JPS6126689A - Fluorescent material - Google Patents

Abstract

PURPOSE:To provide a red light-emitting fluorescent material having improved luminance-saturation phenomenon in a high current-density range, and useful for a color CRT, displaying CRT, etc., by adding a specific small amount of Pr to a specific Eu-doped yttrium oxysulfide. CONSTITUTION:(A) The fluorescent material of formula (0.0002<=a<=0.2) is doped with (B) 2-10ppm (preferably 4-8ppm) of Pr to obtain the objective fluorescent material. The fluorescent material can be prepared by (1) dissolving high-purity Y2O3 and Eu2O3 in concentrated hydrochloric acid, (2) diluting the solution with pure water, (3) adding a solution of praseodymium chloride to the mixture, (4) adding a solution of oxalic acid to effect the co-precipitation of the oxalates of Y, Eu and Pr, (5) collecting the precipitate by filtration, (6) converting the oxalate to oxide by heating at 800 deg.C, and (7) calcining the product in the presence of S, Na2CO3, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Industrial Field of Application The present invention mainly relates to Eurobiu-11-activated 11fliFt yttrium (Y2O2
S: Eu) Concerning the improvement of phosphors, especially europium-activated yttrium oxysulfide, which has better properties than conventional europium-activated yttrium oxysulfide (Y2O2S:Ell) phosphors in the case of electron beam stimulation. Regarding phosphors.

In this specification, ・Current saturation characteristic means that when the acceleration voltage of the electron beam is kept constant and the current density of the phosphor is increased, the luminance of the phosphor increases by -E in proportion to the current density. This means that saturation does not occur, but if the brightness does not reach a value that should be proportional to the current density and becomes a value lower than 11α, saturation occurs.

B. Conventional technology europium activated yttrium oxysulfide (Y 202S:
Eu) The phosphor is manufactured by R, C, A company in the United States.
59 (Registration No. 0Fi3795/1).

Since this patent was published, various proposals have been made to improve the characteristics of this phosphor. For example, as a means to improve brightness, etc., there are four techniques for adding a trace amount (several tens of ppm) of terbium (Th) (Japanese Patent Publication No. 47-1 A2
zi 3') or a method of introducing a small amount (a few tenths of a percent) of samarium (Sm) (Japanese Patent Publication No. 57-354.
, Registration No. 1161508) is known.

Furthermore, praseodymium (
A phosphor containing europium (monoactive yttrium oxysulfide (Y2O2S: E t+)) has also been developed. (Special Publication No. 4B=31830)
In the europium-activated yttrium oxysulfide (Y2O2S:Eu) phosphor disclosed in Publication No. 31830, the activation amount of Eu is adjusted to 2X10-' to 0.2 mol, and 10 to 50 ppm of Pr coexists with this. A technique has been disclosed for increasing the brightness by 20 to 30 times.

C0 Problems to be Solved by the Invention Incidentally, in recent years, there has been an increase in demand for cathode ray tubes, such as color display tubes and projection tubes, in addition to color picture tubes, and in these tubes, the current density of the stimulating electron beam is higher than that of the conventional one. The current density increased further than 0.5μA/cl12, and stimulation was often performed at a high current density of about 51iA/cm2 at maximum. This caused a saturation phenomenon in the luminance of the phosphor, making it easier for color shifts to occur in the color tone of the cathode ray tube. On the phosphor side, there is a need to solve this saturation phenomenon, and the present invention improves these characteristics.

The present invention utilizes europium-activated yttrium oxysulfide (Y2
O2S: Europium-activated yttrium oxysulfide (Y20
2S: Eu') Aims to improve the phenomenon of brightness of phosphor.

Means for Solving the D0 Problem The present invention provides a europium-activated yttrium oxysulfide phosphor as a base material with 2 ppm or more of 1 as an Eu co-activator.
Ultra-trace amounts of Pr, less than 0 ppm, are used. Also, the general formula europium activated yttrium oxysulfide Y +2-al
E.1. + ao 2'S, the activation amount of E II and the value of hitting a are specified as 0.0002≦a≦0.2.

89 action An ultra-trace amount of Pr is activated by europium-activated yttrium oxysulfide together with Eu to improve the brightness saturation phenomenon in the high current density region of the europium-activated yttrium oxysulfide (Y2O2S:Ell) phosphor.

F, Experimental example europium activated yttrium oxysulfide (Y 202S:
In the production of the Eu) phosphor, the Y2O3 used as a raw material for the parent europium-activated yttrium oxysulfide was of high purity and contained rare earth impurities of 2 ppm or less for each compound. That is, Y
For 2O3, CeO2 is 1ppm or less, PraO++ is 0.5ppm or less, Nd2O3 is 1ppm or less, Sm2
O3 is 2ppm or less, Tba07 is lppm or less, Dy
2O3 is 2ppm or less, HO203 is 2ppm or less, E
u2O3 is 2ppm or less, Tm2O3 is 1ppm or less,
A raw material containing Yb2O3 of 1 ppm or less was used.

