JP5644196B2 - Compound, charge transport material, composition for organic electroluminescence device, organic electroluminescence device, organic EL display device and organic EL illumination - Google Patents

Description

  The present invention relates to a compound suitably used for an organic electroluminescence device and its use. More specifically, by using it as a charge transport material, a compound capable of obtaining an organic electroluminescence device having high luminous efficiency and excellent driving life, a composition for an organic electroluminescence device containing the compound, and the organic electroluminescence device The present invention relates to an organic electroluminescent element, an organic EL display device, and organic EL illumination using the composition for an application.

  In recent years, high-efficiency thin-film organic electroluminescent devices have been actively developed. Organic electroluminescent devices are usually formed by providing a hole injection layer, a hole transport layer, an organic light emitting layer, an electron transport layer, etc. between the anode and the cathode, and materials suitable for each layer are being developed. . In addition, the light emission colors of organic electroluminescent elements are being developed in red, green, and blue, respectively.

  However, blue organic electroluminescent elements have not been realized yet in terms of efficiency, life, and heat resistance, and there is a problem that there are restrictions on application to full color display applications and organic EL lighting applications. It was.

  As a method for forming each constituent layer of the organic electroluminescent element, there are a vacuum vapor deposition method and a wet film formation method. The vacuum deposition method generally has problems such as low use efficiency of the vapor deposition material, a long time required for one film formation process, and a low product yield. Therefore, it is considered industrially that the wet film-forming method is advantageous.

  However, in order to form an organic layer of an organic electroluminescent element by a wet film formation method, the material for forming the organic layer is sufficiently dissolved in a solvent, and high performance required as a component layer of the element even after wet film formation It is desirable to have

  Particularly in recent years, when producing full color displays using organic electroluminescent elements by wet film formation, the light emitting elements have become smaller and more precise, and variations in the amount of luminescent material solution applied to one pixel and variations in coating thickness have occurred. A material that can precisely control application conditions such as suppression has been demanded.

These are carried out by adjusting the viscosity, polarity, volatilization rate and affinity with other materials for the coating solution. Therefore, the organic materials for organic electroluminescent elements used here are required to have extremely high solubility in various organic solvents, particularly in the types of solvents suitable for the wet film forming method, as basic properties. is there.
On the other hand, performances such as driving voltage and light emission lifetime must be sufficient at the same time.

  However, many conventionally developed materials for wet film formation, particularly blue light-emitting materials, do not satisfy the conditions required for the recent wet film formation methods described above.

  Conventionally, as a compound used for the light emitting layer of an organic electroluminescent element, for example, Patent Document 1 discloses a material represented by the following formula.

  Patent Document 2 discloses a material represented by the following formula.

  Patent Documents 3 and 4 each disclose an anthracene compound represented by the following formula.

International Publication No. 2006/070712 Pamphlet International Publication No. 2005/054162 Pamphlet International Publication No. 2002/038524 Pamphlet US Patent Application Publication No. 2005/0089715

However, these materials do not satisfy the physical properties required for the wet film formation process, such as high solubility in organic solvents and heat resistance, and the driving voltage is high even when used in devices, and sufficient lifetime is obtained. There was a problem such as not being able to.
In addition, all of the compounds specifically described in these documents are suitable for vacuum deposition, and have low or little solubility in organic solvents. It is difficult.

  The present invention provides an organic compound and an organic compound capable of forming an organic layer of an organic electroluminescent element by a wet film forming method, and capable of producing an organic electroluminescent element having a low driving voltage and a sufficient emission lifetime. Composition for electroluminescent element, organic electroluminescent element having organic layer formed by wet film formation method using composition for organic electroluminescent element, organic EL display device including organic electroluminescent element and organic It is an object to provide EL lighting.

  As a result of intensive studies by the present inventors, the anthracene compound having a specific chemical structure has a sufficiently high solubility in an organic solvent and has a sufficiently low driving voltage and a sufficiently long time when an organic electroluminescent element is used. The present invention has been completed by finding out that the above-mentioned problem of showing a light emission lifetime is solved.

That is, the present invention
A compound represented by the following general formula (I):
A charge transport material comprising this compound,
A composition for an organic electroluminescent device comprising the compound and a solvent,
An organic electroluminescent device having an organic layer between an anode and a cathode, wherein the organic layer includes a light emitting layer, and includes an organic layer including a layer formed by a wet film formation method using the composition for organic electroluminescent devices. Electroluminescent elements,
An organic EL display device and an organic EL illumination including the organic electroluminescent element,
Exist.

(In the above general formula (I), each of the phenyl groups A and B may be independently substituted at the m-position with a monovalent group formed by linking 1 to 3 benzene rings and / or naphthalene rings. It often shows structures different from each other including the substituent, provided that the phenyl groups A and B are not condensed with any other ring to form a part of the condensed ring group.

  Hereinafter, the compound of the present invention represented by the general formula (I) may be referred to as “compound (I)”.

  Compound (I) of the present invention has an asymmetric structure with respect to the anthracene skeleton by having different specific (substituted) phenyl groups via the m-phenylene group at the 9th and 10th positions of the anthracene ring, In addition to exhibiting high solubility in a solvent, it is possible to achieve both a long light emission lifetime and other good performance when applied to an organic electroluminescent device.

  Therefore, by using this compound (I), it becomes possible to form an organic layer of an organic electroluminescent element by a wet film forming method, and an organic electroluminescent element having a low driving voltage and a sufficient emission lifetime is provided. It can be produced.

It is sectional drawing which shows typically an example of the structure of the organic electroluminescent element of this invention. 2 is a ¹ H-NMR spectrum chart of the compound H-1 of the present invention synthesized in Synthesis Example 1. FIG. 3 is a ¹ H-NMR spectrum chart of the compound H-2 of the present invention synthesized in Synthesis Example 2.

  Embodiments of the present invention will be described in detail below. However, the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the invention.

[Explanation of words]
In the present invention, the simple term “aromatic ring” includes both an aromatic hydrocarbon ring and an aromatic heterocyclic ring.
In the present invention, the term “(hetero) aryl” includes both an aromatic hydrocarbon ring and an aromatic heterocycle.
In the present invention, “may have a substituent” means that one or more substituents may be present.

  Further, the wet film forming method in the present invention is 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 ink jet method, a nozzle jet method, A method of forming a film using an ink containing a solvent, such as a screen printing method, a gravure printing method, a flexographic printing method, and an offset printing method. Of these, a die coating method, a roll coating method, a spray coating method, an ink jet method, a nozzle jet method, and a flexographic printing method are preferable from the viewpoint of easy patterning.

[Compound (I)]
The compound (compound (I)) of the present invention is represented by the following general formula (I).

(In the general formula (I), the phenyl groups A and B may each independently have an arbitrary substituent, and each of the phenyl groups A and B has a different structure including the substituent. None of them can be condensed with any other ring to form part of the fused ring group.)

<Advantage of the m-phenylene group as the phenylene group for bonding the anthracene ring to the phenyl groups A and B>
In the compound (I), the phenylene group bonded to the 9-position and 10-position of the anthracene ring is an m-phenylene group, so that it exhibits high solubility in a solvent and is used for an organic electroluminescence device. Long emission lifetime can be achieved.

  On the other hand, in the compound in which the phenylene group bonded to the 9-position and 10-position of the anthracene ring is a p-phenylene group, the following formula portion exists on the same plane, Solubility becomes insufficient.

  In addition, a compound in which the phenylene group bonded to the 9-position and the 10-position of the anthracene ring is an o-phenylene group can ensure solubility in a solvent, but becomes a compound having a sterically distorted structure. The light emission lifetime of the organic electroluminescent element using this deteriorates.

<Advantage of phenyl groups A and B not being condensed>
In the compound (I), the phenyl groups A and B are not condensed with any other ring to form a part of the condensed ring group, so that the solubility in a solvent is good. When used in an organic electroluminescent device, the driving voltage can be lowered.

  On the other hand, if a rigid condensed ring structure is introduced at a site close to a flat and rigid anthracene skeleton (directly linked to anthracene or via a single phenylene group), the rigidity of the whole molecule increases. As a result, sufficient solvent solubility cannot be obtained, and the driving voltage of the organic electroluminescence device containing such a compound is increased.

<Advantage of phenyl groups A and B having different structures including substituents they have>
In the compound (I), the phenyl groups A and B may each independently have any substituent, and each of the phenyl groups A and B has a different structure including the substituent, that is, the compound (I) has an anthracene skeleton. By being an asymmetric compound, the following effects are exhibited.

  That is, by making the 9- and 10-positions of the anthracene ring having oxidation-reduction durability and charge transfer ability an asymmetric structure, solubility in an organic solvent and organic solvent when forming a layer by a wet film-forming method This suppresses the microcrystallization of the compound (I) when evaporating and promotes the formation of an amorphous film, resulting in an improvement in device performance when applied to an organic electroluminescence device such as a long emission lifetime.

<Advantage of an unsubstituted anthracene skeleton and an m-phenylene group bonded thereto>
As shown in the general formula (I), the compound (I) has the following effects when both the anthracene skeleton and the m-phenylene group bonded thereto are unsubstituted.

In the anthracene compound, the portion that transports the charge is an anthracene ring portion. Therefore, if a substituent is introduced in the vicinity of the anthracene compound, the HOMO and LUMO values are greatly changed, and the charge transport performance is degraded. Furthermore, at the time of charge transport, the bond with the substituent introduced at this site is easily cleaved. As a result, the light emitting life of the device is shortened, or the device performance is deteriorated, for example, the drive voltage is increased.
On the other hand, compound (I) does not have the above-mentioned problems because both the anthracene skeleton and the m-phenylene group bonded thereto are unsubstituted.

<Advantage of phenyl group A or B having a benzene ring or a naphthalene ring linked to each other and a phenylene group or a naphthylene group contained in the group linked at the m-position>
In the compound (I), each of the phenyl groups A and B may be independently substituted with a monovalent group in which 1 to 3 benzene rings and / or naphthalene rings are connected, and the benzene ring and / or In a monovalent group in which 1 to 3 naphthalene rings are bonded, the phenylene group and the naphthylene group contained in the group may be linked at the m-position instead of the p-position or the o-position. preferable.
Moreover, it is preferable that the monovalent group formed by bonding 1 to 3 benzene rings and / or naphthalene rings is also linked to the m-positions of the phenyl groups A and B.

This has the following advantages.
That is, when the monovalent phenylene group or naphthylene group formed by bonding 1 to 3 benzene rings and / or naphthalene rings is connected at the p-position, the rigidity of the corresponding portion increases, and the solvent solubility of the compound increases. It becomes insufficient. Further, in the o-position connection, it is considered that the oxidative decomposition as shown in the following formula occurs in the vicinity of the connection portion, and as a result, the light emission lifetime of the device is shortened. On the other hand, the above problem is solved by the m-position connection.

<Substituents that the phenyl groups A and B may have>
In the compound (I), the substituents that the phenyl groups A and B can have include phenyl groups A and B having different structures from each other, and a benzene ring and / or a naphthalene ring having 1 to 3 substituents. In the case of a monovalent group formed by linking each group, preferably, all of the phenylene groups contained in this group are m-phenylene groups, and the naphthylene groups are in the 1,3-position, 1,6-position, 1, As long as it is a group linked at the 7-position or the 2,7-position, there is no particular limitation. When the other (for example, the substituent of the phenyl group B) is a condensed aromatic ring group having 10 or more carbon atoms (for example, a naphthyl group), the physical properties of the film formed when the device is formed, Especially increase the glass transition temperature Bets can be, and very high solubility in an organic solvent of the compound (I), can be achieved both in improved performance of the resulting device, preferably.

