JP2005267935A - Ink for organic electroluminescent element, the organic electroluminescent element, and light-emitting panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink for an organic electroluminescent element superior in aptitude of painting and heat resistant property, and an organic electroluminescent element and a light-emitting panel using the ink for organic electroluminescent element, superior in element characteristics. <P>SOLUTION: The ink for the organic electroluminescent element contains at least maleimide-based polymer, having a principal chain skeleton including structural unit 1 expressed by Formula (1) as an essential component, and an organic electroluminescent element and a light-emitting panel are manufactured by using the above ink. In the formula, R<SP>1</SP>denotes a group exerting electric charge transport function by the impression of voltage. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an ink for an organic electroluminescent element used for forming an organic layer required to have a charge transport property such as a charge transport layer included in the organic electroluminescent element, and a charge transport layer using the ink. The present invention relates to an organic electroluminescent element having an organic layer formed thereon, and a light emitting panel assembled using the organic electroluminescent element.

In recent years, a flat panel display (FPD) has been put to practical use as an alternative to a CRT (Cathode-Ray-Tube) display having a large occupation area and a large weight. As FPDs, liquid crystal displays (LCDs) are currently widely used as displays for various portable electronic devices, notebook computers, and small televisions, and FPDs other than LCDs such as plasma display panels (PDPs) have also been put into practical use. Has been.
One such FPD is an electroluminescent (hereinafter sometimes referred to as EL) display. Although the EL display has been developed for a relatively long time, there are problems in terms of full color, brightness, life, and the like, and it has not yet become widespread.

  In addition, an inorganic compound thin film has been conventionally used as a light emitting layer of an EL element which is a main part of an EL display. However, an EL element using an inorganic compound thin film has a high driving voltage and a low luminous efficiency. Only brightness display was possible. On the other hand, in recent years, a light emitting layer of an EL element has been used which uses an organic compound thin film having a low driving voltage and high light emission efficiency. In addition, organic EL devices using organic compound thin films have had problems in terms of lifetime, but the development of light-emitting materials that can extend the lifetime has been promoted, and it is possible to put it to practical use at a level that can compete with LCDs. became.

  The organic EL element has a basic structure in which at least one organic layer is sandwiched between two electrode layers. When the organic layer is a single layer type, the organic compound forming the single layer needs to have functions such as charge transport and light emission, and it is often difficult to obtain high luminous efficiency. Therefore, in order to improve luminous efficiency, this organic layer has a multilayer structure in which a plurality of layers having each required function are formed, for example, an electron transport layer and a hole transport layer formed from a material having a charge transport property, etc. A multilayer structure in which a light emitting layer is sandwiched between other charge transport layers is also performed.

In general, the organic layer of such an organic EL element is formed by depositing a low molecular weight organic compound on a support by a vacuum deposition method. However, an organic EL device using a low-molecular organic compound has a problem that the organic layer is crystallized or aggregated with time, and the device is deteriorated to greatly affect the device life. Furthermore, in the case of a vapor phase film forming method such as vacuum vapor deposition, there is a problem that a large vapor deposition apparatus is required and the cost is high, and further, it is difficult to increase the area of the base material. Also, even if an attempt is made to prepare a coating liquid by dissolving or dispersing a low molecular weight organic compound in a solvent, the solubility and dispersibility are poor, so a uniform and stable coating liquid cannot be obtained. It is difficult to use the film method.
On the other hand, the light emitting layer or the above light emitting layer is formed by a wet film formation method (spin coating method, printing method, ink jet method, etc.) in which a high molecular organic compound having light emitting property, charge transporting property, etc. is dissolved or dispersed in a solvent and applied to a substrate. An organic EL element having a charge transport layer or the like has been proposed. The wet film-forming method applied to a substrate using a solvent is advantageous in that the cost is lower than that of the vacuum deposition method and the substrate can have a large area.

  Examples of the charge transport material used in such a wet film-forming method include a conductive polymer material that is soluble or dispersible in an organic solvent or water, or a low molecular organic compound having a charge transport property. In many cases, a material substituted with a chain or a side chain is used. However, these charge transport materials are insufficient in stability such as heat resistance and charge transport performance, and these improvements remain as problems.

  In Patent Document 1, it is proposed to polymerize by introducing a vinyl group into a charge transporting low molecular weight organic compound and polymerizing it. This polymer material has the merit that the charge transport performance can be changed by changing the concentration of the charge transporting organic compound or combining different charge transporting low molecular weight organic compounds in the polymer. There is a problem that a polymer obtained by polymerizing a group has low heat resistance. Organic electroluminescent elements and light-emitting panels may be subjected to a process of heating to a high temperature in the course of production, or are affected by temperature rise during use of the display device, so that the element material has sufficient heat resistance. Otherwise, there is a problem that the display quality is deteriorated by changing the color tone by changing the color or lowering the luminance.

  On the other hand, maleimide copolymer is known as a resin having high heat resistance, thermal stability and transparency, and has been used for heat resistance improvers and films or molded products that require heat resistance and transparency. Yes. Further, for example, Patent Document 2 and Patent Document 3 propose use of a maleimide copolymer as a binder component of a resin composition that forms a colored layer, a protective film, and the like of a color filter.

JP 2003-342325 A JP 9-311211 A Japanese Patent Laid-Open No. 10-300922

The present invention has been accomplished in view of such circumstances, and a first object thereof is to provide an ink for an organic electroluminescent element having excellent coating suitability and high heat resistance.
The second object of the present invention is to provide an organic electroluminescent device and a light emitting panel excellent in device characteristics such as luminous efficiency and heat resistance, using the organic electroluminescent device ink according to the present invention as described above. There is to do.

  In the present invention, the organic electroluminescent element ink for achieving the first object is at least represented by the following formula (1).

(In the formula, R ¹ represents a group that exhibits a charge transport function when a voltage is applied.)
A maleimide polymer having a main chain skeleton containing the structural unit 1 represented by the formula (1) is contained as an essential component.

  The ink for an organic electroluminescent element according to the present invention includes (1) a structural unit of the formula (1) having a group (hereinafter sometimes referred to as a charge transporting group) that exhibits a charge transport function contained in a maleimide polymer. By changing the concentration of 1 or by changing the type of the charge transporting group of the structural unit 1 of the formula (1) contained in the maleimide polymer, or by changing the type of the charge transporting group (1 By combining two or more structural units 1), the charge transport performance of a layer constituting the organic electroluminescent device (hereinafter sometimes referred to as an organic layer) is adjusted according to the purpose. Device characteristics such as luminous efficiency can be changed, and (2) coating suitability is improved by introducing an appropriate copolymerization monomer into the maleimide polymer, and the layer form and electrical properties are optimized. DOO can have the advantage that.

  In addition, since the ink for organic electroluminescent elements according to the present invention uses the maleimide polymer having high heat resistance as a material for electroluminescent elements, even if it is heated to a high temperature during the production of a display element, the yellowing occurs. It is difficult to cause discoloration and brightness reduction. Furthermore, not only when exposed to a heating process for manufacturing an organic electroluminescent element, but also because the display device is left outdoors after production or the temperature of the display device rises during use. Even when exposed to a high temperature environment, discoloration such as yellowing and a decrease in luminance hardly occur, and display quality deterioration can be prevented. Therefore, an organic electroluminescent element excellent in display quality and excellent in durability can be obtained.

In addition, the organic electroluminescent element ink according to the present invention contains the maleimide polymer as an essential component and is excellent in solubility or dispersibility in a solvent and coating suitability. An organic electroluminescent element can be formed by a wet film forming method. Therefore, when the ink for organic electroluminescent elements according to the present invention is used, the production cost is lower than that of the vacuum deposition method, and it can be easily applied to a large-area substrate.
As the maleimide polymer, the structural unit 1 is represented by the following formula (2).

（式中、Ｒ^1aは単結合又は二価の基であり、Ｒ^1bは電圧の印加によって電荷輸送機能を発揮する有機化合物の残基である。）

(In the formula, R ^1a is a single bond or a divalent group, and R ^1b is a residue of an organic compound that exhibits a charge transport function when a voltage is applied.)

