KR102379434B1 - Composition for organic electroluminescent elements, organic electroluminescent element, display device and lighting device - Google Patents

Abstract

The present invention provides a composition for an organic electroluminescent device with high storage stability and film-forming process stability, an organic electroluminescent device with high current efficiency produced using the composition, and a display device and a lighting device using the organic electroluminescent device. to provide. The present invention relates to at least a phosphorescent light emitting material, a charge-transporting compound, and a phenolic hydroxyl group having a phenolic hydroxyl group and having a substituent at only any two of the 2-position, 4-position, and 6-position when the phenolic hydroxyl group is at 1-position. It relates to a composition for an organic electroluminescent device containing the compound.

Description

A composition for an organic electroluminescent device, an organic electroluminescent device, a display device, and a lighting device TECHNICAL FIELD

The present invention relates to a composition for an organic electroluminescent device, comprising a composition for an organic electroluminescent device for providing an organic electroluminescent device with high efficiency, an organic electroluminescent device manufactured using the composition, and the organic electroluminescent device It relates to a display device and a lighting device comprising the.

In recent years, various electronic devices using organic electroluminescent elements (hereinafter sometimes referred to as "organic EL elements"), such as organic electroluminescent lighting (organic EL lighting) and organic electroluminescent displays (organic EL displays), have been put to practical use. . The organic EL panel has a low applied voltage, low power consumption, is surface light emitting, and can emit light in three primary colors, so that its application to lighting and displays is being actively studied. Moreover, reduction of manufacturing cost and practical use of the electronic device using the organic electroluminescent panel of a large area are calculated|required.

On the other hand, for its practical use, longer life and higher efficiency are further demanded. An organic electroluminescent element emits light when electric charges injected from an anode and a cathode recombine on a light emitting layer, and exciton generate|occur|produces. Therefore, as a means of improving the efficiency, confinement of the charges injected into the light emitting layer is effective. As a typical method, there is a method of preventing diffusion of generated excitons, and forming an exciton diffusion preventing layer in a layer adjacent to the cathode side of the light emitting layer (Patent Document 1) is mentioned.

As a method of confining electric charges in the light emitting layer for realizing high efficiency inside the light emitting layer, a means of using a material having charge trapping properties for the light emitting layer can be considered. As one of the means for realizing this, a method of trapping and confining electric charges by lone pairs of electrons of hetero atoms can be considered. Examples of the compound having a hetero atom having a lone pair of electrons include compounds having a phenolic hydroxyl group. The compound which has this phenolic hydroxyl group has been conventionally used as antioxidant (patent document 2, patent document 3).

Moreover, in patent document 4, since organic electroluminescent element performance, such as external quantum efficiency, will fall when a phenolic antioxidant remains, using the antioxidant which does not remain is described. Patent Document 5 describes that the stabilizer, which is a compound having a phenolic hydroxyl group, is removed in order to significantly deteriorate device performance.

Patent Document 1: International Publication No. 2012/070226 Patent Document 2: Japanese Patent Laid-Open No. Hei 10-255981 Patent Document 3: Japanese Patent Laid-Open No. 2004-088094 Patent Document 4: Japanese Patent Laid-Open No. 2013-165089 Patent Document 5: Japanese Patent Laid-Open No. 2013-060396

However, when the compound which has a phenolic hydroxyl group is made to coexist with the material of the light emitting layer containing a phosphorescent light emitting material as described in patent documents 2 and 3, the possibility of causing deterioration of a characteristic is considered. Therefore, as also described in Patent Documents 4 and 5, the premise is to remove the compound having a phenolic hydroxyl group in order to avoid adverse effects on the light emitting material including the phosphorescent material.

That is, it was considered by those skilled in the art that it is preferable that the compound exerting such adverse effects is removed and does not remain. Due to such a technical background, measures such as actively using a compound having a phenolic hydroxyl group and confinement of electric charge were not implemented.

Therefore, in this invention, it makes it a subject to provide the composition used for the organic electroluminescent element with high efficiency.

As a result of intensive studies in view of the above problems, the present inventors surprisingly found a specific phenolic compound, i.e., when the phenolic hydroxyl group has a phenolic hydroxyl group and the phenolic hydroxyl group is the 1-position, any 2 at the 2-position, 4-position, and 6-position An organic electroluminescent device manufactured using a composition containing at least a phenolic compound having a substituent only in dogs, a phosphorescent light emitting material, and a charge transporting compound does not impair current efficiency, but rather improves current efficiency, and increases lifespan The present invention was completed by discovering that an effect can be obtained.

In addition, the action mechanism of this invention is estimated as follows.

The electric charge injected into the light emitting layer is transported by hopping conduction over the charge transporting compound contained in the light emitting layer. Since the hydroxyl group has a lone pair of electrons and has a high electron density, it is estimated that it inhibits transport of hopping holes and enhances the effect of confining holes in the light emitting layer.

However, when a substituent does not exist in both ortho positions, it will be in a state in which a hydroxyl group is not protected, and it is thought that it exerts a bad influence on the surrounding charge-transporting compound and a light emitting material. That is, when viewed from the hydroxyl group, the ortho-position and the para-position have a large influence on the phenolic hydroxyl group, and therefore, when the phenolic hydroxyl group is set to the 1-position, only any two of the 2-position, the 4-position, and the 6-position It is thought that this invention shows an effect by having a substituent.

That is, the summary of this invention is as follows.

1. At least a phosphorescent material, a charge-transporting compound, and a phenolic compound having a phenolic hydroxyl group and having a substituent at only any two of the 2-position, 4-position, and 6-position when the phenolic hydroxyl group is at 1-position A composition for an organic electroluminescent device containing a.

2. The composition for an organic electroluminescent device according to 1, wherein the phenolic compound has only one phenolic structure.

3. When the said phenolic compound makes a phenolic hydroxyl group into 1-position, it has a substituent only at any two of 2-position, 4-position, and 6-position, 3-position and 5-position are unsubstituted phenolic The composition for an organic electroluminescent device according to 1 or 2, which is a compound.

4. Any one of the above 1 to 3 wherein the substituent is selected from an aryloxy group using an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 18 carbon atoms, and an aralkyl group having 1 to 24 carbon atoms. The composition for an organic electroluminescent device according to claim.

5. The composition for an organic electroluminescent device according to any one of items 1 to 4, wherein the substituent is selected from an alkyl group having 1 to 12 carbon atoms or an alkoxy group having 1 to 12 carbon atoms.

6. The composition for an organic electroluminescent device according to any one of 1 to 5, wherein the phenolic compound is 0.01 mass% or more and 10 mass% or less with respect to the total amount of the charge-transporting compound in the composition.

7. The composition for an organic electroluminescent device according to any one of 1 to 6, wherein the phenolic compound is 0.1 mass% or more and 1 mass% or less with respect to the total amount of the charge-transporting compound contained in the composition.

8. An organic electroluminescent device having an anode, a cathode, and at least one light emitting layer between the anode and the cathode, wherein at least one layer of the light emitting layer is the organic electroluminescent device according to any one of 1 to 7 above. An organic electroluminescent device formed by wet film deposition using a solvent composition.

9. A display device having the organic electroluminescent element according to 8 above.

10. A lighting device having the organic electroluminescent element according to 8 above.

According to the composition for an organic electroluminescent device of the present invention, the organic electroluminescent device obtained by using the same exhibits high current efficiency, and it is possible to increase the lifespan. Process stability is expected, it is a compatible technique, and it is very useful as a composition for organic electroluminescent elements.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows typically an example of the structure of the organic electroluminescent element of this invention.

EMBODIMENT OF THE INVENTION Although embodiment of this invention is described in detail below, this invention is not limited to the following embodiment, It can variously deform and implement within the scope of the summary.

<Phosphorescence emitting material>

The phosphorescent material of the present invention refers to a material that emits light from a triplet excited state. For example, a metal complex compound having Ir, Pt, Eu or the like is a representative example thereof, and it is preferable to include the metal complex as a structure of the material.

Among metal complexes, phosphorescent organometallic complexes emitting light via a triplet state, long-period periodic table (hereinafter, when referred to as "periodic table" unless otherwise specified, refer to long-period periodic table) Groups 7 to 11 and a Werner-type complex or an organometallic complex compound containing a metal selected from among as a central metal. Preferably, the compound represented by the following formula (I) or formula (II) is mentioned.

ML _(qj) L' _j ㆍㆍㆍ (I)

(In formula (I), M represents a metal, q represents a valence of the metal. In addition, L and L' represent a diligand. j represents a number of 0, 1 or 2. L or L' In the case of this plurality, a plurality of L or a plurality of L' may be the same or different, respectively.)

(In formula (II), M ² represents a metal, T represents a carbon atom or a nitrogen atom. R ⁹² to R ⁹⁵ each independently represents a substituent. However, when T is a nitrogen atom, R ⁹⁴ and R ⁹⁵ does not exist.)

The compound represented by Formula (I) is demonstrated.

In formula (I), M is a metal selected from Groups 7 to 11 of the periodic table. Preferably, ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum, gold|metal|money etc. are mentioned. Among them, iridium or platinum is more preferable. From the viewpoint of high stability and high luminous efficiency, iridium is most preferred.

