Solvent-free quantum dot composition, method of preparing the same, and cured film, color filter, and display device comprising the same

Abstract

The present invention relates to a quantum dot composition, a method for preparing the same, and a cured film, a color filter, and a display device comprising the same. Specifically, the solvent-free quantum dot composition of the present invention comprises quantum dots surface-modified using two kinds of ligands, and exhibits low viscosity, excellent optical properties, and high storage stability.

Description

TECHNICAL FIELD

[0001] The present application relates to a solvent-free quantum dot composition, a method for preparing the same, and a cured film, a color filter, and a display device comprising the same. BACKGROUND

[0002] Quantum dots (QD) are so-called semiconductor nanocrystals that produce various colors by producing different wavelengths of light for each particle size without changing the type of material, and are attracting attention as next-generation light emitting devices because they have the advantages of higher color purity and light stability than existing light emitters.

[0003] In particular, quantum dots have become a new trend in the display field, and can be applied to various displays and electronic devices, etc. in addition to TVs and LEDs. Quantum dots represented by CdSe, Inp, etc. are rapidly developing in terms of quantum yield, and a synthesis method with a quantum yield close to 100% has been introduced. Based on this, TVs using quantum dot sheets are currently being commercialized. Next, quantum dot TVs are being developed as a self-emitting version by including quantum dots (excluding pigments and dyes) in the color filter layer of existing LED TVs instead of the filtering method in the color filter layer. The core of developing such quantum dot TVs lies in how much light efficiency of quantum dots can be maintained in the process of configuring pixels and the manufacturing process.

[0004] On the other hand, materials for color filters require high sensitivity, adhesion to substrates, chemical resistance, heat resistance, etc. Color filters applied to conventional displays are generally formed by a desired pattern through an exposure process using a photosensitive resist composition and applying a photomask, and then through a patterning process in which unexposed portions are dissolved and removed through a developing process.

[0005] Recently, in order to solve the high quality of materials used for pixels and the resulting increase in cost, a method of suppressing the use of materials as much as possible by using materials only on desired portions is attracting attention compared to patterning by conventional spin coating or slot coating. The most representative method is an inkjet method, and since the inkjet method uses only the materials of the required pixels, it can prevent unnecessary material waste.

[0006] However, since the viscosity of the quantum dot composition used in the inkjet method needs to be 100 cps or less, preferably 50 cps or less, a solvent is included as an essential ingredient to achieve low viscosity. As such, since the quantum dot composition includes a solvent, thickness deviation becomes serious after curing or there is a limitation in increasing the film thickness, and there is a concern about environmental pollution due to the use of an organic solvent.

[0007] Accordingly, there is a need to develop a quantum dot composition which is free of solvent, has low viscosity, and has excellent optical properties. SUMMARY

[0008] TECHNICAL PROBLEM

[0009] The present application is to provide a solvent-free quantum dot composition which has low viscosity, excellent optical properties, and high storage stability.

[0010] Another problem to be solved by the present application is to provide a cured film, a color filter, and a display device comprising the above-described solvent-free quantum dot composition.

[0011] SOLUTION TO PROBLEM

[0012] To solve the above-described technical problem, the present application provides a solvent-free quantum dot composition comprising quantum dots and a photopolymerization monomer, the quantum dots being surface-modified with a first ligand represented by the following Chemical Formula 1 and a second ligand comprising a carboxyl group and having a carbon atom number of 3 to 40.

[0013] Chemical Formula 1:

[0014] (In the above Chemical Formula 1, M is a divalent to tetravalent metal, X is an organic group having a carbon atom number of 3 to 20, and n is an integer of 2 to 4.)

[0015] Further, the present application provides a cured film, a color filter, and a display device comprising the above-described solvent-free quantum dot composition.

[0016] EFFECT OF THE INVENTION

[0017] The solvent-free quantum dot composition of the present application can exhibit excellent miscibility between quantum dots and monomers without including a solvent. Further, the solvent-free quantum dot composition of the present application has excellent optical properties and low viscosity, and thus can be used for inkjet printing. DETAILED DESCRIPTION

[0018] Hereinafter, the present application will be described.

[0019] Unless otherwise defined, all terms (including technical and scientific terms) used in the present specification can be used as commonly understood meaning by one of ordinary skill in the art to which the present application belongs. Further, unless explicitly specifically defined, terms defined in commonly used dictionaries are not to be interpreted in an ideally or over-interpretive manner.

[0020] Also, throughout the specification, when a certain part "comprises" a certain constitutional element, it means that it can further include other constitutional elements unless otherwise specifically stated, and does not exclude other constitutional elements.

[0021] Also, in the present specification, "(meth)acrylate" indicates acrylate and methacrylate, "(meth)acrylic acid" indicates acrylic acid and methacrylic acid, and "(meth)acryloyl" indicates acryloyl and methacryloyl.

[0022] Also, in the present specification, "monomer" and "monomer (monomer)" have the same meaning. The monomer in the present invention is distinguished from an oligomer and a polymer, and indicates a compound having a weight average molecular weight of 1000 or less. In the present specification, "photopolymerizable monomer" indicates a group such as a (meth)acrylate group that participates in a polymerization reaction.

[0023] In the present specification, "substitution" indicates that hydrogen in a compound or a functional group is substituted with one or more substituents selected from the group consisting of C1 to C30 alkyl, C2 to C30 alkenyl, C2 to C30 alkynyl, C1 to C30 alkoxy, C1 to C30 heteroalkyl, C3 to C30 heteroalkylaryl, C3 to C30 cycloalkyl, C3 to C15 cycloalkenyl, C6 to C30 cycloalkynyl, C2 to C30 heterocycloalkyl, halogen (-F, -Cl, -Br, or -I), hydroxyl (-OH), nitro (-NO2), cyano (-CN), ester (-C(=O)OR, wherein R is C1 to C10 alkyl or alkenyl), ether (-O-R, wherein R is C1 to C10 alkyl or alkenyl), carbonyl (-C(=O)-R, wherein R is C1 to C10 alkyl or alkenyl), carboxyl (-COOH), and combinations thereof.