And a maleimide polymer represented by the formula:
In the above formula (2), R ^1b is at least one compound selected from the group consisting of carbazole or a derivative thereof, biscarbazole biphenyl or a derivative thereof, triarylamine or a derivative thereof, oxadiazole or a derivative thereof, triazine or a derivative thereof The above residues are preferable because a charge transport layer having high charge transport performance and high heat resistance can be obtained.
Further, the maleimide polymer has the following formula (3):

(In the formula, R ² represents a group that emits light when a voltage is applied.)
Is included in the main chain skeleton because a layer having a light-emitting property as well as a charge-transporting property can be obtained. Specifically, the structural unit 2 is represented by the following formula (4):

(In the formula, R ^2a is a single bond or a divalent group, and R ^2b is a residue of an organic compound that emits light when a voltage is applied.)
And a maleimide polymer represented by the formula:

As R ^2b , a fluorescent or phosphorescent group can be introduced. R ^2b is a pyrene compound, perylene compound, naphthalene compound, phenanthrene compound, tetracene compound, quinacridone compound, dioxazine compound, coronene compound, fluorescein compound, coumarin compound, quinoline metal complex compound, rare earth In the case of a fluorescent or phosphorescent group composed of a residue of at least one compound selected from the group consisting of a metal coordination compound and an iridium coordination compound, the light emitting layer having its own light emitting ability and high charge transportability Since it is obtained, it is preferable.

  In the present invention, an organic electroluminescent element for achieving the second object is at least represented by the following formula (1).

(In the formula, R ¹ represents a group that exhibits a charge transport function when a voltage is applied.)
And a layer containing a maleimide polymer having a main chain skeleton containing the structural unit 1 represented by the following as an essential component.
Further, the maleimide polymer has the following formula (3):

(In the formula, R ² represents a group that emits light when a voltage is applied.)
In the main chain skeleton, a layer having a light-emitting property as well as a charge-transporting property can be provided.

  The organic electroluminescent element according to the present invention can be formed using the ink for organic electroluminescent elements according to the present invention. Accordingly, a highly durable organic electroluminescent device having high productivity, a large display area, little deterioration in display quality, and a light emitting panel excellent in display quality using the organic electroluminescent device. can get.

As described above, the maleimide polymer contained in the organic electroluminescent element ink of the present invention has a voltage at the N-substitution position of the repeating unit having a maleimide structure which is a main main chain constituent unit of the polymer. Has a structure in which a group (charge transporting group) that exhibits a charge transport function by covalent application is covalently bonded.
This maleimide polymer can arbitrarily select a charge transporting group that is covalently bonded to the N-substituted position of the structural unit 1 represented by the formula (1), and has different charge transporting groups. It can be set as the connection structure which combined 2 or more types of structural units 1 represented by Formula (1) freely, and also can copolymerize with the other monomer polymerizable with maleimide. Further, this maleimide polymer has a high heat resistance because the main chain skeleton has a maleimide structure, and hardly undergoes discoloration such as yellowing even when exposed to a high temperature environment.

Therefore, the ink for organic electroluminescent elements according to the present invention can be obtained by (1) changing the concentration of the structural unit 1 of the formula (1) having a charge transporting group contained in the maleimide polymer, By changing the type of the charge transporting group of the structural unit 1 of the formula (1) contained in the combination, or by combining two or more types of the structural unit 1 of the formula (1) having different types of charge transporting groups, By adjusting the charge transport performance of the layers constituting the organic electroluminescent device according to the purpose, it is possible to change the device characteristics such as the luminous efficiency of the organic electroluminescent device, and (2) suitable for the maleimide polymer By introducing such a copolymerization monomer, the coating suitability can be improved, and the layer form and electrical properties can be optimized.
In addition, when the maleimide polymer further includes a structural unit in which a group that emits light by application of a voltage is covalently bonded to the N-substituted position of a repeating unit having a maleimide structure that is a main main chain structural unit, It is possible to form a layer that has charge transporting properties and emits light by itself.

In addition, since the ink for organic electroluminescent elements according to the present invention uses the maleimide polymer having high heat resistance as a material for electroluminescent elements, even if it is heated to a high temperature during the production of a display element, the yellowing occurs. It is difficult to cause discoloration and brightness reduction. Furthermore, not only when exposed to a heating process for manufacturing an organic electroluminescent element, but also because the display device is left outdoors after production or the temperature of the display device rises during use. Even when exposed to a high temperature environment, discoloration such as yellowing and a decrease in luminance hardly occur, and display quality deterioration can be prevented. Therefore, an organic electroluminescent element excellent in display quality and excellent in durability can be obtained.
In addition, the organic electroluminescent element ink according to the present invention contains the maleimide polymer as an essential component and is excellent in solubility or dispersibility in a solvent and coating suitability. An organic electroluminescent element can be formed by a wet film forming method. Therefore, when the ink for organic electroluminescent elements according to the present invention is used, the production cost is lower than that of the vacuum deposition method, and it can be easily applied to a large-area substrate.

Furthermore, hole charge transportability, electron charge transportability, which could only be formed by a dry film-forming method such as a conventional vacuum deposition method, with a maleimide polymer contained in the ink for an organic electroluminescence device according to the present invention. Alternatively, coating suitability is imparted to low molecular weight compounds having both charge transport properties, and a wet film forming method can be used while maintaining the characteristics of these low molecular weight compounds, and combinations of these low molecular weight compounds can be used. Also has the advantage that it can be freely used.
Furthermore, by using the organic electroluminescent element ink according to the present invention, a highly durable organic electroluminescent element having high productivity, a large display area, and little deterioration in display quality, and the organic A light-emitting panel using an electroluminescent element and having excellent display quality can be obtained.

(1) Maleimide polymer The maleimide polymer used in the present invention has at least the following formula (1).

(In the formula, R ¹ represents a group that exhibits a charge transport function when a voltage is applied.)
It has the main chain skeleton containing the structural unit 1 represented by these.

Here, in the present invention, the group (charge transporting group) that exhibits a charge transport function when a voltage is applied is a group that exhibits a function of delivering a charge to another compound when a voltage is applied.
The charge transporting group in the present invention may be a bipolar group having both hole transporting properties and electron transporting properties in addition to typical hole transporting properties and electron transporting properties.
Further, in the present invention, charge transport means hole transport, electron transport, or both charge transport obtained by applying a voltage to a compound having charge transport properties, and includes bipolar charge transport modes.
Furthermore, unless otherwise specified, “application” in the present invention broadly encompasses a method that can form a liquid layer on a support, such as a printing method and an inkjet method, in addition to a typical coating method. .

The maleimide polymer has a structure in which the charge transporting group is covalently bonded to the N-substituted position of a repeating unit having a maleimide structure which is a main main chain constituent unit of the polymer. Charge can be transported by application.
In this maleimide polymer, a charge transporting group covalently bonded to the N-substituted position of the structural unit represented by the formula (1) can be arbitrarily selected, and the groups (1) are different from each other. )) Can be arbitrarily combined, so that the types and combinations of the charge transporting groups can be freely designed in accordance with the required EL characteristics. Further, the structural unit represented by the formula (1) has the same charge transfer property as the N-substituted position of the same maleimide skeleton as that of the structural unit represented by the formula (1). It is also possible to form a linked structure in which structural units substituted with a residue (for example, a doping group) of a compound having a function of improving or modifying the properties of the transport material are combined. Accordingly, it is possible to obtain characteristics that were impossible or difficult to achieve with the above charge transporting group alone.

The maleimide polymer can also be copolymerized with other monomers polymerizable with maleimide. As a result, the concentration of the structural unit of the formula (1) can be changed. For example, when used in the formation of a layer of an organic electroluminescent device, the charge transport performance is adjusted according to the purpose or the dissolution in a solvent. -It is possible to improve dispersibility and applicability, and to optimize the layer form and electrical properties.
Since the maleimide polymer used in the present invention is excellent in solubility or dispersibility in a solvent and can be prepared with excellent coating suitability, an organic electroluminescent element or other functional layer is formed by a wet film formation method. It is possible to form. Regarding the coating suitability, in particular, the maleimide polymer according to the present invention has a hole transport property, an electron transport property, or both charges, which can only be used for forming an organic layer only by a dry film formation method such as a conventional vacuum deposition method. By introducing a low molecular compound having a transport property as a compound having a charge transport function, a wet film-forming method can be used while maintaining the characteristics of these low molecular compounds. There is a merit that the combination of them becomes possible freely.

