Quantum dot-containing composition, wavelength conversion layer, wavelength conversion substrate, and display device

Abstract

Provided is a quantum dot-containing composition which has excellent light emission characteristics and excellent curability. A quantum dot-containing composition according to an embodiment of the present invention contains quantum dots, a polyfunctional (meth)acrylate, a photopolymerization initiator, and a monofunctional thiol compound represented by general formula (I). Formula (I): SH-X-R (In the formula, X represents -CH2-CH2-, and R represents an aliphatic organic group that contains 9 or more carbon atoms.)

Description

Quantum dot-containing composition, wavelength conversion layer, wavelength conversion substrate, and display device

[0001] This disclosure relates to a quantum dot-containing composition, a wavelength conversion layer, a wavelength conversion substrate, and a display device.

[0002] In recent years, there has been a strong demand for improved color reproduction in the field of display devices such as liquid crystal displays and micro-LED displays in order to obtain higher-resolution images. As one means of improving color reproduction, the development of materials using quantum dots (also called QDs) has been actively pursued, as shown in, for example, Patent Documents 1 and 2. Fluorescence produced by quantum dots is highly luminous and has a small full width at half maximum, so display devices using quantum dots have excellent color reproduction.

[0003] Quantum dots are, for example, incorporated as light-emitting materials in the wavelength conversion layer of a wavelength conversion component in a display device. A wavelength conversion component is a component that converts the wavelength of light incident from a light source and emits it. In a wavelength conversion layer containing quantum dots as light-emitting materials that convert blue light having a peak wavelength of 430 nm to 480 nm into red light having a peak wavelength of 600 to 680 nm, or blue light into green light having a peak wavelength of 520 to 560 nm, red or green light can be generated by utilizing the fluorescence emitted by quantum dots excited by blue light incident from a light source.

[0004] Special table publication No. 2016-511709 Publication Patent No. 5940079

[0005] Wavelength conversion components used in display devices require high levels of luminescence characteristics, such as improved luminescence quantum yield from the viewpoint of reducing power consumption. Therefore, this disclosure aims to provide a quantum dot-containing composition suitable as an ink composition that can form a wavelength conversion layer having excellent luminescence quantum yield. Furthermore, this disclosure aims to provide a quantum dot-containing composition with excellent luminescence characteristics.

[0006] According to one aspect of the present invention, a quantum dot-containing composition is provided, comprising a quantum dot, a polyfunctional (meth)acrylate, a photopolymerization initiator, and a monofunctional thiol compound represented by general formula (I). SH-X-R (I) where X is -CH ２ -CH ２ The dash (-) represents a hyphen, and R represents an aliphatic organic group containing nine or more carbon atoms.

[0007] According to another aspect of the present invention, a quantum dot-containing composition is provided in which the aliphatic organic group is any of an aliphatic hydrocarbon group, an aliphatic hydrocarbon group containing an ester bond, an aliphatic hydrocarbon group containing an ether bond, or an aliphatic hydrocarbon group containing a ketone group.

[0008] According to yet another aspect of the present invention, a quantum dot-containing composition according to any of the above aspects is provided, comprising the monofunctional thiol compound in a concentration of 3 to 10% by mass relative to the total mass of nonvolatile components in the composition.

[0009] According to yet another aspect of the present invention, a quantum dot-containing composition relating to any of the above aspects is provided, further comprising light-scattering particles.

[0010] According to yet another aspect of the present invention, a quantum dot-containing composition according to any of the above aspects is provided, comprising one or more monofunctional thiol compounds selected from 1-dodecanethiol, 2-ethylhexyl 3-mercaptopropionate, and tridecyl 3-mercaptopropionate.

[0011] According to yet another aspect of the present invention, the content of the monofunctional thiol compound in the quantum dot-containing composition is M ＳＨ The content of the above quantum dots is M ＱＤ In this case, the mass ratio M ＳＨ / M ＱＤ A quantum dot-containing composition relating to any of the above aspects is provided, wherein the value is within the range of 0.08 to 0.5.

[0012] According to yet another aspect of the present invention, a quantum dot-containing composition according to any of the above aspects is provided, comprising the above-mentioned polyfunctional (meth)acrylate in a concentration within the range of 50 to 75% by mass relative to the total mass of nonvolatile components in the composition.

[0013] According to yet another aspect of the present invention, a quantum dot-containing composition is provided, comprising a quantum dot, a polyfunctional (meth)acrylate, a photopolymerization initiator, and a monofunctional thiol compound represented by general formula (I), wherein the monofunctional thiol compound comprises one or more selected from 1-dodecanethiol, 2-ethylhexyl 3-mercaptopropionate, and tridecyl 3-mercaptopropionate, the monofunctional thiol compound is contained in a concentration of 3 to 10% by mass relative to the total mass of nonvolatile components, and the polyfunctional (meth)acrylate is contained in a concentration of 45 to 90% by mass relative to the total mass of nonvolatile components. SH-X-R (I) In the formula, X is -CH ２ -CH ２ The dash (-) represents a hyphen, and R represents an aliphatic organic group containing nine or more carbon atoms.

[0014] According to yet another aspect of the present invention, a quantum dot-containing composition relating to any of the above aspects is provided for use in forming a wavelength conversion layer.

[0015] According to yet another aspect of the present invention, a wavelength conversion layer is provided which is made of a cured product of a quantum dot-containing composition according to any of the above aspects.

[0016] According to yet another aspect of the present invention, a wavelength conversion substrate is provided that includes a wavelength conversion layer according to the above aspect.

[0017] According to yet another aspect of the present invention, a display device is provided that includes a wavelength conversion substrate according to the above aspect.

[0018] According to this disclosure, a quantum dot-containing composition with excellent luminescence properties and curability is provided.

[0019] Figure 1 is a cross-sectional view of a display device according to one embodiment of the present invention.

[0020] Embodiments of the present invention will be described below. The embodiments described below are more specific to any of the above aspects. The matters described below can be incorporated into each of the above aspects, individually or in combination.

