JPS6137868A - Electroluminescent element - Google Patents

Abstract

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

Description

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

[Prior art]

An EL element has a structure in which a light-emitting layer containing a material with an EL function, that is, a material that emits light when placed in an electric field, is placed between two electrodes, and a voltage is applied between these electrodes. A light-emitting element that generates light by generating an electric field and converting electrical energy directly into light.
For example, unlike traditional light emitting methods, such as incandescent light bulbs where a filament is heated to emit light, or fluorescent light, where electrically excited gas imparts energy to a phosphor and causes it to emit light, thin panels are used. Possibility of realizing light-emitting bodies such as lamps, lines, diagrams, images, etc., or as components of display media such as lamps, lines, diagrams, images, etc., or as light-emitting bodies such as large-area panel lamps. It is attracting attention as having the following.

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

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

In addition, the materials having the above-mentioned EL function include:

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

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

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

However, in this powder type EL element, when the layer thickness is formed thin, defects such as pinholes are likely to occur in the light emitting layer. There are structural limits to making it thinner, making it impossible to obtain sufficient light emission, especially high brightness, and because the layer thickness is relatively thick, power consumption increases to generate a stronger electric field. It had the following problems. An improved powder-type EL device was developed in Japanese Patent Application Laid-Open No. 581-111, in which an intermediate dielectric layer made of vinylidene fluoride polymer was provided in the light-emitting layer of the powder-type EL device to generate a stronger electric field.
Although it is known from the publication No. 72891, the current situation is that satisfactory performance in terms of brightness, power consumption, etc. is not achieved.

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 that have the ability to form thin films with high precision, and optical and As materials for electronics, their use in applications such as electrochromic elements, piezoelectric elements, pyroelectric elements, nonlinear optical elements, and ferroelectric liquid crystals is drawing attention. It is expected that it will be used as a material for

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

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

[Purpose of the invention]

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

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

[Structure of the invention]

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

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

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

that's all. The EL device 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 is placed between a third layer 4-1.4-3 which serves as an insulating layer laminated on both the upper and lower ends. , the second layer 8-1, 6-2 and the third layer 4-2 are alternately stacked to form a multilayer structure, and the second layer 6-
1.6-2 and the third layer 4-1.4-2, 4-3,
Each layer is formed from a monomolecular film of a compound 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 and 7-2, when a voltage is applied to the electrodes 1 and 2 and an electric field is applied to the light emitting layer 3, E
A compound and ED compound form a complex in an excited state,
When this exciplex returns to the ground state, excitation energy is generated as light from the complex, EA compound, and/or ED compound in the excited state. In this way, the EL of the present invention
Is this interface the source of light emission in the device? -1,? -2 is the main light source.

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

In addition, the second layer 6-1, 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. The first layer 5-1, 5-2 and the second layer constituting the light-emitting layer of the EL element of the present invention may have a function of controlling the light emitting layer in addition to the above-mentioned functions. 8-
1.8-2 contains as a main component a compound molecule directly involved in the formation of an electric field excited complex as shown below, or a compound molecule having at least one of the compounds as a functional moiety, and a second Layers Ef-1 and Ef-6-2 are formed from monomolecular films or monomolecular cumulative films.

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 EL function (mainly emitting light) based on exciplex formation is arranged in each of 2.

(b) Based on exciplex formation in the first layer 5-1.5-2<
Compound molecules having an EL function are arranged, and molecules of a compound (ED compound) that can serve as an electron donor for these compound molecules are arranged in the second layer 8-1, 6-2, respectively.

(c) Based on exciplex formation in the second layer 6-1.6-2
A compound in which a compound molecule having ELJ1 ability is arranged and can act as an electron acceptor for these compounds (EA compound)
Molecules are respectively arranged in the first layer 5-1, 5-2.

Based on the above-mentioned exciplex formation (as a compound having an EL function), 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.
The first layer is formed by vapor deposition, CVD
The second layer can be formed using a single molecule accumulation method described later.

