JPH09296168A - Method for producing rare earth phosphate phosphor - Google Patents

Abstract

(57) Abstract: A method for producing a rare earth phosphate phosphor capable of effectively improving lamp characteristics is provided. SOLUTION: The general formula (La _1-xy Ce _x Tb _y ) PO ₄
(However, x> 0, Y> 0, 0.1 ≦ x + y ≦ 0.8)
In the method for producing a rare earth phosphate phosphor shown by,
A rare earth phosphate produced by a reaction by mixing a solution containing a rare earth element and a solution containing a phosphoric acid compound in an acidic solution having a pH value of 3 or less or a solution containing a hydroxide of a rare earth element. A method for producing a rare earth phosphate phosphor, which comprises separating and purifying the phosphor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a rare earth phosphate phosphor, and in particular, has a spherical particle shape, a uniform particle diameter, and a low risk of aggregation and solidification.
The present invention relates to a method for producing a rare earth phosphate phosphor that can effectively improve lamp characteristics when used as a constituent material of a phosphor layer.

[0002]

2. Description of the Related Art La (lantern) and Ce in the 1970s
Since it was discovered that a phosphate containing a rare earth element such as (cerium) and Tb (terbium) has high luminescence characteristics in the green emission region, the rare earth phosphate phosphor has been used as a triple wavelength fluorescent substance. It is widely used as a green-emitting component phosphor for lamps.

Although various methods for producing the above-mentioned rare earth phosphate phosphor have been proposed, they are generally classified into a dry method and a wet method shown below. As a dry method, generally used is a method in which an oxide containing a rare earth element and a phosphoric acid compound are mixed and then fired to obtain a rare earth phosphate having a predetermined composition.

However, since the rare earth phosphate produced by the dry method has a very high hardness, the pulverization process is indispensable in the step of producing the green light emitting phosphor powder.
However, the phosphor powder obtained by the pulverization has a defect that the particle sizes are not uniform and the particle shape is not spherical. When a fluorescent lamp is manufactured using this phosphor powder, the phosphor layer having a smooth surface cannot be obtained due to the influence of the shape of the phosphor particles. As a result, there has been a problem that the deterioration of the total luminous flux of the fluorescent lamp over time becomes large and the luminous flux maintenance factor is likely to decrease.

In order to solve the above problems, it is considered necessary to make the particle diameters of the phosphors uniform and to make the particle shape spherical, and as a manufacturing method which meets the purpose, a wet method is widely used. It has been implemented. As a wet method, there is a method of directly generating an aqueous solution of a rare earth element in an aqueous solution of a phosphate, or conversely, directly adding an aqueous solution of a phosphate in an aqueous solution of a rare earth element to produce a rare earth phosphate by a reaction. Has been adopted.

[0006]

However, in the above-described conventional method for producing a phosphor by the wet method, when the aqueous solution of the rare earth element and the aqueous phosphate solution are simply mixed, the particle size is very fine with a particle size of less than 1 μm immediately after mixing. However, there has been a problem that various rare earth phosphates are produced one after another, and the separation and purification steps thereof are complicated. That is, since the sedimentation rate when washing the fine rare earth phosphate purified by the reaction is extremely small and the filterability is poor, there is a problem that the sedimentation separation operation takes a long time and the production efficiency is low. there were.

Further, when the separated rare earth phosphate particles are hot-air dried, the particles have a property of coagulating with each other and solidifying. In any case, a uniform phosphor layer having a smooth surface cannot be obtained, and the lamp There was a problem that the characteristics deteriorate.
On the other hand, according to the vacuum drying treatment, the fine phosphor particles are less aggregated and less likely to be solidified. However, the vacuum dryer has high initial equipment cost and operation cost, and it is essential to use a cheaper hot air dryer in order to improve mass productivity of the phosphor and reduce the manufacturing cost. Therefore, it was a technical problem to establish a method for producing a rare earth phosphate phosphor that does not aggregate and solidify even by hot air drying.

The present invention has good settling properties and filterability in the manufacturing process, has no characteristic of coagulation and solidification even when subjected to hot air drying, and has a spherical and uniform shape. An object of the present invention is to provide a method for producing a rare earth phosphate phosphor, which can effectively improve lamp characteristics when used as a layer constituent material.

