JPH0279391A - Electroluminescence element - Google Patents

Abstract

PURPOSE:To contrive to improve luminous efficiency of a powder EL element, longer life and higher contrast by adding an organic compound, which has a functional group which reacts on the surface of inorganic ultra-fine grains, in a reactive mixture. CONSTITUTION:In an electroluminescence element which provides a luminous layer 3 containing powder grains between a pair of electrodes 2, 5, the layer of an organic atom group is provided on the surface of the powder grains. For the layer of the organic atom group, a general interfacial activator or a so-called coupling agent such as silane, titanate, aluminium and zircoalminate series is used. This coupling agent normally brings better affinity on the interface of an organic matter with an inorganic matter or has function of coupling them. Therefore, since the luminous layer is constituted by monodispersive ultra-fine grains, threshold-value voltage produced so that the powder grains can form the secondary grains is prevented from dispersion and uniformized, and a transparent luminous layer with durability and uniform distribution is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electroluminescent device, and particularly to an electroluminescent device (hereinafter abbreviated as EL device) with excellent durability.

[Conventional technology]

Conventionally, a phosphor layer (light-emitting layer) comprising first powder particles such as Z, S:M, etc. and a conductive layer comprising dark-colored second powder particles such as M, IO□, etc. An EL element having a control layer is known.

(For example, JP-A-62-61293) The above EL device is produced by preparing a homogeneous suspension in which zinc sulfide/manganese fine particles are dispersed in dilute nitrocellulose as a binder, and then coating the suspension with a transparent conductive coating. dipping the glass, pulling it up and air-drying it to form a phosphor layer, and then applying a nitrocellulose binder dispersion of manganese dioxide on the created phosphor layer to form a control layer;
Thereafter, a back electrode made of aluminum or the like is formed on the created control layer.

Further, as an EL element having no control layer, for example, Z having a particle size of several tens to several 1100 nanometers. A generation layer of a substance different from that of the luminescent material or a generation layer having different properties is formed on the surface of powder particles of a luminescent material such as S, thereby forming a heterobond or P
A BL element is known in which a light-emitting layer in which -N junction-formed powder is fixed with an organic binder is provided between a pair of electrodes.

(For example, the EL device mentioned above in JP-A-63 is made by heating Z.S:M,i particles in a fluidized bed of 02 gas to form an oxide film on the surface of the particles. Fine particles with an oxide film are dispersed in an organic binder to form a suspension, the suspension is used to form a light-emitting layer on a glass substrate with a transparent electrode, and a back electrode is formed on the transferred light-emitting layer. manufactured by the method.

[Problem to be solved by the invention]

According to the conventional manufacturing method described above, compared to an EL device using a thin film-like light emitting layer created by, for example, a vapor deposition method, it has the advantage of being able to manufacture an EL device at a low cost and with a high yield. However, there was a problem in that an overcurrent would flow and cause partial burnout (breakdown), making it impossible to obtain a uniform light emitting surface. Another problem is that it is difficult to obtain an EL element that emits light with uniform intensity over a large area.

[Means to solve the problem]

The present invention has been made in order to solve the above-mentioned conventional problems, and includes an electroluminescent element in which a light-emitting layer containing powder particles is provided between a pair of electrodes. There are several layers.

As the layer of organic atomic groups, general surfactants and so-called camping agents such as silane-based, titanate-based, aluminum-based, and zircoaluminate-based compounds can be suitably used.

Examples of surfactants include those in which a long chain alkyl group ends with sulfonic acid, phosphoric acid, carboxylic acid, or a salt thereof. Examples of surfactants suitable for use in the present invention include: Examples include sodium hexanoate, sodium dodecanoate, sodium octoate, sodium laurylhenzenesulfonate, aerosol OT, and octyl sesquiphosphate.

A coupling agent generally refers to a compound that has the function of improving the affinity at the interface between an organic substance and an inorganic substance or binding them.

