Ink composition, layer using the same, and electrophoretic device and display device including the layer

Abstract

Provided are an ink composition, a layer formed using the ink composition, and an electrophoretic device and a display device including the layer, in which the ink composition includes: (A) a semiconductor nanorod; and (B) a solvent satisfying a specific mathematical formula.

Description

Technical Field

[0001] The present disclosure relates to an ink composition, a layer using the ink composition, and an electrophoretic device and a display device including the layer. Background Art

[0002] LEDs have been actively developed since Nakamura and others from Nichia Corporation of Japan succeeded in fusing high-quality single-crystal GaN nitride semiconductors by applying a low-temperature GaN compound buffer layer in 1992. LEDs are semiconductor devices that convert electrical signals into light having a wavelength in a desired region by using the characteristics of a compound semiconductor having a structure in which an n-type semiconductor crystal in which a plurality of carriers are electrons and a p-type semiconductor crystal in which a plurality of carriers are holes are combined with each other.

[0003] This LED has a high light conversion efficiency, so it consumes very little energy, has a semi-permanent lifespan, and is also environmentally friendly, so it is called a revolution in light as a green material. Recently, with the development of compound semiconductor technology, high-brightness red, orange, green, blue and white LEDs have been developed, and they are used in many fields (such as traffic lights, mobile phones, car headlights, outdoor billboards, LCD BLU (backlight units) and indoor / outdoor lighting), which has been actively studied at home and abroad. Specifically, GaN-based compound semiconductors with a wide bandgap are materials for manufacturing LEDs that emit light in the green region, the blue region and the ultraviolet (UV) region, and since blue LED devices are used to manufacture white LED devices, a lot of research is being conducted on this.

[0004] Among these series of research, research on using ultra-small LED devices having a nanometer unit size or a micrometer unit size is being actively conducted, and further, research on utilizing these ultra-small LED devices in lighting and display is being continuously conducted. In these research, electrodes capable of applying power to ultra-small LED devices, arrangement of electrodes for reducing the space occupied by electrodes, methods of mounting ultra-small LED devices on the arranged electrodes, and the like continue to attract attention.

[0005] Among these, due to the size limitation of the ultra-small LED device, the method of mounting the ultra-small LED device on the set electrode still makes it difficult to set and mount the ultra-small LED device on the electrode as expected. The reason is that the ultra-small LED device is nano-sized or micro-sized, so it is impossible to manually set and mount it one by one in the target electrode area.

[0006] Recently, as the demand for nano-scale ultra-small LED devices increases, attempts have been made to develop nano-scale GaN-based compound semiconductors or InGaN-based compound semiconductors into light-emitting devices by making them into nanorods and regularly aligning the nanorods. Among them, aligning InGaN nanorod LEDs (NEDs) by using an electric field (electrophoresis or dielectrophoresis) has attracted attention as a method for significantly reducing the complex and expensive process costs of μ-LEDs, mini LEDs, etc.

[0007] Such electrophoretic or dielectrophoretic forces are known to be affected by the dielectric properties of the particles and solvents exposed to an electric field etc., but to date no suitable range of parameters for alignment of InGaN nanorod LEDs (NEDs) has been introduced at all. Summary of the invention

[0008] Technical issues

[0009] The embodiment provides an ink composition having excellent electrophoretic characteristics of semiconductor nanorods.

[0010] Another embodiment provides a layer produced using the ink composition.

[0011] Another embodiment provides an electrophoretic device and a display device including the layer.

[0012] Technical Solution

[0013] The embodiment provides an ink composition including: (A) semiconductor nanorods; and (B) a solvent satisfying Equation 1.

[0014] [Equation 1]

[0015] |ε1–ε2| / ε1*100≤10

[0016] In equation 1,

[0017] ε1 is the dielectric constant of the solvent at 50 Hz, and

[0018] ε2 is the dielectric constant of the solvent at 50 kHz.

[0019] The solvent may satisfy Equation 2.

[0020] [Equation 2]

[0021] |ε1–ε2| / ε1*100≤5

[0022] In equation 2,

[0023] ε1 is the dielectric constant of the solvent at 50 Hz, and

[0024] ε2 is the dielectric constant of the solvent at 50 kHz.

