JP2014148591A - Carbon modified particle for electrowetting display, manufacturing method of carbon modified particle for electrowetting display, ink for electrowetting display and electrowetting display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon modifed particle for electrowetting display capable of being used as a coloring component for electrowetting display.SOLUTION: A carbon modifed particle 21 for electrowetting display includes a carbon particle 22 and a surface part 23 disposed on a surface of the carbon particle 22 and consisting of a particle surface. In the carbon modifed particle 21 for electrowetting display, the particle surface is formed of a compound which the constituent atoms are only a carbon atom and a hydrogen atom, or a compound which the total of the carbon atom, the hydrogen atom, an oxygen atom, a nitrogen atom and a sulfur atom is 95 mass% or more in the total 100 mass% of the constituent atoms, and a ratio of the mass of the carbon atom to the total mass of the oxygen atom, the nitrogen atom and the sulfur atom is 5 or more.

Description

  The present invention relates to a carbon modified particle used for an electrowetting display and a method for producing the carbon modified particle. The present invention also relates to an electrowetting display ink and an electrowetting display using the carbon modified particles.

  In recent years, an electrowetting display (hereinafter, sometimes referred to as EWD) using an electrowetting effect has attracted attention. The EWD includes a hydrophilic liquid and a hydrophobic liquid between two opposing substrates. The hydrophobic liquid generally contains a coloring component. One substrate includes an electrode layer on the surface and a hydrophobic intermediate layer (insulating layer) formed on the surface of the electrode layer. In EWD, when a voltage is applied between the hydrophilic liquid and the electrode layer through the hydrophobic intermediate layer, the hydrophilic liquid is attracted to the hydrophobic intermediate layer, and the interface shape between the hydrophilic liquid and the hydrophobic liquid is Change. As a result, the hydrophobic liquid (oil layer) moves to expose the transparent portion and the like, so that an image is displayed.

  As an example of the hydrophobic liquid, the following Patent Document 1 discloses a composition containing a dye and an oil. The composition contains the dye as a coloring component. Specific examples of the dye include Sudan Red 500, Sudan Blue 673, and Sudan Yellow 172 (manufactured by BASF).

WO2005 / 098524A1

  When the composition containing the dye and oil described in Patent Document 1 is used as an EWD ink, the hiding performance by the coloring component may be low.

  Conventionally, a pigment may be used as a coloring component. However, the pigment used in the conventional EWD has a problem of low dispersibility in the EWD ink. When EWD is produced using the EWD ink in which the pigment is precipitated, the concealment performance of the pigment is lowered, and a clear image cannot be obtained or image unevenness occurs.

  Moreover, the blackness of the carbon pigment is high. For this reason, if a carbon pigment is used as a coloring component for EWD, there is a possibility that the concealability can be improved. However, carbon pigments generally have high electrical conductivity. For this reason, the carbon pigment remains as it is and cannot be used as a coloring component for EWD. If the carbon pigment is used as a coloring component for EWD, the display quality in EWD cannot be improved because the carbon pigment has high conductivity. That is, conventionally, carbon pigments are considered to be inappropriate as a coloring component for EWD, and are not used as a coloring component for EWD.

  The main object of the present invention is to provide carbon modified particles for electrowetting displays and a method for producing carbon modified particles for electrowetting displays that can be used as a coloring component for electrowetting displays.

  A limited object of the present invention is to provide a carbon modified particle for electrowetting display and a method for producing the carbon modified particle for electrowetting display capable of enhancing dispersibility in ink for electrowetting display. That is.

  Another object of the present invention is to provide an electrowetting display ink and an electrowetting display using the carbon modified particles for an electrowetting display.

  According to a wide aspect of the present invention, a carbon particle and a surface portion disposed on the surface of the carbon particle and constituting the particle surface are provided, and the particle surface is composed of carbon atoms and hydrogen. Or the particle surface has a total of 95 mass% or more of carbon atoms, hydrogen atoms, oxygen atoms, nitrogen atoms and sulfur atoms in a total of 100 mass% of the constituent atoms. Provided is a carbon modified particle for EWD, which is formed by a compound having a ratio of the mass of carbon atoms to the total mass of oxygen atoms, nitrogen atoms and sulfur atoms of 5 or more.

  In a specific aspect of the EWD carbon modified particle according to the present invention, the EWD carbon modified particle is obtained by surface-treating the carbon particle so that the particle surface includes only carbon atoms and hydrogen atoms. Or the particle surface has a total of 95 mass% or more of carbon atoms, hydrogen atoms, oxygen atoms, nitrogen atoms and sulfur atoms in a total of 100 mass% of the constituent atoms, and A surface portion constituting the particle surface on the surface of the carbon particles so that the ratio of the mass of carbon atoms to the total mass of oxygen atoms, nitrogen atoms and sulfur atoms is 5 or more; It is obtained by arranging.