Furthermore, compounds that can serve as electron acceptors or electron donors for the above-mentioned compounds having an <EL mechanism based on exciplex formation include heterocyclic compounds other than the above-mentioned compounds and derivatives thereof, aromatic amines, Examples include aromatic polyamines, compounds having a quinone structure, tetracyanoquinodimethane, and tetracyanoethylene, and the above-mentioned compounds and these compounds are appropriately selected and combined to form the first layer and the above-mentioned first layer. Second 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 and is included in the second layer has <EL function (mainly Compounds that emit light), compounds that can act as electron donors or electron acceptors for the compound, compounds that can become a light emitter through excitation energy transfer, and compounds that have at least one of these compound molecules as a functional moiety, etc. can. When forming the first layer and the second layer, these EA-
The 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%.

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 exciplexes, and may also be compounds that have the function of emitting light that is not based on the formation of exciplexes.
The compound that can become the D-a compound may also have an EL function, and light emission in the EL element of the present invention occurs at the interface between the first layer and the second layer. -1,? -2, but is not limited to the emission only in the first layer 5-1.5-2.
And/or it may also include a case where light is emitted within the second layers El-1 and 8-2.

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

This single molecule accumulation method is based on the following principle. In other words, 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 hydrophilic portion facing down.

This monomolecular layer has the characteristics of a two-dimensional system, and when these molecules are sparsely dispersed, the two-dimensional ideal gas equation between the area A per molecule and the surface pressure ■, nA = kT. (
k, Polzmann foot number, T: absolute temperature), and these molecules form "gas H", but when A is made sufficiently small, intermolecular interactions become stronger and these molecules form a two-dimensional solid P condensate film (or This condensed film can be transferred to the surface of a substrate such as glass, and an ultra-thin monomolecular film or a cumulative film thereof can be formed on the substrate.

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

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

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

Basically, the compounds contained in the first layer and the second layer of the light emitting layer of the EL device of the present invention include the above-mentioned E D ,
EA, HD-a and I! It is a compound having at least one A-d compound or 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, depending on the position within the molecule of the functional moiety, As shown in the schematic diagrams of the structure, (a) the functional part 21 is on the hydrophilic part 22 side, (a) (b) the functional part 21 is on the hydrophobic part 23 side, - the 2 (b) (c) 4al+ functional part 21 is located approximately midway between the hydrophobic part 23 and the woody part 22 - It is broadly classified into the three types shown in Fig. 2 (C).

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, amine groups, imino groups,
Examples include hydroxyl J, a quaternary amino group, an oxyamino group, an oxyimino group, a diazonium group, a guanidine group, a hydrazine group, a phosphoric acid group, a silicate group, and an aluminate group.

Each of these can be used alone or in combination to constitute the wood-loving portion 22 in the above compound.

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

On the other hand, the interface between the first layer and the second layer of the light emitting layer of the EL device of the present invention? The orientation and arrangement of the ED compound contained in the monomolecular film at points -1 and 7-2 (parts where light is mainly emitted) are shown in the schematic cross-sectional partial view near the interface 7-1 in Figure 3 (this figure In the case of , the second layer is formed from a monomolecular film containing compound molecules each having one functional moiety consisting of an ED compound molecule, and for molecules having a functional moiety consisting of ED-a compound molecules 35, (Illustration of functional parts is omitted) As shown in (1) (E
The hydrophilic portion 32 having the Ia functional portion 31 (composed of compound D) is the interface? -1 orientation.

(2) The molecular (E) forming the monomolecular film of the second layer 8-1
A hydrophobic portion 33 having a functional portion 31 (composed of compound D) is oriented at the interface 7-1.

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

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

The types of molecules having a functional part consisting of the ED-a compound molecules 35 (not shown) are the interface pattern (1), A suitable type may be appropriately selected depending on the ED compound used in (2).

In the example explained above, the second layer is formed from a monomolecular film, but even when the second layer 6-1.6-2 is formed from a monomolecular cumulative film, the first The interface between the first layer and the second layer so that the interface between the layer and the second layer takes the pattern shown above? What is necessary is to form a monomolecular film of the second layer constituting -1 and 7-2.

