WO2014050705A1 - Phosphor, and method for producing said phosphor - Google Patents

Abstract

A phosphor (1) comprises a base material composed of nanoparticles each having a particle diameter of 5 nm or less and a luminescence center element, e.g., Eu, contained in the base material. The base material comprises an oxide containing an alkali earth metal element, e. g., Ti and Ba. The phosphor (1) can be produced by preparing a nanoparticle dispersion solution in which nanoparticles each comprising a Ti oxide, an alkali earth metal oxide and an oxide containing a luminescence center element are dispersed in a dispersion solution, applying the nanoparticle dispersion solution onto a substrate (2) to form a coating film, and then thermally treating the coating film at a low temperature equal to or lower than 500˚C. The nanoparticle dispersion solution may be prepared employing a microemulsion method. In this manner, a phosphor which has good luminous efficiency and a phosphor production method which makes it possible to produce the phosphor readily at low cost can be achieved.

Description

Phosphor and method for producing the phosphor

The present invention relates to a phosphor and a method for producing the phosphor, and more particularly to a phosphor in which a luminescent center element is contained in a base material made of nanoparticles and a method for producing the phosphor.

Fluorescent substances are substances that convert externally input energy such as ultraviolet rays, infrared rays, and radiation into light, and are used in various applications. Among these phosphors, a phosphor containing an element called a luminescence center (hereinafter referred to as “luminescence center element”) in a base material formed of nanoparticles can emit light with high efficiency. This is possible and is expected to be applied to various fluorescent devices.

In this type of phosphor, good emission efficiency can be obtained by confining the emission center element in the nanoparticle as the host material and resonating the energy level of the host material and the energy level of the emission center element. It is said.

By the way, as a method for producing nanoparticles containing a luminescent center element, a gas phase reaction method, a precipitation method, and the like are known.

For example, Non-Patent Document 1 is known as a prior art document using a gas phase reaction method.

This non-patent document 1 reports the phase structure and fluorescence characteristics of Eu ³⁺ doped TiO ₂ nanocrystals synthesized by Ar / O ₂ high-frequency thermal plasma oxidation of a precursor solution.

In this non-patent document 1, a precursor solution containing titanium tetra-n-butoxide (TTBO) and europium nitrate is put into a high-temperature plasma, thereby producing TiO ₂ nanoparticles doped with Eu ^3+. Yes.

Further, as a prior art document using the precipitation method, for example, Non-Patent Document 2 is known.

This non-patent document 2 reports enhanced fluorescence from Eu ³⁺ for a low-loss glass-ceramic waveguide containing silicon with a high concentration of SnO ₂ .

In this non-patent document 2, a SiO ₂ —SnO ₂ glass ceramic thin film waveguide doped with 1 mol% of Eu ³⁺ is manufactured by a sol-gel method and a dip method.

That is, after several heat treatments using a sol-gel method and a dip method, a SiO ₂ —SnO ₂ film with Eu ³⁺ added is formed on the transparent SiO ₂ surface on the Si substrate, Thereafter, heat treatment is performed at a high temperature of 900 to 1100 ° C., thereby depositing nanocrystals in the amorphous waveguide.

However, according to the research results of the present inventors, it has been found that it is difficult to obtain a sufficiently large luminous efficiency when TiO ₂ as in Non-Patent Document 1 is used as a base material.

Further, since the gas phase reaction method described in Non-Patent Document 1 is processed in high-temperature plasma, there is a problem that a large-scale apparatus and a complicated manufacturing process are required, and the manufacturing cost is expensive.

Further, in Non-Patent Document 1, since the high-temperature heat treatment is performed in the high-temperature plasma as described above, the particle growth of the nanoparticles is promoted and the particle size distribution becomes wide, which may cause deterioration of the fluorescence characteristics. There is.

Further, according to the research results of the present inventor, even when SnO ₂ -based material as in Non-Patent Document 2 is used as a base material, it is difficult to obtain a sufficiently large luminous efficiency as in Non-Patent Document 1. I understood.

Furthermore, since the precipitation method described in Non-Patent Document 2 requires a high-temperature heating process at 900 to 1100 ° C., similarly to Non-Patent Document 1, a large-scale apparatus and a complicated manufacturing process are required. Becomes expensive. In addition, as in Non-Patent Document 1, the growth of nanoparticles is promoted by a high-temperature heating process, the particle size distribution becomes wide, and there is a possibility that the fluorescence characteristics deteriorate.

This invention is made | formed in view of such a situation, Comprising: Provided with the fluorescent substance which has favorable luminous efficiency, and the manufacturing method of the fluorescent substance which can manufacture this fluorescent substance easily at low cost. Objective.

The present inventor conducted intensive research to achieve the above object, and used nanoparticles containing an oxide of Ti and an alkaline earth metal element as a base material, and contained a luminescent center element in the base material. As a result, it has been found that a phosphor having significantly better luminous efficiency than that of the prior art can be obtained.

