JP2005179399A - Manufacturing method of aluminate salt fine particle light-accumulating powder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To industrially advantageously obtain an aluminate salt fine particle light-accumulating powder having a particle size favorable for dispersion in resins or coatings and exhibiting excellent light-accumulating characteristics. <P>SOLUTION: A precursor comprising a double hydroxide comprised of an activating agent Eu, a co-activating agent R (wherein R is at least one element selected from the group consisting of Dy and Nd), Al and M (wherein M is at least one element selected from the group consisting of Ca, Sr and Ba) is prepared. The precursor is dry-baked to give the aluminate salt fine particle light-accumulating powder. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing aluminate-based fine particle phosphorescent powder.

  Among phosphors, those having a long afterglow time are known as phosphorescent materials, and are widely used in fields such as daily necessities, weakly illuminated night signboards, and watches. For example, aluminate activated with europium is a typical phosphor, and is used with improved properties by further adding a co-activator such as dysprosium (see Patent Document 1).

  The aluminate phosphor is manufactured in Patent Document 1 by mixing a raw material oxide such as aluminum oxide and strontium carbonate or carbonate together with a flux such as boric acid and firing it in a dry manner (dry blend firing method). ).

In addition, as a method for producing a particulate aluminate-based phosphorescent powder, a slurry obtained by mixing an aluminum compound and an organic acid using an organic solvent and a cation aqueous solution such as europium are mixed to form a surface of the aluminum compound. A method in which a precursor in which a cation is precipitated as an organic acid salt is calcined, a so-called deposition firing method (see Patent Document 2), a mixed solution containing raw material metal ions and a particle refining agent such as glucose are added to an ammonium solution. Then, a method of oxidizing by irradiating with microwaves after generating a precipitate, so-called microwave irradiation method (see Patent Document 3) is known.
JP 7-11250 A (page 4) JP 2001-107039 A (second page) JP 2002-327173 A (second page)

  However, the aluminate phosphors synthesized by the above dry mixed firing method and pulverized have an average particle size of about several tens of μm, so this is mixed with a binder and a solvent. In the case of a coating material, it was difficult to produce a coating material having excellent coating properties such as dispersion stability due to the particle size, kneading into plastic, and fiberization by injection.

  The aluminate-based phosphorescent powder obtained by the production method described in Patent Document 1 is melted in a glass form. When this material is pulverized strongly by mechanical pulverization, the luminous intensity and the luminescence time are remarkably deteriorated, and since it is not uniformly pulverized, only a very wide particle size distribution can be obtained.

  Moreover, since the manufacturing method described in Patent Document 2 uses an organic acid salt and an organic solvent, there is a problem that handling is difficult and manufacturing cost is increased.

  Furthermore, since the manufacturing method described in Patent Document 3 requires a microwave irradiation device, it is difficult to manufacture industrially.

  The inventors of the present invention have made various studies in order to obtain industrially advantageous aluminate-based fine-particle luminous powders having particle diameters advantageous for dispersibility in resin-based and paint-based systems and having excellent luminous characteristics. , Activator Eu, coactivator R (where R is at least one element selected from the group consisting of Dy and Nd), Al and M (where M is selected from the group consisting of Ca, Sr and Ba) Aluminate-based fine particle phosphorescent powder having desired phosphorescent characteristics and particle diameter can be obtained by using a double hydroxide containing at least one element) as a precursor and firing it dry. The present invention has been completed.

  That is, the present invention includes activator Eu, coactivator R (where R is at least one element selected from the group consisting of Dy and Nd), Al and M (where M is Ca, Sr and Ba). And a double hydroxide containing at least one element selected from the group consisting of dry firing of the aluminate-based fine particle phosphorescent powder.

  By the production method of the present invention, it is possible to industrially advantageously obtain an aluminate-based fine particle phosphorescent powder having a particle size advantageous for dispersibility in a resin system and a paint system and having sufficient phosphorescent properties. .

  The present invention is a method for producing an aluminate-based fine particle phosphorescent powder, comprising an activator Eu and a coactivator R (where R is at least one element selected from the group consisting of Dy and Nd), Al And M (wherein M is at least one element selected from the group consisting of Ca, Sr, and Ba) is dry-fired.