[0021] Furthermore, the embodiments shown below illustrate configurations for realizing the technical concept of the present invention, and the technical concept of the present invention is not limited by the material, shape, and structure of the components described below. Various modifications can be made to the technical concept of the present invention within the technical scope defined by the claims described in the claims.

[0022] <1> Quantum dot-containing composition The quantum dot-containing composition according to the first embodiment of the present invention comprises quantum dots, a polyfunctional (meth)acrylate, a photopolymerization initiator, and a monofunctional thiol compound. The quantum dot-containing composition according to the first embodiment will be described below.

[0023] (Quantum dots) Quantum dots are semiconductor nanoparticles that emit fluorescence when excited by excitation light. Their particle size is, for example, in the range of a few nanometers to tens of nanometers.

[0024] The quantum dot is not particularly limited as long as it is a quantum dot particle capable of emitting light when stimulated by light. For example, semiconductor nanoparticles can be made that contain at least one selected from the group consisting of group II-VI compounds, group III-V compounds, group IV-VI compounds, group I-III-VI compounds, group II-III-VI compounds, group I-II-IV-VI compounds, and group IV compounds.

[0025] Examples of quantum dots include CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, CdSeS, CdSeTe, CdSte, ZnSeS, ZnSeTe, ZnSte, HgSeS, HgSeTe, HgSte, CdZnS, CdZnSe, CdZ II-VI group semiconductor nanoparticles such as nTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZeSe, HgZnTe, CdZnSeS, CdZnSeTe, CdZnSte, CdHgSeS, CdHgSeTe, CdHgSte, HgZnSeS, HgZnSte, HgZnSte, HgZnSte, etc. GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, GaNP, GaNAs, GaNSb, GaPAs , GaPSb, AINP, AINAs, AINSb, AIPAs, AIPSb, InNP, InNAs, InNSb, InPAs, InPSb, GaAINP, GaAI III-V semiconductor nanoparticles such as NAs, GaAINSb, GaAIPAs, GaAIIPSb, GaAINAs, GaAINSb, GaAIPAs, GaAIIPSb, GainNP, GainNAs, GainNSb, GainPAs, GainPSb, inAINP, inAINAs, inAINSb, inAIPAs, inAIIPSb; IV-VI group semiconductor nanoparticles such as SnS, SnSe, SnTe, PbS, PbSe, PbTe, SnSeS, SnSeTe, SnSte, PbSeS, PbSte, PbSte, SnPbS, SnPbSe, SnPbTe, SnPbSSe, SnPbSte, SnPbTe, SnPbSte, SnPbSte, SnPbTe, SnPbSte, etc.; I-III-VI group semiconductor nanoparticles such as CuinS, CuinSe, CuinTe, CuGaS, CuGaS, CuGaS, CuGaSte, AgInS, AgInSe, AgInTe, AgGaS, AgGaS, AgGaSte, CuInGaS, CuInGaS, CuGaSeS, CuGaSeS, AgInGaS, etc.;Examples include II-III-VI group semiconductor nanoparticles such as ZnGaS, ZnAlS, ZnInS, ZnGaSe, ZnAlSe, ZnInSe, ZnGaTe, ZnAlTe, ZnInTe, ZnGaO, ZnAlO, ZnInO, HgGaS, HgAlS, HgInS, HgGaSe, HgAlSe, HgInTe, HgAlTe, HgInTe, MgGaS, MgAlS, MgInS, MgGaSe, MgAlSe, MgInSe, etc.; I-II-IV-VI group semiconductor nanoparticles such as CuZnSnSe, CuZnSnS, etc.; and IV group semiconductor nanoparticles such as Si, Ge, SiC, SiGe, etc.

[0026] Quantum dots, for example, have a core-shell structure. The core is made of a semiconductor responsible for light emission. The shell is a thin layer epitaxially grown on the surface of the core, with a thickness of one to four atoms. The shell contributes to improving and stabilizing the light emission efficiency. The shell may have a single-layer structure or a multilayer structure. For example, the shell may include one or more selected from the group consisting of ZnSe, ZnS, and ZnTe, but is not limited to these.

[0027] Examples of core and shell combinations (core / shell) include CdSe / ZnS, InP / ZnS, CdSe / CdS, CdTe / CdS, CdTe / ZnS, InP / ZnS, InP / ZnSe, InP / GaP / ZnS, InP / ZnSe / ZnS, InP / ZnSeTe / ZnS, and InP / MnSe / ZnS.

[0028] A quantum dot-containing composition may contain one type of quantum dot alone, or it may contain a combination of two or more types of quantum dots. The emission center wavelength of the quantum dot can be controlled by changing at least one of the quantum dot's composition and particle size.

[0029] When blue light is used as the excitation light, the quantum dot-containing composition may contain quantum dots that emit red light when excited by blue light, and quantum dots that emit green light when excited by blue light.

[0030] Also, when ultraviolet light is used as the excitation light, the quantum dot-containing composition can contain quantum dots that are excited by ultraviolet light to emit red light, quantum dots that are excited by ultraviolet light to emit green light, and quantum dots that are excited by ultraviolet light to emit blue light.

[0031] Examples of the quantum dots that emit red light include those having an emission center wavelength in the wavelength range of 600 to 680 nm. Examples of the quantum dots that emit green light include those having an emission center wavelength in the wavelength range of 520 to 560 nm. Examples of the quantum dots that emit blue light include those having an emission center wavelength in the wavelength range of 430 to 480 nm.

[0032] The content rate of the quantum dots is preferably in the range of 10 to 40% by mass, more preferably in the range of 15 to 35% by mass, and still more preferably in the range of 20 to 30% by mass with respect to the total mass of the non-volatile components in the quantum dot-containing composition.

[0033] Since quantum dots have a high surface energy due to being nanoparticles, they tend to aggregate in the composition. Quantum dots are deactivated by aggregation, and the emission intensity decreases. The problem of this aggregation becomes more serious as the concentration of quantum dots increases. The monofunctional thiol compound described below is considered to have the effect of efficiently coordinating to the surface of quantum dots in the composition, enhancing the dispersibility of quantum dots even with a small addition, and improving the emission characteristics.

