JP2006328234A - Manufacturing process of phosphor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing process by which a group III nitride phosphor having a high light emission efficiency and an excellent reliability is manufactured by controlling the composition and size of the phosphor particle with a simple manufacturing process. <P>SOLUTION: The manufacturing process relates to a group III nitride phosphor having a double layered structure in which a phosphorescent core is covered by a shell. The process includes a step to manufacture the precursor for the core covered by a surfactant, a step to mix the core precursor with the shell precursor in a solution and a step to grow the shell over the core by heating the mixture of the core precursor and the shell precursor. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a phosphor having a two-layer structure in which a fluorescent core is covered with a shell. In particular, the synthesis procedure is simple, the synthesis yield is high, the emission intensity, and the fluorescence emission efficiency are improved. The present invention relates to a method for producing a layered group III nitride phosphor.

It is known that reducing the semiconductor crystal to about the exciton Bohr radius exhibits quantum size effects such as increased bandgap energy, increased transition establishment, increased nonlinear optical coefficient and hole burning. However, since the surface of a semiconductor crystal in which such a quantum size effect appears is predominantly a tangling bond (unbonded hand), the semiconductor crystal is larger than its band gap (referred to below as the energy gap between bands). A technique for capping defects on the surface of a semiconductor crystal by covering with a material having a band gap has been proposed (Non-Patent Document 1). Here, Non-Patent Document 1 proposes using InAs as the semiconductor core and GaAs, InP, or CdSe as the semiconductor shell. In addition, attempts have been made to synthesize nitride semiconductor fine particles as a wide gap semiconductor (Patent Document 1).
Japanese Patent Laid-Open No. 2002-220213 Yun Wei Cao and Uri Banin (Journal of American Chemical Society 2000, 122, 9692) American Chemical Society Publishing

  The InAs core covered with various shells described in Non-Patent Document 1 has an emission wavelength mainly in the near infrared region. Therefore, for example, it is excited by a gallium nitride-based semiconductor light-emitting element as an excitation light source and exhibits red, green, and blue fluorescence, and these cannot be mixed to obtain white light emission. That is, the core / shell semiconductor particles cannot be used as a phosphor. Further, the method for producing core / shell semiconductor particles described in Non-Patent Document 1 employs a two-stage production method in which a core is once produced and then a shell is produced on the core surface. On the other hand, the nitride semiconductor fine particles described in Patent Document 1 are not surface-modified, and the method for controlling the particle size of the fine particles depends only on the reaction temperature and the reaction time.

  In view of the above circumstances, the present invention provides a method for producing a group III nitride phosphor that has high emission efficiency (referred to as internal quantum efficiency during light emission, hereinafter the same) and high reliability with a simple production method. With the goal.

  The present invention is a method for producing a phosphor having a two-layer structure in which a fluorescent core is covered with a shell, the production process of the precursor of the core encapsulated with a surfactant, the precursor of the core, and the Mixing the precursor of the shell in solution; and heating the mixture of the precursor of the core and the precursor of the shell to grow a shell on the core. The present invention relates to a method for manufacturing a phosphor. Here, it is desirable that the core precursor and the shell precursor are compounds having a bond of a group III element and nitrogen in the molecule. The core precursor and / or the shell precursor is preferably an indium compound synthesized from indium trichloride and lithium dimethylamide.

  In the method for producing a phosphor of the present invention, it is desirable that the core precursor is a compound having a bond of a group III element and nitrogen in the molecule, and the shell precursor is an oxide. . Here, the group III element is preferably indium and / or gallium. Further, in the production method of the present invention, the core is preferably adjusted to fine particles having an exciton Bohr radius of 2 times or less.

  Furthermore, in the phosphor manufacturing method of the present invention, the temperature of heating the mixture of the core precursor and the shell precursor is 180 to 500 ° C., and the core precursor and the shell precursor are heated. The time for heating the mixture is preferably 6 to 72 hours.

