JP5795896B2 - Organic electroluminescent material and organic electroluminescent device using the same - Google Patents

Description

  The present invention relates to an organic electroluminescent material (hereinafter also referred to as an organic EL material) and an organic electroluminescent element (hereinafter also referred to as an organic EL element).

  When a voltage is applied to the organic EL element, holes from the anode and electrons from the cathode are injected into the light emitting layer. Then, in the light emitting layer, the injected holes and electrons are recombined to form excitons. At this time, singlet excitons and triplet excitons are generated at a ratio of 25%: 75% according to the statistical rule of electron spin. When classified according to the light emission principle, the fluorescence type uses light emitted from singlet excitons, and therefore the internal quantum efficiency of the organic EL element is said to be limited to 25%. On the other hand, in the phosphorescent type, since light emission by triplet excitons is used, it is known that the internal quantum efficiency can be increased to 100% when intersystem crossing is efficiently performed from singlet excitons.

Conventionally, in an organic EL element, an optimal element design has been made according to a light emission mechanism of a fluorescent type and a phosphorescent type. In particular, it is known that phosphorescent organic EL elements cannot obtain high-performance elements by simple diversion of fluorescent element technology because of their light emission characteristics. The reason is generally considered as follows.
First, since phosphorescence emission is emission using triplet excitons, the energy gap of the compound used in the light emitting layer must be large. This is because the value of the singlet energy of a compound (the energy difference between the lowest excited singlet state and the ground state) is usually the triplet energy of the compound (the energy between the lowest excited triplet state and the ground state). This is because it is larger than the value of the difference.
Therefore, in order to efficiently confine the triplet energy of the phosphorescent dopant material in the device, first, a host material having a triplet energy larger than the triplet energy of the phosphorescent dopant material must be used for the light emitting layer. I must. Further, when providing the electron transport layer and the hole transport layer adjacent to the light emitting layer, a compound having a triplet energy larger than that of the phosphorescent dopant material must be used for the electron transport layer and the hole transport layer. Thus, when based on the element design concept of the conventional organic EL element, it leads to using a compound having a larger energy gap for the phosphorescent organic EL element as compared with the compound used for the fluorescent organic EL element. The drive voltage of the whole organic EL element rises.

  In addition, hydrocarbon compounds with high oxidation resistance and reduction resistance, which are useful in fluorescent elements, have a large energy gap due to a large spread of π electron clouds. Therefore, in the phosphorescent organic EL element, such a hydrocarbon compound is difficult to select, and an organic compound containing a hetero atom such as oxygen or nitrogen is selected. As a result, the phosphorescent organic EL element is There is a problem that the lifetime is shorter than that of a fluorescent organic EL element.

Furthermore, the fact that the exciton relaxation rate of the triplet exciton of the phosphorescent dopant material is much longer than that of the singlet exciton also greatly affects the device performance. That is, since light emitted from singlet excitons has a high relaxation rate that leads to light emission, the diffusion of excitons to the peripheral layers of the light-emitting layer (for example, a hole transport layer or an electron transport layer) hardly occurs and is efficient. Light emission is expected. On the other hand, light emission from triplet excitons is spin-forbidden and has a slow relaxation rate, so that excitons are likely to diffuse to the peripheral layer, and thermal energy deactivation occurs from other than specific phosphorescent compounds. End up. That is, control of the recombination region of electrons and holes is more important than the fluorescent organic EL element.
For the above reasons, in order to improve the performance of phosphorescent organic EL elements, material selection and element design different from those of fluorescent organic EL elements are required.

As literature which discloses organic EL material, patent documents 1-3 are mentioned, for example.
Patent Document 1 discloses a polycyclic compound having a π-conjugated heteroacene skeleton bridged by a carbon atom, a nitrogen atom, an oxygen atom or a sulfur atom, and an organic EL device using the same, and the effects of the invention are disclosed. Describes a high luminous efficiency and long life.
Patent Document 2 discloses an organic EL compound having a structure obtained by crosslinking a terphenylene skeleton with a carbon atom, a nitrogen atom, an oxygen atom, a sulfur atom, and the like, and an organic EL element using the same. As an effect of the invention, high luminous efficiency and long life are described.
Patent Document 3 discloses an indenocarbazole derivative having electron and hole transport performance and an organic EL device using the indenocarbazole derivative. Further, there is a description that the indenocarbazole derivative is particularly useful for a light emitting layer and / or a charge transport layer.

WO2009 / 148015 WO2010 / 107244 WO2010 / 136109

  An object of this invention is to provide the organic EL material for implement | achieving the organic EL element with a low drive voltage, high luminous efficiency, and long lifetime.

  As a result of intensive studies to achieve the above object, the present inventors have obtained a structure in which a structure obtained by crosslinking a terphenylene skeleton with a carbon atom, a nitrogen atom, an oxygen atom, a sulfur atom, etc. is used as a mother skeleton, The mother skeleton is a structure in which the first and second benzene rings of the terphenylene skeleton are bridged by nitrogen atoms, and the second and third benzene rings are bridged by oxygen atoms. The nitrogen atom is directly or indirectly linked to a nitrogen-containing 6-membered ring (pyridine, diazine, or triazine), and the nitrogen-containing 6-membered ring is further linked to a specific group. It was found that the above-mentioned object was achieved by using the compound as an organic EL material, and the present invention was completed.

  That is, this invention provides the organic electroluminescent material represented by Formula (1).

[In Formula (1),
m represents an integer of 1 to 4;
Har represents a monovalent group formed by combining the partial structure represented by the formula (2A) and the partial structure represented by the formula (2B);
L is a single bond, a substituted or unsubstituted divalent aromatic hydrocarbon group having 6 to 12 ring carbon atoms, or a substituted or unsubstituted divalent aromatic heterocyclic group having 5 to 13 ring atoms. Represents;
Az represents a (m + 1) -valent group represented by the formula (3);
Ar represents a monovalent group selected from the group consisting of the following (S1) and (S2), and when there are a plurality of Ar, each Ar may be the same as or different from each other.
(S1) Substituted or unsubstituted monovalent aromatic hydrocarbon group having 12 to 24 ring carbon atoms (S2) Monovalent group represented by formula (5)]

[In the formulas (2A) and (2B)
a represents an integer of 0 to 4;
b represents an integer of 0 to 2;
c represents an integer of 0 to 4;
Ra ^{1 to} Ra ³ each independently represents a substituent;
* ₁ represents a bond with L;
Two * ₂ represents a 1-position and the carbon in position 2, with the carbon of the 2 and 3 positions, or positions 3 and 4 of the bond to the carbon of formula (2A). ]

[In Formula (3),
One of Y _{1 to} Y ₅ represents C- * ₃ ;
M of Y _{1 to} Y ₅ represents C- * ₄ ;
Y _{1 to} Y ₅ which do not represent any of C- * ₃ and C- * ₄ each independently represent C-Rb ¹ or a nitrogen atom;
Rb ¹ represents a hydrogen atom or a substituent;
* ₃ represents a bond with L;
* ₄ represents a bond with Ar. ]

[In Formula (5),
s and t each independently represents an integer of 0 to 3;
X ₁ represents O or S;
Rc ¹ and Rc ² are each independently a halogen atom, a cyano group, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, or 1 to 20 carbon atoms. Alkoxy group of 1 to 20 carbon atoms, haloalkoxy group of 1 to 20 carbon atoms, silyl group, alkylsilyl group of 1 to 10 carbon atoms, monovalent aromatic carbonization of 6 to 30 ring carbon atoms A hydrogen group, an arylsilyl group having 6 to 30 carbon atoms, an aralkyl group having 7 to 30 carbon atoms, or a monovalent aromatic heterocyclic group having 3 to 30 ring atoms;
Q ¹ and Q ² each independently represents a saturated or unsaturated ring having 5 to 12 ring atoms;
* ₅ represents a bond with Az. ]

  Furthermore, the present invention provides an organic electroluminescent device having a plurality of organic thin film layers including a light emitting layer between a cathode and an anode, wherein at least one of the organic thin film layers includes the organic electroluminescent material. Is.

  According to the present invention, it is possible to provide an organic EL element having a low driving voltage, a high luminous efficiency, and a long lifetime, and an organic EL material that realizes the organic EL element.

FIG. 1 is a schematic cross-sectional view showing an example of the organic EL element of the present invention.

  In the present specification, “carbon number ab” in the expression “substituted or unsubstituted X group having carbon number ab” represents the number of carbons when X group is unsubstituted, When the group is substituted, the carbon number of the substituent is not included.

(Organic EL material)
The organic EL material of the present invention is represented by the formula (1).

In the formula (1), m represents an integer of 1 to 4; Har represents a monovalent group formed by combining the partial structure represented by the formula (2A) and the partial structure represented by the formula (2B). L represents a single bond, a substituted or unsubstituted divalent aromatic hydrocarbon group having 6 to 12 ring carbon atoms, or a substituted or unsubstituted divalent aromatic heterocyclic group having 5 to 13 ring atoms. Az represents a (m + 1) -valent group represented by formula (3); Ar represents a monovalent group selected from the group consisting of the following (S1) and (S2); When there are a plurality of Ar, each Ar may be the same as or different from each other.
(S1) A substituted or unsubstituted monovalent aromatic hydrocarbon group having 12 to 24 ring carbon atoms (S2) A monovalent group represented by the formula (5)

In the formulas (2A) and (2B), a represents an integer of 0 to 4; b represents an integer of 0 to 2; c represents an integer of 0 to 4; Ra ^{1 to} Ra ³ are each independently represents a substituent; * ₁ represents a bond to L; 2 two * _2, the 1-position and 2-position carbons of the formula (2A), and the 2-position and 3-position carbon Or a bond with the 3rd and 4th carbons.

In the formula (3), one of Y ₁ to Y ₅ is C-* ₃ a represents; m pieces of Y ₁ to Y ₅ represents a C-* _4; of Y ₁ to Y ₅ C - * ₃ and C-* ₄ of not represent any independently represent a C-Rb ¹ or a nitrogen atom; Rb ¹ represents a hydrogen atom or a substituent; * _3, the bond between L * ₄ represents a bond with Ar.

In formula (5), s and t each independently represent an integer of 0 to 3; X ₁ represents O or S; Rc ¹ and Rc ² each independently represent a halogen atom, a cyano group, C1-C20 alkyl group, C2-C20 alkenyl group, C3-C20 cycloalkyl group, C1-C20 alkoxy group, C1-C20 haloalkyl group, C1-C1 20 haloalkoxy groups, silyl groups, alkylsilyl groups having 1 to 10 carbon atoms, monovalent aromatic hydrocarbon groups having 6 to 30 ring carbon atoms, arylsilyl groups having 6 to 30 carbon atoms, and 7 to 7 carbon atoms 30 represents an aralkyl group or a monovalent aromatic heterocyclic group having 3 to 30 ring atoms; Q ¹ and Q ² are each independently a saturated or unsaturated ring having 5 to 12 ring atoms; * ₅ represents a bond with Az.

The Har of the formula (1) will be described below.
Har represents a monovalent group formed by combining the partial structure represented by the formula (2A) and the partial structure represented by the formula (2B).

In the formulas (2A) and (2B), a represents an integer of 0 to 4; b represents an integer of 0 to 2; c represents an integer of 0 to 4; Ra ^{1 to} Ra ³ are each independently represents a substituent; * ₁ represents a bond to L; 2 two * _2, the 1-position and 2-position carbons of the formula (2A), and the 2-position and 3-position carbon Or a bond with the 3rd and 4th carbons.
The case where a is 0 means that Ra ¹ is not substituted on the benzene ring (that is, unsubstituted). The same applies when b and c are 0.
Also, Ra ² is a substituted group, * ₂ are those that can be substituted on the linked non carbon atoms, not substituted on the carbon atom linked to the * _2.

a is an integer of 0 to 4, preferably 0 to 1. b is an integer of 0-2, preferably 0-1. c is an integer of 0 to 4, preferably 0 to 1.
* ₁ represents a bond and is linked to L. However, when L is a single bond, it means that * ₁ is substantially connected to Az.
* ₂ represents a bond, two * ₂ is connected to the 1-position and 2-position carbons of the carbazole structure of formula (2A), and the 2-position and 3-position carbon, or a 3-position and 4-position carbons . Thereby, the partial structure of formula (2A) and the partial structure of formula (2B) are linked to form a monovalent group.

