KR102770715B1 - Light Conversion Ink Composition, Color Filter and Display Device - Google Patents

Abstract

The present invention provides a photoconversion ink composition comprising quantum dots, a curable monomer and a nonionic photoacid generator, wherein the curable monomer has a viscosity of 30 cP or less at 25°C, a color filter formed using the same, and an image display device having the color filter. The photoconversion ink composition according to the present invention has excellent optical characteristics because optical characteristics are not degraded in a UV or post-bake process, and has excellent long-term reliability under high humidity conditions. Therefore, the photoconversion ink composition according to the present invention can be effectively used to manufacture a color filter by an inkjet printing method.

Description

{Light Conversion Ink Composition, Color Filter and Display Device}

The present invention relates to a photoconversion ink composition, a color filter, and an image display device, and more specifically, to a photoconversion ink composition having excellent optical characteristics because no degradation of optical characteristics occurs during a UV or post-bake process and excellent long-term reliability in a high-humidity state, a color filter formed using the same, and an image display device equipped with the color filter.

A color filter is a thin film-type optical component that extracts three colors, red, green, and blue, from white light and enables fine pixel units.

In this regard, a method for manufacturing a color filter using a self-luminous photosensitive resin composition containing quantum dots has been recently proposed to exhibit not only excellent pattern characteristics but also high color reproducibility.

The photolithography method using a self-luminous photosensitive resin composition containing commonly known quantum dots is a method of forming a color filter through coating, exposure, development, and curing. Although it is excellent in terms of the precision and reproducibility of the color filter, the coating, exposure, development, and curing processes are separately required for each color to form pixels, which increases the manufacturing process, time, and cost, and the number of control factors between processes increases, which may make it difficult to manage the yield.

Accordingly, instead of the photolithography method, an inkjet method capable of coloring multiple colors including red, green, and blue at once is being proposed.

Korean Patent No. 10-1475520 discloses a quantum dot ink composition for inkjet printing, which comprises quantum dots, a solvent, and a high-viscosity polymer additive, and enables the discharge of quantum dots by an inkjet method, freely controls the concentration of quantum dots, and reduces the loading amount of quantum dots.

However, since the quantum dot ink composition does not have a separate curing accelerating component added to promote curing of the film, there is a problem in that reliability is reduced when the film is exposed to high humidity for a long period of time. In addition, if a conventional photopolymerization initiator is added to solve this problem, radicals generated during the UV or post-bake process come into contact with the QD surface, causing surface oxidation, which ultimately leads to a deterioration in the optical characteristics of the quantum dot, and thus a deterioration in the optical characteristics of the photoconversion pixel.

Therefore, there is an urgent need for the development of a photoconversion ink composition that has excellent optical properties and long-term reliability under high humidity conditions without degradation of optical properties during UV or post-baking processes.

Republic of Korea Patent No. 10-1475520

One purpose of the present invention is The purpose is to provide a photoconversion ink composition having excellent optical properties and excellent long-term reliability under high humidity conditions, without any degradation of optical properties during a UV or post-baking process.

Another object of the present invention is to provide a photoconversion pixel comprising a cured product of the photoconversion ink composition.

Another object of the present invention is to provide a color filter including the photoconversion pixel.

Another object of the present invention is to provide an image display device having the color filter.

On the one hand, the present invention provides a photoconversion ink composition comprising quantum dots, a curable monomer and a nonionic photoacid generator, wherein the curable monomer has a viscosity of 30 cP or less at 25°C.

In one embodiment of the present invention, the curable monomer may include a monofunctional (meth)acrylate or a polyfunctional (meth)acrylate having a viscosity of 30 cP or less at 25°C.

In one embodiment of the present invention, the nonionic photoacid generator may generate an acid compound represented by the following chemical formula 1.

[Chemical Formula 1]

In the above formula, R is an aliphatic hydrocarbon group of C ₁ -C ₄ .

In one embodiment of the present invention, the nonionic photoacid generator may include one or more of the compounds represented by the following chemical formulas 2 to 3.

[Chemical formula 2]

[Chemical Formula 3]

In the above formula, R is an aliphatic hydrocarbon group of C ₁ -C ₄ .

In one embodiment of the present invention, the nonionic photoacid generator may be included in an amount of 0.1 to 10 wt% based on 100 wt% of the total composition.

The photoconversion ink composition according to one embodiment of the present invention may additionally include at least one selected from the group consisting of scattering particles, a photopolymerization initiator, a surfactant, and an antioxidant.

The photoconversion ink composition according to one embodiment of the present invention may contain a solvent in an amount of 1 wt% or less.

On the other hand, the present invention provides a photoconversion pixel comprising a cured product of the photoconversion ink composition.

On the other hand, the present invention provides a color filter including the photoconversion pixel.

On the other hand, the present invention provides an image display device equipped with the color filter.

The photoconversion ink composition according to the present invention has excellent optical properties since no degradation of optical properties occurs during the UV or post-bake process, and has excellent long-term reliability under high humidity conditions. In addition, the photoconversion ink composition according to the present invention can implement low viscosity even without substantially containing a solvent, and has excellent quantum dot dispersibility. Therefore, the photoconversion ink composition according to the present invention can be effectively used to manufacture a color filter by an inkjet printing method.

Hereinafter, the present invention will be described in more detail.

In the present invention, when it is said that a certain member is located "on" another member, this includes not only a case where a certain member is in contact with another member, but also a case where another member exists between the two members.

