JP7591778B2 - Method for producing photoluminescent materials - Google Patents

Description

The present invention relates to a method for producing a photoluminescent material. Here, "photoluminescent material" means "a material used in applications that utilize photoluminescence (i.e., the phenomenon of emitting visible light when irradiated with light)."

Photoluminescent materials, which emit visible light when exposed to light, are used in lighting devices, backlights for liquid crystal displays, plasma displays, and more.

A variety of photoluminescent materials have been developed to date. For example, Patent Document 1 discloses a photoluminescent material that is a faujasite-type zeolite containing silver atoms (silver ions). Patent Documents 2 to 4 disclose photoluminescent materials that are A-type zeolite containing silver atoms (silver ions). Patent Document 5 discloses a photoluminescent material that is a sodalite containing silver atoms.

JP 2012-52102 A JP 2014-37492 A International Publication No. 2017/209033 JP 2018-197296 A International Publication No. 2016/190356

In photoluminescent materials containing silver atoms as described in Patent Documents 1 to 5, if the silver atom content is high, the resulting mixture may become colored when mixed with resin or rubber. The present invention has been made in light of these circumstances, and its purpose is to produce a photoluminescent material with a reduced silver atom content.

The present invention capable of achieving the above object is as follows.
[1] A method for producing a photoluminescent material that emits visible light when irradiated with light, comprising the steps of:
The method includes obtaining a photoluminescent material II having a reduced content of silver atoms by extracting silver atoms from a photoluminescent material I containing silver atoms in an aqueous solution containing cations other than silver ions and ammonia, and the photoluminescent material I is a zeolite containing silver atoms.
[2] The method according to [1] above, wherein the photoluminescent material I is at least one selected from the group consisting of faujasite-type zeolite containing silver atoms, A-type zeolite containing silver atoms, and sodalite containing silver atoms.
[3] The method according to the above [2], wherein the faujasite-type zeolite containing silver atoms is a faujasite-type zeolite containing 5% by weight or more and 30% by weight or less of silver ions.
[4] The method according to [2] or [3], wherein the A-type zeolite containing silver atoms is an A-type zeolite containing 2.5% by weight or more and 40% by weight or less of silver ions.
[5] The method according to any one of [2] to [4], wherein the sodalite containing silver atoms is a sodalite containing 0.25% by weight or more and 51% by weight or less of silver atoms.
[6] The method according to any one of [1] to [5] above, wherein the cations other than silver ions include alkali metal ions and/or alkaline earth metal ions.
[7] The method according to any one of [1] to [6] above, wherein the ratio of the silver atom content of the photoluminescent material II to the silver atom content of the photoluminescent material I (silver atom content of the photoluminescent material II/silver atom content of the photoluminescent material I) is 3/100 to 9/10.
[8] A photoluminescent material produced by the method according to any one of [1] to [7] above.

According to the present invention, it is possible to produce a photoluminescent material with a reduced content of silver atoms.

One of the features of the present invention is to obtain a photoluminescent material II with a reduced content of silver atoms by extracting silver atoms from a photoluminescent material I containing silver atoms in an aqueous solution containing cations other than silver ions and ammonia. It is presumed that such an operation causes silver atoms (silver ions or silver clusters) at sites in photoluminescent material I that do not contribute to light emission to be ammine complexed and dissolved in the aqueous solution, and cations other than silver ions in the aqueous solution are incorporated into the photoluminescent material in place of the dissolved silver atoms, resulting in a photoluminescent material II with a reduced content of silver atoms. However, the present invention is not limited to such a presumed mechanism.

The reduction in the silver atom content can be confirmed, for example, by measurements using a wavelength-dispersive X-ray fluorescence device, which can also measure the content of each atom (each cation) in the photoluminescent material.

A mixture obtained by mixing a photoluminescent material with a high content of silver atoms with resin or rubber has the problem that it turns black and the luminescence intensity decreases. On the other hand, a photoluminescent material with a reduced content of silver atoms can suppress such discoloration and decrease in luminescence intensity. Furthermore, if the method of the present invention can be used to recover silver dissolved in an aqueous solution and use it in the production of a photoluminescent material, it is expected that production costs can be reduced.

As shown in the following examples and comparative examples, the luminescence intensity of photoluminescent material II obtained by reducing the content of silver atoms in photoluminescent material I was surprisingly equal to or greater than that of photoluminescent material I. Here, "the luminescence intensity of photoluminescent material II is equal to that of photoluminescent material I" means that the relative luminescence intensity of photoluminescent material II, calculated assuming that the luminescence intensity of photoluminescent material I is 1, is within the range of 0.9 to 1.1.

The photoluminescent material I used in the present invention can be produced by ion exchange of the raw material zeolite. This ion exchange can be carried out by stirring and holding the zeolite in a silver ion-containing aqueous solution. Examples of the silver ion-containing aqueous solution include a silver nitrate aqueous solution. If it is necessary to contain ions other than silver ions (hereinafter sometimes abbreviated as "other ions") in the photoluminescent material I, the other ions may be present in the silver ion-containing aqueous solution used for ion exchange, or ion exchange using the silver ion-containing aqueous solution and ion exchange using the aqueous solution containing the other ions may be carried out sequentially. Examples of the aqueous solution containing other ions include a zinc sulfate aqueous solution, a calcium nitrate aqueous solution, a magnesium sulfate aqueous solution, and a potassium sulfate aqueous solution. In addition, the concentration of the silver ions and other ions in the aqueous solution can be appropriately adjusted according to the design value of the content of the silver ions and other ions in the photoluminescent material I. The ion exchange can be carried out at room temperature. The time for ion exchange (i.e., the stirring and holding time of the zeolite in the ion-containing aqueous solution) is usually 30 minutes or more and 10 hours or less, and preferably 5 hours or less.

When the zeolite used as the raw material for the photoluminescent material I is a faujasite-type zeolite or an A-type zeolite, it is preferable to filter the ion-exchanged zeolite from the ion-containing aqueous solution, wash it with water, and then dry it. Drying can be performed in an air atmosphere, an inert gas (e.g., nitrogen gas) atmosphere, or a reduced pressure atmosphere. Among these, drying in an air atmosphere is preferable because it allows simple operation. The drying time is usually 1 hour or more and 30 hours or less, and preferably 20 hours or less. The drying temperature is preferably 300°C or less, more preferably 200°C or less, and preferably 50°C or more, more preferably 100°C or more. The drying conditions can be adjusted appropriately depending on the type of zeolite used.

