JPH07188651A - Electroluminescent fluorescencer and its production - Google Patents

Abstract

PURPOSE:To obtain an electroluminescent fluorescencer which has a practically enough ultraviolet resistance and can fully exhibit characteristics inherent in a fluorescencer. CONSTITUTION:An electroluminescent fluorescencer contains zinc sulfide as the matrix, at least either copper or manganese as the activator, and at least one element selected from the group consisting of chlorine, bromine, iodine, and aluminum as the coactivator provided the surface of a particle of the fluorescencer is coated with 0.1-2wt.% zinc silicate.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Organic dispersion type electroluminescent phosphors (hereinafter referred to as E
L phosphor) is dispersed in a dielectric material to form a light emitter layer, electrodes are arranged on both sides of this light emitter layer, and at least one electrode is composed of a transparent electrode. Light is emitted by applying an AC voltage between the electrodes. As such an EL phosphor, it is common to use zinc sulfide (ZnS) as a base material, and add copper or manganese as an activator and chlorine, bromine, iodine, aluminum or the like as a co-activator. It is used for.

The organic dispersion type EL panel using the EL phosphor as described above has been developed as a flat type light emitting device or the like in electronic equipment such as a backlight of a liquid crystal display device. As a new application, the application of road signs to night lighting is being studied, and it is considered that such outdoor applications will increase in the future.

However, since the EL phosphor used in the organic dispersion type EL panel has zinc sulfide as the base material as described above, the crystal surface and the adsorbed water react with each other by the irradiation of ultraviolet rays to precipitate metallic zinc, and It has been clarified that the color becomes black and the emission luminance is significantly reduced. Since the influence of ultraviolet rays is great outdoors, it is important to prevent the decrease of the emission brightness due to the irradiation of ultraviolet rays.

[0005]

As described above, the organic dispersion type EL panel using the conventional EL phosphor has a problem that the emission brightness is significantly reduced by the irradiation of ultraviolet rays. For this reason, in order to adapt to, for example, outdoor applications, it is strongly desired to take measures to reduce the emission brightness of the EL phosphor due to ultraviolet irradiation.

The present invention has been made in order to solve such a problem, and it is possible to impart sufficient ultraviolet resistance in practical use, and at the same time, it is possible to sufficiently exhibit the original characteristics of the phosphor. It is intended to provide a phosphor.

[0007]

The electroluminescent phosphor of the present invention comprises zinc sulfide as a base material, at least one selected from copper and manganese as an activator, and chlorine and bromine as coactivators. , An electroluminescent phosphor containing at least one selected from iodine and aluminum, characterized in that the phosphor particle surface is coated with 0.1 to 2% by weight of zinc silicate. .

The electroluminescent phosphor of the present invention has a particle surface coated with zinc silicate. The coating amount with this zinc silicate is 0.1 to 2 weight per phosphor particle.
The range is%. If the coating amount is less than 0.1% by weight, it becomes insufficient to cover the phosphor particles and sufficient UV resistance cannot be obtained, and if it exceeds 2% by weight, the emission brightness of the phosphor is reduced. .

The electroluminescent phosphor having the zinc silicate coating of the present invention is manufactured, for example, as follows.

First, zinc sulfide is used 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 co-activator. And are mixed to prepare a raw material. Next, after firing this raw material, an appropriate washing treatment is applied to obtain an electroluminescent phosphor.

Next, in the dispersion liquid of the above electroluminescent phosphor,
After adding an aqueous solution containing a silicic acid raw material, for example, an aqueous solution of water glass and stirring sufficiently, an aqueous solution containing zinc ions, for example, an aqueous solution of zinc sulfate or the like is added in an appropriate amount, and this phosphor suspension is allowed to stand, The surface of the phosphor particles is coated with zinc silicate by a precipitation reaction. In this way, an electroluminescent phosphor coated with zinc silicate is obtained.

[0012]

In the electroluminescent phosphor of the present invention, the surface of the phosphor particles is coated with an appropriate amount of zinc silicate. Zinc silicate is
Due to its excellent resistance to ultraviolet rays, the reaction between the crystal surface and adsorbed moisture can be suppressed. As a result, even when used outdoors, for example, it is possible to significantly suppress a decrease in emission luminance due to blackening of the body color.

[0013]

EXAMPLES Next, examples of the present invention will be described.

Comparative Example 1 A ZnS matrix was prepared by adding CuSO ₄ as an activator and NaB as a co-activator.
r and KBr were wet-mixed, and the slurry was dried and then fired at 900 ° C. for 120 minutes in an H ₂ S atmosphere to obtain a ZnS: Cu, Br type EL phosphor.