[0009]

The first method for producing a rare earth phosphate phosphor according to the present invention comprises the general formula (La _1-xy C
e _x Tb _y) PO ₄ (provided that, x> 0, Y> 0,0.1 ≦
x + y ≦ 0.8) in the method for producing a rare earth phosphate phosphor, a solution containing a rare earth element and a solution containing a phosphoric acid compound are mixed in an acidic solution having a pH value of 3 or less, The rare earth phosphate produced by the reaction is separated and purified.

Here, it is preferable to add 1 to 5% by weight of the coagulant with respect to the rare earth phosphate in the acidic solution. further,
The acidic solution may contain a boric acid compound of at least one of boric acid and ammonium borate, and in this case, the concentration of the boric acid compound is preferably 0.0001 to 0.1M. The solution concentration of the rare earth element is 0.1
3.0M is preferred. Furthermore, the reaction temperature is 20 to 90 ° C.
Is preferred.

The separated and purified rare earth phosphate is preferably further heat-treated at a temperature of 400 to 900 ° C. in an inert gas atmosphere. Further, the average particle size of the rare earth phosphate is preferably 1.0 to 3.0 μm.

[0012] The second method for producing a rare earth phosphate phosphor of the present invention, the general formula _{(La 1-xy Ce x Tb} y) PO 4
(However, x> 0, Y> 0, 0.1 ≦ x + y ≦ 0.8)
In the method for producing a rare earth phosphate phosphor shown by,
It is characterized in that a solution containing a rare earth element and a solution containing a phosphoric acid compound are mixed in a solution containing a hydroxide of a rare earth element, and the rare earth phosphate produced by the reaction is separated and purified. .

Here, the hydroxide of the rare earth element is La,
It is preferably a hydroxide of at least one element selected from the group consisting of Ce and Y.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION First Production Method First, as a rare earth component raw material, nitrates, oxides, carbonates, chlorides, etc. of La, Ce, Tb are used, while as a phosphate compound, ammonium phosphate, Using monoammonium hydrogen phosphate, diammonium hydrogen phosphate, etc.,
A solution containing a rare earth element and a solution containing a phosphoric acid compound are prepared. The concentration of these two kinds of aqueous solutions is 1. In the case of a solution containing a rare earth element, considering the particle size of the produced rare earth phosphate and the production efficiency.
While it is in the range of 0 to 2.0M, it is preferably in the range of 1.5 to 3.0M in the case of a solution containing a phosphoric acid compound. In addition, it is advisable to prepare an excessive amount of the aqueous solution in the range of 1,000 to 1,500 times the theoretically required amount of the rare earth element and the phosphate compound.

Next, the prepared solution containing the rare earth element and the solution containing the phosphoric acid compound were adjusted to pH with nitric acid or the like.
Simultaneously drop into separate reaction tanks filled with acidic solutions with values adjusted to 3 or less. At this time, the dropping rate is set so that the pH value of the acidic solution does not fluctuate significantly and can maintain a constant value. Then, each component solution is dropped, and both components are reacted with stirring at a slow speed to synthesize a rare earth phosphate.

The mixing method of the solution containing the rare earth element and the solution containing the phosphoric acid compound is not limited to the method of dropping simultaneously in the separate reaction tanks filled with the acidic solution as described above, Such a mixing method can also be adopted. That is, nitric acid or the like is added to at least one of a solution containing a rare earth element and a solution containing a phosphoric acid compound to adjust the pH value to 3 or less, and then the other solution is added and mixed. May be adopted.

FIGS. 1 and 2 are graphs showing the relationship between the pH value of the acidic solution during the synthesis of the rare earth phosphate, the particle size of the rare earth phosphate produced by the synthesis reaction, and the settling time, respectively.

As shown in FIG. 1 and FIG.
By setting the pH value to 3 or less, it is possible to obtain a rare earth phosphate phosphor having a certain size and good sedimentation property. Particularly, in the synthesis reaction step,
By setting the pH value in the range of 0.5 to 3.0, it is possible to synthesize a rare earth phosphate having an average particle size of 1.0 to 2.3 μm and good sedimentation properties. Further, by setting the pH value in the range of 1.0 to 1.5, the sedimentation rate is high, and the particles do not aggregate and solidify even after the hot air drying treatment, and the particle size is 1.6 to 2.2 μm, which is suitable as a phosphor powder. A rare earth phosphate having a (particle size) is obtained.

Even when the reaction temperature is changed in the range of 20 to 90 ° C., there is little change in the particle size of the produced rare earth phosphate, and the rare earth phosphate having an average particle size of 1.6 to 2.2 μm. Is obtained. The preferred reaction temperature is 30-80
° C.

