WO2019065068A1

WO2019065068A1 - Microcapsule and film

Info

Publication number: WO2019065068A1
Application number: PCT/JP2018/032212
Authority: WO
Inventors: 高央溝口
Original assignee: 富士フイルム株式会社
Priority date: 2017-09-26
Filing date: 2018-08-30
Publication date: 2019-04-04
Also published as: JPWO2019065068A1; JP6884873B2

Abstract

The present invention addresses the problem of providing: a microcapsule having excellent quantum yield and durability; and a film containing the microcapsule. The microcapsule according to the present invention contains a core substance and an outer shell layer that covers the core substance, wherein the core substance contains quantum dots and a dispersion medium that has a liquid form at 25°C, the material for the outer shell layer is at least one resin selected from the group consisting of a urea-based resin, a melamine-based resin, a polyurethane-based resin, a polyurea-based resin, a polyamide-based resin and a copolymer resin composed of at least two of these resins, the core substance has a radius of 10 nm to 10 μm inclusive, the outer shell layer has a thickness of 5 nm to 9 μm inclusive, and the ratio of the thickness of the outer shell layer to the radius of the core substance is 0.50 to 0.90 inclusive.

Description

Microcapsule and film

The present invention relates to microcapsules and films.

Colloidal semiconductor nanoparticles (quantum dots) of single nanosize level obtained by chemical synthesis method in solution containing metallic elements have begun to be put into practical use as fluorescent materials in wavelength conversion films for some display applications Also, applications to biological labels, light emitting diodes, solar cells, thin film transistors and the like are expected.
On the other hand, since quantum dots have a large specific surface area and high surface activity, methods of microencapsulating for stabilization etc. are known (for example, Patent Document 1).

JP, 2017-112174, A

Recently, with the progress of commercialization of quantum dots, further improvement of quantum yield is required. In addition, since quantum dots are easily degraded by oxygen and the like in the air, it is required to improve the difficulty (durability) of lowering the quantum yield when stored in the air.
Under these circumstances, when the present inventors manufactured microcapsules with reference to Patent Document 1, it became clear that the quantum yield and the durability do not necessarily satisfy the level required nowadays.

Then, in view of the said situation, an object of this invention is to provide the film containing the microcapsule which was excellent in the quantum yield and durability, and the said microcapsule.

As described above, it is known that quantum dots are easily degraded by oxygen and the like in the air.
Under these circumstances, the inventor of the present invention examined the ratio of the radius of the core material of the microcapsule (the internal radius of the microcapsule) to the thickness of the outer shell layer. It has become clear that a correlation can be seen, and by setting the above ratio to a specific range, it is possible to significantly suppress the degradation and achieve a high level of quantum yield.
The present invention is based on the above findings, and the specific configuration thereof is as follows.

(1) A microcapsule having a core substance and an outer shell layer covering the core substance,
The core material contains quantum dots and a dispersion medium that is liquid at 25 ° C .;
The material of the outer shell layer is at least one selected from the group consisting of urea resins, melamine resins, polyurethane resins, polyurea resins, polyamide resins, and two or more of these copolymer resins. It is a resin,
The radius of the core substance is 10 nm or more and 10 μm or less,
The thickness of the outer shell layer is 5 nm or more and 9 μm or less,
The microcapsule whose ratio of the thickness of the said outer shell layer with respect to the radius of the said core substance is 0.50-0.90.
(2) The above quantum dot is
Hydrophobic having at least one group selected from the group consisting of carboxy group, amino group, thiol group, phosphido group, phosphine oxide group, phosphine sulfide group, phosphonic acid group and sulfide group, having 6 or more carbon atoms The microcapsule according to (1) above, which has a sex ligand.
(3) The microcapsule according to (1) or (2), wherein the ratio of the thickness of the outer shell layer to the radius of the core substance is 0.60 or more and 0.90 or less.
(4) The microcapsule as described in said (3) whose ratio of the thickness of the said outer shell layer with respect to the radius of the said core substance is 0.65 or more and less than 0.90.
(5) The microcapsule according to (4), wherein the ratio of the thickness of the outer shell layer to the radius of the core substance is 0.65 or more and 0.85 or less.
(6) The microcapsule according to any one of the above (1) to (5), wherein the boiling point of the dispersion medium is 120 ° C. or more.
(7) The microcapsule as described in said (6) whose boiling point of the said dispersion medium is 180 degreeC or more.
(8) Any of the above (1) to (7), wherein the material of the outer shell layer is at least one resin selected from the group consisting of polyurethane resins, polyurea resins, and polyurethaneurea resins The microcapsule described in.
(9) A method for producing a microcapsule, which produces the microcapsule according to any one of (1) to (8) above,
A dispersion liquid containing quantum dots, a low polarity dispersion medium which is liquid at 25 ° C., and a monomer which becomes a resin which is a material of an outer shell layer of the microcapsule after polymerization, and a solvent having a polarity higher than the dispersion medium Mixing, at least mixing with a surfactant to obtain a mixed solution,
By heating the mixture while stirring, the micelles of the dispersion are formed, and the monomer is polymerized at the interface of the micelles to form a core substance containing the quantum dots and the dispersion medium. A microencapsulation step of coating with a resin-made outer shell layer;
A method of manufacturing a microcapsule, comprising:
(10) A film containing the microcapsule according to any one of the above (1) to (8).

As described below, according to the present invention, a microcapsule having excellent quantum yield and durability, and a film containing the above-mentioned microcapsule can be provided.

FIG. 1 is a schematic cross-sectional view of one embodiment of the microcapsule of the present invention. FIG. 2A is a schematic view of an embodiment of a preferred embodiment of the method of producing the microcapsule of the present invention. FIG. 2B is a schematic view of an embodiment of a preferred embodiment of the method of producing the microcapsule of the present invention.

Hereinafter, the present invention will be described in detail.
Although the description of the configuration requirements described below may be made based on the representative embodiments of the present invention, the present invention is not limited to such embodiments.
In the present specification, a numerical range represented using “to” means a range including numerical values described before and after “to” as the lower limit value and the upper limit value.

[1] Microcapsule The microcapsule of the present invention has a core substance and an outer shell layer covering the core substance.
Here, the core material contains quantum dots and a dispersion medium that is liquid at 25 ° C.
The material of the outer shell layer is at least one selected from the group consisting of urea resins, melamine resins, polyurethane resins, polyurea resins, polyamide resins, and two or more of these copolymer resins. It is a kind of resin.
The radius of the core substance is 10 nm to 10 μm, the thickness of the outer shell layer is 5 nm to 9 μm, and the ratio of the thickness of the outer shell layer to the radius of the core substance is 0.50 to 0. It is 90 or less.

