JPS6137874A - Electroluminescent element - Google Patents

Abstract

PURPOSE:To provide the titled element having a high luminescence efficacy even by low voltage drive, by providing a luminous layer in which a layer of an electron-accepting org. compd. and the like, a layer of an electron-donating org. compd. and the like, and an insulating layer are laminated at least two-folds between two transparent electrode layers. CONSTITUTION:Between electrode layers 1, 2 with a thickness of 0.01-0.3mum at least one of which is transparent, the first layer with a thickness of 300Angstrom or less comprising a monomolecular (cumulative) film of a relatively electron-accepting org. compd. and any other compd. capable of serving as an electron acceptor thereto 5-1, 5-2, the second layer with a thickness of 300Angstrom or less comprising a monomolecular (cumulative) film of a relatively electron-donating org. compd. and any other compd. capable of serving as an electron donor thereto 6-1, 6-2, and the third layer with a thickness of 300Angstrom or less comprising a monomolecular (cumulative) film of an insulating compd. 4-1-4-3 are laminated at least two- folds in the order of the third layer 4-1, the first layer 5-1, the second layer 6-1, the third layer 4-2, etc. to form a luminous layer 3 with a thickness of 1mum or less.

Description

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

Specifically, the present invention relates to an EL element that has a layer with an EL function 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. .

[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, as a material having the above-mentioned EL function, N
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 two thin light-emitting layers, allowing the distance between the electrodes to be sufficiently shortened, generating a stronger electric field within the light-emitting layer, and improving brightness even when driven at low voltage. 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, an improved powder type EL element was developed in which an intermediate dielectric layer made of a polynylidene heptafide polymer was provided in the light emitting layer of the powder type EL element. 58-
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. As a material for electroluminescence, it is attracting attention to be applied to electrochromic elements, piezoelectric elements, pyroelectric elements, nonlinear optical elements 1 ferroelectric liquid crystal, etc. Furthermore, EL elements of these materials can be used to form a light-emitting layer in advance. There are high expectations for its application 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 monomolecular cumulative films of these materials are used as the light-emitting layer. A carrier injection EL type device 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 A first compound containing an organic compound exhibiting electron-accepting properties.
a second layer containing an organic compound relatively exhibiting electron-donating properties, and a third layer having electrically insulating properties; , and the second layer contains another compound that can serve as an electron donor for the organic compound that relatively exhibits electron donating properties. The first layer, the second layer and the third layer are repeated two or more times in this order on the third layer from one of the electrode layers to the other. The first layer, the second layer and the third layer are composed of a monomolecular film or a monomolecular cumulative film of a compound capable of forming each of these layers. shall be.

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 referred to as EII-d compounds) that can form 4 electrons with respect to the compound are arranged around the compound D, and when these compounds are placed in an electric field, Due to the interaction between.

Among them, the main light emitting source is a light emission effect based on the formation of an exciplex accompanying the transfer of electrons between the above-mentioned EI) compound and the EA compound, and furthermore, such an exciplex can efficiently emit light with the generation of an electric field. It is characterized by having a structure suitable for being formed.

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.

2 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 6-1.8-2 and the third layer 4-2 are alternately stacked, and each layer is made of a compound that can form the respective layer. It is formed from a monomolecular film 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 6-1, 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 B-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
The relationship between
-2 is uniquely formed.

These interfaces? -1, 7-2, when a voltage is applied to the electrodes l 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, one 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, in the second layer e-t, 6-2, FD-
d compound is mixed, and this HD-d compound also mainly has the function of increasing the electric field excitation efficiency of the ED compound by interacting with the ED compound such as donating electrons to the ED compound. .

The ED-d and EA-a compounds described above 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 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. EA-a that can be an electron acceptor
The compound is contained as a subcomponent, and the second layer 8-1.
6-2 contains as a subcomponent an EII-d compound that can serve as an electron donor to the ED compound that is the main component of these layers.

As for the arrangement in the light-emitting layer 3 of the compound molecules that are included as main components in the first layer and the second layer and are directly involved in the formation of the electric field excited complex, the following combinations are typical. It can be mentioned as follows.

