JP6908504B2 - Lanthanide-containing inorganic material fine particles - Google Patents

Description

The present invention relates to lanthanide-containing inorganic material fine particles capable of suppressing deterioration due to ultraviolet rays, having excellent moisture resistance, and exhibiting a stable wavelength conversion function for a long period of time. Further, according to the present invention, a wavelength conversion ink that can maintain high emission intensity at the time of wavelength conversion for a long period of time and can be produced regardless of the polarity of the dispersion medium, a coated product having the wavelength conversion ink, and determination. Regarding the device.

Inorganic fine particles having an "up-conversion" function that converts long-wavelength light such as infrared rays into short-wavelength light such as visible light and ultraviolet rays are expected to be applied to medical applications such as biomarkers. Further, in recent years, a highly functional material having an up-conversion function by dispersing such inorganic fine particles in a matrix material has been attracting attention.

As inorganic fine particles having an up-conversion function, those mainly containing lanthanoid elements are known, and a phenomenon called "multiphoton excitation" due to the energy level difference of these elements is used.
As a host material for inorganic fine particles having an up-conversion function, a material with low fluoride energy and high chemical stability is required so as not to interfere with the light absorption, energy transfer, and light emission processes of lanthanoid elements. Oxide materials and fluoride materials are known as materials.

Further, Patent Document 1 proposes an anti-counterfeit material containing inorganic fine particles having an up-conversion function. In such an anti-counterfeit material, an infrared fluorescent ink containing fine particles of an inorganic material having an up-conversion function is used. Since such infrared fluorescent ink is transparent to visible light, it is possible to add second information in addition to the information that can be visually recognized by visible light to the printed matter, so that anti-counterfeiting and information leakage can be prevented. It is used for security purposes.

Japanese Unexamined Patent Publication No. 2012-149139

Conventional ultraviolet fluorescent inks have a problem that the printed matter is deteriorated by irradiation with ultraviolet rays, but there is an advantage that deterioration of the printed matter can be suppressed by using infrared rays.

On the other hand, the printed matter coated with infrared fluorescent ink to prevent counterfeiting and information leakage does not require ultraviolet irradiation to confirm the second information, but for a long period of time such as banknotes. When used, there is a problem that the up-conversion function is deteriorated due to deterioration due to ultraviolet rays, and it becomes difficult to confirm the second information.
As a method of preventing such deterioration of ultraviolet rays, it is conceivable to form an ultraviolet protective film, but even if such a protective film is formed, the protective film itself will be peeled off by long-term use. However, there was a problem that the deterioration of the up-conversion function could not be sufficiently prevented.

Furthermore, the inorganic fine particles having an up-conversion function have low water resistance, and when used for infrared fluorescent ink, the inorganic fine particles deteriorate due to moisture in the environment and the light emission behavior changes over time, or the printed matter becomes moisture. There were problems such as the elution of inorganic fine particles and the deterioration of the up-conversion function when touched. Therefore, as the inorganic fine particles, fine particles using a hydrophobic material and fine particles surface-treated with a hydrophobic material are used, but infrared fluorescent ink using such fine particles is non-polar as a solvent. However, there are problems that printing cannot be performed or printing defects occur depending on the type of printed matter.

An object of the present invention is to provide lanthanide-containing inorganic material fine particles capable of suppressing deterioration due to ultraviolet rays, having excellent moisture resistance, and exhibiting a stable wavelength conversion function for a long period of time. Further, according to the present invention, a wavelength conversion ink that can maintain high emission intensity at the time of wavelength conversion for a long period of time and can be produced regardless of the polarity of the dispersion medium, a coating material having the wavelength conversion ink, and determination. The purpose is to provide the device.

The present invention is a lanthanoid-containing inorganic material fine particle having a wavelength conversion function from long-wavelength light to short-wavelength light, which has a core particle and a shell layer, and the core particle is a lanthanoid having a light absorption function. The shell layer contains lanthanoids having a light emitting function, and the shell layer is lanthanoid-containing inorganic material fine particles containing a metal oxide having a band gap of 3.0 to 4.5 eV.
The present invention will be described in detail below.

As a result of diligent studies, the present inventor can suppress deterioration due to ultraviolet rays and improve moisture resistance by forming a shell layer containing a metal oxide having a band gap within a predetermined range on the outside of the core particles. We have found that it is possible to complete the present invention.

The lanthanoid-containing inorganic material fine particles of the present invention have core particles containing a lanthanoid having a light absorbing function and a lanthanoid having a light emitting function.
By having the lanthanoid having the light absorption function and the lantanoid having the light emission function, it absorbs long-wavelength light such as infrared rays and converts the energy of the absorbed light into short-wavelength light such as visible light and ultraviolet rays. It is possible to demonstrate the "up-conversion function" that converts to.

