JPS585220B2 - Keikoutai no Seizouhouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a phosphovanadate blue phosphor, which is effective for improving brightness when applied to luminescent screens of various display devices and illumination light sources. This invention relates to improvements in manufacturing methods.

General composition formula MPX■1-X04, where M is yttrium (Y), gadolinium (Gd), lutetium (Lu)
At least one element selected from 0 < x < 1
．． The phosphovanadate fluorophore represented by 0 is 253.
Ultraviolet excitation such as 7 nm, 365 nm, or 8 to 25 nm
It is known that KeV electron beam excitation causes blue light emission due to transition within the trivalent vanadate ion (VO43-) constituting the base.

There are also a few reports regarding methods for producing this type of phosphor.

For example, H. Schwarz published a paper in 1963, “Die Phosphate, Ar5.
Enate und Vanadate' der 5
elten Erden” (Zeitschri
ft fiira norganische und a
llgemeine chemie, Band323
．． 44-56.1963), various rare earth phosphates are classified as rare earth ditrioxides.
reported on a method for synthesizing various rare earth vanadates at 1100 to 1200 °C using phosphorus pentoxide (P2O3), diammonium phosphate C(NH4)2HPO4) as starting materials, and also synthesized various rare earth vanadate salts with rare earth ditrioxides. They also report a method for synthesizing the compound, vanadium pentoxide (V 205, at 950-1100°C) as a starting material.

Therefore, in a rare earth phosphovanadate blue phosphor consisting of a solid solution system of a rare earth phosphate and a vanadate and emitting light from trivalent vanadate ions, the material is produced by using ammonium phosphate as the raw material for phosphorus and firing at 1200°C. Methods of manufacturing phosphors are considered known.

However, the above-described manufacturing method has a major drawback in obtaining good light emission characteristics regardless of the excitation source.

This is because trivalent vanadate ions (VO-), which constitute the matrix of the phosphor and form the luminescent center, are reduced to V4+ by ammonia gas generated by decomposition of ammonium phosphate during the firing process. , V3+, V2+
This is because the phosphor is precipitated as a lower oxide consisting of low-valent vanadium ions such as vanadium ions, and the phosphor is partially colored brown or black-gray.

These lower oxides can hardly be separated and removed even by post-treatment of the phosphor with an alkaline solution.

As a result, the absorption and emission of excitation lines are inhibited by these precipitated coexisting substances, making it impossible to obtain good luminous efficiency as a blue phosphor.

The purpose of the present invention is to improve the conventional manufacturing method of a blue phosphor containing phosphovanadate as a main component, and to apply it to luminescent screens of various display devices and illumination light sources, thereby improving brightness. Our goal is to provide fluorescent materials.

The first point of the production method selected for this purpose is that in order to avoid the reduction of vanadate ions during the firing process, yttrium phosphate, cadrinium phosphate, lutetium phosphate, etc. are used instead of the conventionally used diammonium phosphate. The second point of the production method is to use orthophosphate of It is also fired at a higher temperature.

The reason why high temperature firing is particularly required is that a high melting point phosphate is used in place of diammonium phosphate, which decomposes at low temperatures.

The effects of the above two improvements in the manufacturing method are as follows:■1-x0
4. M is at least one element selected from Y, Gd, and Lu, and when O<x<1.0, it is particularly noticeable in the composition region where X is large.

The effects of the present invention will be explained in detail below using examples.

Example I A blue phosphor represented by <1.0 to YPXVl-XO4,0 was synthesized by the following two methods.

The first method is a production method according to the present invention in which yttrium phosphate is used as a raw material for phosphorus, and the second method is a conventional production method in which diammonium phosphate is used as a raw material for phosphorus.

For example, if the total amount is 100 grams and x=0.85, YPo, 8. For vo, 1504, the first method involves yttrium phosphate (ypo, .2H20) 8°4°9'' Yttrium oxide (Y2O3) 7.7 grams Vanadium pentoxide (V2O5) 6.8 grams Soda carbonate (Na2 co8 ) 0.6 grams as the starting material, the second method uses 0.6 grams of ammonium phosphate.

Yttrium oxide (V2O8) 43.3 grams Vanadium pentoxide (V2O5) 5.8 grams Soda carbonate (Na2 C08) 3.6 grams were used as starting materials.

After thoroughly mixing these, they were filled into an opaque quartz crucible and fired in the air at 1200° C. for 3 hours in a semi-closed state.

After calcination, in order to remove unreacted V2O5, the obtained calcination product was poured with water, left to stand for an appropriate period of time, passed through a 250-mesh sieve, left to stand, and the supernatant liquid was removed.

