JP4960644B2 - Phosphor particles, wavelength converter and light emitting device - Google Patents

Description

  The present invention relates to a phosphor suitably used for a light-emitting device such as a backlight power source for an electronic display and a fluorescent lamp, and more specifically, is used for converting the wavelength of light emitted from a light-emitting element to the outside. The present invention relates to a phosphor, a phosphor particle, a wavelength converter, and a light-emitting device that are particularly high in luminous efficiency and excellent in long-term reliability.

  A light-emitting element made of a semiconductor material (hereinafter referred to as an LED chip) is small in size, power efficient, and vividly colors. LED chips have excellent characteristics such as long product life, strong on / off lighting repeatability, and low power consumption, so they are expected to be applied to backlight sources such as liquid crystals and lighting sources such as fluorescent lamps. Has been.

  The application of the LED chip to the light emitting device is that the wavelength of part of the light of the LED chip is converted with a phosphor, and the wavelength-converted light and the light of the LED that is not wavelength-converted are mixed and emitted, thereby It has already been manufactured as a light emitting device that emits a color different from that of light.

Specifically, in order to emit white light, a light emitting device in which a wavelength conversion layer containing a phosphor is provided on the surface of an LED chip has been proposed. For example, in a light emitting device in which a matrix layer including a YAG phosphor expressed by a composition formula of (Y, Gd) ₃ (Al, Ga) ₅ O ₁₂ is formed on a blue LED chip using an nGaN-based material, Since blue light is emitted from the chip and a part of the blue light is changed to yellow light in the matrix layer, a light emitting device in which blue and yellow light are mixed and white is proposed (for example, Patent Document 1). .

  Usually, the phosphor is dispersed in a matrix resin and has a structure that emits fluorescence upon receiving light from the LED. Here, since the light from the LED is light from the blue side to the low wavelength side, the energy is high and it is expected that the resin is deteriorated. As resin for LED, low-cost epoxy resin and silicone resin with excellent heat resistance and light transmission are used. Epoxy resin has a carbon-carbon bond as its main skeleton, so its binding energy Is as low as 83 kcal / mol.

  On the other hand, the silicone oxygen bond of the silicone resin is 108 kcal / mol, which is stronger than that of the epoxy resin, so that the silicone resin has been used for the purpose of long life. Furthermore, since the LED light is light from the blue to the low wavelength side, a structure having a functional group such as a phenyl group such as an epoxy resin absorbs light and deteriorates its transparency. For this reason, silicone resin is often used even when light transmittance is important (for example, Patent Document 2).

  Moreover, since the surface area of the semiconductor particles is very large compared to the surface area of the phosphor having an average particle diameter of several μm, which is mainly used at present, for example, when the semiconductor particles are assumed to be true spheres, With respect to the surface area, the one with a particle size of 2 nm is very large, 1000 times the one with a particle size of 2 μm. Therefore, when semiconductor particles having an average particle size of 10 nm or less and phosphors having an average particle size of several μm have defects on the surface of the particles at the same ratio, the wavelength conversion efficiency of semiconductor particles having an average particle size of 10 nm or less Will be reduced.

  In order to improve the wavelength conversion efficiency due to defects on the surface of the particles, organic substances such as organic amines are bonded to the surface of the semiconductor particles to repair the surface defects electrochemically and stabilize the level of the discrete band gap energy. Attempts have been made to increase the wavelength conversion efficiency of semiconductor particles having an average particle diameter of 10 nm or less (see, for example, Non-Patent Document 1 and Patent Document 3).

  As a method for synthesizing semiconductor particles having an average particle size of 0.5 to 10 nm, there is a hot soap method in which synthesis is performed in an organic solvent not containing water such as TOPO and dodecylamine. There is a reverse micelle method (Non-Patent Documents 2 and 3) in which synthesis is performed in an existing system.

JP 11-261114 A JP 2000-136275 A JP 2005-103746 A Dmitry Vee. Dmitri V. Talapin, Andreiell. "Colloid and Surface, A" by Andrey L. Rogach, Ivo Mekis, Stephan Haubold, Andreas Kornowski, Markus Haase, Horst Weller (Colloids and Surfaces, A) ", 2002, 202, p.145 Tetsuhiko Isobe, Surface Chemistry, 22, 315, (2001) Aggie A. Born (Ageeth A.Bol), Andreas Meijerink, "Journal of Physics Chemistry B" (2001, Volume 105, p.10197)

  However, when the semiconductor ultrafine particles are held by the resin, a gap or a stress may be generated between the semiconductor ultrafine particles and the resin due to the difference in thermal expansion coefficient between the two. There was a problem that lattice defects were likely to occur and the luminous efficiency of the semiconductor ultrafine particles was lowered.

  In addition, even when the semiconductor particles synthesized with a water-containing solvent containing a large amount of water are converted to a state soluble in a non-aqueous solvent, the surface of the semiconductor particles is once in contact with water. The semiconductor particles chemically react with water to alter the surface of the semiconductor particles, and the surface of the semiconductor particles is covered with OH groups. Then, the OH groups on the surface of the semiconductor particles make the semiconductor particles highly hydrophilic, and it is easy to take in moisture that enters the wavelength converter from the atmosphere. Further, once the water attached to the surface of the semiconductor particles is difficult to remove, even if the solvent is replaced in the ligand exchange step, it is difficult to completely remove the water from the surface of the semiconductor particles.

  Therefore, when semiconductor particles synthesized in an aqueous solution are used as phosphor particles in a wavelength converter, the emission wavelength conversion efficiency is extremely lowered due to a chemical reaction between the semiconductor particles and water existing on the surface during excitation light irradiation. There's a problem. Such a problem is not a problem when the semiconductor particles are used as a biomarker or the like because it is sufficient if the light emission efficiency is sufficient to detect even if the light emission efficiency is low. In addition, when used as a biomarker, since it is also required that the semiconductor particles have high hydrophilicity, it is common knowledge to synthesize semiconductor particles in an aqueous solution and has sufficiently high luminous efficiency that can be used for lighting applications. No wavelength converter is provided.

