JPS6137877A - Electroluminescent element - Google Patents

Abstract

PURPOSE:An inexpensive electroluminescent element which can be easily manufactured, has a good emission efficiency and gives high luminance by low-voltage driving, made by repeating lamination in the order of an electron-accepting layer, an electron-donating layer and an electrical insulating layer to form a light-emitting layer in which a specified layer consists of a monomolecular (cumulative) film. CONSTITUTION:A light-emitting layer 3 having an electroluminescent function is provided between electrodes 1 and 2, of which the electrode 1 is a transparent one for passing emitted light. In said layer 3, a first layer 5-1, 5-2 contg. an electron-accepting org. compd., a second layer 6-1, 6-2 contg. an electron-donating org. compd. and a third layer 4-2 are repeatedly laminated between third layers 4-1 and 4-3 serving as insulating layers laminated at the top and bottom ends, and the first layer 5-1, 5-2 and the third layer 4-1, 4-3 are formed from a monomolecular film or monomolecular cumulative film of a compd. respectively forming the layer. By such a constitution, said element is inexpensive and can be easily manufactured, has a good light emission efficiency and gives very high luminance by low-voltage driving.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an electroluminescent (EL) device that emits electroluminescence.

In detail, it is an EL element that has an EL layer that is a combination of two types of thin films made of organic compounds with different electrochemical properties, and that can emit light efficiently even when driven at a low voltage and has sufficient brightness. Regarding.

[Prior art]

An EL element has a structure in which a light-emitting layer containing a material with an EL function, that is, a material that emits light when placed in an electric field, is placed between two electrodes, and a voltage is applied between these electrodes. It is a light-emitting element that generates light by applying an electric field and converting electrical energy directly into light. Unlike conventional light emitting methods, in which a gas excited by the phosphor imparts energy to the phosphor and causes it to emit light, it can be
It is attracting attention as it has the potential to realize various shapes such as cylindrical shapes, for example, as a component of display media used to display lamps, lines, diagrams, images, etc., or as a material that can realize light-emitting bodies such as large-area panel lamps. has been done.

These EL devices differ in their light emission methods; one is an intrinsic EL method that performs field-excited light emission due to the movement of carriers within the light-emitting layer, and the other is an intrinsic EL method that performs field-excited light emission by injecting carriers into the light-emitting layer from an electrode. There are two main types: the carrier injection EL method and the carrier injection EL method.

Furthermore, due to the differences in the structure of the light-emitting layer of the device, EL devices are divided into thin film types, which have a thin film made of a material that has an EL function as a light-emitting layer, and light-emitting devices that have a material that has an EL function dispersed in a binder. It is broadly classified into two types: a powder type with layers and a powder type with layers.

In addition, as a material having the above-mentioned EL@ ability.

Conventionally, inorganic metal materials such as ZnS containing Nn, Cu, or ReF3 (Re represents a rare earth) as an activator have been mainly used.

Thin-film EL devices have thin light-emitting layers that allow the distance between the electrodes to be sufficiently shortened, and a stronger electric field is generated within the light-emitting layer, resulting in lower brightness even when driven at low voltages. It has a structure suitable for obtaining high-quality light emission. However, if this type of EL device is manufactured by forming a thin light-emitting layer using the above-mentioned inorganic metal material mainly consisting of ZnS using a thin film forming method such as vapor deposition, the manufacturing cost becomes extremely high. In addition, since it is extremely difficult to form a light-emitting layer made of a uniform thin film over a large area, it has not been possible to mass-produce high-quality, large-area EL elements.

On the other hand, E
As an L element, an intrinsic E in which a light-emitting layer is formed by dispersing the above-mentioned ZnS-based EL inorganic material in an organic binder.
An L-type organic powder type EL element is known.

However, in this powder type EL element, when the layer thickness is formed thin, defects such as pinholes are likely to occur in the light emitting layer. There are structural limits to making it thinner, making it impossible to obtain sufficient light emission, especially high brightness, and because the layer thickness is relatively thick, power consumption increases to generate a stronger electric field. It had the following problems. In order to generate a stronger electric field in the light-emitting layer of this powder-type EL element, an improved powder-type EL element was developed, in which an intermediate dielectric layer made of vinylidene fluoride polymer was provided.
Although it is known from the publication No. 1728131, the current situation is that satisfactory performance in terms of brightness, power consumption, etc. is not obtained.

On the other hand, recently, various thin film formation methods have been used to control the chemical structure and higher-order structure of organic compound materials, which can form thin films with high precision, and are being used in optical and electronic applications instead of conventionally used metals and inorganic materials. It is attracting attention for its application as a material for electrochromic elements, piezoelectric elements, pyroelectric elements, nonlinear optical elements, ferroelectric liquid crystals, etc. Furthermore, it is also possible to use these materials to form the light emitting layer of EL elements. It is expected to be used as a material.

Among these, anthracene, pyrene, perylene, or their derivatives are known as organic materials for the light-emitting layer of EL devices, and carrier injection using a monomolecular cumulative film of these materials as the light-emitting layer is known. An EL type element is known from Japanese Patent Laid-Open No. 52-35587.

