JP7342484B2 - Method for manufacturing luminescent material and luminescent material - Google Patents

Description

The present invention relates to a method for producing a luminescent material and a luminescent material.

A luminescent material is a material that stores the energy of irradiated light and emits light even after the light irradiation is stopped. Luminescent materials are used in daily necessities such as clock faces and key chains, as well as evacuation guide boards in underground facilities.
The currently popular green phosphorescent material is SrAl ₂ O ₄ activated with two types of rare earth elements, europium and dysprosium. It is known that there is a correlation between the amount of rare earth added and the afterglow characteristics of the phosphorescent material, and if the amount added is small, the luminescent characteristics will deteriorate (see Patent Document 1). Regarding luminescent materials, various studies have been made to improve the afterglow characteristics (see Patent Documents 2 to 9).

Patent No. 4597865 Japanese Patent Application Publication No. 2015-214702 Japanese Patent Application Publication No. 2006-152242 Japanese Patent Application Publication No. 2001-271064 Japanese Unexamined Patent Publication No. 8-127772 Japanese Patent Application Publication No. 7-324186 Japanese Patent Application Publication No. 7-11250 International Publication No. 2005/044944 Japanese Patent Application Publication No. 2004-323656

As mentioned above, the currently popular phosphorescent materials are made by activating rare earth elements in a base material such as SrAl ₂ O ₄ , but due to the rarity of rare earth elements compared to other metals and their ubiquitous distribution, Concerns have arisen about Japan's ability to secure a stable supply over the medium to long term due to the high dependence on specific producing countries and the difficulty of replacing them. Therefore, there is a need to replace and reduce the amount of rare earth elements used, but as shown in Patent Document 1 mentioned above, there is a correlation between the amount of rare earth elements added and the phosphorescent properties of the phosphorescent material, and if the amount added is small, The phosphorescent properties will deteriorate. In addition, when manufacturing a luminescent material using SrAl ₂ O ₄ as a base material, the amount of Al is generally added to the amount of Sr so that it is more than the stoichiometric composition, but in this case, Sr ₄ Al ₁₄ Strontium aluminate having other composition ratios such as O ₂₅ is produced as a by-product, resulting in a mixed phase state. Since the rare earth element is also dissolved in the by-produced heterophase, the amount of the rare earth element dissolved in solid solution in SrAl ₂ O ₄ is reduced, and the phosphorescence brightness is lowered, so it is necessary to add an excessive amount of the rare earth element. For these reasons, it is currently difficult to reduce the amount of rare earth elements added.
Furthermore, in the conventionally commonly adopted process (dry raw material mixing → calcination → pulverization), there is a problem that different phases are likely to occur because the pulverization and mixing of the raw materials is insufficient. Furthermore, since the phosphorescent material obtained by firing is sintered and very hard, a large amount of fine particles are generated during the pulverization process, resulting in a very broad particle size distribution. The phosphorescence intensity and phosphorescence time of a phosphorescent material are correlated with particle size, and smaller particles tend to have lower phosphorescence brightness and shorter phosphorescence time. In other words, if particles with widely different particle sizes are mixed into resin etc., the light emission will be uneven, so a classification process to remove fine particles and coarse particles is essential in the manufacturing process of phosphorescent materials. The problem is that the yield is low, which is one of the causes of high costs.
As described above, there are currently various problems that need to be solved with conventional luminescent materials.

In view of the above-mentioned current situation, an object of the present invention is to provide a method for manufacturing a phosphorescent material that has high luminance characteristics and emits homogeneous light even when using fewer rare earth elements than before.

The present inventors investigated a method for manufacturing a luminescent material that has high luminance characteristics and emits homogeneous light even when using fewer rare earth elements than conventional methods, and found that a reaction vessel equipped with a grinding media agitation type grinder was used. After obtaining a raw material mixture by supplying water and/or an organic solvent, an alkaline earth metal compound, an alkali metal compound, a rare earth compound, and a Group 13 element compound at a predetermined molar ratio into the reaction vessel, Then, the mixing/pulverizing process to obtain a mixed slurry from the raw material mixture is performed until D50 calculated from the particle size distribution of the mixed slurry becomes 1.7 μm or less and D90 becomes 2.7 μm or less, and the mixing/pulverizing process When the mixed slurry obtained in step 1 is adjusted to a viscosity of 40 mPa・sec or higher and then spray-dried to produce a luminescent material, it has high luminance characteristics and emits homogeneous light even with the use of less rare earth elements than before. It was discovered that a luminescent material can be obtained, and the present invention was completed.

That is, the present invention provides water and/or an organic solvent, an alkaline earth metal compound, an alkali metal compound, a rare earth compound, and a Group 13 element compound in the following molar ratio in a reaction vessel equipped with a grinding media stirring type grinder. (1) to obtain a raw material mixture by supplying the mixed slurry with a mixture slurry, and mixing the raw material mixture in the reaction vessel until D50 calculated from the particle size distribution of the mixed slurry becomes 1.7 μm or less and D90 becomes 2.7 μm or less.・Includes a step (2) of performing a pulverization treatment to obtain a mixed slurry, and a step (3) of spray-drying the mixed slurry obtained by the mixing and pulverization treatment after adjusting it to a viscosity of 40 mPa·sec or more. This is a method for producing a luminescent material characterized by the following.
1.88<E/(A+B+C)≦2.10
0.001<D/(A+B+C)<0.025
0<B/(A+B+C)<0.02
0<F/(A+B+C)<0.03
A: Total number of moles of alkaline earth metal elements in the alkaline earth metal compound B: Total number of moles of alkali metal elements in the alkali metal compound C: Total number of moles of rare earth elements in the rare earth compound D: In each rare earth compound Number of moles of each rare earth element E: Total number of moles of Group 13 elements excluding boron in the Group 13 element compound F: Number of moles of boron in the Group 13 element compound

The above-mentioned grinding media stirring type grinder is preferably a bead mill.

The Group 13 element compounds fed into the reaction vessel are preferably aluminum compounds and boron compounds.