(a) First layer 5-1.5-2 and second layer 6-1.8-
Compound molecules having an EL mechanism (mainly emitting light) based on exciplex formation are arranged in each of 2.

(b) First layer 5-! , 5-2 based on exciplex formation <
Compound molecules having an EL function are arranged, and compound (ED compound) molecules that can serve as electron donors for these compound molecules are arranged in the second layer 13-1.6-2.

(C) Based on exciplex formation in the second layer 6-1.6-2<
ELI! A compound (EA compound) in which compound molecules having the ability are arranged and can act as an electron acceptor for these compounds.
Molecules are respectively arranged in the first layer 5-1, 5-2.

As the compound having the EL function based on the formation of an exciplex, 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, benzophenones, phthalocyanines, metal complexes of phthalocyanines, 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. are selected and combined as appropriate to form the structure of the first layer and second layer* (a
) can be formed using the single molecule accumulation method described later.

Further, as compounds that can serve as electron acceptors or electron donors for compounds having an EL function based on exciplex formation, examples include heterocyclic compounds other than the above-mentioned compounds, derivatives thereof, aromatic amines, and aromatic amines. Group polyamines, compounds having a quinone structure, tetracyanoquinodimethane, tetracyanoethylene, etc. can be mentioned, and the above-mentioned compounds and these compounds can be appropriately selected and combined to form the first layer and the first layer. 2 layer configuration (b) or (
A light emitting layer having C) can be formed.

Furthermore, EA which is the main component of the first layer contained in the first layer
an FA-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 (emit light), compounds that can act as electron donors or acceptors for the compound, compounds that can become a light emitter through transfer of excitation energy, and compounds that have at least one of these compound molecules as a functional moiety. be able to. When forming the first layer and the second layer, depending on the compound used as the main component of the first layer and the second layer, these F
The A-a and ED-d compounds may be appropriately selected and used so as to have the above-mentioned functions. Amount of EA-a compound relative to EA compound and ED-d relative to ED compound
The amount of compound will vary depending on the compounds used in the first layer and the second layer - cannot be generally specified, but typically EA
-a compound: 10 mol% to 0.0% of the EA compound.
For the ED-d compound, it is about 10 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 light emission is not limited to only at the interface 7-1.7-2 between the layer 5-1.5-2 and the second layer 8-1. , 6-2 may also include a case where light is emitted.

In order to form the first layer 5-1.5-2 and the second layer e-t, 6-2 consisting of a monomolecular film or a monomolecular cumulative film having such a configuration, highly ordered molecular orientation and This allows for easy formation of ultra-thin film layers. A so-called single molecule accumulation method 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 hydrophilic part and a hydrophobic part, when the balance between the two (amphiphilic balance) is maintained at an appropriate level, many of these molecules have a hydrophilic part and a hydrophobic part on the water surface. Form a monolayer 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 constant, T: absolute temperature) holds,
These molecules form a "gas film", but when A is made sufficiently small, the intermolecular interaction becomes stronger and these molecules form a two-dimensional solid "condensation film (or solid film)".This condensation film is made of glass, etc. It can be transferred onto the surface of a substrate, 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 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 ED, EA,
, FD-d and FA-a compounds, or a compound having at least one of these compounds as a functional moiety. Among such compounds, monolayer-forming compounds have, for example, monolayer-forming compounds that have one functional moiety. As shown in the schematic diagram of the structure, (a) the functional part 21 is on the side of the hydrophilic part 22, - 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 a hydrophobic part 23 and a woody part 22
- It is broadly classified into the three types shown in Figure 2 (e).

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, amide groups, imino groups,
Examples include hydroxyl group, quaternary amino group, oxyamino group, oximino 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 tree-friendly portion 22 inside can be constructed.

Further, as the constituent elements of the hydrophobic portion 23, linear or branched alkyl groups, vinylene, vinylidene,
Hydrophobic groups such as olefinic hydrocarbons such as acetylene, synthetic polycyclic phenyl groups such as phenyl, naphthyl, and anthranyl, and chain polycyclic phenyl groups such as biphenyl can be mentioned, and each of these groups can also be used individually. Alternatively, they can be combined to constitute the hydrophobic portion 23 in the upper compound.