The microcapsule of the present invention is considered to exhibit a desired effect by taking such a configuration. The reason is not clear in detail, but is presumed to be as follows.
In the microcapsules of the present invention, the core material containing quantum dots is protected by an outer shell layer made of a specific resin. The outer shell layer is considered to have a role of blocking factors (such as oxygen) that deteriorate the quantum dots. Here, from the study of the present inventor, it is known that simply increasing the thickness of the shell layer does not necessarily improve the durability. For example, it has been found that even if the shell layer is thickened, the durability is insufficient when the radius (inner radius) of the core material is also large. This is because, even if the shell layer is thickened, if the ratio of the thickness of the shell layer to the radius (inner radius) of the core material is small, the microcapsules are distorted and the deterioration factor such as oxygen is not sufficiently blocked It is guessed that.
On the other hand, in the microcapsules of the present invention, not only the absolute value of the thickness of the shell layer is specified, but also the ratio of the thickness of the shell layer to the inner radius is in a specific range. And the distortion as described above is less likely to occur. As a result, the microcapsules of the present invention are considered to exhibit extremely excellent durability.

First, the microcapsules of the present invention will be described with reference to the drawings. However, the microcapsule of the present invention is not limited to this.
FIG. 1 is a schematic cross-sectional view of one embodiment of the microcapsule of the present invention.
The microcapsule 10 shown in FIG. 1 has a core substance 3 containing quantum dots 1 and a dispersion medium 2 which is liquid at 25 ° C., and an outer shell layer 4 covering the core substance 3.
Here, the material of the outer shell layer 4 is at least selected from the group consisting of a urea resin, a melamine resin, a polyurethane resin, a polyurea resin, a polyamide resin, and two or more of these copolymer resins. It is one kind of resin.
Also, the core substance 3 is spherical with a radius r, and this core substance 3 is covered with the outer shell layer 4 of thickness d. The microcapsules 10 are spherical with a radius r + d.
The radius r of the core substance 3 is 10 nm to 10 μm, the thickness d of the outer shell layer 4 is 5 nm to 9 μm, and the ratio of the thickness d of the outer shell layer to the radius r of the core substance (d / r) Is 0.50 or more and 0.90 or less.

Hereinafter, each structure of the microcapsule of this invention is explained in full detail.

[Core substance]
The core material contains quantum dots and a dispersion medium that is liquid at 25 ° C.
The core material preferably contains a plurality of quantum dots because the effect of the present invention is more excellent.

[Quantum dot]
The quantum dot contained in the core substance refers to a semiconductor nanoparticle having a quantum confinement effect.
The particle size of the quantum dots (semiconductor nanoparticles) is generally in the range of 1 to 10 nm.
When the quantum dot absorbs light from the excitation source and reaches an energy excited state, it emits energy corresponding to the energy band gap of the quantum dot. Thus, by adjusting the size of the quantum dot or the composition of the substance, the energy band gap can be adjusted, and energy of various levels of wavelength bands can be obtained.

<Material>
The material of the quantum dot is not particularly limited, but specific examples thereof include simple substances of Group IV elements such as carbon, silicon, germanium and tin, simple substances of Group V elements such as phosphorus (black phosphorus), and VI such as selenium and tellurium A single group element, a compound comprising a plurality of group IV elements such as silicon carbide (SiC), tin oxide (IV) (SnO ₂ ), tin sulfide (II, IV) (Sn (II) Sn (IV) S ₃ ) , Tin sulfide (IV) (SnS ₂ ), tin sulfide (II) (SnS), tin selenide (II) (SnSe), tin (II) telluride (SnTe), lead sulfide (II) (PbS), selenium Group IV-VI semiconductors such as lead (II) halide (PbSe) and lead (II) telluride (PbTe), boron nitride (BN), boron phosphide (BP), boron arsenide (BAs), aluminum nitride (AlN) , Phosphide aluminum (AlP), aluminum arsenide (AlAs), aluminum antimonide (AlSb), gallium nitride (GaN), gallium phosphide (GaP), gallium arsenide (GaAs), gallium antimonide (GaSb), indium nitride (InN), phosphorus Group III-V semiconductors such as indium phosphide (InP), indium arsenide (InAs) and indium antimonide (InSb), aluminum sulfide (Al ₂ S ₃ ), aluminum selenide (Al ₂ Se ₃ ), gallium sulfide (Ga ₂₎ S ₃ ), Gallium selenide (Ga ₂ Se ₃ ), Gallium telluride (Ga ₂ Te ₃ ), Indium oxide (In ₂ O ₃ ), Indium sulfide (In ₂ S ₃ ), Indium selenide (In ₂ Se ₃₎ ) and III such telluride, indium _(in 2 Te ₃₎ III-VII semiconductors such as Group VI semiconductors, thallium (I) chloride (TlCl), thallium (I) bromide (TlBr) and thallium (I) iodide (TlI), zinc oxide (ZnO), zinc sulfide (ZnS) ), Zinc selenide (ZnSe), zinc telluride (ZnTe), cadmium oxide (CdO), cadmium sulfide (CdS), cadmium selenide (CdSe), cadmium telluride (CdTe), mercury sulfide (HgS), selenization II-VI semiconductors such as mercury (HgSe) and mercury telluride (HgTe), arsenic (III) sulfide (As ₂ S ₃ ), arsenic selenide (III) (As ₂ Se ₃ ), arsenic telluride (III) _(As 2 _Te 3), antimony sulfide _{_{(III) (Sb 2 S 3}} ), selenium antimony _{_{(III) (Sb 2 Se 3}} ), tellurium Kaa Chimon _{_{(III) (Sb 2 Te 3}} ), bismuth sulfide _{_{(III) (Bi 2 S 3}} ), bismuth selenide _{_{(III) (Bi 2 Se 3}} ) and bismuth telluride _{_{(III) (Bi 2 Te 3}} ) , such as Examples thereof include V-VI group semiconductors, etc. One of these may be used or two or more may be used in combination. The material of the quantum dot is preferably at least one selected from the group consisting of III-V semiconductors and II-VI semiconductors because the effects of the present invention are more excellent.

<Hydrophobic ligand>
The above-mentioned quantum dot has 6 or more carbon atoms, a carboxy group (—COOH), an amino group (—NR ₂ : R is a hydrogen atom or a hydrocarbon group), a thiol group (the hydrogen atom or hydrocarbon group). -SH), phosphide group (-PR ₂ : R is a hydrogen atom or a hydrocarbon group), phosphine oxide group (-PR ₂ (= O): R is a hydrogen atom or a hydrocarbon group), phosphine sulfide group (-PR ₂ (= S): R is a hydrogen atom or a hydrocarbon group, at least one group selected from the group consisting of a phosphonic acid group (-P (= O) (OH) ₂ ) and a sulfide group (-S-) It is preferred to have a hydrophobic ligand.
The number of carbon atoms is preferably 8 to 35, and more preferably 10 to 25 because the effect of the present invention is more excellent.
The group is preferably a thiol group because the effect of the present invention is more excellent.
Specific examples of the hydrophobic ligand include oleylamine, dodecylamine, dodecanethiol, 1,2-hexadecanethiol and trioctylphosphine oxide.
The quantum dot preferably has the hydrophobic ligand on the surface.