Ra ^{1 to} Ra ³ each independently represents a substituent. Examples of the substituent include a halogen atom, a cyano group, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, and a substituted or unsubstituted carbon number of 2 -20 alkenyl group, substituted or unsubstituted cycloalkyl group having 3 to 20 carbon atoms, substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms, substituted or unsubstituted haloalkyl group having 1 to 20 carbon atoms, substituted Or an unsubstituted haloalkoxy group having 1 to 20 carbon atoms, a silyl group, a substituted or unsubstituted alkylsilyl group having 1 to 10 carbon atoms, a substituted or unsubstituted monovalent aromatic group having 6 to 30 ring carbon atoms. Hydrocarbon group, substituted or unsubstituted arylsilyl group having 6 to 30 carbon atoms, substituted or unsubstituted aralkyl group having 7 to 30 carbon atoms, and substituted or unsubstituted ring former A monovalent aromatic heterocyclic group having 3 to 30 are exemplified.
Ra ^{1 to} Ra ³ are preferably a substituted or unsubstituted monovalent aromatic hydrocarbon group having 6 to 30 ring carbon atoms.

When there are a plurality of Ra ¹ (ie, when a = 2 to 4), each Ra ¹ may be the same as or different from each other.
When there are a plurality of Ra ² (that is, when b = 2), each Ra ² may be the same as or different from each other.
When there are a plurality of Ra ³ (that is, when c = 2 to 4), each Ra ³ may be the same as or different from each other.

Examples of the halogen atom represented by Ra ^{1 to} Ra ³ include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, preferably a fluorine atom.

Examples of the alkyl group represented by Ra ^{1 to} Ra ³ include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, s-butyl group, isobutyl group, t-butyl group, n- Pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group, n-tridecyl group, n-tetradecyl group, n- Pentadecyl group, n-hexadecyl group, n-heptadecyl group, n-octadecyl group, neopentyl group, 1-methylpentyl group, 2-methylpentyl group, 1-pentylhexyl group, 1-butylpentyl group, 1-heptyloctyl group And 3-methylpentyl group, and the like, preferably methyl group, t-butyl group, ethyl group, n-propyl group, and isopropyl group.

Examples of the alkenyl group represented by Ra ^{1 to} Ra ³ are vinyl group, allyl group, 1-butenyl group, 2-butenyl group, 3-butenyl group, 1,3-butanedienyl group, 1-methylvinyl group, 1-methylallyl group, 2-methylallyl group, 1,1-dimethylallyl group, 1,2-dimethylallyl group and the like can be mentioned, preferably vinyl group, allyl group, 1-butenyl group, 2-butenyl group, and 3-butenyl group.

Examples of the cycloalkyl group represented by Ra ^{1 to} Ra ³ include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cyclooctyl group, and the like, preferably a cyclopentyl group and a cyclohexyl group.

Examples of the alkoxy group represented by Ra ^{1 to} Ra ³ include a group represented by —OY (where Y is the above alkyl group), preferably a methoxy group, an ethoxy group, and a propoxy group. .

Examples of the haloalkyl group represented by Ra ^{1 to} Ra ³ are obtained by substituting at least one hydrogen atom of the alkyl group with a halogen atom selected from a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Groups, preferably trifluoromethyl group, 2,2,2-trifluoroethyl group, 1,1,2,2,2-pentafluoroethyl group, and 1,1,1,3,3, 3-hexafluoro-2-propyl group.

Examples of the haloalkoxy group represented by Ra ^{1 to} Ra ³ include a group represented by —OY ′ (where Y ′ is the above haloalkyl group), preferably a trifluoromethoxy group, 2,2 , 2-trifluoroethoxy group, 1,1,2,2,2-pentafluoroethoxy group, and 1,1,1,3,3,3-hexafluoro-2-propoxy group.

Examples of alkylsilyl group represented by ra ¹ to Ra ³ is, -SiH ₂ R, -SiHR _2, or -SiR ₃ (wherein R is an alkyl group of the two or three R can be the same And may be different from each other, preferably a trimethylsilyl group, a triethylsilyl group, and a t-butyldimethylsilyl group.

Examples of monovalent aromatic hydrocarbon groups represented by Ra ^{1 to} Ra ³ include phenyl group, naphthyl group, biphenyl group, terphenyl group, quarterphenyl group, fluorenyl group, fluoranthenyl group, benzofluorane Tenenyl group, dibenzofluoranthenyl group, phenanthrenyl group, benzophenanthrenyl group, triphenylenyl group, benzotriphenylenyl group, dibenzotriphenylenyl group, naphthotriphenylenyl group, chrysenyl group, benzochrysenyl group, picenyl group, and Binaphthyl group etc. are mentioned.

Examples of the arylsilyl group represented by Ra ^{1 to} Ra ³ include —SiH ₂ R ′, —SiHR ′ ₂ , and —SiR ′ ₃ (where R ′ is a monovalent aromatic hydrocarbon group described above). 2 or 3 R ′ may be the same or different), and is preferably a triphenylsilyl group.

Examples of the aralkyl group represented by Ra ^{1 to} Ra ³ include groups having 7 to 30 carbon atoms obtained by substituting one hydrogen atom of the alkyl group with the monovalent aromatic hydrocarbon group. Preferably, they are a benzyl group and a naphthylmethyl group.

Examples of the monovalent aromatic heterocyclic group represented by Ra ^{1 to} Ra ³ include pyrrolyl group, furyl group, thienyl group, pyridyl group, pyridazinyl group, pyrimidinyl group, pyrazinyl group, triazinyl group, imidazolyl group, oxazolyl group, Thiazolyl, pyrazolyl, isoxazolyl, isothiazolyl, oxadiazolyl, thiadiazolyl, triazolyl, indolyl, isoindolyl, benzofuranyl, isobenzofuranyl, benzothiophenyl, indolizinyl, quinolidinyl, quinolyl, Isoquinolyl group, cinnolyl group, phthalazinyl group, quinazolinyl group, quinoxalinyl group, benzimidazolyl group, benzoxazolyl group, benzthiazolyl group, indazolyl group, benzisoxazolyl group, benzisothiazolyl group Carbazolyl group, dibenzofuranyl group, dibenzothiophenyl group, phenanthridinyl group, acridinyl group, phenanthrolinyl group, phenazinyl group, phenothiazinyl group, phenoxazinyl group, and xanthenyl group.

  As an arbitrary substituent in the expression “substituted or unsubstituted” described above and below, a halogen atom, a cyano group, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, and an alkyl group having 3 to 20 carbon atoms. A cycloalkyl group, an alkoxy group having 1 to 20 carbon atoms, a haloalkyl group having 1 to 20 carbon atoms, a haloalkoxy group having 1 to 20 carbon atoms, a silyl group, an alkylsilyl group having 1 to 10 carbon atoms, and a ring forming carbon number of 6 A monovalent aromatic hydrocarbon group having 30 to 30 carbon atoms, an arylsilyl group having 6 to 30 carbon atoms, an aralkyl group having 7 to 30 carbon atoms, or a monovalent aromatic heterocyclic group having 3 to 30 ring atoms. It is done. Specific examples of these optional substituents are the same as those described above. These optional substituents may be plural, and when plural, they may be the same as or different from each other.

  Specific examples of the structure of Har include monovalent groups represented by formulas (2-1) to (2-6). Among these, monovalent groups represented by formulas (2-1) to (2-2) are preferable.

In the formula (2-1) ~ (2-6), a, b, Ra 1, Ra 2 and * ₁ are a respective formulas (2A), b, and Ra ^1, Ra ² and * ₁ synonymous ; c and Ra ³ are the same meaning as c and Ra ³ each formula (2B).

Az in the formula (1) will be described below.
Az represents an (m + 1) -valent group represented by the formula (3).

In the formula (3), one of Y ₁ to Y ₅ is C-* ₃ a represents; m pieces of Y ₁ to Y ₅ represents a C-* _4; of Y ₁ to Y ₅ C - * ₃ and C-* ₄ of not represent any independently represent a C-Rb ¹ or a nitrogen atom; Rb ¹ represents a hydrogen atom or a substituent; * _3, and L or Har * ₄ represents a bond with Ar.

Rb ¹ represents a hydrogen atom or a substituent, and examples of the substituent include a halogen atom, a cyano group, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, and a substituted or unsubstituted alkenyl group having 2 to 20 carbon atoms. Group, substituted or unsubstituted cycloalkyl group having 3 to 20 carbon atoms, substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms, substituted or unsubstituted haloalkyl group having 1 to 20 carbon atoms, substituted or unsubstituted A haloalkoxy group having 1 to 20 carbon atoms, a silyl group, a substituted or unsubstituted alkylsilyl group having 1 to 10 carbon atoms, a substituted or unsubstituted monovalent aromatic hydrocarbon group having 6 to 30 ring carbon atoms, A substituted or unsubstituted arylsilyl group having 6 to 30 carbon atoms, a substituted or unsubstituted aralkyl group having 7 to 30 carbon atoms, and a substituted or unsubstituted ring atom number of 3 to 30 Monovalent aromatic heterocyclic groups.
When the Rb ¹ there are a plurality, also each of Rb ¹ are the same as each other or may be different.
A halogen atom represented by Rb ¹ , an alkyl group, an alkenyl group, a cycloalkyl group, an alkoxy group, a haloalkyl group, a haloalkoxy group, an alkylsilyl group, a monovalent aromatic hydrocarbon group, an arylsilyl group, an aralkyl group, and Specific examples of the monovalent aromatic heterocyclic group include a halogen atom represented by Ra ^{1 to} Ra ³ , an alkyl group, an alkenyl group, a cycloalkyl group, an alkoxy group, a haloalkyl group, a haloalkoxy group, an alkylsilyl group, Examples thereof are the same as specific examples of the monovalent aromatic hydrocarbon group, arylsilyl group, aralkyl group, and monovalent aromatic heterocyclic group.
Rb ¹ is preferably a hydrogen atom or a substituted or unsubstituted monovalent aromatic hydrocarbon group having 6 to 30 ring carbon atoms, and more preferably a hydrogen atom or a phenyl group.

As a specific structure of Az is represented by the formula (3-1) (m ₁ +1) valent group, represented by the formula (3-2) ~ (3-4) ( m 2 +1) valent A (m ₃ +1) -valent group represented by formulas (3-5) to (3-7), and a divalent group represented by formulas (3-8) to (3-10) Can be mentioned. Among these, the (m ₂ +1) -valent group represented by the formula (3-2) and the (m ₃ +1) -valent group represented by the formula (3-5) are preferable.

In formulas (3-1) to (3-10), m ₁ represents an integer of 1 to 4; m ₂ represents an integer of 1 to ₃ ; m ₃ represents an integer of 1 to 2; Rb ^1, * ₃ and * _4, Rb ^1, respectively formula (3), * ₃ and * ₄ are dove synonymous.
m ₁ is preferably 1-2, and m ₂ is preferably 1-2.

Among the represented by (m ₂ +1) valent group in the formula (3-2) is preferably represented by the formula (3-2-1) (m ₂ +1) valent group, more preferably the formula It is a trivalent group represented by either (3-2-1A) or (3-2-1B).

