JPH11256150A - Electroluminescent fluorescent substance, its production and el panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an electroluminescent fluorescent substance having practically sufficient moistureproofness and capable of sufficiently manifesting characteristics essential to the fluorescent substance without deteriorating the characteristics and to provide both a method for producing the fluorescent substance and an electroluminescent(EL) panel using the fluorescent substance. SOLUTION: This electroluminescent fluorescent substance comprises electroluminescent fluorescent substance particles containing at least one kind selected from copper and manganese as an activator and at least one kind selected from chlorine, bromine, iodine and aluminum as a coactivator in zinc sulfide as a matrix. The surfaces of the fluorescent substance particles are coated with a metal hydroxide.

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 electroluminescent phosphor, and an EL panel, and more particularly to an electroluminescent phosphor having sufficient moisture-proof characteristics for practical use and exhibiting the intrinsic luminance characteristics of the phosphor. The present invention relates to a phosphor, a method for producing the phosphor, and an EL panel.

[0002]

2. Description of the Related Art An organic dispersion type EL panel is, for example, shown in FIG.
As shown in FIG. 1, an organic binder such as cyanoethyl cellulose is formed on the upper surface of the back electrode layer 1 made of Al foil or the like.
High dielectric layer (insulator layer) made by dispersing BaO ₃ etc.
2, a phosphor layer 3 in which electroluminescent phosphor (EL phosphor) particles are dispersed in an organic binder such as cyanoethylcellulose, and In ₂ O supported on a moisture-proof film layer 5.
_{And a} transparent electrode layer 4 made of a material such as ₃ is integrally laminated to form a film-shaped panel main body. This panel main body is covered and sealed with a moisture-proof film layer 5 having a low moisture permeability such as a polychlorotrifluoroethylene film. It is configured.

An AC voltage is applied between the back electrode layer 1 and the transparent electrode layer 4 disposed on both sides of the phosphor layer 3 to cause the phosphor particles to emit light and display predetermined image information. It is. This type of EL panel has flexibility, is easy to handle, and can be obtained at relatively low cost, so that it is used for, for example, a liquid crystal display element or a backlight of a liquid crystal display device. Widely used for.

The EL phosphor used in the EL panel is based on zinc sulfide (ZnS), and contains copper or manganese as an activator, and chlorine, iodine, or co-activator as a coactivator. Phosphor particles containing aluminum or the like are generally used.

However, the organic dispersion type EL panel using the EL phosphor as described above is inferior in brightness (luminance) and life as compared with other display elements. I have. For example, this type of EL phosphor is
When light is emitted in an environment where moisture is present, there is a problem that deterioration rapidly proceeds.

Therefore, in the conventional organic dispersion type EL panel, as shown in FIG. 4, the phosphor layer 3 which is a light emitting layer is sufficiently dried at the time of manufacturing the panel, and thereafter, the moistureproof film layers 5, 5 and the packaging film layer are formed. The structure which protects multiple by 6 and 6 is adopted. As the film layer, a film material such as poly (trifluorochloroethylene) is generally used.

However, this film material is expensive and uses fluorocarbon, which is a cause of destruction of the ozone layer, as a raw material. The development of an organic dispersion type EL panel that does not use such a moisture-proof material is desired. However, a suitable moisture-proof material which can be substituted for the above-mentioned poly (trifluorochloroethylene) has not yet been found so far.

As a measure for overcoming such a problem, studies have been made to give the EL phosphor itself moisture-proof properties by, for example, subjecting the EL phosphor particles to a surface treatment. For example, JP-A-63-23987 and JP-A-7-239
In Japanese Patent No. 173086, the surface of EL phosphor particles is coated with fine particles made of a metal oxide such as aluminum oxide, silicon oxide, or calcium oxide, or is coated with calcium fluoride, strontium fluoride, magnesium fluoride, or fluoride. Moisture proof measures such as coating fine particles made of metal fluorides such as zinc and barium fluoride have been proposed.

However, these moisture proof measures have a problem that the phosphor surface cannot be completely isolated from moisture, and the moisture proof property is incomplete. Therefore, in the EL panel from which the water catching film and the moisture-proof film have been removed, practically sufficient life characteristics have not yet been obtained.

