WO2014017177A1

WO2014017177A1 - Carbon ink, method for producing carbon ink, and electrophoretic display device

Info

Publication number: WO2014017177A1
Application number: PCT/JP2013/065470
Authority: WO
Inventors: 修二藤田; 俊山ノ井
Original assignee: ソニー株式会社
Priority date: 2012-07-24
Filing date: 2013-06-04
Publication date: 2014-01-30

Abstract

A carbon ink contains carbon particles (11) to which a positively or negatively charged aromatic compound (13) is bonded. The carbon particles (11) may be microporous carbon particles having micropores on the surface. A polyvalently ionizable compound is further bonded to the aromatic compound (13) as needed. Either a polyaromatic compound or a substance that bonds to carbon by π bonds is used as the aromatic compound. At least one type selected from the group consisting of carbon black, natural graphite, graphite, glassy carbon, carbon nanotubes, highly-ordered pyrolytic graphite (HOPG), plastic formed carbon, activated carbon, and porous carbon is used as the carbon particles (11).

Description

Carbon ink, carbon ink manufacturing method, and electrophoretic display device

The present disclosure relates to carbon ink, a carbon ink manufacturing method, and an electrophoretic display device, and is suitable for application to, for example, electronic paper.

An electrophoretic display device used for electronic paper or the like uses a carbon ink in which charged carbon particles are dispersed in a dispersion medium to apply a voltage between a pair of electrodes to apply an electric field to the charged carbon particles. The image is displayed by being attracted to the electrode side by electrophoresis.

Conventionally, as a method of charging carbon particles, a method of heating the carbon particles to 60 ° C. or higher, or treating the carbon particles with a strong acid or a strong alkali substance is known.

It is known that chemical treatment or molecular modification is performed as a surface modification treatment of fine particles for image display made of a porous carbon material dispersed in an electrophoretic dispersion liquid sealed between two opposing substrates. (See Patent Document 1). Molecular modification can increase the positive charge retention of image display fine particles by modifying with positively charged molecules such as amino groups, and negative charges such as hydroxyl groups, carboxy groups, ketone groups, and ester groups. It is described that the negative charge retention amount of the fine particles for image display can be increased by modifying the molecule with a molecule having a.

JP 2012-22295 A JP 2008-273816 A

However, it is difficult to charge the carbon particles of the carbon ink for the conventional electrophoretic display device with high density. In addition, the conventional carbon particle charging method requires heating at a temperature of 60 ° C or higher, and it is necessary to frequently use harmful organic solvents in addition to dangerous strong acids and strong alkaline substances. There were difficulties in that it had to be. Further, the time required for producing the charged carbon particles is 5 hours or more, generally 10 hours or more in the early case. Furthermore, when carbon ink is actually used in an electrophoretic display device, it is necessary to use about 3% of a dispersant in order to highly disperse carbon particles in a dispersion medium. In this case, problems such as current leakage occur due to the addition of the dispersant, but it is difficult to reduce the amount of the dispersant used from the viewpoint of maintaining the dispersibility.

Therefore, the problem to be solved by the present disclosure is a carbon ink in which carbon particles holding a sufficiently high-density electric charge are dispersed with high dispersibility, and the amount of dispersant used can be greatly reduced, and the production thereof Is to provide a method.

Another problem to be solved by the present disclosure is to provide a high-performance electrophoretic display device using the above-described excellent carbon ink as an electrophoretic dispersion.

The above and other problems will become apparent from the following description of the present specification with reference to the accompanying drawings.

In order to solve the above problems, the present disclosure provides:
This is a carbon ink containing carbon particles to which a positively or negatively charged aromatic compound is bonded.

In addition, this disclosure
This is a method for producing a carbon ink having a step of mixing and stirring carbon particles to which a positively or negatively charged aromatic compound is bonded and a dispersion medium.

Here, the method for producing the carbon ink further includes a step of binding a compound that is polyvalently ionized to an aromatic compound as necessary.

In addition, this disclosure
An electrophoretic display device having a carbon ink containing carbon particles to which a positively or negatively charged aromatic compound is bonded.

In the present disclosure, the bonding (or adsorption) of the aromatic compound to the carbon particles can be easily performed via a functional group or a reactive group of the aromatic compound. In order to bond the aromatic compound to the carbon particles, it is preferable that the aromatic portion of the aromatic compound is planar and that the aromatic portion has a larger number of π electrons. From this viewpoint, the aromatic compound is preferably, for example, a polycyclic aromatic compound or a substance that is bonded to carbon by a π bond. If necessary, a compound to be multivalently ionized is bound to the aromatic compound. Bonding of a compound that is polyvalently ionized to an aromatic compound can be easily performed via a functional group or a reactive group of the aromatic compound. In this way, by binding the compound that is polyvalently ionized to the aromatic compound, it is possible to hold the carbon particles with a high density of charges. The carbon particles may be porous carbon particles having pores on the surface.

