Lanthanoid-containing inorganic material microparticles, wavelength-converting ink, coated article, and determination apparatus
11274248 · 2022-03-15
Assignee
Inventors
Cpc classification
B82Y20/00
PERFORMING OPERATIONS; TRANSPORTING
B82Y40/00
PERFORMING OPERATIONS; TRANSPORTING
C09K11/025
CHEMISTRY; METALLURGY
International classification
B82Y40/00
PERFORMING OPERATIONS; TRANSPORTING
C09K11/02
CHEMISTRY; METALLURGY
Abstract
A lanthanoid-containing inorganic material fine particle having a function of converting a wavelength of light to a shorter wavelength, the lanthanoid-containing inorganic material fine particle including: a core particle; and a shell layer, the core particle containing a lanthanoid having a light-absorbing function and a lanthanoid having a light-emitting function, the shell layer including at least an outer shell containing a rare earth element, the total amount of the lanthanoid having a light-absorbing function and the lanthanoid having a light-emitting function in the outer shell being 2 mol % or less based on the amount of the rare earth element contained in the outer shell, the outer shell having a thickness of 2 to 20 nm, the core particle and the shell layer having no interface at a contact face to form a continuous body.
Claims
1. A lanthanoid-containing inorganic material fine particle having a function of converting a wavelength of light to a shorter wavelength, the lanthanoid-containing inorganic material fine particle comprising: a core particle; and a shell layer, the core particle containing a lanthanoid having a light-absorbing function and a lanthanoid having a light-emitting function, the shell layer comprising at least an outer shell containing a rare earth element, a total amount of the lanthanoid having a light-absorbing function and the lanthanoid having a light-emitting function in the outer shell being 2 mol % or less based on an amount of the rare earth element contained in the outer shell, the outer shell having a thickness of 2 to 20 nm, the core particle and the shell layer having no interface at a contact face to form a continuous body, and the lanthanoid-containing inorganic material fine particle further having a fatty acid and an organophosphorus compound on a surface of the shell layer.
2. The lanthanoid-containing inorganic material fine particle according to claim 1, wherein the shell layer further comprises an inner shell containing a rare earth element, an amount of the lanthanoid having a light-absorbing function in the inner shell is 75 mol % or less and an amount of the lanthanoid having a light-emitting function in the inner shell is 2 mol % or less, based on an amount of the rare earth element contained in the inner shell, and the inner shell and the outer shell have no interface at a contact face to form a continuous body.
3. The lanthanoid-containing inorganic material fine particle according to claim 2, wherein the inner shell has a thickness of 2 to 20 nm.
4. The lanthanoid-containing inorganic material fine particle according to claim 1, wherein the core particle has an average particle size of 5 to 250 nm.
5. The lanthanoid-containing inorganic material fine particle according to claim 1, containing: a fluoride containing an alkali metal and a rare earth element; or a fluoride containing oxygen, an alkali metal and a rare earth element.
6. The lanthanoid-containing inorganic material fine particle according to claim 1, further comprising a polymer layer containing a polymer and noble metal particles around the shell layer.
7. The lanthanoid-containing inorganic material fine particle according to claim 6, wherein the polymer layer is a polymer brush layer.
8. The lanthanoid-containing inorganic material fine particle according to claim 6, further comprising an intermediate layer between the shell layer and the polymer layer.
9. An wavelength conversion ink comprising: the lanthanoid-containing inorganic material fine particle according to claim 1; and a solvent.
10. The wavelength conversion ink according to claim 9, which is a security ink.
11. A coated article comprising: the wavelength conversion ink according to claim 9; and a substrate.
12. A lanthanoid-containing inorganic material fine particle having a function of converting a wavelength of light to a shorter wavelength, the lanthanoid-containing inorganic material fine particle comprising: a core particle; and a shell layer, the core particle containing a lanthanoid having a light-absorbing function and a lanthanoid having a light-emitting function, the shell layer comprising at least an outer shell containing a rare earth element, a total amount of the lanthanoid having a light-absorbing function and the lanthanoid having a light-emitting function in the outer shell being 2 mol % or less based on an amount of the rare earth element contained in the outer shell, the outer shell having a thickness of 2 to 20 nm, the core particle and the shell layer having no interface at a contact face to form a continuous body, and the lanthanoid-containing inorganic material fine particle further comprising a polymer layer containing a polymer and noble metal particles around the shell layer.
13. A method for determining authenticity of information printed on a substrate with the wavelength conversion ink according to claim 9 by evaluating an emission spectrum and a printing pattern of the wavelength conversion ink, comprising: irradiating using an irradiation means for infrared irradiation of a coated article comprising the wavelength conversion ink and the substrate, and detecting using a detection means for detecting an emission spectrum generated by the infrared irradiation and a printing pattern of the wavelength conversion ink.
Description
BRIEF DESCRIPTION OF DRAWINGS
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
DESCRIPTION OF EMBODIMENTS
(9) The present invention is more specifically described in the following with reference to, but not limited to, examples.
