JPS6144912B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an EL phosphor for a planar light source or display element that has high brightness and a long life, and a method for manufacturing the same. Conventionally, this type of EL phosphor uses zinc sulfide (ZnS) as a matrix, contains an activator such as copper or silver, a co-activator such as aluminum, chlorine or bromine, and contains ammonium chloride (NH ₄ Cl). ) etc. were used as flux for firing. However, all of these have the drawbacks of severe deterioration and short lifespan. The basic idea is that this deterioration is due to S defects contained in the ZnS crystal and the diffusion of copper, etc., and that it is possible to extend the life by introducing ions with a large ionic radius into the crystal to prevent diffusion. It was considered. Based on this, various attempts have been made to obtain long-life phosphors. For example, Westinghouse's Lehmann has
It has been announced that a phosphor that replaces a portion of the zinc with cadmium, which has a larger ionic radius, and uses bromine, which has a larger ionic radius than chlorine, as a coactivator does not deteriorate. [J.Electrochem.Soc., vol 113, P.40
(1966)] However, this phosphor
Not only does it pose a pollution problem because it contains cadmium, but the authenticity of this announcement has also been questioned.
(Society for Information´mation by WEHoward
Display's 1980 Seminar Lecture Notes,
Vol. 1, April 28. P. 78 onwards) In addition, phosphor (ZnS: Cu, Br), which is made by adding copper as an activator and bromine as a co-activator to ZnS, is mixed with copper nitrate [Cu (NO ₃ )]. ₂ ] and ammonium bromide (NH ₄ Br)
Cu(NO ₃ ) ₂ 1.3× for 1 mol of ZnS as raw material
There is also an example of manufacturing by firing a phosphor to which 10 ^-3 mol and NH ₄ Br2×10 ^-2 mol are added. (Refer to Mitsubishi Electric Technical Report, Vol. 44, p. 1534, 1970) However, these have low brightness due to the small amount of activator and co-activator added. In other words, despite the various attempts mentioned above, it has not been possible to optimize the amounts of copper and bromine added and the firing conditions, and it has not been possible to obtain a phosphor with high brightness and long life. I haven't reached it yet. The present invention has been made in view of the current situation, and its purpose is to solve the above-mentioned drawbacks and problems, and to provide a phosphor based on ZnS with high brightness and long life, and a method for manufacturing the same. It is to be. To summarize the present invention, the EL phosphor of the present invention (first invention) is characterized by comprising zinc sulfide and 0.1 to 0.5 mol% copper and 0.05 to 0.5 mol% bromine relative to zinc sulfide. Also, the present invention
The method for manufacturing an EL phosphor (second invention) is
In producing an EL phosphor consisting of zinc sulfide and 0.1 to 0.5 mol % of copper and 0.05 to 0.5 mol % of bromine based on zinc sulfide, copper acetate and 0.15 to 1.5 mol % of copper acetate and zinc sulfide are used. 0.15~24
The method is characterized in that a mixture consisting of mol% ammonium bromine is calcined in an atmosphere containing hydrogen sulfide. The present inventors have developed a zinc sulfide-based EL phosphor (hereinafter referred to as phosphor) that uses zinc sulfide as a matrix, to which copper is added as an activator, and bromine is added as a co-activator.
As a result of various studies, we found that the lifetime of a phosphor greatly depends on the crystallinity of the phosphor, and in order to improve this and provide excellent brightness, the addition and content of copper and bromine must be kept within the optimal range. The present invention was achieved by discovering that it is necessary to do so. In the present invention, the phosphor contains 0.1 to 0.5 mol %, preferably 0.2 to 0.3 %, of copper and 0.05 to 0.5 mol %, preferably 0.2 to 0.3 % of bromine based on zinc sulfide. If the content of both is less than this range, the life will be reduced, and if it exceeds this range, the brightness will be reduced. Moreover, if there is a difference in the content of both, it is recognized that both the life span and the brightness tend to decrease, so it is particularly desirable that the content be close to equimolar %. In producing the phosphor of the present invention having the above composition, 0.15 to 0.5 mol% of a copper salt such as copper acetate and 0.15 to 24 mol% of ammonium bromide are mixed with zinc sulfide. Then perform firing.
One part of copper acetate goes into the crystal, and the other part adheres to the crystal surface and is washed away, so use an excess amount.
Furthermore, bromine sublimes easily and is less likely to enter the phosphor than copper, so a relatively large amount of ammonium bromide flux is used. By performing the calcination in an atmosphere containing a sulfur compound such as hydrogen sulfide, S defects, that is, deterioration of crystallinity, are prevented. Further, the firing temperature is suitably as low as possible, around 900°C; if it is higher than 1000°C, bromine will sublimate and will be difficult to enter the crystal, resulting in a decrease in crystallinity, and at low temperatures, the firing will be incomplete. Furthermore, as mentioned above, a phosphor containing a large amount of copper compared to bromine will generate S defects due to charge compensation, resulting in a decrease in crystallinity, so from this point of view as well, low temperature firing is desirable. It is desirable that the combined amount of is close to equimolar. Next, the present invention and its effects will be explained by examples, but the present invention is not limited to these in any way. Examples 1 to 12 Copper acetate (cupric) and ammonium bromine were mixed well with zinc sulfide in the cases shown in Table 1 below (preparation ratio: mol%), and in an atmosphere containing hydrogen sulfide,
It was baked at 900°C for 4 to 8 hours. The thus obtained phosphor was used as a binder with fluorocarbon rubber (manufactured by Daikin Industries, Ltd., G501).
The mixing ratio of phosphor and binder is 6:4 by volume.
We fabricated an EL device by forming a light-emitting layer on a transparent electrode, and investigated its brightness and lifetime. That is, an alternating current voltage of 10 KHz was applied to these EL elements, and the brightness when the electric field strength of the light emitting layer was 4×10 ⁴ V/cm was measured, and this was taken as the brightness of each phosphor.
Also, the lifespan is when 400Hz AC voltage is applied.
Defined as the time it takes for the initial brightness of 50 nits to decrease by half. The results obtained are shown in Table 1 below.