The present invention has been made on the basis of such knowledge. In the phosphor according to the present invention, a luminescent center element is contained in a base material formed of nanoparticles, and the base material includes at least Ti and It is characterized by containing an oxide containing an alkaline earth metal element.

In the phosphor of the present invention, the ratio of the luminescent center element to the total of Ti and the alkaline earth metal element is preferably 0.03 to 0.10 in molar ratio.

In the phosphor of the present invention, the ratio of Ti to the alkaline earth metal element is preferably 1/9 to 9/1 in molar ratio.

In the phosphor of the present invention, the alkaline earth metal element is preferably Ba.

In the phosphor of the present invention, it is preferable that the emission center element is any one of a rare earth element and a transition metal element.

Furthermore, in the phosphor of the present invention, the rare earth element is preferably Eu.

In addition, as a result of further extensive research by the present inventors, a nanoparticle dispersion solution in which nanoparticles containing Ti oxide, alkaline earth metal oxide, and oxide containing a luminescent center element are dispersed in a dispersion solution is obtained. The coating film can be baked without grain growth by preparing and coating the nanoparticle dispersion solution on a substrate to form a coating film and then heat-treating it at a low temperature of 500 ° C. or lower. As a result, it was found that a nanoparticle aggregate having a minute particle diameter can be obtained, and that the phosphor having good luminous efficiency can be produced.

That is, the method for producing a phosphor according to the present invention produces a nanoparticle dispersion solution in which nanoparticles containing Ti oxide, alkaline earth metal oxide, and an oxide containing an emission center element are dispersed in a dispersion solution. A nanoparticle dispersion solution preparation step, a coating film formation step of coating the nanoparticle dispersion solution on a substrate to form a coating film, and a heat treatment step of heat-treating the coating film, A heat treatment is performed at a temperature of 500 ° C. or lower to produce a phosphor in which a luminescent center element is added to a base material containing an oxide containing Ti and an alkaline earth metal element.

Thus, a desired phosphor can be obtained at a low cost without requiring a high-temperature heating process and, therefore, without requiring a large-scale apparatus or a complicated manufacturing process. In addition, since the nanoparticle aggregate forming the phosphor is heat-treated at a low temperature of 500 ° C. or lower, it is possible to suppress the nanoparticle from causing grain growth, and to achieve a desired quantum size effect with a uniform particle size distribution. A phosphor capable of expression can be obtained.

The phosphor production method of the present invention comprises a microemulsion solution preparation step of preparing a water-in-oil microemulsion solution in which a hydrophobic solvent, a surfactant, and water are mixed to form a water-in-oil microemulsion solution in which water droplets are dispersed in oil. A mixed alkoxide solution preparation step of preparing a mixed alkoxide solution by mixing a plurality of alkoxides including Ti alkoxide, an alkoxide containing an alkaline earth metal element, and an alkoxide containing a luminescent center element in a solvent, and the mixed alkoxide It is preferable to include a hydrolysis step of injecting the solution into the microemulsion solution to cause a hydrolysis reaction.

This makes it possible to easily obtain a phosphor having a desired composition simply by adjusting the composition of the mixed alkoxide solution dropped into the microemulsion solution. Moreover, it is possible to arbitrarily select the luminescent center element and the base material simply by changing the raw material species for forming the mixed alkoxide solution, and the desired component composition can be obtained without requiring a large-scale apparatus or complicated processes. Can easily be manufactured.

According to the phosphor of the present invention, the matrix material formed of the nanoparticles contains the luminescent center element, and the matrix material contains an oxide containing at least Ti and an alkaline earth metal element. Thus, it is possible to obtain a phosphor having much better light emission efficiency than conventional ones. That is, by mixing a divalent alkaline earth metal element and a tetravalent Ti in the base material, the 2p orbit of O, the 3d orbit of Ti, and the outermost orbit of the alkaline earth metal element forming these base materials. A hybrid orbit is formed between the two. Since this hybrid orbital has an energy level close to that of the electron orbit of the luminescent center element, resonance energy transfer occurs. As a result, the efficiency of energy transition to the luminescent central element is improved, and the luminous efficiency can be significantly improved as compared with the conventional case.

In addition, according to the method for producing a phosphor of the present invention, a nanoparticle dispersion in which nanoparticles containing at least a Ti oxide, an alkaline earth metal oxide, and an oxide containing an emission center element are dispersed in a dispersion solution. A nanoparticle dispersion solution preparation step for preparing a solution, a coating film formation step for forming a coating film by applying the nanoparticle dispersion solution on a substrate, and a heat treatment step for heat-treating the coating film, and the heat treatment step Performs the heat treatment at a temperature of 500 ° C. or less, and produces a phosphor in which a luminescent center element is added to a base material made of an oxide containing at least Ti and an alkaline earth metal element, and thus requires a high-temperature heating process. Therefore, a desired phosphor can be obtained at low cost without requiring a large-scale apparatus or a complicated manufacturing process. Moreover, since the nanoparticles are heat-treated at a low temperature of 500 ° C. or lower, it is possible to suppress the occurrence of grain growth and obtain a phosphor capable of exhibiting a desired quantum size effect with a uniform particle size distribution. it can.