  As the firing raw material (precursor) of the aluminate-based phosphorescent material, a mixture of metal element compounds (oxides, carbonates, etc.) constituting the phosphorescent material, and the constituent metal elements other than aluminum are coated on the surface of the aluminum compound particles. What is worn is known. The precursor used in the present invention is different from the mixture and the deposition composition described above, and is an activator Eu and a coactivator R (where R is at least one element selected from the group consisting of Dy and Nd). , Al and M (wherein M is at least one element selected from the group consisting of Ca, Sr and Ba). The precursor only needs to have at least Al and M as double hydroxides, and the activator and co-activator are present in the Al and M double hydroxide particles, and also adhere to the particle surface. May be. Since the double hydroxide used in the present invention contains at least Al and M homogeneously in individual particles, a composite oxide of Al and M is easily generated by heating, and a flux such as boric acid is intentionally used during firing. There is no need to add.

  In order to obtain the double hydroxide, (1) a method of subjecting each of the elements (M, Al, Eu and R) constituting the hydroxide to a wet heat treatment, (2) each element A method in which a solution containing ions is neutralized to form a slurry containing coprecipitate, followed by wet heat treatment. (3) After a solution containing ions of each element is neutralized to produce a coprecipitate (4) Al and M double water obtained by wet heat treatment of a slurry containing each of Al and M hydroxides A method of attaching a hydroxide of an element represented by Eu and R to the surface of the oxide can be used. In the present invention, the method (1) is preferable because the particle size can be easily controlled. Further, it is preferable to perform wet heat treatment after adding aqueous ammonia to the slurry to increase the alkali concentration because double hydroxides are likely to grow.

  The wet heat treatment is a step of generating double hydroxide particles having a uniform composition, and the treatment conditions can be appropriately set according to the composition and particle diameter of the intended phosphorescent powder. For example, the slurry concentration is preferably in the range of 10 to 700 g / liter, more preferably in the range of 100 to 500 g / liter. Increasing the slurry concentration can make the particle size of the double hydroxide produced uniform, but the above range is preferred from the slurry-viscosity relationship.

  In addition, the slurry pH of the wet heat treatment is preferably 6.5 or more, and it is preferable to increase the alkali concentration with ammonia water or the like because double hydroxides are easily generated. Furthermore, the temperature of the wet heat treatment is preferably in the range of 80 to 300 ° C, and more preferably in the range of 100 to 250 ° C. When processing at a temperature exceeding the boiling point of the slurry, it is processed using an autoclave. By setting the treatment pH and treatment temperature within the above ranges, the formation reaction of double hydroxide proceeds and it can be controlled to an appropriate particle size.

  The wet-heated slurry is spray-dried, evaporated to dryness, or filtered and dried to obtain a double hydroxide powder.

  Next, the obtained double hydroxide is fired dry to obtain the aluminate-based fine particle phosphorescent powder of the present invention. The double hydroxide becomes a complex oxide at a temperature higher than about 900 ° C., but the firing temperature is in the range of 1100 to 1600 ° C. in order to increase the crystallinity of the generated particles and obtain the desired particle size and luminous characteristics. A temperature in the range of 1300 to 1550 ° C is more preferable. In firing, there is no problem even if a small amount of a flux such as boric acid is used, but this is not always necessary.

  Further, the atmosphere during dry firing is preferably a non-oxidizing atmosphere. Examples of the non-oxidizing atmosphere include an inert atmosphere such as a nitrogen atmosphere, and a weak reducing atmosphere in which a small amount of a reducing gas such as hydrogen is included in the inert atmosphere. For example, the hydrogen concentration in the weak reducing atmosphere is 0.5 / 99.5 to 30/70 in terms of hydrogen / nitrogen ratio.

Using double hydroxides with different constituent ratios of the respective metal elements represented by M, Al, Eu and R as precursors, and by subjecting these to dry firing, the constituent ratios of the metal elements contained in the precursors are changed. Various inherited aluminate-based fine-particle phosphorescent powders can be obtained. An aluminate-based fine particle phosphorescent powder in which Sr is selected as M and Dy is selected as R is preferable because it has excellent phosphorescent characteristics. The composition ratio (molar ratio) is preferably 0.05 to 2 in terms of M / Al, 0.0001 to 0.5 in terms of Eu / Al, and 0.0001 to 0.5 in terms of R / Al. . By appropriately setting the composition ratio within the above range, aluminate-based fine-particle phosphorescent powders having various compositions, for example, SrAl ₂ O ₄ : Eu, Dy can be obtained.

