JP2001200248A - Electroluminescent phosphor, production method therefor, and electroluminescent element of organic dispersion type - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the luminance of a zinc sulfide electroluminescent phosphor and to enhance the luminance of an electroluminescent element of an organic dispersion type by using the above electroluminescent phosphor improved in luminance. SOLUTION: In sifting electroluminescent phosphor particles containing zinc sulfide as the host compound, an activator comprising at least either copper or manganese, and at least one coactivator selected from among chlorine, bromine, iodine, and aluminum, a water-absorbing substance such as anhydrous magnesium chloride is mixed. The luminescent layer of an electroluminescent element of an organic dispersion type is formed by dispersing an electroluminescent phosphor prepared by the above treatment in a dielectric.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroluminescent phosphor, a method for producing the same, and an organic electroluminescent device using such an electroluminescent phosphor.

[0002]

2. Description of the Related Art An organic dispersion type electroluminescent device has a structure in which electrodes are arranged on both sides of a luminescent layer in which an electroluminescent phosphor is dispersed in a dielectric, and at least one of the electrodes is a transparent electrode. The element emits light by applying an AC voltage between these electrodes. Main applications of such an organic dispersion type electroluminescent device include a display device and a backlight of the display device.

The electroluminescent phosphor used in the organic dispersion type electroluminescent device is based on zinc sulfide, at least one of copper and manganese as an activator, and chlorine and bromine as co-activators. And at least one selected from iodine and aluminum.

[0004] The zinc sulfide-based electroluminescent phosphor described above is generally manufactured as follows. First, an activator raw material and a co-activator raw material are added to and mixed with zinc sulfide as a base material. Further, a crystal growth agent such as magnesium chloride, barium chloride, and sodium chloride is added and mixed well. The mixture is fired at a temperature of 1000-1300C. Thereafter, the obtained fired product is pulverized, washed with water to remove a crystal growth agent and the like, dried, and further sieved to obtain a zinc sulfide-based electroluminescent fluorescence containing an activator and a coactivator. (USP 2,957,830, USP
No. 4,859,361).

[0005]

However, the conventional zinc sulfide-based electroluminescent phosphor manufactured as described above has a problem that water is adsorbed in a sieving step after drying of the fired product, thereby lowering the initial luminance. There is a need for countermeasures.

It is considered that this is because the conductive acicular phase such as CuS precipitated in the host crystal is extremely unstable to moisture.

That is, in this type of zinc sulfide electroluminescent phosphor, electrons and holes are injected and recombined when an electric field is concentrated at the tip of a conductive needle-like phase precipitated in a host crystal. As a result, it fluoresces, and thus it is essential for the emission of such a conductive needle-like phase in the host crystal to emit light. However, it is considered that the needle-like phase is extremely unstable in water, so that water is adsorbed in the sieving step to lower the initial luminance.

SUMMARY OF THE INVENTION The present invention has been made to address such a problem, and an electroluminescent phosphor having an improved initial luminance characteristic by preventing the adsorption of water at the time of sieving and a method of manufacturing the same. It is intended to provide, furthermore, by using such an electroluminescent phosphor,
It is an object of the present invention to provide an organic dispersion type electroluminescent device which has realized high brightness.

[0009]

The electroluminescent phosphor according to the present invention comprises zinc sulfide as a base,
An electroluminescent phosphor comprising phosphor particles containing at least one selected from copper and manganese as an activator and at least one selected from the group consisting of chlorine, bromine, iodine and aluminum as a coactivator. Wherein a water-absorbing substance is attached to the surface of the phosphor particles.

In the electroluminescent phosphor of the present invention, the amount of the water-absorbing substance attached is preferably at least 10 ppm with respect to the phosphor particles, as described in claim 2.
As described in above, it is more preferable that the content is 10 to 1000 ppm based on the phosphor particles. If the amount of the water-absorbing substance adhered to the phosphor particles is less than 10 ppm, the effect due to the adhesion is not sufficiently obtained, and if it exceeds 1000 ppm, the amount of the adsorbed substance may be too large and the luminescence of the phosphor may be insufficient. . A more preferable range of the amount of the water-absorbing substance is 10 to 50 with respect to the phosphor particles.
0 ppm, more preferably 10 to 400 ppm based on the phosphor particles.