The lanthanoid having a light absorbing function constituting the core particles is not particularly limited as long as it is a lanthanoid capable of absorbing long wavelength light such as infrared rays, and examples thereof include ytterbium (Yb) and neodym (Nd). Can be mentioned. In particular, ytterbium is preferable because it has strong absorption in the vicinity of ^{10000 cm-1} when used as light for absorbing near-infrared light. These lanthanoids may be used alone or in combination of two or more.

The lanthanoid having a light emitting function constituting the core particles is not particularly limited as long as it is a lanthanoid capable of emitting light by being excited by energy from the lanthanoid having a light absorbing function. For example, erbium (Er), etc. Examples include holmium (Ho) and thulium (Tm). In particular, erbium, holmium, and thulium whose wavelengths are in the visible light region and the ultraviolet light region are preferable. These lanthanoids may be used alone or in combination of two or more.

The combination of the lanthanoid having the light absorbing function and the lanthanoid having the light emitting function constituting the core particles is not particularly limited. The combination of itterbium, ^{which has strong absorption near 10000 cm -1,} emits light by receiving energy transfer from itterbium, and the wavelength of the obtained light is in the visible light range or ultraviolet light range, such as infrared rays. This is preferable when absorbing long-wavelength light and converting it into short-wavelength light such as visible light or ultraviolet light.

The core particles are not particularly limited as long as they contain the lanthanoid having the light absorption function and the lanthanoid having the light emitting function, and for example, the lanthanoid having the light absorbing function and the lanthanoid having the light emitting function. Those containing oxides, halides and the like can be mentioned. Fluoride is preferable as the halide.

Further, the core particles preferably contain an element having an ionic radius and a structure at the time of crystallization similar to the lanthanide having a light absorbing function and the lanthanoid having a light emitting function, or a compound thereof. Examples of the lanthanoid having the light absorbing function and the element having the same ionic radius and structure at the time of crystallization as the lanthanoid having the light emitting function include rare earth elements other than the lanthanoid, and the compound thereof is other than the lanthanoid. Examples include oxides and halides of rare earth elements. As the halide, a fluoride is preferable, and a fluoride containing an alkali metal and a rare earth element, or a fluoride containing oxygen, an alkali metal and a rare earth element is preferable.
Examples of rare earth elements other than the above lanthanoids include yttrium (Y), gadolinium (Gd), scandium (Sc) and the like. Examples of compounds of rare earth elements other than the above lanthanoids include oxides or halides of yttrium, gadolinium and scandium.
Among them, the core particles preferably contain yttrium, an oxide of yttrium, or a halide of yttrium, because high efficiency can be expected with respect to energy transfer between lanthanoids and improvement of luminous efficiency can be expected. Yttrium oxide _{is preferably Y 2} O ₃ , and yttrium halide is preferably _{Na YF 4.}

The core particles, as compound of an element having a structure in the ion radius and crystallization similar to lanthanides having the lanthanides and the light emitting function having the light absorption function, to contain Y ₂ O ₃ or NaYF ₄ preferable. Further, it is preferable to contain ytterbium as the lanthanoid having a light absorbing function and at least one selected from the group consisting of erbium, holmium and thulium as the lanthanoid having a light emitting function.

The content of the lanthanoid having the light absorbing function in the core particles has a preferable lower limit of 2 with respect to the total of the lanthanides contained in the core particles and the elements having an ionic radius and a structure at the time of crystallization similar to the lanthanoids. The mol%, the more preferred lower limit is 2.5 mol%, the preferred upper limit is 50 mol%, and the more preferred upper limit is 25 mol%. When the content of the lanthanoid having the light absorption function is not less than the above-mentioned preferable lower limit and not more than the above-mentioned preferable upper limit, the energy of the light reaching the core particles can be efficiently absorbed.
The content of the lanthanoids constituting the core particles can be measured using, for example, a fluorescent X-ray analyzer (EDX-800HS, manufactured by Shimadzu Corporation).

The preferable lower limit of the content of the lanthanoid having the light emitting function in the core particles is 0 with respect to the total of the lanthanides contained in the core particles and the elements having an ionic radius and a structure at the time of crystallization similar to the lanthanoids. The preferred lower limit is 0.01 mol%, the preferred upper limit is 20 mol%, and the more preferred upper limit is 10 mol%. When the content of the lanthanoid having the light emitting function is not less than the above-mentioned preferable lower limit and not more than the above-mentioned preferable upper limit, the absorbed energy can be received and the light emitting function can be efficiently exhibited.