The present invention also provides a luminous material in which a compound represented by SrAl ₂ O ₄ is used as a host crystal and europium, dysprosium, lithium, and boron are added,
The value obtained by dividing the number of moles of europium by the total number of moles of strontium, europium, dysprosium and lithium is more than 0.001 and less than 0.025,
The value obtained by dividing the number of moles of dysprosium by the total number of moles of strontium, europium, dysprosium and lithium is more than 0.001 and less than 0.025,
The value obtained by dividing the number of moles of aluminum by the total number of moles of strontium, europium, dysprosium and lithium exceeds 1.88 and is not more than 2.10,
The value obtained by dividing the number of moles of lithium by the total number of moles of strontium, europium, dysprosium and lithium is greater than 0 and less than 0.02,
It is also a luminescent material characterized in that the value obtained by dividing the number of moles of boron by the total number of moles of strontium, europium, dysprosium, and lithium is greater than 0 and less than 0.03.

The luminescent material preferably has a rare earth element maldistribution rate of 1% or less, which is determined by the following method from image analysis of a reflected electron image of a cross section of the luminescent material.
[Measurement of uneven distribution rate of rare earth atoms]
In the histogram of the result of color determination using 256 gray levels for each pixel of the backscattered electron image of the cross section of the luminescent material, the peak area a is between 150 and 200 gray levels, which is the area occupied by the host crystal, and the rare earth element The value (b/a) obtained by dividing the peak area b in the range where the gray level, which is the area occupied, is 250 or more is defined as the uneven distribution ratio of rare earth atoms.

The above-mentioned phosphorescent material may have a D25 value divided by a D75 value obtained by particle size distribution measurement using a laser diffraction/scattering particle size distribution meter using ethanol as a dispersion medium, and the value may exceed 0.45. preferable.

The method for producing a phosphorescent material of the present invention is a useful method for producing a phosphorescent material that can produce a phosphorescent material that has excellent luminance characteristics and emits homogeneous light even when using fewer rare earth elements than conventional methods.

Preferred embodiments of the present invention will be specifically described below, but the present invention is not limited to the following description, and can be applied with appropriate modifications within the scope of the gist of the present invention.

1. Method for producing a luminescent material The method for producing a luminescent material of the present invention involves adding water and/or an organic solvent, an alkaline earth metal compound, an alkali metal compound, a rare earth compound, and , Step (1) of supplying a group 13 element compound at a predetermined ratio to obtain a raw material mixture, and until D50 calculated from the particle size distribution of the mixed slurry becomes 1.7 μm or less and D90 becomes 2.7 μm or less. In the reaction vessel, a step (2) of mixing and pulverizing the raw material mixture obtained in step (1) to obtain a mixed slurry; It is characterized by including a step (3) of adjusting the viscosity to 40 mPa·sec or more and then spray drying.
When manufactured by a manufacturing method including such steps, the rare earth element can be efficiently solid-dissolved in the base material, and a luminescent material with uniform particle size and narrow particle size distribution can be obtained. As a result, it is possible to obtain a phosphorescent material that has excellent brightness characteristics and uniformity of light emission, and has less unevenness in brightness when formed into a sheet, even when using a smaller amount of rare earth elements than in the past. In addition, since a phosphorescent material with a narrow particle size distribution can be obtained, there is no need for a classification process, and even if a classification process is provided, the proportion of phosphorescent material that is sorted out is small, resulting in a high yield and excellent characteristics. materials can be obtained.

In the above step (1), water and/or an organic solvent, an alkaline earth metal compound, an alkali metal, a rare earth compound, and a Group 13 element compound are supplied into a reaction vessel equipped with a grinding media stirring type grinder. Ru. The ratio of these raw materials supplied is characterized by the following molar ratio.
1.88<E/(A+B+C)≦2.10
0.001<D/(A+B+C)<0.025
0<B/(A+B+C)<0.02
0<F/(A+B+C)<0.03
A: Total number of moles of alkaline earth metal elements in the alkaline earth metal compound B: Total number of moles of alkali metal elements in the alkali metal compound C: Total number of moles of rare earth elements in the rare earth compound D: In each rare earth compound Number of moles of each rare earth element E: Total number of moles of Group 13 elements excluding boron in the Group 13 element compound F: Number of moles of boron in the Group 13 element compound It can be said that just the right amount of phosphorescent material is supplied, and the by-product of foreign phases is sufficiently suppressed, so that the obtained phosphorescent material has excellent phosphorescent brightness.

The amount of water and/or organic solvent supplied in the above step (1) is based on a total of 100 parts by weight of the alkaline earth metal compound, alkali metal, rare earth compound, and Group 13 element compound supplied into the reaction vessel. The amount is preferably 100 to 300 parts by weight. With such a ratio, the raw materials can be efficiently pulverized and mixed.
Note that the "amount of water and/or organic solvent" here refers to the amount when only either water or organic solvent is supplied, and the amount when both water and organic solvent are supplied. means their total amount.

The alkaline earth metal compound supplied in the above step (1) is not particularly limited, but includes compounds of one or more metals selected from Be, Mg, Ca, Sr, and Ba. Examples of such compounds include carbonates, oxides, chlorides, sulfates, and nitrates of the above metals.
Among them, a compound of at least one metal selected from calcium (Ca), strontium (Sr), and barium (Ba) is preferred, and strontium carbonate is particularly preferred because it is easy to handle.

The alkali metal compound supplied in the above step (1) is not particularly limited, but includes compounds of one or more metals selected from Li, Na, K, Rb, Cs, and Fr. Examples of such compounds include carbonates, oxides, chlorides, sulfates, and nitrates of the above metals.
Among them, a compound of at least one metal selected from lithium (Li), sodium (Na), and potassium (K) is preferred, and lithium carbonate is particularly preferred because it is easy to handle.

The rare earth compound supplied in the above step (1) is selected from Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, etc. Examples include compounds of one or more metals. Examples of such compounds include carbonates, oxides, chlorides, sulfates, and nitrates of the above metals.
Among these, compounds of at least one metal selected from cerium (Ce), neodymium (Nd), europium (Eu), dysprosium (Dy), holmium (Ho), and erbium (Er) are preferred, and among these compounds, europium ( Eu) compounds are preferred, and europium oxide is particularly preferred since it is easy to handle. This is because Eu is an element that strongly acts as a luminescent center of the material. Further, adding rare earth elements such as Dy, Ho, Ce, Nd, and Er to the Eu luminescent center has the effect of lengthening the phosphorescence time, so the combination and amount thereof are important from the viewpoint of phosphorescence.

