JPS6137866A - Electroluminescent element - Google Patents

Abstract

PURPOSE:To yield an improved luminescence efficacy and high luminance even by low-voltage drive, by a construction wherein two thin films comprising an org. compd. and having electrochemical properties different from each other are combined to yield layers having an EL function, which are laminated to form a luminous layer. CONSTITUTION:A luminous layer 3 comprising a plurality of layers is provided between a transparent electrode 1 and a back electrode 2. In the formation of the luminous layer 3, the third layer comprising a monomolecular (cumulative) film of an insulating compd. 4-1, the first layer comprising a monomolecular (cumulative) film of a mixture of a relatively electron-accepting org. compd. (e.g., of formula I ) and an electron donor (e.g., of formula II) 5-1, and the second layer comprising a monomolecular (cumulative) film of a mixture of a relatively electron-donating org. compd. (e.g., of formula III) and an electron acceptor (e.g., of formula IV) 6-1 are formed successively on the transparent electrode 1. The luminous layer 3 is formed by laminating repeatedly again in this order on the above construction, thus yielding the intended electroluminescent element.

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, in which a filament is heated to emit light, or fluorescent lights, in which an electrically excited gas imparts energy to a phosphor, causing it to emit light, it is thin. Panel-shaped, belt-shaped,
It is attracting attention as it has the potential to realize various shapes such as cylindrical shapes, for example, as a component of display media used to display lamps, lines, diagrams, images, etc., or as a material that can realize light-emitting bodies such as large-area panel lamps. has been done.

There are two types of EL devices: one is an intrinsic EL device that performs field-excited light emission due to the movement of carriers within the light-emitting layer, and the other is an intrinsic EL device 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 structures of actual EL devices and the light-emitting layer of the device, there are two types: a thin-film type that has a thin film made of a material with an EL function as a light-emitting layer, and a light-emitting type formed by dispersing a material with an EL function in a binder. It is broadly classified into two types: a powder type with layers and a powder type with layers.

Note that, as the material having the above-mentioned EL functionality, inorganic metal materials such as ZnS containing Cu, ReF3 (Re represents a rare earth element), etc. as an activator have been mainly used in the past.

Thin-film type EL actual element, the light-emitting layer is formed thinly, the distance between the electrodes can be made sufficiently short, and a stronger electric field is generated within the light-emitting layer, resulting in improved brightness even when driven at low voltage. It has a structure suitable for obtaining high-quality light emission. However, if an actual EL element of this type is manufactured by forming a thin light-emitting layer using a thin film forming method such as vapor deposition using the above-mentioned inorganic metal material mainly consisting of ZnS, the manufacturing cost will be 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 devices.

On the other hand, E
Intrinsic E, in which the above-mentioned ZnS-based EL inorganic material is dispersed in an organic binder to form a light-emitting layer, is used as an L real element.
An L-type organic powder type EL element is known.

However, in this powder-type EL actual device, when the layer thickness is thin, defects such as pinholes are likely to occur in the light-emitting layer. - There is a limit to the structure of thinning the layer, making it impossible to obtain sufficient light emission, especially high brightness, and since the layer thickness is relatively thick, power consumption is high in order to generate a stronger electric field. It had problems such as: 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 vinylidene fluoride polymer was provided in the light emitting layer of this actual powder type EL element.
Although this is known from Japanese Patent 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., and furthermore, it is possible to use these materials to form light-emitting layers of actual EL devices. 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 actual 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 actual element that has good luminous efficiency, can obtain 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 element of the present invention has two electrode layers, at least one of which is transparent, and a luminescent layer provided between these electrode layers, in which the luminescence ephemeris is relatively electronic. 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 compounds are arranged in a direction from one side of the electrode layer to the other. On the third layer, the first layer, the second layer, and the third layer are repeatedly stacked in this order twice or more, and the first layer, the second layer, and the third layer are further stacked on the third layer. No. 3 is characterized in that it consists 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 that can serve as electron acceptors for the compound (hereinafter referred to as Ell-a compounds) are arranged around the D compound, and when these compounds are placed in an electric field, the relationship between these compounds is The main source of light is the luminescence effect based on the formation of an exciplex through the exchange of electrons between the ED compound and the E and A compounds. It is characterized by having a structure suitable for being efficiently formed as an electric field is generated.

