Method for manufacturing a recycled quantum dot ink composition, the recycled quantum dot ink composition manufactured thereby, a color filter containing the cured product thereof, and a display device.

Abstract

The present invention relates to a method for producing a recycled quantum dot ink composition, a recycled quantum dot ink composition produced by the method, a color filter containing a cured product of the recycled quantum dot ink composition, and a display device, and provides a high-quality display device that reduces the manufacturing cost of expensive quantum dots, has good viscosity and long-term storage stability of the recycled quantum dot ink composition, can be effectively applied in an inkjet process, and has further improved optical properties.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a recycled quantum dot ink composition, the recycled quantum dot ink composition produced thereby, a color filter including a cured product thereof, and a display device.

Background Art

[0002] Quantum dots (QD), also known as semiconductor nanocrystals, can emit light of different wavelengths depending on the particle size even without a change in composition, and can exhibit various colors. Since they have advantages such as higher color purity and light stability than conventional light emitters, they have attracted attention as next-generation light-emitting elements.

[0003] Particularly, quantum dots, which are positioned as a new trend in the display field, can be applied to various displays, electronic devices, etc., in addition to televisions (TVs) and LEDs. Quantum dots represented by CdSe, InP, etc. have rapidly developed in terms of luminous efficiency (Quantum Yield), and a synthesis method with a luminous efficiency close to 100% has been introduced. Based on this, currently, TVs applying quantum dot sheets have been commercialized.

[0004] However, since these quantum dots are very expensive, a method of minimizing the use of materials by using the material only in the necessary parts has attracted attention. The most typical method is the inkjet process. Since the inkjet process uses the material only for the necessary pixels, it is possible to prevent waste of unnecessary materials. For such an inkjet process, a quantum dot ink composition having excellent dispersibility of quantum dots and low viscosity characteristics even without containing a solvent is used.

[0005] In this regard, Korean Patent No. 10-1628065 discloses quantum dots and quantum dot compositions containing them that exhibit excellent dispersibility and stability within a resin, but it has the problem of insufficient long-term storage stability. Furthermore, there is a fundamental problem that material loss cannot be completely prevented even by the inkjet process.

[0006] Therefore, there is a need for research on methods to recover and regenerate quantum dots from quantum dot compositions that are discarded due to reasons such as process losses or changes in physical properties due to long-term storage (waste quantum dot compositions). [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] To solve the aforementioned problems, the present invention aims to provide a method for producing a recycled quantum dot ink composition by recovering quantum dots from a waste quantum dot ink composition.

[0008] Furthermore, the present invention aims to provide a method for producing a recycled quantum dot ink composition that further improves the viscosity and long-term storage stability of the recycled quantum dot ink composition.

[0009] Furthermore, the present invention aims to provide a method for manufacturing a recycled quantum dot ink composition that allows for precise adjustment of the content of quantum dots and scattering particles in the recycled quantum dot ink composition, thereby facilitating consistent control of product quality.

[0010] Furthermore, the present invention aims to provide a recycled quantum dot ink composition manufactured by the above manufacturing method, a color filter containing the cured product thereof, and a display device.

[0011] However, the problems that this invention aims to solve are not limited to those described above, and other problems not mentioned can be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0012] To achieve the above objective, the present invention provides a method for producing a regenerated quantum dot ink composition, comprising the steps of (a) removing scattering particles from a quantum dot ink composition, (b) recovering quantum dots from the quantum dot ink composition from which the scattering particles have been removed, (c) adding a ligand to the recovered quantum dots to re-substitute the ligand, and (d) dispersing the quantum dots with the re-substituted ligand in a photopolymerizable monomer.

[0013] In the above manufacturing method, step (a) may include a step of mixing a solvent with the quantum dot ink composition to selectively precipitate the scattering particles.

[0014] In the above manufacturing method, the solvent may be soluble in the quantum dots contained in the quantum dot ink composition.

[0015] In the above manufacturing method, the solvent may have a polarity index of 2.4 to 7.2.

[0016] In the above manufacturing method, the solvent may be one or more selected from the group consisting of toluene, methyl t-butyl ether, xylene, benzene, diethyl ether, dichloromethane, dichloroethane, butyl acetate, isopropyl alcohol, butanol, tetrahydrofuran, propanol, acetonitrile, acetic acid, dimethylformamide, dimethyl sulfoxide, acetone, ethyl acetate, cyclohexyl acetate, chloroform, 2-butanone, dioxane, methanol, ethanol, and propylene glycol monomethyl ether acetate.

[0017] In the above manufacturing method, the content of scattering particles in the quantum dot ink composition from which the scattering particles have been removed may be 400 mg / L or less.

[0018] In the manufacturing method, the step (b) may include a step of mixing a non-solvent with the quantum dot ink composition from which the scattering particles have been removed to selectively precipitate the quantum dots.

[0019] In the manufacturing method, the non-solvent may have a polarity index of 1 or less.

[0020] In the manufacturing method, the ligand may include a ligand having 3 to 40 carbon atoms containing a carboxyl group.

[0021] In the manufacturing method, the ligand having 3 to 40 carbon atoms containing a carboxyl group may be a compound represented by Chemical Formula 2.

[0022] [Chemical Formula 2] [Chemical Formula 2]

[0023] (In Chemical Formula 2, L is a single bond or is selected from the group consisting of a substituted or unsubstituted C1-C20 alkylene group and a substituted or unsubstituted C1-C20 alkenylene group, A is a single bond or is a C1-C20 alkylene group or alkenylene group containing at least one or more functional groups selected from the group consisting of ester (-C(=O)O-), ether (-O-), carbonyl (-C(=O)-), sulfonyl (-SO2-), sulfide (-S-), and sulfoxide (-SO-), and R is hydrogen or is selected from the group consisting of a substituted or unsubstituted C1-C20 alkyl group and a substituted or unsubstituted C1-C20 alkenyl group.)

[0024] In the manufacturing method, the compound represented by Chemical Formula 2 may be at least one selected from the group consisting of 2-carboxyethyl acrylate, mono-2-(acryloyloxy)ethyl succinate, mono-2-(methacryloyloxy)ethyl succinate, mono-2-(methacryloyloxy)ethyl maleate, 2-[2-(2-methoxyethoxy)ethoxy]acetic acid, and 2-(2-methoxyethoxy)acetic acid.

[0025] In the manufacturing method, the photopolymerizable monomer may contain a (meth)acrylate-based monomer.

[0026] In the manufacturing method, the quantum dot ink composition in step (a) may be a waste quantum dot ink composition.

[0027] The present invention also provides a recycled quantum dot ink composition produced by the manufacturing method.

[0028] In the composition, the viscosity change of the recycled quantum dot ink composition with respect to the initial viscosity may be +1.6 cps or less after being stored at 50°C for 4 weeks.

[0029] In the composition, the recycled quantum dot ink composition may be for inkjet printing.

[0030] The present invention also provides a color filter including a cured product of the recycled quantum dot ink composition.

[0031] Furthermore, the present invention provides a display device including the color filter. [Effects of the Invention]

[0032] The method for producing a recycled quantum dot ink composition according to the present invention involves recovering quantum dots from a waste quantum dot ink composition to produce a recycled quantum dot ink composition, which can then be used in the manufacture of color filters and the like, thereby reducing the manufacturing cost of products to which expensive quantum dots are applied.

[0033] Furthermore, the present invention includes a step of re-substituting the ligand of quantum dots recovered from the waste quantum dot ink composition, which has the effect of further improving the viscosity and long-term storage stability of the recycled quantum dot ink composition.

[0034] Furthermore, the present invention allows for precise control of the quantum dot and scattering particle content in a recycled quantum dot ink composition by selectively removing scattering particles contained in the waste quantum dot ink composition and then recovering the quantum dots. This makes it easier to maintain consistent quality in products to which quantum dots are applied.

[0035] Furthermore, the recycled quantum dot ink composition produced by the method for producing recycled quantum dot ink compositions of the present invention has excellent viscosity and long-term storage stability, so it can be effectively applied in the inkjet process, thereby providing a high-quality display device. [Brief explanation of the drawing]

[0036] [Figure 1] This flowchart schematically shows the method for producing the recycled quantum dot ink composition according to the present invention. [Figure 2A] The following shows the results of evaluating the settling properties of scattered particles in a green quantum dot ink composition using four solvents (acetone, ethyl acetate, cyclohexyl acetate, and isopropyl alcohol). [Figure 2B]The following shows the results of evaluating the sedimentation properties of scattered particles in a red quantum dot ink composition using four solvents (acetone, ethyl acetate, cyclohexyl acetate, and isopropyl alcohol). [Modes for carrying out the invention]

[0037] The present invention relates to a method for producing a recycled quantum dot ink composition by recovering quantum dots from a waste quantum dot ink composition and then re-substituting ligands, a recycled quantum dot ink composition produced by the said production method, and a color filter and display device containing a cured product of the recycled quantum dot ink composition.

[0038] More specifically, the present invention relates to a method for producing a regenerated quantum dot ink composition, comprising the steps of (a) removing scattering particles from a quantum dot ink composition, (b) recovering quantum dots from the quantum dot ink composition from which the scattering particles have been removed, (c) adding a ligand to the recovered quantum dots to re-substitute the ligand, and (d) dispersing the quantum dots with the re-substituted ligand in a photopolymerizable monomer.

[0039] Furthermore, the present invention relates to a recycled quantum dot ink composition produced by the above-described manufacturing method.

[0040] The present invention also relates to a color filter containing a cured product of a recycled quantum dot ink composition and a display device containing the same.

[0041] All terms used herein (including technical and scientific terms) are used in a way that is commonly understood by those skilled in the art, unless otherwise defined. Furthermore, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless specifically defined otherwise.

[0042] Furthermore, as used herein, “including” and / or “contained” are used in the sense that they do not exclude the presence or addition of one or more other components and / or processes other than those mentioned.

