Quantum dot ink composition, preparation method thereof, cured film containing quantum dot ink composition, color filter and display device

Abstract

A quantum dot ink composition, a method of preparing the same, and a cured film, a color filter and a display device including the same are disclosed. The quantum dot ink composition includes a ligand compound particularly suitable for AIGS quantum dots, thereby further improving the optical properties and stability of the quantum dots. Furthermore, the method for preparing the quantum dot ink composition allows a ligand compound to be substituted on the surface of the quantum dot with good efficiency, and the substituted ligand compound can be more strongly bonded to the surface of the quantum dot to prepare the quantum dot ink composition having good physical properties, thus, a high-quality display device having further improved optical properties is provided.

Description

Technical Field

[0001] This invention relates to quantum dot ink compositions, methods for their preparation, and cured films, color filters, and display devices containing the same. Background Technology

[0002] Quantum dots (QDs), also known as semiconductor nanocrystals, can emit various colors by producing light with different wavelengths depending on their particle size. Compared with typical light-emitting materials, they have the advantages of better color purity and photostability, and are therefore attracting attention as the next generation of light-emitting elements.

[0003] In particular, as a new trend in the display field, quantum dots can be applied to various displays, electronic devices, televisions, and LEDs. Quantum dots, represented by CdSe, InP, etc., have achieved rapid improvements in luminous efficiency (quantum yield), and various methods for synthesizing quantum dots with luminous efficiency approaching 100% have been introduced into the technology. As a result, televisions with quantum dot sheets have been commercialized in the technology. In contrast to quantum dot LED televisions (where light is filtered through a color filter layer incorporating quantum dots (excluding pigments and dyes), the next generation of self-emissive quantum dot televisions is under development. In the development of such quantum dot televisions, the main issue is how long the quantum dots can maintain optical efficiency during the pixel formation and manufacturing processes.

[0004] Recently, in response to advancements in material usage for pixels and to address the resulting increases in manufacturing costs, there has been growing interest in methods that minimize material usage by applying material only to the desired areas, rather than through patterning via spin coating or slot coating as in previous technologies. The most representative approach is inkjet printing, where material is used only for the desired pixels to prevent material waste.

[0005] Quantum dot compositions with high viscosity used in inkjet printing methods may suffer from poor processability. To address this issue, Korean Patent Publication No. 10-2022-0023000 discloses a solvent-free quantum dot composition that achieves low viscosity by eliminating the need for a solvent. However, to achieve low viscosity, the quantum dot content is also limited to a specific level or below, resulting in an increase in the thickness of the pixel layer to achieve good optical efficiency. Summary of the Invention

[0006] Technical issues

[0007] One object of the present invention is to provide solvent-free quantum dot ink compositions comprising novel quantum dots exhibiting improved optical properties and stability, and ligand compounds suitable for the novel quantum dots.

[0008] Another object of the present invention is to provide a quantum dot ink composition that achieves low viscosity and exhibits good light absorption and light conversion efficiency even at thin film thicknesses.

[0009] A further object of the present invention is to provide a cured film, a color filter, and a display device comprising a cured product containing a quantum dot ink composition.

[0010] Another object of the present invention is to provide a method for preparing quantum dot ink compositions.

[0011] It should be understood that the present invention is not limited to the above objectives, and the above and other objectives will become apparent to those skilled in the art from the following description.

[0012] Technical solution

[0013] According to one aspect of the present invention, a quantum dot ink composition is provided, comprising: quantum dots having a ligand layer on their surface; and a photopolymerizable monomer, wherein the quantum dots comprise silver, indium, gallium, and sulfur, and the ligand layer comprises a compound represented by Formula 1.

[0014] [Formula 1]

[0015]

[0016] (In Equation 1,

[0017] R 1 and R 2 Each can be independently a hydrogen atom or a methyl group.

[0018] L 1 L 2 and L 3 Each independently is C1 to C 20 hydrocarbon group, and

[0019] (n is an integer from 1 to 20.)

[0020] In quantum dot ink compositions, compounds represented by Formula 1 may have a weight-average molecular weight (Mw) of 100 to 2,000.

[0021] In quantum dot ink compositions, quantum dots can be present in amounts ranging from 1 wt% to 50 wt%, depending on the total weight of the composition.

[0022] In quantum dot ink compositions, the ligand layer may include a compound represented by Formula 2.

[0023] [Equation 2]

[0024]

[0025] (In Equation 2,

[0026] R 3 and R 4 Each is independently a hydrogen atom or a methyl group, and

[0027] o is an integer from 1 to 20.

[0028] The composition of quantum dot ink may further include at least one selected from the group consisting of photoinitiators and scattering particles.

[0029] In quantum dot ink compositions, photoinitiators may include at least one selected from the group consisting of phosphine oxide compounds, acetophenone compounds, benzophenone compounds, triazine compounds, diimidazole compounds, oxime compounds, and thioxanthone compounds.

[0030] In the composition of quantum dot ink, the scattering particles may include at least one selected from the group consisting of Al2O3, SiO2, ZnO, ZrO2, CaCO3, BaSO4, BaTiO3, TiO2, Ta2O5, Ti3O5, ITO, IZO, ATO, ZnO-Al, Nb2O3, SnO and MgO.

[0031] Quantum dot ink compositions can have a viscosity of 30 cP or less, and when measured on a cured product of quantum dot ink composition with a thickness of 7 μm, they exhibit a light conversion efficiency of 29% or higher relative to blue light.

[0032] According to another aspect of the present invention, a method for preparing a quantum dot ink composition is provided, comprising: (a) performing primary surface modification on quantum dots comprising silver, indium, gallium and sulfur using an X-type ligand; (b) performing secondary surface modification on the quantum dots subjected to primary surface modification using a compound represented by Formula 1; and (c) dispersing the quantum dots subjected to secondary surface modification in a photopolymerizable compound.

[0033] According to another aspect of the present invention, a cured film comprising a cured product containing a quantum dot ink composition is provided.

[0034] According to another aspect of the present invention, a color filter comprising a cured film is provided.

[0035] According to another aspect of the present invention, a display device including a color filter is provided.

[0036] Beneficial effects

[0037] The quantum dot ink composition according to the present invention includes ligand compounds particularly suitable for AIGS quantum dots, thereby further improving the optical properties and stability of quantum dots.

[0038] The method for preparing quantum dot ink compositions according to the present invention can prepare quantum dot ink compositions with good physical properties by efficiently replacing the ligand compounds on the surface of quantum dots and allowing the replaced ligand compounds to bind more strongly to the surface of quantum dots.

[0039] The quantum dot ink composition according to the present invention achieves low viscosity to ensure good processability in inkjet printing, while exhibiting improved light absorption and light conversion efficiency, thus enabling its application in high-quality display devices. Detailed Implementation

[0040] Unless otherwise defined herein, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by those skilled in the art. Terms such as those defined in common dictionaries should be interpreted as having the same meaning as they have in the relevant technical context and should not be interpreted in an idealized or overly formal sense unless expressly defined herein.

[0041] Furthermore, as used herein, the terms “comprising” and / or “including” identify the presence of the stated feature, integer, step, operation, element, component, and / or group thereof, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0042] Furthermore, as used herein, “(meth)acrylate” refers to acrylate and methacrylate, “(meth)acryl” refers to acrylate and methacryl, and “(meth)acryloyl” refers to acryloyl and methacryloyl.

[0043] Furthermore, as used herein, the terms "monomer product" and "monomer" have the same meaning. In the context of the invention, a monomer is distinguished from oligomers and polymers, and is a compound having a weight average molecular weight of 1,000 or less. Herein, "photopolymerizable monomer" refers to a monomer containing a functional group that participates in the polymerization reaction, such as a (meth)acrylate group.

[0044] <Quantum dot composition>

[0045] The quantum dot ink composition according to the present invention is used in inkjet printing processes and comprises quantum dots having a ligand layer on their surface and photopolymerizable monomers. The quantum dot ink composition may further comprise at least one selected from the group consisting of photoinitiators, scattering particles, polymerization inhibitors, and other additives.

[0046] In one embodiment, the quantum dot ink composition can be a solvent-free quantum dot ink composition that does not contain solvent, and it achieves good dispersibility and low viscosity of quantum dots even without solvent. Furthermore, the quantum dot ink composition can be used for inkjet printing suitable for inkjet processes.

[0047] In one embodiment, the quantum dot ink composition may be substantially resin-free. By omitting the resin component, the quantum dot ink composition exhibits low viscosity, thereby ensuring good inkjet processability.

[0048] In one embodiment, the quantum dot ink composition may have a viscosity of 30 cP or less and exhibit a light conversion efficiency of 29% or higher relative to blue light when measured on a cured product of the quantum dot ink composition with a thickness of 7 μm. Preferably, the quantum dot ink composition has a viscosity of 25 cP or less and exhibits a light conversion efficiency of 30% or higher relative to blue light when measured on a cured product of the quantum dot ink composition with a thickness of 7 μm. More preferably, the quantum dot ink composition has a viscosity of 21 cP or less and exhibits a light conversion efficiency of 31% or higher relative to blue light when measured on a cured product of the quantum dot ink composition with a thickness of 7 μm.