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, 6-2 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 6-1 is laminated in direct contact with the first layer 5-1.
Contains as a main component a compound that can be 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 8-1 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.

At these interfaces 7-1.7-2, when a voltage is applied to the electrode 1.2 and an electric field is applied to the light emitting layer 3, E
A compound and ED compound form a complex in an excited state,
When this exciplex returns to the ground state, excitation energy is generated as light from the complex, EA compound, and/or ED compound in the excited state. In this way, the EL of the present invention
The main source of light emission in the device is light emission at this interface 7-1, 7-2.

Furthermore, the first layer 5-1.5-2 contains EA- which can act as an electron 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 ED-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 8-1.6-2 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. 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 6-1.6-
A compound molecule having an <E LfI& ability (mainly emitting light) based on exciplex formation is placed in each of 2.

(b) Based on exciplex formation in the first layer 5-1.5-2<
Compound molecules having an EL function are arranged, and molecules of a compound (ED compound) that can serve as an electron donor for these compound molecules are arranged in the second layer 6-1.8-2.

(C) Compound molecules having an EL function based on exciplex formation are arranged in the second layer θ-1, 8-2, and a compound that can act as an electron acceptor for these compounds (EA compound)
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 (a) of the first layer and second layer described above.
A light-emitting layer having the following can be formed using a 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 EA-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 is an ED-a compound that has <EL function (mainly Compounds that emit light when the compound emit light, compounds that can act as electron donors or acceptors for the compound, compounds that can become a light emitter due to excitation energy transfer, and compounds that have at least one of these compound molecules as a functional moiety. When forming the first layer and the second layer, these EA-
The compounds d and ED-a may be appropriately selected and used so as to have the above-mentioned functions. E for EA compounds
The amount of A-d compound and the amount of ED-a compound relative to the ED compound will vary depending on the compounds used in the first layer and the second layer and - cannot be generally specified, but typically EA-d
Regarding the compound, about 10 mol% to 0.1 mol% of the EA compound, and about 1 mol% of the ED compound for the ED-a compound.
The content is approximately 0 mol% to 0.1 mol%.

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 also light emission in the first layer 5-1, 5-2 and/or the second layer 8-1, 8-2. It may also include cases in which it is carried out.

In order to form the first layer 5-1.5-2 and the second layer 6-1.6-2 consisting of a monomolecular film or a monomolecular cumulative film having the structure shown in 1. The so-called single molecule accumulation method, which enables orientation and alignment and allows easy formation of ultra-thin film layers, 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"; however, when A is made sufficiently small, intermolecular state interactions become stronger, and these molecules form a two-dimensional solid "condensed film" (or solid film). 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 molecules forming the monomolecular film are arranged in such a way that, for example, almost all of the tree-philic parts of the constituent molecules are oriented toward the substrate in a highly ordered manner! , can be uniform within one monolayer. Therefore, the first EL element of the present invention
The interface between the layer and the second layer is formed by a monomolecular film, so that the functional portion consisting of compound molecules directly involved in the formation of an exciplex contained in the first layer and the second layer, respectively. can be arranged at high density at the interface between the first layer and the second layer.

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

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

Basically, the compounds contained in the first layer and the second layer of the light emitting layer of the EL device of the present invention include the above-mentioned E D ,
It is a compound having at least one of EA, ED-a, and EA-d compounds, or any of these compounds as a functional moiety. Among such compounds, monolayer-forming compounds have, for example, monolayer-forming compounds that have one functional moiety, depending on the position within the molecule of the functional moiety, As shown in the schematic diagram of the structure, (a) the functional part 21 is on the side of the tree-loving part 22, - Figure 2 (a) (b) the functional part 21 is on the side of the hydrophobic part 23, - FIG. 2(b) (c) The functional part 21 is a hydrophobic part 23 and a hydrophilic part 22
- It is broadly classified into the three types shown in Figure 2 (e).