The Group 13 element compound supplied in the above step (1) is not particularly limited, but includes compounds of one or more elements selected from B, Al, Ga, In, Tl, etc. Examples of such compounds include oxides, hydroxides, chlorides, sulfates, and nitrates.
Among these, aluminum (Al) compounds are preferred, and aluminum oxide is particularly preferred since it is easy to handle.

A boron compound is also preferred as the Group 13 element compound. Examples of boron compounds include boric acid and boron oxide.

In the above step (1), water and/or an organic solvent is supplied, and examples of the organic solvent include alcohols such as methanol, ethanol, isopropyl alcohol, and ethylene glycol, and ketones such as acetone and methyl ethyl ketone. Examples include water-soluble organic solvents such as . Further, other dispersion media may be included within a range that does not impair the effects of the present invention.

The raw material supplied in step (1) above may contain other components as long as it contains water and/or an organic solvent, an alkaline earth metal compound, an alkali metal, a rare earth compound, and a Group 13 element compound. Good too.
Other components include a dispersant for improving the dispersibility of the particles, a flux component for increasing the crystallinity of the particles, and the like.

Examples of the dispersant include, but are not particularly limited to, anionic surfactants and nonionic surfactants. Examples of anionic surfactants include ammonium polycarboxylate, sodium polycarboxylate, sodium hexametaphosphate, etc. Examples of nonionic surfactants include polyoxyethylene alkyl ether, polyoxyethylene hydrogenated castor oil, polyoxyethylene Examples include monofatty acid ester, polyoxyethylene sorbitan monofatty acid ester, and the like. These may be used alone or in combination of two or more.

Flux components for increasing the crystallinity of the particles include, but are not particularly limited to, calcium fluoride, magnesium fluoride, aluminum fluoride, ammonium fluoride, sodium chloride, potassium chloride, lithium chloride, ammonium bromide, and iodide. Examples include compounds such as ammonium, potassium iodide, sodium hydroxide, potassium hydroxide, ammonium sulfate, sodium sulfate, potassium sulfate, sodium nitrate, and ammonium nitrate. These may be used alone or in combination of two or more.

In step (1) above, a reaction vessel equipped with a grinding media agitation type grinder is used. Here, a grinding media agitation type grinder is defined as a grinding medium that is put into a grinding container, and is stirred together with the material to be ground by shaking or rotating the grinding container (rotation or revolution), or A pulverizer that performs pulverization by directly stirring.
Examples of the grinding media agitation type grinder are not particularly limited, but preferably any one selected from the group consisting of planetary mills, bead mills, and vibration mills. Among these, bead mills are particularly preferred.

The above-mentioned grinding media include, but is not particularly limited to, alumina balls, zirconia balls, silicon nitride balls, carbon nitride balls, glass beads, nylon-coated iron core balls, etc., and those having a diameter of 10 mm or less are mainly used. Among them, alumina balls are preferred. This is because Group 13 elements are included as constituent elements of the raw material mixture, so even if those components are mixed in from balls made of materials composed of elements of the same group, their effect as impurities is small.
By using a grinding medium of a size appropriate for the purpose, the raw material mixture is strongly stirred together with the grinding medium in the grinding container, allowing efficient grinding, mixing, and dispersion into the dispersion medium. .

The above step (2) uses a grinding media agitation type pulverizer to perform a mixing and pulverizing process to obtain a mixed slurry from the raw material mixture obtained in the above step (1), with a D50 calculated from the particle size distribution of the mixed slurry. This step is performed until the thickness is 1.7 μm or less and D90 is 2.7 μm or less. Through this mixing and pulverizing process, the raw materials are pulverized, mixed, and dispersed into the dispersion medium at the same time.
In the present specification, "D50 (or D90) calculated from the particle size distribution of the slurry" refers to particles present in the water and/or organic solvent supplied in step (1), such as the alkaline earth metal compound of the raw material. , a D50 (or D90) value calculated from the particle size distribution measured without distinguishing between particles made of alkali metal compounds, rare earth compounds, Group 13 element compounds, and their reactants and composites.
D50 and D90 calculated from the particle size distribution are the volume-based cumulative 50% particle diameter and the volume-based cumulative 90% particle diameter, respectively, that is, in the cumulative particle amount curve of the particle size distribution measurement results, the cumulative amount is 50% and 90%. It means the particle size when it occupies %. The particle size distribution can be measured by a laser diffraction/scattering type particle size distribution measuring device described below.

The mixing and pulverizing treatment in step (2) above may be performed until D50 calculated from the particle size distribution of the mixed slurry is 1.7 μm or less and D90 is 2.7 μm or less, but D50 is 1.7 μm or less. D90 is preferably 2.5 μm or less. Further, the lower limits of D50 and D90 are not particularly limited, but in reality, both D50 and D90 usually take values of 0.1 μm or more.

The mixing and pulverizing process in the above step (2) is not particularly limited in its method as long as the D50 and D90 of the mixed slurry are below predetermined values. It is preferable to carry out the process under the condition that G≧7.1, where G is G (m/sec ² ). By performing the mixing under such conditions, the raw materials can be more thoroughly dispersed and pulverized, and the resulting phosphorescent material has better phosphorescence brightness. The upper limit of G is not particularly limited, and can be appropriately set by those skilled in the art within the range of normal operating conditions based on the capacity and specifications of the grinding media agitation type grinder.

Here, "centrifugal acceleration" means a physical quantity expressed by rω ² that occurs when a certain object is rotated at a rotation radius r and a rotational angular velocity ω. Generally, the unit of centrifugal acceleration is "relative centrifugal acceleration," which is expressed as a ratio to the earth's gravitational acceleration. As an example, if an object is rotating N around the rotation axis, ω = 2πN/60 (rad/s), Earth's gravitational acceleration = 9.81 (m/s ² ), and the relative centrifugal acceleration G is as follows: It can be expressed by the following formula (1).

