JPH05331463A - Blue luminescent fluorescencer and its production - Google Patents

Abstract

PURPOSE:To obtain a blue luminascent fiuorescencer having excellent particle size distribution while simply controlling particle diameters without changing a burning temperature, burning time, etc., by blending zinc sulfide with silver and a specific amount of antimony and burning in a sulfur-containing reducing atmosphere. CONSTITUTION:First, zinc sulfide is blended with a silver compound (e.g. AgCl) and <=0.02% based on zinc sulfide of an antimony compound (preferably Sb2S3). Then the mixture is burnt in a sulfur containing reducing atmosphere usually at 750-1,100 deg.C for 30 minutes to 10 hours to give the objective fluorescencer. containing <=0.01% antimony based on the parent material of zinc sulfide in the silver-activated zinc sulfide fluorescencer. Zinc sulfide is generally obtained by introducing a hydrogen sulfide gas to an aqueous solution containing Zn ion such as aqueous solution of zinc sulfate to form precipitate of zinc sulfide, separating and drying the precipitate. The amount of Ag is usually 0.01-0.5% based on the parent material of zinc sulfide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silver-activated zinc sulfide blue light-emitting phosphor for a cathode ray tube which contains zinc sulfide as a base material and silver as an activator, and a method for producing the same.

[0002]

As a blue light emitting phosphor for a cathode ray tube, a general formula is ZnS: Ag, X (where X is a halogen element, Al
At least one of. ) A silver-activated zinc sulfide phosphor represented by (1) is known. In general, this phosphor is obtained by adding a compound containing Ag such as AgCl or AgNO ₃ as an activator to zinc sulfide which is a matrix obtained by a wet reaction.
KCl, NaCl, Al as co-activator or flux
₂ (SO ₄ ) _{3 and} other compounds containing an X element are mixed together, and the mixture is mixed in a hydrogen sulfide atmosphere or a reducing atmosphere containing hydrogen at 75
It is obtained by firing at 0 ° C to 1100 ° C.

In the above manufacturing method, in order to obtain a silver-activated zinc sulfide phosphor having a desired particle diameter, a means for adjusting the firing temperature, the firing time, and the amount of the flux added is generally used. Is performed not only for silver-activated zinc sulfide phosphors but also for general zinc sulfide-based phosphors in general. Also,
For the cathode ray tube, a phosphor having an average particle size adjusted to about 5 μm to 8 μm is most preferably used.

[0004]

However, the means for adjusting the particle size by the firing temperature, the firing time, the amount of the flux added, etc. must repeat long-term experiments, and the technology obtained by the experiments is a know-how. It is the actual situation that it is preserved as and is rarely disclosed.

At present, silver-activated zinc sulfide phosphor has the highest brightness among phosphors known as blue light-emitting phosphors for cathode ray tubes and is relatively stable to electron beams, and thus is widely used. However, with the development of HDTVs, large-screen cathode ray tubes, and the like, there has been a growing demand for large-particle phosphors having an average particle diameter of 9 μm or more.

On the other hand, the phosphors of large particles obtained by the conventional method have a poor particle size distribution, and a large amount of coarse particles and phosphors of small particles are distributed. There is a problem that a uniform coating surface cannot be formed and coating characteristics are poor. For example, the index indicating the particle size distribution is σl
log or log σ (standard deviation for median particle diameter d50)
If the value is about 0.5 or more, it is necessary to classify and remove a large amount of coarse particles and small particles, resulting in a marked decrease in productivity.

Therefore, the present invention has been made in view of such circumstances, and an object of the present invention is to easily carry out without changing the baking temperature, the baking time, and the amount of the flux as in the conventional case. The present invention provides a method for producing a silver-activated zinc sulfide phosphor capable of adjusting the particle size, and a silver-activated zinc sulfide phosphor excellent in particle size distribution.

[0008]

[Means for Solving the Problems] In addition to the conventionally added fluxes, we have made a number of studies on substances that can be used as fluxes that grow crystals without lowering the brightness of silver-activated zinc sulfide phosphor. As a result of repeated experiments, it was newly found that the above problems can be solved by activating a low melting point substance containing a specific element to a silver activated zinc sulfide phosphor, and the present invention has been accomplished.