Further, in Japanese Patent Application Laid-Open No. 2-38482 and US Pat. No. 4,585,673, EL phosphor particles are blown into a container containing a phosphor maintained at a high temperature by blowing a triethylaluminum (TEA) solution. A method of adhering a coating of aluminum oxide to the surface of the substrate has been proposed.

[0011] However, this method is excellent in removing moisture causing deterioration of the phosphor and forming a uniform coating layer. However, this method involves exposing the EL phosphor to a considerably high temperature for treatment. In addition, there is a problem that the characteristics of the phosphor such as emission color tone and emission brightness are adversely affected. Furthermore, since triethylaluminum having explosive properties is used, there is another problem that complicated measures are required to ensure safety in the manufacturing process.

[0012]

As described above, the EL
In the conventional method of performing a moisture-proof treatment on the phosphor itself, a practically sufficient moisture-proof effect cannot be obtained, and the life characteristics are deteriorated as compared with a conventional EL panel using a moisture-proof film made of poly (trifluorochloroethylene) ethylene. And various problems such as adversely affecting various characteristics of the EL phosphor. Against this background, when creating an organic dispersion type EL panel,
Practically sufficient life characteristics (moisture proof) can be obtained without using a moisture-proof film made of poly (trifluorochloroethylene), and it is easy and safe without adversely affecting phosphor characteristics such as fluorescent luminance. There is a strong demand for the development of a moisture-proof treatment method for various phosphors.

SUMMARY OF THE INVENTION The present invention has been made to address such a problem, and has a practically sufficient moisture-proof property, and can be sufficiently exerted without impairing the intrinsic characteristics of the phosphor. An object of the present invention is to provide an electroluminescent phosphor, a method for producing the same, and an EL panel using the phosphor.

[0014]

In order to achieve the above object, an electroluminescent phosphor according to the present invention comprises zinc sulfide as a host, and at least one selected from copper and manganese as an activator. And electroluminescent phosphor particles containing at least one selected from the group consisting of chlorine, bromine, iodine and aluminum as a co-activator, and the surface of the phosphor particles is coated with a metal hydroxide. Features.

Further, the metal constituting the metal hydroxide is represented by II
Desirably, it is at least one metal element selected from the group a, group IIIa and group IIIb elements. Further, the metal constituting the metal hydroxide is preferably at least one selected from yttrium, magnesium and aluminum. Further, the coating amount of the metal hydroxide coated on the surface of the phosphor particles is 0.01 to 10% by weight based on the weight of the phosphor particles. Further, it is preferable that the coating amount of the metal hydroxide coated on the surface of the phosphor particles is 0.5 to 5% by weight based on the weight of the phosphor particles.

Further, the method for producing an electroluminescent phosphor according to the present invention is characterized in that zinc sulfide is used as a host, at least one selected from copper and manganese as an activator, and chlorine and bromine as co-activators. Preparing electroluminescent phosphor particles containing at least one selected from iodine and aluminum in an alkaline solution to prepare a phosphor dispersion, and preparing an acid salt solution containing metal ions. A step of coating a metal hydroxide precipitated by a neutralization reaction that occurs when the acid salt solution is added to and mixed with the phosphor dispersion liquid on the surface of the electroluminescent phosphor particles, and coating the metal hydroxide. Filtering the electroluminescent phosphor particles, and heat-treating the particles.

The electroluminescent phosphor coated with the metal hydroxide may be heat-treated at a temperature of 100 ° C. or less.

Further, the EL panel according to the present invention is an EL panel comprising a back electrode layer, an insulator layer, a phosphor layer and a transparent electrode layer sequentially laminated, wherein the phosphor layer comprises the metal hydroxide. It is characterized by containing a coated electroluminescent phosphor.

That is, the electroluminescent phosphor of the present invention comprises zinc sulfide (ZnS) as a matrix, and at least one selected from copper (Cu) and manganese (Mn) as an activator. Chlorine (Cl), bromine (B
r), an electroluminescent phosphor containing at least one selected from iodine (I) and aluminum (Al), wherein the surface of the phosphor particles is coated with a metal hydroxide. You.