In addition, the phenyl groups A and B may have different structures by either having a substituent and the other not having a substituent.
Therefore, for example, a phenyl group A is unsubstituted or a group in which 1 to 3 benzene rings are linked at the m-position is linked to the m-position, and the phenyl group B has 10 or more carbon atoms. It is preferable that a condensed aromatic ring group (for example, naphthyl group) is linked to the m-position directly or via one or two m-phenylene groups.
Here, as the terminal condensed ring aromatic ring group having 10 or more carbon atoms, 2-4 condensed ring aromatics such as naphthalene ring, fluorene ring, phenanthrene ring, anthracene ring, pyrene ring, chrysene ring, naphthacene ring, etc. Group derived from an aromatic hydrocarbon ring is exemplified, but the group is not limited thereto.

  Further, as shown in the general formula (I), the compound (I) is linked to the phenyl groups A and B, although the anthracene ring and the phenylene group connecting the anthracene ring and the phenyl groups A and B are unsubstituted. The phenylene group or the condensed aromatic ring group having 10 or more carbon atoms as a substituent may have an arbitrary substituent, and examples of the substituent include an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group. Group, aryloxy group, dialkylamino group, diarylamino group, halogen atom, alkylthio group, arylthio group, silyl group, siloxy group, cyano group, aromatic hydrocarbon group, aromatic heterocyclic group and the like.

  Compound (I) is a molecule of an anthracene ring-anthracene ring with a neighboring molecule by introducing into the anthracene skeleton a group containing an appropriate number of phenylene groups as phenyl groups A and B and a substituent they have. It is possible to adjust the electron mobility by separating the distance. As a result of adjusting the electron mobility, the recombination probability between holes and electrons can be increased in the light emitting layer, the luminous efficiency of the resulting device is increased, and the drive life is long. There is an effect.

<Molecular weight>
The molecular weight of the compound (I) is usually 2000 or less, and when considering the ease of purification of the compound, the molecular weight is preferably 1500 or less, and when considering the solubility in a solvent, it is particularly preferably 1200 or less. When considering the high purity by, most preferably 1000 or less. In general, the molecular weight of the compound (I) is 500 or more, and when considering the thermal stability of the compound, the molecular weight is preferably 550 or more.

<Solubility in solvents>
The compound (I) of the present invention is preferable because of its high solubility in an organic solvent contained in the composition for organic electroluminescent elements of the present invention described later.
The compound (I) of the present invention more preferably has, for example, a solubility in cyclohexylbenzene of usually 8% by weight or more, preferably 9% by weight or more, more preferably 10% by weight or more at 25 ° C. under atmospheric pressure (1013 hPa). It is a compound which is. In addition, cyclohexylbenzene is mentioned as an index indicating the solubility of the compound, and the solvent contained in the composition for an organic electroluminescence device of the present invention described later is not limited thereto.
In addition, the solubility with respect to the cyclohexylbenzene of compound (I) is calculated | required by the method described in the term of the below-mentioned Example.

<Glass transition temperature>
Compound (I) preferably has a glass transition temperature Tg of 100 ° C. or higher.

<Specific example>
Although the specific example of compound (I) is given to the following, it is not limited to the following exemplary compounds.

<Synthesis Method of Organic Compound>
Compound (I) of the present invention can be synthesized by selecting a raw material according to the structure of the target compound and using a known method.
For example, as shown in the following figure, by performing a combination of a boronic acid or a boronic acid ester and a halogen compound, a Suzuki coupling, a halogenation of an aromatic ring, and a reaction of converting a halogen moiety into a boronic acid or a boronic acid ester, Although the method etc. which produce | generate an aromatic-aromatic bond can be used preferably, it is not limited to this.

<Application>
Although the use of compound (I) is not particularly limited, the organic layer of the organic electroluminescent device, due to its excellent solvent solubility, driving voltage when applied to an organic electroluminescent device, and effects on the luminescence lifetime, In particular, it is suitable as a charge transport material for forming a light emitting layer by a wet film formation method.

[Composition for organic electroluminescence device]
The composition for organic electroluminescent elements of the present invention comprises the compound (I) of the present invention and a solvent.
This composition for organic electroluminescent elements is an organic solvent comprising a carbon atom and a hydrogen atom, or a carbon atom, a hydrogen atom and an oxygen atom as a solvent, and has a viscosity at 25 ° C. of 0.0001 to 0.01 Pas. It is preferable that the boiling point at 1013 hPa is 50 to 300 ° C.

<Solvent>
The solvent contained in the composition for organic electroluminescent elements containing the compound (I) of the present invention is a volatile liquid component used for forming a layer containing an organic electroluminescent element material by wet film formation. .

  The solvent is not particularly limited as long as it is a solvent in which the compound (I) of the present invention as a solute, a light emitting material described later, and the like are satisfactorily dissolved. Preferred solvents include the following.

For example, alkanes such as n-decane, cyclohexane, ethylcyclohexane, decalin, and bicyclohexane; aromatic hydrocarbons such as toluene, xylene, methicylene, cyclohexylbenzene, and tetralin; halogenated fragrances such as chlorobenzene, dichlorobenzene, and trichlorobenzene Group hydrocarbons: 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, anisole, phenetole, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole, 2,4-dimethyl Aromatic ethers such as anisole and diphenyl ether; aromatic esters such as phenyl acetate, phenyl propionate, methyl benzoate, ethyl benzoate, ethyl benzoate, propyl benzoate, and n-butyl benzoate; Alicyclic ketones such as Sanone, Cyclooctanone and Fencon; Alicyclic alcohols such as cyclohexanol and cyclooctanol; Aliphatic ketones such as methyl ethyl ketone and dibutyl ketone; Aliphatic alcohols such as butanol and hexanol; Ethylene And aliphatic ethers such as glycol dimethyl ether, ethylene glycol diethyl ether, and propylene glycol monomethyl ether acetate (PGMEA).

  The boiling point of the solvent is usually 50 ° C. or higher, preferably 100 ° C. or higher, more preferably 150 ° C. or higher. Below this range, there is a possibility that the film formation stability may be reduced due to solvent evaporation from the composition for organic electroluminescent elements during wet film formation.

  In order to obtain a more uniform film, it is preferable that the solvent evaporates from the liquid film immediately after the film formation at an appropriate rate. For this reason, the boiling point of the solvent is usually 300 ° C. or lower, preferably 280 ° C. or lower, more preferably 250 ° C. or lower.

  One of these solvents may be used alone, or two or more thereof may be used in any combination and ratio.

<Preferred solvent>
In the present invention, the solvent contained in the composition for organic electroluminescent elements is preferably an organic solvent composed of carbon atoms and hydrogen atoms, or carbon atoms, hydrogen atoms and oxygen atoms. The reason for this is that when there are atoms other than the above, the solvent molecules slightly remaining in the film after the film formation may thermally move or trap the charge when the element is driven, so that device characteristics can be degraded. Because there is sex.

  Moreover, the solvent contained in the composition for organic electroluminescent elements is preferably a solvent having a viscosity of 0.0005 to 0.005 Pas at 25 ° C. and a boiling point of 100 to 250 ° C. at 1013 hPa. This is because the film can be easily formed by a known film formation process and the state of the obtained film becomes uniform and flat.

  As such an organic solvent, preferably, toluene (viscosity 0.00059 Pas, boiling point 110.8 ° C.), xylene (viscosity 0.00058 Pas, boiling point 139 ° C.), cyclohexylbenzene (viscosity 0.0037 Pas, boiling point 240). C), cyclohexanone (viscosity 0.0022 Pas, boiling point 155.6 ° C.), trimethylcyclohexanone (viscosity 0.0025 Pas, boiling point about 190 ° C.), propylene glycol monomethyl ether acetate (viscosity 0.0011 Pas, boiling point 146 ° C.), and the like. It is done.

  One of these solvents may be used alone, or two or more thereof may be used in any combination and ratio.

<Light emitting material>
The composition for organic electroluminescent elements of the present invention may further contain a luminescent material.
In this case, the composition for an organic electroluminescent device may contain the compound (I) of the present invention as a host material and the light emitting material as a dopant material, or the compound (I) of the present invention as a dopant material, A light emitting material may be included as a host material. Further, both the dopant material and the host material may be the compound (I) of the present invention.

  Examples of the light emitting material include aromatic amine compounds. More specifically, it is a compound having a structure in which an amino group is directly bonded to an aromatic hydrocarbon ring formed by condensation of two or more benzene rings, and preferably two amino groups are bonded to the chrysene ring. A chrysenediamine compound is preferred.

  Examples of the chrysenediamine compound include a compound represented by the following general formula (II) (hereinafter sometimes referred to as “compound (II)”).

(In the general formula (II), R ^{1 to} R ⁸ represent an arbitrary substituent, and n ¹ , n ² , n ⁴ , n ⁵ , n ⁶ , and n ⁸ each independently represents an integer of 0 to 5. N ³ and n ⁷ each independently represents an integer of 0 to 4.
However, at least two of R ^{1 to} R ⁸ are linear or branched alkyl groups having 6 or more carbon atoms or aralkyl groups having 7 or more carbon atoms.
In the case that includes a plurality of R ¹ to R ⁸ in one molecule, R ¹ to R ⁸ contained more may be the same or may be different. )

(Features of compound (II))
In the compound (II), at least one of the aromatic rings bonded to the two amino groups of the chrysene skeleton is a biphenyl skeleton, and an alkyl group having 6 or more carbon atoms or an aralkyl group having 7 or more carbon atoms is further introduced into the molecule. A compound.
When the biphenyl skeleton is introduced, the portion conjugated with the amino group is expanded, and when the portion centered on the amino group is charged, the charge is delocalized and the compound is presumed to be stabilized.
In addition, by introducing an alkyl group having 6 or more carbon atoms or an aralkyl group having 7 or more carbon atoms, it becomes easy to cause steric hindrance, or by protecting the periphery of the N atom of the amino group, the N atom is charged. It is estimated that an effect of preventing deterioration from the state is brought about.
Further, by introducing an alkyl group having 6 or more carbon atoms or an aralkyl group having 7 or more carbon atoms, improvement in solubility and dispersibility in a solvent can be obtained.
Therefore, by using the compound (II) in the organic layer of the organic electroluminescent element formed by the wet film forming method, the durability of the organic electroluminescent element and the driving life are improved.

  Hereinafter, each component in the general formula (II) will be described in detail.

(For R ¹ ~R ⁸⁾
R ^{1 to} R ⁸ represent an arbitrary substituent.
However, at least two of R ^{1 to} R ⁸ are linear or branched alkyl groups having 6 or more carbon atoms or aralkyl groups having 7 or more carbon atoms.
The optional substituents for R ^{1 to} R ⁸ include a halogen atom, an alkyl group having 1 to 20 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, an aromatic hydrocarbon group having 6 to 25 carbon atoms, and 3 carbon atoms. -20 aromatic heterocyclic group, C1-C20 alkoxy group, C3-C20 (hetero) aryloxy group, C1-C20 alkylthio group, C3-C20 (hetero) arylthio Group, cyano group and the like. Specific examples thereof are the same as those of the substituent group Z below.

Among these, from the viewpoint of the stability of the compound, it is preferably a hydrogen atom instead of a substituent, or an alkyl group having 1 to 20 carbon atoms or an aromatic hydrocarbon group having 6 to 25 carbon atoms, preferably a hydrogen atom, carbon An aromatic hydrocarbon group having a number of 6 to 25 is particularly preferable.
In the case that includes a plurality of R ¹ to R ⁸ in one molecule, R ¹ to R ⁸ contained more may be the same or may be different.
A plurality of R ^{1 to} R ⁸ may be bonded to each other to form a ring. When a ring is formed, R ^{2 to} R ⁴ and R ⁶ to R ⁶ are used in terms of color tone control and durability improvement. R ⁸ preferably forms a ring.

