JPS6137867A - Electroluminescent element - Google Patents

Abstract

PURPOSE:To provide an intrinsic electroluminescent element in the form of thin film achieving an excellent luminescence efficacy by low drive voltage, by a construction wherein an insulating layer, electron-accepting layer, and electron- donating layer the laminated repeatedly in this order to form a luminous layer and furthermore, a particular layer is composed of a monomolecular (cumulative film). CONSTITUTION:The third layer comprising an insulating material 4-1 (or 4-2, 4-3), the first layer comprising an electron-accepting org. compd. (contg. a relatively electron-donating org. compd.) 5-1 or (5-2), and the second layer comprising an electron-donating org. compd. (contg. a relatively electron-accepting org. compd.) 6-1 (or 6-2) are laminated to form a luminous layer 3 [with the proviso that the first and second layers are composed of a monomolecular (cumulative) film]. Then, a transparent electrode 1 and an electrode 2 respectively are provided on each side of said luminous layer 3 to yield an electroluminescent element emitting mainly at interfaces 7-1, 7-2.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to an electroluminescent (EL) device that performs electroluminescence, and more particularly, it relates to an electroluminescent (EL) device that emits electroluminescence. The present invention relates to an EL element that has layers having a combination of EL functions, can emit light efficiently even when driven at a low voltage, and has sufficient brightness.

[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. A light-emitting element that generates light by generating an electric field and converting electrical energy directly into light.
For example, unlike traditional light emitting methods, such as incandescent light bulbs where a filament is heated to emit light, or fluorescent light, where electrically excited gas imparts energy to a phosphor and causes it to emit light, thin panels are used. Possibility of realizing light-emitting bodies such as lamps, lines, diagrams, images, etc., or as components of display media such as lamps, lines, diagrams, images, etc., or as light-emitting bodies such as large-area panel lamps. It is attracting attention as having the following.

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, conventionally, as a material having the above-mentioned EL function, M
n, Cu or ReF3 (Re represents rare earth)
Inorganic metal materials such as ZnS containing ZnS and the like as activators 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. 172891, it is currently not possible to obtain satisfactory performance in terms of brightness, power consumption, etc.

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 the light-emitting 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 electrically insulating properties, and the first layer further contains another compound that can serve as an electron donor to the relatively electron-accepting organic compound. ,
and the second layer contains another compound that can serve as an electron acceptor for the relatively electron-donating organic compound, and these layers are arranged in a direction from one of the electrode layers to the other. On the third layer, the first layer, the second layer, and the third layer are stacked in this order twice or more, and the first layer and the second 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 donor to the EA compound (hereinafter referred to as an EA-d compound) is placed at 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-a compounds) that can serve as electron acceptors for the compound are arranged around the D compound, and when these compounds are placed in an electric field, the 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 and 2 are electrodes 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 a first layer 5-1.5-2, It has a multilayer structure in which the second layer 8-1, 6-2 and the third layer 4-2 are alternately stacked, and the first layer 5-
1.5-2 and the second layer 6-1.8-2 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 8-1 laminated in direct contact with the first layer 5-
Contains as a main component a compound that can become an ED compound with respect to the EA compound contained in 1, and the interface 7-1 between the first layer 5-1 and the second layer 6-1 is the contact between the EA compound and the ED compound. It is a face. First layer 5-2 and second layer 6-2
Is the relationship similar to this, and the interface between these layers?
-2 is 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
Light emission in the element occurs at this interface 7-1, ? -2 is the main light source.

Furthermore, the first layer 5-1.5-2 contains EA- which can act as an electron donor for the EA compound which is the main component of these layers.
d compound is mixed, and this EA-d 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 donating electrons to the A compound.

In addition, the second layer 8-1.6-2 contains ED-, which can act as an electron acceptor for the ED compound that is the main component of these layers.
A compound is mixed therein, and this ED-a compound also mainly has the function of increasing the electric field excitation efficiency of the ED compound through interaction with the ED compound, such as receiving electrons from the ED compound.