Further, when the solution containing the rare earth element and the solution containing the phosphoric acid compound are mixed in an acidic solution,
It is advisable to add 1 to 5% by weight of the coagulant with respect to the produced rare earth phosphate in the acidic solution. As the aggregating agent, methacrylic acid N—N diacrylquinanoalkyl ester acrylamide copolymer, polymethacrylic acid ester, chitosan and the like are used.

By adding the aggregating agent and reacting it in a temperature range of room temperature to 100 ° C. for 1 hour or more while keeping the pH value at 3 or less, fine fluorescent particles having a particle size of less than 1 μm produced in an acidic solution. By agglomerating body particles, a rare earth phosphate containing a large amount of particles having a particle size of 2 μm or more can be produced. Thus, the rare earth phosphate aggregated to a size of about 1 to 3 μm has a good sedimentation property, is less likely to aggregate and solidify, and can be easily separated by filtration after washing. Even after drying, without solidifying,
Holds moderate softness.

When the amount of the above flocculant added is less than 1% by weight based on the produced rare earth phosphate,
The above-mentioned aggregating effect is not sufficiently exerted, fine particles having a particle size of less than 1 μm do not aggregate, and phosphate particles having a particle size of 2 μm or more rarely grow. On the other hand, even if the amount of the aggregating agent is excessively added to exceed 5% by weight, the aggregating effect is saturated and the amount of impurities is rather increased, so that the light emission characteristics are impaired. Therefore, the amount of coagulant added is 1 to 5
It is preferable to set the weight% in the range.

Furthermore, by adding a predetermined amount of the boric acid compound as an impurity to the acidic solution, a part of the compound remains in the phosphor powder and the characteristics of the phosphor can be improved. That is, by setting the concentration of the boric acid compound in the acidic solution to 0.0001 M or more, it is possible to improve the emission brightness of the rare earth phosphate produced by the synthetic reaction as a phosphor. However, when the concentration of the boric acid compound exceeds 0.1 M, the particle size of the rare earth phosphate produced by the reaction becomes sharply small, the sedimentation property deteriorates and the filterability also deteriorates, and the separation operation becomes complicated. . Therefore, the concentration of the boric acid compound in the acidic solution is 0.
It is set in the range of 0001 to 0.1M.

After the aqueous solution of the rare earth element and the aqueous solution of the phosphoric acid compound were dropped into the acidic solution, the pH of the reaction solution and the reaction temperature were kept constant, and the mixture was stirred at a slow speed to sufficiently age the rare earth phosphate formed. Grow. Then, after aging and growing, an acidic solution containing the generated rare earth phosphate,
The supernatant liquid is washed repeatedly until the electric conductivity becomes 0.3 ms / cm or less, filtered, and the residue on the filter paper is dried with hot air, so that it does not solidify due to aggregation and is a soft rare-earth phosphate fluorescence. A body powder is obtained.

In place of the hot air drying treatment, the separated and purified rare earth phosphate is added in an inert gas atmosphere at 400-9.
It may be calcined at a temperature of 00 ° C. In particular, the rare earth phosphate calcined under the above treatment conditions improves the brightness as a phosphor,
It is possible to improve the characteristics of the fluorescent lamp.

Further, a rare earth phosphate powder which has been subjected to a hot air drying treatment or a calcination treatment is mixed with an alkali metal compound such as a lithium halide as a flux or a borate compound, and the mixture is subjected to an atmosphere or a reducing atmosphere. Baking is performed at a temperature of 1,000 to 1,200 ° C. for 1 to 5 hours, more preferably 2 to 4 hours. After firing, the obtained fired product is mixed in a wet ball mill (wet BM), and then washed, filtered, dried and sieved to obtain the rare earth phosphate green phosphor according to the present invention.

Second Manufacturing Method The solution containing a rare earth element and the solution containing a phosphoric acid compound used in the second manufacturing method are as described in the first manufacturing method.

The solution containing a hydroxide of a rare earth element used in the second production method preferably contains a hydroxide of at least one element selected from the group consisting of La, Ce and Y. Solution. Such a hydroxide-containing aqueous solution can be obtained, for example, by dissolving a nitrate, carbonate, chloride or the like of a rare earth element in water, and adding ammonia to the aqueous solution to raise the pH. Further, the hydroxide concentration of the rare earth element is not particularly limited.

In addition, the method of adding the solution containing the rare earth element or the solution containing the phosphoric acid compound to the solution containing the hydroxide of the rare earth element, and other additives are not particularly limited, and the first You may employ the same addition method as a manufacturing method, and may use the same additive.