[0024] In the present specification, "organic group" indicates C1 to C30 straight chain or branched alkyl, C2 to C30 straight chain or branched alkenyl, and C2 to C30 straight chain or branched alkynyl. Also, the above alkyl, alkenyl, and alkynyl can be substituted or unsubstituted, respectively.

[0025] In the present specification, "alkyl" indicates a monovalent substituent derived from a straight chain or branched saturated hydrocarbon having 1 to 40 carbon atoms. As examples thereof, a methyl group, an ethyl group, a propyl group, an isobutyl group, a sec-butyl group, a pentyl group, an iso-pentyl group, a hexyl group, and the like can be included, but are not limited thereto.

[0026] In the present specification, "alkenyl" refers to a monovalent substituent derived from a straight-chain or branched-chain unsaturated hydrocarbon having one or more carbon-carbon double bonds and having 2 to 40 carbon atoms. As examples thereof, a vinyl group, an allyl group, an isopropenyl group, a 2-butenyl group, and the like can be included, but are not limited thereto.

[0027] <Non-solvent quantum dot composition>

[0028] The quantum dot composition according to an embodiment of the present application is a non-solvent quantum dot composition, and specifically, has low viscosity and excellent optical properties without including a solvent, and thus can be applied to inkjet printing.

[0029] Specifically, a non-solvent quantum dot composition is provided, which includes quantum dots and a photopolymerization monomer, the quantum dots being surface-modified with a first ligand represented by the following Chemical Formula 1 and a second ligand including a carboxyl group and having 3 to 40 carbon atoms.

[0030] Chemical Formula 1:

[0031] (In the above Chemical Formula 1, M is a divalent to tetravalent metal, X is an organic group having 3 to 20 carbon atoms, and n is an integer of 2 to 4.)

[0032] Hereinafter, the composition of the above quantum dot composition will be specifically described.

[0033] Quantum dots

[0034] A quantum dot (QD) is a nanoscale semiconductor material, and can have different energy bandgaps according to differences in size and composition thereof, thereby emitting light of various wavelengths.

[0035] Such a quantum dot can have a homogeneous single-layer structure, a multi-layer structure such as a core-shell form, a gradient structure, or a mixed structure thereof. When the shell is multi-layered, each layer can include different components from each other, such as (quasi-)metal oxides.

[0036] The quantum dot (QD) can be freely selected from among a group II-VI compound, a group III-V compound, a group IV-VI compound, a group IV element, a group IV compound, and combinations thereof. When the quantum dot is in a core-shell form, the core and the shell can be freely composed of the following exemplified components, respectively.

[0037] As an example, the II-VI compound can be selected from the group consisting of: a binary compound selected from the group consisting of CdO, CdS, CdSe, CdTe, ZnO, ZnS, ZnSe, ZnTe, HgS, HgSe, HgTe, MgSe, MgS, and mixtures thereof; a ternary compound 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; and a quaternary compound selected from the group consisting of CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, HgZnSTe, and mixtures thereof.

[0038] As another example, the III-V compound can be selected from the group consisting of: a binary compound selected from the group consisting of GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, and mixtures thereof; a ternary compound 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 a quaternary compound selected from the group consisting of GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, InAlPSb, and mixtures thereof.

[0039] As another example, the IV-VI compound can be selected from the group consisting of: a binary compound selected from the group consisting of SnS, SnSe, SnTe, PbS, PbSe, PbTe, and mixtures thereof; a ternary compound selected from the group consisting of SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, and mixtures thereof; and a quaternary compound selected from the group consisting of SnPbSSe, SnPbSeTe, SnPbSTe, and mixtures thereof.

[0040] As another example, the Group IV element can be selected from the group consisting of Si, Ge, and mixtures thereof. The Group IV compound can be a binary compound selected from the group consisting of SiC, SiGe, and mixtures thereof.

[0041] The above-described binary compound, ternary compound, or quaternary compound can exist in the particle at a uniform concentration, or can exist in the same particle in a state in which the concentrations are partially different. Also, one quantum dot can have a core / shell structure surrounding another quantum dot. The interface between the core and the shell can have a concentration gradient in which the concentration of the element present in the shell decreases toward the center.

[0042] The shape of the quantum dot is not particularly limited, as long as it is a shape commonly used in the art. As an example, a spherical, rod-shaped, pyramid-shaped, disc-shaped, multi-arm, or cubic nanoparticle, nanotube, nanowire, nanofiber, flake-shaped nanoparticle, or the like can be used.

[0043] In addition, the size of the quantum dot is not particularly limited, and can be appropriately adjusted within a conventional range known in the art. As an example, the average particle diameter (D 50 ) of the quantum dot can be about 2 nm to 10 nm. In this way, when the particle diameter of the quantum dot is controlled within a range of about 2 nm to 10 nm, light of a desired color can be emitted. For example, when the particle diameter of a quantum dot core / shell containing InP is about 5 nm to 6 nm, light having a wavelength of about 520 nm to 550 nm can be emitted, and when the particle diameter of a quantum dot core / shell containing InP is about 7 nm to 8 nm, light having a wavelength of about 620 nm to 640 nm can be emitted. For example, as a blue-emitting QD (Quantum dot), a non-cadmium (Cd)-based III-V group QD (e.g., InP, InGaP, InZnP, GaN, GaAs, GaP) can be used.

[0044] Also, the above-described quantum dot can have a full width of half maximum (FWHM) of a light emission wavelength spectrum of about 40 nm or less, and within this range, color purity or color reproducibility can be improved. In addition, since light emitted by such a quantum dot is emitted in various directions, a wide viewing angle can be improved.

[0045] According to an embodiment of the present application, the content of the above-described quantum dot can be 1 to 60 weight percent, and preferably can be 20 to 50 weight percent, based on the total weight of the above-described solvent-free quantum dot composition.

[0046] Ligand

[0047] In the solvent-free quantum dot composition of the present application, a ligand is used to modify the surface of the quantum dot. The quantum dot has a barrier to the dispersion of the photopolymerization monomer due to its hydrophobic surface characteristics, and the miscibility between the quantum dot and the photopolymerization monomer can be improved by modifying the surface of the quantum dot with an appropriate ligand.