  According to the phosphor production method of the present invention, phosphor particles can be synthesized in a high yield and in a large amount by liquid phase synthesis by a one-stage production operation in which heating is performed in a solution. The core particle size can be controlled by adjusting the size of the micelle field created by the surfactant. Since the core precursor and the shell precursor are separated by a surfactant, the excitation light can be absorbed by the shell with 400 to 410 nm excitation light by controlling the mixing ratio of each precursor. Thus, a group III nitride phosphor having high luminous efficiency can be synthesized by energy transition from the shell to the core and light emission from the core.

  Furthermore, the surface defects of the core can be covered by using an oxide precursor compound as the shell precursor. Since the group III element of the compound having a bond between the group III element and nitrogen used as the core precursor and the shell precursor is indium and gallium, it absorbs excitation light of 400 to 410 nm with high efficiency and emits light. Efficient red, green, and blue light emission is possible, and these colors can be mixed to obtain white light emission. By controlling the particle diameter to not more than twice the exciton Bohr radius, it is possible to produce a highly efficient phosphor exhibiting a quantum size effect.

  By adjusting the temperature at which the mixture of the core precursor and the shell precursor is heated to the range of 180 to 500 ° C., the operation is simpler than the gas phase reaction. Further, by setting the heating time to 6 to 72 hours, the phosphor particles can be adjusted to have sufficiently high crystallinity and few defects.

Embodiment 1 FIG.
The present invention is a method for producing a phosphor having a two-layer structure in which a fluorescent core is covered with a shell, the production process of the precursor of the core encapsulated with a surfactant, the precursor of the core, and the Mixing a precursor of the shell in solution and heating a mixture of the precursor of the core and the precursor of the shell to grow a shell on the core.

  For example, in FIG. 1 showing a flow of a method for manufacturing a phosphor, after the core precursor and the shell precursor are mixed in a solution, the mixture is heated and reacted in one step. A phosphor having a two-layer structure is manufactured through a cooling recovery process. As shown in FIG. 3, the obtained phosphor has a two-layer structure of a core 21 and a shell 22 that covers the core 21.

Hereinafter, the production method of the present invention will be described in detail.
<Process for producing core precursor>
As the core precursor, a compound having a bond of a group III element and nitrogen in the molecule is preferably used. Therefore, a core precursor manufacturing method using a compound having a bond of indium and nitrogen and a bond of gallium and nitrogen in the molecule will be described below as an example.

  While stirring lithium dimethylamide and indium trichloride in a solvent of n-hexane, the reaction temperature is 5 ° C. to 30 ° C., more preferably 10 ° C. to 25 ° C., and the reaction time is 24 hours to 120 hours, more preferably 48 hours to 72 hours. After completion of the reaction, by-product lithium chloride is removed, and tris (dimethylamino) indium dimer is taken out. This reaction is represented by chemical formula (1).

  In the same manner, tris (dimethylamino) gallium dimer is synthesized while stirring lithium dimethylamide and gallium trichloride in an n-hexane solvent. This reaction is represented by chemical formula (2).

  Next, while stirring the tris (dimethylamino) indium dimer and tris (dimethylamino) gallium dimer synthesized by the above method in an n-hexane solvent, the synthesis temperature is 5 ° C. to 30 ° C., more preferably 10 ° C. to 25 ° C. The reaction is carried out at a temperature of 24 hours to 120 hours, more preferably 48 hours to 72 hours, and hexa (dimethylamino) indium gallium is taken out. This reaction is represented by chemical formula (3).

Lithium dimethylamide and the product tris (dimethylamino) indium dimer, tris (dimethylamino) gallium dimer and hexa (dimethylamino) indium gallium are all highly reactive and therefore preferably carried out in an inert gas atmosphere.
<Incorporation of core precursor with surfactant>
The core precursor is encapsulated with a surfactant. In the present invention, the surfactant is a compound in which an organic group which is a large non-polar hydrocarbon terminal showing oil solubility and a hydrophilic group which is a polar terminal showing water solubility are present. The inclusion means a state in which the core precursor 11 is held inside the hydrophilic group of the micelle formed by the surfactant 13 as shown in FIG. The particle diameter of the core in the micelle is adjusted by the type of surfactant and the length of the organic group.

Examples of the surfactant used in the present invention include sodium lauryl phosphate (C ₁₂ H ₂₇ O ₄ PNa), sodium lauryl sulfate (C ₁₂ H ₂₇ O ₄ SNa), sodium dioctylsulfosuccinate (C ₂₀ H _37). O ₇ SNa).