Silane-based camping agents usually have a trimethoxysilyl group or trichlorosilyl group bonded to an organic atomic group via a 5i-C bond, and the organic atomic group is α-
Methacryloxypropyl group, α-aminopropyl group, α
-glycidoxypropyl group, β-aminoethylaminopropyl group, α-chloropropyl group, α-mercaptopropyl group, methyl group, etc., and the type of organic group to be used is determined by Atrix and It is determined depending on the binder resin. The reaction of such a silane camping agent occurs as follows.

For example, in the case of α-glycidoxyprobyltrimethoxysilane, the trimethoxysilyl group is hydrolyzed to form a trisilanol group, which undergoes a dehydration condensation reaction with the mercapto group on the surface of the powder particles used in the present invention to form metalloxane. An α-glycidoxypropylsilyl group is introduced onto the surface of the ultrafine particles. For example, if the matrix resin has a carboxy group or an epoxy group, the glycidyl group reacts with these atomic groups to form a bond.

In the case of a titanate-based coupling agent, the alkoxytitano group also reacts with the inorganic surface.

The organic atomic group is bonded to the titanium atom via a carboxyl group, a sulfonyl group, a phosphate group, etc., but no functional group is bonded to the organic atomic group itself so as to react with the binder resin. However, it has a great effect on improving the affinity with the binder resin.

Such titanate-based coupling agents have the following general formulas (1) and (2), (R'-0)11-Ti-R"m (1
110\R2Ti -R'm (2)\. It can be expressed as / .

Compounds that can be represented by the general formula (1) include methyltrimethacrylic titanate, methyltrioctanoyltitanate, methyltriisostearoyltitanate, ethyltritutacryltitanate, ethyltrioctanoyltitanate, ethyltriisostearoyltitanate, isopropyl Trimethacrylic titanate, isopropyltrioctanoyltitanate, t-butyltrimethacrylictitanate, t-butyltrioctanoyltitanate, isopropyltriisostearoyltitanate, t-butyltriisostearoyltitanate, tetraoctylbis(ditridecylphosphite)titanate, Tetracyclohexyl bis(ditridecyl phosphite) titanate, Tetramethyl bis(ditridecyl phosphite) titanate, Tetradodecyl bis(ditridecyl phosphite) titanate, Tetraoctyl bis(dioctyl phosphite) titanate, Tetracyclohexyl bis(dioctyl phosphite) )
Titanate, tetra(2,2-diallyloxymethyl-1-butyl)
Bis(ditridecylphosphite) titanate, tetra(2,2-diallyloxymethyl-1-butyl)
Bis(dioctyl phosphite) titanate, Tetraisopropyl bis(dioctyl phosphite) titanate, Tetraisopropyl bis(ditridecyl phosphite)