Accordingly, an object of the present invention is to provide phosphor particles, a wavelength converter, and a light emitting device with high luminous efficiency that can suppress the occurrence of lattice defects on the surface of semiconductor ultrafine particles.
It is an object.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found a solution means having the following constitution and have completed the present invention.
(1) In a shell having an outer shell, encapsulating a wavelength conversion liquid having a light emission efficiency of 40% or more, which contains a semiconductor ultrafine particle for converting the wavelength of light and a liquid, A phosphor particle comprising an inorganic substance having an average particle diameter of 0.05 to 50 μm and a light transmitting property, wherein the water content of the wavelength conversion liquid is 0.1% by mass or less.
(2) The phosphor particles according to (1), wherein the liquid has a water solubility of 0.1% by mass or less.
(3) The phosphor particles according to (1) or (2), wherein the liquid is made of at least one of modified silicone oil or dimethyl silicone oil.
(4) The phosphor particles according to (1) or (2), wherein the liquid is made of at least one of oleylamine or dodecylamine.
(5) The phosphor particles according to any one of (1) to (4), wherein the shell-like body transmits 50% or more of light emitted from the semiconductor ultrafine particles.
(6) The phosphor particles according to any one of (1) to (5), wherein the semiconductor ultrafine particles have an average particle diameter of 10 nm or less.
(7) A wavelength converter formed by fixing the phosphor particles according to any one of (1) to (6) with a resin.
(8) A light-emitting device comprising: a light-emitting element; and the wavelength converter according to (7) that converts the wavelength of light from the light-emitting element.

  According to (1), the structure of the phosphor particles is a structure in which the semiconductor ultrafine particles and the liquid are encapsulated in the shell-like body having the outer shell, so that the semiconductor ultrafine particles are not directly fixed by the resin. Thus, it is possible to suppress the generation of lattice defects on the surface of the semiconductor ultrafine particles, and it is possible to suppress a decrease in the luminous efficiency of the semiconductor ultrafine particles. Moreover, it is a shell-like body having an average particle size of 0.05 to 50 μm and holds the semiconductor ultrafine particles and the liquid, so that it can be handled like a powder, and as a result, the phosphor particles having excellent handleability and Become. In addition, since the shell is made of a light-transmitting inorganic substance, it can block moisture from entering the shell, and light emitted from a light emitting device such as an LED can be transmitted to the shell. Incident light can be incident with high efficiency, and fluorescence emitted from semiconductor ultrafine particles can be efficiently transmitted to the outside. Furthermore, by setting the water content of the wavelength conversion liquid containing the semiconductor ultrafine particles and the liquid to 0.1% by mass or less, the average particle diameter of the semiconductor ultrafine particles is, for example, 10 nm or less and the specific surface area is large. However, it is possible to prevent the semiconductor ultrafine particles from being altered by moisture. Such phosphor particles can produce a wavelength conversion liquid having a luminous efficiency as high as 40% or more by using semiconductor ultrafine particles synthesized in an environment substantially free of water.

According to the above (2), since a liquid having a water solubility of 0.1% by mass or less is used, the liquid has a function of blocking moisture, so that the effect of preventing moisture from reaching the semiconductor ultrafine particles is enhanced. be able to.
According to said (3), what consists of at least 1 sort (s) of a modified silicone oil or a dimethyl silicone oil as a liquid is used suitably from being excellent in heat resistance. The modified silicone oil is a product obtained by attaching a functional group to dimethyl silicone oil or methylphenyl silicone oil.
According to said (4), what consists of at least 1 sort (s) of an oleylamine or dodecylamine as a liquid is used suitably from polarity being high.

According to (5), since the shell transmits 50% or more of the light emitted from the semiconductor ultrafine particles, the light emitted from a light emitting device such as an LED is incident on the shell with high efficiency. And the fluorescence emitted from the semiconductor ultrafine particles can be efficiently transmitted to the outside.
According to (6), since the average particle size of the semiconductor ultrafine particles is 10 nm or less, the energy level of the semiconductor ultrafine particles becomes discrete, and the band gap energy of the semiconductor ultrafine particles is equal to the particle size of the semiconductor ultrafine particles. It changes together. For this reason, by changing the particle diameter of the semiconductor ultrafine particles within a range of 10 nm or less, various light emission from red (long wavelength) to blue (short wavelength) can be obtained, and the phosphor has high color rendering properties and high efficiency. Can be made.

According to said (7), since the fluorescent substance particle of said structure is fixed with resin, it becomes a wavelength converter excellent in handling.
According to said (8), since the light-emitting device of this invention is equipped with a light emitting element and the wavelength converter which has said structure which wavelength-converts the light from this light emitting element, the fall of luminous efficiency is suppressed. It becomes a long-life light emitting device.

<Phosphor particles>
Hereinafter, an embodiment of the phosphor particles of the present invention will be described in detail with reference to the drawings. FIG. 1 is an enlarged schematic cross-sectional view showing the phosphor particles of the present embodiment. As shown in FIG. 1, this phosphor particle 1 includes a wavelength conversion liquid 9 containing a semiconductor ultrafine particle 5 and a liquid 7 in a shell 3 having an outer shell 3a, that is, in a space 3b. Contains.

  By configuring the phosphor particles 1 as described above, it is not necessary to directly hold the semiconductor ultrafine particles with a solid resin, and the resin and the semiconductor ultrafine particles generated due to the difference in the thermal expansion coefficient of the semiconductor ultrafine particles It is possible to suppress the generation of lattice defects on the surface of the semiconductor ultrafine particles caused by the generated gap and the generated stress, and it is possible to suppress the decrease in the light emission efficiency of the semiconductor ultrafine particles. In addition, since the semiconductor ultrafine particles 5 can be cut off from an atmosphere such as water or air, it is possible to prevent the semiconductor ultrafine particles 5 from being altered by an atmosphere such as water or air and impairing the wavelength conversion function. And the phosphor particle comprised in this way can implement | achieve high luminous efficiency.