R ^{1 to} R ³ and R ^{5 to} R ⁷ in the formula are preferably not substituted at the o-position with respect to the nitrogen atom of the general formula (II) from the viewpoint of excellent durability of the compound. Accordingly, these substituents are preferably substituted at the m-position or p-position with respect to the nitrogen atom of the general formula (II).

At least two of R ^{1 to} R ⁸ are linear or branched alkyl groups having 6 or more carbon atoms or aralkyl groups having 7 or more carbon atoms. Here, the linear or branched alkyl group having 6 or more carbon atoms is preferably a linear or branched alkyl group having 6 to 20 carbon atoms, and more preferably a linear or branched alkyl group having 6 to 12 carbon atoms. In particular, n-hexyl group, n-octyl group, 2-methylpentyl group, 2-ethylhexyl group, decyl group and octadecyl group are preferable. The aralkyl group having 7 or more carbon atoms is preferably an aralkyl group having 7 to 20 carbon atoms, more preferably a phenylalkyl group having 7 to 20 carbon atoms, further preferably a phenylalkyl group having 7 to 12 carbon atoms, and further an alkyl moiety. Is preferably a branched alkyl group having 8 to 12 carbon atoms, particularly preferably a benzyl group, a phenylethyl group, a phenyldimethylmethyl group, or a phenylisopropylmethyl group.

Moreover, it is preferable that these alkyl groups or aralkyl groups having two or more specific carbon numbers are two or more of R ² , R ⁴ , R ⁶ and R ⁸ , particularly R ² , R ^4. , R ⁶ and R ⁸ are preferably 2-4. Furthermore, these alkyl groups or aralkyl groups are preferably substituted at the m-position or p-position, particularly at the p-position, with respect to the nitrogen atom in the general formula (II). Is preferred. Here, R ⁴ and R ⁸ are preferably substituted at the p-position of the biphenyl moiety.

R ^{1 to} R ⁸ may further have a substituent unless the effects of the present invention are impaired.
Substituents that do not impair the effects of the present invention may be other than ionic groups, but more preferred specific examples of the substituents that R ^{1 to} R ⁸ may have include the following. Is mentioned.

<Substituent group Z>
As the halogen atom, a fluorine atom is preferable.
Examples of the alkyl group having 1 to 20 carbon atoms include methyl group, ethyl group, propyl group, isopropyl group, butyl group, iso-butyl group, sec-butyl group, tert-butyl group, hexyl group, octyl group and cyclohexyl group. Group, decyl group, octadecyl group and the like. Among these, Preferably, they are a methyl group, an ethyl group, and an isopropyl group, and a methyl group and an ethyl group are preferable from the point of being easy to obtain a raw material and cheap, and an iso-butyl group and a sec-butyl group. , Tert-butyl group is preferable because of its high solubility in nonpolar solvents.

  Examples of the aromatic hydrocarbon group having 6 to 25 carbon atoms include a naphthyl group such as a phenyl group, a 1-naphthyl group and a 2-naphthyl group, a phenanthyl group such as a 9-phenanthyl group and a 3-phenanthyl group, and 1-anthryl. Group, 2-anthryl group, anthryl group such as 9-anthryl group, 1-naphthacenyl group, naphthacenyl group such as 2-naphthacenyl group, 1-chrysenyl group, 2-chrysenyl group, 3-chrysenyl group, 4-chrysenyl group, 5-chrycenyl group, 6-chrycenyl group and other chrycenyl groups, 1-pyrenyl group and other pyrenyl groups, 1-triphenylenyl group and other triphenylenyl groups, 1-coronenyl group and other coronenyl groups, 4-biphenyl group and 3-biphenyl group In view of the stability of the compound, phenyl group, 2-naphthyl group, 1-ant Group, 9-phenanthryl group, 9-anthranyl group, a 4-biphenyl group, a 3-biphenyl group preferably a phenyl group, a 2-naphthyl group, 3-biphenyl group is particularly preferable from the purification ease of the compound.

  Examples of the aromatic heterocyclic group having 3 to 20 carbon atoms include thienyl group such as 2-thienyl group, furyl group such as 2-furyl group, imidazolyl group such as 2-imidazolyl group, and carbazolyl such as 9-carbazolyl group. Groups, pyridyl groups such as 2-pyridyl group, triazin-yl groups such as 1,3,5-triazin-2-yl group, and the like. Of these, a 9-carbazolyl group is preferable from the viewpoint of stability of the compound.

  Examples of the alkoxy group having 1 to 20 carbon atoms include methoxy group, ethoxy group, isopropyloxy group, cyclohexyloxy group, octadecyloxy group and the like.

  Examples of the (hetero) aryloxy group having 3 to 20 carbon atoms include phenoxy group, 1-naphthyloxy group, 9-anthranyloxy group, 2-thienyloxy group and the like.

  Examples of the alkylthio group having 1 to 20 carbon atoms include methylthio group, ethylthio group, isopropylthio group, cyclohexylthio group and the like.

Examples of the (hetero) arylthio group having 3 to 20 carbon atoms include a phenylthio group, a 1-naphthylthio group, a 9-anthranylthio group, and a 2-thienylthio group.
Examples of the halogen include fluorine.

(For n ¹ ~n ^{8)
n 1, n 2, n 4} , n 5, n 6, n 8 each independently represents an integer of 0 to 5, n ^3, n ⁷ are each independently an integer of 0-4.
At least two of n ^{1 to} n ⁸ are preferably 1 or more in terms of improving solubility in organic solvents, and preferably 3 or less from the viewpoint of durability.

(About molecular weight)
The molecular weight of the compound (II) is usually 7000 or less, preferably 5,000 or less when considering the ease of purification of the compound, and particularly preferably 3,000 or less when considering solubility in a solvent. When considering the high purity by, most preferably 1500 or less. In general, the molecular weight of the organic compound represented by the general formula (II) is 500 or more, and when considering the thermal stability of the compound, the molecular weight is preferably 600 or more.

(Concrete example)
Although the preferable specific example of compound (II) is shown below, it is not limited to these.

(Solubility in solvents)
The compound (II) is usually preferably dissolved in toluene at room temperature (25 ° C.) at 0.5% by weight or more, and since it is easy to form a uniform film upon coating, it dissolves at 1.0% by weight or more. In view of the ease of controlling the thickness of the coating film, it is more preferable to dissolve at least 1.5% by weight, and from the viewpoint of long-term storage stability, it is at least 2.0% by weight Particularly preferred are those that dissolve at least 2.5% by weight.

(Method for synthesizing compound (II))
Compound (II) can be synthesized by selecting a raw material according to the structure of the target compound and using a known method.
For example, as shown below, chrysene can be used as a raw material, synthesized by halogenation of the chrysene ring, separately synthesized by a known method, or combined with a commercially available secondary arylamine. Yes, but not limited to this.

(In the above formula, A _{1 to} A ₄ represent an aryl group.)

<Composition>
About the composition for organic electroluminescent elements containing the compound (I) of this invention, content of compound (I) is 50 weight% or more normally in a total solid, Preferably it is 80 weight% or more, More preferably, it is 90 weight%. % Or more, usually 99% by weight or less, preferably 98% by weight or less, more preferably 95% by weight or less. By setting the content of compound (I) in the composition within this range, holes and electrons are efficiently injected from the adjacent layer (for example, hole transport layer or hole blocking layer) to the light emitting layer. In other words, the drive voltage can be reduced. In addition, by dispersing the dopant material or the host material efficiently and uniformly, the effects of suppressing the concentration quenching and improving the light emission efficiency, lowering the voltage, and extending the lifetime can be obtained. In addition, 1 type of compound (I) of this invention may be contained in the composition for organic electroluminescent elements of this invention, and may be contained in combination of 2 or more type.

  Further, the content of the solvent in the composition for organic electroluminescent elements is preferably 10 parts by weight or more, more preferably 50 parts by weight or more, particularly preferably 80 parts by weight with respect to 100 parts by weight of the composition for organic electroluminescent elements. It is not less than 99 parts by weight, preferably not more than 99.95 parts by weight, more preferably not more than 99.9 parts by weight, particularly preferably not more than 99.8 parts by weight. When the content of the solvent is less than this lower limit, the viscosity of the composition for organic electroluminescent elements becomes too high, and the film forming workability may be lowered. On the other hand, if the upper limit is exceeded, the film thickness obtained by removing the solvent after film formation cannot be obtained, and thus film formation tends to be difficult.

  When the composition for organic electroluminescent elements contains a luminescent material such as compound (II), the content of the luminescent material such as compound (II) in the composition for organic electroluminescent elements is usually 0.1% by weight or more, preferably Is 0.5% by weight or more, usually 50% by weight or less, preferably 10% by weight or less. By setting it within this range, the effect of improving the light emission efficiency and lowering the voltage of the element can be obtained. In addition, only 1 type of luminescent materials, such as compound (II), may be contained in the composition and may be contained in combination of 2 or more type.

<Other ingredients>
In addition to the compound (I) of the present invention, the solvent, and the light emitting material, the composition for organic electroluminescent element of the present invention can contain a charge transporting compound used for an organic electroluminescent element, particularly a light emitting layer.

As other charge transporting compounds that can be contained in the composition for organic electroluminescent elements of the present invention, those conventionally used as materials for organic electroluminescent elements can be used. For example, 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) compounds, benzopyran derivatives, rhodamine derivatives, benzothioxanthene derivatives, azabenzothioxanthene, arylamino groups And the condensed aromatic ring compounds and styryl derivatives substituted with an arylamino group.
One of these may be used alone, or two or more may be used in any combination and ratio.

The content of the other charge transporting compound in the composition for organic electroluminescent elements of the present invention is usually 1 part by weight or more and usually 50 parts by weight or less, preferably 30 parts, when the composition is 100 parts by weight. Less than parts by weight.
The content of the other charge transporting compound in the composition for organic electroluminescent elements is usually 50% by weight or less, particularly 30%, based on the compound (I) of the present invention in the composition for organic electroluminescent elements. It is preferably not more than 0.01% by weight, usually not less than 0.01% by weight, particularly preferably not less than 0.1% by weight.

  The composition for organic electroluminescent elements of the present invention may further contain other components in addition to the above components, if necessary. For example, in addition to the above solvent, another solvent may be contained. Examples of such a solvent include amides such as N, N-dimethylformamide and N, N-dimethylacetamide, and dimethyl sulfoxide. One of these may be used alone, or two or more may be used in any combination and ratio.

  Moreover, the organic electroluminescent element material of this invention may contain various additives, such as a leveling agent and an antifoamer, for the purpose of improving film forming property.

[Organic electroluminescence device]
The organic electroluminescent element of the present invention is an organic electroluminescent element having an organic layer between an anode and a cathode, wherein the organic layer includes a luminescent layer and includes the above-described compound (I) of the present invention. It includes a layer formed by a wet film-forming method using the composition. In particular, the layer formed by the wet film formation method using the composition for organic electroluminescent elements of the present invention is preferably a light emitting layer, and a hole transport layer is provided in contact with the light emitting layer. The hole transport layer is also preferably a layer formed by a wet film formation method. This is due to the following reason.
That is, since the film formed by the wet film formation method has a good surface flatness and is well-suited when the organic electroluminescent element composition of the present invention is formed on the film, a good interface is formed. Form. Therefore, an element exhibiting good performance can be obtained as a result, for example, the driving voltage is lowered.

  The structure of the organic electroluminescent element of the present invention will be described according to the element structure of FIG. 1 showing an example of the structure of the organic electroluminescent element of the present invention. The organic electroluminescent element of the present invention has a light emitting layer, and A layer formed by a wet film formation method using the composition for organic electroluminescent elements of the present invention, preferably a light emitting layer may be provided between the anode and the cathode, and other layers are not provided. May not be included.

