Ink composition, layer using the same, and display device

Abstract

An ink composition, a layer manufactured using the ink composition, and a display device including the layer are disclosed. The ink composition includes: (A) semiconductor nanorods; and (B) a solvent including at least one glycol compound, wherein the ink composition has a viscosity greater than or equal to 50 centipoise at 20 to 25°C, and a viscosity less than or equal to 20 centipoise at 35 to 65°C.

Description

TECHNICAL FIELD

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

[0002] Since Nakamura and others from Nichia Crop succeeded in fusing a high-quality single-crystal GaN nitride semiconductor by applying a low-temperature GaN compound buffer layer in 1992, LEDs have been actively developed. An LED is a semiconductor device that converts an electrical signal 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] Such an LED semiconductor has high light conversion efficiency, and thus consumes little energy and has a semi-permanent life, and is also environmentally friendly and thus called a light revolution as a green material. Recently, as compound semiconductor technology has developed, high-brightness red, orange, green, blue, and white LEDs have been developed and applied to many fields, such as traffic lights, mobile phones, car headlights, outdoor billboards, LCD back light units (BLUs), and indoor / outdoor lighting, and active research has been conducted on this both at home and abroad. In particular, GaN-based compound semiconductors having a wide band gap are materials for manufacturing LED semiconductors that emit light in the green, blue, and ultraviolet (UV) regions, and since a blue LED device is used to manufacture a white LED device, much research is being conducted on this.

[0004] In this series of research, research using ultra-small LED devices having a nano or micrometer unit size is actively being conducted, and in addition, research utilizing such ultra-small LED devices in lighting and displays is continuously being conducted. In this research, electrodes that can apply power to ultra-small LED devices, the disposition of electrodes for reducing the space occupied by the electrodes, methods of mounting ultra-small LED devices on disposed electrodes, and the like are continuously attracting attention.

[0005] Among them, due to the size limitation of the ultra-small LED device, the method of mounting the ultra-small LED device on the disposed electrode is still difficult to dispose and mount the ultra-small LED device on the electrode as intended. The reason is that the ultra-small LED device is nanoscale or micrometer scale, and thus can not be disposed and mounted in the target electrode region one by one manually.

[0006] Recently, as the demand for a nanoscale ultra-small LED device increases, attempts have been made to make a nanoscale GaN-based or InGaN-based compound semiconductor into a rod, but there is a problem in that the dispersion stability of the nanorod itself in a solution (or a polymerizable compound) is greatly reduced. However, the dispersion stability in the solution can be greatly reduced due to the large particle size of the nanorod itself. And so far, a technology capable of improving the dispersion stability of the semiconductor nanorod in the solution has not been introduced. SUMMARY

[0007] TECHNICAL PROBLEM

[0008] Embodiments provide an ink composition having a high viscosity at room temperature to impart settling stability to a semiconductor nanorod, and at the same time, having a low viscosity at a high temperature to provide excellent inkjet properties.

[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] Embodiments provide an ink composition including: (A) a semiconductor nanorod; and (B) a solvent including at least one glycol-based compound, wherein the ink composition has a viscosity greater than or equal to 50 centipoises at 20°C to 25°C, and has a viscosity less than or equal to 20 centipoises at 35°C to 65°C.

[0013] The glycol-based compound can be represented by Chemical Formula 1.

[0014] [Chemical Formula 1]

[0015]

[0016] In Chemical Formula 1,

[0017] R 1 and R 2 are each independently hydrogen, a substituted or unsubstituted C1 to C20 alkyl group, a substituted or unsubstituted C3 to C20 cycloalkyl group, or a substituted or unsubstituted C6 to C20 aryl group, and

[0018] L 1 is a substituted or unsubstituted C1 to C20 alkylene group.

[0019] The glycol-based compound can include at least one of the compounds represented by Chemical Formula 1-1 to Chemical Formula 1-5.

[0020] [Chemical Formula 1-1]

[0021]

[0022] [Chemical Formula 1-2]

[0023]

[0024] [Chemical Formula 1-3]

[0025]

[0026] [Chemical Formula 1-4]

[0027]

[0028] [Chemical Formula 1-5]

[0029]

[0030] The solvent can further include a compound represented by Chemical Formula 2 or Chemical Formula 3.

[0031] [Chemical Formula 2]

[0032]

[0033] [Chemical Formula 3]

[0034]

[0035] In Chemical Formula 2 and Chemical Formula 3,

[0036] R 3 to R 5 each independently is a substituted or unsubstituted C1 to C20 alkyl, and

[0037] R 6 to R 8 each independently is a substituted or unsubstituted C1 to C20 alkoxy.