The phosphors obtained by the first manufacturing method and the second manufacturing method have a rounder shape than the rare earth phosphate phosphor particles synthesized by the conventional dry method (solid phase method), It has a uniform diameter and rarely aggregates and solidifies. Various fluorescent lamps were prepared using this phosphor, and
As a result of measuring the total luminous flux after lighting for a long time, the lamp characteristics of all the fluorescent lamps were significantly improved as compared with the fluorescent lamp using the phosphor manufactured by the conventional liquid phase method (wet method).

[0031]

EXAMPLES Example 1 400 ml of a rare earth element aqueous solution having a molar ratio of La, Ce and Tb of 5: 4: 1 and a concentration of 1.5 M, and a concentration of 2.0.
An aqueous solution of M 2 diammonium hydrogen phosphate was prepared. On the other hand, the aqueous rare earth element solution and the diammonium hydrogen phosphate aqueous solution were added dropwise to the acidic solution prepared by adding nitric acid to 500 ml of pure water to adjust the pH value to 1.2 over 60 minutes. In the meantime, the pH value was 1.2 and the temperature was maintained at 30 ° C., and the reaction was carried out with slow stirring. After aging for 1 hour, the reaction product was washed, filtered, dried and sieved to obtain a coprecipitation of rare earth phosphate. The particle size of this rare earth phosphate was measured and found to be 2.2 μm.

Next, the obtained rare earth phosphate and a lithium halide as a flux were mixed, and then the mixture was baked in a reducing atmosphere at a temperature of 1,200 ° C. for 4 hours. The obtained composition was pulverized and mixed in a wet ball mill, and further washed, filtered, dried and sieved to prepare a rare earth phosphate phosphor according to Example 1.

Example 2 Example 2 was carried out in the same procedure as in Example 1 except that the boric acid compound was added to the acidic solution to which the rare earth element aqueous solution and the diammonium hydrogen phosphate aqueous solution were added dropwise to make the concentration 0.001M. A rare earth phosphate phosphor according to No. 2 was prepared.

Example 3 The rare earth phosphate phosphor produced in Example 1 was further heat-treated in an inert gas at a temperature of 800 ° C. to prepare a rare earth phosphate phosphor according to Example 3.

Example 4 A rare earth element aqueous solution having a molar ratio of La, Ce and Tb of 5: 4: 1 and a concentration of 1.5M and a diammonium hydrogenphosphate aqueous solution having a concentration of 3.0M were prepared. . On the other hand, 0.83 g of cerium nitrate was added to 400 ml of pure water, the mixture was stirred for 30 minutes, and then the aqueous cerium hydroxide solution obtained by adding aqueous ammonia was mixed with the rare earth element aqueous solution and the diammonium hydrogen phosphate aqueous solution. 6 over 60 minutes
Simultaneously added dropwise at an equal flow rate of ml / min. During that time, the initial pH of the cerium hydroxide aqueous solution was around 9, but the pH dropped sharply with the addition of both aqueous solutions, and the pH drop became gentle when the pH was around 3, and the pH dropped to 1.3 at the end of the dropping. I settled down in the vicinity. After completion of the dropping, the reaction was carried out while maintaining the temperature at 30 ° C. and stirring at a slow speed. After aging for 1 hour, the reaction product was washed, filtered, dried and sieved to obtain a coprecipitation of rare earth phosphate. The particle size of this rare earth phosphate was measured and found to be 2.8 μm.

Next, after mixing the obtained rare earth phosphate and a lithium halide as a flux, the mixture was fired in a reducing atmosphere at a temperature of 1,200 ° C. for 4 hours. Further, the obtained composition was pulverized and mixed by a wet ball mill, and further washed, filtered, dried and sieved to prepare a rare earth phosphate phosphor according to Example 4.

Examples 5 to 10 Rare earth phosphate phosphors according to Examples 5 to 10 by the same procedure except that the aqueous solution containing the hydroxide of the rare earth element and the concentration thereof were changed to those shown in Table 1. Was prepared.

[0038]

[Table 1]

Comparative Example 1 400 ml of a rare earth element aqueous solution having a molar ratio of La, Ce and Tb of 5: 4: 1 and a concentration of 1.5 M was added to a concentration of 1.5
40% in 500 ml of diammonium hydrogen phosphate aqueous solution of M
It was dripped over a period of minutes. In the meantime, the temperature was kept at 70 ° C., and the reaction was carried out with slow stirring. After aging for 1 hour, the reaction product was washed, filtered, dried and sieved to obtain a coprecipitation of rare earth phosphate. When the particle size of this rare earth phosphate was measured, it was 0.8 μm, which was fine.