The dried A-type zeolite may be further subjected to a heat treatment such as calcination. The heat treatment may be performed in an air atmosphere, an inert gas (e.g., nitrogen gas) atmosphere, or a reduced pressure atmosphere. Heat treatment in an air atmosphere is preferred because it allows for simple operation. The heat treatment temperature is preferably 180°C or higher, more preferably 200°C or higher, and preferably 300°C or lower, more preferably 250°C or lower. The heat treatment time is preferably 1 hour or higher, more preferably 2 hours or higher, and preferably 10 hours or lower, more preferably 5 hours or lower.

When the zeolite used as the raw material for the photoluminescent material I is sodalite, it is preferable to filter the ion-exchanged sodalite from the ion-containing aqueous solution, wash it with water, and then heat treat it. The heat treatment may be performed in an inert gas (e.g., nitrogen gas) atmosphere or in the air. The heat treatment temperature is preferably 50°C or higher and 850°C or lower, more preferably 150°C or higher and 600°C or lower, and can be appropriately adjusted depending on the type of photoluminescent material I produced from sodalite. The heat treatment time is preferably 1 hour or higher and 24 hours or lower, more preferably 2 hours or higher and 24 hours or lower.

The photoluminescent material I used in the present invention is preferably a faujasite-type zeolite containing silver atoms (hereinafter sometimes abbreviated as "photoluminescent material I-1");
A-type zeolite containing silver atoms (hereinafter sometimes abbreviated as "photoluminescent material I-2"), and a sodalite containing silver atoms (hereinafter sometimes abbreviated as "photoluminescent material I-3")
The photoluminescent material is at least one selected from the group consisting of: Photoluminescent material I-1 to photoluminescent material I-3 will be described below in order.

First, photoluminescent material I-1 containing faujasite-type zeolite is, for example, that described in Patent Document 1. Examples of faujasite-type zeolite include X-type zeolite and Y-type zeolite, which are synthetic zeolites, and faujasite, which is a natural zeolite. Among these, X-type zeolite is preferred.

The average particle size of the faujasite-type zeolite, the photoluminescent material I-1 obtained from the faujasite-type zeolite, and the photoluminescent material II obtained from the photoluminescent material I-1 is preferably 0.1 μm or more and 2 μm or less, more preferably 0.5 μm or more and 1.5 μm or less. These average particle sizes can be measured by laser diffraction and laser scattering methods.

Faujasite-type zeolites (faujasite, X-type zeolite, and Y-type zeolite) are commercially available and easily available.

Photoluminescent material I-1 is preferably a faujasite-type zeolite containing 5% to 30% by weight of silver ions, and the silver ion content is more preferably 7% to 20% by weight.

In the present invention, the content of silver atoms in photoluminescent material I or II is a value based on the entire photoluminescent material I or II. The same applies to the content of other atoms or ions.

The photoluminescent material I-1 may contain ions other than silver ions (hereinafter sometimes abbreviated as "other ions"). Only one type of other ion may be used, or two or more types may be used in combination.

Other ions contained in photoluminescent material I-1 can be introduced into photoluminescent material I-1 by ion exchange using an aqueous metal salt solution containing the other ions.

Other ions contained in the photoluminescent material I-1 include, for example, alkali metal ions such as sodium ions and potassium ions, alkaline earth metal ions such as calcium ions and magnesium ions, and zinc ions. Among these, photoluminescent material I-1 containing calcium ions is preferred because it increases the luminescence intensity.

When photoluminescent material I-1 contains other ions, the content of each of them is preferably 1% by weight or more and 10% by weight or less.

Next, a photoluminescent material I-2 containing A-type zeolite will be described.
The average particle size of the A-type zeolite, the photoluminescent material I-2 obtained from the A-type zeolite, and the photoluminescent material II obtained from the photoluminescent material I-2 is preferably 0.1 μm or more and 20 μm or less, more preferably 0.5 μm or more and 15 μm or less.
Type A zeolites are commercially available and readily available.

The photoluminescent material I-2 is preferably an A-type zeolite containing 2.5% by weight or more and 40% by weight or less of silver ions, and more preferably an A-type zeolite containing silver ions and zinc ions, the silver ion content being 2.5% by weight or more and 30% by weight or less, the zinc ion content being 0.5% by weight or more and 15% by weight or less, and the total content of silver ions and zinc ions being 5% by weight or more and 35% by weight or less (hereinafter sometimes abbreviated as "photoluminescent material I-2a");
A-type zeolite containing at least one selected from the group consisting of cesium ions and rubidium ions, silver ions and zinc ions, wherein the total content of at least one selected from the group consisting of cesium ions and rubidium ions is 1% by weight or more and 25% by weight or less, the silver ion content is 2.5% by weight or more and 30% by weight or less, and the zinc ion content is 0.5% by weight or more and 15% by weight or less (hereinafter sometimes abbreviated as "photoluminescent material I-2b"); and A-type zeolite containing silver ions and ammonium ions, wherein the silver ion content is 5% by weight or more and 40% by weight or less, and the ammonium ion content is 0.1% by weight or more and 25% by weight or less (however, A-type zeolite containing zinc ions is excluded) (hereinafter sometimes abbreviated as "photoluminescent material I-2c").
The photoluminescent material I-2a to I-2c are each selected from the group consisting of at least one of the following: Photoluminescent material I-2a to photoluminescent material I-2c are each described in order below.

Examples of photoluminescent material I-2a include those described in Patent Document 2. The silver ion content in photoluminescent material I-2a is more preferably 3.5% by weight or more and 20% by weight or less.

The zinc ion content in photoluminescent material I-2a is more preferably 5% by weight or more and 7% by weight or less.

The total content of silver ions and zinc ions in photoluminescent material I-2a is more preferably 10% by weight or more and 25% by weight or less.

The molar ratio of silver ions to zinc ions in photoluminescent material I-2a is preferably 1:45 to 8:1, more preferably 1:5 to 2:1.

Photoluminescent material I-2a may contain ions other than silver ions and zinc ions (hereinafter sometimes abbreviated as "other ions"). Photoluminescent material I-2a may contain one type of other ion, or may contain two or more types of other ions.