Furthermore, in the case of a planetary mill that rotates and revolves, the relative centrifugal acceleration G can be determined by the following equation (2).

In the formula, rs means the revolution radius (m), rp means the container radius (m), iw means the rotation/revolution ratio, and ω means the revolution speed (rpm).

The time for carrying out the above step (2) is not particularly limited, and may be carried out until the particle size distribution of the mixed slurry reaches a predetermined value, but in consideration of production efficiency, it is preferably carried out for 0.1 to 5 hours. More preferably, it is carried out for 0.1 to 2 hours.

The above step (3) is a step in which the mixed slurry obtained in step (2) is adjusted to a viscosity of 40 mPa·sec or more and then spray-dried. Through this drying process, it is possible to maintain a state in which the raw materials are uniformly mixed together. Furthermore, the dry powder obtained by spray drying has a low density and a narrow particle size distribution.
Here, the spray dryer is equipment that sprays slurry into gas and rapidly dries it to produce dry powder. The gas used for drying is generally a high temperature gas.
Examples of the spraying method include a rotating disk, a pressure nozzle, a two-fluid nozzle, etc. Among them, the rotating disk method is preferable because it allows the particle size of the dry powder to be controlled.

The viscosity of the mixed slurry when spray-drying the mixed slurry in the above step (3) may be 40 mPa·sec or more, but preferably 50 mPa·sec or more. More preferably, it is 60 mPa·sec or more. Further, if the slurry viscosity is too high, it becomes difficult to spray, so the viscosity of the mixed slurry is preferably 150 mPa·sec or less. The viscosity of the mixed slurry can be adjusted by adding or evaporating water and/or an organic solvent as a dispersion medium.
The viscosity of the mixed slurry can be measured by the method described in Examples below.

The mixed slurry concentration when spraying the mixed slurry in the above step (3) is preferably 100 to 750 g/l. If it is less than 100 g/l, spray drying time becomes long and productivity becomes low, which is not preferable. Moreover, if it exceeds 750 g/l, the viscosity of the slurry becomes high and it becomes difficult to spray, which is not preferable. The mixed slurry concentration is more preferably 150 to 700 g/l, and still more preferably 200 to 650 g/l.

Regarding the spray temperature during spray drying in the above step (3), the inlet temperature is preferably 100 to 250°C. Further, the outlet temperature is preferably 50 to 150°C. By spraying at such a temperature, a dried product with a lower moisture content and uniform particle size can be obtained.

The method for producing a luminescent material of the present invention may include other steps as long as the above steps (1) to (3) are included. Other steps include firing, pulverization, classification, surface treatment, and the like.

The temperature in the above firing step is preferably 1200 to 1600°C. More preferably, the temperature is 1300 to 1500°C. By carrying out the process at such a temperature, the obtained luminescent material can be made to have even better luminescence properties.
Further, the time of the firing step is preferably 1 to 12 hours. More preferably, it is 2 to 8 hours.

The firing step is preferably performed in a reducing atmosphere. By carrying out the process in a reducing atmosphere, the resulting luminescent material can have even better luminescence properties.
Firing in a reducing atmosphere may be performed in an atmosphere consisting only of reducing gases such as carbon monoxide or hydrogen, or may be performed in an atmosphere containing gases other than reducing gases, but inert gases such as nitrogen and argon may be used. It is preferable to carry out the process in an atmosphere containing a reducing gas, and it is preferable to carry out the process at a reducing gas concentration in the atmosphere of 0.3 to 5 vol%. More preferably, it is 0.5 to 4 vol%.

2. Luminescent material The present invention also provides a luminescent material in which a compound represented by SrAl ₂ O ₄ is used as a host crystal, and europium, dysprosium, lithium, and boron are added,
The value obtained by dividing the number of moles of europium by the total number of moles of strontium, europium, dysprosium and lithium is more than 0.001 and less than 0.025,
The value obtained by dividing the number of moles of dysprosium by the total number of moles of strontium, europium, dysprosium and lithium is more than 0.001 and less than 0.025,
The value obtained by dividing the number of moles of aluminum by the total number of moles of strontium, europium, dysprosium and lithium exceeds 1.88 and is not more than 2.10,
The value obtained by dividing the number of moles of lithium by the total number of moles of strontium, europium, dysprosium and lithium is greater than 0 and less than 0.02,
It is also a luminescent material characterized in that the value obtained by dividing the number of moles of boron by the total number of moles of strontium, europium, dysprosium, and lithium is greater than 0 and less than 0.03.
That is, in the luminescent material of the present invention, the value obtained by dividing the number of moles of aluminum by the total number of moles of strontium, europium, dysprosium, and lithium exceeds 1.88 and is 2.10 or less, and the Sr ₄ Al at the time of manufacturing the luminescent material It is a material with increased phosphorescence brightness by suppressing the by-product of ₁₄ O ₂₅ and containing lithium and boron.

In the luminescent material of the present invention, the value obtained by dividing the number of moles of europium by the total number of moles of strontium, europium, dysprosium, and lithium is more than 0.001 and less than 0.025, but this value is 0.0015 or more. , is preferably 0.023 or less, more preferably 0.0025 or more and 0.02 or less.
In addition, the value obtained by dividing the number of moles of dysprosium by the total number of moles of strontium, europium, dysprosium, and lithium is more than 0.001 and less than 0.025; It is preferably 0.0025 or more and 0.02 or less.

Further, in the luminescent material of the present invention, the value obtained by dividing the number of moles of lithium by the total number of moles of strontium, europium, dysprosium, and lithium is greater than 0 and less than 0.02.
Further, the value obtained by dividing the number of moles of boron by the total number of moles of strontium, europium, dysprosium, and lithium is greater than 0 and less than 0.03.
Lithium and boron are components that function as reaction aids when mixing materials to produce phosphorescent materials.If these proportions are like this, the reaction will proceed sufficiently in the synthesis of phosphorescent materials, and the resulting product will not be obtained. The resulting phosphorescent material has even more excellent phosphorescence brightness.