Examples of the polycyclic aromatic compound are as follows, and at least one selected from the group consisting of these compounds is used.
・ Pyrene derivatives ・ Coronene derivatives ・ Chrysene derivatives ・ Naphtacene derivatives ・ Pentacene derivatives ・ Picene derivatives ・ Perylene derivatives ・ Anthracene derivatives ・ Phenanthrenes (Phenanthrene) derivatives, Fluorene derivatives, Naphtalene derivatives, Fluoranthene derivatives, Acenaphthene derivatives, Acenaphthylene derivatives, Triphenylene derivatives

Substances that bind to carbon by a π bond are as follows, and at least one selected from the group consisting of these compounds is used.
・ Terthiophene derivative ・ Tetraphenylbenzidine derivative ・ Tetraphenylnaphtacene derivative ・ Benzothiophene derivative ・ Thiophene derivative ・ Pyrrole derivative ・ Carbazole derivative ・Phenanthroline derivatives, phenylpyridine derivatives, quinoline derivatives, triphenylamine derivatives, diphenylamine derivatives, oxazole derivatives, oxadiazole derivatives, p-phenyl (P-Phenyl) Derivatives, Quinacridone Derivatives, Flucrenone Derivatives, Phthalocyanine Derivatives, Spiropyran Derivatives, Viologen Derivatives, Sulfur Pyroperimidine derivative / Phenyl Esters
・ Benzoic Acids
・ Biphenyl derivatives ・ Benzophenone derivatives ・ Diphenylamine derivatives ・ Diphenyl Ethers
・ Diphenyl Sulfides
・ Diphenyl Sulfones
・ Bisphenol derivatives ・ Anthraquinone derivatives ・ Phosphonium compounds ・ Fluorescein derivatives ・ Rhodamine derivatives ・ Coumarin derivatives ・ Cyanine derivatives

In addition, as the positively or negatively charged compound to be bonded to the porous carbon particles, the following can be used. Nucleoside, nucleotide, ribose, sugar, amino acid, lipid, sterol, terpene, steroid, propanoid, arkanoid, alcohol, amine, aminoalcohol, isocyanate, amide, ester, diol, glycidyl compound, hydrazine, silane, polyketide, polyamine Compounds containing cyclic organic compounds such as porphyrins, vitamins, crown ethers, cyclodextrins, diacrylates, dimethacrylates, tetracarboxylic acids, pyrrolidines, alkanols, carboxylic acids, azulene, quaternary ammoniums, fluorocarbons, aryls and cycloalkanes is there.

Among the aromatic compounds, pyrene derivatives are preferable. Pyrene derivatives include, for example, amine groups, sulfone groups, sulfhydryl groups, carboxy groups, hydroxyl groups, azido groups, azo groups, nitro groups, nitrile groups, cyano groups, allene groups, isonitrile groups, urea groups, aldehyde groups, ketone groups, It has functional groups and reactive groups such as NHS ester, imide ester, maleimide, pyridyldithiol, allyl azide, haloacetate, isocyanate, carbodiimide, allyl azide, diazirine, hydrazide, psoralen, iodo, pyridine disulfide, vinyl sulfone. Further, an alkyl group, polyethylene glycol or the like may be separated as a spacer between the functional group and the reactive group and pyrene. In addition, these functional groups, reactive groups, spacers, and the like may be bonded to carbon at any position of pyrene. The pyrene derivative can be covalently bonded to the compound to be multivalently ionized via its functional group or reactive group.

The carbon particles are, for example, at least one selected from the group consisting of carbon black, natural graphite, graphite, glassy carbon, carbon nanotubes, highly oriented pyrolytic graphite (HOPG), plastic formed carbon, activated carbon, and porous carbon. Although there is, it is not limited to this. The porous carbon particles are at least one selected from the group consisting of activated carbon, porous carbon, aggregated particles of the above-mentioned various carbons, carbon black, and biocarbon, but are not limited thereto. The size of these carbon particles or porous carbon particles is not particularly limited, and is selected as necessary. Carbon black includes furnace black, acetylene black, channel black, thermal black, ketjen black and the like. Examples of the activated carbon include wood charcoal such as oak charcoal, kunugi charcoal, cedar charcoal, oak charcoal, hinoki charcoal, rubber charcoal, bamboo charcoal, oga charcoal, and coconut shell charcoal. Biocarbon is made from a plant-derived material with a silicon (silicon) content of 5% by weight or more. The specific surface area by nitrogen BET method is 10 m ² / g or more, and the silicon content is 1% by weight or less. , A porous carbon material having a pore volume of 0.1 cm ³ / g or more by the BJH method and the MP method (see Patent Document 2). Specifically, biocarbon is produced as follows, for example. That is, first, the crushed rice husk (produced in Kagoshima Prefecture, Isehikari rice husk) was carbonized by heating in a nitrogen stream at 500 ° C. for 5 hours to obtain a carbide. Thereafter, 10 g of this carbide was placed in an alumina crucible and heated to 1000 ° C. at a rate of 5 ° C./min in a nitrogen stream (10 liters / min). And after carbonizing at 1000 degreeC for 5 hours and converting into a carbonaceous substance (porous carbon material precursor), it cooled to room temperature. In addition, nitrogen gas was kept flowing during carbonization and cooling. Next, this porous carbon material precursor was subjected to an acid treatment by immersing it overnight in a 46% by volume hydrofluoric acid aqueous solution, and then washed with water and ethyl alcohol until the pH reached 7. And the porous carbon material, ie, biocarbon, is obtained by making it dry at the end. The pore activation treatment of the porous carbon particles may be gas activation such as water vapor or chemical activation with zinc chloride or the like.

The compound to be polyvalently ionized is, for example, at least one selected from the group consisting of polyphosphoric acid and peptides such as polyamine, polycarboxylic acid, polysulfonic acid, polyaniline, polypyrrole, DNA and RNA, but is not limited thereto. It is not a thing. These compounds may be linear or cyclic. Examples of the polyamine include hexaazacyclooctadecane, spermine, spermidine, polylysine, polyarginine, and polyethyleneimine. The polycarboxylic acid includes polyacrylic acid. These compounds may be enantiomers or racemates. The amide bond site of poly-L-lysine may be α-position or ε-position, but ε-position is more preferable. Polyethyleneimine may be branched or linear.

