display device

The electrophoretic particle slurry was prepared by dispersing the white charged particles and the carbon black particles obtained in Examples and Comparative Examples in a hydrocarbon solvent (Isopar G: Halocarbon = 1: 1 solution) at a ratio of 5: 1.

This electrophoretic particle slurry was injected into an ITO cell (40 mm × 45 mm × 80 μm: width × height × height) through which electric current could pass through the upper and lower plates, and voltage / . Specific measurement items and measurement methods are as follows.

(1) Comparison ratio measurement

An electronic ink slurry was injected between the fabricated ITO upper and lower substrates and a voltage of +15 V and -15 V was applied. The absolute value of the maximum value of the white reflectance and the absolute value of the minimum value of the black reflectance were measured, And the ratio was converted into a ratio.

In detail, the brightness realized by the ITO cell was measured using a CHROMA METER CS-100A luminance meter manufactured by KONICA MINOLTA, and the brightness value (L) was obtained. A plate made of barium sulfate (100 cd / And the L * value (luminance) was calculated.

(2) Measurement of reaction rate

Electronic ink slurry was injected between the fabricated ITO upper / lower plate and a voltage of +15 V and -15 V was applied to measure the maximum value of white luminance and the time to reach the minimum value of black luminance.

Results of Experimental Example 5 White particles
Input ratio Control ratio Reaction rate
(Sec) Example 1 10% 15: 1 0.7 Example 2 10% 15: 1 0.5 Example 3 10% 16: 1 0.3 Example 4 10% 16: 1 0.2 Example 5 10% 16: 1 0.2 Comparative Example 1 10% 12: 1 2.5 Comparative Example 2 10% 13: 1 1.2 Comparative Example 3 10% 13: 1 2.0

As shown in Table 2, in the Examples, most of the TiO ₂ particles are located along the surface of the electrophoretic particles, so that an improved control ratio can be achieved even though the same white particles are used. Further, as shown in the results of Examples 1 to 5, the electrophoretic particles of Examples have a relatively low specific gravity, so that the reaction rate can be increased in an electrophoretic display using the same.

Claims (17)

At least one functional group-substituted acrylate-based repeating unit selected from the group consisting of an alkyl group having 3 to 20 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, and an amide group having a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, A core portion including a polymer including the polymer; And
And white or colored inorganic particles bonded to the surface of the core portion,
An average particle diameter of 0.1 to 300 mu m,
An electrophoretic particle having a true specific gravity of 0.8 to 1.5 g / cm &lt; ³ &gt;.
delete The method according to claim 1,
Wherein the polymer contained in the core portion comprises a repeating unit represented by the following Formula 1 or 2:
[Chemical Formula 1]

(2)

In the above formula (1) or (2)
R ₁ is an alkyl group having 3 to 20 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, or an amide group in which an alkyl group having 1 to 20 carbon atoms is substituted or unsubstituted,
And R ₂ is hydrogen or an alkyl group having 1 to 3 carbon atoms.
delete The method according to claim 1,
Wherein the polymer contained in the core portion further comprises a polyfunctional acrylate-based or vinyl-based repeating unit.
The method according to claim 1,
Wherein the core portion further comprises a crosslinking agent.
The method according to claim 1,
Wherein the white charged particles comprise at least one compound selected from the group consisting of titanium oxide, magnesium oxide, zinc oxide, calcium oxide and zirconium oxide.
The method according to claim 1,
Wherein the colored inorganic particles are selected from the group consisting of iron oxide, CrCu, carbon black, phthalocyanine blue, phthalocyanine green, diarylide yellow, diarylide AAOT yellow, and quinacridone, azo, An electrophoretic particle comprising at least one member selected from the group consisting of rhodamine, perylene pigment series and Hansa yellow G particles.
The method according to claim 1,
And a protective layer formed on the core portion.
Dispersing white or colored inorganic particles in a solvent; And
At least one functional group selected from the group consisting of an alkyl group having 3 to 20 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, and an amide group in which an alkyl group having 1 to 20 carbon atoms is substituted or unsubstituted is added to a solvent in which the white or colored inorganic particles are dispersed Adding a substituted acrylate monomer or a vinyl monomer and a polymerization initiator to emulsify; And
And polymerizing the emulsified solution at 10 to 120 ° C for 1 to 50 hours.
11. The method of claim 10,
Wherein the electrophoretic particles have an average particle diameter of 0.1 to 300 μm and a true specific gravity value of 0.8 to 1.5 g / cm ³ .
11. The method of claim 10,
Wherein the solvent in which the white or colored inorganic particles are dispersed further comprises a dispersion stabilizer.
11. The method of claim 10,
Further comprising the step of adding a polyfunctional acrylic monomer or a polyfunctional vinyl monomer to a solvent in which the white or colored inorganic particles are dispersed.
11. The method of claim 10,
Further comprising the step of adding a cross-linking agent to a solvent in which the white or colored inorganic particles are dispersed.
11. The method of claim 10,
Adding a silicone compound or a fluorine-substituted acrylic monomer to a solvent in which the white or colored inorganic particles are dispersed; or
And coating the surface of the white or colored inorganic particles with a silicone compound or an acrylic compound substituted with a fluorine group.
Two substrates facing each other;
An electrophoresis unit formed between the two substrates; And
The electrophoretic display device according to claim 1, wherein the electrophoretic particle is located in the electrophoretic portion.
17. The method of claim 16,
Wherein the electrophoresis portion includes a micro cell or a microcup.

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