The components of the hydrophilic portion 22 of these compounds include:
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,
Hydroxyl groups, quaternary amine groups, oxyamino groups, oximino groups, diazonium groups, guanidine groups, hydrazine groups, phosphoric acid groups, silicic acid groups, aluminic acid groups, etc., each of which can be used alone or in combination to form the above compounds. A hydrophilic portion 22 therein can be configured.・Also, as the constituent elements of the hydrophobic portion 23, linear or branched alkyl groups, olefinic hydrocarbons such as vinylene, vinylidene, and acetylene, fused polycyclic phenyl groups such as phenyl, naphthyl, and anthranyl, and biphenyl Hydrophobic groups such as a chain polycyclic phenyl group such as the following can be mentioned, and these can also constitute the hydrophobic moiety 23 in the upper compound, each singly or in combination.

On the other hand, the interface between the first layer and the second layer of the light emitting layer of the EL device of the present invention? The orientation and arrangement of the ED compound and EA compound contained in the monomolecular film in -1 and 7-2 (parts where light is mainly emitted) are shown in the schematic diagram near the interface 7-1 in Figures 3a and 3b. partial cross-sectional view (in this figure, the layer of node 1 and the second layer are each formed from a monomolecular film containing a compound molecule having one functional part consisting of ED or EA compound molecules; (1) The molecules of the first layer 5-1 are (E) of the molecules contained in the molecular membrane
A wood-loving part 32 having a functional part 31 (consisting of Compound A), and a (
A hydrophilic 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
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 (consisting 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.

- Figure 3b (d) (4) (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 (
A hydrophobic part 33' having a functional part 33' (composed of an ED compound) is oriented at the interface 7-1.

-Figure 3b (1)) 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 the above-mentioned compound, it is preferable to use a compound belonging to the above-mentioned type b in the first layer and a compound belonging to the above-mentioned type a in the second layer.

In addition, ED-a compound molecule 35 or E
The type of molecule having a functional part consisting of the A-d compound molecule 34 is selected from the above-mentioned monolayer-forming compound types a-C, and the interface patterns (1) to
A suitable type may be appropriately selected depending on the ED or EA compound used in (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 8-1.8-2 is composed of a monomolecular 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 8
-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 of the monomolecular cumulative film due to the orientation state of the molecules forming each monolayer is so-called Y-type (between each film, a hydrophilic part and a lignophilic part or a hydrophobic part and a hydrophobic part are formed). structures facing each other), x
type (structure with the hydrophobic part facing the substrate side of each school), Z type (
Various structures can be used, such as a structure in which the parent tree portion faces the substrate side of each school) and modified structures thereof. Further, 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 a sub-component. is E
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 second layer 6-1.6
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 good balance of hydrophilic and hydrophobic parts can be used as they are for forming monolayers,
Other examples include the above-mentioned parent tree groups and/or hydrophobic groups, as well as 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 9, 10゜1
5゜19, 20゜21, 2
2゜ (OH2)n Yb
34゜M=Er, Sm+Eu+Gd, Tb+DLT”, Yl)
M-Er, Sm, Eu, Gd, Tb, Dy, Tm+Yb
R+-H,-Mountain+-0Fs+Figure ■ 86, 37. 3B.

41・42゜4.8.
”・62゜RR F4 65, 66゜6 g, 7
0゜71, 72゜7 &
74°77,
78゜85゜84゜■ (4)2 )n Based on the formation of an exciplex, a compound having an EL function is modified with a hydrophobic group and/or a parent tree group to form a monolayer-forming compound.