The use of the carbon ink according to the present disclosure is not particularly limited, but is preferably an ink for electrophoretic display devices (electrophoretic dispersion liquid). The electrophoretic display device is typically electronic paper.

This electrophoretic display device can be used for various devices using the display device, for example, electronic devices, mobile objects (automobiles, motorcycles, aircraft, rockets, spacecrafts, etc.), power devices, construction machines, machine tools, etc. it can.

Electronic devices may be basically any type, and include both portable and stationary devices. Specific examples include mobile phones, mobile devices (portable information terminals). (PDA, etc.), robots, personal computers (including both desktop and notebook computers), game machines, camera-integrated VTRs (video tape recorders), in-vehicle devices, home appliances, industrial products, and the like.

As described above, in the present disclosure, a positive charge or a negatively charged aromatic compound is bonded to the carbon particle, or further, a compound that is polyvalently ionized is bonded to the aromatic compound, whereby a high-density charge is obtained. Retained carbon particles can be obtained. The carbon particles can be produced under mild conditions such as neutral room temperature conditions. Further, the dispersibility of the carbon particles in the carbon ink is very good.

According to the present disclosure, it is possible to obtain a carbon ink in which carbon particles having a sufficiently high density of charge are dispersed with high dispersibility, and the amount of dispersant used can be significantly reduced. By using this excellent carbon ink as an electrophoretic dispersion liquid, the carbon particles as image display fine particles are charged with high density and in addition, the dispersibility is extremely good, so that display can be performed at high speed. A high-performance electrophoretic display device that can be performed and can reduce power consumption by reducing a voltage necessary for display can be realized.

It is a basic diagram which shows the carbon ink by 1st Embodiment. It is a basic diagram which shows the charged carbon particle which comprises the carbon ink by 1st Embodiment. It is a basic diagram which shows typically the example which the positively charged pyrene derivative couple | bonded with the carbon particle which comprises the carbon ink by 1st Embodiment. It is a basic diagram which shows a mode that the compound which carries out polyvalent ionization couple | bonded with the carbon particle which comprises the carbon ink by 1st Embodiment. It is a basic diagram which shows the electrophoretic display device by 2nd Embodiment. It is an approximate line figure for explaining operation of an electrophoretic display device by a 2nd embodiment. It is an approximate line figure for explaining operation of an electrophoretic display device by a 2nd embodiment. It is a basic diagram which shows the evaluation result of the dispersibility of the carbon ink of Example 1, and the carbon ink of the comparative example 2. FIG. It is a basic diagram which shows the evaluation result of the dispersibility of the carbon ink of Example 2, and the carbon ink of the comparative example 2. FIG. It is a basic diagram which shows the evaluation result of the dispersibility of the carbon ink of Example 3, and the carbon ink of the comparative example 3. FIG. It is a basic diagram which shows the evaluation result of the dispersibility of the carbon ink of Example 4, and the carbon ink of the comparative example 3.

Hereinafter, modes for carrying out the invention (hereinafter referred to as “embodiments”) will be described. The description will be given in the following order.
1. First embodiment (carbon ink and manufacturing method thereof)
2. Second embodiment (electrophoretic display device)

<1. First Embodiment>
[Carbon ink]
FIG. 1 shows a carbon ink according to the first embodiment. As shown in FIG. 1, in this carbon ink, carbon particles 11 to which a positively or negatively charged aromatic compound is bonded are dispersed in a dispersion medium 12. In FIG. 1, the case where the aromatic compound couple | bonded with the carbon particle 11 is positively charged is shown. The aromatic compound is selected as necessary from among the aromatic compounds already described. In addition, the carbon particles are selected, for example, from the already described carbon particles as necessary. The content of each component in the carbon ink and the type of the dispersion medium are appropriately selected according to the use of the carbon ink.

FIG. 2 shows, as an example, carbon particles 11 to which a positively or negatively charged aromatic compound 13 is bonded. Here, the carbon particles 11 and the aromatic compound 13 are bonded by a π-π bond. Alternatively, when the carbon particles 11 are porous carbon particles, the aromatic compound 13 enters the pores of the carbon particles 11 and is adsorbed on the surface of the carbon particles 11.

FIG. 3 shows a case where the aromatic compound 13 is a positively charged pyrene derivative.

As shown in FIG. 4, a compound 15 to be polyionized may be bonded to the aromatic compound 13 bonded to the carbon particles 11. The compound 15 to be polyvalently ionized is selected from among the compounds already described. Specific examples of the compound 15 to be polyvalent ionized are as follows.

[Ε-poly-L-lysine]

[Polyethyleneimine (branch type)]

As the compound 15, α-poly-L-lysine may be used instead of ε-poly-L-lysine.