On the other hand, the ED compound contained in the middle molecular 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. What is the orientation and arrangement of the EA compound at the interface in Figures 3a and 3b? - Schematic partial cross-sectional view near 1 (in this figure, the first layer and the second layer are each formed from a monomolecular film containing a compound molecule having one functional part consisting of an ED or EA compound molecule) As shown in (1) the first layer 5- (E) of the molecules contained in the monolayer of 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 wood-loving portion 32' having a functional portion 31' (composed of an ED compound) is oriented at the interface 7-1.

- Figure 3a (a) (2) (E
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
The hydrophobic part 33' having the functional part 31' (consisting of an ED compound) is an interface? -1 orientation.

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

(4) The (E) of the molecules forming the monolayer of the first layer 5-1
A wood-loving part 32 having a functional part 31 (consisting of Compound A), and a (
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 compounds belonging to the above-mentioned type a in the first layer and the second layer, and to form the bipedal interface pattern (2). It is preferable to use a compound belonging to the above type b in 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). 0, 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.

In addition, ED-d compound molecule 35 or F
As the type of molecule having a functional moiety consisting of the A-a compound molecule 34, the above 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 described below, 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 6-1.6-2 is composed of a medium molecule cumulative film, so that the interface between the first layer and the second layer takes the above pattern. , the first layer and the second
What is necessary is to form a middle molecular film constituting the interface 7-1, 7-2 of the layer.

Note that the first layer 5-1.5-2 and/or the second layer 6
-1.6-2 consists 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 It may be different from other monolayers. Furthermore, the structure based on the orientation state of the molecules forming each middle molecular film of the monomolecular cumulative film is a so-called Y-type structure (between each film, a hydrophilic part and a lignophilic part or a hydrophobic part and a hydrophobic part are formed). structures facing each other),
Various structures can be used, such as an x-type (a structure in which the hydrophobic portion of each layer faces the substrate side), a z-type (a structure in which the hydrophilic portion of each layer faces the substrate side), and modified structures 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 an A-a 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.1 For example, monomolecular films made of compounds belonging to types a, b, or C of the monomolecular film-forming compounds are combined and accumulated in the planar direction of the middle molecular 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 second layer 8-1.6
Compounds that can be used to form -2 include the above-mentioned compounds capable of forming a functional moiety, or compounds containing one or more of these compounds:
Compounds that have a well-balanced lignophilic part and hydrophobic part can be used as they are for forming a monomolecular film,
If this is not the case, a parent tree group and/or a hydrophobic group such as those mentioned above can be newly introduced into the molecule to form 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 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 78゜21, 22゜(OH2)
nX 6≦n≦20 23°CH3 24°O≦n≦2 25°28°M==H2, Ee, Mf, G! a, Cd, 5rAICI
, Yb07 M=Br, Sm, Eu, Gd, Tb, Dy, Tm, Yb
◎＠, -CH3, -t-Bu 84°M=Er, Sm+Eu+Gd, 'I'b, D! /+Tm
, YbM-Er, Sm, Eu, Gd, 'I”b, Dyl
'l'mlybR+ -H, -0T(3, OFs +
C86, 37, 3B.

39.410° 41-　　　　　　　　Country.

4.3. 44.54+,
55°56,
H57, H I3 fI RR 65, 66゜6g, 70゜OR 71, 72・77, 78゜84
, 85・U (CH2) n A compound having an EL function is modified with a hydrophobic group and/or a parent group to form a monolayer-forming compound.

In addition, the compounds of the structural formulas M642 to 酅54 and N685 to Sho8B have a structure in which an alkyl chain is directly bonded to a functional moiety, but the bond of the alkyl chain to the functional moiety is, for example, an ether bond. , a bond via a carbonyl group, etc. may be used.

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 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 XL
J: -COOH, -CONH2, -GOOR, -N
”(CH3)3 ・CI-.

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. Furthermore, the monomolecular film forming the third layer may be a monomolecular film made of one type of compound.

Further, a multi-component monomolecular film composed of two or more kinds of compounds may be used.

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.

