JPS60101172A - Production of phosphor - Google Patents

Abstract

PURPOSE:To obtain a SrS:Eu phosphor which exhibits high brightness and has excellent aftergrow characteristics, by heat-treating a Eu-activated strontium sulfide (SrS:Eu) phosphor in an alkaline earth metal vapor under a specified vapor pressure. CONSTITUTION:A Eu-activated strontium sulfide (SrS:Eu) phosphor is heat- treated in an alkaline earth metal vapor under a vapor pressure of 0.02-10mm.Hg. Though 1/10 afterglow decay time of untreated SrS:Eu is 5ms, that of the treated SrS:Eu is shortened to 0.67ms at max. The brightness of the treated phosphor is improved by at most 35%. The afterglow time and the brightness are dependent on the heat treating temp. of Sr, A remarkable effect of improving the afterglow characteristics and the brightness can be obtd. in the temp. range of 500-900 deg.C (Sr vapor pressure: 0.02-10mm.Hg).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for producing an electric field, ultraviolet or cathode ray excitable strontium sulfide (ELIEu) activated photomaterial.

[Background of the invention]

Strontium sulfide (srs) is known as a luminescent host, and for example, when activated with Eu, it is known to exhibit red luminescence (peak wavelength 590 nm) when stimulated with ultraviolet light and cathode rays (S, P, Keller, J.

Chem, phys, 29180, 1958)
. In addition, methods for producing this phosphor include a method in which strontium sulfate is used as a starting material and fired at Hz or HxS, and a method in which strontium carbonate is used as a starting material and S and NH4Cl
A method is known in which the carbon dioxide is added and fired in a neutral atmosphere (Ar, etc.). However, SrS produced by these methods
: E Ll has the disadvantages of low luminous efficiency and an excessively long afterglow decay time. As is well known, afterglow characteristics and brightness are extremely important factors for evaluating the practicality of fluorescent materials, and for this reason Sr8:Eu has not yet been put into practical use.

[Purpose of the invention]

An object of the present invention is to provide a SrS:Eu phosphor with high brightness and excellent afterglow properties, which cannot be achieved by conventional methods.

[Summary of the invention]

In order to achieve the above object, the manufacturing method of the present invention is as follows:
As a result of subjecting the SrS:Eu phosphor obtained by the conventional manufacturing method to heat treatment again in Sr metal vapor, we found that the afterglow time of this phosphor was significantly reduced and its brightness was also improved.
This is what was used.

The 1/1o afterglow decay time of untreated SrS:Eu is approximately 5
rnS but Srs treated in Sr vapor:E
That of u is shortened to a maximum of about 0.67 m s. On the other hand, brightness was improved by up to 35%. The afterglow time and brightness depend on the heat treatment temperature of sr. This relationship is shown in FIG. 1 and Table 1. The improvement effect is greatest for both afterglow time and luminance when the processing temperature is 750°C; changes are rapid at lower temperatures, while changes are slower at higher temperatures.

However, at temperatures above 900C, sr gold metal precipitates on the surface of the phosphor, and the brightness decreases. After all, the temperature range where the afterglow characteristic or brightness is significantly improved is 500C to 900C.
It can be seen that the Sr vapor pressure is between 0.02 mHg and 10++o++Hg.

It is believed that the above-mentioned effects are produced as a result of Sr defects existing in the srs crystal lattice being crushed by Sr vapor. Therefore, in place of sr, the homologous elements Ca and M
A similar effect is expected when using Ca, but in reality Ca
, Mg, and 13a, effects similar to those described above were observed.

Table 1 (9KV-100mA excitation) [Embodiments of the invention] Hereinafter, the present invention will be explained in detail with reference to Examples.

<Example 1> High purity strontium carbonate (SrCOs) 14.763
g High purity europyram oxide (Eu203) 0.018
A homogeneous mixture of 1 g was filled into an alumina crucible, and 1
Bake at 200 tl' for 6 hours. Next, crush the fired body thoroughly, place it in a quartz port, and put it into a quartz tube at H2
Bake at 1200G for 4 hours while flowing S gas.

2.0 g of the SrS:Eu (0.1%) phosphor powder that has undergone the above manufacturing process is placed in the bottom of a single-sealed quartz capillary with a length of 30 crn. Next, a small piece of high-purity SR metal was placed near the inlet of the quartz tube, connected to a vacuum exhaust system, and the vacuum level was 10-"l'.
Seal the quartz tubule under a vacuum of orr.

Next, this quartz tube is placed in a reaction furnace with a temperature gradient such that the phosphor side is at a high temperature and the Sr metal side is at a low temperature. The temperature settings are such that the high temperature part is 1100p and the low temperature part is 750C. After keeping it as it is for 2 hours, it is taken out of the furnace and rapidly cooled. The SrS:Eu phosphor obtained in this way is f3r
It shows a high brightness of 135- compared to the phosphor before steam treatment, and the 1/1.0 afterglow decay time also decreases from 5ms to 0.67m5.
It was shortened to .

<Example 2> The brightness of the phosphor obtained under the same conditions as in Example 1 except that only the low temperature part <sr metal part) was 550 C was 115% of that of the phosphor before Sr vapor treatment. Further, the 1/10 decay time was 1 m 5.

<Example 3> Similarly, 900 C (in case of D, brightness 110%, 1/10
The decay time was 0.85 m5.

<Example 4> Under the same conditions as in Example 1, when Ca was used instead of 3r as the metal piece, the brightness and 1/10 decay time were 125% and 0.75 m5, respectively.

As mentioned above, the afterglow characteristics and brightness of SrS:Eu are
This is because the pressure inside the quartz tube changes with the heating temperature. The pressure inside the tube matches the equilibrium vapor pressure of Sr solid-vapor when the temperature of the Sr metal part is constant. For example, 550C has 0.02 Hg, and 750U has 1.1 Hg.

At 900C, it becomes 10m++IHg, and the vapor pressure increases monotonically with temperature. In this example, one method of atmosphere control using a sealed tube method was described, but a method using a decomposition reaction of a compound containing Sr as a source of Sr vapor, or
Other devices (open tube method) that can keep the vapor pressure constant can also be used. It is clear from the principle of the present invention that effects similar to those described here can be obtained.

〔Effect of the invention〕

According to the present invention, it is possible to obtain an srs:Eu phosphor that has higher luminance than that obtained by conventional manufacturing methods and has excellent afterglow characteristics. In addition, in this manufacturing method, not only the brightness but also the afterglow characteristics can be controlled by selecting the vapor pressure of Sr, so it is possible to easily obtain 8rS:Eu suitable for various uses.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between 1/10 afterglow decay time and Sr heating temperature. 1...1710 afterglow decay time before Sr vapor treatment (conventional method). 2...Curve showing the relationship between 1/10 afterglow decay time and Sr heating temperature after Sr vapor treatment. Explanations with arrows on the horizontal axis indicate fJ+ at that temperature.
Figure 6 Processing Al (°S)

Claims (1)

[Claims] In the production of Eu-activated strontium sulfide (8r8:Eu) phosphor, the phosphor is heat-treated in alkaline earth metal vapor, and the vapor pressure is in the range of 0.02 WHg to 10 wHg. Method of manufacturing phosphor.