JP2005232414A - Strontium aluminate-based luminous powder and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an Eu-activated strontium aluminate-based luminous powder having a property of excellent long afterglow without using an expensive coactivator such as dysprosium. <P>SOLUTION: The strontium aluminate-based luminous powder has a stuffed tridimyte structure comprising a host crystal expressed by: SrAl<SB>2</SB>O<SB>4</SB>and is activated with Eu, wherein the face interval of (-211) face is in the range of 0.3120-0.3140 nm. The Eu-activated strontium aluminate-based luminous powder is obtained by the following: when producing a strontium alminate-based luminous powder by blending a raw material containing a strontium compound, an aluminum compound, a europium compound and a boron compound followed by heating and firing the resultant blend in a non-oxidizing atmosphere, at least one of the compounds is a nitride-containing compound as the raw material. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a strontium aluminate phosphorescent powder excellent in afterglow characteristics and a method for producing the same.

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. Although strontium aluminate (SrAl ₂ O ₄ ) activated with europium has fluorescence characteristics, it has little long afterglow and is not useful as a phosphorescent material (see, for example, Non-Patent Document 1). Therefore, a long afterglow is imparted by further adding a rare earth element such as dysprosium as a co-activator to this material, and it is used as a phosphorescent material.
“Phosphor Handbook” (USA), CRC Press, 1998, p. 655-656

  However, since europium-activated strontium aluminate containing the rare earth element used as a phosphorescent agent as a coactivator currently uses an expensive rare earth element, a phosphorescent material that can be manufactured at a lower cost is required. ing.

  The inventors of the present invention have made various studies to find a strontium aluminate phosphorescent powder having excellent afterglow characteristics without using expensive rare earth elements. As a result, strontium compounds, aluminum compounds, etc., which are raw materials for producing phosphorescent powders, etc. When these nitrides are used as the compound of the metal element constituting the phosphorescent powder, the obtained europium-activated strontium aluminate has long persistence, and the phosphorescent powder obtained has a normal crystal lattice. The present invention was completed by finding that it has a contracted structure as compared with strontium aluminate.

That is, the present invention is a strontium aluminate-based phosphorescent powder in which a base crystal has a stuffed tridymite structure represented by SrAl ₂ O ₄ and is activated by europium, and has a surface spacing of (−211) planes. It is a strontium aluminate based phosphorescent powder characterized by being in the range of 0.3120 to 0.3140 nm.

  Furthermore, the present invention is a method for producing the above strontium aluminate phosphorescent powder, comprising mixing raw materials containing a strontium compound, an aluminum compound, a europium compound and a boron compound, followed by heating and firing in a non-oxidizing atmosphere. In the method for producing a strontium acid phosphorescent powder, at least one compound as a raw material contains a nitride, which is a method for producing a strontium aluminate phosphorescent powder.

  The strontium aluminate phosphorescent powder activated with europium of the present invention is a phosphorescent powder having long afterglow without using an expensive rare earth element such as dysprosium as a coactivator. Furthermore, the production method of the present invention is an industrially advantageous production method because the phosphorescent powder uses an inexpensive raw material.

The present invention is a strontium aluminate based phosphorescent powder having a stuffed tridymite structure represented by SrAl ₂ O ₄ and activated by europium, wherein the (−211) plane spacing is 0. It is a strontium aluminate-based phosphorescent powder characterized by being in the range of 3120 to 0.3140 nm. It is known that strontium aluminate represented by SrAl ₂ O ₄ has a stuffed tridymite structure, and its (−211) plane spacing is 0.3144 nm (PDF # 74-0794). On the other hand, the strontium aluminate of the present invention has a smaller lattice than the conventionally known strontium, and is in the range of 0.3120 to 0.3140 nm when expressed in terms of the (-211) plane spacing. . Thus, it is considered that the long afterglow excellent in europium-activated strontium aluminate, which has been considered to have no long afterglow, has been developed by shrinking the crystal lattice.

In the present invention, the amount of europium contained as an activator is preferably 0.002 to 20 mol% with respect to strontium. If the amount of europium is less than the above range, it is difficult to impart long afterglow, and if it is more than the above range, further improvement in long afterglow cannot be expected. It becomes difficult to maintain the structure. When the composition of the strontium aluminate phosphorescent powder of the present invention is expressed in a form including europium, Sr _1-x Eu _x Al ₂ O ₄ (where 0.00002 ≦ X ≦ 0.20) is obtained.