  Confirmation that the phosphor particles 1 are configured as described above is confirmed by, for example, a transmission electron microscope (TEM), energy dispersive X-ray analysis (EDS), and gas chromatographic measurement, as described later. be able to.

(Shell)
The shell 3 is composed of an outer shell 3a and a space 3b, and has an average particle diameter of 0.05 μm (50 nm) to 50 μm. Thereby, since the phosphor particles 1 can be handled like a powder while the liquid 7 exists around the semiconductor ultrafine particles 5, the phosphor particles 1 are excellent in handleability. The lower limit of the average particle diameter is 0.05 μm or more, preferably 1 μm or more, more preferably 3 μm or more from the viewpoint of handleability. The upper limit of the average particle diameter is desirably 50 μm or less, preferably 10 μm or less, more preferably 5 μm or less from the viewpoint of extracting light to the outside. The average particle diameter is, for example, a value obtained by measuring the shell 3 (phosphor particles 1) with a particle size distribution measuring device (“Microtrack” manufactured by Nikkiso Co., Ltd.).

  The shell 3 is made of a light-transmitting inorganic substance. Thereby, while being able to block moisture such as water vapor from entering the shell 3 from the outside, light emitted from a light emitting device such as an LED is incident on the shell 3 with high efficiency, and The fluorescence emitted from the semiconductor ultrafine particles 5 can be efficiently transmitted to the outside.

  In order to efficiently take light emitted from a light emitter such as an LED into the shell 3 and change the wavelength of the semiconductor ultrafine particles 5 to efficiently extract the emitted light to the outside, the shell 3 It is preferable to transmit light emitted from the semiconductor ultrafine particles 5 by 50% or more, preferably 70% or more, more preferably 80% or more. The value indicating the transmission ratio is the transmittance, and the transmittance is a transmittance measuring device for only the shell 3 that does not contain the wavelength conversion liquid 9 (“Spectrophotometer” manufactured by Hitachi, Ltd.). It is a value obtained by measuring with.

The material constituting the shell 3 is not particularly limited as long as it is an inorganic substance having translucency. For example, at least one selected from glass compositions or ceramics having translucency as exemplified below. Preferably it consists of seeds. As the glass composition, for example, SiO _{2 -CaO-MgO-based, SiO 2 -BaO-Al 2 O} 3 based, SiO ₂ -B ₂ O _{3 based, SiO 2 -B 2 O 3 -Al} 2 O 3 system, Examples thereof include SiO ₂ -Al ₂ O ₃ -alkali metal oxide systems, and compositions obtained by blending these systems with alkali metal oxides, ZnO, PbO, Pb, ZrO ₂ , TiO _{2 and the} like. Examples of the ceramic include Al ₂ O ₃ , SiO ₂ , Y ₂ O ₃ , MgO, CaO, TiO ₂ , InO ₂ , SnO ₂ , BeO, ZrO ₂ , HfO ₂ , ThO ₂ , Dy ₂ O ₃ , Examples include ceramics including at least one selected from Ho ₂ O ₃ , Er ₂ O ₃ , MgAlO ₄ , SiC, TiC, Si ₃ N ₄ , TiN, and the like. Further, Al ₂ is known as a translucent ceramic. At least one selected from O ₃ , SiO ₂ , Y ₂ O ₃ , MgO, CaO, BeO, ZrO ₂ , HfO ₂ , ThO ₂ , Dy ₂ O ₃ , Ho ₂ O ₃ , Er ₂ O ₃ , MgAlO _{4 and the} like. Include ceramics. When these ceramics are used, the deterioration of characteristics due to moisture is suppressed, and light emitted from a light emitting device such as an LED is efficiently taken into the shell 3 and the wavelength of the semiconductor ultrafine particles 5 is reduced. It is possible to efficiently extract the light emitted by changing the light to the outside of the shell 3.

  As a manufacturing method of the shell 3 as described above, it can be manufactured by a generally known method such as a physical method, a mechanical method, a physicochemical method, a chemical method, or the like. Among the manufacturing methods described above, the physicochemical method and the chemical method can easily control the particle diameter of the shell 3 and can easily manufacture a small one of several μm, and the wall film has high density. Since the shell-like body 3 is obtained, it can be suitably used.

  In particular, the coacervation method, which is a physicochemical method, is optimal because the shell 3 can be formed only from a hydrophobic solution, whereas the chemical method must use both a hydrophobic and a hydrophilic solution. It is. As an example of the coacervation method, sodium silicate is added to a linseed oil solution in which polyoxyethylene sorbitan monooleate is dissolved, and the mixture is stirred and mixed to prepare an O / W emulsion, and sorbitan monostearate and polyoxy The above O / W emulsion is added to a benzene solution in which a mixture of ethylene sorbitan monooleate is dissolved and mixed by shaking to obtain an O / W / O emulsion, and the above O / W / O is added to an aqueous calcium chloride solution. Add O-type emulsion with stirring and react. In this method, a light yellow calcium silicate shell 3 containing linseed oil can be produced.

(Wavelength conversion liquid)
The wavelength conversion liquid 9 has a luminous efficiency of 40% or more, preferably 50% or more. Such high luminous efficiency can be realized by using the semiconductor ultrafine particles 5 synthesized in an environment substantially free of water. The luminous efficiency is a value obtained by measurement with a total luminous flux measurement system manufactured by Labsphere, as will be described later.

  Specifically, first, (A) the output energy of the LED chip is obtained, and the maximum value of the output wavelength of the LED chip is obtained. The LED chip has an In—Ga—N composition of size 0.3 × 0.3 mm that outputs light with a wavelength of 395 nm, for example. Next, (B) the phosphor particles 1 containing the wavelength conversion liquid 9 are prepared in a wavelength converter 11 to be described later, and the wavelength conversion is performed by causing the LED chip to emit light in a state where the wavelength converter 11 is placed on the LED chip. The device 11 is irradiated with light, the light in the range of 220 to 1100 nm output from the wavelength converter 11 is collected by an integrating sphere, and the collected energy is obtained. And (C) Among this energy, the energy of the wavelength below the maximum value of the output wavelength of a LED chip is handled as unconverted energy.