Next, the obtained rare earth phosphate was mixed with lithium halide as a flux, and then the mixture was calcined in a reducing atmosphere at a temperature of 1,200 ° C. for 4 hours. Further, the obtained composition was pulverized and mixed by a wet ball mill, and further washed, filtered, dried and sieved to prepare a rare earth phosphate phosphor according to Comparative Example 1.

The particle sizes of the rare earth phosphates of Examples 1 to 10 and Comparative Example 1 thus prepared were measured and the results shown in Table 2 were obtained. In addition, using each rare earth phosphate phosphor, a 30 W type fluorescent lamp was prototyped according to a conventional method, and the total luminous flux of each lamp after being lit for 1,000 hours was measured. Was calculated.
In addition, the total luminous flux ratio of each example is shown relative to the total luminous flux ratio of the fluorescent lamp according to Comparative Example 1 as a reference value (100%). The measurement calculation results are shown in Table 2 below.

[0042]

[Table 2]

As is clear from the results shown in Table 2 above,
The particle size of each phosphor of Examples 1 to 10 is larger than that of the phosphor of Comparative Example 1 and is excellent as a constituent material of the phosphor layer for a fluorescent lamp.

Observation with a scanning electron microscope (SEM) revealed that all the phosphor particles of Example 1 had a spherical particle shape and a uniform particle size. In addition, also in Examples 2 to 10, similarly round phosphor particles having a uniform particle size were obtained.

Further, in the fluorescent lamps formed by using the phosphors of the respective examples, the total luminous flux ratio after lighting for 1,000 hours was 102 based on the total luminous flux ratio (100%) of the lamp of Comparative Example 1. It was found to be improved to ~ 105%. That is, according to the method for producing a rare earth phosphate phosphor according to this example, it is possible to obtain a rare earth phosphate phosphor having a uniform particle size and a spherical particle shape. It has become possible to improve the light emission characteristics of a fluorescent lamp using.

Next, the effect of using an aggregating agent during the reaction synthesis will be specifically described with reference to the following examples.

Example 11 and Comparative Example 2 0.50 mol of lanthanum chloride, 0.4, as shown in Table 3.
1 liter of a solution containing 0 cerium chloride and 0.10 mol terbium chloride and an aqueous solution containing 1.20 mol diammonium hydrogen phosphate were simultaneously added dropwise to a nitric acid solution having a pH of 2.5, and agglomerated. A methacrylic acid NN diacrylquinoalkyl ester acrylamide copolymer as an agent is added to the produced rare earth phosphate by 2
% By weight. After addition, the pH of the mixed solution using nitric acid
Temperature is adjusted to 60 ℃ while adjusting to keep the value at 2.5.
And reacted for 2 hours to synthesize a rare earth phosphate.

Next, the mixed solution containing the obtained reaction product is repeatedly washed until the electric conductivity of the supernatant becomes 0.3 ms / cm or less, and further filtered and dried to obtain a rare earth phosphorus. An acid salt powder was obtained.

Furthermore, 2 wt% of lithium fluoride as a flux and 20 wt% of boric acid were mixed with the obtained rare earth phosphate powder, and the obtained mixture was filled in an alumina crucible, and nitrogen and nitrogen were added. The rare earth phosphate phosphor according to Example 11 was manufactured by firing in a reducing atmosphere of hydrogen at a temperature of 1,200 ° C. for 4 hours.

The composition of the obtained phosphor is (La _0.5 Ce
_0.4 Tb _0.1 ) PO ₄ , and this phosphor showed green emission with an emission peak wavelength near 545 nm when excited by ultraviolet rays. In addition, this phosphor is used as a scanning electron microscope (SEM).
As a result of observation, it was confirmed that the particle size was uniform and uniform, and the shape was almost spherical, as in the phosphor of Example 1.

On the other hand, according to the conventional dry method, a rare earth phosphate phosphor of Comparative Example 2 having the same composition as that of Example 11 was manufactured by the following procedure. That is, 0.5 mol of lanthanum oxide, 0.4 mol of cerium oxide, 0.1 mol of terbium oxide and 1.2 mol of diammonium hydrogen phosphate were mixed sufficiently uniformly, and the resulting mixture was placed in an aluminum crucible. It was housed and baked in a nitrogen atmosphere at a temperature of 1,000 ° C. for 3 hours. Next, the obtained composition was treated according to a usual dry method of crushing, washing, filtering and drying to prepare a rare earth phosphate phosphor powder.

