JPS6367516B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a phosphor, and more particularly to a divalent metal borate phosphor whose luminance decreases little over time.

Conventionally, divalent metal borate-based phosphors have been known as a group of phosphors. A divalent metal borate phosphor is one whose matrix is at least a divalent metal oxide (M〓
O, where M〓 is at least one of Ca, Sr, Ba, Be, Mg, Zn, and Cd) and boron oxide (B ₂ O ₃ ). To date, many phosphors have been known that differ in matrix composition, activator, or both. This divalent metal borate-based phosphor generally emits high-intensity light when excited by ultraviolet rays, electron beams, etc.
It is particularly useful as a phosphor for lamps.

By the way, in the production of phosphors, after a firing step in which phosphor raw materials are fired to form phosphors, the produced phosphors are generally washed. This cleaning of the phosphor is carried out to remove soluble impurities contained in the phosphor such as unreacted soluble phosphor raw materials and soluble flux added to the phosphor raw materials.
Water is generally used as the cleaning liquid, and in some cases, a weak acid aqueous solution is used to enhance the cleaning effect.

It is not possible to directly quantify the soluble impurities contained in the fluorophore. Therefore, in order to find out the amount of soluble impurities contained in a phosphor, a certain amount of soluble impurities contained in a phosphor is eluted into a certain amount of water, and then the conductivity of the water is measured. This indirect method is generally used. For example, in this indirect method, 1 g of phosphor is poured into 50 cc of water at 100°C, allowed to cool while stirring until the water temperature reaches 20°C, and the conductivity of the water at 20°C is measured. (Hereinafter, the electrical conductivity measured in this way will be referred to as "eluted electrical conductivity"). Of course, the higher the measured elution conductivity value, the more soluble impurities the phosphor contains.

For many phosphors, soluble impurities contained in the phosphor after firing can be efficiently removed by the above-mentioned washing treatment with water or a weak acid aqueous solution, and the phosphor generally dissolves after the washing treatment. The conductivity can be made to be approximately several μ/cm. However, divalent metal borate phosphors have a common feature in that soluble impurities contained in the phosphor after firing cannot be sufficiently removed by the cleaning treatment with water or a weak acid aqueous solution. are doing.
In other words, even if a divalent metal borate phosphor is carefully cleaned by increasing the number of times it is washed or by increasing the temperature of the cleaning solution, the elution conductivity of the phosphor after the cleaning process is It was generally higher than about 400μ/cm. The soluble impurities contained in the divalent metal borate-based phosphor after firing are unreacted phosphor raw materials such as divalent metal salts, fluxes, etc., but why are these soluble impurities not efficiently cleaned by the cleaning process? The reason why it cannot be removed well has not yet been clarified.

As mentioned above, conventional divalent metal borate phosphors contain significantly larger amounts of soluble impurities than many other phosphors. That is, the elution conductivity of many phosphors is generally on the order of several μ/cm, whereas the elution conductivity of divalent metal borate phosphors is generally higher than about 400 μ/cm. Divalent metal borate phosphors having elution conductivities lower than about 400 μ/cm have not been previously known. Furthermore, no research has been conducted on how the large amount of soluble impurities contained (remaining) in conventional divalent metal borate phosphors affects the luminescent properties of the phosphors. Nakatsuta.

The present inventors have found that a novel treatment method using an ion exchange resin removes soluble impurities contained on the fired divalent metal borate phosphor much more efficiently than the conventional cleaning treatment described above. It has been found that the elution conductivity of the phosphor after treatment can be reduced to about several μ/cm.
Using this new processing method, we prepared a large number of phosphors with different elution conductivities, and investigated the relationship between elution conductivity and luminescence properties in divalent metal borate phosphors, in other words, the relationship between soluble impurity content and We conducted various studies on the relationship with luminescence characteristics. the result,
In divalent metal borate phosphors, elution conductivity,
That is, the soluble impurity content is a function of the decrease in emission brightness over time, and a divalent metal borate phosphor with an elution conductivity in the range of 15 to 150 μ/cm should have an elution conductivity of at least about 400 μ/cm. The inventors have now completed the present invention by discovering that the luminance decreases less over time than conventional divalent metal borate-based phosphors.

