JP2006096897A - Fluorescent material, method for producing the same and luminous device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an energy transfer type fluorescent material using an inorganic material, and to provide a method for producing the fluorescent material. <P>SOLUTION: A fluorescent material 100 comprises at least a pair of semiconductor layers 110 and a rare earth ion layer 120, wherein the semiconductor layer has negative charge, the rare earth ion layer has positive charge and contains at least one rare earth ion, each of the semiconductor layers and each of the rare earth ion layers are laminated to adjoin each other, and energy E<SB>D</SB>of the semiconductor donor level and energy E<SB>Re</SB>of the excited state of at least one rare earth ion satisfy a relation E<SB>D</SB>>E<SB>Re</SB>. The process for producing the fluorescent material comprises a step for purifying a suspension containing the semiconductor layer, a step for preparing a reaction solution containing the rare earth ion and a step for mixing the suspension and the reaction solution. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fluorescent material containing rare earth ions and a method for producing the same, and more particularly to a fluorescent material that emits light by energy transfer to the contained rare earth ions and a method for producing the same.

  There is great interest in the technical applications of fluorescent materials containing rare earth ions or lanthanoid (Ln) ions, such as electroluminescent devices, optoelectronics and flat panel displays.

One such fluorescent material is a fluorescent complex containing a rare earth element and a ligand. The fluorescent complex is obtained by mixing a rare earth element salt (eg, europium, neodymium) and a low molecular ligand (eg, β-diketone compound) in a solvent, and adding a basic compound to adjust the pH. . In such a fluorescent complex, when the ligand is excited, energy transfer from the ligand to the rare earth ion occurs, and strong fluorescence due to the rare earth ion is observed.

  Such fluorescence is advantageous as compared with the case where the rare earth ions are directly excited because the ligand only needs to be excited. This is because the ligand has absorption in a wider wavelength range than the rare earth ions, and thus there is no limitation on the excitation wavelength. However, since such a fluorescent complex is an organic substance, application technology may be limited. In addition, organic substances have a problem that they are thermally unstable.

  In order to overcome such problems, in recent years, development of inorganic semiconductor materials containing rare earth elements has been advanced (see, for example, Non-Patent Document 1). Non-Patent Document 1 discloses a technique for producing titanium oxide (titania) containing various europium concentrations from a mixed solution of a titanium isopropoxide solution and a europium nitrate solution using a sol-gel method. .

A. Conde-Gallardo, et al., Applied Physics Letters, Vol. 78, no. 22, pp. 3436

  However, the titanium oxide containing europium described in Non-Patent Document 1 does not show sufficient fluorescence due to energy transfer from titanium oxide to europium. This is because the amount of europium adsorbed on the surface of titanium oxide is larger than the amount of europium contained in the crystal lattice of titanium oxide in the amount of doping preparation of europium. Further, with the technique described in Non-Patent Document 1, it is difficult to contain a sufficient amount of europium in the crystal lattice of titanium oxide to obtain sufficient light emission intensity.

  Accordingly, an object of the present invention is to provide an energy transfer type fluorescent material using an inorganic material and a method for producing the same.

In the fluorescent material comprising at least a pair of semiconductor layers and a rare earth ion layer according to the present invention, the semiconductor layer has a negative charge, the rare earth ion layer has a positive charge, and at least one kind of rare earth Each of the at least one pair of the semiconductor layer and the rare earth ion layer including ions is stacked so as to be adjacent to each other, the defect level energy E _{D of the} semiconductor layer, and the at least one kind of rare earth ions Excited state energy E _{Re
Satisfies the} relationship E _D > E _Re and thereby achieves the above objective.

  The semiconductor layer may be selected from the group consisting of titanium oxide nanosheets, manganese oxide nanosheets, niobium oxide nanosheets, titanium oxide / niobium nanosheets, perovskite type niobium oxide nanosheets, perovskite type tantalum oxide nanosheets, and perovskite type titanium oxide nanosheets. Good.

The at least one rare earth ion is Sm ³⁺ , Eu ³⁺ , Tb ³⁺ , Dy ³⁺ , Pr ³⁺ , Nd ³⁺ , Ho ³⁺ , Er ³⁺ , Tm ³⁺ , and Yb ^3+. May be selected from the group consisting of

The rare earth ion layer may further include ions selected from the group consisting of alkali metal ions, alkaline earth metal ions, transition metal ions, hydrogen ions, and ammonium ions.
The semiconductor layer may have a thickness in the range of 0.5 nm to 2 nm.