Titanate, Tetraisopropyl bis(dicyclohexylphosphite) titanate, Isopropyl tris(dioctylpyrophosphate)
Titanate, Ethyl Tris (Dioctyl Pyrophosphate) Titanate, Methyl Tris (Dioctyl Pyrophosphate) Titanate, Isopropyl Tris (Didodecyl Pyrophosphate)
Titanate, Ethyltris(didodecylpyrophosphate) titanate, 2,2-Diallyloxymethyl-1-butyltris(didodecylpyrophosphate) titanate, Octyltris(dioctylpyrophosphate) titanate, Octyltris(dipentylbirophosphate) titanate, Isopropylditris Methacryl Isostearoyl Titanate, Isopro and Dimethacrylic Octanoyl Titanate, Isopropyl Methacrylic Diisostearoyl Titanate, Isopropyl Methacryl Dioctanoyl Titanate, Cyclohexyl Dimethacrylic Isostearoyl Titanate, Cyclohexyl Dimethacrylic Octanoyl Titanate, Cyclohexyl Methacrylic Dioctanoyl Titanate Isostearoyl titanate, cyclohexylmethacrylyldoctanoyltitanate, n-butyldimethacrylyloctanoyltitanate, n-butyldimethacrylylisostearoyltitanate, isopropyltridodecylbenzenesulfonyltitanate, isopropyltriisostearylbenzenesulfonyltitanate, isopropyltrioctyl Benzenesulfonyl titanate, Ethyl tridodecylbenzenesulfonyl titanate, Ethyltriisostearylbenzenesulfonyl titanate, Ethyltrioctylbenzenesulfonyl titanate, Hexyltridodecylbenzenesulfonyl titanate, Hexyltriisostearylbenzenesulfonyl titanate, Hexyltrioctylbenzenesulfonyl titanate , 2.2-diallyloxymethyl-1-butyltridodecylbenzenesulfonyl titanate, 2.2-diallyloxymethyl-1-butyltriisostearylbenzenesulfonyl titanate, 2.2-diallyloxymethyl-
1-Butyltrioctylbenzenesulfonyl titanate, Isopropyltri(dioctylphosphate)titanate, Isopropyltri(ditridecylphosphate)titanate, Isopropyltri(dibentylphosphate)titanate, Ethyltri(dioctylphosphate)titanate, Ethyltri(ditridecylphosphate)titanate , Ethyl tri (dipentyl phosphate) titanate, Hexyl tri (dioctyl phosphate) titanate, Hexyl tri (ditridecyl phosphate) titanate, Hexyl tri (dibentyl phosphate) titanate, 2,2-Diallyloxymethyl-1-butyl tri (dioctyl bosphate) titanate, 2.2-Diallyloxymethyl-1-butyltri(ditridecylphosphate) titanate, 2.2-diallyloxymethyl-
1-Butyl tri(dipentyl phosphate) titanate, isopropyl tricumylphenyl titanate, isopropyl trioctylphenyl titanate, isopropyl triisostearylphenyl titanate, hexyl tricumylphenyl titanate, hexyl trioctylphenyl titanate, hexyl triisophthialyl phenyl titanate, 2. Examples include 2-diallyloxymethyl-1-butyltricumylphenyl titanate, 2.2-diallyloxymethyl-1-butyltrioctylphenyl titanate, 2.2-diallyloxymethyl-1-butyltriisostearylphenyl titanate, and the like. It will be done.