[0048] According to an embodiment of the present application, the above-described ligand can include a first ligand represented by the following Chemical Formula 1, and a second ligand including a carboxyl group and having a carbon number of 3 to 40.

[0049] Chemical Formula 1:

[0050] In the above-described Chemical Formula 1, M is a divalent to tetravalent metal, X is an organic group having a carbon number of 3 to 20, and n is an integer of 2 to 4.

[0051] The above-described first ligand can be a metal-thiol compound formed by reacting a metal salt with a thiol compound.

[0052] In the above-described first ligand, M is a divalent to tetravalent metal. For example, the above-described M can be a Group 2 to Group 14 metal 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. In the above-described Chemical Formula 1, n is determined according to the valence of M, and is an integer of 2 to 4.

[0053] Also, in the above-described Chemical Formula 1, X can be an organic group having a carbon number of 3 to 20. For example, the above-described X can be an alkylene or alkenylene group having a carbon number of 3 to 20 including one or more functional groups selected from the group consisting of an ester (-C(=O)O-), ether (-O-), carbonyl (-C(=O)-), carboxyl (-C(=O)-OH), sulfonyl (-SO2-), thioether (-S-), and sulfoxide (-SO-), alkoxy (-C(=O)-), and hydroxyl (-OH). Specifically, X can be an organic group having a carbon number of 4 to 15 including an ester (-COO-) functional group.

[0054] Since the thiol group in the first ligand has excellent affinity with the surface of the quantum dot, dispersibility of the quantum dot in the photopolymerizable monomer can be improved. Also, the first ligand contains not only a thiol group but also an ester, an ether, a carbonyl group, a carboxyl group, an alkoxy group, a cyclic base, or a hydroxyl group, so that dispersibility of the surface-modified quantum dot in a hydrophobic polar monomer can be maximized. In addition, a quantum dot composition including such a quantum dot can have advantageous properties (e.g., low viscosity) for a display process. On the other hand, when a thiol compound having 3 or less carbon atoms is used, surface modification of the quantum dot can be performed, but dispersibility of the surface-modified quantum dot in general solvents and monomers can be difficult due to high polarity of the surface-modified quantum dot.

[0055] The second ligand can have 3 to 40 carbon atoms and include a carboxyl group. Also, according to an embodiment of the present application, the second ligand can not include a thiol group.

[0056] According to an embodiment of the present application, the second ligand can be represented by the following Chemical Formula 2.

[0057] Chemical Formula 2:

[0058] In the Chemical Formula 2, L is a single bond or selected from the group consisting of substituted or unsubstituted C1 to C20 alkylene and substituted or unsubstituted C1 to C20 alkenylene, A is a single bond or C1 to C20 alkylene or alkenylene including one or more functional groups selected from the group consisting of an ester (-C(=O)O-), an ether (-O-), a carbonyl group (-C(=O)-), a sulfonyl group (-SO2-), a sulfide (-S-), and a sulfoxide (-SO-), and R is hydrogen or selected from the group consisting of substituted or unsubstituted C1 to C20 alkyl and substituted or unsubstituted C1 to C20 alkenyl.

[0059] Preferably, in the second ligand, A can include an ester (-COO-), an ether (-CO-), or a combination thereof. Also, A can be C2 to C15 alkylene or alkenylene, and preferably can be C2 to C10 alkylene or alkenylene.

[0060] In general, it is known that thiol-based ligands have high reactivity with the surface of quantum dots. However, quantum dot compositions containing only thiol-based ligands are not suitable for use in compositions for inkjet because they generate harmful odor or deteriorate storage stability due to an increase in viscosity. The quantum dot composition of the present invention uses a first ligand containing a thiol-based ligand and a second ligand not containing a thiol group together, thus exhibiting low viscosity and excellent storage stability. Also, the above-described second ligand contains a functional group such as an ester (-C(=O)O-), an ether (-O-), a carbonyl (-C(=O)-), a carboxyl (-C(=O)-OH), etc., thus exhibiting excellent dispersibility in photopolymerizable monomers. On the other hand, when the number of carbon atoms of the second ligand is 16 or more, the surface of the quantum dot can not be modified, or can hinder dispersibility in common solvents and monomers.

[0061] According to an embodiment of the present invention, the mixing ratio of the above-described first ligand to the second ligand can be 1:0.1 to 20 molar ratio, and preferably can be 1:0.2 to 10 molar ratio, but is not limited thereto.

[0062] Also, according to an embodiment of the present invention, the mixing ratio of the above-described quantum dot to the ligand can be 1:0.05 to 1 weight ratio, and preferably can be 1:0.1 to 0.5 weight ratio. Here, the ligand refers to a combination of the first ligand and the second ligand.

[0063] Photopolymerizable monomer

[0064] In the quantum dot composition of the present invention, a photopolymerizable monomer is used to exhibit the structure and physical properties of the matrix by controlling the total crosslinking density of the dosage form (i.e., polymer matrix) in which the quantum dot (QD) is dispersed. Also, flexibility and adhesion and attachment to other materials can be improved.

[0065] The above-described photopolymerizable monomer can include a (meth)acrylate-based monomer.

[0066] Any monomer commonly used in the art can be used without particular limitation.

[0067] As an example, the (meth)acrylate monomer can include at least one of a (meth)acryl group, a vinyl group, and an allyl group. Specifically, 1,6-hexanediol diacrylate, 1,6-cyclohexanediol diacrylate, 2,2-dimethyl-1,3-propanediol diacylate, diethylene glycol diacrylate, dipropylene glycol diacrylate, 1,3-butylene glycol dimethacrylate, trimethylolpropane trimethacrylate, isobonyl acrylate, isobonyl methacrylate, tetrahydrofurylacrylate, acryloyl morpholine, 2-phenoxyethyl acrylate, tripropylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol mono(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, dipentaerytritol hexaacrylate, and dipentaerytritol hexamethacrylate, etc. can be included. They can be used alone or in a mixture of two or more.