A method for producing a fluorescent material comprising a semiconductor layer and a rare earth ion layer according to the present invention includes a step of producing a suspension containing the semiconductor layer having a negative charge, and a reaction solution containing at least one kind of rare earth ions. A defect level energy E _{D of the} semiconductor layer and an excited state energy E _{Re of the} at least one rare earth element satisfy the relationship E _D > E _Re ; A step of mixing the suspension and the reaction solution, wherein the rare earth ion layer having a positive charge and including the at least one kind of rare earth ions is formed on the semiconductor layer. This achieves the above object.

  The semiconductor layer may be selected from the group consisting of titanium oxide nanosheets, manganese oxide nanosheets, niobium oxide nanosheets, titanium oxide / niobium nanosheets, perovskite type niobium oxide nanosheets, perovskite type tantalum oxide nanosheets, and perovskite type titanium oxide nanosheets. Good.

The at least one rare earth ion is Sm ³⁺ , Eu ³⁺ , Tb ³⁺ , Dy ³⁺ , Pr ³⁺ , Nd ³⁺ , Ho ³⁺ , Er ³⁺ , Tm ³⁺ , and Yb ^3+. May be selected from the group consisting of

The step of preparing may include a step of further adding ions selected from the group consisting of alkali metal ions, alkaline earth metal ion transition metal ions, hydrogen ions, and ammonium ions to the reaction solution.
The thickness of the semiconductor layer may be in the range of 0.2 nm to 2 nm.

In the mixing step, the suspension may be added to the reaction solution at a rate of 0.5 to 50 ml / min and held in a temperature range of room temperature to 100 ° C. for 1 to 24 hours.
After the step of mixing, a step of washing and drying the fluorescent material may be further included.

  The light emitting device according to the present invention achieves the above object by using the fluorescent material.

The fluorescent material according to the present invention includes at least a pair of semiconductor layers and a rare earth ion layer containing at least one kind of rare earth ions. The semiconductor layer has a negative charge, and the rare earth ion layer has a positive charge. Accordingly, at least the pair of semiconductor layers and the rare earth ion layer are laminated so as to be adjacent to each other. As a result, rare earth ions can be contained at a high concentration.
Since the energy E _D of the defect level of the semiconductor layer and the energy E _Re of the excited state of at least one rare earth ion satisfy the relationship E _D > E _Re , by irradiating excitation light based on the semiconductor layer, The absorption energy can be easily transferred to the rare earth ions, and the fluorescence based on the rare earth ions can be easily generated instead of the fluorescence based on the defect level of the semiconductor layer. Therefore, fluorescence via energy transfer can be generated with high efficiency. Moreover, since the fluorescent material according to the present invention does not use an organic substance, it is thermally stable. As a result, a device having a long lifetime can be obtained by using the fluorescent material of the present invention.

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
FIG. 1 is a schematic view of a fluorescent material according to the present invention.
The fluorescent material 100 according to the present invention includes a set 130 of a semiconductor layer 110 and a rare earth ion layer 120. The semiconductor layer 110 and the rare earth ion layer 120 are stacked adjacent to each other.

The semiconductor layer 110, the energy E _D in semiconductor defect levels, rare earth ions layer 1 to be described later
Any material can be used as long as it is higher than the excited state energy E _{Re of} 20 rare earth ions and has a negative charge. The semiconductor layer 110 is preferably selected from the group consisting of titanium oxide nanosheets, manganese oxide nanosheets, niobium oxide nanosheets, titanium oxide / niobium nanosheets, perovskite-type niobium oxide nanosheets, and perovskite-type titanium oxide nanosheets.

In the present specification, the titanium oxide nanosheet includes Ti _1-x O ₂ (x <0.15), Ti ₃ O ₇ , Ti ₄ O ₉ , and Ti ₅ O ₁₁ . In addition, manganese oxide nanosheets are Mn
Mn _1-δ Co _δ O _{2 in which} O ₂ , Mn ₃ O ₇ , and other transition metals are dissolved (where δ <0.
5) and Mn _1-δ Fe _δ O ₂ (where δ <0.2). The niobium oxide nanosheet contains Nb ₆ O ₁₇ and Nb ₃ O ₈ . The titanium oxide / niobium nanosheet contains TiNbO ₅ and Ti ₂ NbO ₇ . The perovskite type niobium oxide nanosheet contains Ca ₂ Nb ₃ O ₁₀ , Sr ₂ Nb ₃ O ₁₀ , and Pb ₂ Nb ₃ O ₁₀ . The perovskite tantalum oxide nanosheet contains Ca ₂ Ta ₃ O ₁₀ , Sr ₂ Ta ₃ O ₁₀ , and Pb ₂ Ta ₃ O ₁₀ . The perovskite type titanium oxide nanosheet is La ₂ Ti ₃ O ₁₀ .