Compounds that can be represented by general formula (2) include bis(dioctyl pyrophosphate) oxyacetate titanate, bis(diisostearyl pyrophosphate) oxyacetate titanate, bis(didodecyl pyrophosphate) oxyacetate titanate, and bis(dioctyl pyrophosphate) oxyacetate titanate. pyrophosphate) oxypropionate titanate, bis(diisostearyl pyrophosphate) oxypropionate titanate, bis(didodecyl pyrophosphate) oxypropionate titanate, bis(dioctyl pyrophosphate) ethylene titanate, bis(diisostearyl pyrophosphate) oxypropionate titanate pyrophosphate) ethylene titanate, bis(didodecyl pyrophosphate) ethylene titanate, bis(dioctyl pyrophosphate) propylentitanate, bis(diisostearyl pyrophosphate) propylentitanate, bis(didodecyl pyrophosphate) propylentitanate, bis(dioctyl pyrophosphate) propylentitanate Examples include bosphate) butylene titanate, bis(diisostearylpyrophosphate) butylentitanate, bis(didodecylpyrophosphate) butylentitanate, and the like.

As an aluminum-based coupling agent, the following general formula (
3) Compounds that can be represented by the following are generally used, and examples of such compounds include acetooctyloxyaluminum diisopropylate, acetododecyloxyaluminum diisopropylate, acetooctyloxyaluminum dimethylate, and acetododecyloxy. Aluminum dimethylate, Acetooctyloxyaluminum diethylate, Acetododecyloxyaluminum diethylate, Acetomethacryloxyethyloxyaluminum diisopropylate, Acetomethacryloxyethyloxyaluminum diethylate, Acetomethacryloxyethyloxyaluminum dihexylate , acetoglycidoxypropyloxyaluminum diisopropylate - acetoglycidoxypropyloxyaluminum diethylate, acetoglycidoxypropyloxyaluminum dihexylate, acetohydroxyoctyloxyaluminum diisopropylate, acetohydroxyoctyloxyaluminum diisopropylate Diethylate, Acetohydroxyoctyloxyaluminum dihexylate, Acetomercaptododecyloxyaluminum diisopropylate, Acetomercaptododecyloxyaluminum diethylate, Acetomercaptododecyloxyaluminum dihexylate, Acetochloropropyloxyaluminum dihexylate Acetochloropropyloxyaluminum diisopropylate, Acetochloropropyloxyaluminum diethylate, Acetocarboxyloctyloxyaluminum diethylate, Acetocarboxyloctyloxyaluminum diisopropylate, Acetocarboxyloctyloxyaluminum dihexylate , ace1-isocyanuropentyloxyaluminum dihexylate, acetoisocyanurpentyloxyaluminum diisopropylate, acetoisocyanurpentyloxyaluminum diethylate, acetaminododecyloxyaluminum diethylate, acetaminododecyloxyaluminum diisopropylate, Acetaminododecyloxyaluminum dihexylate, Acetosulfonylstearyloxyaluminum dihexylate, Acetosulfonylstearyloxyaluminum diisopropylate, Acetosulfonylstearyloxyaluminum diethylate, Acetonitrophenyloctyloxyaluminum diethylate, Acetonitrophenyl octyl Examples include oxydialuminum diisopropylate, acetonitrophenyl octyloxyaluminum dihexylate, and the like.

A zircoaluminate coupling agent contains one zirconium atom and one aluminum atom in one molecule, and bonds with the surface of an inorganic substance are formed by hydroxyl groups bonded to these metal atoms. Examples of such zircoaluminate coupling agents include those represented by the following general formula (4).

These compounds coat the surfaces of powder particles (hereinafter referred to as ultrafine particles), and the term "coating" as used herein means that they are relatively firmly bonded by reaction or adsorption. The surface of the ultrafine particles in the present invention is preferably covered with a layer of the compound having a thickness of about 1 nm to 3 nm to form an organic surface. However, electrically, this level of thickness often has little effect, but a PN junction or a Peter junction may be formed at the interface.

The method of coating the surface of the ultrafine particles with the above compound is as follows:
A common method is to add the sol in which the ultrafine particles are dispersed into a reaction mixture and stir the mixture. The solvent used here is preferably an alcohol-based solvent if the reaction mixture of the sol is aqueous. Alternatively, water can also be used depending on the type of compound.

In the above manner, a reaction mixture in which ultrafine particles of a luminescent material whose surfaces are coated with organic atomic groups are dispersed or precipitated in an aqueous system is obtained, but water can be removed from this system in the following manner. The simplest method for removing water is flushing with an organic solvent. This is done by adding an organic solvent that is immiscible with water, especially a hydrocarbon solvent, and stirring it to transfer the ultrafine particles coated with organic atomic groups to the organic solvent side.
This is a redispersion operation, and by this operation, the dispersion medium of the ultrafine particle sol whose surface is coated with organic atomic groups can be changed from water to an organic solvent. Another way to achieve this is to gradually add and distill off the solvent, shifting the added solvent from hydrophilic to hydrophobic, but flushing is more effective. It's simple.

The luminescent material ultrafine particles that have become an organosol (a sol of ultrafine particles dispersed in an organic solvent) may not be completely crystallized in this state, so the organic solvent is then distilled off. Crystallization can also be promoted by drying and firing at a temperature of, for example, about 300°C. One of the characteristics of ultrafine particles is that sintering occurs at low temperatures, but crystallization can also be promoted at low temperatures. In this case, since the surface is covered with organic atomic groups, the formation of secondary particles through sintering and agglomeration no longer occurs.
The powder thus obtained is quickly dispersed again in the organic solvent or binder resin, and is never dispersed in water again. The organosol obtained by redispersing it in an organic solvent is completely transparent to visible light if the powder is fine particles.

The organic atomic group-coated luminescent substance ultrafine particles are fixed using a binder resin to form the luminescent layer of the EL device of the present invention.

As the powder particles used for forming the light-emitting layer, a ■-■ group compound semiconductor can be exemplified.