The reflectance of the EL phosphor thus obtained at 550 nm was measured. Next, add 365 nm to the above EL phosphor.
After irradiating it with ultraviolet rays for 12 hours, the reflectance at 550 nm was similarly measured. As a result, the reflectance is 72.3% before UV irradiation.
However, the reflectance was 5 after 12 hours of UV irradiation.
It fell to 4.9%.

Example 1 A ZnS matrix was prepared by using CuSO ₄ as an activator and NaB as a co-activator.
r and KBr were wet-mixed, and the slurry was dried and then fired at 900 ° C. for 120 minutes in an H ₂ S atmosphere to obtain a ZnS: Cu, Br type EL phosphor.

Next, 100 g of the above ZnS: Cu, Br type EL phosphor was dispersed in water, and 0.1 mol / l of a water glass aqueous solution and 0.1 cc and 0.03 mol / l of a zinc sulfate aqueous solution were dispersed in this dispersion. The 1
cc was added and stirred for 15 minutes. Then, after leaving still, discarding the supernatant liquid, washing with deionized water 5 times, filtration, drying and sieving steps are carried out to obtain the desired zinc silicate-coated E
L phosphor was obtained.

As a result of chemical analysis of the EL phosphor thus obtained, it was confirmed that zinc silicate was attached to the surface of the phosphor particles in an amount of 0.1% by weight based on the phosphor particles. Next, this EL phosphor was irradiated with 365 nm ultraviolet rays for 12 hours, and then the reflectance at 550 nm was measured. As a result, the reflectance is
It was 60.6% and blackening occurred, but it was revealed that the degree of blackening was suppressed more than in Comparative Example 1 above.

Example 2 CuSO ₄ as an activator and NaB as a co-activator were added to a ZnS matrix.
r and KBr were wet-mixed, and the slurry was dried and then fired at 900 ° C. for 120 minutes in an H ₂ S atmosphere to obtain a ZnS: Cu, Br type EL phosphor.

Next, 100 g of the above-mentioned ZnS: Cu, Br type EL phosphor was dispersed in water, and then 0.1 cc / l water glass aqueous solution was added to this dispersion and 0.2 cc and 0.03 mol / l zinc sulfate aqueous solution were added. The 2
cc was added and stirred for 15 minutes. Then, after leaving still, discarding the supernatant liquid, washing with deionized water 5 times, filtration, drying and sieving steps are carried out to obtain the desired zinc silicate-coated E
L phosphor was obtained.

As a result of chemical analysis of the EL phosphor thus obtained, it was confirmed that zinc silicate was attached to the surface of the phosphor particles in an amount of 0.2% by weight based on the phosphor particles. Next, this EL phosphor was irradiated with 365 nm ultraviolet rays for 12 hours, and then the reflectance at 550 nm was measured. As a result, the reflectance is
Although a slight blackening occurred at 68.7%, it was confirmed that the degree of blackening was significantly suppressed as compared with Comparative Example 1 above.

Example 3 A ZnS matrix was prepared by adding CuSO ₄ as an activator and NaB as a co-activator.
r and KBr were wet-mixed, and the slurry was dried and then fired at 900 ° C. for 120 minutes in an H ₂ S atmosphere to obtain a ZnS: Cu, Br type EL phosphor.

Next, 100 g of the above ZnS: Cu, Br type EL phosphor was dispersed in water, and then 0.1 cc / l of water glass aqueous solution was added to this dispersion and 0.3 cc and 0.03 mol / l of zinc sulfate aqueous solution were added. The 3
cc was added and stirred for 15 minutes. Then, after leaving still, discarding the supernatant liquid, washing with deionized water 5 times, filtration, drying and sieving steps are carried out to obtain the desired zinc silicate-coated E
L phosphor was obtained.

As a result of chemical analysis of the EL phosphor thus obtained, it was confirmed that 0.3% by weight of zinc silicate was attached to the surface of the phosphor particles with respect to the phosphor particles. Next, this EL phosphor was irradiated with 365 nm ultraviolet rays for 12 hours, and then the reflectance at 550 nm was measured. As a result, the reflectance is
It was 72.2%, and the same result as that before the ultraviolet irradiation in Comparative Example 1 was obtained.

Example 4 CuSO ₄ as an activator and NaB as a co-activator were added to a ZnS matrix.
r and KBr were wet-mixed, and the slurry was dried and then fired at 900 ° C. for 120 minutes in an H ₂ S atmosphere to obtain a ZnS: Cu, Br type EL phosphor.

Next, 100 g of the above ZnS: Cu, Br type EL phosphor was dispersed in water, and then 0.5 mol of a 0.1 mol / l water glass aqueous solution and 0.03 mol / l zinc sulfate aqueous solution were added to the dispersion. The 5
cc was added and stirred for 15 minutes. Then, after leaving still, discarding the supernatant liquid, washing with deionized water 5 times, filtration, drying and sieving steps are carried out to obtain the desired zinc silicate-coated E
L phosphor was obtained.