  The thickness of the semiconductor layer 110 is in the range of 0.5 nm to 2 nm. The semiconductor layer 110 having such a thickness has molecular side surfaces.

  The rare earth ion layer 120 is adjacent to the semiconductor layer 110 and includes at least one kind of rare earth ions. The rare earth ion layer 120 has a positive charge. As a result, the semiconductor layer 110 can be adjacent to each other by the negative charge and attractive force, and a stacked structure can be formed.

  With such a stacked structure, the rare-earth ions between the semiconductor layers 110 are substantially compensated between the charges of the semiconductor layer 110 and the charges of the rare-earth ion layer 120 (satisfying electrical neutrality). Can be contained.

  Therefore, a desired amount of rare earth ions can be reliably contained in the semiconductor material as compared with the conventional case. The concentration of rare earth ions contained may depend on the semiconductor material selected and the rare earth ions.

Note that in this specification, substantially “charge compensation (electric neutrality is satisfied)” means that charge compensation is not completely performed between the semiconductor layer 110 and the rare earth ion layer 120 (that is, electrical compensation is performed). (Neutral is not satisfied), but it does not affect the device. Also, the layer spacing D of the semiconductor layer 110 depends on the diameter of the selected rare earth ions and the thickness of the nanosheet and can be in the range of 1-3 nm.

The excited state energy E _Re of at least one kind of rare earth ions contained in the rare earth ion layer 120 is satisfied to be lower than the energy E _D of the defect level of the semiconductor layer 110 described later. Specifically, at least one kind of rare earth ions may satisfy the condition that the energy difference (f-f transition) between the excited level and the ground level of the rare earth ions exists in the visible light to infrared range. The at least one rare earth ion is preferably Sm ³⁺ , Eu ³⁺ , Tb ³⁺ , Dy ³⁺ , Pr ³⁺ , Nd ³⁺ , Ho ³⁺ , Er ³⁺ , Tm ³⁺ , and Yb Selected from the group consisting of ³⁺ .

  The rare earth ion layer 120 may contain a combination of the rare earth ions described above so as to substantially compensate the charge (satisfy electrical neutrality) with the semiconductor layer 110. In this case, light emission having various types of wavelengths can be extracted depending on the type of rare earth ions contained. The rare earth ion layer 120 may further include ions selected from the group consisting of alkali metal ions, alkaline earth metal ions, transition metal ions, hydrogen ions, and ammonium ions in addition to the rare earth ions. Thereby, you may adjust the density | concentration of the rare earth ion contained so that it may become a desired density | concentration. Thus, by controlling the concentration of rare earth ions that contribute to light emission, the light emission intensity can be controlled.

Next, the fluorescence mechanism of the fluorescent material according to the present invention will be described.
FIG. 2 is a schematic diagram showing the fluorescence mechanism of the fluorescent material according to the present invention.

  The host which is the semiconductor layer 110 (FIG. 1) has a valence band (VB) and a conduction band (CB). Light is irradiated to the fluorescent material 100 (FIG. 1), and electrons existing in VB of the semiconductor layer 110 are excited by CB (solid line A).

  In the case of a conventional fluorescent material, whether electrons excited in CB directly transition to VB (dotted line B) or are trapped in a defect level and then recombined with VB holes (dotted line C). Either way, excess energy was emitted as fluorescence.

  However, in the fluorescent material 100 according to the present invention, the electrons excited in the CB are trapped in the defect level without directly transitioning to the VB, and then are recombined with the holes in the VB and are not in the excited level of the rare earth ions. Energy transfer is possible (solid line D).

  Such energy transfer is caused by the proximity of the host semiconductor layer and the rare earth ions. More specifically, since the semiconductor layer 110 having a thickness of 0.5 to 2 nm which is a host and the rare earth ions in the rare earth ion layer 120 are mixed at the crystal lattice level, they are trapped by defects in the host. The electrons can easily transfer energy to the excited level of rare earth ions.

  As described above, according to the fluorescent material of the present invention, the fluorescent material is easily extracted by irradiating the fluorescent material with light having a wavelength that causes absorption in the semiconductor layer serving as the host of the fluorescent material. Can do.

  Since the light to be irradiated to the fluorescent material only needs to be absorbed in the semiconductor layer, its wavelength range is sufficiently wider than the wavelength range of absorption in rare earth ions. Therefore, when designing a device using the fluorescent material of the present invention, the limitation of the light source may be small and advantageous.

  In addition, since the fluorescent material according to the present invention is made of an inorganic material, it has a higher resistance to the operating environment than a device using a fluorescent material made of a conventional organic material, and can operate the device stably.