The phosphor of the present invention has a divalent metal oxide (M〓O, where M〓 is Ca, Sr, Ba, Be, Mg, Zn
and Cd) and boron oxide (B ₂ O ₃ ), the elution conductivity of the phosphor is 15 to 150μ. /cm.

As is clear from the above description of the prior art, the present invention has a dissolution conductivity of 15 to 150μ/cm.
A valent metal borate-based phosphor was completely unknown until now, and it is also known that a divalent metal borate-based phosphor with such elution conductivity exhibits excellent luminescent properties (i.e., luminance This was also completely unknown until now.

The divalent metal borate phosphor of the present invention having an elution conductivity of 15 to 150 μ/cm is obtained by processing the divalent metal borate phosphor after firing using a novel treatment method using the following ion exchange resin. It can be adjusted by processing. That is, in the new treatment method, the fired phosphor is first placed in boiling water in which an anion exchange resin is dispersed, and the mixed system is thoroughly stirred. By this treatment with an anion exchange resin in boiling water, anion components of soluble impurities contained in the phosphor are removed. Thereafter, the phosphor is separated from the mixed system, and then placed in boiling water in which the cation exchange resin is dispersed, and the mixed system is thoroughly stirred. By this treatment with a cation exchange resin in boiling water, cationic components of soluble impurities contained in the phosphor are removed. The phosphor is then separated from the mixed system and dried.

According to the above processing method, it is possible to obtain a divalent metal borate phosphor having an elution conductivity lower than about 400 μ/cm, which could not be obtained by conventional cleaning processes. In the above processing method, there are various variables that are a function of the elution conductivity of the obtained phosphor (in other words, the amount of soluble impurities removed), but in general, variables other than the processing time are appropriately kept constant, By varying only the processing time, a phosphor with the desired elution conductivity can be tailored. Of course, the longer the treatment time, the lower the elution conductivity of the phosphor obtained. The elution conductivity of the phosphor obtained by the above treatment method is approximately 20μ/cm.
In the following cases, a small amount of acid is added to the boiling water in any ion exchange resin dispersion,
Boiling water is made into a weak acid aqueous solution. It is very difficult to obtain phosphors with elution conductivities below about 20 μ/cm if no acid is added. Furthermore, in the above treatment method, by forcibly blowing high-temperature steam into the ion exchange resin dispersion during phosphor treatment, the treatment effect can be enhanced and the treatment time can be shortened.

The drawing shows 0.8MgO, which is a type of divalent metal borate phosphor treated by the above treatment method after firing.
B ₂ O ₃ :Ce, is a graph showing the relationship between the elution conductivity in a Tb phosphor and the relative emission brightness with respect to the emission brightness (100%) at the initial stage of excitation after continuously exciting the phosphor for 100 hours. . The graph in the drawing shows the manufacturing of a large number of low-pressure mercury vapor fluorescent lamps using a large number of 0.8MgO・B ₂ O ₃ :Ce, Tb phosphors with different elution conductivities and using these phosphors as a fluorescent film. Measure the luminance of each fluorescent lamp at the initial lighting stage and after 100 hours of continuous lighting to determine the relative luminance of each fluorescent lamp after 100 hours of continuous lighting with respect to the initial luminance (100%). This was obtained by plotting the elution conductivity of the 0.8MgO.B ₂ O ₃ :Ce, Tb phosphor used on the vertical axis and on the horizontal axis.

