Metal oxide nanoparticles dispersible in a nonpolar solvent, an ink composition for an electron transport layer for inkjet printing containing the same, a method for producing the same, a light-emitting element containing the same, and a display

Abstract

To provide metal oxide nanoparticles dispersible in a non-polar solvent, an electron transport layer ink composition for inkjet printing containing the same and a method for producing the same, and a light emitting device and a display containing the same.SOLUTION: There are provided metal oxide nanoparticles, an electron transport layer ink composition for inkjet printing containing the same and a method for producing the same and a light emitting device and a display containing the same, specifically, metal oxide nanoparticles which can be dispersed in a non-polar solvent and can prevent etching of a polar solvent type light emitting layer, an electron transport layer ink composition for inkjet printing containing the same and a method for producing the same and a light emitting device and a display containing the same.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to metal oxide nanoparticles, an ink composition for an electron transport layer for inkjet printing containing the same, a method for manufacturing the same, a light-emitting device and a display manufactured using the same. Specifically, the present invention relates to metal oxide nanoparticles that can be dispersed in a non-polar solvent and can prevent an etching of a polar solvent type light-emitting layer, an ink composition for an electron transport layer for inkjet printing containing the same, a method for manufacturing the same, a light-emitting device and a display manufactured using the same.

Background Art

[0002] Quantum dots (QD) are so-called semiconductor nanocrystals, and can generate light of different wavelengths according to particle size without changing the type of substance, creating various colors. Since they have the advantages of higher color purity and light stability than existing light emitters, they have attracted attention as next-generation light-emitting devices.

[0003] Particularly, quantum dots, which have become a new trend in the display field, are dispersed in a polymer matrix and can be applied in the form of a composite to various displays and electronic devices other than TVs and LEDs. On the other hand, materials for color filters are required to have high sensitivity, adhesion to a substrate, chemical resistance, heat resistance, etc. Conventionally, color filters applied to displays have generally been formed through a patterning process in which a desired pattern is formed through an exposure process in which a photomask is applied using a photosensitive resist composition, and then the unexposed portion is dissolved and removed through a development process. However, this has caused a problem of increased cost due to the discarded materials.

[0004] Recently, in order to upgrade the materials used for pixels and eliminate the resulting cost increase, rather than performing existing spin coating or slit coating for patterning, a method of using materials only in desired portions and minimizing the use of materials has attracted attention. The most typical method is the inkjet method, which can be broadly classified into the bubble jet method and the piezo method. Since the inkjet method uses materials only in desired pixels, it can prevent waste of unnecessary materials.

[0005] Thus, although quantum dot solutions using the inkjet printing method have been widely studied, little research has been conducted on the electron transport layer (ETL) composition for inkjet use. As a prior invention related to the electron transport layer (ETL) composition for inkjet, there is an invention disclosed in Korean Patent Publication No. 10-2007-0078615 (August 1, 2007).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] Currently, in the case of quantum dot light-emitting layers used in self-emitting displays for inkjet printing, the solvent type is not clear, and various types of solvents are being researched and developed. However, when a light-emitting layer of a polar solvent type is used, there is a technical problem that the light-emitting layer will be etched if an electron transport layer ink composition of the same polar solvent type is used. Therefore, metal oxide nanoparticles dispersible in non-polar solvents and an electron transport layer (ETL) composition are required.

[0008] The problem to be solved by the present invention is to provide metal oxide nanoparticles and an electron transport layer ink composition that can be inkjet printed when using a polar solvent type light emitting layer. Since the surface of the metal oxide nanoparticles, which are hydrophilic, is modified to be dispersible in a non-polar solvent and viscosity adjustment is easy.

Means for Solving the Problems

[0009] According to one aspect of the present invention for solving the above problems, there are provided metal oxide nanoparticles, the metal oxide nanoparticles are surface-modified, and provide metal oxide nanoparticles for inkjet printing that are dispersible in a non-polar solvent.

[0010] Preferably, the surface of the metal oxide nanoparticles is modified with an organic ligand having a hydrophobic moiety, and provide metal oxide nanoparticles for inkjet printing.

[0011] Preferably, the non-polar solvent is a mixture of at least two solvents, and provide metal oxide nanoparticles for inkjet printing.

[0012] Preferably, the non-polar solvent contains cyclohexylbenzene, and provide metal oxide nanoparticles for inkjet printing.

[0013] Preferably, the organic ligand is contained in the range of 0.0001 to 10 moles per mole of the metal contained in the metal oxide nanoparticles, and provide metal oxide nanoparticles for inkjet printing.

[0014] Preferably, the metal oxide nanoparticles are metal oxide nanoparticles containing zinc (Zn), and provide metal oxide nanoparticles for inkjet printing.