Next, the manufacturing method of the fluorescent material according to the present invention will be described.
FIG. 3 is a flowchart showing a process of manufacturing a fluorescent material according to the present invention.

Each process will be described.
Step S310: A suspension containing the semiconductor layer is generated. If the semiconductor layer has a semiconductor defect level energy E _D higher than the excited state energy E _Re of the rare earth ions contained in the rare earth ion layer to be generated later, and has a negative charge, Any material can be used. The semiconductor layer is preferably selected from the group consisting of titanium oxide nanosheets, manganese oxide nanosheets, niobium oxide nanosheets, titanium oxide / niobium nanosheets, perovskite-type niobium oxide nanosheets, and perovskite-type titanium oxide nanosheets.

In the present specification, the titanium oxide nanosheet contains Ti _1-x O ₂ (<0.15), Ti ₃ O ₇ , Ti ₄ O ₉ , and Ti ₅ O ₁₁ . In addition, the manganese oxide nanosheets are made of MnO ₂ , Mn ₃ O ₇ , and Mn _1-δ Co _δ O ₂ (where δ <0.5) in which other transition metals are dissolved, and Mn _1-δ Fe _δ O ₂ (where δ <0.2) is included. The niobium oxide nanosheet contains Nb ₆ O ₁₇ and Nb ₃ O ₈ . The titanium oxide / niobium nanosheet contains TiNbO ₅ and Ti ₂ NbO ₇ . The perovskite type niobium oxide nanosheet contains Ca ₂ Nb ₃ O ₁₀ , Sr ₂ Nb ₃ O ₁₀ , and Pb ₂ Nb ₃ O ₁₀ . The perovskite tantalum oxide nanosheet contains Ca ₂ Ta ₃ O ₁₀ , Sr ₂ Ta ₃ O ₁₀ , and Pb ₂ Ta ₃ O ₁₀ . The perovskite type titanium oxide nanosheet is La ₂ Ti ₃ O ₁₀ . The thickness of the semiconductor layer 110 is in the range of 0.5 nm to 2 nm.

In addition, although such a semiconductor layer can be manufactured using the technique described in patent 1966650 and patent 2671949, the semiconductor layer obtained by arbitrary methods is employable, for example.
The semiconductor layer is dispersed in a dispersion medium to generate a suspension. The dispersion medium can be, for example, water, but any solvent can be used as long as both the semiconductor layer and the rare earth ions described below are soluble. Here, the semiconductor layer can be held in a state of being dispersed one by one in the dispersion medium.

Step S320: A reaction solution containing at least one kind of rare earth ions is prepared. At least one kind of rare earth ions may satisfy the condition that the energy difference (f-f transition) between the excited level and the ground level of the rare earth ions exists in the visible light to infrared region. The at least one rare earth ion is preferably Sm ³⁺ , Eu ³⁺ , Tb ³⁺ , Dy ³⁺ , Pr ³⁺ , Nd ³⁺ , Ho ³⁺ , Er ³⁺ , Tm ³⁺ , and Yb Selected from the group consisting of ³⁺ .

  The nitrate solution, sulfate solution, or acetate solution containing rare earth ions selected from these substantially compensates for the negative charge of the semiconductor layer used in step S310 (satisfying electrical neutrality). In this way, the rare earth ion concentration can be adjusted. Note that the solution containing rare earth ions is not limited to the above, and any solution can be used as long as it is soluble in the suspension prepared in step S310.

In addition to rare earth ions, ions selected from alkali metal ions, alkaline earth metal ions, transition metal ions, hydrogen ions, and ammonium ions may be added to the reaction solution. In this case, these added metal ions can also be added as a nitrate solution, a sulfate solution, or an acetate solution, but any solution can be used as long as it is soluble in the suspension prepared in step S310. Can be used. By adding additional metal ions, the concentration of rare earth ions may be adjusted to a desired concentration.

  Step S330: The colloidal suspension generated in Step S310 is mixed with the reaction solution prepared in Step S320. The reaction solution may be mixed with a colloidal suspension manually or dropwise using an apparatus. When using an apparatus, the colloidal suspension is added to the reaction solution at a rate of 0.5-50 ml / min. Step S330 is performed in a temperature range of room temperature to 100 ° C., and is maintained for 1 to 24 hours after mixing. In addition, in this specification, room temperature intends the temperature range of 10 degreeC-35 degreeC.