Further, the water-absorbing powder may be composed of anhydrous magnesium chloride, anhydrous calcium chloride,
It is preferably at least one selected from the group consisting of anhydrous zinc chloride, anhydrous calcium bromide, anhydrous zinc bromide, calcium oxide, silica gel and anhydrous copper sulfate.
As described in above, it is more preferable that the magnesium chloride is anhydrous magnesium chloride.

According to a sixth aspect of the present invention, there is provided a method for producing an electroluminescent phosphor, wherein zinc sulfide is used as a base and at least one of copper and manganese is used as an activator.
After drying the phosphor particles containing one kind and at least one kind selected from chlorine, bromine, iodine and aluminum as a co-activator, the phosphor particles are mixed with a water-absorbing substance upon sieving. , Followed by sieving.

In the method for producing an electroluminescent phosphor according to the present invention, the water-absorbing substance is preferably mixed with the phosphor particles in an amount of at least 1% by weight.
Further, as described in claim 8, the water-absorbing substance is preferably a powder having a particle size of 1 mm to 30 mm. Further, the water-absorbing substance is preferably anhydrous magnesium as described in claim 9.

According to a tenth aspect of the present invention, there is provided an organic dispersion-type electroluminescent device comprising a luminescent layer containing the above-described electroluminescent phosphor of the present invention.

As a specific structure of the organic dispersion type electroluminescent device of the present invention, as described in claim 11, a luminescent layer containing the electroluminescent phosphor of the present invention and one of the luminescent layers are used. A configuration including a back electrode layer integrally disposed along a surface with a reflective insulating layer interposed therebetween and a transparent electrode layer integrally disposed along the other main surface of the luminous body layer. .

The electroluminescent phosphor of the present invention is produced by the method for producing an electroluminescent phosphor of the present invention.
In the method for producing an electroluminescent phosphor of the present invention, by admixing the phosphor particles with a water-absorbing substance, adsorption of water on the phosphor particles in the sieving step is prevented, and the electroluminescent phosphor having a high initial luminance is obtained. You can get the body. And
The organic dispersion type electroluminescent device of the present invention containing the electroluminescent phosphor thus obtained has a high initial luminance.

[0017]

Embodiments of the present invention will be described below.

The electroluminescent phosphor of the present invention is manufactured by the following method.

First, a predetermined amount of pure water is added to zinc sulfide powder having a particle size of about 1 to 3 μm to form a slurry, and a predetermined amount of an activator material such as copper sulfate or manganese carbonate is added to the slurry. , Barium chloride, sodium chloride, etc., and mix well.

The above-mentioned chloride also serves as a starting material for chlorine as a coactivator. When bromine, iodine, or aluminum other than chlorine is used as the coactivator, potassium bromide, sodium bromide, barium iodide, aluminum fluoride, or the like is added.

Next, after drying such a slurry-like mixture, the mixture is filled in a quartz crucible, and dried in a reducing atmosphere.
Bake at a temperature of 0-800 ° C for 1-3 hours. The fired product is dispersed in pure water, and the mixture is repeatedly washed, stirred, settled, and drained supernatant several times, and dried to obtain electroluminescent phosphor particles.

Thereafter, a water-absorbing substance is mixed with the electroluminescent phosphor particles, and sieving is performed.

As a result, zinc sulfide is used as a matrix, and at least one selected from copper and manganese is used as an activator.
The electroluminescent phosphor of the present invention is obtained in which a water-absorbing substance is attached to the surface of phosphor particles containing a seed and at least one selected from chlorine, bromine, iodine and aluminum as a coactivator.

In the electroluminescent phosphor thus manufactured, the adhesion of moisture to the phosphor particles in the sieving process is prevented by the water-absorbing substance absorbing the moisture. It becomes a high electroluminescent phosphor.