<Preferred embodiment>
It is preferable that the said quantum dot is a core-shell particle from the reason which the effect of this invention is more excellent.
As a first preferred embodiment in the case where the quantum dot is a core-shell particle, for example, a core containing a group III element and a group V element, and a group II element and a group VI covering at least a part of the surface of the core The aspect (single shell form) which has a shell containing an element is mentioned.
Further, as a second preferred embodiment in the case where the quantum dot is a core-shell particle, for example, a core containing a group III element and a group V element, and a first shell covering at least a part of the surface of the core And a second shell covering at least a part of the first shell (multi-shell shape).

<Core>
When the quantum dot is a core-shell particle, the core of the core-shell particle is preferably a so-called III-V semiconductor containing a group III element and a group V element because the effect of the present invention is more excellent.

(Group III element)
Specific examples of the group III element include, for example, indium (In), aluminum (Al), and gallium (Ga). Among them, In is particularly preferably In because the effect of the present invention is more excellent. Is preferred.

(Group V element)
Specific examples of the group V element include P (phosphorus), N (nitrogen), and As (arsenic), and the like. Among them, P is P because the effect of the present invention is more excellent. Is preferred.

In the present invention, a III-V group semiconductor appropriately combining the above-described examples of the group III element and the group V element can be used as the core, but InP, InN, or InAs is preferable, and InP is more preferable.

In the present invention, it is preferable to further contain a Group II element in addition to the Group III element and the Group V element mentioned above because the effect of the present invention is more excellent, and in particular when the core is InP, Group II By doping Zn as an element, the lattice constant is reduced, and lattice matching with a shell (for example, GaP, ZnS or the like described later) having a smaller lattice constant than InP is enhanced.

<Shell>
When the quantum dot is a single-shell core-shell particle, the shell is a material covering at least a part of the surface of the core, and contains a group II element and a group VI element because the effect of the present invention is more excellent. So-called II-VI semiconductors are preferred.
Here, in the present invention, whether or not the shell covers at least a part of the surface of the core can be determined, for example, by energy dispersive X-ray spectroscopy (TEM (Transmission Electron Microscope)) using a transmission electron microscope. It can also be confirmed by composition distribution analysis by EDX (Energy Dispersive X-ray spectroscopy).

(Group II element)
Specific examples of the Group II element include zinc (Zn), cadmium (Cd), and magnesium (Mg), among which Zn is particularly preferable because the effect of the present invention is more excellent. Is preferred.

(Group VI element)
Specific examples of the Group VI element include, for example, sulfur (S), oxygen (O), selenium (Se), and tellurium (Te). Among them, the reason why the effect of the present invention is more excellent From the above, S or Se is preferable, and S is more preferable.

In the present invention, although a II-VI group semiconductor appropriately combining the above-described examples of the group II element and the group VI element can be used as the shell, it is the same as the core described above because the effect of the present invention is more excellent. Or similar crystal systems are preferred.
Specifically, ZnS and ZnSe are preferable because the effect of the present invention is more excellent, and ZnS is more preferable from the viewpoint of safety and the like.

<First shell>
When the quantum dot is a core-shell particle having a multi-shell shape, the first shell is a material covering at least a part of the surface of the core.
Here, in the present invention, whether or not the first shell covers at least a part of the surface of the core can be determined, for example, by energy dispersive X-ray spectroscopy (TEM-EDX) using a transmission electron microscope. It can also be confirmed by composition distribution analysis.

In the present invention, it is preferable that the first shell contains a group II element or a group III element because it is easy to suppress interface defects with the core.
Here, when the first shell contains a group III element, the group III element contained in the first shell is a group III element different from the group III element contained in the core described above.
Also, as the first shell containing a Group II element or a Group III element, for example, a Group III-VI semiconductor containing a Group III element and a Group VI element in addition to a Group II-VI semiconductor and a Group III-V semiconductor described later (For example, Ga ₂ O ₃ , Ga ₂ S _{3 and the} like) and the like.

In the present invention, the first shell contains a group II-VI semiconductor containing a group II element and a group VI element or a group III element and a group V element because a high quality crystal phase with few defects is obtained. The semiconductor device is preferably a group III-V semiconductor, more preferably a group III-V semiconductor having a small difference in lattice constant with the core described above.
Here, when the first shell is a group III-V semiconductor, the group III element contained in the group III-V semiconductor is a group III element different from the group III element contained in the core described above.

(1) II-VI Group Semiconductor Examples of the II group element contained in the above-mentioned II-VI semiconductor include zinc (Zn), cadmium (Cd), magnesium (Mg) and the like. Among them, Zn is preferable because the effect of the present invention is more excellent.
Specific examples of the group VI element contained in the group II-VI semiconductor include sulfur (S), oxygen (O), selenium (Se), and tellurium (Te). Among these, S or Se is preferable, and S is more preferable because the effect of the present invention is more excellent.

As the first shell, a II-VI group semiconductor obtained by combining the above-described examples of the II group element and the VI group element can be used as appropriate, but the same or similar core as the above core can be obtained because the effect of the present invention is more excellent. It is preferably crystalline (eg, zinc blende structure). Specifically, ZnSe, ZnS, or a mixed crystal thereof is preferable, and ZnSe is more preferable because the effect of the present invention is more excellent.

(2) Group III-V Semiconductor Specific examples of group III elements contained in the group III-V semiconductor include indium (In), aluminum (Al), and gallium (Ga). Among them, Ga is preferable because the effect of the present invention is more excellent. As described above, the group III element contained in the group III-V semiconductor is a group III element different from the group III element contained in the core described above, and, for example, the group III element contained in the core is In In such a case, the Group III element contained in the Group III-V semiconductor is Al, Ga or the like.
Specific examples of the group V element contained in the above-mentioned group III-V semiconductor include P (phosphorus), N (nitrogen), and As (arsenic), and the like, and the present invention is particularly preferably It is preferable that it is P because the effect of is more excellent.

As the first shell, a group III-V semiconductor obtained by appropriately combining the examples of the group III element and the group V element described above can be used, but the same or similar as the core described above because the effect of the present invention is more excellent. It is preferably crystalline (eg, zinc blende structure). Specifically, GaP is preferable.

In the present invention, it is preferable that the difference in lattice constant between the core and the first shell described above be small because the surface defects of the obtained core-shell particles are reduced. Specifically, the core and the first shell described above It is preferable that the difference of the lattice constant of is 10% or less.
Specifically, when the above-mentioned core is InP, as described above, the first shell is ZnSe (difference in lattice constant: 3.4%) or GaP (difference in lattice constant: 7.1%) In particular, it is more preferable to use GaP which is the same III-V semiconductor as the core and which can easily form a mixed crystal state at the interface between the core and the first shell because the effect of the present invention is more excellent. .