  In the meantime, the semiconductor layer sandwiches rare earth ions and precipitates (flocculation). This flocculation proceeds in a self-organized manner by the attractive force between the negative charge of the semiconductor layer and the positive charge of the rare earth ions. The obtained precipitate is the fluorescent material 100 (FIG. 1) according to the present invention. After filtering the precipitate, the precipitate may be washed with an arbitrary washing solution (ultra pure water or the like) and dried. Note that step S310 and step S320 may be performed in any order.

  Thus, according to the method of the present invention, a fluorescent material can be easily obtained simply by preparing a colloidal suspension serving as a host and a reaction solution containing rare earth ions and mixing them. In addition, since the semiconductor layers and the rare earth ions are alternately stacked in a self-organized manner, the rare earth ions contained in the obtained fluorescent material correspond to being incorporated into the crystal lattice of the host, and have an electrical neutrality. A satisfactory high concentration of rare earth ions can be inserted between the semiconductor layers. Thereby, the fluorescent material capable of efficient energy transfer from the defect level of the host to the excited level of the rare earth ions described with reference to FIG. 2 can be manufactured.

(Embodiment 2)
FIG. 4 is a perspective view of a display device using the fluorescent material according to the present invention.
The display device 400 is an AC surface emission type plasma display (PDP). Display device 400 includes a front portion 410 and a rear portion 420.

  The front portion 410 includes a first glass substrate 411, a display electrode 412 formed on the first glass substrate 411, a first dielectric layer 413 formed on the display electrode 412, and a first dielectric And a protective layer 414 formed on the body layer 413.

  The rear portion 420 includes a second glass substrate 421, an address electrode 422 formed on the second glass substrate 421, a second dielectric layer 423 formed on the address electrode 422, and a second dielectric A partition 424 formed on the body layer 423 and a fluorescent material 425 disposed between the partitions 424 are included.

  The first glass substrate 411 can be, for example, high silicate glass, borosilicate glass, or quartz glass. The second glass substrate 421 may be the same material as the first glass substrate 411 or may be a different material (for example, soda lime glass).

  The display electrode 412 is a transparent electrode, and may be, for example, a Cr / Al film or an ITO film. The address electrode 422 may be the same material as the display electrode 112, or may be a different material (for example, Al).

  The first dielectric layer 413 and the second dielectric layer 423 can be formed of, for example, glass and function as a capacitor. The protective layer 414 can be, for example, magnesium oxide.

  The partition wall 424 may be a glass paste, for example. The partition walls 424 are arranged at a predetermined interval, whereby the cells 430 are formed. The fluorescent material 425 is the fluorescent material according to the present invention described in the first embodiment. Each cell 430 is filled with, for example, a mixed gas of an inert gas containing Xe, and has a wavelength that can excite the semiconductor layer 110 (FIG. 1) included in the fluorescent material 425 of the present invention. Any gas can be used as long as the light it has is emitted.

A display operation of the PDP 400 thus formed will be described.
An AC voltage is applied between the display electrode 412 and the address electrode 422. A voltage is applied to the cell 430 selected by the display electrode 412 and the address electrode 422. Next, plasma is generated in the cell 430. The semiconductor layer 110 included in the fluorescent material 425 is excited by ultraviolet rays emitted during this discharge. After the semiconductor layer 110 is excited, energy transfer occurs as described with reference to FIG. 2, and fluorescence (visible light) based on rare earth ions contained in the fluorescent material 425 is emitted.

  The fluorescence emitted from the fluorescent material 425 is emitted through the protective layer 414, the first dielectric layer 413, the display electrode 412, and the first glass substrate 411, and is recognized as display light by an observer (not shown). Is done.

  Since the display device 400 according to the present invention uses the fluorescent material described in Embodiment 1, the display device 400 has higher operational stability than the display device using a fluorescent material made of an organic material, and is resistant to the operating environment. Can be resistant.

  It should be understood that the PDP 400 described in the second embodiment is only an example to which the fluorescent materials 100 and 425 of the present invention are applied. The fluorescent material 100, 425 of the present invention may be applied to a light emitting device such as an optical amplifier, a microlaser, a television screen, and a lighting fixture. Also in this case, the above-described effects can be achieved.

  Next, examples will be described, but it should be noted that the present invention is not limited to the examples.

Disperse Ti _0.91 O ₂ nanosheet in tetrabutylammonium hydroxide aqueous solution, pH 9
A colloidal suspension of 0.4 wt%, 100 cm ³ was prepared. The Ti _0.91 O ₂ nanosheet was synthesized by exfoliating proton layered titanate H _0.7 Ti _1.825 O _{4 .H 2} O into a single layer. The used Ti _0.91 O ₂ nanosheet has a thickness of 0.75 nm and a lateral length of 0.1 to 0.1 nm.
It was 1 μm. As a reaction solution, 100 cm ³ of 0.1 mold ⁻³ EuCl ₃ .6H ₂ O aqueous solution was prepared.