[0038] In Chemical Formula 2, R 3 to R 5 may each independently be a C2 to C10 alkenyl-substituted or unsubstituted C1 to C20 alkyl.

[0039] In Chemical Formula 3, R 6 to R 8 may each independently be a C2 to C10 alkenyl-substituted or unsubstituted C1 to C20 alkoxy.

[0040] The compound represented by Chemical Formula 2 can include at least one selected from Chemical Formula 2-1 and Chemical Formula 2-2.

[0041] [Chemical Formula 2-1]

[0042]

[0043] [Chemical Formula 2-2]

[0044]

[0045] The compound represented by Chemical Formula 3 can include at least one selected from the compounds represented by Chemical Formula 3-1 and Chemical Formula 3-2.

[0046] [Chemical Formula 3-1]

[0047]

[0048] [Chemical Formula 3-2]

[0049]

[0050] The compound represented by Chemical Formula 2 or Chemical Formula 3 can be included in an amount less than the compound having a diol structure.

[0051] The solvent can further include a compound represented by Chemical Formula 4.

[0052] [Chemical Formula 4]

[0053]

[0054] In Chemical Formula 4,

[0055] R 9 to R 11 each independently is a hydrogen atom or a C1 to C10 alkyl group,

[0056] R 12 is a hydrogen atom or * -C(=O)R 13 (R 13 is a C1 to C10 alkyl group),

[0057] L 16 and L 17 each independently is a substituted or unsubstituted C1 to C20 alkylene group or a substituted or unsubstituted C6 to C20 arylene group, and

[0058] L 18 is a -O-*, -S-*, or -NH-*.

[0059] The diol compound and the compound represented by Chemical Formula 4 can be included in a weight ratio of 3:7 to 8:2.

[0060] The semiconductor nanorod can have a diameter of 300 nm to 900 nm.

[0061] The semiconductor nanorods can have a length of 3.5 microns to 5 microns.

[0062] The semiconductor nanorods can include a GaN-based compound, an InGaN-based compound, or a combination thereof.

[0063] The semiconductor nanorods can have a surface coated with a metal oxide.

[0064] The metal oxide can include aluminum oxide, silicon oxide, or a combination thereof.

[0065] The semiconductor nanorods can be included in an amount of 0.01 wt% to 10 wt% based on a total amount of the ink composition.

[0066] The ink composition can further include a polymerization inhibitor, malonic acid, 3-amino-1,2-propanediol, a silane-based coupling agent, a leveling agent, a fluorine-based surfactant, or a combination thereof.

[0067] The ink composition can be an ink composition for an electrophoretic device.

[0068] Another embodiment provides a layer manufactured using the ink composition.

[0069] Another embodiment provides a display device including the layer.

[0070] Other embodiments of the present invention include those described in the following detailed description.

[0071] Advantages

[0072] According to embodiments, the ink composition can have both excellent dielectrophoretic properties and dispersion stability of the semiconductor nanorods. BRIEF DESCRIPTION OF DRAWINGS

[0073] Figure 1 An example of a cross-sectional view of a semiconductor nanorod for an ink composition according to embodiments. DETAILED DESCRIPTION

[0074] Hereinafter, embodiments of the present invention are described in detail. However, these embodiments are illustrative, the present invention is not limited thereto and the present invention is defined by the scope of claims.

[0075] As used herein, unless otherwise specified, “alkyl” refers to C1 to C20 alkyl, “alkenyl” refers to C2 to C20 alkenyl, “cycloalkenyl” refers to C3 to C20 cycloalkenyl, “heterocyclic alkenyl” refers to C3 to C20 heterocyclic alkenyl, “aryl” refers to C6 to C20 aryl, “aranealkyl” refers to C6 to C20 aranealkyl, “alkylene” refers to C1 to C20 alkylene, “arylene” refers to C6 to C20 arylene, “alkylarylene” refers to C6 to C20 alkylarylene, “heteroarylene” refers to C3 to C20 heteroarylene, and “alkoxide” refers to C1 to C20 alkoxide.

[0076] As used herein, unless otherwise specifically defined, “substituted” means that at least one hydrogen atom 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, a formamidinyl group, a hydrazinyl group, a carbonyl group, a carboxyl 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 heterocyclic alkyl group, a C2 to C20 heterocyclic alkenyl group, a C2 to C20 heterocyclic alkynyl group, a C3 to C20 heteroaryl group, or a combination thereof.

[0077] As used herein, unless otherwise specifically defined, the term "heterogeneous" refers to a chemical formula containing at least one heteroatom selected from N, O, S, and P.