The wavelength conversion liquid obtained by applying (A) the output energy of the LED chip obtained above, (B) the recovered energy, and (C) the unconverted energy to the following formula (I) and calculating the wavelength conversion liquid. The luminous efficiency was 9.

  Moreover, the wavelength conversion liquid 9 contains the semiconductor ultrafine particles 5 and the liquid 7, and has a water content of 0.1% by mass or less, preferably 0.05% by mass or less, more preferably 0.01% by mass or less. It is important that it is substantially free of water. Thereby, it can suppress that the semiconductor ultrafine particle 5 changes in quality with a water | moisture content.

  In the wavelength conversion liquid 9, the ratio of the semiconductor ultrafine particles 5 to the liquid 7 is such that the content of the semiconductor ultrafine particles 5 is 0.01 to 10.0 mass%, preferably 0.1 to 5. mass% with respect to the total amount of the liquid 7. It is good that it is 0% by mass. Further, in order to set the water content of the wavelength conversion liquid 9 to 0.1% by mass or less, for example, water contained in the liquid 7 described later is removed, and the water content of the liquid 7 is set to 0.1% by mass or less. That's fine. As a method for removing moisture from the liquid 7, for example, a method of adding about 10% by weight of molecular sieves to the total amount of the liquid 7 and adsorbing moisture can be cited. Further, it is preferable that the semiconductor ultrafine particles 5 are also dried with a dryer or the like. The water content can be measured, for example, by titrating the wavelength conversion liquid 9 by the Karl Fischer titration method (moisture vaporization method) defined in JIS K 0068, as will be described later.

(Semiconductor ultrafine particles)
The semiconductor ultrafine particles 5 contained in the wavelength conversion liquid 9 described above have a function of converting the wavelength of light. The average particle diameter of the semiconductor ultrafine particles 5 is 10 nm or less, preferably 5 nm or less. When the average particle diameter of the semiconductor ultrafine particles 5 is 10 nm or less, scattering of light emitted from a light emitting device such as an LED or the semiconductor ultrafine particles 5 itself can be suppressed, and light can be efficiently extracted to the outside. Furthermore, the quantum effect and the like can be effectively utilized. The average particle diameter can be measured, for example, by observation with an accelerating voltage of 200 kV using a transmission electron microscope (TEM) [“JEM2010F” manufactured by JEOL Co., Ltd.] as described later.

  The semiconductor ultrafine particles 5 preferably absorb ultraviolet light having a wavelength of 370 to 420 nm, convert the absorbed ultraviolet light into visible light having a wavelength of 430 to 700 nm, and emit it. It is preferable that it is 60% or more. If it is less than 60%, the fluorescence intensity of the corresponding phosphor 1 is reduced with respect to the optimal white light spectrum, and at the same time, the color rendering property Ra of the output light emitted from the semiconductor ultrafine particles 5 is reduced. The light emission efficiency of the output light is reduced.

  Examples of the semiconductor ultrafine particles 5 described above include a compound of a periodic table group 14 element and a periodic table group 16 element, a compound of a periodic table group 13 element and a periodic table group 15 element, and a periodic table group 13 element. Compounds of group elements and group 16 elements of the periodic table, compounds of group 13 elements of the periodic table and group 17 elements of the periodic table, compounds of group 12 elements of the periodic table and group 16 elements of the periodic table, periodic table Compound of group 15 element and group 16 element of periodic table, compound of group 11 element of periodic table and group 16 element of periodic table, compound of group 11 element of periodic table and group 17 element of periodic table, periodic table A compound of a Group 10 element and a Group 16 element of the Periodic Table, a compound of a Periodic Table Group 9 element of the Periodic Table and a Group 16 element, a compound of a Group 8 element of the Periodic Table and a Group 16 element of the Periodic Table, Periodic table group 7 element and periodic table group 16 element compound, periodic table group 6 element and periodic table element Compounds with Group 6 elements, Periodic Table Group 5 elements and Periodic Table Group 16 elements, Periodic Table Group 4 elements with Periodic Group 16 elements, Periodic Table Group 2 elements and Periodic Examples include compounds with Group 16 elements, chalcogen spinels, and the like.