EXAMPLE 1
(10) (Preparation of Lanthanoid-Containing Inorganic Material Fine Particles)
(11) (Preparation of Core Particles)
(12) A metal ion-containing solution A-1 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 solvent mixture containing 11.13 g of oleic acid, 10.39 g of trioctyl phosphine, and 46.03 g of octadecene. A solution obtained by dissolving 0.15 g of sodium hydroxide and 0.39 g of ammonium fluoride in 15 g of methanol was added right after the preparation thereof to the metal ion-containing solution A-1, thereby preparing a reaction precursor solution A-1.
(13) The reaction precursor solution A-1 was heated with stirring in vacuum at 50° C. for 15 minutes so that methanol was vaporized to be removed from the solution. Then, the resulting solution was further heated with stirring in nitrogen atmosphere at 315° C. for 60 minutes so that fine particles were precipitated in the solution.
(14) The solution was cooled to room temperature and 25 g of ethanol was added thereto so that the fine particles were settled. The fine particles were recovered using a centrifugation device. Washing treatment was repeated several times in which the recovered fine particles were re-dispersed in 25 g of toluene, 25 g of ethanol was again added thereto for re-aggregation of the fine particles, and the re-aggregated fine particles were recovered using a centrifugation device. Core particles were thus obtained.
(15) (Formation of a Shell Layer (Outer Shell))
(16) A metal ion-containing solution A-2 was prepared by dissolving 0.51 g of yttrium acetate in a solvent mixture containing 16.69 g of oleic acid, 5.19 g of trioctyl phosphine, and 46.03 g of octadecene. A solution obtained by dissolving 0.15 g of sodium hydroxide and 0.39 g of ammonium fluoride in 15 g of methanol was added right after the preparation thereof to the metal ion-containing solution A-2, thereby preparing a reaction precursor solution A-2.
(17) The core particles obtained in (Preparation of core particles) were added to the reaction precursor solution A-2 and dispersed therein. The resulting reaction precursor solution A-2 containing the core particles dispersed therein was heated with stirring in vacuum at 50° C. for 15 minutes so that methanol was vaporized to be removed from the solution. The resulting solution was heated with stirring in nitrogen atmosphere at 315° C. for 60 minutes so that fine particles each including a core particle and a shell layer (outer shell) formed on the surface of the core particle were precipitated.
(18) The solution was cooled to room temperature, and 25 g of ethanol was added thereto so that the fine particles were settled. The fine particles were recovered using a centrifugation device. Washing treatment was repeated several times in which the recovered fine particles were re-dispersed in 25 g of toluene, 25 g of ethanol was again added thereto for re-aggregation of the fine particles, and the re-aggregated fine particles were recovered using a centrifugation device. Lanthanoid-containing inorganic material fine particles were thus obtained.
(19) The washing solvent remaining in the obtained lanthanoid-containing inorganic material fine particles was removed using a vacuum dryer, and the lanthanoid-containing inorganic material fine particles were sealed in a nitrogen-atmosphere hermetic container until the evaluation was performed.
(20) The amounts of a lanthanoid having a light-absorbing function, a lanthanoid having a light-emitting function, and an element having a similar ionic radius or a similar structure upon crystallization to that of the lanthanoids contained in the core particle and the shell layer of the obtained lanthanoid-containing inorganic material fine particle were measured using a fluorescence X-ray analyzer (EDX-800HS available from Shimadzu Corporation).
(21) In addition, the presence of NaYF.sub.4 in the core particle and the shell layer was confirmed based on the peak pattern using an X-ray diffractometer.
EXAMPLE 2
(22) Lanthanoid-containing inorganic material fine particles were obtained in the same manner as in Example 1, except that 0.26 g of yttrium acetate, 0.07 g of sodium hydroxide, and 0.19 g of ammonium fluoride were used in (Formation of a shell layer (outer shell)) in Example 1.
EXAMPLE 3
(23) Lanthanoid-containing inorganic material fine particles were obtained in the same manner as in Example 1, except that 5.1 g of yttrium acetate, 45 g of methanol, 1.5 g of sodium hydroxide, and 3.9 g of ammonium fluoride were used in (Formation of a shell layer (outer shell)) in Example 1.
EXAMPLE 4
(24) (Formation of an Intermediate Layer)
(25) A dispersion was prepared by dispersing 0.1 g of the lanthanoid-containing inorganic material fine particles obtained in Example 1 in 200 ml of cyclohexane. To the obtained dispersion was added a mixed liquid obtained by mixing 50 ml of cyclohexane and 25 ml of a surfactant (Igepal-520 available from Sigma-Aldrich Co. LLC.). To the resulting mixture was further added 20 ml of 28% ammonia water, and the mixture was stirred for one hour. Then, 2.5 ml of tetraethyl orthosilicate (TEOS) was added, followed by stirring for 24 hours. Washing treatment was repeated several times in which the fine particles were recovered using a centrifugation device, re-dispersed in ethanol, and recovered again using a centrifugation device. Thus, SiO.sub.2 layer-formed fine particles each including a SiO.sub.2 layer on the surface as an intermediate layer were produced.
