JP6230116B2 - Phosphor, lighting apparatus and image display device - Google Patents

Description

  The present invention relates to a phosphor including metal particles and ceramic particles, a lighting fixture using the phosphor, and an image display device.

  The phosphor is a fluorescent display tube (VFD (Vacuum-Fluorescent Display)), a field emission display (FED (Field Emission Display)) or a SED (Surface-Condition Electron-Emitter Display (P panel)). ), Cathode ray tube (CRT (Cathode-Ray Tube)), white light emitting diode (LED (Light-Emitting Diode)), and the like. In any of these applications, in order to make the phosphor emit light, it is necessary to supply the phosphor with energy for exciting the phosphor, and the phosphor is not limited to vacuum ultraviolet rays, ultraviolet rays, electron beams, blue light, etc. When excited by an excitation source having high energy, visible light such as blue light, green light, yellow light, orange light, and red light is emitted. However, as a result of exposure of the phosphor to the excitation source as described above, there is a demand for a phosphor that is liable to lower the luminance of the phosphor and has no luminance reduction. Therefore, instead of conventional phosphors such as silicate phosphors, phosphate phosphors, aluminate phosphors and sulfide phosphors, sialon phosphors can be used as phosphors with little reduction in luminance even when excited with high energy. There have been proposed phosphors based on inorganic crystals containing nitrogen in the crystal structure such as oxynitride phosphors and nitride phosphors.

An example of this sialon phosphor is manufactured by a manufacturing process generally described below. First, silicon nitride (Si ₃ N ₄ ), aluminum nitride (AlN), and europium oxide (Eu ₂ O ₃ ) are mixed at a predetermined molar ratio, and the temperature is 1700 ° C. in nitrogen at 1 atm (0.1 MPa). It is produced by holding for 1 hour and firing by a hot press method (see, for example, Patent Document 1). It has been reported that α sialon activated by Eu ²⁺ ions obtained by Patent Document 1 is a phosphor that emits yellow light of 550 to 600 nm when excited by blue light of 450 to 500 nm. It is also known that the emission wavelength changes by changing the ratio of Si and Al or the ratio of oxygen and nitrogen while maintaining the crystal structure of α sialon (for example, Patent Document 2 and (See Patent Document 3).

As another example of the sialon phosphor, a green phosphor in which Eu ²⁺ is activated to β sialon is known (see, for example, Patent Document 4). In this phosphor, it is known that the emission wavelength changes to a short wavelength by changing the oxygen content while maintaining the crystal structure (see, for example, Patent Document 5). Further, it is known that when Ce ³⁺ is activated, a blue phosphor is formed (for example, see Patent Document 6).

An example of an oxynitride phosphor, JEM phase _{(LaAl (Si 6-z Al} z) N 10-z O z) blue phosphor were activated with Ce as host crystal (e.g., see Patent Document 7) It has been known. In this phosphor, it is known that by exchanging a part of La with Ca while maintaining the crystal structure, the excitation wavelength becomes longer and the emission wavelength becomes longer.

As another example of an oxynitride phosphor, a blue phosphor in which Ce is activated using a La—N crystal La ₃ Si ₈ N ₁₁ O ₄ as a base crystal (see, for example, Patent Document 8) is known. .

As an example of a nitride phosphor, a red phosphor in which Eu ²⁺ is activated using CaAlSiN ₃ as a base crystal (see, for example, Patent Document 9) is known. By using this phosphor, there is an effect of improving the color rendering properties of the white LED. A phosphor added with Ce as an optically active element has been reported as an orange phosphor.

  In addition, studies on phosphor emission enhancement using metal plasmon resonance have been conducted (see, for example, Non-Patent Document 1).