In the formulas (3-2-1), (3-2-1A), and (3-2-1B), m ₂ , Rb ¹ , * _3, and * ₄ represent m ₂ in the formula (3-2), rb ^1, is synonymous with * ₃ and * _4.

L in Formula (1) will be described below.
L is a single bond, a substituted or unsubstituted divalent aromatic hydrocarbon group having 6 to 12 ring carbon atoms, or a substituted or unsubstituted divalent aromatic heterocyclic group having 5 to 13 ring atoms. And preferably a single bond.

Examples of the divalent aromatic hydrocarbon group represented by L include a phenylene group, a naphthylene group, and a biphenylylene group.
Examples of the divalent aromatic heterocyclic group represented by L include pyrroldiyl group, furylene group, thienylene group, pyridinylene group, pyridazinylene group, pyrimidinylene group, pyrazinylene group, triazinylene group, imidazolylene group, oxazolylene group, thiazolylene group, pyrazolylene group. Group, isoxazolylene group, isothiazolylene group, oxadiazolylene group, thiadiazolylene group, triazolylene group, indoleylene group, isoindoleylene group, benzofuranylene group, isobenzofuranylene group, benzothiophenylene group, indolizinylene group, quinolidinylene group Group, quinolylene group, isoquinolylene group, cinnolinylene group, phthalazinylene group, quinazolinylene group, quinoxalinylene group, benzimidazolylene group, benzoxazolylene group, benzthiazolylene group, indazo Ren group, benzisoxazolyl alkylene group, benzisothiazolyl alkylene group, carbazolylene group, dibenzo furanyl alkylene group, and a dibenzothiophenyl phenylene group and the like.

M and Ar in the formula (1) will be described below.
m is an integer of 1-4, Preferably it is 1-2.
Ar represents a monovalent group selected from the group consisting of the following (S1) and (S2).
(S1) A substituted or unsubstituted monovalent aromatic hydrocarbon group having 12 to 24 ring carbon atoms (S2) A monovalent group represented by the formula (5)

In formula (5), s and t each independently represent an integer of 0 to 3; X ₁ represents O or S; Rc ¹ and Rc ² each independently represent a halogen atom, a cyano group, C1-C20 alkyl group, C2-C20 alkenyl group, C3-C20 cycloalkyl group, C1-C20 alkoxy group, C1-C20 haloalkyl group, C1-C1 20 haloalkoxy groups, silyl groups, alkylsilyl groups having 1 to 10 carbon atoms, monovalent aromatic hydrocarbon groups having 6 to 30 ring carbon atoms, arylsilyl groups having 6 to 30 carbon atoms, and 7 to 7 carbon atoms 30 represents an aralkyl group or a monovalent aromatic heterocyclic group having 3 to 30 ring atoms; Q ¹ and Q ² are each independently a saturated or unsaturated ring having 5 to 12 ring atoms; * ₅ represents a bond with Az.

In the organic EL material of the present invention, by introducing the specific group as Ar before the Az (azine) unit, LUMO (Lowest Unoccupied Molecular Orbital) spreads and the affinity (electron affinity) increases. Therefore, when the organic EL material is used in an organic EL element (particularly when used in the light emitting layer), the electron affinity (Af) of the organic EL material is large, so that the electron injection property into the light emitting layer is improved. The voltage is lowered and fewer electrons penetrate through the hole transport layer. Thereby, the external quantum yield of the organic EL element is improved and the lifetime is improved.
Moreover, by introducing a specific group into the Az (azine) unit, the glass transition point of the organic EL material of the present invention is increased, the heat resistance of the resulting device is improved, and the vapor deposition process for device formation is improved. Stabilize.
When there are a plurality of Ars (that is, when m = 2 to 4), each Ar may be the same as or different from each other. When they are different from each other, the symmetry of the organic EL material of the formula (1) is reduced, so that the crystallization of the material is suppressed, and the stability of the thin film formed using the material is improved. As a result, it can be expected that the organic EL element will have a longer lifetime.

  As the above (S1), monovalent groups represented by formulas (4-1) to (4-4) are preferable.

In formulas (4-1) to (4-4), p represents an integer of 1 to 3; q represents an integer of 1 or 2, and d, f, g, k and v are each independently E, h, j and l each independently represents an integer of 0 to 5; i and u each represents an integer of 0 to 3; Rc ^{3 to} Rc ¹³ are Independently, a halogen atom, a cyano group, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, and 1 carbon atom -20 haloalkyl group, haloalkoxy group having 1 to 20 carbon atoms, silyl group, alkylsilyl group having 1 to 10 carbon atoms, monovalent aromatic hydrocarbon group having 6 to 30 ring carbon atoms, 6 to 6 carbon atoms 30 arylsilyl groups, 7 to 30 aralkyl groups, or monovalent 3 to 30 ring atoms It represents an aromatic heterocyclic group; Rb ² and Rb ³ each independently represent a hydrogen atom or a substituent; * ₅ represents a bond to Az.
The case where d is 0 means that Rc ³ is not substituted on the benzene ring (that is, unsubstituted). The same applies to cases where e to l, u, and v are 0.

p is preferably 1-2.
d, e, f, g, h, i, j, k, l, u and v are preferably 0 to 1.
Rc ³ halogen atoms represented by to Rc ^13, an alkyl group, an alkenyl group, a cycloalkyl group, an alkoxy group, a haloalkyl group, a haloalkoxy group, an alkylsilyl group, a monovalent aromatic hydrocarbon group, an aryl silyl group, an aralkyl Specific examples of the group and the monovalent aromatic heterocyclic group include a halogen atom, an alkyl group, an alkenyl group, a cycloalkyl group, an alkoxy group, a haloalkyl group, a haloalkoxy group, an alkyl represented by Ra ^{1 to} Ra ³ . Examples thereof are the same as specific examples of the silyl group, monovalent aromatic hydrocarbon group, arylsilyl group, aralkyl group, and monovalent aromatic heterocyclic group.

Rb ² and Rb ³ each independently represent a hydrogen atom or a substituent, the substituent, a halogen atom, a cyano group, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted An alkenyl group having 2 to 20 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 20 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted haloalkyl having 1 to 20 carbon atoms Group, substituted or unsubstituted haloalkoxy group having 1 to 20 carbon atoms, silyl group, substituted or unsubstituted alkylsilyl group having 1 to 10 carbon atoms, substituted or unsubstituted monovalent group having 6 to 30 ring carbon atoms Aromatic hydrocarbon group, substituted or unsubstituted arylsilyl group having 6 to 30 carbon atoms, substituted or unsubstituted aralkyl group having 7 to 30 carbon atoms, and substituted or unsubstituted Examples thereof include monovalent aromatic heterocyclic groups having 3 to 30 ring atoms.
Halogen atom represented by Rb ² and Rb ^3, alkyl group, alkenyl group, cycloalkyl group, alkoxy group, haloalkyl group, haloalkoxy group, alkylsilyl group, a monovalent aromatic hydrocarbon group, an aryl silyl group, an aralkyl Specific examples of the group and the monovalent aromatic heterocyclic group include a halogen atom, an alkyl group, an alkenyl group, a cycloalkyl group, an alkoxy group, a haloalkyl group, a haloalkoxy group, an alkyl represented by Ra ^{1 to} Ra ³ . Examples thereof are the same as specific examples of the silyl group, monovalent aromatic hydrocarbon group, arylsilyl group, aralkyl group, and monovalent aromatic heterocyclic group.
Rb ² and Rb ³ are preferably a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, and more preferably a methyl group.

With regard to the above (S2), the preferred mode of each symbol in the formula (5) is as follows.
s and t each independently represent an integer of 0 to 3, preferably 0 to 1.
X ₁ represents O or S, and is preferably O from the stability of the compound.
Halogen atom, alkyl group, alkenyl group, cycloalkyl group, alkoxy group, haloalkyl group, haloalkoxy group, alkylsilyl group, monovalent aromatic hydrocarbon group, arylsilyl group, aralkyl represented by Rc ¹ and Rc ² Specific examples of the group and the monovalent aromatic heterocyclic group include a halogen atom, an alkyl group, an alkenyl group, a cycloalkyl group, an alkoxy group, a haloalkyl group, a haloalkoxy group, an alkyl represented by Ra ^{1 to} Ra ³ . Examples thereof are the same as specific examples of the silyl group, monovalent aromatic hydrocarbon group, arylsilyl group, aralkyl group, and monovalent aromatic heterocyclic group.

Examples of the saturated or unsaturated ring having 5 to 12 ring atoms represented by Q ¹ and Q ² include a saturated aliphatic ring having 5 to 12 ring atoms and an unsaturated fat having 5 to 12 ring atoms. Examples include aromatic rings, aromatic hydrocarbon rings having 5 to 12 ring atoms, and aromatic heterocycles having 5 to 12 ring atoms, and aromatic hydrocarbon rings and rings having 5 to 12 ring atoms. An aromatic heterocyclic ring having 5 to 12 atoms is preferable, and an aromatic hydrocarbon ring having 5 to 12 ring atoms is more preferable.
Specific examples of the aromatic hydrocarbon ring include a benzene ring, and specific examples of the aromatic heterocyclic ring include a furan ring, a thiophene ring, a pyrrole ring, a pyridine ring, and a pyridine ring.

  Among the above (S2), a monovalent group represented by the formula (5-1) is preferable.

In the formula (5-1), s, t, X 1, Rc 1, Rc 2 and * ₅ are the s of each formula (5), t, and X ^_1, Rc _1, Rc ² and * ₅ synonymous .

  Preferable specific examples of Ar include, but are not limited to, the following monovalent groups.

  In the above specific example, * 5 represents a bond with Az.

  Specific examples of the organic EL element material represented by the formula (1) of the present invention are shown below, but the present invention is not limited to these exemplified compounds.

(Organic EL device)
Next, the organic EL element of the present invention will be described.
The organic EL element of the present invention has a plurality of organic thin film layers including a light emitting layer between a cathode and an anode, and at least one of the organic thin film layers includes the above-described organic EL material of the present invention. Features. When the organic EL material of the present invention is contained in at least one of the organic thin film layers of the organic EL element of the present invention, the organic EL element can be expected to have low driving voltage, high luminous efficiency, and long life. .
Examples of the organic thin film layer containing the organic EL material of the present invention include, but are not limited to, a light emitting layer, a space layer, and a barrier layer. The organic EL material of the present invention is particularly preferably contained as a host material for the light emitting layer. The light emitting layer preferably contains a phosphorescent light emitting material.

  The organic EL element of the present invention may be a phosphorescent monochromatic light emitting element, a fluorescent / phosphorescent white light emitting element, a simple type having a single light emitting unit, It may be a tandem type having the light emitting unit. Here, the “light emitting unit” refers to a minimum unit that includes one or more organic layers, one of which is a light emitting layer, and can emit light by recombination of injected holes and electrons.

Accordingly, typical element configurations of simple organic EL elements include the following element configurations.
(1) Anode / light emitting unit / cathode The above light emitting unit may be a laminated type having a plurality of phosphorescent light emitting layers and fluorescent light emitting layers. In that case, the light emitting unit is generated by a phosphorescent light emitting layer between the light emitting layers. In order to prevent the excitons from diffusing into the fluorescent light emitting layer, a space layer may be provided. A typical layer structure of the light emitting unit is shown below.
(A) Hole transport layer / light emitting layer (/ electron transport layer)
(B) Hole transport layer / first phosphorescent light emitting layer / second phosphorescent light emitting layer (/ electron transport layer)
(C) Hole transport layer / phosphorescent layer / space layer / fluorescent layer (/ electron transport layer)
(D) Hole transport layer / first phosphorescent light emitting layer / second phosphorescent light emitting layer / space layer / fluorescent light emitting layer (/ electron transport layer)
(E) Hole transport layer / first phosphorescent light emitting layer / space layer / second phosphorescent light emitting layer / space layer / fluorescent light emitting layer (/ electron transport layer)
(F) Hole transport layer / phosphorescent layer / space layer / first fluorescent layer / second fluorescent layer (/ electron transport layer)

Each phosphorescent or fluorescent light-emitting layer may have a different emission color. Specifically, in the laminated light emitting layer (d), hole transport layer / first phosphorescent light emitting layer (red light emitting) / second phosphorescent light emitting layer (green light emitting) / space layer / fluorescent light emitting layer (blue light emitting) / A layer structure such as an electron transport layer can be used.
An electron barrier layer may be appropriately provided between each light emitting layer and the hole transport layer or space layer. Further, a hole blocking layer may be appropriately provided between each light emitting layer and the electron transport layer. By providing an electron barrier layer or a hole barrier layer, electrons or holes can be confined in the light emitting layer, the recombination probability of charges in the light emitting layer can be increased, and the light emission efficiency can be improved.