The luminescent material of the present invention preferably has a rare earth element maldistribution rate of 1% or less, which is determined by the following method from image analysis of a backscattered electron image of a cross section of the luminescent material. In this way, if the rare earth element is efficiently dissolved in the base material with less segregation, the material will have a lower rare earth element content than conventional phosphorescent materials, but will have better phosphorescence brightness. . The uneven distribution rate is preferably 0.8% or less, more preferably 0.55% or less. It can be said that the smaller the maldistribution rate, the more efficiently the rare earth element can be solid-dissolved in the host crystal.
Further, the luminescent material of the present invention preferably has an average particle diameter D50 (μm) of 100 μm or less. More preferably, it is 20 to 80 μm.
[Measurement of uneven distribution rate of rare earth atoms]
In the histogram of the result of color determination using 256 gray levels for each pixel of the backscattered electron image of the cross section of the luminescent material, the peak area a is between 150 and 200 gray levels, which is the area occupied by the host crystal, and the rare earth element The value (b/a) obtained by dividing the peak area b in the range where the gray level, which is the area occupied, is 250 or more is defined as the uneven distribution ratio of rare earth atoms.

In the luminescent material of the present invention, the value obtained by dividing the D25 value by the D75 value obtained by particle size distribution measurement using a laser diffraction/scattering particle size distribution meter using ethanol as a dispersion medium exceeds 0.45. It is preferable. Such particles have uniform particle sizes, have good dispersibility when blended into resins, etc., and emit light uniformly. The value obtained by dividing the D25 value by the D75 value is more preferably 0.50 or more, and still more preferably 0.55 or more.

Specific examples are given below to explain the present invention in detail, but the present invention is not limited only to these examples. Unless otherwise specified, "%" and "wt%" mean "% by weight (% by mass)".

Example 1
Strontium carbonate (SW-K manufactured by Sakai Chemical Industry Co., Ltd., 24.58 g), europium oxide (purity 99.9%, 0.30 g), dysprosium oxide (purity 99.9%, 0.32 g), aluminum oxide (purity 99.9%). 99%, 17.01 g), lithium carbonate (purity 99.0%, 0.0063 g), and boric acid (purity 99.5%, 0.11 g) were weighed and placed in water (85 mL) to make the raw material mixture. A slurry-like composition for a green phosphorescent material was obtained by dispersing, pulverizing, and mixing at 250 rpm for 90 minutes using a planetary ball mill using 3 mm diameter alumina balls (manufactured by Nikkato Co., Ltd., SSA-999W, 190 g) as a grinding media. I got it. Water was added to the obtained mixed slurry to adjust the viscosity to 60 mPa·sec, followed by spray drying to obtain a powdery composition for a green phosphorescent material. Next, the composition for a green phosphorescent material was filled into an alumina crucible, and the temperature was raised to 1400°C at a rate of 200°C/hour in a reducing atmosphere (nitrogen containing 2% hydrogen), and after being maintained for 4 hours, The temperature was lowered to room temperature at a rate of °C/hour.
The thus obtained fired product was crushed in a mortar and passed through a sieve to obtain the desired green phosphorescent material as a powder. The viscosity of the mixed slurry was measured at 20±1° C. using a B-type viscometer (manufactured by Tokyo Keiki, model: BM).

Example 2
The weight of the raw materials is strontium carbonate (SW-K manufactured by Sakai Chemical Industry Co., Ltd., 25.08 g), europium oxide (purity 99.9%, 0.08 g), dysprosium oxide (purity 99.9%, 0.08 g), aluminum oxide. Same as Example 1 except that (purity 99.99%, 17.10g), lithium carbonate (purity 99.0%, 0.0063g), and boric acid (purity 99.5%, 0.11g) were used. The desired green phosphorescent material was obtained as a powder.

Example 3
Weighed the raw materials: strontium carbonate (SW-K manufactured by Sakai Chemical Industry Co., Ltd., 23.91 g), europium oxide (purity 99.9%, 0.60 g), dysprosium oxide (purity 99.9%, 0.63 g), aluminum oxide Same as Example 1 except that lithium carbonate (purity 99.99%, 16.89 g), lithium carbonate (purity 99.0%, 0.0062 g), and boric acid (purity 99.5%, 0.10 g) were used. The desired green phosphorescent material was obtained as a powder.

Example 4
Weighed the raw materials: strontium carbonate (SW-K manufactured by Sakai Chemical Industry Co., Ltd., 24.58 g), europium oxide (purity 99.9%, 0.30 g), dysprosium oxide (purity 99.9%, 0.32 g), aluminum oxide (purity 99.99%, 17.01g), lithium carbonate (purity 99.0%, 0.0063g), boric acid (purity 99.5%, 0.21g), and the viscosity of the mixed slurry to be subjected to spray drying was determined. The desired green phosphorescent material was obtained as a powder by carrying out the same procedure as in Example 1 except that the pressure was adjusted to 93 mPa·sec.

Example 5
The weight of the raw materials is strontium carbonate (SW-K manufactured by Sakai Chemical Industry Co., Ltd., 24.45 g), europium oxide (purity 99.9%, 0.30 g), dysprosium oxide (purity 99.9%, 0.32 g), aluminum oxide. (purity 99.99%, 17.27 g), lithium carbonate (purity 99.0%, 0.0063 g), and boric acid (purity 99.5%, 0.21 g), the viscosity of the mixed slurry to be subjected to spray drying was determined. The desired green phosphorescent material was obtained as a powder by carrying out the same procedure as in Example 1 except that the pressure was adjusted to 93 mPa·sec.

Example 6
The weight of the raw materials is strontium carbonate (SW-K manufactured by Sakai Chemical Industry Co., Ltd., 24.14 g), europium oxide (purity 99.9%, 0.29 g), dysprosium oxide (purity 99.9%, 0.31 g), aluminum oxide. (purity 99.99%, 17.90g), lithium carbonate (purity 99.0%, 0.0062g), boric acid (purity 99.5%, 0.21g), and the viscosity of the mixed slurry to be subjected to spray drying was determined. The desired green phosphorescent material was obtained as a powder by carrying out the same procedure as in Example 1 except that the pressure was adjusted to 93 mPa·sec.