■-■ group compound semiconductors generally include one or more metal elements selected from magnesium, calcium, strontium, barium, zinc, and cadmium, and one or more chalcogen elements selected from sulfur, selenium, and tellurium. For example, zinc sulfide, cadmium sulfide,
Magnesium sulfide, calcium sulfide, strontium sulfide, barium sulfide, zinc selenide, cadmium selenide, magnesium selenide, calcium selenide, strontium selenide, barium selenide, zinc telluride,
Examples include cadmium telluride, magnesium telluride, calcium telluride, strontium telluride, barium telluride, etc., but of course, as in the above example, there are not only one metal and one type of chalcogen element, but for example, calcium sulfate selenide. A material containing two or more types of metal and/or chalcogen elements, such as strontium, can also be used.

At least one element selected from manganese and rare earth elements is usually added to the above n-vr group compound semiconductor as a luminescent center. Such elements include manganese, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. These may be used alone or in combination of two or more.

In addition to the luminescent center described above, a substance called a coactivator may be added to the powder particles used in the present invention, and such substances include alkali metals such as lithium, sodium, potassium, rubidium, cecilam, Examples of halogen elements include fluorine, chlorine, bromine, and iodine.

The concentration of the above-mentioned luminescent center and co-activator in the II-VI group compound is preferably 0.1 to 5 mol%.

The preferred particle size of powder particles made of an n-vr group compound to which such a luminescent center is added is 1 to 1100 nm, more preferably 1 to 20 nm. Normally, in a system in which particles are uniformly dispersed and the refractive index of the particles is different from the refractive index of the matrix, the particle size and wavelength λ are different.

The relationship between 20L<λ.

When , it is said that the system will not scatter any light of wavelength λ such that λ>λ0. That is, when the particle size of the ultrafine particles is 20 nm or less, a film in which the ultrafine particles are fixed with a binder resin becomes completely transparent to visible light.

However, the smaller the better (if the particle size is less than lnm, the ratio of surface atoms to the whole particle becomes too large and the material no longer exhibits its original properties, so the lower limit of the particle size is Inm). be.

Furthermore, it is preferable that the particles not only have a particle size within this range but also be monodisperse particles that are as uniform as possible. There are two main methods for producing such ultrafine particles: a gas phase method and a liquid phase method. When manufacturing using a gas phase method, agglomeration occurs at the stage of collecting the particles, resulting in formation of secondary particles. is formed, making it difficult to obtain ultrafine particles that can achieve the purpose of the present invention. Therefore, a liquid phase method is appropriate.

n-v with the above luminescent center added by the liquid phase method
In order to produce ultrafine particles of group I compound semiconductors, acid decomposition and the addition of a precipitant are generally used. For example, in the case of zinc sulfide ultrafine particles containing manganese, a mixture of zinc sulfate and manganese sulfate is It can be synthesized by adding ethylenediamine to a solution and passing hydrogen sulfide.In the case of cerium-added strontium sulfide ultrafine particles, thioacetamide and nitric acid are added to a mixed solution of strontium nitrate and cerium nitrate to generate seed particles. It can be synthesized by adding thioacetamide after the addition of thioacetamide.

The operation of coating the surface of the powder particles with organic atomic groups is extremely difficult when producing powder particles using a gas phase method, but it can be accomplished relatively easily when producing powder particles using a liquid phase method. It is. That is, an organic compound having a functional group capable of reacting with the surface of the inorganic ultrafine particles as used in the present invention may be added to the reaction mixture.

As the binder resin, ordinary organic polymer substances and silicone resins can be used.

Examples of these include vinyl resins, polyester resins, polyamide resins, polyimide resins, cellulose resins, polyurethane resins, urea resins, epoxy resins, melamine resins, silicone resins, etc. In particular, polymeric materials having polar groups are preferably used.

Examples of polymeric materials with polar groups include vinyl alcohol, acrylic acid, methacrylic acid, copolymers with N,N-dimethylaminomethacrylate residues, polyurethanes and silicone resins containing polyols in excess of the equivalent amount. Can be mentioned.