The case where the carbon ink is an electrophoretic display ink, that is, an electrophoretic dispersion will be described. In this case, the carbon particles 11 are fine particles for image display. The ratio of the fine particles for image display to the dispersion medium in the electrophoretic dispersion is, for example, 0.1 parts by mass or more and 15 parts by mass or less, preferably 1 part by mass or more with respect to 100 parts by mass of the dispersion medium. It is 10 parts by mass or less. As the dispersion medium for dispersing the image display fine particles, a colorless and transparent liquid having high insulation properties is preferably used. Specific examples of the dispersion medium include nonpolar dispersion media, and more specifically, aliphatic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, and silicone oils. Examples of the aliphatic hydrocarbon include pentane, hexane, cyclohexane, heptane, octane, nonane, decane, dodecane, ligroin, solvent naphtha, kerosene, normal paraffin, and isoparaffin. In addition, examples of the aromatic hydrocarbon include benzene, toluene, xylene, and alkylbenzene. Examples of the silicone oil include various dimethylpolysiloxanes containing modified silicone oil. More specifically, Isopar G, H, L, M, Exol D30, D40, D80, D110, D130 manufactured by ExxonMobil Co., Ltd., IP Solvents 1620, 2028, 2835 manufactured by Idemitsu Petrochemical Co., Ltd., Shell Chemicals Japan Examples thereof include Shellsol 70, 71, 72, A, AB, and Naphthesol L, M, H, manufactured by Nippon Oil Corporation. In addition, these may be used independently and 2 or more types may be mixed and used. An oil-soluble dye may be used to color the dispersion medium. Specifically, for example, a yellow dye comprising an azo compound, an orange dye, a brown dye, a red dye, or a blue dye comprising anthraquinones. And green dyes and purple dyes. These dyes may be used alone or in combination of two or more. The concentration of the dye is preferably 0.1 parts by mass or more and 3.5 parts by mass or less with respect to 100 parts by mass of the dispersion medium, but is not limited thereto.

If necessary, a positive charge control agent may be used in combination to positively charge the fine particles for image display. Examples of the positive charge control agent include nigrosine-based dyes such as nigrosine base EX (manufactured by Orient Chemical Co., Ltd.), P-51 (manufactured by Orient Chemical Co., Ltd.), copy charge PX VP435 (manufactured by Hoechst Japan Co., Ltd.) and the like. Examples thereof include quaternary ammonium salts, alkoxylated amines, alkylamides, molybdate chelate pigments, imidazole compounds such as PLZ1001 (eg, Shikoku Kasei Kogyo Co., Ltd.), and transparent or white onium compounds. The onium compound can be freely selected from primary to quaternary, and is selected from an ammonium compound, a sulfonium compound, and a phosphonium compound, for example, a substituent bonded to a nitrogen, sulfur, or phosphorus atom. Is an alkyl group or an aryl group, and as a salt, a halogen element typified by chlorine, a hydroxy group, a carboxylic acid group or the like is suitable as a counter ion, but is not limited thereto. Of these, primary to tertiary amine salts and quaternary ammonium salts are particularly preferable. If necessary, a negative charge control agent may be used to negatively charge the fine particles for image display. Examples of the negative charge control agent include Bontron S-22, Bontron S-34, Bontron E-81, Bontron E-84 (above, manufactured by Orient Chemical Co., Ltd.), Spiron Black TRH (Hodogaya Chemical Co., Ltd.). Metal complexes such as thioindigo pigments, quaternary ammonium salts such as copy charge NXVP434 (manufactured by Hoechst Japan Ltd.), calixarene compounds such as Bontron E-89 (manufactured by Orient Chemical Industries Ltd.), LR147 (Japan) Borit compounds such as Carlit Co., Ltd.), fluorine compounds such as magnesium fluoride and carbon fluoride, aluminum stearate, calcium stearate, aluminum laurate, barium laurate, sodium oleate, zirconium octylate, cobalt naphthenate Any or known metal soap, it may be mentioned salicylic acid metal complexes and phenolic condensates of azine compounds.

Examples of the dispersant added to the electrophoretic dispersion include sorbitan fatty acid esters (for example, sorbitan monooleate, sorbitan monolaurate, sorbitan sesquioleate, sorbitan trioleate), polyoxyethylene sorbitan fatty acid esters (for example, Polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, etc.), polyethylene glycol fatty acid esters (eg, polyoxyethylene monostearate, polyethylene glycol diisostearate, etc.), polyoxyethylene alkyl phenyl ethers (eg, Polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, etc.), nonionic surface actives such as aliphatic diethanolamides Agent can be used. Examples of the polymer dispersant include styrene-maleic acid resin, styrene-acrylic resin, rosin, urethane polymer compound BYK-160, 162, 164, 182 (manufactured by BYK Chemie), urethane dispersant EFKA-47. LP-4050 (manufactured by EFKA), polyester polymer compound Solsperse 24000 (manufactured by Geneca Corporation), aliphatic diethanolamide polymer compound Solsperse 17000 (manufactured by Geneca Corporation), and the like. In addition, as other polymeric dispersants, monomers such as lauryl methacrylate, stearyl methacrylate, 2-ethylhexyl methacrylate, cetyl methacrylate and the like that can form a solvated part in the dispersion medium, a part that is difficult to solvate in the dispersion medium Random copolymer of monomers such as methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, styrene, vinyltoluene and the like and monomers having a polar functional group, which are capable of forming styrene, grafts disclosed in JP-A-3-188469 A copolymer etc. can be mentioned. Examples of monomers having polar functional groups include monomers having acidic functional groups such as acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid, styrene sulfonic acid, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, and vinylpyridine. Monomers having basic functional groups such as vinylpyrrolidine, vinylpiperidine, vinyllactam, salts thereof, styrene-butadiene copolymers, styrene and long chain disclosed in JP-A-60-10263 Examples thereof include block copolymers of alkyl methacrylate. Further, a dispersant such as a graft copolymer disclosed in JP-A-3-188469 may be added. The addition amount of the dispersant may be 0.01 to 5 parts by mass with respect to 100 parts by mass of the image display fine particles, but usually 2 parts by mass or less, that is, 2% or less is sufficient. An ionic surfactant may be added to the electrophoretic dispersion in order to more effectively cause electrophoresis of the image display fine particles. Specific examples of the anionic surfactant include sodium dodecylbenzenesulfonate, sodium dodecylsulfate, sodium alkylnaphthalenesulfonate, sodium dialkylsulfosuccinate and the like. Specific examples of the cationic surfactant include alkylbenzene dimethyl ammonium chloride, alkyl trimethyl ammonium chloride, distearyl ammonium chloride and the like. An ionic additive that is soluble in a nonpolar dispersion medium, such as a trifluorosulfonylimide salt, trifluoroacetate salt, trifluorosulfate salt, or the like, may be added. The addition amount of the ionic additive is, for example, from 1 part by mass to 10 parts by mass with respect to 100 parts by mass of the image display fine particles.