In the formula (I), the diligand L represents a ligand having a partial structure represented by the following formula (III).

In the partial structure of the formula (III), ring A1 represents an aromatic ring group which may have a substituent. An aromatic hydrocarbon ring group may be sufficient as the aromatic ring group in this invention, and an aromatic heterocyclic group may be sufficient as it.

In addition, in the partial structure of said Formula (III), ring A2 represents the nitrogen-containing aromatic heterocyclic group which may have a substituent.

In the formula (I), the diligand L' represents a ligand having the following partial structures.

Among these, as L', from a viewpoint of stability of a complex, the ligand listed below is preferable.

As the compound represented by formula (I), more preferably, compounds represented by the following formulas (Ia), (Ib) and (Ic) are exemplified.

(In the formula (Ia), M ⁴ represents the same metal as M, w represents the valence of the metal, ring A1 represents an aromatic ring group which may have a substituent, and ring A2 represents a nitrogen-containing aromatic group which may have a substituent) Represents a heterocyclic group. When w is 2 or more and there are a plurality of rings A1 and A2, the plurality of rings A1 or A2 may be the same or different, respectively.)

(In formula (Ib), M ⁵ represents the same metal as M, w-1 represents the valence of the metal, ring A1 represents an aromatic ring group which may have a substituent, and ring A2 may have a substituent Represents a nitrogen aromatic heterocyclic group. When w is 3 or more and there are a plurality of rings A1 and A2, the plurality of rings A1 or A2 may be the same or different, respectively.)

(In the formula (Ic), M ⁶ represents the same metal as M, w represents the valence of the metal, j represents 0, 1 or 2, and each of ring A1 and ring A1' independently has a substituent may represent an aromatic ring group, and ring A2 and ring A2' each independently represent a nitrogen-containing aromatic heterocyclic group which may have a substituent, wj is 2 or more, or j is 2 or more, and ring A1, ring A1', ring A2 Alternatively, when there are a plurality of rings A2', the plurality of rings A1, ring A1', ring A2, or ring A2' may be the same or different, respectively.)

In the formulas (Ia) to (Ic) and (III), the aromatic ring of the ring A1 and the ring A1' is an aromatic hydrocarbon group or an aromatic heterocyclic group. Preferably, they are a benzene ring, a naphthalene ring, an anthracene ring, a triphenylyl ring, an acenaphthene ring, a fluoranthene ring, a fluorene ring, a furan ring, a benzofuran ring, a thiophene ring, and a benzothiophene ring which have two free valences. . More preferably, they are a benzene ring and a naphthalene ring, Most preferably, they are a benzene ring.

Here, as used herein, the free valence refers to one capable of forming a bond with another free valence as described in Organic Chemistry and Biochemical Nomenclature (Upper) (Revised 2nd ed., Nankodo, published in 1992). That is, for example, "a benzene ring having one free valence" refers to a phenyl group, and "a benzene ring having two free valences" refers to a phenylene group.

In the formulas (Ia) to (Ic) and (III), the nitrogen-containing aromatic heterocyclic group of the rings A2 and A2' is preferably a pyridyl group, a pyrimidyl group, a pyrazinyl group, a triazinyl group, and an imida group. Jolyl group, oxazolyl group, thiazolyl group, benzothiazolyl group, benzooxazolyl group, benzoimidazolyl group, quinolyl group, isoquinolyl group, quinoxalyl group, quinazolyl group, phenanthridinyl group, benzo It is a thiazole group.

More preferably, they are a pyridyl group, a pyrazinyl group, a pyrimidyl group, an imidazolyl group, a quinolyl group, an isoquinolyl group, a quinoxalyl group, a quinazolyl group, Especially preferably, a pyridyl group, an imidazolyl group, They are a quinolyl group, an isoquinolyl group, a quinoxalyl group, and a quinazolyl group.

Most preferably, they are a pyridyl group, an imidazolyl group, a quinolyl group, a quinoxalyl group, and a quinazolyl group.

In the formulas (Ia) to (Ic) and (III), the combined structure of the ring A1 and the ring A2 or the combined structure of the ring A1' and the ring A2' is most preferably phenyl-pyridine which may have a substituent structure, the phenyl-quinoline structure which may have a substituent, the phenyl-quinoxaline structure which may have a substituent, the phenyl-imidazole structure which may have a substituent, and the phenyl-quinazoline structure which may have a substituent.

Examples of the substituent that the ring A1, ring A1', ring A2 and ring A2' may have in the formulas (Ia) to (Ic) and (III) include a halogen atom, an alkyl group having 1 to 12 carbon atoms, and an alkyl group having 1 to 12 carbon atoms. Alkenyl group, C1-C12 alkoxycarbonyl group, C1-C12 alkoxy group, C1-C24 aralkyl group, C1-C12 aryloxy group, C1-C24 dialkylamino group, C8-24 and a diarylamino group, a 5- or 6-membered monocyclic or 2- to 4-condensed aromatic hydrocarbon ring group, an aromatic hydrocarbon group having 6 to 24 carbon atoms, a carbazolyl group, an acyl group, a haloalkyl group, and a cyano group.

Preferably, the aromatic hydrocarbon is an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aralkyl group having 1 to 24 carbon atoms, a diarylamino group having 8 to 24 carbon atoms, and a monocyclic or 2 to 4 condensed ring of 5 or 6 membered rings. They are a ventilation, a C6-C24 aromatic hydrocarbon group, and a carbazolyl group.

A diarylamino group having 8 to 24 carbon atoms, a monocyclic or 2 to 4 condensed 5 or 6 membered ring aromatic hydrocarbon ring group, an aromatic hydrocarbon group having 6 to 24 carbon atoms, and a carbazolyl group further have a substituent at the aryl moiety constituting the group good to be Examples of the substituent include an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aralkyl group having 1 to 24 carbon atoms, and a monovalent aromatic hydrocarbon group having 6 to 24 carbon atoms which may be substituted with an alkyl group having 1 to 12 carbon atoms. there is. The monovalent aromatic hydrocarbon group having 6 to 24 carbon atoms is preferably a monovalent group in which 1 to 4 benzene rings are linked.

Moreover, these substituents may connect with each other and may form a ring. As a specific example, a single condensed ring may be formed by bonding the substituent of ring A1 and the substituent of ring A2, or bonding of the substituent of ring A1' and the substituent of ring A2'.

A 7,8-benzoquinoline group etc. are mentioned as such a condensed ring. The ring formed by connecting these substituents to each other may further have the said substituent. In addition, the said substituent may have one, and may have the same or different 2 or more substituents.

In addition, as a preferable example of M in Formulas (Ia) - (Ic), it is the same as M in Formula (I).

Next, the compound represented by Formula (II) is demonstrated.

In formula ( ^II ), M2 represents a metal. Specific examples include the metals described above as metals selected from Groups 7 to 11 of the periodic table. Among them, ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum, or gold is particularly preferred, and divalent metals such as platinum and palladium are particularly preferred.

In the formula (II), R ⁹² and R ⁹³ each independently represent a hydrogen atom, a halogen atom, an alkyl group, an aralkyl group, an alkenyl group, a cyano group, an amino group, an acyl group, an alkoxycarbonyl group, a carboxyl group, an alkoxy group, or an alkyl group. an amino group, an aralkylamino group, a haloalkyl group, a hydroxyl group, an aryloxy group, an aromatic hydrocarbon group, or an aromatic heterocyclic group.

In addition, when T is a carbon atom, R ⁹⁴ and R ⁹⁵ each independently represent a substituent represented by the same example as R ⁹² and R ⁹³ . In addition, when T is a nitrogen atom, R ⁹⁴ or R ⁹⁵ directly bonded to T does not exist.

In addition, R ⁹² to R ⁹⁵ may further have a substituent. As a substituent, it can be set as the said substituent.

Further, any two or more groups of R ⁹² to R ⁹⁵ may be linked to each other to form a ring. The phosphorescent organometallic complex is preferably a compound represented by formula (I).

<Phenolic compound>

The phenolic compound in the present invention is particularly limited as long as it is a phenolic compound having a phenolic hydroxyl group and having a substituent at only any two of the 2-position, 4-position, and 6-position when the phenolic hydroxyl group is at 1-position. is absent, and the 3-position and/or 5-position may be unsubstituted or may have a substituent.

Preferably, the compound has a lone pair of electrons and has no charge transporting property. More preferably, when a phenolic hydroxyl group is made into 1-position, it has a substituent only at any two of 2-position, 4-position, and 6-position, 3-position and 5-position are unsubstituted phenolic compounds. .

The substituent is not particularly limited, and in the present compound, one or more phenol structures may exist, and when two or more phenol structures exist, the structure prescribed by the present invention may be included in a certain structure. Preferably, only one of the phenolic compounds has a phenolic structure.

Among these substituents, an alkyl group, an alkoxy group, an aryloxy group using an aryl group, and an aralkyl group are preferable. Specifically, it is more preferably a group selected from an aryloxy group using an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or an aryl group having 6 to 18 carbon atoms, and an aralkyl group having 1 to 24 carbon atoms.