It is sectional drawing which shows typically one Embodiment of the fluorescent substance which concerns on this invention. It is the front view which showed typically one Embodiment of the nanoparticle dispersion solution produced with the manufacturing method of this invention. FIG. 3 is an enlarged view of a main part of FIG. 2. It is a schematic diagram for demonstrating the manufacturing method of the said nanoparticle dispersion solution. It is a figure which shows the fluorescence spectrum of the sample number 1. FIG. It is a figure which shows the fluorescence spectrum of sample number 2. FIG. It is a figure which shows the fluorescence spectrum of the sample number 3. FIG. It is a figure which shows the fluorescence spectrum of the sample number 4. FIG. FIG. 6 is a diagram showing fluorescence spectra of sample numbers 2 to 4. It is a figure which shows the fluorescence spectrum of the sample number 5. FIG. It is a figure which shows the fluorescence spectrum of the sample number 6. FIG. It is a figure which shows the fluorescence spectrum of the sample number 7. FIG. It is a figure which shows the fluorescence spectrum of sample number 2 and 5-7.

Next, an embodiment of the present invention will be described in detail.

FIG. 1 is a cross-sectional view schematically showing an embodiment of a phosphor according to the present invention. The phosphor 1 is formed on a substrate 2 made of quartz glass or the like.

The phosphor 1 includes a luminescent center element L contained in a matrix material formed of nanoparticles having a particle size of 5 nm or less, and the matrix material contains at least Ti and an alkaline earth metal element M. Is included. As a result, the luminous efficiency can be significantly improved as compared with the conventional case.

That is, in the Ti—O-based energy structure, the valence band is mainly formed by 2p orbitals of O, and the conduction band is mainly formed by 3d orbitals of Ti. When external energy is applied to the phosphor 1 and the host material absorbs excitation light, the electrons are excited from the O2p orbital of the valence band to the Ti3d orbital of the conduction band, and the electrons have an energy level in the valence band. The phosphor 1 emits light by transitioning to an emission center element having an energy level intermediate between the upper end and the lower end of the conduction band and resonating with Ti—O.

However, when a divalent alkaline earth metal element M having a lower energy level than Ti is mixed in such a Ti—O system, the s orbit of the outermost shell of the alkaline earth metal element M (for example, in the case of Ba) 6s orbit) overlaps with the 2p orbit of O and the 3d orbit of Ti, and orbital hybridization occurs, forming a hybrid orbital. Since this hybrid orbital is close in energy level to the electron orbit of the luminescent center element, resonance energy transfer occurs. As a result, the energy transition efficiency of the electrons excited from the upper end of the valence band to the lower end of the conduction band to the luminescent central element is improved.

In particular, in this embodiment, the base material made of M-Ti-O is formed of nanoparticles of 5 nm or less, and the light absorption efficiency is increased by the quantum size effect. The energy transition efficiency to the element L can be remarkably improved, and the light emission efficiency can be remarkably improved.

As the luminescent center element L, various rare earth elements and transition metal elements having an energy level that resonates with the energy level of the base material can be used.

For example, the rare earth element includes at least one element selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. Can be used.

Examples of the transition metal element include Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, and Cd. One or more selected elements can be used.

Among these many elements, a luminescent center element is used in which the energy level of the alkaline earth metal element M is located between the energy level at the lower end of the conduction band and the excitation energy level of the luminescent center element L. For example, Eu can be preferably used.

Further, the alkaline earth metal element M is not particularly limited, and Mg, Ca, Sr, Ba, and the like can be appropriately selected according to the type of the luminescent center element L. Usually, Ba is preferred. Can be used.

Next, a method for manufacturing the phosphor 1 will be described in detail.

First, a nanoparticle dispersion solution in which nanoparticles having a Ti oxide, an alkaline earth metal oxide, and an oxide containing an emission center element are dispersed in a dispersion solution is prepared.

Here, the method for producing the nanoparticle dispersion solution is not particularly limited, but it is possible to easily obtain ultrafine nanoparticles of 5 nm or less that have a narrow particle size distribution and can exhibit a desired quantum size effect, and It is preferable to use a microemulsion method that can easily change the type of nanoparticles simply by selecting a raw material and has a high degree of design freedom.

Moreover, in this microemulsion method, since the nanoparticles are already formed in the dispersion solution, the heat treatment necessary to burn and decompose the hydrophobic solvent and the surfactant may be performed as described later. A highly efficient phosphor 1 can be produced by a low temperature process.

The following explains how to prepare a nanoparticle dispersion using this microemulsion method.

