JP2018137281A - Light emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light emitting device high in heat resistance and having luminous efficiency less likely to decrease.SOLUTION: A light emitting device includes a light source and a wavelength conversion part converting light emitted from the light source into converted light with a wavelength different from that of the light and emitting the converted light. The wavelength conversion part includes nano particle phosphors and a matrix in which the nano particle phosphors are dispersed. Each of the nano particle phosphors includes a quantum dot and a surface modification part covering the surface of the quantum dot and having a first functional group. The matrix contains a polymer comprising a constitutional unit derived from an ionic liquid and a second functional group that can be covalently bonded with the first functional group, at least parts of the first functional groups and the second functional groups forming a covalent bond.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a light emitting device.

  Conventionally, as a next-generation light-emitting device, a light-emitting device using phosphor particles having a nano-sized particle diameter has been developed (see, for example, Patent Document 1). The “phosphor particles having a nano-sized particle diameter” are referred to as “quantum dots”. A light emitting device using quantum dots is superior in light emission efficiency and color reproducibility compared to a light emitting device using a conventional phosphor.

The emission wavelength of the quantum dot, that is, the fluorescent color of the quantum dot, corresponds to the particle diameter of the quantum dot. Therefore, quantum dots have the advantage that the fluorescent color can be easily controlled by controlling the particle diameter.
In addition, the emission fluorescence obtained from quantum dots has a narrow spectral line width. Therefore, a light emitting device using quantum dots is excellent in color reproducibility.

JP 2014-170938 A

  The light-emitting device described in Patent Document 1 includes a light source that emits excitation light, and a phosphor layer and a quantum dot layer that absorb the excitation light and convert it into fluorescence. In such a light emitting device, there is a possibility that the quantum dot layer is deteriorated by the heat generated by the light source and the luminous efficiency is lowered. In addition, since the deterioration of the quantum dot layer is manifested as a decrease in the light amount of the light emitting device, improvement has been demanded.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a light-emitting device that has high heat resistance and is unlikely to have low luminous efficiency.

  The inventor considered that the deterioration of the quantum dot layer was caused by the following mechanism.

  First, the quantum dot layer is heated by the heat generated by the light source during operation of the light emitting device. At this time, when the matrix is a resin, the phosphor particles dispersed in the matrix are likely to flow when the matrix exceeds the softening point by heating. As a result, the phosphor particles may agglomerate and a desired dispersed state may not be maintained.

  In addition, when dispersing particles in the matrix, the particle surface may be modified with a surface treatment agent in order to improve the dispersibility of the particles. When surface treatment is performed on the quantum dots, it can be expected that dispersibility is improved and aggregation is suppressed. However, if the surface treatment agent is desorbed from the particle surface due to heat generated by the light source during operation, the phosphor particles tend to aggregate and the quantum dot layer may deteriorate.

  The inventor has intensively studied that the aggregation of the phosphor particles generated as described above is one of the causes of the deterioration of the quantum dot layer, and as a result, completed the present invention.

  In order to solve the above problems, one aspect of the present invention includes a light source and a wavelength conversion unit that converts light emitted from the light source into converted light having a wavelength different from that of the light, and emits the converted light. The wavelength conversion unit includes a nanoparticle phosphor and a matrix in which the nanoparticle phosphor is dispersed, the nanoparticle phosphor covers a quantum dot and a surface of the quantum dot, and includes a first functional group. The matrix includes a polymer having a structural unit derived from an ionic liquid and a second functional group that can be covalently bonded to the first functional group, Provided is a light-emitting device in which at least a part of one functional group and the second functional group are covalently bonded.

  In one aspect of the present invention, the wavelength conversion unit includes a plurality of layers that convert the light into the converted light and emit the converted light, and at least one of the plurality of layers includes the nanoparticle phosphor. It is good also as a structure which has the said matrix.

  In one form of the present invention, at least one layer of the plurality of layers that is closest to the light source along the optical path of the light may include the nanoparticle phosphor and the matrix.

  In one form of this invention, the said wavelength conversion part is good also as a structure which has the 2 or more types of said nanoparticle fluorescent substance from which an average particle diameter differs.

  In one form of this invention, the said wavelength conversion part is good also as a structure which covers the said light source and is provided in contact with the said light source.

  In one form of this invention, the said wavelength conversion part is good also as a structure which has a gas barrier layer which covers the light emission surface of the said wavelength conversion part.

  In one embodiment of the present invention, the gas barrier layer may have a light scattering property.

  According to the present invention, it is possible to provide a light-emitting device that has high heat resistance and is less likely to reduce light emission efficiency.

1 is a schematic cross-sectional view showing a light emitting device 10 according to a first embodiment. The enlarged schematic diagram of the wavelength conversion part which the light-emitting device 10 has. Explanatory drawing of the light-emitting device which concerns on 2nd Embodiment. The schematic diagram of the emission spectrum of the light-emitting device 11 which has the light source 1 which inject | emits blue light. Explanatory drawing of the light-emitting device 12 which concerns on 3rd Embodiment. Explanatory drawing of the light-emitting device 13 which concerns on 4th Embodiment. The graph which shows the result of an Example.