[0034] (Monofunctional thiol compound) The quantum dot-containing composition contains a monofunctional thiol compound. The monofunctional thiol compound is a thiol compound having one mercapto group (—SH) in one molecule, represented by the following general formula (I). SH—X—R (I) In the formula, X represents —CH ２ —CH ２ —, and R represents an aliphatic organic group containing 9 or more carbon atoms.

[0035] The monofunctional thiol compound represented by general formula (I) coordinates to the surface of quantum dots in a quantum dot-containing composition, using a mercapto group as a coordinating group. The coordination of the monofunctional thiol compound to the quantum dot surface stabilizes the surface state of the quantum dots, thereby improving their luminescence properties. In this case, since the monofunctional thiol compound has only one mercapto group per molecule, it coordinates more easily to the quantum dot surface than polyfunctional thiol compounds that have two or more mercapto groups per molecule. Therefore, compared to polyfunctional thiol compounds, the monofunctional thiol compound can efficiently coordinate to the quantum dot surface with a smaller amount of addition, improving luminescence properties. If the concentration of the compound added as a ligand to the quantum dots in the quantum dot-containing composition can be kept low, the concentration of the curable compound can be relatively increased. Thus, by using the above-mentioned monofunctional thiol compound, it is possible to provide a quantum dot-containing composition with excellent luminescence properties and curability.

[0036] Furthermore, monofunctional thiol compounds represented by general formula (I) exhibit superior luminescence enhancement compared to monofunctional thiol compounds that do not satisfy general formula (I). Specifically, monofunctional thiol compounds represented by general formula (I) have a mercapto group with -CH represented by X. ２ -CH ２ It has a structure in which an aliphatic organic group R containing nine or more carbon atoms is bonded via a -. In contrast, for example, the -CH corresponding to X ２ -CH ２ Compared to monofunctional thiol compounds without the - group, or monofunctional thiol compounds in which the aliphatic organic group corresponding to R contains eight or fewer carbon atoms, it exhibits superior luminescence enhancement. Although the reason is not entirely clear, it is presumed that monofunctional thiol compounds having a structure in which the -X-R group is bonded to a mercapto group have excellent performance in improving the dispersibility of quantum dots, effectively suppressing the decrease in luminescence intensity caused by the aggregation and deactivation of quantum dots. Thus, quantum dot-containing compositions containing monofunctional thiol compounds represented by general formula (I) achieve a high level of both luminescence and curability.

[0037] Here, the aliphatic organic group represented by R, which contains nine or more carbon atoms, is preferably an aliphatic hydrocarbon group, an aliphatic hydrocarbon group containing an ester bond, an aliphatic hydrocarbon group containing an ether bond, or an aliphatic hydrocarbon group containing a ketone group, with a total of nine or more carbon atoms in the aliphatic organic group.

[0038] When R is an aliphatic hydrocarbon group, the number of carbon atoms in R is 9 to 20 in one example, 9 to 18 in another example, and 9 to 15 in yet another example.

[0039] The aliphatic hydrocarbon group R is linear in one example, branched in another, and contains a cyclic structure in yet another. Furthermore, the aliphatic hydrocarbon group R is saturated in one example and unsaturated in another.

[0040] R may be an aliphatic hydrocarbon group consisting solely of hydrocarbons. Specific examples of an aliphatic hydrocarbon group R containing nine or more carbon atoms and consisting solely of hydrocarbons include 1-dodecanethiol, 1-tridecanethiol, 1-pentadecanethiol, and 1-hexadecanethiol.

[0041] If R is an aliphatic hydrocarbon group containing an ester bond, the number of carbon atoms in R is 9 to 20 in one example, 9 to 18 in another example, and 9 to 15 in yet another example.

[0042] Specific examples of an aliphatic hydrocarbon group R containing nine or more carbon atoms and an ester bond include 2-ethylhexyl 3-mercaptopropionate, tridecyl 3-mercaptopropionate, and octadecyl 3-mercaptopropionate.

[0043] If R is an aliphatic hydrocarbon group containing an ether bond, the number of carbon atoms in R is 9 to 20 in one example, 9 to 18 in another example, and 9 to 15 in yet another example.

[0044] If R is an aliphatic hydrocarbon group containing a ketone group, the number of carbon atoms in R is 9 or more and 20 or less in one example, 9 or more and 18 or less in another example, and 9 or more and 15 or less in yet another example.

[0045] The content of the monofunctional thiol compound represented by general formula (I) is preferably in the range of 3% to 10% by mass, more preferably in the range of 4% to 9% by mass, and even more preferably in the range of 5% to 8% by mass, relative to the total mass of nonvolatile components in the quantum dot-containing composition. Although increasing the concentration of the added thiol compound tends to improve the luminescence properties, it leads to a problem of reduced curability because the concentration of curable components in the composition decreases relatively. Having the content of the monofunctional thiol compound represented by general formula (I) within the above range is preferable because it contributes to providing a quantum dot-containing composition with excellent luminescence properties and curability.

[0046] Furthermore, the content of the monofunctional thiol compound represented by general formula (I) in the quantum dot-containing composition is M ＳＨ The quantum dot content is M ＱＤ In this case, the mass ratio M ＳＨ / M ＱＤ In one example, it is in the range of 0.08 to 1, in another example, it is in the range of 0.08 to 0.5, and in yet another example, it is in the range of 0.08 to 0.33. The mass ratio M of the monofunctional thiol compound represented by general formula (I) to the quantum dot. ＳＨ / M ＱＤ It is preferable that the above range is present because it enhances the stability and dispersibility of the quantum dots and contributes to improving the luminescence properties of the quantum dot-containing composition.

[0047] (Polyfunctional (meth)acrylate) The quantum dot-containing composition contains polyfunctional (meth)acrylate as a curable component. Polyfunctional (meth)acrylate has the property of polymerizing and curing to form a transparent resin when irradiated with active energy rays such as ultraviolet light. Polyfunctional (meth)acrylate is a compound having two or more (meth)acryloyl groups in one molecule. Here, "(meth)acrylate" means either acrylate or methacrylate, or both. "(meth)acryloyl" means either acryloyl or methacryloyl, or both.