Other ions contained in the photoluminescent material I-2a can be introduced into the photoluminescent material I-2a by ion exchange using an aqueous solution of a salt containing the other ions.

Other ions contained in the photoluminescent material I-2a include, for example, alkali metal ions such as sodium ions and potassium ions; alkaline earth metal ions such as calcium ions and magnesium ions; and ammonium ions. Among these, ammonium ions are preferred.

When the photoluminescent material I-2a contains other ions (e.g., ammonium ions), the content of each is preferably 1% by weight or more and 10% by weight or less.

Examples of photoluminescent material I-2b include those described in Patent Document 3. Photoluminescent material I-2b contains at least one ion selected from the group consisting of cesium ions and rubidium ions, and preferably contains cesium ions.

The total content of at least one selected from the group consisting of cesium ions and rubidium ions in photoluminescent material I-2b (when there is only one of them, the content of that ion) is more preferably 2% by weight or more and 23% by weight or less.

The silver ion content in photoluminescent material I-2b is more preferably 3.5% by weight or more and 28% by weight or less.

The zinc ion content in photoluminescent material I-2b is more preferably 5% by weight or more and 13% by weight or less.

Photoluminescent material I-2b may contain ions other than cesium ions, rubidium ions, silver ions, and zinc ions (hereinafter sometimes abbreviated as "other ions"). Photoluminescent material I-2b may contain one type of other ion, or may contain two or more types of other ions.

Other ions contained in photoluminescent material I-2b can be introduced into photoluminescent material I-2b by ion exchange using an aqueous solution containing the other ions.

Other ions contained in photoluminescent material I-2b include, for example, ammonium ions, sodium ions, potassium ions, calcium ions, magnesium ions, etc.

Examples of photoluminescent material I-2c include those described in Patent Document 4. The silver ion content in photoluminescent material I-2c is more preferably 7% by weight or more and 35% by weight or less.

The ammonium ion content in the photoluminescent material I-2c is preferably 0.1% by weight or more and 25% by weight or less, more preferably 1% by weight or more and 15% by weight or less.

The total content of silver ions and ammonium ions in the photoluminescent material I-2c is preferably 6% by weight or more and 40% by weight or less, more preferably 10% by weight or more and 35% by weight or less.

Photoluminescent material I-2c may contain ions other than silver ions and ammonium ions (excluding zinc ions) (hereinafter sometimes abbreviated as "other ions"). Photoluminescent material I-2c may contain one type of other ion, or may contain two or more types of other ions.

Other ions contained in photoluminescent material I-2c can be introduced into photoluminescent material I-2c by ion exchange using an aqueous solution containing the other ions.

Other ions contained in the photoluminescent material I-2c include, for example, alkali metal ions such as sodium ions, potassium ions, and cesium ions; alkaline earth metal ions such as calcium ions, strontium ions, and barium ions; and other metal ions such as nickel ions, copper ions, manganese ions, and aluminum ions. Of these, cesium ions are preferred.

When photoluminescent material I-2c contains other ions, the content thereof (when two or more types of other ions are contained, the total content of the other ions) is preferably 0.1% by weight or more and 40% by weight or less.

Photoluminescent material I-3 containing sodalite is described in, for example, Patent Document 5. Photoluminescent material I-3 can be produced by ion-exchanging sodalite by stirring and holding it in an aqueous solution containing silver ions, filtering, washing with water, and then heat-treating the resulting ion-exchanged sodalite. The heat-treatment conditions vary depending on the content of silver atoms and, if necessary, the content of zinc atoms. In the production of photoluminescent material I-3, drying at a temperature higher than room temperature is included in the heat treatment. Sodalite is easily available as a by-product of A-type zeolite, which is currently mass-produced at low cost.

The average particle size of sodalite, photoluminescent material I-3 obtained from sodalite, and photoluminescent material II obtained from photoluminescent material I-3 is preferably 0.05 μm or more and 500 μm or less, more preferably 0.5 μm or more and 50 μm or less.

Photoluminescent material I-3 is preferably sodalite containing 0.25% by weight or more and 51% by weight or less of silver atoms, more preferably sodalite containing 0.25% by weight or more and 10% by weight or less of silver atoms (hereinafter sometimes abbreviated as "photoluminescent material I-3a");
Sodalite containing 12% by weight or more and 18% by weight or less of silver atoms, produced through heat treatment at a temperature of less than 300° C. (hereinafter sometimes abbreviated as “photoluminescent material I-3b”);
Sodalite containing 20% by weight or more and 31% by weight or less of silver atoms and 7% by weight or more and 17% by weight or less of zinc atoms (hereinafter sometimes abbreviated as "photoluminescent material I-3c"), and sodalite containing 33% by weight or more and 51% by weight or less of silver atoms and 0.5% by weight or more and 11% by weight or less of zinc atoms, which is produced through heat treatment at a temperature of 300°C to 850°C (hereinafter sometimes abbreviated as "photoluminescent material I-3d").
It is at least one selected from the group consisting of. Photoluminescent material I-3a and photoluminescent material I-3b preferably do not contain an oxalate anion. Photoluminescent materials I-3a to I-3d will be described below.

Photoluminescent material I-3b (silver atom content: 12% by weight or more and 18% by weight or less) needs to be manufactured through heat treatment at a temperature of less than 300°C. On the other hand, photoluminescent material I-3d (silver atom content: 33% by weight or more and 51% by weight or less) needs to be manufactured through heat treatment at a temperature of 300°C or more. When the silver atom content is 0.25% by weight or more and 10% by weight or less (photoluminescent material I-3a) and when the silver atom content is 20% by weight or more and 31% by weight or less (photoluminescent material I-3c), they can be manufactured through heat treatment at a temperature of 300°C or more or less than 300°C.

The reason for the difference in heat treatment temperatures for producing photoluminescent material I-3 is presumed to be that the form of silver atoms required for luminescence differs in sodalite depending on the silver atom content. In sodalite obtained by low-temperature heat treatment, silver atoms exist in the form of silver ions, and in sodalite obtained by high-temperature heat treatment, silver atoms are presumed to be in the form of silver ions or silver clusters, or some of them are in the form of silver ions and the rest are in the form of silver clusters.

The temperature of the heat treatment for producing the photoluminescent material I-3a is preferably 50°C or more and 850°C or less, more preferably 100°C or more and 700°C or less, and even more preferably 150°C or more and 600°C or less. The time of the heat treatment for producing the photoluminescent material I-3a is preferably 1 hour or more and 24 hours or less, and more preferably 2 hours or more and 24 hours or less.