Further, in the present invention, when the first shell is a III-V group semiconductor, other elements (for example, the above-described elements) may be used as long as the magnitude relation of the band gap with the core (core <first shell) is not affected. Group II element and group VI element) may be contained or doped. Similarly, in the case where the first shell is a II-VI group semiconductor, other elements (for example, the aforementioned group III elements and the above-described elements) can be used as long as the magnitude relation of the band gap with the core (core <first shell) is not affected. Group V element) may be contained or doped.

<Second shell>
When the quantum dot is a core-shell particle having a multi-shell shape, the second shell is a material covering at least a part of the surface of the first shell described above.
Here, in the present invention, whether or not the second shell covers at least a part of the surface of the first shell can be determined, for example, by energy dispersive X-ray spectroscopy (TEM-EDX) using a transmission electron microscope. It is possible to confirm also by composition distribution analysis by.

In the present invention, the second shell contains a group II element and a group VI element because it suppresses interface defects with the first shell and provides a high quality crystal phase with few defects. It is preferable that the material is a semiconductor or a group III-V semiconductor containing a group III element and a group V element, and a shell having high reactivity of the material itself and higher crystallinity can be easily obtained. It is more preferable to be a group semiconductor.
In addition, as the group II element, the group VI element, the group III element and the group V element, those described in the first shell can be mentioned.

As the second shell, a II-VI group semiconductor obtained by combining the above-described examples of the II group element and the VI group element can be used as appropriate, but the same or similar core as the above core can be obtained because the effect of the present invention is more excellent. It is preferably crystalline (eg, zinc blende structure). Specifically, ZnSe, ZnS, or a mixed crystal thereof is preferable, and ZnS is more preferable.

Although the III-V group semiconductor which combined the illustration of the III group element and the V group element mentioned above suitably can be used as the 2nd shell, it is the same as or similar to the core mentioned above because the effect of the present invention is more excellent. It is preferably crystalline (eg, zinc blende structure). Specifically, GaP is preferable.

In the present invention, it is preferable that the difference in lattice constant between the first shell and the second shell described above be small, because the surface defects of the obtained core-shell particles are reduced. Specifically, with the first shell described above The difference in lattice constant with the second shell is preferably 10% or less.
Specifically, when the first shell described above is GaP, as described above, the second shell is ZnSe (difference in lattice constant: 3.8%), or ZnS (difference in lattice constant: 0.8%) Is preferable, and ZnS is more preferable.

Further, in the present invention, when the second shell is a II-VI group semiconductor, other elements (for example, the above-described elements) can be used as long as the magnitude relationship of the band gap with the core (core <second shell) is not affected. Group III elements and group V elements) may be contained or doped. Similarly, when the second shell is a III-V group semiconductor, other elements (for example, the above-mentioned II group elements and the above-described elements) can be used as long as the magnitude relationship of the band gap with the core (core <second shell) is not affected. Group VI element) may be contained or doped.

In the present invention, the above-mentioned core, the first shell, and the second shell are all crystal systems having a zinc-blende structure because epitaxial growth is facilitated and interface defects between layers are easily suppressed. Preferably there.

Further, in the present invention, the band gap of the core is the smallest among the cores, the first shell and the second shell described above because the probability that excitons stay in the core increases and the light emission efficiency becomes higher. Preferably, the core and the first shell are core-shell particles exhibiting a band structure of type 1 (type I).

<Method of manufacturing quantum dot>
The method for producing the quantum dot is not particularly limited, and a known method can be used.
When the quantum dot is a core-shell particle having a core of a III-V semiconductor and a shell of a II-VI semiconductor covering at least a part of the core, the method of producing a quantum dot is more excellent in the effect of the present invention For the reason, after adding a Group III raw material and a Group V raw material to the solvent and heating to form a core of the III-V semiconductor, a Group II raw material and a Group VI raw material are added and heated. Preferably, a method of forming a shell of a II-VI semiconductor covering at least a part of the core is preferable.
In addition, as a method of producing a quantum dot having a hydrophobic ligand described above, for example, a method of adding a hydrophobic ligand when producing a quantum dot, and a method of using a hydrophobic ligand as a raw material of quantum dots ( For example, the method of using an alkyl thiol as a VI group raw material etc. are mentioned.

(solvent)
The above solvent is preferably a nonpolar solvent because the effect of the present invention is more excellent.
Examples of nonpolar solvents include aliphatic saturated hydrocarbons such as n-decane, n-dodecane, n-hexadecane and n-octadecane; aliphatics such as 1-undecene, 1-dodecene, 1-hexadecene and 1-octadecene Unsaturated hydrocarbon; trioctyl phosphine; and the like. Among them, aliphatic unsaturated hydrocarbons having 12 or more carbon atoms are preferable, and 1-octadecene is more preferable because the effect of the present invention is more excellent.

(Group III raw material)
Examples of the source III include indium chloride, indium oxide, fatty acid indium (eg, indium acetate and indium myristate), indium nitrate, indium sulfate, and indium acid; aluminum phosphate, aluminum acetylacetonate aluminum, aluminum chloride, Aluminum fluoride, aluminum oxide, aluminum nitrate, and aluminum sulfate; and acetylacetonatogallium, gallium chloride, gallium fluoride, gallium oxide, gallium nitrate, and gallium sulfate; Or two or more may be used in combination.
Among them, an indium compound is preferable because the quantum yield and durability of the obtained microcapsule are more excellent (hereinafter, also simply referred to as “more excellent in the effect of the present invention”), and impurity ion such as chloride is preferable. It is more preferable to use indium acetate which is difficult to be incorporated into the core and which can easily realize high crystallinity.

(Group V raw material)
Examples of the group V raw materials include tristrialkylsilylphosphine, trisdialkylsilylphosphine, and trisdialkylaminophosphine; arsenic oxide, arsenic chloride, arsenic sulfate, arsenic bromide, and arsenic iodide; Nitrogen, nitric acid, and ammonium nitrate; and the like can be mentioned, and these may be used alone or in combination of two or more.
Among them, a compound containing P is preferable because the effect of the present invention is more excellent. For example, it is preferable to use tristrialkylsilyl phosphine or trisdialkylamino phosphine. Specifically, tristrimethylsilyl is preferable. It is more preferred to use phosphine.

(Group II raw material)
Examples of the group II raw materials include dimethyl zinc, diethyl zinc, zinc carboxylate, acetylacetonato zinc, zinc iodide, zinc bromide, zinc chloride, zinc fluoride, zinc carbonate, zinc cyanide, zinc nitrate, Zinc oxide, zinc peroxide, zinc perchlorate, fatty acid zinc (eg, zinc acetate, zinc stearate), zinc sulfate and the like may be mentioned, and one or more of these may be used alone. You may use together.
Among them, it is preferable to use fatty acid zinc because the effect of the present invention is more excellent.