[0048] It is preferable from the viewpoint of curability and reactivity that the quantum dot-containing composition contains a polyfunctional (meth)acrylate having two or more (meth)acryloyl groups in one molecule. The polyfunctional (meth)acrylate is preferably a compound having two to six (meth)acryloyl groups in one molecule, and more preferably a compound having two to three (meth)acryloyl groups in one molecule.

[0049] Specific examples of bifunctional (meth)acrylates include alkane diol di(meth)acrylates such as 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, and tricyclodecanedimethanol di(meth)acrylate; bisphenol-modified di(meth)acrylates such as bisphenol A ethylene oxide-modified di(meth)acrylate and bisphenol F ethylene oxide-modified di(meth)acrylate; polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, and epoxy di(meth)acrylate.

[0050] Specific examples of trifunctional (meth)acrylates include trimethylolpropane tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, propoxylated trimethylolpropane tri(meth)acrylate, tris-2-hydroxyethyl isocyanurate tri(meth)acrylate, glycerin tri(meth)acrylate, and other trifunctional (meth)acrylates such as pentaerythritol tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, and ditrimethylolpropane tri(meth)acrylate. Examples include polyfunctional (meth)acrylates with three or more functions, such as pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, ditrimethylolpropane penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and ditrimethylolpropane hexa(meth)acrylate, as well as polyfunctional (meth)acrylates in which some of these (meth)acrylates are replaced with alkyl groups or ε-caprolactone.

[0051] The quantum dot-containing composition may contain one type of polyfunctional (meth)acrylate alone, or it may contain a combination of two or more types of polyfunctional (meth)acrylates. Furthermore, the (meth)acrylates mentioned above may be monomers in the quantum dot-containing composition, or they may be oligomers in which a portion has been polymerized.

[0052] The content of the polyfunctional (meth)acrylate is preferably in the range of 45 to 90% by mass, more preferably in the range of 50 to 75% by mass, and even more preferably in the range of 50 to 65% by mass, based on the total mass of nonvolatile components in the quantum dot-containing composition.

[0053] Furthermore, the content of the monofunctional thiol compound represented by general formula (I) in the quantum dot-containing composition is M ＳＨ The content of polyfunctional (meth)acrylate is M ＡＣ In this case, the mass ratio M ＳＨ / M ＡＣIn one example, it is within the range of 0.03 to 0.22, in another example, it is within the range of 0.03 to 0.20, and in yet another example, it is within the range of 0.03 to 0.15.

[0054] (Photopolymerization Initiator) The quantum dot-containing composition contains a photopolymerization initiator to improve curability. Specific examples of photopolymerization initiators include benzoins (benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and other benzoin alkyl ethers), phenyl ketones [e.g., acetophenones (e.g., acetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 1,1-dichloroacetophenone, etc.), alkylphenyl ketones such as 2-hydroxy-2-methylpropiophenone; cycloalkylphenyl ketones such as 1-hydroxycyclohexylphenyl ketone, etc.], and aminoacetophenones {2-methyl-1-[4-(methylthio)phenyl Examples include 2-morpholinoaminopropanone-1, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, anthraquinones (anthraquinone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-t-butylanthraquinone, 1-chloroanthraquinone, etc.), thioxanthones (2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone, 2,4-diisopropylthioxanthone, etc.), ketals (acetophenone dimethyl ketal, benzyl dimethyl ketal, etc.), benzophenones (benzophenone, etc.), xanthones, phosphine oxides (e.g., 2,4,6-trimethylbenzoyldiphenylphosphine oxide, etc.). These photopolymerization initiators (B) may be used individually or in combination of two or more.

[0055] The content of the photopolymerization initiator is preferably in the range of 0.001 to 3% by mass, and more preferably in the range of 0.1 to 1% by mass, relative to the total mass of nonvolatile components in the quantum dot-containing composition.

[0056] (Light-scattering particles) The quantum dot-containing composition may further contain light-scattering particles. The light-scattering particles contribute to improving the light absorption efficiency of the quantum dots by scattering light within the light wavelength conversion layer, thereby extending the effective optical path length. Examples of light-scattering particles include inorganic white pigments, organic white pigments, and polymer microparticles.

[0057] Examples of inorganic white pigments include metal oxides such as titanium dioxide, zinc oxide, and alumina; alkaline earth metal carbonates such as calcium carbonate; and silica, calcium silicate, lead white, talc, and clay. Examples of organic white pigments include bistyryl derivative white pigments and alkylene bismelamine derivative white pigments.

[0058] Among these, metal oxides are preferred as light-scattering particles, and titanium oxide is more preferred. Titanium oxide has crystalline forms such as rutile, anatase, and blue-kite, and the rutile type, which has low light transmittance and high opacity, is preferably used. Furthermore, titanium oxide may be surface-treated. Any known surface treatment method or surface treatment agent can be used as desired.

[0059] When a quantum dot-containing composition contains light-scattering particles, the content of the light-scattering particles is preferably in the range of 3 to 20% by mass, and more preferably in the range of 8 to 15% by mass, relative to the total mass of non-volatile components in the quantum dot-containing composition.

[0060] The quantum dot-containing composition may further contain other components, such as dispersants, solvents, antioxidants, and viscosity modifiers.

[0061] The method for preparing the quantum dot-containing composition is not particularly limited and can be carried out using general procedures for preparing polymerizable compositions.

[0062] Next, other embodiments of the present invention will be described with reference to the drawings. Elements having similar or identical functions will be given the same reference numerals in the drawings referred to below, and redundant explanations will be omitted. Furthermore, the drawings are schematic, and the relationships between dimensions in one direction and those in another, and the relationships between the dimensions of one component and those of another, may differ from those in reality.