The total content of the lanthanoid having the light absorbing function and the lanthanoid having the light emitting function constituting the core particle has an ionic radius similar to that of the lanthanoid contained in the core particle and a structure at the time of crystallization. The preferable lower limit is 2 mol% and the preferable upper limit is 50 mol% with respect to the total of the elements. Further, the more preferable lower limit is 2.5 mol%, and the more preferable upper limit is 25 mol%. When the total content of the lanthanoids constituting the core particles is equal to or more than the above-mentioned preferable lower limit and equal to or less than the above-mentioned preferable upper limit, the lanthanoids in the core particles have an ionic radius similar to that of the lanthanoids and a structure at the time of crystallization. It can be substituted and doped without destroying the crystal structure composed of the elements. Therefore, it can be retained without impairing the efficiency of energy transfer in the lanthanide-containing inorganic material fine particles.

In the core particles, the ratio of the content of the lanthanoid having the light absorbing function to the content of the lanthanoid having the light emitting function (content of the lanthanoid having the light absorbing function / content of the lanthanoid having the light emitting function). In terms of molar ratio, the preferable lower limit is 2, the more preferable lower limit is 5, the preferable upper limit is 100, and the more preferable upper limit is 75.
When the above ratio is equal to or more than a preferable lower limit and not more than a preferable upper limit, the energy absorbed by the lanthanide having a light absorbing function can be uniformly transferred to the lanthanide having a light emitting function without excess or deficiency. The efficiency of

The content of elements having an ionic radius similar to that of the lanthanoid and a structure at the time of crystallization has a preferable lower limit of 5 mol% and a more preferable lower limit of 10 mol% with respect to the total of rare earth elements contained in the core particles. The upper limit is 98 mol%, and the more preferable upper limit is 80 mol%. When the content of an element having an ionic radius similar to that of the lanthanide and a structure at the time of crystallization is equal to or higher than the above-mentioned preferable lower limit and equal to or lower than the above-mentioned preferable upper limit, a regular arrangement of the crystal structure is used as a host material to dope the lanthanide. The structure can be formed, the efficiency of energy transfer in the lanthanide-containing inorganic material fine particles can be increased, and the light emission efficiency can be improved.
The content of elements having an ionic radius similar to that of the lanthanoids constituting the core particles and a structure at the time of crystallization can be measured using, for example, a fluorescent X-ray analyzer (EDX-800HS manufactured by Shimadzu Corporation). can.

The average particle size of the core particles has a preferable lower limit of 5 nm, a more preferable lower limit of 7.5 nm, a preferable upper limit of 250 nm, and a more preferable upper limit of 200 nm. When the average particle size of the core particles is equal to or greater than the above-mentioned preferable lower limit and equal to or less than the above-mentioned preferable upper limit, for example, when used in combination with another material (transparent binder), dispersibility and optical permeability can be obtained. Can be compatible with each other. The average particle size of the core particles can be determined by measuring the particle size of the core particles using an electron microscope.

The lanthanoid-containing inorganic material fine particles of the present invention further have a shell layer. By having the shell layer, deterioration of the core particles due to ultraviolet rays can be suppressed, and moisture resistance can also be improved.

The shell layer contains a metal oxide. When the shell layer contains a metal oxide, the obtained lanthanoid-containing inorganic material fine particles are easily dispersed in both a polar solvent and a non-polar solvent, and are reactive with a dispersant such as a silane coupling agent. It is possible to improve the printability of the obtained wavelength-changing ink.
The metal oxide has a lower limit of the bandgap of 3.0 eV and an upper limit of 4.5 eV.
When the band gap of the metal oxide is at least the above lower limit and at least the above upper limit, the ultraviolet transmittance of the obtained shell layer can be lowered, and the transmittance of visible light and infrared rays is sufficiently high. It is possible to suppress deterioration of core particles and achieve high emission intensity at the same time.

Examples of the metal oxide include titanium oxide (bandgap: 3.2 eV), zinc oxide (bandgap: 3.37 eV), cerium oxide (bandgap: 3.1 eV), and the like.

Further, in the lanthanide-containing inorganic material fine particles of the present invention, the preferable lower limit of the content of the metal oxide contained in the shell layer is 25 mol%, and the preferable upper limit is 100 mol%. When the content of the metal oxide in the shell layer is equal to or higher than the preferable lower limit, the transmission of ultraviolet rays in the shell layer can be sufficiently suppressed.