Further, this maleimide polymer has a high heat resistance because the main chain skeleton has a maleimide structure, and hardly undergoes discoloration such as yellowing even when exposed to a high temperature environment.
Specifically, as the maleimide polymer, the structural unit 1 is represented by the following formula (2).

(In the formula, R ^1a is a single bond or a divalent group, and R ^1b is a residue of an organic compound that exhibits a charge transport function when a voltage is applied.)
And a maleimide polymer represented by the formula:

Here, in the present invention, an organic compound that exhibits a charge transport function when a voltage is applied (hereinafter referred to as “organic charge transport compound”) is an organic compound having a chemical structure that exhibits a charge transport function when a voltage is applied. is there. Examples of the organic charge transport compound include materials for organic EL devices having a charge transport function. For example, typical low molecular weight electron transport materials and low molecular weight hole transport materials conventionally used in vacuum deposition methods, In addition, polymer electron transport materials, polymer hole transport materials, and the like described in Patent Document 1 are included, but these are representative examples and are not particularly limited. Auxiliary materials such as various doping compounds using a transport compound as a host material are also used as the organic charge transporting compound. The organic charge transporting compound in the present invention may be either a typical hole transporting property or electron transporting property, and may be a bipolar one having both hole transporting property and electron transporting property.
Further, the residue of the organic charge transport compound in the present invention is a monovalent organic group having a structure in which one atom or atomic group is removed from the organic charge transport compound, and the function related to the charge transport is lost. It means what is held without.

In formula (2), R ^1b which is the residue of the organic charge transport compound is carbazole or a derivative thereof, biscarbazole biphenyl or a derivative thereof, triarylamine or a derivative thereof, oxadiazole or a derivative thereof, triazine or a derivative thereof. A residue of at least one compound selected from the group is preferable because a charge transporting material having high charge transport performance and high heat resistance can be obtained.

  Examples of carbazole or derivatives thereof include carbazole, N-position alkyl-substituted carbazole, N-position phenyl-substituted carbazole, alkyl-substituted carbazole, and alkyl ether-substituted carbazole. Biscarbazole biphenyl or derivatives thereof include biscarbazole biphenyl (CBP), Examples include alkyl-substituted biscarbazole biphenyl, alkyl ether-substituted biscarbazole biphenyl, and the like, and triarylamine or derivatives thereof include triphenylamine, 4,4,4-tris (N-3-methylphenyl-N-phenylamino) And triphenylamine, N, N-bis- (3-methylphenyl) -N, N-bis (phenyl) benzidine, N, N-di (naphthalen-1-yl) -N, N-diphenylbenzidine and the like. As oxadiazole or derivatives thereof, 2- (4-biphenylyl) -5- (4-butylphenyl) -1,3,4-oxadiazole, 1,3,4-oxadiazole, 2,2- (1,3-phenylene) bis-5- [4- (1,1-dimethylethyl) phenyl] and the like. Examples of triazine or derivatives thereof include 2,4,6-triazine. And phenyl-triazine, 2,4,6-triphenyl-triazine alkyl substituents, and the like.

  Among these, the hole transporting group is a residue of carbazole or a derivative thereof, the electron transporting group is a residue of oxadiazole or a derivative thereof, and the bipolar group is a residue of biscarbazole biphenyl or a derivative thereof. Each is preferable, and excellent charge transport performance can be obtained.

R ^1b having a charge transporting property may be directly bonded to the N-position of the maleimide group of the structural unit represented by the formula (2), but the solvent solubility of the resulting polymer and the synthesis efficiency of the polymer are reduced. In consideration, the residue R ^1b of the organic charge transport compound is preferably bonded to the N position via a divalent group.
Examples of the divalent group include a divalent alkyl group (alkylene group), an alkyl ether group, an alkyl thioether group, an ester group, a thioester group, a carbamate group, a urea group, a thiourea group and the like. A cyclic functional group which may contain a hetero atom such as an aromatic group, a divalent phenylene group, a biphenylene group, a terphenylene group, an arylene group, a thiophene group, a pyrrole group, a furan group, a quinoline group or a quinoxaline group, or an aromatic group An organic group such as a group group or a hetero atom itself such as silicon can be selected. In order to obtain high charge transportability, the aliphatic group preferably has about 2 to 4 carbon atoms, and the aromatic group usually contains about 1 to 2 benzene rings.

  The doping group may be a residue of a low-molecular compound having a doping function, such as a perylene derivative, a coumarin derivative, a rubrene derivative, a quinacridone derivative, a squalium derivative, a porphyrin derivative, a styryl dye, a tetracene derivative, Examples thereof include a residue of at least one compound selected from the group consisting of a pyrazoline derivative, decacyclene, phenoxazone, quinoxaline derivative, carbazole derivative, fluorene derivative and the like.

  The maleimide polymer according to the present invention further comprises the following formula (3):

(In the formula, R ² represents a group that emits light when a voltage is applied.)
When the structural unit 2 represented by the formula is included in the main chain skeleton, the charge can be transported by applying a voltage, and further the light can be emitted by itself. A light emitting layer is obtained.
Specifically, as the compound of the formula (3), the structural unit 2 is represented by the following formula (4).

(In the formula, R ^2a is a single bond or a divalent group, and R ^2b is a residue of an organic compound that emits light when a voltage is applied.)
And a maleimide polymer represented by the formula:

Here, in the present invention, the group that emits light when a voltage is applied is a group that itself emits light when a voltage is applied. Such a group that emits light by application of voltage includes, for example, various fluorescent materials used as an organic EL material, but is not particularly limited, and is of another light emitting type such as phosphorescence. Also good.
In the present invention, the organic compound that emits light when a voltage is applied (hereinafter referred to as an organic light-emitting compound) is an organic compound that contains a chemical structure that emits light when a voltage is applied. The residue of the organic light-emitting compound is a monovalent organic group having a structure in which one atom or atomic group is removed from the organic light-emitting compound, and the function relating to the organic electroluminescence is retained without loss. Say what you are.
Furthermore, in the present invention, electroluminescence means light emission obtained by applying an electric field to the organic light-emitting compound, and includes, for example, fluorescence by typical electroluminescence, but is not limited thereto. Alternatively, other light emission types such as phosphorescence may be used.

As R ^2b , residues of various organic light-emitting compounds, such as fluorescent or phosphorescent groups, can be introduced.
As the fluorescent or phosphorescent group, a residue of various low molecular compounds having fluorescence or phosphorescence can be used as well as a fluorescent dye known as an organic EL fluorescent material. . Examples of the fluorescent light-emitting group include pyrene compounds, perylene compounds, naphthalene compounds, phenanthrene compounds, tetracene compounds, quinacridone compounds, dioxazine compounds, coronene compounds, fluorescein compounds, coumarin compounds, quinolines. Examples include a residue of at least one compound selected from the group consisting of metal complex compounds, styryl compounds, silole compounds, oxadiazole compounds, and the like. Examples of the phosphorescent group include residues such as rare earth metal coordination compounds and iridium coordination compounds.

  Among these, pyrene compounds, perylene compounds, naphthalene compounds, phenanthrene compounds, tetracene compounds, quinacridone compounds, dioxazine compounds, coronene compounds, fluorescein compounds, coumarin compounds, quinoline metal complex compounds, rare earths The residue of at least one compound selected from the group consisting of a metal coordination compound and an iridium coordination compound is preferable because a light emitting layer having high light emission ability and high heat resistance can be obtained.