{substrate}
The substrate 1 serves as a support for the organic electroluminescent element, and a quartz or glass plate, a metal plate or a metal foil, a plastic film, a sheet, or the like is used. In particular, a glass plate or a transparent synthetic resin plate such as polyester, polymethacrylate, polycarbonate, or polyethersulfone is preferable. When using a synthetic resin substrate, it is necessary to pay attention to gas barrier properties. If the gas barrier property of the substrate is too small, the organic electroluminescent element may be deteriorated by the outside air that has passed through the substrate, which is not preferable. For this reason, a method of providing a gas barrier property by providing a dense silicon oxide film or the like on at least one surface of the synthetic resin substrate is also a preferable method.

{anode}
An anode 2 is provided on the substrate 1. The anode 2 plays a role of hole injection into a layer (hole injection layer 3 or the like) on the light emitting layer side.

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

  In general, the anode 2 is often formed by sputtering, vacuum deposition, or the like. In addition, when forming an anode using fine metal particles such as silver, fine particles such as copper iodide, carbon black, conductive metal oxide fine particles, or conductive polymer fine powder, an appropriate binder resin solution is used. The anode 2 can also be formed by dispersing and coating the substrate 1. Further, in the case of a conductive polymer, a thin film can be directly formed on the substrate 1 by electrolytic polymerization, or the anode 2 can be formed by applying a conductive polymer on the substrate 1 (Appl. Phys. Lett. 60, 2711, 1992).

  The anode 2 usually has a single-layer structure, but it can also have a laminated structure made of a plurality of materials if desired.

  The thickness of the anode 2 varies depending on the required transparency. When transparency is required, the visible light transmittance is usually 60% or more, preferably 80% or more. In this case, the thickness of the anode is usually 5 nm or more, preferably 10 nm or more, and usually 1000 nm or less, preferably about 500 nm or less. When it may be opaque, the thickness of the anode 2 is arbitrary, and the anode 2 may be the same as the substrate 1. Furthermore, it is also possible to laminate different conductive materials on the anode 2 described above.

  The surface of the anode is treated with ultraviolet (UV) / ozone, oxygen plasma, or argon plasma for the purpose of removing impurities adhering to the anode and adjusting the ionization potential to improve hole injection. Is preferred.

{Hole injection layer}
The hole injection layer 3 is a layer that transports holes from the anode 2 to the light emitting layer 5, and is usually formed on the anode 2.
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 is not particularly limited, but the hole injection layer 3 is formed by a wet film formation method from the viewpoint of reducing dark spots. It is preferable.
The thickness of the hole injection layer 3 is usually 5 nm or more, preferably 10 nm or more, and usually 1000 nm or less, preferably 500 nm or less.

<Formation of hole injection layer by wet film formation method>
When forming the hole injection layer 3 by wet film formation, the material for forming the hole injection layer 3 is usually mixed with an appropriate solvent (hole injection layer solvent) to form a film-forming composition (positive A composition for forming a hole injection layer), and applying the composition for forming a hole injection layer on a layer (usually an anode) corresponding to the lower layer of the hole injection layer 3 by an appropriate technique. The hole injection layer 3 is formed by coating and drying.

(Hole transporting compound)
The composition for forming a hole injection layer usually contains a hole transporting compound and a solvent as a constituent material of the hole injection layer.

  The hole transporting compound is a compound having a hole transporting property that is usually used in a hole injection layer of an organic electroluminescence device, and may be a polymer compound or the like, a monomer or the like. Although it may be a low molecular weight compound, it is preferably a high molecular weight compound.

  The hole transporting compound is preferably a compound having an ionization potential of 4.5 eV to 6.0 eV from the viewpoint of a charge injection barrier from the anode 2 to the hole injection layer 3. Examples of hole transporting compounds include aromatic amine derivatives, phthalocyanine derivatives, porphyrin derivatives, oligothiophene derivatives, polythiophene derivatives, benzylphenyl derivatives, compounds in which tertiary amines are linked by a fluorene group, hydrazone derivatives, silazane derivatives, silanamines Derivatives, phosphamine derivatives, quinacridone derivatives, polyaniline derivatives, polypyrrole derivatives, polyphenylene vinylene derivatives, polythienylene vinylene derivatives, polyquinoline derivatives, polyquinoxaline derivatives, carbon and the like.

  In the present invention, the derivative includes, for example, an aromatic amine derivative, and includes an aromatic amine itself and a compound having an aromatic amine as a main skeleton. It may be a mer.

  The hole transporting compound used as the material for the hole injection layer 3 may contain any one of these compounds alone, or may contain two or more. In the case of containing two or more kinds of hole transporting compounds, the combination is arbitrary, but one or more kinds of aromatic tertiary amine polymer compounds and one or two kinds of other hole transporting compounds. It is preferable to use the above in combination.

  Among the above examples, an aromatic amine compound is preferable from the viewpoint of amorphousness and visible light transmittance, and an aromatic tertiary amine compound is particularly preferable. 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 from the viewpoint of uniform light emission due to the surface smoothing effect, a polymer compound having a weight average molecular weight of 1,000 or more and 1,000,000 or less (a polymerizable compound in which repeating units are linked) is further included. preferable. Preferable examples of the aromatic tertiary amine polymer compound include a polymer compound having a repeating unit represented by the following formula (III).

(In the formula (III), Ar ¹ and Ar ² each independently represent an aromatic hydrocarbon group which may have a substituent or an aromatic heterocyclic group which may have a substituent. Ar ^{3 to} Ar ⁵ each independently represents a divalent aromatic hydrocarbon group which may have a substituent or a divalent aromatic heterocyclic group which may have a substituent. Y represents a linking group selected from the following group of linking groups, and two groups bonded to the same N atom among Ar ^{1 to} Ar ⁵ may be bonded to each other to form a ring. Good.

(In the above formulas, Ar ^{6 to} Ar ¹⁶ are each independently a monovalent or divalent aromatic hydrocarbon group which may have a substituent or a monovalent which may have a substituent. Or a divalent aromatic heterocyclic group, R ¹¹ and R ¹² each independently represents a hydrogen atom or an optional substituent.))

Examples of the monovalent or divalent aromatic hydrocarbon group and aromatic heterocyclic group of Ar ^{1 to} Ar ¹⁶ include a benzene ring and a naphthalene from the viewpoint of the solubility, heat resistance, and hole injection / transport properties of the polymer compound. A group derived from a ring, a phenanthrene ring, a thiophene ring or a pyridine ring is preferred, and a group derived from a benzene ring or a naphthalene ring is more preferred.

The monovalent or divalent aromatic hydrocarbon group and aromatic heterocyclic group of Ar ^{1 to} Ar ¹⁶ may further have a substituent. The molecular weight of the substituent is usually 400 or less, preferably about 250 or less. As the substituent, an alkyl group, an alkenyl group, an alkoxy group, an aromatic hydrocarbon group, an aromatic heterocyclic group and the like are preferable.

When R ¹¹ and R ¹² are optional substituents, examples of the substituent include alkyl groups, alkenyl groups, alkoxy groups, silyl groups, siloxy groups, aromatic hydrocarbon groups, aromatic heterocyclic groups, and the like. .

Specific examples of the aromatic tertiary amine polymer compound having a repeating unit represented by the formula (III) include those described in International Publication No. 2005/089024.
In addition, as a hole transporting compound, a conductive polymer (PEDOT / PSS) obtained by polymerizing 3,4-ethylenedioxythiophene (3,4-ethylenedioxythiophene), a polythiophene derivative, in high molecular weight polystyrene sulfonic acid. Is also preferred. Moreover, the end of this polymer may be capped with methacrylate or the like.

  Furthermore, as the hole transporting compound, a crosslinkable compound described in the item {Hole transporting layer} described later may be used. When a crosslinkable compound is used, the film forming method is the same.

  The concentration of the hole transporting compound in the composition for forming a hole injection layer is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.01% by weight or more, preferably in terms of film thickness uniformity. Is 0.1% by weight or more, more preferably 0.5% by weight or more, and usually 70% by weight or less, preferably 60% by weight or less, more preferably 50% by weight or less. If this concentration is too high, film thickness unevenness may occur, and if it is too low, defects 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 is preferably a compound having an oxidizing power and the ability to accept one electron from the above-described hole transporting compound, specifically, a compound having an electron affinity of 4 eV or more is preferable, and 5 eV or more. The compound which is the compound of these is further more preferable.

  Examples of such electron-accepting compounds include triarylboron compounds, metal halides, Lewis acids, organic acids, onium salts, salts of arylamines and metal halides, and salts of arylamines and Lewis acids. Examples thereof include one or more compounds selected from the group. More specifically, an onium salt substituted with an organic group such as 4-isopropyl-4′-methyldiphenyliodonium tetrakis (pentafluorophenyl) borate and triphenylsulfonium tetrafluoroborate (International Publication No. WO 2005/089024); High valent inorganic compounds such as iron (III) chloride (Japanese Patent Laid-Open No. 11-251067), ammonium peroxodisulfate; cyano compounds such as tetracyanoethylene, tris (pendafluorophenyl) borane (Japanese Patent Laid-Open No. 2003-31365) Aromatic boron compounds such as); fullerene derivatives; iodine; sulfonate ions such as polystyrene sulfonate ions, alkylbenzene sulfonate ions, camphor sulfonate ions, and the like.

  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 in the hole-injecting layer or the composition for forming a hole-injecting layer with respect to the hole-transporting compound is usually 0.1 mol% or more, preferably 1 mol% or more. However, it is usually 100 mol% or less, preferably 40 mol% or less.

(Other components)
As a material for the hole injection layer, other components may be further contained in addition to the above-described hole transporting compound and electron accepting compound as long as the effects of the present invention are not significantly impaired. Examples of other components include various light emitting materials, electron transporting compounds, binder resins, and coating property improving agents. In addition, only 1 type may be used for another component and it may use 2 or more types together by arbitrary combinations and ratios.

(solvent)
At least one of the solvents of the composition for forming a hole injection layer used in the wet film formation method is preferably a compound that can dissolve the constituent material of the hole injection layer. The boiling point of this solvent is usually 110 ° C. or higher, preferably 140 ° C. or higher, particularly 200 ° C. or higher, usually 400 ° C. or lower, and preferably 300 ° C. or lower. If the boiling point of the solvent is too low, the drying speed is too high and the film quality may be deteriorated. Further, if the boiling point of the solvent is too high, it is necessary to increase the temperature of the drying step, which may adversely affect other layers and the substrate.
Examples of the solvent include ether solvents, ester solvents, aromatic hydrocarbon solvents, amide solvents, and the like.

Examples of ether solvents 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 , Phenetole, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole, aromatic ethers such as 2,4-dimethylanisole, and the like.
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-isopropylpropylphenyl, 1,2,3,4-tetramethylbenzene, 1,4-diisopropylbenzene, cyclohexylbenzene, and methylnaphthalene. Can be mentioned.
Examples of the amide solvent include N, N-dimethylformamide, N, N-dimethylacetamide, and the like.
In addition, dimethyl sulfoxide and the like can also be used.

  These solvent may use only 1 type and may use 2 or more types by arbitrary combinations and a ratio.

(Film formation method)
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 formation, and dried. The hole injection layer 3 is formed.

  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 the formation of crystals in the composition.

  Although the relative humidity in an application | coating process is not limited unless the effect of this invention is impaired remarkably, it is 0.01 ppm or more normally, and usually 80% or less.

  After coating, the film of the composition for forming a hole injection layer is usually dried by heating or the like. Examples of the heating means used in the heating step include a clean oven, a hot plate, infrared rays, a halogen heater, microwave irradiation and the like. Among them, a clean oven and a hot plate are preferable in order to uniformly apply heat to the entire film.