When it is said that a part of the present invention "includes" a certain component, this does not exclude other components, unless otherwise specifically stated, but rather means that other components may be included.

One embodiment of the present invention relates to a photoconversion ink composition comprising a quantum dot (A), a curable monomer (B), and a nonionic photoacid generator (C), wherein the curable monomer (B) comprises a low viscosity curable monomer having a viscosity of 30 cP or less at 25°C.

Quantum Dot (A)

In one embodiment of the present invention, the quantum dot has a ligand layer on its surface.

For example, the quantum dot may have a ligand layer including a compound represented by the following chemical formula 4 on its surface.

[Chemical Formula 4]

In the above formula,

R' and R'' are each independently a hydrogen atom; a carboxyl group; a phenyl group; or a C ₁ -C ₂₀ alkyl group substituted or unsubstituted with a thiol group,

R' and R" are not simultaneously a hydrogen atom; a phenyl group; or an unsubstituted C ₁ -C ₂₀ alkyl group,

n is an integer from 1 to 20.

As used herein, the C ₁ -C ₂₀ alkyl group means a straight-chain or branched monovalent hydrocarbon having 1 to 20 carbon atoms, and examples thereof include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, sec-butyl, 1-methyl-butyl, 1-ethyl-butyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, n-hexyl, 1-methylpentyl, 2-methylpentyl, 4-methyl-2-pentyl, 3,3-dimethylbutyl, 2-ethylbutyl, n-heptyl, 1-methylhexyl, n-octyl, tert-octyl, 1-methylheptyl, 2-ethylhexyl, 2-propylpentyl, n-nonyl, 2,2-dimethylheptyl, n-decyl, and the like.

In one embodiment of the present invention, specific examples of the compound represented by the chemical formula 4 include, but are not limited to, 2-(2-methoxyethoxy)acetic acid (WAKO), 2-[2-(2-methoxyethoxy)ethoxy]acetic acid (WAKO), {2-[2-(carboxymethoxy)ethoxy]ethoxy}acetic acid (WAKO), 2-[2-(benzyloxy)ethoxy]acetic acid, (2-(carboxymethoxy)ethoxy)acetic acid (WAKO), (2-butoxyethoxy)acetic acid (WAKO), carboxy-EG6-undecanethiool, and the like.

The above quantum dots have excellent optical properties by including a polyethylene glycol-based ligand represented by chemical formula 4, and can exhibit good dispersion properties with only the curable monomer described below without a solvent.

The compound represented by the above chemical formula 4 may cover a surface area of 5% or more with respect to the total surface area of the quantum dot.

At this time, the content of the compound represented by the chemical formula 4 may be 0.1 to 10 moles per 1 mole of quantum dots.

The ligand layer including the compound represented by the chemical formula 4 may have a thickness of 0.1 nm to 2 nm, for example, a thickness of 0.5 nm to 1.5 nm.

In one embodiment of the present invention, the quantum dot may refer to a semiconductor material of nano size. Atoms form molecules, and molecules form a collection of small molecules called clusters to form nanoparticles. When these nanoparticles have semiconductor properties, they are called quantum dots. When the quantum dot receives energy from the outside and reaches an excited state, it emits energy according to the energy band gap corresponding to the quantum dot itself. For example, the photoconversion ink composition of the present invention can convert incident blue light into green light and red light by including such quantum dots.

In one embodiment of the present invention, the quantum dots may be non-cadmium quantum dots.

The above-mentioned non-cadmium quantum dots are not particularly limited as long as they are quantum dot particles that can emit light when stimulated by light. For example, they may be selected from the group consisting of II-VI group semiconductor compounds; III-V group semiconductor compounds; IV-VI group semiconductor compounds; IV group elements or compounds containing them; and combinations thereof, and these may be used singly or in combination of two or more.

Specifically, the II-VI group semiconductor compound may be selected from, but is not limited to, a binary compound selected from the group consisting of ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, and mixtures thereof; a ternary compound selected from the group consisting of ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, HgZnS, HgZnSe, HgZnTe, and mixtures thereof; and a quaternary compound selected from the group consisting of HgZnSeS, HgZnSeTe, HgZnSTe, and mixtures thereof.

The above III-V group semiconductor compound 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, GaAlNP, and mixtures thereof; and quaternary compounds selected from the group consisting of GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, InAlPSb, and mixtures thereof, but is not limited thereto.

The above IV-VI group semiconductor compound may be at least one 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, but is not limited thereto.

Although not limited thereto, the group IV element or compound containing the same may be selected from the group consisting of an element selected from the group consisting of Si, Ge, and mixtures thereof; and a group consisting of binary compounds selected from the group consisting of SiC, SiGe, and mixtures thereof.

The quantum dot may have a homogeneous single structure; a dual structure such as a core-shell or gradient structure; or a mixed structure thereof. Preferably, the quantum dot may have a core-shell structure including a core and a shell covering the core.

Specifically, in the above core-shell dual structure, the materials forming each core and shell can be formed of different semiconductor compounds as mentioned above. For example, the core may include at least one selected from the group consisting of GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs, InPSb, GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, and InAlPSb, and the shell may include at least one selected from the group consisting of ZnSe, ZnS, and ZnTe, but is not limited thereto.

For example, quantum dots with core-shell structures include InP/ZnS, InP/ZnSe, InP/GaP/ZnS, InP/ZnSe/ZnS, InP/ZnSeTe/ZnS, and InP/MnSe/ZnS.

