JPWO2016133058A1 - Electroluminescent device - Google Patents

Abstract

An electroluminescent device having a long lifetime is provided. An electroluminescent device having at least one light emitting layer sandwiched between a pair of electrodes composed of an anode and a cathode and a hole injection layer containing an electron acceptor, wherein the hole injection layer comprises: An electroluminescent element comprising a pyrene derivative represented by the following general formula (1). (In the general formula (1), X1 to X10 are substituents, and each independently represents a hydrogen atom, a substituted or unsubstituted aryl group, a substituted or unsubstituted heterocyclic group, a substituted or unsubstituted group. Represents an alkyl group, an alkoxy group, a silyl group, a halogen atom, a cyano group, a nitro group, a hydroxyl group, or a thiol group, and two or more of X1 to X10 are each independently a substituted or unsubstituted aryl group, Or a substituted or unsubstituted heterocyclic group.) [Selection] FIG.

Description

  The present invention relates to an electroluminescent device.

  Electroluminescent devices have features such as self-emission and high-speed response, and are expected to be applied to flat panel displays. In particular, since a two-layered type (laminated type) in which a hole-transporting organic thin film (hole-transporting layer) and an electron-transporting organic thin film (electron-transporting layer) are reported has been reported, a low voltage of 10 V or less It has attracted attention as a large-area light-emitting element that emits light with voltage. The laminated electroluminescent element is composed of a thin film having a basic structure of positive electrode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection layer / negative electrode. Among these, the light emitting layer may have the function of the hole transport layer and the electron transport layer as in the case of the two-layer type. Further, since various colors can be emitted by selecting the type of the fluorescent organic compound, application to various light emitting elements, display elements and the like is expected.

  An electroluminescent element is a device that emits light by injecting holes from an anode and electrons from a cathode, transporting them to a light emitting layer, and then recombining both carriers. In order to inject and transport holes from the anode to the light emitting layer, the energy barrier usually has to exceed 0.3 to 1 eV, and a voltage corresponding to the device configuration is required. For this reason, in a device with a large energy barrier such as a blue light-emitting device or a phosphorescent light-emitting device, the power consumption caused by the drive voltage has been a problem.

  In order to reduce the driving voltage due to such an energy barrier, a technique of doping an electron acceptor or an electron donor into an organic material has been attempted. In these devices, by forcibly oxidizing or reducing the organic material, holes or electrons are generated in the organic layer, respectively, and the driving voltage can be greatly reduced.

  In the case of using an electron acceptor, usually, a typical hole injection material or a triarylamine which is a hole transport material is mostly doped, but Patent Document 1 discloses an anthracene derivative which is a hydrocarbon compound. An example of doping is shown. Succeeded in reducing the hole injection barrier from the anode to the light-emitting layer by doping an anthracene derivative with a large ionization potential into a hole-injection layer and using an anthracene derivative in the hole-transport layer. doing.

  However, the ionization potential of an anthracene derivative is about 0.5 eV higher than that of a phthalocyanine derivative or a triarylamine derivative generally used for a hole injection layer when an electron acceptor is not doped. Therefore, the radical cation of the anthracene derivative generated by doping the electron acceptor is more unstable. The radical cation of an unstable anthracene derivative reacts with oxygen and moisture that have penetrated into the electroluminescent element, or reacts with adjacent molecules to cause decomposition or alteration. When the radical cation of the anthracene derivative is decomposed or altered, the number of carriers that can be injected is reduced, so that the carrier balance is changed and the luminous efficiency is lowered. In addition, since the decomposed or altered anthracene derivative becomes a quenching site, the light emission efficiency is lowered. For these reasons, the electroluminescent device using an anthracene derivative doped with an electron acceptor for the hole injection layer has poor lifetime characteristics.

  In addition, when an anthracene derivative doped with an electron acceptor is used as a hole injection layer and an anthracene derivative is also used for the hole transport layer, there is no barrier for electron injection from the hole transport layer to the hole injection layer. Electrons flow into the injection layer. As a result, the radical cation generated by the electron acceptor reacts with the electrons flowing into the hole injection layer and deactivates, so that the light emission efficiency decreases. Therefore, an electroluminescent device using an anthracene derivative doped with an electron acceptor as a hole injection layer and also using an anthracene derivative in the hole transport layer has poor lifetime characteristics.

Japanese Patent No. 5072271

  Therefore, an object of the present invention is to provide an electroluminescent device having a longer lifetime.

（一般式（１）において、Ｘ^１からＸ^１０は置換基であり、それぞれ独立に、水素原子、置換または無置換のアリール基、置換または無置換の複素環基、置換または無置換のアルキル基、アルコキシ基、シリル基、ハロゲン原子、シアノ基、ニトロ基、ヒドロキシル基、チオール基の何れかを表し、Ｘ^１からＸ^１０のうち２つ以上がそれぞれ独立に、置換または無置換のアリール基、もしくは置換または無置換の複素環基である。）In order to achieve the above object, an electroluminescent device of the present invention has at least one light emitting layer sandwiched between a pair of electrodes consisting of an anode and a cathode, and a hole injection layer containing an electron acceptor. In the electroluminescent element, the hole injection layer preferably contains a pyrene derivative represented by the following general formula (1).

(In the general formula (1), X ¹ to X ¹⁰ are substituents, and each independently represents a hydrogen atom, a substituted or unsubstituted aryl group, a substituted or unsubstituted heterocyclic group, or a substituted or unsubstituted alkyl group. , An alkoxy group, a silyl group, a halogen atom, a cyano group, a nitro group, a hydroxyl group, or a thiol group, and two or more of X ¹ to X ¹⁰ are each independently a substituted or unsubstituted aryl group, Or a substituted or unsubstituted heterocyclic group.)