[0043] Furthermore, as used herein, "(meth)acrylate" means acrylate and methacrylate, "(meth)acrylic" means acrylic and methacrylic, and "(meth)acryloyl" means acryloyl and methacryloyl.

[0044] Furthermore, as used herein, “monomer” and “monomer” have the same meaning. In the present invention, a monomer is distinguished from oligomers and polymers and means a compound having a weight-average molecular weight of 1,000 or less. As used herein, a “photopolymerizable monomer” means a monomer having a group that participates in photopolymerization reactions, such as a (meth)acrylate group.

[0045] As used herein, "substitution" refers to a compound or functional group in which a hydrogen atom is replaced by a C1-C30 alkyl group, a C2-C30 alkenyl group, a C2-C30 alkynyl group, a C1-C30 alkoxy group, a C1-C30 heteroalkyl group, a C3-C30 heteroalkylaryl group, a C3-C30 cycloalkyl group, a C3-C15 cycloalkenyl group, a C6-C30 cycloalkynyl group, a C2-C30 heterocycloalkyl group, a halogen (-F, -Cl, -Br, or -I), or a hydroxyl group. This means that the molecule is substituted with substituents selected from roxy (-OH), nitro (-NO2), cyano (-CN), ester (-C(=O)-OR, where R is a C1-C10 alkyl or alkenyl group), ether (-OR, where R is a C1-C10 alkyl or alkenyl group), carbonyl (-C(=O)-R, where R is a C1-C10 alkyl or alkenyl group), carboxyl (-COOH), and combinations thereof.

[0046] As used herein, "organic group" means a linear or branched alkyl group of C1 to C30, a linear or branched alkenyl group of C2 to C30, or a linear or branched alkynyl group of C2 to C30. Furthermore, the alkyl group, alkenyl group, and alkynyl group may each be substituted or unsubstituted.

[0047] As used herein, “alkyl” means a monovalent substituent derived from a straight-chain or branched-chain saturated hydrocarbon having 1 to 40 carbon atoms. Examples of such “alkyl” include, but are not limited to, methyl, ethyl, propyl, isobutyl, sec-butyl, pentyl, iso-amyl, and hexyl.

[0048] As used herein, "alkenyl" means a monovalent substituent derived from a straight-chain or branched-chain unsaturated hydrocarbon having 2 to 40 carbon atoms and having one or more carbon-carbon double bonds. Examples of "alkenyl" include, but are not limited to, vinyl, allyl, isopropenyl, and 2-butenyl.

[0049] As used herein, "alkynyl" means a monovalent substituent derived from a straight-chain or branched-chain unsaturated hydrocarbon having 2 to 40 carbon atoms and having one or more carbon-carbon triple bonds. Examples of "alkynyl" include, but are not limited to, ethynyl and propynyl.

[0050] The present invention relates to a method for producing a recycled quantum dot ink composition, characterized by recovering quantum dots from a quantum dot ink composition and using them in the production of a recycled quantum dot ink composition. Prior to describing the production method according to the present invention, the quantum dot ink composition from which quantum dots are to be recovered and the components contained therein will be described.

[0051] <Quantum dot ink composition> The quantum dot ink composition is intended for use in inkjet processes and contains quantum dots and photopolymerizable monomers. The quantum dot ink composition may also optionally further contain at least one selected from the group consisting of photoinitiators, scattering particles, polymerization inhibitors, stabilizers, and other additives. Furthermore, the quantum dot ink composition may be a solvent-free type quantum dot ink composition that does not contain a solvent.

[0052] Quantum dots Quantum dots (QDs) are nanoscale semiconductor materials that have different energy band gaps depending on their size and composition, and therefore emit light at a variety of wavelengths.

[0053] These quantum dots can be homogeneous monolayer structures, core-shell structures, multilayer structures such as gradient structures, or hybrid structures thereof. In the case of a core-shell structure where the shell consists of multiple layers, each layer may contain different components, such as (quasi)metallic oxides.

[0054] Quantum dots (QDs) can be freely selected from group II-VI compounds, group III-V compounds, group IV-VI compounds, group IV elements, group IV compounds, and combinations thereof. If the quantum dot is in a core-shell configuration, the core and shell can each be freely composed of the following exemplary components.

[0055] As an example, group II-VI compounds include binary compounds selected from the group consisting of CdO, CdS, CdSe, CdTe, ZnO, ZnS, ZnSe, ZnTe, HgS, HgSe, HgTe, MgSe, MgS and mixtures thereof, and ternary compounds selected from the group consisting of CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, MgZnSe, MgZnS and mixtures thereof. The compound may be selected from the group consisting of CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, HgZnSTe, and mixtures thereof.

[0056] As another example, the group III-V compounds may be selected from the group consisting of binary compounds selected from the group consisting of GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb and mixtures thereof; ternary compounds selected from the group consisting of GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs, InPSb and mixtures thereof; and quaternary compounds selected from the group consisting of GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlSb, InAlPAs, InAlPsb and mixtures thereof.

[0057] As another example, group IV-VI compounds may be selected from the group consisting of binary compounds selected from the group consisting of SnS, SnSe, SnTe, PbS, PbSe, PbTe and mixtures thereof; ternary compounds selected from the group consisting of SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe and mixtures thereof; and quaternary compounds selected from the group consisting of SnPbSSe, SnPbSeTe, SnPbSTe and mixtures thereof.

[0058] As another example, Group IV elements may be selected from the group consisting of Si, Ge, and mixtures thereof. Group IV compounds may be binary compounds selected from the group consisting of SiC, SiGe, and mixtures thereof.

[0059] The aforementioned binary, ternary, or quaternary compounds may exist within a particle at a uniform concentration, or they may be separated within the same particle with partially different concentration distributions. Furthermore, they may form a core-shell structure in which one quantum dot surrounds another. The interface between the core and the shell may have a concentration gradient in which the concentration of elements present in the shell decreases towards the center.

[0060] The form of quantum dots is not particularly limited as long as it is a form commonly used in this field. For example, spherical, rod-shaped, pyramidal, disc-shaped, multi-arm, or cubic nanoparticles, nanotubes, nanowires, nanofibers, and nano-flakes can be used.

[0061] Furthermore, the size of the quantum dots is not particularly limited and can be adjusted as appropriate within the usual range known in this field. For example, the average particle size D50 of the quantum dots may be about 2 to 10 nm. When the particle size of the quantum dots is controlled in the range of about 2 to 10 nm, it is possible to emit light of a desired color. For example, if the core / shell particle size of a quantum dot containing InP is about 5 to 6 nm, it emits light with a wavelength of about 520 to 550 nm. On the other hand, if the core / shell particle size of a quantum dot containing InP is about 7 to 8 nm, it emits light with a wavelength of about 620 to 640 nm. For example, as blue-emitting quantum dots (QDs), cadmium-free III-V group QDs (e.g., InP, InGaP, InZnP, GaN, GaAs, GaP) can be used.

[0062] Furthermore, quantum dots may have a half-width (FWHM) of emission wavelength spectrum below approximately 40 nm, and color purity and color reproduction can be improved within this range. In addition, since the light emitted by these quantum dots is emitted in all directions, the viewing angle is improved.

[0063] The quantum dot content may be in the range of 1 to 60% by weight, preferably 20 to 50% by weight, based on the total weight of the quantum dot ink composition.

[0064] Ligand The quantum dot has a ligand layer on its surface, and the ligand contained in the ligand layer plays a role in modifying the surface of the quantum dot. Due to the hydrophobic surface properties of the quantum dot, there are limitations to its dispersion in photopolymerizable monomers, but the miscibility of the quantum dot with photopolymerizable monomers can be improved by modifying the surface of the quantum dot with an appropriate ligand.

[0065] The ligand is not particularly limited as long as it improves the miscibility with the photopolymerizable monomer of the quantum dot, but for example, it may include a first ligand represented by the following chemical formula 1 and a second ligand having 3 to 40 carbon atoms and containing a carboxyl group.

[0066] [ka] [Chemical formula 1]

[0067] In the above chemical formula 1, M is a 2- to 4-valent metal, X is an organic group having 3 to 20 carbon atoms, and n is an integer from 2 to 4.

[0068] The first ligand may be a metal-thiol compound formed by reacting a metal salt with a thiol compound.

[0069] In the aforementioned chemical formula 1, M is a 2- to 4-valent metal. For example, M may be a metal from groups 2 to 14, such as Mg, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Cd, In, or Sn.

[0070] In the above chemical formula 1, n is determined by the valency of M and is an integer between 2 and 4.

[0071] Furthermore, in the above chemical formula 1, X is an organic group having 3 to 20 carbon atoms. For example, X is an ester (-C(=O)O-), ether (-O-), carbonyl (-C(=O)-), carboxyl group (-C(=O)-OH), sulfonyl (-SO2-), sulfide (-S-), sulfoxide (-SO-), or alkoxy group (C n H 2n+1 It may be an alkylene group or alkenylene group having 3 to 20 carbon atoms, containing one or more functional groups selected from the group consisting of (O-) and a hydroxyl group (-OH). Specifically, X may be an organic group having 4 to 15 carbon atoms, containing an ester (-C(=O)O-) functional group.

[0072] Examples of compounds represented by chemical formula 1 include, but are not limited to, Zn-(3-methoxybutyl 3-mercaptopropionate)2, Zn-(3-methoxybutyl thioglycolate)2, Zn-(2-ethylhexyl thioglycolate)2, Zn-(butyl mercaptopropionate)2, Zn-(isopropyl mercaptopropionate)2, and Zn-(PEG-thiol)2.

[0073] The second ligand has 3 to 40 carbon atoms and may contain a carboxyl group. Furthermore, the second ligand does not need to contain a thiol group.

[0074] The second ligand may be a compound represented by the following chemical formula 2.