(26) (Formation of a Polymer Layer)
(27) A fine particle dispersion was prepared by dissolving 0.1 g of the obtained SiO.sub.2 layer-formed fine particles in 100 ml of pure water. To the obtained fine particle dispersion was added 0.01 g of a silane coupling agent (Tokyo Chemical Industry Co., Ltd., 3-chloropropyltriethoxysilane). The mixture was stirred for one hour, thereby producing fine particles each having a chlorine-introduced surface. The fine particles each having a chlorine-introduced surface were recovered using a centrifugation device. The recovered fine particles were re-dispersed in 10 ml of pure water, and 0.3 mmol of dimethylaminoethyl methacrylate (DMAEMA), 0.015 mmol of copper chloride, 0.015 mmol of tris[2-(dimethylamino)ethyl]amine (ME.sub.6TREN), and 0.0012 mmol of ascorbic acid were added thereto. The mixture was stirred in nitrogen atmosphere for six hours, thereby producing fine particles each having a DMAEMA polymer brush bonded thereto. Then, 0.15 mmol of chlorauric acid was added thereto, and the mixture was stirred for 24 hours. Washing treatment was repeated several times in which the fine particles were recovered using a centrifugation device, re-dispersed in ethanol, and recovered again using a centrifugation device. Lanthanoid-containing inorganic material fine particles each having, as a polymer layer, a polymer brush layer containing gold particles were produced.
EXAMPLE 5
(28) (Preparation of Lanthanoid-Containing Inorganic Material Fine Particles)
(29) (Preparation of Core Particles)
(30) A metal ion-containing solution B-1 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 solvent mixture containing 11.13 g of oleic acid, 10.39 g of trioctyl phosphine, and 46.03 g of octadecene. A solution obtained by dissolving 0.15 g of sodium hydroxide and 0.39 g of ammonium fluoride in 15 g of methanol was added right after the preparation thereof to the metal ion-containing solution B-1, thereby preparing a reaction precursor solution B-1.
(31) The reaction precursor solution B-1 was heated with stirring in vacuum at 50° C. for 15 minutes so that methanol was vaporized to be removed from the solution. Then, the resulting solution was further heated with stirring in nitrogen atmosphere at 315° C. for 60 minutes so that fine particles were precipitated in the solution.
(32) The solution was cooled to room temperature and 25 g of ethanol was added thereto so that the fine particles were settled. The fine particles were recovered using a centrifugation device. Washing treatment was repeated several times in which the recovered fine particles were re-dispersed in 25 g of toluene, 25 g of ethanol was again added thereto for re-aggregation of the fine particles, and the re-aggregated fine particles were recovered using a centrifugation device. Core particles were thus obtained.
(33) (Formation of an Inner Shell)
(34) A metal ion-containing solution B-2 was prepared by dissolving 0.41 g of yttrium acetate and 0.13 g of ytterbium acetate in a solvent mixture containing 16.69 g of oleic acid and 5.19 g of trioctyl phosphine, and 46.03 g of octadecene. A solution obtained by dissolving 0.15 g of sodium hydroxide and 0.39 g of ammonium fluoride in 15 g of methanol was added right after the preparation thereof to the metal ion-containing solution B-2, thereby preparing a reaction precursor solution B-2.
(35) The core particles obtained in (Preparation of core particles) were added to the reaction precursor solution B-2 and dispersed therein. The resulting reaction precursor solution B-2 containing the core particles dispersed therein was heated with stirring in vacuum at 50° C. for 15 minutes so that methanol was vaporized to be removed from the solution. The resulting solution was heated with stirring in nitrogen atmosphere at 315° C. for 60 minutes so that fine particles each including a core particle and an inner shell formed on the surface of the core particle were precipitated.
(36) The solution was cooled to room temperature, and 25 g of ethanol was added thereto so that the fine particles were settled. The fine particles were recovered using a centrifugation device. Washing treatment was repeated several times in which the recovered fine particles were re-dispersed in 25 g of toluene, 25 g of ethanol was again added thereto for re-aggregation of the fine particles, and the re-aggregated fine particles were recovered using a centrifugation device. Inner shell-formed fine particles were thus obtained.
(37) (Formation of an Outer Shell)
(38) A metal ion-containing solution B-3 was prepared by dissolving 0.51 g of yttrium acetate in a solvent mixture containing 16.69 g of oleic acid, 5.19 g of trioctyl phosphine, and 46.03 g of octadecene. A solution obtained by dissolving 0.15 g of sodium hydroxide and 0.39 g of ammonium fluoride in 15 g of methanol was added right after preparation thereof to the metal ion-containing solution B-3, thereby preparing a reaction precursor solution B-3.