For example, a predetermined amount of hexa (dimethylamino) indium gallium and tris (dimethylamino) gallium dimer as a core precursor material is mixed into a solution in which benzene, water and sodium lauryl phosphate (C ₁₂ H ₂₇ O ₄ PNa) are mixed. When dissolved and well agitated, the core precursor can be included with the surfactant. At this time, the core precursor strongly aggregates inside the micelle.

Here, the particle diameter of the core is adjusted by selecting an appropriate surfactant and mixing ratio with the solvent. For example, in the case of a surfactant that generally has a long organic group and is bulky, the particle diameter of the core is small. Further, when the amount of benzene with respect to the water in the solution is reduced, the particle size of the core is accordingly reduced.
<Process of mixing core precursor and shell precursor>
FIG. 2 is a structural diagram showing a process of mixing a core precursor and a shell precursor. In this state, the core precursor 11 is surrounded by the surfactant 13 in the solution, and the shell precursor 12 is covered around the core precursor 11 so as to enclose the surfactant. It should be noted that the core precursor / micelle and the shell precursor in solution are sufficiently thin so that the shell precursor does not enter the core precursor / micelle.

  By heating this mixed solution, a method for producing a phosphor having a core / shell two-layer structure in one stage becomes possible. The precursor of the shell is preferably a compound having a group III element and nitrogen bond in the molecule. Therefore, a method using a compound having a bond of indium and nitrogen and a bond of gallium and nitrogen in the molecule will be described below as an example.

First, hexa (dimethylamino) indium gallium is manufactured by the same method described in the core precursor manufacturing process. Then, in the micelle solution in which the core precursor included in the surfactant is stirred, hexa (dimethylamino) indium gallium and tris (dimethylamino) gallium dimer are used as the precursor of the indium / gallium mixed crystal shell. Mix in a predetermined amount.
<Step of growing a shell on the core>
Next, by heating the mixed liquid of the fluorescent core precursor and the shell precursor encapsulated with the surfactant at once, the shell grows with the core as a nucleus. This heating is performed in an inert gas atmosphere, and the reaction is performed at a synthesis temperature of 180 ° C. to 500 ° C., more preferably 280 ° C. to 400 ° C., for 6 hours to 72 hours, and more preferably for 12 hours to 48 hours.

After heating, the product is washed several times with n-hexane and anhydrous methanol to remove organic impurities when cooled and recovered.
<Description of the phosphor having a two-layer structure>
The phosphor core obtained by the above-described manufacturing method is a Ga _x1 In _(1-x1) N crystal, and the shell is composed of two layers of Ga _x2 In _(1-x2) N crystals. As shown in FIG. 3, the phosphor of the present invention has a two-layer structure in which a core 21 of a compound having a bond between a group III element and nitrogen is covered with a shell 22 of a compound having a bond between a group III element and nitrogen. is there. The core particle diameter and the shell thickness can be confirmed by performing TEM observation and confirming the lattice image with an observation image at a high magnification.

  Here, the average particle diameter of the core is usually estimated to be 5 to 6 nm from the spectrum half-value width as a result of X-ray diffraction measurement, which is a fine particle having twice or less the exciton Bohr radius, and the thickness of the shell is The range is adjusted to 1 to 10 nm. Here, if the thickness of the shell is smaller than 1 nm, the surface of the core cannot be sufficiently covered, and the effect of quantum confinement becomes weak. On the other hand, when the thickness is larger than 10 nm, it is difficult to make a shell uniformly and defects are increased, which is undesirable in terms of raw material costs.

  The light emission mechanism of the phosphor having a two-layer structure according to the present invention is as follows. The energy of the excitation light is absorbed by the outer shell and then transitions to the core surrounded by the shell. Here, since the particle diameter of the core is small enough to have a quantum size effect, the core can take only a plurality of discretized energy levels, but may have one level. The light energy transitioned to the core transitions between the ground level of the conduction band and the ground level of the valence band, and light having a wavelength corresponding to the energy is emitted.

