JP2005120117A - Phosphor and porous body and filter using the same - Google Patents

Abstract

Provided is a phosphor capable of emitting visible light to ultraviolet light capable of efficiently exciting a photocatalyst by applying an alternating voltage. Various uses such as filtration filters and sterilization light sources are conceivable.
A first additive element (Cu, Ag) that forms an acceptor level in a semiconductor containing ZnS as a first main component and part or no II-VI group compound semiconductor as a second component. , Au, Li, Na, N, As, P, Sb) and a second additive element (Cl, Al, I, F, Br) forming a donor level, and by electroluminescence, photoluminescence, and cathodoluminescence A phosphor having a function of emitting visible light or ultraviolet light having a wavelength of 400 nm or less. Further, the filter is a porous body and a light emitting device made of such a phosphor, and further a combination of a light emitting device and a material having a photocatalytic function.
[Selection figure] None

Description

  The present invention relates to a phosphor particularly useful for electroluminescence, a porous body using the same, and a filter.

Due to environmental problems in recent years, there is a strong demand for a function of separating, decomposing, or sterilizing harmful substances, bacteria and viruses.
For separation, there is a method of using a filtration filter and separating with a filtration filter having a pore size smaller than the size of bacteria or viruses, but since bacteria and viruses are only physically separated, they do not die. Sex matters.

On the other hand, photocatalytic materials are attracting attention as a means for decomposing and sterilizing. A typical photocatalyst is TiO ₂ , which is generally a material that exhibits a photocatalytic function with ultraviolet light having a wavelength of 400 nm or less, and therefore, can hardly exhibit a catalytic effect in sunlight with a low ultraviolet content. . Therefore, it is necessary to use a separate light source such as a mercury lamp, which obstructs the compactness of the reaction vessel and needs to use mercury, which is a harmful substance. Recently, a light emitting diode (LED) that emits ultraviolet rays is used as a light source instead of a mercury lamp. When these external light sources are used, it is necessary to uniformly irradiate the surface of the photocatalyst particles with ultraviolet rays, but there are the following problems.

(1) When the object is a gas, it is necessary to float TiO ₂ particles, which are photocatalysts, in the reaction vessel, so a special device is required. In the case of a liquid, it is necessary to disperse the liquid in the liquid.
(2) Since ultraviolet rays are easily absorbed in the atmosphere, it is necessary to bring the light source closer, and it is difficult to apply to large reaction vessels. In particular, when the object is a turbid liquid, the attenuation of ultraviolet rays is severe, and the external light source method cannot be applied.

Patent Document 1 has been invented as a ceramic filter that has not only a simple filtration function but also a function that the filter itself emits ultraviolet rays during filtration to decompose organic substances or sterilize bacteria, viruses, and the like. This is to make the luminescent layer porous and to have a filter function, to generate ultraviolet rays while passing through the pores of the filter during filtration, and to separate or sterilize organic particles, bacteria, viruses, etc. in combination with a photocatalyst It is. The light emitter is a light emitting layer, GaN and ZnO, or a semiconductor material alone, such as ZnS, or, _ZnF doped with Gd in ZnF ₂ 2: Gd etc. can be used.

  ZnS-based materials are well known as phosphor materials that emit light with high efficiency by electroluminescence. The light emission mechanism of the ZnS phosphor is as shown in FIG.

ZnS is doped with Cl or Al as the second additive element. These additive elements form a donor level under the conduction band of ZnS. On the other hand, Cu, Ag, or the like is doped as the first additive element. These elements form acceptor levels on the ZnS valence band. When energy such as an electron beam or ultraviolet light is irradiated into ZnS, electrons in the valence band are once excited to the conduction band and then trapped in the donor level. On the other hand, holes newly generated in the valence band are trapped in the acceptor level. Light emission occurs when electrons in the donor level recombine with holes in the acceptor level. This is a type of light emission called donor-acceptor (DA) light emission, which is a light emission mechanism that provides extremely high light emission efficiency. As shown in the equation (1), the emission wavelength is basically determined by the energy difference between the donor level and the acceptor level, and the larger this is, the shorter the wavelength is emitted. That is, the light emission energy hν is
_{hν = E g - (E D} + E A) + e 2 / (4πε 0 ε r r) (1)
Here, E _g is the band gap energy of ZnS, E _D is the donor of binding energy, E _A is the binding energy of the acceptor, e is elementary charge quantity, epsilon ₀ is the vacuum dielectric constant, epsilon _r is the ratio electrostatic permittivity , R is the distance between the donor and the acceptor.