Among these, an alkyl group or an alkoxy group is preferable, a C1-C12 alkyl group or a C1-C12 alkoxy group is more preferable, Especially preferably, it is a C1-C12 alkyl group.

When the phenolic hydroxyl group is at the 1-position, the 2-position, 4-position, and 6-position have a similar π-conjugation effect at only any two, it is thought to have When the lone pair is stabilized, the proton from the phenolic hydroxyl group is easily released, and there is a concern about an adverse effect caused by the detached proton.

By having a substituent at these positions, the stability of the phenolic compound is improved. Moreover, when a substituent is an electron-donating group like an alkyl group or an alkoxy group, the electron density of the lone electron pair of an oxygen atom increases, and it is thought that the hole confinement effect improves.

The phenolic structure delocalizes at the 2-position, 4-position, and 6-position when a negative charge makes the phenolic hydroxyl group 1-position on an oxygen atom by a resonance effect. Since the position where the negative charge is localized has high reactivity, the stability of the phenolic compound itself of BHT, which is a commonly used antioxidant, is improved by the alkyl group at the 2-position, 4-position, and 6-position.

However, surprisingly, in the case of a phenolic compound used for a light emitting layer of an organic electroluminescent device containing a phosphorescent material and a charge transporting compound, the 2-position, 4-position, and 6-position when the phenolic hydroxyl group is the 1-position. By using a compound that has a substituent at only any two and does not have a substituent at one of positions considered to have a high negative charge density and high reactivity, the efficiency of the organic electroluminescent device is improved, and the driving stability is improved thing was found

The reason is thought to be that the effect of confining a hole is improved by the existence of one position having a high negative charge density other than the oxygen atom. Therefore, the number of the substituents at the 2-position, 4-position, and 6-position when a phenolic hydroxyl group is made into 1-position is not three, but is required to be two.

More preferably, a phenolic compound has a substituent only at any two of 2-position, 4-position, and 6-position when a phenolic hydroxyl group is made into 1-position. The reason is thought to be that, when a phenolic hydroxyl group is made into 1-position, by having a substituent only at any two of 2-position, 4-position, and 6-position, the hopping transport of an electric charge is hard to be inhibited.

In addition, when the phenolic hydroxyl group has a substituent in only two of the 2-position, 4-position, and 6-position when the phenolic hydroxyl group is the 1-position, the lone pair of electrons of the oxygen atom of the hydroxyl group is Since it is protected and a phenolic compound becomes the most stable, while improving the efficiency of an organic electroluminescent element, it is thought that drive stability also improves, and it is especially preferable.

In addition, when a substituent is an alkoxy group, by having a substituent only at any two of 2-position, 4-position, and 6-position when a phenolic hydroxyl group is made into 1-position, the oxygen atom of a phenolic hydroxyl group and an alkoxy group It is considered that the electron density of oxygen atoms is appropriately increased and the state excellent in stability is maintained while improving the effect of confinement of holes.

In addition, as a specific structural formula, the phenolic compound in this invention can also be represented by following formula (1). However, the present compound is not limited to the following structural formula.

However, A is a phenol structure which has a substituent. n is an integer of 1-5. Preferably, L is absent when n=1 and is a linking group when n=2 to 5. When n is 2-5, the substituent which A has may be same or different.

A, when n=1, has a substituent at the 2-position, 4-position, and 6-position when the hydroxyl group of the phenol structure is at 1-position, and at the 3-position or 5-position You may have a substituent.

The substituent A may have is an aryloxy group using an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 18 carbon atoms, or an aralkyl group having 1 to 24 carbon atoms.

Preferably, the 2-position or 6-position when the hydroxyl group of a phenol structure is 1-position from a viewpoint of stability of a compound is an alkyl group. In addition, the alkyl group substituted at the 2-position and the 6-position is a secondary alkyl group (isopropyl group, etc.) or a tertiary alkyl group (tert-butyl group) having a steric hindrance in order to avoid interference with other materials in the composition for forming a light emitting layer. etc.) is preferred, and a tertiary alkyl group having the highest steric hindrance is most preferred.

When n=2-5, A has a linking group L. L is bonded to A by carbon or oxygen having an sp ³ hybrid orbital. L may be substituted in any of 2-position to 6-position, but when substituted in 2-position, 4-position, or 6-position, "2-position, 4-position, It has a substituent in only any two places at the 6-position".

That is, at the 2-position, 4-position, and 6-position of frame|skeleton A, only any two places are substituted by a linking group and 1 type of substituent other than that. Although n is not specifically limited, Preferably it is 3 or less, More preferably, it is 2 or less, Most preferably, it is 1. This is because it is presumed that since the phenolic hydroxyl group concentration is uniformly expanded after formation of the light emitting layer, charge traps are uniformly generated and charge recombination occurs uniformly in the film to prevent concentration quenching of excitons.

L is not particularly limited as long as it bonds with carbon or oxygen having an sp ³ hybrid orbital. Preferably, it is alkylene which may have a substituent of a C1-C12 alkyl group. When it has a conjugated chain, it is preferable that carbon number of the said alkyl group is 2-6. The reason is that, in the case of coexistence with a light emitting material, it is to exclude an element that may be a quenching factor, that is, to prevent an energy transfer type quenching by expansion of a conjugated chain.

Specific structures include 2,6-tert-butylphenol, 4-methoxy-2-tert-butylphenol, 4,4'-butylidenebis(6-t-butyl-3-methylphenol), etc. and the compounds described.

<Charge-transporting compound>

As the charge-transporting compound that can be contained in the composition of the present invention, those conventionally used as materials for organic electroluminescent devices can be used. For example, pyridine, carbazole, naphthalene, perylene, pyrene, anthracene, chrysene, naphthacene, phenanthrene, coronene, fluoranthene, benzophenanthrene, fluorene, acetonaphthofluoranthene, coumarin, p- Bis(2-phenylethenyl)benzene and derivatives thereof, quinacridone derivatives, DCM(4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran)-based compounds , benzopyran derivatives, rhodamine derivatives, benzothioxanthene derivatives, azabenzothioxanthene, condensed aromatic ring compounds substituted with arylamino groups, styryl derivatives substituted with arylamino groups, and the like.

These may be used individually by 1 type, and may use 2 or more types by arbitrary combinations and a ratio.

Content of the charge-transporting compound in the composition of this invention is 0.01 mass % or more normally, Preferably it is 0.1 mass % or more. Moreover, content of the charge-transporting compound in the composition of this invention is 50 mass % or less normally, Preferably it is 30 mass % or less, More preferably, it is 10 mass % or less.

<Composition for light emitting layer formation>

The composition of the present invention contains at least a phosphorescent material, a charge-transporting compound, and the phenolic compound. Moreover, you may contain a solvent in compositions, such as an ink. The composition of the present invention is usually used for forming a layer or a film by a wet film forming method, and particularly preferably used for forming a light emitting layer of an organic electroluminescent device.

That is, it is preferable that the composition of this invention is a composition for organic electroluminescent elements, and it is especially preferable that it is used as a composition for light emitting layer formation of an organic electroluminescent element.

The content of the phosphorescent material in the composition of the present invention is usually 1% by mass or more, preferably 5% by mass or more, more preferably 15% by mass or more with respect to the total amount of the charge-transporting compound. In addition, the content of the phosphorescent material in the composition of the present invention is usually 50 mass% or less, preferably 40 mass% or less, with respect to the total amount of the charge-transporting compound.

By making the content of the phosphorescent material in the composition within the above range, for example, when a light emitting layer is formed using this composition, holes or electrons are efficiently transferred from an adjacent layer (eg, a hole transport layer or a hole blocking layer) to the light emitting layer. Implantation is performed, so that the driving voltage can be reduced. In addition, only 1 type may be contained in a composition, and 2 or more types may be combined and the phosphorescence emitting material may be contained in a composition.

In addition, although the emission color of a light emitting material is not specifically limited, The direction of a long wavelength is preferable. Specifically, it is preferable that the color (peak wavelength) of light emission of the coating film of this composition is longer than green (500 nm or more), and more preferably longer than yellow-green (550 nm or more).

From the light emission principle of the phosphorescent light emitting layer, the triplet excited state is quenched by the lone pair of electrons, but the excited state of the long wavelength emission has lower energy than the excited state of the short wavelength emission, and the triplet excited state itself is stable. , and therefore it is estimated that it is difficult to be affected by the extinction by the lone pair of electrons.

Content of the phenolic compound with respect to the solvent in the composition of this invention is 0.01 mass % or more normally with respect to the total amount of the charge-transporting compound in a composition, Preferably it is 0.1 mass % or more. Moreover, with respect to the total amount of the charge-transporting compound in a composition, it is 10 mass % or less normally, More preferably, it is 5 mass % or less, More preferably, it is 1 mass % or less.

It is because the improvement of the efficiency by capture|acquisition of an electric charge will generate|occur|produce that it is more than a lower limit. Moreover, when it contains excessively, it is because the possibility of quenching by expression of the interaction of a lone pair exceeding the steric hindrance of 2-position and 6-position when a film|membrane is formed using a composition is predicted.