As the above-mentioned water-absorbing substance, it is desirable to use a substance which can be separated and removed from the phosphor particles by a sieving treatment in order to absorb moisture well and not to deteriorate the luminescence characteristics of the phosphor. From such a viewpoint, the water-absorbing substance includes powdered anhydrous magnesium chloride, anhydrous calcium chloride, anhydrous zinc chloride, anhydrous calcium bromide, anhydrous zinc bromide, calcium oxide, silica gel, anhydrous silica powder having a particle size of 1 mm to 30 mm. At least one selected from the group of copper sulfate
The use of species is preferred. Of these, the use of anhydrous magnesium chloride is preferred. If the particle size is less than 1 mm, there is a risk of penetrating between the phosphor particles and reducing the light emission characteristics,
Conversely, if the particle size exceeds 30 mm, a sufficient water absorbing effect may not be obtained. A more preferred particle size is in the range of 1 mm to 5 mm. From the same viewpoint, the amount of the water-absorbing substance is preferably 1% by weight or more based on the phosphor particles. If the amount is less than 1% by weight, it is possible to sufficiently prevent water from adhering to the phosphor particles. May not be possible. The more preferable mixing amount of the water-absorbing substance is in the range of 1 to 20% by weight based on the phosphor particles.

When a powdery water-absorbing substance having a particle diameter of 1 mm to 30 mm is mixed in an amount of 1% by weight or more with respect to the phosphor particles, the water-absorbing substance is applied to the surface of the phosphor particles.
An electroluminescent phosphor adhered to at least 10 ppm can be obtained. Also,
When mixed in the range of 1 to 20% by weight with respect to the phosphor particles, the water-absorbing substance is applied to the surface of the phosphor particles with respect to the phosphor particles.
An electroluminescent phosphor deposited in the range of 10-1000 ppm is obtained.

The electroluminescent phosphor of the present invention is used, for example, in the luminescent layer 2 of an organic dispersion type electroluminescent device 1 as shown in FIG. In the organic dispersion type electroluminescent device 1 shown in FIG. 1, the electroluminescent phosphor particles of the present invention described above are dispersed and contained in an organic polymer binder having a high dielectric constant such as cyanoethyl cellulose (organic dielectric). It has a light emitting layer 2.

On one main surface of the light emitting layer 2, for example, T
The reflective insulating layer 3 is formed by laminating a highly reflective inorganic oxide powder such as TiO ₂ or BaTiO ₃ in an organic polymer binder having a high dielectric constant such as cyanoethyl cellulose. The back electrode layer 4 made of a metal foil such as an Al foil or a metal film is disposed integrally on one main surface of the luminous body layer 2 via the reflective insulating layer 3.

On the other main surface of the light emitting layer 2, a transparent electrode layer (transparent electrode sheet) 5 in which an ITO film or the like is formed on a transparent insulating film such as a polyester (PET) film is integrally formed. Are located. Transparent electrode sheet 5
Are arranged so that the electrode film (ITO film) faces the light emitting layer 2.

The organic dispersion type electroluminescent device 1 is formed by, for example, thermocompression bonding the transparent electrode layer 5, the luminous body layer 2, the reflective insulating layer 3, and the back electrode layer 4. Although illustration is omitted, electrodes are respectively drawn from the back electrode layer 4 and the transparent electrode layer 5, and an AC voltage is applied to the light emitting layer 2 from these electrodes.

The organic dispersion type electroluminescent device 1 composed of the above-mentioned laminate (thermocompression body) is covered with transparent packaging films 6 and 6. As the packaging film 6, a moisture-proof film such as a polychlorotrifluoroethylene (PCTFE) film having a small water permeability is used. On the transparent electrode layer 3 side, a hygroscopic film (not shown) such as a 6-nylon film is disposed as necessary. Then, the protruding portion of the packaging film 6 is thermocompression-bonded, and the organic dispersion type electroluminescent element 1 is sealed, thereby forming an electroluminescent panel (EL panel).

According to the organic dispersion type electroluminescent device 1 and the EL panel using the same, it is possible to achieve high brightness by improving the initial brightness of the electroluminescent phosphor in the luminescent layer 2. Become.