[0015] Preferably, the metal oxide nanoparticles containing zinc (Zn) are metal oxide nanoparticles for inkjet printing alloyed with a metal capable of increasing the band gap of zinc oxide (ZnO).

[0016] Preferably, the metal oxide nanoparticles containing zinc (Zn) are zinc magnesium oxide (ZnMgO), providing metal oxide nanoparticles for inkjet printing.

[0017] In another aspect of the present invention, there are provided metal oxide nanoparticles surface-modified with an organic ligand and a non-polar solvent, and an electron transport layer ink composition for inkjet printing that can be ejected by inkjet is provided. Preferably, the non-polar solvent is a mixture of at least two solvents, providing an electron transport layer ink composition for inkjet printing.

[0018] Preferably, the non-polar solvent contains cyclohexylbenzene, providing an electron transport layer ink composition for inkjet printing.

[0019] Preferably, the non-polar solvent further contains one or more solvents selected from the group consisting of styrene, hexadecane, anisole, and cyclohexanone, providing an electron transport layer ink composition for inkjet printing.

[0020] Preferably, the mixed non-polar solvent

[0021] has a viscosity of 1 to 6 cps at 20°C, has a vapor pressure of 0.001 to 0.1 mmHg at 20°C, has a surface tension of 30 to 40 dyn / cm at 20°C, providing an electron transport layer ink composition for inkjet printing.

[0022] ​Preferably, a volume ratio of the cyclohexylbenzene to other solvents is 7:3 to 20:1, and there is provided an electron transport layer ink composition for inkjet printing.

[0023] Preferably, the composition has a viscosity at 20 °C of 1.0 to 5.0 cps, has a vapor pressure at 20 °C of 0.6 to 45 mmHg, and has a solid content of 5 to 30% by weight, and there is provided an electron transport layer ink composition for inkjet printing.

[0024] Preferably, the organic ligand is an organic ligand having a hydrophobic moiety, and there is provided an electron transport layer ink composition for inkjet printing.

[0025] Preferably, the metal oxide nanoparticles are metal oxide nanoparticles containing zinc (Zn), and there is provided an electron transport layer ink composition for inkjet printing.

[0026] Preferably, the metal oxide nanoparticles containing zinc (Zn) are alloyed with a metal capable of increasing a band gap of zinc oxide (ZnO), and there is provided an electron transport layer ink composition for inkjet printing.

[0027] Preferably, the metal oxide nanoparticles containing zinc (Zn) are zinc magnesium oxide (ZnMgO), and there is provided an electron transport layer ink composition for inkjet printing.

[0028] Preferably, the organic ligand is contained in a range of 0.0001 to 10 moles with respect to 1 mole of the metal contained in the metal oxide nanoparticles, and there is provided an electron transport layer ink composition for inkjet printing.

[0029] In still another aspect of the present invention, there is provided a method for manufacturing an electron transport layer ink composition for inkjet printing, which includes, after manufacturing metal oxide nanoparticles, adding an organic ligand to modify the surface of the metal oxide nanoparticles, and mixing with a nonpolar solvent.

[0030] Preferably, there is provided a method for manufacturing an electron transport layer ink composition for inkjet printing, wherein the organic ligand is contained in a range of 0.0001 to 10 moles with respect to 1 mole of the main metal contained in the metal oxide nanoparticles.

[0031] Preferably, the nonpolar solvent is cyclohexylbenzene and one or more solvents selected from the group consisting of styrene, hexadecane, anisole, and cyclohexanone, and is manufactured by mixing them. There is provided a method for manufacturing an electron transport layer ink composition for inkjet printing.

[0032] Preferably, the volume ratio of the cyclohexylbenzene to the other solvent is 7:3 to 20:1. There is provided a method for manufacturing an electron transport layer ink composition for inkjet printing.

[0033] In still another aspect of the present invention, there is provided a light-emitting device including an electron transport layer manufactured by the aforementioned composition.

[0034] Preferably, there is provided a light-emitting device, wherein the electron transport layer is formed through inkjet printing.

[0035] In still another aspect of the present invention, there is provided a display including the light-emitting device.

Effects of the Invention

[0036] According to an embodiment of the present invention, it can be mixed with two nonpolar solvents through surface modification of metal oxide nanoparticles, and uniform ejection by an inkjet method is easy.

[0037] In addition, when using a polar solvent type light-emitting layer, an electron transport layer ink composition for inkjet printing capable of forming a uniform film on the upper end of the light-emitting layer can be provided, and the etching problem of the polar solvent type light-emitting layer can be solved.