  According to a wide aspect of the present invention, by surface-treating carbon particles, a surface portion constituting the particle surface is disposed on the surface of the carbon particles, and the particle surface is composed of carbon atoms and hydrogen. Or the particle surface has a total of 95 mass% or more of carbon atoms, hydrogen atoms, oxygen atoms, nitrogen atoms and sulfur atoms in a total of 100 mass% of the constituent atoms. And a step of obtaining a carbon modified particle for EWD comprising a step of obtaining a carbon modified particle for EWD formed by a compound having a ratio of the mass of carbon atom to the total mass of oxygen atom, nitrogen atom and sulfur atom being 5 or more. A method for producing a particulate is provided.

  According to a wide aspect of the present invention, there is provided an EWD ink containing the above-described carbon modified particles for EWD and a hydrophobic solvent.

  According to a wide aspect of the present invention, the first and second substrates facing each other, the first liquid disposed on the first substrate side between the first and second substrates, and the first 1, an EWD ink disposed between the second substrate and the second substrate, wherein the EWD ink includes the above-described EWD carbon-modified particles and a hydrophobic solvent. Provided.

  The carbon modified particles for an electrowetting display according to the present invention include carbon particles and a surface portion that is disposed on the surface of the carbon particles and that constitutes the particle surface. Or the surface of the particle is composed of carbon atoms, hydrogen atoms, oxygen atoms, nitrogen atoms and sulfur atoms in a total of 100% by mass of the constituent atoms. Is formed of a compound having a ratio of the mass of carbon atoms to the total mass of oxygen atoms, nitrogen atoms, and sulfur atoms of 5 or more. And the carbon modified particles can be used in electrowetting displays. By using the carbon modified particles for an electrowetting display according to the present invention, the display quality of the electrowetting display can be improved.

  The method for producing carbon modified particles for an electrowetting display according to the present invention is such that the surface of the particles is formed by a compound whose constituent atoms are only carbon atoms and hydrogen atoms, by treating the carbon particles. Alternatively, the particle surface has a total of 95% by mass or more of carbon atoms, hydrogen atoms, oxygen atoms, nitrogen atoms and sulfur atoms in a total of 100% by mass of constituent atoms, and oxygen atoms and nitrogen having a mass of carbon atoms. An electrowetting display is provided by disposing a surface portion constituting the particle surface on the surface of the carbon particle so as to be formed of a compound having a ratio of the total mass of atoms and sulfur atoms of 5 or more. The process of obtaining carbon modified particles for use in the process reduces the conductivity of the carbon modified particles, so that the carbon modified particles are electrowetted. It becomes available on the display. By using the carbon modified particles for an electrowetting display according to the present invention, the display quality of the electrowetting display can be improved.

FIG. 1 is a cross-sectional view schematically showing carbon modified particles for an electrowetting display according to an embodiment of the present invention. FIG. 2 is a cross-sectional view schematically showing an electrowetting display using carbon modified particles for an electrowetting display according to an embodiment of the present invention. FIG. 3 is a schematic cross-sectional view for explaining the operation concept of the electrowetting display shown in FIG.

  Details of the present invention will be described below.

(Carbon modified particles for EWD)
FIG. 1 is a cross-sectional view schematically showing carbon modified particles for an electrowetting display (EWD) according to an embodiment of the present invention.

  A carbon modified particle 21 for EWD shown in FIG. 1 includes carbon particles 22 and a surface portion 23 that is disposed on the surface of the carbon particles 22 and that constitutes the particle surface. The surface portion 23 is preferably a surface layer.

  In the carbon modified particle 21 for EWD, the particle surface is formed of the first compound whose constituent atoms are only carbon atoms and hydrogen atoms, or the particle surface is in a total of 100 mass% of the constituent atoms. The total of carbon atoms, hydrogen atoms, oxygen atoms, nitrogen atoms and sulfur atoms is 95% by mass or more, and the ratio of the mass of carbon atoms to the total mass of oxygen atoms, nitrogen atoms and sulfur atoms is 5 or more. It is formed by a certain second compound. In other words, the carbon modified particles 21 for EWD have a particle surface formed by the first compound whose constituent atoms are only carbon atoms and hydrogen atoms, or carbon in a total of 100 mass% of the constituent atoms. The sum of atoms, hydrogen atoms, oxygen atoms, nitrogen atoms and sulfur atoms is 95% by mass or more, and the ratio of the mass of carbon atoms to the total mass of oxygen atoms, nitrogen atoms and sulfur atoms is 5 or more. It has the particle | grain surface formed with the 2nd compound. The total of 100% by mass of the constituent atoms is 100% by mass of the total of the atoms constituting the first and second compounds. The total of carbon atoms, hydrogen atoms, oxygen atoms, nitrogen atoms and sulfur atoms in a total of 100 mass% of the constituent atoms of the second compound is 95 mass% or more. In the second compound, the ratio of the mass of carbon atoms to the total mass of oxygen atoms, nitrogen atoms, and sulfur atoms is 5 or more.

  Since the carbon modified particle for EWD according to the present invention has a particle surface formed by the compound having the specific atomic structure described above, even if the carbon particle itself has high conductivity, The conductivity can be lowered. For this reason, carbon particles that could not be used for EWD conventionally can be used for EWD in the form of carbon modified particles. By using the carbon modified particles for EWD according to the present invention, the display quality of EWD can be improved.