  In general, a pyrene derivative has a lower ionization potential than an anthracene derivative. By using a pyrene derivative with a small ionization potential doped with an electron acceptor in the hole injection layer, the stability of the generated radical cation is increased, and the light emission of the electroluminescent device due to the presence of an unstable and highly reactive cation radical Since a reduction in efficiency can be suppressed, a long-life electroluminescent element can be realized.

（一般式（２）、一般式（３）、一般式（４）において、Ｘ^１１からＸ^６４は置換基であり、それぞれ独立に、水素原子、置換または無置換のアリール基、置換または無置換の複素環基、置換または無置換のアルキル基、アルコキシ基、シリル基、ハロゲン原子、シアノ基、ニトロ基、ヒドロキシル基、チオール基の何れかを表す。連結基Ｌは、置換または無置換のアリーレン基、置換または無置換の複素環基、置換または無置換のアルキレン基を示す。）The electroluminescent device according to the present invention is an electroluminescent device having at least one light emitting layer sandwiched between a pair of electrodes composed of an anode and a cathode, and a hole injection layer containing an electron acceptor. The hole injection layer preferably includes a pyrene derivative represented by any one of the following general formula (2), the following general formula (3), and the following general formula (4).

(In General Formula (2), General Formula (3), and General Formula (4), X ¹¹ to X ⁶⁴ are substituents, each independently a hydrogen atom, a substituted or unsubstituted aryl group, substituted or unsubstituted. Represents a heterocyclic group, a substituted or unsubstituted alkyl group, an alkoxy group, a silyl group, a halogen atom, a cyano group, a nitro group, a hydroxyl group, or a thiol group, and the linking group L is a substituted or unsubstituted arylene. A group, a substituted or unsubstituted heterocyclic group, or a substituted or unsubstituted alkylene group.)

  The pyrene derivative represented by any one of the general formula (2), the general formula (3), and the general formula (4) has high thermal stability, and can form a stable thin film with low crystallinity. A long-life electroluminescent element can be realized.

（一般式（１）、一般式（２）、一般式（３）、一般式（４）において、Ｘ^１からＸ^６４は置換基であり、それぞれ独立に、水素原子、置換または無置換のアリール基、置換または無置換の複素環基、置換または無置換のアルキル基、アルコキシ基、シリル基、ハロゲン原子、シアノ基、ニトロ基、ヒドロキシル基、チオール基の何れかを表し、Ｘ^１からＸ^１０のうち２つ以上がそれぞれ独立に、置換または無置換のアリール基、もしくは置換または無置換の複素環基である。連結基Ｌは、置換または無置換のアリーレン基、置換または無置換の複素環基、置換または無置換のアルキレン基を示す。
一般式（５）において、Ａｒ^１からＡｒ^５は、それぞれ独立に、置換または無置換のアリール基であり、ｉは０〜２の整数である。）The electroluminescent device according to the present invention has at least one light emitting layer sandwiched between a pair of electrodes composed of an anode and a cathode, a hole injection layer containing an electron acceptor, and a hole transport layer. The hole injection layer includes a pyrene derivative represented by any one of the following general formula (1), the following general formula (2), the following general formula (3), or the following general formula (4), The hole transport layer preferably contains an anthracene derivative represented by the following general formula (5).

(In General Formula (1), General Formula (2), General Formula (3), and General Formula (4), X ¹ to X ⁶⁴ are substituents, each independently a hydrogen atom, substituted or unsubstituted aryl Represents any one of a group, a substituted or unsubstituted heterocyclic group, a substituted or unsubstituted alkyl group, an alkoxy group, a silyl group, a halogen atom, a cyano group, a nitro group, a hydroxyl group, and a thiol group, and X ¹ to X ¹⁰ And two or more of them are each independently a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group, and the linking group L is a substituted or unsubstituted arylene group, substituted or unsubstituted heterocyclic ring A group, a substituted or unsubstituted alkylene group;
In General Formula (5), Ar ¹ to Ar ⁵ are each independently a substituted or unsubstituted aryl group, and i is an integer of 0 to 2. )

  By using an anthracene derivative having a higher electron affinity than the pyrene derivative for the hole transport layer, it is possible to suppress the inflow of electrons from the hole transport layer to the hole injection layer containing the pyrene derivative. Can be realized.

（一般式（１）、一般式（２）、一般式（３）、一般式（４）において、Ｘ^１からＸ^６４は置換基であり、それぞれ独立に、水素原子、置換または無置換のアリール基、置換または無置換の複素環基、置換または無置換のアルキル基、アルコキシ基、シリル基、ハロゲン原子、シアノ基、ニトロ基、ヒドロキシル基、チオール基の何れかを表し、Ｘ^１からＸ^１０のうち２つ以上がそれぞれ独立に、置換または無置換のアリール基、もしくは置換または無置換の複素環基である。連結基Ｌは、置換または無置換のアリーレン基、置換または無置換の複素環基、置換または無置換のアルキレン基を示す。なお、前記正孔注入層と前記正孔輸送層とに含まれるピレン誘導体は同じであっても異なっていてもよい。
一般式（５）において、Ａｒ^１からＡｒ^５は、それぞれ独立に、置換または無置換のアリール基であり、ｉは０〜２の整数である。）The electroluminescent device according to the present invention has at least one light emitting layer sandwiched between a pair of electrodes composed of an anode and a cathode, a hole injection layer containing an electron acceptor, and a hole transport layer. The hole injection layer and the hole transport layer are represented by any one of the following general formula (1), the following general formula (2), the following general formula (3), or the following general formula (4). It is preferable that the light emitting layer contains a pyrene derivative and the light emitting layer contains an anthracene derivative represented by the following general formula (5).