[0075] [ka] [Chemical formula 2]

[0076] In the aforementioned chemical formula 2, L is either a single bond or selected from the group consisting of substituted or unsubstituted C1-C20 alkylene groups and substituted or unsubstituted C1-C20 alkenylene groups. A is either a single bond or a C1-C20 alkylene or alkenylene group containing one or more functional groups selected from the group consisting of ester (-C(=O)O-), ether (-O-), carbonyl (-C(=O)-), sulfonyl (-SO2-), sulfide (-S-), and sulfoxide (-SO-). R is either hydrogen or selected from the group consisting of substituted or unsubstituted C1-C20 alkyl groups and substituted or unsubstituted C1-C20 alkenyl groups.

[0077] Preferably, in the chemical formula 2, A may include esters (-COO-), ethers (-O-), and combinations thereof. Also, A is a C2-C15 alkylene group or alkenylene group, preferably a C2-C10 alkylene group or alkenylene group.

[0078] Examples of compounds represented by chemical formula 2 include, but are not limited to, 2-carboxyethyl acrylate, mono-2-(acryloyloxy)ethyl succinate, mono-2-(methacryloyloxy)ethyl succinate, mono-2-(methacryloyloxy)ethyl maleate, 2-[2-(2-methoxyethoxy)ethoxy]acetic acid, and 2-(2-methoxyethoxy)acetic acid.

[0079] The molar ratio of the first ligand to the second ligand is 1:0.1 to 20, preferably 1:0.2 to 10, but is not limited to these values.

[0080] Furthermore, the mixed weight ratio of the quantum dots to the ligand may be 1:0.05 to 1, preferably 1:0.1 to 0.5. Here, the weight of the ligand refers to the total amount of the first ligand and the second ligand.

[0081] Photopolymerizable monomers Photopolymerizable monomers play a role in controlling the overall crosslinking density of the polymer matrix, i.e., the formulation in which quantum dots (QDs) are dispersed, thereby exhibiting the structure and various properties of the matrix. Furthermore, photopolymerizable monomers improve flexibility and adhesion to other materials.

[0082] The photopolymerizable monomer may include (meth)acrylate monomers. Any monomer commonly used in this art can be used without particular limitations.

[0083] The (meth)acrylate monomer may contain at least one of a (meth)acrylic group, a vinyl group, and an allyl group.Specifically, 1,6-hexanediol diacrylate, 1,6-cyclohexanediol diacrylate, 2,2-dimethyl-1,3-propanediol diacrylate, diethylene glycol diacrylate, dipropylene glycol diacrylate, 1,3-butylene glycol dimethacrylate, trimethylolpropane trimethacrylate, isobornyl acrylate, isobornyl methacrylate, tetrahydrofuryl acrylate, acryloyl morpholine, 2-phenoxyethyl acrylate Examples include tripropylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol mono(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, dipentaerythritol hexaacrylate, and dipentaerythritol hexamethacrylate.These can be used individually or in combination of two or more types.

[0084] The content of the photopolymerizable monomer may be 35 to 80% by weight, preferably 45 to 70% by weight, based on the total weight of the quantum dot ink composition.

[0085] Photoinitiator Photoinitiators are components that are excited by light sources such as ultraviolet (UV) light to initiate photopolymerization, and conventional photopolymerization photoinitiators in this field can be used without limitation. Examples include acetophenone compounds, benzophenone compounds, thioxanthone compounds, benzoin compounds, triazine compounds, and oxime compounds.

[0086] Non-limiting examples of available photoinitiators include ethyl(2,4,6-trimethylbenzoyl)phenylphosphinate, Irgacure 184, Irgacure 369, Irgacure 651, Irgacure 819, Irgacure 907, TPO-L, benzionalkylether, benzophenone, benzyldimethylkatal, hydroxycyclohexylphenylacetone, chloroacetophenone, 1,1-dichloroacetophenone, diethoxyacetophenone, and hydroxyacetophenone. Examples include acetophenone, 2-chlorothioxanthone, 2-ETAQ (2-ethylAnthraquinone), 1-hydroxycyclohexylphenyl-ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone, and methylbenzoylformate. These can be used individually or in combination of two or more.

[0087] The content of the photoinitiator can be adjusted as appropriate within the range known in the art. For example, it may be 0.01 to 10% by weight, preferably 0.1 to 5% by weight, based on the total weight of the quantum dot ink composition.

[0088] scattering particles Scattering particles increase the overall light conversion efficiency by either reflecting unabsorbed light from quantum dots and allowing that reflected light to be absorbed by the quantum dots, thereby increasing the amount of light emitted from the quantum dots, or by reflecting light emitted from the quantum dots to extend the optical path and increase the amount of light emitted from the quantum dots.

[0089] The scattering particles can be any known in the art without limitation. For example, the scattering particles may include, but are not limited to, barium sulfate (BaSO4), calcium carbonate (CaCO3), titanium dioxide (TiO2), zirconia (ZrO2), or a combination thereof, with an average particle size (D50) of 150 nm to 250 nm.

[0090] The content of the scattering particles can be appropriately adjusted within the range known in the art. For example, it may be 0.01 to 10% by weight, preferably 0.1 to 5% by weight, based on the total weight of the quantum dot ink composition.

[0091] Polymerization inhibitors Polymerization inhibitors are substances that react with radicals to form low-reactivity radicals or compounds that prevent polymerization reactions from occurring, and can be added to control the rate of photopolymerization reactions.

[0092] The polymerization inhibitor can be any substance known in the art without limitation. For example, quinone compounds, phenol or aniline compounds, or aromatic nitro or nitroso compounds can be used as polymerization inhibitors. These can be used individually or in combination of two or more.

[0093] Specifically, examples of the quinone compounds include hydroquinone (HQ), methylhydroquinone (THQ), hydroquinone monomethyl ether (MEHQ), hydroquinone monoethyl ether (EEHQ), 1,4-benzoquinone (BQ), 2,5-diphenylbenzoquinone (DPBQ), and phenyl-1,4-benzoquinone (PBQ).

[0094] Examples of the aforementioned phenol or aniline compounds include 2,6-di-tert-butyl-4-methylphenol (BHT), 2,6-diphenyl-4-octadecyloxyphenol, and catechol.

[0095] Examples of the aforementioned aromatic nitro or nitroso compounds include phenothiazine, bis(α-methylbenzyl)phenothiazine, 3,7-dioctylphenothiazine, bis(α,α-dimethylbenzyl)phenothiazine, dimethyldithiokabamic acid, diethyldithiokabamic acid, dipropyldithiokabamic acid, dibutyldithiokabamic acid, and diphenyldithiokabamic acid.

[0096] The content of the polymerization inhibitor can be appropriately adjusted within the range known in the art. For example, it may be 0.01 to 2% by weight, preferably 0.05 to 1% by weight, based on the total weight of the quantum dot ink composition.

[0097] Stabilizer Stabilizers can be added to improve the stability and dispersibility of quantum dots. The stabilizers are substituted onto the shell surface of the quantum dots, improving their dispersion stability in the solvent and thus stabilizing the quantum dots.

[0098] Any stabilizer that can improve the stability and dispersibility of quantum dots in the art can be used without limitation, for example, a thiol-based stabilizer can be used. The thiol-based stabilizer improves the dispersibility of quantum dots in relation to the photopolymerizable monomer. Furthermore, the thiol groups of the thiol-based stabilizer react with the acrylic groups of the photopolymerizable monomer to form covalent bonds, thereby improving the heat resistance of the quantum dot composition.

[0099] The thiol-based stabilizer may have seven or more carbon atoms and may have 2 to 10, for example, 2 to 6 thiol groups (-SH) at its terminals depending on its structure, but is not particularly limited thereto. Non-exclusive examples of usable thiol stabilizers include pentaerythritol tetrakis (3-mercaptopropionate), trimethylolpropane tris (3-mercaptopropionate), pentaerythritol tetrakis (mercaptoacetate), trimethylolpropane tris (2-mercaptoacetate), glycol di-3-mercaptopropionate, or mixtures thereof.

[0100] Other additives In addition to the components described above, the quantum dot composition of the present invention may optionally use additives known in the art without limitation. In this case, the content of the additives can be appropriately adjusted within the range known in the art.

[0101] Examples of usable additives include silane compounds, siloxane compounds, antioxidants, polymerization inhibitors, lubricants, surface modifiers, surfactants, adhesion promoters, defoamers, slip agents, solvents, wetting agents, light stabilizers, anti-fouling agents, softeners, thickeners, and polymers. These can be used individually or in combination of two or more.

[0102] Silane compounds provide adhesion to the matrix, while siloxane compounds provide wettability. Such silane and siloxane compounds can be any known components in this field without limitation.

[0103] Antioxidants prevent discoloration due to heat and light irradiation, as well as ozone, reactive oxygen species, and NO. X , SO X In this invention, discoloration caused by various oxidizing gases such as (X is an integer) is suppressed, and by adding antioxidants, coloring of the matrix and reduction of film thickness due to decomposition are suppressed. Examples of usable antioxidants include hydrazides, hindered amine antioxidants, nitrogen-containing heterocyclic mercapto compounds, thioether antioxidants, hindered phenol antioxidants, ascorbic acids, zinc sulfate, thiocyanates, thiourea derivatives, sugars, nitrites, sulfites, thiosulfates, and hydroxylamine derivatives.

[0104] The leveling agent is included to level the quantum dot composition so that it is coated flat and smoothly, and to further enhance the adhesion within the composition. The leveling agent may include acrylic, silicone, etc., either alone or in a mixture of two or more. As an example, it may include a polyether-modified polydimethylsiloxane in which (meth)acryloyl groups have been introduced into the polyether chain.

[0105] Surfactants are included to improve the miscibility and uniformity of the quantum dot composition. Conventional cationic, anionic, and nonionic surfactants known in the art can be used as the surfactant, and for example, one or more of fluorinated surfactants, silicone surfactants, and fluorosilicone surfactants can be used.