The above quantum dots can be synthesized by, but are not limited to, a wet chemical process, a metal organic chemical vapor deposition (MOCVD) process, or a molecular beam epitaxy (MBE) process, but preferably, synthesizing them by a wet chemical process can obtain quantum dots with better optical properties.

The above wet chemical process is a method of growing particles by adding a precursor material to an organic solvent. When the crystal grows, the organic solvent is naturally coordinated to the surface of the quantum dot crystal and acts as a dispersant to control the growth of the crystal. Therefore, the growth of nanoparticles can be controlled through a process that is easier and cheaper than a vapor deposition method such as an organometallic chemical vapor deposition process or molecular beam epitaxy. Therefore, it is preferable to manufacture the quantum dots using the above wet chemical process.

When producing quantum dots by a wet chemical process, organic ligands are used to prevent aggregation of quantum dots and to control the particle size of quantum dots to the nano level. Oleic acid can generally be used as such organic ligands.

In one embodiment of the present invention, the oleic acid used in the process of manufacturing the quantum dots is replaced by a polyethylene glycol compound of the chemical formula 4 through a ligand exchange method.

The above ligand exchange can be performed by adding an organic ligand to be exchanged, i.e., a polyethylene glycol-based compound of chemical formula 4, to a dispersion containing quantum dots having an original organic ligand, i.e., oleic acid, and stirring the mixture at room temperature to 200° C. for 30 minutes to 3 hours to obtain quantum dots to which the polyethylene glycol-based compound of chemical formula 4 is bound. If necessary, a process of separating and purifying the quantum dots to which the polyethylene glycol-based compound of chemical formula 4 is bound can be additionally performed.

The quantum dots may be included in an amount of 1 to 40 wt%, preferably 2 to 30 wt%, based on 100 wt% of the total light conversion ink composition. When the quantum dots are included within the above range, there are advantages of excellent luminescence efficiency and excellent reliability of the coating layer. When the quantum dots are included in an amount less than the above range, the light conversion efficiency of green light and red light may be low, and when the quantum dots are included in an amount exceeding the above range, the emission of blue light may be relatively reduced, resulting in a problem of poor color reproducibility.

Curable monomer (B)

In one embodiment of the present invention, the curable monomer (B) includes a curable monomer having a viscosity of 30 cP or less at 25°C, for example, a viscosity of 5 to 30 cP, i.e., a low-viscosity curable monomer.

A photoconversion ink composition according to one embodiment of the present invention can exhibit a low viscosity suitable for inkjet printing while having good surface curability and coating properties by including a low-viscosity curable monomer as a curable monomer.

The above low viscosity curable monomer may include a monofunctional (meth)acrylate or a polyfunctional (meth)acrylate having a viscosity of 30 cP or less at 25°C.

For example, the low viscosity curable monomers include monofunctional alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, lauryl (meth)acrylate, and stearyl (meth)acrylate; bifunctional (meth)acrylates having an alkylene chain such as 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, and 1,10-decanediol diacrylate; Examples of (meth)acrylates having a hydroxyl group, such as 2-hydroxy-3-acryloyloxypropyl (meth)acrylate, 2-hydroxy-3-phenoxyethyl (meth)acrylate, 1,4-cyclohexanedimethanol mono(meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, and 2-hydroxypropyl (meth)acrylate; isobornyl (meth)acrylate; acryloylmorpholine; and glycidyl methacrylate, can be used. These can be used alone or in combination of two or more.

The above-mentioned curable monomer (B) may be included in an amount of 20 to 90 wt%, preferably 30 to 80 wt%, based on 100 wt% of the total weight of the photoconversion ink composition. When the above-mentioned curable monomer is included within the above range, there is a desirable advantage in terms of the strength or smoothness of the pixel portion. When the above-mentioned curable monomer is included in an amount less than the above range, the strength of the pixel portion may be somewhat reduced, and when the above-mentioned curable monomer is included in an amount exceeding the above range, the smoothness may be somewhat reduced, and therefore it is preferable that the above-mentioned range be included.

Nonionic photoacid generator (C)

In one embodiment of the present invention, the nonionic photoacid generator (C) is a compound capable of generating an acid by the action of light or radiation, and may not cause surface oxidation of the quantum dot, thereby preventing deterioration of the optical properties of the quantum dot.

The above nonionic photoacid generator may generate an acid compound represented by the following chemical formula 1.

[Chemical Formula 1]

In the above formula, R is an aliphatic hydrocarbon group of C ₁ -C ₄ .

The C ₁ -C ₄ aliphatic hydrocarbon group used herein is a linear or branched monovalent hydrocarbon group consisting of 1 to 4 carbon atoms, and includes those consisting of only carbon-carbon single bonds, or those having one or more carbon-carbon double bonds or triple bonds. For example, the C ₁ -C ₄ aliphatic hydrocarbon group includes, but is not limited to, methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, ethylenyl, propenyl, butenyl, acetylenyl, propynyl, butynyl, and the like.

In one embodiment of the present invention, the nonionic photoacid generator may include one or more of the compounds represented by the following chemical formulas 2 to 3.

[Chemical formula 2]

[Chemical Formula 3]

In the above formula, R is an aliphatic hydrocarbon group of C ₁ -C ₄ .

In one embodiment of the present invention, the nonionic photoacid generator may include at least one of the compounds represented by the following chemical formulas 5 to 8.

