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

Abstract

Disclosed are an ink composition, a layer manufactured using the ink composition, and a display device including the ink composition. The ink composition comprises (A) semiconductor nanorods and (B) a mixed solvent that simultaneously satisfies three specific conditions.

Description

Technical Field

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

[0002] Since 1992, when Nakamura et al. at Nichia Corp. successfully fused high-quality single-crystal GaN nitride semiconductors using a low-temperature GaN compound buffer layer, light-emitting diodes (LEDs) have been actively developed. LEDs are semiconductor devices that utilize the properties of compound semiconductors to convert electrical signals into light within a desired wavelength range. They have a structure in which an n-type semiconductor crystal, where the majority of carriers are electrons, is bonded to a p-type semiconductor crystal, where the majority of carriers are holes.

[0003] Such LED semiconductors have high light conversion efficiency, consuming very little energy and possessing a semi-permanent lifespan. Furthermore, they are environmentally friendly and, as such, are considered a green material, often referred to as a revolution in light. Recently, with the advancement of compound semiconductor technology, high-brightness red, orange, green, blue, and white LEDs have been developed and are being applied to a wide range of fields, such as traffic lights, mobile phones, car headlights, outdoor billboards, liquid crystal display backlight units (LCD BLUs), and indoor / outdoor lighting. Active research is underway both domestically and internationally. Specifically, wide-bandgap GaN-based compound semiconductors are materials used to manufacture LED semiconductors that emit light in the green, blue, and ultraviolet (UV) regions. Since blue LED devices are often used to manufacture white LED devices, extensive research has been conducted on this topic.

[0004] Within this series of research, research into the use of ultra-small LED devices with nanometer or micrometer dimensions is actively underway, and research into utilizing these ultra-small LED devices in lighting and displays continues. Within this research, attention continues to be focused on electrodes capable of supplying power to ultra-small LED devices, electrode placement methods for reducing the space occupied by electrodes, and methods for mounting ultra-small LED devices on these electrodes.

[0005] However, due to the size limitations of ultra-small LED devices, the method of mounting ultra-small LED devices on electrodes still has difficulty in positioning and mounting the ultra-small LED devices on electrodes as intended. This is because ultra-small LED devices are nano-scale or micro-scale and therefore cannot be manually positioned and mounted one by one on the target electrode area.

[0006] Recently, with the increasing demand for nanoscale, ultra-small LED devices, attempts have been made to manufacture nanoscale GaN-based or InGaN-based compound semiconductors into rods. However, the dispersion stability of the nanorods themselves in solvents (or polymerizable compounds) can be significantly reduced. Furthermore, to date, no technology has been introduced that can improve the dispersion stability of semiconductor nanorods in solvents (or polymerizable compounds). Therefore, research continues on ink compositions containing semiconductor nanorods that can improve the dispersion stability of semiconductor nanorods in solvents (or polymerizable compounds) and achieve high dielectrophoresis rates. Summary of the Invention

[0007] Technical issues

[0008] The embodiment provides an ink composition having excellent migration properties and storage stability of semiconductor nanorods.

[0009] Another embodiment provides a layer manufactured using the ink composition.

[0010] Another embodiment provides a display device including the layer.

[0011] Technical Solution

[0012] The embodiment provides an ink composition, comprising (A) semiconductor nanorods; and (B) a mixed solvent, and simultaneously satisfying the following conditions i), ii), and iii).

[0013] i) Dielectric constant less than or equal to 20,

[0014] ii) a viscosity of 60 centipoise (cps) to 110 cps, and

[0015] iii) The volatilization temperature is 200°C to 400°C.

[0016] The solvent may include two or more of the compounds represented by Chemical Formula 1 to Chemical Formula 7.

[0017] [Chemical Formula 1]

[0018]

[0019] [Chemical Formula 2]

[0020]

[0021] [Chemical Formula 3]

[0022]

[0023] [Chemical Formula 4]

[0024]

[0025] [Chemical Formula 5]

[0026]

[0027] [Chemical Formula 6]

[0028]

[0029] [Chemical Formula 7]

[0030]

[0031] The semiconductor nanorods may have a diameter of 300 nanometers to 900 nanometers.