The preferred lower limit of the thickness of the shell layer is 2 nm, and the preferred upper limit is 20 nm. When the thickness of the shell layer is not less than the above-mentioned preferable lower limit and not more than the above-mentioned preferable upper limit, it does not prevent long-wavelength light such as infrared rays from reaching the core particles having a light absorption function, and also. Loss during light emission can be reduced. In addition, it is possible to sufficiently suppress the transmission of ultraviolet rays and suppress the deterioration of the wavelength conversion function of the core particles. The thickness of the shell layer has a more preferable lower limit of 2.5 nm and a more preferable upper limit of 10 nm. The thickness of the shell layer is measured by measuring the particle size of the fine particles having the shell layer formed on the surface of the core particles using an electron microscope and calculating the difference from the average particle size of the core particles. can do.

The ratio of the average particle size of the core particles to the thickness of the shell layer (average particle size of the core particles / thickness of the shell layer) has a preferable lower limit of 2, a more preferable lower limit of 2.5, and a preferable upper limit of 50. , A more preferred upper limit is 25. When the ratio to the thickness is not less than the above-mentioned preferable lower limit and not more than the above-mentioned preferable upper limit, energy loss can be reduced without hindering the arrival of light at the core particles. Moreover, the energy loss at the time of light emission can be further reduced. Further, it is possible to suppress the transmission of ultraviolet rays and sufficiently suppress the deterioration of the wavelength conversion function of the core particles.

The average particle size of the lanthanide-containing inorganic material fine particles of the present invention has a preferable lower limit of 10 nm, a more preferable lower limit of 15 nm, a preferable upper limit of 300 nm, and a more preferable upper limit of 200 nm. When the average particle size of the core particles is equal to or greater than the above-mentioned preferable lower limit and equal to or less than the above-mentioned preferable upper limit, for example, when used in combination with another material (transparent binder), dispersibility and optical permeability can be obtained. Can be compatible with each other. The average particle size of the lanthanoid-containing inorganic material fine particles can be determined by measuring the particle size of the lanthanide-containing inorganic material fine particles using an electron microscope.

The method for producing the lanthanoid-containing inorganic material fine particles of the present invention is not particularly limited, but for example, after producing core particles containing a lanthanide having a light absorption function and a lanthanoid having a light emitting function, further core particles A method of forming a shell layer on the surface of the above can be considered.

The method for producing the core particles containing the lanthanoid having a light absorbing function and the lanthanoid having a light emitting function is not particularly limited. For example, a metal salt containing a lanthanoid having a light absorbing function, a metal salt containing a lanthanoid having a light emitting function, a metal salt containing an element having an ion radius similar to that of the lantanoid and a structure at the time of crystallization, an alkaline solution, Then, the fluoride solution is dissolved in a solvent composed of an organic compound to prepare a metal ion-containing solution. Further, a method of precipitating core particles made of fluoride by heating the obtained metal ion-containing solution at a high temperature can be mentioned.

Examples of the metal salt containing a lanthanoid having a light absorbing function and the metal salt containing a lanthanoid having a light emitting function include nitrates, sulfates, phosphates, borates, silicates and vanadic acids of lantanoids. Examples thereof include oxyphosphates such as salts. In addition, carboxylates such as acetic acid salts of lanthanoids, sulfonates, phenol salts, sulfates, salts of 1,3-diketone-type compounds, thiophenol salts, oxime salts, salts of aromatic sulfonamides, primary grades. And organic acid salts such as salts of secondary nitro compounds, chlorides of lanthanoids and the like. Of these, a carboxylic acid salt such as acetate is preferable.

The solvent used in the metal ion-containing solution may be, for example, a mixed solvent containing at least two organic compounds selected from the group consisting of fatty acids, organic phosphorus compounds, organic sulfur compounds, and amine compounds. preferable. By using the above-mentioned mixed solvent, the surface of the obtained core particles can be effectively suppressed from being contaminated by oxidation or the like by coordinating firmly on the surface of the fine particles of the inorganic material.
The mixed solvent preferably further contains an organic solvent for the purpose of diluting octadecene or the like.

Examples of the metal salt containing an element having an ionic radius similar to that of the lanthanoid and a structure at the time of crystallization include nitrates, sulfates and phosphates of elements having an ionic radius similar to that of the lantanoid and a structure at the time of crystallization. Examples thereof include oxidates such as borates, silicates and vanazine salts, and carboxylates such as acetates. In addition, sulfonates, phenol salts, sulfinates, salts of 1,3-diketone-type compounds, thiophenol salts, oxime salts, salts of aromatic sulfonamides, salts of primary and secondary nitro compounds, etc. Examples include organic acid salts and chlorides. Of these, carboxylic acid salts such as acetate are preferable.

Examples of the alkaline solution include those containing sodium hydroxide, calcium hydroxide, ammonium fluoride and the like.
The amount of the alkaline solution added can be appropriately selected depending on the type and concentration of the metal ion-containing solution.