The temperature of the heat treatment for producing the photoluminescent material I-3b must be less than 300°C, and is preferably 50°C or higher and lower than 300°C, more preferably 100°C or higher and 270°C or lower, and even more preferably 150°C or higher and 250°C or lower. The time of the heat treatment for producing the photoluminescent material I-3b is preferably 1 hour or higher and 24 hours, and more preferably 2 hours or higher and 16 hours or lower.

The temperature of the heat treatment for producing the photoluminescent material I-3c is preferably 50°C or more and 850°C or less, more preferably 100°C or more and 700°C or less, and even more preferably 150°C or more and 600°C or less. The time of the heat treatment for producing the photoluminescent material I-3c is preferably 1 hour or more and 24 hours or less, and more preferably 2 hours or more and 24 hours or less.

The temperature of the heat treatment for producing the photoluminescent material I-3d must be 300°C or higher and 850°C or lower, preferably 300°C or higher and 700°C or lower, more preferably 350°C or higher and 650°C or lower, and even more preferably 400°C or higher and 600°C or lower. The time of the heat treatment for producing the photoluminescent material I-3d is preferably 1 hour or higher and 12 hours or lower, more preferably 2 hours or higher and 8 hours or lower.

In photoluminescent material I-3a and photoluminescent material I-3b, which have a silver atom content of 18% by weight or less, zinc atoms are not required for emission. However, photoluminescent material I-3a and photoluminescent material I-3b may also contain zinc atoms. On the other hand, in photoluminescent material I-3c and photoluminescent material I-3d, which have a silver atom content of 20% by weight or more, zinc atoms are required in addition to silver atoms for emission. The reason that zinc atoms are required when the silver atom content is high is presumably because, as described above, the form of silver atoms required for emission differs in sodalite depending on the silver atom content.

Photoluminescent material I-3 may contain atoms (hereinafter referred to as "other atoms") and/or ions (hereinafter referred to as "other ions") other than silver atoms and zinc atoms. Examples of the other atoms include transition metal atoms other than silver and zinc, alkali metal atoms, alkaline earth metal atoms, halogen atoms, etc. Examples of the other ions include ammonium ions, halide ions, etc. However, photoluminescent material I-3a and photoluminescent material I-3b preferably do not contain oxalate anions.

The content of silver atoms in the photoluminescent material I-3a is preferably 2.5% by weight or more and 10% by weight or less, more preferably 3.5% by weight or more and 8% by weight or less. The photoluminescent material I-3a may contain zinc atoms. The content of zinc atoms in the photoluminescent material I-3a is preferably 25% by weight or less, more preferably 5% by weight or more and 25% by weight or less.

The content of silver atoms in photoluminescent material I-3b is preferably 12% by weight or more and 18% by weight or less, more preferably 13% by weight or more and 17% by weight or less. Photoluminescent material I-3b may contain zinc atoms. The content of zinc atoms in photoluminescent material I-3b is preferably 0% by weight or more and 21% by weight or less, more preferably 5% by weight or more and 21% by weight or less.

The content of silver atoms in the photoluminescent material I-3c is preferably 20% by weight or more and 31% by weight or less, more preferably 22% by weight or more and 31% by weight or less. The content of zinc atoms in the photoluminescent material I-3c is preferably 7% by weight or more and 17% by weight or less, more preferably 8.5% by weight or more and 17% by weight or less.

The content of silver atoms in the photoluminescent material I-3d is preferably 33% by weight or more and 50.5% by weight or less, more preferably 35% by weight or more and 49% by weight or less. The content of zinc atoms in the photoluminescent material I-3d is preferably 0.5% by weight or more and 11% by weight or less, more preferably 0.8% by weight or more and 11% by weight or less.

The aqueous solution for extracting silver atoms from the photoluminescent material I (hereinafter sometimes abbreviated as "aqueous extraction solution") contains ammonia and cations other than silver ions. The cations other than silver ions may be nonmetallic ions such as ammonium ions, or metal ions such as alkali metal ions, alkaline earth metal ions, and zinc ions.

The cations other than silver ions preferably include alkali metal ions and/or alkaline earth metal ions. As alkali metal ions, lithium ions, sodium ions, potassium ions, and cesium ions are preferred. As alkaline earth metal ions, strontium ions and barium ions are preferred. As cations other than silver ions, more preferably, they include at least one selected from the group consisting of lithium ions, sodium ions, potassium ions, cesium ions, strontium ions, and barium ions, even more preferably, they include at least one selected from the group consisting of sodium ions, potassium ions, cesium ions, strontium ions, and barium ions, particularly preferably, they include at least one selected from the group consisting of sodium ions, potassium ions, and strontium ions, and most preferably, they include sodium ions and/or strontium ions.

Only one type of cation other than silver ions may be used, or two or more types may be used. For example, two or more types of alkali metal ions may be used as cations other than silver ions, or alkali metal ions and other cations (e.g., zinc ions) may be used.

In photoluminescent material I-2a or I-2b containing silver and zinc, if zinc ions are extracted along with silver ions, the luminescence intensity may decrease. Therefore, when using photoluminescent material I-2a or I-2b, it is preferable that the cations other than silver ions contain zinc ions. By using zinc ions, it is possible to suppress the decrease in the luminescence intensity of photoluminescent material II obtained from photoluminescent material I-2a or I-2b.

By using a cation with a small atomic weight (e.g., a sodium ion) as a cation other than silver ions, the density of photoluminescent material II can be made lower than the density of photoluminescent material I. A low-density photoluminescent material can maintain a good dispersion state in a mixture with resin, rubber, solvent, etc., compared to a high-density photoluminescent material.

The operation of extracting silver atoms from the photoluminescent material I by using an extraction aqueous solution (hereinafter referred to as "extraction operation") may be performed once or more than once. The extraction operation may be performed two or more times using one type of extraction aqueous solution (e.g., an extraction aqueous solution containing sodium ions and ammonia). The extraction operation may be performed two or more times using two or more different types of extraction aqueous solutions. For example, an extraction operation may be performed using an extraction aqueous solution containing sodium ions and ammonia, and then an extraction operation may be performed using an extraction aqueous solution containing potassium ions and ammonia.