[0032] The semiconductor nanorods may have a length of 3.5 micrometers to 5 micrometers.

[0033] The semiconductor nanorods may include GaN-based compounds, InGaN-based compounds, or a combination thereof.

[0034] The semiconductor nanorods may have a surface coated with a metal oxide.

[0035] The metal oxide may include aluminum oxide, silicon dioxide, or a combination thereof.

[0036] The semiconductor nanorods may be included in an amount of 0.01 wt % to 10 wt % based on the total amount of the ink composition.

[0037] The ink composition may further include malonic acid; 3-amino-1,2-propanediol; a silane coupling agent; a leveling agent; a fluorine-based surfactant; or a combination thereof.

[0038] The ink composition may be an ink composition for an electrophoretic device.

[0039] Another embodiment provides a layer manufactured using the ink composition.

[0040] Another embodiment provides a display device including the layer.

[0041] Other embodiments of the invention are included in the detailed description that follows.

[0042] Beneficial effects

[0043] The ink composition including semiconductor nanorods according to the embodiment may have excellent migration properties and storage stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 is an example of a cross-sectional view of a semiconductor nanorod used in the ink composition according to the embodiment. DETAILED DESCRIPTION

[0045] Hereinafter, embodiments of the present invention are described in detail. However, these embodiments are exemplary and the present invention is not limited thereto, and the present invention is defined by the scope of the claims.

[0046] As used herein, when a specific definition is not otherwise provided, “alkyl” refers to a C1 to C20 alkyl group, “alkenyl” refers to a C2 to C20 alkenyl group, “cycloalkenyl” refers to a C3 to C20 cycloalkenyl group, “heterocycloalkenyl” refers to a C3 to C20 heterocycloalkenyl group, “aryl” refers to a C6 to C20 aryl group, “arylalkyl” refers to a C6 to C20 arylalkyl group, “alkylene” refers to a C1 to C20 alkylene group, “arylene” refers to a C6 to C20 arylene group, “alkylarylene” refers to a C6 to C20 alkylarylene group, “heteroarylene” refers to a C3 to C20 heteroarylene group, and “alkyleneoxy” refers to a C1 to C20 alkyleneoxy group.

[0047] As used herein, when a specific definition is not otherwise provided, “substituted” means that at least one hydrogen is replaced by a halogen atom (F, Cl, Br or I), a hydroxyl group, a C1 to C20 alkoxy group, a nitro group, a cyano group, an amino group, an imino group, an azide 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 phosphate group or a salt thereof, a C1 to C20 alkyl group, a C2 to C20 alkenyl group, a C2 to C20 alkynyl group, a C6 to C20 aryl group, a C3 to C20 cycloalkyl group, a C3 to C20 cycloalkenyl group, a C3 to C20 cycloalkynyl group, a C2 to C20 heterocycloalkyl group, a C2 to C20 heterocycloalkenyl group, a C2 to C20 heterocycloalkynyl group, a C3 to C20 heteroaryl group, or a combination thereof.

[0048] As used herein, when a specific definition is not otherwise provided, "hetero" refers to a group including at least one heteroatom selected from N, O, S and P in a chemical formula.

[0049] As used herein, when specific definitions are not otherwise provided, “(meth)acrylate” refers to both “acrylate” and “methacrylate”, and “(meth)acrylic acid” refers to both “acrylic acid” and “methacrylic acid”.

[0050] As used herein, when no specific definition is otherwise provided, "combination" means mixing or copolymerization.

[0051] As used herein, unless a specific definition is provided otherwise, when a chemical bond is not drawn at a position where a chemical bond should be drawn, a hydrogen atom is bonded to the position.

[0052] As used herein, "semiconductor nanorods" refers to rod-shaped semiconductors having a nanometer-sized diameter.

[0053] As used herein, the volatilization temperature means the temperature at which all the solvent is volatilized.

[0054] As used herein, when a specific definition is not otherwise provided, "*" indicates a point of attachment to which the same or different atoms or chemical formulas are attached.