The remaining precipitate was 2% by weight of ammonium carbonate [(NH4
)2CO8] was carefully washed with an aqueous solution, finally washed with water, and dried at 200° C. for a day and night to obtain the required yttrium phosphovanadate phosphor.

Figure 1 shows 253 phosphors obtained by the above two methods.
．． This is a comparison of emission spectra by 7 nm excitation.
Curve 1 represents the characteristics of the sample according to the first method according to the present invention, and curve 2 represents the characteristics of the sample according to the second method, which is a conventional method.

Even when fired at 1200°C, the luminescence intensity of curve 10 is the same as curve 20.
5% thicker than the luminescence intensity.

Figure 2 shows the diffuse reflection spectra of both phosphors in the visible region, and the diffuse reflectance at 430 nm, which corresponds to the emission peak wavelength of both phosphors (the reflectance of an alumina standard white plate is taken as 100%). ) reaches 97% for 1, but remains at 87% for 2.

As explained earlier, in 2, lower vanadium oxides are precipitated due to ammonia gas generated by the decomposition of ammonium phosphate, suggesting that this is the main factor in reducing the diffuse reflectance. .

Example 2 YP o, 35 Vo, i! For the purpose of synthesizing iO4, a total of 14 samples were prepared using the same two types of formulations as in Example 1, and only the calcination temperature was varied from 1100 °C to 1700 °C in 7 steps at 100 °C intervals.

Figure 3 shows the relationship between the emission peak intensity by 253.7 nm excitation and the firing temperature. Similarly to Figures 1 and 2, curve 1 is for yttrium phosphate according to the present invention, and curve 2 is for The characteristics of samples using the conventional method of ammonium phosphate as the starting material for phosphorus are shown.

As is clear from the figure, the difference between the two lines becomes significant above 1150°C, and the emission peak intensity of 2 reaches its maximum near 1300°C, and the intensity decreases monotonically in the higher temperature range, whereas 1 There is a very thick emission peak intensity between 1500 and 1600°C, and no significant decrease in emission intensity is observed even at temperatures above 1600°C.

The decrease in luminescence intensity at 1600° C. or higher is thought to be due to the fact that coarse pulverization was performed immediately before measurement, since the amount of sintering increases slightly with high-temperature firing.

FIG. 3 is a characteristic example clearly showing the effect of the present invention in the production of ypo35V0.1504, that is, the superiority of the method of using yttrium phosphate as a raw material for phosphorus and firing at a high temperature over the conventional method.

Improvements in luminescent properties due to improvements in manufacturing methods are due to the above-mentioned two factors.
The excitation is not limited to 53.7 μm excitation, and similar effects can be obtained by excitation with ultraviolet rays or electron beams of other wavelengths.

For example, the phosphovanadate-based blue phosphor produced by this manufacturing method has remarkable effects when applied to the blue-emitting screen of a plasma color television, which is characterized by a large screen and a flat display with high address accuracy.

Figure 4 shows an example of application to a plasma color television using Zenon (Xe) resonance line excitation at 147 μm. The relationship between strength and firing temperature is shown.

The vertical axis of the figure is lead-activated calcium tungstate (CaW).
It represents a relative value with the emission intensity of the above wavelength component by 147 μm excitation of O4:Pb) set as 100.

The tendency for the characteristics of curve 1 related to the present invention to exceed the characteristics of curve 2 related to the conventional method is similar to that shown in FIG. The phenomenon of crystal plane development has been confirmed by electron microphotograph observation.

Furthermore, the equivalent circle diameter of the sample of curve 1 related to the present invention determined from electron micrographs is 1.3μ at 1300°C, and 1.3μ at 1400°C.
The value is 1.6μ at 1500℃, and 2.4μ at 1500℃.
This proves that vacuum ultraviolet light excitation, such as m-excitation, contributes to the improvement of luminescent properties.

Example 3 In Example 1.2, soda carbonate was used in the formulation, but here a manufacturing method that does not use soda carbonate was used.

In other words, for the purpose of synthesizing YPo, 85vo-1504'), 83.9 grams of yttrium phosphate (YP
o4・2H20) After thoroughly mixing 7.8 grams of yttrium oxide (Y2O2) and 6.3 grams of vanadium pentoxide (V2O3), this was filled into an opaque quartz crucible, and 1
After firing in the air at 520° C. for 3 hours, the same post-treatment as in Example 1 was performed.

470± due to 253.7μm excitation of the obtained phosphor
The intensity of the 7.5 Hm component reached 108% of that of CaWO4:Pb, and the intensity of the same emission component by 147 μm excitation reached 147% of that of CaWO42Pb.
It was confirmed that good luminescent properties could be obtained by using yttrium phosphate as the phosphorus raw material and performing high temperature firing without using soda carbonate.