[0106] Light stabilizers act as UV absorbers, enhancing the weather resistance of the matrix. Softeners mitigate crack formation within the dried polymer matrix and improve impact and flexural resistance by reducing crack formation within the cured matrix.

[0107] <Method for manufacturing recycled quantum dot ink composition> The present invention provides a method for producing a recycled quantum dot ink composition, comprising the steps of (a) removing scattering particles from a quantum dot ink composition, (b) recovering quantum dots from the quantum dot ink composition from which the scattering particles have been removed, (c) adding a ligand to the recovered quantum dots to re-substitute the ligand, and (d) dispersing the quantum dots with the re-substituted ligand in a photopolymerizable monomer.

[0108] In the method for producing the recycled quantum dot ink composition of the present invention, the same applies to the quantum dot ink composition subject to quantum dot recovery and each component contained therein as described above for the <quantum dot ink composition>.

[0109] Figure 1 is a schematic flowchart showing the manufacturing method of the recycled quantum dot ink composition according to the present invention. The manufacturing method of the present invention will be described in detail below, step by step, with reference to Figure 1.

[0110] (a) Steps to remove scattered particles from the quantum dot ink composition. In the present invention, the quantum dot ink composition of step (a) may be a waste quantum dot ink composition. The waste quantum dot ink composition is not particularly limited as long as it is a discarded quantum dot ink composition, and means, for example, a quantum dot ink composition discarded due to loss generated in the inkjet process, and a quantum dot ink composition that was not used in the actual inkjet process but was discarded because its physical properties such as viscosity and dispersibility changed due to long-term storage, making it unusable in the inkjet process.

[0111] Generally, quantum dot ink compositions contain scattering particles along with quantum dots, so it is necessary to remove the scattering particles from the quantum dot ink composition beforehand before recovering the quantum dots. If the scattering particles are not removed at all, or are not sufficiently removed, when the quantum dots are recovered, a certain amount of scattering particles may be incorporated into the recovered quantum dots. It is difficult to accurately determine the amount of scattering particles incorporated into the recovered quantum dots in this way. Therefore, when manufacturing recycled quantum dot ink compositions using recovered quantum dots, it may be difficult to precisely adjust the content of quantum dots and scattering particles, which can lead to problems in maintaining consistent quality.

[0112] In one embodiment of the present invention, step (a) may include a step of mixing a solvent with the quantum dot ink composition to selectively precipitate scattering particles. In this case, the solvent may be insoluble with respect to the scattering particles contained in the quantum dot ink composition, but soluble with respect to the quantum dots.

[0113] The solvent is not particularly limited as long as it selectively precipitates the scattering particles, but preferably a solvent with a polarity index of 2.4 to 7.2 can be used, and more preferably a solvent with a polarity index of 4.1 to 5.2 can be used, which has the advantage of increasing the efficiency of selectively precipitating only the scattering particles from the quantum dot ink composition.

[0114] The solvent having a polarity index of 2.4 to 7.2 may include, but is not limited to, at least one selected from the group consisting of toluene, methyl t-butyl ether, xylene, benzene, diethyl ether, dichloromethane, dichloroethane, butyl acetate, isopropyl alcohol, butanol, tetrahydrofuran, propanol, acetonitrile, acetic acid, dimethylformamide, dimethyl sulfoxide, acetone, ethyl acetate, cyclohexyl acetate, chloroform, 2-butanone, dioxane, methanol, ethanol, and propylene glycol monomethyl ether acetate. Among these, it is preferable to include at least one selected from the group consisting of acetone, ethyl acetate, cyclohexyl acetate, chloroform, 2-butanone, dioxane, methanol, ethanol, and propylene glycol monomethyl ether acetate, having a polarity index of 4.1 to 5.2.

[0115] On the other hand, if a solvent with a polarization index of less than 2.4 or greater than 7.2 is used as the solvent, there is a risk that quantum dots may precipitate together with scattered particles from the quantum dot ink composition. Therefore, such a solvent may not be suitable for selectively removing only scattered particles from the quantum dot ink composition.

[0116] The solvent is mixed in an amount of 1 to 4 times the total weight of the quantum dot ink composition, preferably 1.5 to 3 times the total weight.

[0117] The precipitated scattering particles can be removed by centrifugation, thereby obtaining a quantum dot ink composition from which the scattering particles have been removed (hereinafter also referred to as a quantum dot dispersion from which the scattering particles have been removed).

[0118] The aforementioned centrifugation can be performed once or twice. Performing centrifugation once has the advantage of selectively removing scattered particles while minimizing the degradation of the physical properties of the quantum dots due to centrifugation. Performing centrifugation twice further reduces the content of scattered particles in the quantum dot ink composition, which has the advantage of allowing for more precise control of the quantum dot and scattered particle content when manufacturing a regenerated quantum dot ink composition in a subsequent process.

[0119] If centrifugation is performed twice, the amount of remaining scattered particles is at the level of a few ppm, so additional centrifugation may not be necessary. As the number of centrifugation cycles increases, the amount of ligand desorbed from the quantum dots increases, which can significantly degrade the physical properties of the quantum dots. Therefore, it is preferable to perform centrifugation once or twice to remove the settled scattered particles.

[0120] The aforementioned centrifugation can be performed at 4000 to 6000 rpm for 10 to 30 minutes, preferably at 6000 rpm for 10 to 20 minutes. This can also be applied to the centrifugation in the process described later.

[0121] The content of scattering particles in the quantum dot ink composition from which the scattering particles have been removed is 400 mg / L or less, preferably 100 mg / L or less, more preferably 40 mg / L or less, and most preferably 20 mg / L or less. When the content of scattering particles in the quantum dot ink composition from which the scattering particles have been removed satisfies the above range, the content of quantum dots and scattering particles can be adjusted more precisely when manufacturing the regenerated quantum dot ink composition in a subsequent step, which is preferable because it makes it easier to control the quality of the product.

[0122] (b) A step of recovering quantum dots from the quantum dot ink composition from which scattered particles have been removed. Since the quantum dots in the quantum dot ink composition from which the scattering particles have been removed are dissolved by the solvent mixed in step (a), it is necessary to precipitate the quantum dots from the quantum dot ink composition in order to recover them.

[0123] In one embodiment of the present invention, step (b) may include mixing a nonsolvent with the quantum dot ink composition from which the scattering particles have been removed to selectively precipitate the quantum dots.

[0124] In the present invention, the non-solvent refers to a solvent used to precipitate quantum dots dissolved in a quantum dot ink composition, and means a solvent that is incompatible with or has very little compatibility with quantum dots, i.e., insoluble with quantum dots.

[0125] The non-solvent is not particularly limited as long as it precipitates the quantum dots, and is appropriately selected depending on the type of solvent mixed in step (a) and the type of ligand substituted on the surface of the recovered quantum dots. It is preferable to use a solvent with a polarity index of 1 or less. Examples of solvents with a polarity index of 1 or less include cyclohexane, hexane, pentane, heptane, and trichloroethylene, which can be used individually or in combination of two or more. Among these, the use of cyclohexane is particularly preferred.

[0126] The quantum dots selectively precipitated from the quantum dot ink composition can be recovered by centrifugation.

[0127] In one embodiment of the present invention, the filtrate of the quantum dot ink composition from which the scattered particles have been removed is mixed with a non-solvent in a weight ratio of 1 to 4 times, and centrifugation is performed once to obtain a solid. Then, a solvent (such as acetone) in a weight ratio of 0.5 to 2 times the obtained solid is mixed with the obtained solid to disperse the solid, and a non-solvent in a weight ratio of 6 to 15 times the solid is mixed with the solid, and centrifugation is performed again to recover the quantum dots.

[0128] (c) A step of adding a ligand to the recovered quantum dots and replacing the ligand. The ligands on the surface of quantum dots recovered from a quantum dot ink composition may be damaged during the process of steps (a) and (b) described above, and the ligands on the surface of quantum dots may also be damaged during the process of discarding the quantum dot ink composition. When a regenerated quantum dot ink composition is manufactured using quantum dots with such damaged ligands, problems may arise such as a decrease in properties of the composition, such as viscosity and long-term storage stability. Therefore, in order to restore the physical properties of the recovered quantum dots, it is necessary to re-modify the surface of the recovered quantum dots.

[0129] For re-modification of the quantum dot surface, step (c) herein includes adding a ligand to the quantum dots recovered in step (b) and re-substituting the ligand.

[0130] The ligand may include a ligand having 3 to 40 carbon atoms that contains a carboxyl group.

[0131] In one embodiment of the present invention, a ligand having 3 to 40 carbon atoms and containing a carboxyl group is added to the quantum dots recovered in step (b), and the reaction is carried out at 25 to 100°C for 2 to 7 hours to re-modify the surface of the quantum dots.

[0132] The ligand content added in step (c) above may be 1 to 20% by weight, preferably 1 to 15% by weight, and more preferably 1 to 7% by weight, based on the total weight of the solids of the recovered quantum dots. When the ligand content of the added material satisfies the above range, it is preferable because it can appropriately re-modify the quantum dot surface to improve miscibility with photopolymerizable monomers, viscosity, and long-term storage stability.

[0133] Quantum dots whose surfaces have been modified in this manner can be obtained by centrifugation. The centrifugation can be performed once or twice, and it is preferable to perform it once.

[0134] The ligand having 3 to 40 carbon atoms and containing the carboxyl group may be a compound represented by the following chemical formula 2.

[0135] [ka] [Chemical formula 2]

[0136] In the aforementioned chemical formula 2, L is selected from the group consisting of single bonds, substituted or unsubstituted C1-C20 alkylene groups, and substituted or unsubstituted C1-C20 alkenylene groups. A is either a single bond or a C1-C20 alkylene or alkenylene group containing at least one functional group selected from the group consisting of ester (-C(=O)O-), ether (-O-), carbonyl (-C(=O)-), sulfonyl (-SO2-), sulfide (-S-), and sulfoxide (-SO-). R is either hydrogen, or selected from the group consisting of substituted or unsubstituted C1-C20 alkyl groups and substituted or unsubstituted C1-C20 alkenyl groups.