[0038] Thereby, the electron transport layer ink composition of the present invention is not only usefully applicable to the production of light-emitting elements, specifically self-emitting displays, through the inkjet printing process, but also exhibits advantageous effects in commercialization and enlargement through the application of a simple and inexpensive inkjet process.

[0039] The effects according to the present invention are not limited to the contents exemplified above, and more diverse effects are included in this specification.

Brief Description of the Drawings

[0040]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0041] The present invention will be described below.

[0042] All terms (including technical and scientific terms) used in this specification can be used with a meaning commonly understood by those having ordinary knowledge in the technical field to which the present invention pertains, unless otherwise defined. Also, terms defined in commonly used dictionaries are not ideally or unduly interpreted unless specifically defined otherwise.

[0043] Also, throughout this specification, when a certain part "includes" a certain component, this means that, unless otherwise stated to the contrary, it does not exclude other components and may further include other components.

[0044] In this specification, "organic group" means a linear or branched alkyl group having 1 to 30 carbon atoms, a linear or branched alkenyl group having 2 to 30 carbon atoms, or a linear or branched alkynyl group having 2 to 30 carbon atoms. Also, the alkyl group, alkenyl group, and alkynyl group are each either substituted or unsubstituted.

[0045] In this specification, "alkyl" means a monovalent substituent derived from a linear or side-chain saturated hydrocarbon having 1 to 30 carbon atoms. Examples thereof include, but are not limited to, methyl, ethyl, propyl, isobutyl, sec-butyl, pentyl, isobutyl, hexyl, etc.

[0046] In this specification, "alkenyl" means a monovalent substituent derived from a linear or side-chain unsaturated hydrocarbon having 2 to 30 carbon atoms and having one or more carbon-carbon double bonds. Examples thereof include, but are not limited to, vinyl, allyl, isopropenyl, 2-butenyl, etc.

[0047] As used herein, "alkynyl" means a monovalent substituent derived from a linear or branched unsaturated hydrocarbon having 2 to 30 carbon atoms and having one or more carbon-carbon triple bonds. Examples thereof include, but are not limited to, ethynyl, n-propynyl, n-but-2-enyl, n-hex-3-enyl, and the like.

[0048] <Electron transport layer ink composition> The electron transport layer ink composition according to one embodiment of the present invention is an ink composition that can be ejected by a general inkjet method and can form an electron transport layer (ETL).

[0049] The electron transport layer ink composition according to one embodiment of the present invention may include metal oxide nanoparticles surface-modified with an organic ligand and a nonpolar solvent.

[0050] Hereinafter, the composition of the electron transport layer ink composition will be specifically described as follows.

[0051] Metal oxide nanoparticles The metal oxide nanoparticles can be used without limitation to substances used in the electron transport layer in the art. As an example, ordinary metal oxide nanoparticles used as dopant substances can be used, and non-limiting examples thereof include In 2 S 3 、Cu 2 S、Ag 2 S、ZnSe、ZnS、ZnO、ZnTe、ZnSe、TiO 2 、SnO 2 、ZnS, or a form in which at least one element is added to the aforementioned components may also be included.

[0052] For example, in one specific example, the metal oxide nanoparticles are zinc (Zn)-containing metal oxide nanoparticles, and more specifically, they may be those in which a metal (M) capable of increasing the band gap of zinc oxide (ZnO) is alloyed [ZnMO (M = Ca, Mg)]. The metal (M) capable of increasing the band gap of ZnO is calcium (Ca) or magnesium (Mg). Since these metals are similar to the ionic radius of Zn, they can be incorporated into the ZnO lattice without stress induction, and the band gap of ZnO can be increased through the size reduction of ZnO. Preferably, it is zinc magnesium oxide (ZnMgO).

[0053] In this way, if the band gap of ZnO nanoparticles is increased by an alloy and applied to the electron transport layer, an upshift of the conduction band minimum (CBM) level occurs, resulting in an energy proximity between the CBM of the quantum dot light-emitting layer and the electron transport layer. This reduces the electron energy barrier and, as a result, promotes the injection of electrons into the quantum dot region. Thus, a light-emitting device comprising an electron transport layer containing alloyed ZnO nanoparticles is superior in terms of luminance and efficiency compared to a device comprising an electron transport layer containing ZnO nanoparticles, and can have a higher light-emitting efficiency even at a lower driving voltage. That is, when the aforementioned electron transport layer is applied, the effect of reducing the electron injection barrier, reducing the driving voltage of the QLED, improving the efficiency, and further reducing the power consumption can be obtained. If the driving voltage of the device is reduced, the heat generation of the device is also reduced, and thereby, an increase in the lifespan of the device can be expected.

