JPH048793A - Method for manufacturing phosphor powder - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing a phosphor powder that emits light upon excitation with X-rays, electron beams, ultraviolet rays, etc. and is used in cathode ray tubes, fluorescent lamps, etc. .

[Prior Art] Conventionally, when synthesizing a rare earth silicate phosphor, the desired fluorophore is produced by uniformly mixing a raw material powder such as a rare earth oxide and silicon dioxide, and accelerating the solid-state reaction by heating at a high temperature. It has a luminous powder. For example, Tokuko Sho 48-3787
As shown in Publication No. 0, in the case of lanthanum and yttrium silicate phosphors, rare earth oxides and silicon dioxide, which serve as luminescent centers and base materials, are completely mixed, and 1,000 to 1
．． This phosphor is obtained by firing at 500°C and then mechanically pulverizing it into a fine powder. Another method is to mix a rare earth nitrate aqueous solution and an oxalate aqueous solution to form a coprecipitate of oxalate, mix this with silicon dioxide, and then sinter it to obtain the phosphor.

[Problem to be solved by the invention] However, when using such a solid phase reaction,
Variations in the surface shape of the powder particles due to the type of silicon dioxide, loft difference, etc. greatly affect the degree of progress of the solid phase reaction, so there is a drawback that the luminescent properties are extremely dependent on the material. Furthermore, in a phosphor obtained by a solid phase reaction, the brightness generally increases as the firing temperature increases, but sintering at grain boundaries progresses and the grains become coarser. Therefore, mechanical pulverization using a ball mill or the like is required for post-processes such as coating, which causes various defects on the particle surface, causing problems such as deterioration of brightness due to deterioration of crystallinity and widening of particle size distribution.

Further, in the above-mentioned known example, when a solid phase reaction is used so that silicon dioxide is mixed at a ratio of about 1.5 mol to 1 mol of rare earth oxide, for example,
Considering the large difference in melting point between rare earth oxides (or oxalates) and silicon dioxide, it is common to add silicon dioxide in excess in order to spread the reaction throughout the material.
The amount to be added in excess is set so that the luminescence intensity of the final synthesized phosphor is maximized. However, if excess silicon dioxide is present, the desired matrix composition (e.g. Y2S
It has been found that the mixing of foreign phase components other than [Os] that deviate from the stoichiometric composition may have an adverse effect on lifespan and other aspects.

The present invention has been made in view of the problems of the conventional method for producing phosphor powder, and an object of the present invention is to provide a method for producing phosphor powder with excellent luminous efficiency and brightness life.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present inventors, for example, added silicon dioxide,
An example of obtaining spherical zinc silicate phosphor powder by spraying a solution containing a zinc compound and an activator in the form of droplets and evaporating the solvent, and then hydrothermally treating the particles obtained (Japanese Patent Application Laid-Open No. 1-272689).
As a result of various studies, the present invention has been achieved as a result of various studies on examples of forming light-emitting thin films of composite oxides using the sol-gel method (Japanese Patent Application Laid-Open No. 109641/1996).

That is, the present invention provides a solution containing a rare earth element ion serving as a luminescence center, another rare earth element ion serving as a base, and a silicate alkoxide, by removing the solvent in the solution and obtaining a homogeneous composition using a method such as spray drying or freeze drying. A method for producing powder particles that rapidly removes the solvent in a solution to produce powder particles having a homogeneous composition and at least a portion of an amorphous portion,
This is a method for producing a phosphor powder, which includes a step of finally heating and baking the powder to obtain a crystalline phosphor powder.

Note that in this specification, the term "solution" is a concept that also includes substantially homogeneous suspensions, dispersions, and the like.

[Function] In the present invention, rare earth element ions and silicate alkoxide are uniformly mixed in a solution state and then turned into a powder with a homogeneous composition. A desired single composition can be changed, and a phosphor powder with excellent luminous efficiency and brightness life can be changed. In addition, since it has a controlled particle size distribution, it does not require a pulverization process and has the effect of regenerating crystals with fewer surface defects.

[Example] The phosphor according to the present invention is a silicate containing a rare earth element ion serving as a luminescent center and another rare earth element ion serving as a parent body.

Rare earth element ions that serve as the luminescent center of the former include, for example, Tb, Ce, Gd, Nd, Pr, and Dys.
There are ions such as Eux SI1%Tm, one of which
Species or 2fii or more are selected.

In addition, examples of the rare earth element ions constituting the matrix include ions such as Sc, Y, La, Gd, and Lu, and one or more of these ions are selected.

Examples of compositions of silicates that can be obtained using silicate alkoxide and can serve as a matrix include SC25i05 and Y25i0.
5, La25i05, Gd25i05, SC2S+20
7, Y2 Si207, La2Slz 07, etc.