[0078] As used herein, unless otherwise specified, “(meth)acrylate” means both “acrylate” and “methacrylate”, and “(meth)acrylic acid” means both “acrylic acid” and “methacrylic acid”.

[0079] As used in this article, unless otherwise specified, “combination” means blending or copolymerization.

[0080] As used herein, unless otherwise specifically defined, hydrogen atoms are bonded at the locations where chemical bonds are not drawn where they should be.

[0081] As used in this article, "semiconductor nanorod" refers to a rod-shaped semiconductor with a diameter of nanometer size.

[0082] As used in this article, unless otherwise specifically defined, " * "Indicates the points that connect the same or different atoms or chemical formulas."

[0083] The ink composition according to the embodiment comprises: (A) semiconductor nanorods; and (B) a solvent comprising at least one glycol compound, wherein the ink composition has a viscosity greater than or equal to 50 centipoise at 20 to 25°C and a viscosity less than or equal to 20 centipoise at 35 to 65°C.

[0084] Recently, research on various concepts having improved energy efficiency and preventing effects of reducing the efficiency of conventional LEDs such as micro-LEDs, mini-LEDs, and the like has been actively conducted. Among them, the use of electric fields for alignment (electrophoresis) of InGaN-based nanorod LEDs has attracted attention as a method of significantly reducing the complexity and expensive process costs of micro-LEDs, mini-LEDs, and the like.

[0085] In order to coat semiconductor nanorods on a substrate for electrophoresis, a semiconductor nanorod dispersion should be jetted or slot-coated. In particular, for large-area coating and panel production, semiconductor nanorods should be uniformly coated, which can be achieved by ensuring the dispersion stability of a semiconductor nanorod solution. In addition, to improve the light-emitting efficiency of LEDs, a high electrophoretic rate is a necessary parameter. The present invention relates to a new type of inkjet ink composition capable of simultaneously achieving dispersion stability and a high electrophoretic rate of semiconductor nanorods.

[0086] Hereinafter, each component is described in detail.

[0087] (A) Semiconductor nanorods

[0088] The semiconductor nanorods can include a GaN-based compound, an InGaN-based compound, or a combination thereof, and the surface thereof can be coated with a metal oxide.

[0089] To ensure the dispersion stability of a semiconductor nanorod ink solution (semiconductor nanorods + solvent), it usually takes 3 hours, which is not enough to perform a large-area inkjet process. Therefore, the inventors of the present invention have developed an insulating film (Al2O3 or SiO x ) by coating a metal oxide such as alumina, silica, or a combination thereof on the surface of the semiconductor nanorods after a large number of trial-and-error studies to maximize the compatibility with the solvent described below.

[0090] For example, the insulating film coated with a metal oxide can have a thickness of 40 to 60 nm.

[0091] 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. (Refer to FIG. 1) Figure 1

[0092] ​For example, the semiconductor nanorod can have a diameter of 300 nm to 900 nm, for example, 600 nm to 700 nm.

[0093] For example, the semiconductor nanorod can have a length of 3.5 μm to 5 μm.

[0094] For example, when the semiconductor nanorod can include an aluminum oxide insulating layer, it can have a density of 5 g / cm3to 6 g / cm3.

[0095] For example, the semiconductor nanorod can have a mass of 1 x 10 -13 g to 1 x 10 -11 g.

[0096] When the semiconductor nanorod has the above diameter, length, density, and type, surface coating of the metal oxide can be easily performed, so that the dispersion stability of the semiconductor nanorod can be maximized.

[0097] The semiconductor nanorod can be included in an amount of 0.01 wt% to 10 wt%, for example, 0.02 wt% to 8 wt%, for example, 0.03 wt% to 5 wt%, based on the total amount of the ink composition. When the semiconductor nanorod is included in the above range, the dispersion in the ink is good, and the pattern prepared can have excellent brightness.

[0098] (B) Solvent

[0099] The ink composition according to the embodiment includes a solvent.

[0100] Organic solvents such as propylene glycol monomethyl ether acetate (PEGMEA), Y-butyrolactone (GBL), polyethylene glycol methyl ether (PGME), ethyl acetate, isopropyl alcohol (IPA), and the like, which have been used in conventional displays and electronic materials, have a very low viscosity so that inorganic material nanorod particles having a high density are settled too fast, thereby generating unsatisfactory dielectrophoresis properties. Therefore, in order to develop a nanorod led (NED) ink, a solvent capable of imparting settlement stability should be used. However, a solvent having only a high viscosity has a problem of not being jetted during inkjet. To improve this problem, the present inventors have developed a solvent having a high viscosity at room temperature but at the same time having a low viscosity at a temperature higher than room temperature by increasing the inkjet temperature, and finally completed an ink composition including a solvent having such characteristics.