[0068] In the present application, the content of the (meth)acrylamide monomer can be 25 to 70% by weight, preferably 35 to 60% by weight, based on the total weight of the above-described solvent-free quantum dot composition.

[0069] Photoinitiator

[0070] In the solvent-free quantum dot composition of the present application, the photoinitiator is a component that is excited by a light source such as ultraviolet (UV) and is used to initiate photopolymerization, and a photopolymerization photoinitiator conventional in the art can be used without limitation. As an example, a benzophenone compound, a thioxanthone compound, a benzoin compound, a triazine compound, an oxime compound, and the like can be used.

[0071] Non-limiting examples of photoinitiators that can be used include Ethyl (2,4,6-trimethylbenzoyl) phenylphosphinate, Irgacure 184, Irgacure 369, Irgacure 651, Irgacure 819, Irgacure 907, Benzion alkylether, Benzophenone, Benzyl dimethyl ketal, Hydroxycyclohexyl phenylacetone, Chloroacetophenone, 1,1-Dichloro acetophenone, Diethoxy acetophenone, Hydroxy Acetophenone, 2-Choro thioxanthone, 2-EthylAnthraquinone, 2-ETAQ, 1-Hydroxy-cyclohexyl-phenyl-ketone, 2-Hydroxy-2-methyl-1-phenyl-1-propanone, 2-Hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone, methylbenzoylformate, and the like. They can be used alone or in a mixture of two or more.

[0072] The content of the above-described photoinitiator can be appropriately adjusted within a range known in the art. As an example, the content of the above-described photoinitiator can be 0.01 to 10% by weight, and preferably can be 0.1 to 5% by weight, based on the total weight of the solvent-free quantum dot composition. When the content of the above-described photoinitiator falls within the above-described range, the photopolymerization reaction can be sufficiently performed without deteriorating the physical properties of the matrix.

[0073] Diffusing agent

[0074] In the solvent-free quantum dot composition of the present application, the diffuser reflects light that is not absorbed by the light-converting material, and enables the light-converting material to re-absorb the above-described reflected light. That is, the diffuser can increase the light-conversion efficiency by increasing the amount of light absorbed by the light-converting material.

[0075] As the above-described diffuser, any diffuser component known in the art can be used without limitation. Such a diffuser can be a solid diffuser, or a dispersion liquid in which the diffuser is dispersed. The dispersion liquid in which such a diffuser is dispersed can be an organic solvent, for example, PGMEA.

[0076] Non-limiting examples of the diffuser that can be used can include barium sulfate (BaSO4), calcium carbonate (CaCO3), titanium dioxide (TiO2), zirconium oxide (ZrO2), or a combination thereof. In addition, the average particle diameter or shape of the diffuser is not particularly limited, and can be appropriately selected from structures known in the art. As an example, the average particle diameter (D 50 ) can be 150 to 250 nm, and particularly can be 180 to 230 nm. When the average particle diameter of the above-described diffuser falls within the above-described range, a more excellent light diffusion effect can be exhibited, and the light-conversion efficiency can be improved.

[0077] The content of the above-described diffuser can be appropriately adjusted within a range known in the art. As an example, the content of the above-described diffuser can be 0.01 to 10% by weight, and preferably can be 0.1 to 5% by weight, based on the total weight of the solvent-free quantum dot composition. When the content of the diffuser falls within the above-described range, the effect of improving the light-conversion efficiency can be exhibited without deteriorating the physical properties of the matrix.

[0078] Polymerization inhibitor

[0079] In the solvent-free quantum dot composition of the present application, the polymerization inhibitor is a substance that reacts with a free radical to form a low-reactivity free radical or compound that cannot cause a polymerization reaction, and can adjust the speed of the photopolymerization reaction.

[0080] As the above-described polymerization inhibitor, a substance known in the art can be used without limitation. For example, as the polymerization inhibitor, a quinone compound, a phenol compound or an aniline compound, an aromatic nitro and nitroso compound can be used. Specifically, p-benzoquinone (HQ), methyl-p-benzoquinone (THQ), hydroquinone monomethyl ether (MEHQ), and p-benzoquinone monoethyl ether (EEHQ), 1,4-benzoquinone (BQ), 2,5-diphenylbenzoquinone (DPBQ), methyl-1,4-benzoquinone (MBQ), methyl-1,4-benzoquinone (PBQ); 2,6-di-tert-butyl-4-methylphenol (BHT), 2,6-diphenyl-4-octadecyloxyphenol, catechol; phenothiazine, bis(α-methylbenzyl)phenothiazine, 3,7-dioctylphenothiazine, bis(α,α-dimethylbenzyl)phenothiazine; dimethyl dithiocarbamic acid, diethyl dithiocarbamic acid, dipropyl dithiocarbamic acid, dibutyl dithiocarbamic acid, diphenyl dithiocarbamic acid, and the like can be included. They can be used alone or in a mixture of two or more.

[0081] The content of the above-described polymerization inhibitor can be appropriately adjusted within a range known in the art. As an example, the content of the above-described polymerization inhibitor can be 0.01 to 2% by weight, and preferably 0.05 to 1% by weight, based on the total weight of the solvent-free quantum dot composition.

[0082] Stabilizer

[0083] In the solvent-free quantum dot composition of the present application, a stabilizer can be added to improve the stability and dispersibility of the quantum dots. The stabilizer can improve the dispersion stability of the quantum dots in a solvent by substituting the surface of the shell of the quantum dots, thereby stabilizing the quantum dots.

[0084] Any stabilizer that can be used in the art can be used without limitation, as long as it can improve the stability and dispersibility of the quantum dots, and for example, a mercaptan-based stabilizer can be used. The above-described mercaptan-based stabilizer can improve the dispersibility of the quantum dots in the photopolymerizable monomer. In addition, the mercaptan group of the mercaptan-based stabilizer reacts with the propyl acyl group of the photopolymerizable monomer to form a covalent bond, thereby improving the heat resistance of the quantum dot composition.