[0049] In one embodiment, the cured product of the quantum dot ink composition can be obtained by heat treatment at 180 degrees Celsius for 30 minutes.

[0050] In one implementation, blue light may have a wavelength of 450 nanometers.

[0051] quantum dots

[0052] Quantum dots are (e.g., semiconductor-based) nanocrystals that exhibit quantum confinement or exciton confinement and are a type of luminescent (e.g., capable of emitting light upon energy excitation) nanostructures. In other words, quantum dots are nanoscale semiconductor materials that can have different band gaps depending on their size and composition, and therefore can emit light with different emission wavelengths.

[0053] Quantum dots can have homogeneous monolayer structures, multilayer structures (such as core-shell structures, gradient structures, etc.), or mixtures thereof. When the shell has a multilayer structure, each layer can contain different components.

[0054] Quantum dots can have any typical shape commonly used in the technology. For example, quantum dots can be nanoparticles, nanotubes, nanowires, nanofibers, or nanosheets with shapes such as spheres, rods, cones, disks, multi-arm shapes, and cubic shapes.

[0055] In one embodiment, the quantum dot may be an Ag-In-Ga-S (AIGS) quantum dot comprising silver, indium, gallium, and sulfur. Furthermore, the quantum dot may include gallium and zinc on its surface.

[0056] In one implementation, the quantum dots may not include cadmium, and may not include mercury, lead, or a combination thereof.

[0057] In one implementation, the quantum dot may or may not include copper.

[0058] In one implementation, the quantum dots may not include lithium, and may not include alkali metals such as sodium, potassium, etc.

[0059] The molar ratio between components in a quantum dot can be adjusted to ensure that the final quantum dot can exhibit the target composition and optical properties.

[0060] In one embodiment, the molar ratio of sulfur in the quantum dot to the sum of silver, indium, and gallium (S / (Ag+In+Ga)) can be 0.65 or more, 0.68 or more, 0.7 or more, 0.75 or more, 0.8 or more, 0.85 or more, 0.9 or more, 0.95 or more, 1 or more, 1.1 or more, 1.2 or more, 1.3 or more, 1.35 or more, 1.36 or more, 1.38 or more, 1.4 or more, or 1.45 or more. The molar ratio of sulfur to the sum of silver, indium, and gallium (S / (Ag+In+Ga)) can be 3 or less, 2.5 or less, 2 or less, 1.9 or less, 1.88 or less, 1.6 or less, 1.55 or less, 1.5 or less, 1.45 or less, 1.4 or less, 1.35 or less, 1.33 or less, 1.3 or less, 1.25 or less, 1.2 or less, 1.17 or less, 1.15 or less, 1.09 or less, 1.05 or less, or 1.02 or less.

[0061] In one embodiment, the molar ratio of indium and gallium to silver ((In+Ga) / Ag) in the quantum dot can be 1.3 or more, 1.4 or more, 1.5 or more, 1.65 or more, 1.7 or more, 1.75 or more, 1.8 or more, 1.85 or more, 1.9 or more, 1.95 or more, 1.99 or more, 2 or more, 2.1 or more, 2.2 or more, 2.3 or more, or 2.35 or more. The molar ratio of indium and gallium to silver ((In+Ga) / Ag) can be 7 or less, 6.5 or less, 6.3 or less, 6 or less, 5.9 or less, 5.7 or less, 5.66 or less, 5.5 or less, 5.3 or less, 5.1 or less, 4.5 or less, 4 or less, 3.5 or less, 3.2 or less, 3 or less, 2.8 or less, 2.6 or less, or 2.4 or less.

[0062] In one embodiment, the molar ratio of gallium to the sum of indium and gallium (Ga / (In+Ga)) in the quantum dot can be 0.5 or more, 0.55 or more, 0.6 or more, 0.65 or more, 0.7 or more, 0.75 or more, 0.8 or more, or 0.85 or more. The molar ratio of gallium to the sum of indium and gallium (Ga / (In+Ga)) can be 0.99 or less, 0.98 or less, 0.97 or less, 0.96 or less, 0.95 or less, 0.94 or less, 0.93 or less, 0.92 or less, 0.91 or less, 0.9 or less, or 0.83 or less.

[0063] In one embodiment, the molar ratio of gallium to sulfur (Ga / S) in the quantum dot can be 0.1 or more, 0.15 or more, 0.2 or more, 0.25 or more, 0.3 or more, 0.31 or more, 0.32 or more, 0.33 or more, 0.34 or more, 0.35 or more, 0.38 or more, 0.4 or more, 0.47 or more, 0.5 or more, 0.53 or more, 0.55 or more, 0.56 or more, 0.58 or more, 0.6 or more, or 0.62 or more. The molar ratio of gallium to sulfur (Ga / S) can be 1 or less, 0.9 or less, 0.8 or less, 0.6 or less, 0.55 or less, 0.45 or less, 0.42 or less, 0.41 or less, or 0.4 or less.

[0064] In one embodiment, the molar ratio of silver to sulfur (Ag / S) in the quantum dot can be 0.03 or more, 0.05 or more, 0.06 or more, 0.07 or more, 0.08 or more, 0.09 or more, 0.1 or more, 0.15 or more, 0.2 or more, 0.25 or more, 0.3 or more, 0.35 or more, 0.4 or more, or 0.45 or more. The molar ratio of silver to sulfur (Ag / S) can be 1 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.38 or less, 0.36 or less, 0.35 or less, 0.3 or less, 0.25 or less, 0.24 or less, or 0.23 or less.

[0065] In one embodiment, the molar ratio of indium to sulfur (In / S) in the quantum dot can be 0.01 or more, 0.05 or more, 0.08 or more, 0.09 or more, or 0.1 or more. The molar ratio of indium to sulfur (In / S) can be 0.5 or less, 0.4 or less, 0.3 or less, 0.25 or less, 0.15 or less, 0.14 or less, 0.13 or less, or 0.12 or less.

[0066] In one embodiment, the molar ratio of silver to indium (Ag / In) in the quantum dot can be 1.5 or more, 1.7 or more, 1.8 or more, 1.88 or more, or 2 or more. The molar ratio of silver to indium (Ag / In) can be 3.5 or less, 3 or less, 2.94 or less, 2 or less, 1.88 or less, or 1.8 or less.

[0067] In one embodiment, the molar ratio of zinc to sulfur (Zn / S) in the quantum dot may be 0.01 or more, 0.05 or more, or 0.1 or more. The molar ratio of zinc to sulfur (Zn / S) may be 0.8 or less, 0.3 or less, or 0.25 or less.

[0068] In one embodiment, the molar ratio of zinc to silver (Zn / Ag) in the quantum dot can be 0.3 or more, 0.35 or more, 0.4 or more, 0.45 or more, 0.5 or more, 0.55 or more, 0.6 or more, 0.65 or more, 0.7 or more, 0.75 or more, 0.8 or more, 0.85 or more, 0.9 or more, 0.95 or more, 1 or more, 1.2 or more, 1.4 or more, 1.6 or more, 1.7 or more, 1.9 or more, 2 or more, 2.5 or more, 3 or more, 3.5 or more, or 4 or more. The molar ratio of zinc to silver (Zn / Ag) can be 5 or less, 4.7 or less, 4.4 or less, 4.1 or less, 3.9 or less, 3.7 or less, 3.5 or less, 3 or less, 2.7 or less, 2.6 or less, or 2.3 or less.

[0069] In one embodiment, the molar ratio of zinc to indium (Zn / In) in the quantum dot can be 0.1 or more, 0.3 or more, 0.5 or more, 0.7 or more, 0.75 or more, 0.78 or more, 0.9 or more, 1 or more, 1.1 or more, 1.2 or more, 1.3 or more, 1.4 or more, 1.5 or more, 1.6 or more, 1.7 or more, 1.72 or more, 1.9 or more, 2.1 or more, 2.3 or more, 2.5 or more, 2.7 or more, 2.9 or more, or 3 or more. The molar ratio of zinc to indium (Zn / In) can be 10 or less, 8 or less, 6 or less, 5 or less, 4.5 or less, 4 or less, 3 or less, 3.5 or less, 2 or less, 1.9 or less, 1.85 or less, 1.75 or less, 1.7 or less, 1.72 or less, or 1.6 or less.

[0070] In one embodiment, the molar ratio of zinc to gallium (Zn / Ga) in the quantum dot can be 0.1 or more, 0.2 or more, 0.3 or more, 0.35 or more, 0.4 or more, 0.45 or more, or 0.5 or more. The molar ratio of zinc to gallium (Zn / Ga) can be 3 or less, 2.5 or less, 2 or less, 1.9 or less, 1.7 or less, 1.5 or less, 1.4 or less, 1.2 or less, 1.1 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, or 0.49 or less.

