JP3801261B2 - Ba-Eu coprecipitated carbonate fine powder for blue phosphor material for three-wavelength fluorescent lamp and method for producing the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a Ba-Eu coprecipitated carbonate fine powder useful as a raw material for a blue phosphor for a three-wavelength fluorescent lamp and a method for producing the same.
[0002]
[Prior art]
Eu ²⁺ -activated aluminate is known as a raw material for the blue phosphor of the three-wavelength fluorescent lamp, and Ba Mg ₂ Al ₁₆ O ₂₇ : Eu ²⁺ can be cited as an example of the composition. . Here, it has been confirmed that Eu ²⁺ is substituted at the site of Ba.
The production method of Ba Mg ₂ Al ₁₆ O ₂₇ : Eu ²⁺ phosphor is described as “Ba CO ₃ as a raw material, Ba (NO ₃ ) ₂ and Mg ₄ (CO ₃ ) ₃ OH 3H ₂ O and other alkaline earth metal carbonates, α-Al ₂ O ₃ , Eu ₂ O ₃ and a suitable amount of flux are mixed in a ball mill or the like. Baked in a slightly reducing airflow (2% H ₂ / N ₂ ) at 1200 ° C for 2 hours, cooled in the same airflow, crushed and sieved, and then in 1200 ° C for 2 hours in a slightly reducing airflow The target phosphor is obtained by firing again. "
However, since it is very difficult to uniformly mix the raw materials in such a powder mixing method, a local non-uniform state is likely to occur, and the composition between the individual particles of the finally obtained phosphor In particular, the variation in the composition of Eu ²⁺ will adversely affect the characteristics of the phosphor.
[0003]
[Problems to be solved by the invention]
In view of the above problems, the present invention aims to improve the uniformity of the composition of Eu ²⁺ , which is a luminescent component, and is suitable for a raw material of Eu ²⁺ activated aluminate blue phosphor. It is an object of the present invention to provide a Ba-Eu coprecipitated carbonate having a diameter and a method for producing the same.
[0004]
[Means for Solving the Problems]
In order to solve the above problems, the present inventor has studied the coprecipitation conditions of Ba and Eu in various ways, and has completed the present invention.
Ba-Eu coprecipitated carbonate fine powder having an average particle size of 1 μm or more and 5 μm or less, an aqueous solution containing Ba ions and Eu ions (referred to as liquid A), and an aqueous solution including carbonate ions (referred to as liquid B) ) To precipitate Ba-Eu coprecipitated carbonate, when B liquid is added to A liquid, A liquid is added to B liquid, or A liquid and B liquid are simultaneously mixed. in any of the cases to be introduced also characterized by the on time more than 5 minutes or 5 seconds, and the proportion of carbonate ions relative to Ba and Eu ions, all Ba ions as BaCO _3, and Eu Io feedstock Ba -Eu co沈炭salt of the blue phosphor of the three band fluorescent lamp Ru 1.0 to 1.1 Baidea stoichiometry required to precipitation lees all as EuCO ₃ of emissions a fine powder and a manufacturing method thereof.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
Ba-Eu coprecipitated carbonate is precipitated by mixing an aqueous solution containing Ba ions and Eu ions (referred to as solution A) and an aqueous solution containing carbonate ions (referred to as solution B). The mixing method includes a method in which the B solution is added to the A solution, a method in which the A solution is introduced into the B solution, and a method in which the A solution and the B solution are added simultaneously. The main factor that influences the particle size is the liquid charging time, and the mixing method may be any of the above three methods as long as the charging time is controlled.
The particle size is reduced if the liquid charging time is shortened, and the particle size is increased by grain growth if it is lengthened. However, Ba-Eu coprecipitated carbonate particles having an average particle diameter of 1 μm to 5 μm, which is the object of the present invention, are produced. In order to achieve this, it is necessary that the charging time of the liquid is 5 seconds or more and 5 minutes or less. If it is less than 5 seconds (including 5 seconds below), the primary particles become small and agglomerate, and if it exceeds 5 minutes, the average particle size increases due to particle growth.
[0006]
The next most important factor after the charging time is the ratio of carbonate ions to Ba ions and Eu ions. The ratio of carbonate ions to Ba ions and Eu ions should be 1.0 to 1.1 times the stoichiometric ratio required to precipitate all of the Ba ions and Eu ions as carbonates. Here, the stoichiometric ratio of carbonate ions to Ba ions and Eu ions is calculated as follows: Ba ions calculated as Ba CO ₃ and Eu ions precipitated as Eu ₂ (CO ₃ ) _3. This refers to the molar ratio of carbonate ions in solution B to Eu ions. If the ratio is less than 1.0, the yield of Ba-Eu coprecipitated carbonate decreases, and if it exceeds 1.1, Ba re-dissolves and the yield decreases.
[0007]
The concentration of Ba, Eu and carbonate ions in the liquid is not a dominant factor for the particle size and yield, but is preferably 0.05 mol / L or more from the viewpoint of productivity. The upper limit is not particularly limited, and can be carried out even at a saturated concentration.
There is no particular restriction on the temperature, and it is most economical to carry out at room temperature that does not require energy for heating and cooling. However, when barium nitrate is used as the Ba salt, it is about 50 to 80 ° C. in order to increase the solubility. Heating is more advantageous because it increases productivity.
[0008]
Ba CO ₃ -Eu ₂ (CO ₃ ) ₃ , which is a precipitate obtained by mixing an aqueous solution containing Ba ions and Eu ions and an aqueous solution containing carbonate ions, is filtered, washed and dried by a known method to obtain a dry powder. Is supplied to the phosphor manufacturing process.