In the phosphor of indium / gallium mixed crystal core / shell two-layer structure, the indium composition ratio of the shell is adjusted so that a blue light emitting element made of group III nitride can be used as an excitation light source. It is possible to efficiently absorb light with a high wavelength. Further, by adjusting the indium composition ratio of the fluorescent core, red, green, and blue fluorescence can be exhibited by energy transition from the shell to the core.
Embodiment 2. FIG.
In the step of mixing the core precursor and the shell precursor shown in the first embodiment, a gallium oxide shell precursor may be used instead of the indium gallium mixed crystal shell precursor. . In this case, gallium nitrate and urea are mixed in a predetermined amount to the micelle solution in which the core precursor included in the surfactant is stirred, and heating is performed as in the first embodiment. As a result, the indium / gallium mixed crystal core 21 which is a compound having a bond between a group III element and nitrogen as shown in FIG. 5 is covered with a shell 31 of gallium oxide which is an oxide. A body 20 is obtained.
Embodiment 3 FIG.
In the step of mixing the core precursor and the shell precursor shown in the first embodiment, a silicon oxide shell precursor can be used instead of the indium gallium mixed crystal shell precursor. . In this case, a predetermined amount of tetraethoxyorthosilicate and urea are mixed in the micelle solution as a precursor of the silicon oxide shell to the micelle solution in which the core precursor included in the surfactant is stirred, Heating is performed as in 1. As a result, the indium / gallium mixed crystal core 21, which is a compound having a bond between a group III element and nitrogen, as shown in FIG. A body 20 is obtained.

Example 1
The synthesis of a compound having a bond of indium and nitrogen and a bond of gallium and nitrogen in a molecule used as a core or shell precursor will be described. According to the chemical formulas (1) to (3), hexa (dimethylamino) indium gallium can be synthesized.

  Lithium dimethylamide and the product tris (dimethylamino) indium dimer, tris (dimethylamino) gallium dimer and hexa (dimethylamino) indium gallium were highly reactive, and all were carried out in an inert gas atmosphere.

  First, 0.03 mol of lithium dimethylamide and 0.01 mol of indium trichloride were weighed in a glove box, and reacted at a heating temperature of 20 ° C. for 50 hours while stirring in n-hexane. After completion of the reaction, by-product lithium chloride was removed, and tris (dimethylamino) indium dimer was taken out (chemical formula (1)).

  By the same method, tris (dimethylamino) gallium dimer was synthesized (chemical formula (2)). Further, 0.005 mol of tris (dimethylamino) indium dimer and 0.005 mol of tris (dimethylamino) gallium dimer synthesized by the above method were weighed and stirred in n-hexane at a heating temperature of 20 ° C. The reaction was carried out for 50 hours. Then, hexa (dimethylamino) indium gallium was taken out (chemical formula (3)).

Next, 0.02 mol of hexa (dimethylamino) indium gallium and 0.03 mol of tris (dimethylamino) gallium dimer, 10 g of sodium lauryl phosphate (C ₁₂ H ₂₇ O ₄ PNa), 20 ml of benzene, and 200 ml of water Was dissolved in a mixed solution to produce a core precursor (core growth: see chemical formula (4)).

  After sufficiently stirring, 0.04 mol of hexa (dimethylamino) indium gallium and 0.01 mol of tris (dimethylamino) gallium dimer were further mixed into the micelle solution as shell precursors (shell growth). : Chemical formula (5)). This solution was heated.

  This heating was performed in an inert gas atmosphere, and the reaction was performed at a heating temperature of 300 ° C. for 15 hours.

  Next, in order to remove organic impurities, washing was performed several times with n-hexane and anhydrous methanol. As a result, a phosphor having an indium / gallium mixed crystal core / shell two-layer structure as shown in FIG. 3 was obtained.

In this phosphor, the In _0.1 Ga _0.9 N semiconductor in the shell has an indium composition ratio adjusted so that the absorption edge is 420 nm. Therefore, a blue light-emitting element made of Group III nitride can be used as an excitation light source. In particular, 405 nm light having a high external quantum efficiency was efficiently absorbed. Further, since the indium composition ratio of the core In _0.2 Ga _0.8 N semiconductor was adjusted so that the emission wavelength was 460 nm, blue light emission could be exhibited by the energy transition from the shell to the core.