Japanese Patent No. 3668770 Japanese Patent No. 3837551 Japanese Patent No. 4524368 Japanese Patent No. 3921545 International Publication No. 2007/066673 International Publication No. 2006/101096 International Publication No. 2005/019376 JP 2005-112922 A Japanese Patent No. 3837588

T. T. Tanaka et al., Applied Physics Express 4, 2011, 031205-032108

These phosphors have excellent durability and temperature characteristics and are suitable for uses in harsh environments. However, the emission intensity may not be sufficient depending on the composition. One of the causes is that the excitation light cannot be sufficiently absorbed depending on the composition. The present invention is intended to meet such a demand, and one of the objects is to provide a phosphor that efficiently absorbs excitation light and has high emission intensity. Another object of the present invention is to provide a lighting apparatus and an image display device having excellent durability using such a phosphor.

  As a result of intensive studies, the present inventor has succeeded in providing a phosphor exhibiting a light emission phenomenon with high luminance in a specific wavelength region by adopting the configuration described below. Furthermore, the present inventors have succeeded in providing a lighting apparatus and an image display device having excellent characteristics by using the phosphor and adopting the configuration described below.

The phosphor according to the present invention includes metal particles and ceramic particles, the metal particles absorb light having a wavelength of 400 nm to 500 nm, and the ceramic particles emit light having a wavelength of 500 nm to 650 nm. This solves the above problem.
The metal particles may be silver particles.
The metal particles may be prismatic.
The average particle diameter (volume reference median diameter d50) of the metal particles may be 30 nm or more and 80 nm or less.
The ceramic particles may be selected from the group consisting of β-sialon containing Eu, α-sialon containing Eu, and CaAlSiN ₃ containing Eu.
The metal particles and the ceramic particles may further include a light-transmitting substance, and may be dispersed in the light-transmitting substance.
The translucent material may be glass.
The luminaire according to the present invention includes an excitation light source and a phosphor, the excitation light source emits light having a wavelength of 400 nm to 500 nm, and the phosphor includes at least the above-described phosphor, and thereby the above-described problem. To solve.
The excitation light source may be selected from the group consisting of an LED, a laser diode, and an organic EL.
An image display device according to the present invention includes an excitation light source and a phosphor, and the excitation light source emits light having a wavelength of 400 nm to 500 nm, and the phosphor includes at least the above-described phosphor, thereby Solve the problem.
The excitation light source may be selected from the group consisting of an LED, a laser diode, and an organic EL.

  The phosphor according to the present invention includes metal particles that absorb light of 400 nm to 500 nm and ceramic particles that emit light of 500 nm to 650 nm, and the metal particles have a strong plasmon absorption peak at the excitation wavelength of the ceramic particles. As a result, it emits light with high brightness. By using the phosphor according to the present invention, it is possible to provide a lighting apparatus having high luminous efficiency and a small temperature fluctuation, and a vivid color display device.

The figure which shows the SEM image of silver nanocube Diagram showing resonance absorption spectrum of silver nanocube solution The figure which shows the emission spectrum by Examples 1-4 and Comparative Example 5

  The present inventors have conducted detailed studies mainly on phosphors that emit visible light, and have found that high-intensity fluorescence is emitted by the coexistence of ceramic particles (phosphor particles) and metal particles. In addition, it has been found that a combination of specific metal particles and specific ceramic particles efficiently absorbs blue excitation light and efficiently emits visible light of 500 nm or more.

  The phosphor of the present invention includes metal particles and ceramic particles. The metal particles absorb light having a wavelength of 400 nm to 500 nm. That is, the metal particle has a strong plasmon absorption peak at a wavelength in the range of 400 nm to 500 nm. Such metal particles are preferably silver particles.

The ceramic particles are excited by light having a wavelength of 400 nm to 500 nm and emit light having a wavelength of 500 nm to 650 nm. Such ceramic particles are selected from the group consisting of β-sialon containing Eu, α-sialon containing Eu and CaAlSiN ₃ containing Eu. Note that any of β-sialon containing Eu, α-sialon containing Eu, and CaAlSiN ₃ containing Eu may contain additional elements other than the constituent elements as long as the crystal structure of each parent crystal is not impaired. For example, an α sialon containing Eu includes a Ca-α sialon activated by Eu.