The following element structure can be mentioned as a typical element structure of a tandem type organic EL element.
(2) Anode / first light emitting unit / intermediate layer / second light emitting unit / cathode Here, as the first light emitting unit and the second light emitting unit, for example, the same light emitting unit as that described above is selected independently. can do.
The intermediate layer is generally called an intermediate electrode, an intermediate conductive layer, a charge generation layer, an electron extraction layer, a connection layer, or an intermediate insulating layer, and holes are provided to the first light emitting unit and electrons are provided to the second light emitting unit. A known material structure to be supplied can be used.

  In FIG. 1, schematic structure of an example of the organic EL element of this invention is shown. The organic EL element 1 includes a substrate 2, an anode 3, a cathode 4, and a light emitting unit 10 disposed between the anode 3 and the cathode 4. The light emitting unit 10 includes a light emitting layer 5 including at least one phosphorescent light emitting layer including a phosphorescent host material and a phosphorescent dopant. A hole transport layer 6 or the like may be formed between the light emitting layer 5 and the anode 3, and an electron transport layer 7 or the like may be formed between the light emitting layer 5 and the cathode 4. Further, an electron barrier layer may be provided on the anode 3 side of the light emitting layer 5, and a hole barrier layer may be provided on the cathode 4 side of the light emitting layer 5. Thereby, electrons and holes can be confined in the light emitting layer 5, and the exciton generation probability in the light emitting layer 5 can be increased.

  In this specification, a host combined with a fluorescent dopant is referred to as a fluorescent host, and a host combined with a phosphorescent dopant is referred to as a phosphorescent host. The fluorescent host and the phosphorescent host are not distinguished only by the molecular structure. That is, the phosphorescent host means a material constituting a phosphorescent light emitting layer containing a phosphorescent dopant, and does not mean that it cannot be used as a material constituting a fluorescent light emitting layer. The same applies to the fluorescent host.

(substrate)
The organic EL element of the present invention is produced on a translucent substrate. The light-transmitting substrate is a substrate that supports the organic EL element, and is preferably a smooth substrate having a light transmittance in the visible region of 400 nm to 700 nm of 50% or more. Specifically, a glass plate, a polymer plate, etc. are mentioned. Examples of the glass plate include those using soda lime glass, barium / strontium-containing glass, lead glass, aluminosilicate glass, borosilicate glass, barium borosilicate glass, quartz and the like as raw materials. Examples of the polymer plate include those using polycarbonate, acrylic, polyethylene terephthalate, polyether sulfide, polysulfone and the like as raw materials.

(anode)
The anode of the organic EL element plays a role of injecting holes into the hole transport layer or the light emitting layer, and it is effective to use a material having a work function of 4.5 eV or more. Specific examples of the anode material include indium tin oxide alloy (ITO), tin oxide (NESA), indium zinc oxide, gold, silver, platinum, copper, and the like. The anode can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering. When light emitted from the light emitting layer is extracted from the anode, it is preferable that the transmittance of light in the visible region of the anode is greater than 10%. The sheet resistance of the anode is preferably several hundred Ω / □ or less. The film thickness of the anode depends on the material, but is usually selected in the range of 10 nm to 1 μm, preferably 10 nm to 200 nm.

(cathode)
The cathode plays a role of injecting electrons into the electron injection layer, the electron transport layer or the light emitting layer, and is preferably formed of a material having a small work function. The cathode material is not particularly limited, and specifically, indium, aluminum, magnesium, magnesium-indium alloy, magnesium-aluminum alloy, aluminum-lithium alloy, aluminum-scandium-lithium alloy, magnesium-silver alloy and the like can be used. Similarly to the anode, the cathode can be produced by forming a thin film by a method such as vapor deposition or sputtering. Moreover, you may take out light emission from the cathode side as needed.

(Light emitting layer)
An organic layer having a light emitting function, and when a doping system is employed, includes a host material and a dopant material. At this time, the host material mainly has a function of encouraging recombination of electrons and holes and confining excitons in the light emitting layer, and the dopant material efficiently emits excitons obtained by recombination. It has a function.
In the case of a phosphorescent element, the host material mainly has a function of confining excitons generated by the dopant in the light emitting layer.

Here, the light emitting layer employs, for example, a double host (also referred to as host / cohost) that adjusts the carrier balance in the light emitting layer by combining an electron transporting host and a hole transporting host. Also good.
Moreover, you may employ | adopt the double dopant from which each dopant light-emits by putting in 2 or more types of dopant materials with a high quantum yield. Specifically, a mode in which yellow emission is realized by co-evaporating a host, a red dopant, and a green dopant to make the light emitting layer common is used.

  The above light-emitting layer is a laminate in which a plurality of light-emitting layers are stacked, so that electrons and holes are accumulated at the light-emitting layer interface, and the recombination region is concentrated at the light-emitting layer interface to improve quantum efficiency. Can do.

  The ease of injecting holes into the light emitting layer may be different from the ease of injecting electrons, and the hole transport ability and electron transport ability expressed by the mobility of holes and electrons in the light emitting layer may be different. May be different.

  A light emitting layer can be formed by well-known methods, such as a vapor deposition method, a spin coat method, LB method, for example. The light emitting layer can also be formed by thinning a solution obtained by dissolving a binder such as a resin and a material compound in a solvent by a spin coating method or the like.

  The light emitting layer is preferably a molecular deposited film. The molecular deposited film is a thin film formed by deposition from a material compound in a gas phase state or a film formed by solidifying from a material compound in a solution state or a liquid phase state. The thin film (molecular accumulation film) formed by the LB method can be classified by the difference in the aggregation structure and the higher-order structure, and the functional difference resulting therefrom.

  The phosphorescent dopant (phosphorescent material) that forms the light emitting layer is a compound that can emit light from the triplet excited state, and is not particularly limited as long as it emits light from the triplet excited state, but Ir, Pt, Os, Au, Cu, An organometallic complex containing at least one metal selected from Re and Ru and a ligand is preferable. The ligand preferably has an ortho metal bond. A metal complex containing a metal atom selected from Ir, Os and Pt is preferred in that the phosphorescent quantum yield is high and the external quantum efficiency of the light emitting device can be further improved, and an iridium complex, an osmium complex, or a platinum complex. Are more preferable, iridium complexes and platinum complexes are more preferable, and orthometalated iridium complexes are particularly preferable.

  There is no restriction | limiting in particular in content in the light emitting layer of a phosphorescent dopant, Although it can select suitably according to the objective, For example, 0.1-70 mass% is preferable and 1-30 mass% is more preferable. If the phosphorescent dopant content is 0.1% by mass or more, sufficient light emission can be obtained, and if it is 70% by mass or less, concentration quenching can be avoided.

  Specific examples of preferable organometallic complexes are shown below.

The phosphorescent host is a compound having a function of efficiently emitting the phosphorescent dopant by efficiently confining the triplet energy of the phosphorescent dopant in the light emitting layer. Although the organic EL material of the present invention is useful as a phosphorescent host, a compound other than the organic EL material of the present invention can be appropriately selected as the phosphorescent host depending on the purpose.
The organic EL material of the present invention and other compounds may be used in combination as a phosphorescent host material in the same light emitting layer. When there are a plurality of light emitting layers, the phosphorescent host material of one of the light emitting layers is used. The organic EL material of the present invention may be used, and a compound other than the organic EL material of the present invention may be used as the phosphorescent host material of another light emitting layer. In addition, the organic EL material of the present invention can be used for organic layers other than the light emitting layer, and in that case, a compound other than the organic EL material of the present invention may be used as the phosphorescent host of the light emitting layer.

  Specific examples of compounds other than the organic EL material of the present invention and suitable as a phosphorescent host include carbazole derivatives, triazole derivatives, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives. , Phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aromatic tertiary amine compounds, styrylamine compounds, aromatic dimethylidene compounds, porphyrin compounds , Anthraquinodimethane derivatives, anthrone derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, carbodiimide derivatives, fluorenylidenemethane derivatives , Metal complexes of heterocyclic tetracarboxylic anhydrides such as styrylpyrazine derivatives, naphthaleneperylene, phthalocyanine derivatives, 8-quinolinol derivatives, metal phthalocyanines, metal complexes having benzoxazole and benzothiazole as ligands Polymers such as metal complex polysilane compounds, poly (N-vinylcarbazole) derivatives, aniline copolymers, thiophene oligomers, conductive polymer oligomers such as polythiophene, polythiophene derivatives, polyphenylene derivatives, polyphenylene vinylene derivatives, polyfluorene derivatives, etc. Compounds and the like. A phosphorescent host may be used independently and may use 2 or more types together. Specific examples include the following compounds.

  The thickness of the light emitting layer is preferably 5 to 50 nm, more preferably 7 to 50 nm, and still more preferably 10 to 50 nm. When the thickness is 5 nm or more, it is easy to form a light emitting layer, and when the thickness is 50 nm or less, an increase in driving voltage is avoided.

(Electron donating dopant)
The organic EL device of the present invention preferably has an electron donating dopant in the interface region between the cathode and the light emitting unit. According to such a configuration, it is possible to improve the light emission luminance and extend the life of the organic EL element. Here, the electron donating dopant means a material containing a metal having a work function of 3.8 eV or less, and specific examples thereof include alkali metals, alkali metal complexes, alkali metal compounds, alkaline earth metals, alkaline earths. Examples thereof include at least one selected from metal complexes, alkaline earth metal compounds, rare earth metals, rare earth metal complexes, rare earth metal compounds, and the like.

  Examples of the alkali metal include Na (work function: 2.36 eV), K (work function: 2.28 eV), Rb (work function: 2.16 eV), Cs (work function: 1.95 eV), and the like. A function of 2.9 eV or less is particularly preferable. Of these, K, Rb, and Cs are preferred, Rb and Cs are more preferred, and Cs is most preferred. Examples of the alkaline earth metal include Ca (work function: 2.9 eV), Sr (work function: 2.0 eV to 2.5 eV), Ba (work function: 2.52 eV), and the like. The thing below 9 eV is especially preferable. Examples of rare earth metals include Sc, Y, Ce, Tb, Yb, and the like, and those having a work function of 2.9 eV or less are particularly preferable.

Examples of the alkali metal compound include alkali oxides such as Li ₂ O, Cs ₂ O, and K ₂ O, and alkali halides such as LiF, NaF, CsF, and KF, and LiF, Li ₂ O, and NaF are preferable. Examples of the alkaline earth metal compound include BaO, SrO, CaO, and Ba _x Sr _1-x O (0 <x <1), Ba _x Ca _1-x O (0 <x <1) mixed with these. BaO, SrO, and CaO are preferable. The rare earth metal _{compound, YbF 3, ScF 3, ScO} 3, Y 2 O 3, Ce 2 O 3, GdF 3, TbF 3 and the _{like, YbF 3, ScF 3, TbF} 3 are preferable.