The colloidal suspension was then slowly added manually to the reaction solution at room temperature with stirring. At the same time that the colloidal suspension was added dropwise, a white precipitate was observed. The precipitate was filtered, washed with ultrapure water, and then dried in the atmosphere at 25 ° C. overnight. The powder obtained after drying (hereinafter referred to as Ti _0.91 O ₂ / Eu) was white.

FIG. 5 is a view showing an X-ray diffraction pattern of Ti _0.91 O ₂ / Eu obtained in Example 1.
The structure of Ti _0.91 O ₂ / Eu obtained using a RINT 2000S powder X-ray diffraction apparatus (Rigaku, Japan) was evaluated. The operating conditions of the X-ray diffractometer are Cu-Kα rays (
(λ = 0.15405 nm), the scanning speed was 40 kV / 40 mA, 1.5 ° 2θ / min. The circles shown in FIG. 5 are 8.2 ° and 15 °, respectively. In Ti _0.91 O ₂ / Eu obtained from these values, the Ti _0.91 O ₂ nanosheet is 1.06 nm (including the thickness of the nanosheet). ) Was confirmed to be stacked at intervals. Further, this value is reasonable if it is considered that Eu ions are arranged between the Ti _0.91 O ₂ nanosheets as a rare earth ion layer (120 in FIG. 1).

The peaks indicated by triangles and squares shown in FIG. 5 are 48 ° and 62 °, respectively, indicating the period of the two-dimensional atomic arrangement of the Ti _0.91 O ₂ nanosheet. More specifically, these 48
° and 62 ° are 20 and 02 reflections from a two-dimensional face-centered rectangular grid of 0.38 nm x 0.30 nm. These results, in the obtained powder, 2-dimensional atomic arrangement satisfies the atomic arrangement of the _{Ti 0.91 O 2, Ti 0.91 O} 2 nanosheet was confirmed to be laminated with 1.06nm intervals.

6 shows a TEM image of the powder obtained in Example 1. FIG.
Ti _0.91 O ₂ / Eu was observed with a high-resolution transmission electron microscope using JEM-3000F (JEOL, Japan). Observation was performed at an acceleration voltage of 300 kV. As shown in FIG. 6, it was confirmed that Ti _0.91 O ₂ / Eu had a layered lamellar structure. The layer spacing was about 1 nm as in the X-ray diffraction results shown in FIG.

FIG. 7 is a diagram showing an EDS spectrum of Ti _0.91 O ₂ / Eu obtained in Example 1.
The composition of Ti _0.91 O ₂ / Eu was identified using an energy dispersive X-ray analyzer (EDS) attached to JEM-3000F. As shown in FIG. 7, mainly Ti, O and E
u was detected. The Eu concentration calculated from the spectral intensity ratio of each component was 10%. This indicates that in the obtained Ti _0.91 O ₂ / Eu, Ti _0.91 O ₂ ^0.36- and Eu ³⁺ substantially satisfy electrical neutrality.

From the results shown in FIGS. 5 to 7, the obtained Ti _0.91 O ₂ / Eu has a Ti _0.91 O ₂ nanosheet as the semiconductor layer 110 (FIG. 1) and the rare earth ion layer 12 as shown in FIG.
0 (FIG. 1) was found to have a laminated structure containing Eu ³⁺ ions.

The absorption spectrum of the obtained Ti _0.91 O ₂ / Eu was _measured using a U-4000 type spectrophotometer (Hit
achi, Japan). The measurement was performed in a diffuse reflection mode at a measurement wavelength of 200 nm to 700 nm.
The PL spectrum of the obtained Ti _0.91 O ₂ / Eu was measured by F-4500 fluorescence spectrophotometer (Hi
(tachi, Japan). The measurement was performed in a fluorescence mode at a measurement wavelength of 200 nm to 750 nm.
These results are shown in FIGS. 8 and 9 and will be described later.

(Comparative Example 1)
For aqueous HCl 0.1 mol ^-3 as the reaction solution except that 100 cm ³ prepared the same as in Example 1, the description thereof is omitted. The powder obtained in Comparative Example 1 (hereinafter referred to as Ti _0.91 O ₂ / H) was the same as Example 1 except that it did not contain rare earth ions.
The absorption spectrum and emission spectrum of the obtained Ti _0.91 O ₂ / H are respectively represented by U-
Measurements were made using a 4000-type spectrophotometer and an F-4500 fluorescence spectrophotometer. The measurement conditions are the same as in Example 1. These results are shown in FIGS. 8 and 9 and will be described later.