[0063] <2> Display Device Figure 1 is a cross-sectional view of a display device according to a second embodiment of the present invention. In Figure 1, the X and Y directions are parallel to the display surface of the display device 1 and intersect each other. For example, the X and Y directions are perpendicular to each other. The Z direction is perpendicular to the X and Y directions. That is, the Z direction is the thickness direction of the display device 1.

[0064] The display device 1 shown in Figure 1 is a microLED display capable of color display using an active matrix driving method, and each subpixel contains a light-emitting diode (LED). The display device 1 includes a dimming device 2, a wavelength conversion substrate 3, and an adhesive layer 4.

[0065] The dimming device 2 emits light toward the wavelength conversion substrate 3 and is capable of adjusting at least one of the intensity of this light and the duration of light emission for each pixel or sub-pixel. The dimming device 2 includes a substrate 21, a multilayer wiring layer 22, and a light-emitting diode 23.

[0066] The substrate 21 includes, for example, an insulating substrate such as a glass substrate. The substrate 21 may further include an undercoat layer provided on the main surface of the insulating substrate facing the wavelength conversion substrate 3. The undercoat layer is, for example, a laminate of silicon nitride layers and silicon oxide layers sequentially stacked on the insulating substrate. The substrate 21 may also be a semiconductor substrate such as a silicon substrate. The substrate 21 may be rigid or flexible.

[0067] The multilayer wiring layer 22 is provided on the main surface of the substrate 21 facing the wavelength conversion substrate 3. The multilayer wiring layer 22 includes video signal lines, first power lines, second power lines, scanning signal lines, pixel circuits, and interlayer insulating films.

[0068] The video signal lines each extend in the Y direction and are arranged in the X direction. The scan signal lines each extend in the X direction and are arranged in the Y direction. The first and second power lines each extend in the Y direction and are arranged in the X direction, corresponding to the video signal lines. The first and second power lines may each extend in the X direction and be arranged in the Y direction, corresponding to the scan signal lines. Alternatively, one of the first and second power lines may each extend in the Y direction and be arranged in the X direction, corresponding to the video signal lines, while the other of them may each extend in the X direction and be arranged in the Y direction, corresponding to the scan signal lines.

[0069] The pixel circuits are arranged in the X and Y directions on the main surface of the substrate 21. Each pixel circuit includes a drive control element, a switch, and a capacitor. The drive control element is, for example, a p-channel field-effect transistor with its source connected to a first power line. The switch is, for example, an n-channel field-effect transistor with its gate connected to a scan signal line, its source connected to a video signal line, and its drain connected to the gate of the drive control element. The capacitor is, for example, a thin-film capacitor with one electrode connected to the gate of the drive control element and the other electrode connected to the first power line. The pixel circuits may have other configurations.

[0070] The light-emitting diode 23 has a multilayer structure. Here, the stacking direction of the layers contained in the light-emitting diode 23 is the Z direction. This stacking direction may be perpendicular to the Z direction.

[0071] The light-emitting diodes 23 have identical emission spectra. The light-emitting diodes 23 emit short-wavelength light, such as blue light and ultraviolet light. Here, as an example, we assume that the light-emitting diodes 23 are blue light-emitting diodes that emit blue light.

[0072] The light-emitting diodes 23 are arranged on the multilayer wiring layer 22 in accordance with the pixel circuit. Each of the light-emitting diodes 23 has its anode connected to the drain of the drive control element and its cathode connected to the second power line.

[0073] The wavelength conversion substrate 3 faces the dimming device 2. Specifically, the wavelength conversion substrate 3 faces the substrate 21 with the light-emitting diode 23 and the like in between.

[0074] The wavelength conversion substrate 3 includes a transparent substrate 31, a black matrix 32, a color filter 33 including a first color layer 33R, a second color layer 33G, and a base layer 33B, a resin layer 34, an inorganic coating layer 35, filling layers 36R, 36G, and 36B, and an inorganic barrier layer 37.

[0075] The transparent substrate 31 is transparent to visible light. The transparent substrate 31 is, for example, a colorless substrate. The transparent substrate 31 may have a single-layer structure or a multi-layer structure. The transparent substrate 31 is made of, for example, glass, transparent resin, or a combination thereof. The transparent substrate 31 may be rigid or flexible. The transparent substrate 31 has a first main surface facing the dimming device 2 and a second main surface which is the back surface of the first main surface.

[0076] The black matrix 32 is provided on the first main surface of the transparent substrate 31. The black matrix 32 is a black layer that blocks visible light. The black matrix 32 constitutes a part of the resin-containing layer.

[0077] The black matrix 32 consists of, for example, a mixture containing a binder resin and a colorant. The colorant is, for example, a black pigment, or a mixture of pigments that produce black by subtractive color mixing, such as a mixture containing a blue pigment, a green pigment, and a red pigment.

[0078] The black matrix 32 has second through-holes at the positions of the light-emitting diodes 23. The opening on the transparent substrate 31 side of each second through-hole is larger in the direction perpendicular to the Z direction compared to the light-emitting diodes 23.

[0079] Here, the second through-holes are arranged in a first and second direction that intersect each other. The first and second directions are the X and Y directions, respectively. Each of the second through-holes has a shape that extends in the second direction.

[0080] The first colored layer 33R, the second colored layer 33G, and the base layer 33B form a stripe arrangement on the transparent substrate 31 on which the black matrix 32 is provided. These form multiple pixels, each composed of the first colored layer 33R, the second colored layer 33G, and the base layer 33B, and these pixels are arranged in the X and Y directions. The first colored layer 33R, the second colored layer 33G, and the base layer 33B constitute a color filter 33. The color filter 33 also constitutes another part of the resin-containing layer.

[0081] As described above, the first colored layer 33R is a red colored layer, and the second colored layer 33G is a green colored layer. The base layer 33B is a colorless light-transmitting layer or a blue colored layer. Each of the first colored layers 33R fills one of the second through holes. Each of the second colored layers 33G fills another of the second through holes. Each of the base layers 33B fills yet another of the second through holes.