Further, a flux was mixed with the obtained phosphor powder under the same conditions as in Example 1, and the obtained mixture was fired to prepare a rare earth phosphate phosphor according to Comparative Example 2.

The phosphors of Example 11 and Comparative Example 2 thus manufactured were heated, and the brightness of the powder after heating was measured to obtain the results shown in Table 4. In addition, the powder brightness of the phosphor of each example is shown relative to the powder brightness of the corresponding comparative example manufactured by the dry method as a reference value (100%).

A 30 W type fluorescent lamp was prepared using the phosphors of Example 11 and Comparative Example 2, and
The emission intensity after lighting for a while was measured and the results shown in Table 4 were obtained. In addition, the emission intensity of the example is shown relative to the emission intensity of the lamp of the comparative example manufactured by the dry method as a reference value (100%).

As is clear from the results shown in Table 4, in the powder brightness of the phosphor after heating, the brightness is improved by 3% in Example 11 as compared with the case of the corresponding Comparative Example 2. There was found. As for the emission intensity of the fluorescent lamp after lighting for 1,000 hours, the size of the particles of the phosphor in Example 11 was more uniform than that in Comparative Example 2, and the shape was almost spherical. A smooth phosphor layer could be formed, the brightness was improved by 4%, and a good luminous flux maintenance factor was obtained.

Example 12 and Comparative Example 3 0.70 mol of lanthanum carbonate, 0.2, as shown in Table 3.
While simultaneously adding 1 liter of an aqueous solution containing 0 mol of cerium carbonate and 0.10 mol of terbium carbonate and a solution containing 1.10 mol of diammonium hydrogen phosphate dropwise to a nitric acid solution having a pH of 1.0, Polymethacrylic acid ester as a coagulant was added in an amount of 5% by weight with respect to the produced rare earth phosphate. After the addition, nitric acid was used to adjust the pH value of the mixed solution to 1.0, and the mixture was reacted at a temperature of 40 ° C. for 2 hours to synthesize a rare earth phosphate phosphor.

Next, the mixed solution containing the obtained reaction product is repeatedly washed until the electric conductivity of the supernatant becomes 0.3 ms / cm or less, and further filtered and dried to obtain a rare earth phosphorus. An acid salt powder was obtained.

Further, 2 wt% of lithium fluoride as a flux and 20 wt% of boric acid were blended with the obtained rare earth phosphate powder, and the obtained mixture was filled in an alumina crucible, and nitrogen and nitrogen were added. The rare earth phosphate phosphor according to Example 12 was manufactured by firing in a reducing atmosphere of hydrogen at a temperature of 1,200 ° C. for 4 hours.

The composition of the obtained phosphor is (La _0.7 Ce
_0.2 Tb _0.1 ) PO ₄ , and this phosphor showed green emission with an emission peak wavelength near 545 nm when excited by ultraviolet rays. In addition, this phosphor is used as a scanning electron microscope (SEM).
As a result of observation, it was confirmed that the particle size was uniform and uniform, and the shape was almost spherical, as in the phosphor of Example 1.

On the other hand, according to the conventional dry method, a rare earth phosphate phosphor of Comparative Example 3 having the same composition as that of Example 12 was manufactured by the following procedure. That is, 0.7 mol of lanthanum oxide, 0.2 mol of cerium oxide, 0.1 mol of terbium oxide, and 1.1 mol of diammonium hydrogen phosphate were uniformly mixed, and the resulting mixture was placed in an aluminum crucible. It was housed and baked in a nitrogen atmosphere at a temperature of 1,000 ° C. for 3 hours. Next, the obtained composition was treated according to a usual dry method of crushing, washing, filtering and drying to prepare a rare earth phosphate phosphor powder.

A flux was added to the obtained phosphor powder under the same conditions as in Example 12, and the obtained mixture was fired to prepare a rare earth phosphate phosphor according to Comparative Example 3.

The phosphors of Example 12 and Comparative Example 3 thus manufactured were heated, and the brightness of the powder after heating was measured to obtain the results shown in Table 4.

A 30 W type fluorescent lamp was prepared using the phosphors of Example 12 and Comparative Example 3, and
The emission intensity after lighting for a while was measured and the results shown in Table 4 were obtained.