As is clear from the drawing, the degree of decrease in luminance after 100 hours of continuous excitation compared to the initial luminance is
0.8MgO・B ₂ O ₃ : Elution conductivity of Ce, Tb phosphor,
In other words, it depends on the soluble impurity content,
Until the elution conductivity reaches around 50 μ/cm, the degree of reduction in luminescence brightness gradually decreases as the elution conductivity decreases. When the elution conductivity is around 50μ/cm, the degree of decrease in luminance becomes minimum, and when the elution conductivity is around 50μ
When the value is further lower than /cm, the degree of reduction in luminance becomes larger as the elution conductivity becomes lower. This is presumed to be due to a long processing time, acid, etc., which caused part of the phosphor to decompose or become fine particles, resulting in a decrease in brightness. And the conventional approximately 400μ
0.8MgO with elution conductivity higher than /cm
B ₂ O ₃ :Ce, Tb phosphor has higher luminescence brightness than B ₂ O ₃ :Ce, Tb phosphor, which has elution conductivity of 15 to 400 μ/cm, which was previously unknown. The degree of decrease is small. That is, in the latter case, the luminance decreases less over time than in the former case.

As mentioned above, the drawing shows 0.8MgO・B ₂ O ₃ :Ce,
This is data measured for Tb phosphor.

Since the present invention is concerned with the problem of brightness deterioration due to elution of the matrix of the phosphor, which is a divalent metal borate, there is almost no difference in effectiveness depending on the activator. This was also confirmed in Examples in which the activator was changed to Mn, Tb, or Eu.

The present inventors used Tb, Dy, and Pb as activators.
Various divalent metal borate-based fluorescers using phosphors, etc., and various divalent metal borate-based fluorescers in which part of the parent boron and divalent metals are replaced with other elements such as phosphorus or silicon. The same data as in the drawings were also measured for the body. As a result, divalent metal borate phosphors, which generally have an elution conductivity of 15 to 150 μ/cm, have a divalent metal borate phosphor that has an elution conductivity higher than the conventional 400 μ/cm.
It has been found that the luminance decreases less over time than the valent metal borate-based phosphors. In the present invention, 2
The elution conductivity of the valent metal borate phosphor is 15 to 15.
The reason why it is limited to 150 μ/cm is based on the above-mentioned knowledge obtained through numerous experiments. Among the phosphors of the present invention, phosphors having an elution conductivity of 20 to 130 .mu./cm generally exhibit particularly little decline in luminance over time.

As explained above, the present invention provides a divalent metal borate-based phosphor whose luminance decreases less over time than conventional divalent metal-borate-based phosphors, Its practical value is great.

Next, the present invention will be explained with reference to Examples.

Example 1 Magnesium nitrate [Mg(NO ₃ ) ₂・6H ₂ O], boron oxide (B ₂ O ₃ ), cerium nitrate [Ce(NO ₃ ) ₃・
6H ₂ O] and terbium nitrate [Tb(NO ₃ ) ₃ .
6H ₂ O] in a molar ratio of 0.8:1.0:0.16:0.06, and further mixed with an appropriate amount of lithium nitrate (LiNO ₃ ) as a flux to prepare a phosphor raw material mixture. This phosphor raw material mixture was fired at a temperature of 1030°C for 3 hours in a reducing atmosphere, and the MgO.
A 1.25B ₂ O ₃ :0.2Ce, 0.075Tb phosphor was obtained. The phosphor obtained after firing was poured into boiling water in which an anion exchange resin was dispersed, and the mixture was thoroughly stirred. Thereafter, the phosphor was separated from the anion exchange resin dispersion, and then poured into boiling water in which the cation exchange resin was dispersed, and thoroughly stirred. In this case, stirring was performed by forcibly blowing steam at 120°C into the cation exchange resin dispersion. The phosphor was then separated from the cation exchange resin dispersion and dried.

If the above-mentioned post-firing treatment is carried out,
The elution conductivity of the 0.8MgO.B ₂ O ₃ :0.16Ce, 0.06Tb phosphor was 74 μ/cm. Furthermore, in a low-pressure mercury vapor fluorescent lamp using this phosphor as a fluorescent film, the luminance after 100 hours of continuous lighting was 96%, assuming that the initial luminance was 100%.

On the other hand, 0.8MgO produced in the same manner as above
B ₂ O ₃ :0.16Ce, 0.06Tb After firing, the phosphor was poured into water at 80° C. and thoroughly stirred for washing treatment, and then the phosphor was separated from the washing water and dried.