(In General Formula (1), General Formula (2), General Formula (3), and General Formula (4), X ¹ to X ⁶⁴ are substituents, each independently a hydrogen atom, substituted or unsubstituted aryl Represents any one of a group, a substituted or unsubstituted heterocyclic group, a substituted or unsubstituted alkyl group, an alkoxy group, a silyl group, a halogen atom, a cyano group, a nitro group, a hydroxyl group, and a thiol group, and X ¹ to X ¹⁰ And two or more of them are each independently a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group, and the linking group L is a substituted or unsubstituted arylene group, substituted or unsubstituted heterocyclic ring Represents a group, a substituted or unsubstituted alkylene group, and the pyrene derivatives contained in the hole injection layer and the hole transport layer may be the same or different.
In General Formula (5), Ar ¹ to Ar ⁵ are each independently a substituted or unsubstituted aryl group, and i is an integer of 0 to 2. )

  When a pyrene derivative doped with an electron acceptor is used for the hole injection layer and a pyrene derivative is used for the hole transport layer, an anthracene derivative having an electron affinity higher than that of the pyrene derivative is used for the light emitting layer. Since the inflow of electrons to the hole transport layer and the hole injection layer can be suppressed, a long-life electroluminescent element can be realized.

  According to the present invention, an electroluminescent element having a longer life can be provided.

It is the outline of the element of this embodiment.

  An embodiment of the present invention will be described with reference to FIG. As shown in FIG. 1, the electroluminescent device 1 includes an anode 3, a hole injection layer 4, a hole transport layer 5, a light emitting layer 6, an electron transport layer 7, an electron injection layer 8, and a cathode 9 on a substrate 2. Have sequentially.

  The substrate 2 is preferably formed of a transparent or translucent material, such as a glass plate, a transparent plastic sheet, a translucent plastic sheet, quartz, transparent ceramics, or a composite sheet combining these. The substrate 2 may be formed from an opaque material. In this case, an element structure in which light is extracted from the opposite side of the substrate 2 may be used. Furthermore, the emission color may be controlled by combining the substrate 2 with, for example, a color filter film, a color conversion film, a dielectric reflection film, or the like.

  The anode 3 preferably uses a metal, an alloy or an electrically conductive compound having a relatively large work function as an electrode material. Examples of the electrode material used for the anode 3 include gold, platinum, silver, copper, cobalt, nickel, palladium, vanadium, tungsten, tin oxide, zinc oxide, ITO (indium tin oxide), polythiophene, and polypyrrole. is there. These electrode materials may be used alone or in combination. The anode 3 can form these electrode materials on the substrate 2 by, for example, a vapor phase growth method such as a vapor deposition method or a sputtering method. The anode 3 may have a single layer structure or a multilayer structure.

（一般式（１）、一般式（２）、一般式（３）、一般式（４）において、Ｘ^１からＸ^６４は置換基であり、それぞれ独立に、水素原子、置換または無置換のアリール基、置換または無置換の複素環基、置換または無置換のアルキル基、アルコキシ基、シリル基、ハロゲン原子、シアノ基、ニトロ基、ヒドロキシル基、チオール基の何れかを表し、Ｘ^１からＸ^１０のうち２つ以上がそれぞれ独立に、置換または無置換のアリール基、もしくは置換または無置換の複素環基である。連結基Ｌは、置換または無置換のアリーレン基、置換または無置換の複素環基、置換または無置換のアルキレン基を示す。）The hole injection layer 4 is a layer having a function of facilitating injection of holes from the anode 3 and a function of transporting injected holes and injecting them into the hole transport layer 5. In general, triarylamine derivatives such as copper phthalocyanine and starburst amine, and polymer compounds such as polythiophene and polyaniline are used. The hole injection layer 4 used in the present embodiment includes an electron acceptor and the following general formula ( 1) or a pyrene derivative represented by any one of the following general formula (2), the following general formula (3), and the following general formula (4). Since holes are generated on the pyrene derivative by the action of the electron acceptor, the hole injection barrier from the anode 3 can be greatly reduced.

(In General Formula (1), General Formula (2), General Formula (3), and General Formula (4), X ¹ to X ⁶⁴ are substituents, each independently a hydrogen atom, substituted or unsubstituted aryl Represents any one of a group, a substituted or unsubstituted heterocyclic group, a substituted or unsubstituted alkyl group, an alkoxy group, a silyl group, a halogen atom, a cyano group, a nitro group, a hydroxyl group, and a thiol group, and X ¹ to X ¹⁰ And two or more of them are each independently a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group, and the linking group L is a substituted or unsubstituted arylene group, substituted or unsubstituted heterocyclic ring Group, a substituted or unsubstituted alkylene group.)

  The pyrene derivative used for the hole injection layer 4 has an ionization potential of about 0.1 to 0.2 eV smaller than the anthracene derivative. Therefore, the radical cation of the pyrene derivative generated by doping with the electron acceptor is more stable than the radical cation of the anthracene derivative. As a result, the decomposition and alteration of the material due to the instability of the radical cation are reduced, so that the generation of quenching sites and the deterioration of the carrier balance are suppressed. Therefore, by using a pyrene derivative, it is possible to prevent a decrease in light emission efficiency of the electroluminescent element due to driving, and thus it is possible to realize a long-life electroluminescent element.

  In addition, the pyrene derivative represented by the general formula (1) has two or more substituted or unsubstituted aryl groups or substituted or unsubstituted heterocyclic groups. For this reason, since there are many rotatable bonds in the molecule and there are various possible conformations, the film made of the pyrene derivative represented by the general formula (1) is difficult to crystallize and can form a stable thin film. Therefore, a long-life electroluminescent element can be realized.