[0085] The above-mentioned mercaptan stabilizer can have 7 or more carbon atoms, and depending on its structure, can have 2 to 10, for example, 2 to 6 mercaptan groups (-SH) at the terminal end, but is not particularly limited thereto. Non-limiting examples of mercaptan stabilizers that can be used include pentaerythritol tetrakis(3-mercaptopropionate), trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetrakis(mercaptoacetate), trimethylolpropane tris(2-mercaptoacetate), glycol di-3-mercaptopropionate, or mixtures thereof, and the like.

[0086] Other additives

[0087] In addition to the above-mentioned components, the quantum dot composition of the present application can use additives known in the art without limitation within a range that does not hinder the effects of the present application. At this time, the content of the additives can be appropriately adjusted within a range known in the art.

[0088] Examples of additives that can be used include silane-based compounds, siloxane-based compounds, antioxidants, polymerization inhibitors, lubricants, surface modifiers, surfactants, adhesion promoters, antifoaming agents, slip agents, solvents, wetting agents, light stabilizers, stain-proofing agents, softening agents, thickening agents, polymers, and the like. They can be used alone or in a mixture of two or more.

[0089] Silane-based compounds are used to impart adhesion to the matrix, and siloxane-based compounds are used to impart wettability. Such silane-based compounds and siloxane-based compounds can use components known in the art without limitation.

[0090] Antioxidants inhibit discoloration caused by heat or light irradiation, as well as discoloration caused by various oxidizing gases such as ozone, active oxygen, NOx, SOx (X is an integer), and the like, and in the present application, the coloring of the matrix or the thinning of the film thickness due to decomposition can be prevented or reduced by adding an antioxidant. Examples of antioxidants that can be used include hydrazide-based, hindered amine-based antioxidants, nitrogen-containing heterocyclic mercapto-based compounds, sulfide-based antioxidants, hindered phenol-based antioxidants, ascorbic acid-based, zinc sulfate, thiocyanate-based, thiourea derivatives, sugar-based, nitrite-based, sulfite-based, thiosulfate-based, hydroxylamine derivatives, and the like.

[0091] For the purpose of further increasing the adhesion in the composition by leveling the quantum dot composition, a leveling agent can be included so that the quantum dot composition can be coated flat and smoothly at the time of coating. The above leveling agent can include one or two or more of an acrylic type, a silicone type, etc. As an example, a polyether-modified polydimethylsiloxane can be included, and a (meth)acryl group can be added to the above polyether chain.

[0092] For the uniformity of mixing and coating of the above quantum dot composition, a surfactant can be included. As the above surfactant, a conventional cationic, anionic, zwitterionic, and nonionic surfactant known in the art can be used, and as an example, one or more of a fluorine-based surfactant, a silicone-based surfactant, and a fluorine / silicone-based surfactant can be used.

[0093] The light stabilizer is an ultraviolet absorber, and has an effect of increasing the weather resistance of the matrix.

[0094] The softener serves to reduce cracks in the dried polymer matrix, and can improve impact resistance and bending resistance by reducing cracks in the cured matrix.

[0095] The solvent-free quantum dot composition according to the present application includes quantum dots surface-modified with two or more ligands and a photopolymerizable monomer having excellent miscibility with the quantum dots substituted with the above ligands.

[0096] The above solvent-free quantum dot composition of the present application has excellent optical properties such as light absorption and light conversion, and can achieve low viscosity. Specifically, the viscosity at room temperature (25°C) can be 30 cps or less, preferably 28 cps or less, and more preferably 25 cps or less. By adjusting the viscosity within a suitable range, the above solvent-free quantum dot composition not only has excellent workability and processability, but also has excellent storage stability at high temperatures. In addition, since the solvent-free quantum dot composition of the present application can achieve low viscosity, it can be used for inkjet printing.

[0097] <Method for preparing a solvent-free quantum dot composition>

[0098] In an embodiment of the present application, the quantum dot composition can be prepared by a method including the steps of: step (a), surface-modifying quantum dots using a first ligand represented by the following Chemical Formula 1 and a second ligand including a carboxyl group and having a carbon atom number of 3 to 40; step (b), centrifuging the product of the above step (a) to obtain surface-modified quantum dots; and step (c), dispersing the obtained surface-modified quantum dots in a photopolymerizable monomer.

[0099] Chemical Formula 1:

[0100] (In the above Chemical Formula 1, M is a divalent to tetravalent metal, X is an organic group having 3 to 20 carbon atoms, and n is an integer of 2 to 4.)

[0101] wherein the quantum dots, the first ligand, the second ligand, and the photopolymerizable monomer are as described above.

[0102] Also, the above step (a) can include: step (a-1) of putting the first ligand into the above quantum dot dispersion liquid to react and modify the surface of the quantum dots, and then putting the second ligand to react and modify the surface of the quantum dots; or step (a-2) of simultaneously putting the above first ligand and the second ligand to react and modify the surface of the quantum dots.

[0103] Specifically, in the above step (a-1), the above first ligand can be put into the above quantum dots and reacted at 25 to 170°C for 30 minutes to 3 hours, and then the reaction temperature can be lowered to 25 to 70°C, and then the second ligand can be put in to react for 30 minutes to 3 hours to modify the surface of the quantum dots.

[0104] In the above step (a-1), the surface modification of the quantum dots is performed in two steps, thereby preventing the first ligand from reacting with the second ligand to form a by-product, and the ligand exchange of the quantum dots can be optimized.

[0105] On the other hand, when the above first ligand and the second ligand are simultaneously put into the above quantum dots, a by-product can be formed due to a thiol-ene reaction between the thiol group of the first ligand and the acrylate group of the second ligand. Such a by-product can increase the viscosity of the quantum dot composition when the surface-modified quantum dots are dispersed in the photopolymerizable monomer.

[0106] Also, in the above step (a-1), the surface of the quantum dots is modified with the first ligand at a high temperature of 130 to 170°C, thereby the conversion rate of the surface modification can be improved. As the reaction temperature increases, the modification rate of the surface of the quantum dots increases, and thus the surface of the quantum dots can be uniformly modified. However, the reaction temperature can not be limited by the ligand material, the reaction time, or the stirring speed.