[0055] The ink composition according to the embodiment includes (A) semiconductor nanorods; and (B) a mixed solvent, and satisfies the following three conditions (i, ii, and iii):

[0056] i) Dielectric constant less than or equal to 20,

[0057] ii) a viscosity of 60 centipoise to 110 centipoise, and

[0058] iii) The volatilization temperature is 200°C to 400°C.

[0059] Recently, research has been actively conducted on various concepts that can improve the energy efficiency of conventional LEDs, such as micro-LEDs, mini-LEDs, and similar LEDs, and prevent their efficiency from decreasing. Among these, alignment (electrophoresis) of InGaN-based nanorod LEDs using an electric field has attracted attention as a method for significantly reducing the complexity and expensive manufacturing process costs of micro-LEDs, mini-LEDs, and similar LEDs.

[0060] However, organic solvents conventionally used in display and electronic materials (propylene glycol monomethyl ether acetate (PGMEA), gamma-butyrolactone (GBL), polyethylene glycol methyl ether (PGME), ethyl acetate, isopropyl alcohol (IPA), and the like) have low viscosity, and thus inorganic nanorod particles having a high density may settle too quickly and thus agglomerate, and in addition, the organic solvents may evaporate quickly and thus alignment characteristics may deteriorate during solvent drying after dielectrophoresis. Therefore, in order to develop an ink composition containing inorganic material nanorods (semiconductor nanorods), a solvent with high viscosity and high boiling point and therefore excellent dielectrophoretic properties is required to improve the sedimentation stability of the nanorods. After many experiments, the inventors of the present invention significantly improved the migration properties and especially the normal alignment degree of the semiconductor nanorods in the ink composition, while maintaining the inkjet properties of the ink composition, and also achieved excellent storage stability by limiting the solvent used with the semiconductor nanorods to a three-component system.

[0061] Hereinafter, each component will be described in detail.

[0062] (A) Semiconductor nanorods

[0063] The semiconductor nanorods may include GaN-based compounds, InGaN-based compounds, or a combination thereof, and their surfaces may be coated with a metal oxide.

[0064] Ensuring the dispersion stability of the semiconductor nanorod ink solution (semiconductor nanorods + solvent) typically takes three hours, which is insufficient for large-area inkjet processing. Therefore, after numerous experiments, the inventors developed an insulating film (Al2O3 or SiOx) by coating the surface of the semiconductor nanorods with a metal oxide (e.g., aluminum oxide, silicon dioxide, or a combination thereof) to maximize compatibility with the solvents described below.

[0065] For example, the insulating film coated with metal oxide may have a thickness of 40 nm to 60 nm.

[0066] The semiconductor nanorods include an n-type confinement layer and a p-type confinement layer, and a multi-quantum well (MQW) active region can be disposed between the n-type confinement layer and the p-type confinement layer.

[0067] For example, semiconductor nanorods may have a diameter of 300 nm to 900 nm, such as 600 nm to 700 nm.

[0068] For example, the semiconductor nanorods may have a length of 3.5 microns to 5 microns.

[0069] For example, when the semiconductor nanorods include an aluminum oxide insulating layer, they may have a density of 5 g / cm 3 to 6 g / cm 3 .

[0070] For example, the semiconductor nanorods may have a mass of 1×10 −13 to 1×10 −11 grams.

[0071] When the semiconductor nanorods have the above-described diameter, length, density, and type, surface coating of the metal oxide can be easily performed, so that the dispersion stability of the semiconductor nanorods can be maximized.

[0072] The semiconductor nanorods may be included in an amount of 0.01 to 10% by weight, for example, 0.01 to 5% by weight, based on the total weight of the ink composition. Alternatively, the semiconductor nanorods may be included in an amount of 0.01 to 0.5 parts by weight, for example, 0.01 to 0.1 parts by weight, based on 100 parts by weight of the solvent in the ink composition. When the semiconductor nanorods are included within this range, they are well dispersed in the ink, and the resulting pattern can have excellent brightness.

[0073] (B) Solvent

[0074] The ink composition according to the embodiment includes a mixed solvent that satisfies the above three conditions simultaneously.

[0075] In recent years, with the growing demand for nanoscale micro-LED devices, attempts have been made to manufacture nanoscale GaN-based or InGaN-based compound semiconductors into rods. However, the nanorods themselves suffer from a significant degradation in dispersion stability in solvents (or polymerizable compounds). To date, no technology has been introduced to improve the dispersion stability of semiconductor nanorods in solvents (or polymerizable compounds).

