JP6755113B2 - Organic electroluminescence element - Google Patents

Description

The present invention relates to an organic electroluminescence device and an electronic device equipped with the organic electroluminescence device.

In order to improve the luminous efficiency of the organic electroluminescence element (organic EL element), a method of adjusting the optical interference distance is used. Further, in the upper surface emitting type organic EL element, as a means for improving the luminous efficiency, sharpening the emission spectrum and adjusting the peak wavelength, the organic layer including the light emitting layer is sandwiched between the metal electrode and the translucent metal electrode to perform optics. A method of adjusting the emission spectrum by constructing a typical resonator is used. The cavity length is adjusted by changing the distance between the metal and translucent metal electrodes, but the method of adjusting the optical interference by changing the film thickness of the organic layer changes the luminous efficiency due to the change in carrier balance. Occurs. Therefore, the film thickness of the organic layer is restricted by the conditions under which the carrier balance is maintained, and there is a limit to the adjustment of the cavity length.

As a method for adjusting the optical interference distance so as not to change the carrier balance in the top-emitting organic EL element, a method of providing a thin film structure capable of adjusting the optical interference distance on the upper translucent metal electrode has been proposed. There is. In Patent Document 1, a resonator is provided on the upper electrode, and the peak wavelength is adjusted by adjusting the resonator length so as to match the optical path length of the element to an integral multiple of a half wavelength like a Fabry-Perot resonator. Do. Further, Patent Document 2 proposes a method of adjusting the optical interference distance by forming an optical adjustment layer of several nm to several hundred nm on the upper electrode.

In Patent Document 2, an organic capping layer having a refractive index of 1.7 or more and a film thickness of 600 Å is formed on the upper electrode of a top-emission type organic EL element to enhance light emission of about 1.5 times in red and green light emitting elements. It has gained.
Patent Document 3 discloses an invention relating to suppression of external light reflection and high contrast by high-efficiency light emission by an organic capping layer doped with a Nile red dye on the upper electrode of a top-emission type organic EL element.
Patent Document 4 discloses a technique for improving the luminous efficiency by using a specific compound in the luminous efficiency improving layer of the organic light emitting device.

International Publication No. 2001/039554 Pamphlet Japanese Unexamined Patent Publication No. 2006-156390 JP-A-2007-103303 JP-A-2010-45033 International Publication No. 2011-043083 Pamphlet

Yuyuki Fujiwara, "Spectroscopic Ellipsometry", Maruzen Publishing, May 2011, p. 176

However, the luminous efficiency of the conventional organic EL element is still insufficient, and there is room for improvement. An object of the present invention is to provide an organic EL device having excellent luminous efficiency.

A method of increasing the refractive index of the capping layer can be considered in order to improve the luminous efficiency, but increasing the refractive index also increases the extinction coefficient (Kramers-Kronig relational expression (Non-Patent Document 1)), and emits light. There is a problem that the increase in efficiency and the loss due to the absorption of light occur at the same time. Therefore, it was necessary to keep the extinction coefficient low while increasing the refractive index. In addition, it was necessary to adjust the wavelength dispersion in the visible light region.

As a result of diligent studies by the present inventors, it has been found that the refractive index (n) can be improved while keeping the extinction coefficient (k) low by using a material having a strong orientation like the present invention for the capping layer. It was. It was also found by optical calculation that the improvement of luminous efficiency by the capping layer strongly depends on the magnitude of the refractive index in the in-plane direction (horizontal to the surface of the substrate of the organic EL element).
Further, according to the present invention, it is possible to maintain a high refractive index particularly in the region of wavelengths of 430 nm to 600 nm. Non-Patent Document 5 has specialized in improving the luminous efficiency in the blue wavelength region, but in the present invention, since it is possible to suppress the absorption of the luminous energy on the longer wavelength side than blue, not only blue emission but also white emission Can be expected to develop.
According to one aspect of the present invention, the following organic electroluminescence devices and the like are provided.
A first electrode, one or more organic layers including a light emitting layer, a second electrode, and a capping layer are provided in this order.
An organic electroluminescence device in which the capping layer contains a compound represented by the following formula (1).
(In the formula (1), A is a group represented by the following formula (A1) or (A2).
L is an aromatic hydrocarbon group having 6 to 30 substituted or unsubstituted ring-forming carbon atoms, or an aromatic heterocyclic group having 5 to 30 substituted or unsubstituted ring-forming atoms. n is an integer from 0 to 5, and when n is 0, L and HAR are connected by a single bond, and when n is 2 or more, a plurality of Ls may be the same or different, and n is 2 or more. In the case of, a plurality of Ls may be bonded to each other to form a ring.
HAR is an aromatic heterocyclic group having 5 to 30 substituted or unsubstituted ring-forming atoms.
(In formula (A1), R _{1 to} R ₁₀ are single bonds used for bonding with a hydrogen atom, a substituent, or L, respectively. R ₁ and R ₂ , R ₂ and R ₃ , R ₃ and One or more combinations selected from R ₄ , R ₅ and R ₆ , R ₆ and R ₇ , R ₇ and R ₈ , R ₈ and R ₉ , R ₉ and R ₁₀ , and R ₁₀ and R ₁ are mutually exclusive. The group may be bonded to form a ring. The group represented by the formula (A1) may be bonded to L at any position on the ring formed from the combination.
In formula (A2), R _{101 to} R ₁₁₀ are single bonds used for bonding with a hydrogen atom, a substituent, or L, respectively. R ₁₀₁ and R ₁₀₂ , R ₁₀₂ and R ₁₀₃ , R ₁₀₃ and R ₁₀₄ , R ₁₀₄ and R ₁₀₅ , R ₁₀₅ and R ₁₀₆ , R ₁₀₆ and R ₁₀₇ , R ₁₀₇ and R ₁₀₈ , R ₁₀₈ and R ₁₀₉ , R ₁₀₉ And R ₁₁₀ , and one or more combinations selected from R ₁₁₀ and R ₁₀₁ combine with each other to form a ring. The group represented by the formula (A2) may be bonded to L at any position on the ring formed from the combination. )))