[0101] Specifically, the embodiments introduce compounds having a diol structure with hydrogen bonds into the solvent to ensure both increased viscosity and decreased viscosity of the ink composition at temperatures above room temperature. However, when compounds having hydrogen-bonded structures other than diol structures, such as compounds having a polyol structure with three or more hydroxyl groups, are introduced into the solvent, the solvent may be unsuitable for use in the ink composition according to the embodiments because the dielectric constant is too high to reduce the dielectric properties.

[0102] When the viscosity of the solvent is high at room temperature, the dispersion stability can be maintained for 10 hours or more. In order to maintain dispersion stability over a long period of time, it is desirable for the solvent to have the highest possible viscosity at room temperature, and specifically, a viscosity of 50 centipoise or higher (e.g., 50 centipoise to 2,000 centipoise) at 20°C to 25°C.

[0103] More specifically, in order to ensure inkjet characteristics, the viscosity of the solvent at high temperatures (35°C to 65°C, for example 40°C to 50°C) should be 20 centipoise or less (for example 1 centipoise to 20 centipoise). In order to ensure that the solvent has a large viscosity difference between room temperature (for example 20°C to 25°C) and high temperature, diol compounds represented by chemical formula 1 can be applied alone or as a mixture to control dielectric constant and viscosity.

[0104] [Chemical Formula 1]

[0105]

[0106] In chemical formula 1,

[0107] R 1 and R 2 Each is independently hydrogen, a substituted or unsubstituted C1 to C20 alkyl, a substituted or unsubstituted C3 to C20 cycloalkyl, or a substituted or unsubstituted C6 to C20 aryl, and

[0108] L 1 It is a substituted or unsubstituted C1 to C20 alkylene group.

[0109] For example, diols may include, but are not limited to, at least one of the compounds represented by chemical formulas 1-1 to 1-5.

[0110] [Chemical Formula 1-1]

[0111]

[0112] [Chemical Formula 1-2]

[0113]

[0114] [Chemical Formula 1-3]

[0115]

[0116] [Chemical Formula 1-4]

[0117]

[0118] [Chemical Formula 1-5]

[0119]

[0120] For example, the diol compound can be contained in an amount of 20 to 85% by weight, for example, 30 to 80% by weight, based on the total amount of the ink composition. When the content of the compound having a diol structure is within the above range, the semiconductor nanorod dispersion stability can be improved while having a suitable dielectric constant.

[0121] For example, the solvent can further contain at least one or more of the compounds represented by Chemical Formula 2, Chemical Formula 3, and Chemical Formula 4.

[0122] [Chemical Formula]

[0123]

[0124] [Chemical Formula]

[0125]

[0126] [Chemical Formula]

[0127]

[0128] In Chemical Formula 2 to Chemical Formula 4,

[0129] R 3 to R 5 each independently is a substituted or unsubstituted C1 to C20 alkyl, and

[0130] R 6 to R 8 each independently is a substituted or unsubstituted C1 to C20 alkoxy.

[0131] R 9 to R 11 each independently is a hydrogen atom or a C1 to C10 alkyl,

[0132] R 12 is a hydrogen atom or * -C(=O)R 13 (R 13 is a C1 to C10 alkyl),

[0133] L 16 and L 17 each independently is a substituted or unsubstituted C1 to C20 alkylene or a substituted or unsubstituted C6 to C20 arylene, and

[0134] L 18 is *-O-*, *-S-* or *-NH-*.

[0135] For example, in Chemical Formula 2, R 3 to R 5 may each independently be a C1 to C20 alkyl substituted with or without C2 to C10 alkenyl.

[0136] For example, in Chemical Formula 3, R 6 to R 8 may each independently be a C1 to C20 alkoxy substituted with or without C2 to C10 alkenyl.

[0137] For example, the compound represented by Chemical Formula 2 can include at least one selected from Chemical Formula 2-1 and Chemical Formula 2-2, but is not necessarily limited thereto.

[0138] [Chemical Formula 2-1]

[0139]

[0140] [Chemical Formula 2-2]

[0141]

[0142] For example, the compound represented by Chemical Formula 3 can include at least one selected from the compounds represented by Chemical Formula 3-1 and Chemical Formula 3-2.

[0143] [Chemical Formula 3-1]

[0144]

[0145] [Chemical Formula 3-2]

[0146]

[0147] For example, the compound represented by Chemical Formula 4 can be citric acid.

[0148] For example, the compound represented by Chemical Formula 4 can be represented by any one of Chemical Formula 4-1 to Chemical Formula 4-6, but is not necessarily limited thereto.