[First Embodiment]
The light emitting device according to the first embodiment of the present invention will be described below with reference to FIGS. In all the drawings below, the dimensions and ratios of the constituent elements are appropriately changed in order to make the drawings easy to see.

  FIG. 1 is a schematic cross-sectional view showing a light emitting device 10 according to this embodiment. The light emitting device 10 includes a light source 1, a wavelength conversion unit 8, an anode 4, a cathode 5, a substrate 9, a package 6, and a bonding wire 7.

  As the substrate 9, either a transparent substrate or an opaque substrate may be used. Examples of the material of the transparent substrate include inorganic materials such as glass, quartz glass, and silicon nitride, and resin materials such as acrylic resin and polycarbonate resin. Examples of the material for the opaque substrate include inorganic materials such as ceramics and resin materials. Or what performed the insulation process on the surface of the metal substrate may be used. A substrate made of a composite material in which the above materials are laminated or mixed may be used. A known planarization layer made of a resin material may be formed on the surface of the substrate 9.

  The package 6 is provided on one surface of the substrate 9. The package 6 is made of, for example, an insulating ceramic material. The inner wall of the package 6 may be covered with a light reflective material. Alternatively, the package 6 may be formed of a light reflective material. Examples of the light reflecting material include a highly reflective resin material in which an inorganic filler having a high refractive index such as titanium oxide is dispersed in a high concentration in a light transmissive resin material, and a metal material such as aluminum and silver. it can. When the material that covers the inner wall of the package 6 or the material for forming the package 6 is a metal material such as aluminum or silver, it is necessary to insulate the anode 4 and the cathode 5 described later from the package 6.

  The anode 4 and the cathode 5 are provided on one surface of the substrate 9. The anode 4 and the cathode 5 supply electric power for driving the light source 1. The anode 4 and the cathode 5 are insulated by being arranged at a predetermined interval. Alternatively, an insulating material may be interposed between the anode 4 and the cathode 5. The anode 4 and the cathode 5 are electrically connected to the light source 1 through a bonding wire 7. As a material of the bonding wire 7, Au is mainly used, but it is not particularly limited.

  The light source 1 is provided on one surface of the substrate 9. The light source 1 is composed of a light emitting element that emits excitation light having a wavelength of 400 nm or less for exciting the phosphor particles 2. In the present embodiment, a light emitting element such as an LED or a laser diode can be used as the light source 1. Furthermore, as the light source 1, a light emitting element that emits near-ultraviolet light can be used, and is not particularly limited. In addition to near-ultraviolet light, a light-emitting element that can emit light in a wavelength region such as blue-violet light, violet light, and ultraviolet light can also be used. Examples of the constituent material of the light emitting element include GaN, InGaN, AlGaInN, AlGaN, GaAs, ZnSe and the like.

  The wavelength conversion unit 8 covers the inner wall of the package 6 and the light source 1 and is provided in contact with the light source 1. The wavelength conversion unit 8 includes a plurality of phosphor particles (nanoparticle phosphors) 2 and a matrix 3 in which the phosphor particles 2 are dispersed. The wavelength converter 8 converts the light (excitation light) emitted from the light source 1 into converted light (fluorescence) having a wavelength different from that of the excitation light and emits the converted light.

  FIG. 2 is an enlarged schematic diagram of the wavelength conversion unit 8 included in the light emitting device 10. The wavelength conversion unit includes phosphor particles 2 and a matrix 3 in which the phosphor particles 2 are dispersed. In the matrix 3, a light scattering material made of an inorganic material may be dispersed as long as the effects of the invention are not impaired.

(Phosphor particles 2)
As shown in FIG. 2, the phosphor particle 2 includes a quantum dot 21 and a surface modification unit 22 that covers the surface of the quantum dot 21 and has a first functional group 221.

The formation material of the quantum dot 21 is not particularly limited, and a conventionally known formation material can be used. As a material for forming the quantum dots 21, for example, conventionally used InP, InN, InAs, InSb, InBi, ZnO, In ₂ O ₃ , Ga ₂ O ₃ , ZrO ₂ , In ₂ S ₃ , Ga ₂ S ₃ , In ₂ Se ₃ , Ga ₂ Se ₃ , In ₂ Te ₃ , Ga ₂ Te ₃ , CdSe, CdTe, CdS, ZnO, CuInS ₂ , CuInSe ₂ , and CuInTe ₂ are included. Among them, because of the good visual emission characteristics and stability, InP, InN, InAs, InSb, InBi, ZnO, In ₂ O ₃ , Ga ₂ O ₃ , ZrO ₂ , In ₂ S ₃ , Ga ₂ S ₃ , It is preferable to include at least one material selected from the group consisting of In ₂ Se ₃ , Ga ₂ Se ₃ , In ₂ Te ₃ , Ga ₂ Te ₃ , CdSe, CdTe and CdS, and selected from CdSe, CdTe and InP. It is particularly preferable to include at least one kind of material.