  Examples of the pyrene compound include pyrene, aminopyrene, bromopyrene, chloromethylpyrene, pyrenebutylcarboxylic acid, and pyrenemethanol; examples of the perylene compound include perylene and perylenetetracarboxylic acid diimide; Include naphthalene, naphthalenetetracarboxylic acid diimide, naphthalimide, aminonaphthalene, etc .; phenanthrene compounds include phenanthrene, phenanthroline, phenanthrenequinone, etc .; tetracene compounds include tetracene, tetracenequinone, Aminotetracene rubrene and the like; quinacridone compounds include quinacridone, dichloroquinacridone, N, N′-dimethylquinacridone, quinacridine, dibenzoquinacridone and the like. Examples of the dioxazine compound include dioxazine, N, N′-dimethyldioxazine, and dibenzodioxazine; examples of the coronene compound include coronene, coronene diimide, and amino coronene; and examples of the fluorescein compound Fluorescein, fluorescein chloride, fluorescin and the like; coumarin compounds include coumarin, benzothiazoyldiethylaminocoumarin, coumarone and the like; quinoline metal complex compounds include aluminum-triquinolinol complex, zinc-diquinolinol Complex, lithium boron-tetraquinolinol complex, etc .; styryl compounds include distyrylbenzene, distyrylarylene, biscarbazolebenzidine, etc .; rare earth metal coordination Examples of the compound include europium-acetylacetone complex, europium-diphenylphenanthroline complex, europium-dibenzoylmethane complex and the like; examples of the iridium coordination compound include iridium-phenylpyridine complex, iridium-acetylacetone complex, iridium-phenanthroline complex and the like. Is mentioned.

Among these, when forming a light-emitting layer having a charge transport property using the maleimide polymer, pyrene, perylene, quinacridone, coumarin, and iridium coordination compounds are particularly preferable in terms of thermal stability and light-emitting properties. preferable. In particular, an iridium compound that is a phosphorescent group has a higher luminous efficiency than a fluorescent group and is preferable.
The residue of the organic light emitting compound may have a substituent for the purpose of adjusting the solubility and emission wavelength of the maleimide polymer and increasing the light emission efficiency. Examples of the substituent introduced into the residue of the organic light emitting compound include an alkyl group, an alkoxyl group, a halogen group, and a halogenated alkyl group.

The luminescent R ^2b may be directly bonded to the N-position of the maleimide group of the structural unit represented by the formula (4), but considering the solvent solubility of the polymer obtained and the synthesis efficiency of the polymer. Then, it is preferable that the residue R ^2b of the organic light emitting compound is bonded to the N position via a divalent group.
Examples of the divalent group include a divalent alkyl group (alkylene group), an alkyl ether group, an alkyl thioether group, an ester group, a thioester group, a carbamate group, a urea group, a thiourea group and the like. A cyclic functional group which may contain a hetero atom such as an aromatic group, a divalent phenylene group, a biphenylene group, a terphenylene group, an arylene group, a thiophene group, a pyrrole group, a furan group, a quinoline group or a quinoxaline group, or an aromatic group An organic group such as a group group or a hetero atom itself such as silicon can be selected. In order to obtain high light-emitting properties, the aliphatic group preferably contains about 2 to 4 carbon atoms, and the aromatic group usually contains about 1 to 2 benzene rings.

  The maleimide polymer of the present invention is suitable for coating film formation itself, and without adding a binder material, a charge transport layer that exhibits the desired charge transport performance, a light emitting layer having charge transport properties, etc. It can be formed easily and the manufacturing process can be simplified.

  In addition to the essential structural unit of the above formula (1) and the structural unit having the light-emitting property of the above formula (3), the maleimide polymer can be used for adjusting the light intensity by changing the concentration of the charge transporting group. In order to improve coating suitability such as solubility, other copolymerizable components copolymerizable with maleimide can be included. Examples of other copolymer components include N-substituted maleimide monomers, compounds having an ethylenic double bond, and other double bonds. N-substituted maleimide monomers include aromatic substitution such as N-phenylmaleimide, N-benzylmaleimide, N-hydroxyphenylmaleimide, N-methylphenylmaleimide, N-methoxyphenylmaleimide, N-chlorophenylmaleimide, N-naphthylmaleimide, etc. In addition to maleimide, alkyl-substituted maleimides such as N-methylmaleimide, N-ethylmaleimide, N-propylmaleimide, N-cyclohexylmaleimide and the like can be mentioned. Examples of the compound having an ethylenic double bond and other double bonds include styrene, α-methylstyrene, o-vinyltoluene, m-vinyltoluene, p-vinyltoluene, p-chlorostyrene, o-methoxystyrene, Aromatic vinyl compounds such as m-methoxystyrene, p-methoxystyrene, indene, p-vinylbenzylmethyl ether, p-vinylbenzylglycidyl ether; methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate, n -Propyl methacrylate, i-propyl acrylate, i-propyl methacrylate, n-butyl acrylate, n-butyl methacrylate, i-butyl acrylate, i-butyl methacrylate, sec-butyl acrylate, ec-butyl methacrylate, t-butyl acrylate, t-butyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate 2-hydroxybutyl acrylate, 2-hydroxybutyl methacrylate, 3-hydroxybutyl acrylate, 3-hydroxybutyl methacrylate, 4-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate, allyl acrylate, allyl methacrylate, benzyl acrylate, benzyl methacrylate, phenyl Acrylate, phenyl methacrylate, methoxytriethylene gluco Unsaturated carboxylic acid esters such as acrylate acrylate and methoxytriethylene glycol methacrylate; acrylic acid, methacrylic acid, crotonic acid, α-chloroacrylic acid, ethacrylic acid, cinnamic acid, ω-carboxy-polycaprolactone monoacrylate, ω- Unsaturated monocarboxylic acids such as carboxy-polycaprolactone monomethacrylate, 2-acryloyloxyethyl succinic acid, 2-methacryloyloxyethyl succinic acid; maleic acid, maleic anhydride, fumaric acid, itaconic acid, itaconic anhydride, citracone Unsaturated dicarboxylic acids (anhydrides) such as acid, citraconic anhydride, mesaconic acid; trivalent or higher unsaturated polycarboxylic acids (anhydrides); 2-aminoethyl acrylate, 2-aminoethyl methacrylate, 2- Aminopropyl acrylate, 2 Unsaturated carboxylic acid aminoalkyl esters such as aminopropyl methacrylate, 3-aminopropyl acrylate and 3-aminopropyl methacrylate; Unsaturated carboxylic acid glycidyl esters such as glycidyl acrylate and glycidyl methacrylate; vinyl acetate, vinyl propionate and vinyl butyrate Carboxylic acid vinyl esters such as vinyl benzoate; unsaturated ethers such as vinyl methyl ether, vinyl ethyl ether, allyl glycidyl ether, methallyl glycidyl ether; acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, vinylidene cyanide, etc. Vinyl cyanide compounds: acrylamide, methacrylamide, α-chloroacrylamide, N-hydroxyethyl acrylamide, N-hydroxyethyl methacrylate Unsaturated amides such as chloramide; aliphatic conjugated dienes such as 1,3-butadiene, isoprene and chloroprene; polystyrene, polymethyl acrylate, polymethyl methacrylate, poly-n-butyl acrylate, poly-n-butyl methacrylate, poly Examples thereof include macromonomers having a monoacryloyl group or a monomethacryloyl group at the end of a polymer molecular chain such as siloxane; vinylpyrrolidone, vinylcarbazole and the like.

  Among these, as the other copolymer component of the maleimide copolymer in the present invention, a styrene monomer, a (meth) acrylate monomer, and vinyl carbazole are preferable from the viewpoint of heat resistance, transparency, and reactivity. , Methyl methacrylate, and vinyl carbazole are preferable. The other copolymerization components can be used alone or in admixture of two or more.

In the maleimide polymer, an optimum constituent unit is selected in accordance with required characteristics, and the proportion of the constituent unit is adjusted. Any number of types of structural units may be included, and the proportion of each structural unit can be arbitrarily contained.
In order to impart sufficient charge transport performance and heat resistance to the maleimide polymer of the present invention, the copolymerization ratio of the structural unit represented by the formula (1) contained in the maleimide polymer is 0.1 mol%. Preferably, it is preferably 10 mol% or more, more preferably 30 mol% or more.