[0025] The solvent may be a single non-citrate compound.

[0026] The solvent may include two or more compounds.

[0027] The solvent may include three or more compounds.

[0028] The semiconductor nanorods may have a diameter of about 300 nm to about 900 nm.

[0029] The semiconductor nanorods may have a length of about 3.5 μm to about 6 μm.

[0030] The semiconductor nanorods may include a GaN-based compound, an InGaN-based compound, or a combination thereof.

[0031] The semiconductor nanorods may have a surface coated with a metal oxide.

[0032] The metal oxide may include aluminum oxide, silicon dioxide, or a combination thereof.

[0033] The semiconductor nanorods may be included in an amount of about 0.01 wt % to about 10 wt % based on the total amount of the ink composition.

[0034] The ink composition may include: malonic acid; 3-amino-1,2-propanediol; a silane-based coupling agent; a leveling agent; a fluorine-based surfactant; or a combination thereof.

[0035] The ink composition may be an ink composition for an electrophoretic device.

[0036] Another embodiment provides a layer produced using the ink composition.

[0037] Another embodiment provides an electrophoretic device including the layer.

[0038] Another embodiment provides a display device including the layer.

[0039] Other embodiments are included in the detailed description below.

[0040] Beneficial Effects

[0041] An ink composition including semiconductor nanorods can provide an ink composition having excellent electrophoretic characteristics (achieving a high degree of alignment). BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 is an example of a cross-sectional view of a semiconductor nanorod used in a curable composition according to an embodiment.

[0043] Figure 2is the real part of the dielectric constant of the solvent (ε' r ) and the imaginary part (ε” r ) is a graph showing the changing trend of frequency. DETAILED DESCRIPTION

[0044] Hereinafter, embodiments are described in detail. However, these embodiments are exemplary, the present invention is not limited thereto, and the present invention is defined by the scope of the claims.

[0045] As used herein, when no specific definition is otherwise provided, "alkyl" refers to a C 1 To C 20 Alkyl, "alkenyl" refers to C 2 To C 20 Alkenyl, "cycloalkenyl" refers to C 3 To C 20 Cycloalkenyl, "heterocycloalkenyl" refers to C 3 To C 20 Heterocycloalkenyl, "aryl" refers to C 6 To C 20 Aryl, "arylalkyl" refers to C 6 To C 20 Arylalkyl, "alkylene" refers to C 1 To C 20 Alkylene, "arylene" refers to C 6 To C 20 Arylene, "alkylenaryl" refers to C 6 To C 20 Alkylene aryl, "heteroarylene" refers to C 3 To C 20 heteroarylene, and "alkyleneoxy" refers to C 1 To C 20 Alkylene oxide.

[0046] As used herein, when no specific definition is otherwise provided, "substituted" may refer to replacement of at least one hydrogen with a halogen atom (F, Cl, Br, I), a hydroxyl group, a C 1 To C 20 an alkoxy group, a nitro group, a cyano group, an amino group, an imino group, an azido group, an amidine group, a hydrazine group, a hydrazone group, a carbonyl group, a carbamoyl group, a thiol group, an ester group, an ether group, a carboxyl group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 To C 20 Alkyl, C 2 To C 20 Alkenyl, C 2 To C 20 Alkynyl, C 6 To C 20 Aryl, C 3 To C 20 Cycloalkyl, C 3 To C20 Cycloalkenyl, C 3 To C 20 Cycloalkynyl, C 2 To C 20 Heterocycloalkyl, C 2 To C 20 Heterocycloalkenyl, C 2 To C 20 Heterocycloalkynyl, C 3 To C 20 or a combination thereof.

[0047] As used herein, when a specific definition is not otherwise provided, "hetero" may refer to a structure substituted with at least one hetero atom of N, O, S, and P in a chemical formula.

[0048] As used herein, when no specific definition is otherwise provided, “(meth)acrylate” refers to both “acrylate” and “methacrylate”, and “(meth)acryloyl” refers to both “acryloyl” and “methacryloyl”.

[0049] As used herein, when no specific definition is otherwise provided, the term "combination" means mixing or copolymerization.

[0050] As used herein, unless a specific definition is otherwise provided, when a chemical bond is not drawn at a position where it should be given, a hydrogen atom is bonded at that position.