However, in this EL device, although one emissive layer is formed as a thin film with high precision, the density of electrons or holes, which are carriers, is very low, and the probability of excitation of functional molecules due to carrier movement or recombination is low. low,
At present, it is not possible to obtain efficient light emission, and the results are not particularly satisfactory in terms of power consumption and brightness.

[Purpose of the invention]

An object of the present invention is to provide a novel EL element that has good luminous efficiency, can provide sufficiently high luminance even when driven at low voltage, is inexpensive, and has a structure that is easy to manufacture.

Another object of the present invention is to enable EL devices to be formed by appropriately selecting various organic compound materials and combining the optimal thin film formation method for the material, and to easily impart desired light emitting characteristics. An object of the present invention is to provide an EL element having a structure that allows for.

[Structure of the invention]

That is, the electroluminescent device of the present invention is an electroluminescent device having two electrode layers, at least one of which is transparent, and a light emitting layer provided between these electrode layers, in which the light emitting layer is relatively free of electrons. A first layer containing an organic compound exhibiting acceptability, and a second layer containing an organic compound relatively exhibiting electron donating property.
and a third layer having electrical insulation properties, and the first layer further contains another compound that can serve as an electron acceptor for the organic compound that relatively exhibits electron acceptability. ,
and the second layer contains another compound that can serve as an electron donor for the relatively electron-donating organic compound, and these layers extend from one side of the electrode layer to the other. The first layer, the second layer, and the third layer are laminated in this order twice or more on the third layer, and the first layer and the third layer further include: It is characterized by being composed of a monomolecular film or a monomolecular cumulative film of a compound capable of forming each of these layers.

The light-emitting element of the present invention basically has two electrode layers, at least one of which is transparent, and a light-emitting layer with an EL function provided between these electrode layers with an insulating layer interposed therebetween. It is a thin film type EL element, and its feature lies in the structure of the light emitting layer.

The light-emitting layer of the EL device of the present invention includes an organic compound (hereinafter abbreviated as EA compound) that exhibits a relatively electron-accepting property;
A compound that can become an electron acceptor for the EA compound (hereinafter referred to as an EA-a compound) is placed in a position where organic compounds that are relatively electron-donating (hereinafter referred to as ED compounds) are in contact with each other and around the EA compound. (abbreviated as E), but also the above E
It has a structure in which compounds (hereinafter abbreviated as FD-d compounds) that can serve as electron donors for the compound are arranged around the D compound, and the relationship between these compounds when placed in an electric field is The main source of light is a luminescence effect based on the formation of an exciplex through the exchange of electrons between the ED compound and the EA compound. It is characterized by having a structure suitable for efficient formation as it occurs.

Hereinafter, the EL element of the present invention will be explained in more detail using the drawings.

FIG. 1 is a schematic cross-sectional view of an example of the EL element of the present invention.

1.2 is an electrode for generating an electric field by applying a voltage, and 1 is a transparent electrode for extracting the generated light. 3 is a light emitting layer having an EL function, and the first layer 5-1.5-2. It has a multilayer structure in which the second layer 6-1, 6-2 and the third layer 4-2 are alternately stacked, and the first layer 5-
1, 5-2 and the third layer 4-1.4-2.4-3 are formed from a monomolecular film of a compound capable of forming each layer or a cumulative film thereof.

The first layer 5-1 of the light-emitting layer 3 contains as a main component a compound that can be an EA compound with respect to the above-mentioned ED compound contained in the second layer 8-1, and this first layer 5-1 The second layer 1 laminated in direct contact with the first layer 5-1
The first layer 5-1 and the second
Interface 7-1 of layer B-1 serves as a contact surface between the EA compound and the ED compound. The relationship between the first layer 5-2 and the second layer 8-2 is also similar to this, and the interface 7-
2 are uniquely formed.

At these interfaces 7-1 and 7-2, when a voltage is applied to the electrodes 1 and 2 and an electric field is applied to the light emitting layer 3, E
A compound and ED compound form a complex in an excited state,
When this exciplex returns to the ground state, excitation energy is generated as light from the complex, EA compound, and/or ED compound in the excited state. In this way, the EL of the present invention
The main source of light emission in the device is light emission at this interface 7-1, 7-2.

Furthermore, the first layer 5-1.5-2 contains EA-, which can act as an electron acceptor for the EA compound that is the main component of these layers.
a compound is mixed, and this EA-a compound is E
It mainly has the function of increasing the electric field excitation efficiency of the EA compound through interaction with the EA compound, such as receiving electrons from the A compound.

In addition, the second layer 64.8-2 contains ED-d, which can act as an electron donor for the ED compound that is the main component of these layers.
The compounds are mixed, and this FD-d compound is also
It mainly has the function of increasing the electric field excitation efficiency of the ED compound through interaction with the ED compound, such as donating electrons to the ED compound.

Note that - the above-mentioned EA-a and ED-d compounds can control the electrochemical properties of the first layer and the second layer as desired, such as controlling the emission color, by interacting with the EA compound and the ED compound. It may also have a function to control accordingly in addition to the above functions.