[0054] For example, in one specific example, an organic ligand having a hydrophobic moiety can be attached to a part or all of the surface of the metal oxide nanoparticles.

[0055] Organic ligands can be used without limitation from those known in the art, and some of the organic ligands can have functional groups with excellent affinity for the quantum dot surface. Specifically, there are carboxylic acids, acrylates, pyridines, thiols, phosphines, phosphine oxides, primary amines, secondary amines, or combinations thereof.

[0056] The organic ligand may contain a hydrophobic moiety. Specifically, it is a C1-C30 straight-chain or branched-chain alkyl group, a C2-C30 straight-chain or branched-chain alkenyl group, or a C2-C30 straight-chain or branched-chain alkynyl group. Preferably, it is a C5-C30 straight-chain or branched-chain alkyl group, a C5-C30 straight-chain or branched-chain alkenyl group, or a C5-C30 straight-chain or branched-chain alkynyl group.

[0057] Non-limiting examples of usable organic ligands include oleic acid, myristic acid, lauric acid, palmitic acid, stearic acid, oleylamine, n-octylamine, hexadecylamine, hexylphosphonic acid, n-octylphosphonic acid, tetradecylphosphonic acid, octadecylphosphonic acid, or combinations thereof.

[0058] Such organic ligands are attached to the surface of the metal oxide nanoparticles, surround the surface of the nanoparticles with hydrophobic moieties, are mixed and dispersed in non-polar solvents, and can play a role in ensuring film uniformity by exerting an improvement effect on the coffee-ring effect (CRE) during inkjet ejection.

[0059] Here, the coffee-ring effect (CRE) refers to the phenomenon in which colloidal particles move to the edge due to the hydrodynamic effect during the evaporation process, resulting in a non-uniform density distribution of the particles. That is, the smaller the particle size, the more it can move to the edge. Therefore, smaller particles are distributed closer to the edge of the droplet, and relatively larger particles are distributed closer to the center of the droplet.

[0060] The content of the organic ligand is not particularly limited and can be appropriately adjusted within the range of contents known in the art. Considering the dispersibility and film uniformity, it is contained in the range of 0.001 to 10 moles, specifically in the range of 0.001 to 5 moles, relative to 1 mole of the metal contained in the metal oxide nanoparticles, such as zinc (Zn).

[0061] On the other hand, in the present invention, metal oxide nanoparticles are mainly described as the substance constituting the electron transport layer. However, it is not limited to the aforementioned substance, and applying an organic substance or an organic-inorganic composite that can be used as an electron transport layer substance in the art also belongs to the scope of the present invention.

[0062] In the present invention, the content of the metal oxide nanoparticles is not particularly limited and can be appropriately adjusted within the range known in the art. As an example, it is 5 to 30 parts by weight, specifically 10 to 20 parts by weight, based on the total weight (for example, 100 parts by weight) of the electron transport layer ink composition.

[0063] Nonpolar solvent Conventional metal oxide nanoparticles, such as ZnMgO, use an alcohol-based solvent as a dispersion medium due to the characteristics of the material. However, when ethanol is used alone, the characteristics of the device are realized, but inkjet ejection is not performed. In addition, when a light-emitting layer of the same polar solvent type as ethanol is used, it is inevitable that the light-emitting layer is etched due to the use of the same solvent. It has remained a very difficult problem in the industry to disperse metal oxide nanoparticles in a non-polar solvent and find a non-polar solvent that meets the inkjet ejection conditions.

[0064] On the one hand, the ejection conditions of the inkjet equipment can be broadly divided into viscosity and vapor pressure. If the viscosity is excessively high or low, a uniform film cannot be obtained, and the ejection degree is determined by the vapor pressure. In the present invention, at least two kinds of mixed solvents that can satisfy such physical properties are selected in consideration of the viscosity and vapor pressure appropriate for inkjet ejection, the mixing ratio thereof is controlled within a predetermined range, and it is characterized in that it is composed of the solvent of the electron transport layer ink composition.

[0065] Taking a specific example, the electron transport layer ink composition of the present invention containing at least two kinds of solvents has a viscosity of 1.0 to 5.0 cps at 20 ° C, a vapor pressure of 0.6 to 45 mmHg at 20 ° C, and a solid content of 5 to 30% by weight. More specifically, it can have a viscosity of 1.2 to 3.0 cps, a vapor pressure of 1.0 to 30 mmHg, and a solid content of 5 to 25% by weight.

[0066] When having the physical properties of the solid content, viscosity, and vapor pressure described above, not only is inkjet ejection easy, but the characteristics of the device can be realized by the uniformity of the ejected ink.