[0051] In this specification, a semiconductor nanorod refers to a rod-shaped semiconductor having a nanometer-sized diameter.

[0052] As used herein, when a specific definition is not otherwise provided, "*" indicates a point of connection that is the same or different atoms or chemical formulas.

[0053] The ink composition according to the embodiment includes: (A) semiconductor nanorods; and (B) a solvent satisfying Equation 1.

[0054] [Equation 1]

[0055] |ε1–ε2| / ε1*100≤10

[0056] In equation 1,

[0057] ε1 is the dielectric constant of the solvent at 50 Hz, and

[0058] ε2 is the dielectric constant of the solvent at 50 kHz.

[0059] For example, the solvent may satisfy Equation 2.

[0060] [Equation 2]

[0061] |ε1–ε2| / ε1*100≤5

[0062] In equation 2,

[0063] ε1 is the dielectric constant of the solvent at 50 Hz, and

[0064] ε2 is the dielectric constant of the solvent at 50 kHz.

[0065] However, organic solvents (PGMEA, GBL, PGME, ethyl acetate, IPA, etc.) conventionally used in displays and electronic materials have low viscosity, and thus inorganic nanorod particles having a high density may settle too quickly and thus aggregate, and further, may volatilize quickly and thus may deteriorate alignment characteristics during solvent drying after dielectrophoresis. Conventionally, efforts have been made to discover new solvents to solve this problem, but unlike the existing methods, the present inventors have confirmed that the alignment characteristics of semiconductor nanorods can be significantly improved by limiting the dielectric constant of the solvent in the ink composition to a specific range, thereby completing the present invention.

[0066] Specifically, signals of various waveforms and frequencies are applied in a complex manner rather than a simple waveform AC signal in order to precisely control and constantly align the semiconductor nanorods between the electrodes. However, when signals of various frequencies are applied, electrical properties such as dielectric constant may change due to molecular structural properties of the solvent, impurities, etc.

[0067] Specifically, the phenomenon in which the dielectric constant decreases with increasing frequency is called dielectric loss, where the dielectric loss phenomenon is caused by the interface and space charges, orientation dipoles, ionic and electronic polarization of the solvent (see Figure 2 The dielectric loss phenomenon may cause the energy of the electric field applied to the solvent to be lost as heat energy, and further, cause the degradation of the alignment of the semiconductor nanorods by weakening the energy of the AC signal applied during the alignment of the semiconductor nanorods.

[0068] Hereinafter, each component is described in detail.

[0069] (A) Semiconductor Nanorods

[0070] As the dispersion stability of the ink composition including semiconductor nanorods and a solvent increases, large-area inkjet and dielectrophoresis processability improves.

[0071] The semiconductor nanorods may include a GaN-based compound, an InGaN-based compound, or a combination thereof, and may have a surface coated with a metal oxide.

[0072] For the dispersion stability of the semiconductor nanorod ink solution (semiconductor nanorods + solvent), it usually takes about 3 hours, which is extremely insufficient time for performing a large-area inkjet process. However, by coating the surface of the semiconductor nanorods with a metal oxide including aluminum oxide, silicon dioxide or a combination thereof to form a coating or insulating layer (Al 2 O 3 or SiO x ), which can maximize the compatibility with the solvent described later.

[0073] For example, the coating layer coated with the metal oxide or the insulating layer may have a thickness of about 40 nm to about 60 nm.

[0074] For example, a functional group such as a siloxane group may be attached to a metal oxide coating or an insulating layer on the surface of the semiconductor nanorod. In this case, since the compatibility with a solvent described later becomes very excellent, both the dispersion stability of the semiconductor nanorod and the dielectrophoretic characteristics of the ink composition can be greatly improved.

[0075] The semiconductor nanorod may include an n-type confinement layer and a p-type confinement layer, and a multi-quantum well active portion (MQW active region; multi-quantum well active region) may be located between the n-type confinement layer and the p-type confinement layer.

[0076] For example, the semiconductor nanorods can have a diameter of about 300 nm to about 900 nm (eg, about 600 nm to about 800 nm).

[0077] For example, the semiconductor nanorods may have a length of about 3.5 μm to about 6 μm (eg, about 3.5 μm to about 5 μm).