(39) The inner shell-formed fine particles obtained in (Formation of an inner shell) were added to the reaction precursor solution B-3 and dispersed therein. The resulting reaction precursor solution B-3 containing the inner shell-formed fine particles dispersed therein was heated with stirring in vacuum at 50° C. for 15 minutes so that methanol was vaporized to be removed from the solution. The resulting solution was heated with stirring in nitrogen atmosphere at 315° C. for 60 minutes so that fine particles each including an inner shell-formed fine particle and an outer shell formed on the surface of the inner shell-formed fine particle were precipitated.
(40) The solution was cooled to room temperature, and 25 g of ethanol was added thereto so that the fine particles were settled. The fine particles were recovered using a centrifugation device. Washing treatment was repeated several times in which the recovered fine particles were re-dispersed in 25 g of toluene, 25 g of ethanol was again added thereto for re-aggregation of the fine particles, and the re-aggregated fine particles were recovered using a centrifugation device. Lanthanoid-containing inorganic material fine particles were thus obtained.
(41) The washing solvent remaining in the obtained lanthanoid-containing inorganic material fine particles was removed using a vacuum dryer, and the lanthanoid-containing inorganic material fine particles were sealed in a nitrogen-atmosphere hermetic container until the evaluation was performed.
(42) The amounts of a lanthanoid having a light-absorbing function, a lanthanoid having a light-emitting function, and an element having a similar ionic radius or a similar structure upon crystallization to that of the lanthanoids contained in the core particle, the inner shell, and the outer shell of the obtained lanthanoid-containing inorganic material fine particle were measured using a fluorescence X-ray analyzer (EDX-800HS available from Shimadzu Corporation).
(43) In addition, the presence of NaYF.sub.4 in the core particle, the inner shell, and the outer shell was confirmed based on the peak pattern using an X-ray diffractometer.
EXAMPLE 6
(44) Lanthanoid-containing inorganic material fine particles were obtained in the same manner as in Example 5 except that 0.31 g of yttrium acetate, 0.08 g of sodium hydroxide, and 0.23 g of ammonium fluoride were used in (Formation of an outer shell) in Example 5.
EXAMPLE 7
(45) Lanthanoid-containing inorganic material fine particles were obtained in the same manner as in Example 5 except that 6.1 g of yttrium acetate, 55 g of methanol, 1.8 g of sodium hydroxide, and 4.7 g of ammonium fluoride were used in (Formation of an outer shell) in Example 5.
EXAMPLE 8
(46) Lanthanoid-containing inorganic material fine particles were obtained in the same manner as in Example 5 except that 0.30 g of yttrium acetate and 0.25 g of ytterbium acetate were used in (Formation of an inner shell) in Example 5.
EXAMPLE 9
(47) Lanthanoid-containing inorganic material fine particles were obtained in the same manner as in Example 1 except that 0.20 g of yttrium acetate and 0.38 g of ytterbium acetate were used in (Formation of an inner shell) in Example 5.
EXAMPLE 10
(48) (Formation of an Intermediate Layer)
(49) A dispersion was prepared by dispersing 0.1 g of the lanthanoid-containing inorganic material fine particles obtained in Example 5 in 200 ml of cyclohexane. To the obtained dispersion was added a mixed liquid obtained by mixing 50 ml of cyclohexane and 25 ml of a surfactant (Igepal-520 available from Sigma-Aldrich Co. LLC.). To the mixture was further added 10 ml of 28% ammonia water. The mixture was stirred for one hour. Then, 2.5 ml of tetraethyl orthosilicate (TEOS) was added to the mixture, followed by stirring for 24 hours. Washing treatment was performed several times in which the fine particles were recovered using a centrifugation device, re-dispersed in ethanol, and then recovered again using a centrifugation device. Thus, SiO.sub.2 layer-formed fine particles each including a SiO.sub.2 layer on the surface as an intermediate layer were produced.
(50) (Formation of a Polymer Layer)
(51) A fine particle dispersion was prepared by dispersing 0.1 g of the obtained SiO.sub.2 layer-formed fine particles in 100 ml of pure water. To the obtained fine particle dispersion was added 0.01 g of a silane coupling agent (Tokyo Chemical Industry Co., Ltd., 3-chloropropyltriethoxysilane). The mixture was stirred for one hour, thereby producing fine particles each having a chlorine-introduced surface. The fine particles each having a chlorine-introduced surface were recovered using a centrifugation device. The recovered fine particles were re-dispersed in 10 ml of pure water, and 0.3 mmol of dimethylaminoethyl methacrylate (DMAEMA), 0.015 mmol of copper chloride, 0.015 mmol of tris[2-(dimethylamino)ethyl]amine (ME.sub.6TREN), and 0.0012 mmol of ascorbic acid were added thereto. The mixture was stirred in nitrogen atmosphere for six hours, thereby producing fine particles each having a DMAEMA polymer brush bonded thereto. Then, 0.015 mmol of chlorauric acid was added thereto, and the mixture was stirred for 24 hours. The fine particles were recovered using a centrifugation device. Washing treatment was repeated several times in which the fine particles were recovered using a centrifugation device, re-dispersed in ethanol, and recovered again using a centrifugation device. Lanthanoid-containing inorganic material fine particles each having, as a polymer layer, a polymer brush layer containing gold particles were obtained.