That is, the method for producing a blue light-emitting phosphor of the present invention uses zinc sulfide, at least silver, and zinc sulfide of 0.1%.
It is characterized by mixing with 02% or less of antimony and firing in a reducing atmosphere containing sulfur. More specifically, first, a zinc sulfide precipitate obtained by blowing hydrogen sulfide gas into an aqueous solution containing Zn ions such as an aqueous zinc sulfate solution is separated, and dried zinc sulfide raw powder is mixed with AgCl, Ag.
A compound containing Ag such as NO ₃ and a flux such as NH ₄ Cl,
After adding and mixing antimony and antimony in a proportion of 0.02% or less with respect to the zinc sulfide raw powder,
Put in a crucible, and 750 ℃ ~ 11 in a reducing atmosphere containing sulfur
It can be obtained by baking in a temperature range of 00 ° C. for 30 minutes to 10 hours. In the manufacturing method of the present invention of claim 2, silver and antimony mixed with zinc sulfide mean a compound containing a metal and these elements and having a melting point of 1100 ° C. or lower.

In the blue light emitting phosphor of the present invention thus obtained, at least 0.01% of antimony is contained in the zinc sulfide base material in the zinc sulfide phosphor activated with silver. It can be represented by the general formula ZnS: Ag, Sb, X. In this phosphor, the Ag amount is usually 0.0 with respect to the ZnS matrix.
01% to 0.1%, X amount which is a co-activator is 0.0
It is adjusted in the range of 01% to 0.5%. It is known that the afterglow property of the phosphor is improved as the amount of X is increased. However, setting the amounts of Ag and X out of the above range is effective in terms of emission brightness and chromaticity point. Is not preferable.

In the production method of the present invention, it is most preferable to add Sb ₂ S ₃ to antimony, and to add other Sb.
Antimony halides such as F ₃ and SbCl ₃ , Sb ₂ O ₃ ,
When firing in an atmosphere containing sulfur, such as Sb ₂ (SO ₄ ) ₃ , an antimony compound having a low melting point that can be decomposed and reacted to form Sb ₂ S ₃ can be added. It is important to set the firing atmosphere as a reducing atmosphere containing sulfur, and the added Sb compound is decomposed by heat and reacts with S to form Sb ₂ S ₃
And acts as a flux for the phosphor.

[0012]

In general, the silver-activated zinc sulfide phosphor obtained by the conventional method generally has a poor particle size distribution and a good crystal form. For example, FIG. 2 shows Ag
Is an electron micrograph (650 times) showing the crystal structure of ZnS: Ag, Al phosphor containing 0.02% of Al and 0.02% of Al and having an average particle diameter of 7.5 μm. As described above, many conventional phosphors have so-called onigiri-type and flat-type crystal shapes, and their particle size distribution is also broad.

On the other hand, FIG. 1 is an electron micrograph (650 showing the crystal structure of the silver activated zinc sulfide phosphor of the present invention.
Times). This phosphor also has Ag of 0.02%, A
It is a ZnS: Ag, Sb, Al phosphor having an average particle size of 7.8 μm containing 0.02% of 1 and 0.001% of Sb. In the phosphor of No. 3, the particles have a round shape as a whole, and the number of flat type and rice ball type crystals is small as in the conventional case.

FIG. 3 shows that zinc sulfide raw powder having an average particle size of 2 μm contains 0.02% of Ag and 0.02% of Al.
gCl, Al ₂ (NO ₃ ) ₃ and a flux were mixed at 5%, and the mixing amount of Sb ₂ S ₃ was changed, and the firing conditions were set to 960 ° C.
It is a figure which shows the relationship between the addition amount of Sb with respect to zinc sulfide raw powder, and the particle size of a fluorescent substance by experimentally manufacturing a ZnS: Ag, Sb, Al fluorescent substance in 5 hours. The horizontal axis is the Sb conversion value.