  As described above, in the present invention, a phosphorescent powder having a wide range of particle diameters can be obtained by changing the double hydroxide production conditions and the dry firing conditions, for example, in the range of 0.5 to 10 μm. An aluminate-based fine particle phosphorescent powder having an average particle diameter and a uniform particle size distribution can be obtained.

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

Examples 1-3
1.174 g of europium oxide and 1.244 g of dysprosium oxide were weighed and placed in a beaker having an internal volume of 300 ml to form a slurry with a small amount of water, and nitric acid was added little by little while being heated and dissolved. Pure water was added to make 200 ml, and ammonia water was added to adjust the pH to 8.0 to obtain a slurry containing Eu and Dy hydroxides. The obtained slurry was transferred to an autoclave (titanium lining) having an internal volume of 2.5 liters, and pure water was added to make 1 liter. Into this, 52.00 g of aluminum hydroxide and 85.02 g of strontium hydroxide octahydrate were added, and pure water was added to make 2 liters, followed by hydrothermal treatment at a temperature of 170 ° C. for 5 hours.
The slurry after the hydrothermal treatment was evaporated to dryness to obtain a double hydroxide containing Eu, Dy, Sr and Al. When the obtained double hydroxide was analyzed with an energy dispersive X-ray analyzer, it was confirmed that Sr and Al were contained in the same particle. The obtained double hydroxide was pulverized in an agate mortar and then subjected to dry firing at a temperature of 1300 ° C., 1400 ° C. and 1500 ° C. for 2 hours in a 3% H ₂ /97% N ₂ atmosphere. The fired product was coarsely crushed to obtain phosphorescent powders (samples A, B and C) of the present invention. Respectively, it is set as Examples 1-3. The composition of the obtained luminous powder contained 0.48 mol of Sr, 0.01 mol of Eu, and 0.01 mol of Dy with respect to 1 mol of Al.

  The specific surface areas and afterglow luminances of the obtained samples A to C were measured. The specific surface area was measured using a specific surface area meter monosorb manufactured by Yuasa Ionics. The afterglow brightness was measured by the following method. The results are shown in Table 1.

(Measurement method of afterglow brightness)
A D65 lamp was used as a sample, and the sample was irradiated with light at an illuminance of 200 lux for 20 minutes. Thereafter, the light irradiation was stopped, and the luminance after 30 minutes was measured using a photosensor. In addition, it represented with the relative intensity | strength which made the afterglow brightness | luminance of the sample C 100.

(Visibility of afterglow)
Furthermore, after the sample A was stored in a dark room for 1 day, it was irradiated with light for 20 minutes at an illuminance of 200 lux using a D65 lamp. Even after 1 hour from the stop of light irradiation, the sample A was easily visible in the dark room.
Similarly, after the sample C was stored in a dark room for 1 day, it was irradiated with light for 20 minutes at an illuminance of 200 lux using a D65 lamp. Even after 10 hours from the stop of the light irradiation, the sample C was easily visible in the dark room.

  Further, a scanning electron micrograph of Sample C is shown in FIG. As shown in FIG. 1, Table 1, and afterglow, the aluminate-based phosphorescent powder obtained by the production method of the present invention has sufficient afterglow brightness despite having a large specific surface area (small particle diameter). I understood.

Example 4
3.522 g of europium oxide and 7.464 g of dysprosium oxide were weighed and placed in a beaker with an internal volume of 300 ml to form a slurry with a small amount of water, and nitric acid was added in small portions while heating and dissolved. Pure water was added to make 200 ml, and then ammonia water was added to adjust the pH to 8.0 to obtain a slurry containing Eu and Dy hydroxides. The obtained slurry was transferred to an autoclave (titanium lining) having an internal volume of 2.5 liters, and pure water was added to make 1 liter. After adding 156.00 g of aluminum hydroxide and 249.75 g of strontium hydroxide octahydrate, 2 liters of pure water was added thereto, followed by hydrothermal treatment at 200 ° C. for 5 hours.
The slurry after the hydrothermal treatment was evaporated to dryness to obtain a double hydroxide containing Eu, Dy, Sr and Al. The obtained double hydroxide was pulverized in an agate mortar and then dry-baked at a temperature of 1500 ° C. for 2 hours in a 3% H ₂ /97% N ₂ atmosphere.
After roughly crushing the fired product, 3 g was pulverized for 3 minutes using an Ishikawa-type pulverizer to obtain a phosphorescent powder (sample D) of the present invention. Sample D contained 0.47 mol of Sr, 0.01 mol of Eu, and 0.02 mol of Dy with respect to 1 mol of Al.