FIG. 2 is a front view schematically showing a nanoparticle dispersion solution prepared by a microemulsion method.

That is, in the nanoparticle dispersion solution 3, the nanoparticles 4 are dispersed and suspended in the hydrophobic solvent 6 in a form surrounded by the surfactant 5, and the dispersion solution 3 is contained in the container 7. Yes.

Specifically, as shown in FIG. 3, the surfactant 5 has a main surfactant 8 and a subsurfactant 9.

The main surfactant 8 has a hydrophobic group 8 a and a hydrophilic group 8 b, the hydrophobic group 8 a is adsorbed on the hydrophobic solvent 6, and the hydrophilic group 8 b is adsorbed on the nanoparticles 4.

Here, as the main surfactant 8, polyoxyethylene alkylphenyl ether (APE (n)) capable of obtaining hydrophilicity at the polyoxyethylene group ((CH ₂ CH ₂ O) _n ) portion is used. In particular, polyoxyethylene nonylphenyl ether (NPE (n)) represented by the chemical formula H ₃ C (CH ₂ ) ₈ C ₆ H ₄ O (CH ₂ CH ₂ O) _n H is preferably used.

Then, by changing the side chain length n of APE (n), it is possible to control the average particle diameter D ₅₀ of the resulting nanoparticles 4. That is, as the length of the side chain length n increases, the average particle diameter D ₅₀ of the nanoparticles 4 tends to be smaller than when the length of the side chain length n is short. This is because, as the side chain length n increases, the hydrophilic group also increases, so that the adsorption force to the water droplets contributing to the generation of the nanoparticles 4 becomes stronger and the water droplet diameter becomes smaller. This is probably because the average particle diameter D ₅₀ of the nanoparticles 4 to be produced is also reduced.

Thus, the average particle diameter D ₅₀ of the nanoparticles 4 can be controlled by utilizing the difference in the side chain length n of APE (n). Therefore, it becomes possible to control the average particle diameter D ₅₀ of the nanoparticles 4 only by selecting APE (n) having different side chain lengths n.

Further, the sub-surfactant 9 enters the hydrophilic group 8b of the main surfactant 8 to reduce the interfacial energy with water during the preparation of the microemulsion described later, and the side chain of the hydrophilic group 8b. This has the effect of reducing steric hindrance due to the length n, thereby contributing to the stabilization of water droplets. And when this nanosurfactant 4 is produced | generated, this subsurfactant 9 is adsorb | sucked by the nanoparticle 4 with the hydrophilic group 8b of the main surfactant 8, and the nanoparticle 4 in the form which surrounds the nanoparticle 4, and nanoparticle 4 Contributes to stable dispersion in the hydrophobic solvent 6.

As such a subsurfactant 9, a medium chain alcohol represented by the chemical formula C _m H _{2m + 1} OH (where m is 4 to 10), for example, 1-octanol (C ₈ H ₁₇ OH) is used. can do. That is, the carbon number m depends on the length of the side chain length n of the hydrophilic group 8b of the main surfactant 8. However, if the carbon number m is less than 4, the hydrophilicity becomes too large, so that a microemulsion is produced. Occasionally, it dissolves in the water droplets, so that the secondary surfactant 9 may not be present only at the interface between the main surfactant 8 and water. On the other hand, when the carbon number m exceeds 10, the hydrophobicity may be excessively increased or the steric hindrance may be increased, which is not preferable.

As the hydrophobic solvent 6, nonpolar hydrocarbons such as cyclohexane, hexane, cyclopentane, benzene, and octane, ethers such as diethyl ether and isopropyl ether, petroleum hydrocarbons such as kerosene, etc. may be used. Of these hydrophobic solvents 6, cyclohexane and benzene can be preferably used.

The dispersion of the nanoparticles 4 in the solution can be confirmed directly by a transmission electron microscope (hereinafter referred to as “TEM”) or by a limited-field electron diffraction pattern. it can.

And this nanoparticle dispersion solution 3 is manufactured by the following methods.

First, the hydrophobic solvent 6, the surfactant 5 (the main surfactant 8 and the subsurfactant 9), and water are put in the container 7 and mixed and stirred. Then, as shown in FIG. 4 (a), the hydrophobic group 8a of the main surfactant 8 is adsorbed by the hydrophobic solvent 6, while the hydrophilic group 8b of the main surfactant 8 is adsorbed by water, The subsurfactant 9 enters the hydrophilic group 8b of the main surfactant 8 and the interfacial energy with water decreases. As a result, the water becomes ultrafine water droplets 10 and is confined inside the surfactant 5 (the main surfactant 8 and the subsurfactant 9). That is, the water droplets 10 are dispersed in the hydrophobic solvent 6 in a form surrounded by the surfactant 5, whereby a water-in-oil microemulsion solution is produced.