Traditional cleaning processes such as those described above are not recommended.
The elution conductivity of the 0.8MgO.B ₂ O ₃ :0.16Ce, 0.06Tb phosphor was 410 μ/cm. Furthermore, when the initial luminance of a low-pressure mercury vapor fluorescent lamp using this phosphor as a fluorescent film is 100%, the luminance after 100 hours of continuous lighting was 70%.

Example 2 Cadmium carbonate (CdCO ₃ ), ammonium borate (NH ₄ HB ₄ O _{7.3H 2} O) and manganese carbonate (MnCO ₃ ) were mixed in a molar ratio of 1:0.3:0.025, and then fused to this. A phosphor raw material mixture was prepared by adding and mixing 3% by weight of ammonium chloride (NH ₄ Cl) as an agent. This phosphor raw material mixture was heated to 800℃.
A Cd ₂ B ₂ O ₅ :Mn phosphor was obtained by firing at a temperature of 2 hours. The phosphor obtained after firing was poured into boiling water in which an anion exchange resin was dispersed, and the mixture was thoroughly stirred. Thereafter, the phosphor was separated from the anion exchange resin dispersion, and then poured into boiling water in which the cation exchange resin was dispersed, and thoroughly stirred. In this case, stirring was performed by forcibly blowing steam at 120°C into the cation exchange resin dispersion. The fluorophore is then separated from the anion exchange resin dispersion,
Dry.

If the above-mentioned post-firing treatment is carried out,
Cd ₂ B ₂ O ₅ :The elution conductivity of Mn phosphor is 50μ/cm
It was hot. Furthermore, when the initial luminance of a low-pressure mercury vapor fluorescent lamp using this phosphor as a fluorescent film is 100%, the luminance after 100 hours of continuous lighting was 80%.

On the other hand, Cd ₂ B ₂ O ₅ produced in the same manner as above:
After firing, the Mn phosphor was poured into water at 80° C. and thoroughly stirred for washing treatment, and then the phosphor was separated from the washing water and dried.

Traditional cleaning processes such as those described above are not recommended.
Cd ₂ B ₂ O ₅ :The elution conductivity of Mn phosphor is 400μ/cm
It was hot. In addition, a low-pressure mercury vapor fluorescent lamp using this phosphor as a fluorescent film had an emission volatility of 75% after 100 hours of continuous lighting, assuming that the initial emission brightness was 100%.

Example 3 Barium carbonate (BaCO ₃ ), potassium carbonate (K ₂ CO ₃ ), magnesium oxide (MgO), boric acid (H ₃ BO ₃ ) and terbium oxide (Tb ₄ O ₇ ) in a molar ratio of 1.76:0.06:1 :2:0.03 ratio,
Furthermore, an appropriate amount of acidified ammonium (NH ₄ HF ₂ ) as a flux was added and mixed to prepare a phosphor raw material mixture. This phosphor raw material mixture was fired twice for 3 hours at a temperature of 900°C in a reducing atmosphere to give Ba _1.76.
A K _0.12 Tb _0.12 Mg (BO ₃ ) ₂ fluorophore was obtained. The phosphor obtained after firing was poured into boiling water in which an anion exchange resin was dispersed, and the mixture was thoroughly stirred. Thereafter, the phosphor was separated from the anion exchange resin dispersion, and then poured into boiling water in which the cation exchange resin was dispersed, and thoroughly stirred. In this case, stirring was performed by forcibly blowing steam at 120°C into the cation exchange resin dispersion. Thereafter, the phosphor was separated from the anion exchange resin dispersion and dried.

Ba _1.76 subjected to post-calcination treatment as above
K _0.12 Tb _0.12 Mg (BO ₃ ) ₂ The elution conductivity of the phosphor is 40μ
/ cm. In addition, a low-pressure mercury vapor fluorescent lamp using this phosphor as a fluorescent film has an initial luminance of 100%.
%, the luminance after 100 hours of continuous lighting is 100
It was %.