[0149] [Chemical Formula 4-1]

[0150]

[0151] [Chemical Formula 4-2]

[0152]

[0153] [Chemical Formula 4-3]

[0154]

[0155] [Chemical Formula 4-4]

[0156]

[0157] [Chemical Formula 4-5]

[0158]

[0159] [Chemical Formula 4-6]

[0160]

[0161] For example, the compound represented by Chemical Formula 2 or Chemical Formula 3 can be contained in an amount less than that of the diol compound.

[0162] For example, the diol compound and the compound represented by Chemical Formula 4 can be contained in a weight ratio of 3:7 to 8:2.

[0163] Conventional organic solvents such as propylene glycol monomethyl ether acetate (PEGMEA), γ-butyrolactone (GBL), polyethylene glycol methyl ether (PGME), ethyl acetate, isopropyl alcohol (IPA), and the like have low viscosity, and thus have limitations in improving the settling stability of high-density semiconductor nanorods, but when at least one compound represented by Chemical Formula 2 to Chemical Formula 4 is additionally used together with the diol compound, the settling stability of the semiconductor nanorods can be greatly improved since the viscosity of the ink composition can be easily controlled at room temperature and at a temperature higher than room temperature, and in addition, a suitable dielectric constant can be secured, thereby greatly increasing the dielectrophoretic rate.

[0164] The solvent can be contained in an amount of 15% by weight to 99.9% by weight, for example, 15% by weight to 99.8% by weight, for example, 20% by weight to 99.7% by weight, based on the total amount of the ink composition.

[0165] Polymerizable monomer

[0166] The ink composition according to the embodiment can further include a polymerizable monomer having a carbon-carbon double bond at a terminal thereof.

[0167] The polymerizable monomer can be used by mixing monomers or oligomers generally used in conventional curable compositions.

[0168] For example, the polymerizable monomer can be a polymerizable monomer having at least one functional group represented by Chemical Formula 5 at a terminal end.

[0169] [Chemical Formula 5]

[0170]

[0171] In Chemical Formula 5,

[0172] R 14 is a hydrogen atom or a substituted or unsubstituted C1 to C20 alkyl group.

[0173] The polymerizable monomer includes at least one carbon-carbon double bond at a terminal end, in particular, at least one functional group represented by Chemical Formula 5, thereby forming a crosslinked structure having a semiconductor nanorod, further improving the dispersion stability of the semiconductor nanorod.

[0174] For example, the polymerizable monomer including at least one functional group represented by Chemical Formula 5 at a terminal end can be ethylene glycol diacrylate, triethylene glycol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, neopentatyl glycol diacrylate, neopentatyl glycol triacrylate, di-neopentatyl glycol diacrylate, di-neopentatyl glycol triacrylate, di-neopentatyl glycol pentaacrylate, di-neopentatyl glycol hexaacrylate, bisphenol A diacrylate, trimethylolpropane triacrylate, phenol novolac epoxy acrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, propylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, polyfunctional epoxy (meth)acrylate, polyfunctional polyamine ester (meth)acrylate, KAYARAD DPCA-20, KAYARAD DPCA-30, KAYARAD DPCA-60, KAYARAD DPCA-120, KAYARAD DPEA-12, or a combination thereof, manufactured by Japan Chemical Co., Ltd., but not necessarily limited thereto.

[0175] Polymerization initiator

[0176] The ink composition according to the embodiments can further include a polymerization initiator, for example, a photopolymerization initiator, a thermal polymerization initiator, or a combination thereof.

[0177] The photopolymerization initiator can be an initiator commonly used in a curable composition, for example, a phenone compound, a benzophenone compound, a thioxanthone compound, a benzoin compound, a triazine compound, an oxime compound, and an aminoketone compound, but not necessarily limited thereto.

[0178] Examples of acetophenone compounds can be 2,2'-diethoxyacetophenone, 2,2'-dibutoxyacetophenone, 2-hydroxy-2-methylpropiophenone, p-tert-butylchloroacetophenone, p-tert-butyldichloroacetophenone, 4-chloroacetophenone, 2,2'-dichloro-4-phenoxyacetophenone, 2-methyl-l-(4-(methylthio)phenyl)-2-(N-morpholinyl)propan-l-one, 2-benzyl-2-dimethylamino-l-(4-N-morpholinylphenyl)-butan-l-one, and the like.

[0179] Examples of benzophenone compounds can include benzophenone, benzyl benzoate, benzoyl methyl benzoate, 4-phenylbenzophenone, hydroxybenzophenone, benzophenone acrylate, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, 4,4'-dimethylaminobenzophenone, 4,4'-dichlorobenzophenone, 3,3'-dimethyl-2-methoxybenzophenone, and the like.