The surfactant 5 and water are, for example, water / surfactant = 0.005 so that the average particle diameter D ₅₀ of the final product nanoparticles is 5 nm or less (preferably 3 nm or less). It is blended so that it becomes ˜0.05 and put into the container 7.

Next, a mixed alkoxide solution as a raw material for the nanoparticles 4 is prepared.

That is, in order to obtain nanoparticles 4 having a desired particle size with a very small particle size distribution, it is necessary to avoid an increase in the water droplet size of the water droplet 10 consumed in the hydrolysis reaction. It is desirable to use an anhydride such as an alkoxide.

Therefore, Ti alkoxide, M alkoxide containing alkaline earth metal element M, and L alkoxide containing luminescent center element L are prepared, and these alkoxides are dissolved in an alcohol solution such as isopropyl alcohol, whereby a mixed alkoxide solution is prepared. Make it.

Here, the ratio L / (M + Ti) of the luminescent center element L to the total of the alkaline earth metal elements M and Ti in the mixed alkoxide solution is not particularly limited, but is preferably 0.03 in molar ratio. Set to ~ 0.1. In order to obtain better luminous efficiency, the ratio L / (M + Ti) is more preferably large in the range of 0.03 to 0.1.

Further, the alkaline earth metal elements M and Ti and the ratio M / Ti in the mixed alkoxide solution are not particularly limited, and can be arbitrarily adjusted within a range of, for example, 1/9 to 9/1 in molar ratio. it can.

The mixed alkoxide solution is preferably prepared in an inert atmosphere such as an Ar atmosphere from the viewpoint of preventing moisture in the air from entering the mixed alkoxide solution. That is, by preparing the mixed alkoxide solution in an inert atmosphere, excess components do not enter the microemulsion solution, thereby suppressing an increase in the particle size of the nanoparticles 4.

Next, the mixed alkoxide solution prepared in this manner is dropped into the microemulsion solution, and stirred and mixed for a predetermined time in an inert atmosphere such as an Ar atmosphere. Then, a hydrolysis reaction occurs between the mixed alkoxide solution and the water droplet 10.

That is, the hydrolysis reaction proceeds using the water droplets 10 surrounded by the surfactant 5 as a reaction field, and as shown in FIG. 4B, the water droplets 10 are consumed and titanium oxide, alkaline earth metal oxide, And the nanoparticle 4 which consists of a mixture of the oxide containing a luminescent center element is produced | generated, and the nanoparticle dispersion solution 3 is produced by this.

Here, the mixed alkoxide solution is dropped into the microemulsion solution so that the amount of water in the microemulsion solution is 1 to 1.2 times the amount of water necessary for hydrolysis of the mixed alkoxide. This is because when the amount of water in the microemulsion solution is less than 1 times the amount of water required for hydrolysis of the mixed alkoxide, the desired hydrolysis reaction does not proceed, while when it exceeds 1.2 times, the amount of water increases. This is because the water droplet 10 becomes large, and therefore, the average particle diameter D _{50 of} the produced nanoparticles 4 may be increased according to the increased water droplet diameter.

The type of alkoxide is not particularly limited, and ethoxide, propoxide, butoxide and the like can be used.

Thereafter, the phosphor 1 is prepared using the nanoparticle dispersion solution 3.

That is, the nanoparticle dispersion solution 3 is uniformly applied onto the substrate 2 by a spin coating method or the like to form a coating film.

Specifically, after the nanoparticle dispersion solution 3 is dropped on the substrate 2, the substrate 2 is rotated at a predetermined rotation speed for a predetermined time, so that the nanoparticle dispersion solution 3 is uniformly applied on the substrate 2. The Thereafter, heat treatment is performed at a low temperature of 500 ° C. or lower. As a result, the hydrophobic solvent 6, the surfactant 5, and the like are burned and decomposed, and an oxide of Ti and the alkaline earth metal element M is used as a base material, and the luminescent center element L is added to the base material. The phosphor 1 made of MO is manufactured.

That is, since the nanoparticles 4 are already produced in the nanoparticle dispersion solution 3, the phosphor 1 is produced by a low-temperature process capable of burning and decomposing organic substances such as the hydrophobic solvent 6 and the surfactant 5. be able to.

In addition, when the heat treatment temperature exceeds 500 ° C., it is not preferable because it promotes nanoparticle growth and the particle size may exceed 5 nm.

The lower limit of the heat treatment temperature is not particularly limited, but is preferably a temperature at which the hydrophobic solvent 6 can be sufficiently volatilized, for example, 100 ° C. or higher.

Thus, the heat treatment temperature can be adjusted to an appropriate temperature in the range of 100 to 500 ° C. according to the type of the base material, that is, the alkaline earth metal element M to be used.