Specifically, as a compound of a group 14 element of the periodic table and a group 16 element of the periodic table, for example, tin (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 telluride (II) (SnTe), lead sulfide (PbS), selenium Examples of compounds of Group 13 elements of the periodic table and Group 15 elements of the periodic table such as lead halide (PbSe) and lead telluride (PbTe) include boron nitride (BN), boron phosphide (BP), boron arsenide (BAs). ), Aluminum nitride (AlN), aluminum phosphide (AlP), aluminum arsenide (AlAs), aluminum antimonide (AlSb), gallium nitride (GaN), gallium phosphide (GaP), gallium arsenide (GaAs) Gallium antimonide (GaSb), indium nitride (InN), indium phosphide (InP), indium arsenide (InAs), indium antimonide (InSb), etc. Examples of the compound include aluminum sulfide (Al ₂ S ₃ ), aluminum selenide (Al ₂ Se ₃ ), gallium sulfide (Ga ₂ S ₃ ), gallium selenide (Ge ₂ Se ₃ ), and gallium telluride (Ga ₂ Te _3). ), Indium oxide (In ₂ O ₃ ), indium sulfide (In ₂ S ₃ ), indium selenide (In ₂ Se ₃ ), indium telluride (In ₂ Te ₃ ), etc. Examples of compounds with Group 17 elements include thallium (I) chloride (TlCl), thallium bromide (I) (TlBr), and thallium iodide (I). TlI) and the like, as compounds of Group 12 elements of the periodic table and Group 16 elements of the periodic table, for example, zinc oxide (ZnO), zinc sulfide (ZnS), zinc selenide (ZnSe), zinc telluride (ZnTe), oxidation Periodic Table 15 Examples of the compound of a group element and a group 16 element of the periodic table include, for example, antimony (III) sulfide (Sb ₂ S ₃ ), antimony selenide (III) (Sb ₂ Se ₃ ), antimony telluride (III) (Sb ₂ Te ₃ ), bismuth sulfide (III) (Bi ₂ S ₃ ), bismuth selenide (III) (Bi ₂ Se ₃ ), bismuth telluride (III) (Bi ₂ ) Te ₃ ) and the like, and as a compound of the periodic table group 11 element and the periodic table group 16 element, for example, copper (I) (Cu ₂ O) and the like, the periodic table group 11 element and the periodic table group 17 element As the compound of, for example, copper chloride (I) (CuCl), copper bromide (I) (CuBr), copper iodide (I) (CuI), silver iodide (AgI), silver chloride (AgCl), silver bromide (AgBr) or the like, a compound of a periodic table group 10 element and a periodic table group 16 element, for example, nickel oxide (II) (NiO) or the like, a compound of a periodic table group 9 element and a periodic table group 16 element As a compound of a periodic table group 8 element and a periodic table group 16 element such as cobalt oxide (II) (CoO) and cobalt sulfide (II) (CoS), for example, triiron tetroxide (Fe ₃ O ₄ ), Iron (II) sulfide (FeS), etc. As a compound of Group 6 element, for example, manganese oxide (II) (MnO) or the like, as a compound of a periodic table group 6 element and Periodic Table Group 16 element, for example, molybdenum sulfide (IV) (MoS _2), tungsten oxide (IV) (WO ₂ ) and other compounds of Group 5 elements of the periodic table and Group 16 elements of the periodic table include, for example, vanadium (II) oxide (VO), vanadium oxide (II) (VO ₂ ), tantalum oxide ( V) (Ta ₂ O ₅ ) and the like, as a compound of Group 4 elements of the periodic table and Group 16 elements of the periodic table, for example, titanium oxide (TiO ₂ , Ti ₂ O ₅ , Ti ₂ O ₃ , Ti ₅ O _9, etc.) ), Etc., as compounds of Group 2 elements of the periodic table and Group 16 elements of the periodic table, for example, magnesium sulfide (MgS), magnesium selenide (MgSe), etc., as chalcogen spinels, for example, cadmium oxide (II) Chromium (III) (CdCr ₂ O ₄ ), Cadmium selenide (II) Chromium (III) (CdCr ₂ Se ₄ ), Copper (II) sulfide (III) (CuCr ₂ S ₄ ), Mercury selenide (II) And chromium (III) (HgCr ₂ Se ₄ ).

  Among those exemplified above, in particular, a group 11-17 compound semiconductor such as AgI, a group 12-16 compound semiconductor such as CdSe, CdS, ZnS and ZnSe, and a group 13-15 compound semiconductor such as InAs and InP are mainly used. Any of the compound semiconductors described above is desirable. In addition, the periodic table used by this invention shall follow the IUPAC inorganic chemical nomenclature 1990 rule.

  In the semiconductor ultrafine particles 5 of the present invention, the band gap energy of the semiconductor composition is preferably in the range of 1.5 to 2.5 eV. Thereby, when the semiconductor ultrafine particles 5 are nano-sized, fluorescence in the visible light region in the range of 430 to 700 nm can be expressed.

(liquid)
The liquid 7 contained in the wavelength conversion liquid 9 has a function of appropriately adjusting the concentration of the semiconductor ultrafine particles 5 and a function of blocking the semiconductor ultrafine particles 5 from an atmosphere such as water or air. Examples of the liquid 7 include silicone oil such as dimethyl silicone oil and modified silicone oil, liquid paraffin, n-hexane, cyclohexane, n-octane, n-decane, n-hexadecane, n-octadecane, hexene, octene, Examples include hydrocarbons having about 6 to 20 carbon atoms such as decene, octadecene, toluene, xylene, benzine, oleylamine, 2-ethylhexanoic acid, decanol, and particularly modified silicone oil or dimethylsilicone oil having excellent heat resistance. Is preferred.

  Further, it is preferable to use a liquid having polarity as the liquid 7. Thereby, since the liquid 7 can achieve the effect of repairing defects on the surface of the semiconductor ultrafine particles 5, it is not necessary to repair defects on the surface of the semiconductor ultrafine particles 5 with an organic amine or the like in advance. Even when a compound such as an organic amine that repairs defects on the surface of the semiconductor ultrafine particles 5 is detached, the liquid 7 present around the semiconductor ultrafine particles 5 is replaced with the semiconductor ultrafine particles 5 instead of the compound. Since defects on the surface can be repaired, the defect repair on the surface of the semiconductor ultrafine particles 5 is not impaired even for long-term use, and the phosphor particles 1 can be made stable over a long period of time.

  Specifically, for example, a dispersion medium having a polarity introduced by grafting an amino group to a dispersion medium in which the semiconductor ultrafine particles 5 are not bonded in advance to the surface of the semiconductor ultrafine particles 5 and having a defect repairing effect bonded thereto in advance. It is possible to make the dispersion medium have a defect repairing action directly by dissolving the polar compound in a nonpolar liquid.

  Examples of the liquid having the above polarity include xylene, toluene, oleylamine, dodecanethiol, oleic acid, modified silicone oil, 2-ethylhexanoic acid, and the like. Examples of dissolving a polar compound in a non-polar liquid include, for example, combining octadecene and oleic acid, combining octadecene and octadecylamine, or combining silicone oil and modified silicone oil. In particular, in the present invention, oleylamine or dodecylamine having high polarity is preferable.

  The liquid 7 is a combination of a plurality of types of semiconductor ultrafine particles 5 or semiconductor ultrafine particles 5 and phosphors other than the semiconductor ultrafine particles 5, and other functional material particles for adjusting the refractive index, for example. In the case of construction, it is desirable to have a function of holding them without being biased or agglomerated.