First layer 5 constituting the light emitting layer of the EL element of the present invention
-1.5-2 and the second layer 6-1.6-2 contain compound molecules directly involved in the formation of the field-excited complex as shown below, or at least one of the compounds as a functional moiety. The first layer 5-
1.5-2 is formed from a monomolecular film or a monomolecular cumulative film.

Furthermore, the first layer 5-1.5-2 contains EA-a, which can act as an electron acceptor for the EA compound that is the main component of these layers.
The compound is contained as a subcomponent, and the second layer 6-1.
8-2 contains as a subcomponent an FD-d compound which can serve as an electron donor to the ED compound which is the main component of these layers.

A light emitting layer 3 of a compound molecule directly involved in the formation of an electric field excited complex contained as a main component in the first layer and the second layer.
As for the arrangement within, the following combinations can be cited as typical ones.

(a) First layer 5-1.5-2 and second layer El-1, 8
A compound molecule having an EL function (mainly emitting light) based on the formation of an exciplex is placed in each of -2.

(b) Based on exciplex formation in the first layer 5-1.5-2<
' Compound molecules having an EL function are arranged, and molecules of a compound (ED compound) that can serve as an electron donor for these compound molecules are arranged in the second layer 8-1. It is located at e-2.

(c) Based on exciplex formation in the second layer 6-1.6-2
A compound molecule having EL41i ability is placed.

Compounds that can act as electron acceptors for these compounds (E
A compound) molecules are arranged in the first layer 5-1, 5-2, respectively.

As the compound having the <ELt1 enzymatic structure based on the exciplex formation described above, it is preferable to use an organic compound that has a high luminous quantum efficiency, has a π-electron system that is easily susceptible to external perturbations, and is easily excited by an electric field. It will be done.

Examples of such compounds include fused polycyclic aromatic hydrocarbons, p-terphenyl, 2,5-diphenyloxazole, 1,4-bis-(2-methylstyryl)-benzene, xanthine, coumarin, acridine 2-cyanine, Pigments, benzophenone diphthalocyanine, metal complexes of phthalocyanine, porphyrin, metal complexes of porphyrin, 8-hydroxyquinoline, metal complexes of 8-hydroxyquinoline, ruthenium-11 complexes, rare earth complexes, and derivatives of these compounds, and complexes other than the above. Among cyclic compounds and their derivatives, aromatic amines, aromatic polyamines, and compounds with a quinone structure, <E
Among these compounds, one or more compounds that can relatively become an EA compound and one or more compounds that can become an ED compound are appropriately selected and combined, and the above-mentioned first A light-emitting layer having the structure (a) of a layer and a second layer is prepared by using the single-shot accumulation method described later for the first layer, and the vapor deposition method for the second layer.
It can be formed using a thin film forming method such as a CVD method.

Furthermore, compounds that can serve as electron acceptors or electron donors for the compound having <EL function based on exciplex formation described above include heterocyclic compounds other than the above-mentioned compounds and derivatives thereof, aromatic amines, Examples include aromatic polyamines, compounds having a quinone structure, tetracyanoquinodimethane, and tetracyanoethylene, and the above-mentioned compounds and these compounds are appropriately selected and combined to form the first layer and the above-mentioned first layer. A light-emitting layer having the second layer configuration (b) or (C) can be formed.

Furthermore, EA which is the main component of the first layer contained in the first layer
an EA-a compound that can serve as an electron acceptor for the compound;
The ED-d compound that can act as an electron donor for the ED compound that is the main component of the second layer and is included in the second layer has <EL function (mainly Compounds that emit light), compounds that can act as electron donors or electron acceptors for the compound, compounds that can become a light emitter through excitation energy transfer, and compounds that have at least one of these compound molecules as a functional moiety, etc. can. When forming the first layer and the second layer, these EA-
The a and ED-d compounds may be appropriately selected and used so as to have the above-mentioned functions. E for EA compounds
E! for the amount of A-a compound and ED compound. ]-d The amount of the compound varies depending on the compounds used in the first layer and the second layer, and cannot be generally specified, but usually EA-
For compound a, 10 mol% to 0.1 of the EA compound
For the ED-d compound, it is about lθ mol% to 0.1 mol% of the ED compound.

Note that the compounds mentioned above that can be used as ED and EA compounds may be compounds that have a function of emitting light that is not based on the formation of an exciplex, and furthermore, EA-a and ED.
The compound that can become the -d compound may also have an EL function, and the light emission in the EL element of the present invention is caused by the first
The interface between the layer and the second layer? -1, 7-2, but the light emission is not limited to only in the first layer 5-1, 5-2 and/or the second layer B-1, 8-2. It may also include cases in which it is carried out.

In order to form a monomolecular film or a monomolecular cumulative film containing the above-mentioned compound or a compound having the compound molecule as a functional part, it is necessary to enable highly ordered molecular orientation and arrangement and to easily form an ultra-thin film layer. The so-called single molecule accumulation method can be suitably applied.