  Further, the pyrene derivative represented by any one of the general formula (2), the general formula (3), and the general formula (4) is represented by the general formula (1) due to the presence of two pyrene rings. The molecular weight increases as compared with the pyrene derivative, and the conformation that can be taken by the pyrene ring as the main skeleton is diversified. As a result, the film made of a pyrene derivative represented by any one of the general formula (2), the general formula (3), and the general formula (4) is suppressed in terms of crystallization due to element driving and heat generation, and is stable. Since a thin film can be formed, a long-life electroluminescent element can be realized.

The substituted or unsubstituted aryl group in the general formula (1), the general formula (2), the general formula (3), or the general formula (4) may be monocyclic or polycyclic, and may be a condensed ring or a ring. Sets are also included. Such aryl groups are preferably those having 6 to 22 carbon atoms, and specifically include phenyl, naphthyl, anthryl, phenanthryl, pyrenyl, perylenyl, benzoanthryl, and dibenzoanthryl. Group, fluoranthenyl group, benzofluoranthenyl group and o-biphenyl group, m-biphenyl group, p-biphenyl group, terphenyl group and the like, and particularly preferably phenyl group, naphthyl group, o-, m -Or p-biphenyl group is mentioned. These substituents are easy to synthesize.
Preferred substitution positions are X ¹ , X ⁴ , X ⁵ , X ⁶ , X ⁹ , X ¹⁰ , and General formula (2) in the general formula (1) from the viewpoint of ease of synthesis and stability of the compound. X ¹⁸ , X ²⁴ , X ³⁷ , X ^{42 in} the general formula (3), and X ⁵⁴ , X ⁵⁹ in the general formula (4).
These series of aryl groups may be further substituted, such as alkyl groups, alkoxy groups, aryl groups, aryloxy groups, silyl groups, halogen atoms, cyano groups, nitro groups, hydroxyl groups, Examples include thiol groups.

As the substituted or unsubstituted heterocyclic group in the general formula (1), the general formula (2), the general formula (3), and the general formula (4), 5-membered or 6 containing O, N, S as a hetero atom. Examples thereof include a membered aromatic heterocyclic group, and a condensed polycyclic aromatic heterocyclic group having 8 to 20 carbon atoms. Examples of the aromatic heterocyclic group and the condensed polycyclic aromatic heterocyclic group include thienyl group, furyl group, pyrrolyl group, pyridyl group, quinolyl group, quinoxalyl group, carbazoyl group, dibenzothienyl group, dibenzofuranyl group and the like. Can be mentioned. Since the heterocyclic group imparts polarity to the molecule, adhesion to the anode, which is an inorganic substance, may be improved. In particular, a carbazoyl group, a dibenzothienyl group, and a dibenzofuranyl group are preferable materials because they do not greatly change physical property values related to energy levels such as HOMO and LUMO of the main skeleton. Among them, the carbazoyl group is a particularly preferable material because it is easy to synthesize and can select various substitution positions. These heterocyclic groups may be further substituted. Examples of such substituents include alkyl groups, alkoxy groups, aryl groups, aryloxy groups, aromatic amino groups, silyl groups, halogen atoms, cyano groups, nitro groups, Group, hydroxyl group, thiol group and the like.
In the general formula (1), preferred substitution positions are X ¹ , X ⁴ , X ⁵ , X ⁶ , X ⁹ , X ¹⁰ , general, from the viewpoint of ease of synthesis and stability of the compound, as in the aryl group. In the formula (2), X ¹⁸ and X ²⁴ , in the general formula (3), X ³⁷ and X ⁴² , and in the general formula (4), X ⁵⁴ and X ⁵⁹ .

  The alkyl group in general formula (1), general formula (2), general formula (3), or general formula (4) may be linear, branched or cyclic, and has 1 to 10 carbon atoms. Are preferred. Examples of such an alkyl group include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an i-butyl group, an s-butyl group, a t-butyl group, and a cyclohexyl group. . These alkyl groups may further have a substituent, and examples of the substituent include an alkoxy group, an aryl group, an aryloxy group, an aromatic amino group, a silyl group, a halogen atom, a cyano group, and a nitro group. , Hydroxyl group, thiol group and the like.

  The alkoxy group in general formula (1), general formula (2), general formula (3), and general formula (4) may be linear or branched, and has a substituent. And those having 1 to 10 carbon atoms are preferred. Examples of such an alkoxy group include a methoxy group, an ethoxy group, and a t-butoxy group. Examples of the substituent include an alkyl group, an alkoxy group, an aryl group, an aryloxy group, an aromatic amino group, a silyl group, a halogen atom, a cyano group, a nitro group, a hydroxyl group, and a thiol group.

  The linking group L in the general formula (2), the general formula (3), and the general formula (4) represents a substituted or unsubstituted arylene group, a substituted or unsubstituted heterocyclic group, or a substituted or unsubstituted alkylene group. A substituted or unsubstituted arylene group is particularly preferred. Specific examples include a phenylene group, a biphenylene group, and a naphthylene group, and a phenylene group is preferable. In the case of selecting a substituted or unsubstituted heterocyclic group, a substituted or unsubstituted carbazoyl group is preferred because the physical property value relating to the energy level such as HOMO and LUMO of the main skeleton does not change greatly.

Although the specific example of the compound of this embodiment represented by General formula (1) below is shown, it is not limited to these.

Although the specific example of the compound of this embodiment represented by General formula (2) below is shown, it is not limited to these.

Although the specific example of the compound of this embodiment represented by General formula (3) below is shown, it is not limited to these.

Although the specific example of the compound of this embodiment represented by General formula (4) below is shown, it is not limited to these.