[Method for producing carbon ink]
This carbon ink can be manufactured as follows. First, the carbon particles 11 and the aromatic compound 13 are mixed with a solvent and stirred. As the solvent, for example, water, an organic solvent, a mixed solvent of water and an organic solvent, or the like can be used. Next, the carbon particles 11 are recovered from the solution by centrifugation or filtration. Next, the collected carbon particles 11 are washed. In the case where a compound 15 that is polyvalently ionized, that is, a highly charged compound, is bonded to the aromatic compound 13, the aromatic compound 13 is bonded to the carbon particles 11, and then the aromatic compound 13 is mixed with the aromatic compound 13 by a similar method. The compound 15 to be ionized is bound. Alternatively, a compound in which a polyvalent ionized compound 15 is bonded to the aromatic compound 13 may be formed, and the aromatic compound 13 may be bonded to the carbon particles 11. When the compound 15 to be polyvalent ionized is bonded to the aromatic compound 13, a coupling reaction such as an amide bond or a thioether bond can be used. These methods can be easily carried out under mild conditions under neutral room temperature conditions. In this way, the carbon particles 11 bonded with the positively or negatively charged aromatic compound 13 or further bonded with the aromatic compound 13 and the compound 15 capable of polyvalent ionization and the dispersion medium 12 are mixed and stirred, whereby carbon Manufacture ink.

As described above, according to the first embodiment, the compound 15 that binds the positively or negatively charged aromatic compound 12 to the carbon particles 11 or further multivalently ionizes the aromatic compound 12 is obtained. By bonding, carbon particles 11 having a high density of charge can be obtained. Moreover, this carbon particle 11 can be manufactured on mild conditions, such as neutral room temperature conditions, for example. Furthermore, the dispersibility of the carbon particles 11 in the carbon ink is very good. For this reason, by using this carbon ink as an electrophoretic dispersion liquid, the carbon particles 11 are charged with a high density and, in addition, the dispersibility is extremely good, so that electrophoresis can be performed at high speed. Power consumption can be reduced by reducing the voltage required for electrophoresis. This carbon ink is suitable for use in an electrophoretic display ink, that is, an electrophoretic dispersion.

<2. Second Embodiment>
[Electrophoretic display device]
FIG. 5 shows an electrophoretic display device according to a second embodiment. As shown in FIG. 5, in the electrophoretic display device, pixel electrodes 52 having a predetermined shape are provided in a matrix on a substrate 51, and an insulating film 53 is provided so as to cover these pixel electrodes 52. A substrate 54 is provided facing the substrate 51. A counter electrode 55 and an insulating film 56 are sequentially provided on the surface of the substrate 54 on the substrate 51 side. The outer peripheral portions of the substrate 51 and the substrate 54 are sealed with a sealing material 57. The space between the insulating film 53 on the substrate 51 and the insulating film 56 on the substrate 54 is divided for each pixel by a partition wall 58 provided between the insulating

films

53 and 54. Each space divided by the partition wall 58 is filled with an electrophoretic dispersion 59 made of carbon ink according to the first embodiment. A voltage can be applied between each pixel electrode 52 and the counter electrode 55 independently of each other. The electrophoretic dispersion 59 includes carbon particles 11 as electrophoretic particles and a dispersion medium 12. A compound 13 that is positively or negatively charged is bonded to the carbon particles 11, or a compound 15 that is polyvalently ionized is bonded to the compound 13.

In this electrophoretic display device, a display image is observed from the outside of the substrate 54. As the substrate 54, for example, an electrically insulating transparent glass substrate or a transparent plastic substrate can be used. The substrate 51 is not particularly limited as long as it is an electrically insulating substrate. For example, a glass substrate or a plastic substrate can be used. Specifically, as the substrate 51, a substrate made of a transparent inorganic material such as quartz, sapphire, glass, polyethylene terephthalate, polyethylene naphthalate, polycarbonate, polyethersulfone, polystyrene, polyethylene, polypropylene, polyphenylene sulfide, polyvinylidene fluoride. A transparent plastic substrate made of tetraacetylcellulose, brominated phenoxy, aramids, polyimides, polystyrenes, polyarylates, polysulfones, polyolefins, or the like can be used. If the thickness of the

substrates

51 and 54 is too small, it will be difficult to ensure the strength and uniformity of the spacing between the

substrates

51 and 54. On the other hand, if the thickness of the

substrates

51 and 54 is too large, the sharpness of the image as a display device and a decrease in contrast occur. In particular, when this electrophoretic display device is applied to electronic paper, it is flexible. May be lacking. For this reason, the thickness of the

substrates

51 and 54 is, for example, preferably 2 μm to 5 mm, and more preferably 5 μm to 1 mm.