Examples of the fluoride solution include those containing sodium fluoride, ammonium fluoride and the like. The amount of the fluoride solution added can be appropriately selected depending on the type and concentration of the metal ion-containing solution.

The method for further forming the shell layer on the core particles is not particularly limited, but for example, metal oxidation of an alkaline aqueous solution, a metal alkoxide, or the like is added to a solution obtained by adding a surfactant and core particles to a dispersion medium. A method of forming a shell layer containing a metal oxide on the surface of core particles by adding a substance precursor or the like can be used.

Examples of the dispersion medium include hydrocarbons such as cyclohexane and benzene, linear alcohols such as hexanol, and ketones such as acetone.

As the above-mentioned surfactant, a nonionic surfactant, an anionic surfactant, a cationic surfactant and the like can be used.
Examples of the nonionic surfactant include a polyoxyethylene nonylphenyl ether-based surfactant such as polyoxyethylene (5) nonylphenyl ether, and a polyoxyethylene octylphenyl ether-based surfactant such as polyoxyethylene (10) octylphenyl ether. Activators and the like can be mentioned. Examples thereof include polyoxyethylene alkyl ether-based surfactants such as polyoxyethylene (7) cetyl ether, and polyoxyethylene sorbitan-based surfactants such as polyoxyethylene sorbitan triolate.
Examples of the anionic surfactant include sodium di-2-ethylenehexyl sulfosulfoate, and examples of the cationic surfactant include cetyltrimethylammonium chloride and cetyltrimethylammonium bromide.

Examples of the alkaline aqueous solution include aqueous ammonia and the like.

The metal alkoxide may be any carrier of the metal oxide, and examples thereof include methoxide such as titanium, zinc and cerium, ethoxide, propoxide and butoxide.
Specific examples thereof include titanium tetraisopropoxide, zinc dipropoxide, and cerium triisopropoxide.

The lanthanide-containing inorganic material fine particles of the present invention can be used, for example, in medical applications such as biomarkers, solar cells such as dye-sensitized solar cells, and wavelength conversion inks such as security inks.
The wavelength conversion ink containing the lanthanoid-containing inorganic material fine particles of the present invention is also one of the present inventions.

The wavelength conversion ink of the present invention contains the lanthanide-containing inorganic material fine particles and the solvent of the present invention.
By containing the lanthanide-containing inorganic material fine particles of the present invention, the wavelength conversion ink of the present invention maintains a strong readable emission intensity for a long period of time by being irradiated with long wavelength light when printed on a printed matter. be able to. Further, even when the coated product printed with the wavelength conversion ink of the present invention gets wet with water, the wavelength conversion ink repels water, so that the lanthanoid-containing inorganic material fine particles are eluted or the ink-coated portion is formed. It is possible to suppress the disintegration and keep the printed pattern in a good state.

The preferable lower limit of the content of the lanthanide-containing inorganic material fine particles in the wavelength conversion ink of the present invention is 0.01% by weight, and the preferable upper limit is 75% by weight.

The solvent is not particularly limited as long as the lanthanoid-containing inorganic material fine particles can be easily dispersed. For example, alcohols such as ethanol, methyl ethyl ketone, toluene, hexane, cyclohexane, heptane, cycloheptane, octane, decane, undecane, dodecane, etc. Examples thereof include tridecane, trimethylpentane, benzene and xylene.

The preferable lower limit of the content of the solvent in the wavelength conversion ink of the present invention is 1% by weight, and the preferable upper limit is 99.99% by weight.

The wavelength conversion ink of the present invention may further contain additives such as a binder, a dispersant, and a viscosity modifier.

The use of the wavelength conversion ink of the present invention is not particularly limited. Second information that is transparent to visible light and emits light when irradiated with long-wavelength light such as infrared light can be given to the printed matter, and the composition of the lanthanoid-containing inorganic material fine particles constituting the wavelength conversion ink Since the emission spectrum can be adjusted, it is particularly useful as a security ink for the purpose of preventing counterfeiting.

The method for producing the wavelength conversion ink of the present invention is not particularly limited, and for example, the above-mentioned lanthanoid-containing inorganic material fine particles and additives such as a binder to be blended as needed are used in the above-mentioned ultrasonic disperser or the like. Examples thereof include a method of dispersing and dissolving in a solvent to obtain ink.

By applying the wavelength conversion ink of the present invention to a base material, it is possible to print a pattern that is transparent to visible light and emits light having a long wavelength such as infrared rays.
A coated product on which the wavelength conversion ink of the present invention is printed is also one of the present inventions.