[0071] In one embodiment, the molar ratio of zinc to the sum of gallium, indium, and silver in the quantum dot (Zn / (Ga+In+Ag)) can be 0.05 or more, 0.1 or more, 0.2 or more, 0.25 or more, 0.3 or more, 0.35 or more, or 0.4 or more. The molar ratio of zinc to the sum of gallium, indium, and silver (Zn / (Ga+In+Ag)) can be 2 or less, 1.7 or less, 1.4 or less, 1.1 or less, 0.9 or less, 0.7 or less, 0.5 or less, or 0.45 or less.

[0072] In one embodiment, the molar ratio of zinc to the sum of gallium and indium in the quantum dot (Zn / (Ga+In)) can be 0.05 or more, 0.1 or more, 0.2 or more, 0.25 or more, 0.3 or more, 0.35 or more, or 0.4 or more. The molar ratio of zinc to the sum of gallium and indium (Zn / (Ga+In)) can be 2 or less, 1.7 or less, 1.4 or less, 1.1 or less, 0.9 or less, 0.7 or less, 0.5 or less, or 0.45 or less.

[0073] In quantum dots, the indium content may have a concentration gradient that varies (e.g., decreases) in the radial direction (e.g., from the center of the quantum dot to its outer periphery). In one embodiment, the indium content in the region of the quantum dot adjacent to its surface (e.g., the shell or outermost layer) may be less than the indium content in the inner region of the quantum dot. In one embodiment, the region of the quantum dot adjacent to its surface (e.g., the shell or outermost layer) may not contain indium.

[0074] In quantum dots, gallium may be present on the surface of the quantum dot or on a surface that can be exposed to the quantum dot, zinc may be present on the surface of the quantum dot, and ligand compounds may be configured to be on a surface adjacent to or in contact with the surface of the quantum dot.

[0075] Quantum dots may have a core-shell structure. The core may have a different composition than the shell. The quantum dot or shell may further include an outermost inorganic layer, which may include, for example, zinc sulfides (e.g., including third semiconductor nanocrystals). Zinc sulfides may include zinc; and selenium, sulfur, or combinations thereof. Zinc sulfides may include ZnSe, ZnSeS, ZnS, or combinations thereof.

[0076] The core may have a size or average size (hereinafter referred to as "particle size") of 0.5 nanometers or more, 1 nanometer or more, 1.5 nanometers or more, 1.7 nanometers or more, 1.9 nanometers or more, 2 nanometers or more, 2.1 nanometers or more, 2.3 nanometers or more, 2.5 nanometers or more, 2.7 nanometers or more, 2.9 nanometers or more, 3 nanometers or more, 3.1 nanometers or more, 3.3 nanometers or more, 3.5 nanometers or more, 3.7 nanometers or more, or 3.9 nanometers or more. The core may have a particle size of 5 nanometers or less, 4.5 nanometers or less, 4 nanometers or less, 3.5 nanometers or less, 3 nanometers or less, 2.5 nanometers or less, 2 nanometers or less, or 1.5 nanometers or less.

[0077] The shell may have a thickness or average thickness (hereinafter referred to as "thickness") of 0.1 nanometers or more, 0.3 nanometers or more, 0.5 nanometers or more, 0.7 nanometers or more, 1 nanometer or more, 1.5 nanometers or more, 1.7 nanometers or more, 1.9 nanometers or more, 2 nanometers or more, 2.1 nanometers or more, 2.3 nanometers or more, 2.5 nanometers or more, 2.7 nanometers or more, 2.9 nanometers or more, 3 nanometers or more, 3.1 nanometers or more, 3.3 nanometers or more, 3.5 nanometers or more, 3.7 nanometers or more, or 3.9 nanometers or more. The shell may have a thickness of 5 nanometers or less, 4.5 nanometers or less, 4 nanometers or less, 3.5 nanometers or less, 3 nanometers or less, 2.5 nanometers or less, 2 nanometers or less, or 1.5 nanometers or less.

[0078] In one embodiment, the inorganic layer may have any suitable thickness. The inorganic layer may have a thickness of 0.1 nm or more, 0.3 nm or more, 0.5 nm or more, or 0.7 nm or more. The inorganic layer may have a thickness of 5 nm or less, 4 nm or less, 3.5 nm or less, 3 nm or less, 2.5 nm or less, 2 nm or less, 1.5 nm or less, 1 nm or less, or 0.8 nm or less. The inorganic layer may have a thickness of 0.1 nm to 5 nm, 0.3 nm to 4 nm, 0.5 nm to 3.5 nm, 0.7 nm to 3 nm, 0.9 nm to 2.5 nm, 1 nm to 2 nm, 1.5 nm to 1.7 nm, or combinations thereof.

[0079] Quantum dots can have particle sizes of 1 nanometer or more, 1.5 nanometers or more, 2 nanometers or more, 2.5 nanometers or more, 3 nanometers or more, 3.5 nanometers or more, 4 nanometers or more, 4.5 nanometers or more, 5 nanometers or more, 5.5 nanometers or more, 6 nanometers or more, 6.5 nanometers or more, 7 nanometers or more, 7.5 nanometers or more, 8 nanometers or more, 8.5 nanometers or more, 9 nanometers or more, 9.5 nanometers or more, 10 nanometers or more, or 10.5 nanometers or more. Quantum dots can also have particle sizes of 50 nanometers or less, 48 ​​nanometers or less, 46 nanometers or less, 44 nanometers or less, 42 nanometers or less, 40 nanometers or less, 35 nanometers or less, 30 nanometers or less, 25 nanometers or less, 20 nanometers or less, 18 nanometers or less, 16 nanometers or less, 14 nanometers or less, 12 nanometers or less, 11 nanometers or less, 10 nanometers or less, 8 nanometers or less, 6 nanometers or less, or 4 nanometers or less. Particle size can be the particle diameter.

[0080] Based on the total weight of the quantum dot ink composition, quantum dots may be present in amounts ranging from 1 wt% to 50 wt%, preferably from 20 wt% to 40 wt%, and more preferably from 25 wt% to 35 wt%.

[0081] Ligand

[0082] Quantum dots possess a ligand layer on their surface, and the ligands in the ligand layer modify the surface of the quantum dots. Since the hydrophobic nature of the quantum dot surface hinders the dispersion of photopolymerizable monomers, the miscibility of quantum dots with photopolymerizable monomers can be improved by surface modification of the quantum dots using appropriate ligands.

[0083] The ligands included in the ligand layer are not limited to specific compounds, as long as the ligand compound can improve the miscibility of quantum dots and photopolymerizable monomers, and may include, for example, compounds represented by Formula 1.

[0084] [Formula 1]

[0085]

[0086] Compounds represented by Formula 1 include (meth)acrylate groups, alkylene oxide groups, ester groups and carboxylic acid groups in their molecular structure, especially multiple ester groups.

[0087] The compound represented by Formula 1 may have a weight average molecular weight (Mw) of 100 to 2,000, preferably 400 to 1,500. When the compound represented by Formula 1 meets this range of weight average molecular weight, the compound can improve the miscibility of quantum dots with photopolymerizable monomers and can exhibit good optical properties while maintaining appropriate viscosity of the quantum dot ink composition.

[0088] Furthermore, in Equation 1, R 1 and R 2 Each can be a hydrogen atom or a methyl group independently.

[0089] Furthermore, in Equation 1, L 1 L 2 and L 3 Each can be independently represented as C1 to C 20 Hydrocarbon group.

[0090] Furthermore, in Equation 1, n can be an integer from 1 to 20, preferably an integer from 2 to 15, and even more preferably an integer from 3 to 12.

[0091] C1 to C 20 The hydrocarbon group can be divalent, ranging from C1 to C2. 20 Aliphatic hydrocarbon groups or divalent C6 to C 20 Aromatic hydrocarbon group.

[0092] Aliphatic hydrocarbon groups can be saturated or unsaturated, as well as cyclic or alicyclic hydrocarbon groups. Furthermore, alicyclic hydrocarbon groups can be monocyclic or polycyclic.

[0093] Divalent saturated hydrocarbon groups may include straight-chain alkylene groups, such as methylene, ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, dodecylene, hexadecylene, eicosylene, etc.; branched alkylene groups, such as isopropylene, isobutylene, isopentylene, neopentylene, 2-ethylhexylene, sec-butylene, 1,3-dimethylbutylene, 2-ethylbutylene, etc.; and alicyclic alkylene groups, such as cyclopropylene, cyclopentylene, cyclohexylene, cycloheptylene, cyclooctylene, tricyclodecylene, etc. The divalent saturated hydrocarbon group may have 1 to 10 carbon atoms, more preferably 1 to 5, and even more preferably 1 to 3.

[0094] The divalent aromatic hydrocarbon group may include phenylene, benzylene, tolylene, xylene, naphthylene, etc., preferably phenylene, benzylene, and tolylene. The divalent aromatic hydrocarbon group may have 6 to 15 carbon atoms, more preferably 6 to 12, and even more preferably 6 to 10.

[0095] The ligands in the ligand layer may include compounds represented by Formula 2.

[0096] [Equation 2]

[0097]

[0098] In Equation 2, R 3 and R 4 Each can be a hydrogen atom or a methyl group independently.

[0099] Furthermore, in Equation 2, o can be an integer from 1 to 20, preferably an integer from 2 to 15, and even more preferably an integer from 3 to 12.