  The alkali metal complex, alkaline earth metal complex, and rare earth metal complex are not particularly limited as long as each metal ion contains at least one of an alkali metal ion, an alkaline earth metal ion, and a rare earth metal ion. The ligands include quinolinol, benzoquinolinol, acridinol, phenanthridinol, hydroxyphenyl oxazole, hydroxyphenyl thiazole, hydroxydiaryl thiadiazole, hydroxydiaryl thiadiazole, hydroxyphenylpyridine, hydroxyphenylbenzimidazole, hydroxybenzotriazole, Hydroxyfulborane, bipyridyl, phenanthroline, phthalocyanine, porphyrin, cyclopentadiene, β-diketones, azomethines, and derivatives thereof are preferred, but not limited thereto.

  As an addition form of the electron donating dopant, it is preferable to form a layered or island shape in the interface region. As a forming method, while depositing an electron donating dopant by resistance heating vapor deposition, an organic compound (light emitting material or electron injecting material) that forms an interface region is simultaneously deposited, and the electron donating dopant is dispersed in the organic compound. Is preferred. The dispersion concentration is organic compound: electron-donating dopant = 100: 1 to 1: 100, preferably 5: 1 to 1: 5 in molar ratio.

In the case where the electron donating dopant is formed in a layered form, after forming the light emitting material or the electron injecting material, which is an organic layer at the interface, in a layered form, the reducing dopant is vapor-deposited by a resistance heating vapor deposition method. .1 nm to 15 nm. When the electron donating dopant is formed in an island shape, after forming the light emitting material and the electron injecting material, which are organic layers at the interface, in an island shape, the electron donating dopant is deposited by resistance heating vapor deposition alone, preferably The island is formed with a thickness of 0.05 nm to 1 nm.
In the organic EL device of the present invention, the ratio of the main component to the electron donating dopant is preferably in the molar ratio of main component: electron donating dopant = 5: 1 to 1: 5, and 2: 1 to 1: 2. More preferably.

(Electron transport layer)
An organic layer formed between the light emitting layer and the cathode, and has a function of transporting electrons from the cathode to the light emitting layer. When the electron transport layer is composed of a plurality of layers, an organic layer close to the cathode may be defined as an electron injection layer. The electron injection layer has a function of efficiently injecting electrons from the cathode into the organic layer unit.

As the electron transporting material used for the electron transporting layer, an aromatic heterocyclic compound containing one or more heteroatoms in the molecule is preferably used, and a nitrogen-containing ring derivative is particularly preferable. The nitrogen-containing ring derivative is preferably an aromatic ring having a nitrogen-containing 6-membered ring or 5-membered ring skeleton, or a condensed aromatic ring compound having a nitrogen-containing 6-membered ring or 5-membered ring skeleton.
As this nitrogen-containing ring derivative, for example, a nitrogen-containing ring metal chelate complex represented by the following formula (A) is preferable.

R ^{2 to} R ⁷ in formula (A) are each independently a hydrogen atom, a deuterium atom, a halogen atom, a hydroxyl group, an amino group, a hydrocarbon group having 1 to 40 carbon atoms, or an alkoxy group having 1 to 40 carbon atoms. , An aryloxy group having 6 to 50 carbon atoms, an alkoxycarbonyl group, or an aromatic heterocyclic group having 5 to 50 ring carbon atoms, which may be substituted.

  Examples of the halogen atom include fluorine, chlorine, bromine, iodine and the like.

Examples of the amino group which may be substituted include an alkylamino group, an arylamino group and an aralkylamino group.
The alkylamino group and the aralkylamino group are represented as —NQ ¹ Q ² . Q ¹ and Q ² each independently represents an alkyl group having 1 to 20 carbon atoms or an aralkyl group having 1 to 20 carbon atoms. One of Q ¹ and Q ² may be a hydrogen atom or a deuterium atom.
The arylamino group is represented as —NAr ¹ Ar ^2, and Ar ¹ and Ar ² each independently represent a non-condensed aromatic hydrocarbon group and a condensed aromatic hydrocarbon group having 6 to 50 carbon atoms. One of Ar ¹ and Ar ² may be a hydrogen atom or a deuterium atom.

  The hydrocarbon group having 1 to 40 carbon atoms includes an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, and an aralkyl group.

  The alkoxycarbonyl group is represented as —COOY ′, and Y ′ represents an alkyl group having 1 to 20 carbon atoms.

  M is aluminum (Al), gallium (Ga) or indium (In), and is preferably In.

  L is a group represented by the following formula (A ′) or (A ″).

In formula (A ′), R ^{8 to} R ¹² are each independently a hydrogen atom, a deuterium atom, or a substituted or unsubstituted hydrocarbon group having 1 to 40 carbon atoms, and groups adjacent to each other are cyclic structures May be formed. In the formula (A ″), R ^{13 to} R ²⁷ are each independently a hydrogen atom, a deuterium atom, or a substituted or unsubstituted hydrocarbon group having 1 to 40 carbon atoms, and groups adjacent to each other are An annular structure may be formed.

The hydrocarbon group having 1 to 40 carbon atoms represented by R ^{8 to} R ¹² and R ^{13 to} R ^{27 in the} formula (A ′) and the formula (A ″) is represented by R ^{2 to} R ⁷ in the formula (A). The divalent groups in the case where the adjacent groups of R ^{8 to} R ¹² and R ^{13 to} R ²⁷ form a cyclic structure include tetramethylene, pentamethylene, hexa Examples include methylene group, diphenylmethane-2,2′-diyl group, diphenylethane-3,3′-diyl group, diphenylpropane-4,4′-diyl group and the like.

  As the electron transport compound used for the electron transport layer, 8-hydroxyquinoline or a metal complex of its derivative, an oxadiazole derivative, and a nitrogen-containing heterocyclic derivative are preferable. As a specific example of the metal complex of 8-hydroxyquinoline or a derivative thereof, a metal chelate oxinoid compound containing a chelate of oxine (generally 8-quinolinol or 8-hydroxyquinoline), for example, tris (8-quinolinol) aluminum is used. Can do. And as an oxadiazole derivative, the following can be mentioned.

In the above formula, Ar ¹⁷ , Ar ¹⁸ , Ar ¹⁹ , Ar ²¹ , Ar ²² and Ar ²⁵ each represent a substituted or unsubstituted aromatic hydrocarbon group or condensed aromatic hydrocarbon group having 6 to 50 carbon atoms, Ar ¹⁷ and Ar ¹⁸ , Ar ¹⁹ and Ar ²¹ , Ar ²² and Ar ²⁵ may be the same or different. Examples of the aromatic hydrocarbon group or the condensed aromatic hydrocarbon group include a phenyl group, a naphthyl group, a biphenyl group, an anthranyl group, a perylenyl group, and a pyrenyl group. Examples of these substituents include an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, and a cyano group.

Ar ²⁰ , Ar ^23, and Ar ²⁴ each represent a substituted or unsubstituted divalent aromatic hydrocarbon group or condensed aromatic hydrocarbon group having 6 to 50 carbon atoms, and Ar ²³ and Ar ²⁴ are identical to each other. But it can be different. Examples of the divalent aromatic hydrocarbon group or condensed aromatic hydrocarbon group include a phenylene group, a naphthylene group, a biphenylene group, an anthranylene group, a peryleneylene group, and a pyrenylene group. Examples of these substituents include an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, and a cyano group.

  As these electron transfer compounds, those having good thin film forming properties are preferably used. Specific examples of these electron transfer compounds include the following.

  The nitrogen-containing heterocyclic derivative as the electron transfer compound is a nitrogen-containing heterocyclic derivative composed of an organic compound having the following general formula, and includes a nitrogen-containing compound that is not a metal complex. Examples thereof include a 5-membered ring or 6-membered ring containing a skeleton represented by the following formula (B) and a structure represented by the following formula (C).

In the formula (C), X represents a carbon atom or a nitrogen atom. Z ₁ and Z ₂ each independently represents an atomic group capable of forming a nitrogen-containing heterocycle.

  The nitrogen-containing heterocyclic derivative is more preferably an organic compound having a nitrogen-containing aromatic polycyclic group consisting of a 5-membered ring or a 6-membered ring. Further, in the case of such a nitrogen-containing aromatic polycyclic group having a plurality of nitrogen atoms, the nitrogen-containing compound having a skeleton in which the above formulas (B) and (C) or the above formula (B) and the following formula (D) are combined. Aromatic polycyclic organic compounds are preferred.

  The nitrogen-containing group of the nitrogen-containing aromatic polycyclic organic compound is selected from, for example, nitrogen-containing heterocyclic groups represented by the following general formula.

  In each of the above formulas, R is an aromatic hydrocarbon group or condensed aromatic hydrocarbon group having 6 to 40 carbon atoms, an aromatic heterocyclic group or condensed aromatic heterocyclic group having 3 to 40 carbon atoms, or 1 to 1 carbon atoms. 20 is an alkyl group or an alkoxy group having 1 to 20 carbon atoms, n is an integer of 0 to 5, and when n is an integer of 2 or more, a plurality of R may be the same or different from each other.

Furthermore, preferred specific compounds include nitrogen-containing heterocyclic derivatives represented by the following formula.
HAr-L ¹ -Ar ¹ -Ar ²

In the above formula, HAr is a substituted or unsubstituted nitrogen-containing heterocyclic group having 3 to 40 carbon atoms, and L ¹ is a single bond, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 40 carbon atoms or a condensed group. An aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group having 3 to 40 carbon atoms or a condensed aromatic heterocyclic group, and Ar ¹ is a substituted or unsubstituted divalent aromatic group having 6 to 40 carbon atoms Ar ² is a substituted or unsubstituted aromatic hydrocarbon group having 6 to 40 carbon atoms, a condensed aromatic hydrocarbon group, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 40 carbon atoms Or it is a condensed aromatic heterocyclic group.

  HAr is selected from the following group, for example.

L ¹ is selected from the following group, for example.

Ar ¹ is selected from, for example, the following arylanthranyl groups.

In the above formula, R ^{1 to} R ¹⁴ are each independently a hydrogen atom, a deuterium atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, or an alkyl group having 6 to 40 carbon atoms. An aryloxy group, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 40 carbon atoms or a condensed aromatic hydrocarbon group, or a substituted or unsubstituted aromatic heterocyclic group having 3 to 40 carbon atoms or a condensed aromatic complex; Ar ³ is a substituted or unsubstituted aromatic hydrocarbon group having 6 to 40 carbon atoms, a condensed aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group having 3 to 40 carbon atoms, or A condensed aromatic heterocyclic group. Further, R ^{1 to} R ⁸ may be nitrogen-containing heterocyclic derivatives each of which is a hydrogen atom or a deuterium atom.

Ar ² is selected from the following group, for example.

  In addition to these, the following compounds are also preferably used as the nitrogen-containing aromatic polycyclic organic compound as the electron transfer compound.

In the above formula, R _{1 to} R ₄ each independently represent a hydrogen atom, a deuterium atom, a substituted or unsubstituted aliphatic group having 1 to 20 carbon atoms, or a substituted or unsubstituted aliphatic group having 3 to 20 carbon atoms. And a substituted or unsubstituted aromatic ring group having 6 to 50 carbon atoms, a substituted or unsubstituted heterocyclic group having 3 to 50 carbon atoms, and X ₁ and X ₂ are each independently an oxygen atom Represents a sulfur atom or a dicyanomethylene group.

  In addition, the following compounds are also preferably used as the electron transfer compound.

In the above formula, R ¹ , R ² , R ³ and R ⁴ are the same or different groups, and are an aromatic hydrocarbon group or a condensed aromatic hydrocarbon group represented by the following formula.