(Group VI raw material)
Examples of the group VI raw materials include sulfur, alkyl thiols, trialkyl phosphine sulfides, trialkenyl phosphine sulfides, alkyl amino sulfides, alkenyl amino sulfides, cyclohexyl isothiocyanate, diethyl dithiocarbamic acid, and diethyl dithiocarbamic acid; Phosphine selenium, trialkenyl phosphine selenium, alkylaminoselenium, alkenylaminoselenium, trialkylphosphine telluride, trialkenylphosphine telluride, alkylaminotelluride, and alkenylaminotelluride; Or two or more may be used in combination.
Among them, it is preferable to use alkylthiol because the effect of the present invention is more excellent. Specifically, it is more preferable to use dodecanethiol or octanethiol, and it is more preferable to use dodecanethiol.

<Content>
The content of the quantum dots in the core substance is not particularly limited, but is preferably 0.1 to 50% by mass, and more preferably 0.5 to 30% by mass because the effect of the present invention is more excellent. More preferable.
The above quantum dots may be used alone or in combination of two or more.

[Dispersion medium]
The dispersion medium contained in the core substance is not particularly limited as long as the dispersion medium is a liquid at 25 ° C.
The dispersion medium that is liquid at 25 ° C. may be a highly polar dispersion medium (highly polar dispersion medium) (for example, water) or a low polarity dispersion medium (lowly polar dispersion medium). It is preferable that it is a low-polar dispersion medium from the reason of being excellent, and it is preferable that it is a low-polar dispersion medium whose polarity is lower than water.

Examples of the low-polar dispersion medium include aromatic hydrocarbons such as toluene and mesitylene; halogenated alkyl such as chloroform; and aliphatics such as hexane, octane, n-decane, n-dodecane, n-hexadecane and n-octadecane Saturated hydrocarbons; aliphatic unsaturated hydrocarbons such as 1-undecene, 1-dodecene, 1-hexadecene and 1-octadecene; trioctyl phosphine; (meth) acrylates; etc., among which the effect of the present invention is For the reason of being more excellent, aromatic hydrocarbons and (meth) acrylates are preferable, and (meth) acrylates are more preferable.

Examples of the (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, cyclohexyl (meth) acrylate, tetrahydrofulf Furyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, dodecyl (meth) acrylate, isononyl (meth) acrylate, isodecinonyl (meth) acrylate, stearyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxy Propyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, isobornyl (meth) acrylate, butoxydiethylene glycol (meth) acrylate, benzyl ) Acrylate, dicyclohexyl (meth) acrylate, 2-dicyclohexyloxyethyl (meth) acrylate, morpholino (meth) acrylamide, phenoxyethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, ethylene glycol di (meth) acrylate, 1,1 4-butanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, nonanediol di (meth) acrylate, tris (2- (meth) acryloyloxyethyl) isocyanurate, 2-morpholinoethyl (meth) acrylate, 9-anthryl (meth) acrylate, 2,2-bis (4- (meth) acrylic acid Iroxyphenyl) propane, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, trans-1,4-cyclohexanediol di (meth) acrylate, dicyclopentenyloxyethyl methacrylate and dicyclopentanyl acrylate ( Among them, dicyclopentanyl acrylate (DCP) is preferable because the effect of the present invention is more excellent.

The boiling point of the dispersion medium which is liquid at 25 ° C. is not particularly limited, but is preferably 100 ° C. or more, more preferably 120 ° C. or more, and more preferably 180 ° C. or more because the effect of the present invention is more excellent. C., more preferably 200.degree. C. or more.
The upper limit of the boiling point of the dispersion medium which is liquid at 25 ° C. is not particularly limited, but is preferably 350 ° C. or less because the effect of the present invention is more excellent.
In addition, the said boiling point is taken as the value in 1 atmosphere.

The content of the dispersion medium which is liquid at 25 ° C. in the core substance is not particularly limited, but is preferably 50 to 99.9% by mass, and more preferably 70 to 99. More preferably, it is 5% by mass.
The dispersion medium which is liquid at 25 ° C. may be used alone or in combination of two or more.

[Other ingredients]
The core material may contain other components that do not correspond to any of the quantum dots and the dispersion medium that is liquid at 25 ° C., but the content of the other components in the core material is It is preferable that it is 5 mass% or less from the reason which the effect of invention is more excellent.

Outer shell layer
As mentioned above, the microcapsules of the present invention have an outer shell layer covering the core substance.
The material of the outer shell layer is at least one selected from the group consisting of urea resins, melamine resins, polyurethane resins, polyurea resins, polyamide resins, and two or more of these copolymer resins. It is a resin.
Here, "urea-based resin" is a resin obtained by polycondensation of urea and formaldehyde, and "melamine-based resin" is a resin obtained by polycondensation of melamine and formaldehyde, "polyurethane-based resin""Resin" is a resin having a urethane bond (-NHCOO-) in the main chain, "polyurea resin" is a resin having a urea bond (-NHCONH-) in the main chain, "polyamide resin" Is a resin having an amide bond (-NRCO-: R is a hydrogen atom or a hydrocarbon group) in the main chain.
In addition, as “these two or more copolymer resins”, for example, urea melamine resin (resin obtained by polycondensation of urea, melamine and formaldehyde), polyurethane urea resin (urethane bond and urea bond in main chain) Resin, polyurethane amide resin (resin having urethane bond and amide bond in main chain), polyurethane urea amide resin (resin having urethane bond, urea bond and amide bond in main chain), etc. .

The material of the outer shell layer is selected from the group consisting of a resin having a urethane bond and / or a urea bond in the main chain (polyurethane resin, polyurea resin, and polyurethaneurea resin, for the reason that the effect of the present invention is more excellent The resin is preferably at least one kind of resin), and more preferably a resin having a urethane bond and a urea bond in the main chain (polyurethane urea resin).

[Core substance radius, shell thickness, and thickness / radius]
Hereinafter, in the microcapsule of the present invention, the radius of the core substance (core substance radius), the thickness of the outer shell layer (outer shell layer thickness), and the ratio of the thickness of the outer shell layer to the radius of the core substance (thickness / radius) Will be explained.
The core substance and the microcapsules are usually spherical, but not limited thereto.

[Core material radius]
In the microcapsule of the present invention, the core material radius is 10 nm or more and 10 μm or less. Especially, it is preferable that they are 2 micrometers or more and 8 micrometers or less from the reason which the effect of this invention is more excellent.
Here, the core material radius corresponds to the internal radius of the microcapsule. For the core material radius (inner radius of microcapsules), observe at least 20 microcapsules with a SEM (scanning electron microscope), and calculate the radius of a circle having the same area as the projected area inside the outer shell layer , Find them by arithmetic averaging.

[Shell thickness]
In the microcapsule of the present invention, the shell thickness is 5 nm or more and 9 μm or less. Especially, it is preferable that they are 1 micrometer or more and 7 micrometers or less from the reason which the effect of this invention is more excellent.
Here, the shell layer thickness corresponds to a value obtained by subtracting the core material radius (the inner radius of the microcapsule) from the radius of the microcapsule. Outer shell layer thickness observes at least 20 microcapsules by SEM (scanning electron microscope), calculates the radius of a circle having the same area as the projected area outside the outer shell layer, and arithmetically averages them To determine the radius of the microcapsule, and then subtracting the core material radius (the internal radius of the microcapsule) from the radius of the microcapsule. The method of determining the core substance radius (the internal radius of the microcapsule) is as described above.

