JPS60195180A - Alkaline earth metal sulfide fluorescent material - Google Patents

Abstract

PURPOSE:To provide a fluorescent material for B/W or color CRT tube, composed of a Tb- and Zn-doped alkaline earth metal sulfide fluorescent material, having excellent afterglow property and controlled particle size. CONSTITUTION:The objective fluorescent material is represented by the formula XS:TbZn (X is Ca or Sr) wherein the amount of doped Zn is >=1X10<-4>g-atom (preferably >=4X10<-4>g-atom per 1mol of the alkaline earth metal. The fluorescent material can be prepared e.g. by oxidizing and sintering CaCO3 containing 0.1mol% Tb in air at 1,250 deg.C, pulverizing 1mol of the sintered material, mixed thoroughly with 10<-3>mol of ZnO and 2mol of sulfur by physical means, and calcining at 1,000 deg.C in a reducing atmosphere for 3hr.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a phosphor for monochrome or color display cathode ray tubes, and particularly to a phosphor having desirable afterglow characteristics and graininess.

[Technical background of the invention and its problems]

In terminal display devices, monochrome or color display cathode ray tubes have the same resolution, active display, and high reliability.

It is still not as economical as other display devices, and the demand for it is increasing. Therefore, there is a strong demand for phosphors used in these devices, and various improvements and developments are being attempted.

As is well known, the phosphors of cathode ray tubes for display use require not only high luminescence but also long afterglow properties to suppress flickering on the screen. Small grain size is required. Currently, green and orange are the main colors displayed on monochrome display tubes. Green monochrome display cathode ray tubes, which have been gaining popularity in recent years, generally use Zn25I04: Mn, As due to their afterglow, graininess, etc.
is used.

However, this phosphor is not desirable for end consumers because it contains toxic arsenic. On the other hand, ZnS :Cu, C, (3 or Zn8
:Although phosphors such as Cu, Au, and human e are not polluting,
Since the afterglow time is short and the phosphor particle size tends to become large, the image quality (resolution) remains unaffected.

That is, it is necessary to take measures such as reducing the particle size at the expense of luminous efficiency.

Calcium sulfide is manufactured by Lehmann (W, Lehmann)
Journal of Obluminescence (J.

As reported in Luminescence 5 (1972) 87), by adding an appropriate activator, a phosphor with high luminous efficiency can be obtained. Tb, one of the activators, forms a good luminescent center in CaS,
It emits green light. However, its afterglow time is about 2
The duration is milliseconds, so it cannot be said to have a long afterglow.

The present inventors have focused on the high efficiency of Tb-activated alkaline earth metal sulfide phosphors, and have attempted to improve their afterglow properties and control particle size, which would reduce this good efficiency. In order to make this possible, we have repeatedly investigated co-activators. As a result, it has been found that containing Zn element as a co-activator has a remarkable effect on the afterglow characteristics and particle size control, leading to the present invention.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a terbium-activated alkaline earth metal sulfide phosphor with improved afterglow properties and a controlled diameter.

[Summary of the invention]

The phosphor according to the present invention is characterized by containing Zn in the Tb-activated alkaline earth metal sulfide phosphor, and its afterglow time is longer than when no Zn is added. It has the effect of lengthening the length.

Figure 1 shows one of the phosphors according to the present invention, a Cab:Tb phosphor, in which the Zn content is 10% per mole of the matrix.
In the case of gram atoms (curve 1) and in the case of no Zn addition (
FIG. 2 is a diagram showing the afterglow characteristics of curve 2) and Zn S :L u * C, I3 phosphor (curve 8). In FIG. 1, the vertical axis represents the relative intensity with the emission intensity immediately after excitation stopped as 100, and the horizontal axis represents the time axis in milliseconds. Santsubaki Sez'4
The improvement in the afterglow properties of the Cab:Tb phosphor by addition is obvious.

The fact that the Tb-activated CaS phosphor emits green light having a main peak wavelength at about 550 nm is known from the Lehman (W,
Lehmann).

Since it is a practically effective phosphor that emits green light, the amount of Tb as an activator is 10-4 to 10-1 per mole of the base material.
Gram atoms are preferred. Outside this range, the luminescence intensity decreases significantly and the Z according to the present invention exhibits a good luminescence color.
No effect of n addition was observed.

The effect of particle size control by adding Zn is clear from FIG. The amount of Zn added according to the present invention is desirably 10@-4 gram atoms or more per mole of the base material.

When the amount of Zn added is less than 1, the effects of improving afterglow and graininess are poor. On the other hand, when it exceeds 10-2 gram atoms, the luminescence intensity decreases significantly.

Figure 8 shows Tb in an alkaline earth metal sulfide phosphor.
FIG. 3 is a diagram showing the effect of improving the afterglow time caused by adding Zn when the activated phosphor is 10 −3 gram atoms. The vertical axis in FIG.
It is a relative afterglow time with 1/0 afterglow time as 1, and the horizontal axis is the amount of Zn added.