<Other ingredients>

When the composition of the present invention is used for, for example, an organic electroluminescent device, the composition may contain, in addition to the above-described phosphorescent material, a compound having a phenolic hydroxyl group, and a charge-transporting compound, a solvent when used in an ink.

The solvent which may be contained in the composition of the present invention is a liquid component having volatility used to form a layer containing a metal complex compound by wet film formation.

The solvent will not be specifically limited as long as it is a solvent in which the metal complex compound which is a solute, the charge-transporting compound mentioned later, and the phenolic compound of this invention melt|dissolve favorably.

Preferred examples of the solvent include alkanes such as n-decane, cyclohexane, ethylcyclohexane, decalin, and bicyclohexane; aromatic hydrocarbons such as toluene, xylene, mesitylene, phenylcyclohexane and tetralin; halogenated aromatic hydrocarbons such as chlorobenzene, dichlorobenzene and trichlorobenzene; 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, anisole, phenetol, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole, 2, aromatic ethers such as 4-dimethylanisole and diphenyl ether; aromatic esters such as phenyl acetate, phenyl propionate, methyl benzoate, ethyl benzoate, propyl benzoate, and n-butyl benzoate; alicyclic ketones such as cyclohexanone, cyclooctanone and pencon; alicyclic alcohols such as cyclohexanol and cyclooctanol; aliphatic ketones such as methyl ethyl ketone and dibutyl ketone; aliphatic alcohols such as butanol and hexanol; aliphatic ethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and propylene glycol-1-monomethyl ether acetate (PGMEA); and the like.

Among them, alkanes and aromatic hydrocarbons are preferable. In particular, phenylcyclohexane has preferable viscosity and boiling point in a wet film forming process.

These solvents may be used individually by 1 type, and may use 2 or more types by arbitrary combinations and a ratio.

The boiling point of the solvent is usually 80°C or higher, preferably 90°C or higher, more preferably 100°C or higher, and particularly preferably 110°C or higher. Moreover, the boiling point of a solvent is 300 degrees C or less normally, Preferably it is 280 degrees C or less, More preferably, it is 250 degrees C or less. When the boiling point of a solvent is less than the said minimum, at the time of wet film-forming, film-forming stability may fall by solvent evaporation from a composition.

Content of the solvent in the composition of this invention is 10 mass % or more normally, Preferably it is 20 mass % or more, More preferably, it is 50 mass % or more, More preferably, it is 80 mass % or more. Moreover, content of the solvent in the composition of this invention is 99.99 mass % or less normally, Preferably it is 99.95 mass % or less, More preferably, it is 99.9 mass % or less, More preferably, it is 99.8 mass % or less.

For example, the light emitting layer is usually formed to have a thickness of about 3 to 200 nm, but when the light emitting layer with such a thickness is formed using the composition of the present invention, if the content of the solvent is less than the above lower limit, the viscosity of the composition becomes excessively high and the film is formed. There is a possibility that workability may deteriorate. On the other hand, when the upper limit is exceeded, the thickness of the film obtained by removing the solvent after film formation cannot be increased, so that film formation tends to be difficult.

The composition of the present invention may further contain other compounds, etc. in addition to the above-mentioned compounds, etc. as needed. For example, you may contain another solvent other than the said solvent. Examples of such a solvent include amides such as N,N-dimethylformamide and N,N-dimethylacetamide, and dimethyl sulfoxide. These may be used individually by 1 type, and may use 2 or more types by arbitrary combinations and a ratio.

<Wet film forming method>

The wet film-forming method refers to a method in which a composition containing a solvent is applied on a substrate and the solvent is removed by drying to form a film. The coating method is not particularly limited, and for example, a spin coating method, a dip coating method, a die coating method, a bar coating method, a blade coating method, a roll coating method, a spray coating method, a capillary coating method, an inkjet method, and screen printing. method, a gravure printing method, a flexographic printing method, etc. are mentioned.

As a method of drying and removing a solvent, heat-drying is performed normally. A clean oven, a hot plate, and infrared heating are mentioned as an example of the heating means used in a heating process. As infrared heating, a halogen heater, a ceramic-coated halogen heater, a ceramic heater, etc. can be used.

Since heating by infrared rays directly applies thermal energy to the substrate or film, drying in a shorter period of time is possible compared to heating using an oven or a hot plate. Therefore, the influence of the gas (moisture or oxygen) in the heating atmosphere and the influence of fine dust can be minimized, and the productivity is improved, which is preferable.

Heating temperature is 70 degreeC or more normally, Preferably it is 75 degreeC or more, More preferably, it is 80 degreeC or more. Moreover, heating temperature is 150 degrees C or less normally, Preferably it is 140 degrees C or less, More preferably, it is 130 degrees C or less.

The heating time is usually 10 seconds or longer, preferably 60 seconds or longer, more preferably 90 seconds or longer, and usually 120 minutes or shorter, preferably 60 minutes or shorter, more preferably 30 minutes or shorter.

Moreover, it is also preferable to perform vacuum drying before heat drying.

The film thickness of the organic layer formed by the wet film-forming method of the composition of this invention is 5 nm or more normally, Preferably it is 10 nm or more, More preferably, it is 20 nm or more. Moreover, the film thickness is usually 500 nm or less, Preferably it is 300 nm or less, More preferably, it is 200 nm or less.

[Organic electroluminescent device]

The organic electroluminescent device according to the present invention is an organic electroluminescent device having an anode, a cathode, and at least one organic layer therebetween, wherein at least one of the organic layers is formed by wet film forming using the composition of the present invention It is characterized as a layer. It is preferable that this layer is a light emitting layer.

1 is a schematic diagram of a cross-section showing a structural example suitable for an organic electroluminescent device according to the present invention. In FIG. 1, reference numeral 1 denotes a substrate, reference numeral 2 denotes an anode, reference numeral 3 denotes a hole injection layer, and reference numeral 4 denotes a hole transport layer; Reference numeral 5 denotes a light emitting layer, reference numeral 6 a hole blocking layer, reference numeral 7 an electron transporting layer, reference numeral 8 an electron injection layer, and reference numeral 9 a cathode.

[1] Substrate

The substrate 1 serves as a support for the organic electroluminescent element, and a quartz or glass plate, a metal plate or metal foil, a plastic film, or a sheet is used. In particular, a glass plate or a plate made of a transparent synthetic resin such as polyester, polymethacrylate, polycarbonate or polysulfone is preferable.

When using a synthetic resin substrate, it is necessary to pay attention to gas barrier property. When the gas barrier property of a board|substrate is too small, since the organic electroluminescent element may deteriorate by the external air which passed through the board|substrate, it is unpreferable. For this reason, a method for securing gas barrier properties by forming a dense silicon oxide film or the like on at least one surface of the synthetic resin substrate is also one of the preferred methods.

[2] Anode

An anode 2 is installed on the substrate 1 . The anode 2 plays a role of injecting holes into a layer on the light-emitting layer side (such as the hole injection layer 3, the hole transport layer 4, or the light-emitting layer 5).

The anode 2 is usually a metal such as aluminum, gold, silver, nickel, palladium and platinum, a metal oxide such as an oxide of indium and/or tin, a metal halide such as copper iodide, carbon black, or poly( 3-methylthiophene), polypyrrole, and a conductive polymer such as polyaniline.

Formation of the anode 2 can be normally performed by a sputtering method, a vacuum vapor deposition method, etc. In the case of forming the anode using fine metal particles such as silver, fine particles such as copper iodide, carbon black, conductive metal oxide particles, conductive polymer fine powder, etc., it is dispersed in a suitable binder resin solution and applied on the substrate 1 . By doing so, the anode 2 can also be formed. Further, in the case of a conductive polymer, a thin film may be formed directly on the substrate 1 by electrolytic polymerization, or the anode 2 may be formed by coating a conductive polymer on the substrate 1 (Appl. Phys. Lett., Volume 60, p. 2711, 1992).

The anode 2 is usually a single layer structure, but it is also possible to have a layered structure made of a plurality of materials if necessary.

The thickness of the anode 2 varies depending on the required transparency. When transparency is required, the transmittance|permeability of visible light is 60 % or more normally, Preferably it is 80 % or more. In this case, the thickness of the anode is usually 5 nm or more, preferably 10 nm or more. In this case, the thickness of the anode is usually 1000 nm or less, preferably about 500 nm or less. When it may be opaque, the thickness of the anode 2 may be arbitrary, and the anode 2 may be the same as that of the board|substrate 1 . Moreover, it is also possible to laminate|stack different electrically-conductive materials on the said positive electrode 2 further.

For the purpose of removing impurities adhering to the anode and adjusting the ionization potential to improve hole injection properties, it is preferable to treat the surface of the anode by ultraviolet (UV)/ozone treatment, oxygen plasma treatment, or argon plasma treatment. .

[3] hole injection layer

The hole injection layer 3 is a layer which transports a hole from the anode 2 to the light emitting layer 5, and can be formed on the anode 2 normally.

The method for forming the hole injection layer 3 according to the present invention may be a vacuum deposition method or a wet film formation method, and there is no particular limitation. desirable.