As a result of chemical analysis of the EL phosphor thus obtained, it was confirmed that zinc silicate was attached to the surface of the phosphor particles in an amount of 0.5% by weight based on the phosphor particles. Next, this EL phosphor was irradiated with 365 nm ultraviolet rays for 12 hours, and then the reflectance at 550 nm was measured. As a result, the reflectance is
It was 72.2%, and the same result as that before the ultraviolet irradiation in Comparative Example 1 was obtained.

Example 5 CuSO ₄ as an activator and NaB as a co-activator were added to a ZnS matrix.
r and KBr were wet-mixed, and the slurry was dried and then fired at 900 ° C. for 120 minutes in an H ₂ S atmosphere to obtain a ZnS: Cu, Br type EL phosphor.

Next, 100 g of the above ZnS: Cu, Br type EL phosphor was dispersed in water, and then 0.1 mol / l of a water glass aqueous solution was added to this dispersion, 1.0 cc and 0.03 mol / l of a zinc sulfate aqueous solution. A 10
cc was added and stirred for 15 minutes. Then, after leaving still, discarding the supernatant liquid, washing with deionized water 5 times, filtration, drying and sieving steps are carried out to obtain the desired zinc silicate-coated E
L phosphor was obtained.

As a result of chemical analysis of the EL phosphor thus obtained, it was confirmed that zinc silicate was attached to the surface of the phosphor particles in an amount of 1.0% by weight based on the phosphor particles. Next, this EL phosphor was irradiated with 365 nm ultraviolet rays for 12 hours, and then the reflectance at 550 nm was measured. As a result, the reflectance is
The result was 72.3%, which was equivalent to that before the ultraviolet irradiation in Comparative Example 1.

Example 6 CuSO ₄ as an activator and NaB as a co-activator were added to a ZnS matrix.
r and KBr were wet-mixed, and the slurry was dried and then fired at 900 ° C. for 120 minutes in an H ₂ S atmosphere to obtain a ZnS: Cu, Br type EL phosphor.

Next, 100 g of the above-mentioned ZnS: Cu, Br type EL phosphor was dispersed in water, and then 0.1 mol / l water glass aqueous solution was added to this dispersion to 2.0 cc and 0.03 mol / l zinc sulfate aqueous solution. 20
cc was added and stirred for 15 minutes. Then, after leaving still, discarding the supernatant liquid, washing with deionized water 5 times, filtration, drying and sieving steps are carried out to obtain the desired zinc silicate-coated E
L phosphor was obtained.

As a result of chemical analysis of the EL phosphor thus obtained, it was confirmed that zinc silicate was attached to the surface of the phosphor particles in an amount of 2.0% by weight based on the phosphor particles. Next, this EL phosphor was irradiated with 365 nm ultraviolet rays for 12 hours, and then the reflectance at 550 nm was measured. As a result, the reflectance is
The result was 72.3%, which was equivalent to that before the ultraviolet irradiation in Comparative Example 1.

Further, FIG. 1 collectively shows the measurement results of the reflectance in each of the above Examples and Comparative Examples as a relationship with the coating amount of zinc silicate. As is clear from the figure, the reflectance increases with an increase in the coating amount of zinc silicate, and it can be seen that the decrease in the emission brightness due to the irradiation of ultraviolet rays can be significantly suppressed. However, the amount of coating with zinc silicate is
If it exceeds 2.0% by weight, the luminescent properties of the phosphor are adversely affected, so the coating amount with zinc silicate is 2.0% by weight or less. Therefore, by using the EL phosphor of the present invention to produce an organic dispersion-type EL panel, it becomes possible to achieve adaptation to outdoor applications, for example.

In each of the above embodiments, ZnS: Cu, Br
Although an example using the type EL phosphor has been described, the present invention is effective for various zinc sulfide phosphors using copper or manganese as an activator and chlorine, bromine, iodine, aluminum, etc. as a coactivator. Is.

[0036]

As described above, according to the electroluminescent phosphor of the present invention, since the surface of the phosphor particles is coated with an appropriate amount of zinc silicate, the characteristics of the phosphor are not adversely affected, and The ultraviolet property can be greatly improved. Therefore, it becomes possible to manufacture a long-life EL panel excellent in ultraviolet resistance, which greatly contributes to the practical application of the EL panel to outdoor applications.

[Brief description of drawings]

FIG. 1 is a diagram showing the reflectance of an EL phosphor of the present invention after being irradiated with ultraviolet rays in comparison with a conventional example.

Claims (1)

[Claims] 1. 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 co-activator. An electroluminescent phosphor, containing 0.1 to 2% by weight of zinc silicate, on the surface of the phosphor particles.