When manufacturing an organic dispersion type electroluminescent device and an EL panel using the same, PCTFE was used.
The surface of each particle of the electroluminescent phosphor may be subjected to a moisture-proof treatment without using a moisture-proof film such as a film. The present invention is also applicable to electroluminescent phosphors that have been subjected to a moisture-proof treatment with a metal oxide, a resin, or the like. That is, the electroluminescent phosphor of the present invention may have a protective film (moisture-proof film) made of at least one selected from alumina, silica and titania on the surface of the phosphor particles to which the water-absorbing substance is attached. Good. Since the electroluminescent phosphor particles covered with such a protective film have moisture-proof properties by themselves, the use of a moisture-absorbing film or a moisture-proof film does not use the electroluminescent phosphor to reduce the emission characteristics due to moisture. Thus, it is possible to maintain excellent initial luminance characteristics for a long period of time.

[0034]

Next, specific examples of the present invention and evaluation results thereof will be described.

Example 1 First, 500 g of pure water was added to 500 g of zinc sulfide powder having a particle size of about 2 μm to form a slurry. Thereto, 1.5 g of copper sulfate, 20 g of sodium bromide and 20 g of potassium bromide were added and mixed well. The slurry-like mixture was dried at 150 ° C. for 12 hours, filled in a quartz crucible, and fired at 900 ° C. for 120 minutes in a reducing atmosphere (hydrogen sulfide gas).

The calcined product was dispersed in 2000 ml of pure water, and the mixture was stirred, settled, and drained supernatant five times, filtered, dried, and activated with copper / bromine-activated zinc sulfide phosphor particles (ZnS: C).
u, Br).

Obtained activated zinc sulfide phosphor particles with copper and bromine
For 1 kg, mix 10 g of anhydrous magnesium chloride, 325
A sieving process was performed using a mesh sieve to obtain the electroluminescent phosphor of the present invention.

The zinc sulfide electroluminescent phosphor thus obtained was subjected to chemical analysis by ICP. As a result, magnesium chloride (MgCl ₂ ) was present on the surface of the phosphor particles at a ratio of 10 ppm to the weight of the phosphor particles. It was confirmed that it had adhered.

Using the obtained zinc sulfide-based electroluminescent phosphor, an organic dispersion type electroluminescent device 1 shown in FIG. 1 was prepared, and the luminance was measured. That is, the reflective insulating layer 3 in which TiBaO3 is dispersed in cyanoethylcellulose as an organic binder is provided on the upper surface of the back electrode layer 4 made of Al foil.
And a light-emitting layer 2 having a thickness of 50 μm and a transparent electrode layer 5 made of InO 3 were laminated, and packaging films 6 and 6 were respectively disposed on both surfaces of the laminated body. The luminous body layer 2 was formed by mixing the phosphor and the castor oil as an organic binder so that the weight ratio was 5: 1. The luminance was measured by applying a 100 V, 400 Hz, and 200 V, 400 Hz AC voltage between the transparent electrode layer 5 and the back electrode layer 4 with a luminance colorimeter Minolta CL-100 manufactured by Minolta. Table 1 shows the measurement results. The measurement results were as follows: the luminance of the standard phosphor (copper-activated zinc sulfide phosphor) measured under the conditions of an applied voltage of 200 V / 400 Hz (AC voltage) was 43 cd, and an applied voltage of 100 V / 400 Hz (AC Voltage)
And the relative value when the luminance measured in the same manner as 100 was taken as 100.

Example 2 The electroluminescent phosphor of the present invention was prepared in the same manner as in Example 1 except that the amount of anhydrous magnesium chloride used in the sieving step was 30 g per 1 kg of the zinc sulfide-based electroluminescent phosphor particles. Prepared.

The zinc sulfide electroluminescent phosphor thus obtained was subjected to chemical analysis by ICP. As a result, magnesium chloride (MgCl ₂ ) was present on the surface of the phosphor particles at a ratio of 20 ppm to the weight of the phosphor particles. It was confirmed that it had adhered.

Using the obtained zinc sulfide-based electroluminescent phosphor, an organic dispersion type electroluminescent device was produced in the same manner as in Example 1, and the luminance was measured. The measurement results are shown in Table 1.