  The heating temperature in the heating step is preferably heated at a temperature equal to or higher than the boiling point of the solvent used in the composition for forming a hole injection layer as long as the effects of the present invention are not significantly impaired. In the case of a mixed solvent containing two or more types of solvents used in the hole injection layer, at least one type is preferably heated at a temperature equal to or higher than the boiling point of the solvent. In consideration of an increase in the boiling point of the solvent, the heating step is preferably performed at 120 ° C. or higher, preferably 410 ° C. or lower.

  In the heating step, the heating time is not limited as long as the heating temperature is not lower than the boiling point of the solvent of the composition for forming a hole injection layer and sufficient insolubilization of the coating film does not occur. Is less than a minute. If the heating time is too long, the components of the other layers tend to diffuse, and if it is too short, the hole injection layer tends to be inhomogeneous. Heating may be performed in two steps.

<Formation of hole injection layer by vacuum deposition>
When the hole injection layer 3 is formed by vacuum deposition, one or more of the constituent materials of the hole injection layer 3 (the aforementioned hole transporting compound, electron accepting compound, etc.) are placed in a vacuum vessel. Put in crucibles installed (in case of using two or more kinds of materials, put them in each crucible), evacuate the inside of the vacuum vessel to about 10 ^-4 Pa with a suitable vacuum pump, and then heat the crucible (two kinds When using the above materials, heat each crucible) and control the evaporation amount to evaporate (when using two or more materials, control each evaporation amount independently) and face the crucible Then, the hole injection layer 3 is formed on the anode 2 of the substrate placed on the substrate. In addition, when using 2 or more types of materials, the hole injection layer 3 can also be formed by putting those mixtures into a crucible, heating and evaporating.

The degree of vacuum at the time of vapor deposition is not limited as long as the effects of the present invention are not significantly impaired, but usually 0.1 × 10 ⁻⁶ Torr (0.13 × 10 ⁻⁴ Pa) or more, usually 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 Å / second or more and usually 5.0 Å / second or less. The film forming temperature at the time of vapor deposition is not limited as long as the effect of the present invention is not significantly impaired, but is preferably 10 ° C. or higher, preferably 50 ° C. or lower.

{Hole transport layer}
The hole transport layer 4 can be formed on the hole injection layer 3 when there is a hole injection layer and on the anode 2 when there is no hole injection layer 3.
The organic electroluminescent device of the present invention may have a configuration in which the hole transport layer is omitted.

  The method for forming the hole transport layer 4 according to the present invention may be a vacuum deposition method or a wet film formation method, and is not particularly limited, but the hole transport layer 4 is formed by a wet film formation method from the viewpoint of reducing dark spots. It is preferable.

  The material for forming the hole transport layer 4 is preferably a material having high hole transportability and capable of efficiently transporting 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 stability is high, and impurities that become traps are not easily generated during manufacturing or use. In many cases, it is preferable not to quench the light emitted from the light emitting layer 5 or to form an exciplex with the light emitting layer 5 to reduce the efficiency because it is in contact with the light emitting layer 5.

  Such a material for the hole transport layer 4 may be any material conventionally used as a constituent material for the hole transport layer. For example, the hole transport property used for the hole injection layer 3 described above. What was illustrated as a compound is mentioned. In addition, arylamine derivatives, fluorene derivatives, spiro derivatives, carbazole derivatives, pyridine derivatives, pyrazine derivatives, pyrimidine derivatives, triazine derivatives, quinoline derivatives, phenanthroline derivatives, phthalocyanine derivatives, porphyrin derivatives, silole derivatives, oligothiophene derivatives, condensed polycyclic aromatics Group derivatives, metal complexes and the like.

In addition, for example, polyvinylcarbazole derivatives, polyarylamine derivatives, polyvinyltriphenylamine derivatives, polyfluorene derivatives, polyarylene derivatives, polyarylene ether sulfone derivatives containing tetraphenylbenzidine, polyarylene vinylene derivatives, polysiloxane derivatives, polythiophenes Derivatives, poly (p-phenylene vinylene) derivatives, and the like. These may be any of an alternating copolymer, a random polymer, a block polymer, or a graft copolymer. Further, it may be a polymer having a branched main chain and three or more terminal portions, or a so-called dendrimer.
Of these, polyarylamine derivatives and polyarylene derivatives are preferred.

The polyarylamine derivative is preferably a polymer containing a repeating unit represented by the following formula (IV). In particular, the polymer is preferably a polymer composed of repeating units represented by the following formula (IV). In this case, Ar ^a or Ar ^b may be different in each repeating unit.

(In the formula (IV), Ar ^a and Ar ^b are each independently a monovalent or divalent aromatic hydrocarbon group which may have a substituent, or a monovalent or divalent aromatic complex. Represents a cyclic group.)

  Examples of the aromatic hydrocarbon group which may have a substituent include, for example, a benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, tetracene ring, pyrene ring, benzpyrene ring, chrysene ring, triphenylene ring, and acenaphthene. Examples include a group derived from a 6-membered monocyclic ring or a 2-5 condensed ring, such as a ring, a fluoranthene ring, a fluorene ring, and a group in which these rings are linked by a direct bond.

  Examples of the aromatic heterocyclic group which may have a substituent include a furan ring, a benzofuran ring, a thiophene ring, a benzothiophene ring, a pyrrole ring, a pyrazole ring, an imidazole ring, an oxadiazole ring, an indole ring, and a carbazole ring. , Pyrroloimidazole ring, pyrrolopyrazole ring, pyrrolopyrrole ring, thienopyrrole ring, thienothiophene ring, furopyrrole ring, furofuran ring, thienofuran ring, benzoisoxazole ring, benzoisothiazole ring, benzimidazole ring, pyridine ring, pyrazine ring, pyridazine Ring, pyrimidine ring, triazine ring, quinoline ring, isoquinoline ring, sinoline ring, quinoxaline ring, phenanthridine ring, benzimidazole ring, perimidine ring, quinazoline ring, quinazolinone ring, azulene ring, etc. ring Are those groups group and the rings of from 2-4 fused ring is linked by a direct bond or two or more rings.

Ar ^a and Ar ^b are each independently a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, a triphenylene ring, a pyrene ring, a thiophene ring, a pyridine ring, a fluorene from the viewpoint of solubility and heat resistance in an organic solvent. A group derived from a ring selected from the group consisting of rings or a group formed by linking two or more benzene rings (for example, a biphenyl group (biphenylene group) or a terphenyl group (terphenylene group)) is preferable.
Among these, a group derived from a benzene ring (phenyl group), a group formed by connecting two benzene rings (biphenyl group), and a group derived from a fluorene ring (fluorenyl group) are preferable.

Examples of the substituent that the aromatic hydrocarbon group and aromatic heterocyclic group in Ar ^a and Ar ^b may have include an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, an aryloxy group, an alkoxycarbonyl group, and a dialkyl. Examples thereof include an amino group, a diarylamino group, an acyl group, a halogen atom, a haloalkyl group, an alkylthio group, an arylthio group, a silyl group, a siloxy group, a cyano group, an aromatic hydrocarbon ring group, and an aromatic heterocyclic group.

As the polyarylene derivative, an arylene group such as an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent exemplified as Ar ^a or Ar ^b in the formula (IV) is used as its repeating unit. The polymer which has is mentioned.

  As a polyarylene derivative, the polymer which has a repeating unit which consists of following formula (V-1) and / or following formula (V-2) is preferable.

(In formula (V-1), R ^a , R ^b , R ^c and R ^d each independently represents an alkyl group, an alkoxy group, a phenylalkyl group, a phenylalkoxy group, a phenyl group, a phenoxy group, an alkylphenyl group, Represents an alkoxyphenyl group, an alkylcarbonyl group, an alkoxycarbonyl group, or a carboxy group, and t and s each independently represent an integer of 0 to 3. When t or s is 2 or more, they are contained in one molecule. A plurality of R ^a or R ^b may be the same or different, and adjacent R ^a or R ^b may form a ring.)

(In formula (V-2), R ^e and R ^f are each independently synonymous with R ^a , R ^b , R ^c or R ^d in formula (V-1). R and u are each Independently represents an integer of 0 to 3. When r or u is 2 or more, a plurality of R ^e and R ^f contained in one molecule may be the same or different, and adjacent R ^e or R R ^f may form a ring, and X represents an atom or an atomic group constituting a 5-membered ring or a 6-membered ring.)

Specific examples of X are —O—, —BR—, —NR—, —SiR ₂ —, —PR—, —SR—, —CR ₂ —, or a group formed by bonding thereof. R represents a hydrogen atom or an arbitrary organic group. The organic group in the present invention is a group containing at least one carbon atom.

  Moreover, as a polyarylene derivative, in addition to the repeating unit which consists of said Formula (V-1) and / or said Formula (V-2), it further has a repeating unit represented by the following formula (V-3). Is preferred.

(In formula (V-3), Ar ^{c to} Ar ^j are each independently a monovalent or divalent aromatic hydrocarbon group or monovalent or divalent aromatic which may have a substituent. Represents a heterocyclic group, and v and w each independently represent 0 or 1.)

Specific examples of Ar ^{c to} Ar ^j are the same as Ar ^a and Ar ^b in the formula (IV).

  Specific examples of the above formulas (V-1) to (V-3) and specific examples of polyarylene derivatives include those described in JP-A-2008-98619.

  In the case of forming the hole transport layer 4 by a wet film formation method, a composition for forming a hole transport layer is prepared in the same manner as the formation of the hole injection layer 3 and then heated and dried after the wet film formation. .

  The composition for forming a hole transport layer contains a solvent in addition to the above hole transport compound. The solvent used is the same as that used for the composition for forming a hole injection layer. The film forming conditions, heat drying conditions, and the like are the same as in the case of forming the hole injection layer 3.

  In the case where the hole transport layer is formed by the vacuum deposition method, the film forming conditions are the same as those in the case of forming the hole injection layer 3.

  The hole transport layer 4 may contain various light emitting materials, electron transport compounds, binder resins, coating property improving agents, and the like in addition to the hole transport compound.

  The hole transport layer 4 may also be a layer formed by crosslinking a crosslinkable compound. The crosslinkable compound is a compound having a crosslinkable group, and forms a network polymer compound by crosslinking.

  Examples of this crosslinkable group include groups derived from cyclic ethers such as oxetane and epoxy; groups derived from unsaturated double bonds such as vinyl, trifluorovinyl, styryl, acrylic, methacryloyl and cinnamoyl; benzo Examples include groups derived from cyclobutene.

  The crosslinkable compound may be any of a monomer, an oligomer, and a polymer. The crosslinkable compound may have only 1 type, and may have 2 or more types by arbitrary combinations and ratios.

  As the crosslinkable compound, a hole transporting compound having a crosslinkable group is preferably used. Examples of the hole transporting compound include those exemplified above, and those having a crosslinkable group bonded to the main chain or side chain with respect to these hole transporting compounds. In particular, the crosslinkable group is preferably bonded to the main chain via a linking group such as an alkylene group. In particular, the hole transporting compound is preferably a polymer containing a repeating unit having a crosslinkable group, and the above formula (IV) and formulas (V-1) to (V-3) are represented by a crosslinkable group. Is preferably a polymer having a repeating unit bonded directly or via a linking group.

  As the crosslinkable compound, a hole transporting compound having a crosslinkable group is preferably used. Examples of hole transporting compounds include nitrogen-containing aromatic compound derivatives such as pyridine derivatives, pyrazine derivatives, pyrimidine derivatives, triazine derivatives, quinoline derivatives, phenanthroline derivatives, carbazole derivatives, phthalocyanine derivatives, porphyrin derivatives; triphenylamine derivatives Silole derivatives; oligothiophene derivatives, condensed polycyclic aromatic derivatives, metal complexes and the like. Among them, nitrogen-containing aromatic derivatives such as pyridine derivatives, pyrazine derivatives, pyrimidine derivatives, triazine derivatives, quinoline derivatives, phenanthroline derivatives, carbazole derivatives; triphenylamine derivatives, silole derivatives, condensed polycyclic aromatic derivatives, metal complexes, etc. Particularly preferred are triphenylamine derivatives.