[0076] Organic solvents used in conventional displays and electronic materials (e.g., propylene glycol monomethyl ether acetate (PGMEA), γ-butyrolactone (GBL), polyethylene glycol methyl ether (PGME), ethyl acetate, isopropyl alcohol (IPA), and the like) have low viscosities, causing high-density inorganic nanorod particles to settle too quickly, resulting in unsatisfactory dielectrophoretic properties. Therefore, as described above, in order to develop an ink composition containing inorganic nanorods (semiconductor nanorods) for electrophoretic devices, a solvent that can impart sedimentation stability to the nanorods should be used.

[0077] Specifically, in order to improve the storage stability of the nanorods and impart sedimentation stability to the nanorods, the solvent is controlled to have a dielectric constant less than or equal to 20 and a viscosity of 60 to 110 centipoise, and at the same time should be completely volatilized from the composition at 200° C. to 400° C. during drying.

[0078] Since the solvent in the ink composition according to the embodiment satisfies the aforementioned conditions regarding dielectric constant, viscosity, and evaporation temperature, the nanorods can have a normal alignment greater than or equal to 80% and a storage stability greater than or equal to 7 hours.

[0079] For example, the solvent may include two or more of the compounds represented by Chemical Formula 1 to Chemical Formula 7.

[0080] [Chemical Formula 1]

[0081]

[0082] [Chemical Formula 2]

[0083]

[0084] [Chemical Formula 3]

[0085]

[0086] [Chemical Formula 4]

[0087]

[0088] [Chemical Formula 5]

[0089]

[0090] [Chemical Formula 6]

[0091]

[0092] [Chemical Formula 7]

[0093]

[0094] The solvent may be included in an amount of 15 wt % to 99.99 wt %, for example, 20 wt % to 99.7 wt %, based on the total amount of the ink composition.

[0095] polymerizable monomers

[0096] The ink composition according to the embodiment may further include a polymerizable compound. The polymerizable compound may be used by mixing monomers or oligomers generally used in conventional curable compositions.

[0097] For example, the polymerizable compound may be a polymerizable monomer having a carbon-carbon double bond at a terminal end.

[0098] For example, the polymerizable compound may be a polymerizable monomer having at least one of the functional group represented by Chemical Formula A-1 or the functional group represented by Chemical Formula A-2 at the terminal.

[0099] [Chemical Formula A-1]

[0100]

[0101] [Chemical Formula A-2]

[0102]

[0103] In Chemical Formula A-1 and Chemical Formula A-2,

[0104] L1 is a substituted or unsubstituted C1 to C20 alkylene group, and

[0105] R4 is a hydrogen atom or a substituted or unsubstituted C1 to C20 alkyl group.

[0106] The polymerizable compound can form a crosslinked structure with the surface-modifying compound by including at least one carbon-carbon double bond, specifically a functional group represented by Chemical Formula A-1 or a functional group represented by Chemical Formula A-2. The crosslinked structure can further improve the dispersion stability of the semiconductor nanorods by doubling one type of steric hindrance effect.

[0107] For example, examples of the polymerizable compound including at least one functional group represented by Chemical Formula A-1 at the terminal may include divinylbenzene, triallyl cyanurate, triallyl isocyanurate, triallyl trimellitate, triallyl phosphate, triallyl phosphite, triallyl triazine, diallyl phthalate, or a combination thereof, but are not necessarily limited thereto.

[0108] For example, the polymerizable compound including at least one functional group represented by Chemical Formula A-2 at the terminal may include 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 manufactured by Japan Chemical Co., Ltd. DPCA-20, KAYARAD DPCA-30, KAYARAD DPCA-60, KAYARAD DPCA-120, KAYARAD DPCA-12 or a combination thereof, but not necessarily limited thereto.

[0109] In order to impart more excellent developability, the polymerizable compound may be treated with an acid anhydride.

[0110] Polymerization initiator

[0111] The ink composition according to the embodiment may further include a polymerization initiator, such as a photopolymerization initiator, a thermal polymerization initiator, or a combination thereof.