[0107] Also, in the above step (a-2), the above first ligand and the second ligand can be simultaneously put into the above quantum dots and reacted at 25 to 100°C for 30 minutes to 3 hours to modify the surface of the quantum dots.

[0108] The surface of the quantum dots is modified by the above method, and then the surface-modified quantum dots are obtained by centrifugation. Also, a solvent-free quantum dot composition can be prepared by dispersing the obtained surface-modified quantum dots in a polymerizable monomer.

[0109] Cured film, color filter, and display device

[0110] The present application can provide a cured film including the above-described solvent-free quantum dot composition. The cured film of the present application has excellent optical properties, and in particular, the light absorption rate can be 75% or more, and preferably 78% or more. Also, the light conversion rate of the above-described cured film can be 25% or more, and in particular, 29% or more.

[0111] The above-described cured film can be prepared by a method including the steps of forming a pattern by jetting the above-described solvent-free quantum dot composition on a substrate by an inkjet method; and curing the above-described pattern.

[0112] The present application provides a color filter including the above-described solvent-free quantum dot composition. The color filter is an optical element in the form of a thin film that extracts red, green, and blue colors in pixel units from white light emitted from a rear light source to achieve color in a liquid crystal display.

[0113] Such a color filter can be prepared by methods such as a dyeing method, a pigment dispersion method, a printing method, and an electrodeposition method. Also, the color filter including the quantum dot composition can be prepared by an inkjet method. Since the inkjet method uses only materials for the desired pixels, it can prevent unnecessary material waste.

[0114] Also, the present application provides a display device including the above-described quantum dot composition. The display device includes a liquid crystal display (LCD), an electroluminescent display (EL), a plasma display (PDP), a field emission display (FED), an organic light emitting device (OLED), etc., but is not limited thereto.

[0115] Hereinafter, the present application will be described in more detail through examples. However, the following examples are only for exemplifying the present application, and the scope of the present application is not limited to the examples.

[0116] [Preparation Example 1-1] Preparation of first ligand 1-1

[0117] Into a round bottom flask, 13.6 g of zinc chloride (ZnCl2) and 57.7 g of a compound represented by Chemical Formula A-1 and 285 g of cyclohexyl acetate were put, and then dissolved by hot stirring at 60°C. Thereafter, hydrogen chloride (HCl) was removed under vacuum for 2 hours to prepare a first ligand 1-1.

[0118]

[0119] [Preparation Example 1-2] Preparation of first ligand 1-2

[0120] A first ligand 1-2 was prepared in the same manner as in Preparation Example 1-1, except that 53.4 g of a compound represented by Chemical Formula A-2 was used instead of the compound represented by Chemical Formula A-1 in Preparation Example 1-1.

[0121]

[0122] [Preparation Example 1-3] Preparation of first ligand 1-3

[0123] A first ligand 1-3 was prepared in the same manner as in Preparation Example 1-1, except that 61.2 g of a compound represented by Chemical Formula A-3 was used instead of the compound represented by Chemical Formula A-1 in Preparation Example 1-1.

[0124]

[0125] [Preparation Example 1-4] Preparation of first ligand 1-4

[0126] A first ligand 1-4 was prepared in the same manner as in Preparation Example 1-1, except that 48.6 g of a compound represented by Chemical Formula A-4 was used instead of the compound represented by Chemical Formula A-1 in Preparation Example 1-1.

[0127]

[0128] [Preparation Example 1-5] Preparation of first ligand 1-5

[0129] A first ligand 1-5 was prepared in the same manner as in Preparation Example 1-1, except that 44.4 g of a compound represented by Chemical Formula A-5 was used instead of the compound represented by Chemical Formula A-1 in Preparation Example 1-1.

[0130]

[0131] [Preparation Example 2-1] Preparation of second ligand 2-1

[0132] A second ligand 2-1 was prepared by placing 20 g of a compound represented by Chemical Formula B-1 and 80 g of cyclohexyl acetate in a round bottom flask, and then stirring at room temperature for 1 hour.

[0133]

[0134] [Preparation Example 2-2] Preparation of second ligand 2-2

[0135] A second ligand 2-2 was prepared in the same manner as in Preparation Example 2-1, except that a compound represented by Chemical Formula B-2 was used instead of the compound represented by Chemical Formula B-1 in Preparation Example 2-1.

[0136]

[0137] [Preparation Example 2-3] Preparation of second ligand 2-3

[0138] A second ligand 2-3 was prepared in the same manner as in Preparation Example 2-1, except that the compound represented by Chemical Formula B-3 was used instead of the compound represented by Chemical Formula B-1 in Preparation Example 2-1.

[0139]

[0140] [Preparation Example 2-4] Preparation of second ligand 2-4

[0141] A second ligand 2-4 was prepared in the same manner as in Preparation Example 2-1, except that the compound represented by Chemical Formula B-4 was used instead of the compound represented by Chemical Formula B-1 in Preparation Example 2-1.

[0142]

[0143] [Preparation Example 2-5] Preparation of second ligand 2-5

[0144] A second ligand 2-5 was prepared in the same manner as in Preparation Example 2-1, except that the compound represented by Chemical Formula B-5 was used instead of the compound represented by Chemical Formula B-1 in Preparation Example 2-1.

[0145]

[0146] [Preparation Example 2-6] Preparation of second ligand 2-6

[0147] A second ligand 2-6 was prepared in the same manner as in Preparation Example 2-1, except that the compound represented by Chemical Formula B-6 was used instead of the compound represented by Chemical Formula B-1 in Preparation Example 2-1.

[0148]

[0149] [Preparation Example 3] Preparation of ligand 3

[0150] A ligand 3 was prepared by putting 57 g of a compound represented by Chemical Formula A-1 and 228 g of cyclohexyl acetate into a round bottom flask and then dissolving by stirring.

