JPS59179578A - Production of fluorescent substance - Google Patents

Abstract

PURPOSE:To obtain a fluorescent substance, expressed by a specific formula, capable of emitting green light of high brightness, and having improved temperature quenching characteristics, by incorporating a specific amount of a raw material capable of forming PO4 by a calcination with an La, Ce and Tb oxalate, mixing the resultant mixture with a rare earth oxalate, and calcining the mixture. CONSTITUTION:A raw material, e.g. ammonium phosphate, capable of forming phosphate radicals by calcination in an amount of 1.04-1.45 times of that of the stoichiometric composition is incorporated with an La (or Y or Gd) Ce and Tb oxalate, mixed by the direct dry method, and then calcined preferably at 1,100-1,200 deg.C in air to give the aimed fluorescent substance expressed by the formula (M is La, Y or Gd; x and y are as follows; 0.15<=x<=0.5; 0.1<=y<=0.35). USE:Suitable for single base low-pressure vapor electric discharge lamps raising the tube wall temperature.

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention is useful for use in mercury vapor discharge lamps, and is particularly suitable for use in single-cap low-pressure vapor discharge lamps where the temperature of the tube wall increases, e.g. Concerning a method of manufacturing a body.

[Background technology]

Tb, Ce-activated lanthanum orthophosphate phosphors have been known for a long time and are not particularly new. In recent years, JP-A-57
-23674, among mercury vapor discharge lamps, it has been reported to be used as a green component in three-wavelength fluorescent lamps that require high luminous flux and high color rendering properties.

The Tb, Ce-activated lanthanum orthophosphate (or yttrium, or gadolinium) phosphor is a synthetic method.

Although the firing conditions are not particularly difficult,
Since the phosphor contains Tb and Ce, firing in a weakly reducing atmosphere was necessary.

[Purpose of the invention]

An object of the present invention is to provide a method for producing the phosphor in a simple manner.

[Summary of the invention]

The present invention provides La (or Y or Qd), Ce, T
b) It is easy to use the high brightness green phosphor La (or Y or Qd).
), Ce, Tb orthozaphosphate can be obtained, and further by selecting the composition of the rare earth and the composition of the phosphate group,
100~200tl? It is possible to obtain a phosphor without temperature quenching even at a temperature of .

Conventional methods for synthesizing rare earth pressure phosphates include (1) co-precipitation of phosphate in a wet process, or (2) mixing rare earth oxides and ammonium phosphate in a dry process and firing in a weakly reducing atmosphere. It has been known. The former wet phosphate coprecipitation method had problems with workability, as the precipitate was fine particles, which took time to wash and filter, and solidified after drying, making grinding difficult. In addition, the latter generates air bubbles during firing and becomes pumice-like. Moreover, rare earth oxides usually contain a main component (La, Y or Gd) and an activator (Ce, Tb).
) is co-precipitated as a rare earth oxuate, washed with water, dried, and then thermally decomposed and used. In the present invention, a high-luminance green phosphor can be obtained by directly mixing rare earth oxalate with ammonium phosphate or the like and firing the mixture in air.

[Embodiments of the invention]

Hereinafter, the method for synthesizing the Ce, Tb activated lanthanum phosphate (or indium or gadolinium) phosphor of the present invention will be shown in Examples.

Example 1 (La0-7-FCeO, 3Tby)2(C204)s
・Add 1.1 times the stoichiometric amount of ammonium phosphate (NHa) 2HP 04 to 2H20()'='0.05-0.40) and mix well. This is 1.
150tl? Bake in air for 2 hours. The baked product has no lumps and can be easily taken out from the baking container. This is crushed, sieved, thoroughly washed with water, and dried. The resulting phosphor emits green light when excited by the mercury vapor resonance line. Manganese-activated zinc silicate (Z”2 S504: Mn.