  In this phosphor emission mechanism, the energy of excitation light is absorbed by the shell of the outer layer, and then transitions to the core surrounded by the shell. Here, since the particle diameter of the core is small enough to have a quantum size effect, the core can take only a plurality of discretized energy levels, but may have one level. The light energy transitioned to the core transitions between the ground level of the conduction band and the ground level of the valence band, and light having a wavelength corresponding to the energy is emitted. It is excited efficiently by excitation light of 405 nm and emits blue light.

  As a result of the X-ray diffraction measurement of the phosphor obtained based on Example 1, the average particle diameter (diameter) of the core estimated from the spectrum half-width is 5 nm when the Scherrer equation (Formula (1)) is used. It was estimated that the quantum size effect was exhibited and the luminous efficiency was improved. The yield of the phosphor obtained in this example was 95%.

Where B: X-ray half width [deg],
λ: X-ray wavelength [nm],
Θ: Bragg angle [deg],
R: Particle diameter [nm]
It is.

(Example 2)
The same operation as in Example 1 was performed to synthesize tris (dimethylamino) indium dimer, tris (dimethylamino) gallium dimer, and hexa (dimethylamino) indium gallium. Next, according to chemical reaction formulas (4) and (6), 0.02 mol of hexa (dimethylamino) indium gallium and 0.03 mol of tris (dimethylamino) gallium dimer are converted into sodium lauryl phosphate (C ₁₂ H ₂₇ O ₄ PNa) 10 g, benzene 20 ml, and water 200 ml were dissolved in a mixed solution (chemical formula (4)), and after sufficient stirring, 0.1 mol of gallium nitrate and 0.5 mol of urea were further added to the micelles. The solution was mixed (Chemical Formula (6)) and heated.

  This heating was performed in an inert gas atmosphere, and the reaction was performed at a heating temperature of 300 ° C. for 50 hours.

  Next, in order to remove organic impurities, washing was performed several times with n-hexane and anhydrous methanol. As a result, a phosphor having an indium gallium mixed crystal core / gallium oxide shell two-layer structure as shown in FIG. 5 was obtained.

The phosphor obtained in this example is an indium / gallium mixed crystal core / gallium oxide shell two-layer phosphor. In this phosphor, the shell Ga ₂ O ₃ serves to protect the surface of the core In _0.2 Ga _0.8 N. In the phosphor emission mechanism, the In composition ratio is adjusted so that the absorption edge is 420 nm. Therefore, a blue light-emitting element made of a group III nitride can be used as an excitation light source, and particularly 405 nm with high external quantum efficiency. Can be efficiently absorbed.

  In this phosphor emission mechanism, the energy of the excitation light is absorbed by the core, and the light energy absorbed by the core transitions between the ground level of the conduction band and the ground level of the valence band, and the energy The light of the wavelength corresponding to is emitted. It is excited efficiently by excitation light of 405 nm and emits blue light.

  As a result of the X-ray diffraction measurement of the obtained phosphor, the average particle diameter (diameter) of the core estimated from the spectrum half-width is estimated to be 5 nm using the Scherrer equation (Equation (1)), The quantum size effect was shown, and the luminous efficiency was improved.

(Example 3)
Except for using 0.03 mol of hexa (dimethylamino) indium gallium and 0.02 mol of tris (dimethylamino) gallium dimer as the core precursor, an indium gallium mixture was prepared by the same production method as in Example 1. A crystal core / shell two-layer green phosphor can be obtained. As a result of the X-ray diffraction measurement of the obtained phosphor, the average particle diameter (diameter) of the core estimated from the spectrum half-width is estimated to be 5 nm using the Scherrer equation (Equation (1)), The quantum size effect was shown, and the luminous efficiency was improved.

Example 4
A red phosphor with an indium / gallium mixed crystal core / shell two-layer structure is obtained by the same manufacturing method as in Example 1 except that 0.1 mol of hexa (dimethylamino) indium / gallium is used as the core precursor. be able to. As a result of the X-ray diffraction measurement of the obtained phosphor, the average particle diameter (diameter) of the core estimated from the spectrum half-width is estimated to be 5 nm using the Scherrer equation (Equation (1)), The quantum size effect was shown, and the luminous efficiency was improved.