A transparent electrode can be used as the counter electrode 55. Specific examples of the material constituting the transparent electrode include, for example, indium-tin composite oxide (ITO), fluorine-doped SnO ₂ (FTO), F-doped In ₂ O ₃ (IFO), antimony-doped SnO ₂ (ATO ), SnO ₂ , ZnO (including Al-doped ZnO and B-doped ZnO), indium-zinc composite oxide (IZO), spinel oxide, oxide having YbFe ₂ O ₄ structure, polyaniline, polypyrrole, polythiophene, etc. A conductive polymer or the like can be used. As the counter electrode 55, two or more of these materials can be used in combination. The pixel electrode 52 can be composed of not only the material constituting the transparent electrode but also a metal such as gold, silver, copper, aluminum, or an alloy of these metals, and a black electrode material layer (specifically, Can be composed of, for example, a titanium carbide layer, a blackened chromium layer, an aluminum layer having a black layer formed on the surface, or a titanium black layer).

As a material constituting the insulating

films

53 and 56, for example, a colorless and transparent insulating resin can be used. Specific examples of the colorless and transparent insulating resin include acrylic resin, epoxy resin, fluorine resin, silicone resin, polyimide resin, and polystyrene resin. If necessary, fine particles for scattering light such as aluminum oxide and titanium oxide may be added to the colorless and transparent insulating resin.

The width of the partition wall 58 is, for example, 1 × 10 ⁻⁶ m or more and 1 × 10 ⁻³ m or less, preferably 3 × 10 ⁻⁶ m or more and 5 × 10 ⁻⁴ m. The height of the partition wall 58 is, for example, 1 × 10 ⁻⁵ m to 5 mm, preferably 1 × 10 ⁻⁵ m to 0.5 mm. The planar shape of the pixel surrounded by the partition wall 58 is not particularly limited. For example, a quadrangle, a triangle, a circle, a hexagon (honeycomb structure), or the like can be used. The size of the pixel surrounded by the partition wall 58 is determined based on specifications required for the electrophoretic display device. For example, the length of one side is preferably 1 × 10 ⁻⁵ m or more and 5 mm or less. Is 3 × 10 ⁻⁵ m or more and 0.5 mm or less. When the volume of the pixels surrounded by the partition wall 58 is 1, the volume ratio of the carbon particles 11 in each pixel is, for example, 0.1 or more and 0.8 or less, preferably 0.1 or more and 0.7 or less. To do. The partition wall 58 is formed of, for example, a photosensitive resin, but is not limited thereto. The method of filling the electrophoretic dispersion liquid 59 into each pixel is not particularly limited, but, for example, an ink jet method can be adopted.

[Operation of electrophoretic display device]
Here, a case where the carbon particles 11 constituting the dispersion liquid 59 for electrophoresis of the electrophoretic display device are positively charged will be described as an example.

In the electrophoretic display device shown in FIG. 5, a voltage is applied between each pixel electrode 52 and the counter electrode 55 in accordance with an image to be displayed. By applying this voltage, an electric field E is generated between each pixel electrode 52 and the counter electrode 55, and this electric field E is applied to the dispersion liquid 59 for electrophoresis of each pixel. For example, when a voltage that increases the potential of the pixel electrode 52 is applied to the counter electrode 55 between the pixel electrode 52 and the counter electrode 55, the pixel electrode 52 moves toward the counter electrode 55. An electric field E is applied to the electrophoretic dispersion 59 of the pixel. The state of the electrophoresis dispersion 59 at this time is shown in FIG. As shown in FIG. 6, the positively charged carbon particles 11 contained in the electrophoresis dispersion liquid 59 migrate toward the counter electrode 55. Although not shown, conversely, when an electric field E directed from the counter electrode 55 to the pixel electrode 52 is applied to the electrophoretic dispersion 59 of the pixel, the positively charged carbon particles 11 are directed toward the pixel electrode 52. Run. Thus, for example, as shown in FIG. 7, the carbon particles 11 in the electrophoresis dispersion liquid 59 are attracted to the counter electrode 55 side for each pixel according to the displayed image, or the electrophoresis dispersion liquid The carbon particles 11 in 59 are attracted to the pixel electrode 52 side.

According to the second embodiment, by using the excellent carbon ink according to the first embodiment as the electrophoretic dispersion liquid, the carbon particles 11 as the image display fine particles are charged with high density. In addition to the extremely good dispersibility, a high-performance electrophoretic display device capable of displaying at high speed and reducing power consumption by reducing the voltage required for display is realized. Can do. This electrophoretic display device is suitable for application to electronic paper, for example.

Examples will be described below.
<Example 1>
A carbon ink using biocarbon as the carbon particles 11, NHS pyrene as the compound 13, and ε-poly-L-lysine (ε-PLL) modified as the compound 15 as the NHS pyrene was prepared as follows. .

The biocarbon was dispersed by adding 20 mL of NHS pyrene in an amount of 10 mg / mL (acetone: water = 9: 1) to 300 mg of biocarbon.

Next, after the liquid in which biocarbon was dispersed as described above was agitated by ultrasonic treatment, biocarbon was recovered by centrifugation. Note that a vortex may be used instead of the ultrasonic treatment, and biocarbon may be recovered by filtration instead of centrifugation.

Next, the recovered biocarbon was washed twice with 10 mL of acetone.

Next, the recovered biocarbon was dispersed in 20 mL of 5% ε-poly-L-lysine (acetone: water = 1: 1) and left at room temperature for 1 hour with appropriate stirring.

Next, the biocarbon was recovered from the liquid in which the biocarbon was dispersed by centrifugation. Biocarbon may be recovered by filtration.

Next, the recovered biocarbon was washed twice with 10 mL of a mixed solution of acetone and water (acetone: water = 1: 1) and then dried.