The metal constituting the metal hydroxide includes a group IIA element such as Mg, Ca, Sr and Ba, a group IIIa element such as a rare earth element containing Y and Al, Ga, I
One or more metal elements selected from Group IIIb elements such as n and Tl are preferred. Of the above metal elements,
Particularly, yttria (Y), magnesium (Mg), and aluminum (Al) are more preferable.

The electroluminescent phosphor of the present invention has a particle surface coated with a metal hydroxide. The coating amount of the metal hydroxide is in the range of 0.01 to 10% by weight based on the weight of the phosphor particles. This coating amount is 0.
When the content is less than 01% by weight, it is difficult to cover the entire surface of the phosphor particles, and sufficient moisture-proof property by the metal hydroxide cannot be obtained. On the other hand, if the coating amount exceeds 10% by weight, the emission luminance of the phosphor is reduced, so that the coating amount is 0.1%.
01 to 10% by weight, but 0.5 to 5% by weight
Is more preferable.

The electroluminescent phosphor having a metal hydroxide coating as in the present invention is produced, for example, by the following procedure.

First, zinc sulfide is used as a matrix, 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. The raw material mixture is prepared by mixing uniformly. Next, after baking this raw material mixture in a non-oxidizing atmosphere, a washing treatment is performed to obtain electroluminescent phosphor particles.

Next, the electroluminescent phosphor particles are dispersed in an alkaline solution to prepare a dispersion, while an aqueous solution of an acidic salt containing metal ions for coating is prepared. The electroluminescent phosphor coated with a stable metal hydroxide by coating the surface of the electroluminescent phosphor particles with the metal hydroxide precipitated by the neutralization reaction after being added to and mixed with the dispersion, followed by filtration and heat treatment. Is obtained.

When the above heat treatment is performed, heating the electroluminescent phosphor coated with the metal hydroxide at a temperature of 100 ° C. or lower results in a heat treatment at a temperature lower than the decomposition temperature of the metal hydroxide. It is possible to form a stable metal hydroxide film solidified in a gel state without converting the metal hydroxide into an oxide only by evaporating excess water.

According to the electroluminescent phosphor and the method of manufacturing the same according to the above-described structure, a metal hydroxide film is formed on the surface of the phosphor particles by a liquid phase reaction, and the phosphor particles need to be treated at a high temperature. As a result, an electroluminescent phosphor having a sufficient moisture-proof property can be obtained without adversely affecting the intrinsic characteristics of the phosphor such as emission luminance.

Further, a coating made of a metal hydroxide has a smaller effect on light emission luminance than a conventional metal oxide coating such as an alumina film. Therefore, by forming the film of the metal hydroxide in an appropriate thickness range, it is possible to sufficiently maintain the light emission luminance originally possessed by the phosphor.

Further, by using the phosphor particles having the metal hydroxide film formed thereon, it is possible to manufacture an EL panel having excellent moisture-proof properties without using a conventional moisture-proof film made of poly (trifluorochloroethylene) ethylene. , And a great effect is exerted on extending the life of the EL panel and simplifying the manufacturing process.

[0029]

Next, an embodiment of the present invention will be described.
This will be described more specifically with reference to the following examples and drawings.

Example 1 Copper / chlorine-activated zinc sulfide phosphor (ZnS: Cu, Cl type E)
(L phosphor) 100 g of particles were suspended in 500 cc of deionized water and stirred to form a suspension. A phosphor dispersion liquid was prepared by adding 20 cc of a 5% aqueous solution of sodium hydroxide to the suspension and stirring for 5 minutes.

Next, 100 cc of a 3% aqueous solution of magnesium nitrate was added to the obtained phosphor dispersion liquid, and the mixture was further stirred for 2 hours. Thereafter, the mixture is allowed to stand, the supernatant is discarded, and the precipitate is washed three times with deionized water. Then, a filtration, drying, and sieving process is performed to attach a magnesium hydroxide coating to the phosphor particle surfaces. The EL phosphor according to Example 1 thus prepared was prepared. As a result of conducting a chemical analysis of the EL phosphor thus obtained, a coating made of magnesium hydroxide (Mg (OH) ₂ ) was formed on the surface of the phosphor particles at a ratio of 1.0% by weight based on the weight of the phosphor particles. It was confirmed that it had adhered.