COMPARATIVE EXAMPLE 1
(52) Lanthanoid-containing inorganic material fine particles were obtained in the same manner as in Example 1 except that the process of (Formation of a shell layer (outer shell) in Example 1 was not performed.
(53) The washing solvent remaining in the obtained lanthanoid-containing inorganic material fine particles was removed using a vacuum dryer, and the lanthanoid-containing inorganic material fine particles were sealed in a nitrogen-atmosphere hermetic container until the evaluation was performed.
COMPARATIVE EXAMPLE 2
(54) Lanthanoid-containing inorganic material fine particles were obtained in the same manner as in Example 1 except that a solvent mixture containing 11.13 g of oleic acid and 46.03 g of octadecene was used in (Preparation of core particles) and (Formation of a shell layer (outer shell)) in Example 1.
COMPARATIVE EXAMPLE 3
(55) Lanthanoid-containing inorganic material fine particles were obtained in the same manner as in Example 1 except that a solvent mixture containing 20.78 g of trioctyl phosphine and 46.03 g of octadecene was used in (Preparation of core particles) and (Formation of a shell layer (outer shell)) in Example 1.
COMPARATIVE EXAMPLE 4
(56) Lanthanoid-containing inorganic material fine particles were obtained in the same manner as in Example 1 except that 0.15 g of yttrium acetate, 0.045 g of sodium hydroxide, and 0.13 g of ammonium fluoride were used in (Formation of a shell layer (outer shell)) in Example 1.
COMPARATIVE EXAMPLE 5
(57) Lanthanoid-containing inorganic material fine particles were obtained in the same manner as in Example 1 except that 7.65 g of yttrium acetate, 60 g of methanol, 2.25 g of sodium hydroxide, and 5.85 g of ammonium fluoride were used in (Formation of a shell layer (outer shell)) in Example 1.
COMPARATIVE EXAMPLE 6
(58) Lanthanoid-containing inorganic material fine particles were obtained in the same manner as in Example 1 except that 0.013 g of ytterbium acetate and 0.0013 g of erbium acetate were used in addition to 0.49 g of yttrium acetate in (Formation of a shell layer (outer shell)) in Example 1.
COMPARATIVE EXAMPLE 7
(59) Lanthanoid-containing inorganic material fine particles were obtained in the same manner as in Example 5 except that a solvent mixture containing 11.13 g of oleic acid and 46.03 g of octadecene was used in (Preparation of core particles), (Formation of an inner shell), and (Formation of an outer shell) in Example 5.
COMPARATIVE EXAMPLE 8
(60) Lanthanoid-containing inorganic material fine particles were obtained in the same manner as in Example 5 except that a solvent mixture containing 20.78 g of trioctyl phosphine and 46.03 g of octadecene was used in (Preparation of core particles), (Formation of an inner shell), and (Formation of an outer shell) in Example 5.
COMPARATIVE EXAMPLE 9
(61) Lanthanoid-containing inorganic material fine particles were obtained in the same manner as in Example 5 except that 0.18 g of yttrium acetate, 0.054 g of sodium hydroxide, and 0.16 g of ammonium fluoride were used in (Formation of an outer shell) in Example 5.
COMPARATIVE EXAMPLE 10
(62) Lanthanoid-containing inorganic material fine particles were obtained in the same manner as in Example 5, except that 9.18 g of yttrium acetate, 75 g of methanol, 2.70 g of sodium hydroxide, and 7.02 g of ammonium fluoride were used in (Formation of an outer shell) in Example 5.
COMPARATIVE EXAMPLE 11
(63) Lanthanoid-containing inorganic material fine particles were obtained in the same manner as in Example 5 except that 0.013 g of ytterbium acetate and 0.0013 g of erbium acetate were used in addition to 0.49 g of yttrium acetate in (Formation of an outer shell) in Example 5.
COMPARATIVE EXAMPLE 12
(64) Lanthanoid-containing inorganic material fine particles having an average particle size of 64.7 nm were obtained by pulverizing a lanthanoid-containing inorganic crystal (Sigma-Aldrich Co. LLC., Er- and Yb-doped NaYF.sub.4 (Er content: 2 mol %, Yb content: 20 mol %) using a bead mill.
(65) (Evaluation)
(66) The lanthanoid-containing inorganic material fine particles obtained in the examples and comparative examples were evaluated as follows. Tables 1 and 2 show the results.