Thus obtained NHS pyrene binds to this NHS pyrene with ε-poly-L-lysine modified biocarbon and the dispersant Solsperse 17000 to 1% each with respect to Isopar G as a dispersion medium. Added to. Beads having a diameter of 0.1 mm were put into the obtained solution, stirred for 1 hour with a homogenizer, and then centrifuged at 3000 rpm for 15 minutes to collect the supernatant, thereby forming an ink. A carbon ink was thus prepared.

<Example 2>
Carbon ink using biocarbon as the carbon particles 11, NHS pyrene as the compound 13, and NHS pyrene modified with polyethyleneimine (PEI) as the compound 15 was produced in the same manner as in Example 1.

<Example 3>
Carbon ink using carbon black (CB) as the carbon particles 11, NHS pyrene as the compound 13, and ε-poly-L-lysine (ε-PLL) as the compound 15 modified to NHS pyrene as Example 1 It produced similarly.

<Example 4>
A carbon ink using carbon black (CB) as the carbon particles 11, NHS pyrene as the compound 13, and polyethyleneimine (PEI) as the compound 15 modified to NHS pyrene was produced in the same manner as in Example 1.

<Comparative example 1>
A carbon ink was produced as follows.
That is, 0.6 g of biocarbon, 0.15 g of 4-vinylaniline, and 0.9 mL of 2 molar HCl were added to 150 mL of pure water and heated to 40 ° C. with stirring. Next, a solution in which 0.087 g of sodium nitrite was dissolved in 10 mL of pure water was added and stirred for 16 hours. Then, the reaction-completed solution was centrifuged, and the operations of dispersion of solids using acetone and precipitation by centrifugation were repeated twice. Thereafter, the solid was dried under reduced pressure at room temperature for 24 hours and at 70 ° C. for 2 hours. The material thus obtained was dissolved in 300 mL of ethyl acetate, 4 g of 2-ethylhexyl methacrylate was added, heated to 50 ° C., and stirred for 1 hour. Next, 0.1 gram of AIBN was added, heated to 65 ° C. and stirred for 7 hours. Thereafter, the obtained solution was centrifuged, and dispersion and centrifugation using ethyl acetate were repeated twice. Next, the obtained solid was dried under reduced pressure at room temperature for 24 hours and at 70 ° C. for 2 hours to obtain positively charged biocarbon.

Thus obtained positively charged biocarbon and Solsperse 17000 as a dispersant were added to Isopar G as a dispersion medium so that Biocarbon was 1% and Solsperse 17000 was 1.5%. Beads having a diameter of 0.1 mm were put into the obtained solution, stirred for 4 hours with a homogenizer, and then centrifuged at 5000 rpm for 15 minutes to collect the supernatant, thereby forming an ink. A carbon ink was thus prepared.

<Comparative example 2>
A carbon ink was produced in the same manner as in Example 1 using biocarbon (BC) that does not bind

compounds

13 and 15.

<Comparative Example 3>
A carbon ink was produced in the same manner as in Example 1 using carbon black (CB) to which compounds 13 and 15 were not bonded. However, the content of Solsperse 17000, which is a dispersant, was 0.1%.

[Evaluation results]
In the carbon inks of Examples 1 to 4, the black carbon particles were well dispersed, whereas in the carbon inks of Comparative Examples 1 to 5, the black carbon particles were precipitated and were colorless and transparent.

The absorbance at a wavelength of 600 nm of the carbon particles dispersed in the carbon inks of Examples 1 to 4 and Comparative Examples 2 and 3 was measured with a spectrophotometer to estimate the dispersibility. The results are shown in FIGS. 8 is a comparison between Example 1 and Comparative Example 2, FIG. 9 is a comparison between Example 2 and Comparative Example 2, FIG. 10 is a comparison between Example 3 and Comparative Example 3, and FIG. 11 is a comparison with Example 4. A comparison with Example 3 is shown. 8 to 11 indicate the relative absorbance with respect to Comparative Example 2 or 3.

As can be seen from FIG. 8 and FIG. 9, in the biocarbon (BC), the

compounds

13 and 15 were used both when ε-poly-L-lysine (ε-PLL) was modified and when polyethyleneimine (PEI) was modified. It is dispersed 2500 times as compared with the case where they are not coupled. Further, as can be seen from FIGS. 10 and 11, in carbon black (CB), when polyethyleneimine (PEI) is modified, it is dispersed 700 times as compared with the case where compounds 13 and 15 are not bound, Even when ε-poly-L-lysine (ε-PLL) is modified, it is dispersed 13 times.

Further, in the carbon ink of Example 1, NHS pyrene was bonded, and the zeta potential of biocarbon in which NHS pyrene was modified with ε-poly-L-lysine was measured and found to be 7.5 mV.

Although the embodiments and examples of the present disclosure have been specifically described above, the present disclosure is not limited to the above-described embodiments and examples, and various modifications can be made.

For example, the numerical values, structures, configurations, shapes, materials, and the like given in the above-described embodiments and examples are merely examples, and different numerical values, structures, configurations, shapes, materials, etc. are used as necessary. Also good.

In addition, this technique can also take the following structures.
(1) A carbon ink containing carbon particles bonded with positively or negatively charged aromatic compounds.

(2) The carbon ink according to (1), wherein the aromatic compound is a polycyclic aromatic compound or a substance that bonds to carbon by a π bond.

(3) The carbon ink according to (1) or (2), wherein the carbon particles are porous carbon particles having pores on the surface.

(4) The carbon ink according to any one of (1) to (3), wherein the aromatic compound is bonded with a compound that is polyvalently ionized.

(5) The carbon ink according to any one of (1) to (4), wherein the carbon ink is an ink for an electrophoretic display device.