  The shape of the quantum dot 21 is not particularly limited, and any conventionally known appropriate shape such as a spherical shape, a rod shape, or a wire shape can be used without any particular limitation. As described above, since the emission wavelength of the quantum dot changes by controlling the shape and particle diameter, a spherical quantum dot is preferable from the viewpoint of easy wavelength control.

  When the light emitting device 10 is used as a light source for general illumination or a liquid crystal backlight, the emission wavelength of the quantum dots 21 is preferably included in the visible light region of 380 to 780 nm. It is preferable to use a particle whose particle shape and particle diameter are controlled so that the emission wavelength of the quantum dots 21 is included in the above range.

  The particle diameter of the quantum dots 21 can be appropriately selected according to the raw material and the desired emission wavelength. The particle diameter of the quantum dots 21 is not particularly limited, but is preferably 1 nm or more and 20 nm or less, and more preferably 2 nm or more and 5 nm or less.

When the particle diameter of the quantum dots 21 is 1 nm or more, the ratio of the entire surface area of the quantum dots 21 to the entire volume of the quantum dots 21 is suppressed, the surface defects are less likely to be dominant, and the light emission efficiency is unlikely to decrease.
When the particle diameter of the quantum dots 21 is 20 nm or less, it is preferable because aggregation / precipitation of the quantum dots 21 hardly occurs.

  Here, when the quantum dot 21 is spherical, the particle diameter of the quantum dot 21 refers to the average particle diameter measured by a particle size distribution measuring device or the size of particles observed by an electron microscope. When the shape of the quantum dot 21 is a rod shape, the particle diameter of the quantum dot 21 is represented by the size of the short axis and the long axis measured by an electron microscope. Furthermore, when the shape of the quantum dot 21 is a wire shape, the particle diameter of the quantum dot 21 is represented by the size of the short axis and the long axis measured by an electron microscope.

  Although content in particular of quantum dot 21 is not restrict | limited, It is preferable that they are 0.001 mass part or more and 50 mass parts or less with respect to the matrix 3 whole quantity (100 mass parts), and 0.01 mass part or more and 20 mass parts or less. It is more preferable that When the content of the quantum dots 21 is 0.001 parts by mass or more with respect to the total amount of the matrix 3, the amount of light emitted from the quantum dots 21 can be sufficiently secured. In addition, when the content of the quantum dots 21 is 50 parts by mass or less with respect to the total amount of the matrix 3, the quantum dots 21 can be uniformly dispersed in the matrix 3.

  The surface modifier 22 uses a surface modifier that modifies the particle surface of the quantum dots 21 as a forming material. The surface modifier 22 modifies the surface of the quantum dot 21. As a result, the dispersibility with respect to the matrix 3 is improved as a whole of the phosphor particles 2.

  The surface modifier 22 has a first functional group 221. The first functional group 221 can be covalently bonded to a second functional group (described later) included in the matrix 3.

  The material for forming the surface modification portion 22 has a functional group that binds to the particle surface of the quantum dot 21 and a first functional group 221. Examples of the material for forming the surface modification portion 22 include carboxylic acids having a mercapto group. In this case, the mercapto group corresponds to “a functional group that binds to the particle surface of the quantum dot 21”, and the carboxy group that the carboxylic acid has corresponds to the first functional group 221.

  Examples of such compounds include mercaptopropionic acid, thioglycolic acid, and mercaptosuccinic acid.

  In the present embodiment, the material for forming the surface modification portion 22 is the above-described mercaptopropionic acid. That is, in the present embodiment, the first functional group 221 is a carboxy group.

(Matrix 3)
The matrix 3 includes a polymer 31 having a structural unit 311 derived from an ionic liquid and a second functional group 312 that can be covalently bonded to the first functional group 221. The polymer 31 is obtained by polymerizing a monomer having (i) a structural unit derived from an ionic liquid, (ii) a polymerizable functional group, and (iii) a second functional group 312. Hereinafter, such a monomer may be referred to as a “first monomer”. The first monomer is obtained by modifying the polymerizable functional group and the second functional group 312 in an ionic liquid by a generally known method.

The “ionic liquid” that is the basic structure of the first monomer is a molten salt (molten salt). Examples of the ionic liquid include compounds represented by the following general formula (I).
X ⁺ Y ^- ... (I)

In FIG. 2, the code | symbol 311a points out X ^<+> in the said general formula (I).
X ⁺ is a cation selected from the group consisting of imidazolium ion, pyridinium ion, phosphonium ion, aliphatic quaternary ammonium ion, pyrrolidinium, and sulfonium. Among these, aliphatic quaternary ammonium ions are preferable because of excellent thermal stability and stability in the air.