[0180] Examples of thioxanthone compounds can be thioxanthone, 2-methylthioxanthone, isopropylthioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, 2-chlorothioxanthone, and the like.

[0181] Examples of benzoin compounds can be benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzyl dimethyl ketal, and the like.

[0182] Examples of triazine compounds can be 2,4,6-trichloro-s-triazine, 2-phenyl-4,6-bis(trichloromethyl)-s-triazine, 2-(3',4'-dimethoxystyryl)-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, 2-biphenyl-4,6-bis(trichloromethyl)-s-triazine, bis(trichloromethyl)-6-styryl-s-triazine, 2-(naphtho-l-yl)-4,6-bis(trichloromethyl)-s-triazine, 2-(4-methoxynaphtho-l-yl)-4,6-bis(trichloromethyl)-s-triazine, 2-4-bis(trichloromethyl)-6-sunburystyl-s-triazine, 2-4-bis(trichloromethyl)-6-(4-methoxystyryl)-s-triazine, and the like.

[0183] Examples of oxime compounds can include aniloxime 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-alpha- oximino-1-phenylpropan-1-one, and the like. Specific examples of aniloxime compounds can include 1,2-octanedione, 2-dimethylamino-2-(4-methylbenzyl)-1-(4- morpholin-4-yl-phenyl)-butan-1-one, 1-(4-phenylthiophenyl)-butane-1,2-dione-2-oxime- O-benzoate, 1-(4-phenylthiophenyl)-octane-1,2-dione-2-oxime-o-benzoate, 1-(4- phenylthiophenyl)-octan-1-one oxime-o-acetic acid ester, 1-(4-phenylthiophenyl)-butan-1- one oxime-o-acetic acid ester, and the like.

[0184] Examples of aminoketone compounds can include 2-benzyl-2-dimethylamino-1-(4- morpholinylphenyl)-butanone-1.

[0185] In addition to the compounds, the photopolymerization initiator can further include carbazole compounds, diketone compounds, sulfonium borate compounds, diazo compounds, imidazole compounds, bisimidazole compounds, and the like.

[0186] The photopolymerization initiator can be used together with a photosensitizer capable of causing a chemical reaction by absorbing light and becoming excited and then transferring its energy.

[0187] Examples of the photosensitizer can be tetraethylene glycol bis-3-mercaptopropionate, isopentyldiol tetra-3-mercaptopropionate, diisopentyldiol tetra-3- mercaptopropionate, and the like.

[0188] Examples of the thermal polymerization initiator can be peroxides, in particular, benzoyl peroxide, dibenzoyl peroxide, lauroyl peroxide, dilauroyl peroxide, di-tert-butyl peroxide, cyclohexane peroxide, methyl ethyl ketone peroxide, hydrogen peroxide (e.g., tert-butylhydroperoxide, cumene hydroperoxide), di-cyclohexyl peroxydicarbonate, 2,2-azo-bis(isobutyronitrile), tert-butyl perbenzoate, and the like, and also 2,2'-azo-bis-2-methylpropionitrile and the like, but not necessarily limited thereto and can include any compound widely known in the related art.

[0189] The polymerization initiator can be included in an amount of 1 to 5 wt%, for example, 2 to 4 wt% based on the total solid content of the ink composition. When the polymerization initiator is included within the range, the ink composition can be sufficiently cured during exposure or thermal curing and thus excellent reliability is obtained.

[0190] Other additives

[0191] The ink composition according to the embodiments can further include a polymerization inhibitor including a hydroquinone-based compound, a catechol-based compound, or a combination thereof. Since the ink composition according to the embodiments further includes a hydroquinone-based compound, a catechol-based compound, or a combination thereof, crosslinking at room temperature can be prevented during exposure after the ink composition is printed (applied).

[0192] For example, the hydroquinone-based compound, the catechol-based compound, or the combination thereof can include hydroquinone, methylhydroquinone, methoxyhydroquinone, tertiary butylhydroquinone, 2,5-di-tert-butylhydroquinone, 2,5-bis(1,1-dimethylbutyl)hydroquinone, 2,5-bis(1,1,3,3-tetramethylbutyl)hydroquinone, catechol, tertiary butylcatechol, 4-methoxyphenol, pyrogallol, 2,6-di-tert-butyl-4-methylphenol, 2-naphthol, tris(N-hydroxy-N-nitrosophenylazinyl-O,O')aluminum, or a combination thereof, but is not necessarily limited thereto.