For the first layer, 300 A or less, preferably 10
0A or less, for the second layer, 300A or less, preferably 100A or less, for the third layer, 300A or less, preferably too A or less, and furthermore, the layer thickness of the entire light emitting layer is lμs or less, preferably It is desirable that the current be 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, insium tin oxide (1,'r,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 used as a light emitting layer. 3. It can be formed by directly laminating it.

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 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 thickness of these electrode layers is about 0.01g to 0.34a,
Preferably it is about 0.053LII to 0.2μ.

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 monomolecular film, and this substrate may be in the form of a plate, a belt, etc. A desired shape and size can be obtained by using a cylindrical shape or 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, 1xt in the light emitting layer 3.
By applying direct current, alternating current, or pulse voltage so that an electric field of about os to 3 x 10 G is applied, good light emission can be obtained from the light emitting layer 3 through the transparent electrode.

Hereinafter, Langmu 7 applied to the formation of the light emitting layer of the present invention will be described.
#A typical operation of the single molecule accumulation method represented by the project method (LB method) will be explained.

An aqueous phase for forming a monomolecular film is provided in a water bath, and a clean substrate is immersed in the aqueous phase.Next, a predetermined amount of a solution of the compound for forming a monomolecular film dissolved or dispersed in an appropriate solvent is added. is developed in the aqueous phase, and this compound is deposited in the form of a film on the surface of the aqueous phase. In this poem, in order to prevent this precipitate from freely diffusing on the water phase and spreading too much, a partition plate (or float) is provided to limit the development area and control the aggregation state of the membrane material.
Obtain a surface pressure (■) proportional to the aggregate state. Then, the partition plate is operated to reduce the developed area and gradually increase the surface pressure n 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 monomolecular film is formed as the substrate moves upward and downward. is transferred onto the substrate to form a monomolecular cumulative film.

To transfer a monomolecular film onto a substrate, in addition to the vertical immersion method mentioned above, there are also horizontal attachment methods in which the substrate is brought into contact with the water phase horizontally while keeping it parallel to the surface, 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 light-emitting layer of the EL device of the present invention by the single molecule accumulation method, the type and amount of additives for adjusting the pH of the aqueous phase, the temperature of the aqueous phase, and the raising and lowering of the substrate. Operating conditions such as speed and surface pressure may be appropriately selected depending on the type of monomolecular film-forming compound used, the characteristics of the film to be formed, and the like.

By the single molecule accumulation method as described above, the light emitting layer of the present invention can be formed, for example, in the following manner.

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, a first layer and a second layer consisting of a monomolecular film or a monomolecular cumulative film having a desired configuration are formed in this order using a material capable of forming the first layer and second layer described above. Laminated on the previously formed third layer.

Further, a third layer is laminated on the second layer-L to form the desired first layer.
This operation of forming the first layer to the third layer is repeated two or more times depending on the number of interfaces between the layer and the second layer.

Finally, the EL element of the present invention can be formed by laminating a metal such as AI, Ag, or Au on this third layer 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 initial monolayer formation, 1. Materials for forming transparent electrode layers such as T and Q may be laminated by vapor deposition or the like.

In addition, if the two electrodes are both transparent, the transparent electrode layer may be formed using the above-mentioned material on the transparent substrate for monomolecular film formation, 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. 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, 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 element of the present invention, the composition of the two layers constituting the interfaces is changed for each interface, and these are combined to produce a desired luminescent color at multiple interfaces that mainly emit light. It is now possible to control accordingly.

In addition, although the light-emitting layer of the EL element of the present invention is composed of a plurality of monomolecular films and has a multilayer structure with a plurality of interfaces that emit light as described above, the entire light-emitting layer is The thickness is extremely thin, and efficient light emission can be achieved even when driven at low voltage.

Sufficient brightness could be obtained.

Moreover, in the EL device of the present invention, each layer of the light emitting layer is formed of a monomolecular film, so the functional parts of the compound directly involved in light emission are directed toward the interface with high order and precision. The light-emitting layer contains a compound that can act as an electron acceptor and a compound that can act as an electron donor for compounds that are oriented and arranged and are directly involved in light emission, resulting in more efficient transfer of electrons. Light emission based on the formation of exciplexes has become possible.