  In the maleimide polymer of the present invention, the sum of the copolymerization ratios of the structural unit 1 represented by the above formula (1) and N-substituted maleimide monomer units as other copolymerization components is 30 mol% or more. And more preferably 50 mol% or more. When the sum of the copolymerization ratios of the N-substituted maleimide monomer units is less than 30 mol%, the heat resistance may be lowered. Therefore, in accordance with the required heat resistance, the above formula (1) and other N -The proportion of substituted maleimide monomer units needs to be adjusted.

When the maleimide polymer of the present invention contains the structural unit 1 represented by the formula (3) having a light-emitting property together with the structural unit 1 represented by the formula (1) having a charge transporting property, sufficient In order to impart excellent charge transport performance and light-emitting performance, it is preferable to use a copolymer containing 50 to 90 mol% of the structural unit 2 and 50 to 90 mol% of the other component including the structural unit 1.
When the maleimide polymer of the present invention is used for forming a single layer structure in an organic electroluminescent device, that is, when used for forming a light emitting layer having both a hole transporting property and an electron transporting property. It is necessary to impart the property of being able to sufficiently transport both holes and electrons and emitting light. In such a case, the maleimide polymer of the present invention, for example, when the residue of a pyrene compound is used as R ^2b in the structural unit 2 represented by the above formula (4), the structural unit 2 Is preferably contained in a proportion of 50 to 90 mol%, and when a residue of a quinacridone compound is used as R ^2b , the structural unit 2 is It is preferable to contain 50 to 90 mol% of other components including the structural unit 1 in a proportion of 50 to 90 mol%, or when a residue of a rare earth metal coordination compound is used as R ^2b It is preferable to contain 20 to 10 mol% of the unit 2 and 80 to 90 mol% of other components including the structural unit 1.

The molecular weight of the maleimide polymer is preferably 10,000 to 100,000 in terms of weight average molecular weight and most preferably 10,000 to 50,000 in order to maintain solvent solubility and uniform film-forming properties. If a weight average molecular weight is the said range, solvent solubility, film-forming property, heat resistance, and heat stability will be hold | maintained preferably.
The maleimide polymer preferably has a weight average molecular weight to number average molecular weight ratio (Mw / Mn) measured by GPC (gel permeation chromatography) of 3 or less, more preferably 2.5 or less. The following are most preferred. If it is the said range, heat resistance, thermal stability, a charge transport characteristic, etc. will be hold | maintained preferably.

In the maleimide polymer according to the present invention, one or more N-substituted maleimide monomers corresponding to the structural unit represented by the formula (1) are (co) polymerized with other monomers as necessary. Can be synthesized.
As a method for synthesizing the maleimide polymer, known solution polymerization, suspension polymerization, emulsion polymerization and the like can be adopted, but suspension polymerization and emulsion polymerization are mixed with a suspending agent and an emulsifier. In addition, there is a possibility that the charge transport property may be lowered. Therefore, it is preferable to use a solution obtained by a solution polymerization method in which copolymerization is performed in the presence of a solvent.
The polymerization temperature in the polymerization reaction may be set according to the polymerization initiator to be used, and is not particularly limited, but is preferably 50 to 150 ° C, and more preferably 70 to 120 ° C. When the polymerization temperature is lower than the above range, it is necessary for an initiator having a low decomposition temperature, which is disadvantageous for industrial production, such as requiring equipment for cooling and storing the initiator. On the other hand, when the polymerization temperature exceeds the above range, the polymerization component starts to thermally polymerize before reaching the decomposition temperature of the initiator, which is not preferable.

  The solvent used in the solution polymerization is not particularly limited as long as it does not interfere with the solution polymerization reaction and can dissolve both the raw material polymerization component and the produced maleimide polymer. For example, methanol Aliphatic alcohols having 1 to 3 carbon atoms such as ethanol, glycol, etc .; cellosolves such as cellosolve and butylcellosolve; carbitols such as carbitol and butylcarbitol; cellosolve acetate, carbitol acetate, propylene glycol monomethyl ether acetate Esters such as diethylene glycol dimethyl ether; cyclic ethers such as tetrahydrofuran; ketones such as cyclohexanone, methyl ethyl ketone and methyl isobutyl ketone; or having polarity such as dimethyl sulfoxide and dimethylformamide A solvent may be used. The solvent used for non-aqueous dispersion polymerization is not particularly limited as long as the polymerization component as a raw material can be dissolved and the produced maleimide polymer is insoluble, and for example, benzene, toluene, hexane, Liquid hydrocarbons such as cyclohexane or other non-polar organic solvents can be used. The amount of the solvent used in the above solution polymerization or non-aqueous dispersion polymerization is preferably 70 to 95% by weight, more preferably 85 to 95% by weight based on the total weight of the polymerization components. If the amount of the solvent is within the above range, there is no fear that stirring will be insufficient due to thickening at the end of the polymerization, and there is no fear that the molecular weight of the maleimide polymer produced will be too small.

As a polymerization initiator for producing a maleimide polymer, a peroxide or an azo initiator which is a known radical polymerization initiator is preferably used. A polymerization initiator is suitably selected according to polymerization temperature, and is normally used in the ratio of 0.001-5.0 weight% with respect to the total amount of a copolymerization component.
In order to adjust the molecular weight of the maleimide polymer, a chain transfer agent can be used during polymerization, and examples thereof include α-methylstyrene and mercaptan chain transfer agents.
After completion of the polymerization reaction, the maleimide polymer can be separated by removing volatiles from the reaction solution. The reaction solution is heated under vacuum, the reaction solution is poured into a poor solvent, precipitated, and filtered. Method can be adopted.

(2) Ink for organic electroluminescent elements The ink for organic electroluminescent elements according to the present invention contains, as an essential component, a maleimide polymer having a main chain skeleton containing at least the structural unit 1 represented by the formula (1). It is characterized by doing.
Therefore, the ink for organic electroluminescent elements according to the present invention can be obtained by (1) changing the concentration of the structural unit 1 of the formula (1) having a charge transporting group contained in the maleimide polymer, By changing the type of the charge transporting group of the structural unit 1 of the formula (1) contained in the combination, or by combining two or more types of the structural unit 1 of the formula (1) having different types of charge transporting groups, By adjusting the charge transport performance of the layers constituting the organic electroluminescent device according to the purpose, the device characteristics such as the luminous efficiency of the organic electroluminescent device can be changed, and (2) suitable for maleimide polymers By introducing such a copolymerization monomer, the coating suitability can be improved, and the layer form and electrical properties can be optimized.

In addition, since the ink for organic electroluminescent elements according to the present invention uses the maleimide polymer having high heat resistance as a material for electroluminescent elements, even if it is heated to a high temperature during the production of a display element, the yellowing occurs. It is difficult to cause discoloration and brightness reduction. Furthermore, not only when exposed to a heating process for manufacturing an organic electroluminescent element, but also because the display device is left outdoors after production or the temperature of the display device rises during use. Even when exposed to a high temperature environment, discoloration such as yellowing and a decrease in luminance hardly occur, and display quality deterioration can be prevented. Therefore, an organic electroluminescent element excellent in display quality and excellent in durability can be obtained.
In addition, the organic electroluminescent element ink according to the present invention contains the maleimide polymer as an essential component and is excellent in solubility or dispersibility in a solvent and coating suitability. An organic electroluminescent element can be formed by a wet film forming method. Therefore, when the ink for organic electroluminescent elements according to the present invention is used, the production cost is lower than that of the vacuum deposition method, and it can be easily applied to a large-area substrate.

In addition, when the maleimide polymer contained in the organic electroluminescent element ink according to the present invention contains the structural unit 2 of the formula (3) having luminescent property in the main chain skeleton, the luminescent property as well as the charge transporting property is exhibited. An organic electroluminescent element ink having the above can be obtained, and an organic layer that is required to emit light as well as charge transport can be formed, and the manufacturing process can be simplified.
Furthermore, hole charge transportability, electron charge transportability, which could only be formed by a dry film-forming method such as a conventional vacuum deposition method, with a maleimide polymer contained in the ink for an organic electroluminescence device according to the present invention. Alternatively, coating suitability is imparted to low molecular weight compounds having both charge transport properties, and a wet film forming method can be used while maintaining the characteristics of these low molecular weight compounds, and combinations of these low molecular weight compounds can be used. Also has the advantage that it can be freely used.