  Examples of the electron acceptor used for the hole injection layer 4 include inorganic compounds such as antimony chloride, vanadium oxide, molybdenum oxide, ruthenium oxide, tungsten oxide, zinc oxide, tin oxide, and iron oxide, and hexacyanoazatriphenylene and its derivatives. Although organic substances can be used, inorganic compounds such as antimony chloride, vanadium oxide, and molybdenum oxide are preferable.

（一般式（５）において、Ａｒ^１からＡｒ^５は、それぞれ独立に、置換または無置換のアリール基であり、ｉは０〜２の整数である。）The hole transport layer 5 is a layer having a function of transporting holes and injecting them into the light emitting layer 6 and a function of preventing electrons from being injected from the light emitting layer 6 into the hole transport layer 7. In general electroluminescent devices, triarylamine derivatives are preferably used. In this embodiment, any one of general formula (1), general formula (2), general formula (3), or general formula (4) is used. Or an anthracene derivative represented by the following general formula (5) is preferable. When pyrene derivatives are used for the hole injection layer 4 and the hole transport layer 5, the pyrene derivatives contained in the hole injection layer 4 and the hole transport layer 5 may be the same or different. Good, but more preferably the same.

(In General Formula (5), Ar ¹ to Ar ⁵ are each independently a substituted or unsubstituted aryl group, and i is an integer of 0 to 2.)

  The substituted or unsubstituted aryl group in the general formula (5) may be monocyclic or polycyclic, and includes condensed rings and ring assemblies. Such aryl groups are preferably those having 6 to 22 carbon atoms, and specifically include phenyl, naphthyl, anthryl, phenanthryl, pyrenyl, perylenyl, benzoanthryl, and dibenzoanthryl. Group, fluoranthenyl group, benzofluoranthenyl group, and o-biphenyl group, m-biphenyl group, p-biphenyl group, terphenyl group, and the like, particularly preferably phenyl group, naphthyl group, o-, Examples include m- or p-biphenyl groups. These substituents are easy to synthesize. These series of aryl groups may be further substituted, such as alkyl groups, alkoxy groups, aryl groups, aryloxy groups, silyl groups, halogen atoms, cyano groups, nitro groups, hydroxyl groups, Examples include thiol groups.

Although the specific example of the compound of this embodiment represented by General formula (5) below is shown, it is not limited to these.

  In general, a pyrene derivative has an electron affinity of about 0.1 to 0.2 eV smaller than an anthracene derivative. This means that there is an electron injection barrier from the anthracene derivative to the pyrene derivative. In addition, when electrons flow into the hole injection layer, radical cations generated by the electron acceptor react with the flowed electrons and are deactivated, resulting in a decrease in light emission efficiency. From the above, when a pyrene derivative doped with an electron acceptor is used for the hole injection layer, the inflow of electrons to the hole injection layer can be suppressed by using an anthracene derivative for the hole transport layer. An electroluminescent element can be realized.

  The light-emitting layer 6 is a layer having a function of transporting injected holes and electrons, a function of generating excitons by recombination of holes and electrons, and a host material having a function of transporting carriers and a thin film structure. And a light emitting dopant having a light emitting function. Common host materials include organometallic complexes such as tris (8-quinolinolato) aluminum, hydrocarbon compounds such as naphthalene, anthracene, naphthacene, pyrene, and perylene, and heterocyclic derivatives such as carbazole, thiophene, and furan, and triaryl. An amine derivative or the like can be used. In the present embodiment, a pyrene derivative represented by any one of the general formula (1), the general formula (2), the general formula (3), and the general formula (4), or the general formula (5) An anthracene derivative is preferable, and when a pyrene derivative is used for the hole transport layer 5, the lifetime of the electroluminescent device can be extended by suppressing the inflow of electrons to the hole injection layer. Anthracene derivatives represented by

  The luminescent dopant is a compound that emits light by exciton energy generated by recombination of holes and electrons. A material having a high emission quantum yield is preferable, and a material having a function of trapping holes and electrons is more preferable. In the present embodiment, conventionally used light-emitting dopants can be used. Specifically, aromatic hydrocarbons, aromatic amine compounds, styrylamine compounds, aromatic hydrocarbon compounds having a cyano group as a substituent, Examples include quinacridone, coumarin, and rhodamine. Particularly, aromatic amine compounds that are hole trapping dopants, styrylamine compounds, or aromatic hydrocarbon compounds having a cyano group that is an electron trapping dopant as a substituent. preferable. In addition, since the electroluminescent device using a pyrene derivative as the hole injection layer and the hole transport layer and an anthracene derivative as the light emitting layer in this embodiment can suppress the outflow of electrons from the light emitting layer, a cyano group When an electron trapping dopant such as an aromatic hydrocarbon compound having a substituent is used, light can be emitted with high efficiency.

  The content of the light emitting dopant with respect to the host compound is preferably 0.01 to 20 wt%, and more preferably 0.1 to 15 wt%.

  The light emitting layer 6 may further contain other compounds. By mixing the carrier transport material, the carrier transport property of the light emitting layer can be adjusted, and the luminescent color can be converted and used by mixing fluorescent dyes. Examples of such compounds include dye compounds such as quinacridone, rubrene, and styryl dyes, and carrier transporting compounds such as triarylamine derivatives.