The above EII-a and EA-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. In addition to the above-mentioned functions, the controller may also have a function of controlling the above-mentioned functions.

First layer 5 constituting the light emitting layer of the EL element of the present invention
-1.5-2 and the second layer e-i, 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. It is formed from a monomolecular film or a monomolecular cumulative film containing compound molecules having as a main component.

Furthermore, the first layer 5-1.5-2 contains EA-d, which can act as an electron donor 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.
6-2 contains as a subcomponent an ED-a compound which can serve as an electron acceptor for 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 6-! , 6-
A compound molecule having an EL function (mainly emitting light) based on exciplex formation is arranged 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 compounds (ED compounds) that can serve as electron donors for these compound molecules are arranged in the second layer 6-1, 6-2, respectively.

(C) Based on exciplex formation in the second layer 8-1.6-2<
Compound molecules having an EL function are arranged, and compound (E'A compound) molecules that can serve as electron acceptors for these compounds are arranged in the first layer 5-1, 5-2, respectively.

As the compound having <ELm ability based on the above-mentioned exciplex formation, an organic compound that has a high luminescence quantum efficiency, has a π-electron system that is easily susceptible to external perturbation, and is easily excited by an electric field is preferably used.

Examples of such compounds include fused polycyclic aromatic hydrocarbons, P-terphenyl, 2,5-diphenyloxazole, 1,4-bis-(2-methylstyryl)-benzene, xanthine, coumarin, acridine, and cyanine. Pigments, benzophenone, phthalocyanine, metal complexes of phthalocyanine, porphyrins, metal complexes of porphyrins,
8-hydroxyquinoline, metal complexes of 8-hydroxyquinoline, ruthenium complexes, rare earth complexes, and derivatives of these compounds, as well as heterocyclic compounds other than the above and their derivatives, aromatic amines, aromatic polyamines, and quinone structures. Among the compounds, there are compounds that have an EL function based on exciplex formation, and among these compounds, there are one or more compounds that can be relatively EA compounds, and one or more compounds that can be relatively ED compounds. The structure of the first layer and second layer described above (a
) can be formed using the single molecule accumulation method described later.

Furthermore, based on the exciplex formation described above, <ELI! Compounds that can act as electron acceptors or electron donors for compounds having this ability include heterocyclic compounds other than the above-mentioned compounds and their derivatives, aromatic amines, aromatic polyamines, compounds with a quinone structure, and tetracyanoquinone. Dimethane, tetracyanoethylene, etc. can be mentioned, and the above-mentioned compounds and these compounds can be appropriately selected and combined to form the above-described first layer and second layer structure (b) or (C). A light-emitting layer can be formed.

Furthermore, EA which is the main component of the first layer contained in the first layer
an FA-d compound that can serve as an electron donor to the compound;
The ED-a compound that can serve as an electron acceptor for the ED compound that is the main component of the second layer and is included in the second layer has <ELe1 ability (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 HAs are selected depending on the compound used as the main component of the first layer and the second layer.
-d and HD-a compounds may be appropriately selected and used so as to have the above-mentioned functions. Amount of EA-d compound relative to EA compound and EII-a relative to ED compound
The acidity of the compound will vary depending on the compounds used in the first layer and the second layer - cannot be generally specified, but is usually EA
-d compounds, from 10 mol% to 0.0% of the EA compound.
For the ED-a compound, it is about 10 mol% to 0.1 mol% of the ED compound.

Note that the compounds that can be the ED and EA compounds mentioned above may be compounds that have a function of emitting light that is not based on the formation of an exciplex, and furthermore, the compounds that can be used as the ED and EA compounds may be compounds that have a function of emitting light that is not based on the formation of an exciplex.
The compound that can become the -a 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 light emission may occur within the first layer 5-1, 5-2 and/or the layers 6-1, 8-2 of 82. It may also include cases where

In order to form the first layer 5-1.5-2 and the second layer 8-1.6-2 consisting of a monomolecular film or a monomolecular cumulative film having such a configuration, highly ordered molecular orientation and The so-called single molecule accumulation method, which enables alignment and easily forms an ultra-thin film, can be suitably applied.