[0067] The electron transport layer ink composition according to the present invention is not particularly limited in terms of the specific components and / or the content thereof of at least two or more solvents constituting the composition as long as it satisfies the characteristics of the solid content, viscosity, and vapor pressure described above.

[0068] Taking a specific example, the nonpolar solvent may contain cyclohexylbenzene (CHB).

[0069] That is, in the present invention, CHB with good dispersibility can be used as the main solvent. Considering the inkjet ejection application, when the CHB solvent is used alone, it is not suitable in terms of viscosity. Accordingly, other nonpolar solvents having viscosities different from that of CHB are mixed, and the volume ratio of each is adjusted so that the final composition can be controlled to simultaneously satisfy the characteristics of the solid content, viscosity, and vapor pressure described above.

[0070] Other non-polar solvents having a viscosity different from that of CHB may include one or more solvents selected from the group consisting of styrene, hexadecane, anisole, and cyclohexanone.

[0071] At this time, CHB can be a main solvent and can be configured to have 70% by volume or more based on 100% by volume of the total solvent. The volume ratio of cyclohexylbenzene to other non-polar solvents is 7:3 to 20:1, preferably 7:3 to 9.5:0.5, and more preferably 7:3 to 9:1. When other non-polar solvents that are not cyclohexylbenzene exceed 30% by volume of the total solvent, the viscosity of the total solvent increases, and the ejection property of the inkjet may decrease.

[0072] In addition, the characteristics of the non-polar solvent mixed in the present invention are characterized in that the viscosity at 20°C is 1 to 6 cps, the vapor pressure at 20°C is 0.001 to 0.1 mmHg, and the surface tension at 20°C is 30 to 40 dyn / cm. When the characteristics of the mixed non-polar solvent are within the above range, it is suitable for use in an ink composition for inkjet printing.

[0073] In the present invention, the total content of the non-polar solvent in the ink composition is not particularly limited and can be appropriately adjusted within a range known in the art. As an example, it is the remaining amount that fills 100 parts by weight of the electron transport layer ink composition, specifically, 70 to 95 parts by weight.

[0074] Other additives In addition to the above-mentioned components, the electron transport layer ink composition of the present invention can be used without limitation at least one additive known in the art within a range that does not inhibit the effects of the invention.

[0075] As an example of the possible additives, there are included light stabilizers, heat stabilizers, photoinitiator accelerators, thermal initiator accelerators, smoothing agents, toughening agents, thickeners, colorants, reactive diluents, coupling agents, dispersants, etc. These may be used alone or in combination of two or more. At this time, the content of the additive can be appropriately adjusted within the range known in the art and is not particularly limited. As an example, the at least one additive is contained in an amount of 0.01 to 5 parts by weight, specifically 0.01 to 2 parts by weight, based on the total weight of the electron transport layer ink composition.

[0076] <Method for manufacturing electron transport layer ink composition> The electron transport layer ink composition for inkjet printing according to the present invention can be manufactured by mixing and stirring the aforementioned surface-modified metal oxide nanoparticles, at least two nonpolar solvents, and other additives blended as necessary by a conventional method known in the art.

[0077] As one embodiment according to the present invention, after manufacturing the metal oxide nanoparticles, an organic ligand is added to modify the surface of the metal oxide nanoparticles, followed by centrifugation and mixing with a nonpolar solvent to manufacture an electron transport layer ink composition for inkjet printing.

[0078] At this time, the organic ligand can be added in the range of 0.0001 to 10 moles per 1 mole of the main metal contained in the metal oxide nanoparticles.

[0079] Also, the nonpolar solvent is a mixture of two nonpolar solvents. Specifically, it is a mixture of cyclohexylbenzene and other nonpolar solvents, and is a mixture of cyclohexylbenzene and other nonpolar solvents in a volume ratio of 7:3 to 20:1.

[0080] Regarding one embodiment of manufacturing the electron transport layer ink composition, (i) a basic substance is added to a reaction solution in which a zinc-containing compound and a metal-containing compound capable of increasing the bandgap of ZnO are dissolved in a solvent, and the mixture is stirred and heated at a uniform rate at about 50 to 80 °C for 30 minutes to 2 hours. (ii) An organic ligand is added to the reaction solution in a molar amount in the range of 10 to 70% with respect to the number of moles of zinc ions contained in the zinc-containing substance, and the mixture is stirred and heated at a uniform rate at about 80 to 120 °C for 10 minutes to 1 hour. (iii) Hexane and acetone are added to the solution after the reaction is completed, and centrifugation is performed to obtain surface-modified metal oxide nanoparticles. (iv) The surface-modified metal oxide nanoparticles can be mixed and dispersed in a solvent obtained by mixing cyclohexylbenzene and other non-polar solvents at a volume ratio of 7:3 to manufacture an electron transport layer ink composition.