  Further, when the carbon particles or the carbon modified particles do not have the specific particle surface, the dispersibility of the particles in the hydrophobic solvent is lowered.

  On the other hand, in the carbon modified particles for EWD according to the present invention, since the specific particle surface is formed, the hydrophobicity of the particle surface can be sufficiently increased. Therefore, the dispersibility of the EWD carbon-modified particles in the EWD ink can be enhanced by using the EWD carbon-modified particles according to the present invention for the EWD ink. In addition, the ratio (mass (C) / (mass (O) + mass (N) + mass (S)) of the mass of carbon atoms in the second compound to the total mass of oxygen atoms, nitrogen atoms and sulfur atoms. The larger the is, the higher the hydrophobicity of the surface of the carbon modified particles for EWD.

  Further, since the carbon modified particles for EWD according to the present invention use carbon particles, the blackness of the EWD ink can be considerably increased, and a considerably high concealing property is exhibited.

  In the carbon modified particles for EWD, the particle surface is preferably formed of the first compound, and is preferably formed of the second compound.

  Further, in the EWD carbon modified particles according to the present invention, even if the amount of the surfactant added in the EWD ink is small, and even if no surfactant is added in the EWD ink, the EWD The dispersibility of the carbon modified particles can be enhanced. By not using a surfactant in the EWD ink or reducing the amount of surfactant added, the EWD drive response of the EWD ink is further improved.

  In addition, the whole area | region of the particle | grain surface of the carbon modified particle for EWD which concerns on this invention may not be the particle | grain surface formed with the compound which has the said atomic structure. Of the total surface area of the particle surface of the carbon modified particles for EWD, the surface area of the particle surface formed by the compound having the atomic configuration is preferably 50% or more, more preferably 80% or more, and still more preferably 90% or more. Particularly preferably, it is 95% or more, and most preferably 99% or more. The larger the particle surface portion formed by the compound having the above-mentioned atomic structure, the higher the surface hydrophobicity of the EWD carbon modified particles, and the higher the dispersibility of the EWD carbon modified particles in the hydrophobic solvent. .

  Since it is easy to make the particle surface have the atomic configuration described above, the carbon modified particle is formed by a compound in which the particle surface is composed of only carbon atoms and hydrogen atoms, or particles The surface has a total of 95% by mass or more of carbon atoms, hydrogen atoms, oxygen atoms, nitrogen atoms, and sulfur atoms in a total of 100% by mass of constituent atoms, and oxygen atoms, nitrogen atoms, and sulfur having a mass of carbon atoms. A surface portion constituting the particle surface is disposed on the surface of the carbon particle by subjecting the carbon particle to a surface treatment so as to be formed by a compound having a ratio with respect to a total mass with atoms of 5 or more. Is preferably obtained. That is, the carbon modified particles are formed on the surface of the carbon particles by surface-treating the carbon particles such that the particle surfaces of the obtained carbon modified particles have a specific atomic configuration. It is preferable that it is obtained by arranging the surface part which is carrying out.

  Since it is easy to make the particle surface have the atomic configuration described above, the carbon modified particles for EWD preferably have a core and a shell covering the surface of the core. The carbon modified particles for EWD are preferably core-shell particles. It is preferable that the core is the carbon particle. It is preferable that the shell is the surface portion.

  The entire area of the surface of the core may not be covered with the shell. The total surface area of the surface of the core covered by the shell is preferably 50% or more, more preferably 80% or more, still more preferably 90% or more, particularly preferably 95% or more, and most preferably 99%. % Or more. The larger the portion covered with the shell, the higher the hydrophobicity of the surface of the carbon modified particles for EWD due to the shell. Furthermore, the larger the portion covered with the shell, the higher the dispersibility of the carbon modified particles for EWD.

  The average particle diameter of the carbon modified particles for EWD is preferably 20 nm or more, more preferably 50 nm or more, preferably 300 nm or less, more preferably 250 nm or less. When the average particle diameter is not less than the above lower limit and not more than the above upper limit, the concealing property by the carbon modified particles is further enhanced, the dispersion stability of the carbon modified particles in the ink is further enhanced, and in the ink The fluidity of the carbon-modified particles at this point is further increased.

  The average particle size means a particle size at an integrated value of 50% in a particle size distribution on a volume basis measured using a dynamic light scattering particle size distribution meter.

  The specific gravity of the carbon modified particles for EWD is preferably 3 or less, more preferably 2 or less. When the specific gravity is not more than the above upper limit, the dispersion stability of the carbon-modified particles in the ink is further enhanced.

  From the viewpoint of further improving the display quality of EWD using the carbon modified particles for EWD, the carbon modified particles for EWD are preferably spherical. The average aspect ratio of the spherical modified carbon particles for EWD is 1.5 or less. The average aspect ratio of the carbon modified particles for EWD is preferably 1.5 or less. The aspect ratio is the ratio of the major axis to the minor axis (major axis / minor axis). When the average aspect ratio is less than or equal to the above upper limit, light scattering by the carbon-modified particles tends to be isotropic, and an even better display image can be obtained.