In order to efficiently extract silver atoms from the photoluminescent material I, the concentration of cations other than silver ions in the extraction aqueous solution (when two or more cations are used, the total concentration of these cations) is preferably 0.3% by weight to 20% by weight, more preferably 0.45% by weight to 20% by weight. For the same reason, the concentration of ammonia in the extraction aqueous solution is preferably 0.12% by weight to 30% by weight, more preferably 0.18% by weight to 30% by weight.

When only alkali metal ions are used as cations other than silver ions, the preferred range of the concentration of alkali metal ions in the aqueous extract is the same as the preferred range of the concentration of cations other than silver ions in the aqueous extract described above. When cations other than alkali metal ions and alkali metal ions are used in combination as cations other than silver ions, the concentration of alkali metal ions in the aqueous extract (the total concentration when two or more types of alkali metal ions are used) is preferably 0.05% by weight or more and 10% by weight or less, more preferably 0.1% by weight or more and 5% by weight or less.

When only alkaline earth metal ions are used as cations other than silver ions, the preferred range of the concentration of alkaline earth metal ions in the aqueous extract is the same as the preferred range of the concentration of cations other than silver ions in the aqueous extract described above. When cations other than alkaline earth metal ions and alkaline earth metal ions are used in combination as cations other than silver ions, the concentration of alkaline earth metal ions in the aqueous extract (when two or more types of alkaline earth metal ions are used, the total concentration of these ions) is preferably 0.05% by weight or more and 10% by weight or less, more preferably 0.1% by weight or more and 5% by weight or less.

When only zinc ions are used as the cations other than silver ions, the preferred range of the zinc ion concentration in the aqueous extract is the same as the preferred range of the concentration of the cations other than silver ions in the aqueous extract described above. When zinc ions are used in combination with cations other than zinc ions as the cations other than silver ions, the concentration of zinc ions in the aqueous extract is preferably 0.15% by weight or more and 0.30% by weight or less, more preferably 0.20% by weight or more and 0.26% by weight or less.

The aqueous extract may contain an organic solvent that is miscible with water. Examples of organic solvents include alcohols such as methanol and ethanol, and ketones such as acetone. From the viewpoint of dissolving silver ions in the aqueous extract, the content of the organic solvent is preferably 50% by weight or less of the entire aqueous extract, and more preferably 20% by weight or less. The content of the organic solvent is a value based on the entire aqueous extract. It is most preferable that the aqueous extract does not contain an organic solvent.

To efficiently extract silver atoms from photoluminescent material I, the amount of extraction solution used is preferably 5 to 500 mL, more preferably 7.5 to 300 mL, and even more preferably 10 to 100 mL per 1 g of photoluminescent material I.

The temperature of the aqueous extraction solution during the extraction operation is preferably 0 to 30°C, more preferably 5 to 25°C, from the viewpoints of the solubility of the cations and the volatility of ammonia. The time for the extraction operation is preferably 5 minutes to 24 hours, more preferably 10 minutes to 16 hours, from the viewpoints of the volatility of ammonia and the reaction time required for the formation of an ammine complex with silver.

When photoluminescent material I-1 is used as photoluminescent material I, the silver atom content of photoluminescent material II obtained by the above-mentioned extraction operation is preferably 0.9% by weight or more and 18% by weight or less, and more preferably 1.2% by weight or more and 15% by weight or less.

When photoluminescent material I-2a is used as photoluminescent material I, the silver atom content of photoluminescent material II obtained by the above-mentioned extraction operation is preferably 0.3% by weight or more and 18% by weight or less, more preferably 0.4% by weight or more and 16% by weight or less.

When photoluminescent material I-2b is used as photoluminescent material I, the silver atom content of photoluminescent material II obtained by the above-mentioned extraction operation is preferably 0.3% by weight or more and 25% by weight or less, more preferably 0.4% by weight or more and 22% by weight or less.

When photoluminescent material I-2c is used as photoluminescent material I, the silver atom content of photoluminescent material II obtained by the above-mentioned extraction operation is preferably 0.3% by weight or more and 31% by weight or less, more preferably 0.4% by weight or more and 28% by weight or less.

When photoluminescent material I-3a is used as photoluminescent material I, the silver atom content of photoluminescent material II obtained by the above-mentioned extraction operation is preferably 0.1% by weight or more and 7.2% by weight or less, more preferably 0.2% by weight or more and 6.4% by weight or less.

When photoluminescent material I-3b is used as photoluminescent material I, the silver atom content of photoluminescent material II obtained by the above-mentioned extraction operation is preferably 0.39% by weight or more and 15% by weight or less, more preferably 0.52% by weight or more and 14% by weight or less.

When photoluminescent material I-3c is used as photoluminescent material I, the silver atom content of photoluminescent material II obtained by the above-mentioned extraction operation is preferably 0.66% by weight or more and 27% by weight or less, more preferably 0.88% by weight or more and 25% by weight or less.

When photoluminescent material I-3d is used as photoluminescent material I, the silver atom content of photoluminescent material II obtained by the above-mentioned extraction operation is preferably 1.05% by weight or more and 44% by weight or less, more preferably 1.4% by weight or more and 39% by weight or less.

The ratio of the silver atom content of photoluminescent material II obtained by the method of the present invention to the silver atom content of photoluminescent material I (silver atom content of photoluminescent material II/silver atom content of photoluminescent material I) is preferably 3/100 to 9/10, more preferably 1/25 to 3/4, and even more preferably 1/20 to 1/2. Here, the unit of content used in the ratio is "wt%".

The present invention provides a photoluminescent material (i.e., photoluminescent material II with a reduced content of silver atoms) produced by the above-mentioned method. Photoluminescent material II may be used alone or in combination of two or more types. Photoluminescent material II may also be used in combination with other photoluminescent materials. Photoluminescent material II can be used, for example, in lighting devices, luminescent paints, luminescent fibers, resin molded products, rubber molded products, light-emitting elements, sensors, etc.

The present invention will be explained in more detail below with reference to examples. However, the present invention is not limited to the following examples, and can be practiced with appropriate modifications within the scope of the above-mentioned intent, and all such modifications are included in the technical scope of the present invention.

The raw materials (e.g., A-type zeolite) used in the following examples and comparative examples were the same and obtained from the same manufacturer (e.g., Union Showa Co., Ltd.) unless otherwise specified.