Regarding ZnS-based phosphors having such a light emission mechanism, ZnS: Ag and Cl are put into practical use as blue phosphors, and ZnS: Cu and Al as green phosphors (see Non-Patent Document 1). However, these phosphors can only emit visible light.
In addition, regarding ZnS-based phosphors, there are those in which ZnS is doped with various rare earth elements such as Tm, Tb, and Sm (see Patent Document 2). These are phosphors of a type that directly excites rare earth elements and emits visible light such as blue and green. However, these phosphors have lower emission efficiency in electroluminescence than phosphors that emit donor-acceptor light.
Japanese Patent Application No. 2002-202837 Japanese Patent No. 2715620 Principle of light emission, written by Hiroshi Kobayashi, published by Asakura Shoten, pages 66-69

  The conventional ultraviolet light emitting porous body has a problem in that the power consumption is slightly increased because the luminous efficiency is lower than that of a semiconductor material that emits visible light. The ZnS phosphor can emit only visible light. In addition, the luminous efficiency of electroluminescence is lower than that of a phosphor emitting donor-acceptor light. Therefore, the present invention provides a phosphor capable of emitting visible light to ultraviolet light with high luminous efficiency. Moreover, if it is a porous body, it can be set as an efficient filtration filter.

As a result of earnestly searching for a phosphor capable of efficiently emitting ultraviolet rays, the inventors have arrived at the following inventions (1) to (19).
(1) a first additive component that forms an acceptor level in a semiconductor that contains ZnS as a first main component and partly or does not contain a II-VI group compound semiconductor as a second component, and a donor level A phosphor having a function of emitting visible light or ultraviolet light having a wavelength of 400 nm or less by electroluminescence, photoluminescence, or cathodoluminescence.
(2) The first additive element is at least one of Cu, Ag, Au, Li, Na, N, As, P, and Sb, and the second additive element is at least one of Cl, Al, I, F, and Br. The phosphor according to (1).
(3) The phosphor according to (1), wherein the first additive element is Ag and the emission wavelength is 350 nm or less.

(4) The phosphor according to (1), wherein the second component semiconductor contains at least one of MgS, CaS, SrS, BeS, and BaS.
(5) A core-shell structure in which the phosphor according to (1) having a core particle size of 10 nm or less is dispersed in a shell material having a band gap larger than the band gap corresponding to the emission wavelength of the phosphor. A phosphor characterized by having.
(6) A phosphor having a core-shell structure in which the phosphor according to the above (1) having a core particle size of 10 nm or less is dispersed in a shell material having a photocatalytic function.
(7) The phosphor according to (5) or (6) above, wherein the shell material has a high dielectric constant.

(8) A porous body comprising the phosphor according to (1).
(9) A porous body comprising the phosphor according to (5).
(10) A porous body comprising the phosphor according to (6).
(11) A light emitting device comprising the phosphor according to (1).
(12) A light emitting device comprising the phosphor according to (5).
(13) A light emitting device comprising the phosphor according to (6).
(14) A light emitting device comprising the porous material according to (8).
(15) A light emitting device comprising the porous material according to (9).
(16) A light emitting device comprising the porous material according to (10).

(17) A filtration filter comprising a combination of the light emitting device according to (14) and a material having a photocatalytic function.
(18) A filtration filter comprising a combination of the light emitting device according to (15) and a material having a photocatalytic function.
(19) A filtration filter comprising a combination of the light emitting device according to (16) and a material having a photocatalytic function.