[0100] Furthermore, quantum dots and ligands can exist in their mixture at a weight ratio of 1:0.05 to 1 (preferably 1:0.1 to 0.5). Within this range, it is possible to improve the miscibility of quantum dots with photopolymerizable monomers through surface modification of the quantum dots, while simultaneously improving the balance between optical properties and stability.

[0101] Photopolymerizable monomers

[0102] In the quantum dot composition according to the invention, photopolymerizable monomers are used to control the formulation in which quantum dots are dispersed, i.e., the overall crosslinking density of the polymer matrix, thereby achieving the structure and other properties of the matrix. Furthermore, photopolymerizable monomers can improve flexibility, as well as adhesion and bonding to other materials.

[0103] Photopolymerizable monomers may include at least one selected from the group consisting of monofunctional to hexafunctional (meth)acrylate compounds. Monofunctional to hexafunctional (meth)acrylate compounds may be any monomer commonly used in the art, without limitation.

[0104] Examples of monofunctional (meth)acrylate compounds may include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, octadecyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, isodecanyl (meth)acrylate, isobornyl (meth)acrylate, etc.

[0105] Examples of bifunctional (meth)acrylate compounds may include 1,6-hexanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 3-methylpentyl glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, etc., with 1,6-hexanediol di(meth)acrylate being preferred.

[0106] Examples of trifunctional to hexafunctional (meth)acrylate compounds may include trimethylolpropane tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, propoxylated trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, ethoxylated dipentaerythritol hexa(meth)acrylate, propoxylated dipentaerythritol hexa(meth)acrylate, dipentaerythritol hexa(meth)acrylate, etc.

[0107] On the other hand, while monofunctional (meth)acrylate compounds typically have low molecular weights, which is advantageous for controlling the viscosity of quantum dot ink compositions, they may also exhibit increased volatility at high temperatures, leading to increased degassing during high-temperature processes such as post-baking. This increased degassing can cause defects such as cracking in the coating. Therefore, photopolymerizable monomers preferably include at least one type selected from difunctional to hexafunctional (meth)acrylate compounds.

[0108] Furthermore, although increasing the molecular weight generally reduces degassing during high-temperature processes, increasing the number of functional groups in (meth)acrylate compounds may lead to decreased inkjet processability and storage stability through increased viscosity of the quantum dot ink composition. Therefore, photopolymerizable monomers preferably include at least one selected from difunctional to trifunctional (meth)acrylate compounds, more preferably difunctional (meth)acrylate compounds, and most preferably 1,6-hexanediol diacrylate.

[0109] Based on the total weight of the quantum dot ink composition, the photopolymerizable monomer may be present in an amount of 35% to 80% by weight, preferably 45% to 70% by weight.

[0110] Photoinitiator

[0111] Photoinitiators are used to initiate photopolymerization by excitation by light (e.g., ultraviolet (UV) light) and can be selected from typical photopolymerizable initiators in the technology without limitation.

[0112] In one embodiment, the photoinitiator may include at least one selected from the group consisting of phosphine oxide compounds, acetophenone compounds, benzophenone compounds, triazine compounds, diimidazole compounds, oxime compounds, and thioxanthone compounds.

[0113] Examples of phosphine oxide compounds may include bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, trimethylbenzoylphenylphosphine oxide, ethyl(2,4,6-trimethylbenzoyl)phenylphosphine ester, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, etc. TPO-L from IGM can be used as a commercially available phosphine oxide compound.

[0114] Examples of acetophenone compounds may include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylprop-1-one, benzyl dimethyl ketal, 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methylprop-1-one, 1-hydroxycyclohexylphenyl ketone, 2-methyl-1-(4-methylthiophenyl)-2-morpholinylprop-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinylphenyl)but-1-one, 2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]prop-1-one, 2-(4-methylbenzyl)-2-(dimethylamino)-1-(4-morpholinylphenyl)but-1-one, etc.

[0115] Examples of benzophenone compounds may include benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4-benzoyl-4'-methyldiphenyl sulfide, 3,3',4,4'-tetra(tert-butylperoxycarbonyl)benzophenone, 2,4,6-trimethylbenzophenone, etc.

[0116] Examples of triazine compounds may include 2,4-bis(trichloromethyl)-6-(4-methoxyphenyl)-1,3,5-triazine, 2,4-bis(trichloromethyl)-6-(4-methoxynaphthyl)-1,3,5-triazine, 2,4-bis(trichloromethyl)-6-piperyl-1,3,5-triazine, 2,4-bis(trichloromethyl)-6-(4-methoxystyryl)-1,3,5-triazine, 2,4-bis(trichloromethyl)-6-[2 [-(5-methylfuran-2-yl)vinyl]-1,3,5-triazine, 2,4-bis(trichloromethyl)-6-[2-(furan-2-yl)vinyl]-1,3,5-triazine, 2,4-bis(trichloromethyl)-6-[2-(4-diethylamino-2-methylphenyl)vinyl]-1,3,5-triazine, 2,4-bis(trichloromethyl)-6-[2-(3,4-dimethoxyphenyl)vinyl]-1,3,5-triazine, etc.

[0117] Examples of diimidazole compounds may include 2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetraphenyldiimidazole, 2,2'-bis(2,3-dichlorophenyl)-4,4',5,5'-tetraphenyldiimidazole, 2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetra(alkoxyphenyl)diimidazole, 2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetra(trialkoxyphenyl)diimidazole, 2,2-bis(2,6-dichlorophenyl)-4,4',5,5'-tetraphenyl-1,2'-diimidazole, and diimidazole compounds in which the phenyl group at the 4,4',5,5' position is substituted with a carboxyalkoxy group, etc. Among them, 2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetraphenylbisimidazole, 2,2'-bis(2,3-dichlorophenyl)-4,4',5,5'-tetraphenylbisimidazole, 2,2-bis(2,6-dichlorophenyl)-4,4',5,5'-tetraphenyl-1,2'-bisimidazole and 2,2-bis(2,6-dichlorophenyl)-4,4',5,5'-tetraphenyl-1,2'-bisimidazole are preferred.

[0118] Examples of oxime compounds may include o-ethoxycarbonyl-α-oxoimino-1-phenylprop-1-one, 2-((benzoyloxy)imino)-1-(4-(phenylthio)phenyl)oct-1-one, etc. Commercially available oxime compounds include Irgacure OXE 01 and OXE 02 from BASF.

[0119] Examples of thioxanthone compounds may include 2-isopropylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone, 1-chloro-4-propoxythioxanthone, etc.

[0120] Based on the total weight of the quantum dot ink composition, the photoinitiator may be present in an amount from 0.01 wt% to 10 wt%, preferably from 0.1 wt% to 5 wt%.

[0121] Scattering particles

[0122] Scattering particles are used to increase the light path emitted from the light source, thereby increasing the overall light conversion efficiency of the light-scattering pixels.

[0123] The scattering particles can be selected from any typical inorganic material, preferably metal oxides.

[0124] The scattering particles may include at least one selected from the group consisting of, for example, Al₂O₃, SiO₂, ZnO, ZrO₂, CaCO₃, BaSO₄, BaTiO₃, TiO₂, Ta₂O₅, Ti₃O₅, ITO, IZO, ATO, ZnO-Al, Nb₂O₃, SnO, and MgO. Preferably, the scattering particles include at least one selected from the group consisting of CaCO₃, BaSO₄, TiO₂, and ZrO₂, and more preferably TiO₂.

[0125] The scattering particles may have a primary average particle size (D90) of 300 nm or smaller, preferably 150 nm to 250 nm, more preferably 180 nm to 230 nm, but are not limited thereto.

[0126] Based on the total weight of the quantum dot ink composition, the scattering particles may be present in an amount from 0.01 wt% to 10 wt%, preferably from 0.1 wt% to 5 wt%.

[0127] Polymer inhibitors

[0128] Polymerization inhibitors react with free radicals to form low-reactivity free radicals or compounds that cannot cause polymerization, and can be added to control the rate of photopolymerization.

[0129] Polymerization inhibitors can be any substance known in the art without limitation. For example, polymerization inhibitors may include quinone compounds, phenolic or aniline compounds, and aromatic nitro or nitroso compounds. These can be used alone or in combination.

[0130] Specifically, quinone compounds may include, for example, hydroquinone (HQ), methylhydroquinone (THQ), hydroquinone monomethyl ether (MEHQ), hydroquinone monoethyl ether (EEHQ), 1,4-benzoquinone (BQ), 2,5-diphenylbenzoquinone (DPBQ), methyl-1,4-benzoquinone (MBQ), phenyl-1,4-benzoquinone (PBQ), etc.

[0131] Phenolic or aniline compounds may include, for example, 2,6-di-tert-butyl-4-methylphenol (BHT), 2,6-diphenyl-4-octadecyloxyphenol, catechol, etc.

[0132] Aromatic nitro or nitroso compounds may include, for example, phenothiazine, bis(α-methylbenzyl)phenothiazine, 3,7-dioctylphenothiazine, bis(α,α-dimethylbenzyl)phenothiazine, dimethyl dithiocarbamate, diethyl dithiocarbamate, dipropyl dithiocarbamate, dibutyl dithiocarbamate, diphenyl dithiocarbamate, etc.