FIG. 8 is a diagram showing absorption spectra of Ti _0.91 O ₂ / Eu (a) obtained in Example 1 and Ti _0.91 O ₂ / H (b) obtained in Comparative Example 1.
In FIG. 8, strong UV absorption was confirmed in the vicinity of about 380 nm in both (a) and (b). The band gap calculated from this UV absorption was 3.24 eV. From this value, it was confirmed that the powder obtained in Example 1 and Comparative Example 1 was titania having a band gap similar to that of known anatase band gap (3.18 eV) and rutile (3.03 eV). .

The absorption spectrum of FIG. 8A has three peaks on the longer wavelength side than 380 nm (see inset). On the other hand, in the absorption spectrum of FIG. 8B, no peak other than the absorption at 380 nm was observed. These three peak positions were 395 nm, 464 nm, and 536 nm, respectively. These three peaks correspond to the known Eu ³⁺ 4f-4f core transition.

FIG. 9 is a diagram showing PL spectra of Ti _0.91 O ₂ / Eu (a) obtained in Example 1 and Ti _0.91 O ₂ / H (b) obtained in Comparative Example 1.
The excitation spectrum of FIG. 9A has three peaks on the longer wavelength side than 380 nm (however, for the sake of clarity, the spectrum on the longer wavelength side than 500 nm is omitted). These three peak positions were 395 nm, 464 nm, and 536 nm (not shown), respectively, and coincided with the absorption spectrum shown in FIG. The fluorescence spectrum (dotted line) in the case where Ti _0.91 O ₂ / Eu was irradiated with light having a wavelength of 395 nm (absorption wavelength by Eu ³⁺ ) as excitation light showed a fluorescence spectrum peculiar to Eu ³⁺ . Specifically, four peaks (590 nm, 612 nm, 653 nm and 693 nm) were confirmed. These peaks are attributed to the ⁵ D ₀ → ⁷ F ^j (j = 1 to 4) transition, respectively. The fluorescence in this case is fluorescence obtained by directly exciting Eu ³⁺ in Ti _0.91 O ₂ / Eu.

Fluorescence spectrum (solid line) when Ti _0.91 O ₂ / Eu is irradiated with light having a wavelength of 250 nm as excitation light (absorption wavelength by host Ti _0.91 O ₂ ) is also characteristic of Eu ³⁺ as in the above case. The fluorescence spectrum of was shown. The fluorescence in this case is fluorescence obtained by exciting Ti _0.91 O ₂ which is a host of Ti _0.91 O ₂ / Eu. As a result, Ti _0.91
O ₂ / Eu excites Ti _0.91 O ₂ which is a host, and the excited electrons become Ti _0.91 O _2.
It was confirmed that Eu ³⁺ fluorescence was obtained by transferring energy from Eu ³⁺ to Eu ³⁺ . In addition, it was confirmed that the Eu ³⁺ fluorescence thus obtained has sufficient intensity for application to a light-emitting device. Further, it was visually confirmed that such fluorescence was red light emission.

In the excitation spectrum (dotted line) in FIG. 9B, no peak other than 380 nm was observed as in the absorption spectrum shown in FIG. No fluorescence spectrum (solid line) was observed except for a relatively weak peak at 395 nm when Ti _0.91 O ₂ / H was irradiated with light having a wavelength of 250 nm as excitation light. This peak is attributed to the defect state of Ti _0.91 O ₂ / H, and this result is similar to the fluorescence spectrum of a known Ti _0.91 O ₂ nanosheet.

From the above, it was confirmed that Ti _0.91 O ₂ / Eu can easily extract fluorescence due to Eu ³⁺ having a sufficient intensity only by exciting Ti _0.91 O ₂ .

  As described above, according to the fluorescent material of the present invention, the fluorescence based on the rare earth ions contained therein can be easily taken out by irradiating the fluorescent material with light having a wavelength that causes absorption in the semiconductor layer serving as the host of the fluorescent material. Can do. Since the irradiation light only needs to be absorbed in the semiconductor layer, the wavelength range of the excitation light is wider than the wavelength range of absorption in the rare earth ions. Therefore, when designing a device using the fluorescent material of the present invention, the limitation of the light source may be small and advantageous. The fluorescent material according to the present invention can be applied to display devices, optical amplifiers, microlasers, television screens, lighting fixtures and the like.