  In the present invention, the reaction liquid obtained by synthesizing the maleimide polymer may be used as an organic electroluminescent element ink as it is, or a reaction liquid containing the maleimide polymer or the reaction liquid. The ink for organic electroluminescence device may be prepared by dissolving or dispersing the maleimide polymer separated from the solvent in a solvent to adjust the concentration so that it can be applied, and adding other components as necessary.

Other components blended in the ink for an organic electroluminescent element vary depending on the use of the ink. For example, a charge transport layer using a maleimide polymer introduced with a residue of an organic compound having a charge transport function In the case of an ink for use, a doping agent may be added for the purpose of improving charge transport performance and light emission efficiency. Examples of such doping agents include perylene derivatives, coumarin derivatives, rubrene derivatives, quinacridone derivatives, squalium derivatives, porphyrin derivatives, styryl dyes, tetracene derivatives, pyrazoline derivatives, decacyclene, phenoxazone, quinoxaline derivatives, carbazole derivatives, fluorene derivatives, etc. Can be mentioned.
Furthermore, various additives can also be mix | blended with the ink for organic electroluminescent elements of this invention as needed. For example, for example, polysiloxane can be blended to improve the leveling property.

  As a solvent for preparing the ink for an organic electroluminescent element of the present invention, it is desired that a maleimide polymer is dissolved, has a high boiling point, and has good coating properties. Examples of usable solvents include alcohol solvents such as methyl alcohol, ethyl alcohol, N-propyl alcohol, and i-propyl alcohol; cellosolv solvents such as methoxy alcohol and ethoxy alcohol; carbs such as methoxyethoxyethanol and ethoxyethoxyethanol. Toll solvents; ester solvents such as ethyl acetate, butyl acetate, methyl methoxypropionate, ethyl ethoxypropionate, and ethyl lactate; ketone solvents such as acetone, methyl isobutyl ketone, cyclohexanone; methoxyethyl acetate, ethoxyethyl acetate, ethyl Cellosolve acetate solvents such as cellosolve acetate; Carbitol acetates such as methoxyethoxyethyl acetate and ethoxyethoxyethyl acetate Solvents; ether solvents such as diethyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and tetrahydrofuran; aprotic amide solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, and N-methylpyrrolidone; and γ-butyrolactone Lactone solvents; unsaturated hydrocarbon solvents such as benzene, toluene, xylene and naphthalene; organic solvents such as saturated hydrocarbon solvents such as N-heptane, N-hexane and N-octane, or a mixed solvent thereof It can be illustrated.

Among these solvents, ethyl lactate, tetrahydrofuran, dimethylformamide, and the like are preferable from the viewpoint of solubility, and toluene, xylene, and the like are preferable from the viewpoint of film formability. In practice, it is preferable to use a mixed solvent thereof.
In particular, when the layer is formed through a rotation processing step as will be described later, the rotation processing step is performed after the coating step, so that it is possible to ensure smoothness during the rotation processing step if it is volatilized immediately. Therefore, it is preferable to use a solvent having as low a volatility as possible. Specific examples include trichloroethane, xylene, toluene, ethanol, water, cyclohexanone, 1,4-dioxane, diphenyl ether, monochlorobenzene, mesitylene, cymene, phenetole, anisole, dodecylbenzene, tetralin and the like.

  The amount of the solvent used is appropriately adjusted in consideration of the dissolved state of the compounding components and the coating properties, but is usually adjusted so that the solid content concentration is about 0.5% to 5%. In particular, when a layer is formed through a rotation process as described later, the concentration of such ink depends on the desired film thickness of the layer to be formed, the material to be dissolved or dispersed, the type of solvent, and the like. Although it is greatly different, if the concentration is too high, the layer cannot have a desired thickness, and if it is too low, it is difficult to ensure smoothness. Therefore, the solid content concentration is usually in the range of 0.01% to 20% by weight, in particular in the range of 0.1% to 10% by weight, in particular in the range of 0.2% to 5.0% by weight. Is preferably used.

  The ink for organic electroluminescence device thus obtained has a charge transport layer such as a hole transport layer and an electron transport layer, and a charge integrated with a charge injection layer provided with a charge injection function. A light emitting layer integrated with a charge transport layer in which a charge transport function is added to the transport layer and the light emitting layer can be formed.

(3) Organic electroluminescent device The organic electroluminescent device according to the present invention includes a layer containing, as an essential component, a maleimide polymer having a main chain skeleton containing at least the structural unit 1 represented by the formula (1). It is characterized by that.
The ink containing the maleimide polymer according to the present invention is coated on an appropriately selected substrate by a wet method, and has a charge transport layer and a charge transport function by drying and / or curing as necessary. An organic electroluminescent element can be produced by forming a functional layer such as a light emitting layer that requires charge transporting properties.

  Since the organic electroluminescent device according to the present invention uses the maleimide polymer as a charge transporting material, as described above, the type and concentration of the structural unit 1 of the formula (1) contained in the maleimide polymer. Or the charge transport efficiency of the layer constituting the organic electroluminescent element is adjusted by combining two or more structural units 1 of the formula (1), and the device characteristics such as the luminous efficiency of the organic electroluminescent element Can be optimized as appropriate, or by introducing a suitable copolymerization monomer into the maleimide polymer, the coating suitability can be improved, or the properties of the charge transport layer included in the electroluminescent device can be optimized. It has the merit of being able to. Further, when the maleimide polymer contains the structural unit 2 represented by the formula (3) in the main chain skeleton, an organic electroluminescence device having a light emitting layer having a charge transporting function is formed. And the manufacturing process can be simplified.

In addition, since the maleimide polymer is excellent in heat resistance, it is difficult to cause discoloration such as yellowing or a decrease in luminance, and an organic electroluminescence device excellent in durability with little deterioration in display quality can be obtained.
Moreover, since the ink for organic electroluminescent elements containing the said maleimide polymer is excellent in application | coating suitability as mentioned above, it is possible to form an organic electroluminescent element with a wet film-forming method. Therefore, an organic electroluminescence device having high productivity and a large area can be obtained.

Hereinafter, among organic electroluminescent elements according to the present invention, an organic EL element will be described as an example.
The base material used in the present invention is not particularly limited, and may be formed so as to serve as the electrode layer as long as the electrode layer has a necessary strength.
The material of the substrate may be a flexible material or a hard material depending on the application. Specific examples of materials that can be used include glass, polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polymethyl acrylate, polyester, and polycarbonate. These base materials need to be transparent when the light emitted from the light emitting layer is extracted through the substrate side, but transparent when extracted from the opposite side of the substrate. The material is not limited to this.
Further, the shape of the base material may be a single wafer shape or a continuous shape. Specific examples of the shape include a card shape, a film shape, a disk shape, and a chip shape.

The layer containing the maleimide polymer as an essential component is formed on the electrode layer formed on the substrate surface. The electrode layer is formed on the above-described substrate by, for example, a method such as vacuum sputtering or vacuum deposition, a method of forming by applying a coating liquid, and the manufacturing method thereof is not particularly limited.
Similarly to the base material, the electrode layer has different transparency requirements depending on the direction in which the light emitted from the light-emitting layer is extracted. It needs to be formed of a material and does not need to be transparent when taken from the opposite side of the substrate.

  Further, the electrode layer may be an anode or a cathode, but is usually formed as an anode. Examples of the material for the electrode layer when formed as such an anode include metals having a large work function such as indium tin oxide (ITO), indium oxide, and gold, polyaniline, polyacetylene, polyalkylthiophene derivatives, and polysilane derivatives. And the like, and the like. On the other hand, materials used when this electrode layer is formed as a cathode include magnesium alloys such as MgAg, aluminum alloys such as AlLi, AlCa, and AlMg, alkali metals such as Li and Ca, and these alkali metals. A metal having a small work function such as an alloy of

  An EL element is formed on the surface of the base material on which such an electrode layer is formed. Here, the EL element is formed of one or more organic layers including a light emitting layer and an electrode. That is, an EL element is a layer including at least a light emitting layer, and an organic element having a layer configuration of one or more organic layers. Usually, when an EL element is formed by a wet method by coating, it is difficult to stack a large number of layers in relation to the solvent, so that it is often formed by one or two organic layers. Further, it is possible to further increase the number of layers by devising organic materials or combining vacuum deposition methods.