[0137] Preferably, A in chemical formula 2 may include a functional group selected from esters (-COO-), ethers (-O-), or combinations thereof. Alternatively, A may be a C2-C15 alkylene group or alkenylene group, preferably a C2-C10 alkylene group or alkenylene group.

[0138] The compound represented by chemical formula 2 includes, but is not limited to, 2-carboxyethyl acrylate, mono-2-(acryloyloxy)ethyl succinate, mono-2-(acryloyloxy)ethyl succinate, mono-2-(methacryloyloxy)ethyl maleate, 2-[2-(2-methoxyethoxy)ethoxy]acetic acid, and 2-(2-methoxyethoxy)acetic acid, and preferably mono-2-(acryloyloxy)ethyl succinate (MAES).

[0139] On the other hand, the ligand added to step (c) does not have to include the compound represented by the following chemical formula 1.

[0140] [ka] [Chemical formula 1]

[0141] In the above chemical formula 1, M is a 2- to 4-valent metal, X is an organic group having 3 to 20 carbon atoms, and n is an integer from 2 to 4.

[0142] The compound represented by chemical formula 1 may be a metal-thiol compound formed by reacting a metal salt with a thiol compound.

[0143] In the above chemical formula 1, M is a 2- to 4-valent metal. For example, M is a metal from group 2 to group 14, such as Mg, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Cd, In, or Sn.

[0144] In the above chemical formula 1, n is determined by the valency of M and is an integer between 2 and 4.

[0145] Furthermore, in the above chemical formula 1, X can be an organic group having 3 to 20 carbon atoms. For example, X can be an ester (-C(=O)O-), an ether (-O-), a carbonyl (-C(=O)-), a carboxyl group (-C(=O)-OH), a sulfonyl (-SO2-), a sulfide (-S-), a sulfoxide (-SO-), or an alkoxy group (C n H 2n+1 It may be an alkylene group or alkenylene group having 3 to 20 carbon atoms, containing one or more functional groups selected from the group consisting of (O-) and a hydroxyl group (-OH). Specifically, X may be an organic group having 4 to 15 carbon atoms, containing an ester (-C(=O)O-) functional group.

[0146] The compound represented by chemical formula 1 contains a thiol group. The thiol group has excellent affinity for the quantum dot surface, thereby improving the dispersibility of quantum dots in photopolymerizable monomers. However, if thiol ligands are excessively substituted, it may result in the generation of harmful odors, increased viscosity, and reduced storage stability, potentially making it difficult to apply quantum dots to ink compositions.

[0147] Therefore, in order to prevent an increase in viscosity of the recycled quantum dot ink composition and to further improve storage stability, it is preferable not to use the compound represented by chemical formula 1, which is a thiol-based ligand, in the ligand resubstitution step.

[0148] The compound represented by chemical formula 1 includes, but is not limited to, Zn-(3-methoxybutyl 3-mercaptopropionate)2, Zn-(3-methoxybutyl thioglycolate)2, Zn-(2-ethylhexyl thioglycolate)2, Zn-(butyl mercaptopropionate)2, Zn-(isopropyl mercaptopropionate)2, and Zn-(PEG-thiol)2.

[0149] (d) Dispersing the ligand-substituted quantum dots in a photopolymerizable monomer. The recycled quantum dot ink composition of the present invention can be produced by dispersing quantum dots, whose ligands have been resubstituted in step (c), in a photopolymerizable monomer, and may optionally contain one or more additives selected from the group consisting of photoinitiators, scattering particles, polymerization inhibitors, stabilizers, and other additives.

[0150] The photopolymerizable monomer, photoinitiator, scattering particles, polymerization inhibitor, stabilizer, and other additives can be applied in the same manner as described above for the <quantum dot ink composition>.

[0151] In one embodiment of the present invention, the content of the resubstituted quantum dots with ligands may be 1 to 60% by weight, preferably 20 to 50% by weight, based on the total weight of the regenerated quantum dot ink composition.

[0152] Furthermore, the photopolymerizable monomer may include (meth)acrylate monomers. The (meth)acrylate monomer may include 1,6-hexanediol diacrylate, which is preferable because it allows the viscosity of the recycled quantum dot composition to be adjusted to an appropriate level. The content of the photopolymerizable monomer may be 40 to 70% by weight, preferably 50 to 60% by weight, based on the total weight of the recycled quantum dot ink composition.

[0153] When the regenerated quantum dot ink composition of the present invention contains a photoinitiator, the content of the photoinitiator is 0.01 to 10% by weight, preferably 0.1 to 5% by weight, based on the total weight of the regenerated quantum dot ink composition. When the content of the photoinitiator satisfies the above range, it is preferable because it has the advantage that the photopolymerization reaction is carried out sufficiently without degrading the physical properties of the composition.

[0154] Furthermore, if the recycled quantum dot ink composition of the present invention contains scattering particles, the content of the scattering particles is 0.01 to 10% by weight, preferably 1 to 7% by weight, based on the total weight of the recycled quantum dot ink composition. When the content of scattering particles satisfies the above range, it is preferable because it has the advantage of improving the light conversion efficiency without degrading the physical properties of the composition.

[0155] <Recycled quantum dot ink composition, color filter, and display device> The present invention provides a recycled quantum dot ink composition produced by a method for producing recycled quantum dot ink compositions described later.

[0156] The recycled quantum dot ink composition of the present invention is manufactured by the method for manufacturing the recycled quantum dot ink composition described above, and the contents of the <quantum dot ink composition> and <method for manufacturing the recycled quantum dot ink composition> described above can be applied in the same manner.

[0157] The recycled quantum dot ink composition of the present invention may be solvent-free. Furthermore, the recycled quantum dot ink composition may be suitable for inkjet printing processes.

[0158] The recycled quantum dot ink composition produced by the method for producing recycled quantum dot ink compositions of the present invention exhibits a viscosity change of +1.6 cps or less, preferably +0.5 cps or less, relative to its initial viscosity when stored at 50°C for 4 weeks.

[0159] The present invention provides a color filter containing a cured product of the recycled quantum dot ink composition. The cured product can be manufactured by a method comprising the steps of applying the recycled quantum dot ink composition onto a substrate by an inkjet ejection method to form a pattern, and curing the pattern.

[0160] The aforementioned color filters can be manufactured by methods such as dyeing, pigment dispersion, printing, and electrodeposition. Furthermore, color filters containing cured recycled quantum dot ink compositions can be manufactured by inkjet technology.

[0161] Furthermore, the present invention provides a display device including the color filter. The display device includes, but is not limited to, a liquid crystal display (LCD), an electroluminescent display (EL), a plasma display (PDP), a field emission display (FED), an organic EL display (OLED), and the like. [Examples]

[0162] The present invention will be described in more detail below with reference to examples. However, the following examples are for illustrative purposes only, and the scope of the present invention is not limited by these examples.

[0163] <Examples> Manufacturing Example 1: Production of waste quantum dot dispersion 1 from which scattered particles have been removed. A waste quantum dot ink composition (HIQ-100G, Hansol Chemical Co.) was prepared containing green quantum dots (InP / ZnSe / ZnS; ligands: MAES and Zn-(PEG550-Thiol)2; solids content 40 wt%), scattering particles (TiO2, D50: 170 nm, solids content 4 wt%), and a photopolymerizable monomer (1,6-hexanediol diacrylate). 50 wt parts of the waste quantum dot ink composition were mixed with 100 wt parts of acetone (polarization index: 5.1) as a solvent, and the precipitated scattering particles were removed by centrifugation (6000 rpm, 15 min) (1st separation). Subsequently, the filtrate from which the precipitated scattering particles had been removed was centrifuged again (6000 rpm, 15 min) (2nd separation) to produce waste quantum dot dispersion 1 from which the scattering particles had been removed.

[0164] Manufacturing Example 2: Production of Waste Quantum Dot Dispersion 2 with Scattered Particles Removed A waste quantum dot dispersion 2 was prepared in the same manner as in Production Example 1, except that ethyl acetate (EA, polarity index: 4.4) was used as the solvent instead of acetone.

[0165] Manufacturing Example 3: Manufacturing of waste quantum dot dispersion 3 from which scattered particles have been removed A waste quantum dot dispersion 3 was prepared in the same manner as in Production Example 1, except that cyclohexyl acetate (CHA, polarity index: 4.8) was used as the solvent instead of acetone.

[0166] Manufacturing Example 4: Production of waste quantum dot dispersion 4 from which scattered particles have been removed A waste quantum dot dispersion 4 was prepared in the same manner as in Production Example 1, except that isopropyl alcohol (IPA, polarity index: 3.9) was used as the solvent instead of acetone.

[0167] Manufacturing Example 5: Production of waste quantum dot dispersion 5 from which scattered particles have been removed. A waste quantum dot ink composition (HIQ-200R, Hansol Chemical Co.) was prepared containing red quantum dots (InP / ZnSe / ZnS; ligand: MAES, and Zn-(PEG550-Thiol)2; solids content 36 wt%), scattering particles (TiO2, D50: 170 nm, solids content 5 wt%), and a photopolymerizable monomer (1,6-hexanediol diacrylate). 50 wt parts of the waste quantum dot ink composition were mixed with 100 wt parts of acetone (polarization index: 5.1) as a solvent, and the precipitated scattering particles were removed by centrifugation (6000 rpm, 15 min) (1st separation). Subsequently, the filtrate from which the precipitated scattering particles had been removed was centrifuged again (6000 rpm, 15 min) (2nd separation) to produce a waste quantum dot dispersion 5 from which the scattering particles had been removed.