[Table] As is clear from Table 1, in both cases,
The lifespan is over 2000 hours, and the brightness is over 100 nits. In particular, in Example 11, a long life of over 15,000 hours was achieved, and the brightness was as high as 450 nits. Reference Examples 1-2 EL devices were produced in the same manner as in Example 1, except that the content of additives was reduced as shown in Table 2 below, and their brightness and lifespan were examined. The results obtained are shown in Table 2 below.

[Table] As is clear from Table 2, when the content of copper and bromine is low, of course there is also little ammonium bromide as a flux, so crystallinity does not improve and the life tends to be shortened. . Reference Examples 3 to 4 EL devices were produced in the same manner as in Example 1, except that the content of additives was increased as shown in Table 3 below, and their brightness and lifespan were examined. The results obtained are shown in Table 3 below.

[Table] As is clear from Table 3, when the content of additives is increased, the lifespan is relatively long, but
The content of copper and bromine tends to deviate from equimolar % to higher amounts of copper, and the brightness tends to decrease. As explained above, according to the present invention, by optimizing the raw materials for additives and their amounts, it is possible to improve the crystallinity of the EL phosphor, thereby producing an EL phosphor with high brightness and long life. You get a body.
Therefore, the present invention makes a significant contribution to improving the characteristics of flat light sources or display elements.

Claims (1)

[Claims] 1. Zinc sulfide and 0.1 to 0.5 mol% relative to zinc sulfide
of copper and 0.05 to 0.5 mol% of bromine. 2 Zinc sulfide and 0.1 to 0.5 mol% relative to zinc sulfide
EL consisting of copper and 0.05-0.5 mol% bromine
In producing the phosphor, zinc sulfide and 0.15 to 1.5 mol% of copper acetate and 0.15 to 1.5 mol% of zinc sulfide are used.
A method for producing an EL phosphor, comprising firing a mixture consisting of 24 mol% ammonium bromide in an atmosphere containing hydrogen sulfide.