In the above formula, R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ are the same or different from each other, and are a hydrogen atom, a deuterium atom, a saturated or unsaturated C 1-20 alkoxyl group, a saturated group. Alternatively, it is an unsaturated alkyl group having 1 to 20 carbon atoms, an amino group, or an alkylamino group having 1 to 20 carbon atoms. At least one of R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ is a group other than a hydrogen atom or a deuterium atom.

  Further, the electron transport compound may be a polymer compound containing the nitrogen-containing heterocyclic group or the nitrogen-containing heterocyclic derivative.

  The electron transport layer of the organic EL device of the present invention particularly preferably contains at least one nitrogen-containing heterocyclic derivative represented by the following formulas (60) to (62).

(In the formula, Z ¹ , Z ² and Z ³ are each independently a nitrogen atom or a carbon atom.
R ¹ and R ² are each independently a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms, a substituted or unsubstituted heteroaryl group having 5 to 50 ring atoms, substituted or unsubstituted carbon They are a C1-C20 alkyl group, a substituted or unsubstituted C1-C20 haloalkyl group, or a substituted or unsubstituted C1-C20 alkoxy group.
n is an integer of 0 to 5, and when n is an integer of 2 or more, the plurality of R ¹ may be the same or different from each other. Further, two adjacent R ^{1 's} may be bonded to each other to form a substituted or unsubstituted hydrocarbon ring.
Ar ¹ is a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms or a substituted or unsubstituted heteroaryl group having 5 to 50 ring atoms.
Ar ² is a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted haloalkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms, substituted Alternatively, it is an unsubstituted aryl group having 6 to 50 ring carbon atoms or a substituted or unsubstituted heteroaryl group having 5 to 50 ring atoms.
However, either Ar ¹ or Ar ² is a substituted or unsubstituted condensed aromatic hydrocarbon ring group having 10 to 50 ring carbon atoms or a substituted or unsubstituted condensed aromatic group having 9 to 50 ring atoms. It is a heterocyclic group.
Ar ³ is a substituted or unsubstituted arylene group having 6 to 50 ring carbon atoms or a substituted or unsubstituted heteroarylene group having 5 to 50 ring atoms.
L ¹ , L ^2, and L ³ are each independently a single bond, a substituted or unsubstituted arylene group having 6 to 50 ring carbon atoms, or a substituted or unsubstituted divalent ring having 9 to 50 ring atoms. A condensed aromatic heterocyclic group. )

Examples of the aryl group having 6 to 50 ring carbon atoms include phenyl, naphthyl, anthryl, phenanthryl, naphthacenyl, chrysenyl, pyrenyl, biphenyl, terphenyl, tolyl, fluoranthenyl, fluorenyl Group and the like.
Examples of heteroaryl groups having 5 to 50 ring atoms include pyrrolyl, furyl, thienyl, silolyl, pyridyl, quinolyl, isoquinolyl, benzofuryl, imidazolyl, pyrimidyl, carbazolyl, selenophenyl Group, oxadiazolyl group, triazolyl group, pyrazinyl group, pyridazinyl group, triazinyl group, quinoxalinyl group, acridinyl group, imidazo [1,2-a] pyridinyl group, imidazo [1,2-a] pyrimidinyl group and the like.
Examples of the alkyl group having 1 to 20 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group.
Examples of the haloalkyl group having 1 to 20 carbon atoms include groups obtained by substituting one or more hydrogen atoms of the alkyl group with at least one halogen atom selected from fluorine, chlorine, iodine and bromine.
Examples of the alkoxy group having 1 to 20 carbon atoms include groups having the alkyl group as an alkyl moiety.
Examples of the arylene group having 6 to 50 ring carbon atoms include a group obtained by removing one hydrogen atom from the aryl group.
Examples of the divalent condensed aromatic heterocyclic group having 9 to 50 ring atoms include groups obtained by removing one hydrogen atom from the condensed aromatic heterocyclic group described as the heteroaryl group.

  Although the film thickness of an electron carrying layer is not specifically limited, Preferably it is 1 nm-100 nm.

  Moreover, it is preferable to use an insulator or a semiconductor as an inorganic compound in addition to the nitrogen-containing ring derivative as a component of the electron injection layer that can be provided adjacent to the electron transport layer. If the electron injection layer is made of an insulator or a semiconductor, current leakage can be effectively prevented and the electron injection property can be improved.

As such an insulator, it is preferable to use at least one metal compound selected from the group consisting of alkali metal chalcogenides, alkaline earth metal chalcogenides, alkali metal halides and alkaline earth metal halides. If the electron injection layer is composed of these alkali metal chalcogenides or the like, it is preferable in that the electron injection property can be further improved. Specifically, preferable alkali metal chalcogenides include, for example, Li ₂ O, K ₂ O, Na ₂ S, Na ₂ Se, and Na ₂ O, and preferable alkaline earth metal chalcogenides include, for example, CaO, BaO. , SrO, BeO, BaS and CaSe. Further, preferable alkali metal halides include, for example, LiF, NaF, KF, LiCl, KCl, and NaCl. Examples of preferable alkaline earth metal halides include fluorides such as CaF ₂ , BaF ₂ , SrF ₂ , MgF ₂ and BeF ₂ , and halides other than fluorides.

  Further, as a semiconductor, an oxide, nitride, or oxynitride containing at least one element of Ba, Ca, Sr, Yb, Al, Ga, In, Li, Na, Cd, Mg, Si, Ta, Sb, and Zn. One kind alone or a combination of two or more kinds of products may be mentioned. In addition, the inorganic compound constituting the electron injection layer is preferably a microcrystalline or amorphous insulating thin film. If the electron injection layer is composed of these insulating thin films, a more uniform thin film is formed, and pixel defects such as dark spots can be reduced. Examples of such inorganic compounds include alkali metal chalcogenides, alkaline earth metal chalcogenides, alkali metal halides, and alkaline earth metal halides.

  When such an insulator or semiconductor is used, the preferred thickness of the layer is about 0.1 nm to 15 nm. Further, the electron injection layer in the present invention is preferable even if it contains the above-mentioned electron donating dopant.

(Hole transport layer)
An organic layer formed between the light emitting layer and the anode, and has a function of transporting holes from the anode to the light emitting layer. When the hole transport layer is composed of a plurality of layers, an organic layer close to the anode may be defined as a hole injection layer. The hole injection layer has a function of efficiently injecting holes from the anode into the organic layer unit.

  As another material for forming the hole transport layer, an aromatic amine compound, for example, an aromatic amine derivative represented by the following general formula (I) is preferably used.

In the general formula (I), Ar ^{1 to} Ar ⁴ are substituted or unsubstituted aromatic hydrocarbon groups having 6 to 50 ring carbon atoms or condensed aromatic hydrocarbon groups, substituted or unsubstituted ring forming atoms 5 -50 aromatic heterocyclic group or condensed aromatic heterocyclic group, or a group in which the aromatic hydrocarbon group or condensed aromatic hydrocarbon group and the aromatic heterocyclic group or condensed aromatic heterocyclic group are bonded. .
In the general formula (I), L represents a substituted or unsubstituted aromatic hydrocarbon group or condensed aromatic hydrocarbon group having 6 to 50 ring carbon atoms, or a substituted or unsubstituted ring forming atom number of 5 to 5. Represents 50 aromatic heterocyclic groups or condensed aromatic heterocyclic groups.

  Specific examples of the compound of the general formula (I) are described below.

In addition, an aromatic amine of the following formula (II) is also preferably used for forming the hole transport layer.

In the formula (II), the definitions of Ar ^{1 to} Ar ³ are the same as the definitions of Ar ^{1 to} Ar ^{4 in} the general formula (I). Specific examples of the compound of the general formula (II) are shown below, but are not limited thereto.

  The hole transport layer of the organic EL device of the present invention may have a two-layer structure of a first hole transport layer (anode side) and a second hole transport layer (cathode side).

  Although the film thickness of a positive hole transport layer is not specifically limited, It is preferable that it is 10-200 nm.

  In the organic EL device of the present invention, a layer containing an electron accepting compound may be bonded to the positive hole transport layer or the anode side of the first hole transport layer. This is expected to reduce drive voltage and manufacturing costs.

  The electron accepting compound is preferably a compound represented by the following formula (10).

(In the formula (10), R ⁷ ~R ¹² may be the same or different, each independently cyano, -CONH _2, alkyl carboxyl group, or -COOR ¹³ (R ¹³ having 1 to 20 carbon atoms Group or a cycloalkyl group having 3 to 20 carbon atoms, provided that one or more pairs of R ⁷ and R ⁸ , R ⁹ and R ¹⁰ , and R ¹¹ and R ¹² are combined together to form —CO—. A group represented by O—CO— may be represented.)

Examples of R ¹³ include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, a cyclopentyl group, and a cyclohexyl group.

  The thickness of the layer containing the electron-accepting compound is not particularly limited, but is preferably 5 to 20 nm.

(N / p doping)
In the hole transport layer and the electron transport layer described above, as described in Japanese Patent No. 3695714, the carrier injection ability is improved by doping the donor material (n) and acceptor material (p). Can be adjusted.
A typical example of n doping is a method of doping an electron transport material with a metal such as Li or Cs. A typical example of p doping is a method of doping an acceptor material such as F ₄ TCNQ into a hole transport material. Is mentioned.

(Space layer)
For example, when the fluorescent layer and the phosphorescent layer are laminated, the space layer is a fluorescent layer for the purpose of adjusting the carrier balance so that excitons generated in the phosphorescent layer are not diffused into the fluorescent layer. It is a layer provided between the layer and the phosphorescent light emitting layer. In addition, the space layer can be provided between the plurality of phosphorescent light emitting layers.
Since the space layer is provided between the light emitting layers, a material having both electron transport properties and hole transport properties is preferable. In order to prevent diffusion of triplet energy in the adjacent phosphorescent light emitting layer, the triplet energy is preferably 2.6 eV or more. Examples of the material used for the space layer include the same materials as those used for the above-described hole transport layer.

(Barrier layer)
The organic EL device of the present invention preferably has a barrier layer such as an electron barrier layer, a hole barrier layer, or a triplet barrier layer in a portion adjacent to the light emitting layer. Here, the electron barrier layer is a layer that prevents electrons from leaking from the light emitting layer to the hole transport layer, and the hole barrier layer is a layer that prevents holes from leaking from the light emitting layer to the electron transport layer. is there.
As will be described later, the triplet barrier layer prevents the triplet excitons generated in the light emitting layer from diffusing into the surrounding layers, and confines the triplet excitons in the light emitting layer, thereby emitting the triplet excitons. It has a function of suppressing energy deactivation on the molecule of the electron transport layer other than the dopant.
When providing the triplet barrier layer, the triplet energy E ^T _d of the phosphorescent dopant in the light emitting layer and the triplet energy of the compound used as a triplet barrier layer and E ^T _TB, energy E ^T _d <E ^T _TB If the size relationship is large, the triplet exciton of the phosphorescent dopant is confined (cannot move to other molecules) in terms of energy, and the energy deactivation path other than light emission on the dopant is interrupted, resulting in high efficiency. It is estimated that light can be emitted. However, even if the relationship of E ^T _d <E ^T _TB is satisfied, if this energy difference ΔE ^T = E ^T _TB −E ^T _d is small, under the environment of room temperature, which is the actual element driving environment, , endothermically triplet excitons overcame this energy difference Delta] E ^T by thermal energy near is considered to be possible to move to another molecule. In particular, in the case of phosphorescence emission, the exciton lifetime is longer than that of fluorescence emission, so that the influence of the endothermic exciton transfer process is likely to appear. The energy difference ΔE ^T is preferably as large as possible relative to the thermal energy at room temperature, more preferably 0.1 eV or more, and particularly preferably 0.2 eV or more.