(Example 5)
Except for using 0.03 mol of hexa (dimethylamino) indium gallium and 0.02 mol of tris (dimethylamino) gallium dimer as the core precursor, an indium gallium mixture was produced by the same production method as in Example 2. A green phosphor with a crystal core / gallium oxide shell two-layer structure can be obtained. As a result of the X-ray diffraction measurement of the obtained phosphor, the average particle diameter (diameter) of the core estimated from the half-width of the spectrum is estimated to be 6 nm using the Scherrer formula (Formula (1)), The quantum size effect was shown, and the luminous efficiency was improved.

(Example 6)
The indium / gallium mixed crystal core / gallium oxide shell two-layer red phosphor is manufactured by the same manufacturing method as in Example 2 except that 0.1 mol of hexa (dimethylamino) indium / gallium is used as the core precursor. Can be obtained. As a result of the X-ray diffraction measurement of the obtained phosphor, the average particle diameter (diameter) of the core estimated from the half-width of the spectrum is estimated to be 6 nm using the Scherrer formula (Formula (1)), The quantum size effect was shown, and the luminous efficiency was improved.

(Example 7)
Except for using tetraethoxyorthosilicate ((C ₂ H ₅ O) ₄ Si) instead of gallium nitrate, the same manufacturing method as in Example 2 was used to produce an indium gallium mixed crystal core / silicon oxide shell two-layer structure. A blue phosphor can be obtained. As a result of the X-ray diffraction measurement of the obtained phosphor, the average particle diameter (diameter) of the core estimated from the half-width of the spectrum is estimated to be 6 nm using the Scherrer formula (Formula (1)), The quantum size effect was shown, and the luminous efficiency was improved.

(Example 8)
Except for using tetraethoxyorthosilicate ((C ₂ H ₅ O) ₄ Si) instead of gallium nitrate, the same manufacturing method as in Example 5 was used to produce an indium gallium mixed crystal core / silicon oxide shell two-layer structure. A green phosphor can be obtained. As a result of the X-ray diffraction measurement of the obtained phosphor, the average particle diameter (diameter) of the core estimated from the half-width of the spectrum is estimated to be 6 nm using the Scherrer formula (Formula (1)), The quantum size effect was shown, and the luminous efficiency was improved.

Example 9
Except for using tetraethoxyorthosilicate ((C ₂ H ₅ O) ₄ Si) instead of gallium nitrate, the same manufacturing method as in Example 6 was used to produce an indium gallium mixed crystal core / silicon oxide shell two-layer structure. A red phosphor can be obtained. As a result of the X-ray diffraction measurement of the obtained phosphor, the average particle diameter (diameter) of the core estimated from the half-width of the spectrum is estimated to be 6 nm using the Scherrer formula (Formula (1)), The quantum size effect was shown, and the luminous efficiency was improved.

(Comparative Example 1)
Trioctylphosphine ((C ₈ H ₁₇ ) ₃ P) 0.007 mol of gallium trichloride, 0.003 mol of indium trichloride, 0.01 mol of nonamethyltrisilazane (N (Si (CH ₃ ) ₃ ) ₃ ) The core was synthesized by mixing in 30 ml and reacting at a synthesis temperature of 260 ° C. for 3 hours. The reaction solution was cooled to room temperature to obtain a core trioctylphosphine solution.

Next, trioctylphosphine solution of the core, 0.009 mol of gallium trichloride, 0.001 mol of indium trichloride, 0.01 mol of nonamethyltrisilazane (N (Si (CH ₃ ) ₃ ) ₃ ) The mixture was mixed with 30 ml of octylphosphine and reacted at a synthesis temperature of 330 ° C. for 24 hours to synthesize a phosphor having a core / shell two-layer structure.