Note 1. t42～. The compounds of the structural formulas J54 and Susu 85 to Susu 8B have a structure in which an alkyl chain is directly bonded to a functional moiety. It is also possible to use a bond via an intermediary.

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 having accurate and uniform insulation properties is: % formula %) (In the above formula, n is 10 ≦n≦30, and X
is -COOH, -CONH2, -GOOR, -N+(C
H3)3. l::l-.

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

This third layer may also 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 It may be different from other monolayers. Further, the monomolecular film forming the third layer may be a monomolecular film made of one type of compound, or may be a multicomponent monomolecular film made of two or more types of compounds.

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

The thickness of each layer constituting the light-emitting layer of the EL device of the present invention having the structure shown below varies depending on the number of interfaces the EL device has and the structure of each layer itself, but for the first layer, 3008 or less, preferably 1008 or less, for the second layer, 3008 or less, preferably 100A or less, for the third layer, 3008 or less, preferably 100A or less
In order to obtain a good light emitting state even in low voltage driving, it is preferable that the thickness of the entire light emitting layer is 1 μ or less, preferably 3000 μm or less.

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, Sn02, insium tin oxide (1,7,0), 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. It can be formed by direct lamination.

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 thickness of these electrode layers is 0.01. - About 0.3u.

Preferably, the size is about 0.05μ 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 may be a substrate for forming a monomolecular film, and this substrate may be plate-shaped, A desired shape and size can be obtained by using a belt-like or 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, a 1×1
By applying direct current, alternating current, or pulse voltage so that an electric field of about 05 to 3 x 10' is applied, good light emission can be obtained from the light emitting layer 3 through the transparent electrode.

Hereinafter, typical operations of the single-molecule accumulation method, typified by the Langmuir-Blodgett method (LB method), applied to the formation of the light-emitting layer of the EL element of the present invention will be explained.

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 compound for forming a monomolecular film dissolved or dispersed in a suitable solvent is spread on the aqueous phase Φ, 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 this precipitate from freely diffusing on the water phase and spreading too much, a partition plate (or float) is installed to limit the development area and control the state of aggregation of the membrane material. Obtain a surface pressure ■ proportional to the state. Then, the partition plate is operated to reduce the developed area and gradually increase the surface pressure (2) to set the surface pressure (H) to a value suitable for forming a monomolecular film. Now, when the substrate that has already been immersed in the water is gently moved up and down in the direction perpendicular to the surface of the water while maintaining this surface pressure, a single molecule will be generated each time the substrate moves upward and downward. The film is transferred onto a substrate to form a monomolecular cumulative film.

゛In order to transfer a monomolecular film onto a substrate, in addition to the vertical immersion method mentioned above, there is also a horizontal deposition method in which the substrate is brought into contact with the water phase horizontally while keeping the surface parallel to it, and a cylindrical substrate is placed above the water surface. Various methods can be applied, such as a rotating cylinder method in which the monomolecular film is transferred to the substrate surface by rotating the substrate, or a method in which the substrate is extruded from a substrate roll into an aqueous phase. - In the above vertical immersion method,
Normally, the orientation of the film-forming molecules is 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 types and acids of additives used to adjust the pH of the aqueous phase, the temperature of the aqueous phase, and the - Operating conditions such as the lowering rate or the 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.

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

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

If a substrate with a non-transparent electrode plate or electrode layer is used as the substrate for initial monolayer formation, 1. Materials such as T and O for forming a transparent electrode layer may be laminated by a vapor deposition method 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 configurations of the two layers constituting the interfaces are changed for each interface for the plurality of interfaces that mainly emit light, and by combining these layers, the emitted light color can be adjusted as desired. It is now possible to control the

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 multiple interfaces that emit light as described above, the entire light-emitting layer is The thickness is extremely thin, and even when driven at a low voltage, an efficient Q state of light emission can be obtained, and sufficient brightness can 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,
Organic compounds that are sensitive to heat, which could not be used in the conventional methods such as the base method, can be used as constituent materials, and the EL device of the present invention is an inexpensive EL device with acidity.