(67) (1) Measurement of the Average Particle Size of Core Particles and Thickness of the Inner Shell, Outer Shell, Intermediate Layer, and Polymer Layer
(68) The core particles, inner shell-formed fine particles, and lanthanoid-containing inorganic material fine particles obtained in each of the examples and comparative examples were observed using a transmission electron microscope. The average of the particle sizes of 300 particles in the obtained image was calculated to determine the average particle size of each particle type. In Examples 1 to 4 and Comparative Examples 2 to 6, the difference in the average particle size between the core particles before formation of the shell layer (outer shell) and the lanthanoid-containing inorganic material fine particles after formation of the shell layer was obtained, thereby determining the thickness of the shell layer (outer shell). In Examples 5 to 10 and Comparative Examples 7 to 11, the difference in the average particle size between the fine particles before formation of each shell and the fine particles after formation of each shell was obtained, thereby determining the thicknesses of the inner shell and the outer shell. In Examples 4 and 10, the average particle size of the fine particles each having an intermediate layer formed thereon and the average particle size of the lanthanoid-containing inorganic material fine particles each further having a polymer layer formed thereon were measured. The differences between the obtained average particle sizes and the average particle size of the lanthanoid-containing inorganic material fine particle obtained in Example 1 or 5 were calculated, thereby determining the thicknesses of the intermediate layer and the polymer layer.
(69)
(70) (2) Measurement of the Amount and Average Particle Size of Noble Metal Particles
(71) The lanthanoid-containing inorganic material fine particles obtained in Examples 4 and 10 were observed using a transmission electron microscope. Based on the difference in contrast between the polymer layer and noble metal particles contained in the polymer layer in the obtained image, the volume of the polymer layer and the volume of the noble metal particles were calculated by binarization by image analysis. The amount of the noble metal particles in the polymer layer was thus determined.
(72) In addition, the average of particle sizes of 300 noble metal particles was calculated, thereby determining the average particle size of the noble metal particles contained in the polymer layer.
(73) (3) Check on Contact Face (Check on Crystal Structure)
(74) The crystal structures of the core particles and the lanthanoid-containing inorganic material fine particles obtained in Examples 1 to 4 and Comparative Examples 2 to 6 were analyzed using an X-ray diffractometer and the peaks obtained before and after the formation of a shell layer (outer shell) were checked to evaluate the continuousness of the crystal structures of the core particle and the shell layer.
(75) The crystal structures of the core particles, the inner shell-formed fine particles, and the lanthanoid-containing inorganic material fine particles obtained in Examples 5 to 10 and Comparative Examples 7 to 11 were analyzed using an X-ray diffractometer and the peaks obtained before and after the formation of a shell layer were checked to evaluate the continuousness of the crystal structures of the core particle and the inner shell and the continuousness of the crystal structures of the inner shell and the outer shell.
(76) The case where the peaks observed were the same was rated “∘ (Good)” and the case where the peaks observed were different from each other was rated “× (Poor)”. In the case where the same peaks were observed, the shell layer was considered to be continuously formed. In the case where the peak(s) observed after the formation of the shell layer was(were) different that(those) before the formation of the shell layer, crystals were considered to have grown discontinuously at each contact face to form an interface.
(77)
(78) (4) Confirmation of the Presence or Absence of Contamination in the Shell Layer (Oxygen Relative Increase Rate)
(79) Dispersions were prepared by individually dispersing the lanthanoid-containing inorganic material fine particles obtained in Examples 1 to 4 and Comparative Examples 2 to 6 in toluene. Each dispersion was applied to the surface of a silicon wafer to form a single particle layer having a close-packed structure of the lanthanoid-containing inorganic material fine particles. The surface of the obtained single particle layer was subjected to irradiation using an Ar-sputter gun so that the lanthanoid-containing inorganic material fine particles were cut at a rate of 5 nm per minute. The elemental contents (carbon, oxygen, yttrium) in the cutting direction were analyzed using an Auger electron spectrometer. In the case where the relative proportion of an increase in the detected amount of the oxygen element after the cutting to the depth corresponding to the thickness of the shell layer (outer shell) was 25% or more relative to the detected amount in a part corresponding to the shell layer (outer shell), formation of an interface due to oxidation at the contact face between the core particle and the shell layer (outer shell) was confirmed.
(80) Dispersions were prepared by individually dispersing the lanthanoid-containing inorganic material fine particles obtained in Examples 5 to 10 and Comparative Examples 7 to 11 in toluene. Each dispersion was applied to the surface of a silicon wafer to form a single particle layer having a close-packed structure of the lanthanoid-containing inorganic material fine particles. The surface of the obtained single particle layer was subjected to irradiation using an Ar-sputter gun so that the lanthanoid-containing inorganic material fine particles were cut at a rate of 5 nm per minute. The elemental contents (carbon, oxygen, yttrium) in the cutting direction were analyzed using an Auger electron spectrometer. In the case where the relative proportion of an increase in the detected amount of the oxygen element after the cutting to the depth corresponding to the thickness of the outer shell was 25% or more relative to the detected amount in a part corresponding to the outer shell, formation of an interface due to oxidation at the contact face between the outer shell and the inner shell was confirmed. In the case where an interface due to oxidation at the contact face between the outer shell and the inner shell is formed, an interface due to oxidation is presumably also formed at the contact face between the core particle and the inner shell.