[0078] For example, when the semiconductor nanorods include an aluminum oxide insulating layer, the semiconductor nanorods may have a relative humidity of about 5 g / cm 3 About 6g / cm 3 density.

[0079] For example, a semiconductor nanorod can have a -13 g to about 1×10 -11 The mass of g.

[0080] When the semiconductor nanorods have the above-described diameter, length, density, and mass, surface coating of the metal oxide may be promoted, and dispersion stability of the semiconductor nanorods may be maximized.

[0081] Based on the total amount of the ink composition, the semiconductor nanorods may be included in an amount of about 0.01 wt % to about 10 wt % (e.g., about 0.01 wt % to about 5 wt %). Alternatively, based on 100 parts by weight of the solvent in the ink composition, the semiconductor nanorods may be included in an amount of about 0.01 parts by weight to about 0.5 parts by weight (e.g., about 0.01 parts by weight to about 0.1 parts by weight). When the semiconductor nanorods are included within the above range, the dispersibility in the ink is good, and the pattern produced may have excellent brightness.

[0082] (B) Solvent

[0083] An embodiment is to improve the alignment, and specifically bias the alignment, of semiconductor nanorods by dielectrophoresis or electrophoresis by introducing into the ink composition a solvent having a dielectric constant that varies less than about 10% (eg, less than about 5%) as a function of frequency.

[0084] A solvent whose dielectric constant varies by less than about 10% according to frequency may be represented by Equation 1, and a solvent whose dielectric constant varies by less than 5% according to frequency may be represented by Equation 2.

[0085] Specifically, when the difference between the dielectric constant at about 50 Hz and the dielectric constant at about 50 kHz is less than about 10% (e.g., less than about 5%), high alignment of semiconductor nanorods can be achieved, but when the difference between the dielectric constant at about 0 Hz and the dielectric constant at about 50 kHz is greater than about 10%, high alignment of semiconductor nanorods may not be achieved.

[0086] For example, the solvent may be a single non-citrate compound. When the solvent is a single citrate compound, the solvent may not satisfy Equation 1 and Equation 2, and it is difficult to achieve a high degree of alignment of the semiconductor nanorods.

[0087] For example, the solvent may include about 2 or more compounds, for example, about 3 or more compounds. When the solvent is not a single compound but a mixture of about 2 or more compounds, a citrate compound may be included. Even if the mixture includes a citrate compound, it is easy to control the dielectric constant of the mixed solvent according to the change in frequency within about 10% (e.g., about 5%) through interaction with other compounds.

[0088] For example, the solvent can have a viscosity greater than or equal to about 3 cps at 50°C.

[0089] For example, the citrate-based compound may be represented by Chemical Formula 3.

[0090] [Chemical formula 3]

[0091]

[0092] In chemical formula 3,

[0093] R 11 is a hydrogen atom or *-C(=O)R' (wherein R' is a hydrogen atom or a substituted or unsubstituted C 1 To C 10 alkyl),

[0094] R 12 To R 14 are independently substituted or unsubstituted C 2 To C 20 Alkyl, and

[0095] L 11 and L 12 are independently substituted or unsubstituted C 1 To C 20 Alkylene.

[0096] For example, in the present specification, a single non-citrate ester compound may refer to a compound not represented by Chemical Formula 3.

[0097] For example, the compound represented by Chemical Formula 3 may include a compound represented by Chemical Formula 3-1 or Chemical Formula 3-2.

[0098] [Chemical formula 3-1]

[0099]

[0100] [Chemical formula 3-2]

[0101]

[0102] The solvent may be included in an amount of about 5 wt % to about 99.99 wt % (eg, about 20 wt % to about 99.95 wt %, for example, about 90 wt % to about 99.99 wt %) based on the total amount of the ink composition.

[0103] Polymerizable monomer

[0104] The ink composition according to the embodiment may further include a polymerizable compound, if necessary. The polymerizable compound may be used by mixing a monomer or an oligomer generally used in a conventional curable composition.

[0105] For example, the polymerizable compound may be a polymerizable monomer having a carbon-carbon double bond at its terminal.