  Furthermore, since the liquid 7 serves as an optical path for the light output from the LED chip to reach the semiconductor ultrafine particles 5 and an optical path for the light converted from the wavelength of the semiconductor ultrafine particles 5 to go out of the light emitting device, the transmittance of these lights Is desirable. It is desirable that the LED chip does not deteriorate due to light output from the LED chip, light converted from the wavelength of the semiconductor ultrafine particles 5, or heat generated by the LED chip. The liquid 7 does not need to be composed of a single component, and may be composed of a plurality of components.

  The liquid 7 has a water solubility of 0.1% by mass or less, preferably 0.05% by mass or less, more preferably 0.02% by mass or less. The solubility of water in the liquid 7 affects the long-term decrease in wavelength conversion efficiency. By making the solubility of water below a predetermined value, the water contacts the semiconductor ultrafine particles 5 via the liquid 7. Can be suppressed. The water solubility in the present invention means mass% of water dissolved in the liquid 7 at 25 ° C.

<Wavelength converter>
Next, an embodiment of the wavelength converter of the present invention will be described in detail with reference to the drawings. FIG. 2 is a schematic cross-sectional view showing the wavelength converter according to the present embodiment. In FIG. 2, the same or equivalent parts as those in FIG. 1 described above are denoted by the same reference numerals and description thereof is omitted.

  As shown in FIG. 2, this wavelength converter 11 fixes the phosphor particles 1 described above with a resin 13 as a matrix. As the resin 13 used as this matrix, for example, epoxy resin, silicone resin, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polystyrene, polycarbonate, polyethersulfone, cellulose acetate, polyarylate, and derivatives of these materials are preferably used. It is done.

  Moreover, it is preferable that the resin 13 has a light transmittance. In addition to such transparency, an epoxy resin and a silicone resin are more preferably used from the viewpoint of heat resistance. The silicone resin may be linear or cross-linked and is not particularly limited. Examples of the substituent bonded to silicon of the silicone resin include, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, n-pentyl group, cyclopentyl group, and n-hexyl. Group, cyclohexyl group, octyl group, decyl group, dodecyl group, hexadecyl group, octadecyl group and other alkyl groups having about 1 to 20 carbon atoms, phenyl group, benzyl group, naphthyl group, naphthylmethyl group and other aromatic hydrocarbon groups In particular, a linear alkyl group having a small number of carbon atoms such as a methyl group and an ethyl group is preferable from the viewpoint of dispersibility of the inorganic particles.

  Furthermore, in the present invention, a polyvinyl alcohol resin that hardly permeates oxygen may be used as the resin 13. The average molecular weight of the polyvinyl alcohol resin is about 10,000 to 100,000, preferably about 20,000 to 90,000. On the other hand, if the average molecular weight is less than 10,000, the film does not cure and cannot be formed into a film, and if it exceeds 100,000, it is difficult to dissolve in water. In addition, the said molecular weight means a weight average molecular weight, the said polyvinyl alcohol resin is measured by a gel permeation chromatography (GPC), and is the value which carried out polystyrene conversion of the obtained measured value.

<Light emitting device>
Next, an embodiment of the light emitting device of the present invention will be described in detail with reference to the drawings. FIG. 3 is a schematic cross-sectional view showing the light emitting device according to the present embodiment. In FIG. 3, the same or equivalent parts as those in FIGS.

  As shown in FIG. 3, the light emitting device 17 includes a light emitting element 15 and the wavelength converter 11 described above that receives light from the light emitting element 15 and converts the wavelength of the light. Specifically, the light-emitting device 17 includes a substrate 21 on which an electrode 19 is formed, a light-emitting element 15 including a semiconductor material that emits light having a central wavelength of 450 nm or less on the substrate 21, and a light-emitting element 15 on the substrate 21. It consists of the wavelength converter 11 formed so that it may cover. The wavelength converter 11 contains the phosphor particles 1 described above. The light emitting element 15 fixed to the substrate 21 with the adhesive 23 and the electrode 19 are connected by a wire 25.

  While a part of the excitation light emitted from the light emitting element 15 passes through the wavelength converter 11, it is absorbed by the phosphor particles 1 and emits output light. If desired, the side surface of the light emitting element 15 may be provided with a reflector that reflects light, and the light escaping to the side surface may be reflected forward to increase the intensity of the output light.

  As the substrate 21, a substrate having excellent thermal conductivity and a large total reflectance is used. For example, in addition to a ceramic material such as alumina or nitrogen aluminum, a polymer resin in which metal oxide fine particles are dispersed is preferably used. .

  The light-emitting element 15 preferably emits ultraviolet light having a center wavelength of 450 nm or less, particularly 370 to 420 nm. By using excitation light in the wavelength range of this range, the phosphor can be excited efficiently, the intensity of output light can be increased, and a light emitting device with higher emission intensity can be obtained. The light emitting element 15 is not particularly limited as long as it emits the central wavelength, but the light emitting element substrate has a structure (not shown) including a light emitting layer made of a semiconductor material on the surface of the light emitting element substrate. This is preferable in that it has a high external quantum efficiency. Examples of such semiconductor materials include various semiconductors such as ZnSe and nitride semiconductors (GaN and the like). However, the type of the semiconductor material is not particularly limited as long as the emission wavelength is in the above wavelength range. A stacked structure including a light-emitting layer made of a semiconductor material may be formed over a light-emitting element substrate using a crystal growth method such as a metal organic chemical vapor deposition method (MOCVD method) or a molecular beam epitaxial growth method.

The substrate 21 can be selected in consideration of the combination with the light emitting layer. For example, when a light emitting layer made of a nitride semiconductor is formed on the surface, sapphire, spinel, SiC, Si, ZnO, ZrB ₂ , GaN and A material such as quartz is preferably used. In order to form a nitride semiconductor with good crystallinity with high productivity, it is preferable to use a sapphire substrate.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further in detail, this invention is not limited to a following example.