Example 5
A phosphorescent powder (sample E) of the present invention was obtained in the same manner as in Example 4 except that the dry firing atmosphere was changed to 10% H ₂ /90% N ₂ .

Example 6
A phosphorescent powder (sample F) of the present invention was obtained in the same manner as in Example 4 except that the dry firing atmosphere was changed to 30% H ₂ /70% N ₂ .

Example 7
Example 4 except that the amount of dysprosium oxide added was 3.732 g, the amount of strontium hydroxide octahydrate added was 255.06 g, and the dry firing atmosphere was 10% H ₂ /90% N ₂ Thus, the phosphorescent powder (sample G) of the present invention was obtained. Sample G contained 0.48 mol of Sr, 0.01 mol of Eu, and 0.01 mol of Dy with respect to 1 mol of Al.

Example 8
Example 4 except that the amount of europium oxide added was 7.044 g, the amount of strontium hydroxide octahydrate added was 239.34 g, and the dry firing atmosphere was 10% H ₂ /90% N _2. Thus, the phosphorescent powder (sample H) of the present invention was obtained.
Sample H contained 0.46 mol of Sr, 0.02 mol of Eu, and 0.02 mol of Dy with respect to 1 mol of Al.

Example 9
The present invention was carried out in the same manner as in Example 4 except that the amount of europium oxide added was 1.761 g, the amount of dysprosium oxide added was 3.732 g, and the amount of strontium hydroxide octahydrate added was 93.01 g. A phosphorescent powder (Sample I) was obtained.
Sample I contained 0.175 mol of Sr, 0.005 mol of Eu and 0.01 mol of Dy with respect to 1 mol of Al.

  The specific surface area and afterglow brightness of samples D to I obtained in Examples 4 to 9 were measured. The results are shown in Table 2. The afterglow luminance was expressed as a relative intensity with the value of Sample D as 100.

  From Table 2, it was found that even if the addition amount of the activator and the coactivator, the ratio of Al and Sr, and the atmosphere during the dry firing were changed, a fine particle phosphor powder having sufficient afterglow luminance was obtained.

Subsequently, using 3 g of the phosphorescent powder (sample C) obtained in Example 3, changes in specific surface area and afterglow luminance depending on the degree of grinding (grinding time) were examined. The results are shown in Table 3.
Further, the particle size distribution of the sample ground for 6 minutes was read from a scanning electron micrograph and shown in FIG. The average particle size of the sample ground for 6 minutes was 2.4 μm.

From Table 3 and FIG. 2, it was found that the aluminate phosphors obtained by the production method of the present invention were easily refined by grinding, had a good particle size distribution, and had sufficient afterglow luminance.

2 is a scanning electron micrograph (magnification 5000 times) showing the particle shape of sample C. FIG. 3 is a histogram showing the particle size distribution of Sample C.

Claims (8)

Activator Eu, co-activator R (where R is at least one element selected from the group consisting of Dy and Nd), Al and M (where M is selected from the group consisting of Ca, Sr and Ba) A method for producing an aluminate-based fine particle phosphorescent powder comprising dry firing a double hydroxide containing at least one element). 2. The aluminate according to claim 1, wherein the double hydroxide is obtained by wet-treating a slurry containing a hydroxide of each element (Eu, R, Al and M) constituting the double hydroxide. Of producing fine-particle-based phosphorescent powder. The method for producing an aluminate-based fine particle phosphorescent powder according to claim 2, wherein the wet heat treatment is performed at a temperature in the range of 80 to 300 ° C. The method for producing an aluminate-based fine particle phosphorescent powder according to claim 1, wherein dry firing is performed in a non-oxidizing atmosphere. 6. The method for producing an aluminate-based fine-particle phosphorescent powder according to claim 5, wherein dry firing is performed at a temperature in the range of 1100 ° C. to 1600 ° C. M is Sr, The manufacturing method of the aluminate type fine particle luminous powder of Claim 1 characterized by the above-mentioned. R is Dy, The manufacturing method of the aluminate type fine particle luminous powder of Claim 1 characterized by the above-mentioned. The double hydroxide is Al in the range of 0.05 to 2 mol, Eu in the range of 0.0001 to 0.5 mol, R in the range of 0.0001 to 0.5 mol with respect to 1 mol of Al, Al, M, Eu and R. The manufacturing method of the aluminate type fine particle luminous powder of Claim 1 characterized by the above-mentioned.

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