[0133] Based on the total weight of the quantum dot ink composition, the polymerization inhibitor may be present in an amount of 0.01% to 2% by weight, preferably 0.05% to 1% by weight.

[0134] Other additives

[0135] In addition to the components described above, the quantum dot ink composition according to the present invention may include any additives known in the art without limitation. Here, the content of the additives may be appropriately adjusted within the range known in the art.

[0136] Examples of additives include silane compounds, siloxane compounds, antioxidants, lubricants, surface modifiers, surfactants, adhesion enhancers, defoamers, slip agents, solvents, wetting agents, light stabilizers, antifouling agents, softeners, thickeners, polymers, etc. These additives can be used alone or as mixtures thereof.

[0137] Silane compounds are used to impart adhesive properties to the matrix, while siloxane compounds are used to impart wetting properties. Both silane and siloxane compounds can be selected from typical compounds known in the art.

[0138] Antioxidants are used to inhibit discoloration caused by heat or light exposure, as well as discoloration caused by various oxidizing gases (such as ozone, reactive oxygen species, NO). x SO x (where x is an integer) and other factors causing discoloration. In this invention, antioxidants can prevent matrix discoloration or inhibit film thickness reduction due to degradation. Examples of antioxidants include hydrazides, hindered amine antioxidants, nitrogen-enriched cyclic thiol compounds, thioether antioxidants, hindered phenolic antioxidants, ascorbic acid, zinc sulfate, thiocyanate, thiourea derivatives, sugars, nitrites, sulfites, thiosulfates, hydroxylamine derivatives, etc.

[0139] Leveling agents can be used to further enhance the adhesion of quantum dot compositions by leveling them so that the quantum dot compositions can be coated flatly and uniformly. Leveling agents may include acrylic compounds, silicone compounds, or mixtures thereof. For example, a leveling agent may include a polyether-modified polydimethylsiloxane containing (meth)acryloyl groups added to its polyether chain.

[0140] Surfactants can be used to improve the mixing and coating uniformity of quantum dot compositions. Surfactants can be selected from typical cationic, anionic, and nonionic surfactants known in the art. For example, surfactants may include at least one selected from fluorinated surfactants, silicone surfactants, and fluorosilicone surfactants.

[0141] Light stabilizers are UV absorbers and increase the weather resistance of the matrix. Softeners are used to reduce cracking in the dried polymer matrix and can improve impact resistance and flexural strength by reducing cracking in the cured matrix.

[0142] <Methods for preparing quantum dot ink compositions>

[0143] The present invention provides a method for preparing a quantum dot ink composition. The method may include: (a) performing primary surface modification on quantum dots comprising silver, indium, gallium and sulfur using an X-type ligand; (b) performing secondary surface modification on the quantum dots subjected to primary surface modification using a compound represented by Formula 1; and (c) dispersing the quantum dots subjected to secondary surface modification in a photopolymerizable compound.

[0144] For details regarding the components used in the method for preparing quantum dot ink compositions according to the present invention, please refer to the description of the above-mentioned <Quantum Dot Compositions>.

[0145] In step (a), quantum dots comprising silver, indium, gallium, and sulfur can be prepared by any method known in the art (e.g., hot-injection method, microfluidic reactor method, microwave irradiation-based method, etc.). For example, quantum dots comprising silver, indium, gallium, and sulfur can be prepared by reacting silver precursors, indium precursors, gallium precursors, and sulfur precursors in a solution containing organic ligands and organic solvents at a predetermined temperature (e.g., 20°C to 300°C, 80°C to 295°C, 120°C to 290°C, or 200°C to 280°C), followed by centrifugation.

[0146] There are no particular limitations on the silver precursor and it can be appropriately selected. The silver precursor may include, for example, silver powder, silver alkylation compounds, silver alkoxide, silver carboxylate, silver acetylacetonate, silver nitrate, silver sulfate, silver halide, silver cyanide, silver hydroxide, silver oxide, silver peroxide, silver carbonate, or combinations thereof, preferably silver nitrate, silver acetate, silver acetylacetonate, silver chloride, silver bromide, silver iodide, or combinations thereof, but is not limited thereto.

[0147] There are no particular limitations on the indium precursor and it can be appropriately selected. Indium precursors may include, for example, indium powder, indium alkylation compounds, indium alkoxide, indium carboxylate, indium nitrate, indium perchlorate, indium sulfate, indium acetylacetone, indium halide, indium cyanide, indium hydroxide, indium oxide, indium peroxide, indium carbonate, indium acetate, or combinations thereof, preferably indium carboxylate, such as indium oleate and indium myristate, indium acetate, indium hydroxide, indium chloride, indium bromide, indium iodide, or combinations thereof.

[0148] There are no particular limitations on gallium precursors, and they can be appropriately selected. Gallium precursors may include, for example, gallium powder, gallium alkylation compounds, gallium alkoxide, gallium carboxylate, gallium nitrate, gallium perchlorate, gallium sulfate, gallium acetylacetonate, gallium halide, gallium cyanide, gallium hydroxide, gallium oxide, gallium peroxide, gallium carbonate, gallium chloride, gallium bromide, gallium iodide, or combinations thereof, preferably gallium chloride, gallium iodide, gallium bromide, gallium acetate, gallium acetylacetonate, gallium oleate, gallium palmitate, gallium stearate, gallium myristate, gallium hydroxide, or combinations thereof.

[0149] There are no particular restrictions on the sulfur precursor, and it can be appropriately selected. The sulfur precursor can be an organic solvent dispersion of sulfur or a reaction product, such as s-oleylamine, s-dodecylamine, s-octadecene (S-ODE), trioctylphosphine sulfide (S-TOP), tributylphosphine sulfide (S-TBP), triphenylphosphine sulfide (S-TPP), s-trioctylamine (S-TOA), trimethylsilylalkyl sulfide, bis(trimethylsilyl) sulfide, mercaptopropylsilane, ammonium sulfide, sodium sulfide, C1 to C2... 30 Thiols (e.g., α-toluenethiol, octylthiol, dodecylthiol, octadecenethiol, etc.), isothiocyanate compounds (e.g., cyclohexyl isothiocyanate), alkyltrithiocarbonates (e.g., ethyltrithiocarbonate), allyl thiols, thiourea compounds (e.g., thiourea, dialkylthiourea, phenylthiourea) or combinations thereof.

[0150] In step (a), the X-type ligand is a ligand that is attached to the surface of the quantum dot by a negatively charged functional group selected from a group composed of carboxylate, phosphonate, and thiolate groups, and can be derived from C5 to C6. 30 Compounds of fatty acids. X-type ligands can be derived from saturated or unsaturated fatty acids, such as caprylic acid, capric acid, dodecanoic acid, myristic acid, palmitic acid, stearic acid, oleic acid, etc., with oleic acid derivatives being preferred.

[0151] There are no particular restrictions on oleic acid derivatives, and appropriate selection is permissible. Oleic acid derivatives may include zinc carboxylate, zinc phosphonate, zinc oleate, or combinations thereof.

[0152] In step (a), primary surface modification can be performed, but is not limited to, introducing X-type ligands into quantum dots including silver, indium, gallium and sulfur, followed by reacting at 25 to 100 degrees Celsius for 30 minutes to 5 hours to modify the surface of the quantum dots.

[0153] In step (b), the secondary surface modification can be performed by adding a compound represented by Formula 1 to the quantum dots that have undergone primary surface modification, followed by reacting at 25 to 100 degrees Celsius for 30 minutes to 5 hours to modify the surface of the quantum dots, but is not limited thereto.

[0154] Typically, AIGS quantum dots are prepared in the presence of compounds including amino, thiol, phosphine, or phosphine oxide groups. Therefore, the ligand compound binds to the surface of the AIGS quantum dots via non-covalent electron pairs selected from functional groups composed of amino, thiol, phosphine, and phosphine oxide groups, thereby transforming the surface of the quantum dots into an L-shape.

[0155] L-type ligands are bonded to the surface of quantum dots via coordinate bonds through non-covalent electron pairs, while X-type ligands are bonded to the surface of quantum dots via electroweak interactions. The compound represented by Formula 1 used for secondary surface modification is an X-type ligand containing a carboxylate group, which reduces the yield of surface substitution reactions when directly surface-modified on quantum dots containing L-type ligands. Therefore, AIGS quantum dots can undergo primary surface modification using X-type ligands (step a) and secondary surface modification using the compound represented by Formula 1 (step b) in sequence, thereby significantly increasing the yield of surface substitution reactions on quantum dots.

[0156] In one embodiment, the secondary surface modification in step (b) can be carried out in the presence of a metal salt, preferably a metal chloride, and more preferably zinc chloride (ZnCl2).

[0157] Quantum dots that have undergone secondary surface modification can be obtained by centrifugation and dispersed in photopolymerizable compounds to prepare solvent-free quantum dot ink compositions.