Next, the EL phosphor according to the first embodiment,
An EL panel structure as shown in FIG. 1 was prepared using an EL phosphor having the same composition without a coating, and their life characteristics were measured and compared. That is,
An insulating layer 2 in which TiBaO ₃ is dispersed in cyanoethyl cellulose as an organic binder, a phosphor layer 3 having a thickness of 50 μm,
The transparent electrode layer 4 made of O ₃ was laminated, and the packaging film layers 6 and 6 were disposed on both surfaces of the laminate. The phosphor layer 3 was formed by mixing the phosphor particles and castor oil as an organic binder in a volume ratio of 7: 3.

The life of each phosphor was measured as a luminance maintenance ratio when an AC voltage of 200 V and 800 Hz was continuously applied between the transparent electrode layer 4 and the back electrode layer 1 for one hour. As a result, in the EL panel using the EL phosphor according to Example 1 in which the magnesium hydroxide coating was formed, the EL panel using the conventional EL phosphor in which no coating was formed was used.
Compared to the panel, the initial light emission luminance was almost the same, but the luminance maintenance ratio was improved by 40% or more.

Thus, the magnesium hydroxide coating was
By forming it on the surface of the L phosphor particles, it became possible to obtain an EL panel having good life characteristics without using a moisture-proof film made of poly (trifluorochloroethylene) ethylene.

Example 2 Copper / chlorine activated zinc sulfide phosphor (ZnS: Cu, Cl type E)
(L phosphor) 100 g of particles were suspended in 500 cc of deionized water and stirred to form a suspension. A phosphor dispersion liquid was prepared by adding 20 cc of a 5% aqueous solution of sodium hydroxide to the suspension and stirring for 5 minutes.

Next, 100 cc of a 0.1% aqueous solution of magnesium nitrate was added to the obtained phosphor dispersion liquid, and a further 2 cc.
Stirred for hours. Thereafter, the mixture is allowed to stand, the supernatant is discarded, and the precipitate is washed three times with deionized water. Then, a filtration, drying, and sieving process is performed to attach a magnesium hydroxide coating to the phosphor particle surfaces. E according to Example 2
An L phosphor was prepared. As a result of the chemical analysis of the EL phosphor thus obtained, a coating of magnesium hydroxide (Mg (OH) ₂ ) was formed on the surface of the phosphor particles at a rate of 0.01% by weight based on the weight of the phosphor particles. It was confirmed that it had adhered.

Next, the EL phosphor according to the second embodiment,
An EL panel structure as shown in FIG. 1 was prepared in the same manner as in Example 1 using an EL phosphor having the same composition without a coating formed thereon, and their life characteristics were measured and compared. .

As a result, in the EL panel using the EL phosphor according to Example 2 in which the magnesium hydroxide coating was formed, the E panel using the conventional EL phosphor in which no coating was formed was used.
Compared to the L panel, the initial light emission luminance was almost the same, but the luminance maintenance ratio was improved by 10% or more.

Example 3 Copper / chlorine activated zinc sulfide phosphor (ZnS: Cu, Cl type E)
(L phosphor) 100 g of particles were suspended in 500 cc of deionized water and stirred to form a suspension. A phosphor dispersion liquid was prepared by adding 20 cc of a 5% aqueous solution of sodium hydroxide to the suspension and stirring for 5 minutes.

Next, 100 cc of a 3% aqueous solution of yttrium nitrate was added to the obtained phosphor dispersion liquid, and the mixture was further stirred for 2 hours. Thereafter, the mixture is left standing, the supernatant liquid is discarded, and the precipitate is washed three times with deionized water. Then, the filtration, drying and sieving steps are performed to attach a yttrium hydroxide coating to the phosphor particle surfaces. The EL phosphor according to Example 3 was prepared. As a result of the chemical analysis of the EL phosphor thus obtained, a coating of yttrium hydroxide (Y (OH) ₃ ) was formed on the surface of the phosphor particles at a ratio of 1.0% by weight based on the weight of the phosphor particles. It was confirmed that it had adhered.