This single molecule accumulation method is based on the following principle. In other words, for example, in a molecule that has a lignophilic part and a hydrophobic part in the molecule, when the balance between the two (amphiphilic balance) is maintained appropriately, many of these molecules will be on the water surface. Form a monomolecular layer with the woody part 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 area A per molecule and the surface pressure ■; nA = kT.
(k: Portzmann's constant, T: absolute temperature), and these molecules form a "gas film", but when A is made sufficiently small, intermolecular interactions become stronger, and these molecules form a "condensed film" of a two-dimensional solid (or solid membrane) forms a membrane. This condensed film can be transferred to the surface of a substrate such as glass, and an ultra-thin monomolecular film or a cumulative film thereof can be formed on the 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, the first EL element of the present invention
By making the interface between the first layer and the second layer an interface formed by a monomolecular film, the functional portion consisting of compound molecules directly involved in exciplex formation contained in the first layer and the second layer is transferred to the first layer. It becomes possible to arrange the layer at high density at the interface between the layer and the second layer.

Various solutions can be used as the solution for forming a single molecule in this single molecule accumulation method, and depending on the solution used, a single molecule having a well-balanced portion with different affinity for the solution can be used. A monomolecular film can be formed by appropriately selecting a film-forming compound. 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, ED-a, and EA-d compounds, or any of these compounds as a functional moiety. Among such compounds, there are monolayer-forming compounds.For example, taking a monolayer-forming compound that has one functional moiety, the molecule shown in Figure 2 depends on the position of the functional moiety within the molecule. As shown in the schematic diagram of the structure, (a) the functional part 21 is on the hydrophilic part 22 side, - Figure 2 (a) (b) the functional part 21 is on the hydrophobic part 23#, - Figure 2 (b) (C) The functional part 21 is a hydrophobic part 23 and a woody part 22
- It is broadly classified into the three types shown in Figure 2 (c).

The constituent elements of the wood-loving portion 22 of these compounds are:
For example, carboxyl groups and their metal salts, amine salts and esters, sulfonic acid 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, oximino group, diazonium group, guanidine group, hydrazine group, phosphoric acid group, silicic acid group, aluminic acid group, etc. Each of the above may be used singly or in combination. It can constitute the woody part 22 in the compound.

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 hydrophobic groups such as chain polycyclic phenyl groups such as biphecol. They can constitute the hydrophobic moiety 23 in the above compound either alone or in combination.

On the other hand, the ED compound contained in the monomolecular film at the interface 7-1.7-2 (the part where light emission mainly occurs) between the first layer and the second layer of the light emitting layer of the EL element of the present invention. The orientation and arrangement of the EA compound are shown in the schematic partial cross-sectional view near the interface 7-1 in Figures 3a and 3b (in this figure, the first layer and the second layer are each composed of ED or EA compound molecules). It is formed from a monomolecular film containing a compound molecule having one functional moiety, and the illustration of the functional moiety is omitted for molecules having a functional moiety consisting of an ED-a compound molecule 35 and an EA-d compound molecule 34. As shown in (1) the (E
A hydrophilic portion 32 having a functional portion 31 (consisting of compound A) and a hydrophilic portion 32 having a functional portion 31 (composed of compound A), and (
Is the interface between the functional part 31' (composed of an ED compound) and the wood-loving part 32'? -1 orientation.

201 Figure 3a (a) (2) (E) of the molecules forming the monomolecular film of the first layer 5-1
A hydrophobic part 33 having a functional part 31 (consisting of compound A) and a hydrophobic part 33 having a functional part 31 (composed of compound A), and
A hydrophobic part 33' having a functional part 31' (composed of an ED compound) is oriented at the interface 7-1.

(3) (E) of the molecules forming the monomolecular film of the first layer 5-1
A hydrophobic part 33 having a functional part 31 (consisting of compound A) and a hydrophobic part 33 having a functional part 31 (composed of compound A), and
A wood-loving portion 32' having a functional portion 31' (composed of an ED compound) is oriented at the interface 7-1.