[0158] <Curated films, color filters, and display devices>

[0159] This invention provides a cured film comprising a cured product of a quantum dot ink composition. The cured product is prepared by applying the quantum dot ink composition to a substrate to form a pattern using an inkjet method; and curing the pattern.

[0160] The substrate can be a substrate with a flat surface, such as a glass substrate, silicon substrate, polycarbonate substrate, polyester substrate, aramid substrate, polyamide-imide substrate, polyimide substrate, Al substrate, GaAs substrate, etc., but is not limited to these. The substrate can undergo pretreatment, such as chemical treatment using a silane coupling agent, plasma treatment, ion plating, sputtering, vapor phase reaction, vacuum deposition, etc. In addition, the substrate can have a partition matrix formed thereon.

[0161] The present invention also provides a color filter comprising a cured film. The color filter may comprise a pixel layer formed by applying the aforementioned quantum dot ink composition to a substrate in a predetermined pattern, followed by curing the quantum dot ink composition. The composition and manufacturing method of the color filter are known in the art and will not be described in detail.

[0162] The present invention also provides a display device including a color filter. The display device may include, but is not limited to, liquid crystal displays (LCDs), electroluminescent displays (ELs), plasma displays (PDPs), field emission displays (FEDs), organic light-emitting diodes (OLEDs), etc. The display device according to the present invention may further include a blue light source and a color filter, and may include configurations known in the art as needed.

[0163] Methods of implementing the invention

[0164] The invention will now be described in more detail with reference to some embodiments. It should be understood that these examples are for illustrative purposes only and should not be construed as limiting the invention in any way.

[0165] <Example>

[0166] Preparation Example 1: Preparation of AIGS Quantum Dots

[0167] A 0.06 M silver-containing precursor solution (hereinafter referred to as "silver precursor") was prepared by dissolving silver acetate in oleylamine; a 1 M sulfur-containing precursor solution (hereinafter referred to as "sulfur precursor") was prepared by dispersing sulfur in oleylamine; and a 0.2 M indium-containing precursor solution (hereinafter referred to as "indium precursor") was prepared by dissolving indium(III) chloride in ethanol.

[0168] In a 100 mL reaction flask, gallium acetylacetonate, octadecene (ODE), and 1-dodecylthiol were placed and heated under vacuum at 120°C for 10 minutes. After cooling the flask to room temperature and purging with nitrogen, silver, sulfur, and indium precursors were added. The flask temperature was then increased to 210°C to allow the reaction to proceed for 60 minutes or less. After lowering the flask temperature to 180°C, trioctylphosphine (TOP) was added to the resulting mixture, which was then cooled to room temperature. Hexane and ethanol were added to the resulting mixture to promote precipitation. The first semiconductor nanocrystals (quantum dot cores) were obtained by centrifugation and redispersed in toluene. The molar ratio of indium, gallium, and sulfur precursors used was 1:2.3:4.8.

[0169] A 4.5 M gallium-containing precursor solution (hereinafter referred to as "gallium precursor") was prepared by dissolving gallium chloride in toluene.

[0170] Dimethylthiourea (DMTU), oleylamine, and dodecyl mercaptan were placed in a flask and heated under vacuum at 120°C for 10 minutes. The flask was then purged with N2 and heated to 240°C. First semiconductor nanocrystals, gallium precursors, and silver precursors were then added to the flask. The reactor was then heated to 320°C and the resulting solution was reacted for approximately 10 minutes. The temperature of the resulting solution was raised to 180°C, and trioctylphosphine was added to the resulting mixture, which was then cooled to room temperature. Hexane and ethanol were added to the resulting mixture to precipitate the obtained nanoparticles. AIGS quantum dots were obtained by centrifugation and redispersed in toluene. The molar ratio of gallium precursor, silver precursor, and sulfur precursor was 1:0.5:1.

[0171] Preparation Example 2: Preparation of Zinc Oleate

[0172] In a 2 L flask, 250 mmol of zinc acetate, 500 mmol of oleic acid, and 500 mL of trioctylamine were placed and stirred with a stir bar, followed by vacuum treatment. The resulting mixture was heated to 120°C over 30 minutes and maintained for 40 minutes. After switching the flask to N2 purging, the mixture was heated to 280°C and maintained for 90 minutes. After the reaction was complete, the heating mantle was removed and the mixture was cooled by blowing air, thus preparing zinc oleate.

[0173] Preparation Example 3: Preparation of ligand compound A-1

[0174] Step 1

[0175] In a cooled water bath, 0.3 mol (64.9 g) of mono(2-acryloyloxyethyl)succinate, 1.5 mol (291 g) of tetraethylene glycol, 0.03 mol (3.7 g) of 4-(dimethylamino)pyridine, and 150 g of dichloromethane were placed and stirred. Then, 300 mL of 1.0 M 1,3-dicyclohexylcarbodiimide was slowly added and stirred at room temperature for 1 hour under a nitrogen atmosphere. The reaction product was filtered, extracted and neutralized using 10% aqueous HCl, 1 M aqueous NaHCO3, and distilled water. After neutralization, residual water was removed using magnesium sulfate (MgSO4), and the resulting product was concentrated using a vacuum evaporator.

[0176] Step 2

[0177] In a flask, 0.24 mol (72.5 g) of the product prepared in step 1, 0.24 mol (23.9 g) of succinic anhydride, 0.024 mol (2.93 g) of 4-(dimethylamino)pyridine, and 220 g of 1,2-dichloroethane were placed and dispersed under a nitrogen atmosphere. The condenser was connected to the flask, and the resulting mixture was heated to 65°C and stirred for 1 hour or longer. After stirring, the reaction product was extracted and neutralized using a 10% aqueous HCl solution and distilled water. After neutralization, residual water was removed using MgSO4, and the resulting product was concentrated using a vacuum evaporator and dried in a vacuum oven, thereby preparing compound A-1 (molecular weight: 492.47 g / mol) represented by Formula 3.

[0178] [Formula 3]

[0179]

[0180] Preparation Example 4: Preparation of ligand compound a-1

[0181] 0.271 mol of thioglycolic acid, 0.276 mol of poly(ethylene glycol) methyl ether 550 (Mn 550) and 0.027 mol of p-toluenesulfonic acid monohydrate were mixed with 350 ml of cyclohexane and reacted at 80°C for 18 hours under a nitrogen atmosphere.

[0182] After the reaction was complete, cyclohexane was removed from the reaction product, and the product was then dissolved in chloroform. The product was neutralized with an aqueous solution of sodium bicarbonate (NaHCO3), and the residual solvent was removed with MgSO4, thereby preparing compound a-1 (PEG-550T) represented by Formula 4.

[0183] [Formula 4]

[0184]

[0185] Preparation Example 5: Preparation of ligand compound a-2

[0186] Step 1

[0187] 20 g (0.05 mol) of MPEG-400 (polyoxyethylene monomethyl ether, Green Chemicals Co., Ltd.) and 5.1 g (0.05 mol) of triethylamine were dissolved in 350 mL of dichloromethane. 9.5 g (0.05 mol) of p-toluenesulfonyl chloride was slowly added dropwise to the resulting solution at 0°C, and the reaction was stirred at room temperature for 12 hours. The reaction product was extracted with distilled water, and residual water was removed from the organic layer using anhydrous magnesium sulfate. The reaction product was then concentrated using a vacuum evaporator.

[0188] Step 2

[0189] The final 27 g (0.05 mol) product obtained in step 1 was dissolved in 200 ml of water, and 16.3 g (0.25 mol) of sodium azide was added to the resulting solution under a nitrogen atmosphere. The reaction was then stirred at 80°C for 18 hours. After the reaction was complete, the product was extracted with dichloromethane, and residual water was removed from the organic layer using anhydrous magnesium sulfate. The product was then concentrated using a vacuum evaporator.

[0190] Step 3

[0191] In a flask, 20.4 g (0.05 mol) of the product finally obtained in step 2 and 13.9 g (0.053 mol) of triphenylphosphine were placed and stirred at 50°C for 18 hours. After the reaction was complete, 100 mL of water was added to the reaction product, and the mixture was stirred for 30 minutes. The solids formed during the reaction were filtered off, and the filtrate was concentrated using a vacuum evaporator, thereby preparing compound a-2 represented by Formula 5.

[0192] [Formula 5]

[0193]

[0194] Preparation Example 6: Preparation of ligand compound a-3

[0195] Except for changing MPEG-400 in Preparation Example 5 to MPEG-550 (Green Chemicals Co., Ltd.), the compound represented by Formula 6 (a-3) was obtained in the same manner as in Preparation Example 5.

[0196] [Formula 6]

[0197]

[0198] Preparation Example 7: Preparation of ligand compound a-4

[0199] 20 g (0.14 mol) of 2-phenoxyethanol and 14.5 g (0.14 mol) of succinic anhydride were dissolved in 350 mL of dichloroethane, and 1.8 g (0.014 mol) of 4-(dimethylamino)pyridine was added to the resulting solution. The mixture was then stirred under a nitrogen atmosphere. A condenser was connected to the flask inlet, and the reaction was refluxed at 65°C for 3 hours. After the reaction was complete, the reaction product was extracted and neutralized with 10% aqueous hydrogen chloride solution and distilled water. After neutralization, residual water was removed using anhydrous magnesium sulfate, and the reaction product was then concentrated using a vacuum evaporator to prepare compound a-4 represented by Formula 7.