[0082] The resin layer 34 is provided on a composite film consisting of a first colored layer 33R, a second colored layer 33G, and a base layer 33B. In one example, the resin layer 34 is transparent. In this case, the resin layer 34 may be colored or colorless. The resin layer 34 may have light-scattering properties.

[0083] The resin layer 34 is made of, for example, an acrylic resin, a siloxane resin, an epoxy resin, a polyimide resin, or two or more cured products thereof. From the viewpoint of adhesion with the inorganic barrier layer 37, it is preferable that the resin layer 34 does not contain a fluorine compound.

[0084] The resin layer 34 is a partition layer having first through-holes at the positions of the second through-holes. Here, the first through-holes are arranged in a first direction and a second direction that intersect each other, corresponding to the second through-holes. As described above, the first direction and the second direction are the X direction and the Y direction, respectively. Each of the second through-holes has a shape that extends in the second direction. For example, the contour of the orthogonal projection of each of the second through-holes onto the first main surface of the opening on the transparent substrate 31 side (hereinafter referred to as the first contour) is approximately rectangular.

[0085] Furthermore, in the first through-hole, the first contour is provided such that each first contour surrounds the contour of the orthogonal projection of the second through-hole onto the first main surface (hereinafter referred to as the second contour). The first contour does not necessarily have to surround the second contour. In a structure where the first contour surrounds the second contour, the influence of stray light on the display is smaller compared to a structure where the first contour does not surround the second contour.

[0086] The portion of the resin layer 34 sandwiched between adjacent first through holes has a rectangular cross-sectional shape. This portion may have a forward tapered cross-sectional shape, an inverse tapered cross-sectional shape, or any other cross-sectional shape.

[0087] The inorganic coating layer 35 covers each side wall of the first through-hole and the upper surface of the resin layer 34. The inorganic coating layer 35 is open at the location of the first through-hole.

[0088] The inorganic coating layer 35 may have a single-layer structure or a multi-layer structure. The layers included in the inorganic coating layer 35 are, for example, layers made of metal, alloy, or transparent dielectric. The metal or alloy is, for example, aluminum, titanium, chromium, neodymium, or an alloy containing one or more of these.

[0089] The inorganic coating layer 35 can be formed by vapor deposition methods such as sputtering. Furthermore, the openings in the inorganic coating layer 35 can be formed, for example, by etching.

[0090] The inorganic coating layer 35 can function as a reflective layer. In one example, the inorganic coating layer 35 has a reflectivity of 70% or more across the entire visible light range, and in another example, it is in the range of 70% to 98%. Here, the visible light range is defined as the wavelength range of 400 nm to 700 nm.

[0091] Furthermore, the inorganic coating layer 35, together with the inorganic barrier layer 37, can play a role in suppressing the degradation of the wavelength conversion layer containing quantum dots due to moisture. The thickness of the inorganic coating layer 35 is preferably in the range of 100 nm to 300 nm.

[0092] The packed layer 36R is provided on the first colored layer 33R. The packed layer 36R is a first wavelength conversion layer containing quantum dots and transparent resin. Here, the packed layer 36R converts the blue light emitted by the light-emitting diode 23 into red light.

[0093] The packed layer 36G is provided on the second colored layer 33G. The packed layer 36G is a second wavelength conversion layer containing quantum dots and transparent resin. Here, the packed layer 36G converts the blue light emitted by the light-emitting diode 23 into green light.

[0094] The filling layer 36B is provided on the base layer 33B. As described above, the filling layer 36B here is a colorless and transparent layer. In this case, the filling layer 36B is made of, for example, a transparent resin.

[0095] When the light-emitting diode 23 is an ultraviolet light-emitting diode, the packed layer 36B is a third wavelength conversion layer. The third wavelength conversion layer is made of a cured product of the quantum dot-containing composition according to the first embodiment described above. The third wavelength conversion layer converts, for example, the ultraviolet light emitted by the ultraviolet light-emitting diode into blue light. In this case, the packed layer 36R (first wavelength conversion layer) and the packed layer 36G (second wavelength conversion layer) convert the ultraviolet light emitted by the ultraviolet light-emitting diode into red light and green light, respectively.

[0096] In the display device 1, one or more of the first to third wavelength conversion layers are made of a cured product of the quantum dot-containing composition according to the first embodiment described above.

[0097] Each of the first to third wavelength conversion layers can be formed by printing using the quantum dot-containing composition according to the first embodiment. For example, inkjet printing can be used for this printing. The coating formed by printing can be cured by light irradiation.

[0098] The inorganic barrier layer 37 covers the upper surfaces of the filling layers 36R, 36G, and 36B, and the areas of the inorganic coating layer 35 that are exposed from the filling layers 36R, 36G, and 36B. The inorganic barrier layer 37 is interposed between the filling layers 36R, 36G, and 36B and the adhesive layer 4, preventing the migration of moisture from the adhesive layer 4 to the filling layers 36R, 36G, and 36B.

[0099] The inorganic barrier layer 37 has light transmittance, allowing light emitted by the light-emitting diode 23 to pass through. The inorganic barrier layer 37 may have a single-layer structure or a multilayer structure. For example, the inorganic barrier layer 37 includes at least one of a layer made of silicon oxide and a layer made of silicon nitride. The layers included in the inorganic barrier layer 37 can be formed, for example, by vapor deposition methods such as chemical vapor deposition and sputtering.

[0100] The adhesive layer 4 is interposed between the dimming device 2 and the wavelength conversion substrate 3, bonding them together. The adhesive layer 4 transmits the light emitted by the light-emitting diode 23. The adhesive layer 4 is, for example, a colorless and transparent layer. The adhesive layer 4 is made of an adhesive or tack.

[0101] In the display device 1, one or more of the first wavelength conversion layer (packed layer 36R), the second wavelength conversion layer (packed layer 36G), and the third wavelength conversion layer (packed layer 36B) are made of a cured product of the quantum dot-containing composition according to the first embodiment, as described above. Since the quantum dot-containing composition according to the first embodiment has excellent luminescence properties, the luminescence properties are improved in the display device 1 that includes a wavelength conversion layer made of this cured product.