  That is, the present invention is an ultraviolet light-emitting phosphor that takes advantage of the high-efficiency light emission of the donor-acceptor light-emitting mechanism that is a feature of ZnS-based phosphors. The present invention relates to a phosphor that emits ultraviolet light with high luminous efficiency by electroluminescence, photoluminescence, and cathodoluminescence, a porous body using the phosphor, a light emitting device, and a filtration filter. In particular, the main purpose is to emit light by electroluminescence. This is explained below.

From the equation (1), it can be seen that the emission wavelength is mainly determined by the band gap of the semiconductor material, the donor, and the acceptor level. That is, to the emission wavelength to the short wavelength, (1) the large _{E g,} (2) _E small _D, but it is necessary to reduce the (3) _{E A,} these, _{E D} is It does not change greatly depending on the element to be doped at about 0.1 eV. Also, _{E A} is, 1.2 eV in Cu doping, since it is 0.7eV with Ag doping, in order to shorten the wavelength of the emission wavelength, Ag addition is preferred. However, it is most important to increase E _g substantially.
Examples of additive elements that form acceptor levels include Cu, Ag, Au, Li, Na, N, As, P, and Sb. Examples of the additive element that forms a donor level include Cl, Al, I, F, and Br.

There are mainly two methods for increasing the band gap energy (E _g ). One is to use a mixed crystal of ZnS and the second component semiconductor having a larger band gap than ZnS (E _g = 3.7 eV) as the base material semiconductor. As the second component semiconductor, there is the same II-VI compound semiconductor as ZnS, and it may be a selenide such as MgSe (E _g = 4.0 eV) or BeSe (E _g = 4.7 eV), but the same sulfide. It is easier to make a product by selecting the product. For example, MgS is preferable because E _g = 5.1 eV, CaS = 4.4 eV, and SrS = 4.3 eV. In addition, BaS and BeS are also candidates, but MgS is most preferable.

Another way to increase the bandgap is to reduce the size of the ZnS particles to nanosize. As the particle size decreases, the quantum size effect appears and the band gap increases. Of course, the particle size of the mixed crystal may be reduced. In this case, the particle size may be larger than that using ZnS alone. The particle size quantum size effect appears varies by E _g and E _A. For example, if ZnS alone doped with Ag or Cl is 5 nm or less, and the same doped ZnS · 10 mol% MgS is 9 nm or less, the emission wavelength is 400 nm or less.

With ZnS · 20 mol% MgS, the emission wavelength is 400 nm or less regardless of the particle diameter. As described above, when the amount of MgS is large, there is a tendency that the restriction on the particle diameter is eliminated. However, when the amount of MgS is large, the light emission efficiency may be decreased. The same applies to other second component semiconductors. In that sense, the standard particle size is 10 nm or less. In the case of using such nanoparticles, if the surface of the nanoparticles is exposed, many defects on the surface of the nanoparticles become emission killer, and the emission intensity decreases. However, it is necessary to have a core-shell structure dispersed in a shell material having a band gap larger than the band gap corresponding to the emission wavelength of the nanoparticles. When the band gap of the shell material is smaller than the band gap corresponding to the emission wavelength of the nanoparticles, the light emitted from the nanoparticles is absorbed by the shell, which is not preferable. By using such a band gap relationship, a so-called quantum confinement effect in which electrons and holes contributing to light emission are confined in the nanoparticles is exhibited, and the light emission luminance is increased. However, it does not matter if the shell is a material having a photocatalytic function, for example, TiO ₂ itself.

It is very preferable to use a high dielectric constant material such as BaTiO ₃ as the shell material. Since BaTiO ₃ has a very high dielectric constant of about 2000 at room temperature, a high electric field can be efficiently applied to a semiconductor when an electroluminescence voltage is applied, so that there is an advantage that light emission luminance and light emission efficiency are increased. As the high dielectric constant material, Ta ₂ O ₅ having a dielectric constant of 22 and TiO ₂ having a dielectric constant of 60, an inorganic material such as PbTiO ₃ , PbZrO ₃ , and SrTiO ₃ , and a resin such as cyanoresin may be used.