Thus, in this Embodiment, after apply | coating the nanoparticle dispersion solution 3 to the board | substrate 2, it heat-processes at the low temperature of 500 degrees C or less, and is producing the fluorescent substance 1, Therefore Forming the fluorescent substance 1 at low temperature Therefore, the grain growth is suppressed, and the phosphor 1 whose base material is nanoparticles having an ultrafine particle diameter with a narrow particle size distribution can be easily obtained.

In addition, since the phosphor 1 can be manufactured by a low-temperature process in this way, it can be formed on a low-melting-point substrate such as a resin and can be applied to a flexible device.

Also, a high temperature and high pressure environment such as a vapor phase growth method and a precipitation method is not required, and therefore a desired nanoparticle can be obtained by a simple method without requiring a large-scale facility.

In addition, since the hydrolysis reaction proceeds only by stirring at room temperature, the desired nanoparticles 4 can be obtained very simply without requiring a process such as heat treatment.

In addition, since the reaction is performed with the minimum amount of water, it is possible to suppress the incorporation of hydroxyl groups into the nanoparticles 4 and the occurrence of defects. In addition, by changing the side chain length n of the hydrophilic group 8b of the main surfactant 8 to be used, the particle diameter of the produced nanoparticles 4 can be controlled, and therefore the degree of freedom in designing the material is also improved. A large phosphor 1 having a desired ultrafine particle diameter can be obtained.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention. For example, in the above embodiment, the thin-film phosphor 1 is produced on the substrate 2. However, the phosphor 1 can be peeled off from the substrate 2 and pulverized to obtain the powder phosphor 1.

Next, specific examples of the present invention will be described.

[Sample No. 1]
Cyclohexane as a hydrophobic solvent, NPE (10) having a side chain length n of a hydrophilic group as 10 as a main surfactant, 1-octanol as a secondary surfactant, and water were prepared.

These were mixed and stirred so that cyclohexane: NPE (10): 1-octanol: water = 30: 1.4: 1.7: 0.03, whereby a water-in-oil microemulsion solution was obtained. Was made.

Next, Ba isopropoxide (Ba (OC ₃ H ₇ ) ₂ ) as Ba alkoxide containing Ba (alkaline earth metal element), Ti isopropoxide (Ti (OC ₃ H ₇ ) ₄ as Ti alkoxide. And Eu isopropoxide (Eu (OC ₃ H ₇ ) ₃ ) as Eu alkoxide containing trivalent Eu (emission center element).

Ba isopropoxide, so that the ratio Ba / Ti of Ba to Ti is 1 in molar ratio, and the ratio Eu / (Ba + Ti) of Eu to the total of Ba and Ti is 0.10 in molar ratio, Ti isopropoxide and Eu isopropoxide were weighed and dissolved in an isopropyl alcohol solution to prepare a mixed alkoxide solution.

Next, this mixed alkoxide solution was added dropwise to the microemulsion solution, and further stirred for one week or more, thereby causing hydrolysis to prepare a nanoparticle dispersion solution.

Here, the dripping amount of the mixed alkoxide solution is 1.2 times the amount of water used as a reaction field in terms of molar ratio, which is necessary for hydrolysis of Ba isopropoxide, Ti isopropoxide, and Eu isopropoxide. It adjusted so that it might become.

The nanoparticle dispersion solution thus obtained is applied onto a quartz glass substrate and heated in the atmosphere at a heat treatment temperature of 300 ° C. for 0.5 hours to burn and decompose the surfactant and the hydrophobic solvent. A sample No. 1 was prepared.

Next, when the sample No. 1 was observed with a transmission electron microscope (hereinafter referred to as “TEM”), it was found that a nanoparticle aggregate having a particle diameter of 1 to 2 nm was formed.

Next, using a xenon lamp, the sample No. 1 was irradiated with excitation light having a wavelength of 275 nm, and a fluorescence spectrum was measured using a spectroscope (TRIAX320 manufactured by SPECS).

FIG. 5 shows the measurement results. The horizontal axis represents the emission wavelength (nm), and the vertical axis represents the emission intensity (counts).

As is apparent from FIG. 5, fluorescence peaks specific to Eu were observed at wavelengths of 590 nm, 613 nm, and 697 nm, and particularly a sharp fluorescence peak with a narrow half-value width was observed at a wavelength of 613 nm.

And this sample is known to absorb light having a wavelength of 375 nm or less from the light absorption characteristics.

Therefore, the sample of sample number 1 absorbs light of 275 nm which is an excitation wavelength to form an electron / hole pair, and the energy transitions to the emission wavelength of Eu, so that the luminous efficiency is remarkably improved. I understood.

[Sample No. 2]
Sample No. 2 was prepared by the same method and procedure as [Sample No. 1] except that the heat treatment temperature was 500 ° C.

Then, when the sample of sample number 2 was observed with a TEM, it was found that a nanoparticle aggregate having a particle size of 1 to 2 nm was formed.

Next, the fluorescence spectrum of this sample number 2 was also measured in the same manner as in sample number 1.