  The phosphor obtained in Comparative Example 1 has a two-step temperature rising synthesis process. In addition, since the phosphor precursor does not have a bond between a group III element and nitrogen, a blue light emitting element made of group III nitride is used as an excitation light source, and a precise group III element for realizing a desired emission wavelength is used. It is difficult to control the mixed crystal composition. Moreover, since control of a core particle diameter is dependent only on reaction temperature and reaction time, control of a particle diameter is difficult. As a result of X-ray diffraction measurement of the obtained phosphor, the average particle diameter (diameter) of the core estimated from the spectrum half-width is estimated to be 20 nm using the Scherrer equation (Equation (1)), Does not show quantum size effects. The yield of the phosphor obtained in Comparative Example 1 was 60%. Since there are two stages of synthesis, the yield is lower than in Example 1 where the synthesis is performed in one stage.

  FIG. 4 is a light emission intensity-core particle diameter characteristic diagram showing the light emission characteristics of the phosphor. In the figure, point (a) is the emission intensity of the phosphor of Example 1, and point (b) is the emission intensity of the phosphor of Comparative Example 1.

  In FIG. 6, the flowchart of the manufacturing method of the comparative example 1 is shown. First, a fluorescent core is manufactured by heating and cooling the precursor of the fluorescent core. Then, it is mixed with a precursor of a fluorescent shell that encloses the core, and heated and cooled again to obtain a phosphor having a core / shell two-layer structure.

  According to the present invention, a method for producing a phosphor having a two-layer structure in which a fluorescent core is covered with a shell, the production operation is simple, the synthesis yield is high, the emission intensity, and the fluorescence emission efficiency are improved. A method for producing a group III nitride phosphor having a two-layer structure is provided.

  In particular, according to the method for producing a phosphor of the present invention, phosphor particles can be synthesized in a high yield and in a large amount by liquid phase synthesis by a one-stage production operation in which heating is performed in a solution. Since the core precursor and the shell precursor are separated by a surfactant, the excitation light can be absorbed by the shell with 400 to 410 nm excitation light by controlling the mixing ratio of each precursor. Thus, a group III nitride phosphor having high luminous efficiency can be synthesized by energy transition from the shell to the core and light emission at the core.

It is the flowchart which showed the manufacturing method outline | summary of the fluorescent substance by this invention. It is the structure figure which showed the process of mixing the precursor of a core, and the precursor of a shell. FIG. 3 is a structural diagram of a phosphor having a group III nitride core / shell two-layer structure. It is a light emission intensity-core particle diameter characteristic view which compares the fluorescent substance obtained by the Example of this invention with the fluorescent substance obtained by the comparative example. FIG. 3 is a structural diagram of a phosphor having a group III nitride core / oxide shell two-layer structure. It is the flowchart which showed the manufacturing method of the comparative example 1 of this invention.

Explanation of symbols

  10 core / shell precursor micelle solution, 11 core precursor, 12 shell precursor, 13 surfactant, 20 core / shell phosphor, 21 group III nitride core, 22 group III nitride shell, 31 oxidation Shell.

Claims (8)

A method for producing a phosphor having a two-layer structure in which a fluorescent core is covered with a shell,
A process for producing a precursor of the core encapsulated with a surfactant;
Mixing the core precursor and the shell precursor in solution;
Heating a mixture of the core precursor and the shell precursor to grow a shell on the core;
The method for producing a phosphor having the two-layer structure as described above.   The method for producing a phosphor according to claim 1, wherein the precursor of the core and the precursor of the shell are compounds having a bond between a group III element and nitrogen in the molecule.   The method for producing a phosphor according to claim 1, wherein the core precursor and / or the shell precursor is an indium compound synthesized from indium trichloride and lithium dimethylamide.   The method for producing a phosphor according to claim 1, wherein the core precursor is a compound having a bond between a group III element and nitrogen in a molecule, and the shell precursor is an oxide.   The method for producing a phosphor according to claim 2, wherein the group III element is indium and / or gallium.   The method for producing a phosphor according to claim 1, wherein the core is a fine particle having an exciton Bohr radius of not more than twice.   The method for producing a phosphor according to claim 1, wherein a temperature at which the mixture of the core precursor and the shell precursor is heated is 180 to 500 ° C.   2. The method for producing a phosphor according to claim 1, wherein the time for heating the mixture of the core precursor and the shell precursor is 6 to 72 hours.

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