[0112] The photopolymerization initiator may be an initiator commonly used in curable compositions, such as acetophenone-based compounds, benzophenone-based compounds, thioxanthone-based compounds, benzoin-based compounds, triazine-based compounds, oxime-based compounds, and aminoketone-based compounds, but is not necessarily limited thereto.

[0113] Examples of the acetophenone-based compound may 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-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one, and the like.

[0114] Examples of the benzophenone-based compound may 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.

[0115] Examples of the thioxanthone-based compound may include thioxanthone, 2-methylthioxanthone, isopropylthioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, 2-chlorothioxanthone, and the like.

[0116] Examples of the benzoin-based compound may include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzyl dimethyl ketal, and the like.

[0117] Examples of triazine compounds 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, 2-(p-tolyl)-4,6-bis(trichloromethyl)-s-triazine, triazine, 2-biphenyl-4,6-bis(trichloromethyl)-s-triazine, bis(trichloromethyl)-6-phenylvinyl-s-triazine, 2-(naphtho-1-yl)-4,6-bis(trichloromethyl)-s-triazine, 2-(4-methoxynaphthol-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 and the like.

[0118] Examples of the oxime compound may include O-acyl oxime compounds, 2-(O-benzoyloxime)-1-[4-(phenylthio)phenyl]-1,2-octanedione, 1-(O-acetyloxime)-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-based compounds may include 1,2-octanedione, 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one, 1-(4-phenylthiophenyl)-butan-1,2-dione-2-oxime-O-benzoate, 1-(4-phenylthiophenyl)-octan-1,2-dione-2-oxime-O-benzoate, 1-(4-phenylthiophenyl)-octan-1-one oxime-O-acetate, 1-(4-phenylthiophenyl)-butan-1-one oxime-O-acetate, and the like.

[0119] Examples of the aminoketone-based compound may include 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1-.

[0120] The photopolymerization initiator may further include a carbazole-based compound, a diketone-based compound, a sulfonium borate-based compound, a diazo-based compound, an imidazole-based compound, a biimidazole-based compound, and the like in addition to the above-mentioned compounds.

[0121] The photopolymerization initiator may be used together with a photosensitizer capable of causing a chemical reaction by absorbing light and becoming excited and then transmitting its energy.

[0122] Examples of the photosensitizer may be tetraethylene glycol bis-3-mercaptopropionate, pentaerythritol tetrakis-3-mercaptopropionate, dipentaerythritol tetrakis-3-mercaptopropionate, and the like.

[0123] Examples of thermal polymerization initiators include peroxides, specifically benzoyl peroxide, dibenzoyl peroxide, lauroyl peroxide, dilauroyl peroxide, di-t-butyl peroxide, cyclohexane peroxide, methyl ethyl ketone peroxide, hydroperoxides (e.g., t-butyl hydroperoxide, cumene hydroperoxide), dicyclohexyl peroxydicarbonate, 2,2-azobis(isobutyronitrile), t-butyl perbenzoate, and the like. Examples include 2,2′-azobis-2-methylpropionitrile, and the like, but are not necessarily limited thereto and may include any initiator known in the art.

[0124] The polymerization initiator may be included in an amount of 1 to 5 wt %, for example, 2 to 4 wt %, based on the total solids content of the ink composition. When the polymerization initiator is included within this range, the ink composition can be sufficiently cured during exposure or thermal curing, thereby achieving excellent reliability.

[0125] Other additives

[0126] The ink composition according to the embodiment may further include a polymerization inhibitor including a hydroquinone compound, a catechol compound, or a combination thereof. Since the ink composition according to the embodiment further includes a hydroquinone compound, a catechol compound, or a combination thereof, crosslinking at room temperature can be prevented during exposure after the ink composition is printed (applied).

[0127] For example, the hydroquinone-based compound, the catechol-based compound, or a combination thereof may include hydroquinone, methylhydroquinone, methoxyhydroquinone, t-butylhydroquinone, 2,5-di-t-butylhydroquinone, 2,5-bis(1,1-dimethylbutyl)hydroquinone, 2,5-bis(1,1,3,3-tetramethylbutyl)hydroquinone, catechol, t-butylcatechol, 4-methoxyphenol, gallol, 2,6-di-t-butyl-4-methylphenol, 2-naphthol, tris(N-hydroxy-N-nitrosophenylamino-O,O')aluminum, or a combination thereof, but is not necessarily limited thereto.