Next, the EL phosphor according to the third embodiment,
An EL panel structure as shown in FIG. 1 was prepared in the same manner as in Example 1 using an EL phosphor having the same composition without a coating formed thereon, and their life characteristics were measured and compared. .

As a result, in the EL panel using the EL phosphor according to Example 3 in which the yttrium hydroxide coating was formed, the E panel using the conventional EL phosphor in which no coating was formed was used.
Compared to the L panel, the initial light emission luminance was almost the same, but the luminance maintenance ratio was improved by 30% or more.

Example 4 Copper / chlorine activated zinc sulfide phosphor (ZnS: Cu, Cl type E)
(L phosphor) 100 g of particles were suspended in 500 cc of deionized water and stirred to form a suspension. A phosphor dispersion liquid was prepared by adding 20 cc of a 5% aqueous solution of sodium hydroxide to the suspension and stirring for 5 minutes.

Next, 100 cc of a 3% aqueous solution of aluminum nitrate was added to the obtained phosphor dispersion liquid, and the mixture was further stirred for 2 hours. Thereafter, the mixture is left standing, the supernatant liquid is discarded, and the precipitate is washed three times with deionized water. Then, a filtration, drying, and sieving process is performed to attach an aluminum hydroxide coating to the phosphor particle surfaces. The EL phosphor according to Example 4 was prepared. As a result of a chemical analysis of the EL phosphor thus obtained, a coating of aluminum hydroxide (Al (OH) ₃ ) was formed on the surface of the phosphor particles at a ratio of 1.0% by weight based on the weight of the phosphor particles. It was confirmed that it had adhered.

Next, the EL phosphor according to the fourth embodiment is
An EL panel structure as shown in FIG. 1 was prepared in the same manner as in Example 1 using an EL phosphor having the same composition without a coating formed thereon, and their life characteristics were measured and compared. .

As a result, in the EL panel using the EL phosphor according to Example 4 in which the aluminum hydroxide coating was formed, the E panel using the conventional EL phosphor in which no coating was formed was used.
Compared to the L panel, the initial light emission luminance was almost the same, but the luminance maintenance ratio was improved by 30% or more.

Example 5 Phosphor particles in which magnesium hydroxide, yttrium hydroxide and aluminum hydroxide as metal hydroxides were formed as a coating on the surface of the phosphor particles at a ratio of 1% by weight based on the weight of the phosphor particles ( An EL panel structure as shown in FIG. 1 was prepared using ZnS: Cu, Cl) and phosphor particles not forming a coating.

Then, each EL panel was placed in an atmosphere at a temperature of 40 ° C. and a relative humidity of 90%, and an AC voltage of 100 V, 400 Hz was applied between the back electrode layer and the transparent electrode layer to continuously form an electric field. The change in luminance at that time was measured, and the results shown in FIG. 2 were obtained.

As is apparent from the results shown in FIG. 2, in the EL panel structure formed by using the phosphor particles having various metal hydroxide coatings formed thereon, the conventional phosphor having no coating formed thereon was used. Compared with the EL panel, the luminance retention rate is less reduced, an excellent moisture-proof effect is obtained, and a long life E
It turned out that an L panel was obtained.

Example 6 Phosphor particles (ZnS: Cu, MgS) formed by coating magnesium hydroxide as a metal hydroxide on the surface of the phosphor particles at a ratio of 0 to 30% by weight based on the weight of the phosphor particles.
Cl), respectively, to produce EL panel structures as shown in FIG.

Then, each EL panel is placed in an atmosphere at a temperature of 40 ° C. and a relative humidity of 90%, and an AC voltage of 100 V, 400 Hz is applied between the back electrode layer and the transparent electrode layer for 100 hours to form an electric field. The luminance and the luminance maintenance rate when the measurement was continued were measured, and the results shown in FIG. 3 were obtained.