As shown in the figure, when antimony is not added, the particle size grows up to about 8 μm, but by increasing the amount of antimony, the particle size of the silver activated zinc sulfide phosphor is increased. Can be done, and the relationship is almost proportional. From the above, it can be seen that antimony acts as a flux for crystal growth. When the firing temperature is 750 ° C., the slope of this figure is almost halved, and the grain size grows to almost 20 μm when the Sb addition amount is 0.02%. Since particles of 20 μm or more are not practical, 0.02% was made the maximum addition amount.

In FIG. 4, Ag is 0.02% and Al is 0.0
2% activated average particle size 9.4 μm, d50 value 10.9 μ
FIG. 3 is a diagram showing the relationship between the amount of Sb directly activated and the particle size distribution of the phosphor in the ZnS: Ag, Sb, Al phosphor of m. The particle size distribution is expressed by log σ as described above, and its formula is log σ = 1/2 (lnD84.13-lnD15.87) (ln = loge, and D84.13 and D15.87 are the integration of the particle size distribution of the phosphor. 84.13% in distribution, and 15.
A particle size value of 87%. ) Can be represented.

As can be seen from this figure, Z of the present invention
Since the nS: Ag, Sb, Al phosphor contains Sb, the particle size distribution is very excellent, and the Sb content is 0.01
Even in%, the value is 0.35, and the particle size distribution is very sharp.

FIG. 5 shows a ZnS: Ag, Sb, Al phosphor in which Ag is 0.02% and Al is in an amount of 0.02% and the amount of Sb directly activated and the phosphor powder. It is a figure which shows the relationship of brightness. The relative brightness of 100% is the brightness value of the phosphor containing no Sb.

Even if ZnS: Ag, Al phosphor is activated with Sb, its brightness is hardly reduced, and the Sb content is 0.00
It is almost constant up to 5%. However, there is a tendency for the value to drop abruptly after exceeding 0.01%, so 0.01% was made the limiting value as the Sb activation amount that can maintain a brightness of 95% or more.

According to our experiments, a part of the antimony compound added to zinc sulfide is scattered by firing, and it is activated in the phosphor by about 1/10 to 1 /.
It is 2. Therefore, by adjusting the amount of antimony mixed with the raw zinc sulfide powder to 0.02% or less, the amount of antimony that directly activates the phosphor can be adjusted to 0.01% or less.

By the way, as a technique similar to the present invention,
JP-A-53-141185, JP-A-53-141
Japanese Patent No. 186 discloses a copper activated zinc sulfide green light emitting phosphor represented by ZnS: Cu, Al containing Sb in an amount of 0.01% or less. However, even if Sb was added to the copper-activated zinc sulfide phosphor, the effect of adjusting the crystal shape and sharpening the particle size distribution as in the present invention was not obtained.

[0022]

【Example】

[Example 1] ZnS raw powder (average particle diameter 2.5 μm) 1 kg AgCl 0.266 g (Ag: 0.
02%) Al ₂ (SO ₄ ) ₃ 0.634 g (as Al: 0.
01%) Sb ₂ S ₃ 0.029 g (0.
(002%) KCl 2 g NaCl 1 g Sulfur 20 g After thoroughly mixing the above raw materials, the raw material was filled in a quartz crucible and fired at 850 ° C. for 5 hours in a hydrogen sulfide atmosphere to obtain a phosphor of the present invention. This phosphor has an average particle size of 9.0 μm.
And had a very sharp particle size distribution with a log σ of 0.26. As a result of analysis, the amount of antimony directly activated by the phosphor was 0.001%.

Further, using this phosphor, a phosphor screen was formed according to a conventional method. The average particle size was 6.5 μm, log
The surface brightness was approximately 10% higher than that of a phosphor screen formed of a conventional ZnS: Ag, Al phosphor having σ 0.42.