[0128] The hydroquinone compound, catechol compound, or combination thereof may be used in a dispersion form. A dispersion-type polymerization inhibitor may be included in an amount of 0.001% to 1% by weight, for example, 0.01% to 0.1% by weight, based on the total weight of the ink composition. Including a stabilizer within this range can address room temperature aging issues and prevent sensitivity loss and surface peeling.

[0129] In addition to the polymerization inhibitor, the ink composition according to the embodiment may further include malonic acid; 3-amino-1,2-propanediol; a silane coupling agent; a leveling agent; a fluorine-based surfactant; or a combination thereof.

[0130] For example, the ink composition may further include a silane coupling agent having a reactive substituent such as a carboxyl group, a methacryloyl group, an isocyanate group, an epoxy group, and the like to improve its adhesion to the substrate.

[0131] Examples of silane coupling agents include trimethoxysilylbenzoic acid, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, vinyltrimethoxysilane, γ-isocyanatepropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, β-(epoxycyclohexyl)ethyltrimethoxysilane, and the like. These coupling agents may be used alone or in combination of two or more.

[0132] The silane coupling agent may be included in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the ink composition. When the silane coupling agent is included within the above range, close contact properties, storage properties, and the like may be improved.

[0133] In addition, if necessary, the ink composition may further include a surfactant (eg, a fluorine-based surfactant) to improve coating and prevent defects.

[0134] Examples of fluorine-based surfactants include BM- and BM- Dainippon Ink Kagaku Kogyo Co., Ltd.'s MEGAFACE F Megafa F Megafa F and Megafa F Sumitomo 3M Co., Ltd.'s FULORAD FC- Florad FC- Florad FC- Florad FC- Asahi Glass Co., Ltd.'s SURFLON S- Saffron S- Saffron S- Saffron S- and Saffron S- and Toray Silicone Co., Ltd.'s SH- SH- SH- SZ- and SF- and similar products; F-482, F-484, F-478, F-554 and similar products of DIC Co., Ltd.

[0135] The fluorine-based surfactant may be included in an amount of 0.001 to 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, excellent wettability and coating uniformity on the glass substrate can be ensured, and stains can be prevented.

[0136] In addition, a certain amount of other additives (eg, antioxidants and stabilizers) may be added to the ink composition within a range that does not impair the physical properties.

[0137] Another embodiment provides a layer using the ink composition.

[0138] Another embodiment provides a display device comprising the layer, and for example, the display device may be an electrophoretic device.

[0139] Invention Mode

[0140] The present invention is described in more detail below with reference to examples, which, however, should not be construed as limiting the scope of the present invention in any sense.

[0141] (Preparation of ink composition)

[0142] Examples 1 to 8 and Comparative Examples 1 to 12

[0143] An InGaN wafer (4 inches) patterned with nanorods was reacted in 40 ml of stearic acid (1.5 millimoles / liter (mM)) at room temperature for 24 hours. After the reaction, the InGaN wafer patterned with nanorods was immersed in 50 ml of acetone for 5 minutes to remove excess stearic acid, and the surface of the wafer was rinsed with 40 ml of acetone. The cleaned wafer was placed in a 27 kW bath ultrasonic oscillator together with 35 ml of gamma-butyrolactone (GBL) and then ultrasonicated for 5 minutes to separate the rods from the wafer surface. The separated rods were placed in a FALCON tube and centrifuged, and 10 ml of GBL was added thereto to additionally wash the rods on the surface of the bath. The supernatant was then discarded by centrifugation at 4000 rpm for 10 minutes, and the precipitate therein was redispersed in 40 ml of acetone and filtered with a 10 micron mesh filter. After additional centrifugation (4000 rpm, 10 minutes), the precipitate was dried in a drying oven (100° C., 1 hour), weighed, and dispersed to 0.05 w / w % to prepare each ink composition having the composition shown in Table 1.