  Hereinafter, each component used when obtaining the carbon modified particles for EWD will be described.

[Carbon particles]
The carbon particles are generally black and are black particles. Examples of the carbon material constituting the carbon particles include carbon black, carbon nanotube, fullerene, graphene, and graphite. The carbon material is preferably carbon black. Examples of the carbon black include ketjen black, acetylene black, channel black, thermal black, and furnace black.

[Surface forming material]
The carbon modified particles for EWD are preferably obtained using the carbon particles and a surface forming material. By using the surface forming material, it is easy to make the particle surface have the atomic configuration described above. As for the said surface forming material, only 1 type may be used and 2 or more types may be used together.

  From the viewpoint of effectively increasing the dispersibility of the carbon modified particles for EWD, the particle surface of the carbon modified particles for EWD is preferably formed of the surface forming material, and the surface portion is formed of the surface. It is preferable that it is formed of a forming material. The compound on the particle surface of the carbon modified particles for EWD is preferably a compound derived from the surface forming material, and the compound constituting the surface portion is a compound derived from the surface forming material. Is preferred. From the viewpoint of effectively increasing the dispersibility of the carbon modified particles for EWD, the carbon modified particles for EWD are shells derived from the carbon particles and the surface forming material covering the surfaces of the carbon particles. It is preferable to have. It is preferable that the shell is the surface portion.

  Specific examples of the surface forming material include long-chain hydrocarbons such as polyethylene, polypropylene, and polyisobutylene, polymers of alkyl (meth) acrylates having an alkyl group having 12 to 18 carbon atoms, polymers of diene compounds, and the like. Hydrogenated product, isobutene / isoprene copolymer, styrene / butadiene copolymer, styrene / isoprene copolymer, butadiene / acrylonitrile copolymer, alkyl vinyl ether polymer having an alkyl group having 12 to 18 carbon atoms, α- Examples thereof include a copolymer of an olefin and an alkyl vinyl ether, a copolymer of an α-olefin and a diene compound, and the like. Examples of the diene compound include isoprene and butadiene. Other surface forming materials may be used.

  From the viewpoint of further improving the dispersibility of the carbon modified particles for EWD, in the surface forming material, the constituent atoms are only carbon atoms and hydrogen atoms, or carbon atoms in a total of 100 mass% of the constituent atoms. And the sum of hydrogen atoms, oxygen atoms, nitrogen atoms and sulfur atoms is 95% by mass or more, and the ratio of the mass of carbon atoms to the total mass of oxygen atoms, nitrogen atoms and sulfur atoms is 5 or more. Is preferred. When the surface forming material contains carbon atoms, hydrogen atoms, oxygen atoms, nitrogen atoms, and sulfur atoms, the total mass of oxygen atoms, nitrogen atoms, and sulfur atoms of the carbon atoms in the surface forming material The ratio to is preferably 5 or more.

  From the viewpoint of further improving the dispersibility of the carbon modified particles for EWD, the surface forming material is a polymer of at least one polymerization component selected from the group consisting of styrene, isoprene, isobutylene and butadiene, or the polymer. Or a polymer of alkyl (meth) acrylate having an alkyl group having 12 to 18 carbon atoms. The surface forming material is preferably a polymer of at least one polymerization component selected from the group consisting of styrene, isoprene, isobutylene and butadiene, and is preferably a hydrogenated product of the polymer. An alkyl (meth) acrylate polymer having an alkyl group having 12 to 18 carbon atoms is also preferable. The constituent atoms of the polymer of at least one polymerization component selected from the group consisting of styrene, isoprene, isobutylene, and butadiene are preferably only carbon atoms and hydrogen atoms. The constituent atoms of the hydrogenated product of the polymer are preferably only carbon atoms and hydrogen atoms. The total of carbon atoms, hydrogen atoms, oxygen atoms, nitrogen atoms, and sulfur atoms in a total of 100 mass% of the constituent atoms of the alkyl (meth) acrylate polymer having an alkyl group having 12 to 18 carbon atoms is 95 mass%. The above is preferable. The ratio of the mass of carbon atoms to the total mass of oxygen atoms, nitrogen atoms, and sulfur atoms in the polymer of alkyl (meth) acrylate having an alkyl group having 12 to 18 carbon atoms is preferably 5 or more.

  From the viewpoint of effectively increasing the dispersibility of the carbon modified particles for EWD, the surface forming material is preferably a surface forming material that is an organic polymer. The weight average molecular weight of the organic polymer surface forming material is preferably 10,000 or more, and preferably 1,000,000 or less. It is preferable that the weight average molecular weight of the surface forming material which is the organic polymer forming the particle surface of the carbon modified particles for EWD is not less than the above lower limit and not more than the above upper limit.

  The weight average molecular weight indicates a weight average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC). Examples of the column used for GPC measurement include “Shodex LF-804” manufactured by Showa Denko KK.

  From the viewpoint of easily forming the particle surface of the carbon modified particles for EWD with the surface forming material, the surface forming material is preferably soluble in a hydrophobic solvent described later.