In a normal electroluminescence device, the threshold voltage for emitting light is approximately 1 × 10 ⁴ to 1 × 10 ⁶ V / cm. By making the light emitting particles covered with a high dielectric constant material, The threshold voltage can also be lowered.
The emission wavelength is preferably 350 nm or less because the photocatalyst can be excited most efficiently. The photocatalyst is mainly preferably anatase TiO _{2 in} a crystal system, but may be a rutile type or a blockite type which are other crystal systems.

Mixed crystal phosphors or doping methods include, for example, a method in which Cl and Ag metal are added to a mixed powder of ZnS and MgS and mechanically alloyed and pulverized, and mixed crystal and doping are performed simultaneously, or reverse micelle Various methods such as a liquid phase method such as a method can be considered.
The phosphor produced as described above becomes a phosphor that emits light with high luminous efficiency. It is particularly excellent as a phosphor for electroluminescence.

  By making the phosphor of the above invention a porous body, it becomes an ultraviolet light source that emits light with high brightness and low power consumption. Therefore, by combining with a photocatalyst and making an electroluminescence light emitting device, it has an extremely high decomposition and sterilization function. It also becomes a filtration filter.

  The product of the present invention is a phosphor that can emit visible light to ultraviolet light that can efficiently excite a photocatalyst by application of an alternating voltage, and in particular, when used as a phosphor for electroluminescence, a light source with high luminous efficiency can be produced. When the electroluminescent device is used as a so-called particle dispersion type EL device in which phosphor particles are dispersed in a high dielectric constant material, the threshold voltage of fluorescence can be lowered. Of course, when the phosphor powder is hardened as a target material and a thin film is produced by sputtering or the like, the same excellent performance as a thin film phosphor can be exhibited.

  When the product of the present invention is used as a porous body, it becomes a filtration filter that can efficiently decompose and sterilize organic matter, bacteria, viruses and the like. Applications include decomposition and removal of NOx, SOx, CO gas, diesel particulates, pollen, dust, mites, etc., organic compounds contained in sewage, general bacteria, viruses, etc. It can be applied to various fields such as sterilization light source, decomposition of harmful gas generated in chemical plant, decomposition of odor components, surface / line light source for lighting, light source of photocatalyst, sterilization light source in ultrapure water production equipment. In addition, as product types, it can be applied to all types of filters in the above fields, such as honeycomb materials for automobile exhaust gas treatment, filters for air purifiers, sewage filtration filters, various water purifiers, insect repellents, and other large-area luminescent glasses and walls. Applicable.

In addition, since ultraviolet rays are effective for raising reptiles, they are also effective as an ultraviolet light source for raising reptiles. If various phosphors that emit light by ultraviolet irradiation are placed on the surface of this porous semiconductor device, visible light can be generated from the phosphors excited by the emitted ultraviolet rays. And a device that emits both visible light and light.
Ultraviolet rays are light necessary for growing vitamin D, and vitamin D can be efficiently synthesized using the pores in the porous semiconductor as a hotbed, and can be effectively used as such a bioreactor.

Next, the present invention will be described more specifically with reference to examples.
Example 1
<Fabrication of phosphor>
A mixed powder obtained by mixing 3 μm of ZnS powder with 3 μm of AgCl or CuCl ₂ powder is dispersed in methanol to obtain a solution. After filling the pot with this solution and sealing with argon gas, the planetary ball mill device And pulverizing at an acceleration of 150 G and changing the pulverization time. The AgCl and CuCl ₂ concentrations were adjusted to 5 mol% with respect to ZnS.
The treated pot was opened in Ar gas to volatilize methanol, and the treated powder was changed to (1) an alcohol solution of Ta (OC ₂ H ₅ ) ₅ or (2) Ba (OCH ₃ ) ₂ . An alcohol solution in which Ti (OC ₂ H ₅ ) ₄ is mixed in an equimolar ratio; (3) an alcohol solution in which Sr (OCH ₃ ) ₂ and Ti (OC ₂ H ₅ ) ₄ are mixed in an equimolar ratio; (4) Pb The film was dipped in an alcohol solution in which (OC ₃ H ₇ ) ₂ and Ti (OC ₂ H ₅ ) ₄ were mixed in an equimolar ratio and then pulled up, and baked at 400 ° C. for 2 hours in the air. This was repeated 5 times to obtain a composite powder having a structure in which ZnS particles were dispersed in Ta ₂ O ₅ , BaTiO ₃ , SrTiO ₃ , or PbTiO ₃ powder having a particle size of 1 μm, and then heat treated at 600 ° C. for 1 hr in Ar. And crystallized. The particle size of the ZnS particles was observed with SEM or TEM.