[0106] For example, the polymerizable compound may be a polymerizable monomer having at least one functional group represented by Chemical Formula A-1 or a functional group represented by Chemical Formula A-2 at its terminal.

[0107] [Chemical formula A-1]

[0108]

[0109] [Chemical formula A-2]

[0110]

[0111] In Chemical Formula A-1 and Chemical Formula A-2,

[0112] L a is substituted or unsubstituted C 1 To C 20 an alkylene group, and

[0113] R a is a hydrogen atom or a substituted or unsubstituted C 1 To C 20 alkyl.

[0114] The polymerizable compound includes at least one carbon-carbon double bond at the terminal (specifically, a functional group represented by Chemical Formula A-1 or a functional group represented by Chemical Formula A-2), thereby forming a cross-linked structure with the surface modification compound. The cross-linked body thus formed can further enhance the dispersion stability of the semiconductor nanorods by further doubling one type of steric hindrance effect.

[0115] For example, the polymerizable compound including at least one functional group represented by Chemical Formula A-1 at the terminal may be divinylbenzene, triallyl cyanurate, triallyl isocyanurate, triallyl trimellitate, triallyl phosphate, triallyl phosphite, triallyl triazine, diallyl phthalate, or a combination thereof, but is not necessarily limited thereto.

[0116] For example, the polymerizable compound including at least one functional group represented by Chemical Formula A-2 at the terminal may be ethylene glycol diacrylate, triethylene glycol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate, dipentaerythritol diacrylate, dipentaerythritol triacrylate, dipentaerythritol pentaacrylate, pentaerythritol hexaacrylate, bisphenol A diacrylate, trimethylolpropane triacrylate, novolac epoxy acrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, propylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, multifunctional epoxy (meth) acrylate, multifunctional urethane (meth) acrylate, KAYARAD DPCA-20 of Nippon Chemical Co., Ltd., KAYARAD DPCA-30, KAYARAD DPCA-60, KAYARAD DPCA-120 or KAYARAD DPEA-12 or a combination thereof, but not necessarily limited thereto.

[0117] The polymerizable compound may be used after being treated with an acid anhydride to impart better developability.

[0118] Polymerization initiator

[0119] If necessary, the ink composition according to the embodiment may further include a polymerization initiator, for example, a photopolymerization initiator, a thermal polymerization initiator, or a combination thereof.

[0120] The photopolymerization initiator may be a common initiator used for a curable composition, and may be, for example, acetophenone compounds, benzophenone compounds, thioxanthone compounds, benzoin compounds, triazine compounds, oxime compounds, aminoketone compounds, etc., but is not necessarily limited thereto.

[0121] Examples of acetophenone compounds include 2,2'-diethoxyacetophenone, 2,2'-dibutoxyacetophenone, 2-hydroxy-2-methylpropiophenone, p-tert-butyltrichloroacetophenone, p-tert-butyldichloroacetophenone, 4-chloroacetophenone, 2,2'-dichloro-4-phenoxyacetophenone, 2-methyl-1-(4-(methylthio)phenyl)-2-morpholinopropane-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one, and the like.

[0122] Examples of benzophenone compounds include benzophenone, benzoyl benzoate, benzoylmethyl benzoate, 4-phenylbenzophenone, hydroxybenzophenone, acrylated benzophenone, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, 4,4'-dimethylaminobenzophenone, 4,4'-dichlorobenzophenone, 3,3'-dimethyl-2-methoxybenzophenone, and the like.

[0123] Examples of the thioxanthone-based compound may include thioxanthone, 2-methylthioxanthone, isopropylthioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, 2-chlorothioxanthone, and the like.

[0124] Examples of the benzoin-based compound include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzyl dimethyl ketal, and the like.

[0125] Examples of the triazine compound may include 2,4,6-trichloro-s-triazine, 2-phenyl-4,6-bis(trichloromethyl)-s-triazine, 2-(3',4'-dimethoxyphenyl)-4,6-bis(trichloromethyl)-s-triazine, 2-(4'-methoxynaphthyl)-4,6-bis(trichloromethyl)-s-triazine, 2-(p-methoxyphenyl)-4,6-bis(trichloromethyl)-s-triazine, and 2-(p-tolyl)-4,6-bis(trichloromethyl)-s-triazine. -s-triazine, 2-biphenyl-4,6-bis(trichloromethyl)-s-triazine, bis(trichloromethyl)-6-phenylvinyl-s-triazine, 2-(naphthalene-1-yl)-4,6-bis(trichloromethyl)-s-triazine, 2-(4-methoxynaphthalene-1-yl)-4,6-bis(trichloromethyl)-s-triazine, 2-4-bis(trichloromethyl)-6-piperonyl-s-triazine, 2,4-bis(trichloromethyl)-6-(4-methoxyphenylvinyl)-s-triazine, etc.