Comparative example 1
Water was added to the slurry-like green phosphor composition obtained by dispersing, pulverizing, and mixing the raw materials to adjust the viscosity to 30 mPa·sec, and then drying was carried out in a magnetic dish at 130°C for 5 hours. The desired green phosphorescent material was obtained as a powder in the same manner as in Example 1 except that the composition for a green phosphorescent material was obtained in the form of a powder.

Comparative example 2
The desired green phosphorescent material was obtained as a powder in the same manner as in Example 1, except that the time for dispersing, pulverizing, and mixing the raw materials was 30 minutes, and the viscosity of the mixed slurry to be subjected to spray drying was adjusted to 20 mPa sec. .

Comparative example 3
The weight of the raw materials is strontium carbonate (SW-K manufactured by Sakai Chemical Industry Co., Ltd., 24.84 g), europium oxide (purity 99.9%, 0.30 g), dysprosium oxide (purity 99.9%, 0.32 g), aluminum oxide. (purity 99.99%, 16.49g), lithium carbonate (purity 99.0%, 0.0063g), boric acid (purity 99.5%, 0.11g), and the viscosity of the mixed slurry to be subjected to spray drying was determined. The same procedure as in Example 1 was carried out except that the pressure was adjusted to 35 mPa·sec, and the desired green phosphorescent material was obtained as a powder.

Comparative example 4
The weight of the raw materials is strontium carbonate (SW-K manufactured by Sakai Chemical Industry Co., Ltd., 24.14 g), europium oxide (purity 99.9%, 0.29 g), dysprosium oxide (purity 99.9%, 0.31 g), aluminum oxide. (purity 99.99%, 17.90g), lithium carbonate (purity 99.0%, 0.0062g), boric acid (purity 99.5%, 0.10g), and the viscosity of the mixed slurry to be subjected to spray drying was determined. The same procedure as in Example 1 was carried out except that the pressure was adjusted to 35 mPa·sec, and the desired green phosphorescent material was obtained as a powder.

Comparative example 5
Weighed the raw materials: strontium carbonate (SW-K manufactured by Sakai Chemical Industry Co., Ltd., 23.2659 g), europium oxide (purity 99.9%, 0.74 g), dysprosium oxide (purity 99.9%, 0.79 g), oxidized Viscosity of a mixed slurry of aluminum (purity 99.99%, 16.84 g), lithium carbonate (purity 99.0%, 0.0062 g), and boric acid (purity 99.5%, 0.10 g) to be subjected to spray drying. The desired green phosphorescent material was obtained as a powder in the same manner as in Example 1 except that the pressure was adjusted to 35 mPa·sec.

Comparative example 6
Weighed the raw materials: strontium carbonate (SW-K manufactured by Sakai Chemical Industry Co., Ltd., 24.58 g), europium oxide (purity 99.9%, 0.30 g), dysprosium oxide (purity 99.9%, 0.32 g), aluminum oxide (purity 99.99%, 16.99 g), lithium carbonate (purity 99.0%, 0.0063 g), and the same as Example 1 except that the viscosity of the mixed slurry to be subjected to spray drying was adjusted to 35 mPa・sec. The desired green phosphorescent material was obtained as a powder.

Comparative example 7
Weighed the raw materials: strontium carbonate (SW-K manufactured by Sakai Chemical Industry Co., Ltd., 24.58 g), europium oxide (purity 99.9%, 0.30 g), dysprosium oxide (purity 99.9%, 0.32 g), aluminum oxide The viscosity of the mixed slurry to be subjected to spray drying was The same procedure as in Example 1 was carried out except that the pressure was adjusted to 35 mPa·sec, and the desired green phosphorescent material was obtained as a powder.

Comparative example 8
The weight of the raw materials is strontium carbonate (SW-K manufactured by Sakai Chemical Industry Co., Ltd., 24.59 g), europium oxide (purity 99.9%, 0.30 g), dysprosium oxide (purity 99.9%, 0.32 g), aluminum oxide. (purity 99.99%, 16.99 g) and boric acid (purity 99.5%, 0.11 g), and the viscosity of the mixed slurry to be subjected to spray drying was adjusted to 35 mPa・sec. The desired green phosphorescent material was obtained as a powder.

Comparative example 9
The weight of the raw materials is strontium carbonate (SW-K manufactured by Sakai Chemical Industry Co., Ltd., 24.28 g), europium oxide (purity 99.9%, 0.30 g), dysprosium oxide (purity 99.9%, 0.32 g), aluminum oxide. (purity 99.99%, 17.12g), lithium carbonate (purity 99.0%, 0.13g), boric acid (purity 99.5%, 0.11g), and the viscosity of the mixed slurry to be subjected to spray drying was determined. The same procedure as in Example 1 was carried out except that the pressure was adjusted to 35 mPa·sec, and the desired green phosphorescent material was obtained as a powder.

Comparative example 10
As a conventional luminescent material, N Luminous (G-300M) manufactured by Nemoto Lumimaterial Co., Ltd. was used.

Comparative example 11
Weighed the raw materials: strontium carbonate (SW-K manufactured by Sakai Chemical Industry Co., Ltd., 24.58 g), europium oxide (purity 99.9%, 0.30 g), dysprosium oxide (purity 99.9%, 0.32 g), aluminum oxide (purity 99.99%, 17.01g), lithium carbonate (purity 99.0%, 0.0063g), boric acid (purity 99.5%, 0.21g), and the viscosity of the mixed slurry to be subjected to spray drying was determined. The desired green phosphorescent material was obtained as a powder in the same manner as in Example 1 except that the pressure was adjusted to 33 mPa·sec.