(4) The (E) of the molecules forming the monolayer of the first layer 5-1
The wood-loving portion 32 having the functional portion 31 (consisting of compound A) and the molecule forming the monomolecular film of the second layer 6-1 (
A hydrophobic part 33' having a functional part 33' (composed of an ED compound) is oriented at the interface 7-1.

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

In order to form such a pattern at the interface of the light-emitting layer, for monolayer-forming compounds containing the above-mentioned EA or ED compound molecules as a functional moiety, type a
Compounds belonging to and b are preferably used. 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 and the second layer, and to form the above-mentioned interface pattern (2), It is preferable to use compounds belonging to the above type b for the first layer and the second layer. Furthermore, in order to form the above-mentioned interface pattern (3), it is preferable to use a compound belonging to the above-mentioned type a in the first layer and a compound belonging to the above-mentioned type b in the second layer, and form the above-mentioned interface pattern (3). In order to form 4), it is preferable to use a compound belonging to the above type b in the first layer and a compound belonging to the above type a in the second layer.

ED-a compound molecule 35 or E, not shown
The type of molecule having a functional moiety consisting of the A-d compound molecule 34 is selected from the types a-C of the monolayer-forming compound mentioned above, and the interface patterns (1) to (
A suitable type may be appropriately selected depending on the ED or EA compound used in step 4).

In the example explained above, the first layer and the second layer are formed from a monomolecular film, but the first layer 5-1.5-
2 and/or the second layer 8-1.6-2 is composed of a medium molecule cumulative film, so that the interface between the first layer and the second layer takes the above pattern. A monomolecular film forming the interface 7-1, 7-2 between the first layer and the second layer may be formed.

Note that the first layer 5-1.5-2 and/or the second layer 6
-1.6-2 is composed of a monomolecular cumulative film, each of the monomolecular films constituting the cumulative film may be the same, and one or more of the monomolecular films may be different from other monomolecular films. It may be different from a monomolecular film. Furthermore, the structure based on the orientation state of the molecules forming each monolayer of the monomolecular cumulative film is the so-called Y type (between each film, there is a hydrophilic part and a lignophilic part, or a hydrophobic part and a hydrophobic part). structure in which the two faces each other),
Various structures can be used, such as an x-type (a structure in which the hydrophobic part faces the substrate side of each part), a Z-shape (a structure in which the hydrophilic part faces the board side of each part), and variations thereof. . 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, and E as a subcomponent.
1 of the compounds having A-d compound molecule as a functional moiety
A multi-component monomolecular film containing one or more kinds of compounds other than the above species may be used, and the same applies to the second layer. In such cases, other compounds that do not have a functional moiety but can control the electrochemical properties of the emissive layer through interaction with compounds that do have a functional moiety; Compounds that can increase the strength of the constituent monomolecular layer and improve the adhesion between each layer can be mentioned.

The structure of the monomolecular film or monomolecular cumulative film as described above is determined depending on the desired electrochemical properties of the first layer or the second layer, that is, the formation of the first layer or the second layer. It may be selected as appropriate depending on the compound or the combination of compounds. For example, monolayer films made of compounds belonging to types a, b, or C of the monolayer-forming compounds may be combined and accumulated in the planar direction of the monolayer film. It is possible to control the potential curve of π electrons in the vertical direction, etc.

The above first layer 5-1.5-2 and the second layer! 1-1.
Compounds that can be used to form 6-2 include the above-mentioned compounds that can form a functional moiety, or compounds that have one or more of these compounds, and which have a hydrophilic moiety and a hydrophobic moiety. Compounds that have a well-balanced number of functional moieties can be used as they are for forming a monomolecular film, and those that do not have a hydrophilic group and/or a hydrophobic group as mentioned above newly introduced into the molecule. It can be used as a compound for forming a monomolecular film. 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 tree groups listed above, but when both of these exist in one molecule, even if one of them is the parent tree 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゜15゜19, 20゜21, 22, (G!H
z) nX 6≦n≦20 23゜9I (3 M=H2, Be, Mg, Ca, cd, SrA, lC1,
YbC1 32゜M=Er, Sm, Eu, Gd, Tb, Dy, Tm, Yb
34゜M=Er, Sm, Eu, Gd, Tb, Dy, Tm, Yb
M-Er, Sm, Eu, Gd, Tb, Dy, Tm, Yb
R+ -H+ -CH3+-CF3+ gyu36,
37. 3B.