[0193] The hydroquinone-based compound, the catechol-based compound, or the combination thereof can be used in a dispersion type, and the polymerization inhibitor in the dispersion type can be included in an amount of 0.001 to 1 wt%, for example, 0.01 to 0.1 wt% based on the total amount of the ink composition. When the stabilizer is included within the above range, the problem of aging at room temperature can be solved and a decrease in sensitivity and surface peeling can be prevented.

[0194] In addition to the polymerization inhibitor, the ink composition according to the embodiments can further include malonic acid, 3-amino-1,2-propanediol, a silane-based coupling agent, a leveling agent, a fluorine-based surfactant, or a combination thereof.

[0195] For example, the ink composition for an electrophoretic device can further include a silane coupling agent having a reactive substituent such as a carboxyl group, a methacryl group, an isocyanate group, an epoxy group, and the like to improve its adhesion to a substrate.

[0196] Examples of the silane-based coupling agent can include trimethoxysilylbenzoic acid, γ-methacrylpropyloxytrimethoxysilane, vinyltriacetyloxy silane, vinyltrimethoxysilane, γ-isocyanatopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, β-epoxycyclohexyl)ethyltrimethoxysilane, and the like. These can be used alone or in a mixture of two or more.

[0197] Based on 100 parts by weight of the ink composition, a silane coupling agent may be included in an amount from 0.01 parts by weight to 10 parts by weight. When a silane coupling agent is included within this range, it can improve contact properties, storage properties, and the like.

[0198] In addition, the ink composition may also contain surfactants, such as fluorinated surfactants, to improve coating and prevent defects when necessary.

[0199] An example of fluorinated surfactants is BM Chemie Inc. and MEGAFACEF of Dainippon Ink Kagaku Kogyo Co., Ltd. MEGAFACE F MEGAFACE F and MEGAFACE F FULORAD from Sumitomo 3M Co., Ltd. FULORAD FULORAD and FULORAD SURFLON from Asahi Glass Co., Ltd. SURFLON SURFLON SURFLON and SURFLON And Toray Silicone Co., Ltd. and And similar; DIC Co., Ltd.’s F-482, F-484, F-478, F-554 and similar.

[0200] Based on 100 parts by weight of the ink composition, fluorinated surfactants may be included in an amount from 0.001 parts by weight to 5 parts by weight. When fluorinated surfactants are included within this range, excellent wetting and coating uniformity on the glass substrate are ensured, and no stains are generated.

[0201] In addition, without impairing the physical properties, a certain amount of other additives, such as antioxidants and stabilizers, can be added to the ink composition.

[0202] Another embodiment provides a layer using a printing ink composition.

[0203] Another embodiment provides a display device including a layer, and for example the display device can be an electrophoretic device.

[0204] Inventive modes

[0205] In the following, the application is illustrated in more detail with reference to examples. However, these examples are not to be construed as limiting the scope of the application in any manner.

[0206] (Preparation of ink composition)

[0207] Examples 1 to 6 and Comparative Examples 1 to 6

[0208] Nanorod-patterned GaN wafer (4 inch) was reacted in 40 ml of stearic acid (1.5 mmol) at room temperature for 24 hours. After the reaction, the nanorod-patterned GaN was immersed in 50 ml of acetone for 5 minutes to remove excess stearic acid, and the surface of the wafer was additionally rinsed using 40 ml of acetone. The washed wafer was placed in a 27-kW bath-type ultrasonic generator together with 35 ml of γ-butyrolactone (GBL), and then ultrasonically treated for 5 minutes to separate the rods from the surface of the wafer. 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. Then, the supernatant was discarded by centrifugation at 4000 rpm for 10 minutes, and the precipitate was re-dispersed in 40 ml of acetone and filtered with a 10-μm mesh filter paper. 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 Tables 1 and 2.

[0209] (Table 1)

[0210] (Unit: g)

[0211]

[0212] (Table 2)

[0213] (Unit: g)

[0214]

[0215] Solvent type

[0216] (B-1) 2,4-Diethyl-1,5-pentanediol

[0217] (B-2) 2-Ethyl-1,3-hexanediol

[0218] (B-3) 3-Methyl-1,5-pentanediol

[0219] (B-4) 1,5-pentanediol

[0220] (B-5) propylene glycol

[0221] (B-6) triethyl citrate

[0222] (B-7) triallyl isocyanurate

[0223] (B-8) polyethylene glycol

[0224] (B-9) propylene glycol

[0225] (B-10) 2-methyl-2,4-pentanediol

[0226] (B-11) PGMEA

[0227] (B-12) GBL

[0228] Evaluation: viscosity, dielectric constant, dispersion stability, and dielectrophoresis properties of the ink composition

[0229] The viscosity (25°C, 50°C), dielectric constant, dispersion stability, and dielectrophoresis properties of the ink compositions according to Examples 1 to 6 and Comparative Examples 1 to 6 were measured, and the results are shown in Table 3.