This single molecule accumulation method is based on the following principle. In other words, 1. For example, in a molecule that has a lignophilic part and a hydrophobic part in the molecule, when the balance between the two (balance of amphiphilicity) is maintained appropriately, many of these molecules will be on the water surface. Form a monomolecular layer with the hydrophilic portion facing down.

This monomolecular layer has the characteristics of a two-dimensional system, and when these molecules are sparsely dispersed, the two-dimensional ideal gas equation between the surface IA per molecule and the surface pressure ■, rlA = kT.
(k, Porzubun's constant, T: absolute temperature), and these molecules form a "gas film"; however, when A is made sufficiently small, intermolecular interactions become stronger, and these molecules form a two-dimensional solid "condensed film" (or form a solid film). This condensed film can be transferred to the surface of a substrate such as glass,
An ultra-thin monomolecular film or a cumulative film thereof can be formed on a substrate.

According to this method, the orientation of the molecules forming the monolayer is such that, for example, almost all of the tree-like parts of the constituent molecules are oriented toward the substrate in a highly ordered manner. It can be uniform. Therefore, by making the first layer of the light-emitting layer of the EL element of the present invention a monomolecular film or a monomolecular cumulative film, the functionality consisting of compound molecules directly involved in the formation of an exciplex contained in the first layer can be improved. It becomes possible to arrange the portions at high density at the interface between the first layer and the second layer.

Various solutions can be used as a solution for forming a single molecule in this single molecule accumulation method, and depending on the solution used, a well-balanced number of molecules having different affinity for the solution can be used. A monomolecular film can be formed by appropriately selecting a compound for forming a molecular film. Among such solutions for forming a monomolecular film, water or a solution containing water as a main component is preferably used because it is inexpensive, easy to handle, and safe.

The structure of the light-emitting layer of the EL device of the present invention will be described below, taking as an example the case where a single molecule accumulation method using water or a solution containing water as a main component is applied.

Basically, the compounds contained in the first layer and the second layer of the light emitting layer of the EL device of the present invention include the above-mentioned E D ,
It is a compound having at least one of EA, EA-a, and E[ld compounds, or any of these compounds as a functional moiety. Among these compounds, monolayer-forming compounds, for example, take a compound that has one functional moiety, depending on the position within the molecule that has the functional moiety, as shown in the schematic diagram of the molecular structure in Figure 2. (a) The functional part 21 is on the side of the woody part 22 5 - Figure 2 (a) (b) The functional part 21 is on the side of the hydrophobic part 23 - Figure 2 (b) (c) The functional part 21 is the hydrophobic part 23 and the wood-loving part 22
-Large N is classified into the three types shown in Figure 2 (C).

The hydrophilic portion 22 of these compounds includes 1
For example, carboxyl groups and their metal salts, amine salts and esters, sulfone groups and their metal salts and amine salts, sulfonamide groups, amide groups, amino groups, imino groups,
Examples include hydroxyl group, quaternary amine group, oxyamino group, oxyimitsu group, diazonium group, guanidine group, hydrazine group, phosphoric acid group, silicic acid group, aluminic acid group, etc., each of which can be used alone or in combination to form the above compound. A hydrophilic portion 22 therein can be configured.

Further, as the constituent elements of the hydrophobic portion 23, linear or branched alkyl groups, vinylene, vinylidene,
Examples include olefinic hydrocarbons such as acetylene, fused polycyclic phenyl groups such as phenyl, naphthyl, anthranyl, and chain polycyclic phenyl groups such as biphenyl. Alternatively, they can be combined to constitute the hydrophobic portion 23 in the above compound.

On the other hand, the interface between the first layer and the second layer of the light emitting layer of the EL device of the present invention? The orientation and arrangement of the EA compound contained in the monomolecular film at points -1 and 7-2 (parts where light is mainly emitted) are shown in the schematic cross-sectional partial view near interface 7-1 in Figure 3 (this figure In the case of , the first layer is formed from a monomolecular film containing compound molecules each having one functional moiety consisting of an EA compound molecule, and for molecules having a functional moiety consisting of EA-a compound molecules 34, (Illustration of functional parts is omitted).

(1) Molecules forming the monolayer of the first layer 5-1 (E
Is the parent part 32 having the functional part 31 (consisting of compound A) the interface? -1 orientation.

- Figure 3 (a) (2) (E
A hydrophobic portion 33 having a functional portion 3I (composed of compound A) is oriented at the interface 7-1.

Figure 3 (b) It is basically divided into two patterns.

In order to form such an interface pattern of the light-emitting layer, compounds belonging to types a and b are preferably used as monolayer-forming compounds containing the above-mentioned EA compound molecules as a functional moiety. . Hereinafter, in order to form the above-mentioned interface pattern (1), it is recommended to use a compound belonging to the above-mentioned type a in the first layer.
In order to form 2), it is preferable to use a compound belonging to the above type b in the first layer.

Note that the types of molecules having a functional portion consisting of the EA-a compound molecules 34 (not shown) include the above-mentioned interface pattern (1), E used in (2)
A suitable type may be appropriately selected depending on the A compound.