The film thickness of the hole injection layer 3 is 5 nm or more normally, Preferably it is 10 nm or more. In addition, the film thickness of the hole injection layer 3 is 1000 nm or less normally, Preferably it is the range of 500 nm or less.

<Formation of hole injection layer by wet film formation method>

In the case of forming the hole injection layer 3 by wet film formation, the material constituting the hole injection layer 3 is usually mixed with an appropriate solvent (solvent for the hole injection layer) and a composition for application (for hole injection layer formation) composition) is prepared, this composition for forming the hole injection layer is applied on the layer (usually the anode) corresponding to the lower layer of the hole injection layer 3 by an appropriate method, and dried to form the hole injection layer 3 .

(Hole-transporting compound)

The composition for forming a hole injection layer usually contains a hole transporting compound and a solvent as constituent materials of the hole injection layer. The hole-transporting compound may be a high molecular compound such as a polymer or a low molecular weight compound such as a monomer, as long as it is a compound having a hole transport property normally used in the hole injection layer of an organic electroluminescent device, but is preferably a high molecular compound.

As the hole transporting compound, a compound having an ionization potential of 4.5 eV to 6.0 eV is preferable from the viewpoint of a charge injection barrier from the anode 2 to the hole injection layer 3 .

Examples of the hole-transporting compound include aromatic amine derivatives, phthalocyanine derivatives, porphyrin derivatives, oligothiophene derivatives, polythiophene derivatives, benzylphenyl derivatives, compounds in which a tertiary amine is linked with a fluorene group, hydrazone derivatives, silazane derivatives, sila namine derivatives, phosphamine derivatives, quinacridone derivatives, polyaniline derivatives, polypyrrole derivatives, polyphenylenevinylene derivatives, polythienylenevinylene derivatives, polyquinoline derivatives, polyquinoxaline derivatives, carbon, and the like.

In the present specification, a derivative includes, for example, an aromatic amine derivative, including aromatic amine itself and a compound having an aromatic amine as a main skeleton, and may be a polymer or a monomer.

Among those exemplified above, an aromatic amine compound is preferable, and an aromatic tertiary amine compound is particularly preferable from the viewpoint of amorphousness and the transmittance of visible light. Here, the aromatic tertiary amine compound is a compound having an aromatic tertiary amine structure, and includes a compound having a group derived from an aromatic tertiary amine.

The type of the aromatic tertiary amine compound is not particularly limited, but a high molecular weight compound having a weight average molecular weight of 1000 or more and 1000000 or less (a polymer compound with a continuous repeating unit) is more preferable from the viewpoint of uniform light emission due to the surface smoothing effect. .

As a material of such a high molecular compound, a compound conventionally used as a compound for a hole injection layer can be used, for example, in Japanese Patent Application Laid-Open No. 2009-212510, International Publication No. 2012/096352, International Publication No. 2013/191137, etc. The disclosed compounds can be used.

Further, as the hole-transporting compound, a conductive polymer (PEDOT/PSS) formed by polymerizing 3,4-ethylenedioxythiophene (3,4-ethylenedioxythiophene), which is a derivative of polythiophene, in high molecular weight polystyrenesulfonic acid is also preferable. Moreover, what capped the terminal of this polymer with methacrylate etc. may be sufficient.

The concentration of the hole-transporting compound in the composition for forming a hole injection layer is arbitrary as long as the effects of the present invention are not significantly impaired. Preferably, it is 0.5 mass % or more. The concentration of the hole transporting compound in the composition for forming a hole injection layer is usually 70 mass% or less, preferably 60 mass% or less, and more preferably 50 mass% or less. When this concentration is too high, there is a possibility that the film thickness may not be non-uniform, and when this concentration is too low, there is a possibility that a defect may occur in the formed hole injection layer.

(electron accepting compound)

The composition for forming a hole injection layer preferably contains an electron-accepting compound as a constituent material of the hole injection layer.

The electron-accepting compound has an oxidizing power and is preferably a compound having the ability to accept one electron from the aforementioned hole transporting compound, specifically, a compound having an electron affinity of 4 eV or more, more preferably a compound of 5 eV or more .

Examples of the electron-accepting compound include one or more selected from the group consisting of a triaryl boron compound, a metal halide, a Lewis acid, an organic acid, an onium salt, a salt of an arylamine and a metal halide, and a salt of an arylamine and a Lewis acid. compounds, and the like.

More specifically, high valence inorganic compounds, such as iron(III) chloride (Unexamined-Japanese-Patent No. 11-251067) and ammonium peroxodisulfate; Aromatic boron compounds, such as cyano compounds, such as tetracyanoethylene, and tris (pentafluorophenyl) borane (Unexamined-Japanese-Patent No. 2003-31365); onium salts substituted with organic groups (International Publication No. 2005/089024); fullerene derivatives; iodine; Sulfonic acid ions, such as a polystyrenesulfonic acid ion, an alkylbenzenesulfonate ion, and camphor sulfonic acid ion, etc. are mentioned.

These electron-accepting compounds can improve the conductivity of the hole injection layer by oxidizing the hole-transporting compound.

The content of the electron-accepting compound to the hole-transporting compound in the hole injection layer or the composition for forming a hole injection layer is usually 0.1 mol% or more, preferably 1 mol% or more. However, it is 100 mol% or less normally, Preferably it is 40 mol% or less.

(menstruum)

It is preferable that at least 1 sort(s) of the solvent of the composition for hole injection layer formation used for the wet film-forming method is a compound which can melt|dissolve the constituent material of the hole injection layer mentioned above. Moreover, the boiling point of this solvent is 80 degreeC or more normally, Preferably it is 100 degreeC or more, More preferably, it is 110 degreeC or more. It is preferable that the boiling point of a solvent is 300 degrees C or less normally, Preferably it is 280 degrees C or less.

When the boiling point of the solvent is too low, the drying rate is too fast, and there is a possibility that the film quality is deteriorated. Moreover, when the boiling point of a solvent is too high, it is necessary to make the temperature of a drying process high, and it may exert a bad influence on another layer or a board|substrate.

Examples of the solvent include ether solvents, ester solvents, aromatic hydrocarbon solvents, and amide solvents.

Examples of the ether-based solvent include aliphatic ethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and propylene glycol-1-monomethyl ether acetate (PGMEA); 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, anisole, phenetol, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole, 2, Aromatic ethers, such as 4-dimethylanisole, etc. are mentioned.

Examples of the ester solvent include aromatic esters such as phenyl acetate, phenyl propionate, methyl benzoate, ethyl benzoate, propyl benzoate, and n-butyl benzoate.

Examples of the aromatic hydrocarbon solvent include toluene, xylene, cyclohexylbenzene, 3-isopropylbiphenyl, 1,2,3,4-tetramethylbenzene, 1,4-diisopropylbenzene, and methylnaphthalene. there is.

Examples of the amide solvent include N,N-dimethylformamide and N,N-dimethylacetamide.

In addition, dimethyl sulfoxide etc. can be used.

These solvents may use only 1 type, and may use 2 or more types by arbitrary combinations and ratios.

(Method of film formation)

After preparing the composition for forming the hole injection layer, the composition is applied on the layer corresponding to the lower layer of the hole injection layer 3 (usually the anode 2) by wet film-forming, and dried to apply the composition to the hole injection layer 3 to form

The temperature in the coating step is preferably 10°C or higher, and preferably 50°C or lower, in order to prevent film loss due to crystals forming in the composition.

The relative humidity in the application step is not limited as long as the effect of the present invention is not significantly impaired, but is usually 0.01 ppm or more and usually 80% or less.

After application, if necessary, the solvent is roughly removed by vacuum drying or the like, and then the film of the composition for forming a hole injection layer is dried by heating. When the example of the heating means used in a heating process is given, a clean oven, a hot plate, an infrared heater (halogen heater), etc. are mentioned.

The heating temperature in the heating step is preferably heated to a temperature equal to or higher than the boiling point of the solvent used in the composition for forming the hole injection layer, unless the effects of the present invention are significantly impaired. In the case of a mixed solvent containing two or more solvents used in the hole injection layer, it is preferable that at least one solvent be heated to a temperature equal to or higher than the boiling point of the solvent. When the boiling point rise of a solvent is considered, in a heating process, it is preferable to heat at 120 degreeC or more and 300 degrees C or less.

In the heating step, if the heating temperature is not less than the boiling point of the solvent of the composition for forming a hole injection layer and sufficient insolubilization of the film does not occur, the heating time is not limited, but is preferably 10 seconds or more, and usually 180 minutes or less. . If the heating time is too long, the components of the other layers tend to diffuse, and if the heating time is too short, the hole injection layer tends to become heterogeneous. You may divide a heating into 2 times and may perform it.

<Formation of hole injection layer by vacuum evaporation method>

In the case of forming the hole injection layer 3 by vacuum deposition, first, one or two or more of the constituent materials of the hole injection layer 3 (the above-described hole transporting compound, electron accepting compound, etc.) are placed in a vacuum container. Put it in the installed crucible (in case of using two or more types of material, put it in each crucible).