Comparative Example 1 An electroluminescent phosphor was prepared in the same manner as in Example 1, except that the sieving treatment was performed without using anhydrous magnesium chloride.

Using the obtained zinc sulfide-based electroluminescent phosphor, an organic dispersion type electroluminescent device was produced in the same manner as in Example 1, and the luminance was measured. The measurement results are shown in Table 1.

[0045]

[Table 1]

As is clear from Table 1, in the examples in which anhydrous magnesium chloride was used in the sieving step and the amount of magnesium chloride was adhered to the surface by 10 ppm or more, the luminance was lower than that in the comparative example where no magnesium chloride was adhered. Improvement was observed.

[0047]

As described above, according to the present invention,
Since the water-absorbing substance is mixed during the sieving process, water absorption in the sieving step is prevented, and an electroluminescent phosphor with high luminance can be obtained.

Further, according to the organic dispersion type electroluminescent device of the present invention using such an electroluminescent phosphor, it is possible to increase the luminance.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a main structure of an embodiment of an organic dispersion type electroluminescent device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Organic dispersion type electroluminescent element 2 ... Light emitting layer 3 ... Reflective insulating layer 4 ... Back electrode layer 5 ... Transparent electrode layer

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tsutomu Ishii 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Inside Toshiba Yokohama Office (72) Inventor Mitsuhiro Oikawa 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa F-term in Toshiba Yokohama Office (reference) 3K007 AB02 AB13 BB01 BB05 CA06 CB01 DA04 DA05 DB02 DC01 DC02 EC01 FA01 4H001 CC02 CC03 CC08 CC11 CF01 XA16 XA30 YA13 YA17 YA25 YA29 YA35

Claims (11)

[Claims] Claims: 1. A zinc sulfide as a matrix, comprising at least one selected from the group consisting of copper and manganese as an activator and at least one selected from the group consisting of chlorine, bromine, iodine and aluminum as a coactivator. An electroluminescent phosphor comprising phosphor particles contained therein, wherein a water-absorbing substance is attached to the surface of the phosphor particles. 2. The electroluminescent phosphor according to claim 1, wherein the amount of the water-absorbing substance attached is 10 ppm or more with respect to the phosphor particles. 3. The electroluminescent phosphor according to claim 1, wherein the amount of the water-absorbing substance is 10 to 1000 ppm based on the phosphor particles.
An electroluminescent phosphor, characterized in that: 4. The electroluminescent phosphor according to claim 1, wherein the water-absorbing substance is anhydrous magnesium chloride, anhydrous calcium chloride, anhydrous zinc chloride, anhydrous calcium bromide, anhydrous zinc bromide. Electroluminescent phosphor, which is at least one selected from the group consisting of calcium oxide, silica gel, and anhydrous copper sulfate. 5. The electroluminescent phosphor according to claim 1, wherein the water-absorbing powder is anhydrous magnesium chloride. 6. A composition comprising zinc sulfide as a base material and at least one selected from copper and manganese as an activator and at least one selected from chlorine, bromine, iodine and aluminum as a coactivator. A method for producing an electroluminescent phosphor, characterized in that the phosphor particles are mixed with a water-absorbing substance and then sieved when the phosphor particles are dried and sieved. 7. The method for producing an electroluminescent phosphor according to claim 6, wherein the water-absorbing substance is mixed in an amount of 1% by weight or more with respect to the phosphor particles. 8. The method for producing an electroluminescent phosphor according to claim 6, wherein the water-absorbing substance is a powder having a particle size of 1 mm to 30 mm. 9. The method for producing an electroluminescent phosphor according to claim 6, wherein the water-absorbing substance is anhydrous magnesium. 10. An organic dispersion-type electroluminescent device comprising a luminescent layer containing the electroluminescent phosphor according to claim 1. Description: 11. The organic electroluminescent device according to claim 10, further comprising: a back electrode layer integrally disposed along one main surface of the luminous body layer via a reflective insulating layer; A transparent electrode layer integrally disposed along the other main surface of the luminous body layer so as to face each other.