FIG. 6 shows the measurement results. The horizontal axis represents the emission wavelength (nm), and the vertical axis represents the emission intensity (counts).

As is clear from FIG. 6, in Sample No. 2, similarly to Sample No. 1, Eu-specific fluorescence peaks were observed at wavelengths of 590 nm, 613 nm, and 697 nm. In particular, at a wavelength of 613 nm, Sample No. 1 heat-treated at a temperature of 300 ° C. had a count of about 8.5 × 10 ⁷ , whereas Sample No. 2 heat-treated at a temperature of 500 ° C. was about 1.6 × 10 7. ^The emission intensity increased to ⁸ counts.

That is, as is clear from the comparison between sample numbers 1 and 2, sufficient light emission intensity can be obtained even when the heat treatment temperature is 300 ° C., but by increasing the heat treatment temperature to 500 ° C., further light emission intensity can be obtained. It was found that the improvement of can be achieved. In other words, it was confirmed that the light emission intensity can be arbitrarily controlled by heat treatment at 500 ° C. or lower.

[Sample No. 3]
Except for adjusting the mixing ratio of the mixed alkoxide so that the Eu ratio Eu / (Ba + Ti) with respect to the total of Ba and Ti is 0.03 in terms of molar ratio, the same method and procedure as in sample number 2 (heat treatment temperature: 500 ° C.), sample No. 3 was prepared, and the fluorescence spectrum was measured by the same method and procedure as Sample No. 1.

FIG. 7 shows the measurement results. The horizontal axis represents the emission wavelength (nm), and the vertical axis represents the emission intensity (counts).

As is clear from FIG. 7, in Sample No. 3, as in Sample Nos. 1 and 2, fluorescence peaks specific to Eu were observed at wavelengths of 590 nm, 613 nm, and 697 nm.

[Sample No. 4]
Except for adjusting the mixing ratio of the mixed alkoxide so that the Eu ratio Eu / (Ba + Ti) with respect to the total of Ba and Ti is 0.05, the same procedure and procedure (heat treatment temperature: The sample No. 4 was prepared at 500 ° C., and the fluorescence spectrum was measured by the same method and procedure as Sample No. 1.

FIG. 8 shows the measurement results. The horizontal axis represents the emission wavelength (nm), and the vertical axis represents the emission intensity (counts).

As is clear from FIG. 8, in Sample No. 4, as in Sample Nos. 1 to 3, fluorescence peaks specific to Eu were observed at wavelengths of 590 nm, 613 nm, and 697 nm.

FIG. 9 is a diagram comparing the fluorescence spectra of the samples of sample numbers 2-4. The horizontal axis indicates the emission wavelength (nm), and the vertical axis indicates the emission intensity (counts).

As is apparent from FIG. 9, sample numbers 3 and 4 have emission intensity of 1.0 × 10 ⁸ counts or more at a temperature of 300 ° C., although the fluorescence intensity is slightly lower than that of sample number 2. It can be seen that the emission intensity is stronger than the heat-treated sample No. 1. As is clear from Sample Nos. 1 to 4, it was confirmed that a phosphor having an arbitrary emission intensity can be obtained by changing the heat treatment temperature and the mixing ratio of each alkoxide solution in the mixed alkoxide solution.

[Sample No. 5]
A sample No. 5 having a base material of BaO was prepared by the same method and procedure (heat treatment temperature: 300 ° C.) as Sample No. 1 except that Ti isopropoxide was not mixed in the mixed alkoxide solution.

When this sample was observed with a TEM, it was found that a nanoparticle aggregate having a particle size of 1 to 2 nm was formed.

Next, the fluorescence spectrum of this sample No. 5 was also measured in the same manner as Sample No. 1.

FIG. 10 shows the measurement results. The horizontal axis represents the emission wavelength (nm), and the vertical axis represents the emission intensity (counts).

As is clear from FIG. 10, in Sample No. 5 as well as in Sample No. 1, although a fluorescence peak specific to Eu was observed, for example, the emission intensity of the fluorescence peak with a wavelength of 613 nm was about 1.8 × 10 × 10. ^{It was 6} counts, and it was found that only a weak emission intensity of about 1 to 2% was obtained as compared with sample numbers 1 to 4. This is presumably because the base material did not contain Ti and was formed of BaO outside the scope of the present invention.

Separately, a sample was prepared with a heat treatment temperature of 350 ° C., and the sample was observed with a TEM. As a result, it was confirmed that grain growth occurred and the particle size exceeded 5 nm. Moreover, when the fluorescence spectrum was observed also about the sample heat-processed at 350 degreeC, it was confirmed that the fluorescence peak intrinsic | native to Eu becomes extremely weak.

[Sample No. 6]
A sample No. 6 having a base material made of TiO ₂ was prepared in the same manner and procedure as Sample No. 1 except that Ba isopropoxide was not mixed in the mixed alkoxide solution and the heat treatment temperature was 200 ° C. .