[0126] Examples of oxime compounds include O-acyl oxime compounds, 2-(O-benzoyl oxime)-1-[4-(phenylthio)phenyl]-1,2-octanedione, 1-(O-acetyl oxime)-1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]ethanone, O-ethoxycarbonyl-α-oxyamino-1-phenylpropan-1-one, and the like. Specific examples of O-acyl oxime compounds include 1,2-octanedione, 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholin-4-yl-phenyl)-butane-1-one, 1-(4-phenylsulfanylphenyl)-butane-1,2-dione-2-oxime-O-benzoate, 1-(4-phenylsulfanylphenyl)-octane-1,2-dione-2-oxime-O-benzoate, 1-(4-phenylsulfanylphenyl)-octane-1-one oxime-O-acetate, 1-(4-phenylsulfanylphenyl)-butane-1-one oxime-O-acetate, and the like.

[0127] Examples of aminoketone compounds include 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone and the like.

[0128] In addition to the above compounds, the photopolymerization initiator may further include carbazole compounds, diketone compounds, sulfonium borate compounds, diazo compounds, imidazole compounds, biimidazole compounds, and the like.

[0129] The photopolymerization initiator may be used together with a photosensitizer capable of causing a chemical reaction by absorbing light and becoming excited and then transferring its energy.

[0130] Examples of the photosensitizer may include tetraethylene glycol bis-3-mercaptopropionate, pentaerythritol tetrakis-3-mercaptopropionate, dipentaerythritol tetrakis-3-mercaptopropionate, and the like.

[0131] Examples of thermal polymerization initiators may include peroxides (specifically, benzoyl peroxide, dibenzoyl peroxide, lauroyl peroxide, dilauroyl peroxide, di-tert-butyl peroxide, cyclohexane peroxide, methyl ethyl ketone peroxide), oxides, hydroperoxides (e.g., tert-butyl hydroperoxide, cumene hydroperoxide, etc.), dicyclohexyl peroxydicarbonate, 2,2-azo-bis(isobutyronitrile), tert-butyl perbenzoate, 2,2'-azobis-2-methylpropionitrile, and the like, but are not necessarily limited thereto, and any one widely known in the art may be used.

[0132] The polymerization initiator may be included in an amount of about 1 wt % to about 5 wt % (e.g., about 2 wt % to about 4 wt %) based on the total amount of solid components constituting the ink composition. When the polymerization initiator is included within the above range, excellent reliability may be obtained due to sufficient curing during exposure or thermal curing.

[0133] Other additives

[0134] The ink composition according to the embodiment may further include an inhibitor as needed, the inhibitor including a hydroquinone compound, a catechol compound, or a combination thereof. Since the ink composition according to the embodiment also includes a hydroquinone compound, a catechol compound, or a combination thereof, crosslinking at room temperature can be prevented during exposure after printing (coating) the ink composition.

[0135] For example, the hydroquinone compound, the catechol compound or a combination thereof may be hydroquinone, methylhydroquinone, methoxyhydroquinone, tert-butylhydroquinone, 2,5-di-tert-butylhydroquinone, 2,5-bis(1,1-dimethylbutyl)hydroquinone, 2,5-bis(1,1,3,3-tetramethylbutyl)hydroquinone, catechol, tert-butylcatechol, 4-methoxyphenol, pyrogallol, 2,6-di-tert-butyl-4-methylphenol, 2-naphthol, tris(N-hydroxy-N-nitrosoanilino-O,O')aluminum or a combination thereof, but are not necessarily limited thereto.