[0168] Manufacturing Example 6: Production of waste quantum dot dispersion 6 from which scattered particles have been removed A waste quantum dot dispersion 6 was prepared in the same manner as in Production Example 5, except that ethyl acetate (EA, polarity index: 4.4) was used as the solvent instead of acetone.

[0169] Manufacturing Example 7: Manufacturing of waste quantum dot dispersion 7 from which scattered particles have been removed. A waste quantum dot dispersion 7 was prepared in the same manner as in Production Example 5, except that cyclohexyl acetate (CHA, polarity index: 4.8) was used as the solvent instead of acetone.

[0170] Manufacturing Example 8: Manufacturing of a waste quantum dot dispersion 8 from which scattered particles have been removed. A waste quantum dot dispersion 8 was prepared in the same manner as in Production Example 5, except that isopropyl alcohol (IPA, polarity index: 3.9) was used as the solvent instead of acetone.

[0171] Example 1: Production of recycled quantum dot ink composition 1 1-1. Quantum dot recovery To the waste quantum dot dispersion 1 from which scattered particles were removed according to the above production example 1, 2 times the weight of cyclohexane was mixed and centrifuged (6000 rpm, 5 minutes). Based on the solid content obtained, 1 time the weight of acetone was mixed to disperse the solid content, and then 12 times the weight of cyclohexane was mixed based on the solid content and centrifuged again (6000 rpm, 5 minutes). The solid content obtained by centrifugation was vacuum dried to obtain quantum dot powder.

[0172] 1-2. Re-modification of quantum dot surfaces A quantum dot dispersion was prepared by dispersing the quantum dot powder obtained in 1-1 in cyclohexyl acetate at a concentration of 20% by weight, and the dispersion was heated to 60°C and maintained therein. Next, 5 parts by weight of a solution of mono-2-(acryloyloxy)ethyl succinate diluted in cyclohexyl acetate at a concentration of 20% by weight was mixed with 100 parts by weight of the quantum dot dispersion, and the mixture was stirred under a nitrogen atmosphere for 3 hours. After that, it was cooled to room temperature to complete the re-modification reaction of the quantum dot surface.

[0173] 1-3. Preparation of quantum dot dispersion after surface re-modification is complete. Cyclohexane was mixed with the solution containing the quantum dots whose surface had been remodified in steps 1-2 above, and the solution was centrifuged (6000 rpm, 5 minutes) to obtain quantum dot powder whose surface had been remodified. The obtained quantum dot powder was dispersed in 1,6-hexanediol diacrylate at a concentration of 50% by weight to prepare a quantum dot dispersion.

[0174] 1-4. Manufacturing of recycled quantum dot ink compositions A scattering particle dispersion was prepared by dispersing titanium dioxide (TiO2, D50:170nm) powder in 1,6-hexanediol diacrylate at a concentration of 50% by weight. Next, 80 parts by weight of the quantum dot dispersion prepared in 1-3, 8 parts by weight of the scattering particle dispersion, 1 part by weight of TPO-L, and 11 parts by weight of 1,6-hexanediol diacrylate were mixed to produce recycled quantum dot ink composition 1.

[0175] Example 2: Production of Recycled Quantum Dot Ink Composition 2 2-1. Quantum dot recovery Quantum dot powder was obtained by the same method as in 1-1 of Example 1 described above.

[0176] 2-2. Re-modification of quantum dot surfaces The re-modification reaction of the quantum dot surface was completed using the same method as in Examples 1-2 of the above-mentioned Example 1.

[0177] 2-3. Preparation of quantum dot dispersion after surface re-modification is complete. A solution containing quantum dots whose surface had been re-modified according to 2-2 above was mixed with cyclohexane and centrifuged (6000 rpm, 5 min) to obtain solids. Based on the solids, acetone was mixed in at a weight of 1:1 and dispersed, then cyclohexane was mixed and centrifuged (6000 rpm, 5 min) to obtain quantum dot powder whose surface had been re-modified. The obtained quantum dot powder was dispersed in 1,6-hexanediol diacrylate at a concentration of 50% by weight to prepare a quantum dot dispersion.

[0178] 2-4. Manufacturing of recycled quantum dot ink compositions The recycled quantum dot ink composition 2 was manufactured in the same manner as in 1-4 of Example 1, except that the quantum dot dispersion prepared in 2-3 above was used.

[0179] Example 3: Production of recycled quantum dot ink composition 3 3-1. Recovery of quantum dots Quantum dot powder was obtained by the same method as in 1-1 of Example 1 described above.

[0180] 3-2. Re-modification of quantum dot surfaces The re-modification reaction of the quantum dot surface was completed in the same manner as in Example 1-2, except that 3 parts by weight of a solution of mono-2-(acryloyloxy)ethyl succinate diluted in cyclohexyl acetate to a concentration of 20% by weight was used.

[0181] 3-3. Preparation of quantum dot dispersion after surface re-modification is complete. A quantum dot dispersion was prepared in the same manner as in 2-3 of Example 2, except that a solution containing quantum dots whose surface had been re-modified according to 3-2 above was used.

[0182] 3-4. Manufacturing of recycled quantum dot ink compositions The recycled quantum dot ink composition 3 was manufactured in the same manner as in 1-4 of Example 1, except that the quantum dot dispersion prepared in 3-3 above was used.

[0183] Example 4: Production of recycled quantum dot ink composition 4 4-1. Quantum dot recovery Quantum dot powder was obtained by the same method as in 1-1 of Example 1 described above.

[0184] 4-2. Re-modification of quantum dot surfaces The re-modification reaction of the quantum dot surface was completed in the same manner as in Example 1-2, except that 10 parts by weight of a solution of mono-2-(acryloyloxy)ethyl succinate diluted in cyclohexyl acetate to a concentration of 20% by weight was used.

[0185] 4-3. Preparation of quantum dot dispersion after surface re-modification is complete. A quantum dot dispersion was prepared in the same manner as in Example 2, Sections 2-3, except that a solution containing quantum dots whose surface had been re-modified according to Section 4-2 above was used.

[0186] 4-4. Manufacturing of Recycled Quantum Dot Ink Compositions The recycled quantum dot ink composition 4 was manufactured in the same manner as in 1-4 of Example 1, except that the quantum dot dispersion prepared in 4-3 above was used.

[0187] Example 5: Production of recycled quantum dot ink composition 5 5-1. Quantum dot recovery Quantum dot powder was obtained by the same method as in 1-1 of Example 1 described above.

[0188] 5-2. Re-modification of quantum dot surfaces The re-modification reaction of the quantum dot surface was completed in the same manner as in Example 1-2, except that 15 parts by weight of a solution of mono-2-(acryloyloxy)ethyl succinate diluted in cyclohexyl acetate to a concentration of 20% by weight was used.

[0189] 5-3. Preparation of quantum dot dispersion after surface re-modification is complete. A quantum dot dispersion was prepared in the same manner as in Example 2, Section 2-3, except that a solution containing quantum dots whose surface had been re-modified according to Section 5-2 above was used.

[0190] 5-4. Manufacturing of Recycled Quantum Dot Ink Compositions The recycled quantum dot ink composition 5 was manufactured in the same manner as in 1-4 of Example 1, except that the quantum dot dispersion prepared in 5-3 above was used.

[0191] Example 6: Production of recycled quantum dot ink composition 6 6-1. Quantum dot recovery Quantum dot powder was obtained in the same manner as in Example 1-1, except that the waste quantum dot dispersion 2 obtained by removing the scattered particles from Production Example 2 was used.

[0192] 6-2. Re-modification of quantum dot surfaces The re-modification reaction of the quantum dot surface was completed in the same manner as in Example 1-2, except that the quantum dot powder obtained in 6-1 above was used.

[0193] 6-3. Preparation of quantum dot dispersion after surface re-modification is complete. A quantum dot dispersion was prepared in the same manner as in 1-3 of Example 1, except that a solution containing quantum dots whose surface had been re-modified according to 6-2 above was used.

[0194] 6-4. Manufacturing of Recycled Quantum Dot Ink Compositions The recycled quantum dot ink composition 6 was produced in the same manner as in 1-4 of Example 1, except that the quantum dot dispersion prepared in 6-3 above was used.

[0195] Example 7: Production of recycled quantum dot ink composition 7 7-1. Recovery of quantum dots Quantum dot powder was obtained by the same method as in 6-1 of Example 6 described above.

[0196] 7-2. Re-modification of quantum dot surfaces The re-modification reaction of the quantum dot surface was completed in the same manner as in Example 1-2, except that the quantum dot powder obtained in 7-1 above was used.

[0197] 7-3. Preparation of quantum dot dispersion after surface re-modification is complete. A quantum dot dispersion was prepared in the same manner as in Example 2, Sections 2-3, except that a solution containing quantum dots whose surface had been re-modified according to Section 7-2 was used.

[0198] 7-4. Manufacturing of Recycled Quantum Dot Ink Compositions The recycled quantum dot ink composition 7 was produced in the same manner as in 1-4 of Example 1, except that the quantum dot dispersion prepared in 7-3 above was used.

[0199] Example 8: Production of recycled quantum dot ink composition 8 8-1. Recovery of quantum dots Quantum dot powder was obtained in the same manner as in Example 1-1, except that a waste quantum dot dispersion 5, from which scattered particles were removed according to Production Example 5, was used.

[0200] 8-2. Re-modification of quantum dot surfaces The re-modification reaction of the quantum dot surface was completed in the same manner as in Example 1-2, except that the quantum dot powder obtained in 8-1 above was used.

[0201] 8-3. Preparation of quantum dot dispersion after surface re-modification is complete. A quantum dot dispersion was prepared in the same manner as in 1-3 of Example 1, except that a solution containing quantum dots whose surface had been re-modified according to 8-2 above was used.