However, for Y2O3, materials outside the impurity concentration range, for example, raw materials containing each impurity of 5 ppm or less can also be used.

In addition, europium oxide (EL) is used as an activator raw material.
I203), Eu in Y2O2S:Eu
Since the content of yttrium oxysulfide (Y2O2S:
E t+ ) in each case was 1 ppm or less, so those with such purity were used.

The present inventors have proposed that europium-activated yttrium oxysulfide (Y2O2S:E
lf) A phosphor was prototyped. As a result, an ultra-trace amount of Pr was
Europium-activated yttrium oxysulfide (
It has been found that only the Y2O2S:Ell) phosphor exhibits excellent current saturation characteristics.

In this experiment, the optimal content of P was determined in the following way.
Select a high quality product with a pm or less and weigh 476g. Eu20324. , Og in concentrated hydrochloric acid and then diluted with pure water to a volume of 3 liters. Then, a praseodymium chloride (PrC13) solution containing 0.1 mg of Pr in 1 milliliter was prepared, and this was mixed with the above-mentioned yttrium chloride (YCl3) and europium chloride (
A mixed solution of EuC13) was added. The amount of praseodymium chloride added is 0ml, 10ml, 1
Eight types of mixed solutions were prepared in 5 ml, 20 ml, 30 ml, 40 ml, 50 ml, and 60 ml. Next, oxalic acid solution (1200 g of oxalic acid dihydrate dissolved in 3 liters of pure water) was added to the mixed solution of each concentration to obtain Y, Eu, Pr.
Co-precipitate oxalate. It is heat treated at 800°C to convert it into an oxide. The method for obtaining a phosphor by firing using S, Na2CO3, etc. was as described in the following example. The eight types of phosphor samples obtained in this way have the general formula (Y +93eE u alIr+
2) 02S:P'r (1 ppm or less to 12 ppm), and 10 ppm of Pr is expressed as Eu[ll+62 in the above formula, P r [1,+! [1111111
It is about 8, which is a very small amount.

For these samples, the stimulation voltage was 27 KV (constant) and the current density was 0.05. uA/cm2, 0.17LA/cm2゜0, 57zA/cm2. 1. 07zA
/cm2. 5. When the values measured under each condition of 071 A/cm2 were plotted, the brightness saturation curve against current as shown in FIG. 1 was obtained.

The brightness saturation characteristics with respect to the current shown in Figure 1 are based on an ideal phosphor that does not cause brightness saturation in each current range, that is, a phosphor whose brightness increases in proportion to the current density as 100%. The rate at which the brightness decreases is expressed in %.

Therefore, the ideal phosphor is 100% horizontal in FIG. 1 regardless of the current density.

In Fig. 1, curve A shows a case where the Pr content is below the impurity concentration, that is, 0.5 ppm or below, and curve B shows a case where the Pr content is below 2.
ppm, song! IC has a Pr content of 3 ppm or 4 ppm
m, the curve has a pr content of 6 ppm or 5 ppm, and the curve E has a pr content of 8 ppm, 10 ppm, or 12 ppm.
The brightness saturation curve of the Pr phosphor is shown at −,Y 1.938EUθ1la202S:Pr phosphor.

As is clear from this figure, J 5 /Z A / c
In the case of m2, a phosphor without Pr added, i.e.
Pr.

The europium-activated yttrium oxysulfide (Y2O2S: Eu) phosphor with a content of 0.5 p/pm or less is
The brightness is 30% lower than that of an ideal phosphor that does not cause brightness saturation.
% also decreased. On the other hand, the phosphor of the present invention containing 2 ppm of Pr showed a reduction in brightness of 16%, and an additional 3 ppm of Pr.
A phosphor containing ~12 ppm Pr has a brightness reduction of 10-7
%, and the brightness saturation phenomenon has decreased. Dry P
When the r content is 18 ppm to 12 ppm, the reduction in brightness saturation does not improve and the values are almost the same.

lO- On the other hand, the content of Pr did not affect the brightness of the phosphor. That is, the brightness in a low current density region where brightness saturation does not occur is affected by the content, and as the amount of Pr added increases, the brightness tends to decrease by about 5 to 10%. This state is shown in FIG. The falling point of brightness begins around 8 ppm of Pr content. Therefore, when considering both current saturation and brightness, Pr.

The range of addition is 2 ppm or more and less than 10 ppm, preferably 4 ppm-8 ppm. In any case, it has been found that the properties of the phosphor are improved within a very narrow range of Pr content.