The properties of the resulting photoluminescent material were evaluated as follows.
The composition of the photoluminescent material was measured using a scanning X-ray fluorescence analyzer ZSX Primus III+ manufactured by Rigaku Corporation, and the mass (A) per mole of the photoluminescent material was calculated based on the results. Next, the lattice constant of the photoluminescent material was measured using a fully automatic multipurpose X-ray diffraction device SmartLab manufactured by Rigaku Corporation, and the lattice constant was cubed to calculate the volume (B, unit: cm ³ ) per molecule of the photoluminescent material. From these values, the density (unit: g/cm ³ ) of the photoluminescent material was calculated using the following formula.
Density (g/cm ³ )=A (g)/Avogadro's constant (6.02×10 ⁻²³ )/B (cm ³ )
Furthermore, the emission intensity of this photoluminescent material was measured using a FluoroMax-4 fluorescence spectrophotometer manufactured by Horiba, Ltd.

Example 1
(1) Production of photoluminescent material I (A-type zeolite containing silver atoms) 5.00 g of A-type zeolite (manufactured by Union Showa Co., Ltd., average particle size 5 μm, containing 11 wt% sodium ions as exchangeable cations), 0.93 g of silver nitrate (manufactured by Inshou Kikinzoku Co., Ltd., purity 99.8 wt%), 2.85 g of zinc nitrate hexahydrate (manufactured by Kishida Chemical Co., Ltd., purity 99 wt%), and 30 mL of ion-exchanged water were mixed, and the resulting mixture was stirred and held at room temperature for 1 hour. Thereafter, stirring was stopped, and the solid was collected by suction filtration, and the collected solid was dried at 105 ° C. for 16 hours and then calcined at 230 ° C. for 16 hours to obtain 5.95 g of photoluminescent material (A-type zeolite containing silver atoms).

(2) Production of Photoluminescent Material II with Reduced Content of Silver Atoms 0.28 g of sodium nitrate (Nacalai Tesque, Inc., purity 99 wt%), 0.33 g of zinc nitrate hexahydrate, 1.5 mL of aqueous ammonia (Kishida Chemical Co., Ltd., ammonia concentration 28.7 wt%), and 30 mL of ion-exchanged water were mixed to obtain an aqueous extract (sodium ion concentration in the aqueous extract: 0.24 wt%, zinc ion concentration: 0.23 wt%, ammonia concentration: 1.20 wt%).

1.00 g of the photoluminescent material (A-type zeolite containing silver atoms) obtained in (1) above was added to the obtained aqueous extract solution, and the resulting mixture was stirred at room temperature for 1 hour. The solid was then collected by suction filtration and dried at 105°C for 16 hours to obtain 0.98 g of a photoluminescent material with a reduced content of silver atoms.

Comparative Example 1: Photoluminescent material (A-type zeolite containing silver atoms)
The photoluminescent material (A-type zeolite containing silver atoms) produced in Example 1(1) was used as Comparative Example 1.

Comparative Example 2: Production of photoluminescent material (A-type zeolite containing silver atoms) 5.00 g of A-type zeolite, 0.093 g of silver nitrate, 2.85 g of zinc nitrate hexahydrate, and 30 mL of ion-exchanged water were mixed, and the resulting mixture was stirred and held at room temperature for 1 hour. After that, the stirring was stopped, and the solid was collected by suction filtration. The collected solid was dried at 105°C for 16 hours, and then calcined at 230°C for 16 hours to obtain 5.60 g of photoluminescent material (A-type zeolite containing silver atoms).

The compositions and densities of the photoluminescent materials obtained in Example 1 (2) and Comparative Examples 1 and 2 are shown in Table 1. Table 1 also shows the relative luminescence intensities of the photoluminescent materials obtained in Example 1 (2) and Comparative Examples 1 and 2, calculated with the luminescence intensity of the photoluminescent material obtained in Comparative Example 1 set to 1.

The photoluminescent material obtained in Example 1(2) had a lower silver atom content than that obtained in Comparative Example 1, but the luminescence intensity of the photoluminescent material obtained in Example 1(2) was higher than that of the photoluminescent material obtained in Comparative Example 1.

The silver atom content of the photoluminescent materials obtained in Example 1 (2) and Comparative Example 2 was equivalent, but the luminescence intensity of the photoluminescent material obtained in Example 1 (2) was higher than that of the photoluminescent material obtained in Comparative Example 2, which did not include a step of reducing silver atoms.

Example 2
(1) Production of photoluminescent material I (sodalite containing silver atoms) 10.00 g of A-type zeolite, 25.60 g of sodium hydroxide (manufactured by Nacalai Tesque, Inc., purity 97% by weight), and 38.40 g of ion-exchanged water were mixed, and the resulting mixture was allowed to stand for 16 hours at 95° C. Thereafter, the solid was collected by suction filtration and dried at 105° C. for 16 hours to obtain 10.00 g of sodalite (average particle size 3 μm, containing 12% by weight of sodium ions as exchangeable cations).

5.00 g of the obtained sodalite, 0.070 g of silver nitrate, 1.85 g of zinc nitrate hexahydrate, 2.51 g of potassium nitrate (Nacalai Tesque, purity 99 wt%), and 30 mL of ion-exchanged water were mixed, and the resulting mixture was stirred at room temperature for 1 hour. The solid was then collected by suction filtration, dried at 105°C for 16 hours, and then calcined at 230°C for 16 hours to obtain 5.57 g of photoluminescent material (sodalite containing silver atoms).

(2) Preparation of photoluminescent material II with reduced silver atom content 0.28 g of sodium nitrate, 0.25 g of potassium nitrate, 0.4 mL of ammonia water, and 30 mL of ion-exchanged water were mixed to obtain an aqueous extract solution (the concentration of sodium ions in the aqueous extract solution was 0.25 wt %, the concentration of potassium ions was 0.31 wt %, and the concentration of ammonia was 0.33 wt %).

1.00 g of the photoluminescent material (sodalite containing silver atoms) obtained in (1) above was added to the obtained aqueous extract solution, and the resulting mixture was stirred at room temperature for 1 hour. The solid was then collected by suction filtration and dried at 105°C for 16 hours to obtain 0.99 g of a photoluminescent material with a reduced content of silver atoms.

Comparative Example 3: Photoluminescent material (sodalite containing silver atoms)
The photoluminescent material (sodalite containing silver atoms) produced in Example 2(1) was used as Comparative Example 3.