[0144] (The composition of the mixed solvent and the dielectric constant, viscosity, and evaporation temperature of the solvent are shown in Tables 2 and 3.)

[0145] [Table 1]

[0146] (Unit: weight %)

[0147]

[0148] [Table 2]

[0149]

[0150] [Table 3]

[0151]

[0152] The dielectric constant of each mixed solvent was measured by placing 40 ml of each solvent composition according to the Examples and Comparative Examples in a conical tube and using a liquid dielectric constant measuring device (Model 871, Furuto Industrial Co., Ltd.) at room temperature (25° C.), and the viscosity was measured by filling 2 ml of the solvent composition and using a rheometer (Haake Technik GmbH) at room temperature (25° C.).

[0153] Evaluation: Dielectrophoretic properties and storage stability

[0154] (1) Dielectrophoretic properties

[0155] 500 μl of the ink compositions of Examples 1 to 8 and Comparative Examples 1 to 12 were each applied to a thin-film gold basic interdigitated linear electrode (ED-cIDE4-Au, Micrux Technologies). An electric field (25 kHz, ±30 volts) was applied and the electrodes were allowed to stand for 1 minute. The solvent was then dried using a hot plate, and the electrodes were examined microscopically to count the number of aligned nanorod particles (e) and the number of unaligned nanorod particles (e) in the center between the electrodes. The dielectrophoretic properties were evaluated, as shown in Tables 4 and 5.

[0156] (2) Storage stability

[0157] 10 ml of each of the ink compositions of Examples 1 to 8 and Comparative Examples 1 to 12 were taken and placed in a test tube (diameter: 1 cm, height: 13 cm), and then measured with reference to the time for bottom sediment to be generated at room temperature (25°C). The results are shown in Tables 4 and 5.

[0158] [Table 4]

[0159] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Dielectrophoresis (%) 91 95 93 82 83 81 90 82 Storage stability (hours) >7 >7 >7 >7 >7 >7 >7 >7

[0160] [Table 5]

[0161]

[0162] As shown in Table 4 and Table 5, compared with Comparative Examples 1 to 12, Examples 1 to 8 exhibited excellent dielectrophoretic properties and storage stability.

[0163] Although the present invention has been described in conjunction with what are presently considered to be feasible exemplary embodiments, it should be understood that the present 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. Therefore, the above embodiments should be understood as illustrative and not limiting in any way.

Claims

1. An ink composition comprising: (A) semiconductor nanorods; and (B) a mixed solvent that satisfies the following conditions i), ii), and iii) at the same time: i) Dielectric constant less than or equal to 20, ii) a viscosity of 60 centipoise to 110 centipoise, and iii) Volatility temperature is 200°C to 400°C, The mixed solvent comprises two or more compounds represented by Chemical Formula 1 to Chemical Formula 7: [Chemical Formula 1] [Chemical Formula 2] [Chemical Formula 3] [Chemical Formula 4] [Chemical Formula 5] [Chemical Formula 6] [Chemical Formula 7] 2 . The ink composition according to claim 1 , wherein the semiconductor nanorods have a diameter of 300 nm to 900 nm. 3 . The ink composition according to claim 1 , wherein the semiconductor nanorods have a length of 3.5 μm to 5 μm. 4 . The ink composition according to claim 1 , wherein the semiconductor nanorods comprise GaN-based compounds, InGaN-based compounds, or a combination thereof. The ink composition according to claim 1 , wherein the semiconductor nanorods have a surface coated with a metal oxide. The ink composition according to claim 5 , wherein the metal oxide comprises aluminum oxide, silicon dioxide, or a combination thereof. 7 . The ink composition according to claim 1 , wherein the content of the semiconductor nanorods is 0.01 wt % to 10 wt % based on the total weight of the ink composition.

8. The ink composition according to claim 1, wherein the ink composition further comprises malonic acid; 3-amino-1,2-propanediol; a silane coupling agent; a leveling agent; a fluorine-based surfactant; or a combination thereof. 9 . The ink composition according to claim 1 , wherein the ink composition is an ink composition for an electrophoretic device. 10 . A layer produced using the ink composition according to claim 1 .

11. A display device comprising the layer according to claim 10.

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