Subsequently, after evacuating the inside of the vacuum container to about 10 ^-4 Pa with an appropriate vacuum pump, the crucible is heated (when two or more types of materials are used, each crucible is heated), the evaporation amount is controlled, and the hole injection layer ( By evaporating the constituent materials of 3) (in the case of using two or more types of materials, each independently control the evaporation amount to evaporate), the hole injection layer 3 is formed on the anode 2 of the substrate disposed opposite the crucible. .

Moreover, when using two or more types of materials, these mixtures may be put into a crucible, and the hole injection layer 3 may be formed by heating and evaporating.

The degree of vacuum at the time of deposition is not limited as long as the effects of the present invention are not significantly impaired, but usually 0.1×10 ^-7 Torr (1.3×10 ^-6 Pa) or more, normally 9.0×10 ^-6 Torr (12.0×10 ^-4 ) Pa) or less.

The deposition rate is not limited as long as the effect of the present invention is not significantly impaired, but is usually 0.1 angstrom/sec or more and usually 5.0 angstrom/sec or less.

[4] hole transport layer

The hole transport layer 4 can be formed on the hole injection layer 3 when the hole injection layer 3 is present, and on the anode 2 when the hole injection layer 3 is not present. Moreover, the structure which abbreviate|omitted the hole transport layer may be sufficient as the organic electroluminescent element of this invention.

A method of forming the hole transport layer 4 may be a vacuum deposition method or a wet film formation method, and there is no particular limitation, but from the viewpoint of reducing dark spots, it is preferable to form the hole transport layer 4 by a wet film formation method.

The material for forming the hole transport layer 4 is preferably a material that has high hole transport properties and can efficiently transport the injected holes. Therefore, it is preferable that the ionization potential is small, the transparency to visible light is high, the hole mobility is large, the hole mobility is excellent, and the impurity which becomes a trap is difficult to generate|occur|produce at the time of manufacture or use. Moreover, in many cases, in order to contact the light emitting layer 5, it is preferable not to quench the light emission from the light emitting layer 5, or to form an exciplex between the light emitting layer 5 and to reduce efficiency.

As a material of such a hole transport layer 4, the material conventionally used as a hole transport layer material can be used, For example, Unexamined-Japanese-Patent No. 2009-212510, International Publication No. 2012/096352, International Publication No. 2013/191137 The compounds disclosed in No. et al. can be used.

When forming the hole transport layer 4 by the wet film-forming method, it carries out similarly to the formation of the said hole injection layer 3, after preparing the composition for hole transport layer formation, it apply|coats and heat-dries.

The composition for hole transport layer formation contains a solvent in addition to the hole transport compound mentioned above. The solvent used is the same as that used for the composition for forming the hole injection layer. In addition, application|coating conditions, heat-drying conditions, etc. are the same as that in the case of formation of the positive hole injection layer 3 .

Also in the case of forming the hole transport layer by vacuum deposition, the film formation conditions and the like are the same as in the case of forming the hole injection layer 3 .

The thickness of the hole transport layer 4 thus formed is usually 5 nm or more, preferably 10 nm or more, and is usually 1000 nm or less, preferably 500 nm or less.

[5] light emitting layer

A light emitting layer 5 is usually formed on the hole transport layer 4 . The light emitting layer 5 is between the electrodes to which the electric field is applied, the recombination of holes injected from the anode 2 through the hole injection layer 3 and electrons injected from the cathode 9 through the electron transport layer 7 . It is a layer that becomes the main light emitting source excited by

It is preferable that the light emitting layer 5 contains a light emitting material (dopant) and 1 type, or 2 or more types of host materials. The light emitting material is preferably a metal complex compound according to the present invention, and the host material is preferably a charge transporting compound according to the present invention. It is preferable that the light emitting layer 5 is a layer formed by wet-forming the composition of this invention into a film. The light emitting layer 5 may further have a layer formed by the vacuum vapor deposition method.

Moreover, the light emitting layer 5 may contain other materials and components other than a light emitting material (dopant) and a host material in the range which does not impair the performance of this invention.

The organic electroluminescent element may have two or more light emitting layers. When two or more light-emitting layers are formed, any one light-emitting layer may satisfy the provisions of the present invention. In the case of two or more layers, each light emitting layer may be in direct contact with each other, or another layer may be interposed therebetween. As another layer interposed therebetween, a charge transport layer, a block layer, a charge generation layer, etc. are mentioned.

When the light-emitting layer is two or more layers, it is preferably a structure having a light-emitting layer formed by a vapor deposition method on a layer formed by wet-forming the composition of the present invention. More preferably, it is a structure which has a fluorescent-emitting layer formed by the vapor deposition method on the layer formed by wet-forming the composition of this invention into a film.

By forming the light emitting layer by a vapor deposition method on the layer formed by wet deposition of the composition of the present invention, the light emitting layer can be uniformly laminated, which is preferable. In addition, if the light emitting layer formed by the vapor deposition method on the layer formed by wet deposition of the composition of the present invention is a fluorescent light emitting layer, the fluorescent light emitting material usually does not contain heavy atoms and can be deposited at a relatively low temperature. It is preferable because the energy when the composition of the present invention as the lower layer is wet-formed and adheres to the layer formed is low and there is no damage to the lower layer.

[6] hole blocking layer

The hole blocking layer 6 can be laminated on the light emitting layer 5 so as to be in contact with the interface on the cathode side of the light emitting layer 5 . In particular, when a phosphorescent material or a blue light-emitting material is used as the light-emitting material of the light-emitting layer 5, it is effective to form the hole-blocking layer 6 .

The hole blocking layer 6 has a function of improving luminous efficiency by confining holes and electrons in the light emitting layer 5 . That is, the hole blocking layer 6 blocks the holes moving from the light emitting layer 5 from reaching the electron transport layer 7 , thereby increasing the recombination probability with electrons in the light emitting layer 5 and transferring the generated excitons to the light emitting layer. There is a role of confinement in (5) and a role of efficiently transporting electrons injected from the electron transport layer 7 in the direction of the light emitting layer 5 .

The physical properties required for the material constituting the hole blocking layer 6 include high electron mobility and low hole mobility, large energy gap (difference between HOMO and LUMO), and high excitation triplet level (T1). thing can be heard

As the hole blocking layer material satisfying these conditions, for example, bis(2-methyl-8-quinolinolato) (phenollato)aluminum, bis(2-methyl-8-quinolinolato) (triphenylsilanolato) ) a mixed ligand complex such as aluminum, a metal complex such as bis(2-methyl-8-quinolato)aluminum-μ-oxo-bis-(2-methyl-8-quinolinolato)aluminum binuclear metal complex; Styryl compounds such as distyrylbiphenyl derivatives (Japanese Patent Laid-Open No. 11-242996), 3-(4-biphenylyl)-4-phenyl-5(4-tert-butylphenyl)-1,2,4 -triazole derivatives, such as triazole (Unexamined-Japanese-Patent No. 7-41759), and phenanthroline derivatives, such as vasocuproin (Unexamined-Japanese-Patent No. 10-79297), are mentioned. Further, compounds having at least one pyridine ring substituted at the 2-position, 4-position, or 6-position described in International Publication No. 2005/022962 are also preferable as the hole blocking material.

Moreover, only 1 type may be used for the material of the positive hole blocking layer 6, and may use 2 or more types together by arbitrary combinations and a ratio.

The film thickness of the hole blocking layer 6 is 0.3 nm or more normally, Preferably it is 0.5 nm or more. The film thickness of the hole blocking layer 6 is 100 nm or less normally, Preferably it is 50 nm or less.

Although the hole blocking layer 6 can be formed by the method similar to the hole injection layer 3, a vacuum vapor deposition method is used normally.

[7] electron transport layer

The electron transport layer 7 may be formed between the hole blocking layer 6 and the electron injection layer 8 to be described later for the purpose of further improving the luminous efficiency of the device. The electron transport layer 7 is formed of a compound capable of efficiently transporting electrons injected from the cathode 9 in the direction of the light emitting layer 5 between the electrodes to which the electric field is applied.

The electron transport compound used in the electron transport layer 7 is a compound that has high electron injection efficiency from the cathode 9 or the electron injection layer 8 and can efficiently transport the injected electrons with high electron mobility. something is needed

Examples of the material satisfying these conditions include a metal complex such as an aluminum complex of 8-hydroxyquinoline (Japanese Patent Application Laid-Open No. 59-194393), a metal complex of 10-hydroxybenzo[h]quinoline, an oxadiazole derivative; Distyrylbiphenyl derivatives, silol derivatives, 3- or 5-hydroxyflavone metal complexes, benzoxazole metal complexes, benzothiazole metal complexes, trisbenzimidazolylbenzene (specification of U.S. Patent No. 5,645,948), quinoxaline compounds ( Japanese Patent Laid-Open No. 6-207169), a phenanthroline derivative (Japanese Patent Laid-Open No. 5-331459), 2-t-butyl-9,10-N,N'-dicyanoanthraquinonediimine, n and hydrogenated amorphous silicon carbide, n-type zinc sulfide, and n-type zinc selenide.

As for the thickness of the electron transport layer 7, the lower limit is usually about 1 nm, preferably about 5 nm, and the upper limit is usually about 300 nm, preferably about 100 nm.