For comparison, a similar experiment was performed except that metal Tb or metal Tm having a particle size of 3 μm was used instead of AgCl or CuCl ₂ powder (Tb or Tm concentration was 5 mol% with respect to ZnS).

<Production and evaluation of EL device>
One surface of the glass substrate was coated with 0.5 μm of Al to form a back electrode.
A slurry obtained by mixing cyanoresin resin and BaTiO ₃ having an average particle diameter of 3 μm in a volume ratio of 2: 1 was applied to an Al-coated glass substrate with a roller by about 30 μm to form an insulating layer. Next, a slurry in which the produced composite powder, BaTiO ₃ powder, and cyanoresin resin were mixed at a volume ratio of 1: 1: 1 was similarly applied to the surface of the insulating layer to form a light emitting layer having a thickness of about 50 μm. After a similar insulating layer was formed on this surface, an ITO film was further coated on the outermost surface by sputtering to a thickness of 0.2 μm to form a surface electrode.
An AC electric field of 250 V and 1 kHz was applied between both electrodes. The spectrum of the emitted light was measured with a photonic analyzer. Luminous luminance was measured, and luminous efficiency was calculated from the value and input power.

The results are shown in Table 1.
The peak wavelength (the wavelength with the highest emission intensity) is described in the table as the emission wavelength.

The longer the pulverization time, the smaller the ZnS particle size, and the smaller the emission wavelength. When the average diameter of the core particles was 4.5 nm or less, the wavelength was 400 nm or less. The average particle diameter of the core particles was directly observed with a transmission electron microscope (TEM). When BaTiO ₃ was used as the shell material, the luminous efficiency was higher. The comparative material had low luminous efficiency.

Example 2
<Fabrication of phosphor>
First, a magnetic stirrer was prepared by mixing 80 ml of a zinc acetate methanol solution (0.13 mol / l), 6 to 80 ml of a magnesium acetate methanol solution (0.13 mol / l) and 25 ml of an AgI methanol solution (0.008 mol / l). Was used for 10 minutes to obtain a mixed solution. Next, the above-mentioned mixed solution was added to 58 ml of an aqueous solution (0.38 mol / l) of sodium sulfide in a state of being stirred using a magnetic stirrer, and further stirred for 15 minutes. After centrifuging at 4000 rpm for 20 minutes using a centrifuge, the centrifuged precipitate was taken out in Ar gas, dipped in an alcohol solution of Ti (OC ₂ H ₅ ) ₄ and then pulled up. Firing was performed at 400 ° C. for 30 minutes in the air. This was repeated 5 times to obtain a composite powder having a structure in which ZnS / MgS-based particles were dispersed in TiO ₂ powder having a particle diameter of 1 μm. This was again dispersed in ethanol to form a suspension.

<Production of EL device>
One side of a SiC porous substrate having a diameter of 25 mm, a thickness of 1 mm, a porosity of 50% and an average pore diameter of 0.5 μm was coated with porous Al to a thickness of 0.5 μm by sputtering to form a back electrode. . The above suspension was filtered with this substrate to form a ZnS / MgS core / TiO ₂ shell layer having a thickness of 10 μm on the substrate, and then fired at 500 ° C. for 10 hours in the air to halve the shell TiO ₂ . A porous body layer having a porosity of 50% was formed by sintering. Furthermore, an Al film was coated on the outermost surface with a thickness of 0.5 μm to form a surface electrode to obtain a porous light emitting device.