In Figure 2, reference numeral 311b is, Y in the general Formulas (I) ^- refers to.
Y ^- is tetrafluoroborate ion, hexafluorophosphate ion, bis (trifluoromethylsulfonyl) imide ion, soluble chlorate ion, tris (trifluoromethylsulfonyl) carbon ion, trifluoromethanesulfonate ion, trifluoroacetate ion , An anion selected from the group consisting of carboxylate ions and halogen ions. Among these, bistrifluoromethylsulfonylimido ion is preferable because of excellent thermal stability and stability in the air.
An ionic liquid can be obtained by appropriately combining X + and Y−. The ionic liquid is preferably liquid at room temperature (for example, 25 ° C.), that is, its melting point is less than room temperature.

  (Ii) As the polymerizable functional group, a conventionally known functional group can be adopted as long as the polymer 31 can be formed. As the polymerizable functional group, a (meth) acryloyloxy group is preferable because polymerization is easy.

  By polymerizing the polymerizable functional group, the polymer 31 including the structural unit derived from the ionic liquid is obtained. Further, wavelength conversion in which the phosphor particles 2 are dispersed in the polymer 31 (matrix 3) by polymerizing the polymerizable functional group in a state where the phosphor particles 2 are dispersed in the monomer mixture containing the first monomer. The part 8 can be manufactured easily. Thus, by obtaining the wavelength conversion part 8 in which the phosphor particles 2 are dispersed in the polymer 31, aggregation of the phosphor particles 2 can be suppressed.

  (Iii) The second functional group 312 is a functional group that can be covalently bonded to the first functional group 221. For example, when the first functional group 221 is a carboxy group as described above, a hydroxy group or an amino group can be adopted as the second functional group 312.

In this case, when the second functional group 312 is a hydroxy group, the first functional group 221 and the second functional group 312 can form an ester bond that is a covalent bond.
When the second functional group 312 is an amino group, the first functional group 221 and the second functional group 312 can form an amide bond that is a covalent bond.

  Examples of such a first monomer include 2-hydroxy-3- (methacryloyloxy) -propyltrimethylammonium-bis (trifluoromethanesulfonyl) imide (the following formula (II)).

  In the ionic liquid having the polymerizable functional group and the second functional group 312 as described above, the polymerizable functional group and the second functional group 312 are introduced into a conventionally known appropriate ionic liquid by a conventionally known appropriate method. It is obtained by doing. Of course, you may use a commercial item.

  In the present embodiment, the polymer 31 is a polymer obtained by polymerizing the above-described 2-hydroxy-3- (methacryloyloxy) -propyltrimethylammonium-bis (trifluoromethanesulfonyl) imide. That is, in the present embodiment, the second functional group 312 is a hydroxy group.

  Further, when the first monomer is polymerized, (i) a structural unit derived from the ionic liquid, (ii) a second monomer having a polymerizable functional group and not having the second functional group 312 is copolymerized. May be. Examples of such a second monomer include 2- (methacryloyloxy) -ethyltrimethylammonium bis (trifluoromethanesulfonyl) imide represented by the following formula (III), and 1- (3- And acryloyloxy-propyl) -3-methylimidazolium bis (trifluoromethanesulfonyl) imide.

  Many first monomers have a relatively high melting point and are solid at room temperature. Therefore, in many cases, when the phosphor particles 2 are dispersed in the first monomer, it is necessary to heat the first monomer or a dispersion liquid in which the phosphor particles 2 are dispersed in the first monomer. Such heating may cause the first monomer and the phosphor particles 2 to deteriorate.

  On the other hand, when the second monomer is mixed with the first monomer and used, the melting point of the mixture is lowered due to the freezing point depression, and the mixture is easily made liquid. As a result, the heating temperature can be lowered when the phosphor particles 2 are dispersed in the monomer mixture. Or heating becomes unnecessary.

  Furthermore, when the monomer is polymerized, a third monomer having a polymerizable functional group and not having a structural unit derived from (i) an ionic liquid may be copolymerized. As the third monomer, a commonly known monomer capable of copolymerization can be used.

  The polymerization conditions of the monomer mixture containing the monomer, for example, the conditions such as polymerization temperature and polymerization time, are suitably selected according to the type and amount of the monomer used.

  In addition, when a catalyst is used for the polymerization of the monomer, the type of the catalyst is not particularly limited. For example, conventionally known azobisisobutyronitrile, dimethyl 2,2'-azobis (2-methylpropionate) and the like can be used. Among these, azobisisobutyronitrile is preferably used as a catalyst because it facilitates polymerization.

(Wavelength converter 8)
In the wavelength converter 8 having such phosphor particles 2 and matrix 3, the following effects can be expected.

  First, the phosphor particles 2 are dispersed in the polymer 31 including the structural unit 311 derived from the first monomer, so that the phosphor particles 2 are electrostatically stabilized and the phosphor particles 2 are strongly protected. be able to. Thereby, the phosphor particles 2 can be protected from air and moisture, and a light emitting device with high luminous efficiency can be realized.