In addition, when the second M6-1.6-2 is composed of a monomolecular cumulative film, each of the monomolecular films constituting the cumulative film may be the same, and the monomolecular films may be the same. One or more of the monolayers may be different from other monolayers. Furthermore, the structure based on the orientation state of the molecules forming each monomolecular film of the monomolecular cumulative film is so-called Y-type (between each film, there are a woody part and a woody part, or a hydrophobic part and a hydrophobic part). structure in which the hydrophobic parts face each other), x-type (structure in which the hydrophobic part faces the substrate side of each school), Z-type (structure in which the parent part faces the board side in each school), and their modified structures, etc. can have a variety of structures. Furthermore, the monomolecular H that forms the second layer constituting the light-emitting layer of the EL device of the present invention is composed of one or more compounds having an EA compound as a main component and a molecule as a functional part, and a sub-component. A multi-component monomolecular film containing one or more compounds other than one or more compounds having a certain ED-a compound molecule as a functional moiety may also be used. In such a case,
Other compounds include compounds that do not have a functional moiety but can control the electrochemical properties of the light-emitting layer by interacting with compounds that do, and even increase the strength of the monolayer. , compounds that can improve adhesion with other layers, and the like.

The structure of the monomolecular film or monomolecular cumulative film as described above depends on the desired electrical characteristics of the second layer.
For example, monomolecular films made of compounds belonging to type a, b, or type C of the above-mentioned monomolecular film-forming compounds may be combined and accumulated to form a monomolecular film. It is possible to control the potential curve of π electrons in the direction perpendicular to the surface direction of the film.

Compounds that can be used to form the above-mentioned second Fit 8-1.6-2 include the above-mentioned compounds capable of forming the functional moiety, or having one or more of the above-mentioned compounds. Among compounds, those that have a good balance of hydrophilic and hydrophobic parts can be used as is for forming monolayers, and those that do not have hydrophilic and/or hydrophobic groups as mentioned above. A group can be newly introduced into the molecule to form a monomolecular film-forming compound.

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

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

5.6゜7.8゜21, 22゜(CH
z) nX 6≦n≦20 28°H3 □ 0≦n≦2 25°26°28°M==H2, Be, Mg, Ca, Cd,
5rklcl, YbCl M=Er, Sm, Eu, Qd, Tb, Dy, Tm, Yb
◎D, -Fu + -t-Bu 34゜M=Er, Sm, Eu, Gd, Tb, Dy, Tm, Yb
M-Er, Sm, Eu, Gd, Tb+Dy, Tm+Yb
R+ -H, -CH3+ CF3+< 86, 37. 3B.

89, 4Q.

48, 44゜■
(α12)XRR EF4 65, 66, 69,
70°78. 77. □ 88° Summer 89° Among these compounds, the compound with the structural formula at 1-435 has an EL function based on the formation of an exciplex among the compounds that can form the functional moiety listed above. A compound is modified with a hydrophobic group and/or a parent group to form a monolayer-forming compound.

The compounds of the structural formulas Masaru 42 to Sui 54 and Sui 85 to Sui 8B have a structure in which an alkyl chain is directly bonded to a functional moiety. It may be an ether bond, a bond via a carbonyl group, or the like.

Furthermore, among the monolayer-forming compounds exemplified here,
Compounds that can be used in other thin film formation methods such as vapor deposition methods include
It can also be used to form layers. In addition, the first layer also contains one or more compounds having molecules of the EA compound as the main component as a functional part, and EA-d compound molecules as the subcomponent. It may also contain one or more other compounds other than one or more of the compounds it has as a moiety, and in such a case, the other compound may include a compound that does not have a functional moiety but does not have a functional moiety. Compounds that can control the electrochemical properties of the light-emitting layer through interaction with other layers, as well as compounds that can increase the strength of the first layer and improve adhesion with other layers, etc. .

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 that takes care of insulation, and especially the third layer 4-1. .4-3 has the function of increasing the insulation of the capacitor structure of the EL element of the present invention, and the third layer 4-2 confines the movement of electrons within the necessary minimum area and allows efficient transfer and reception of electrons. It has the function of emitting light by As a material that can form these third layers, the general formula that can form a monomolecular film with accurate and uniform insulation properties is: (% formula %): (In the above formula, n is 10≦n≦30, and X is -〇〇〇〇, -COHH2, -GOOR, -N+(C
H3) 3・Cdo.

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 above structure varies depending on the number of interfaces the EL device has and the structure of each layer itself, but for the first layer,
500A or less, preferably 200A or less, for the second layer, 300A or less, preferably 100A or less, the third layer
For the layer, it is 300A or less, preferably 100A or less, and the thickness of the entire light emitting layer is 1) ua or less, preferably 3000A or less, in order to obtain a good light emission state even in low voltage driving. desirable.