(81) (5) Measurement of Emission Intensity
(82) The lanthanoid-containing inorganic material fine particles obtained in each example and comparative example were irradiated with infrared rays using an infrared generator (L980P300J available from THORLABS) set at a wavelength of 980 nm and an output of 300 mW as an external light source. The obtained fluorescence emission spectrum was analyzed using a fluorescence spectrophotometer (U-2700 available from Hitachi High-Technologies Corporation). The emission intensity was evaluated by calculating the relative value of the maximum strength in the fluorescence emission spectrum of each example and comparative example with the maximum strength in the spectrum in Comparative Example 1 set to 1.
(83)
(84) (6) Humidity Resistance of the Lanthanoid-Containing Inorganic Material Fine Particles (Retention Rate of Emission Intensity After High-Temperature, High-Humidity Test)
(85) The lanthanoid-containing inorganic material fine particles obtained in each of the examples and comparative examples were left in a high-temperature, high-humidity tester (85° C., 85% RH) for 500 hours. The emission intensity of the lanthanoid-containing inorganic material fine particles after the high-temperature, high-humidity test was measured in the same manner as in (5) Measurement of emission intensity. The humidity resistance was evaluated by calculating the retention rate of the emission intensity after the high-temperature, high-humidity test with the emission intensity before the high-temperature, high-humidity test set to 100%.
(86) (7) Water Resistance of Wavelength Conversion Ink (Line Width Increase Rate)
(87) A wavelength conversion ink was prepared by mixing 0.1 g of the lanthanoid-containing inorganic material fine particles obtained in each of the examples and comparative examples and 9.9 g of cyclohexane. A bar-code pattern (line width: 100 μm, line interval: 100 μm) was printed on copy paper (10 cm×10 cm) with the obtained wavelength conversion ink using an inkjet printer (NanoPrinter 3000 available from Microjet Corporation). The copy paper with a pattern printed with the wavelength conversion ink was sunk in a container sufficiently filled with water (water depth: 10 cm) at a rate of 1 cm per second. One minute later, the copy paper was lifted out of the container at a lifting rate of 1 cm per second. The line widths (width of ink bleeding) before and after the immersion were measured by observation using a microscope under irradiation with infrared rays. The water resistance of the printing pattern was evaluated by calculating the increase rate of the line width after the immersion with the line width before the immersion set to 100%.
(88) TABLE-US-00001 TABLE 1 Lanthanoid-containing inorganic material particle *1 Shell layer Core particle Inner shell Outer shell Amount of Amount of Amount of Amount of Amount of Amount of lanthanoid lanthanoid lanthanoid lanthanoid lanthanoid lanthanoid having light- having light- Average having light- having light- having light- having light- Intermediate layer absorbing emitting particle absorbing emitting Thick- absorbing emitting Thick- Thick- function function size function function ness function function ness Struc- ness (mol %) (mol %) (nm) (mol %) (mol %) (nm) (mol %) (mol %) (nm) ture (nm) Example 1 20.3 1.96 27.3 — — — 0.0 0.0 5.5 — — Example 2 20.3 1.96 27.3 — — — 0.0 0.0 2.6 — — Example 3 20.3 1.96 27.3 — — — 0.0 0.0 18.2 — — Example 4 20.3 1.96 27.3 — — — 0.0 0.0 5.5 SiO.sub.2 1.7 Example 5 20.3 1.96 27.3 19.4 0.0 5.4 0.0 0.0 5.0 — — Example 6 20.3 1.96 27.3 19.4 0.0 5.4 0.0 0.0 2.1 — — Example 7 20.3 1.96 27.3 19.4 0.0 5.4 0.0 0.0 17.5 — — Example 8 20.3 1.96 27.3 41.7 0.0 5.1 0.0 0.0 5.0 — — Example 9 20.3 1.96 27.3 58.7 0.0 4.8 0.0 0.0 5.4 — — Example 10 20.3 1.96 27.3 19.4 0.0 5.4 0.0 0.0 5.0 SiO.sub.2 1.3 Lanthanoid-containing inorganic material particle *1 Polymer layer Noble metal particles Evaluation Average Check Oxygen relative Emission intensity Line- particle Thick- on increase rate Emission retention rate after width Noble Amount size ness contact by elemental intensity high-temperature, increase Polymer metal (vol %) (nm) (nm) face