The example explained above is a case where the first layer is formed from a monomolecular film, but even when the first layer 5-1, 5-2 is formed from a monomolecular cumulative film, the first layer is formed from a monomolecular film. The monomolecular film of the first layer constituting the interface 7-1. Just form it.

In addition, when the first layer 5-1.5-2 consists of a monomolecular cumulative film, each monomolecular film constituting the cumulative film may be the same, or the monomolecular film One or more of these may be different from other monolayers. Furthermore, the structure based on the orientation state of the molecules forming each monomolecular film of the monomolecular cumulative film is a so-called Y-type structure (between each film, a phyllophilic part and a hydrophilic part or a hydrophobic part and a hydrophobic part are formed). (structures facing each other), Various structures are possible. Furthermore, the monomolecular film forming the first layer constituting the light-emitting layer of the EL device of the present invention contains one or more compounds having an EA compound as a main component as a functional moiety;
A multi-component monomolecular film containing one or more compounds other than one or more compounds having EA-a compound molecules as a functional part as a subcomponent may also be used. In such cases, other compounds may include compounds that do not have a functional moiety but can control the electrochemical properties of the emissive layer through interaction with compounds that do, and even monolayers. Examples include compounds that can increase the strength of the layer and improve the adhesiveness with other layers.

The structure of the monomolecular film or monomolecular cumulative film as described above is appropriately selected depending on the desired electrochemical properties of the first layer, that is, the compound or combination of compounds forming the first layer. For example, a potential curve of π electrons in a direction perpendicular to the surface direction of the monolayer by combining and accumulating monolayers made of compounds belonging to types a, b, or C of the monolayer-forming compounds described above may be obtained. can be controlled, etc.

Compounds that can be used to form the first layer 5-1.5-2 include the above-mentioned compounds capable of forming a functional part, or having one or more of these compounds. Among the compounds, those that have a well-balanced tree-philic moiety and hydrophobic moiety can be used as they are for forming a monolayer, while those that do not have a tree-philic moiety and/or hydrophobic moiety can be used as is. Alternatively, a hydrophobic group can be newly introduced into the molecule to form a monolayer-forming compound.

Examples of such compounds include compounds represented by the following structural formulas.

In addition, in the structural formula shown below, X and Y represent the parent wood group as mentioned above, but when both of these exist in one molecule, even if either one is the parent wood group, In such a case, the other one will be hydrogen. Further, R represents a linear or side chain alkyl group having about 4 to 30 carbon atoms, preferably about 10 to 25 carbon atoms.

5, 6゜6≦m
+n 7, 8°21,
22.
27゜6≦n≦20 23゜9Hs 2
9・24゜0≦n≦2 25゜M-H21Be +Mg + Oa l cal 5
rAICI, YbC1 M=Er, Sm, Eu, Gd, Tb, Dy, Tm, Yb
34, M=Er, Sm, Eu, Gd, Tb, DLTm+YbM
-Er, Sm, Eu, Gd, T'b, Dy, Tm+Yb
R! -H', -0T(3, -0F3, *■86,
37. as.

39, 4Q.

48, 44°H (,QH
2) X 1N N
62°BF4 65, 66°R70°69°OR 88°89°Among these compounds! The compound having the structural formula of l-positive 35 is obtained by modifying a compound having an EL function with a hydrophobic group and/or a parent tree group based on the formation of an exciplex among the compounds that can form the functional moiety listed above. This is a compound for forming a monolayer film.

In addition, the compounds with the structural formulas of 鐅42 to 酅54 and P/EL85 to Sui 86 have a structure in which an alkyl chain is directly bonded to the functional moiety, but the bond of the alkyl chain to the functional moiety is 1. For example, it may be an ether bond, a bond via a carbonyl group, or the like.

Furthermore, among the monolayer-forming compounds exemplified here,
Compounds that can be used in other thin film formation methods such as vapor deposition methods include secondary
It can also be used to form layers. Further, the second layer also contains one kind of compound having the ED compound decile as a functional part, which is the main component, similarly to the first layer,
It may contain one or more compounds other than one of the compounds having the FD-d compound molecule as a functional moiety, which is a subcomponent, and in such a case, the other compounds have only one functionality. Compounds that do not have moieties but can control the electrochemical properties of the emissive layer by interaction with compounds that have functional moieties, as well as increasing the strength of the second layer and adhesion to other layers. Examples include compounds that can improve properties.

The third layer 4-1.4-2, 4-3, which is another layer of the light-emitting layer of the EL element of the present invention, is a layer having an insulating property, and in particular, the third layer 4-1. 4-3 is the EL of the present invention
It has the function of increasing the insulation of the element's capacitor structure,
The third layer 2 has the function of confining the movement of electrons within a necessary minimum area and emitting light by efficient exchange of electrons. As a material that can form these third layers, the general formula that can form a monomolecular film with accurate and uniform insulation properties is: % formula %) (In the above formula, n is 10 ≦n≦30, and X is -COOH, -CONH2, -GOOR, -N"CCH
3) 3.Gl-.

