JPS6059943B2 - Manufacturing method of zinc oxide phosphor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a zinc oxide phosphor, and an object of the present invention is to provide a method for producing a bright phosphor that has good adhesion to a supporting substrate.

Zinc oxide phosphors have been recently used for low-speed electron beams in fluorescent display tubes of electronic desktop calculators and various electronic devices because of their extremely low emission initiation excitation voltage and blue-green emission with relatively high visibility. Widely used as a luminescent material.

When applying a phosphor for low-speed electron beams to form a fluorescent film, if a binder such as water glass is used, the loss of electron beam energy will increase and the effect will be reduced ↓1
-L-3' Since the phosphor must be coated on the electrode by screen printing method or electrostatic coating method without using PP adhesive, it is necessary to apply particles as much as possible to increase the coating strength of the phosphor film. It uses a phosphor with a small diameter.

However, fine particle phosphors are undesirable because their luminance is low. In consideration of these drawbacks, in order to produce a bright zinc oxide phosphor with strong adhesion, the outer shape of each phosphor particle was made into a plate shape. As a result, by forming the phosphor into a plate shape, it was possible to produce a bright phosphor with good adhesion between phosphor particles and to electrodes. By using this, a high quality fluorescent display tube could be manufactured. The present invention realizes a method useful for easily manufacturing such a plate-shaped zinc oxide phosphor.

That is, basic zinc sulfate in the form of plate-like crystals is prepared, thermally decomposed to form zinc oxide in the form of plate-like crystals, and further heat-treated in a reducing atmosphere to obtain a phosphor. , by adding ammonia water to a zinc sulfate solution and heating and stirring. Before explaining the details of the method of the present invention, first, a method for measuring the adhesive strength and luminescence brightness of the obtained phosphor will be described.

FIG. 1 shows an apparatus for measuring the coating strength of phosphors.

In Figure 1A, 1 is an alumina porcelain substrate on which a phosphor is applied by screen printing to approximately 5m9/C7l.
The fluorescent surface 2 is formed by coating at a ratio of f. This base 1
is fixed to a jig 3 with the fluorescent surface facing downward, as shown in FIG. 1B, and the jig 3 is hung with a string 4 so as to be horizontal. 5 is a pulley which can rotate freely.

The jig 3 is dropped from various heights, and the height at which the fluorescent film is almost completely peeled off is read using a scaled support rod 6 to measure the relative adhesion strength of the fluorescent film. According to this method, the height of the commercially available product is 5d,
This is expressed as a relative value using this as a reference (100). FIG. 2 shows an apparatus for measuring the luminescence intensity of a phosphor.

In the figure, reference numeral 11 is an alumina substrate, on one surface of which a silver/paldium paste is screen printed and baked as an anode 12. On top of that, phosphor was applied at a rate of 5 mg/Clt using the same screen printing method, and the fluorescent surface 13
And so. 14 is a mica spacer, and 15 is a mesh-like stainless steel grid.

16 is a hot cathode, which is a thermionic emission source.

The whole is vacuum-sealed in a glass container 17. Fluorescent display tubes currently in use have, in principle, the same structure as this measuring device. Eb is the anode voltage (excitation voltage), Ec is the grid voltage, Ef is the heater voltage, Ef = 3.0V
．． ．． By keeping EC=18V constant and changing Eb, fluorescent surface 1
The brightness of the light emitted from No. 3 is measured using a photometer 18.

Comparison of brightness between samples was performed relative to the value at Eb=20V, which was converted to an excitation current of 2.5n1A/Crl. Next, examples and comparative examples of the method of the present invention will be described. 0.5 mol of zinc sulfate ZnsO4.7H20 was dissolved in 2e of pure water, and ammonia water was dissolved in ZnS
O4+2N80H+Zn(0H)2+(NH4)2S0
, was added in an amount of 10 to 100% of the equivalent required for the neutralization reaction.

After examining each precipitate obtained from this neutralization reaction,
Furthermore, each was heated at a temperature within the range of 60 to 10 degrees.
The mixture was stirred for about 1 hour. Then, filter, wash with water, and hold at 100°C.
It was dried with.