[Example]
<Preparation of phosphor particles>
(Sample Nos. 1-17, 19-37)
First, CdSe semiconductor ultrafine particles and ZnS semiconductor ultrafine particles were synthesized under conditions where water was not mixed. Specifically, CdSe semiconductor particles were synthesized as follows. First, 12.5 g of trioctylphosphine and 0.395 g of selenium were added to a flask in a glove box in a nitrogen atmosphere dried with phosphorus pentoxide, and the mixture was stirred for 1 hour. Next, 20 g of trioctylphosphine, 0.266 g of cadmium acetate, and 20 ml of dodecylamine (first liquid) previously mixed at 130 ° C. were added thereto. This was heated to 200 ° C., maintained at 200 ° C. while stirring, and stirred for 10 minutes to synthesize CdSe semiconductor particles.

  The synthesis of ZnS semiconductor particles was performed as follows. First, 12.5 g of trioctylphosphine and 0.16 g of sulfur were added to a flask in a glove box in a nitrogen atmosphere dried with phosphorus pentoxide, and this was stirred for 1 hour. Next, 20 g of trioctylphosphine, 0.212 g of zinc acetate, and 20 ml of dodecylamine previously mixed at 130 ° C. were added thereto. This was heated to 200 ° C., maintained at 200 ° C. while stirring, and stirred for 10 minutes to synthesize ZnS semiconductor particles.

  In addition, the dodecylamine used as a solvent used what removed the water by distilling, after adding calcium oxide beforehand and carrying out a return distillation for 2 hours.

  Furthermore, ZnS semiconductor ultrafine particles were synthesized in a hydrous solvent system as a comparative example. Specifically, first, 1.6 g of sodium bis (2-ethylhexyl) sulfosuccinate was dissolved in 15 ml of heptane, and 0.518 g of water was added thereto. To this was added 1.17 g of sodium sulfide. Separately from this, 1.6 g of sodium bis (2-ethylhexyl) sulfosuccinate was dissolved in 15 ml of heptane, and 0.518 g of water was added thereto. In this solution, 5.5 g of zinc acetate was dissolved. Next, these two solutions were mixed and stirred for 24 hours to synthesize ZnS semiconductor particles.

  The average particle size of the CdSe semiconductor ultrafine particles and ZnS semiconductor ultrafine particles synthesized as described above was confirmed as follows. First, a particle dispersion having a particle concentration in the range of 0.002 to 0.02 mol / liter was prepared. Note that isopropyl alcohol (IPA) or toluene was used as the solvent.

  Next, a transmission electron microscope (TEM) observation microgrid is immersed in the particle dispersion prepared above to adhere the particles, and is left in a desiccator at room temperature to dry the particle dispersion, and semiconductor nanoparticles A TEM observation microgrid having a surface attached to was prepared for measurement.

  The measurement was performed using a transmission electron microscope (TEM) [“JEM2010F” manufactured by JEOL Co., Ltd.] at an acceleration voltage of 200 kV. At this time, the magnification was 500,000 to 1,000,000 times, and the particles were focused so that the lattice fringes of the particles could be seen. When the particle size is large and the entire particle does not enter the field of view, after confirming that it is a primary particle at a high magnification at which lattice fringes can be seen, observe the TEM image at a magnification that allows the entire particle to enter the field of view and measure the particle size did.

  At this time, the semiconductor ultrafine particles are intended only for the portions where the lattice stripes are visible, and organic substances such as organic ligands adsorbed on the particle surfaces are not converted into particle sizes. Further, the particle diameter of sub-micron or larger particles that are sufficiently larger than the ultrafine semiconductor particles was measured for 200 or more particles by observing the fracture surface of the resin with a scanning electron microscope. At this time, the diameter of the particle was handled as the diameter of the whole particle by multiplying the diameter of the portion exposed on the surface of the fracture surface by a factor of 1.5 (intercept method, “ceramics characterization technology” pp. 7). ~ 8, published by the Ceramic Industry Association, published by the Ceramic Industry Association).

The diameter of the measured particles was calculated statistically by writing a histogram, thereby calculating the length average diameter. The length average diameter was calculated by counting the number of particles belonging to the particle diameter group and dividing the sum of the product of the center value and the number of particle diameter groups by the total number of particles measured ( Average particle diameter shape and calculation formula, “Ceramic manufacturing process”, pp. 11-12, edited by Ceramic Industry Association Editorial Committee, Lecture Committee, published by Association of Ceramic Industry). The length average diameter thus calculated was treated as the average particle diameter.
The image obtained by TEM observation was copied onto a transparent resin film sheet, and it was confirmed that the measurement was possible by a method of obtaining the average particle diameter of the particles using an image analysis processor.

The average particle diameter of each semiconductor ultrafine particle measured as described above was as shown below.
CdSe semiconductor ultrafine particles: 3.3 nm
ZnS semiconductor ultrafine particles: 3.5 nm
-ZnS semiconductor ultrafine particles prepared in a hydrous solvent system: 3.5 nm

  Next, with respect to the liquids shown in Table 1 and Table 2, each of the semiconductor ultrafine particles prepared above was mixed at a ratio of 0.5% by mass in the combinations shown in Table 1 and Table 2 to prepare a wavelength conversion liquid. . In addition, water was added to the liquids in Tables 1 and 2 in advance so that the water contents in Tables 1 and 2 were obtained. The water content of the wavelength conversion liquid was determined by the Karl Fischer titration method (moisture vaporization method) defined in JIS K 0068.

Next, a ligand (silicone oil) was added to the wavelength conversion solution prepared above to prepare a mixed solution. Then, it was prepared by adding a solution obtained by dissolving 10 wt% sorbitan monolaurate in a silicone oil into an aqueous solution of sodium silicate (5 mol% as SiO ₂₎ emulsion. To this solution, the above emulsion was added to a toluene solution of sorbitan monooleate and stirred. Next, an aqueous ammonium sulfate solution was added dropwise to the solution while stirring to react. After centrifuging the reaction solution, the supernatant was removed and dried to obtain phosphor particles enclosing a wavelength conversion solution in a shell having an outer shell (Sample Nos. In Tables 1 and 2). .1-17, 19-37).