[0200] [Formula 7]

[0201]

[0202] Preparation Example 8: Preparation of ligand compound a-5

[0203] 67.2 g (0.33 mol) of propylene glycol and 30 g (0.33 mol) of thioglycolic acid were dissolved in 350 mL of toluene, and 6.2 g (0.033 mol) of p-toluenesulfonic acid was added to the resulting solution. The mixture was then stirred at 115°C for 24 hours. After the reaction was complete, the reaction product was extracted and neutralized with 1 M sodium bicarbonate (NaHCO3) aqueous solution and distilled water. After neutralization, residual water was removed using anhydrous magnesium sulfate, and the reaction product was then concentrated using a vacuum evaporator to prepare compound a-5 represented by Formula 8.

[0204] [Formula 8]

[0205]

[0206] Example 1: Preparation of Quantum Dot Ink Composition

[0207] 1) Zinc oleate treatment

[0208] The AIGS quantum dots prepared in Preparation Example 1 were dispersed in cyclohexyl acetate at 10% by weight, and zinc oleate (0.43 M) was added to the resulting solution. The mixture was then stirred at room temperature for 3 hours. After the reaction was complete, ethanol was added to the resulting mixture, followed by centrifugation to recover the zinc oleate-treated quantum dots. After recovery, the quantum dots were dried in a vacuum oven at room temperature for 2 hours and dispersed in cyclohexyl acetate at 10% by weight.

[0209] 2) Surface modification of quantum dots

[0210] 0.68 g of ZnCl2 solution (dispersed in ethanol at 10 wt%) was added to 10 g of zinc oleate-treated quantum dot dispersion (dispersed in cyclohexyl acetate at 10 wt%), and the mixture was stirred at room temperature for 10 minutes. Then, 3.66 g of the ligand compound A-1 dispersion prepared in Preparation Example 3 (dispersed in cyclohexyl acetate at 10 wt%) was added, and the mixture was stirred at room temperature for 3 hours. After the reaction was complete, cyclohexane was added to the resulting mixture, and chemical precipitation was performed using a centrifuge. The precipitated quantum dots were separated, and the supernatant was discarded. The separated quantum dots were dried in a vacuum oven for 2 hours to obtain surface-modified quantum dots.

[0211] 3) Preparation of quantum dot ink components

[0212] A dispersion of surface-modified quantum dots (dispersed in 1,6-hexanediol diacrylate at 40% by weight) and a dispersion of TiO2 with a particle size (D90) not exceeding 300 nm (dispersed in 1,6-hexanediol diacrylate at 50% by weight) were prepared.

[0213] The quantum dot ink composition was prepared by mixing 75 g of quantum dot dispersion, 10 g of TiO2 dispersion, 1.5 g of TPO-L, 0.5 g of polymerization inhibitor (MEHQ), and 13 g of additional 1,6-hexanediol diacrylate.

[0214] Comparative Example 1: Preparation of Quantum Dot Ink Composition

[0215] 1) Zinc oleate treatment

[0216] A quantum dot dispersion treated with zinc oleate was prepared in the same manner as in 1) of Example 1.

[0217] 2) Surface modification of quantum dots

[0218] 0.169 g of ZnCl2 solution (dispersed in ethanol at 10 wt%) was added to 10 g of a zinc oleate-treated quantum dot dispersion (dispersed in cyclohexyl acetate at 10 wt%), and stirred at room temperature for 10 min. Then, 1.83 g of a dispersion of ligand compound a-1 prepared in Preparation Example 4 (dispersed in cyclohexyl acetate at 10 wt%) was added, and stirred at room temperature for 1 hour and 30 min. After the reaction was complete, 2 g of a dispersion of mono-2-(acryloyloxy)ethyl succinate (MAES) (dispersed in cyclohexyl acetate at 10 wt%) was added, and stirred at room temperature for 1 hour and 30 min. After the reaction was complete, cyclohexane was added to the resulting product, followed by chemical precipitation using a centrifuge. The precipitated quantum dots were separated, and the supernatant was discarded. The separated quantum dots were dried in a vacuum oven for 2 hours to obtain surface-modified quantum dots.

[0219] 3) Preparation of quantum dot ink components

[0220] Except for the quantum dot dispersion (dispersed in 1,6-hexanediol diacrylate at 40% by weight) prepared in Comparative Example 1 (2), the quantum dot ink composition was prepared in the same manner as in Example 1 (3).

[0221] Comparative Example 2: Preparation of Quantum Dot Ink Composition

[0222] 1) Zinc oleate treatment

[0223] A quantum dot dispersion treated with zinc oleate was prepared in the same manner as in 1) of Example 1.

[0224] 2) Surface modification of quantum dots

[0225] Except that the dispersion of ligand compound A-1 prepared in Preparation Example 3 was changed to a dispersion of succinate mono-2-(acryloyloxy)ethyl ester (dispersed in cyclohexyl acetate at 10% by weight), the surface-modified quantum dots were prepared in the same manner as in 2) of Example 1.

[0226] 3) Preparation of quantum dot ink components

[0227] Except that the quantum dot dispersion (dispersed in 1,6-hexanediol diacrylate at 40% by weight) prepared in Comparative Example 2 (2) was used as the quantum dot dispersion, the quantum dot ink composition was prepared in the same manner as in Example 1 (3).

[0228] Comparative Example 3: Preparation of Quantum Dot Ink Composition

[0229] 1) Zinc oleate treatment

[0230] A quantum dot dispersion treated with zinc oleate was prepared in the same manner as in 1) of Example 1.

[0231] 2) Surface modification of quantum dots

[0232] Except that the dispersion of ligand compound A-1 prepared in Preparation Example 3 was changed to the dispersion of ligand compound A-4 prepared in Preparation Example 7 (dispersed in cyclohexyl acetate at 10% by weight), the surface-modified quantum dots were prepared in the same manner as in 2) of Example 1.

[0233] 3) Preparation of quantum dot ink components

[0234] Except that the quantum dot dispersion (dispersed in 1,6-hexanediol diacrylate at 40% by weight) prepared in Comparative Example 3,2) was used as the quantum dot dispersion, the quantum dot ink composition was prepared in the same manner as in Example 1,3).

[0235] Comparative Example 4: Preparation of Quantum Dot Ink Composition

[0236] 1) Surface modification of quantum dots

[0237] 10 g of the AIGS quantum dot dispersion prepared in Preparation Example 1 (dispersed in cyclohexyl acetate at 10 wt%) was added to a dispersion of ligand compound a-2 prepared in Preparation Example 5 (dispersed in ethanol at 10 wt%), and the mixture was stirred at room temperature for 3 hours. After the reaction was complete, cyclohexane was added to the resulting mixture, followed by chemical precipitation using a centrifuge. The precipitated quantum dots were separated, and the supernatant was discarded. The separated quantum dots were dried in a vacuum oven for 2 hours to obtain surface-modified quantum dots.

[0238] 2) Preparation of quantum dot ink components

[0239] Except that the quantum dot dispersion (dispersed in 1,6-hexanediol diacrylate at 40% by weight) prepared in Comparative Example 4(1) was used as the quantum dot dispersion, the quantum dot ink composition was prepared in the same manner as in Example 1(3).

[0240] Comparative Example 5: Preparation of Quantum Dot Ink Composition

[0241] 1) Surface modification of quantum dots

[0242] Except that the dispersion of ligand compound a-2 prepared in Preparation Example 5 was changed to the dispersion of ligand compound a-3 prepared in Preparation Example 6 (dispersed in cyclohexyl acetate at 10% by weight), the surface-modified quantum dots were prepared in the same manner as in Comparative Example 4, 1).

[0243] 2) Preparation of quantum dot ink components

[0244] Except that the quantum dot dispersion (dispersed in 1,6-hexanediol diacrylate at 40% by weight) prepared in Comparative Example 5(1) was used as the quantum dot dispersion, the quantum dot ink composition was prepared in the same manner as in Example 1(3).

[0245] Comparative Example 6: Preparation of Quantum Dot Ink Composition

[0246] 1) Surface modification of quantum dots

[0247] 10 g of the AIGS quantum dot dispersion prepared in Preparation Example 1 (dispersed in cyclohexyl acetate at 10 wt%) was added to a dispersion of ligand compound a-5 prepared in Preparation Example 8 (dispersed in cyclohexyl acetate at 10 wt%), and the mixture was stirred at 80°C for 1 hour and 30 minutes. After the reaction was complete, ethanol was added to the resulting mixture, and the quantum dots were recovered using a centrifuge. The recovered quantum dots were dispersed in cyclohexyl acetate at 10 wt%. Then, 15 g of the dispersion of ligand compound a-3 prepared in Preparation Example 6 (dispersed in cyclohexyl acetate at 10 wt%) was added, and the mixture was stirred at 80°C for 1 hour and 30 minutes. After the reaction was complete, cyclohexane was added to the reaction product, followed by chemical precipitation using a centrifuge. The precipitated quantum dots were separated, and the supernatant was discarded. The separated quantum dots were dried in a vacuum oven for 2 hours to obtain surface-modified quantum dots.