[0202] 8-4. Manufacturing of Recycled Quantum Dot Ink Compositions A scattering particle dispersion was prepared by dispersing titanium dioxide (TiO2, D50:170nm) powder in 1,6-hexanediol diacrylate at a concentration of 50% by weight. A recycled quantum dot ink composition 8 was produced by mixing 72 parts by weight of the quantum dot dispersion prepared in 8-3, 10 parts by weight of the scattering particle dispersion, 1 part by weight of TPO-L, and 17 parts by weight of 1,6-hexanediol diacrylate.

[0203] Example 9: Production of recycled quantum dot ink composition 9 9-1. Quantum dot recovery Quantum dot powder was obtained in the same manner as in 8-1 of Example 8 described above.

[0204] 9-2. Re-modification of quantum dot surfaces The re-modification reaction of the quantum dot surface was completed in the same manner as in Example 1-2, except that the quantum dot powder obtained in 9-1 above was used.

[0205] 9-3. Preparation of quantum dot dispersion after surface re-modification is complete. A quantum dot dispersion was prepared in the same manner as in Example 2, Sections 2-3, except that a solution containing quantum dots whose surface had been re-modified according to Section 9-2 above was used.

[0206] 9-4. Manufacturing of Recycled Quantum Dot Ink Compositions The recycled quantum dot ink composition 9 was manufactured in the same manner as in 8-4 of Example 8, except that the quantum dot dispersion prepared in 9-3 above was used.

[0207] Example 10: Production of recycled quantum dot ink composition 10 10-1. Recovery of quantum dots Quantum dot powder was obtained in the same manner as in 8-1 of Example 8 described above.

[0208] 10-2. Re-modification of quantum dot surfaces The re-modification reaction of the quantum dot surface was completed in the same manner as in Example 1-2, except that 3 parts by weight of a solution of mono-2-(acryloyloxy)ethyl succinate diluted in cyclohexyl acetate to a concentration of 20% by weight was used.

[0209] 10-3. Preparation of quantum dot dispersion after surface re-modification is complete. A quantum dot dispersion was prepared in the same manner as in Example 2-2-3, except that a solution containing quantum dots whose surface had been re-modified according to 10-2 above was used.

[0210] 10-4. Manufacturing of Recycled Quantum Dot Ink Compositions The recycled quantum dot ink composition 10 was manufactured in the same manner as in 8-4 of Example 8, except that the quantum dot dispersion prepared in 10-3 above was used.

[0211] Example 11: Production of recycled quantum dot ink composition 11 11-1. Recovery of quantum dots Quantum dot powder was obtained in the same manner as in 8-1 of Example 8 described above.

[0212] 11-2. Re-modification of quantum dot surfaces The re-modification reaction of the quantum dot surface was completed in the same manner as in Example 1-2, except that 10 parts by weight of a solution of mono-2-(acryloyloxy)ethyl succinate diluted in cyclohexyl acetate to a concentration of 20% by weight was used.

[0213] 11-3. Preparation of quantum dot dispersion after surface re-modification is complete. A quantum dot dispersion was prepared in the same manner as in Example 2-2-3, except that a solution containing quantum dots whose surface had been re-modified according to 11-2 above was used.

[0214] 11-4. Manufacturing of Recycled Quantum Dot Ink Compositions The recycled quantum dot ink composition 11 was manufactured in the same manner as in 8-4 of Example 8, except that the quantum dot dispersion prepared in 11-3 above was used.

[0215] Example 12: Production of recycled quantum dot ink composition 12 12-1. Quantum dot recovery Quantum dot powder was obtained in the same manner as in 8-1 of Example 8 described above.

[0216] 12-2. Re-modification of quantum dot surfaces The re-modification reaction of the quantum dot surface was completed in the same manner as in Example 1-2, except that 15 parts by weight of a solution of mono-2-(acryloyloxy)ethyl succinate diluted in cyclohexyl acetate to a concentration of 20% by weight was used.

[0217] 12-3. Preparation of quantum dot dispersion after surface re-modification is complete. A quantum dot dispersion was prepared in the same manner as in Example 2-2-3, except that a solution containing quantum dots whose surface had been re-modified according to 12-2 above was used.

[0218] 12-4. Manufacturing of Recycled Quantum Dot Ink Compositions The recycled quantum dot ink composition 12 was produced in the same manner as in 8-4 of Example 8, except that the quantum dot dispersion prepared in 12-3 was used.

[0219] Example 13: Production of recycled quantum dot ink composition 13 13-1. Quantum dot recovery Quantum dot powder was obtained in the same manner as in Example 1-1, except that a waste quantum dot dispersion 6, from which scattered particles from the above-mentioned Production Example 6 had been removed, was used.

[0220] 13-2. Re-modification of quantum dot surfaces The re-modification reaction of the quantum dot surface was completed in the same manner as in Example 1-2, except that the quantum dot powder obtained in 13-1 was used.

[0221] 13-3. Preparation of quantum dot dispersion after surface re-modification is complete. A quantum dot dispersion was prepared in the same manner as in 1-3 of Example 1, except that a solution containing quantum dots whose surface had been re-modified according to 13-2 above was used.

[0222] 13-4. Manufacturing of Recycled Quantum Dot Ink Compositions The recycled quantum dot ink composition 13 was manufactured in the same manner as in 8-4 of Example 8, except that the quantum dot dispersion prepared in 13-3 above was used.

[0223] Example 14: Production of recycled quantum dot ink composition 14 14-1. Quantum dot recovery Quantum dot powder was obtained in the same manner as in 13-1 of Example 13 described above.

[0224] 14-2. Re-modification of quantum dot surfaces The re-modification reaction of the quantum dot surface was completed in the same manner as in Example 1-2, except that the quantum dot powder obtained in 14-1 was used.

[0225] 14-3. Preparation of quantum dot dispersion after surface modification is complete. A quantum dot dispersion was prepared in the same manner as in Example 2-2-3, except that a solution containing quantum dots whose surface had been re-modified according to 14-2 above was used.

[0226] 14-4. Manufacturing of Recycled Quantum Dot Ink Compositions The recycled quantum dot ink composition 14 was manufactured in the same manner as in 8-4 of Example 8, except that the quantum dot dispersion prepared in 14-3 above was used.

[0227] Comparative Example 1: Production of recycled quantum dot ink composition a 15-1. Recovery of quantum dots Quantum dot powder was obtained by the same method as in 1-1 of Example 1 described above.

[0228] 15-2. Re-modification of quantum dot surfaces The re-modification reaction of the quantum dot surface was not performed.

[0229] 15-3. Preparation of quantum dot dispersion after surface re-modification is complete. A quantum dot dispersion was prepared by dispersing the quantum dot powder obtained in 15-1 above in 1,6-hexanediol diacrylate at a concentration of 50% by weight.

[0230] 15-4. Manufacturing of Recycled Quantum Dot Ink Compositions A recycled quantum dot ink composition a was produced in the same manner as in 1-4 of Example 1, except that the quantum dot dispersion prepared in 15-3 above was used.

[0231] Comparative Example 2: Production of recycled quantum dot ink composition b 16-1. Quantum dot recovery Quantum dot powder was obtained by the same method as in 1-1 of Example 1 described above.

[0232] 16-2. Re-modification of quantum dot surfaces The re-modification reaction of the quantum dot surface was completed in the same manner as in Example 1-2, except that Zn-(PEG550-Thiol)2 was used instead of mono-2-(acryloyloxy)ethyl succinate.

[0233] 16-3. Preparation of quantum dot dispersion after surface re-modification is complete. A quantum dot dispersion was prepared in the same manner as in Example 2-2-3, except that a solution containing quantum dots whose surface had been re-modified according to 16-2 above was used.

[0234] 16-4. Manufacturing of Recycled Quantum Dot Ink Compositions Regenerated quantum dot ink composition b was produced in the same manner as in 1-4 of Example 1, except that the quantum dot dispersion prepared in 16-3 above was used.

[0235] Comparative Example 3: Production of recycled quantum dot ink composition c 17-1. Recovery of quantum dots Quantum dot powder was obtained in the same manner as in 8-1 of Example 8 described above.

[0236] 17-2. Re-modification of quantum dot surfaces The re-modification reaction of the quantum dot surface was not performed.

[0237] 17-3. Preparation of quantum dot dispersion after surface re-modification is complete. A quantum dot dispersion was prepared by dispersing the quantum dot powder obtained in 17-1 above in 1,6-hexanediol diacrylate at a concentration of 50% by weight.

[0238] 17-4. Manufacturing of Recycled Quantum Dot Ink Compositions A regenerated quantum dot ink composition c was produced in the same manner as in 1-4 of Example 1, except that the quantum dot dispersion prepared in 17-3 was used.

[0239] Comparative Example 4: Production of regenerated quantum dot ink composition d 18-1. Recovery of quantum dots Quantum dot powder was obtained in the same manner as in 8-1 of Example 8.

[0240] 18-2. Re-modification of the quantum dot surface The re-modification reaction of the quantum dot surface was completed in the same manner as in 16-2 of Comparative Example 2, except that the quantum dot powder obtained in 18-1 was used.

[0241] 18-3. Preparation of a quantum dot dispersion with completed surface re-modification A quantum dot dispersion was prepared in the same manner as in 2-3 of Example 2, except that a solution containing quantum dots with completed surface re-modification according to 18-2 was used.

[0242] 18-4. Production of regenerated quantum dot ink composition A regenerated quantum dot ink composition d was produced in the same manner as in 1-4 of Example 1, except that the quantum dot dispersion prepared in 18-3 was used.

[0243] <Experimental Example> 1. Evaluation of sedimentation property of scattering particles For the waste quantum dot dispersions 1-8 from which scattering particles were removed according to Production Examples 1-8, the sedimentation property of the scattering particles was visually evaluated for each solvent, and the results are shown in Figure 2.

[0244] Referring to Figure 2, it was confirmed that for Production Examples 1, 2, 5, and 6 using acetone and ethyl acetate (EA) as solvents for precipitating scattering particles, the scattering particles selectively precipitated and the other components were well dispersed to form a transparent filtrate.