  When forming the said surface part on the surface of the said carbon particle, and when surface-treating the said carbon particle, the usage-amount of the said surface forming material is not specifically limited. When the usage-amount of the said surface forming material is illustrated, the usage-amount of the said surface forming material with respect to 100 mass parts of said carbon particles becomes like this. Preferably it is 0.05 mass part or more, More preferably, it is 0.1 mass part or more, Furthermore Preferably it is 0.5 mass part or more, Preferably it is 500 mass part or less, More preferably, it is 100 mass part or less.

[Hydrophobic solvent]
The carbon modified particles for EWD are preferably obtained by disposing the surface portion on the surface of the carbon particles in a hydrophobic solvent. The carbon modified particles for EWD are preferably obtained by surface-treating the carbon particles in a hydrophobic solvent.

  The hydrophobic solvent is not compatible with water. Whether or not it is compatible with water can be determined by whether or not the hydrophobic solvent and water are separated when 100 mL of water and 100 mL of solvent are mixed at room temperature (23 ° C.). As for the said hydrophobic solvent, only 1 type may be used and 2 or more types may be used together.

  The SP value of the hydrophobic solvent is preferably 9 or less because it is incompatible with water. By using a hydrophobic solvent having high hydrophobicity, carbon modified particles for EWD that are more excellent in dispersibility can be obtained, and further, the dispersibility of the carbon modified particles in the ink is further enhanced.

  The SP value (solubility parameter) can be calculated using the Fedors method (R. F. Fedors, Polym. Eng. Sci., 14, 147 (1974)).

  Specific examples of the hydrophobic solvent include octane (SP value 7.5), nonane (SP value 7.5), decane (SP value 7.6), undecane (SP value 7.6), dodecane (SP value). 7.7), toluene (SP value 8.8), xylene (SP value 8.8) and the like. Hydrophobic solvents other than these may be used.

  When the surface portion is formed on the surface of the carbon particles and when the carbon particles are surface-treated, the amount of the carbon particles and the hydrophobic solvent used is not particularly limited. When the usage amount of the carbon particle and the hydrophobic solvent is exemplified, the usage amount of the carbon particle is preferably 0.05% by mass or more, more preferably in a total of 100% by mass of the carbon particle and the hydrophobic solvent. Is 0.5% by mass or more, preferably 10% by mass or less, more preferably 5% by mass or less.

[Other ingredients]
An acid / base adjuster and a surfactant may be used when the surface portion is formed on the surface of the carbon particles and when the carbon particles are surface-treated.

  Specific examples of the surfactant include sodium di (2-ethylhexyl) sulfosuccinate and alkylbenzene sulfonate.

[Method for producing carbon modified particles for EWD]
In the method for producing carbon modified particles for EWD according to the present invention, the surface of the carbon modified particles is disposed on the surface of the carbon modified particles by subjecting the carbon particle material to surface treatment. The surface is formed of a compound whose constituent atoms are only carbon atoms and hydrogen atoms, or the particle surface is a carbon atom, hydrogen atom, oxygen atom, nitrogen atom and sulfur in a total of 100% by mass of the constituent atoms. Carbon modified particles for EWD formed by a compound having a total amount of 95% by mass or more with atoms and a ratio of the mass of carbon atoms to the total mass of oxygen atoms, nitrogen atoms and sulfur atoms being 5 or more The process of obtaining.

  From the viewpoint of efficiently obtaining the carbon modified particles for EWD that are more excellent in dispersibility, it is preferable to obtain the carbon modified particles for EWD using the carbon particles and the hydrophobic solvent. It is more preferable to obtain carbon modified particles for EWD using a hydrophobic solvent and the surface forming material.

  When the carbon modified particles for EWD are formed, the surface forming material may be used. After preparing the core (carbon particles), the surface of the core may be coated with the surface forming material or the like in one or more stages. Coating methods include a coating method in which the surface forming material is adsorbed on the surface of the core, a graft reaction method in which the surface forming material is chemically bonded to the surface of the core, and a graft that polymerizes the monomer that forms the surface forming material from the core surface Examples thereof include a polymerization method.

(Ink for electrowetting)
The ink for EWD according to the present invention includes the above-described carbon modified particles for EWD and a hydrophobic solvent. As for the said hydrophobic solvent, only 1 type may be used and 2 or more types may be used together.

  The hydrophobic solvent that can be used in the EWD ink includes the above-described hydrophobic solvent that can be used when the surface portion is formed on the surface of the carbon particles and when the carbon particles are surface-treated. Similar solvents are mentioned. After obtaining the EWD carbon-modified particles using the hydrophobic solvent, the EWD carbon-modified particles are taken out from the hydrophobic solvent, and the EWD carbon-modified particles are dispersed in the hydrophobic solvent. Thus, it is preferable to obtain the EWD ink.

  In order to further enhance the dispersibility of the carbon modified particles for EWD, the EWD ink may contain a surfactant. However, from the viewpoint of further improving the EWD drive response of the EWD ink, the smaller the content of the surfactant, the better. Therefore, it is preferable that the EWD ink does not contain or contain a surfactant, and the content of the surfactant in 100% by mass of the ink is 5% by mass or less.