The coated product of the present invention has the wavelength conversion ink of the present invention and a base material.
The base material is not particularly limited, and examples thereof include paper using pulp, cotton, and other plant fibers, and plastic films such as polycarbonate, polyethylene, polypropylene, and polyethylene terephthalate.

The method for printing the wavelength conversion ink of the present invention on the substrate is not particularly limited, and a conventionally known printing method can be used.

The print pattern of the wavelength conversion ink printed on the coated product of the present invention can be confirmed by irradiating infrared rays. Since the wavelength conversion ink of the present invention has a wavelength conversion function, it is possible to visually recognize a print pattern by emitting visible light by irradiating infrared rays. Further, by determining the emission spectrum and the printing pattern of the wavelength conversion ink printed on the coated product of the present invention, the authenticity of the information printed on the substrate can be analyzed in detail.
A determination device for determining the emission spectrum and the print pattern of the wavelength conversion ink printed on the coated product of the present invention is also one of the present inventions.

The determination device of the present invention includes an irradiation means for irradiating the coated object of the present invention with infrared rays, and a detection means for detecting an emission spectrum and a print pattern of a wavelength conversion ink generated by the irradiation of infrared rays.

The irradiation means constituting the determination device of the present invention is not particularly limited as long as it can irradiate infrared rays capable of emitting lanthanoid-containing inorganic material fine particles contained in the wavelength conversion ink of the present invention, and is conventionally known. An infrared irradiation device can be used.

The detection means constituting the determination device of the present invention includes a function of detecting the emission spectrum, color coordinates, etc. emitted by the lanthanoid-containing inorganic material fine particles contained in the wavelength conversion ink of the present invention, and a function of detecting the print pattern of the wavelength conversion ink. It suffices to have.
As the detection means, an apparatus for detecting an emission pattern and a device for detecting a print pattern may be used alone, or an apparatus for detecting an emission spectrum and an apparatus for detecting a print pattern may be used in combination.

According to the present invention, it is possible to provide lanthanide-containing inorganic material fine particles capable of suppressing deterioration due to ultraviolet rays, having excellent moisture resistance, and exhibiting a stable wavelength conversion function for a long period of time. Further, according to the present invention, a wavelength conversion ink that can maintain high emission intensity at the time of wavelength conversion for a long period of time and can be produced regardless of the polarity of the dispersion medium, and a coating product having the wavelength conversion ink. And a determination device can be provided.

It is an electron micrograph which photographed the lanthanoid-containing inorganic material fine particle obtained in Example 1. FIG. In the measurement of the emission intensity, it is a graph which shows the fluorescence emission peak (solid line) before the deterioration test and the fluorescence emission peak (broken line) after the deterioration test with respect to the 980 nm incident light of the lanthanide-containing inorganic material fine particles obtained in Example 1. In the measurement of the emission intensity, it is a graph which shows the fluorescence emission peak (solid line) before the deterioration test and the fluorescence emission peak (broken line) after the deterioration test with respect to the 980 nm incident light of the lanthanide-containing inorganic material fine particles obtained in Comparative Example 1.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

(Example 1)
(Preparation of core particles)
A metal ion-containing solution was prepared by dissolving 0.40 g of yttrium acetate, 0.13 g of ytterbium acetate, and 0.013 g of erbium acetate in a mixed solvent of 11.13 g of oleic acid, 10.39 g of trioctylphosphine, and 46.03 g of octadecene. did. Further, a reaction precursor solution was prepared by dissolving 0.15 g of sodium hydroxide and 0.39 g of ammonium fluoride in 15 g of methanol and adding the resulting solution to a metal ion-containing solution immediately after the preparation.
Methanol is volatilized and removed from the reaction precursor solution by heating under vacuum at 50 ° C. for 15 minutes with stirring, and then fine particles are added to the solution by heating under a nitrogen atmosphere at 317 ° C. for 90 minutes with stirring. Precipitated.
Further, after cooling to room temperature, 25 g of ethanol was added to precipitate the fine particles, and the fine particles were recovered using a centrifuge. After the recovered fine particles were redispersed in 25 g of toluene, 25 g of ethanol was added again to re-aggregate the fine particles, and the washing with a centrifuge was repeated several times to obtain core particles.
A fluorescent X-ray analyzer (Shimadzu Seisakusho Co., Ltd.) determines the content of lanthanoids having a light absorbing function, lanthanoids having a light emitting function, and elements having an ionic radius similar to that of lanthanoids and a structure at the time of crystallization contained in the obtained core particles. Manufactured by EDX-800HS).