[Chemical Formula 5]

[Chemical formula 6]

[Chemical formula 7]

[Chemical formula 8]

In one embodiment of the present invention, the nonionic photoacid generator may be included in an amount of 0.1 to 10 wt%, preferably 0.1 to 5 wt%, based on 100 wt% of the total composition. If the nonionic photoacid generator is included in an amount less than 0.1 wt%, the required exposure amount for pattern formation may increase, thereby lowering sensitivity, and if it is included in an amount greater than 10 wt%, surface roughness may increase.

Scattered particles (D)

The photoconversion ink composition according to one embodiment of the present invention may additionally include scattering particles (D).

The above scattering particles serve to increase the overall light efficiency by increasing the path of light emitted from the quantum dot.

As the above scattering particles, conventional inorganic materials can be used, and preferably, metal oxides can be used.

The above metal oxide may be an oxide including one metal selected from the group consisting of Li, Be, B, Na, Mg, Al, Si, K, Ca, Sc, V, Cr, Mn, Fe, Ni, Cu, Zn, Ga, Ge, Rb, Sr, Y, Mo, Cs, Ba, La, Hf, W, Tl, Pb, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Ti, Sb, Sn, Zr, Nb, Ce, Ta, In, and combinations thereof, but is not limited thereto.

Specifically, one selected from the group consisting of Al ₂ O ₃ , SiO ₂ , ZnO, ZrO ₂ , BaTiO ₃ , TiO ₂ , Ta ₂ O ₅ , Ti ₃ O ₅ , ITO, IZO, ATO, ZnO-Al, Nb ₂ O ₃ , SnO, MgO and combinations thereof is possible. If necessary, a material surface-treated with a compound having an unsaturated bond such as acrylate can also be used.

The scattering particles may have an average particle size of 50 to 1000 nm, preferably 100 to 500 nm, and more preferably 150 to 300 nm. If the particle size is too small, sufficient scattering effect of light emitted from the quantum dots cannot be expected, and conversely, if it is too large, it may sink into the composition or a light conversion layer surface of uniform quality may not be obtained. Therefore, it is appropriately adjusted and used within the above range.

In the present invention, the average particle diameter may be a number-average particle diameter, and may be obtained from an image observed by, for example, a field emission scanning electron microscope (FE-SEM) or a transmission electron microscope (TEM). Specifically, several samples may be extracted from an observation image of an FE-SEM or TEM, and the diameters of these samples may be measured and obtained as an arithmetic average.

The scattering particles may be included in an amount of 0.5 to 20 wt%, preferably 1 to 15 wt%, based on 100 wt% of the total light conversion ink composition. When the scattering particles are included within the above range, the effect of increasing luminescence intensity can be maximized, which is preferable. When the scattering particles are included in an amount less than the above range, it may be somewhat difficult to secure the desired luminescence intensity, and when the particles are included in an amount exceeding the above range, the transmittance of blue irradiation light may be reduced, which may cause problems in luminescence efficiency.

Photopolymerization initiator (E)

The photoconversion ink composition according to one embodiment of the present invention may additionally contain a photopolymerization initiator (E).

In one embodiment of the present invention, the photopolymerization initiator (E) can be used without particular limitation as long as it can polymerize the curable monomer. In particular, from the viewpoints of polymerization characteristics, initiation efficiency, absorption wavelength, availability, price, etc., it is preferable to use an acetophenone-based compound, a benzophenone-based compound, a triazine-based compound, a biimidazole-based compound, an oxime-based compound, a thioxanthone-based compound, an acylphosphine oxide-based compound, etc., and an acylphosphine oxide-based compound is particularly preferable. These photopolymerization initiators can be used alone or in combination of two or more.

Specific examples of the above acetophenone compounds include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyldimethylketal, 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methylpropan-1-one, 1-hydroxycyclohexylphenyl ketone, 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butan-1-one, 2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propan-1-one, 2-(4-methylbenzyl)-2-(dimethylamino)-1-(4-morpholinophenyl)butan-1-one, etc.

Examples of the above benzophenone compounds include benzophenone, o-benzoyl methyl benzoate, 4-phenylbenzophenone, 4-benzoyl-4'-methyldiphenyl sulfide, 3,3',4,4'-tetra(tert-butylperoxycarbonyl)benzophenone, 2,4,6-trimethylbenzophenone, etc.

Specific examples of the above triazine compounds include 2,4-bis(trichloromethyl)-6-(4-methoxyphenyl)-1,3,5-triazine, 2,4-bis(trichloromethyl)-6-(4-methoxynaphthyl)-1,3,5-triazine, 2,4-bis(trichloromethyl)-6-piperonyl-1,3,5-triazine, 2,4-bis(trichloromethyl)-6-(4-methoxystyryl)-1,3,5-triazine, 2,4-bis(trichloromethyl)-6-[2-(5-methylfuran-2-yl)ethenyl]-1,3,5-triazine, 2,4-bis(trichloromethyl)-6-[2-(furan-2-yl)ethenyl]-1,3,5-triazine, Examples thereof include 2,4-bis(trichloromethyl)-6-[2-(4-diethylamino-2-methylphenyl)ethenyl]-1,3,5-triazine, 2,4-bis(trichloromethyl)-6-[2-(3,4-dimethoxyphenyl)ethenyl]-1,3,5-triazine, etc.