NB51021. Figure 1 shows the brightness based on the standard (manufactured by National, Bureau, and Stantard). Similarly (La0.7-F Ce0-3 Tb,)2
(CP, 04)3 ・2H20(y=0.05~0.4
The brightness results obtained by adding 1.3 times the stoichiometric composition of NH4) 2 HP 04 to 0), firing, and post-treatment are shown in FIG. 1 and 2. In both cases, the highest brightness was obtained at a Tb concentration of around 0.2 mol.

Example 2 (Lao, 6Ceo, s Tbo, l) 2 (C204
)3 NH4'l 2 HP 0 for 2H20
4 was added from 0.9 to 1.5 times the stoichiometric composition, and the mixture was fired and post-treated as in Example 1 to obtain a phosphor. (NH4
) 2 HP The relationship between O4 content and brightness is shown in Figure 2. Below 1.0, the brightness decreases rapidly. Figure 3 also shows (NH4) 2 HPO4 with a stoichiometric composition of 1.01.
, 1.1 and 1.18 times, and the temperature quenching characteristics due to ultraviolet excitation of the fired phosphors were measured at 30C, respectively.
It is shown in Figure 3.4.5. At 1.01, the brightness decreases as the heating temperature increases. However, as the amount of NH4)zHPo4 added increases, the maximum brightness shifts to the higher temperature side.

Example 3 (La0.86-, Ce, Tbols)2 (
1.1 times the stoichiometric composition of (NH4) 2 HP 04 was added to C204)3 2H20 (X-〇1~O, SO) and mixed, followed by firing in air at 1150 U for 2 hours. It was post-treated and measured for brightness in the same manner as in Example 1, and the results are shown in FIG. The optimum Ce concentration was around 0.3 mol.

Example 4 (Lao,sCeo-3Tbo-s)2 (C20
4) Add 1.1 times the stoichiometric composition of NH4)tHPOt to 3.2H20, mix, bake in 1.150 tr air for 1 to 6 hours, post-process in the same manner as Example 1, and measure brightness. The results are shown in Figure 5. Brightness is not significantly affected by firing time. Further, the temperature quenching characteristics are shown in FIG. Items 6, 7, and 8 in the figure are fired for 1, 2, and 4 hours, respectively. The longer the firing time, the better the temperature quenching properties.

Example 5 (Gdo-s Ce0-3 Tb0.2 )2 (C2
04)s ・2H20 (NH4) 2 HP
O< was added in an amount 1.1 times the stoichiometric composition, mixed well, and fired and post-treated in the same manner as in Example 1. The brightness due to mercury vapor resonance line excitation is vs. NB5-1021'
I got 125 chi.

Example 6 L ao-ss CEO, 3T bO,! 5 and La
o, os Yo-os Ceo-s T bO-2 (NH4), 2HP O,4 was added in an amount 1.1 times the stoichiometric composition, and the mixture was calcined in air at 1150C for 12 hours and heated at 1050 t. Table 1 shows a comparison of powder brightness when the powder was fired in the air for 2 hours, thoroughly crushed, and then fired at 1150 r for 4 hours in a slightly reducing atmosphere. It was 13 to 20 inches brighter when fired in the air.

Table 1 [Effects of the Invention] According to the present invention, as shown in the examples, the calcination process can be simplified by directly using rare earth oxalates, which were conventionally used as rare earth oxides by thermal decomposition, and Safety is also improved because only air firing is performed without using a reducing atmosphere. Furthermore, the brightness is equal to or higher than that obtained by firing in a reducing atmosphere.

[Brief explanation of the drawing]

Claims (1)

[Claims] 1. General formula M+---y Ce-TbFPO4 (where M is at least one type of base selected from the group consisting of La, Y, and Gd, and y is 0.15≦・≦0. 5.0, 1≦y
In the manufacturing method of a phosphor expressed by ≦0.35, a raw material that generates PO4 in the general formula by firing is blended at 1.04 to 1.45 times the stoichiometric composition. A method for producing a phosphor, characterized by firing raw materials. 2. The method for producing a phosphor according to claim 1, wherein the raw material for the phosphor is composed of oxalates of M, Ce, and Tb, and a raw material that produces phosphate groups upon firing.