[0081] In the above embodiment, the zinc-containing compound and the metal-containing compound are not particularly limited, and substances known in the art can be used without limitation. As an example, zinc acetate, zinc acetate dihydrate, zinc chloride, zinc nitrate, zinc sulfate, magnesium acetate tetrahydrate, etc. can be used.

[0082] Also, the basic substance is not particularly limited, and substances known in the art can be used without limitation. As an example, at least one substance selected from the group consisting of tetramethylammonium hydroxide (TMAH), potassium hydroxide (KOH), sodium hydroxide (NaOH), and amines can be used.

[0083] Non-limiting examples of solvents that can be used when separating surface-modified metal oxide nanoparticles by utilizing the characteristics of a solvent and a non-solvent include hexane, benzene, xylene, toluene, octane, chloroform, chlorobenzene, tetrahydrofuran (THF), methylene chloride, 1,4-dioxane, diethyl ether, cyclohexane, dichlorobenzene, etc. These may be used alone or in combination of two or more. Non-limiting examples of non-solvents that can be used include acetone, ethanol, methanol, butanol, propanol, isopropyl alcohol, tetrahydrofuran, dimethyl sulfoxide, dimethylformamide, etc. These may be used alone or in combination of two or more.

[0084] The mixing method in the manufacturing method is not particularly limited. As an example, mixers such as ordinary homodisper, homomixer, universal mixer, planetary mixer, kneader, three-roll, etc. known in the art can be used.

[0085] The manufactured electron transport layer ink composition may further contain at least one of other additives such as a dispersant.

[0086] The electron transport layer ink composition of the present invention configured as described above can impart excellent workability and processability by optimizing the characteristics of viscosity and vapor pressure. In particular, in terms of inkjet ejectability, the shape of the ejected ink, and the shape of the ink formed on the substrate, it can be usefully applied to the inkjet printing method by ensuring uniformity and stability in all aspects.

[0087] In addition, in the overlapping range, the electron transport layer ink composition is as described above.

[0088] <Light-emitting element and display device> The light-emitting element according to an embodiment of the present invention is distinguished from conventional light-emitting elements in that it includes an electron transport layer formed from the aforementioned electron transport layer ink composition.

[0089] The light-emitting device according to an embodiment of the present invention includes, but is not limited to, a quantum dot light-emitting device, an organic light-emitting device, etc., and is applicable to various types of light-emitting devices.

[0090] Generally, a light-emitting device includes a first electrode, a second electrode disposed opposite to the first electrode, a light-emitting layer disposed between the first electrode and the second electrode, a hole transport layer disposed between the first electrode and the light-emitting layer, and an electron transport layer disposed between the light-emitting layer and the second electrode and formed by inkjet printing the aforementioned electron transport layer ink composition. Optionally, the light-emitting device may further include at least one of a hole injection layer and an electron injection layer.

[0091] At this time, the electron transport layer facilitates the injection of electrons from the second electrode and plays a role of transmitting electrons to the light-emitting layer. Such an electron transport layer includes Zn-containing metal oxide nanoparticles alloyed with a metal capable of increasing the bandgap of ZnO. As an example, the electron transport layer can be formed by inkjet printing the aforementioned electron transport layer ink composition on the light-emitting layer and then volatilizing the solvent. The electron transport layer of the present invention may be provided in a single-layer structure that also serves as an electron injection layer, or a separate electron injection layer may be formed in a stacked structure.

[0092] In addition, the present invention provides a display device including the aforementioned quantum dot composition. Here, the display device includes, but is not limited to, a liquid crystal display device (LCD), an electroluminescence display device (EL), a plasma display device (PDP), a field emission display device (FED), an organic light-emitting device (OLED), etc.

[0093] Hereinafter, the present invention will be described in more detail through examples. However, the following examples are for illustrative purposes of the present invention, and the scope of the present invention is not limited to the examples.

Examples

[0094] Example 1. Electron transport layer ink composition for non-polar solvent-based inkjet Zinc acetate (Zn(OAc) 2 ) and magnesium acetate tetrahydrate were dissolved in dimethyl sulfoxide (DMSO), and then tetramethylammonium hydroxide (TMAH), a basic substance, was injected, heated to about 60 °C, and reacted for about 1 hour. For Zn(OAc) 2 , oleic acid was added so as to have about 30% molar amount based on the molar number of Zn(OAc)

[0095] Example 2. The same as Example 1, but after centrifuging the solution after surface modification twice, it was dispersed in a non-polar solvent.

[0096] Example 3. The same as Example 1, but it was produced by adding oleic acid so as to have about 50% molar amount based on the molar number of Zn(OAc) 2 .