The electron transport layer 7 is formed by a wet film forming method or a vacuum vapor deposition method in the same manner as the hole injection layer 3, but a vacuum vapor deposition method is usually used.

[8] electron injection layer

The electron injection layer 8 serves to efficiently inject electrons injected from the cathode 9 into the light emitting layer 5 . In order to efficiently inject electrons, the material for forming the electron injection layer 8 is preferably a metal having a low work function, and an alkali metal such as sodium or cesium, or an alkaline earth metal such as barium or calcium is used.

The thickness of the electron injection layer 8 is preferably 0.1 to 5 nm.

In addition, as the electron injection layer 8 at the interface between the cathode 9 and the electron transport layer 7, an ultra-thin insulating film (thickness of about 0.1 to 5 nm) such as LiF, MgF ₂ , Li ₂ O, Cs ₂ CO ₃ is formed. Insertion is also an effective method of improving device efficiency (Appl. Phys. Lett., vol. 70, pp. 152, 1997; Japanese Patent Laid-Open No. 10-74586; IEEETrans. Electron. Devices, vol. 44, 1245). page, 1997; SID 04 Digest, p. 154).

In addition, an alkali metal such as sodium, potassium, cesium, lithium or rubidium is doped into an organic electron transporting material typified by a metal complex such as a nitrogen-containing heterocyclic compound such as vasophenanthroline or an aluminum complex of 8-hydroxyquinoline. (Described in Japanese Patent Application Laid-Open No. 10-270171, Japanese Patent Application Laid-Open No. 2002-100478, Japanese Patent Application Laid-Open No. 2002-100482, etc.), the electron injection/transport property is improved, making it possible to achieve both excellent film quality It is preferable because

In this case, the thickness of the electron injection layer 8 is usually 5 nm or more, preferably 10 nm or more. The thickness of the electron injection layer 8 is usually 200 nm or less, preferably 100 nm or less.

The electron injection layer 8 is formed by a wet film deposition method or a vacuum deposition method in the same manner as the light emitting layer 5 . In the case of vacuum deposition, an evaporation source is put in a crucible or a metal boat installed in a vacuum container, the inside of the vacuum container is evacuated to about 10 ^-4 Pa with an appropriate vacuum pump, and then the crucible or metal boat is heated to evaporate, crucible or An electron injection layer 8 is formed on a substrate disposed to face the metal boat.

Vapor deposition of an alkali metal is performed using the alkali metal dispenser which filled nichrome with the alkali metal chromate and a reducing agent. By heating this dispenser in a vacuum container, the alkali metal chromate is reduced and the alkali metal is evaporated.

When co-evaporating an organic electron transport material and an alkali metal, the organic electron transport material is put into a crucible installed in a vacuum container, the inside of the vacuum container is evacuated to about 10 ^-4 Pa with an appropriate vacuum pump, and then each crucible and dispenser are simultaneously heated and evaporated to form the electron injection layer 8 on the substrate disposed to face the crucible and the dispenser.

At this time, it is uniformly co-deposited in the film thickness direction of the electron injection layer 8, but there may be a density|concentration distribution in the film thickness direction.

[9] Cathode

The cathode 9 plays a role of injecting electrons into a layer on the light emitting layer 5 side (such as the electron injection layer 8 or the light emitting layer 5 ).

As the material used for the cathode 9, the material used for the anode 2 can be used. However, in order to efficiently inject electrons, a metal having a low work function is preferable. For example, an appropriate metal such as tin, magnesium, indium, calcium, aluminum, silver, or an alloy thereof is used. As a specific example, low work function alloy electrodes, such as a magnesium-silver alloy, a magnesium-indium alloy, and an aluminum-lithium alloy, are mentioned.

The film thickness of the cathode 9 is usually the same as that of the anode 2 . For the purpose of protecting a cathode made of a low work function metal, stacking a metal layer having a high work function and stable to the atmosphere thereon increases the stability of the device. For this purpose, metals such as aluminum, silver, copper, nickel, chromium, gold, platinum and the like are used.

[10] Other constituent layers

As mentioned above, although the element of the layer structure shown in FIG. 1 was demonstrated mainly, between the anode 2 and the cathode 9 and the light emitting layer 5 in the organic electroluminescent element of this invention, unless the performance is impaired. , In addition to the layers in the above description, you may have arbitrary layers, and you may abbreviate|omit arbitrary layers other than the light emitting layer 5.

For example, it is also effective to form an electron blocking layer between the hole transport layer 4 and the light emitting layer 5 for the same purpose as the hole blocking layer 6 . The electron blocking layer prevents electrons moving from the light emitting layer 5 from reaching the hole transport layer 4 , thereby increasing the probability of recombination with holes in the light emitting layer 5 , and confines the generated excitons in the light emitting layer 5 . has a role and a role of efficiently transporting the holes injected from the hole transport layer 4 in the direction of the light emitting layer 5 .

Examples of the properties required for the electron blocking layer include a high hole transport property, a large energy gap (difference between HOMO and LUMO), and a high excitation triplet level (T1). In addition, when forming the light emitting layer 5 by a wet film-forming method, it is preferable to also form an electron blocking layer by a wet film-forming method since element manufacture becomes easy.

For this reason, it is preferable that the electron blocking layer also has wet film forming compatibility, and as a material used for such an electron blocking layer, a copolymer of dioctylfluorene and triphenylamine typified by F8-TFB (International Publication No. 2004/084260) h) and the like.

In addition, the structure opposite to Fig. 1, that is, on the substrate 1, the cathode 9, the electron injection layer 8, the electron transport layer 7, the hole blocking layer 6, the light emitting layer 5, the hole transport layer ( 4), it is also possible to laminate the hole injection layer 3 and the anode 2 in this order, and it is also possible to provide the organic electroluminescent device of the present invention between two substrates, at least one of which has high transparency.

Furthermore, it is also possible to set it as the structure in which the layer structure shown in FIG. 1 was superimposed in multiple stages (a structure which laminated|stacked a plurality of light emitting units). In that case, if, for example, V ₂ O ₅ or the like is used as the charge generating layer instead of the interface layer between the stages (between the light emitting units) (two layers when the anode is ITO and the cathode is Al), the barrier between the stages decreases. , more preferable from the viewpoint of luminous efficiency and driving voltage.

The present invention can be applied to any one of a single element, an element having a structure arranged in an array, and a structure in which an anode and a cathode are arranged in an X-Y matrix.

[Display device and lighting device]

The display device and the lighting device of the present invention use the organic electroluminescent device of the present invention as described above. There is no restriction|limiting in particular with respect to the form and structure of the display device of this invention and a lighting device, The organic electroluminescent element of this invention can be used for assembly according to a conventional method.

For example, by a method as described in "Organic EL Display" (Oumsa, published on August 20, 2004, by Shizuo Tokito, Chihaya Adachi, and Hideyuki Murata), a display device and a lighting device of the present invention can be formed. can

Example 1

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples without departing from the gist thereof.

[Example 1]

The organic electroluminescent element shown in FIG. 1 was produced.

First, on a glass substrate 1, an ITO transparent conductive film was deposited to a thickness of 150 nm, and patterned into a 2 mm wide stripe to form an ITO anode 2 (Sanyo Vacuum Co., Ltd., sputter film formation product) About , ultrasonic cleaning with a surfactant aqueous solution, water washing with ultrapure water, ultrasonic cleaning with ultrapure water, washing with ultrapure water in this order, followed by drying with compressed air and UV ozone washing.

Next, 2.0 mass % of a hole-transporting polymer compound having a repeating structure represented by the following (P1) and 4-isopropyl-4'-methyldiphenyliodonium tetrakis (pentafluoro) represented by the following (A1) An ethyl benzoate solution (composition for forming a hole injection layer) containing 0.8% by mass of phenyl) borate was prepared.

A hole injection layer 3 having a film thickness of 40 nm was obtained by applying this composition for forming a hole injection layer on the ITO substrate by a spin coating method under the conditions shown below and baking under the baking conditions shown below. .

<Film formation conditions>

Spin Court Atmosphere Atmosphere Under Atmosphere

Bake conditions Atmospheric atmosphere, 230°C, 1 hour

Thereafter, a 1 mass % cyclohexylbenzene solution (composition for forming a hole transport layer) of the hole transporting polymer compound represented by the following (H1) is prepared, and it is coated on the hole injection layer 3 by spin coating under the conditions shown below. Then, the hole transport layer 4 having a film thickness of 10 nm was formed by performing crosslinking treatment by baking.

<Film formation conditions>

Spin Coat Atmosphere Under Nitrogen Atmosphere

Bake conditions Under nitrogen atmosphere, 230°C, 1 hour

Next, in forming the light-emitting layer 5, the light-emitting material (D-1) shown below, the charge-transporting compounds (h-1 to h-3), and butylhydroxyanisole (3-) as a phenolic compound BHA) was used to prepare a composition for forming a light emitting layer having the composition shown below.

<Composition composition for forming a light emitting layer>

Solvent Cyclohexylbenzene

Component concentration (D-1): 0.3 mass %

(h-1): 2.25 mass %

(h-2): 0.375 mass %

(h-3): 0.375 mass%

3-BHA: 0.01% by mass

On the day the composition for forming the light emitting layer was prepared, using this solution, spin coating was applied to the hole transport layer 4 under the conditions shown below, and baking was performed under the conditions shown below, whereby the light emitting layer having a film thickness of 50 nm (5) was formed.