On the other hand, Ba _1.76 K _0.12 produced in the same manner as above
After firing, the Tb _0.12 Mg (BO ₃ ) ₂ phosphor was poured into water at 80° C. and thoroughly stirred for washing treatment, and then the phosphor was separated from the washing water and dried.

Ba _1.76 with conventional cleaning treatment as described above.
K _0.12 Tb _0.12 Mg (BO ₃ ) ₂ Elution conductivity of phosphor is 500μ
/ cm. In addition, a low-pressure mercury vapor fluorescent lamp using this phosphor as a fluorescent film has an initial luminance of 100%.
%, the luminance brightness after 100 hours of continuous lighting is 85
It was %.

Example 4 Strontium nitrate [Sr(NO ₃ ) ₂ ], calcium nitrate [Ca(NO ₃ ) ₂ ·4H ₂ O], boric acid (H ₃ BO ₃ ) and europium oxide (Eu ₂ O ₃ ) in a molar ratio of 0.9 :
They were mixed in a ratio of 0.1:8:0.008, and an appropriate amount of ammonium chloride (NH ₄ Cl) as a flux was added and mixed to prepare a phosphor raw material mixture. This phosphor raw material mixture was fired at a temperature of 900°C for 2 hours in a reducing atmosphere to form (Sr _0.9 Ca _0.1 )O.2B ₂ O ₃ :Eu ²⁺
I got a phosphor. The phosphor obtained after firing was poured into boiling water in which an anion exchange resin was dispersed, and the mixture was thoroughly stirred. Thereafter, the phosphor was separated from the anion exchange resin dispersion, and then poured into boiling water in which the cation exchange resin was dispersed, and thoroughly stirred. In this case, stirring was performed by forcibly blowing steam at 120°C into the cation exchange resin dispersion. Thereafter, the phosphor was separated from the anion exchange resin dispersion and dried.

The post-firing treatment as described above was carried out (Sr _0.9
Ca _0.1 ) O・2B ₂ O ₃ :Elution conductivity of Eu ²⁺ fluorophore is
It was 30μ/cm. Furthermore, if the initial ultraviolet output of a low-pressure mercury vapor fluorescent lamp using this phosphor as a fluorescent film was 100%, the ultraviolet output after 100 hours of continuous operation was 100%.

On the other hand, produced in the same manner as above (Sr _0.9 Ca _0.1 )
After the O.2B ₂ O ₃ :Eu ²⁺ phosphor was fired, it was poured into water at 80° C. and thoroughly stirred for washing treatment, and then the phosphor was separated from the washing water and dried.

A conventional cleaning process was performed as described above (Sr _0.9
Ca _0.1 ) O・2B ₂ O ₃ :Elution conductivity of Eu ²⁺ fluorophore is
It was 450μ/cm. Furthermore, if the initial ultraviolet output of a low-pressure mercury vapor fluorescent lamp using this phosphor as a fluorescent film was 100%, the ultraviolet output after 100 hours of continuous operation was 90%.

[Brief explanation of drawings]

The drawing is a graph showing an example of the relationship between the elution conductivity in a divalent metal borate phosphor and the relative luminance to the luminescence luminance (100%) at the initial stage of excitation after continuous excitation of the phosphor for 100 hours. It is.

Claims (1)

[Claims] 1. The base material is a divalent metal oxide (M〓O, where M〓 is
In a divalent metal borate-based phosphor consisting of a complex oxide of at least one of Ca, Sr, Ba, Be, Mg, Zn and Cd) and boron oxide (B ₂ O ₃ ), Pour 1 g of phosphor into 50 c.c. of water at 100°C,
Leave to cool while stirring until the water temperature reaches 20℃, and then heat to 20℃.
2, characterized in that when measuring the electrical conductivity of the water, the electrical conductivity is 15 to 150 μ/cm.
Valuable metal borate phosphor. 2. The divalent metal borate phosphor according to claim 1, wherein the conductivity is 20 to 130 μ/cm.