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

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

Example 1 A 1. A T and 0 layer was formed to obtain a transparent electrode plate. This electrode plate was made by Joyce-Loebe1 (7)
4X 1 in Lamgmuir-Trough 4
0′4iol/j! of CdCl2, the pH of which was adjusted to 6.5.

Next, alaxic acid was dissolved in chloroform.IXlo-3m
ol/j! 0.5 m/ml of the solution was spread on the aqueous phase. After chloroform was removed by evaporation from the surface of the aqueous phase, the surface pressure of the aqueous phase was adjusted to 3Qdyne/c+*, 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 at a speed of 2 cm/win in the direction across the water surface to form a monomolecular film consisting of alaxic acid molecules on the electrode layer of the electrode plate. This was pulled out of the aqueous phase and allowed to stand at room temperature for 30 minutes or more to dry. This operation was repeated once again to form an insulating layer in which two araxic acid monomolecular films were accumulated as a 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 H3 was newly added to chloroform at a ratio of 100 mol:1 mol so that the total amount of these was IX 10-3 mol/1. 0.5 m/Cm of the dissolved solution was spread on this aqueous phase to give a concentration of A monomolecular film consisting of the above two types of compound molecules was formed as a first layer on the insulating layer by gently dipping it into the aqueous phase at a speed of 2 cm/+*in in the direction across the water surface of the aqueous phase. . 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 compound left on the surface of the aqueous phase was completely removed, and 0.5 mj of a solution was newly dissolved in chloroform to a concentration of X 10' mol/A. is spread on this water phase, and the surface pressure is set to 3
After adjusting to 0 dyne/cm, the above first layer forming operation was repeated to form a monomolecular film made of the above two types of compounds as a second layer on the previously formed first layer -L. .

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: about 50 OA) having five layer interfaces 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' Torr. An A1 layer of 1500 A was deposited on the last formed third layer at a deposition rate of sec 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.

5V, 400 Hz to this EL nacelle electrode 44.45
An alternating current voltage of 100 mL was applied to emit light, and the luminance and current density of the 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 emitted in the same manner as Example 1', and ζA It was left to dry at room temperature.

Furthermore, the above compounds left on the surface of the aqueous phase were completely removed, and 12H25 was newly added to chloroform at a ratio of 10 mol = 1 mol, so that the total amount of these was 1 x 10.
-3mol/j! 0 of the solution dissolved so that the concentration is
．． 5mj! was developed on this aqueous phase, and the surface pressure was increased for 30dy.
When the ne/cI was adjusted to 11, a monomolecular film consisting of three monomolecular films made of the above two types of compounds was accumulated on the previously formed first layer in the same manner as the formation of the first layer. A cumulative film was formed as the second layer.

After that, the formation operation from the third layer described above (hereinafter formed as a cumulative film of four monomolecular films made of alexic acid) to the second layer was repeated four times, and finally the third layer was laminated. A light emitting layer (layer thickness: l100A) having four interfaces between the first layer and the second layer was formed.

The electrode plate on which the light-emitting 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 105↑orr.
At a deposition rate of J/sec, 1500 people17) The A1 layer was deposited on the last formed third layer to form an EL element 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 cell 43.

The electrodes 44, 45 of such an EL cell have an IOV of 40
An AC voltage of 0 Hz was applied to emit 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 monolayer-forming compound, No. 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: Luminescent layer 4-1.4-2.4-3: Third layer 5 to 1.5-2.5-3: First layer fl -1. e-2.8-3: Second layer? -1.7-2: Interface 21.31.31': Functional part 22.32.32'': Hydrophilic part 23.33.33': Hydrophobic part 34: Contains EA-d compound as a functional part Compound molecule 35: Compound molecule having an E-rho a compound as a functional part 40: EL element 4I Nigarasu seal 42 = silicone oil 43: EL nacelle 0 Fig. 1 Fig. 21m 9゛;s 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 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 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 these respective layers.