  The present inventors have found that emission enhancement by plasmon resonance is caused by the coexistence of metal particles having a strong plasmon absorption peak in a wavelength region corresponding to the excitation wavelength and ceramic particles that are excited at the excitation wavelength and emit fluorescence. It was.

  The metal particles preferably have a prismatic shape. More preferably, the metal particles have a cubic (nanocube) shape. By having such a shape, light emission enhancement by plasmon resonance can be further enhanced.

  The average particle diameter (volume reference median diameter d50) of the metal particles is 30 nm or more and 80 nm or less. For example, since the average particle diameter (d50) of the ceramic particles described above can be 0.1 μm or more and 20 μm or less, the metal particles having such an average particle diameter are surely coated or surrounded by the ceramic particles. Therefore, the emission enhancement by plasmon resonance is ensured.

  Furthermore, the phosphor of the present invention may contain a translucent substance in addition to the metal particles and the ceramic particles. In this case, the metal particles and the ceramic particles are dispersed in the translucent material. Such a phosphor is easy to handle, and diffused reflection of light is suppressed in a light-transmitting substance, so that excellent light emission characteristics can be exhibited.

  The translucent material is preferably glass. In this specification, the glass is not limited to a light-transmitting glass containing silicate as a main component, but is intended to be a light-transmitting substance that is in a glass state. Examples of glasses other than silicate glass include phosphate glass, borate glass, and translucent ceramics. Glass is preferable because it has excellent thermal stability and extremely high translucency.

The translucent material is preferably SiO ₂ . SiO ₂ may be quartz glass containing the above-described silicate as a main component, or may be quartz having a crystal structure of SiO ₂ . SiO ₂ is preferable because it can be vitrified by high translucency and an easy manufacturing process by a sol-gel method.

  Further, the light-transmitting substance may be an inorganic substance obtained by heat-treating an organic substance containing tetramethyl orthosilicate (tetramethoxysilane) and / or tetraethyl orthosilicate (tetraethoxysilane). Such an inorganic substance is, for example, quartz glass, quartz, glass mainly composed of silicate, and a composite thereof. These are preferable because the production process is easy.

  The translucent substance may be a heat resistant resin. Illustratively, the heat resistant resin is selected from the group consisting of polyimide, polybenzoxazole, polycarbonate, SAN (styrene resin), fluororesin, and PTFE (polytetrafluoroethylene). These heat-resistant resins are preferable because they are stable at high temperatures (for example, polyimide is 250 to 300 ° C.) and excellent in translucency.

  The manufacturing method of the fluorescent substance of this invention is illustrated.

  Metal particles and ceramic particles are dispersed in a liquid substance containing an arbitrary material that becomes a light-transmitting solid compound by at least heat treatment or dehydration / reduction treatment to obtain a raw material solution.

Here, the liquid substance is any material that becomes translucent glass or SiO ₂ by heat treatment such as heating. Preferably, the liquid substance is a material containing at least silicon. Thus, the liquid material, a glass composed mainly of silicate or can be converted into SiO ₂ solid compound. Such a liquid substance containing at least silicon is more preferably an organic substance containing tetramethyl silicate (tetramethoxysilane) and / or tetraethyl silicate (tetraethoxysilane), which are obtained and It is known that it is easy to handle and becomes glass containing silicate as a main component or SiO ₂ .

  Alternatively, the liquid material may include a heat-resistant resin precursor having translucency by heat treatment or dehydration / reversion. The precursor of the heat-resistant resin is any substance that becomes a heat-resistant resin selected from the group consisting of polyimide, polybenzoxazole, polycarbonate, SAN (styrene-based resin), fluororesin, and PTFE (polytetrafluoroethylene). .

  In addition, you may add catalysts, such as distilled water, alcohol, ammonia, to a liquid substance suitably. For example, when the liquid substance is an organic substance containing tetramethyl orthosilicate (tetramethoxysilane) and / or tetraethyl orthosilicate (tetraethoxysilane), distilled water and ammonia are added to the liquid substance to promote hydrolysis. be able to. Further, by adding an alcohol having both hydrophobicity and hydrophilicity, such as lower alcohol, to the liquid material, mixing of the hydrophobic liquid material and distilled water can be facilitated.