As a result of observing the core particle diameter in the porous layer with SEM or TEM, it was found that the core particle was a porous body in which nanoparticles having an average particle diameter of 7 nm were formed in TiO ₂ . Furthermore, as a result of measuring the ratio of Mg and Zn in the powder by chemical analysis, it was found that the Mg / (Mg + Zn) was 7-50 mol% of AnS · MgS mixed crystal: Ag, Cl powder.

<Photocatalytic function evaluation>
As shown in FIG. 2, 0.02 mol of trichlorethylene was gasified and sprayed into a 10 liter air cylinder. A gas was supplied from the semiconductor layer side of the sample while applying or not applying an AC voltage having a frequency of 2.5 kHz and a voltage of 280 V, and circulated and filtered. The time until the trichlorethylene concentration in the tank became zero was measured.

The results are shown in Table 2.
The peak wavelength (the wavelength with the highest emission intensity) is described in the table as the emission wavelength.
As the amount of MgS increased, the emission wavelength decreased, and MgS was 10 mol% or more and 400 nm or less. The smaller the emission wavelength, the shorter the decomposition time.

Example 3
<Fabrication of phosphor>
In addition to the magnesium acetate of Example 2, strontium acetate and calcium acetate were used.
First, 80 ml of a methanol solution of zinc acetate (0.05 mol / l), 18 ml of any one of magnesium acetate, strontium acetate and calcium acetate (0.05 mol / l) and a methanol solution of AgCl (0.003 mol / l) l) 25 ml was mixed and stirred for 10 minutes using a magnetic stirrer to obtain a mixed solution. Next, the above mixed solution was added to 60 ml of an aqueous solution of sodium sulfide (0.10 mol / l) in a state of being stirred using a magnetic stirrer, and further stirred for 15 minutes. After centrifuging at 4000 rpm for 20 minutes using a centrifuge, the centrifuged precipitate was taken out in Ar gas, and this was immersed in an alcohol solution of Ti (OC ₂ H ₅ ) ₄ and pulled up. Firing was performed at 400 ° C. for 30 minutes in the air. This was repeated 5 times to obtain a composite powder having a structure in which ZnS / MeS (Me = Mg, Sr, Ca) -based particles were dispersed in TiO ₂ powder having a particle diameter of 1 μm. This was again dispersed in ethanol to form a suspension.

<Production of EL device>
Same as Example 2.
As a result of observing the core particle diameter in the porous layer with SEM or TEM, it was found that the nanoparticle having a core diameter of 4 nm was a porous body formed in TiO ₂ . Further, the ratio of Me and Zn in the powder was measured by chemical analysis. As a result, (Me / (Me + Zn), where Me = Mg, Sr, Ca) was a 20 mol% ZnS / MeS mixed crystal: Ag, Cl powder. I understood that.

<Photocatalytic function evaluation>
Measurement was performed in the same manner as in Example 2.
The results are shown in Table 3.
The peak wavelength (the wavelength with the highest emission intensity) is described in the table as the emission wavelength.
It can be seen that even when a mixed crystal semiconductor base material using CaS or SrS instead of MgS is used, the same decomposition function is exhibited.

Example 4
<Fabrication of phosphor>
First, 80 ml of a methanol solution of zinc acetate (0.5 mol / l), 18 ml of a methanol solution of magnesium acetate (0.5 mol / l), 25 ml of a methanol solution of Ag ₂ SO ₄ (0.04 mol / l), methanol of AlF ₃ 6 ml of the solution (0.03 mol / l) was mixed and stirred for 10 minutes using a magnetic stirrer to obtain a mixed solution. Next, the above-mentioned mixed solution of 60 ml of an aqueous solution of sodium sulfide (1.0 mol / l) stirred with a magnetic stirrer was added, and the mixture was further stirred for 15 minutes and then allowed to stand at a temperature of 50 to 90 ° C. for 24 hours. Finally, after centrifuging at 4000 rpm for 20 minutes using a centrifuge, the liquid was volatilized and the precipitate powder was taken out in the atmosphere.
As a result of observing the particle size of the powder by SEM or TEM, the particle size was 100 to 2000 nm. The higher the standing temperature, the more the grains grew. Furthermore, as a result of measuring the ratio of Mg and Zn in the powder by chemical analysis, it was found that the Mg / (Mg + Zn) was a 20 mol% ZnS / MgS mixed crystal: Ag, Al, F powder.