39, 40°43.
44゜■
(42) Based on the formation of a complex, a compound having an EL function is modified with a hydrophobic group and/or a parent tree group to form a monolayer-forming compound.

The compounds having the structural formulas 42 to 54 and A111L85 to 8B have a structure in which an alkyl chain is directly bonded to a functional moiety. It may be a bond, a bond via a carbonyl group, or the like.

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 4-2 has the function of confining the movement of electrons within a necessary minimum area and emitting light by efficiently transferring and receiving electrons. As for the material that can form these third layers, the general formula that can form an accurate and uniform insulating layer is: % formula %): 3 (In the above formula, n is 1o≦n≦ 30 and X
is -COQH, -CONH2, -GOOR, -N” (
CH3)3' CI-.

etc.), and using one or more of these materials, vapor deposition method, CVD method, etc. can be mentioned.
This third layer can be formed by a thin film forming method such as a method.

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 above structure varies depending on the number of interfaces the EL device has and the structure of each layer itself, but for the first layer,
500A or less, preferably 200A or less, for the second layer, 500A or less, preferably 200A or less, and for the third layer, 300A or less, preferably 100A
Hereinafter, the thickness of the entire light-emitting layer is desirably less than IILll, preferably less than 3000m, in order to obtain a good light-emitting state even in low-voltage driving.

At least one of the two electrode layers 1.2 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, insium tin oxide (IV, 0), etc. are laminated by vapor deposition on a film or sheet such as polyester, or a transparent substrate such as a glass plate, or these materials are directly applied to the light emitting layer. It can be formed by laminating.

In addition, the non-transparent electrode layer may be a thin plate made of a material that can form an ordinary electrode with sufficient conductivity, or may be formed by directly applying AI to a suitable substrate or a light emitting layer formed thereon.
, Ag, Au, etc. can be laminated by a vapor deposition method or the like.

The H height of these electrode layers is about 0.01 g to 0.3 u, preferably about 0.05 IL11 to 0.2 tiles.

Note that the shape and size of the EL element of the present invention can be made into various shapes as desired. For example, when forming a transparent electrode, the substrate is used as a substrate for forming a light emitting layer, and this substrate may be shaped like a plate, a belt, etc. 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.

By applying direct current, alternating current, or pulse voltage so that an electric field of about 1×10 5 to 3×10 6 is applied to the light emitting layer 3 , good light emission can be obtained from the light emitting layer 3 through the transparent electrode.

Below, typical operations of the single-molecule accumulation method represented by the Langmuir-Prodgett method (CLB method) applied to the formation of the first layer and second layer of the light-emitting layer of the EL device of the present invention will be explained. do.

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 a suitable solvent is spread in the aqueous phase, and this compound is deposited in the form of a film on the surface of the aqueous phase. At this time, in order to prevent the precipitates from freely diffusing on the water phase and spreading too much, a partition plate (or float) is provided to limit the area of development and control the aggregation state of the membrane material.
Obtain a surface pressure (■) proportional to the aggregate state. Then, the partition plate is activated 7 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 n, the middle molecules are moved each time the substrate moves to one side and downward. The film is transferred onto a substrate to form a monomolecular cumulative film.

To transfer a monomolecular film onto a substrate, in addition to the vertical dipping method described above, there are also horizontal adhesion methods in which the water phase surface of the substrate is kept parallel and in contact with it horizontally, and a cylindrical substrate is rotated on the water surface. Various methods can be applied, such as a rotating cylinder method in which a monomolecular film is transferred to the surface of a substrate using a rotating cylinder method, 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. Further, according to the horizontal 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 wood groups and hydrophobic groups can also be changed by surface treatment of the substrate.