[0097] Comparative Example. Conventional electron transport layer ink composition for inkjet (polar solvent type) The reaction of the solution after the reaction was completed by the same method as in Example 1 was terminated without adding a separate organic ligand, hexane and acetone were added, the particles were centrifuged, and then dispersed in a solvent in which DMSO, ethanol, 2-methoxyethanol and butanol were mixed at a volume ratio of 5:3:1:1.

[0098] Test Example 1. Spectroscopic evaluation Using the electron transport layer compositions produced in Example 1 and the Comparative Example, absorption spectra were measured.

[0099] Referring to FIG. 1, the UV-visible absorption spectra of the ZnMgO nanoparticles synthesized in Example 1 (blue line) and the UV-visible absorption spectra of the ZnMgO nanoparticles synthesized in the Comparative Example (orange line) are both shown. As shown in FIG. 1, it can be seen that both have similar absorption spectra and particularly have a maximum absorption wavelength at about 305 nm.

[0100] Therefore, it was confirmed that even when using the metal oxide nanoparticles of Example 1, it is possible to exhibit the same spectral characteristics as those of the existing electron transport layer ink composition for polar solvent-based inkjet.

[0101] Test Example 2. TGA Analysis of ZnMgO Produced in Example 1, Example 2 and Comparative Example TGA analysis is a thermal analysis technique that measures the mass change of a sample due to temperature change. The temperature at which the weight change occurs rapidly can be interpreted as the decomposition temperature of the organic matter, and the weight percentage occupied by the organic matter can be numerically confirmed by the degree of total weight loss.

[0102] TGA analysis was performed using the ZnMgO produced in Example 1, Example 2 and Comparative Example, and the results are shown in Table 1 and FIG. 2 below.

[0103]

Table 1

[0104] There was a weight loss of about 10% of the organic matter contained in the nanoparticles produced in the Comparative Example.

[0105] In the case of Example 1, there was a weight loss of about 30% of the organic matter, and in the case of Example 2, there was a weight loss of about 15% of the organic matter. From this, it can be seen that the organic ligands attached to the surface of ZnMgO are separated from the nanoparticles more as the number of centrifugations increases.

[0106] In addition, no organic ligand was added to the nanoparticles produced in the comparative example, and the decomposition temperature was about 300°C. On the other hand, the decomposition temperatures of all the examples were the same at about 360°C. Therefore, it was judged that the organic substances removed from the comparative example were those that were removed less during the centrifugation process, and the organic substances removed from the examples were understood to be the organic ligands attached to the surface of ZnMgO.

[0107] Test Example 3. FT-IR Analysis of ZnMgO Produced in Example 1, 3 and Comparative Example FT-IR analysis was performed using ZnMgO produced in Example 1, 3 and the comparative example, and the results are shown in Figure 3.

[0108] Referring to Figure 3, in Examples 1 and 3, peaks of a similar shape are shown at 2800 - 2900 nm, but in the comparative example, no peak is shown in this range. Therefore, it can be confirmed that organic ligands are well attached to the surface of the ZnMgO produced in the examples.

[0109] Test Example 4. Evaluation of the Dispersibility of ZnMgO Produced in Example 1, 3 and Comparative Example ZnMgO produced in Example 1, 3 and the comparative example was mixed and stirred with a non-polar solvent to confirm whether it could be dispersed. As the non-polar solvent, a solvent obtained by mixing cyclohexylbenzene:styrene in a volume ratio of 7:3 was used. The results are shown in Table 2 below.

[0110]

Table 2

[0111] Both Examples 1 and 3 were dispersible in the non-polar solvent regardless of the difference in the added amount of the organic ligand. However, when the nanoparticles of the comparative example were mixed with the non-polar solvent, the layers were separated and it was shown that they were not mixed at all.

[0112] Test Example 5. Evaluation of Inkjet Ejection Performance Using the electron transport layer ink composition of Example 1, the ejection property by inkjet printing was evaluated. Specifically, each of the manufactured ink compositions was ejected using an inkjet printing apparatus (OMNIJET200). At this time, it was ejected in the form of one drop, and the results are shown in FIG. 4.

[0113] Referring to FIG. 4, each dot is derived in a circular shape, and no deformation such as invading the area of other dots or changing the interval between dots is found.

[0114] Test Example 6. Evaluation of Inkjet Shape (CRF) The electron transport layer ink compositions of Example 1 and the comparative example were ejected using an inkjet printing apparatus (OMNIJET200), and the ink formed on the substrate was analyzed using a three-dimensional surface profiler (NV9000, Zygo). At this time, the following formula 1 was introduced to quantify the degree of the coffee-ring effect, and the results are shown in FIGS. 5 and 6.