Raw materials for rare earth element ions used in the present invention include:
Examples include oxides, chlorides, nitrates, etc., and examples of silicate alkoxides include tetraethoxysilane ((C2H50)
4Si (hereinafter referred to as TE01), tetramethquine silane, tetrapropoxysilane, and tetrabutoxysilane. From a practical point of view (melting point, etc.), TE01 is easy to use as the silicate alkoxide.

Examples of the solvent used in the present invention include pure water, ethanol, methanol, propatool, butanol, and formaldehyde. Note that the solution concentration cannot be uniformly limited because it varies depending on the method such as spray drying or freeze drying.

In addition, nitric acid aqueous solution, which makes it easier to change the homogeneous solution,
It is preferable to use an aqueous hydrochloric acid solution, an aqueous oxalic acid solution, etc. as appropriate.

The method for producing the phosphor powder of the present invention includes, for example, Yz S+
05: Taking Tb as an example, the process is explained as follows.

First of all, Y2O3, Tb4O7 are Y/Tb-1,l
Weigh it so that it becomes 1510.15 (atomic ratio) and dissolve it in a nitric acid aqueous solution. Add a mixed solution of TEOS and ethanol to this and mix thoroughly.

Next, this solution is heated to remove the solvent in the solution using a spray dryer to form a fine powder. The amount of pure water and ethanol used as solvents depends on the temperature of the hot air during spray drying, but if it is too large, the removal of the solvent will tend to be insufficient, and if it is too small, spraying will tend to be difficult. Yz 5in
s: Tb preferably ranges from 0.01 to 2 mol%.

Similarly, when making a fine powder by freeze-drying,
The amount of solvent is determined to ensure sufficient solvent removal.

Finally, the powder obtained by the drying method is packed in an aluminum tube, and if necessary, it is thermally decomposed at 200 to 1,000°C, and then fired at 1,300 to 1,600°C.
Grind into a crystalline powder. The firing time is usually 1 to 10 hours and is not particularly limited. Furthermore, the firing atmosphere may be controlled as necessary. For example, Y2Sins: Tb
'PY25ins: For Ce, it is preferable to use a reducing atmosphere.

Yz 5IO5:T synthesized through the above steps
b The brightness and brightness life of the phosphor are, for example,
As shown in FIG. 2 and FIG. 2, the characteristics are improved compared to the phosphors obtained by conventional manufacturing methods. Note that FIGS. 1 and 2 are graphs showing current density-luminance characteristics and brightness deterioration characteristics when excited with a 20 kV electron beam, respectively, and in each graph, (at) and (a2) are The properties of the phosphor obtained by the method are shown, and (bt
) and (b2) show the characteristics of the phosphor obtained by the conventional method.

Hereinafter, the present invention will be explained based on Examples.

Example 1 Yttrium oxide (YzOs,
99.99? o) Stir 20.89 g and 2.80 s of terbium oxide (Tb+Oy, 99.9%),
45 ml of concentrated nitric acid (HNOx, 85%) was added to dissolve. TEOS ((C2H50)4 S+, reagent special grade) 20
．． 83 g and 80 ml of ethanol were mixed, and this was added to the nitrate aqueous solution and stirred well. After thoroughly mixing the mixture until it became homogeneous, the solvent was evaporated from the mixed solution using a spray dryer to form a powder. The spray drying conditions were: hot air temperature 190°C, spray pressure 1.0 kg/cj, and liquid feeding rate 9.
．． 0 g/gin was chosen. The diameter of the nozzle used was 0.4 mm. When the obtained powder was examined by X-ray diffraction, it was found to be completely amorphous. Pack this powder into an aluminum pot,
After thermal decomposition in the air at 800° C. for 4 hours, calcination was further performed at 1.550° C. for 4 hours in a weakly reducing atmosphere. The phosphor powder thus obtained is monoclinic Yz 5
IOs: It was confirmed by X-ray diffraction that it was Tb. This material can be activated by ultraviolet or electron beam excitation to generate Tb3+
It exhibited green luminescence. The line (al) in FIG. 1 is the current density-luminance characteristic measured using a demountable luminance measuring device. Furthermore, the change in brightness with respect to electron beam irradiation time was measured using the same device (brightness deterioration characteristics), and the line in Figure 2 (
a2).

Example 2 22.02 g of yttrium oxide was stirred in 400 ml of pure water, 45 ml of concentrated nitric acid was added, and cerium nitrate (
Ce(NOs)3 ・6H20,999%) 2.1
7 g was added and sufficiently dissolved. TEOS 20.8Fg
and 20 ml of ethanol were mixed, and this was added to the nitrate aqueous solution and stirred well. After thoroughly mixing until uniform, the mixture was maintained at 80° C. for 10 hours to remove ethanol. The solvent was sufficiently removed from this solution using a freeze dryer. The freeze-drying conditions are as follows: 1 hour after the start of cooling, the sample temperature is 30°C.
℃, and the degree of vacuum was 5 x 10' torr. The obtained powder was thermally decomposed in the air at 600°C for 4 hours, and then fired in a weakly reducing atmosphere at 1,500°C for 6 hours to obtain a phosphor powder. The composition of the phosphor obtained in this way is Yz 5i05.Ce, and C
e” (D exhibited blue light emission.