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 (1,7,0), 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 about 0.01μ to 0.3μ, preferably about 0.05μ 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 light emitting layer, and this substrate may be shaped like a plate, a belt, etc. A desired shape and size can be obtained by using, for example, a cylindrical shape. Further, the two electrode layers may be patterned into various shapes as desired.

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 106 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-Fist-Prodgett method (LB method) applied to the formation of the second layer and third layer of the light-emitting layer of the EL device of the present invention will be described. explain.

An aqueous phase for forming a monomolecular film is provided in a water tank, and a clean substrate is immersed in the aqueous phase. Next, a predetermined amount of a solution of a monomolecular film-forming compound dissolved or dispersed in a suitable solvent is spread in the aqueous phase, and the compound is deposited in the form of a film on the surface of the aqueous phase. At this time, in order to prevent the precipitates from freely diffusing on the water phase and spreading too much, a partition plate (or float) is provided to limit the area of development and control the aggregation state of the membrane material.
Obtain a surface pressure (■) proportional to the aggregate state. Then, the partition plate is activated to reduce the developed area and gradually increase the surface pressure (2) to set the surface pressure (4) suitable for forming a monomolecular film. Now, if the substrate that has already been immersed is gently moved up and down in the direction perpendicular to the water phase surface while maintaining this surface pressure, a single molecule will be generated each time the substrate moves to one side and downward. The film is transferred onto a substrate to form a monomolecular cumulative film.

To transfer a monomolecular film onto a substrate, in addition to the vertical dipping method described above, there are also horizontal adhesion methods in which the water phase surface of the substrate is kept parallel and in contact with it horizontally, and a cylindrical substrate is rotated on the water surface. Various methods can be applied, such as a rotating cylinder method in which a monomolecular film is transferred to the surface of a substrate using a rotating cylinder method, or a method in which the substrate is extruded from a substrate roll into an aqueous phase. In the above-mentioned 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 hydrophilic groups and hydrophobic groups can also be changed by surface treatment of the substrate.

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

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

First, a third layer consisting of a monomolecular film or a monomolecular cumulative film having a desired configuration is formed using the third layer forming material described above on the substrate on which the transparent electrode layer is provided. Next, a first layer having a desired structure is formed on this third layer by vapor deposition or the like using a material capable of forming the first layer described above. Further, on this first layer, a second layer consisting of a monomolecular film or a monomolecular cumulative film having a desired configuration is formed in 8I layers using a material capable of forming the above-described second layer.

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

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

If a substrate with a non-transparent electrode plate or electrode layer is used as the substrate for forming the first light-emitting layer, the final
．． A material for forming a transparent electrode layer, such as T or O, may be laminated on the light emitting layer by a vapor deposition method or the like. In addition, if both electrodes are transparent, a transparent electrode layer may be formed using the above-mentioned material on a transparent substrate for forming a light emitting layer, and another 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 the other first layers.
The same applies to the layer and the third layer. Further, an adhesive layer may be provided between each layer constituting the EL element of the present invention in order to improve the adhesiveness of each layer. Furthermore, 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, for a plurality of interfaces that mainly emit light, the composition of the two layers constituting the interface is changed for each interface, and these are combined to achieve a desired emission color, etc. It became possible to control accordingly.

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

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

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

Furthermore, each layer of the light-emitting layer of the EL device of the present invention can be easily formed as a precise thin film using various organic compound materials, and even when the EL device of the present invention is formed as a large-area EL device, the light-emitting layer The EL device of the present invention is formed with high precision, has good functionality, and is inexpensive and can be mass-produced.

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

Example 1 A 1.7.0 layer with a film thickness of 1500 A was formed by sputtering on a 5 m square glass surface to form a transparent electrode plate. This electrode plate was connected to a Lan manufactured by Joyce-Loebe1.
4X 10'4+ in gmuir-Trough 4
*PH is 8 by containing CdcI2 of ol//
-5 in the aqueous phase.

Next, add stearic acid to chloroform. IXIO-3m
0.5 ml of the solution dissolved at a concentration of ol/A 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 30 dyne/csa, and a film of stearic acid was precipitated on the surface of the aqueous phase.