The phosphor of the present invention has the following characteristics in the final synthesized phosphor:
It is characterized in that the Pr content is specified to be 2 ppm or more and 10 ppm or more. Therefore, by adjusting the amount of Pr contained in the raw material for producing the phosphor, or by using a raw material with a Pr content within a certain range, the produced phosphor has a concentration of 2 ppm to 2 ppm.
It is also possible to use a europium-activated yttrium oxysulfide (Y2(')2S:Eu) phosphor containing 10 ppm of Pr.

Examples of the present invention will be specifically described below.

・Example 1 24.0 g of europium oxide and 0 Pr.

High purity yttrium oxide 476 containing 5 ppm or less.

Dissolve 0 g in concentrated hydrochloric acid and dilute this with pure water to make about 3 liters. Next, 0 in 1 milliliter.

A praseodymium chloride solution containing 1 mg of Pr is prepared, and 25 ml of this solution is added to the above hydrochloric acid solution containing yttrium and europium, mixed well, and then heated to 60°C. Meanwhile, 1200g of oxalic acid dihydrate
An aqueous solution of oxalic acid dissolved in 3 liters of pure water is heated to 80°C, and added to the hydrochloric acid solution heated to 60°C while stirring, and stirred for 10 minutes after the addition is complete. Thus, oxalates of yttrium, europium, and praseodymium are produced and precipitated in the mixed solution. Next, the solution containing the precipitate is allowed to cool, and then washed five times with pure water by denotation, and the precipitate is suction-filtered. This precipitate is thermally decomposed at 800° C. for 3 hours to convert oxalate into an oxide. Rare earth oxide 200 thus obtained
59 g of sulfur and 63 g of sodium carbonate lx, mixed well, and heated to 110 g in a sealed alumina crucible.
After firing at 0°C for 3 hours, the sintered body is ground in a ball mill, thoroughly washed with water, and then dried at 150°C.

The phosphor manufactured here has a general formula of Y1938E u
[1.1+620 25 and contained approximately 5 ppm praseodymium.

In this phosphor, the luminance at a current density of 571 A/cm2 was only -9.0% lower than that at a current density of 0,05/ZA/cm2.

131 Example 2 32.7 g of europium oxide and 0.

The high purity yttrium oxide 467 containing 5 ppm or less,
Dissolve 3 g in concentrated nitric acid and dilute this with pure water to make about 3 liters. Next, O in 1 ml. 1 mg of Pr
Prepare a praseodymium nitrate solution containing 10
Milliliter is added to the nitric acid solution containing the rare earth element, mixed well, and then heated to 60°C. The following operations were carried out in exactly the same manner as in Example 1 above to obtain a Pr-containing Eu-activated europium-activated yttrium oxysulfide Y 20 2S phosphor.

The thus obtained phosphor has a general formula of Y+. e+4Eu
[1.11860 2S contained about 2 ppm of Pr.

This phosphor has a luminance of 0.05 μA when the current density is 5 μA/Cm2. /crn2 compared to 116
The decline was only 1%.

Example 3 Oxidized eurobiuno, 23.0 g and 0°5 pp of Pr
477 g of the high purity yttrium oxide containing less than m is dissolved in concentrated nitric acid and diluted with pure water to make about 3 liters. Next, a praseodymium nitrate solution containing 0.61 mg of Pr in 1 ml is prepared, and 40 ml of this solution is added to the nitric acid solution containing the rare earth element, mixed well, and then heated to 60°C. The following operations were carried out in exactly the same manner as in Example 1 above to obtain a Pr-containing Eu-activated yttrium oxysulfide 1% Y2(')2S phosphor. The thus obtained phosphor is Y 1.9411E I
Ie, a6eo 2S contained about 8 ppm of Pr.

This phosphor has a luminance of -7 when the current density is 57zA/crn2 and 0.0571A/cm2.
, the decrease was only 5%.

G. Effect of the present invention: active yttrium oxysulfide Y2
02S': EU phosphor is EU as shown in FIG.
In addition, by activating with an ultra-trace amount of Pr, the brightness saturation phenomenon in high current density tilted walls can be significantly improved, and it can be conveniently used in projection tubes, color display tubes, etc. In addition, since the amount of Prff1 added is extremely small, the raw material cost is almost the same as that of conventional phosphors, and there is almost no reduction in the brightness of the phosphor itself due to Pr addition, achieving many outstanding effects. .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph showing changes in brightness with respect to current density, and FIG. 2 is a graph showing changes in brightness with respect to the amount of praseodymium mixed. 23 July 1982

Claims (2)

[Claims] (1) General formula Y_(_2_-_a_)Eu_aO_2S
In the phosphor represented by , a is 0.0002≦a≦0.
2, and contains praseodymium (Pr) in a range of 2 ppm or more and less than 10 ppm. (2) Praseodymium (Pr) content is 4ppm to 8p
The phosphor according to claim (1), which is pm.