[0245] In addition, in Production Examples 3 and 7 using cyclohexyl acetate (CHA) as the solvent for precipitating the scattered particles, it was also confirmed that the scattered particles selectively precipitated. However, some of the scattered particles remained without precipitating, showing a slightly opaque filtrate.

[0246] On the other hand, Production Examples 4 and 8 using isopropyl alcohol (IPA) as the solvent for precipitating the scattered particles showed a transparent filtrate, and precipitates could also be confirmed. However, since the amount of the precipitate was significantly larger compared to other production examples, it was suggested that not only the scattered particles but also the quantum dots were precipitated together.

[0247] From the above results, it can be seen that the use of acetone, ethyl acetate (EA) or cyclohexyl acetate (CHA) as the solvent for precipitating the scattered particles from the waste quantum dot ink composition is suitable, and the use of acetone or ethyl acetate (EA) is more preferable.

[0248] 2. Analysis of the remaining amount of scattered particles Regarding the waste quantum dot dispersions 1 to 3 and 5 to 7 from which the scattered particles were removed according to Production Examples 1 to 3 and 5 to 7, the remaining amount of the scattered particles at the time of the first separation and the second separation was analyzed using ICP - OES (Avio200, PerkinElmer), and the results are shown in Table 1.

[0249]

Table 1

[0250] Referring to Table 1 above, when acetone and ethyl acetate were used as the solvent, it was confirmed that the remaining amount of the scattered particles was 400 ppm (mg / L) or less after one centrifugation (first separation), and 20 ppm (mg / L) or less after two centrifugations (second separation).

[0251] 3. Viscosity evaluation The viscosity of each recycled quantum dot ink composition produced by Examples 1-14 and Comparative Examples 1-4 was measured using a viscometer (RheoStress MARS40, HAAKE) at room temperature (25°C) at 100 rpm for 2 minutes, and the results are shown in Tables 2 and 3 below.

[0252] 4. Evaluation of light absorption rate, quantum efficiency, emission wavelength, and full width at half maximum. The recycled quantum dot ink compositions prepared in Examples 1-14 and Comparative Examples 1-4 were coated onto a glass substrate to a thickness of 9 μm using a spin coater (Opticoat MS-A150, Mikasa Corporation), and a cured film was prepared by exposure to 395 nm UV light at 4000 mJ (83°C, 4 seconds). Subsequently, a 2 cm × 2 cm single-film sample of the prepared cured film was cut using an absolute quantum efficiency meter (QE-2100, Otsuka Electronics), and the light absorption rate, initial quantum efficiency (QE), emission wavelength, and full width at half maximum were measured. Furthermore, after heat treatment at 180°C for 30 minutes under a nitrogen atmosphere, the post-bake quantum efficiency (Post-Bake QE) was measured. The results are shown in Tables 2 and 3 below.

[0253] [Table 2]

[0254] [Table 3]

[0255] Referring to Tables 2 and 3, the compositions of Examples 1 to 14 of the present invention, which underwent a step of re-substituting the ligands of quantum dots recovered from the waste quantum dot ink composition, exhibited lower viscosity compared to Comparative Examples 1 to 4, and showed similar levels of light absorption rate, initial quantum efficiency, quantum efficiency after heat treatment, rate of change of quantum efficiency, emission wavelength, and full width at half maximum as the normal products of Reference Examples 1 and 2, confirming that their optical properties were also good. In particular, the compositions of Examples 1, 6, 8, and 13, which underwent only one centrifugation step in the process of obtaining quantum dots after the re-modification of the ligands on the quantum dot surface was completed, showed the lowest viscosity and exhibited physical properties identical to or very similar to those of the normal product.

[0256] In contrast, it was confirmed that the compositions of Comparative Examples 1 and 3, which omitted the step of re-substituting the ligands of the quantum dots recovered from the waste quantum dot ink composition, exhibited higher viscosities than those of the Examples and Reference Examples.

[0257] In addition, in the case of Comparative Examples 2 and 4 using thiol-based ligands in the step of re-substituting the ligands of the quantum dots, it was confirmed that the viscosity was rather higher than that of Comparative Examples 1 and 3 in which the step of re-substituting the ligands was omitted.

[0258] 5. Evaluation of High-temperature Long-term Storage Stability The regenerated quantum dot ink compositions according to Examples 1, 2, 6 to 9, 13 and 14 and Comparative Examples 1 and 3 were stored in an oven at 50 °C, and the initial viscosity and the viscosities after 1 week, 2 weeks, 3 weeks and 4 weeks were measured at room temperature (25 °C) at 100 rpm for 2 minutes using a viscometer (RheoStress MARS40, HAAKE). The results are shown in Tables 4 and 5 below.

[0259] [Table 4]

[0260] [Table 5]

[0261] Referring to Tables 4 and 5 above, it was confirmed that the compositions of Examples 1, 2, 6 to 9, 13 and 14 did not show a significant increase in viscosity even after being stored at 50 °C for 4 weeks, and had excellent long-term storage stability at high temperatures. In particular, the compositions of Examples 1, 6, 8 and 13, in which the quantum dots were subjected to only one centrifugation in the process of obtaining the quantum dots after the re-modification of the ligands on the quantum dot surface was completed, did not show a significant thickening phenomenon even when stored at 50 °C for 4 weeks, and it was confirmed that they exhibited physical properties identical or very similar to those of normal products.

[0262] In contrast, the compositions of Comparative Examples 1 and 3, which omitted the step of re-substituting the ligands of quantum dots recovered from the waste quantum dot ink composition, not only had a higher initial viscosity compared to the Examples and Reference Examples, but it was also confirmed that the viscosity increased significantly when stored at 50°C for 4 weeks.

Claims

1. (a) A step of removing scattered particles from the quantum dot ink composition, (b) A step of recovering quantum dots from the quantum dot ink composition from which the scattering particles have been removed, (c) A step of adding a ligand to the recovered quantum dots to re-substitute the ligand, (d) A step of dispersing the quantum dots in which the ligand has been resubstituted in a photopolymerizable monomer, A method for producing a recycled quantum dot ink composition.

2. The (a) step includes mixing a solvent with the quantum dot ink composition to selectively precipitate the scattering particles, A method for producing the recycled quantum dot ink composition according to claim 1.

3. The solvent is soluble in the quantum dots contained in the quantum dot ink composition. A method for producing the recycled quantum dot ink composition according to claim 2.

4. The solvent has a polarity index of 2.4 to 7.

2. A method for producing the recycled quantum dot ink composition according to claim 2.

5. The solvent comprises at least one selected from the group consisting of toluene, methyl t-butyl ether, xylene, benzene, diethyl ether, dichloromethane, dichloroethane, butyl acetate, isopropyl alcohol, butanol, tetrahydrofuran, propanol, acetonitrile, acetic acid, dimethylformamide, dimethyl sulfoxide, acetone, ethyl acetate, cyclohexyl acetate, chloroform, 2-butanone, dioxane, methanol, ethanol, and propylene glycol monomethyl ether acetate. A method for producing the recycled quantum dot ink composition according to claim 2.

6. The content of scattering particles in the quantum dot ink composition from which the scattering particles have been removed is 400 mg / L or less. A method for producing the recycled quantum dot ink composition according to claim 1.

7. The (b) step includes mixing a non-solvent with the quantum dot ink composition from which the scattering particles have been removed to selectively precipitate the quantum dots. A method for producing the recycled quantum dot ink composition according to claim 1.

8. The aforementioned non-solvent has a polarization index of 1 or less. A method for producing the recycled quantum dot ink composition according to claim 7.

9. The ligand includes a ligand having 3 to 40 carbon atoms and containing a carboxyl group. A method for producing the recycled quantum dot ink composition according to claim 1.

10. The ligand having 3 to 40 carbon atoms and containing the carboxyl group is a compound represented by the following chemical formula 2. A method for producing the recycled quantum dot ink composition according to claim 9. 【Chemistry 1】 [Chemical formula 2] (In the above chemical formula 2, L is selected from the group consisting of single bonds, substituted or unsubstituted C1-C20 alkylene groups, and substituted or unsubstituted C1-C20 alkenylene groups. A is either a single bond, or an ester (-C(=O)O-), ether (-O-), carbonyl (-C(=O)-), or sulfonyl (-SO ２ A C1-C20 alkylene group or alkenylene group having at least one functional group selected from the group consisting of -), sulfide (-S-), and sulfoxide (-SO-), R is selected from the group consisting of hydrogen, substituted or unsubstituted C1-C20 alkyl groups, and substituted or unsubstituted C1-C20 alkenyl groups.

11. The compound represented by the chemical formula 2 is 2-carboxyethyl acrylate, mono-2-(acryloyloxy)ethyl succinate, mono-2-(methacryloyloxy)ethyl succinate, mono-2-(methacryloyloxy)ethyl maleate, and 2-[2-(2-methoxyethoxy)ethoxy]acetic acid. At least one selected from the group consisting of ), and 2-(2-methoxyethoxy)acetic acid. A method for producing the recycled quantum dot ink composition according to claim 10.

12. The photopolymerizable monomer includes a (meth)acrylate monomer. A method for producing the recycled quantum dot ink composition according to claim 1.

13. The quantum dot ink composition in step (a) is a waste quantum dot ink composition. A method for producing the recycled quantum dot ink composition according to claim 1.

14. A recycled quantum dot ink composition produced by the method for producing a recycled quantum dot ink composition described in claim 1.

15. After storage at 50°C for 4 weeks, the viscosity change relative to the initial viscosity is +1.6 cps or less. The recycled quantum dot ink composition according to claim 14.

16. For inkjet printing, The recycled quantum dot ink composition according to claim 14.

17. A color filter comprising a cured product of the recycled quantum dot ink composition described in claim 14.

18. A display device comprising the color filter described in claim 17.

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