<Production and evaluation of EL device>
One surface of the glass substrate was coated with 0.5 μm of Al to form a back electrode.
A slurry obtained by mixing a cyanoresin resin and BaTiO ₃ having an average particle diameter of 3 μm in a volume ratio of 2: 1 was applied to an Al-coated glass substrate with a roller by about 30 μm to form an insulating layer. Next, a slurry in which the prepared composite powder, BaTiO ₃ powder, and cyanoresin resin were mixed at a volume ratio of 1: 1: 1 was similarly applied to the side surface of the Al electrode of the glass substrate to form a light emitting layer of about 50 μm. After a similar insulating layer was formed on this surface, an ITO film was further coated on the outermost surface by sputtering to a thickness of 0.2 μm to form a surface electrode.
An AC electric field of 250 V and 1.5 kHz was applied between the conductive electrodes. The spectrum of the emitted light was measured with a photonic analyzer. Luminous luminance was measured, and luminous efficiency was calculated from the value and input power.

The results are shown in Table 4.
The peak wavelength (the wavelength with the highest emission intensity) is described in the table as the emission wavelength.
By using a ZnS / MgS mixed crystal, the emission wavelength was 400 nm or less and the emission efficiency was high even if the particle size was not reduced to several tens of nanometers.

  A light source with high luminous efficiency can be produced as a thin film phosphor. Moreover, when used as a porous body, a filter can be obtained that can efficiently decompose and sterilize organic matter, bacteria, viruses, and the like. Applications include decomposition and sterilization of NOx, SOx, CO gas, diesel particulates, pollen, dust, mites and the like. Since ultraviolet rays are effective for reptile breeding, they can be used for reptile breeding.

It is explanatory drawing of the light emission mechanism of ZnS type fluorescent substance. It is explanatory drawing of the photocatalyst function evaluation method.

Claims (19)

  A first additive element that forms an acceptor level and a donor level are formed in a semiconductor that contains ZnS as a first main component and partially or does not contain a II-VI group compound semiconductor as a second component. A phosphor comprising a second additive component and having a function of emitting visible light or ultraviolet light having a wavelength of 400 nm or less by electroluminescence, photoluminescence, or cathodoluminescence.   2. The first additive element is at least one of Cu, Ag, Au, Li, Na, N, As, P, and Sb, and the second additive element is at least one of Cl, Al, I, F, and Br. The phosphor described.   The phosphor according to claim 1, wherein the first additive element is Ag and the emission wavelength is 350 nm or less. The phosphor according to claim 1, wherein the second component semiconductor contains at least one of MgS, CaS, SrS, BeS, and BaS.   The phosphor according to claim 1 having a core particle size of 10 nm or less has a core-shell structure dispersed in a shell material having a band gap larger than the band gap corresponding to the emission wavelength of the phosphor. A phosphor.   A phosphor having a core-shell structure in which the phosphor according to claim 1 having a core particle size of 10 nm or less is dispersed in a shell material having a photocatalytic function.   The phosphor according to claim 5 or 6, wherein the shell material has a high dielectric constant.   A porous body comprising the phosphor according to claim 1.   A porous body comprising the phosphor according to claim 5.   A porous body comprising the phosphor according to claim 6.   A light emitting device comprising the phosphor according to claim 1.   A light emitting device comprising the phosphor according to claim 5.   A light emitting device comprising the phosphor according to claim 6.   A light emitting device comprising the porous body according to claim 8.   A light emitting device comprising the porous body according to claim 9.   A light emitting device comprising the porous body according to claim 10.   A filtration filter comprising a combination of the light emitting device according to claim 14 and a material having a photocatalytic function.   A filtration filter comprising a combination of the light emitting device according to claim 15 and a material having a photocatalytic function. A filtration filter comprising a combination of the light emitting device according to claim 16 and a material having a photocatalytic function.