Specific examples of the above biimidazole compounds include 2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetraphenylbiimidazole, 2,2'-bis(2,3-dichlorophenyl)-4,4',5,5'-tetraphenylbiimidazole, 2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetra(alkoxyphenyl)biimidazole, 2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetra(trialkoxyphenyl)biimidazole, 2,2-bis(2,6-dichlorophenyl)-4,4',5,5'-tetraphenyl-1,2'-biimidazole, or biimidazole compounds in which the phenyl group at the 4,4',5,5' position is substituted by a carboalkoxy group. Among these, 2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetraphenylbiimidazole, 2,2'-bis(2,3-dichlorophenyl)-4,4',5,5'-tetraphenylbiimidazole, and 2,2-bis(2,6-dichlorophenyl)-4,4',5,5'-tetraphenyl-1,2'-biimidazole are preferably used.

Specific examples of the above oxime compounds include o-ethoxycarbonyl-α-oxyimino-1-phenylpropan-1-one, and representative commercial products include BASF's Irgacure OXE 01 and OXE 02.

Examples of the above thioxanthone compounds include 2-isopropylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone, 1-chloro-4-propoxythioxanthone, etc.

Examples of the above acylphosphine oxide compounds include 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl-pentylphosphine oxide, etc. Commercially available products include Lucirin TPO manufactured by BASF and Igacure-819 manufactured by Ciba Specialty Chemicals.

The above photopolymerization initiator may be included in an amount of 50 wt% or less based on 100 wt% of the total amount of the nonionic photoacid generator and the photopolymerization initiator. If the above photopolymerization initiator is included in an amount exceeding 50 wt% based on 100 wt% of the total amount of the nonionic photoacid generator and the photopolymerization initiator, it may cause surface oxidation of the quantum dot, thereby deteriorating the optical properties of the quantum dot.

The photopolymerization initiator may be included in an amount of 0.01 to 20 wt%, preferably 0.5 to 15 wt%, based on 100 wt% of the total photoconversion ink composition. When the photopolymerization initiator is included within the above range, the photoconversion ink composition becomes highly sensitive, thus shortening the exposure time, thereby improving productivity, which is preferable. In addition, there is an advantage in that the strength of the pixel portion formed using the photoconversion ink composition according to the present invention and the smoothness on the surface of the pixel portion are improved.

The above photopolymerization initiator (E) may further include a photopolymerization initiation assistant (e1) in order to improve the sensitivity of the photoconversion ink composition according to the present invention. When the above photopolymerization initiation assistant is included, there is an advantage in that the sensitivity is further increased, thereby improving productivity.

The photopolymerization initiation assistant (e1) may preferably be one or more compounds selected from the group consisting of, for example, amine compounds, carboxylic acid compounds, and organic sulfur compounds having a thiol group, but is not limited thereto.

The above photopolymerization initiation auxiliary agent (e1) can be appropriately added and used within a range that does not impair the effects of the present invention.

Additive (F)

The photoconversion ink composition according to one embodiment of the present invention may additionally contain an additive (F) in addition to the above-described components.

The above additives may be surfactants, antioxidants, thermal acid generators, dispersants, fillers, curing agents, adhesion promoters, etc., and these may be used alone or in combination of two or more.

The above surfactant can be used to further improve the film-forming property of the photoconversion ink composition of the present invention, and a fluorine-based surfactant, a silicone-based surfactant, etc. can be preferably used.

Examples of the silicone surfactants that are commercially available include DC3PA, DC7PA, SH11PA, SH21PA, SH8400 from Dow Corning Toray Silicone Co., Ltd., and TSF-4440, TSF-4300, TSF-4445, TSF-4446, TSF-4460, TSF-4452 from GE Toshiba Silicone Co., Ltd. As for the fluorine surfactants that are commercially available include Megapak F-470, F-471, F-475, F-482, F-489, F-554 from Dainippon Ink & Chemical Industry Co., Ltd., for example.

The surfactants exemplified above can be used alone or in combination of two or more.

The above additive may be used in an amount of 0.05 to 10 wt%, specifically 0.1 to 10 wt%, and more specifically 0.1 to 5 wt%, relative to 100 wt% of the total photoconversion ink composition, but is not limited thereto.

The photoconversion ink composition according to one embodiment of the present invention substantially does not contain a solvent, and even if it does contain a solvent, it may be contained in an amount of 1 wt% or less relative to 100 wt% of the total photoconversion ink composition. The photoconversion ink composition according to one embodiment of the present invention is a solvent-free type that does not contain a solvent or a low-solvent type that contains a very small amount of 1 wt% or less, but has excellent optical properties and dispersibility of quantum dots and can implement low viscosity.

In addition, the photoconversion ink composition according to one embodiment of the present invention substantially does not include a resin component, and even if it does include one, it may be included in an amount of 0.5 wt% or less with respect to 100 wt% of the entire photoconversion ink composition. The photoconversion ink composition according to one embodiment of the present invention can implement low viscosity by not including a resin component, and thus has excellent nozzle jetting characteristics of the ink.

One embodiment of the present invention relates to a photoconversion pixel comprising a cured product of the photoconversion ink composition described above.

In addition, one embodiment of the present invention relates to a color filter including the above-described photoconversion pixel.

A method for forming a pattern of a photoconversion ink composition according to the present invention comprises a step of applying the above-described photoconversion ink composition to a predetermined area by inkjet method and a step of curing the applied photoconversion ink composition.

First, the photoconversion ink composition of the present invention is injected into an inkjet injector and printed on a predetermined area of a substrate.