As is clear from the results shown in Table 4, in the powder brightness of the phosphor after heating, the brightness is improved by 4% in Example 12 as compared with the case of the corresponding Comparative Example 3. There was found. Regarding the emission intensity of the fluorescent lamp after lighting for 1,000 hours, the particles of the phosphor of Example 12 are more uniform in size than the case of Comparative Example 3, and the shape is almost spherical. A smooth phosphor layer could be formed, the brightness was improved by 4%, and a good luminous flux maintenance factor was obtained.

Example 13 and Comparative Example 4 0.30 mol of lanthanum oxide, 0.5, as shown in Table 3.
1 liter of a solution containing 0 mol of cerium oxide and 0.10 mol of terbium oxide and 1.40 mol of a solution containing orthophosphoric acid were simultaneously added dropwise to a nitric acid solution having a pH of 2.0 and used as a coagulant. Chitosan of 1% by weight was added to the produced rare earth phosphate. After the addition,
A rare earth phosphate was synthesized by reacting at 70 ° C. for 2 hours while adjusting the pH value of the mixed solution to 2.0 using nitric acid.

Next, the mixed solution containing the obtained reaction product is repeatedly washed until the electric conductivity of the supernatant becomes 0.3 ms / cm or less, and further filtered and dried to obtain a rare earth phosphorus compound. An acid salt powder was obtained.

Further, 2% by weight of lithium fluoride as a flux and 20% by weight of boric acid were mixed with the obtained rare earth phosphate powder, and the obtained mixture was filled in an alumina crucible, and nitrogen and The rare earth phosphate phosphor according to Example 13 was manufactured by firing in a reducing atmosphere of hydrogen at a temperature of 1,200 ° C. for 4 hours.

The composition of the obtained phosphor is (La _0.3 Ce
_0.5 Tb _0.1 ) PO ₄ , and this phosphor showed green emission with an emission peak wavelength near 545 nm when excited by ultraviolet rays. In addition, this phosphor is used as a scanning electron microscope (SEM).
As a result of observation, it was confirmed that the particle size was uniform and uniform, and the shape was almost spherical, as in the phosphor of Example 1.

On the other hand, according to the conventional dry method, the rare earth phosphate phosphor of Comparative Example 4 having the same composition as that of Example 13 was manufactured by the following procedure. That is, 0.3 mol of lanthanum oxide, 0.5 mol of cerium oxide, 0.1 mol of terbium oxide and 1.4 mol of diammonium hydrogen phosphate were mixed sufficiently uniformly, and the resulting mixture was placed in an aluminum crucible. It was housed and baked in a nitrogen atmosphere at a temperature of 1,000 ° C. for 3 hours. Next, the obtained composition was treated according to a usual dry method of crushing, washing, filtering and drying to prepare a rare earth phosphate phosphor powder.

Further, a flux was added to the obtained phosphor powder under the same conditions as in Example 13, and the obtained mixture was fired to prepare a rare earth phosphate phosphor according to Comparative Example 4.

The phosphors of Example 13 and Comparative Example 4 thus produced were heated, and the brightness of the powder after heating was measured to obtain the results shown in Table 4.

A 30 W type fluorescent lamp was prepared using the phosphors of Example 13 and Comparative Example 4, and
The emission intensity after lighting for a while was measured and the results shown in Table 4 were obtained.

As is clear from the results shown in Table 4, with respect to the powder brightness of the phosphor after heating, the brightness is improved by 2% in Example 13 as compared with the case of the corresponding Comparative Example 4. There was found. Regarding the emission intensity of the fluorescent lamp after 1,000 hours of lighting, Example 13 has a more uniform particle size of the phosphor than that of Comparative Example 4, and the shape is almost spherical. A smooth phosphor layer could be formed, the brightness was improved by 3%, and a good luminous flux maintenance factor was obtained.

Examples 14 to 20 and Comparative Examples 5 to 11 Compounds containing rare earth elements as shown in Table 3 below were used, and the amount of the aggregating agent added to the acidic solution during the reaction synthesis is shown in Table 3. In the same manner as in Example 11 except that the content was changed to 1 to 4% by weight, the rare earth element aqueous solution and the phosphoric acid compound aqueous solution were added dropwise to the acidic solution to synthesize the rare earth phosphate. Further, washing, filtration, drying and firing were carried out in the same manner as in Example 11 to prepare the rare earth phosphate phosphors according to Examples 14 to 20 having the compositions shown in Table 3, respectively.