These can be used alone or as a mixture.

The light-emitting layer formed in this manner can emit light either by an alternating current electric field or by a direct current electric field. The light emitting mechanism is a Mis structure in which a dielectric thin film is provided on one side of the light emitting layer.
Various types of structures can be used, such as the currently mainstream double insulation structure in which the light-emitting layer is sandwiched between insulating films, and the DC hybrid structure in which a high-resistance thick film is provided adjacent to the light-emitting layer. If provided, the surface of the ultrafine luminescent material particles can be coated with a different substance before being coated with the organic atomic group. This forms a PN junction or a heterojunction, which can be used as a light-emitting mechanism. Such substances include oxide films, nitride films, sulfide films, chloride films, fluoride films,
Bromide film, iodide film, sulfide film, selenide film, telluride film, phosphide film, cyanide film, etc. can be mentioned, and methods for forming such layers include, for example, ultrafine particle formation. Examples include a method of changing the composition of the extreme surface layer by adding an aqueous solution of another metal salt or a metal alkoxide therein. Of course, if a PN junction or a heterojunction is formed by coating the surface with an organic atomic group, it is not necessary to do this.

Since the light-emitting layer is transparent to visible light, high contrast can be obtained by providing a black layer on the side opposite to the transparent substrate of an EL panel constructed using the light-emitting layer.

[For production]

According to the present invention, since the light-emitting layer is composed of monodisperse ultrafine particles, variations in threshold voltage that conventionally occur due to powder particles forming secondary particles are prevented, and the threshold voltage A powder EL element having a uniform, durable, uniformly distributed and transparent light emitting layer can be manufactured at low cost.

〔Example〕

First, ultrafine particles made of a luminescent substance are synthesized.

In the case of manganese-doped zinc sulfide, hydrogen sulfide is produced by passing it through an aqueous solution of zinc sulfate, manganese sulfate, ethylenediaminetetraacetic acid, and ammonium carbonate at 25°C.

At this stage, a sol is generated in which ultrafine particles of zinc sulfide to which manganese has been added are dispersed in the reaction mixture, but in order to be able to fix this with a binder resin, it is necessary to coat the surface with an organic atomic group. There is. For example, it is also possible to drop methyltrimethoxysilane or α-methacryloxypropyltrimethoxysilane to bind it to the surface, apply it to the substrate, and then bake it, but in this case, the surface coating material becomes the binder as it is. Since it is resin,
In order to widen the range of choices for binder resins, it is better to first produce ultrafine particle powder whose surface is coated with organic atomic groups, which will make subsequent processing easier. For example, a surfactant or a titanium coupling agent is dropped into the sol to adsorb or bind to the particle surface. First, the sol is centrifuged to concentrate the particles, and then pure water is added again. Components other than the ultrafine particles of zinc sulfide added are removed, and then, for example, an aqueous solution of sodium laurylbenzenesulfonate or an isopropyl alcohol solution of isoprobyl trilaurylhenzenesulfonyl titanate is added dropwise, and after the reaction is completed, toluene is added. By adding an aromatic hydrocarbon solvent such as or xylene and flushing to transfer the fine particles into the hydrocarbon and disperse them, an organosol of ultrafine zinc sulfide particles doped with manganese whose surface is coated with organic atomic groups is created. do. This is dried by evaporating the solvent to form a powder, and then fired at a temperature of about 300° C. in order to prepare a crystal structure. A characteristic of ultrafine particles is that the sintering temperature is abnormally lowered, and the preparation of the crystal structure also occurs at low temperatures. In this case, since the surface is covered with organic atomic groups, sintering does not occur during firing, but only rearrangement of the crystal structure occurs.