[0151]

[0152] <Example 1> Preparation of quantum dot composition

[0153] 1-1. Surface modification of quantum dots

[0154] The 100 g of InP / ZnSe / ZnS quantum dot dispersion liquid (HANSUNG, SHQD-533; quantum dot solid content 20%; cyclohexyl acetae) was heated to 140°C under nitrogen atmosphere and stirred. 12 g of the ligand of Preparation Example 1-1 was put in, and after stirring at 140°C for 1.5 hours, it was cooled to 60°C. Thereafter, 30 g of the ligand of Preparation Example 2-1 was put in, and reacted at 60°C for 1.5 hours, thereby preparing surface-modified quantum dots. After completion of the reaction, chemical precipitation was performed using a centrifuge, and the precipitated quantum dots were separated from the supernatant, and the supernatant was discarded. After being sufficiently dried in a vacuum oven for one day, surface-modified quantum dots were obtained.

[0155] 1-2. Preparation of quantum dot composition

[0156] Thereafter, the above surface-modified quantum dots were dispersed in 1,6-hexanediol diacrylate monomer, thereby preparing quantum dot dispersion monomer having a quantum dot solid concentration of 50 wt%.

[0157] The quantum dot composition was prepared by further mixing 1,6-hexanediol diacrylate monomer, ethyl(2,4,6-trimethylbenzoyl)phenyl phosphinate as a photoinitiator, titanium dioxide (TiO2, average particle diameter 200 nm) as a diffusing agent, and hydroquinone monomethyl ether as a polymerization inhibitor in the prepared quantum dot dispersion monomer (QD 50 wt%) in the amounts shown in Table 2 below. In Table 2 below, the amounts of each composition are weight percentages.

[0158] <Examples 2 to 10> Preparation of quantum dot composition

[0159] The quantum dot compositions of Examples 2 to 10 were prepared in the same manner as in Example 1, except that the ligand of Preparation Example 1-1 and the ligand of Preparation Example 2-1 were replaced with the ligands shown in Table 1 below.

[0160] <Comparative Example 1> Preparation of quantum dot composition

[0161] 1-1. Surface modification of quantum dots

[0162] A 100 g of InP / ZnSe / ZnS quantum dot dispersion (Hansung, SHQD-533; quantum dot solid content 20%; cyclohexyl acetae) was warmed to 140°C under a nitrogen atmosphere and stirred. 40 g of the ligand of Preparation Example 1-1 was put in, and reacted at 140°C for 1 hour, thereby preparing surface-modified quantum dots. After the reaction was completed, it was cooled to 25°C, chemical precipitation was performed using a centrifuge, the precipitated quantum dots were separated from the supernatant, and the supernatant was discarded. After being sufficiently dried in a vacuum oven for one day, the surface-modified quantum dots were obtained.

[0163] 1-2. Preparation of quantum dot composition

[0164] A quantum dot composition was prepared in the same manner as in Example 1-2, except that the surface-modified quantum dots of Comparative Example 1-1 were used.

[0165] <Comparative Example 2> Preparation of quantum dot composition

[0166] 2-1. Surface modification of quantum dots

[0167] A 100 g of InP / ZnSe / ZnS quantum dot dispersion (Hansung, SHQD-533; quantum dot solid content 20%; cyclohexyl acetae) was warmed to 60°C under a nitrogen atmosphere and stirred. 30 g of the ligand of Preparation Example 2-1 was put in, and reacted at 60°C for 4 hours, thereby preparing surface-modified quantum dots. After the reaction was completed, chemical precipitation was performed using a centrifuge, the precipitated quantum dots were separated from the supernatant, and the supernatant was discarded. After being sufficiently dried in a vacuum oven for one day, the surface-modified quantum dots were obtained.

[0168] 2-2. Preparation of quantum dot composition

[0169] A quantum dot composition was prepared in the same manner as in Example 1-2, except that the surface-modified quantum dots of Comparative Example 2-1 were used.

[0170] <Comparative Example 3> Preparation of quantum dot composition

[0171] A quantum dot composition was prepared in the same manner as in Comparative Example 2, except that 40 g of the ligand of Preparation Example 3 was used instead of the ligand of Preparation Example 2-1.

[0172] Table 1

[0173]

[0174]

[0175] Table 2

[0176] Content (weight percent) Surface-modified quantum dots 40 Photopolymerizable monomer 54.4 Photoinitiator 1.5 Diffusing agent 4 Polymerization inhibitor 0.1

[0177] <Example 1> Evaluation of light conversion rate and light absorption rate of cured film

[0178] The quantum dot compositions of Examples 1 to 10 and Comparative Examples 1 to 2 were each coated on a glass substrate to a thickness of 10 μm using a spin coater (Mikasa Opticoat MS-A150), and a cured film was prepared by exposure using a 395 nm ultraviolet exposure machine at 4000 mJ (83°C, 4 seconds). Thereafter, a 2 cm x 2 cm single film test piece was loaded into an integrating sphere device (QE-2100, Otsuka Electronics) to measure the initial light absorption rate and light conversion rate. After drying (post bake) the resulting coating film in a nitrogen atmosphere drying oven at 180°C for 30 minutes, the light absorption rate and light conversion rate were measured, and the results are shown in Table 3 below.

[0179] The light conversion rate was measured using the integrating sphere film-type measuring device of Otsuka. After loading the coating film coated with the quantum dot composition, 450 nm blue light was irradiated to the coating film, green light emitted in all directions upward was absorbed, and the integrated value was calculated. The light conversion rate (Green / Blue) was measured by converting the decrease in the blue light absorption peak to the increase in the green light peak.

[0180] Table 3

[0181]

[0182]

[0183] As shown in Table 3 above, it was confirmed that the light absorption rate of the cured film containing the solvent-free quantum dot composition of Examples 1 to 10 was 80% or more, and the light conversion rate was 29.2% or more, exhibiting excellent optical properties. On the other hand, the quantum dot composition of Comparative Example 3 was not dispersed in the photopolymerizable monomer of the quantum dot, and thus the optical properties could not be measured.