The triplet energy in the present invention is measured as follows.
First, a sample is dissolved in EPA solvent (diethyl ether: isopentane: ethanol = 5: 5: 2 (volume ratio)) at 10 μmol / L to obtain a sample for phosphorescence measurement. This phosphorescence measurement sample is put in a quartz cell, irradiated with excitation light at a temperature of 77 K, and the phosphorescence spectrum of the emitted phosphorescence is measured. Based on this, it is defined as a value obtained by a conversion formula E ^T (eV) = 1239.85 / λ _edge . “Λ _edge ” means that when the phosphorescence spectrum is expressed by taking the phosphorescence intensity on the vertical axis and the wavelength on the horizontal axis, a tangent line is drawn with respect to the rising _{edge on} the short wavelength side of the phosphorescence spectrum. It means the wavelength value (unit: nm) at the intersection.
As the host material of the light emitting layer, those satisfying A _b −A _h ≦ 0.1 eV are preferable. Here, A _b represents the affinity of the barrier layer material, and A _h represents the affinity of the light emitting layer host material.
The affinity Af (electron affinity) in the present invention refers to energy released or absorbed when one electron is given to a molecule of the material, and is defined as positive in the case of emission and negative in the case of absorption. The affinity Af is defined as follows by the ionization potential Ip and the optical energy gap Eg (S).
Af = Ip-Eg (S)
Here, the ionization potential Ip means the energy required to remove and ionize electrons from the compound of each material. In the present invention, the ionization potential Ip is a positive value measured with an atmospheric photoelectron spectrometer (AC-3, manufactured by Riken Keiki Co., Ltd.). It is a value with the sign of.
The optical energy gap Eg (S) refers to the difference between the conduction level and the valence level. This is a value having a positive sign obtained by converting the wavelength value of the intersection point into energy.
Further, the electron mobility of the material constituting the triplet barrier layer is preferably 10 ⁻⁶ cm ² / Vs or more in the range of the electric field strength of 0.04 to 0.5 MV / cm. As a method for measuring the electron mobility of an organic material, several methods such as the Time of Flight method are known. Here, the electron mobility is determined by impedance spectroscopy.
The electron injection layer is desirably 10 ⁻⁶ cm ² / Vs or more in the range of electric field strength of 0.04 to 0.5 MV / cm. This facilitates the injection of electrons from the cathode into the electron transport layer, and also promotes the injection of electrons into the adjacent barrier layer and the light emitting layer, thereby enabling driving at a lower voltage.

  EXAMPLES Next, although this invention is demonstrated further in detail using an Example, this invention is not limited to the following Example.

[Synthesis of Intermediates 1-12]
(1) Synthesis of intermediate 1

In an Ar atmosphere, 780 g (4.64 mol) of dibenzofuran was dissolved in 6 L of dehydrated THF, cooled with dry ice / methanol, and 3 L of 1.65 M n-butyllithium was added dropwise. After dropping, the temperature was returned to room temperature, reacted for 5 hours, cooled again, and 600 mL of 1,2-dibromoethane was added dropwise, returned to room temperature, and reacted for 15 hours.
Next, the reaction solution was poured into 10 L of ice water and extracted with methylene chloride, and the methylene chloride layer was washed with 10% aqueous potassium carbonate solution and saturated brine, dried over magnesium sulfate, and concentrated.
Next, column chromatography was performed with a THF / methanol solvent to obtain 4-bromodibenzofuran with a yield of 60% and a yield of 691 g.

Next, 494 g (2 mol) of 4-bromodibenzofuran was dissolved in 6 L of dehydrated THF in an Ar atmosphere, cooled with dry ice / methanol, and 1.5 L of 1.58 M n-butyllithium was added dropwise. After dropping, the mixture was stirred for 30 minutes, 1137 g of triisopyr borate was added dropwise, returned to room temperature, and reacted for 15 hours.
Next, 3 L of water and 3 L of ethyl acetate were added to the reaction solution, and the ethyl acetate layer was washed with saturated brine, dried over magnesium sulfate, and concentrated.
The obtained crystals were recrystallized with toluene / heptane to obtain dibenzofuran-4-boronic acid in a yield of 84% and a yield of 356 g.

Next, in an Ar atmosphere, 280 g (1.39 mol) of 1-bromo-2-nitrobenzene, 323 g (1.53 mol) of dibenzofuran-4-boronic acid, 32 g (0.028 mol) of Pd (PPh ₃ ) ₄ , 6 L of toluene and 2.1 L of 2M sodium carbonate aqueous solution were charged, the temperature was raised, and the mixture was stirred at 86 ° C. for 15 hours.
After completion of the reaction, 3 L of water was added for liquid separation, the toluene layer was concentrated, and column chromatography was performed with a developing solvent of heptane / toluene to obtain Intermediate 1-1 having a yield of 70% and a yield of 337 g. .

Next, 337 g (1.16 mol) of the intermediate 1-1, 764 g (2.91 mol) of triphenylphosphine and 2 L of o-dichlorobenzene were charged in an Ar atmosphere, and the mixture was stirred at 190 ° C. for 10 hours.
The reaction solution was concentrated, 1.5 L of methanol was added, crystals were precipitated, and filtered off.
Washing with toluene was carried out to obtain Intermediate 1 having a yield of 53% and a yield of 157 g.

(2) Synthesis of intermediate 2

166 g (0.67 mol) of 4-bromodibenzofuran, 84 g (0.66 mol) of 2-chloroaniline, 73 g (0.76 mol) of t-butoxy sodium, and 10 g (0) of Pd ₂ (dba) ₃ in an Ar atmosphere 0.011 mol), 27 g (0.044 mol) of rac-BINAP and 2.3 L of toluene were charged and reacted at 80 ° C. for 3 hours.
After washing the reaction solution with water, the toluene layer was concentrated, and column chromatography was carried out using hexane / toluene as a developing solvent to obtain an intermediate 2-1 having a yield of 64% and a yield of 126 g.

Next, in an Ar atmosphere, 126 g (0.43 mol) of intermediate 2-1; 119 g (0.86 mol) of potassium carbonate; 2.9 g (0.013 mol) of palladium acetate; and PCy ₃ -HBF ₄ of 9. 5 g (0.026 mol) and 860 mL of dimethylacetamide were charged and reacted at 130 ° C. for 3 hours.
The reaction solution was concentrated, and the solid was washed with toluene three times to obtain Intermediate 2 with a yield of 50% and a yield of 55.3 g.

(3) Synthesis of intermediate 3

In an Ar atmosphere, 1160 g (4.96 mol) of 4-bromobiphenyl was dissolved in 8.3 L of dehydrated THF, cooled with dry ice / methanol, and 6 L of 1.58 M n-butyllithium was added dropwise. After the dropping, the mixture was stirred for 30 minutes, and 1867 g (9.92 mol) of triisopyr borate was added dropwise, returned to room temperature, and reacted for 15 hours.
Hereinafter, in the synthesis of Intermediate 1, post-treatment was performed in the same manner as in the synthesis of dibenzofuran-4-boronic acid to obtain Intermediate 3-1 with a yield of 95% and a yield of 934 g.

In an Ar atmosphere, 430.5 g (2.35 mol) of 2,4,6-trichloropyrimidine, 906 g (4.58 mol) of intermediate 3-1, 1497 g (14.1 mol) of sodium carbonate, Pd (PPh ₃ ) 108.5 g (0.094 mol) of ₄ was charged with 4.3 L of dimethoxyethane and 9.6 L of water, and the mixture was reacted at 80 ° C. for 2 hours.
The reaction solution was extracted with toluene, concentrated, and recrystallized with toluene to obtain Intermediate 3 with a yield of 28% and a yield of 270 g.

(4) Synthesis of intermediate 4

  In an Ar atmosphere, ice-cooled, 184 g (7.6 mol) of Mg was activated with 0.18 g of iodine in 18 mL of dehydrated THF, and 1472 g (6.32 mol) of 4-bromobiphenyl was dissolved in 5.9 L of dehydrated THF, and added dropwise. A Grignard reagent of Intermediate 4-1 was prepared.

Next, the Grignard reagent was added dropwise at room temperature to a solution prepared by dissolving 466 g (2.53 mol) of cyanuric chloride in 4.7 L of dehydrated THF and allowed to react for 14 hours.
The reaction solution was treated with water, extracted with toluene, and recrystallized with column chromatography with toluene, dimethoxyethane, etc. to obtain Intermediate 4 in a yield of 8% and a yield of 78 g.

(5) Synthesis of intermediate 5

In an Ar atmosphere, 430.5 g (2.35 mol) of 2,4,6-trichloropyrimidine, 286 g (2.35 mol) of phenylboronic acid, 1497 g (14.1 mol) of sodium carbonate, and Pd (PPh ₃ ) ₄ 108.5 g (0.094 mol), 4.3 L of dimethoxyethane and 9.6 L of water were charged and reacted at 80 ° C. for 2 hours.
The reaction solution was extracted with toluene, concentrated, and recrystallized with toluene to obtain Intermediate 5-1 with a yield of 30% and a yield of 159 g.

Next, in an Ar atmosphere, 159 g (0.71 mol) of intermediate 5-1; 169 g (0.71 mol) of 9,9-dimethylfluorene-2-boronic acid; 226 g (2.1 mol) of sodium carbonate; Pd (PPh ₃ ) ₄ (16.4 g, 0.014 mol), dimethoxyethane (1.1 L), and water (2.3 L) were charged and reacted at 80 ° C. for 2 hours.
The reaction solution was extracted with toluene, concentrated, and recrystallized with toluene to obtain Intermediate 5 with a yield of 50% and a yield of 135 g.

(6) Synthesis of intermediate 6

In Ar atmosphere, 43,4 g (2.35 mol) of 2,4,6-trichloropyrimidine, 1090 g (4.58 mol) of 9,9-dimethylfluorene-2-boronic acid, and 1497 g (14.1 mol) of sodium carbonate , 108.5 g (0.094 mol) of Pd (PPh ₃ ) ₄ , 4.3 L of dimethoxyethane, and 9.6 L of water were charged and reacted at 80 ° C. for 2 hours.
The reaction solution was extracted with toluene, concentrated, and recrystallized with toluene to obtain an intermediate 6 having a yield of 25% and a yield of 293 g.

(7) Synthesis of intermediate 7

In an Ar atmosphere, 159 g (0.71 mol) of intermediate 5-1; 151 g (0.71 mol) of dibenzofuran-4-boronic acid; 226 g (2.1 mol) of sodium carbonate; and Pd (PPh ₃ ) ₄ of 16. 4 g (0.014 mol), 1.1 L of dimethoxyethane and 2.3 L of water were charged, and reacted at 80 ° C. for 2 hours.
The reaction solution was extracted with toluene, concentrated, and recrystallized with toluene to obtain Intermediate 7 having a yield of 48% and a yield of 122 g.

(8) Synthesis of intermediate 8

In an Ar atmosphere, 430.5 g (2.35 mol) of 2,4,6-trichloropyrimidine, 971 g (4.58 mol) of dibenzofuran-4-boronic acid, 1497 g (14.1 mol) of sodium carbonate, Pd (PPh _{3 4} ) 108.5 g (0.094 mol), 4.3 L dimethoxyethane, and 9.6 L water were charged and reacted at 80 ° C. for 2 hours.
The reaction solution was extracted with toluene, concentrated, and recrystallized with toluene to obtain Intermediate 8 with a yield of 27% and a yield of 284 g.

(9) Synthesis of intermediate 9

  Intermediate 9 was synthesized by the same synthesis method as that for intermediate 7 except that dibenzofuran-2-boronic acid was used instead of dibenzofuran-4-boronic acid.

(10) Synthesis of intermediate 10

  Intermediate 10 was synthesized by the same synthesis method as that for intermediate 8 except that dibenzofuran-2-boronic acid was used instead of dibenzofuran-4-boronic acid.