  Moreover, since the phosphor particles 2 are dispersed in the polymer 31, aggregation of the phosphor particles 2 can be suppressed.

  Here, a crosslinking agent may be added to the monomer mixture containing the first monomer. By adding a crosslinking agent, the polymer 31 obtained by polymerizing the monomer mixture can be increased in strength, and the stability of the wavelength conversion unit 8 is improved. Moreover, the softening point of the polymer 31 can be raised and the polymer 31 can be made difficult to soften by the heat generated by the light source.

  As the cross-linking agent, any known one can be used as long as it can cross-link with the polymerizable functional group of the ionic liquid, and is not particularly limited. Examples of the crosslinking agent include diethylene glycol dimethacrylate and 1,1,1-trimethylolpropane triacrylate. Among them, 1,1,1-trimethylolpropane triacrylate is preferable because it has a large number of cross-linking sites and is strongly polymerized.

  When the crosslinking agent is added, the addition amount is not particularly limited as long as the effects of the invention are exerted. For example, it is preferably 1 part by mass or more and 50 parts by mass or less, and more preferably 10 parts by mass or more and 30 parts by mass or less with respect to the total monomer amount (100 parts by mass).

  When the addition amount of the crosslinking agent is 1 part by mass or more with respect to the total amount of the monomer, a crosslinked structure is formed, which is effective in improving the strength of the matrix 3. Moreover, when it is 50 mass parts or less with respect to the whole monomer quantity, the fluorescent substance particle 2 disperse | distributes stably.

  Furthermore, in the wavelength conversion unit 8 of this embodiment having the phosphor particles 2 and the matrix 3, at least the first functional group 221 that the phosphor particles 2 have and the second functional group 312 that the matrix 3 has. Some form a covalent bond. In this embodiment, a part of the carboxy group that is the first functional group 221 and a part of the hydroxy group that is the second functional group 312 form an ester bond.

  Thereby, even if the matrix 3 (polymer 31) is softened, the phosphor particles 2 are difficult to move in the matrix 3 and are likely to be localized in the vicinity of the second functional group 312. Therefore, aggregation of the phosphor particles 2 can be suppressed.

  For the amount of the surface treatment agent for treating the quantum dots 21 (molar amount of the first functional group 221) and the amount of the first monomer (molar amount of the second functional group 312), preliminary experiments were conducted in advance. It is recommended to set after confirming thermal stability.

  Furthermore, in the wavelength conversion unit 8, the ratio (molar ratio) of the second functional group 312 to the amount of the first functional group 221 of the phosphor particle 2 is, for example, from the minimum value of the molar ratio set by the preliminary experiment. May be increased.

  For example, when the wavelength conversion unit 8 is heated, the surface modification unit 22 having the first functional group 221 that forms a covalent bond with the second functional group 312 may be detached from the particle surface. In that case, the phosphor particles 2 are likely to move in the matrix 3 and may aggregate.

  However, if many unreacted second functional groups 312 remain in the matrix 3, the unreacted first functional groups 221 included in the phosphor particles 2 moving in the matrix 3 exist in the matrix 3. It can be expected that the unreacted second functional group 312 reacts to form a covalent bond. Therefore, the matrix 3 has the second functional group 312 that is larger than the amount of the first functional group 221 included in the phosphor particle 2, whereby the wavelength conversion unit 8 in which deterioration is suppressed can be obtained.

  According to the light-emitting device having the above-described configuration, it is possible to provide a light-emitting device that has high heat resistance and is unlikely to reduce light emission efficiency.

[Second Embodiment]
FIG. 3 is an explanatory diagram of the light emitting device 11 according to the second embodiment of the present invention. The light emitting device 11 of the present embodiment is different only in the configuration of the wavelength conversion unit, and the other configurations are common to the light emitting device 10 of the first embodiment. Therefore, in the present embodiment, the illustration of the anode 4, the cathode 5, the substrate 9, the package 6, and the bonding wire 7 shown in FIG. 1 is omitted, and the light source 1 and the wavelength conversion unit are shown. Moreover, the same code | symbol is attached | subjected about the component which is common in 1st Embodiment, and detailed description is abbreviate | omitted.

The light emitting device 11 includes a light source 1 and a wavelength conversion unit 81. The wavelength converter 81 covers the light source 1 and is provided in contact with the light source 1. The wavelength conversion unit 81 includes first phosphor particles 2A, second phosphor particles 2B, and a matrix 3.
The light source 1 and the matrix 3 can adopt the same configuration as that shown in the first embodiment.

  The first phosphor particles 2A and the second phosphor particles 2B have different fluorescence emission wavelengths. For example, the first phosphor particle 2A absorbs excitation light and emits red fluorescence. The second phosphor particles 2B absorb excitation light and emit green fluorescence.

  At least one of the first phosphor particles 2A and the second phosphor particles 2B has the above-described quantum dots and a surface modification portion that has a first functional group and modifies the surface of the quantum dots. It is.