[0184] <Example 2> Evaluation of viscosity and stability of solvent-free quantum dot composition

[0185] In order to evaluate the storage stability of the solvent-free quantum dot composition prepared according to Examples 1, Comparative Examples 1 to 2, after storing the solvent-free quantum dot at 40°C, the change in viscosity was measured at room temperature (25°C) at 100 rpm for 2 minutes using a viscometer (RheoStress MARS-40, HAAKE) for 4 weeks, and the results are shown in Table 4 below.

[0186] Table 4

[0187]

[0188] As shown in Table 4 above, the initial viscosities of the solvent-free quantum dot compositions of Comparative Examples 1 and 2 were 30 cps and 38 cps, respectively. In contrast, the initial viscosity of the solvent-free quantum dot composition of Example 1 was 23 cps, and even after 4 weeks of storage, the viscosity was less than 25 cps, confirming excellent storage stability.

[0189] <Example 3> Evaluation of Inkjet Performance

[0190] The solvent-free quantum dot compositions prepared according to Example 1, Comparative Examples 1 to 2 were used to evaluate the inkjet performance by the Omnijet 300 (UNIJET Co.) apparatus. At this time, the temperature of the Dimetix DMC head was maintained at 40°C to confirm the inkjet performance.

[0191] As a result, it was confirmed that the solvent-free quantum dot composition of Example 1 exhibited excellent inkjet performance, and in contrast, the solvent-free quantum dot compositions of Comparative Examples 1 to 2 could not be inkjetted due to their high viscosity.

Claims

1. A solvent-free quantum dot composition, characterized in that, Contains quantum dots and photopolymer monomers, The aforementioned quantum dots are surface modified using a first ligand represented by the following chemical formula 1 and a second ligand containing a carboxyl group and having 3 to 40 carbon atoms, but not 16 to 40, represented by chemical formula 2. Chemical Formula 1: In the above chemical formula 1, M is a divalent to tetravalent metal. X is an organic group from C4 to C15, containing an ester (-C(=O)O-) functional group, and n is an integer from 2 to 4; Chemical formula 2: In the above chemical formula 2, L is a single bond or is selected from the group consisting of C1 to C20 alkylene groups and C1 to C20 alkenyl groups. A is a single bond or a C1 to C20 alkylene or alkenylene group containing one or more functional groups selected from the group consisting of esters (-C(=O)O-) and ethers (-O-), and R is hydrogen or selected from the group consisting of alkyl groups from C1 to C20 and alkenyl groups from C1 to C20.

2. The solvent-free quantum dot composition according to claim 1, characterized in that, The M mentioned above can be Mg, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Sr, Mo, Pd, Cd, In, or Sn.

3. The solvent-free quantum dot composition according to claim 1, characterized in that, The second ligand mentioned above does not contain a thiol group.

4. The solvent-free quantum dot composition according to claim 1, characterized in that, In the above chemical formula 2, A is a C2 to C15 alkylene or alkenylene group comprising an ester (-COO-), an ether (-CO-), or a combination thereof.

5. The solvent-free quantum dot composition according to claim 1, characterized in that, The mixing ratio of the first ligand to the second ligand is 1:0.1 to 20 molar ratio.

6. The solvent-free quantum dot composition according to claim 1, characterized in that, The mixing ratio of the quantum dots and ligands is 1:0.05 to 1 by weight.

7. The solvent-free quantum dot composition according to claim 1, characterized in that, Based on the total weight of the solvent-free quantum dot composition, the content of the quantum dots is from 1% to 60% by weight.

8. The solvent-free quantum dot composition according to claim 1, characterized in that, The aforementioned photopolymerizable monomers are (meth)acrylate monomers.

9. The solvent-free quantum dot composition according to claim 1, characterized in that, It also includes photoinitiators, light diffusing agents, polymerization inhibitors, or combinations thereof.

10. The solvent-free quantum dot composition according to claim 1, characterized in that, Viscosity below 30 cps.

11. The solvent-free quantum dot composition according to claim 1, characterized in that, Used for inkjet printing.

12. A cured film, characterized in that, Prepared using the solvent-free quantum dot composition according to any one of claims 1 to 11.

13. The cured film according to claim 12, characterized in that, The light absorption rate is over 75%, and the light conversion rate is over 25%.

14. A color filter, characterized in that, A solvent-free quantum dot composition comprising any one of claims 1 to 11.

15. A display device, characterized in that, Includes the color filter as described in claim 14.

16. A method for preparing a solvent-free quantum dot composition, characterized in that, include: Step (a) involves surface modification of the quantum dots using a first ligand represented by the following chemical formula 1 and a second ligand containing a carboxyl group and having 3 to 40 carbon atoms but not 16 to 40, and represented by chemical formula 2. Step (b) involves centrifuging the product from step (a) to obtain surface-modified quantum dots; and Step (c) involves dispersing the obtained surface-modified quantum dots in a photopolymerization monomer. Chemical Formula 1: In the above chemical formula 1, M is a divalent to tetravalent metal. X is an organic group from C4 to C15, containing an ester (-C(=O)O-) functional group, and n is an integer from 2 to 4; Chemical formula 2: In the above chemical formula 2, L is a single bond or is selected from the group consisting of C1 to C20 alkylene groups and C1 to C20 alkenyl groups. A is a single bond or a C1 to C20 alkylene or alkenylene group containing one or more functional groups selected from the group consisting of esters (-C(=O)O-) and ethers (-O-), and R is hydrogen or selected from the group consisting of alkyl groups from C1 to C20 and alkenyl groups from C1 to C20.

17. The method for preparing the solvent-free quantum dot composition according to claim 16, characterized in that, Step (a) above includes: Step (a-1): A first ligand is added to the quantum dots to modify their surface, followed by a reaction with a second ligand to further modify the surface; or... Step (a-2) involves simultaneously introducing the first and second ligands mentioned above to react and modify the surface of the quantum dots.

18. A method for preparing a cured film, characterized in that, include: A pattern is formed by coating the solvent-free quantum dot composition of any one of claims 1 to 11 onto a substrate using an inkjet printing method; as well as The above pattern is then solidified.

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