Example 3 Yttrium chloride (YCl) in 300 ml of ethanol
3.6H20,99,9%) 56.12g and terbium chloride (TbC13nHio, 99.9%)
5.87 g (in the case of n-7) was dissolved. TE0
120. Hg and 50 ml of ethanol were mixed, and this was added to the chloride solution and stirred well. After thoroughly and uniformly mixing, spray drying was carried out under the same conditions as in Example 1.

The dried powder was thermally decomposed at 400° C. for 8 hours in the air, and then fired at 1,550° C. for 4 hours in a weakly reducing atmosphere to obtain a phosphor powder. The obtained phosphor exhibited characteristics equivalent to those of Example 1.

Example 4 In Example 1, 5.28% of europium oxide (Eu203.99.9%) was added instead of terbium oxide, and 1.28% of europium oxide (Eu203.99.9%) was added in place of terbium oxide, and 1,500% of europium oxide was added in place of calcination at 1,550"C in a weakly reducing atmosphere. A phosphor powder was synthesized using the same process as in Example 1, which employed firing at 400° C. for 4 hours.

The obtained phosphor was Y25ins:Eu, and exhibited Eu3+ red luminescence upon electron beam excitation.

Example 5 Scandium oxide (Sc203.
99.99o H2, 76g and terbium oxide2.
The mixture was stirred for 80 seconds, and 45 ml of concentrated nitric acid was added to dissolve the mixture.

A mixed solution of 141.67 g of TE01 and 100 ml of ethanol was added to the nitric acid aqueous solution and thoroughly stirred and mixed.

Hereinafter, a phosphor was obtained using the same steps as in Example 1. The composition of this substance is Sc25t20y:Tb, and it emits green light when excited by X-rays, ultraviolet rays, or electron beams.

A comparative example will be described below in order to compare with the conventional synthesis method.

Comparative Example 1 Yttrium oxide 20.89g, terbium oxide 2.8g
0g and silicon dioxide (S102.99.5%) 6.
Put 34g into a ball mill pot and add 100ml of ethanol.
1 was added and mixed for IO hours. After taking it out from the ball mill pot and drying it thoroughly, it was packed in an aluminum crucible and fired at 1,550°C for 4 hours in a slightly reducing atmosphere.

After cooling, it was crushed to obtain a phosphor powder. The obtained phosphor is Y
2S+05; Tb, which emits green light when excited by an electron beam. The current density-brightness characteristics and brightness deterioration characteristics are shown by the line (bl) in Fig. 1 and the line (b1) in Fig. 2, respectively.
Shown in b2).

Comparative Example 2 Yttrium oxide 20.89r in 1,000ml of pure water
and 2.80 tr of terbium oxide, 1 nitrate #4
5ml was added and dissolved. In addition to this, 1,000 m of pure water
nu in 1 (C2HyQa ・2H20, reagent special grade>
45. (A solution in which 10r was dissolved was prepared. The nitrate aqueous solution was added to this oxalic acid aqueous solution to obtain a white precipitate.

This precipitate was washed and filtered, and then dried in an oven.

This powder is thermally decomposed at 1,001)'C to form a composite oxide of yttrium and terbium, which produces 6.34% silicon dioxide.
g and 50 ml of ethanol were placed in the ball mill pot again and mixed for 10 hours. After drying, in a weakly reducing atmosphere 1
, 550° C. for 3 hours, cooled, and then crushed to obtain a phosphor powder. The obtained phosphor exhibited the same characteristics as Comparative Example 1.

[Effects of the Invention] As described above, according to the present invention, rare earth element ions and silicate alkoxide can be uniformly mixed in a solution and made into homogeneous powder particles by spray drying or freeze drying. It has the effect of improving brightness and replacing the phosphor with excellent brightness deterioration characteristics.

[Brief explanation of the drawing]

FIG. 1 is a graph showing an example of the current density-brightness characteristics of the phosphor powder obtained by the method of the present invention in comparison with that obtained by the conventional method. FIG. 2 is the luminance deterioration characteristic of the phosphor powder obtained by the method of the present invention. It is a graph showing an example of this in comparison with a conventional method. Agent Yu Iwamasu, Nihon University Figure 2 Time (hours) (μA/Cm2) Written (self-motivated)

Claims (1)

[Claims] (1) After preparing a solution containing a rare earth element ion that can serve as a luminescence center, other rare earth element ions forming a matrix, and a silicate alkoxide, the solvent in the solution is removed to produce powder particles having a homogeneous composition. 1. A method for producing a phosphor powder, comprising the step of preparing a powder containing at least a portion of an amorphous portion, and heating and baking the powder to obtain a crystalline powder.