Furthermore, the pH of the aqueous phase when forming the first layer and the second layer of the light emitting layer of the EL device of the present invention by the single molecule accumulation method.
1. Operation conditions such as the type and amount of additives for adjusting the pH of the aqueous phase, the temperature of the aqueous phase, the rate of raising and lowering the substrate, or the surface pressure 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 having a desired structure is formed by vapor deposition or the like using the third layer forming material described above on the substrate on which the transparent electrode layer described above is provided. 1
A first layer consisting of a monomolecular film or a medium-molecular cumulative film having a desired configuration using a material capable of forming the second layer, and a third layer formed by forming the second layer in this order first. Layer upon layer.

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, a metal such as AI, Ag, or Au can be laminated on this $3 layer by a vapor deposition method or the like to form the EL element of the present invention.

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 7.0 may be laminated by a vapor deposition method or the like. In addition, when the two electrodes are both transparent, a transparent electrode layer may be formed using the above-mentioned material on a transparent substrate for forming a light emitting layer, and the transparent electrode layer may be laminated after the formation of the light emitting layer is completed.

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 different from each other. The structure of the first layer may be different from that of other first layers. This is the second
The same applies to the layer and the third layer. Furthermore, 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, it is desirable that the EL element of the present invention be provided with a protective 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 having different electrochemical properties, and has a structure in which a plurality of such interfaces are provided in the light extraction direction of the EL device. The amount of light emitted per unit of the light extraction surface is greatly increased compared to conventional EL elements.

Furthermore, in the EL device of the Wood invention, for multiple interfaces that mainly emit light, the composition of the two layers constituting the interface is changed for each interface, and these are combined to produce one emitted color as desired. It is now possible to control the

In addition, the first layer constituting the light emitting layer of the EL device of the wooden invention
The layer and the second layer are composed of a monomolecular film or a monomolecular cumulative film, and although they have a multilayer structure with multiple interfaces that emit light as described above, the overall layer thickness of the light emitting layer is The LED has become thinner, and even when driven at a low voltage, efficient light emitting conditions can be obtained, and sufficient brightness can be obtained.

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.
layer and the second layer are 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 parts of the compound directly involved in light emission are oriented and arranged toward the interface with high precision. On the other hand, since the light-emitting layer contains a compound that can serve as an electron acceptor 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, the first layer and the second layer can be formed at almost normal temperature and pressure, and heat-sensitive organic compounds that could not be used in conventional vapor deposition methods can also be used as constituent materials. The EL element of the present invention is an inexpensive and mass-producible EL element.
It became an L element.

Furthermore, even when the EL device of the present invention is formed as a large-area EL device, the light-emitting layer is formed with high accuracy, and it has good functionality even as a large-area EL device.

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

Example 5 A 1.7.0 layer with a thickness of 1500 Å was formed on a glass surface of 11 square meters by a sputtering method to obtain a transparent electrode plate.

This electrode plate was set at a predetermined position in the vapor deposition tank of the resistance heating vapor deposition apparatus, and methyl stearate (sp, 38°C) was put into the resistance heating port, and the inside of the tank was heated to 10' T.
After reducing the pressure to the vacuum degree of orr, the deposition rate was 2J/se.
Adjust the current flowing through the resistance heating port so that c.
A third deposited layer consisting of 200 methyl stearate layers
was formed as a layer on the transparent electrode layer of the electrode plate. In addition, the degree of vacuum in the tank during settling is 9 x 1O-6To
In rr, the temperature of the substrate holder was set to 20°C.

The electrode plate was made by Joyce-1, Oebe1, I, a.
4X 10'4 in ngmuir-Trough 4
mol/! By containing CaCl2, the pH is 6.
．． It was immersed in an aqueous phase adjusted to 5.