When this sample was observed with a TEM, it was found that the sample was formed of a nanoparticle aggregate having a particle size in the range of 1 to 2 nm.

Next, the fluorescence spectrum of this sample No. 6 was also measured in the same manner as Sample No. 1.

FIG. 11 shows the measurement results. The horizontal axis represents the emission wavelength (nm), and the vertical axis represents the emission intensity (counts).

As can be seen from FIG. 11, the emission intensity of the fluorescence peak with the wavelength of 613 nm is about 2.5 × 10 ⁶ counts in the sample number ^6, which is weaker by about 1 to 3% than the sample numbers 1 to 4. It was found that only emission intensity was obtained. This seems to be because the base material does not contain Ba and is formed of TiO ₂ outside the scope of the present invention.

[Sample No. 7]
Sn isopropoxide (Sn (OC ₃ H ₇ ) ₄ ) was prepared as the Sn alkoxide. Then, Sn isopropoxide and Eu isopropoxide are weighed so that the Eu / Sn ratio Eu / Sn is 0.03 in terms of molar ratio, and Sn isopropoxide and Eu isopropoxide are isopropyl alcohol. A mixed alkoxide solution was prepared by dissolving in the solution.

A sample of sample number 7 in which the base material was formed of SnO ₂ was prepared by the same method and procedure as in sample number 1 (heat treatment temperature: 300 ° C.) except that this mixed alkoxide solution was used.

Next, when this sample was observed with a TEM, it was confirmed that grain growth occurred and the particle diameter exceeded 5 nm.

Next, the fluorescence spectrum of the sample No. 7 was also measured by the same method as Sample No. 1.

FIG. 12 shows the measurement results. The horizontal axis represents the emission wavelength (nm), and the vertical axis represents the emission intensity (counts).

As is clear from FIG. 12, although the presence of a luminescence peak was observed, the luminescence intensity was 6.0 × 10 ⁵ counts or less, which was confirmed to be extremely weak. This seems to be because the base material was formed of SnO ₂ outside the scope of the present invention.

FIG. 13 is a diagram comparing the fluorescence spectra of samples Nos. 2 and 5-7. The horizontal axis indicates the emission wavelength (nm), and the vertical axis indicates the emission intensity (counts).

As is apparent from FIG. 13, sample number 2 can obtain an emission intensity about 100 times that of sample numbers 5 to 7, and sample number 2 within the scope of the present invention is a sample outside the scope of the present invention. It was found that the luminous efficiency was remarkably improved compared to the numbers 5-7.

A phosphor having an average particle diameter of 5 nm or less can be easily obtained, and can be used for various devices such as a light emitting element.

1 Phosphor 2 Substrate 3 Nanoparticle dispersion solution 4 Nanoparticle 5 Surfactant 6 Hydrophobic solvent 10 Water droplet

Claims (8)

1. The matrix material made of nanoparticles contains the luminescent center element,
   The phosphor according to claim 1, wherein the base material contains an oxide containing at least Ti and an alkaline earth metal element.
2. 2. The phosphor according to claim 1, wherein a ratio of the emission center element to a total of the Ti and the alkaline earth metal element is 0.03 to 0.10 in molar ratio.
3. 3. The phosphor according to claim 1, wherein the ratio of Ti to the alkaline earth metal element is 1/9 to 9/1 in molar ratio.
4. The phosphor according to any one of claims 1 to 3, wherein the alkaline earth metal element is Ba.
5. The phosphor according to any one of claims 1 to 4, wherein the emission center element is any one of a rare earth element and a transition metal element.
6. 6. The phosphor according to claim 5, wherein the rare earth element is Eu.
7. A nanoparticle-dispersed solution preparation step of preparing a nanoparticle-dispersed solution in which nanoparticles containing a Ti oxide, an alkaline earth metal oxide, and an oxide containing an emission center element are dispersed in a dispersed solution;
   A coating film forming step of forming a coating film by applying the nanoparticle dispersion solution on a substrate;
   A heat treatment step of heat-treating the coating film,
   The heat treatment step is characterized in that the heat treatment is performed at a temperature of 500 ° C. or less to produce a phosphor in which a luminescent center element is added to a base material containing an oxide containing Ti and an alkaline earth metal element. A method for producing a phosphor.
8. The nanoparticle dispersion solution preparation step comprises mixing a hydrophobic solvent, a surfactant, and water to prepare a water-in-oil microemulsion solution in which water droplets are dispersed in oil, and a microemulsion solution preparation step,
   A mixed alkoxide solution preparation step of preparing a mixed alkoxide solution by mixing Ti alkoxide, an alkoxide containing an alkaline earth metal element, and an alkoxide containing a luminescent center element in a solvent;
   The method for producing a phosphor according to claim 7, further comprising a hydrolysis step of injecting the mixed alkoxide solution into the microemulsion solution to cause a hydrolysis reaction.

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