[0102] Furthermore, since the quantum dot-containing composition according to the first embodiment also has excellent curability, the wavelength conversion layer made of this cured product has high adhesion to the inorganic coating layer 35 and the inorganic barrier layer 37, and therefore delamination at their interfaces is unlikely to occur. In this case, the migration of moisture from the resin layer 34 and the adhesive layer 4 to the wavelength conversion layer is suppressed, and thus deterioration of the wavelength conversion layer containing quantum dots due to moisture is also suppressed.

[0103] The tests conducted in connection with the present invention are described below.

[0104] (1) Preparation of quantum dot-containing composition (1.1) Example 1 A quantum dot-containing composition containing a monofunctional thiol compound represented by general formula (I) was prepared. As the quantum dot, a red quantum dot (R-QD, AgGaSe / ZnS (core / shell)) that converts light with a wavelength of 450 nm to light with a wavelength of 630 nm was used. This quantum dot R-QD was used with a bifunctional methacrylate, tricyclodecanedimethanol dimethacrylate (trade name: DCP, manufactured by Shin Nakamura Chemical Industry Co., Ltd.), and TiO ２ A quantum dot-containing composition 1 was prepared by mixing light-scattering particles consisting of the above, 2,4,6-trimethylbenzoyldiphenylphosphine oxide (trade name: Omnirad® 819, manufactured by IGM Resins B.V.), a phosphine oxide-based photopolymerization initiator, 1-dodecanethiol (1-DDT) as a monofunctional thiol, and PGMEAc as a solvent, in a composition ratio of 40% by mass of solids as shown below.

[0105] <Quantum dot-containing composition 1> Red quantum dots (R-QD, AgGaSe / ZnS (core / shell)) 28% by mass relative to the total mass of nonvolatile components 53% by mass relative to the total mass of bifunctional methacrylate nonvolatile components Light scattering particles (TiO ２ ) 10% by mass relative to the total mass of nonvolatile components Phosphine oxide-based photopolymerization initiator 1% by mass relative to the total mass of nonvolatile components Monofunctional thiol (1-DDT) 8% by mass relative to the total mass of nonvolatile components

[0106] (1.2) Example 2 A quantum dot-containing composition 2 was prepared in the same manner as in Example 1, except as follows: In this example, 2-ethylhexyl 3-mercaptopropionate (EHMP) was used instead of 1-dodecanethiol (1-DDT).

[0107] (1.3) Example 3 A quantum dot-containing composition 3 was prepared in the same manner as in Example 1, except as follows: In this example, tridecyl 3-mercaptopropionate was used instead of 1-dodecanethiol (1-DDT).

[0108] (1.4) Comparative Example 1 A quantum dot-containing composition 4 was prepared in the same manner as in Example 1, except for the following points. In this example, 1-dodecanethiol (1-DDT) was not used, and the content of the bifunctional methacrylate was increased from 53% by mass to 61% by mass. (1.5) Comparative Example 2 A quantum dot-containing composition 5 was prepared in the same manner as in Example 1, except for the following points. In this example, dipentaerythritol hexakis (3-mercaptopropionate) (DPMP) was used instead of 1-dodecanethiol (1-DDT). Furthermore, the content of DPMP was increased from 8% by mass to 16% by mass, and the content of the bifunctional methacrylate was decreased from 53% by mass to 45% by mass.

[0109] (1.6) Comparative Example 3 A quantum dot-containing composition 6 was prepared in the same manner as in Comparative Example 2, except as follows. Specifically, in this example, pentaerythritol tetrakis(3-mercaptopropionate) (PEMP) was used instead of dipentaerythritol hexakis(3-mercaptopropionate) (DPMP).

[0110] (1.7) Comparative Example 4 A quantum dot-containing composition 7 was prepared in the same manner as in Comparative Example 2, except for the following points. In this example, pentaerythritol tetrakis(3-mercaptobutyrate) (PEMP) (trade name: Karenz MT® PE1, manufactured by Resonaq Corporation) was used instead of dipentaerythritol hexakis(3-mercaptopropionate) (DPMP).

[0111] (1.8) Comparative Example 5 A quantum dot-containing composition 8 was prepared in the same manner as in Comparative Example 2, except for the following points. In this example, tetraethylene glycol bis(3-mercaptopropionate) (EGMP) (trade name: EGMP-4, manufactured by Sakai Chemical Industry Co., Ltd.) was used instead of dipentaerythritol hexakis(3-mercaptopropionate) (DPMP).

[0112] (1.9) Comparative Example 6 A quantum dot-containing composition 9 was prepared in the same manner as in Example 1, except as follows: In this example, tetraethylene glycol bis(3-mercaptopropionate) (EGMP) was used instead of 1-dodecanethiol (1-DDT).

[0113] (1.10) Comparative Example 7 A quantum dot-containing composition 10 was prepared in the same manner as in Example 1, except as follows: In this example, 1-octanthiol was used instead of 1-dodecanethiol (1-DDT).

[0114] (1.11) Comparative Example 8 A quantum dot-containing composition 11 was prepared in the same manner as in Example 1, except as follows: In this example, octyl thioglycolate was used instead of 1-dodecanethiol (1-DDT).

[0115] (1.12) Comparative Example 9 A quantum dot-containing composition 12 was prepared in the same manner as in Example 1, except as follows: In this example, 3-methoxybutyl 3-mercaptopropionate was used instead of 1-dodecanethiol (1-DDT).

[0116] The thiol compounds used in the preparation of the quantum dot-containing compositions 1 to 12 described above are shown below.

[0117]

[0118]

[0119] (2) Evaluation (2.1) Preparation of cured film Using a spin coater (manufactured by Mikasa Corporation), each of the quantum dot-containing compositions prepared above was applied to a 5 cm square alkali-free glass substrate to form a coating film, which was then dried on a 90°C hot plate for 60 seconds. Next, the obtained coating film was placed in a nitrogen-purging box. The nitrogen-purging box was filled with nitrogen, and the irradiation dose was 1500 mJ / cm². ２ The coating was cured by ultraviolet irradiation (irradiation wavelength 395 nm), obtaining a cured film with a thickness of 10 μm. For ultraviolet irradiation, an ultraviolet irradiation device manufactured by Fusion UV Systems Japan Co., Ltd. (light source: Semiray® UV 4003 manufactured by Heraeus K.K.) was used.