[Example 2] ZnS raw powder (average particle size 2.5 µm) 1 kg AgCl 0.159 g (Ag: 0.
012%) 0.014 g of Sb ₂ S ₃ (0.
001%) NaCl 5g KCl 1g Sulfur 20g The above materials were mixed and the same was carried out in a hydrogen sulfide atmosphere to obtain 96
The phosphor of the present invention was obtained by firing at 0 ° C. for 5 hours. This phosphor had grown to an average particle size of 9.5 μm and had a sharp particle size distribution with a log σ of 0.26. The amount of antimony activated directly on the phosphor was 0.0003%.

Example 3 ZnS raw powder (average particle size 2.5 μm) 1 kg AgCl 0.531 g (Ag = 0.
04%) 1.902 g of Al ₂ (SO ₄ ) ₃ (0.
03%) Sb ₂ S ₃ 0.070 g (0.
005%) NaCl 2g KCl 1g Sulfur 20g The above raw materials are mixed and the same is carried out in a hydrogen sulfide atmosphere.
The phosphor of the present invention was obtained by firing at 0 ° C. for 5 hours. This phosphor had grown to an average particle size of 12.5 μm and also had a sharp particle size distribution with a log σ of 0.26. The amount of antimony activated directly on the phosphor was 0.0018%.

Example 4 Raw ZnS powder (average particle size 2.5 μm) 1 kg AgCl 0.797 g (Ag = 0.
06%) 3.170 g of Al ₂ (SO ₄ ) ₃ (0.
05%) 0.279 g of Sb ₂ S ₃ (0.
02%) KCl 5 g NaCl 1 g Sulfur 20 g The above raw materials were mixed and the same was carried out in a hydrogen sulfide atmosphere at 75%.
The phosphor of the present invention was obtained by baking at 0 ° C. for 5 hours. This phosphor had grown to an average particle size of 19.5 μm and also had a sharp particle size distribution with a log σ of 0.35. The amount of antimony activated directly on the phosphor was 0.098%.

Comparative Example 1 A silver-activated zinc sulfide phosphor was obtained in the same manner as in Example 1 except that Sb ₂ S ₃ was not added. This phosphor grew only to an average particle size of 7.2 μm and had a log σ of 0.45, which was a broad particle size distribution.

[0028]

As described above, the silver activated zinc sulfide phosphor produced by the method of the present invention has a round particle shape and a very sharp particle size distribution. Therefore, even when the cathode ray tube is applied, it is possible to form a phosphor screen in which the phosphor particles are well clogged (density). Therefore, the phosphor of the present invention has almost the same powder brightness as the conventional phosphor, but when the phosphor screen is formed, the phosphors forming dots and stripes are easily clogged, and thus the surface brightness is improved. Is improved.

Further, according to the production method of the present invention, it was revealed that the amount of antimony added and the grain size of the growing phosphor are in a substantially proportional relationship, and therefore, the silver activated zinc sulfide having the target grain size can be easily obtained. A phosphor can be obtained. Moreover, the particle size distribution of the obtained phosphor is very sharp as described above, and it is possible to provide a suitable phosphor for a cathode ray tube.

[Brief description of drawings]

FIG. 1 is an electron micrograph showing a crystal structure of a silver-activated zinc sulfide phosphor according to an example of the present invention.

FIG. 2 is an electron micrograph showing a crystal structure of a conventional silver-activated zinc sulfide phosphor.

FIG. 3 is a diagram showing the relationship between the amount of Sb added to zinc sulfide and the particle size of a phosphor.

FIG. 4 Sb directly activated on silver activated zinc sulfide phosphor
The figure which shows the relationship between quantity and the particle size distribution of fluorescent substance.

FIG. 5: Sb directly activated on silver activated zinc sulfide phosphor
The figure which shows the relationship between quantity and the powder brightness of a fluorescent substance.

Claims (2)

[Claims] 1. Antimony is contained in a zinc sulfide phosphor activated with at least silver in an amount of 0.01% based on the zinc sulfide matrix.
A blue-emitting phosphor containing the following: 2. A blue light-emitting phosphor prepared by mixing zinc sulfide with at least silver and 0.02% or less of antimony with respect to zinc sulfide and firing the mixture in a reducing atmosphere containing sulfur. Method.