Schematic diagram of fluorescent material according to the present invention Schematic diagram showing the fluorescence mechanism of the fluorescent material according to the present invention The flowchart which shows the process of manufacturing the fluorescent material by this invention The perspective view of the display apparatus using the fluorescent material by this invention Shows the X-ray diffraction pattern of the Ti _0.91 O ₂ / Eu obtained in Example 1 The figure which shows the TEM image of the powder obtained in Example 1 Shows the EDS spectrum of the Ti _0.91 O ₂ / Eu obtained in Example 1 Shows the _{Ti 0.91 O 2 / Eu (a} ) obtained in Example 1, the absorption spectra of the Ti _0.91 was obtained in Comparative Example 1 O ₂ / H (b) Shows the _{Ti 0.91 O 2 / Eu (a} ) obtained in Example 1, the PL spectrum of the resulting _{Ti 0.91 O 2 / H (b} ) in Comparative Example 1

Explanation of symbols

100, 425 Fluorescent material 110 Semiconductor layer 120 Rare earth ion layer 130 Set of semiconductor layer and rare earth ion layer 400 Display device 410 Front portion 420 Rear portion 411 First glass substrate 412 Display electrode 413 First dielectric layer 414 Protective layer 421 Second glass substrate 422 Address electrode 423 Second dielectric layer 424 Partition wall 430 cell

Claims (13)

A fluorescent material comprising at least a pair of semiconductor layers and a rare earth ion layer,
The semiconductor layer has a negative charge;
The rare earth ion layer has a positive charge and includes at least one kind of rare earth ions,
Each of the at least one pair of the semiconductor layer and the rare earth ion layer is laminated so as to be adjacent to each other,
The fluorescent material, wherein the energy E _D of the defect level of the semiconductor layer and the energy E _Re of the excited state of the at least one kind of rare earth ions satisfy the relationship E _D > E _Re .   The semiconductor layer is selected from the group consisting of titanium oxide nanosheets, manganese oxide nanosheets, niobium oxide nanosheets, titanium oxide / niobium nanosheets, perovskite type niobium oxide nanosheets, perovskite type tantalum oxide nanosheets, and perovskite type titanium oxide nanosheets, The fluorescent material according to claim 1. The at least one rare earth ion is Sm ³⁺ , Eu ³⁺ , Tb ³⁺ , Dy ³⁺ , Pr ³⁺ , Nd ³⁺ , Ho ³⁺ , Er ³⁺ , Tm ³⁺ , and Yb ^3+. The fluorescent material according to claim 1, which is selected from the group consisting of:   The fluorescent material according to claim 1, wherein the rare earth ion layer further includes ions selected from the group consisting of alkali metal ions, alkaline earth metal ions, transition metal ions, hydrogen ions, and ammonium ions.   The fluorescent material according to claim 1, wherein a thickness of the semiconductor layer is in a range of 0.5 nm to 2 nm. A method for producing a fluorescent material comprising a semiconductor layer and a rare earth ion layer,
Producing a suspension containing the semiconductor layer having a negative charge;
A step of preparing a reaction solution containing at least one kind of rare earth ions, wherein the defect level energy E _{D of the} semiconductor layer and the excited state energy E _{Re of the} at least one kind of rare earth element are related to each other. A process that satisfies E _D > E _Re ;
A step of mixing the suspension and the reaction solution, wherein the rare earth ion layer having a positive charge including the at least one kind of rare earth ions is formed on the semiconductor layer. ,Method.   The semiconductor layer is selected from the group consisting of titanium oxide nanosheets, manganese oxide nanosheets, niobium oxide nanosheets, titanium oxide / niobium nanosheets, perovskite type niobium oxide nanosheets, perovskite type tantalum oxide nanosheets, and perovskite type titanium oxide nanosheets, The method of claim 6. The at least one rare earth ion is Sm ³⁺ , Eu ³⁺ , Tb ³⁺ , Dy ³⁺ , Pr ³⁺ , Nd ³⁺ , Ho ³⁺ , Er ³⁺ , Tm ³⁺ , and Yb ^3+. The method of claim 6, wherein the method is selected from the group consisting of:   The step of preparing includes a step of further adding an ion selected from the group consisting of an alkali metal ion, an alkaline earth metal ion, a transition metal ion, a hydrogen ion, and an ammonium ion to the reaction solution. The method described in 1.   The method of claim 6, wherein the thickness of the semiconductor layer ranges from 0.2 nm to 2 nm.   The method according to claim 6, wherein in the mixing step, the suspension is added to the reaction solution at a rate of 0.5 to 50 ml / min, and is maintained at a temperature range of room temperature to 100 ° C for 1 to 24 hours. .   The method of claim 6, further comprising washing and drying the fluorescent material after the mixing step. A light emitting device using the fluorescent material according to claim 1.

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