  Next, the present invention is a method for producing the above europium activated strontium aluminate phosphorescent powder, comprising mixing raw materials containing a strontium compound, an aluminum compound, a europium compound and a boron compound, followed by heating and firing in a non-oxidizing atmosphere. In the method for producing a strontium aluminate phosphorescent powder, at least one compound as a raw material contains a nitride. Usually, europium-activated strontium aluminate is obtained by dry-mixing each powder of strontium carbonate, aluminum oxide and europium oxide together with a boron compound used as a flux, followed by heating and firing. In the present invention, europium-activated strontium aluminate obtained by heating and firing by using at least one compound of the above strontium compound, aluminum compound, europium compound and boron compound used as a raw material as a raw material has a long residue. It becomes light.

  Strontium compounds that can be used as raw materials include strontium carbonate, strontium hydroxide, strontium nitride, strontium chloride, strontium sulfate, strontium nitrate, strontium acetate, strontium oxalate, strontium citrate, strontium oxide, strontium aluminate, etc. It is preferable to use strontium carbonate which is deliquescent and chemically stable. Examples of aluminum compounds include aluminum oxide, aluminum hydroxide, aluminum nitride, aluminum chloride, aluminum sulfate, aluminum nitrate, aluminum acetate, aluminum oxalate, aluminum citrate, and strontium aluminate. Use of highly stable aluminum oxide is preferred. Furthermore, examples of the europium compound include europium oxide, europium chloride, europium oxalate, europium sulfide, europium sulfate, europium nitrate, and europium nitride. Examples of the boron compound used as the flux include boric acid and boron oxide.

  The present invention is characterized in that at least one compound as a raw material contains nitride. Examples of the nitride that can be used include aluminum nitride, strontium nitride, europium nitride, and boron nitride. Among these, aluminum nitride is preferably used. For example, as an aluminum compound, aluminum oxide is a main component, and aluminum nitride is partially mixed and used. The amount of nitride used is preferably 0.05 to 10% by weight of nitrogen contained in the nitride with respect to the total amount of raw materials. If the amount of nitride is less than the above range, it will be difficult to impart sufficient phosphorescence to the europium-activated strontium aluminate that is produced. Improvement is unlikely. Moreover, the quantity of the boron compound used as a flux is 0-20 mol% with respect to the total amount of a raw material, Preferably it is 0.1-10 mol%, More preferably, it is 1-10 mol%.

In order to obtain strontium aluminate represented by SrAl ₂ O ₄ having a stuffed tridymite structure, the mixing ratio of the strontium compound and the aluminum compound used as a raw material is expressed as a molar ratio of Sr: Al, and 0.75: It is preferable that it exists in the range of 2-1.5: 2, More preferably, it is 0.85: 2-1.4: 2. Even if the mixing ratio is larger or smaller than the above range, a large amount of components other than SrAl ₂ O ₄ will be by-produced as the produced strontium aluminate, which tends to cause deterioration of the luminous characteristics.

  Subsequently, after mixing the said raw material containing a nitride, it heat-fires in a non-oxidizing atmosphere and obtains the strontium aluminate type phosphorescent powder activated with europium. The atmosphere for heating and baking is non-oxidizing, and examples thereof include an inert atmosphere such as nitrogen, argon, neon, and krypton, and a reducing atmosphere in which they are mixed with hydrogen. Among these, hydrogen: nitrogen (molar ratio) of 0: 1 to 1: 0 inert atmosphere or reducing atmosphere is preferable, more preferably 0.001: 0.9999 to 0.5: 0.5 reducing ability. The atmosphere. Moreover, although the heat-firing temperature should just be a temperature of 600 to 1700 degreeC, Preferably it is 900 to 1600 degreeC, More preferably, it is 1100 to 1500 degreeC.

  The strontium aluminate phosphorescent powder of the present invention obtained by heating and firing can be appropriately pulverized by a known method to adjust the particle size according to the purpose of use. For example, general pulverization methods such as pin mill pulverization, ball mill pulverization, jet mill pulverization, and bantam mill pulverization can be employed.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples.