Examples include compounds represented by (representing a group such as).

This third layer also. It may be a monomolecular film or a monomolecular cumulative film, and in the case of a monomolecular cumulative film, each monomolecular film may be the same or one or more of each monomolecular film may be different from other monomolecular films. It may be. Further, the monomolecular film forming the third layer may be a monomolecular film made of one type of compound, or may be a multicomponent monomolecular film made of two or more types of compounds.

Although the EL element of the present invention having two interfaces formed by the first layer and the second layer shown in FIG. 1 has been described so far, the EL element of the present invention has two interfaces. The number is not limited to this, and may be three or more.

The thickness of each layer constituting the light-emitting layer of the EL device of the present invention having the structure described above varies depending on the number of interfaces the EL device has and the structure of each layer itself, but for the first layer, 300 Å or less, preferably 100 A or less, for the second layer, 5001 or less, preferably 200 A or less,
For the third layer, 300A or less, preferably 100A
Below A, the layer thickness of the entire light emitting layer is 111
11 or less, preferably 3000 A or less, in order to obtain a good light emission state even in low voltage driving.

At least one of the two electrode layers 1 and 2 of the EL element of the present invention is provided as a transparent electrode in order to extract light.

When forming an electrode layer as a transparent electrode, PMMA,
InO2゜5n02. It can be formed by laminating insium tin oxide (1, T, O) or the like by a vapor deposition method or by directly laminating these materials on the light emitting layer.

In addition, the non-transparent electrode layer may be a thin plate made of a material capable of forming an ordinary electrode having sufficient conductivity, or a suitable substrate, or directly on the formed light emitting layer.
, Ag, Au, etc. can be laminated by a vapor deposition method or the like.

The thickness of these electrode layers is about 0.01u to 0.3u, preferably about 0.054m to 0.2 tiles.

Note that the shape and size y of the EL element of the present invention can be made into various shapes as desired.1 For example, when forming a transparent electrode, the substrate for forming a light emitting layer is used as a substrate, and this substrate may be shaped like a plate or a belt. A desired shape and size can be obtained by using, for example, a cylindrical shape. Further, the two electrode layers may be patterned into various shapes as desired.

In the EL element of the present invention having the above configuration, the EL
Between the two electrodes 1 and 2 of the device, for example, lXI is applied to the light emitting layer 3.
By applying direct current, alternating current, or pulse voltage so that an electric field of about O3~3x10θ is applied, good light emission can be obtained from the light emitting layer 3 through the transparent electrode.

Hereinafter, typical operations of the single-molecule accumulation method typified by the Langmuir-Prodgett method (LB method) applied to the formation of the first layer and the third layer of the light emitting layer of the EL device of the present invention will be described. explain.

An aqueous phase for forming a monomolecular film is provided in a water tank, and a clean substrate is immersed in the aqueous phase. Next, a predetermined amount of a solution of a monomolecular film-forming compound dissolved or dispersed in an appropriate solvent is spread into the aqueous phase.

This compound is deposited in the form of a film on the surface of the aqueous phase. At this time, in order to prevent this precipitate from freely diffusing the aqueous phase -L and spreading too much, a partition plate (or float) is provided to limit the area of development and control the state of aggregation of the H-substances. Obtain a surface pressure ■ proportional to the state. Then, the partition plate is operated to reduce the developed area and gradually increase the surface pressure (2) to set it to a surface pressure (n) suitable for forming a monomolecular film. Now, when the substrate that has already been immersed is gently moved up and down in the direction perpendicular to the aqueous phase surface while maintaining this surface pressure, a single molecule is generated each time the substrate moves upward and downward. The film is transferred onto a substrate, forming a monomolecular cumulative film.

To transfer a monomolecular film onto a substrate, in addition to the above-mentioned vertical immersion method, there is also a horizontal adhesion method in which the substrate is brought into contact with the water phase horizontally while keeping it parallel. Various methods can be applied, such as a rotating cylinder method in which the monomolecular film is transferred onto the surface of the substrate, or a method in which the substrate is extruded from a substrate roll into an aqueous phase. In the vertical dipping method, the orientation of the film-forming molecules is usually reversed between the substrate pulling process and the dipping process, so that a so-called Y-shaped film is formed. Also, horizontal 0
According to the deposition method, a monomolecular film with hydrophobic groups facing the substrate side is formed, and when a cumulative film is formed, a so-called X-type film is formed. However, the orientation of such parent tree groups and hydrophobic groups is
It is also possible to change it by surface treatment of the substrate, etc.

Furthermore, the pH of the aqueous phase when forming the first layer and the third layer of the light emitting layer of the EL device of the present invention by the single molecule accumulation method.
1. The type of additive for adjusting the pH value of the aqueous phase and its significance, the temperature of the aqueous phase, the operating conditions such as the rate of raising and lowering the substrate or the surface pressure, etc., are determined by the type of monolayer-forming compound used,
It may be selected appropriately depending on the characteristics of the film to be formed.