Conventional phosphor particles that do not include quantum dots may be used for either one of the first phosphor particles 2A and the second phosphor particles 2B. The conventional phosphor particles have a particle diameter of, for example, about several μm (μm order). In the following description, examples of usable phosphor particles include CaAlSiN ₃ red phosphor and YAG: Ce yellow phosphor.

  Such conventional phosphor particles can function as a scattering source that scatters excitation light emitted from the light source 1 and fluorescence emitted from the phosphor particles. Therefore, a light emitting device that emits light uniformly can be realized.

  When using conventional phosphor particles, the content is preferably 1 part by mass or more and 1000 parts by mass or less, and preferably 10 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the total amount of phosphor particles including quantum dots. More preferably. When the content of the conventional phosphor particles is 1 part by mass or more with respect to 100 parts by mass of the phosphor particles including quantum dots, the effect of scattering can be sufficiently ensured. When the content of the conventional phosphor particles is 1000 parts by mass or less with respect to 100 parts by mass of the phosphor particles including quantum dots, light emission from the phosphor particles including quantum dots can be sufficiently ensured.

  Of course, both the first phosphor particle 2A and the second phosphor particle 2B have a configuration including a quantum dot and a surface modification portion that has a first functional group and modifies the surface of the quantum dot. May be.

  At least a part of the first functional group included in at least one of the first phosphor particle 2A and the second phosphor particle 2B and the second functional group included in the matrix 3 form a covalent bond.

  FIG. 4 is a schematic diagram of an emission spectrum of the light emitting device 11 having the light source 1 that emits blue light. In FIG. 4, the horizontal axis represents wavelength (nm) and the vertical axis represents intensity (au).

  In such a light emitting device 11, the first phosphor particles 2A that have absorbed the excitation light emitted from the light source 1 emit red light. Further, the second phosphor particles 2B that have absorbed the excitation light emitted from the light source 1 emit green light.

  Therefore, the light emitted from the light emitting device 11 is a mixture of blue light emitted from the light source 1, red light emitted from the first phosphor particles 2A, and green light emitted from the second phosphor particles 2B. By doing so, it becomes white light. The color balance of the light emitted from the light emitting device 11 can be controlled by adjusting the amount of the first phosphor particles 2A and the second phosphor particles 2B mixed in the wavelength converter 81.

The light-emitting device 11 having the above-described configuration can also provide a light-emitting device that has high heat resistance and is less likely to reduce light emission efficiency.
[Third Embodiment]
FIG. 5 is an explanatory diagram of the light emitting device 12 according to the third embodiment of the present invention. Also in the embodiments after this embodiment, as in the second embodiment, the illustration of the anode 4, the cathode 5, the substrate 9, the package 6, and the bonding wire 7 shown in FIG. Part. Moreover, the same code | symbol is attached | subjected about the component which is common in 1st Embodiment, and detailed description is abbreviate | omitted.

  The light emitting device 12 includes the light source 1 and a wavelength conversion unit 82. The wavelength conversion unit 82 covers the light source 1 and is provided in contact with the light source 1. The light source 1 can employ the same configuration as that described in the first embodiment.

  The wavelength conversion unit 82 includes a first layer 82A including the first phosphor particles 2A and a second layer 82B including the second phosphor particles 2B. The first layer 82 </ b> A covers the light source 1 and is in contact with the light source 1. The second layer 82B is in contact with the first layer 82A and is stacked on the first layer 82A.

  The first layer 82 </ b> A has the first phosphor particles 2 </ b> A and the matrix 3. The matrix 3 can adopt the same configuration as that shown in the first embodiment. The first phosphor particles 2A absorb excitation light and emit red fluorescence.

  The second layer 82 </ b> B has the second phosphor particles 2 </ b> B and the matrix 3. The matrix 3 can adopt the same configuration as that shown in the first embodiment. The first phosphor particles 2A absorb excitation light and emit red fluorescence.

  At least one of the first phosphor particles 2A and the second phosphor particles 2B has the above-described quantum dots and a surface modification portion that has a first functional group and modifies the surface of the quantum dots. It is. In the case of the light emitting device 12, the first phosphor particle 2 </ b> A included in the first layer 82 </ b> A has a quantum dot and a surface modifier that has a first functional group and modifies the surface of the quantum dot. Good. In such a first layer 82A, at least a part of the first functional group of the first phosphor particle 2A and the second functional group of the matrix 3 form a covalent bond.

  The first layer 82A is provided at a position relatively closer to the light source 1 (closest to the light source) than the second layer 82B along the optical path of the excitation light emitted from the light source 1. Therefore, the first layer 82A is more likely to be deteriorated by heat generated by the light source 1 than the second layer 82B. In the light emitting device 12, in the first layer 82 </ b> A provided at such a position that is easily deteriorated thermally, the first functional group that the first phosphor particles 2 </ b> A have, and the second functional group that the matrix 3 has, The degradation can be suppressed by adopting a structure in which at least a part forms a covalent bond.