[0115] [Formula 1] CRF (Coffee Ring Factor) = Hmax / Hmin In the above formula, Hmax indicates the thickest thickness of the pattern, Hmin indicates the thinnest thickness of the pattern, and the CRF value means the degree of the coffee-ring effect. That is, CRF = 1 indicates that the coffee-ring effect is perfectly removed.

[0116] Referring to FIG. 5, Hmax of the inkjet shape of Example 1 was about 11.86 nm, and Hmin was about 9.49 nm (not shown). Therefore, CRF is a value very close to about 1.25 and 1, and it can be confirmed that it has a uniform shape as a whole rather than a cross section even when looking at the three-dimensional shape.

[0117] On the one hand, referring to FIG. 6, the Hmax of the inkjet shape in the comparative example was about 15.26 nm, and the Hmin was about 9.66 nm (not shown). Therefore, the CRF was about 1.58, a value far from 1. Looking at the three-dimensional shape, it can be seen that not only was the coffee-ring effect clearly shown in only one cross-section, but the coffee-ring phenomenon was shown overall.

[0118] Also, for reference, even when comparing that, although the same amount was ejected in each case, the Hmax was about 11.86 nm in Example 1 and 15.26 nm in the comparative example, it can be predicted that in the comparative example, the deviation in the height of the inkjet shape was very large.

[0119] The present invention is not limited to the above-described embodiments, and it is obvious to those having ordinary knowledge in the technical field to which the present invention belongs that the present invention can be variously modified or deformed and implemented without departing from the gist of the present invention.

Claims

1. 1. A metal oxide nanoparticle comprising: The metal oxide nanoparticles are surface-modified with a surface modifier; 1. A metal oxide nanoparticle for inkjet printing, dispersible in a non-polar solvent, comprising: the metal oxide nanoparticles are ZnMgO nanoparticles; the surface modifier is a compound selected from oleic acid, myristic acid, lauric acid, palmitic acid, stearic acid, hexylphosphonic acid, n-octylphosphonic acid, tetradecylphosphonic acid, octadecylphosphonic acid, or a combination thereof; The non-polar solvent has a viscosity of 1 to 6 cps at 20° C., a vapor pressure of 0.001 to 0.1 mmHg at 20° C., and a surface tension of 30 to 40 dyn / cm at 20° C.

2. 10. The metal oxide nanoparticles for inkjet printing of claim 1, wherein the surface of the metal oxide nanoparticles is modified with a compound selected from oleic acid, myristic acid, lauric acid, palmitic acid, stearic acid, or a combination thereof.

3. The metal oxide nanoparticles for inkjet printing of claim 1 , wherein the non-polar solvent is a mixture of at least two solvents.

4. The metal oxide nanoparticles for inkjet printing of claim 3 , wherein the non-polar solvent comprises cyclohexylbenzene.

5. 2. The metal oxide nanoparticles for inkjet printing according to claim 1, wherein the surface modifier is contained in an amount ranging from 0.0001 to 10 moles per mole of the metal contained in the metal oxide nanoparticles.

6. A metal oxide nanoparticle surface-modified with a surface modifier as described in claim 1; A non-polar solvent as defined in claim 1, An electron transport layer ink composition for ink jet printing that is ink jet jettable.

7. 7. The electron transport layer ink composition for ink jet printing of claim 6 wherein said non-polar solvent is a mixture of at least two solvents.

8. 8. The electron transport layer ink composition for ink jet printing of claim 7 wherein the non-polar solvent comprises cyclohexylbenzene.

9. 9. The electron transport layer ink composition for ink jet printing of claim 8 wherein the non-polar solvent further comprises one or more solvents selected from the group consisting of styrene, hexadecane, anisole, and cyclohexanone.

10. 10. The electron transport layer ink composition for ink jet printing of claim 9, wherein a volume ratio of the cyclohexylbenzene to the other solvent is from 7:3 to 20:

1.

11. The composition comprises: The viscosity at 20°C is 1.0 to 5.0 cps, The vapor pressure at 20°C is 0.6 to 45 mmHg, 7. The electron transport layer ink composition for ink jet printing of claim 6 having a solids content of from 5 to 30 weight percent.

12. 7. The electron transport layer ink composition for ink jet printing of claim 6, wherein the surface modifier is present in an amount of 0.0001 to 10 moles per mole of the metal contained in the metal oxide nanoparticles.

13. A light-emitting device comprising an electron transport layer comprising the metal oxide nanoparticles for inkjet printing described in claim 1.

14. A display comprising the light-emitting element according to claim 13.

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