<Film formation conditions>

Spin Coat Atmosphere Under Nitrogen Atmosphere

Bake conditions Under nitrogen atmosphere, 120°C, 10 minutes

Next, the substrate on which the hole injection layer 3, the hole transport layer 4, and the light emitting layer 5 are wet-formed into a vacuum deposition apparatus is brought into the vacuum deposition apparatus to perform crude exhaust, and then the degree of vacuum in the apparatus is performed using a cryopump. It was evacuated until it became 3.0×10 ^-4 Pa or less. A hole blocking layer 6 was formed by laminating HB1 as a hole blocking material to a thickness of 10 nm at a deposition rate of 0.6 to 1.2 Å/sec on the light emitting layer 5 while maintaining the degree of vacuum at 2.2×10 ⁻⁴ Pa or less. .

Then, tris(8-hydroxyquinolinato)aluminum (Alq3) is heated on the hole blocking layer 6 while maintaining the vacuum degree at 2.2×10 ⁻⁴ Pa or less at a deposition rate of 0.7 to 1.3 Å/sec. The electron transport layer 7 was formed by laminating|stacking with a film thickness of 20 nm.

Here, the element which vapor-deposited up to the electron carrying layer 7 was conveyed from the chamber for organic layer vapor deposition to the chamber for metal vapor deposition. As a mask for cathode deposition, a stripe-shaped shadow mask with a width of 2 mm was placed in close contact with the element so as to be orthogonal to the ITO stripe of the anode 2 . In the same manner as in the deposition of the organic layer, the inside of the apparatus was evacuated until the vacuum degree became 1.1 x 10 ^-4 Pa or less.

Thereafter, lithium fluoride (LiF) is heated using a molybdenum boat on the electron transport layer 7 while maintaining the vacuum degree at 1.0×10 ⁻⁴ Pa or less to a film thickness at a deposition rate of 0.07 to 0.15 Å/sec. The electron injection layer 8 was formed by laminating|stacking 0.5 nm. Next, in the same manner, while maintaining the degree of vacuum at 2.0 × 10 ^-4 Pa, aluminum is heated using a molybdenum boat, and deposited to a thickness of 80 nm at a deposition rate of 0.6 to 10.0 Å/sec. has formed The substrate temperature at the time of vapor deposition of the above electron injection layer 8 and the cathode 9 was maintained at room temperature.

Subsequently, in order to prevent the element from being deteriorated by moisture in the air or the like during storage, sealing was performed by the method described below.

In a nitrogen clove box, a photocurable resin 30Y-437 (manufactured by Threebond) was applied to the outer periphery of a 23 mm x 23 mm glass plate with a width of 1 mm, and a moisture getter sheet (manufactured by Dynic) in the central portion. installed On this, the board|substrate which completed formation of the cathode was carried in, and it joined so that the vapor-deposited surface might face the desiccant sheet|seat. Thereafter, ultraviolet light was irradiated only to the area to which the photocurable resin was applied to cure the resin.

As described above, an organic electroluminescent element having a light emitting area portion having a size of 2 mm x 2 mm and emitting light at a peak wavelength of 560 nm was obtained.

[Example 2]

The organic electroluminescence of Example 2 was carried out in the same manner as in Example 1 except that 4,4'-butylidenebis(6-t-butyl-3-methylphenol) was used instead of 3-BHA as the phenolic compound. got a small

[Example 3]

An organic electroluminescent device of Example 2 was obtained in the same manner as in Example 1 except that 2,6-di-tert-butylphenol (BHB) was used instead of 3-BHA as the phenolic compound.

[Comparative Example 1]

The organic electroluminescent element of Comparative Example 1 was obtained by carrying out operation similar to Example 1 except not using a phenolic compound.

[Comparative Example 2]

An organic electroluminescent device of Example 2 was obtained in the same manner as in Example 1 except that 2,6-di-tert-butyl-4-methyl-phenol (BHT) was used instead of 3-BHA as the phenolic compound. .

[Comparative Example 3]

An organic electroluminescent device of Comparative Example 3 was obtained in the same manner as in Example 1, except that Irganox1330 was used instead of 3-BHA as the phenolic compound.

[Comparative Example 4]

An organic electroluminescent device of Comparative Example 4 was obtained in the same manner as in Example 1, except that 4-tert-octylphenol was used instead of 3-BHA as the phenolic compound.

Regarding Examples 1 to 3 and Comparative Examples 1 to 4, the luminance current efficiency when a current of 10 mA/cm ² was passed and the current value when the initial luminance was 5000 cd/m ² In direct current driving using the current value The relative luminance after 50 hours was measured. Table 1 summarizes the difference between each change rate (relative value) and the relative luminance rate after 50 hours on the basis of Comparative Example 1. In Examples 1 to 3, the luminance current efficiency increased dramatically, and in Comparative Examples 2 and 3 in which alkyl groups were substituted at both the ortho and para positions, the efficiency only slightly increased. Moreover, when the phenolic compound which alkyl-substituted only the para position was used, it was confirmed that the fall of the luminance current efficiency occurred.

Rate of change of luminance current efficiency (relative value):

When the current efficiency of the target Example or Comparative Example is ηE (cd/A) and the current efficiency of Comparative Example 1 is ηR (cd/A),

Rate of change of luminance current efficiency (relative value) = (ηE/ηR-1) × 100 (%)

Difference in relative luminance rate after 50 hours:

When the luminance after 50 hours is set to L50 (cd/m ² ), the initial luminance is 5000 (cd/m ² ),

Relative luminance rate after 50 hours = L50/5000×100 (%).

The relative luminance rate after 50 hours of the target Example or Comparative Example is τE (%),

When the relative luminance ratio after 50 hours of Comparative Example 1 is τR (%),

Difference of relative luminance rate after 50 hours = (τE-τR) (%)

Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. In addition, this application is based on the Japanese patent application (2015-061261) filed on March 24, 2015 and the Japanese patent application (2015-204901) filed on October 16, 2015, the entirety of which is for reference. is invoked by

1: substrate 2: anode
3: hole injection layer 4: hole transport layer
5: light emitting layer 6: hole blocking layer
7: electron transport layer 8: electron injection layer
9: Cathode 10: Organic electroluminescent element

Claims (13)

A composition for an organic electroluminescent device comprising at least a phosphorescent material, a charge-transporting compound, and a phenolic compound represented by the following formula (1).

(wherein n represents an integer of 2 to 5,
L is a linking group and is bonded to A with carbon or oxygen having an sp ³ hybrid orbital;
A is a phenol structure having a substituent, and when the hydroxyl group of the phenol structure is at 1-position, the linking group and one other substituent are substituted at only two positions at 2-position, 4-position, and 6-position,
The substituent is an alkyl group having 1 to 12 carbon atoms or an alkoxy group having 1 to 12 carbon atoms.) The composition for an organic electroluminescent device according to claim 1, wherein the phenolic compound is 0.01 mass% or more and 10 mass% or less with respect to the total amount of the charge-transporting compound in the composition. The composition for an organic electroluminescent device according to claim 1, wherein the phenolic compound is 0.1 mass% or more and 1 mass% or less with respect to the total amount of the charge-transporting compound contained in the composition. The composition for an organic electroluminescent device according to claim 1, further comprising a solvent. 5. The organic electric field of claim 4, wherein the solvent is selected from the group consisting of alkanes, aromatic hydrocarbons, halogenated aromatic hydrocarbons, aromatic ethers, aromatic esters, cycloaliphatic alcohols, aliphatic ketones, aliphatic alcohols, aliphatic ethers, and mixtures thereof. A composition for a light emitting device. 5. The method of claim 4, wherein the solvent is selected from the group consisting of n-decane, cyclohexane, ethylcyclohexane, decalin and bicyclohexane; aromatic hydrocarbons selected from the group consisting of toluene, xylene, mesitylene, phenylcyclohexane and tetralin; Or a composition for an organic electroluminescent device, characterized in that a mixture thereof. The composition for an organic electroluminescent device according to claim 4, wherein the solvent is phenylcyclohexane. The composition for an organic electroluminescent device according to claim 4, wherein the boiling point of the solvent is 80°C or more and 300°C or less. The composition for an organic electroluminescent device according to claim 4, wherein the solvent is 10% by mass or more and 99.99% by mass or less based on the mass of the composition. A method for manufacturing an organic electroluminescent device having an anode, a cathode, and at least one light emitting layer between the anode and the cathode, wherein at least one layer of the light emitting layer uses the composition for an organic electroluminescent device according to claim 1 A method of manufacturing an organic electroluminescent device formed by wet film deposition. An organic electroluminescent device having an anode, a cathode, and at least one light emitting layer between the anode and the cathode, wherein at least one layer of the light emitting layer is wet-formed using the composition for an organic electroluminescent device according to claim 1 . An organic electroluminescent device formed by The display device which has the organic electroluminescent element of Claim 11. The lighting device which has the organic electroluminescent element of Claim 11.

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