Comparative Example 4: Production of photoluminescent material (sodalite containing silver atoms) 5.00g of sodalite, 0.018g of silver nitrate, 1.85g of zinc nitrate hexahydrate, 2.51g of potassium nitrate and 30mL of ion-exchanged water were mixed, and the mixture was stirred at room temperature for 1 hour. Then, the solid was collected by suction filtration, dried at 105°C for 16 hours, and then calcined at 230°C for 16 hours to obtain 5.58g of photoluminescent material (sodalite containing silver atoms).

The compositions and densities of the photoluminescent materials obtained in Example 2(2) and Comparative Examples 3 and 4 are shown in Table 2. Table 2 also shows the relative luminescence intensities of the photoluminescent materials obtained in Example 2(2) and Comparative Examples 3 and 4, calculated with the luminescence intensity of the photoluminescent material obtained in Comparative Example 3 set to 1.

The photoluminescent material obtained in Example 2(2) had a lower silver atom content than that obtained in Comparative Example 3, but the luminescence intensity of the photoluminescent material obtained in Example 2(2) was higher than that of the photoluminescent material obtained in Comparative Example 3.

The silver atom content of the photoluminescent materials obtained in Example 2(2) and Comparative Example 4 was equivalent, but the luminescence intensity of the photoluminescent material obtained in Example 2(2) was higher than that of the photoluminescent material obtained in Comparative Example 4, which did not include a step of reducing silver atoms.

Example 3
(1) Preparation of photoluminescent material I (X-type zeolite containing silver atoms) 0.60 g of silver nitrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was dissolved in ion-exchanged water to prepare 100 mL of aqueous solution. 3.00 g of X-type zeolite (manufactured by Tosoh Corporation, average particle size 5 μm, containing 8 wt% sodium ions as exchangeable cations) was added to the obtained aqueous solution, and the obtained mixture was stirred at 25 ° C. for 2 hours. Then, the solid was collected by suction filtration and dried at 70 ° C. for 24 hours to obtain 4.05 g of photoluminescent material (X-type zeolite containing silver atoms).

(2) Preparation of a photoluminescent material with reduced silver atom content 2.19 g of sodium nitrate and 3.6 mL of aqueous ammonia were mixed with ion-exchanged water to obtain 100 mL of an aqueous extract solution (the concentration of sodium ions in the aqueous extract solution was 0.56 wt %, and the concentration of ammonia was 0.88 wt %).

3.00 g of the photoluminescent material (X-type zeolite containing silver atoms) obtained in (1) above was added to the obtained aqueous extract solution, and the resulting mixture was stirred at room temperature for 2 hours. The solid was then collected by suction filtration and dried at 70°C for 24 hours to obtain 2.36 g of a photoluminescent material with a reduced content of silver atoms.

Comparative Example 5: Photoluminescent material (X-type zeolite containing silver atoms)
The photoluminescent material (X-type zeolite containing silver atoms) produced in Example 3(1) was used as Comparative Example 5.

Comparative Example 6: Production of photoluminescent material (X-type zeolite containing silver atoms) 0.033 g of silver nitrate was dissolved in ion-exchanged water to prepare 100 mL of aqueous solution. 0.95 g of X-type zeolite was added to the obtained aqueous solution, and the obtained mixture was stirred at 25 ° C. for 2 hours. Then, the solid was collected by suction filtration and dried at 70 ° C. for 24 hours to obtain 1.00 g of photoluminescent material (X-type zeolite containing silver atoms).

The compositions and densities of the photoluminescent materials obtained in Example 3(2) and Comparative Examples 5 and 6 are shown in Table 3. In addition, the relative luminescence intensities of the photoluminescent materials obtained in Example 3(2) and Comparative Examples 5 and 6, calculated with the luminescence intensity of the photoluminescent material obtained in Comparative Example 5 set to 1, are shown in Table 3.

The photoluminescent material obtained in Example 3(2) had a lower silver atom content than that obtained in Comparative Example 5, but the luminescence intensity of the photoluminescent material obtained in Example 3(2) was equivalent to that of the photoluminescent material obtained in Comparative Example 5.

The silver atom content of the photoluminescent materials obtained in Example 3(2) and Comparative Example 6 was equivalent, but the luminescence intensity of the photoluminescent material obtained in Example 3(2) was higher than that of the photoluminescent material obtained in Comparative Example 6, which did not include a step of reducing silver atoms.

Example 4
(1) Production of photoluminescent material I (A-type zeolite containing silver atoms) 5.00g of A-type zeolite, 0.47g of silver nitrate, 2.49g of zinc nitrate hexahydrate, 1.97g of ammonium nitrate (Kanto Chemical Co., Ltd., purity 99% by weight), 2.67g of cesium nitrate (Mitsuwa Chemical Co., Ltd., purity 99% by weight) and 30mL of ion-exchanged water were mixed, and the resulting mixture was stirred at room temperature for 1 hour. Then, the solid was collected by suction filtration, dried at 105°C for 16 hours, and then calcined at 150°C for 16 hours to obtain 6.30g of photoluminescent material (A-type zeolite containing silver atoms).

(2) Production of Photoluminescent Material II with Reduced Content of Silver Atoms 0.58 g of strontium nitrate (Kishida Chemical Co., Ltd., purity 98 wt%), 0.4 mL of ammonia water, and 30 mL of ion-exchanged water were mixed to obtain an aqueous extract solution (strontium ion concentration in the aqueous extract solution: 0.76 wt%, ammonia concentration: 0.33 wt%).

1.00 g of the photoluminescent material (A-type zeolite containing silver atoms) obtained in (1) above was added to the obtained aqueous extract solution, and the resulting mixture was stirred at room temperature for 1 hour. The solid was then collected by suction filtration and dried at 105°C for 16 hours, yielding 0.82 g of a photoluminescent material with a reduced content of silver atoms.

Comparative Example 7: Photoluminescent material (A-type zeolite containing silver atoms)
The photoluminescent material I-2b (A-type zeolite containing silver atoms) prepared in Example 4(1) was used as Comparative Example 7.