The light-emitting layer of the present invention can be formed, for example, in the following manner using the single molecule accumulation method as described above and other thin film forming methods such as vapor deposition.

First, a third layer consisting of a monomolecular film or a monomolecular cumulative film having a desired configuration is formed using the third layer forming material described above on the substrate on which the transparent electrode layer is provided. Next, on this third layer, a first layer consisting of a monomolecular film or a monomolecular cumulative film having a desired configuration is formed using a material capable of forming the above-described first layer. Further, on this first layer, a second layer having a desired structure is laminated by a vapor deposition method or the like using a material capable of forming the second layer described above.

Furthermore, a third layer is laminated on the second layer, and the first to third layers are stacked according to the desired number of interfaces between the first layer and the second layer.
Repeat the layer formation operation twice or more.

Finally, on this third layer, A1. An EL element of the present invention can be formed by laminating metals such as Ag and Au by a vapor deposition method or the like.

If a substrate with a non-transparent electrode plate or electrode layer is used as the substrate for forming the first light-emitting layer, the final
．． A material for forming a transparent electrode layer such as No. 7.0 may be laminated on the light emitting layer by vapor deposition or the like. In addition, when both electrodes are transparent, a transparent electrode layer is formed using the material described in -F on the transparent substrate for forming the first light emitting layer, and another transparent electrode layer is laminated after the formation of the first light emitting layer is completed. Good.

Note that the plurality of first layers included in the light emitting layer of the EL element of the present invention may each have the same structure, and the structure of one or more of the plurality of first layers may be It may be different from the structure of other first layers, and this may be different from the structure of other first layers.
The same applies to the layer and the third layer. Further, an adhesive layer may be provided between each layer constituting the EL element of the present invention in order to improve the adhesiveness of each layer. Furthermore, the EL element of the present invention is preferably provided with a protective MMh structure for protecting the element from the effects of moisture and oxygen in the air.

The EL device of the present invention as described above mainly emits light at the interface between two layers with different electrochemical properties (tz), and there may be multiple such interfaces in the light extraction direction of the EL device. With this structure, the amount of light emitted from the middle of the light extraction surface is greatly increased compared to conventional EL elements.

Furthermore, in the EL device of the present invention, the composition of the two layers constituting the interface is changed for each interface with respect to the plurality of interfaces that mainly emit light, and these are combined to produce five luminescent colors etc. as desired. It is now possible to control accordingly.

Furthermore, the light-emitting layer of the EL element of the present invention is mainly formed by combining an organic compound material and a thin film suitable for the material, and in particular, the first layer and the third layer of each layer constituting the light-emitting layer. Because the layer is formed from a monomolecular film or a monomolecular cumulative film, the overall layer thickness of the light emitting layer is thin, even though it has a multilayer structure with multiple interfaces that emit light as described above. The structure is designed to provide efficient light emission even when driven at a low voltage, and sufficient brightness can be achieved.

Moreover, in the EL device of the present invention, the first layer that is involved in direct light emission of the light emitting layer is formed by a monomolecular film or a monomolecular cumulative film.
Since a layer of 1 is formed, the functional parts of the compound directly involved in light emission are oriented and arranged toward the interface with high order and accuracy, and the functional part of the compound directly involved in light emission is oriented and arranged toward the interface, and the functional part of the compound directly involved in light emission is oriented and arranged as an electron acceptor for the compound directly involved in light emission. Since the light-emitting layer contains a compound that can serve as an electron donor and a compound that can serve as an electron donor, it has become possible to emit light based on the formation of an exciplex that accompanies more efficient transfer of electrons.

In addition, monomolecular films can be formed at almost normal temperature and pressure, and conventional methods such as vapor deposition cannot be used for forming the first and third layers constituting one light-emitting layer. It has become possible to use heat-sensitive organic compounds as constituent materials.

Furthermore, each layer of the light-emitting layer of the EL device of the present invention can be easily formed as a precise thin film using various organic compound materials, and even when the EL device of the present invention is formed as a large-sized bond with 9 EL cells, one light emission can be achieved. The layers were formed with high precision, and the EL device of the present invention had good functionality as a large-area EL device, and the EL device of the present invention was an inexpensive and mass-producible EL device.

Hereinafter, the EL device of the present invention will be explained in more detail according to Examples.

Example 1 A film with a thickness of 1500A was deposited on a 50+UA glass surface by sputtering. A T and 0 layer was formed to obtain a transparent electrode plate. The electrode plate was made by Joyce-Loebe1.
4X 10' in angmuir-Trough 4
It was immersed in an aqueous phase whose pH was adjusted to 6.5 by containing mol/7 CdCl2.

Next, stearic acid was dissolved in chloroform.
0.5 mj of a solution dissolved at a concentration of ol/no! was developed on the aqueous phase. After chloroform was removed by evaporation from the surface of the aqueous phase, the surface pressure of the aqueous phase was adjusted to 30 dyne/cm, and a film of stearic acid was precipitated on the surface of the aqueous phase.