The obtained dry powder was placed in the air at a temperature of 700 to 105
It was heated at a temperature in the range of 0° C. to completely decompose it into oxide ZnO. Although the time required for thermal decomposition varies, it was confirmed by X-ray analysis that all of them had decomposed. Then, according to a conventional method, it was heat-treated at 1000° C. for 1 hour in a carbon monoxide atmosphere to obtain a zinc oxide phosphor. The results of experiments conducted using various combinations of neutralization degrees, stirring temperatures and thermal decomposition temperatures are summarized in the table below. In the table, experiment numbers 1 to 5 show the effects of Yang combination with varying degrees of neutralization.

Up to a degree of neutralization of 80%, basic sulfate ZnSO4.32'n (0H) in the shape of a hexagonal plate with an average size of about 2 μm as shown in Figure 3 is used.
2.4H20 occurs. If the degree of neutralization is 10%, the yield is very low and has little practical significance. At 80% neutralization, the amount is very small, but when it reaches 100%, granular Z
nsO4.6Zn(0H)2.4H20 is generated and both brightness and adhesive strength are reduced. Therefore, the appropriate degree of neutralization is 20.
~80%. Experiment numbers 6-8 show the effect of stirring temperature.

If the stirring temperature is below 60°C, plate-shaped crystals will not be formed and granular Z
nsO4・non(0FI)2・4H20 remains,
Both brightness and adhesive strength are low. At temperatures higher than 100° C., since it is an aqueous solution, evaporation becomes rapid, and it is difficult to achieve such a temperature, which is industrially disadvantageous. Therefore, the appropriate stirring temperature is 70 to 100°C. Experiment numbers 9-11 show the effect of stirring time.

When the stirring time was short, the crystals did not grow into plate-like crystals, and the 4 powders remained mostly granular particles. Plate crystals were formed in 1 hour or more, and were almost the same between 1 and 2.

From this result, a stirring time of 1 hour or more is required. Run numbers 12-15 show the effect of pyrolysis temperature.

At 700° C., some ZnsO4 still remained and a phosphor of plate-like particles was obtained, but the brightness was low. temperature 8
It completely changes to ZnO at 00~1000℃, ZnO maintains almost a plate-like external shape, and as a result of Laue X-ray analysis,
Each plate-like particle was single-crystalline. At this time, good brightness and adhesion were obtained. However, at 1050° C., the sinterability becomes intense, the plate shape collapses, and the material becomes somewhat granular. This is directly carried over to the subsequent carbon monoxide treatment at 1000°C, resulting in a decrease in both brightness and adhesive strength. Therefore, the appropriate thermal decomposition temperature is 800 to 1000°C. Experiment No. 16 was shown for comparison with a conventionally used granular ZnO:Zn phosphor. As is clear from the above results, a phosphor with good brightness and adhesive strength can be obtained by adding 20 to 80% of the neutralization equivalent of aqueous ammonia to zinc sulfate at a temperature within the range of 70 to 100°C. The basic sulfate was stirred for more than 1 hour to obtain plate-like crystals of basic sulfate, then pyrolyzed at a temperature in the range of 800 to 100'C, and finally reduced in carbon monoxide at 1000C for 1 hour. You can see what you can get by reading it.

Of course, the final reduction treatment for turning into a fluorophore may be performed by any other conventionally known method. As shown above, the ZnO:Z sequential phosphor obtained by the method of the present invention has improved brightness and adhesion of the phosphor film to the supporting substrate, and can be used for fluorescent display tubes, etc. It is very effective when used.

[Brief explanation of drawings]

Figures 1A and B show the configuration of an apparatus for measuring the coating adhesion strength of the phosphor, and Figure 2 shows the configuration of the apparatus for measuring the luminescence intensity (brightness) of the phosphor. 3 are microscopic and mirror photographs showing an example of basic zinc sulfate plate crystals obtained in the process of carrying out the method of the present invention.

Claims (1)

[Claims] 1. 20 to 8 of the neutralization equivalent of ammonia water to the zinc sulfate solution.
0% and stirred at a temperature within the range of 70 to 100°C for 1 hour or more to obtain plate-shaped crystals of basic zinc sulfate, which were thermally decomposed to form plate-shaped zinc oxide, and then in a reducing atmosphere. A method for producing a zinc oxide phosphor, the method comprising heat-treating the zinc oxide phosphor. 2 Decomposition of basic zinc sulfate in air at 800~
A method for producing a zinc oxide phosphor according to claim 1, wherein the process is carried out at a temperature within a range of 1000°C.