  In order to form a hole transport layer 4 by crosslinking a crosslinkable compound, a composition for forming a hole transport layer in which a crosslinkable compound is dissolved or dispersed in a solvent is usually prepared and deposited by wet film formation. To crosslink.

  The composition for forming a hole transport layer may contain an additive for promoting a crosslinking reaction in addition to the crosslinking compound. Examples of additives that promote the crosslinking reaction include polymerization initiators and polymerization accelerators such as alkylphenone compounds, acylphosphine oxide compounds, metallocene compounds, oxime ester compounds, azo compounds, onium salts; condensed polycyclic hydrocarbons, And photosensitizers such as porphyrin compounds and diaryl ketone compounds.

  Further, it may contain a coating property improving agent such as a leveling agent and an antifoaming agent; an electron accepting compound; a binder resin;

  In the composition for forming a hole transport layer, the crosslinkable compound is usually 0.01% by weight or more, preferably 0.05% by weight or more, more preferably 0.1% by weight or more, usually 50% by weight or less, preferably 20%. It is contained in an amount of not more than wt%, more preferably not more than 10 wt%.

  After forming a composition for forming a hole transport layer containing a crosslinkable compound at such a concentration on the lower layer (usually the hole injection layer 3), the composition is crosslinked by heating and / or irradiation with active energy such as light. Are crosslinked to form a network polymer compound.

  Conditions such as temperature and humidity during film formation are the same as those during the wet film formation of the hole injection layer 3.

The heating method after film formation is not particularly limited. As heating temperature conditions, it is 120 degreeC or more normally, Preferably it is 400 degrees C or less.
The heating time is usually 1 minute or longer, preferably 24 hours or shorter. The heating means is not particularly limited, and means such as placing a laminated body having a coated film layer on a hot plate or heating in an oven is used. For example, conditions such as heating on a hot plate at 120 ° C. or more for 1 minute or more can be used.

  In the case of irradiation with active energy such as light, a method of irradiating directly using an ultraviolet / visible / infrared light source such as an ultra-high pressure mercury lamp, a high-pressure mercury lamp, a halogen lamp, an infrared lamp, or the above-mentioned light source is incorporated. Examples include a mask aligner and a method of irradiation using a conveyor type light irradiation device. In active energy irradiation other than light, for example, there is a method of irradiation using a so-called microwave oven that irradiates a microwave generated by a magnetron. As the irradiation time, it is preferable to set conditions necessary for reducing the solubility of the film, but irradiation is usually performed for 0.1 seconds or longer, preferably 10 hours or shorter.

  The irradiation of active energy such as heating and light may be performed alone or in combination. When combined, the order of implementation is not particularly limited.

  The film thickness of the hole transport layer 4 thus formed is usually 5 nm or more, preferably 10 nm or more, and usually 300 nm or less, preferably 100 nm or less.

{Light emitting layer}
The light emitting layer 5 in the organic electroluminescent device of the present invention is preferably formed by a wet film forming method using the composition for organic electroluminescent device of the present invention.

  The film formation temperature at the time of film formation is not limited, but in order to prevent film loss due to the occurrence of crystals and aggregation in the composition, it is preferably 10 ° C. or higher, more preferably 13 ° C. or higher, further preferably 16 ° C. or higher, Moreover, 50 degrees C or less is preferable and 40 degrees C or less is more preferable.

  The relative humidity during film formation is not limited, but is usually 0.01 ppm or more, preferably 0.05 ppm or more, more preferably 0.1 ppm or more, usually 80% or less, preferably 60% or less, more preferably 15% or less, More preferably, it is 1% or less, and particularly preferably 100 ppm or less. If the relative humidity is too small, it is difficult to control the film forming conditions, and a stable environment cannot be maintained. On the other hand, if it is too large, moisture adsorption on the light emitting layer may be affected.

  After film formation, it is usually dried by heating. Examples of the heating means include a clean oven, a hot plate, infrared rays, a halogen heater, and microwave irradiation. Among them, a clean oven and a hot plate are preferable in order to uniformly apply heat to the entire film.

  The heating direction in the heating step is not limited as long as the effects of the present invention are not significantly impaired. As an example of the heating direction, for example, a film formation substrate is mounted on a hot plate, and the coating film is heated through the hot plate, whereby the coating film is placed on the lower surface of the substrate (a substrate on which no organic layer is applied). A method of heating from the side), a method of heating the coating film from all directions, front, back, left, and right by placing the film formation substrate in a clean oven.

  The heating temperature in the heating step is not particularly limited as long as the effect of the present invention is not significantly impaired, but is usually 90 ° C. or higher, preferably 100 ° C. or higher, and usually 200 ° C. or lower, preferably 140 ° C. or lower. preferable. If the heating temperature is too high, components may diffuse into other layers, and if it is too low, the residual solvent may not be removed sufficiently. Moreover, when it is a mixed solvent in which 2 or more types of solvents are contained in the composition for organic electroluminescent elements, it is preferable that at least 1 type is heated at the temperature more than the boiling point of the solvent.

  The heating time in the heating step is not limited as long as the effect of the present invention is not significantly impaired, but is preferably 15 minutes or more, more preferably 30 minutes or more, further preferably 1 hour or more, and preferably 6 hours or less, more preferably Is 3 hours or less, more preferably 2 hours or less. This heating makes it possible to sufficiently insolubilize the coating film. If the heating time is too long, the components of the other layers tend to diffuse, and if it is too short, sufficient homogeneity cannot be obtained.

  The thickness of the light emitting layer 5 is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 3 nm or more, preferably 5 nm or more, and usually 200 nm or less, preferably 100 nm or less. If the thickness of the light emitting layer 5 is too thin, defects may occur in the light emitting layer 5, and if it is too thick, the driving voltage of the device may increase.

  When a light emitting layer is not formed using the composition for organic electroluminescent elements of the present invention, the light emitting layer can be formed by materials and methods conventionally used as a light emitting layer of an organic electroluminescent element.

{Hole blocking layer}
A hole blocking layer 6 may be provided on the light emitting layer 5. The hole blocking layer 6 has a role of blocking holes moving from the anode 2 from reaching the cathode 9 and a role of efficiently transporting electrons injected from the cathode 9 toward the light emitting layer 5. Have

  The physical properties required for the material constituting the hole blocking layer 6 include high electron mobility, low hole mobility, a large energy gap (difference between HOMO and LUMO), and excited triplet level (T1). Is high. Examples of the material of the hole blocking layer 6 satisfying such conditions include, for example, bis (2-methyl-8-quinolinolato), (phenolato) aluminum, bis (2-methyl-8-quinolinolato), (triphenylsilanolato). ) Mixed ligand complexes such as aluminum, metal complexes such as bis (2-methyl-8-quinolato) aluminum-μ-oxo-bis- (2-methyl-8-quinolinato) aluminum binuclear metal complexes, distyrylbiphenyl Derivatives such as styryl compounds (JP-A-11-242996), 3- (4-biphenylyl) -4-phenyl-5 (4-tert-butylphenyl) -1,2,4-triazole and other triazole derivatives ( JP-A-7-41759), phenanthroline derivatives such as bathocuproine (JP-A-10-79297), etc. It is below. Further, a compound having at least one pyridine ring substituted at positions 2, 4, and 6 described in International Publication No. 2005-022962 is also preferable as a material for the hole blocking layer 6. In addition, the material of the hole-blocking layer 6 may use only 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  There is no restriction | limiting in the formation method of the hole-blocking layer 6. FIG. Therefore, it can be formed by a wet film formation method, a vacuum deposition method, or other methods. A vacuum deposition method is preferred.

  The thickness of the hole blocking layer 6 is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.3 nm or more, preferably 0.5 nm or more, and usually 100 nm or less, preferably 50 nm or less.

{Electron transport layer}
An electron transport layer 7 may be provided between the cathode 8 and the light emitting layer 5. The electron transport layer 7 is provided for the purpose of further improving the light emission efficiency of the device, and efficiently transports electrons injected from the cathode 9 between the electrodes to which an electric field is applied in the direction of the light emitting layer 5. Formed from a compound capable of

  As an electron transporting compound used for the electron transport layer 7, usually, the electron injection efficiency from the cathode 9 or the electron injection layer 8 described later is high, and the injected electrons are transported efficiently with high electron mobility. A compound that can be used is used. Examples of the compound satisfying such conditions include metal complexes such as aluminum complexes of 8-hydroxyquinoline (Japanese Patent Laid-Open No. 59-194393), metal complexes of 10-hydroxybenzo [h] quinoline, oxadiazole derivatives , Distyrylbiphenyl derivatives, silole derivatives, 3-hydroxyflavone metal complexes, 5-hydroxyflavone metal complexes, benzoxazole metal complexes, benzothiazole metal complexes, trisbenzimidazolylbenzene (US Pat. No. 5,645,948), quinoxaline compounds ( JP-A-6-207169), phenanthroline derivative (JP-A-5-331459), 2-t-butyl-9,10-N, N'-dicyanoanthraquinonediimine, n-type hydrogenated amorphous silicon carbide , N-type zinc sulfide, n-type zinc Such as emissions of zinc, and the like. In addition, the material of the electron carrying layer 7 may use only 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  There is no restriction | limiting in the formation method of the electron carrying layer 7. FIG. Therefore, it can be formed by a wet film formation method, a vacuum deposition method, or other methods. A vacuum deposition method is preferred.

  The thickness of the electron transport layer 7 is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 1 nm or more, preferably 5 nm or more, and usually 300 nm or less, preferably 100 nm or less.

{Electron injection layer}
The electron injection layer 8 plays a role of efficiently injecting electrons injected from the cathode 9 into the light emitting layer 5. In order to perform electron injection efficiently, the material for forming the electron injection layer 8 is preferably a metal having a low work function.

  Examples of the material for forming the electron injection layer 8 include alkali metals such as sodium and cesium, and alkaline earth metals such as barium and calcium. In this case, the thickness of the electron injection layer 8 is usually preferably 0.1 nm or more and 5 nm or less.

Furthermore, an organic electron transport compound represented by a metal complex such as a nitrogen-containing heterocyclic compound such as bathophenanthroline or an aluminum complex of 8-hydroxyquinoline is doped with an alkali metal such as sodium, potassium, cesium, lithium, or rubidium ( (As described in JP-A-10-270171, JP-A-2002-1000047, JP-A-2002-1000048, etc.), it is possible to improve the electron injection / transport properties and achieve excellent film quality. preferable. Further, for example, an ultra-thin insulating film (0.1 to 5 nm) formed of lithium fluoride (LiF), magnesium fluoride (MgF ₂ ), lithium oxide (Li ₂ O), cesium carbonate (II) (CsCO ₃ ), or the like. ) Is also an effective method for improving the efficiency of the device (Applied Physics Letters, 1997, Vol. 70, pp. 152; Japanese Patent Laid-Open No. 10-74586; IEEE Transactions on Electron Devices, 1997) Vol. 44, pp. 1245; SID 04 Digest, pp. 154, etc.).

  In this case, the film thickness is usually 5 nm or more, preferably 10 nm or more, and is usually 200 nm or less, preferably 100 nm or less.

  In addition, the material of the electron injection layer 8 may use only 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  There is no restriction | limiting in the formation method of the electron injection layer 8. FIG. Therefore, it can be formed by a wet film formation method, a vacuum deposition method, or other methods.

{cathode}
The cathode 9 serves to inject electrons into the layer on the light emitting layer 5 side.