Example 4 Yl-YGdYPo, 85Vo, 1504, O<y<
A blue phosphor expressed as 1.0 was synthesized.

For example, if y-0.1, YO08Gd6.lPO.3
For 5vO・1504, the following raw materials are used.
7/ Yttrium phosphate (ypo, ・2H20) 74°6″4 Gadolinium phosphate (GdPO, ・H2O) 10.2 grams Yttrium oxide (Y2O2) 6.8 grams Gadolinium oxide (Gd203) 1.2 grams Vanadium pentoxide (V2 .05) After thoroughly mixing 6.7 grams of 0.6 grams of soda carbonate (Na2CO3), calcination and post-treatment were performed in the same manner as in Example 1.

When the obtained phosphor was excited at 253.7 μm and 147 μm, the blue light emission component intensity was 10, similar to that in Example 3.
2% and 149%, showing excellent luminescent properties particularly in the vacuum ultraviolet region where the excitation wavelength is short, confirming that the phosphor produced by this manufacturing method is suitable as a blue luminescent screen for plasma color televisions.

FIG. 5 shows the emission spectrum of the phosphor obtained in this example.

Example 5 For the purpose of synthesizing LLIPo, 85VO-1504, the following four types of raw material lutetium phosphate 88.7 grams (Lu
P04・2H20) After thoroughly mixing lutetium oxide (Lu20g) 7-3 grams vanadium pentoxide (V2O5) 3-7 grams soda carbonate (Na2CO3) 0.3 grams, calcining and post-coating in the same manner as in Example 1. Processed.

The obtained phosphor had a pale gray coloring and had a molecular weight of 253.7n.
The intensity of the blue emission component similar to Example 3 due to m excitation is C
Although the intensity was only 90% of that of aWO4pb, the intensity of the blue light emitting component by excitation at 147 nm reached 145%, confirming that the phosphor produced by this manufacturing method is suitable as a blue light emitting screen for plasma color televisions.

Example 6 For the purpose of synthesizing GdPo, 85Vo, 1504, the following four types of raw materials were used: Gadolinium phosphate (GdPO, .2H20) 82.4 grams Gadolinium oxide (Ga2O3) 9.3 grams Vanadium pentoxide (V2O5) 5-1 grams After thoroughly mixing 3.2 grams of soda carbonate (Na2CO3), the same calcination and post-treatment as in Example 1 were performed.

The obtained phosphor exhibited a pure white matrix color, and the intensity of the blue emission component upon excitation at 147 nm was almost the same as in Example 5.

As is clear from the above examples, the phosphovanadate phosphor according to the production method of the present invention is not only useful as a blue component luminescent screen for a general illumination light source used for mercury beam excitation, but also The phosphors are useful as blue light-emitting screens for display devices, and the phosphors having the compositions described in Examples 1 to 5 all exhibit excellent light-emitting properties as blue screens for plasma color televisions used with 147 nm excitation.

[Brief explanation of the drawing]

Figure 1 shows 253.7n of YPo, 85vo, 1504.
A diagram showing an emission spectrum due to m excitation. Curve 1 uses YPO4 as the phosphorus source. Representing the characteristics of a sample produced by the manufacturing method related to the present invention,
Curve 2 represents the properties of a conventional sample using (NH4)2HPO4 as the phosphorus source. FIG. 2 is a diagram showing the diffuse reflection spectrum tc in the visible region of YPo, 85vo, 1504. Figure 3 shows 253.7n of YPo, 85Vo, 1504.
FIG. 3 is a diagram showing the firing temperature dependence of blue emission peak intensity due to m-excitation. The vertical axis of the figure is a value based on the luminescence peak intensity of lead-activated calcium tungstate (CaWO+:Pb), which is a known blue-emitting phosphor, as 100. FIG. 4 is a diagram showing the firing temperature dependence of the emission intensity of the 470 nm component by 147Hm excitation of YPo, 85vo, and 1504. The vertical axis of the figure is the value with the 470 nm component emission intensity of CaWO4:pb as 100.
The figure which shows the emission spectrum by 253.7 nm excitation of d0*IPO*85vO-1504. Note that the curve 12 in FIGS. 2, 3, and 4 is the first curve.
Follow the explanation of the figure.

Claims (1)

[Claims] 1 General composition formula MPXV1-X04 (where M is yttrium (Y), gadolinium (Gd), and lutetium (
In the method for producing a blue-emitting phosphor, the phosphor represents at least one element selected from the group consisting of as MPO4 (here M represents the above meaning)
Using orthophosphates represented by or their hydrates, 1
A method for producing a phosphor, the method comprising firing at a high temperature of 200°C or higher.