The above substrate is not limited, and examples thereof include flat-surfaced substrates such as a glass substrate, a silicon substrate, a polycarbonate substrate, a polyester substrate, an aromatic polyamide substrate, a polyamideimide substrate, a polyimide substrate, an Al substrate, and a GaAs substrate. These substrates can be pretreated by a chemical treatment using a silane coupling agent or the like, a plasma treatment, an ion plating treatment, a sputtering treatment, a gas phase reaction treatment, or a vacuum deposition treatment. When a silicon substrate or the like is used as the substrate, a charge-coupled device (CCD), a thin film transistor (TFT), or the like can be formed on the surface of the silicon substrate or the like. In addition, a barrier matrix may be formed.

In order to form an appropriate phase on a substrate by being ejected from a piezo inkjet head, which is an example of an inkjet injector, the properties such as viscosity, fluidity, and quantum dot particles must be balanced with those of the inkjet head. The piezo inkjet head used in the present invention is not limited, but ejects ink having a droplet size of about 10 to 100 pL, preferably about 20 to 40 pL.

The viscosity of the photoconversion ink composition of the present invention is suitably controlled to be about 3 to 30 cP at 25°C, and more preferably, to be controlled to be in the range of 7 to 20 cP.

A color filter according to one embodiment of the present invention includes a colored pattern layer formed by the pattern forming method. That is, the color filter is characterized by including a colored pattern layer formed by applying the above-described photoconversion ink composition on a substrate in a predetermined pattern and then curing it. Since the configuration and manufacturing method of the color filter are well known in the art, a detailed description thereof will be omitted.

One embodiment of the present invention relates to an image display device equipped with the color filter described above.

The color filter of the present invention can be applied to various image display devices such as conventional liquid crystal displays (LCDs), electroluminescence displays (ELs), plasma display devices (PDPs), field emission displays (FEDs), and organic light emitting diodes (OLEDs).

The image display device of the present invention includes a configuration known in the art, except that it has the color filter described above.

Hereinafter, the present invention will be described in more detail by examples, comparative examples, and experimental examples. These examples, comparative examples, and experimental examples are only for explaining the present invention, and it is obvious to those skilled in the art that the scope of the present invention is not limited thereto.

Synthesis Example 1: Synthesis of quantum dot (Q-1)

Indium acetate (0.4 mmol) (0.058 g), palmitic acid (0.15 g) and 1-octadecene (20 mL) were placed in a reactor and heated to 120°C under vacuum. After 1 hour, the atmosphere inside the reactor was changed to nitrogen. After heating to 280°C, a mixed solution of 0.2 mmol (58 μL) of tris(trimethylsilyl)phosphine (TMS ₃ P) and 1.0 mL of trioctylphosphine was rapidly injected and reacted for 1 minute.

Then, 2.4 mmol (0.448 g) of zinc acetate, 4.8 mmol of oleic acid, and 20 mL of trioctylamine were placed in the reactor and heated to 120°C under vacuum. After 1 hour, the atmosphere inside the reactor was changed to nitrogen, and the reactor was heated to 280°C. 2 mL of the previously synthesized InP core solution was added, followed by 4.8 mmol of selenium (Se/TOP) in trioctylphosphine, and the final mixture was reacted for 2 hours. Ethanol was added to the reaction solution, which was quickly cooled to room temperature, and the precipitate obtained by centrifugation was filtered under reduced pressure and dried under reduced pressure to form an InP/ZnSe core-shell.

Then, 2.4 mmol (0.448 g) of zinc acetate, 4.8 mmol of oleic acid, and 20 mL of trioctylamine were placed in a reactor, and the reactor was heated to 120°C under vacuum. After 1 hour, the atmosphere inside the reactor was changed to nitrogen, and the reactor was heated to 280°C. 2 mL of the previously synthesized InP/ZnSe core-shell solution was added, followed by 4.8 mmol of sulfur (S/TOP) in trioctylphosphine, and the final mixture was reacted for 2 hours. Ethanol was added to the reaction solution, which was quickly cooled to room temperature, and the resulting precipitate was centrifuged, filtered under reduced pressure, and dried under reduced pressure to obtain a precipitate having an InP/ZnSe/ZnS core-shell structure. The maximum emission peak of the photoluminescence spectrum of the obtained nano quantum dots was 535 nm.

The 5 mL of the quantum dot solution obtained above was placed in a centrifuge tube and 20 mL of ethanol was added to precipitate. The supernatant was discarded after centrifugation, and 2 mL of chloroform was added to the precipitate to disperse the quantum dots. Then, 0.50 g of (2-butoxyethoxy)acetic acid was added and reacted for one hour while heating at 60°C under a nitrogen atmosphere.

Next, 25 mL of n-hexane was added to the reaction mixture to precipitate the quantum dots, and centrifugation was performed to obtain quantum dots (Q-1).

Manufacturing Example 1: Manufacturing of quantum dot dispersion (A-1)

A quantum dot dispersion (A-1) was prepared by mixing 47.6 parts by weight of quantum dots (Q-1) and 52.4 parts by weight of low-viscosity monomer isobornyl acrylate as a diluent and reacting them for 4 hours while heating at 60°C under a nitrogen atmosphere.

Manufacturing Example 2: Manufacturing of quantum dot dispersion (A-2)

A quantum dot dispersion (A-2) was prepared by mixing 47.6 parts by weight of quantum dots (Q-1) and 52.4 parts by weight of low-viscosity monomer 1,6-hexanediol diacrylate as a diluent and reacting them for 4 hours while heating at 60°C under a nitrogen atmosphere.