The green phosphorescent materials obtained in Examples 1 to 6 and Comparative Examples 1 to 11 and the phosphorescent material of Comparative Example 10 were evaluated in the following manner. The evaluation results are shown in Table 1.
<Particle size distribution measurement>
The particle size distribution of the slurry-like green phosphorescent material composition (mixed slurry) was measured using water, and the particle size distribution of the green phosphorescent material powder was measured using ethanol as a dispersion medium. MT-3300EXII) manufactured by Co., Ltd. under the following conditions.
Measurement mode: MT-3000
Measurement upper limit: 1408μm
Measurement lower limit: 0.021μm
Particle refractive index: 1.81
Particle shape: non-spherical Solvent refractive index: 1.36 (when the dispersion medium is ethanol), 1.33 (when the dispersion medium is water)
<Evaluation of presence or absence of abnormality>
X-ray diffraction was measured for the green phosphor powder using the following equipment and conditions, and for the different phase A (Sr ₄ Al ₄ O ₂₅ ), a peak attributed to the (021) plane appearing near 2θ = 28°, The different phase B (Sr ₃ Al ₂ O ₆ ) was determined based on the presence or absence of a peak attributed to the (440) plane appearing near 2θ=32°.
Powder X-ray diffractometer: RINT-TTRIII manufactured by Rigaku
X-ray source: Cu-Kα ray (wavelength: 1.5406 Å, voltage 50 kV, current 300 mA)
Parallel beam optical system (long slit: PSA200/resolution 0.057°)
Measurement range: 2θ=12°~52°
Step width: 0.01°
Counting time: 2s
<phosphorescence brightness evaluation>
The obtained green phosphorescent powder was mixed with transparent acrylic resin in a mortar at a weight ratio of 1:1.4, and then an acrylic resin circular molded body containing the phosphorescent powder was obtained using an embedding press. Ta. Thereafter, the phosphorescence brightness (afterglow brightness after 60 minutes, unit: mcd/m ² ) of this molded body was measured using a phosphorescence brightness meter (BM-100 manufactured by Topcon). At this time, the brightness measurement was conducted in accordance with JIS Z 9107 6.3.2, and was stored in a dark place with no external light exposed for at least 24 hours. It was irradiated for 20 minutes at an illumination intensity of lux, and after the irradiation was stopped, the phosphorescence brightness was measured 60 minutes later.

<Uneven distribution rate of rare earth atoms>
(1) Particle cross-section formation using a cross-section polisher A mixture of powder and epoxy resin was prepared and defoamed by heating at 80°C. After the defoaming was completed, it was heated and solidified at 120°C. The cross section of the solidified resin was set in a precision plane polisher, polished with polishing paper (#400), and then finished polished with polishing paper (#800). The polished resin was set in a cross-sectional sample preparation device (SM-09011) and cut with an argon ion beam to prepare a cross section.
(2) SEM Observation The particle cross section was observed using a scanning electron microscope (manufactured by JEOL Ltd., JSM-7000F).
Acceleration voltage: 15kV
Magnification: Any magnification that can photograph 10 particles (100 to 1000 times)
(3) Calculation of maldistribution rate using image analysis software First, the color of each pixel of the obtained backscattered electron image was determined using 256 gray levels, and a histogram of the color determination results was created. There were three representative peaks in the obtained histogram. The area of each peak corresponded to the following.
(A) Gray level 0 to 150: Area occupied by epoxy resin in backscattered electron image (B) Gray level 150 to 250: Area occupied by base particles in backscattered electron image (C) Gray level 250 or higher: Area occupied by base particles in backscattered electron image , Area occupied by rare earth elements At this time, the value obtained by dividing the area occupied by rare earth elements by the area occupied by base particles was determined as the uneven distribution ratio of rare earth elements. That is, where a is the peak area in the gray level range of 150 to 250, and b is the peak area in the gray level range of 250 or higher, it is the value obtained by dividing b by a (b/a).
In Table 1, those with a maldistribution rate of greater than 1% are marked as ×, those with a maldistribution ratio of greater than 0.4 to 1% are marked as ○, and those with a maldistribution ratio of 0.4% or less are marked as ◎.

In Examples 1 to 6, no foreign phase was observed in the obtained green phosphorescent powder, and the value obtained by dividing the D25 value obtained by the phosphorescence brightness and particle size distribution measurement by the D75 value (D25/D75) was the same as that of Comparative Example 10. (conventional phosphorescent material), and it can be seen that the maldistribution rate of dysprosium is particularly low. This is because the ratio of each element was appropriately set, each raw material was sufficiently uniformly dispersed, pulverized, and mixed, and the viscosity of the mixed slurry was adjusted to 40 mPa·sec or more before spray drying. D25/D75 is superior because of the characteristics of spray drying, that is, after adjusting the viscosity of the mixed slurry, it is sprayed into hot gas, rapidly dried, and granulated according to the size of the sprayed mixed slurry droplets. It is thought that this was because they were used as objects.

In Comparative Example 1, different phases A and B were generated in the obtained green phosphorescent powder, and the phosphorescence brightness was lowered. This is thought to be because while the mixed slurry with a viscosity of 30 mPa/sec was being evaporated and dried, the composition uniformity of the evaporated and dried product became low due to sedimentation of each raw material and segregation of water-soluble components. . Moreover, the D25/D75 of the obtained green phosphorescent material powder was also significantly lowered.

In Comparative Example 2, different phases A and B were generated in the obtained green phosphorescent powder, and the phosphorescence brightness was low. This is because although the ratio of each element is within an appropriate range, the dispersion, pulverization, and mixing time is short, and the dispersion, pulverization, and mixing of each raw material are insufficient. This is considered to be because elemental segregation occurred in the crystal and the host crystal of the present invention represented by SrAl ₂ O ₄ could not be obtained in a single phase. Furthermore, it can be inferred that the dispersion/pulverization/mixing time is insufficient because the values of the particle size distribution D50 and D90 of the mixed slurry are larger than those of Examples 1 to 3. It is also thought that the low viscosity of the mixed slurry during spray drying affected these results.

Different phase B was generated in Comparative Example 3, and different phase A was generated in Comparative Example 4, and the phosphorescence brightness was significantly reduced. This means that even if each element is uniformly dispersed, pulverized, mixed and spray-dried, the number of moles of aluminum is smaller in Comparative Example 3 than the total number of moles of strontium, europium, dysprosium, and lithium, and in Comparative Example 4. This is thought to be due to the generation of crystal phases A and B, which are excessive and have lower phosphorescence generation efficiency than the host crystal of the present invention represented by SrAl ₂ O ₄ . Further, in Comparative Example 10 (conventional phosphorescent material), as in Comparative Example 4, crystal phase A was observed because the number of moles of aluminum was in excess of the total number of moles of strontium, europium, dysprosium, and lithium. It is also thought that the low viscosity of the mixed slurry during spray drying affected these results.