In addition, each layer can be formed at almost normal temperature and pressure,
Heat-sensitive organic compounds, which conventionally could not be used in vapor deposition methods, can also be used as constituent materials, and the EL device of the present invention has become an inexpensive and mass-producible EL device.

Furthermore, even when the EL device of the present invention is formed as a large-area EL device, the light-emitting layer is formed as a thin film with high precision by the single-molecule accumulation method, and it has good functionality even as a large-area EL device. It became a thing.

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

Example 1 A layer of 1.T, 0 of IA was formed on a 50 mm square glass surface with a thickness of 15 (1.T, 0) by sputtering to form a transparent electrode plate. 4, 4X I
It was immersed in an aqueous phase whose pH was adjusted to 6.5 by containing Q''Imol// of CdCl2.

Next, alaxic acid was dissolved in chloroform lXl0-3f
0.5 ml of solution dissolved at a concentration of flo l/I
was developed in the aqueous phase-1-. After evaporating chloroform from the surface of the aqueous phase, the surface pressure of the aqueous phase was reduced to 3θdyne/
cm, and a film of araxic 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 2cm/1n across the water surface to form a medium molecular film made of alaxic acid molecules on the electrode layer of the electrode plate, and this was then removed from the water. It was taken out of the phase and left to dry at room temperature for 30 minutes or more. This operation was repeated once to form an insulating layer in which two layers of alaxic acid medium molecular film were accumulated as the third layer.

Here, the araxic acid remaining on the surface of the aqueous phase was completely removed from the surface of the aqueous phase, and 10 mol of chloroform was newly added.
: At a ratio of 1 mol, the total amount of these is 1 × 10'
mol/j! 0.5 of the solution dissolved to a concentration of
m7 is developed in this aqueous phase-L, and the surface pressure is set to 30 dyne.
/cI was adjusted to 11, and the electrode plate on which the insulating layer made of 7-rachidic acid was formed was again gently immersed in the aqueous phase at a speed of 2 cm/sin in the direction across the water surface of the aqueous phase. A middle molecular film consisting of two types of compound molecules is first
was formed on the insulating layer as a layer. Next, this electrode plate was taken out of the aqueous phase and left to dry again at room temperature for 30 minutes or more.

Furthermore, the above compounds remaining on the surface of the aqueous phase were completely removed, and 0.0% of the solution was newly dissolved in chloroform at a ratio of 100 nol: 1 mol so that the total amount of these compounds was at a concentration of lXl0'mol/I. 5 ml was spread on this aqueous phase and the surface pressure was adjusted to 30 dyne/clIl.
By repeating the layer forming operation, a monomolecular film consisting of the above two types of compounds was formed as a second layer on the previously formed first layer.

Thereafter, the above-described formation operation from the third layer to the second layer is repeated five times, and finally the third layer is laminated to form the first layer and the second layer.
A light-emitting layer (layer thickness: approximately 55 OA) having five layer interfaces was formed.

An electrode plate with a light-emitting layer formed in this way.

The tank was placed in a vapor deposition tank, and the pressure inside the tank was first reduced to a vacuum level of 10' Tart, and then the vacuum level was further adjusted to 10' Tart.
One layer was deposited on the last formed third layer to form an EL element of the present invention as a back electrode. This EL element
As shown in the figure, after sealing with a sealing glass 41, silicone oil 42 that had been purified, degassed, and dehydrated according to a conventional method was injected into the seal to form an EL nacelle 3.

(7) EL nacelle electrode 44.45, 5V, 40
An alternating current voltage of 0 Hz was applied to emit light, and the brightness and current density in one emitted light were measured. The results are shown in Table 1.

Examples 2 to 4 The formation operation from the third layer to the second layer was performed 7 times (Example 2
), 9 times (Example 3) or 15 times (Example 4). (Example 3) Or 1
Five (Example 4) EL elements of the present invention were each formed, and further, an EL nacelle was created using these.

Each EL nacelle was made to emit light in the same manner as in Example 1, and the luminance and radio wave density at that time were measured. The results are shown in Table 1.