In addition to the light-emitting layer, the layers formed in the EL element include a charge injection layer such as a hole injection layer and an electron injection layer, and a charge transport layer such as a hole transport layer and an electron transport layer, and a charge injection layer. In addition, various functional layers such as a charge transport layer, a hole blocking layer, an electron blocking layer, and other layers for preventing carrier penetration and efficiently recombining carriers can be used.
Among the EL element-forming functional layers, at least one layer that requires charge transportability contains, as an essential component, a maleimide polymer having a main chain skeleton containing at least the structural unit 1 represented by the formula (1) When formed using the organic electroluminescent element ink of the present invention, the organic electroluminescent element according to the present invention can be produced. Specifically, the organic electroluminescent element ink according to the present invention is applied to the surface of the base material on which the electrode layer is formed or the functional layer that has already been formed to apply an electronic charge. A functional layer such as a transport layer, a hole charge transport layer, a charge transport layer such as a bipolar charge transport layer, or a light emitting layer having charge transport properties is formed.

The application method is not particularly limited, and any method can be used as long as it can apply the organic electroluminescent element ink on a substrate. Specific examples include spin coating, die coating, bead coating, and blade coating. In order to obtain a layer having a high surface smoothness and high film uniformity even in a large area, it is applied after a coating process such as a bead coating method as disclosed in JP-A-2001-351780. It is preferable to employ a production method that undergoes a rotation treatment step of smoothing the surface of the organic layer by rotating the substrate.
When forming a functional layer involved in electroluminescence, such as the above-described charge transport layer or light-emitting layer having charge transport properties, using the ink for organic electroluminescence elements, the type and formation of the organic electroluminescence element For example, when a charge transport layer or a light-emitting layer having charge transport properties is formed, the film thickness is preferably 10 to 100 nm, and more preferably 50 to 90 nm.

After apply | coating the said ink on a base material, the hardening process etc. according to the property of the ink are given, and a layer is formed. Specifically, the layer is formed by processing by natural drying, vacuum drying, a method of removing the solvent by heating, a method of curing by irradiation with light or the like, and the like.
In the case of producing an organic electroluminescent element, for example, an organic EL element in the present invention, at least one layer that requires charge transportability is formed using the above-described organic electroluminescent element ink among the functional layers for forming an EL element. If necessary, another functional layer is formed by another method. Then, by forming various members necessary for the organic EL element, such as forming a second electrode layer on this one layer or a plurality of functional layers, further forming a protective layer, sealing, etc. An EL element can be obtained.
Other organic electroluminescent elements can also be obtained in the same manner as the organic EL element after changing the method as necessary.

In this way, it is possible to obtain a high-quality organic electroluminescent element that has high heat resistance and does not cause display quality deterioration such as discoloration or luminance reduction. According to the wet method, an organic electroluminescent element having a large display area can be obtained.
The organic electroluminescent element manufactured in this way is subjected to thermocompression bonding with the module obtained through the module process and an anisotropic conductive film (ACF) or the like, whereby a light emitting panel is obtained.

(Example 1)
<Synthesis of N-3- (9-ethylcarbazoyl) maleimide / vinylcarbazole copolymer>
In a 20 ml reaction vessel, 5.0 parts by weight of N-3- (9-ethylcarbazoyl) maleimide, 5.0 parts by weight of vinylcarbazole, 90 parts by weight of methyl ethyl ketone as a solvent, and t-butylperoxy-2-2 as a polymerization initiator. 0.2 parts by weight of ethyl hexanoate (“Perbutyl O” manufactured by Nippon Oil & Fats Co., Ltd.) was added, and after replacing the gas phase with nitrogen, heating was carried out in an oil bath at 80 ° C. to conduct a polymerization reaction for 5 hours. . Thereafter, the reaction product is cooled to room temperature and then poured into a large amount of methanol to precipitate a polymer. The precipitated polymer is filtered, washed with methanol, dried in a vacuum dryer at 100 ° C., and the following formula (5 N-3- (9-ethylcarbazoyl) maleimide / vinylcarbazole copolymer (50/50 weight ratio) represented by the following formula: The yield calculated from the weight of the obtained copolymer was 80%.

(This is a random copolymer. In the formula, l and m are each integers.)
About the obtained copolymer, the glass transition point measured with the differential scanning calorimeter (DSC) ("DSC8230" by Rigaku Denki) is 220 degreeC, and a differential thermothermal weight simultaneous measuring apparatus (TG-DTA) (Science The thermal decomposition temperature (5% weight loss temperature) measured at a heating rate of 10 ° C./min under a nitrogen stream with an electric “TG8120”) was 310 ° C.

(Example 2)
<Iridium acetylacetonate complex of N-3- (9-ethylcarbazoyl) maleimide / N-3- (2-phenylpyridyl) maleimide / vinylcarbazole copolymer>
(Synthesis of precursor copolymer)
In a 20 ml reaction vessel, 3.0 parts by weight of N-3- (9-ethylcarbazoyl) maleimide, 3.0 parts by weight of N-3- (2-phenylpyridyl) maleimide, 4.0 parts by weight of vinylcarbazole, as a solvent 90 parts by weight of methyl ethyl ketone, 0.2 part by weight of t-butyl peroxy-2-ethylhexanoate (“Perbutyl O” manufactured by Nippon Oil & Fats Co., Ltd.) as a polymerization initiator were added, and the gas phase part was replaced with nitrogen. The polymerization reaction was carried out for 5 hours by heating in an oil bath at 80 ° C. Thereafter, the reaction product is cooled to room temperature and then poured into a large amount of methanol to precipitate a polymer. The precipitated polymer is filtered, washed with methanol, dried in a vacuum dryer at 100 ° C., and N-3. -(9-Ethylcarbazoyl) maleimide / N-3- (2-phenylpyridyl) maleimide / vinylcarbazole copolymer (30/30/40 weight ratio) was obtained. The yield calculated from the weight of the obtained copolymer was 80%.

(Synthesis of luminescent maleimide copolymer by iridium complex)
In a 30 ml reaction vessel, 0.5 g of the N-3- (9-ethylcarbazoyl) maleimide / N-3- (2-phenylpyridyl) maleimide / vinylcarbazole copolymer obtained above, iridium acetylacetonate complex ( 0.5 g of Ir (acac) ₃ ) and 20 g of glycerin as a solvent were added and reacted at 180 ° C. for 12 hours under a nitrogen stream. After further cooling to room temperature, 10 g of chloroform was added, and the mixture was reacted for 24 hours under reflux of chloroform.
Thereafter, the reaction mixture was diluted with 20 g of chloroform and washed with dilute aqueous hydrochloric acid. After further washing with ion-exchanged water 5 times, the solvent was distilled off from the organic layer, dissolved again in 2 g of chloroform, poured into a large amount of methanol, and the precipitated yellow powder was filtered. An N-3- (9-ethylcarbazoyl) maleimide / N-3- (2-phenylpyridyl) maleimide / vinylcarbazole copolymer represented by the following formula (6) after being dried in a vacuum dryer at 100 ° C. 0.5 g of iridium acetylacetonate complex was obtained.

(This is a random copolymer. In the formula, l, m and n are each integers.)
The complexing rate of the N-3- (2-phenylpyridyl) maleimide monomer unit determined from elemental analysis of iridium was 60%. The weight average molecular weight determined by gel permeation chromatography (GPC) using polystyrene as a standard substance was 22,000.

(1) Evaluation of film formability A 1% by weight dichloroethane solution of the maleimide copolymer obtained in Example 1 and a 1% by weight dichloroethane solution of the maleimide polymer obtained in Example 2 were each placed on an alkali-free glass substrate. As a result of coating by spin coating, a uniform transparent coating film having no precipitate was formed.

(2) Evaluation of luminous characteristics The luminous characteristics were evaluated with a spectrofluorometer (F-4500, manufactured by Hitachi, Ltd.) using the 1% by weight dichloroethane solution of the maleimide copolymer obtained in Example 2 as a specimen. . As a result, in addition to light emission derived from a broad carbazole component (maximum wavelength 440 nm), good light emission derived from a light emitting group was confirmed at 520 nm.