[Thickness / radius]
In the microcapsules of the present invention, the ratio (thickness / radius) of the thickness of the shell layer to the radius of the core substance is 0.50 or more and 0.90 or less. Especially, it is preferable that they are 0.60 or more and 0.90 or less, more preferably 0.65 or more and less than 0.90, and more preferably 0.70 or more and 0.85 or less because the effect of the present invention is more excellent. It is further preferred that

[Method of producing microcapsules]
The method for producing the microcapsules of the present invention is not particularly limited. For example, micelles of a dispersion containing quantum dots, a dispersion medium, and monomers are formed, and monomers are polymerized at the interface of the micelles to form quantum dots. A method of coating a core material containing a dispersion medium with an outer shell layer (Method 1), preparing microcapsules of only the outer shell layer beforehand, and containing quantum dots and a dispersion medium inside the outer shell layer The method (method 2) etc. which extract core materials are mentioned. Among them, the method 1 is preferable, and the method described in the following preferred embodiment is more preferable because the effect of the present invention is more excellent.

[Preferred embodiment]
The method of producing the microcapsules of the present invention is preferably a method comprising the following steps (1) to (2) (hereinafter also referred to as “the method of the present invention”) because the effects of the present invention are more excellent.
(1) A dispersion containing a quantum dot, a low polarity dispersion medium which is liquid at 25 ° C., and a monomer to be a resin which is a material of an outer shell layer of microcapsules after polymerization, and polarity higher than the above dispersion medium. A mixed solution is obtained by mixing at least a solvent and a surfactant, and mixing step (2) The mixed solution is heated with stirring to form micelles of the dispersion, and the interface of the micelles. Microcapsulation step of polymerizing the above-mentioned monomers and coating the core material containing the above-mentioned quantum dots and the above-mentioned dispersion medium with the outer shell layer made of the above-mentioned resin as a material

First, the method of the present invention will be described using the drawings. However, the method of the present invention is not limited to this.
FIGS. 2A and 2B are schematic views of an embodiment of a preferred embodiment (method of the present invention) of the method of producing the microcapsule of the present invention.
First, in the mixing step, a dispersion containing a quantum dot, a dispersion medium of low polarity that is liquid at 25 ° C., and a monomer that becomes a resin that is a material of the shell layer of microcapsules after polymerization, and the dispersion medium A mixed solution is obtained by mixing at least a highly polar solvent and a surfactant.
Next, the mixed solution is heated with stirring to form micelles 5 of the dispersion in the highly polar solvent 6 (FIG. 2A), and the monomer is polymerized at the interface of the micelles 5 to form the quantum The core material 3 containing the dots and the dispersion medium is covered with the outer shell layer 4 made of the resin. Thus, a microcapsule 10 having the core substance and an outer shell layer covering the core substance is obtained (FIG. 2B).

Each step will be described below.

<Mixing process>
The mixing step includes a dispersion containing a quantum dot, a dispersion medium of low polarity which is liquid at 25 ° C., and a monomer which becomes a resin which is a material of an outer shell layer of microcapsules after polymerization, and more polar than the dispersion medium. This is a step of obtaining a mixed solution by mixing at least a high solvent and a surfactant.

(Quantum dot)
The quantum dots are as described above.

(Dispersion medium)
The dispersion medium is not particularly limited as long as it is a liquid dispersion medium having low polarity at 25 ° C.
The low polarity dispersion medium which is liquid at 25 ° C. is preferably a polarity lower dispersion medium than water because the effect of the present invention is more excellent. Specific examples of the dispersion medium having a polarity lower than that of water are the same as the low polarity dispersion medium described above.

(monomer)
A monomer is a monomer used as resin which is a material of an outer shell layer mentioned above.
When the material of the shell layer is a urea-based resin, examples of the monomer include urea and formaldehyde. Moreover, as a monomer in case the material of an outer shell layer is a melamine resin, a melamine and formaldehyde are mentioned, for example. Moreover, as a monomer in case the material of outer shell layer is a polyurethane-type resin, polyisocyanate and a polyol are mentioned, for example. Moreover, as a monomer in case the material of outer shell layer is polyurea type resin, polyisocyanate is mentioned, for example. Moreover, as a monomer in case the material of outer shell layer is a polyamide-type resin, carboxylic acid (or carboxylic acid derivatives, such as carboxylic acid halide) and amine are mentioned.
For example, in the case of using a mixture of a dispersion containing polyisocyanate as a monomer, water, and a surfactant, the polyisocyanate reacts with water at the interface of micelles in the microcapsulation step to be described later, resulting in a polyurea system. An outer shell layer made of resin is formed.

In addition, when forming an outer shell layer by making two types of monomers react in the microencapsulation process mentioned later, one side is contained in a dispersion medium among two types of monomers, and the other is a dispersion liquid with water and surfactant. Preferably it is mixed with For example, in the case of using a mixture of a dispersion containing isophthaloyl dichloride, water, a surfactant and p-phenylenediamine, isophthaloyl dichloride and p- at the interface of micelles in the microcapsulation step described later. Phenylenediamine is polymerized to form an outer shell layer made of a polyamide resin.

(solvent)
The solvent is not particularly limited as long as it is a solvent having a polarity higher than that of the dispersion medium. Among them, water is preferable because the effect of the present invention is more excellent.

(Surfactant)
The surfactant is not particularly limited, and known ones can be used. Specific examples of the surfactant include anionic surfactants, nonionic surfactants (for example, polyvinyl alcohol (PVA)), cationic surfactants, amphoteric surfactants and the like.

<Microencapsulation process>
The microcapsulation step forms micelles of the dispersion by heating the mixture while stirring, and polymerizing the monomer at the interface of the micelles to contain the quantum dots and the dispersion medium. The core material is coated with an outer shell layer made of the above-mentioned resin.
The heating conditions are not particularly limited as long as the monomers react, but the temperature is preferably 35 to 100 ° C. and the time is 0.5 to 10 hours, because the effect of the present invention is more excellent. Is preferred.

The radius of the core substance can be controlled, for example, by the stirring conditions of the microencapsulation process. Also, the thickness and thickness / radius of the shell layer can be controlled, for example, by the quantitative ratio of the quantum dot and the dispersion medium to the monomer.

[2] Film The film of the present invention is a film containing the above-mentioned microcapsule of the present invention.
Such a film of the present invention exhibits excellent quantum yield and durability, so it is applied to, for example, wavelength conversion films for display applications, photoelectric conversion (or wavelength conversion) films of solar cells, biological markers, thin film transistors, etc. be able to. In particular, the film of the present invention is suitable for application to a down conversion or down shift type wavelength conversion film that absorbs light in the short wave region rather than the absorption edge of the quantum dot and emits longer wave light. .