[0120] (2.2) Curability For each 5 cm square cured film on the alkali-free glass substrate obtained above, a clean paper was brought into contact with a 1.5 cm square area including the center portion. The clean paper was peeled off, and the contact area between the clean paper and the cured film was visually inspected, and the curability of the cured film was evaluated according to the following criteria. The evaluation results are shown in Table 1. A: The clean paper was clean and there was no trace of contact between the clean paper and the cured film. B: The clean paper was clean, but there was trace of contact between the clean paper and the cured film. C: The clean paper was dirty.

[0121] (2.3) Luminescence Characteristics Each of the cured films obtained above was cut into 1 cm square pieces to be used as samples, and the fluorescence quantum yield (QY), light absorption rate (Abs), maximum emission peak wavelength (λmax), and maximum emission peak intensity were measured using a quantum yield analyzer (product name: C11347, manufactured by Hamamatsu Photonics®) with excitation light at 450 nm.

[0122] The luminescence characteristics of each cured film were evaluated according to the following criteria based on the ratio of its fluorescence quantum yield QY to the fluorescence quantum yield QYcomp1 of Comparative Example 1, which does not contain a thiol compound (QY / QYcomp1). The measurement and evaluation results are shown in Table 1. A: The fluorescence quantum yield ratio QY / QYcomp1 is 1.22 or higher. B: The fluorescence quantum yield ratio QY / QYcomp1 is greater than 1.0 and less than 1.22. C: The fluorescence quantum yield ratio QY / QYcomp1 is 1.0 or lower.

[0123]

[0124]

[0125] As shown in Table 1, the cured films of Examples 1 to 3 exhibited excellent luminescence properties and curability. In contrast, the cured films of Comparative Examples 2 to 5 had inferior luminescence properties despite having higher concentrations of thiol compounds than Examples 1 to 3. Furthermore, the cured films of Comparative Examples 2 to 5 also had inferior curability due to their lower concentrations of curing components. Moreover, the luminescence properties of the cured films of Examples 1 to 3 were superior to those of the cured films of Comparative Examples 7 to 9. From this, it can be seen that the improvement in luminescence properties in the cured films of Examples 1 to 3 is also attributable to the structural site bonded to the mercapto group in the monofunctional thiol compound represented by general formula (I).

[0126] 1...Display device, 2...Dimming device, 3...Wavelength conversion substrate, 4...Adhesive layer, 21...Substrate, 22...Multilayer wiring layer, 23...Light-emitting diode, 31...Transparent substrate, 32...Black matrix, 33...Color filter, 33B...Underlayer, 33G...Second coloring layer, 33R...First coloring layer, 34...Resin layer, 35...Inorganic coating layer, 36B...Filling layer, 36G...Filling layer, 36R...Filling layer, 37...Inorganic barrier layer.

Claims

1. A quantum dot-containing composition comprising quantum dots, a polyfunctional (meth)acrylate, a photopolymerization initiator, and a monofunctional thiol compound represented by general formula (I). SH-X-R (I) where X is -CH ２ -CH ２ The dash (-) represents a hyphen, and R represents an aliphatic organic group containing nine or more carbon atoms.

2. The quantum dot-containing composition according to claim 1, wherein the aliphatic organic group is any one of an aliphatic hydrocarbon group, an aliphatic hydrocarbon group containing an ester bond, an aliphatic hydrocarbon group containing an ether bond, or an aliphatic hydrocarbon group containing a ketone group.

3. The quantum dot-containing composition according to claim 1 or 2, wherein the monofunctional thiol compound is contained in a concentration of 3 to 10% by mass relative to the total mass of nonvolatile components in the composition.

4. The quantum dot-containing composition according to any one of claims 1 to 3, further comprising light-scattering particles.

5. The quantum dot-containing composition according to any one of claims 1 to 4, comprising one or more monofunctional thiol compounds selected from 1-dodecanethiol, 2-ethylhexyl 3-mercaptopropionate, and tridecyl 3-mercaptopropionate.

6. The content of the monofunctional thiol compound in the quantum dot-containing composition is M ＳＨ The content of the quantum dots is M ＱＤ In this case, the mass ratio M ＳＨ / M ＱＤ A quantum dot-containing composition according to any one of claims 1 to 5, wherein the value is in the range of 0.08 to 0.

5.

7. The quantum dot-containing composition according to any one of claims 1 to 6, wherein the polyfunctional (meth)acrylate is contained in a concentration of 50 to 75% by mass relative to the total mass of nonvolatile components in the composition.

8. A quantum dot-containing composition comprising quantum dots, a polyfunctional (meth)acrylate, a photopolymerization initiator, and a monofunctional thiol compound represented by general formula (I), wherein the monofunctional thiol compound comprises one or more selected from 1-dodecanethiol, 2-ethylhexyl 3-mercaptopropionate, and tridecyl 3-mercaptopropionate, and the monofunctional thiol compound is contained in a concentration of 3 to 10% by mass relative to the total mass of nonvolatile components, and the polyfunctional (meth)acrylate is contained in a concentration of 45 to 90% by mass relative to the total mass of nonvolatile components. SH-X-R (I) In the formula, X is -CH ２ -CH ２ The dash (-) represents a hyphen, and R represents an aliphatic organic group containing nine or more carbon atoms.

9. A quantum dot-containing composition according to any one of claims 1 to 8, used for forming a wavelength conversion layer.

10. A wavelength conversion layer comprising a cured product of a quantum dot-containing composition according to any one of claims 1 to 9.

11. A wavelength conversion substrate comprising the wavelength conversion layer described in claim 10.

12. A display device comprising the wavelength conversion substrate according to claim 11.

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