[0230] The viscosity of the solvent at 25°C and 50°C was measured by using a rheometer (Haake) and loading 2 milliliters of each composition, respectively.

[0231] The dielectric constant was measured at 25°C by loading 40 milliliters of each ink composition in a conical tube and using a liquid dielectric constant meter (Model 871, Furuto).

[0232] The dispersion stability was measured by loading 10 milliliters of each ink composition in a test tube having a diameter of 1 centimeter and a height of 13 centimeters and then checking the time for the bottom to produce a precipitate at room temperature.

[0233] The dielectrophoresis properties were measured as follows.

[0234] First, 500 microliters of each nanorod ink composition was coated on a thin film gold interdigital linear electrode (ED-cIDE4-Au, Micrux Technologies), and after applying an electric field (25 kilohertz, ±30 volts) thereto, it was left to stand for 1 minute. After drying the solvent on a hot plate, a microscope was used to count the number of disposed nanorods (each) and the number of non-disposed nanorods (each) between the electrodes to evaluate the dielectrophoresis properties.

[0235] (Table 3)

[0236]

[0237] (ND: not detected)

[0238] As shown in Table 3, Examples 1 to 6 exhibit higher viscosity at 25°C and lower viscosity at 50°C compared to Comparative Examples 1 to 6, and thus have a dielectric constant within a proper range, and also exhibit excellent dispersion stability and dielectrophoretic properties, which proves suitable for large-area coating and panel production.

[0239] While the present application has been described in connection with what is presently considered to be the most practical and preferred examples, it is to be understood that the application is not to be limited to the disclosed examples, 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 aforementioned examples should be understood as illustrative only and not limiting in any way.

Claims

1. A printing ink composition, comprising (A) Semiconductor nanorods; and (B) A solvent comprising at least one diol compound and a compound represented by chemical formula 2 or chemical formula 3: [Chemical Formula 2] [Chemical Formula 3] in, In chemical formulas 2 and 3 R 3 To R 5 Each is independently a substituted or unsubstituted C1 to C20 alkyl group, and R 6 To R 8 Each is independently a substituted or unsubstituted C1 to C20 alkoxy group. The ink composition described herein has a viscosity greater than or equal to 50 centipoise at 20°C to 25°C, and a viscosity less than or equal to 20 centipoise at 35°C to 65°C. The semiconductor nanorods are contained in an amount of 0.01% to 5% by weight, based on the total amount of the ink composition. The diol compounds mentioned above include at least one of the compounds represented by chemical formulas 1-1 to 1-5: [Chemical Formula 1-1] [Chemical Formula 1-2] [Chemical Formulas 1-3] [Chemical Formulas 1-4] [Chemical Formulas 1-5] 2. The ink composition according to claim 1, wherein the compound represented by chemical formula 2 or chemical formula 3 includes at least one selected from the compounds represented by chemical formula 2-1, chemical formula 2-2, chemical formula 3-1, and chemical formula 3-2: [Chemical Formula 2-1] [Chemical Formula 2-2] [Chemical Formula 3-1] [Chemical Formula 3-2] 3. The ink composition according to claim 1, wherein the compound represented by chemical formula 2 or chemical formula 3 is contained in an amount less than that of the diol compound.

4. The ink composition according to claim 1, wherein the semiconductor nanorod has a diameter of 300 nanometers to 900 nanometers.

5. The ink composition according to claim 1, wherein the semiconductor nanorod has a length of 3.5 micrometers to 5 micrometers.

6. The ink composition according to claim 1, wherein the semiconductor nanorod comprises GaN-based compounds, InGaN-based compounds, or combinations thereof.

7. The ink composition according to claim 1, wherein the surface of the semiconductor nanorod is coated with a metal oxide.

8. The ink composition according to claim 7, wherein the metal oxide comprises aluminum oxide, silicon oxide, or a combination thereof.

9. The ink composition according to claim 1, wherein the ink composition further comprises a polymerization inhibitor, malonic acid, 3-amino-1,2-propanediol, a silane coupling agent, a leveling agent, a fluorinated surfactant, or a combination thereof.

10. The ink composition according to claim 1, wherein the ink composition is an ink composition for an electrophoresis apparatus.

11. A layer manufactured using the ink composition as described in any one of claims 1 to 10.

12. A display device comprising the layer as claimed in claim 11.

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