(3) Evaluation of heat resistance Each coated film sample obtained in the evaluation of film formability was heated in an oven at 150 ° C. for 1 hour, and then the film surface was observed and the weight reduction rate was investigated (TGA manufactured by PerkinElmer Co., Ltd.). Thermal analyzer was used). As a result, there was no discoloration or alteration of the film, the weight change rate before and after heating was 5% or less, and it was confirmed that the maleimide copolymers obtained in Example 1 and Example 2 have sufficient heat resistance. It was done.

(4) Preparation and operation check of organic EL element <Organic EL element 1>
The substrate on which a transparent conductive film of ITO was formed on a glass substrate was subjected to cleaning and UV / ozone treatment. Subsequently, a poly-3,4-ethylenedioxythiophene / polystyrene sulfonate aqueous dispersion (abbreviated as PEDOT / PSS, trade name Baytron PTP AI4083, manufactured by Bayer) was dropped onto the substrate and spin-coated. Then, a hole injection layer having a film thickness of 50 nm was formed by heating and drying on a hot plate at 140 ° C. for 30 minutes.
Subsequently, a 1% by weight dichloroethane solution of maleimide polymer obtained in Example 1 (maleimide polymer ink) was spin-coated on the hole injection layer. Thereafter, a hole transport layer having a film thickness of 50 nm was formed by heating and drying on a 100 ° C. hot plate. Further, a red light emitting layer ink (trade name: ADS100TS, manufactured by American Dye Source) was dropped on the hole transport layer, spin-coated, and similarly heated and dried on a 100 ° C. hot plate to obtain a film thickness. An 80 nm red light emitting layer was formed. Subsequently, a calcium thin film having a film thickness of 10 nm was vacuum-deposited at a film formation rate of 0.2 nm / s, and a silver thin film having a film thickness of 80 nm was further vacuum-deposited thereon at a film formation speed of 2 nm / s to form an electrode. An organic EL device 1 was obtained.

  When the ITO electrode of the obtained organic EL element 1 was connected to the positive electrode of the variable DC power source, the silver electrode was connected to the negative electrode, and a DC voltage was applied, a maximum luminous efficiency of 0.7 cd / A was obtained from the light emitting layer. Red EL emission was confirmed.

<Organic EL element 2>
The substrate on which a transparent conductive film of ITO was formed on a glass substrate was subjected to cleaning and UV / ozone treatment. Next, an aqueous dispersion of poly-3,4-ethylenedioxythiophene / polystyrene sulfonate (abbreviated as PEDOT / PSS, trade name Baytron PTP AI4083, manufactured by Bayer) was dropped onto the substrate and spin-coated. Then, a hole injection layer having a film thickness of 50 nm was formed by heating and drying on a hot plate at 140 ° C. for 30 minutes.
Subsequently, a 1 wt% solution of maleimide polymer in dichloroethane obtained in Example 2 (maleimide polymer ink) was spin-coated on the hole injection layer. Thereafter, it was heated and dried on a hot plate at 100 ° C. to form a hole transport layer / phosphorescent layer having a thickness of 100 nm. Subsequently, a calcium thin film having a film thickness of 10 nm was vacuum-deposited at a film formation rate of 0.2 nm / s, and a silver thin film having a film thickness of 80 nm was further vacuum-deposited thereon at a film formation speed of 2 nm / s to form an electrode. Organic EL element 2 was obtained.

  When the light emission characteristics of the obtained organic EL element 2 were evaluated by the same method as the organic EL element 1, good green EL light emission with a maximum light emission efficiency of 10 cd / A was confirmed from the hole transport layer / phosphorescent light emitting layer. It was done.

<Organic EL element 3>
In the production of the organic EL device 1, the maleimide polymer obtained in Example 1 was replaced with polyvinylcarbazole (a reagent manufactured by Tokyo Chemical Industry Co., Ltd.), which is a general hole transport material, and the organic EL device was exactly the same. An EL element 3 was produced.
When the light emission characteristics of the obtained organic EL element 3 were evaluated by the same method as that of the organic EL element 2, red light emission with a maximum light emission efficiency of 0.3 cd / A was confirmed from the light emitting layer.

Claims (15)

At least the following formula (1)

(In the formula, R ¹ represents a group that exhibits a charge transport function when a voltage is applied.)
An organic electroluminescent element ink comprising a maleimide polymer having a main chain skeleton containing the structural unit 1 represented by formula (I) as an essential component. The structural unit 1 is represented by the following formula (2)

(In the formula, R ^1a is a single bond or a divalent group, and R ^1b is a residue of an organic compound that exhibits a charge transport function when a voltage is applied.)
The ink for organic electroluminescent elements according to claim 1, represented by: In the above formula (2), R ^1b is at least one compound selected from the group consisting of carbazole or a derivative thereof, biscarbazole biphenyl or a derivative thereof, triarylamine or a derivative thereof, oxadiazole or a derivative thereof, triazine or a derivative thereof The ink for organic electroluminescent elements according to claim 2, which is a residue of The maleimide polymer further comprises the following formula (3):

(In the formula, R ² represents a group that emits light when an electric field is applied.)
The ink for organic electroluminescent elements according to any one of claims 1 to 3, comprising a structural unit 2 represented by: The structural unit 2 is represented by the following formula (4).

(In the formula, R ^2a is a single bond or a divalent group, and R ^2b is a residue of an organic compound that emits light when a voltage is applied.)
The ink for organic electroluminescent elements according to claim 4, which is represented by: The ink for organic electroluminescent elements according to claim 5, wherein R ^2b in the formula (4) is a fluorescent or phosphorescent group. In the formula (4), R ^2b is a pyrene compound, perylene compound, naphthalene compound, phenanthrene compound, tetracene compound, quinacridone compound, dioxazine compound, coronene compound, fluorescein compound, coumarin compound, The organic electroluminescent device according to claim 6, which is a fluorescent or phosphorescent group consisting of a residue of at least one compound selected from the group consisting of a quinoline metal complex compound, a rare earth metal coordination compound, and an iridium coordination compound. Ink. At least the following formula (1)

(In the formula, R ¹ represents a group that exhibits a charge transport function when a voltage is applied.)
An organic electroluminescent device comprising a layer containing a maleimide polymer having a main chain skeleton containing the structural unit 1 represented by The structural unit 1 is represented by the following formula (2)

(In the formula, R ^1a is a single bond or a divalent group, and R ^1b is a residue of an organic compound that exhibits a charge transport function when a voltage is applied.)
The organic electroluminescent element of Claim 8 represented by these. In the above formula (2), R ^1b is at least one compound selected from the group consisting of carbazole or a derivative thereof, biscarbazole biphenyl or a derivative thereof, triarylamine or a derivative thereof, oxadiazole or a derivative thereof, triazine or a derivative thereof The organic electroluminescent element according to claim 9, which is a residue of The maleimide polymer further comprises the following formula (3):

(In the formula, R ² represents a group that emits light when a voltage is applied.)
The organic electroluminescent element in any one of Claims 8 thru | or 10 which contains the structural unit 2 represented by these in a main chain skeleton. The structural unit 2 is represented by the following formula (4).

(In the formula, R ^2a is a single bond or a divalent group, and R ^2b is a residue of an organic compound that emits light when a voltage is applied.)
The organic electroluminescent element of Claim 11 represented by these. The organic electroluminescent element according to claim 12, wherein R ^2b in the formula (4) is a fluorescent or phosphorescent group. In the formula (4), R ^2b is a pyrene compound, perylene compound, naphthalene compound, phenanthrene compound, tetracene compound, quinacridone compound, dioxazine compound, coronene compound, fluorescein compound, coumarin compound, The organic electroluminescent device according to claim 13, which is a fluorescent or phosphorescent group composed of a residue of at least one compound selected from the group consisting of a quinoline metal complex compound, a rare earth metal coordination compound, and an iridium coordination compound. . A light-emitting panel comprising the organic electroluminescent element according to claim 8.