[0136] The hydroquinone compound, the catechol compound, or a combination thereof may be used in the form of a dispersion, and the polymerization inhibitor in the form of a dispersion may be included in an amount of about 0.001 wt % to about 1 wt % (e.g., about 0.01 wt % to about 0.1 wt %) based on the total amount of the ink composition. When the polymerization inhibitor within the range is included, time lapse at room temperature may be resolved, and sensitivity degradation and surface delamination phenomena may be suppressed at the same time.

[0137] In addition to the polymerization inhibitor, the ink composition according to the embodiment may include: malonic acid; 3-amino-1,2-propanediol; a silane-based coupling agent; a leveling agent; a fluorine-based surfactant; or a combination thereof, as needed.

[0138] For example, the ink composition may further include a silane-based coupling agent having a reactive substituent such as a vinyl group, a carboxyl group, a methacryloxy group, an isocyanate group, an epoxy group, etc., in order to improve close contact properties with the substrate.

[0139] Examples of the silane coupling agent may be trimethoxysilylbenzoic acid, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, vinyltrimethoxysilane, γ-isocyanatepropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, β-(epoxycyclohexyl)ethyltrimethoxysilane, and the like, and these may be used alone or in mixture of two or more.

[0140] The silane-based coupling agent may be used in an amount of about 0.01 parts by weight to about 10 parts by weight based on 100 parts by weight of the ink composition. When the silane-based coupling agent is included within the range, close contact properties, storage ability, and the like are improved.

[0141] Furthermore, if necessary, the ink composition may further include a surfactant such as a fluorine-based surfactant in order to improve coating properties and prevent defect formation.

[0142] Examples of fluorinated surfactants include: etc.; MEGAFACE F by Dainippon Ink Kagaku Kogyo Co., Ltd. MEGAFACE F etc.; FULORAD of Sumitomo3M Co., Ltd. FULORAD FULORAD etc.; ASAHI Glass Co., Ltd.

[0143] etc.; Toray Silicone Co., Ltd. etc.; F-482, F-484, F-478, F-554, etc. of DIC Co., Ltd.

[0144] The fluorine-based surfactant may be included in an amount of about 0.001 parts by weight to about 5 parts by weight based on 100 parts by weight of the ink composition. When the fluorine-based surfactant is included within the above range, coating uniformity is ensured, stains do not occur, and wettability to a glass substrate is excellent.

[0145] Furthermore, unless the properties are deteriorated, the ink composition may further include other additives such as an antioxidant, a stabilizer, etc. in a predetermined amount.

[0146] Another embodiment provides a layer using an ink composition.

[0147] Another embodiment may provide an electrophoretic device and / or a display device including the layer.

[0148] [Mode of invention]

[0149] Hereinafter, the present invention is described in more detail with reference to examples. However, these examples are not to be construed as limiting the scope of the invention in any sense.

[0150] (Preparation of ink composition)

[0151] Comparative Example 1

[0152] 40mL of hexyltrimethoxysilane (cas#: 3069-19-0, HSCA, 1.5mM solution in dodecane) was reacted as a ligand on a nanorod patterned GaN wafer (4 inches) at room temperature for 15 hours. After the reaction, the wafer was immersed in 50mL of acetone for 5 minutes to remove excess ligands, and in addition, the wafer surface was rinsed by using 40mL of acetone. The cleaned wafer was placed in a 27kW bath-type sonicator together with 35mL of GBL, and then sonicated for 5 minutes to remove the rods from the wafer surface. The separated rods were placed in a FALCON tube for centrifugation, and 10mL of GBL was added thereto to additionally clean the rods on the bath surface. After discarding the supernatant by centrifugation at 4000rpm for 10 minutes, the precipitate was redispersed in 40mL of acetone and then passed through a 10μm mesh filter to filter out foreign matter. After additional centrifugation (4000 rpm, 10 minutes), the precipitate was dried in a drying oven (100° C., 1 hour), then weighed and dispersed in 0.05 w / w % of triethyl 2-acetyl citrate (TEC-Ac) to prepare an ink composition.

[0153] Comparative Example 2

[0154] An ink composition was prepared in the same manner as in Comparative Example 1, except that tributyl citrate was used instead of 2-acetyl triethyl citrate (TEC-Ac).