Manufacturing Example 3: Manufacturing of quantum dot dispersion (A-3)

A quantum dot dispersion (A-3) was prepared by mixing 47.6 parts by weight of quantum dots (Q-1) and 52.4 parts by weight of high-viscosity monomer ditrimethylolpropanetetra(meth)acrylate as a diluent and reacting them for 4 hours while heating at 60°C under a nitrogen atmosphere.

Manufacturing Example 4: Manufacturing of scattering particle dispersion (D-1)

70.0 parts by weight of TiO ₂ (CR-63, Ishihara) having a particle size of 210 nm as a scattering particle, 4.0 parts by weight of DISPERBYK-2001 (manufactured by BYK) as a dispersant, and 26 parts by weight of low-viscosity monomer 1,6-hexanediol diacrylate as a diluent were mixed and dispersed using a bead mill for 12 hours to prepare a scattering particle dispersion (D-1).

Examples and Comparative Examples: Preparation of Photoconversion Ink Compositions

A photoconversion ink composition was prepared by mixing each component according to the compositions in Table 1 and Table 2 below (weight %).

　 Example 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Quantum dot dispersion A-1 50.0 50.0 　 　 50.0 50.0 　 　 50.0 50.0 　 　 50.0 50.0 　 　 A-2 　 　 50.0 50.0 　 　 50.0 50.0 　 　 50.0 50.0 　 　 50.0 50.0 A-3 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 Curable Monomer B-1 39.2 　 39.2 　 39.2 　 39.2 　 39.2 　 39.2 　 39.2 　 39.2 　 B-2 　 39.2 　 39.2 　 39.2 　 39.2 　 39.2 　 39.2 　 39.2 　 39.2 B-3 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 　 mine generator C-1 2.0 2.0 2.0 2.0 　 　 　 　 1.0 1.0 1.0 1.0 　 　 　 　 C-2 　 　 　 　 2.0 2.0 2.0 2.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Initiator E-1 　 　 　 　 　 　 　 　 　 　 　 　 1.0 1.0 1.0 1.0 scattering particle dispersion D-1 8.6 8.6 8.6 8.6 8.6 8.6 8.6 8.6 8.6 8.6 8.6 8.6 8.6 8.6 8.6 8.6 Additives F-1 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2

　 Comparative example 1 2 3 4 5 6 7 8 9 10 Quantum dot dispersion A-1 　 　 　 50.0 　 50.0 50.0 　 　 　 A-2 　 　 　 　 50.0 　 　 50.0 50.0 　 A-3 50.0 50.0 50.0 　 　 　 　 　 　 50.0 Curable Monomer B-1 39.2 　 　 　 　 39.2 　 39.2 　 39.2 B-2 　 39.2 　 　 　 　 39.2 　 39.2 　 B-3 　 　 39.2 39.2 39.2 　 　 　 　 　 mine generator C-1 2.0 2.0 2.0 2.0 2.0 　 　 　 　 　 C-2 　 　 　 　 　 　 　 　 　 　 Initiator E-1 　 　 　 　 　 2.0 2.0 2.0 2.0 2.0 scattering particle dispersion D-1 8.6 8.6 8.6 8.6 8.6 8.6 8.6 8.6 8.6 8.6 Additives F-1 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2

A-1: Quantum dot dispersion prepared in Manufacturing Example 1 (containing isobornyl acrylate as a diluent)

A-2: Quantum dot dispersion prepared in Manufacturing Example 2 (including 1,6-hexanediol diacrylate as a diluent)

A-3: Quantum dot dispersion prepared in Manufacturing Example 3 (containing ditrimethylolpropanetetra(meth)acrylate as a diluent)

B-1: Isobornyl acrylate (viscosity: 5 ~ 10 cP, 25℃)

B-2: 1,6-Hexanediol diacrylate (Viscosity: 5 ~ 10 cP, 25℃)

B-3: Ditrimethylolpropanetetra(meth)acrylate (Viscosity: 400 ~ 600 cP, 25℃)

C-1: A compound represented by the following chemical formula 5

[Chemical Formula 5]

C-2: A compound represented by the following chemical formula 7

[Chemical formula 7]

D-1: Scatter particle dispersion prepared in Manufacturing Example 4

E-1: TPO (BASF)

F-1: F-554 (DIC Co., Ltd.)

Experimental example:

Using the photoconversion ink compositions manufactured in the above examples and comparative examples, a photoconversion coating layer was manufactured as follows, and the film thickness, brightness, dispersibility, high-humidity condition reliability, and viscosity at this time were measured by the following methods, and the results are shown in Tables 3 and 4 below.

< Manufacturing of photoconversion coating layer >

Each of the photoconversion ink compositions manufactured in the examples and comparative examples was applied onto a 5 cm × 5 cm glass substrate by inkjet, and then irradiated at 1000 mJ/cm2 using a 1 kW high-pressure mercury lamp containing all of the g, h, and i lines as an ultraviolet light source, and then heated in a heating oven at 180°C for 30 minutes to manufacture a photoconversion coating layer.

(1) Film thickness

The film thickness of the photoconversion coating layer manufactured above was measured using a film thickness measuring device (Dektak 6M, Vecco).

(2) Brightness

The photoconversion coating layer manufactured above was placed on top of a blue light source (XLamp XR-E LED, Royal blue 450, Cree), and the brightness was measured when irradiated with blue light using a brightness meter (CAS140CT Spectrometer, Instrument systems).