  Of course, both the first phosphor particle 2A and the second phosphor particle 2B have a configuration including a quantum dot and a surface modification portion that has a first functional group and modifies the surface of the quantum dot. May be.

  The light emitting device 12 having the light source 1 that emits blue light includes blue light emitted from the light source 1, red light emitted from the first phosphor particles 2A, and green light emitted from the second phosphor particles 2B. Emits white light with mixed colors. At this time, since the second phosphor particles 2B that emit green light cannot absorb red light having lower energy than the green light, the red light emitted from the first phosphor particles 2A The second layer 82B passes through the second layer 82B without being absorbed by the second phosphor particles 2B. Therefore, a light emitting device with high light emission efficiency can be obtained.

  Note that the color balance of light emitted from the light emitting device 11 is the type and amount of the first phosphor particles 2A and the second phosphor particles 2B mixed in the wavelength converter 81, and the quantum dots of the phosphor particles. It can be controlled by adjusting the particle size and the like.

  The light-emitting device 12 having the above configuration can also provide a light-emitting device that has high heat resistance and does not easily decrease the light emission efficiency.

[Fourth Embodiment]
FIG. 6 is an explanatory diagram of the light emitting device 13 according to the fourth embodiment of the present invention. The light emitting device 13 includes a gas barrier layer 50 that covers the surface of the wavelength conversion unit 82.

  The gas barrier layer 50 has translucency and has a property of shielding oxygen and moisture. Thereby, it is possible to provide the light emitting device 13 with improved reliability by suppressing the deterioration of the wavelength conversion unit 8 due to oxygen, moisture, and the like.

The gas barrier layer 50 has a gas permeability of 1 cc / (m ² · day / atm) or less in terms of oxygen permeability and 1 g / m ² · day or less in terms of water vapor permeability (using a gas permeability measuring device based on Japanese Industrial Standards) Measured). The material for forming the gas barrier layer 50 is not particularly limited as long as the target performance can be exhibited, but a gas barrier layer formed mainly of glass, silicone resin, acrylic resin, or the like is preferable.

  The thickness of the gas barrier layer 50 is not particularly limited, but is preferably 1 μm or more and 5000 μm or less, and more preferably 10 μm or more and 1000 μm or less. When the thickness of the gas barrier layer 50 is 1 μm or more, sufficient gas barrier performance can be secured. Moreover, when the thickness of the gas barrier layer 50 is 5000 μm or less, the light extraction efficiency can be ensured.

  Further, a scattering material made of an inorganic material may be dispersed in the gas barrier layer 50. Since the scattering material is dispersed, gas permeability such as oxygen and moisture in the air is suppressed as compared with the gas barrier layer in the case where the scattering material is not included, and the wavelength conversion unit can be further protected. Further, there is an advantage that uniform light emission can be realized by scattering light emitted from the light source and the wavelength conversion unit.

  There is no particular limitation on the inorganic material used as the scattering material, and a known material can be used. Examples of the material for forming the scattering material include titanium oxide, aluminum oxide, silicon oxide, barium titanate, gallium oxide, indium oxide, and zinc oxide. Among these, silicon oxide is preferably used as the scattering material because it is easy to produce and handle.

  The addition amount of the scattering material is not particularly limited, but is 0.1 to 100 parts by mass with respect to 100 parts by mass of the main component constituting the gas barrier layer in order to suitably exhibit the intended effect of the scattering material. It is preferable that it is 1 mass part or more and 50 mass parts or less.

  The light-emitting device 12 having the above configuration can also provide a light-emitting device that has high heat resistance and does not easily decrease the light emission efficiency.

  The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but it goes without saying that the present invention is not limited to such examples. Various shapes, combinations, and the like of the constituent members shown in the above-described examples are examples, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention.

  For example, in the light emitting device described above, the wavelength conversion unit is provided so as to be in contact with the light source 1 and cover the light source 1, but the present invention is not limited to this, and the light source and the wavelength conversion unit may be separated. For example, when a laser light source is adopted as the light source, if the wavelength conversion unit is irradiated with laser light, the laser light irradiation part may generate heat and the wavelength conversion unit may be deteriorated. Even in such a case, it is possible to provide a light-emitting device that has high heat resistance and does not easily lower the light emission efficiency by employing the wavelength conversion unit having the configuration of the present invention.

  In addition, the shape of the wavelength converter is not particularly limited, and a sheet shape, a bar shape, or the like can be adopted.

[Example]
EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

Example 1
A compound represented by the following formula (II), which is an ionic liquid having a polymerizable functional group, and a compound represented by the following formula (III), which is an ionic liquid having a polymerizable functional group, were mixed at 1: 1 (volume ratio). The liquid mixture of the ionic liquid was adjusted. The methacryloyloxy group which the following formula (II) (III) has corresponds to the polymerizable functional group described above. The hydroxy group which the following formula (II) has corresponds to the first functional group in the present invention.