The method for preparing the shell is the coacervation method, and the phosphor of the obtained phosphor particles is made of SiO ₂ (glass), and the average particle diameter of each shell is 10 μm. It was. Here, the average particle diameter of the shell was determined by measuring each phosphor particle with a particle size distribution measuring device (“Microtrack” manufactured by Nikkiso Co., Ltd.) as the average particle diameter of the shell.

In addition, each of the obtained phosphor particles is composed of CdSe in which a ligand (silicone oil) is coordinated on the surface in a shell made of SiO ₂ (glass), and each liquid shown in Tables 1 and 2. And toluene was included. The structure in which CdSe and liquid were encapsulated in the SiO ₂ (glass) shell and the presence of silicone oil and toluene were confirmed by TEM, energy dispersive X-ray analysis (EDS), and gas chromatographic measurement, respectively. .

(Sample No. 18)
Samples Nos. 1 and 2 are those in which CdSe semiconductor ultrafine particles having an average particle diameter of 3.5 nm are not in a shell-like structure and are exposed. It was set to 18.

<Evaluation of phosphor particles>
Among the phosphor particles obtained above (Sample Nos. 1 to 37 in Tables 1 and 2), Sample No. For each of the phosphor particles 1 to 19, each phosphor particle was mixed with a thermosetting epoxy resin in an amount of 5% by mass, and then applied to a glass plate with a thickness of 50 μm, and the epoxy resin was applied at 150 ° C. for 2 hours. Each of the wavelength converters was produced by curing. Next, for each of the obtained wavelength converters, the luminous efficiency of the wavelength conversion liquid and the maintenance ratio of the wavelength conversion efficiency after 100 hours were measured using a total sphere measuring system manufactured by Labsphere. Specifically, each wavelength converter is mounted on an In—Ga—N composition LED chip having a size of 0.3 × 0.3 mm that outputs a wavelength of 395 nm, and the luminous efficiency of the wavelength conversion liquid is calculated from the above formula (I). Calculated. Next, in this state, the LED chip is allowed to emit light for 100 hours, and the wavelength converter is irradiated with light. The value after 100 hours with respect to the initial value (that is, the light emission efficiency of the wavelength conversion solution) is expressed by the formula: [1- (100 hours later). Value / initial value)] × 100, and the maintenance ratio of wavelength conversion efficiency was measured. These results are shown together in Tables 1 and 2. In addition, the maximum value of the output wavelength of the LED chip was 430 nm.

  Sample No. About each fluorescent substance particle of 20-37, it replaced with the said epoxy resin, and sample No. was used except having used polyvinyl alcohol resin which is hard to permeate | transmit oxygen. Each wavelength converter was produced like 1-19. Next, for each wavelength converter obtained, sample No. In the same manner as in 1-19, the light emission efficiency of the wavelength conversion liquid and the maintenance ratio of the wavelength conversion efficiency after 100 hours were measured. The results are also shown in Table 1 and Table 2. The polyvinyl alcohol resin had an average molecular weight of 25,000.

  As is clear from Tables 1 and 2, the sample Nos. Whose water content outside the scope of the present invention exceeds 0.1% by mass. In 16, 17, 35, and 36, the wavelength conversion efficiency decreased to 50% or less after 100 hours. In addition, the sample No. which has no shell structure and CdSe is exposed. In 18, the wavelength conversion efficiency decreased to 40% or less after 10 hours. Sample No. In 19 and 37, the initial light emission efficiency was extremely low, and the wavelength conversion efficiency after 100 hours decreased to 37 and 42%, respectively.

  On the other hand, the sample No. 1 having a water content of 0.1% by mass or less according to the present invention. 1 to 15 and 20 to 34, the wavelength conversion efficiency is maintained at 70% or more of the initial value even after 100 hours.

It is an expansion schematic sectional drawing which shows one Embodiment of the fluorescent substance particle concerning this invention. It is a schematic sectional drawing which shows one Embodiment of the wavelength converter concerning this invention. It is a schematic sectional drawing which shows one Embodiment of the light-emitting device concerning this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Phosphor particle 3 ... Shell-like body 3a ... Outer shell 3b ... Space 5 ... Semiconductor ultrafine particle 7 ... Liquid 9 ... Wavelength conversion liquid 11 ... Wavelength conversion Container 13 ... Resin 15 ... Light emitting element 17 ... Light emitting device 19 ... Electrode 21 ... Substrate 25 ... Wire

Claims (8)

In a shell-like body having an outer shell, encapsulating a wavelength conversion liquid having a luminous efficiency of 40% or more, which contains semiconductor ultrafine particles for converting the wavelength of light and a liquid,
The shell is made of an inorganic substance having an average particle size of 0.05 to 50 μm and translucency, and the water content of the wavelength conversion liquid is 0.1% by mass or less. Phosphor particles.   The phosphor particles according to claim 1, wherein the liquid has a water solubility of 0.1 mass% or less.   The phosphor particles according to claim 1 or 2, wherein the liquid comprises at least one of modified silicone oil or dimethyl silicone oil.   The phosphor particles according to claim 1 or 2, wherein the liquid comprises at least one of oleylamine and dodecylamine.   The phosphor particles according to claim 1, wherein the shell-like body transmits 50% or more of light emitted from the semiconductor ultrafine particles.   The phosphor particles according to claim 1, wherein the semiconductor ultrafine particles have an average particle size of 10 nm or less.   A wavelength converter formed by fixing the phosphor particles according to claim 1 with a resin. A light-emitting device comprising: a light-emitting element; and a wavelength converter according to claim 7 that converts the wavelength of light from the light-emitting element.

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