Curve 1 is Ca S :Tb + Zn and curve 2 is S rS : Tb + Zn. As shown in Figure 1, z
Improvement in afterglow time due to n addition is seen at 10-4 gram atoms or more, and is particularly remarkable at 4×10 2 or more.

It is well known that each of these alkaline earth metal sulfide phosphors forms a solid body, and these effects are similar to those of CaS.
It was also found in a solid body made of SrS.

As described above, the phosphor of the present invention, which is a Tb-activated alkaline earth metal sulfide phosphor with an appropriate amount of Zn added, can be applied to cathode ray tubes for monochrome or color displays.
The phosphor has a long afterglow, granularity, and luminescence intensity that are sufficient for practical use.

[Embodiments of the invention]

The present invention will be explained below with reference to Examples.

Example (1) CaCO3 containing 0.1 mo/L/% of Tb is oxidized and sintered at 1250C in air. After pulverizing 1 mol of the obtained sintered body, 10 mol of ZnO and 2 mol of sulfur were thoroughly mixed by physical means, and the mixture was kept at 1000 C for 3 hours in a reducing atmosphere and fired. Cab obtained by this firing: 0.
The average particle size of 001Tb, 0.001Zn phosphor is 4
．． It was Oltm.

The C a S :T b e Zn phosphor obtained in this example was subjected to a pulse width of 10 microseconds, a voltage of 10, and a current of 10.
The emission peak intensity and 1/10 afterglow time when excited with the electron beam of A are expressed as relative values for a CaS:0.001Tb phosphor prepared by the same method except that no Zn was added. Shown in 1.

Example (2) Cac104 containing 0.1 mol of Tb in air at 120F
oxidize and sinter. After the obtained sintered body is pulverized, 10 −3 mol of ZnC2O4 is mixed with 1 mol of the sintered body, and the mixture is fired at 1000 C for 4 hours in hydrogen sulfide. CaS obtained by firing: o, ooi'rb, 0.0
The average particle size of the 01Zn phosphor was 3.8 μm.

Table 1 shows the results of measurements of the emission peak intensity and 1/10 afterglow time of the phosphor obtained in this example under the same conditions as in Example (1). As is clear from Table 1, the afterglow time of the CaS:'rbTb phosphor containing Zn is improved by more than 100 degrees compared to the phosphor containing no Zn.

Example (3) In the above Example (1), Cr was substituted for Ca Co 5
By performing similar firing using C01, 8rS:0.001Tb, 0.001Tb with an average particle size of 3.5μm was obtained.
Zn was obtained.

When the SrS:Tb, Zn phosphor obtained in this example was measured under the same conditions as in Example (1), the emission peak intensity and 1/10 afterglow time were changed, except that Zn was not added. Table 2 shows the relative values for Sr8:Tb fluorophores prepared by the same method.

Example (4) In the above Example (2), Sr was used instead of Ca C204.
By performing the same firing using C, Q, ・H, O, Sr8: 0.001Tb with an average particle size of 3.8Bm,
0.001 Zn was obtained.

When the S r S : T b + Zn phosphor obtained by this method was measured under the same conditions as in Example (1), the emission peak intensity and 1/10 afterglow time were determined without adding Zn. Srs:Tb was produced by the same method except for
The relative values for the fluorophore are shown in Table 2.

As is clear from Table 2, SrS:Tb containing zn
has an afterglow time of 100% compared to a phosphor that does not contain Zn.
Improved by 4 or more.

〔Effect of the invention〕

As mentioned above, Zn-containing alkaline earth metal sulfide phosphors have a long afterglow time, and the Zn content makes it easier to control the particle size, so they are not suitable for industrial use. Therefore, it is particularly suitable as a phosphor for monochrome and color display cathode ray tubes.

Table 1 Table 2

[Brief explanation of drawings]

Figure 1 shows Ca8:Tb, Zn (curve 1), Ca's
Figure 2 shows the afterglow characteristics of a T b (curve 2) and ZnS:CuA4 (curve 8).
+Zn is a diagram showing the relationship between the average particle diameter and the Zn addition V, and FIG. 8 is a diagram showing the relationship between the afterglow time and the Zn addition amount of the Tb-activated alkaline earth metal sulfide phosphor. Agent Patent Attorney Kensuke Chika (and 1 other person) No. 1
Figure $m (mi,・)kiri/・) Figure 2 Figure 3

Claims (1)

[Claims] (1) An alkaline earth sulfide phosphor characterized by having a general formula of XS:TbZn. However, X is at least one of Ca and Sr. (31 'The alkaline earth sulfide phosphor according to claim 1, characterized in that the activation rate of Zn is 4 x 10 7 gram atoms or more per mole of alkaline earth sulfide.