analysis (%) *2 high-humidity test (%) rate (%) Example 1 — — — — — ∘ 8.2 13.4 91.6 105.3 Example 2 — — — — — ∘ 7.0 10.4 90.8 104.9 Example 3 — — — — — ∘ 10.1 11.7 92.9 108.3 Example 4 DMAEMA Gold 25.9 7.5 28.4 ∘ 8.2 39.7 90.1 107.4 polymer Example 5 — — — — — ∘ 10.8 16.9 92.4 105.9 Example 6 — — — — — ∘ 9.4 12.6 94.0 104.7 Example 7 — — — — — ∘ 13.4 12.9 95.6 109.3 Example 8 — — — — — ∘ 17.0 16.7 93.1 103.5 Example 9 — — — — — ∘ 15.7 10.9 92.1 106.8 Example 10 DMAEMA Gold 21.8 6.8 24.9 ∘ 10.8 50.4 91.1 108.4 polymer *1 The amounts of a lanthanoid having a light-absorbing function and a lanthanoid having a light-emitting function each represent a proportion relative to the amount of rare-earth elements contained in the core particle, inner shell, or outer shell. *2 Relative value with the maximum strength of Comparative Example 1 set to 1
(89) TABLE-US-00002 TABLE 2 Lanthanoid-containing inorganic material particle *1 Shell layer Core particle Inner shell Outer shell Amount of Amount of Amount of Amount of Amount of Amount of lanthanoid lanthanoid lanthanoid lanthanoid lanthanoid lanthanoid having light- having light- Average having light- having light- having light- having light- Intermediate layer absorbing emitting particle absorbing emitting Thick- absorbing emitting Thick- Thick- function function size function function ness function function ness Struc- ness (mol %) (mol %) (nm) (mol %) (mol %) (nm) (mol %) (mol %) (nm) ture (nm) Comparative 20.3 1.96 27.3 — — — — — — — — Example 1 Comparative 19.5 2.01 30.1 — — — 0.0 0.0 5.2 — — Example 2 Comparative 19.9 1.9 29.4 — — — 0.0 0.0 4.8 — — Example 3 Comparative 20.3 1.96 27.3 — — — 0.0 0.0 1.5 — — Example 4 Comparative 20.3 1.96 27.3 — — — 0.0 0.0 21.0 — — Example 5 Comparative 20.3 1.96 27.3 — — — 2.1 0.3 4.9 — — Example 6 Comparative 19.5 2.01 30.1 19.4 0.0 5.0 0.0 0.0 5.5 — — Example 7 Comparative 19.9 1.9 29.4 19.4 0.0 4.5 0.0 0.0 5.6 — — Example 8 Comparative 20.3 1.96 27.3 19.4 0.0 5.4 0.0 0.0 1.2 — — Example 9 Comparative 20.3 1.96 27.3 19.4 0.0 5.4 0.0 0.0 20.3 — — Example 10 Comparative 20.3 1.96 27.3 19.4 0.0 5.4 1.9 0.2 5.6 — — Example 11 Comparative 20 2.0 64.7 — — — — — — — — Example 12 Lanthanoid-containing inorganic material particle *1 Polymer layer Noble metal particles Evaluation Average Check Oxygen relative Emission intensity Line- particle Thick- on increase rate Emission retention rate after width Noble Amount size ness contact by elemental intensity high-temperature, increase Polymer metal (vol %) (nm) (nm) face analysis (%) *2 high-humidity test (%) rate (%) Comparative — — — — — — — 1.0 87.9 103.7 Example 1 Comparative — — — — — x 29.4 7.0 65.9 117.4 Example 2 Comparative — — — — — x 34.7 5.0 61.1 119.7 Example 3 Comparative — — — — — ∘ 11.0 7.9 91.6 104.4 Example 4 Comparative — — — — — ∘ 9.2 9.7 94.3 107.4 Example 5 Comparative — — — — — ∘ 12.4 8.0 93.0 105.5 Example 6 Comparative — — — — — x 32.9 8.9 66.6 124.7 Example 7 Comparative — — — — — x 40.0 5.4 59.9 121.9 Example 8 Comparative — — — — — ∘ 16.0 7.9 90.9 102.9 Example 9 Comparative — — — — — ∘ 14.5 9.9 94.7 110.7 Example 10 Comparative — — — — — ∘ 16.3 8.2 90.7 107.1 Example 11 Comparative — — — — — — — 4.8 54.7 138.2 Example 12 *1 The amounts of a lanthanoid having a light-absorbing function and a lanthanoid having a light-emitting function each represent a proportion relative to the amount of rare-earth elements contained in the core particle, inner shell, or outer shell. *2 Relative value with the maximum strength of Comparative Example 1 set to 1
INDUSTRIAL APPLICABILITY
(90) The present invention can provide a lanthanoid-containing inorganic material fine particle that enables achievement of high luminous efficiency with less energy outflow upon conversion of the wavelength of light to a shorter wavelength. The present invention can also provide a wavelength conversion ink capable of maintaining a high emission intensity at the time of wavelength conversion for a long period of time, having high water repellency, and capable of forming a printing pattern excellent in retention properties, a coated article produced using the wavelength conversion ink, and a determination apparatus.