  Next, a raw material solution in which metal particles and ceramic particles are dispersed is applied onto, for example, a desired substrate and dried to obtain a thin film phosphor containing at least metal particles and ceramic particles. Specifically, the coating is dip coating, dropping, spin coating, or the like. Alternatively, the raw material solution in which the metal particles and the ceramic particles are dispersed is allowed to stand and gel, and then heated to obtain a phosphor in which the metal particles and the ceramic particles are dispersed in the translucent material.

  In addition, the ceramic particle used in the above-mentioned manufacturing method can be manufactured with reference to the patent documents 1-5 and 9 mentioned above, for example.

Moreover, although the metal particle used in the above-mentioned manufacturing method may use a commercially available metal particle, for example, when the metal particle is a nanocube made of silver, a silver precursor (for example, AgCF ₃ COO) is added to NaHS. Or by reacting in the presence of hydrochloric acid.

In addition, when silver particles are used as the metal particles, the particle concentration of the metal particles in the raw material solution is preferably greater than 0 and 5 × 10 ¹⁵ particles / L or less. If in this range. Effective emission enhancement by plasmon resonance based on silver particles is obtained. When the particle concentration exceeds 5 × 10 ¹⁵ particles / L, although the light emission enhancement is observed, the enhancement effect may be small.

  A lighting fixture and an image display device can be designed using the phosphor of the present invention thus obtained.

  The luminaire of the present invention is configured using at least an excitation light source and the phosphor of the present invention. Examples of lighting fixtures include LED lighting fixtures and fluorescent lamps. In LED lighting fixtures, the phosphor of the present invention is used to manufacture by a known method as described in JP-A-5-152609, JP-A-7-99345, JP-A-2927279, and the like. Can do. In the lighting fixture of the present invention, the excitation light source emits light having a wavelength of 400 nm or more and 500 nm or less, and is preferably selected from the group consisting of an LED light emitting element, an LD light emitting element, and an organic EL. Some of these light emitting elements are made of nitride semiconductors such as GaN and InGaN, and can be light emitting light sources that emit light of a predetermined wavelength by adjusting the composition.

  In addition to the method of using the phosphor of the present invention alone in a lighting fixture, a lighting fixture emitting a desired color can be configured by using it together with a phosphor having other light emission characteristics.

  The image display device of the present invention is configured using at least an excitation light source and the phosphor of the present invention. In the image display device of the invention, the excitation light source emits light having a wavelength of 400 nm or more and 500 nm or less, and is preferably selected from the group consisting of an LED light emitting element, an LD light emitting element, and an organic EL. The phosphor of the present invention is excited by an excitation light source such as a blue LED to constitute an image display device that displays a desired color.

  Next, the present invention will be described in more detail with reference to the following examples, which are disclosed as an aid for easy understanding of the present invention, and the present invention is limited to these examples. It is not a thing.

  Prior to the production of the phosphor of the present invention, nanocube-like silver particles (referred to as silver nanocubes) were synthesized as metal particles, and α-sialon (referred to as α-sialon phosphor) containing Eu as ceramic particles.

<Synthesis of silver nanocubes>
To ethylene glycol (5 mL) warmed to 150 ° C., 3 mM NaHS ethylene glycol solution (60 μL) was added, then 3 mM ethylene glycol hydrochloride solution (0.5 mL), polyvinylpyrrolidone ethylene glycol solution (1.25 mL), Then, a 282 mM CF ₃ COO silver ethylene glycol solution (0.4 mL) was added and stirred to obtain a single crystal silver nanocube having a particle size of 46 nm. The silver nanocube was observed with a scanning electron microscope (SEM). The observation results are shown in FIG.

  FIG. 1 is a diagram showing an SEM image of silver nanocubes.

  According to FIG. 1, it was confirmed that all of the synthesized silver nanocubes had a prismatic shape, specifically, a nanocube-shaped single crystal having an average particle diameter (d50) of 46 nm.