  The electron transport layer 7 is a layer having a function of transporting injected electrons and a function of preventing holes from being injected from the light emitting layer 6. The electron transport layer 7 is composed of an organometallic complex having an 8-quinolinol or a derivative thereof such as tris (8-quinolinolato) aluminum as a ligand, an oxadiazole derivative, a triazole derivative, a triazine derivative, a perylene derivative, a quinoline derivative, or a quinoxaline derivative. , Heterocyclic compounds such as diphenylquinone derivatives, nitro-substituted fluorenone derivatives, thiopyrandioxide derivatives, pyridine derivatives, pyrimidine derivatives, imidazopyridine derivatives, imidazopyrimidine derivatives, phenanthroline derivatives, anthracene, naphthacene, fluoranthene, acenaphthofluoranthene, etc. It can be formed using at least one kind of hydrocarbon derivative.

  The electron injection layer 8 has a function of facilitating injection of electrons from the cathode 9 and a function of improving adhesion with the cathode 9. The electron injection layer 8 is composed of an organometallic complex having an 8-quinolinol or derivative thereof such as tris (8-quinolinolato) aluminum as a ligand, an oxadiazole derivative, a triazole derivative, a triazine derivative, a perylene derivative, a quinoline derivative, or a quinoxaline derivative. , Diphenylquinone derivatives, nitro-substituted fluorenone derivatives, thiopyrandioxide derivatives, pyridine derivatives, pyrimidine derivatives, imidazopyridine derivatives, imidazopyrimidine derivatives, phenanthroline derivatives, and the like. In addition, by using a material having the functions of the electron injection layer 8 and the electron transport layer 7, a single layer can function as two layers as the electron injection transport layer. Depending on the element configuration, the electron injection layer 8 and the electron transport layer 7 can be used in a further functionally separated form.

  In addition, a technique of doping the electron injection layer 8 with an inorganic compound that functions as an electron donor is also effective in improving the electron injection amount. This is because the organic compound in the electron injection layer 8 is reduced by the electron donor, so that carriers are generated in the electron injection layer 8 and the electron injection barrier from the cathode 9 can be greatly reduced. In this case, a hydrocarbon material such as anthracene can be used in addition to a general electron injection material such as tris (8-quinolinolato) aluminum. As an inorganic compound that functions as an electron donor, it is preferable to use an alkali metal such as lithium, sodium, or potassium and an oxide or halide thereof, or an alkaline earth metal such as calcium or magnesium, or an oxide or halide thereof. .

  For the cathode 9, a metal having a relatively small work function and a salt thereof, an alloy, or an electrically conductive compound can be used as an electrode constituent material. For example, lithium, sodium, calcium, magnesium, indium, ruthenium, titanium, manganese, yttrium, aluminum as metal, lithium oxide, sodium oxide, calcium oxide, magnesium oxide as oxide, lithium fluoride, fluoride as fluoride Sodium, calcium fluoride, magnesium fluoride, alloys include lithium-indium alloy, sodium-potassium alloy, magnesium-silver alloy, magnesium-indium alloy, aluminum-lithium alloy, aluminum-calcium alloy, aluminum-magnesium alloy, electrical conduction Examples of the functional compound include a graphite thin film.

  These electrode constituent materials may be used alone or in combination. The cathode 9 can be formed of these electrode materials on the electron injection layer 8 by a method such as vapor deposition, sputtering, ionized vapor deposition, ion plating, or cluster ion beam. The cathode 9 may have a single layer structure or a multilayer structure. In order to efficiently extract light emitted from the electroluminescent element, it is preferable that at least one of the anode 3 and the cathode 9 is transparent or translucent, and generally has a light transmittance of 80% or more. It is more preferable to set the material and thickness of the anode 3 or the cathode 9.

  Hereinafter, specific examples of the present invention will be shown together with comparative examples, and the present invention will be described in more detail.

Example 1
An ITO transparent electrode thin film having a thickness of 100 nm was formed on a glass substrate by RF sputtering and patterned. This glass substrate with an ITO transparent electrode was subjected to ultrasonic cleaning using a neutral detergent, acetone and ethanol, and then pulled up from boiling ethanol and dried. After the surface of the transparent electrode was washed with UV / O _3, it was fixed to a substrate holder of a vacuum deposition apparatus, and the inside of the tank was depressurized to 1 × 10 ⁻⁴ Pa or less.

  Next, while maintaining the reduced pressure state, Exemplified Compound A3 and molybdenum trioxide as an electron acceptor were vapor-deposited at a film thickness ratio of 95: 5 to a thickness of 60 nm with an overall vapor deposition rate of 0.1 nm / sec. And a hole injection layer.

  Subsequently, exemplary compound A3 was vapor-deposited in the thickness of 10 nm with the vapor deposition rate of 0.1 nm / sec, and it was set as the positive hole transport layer.

  Further, while maintaining the reduced pressure state, the exemplary compound A3 as a host material and F1 having the following structure as a light-emitting dopant with a volume ratio of 97: 3 and a total deposition rate of 0.1 nm / sec and a thickness of 40 nm The light emitting layer was formed by vapor deposition.

Next, while maintaining the reduced pressure state, Exemplified Compound A3 was deposited as an electron transport layer at 25 nm, and subsequently, Tris (8-hydroxyquinoline) aluminum (Alq ₃ ) was deposited as an electron injection layer at 5 nm with a deposition rate of 0.1 nm / sec. did.

  Subsequently, LiF was vapor-deposited at a deposition rate of 0.1 nm / sec to a thickness of 0.5 nm, and subsequently Al was vapor-deposited to a thickness of 100 nm to form a cathode, and finally the glass was sealed to obtain an electroluminescent device.

When a direct current having a current density of 10 mA / cm ² was applied to the electroluminescent element, blue light emission derived from a light emitting dopant having an initial luminance of 1200 cd / m ² and a luminance half life of 1280 hours was obtained.

(Examples 2-29)
An electroluminescent device was obtained in the same manner as in Example 1 except that the compound shown in Table 1 was used instead of the exemplified compound A3 as the hole injection layer, hole transport layer, and light emitting layer host. The test results of initial luminance and luminance half-life are shown in Table 1.