（化合物名：２−ヒドロキシ−３−（メタクリロイルオキシ）−プロピルトリメチルアンモニウムビス（トリフルオロメタンスルホニル）イミド）

(Compound name: 2-hydroxy-3- (methacryloyloxy) -propyltrimethylammonium bis (trifluoromethanesulfonyl) imide)

（化合物名：２−（メタクリロイルオキシ）−エチルトリメチルアンモニウムビス（トリフルオロメタンスルホニル）イミド）

(Compound name: 2- (methacryloyloxy) -ethyltrimethylammonium bis (trifluoromethanesulfonyl) imide)

  A dispersion solution of phosphor particles (manufactured by NN-LABS, model number CZW-R) was mixed with 1 mL of the obtained mixed solution. As the phosphor particles, those having the surface of the CdSe nanoparticles having a quantum dot covered with a shell made of ZnS and a surface modification part covering the surface of the quantum dot were used. As the surface modification part, one containing a carboxy group was used. The carboxy group that the surface modifying portion has corresponds to the second functional group in the present invention.

  After transferring the phosphor particles to the mixed liquid of ionic liquid, the ionic liquid in which the phosphor particles were dispersed was obtained by removing the aqueous layer in a state where it was allowed to stand and separated into two layers.

  Next, 2 mg of azobisisobutyronitrile as a polymerization catalyst was mixed into the ionic liquid in which the phosphor particles were dispersed, and then dropped onto the light emission surface of a blue LED (light source) having an emission peak wavelength of 445 nm. The ionic liquid was polymerized by heating at 80 ° C. for 1 hour to obtain a polymer having a structural unit derived from the ionic liquid. This produced the light-emitting device of Example 1 which has a light source and a wavelength conversion part in which phosphor particles are dispersed in a polymer having a structural unit derived from an ionic liquid.

(Comparative Example 1)
A light emitting device of Comparative Example 1 was produced in the same manner as in Example 1 except that only the compound represented by the above formula (III) was used as the ionic liquid to be mixed with the dispersed aqueous solution of phosphor particles.

  The light emitting devices of Example 1 and Comparative Example 1 were allowed to emit light continuously in an environment of 85 ° C., and changes in the light emission intensity were confirmed. The applied voltage and the amount of power supplied were the same for both Example 1 and Comparative Example 1.

  FIG. 7 is a graph showing a change in light emission intensity with respect to a light emission time when continuous light emission is performed. In the graph shown in FIG. 7, the horizontal axis indicates the light emission time (unit: time), and the vertical axis indicates the light emission intensity. The vertical axis indicates a value normalized with the light emission intensity at the start of the test as 100%.

As shown in the figure, the light emitting device of Example 1 maintained a light emission intensity of 95% or more after 10 hours.
On the other hand, in the light emitting device of Comparative Example 1, the light emission intensity decreased to about 60% of the initial value after 10 hours.

  From the above results, it was found that the present invention is useful.

  DESCRIPTION OF SYMBOLS 1 ... Light source, 2 ... Phosphor particle (nanoparticle fluorescent substance), 3 ... Matrix, 8, 81, 82 ... Wavelength conversion part 10, 11, 12, 13 ... Light-emitting device, 21 ... Quantum dot, 22 ... Surface modification Part, 31 ... polymer, 50 ... gas barrier layer, 221 ... first functional group, 311 ... structural unit derived from ionic liquid, 312 ... second functional group

Claims (7)

A light source;
A wavelength converter that converts the light emitted from the light source into converted light having a wavelength different from that of the light and emits the converted light; and
The wavelength conversion unit includes a nanoparticle phosphor,
A matrix in which the nanoparticle phosphor is dispersed,
The nanoparticle phosphor includes quantum dots,
Covering the surface of the quantum dot, and having a surface modification part having a first functional group,
The matrix includes a polymer having a structural unit derived from an ionic liquid and a second functional group that can be covalently bonded to the first functional group,
A light emitting device in which at least a part of the first functional group and the second functional group are covalently bonded. The wavelength conversion unit has a plurality of layers that convert the light into the converted light and emit it,
The light emitting device according to claim 1, wherein at least one of the plurality of layers includes the nanoparticle phosphor and the matrix.   The light-emitting device according to claim 2, wherein at least one layer closest to the light source along the optical path of the light includes the nanoparticle phosphor and the matrix.   The light emitting device according to any one of claims 1 to 3, wherein the wavelength conversion unit includes two or more kinds of the nanoparticle phosphors having different average particle diameters.   5. The light emitting device according to claim 1, wherein the wavelength conversion unit covers the light source and is in contact with the light source.   The light emitting device according to claim 1, wherein the wavelength conversion unit includes a gas barrier layer that covers a light emission surface of the wavelength conversion unit.   The light emitting device according to claim 6, wherein the gas barrier layer has light scattering properties.

Images