  As the surfactant that can be used in the EWD ink, the above-described surfactant that can be used when the surface portion is formed on the surface of the carbon particles and when the carbon particles are surface-treated, In addition, the same surfactants as those described above that can be used when the polymerizable compound is polymerized are exemplified.

  In 100% by mass of the ink, the content of the carbon modified particles for EWD is preferably 5% by mass or more, more preferably 10% by mass or more, preferably 50% by mass or less, more preferably 30% by mass or less. . When the content of the carbon modified particles for EWD is not less than the above lower limit and not more than the above upper limit, the concealability by the carbon modified particles is further enhanced, and the fluidity of the carbon modified particles in the ink is further enhanced. Therefore, the display quality of EWD is further enhanced.

  The content of the hydrophobic solvent in 100% by mass of the ink is preferably 50% by mass or more, more preferably 70% by mass or more, preferably 95% by mass or less, and more preferably 90% by mass or less. When the content of the hydrophobic solvent is not less than the above lower limit and not more than the above upper limit, the concealability by the carbon modified particles is further increased, and the fluidity of the carbon modified particles in the ink is further enhanced. The display quality of EWD becomes even higher.

  If necessary, an antioxidant, an ultraviolet light inhibitor, an organic dispersant, a surfactant, and the like may be added to the EWD ink.

(Electrowetting display)
An EWD according to the present invention includes a first and second substrates facing each other, a first liquid disposed on the first substrate side between the first and second substrates, and the first and second substrates. EWD ink (second liquid) disposed between the second substrates on the second substrate side. In the EWD according to the present invention, the EWD ink includes the above-described carbon modified particles for EWD and a hydrophobic solvent.

  FIG. 2 is a cross-sectional view schematically showing EWD using carbon modified particles for EWD according to an embodiment of the present invention. FIG. 3 is a schematic cross-sectional view for explaining the operation concept of the EWD. In FIG. 3, the illustration of the configuration of the portion unnecessary for description is simplified.

  The EWD 1 shown in FIG. 2 includes a first substrate 11 and a second substrate 12. The first and second substrates 11 and 12 are disposed so as to face each other with the first liquid 13 interposed therebetween. The first liquid 13 is disposed in a region (cell) partitioned by a sealing material 17 provided along the outer peripheries of the first and second substrates 11 and 12.

  A first liquid 13 is disposed between the first and second substrates 11 and 12 on the first substrate 11 side. Between the first and second substrates 11 and 12, the EWD ink 14 is disposed on the second substrate 12 side.

  The first liquid 13 is a hydrophilic liquid. The first liquid 13 is more hydrophilic than the EWD ink 14. The first liquid 13 is a high surface energy liquid. The high surface energy liquid is a liquid having a relatively high surface energy relative to the EWD ink 14. The EWD ink 14 is more hydrophobic than the first liquid 13. The EWD ink 14 is a low surface energy liquid. The low surface energy liquid is a liquid having a relatively low surface energy relative to the first liquid 13.

  It is preferable that SP value of the 1st liquid 13 and the said hydrophilic liquid is 14 or more. The SP value of the hydrophobic solvent contained in the EWD ink 14 is preferably 9 or less.

  The first substrate 11 includes a base material 11A and a common electrode 11B. The second substrate 12 includes a base material 12A, a TFT 12B, a wiring portion 12C, a planarizing film 12D, a pixel electrode 12E, a common electrode 12F, and an insulating film 12G.

  As base material 11A and base material 12A, the base material normally used as a panel board | substrate of display materials, such as glass, a resin molding, and a film, is used, for example.

  The common electrode 11B is preferably a transparent electrode. As a material constituting the common electrode 11B, for example, ITO (tin-doped indium oxide) is used.

  In the second substrate 12, the surface of the insulating film 12G constituting the inner surface on the cell side is subjected to water repellency by a known method such as application of a fluororesin and heat treatment.

  A pixel wall 15 is formed on the insulating film 12G. The pixel wall 15 is formed in a lattice shape and partitions a plurality of pixels G on the second substrate 12. One pixel G corresponds to one electrowetting (EW) element 16A, 16B, 16C.

  The pixel electrode 12E and the common electrode 12F are formed on the planarizing film 12D, and are connected to the TFT 12B and the wiring part 12C through the contact hole 12Da. Further, a pair of the pixel electrode 12E and the common electrode 12F are arranged in each pixel G. In the area partitioned by the pixel wall 15, the EWD ink 14 is stored. The pixel wall 15 has a surface that is compatible with the first liquid 13.

  ITO, Al, etc. are used as an electrode material which comprises the pixel electrode 12E and the common electrode 12F. When ITO is used as the electrode material, the EWD 1 becomes a transmissive display including a light source (not shown) on the back side of the second substrate 12. When Al is used as the electrode material, the EWD 1 is a reflective display that reflects external light on the electrode surface.