[0009]
【Example】
Hereinafter, although an embodiment and a comparative example are given and an embodiment of the present invention is explained concretely, the present invention is not limited to these at all.
Example 1
A 30 L jacketed stainless steel reaction vessel was charged with 10 L of 0.291 mol / L ammonium carbonate aqueous solution and heated to 50 ° C. To this solution, 10 L of a mixed aqueous solution of 0.25 mol / L barium nitrate and 0.0268 mol / L europium nitrate previously heated to 50 ° C. was added in 3 minutes. At this time, the stoichiometric ratio of carbonate ions to Ba ions and Eu ions was 1.0.
The precipitate was then filtered off with a Buchner funnel and washed with deionized water. Further, the precipitate was dried at 80 ° C. for 16 hours to obtain 531 g of Ba-Eu coprecipitated carbonate. The yield at this time was 96%.
The average particle diameter measured by a particle size distribution measuring apparatus (model number SPA) by Microtrac's laser diffraction method was 3.76 μm.
Regarding the uniformity of composition, the characteristics of Ba and Eu were confirmed by X-ray surface analysis using EPMA (electron beam microanalyzer). The coprecipitated carbonate was pelleted with a mold press to prepare an analytical sample. As a result of analysis, no segregation of Ba and Eu was observed, and it was found that both elements were uniformly distributed.
[0010]
(Example 2)
A 30 L jacketed stainless steel reaction vessel was charged with 10 L of a mixed aqueous solution of 0.25 mol / L barium nitrate and 0.0268 mol / L europium nitrate and heated to 50 ° C. To this solution, 10 L of a 0.291 mol / L aqueous ammonium carbonate solution preheated to 50 ° C. was added in 3 minutes. At this time, the stoichiometric ratio of carbonate ions to Ba ions and Eu ions was 1.0.
The precipitate was then filtered off with a Buchner funnel and washed with deionized water. Further, the precipitate was dried at 80 ° C. for 16 hours to obtain 534 g of Ba-Eu coprecipitated carbonate. The yield at this time was 96%, and the average particle size was 3.24 μm.
As a result of surface analysis by EPMA, no segregation of Ba and Eu was observed, and it was found that both elements were uniformly distributed.
[0011]
Example 3
A 30 L jacketed stainless steel reaction vessel was filled with 8 L deionized water and heated to 50 ° C. To this warm water, 10 L of a mixed aqueous solution of 0.25 mol / L barium nitrate and 0.0268 mol / L europium nitrate previously heated to 50 ° C., and 10 L of a 0.291 mol / L ammonium carbonate aqueous solution previously heated to 50 ° C. Were simultaneously added in 3 minutes. At this time, the stoichiometric ratio of carbonate ions to Ba ions and Eu ions was 1.0.
The precipitate was then filtered off with a Buchner funnel and washed with deionized water. Further, the precipitate was dried at 80 ° C. for 16 hours to obtain 533 g of Ba-Eu coprecipitated carbonate. The yield at this time was 96%, and the average particle size was 3.15 μm.
As a result of surface analysis by EPMA, no segregation of Ba and Eu was observed, and it was found that both elements were uniformly distributed.
[0012]
(Comparative Example 1)
531 g of Ba-Eu coprecipitated carbonate was obtained in the same manner as in Example 1 except that the charging time of the mixed solution of barium nitrate and europium nitrate was 10 minutes. The yield at this time was 95%, and the average particle size was 6.31 μm.
[0013]
(Comparative Example 2)
533 g of Ba-Eu coprecipitated carbonate was obtained in the same manner as in Example 1 except that the charging time of the mixed solution of barium nitrate and europium nitrate was 3 seconds. The yield at this time was 95%. Since the dried product was hard agglomerated, the average particle size was not measured.
[0014]
(Comparative Example 3)
The same method as in Example 1 except that the concentration of ammonium carbonate previously placed in the reaction vessel was 0.35 mol / L (that is, the stoichiometric ratio of carbonate ion to Ba ion and Eu ion was 1.2). Yielded 484 g of Ba-Eu coprecipitated carbonate. The yield at this time was 87%. The average particle size was 4.02 μm, which was within the target range, but the yield was poor and industrial feasibility was poor.
[0015]
【The invention's effect】
According to the present invention, Ba-Eu coprecipitated carbonate fine powder having an average particle diameter of 1 μm or more and 5 μm or less that is useful as a raw material for a blue phosphor for a three-wavelength fluorescent lamp can be produced in high yield, and its industrial use. The value is extremely high.

Claims (3)

Feedstock Ba -Eu co沈炭salt fine powder of the blue phosphor of the three band fluorescent lamp you wherein an average particle diameter of 1μm or more 5μm or less. When an aqueous solution containing Ba ions and Eu ions (referred to as liquid A) and an aqueous solution including carbonate ions (referred to as liquid B) are mixed to precipitate Ba-Eu coprecipitated carbonate, The charging time is set to 5 seconds or more and 5 minutes or less in any of the cases where the A liquid is added to the B liquid, or the A liquid and the B liquid are simultaneously charged. Item 2. A method for producing Ba- Eu coprecipitated carbonate fine powder for a blue phosphor material for a three-wavelength fluorescent lamp according to Item 1. The ratio of carbonate ion to Ba ions and Eu ions, all Ba ions as BaCO _3, you and Eu ions stoichiometric ratio required all to cause precipitation lees as EuCO ₃ of emissions 1.0 to 1 The method for producing Ba- Eu coprecipitated carbonate fine powder for a raw material of a blue phosphor for a three-wavelength fluorescent lamp according to claim 2, which is 1 time.