  As the material of the cathode 9, the material used for the anode 2 can be used. However, a metal having a low work function is preferable for efficient electron injection. For example, tin, magnesium, indium, A suitable metal such as calcium, aluminum, silver, or an alloy thereof is used. Specific examples include low work function alloy electrodes such as magnesium-silver alloy, magnesium-indium alloy, and aluminum-lithium alloy. In addition, the material of the cathode 9 may use only 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  The film thickness of the cathode 9 is usually the same as that of the anode.

  Further, for the purpose of protecting the cathode made of a low work function metal, it is preferable to further stack a metal layer having a high work function and stable to the atmosphere because the stability of the device is increased. For this purpose, for example, metals such as aluminum, silver, copper, nickel, chromium, gold and platinum are used. In addition, these materials may be used only by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

{Other layers}
The organic electroluminescent element of the present invention may have another configuration without departing from the gist thereof. For example, as long as the performance is not impaired, an arbitrary layer other than the layers described above may be provided between the anode 2 and the cathode 9, for example, an electron blocking layer described below, Arbitrary layers may be omitted.

  The electron blocking layer is provided on the anode side of the light emitting layer 5 in contact with the light emitting layer 5 and blocks electrons moving from the light emitting layer 5 from reaching the hole transport layer 4 and the hole injection layer 3. Thus, the probability of recombination of holes and electrons in the light emitting layer 5 is increased, the excitons generated are confined in the light emitting layer 5, and the positive holes injected from the hole transport layer 4 and the hole injection layer 3. There is a role of efficiently transporting the holes in the direction of the light emitting layer. In particular, it is effective when a phosphorescent material or a blue light emitting material is used as the light emitting material.

  The characteristics required for the electron blocking layer include high hole transportability, a large energy gap (difference between HOMO and LUMO), and a high excited triplet level (T1). Furthermore, in the present invention, when the light emitting layer is produced by the wet film formation method using the composition for organic electroluminescence elements of the present invention, the electron blocking layer is also required to be compatible with the wet film formation. Examples of the material used for the electron blocking layer 8 include a copolymer of dioctylfluorene and triphenylamine typified by F8-TFB (described in International Publication No. 2004/084260). In addition, the material of an electron blocking layer may use only 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  There is no restriction | limiting in the formation method of an electron blocking layer. Therefore, it can be formed by a wet film formation method, a vacuum deposition method, or other methods.

  Moreover, in the layer structure demonstrated above, it is also possible to laminate | stack components other than a board | substrate in reverse order. For example, in the case of the layer configuration of FIG. 1, other components are provided in order from the cathode on the substrate 1.

  Furthermore, it is also possible to constitute an organic electroluminescent element by laminating components other than the substrate between two substrates, at least one of which has transparency.

In addition, a structure in which a plurality of components (light emitting units) other than the substrate are stacked in a plurality of layers (a structure in which a plurality of light emitting units are stacked) may be employed. In that case, instead of the interface layer between the steps (between the light emitting units) (when the anode is ITO and the cathode is Al, these two layers), for example, a charge made of vanadium pentoxide (V ₂ O ₅ ) or the like. When a generation layer (Carrier Generation Layer: CGL) is provided, a barrier between steps is reduced, which is more preferable from the viewpoint of light emission efficiency and driving voltage.

  Furthermore, the organic electroluminescent device of the present invention may be configured as a single organic electroluminescent device, or may be applied to a configuration in which a plurality of organic electroluminescent devices are arranged in an array, and an anode and a cathode May be applied to a configuration in which are arranged in an XY matrix.

  In addition, each layer described above may contain components other than those described as the respective layer constituent materials unless the effects of the present invention are significantly impaired.

[Organic EL display device]
The organic EL display device of the present invention uses the above-described organic electroluminescent element of the present invention. There is no restriction | limiting in particular about the model and structure of the organic electroluminescent display apparatus of this invention, It can assemble in accordance with a conventional method using the organic electroluminescent element of this invention.
For example, the organic EL display device of the present invention can be obtained by the method described in “Organic EL display” (Ohm, published on Aug. 20, 2004, Shizushi Tokito, Chiba Adachi, Hideyuki Murata). Can be formed.

[Organic EL lighting]
The organic EL illumination of the present invention uses the above-described organic electroluminescent element of the present invention. There is no restriction | limiting in particular about the model and structure of the organic EL illumination of this invention, It can assemble in accordance with a conventional method using the organic electroluminescent element of this invention.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples, and the present invention can be arbitrarily modified and implemented without departing from the gist thereof.

(Synthesis of compounds)
[Synthesis Example 1: Synthesis of Compound H-1 of the Present Invention]
<Synthesis of Compound 2>

  Compound 1 (3-bromo-iodobenzene) (25 g, 88 mmol) and 1-naphthylboronic acid (13.8 g, 80 mmol) are dissolved in a mixed solvent of 240 ml of toluene / 120 ml of ethanol, and 1 g of tetrakis (triphenylphosphine) palladium, 2M. 125 ml of a tripotassium phosphate aqueous solution was added, and the mixture was allowed to react with stirring under reflux for 4 hours under a nitrogen stream. Toluene and water were added thereto, and the mixture was separated and purified by silica gel column chromatography. This operation was performed twice to obtain 37 g of Compound 2 (1-bromo-3-naphthylbenzene) in total.

<Synthesis of Compound 3>

  Compound 2 (1-bromo-3-naphthylbenzene) (20 g, 71 mmol) was dissolved in 250 ml of dehydrated tetrahydrofuran (THF). The solution was kept at −78 ° C. and 50 ml of 1.2 M n-BuLi in hexane was added. After stirring for 1 hour, 25 ml of trimethyl borate was added, and after stirring for 2 hours, the temperature was gradually raised. Further, 1N hydrochloric acid was added, and 50 ml of methylene chloride was added for extraction, followed by concentration and drying. This operation was repeated twice to obtain 37 g of compound 3 (m-naphthylphenylboronic acid).

<Synthesis of Compound 4>

  Compound 1 (3-bromo-iodobenzene) (17.6 g, 62 mmol) and compound 3 (m-naphthylphenylboronic acid) (14.0 g, 62.1 mmol) were dissolved in a mixed solvent of toluene 170 ml / ethanol 85 ml. A sodium carbonate aqueous solution (85 ml) and tetrakis (triphenylphosphine) palladium (2 g) were added, and the mixture was allowed to react with stirring under reflux in a nitrogen stream for 6 hours. Toluene and water were added thereto, and the mixture was separated and purified by silica gel column chromatography to obtain 13.0 g of compound 4 (3'-bromophenyl-3- (1-naphthyl) benzene).

<Synthesis of Compound 5>

  Compound 4 (3'-bromophenyl-3- (1-naphthyl) benzene) (13.0 g, 36 mmol) was dissolved in 200 ml of dehydrated THF. The solution was kept at −78 ° C. and 24 ml of a 1.05 M n-BuLi hexane solution was added. Further, after stirring for 1 hour, 12 ml of trimethyl borate was added, and after stirring for 2.5 hours, the temperature was gradually raised. Further, 200 ml of 1N hydrochloric acid was added, and 400 ml of ethyl acetate was added for extraction, followed by concentration, drying, and washing with hexane to obtain 13.6 g of compound 5.

<Synthesis of Compound 6>

  3-biphenylboronic acid (12.39 g, 62.6 mmol) and 9-bromoanthracene (12.37 g, 48.1 mmol) were dissolved in a mixed solvent of 80 ml of toluene / 40 ml of ethanol, and 60 ml of 2M tripotassium phosphate aqueous solution was added. Furthermore, 2.2 g of tetrakis (triphenylphosphine) palladium was added, and the reaction was allowed to stir at 80 ° C. for 6.5 hours under a nitrogen stream. Toluene and water were added thereto, and the mixture was separated and purified by silica gel column chromatography to obtain 15.6 g of compound 6 (biphenylanthracene).

<Synthesis of Compound 7>

  Compound 6 (biphenylanthracene) (31.0 g, 93.8 mmol) was added to 550 ml of N, N-dimethylformamide at room temperature and stirred, and N-bromosuccinimide (16.2 g, 93.8 mmol) was separated as a solid. And stirred for another 5 hours. Water and dichloromethane were added thereto, and magnesium sulfate was added to the oil layer. After filtration and purification by silica gel column chromatography, 35.1 g of Compound 7 was obtained.

<Synthesis of Compound H-1>

Compound 7 (12.10 g, 29.6 mmol) and compound 5 (12.0 g, 37.0 mmol) are dissolved in a mixed solvent of toluene (80 ml) / ethanol (40 ml), and 40 mL of 2M tripotassium phosphate aqueous solution is added. Tetrakis (triphenylphosphine) palladium (1.33 g) was added, and the reaction was allowed to stir and reflux for 9 hours under a nitrogen stream. Toluene and water were added thereto, and the mixture was separated, purified by silica gel column chromatography, and then purified by sublimation to obtain 10.3 g of compound H-1. A ¹ H-NMR chart (400 MHz, CDCl ₃ , 25 ° C.) of the obtained compound H-1 is shown in FIG.

[Synthesis Example 2: Synthesis Example of Compound H-2 of the Present Invention]
<Synthesis of Compound 8>

  Compound 5 (5.89 g, 18.2 mmol) and 9-bromoanthracene (3.59 g, 14.0 mmol) were dissolved in a mixed solvent of 30 ml of toluene / 15 ml of ethanol, 17 mL of 2M tripotassium phosphate aqueous solution was added, and tetrakis ( Triphenylphosphine) palladium (0.7 g) was added, and the mixture was allowed to react with stirring under reflux for 4 hours under a nitrogen stream. Toluene and water were added thereto, and the mixture was separated and purified by silica gel column chromatography to obtain 5.78 g of compound 8.

<Synthesis of Compound 9>

  Compound 8 (4.4 g, 9.36 mmol) was added to 160 ml of N, N-dimethylformamide at room temperature and stirred, and N-bromosuccinimide (1.8 g, 10.1 mmol) in N, N-dimethylformamide (40 ml) was stirred. ) The solution was added dropwise at 0 ° C. and stirred for 1 hour, and further stirred at room temperature for 2 hours. Water was added thereto, the precipitate was filtered and dried, and 5.0 g of Compound 9 was obtained.

<Synthesis of Compound 10>

  Compound 1 (3-bromo-iodobenzene) (13.7 g, 48.5 mmol) and biphenyl-3-boronic acid (8.0 g, 40.4 mmol) were dissolved in a mixed solvent of 120 ml of toluene / 60 ml of ethanol, and tetrakis (tri Phenylphosphine) palladium (1 g) and 2M aqueous sodium carbonate solution (30 ml) were added, and the mixture was reacted with stirring under reflux for 6 hours under a nitrogen stream. To this were added ethyl acetate and water, and the mixture was separated and purified by silica gel column chromatography. This operation was performed twice to obtain 10.5 g of Compound 10 in total.

<Synthesis of Compound 11>

  Compound 10 (10.5 g, 34 mmol) was dissolved in 100 ml of dehydrated THF. The solution was kept at −78 ° C., and 25 ml of a 1.05 M n-BuLi hexane solution was added. After stirring for 3 hours, 12 ml of trimethyl borate was added and stirred for 1 hour while gradually warming to room temperature. To this, 100 ml of 1N hydrochloric acid was added, extracted with ethyl acetate, concentrated, dried, and purified by silica gel column chromatography to obtain 8.0 g of compound 11.

<Synthesis of Compound H-2>

Compound 9 (5.0 g, 9.3 mmol) and Compound 11 (3.8 g, 14.0 mmol) were dissolved in a mixed solvent of toluene (160 ml) / ethanol (80 ml), and 40 mL of 2M tripotassium phosphate aqueous solution was added. (Triphenylphosphine) palladium (0.33 g) was added, and the reaction was allowed to stir and reflux for 6 hours under a nitrogen stream. Ethyl acetate and water were added thereto for liquid separation, and after purification by silica gel column chromatography, sublimation purification was performed to obtain 2 g of compound H-2. FIG. 3 shows a ¹ H-NMR chart (400 MHz, CDCl ₃ , 25 ° C.) of the obtained compound H-2.