Furthermore, while keeping the surface pressure constant, the electrode plate was gently pulled up at a speed of 20 inches/inch in the direction across the water surface, and a monomolecular film made of stearic acid molecules as a third layer was applied to the electrode plate. Formed on a layer, pulled this out of the aqueous phase, 30
It was left to dry at room temperature for more than a minute. Furthermore, this operation was repeated twice to form a monomolecular cumulative film in which three monomolecular films made of stearic acid molecules were laminated as a third layer on the electrode layer of the electrode plate. Note that the stearic acid remaining on the surface of the water phase was completely removed from the surface of the water phase.

Next, this electrode plate was set in a predetermined position in the vapor deposition tank of the resistance heating vapor deposition apparatus, and furthermore, anthracene (p, '218°C) was put into one of the resistance heating ports, and anthraquinone (218°C) was put into the other one. s+p, 288°C), and after first reducing the pressure in the tank to a vacuum level of 10' Torr, the current was set so that the anthraquinone deposition rate was about 0.1 person/sec, and anthracene and anthracene were heated. The deposition rate of the entire deposited layer consisting of a mixture of anthraquinones is 2 persons/se.
The current flowing through the port containing anthracene was adjusted so that the current flowing through the port containing anthracene was adjusted, and a evaporated layer of 200 A of a mixture of anthracene and anthraquinone was formed on the insulating layer as the third layer that had been previously formed as the first layer. . The degree of vacuum in the tank during vapor deposition was set to 9 x 10' Tart, and the temperature of the substrate holder was set to 20°C.

After forming the first layer in this way, the electrode substrate was immersed in the aqueous phase from which the remaining stearic acid had been completely removed, and then a new layer of ■1 was added at a ratio of 10 mal: 1 ■O1. Then, 0.5 mA of a solution in which the total amount of these was dissolved in chloroform at a concentration of 1 × 10' + sol/7 was developed on this aqueous phase, the surface pressure was adjusted to 30 dyne/am, and a monomolecular film of the above compound was formed. Once formed on the water phase, the electrode plate was gently moved up and down twice at a speed of 2 cm/win in the direction across the water surface to form a monomolecular cumulative film in which four monomolecular films made of the above compound molecules were accumulated. The second layer was formed on the previously formed first layer. Next, this electrode plate was pulled out of the water phase and again
It was left to dry at room temperature for 0 minutes or more.

Thereafter, in the same manner as described above, a third layer consisting of four monomolecular films made of stearic acid is laminated on the second layer, and the above-described first to third layers are formed. 4 operations
This was repeated several times to form a light-emitting layer (layer thickness: about 11110 OA) having four interfaces between the first layer and the second layer.

The electrode plate on which the light-emitting layer was formed in this way was put back into the vapor deposition tank, and the pressure inside the tank was first reduced to a vacuum level of 10'6 Torr, and then the vacuum level was further adjusted to 10'↑orr.
At a deposition rate of 20 fi and 7 sec, an A1 layer of 1500 A 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 is sealed with a sealing glass 41, and then purified, degassed, and dehydrated using silicone oil 4.
2 was injected into the seal to form the EL nacelle 3.

Kono-like EL-F Iy(r) electrode 44.45 ni, 2
Applying an AC voltage of 0 V and 400 Hz to emit two lights,
When the luminance and current density during light emission were measured, a luminance of 29 Ft-L was measured at a current density of 0.11 mA/cm 2 .

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of an example of the EL element of the present invention, and FIG.
The figure is a schematic diagram of the molecular structure of the monolayer-forming compound, and Figure 3 is a schematic diagram showing a typical example of the arrangement of molecules at the interface between the first layer and the second layer of the EL device of the present invention. , FIG. 4 is a schematic cross-sectional view of an EL nacelle incorporating the EL element of the present invention. 1.44: Transparent electrode layer 2.45: Electrode layer 3: Light emitting layer 4-1.4-2.4-3: Third layer 5-1.5-2.5-3: First layer f3 -1.6-2.8-3: Second layer 7-1. ? -2: Interface 21.31: Functional part 22.32: Hydrophilic part 23.33: Hydrophobic part 35: Compound molecule having ED-a compound as a functional part 40: EL element 41 Niglass seal 42: Silicon Oil 43: EL cell patent applicant Canon Co., Ltd. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

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