The ultrafine luminescent particles used in the present invention are not limited to the above-mentioned zinc sulfide added with manganese, but include a wide variety of materials, such as zinc sulfide added with terbium, calcium sulfide added with europium, and strontium sulfide added with cerium. n- with manganese or rare earth elements added
It can also be manufactured using general vr group compound semiconductors. Further, it is also possible to use a complex compound such as strontium sulfide to which both cerium and europium are added, or calcium telluride sulfide to which a rare earth element is added. In the case of such a composite compound, it can be produced by using a starting solution and a gas to be reacted in combination, as in the case of zinc sulfide to which manganese is added. In other words, to change the composition of metal elements, the starting solution should be one in which sulfates and nitrates of those metals are dissolved in an appropriate ratio, and to change the composition of chalcogen elements, a compound of these metals and hydrogen, i.e. A mixture of gases such as hydrogen sulfide, hydrogen selenide, and hydrogen telluride may be used.

Before the surface of the ultrafine particles used in the present invention is coated with organic atomic groups, a heterojunction or P
In the case of introducing a -N junction, it can be realized by adding a substance that forms a layer of a substance that forms such a junction immediately after the ultrafine particle sol is generated. For example, a mixed gas of hydrogen sulfide and hydrogen selenide is passed through an aqueous solution of strontium nitrate, cerium nitrate, europium nitrate, ethylenediaminetetraacetic acid, and ammonium carbonate to produce a sol of strontium sulfide selenide to which cerium and europium are added. The surface can be coated with a 5in2 film by adding ethyl silicate, or the surface can be coated with a phosphide film by passing phosphine gas. Thereafter, the surface is coated with organic atomic groups. The luminescent substance ultrafine particles thus obtained can be used alone or in a mixture of two or more types in the luminescent layer formed thereby.

The ultrafine luminescent particles produced in this way are then treated with a binder resin, such as polyester (TP-249':
It is dispersed in a solution such as Nippon Gosei) or salt vinyl acetate resin (MR-1108: Nippon Zeon). The solvent used is a mixture of ketones, esters, and aromatic hydrocarbons, such as a mixture of equal amounts of methyl ethyl ketone, methyl isobutyl ketone, solvent naphtha, ethoxypropyl acetate, and 3-methoxy-3-methylbutyl acetate. The reason for mixing in equal amounts from low boiling point to high boiling point is to make the evaporation happen gradually, and this makes it possible to form a smooth current limiting layer with a uniform thickness. . Further, a crosslinking agent such as melamine, isocyanate, or epoxy may be added to the binder solution to increase the cohesive force of the membrane.

In addition, when it is necessary to impart conductivity to the binder resin, a carbon blank or a charge transfer complex, such as tetrathiafulvalene-tetracyanoquinodimethane complex, tetramethyltetrathiafulvalene-biethylene, is added to the binder solution. Dichenylene complexes, triethylamine-parachloranyl complexes, and conductive polymers such as polypyrrole and polythiophene can also be added.

When adding polypyrrole, if iron chloride and pyrrole monoar, which serve as a polymerization catalyst and conductive dopant, are mixed into the binder solution, the polymerization of pyrrole will proceed during coating and drying, forming a light-emitting layer containing polypyrrole. can do.

A schematic cross-sectional view of an EL element according to the present invention is shown in FIGS. 1 and 2. FIG. 1 shows a DC light emitting type, and FIG. 2 shows an AC light emitting type.

Next, an example of the present invention will be described in the first example of a DC light emitting type.
Based on the drawings, the AC light emitting type will be explained based on FIG. 2.

A non-alkali type glass substrate is cleaned and ITO is sputtered to form a transparent conductive film on the glass substrate. This was patterned into a comb shape by photolithography to form a transparent electrode.

Ultrafine strontium sulfide particles to which cerium and europium are added are dissolved in a four-component mixed solvent of salt and vinegar picopolymer MR-110 of methyl ethyl ketone/methyl isobutyl ketone/propylene glycol monoethyl ether acetate/3-methoxy-3-methylbutyl acetate. Spray paint dispersed on the paint and dry it to a thickness of 1 μm.
The light-emitting layer was made m. Up to this point, the process is the same for both the DC light emitting type and the AC light emitting type.

In the case of the DC light emitting type, the steps after forming the light emitting layer are as follows.