5.79 g strontium carbonate (SrCO ₃ ), 0.14 g europium oxide (Eu ₂ O ₃ ), 4.04 g aluminum oxide (α-Al ₂ O ₃ ), 0.03 g aluminum nitride (AlN) and 0 20 g of boric acid (H ₃ BO ₃ ) was ground and mixed for 10 minutes using an automatic agate mortar. The blending ratio of the raw material powder is expressed as a molar ratio and is Sr: Eu: Al = 0.98: 0.02: 2. The compounding amount of nitride (aluminum nitride) is an amount containing 0.112% by weight of nitrogen in the nitride with respect to the total amount of raw materials. Subsequently, the obtained mixture was put in an alumina crucible and heated and fired at a temperature of 1400 ° C. for 2 hours in a weak reducing atmosphere of hydrogen: nitrogen = 3 vol%: 97 vol%. The fired product was pulverized in an automatic agate mortar for 10 minutes to obtain a phosphorescent powder (sample A) of the present invention.

Comparative Example 1
In Example 1, instead of using 4.04 g of aluminum oxide and 0.03 g of aluminum nitride, 4.08 g of aluminum oxide was used in the same manner as in Example 1 except that phosphorescent powder (sample) B) was obtained. Note that the blending ratio of the raw material powder is Sr: Eu: Al = 0.98: 0.02: 2 as in Example 1.

  Samples A and B obtained in Example 1 and Comparative Example 1 were subjected to powder X-ray diffraction using the name of an X-ray diffraction analysis measurement apparatus (RINT1000: manufactured by Rigaku Corporation), and both samples were stuffed tridymite. Although it has a structure, the spacing of the (−211) plane was 0.3131 nm for sample A and 0.3144 nm for sample B.

  Moreover, when the samples A and B obtained in Example 1 and Comparative Example 1 were wet-analyzed to determine the molar ratio of Sr and Al, the composition ratio of any sample was Sr: Eu: Al = 0.98: It was confirmed that the ratio was 0.02: 2.

Furthermore, the luminous characteristics (afterglow luminance) of samples A and B obtained in Example 1 and Comparative Example 1 were evaluated as follows.
(Measurement method of afterglow brightness)
The sample was irradiated with light for 3 minutes at an illuminance of 200 lux using a D65 lamp, and then the light irradiation was stopped, and the luminance after 10 minutes was measured using a photosensor. As a result, the afterglow luminance of sample A was 850 when expressed in relative intensity where the afterglow luminance of sample B was 100.

  From the above results, strontium aluminate activated with europium of the present invention has a stuffed tridymite structure in which the lattice is shrunk, and therefore has excellent phosphorescent characteristics that show long persistence. I found out.

Since the strontium aluminate phosphorescent powder activated with europium of the present invention has long persistence and is inexpensive, it is widely used in the fields of conventional household goods, low-light night signboards, watches, etc. Can be used.

Claims (6)

A matrix crystal is a strontium aluminate-based phosphorescent powder having a stuffed tridymite structure represented by SrAl ₂ O ₄ and activated by europium, wherein the (−211) plane spacing is 0.3120-0. A strontium aluminate-based phosphorescent powder characterized by being in the range of 3140 nm. The strontium aluminate phosphorescent powder according to claim 1, comprising 0.002 to 20 mol% of europium with respect to strontium. In a method for producing a strontium aluminate phosphorescent powder by mixing raw materials containing a strontium compound, an aluminum compound, a europium compound, and a boron compound, followed by heating and firing in a non-oxidizing atmosphere, at least one compound is a nitride as the raw material The manufacturing method of the strontium aluminate type phosphorescent powder characterized by including. The method for producing a strontium aluminate phosphorescent powder according to claim 3, wherein the nitride is aluminum nitride. The method for producing a strontium aluminate phosphorescent powder according to claim 3, wherein the nitrogen contained in the nitride is contained in an amount of 0.05 to 10% by weight based on the total amount of the raw materials. 4. The strontium aluminate phosphorescent composition according to claim 3, wherein the mixing ratio of the strontium compound and the aluminum compound is in the range of 0.75: 2 to 1.5: 2, expressed as a molar ratio of Sr: Al. Powder manufacturing method.