(Comparative Examples 1-3)
As a comparative example, the electroluminescent device was prepared in the same manner as in Example 1 except that the compound shown in Table 1 was used instead of the exemplified compound A3 as the hole injection layer, the hole transport layer, and the light emitting layer host. Obtained. The test results of initial luminance and luminance half-life are shown in Table 1.

  As shown in Table 1, when the pyrene derivative shown in this embodiment is used for a hole injection layer, a hole transport layer, and a light emitting layer host, radical cations generated by doping of an electron acceptor in the hole injection layer are A stabilized and long-life organic electroluminescent device can be obtained.

(Example 30)
An ITO transparent electrode thin film having a thickness of 100 nm was formed on a glass substrate by RF sputtering and patterned. This glass substrate with an ITO transparent electrode was subjected to ultrasonic cleaning using a neutral detergent, acetone and ethanol, and then pulled up from boiling ethanol and dried. After the surface of the transparent electrode was washed with UV / O _3, it was fixed to a substrate holder of a vacuum deposition apparatus, and the inside of the tank was depressurized to 1 × 10 ⁻⁴ Pa or less.

  Next, while maintaining the reduced pressure state, Exemplified Compound A3 and molybdenum trioxide as an electron acceptor were vapor-deposited at a film thickness ratio of 95: 5 to a thickness of 60 nm with an overall vapor deposition rate of 0.1 nm / sec. And a hole injection layer.

  Subsequently, exemplary compound E3 was vapor-deposited at a vapor deposition rate of 0.1 nm / sec to a thickness of 10 nm to form a hole transport layer.

  Further, while maintaining the reduced pressure state, the exemplified compound E3 as the host material and F1 as the luminescent dopant were vapor-deposited at a volume ratio of 97: 3 to a thickness of 40 nm with an overall vapor deposition rate of 0.1 nm / sec. A light emitting layer was obtained.

Next, while maintaining the reduced pressure state, the exemplified compound E3 was deposited as an electron transport layer at 25 nm, and subsequently, tris (8-hydroxyquinoline) aluminum (Alq ₃ ) was deposited as an electron injection layer at 5 nm, with a deposition rate of 0.1 nm / sec. did.

  Subsequently, LiF was vapor-deposited at a deposition rate of 0.1 nm / sec to a thickness of 0.5 nm, and subsequently Al was vapor-deposited to a thickness of 100 nm to form a cathode, and finally the glass was sealed to obtain an electroluminescent device.

When a direct current having a current density of 10 mA / cm ² was applied to the electroluminescent element, blue light emission derived from a light emitting dopant having an initial luminance of 1100 cd / m ² and a luminance half life of 1680 hours was obtained.

(Examples 31-57)
An electroluminescent device was obtained in the same manner as in Example 30 except that Exemplified Compound A3 as the hole injection layer and Exemplified Compound E3 as the hole transport layer and light emitting layer host were changed to the compounds shown in Table 2. Table 2 shows the test results of the initial luminance and luminance half-life.

(Comparative Examples 4-6)
As a comparative example, an electroluminescent device was obtained in the same manner as in Example 30, except that Exemplified Compound A3 as a hole injection layer and Exemplified Compound E3 as a hole transport layer and a light emitting layer host were changed to the compounds shown in Table 2. Got. Table 2 shows the test results of the initial luminance and luminance half-life.

  As shown in Table 2, when the pyrene derivative shown in this embodiment is used for a hole injection layer and an anthracene derivative is used for a hole transport layer and a light emitting layer host, radical cation deactivation caused by doping of an electron acceptor is suppressed. Since it can suppress, a long life organic electroluminescent element is obtained.

(Example 58)
An ITO transparent electrode thin film having a thickness of 100 nm was formed on a glass substrate by RF sputtering and patterned. This glass substrate with an ITO transparent electrode was subjected to ultrasonic cleaning using a neutral detergent, acetone and ethanol, and then pulled up from boiling ethanol and dried. After the surface of the transparent electrode was washed with UV / O _3, it was fixed to a substrate holder of a vacuum deposition apparatus, and the inside of the tank was depressurized to 1 × 10 ⁻⁴ Pa or less.

  Next, while maintaining the reduced pressure state, Exemplified Compound A3 and molybdenum trioxide as an electron acceptor were vapor-deposited at a film thickness ratio of 95: 5 to a thickness of 60 nm with an overall vapor deposition rate of 0.1 nm / sec. And a hole injection layer.

  Subsequently, exemplary compound A3 was vapor-deposited in the thickness of 10 nm with the vapor deposition rate of 0.1 nm / sec, and it was set as the positive hole transport layer.

  Further, while maintaining the reduced pressure state, the exemplified compound E3 as the host material and F1 as the luminescent dopant were vapor-deposited at a volume ratio of 97: 3 to a thickness of 40 nm with an overall vapor deposition rate of 0.1 nm / sec. A light emitting layer was obtained.

  Next, while maintaining the reduced pressure state, Exemplified Compound E3 was deposited as an electron transport layer at 25 nm, and subsequently, Tris (8-hydroxyquinoline) aluminum (Alq3) was deposited as an electron injection layer at 5 nm at a deposition rate of 0.1 nm / sec. .

  Subsequently, LiF was vapor-deposited at a deposition rate of 0.1 nm / sec to a thickness of 0.5 nm, and subsequently Al was vapor-deposited to a thickness of 100 nm to form a cathode, and finally the glass was sealed to obtain an electroluminescent device.