Moreover, the film material as a base material which comprises the film of this invention is not specifically limited, A resin may be sufficient and a thin glass film may be sufficient.
Specifically, ionomers, polyethylene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polypropylene, polyester, polycarbonate, polystyrene, polyacrylonitrile, ethylene vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, ethylene-methacrylic acid A copolymer film, a resin material based on nylon etc. are mentioned.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto.

[Manufacturing of quantum dots]
J. AM. CHEM. SOC. Quantum dots were manufactured with reference to 2008, 130, 11588-11589.
Specifically, 0.1 mmol of indium myristate is dissolved in 10 ml of octadecene, heated to 250 ° C. under N ₂ , and then 0.1 mmol of tristrimethylsilyl phosphine is added and reacted at 250 ° C. for 1 hour for InP An octadecene solution was prepared.
Subsequently, while maintaining the temperature at 250 ° C., add 0.1 mmol of zinc stearate and 0.2 mmol of dodecanethiol and heat for 2 hours to obtain a quantum dot (Hydrophobic ligand) having InP (core) and ZnS (shell) An octadecene dispersion of (with dodecanethiol) was prepared.
10 ml of toluene and 30 ml of acetone were added to 10 ml of the obtained octadecene dispersion liquid of quantum dots to form precipitates of quantum dots. Thereafter, the precipitate was separated by centrifugation, and toluene was added to the precipitate to prepare a toluene dispersion of quantum dots.
Further, 20 ml of acetone was added to 10 ml of the obtained toluene dispersion of quantum dots to form a precipitate. Thereafter, the precipitate is separated by centrifugation, and 10 ml of dicyclopentanyl acrylate (DCP) (liquid at 25 ° C., boiling point: 279 ° C.) is added as a dispersion medium to prepare a DCP dispersion of quantum dots (liquid A). (Concentration of quantum dots in the dispersion: 1.0% by mass).

[Manufacture of microcapsules]
The microcapsules of each example and each comparative example were manufactured as follows.

Example 1
<Mixing process>
5% of the DCP dispersion (quantity A of the quantum dots) manufactured as described above and 1% by mass of polyol based on polyisocyanate (Takenate D-110N manufactured by Mitsui Chemicals, Inc.) (trimethylolpropane adduct of metaxylylene diisocyanate) A solution (solution C) was prepared by mixing 10 mL of the solution (solution B) to which (Exenol 823 manufactured by Asahi Glass Co., Ltd.) was added. And the mixed liquid was prepared by mixing the obtained dispersion liquid (C liquid) and 30 mL of PVA 5 mass% aqueous solution.

<Microencapsulation process>
The resulting mixed solution is heated at 75 ° C. for 2 hours while vigorously stirring to polymerize polyisocyanate and polyol at the interface of micelles, thereby forming a core substance containing quantum dots and a dispersion medium (DCP) as a main chain. And the outer shell layer made of a resin having a urethane bond and a urea bond (polyurethane urea resin) as a material. Thus, microcapsules were produced.
The reason why an outer shell layer made of a resin having a urethane bond and a urea bond in the main chain is formed so as to cover the core material containing the quantum dots and the dispersion medium is presumed as follows. That is, when the resulting mixed solution is heated while being vigorously stirred, the polyisocyanate and the polyol diffuse in the micelle, and the polyisocyanate reacts with water at the interface of the micelle to form a urea bond. Here, due to the high hydrophobicity of the quantum dots, the quantum dots and the dispersion medium are less likely to be close to the interface and closer to the center of the micelles. And, since the polyol is relatively hydrophilic, it tends to the interface side to separate from the quantum dot. Therefore, the polyol reacts with the polyisocyanate near the interface to form a urethane bond. Further, even if the polyisocyanate and the polyol react at the center of the micelle, they do not react with the quantum dots, and the compatibility with the quantum dots is not high, so they diffuse to the interface side. As a result, it is speculated that an outer shell layer formed of a resin (polyurethane urea resin) having a urethane bond and a urea bond in the main chain is formed so as to cover the core substance containing the quantum dots and the dispersion medium. .

<Core material radius, shell thickness, and thickness / radius>
SEM observation was performed about the obtained microcapsule, and the radius (core substance radius) of the core substance and the thickness (outer shell layer thickness) of the outer shell layer were measured. In addition, the ratio (thickness / radius) of the thickness of the shell layer to the radius of the core material was determined from the radius of the core material and the thickness of the shell layer. The results are shown in Table 1. The details of the method of measuring the radius of the core substance and the thickness of the outer shell layer are as described above.

[Examples 2 to 15, Comparative Examples 1 to 5]
Microcapsules were produced according to the same procedure as in Example 1, except that the ratio by volume of the solution A and the solution B and the stirring conditions for the microencapsulation step were changed.
In Example 14, mesitylene (liquid at 25 ° C., boiling point: 165 ° C.) was used instead of DCP as the dispersion medium for solution A. Further, in Example 15, toluene (liquid at 25 ° C., boiling point: 111 ° C.) was used as the dispersion medium for the liquid A, instead of DCP. In Comparative Example 6, a DCP dispersion of Cy5.5 (dye) (concentration of Cy5.5 in the dispersion: 0.2% by mass) was used instead of the DCP dispersion of the quantum dots (liquid A). .
The radius of the core material and the thickness of the outer shell layer were measured in the same manner as in Example 1 for each of the examples and the comparative examples. Also, the thickness / radius was determined. The results are shown in Table 1.

[Example 16]
<Mixing process>
3 mL of isophthaloyl dichloride was added to the above solution A to prepare a dispersion (solution D). Then, a liquid mixture was prepared by mixing the obtained dispersion (liquid D), 30 mL of a 5% by mass aqueous solution of PVA and 7 mL of a 10% by mass aqueous solution of p-phenylenediamine.

<Microencapsulation process>
The resulting mixed solution is heated at 75 ° C. for 2 hours while vigorously stirring to polymerize isophthaloyl dichloride and p-phenylenediamine at the interface of micelles, thereby forming a core material containing quantum dots and a dispersion medium as a polyamide. It was coated with an outer shell layer made of a base resin. Thus, microcapsules were produced.

<Core material radius, shell thickness, and thickness / radius>
The radius of the core substance and the thickness of the outer shell layer were measured for the obtained microcapsules in the same manner as in Example 1. Also, the thickness / radius was determined. The results are shown in Table 1.

[Evaluation]
The following evaluation was performed about the obtained microcapsule.