(11) Synthesis of intermediate 11

  4-Bromobenzaldehyde (15 g, 81 mmol) was dissolved in ethanol (300 mL), 4-acetylbiphenyl (16.3 g, 83 mmol) and 28% sodium methoxide methanol solution (15 g, 81 mmol) were added, and the mixture was stirred at room temperature for 7 hours. After completion of the reaction, the precipitated solid was filtered and washed with methanol, yielding 41% yield and 12.1 g yield of Intermediate 11-1.

Intermediate 11-1 was dissolved in 12.1 g (33 mmol) and ethanol 80 mL, benzamidine hydrochloride 5.2 g (34 mmol), sodium hydroxide 2.6 g (65 mmol)
) And heated to reflux for 15 hours. After completion of the reaction, the reaction mixture was cooled to room temperature, and the precipitated crystals were separated by filtration and washed with water and methanol to obtain Intermediate 11 in a yield of 27% and a yield of 4.1 g.

(12) Synthesis of intermediate 12

  Intermediate 12 was synthesized by the same synthesis method as that for intermediate 8 except that dibenzothiophene-4-boronic acid was used instead of dibenzofuran-4-boronic acid.

Example 1
(Synthesis of Compound 1)
In an Ar atmosphere, 4.0 g (4.37 mmol) of Pd ₂ (dba) ₃ , 2.54 g (8.76 mmol) of t-Bu ₃ P-HBF ₄ and 900 mL of dehydrated xylene were charged and stirred for 30 minutes. Thereafter, 38.9 g (150 mmol) of the intermediate 1 and 62.9 g (150 mmol) of the intermediate 3 and 80 mL of dehydrated xylene were added dropwise, the temperature was raised to 110 ° C., and 19.6 g of sodium t-butoxy was added. . After reacting at 130 ° C. for 2 hours, the precipitated solid was filtered off, washed with xylene and recrystallized with xylene to obtain Compound 1 in a yield of 75% and a yield of 72 g.
Compound 1 was identified by MS, ¹ H-NMR.

Examples 2-11
(Synthesis of Compound 2 to Compound 11)
Compounds 2 to 11 were synthesized by the same synthesis method as in Example 1 except that the intermediates used in the synthesis were changed as shown in Table 1.

Example 12
(Preparation of organic EL element 1)
A glass substrate with an ITO transparent electrode (anode) having a thickness of 25 mm × 75 mm × 1.1 mm (manufactured by Geomatic Co., Ltd.) was subjected to ultrasonic cleaning in isopropyl alcohol for 5 minutes and then UV ozone cleaning for 30 minutes. . The glass substrate with the transparent electrode line after the cleaning was mounted on a substrate holder of a vacuum deposition apparatus, and the compound HT1 was first laminated so as to cover the transparent electrode on the surface on which the transparent electrode line was formed. Thereby, a hole injection layer having a thickness of 5 nm was formed.
On this hole injection layer, the compound HT2 was vapor-deposited to form a 260 nm thick hole transport layer. In this way, a hole transport zone composed of the hole injection layer and the hole transport layer was formed.
On this hole transport zone, the compound 1 synthesized in Example 1 as a phosphorescent host and Ir (piq) ₃ as a phosphorescent dopant were co-evaporated. As a result, a light emitting layer having a thickness of 40 nm showing phosphorescence was formed. The concentration of Ir (piq) ₃ in the light emitting layer was 5% by mass.
Next, the compound ET1 was vapor-deposited on the light emitting layer. Thereby, a barrier layer having a thickness of 20 nm was formed.
And on this barrier layer, compound Liq was vapor-deposited and the 1-nm-thick electron injection layer was formed. In this way, an electron transport zone composed of the barrier layer and the electron injection layer was formed.
Furthermore, metal aluminum (Al) was vapor-deposited on the electron transport zone to form a cathode having a thickness of 80 nm.
The organic EL element 1 was produced by the above.

Examples 13-22
(Preparation of organic EL elements 2 to 11)
Organic EL elements 2 to 11 were produced in the same manner as in Example 11 except that compounds 2 to 11 were used instead of compound 1 as the phosphorescent host.

Comparative Example 1
(Preparation of organic EL element 12)
An organic EL device 12 was produced in the same manner as in Example 12 except that the following compound 12 described in International Publication No. WO2010 / 136109 was used in place of compound 1 as the phosphorescent host.

(Method for evaluating organic EL element)
The organic EL devices produced in the above examples and comparative examples were caused to emit light by direct current driving, and the voltage at a current density of 10 mA / cm ² , the external quantum efficiency, and the lifetime (initial luminance 2000 nit, luminance decreased 10%, ie 1800 nit). The time until the brightness decreases to (LT90)) was measured. The measurement results are shown in Table 2.
The chromaticity of each element was CIEx = 0.68 and CIEy = 0.32.

  Table 3 shows physical property values of the materials of Compound 1 and Compound 12.

  In the compound of the present invention, by introducing a specific group into the Az (azine) unit, LUMO is expanded and affinity (electron affinity) is increased. As a result, the injection property of electrons into the light emitting layer is improved, the voltage is lowered, and the penetration of electrons into the hole transport layer (HT2) is reduced, thereby improving the external quantum yield and improving the lifetime. Conceivable.

  As described above in detail, when the organic EL material of the present invention is used for an organic EL element, an organic EL element having a low driving voltage, a high luminous efficiency, and a long lifetime can be obtained. For this reason, the organic EL element of the present invention is extremely useful as a light source for various electronic devices.

Claims (13)

The organic electroluminescent material represented by Formula (1).

[In Formula (1),
m represents an integer of 1 to 4;
Har represents a monovalent group formed by combining the partial structure represented by the formula (2A) and the partial structure represented by the formula (2B);
L is a single bond, a substituted or unsubstituted divalent aromatic hydrocarbon group having 6 to 12 ring carbon atoms, or a substituted or unsubstituted divalent aromatic heterocyclic group having 5 to 13 ring atoms. Represents;
Az represents a (m + 1) -valent group represented by the formula (3);
Ar represents a monovalent group selected from the group consisting of the following (S1) and (S2), and when there are a plurality of Ar, each Ar may be the same as or different from each other.
(S1) Substituted or unsubstituted monovalent aromatic hydrocarbon group having 12 to 24 ring carbon atoms (S2) Monovalent group represented by formula (5)]

[In the formulas (2A) and (2B)
a represents an integer of 0 to 4;
b represents an integer of 0 to 2;
c represents an integer of 0 to 4;
Ra ^{1 to} Ra ³ each independently represents a substituent;
* ₁ represents a bond with L;
Two * ₂ represents a 1-position and the carbon in position 2, with the carbon of the 2 and 3 positions, or positions 3 and 4 of the bond to the carbon of formula (2A). ]

[In Formula (3),
One of Y _{1 to} Y ₅ represents C- * ₃ ;
M of Y _{1 to} Y ₅ represents C- * ₄ ;
Y _{1 to} Y ₅ that do not represent any of C- * ₃ and C- * ₄ each independently represent C-Rb ¹ or a nitrogen atom;
Rb ¹ represents a hydrogen atom or a substituent;
* ₃ represents a bond with L;
* ₄ represents a bond with Ar. ]

[In Formula (5),
s and t each independently represents an integer of 0 to 3;
X ₁ represents O or S;
Rc ¹ and Rc ² are each independently a halogen atom, a cyano group, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, or 1 to 20 carbon atoms. Alkoxy group of 1 to 20 carbon atoms, haloalkoxy group of 1 to 20 carbon atoms, silyl group, alkylsilyl group of 1 to 10 carbon atoms, monovalent aromatic carbonization of 6 to 30 ring carbon atoms A hydrogen group, an arylsilyl group having 6 to 30 carbon atoms, an aralkyl group having 7 to 30 carbon atoms, or a monovalent aromatic heterocyclic group having 3 to 30 ring atoms;
Q ¹ and Q ² each independently represents a saturated or unsaturated ring having 5 to 12 ring atoms;
* ₅ represents a bond with Az. ]
However, Formula (1) does not become the following compound.

The organic electroluminescent material according to claim 1, wherein (S1) is a monovalent group represented by any one of formulas (4-1) to (4-4).

[In the formulas (4-1) to (4-4),
p represents an integer of 1 to 3;
q represents an integer of 1 or 2;
d, f, g, k and v each independently represents an integer of 0 to 4;
e, h, j and l each independently represent an integer of 0 to 5;
i and u represent an integer of 0 to 3;
Rc ^{3 to} Rc ¹³ are each independently a halogen atom, a cyano group, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, or 1 to 20 carbon atoms. Alkoxy group of 1 to 20 carbon atoms, haloalkoxy group of 1 to 20 carbon atoms, silyl group, alkylsilyl group of 1 to 10 carbon atoms, monovalent aromatic carbonization of 6 to 30 ring carbon atoms A hydrogen group, an arylsilyl group having 6 to 30 carbon atoms, an aralkyl group having 7 to 30 carbon atoms, or a monovalent aromatic heterocyclic group having 3 to 30 ring atoms;
Rb ² and Rb ³ each independently represents a hydrogen atom or a substituent;
* ₅ represents a bond with Az. ] The organic electroluminescent material according to claim 1 or 2, wherein the (S2) is a monovalent group represented by the formula (5-1).

[In the formula (5-1), s, t, X 1, Rc 1, Rc 2 and * _5, s of each formula (5), t, in X ^_1, Rc _1, Rc ² and * ₅ synonymous is there. ] The organic electroluminescent material according to claim 1, wherein Ar is selected from the following monovalent groups.

[* 5 represents a bond with Az. ] The organic electroluminescent material according to any one of claims 1 to 4, wherein Har is a monovalent group represented by any one of formulas (2-1) to (2-2).

[In the formulas (2-1) to (2-2),
a, b, Ra ^1, Ra ² and * ₁ are a respective formulas (2A), b, and Ra ^1, Ra ² and * ₁ synonymous;
c and Ra ³ are the same meaning as c and Ra ³ each formula (2B). ] Az is a (m ₂ +1) -valent group represented by the formula (3-2) or a (m ₃ +1) -valent group represented by the formula (3-5). The organic electroluminescent material in any one.

[In the formulas (3-2) and (3-5),
m ₂ represents an integer of 1 to 3;
m ₃ represents an integer of 1 to 2;
Rb ^1, * ₃ and * _4, Rb ^1, respectively formula (3) has the same meaning as * ₃ and * _4. ] The organic group according to claim 6, wherein the (m ₂ +1) -valent group represented by the formula (3-2) is a (m ₂ +1) -valent group represented by the formula (3-2-1). Electroluminescent material.

[In the formula (3-2-1), m _2, Rb ^1, * ₃ and * _4, m _2, Rb ^1, respectively formula (3-2) has the same meaning as * ₃ and * _4. ] The (m ₂ +1) -valent group represented by the formula (3-2-1) is a trivalent group represented by any one of the formulas (3-2-1A) and (3-2-1B) The organic electroluminescent material according to claim 7.

[In formula (3-2-1A) and ^{(3-2-1B), Rb 1, *} 3 and * _4, Rb ^1, respectively formula (3-2) has the same meaning as * ₃ and * _4. ]   The organic electroluminescent material according to claim 1, wherein L is a single bond. Having a plurality of organic thin film layers including a light emitting layer between a cathode and an anode;
The organic electroluminescent element in which at least 1 layer contains the organic electroluminescent material in any one of Claims 1-9 among the said organic thin film layers.   The organic electroluminescent element according to claim 10, wherein the light emitting layer includes the organic electroluminescent material as a host material.   The organic electroluminescence device according to claim 10 or 11, wherein the light emitting layer contains a phosphorescent material.   The organic electroluminescent device according to claim 12, wherein the phosphorescent material is an orthometalated complex of metal atoms selected from iridium (Ir), osmium (Os), and platinum (Pt).

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