Next, 0.5 mjl of a solution in which these were dissolved in chloroform at a ratio of 50 mol: 50 mol: 1 mol such that the total amount was 1 x 1θ-3111 ol/l was developed on the aqueous phase, and the surface pressure was adjusted to 3Qdyne/l. cm, and after depositing a multicomponent monomolecular film consisting of the three compounds mentioned above on the surface of the aqueous phase, the electrode plate was gently moved up and down twice at a speed of 2 cm/min in the direction across the water surface.
A monomolecular cumulative film as a second layer consisting of four monomolecular films made of a mixture of the above compounds was formed on the previously formed third layer. Here, this electrode plate is pulled out of the water phase and 3
It was left to dry at room temperature for 0 minutes or more.

Furthermore, the above compound left on the surface of the aqueous phase was completely removed, the electrode plate was immersed in the aqueous phase, and a new ((N'(2)e)
0.5 mj! of a solution of C0NT (2) dissolved in chloroform at a ratio of 100 mol: 1 mo+ so that the total amount was IX to -3 mol/A was developed on this aqueous phase, and the surface pressure was adjusted to 30 dyne/A. am, a monomolecular film formed of the above compound was deposited on the aqueous phase, and the electrode plate was gently moved up and down twice at a speed of 2 cm/ff1 inch in the direction across the water surface to separate the molecules of the above compound. A monomolecular cumulative film obtained by stacking four monomolecular films was formed as a first layer on the previously formed second layer.

Thereafter, the above-described formation operation from the third layer to the first layer is repeated four times, and finally the third layer is laminated to form the first layer and the second layer.
A light-emitting layer having four layer interfaces (layer thickness: approximately 170OA)
was formed.

The electrode plate on which the luminescent layer was formed in this way was placed in a vapor deposition tank, and the pressure inside the tank was first reduced to a vacuum level of 10' Torr, and then the vacuum level was further adjusted to 10'5 Torr.
At a deposition rate of 2 QA/see, an A1 layer of 1500 A 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 was sealed with a sealing glass 41, and then silicone oil 42, which had been purified, degassed, and dehydrated according to a conventional method, was injected into the seal to form an EL nacelle 3.

Such an EL nacelle electrode 44.454. :, IOV
, applied an alternating current voltage of 400 Hz to emit light, and measured the luminance and current density of the emitted light. At a current density of 0.0 OmA/cm 2, the luminance was 19.2 F.
t-L There was te.

[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, 3a.
Figures 3 and 3b are schematic diagrams showing typical examples of the arrangement of molecules at the interface between the first layer and the second layer of the EL device of the present invention, and Figure 4 is a schematic diagram showing a typical arrangement of molecules at the interface between the first layer and the second layer of the EL device of the present invention. FIG. 2 is a schematic cross-sectional view of an EL nacelle. 1.44: Transparent electrode layer 2.45: Electrode layer 3: Light emitting layer 4-1.4-2.4-3 = third layer 5-t, 5-2.5-3: first layer 8 -1.8-: L, 8-3: Second layer? -1.7-2: Interface 21.31.31': Functional part 22.32.32': Wood-loving part 23, 33.33': Hydrophobic part 34: EA-d compound as a functional part Compound molecule having 35: Compound molecule having ED-a compound as a functional part 40: EL element 41 Nigarasu seal 42: Silicone oil 43: EL nacelle 5 Figure 1 Figure 2 Figure Box 3a Figure 3b

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 contains an organic compound that relatively exhibits electron-accepting properties. a first layer, a second layer containing an organic compound relatively exhibiting electron-donating properties, and a third layer having electrically insulating properties; Another compound that can serve as an electron donor for the organic compound that exhibits acceptability is contained, and the second layer contains another compound that can serve as an electron acceptor for the organic compound that relatively exhibits electron donor properties. are formed on the third layer from one of the electrode layers to the other,
The first layer, the second layer, and the third layer are stacked in this order twice or more, and the first layer and the second layer can further form each of these layers. An electroluminescent device comprising a monomolecular film or a cumulative monomolecular film of a compound.