As is clear from the results shown in FIG. 3, the amount of magnesium hydroxide added as a metal hydroxide was 0.5%.
When it is in the range of not less than% by weight, the moisture-proof effect is almost saturated, and it is difficult to obtain a further improvement effect of the luminance maintenance ratio. On the other hand, when the addition amount is 2% by weight or more, the brightness tends to gradually decrease. Therefore, when magnesium hydroxide is formed as the metal hydroxide, by setting the amount of addition to be in the range of 0.5 to 2% by weight, the decrease in emission luminance is particularly small and the luminance maintenance ratio is low. It was confirmed that a long-life EL panel having a high moisture-proof property was obtained.

[0053]

As described above, according to the electroluminescent phosphor of the present invention and the method for producing the same, a metal hydroxide film is formed on the surface of the phosphor particles by a liquid phase reaction.
Since it is not necessary to treat the phosphor particles at a high temperature, it does not adversely affect the intrinsic properties of the phosphor such as emission luminance.
An electroluminescent phosphor having a sufficient moisture-proof property is obtained.

Further, a coating made of a metal hydroxide has a smaller effect on light emission luminance than a conventional metal oxide coating such as an alumina film. Therefore, by forming the film of the metal hydroxide in an appropriate thickness range, it is possible to sufficiently maintain the light emission luminance originally possessed by the phosphor.

Further, by using the phosphor particles having the metal hydroxide film formed thereon, it is possible to manufacture an EL panel having excellent moisture-proof properties without using a conventional moisture-proof film made of poly (trichlorofluoroethylene). , And a great effect is exerted on extending the life of the EL panel and simplifying the manufacturing process.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view showing a structure of an EL panel formed using an electroluminescent phosphor according to the present invention.

FIG. 2 is a graph showing a change over time of a luminance maintenance ratio in an EL panel formed using phosphor particles having various metal hydroxide coatings formed thereon.

FIG. 3 is a graph showing the relationship between the amount of magnesium hydroxide added as a metal hydroxide and the luminance maintenance ratio.

FIG. 4 is a partial cross-sectional view showing a structure of a conventional organic dispersion type EL panel.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Back electrode layer 2 High dielectric layer (insulator layer) 3 Phosphor layer 4 Transparent electrode layer 5 Moisture-proof film layer 6 Packaging film layer

Claims (8)

[Claims] A zinc sulfide as a matrix, and at least one selected from copper and manganese as an activator,
Electroluminescent phosphor particles containing at least one selected from the group consisting of chlorine, bromine, iodine and aluminum as a co-activator, wherein the surface of the phosphor particles is coated with a metal hydroxide. Electroluminescent phosphor. 2. The metal constituting the metal hydroxide is IIa
2. The semiconductor device according to claim 1, which is at least one metal element selected from the group III, IIIa and IIIb elements.
An electroluminescent phosphor according to any of the preceding claims. 3. The electroluminescent phosphor according to claim 1, wherein the metal constituting the metal hydroxide is at least one selected from yttrium, magnesium and aluminum. 4. The coating amount of the metal hydroxide coated on the surface of the phosphor particles is 0.01 to 10 with respect to the weight of the phosphor particles.
2. The electroluminescent phosphor according to claim 1, wherein the content is by weight. 5. The electroluminescent device according to claim 1, wherein the coating amount of the metal hydroxide coated on the surface of the phosphor particles is 0.5 to 5% by weight based on the weight of the phosphor particles. Phosphor. 6. A composition comprising zinc sulfide as a matrix, and at least one selected from copper and manganese as an activator,
Preparing a phosphor dispersion by dispersing electroluminescent phosphor particles containing at least one selected from chlorine, bromine, iodine and aluminum as a co-activator in an alkaline solution; A step of preparing an acid salt solution to be contained, and a step of coating the surface of the electroluminescent phosphor particles with metal hydroxide precipitated by a neutralization reaction that occurs when the acid salt solution is added to and mixed with the phosphor dispersion liquid. And a step of subjecting the electroluminescent phosphor particles coated with the metal hydroxide to filtration and then performing a heat treatment. 7. The electroluminescent phosphor according to claim 6, wherein the electroluminescent phosphor coated with the metal hydroxide is heat-treated at a temperature of 100 ° C. or less. 8. An EL panel comprising a back electrode layer, an insulator layer, a phosphor layer and a transparent electrode layer sequentially laminated, wherein the phosphor layer contains the electroluminescent phosphor according to claim 1. Characteristic EL panel.