(Preparation of shell layer)
0.125 g of the obtained core particles and 0.3 g of IGEPAL: CO-520 (polyoxyethylene (5) nonylphenyl ether) as a nonionic surfactant were mixed in 10 g of cyclohexane. Next, 0.01 g of 10% aqueous ammonia and 0.05 g of titanium tetraisopropoxide were added in this order and stirred for 1 day to obtain lanthanoid-containing inorganic material fine particles having a shell layer made of titanium dioxide formed on the surface of the core particles. ..

(Example 2)
In (Preparation of shell layer), lanthanoid-containing inorganic material fine particles were obtained in the same manner as in Example 1 except that a shell layer made of zinc oxide was formed by using zinc diisopropoxide instead of titanium tetraisopropoxide. rice field.

(Example 3)
In (Preparation of shell layer), lanthanoid-containing inorganic material fine particles were obtained in the same manner as in Example 1 except that a shell layer made of cerium oxide was formed by using cerium tetraisopropoxide instead of titanium tetraisopropoxide. rice field.

(Comparative Example 1)
Lanthanide-containing inorganic material fine particles were obtained in the same manner as in Example 1 except that the shell layer was not formed.

(Comparative Example 2)
In (Preparation of shell layer), lanthanide-containing inorganic material fine particles were obtained in the same manner as in Example 1 except that a shell layer made of silicon dioxide was formed by using tetraethoxysilane instead of titanium tetraisopropoxide.

(evaluation)
The lanthanide-containing inorganic material fine particles obtained in Examples and Comparative Examples were evaluated as follows. The results are shown in Table 1.

(1) Evaluation of Optical Characteristics of Shell Layer A solution prepared by mixing 0.05 g of titanium tetraisopropoxide and 9.95 g of ethanol was prepared, and the obtained solution was coated on a quartz glass substrate using a spin coater. Then, the glass substrate for optical measurement was prepared by leaving it in the air for 1 hour to form a thin film made of titanium dioxide (the number of coatings was adjusted so that the film thickness was 250 nm). The optical characteristics of the shell layer of Example 1 were evaluated by measuring the transmittance spectrum of the obtained glass substrate for optical measurement. The transmittance spectrum is obtained by calculating the transmittance when irradiated with ultraviolet rays having a wavelength of 365 nm, visible light having a wavelength of 550 nm, and infrared rays having a wavelength of 1000 nm using a spectrophotometer (UV-2700, manufactured by Shimadzu Corporation). It was measured.
Further, instead of titanium tetraisopropoxide, zinc dipropoxide, cerium tetraisopropoxide, and tetraethoxysilane were used to prepare a glass substrate for optical measurement, and similarly, the shells of Examples 2, 3 and Comparative Example 2 were prepared. The optical properties of the layer were evaluated.

(2) Measurement of average particle size and shell layer thickness For each example and comparative example, the obtained core particles and lanthanoid-containing inorganic material fine particles were observed using a transmission electron microscope, and the obtained images were obtained. The average particle size of each particle was measured by calculating the average particle size of 300 particles in the above. Further, the film thickness of the shell layer was measured by obtaining the difference between the average particle size of the core particles before forming the shell layer and the average particle size of the lanthanoid-containing inorganic material fine particles after forming the shell layer.
An electron micrograph of the lanthanide-containing inorganic material fine particles obtained in Example 1 is shown in FIG.

(3) Measurement of Emission Intensity Infrared light with a wavelength of 980 nm and an output of 300 mW using an infrared generator (L980P300J, manufactured by THORLABS) as an external light source for the lanthanoid-containing inorganic material fine particles obtained in each Example and Comparative Example. The spectrum of the obtained fluorescence emission was measured using a fluorescence spectrophotometer (manufactured by Hitachi High-Tech, U-2700). The emission intensity was evaluated by calculating the relative value of the maximum intensity of the fluorescence emission spectra of each Example and Comparative Example, assuming that the maximum intensity of the spectrum in Comparative Example 1 was 1.00.
The graphs showing the fluorescence emission peaks of the lanthanide-containing inorganic material fine particles obtained in Example 1 and Comparative Example 1 with respect to 980 nm incident light are shown in FIGS. 2 and 3.

(4) Evaluation of UV Weatherability The lanthanoid-containing inorganic material fine particles obtained in each Example and Comparative Example were left to be subjected to a deterioration test for 1000 hours while being irradiated with an ultraviolet lamp (REX-250, manufactured by Asahi Spectrometry Co., Ltd.). .. The luminescence intensity of the lanthanide-containing inorganic material fine particles after the deterioration test is measured in the same manner as in (3) Measurement of luminescence intensity, and the luminescence intensity retention rate is calculated with the luminescence intensity before the deterioration test as 100% to obtain ultraviolet weather resistance. evaluated.