[0248] 2) Preparation of quantum dot ink components

[0249] Except that the quantum dot dispersion (dispersed in 1,6-hexanediol diacrylate at 40% by weight) prepared in Comparative Example 6(1) was used as the quantum dot dispersion, the quantum dot ink composition was prepared in the same manner as in Example 1(3).

[0250] Comparative Example 7: Preparation of Quantum Dot Ink Composition

[0251] 1) Zinc oleate treatment

[0252] A quantum dot dispersion treated with zinc oleate was prepared in the same manner as in 1) of Example 1.

[0253] 2) Surface modification of quantum dots

[0254] Except that the dispersion of ligand compound A-1 prepared in Preparation Example 3 was changed to a dispersion of compound represented by Formula 9 (molecular weight: 232.2 g / mol) (dispersed in cyclohexyl acetate at 10% by weight), the surface-modified quantum dots were prepared in the same manner as in 2) of Example 1.

[0255] [Formula 9]

[0256]

[0257] 3) Preparation of quantum dot ink components

[0258] Except that the quantum dot dispersion (dispersed in 1,6-hexanediol diacrylate at 40% by weight) prepared in Comparative Example 7 (2) was used as the quantum dot dispersion, the quantum dot ink composition was prepared in the same manner as in Example 1 (3).

[0259] The presence of zinc oleate treatment on the surface of quantum dots, the addition of ZnCl2, and the types of the first and second ligands in the quantum dot ink compositions of Examples 1 and Comparative Examples 1 to 7 are summarized in Table 1.

[0260] [Table 1]

[0261]

[0262] To select a suitable ligand family for the AIGS quantum dot ink composition, thiol, acid, and amine ligand compounds were applied to modify the surface of the quantum dots. It was confirmed that, except for amine ligands, acid and thiol ligands required changing the ligand type on the quantum dot surface from L-type to X-type to allow ligand exchange.

[0263] As summarized in Table 1, in the quantum dot ink compositions of Examples 1 and Comparative Examples 1 to 3 and 7, ligand exchange was performed after zinc oleate treatment, and ZnCl2 was added to improve ligand binding and reaction efficiency. Conversely, since the ligand compounds used in Comparative Examples 4 to 6 were amine compounds, which have the same type of ligands as the surface of AIGS quantum dots, surface modification was performed without zinc oleate treatment.

[0264] <Experimental Example>

[0265] 1. Preparation of cured film

[0266] Each of the quantum dot ink compositions prepared in Examples 1 and Comparative Examples 1 to 7 was applied to a glass substrate using a spin coater (Opticoat MS-A150, Mikasa Co., Ltd.), and exposed to light at 4,000 mJ (83°C, 4 seconds) using a 395 nm UV exposure machine to form a film with a thickness of 7 μm. The cured film was then baked in a drying oven at 180°C under a nitrogen atmosphere for 30 minutes to prepare a cured film.

[0267] 2. Evaluation of the light absorption and light conversion efficiency of the cured film

[0268] A 2 cm × 2 cm cured film monolayer specimen was prepared. The specimen was mounted on an integrating sphere apparatus (QE-2100, Otsuka Electronics Co., Ltd.) to measure light absorption and light conversion efficiency. The measurement results are shown in Table 2.

[0269] The light conversion efficiency (green / blue) is calculated by mounting a sample on an integrating sphere, applying blue light at a wavelength of 450 nm to absorb all the green light emitted in the upward direction, measuring the integral value, and calculating the rate of increase of the green conversion peak relative to the decrease of the blue light absorption peak.

[0270] [Table 2]

[0271]

[0272] Referring to Table 2, it can be seen that the composition of Example 1, prepared by surface modification of quantum dots using ligand compound A-1 (corresponding to the compound represented by Formula 1), has good light absorption and light conversion efficiency, especially the light conversion efficiency of 31.7%.

[0273] Conversely, it is evident that the quantum dot ink compositions of Comparative Examples 1 to 7 exhibit significantly reduced light absorption and / or light conversion efficiency compared to the quantum dot ink composition of Example 1. The quantum dot ink composition of Comparative Example 1, prepared using quantum dots surface-modified with thiol ligand compounds, and the quantum dot ink composition of Comparative Example 2, prepared using quantum dots surface-modified with acid ligand compounds, possess fairly good light absorption rates, but show a decreasing trend in light conversion efficiency. In particular, it is evident that the light conversion efficiency of the quantum dot ink compositions of Comparative Examples 4 and 5, prepared using quantum dots surface-modified with amine ligand compounds, is significantly reduced.

[0274] The results show that in the preparation of ink compositions using AIGS quantum dots, acid or thiol ligand compounds that replace the surface of the quantum dots have an advantage over amine ligand compounds in improving light conversion efficiency. Among the acid ligand compounds, the compound represented by Formula 1 with a polyalkylene glycol structure has the best effect.

[0275] The higher light conversion efficiency of quantum dot ink compositions prepared using acid or thiol ligand compounds compared to those prepared using amine ligand compounds is believed to be related to the addition of zinc oleate and zinc chloride (ZnCl2). Zinc oleate is believed to change the surface of AIGS quantum dots from L-type to X-type to create an environment where ligand compounds can bind more strongly to the surface of the quantum dots, and is used together with zinc chloride to increase light conversion efficiency through surface passivation of the quantum dots.

[0276] 3. Initial viscosity assessment of quantum dot ink composition

[0277] The initial viscosity of the quantum dot ink composition prepared in Example 1 was measured using a viscometer (RheoStress MARS-40, HAAKE) at room temperature (25°C) and 100 rpm for 2 minutes. The results are shown in Table 3. For reference, the light absorptivity, light conversion efficiency, emission wavelength, FWHM, and film thickness of the quantum dot ink composition of Example 1 listed in Table 3 are the same as those shown in Table 2.

[0278] [Table 3]

[0279]

[0280] Referring to Table 3, it can be seen that the quantum dot ink composition of Example 1 exhibits good light absorption and light conversion efficiency, and has a viscosity of 30 cP or lower, showing good physical properties suitable for inkjet processes.

Claims

1. A quantum dot ink composition comprising quantum dots having a ligand layer on their surface and photopolymerizable monomers, The quantum dots contain silver, indium, gallium, and sulfur, and The ligand layer contains compounds represented by Formula 1. [Formula 1] (In Equation 1, R 1 and R 2 Each can be independently a hydrogen atom or a methyl group. L 1 L 2 and L 3 Each independently is C1 to C 20 hydrocarbon groups, and n is an integer from 1 to 20.

2. The quantum dot ink composition according to claim 1, wherein the compound represented by formula 1 has a weight average molecular weight (M) of 100 to 2,000. w ).

3. The quantum dot ink composition according to claim 1, wherein the quantum dots are present in an amount of 1% to 50% by weight based on the total weight of the quantum dot ink composition.

4. The quantum dot ink composition according to claim 1, wherein the ligand layer comprises a compound represented by formula 2. [Equation 2] (In Equation 2, R 3 and R 4 Each is independently a hydrogen atom or a methyl group, and o is an integer from 1 to 20.

5. The quantum dot ink composition according to claim 1, further comprising: Choose at least one from the group consisting of a photoinitiator and scattering particles.

6. The quantum dot ink composition of claim 5, wherein the photoinitiator comprises at least one selected from the group consisting of phosphine oxide compounds, acetophenone compounds, benzophenone compounds, triazine compounds, diimidazole compounds, oxime compounds, and thioxanthone compounds.

7. The quantum dot ink composition according to claim 5, wherein the scattering particles comprise at least one selected from the group consisting of Al2O3, SiO2, ZnO, ZrO2, CaCO3, BaSO4, BaTiO3, TiO2, Ta2O5, Ti3O5, ITO, IZO, ATO, ZnO-Al, Nb2O3, SnO, and MgO.

8. The quantum dot ink composition according to claim 1, wherein the quantum dot ink composition has a viscosity of 30 cP or less, and exhibits a light conversion efficiency of 29% or higher relative to blue light when measured on a cured product of the quantum dot ink composition with a thickness of 7 μm.

9. A method for preparing a quantum dot ink composition, comprising: (a) Primary surface modification of quantum dots containing silver, indium, gallium and sulfur using X-type ligands; (b) Performing secondary surface modification on the quantum dots subjected to the primary surface modification using a compound represented by Formula 1; and (c) Disperse the quantum dots that have undergone the secondary surface modification in a photopolymerizable compound. [Formula 1] (In Equation 1, R 1 and R 2 Each can be independently a hydrogen atom or a methyl group. L 1 L 2 and L 3 Each independently is C1 to C 20 hydrocarbon groups, and n is an integer from 1 to 20.

10. A cured film comprising a cured product of the quantum dot ink composition as described in any one of claims 1 to 8.

11. A color filter comprising the cured film as claimed in claim 10.

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

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