  In such an EWD1, as shown in FIG. 3, when a predetermined voltage EV (for example, 30V) is applied to the pixel electrode 12E, the pixel electrode 12E and the first liquid 13 are used as electrodes, and the insulating film 12G is used as a dielectric. A capacitor is formed. As a result, the high surface energy group of the first liquid 13 is attracted by electrostatic action due to the polarization of the insulating film 12G. As a result, the EWD ink 14 on the pixel electrode 12E is pushed onto the common electrode 12F, and the shape changes.

  By applying the voltage in this way, the EWD ink 14 in the pixel G can be selectively moved onto the common electrode 12F.

  Note that the EWD shown in FIG. 2 is merely an example, and the structure of the EWD and the like can be modified as appropriate.

  Hereinafter, the present invention will be specifically described by giving examples and comparative examples. The present invention is not limited to the following examples.

Example 1
Carbon particles (“Denka Black” manufactured by Denki Kagaku Kogyo Co., Ltd., average particle size 35 nm) were prepared.

  5 parts by mass of carbon black was added to a solution obtained by dissolving 5 parts by mass of polystyrene / polyisoprene copolymer (surface forming material) in 200 parts by mass of toluene, and the mixture was treated using an ultrasonic homogenizer. In the course of the treatment, 200 parts by mass of undecane was gradually added to perform further treatment. After the treatment, toluene is removed by removing under reduced pressure, and ultrasonic treatment is performed. Then, the solution is allowed to stand for one day, and the supernatant liquid is collected, and further, centrifuged and washed with undecane to obtain the surface. A surface portion (shell) derived from the forming material was formed to obtain carbon modified particles for EWD (average particle size 210 nm).

  2 parts by mass of the obtained carbon modified particles for EWD were dispersed in 18 parts by mass of undecane to obtain an EWD ink.

  The polystyrene / polyisoprene copolymer (manufactured by Nippon Zeon Co., Ltd.) used in Example 1 has a weight average molecular weight of 160,000.

(Example 2)
EWD carbon modified particles (average particle diameter 150 nm) and EWD ink were obtained in the same manner as in Example 1 except that the type of the surface forming material was changed as shown in Table 1 below.

  In addition, the weight average molecular weight of the polydodecyl methacrylate (in-house synthetic product) used in Example 2 is 50,000.

(Comparative Example 1)
The carbon particles prepared in Example 1 were used as they were as EWD carbon particles without modification. 2 parts by mass of the EWD carbon particles were added to 18 parts by mass of undecane, which is a hydrophobic solvent, and stirred to obtain an EWD ink.

(Comparative Example 2)
EWD carbon modified particles and EWD ink were obtained in the same manner as in Example 1 except that the type of the surface forming material was changed as shown in Table 1 below.

  The molecular weight of polymethyl methacrylate (manufactured by Sigma-Aldrich) used in Comparative Example 2 is 15,000.

(Evaluation)
(1) Atomic structure of compound on particle surface The atomic structure on the particle surface of the obtained carbon modified particles for EWD was measured by the following method.

[Elemental analysis of carbon, hydrogen, nitrogen, oxygen, and sulfur atoms]
The obtained carbon particles for EWD were dried in a vacuum oven for 24 hours. Thereafter, each atom was quantified using a microcoder JM10 manufactured by J Science Lab.

  Also, the mass of carbon atoms (content (C)), the mass of oxygen atoms (content (O)), the mass of nitrogen atoms (content (N)), and the mass of sulfur atoms (content (S)). The ratio of the total to the total mass is calculated by the following formula.

  Ratio = content (C) / (content (O) + content (N) + content (S))

  The atomic composition of the compound on the particle surface was determined according to the following criteria.

[Criteria for atomic composition of compounds on particle surface]
A: The particle surface is formed of a first compound whose constituent atoms are only carbon atoms and hydrogen atoms. B: The particle surface is a carbon atom, hydrogen atom, and oxygen atom in a total of 100 mass% of the constituent atoms. And a ratio of the mass of carbon atoms to the total mass of oxygen atoms, nitrogen atoms, and sulfur atoms is 5 or more. Yes: Does not correspond to both A and B criteria

(2) Dispersibility 1
The EWD ink immediately after preparation was placed in a tubular container having an inner diameter of 1 cm so as to have a height of 10 cm and left for 24 hours. The left EWD ink was observed, and dispersibility 1 was determined according to the following criteria.

[Criteria for dispersibility 1]
○: No transparent supernatant is generated. ×: Carbon modified particles for EWD or carbon particles for EWD are settled, and a transparent supernatant is generated.

(3) Dispersibility 2
Immediately after preparation, 5 g of EWD ink and 5 g of water were placed in a 20 mL sample bottle, stirred, and then allowed to stand. The left EWD ink was observed, and dispersibility 2 was determined according to the following criteria.

[Criteria for dispersibility 2]
○○: EWD carbon modified particles or EWD carbon particles are not agglomerated at the interface between the hydrophobic solvent and water even after 72 hours. ○: Hydrophobic solvent and water even after 24 hours. Although the EWD carbon modified particles or EWD carbon particles are not aggregated at the interface, the EWD carbon modified particles or EWD carbon particles at the interface between the hydrophobic solvent and water are left to stand for 72 hours. Aggregated ×: EWD carbon modified particles or EWD carbon particles are agglomerated at the interface between the hydrophobic solvent and water when left for 24 hours.