When a direct current having a current density of 10 mA / cm ² was applied to the electroluminescent element, blue light emission derived from a light emitting dopant having an initial luminance of 1200 cd / m ² and a luminance half life of 2200 hours was obtained.

(Examples 59 to 85)
Exemplified Compound A3 as a hole injection layer and a hole transport layer, Exemplified Compound E3 as a light emitting layer host, F1 as a luminescent dopant were changed to the compounds shown in Table 3, and the electric field was changed in the same manner as in Example 58. A light emitting device was obtained. Table 3 shows the test results of the initial luminance and the luminance half life. The luminescent dopant F2 has a structure shown below.

(Comparative Examples 7-9)
As a comparative example, Example Compound A3 is used as the hole injection layer and the hole transport layer, Example Compound E3 is used as the light emitting layer host, F1 is used as the light emitting dopant, and Example 58 is used. Similarly, an electroluminescent element was obtained. Table 3 shows the test results of the initial luminance and the luminance half life.

  As shown in Table 3, when the pyrene derivative shown in the present embodiment is used for a hole injection layer and a hole transport layer and an anthracene derivative is used for a light emitting layer host, radical cation deactivation caused by electron acceptor doping is suppressed. Since it can suppress, a long life organic electroluminescent element is obtained.

  As described above, the electroluminescence device according to the present invention is useful as a long-life electroluminescence device. An electroluminescent element utilizing this can be applied to a light emitting device such as a display or illumination.

DESCRIPTION OF SYMBOLS 1 Electroluminescent element 2 Substrate 3 Anode 4 Hole injection layer 5 Hole transport layer 6 Light emitting layer 7 Electron transport layer 8 Electron injection layer 9 Cathode

Claims (4)

Sandwiched between a pair of electrodes consisting of an anode and a cathode,
At least one light emitting layer;
A hole injection layer containing an electron acceptor;
In an electroluminescent device having
The hole injection layer includes a pyrene derivative represented by the following general formula (1).

(In the general formula (1), X ¹ to X ¹⁰ are substituents, and each independently represents a hydrogen atom, a substituted or unsubstituted aryl group, a substituted or unsubstituted heterocyclic group, or a substituted or unsubstituted alkyl group. , An alkoxy group, a silyl group, a halogen atom, a cyano group, a nitro group, a hydroxyl group, or a thiol group, and two or more of X ¹ to X ¹⁰ are each independently a substituted or unsubstituted aryl group, Or a substituted or unsubstituted heterocyclic group.) Sandwiched between a pair of electrodes consisting of an anode and a cathode,
At least one light emitting layer;
A hole injection layer containing an electron acceptor;
In an electroluminescent device having
The hole injection layer includes a pyrene derivative represented by any one of the following general formula (2), the following general formula (3), and the following general formula (4).

(In General Formula (2), General Formula (3), and General Formula (4), X ¹¹ to X ⁶⁴ are substituents, each independently a hydrogen atom, a substituted or unsubstituted aryl group, substituted or unsubstituted. Represents a heterocyclic group, a substituted or unsubstituted alkyl group, an alkoxy group, a silyl group, a halogen atom, a cyano group, a nitro group, a hydroxyl group, or a thiol group, and the linking group L is a substituted or unsubstituted arylene. A group, a substituted or unsubstituted heterocyclic group, or a substituted or unsubstituted alkylene group.) Sandwiched between a pair of electrodes consisting of an anode and a cathode,
At least one light emitting layer;
A hole injection layer containing an electron acceptor;
A hole transport layer, and
The hole injection layer includes a pyrene derivative represented by any one of the following general formulas (1) to (4),
The said hole transport layer contains the anthracene derivative represented by following General formula (5), The electroluminescent element characterized by the above-mentioned.

(In General Formula (1), General Formula (2), General Formula (3), and General Formula (4), X ¹ to X ⁶⁴ are substituents, each independently a hydrogen atom, substituted or unsubstituted aryl Represents any one of a group, a substituted or unsubstituted heterocyclic group, a substituted or unsubstituted alkyl group, an alkoxy group, a silyl group, a halogen atom, a cyano group, a nitro group, a hydroxyl group, and a thiol group, and X ¹ to X ¹⁰ And two or more of them are each independently a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group, and the linking group L is a substituted or unsubstituted arylene group, substituted or unsubstituted heterocyclic ring A group, a substituted or unsubstituted alkylene group;
In General Formula (5), Ar ¹ to Ar ⁵ are each independently a substituted or unsubstituted aryl group, and i is an integer of 0 to 2. ) Sandwiched between a pair of electrodes consisting of an anode and a cathode,
At least one light emitting layer;
A hole injection layer containing an electron acceptor;
A hole transport layer, and
The hole injection layer and the hole transport layer include a pyrene derivative represented by any one of the following general formulas (1) to (4),
The light-emitting layer includes an anthracene derivative represented by the following general formula (5).

(In General Formula (1), General Formula (2), General Formula (3), and General Formula (4), X ¹ to X ⁶⁴ are substituents, each independently a hydrogen atom, substituted or unsubstituted aryl Represents any one of a group, a substituted or unsubstituted heterocyclic group, a substituted or unsubstituted alkyl group, an alkoxy group, a silyl group, a halogen atom, a cyano group, a nitro group, a hydroxyl group, and a thiol group, and X ¹ to X ¹⁰ And two or more of them are each independently a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group, and the linking group L is a substituted or unsubstituted arylene group, substituted or unsubstituted heterocyclic ring Represents a group, a substituted or unsubstituted alkylene group, and the pyrene derivatives contained in the hole injection layer and the hole transport layer may be the same or different.
In General Formula (5), Ar ¹ to Ar ⁵ are each independently a substituted or unsubstituted aryl group, and i is an integer of 0 to 2. )

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