Furthermore, while keeping the surface pressure constant, the electrode plate was gently pulled up at a speed of 2 cm/win in the direction across the water surface, and a monomolecular film made of stearic acid molecules as a third layer was placed on the electrode layer of the electrode plate. was formed and pulled out of the aqueous phase, and 30
It was left to dry at room temperature for more than a minute. Furthermore, this operation is repeated twice to form a monomolecular film 1! in which three monomolecular films made of stearic acid molecules are laminated on the electrode layer of the electrode plate. ! A membrane was formed as the third layer. Note that the stearic acid remaining on the surface of the water phase was completely removed from the surface of the water phase.

Next, the electrode substrate on which the third layer was formed in this way was immersed again in the aqueous phase from which the remaining stearic acid had been completely removed, and then a new layer was added (5 layers mol: 5 layers mol). :
In the proportion of 1 mol, the total amount of these is IX 1(1-
0.5 tsl of a solution dissolved in chloroform to a concentration of 1 mol/) was spread on this aqueous phase, the surface pressure was adjusted to 30 dyne/cm, and a monomolecular film of the above compound was spread on the aqueous phase. Once formed, the electrode plate was gently moved up and down twice at a speed of 2 cm/win in the direction across the water surface to form a monomolecular cumulative film consisting of four monomolecular films made of the above compound molecules as the first layer. Next, this electrode plate was pulled out of the aqueous phase, and the third layer was formed again.
It was left to dry at room temperature for 0 minutes or more.

Next, set this electrode plate at a predetermined position in the vapor deposition tank of the resistance heating vapor deposition apparatus, and then attach the electrode plate to one of the resistance heating ports.
- Add diphenyloxazole.

Anthraquinone is added to the other one, and the vapor deposition rate of anthraquinone is 0.1. The current flowing through the port containing the anthraquinone is kept constant so that it is about fi/see, and? The current flowing through the port containing 2.5-diphenyloxazole was adjusted so that the deposition rate of the entire deposited layer consisting of a mixture of 5-diphenyloxazole and anthraquinone was 2 A/sec.

A vapor deposited layer consisting of a mixture of 2,5-diphenyloxazole and anthraquinone was formed on the insulating layer as the third layer that had been previously formed as the first layer. The degree of vacuum in the tank during vapor deposition was maintained at 9×10' Torr, and the temperature of the substrate holder was 20°C.

Thereafter, in the same manner as described above, a third layer consisting of two monomolecular films made of stearic acid is laminated on the second layer, and the formation from the first layer to the third layer described above is performed. 4 operations
This was repeated several times to form a light-emitting layer (layer thickness: approximately 1,500 layers) having four interfaces between the first layer and the second layer.

The electrode plate on which the luminescent layer was formed in this way was placed into the vapor deposition tank again, and the pressure inside the tank was first reduced to a vacuum level of 10-6↑art, and then the vacuum level was further adjusted to 10' Torr. , 208/sec, an A1 layer of 1500 was deposited on the last formed third layer to form an EL device of the present invention as a back electrode. As shown in FIG. 4, this EL element is sealed with a sealing glass 41, and then purified, degassed, and dehydrated using silicone oil 4.
2 was injected into the seal to form the EL nacelle 3.

To such an EL nacelle electrode 44.45, 20V, 40
When an AC voltage of 0 Hz was applied to cause light to emit light and the luminance and current density of the light emission were measured, the current density was 0. l
A luminance of 211 Ft-L was measured at 1 mA/am 2 .

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of an example of the EL element of the present invention, and FIG.
The figure is a schematic diagram of the molecular structure of a monolayer-forming compound, No. 31.
f! EI of the present invention, the first layer and the second layer of the device
A schematic diagram showing a typical example of the arrangement of molecules at the interface of the layers of
FIG. 4 is a schematic cross-sectional view of an EL nacelle in which the EL element of the present invention is incorporated. ■, 44: Transparent electrode layer 2.45: Electrode layer 3: Luminescent layer 4-1.4-2.4-3: Third layer 5i, 5-2.5-3: First layer 8-1 .8-2.8-3: Second layer? -1.7-2: Interface 21.31: Functional part 22.32: Hydrophilic part 23.33: Hydrophilic part 34: Compound molecule having EA-a compound as a functional part 40: EL element 41 Nigarashi, 42: Silicone oil 43: EL cell Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1) In an electroluminescent device having two electrode layers, at least one of which is transparent, and a light emitting layer provided between these electrode layers. The light-emitting layer includes a first layer containing an organic compound relatively exhibiting electron-accepting properties, a second layer containing an organic compound relatively exhibiting electron-donating properties, and a third layer having electrically insulating properties.
furthermore, the first layer contains another compound that can serve as an electron acceptor for the relatively electron-accepting organic compound, and the second layer contains the relatively contains another compound that can serve as an electron donor for an organic compound exhibiting electron donating properties, and these layers are arranged on the third layer from one of the electrode layers to the other. The first layer, the second layer, and the third layer are laminated in this order twice or more, and the first layer and the third layer are made of a compound capable of forming each of these layers. An electroluminescent device comprising a monomolecular film or a monomolecular cumulative film.