Next, a current limiting layer is formed. The current limiting layer has a specific resistance of lX1
It is preferable to use a film having a film thickness of about 1 to 20 μm and a thickness of 02 to 1X106 Ω·cm. For forming such a current limiting layer, for example, fine powder of manganese dioxide fixed with a binder resin may be used. Electrolytic manganese dioxide is pulverized with a ball mill to an average particle size of about 1100n,
This powder is dispersed in the binder solution used for the luminescent layer, and this is applied onto the luminescent layer by spray painting.
It is dried to form a current limiting layer with a thickness of about 10 μm. On top of this, aluminum is further formed as a back electrode by vacuum evaporation. The back electrode needs to be a comb-shaped electrode that is perpendicular to the transparent electrode on the substrate side, but even if only the electrode is patterned, there is a possibility of crosstalk, so in this case, the current limiting layer below It is best to pattern the light emitting layer and the light emitting layer at the same time. A method for such patterning is to scrape off unnecessary parts by scratching with a diamond needle, resulting in a structure in which the light emitting layer 3, current limiting layer 4, and back electrode 5 are removed, as shown in Figure 1. . The EL element formed in this manner exhibits light emitting characteristics with high brightness and high uniformity due to direct current.

Next, the manufacturing process of an AC light emitting type EL element will be described. AC light-emitting type EL elements include those with a so-called double insulation structure, which has an insulating film on both sides of the light-emitting layer, and those with a so-called MIS type, which have an insulating film on only one side of the light-emitting layer. There are various types, such as those in which electrodes are provided without an insulating film on both sides of a luminescent layer in which luminescent substance powder is fixed with a binder resin with a high dielectric constant.
The figure shows an example of MIS structure. The manufacturing method for this will be described below.

The manufacturing method up to the light emitting layer 3 is the same as that of the DC light emitting type device described above, and the insulating layer 7 is provided thereon.

Various materials can be used for the insulating layer, such as silicon dioxide, silicon oxynitride, tantalum pentoxide, and lead titanate, and methods for forming insulating films using these include vacuum evaporation and sputtering. Although various methods such as ringing can be used, a case will be described here in which barium titanate powder is dispersed in vinylidene fluoride-trifluoroethylene copolymer.

Barium titanate is ground to a particle size of about 1100 nm, or ultrafine powder of barium titanate is prepared and used. This is immersed in toluene, paravinylbenzenesulfonic acid, acrylic acid, α-methacryloxypropyltrimethoxysilane, etc. are added and stirred. Next, fluorinated alkyl methacrylate is added, and hensyl peroxide and azo By adding bisisobutyronitrile and copolymerizing fluorinated alkyl methacrylate with paravinylbenzenesulfonic acid, acrylic acid, α-methacryloxypropyltrimethoxysilane, etc. adsorbed on the barium titanate surface, fluorinated alkyl methacrylate is produced. The polymer adsorbed onto the surface of the barium titanate particles is in a dispersed state.

A copolymer of vinylidene fluoride and trifluoroethylene is added to this and stirred to obtain an insulating film coating. This paint is applied onto the luminescent layer by dip coating or spray coating, and is dried to form an insulating film with a thickness of 1 μm. Furthermore, aluminum was vapor-deposited to form a back electrode, and patterned by photolithography to form a comb-shaped electrode. The BL element formed in this manner exhibits light emitting characteristics with high brightness, high uniformity, and breakdown resistance when exposed to alternating current.

〔Effect of the invention〕

According to the present invention, the luminous efficiency of the powder EL element can be improved, the life span can be extended, and the contrast can be increased.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are cross-sectional views schematically showing the EL elements manufactured in Examples.

Claims (2)

[Claims] (1) An electroluminescent device comprising a light emitting layer containing powder particles between a pair of electrodes, characterized in that a layer of organic atomic groups is provided on the surface of the powder particles. (2) Before forming the organic atomic group layer, the powder particles are made of a II-VI compound semiconductor to which at least one element selected from manganese and rare earth elements is added, and have a particle size of 1 to 10.
The electroluminescent device according to claim 1, which is a powder of 0 nm.