  The results are shown in Table 1 below. The carbon modified particles for EWD obtained in Examples 1 and 2 were core-shell particles having a shell derived from the surface forming material in the entire region of the particle surface. The specific gravity of the carbon modified particles for EWD obtained in Examples 1 and 2 was 2 or less. The average aspect ratio of the carbon modified particles for EWD obtained in Examples 1 and 2 was 1.5 or less.

  In the carbon modified particles of Examples 1 and 2, since the surface portion is formed of a specific resin on the surface of the carbon particles, the conductivity is lower than in the case of the carbon particles alone.

  The first liquid (hydrophilic liquid, high surface energy liquid) and each of the EWD inks obtained in Examples 1 and 2 and Comparative Example 1 are disposed between the first and second substrates. The EWD shown in FIG. 2 was obtained. It was confirmed that the EWD using each of the EWD inks obtained in Examples 1 and 2 provided sufficient concealment and a good display image during driving. On the other hand, the EWD ink obtained in Comparative Example 1 did not provide a good display image during driving because of the high conductivity of the carbon particles.

  Further, in the carbon modified particles of Examples 1 and 2, since the surface portion is formed by a specific resin on the surface of the carbon particles, the dispersibility in a hydrophobic solvent is higher than that in the case of the carbon particles alone. Becomes higher. On the other hand, in Comparative Examples 1 and 2, since the surface portion is not formed of a specific resin, the dispersibility in the hydrophobic solvent is low. For this reason, a good display image could not be obtained during EWD driving.

1. Electrowetting display (EWD)
DESCRIPTION OF SYMBOLS 11 ... 1st board | substrate 12 ... 2nd board | substrate 13 ... 1st liquid 14 ... Ink for electrowetting display (EWD) 15 ... Pixel wall 16A, 16B, 16C ... Electrowetting (EW) element 17 ... Sealing material 21 ... Carbon modified particles for electrowetting display (EWD) 22 ... Carbon particles 23 ... Surface

Claims (7)

Carbon particles and a surface portion disposed on the surface of the carbon particles and constituting the particle surface;
The particle surface is formed by a compound whose constituent atoms are only carbon atoms and hydrogen atoms, or
The particle surface has a total of 95 mass% or more of carbon atoms, hydrogen atoms, oxygen atoms, nitrogen atoms, and sulfur atoms in a total of 100 mass% of the constituent atoms, and oxygen atoms and nitrogen atoms having a mass of carbon atoms, Carbon modified particles for electrowetting displays, which are formed of a compound having a ratio with respect to the total mass of sulfur atoms of 5 or more.   By surface-treating the carbon particles, the particle surface is formed of a compound whose constituent atoms are only carbon atoms and hydrogen atoms, or the particle surface is a carbon atom in a total of 100 mass% of the constituent atoms. And the sum of the hydrogen atom, oxygen atom, nitrogen atom and sulfur atom is 95% by mass or more, and the ratio of the mass of carbon atom to the total mass of oxygen atom, nitrogen atom and sulfur atom is 5 or more The carbon modified particles for an electrowetting display according to claim 1, which are obtained by disposing a surface portion constituting the particle surface on the surface of the carbon particles so as to be formed by the method.   The ink for electrowetting displays containing the carbon modified particle for electrowetting displays of Claim 1 or 2, and a hydrophobic solvent. Opposing first and second substrates;
A first liquid disposed on the first substrate side between the first and second substrates;
An electrowetting display ink disposed on the second substrate side between the first and second substrates;
An electrowetting display, wherein the ink for electrowetting display comprises the carbon modified particles for electrowetting display according to claim 1 or 2 and a hydrophobic solvent. By surface treating the carbon particles, the surface portion constituting the particle surface is arranged on the surface of the carbon particles,
The particle surface is formed of a compound whose constituent atoms are only carbon atoms and hydrogen atoms, or the particle surface is composed of carbon atoms, hydrogen atoms, oxygen atoms and nitrogen atoms in a total of 100% by mass of the constituent atoms. For an electrowetting display formed of a compound having a total amount of 95% by mass or more with sulfur atoms and a ratio of the mass of carbon atoms to the total mass of oxygen atoms, nitrogen atoms and sulfur atoms being 5 or more The manufacturing method of the carbon modified particle for electrowetting displays provided with the process of obtaining carbon modified particle.   The ink for electrowetting displays containing the carbon modified particle for electrowetting displays obtained by the manufacturing method of the carbon modified particles for electrowetting displays of Claim 5, and a hydrophobic solvent. Opposing first and second substrates;
A first liquid disposed on the first substrate side between the first and second substrates;
An electrowetting display ink disposed on the second substrate side between the first and second substrates;
An electrowetting display ink comprising the electrowetting display carbon modified particles obtained by the method for producing electrowetting display carbon modified particles according to claim 5 and a hydrophobic solvent. Display.

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