[Synthesis Examples 3 and 4: Synthesis of Comparative Compounds C-1 and C-2]
Comparative compounds C-1 and C-2 were synthesized in the same manner as in Synthesis Examples 1 and 2.

<Comparative Compound C-1>

<Comparative Compound C-2>

[Solvent solubility]
About this invention compound H-1, H-2 and comparative compound C-1, C-2, the solubility with respect to cyclohexylbenzene in 1013 hPa and 25 degreeC was measured with the following method, and the result was shown in Table 1.

<Solubility measurement method>
In a room adjusted to 25 ° C., 10 mg of the compound of the present invention or the comparative compound was weighed into a glass vial, and cyclohexylbenzene was added dropwise little by little until the vial was completely dissolved while shaking the vial. It was confirmed that the solution was allowed to stand for more than an hour to maintain a uniform solution state. Solubility was calculated from the drop weight of cyclohexylbenzene.

[Creation of organic electroluminescence device]
[Example 1]
An organic electroluminescent element having the structure shown in FIG. 1 was produced by the following method. An indium tin oxide (ITO) transparent conductive film deposited on a glass substrate 1 having a thickness of 150 nm (sputtered film; sheet resistance 15 Ω) is patterned into a 2 mm wide stripe using normal photolithography and hydrochloric acid etching. Thus, an anode 2 was formed. The patterned ITO substrate was cleaned in the order of ultrasonic cleaning with acetone, water with pure water, and ultrasonic cleaning with isopropyl alcohol, then dried with nitrogen blow, and finally subjected to ultraviolet ozone cleaning.

  Next, the hole injection layer 3 was formed by a wet film formation method as follows. As a material for the hole injection layer 3, a polymer compound PB-1 having an aromatic amino group represented by the following formula (weight average molecular weight: 52000, number average molecular weight: 32500) and an electron-accepting compound having the structural formula shown below Using A-2, spin coating was performed under the following film forming conditions using a composition for forming a hole injection layer having the following composition.

<Composition for forming hole injection layer>
Solvent: ethyl benzoate PB-1 concentration: 2.0% by weight
A-2 concentration: 0.4% by weight

<Film formation conditions>
Spinner speed: 2250 rpm
Spinner rotation time: 30 seconds Spin coating atmosphere: 25 ° C under air
Drying conditions: 230 ° C x 60 minutes

  A uniform thin film having a thickness of 30 nm was formed by the above spin coating.

  Subsequently, the hole transport layer 4 was formed by a wet film formation method as follows. Using the charge transport material PB-2 having the structural formula shown below as the material of the hole transport layer 4 and cyclohexylbenzene as the solvent, a composition for forming a hole transport layer having the following composition was prepared. The coating composition was spin-coated under the following film forming conditions.

<Composition for forming hole transport layer>
Solvent: cyclohexylbenzene PB-2 concentration: 1.4% by weight

<Film formation conditions>
Spinner speed: 1500rpm
Spinner rotation time: 120 seconds Spin coat atmosphere: 25 ° C in dry nitrogen
Drying conditions: 230 ° C x 60 minutes (under dry nitrogen)

  A uniform thin film having a thickness of 20 nm was formed by the above spin coating.

  Next, in forming the light emitting layer 5, the compound H-1 synthesized in Synthesis Example 1 is used as the charge transport material, and the organic compound D-1 having the following structure is used as the light emitting material. A layer forming composition (composition for organic electroluminescence device of the present invention) was prepared and spin coated on the hole transport layer 4 under the film forming conditions shown below to obtain a light emitting layer 5 with a film thickness of 45 nm.

<Composition for light emitting layer formation>
Solvent: cyclohexylbenzene H-1 concentration: 5% by weight
D-1 concentration: 0.5% by weight

<Film formation conditions>
Spinner speed: 2000rpm
Spinner rotation time: 120 seconds Spin coating atmosphere: 25 ° C in dry nitrogen
Drying conditions: 130 ° C x 60 minutes (under reduced pressure)

  A uniform thin film having a thickness of 50 nm was formed by the above spin coating.

  Next, a pyridine derivative HB-1 shown below as the hole blocking layer 6 was laminated at a crucible temperature of 251 to 252 ° C. with a deposition rate of 0.08 to 0.12 nm / second and a film thickness of 10 nm. The degree of vacuum during the deposition was 2.1 to 2.4 × 10 −4 Pa (about 1.6 to 1.8 × 10 −6 Torr).

  Next, an aluminum 8-hydroxyquinoline complex ET-1 shown below was deposited as an electron transport layer 7 on the hole blocking layer 6 in the same manner. At this time, the crucible temperature of the aluminum 8-hydroxyquinoline complex ET-1 is controlled in the range of 222 to 239 ° C., and the degree of vacuum during the deposition is 1.7 to 2.0 × 10 −4 Pa (about 1.3 to 1.5 × 10 −6 Torr), the deposition rate was 0.1 nm / second, and the film thickness was 30 nm.

The substrate temperature during vacuum deposition of the hole blocking layer 6 and the electron transport layer 7 was kept at room temperature.
Here, the element that has been deposited up to the electron transport layer 7 is once taken out from the vacuum deposition apparatus into the atmosphere, and a 2 mm wide striped shadow mask is used as a cathode deposition mask. In close contact with the element so as to be orthogonal to each other, it is installed in another vacuum deposition apparatus, and the degree of vacuum in the apparatus is 2.3 × 10 ⁻⁶ Torr (about 3.0 × 10 ⁻⁴ Pa) in the same manner as the organic layer. ) Exhaust until below.

Next, lithium fluoride (LiF) is deposited on the electron transport layer 7 as an electron injection layer 8 by using a molybdenum boat, a deposition rate of 0.015 nm / second, and a degree of vacuum of 2.5 × 10 ⁻⁶ Torr ( The film was formed on the electron transport layer 7 with a film thickness of 0.5 nm at about 3.3 × 10 ⁻⁴ Pa). Next, aluminum is heated as a cathode 9 on the electron injection layer 8 by a molybdenum boat, a deposition rate of 0.5 to 3.0 nm / second, and a degree of vacuum of 3.3 to 7.5 × 10 ⁻⁶ Torr. The cathode 9 was completed by forming a film at (approximately 4.4 to 10.0 × 10 ⁻⁴ Pa) to form an aluminum layer having a thickness of 80 nm.

  The substrate temperature during the deposition of the electron injection layer 8 and the cathode 9 was kept at room temperature.

As described above, an organic electroluminescent element having a light emitting area portion having a size of 2 mm × 2 mm was obtained. The light emission characteristics of this element are as follows.
Luminance / current: 5.4 [cd / A] (@ 1000 cd / m ² )
Voltage: 5.8 [V] (@ 1000 cd / m ² )
Luminous efficiency: 3.0 [1 m / W] (@ 1000 cd / m ² )
The maximum wavelength of the emission spectrum of the device was 465 nm, and the chromaticity was CIE (x, y) = (0.13, 0.17).

[Example 2]
A device was prepared in the same manner as in Example 1 except that the present compound H-2 was used instead of the present compound H-1.
The light emission characteristics of this element are as follows.
Luminance / current: 5.6 [cd / A] (@ 1000 cd / m ² )
Voltage: 6.0 [V] (@ 1000 cd / m ² )
Luminous efficiency: 3.0 [1 m / W] (@ 1000 cd / m ² )
The maximum wavelength of the emission spectrum of the device was 461 nm, and the chromaticity was CIE (x, y) = (0.14, 0.18).

[Comparative Example 1]
An attempt was made to produce a device in the same manner as in Example 1 except that the comparative compound C-1 was used in place of the compound H-1 of the present invention. However, the solubility of the comparative compound C-1 in the solvent was insufficient, and the device could be produced. There wasn't.

[Comparative Example 2]
A device was prepared in the same manner as in Example 1 except that the comparative compound C-2 was used instead of the compound H-1 of the present invention.
The light emission characteristics of this element are as follows.
Luminance / current: 5.2 [cd / A] (@ 1000 cd / m ² )
Voltage: 7.0 [V] (@ 1000 cd / m ² )
Luminous efficiency: 2.4 [1 m / W] (@ 1000 cd / m ² )
The maximum wavelength of the emission spectrum of the device was 461 nm, and the chromaticity was CIE (x, y) = (0.14, 0.17).

For Examples 1 and 2 and Comparative Examples 1 and 2, the evaluation results of the organic electroluminescent elements are summarized in Table 2 below together with the solubility of the used charge transport material in cyclohexylbenzene.
The drive life is expressed as a relative value with a 5% decay life (LT95) of 1 when the element of Comparative Example 2 is driven at 3000 cd / m ² .

  From Table 2, it can be seen that an organic electroluminescence device having a low driving voltage and a long life can be produced by wet film formation using the composition for organic electroluminescence device containing the compound (I) of the present invention. .

DESCRIPTION OF SYMBOLS 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

Claims (15)

The compound represented by the following general formula (I).

(In the above general formula (I), each of the phenyl groups A and B may be independently substituted at the m-position with a monovalent group formed by linking 1 to 3 benzene rings and / or naphthalene rings. It often shows structures different from each other including the substituent, provided that the phenyl groups A and B are not condensed with any other ring to form a part of the condensed ring group. In the monovalent group formed by bonding 1 to 3 benzene rings and / or naphthalene rings, all of the phenylene groups contained in the group are m-phenylene groups, and the naphthylene groups are 1,3-, 1, The compound according to claim 1, which is a 6-, 1,7- or 2,7-naphthylene group. A charge transport material comprising the compound according to claim 1 or 2 . The composition for organic electroluminescent elements containing the compound and solvent of Claim 1 or 2 . The solvent is an organic solvent composed of carbon atoms and hydrogen atoms, or carbon atoms, hydrogen atoms and oxygen atoms. The viscosity of the organic solvent at 25 ° C. is 0.0001 to 0.01 Pas and the boiling point at 1013 hPa is 50 to 50. The composition for organic electroluminescent elements according to claim 4 , which is 300 ° C. The composition for organic electroluminescent elements according to claim 5 , wherein the organic solvent contains at least one selected from toluene, xylene, trimethylbenzene, cyclohexylbenzene, cyclohexanone, trimethylcyclohexanone, and propylene glycol monomethyl ether acetate. Furthermore, the composition for organic electroluminescent elements of any one of Claim 4 thru | or 6 containing an aromatic amine compound as a luminescent material. 8. The organic electroluminescent device according to claim 7 , wherein the aromatic amine compound is a compound having a structure in which an amino group is directly bonded to an aromatic hydrocarbon ring formed by condensation of two or more benzene rings. Composition. The composition for organic electroluminescent elements according to claim 8 , wherein the aromatic amine compound is a chrysenediamine compound in which two amino groups are bonded to a chrysene ring. The organic electroluminescent element which has an organic layer between an anode and a cathode WHEREIN: The said organic layer contains a light emitting layer, and is wet using the composition for organic electroluminescent elements as described in any one of Claim 4 thru | or 9. An organic electroluminescent element including a layer formed by a film forming method. The organic electroluminescent element according to claim 10 , wherein the layer formed by a wet film formation method using the composition for an organic electroluminescent element is a light emitting layer. The organic electric field according to claim 10 or 11 , wherein the organic layer includes a hole transport layer provided in contact with the light emitting layer, and the hole transport layer is a layer formed by a wet film formation method. Light emitting element. The organic electroluminescent element according to claim 12 , wherein the hole transport layer is a layer formed by crosslinking a crosslinkable compound. In any one of claims 10 to 13 including the organic electroluminescent element described in the organic EL display device. Organic electroluminescent illumination containing the organic electroluminescent element as described in any one of Claims 10 thru | or 13 .

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