<Synthesis of α-sialon phosphor>
As raw materials, Si ₃ N ₄ (Ube Industries SN-E10 grade: 64.897 wt%), AlN (Tokuyama grade F: 18.965 wt%), CaCO ₃ (high purity chemical purity 4N: 14.51 wt%) And Eu ₂ O ₃ (purity 99.9% grade manufactured by Shin-Etsu Chemical Co., Ltd .: 1.628 wt%) were mixed with a silicon nitride mortar and pestle. The mixture was placed in a boron nitride crucible and fired in a graphite resistance heating furnace. Specifically, evacuation was performed to a high vacuum of 3 × 10 ⁻³ or less, and the temperature was raised to 1700 ° C. at 20 ° C. per minute in 1 MPa nitrogen gas, and held at 1700 ° C. for 2 hours. After cooling, the fired powder was crushed with a silicon nitride mortar and pestle and passed through a 32 μm sieve. When the obtained fired powder was identified by a crystal phase by X-ray diffraction (XRD), it was confirmed to be α-sialon (that is, Ca-α sialon activated by Eu).

[Examples 1 to 4]
In Examples 1 to 4, silver nanocubes were used as metal particles and α-sialon phosphors were used as ceramic particles, and thin-film phosphors composed of silver nanocubes and α-sialon phosphors were produced.

Si (OC ₂ H ₅ ) ₄ , C ₂ H ₅ OH and H ₂ O were added and mixed with 1.31 ml, 0.97 ml and 0.48 ml, respectively, and mixed with silver nanocubes with various particle concentrations. 0.97 ml of ethanol solution (0.48 × 10 ¹⁵ , 2.4 × 10 ¹⁵ , 4.8 × 10 ¹⁵ , 9.6 × 10 ¹⁵ particles / L) was added. Next, 0.2006 g of α sialon phosphor (50 mass% with respect to glass (SiO ₂ )) was added to these solutions, and the mixture was stirred at room temperature for 24 hours to prepare a raw material solution.

After stirring, 200 microliters of the raw material solution was dropped on a cover glass substrate (24 mm square) and spin-coated at 3000 rpm for 30 sec. Drying was performed at 80 ° C. for 10 minutes to obtain a thin film sample containing α-sialon phosphor and silver nanocubes. The number of coatings was 2. None of the obtained thin film samples peeled off from the glass substrate. The thin film samples of Examples 1 to 4 were silver nanocube ethanol having particle concentrations of 0.48 × 10 ¹⁵ , 2.4 × 10 ¹⁵ , 4.8 × 10 ¹⁵ , and 9.6 × 10 ¹⁵ particles / L, respectively. It is a thin film sample using a solution.

  The plasmon resonance absorption peak of the silver nanocube was measured using an ultraviolet / visible spectrophotometer (UV-VIS). As a sample, an ethanol solution containing silver nanocubes was used. The measurement range was measured at a wavelength of 240 to 800 nm where an absorption peak of silver plasmon resonance can be confirmed. The results are shown in FIG.

  FIG. 2 is a diagram showing a resonance absorption spectrum of a silver nanocube solution.

  According to FIG. 2, it was found that a clear absorption peak due to the silver nanocube exists in the vicinity of a wavelength of 450 nm. This suggests that in the thin film sample according to the present invention, the metal particles that are silver nanocubes absorb light of 400 nm to 500 nm.

  About the obtained thin film sample, the emission spectrum at the time of exciting with the light which has a wavelength of 450 nm was measured using the fluorescence spectrophotometer. The results are shown in FIG.

[Comparative Example 5]
In Comparative Example 5, a thin film phosphor made of α-sialon phosphor was manufactured. The production procedure was the same as in Examples 1 to 4 except that silver nanocubes were not used. The obtained thin film sample had the same appearance as in Examples 1 to 4 without peeling off from the glass substrate. About the obtained thin film sample, the emission spectrum was measured like Examples 1-4. The results are shown in FIG.