[Quantum yield]
The quantum yield (initial) of the obtained microcapsules was measured using an absolute quantum yield meter (C11347-01 manufactured by Hamamatsu Photonics K. K.). At that time, the absorbance at a wavelength of 450 nm was adjusted to 0.1 and measured. Moreover, about the comparative example 1 using Cy5.5 (dye), the absorbance in wavelength 658nm was adjusted to 0.1, and was measured.
Also, the quantum yield (before microcapsule) was similarly measured for the quantum dots before being microcapsuled. And the reduction rate was calculated | required as follows and the quantum yield was evaluated by the following reference | standard.
Decay rate = [quantum yield (before microcapsules)-quantum yield (initial)] / quantum yield (before microcapsules)
The results are shown in Table 1. Practically, A to C is preferable, A or B is more preferable, and A is more preferable.
・ A: Decrease rate is less than 5% ・ B: Decrease rate is 5% to less than 10% ・ C: Decrease rate is 10% to less than 15% ・ D: Decrease rate is 15% or more

〔durability〕
After storing the obtained microcapsules in air for 3 days, the quantum yield (after 3 days) was measured using an absolute quantum yield meter. And the reduction rate was calculated | required as follows and durability was evaluated by the following reference | standard.
The results are shown in Table 1. Practically, AA to C is preferable, AA to B is more preferable, AA or A is more preferable, and AA is particularly preferable.
Decreasing rate = [quantum yield (initial)-quantum yield (after 3 days)] / quantum yield (initial)
・ AA: Decrease rate is less than 1.0% ・ A: Decrease rate is 1.0% to less than 1.5% ・ B: Decrease rate is 1.5% to less than 3% ・ C: Decrease rate is 3% or more Less than 5% · D: Decrease rate of 5% or more

In Table 1, the column of fluorescent material represents the fluorescent material in the core material. "InP / ZnS" represents a quantum dot (having dodecanethiol as a hydrophobic ligand) having InP (core) and ZnS (shell) manufactured as described above.
Further, in Table 1, the column of dispersion medium represents the dispersion medium in the core material.
Moreover, in Table 1, the column of the outer shell layer represents the material of the outer shell layer.

As can be seen from Table 1, Examples 1 to 16 having a thickness / radius of 0.50 or more and 0.90 or less exhibited excellent quantum yield and durability.
From the comparison of Examples 1 to 7 (the comparison of the embodiments in which the dispersion medium is DCP, the material of the outer shell layer is a polyurethane urea resin, and the core material radius is 2 μm), the thickness / radius is 0.60 or more and 0 Examples 2 to 7, which are less than or equal to 90, showed better durability. Among them, Examples 3 to 7 having a thickness / radius of 0.65 or more and 0.90 or less exhibited further excellent durability. Among them, Examples 3 to 6 having a thickness / radius of 0.65 or more and less than 0.90 exhibited more excellent quantum yield. Among them, Examples 3 to 5 having a thickness / radius of 0.65 or more and 0.85 or less exhibited further excellent quantum yield.
Further, from the comparison of Examples 8 to 10 (a comparison of the embodiments in which the dispersion medium is DCP, the material of the outer shell layer is a polyurethane urea resin, and the core material radius is 3 μm), the thickness / radius is 0.60. Examples 9 and 10, which are greater than or equal to 0.90, showed better quantum yield and durability.
Further, from the comparison of Examples 11 to 13 (a comparison of embodiments in which the dispersion medium is DCP, the material of the outer shell layer is a polyurethane urea resin, and the core material radius is 7 μm), the thickness / radius is 0.60. Examples 12 and 13 having a density of 0.90 or less exhibited more excellent durability. Among them, Example 12 having a thickness / radius of 0.65 or more and 0.85 or less exhibited a more excellent quantum yield.
Further, according to the comparison of Examples 3 and 14 and 15 (the comparison of the embodiments in which the material of the outer shell layer is a polyurethane urea resin and the thickness / radius is 0.75), the boiling point of the dispersant is 120 ° C. or higher Certain Examples 3 and 14 showed better quantum yield. Among these, Example 3 in which the boiling point of the dispersant is 180 ° C. or more showed more excellent durability.
Further, from the comparison of Examples 3 and 16 (contrasts in which the dispersant is DCP and the thickness / radius is 0.75), the material of the outer shell layer has a urethane bond and / or a urea bond in the main chain Example 3 which is a resin having at least one resin selected from the group consisting of a polyurethane resin, a polyurea resin, and a polyurethane urea resin, shows a more excellent quantum yield and durability. .

On the other hand, Comparative Examples 1 and 2 in which the thickness / radius was less than 0.50 had insufficient durability. Moreover, the quantum yield of Comparative Examples 3 and 4 in which the thickness / radius exceeds 0.90 was insufficient. In addition, Comparative Example 5 in which a dye was used instead of the quantum dot was insufficient in durability.

Reference Signs List 1 quantum dot 2 dispersion medium 3 core substance 4 outer shell layer 5 micelle 6 solvent 10 microcapsule

Claims

A microcapsule having a core substance and an outer shell layer covering the core substance,
The core material contains quantum dots and a dispersion medium that is liquid at 25 ° C.,
The material of the outer shell layer is at least one selected from the group consisting of urea resins, melamine resins, polyurethane resins, polyurea resins, polyamide resins, and two or more of these copolymer resins. It is a resin,
The radius of the core material is 10 nm or more and 10 μm or less,
The thickness of the outer shell layer is 5 nm or more and 9 μm or less,
The microcapsule whose ratio of the thickness of the said outer shell layer with respect to the radius of the said core substance is 0.50-0.90.
The quantum dot is
Hydrophobic having at least one group selected from the group consisting of carboxy group, amino group, thiol group, phosphido group, phosphine oxide group, phosphine sulfide group, phosphonic acid group and sulfide group, having 6 or more carbon atoms The microcapsule according to claim 1 having a sex ligand.
The microcapsule according to claim 1 or 2, wherein the ratio of the thickness of the outer shell layer to the radius of the core substance is 0.60 or more and 0.90 or less.
The microcapsule according to claim 3, wherein the ratio of the thickness of the shell layer to the radius of the core substance is 0.65 or more and less than 0.90.
The microcapsule according to claim 4, wherein a ratio of a thickness of the outer shell layer to a radius of the core substance is 0.65 or more and 0.85 or less.
The microcapsule according to any one of claims 1 to 5, wherein the boiling point of the dispersion medium is 120 属 C or more.
The microcapsule according to claim 6, wherein the boiling point of the dispersion medium is 180 ° C or more.
The material of the outer shell layer is at least one resin selected from the group consisting of polyurethane resins, polyurea resins, and polyurethane urea resins. Microcapsules.
A method for producing a microcapsule, comprising producing the microcapsule according to any one of claims 1 to 8;
A dispersion liquid containing quantum dots, a low polarity dispersion medium which is liquid at 25 ° C., and a monomer which becomes a resin which is a material of an outer shell layer of the microcapsule after polymerization, and a solvent having a polarity higher than the dispersion medium Mixing, at least mixing with a surfactant to obtain a mixed solution,
By heating the mixture while stirring, micelles of the dispersion are formed, and the monomer is polymerized at the interface of the micelles to form a core substance containing the quantum dots and the dispersion medium. A microencapsulation step of coating with a resin-made outer shell layer;
A method of manufacturing a microcapsule, comprising:
A film containing the microcapsule according to any one of claims 1 to 8.