Compared to Examples 1 to 3, Comparative Example 6 does not add boron, and Comparative Example 8 does not add lithium. However, since both boron and lithium are components that function as reaction aids, it is necessary to add them. It is considered that the solid phase reaction did not proceed sufficiently and the crystallinity of the SrAl ₂ O ₄ phase, which is the host crystal, was low, resulting in low phosphorescence brightness. Furthermore, if the amount is as high as in Comparative Examples 7 and 9, the effect as a reaction aid will be excessive and sintering of the spray-dried granules will proceed, producing coarse particles, or fine particles will be produced when the coarse particles are crushed. It was found that D25/D75 decreased as a result. It is also thought that the low viscosity of the mixed slurry during spray drying affected these results.

In Comparative Example 11, the D25/D75 of the obtained green phosphorescent material powder was inferior to that of the example. From comparison with Example 4, which had the same raw material composition, it was confirmed that the viscosity of the mixed slurry during spray drying also affected the phosphorescence brightness.

Further, from Examples 1 to 3 and Comparative Example 5, it is possible to see the relationship between the amount of rare earth added and the phosphorescence brightness when the amounts of boron and lithium are the same. In terms of reducing the amount of rare earth used, Example 2 has higher phosphorescence brightness and higher D25/D75 than the conventional product, and can be said to be the most excellent result. However, when the rare earth element was increased to Comparative Example 5, the phosphorescence brightness became lower than that of the conventional product even if boron and lithium were co-added. From this, it can be said that the effect of improving phosphorescence brightness by co-adding boron and lithium is remarkable when the amount of rare earth elements used is small. In other words, in addition to the effect as a reaction aid that simply generates a glass component with a low melting point during the solid phase reaction to accelerate the reaction and improve crystallinity, when the amount of rare earth is small, SrAl ₂ O It is believed that this has the effect of promoting solid solution of the rare earth element into the host crystal of the present invention represented by ₄ . Although it is not certain, if we focus on Li and Dy, Li behaves as a monovalent cation (Li ⁺ ), and when Dy ³⁺ , which behaves as a trivalent cation, dissolves in the divalent Sr ²⁺ site, Li It is conceivable that ⁺ also dissolves in solid solution and charge compensation is performed.

Further, from Examples 4 to 6, it can be seen that the relationship between the value obtained by dividing the number of moles of aluminum by the total number of moles of strontium, europium, dysprosium, and lithium and the phosphorescence brightness at the same addition amount of boron and lithium can be seen. In the phosphorescent material of the present invention, the value obtained by dividing the number of moles of aluminum by the total number of moles of strontium, europium, dysprosium, and lithium is from more than 1.88 to less than 2.10, from the viewpoint of the effect of improving phosphorescent brightness. It can be said that it is preferably 1.96 or more and 2.00 or less.

Claims (5)

A raw material is prepared by supplying water and/or an organic solvent, an alkaline earth metal compound, an alkali metal compound, a rare earth compound, and a Group 13 element compound at the following molar ratio into a reaction vessel equipped with a grinding media stirring type grinder. Step (1) of obtaining a mixture;
Step (2) of obtaining a mixed slurry by mixing and pulverizing the raw material mixture in the reaction vessel until D50 calculated from the particle size distribution of the mixed slurry becomes 1.7 μm or less and D90 becomes 2.7 μm or less. and,
A method for producing a luminescent material, comprising a step (3) of adjusting the mixed slurry obtained by the mixing and pulverizing treatment to a viscosity of 40 mPa·sec or more and then spray-drying the slurry.
1.88<E/(A+B+C)≦2.10
0.001<D/(A+B+C)<0.025
0<B/(A+B+C)<0.02
0<F/(A+B+C)<0.03
A: Total number of moles of alkaline earth metal elements in the alkaline earth metal compound B: Total number of moles of alkali metal elements in the alkali metal compound C: Total number of moles of rare earth elements in the rare earth compound D: In each rare earth compound Number of moles of each rare earth element E: Total number of moles of Group 13 elements excluding boron in the Group 13 element compound F: Number of moles of boron in the Group 13 element compound 2. The method for producing a luminescent material according to claim 1, wherein the grinding medium agitation type grinder is a bead mill. 3. The method for producing a luminescent material according to claim 1, wherein the Group 13 element compound supplied into the reaction vessel is an aluminum compound and a boron compound. A compound represented by SrAl ₂ O ₄ is used as a host crystal,
A phosphorescent material doped with europium, dysprosium, lithium, and boron,
The value obtained by dividing the number of moles of europium by the total number of moles of strontium, europium, dysprosium and lithium is more than 0.001 and less than 0.025,
The value obtained by dividing the number of moles of dysprosium by the total number of moles of strontium, europium, dysprosium and lithium is more than 0.001 and less than 0.025,
The value obtained by dividing the number of moles of aluminum by the total number of moles of strontium, europium, dysprosium and lithium exceeds 1.88 and is not more than 2.10,
The value obtained by dividing the number of moles of lithium by the total number of moles of strontium, europium, dysprosium and lithium is greater than 0 and less than 0.02,
The value obtained by dividing the number of moles of boron by the total number of moles of strontium, europium, dysprosium and lithium is greater than 0 and less than 0.03,
A phosphorescent material characterized in that the uneven distribution rate of rare earth elements determined by the following method from image analysis of a backscattered electron image of a cross section of the phosphorescent material is 1% or less.
[Measurement of uneven distribution rate of rare earth atoms]
In the histogram of the result of color determination using 256 gray levels for each pixel of the backscattered electron image of the cross section of the luminescent material, the peak area a is between 150 and 200 gray levels, which is the area occupied by the host crystal, and the rare earth element The value (b/a) obtained by dividing the peak area b in the range where the gray level, which is the area occupied, is 250 or more is defined as the uneven distribution ratio of rare earth atoms. A claim characterized in that the value obtained by dividing the D25 value by the D75 value obtained by particle size distribution measurement using a laser diffraction/scattering particle size distribution meter using ethanol as a dispersion medium exceeds 0.45. 4. The luminescent material according to 4 .