[0155] Comparison Example 3

[0156] An ink composition was prepared in the same manner as in Comparative Example 1, except that diethylene glycol monophenyl ether was used instead of 2-acetyl citrate triethyl (TEC-Ac).

[0157] Example 1

[0158] An ink composition was prepared in the same manner as in Comparative Example 1, except that triacetin was used instead of triethyl 2-acetyl citrate (TEC-Ac).

[0159] Example 2

[0160] An ink composition was prepared in the same manner as in Comparative Example 1, except that 1-(2-methoxyphenoxy)-2-propanol and diethyl terephthalate were used instead of 2-acetyl triethyl citrate (TEC-Ac).

[0161] Example 3

[0162] An ink composition was prepared in the same manner as in Comparative Example 1, except that triethyl citrate and tri-n-propyl-isocyanurate were used instead of 2-acetyl triethyl citrate (TEC-Ac).

[0163] Example 4

[0164] An ink composition was prepared in the same manner as in Comparative Example 1, except that triethyl citrate, 2-ethyl-1,3-hexanediol, and tri-n-propyl-isocyanurate were used instead of 2-acetyl triethyl citrate (TEC-Ac).

[0165] Example 5

[0166] An ink composition was prepared in the same manner as in Comparative Example 1, except that triethyl citrate, diethyl L-tartrate, and triallyl isocyanurate were used instead of triethyl 2-acetyl citrate (TEC-Ac).

[0167] evaluate

[0168] The ink compositions according to Examples 1 to 5 and Comparative Examples 1 to 3 were evaluated regarding dielectric constant of the solvent and change according to frequency, which are shown in Table 1, and further, were evaluated regarding dielectrophoresis / electrophoresis characteristics by using Turbiscan, which are shown in Table 1.

[0169] [Table 1]

[0170]

[0171] Referring to Table 1, the ink compositions including a solvent satisfying Equation 1 (Examples 1 to 5) exhibited excellent alignment characteristics and thus excellent dielectrophoresis characteristics, compared to the ink compositions including a solvent not satisfying Equation 1 (Comparative Examples 1 to 3).

[0172] While the disclosure has been described in conjunction with what are presently considered to be practical example embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but on the contrary is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. An ink composition, comprising: (A) Semiconductor nanorods; as well as (B) A solvent that satisfies equation 1: [Equation 1] |ε1–ε2| / ε1*100≤10 Where, in equation 1, ε1 is the dielectric constant of the solvent at 50 Hz, and ε2 is the dielectric constant of the solvent at 50 kHz.

2. The ink composition according to claim 1, wherein The solvent satisfies Equation 2: [Equation 2] |ε1–ε2| / ε1*100≤5 Where, in equation 2, ε1 is the dielectric constant of the solvent at 50 Hz, and ε2 is the dielectric constant of the solvent at 50 kHz.

3. The ink composition according to claim 1, wherein The solvent is a single non-citrate compound.

4. The ink composition according to claim 1, wherein The solvent includes two or more compounds.

5. The ink composition according to claim 1, wherein The solvent includes three or more compounds.

6. The ink composition according to claim 1, wherein The semiconductor nanorods have a diameter of 300 nm to 900 nm.

7. The ink composition according to claim 1, wherein The semiconductor nanorods have a length of 3.5 μm to 6 μm.

8. The ink composition according to claim 1, wherein The semiconductor nanorods include GaN-based compounds, InGaN-based compounds or a combination thereof.

9. The ink composition according to claim 1, wherein The semiconductor nanorods have surfaces coated with a metal oxide.

10. The ink composition according to claim 9, wherein The metal oxide includes aluminum oxide, silicon dioxide or a combination thereof.

11. The ink composition according to claim 1, wherein The semiconductor nanorods are included in an amount of 0.01 wt % to 10 wt % based on the total amount of the ink composition.

12. The ink composition according to claim 1, wherein The ink composition comprises: malonic acid; 3-amino-1,2-propanediol; a silane coupling agent; a leveling agent; a fluorine-based surfactant; or a combination thereof.

13. The ink composition according to claim 1, wherein The ink composition is an ink composition for an electrophoretic device.

14. A layer produced using the ink composition according to claim 1.

15. An electrophoretic device comprising a layer according to claim 14.

16. A display device comprising a layer according to claim 14.

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