Comparative Example 8: Production of photoluminescent material (A-type zeolite containing silver atoms) 5.00g of A-type zeolite, 0.33g of silver nitrate, 2.85g of zinc nitrate hexahydrate, 1.97g of ammonium nitrate, 0.53g of cesium nitrate, 2.90g of strontium nitrate and 30mL of ion-exchanged water were mixed, and the mixture was stirred at room temperature for 1 hour.Then, the solid was collected by suction filtration, dried at 105°C for 16 hours, and then calcined at 150°C for 16 hours to obtain 5.98g of photoluminescent material (A-type zeolite containing silver atoms).

The compositions and densities of the photoluminescent materials obtained in Example 4(2) and Comparative Examples 7 and 8 are shown in Table 4. Table 4 also shows the relative luminescence intensities of the photoluminescent materials obtained in Example 4(2) and Comparative Examples 7 and 8, calculated with the luminescence intensity of the photoluminescent material obtained in Comparative Example 7 set to 1.

The photoluminescent material obtained in Example 4(2) had a lower silver atom content than that obtained in Comparative Example 7, but the luminescence intensity of the photoluminescent material obtained in Example 4(2) was equivalent to that of the photoluminescent material obtained in Comparative Example 7.

The silver atom content of the photoluminescent materials obtained in Example 4(2) and Comparative Example 8 was equivalent, but the luminescence intensity of the photoluminescent material obtained in Example 4(2) was higher than that of the photoluminescent material obtained in Comparative Example 8, which did not include a step of reducing silver atoms.

Example 5
(1) Production of photoluminescent material I (sodalite containing silver atoms) 5.00 g of sodalite produced in the same manner as in Example 2(1), 0.070 g of silver nitrate, 2.46 g of zinc nitrate hexahydrate, and 30 mL of ion-exchanged water were mixed, and the resulting mixture was stirred for 3 hours at 80° C. Thereafter, the solid was collected by suction filtration, dried at 105° C. for 16 hours, and then baked at 230° C. for 16 hours to obtain 5.81 g of photoluminescent material (sodalite containing silver atoms).

(2) Production of Photoluminescent Material II with Reduced Content of Silver Atoms 0.75 g of sodium nitrate, 0.4 mL of aqueous ammonia, 24 mL of ion-exchanged water, and 6 mL of methanol (Kanto Chemical Co., Ltd., purity 99.8 wt%) were mixed to obtain an aqueous extract (sodium ion concentration in the aqueous extract: 0.68 wt%, ammonia concentration: 0.44 wt%, methanol concentration: 15.9 wt%).

1.00 g of the photoluminescent material (sodalite containing silver atoms) obtained in (1) above was added to the obtained aqueous extract solution, and the resulting mixture was stirred at room temperature for 1 hour. The solid was then collected by suction filtration and dried at 105°C for 16 hours to obtain 0.99 g of a photoluminescent material with a reduced content of silver atoms.

Comparative Example 9: Photoluminescent material (sodalite containing silver atoms)
The photoluminescent material (sodalite containing silver atoms) produced in Example 5(1) was used as Comparative Example 9.

The compositions and densities of the photoluminescent materials obtained in Example 5(2) and Comparative Example 9 are shown in Table 5. In addition, the relative luminescence intensities of the photoluminescent materials obtained in Example 5(2) and Comparative Example 9, calculated with the luminescence intensity of the photoluminescent material obtained in Comparative Example 9 set to 1, are shown in Table 5.

The photoluminescent material obtained in Example 5(2) had a lower silver atom content than that obtained in Comparative Example 9, but the luminescence intensity of the photoluminescent material obtained in Example 5(2) was equivalent to that of the photoluminescent material obtained in Comparative Example 9.

Experimental Example: Measurement of the luminescence intensity of a cured product containing a photoluminescent material 0.75 g of liquid A and 0.75 g of liquid B of a two-component silicone rubber for LEDs ("SCR-1012" manufactured by Shin-Etsu Chemical Co., Ltd.) and 0.05 g of the photoluminescent material obtained in Example 1 (2) or the photoluminescent material of Comparative Example 1 (i.e., the photoluminescent material obtained in Example 1 (1)) were mixed. The luminescence intensity of the resulting mixture immediately after preparation was measured using a FluoroMax-4 fluorescence spectrophotometer manufactured by Horiba, Ltd. Thereafter, the mixture was allowed to stand in a 105°C air blower dryer for 1 hour to prepare a cured product, and the luminescence intensity of the resulting cured product was measured in the same manner as above. The relative luminescence intensity of the cured product, calculated assuming that the luminescence intensity of the mixture immediately after preparation was 1, is shown in Table 6.

The cured product obtained using the photoluminescent material of Comparative Example 1 was visually observed to have discolored, and its luminescence intensity was significantly lower than that of the mixture immediately after preparation. On the other hand, the cured product obtained using the photoluminescent material obtained in Example 1 (2) did not discolor, and its luminescence intensity was almost unchanged compared to that of the mixture immediately after preparation.

The photoluminescent material obtained by the manufacturing method of the present invention can be used, for example, in lighting devices, luminescent paints, luminescent fibers, resin molded products, rubber molded products, light-emitting elements, sensors, etc.

Claims (7)

A method for producing a photoluminescent material that emits visible light when irradiated with light, comprising the steps of:
the method comprising obtaining a photoluminescent material II having a reduced content of silver atoms by extracting silver atoms from a photoluminescent material I containing silver atoms in an aqueous solution containing alkali metal ions and/or alkaline earth metal ions, ammonia, and zinc ions ; and the photoluminescent material I is a zeolite containing silver atoms. The method according to claim 1, wherein the photoluminescent material I is at least one selected from the group consisting of faujasite-type zeolite containing silver atoms, A-type zeolite containing silver atoms, and sodalite containing silver atoms. The method according to claim 2, wherein the faujasite-type zeolite containing silver atoms is a faujasite-type zeolite containing 5% by weight or more and 30% by weight or less of silver ions. The method according to claim 2 or 3, wherein the A-type zeolite containing silver atoms is an A-type zeolite containing 2.5% by weight or more and 40% by weight or less of silver ions. The method according to any one of claims 2 to 4, wherein the sodalite containing silver atoms is sodalite containing 0.25% by weight or more and 51% by weight or less of silver atoms. The method according to any one of claims 1 to 5, wherein the ratio of the silver atomic content of the photoluminescent material II to the silver atomic content of the photoluminescent material I (silver atomic content of the photoluminescent material II/silver atomic content of the photoluminescent material I) is 3/100 to 9/10 . A photoluminescent material produced by the method according to any one of claims 1 to 6 .