(3) Dispersibility

In the process of manufacturing the above photoconversion ink composition, the liquid sample before adding scattering particles was visually inspected and evaluated according to the following evaluation criteria.

<Evaluation criteria>

○: Transparent state

×: cloudy state

(4) Reliability under high humidity conditions

The change in luminous efficiency characteristics due to high humidity conditions for the photoconversion coating layer manufactured above was confirmed using the following mathematical formula 1. Specifically, the photoconversion coating layer was left for 12 hours under high humidity conditions of 85%, and the luminous efficiency before and after leaving was measured to calculate the luminous efficiency maintenance rate using the following mathematical formula 1.

[Mathematical formula 1]

Luminous efficiency maintenance rate (%) = {(luminous efficiency after exposure to high humidity conditions) / (luminous efficiency before exposure to high humidity conditions)} × 100

High humidity condition reliability was evaluated according to the following evaluation criteria.

<Evaluation criteria>

○: Luminous efficiency maintenance rate of 90% or more

×: Luminous efficiency retention rate is less than 90%

(5) Viscosity

The viscosity of the above photoconversion ink composition was measured using an R-type viscometer (VISCOMETER MODEL RE120L SYSTEM, manufactured by Toki Sangyo Co., Ltd.) at a rotation speed of 20 rpm and a temperature of 25°C.

Evaluation Results Film thickness (㎛) Luminance (lx) Dispersive High humidity condition reliability Viscosity (cP) Example 1 10 1214 ○ ○ 9.14 Example 2 10 1208 ○ ○ 14.56 Example 3 10 1217 ○ ○ 12.75 Example 4 10 1220 ○ ○ 17.9 Example 5 10 1183 ○ ○ 9.18 Example 6 10 1179 ○ ○ 14.6 Example 7 10 1198 ○ ○ 12.77 Example 8 10 1195 ○ ○ 18.2 Example 9 10 1202 ○ ○ 9.36 Example 10 10 1211 ○ ○ 14.58 Example 11 10 1216 ○ ○ 12.74 Example 12 10 1223 ○ ○ 18.33 Example 13 10 1148 ○ ○ 9.42 Example 14 10 1160 ○ ○ 14.71 Example 15 10 1125 ○ ○ 12.66 Example 16 10 1147 ○ ○ 18.32

Evaluation Results Film thickness (㎛) Luminance (lx) Dispersive High humidity condition reliability Viscosity (cP) Comparative Example 1 10 1107 ○ × 78.37 Comparative Example 2 10 1114 ○ × 83.85 Comparative Example 3 10 1132 × × 174.9 Comparative Example 4 10 1143 × × 112.7 Comparative Example 5 10 1128 × × 116.4 Comparative Example 6 10 1054 ○ × 13.67 Comparative Example 7 10 1068 ○ × 18.02 Comparative Example 8 10 1039 ○ × 14.36 Comparative Example 9 10 1030 ○ × 18.21 Comparative Example 10 10 1021 × × 78.37

As shown in Tables 3 and 4 above, the photoconversion ink compositions of the examples including a nonionic photoacid generator according to the present invention and a curable monomer having a viscosity of 30 cP or less at 25°C have good dispersibility, no degradation of optical properties occurs after the UV process, so that the optical properties are excellent, and the long-term reliability under high humidity conditions is excellent. On the other hand, the photoconversion ink compositions of the comparative examples not including a nonionic photoacid generator or including a curable monomer having a viscosity of more than 30 cP at 25°C were found to have poor dispersibility, poor optical properties after the UV process, or poor long-term reliability under high humidity conditions.

As described above, specific parts of the present invention have been described in detail. It is obvious to those skilled in the art that these specific descriptions are merely preferred implementation examples and that the scope of the present invention is not limited thereto. Those skilled in the art will be able to make various applications and modifications within the scope of the present invention based on the above contents.

Accordingly, the substantial scope of the present invention will be defined by the appended claims and their equivalents.

Claims (10)

Containing quantum dots, curable monomers and nonionic photoacid generators,
A photoconversion ink composition comprising a curable monomer having a viscosity of 30 cP or less at 25°C. A photoconversion ink composition in claim 1, wherein the curable monomer comprises a monofunctional (meth)acrylate or a polyfunctional (meth)acrylate having a viscosity of 30 cP or less at 25°C. In the first paragraph, the photoconversion ink composition wherein the nonionic photoacid generator generates an acid compound represented by the following chemical formula 1:
[Chemical Formula 1]

In the above formula, R is an aliphatic hydrocarbon group of C ₁ -C ₄ . In the first paragraph, the nonionic photoacid generator is a photoconversion ink composition comprising at least one of the compounds represented by the following chemical formulas 2 to 3:
[Chemical formula 2]

[Chemical Formula 3]

In the above formula, R is an aliphatic hydrocarbon group of C ₁ -C ₄ . A photoconversion ink composition in claim 1, wherein the nonionic photoacid generator is contained in an amount of 0.1 to 10 wt% based on 100 wt% of the total composition. A photoconversion ink composition in claim 1, further comprising at least one selected from the group consisting of scattering particles, a photopolymerization initiator, a surfactant, and an antioxidant. A photoconversion ink composition characterized in that it comprises a solvent in an amount of 1 wt% or less in the first paragraph. A photoconversion pixel comprising a cured product of a photoconversion ink composition according to any one of claims 1 to 7. A color filter comprising a photoconversion pixel according to claim 8. An image display device characterized by being provided with a color filter according to Article 9.