(6) The carbon particles are at least one selected from the group consisting of carbon black, natural graphite, graphite, glassy carbon, carbon nanotubes, highly oriented pyrolytic graphite, plastic formed carbon, activated carbon, and porous carbon. The carbon ink according to any one of (1) to (5).

(7) The porous carbon particles are any one of (1) to (6), which is at least one selected from the group consisting of activated carbon, porous carbon, carbon aggregated particles, carbon black, and biocarbon. Carbon ink described in 1.

(8) The polycyclic aromatic compound includes pyrene derivatives, coronene derivatives, chrysene derivatives, naphthacene derivatives, pentacene derivatives, picene derivatives, perylene derivatives, anthracene derivatives, phenanthrene derivatives, fluorene derivatives, naphthalene derivatives, fluoranthene derivatives, acenaphthene derivatives, The substance that is at least one selected from the group consisting of acenaphthylene derivatives and triphenylene derivatives and binds to carbon by the π bond is a terthiophene derivative, tetraphenylbenzidine derivative, tetraphenylnaphthacene derivative, benzothiophene derivative, thiophene derivative , Pyrrole derivative, carbazole derivative, phenanthroline derivative, phenylpyridine derivative, quinoline derivative, triphenylamine derivative, diphenylamine derivative , Oxazole derivatives, oxadiazole derivatives, p-phenyl derivatives, quinacridone derivatives, fluorenone derivatives, phthalocyanine derivatives, spiropyran derivatives, viologen derivatives, spiroperimidine derivatives, phenyl esters, benzoic acid, biphenyl derivatives, benzophenone derivatives, diphenylamine derivatives, diphenyl ether, diphenyl Any one of the above (1) to (7), which is at least one selected from the group consisting of sulfide, diphenylsulfone, bisphenol derivative, anthraquinone derivative, phosphonium compound, fluorescene derivative, rhodamine derivative, coumarin derivative and cyanine derivative. Carbon ink.

(9) The compound to be polyionized is at least one selected from the group consisting of polyamine, polycarboxylic acid, polysulfonic acid, polyaniline, polypyrrole, polyphosphoric acid, and peptide, any of (4) to (8) The carbon ink according to crab.

DESCRIPTION OF SYMBOLS 11 ... Carbon particle, 12 ... Dispersion medium, 13 ... Positively or negatively charged compound, 15 ... Compound which carries out polyvalent ionization, 51, 54 ... Substrate, 52 ... Pixel electrode 55 ... Counter electrode, 59 ... Electrophoretic dispersion liquid

Claims

A carbon ink containing carbon particles bonded with positively or negatively charged aromatic compounds.
The carbon ink according to claim 1, wherein the aromatic compound is a polycyclic aromatic compound or a substance that is bonded to carbon by a π bond.
The carbon ink according to claim 2, wherein the carbon particles are porous carbon particles having pores on the surface.
The carbon ink according to claim 1, wherein the aromatic compound is bonded with a compound that is polyvalently ionized.
The carbon ink according to claim 1, wherein the carbon ink is an ink for an electrophoretic display device.
2. The carbon particles are at least one selected from the group consisting of carbon black, natural graphite, graphite, glassy carbon, carbon nanotubes, highly oriented pyrolytic graphite, plastic formed carbon, activated carbon and porous carbon. The carbon ink described.
4. The carbon ink according to claim 3, wherein the porous carbon particles are at least one selected from the group consisting of activated carbon, porous carbon, carbon aggregated particles, carbon black, and biocarbon.
The polycyclic aromatic compounds include pyrene derivatives, coronene derivatives, chrysene derivatives, naphthacene derivatives, pentacene derivatives, picene derivatives, perylene derivatives, anthracene derivatives, phenanthrene derivatives, fluorene derivatives, naphthalene derivatives, fluoranthene derivatives, acenaphthene derivatives, acenaphthylene derivatives and The substance that is at least one selected from the group consisting of triphenylene derivatives and binds to carbon by the π bond is a terthiophene derivative, tetraphenylbenzidine derivative, tetraphenylnaphthacene derivative, benzothiophene derivative, thiophene derivative, pyrrole derivative Carbazole derivatives, phenanthroline derivatives, phenylpyridine derivatives, quinoline derivatives, triphenylamine derivatives, diphenylamine derivatives, Sazole derivatives, oxadiazole derivatives, p-phenyl derivatives, quinacridone derivatives, fluorenone derivatives, phthalocyanine derivatives, spiropyran derivatives, viologen derivatives, spiroperimidine derivatives, phenyl esters, benzoic acid, biphenyl derivatives, benzophenone derivatives, diphenylamine derivatives, diphenyl ether, diphenyl sulfide 3. The carbon ink according to claim 2, wherein the carbon ink is at least one selected from the group consisting of diphenylsulfone, bisphenol derivatives, anthraquinone derivatives, phosphonium compounds, fluorescene derivatives, rhodamine derivatives, coumarin derivatives and cyanine derivatives.
5. The carbon ink according to claim 4, wherein the compound to be polyvalent ionized is at least one selected from the group consisting of polyamine, polycarboxylic acid, polysulfonic acid, polyaniline, polypyrrole, polyphosphoric acid and peptide.
An electrophoretic display device having a carbon ink containing carbon particles to which a positively or negatively charged aromatic compound is bonded.
The electrophoretic display device according to claim 10, wherein the electrophoretic display device is electronic paper.
A method for producing a carbon ink, comprising: mixing and stirring carbon particles to which a positively or negatively charged aromatic compound is bonded and a dispersion medium.
13. The method for producing a carbon ink according to claim 12, further comprising a step of binding a compound that is polyvalently ionized to the aromatic compound.