Example 5 A film with a thickness of 1500A was deposited on a 50mm square glass surface by sputtering. A T and 0 layer was formed to obtain a transparent electrode plate. This electrode plate was manufactured by Joyce-Loebe1.
4X 10″ in ngmuir-Trough 4
It was immersed in an aqueous phase whose pH was adjusted to 6.5 by containing Imol// of GdC12.

Next, IXIO = mo
l/j! 0.5 mjl of the solution dissolved at a concentration of was developed into 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 araxic acid was precipitated on the surface of the aqueous phase.

Furthermore, while keeping the surface pressure constant, the electrode plate was gently pulled across the water surface at a speed of 2 cm/+*in to form a monomolecular film consisting of araxic acid molecules on the electrode layer of the electrode plate. This was then taken out of the aqueous phase and allowed to stand at room temperature for 30 minutes or more to dry. This operation was repeated four more times to form a third layer, an insulating layer consisting of five layers of aracic acid medium molecule cumulative film.

Here, the araxic acid remaining on the surface of the aqueous phase is removed from the surface of the aqueous phase.
Completely remove it from L and newly add 1 piece of chloroform C12H2s at a ratio of 10 mol:1 mol so that the total amount of these is 1 x 10
0 of the solution dissolved to a concentration of -3 mol/l
．． 5 m/ was spread on this aqueous phase, and the surface pressure was increased to 30 dy.
After adjusting to ne/cm, the electrode plate on which the middle molecule cumulative film insulating layer made of araxic acid was formed was gently immersed again in the water phase at a speed of 2 cm/win in the direction across the water surface of the water phase. Then, a third layer, which was a stack of three monomolecular films made of the two types of compound molecules described above, was formed on the previously formed insulating layer. Next, this electrode plate was taken out of the aqueous phase and left to dry again at room temperature for 30 minutes or more.

Furthermore, apart from the aqueous phase used so far, [Eu (BF
A) 4] Prepare an aqueous phase saturated with K, and add 1 layer of chloroform on the surface of this aqueous phase at a ratio of 1 mole to 1 mole, so that the total amount of these is 1 × 10
'mol/j! of the solution dissolved to a concentration of 0.
5mj! was developed and the surface pressure was adjusted to 30 dyne/c■.A monomolecular film consisting of the above two types of compounds was then formed on the previously formed first layer in the same manner as the formation of the first layer. A monomolecular stacked film in which three layers were stacked was formed as the second layer.

Next, a third layer consisting of four monomolecular layers of alexic acid is formed on this second layer according to the method described above, and thereafter - from the first layer to the third layer described above, The formation operation was repeated four times to form a light-emitting layer (layer thickness: approximately ttoo A) having four interfaces between the first layer and the second layer.

An electrode plate with a light-emitting layer formed in this way.

The inside of the tank was first depressurized to a vacuum level of 6 Torr, and then the vacuum level was further adjusted to 10' Torr.
One layer was deposited on the last formed third layer to form an EL element of the present invention as a back electrode. This EL element
As shown in the figure, after sealing with a sealing glass 41, an EL cell 43 was formed by injecting silicone oil 42, which had been purified, degassed, and dehydrated according to a conventional method, into the seal.

For such an EL nacelle electrode 44.45, 10■, 40
An alternating current voltage of 0 Hz was applied to emit one light, and the luminance and current density of the emitted light were measured. The results are shown in Table 1.

Table 1

[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 compound for forming a medium molecular film, 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-f, 5-2.5-3: First layer 6 -1.13-2. [i-3: Second layer? -1.7-2
: Interface 21.31.31': Functional part 22.32.32': Hydrophilic part 23.33.33': Hydrophobic part 34: Compound molecule having EA-a compound as a functional part 35: ED- Compound molecule having d compound as a functional part 40: EL element 41 Nigarasu seal 42: Silicone oil 43: EL cell Fig. 1 Fig. 2 Fig. 3a Fig. 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 acceptor for the organic compound that exhibits acceptability is contained, and the second layer contains another compound that can serve as an electron donor for the organic compound that relatively exhibits electron donating 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 further, the first layer,
An electroluminescent device characterized in that the second layer and the third layer are composed of a monomolecular film or a monomolecular cumulative film of a compound capable of forming each of these layers.