On the other hand, Comparative Examples 5 to 11 corresponding to Examples 14 to 20 and having the same composition by treating the rare earth element compound and the phosphoric acid compound according to the conventional dry method as described in Comparative Example 2 are described. Rare earth phosphate phosphors were prepared respectively.

[0076]

[Table 3]

The phosphors of Examples 14 to 20 and Comparative Examples 5 to 11 thus produced were heated, and the powder brightness after heating was measured, and a 30 W type fluorescent lamp was prepared using each phosphor. The light emission intensity after 1,000 hours of lighting was measured and the results shown in Table 4 below were obtained.

[0078]

[Table 4]

As is clear from the results shown in Table 4, the powder brightness of the phosphor after heating was measured in Examples 14 to 15.
It was found that in No. 20, the brightness was improved by 2 to 4.6% as compared with the corresponding Comparative Examples 5 to 11. Also 1,
Regarding the emission intensity of the fluorescent lamp after lighting for 000 hours, the particles of the phosphors of Examples 14 to 20 are more uniform than those of Comparative Examples 5 to 11, and the shape is almost spherical. Therefore, a smooth phosphor layer could be formed, the brightness was improved by 1.5 to 4%, and a good luminous flux maintenance factor was obtained.

[0080]

Industrial Applicability As described above, according to the method for producing a rare earth phosphate phosphor of the present invention, the settling property and the filterability in the production process are good, and further, the coagulation and solidification occur even when the hot air drying treatment is carried out. Does not occur, and has a characteristic that the shape is spherical and uniform, and when used as a constituent material of the phosphor layer, a rare earth phosphate phosphor capable of effectively improving the lamp characteristics is obtained. be able to.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the pH value of an acidic solution during the synthesis of a rare earth phosphate and the particle size of the rare earth phosphate produced by the synthesis reaction.

FIG. 2 is a graph showing the relationship between the pH value of an acidic solution during the synthesis of a rare earth phosphate and the sedimentation time of the rare earth phosphate produced by the synthetic reaction.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hirofumi Takemura Inventor Hirofumi Takemura 8 Shinsita-cho, Isogo-ku, Yokohama-shi, Kanagawa Within the Yokohama Works of Toshiba Corporation (72) Inventor Takeshi Iwasaki 7-1 Nisshin-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Shiba Electronics Engineering Co., Ltd.

Claims (9)

[Claims] 1. A general formula (La _1-xy Ce _x Tb _y ) PO ₄
(However, x> 0, Y> 0, 0.1 ≦ x + y ≦ 0.8)
In the method for producing a rare earth phosphate phosphor shown by,
A rare earth phosphorus characterized by mixing a solution containing a rare earth element and a solution containing a phosphoric acid compound in an acidic solution having a pH value of 3 or less, and separating and purifying a rare earth phosphate produced by the reaction. Method for producing an acid salt phosphor. 2. The method for producing a rare earth phosphate phosphor according to claim 1, wherein 1 to 5% by weight of the rare earth phosphate is added to the acidic solution in the acidic solution. 3. The rare earth phosphate according to claim 1, wherein the acidic solution contains at least one boric acid compound of boric acid and ammonium borate, and the concentration of the boric acid compound is 0.0001 to 0.1M. Method for manufacturing phosphor. 4. The concentration of a solution containing a rare earth element is 0.
The method for producing a rare earth phosphate phosphor according to claim 1, wherein the amount is 1 to 3.0M. 5. The method for producing a rare earth phosphate phosphor according to claim 1, wherein the reaction temperature is 20 to 90 ° C. 6. The method for producing a rare earth phosphate phosphor according to claim 1, wherein the separated and purified rare earth phosphate is further heat-treated at a temperature of 400 to 900 ° C. in an inert gas atmosphere. 7. The average particle size of the rare earth phosphate is 1.0 to
The method for producing a rare earth phosphate phosphor according to claim 1, which has a thickness of 3.0 μm. 8. A compound represented by the general formula (La _1-xy Ce _x Tb _y ) PO ₄
(However, x> 0, Y> 0, 0.1 ≦ x + y ≦ 0.8)
In the method for producing a rare earth phosphate phosphor shown by,
It is characterized in that a solution containing a rare earth element and a solution containing a phosphoric acid compound are mixed in a solution containing a hydroxide of a rare earth element, and the rare earth phosphate produced by the reaction is separated and purified. Rare earth phosphate phosphor manufacturing method. 9. The rare earth phosphate phosphor according to claim 8, wherein the hydroxide of the rare earth element is a hydroxide of at least one element selected from the group consisting of La, Ce and Y. Production method.