  FIG. 3 is a diagram showing emission spectra according to Examples 1 to 4 and Comparative Example 5.

  According to FIG. 3, it was found that the thin film samples of Examples and Comparative Examples were both yellow phosphors having a peak at a wavelength of about 585 nm. Furthermore, the emission peak intensity of the thin film sample of the example was larger than that of the comparative example, and it was a yellow phosphor that emitted light with high luminance. From this, it was confirmed that the luminescence intensity of the α sialon phosphor was increased by plasmon resonance based on silver nanocubes.

Furthermore, according to FIG. 3, it can be seen that the emission enhancement due to plasmon resonance increases as the particle concentration of silver nanocubes decreases, and the emission enhancement due to plasmon resonance decreases as the particle concentration of silver nanocubes increases. This suggests that the particle concentration of the silver nanocube is preferably 5 × 10 ¹⁵ particles / L or less in order to obtain a higher light emission enhancement effect.

[Example 6]
In Example 6, silver nanocubes are used as metal particles, α sialon phosphors are used as ceramic particles, and glass is used as a translucent material. Silver nanocubes and α sialon phosphors are dispersed in glass as a translucent material. A phosphor was manufactured.

Si (CH ₃ ) ₄ , CH ₃ OH and dimethylformamide (DMF) were mixed, and an aqueous ammonia solution was added and stirred. Next, α-sialon phosphor and silver nanocube ethanol solution were added to this at the same concentration as in Example 1, and allowed to stand to gel. Thereafter, the gelled solution was dried at 150 ° C. and sintered at 1050 ° C. to obtain a sample in which α-sialon phosphor and silver nanocubes were dispersed in glass. When the emission spectrum was measured in the same manner as in Examples 1 to 4, emission enhancement by plasmon resonance based on silver nanocubes was confirmed.

  The phosphor of the present invention includes metal particles and ceramic particles, and can emit light with high brightness by plasmon resonance based on the metal particles. In addition, both metal particles and ceramic particles are chemically and thermally stable, and further, since the luminance of the phosphor is not lowered when exposed to an excitation source, it is suitable for VFD, FED, PDP, CRT, white LED, etc. It is a phosphor used in the above. In the future, it can be expected to contribute greatly to the development of the industry in material design for various display devices.

Claims (8)

Including metal particles, ceramic particles and glass,
The metal particles are prismatic,
The metal particles and the ceramic particles are dispersed in the glass,
The metal particles absorb light having a wavelength of 400 nm to 500 nm,
The ceramic particles emit light having a wavelength of 500 nm or more and 650 nm or less;
Wherein the metal particles and the ceramic particles, before Symbol against ceramic particles child 100 parts by weight, before Symbol metal particles child 4.16 × ^{10 -8} parts by mass or more 8.32 × ^{10 -7} parts by weight or less of the range A phosphor that is contained so as to satisfy.   The phosphor according to claim 1, wherein the metal particles are silver particles.   2. The phosphor according to claim 1, wherein an average particle diameter (volume reference median diameter d50) of the metal particles is 30 nm or more and 80 nm or less. 2. The phosphor according to claim 1, wherein the ceramic particles are selected from the group consisting of β-sialon containing Eu, α-sialon containing Eu, and CaAlSiN ₃ containing Eu. A lighting fixture including an excitation light source and a phosphor,
The excitation light source emits light having a wavelength of not less than 400 nm and not more than 500 nm;
The said fluorescent substance is a lighting fixture containing the fluorescent substance of Claim 1 at least. The lighting apparatus according to claim 5, wherein the excitation light source is selected from the group consisting of an LED, a laser diode, and an organic EL. An image display device including an excitation light source and a phosphor,
The excitation light source emits light having a wavelength of not less than 400 nm and not more than 500 nm;
The said fluorescent substance is an image display apparatus containing the fluorescent substance of Claim 1 at least. The image display device according to claim 7, wherein the excitation light source is selected from the group consisting of an LED, a laser diode, and an organic EL.