(5) Moisture resistance The lanthanide-containing inorganic material fine particles obtained in each Example and Comparative Example were exposed to an environment of 85 ° C. and 85% RH for 500 hours to perform a high temperature and high humidity test. The light emission intensity after the high temperature and high humidity test was measured in the same manner as in (3) Measurement of light emission intensity, and the moisture resistance was evaluated by calculating the light emission intensity retention rate with the light emission intensity before the high temperature and high humidity test as 100%.

(6) Ink Dispersity Evaluation 1 g of lanthanide-containing inorganic material fine particles obtained in each Example and Comparative Example was added to 99 g of toluene, and wavelength conversion was performed using an ultrasonic disperser (manufactured by SMT, UH-600). Ink was made.
Further, 1 g of the lanthanide-containing inorganic material fine particles obtained in each Example and Comparative Example were added to 99 g of methyl ethyl ketone to prepare a wavelength conversion ink in the same manner.
The obtained wavelength conversion ink was allowed to stand for 30 days, and the dispersibility was evaluated according to the following criteria.
〇: There was no sedimentation and the dispersed state was maintained.
X: Sedimentation was confirmed and a sedimentary layer was confirmed.

(7) Evaluation of Uniformity of Coated Product A wavelength conversion ink was prepared by mixing 0.5 g of lanthanide-containing inorganic material fine particles, 40 g of toluene, and 9.5 g of polydimethylsiloxane obtained in each Example and Comparative Example. The obtained wavelength conversion ink was applied onto a glass substrate so that the thickness after drying was 100 μm, and the solvent was removed by drying to prepare a coated product.
Further, 0.5 g of lanthanide-containing inorganic material fine particles, 20 g of toluene, 20 g of methyl ethyl ketone, and 9.5 g of polydimethylsiloxane obtained in each Example and Comparative Example were mixed to prepare a wavelength conversion ink in the same manner. This wavelength conversion ink was applied onto a glass substrate so that the thickness after drying was 100 μm, and the solvent was removed by drying to prepare a coated product.
The surface roughness of the obtained coated product was measured using a laser microscope (LEXTOLS4100 manufactured by Olympus Corporation), and the uniformity of the coated product was evaluated from the obtained surface roughness according to the following criteria.
⊚: The surface roughness (Sa) was 15 μm or less.
◯: The surface roughness (Sa) was more than 15 μm and 25 μm or less.
X: The surface roughness (Sa) exceeded 25 μm.

According to the present invention, it is possible to provide lanthanide-containing inorganic material fine particles capable of suppressing deterioration due to ultraviolet rays, having excellent moisture resistance, and exhibiting a stable wavelength conversion function for a long period of time. Further, according to the present invention, a wavelength conversion ink that can maintain high emission intensity at the time of wavelength conversion for a long period of time and can be produced regardless of the polarity of the dispersion medium, and a coating product having the wavelength conversion ink. And a determination device can be provided.

Claims (10)

It is a lanthanoid-containing inorganic material fine particle having a wavelength conversion function from long-wavelength light to short-wavelength light, and has a core particle and a shell layer, and the core particle has a lanthanoid having a light absorption function and a light emitting function. The lanthanoid-containing inorganic material fine particles containing the lanthanoid, and the shell layer contains a metal oxide having a band gap of 3.0 to 4.5 eV. The lanthanide-containing inorganic material fine particles according to claim 1, wherein the metal oxide is at least one selected from the group consisting of titanium oxide, zinc oxide and cerium oxide. The lanthanide-containing inorganic material fine particles according to claim 1 or 2, wherein the average particle size is 10 to 300 nm. The lanthanide-containing inorganic material fine particles according to claim 1, 2 or 3, wherein the core particles have an average particle size of 5 to 250 nm. The lanthanide-containing inorganic material fine particles according to claim 1, 2, 3 or 4, wherein the shell layer has a thickness of 2 to 20 nm. The lanthanide-containing inorganic material fine particles according to claim 1, 2, 3, 4 or 5, wherein the ratio of the average particle size of the core particles to the thickness of the shell layer is 2 to 50. A wavelength conversion ink comprising the lanthanoid-containing inorganic material fine particles and the solvent according to claim 1, 2, 3, 4, 5 or 6. The wavelength conversion ink according to claim 7, wherein the ink is a security ink. A coated product comprising the wavelength conversion ink according to claim 7 or 8 and a base material. A determination device comprising an irradiation means for irradiating the coated object according to claim 9 with infrared rays, and a detection means for detecting an emission spectrum generated by the irradiation with infrared rays and a printing pattern of the wavelength conversion ink.

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