According to the present invention, it is possible to provide an organic EL element having excellent luminous efficiency.

It is a figure which shows one Embodiment of the organic electroluminescence device which concerns on one aspect of this invention.

[Organic electroluminescence element]
The organic electroluminescence device (organic EL device) according to one aspect of the present invention includes a first electrode, one or more organic layers including a light emitting layer, a second electrode, and a capping layer in this order, and the capping layer is of the formula (1). ) Is contained.
Hereinafter, the compound represented by the formula (1), the organic EL device, and the like will be described.

1. 1. The compound represented by the formula (1) The capping layer of the organic EL device according to one aspect of the present invention contains the compound represented by the following formula (1).
In formula (1), A is a group represented by the following formula (A1) or (A2).
L is an aromatic hydrocarbon group having 6 to 30 substituted or unsubstituted ring-forming carbon atoms, or an aromatic heterocyclic group having 5 to 30 substituted or unsubstituted ring-forming atoms. n is an integer of 0 to 5, and when n is 0, L and HAR are connected by a single bond, and when n is 2 or more, the plurality of Ls may be the same or different. When n is 2 or more, a plurality of Ls may be combined with each other to form a ring.
HAR is an aromatic heterocyclic group having 5 to 30 substituted or unsubstituted ring-forming atoms.
(In formula (A1), R _{1 to} R ₁₀ are single bonds used for bonding with a hydrogen atom, a substituent, or L, respectively. R ₁ and R ₂ , R ₂ and R ₃ , R ₃ and One or more combinations selected from R ₄ , R ₅ and R ₆ , R ₆ and R ₇ , R ₇ and R ₈ , R ₈ and R ₉ , R ₉ and R ₁₀ , and R ₁₀ and R ₁ are mutually exclusive. The group may be bonded to form a ring. The group represented by the formula (A1) may be bonded to L at any position on the ring formed from the combination.
In formula (A2), R _{101 to} R ₁₁₀ are single bonds used for bonding with a hydrogen atom, a substituent, or L, respectively. R ₁₀₁ and R ₁₀₂ , R ₁₀₂ and R ₁₀₃ , R ₁₀₃ and R ₁₀₄ , R ₁₀₄ and R ₁₀₅ , R ₁₀₅ and R ₁₀₆ , R ₁₀₆ and R ₁₀₇ , R ₁₀₇ and R ₁₀₈ , R ₁₀₈ and R ₁₀₉ , R ₁₀₉ And R ₁₁₀ , and one or more combinations selected from R ₁₁₀ and R ₁₀₁ combine with each other to form a ring. The group represented by the formula (A2) may be bonded to L at any position on the ring formed from the combination. )

Examples of the ring formed from R _{1 to} R ₁₀ and R _{101 to} R ₁₁₀ include a saturated or unsaturated 5-membered ring or 6-membered ring. Further, a saturated or unsaturated 5-membered ring or 6-membered ring may be formed by two or more substituents substituted on the ring.

In formula (A1), one or more combinations selected from R ₃ and R ₄ and R ₉ and R ₁₀ may combine with each other to form a ring.

The group represented by the formula (A1) is preferably represented by any of the following formulas (A1-1) to (A1-4).
(In formulas (A1-1) to (A1-4), R _{11 to} R ₂₀ , R _{21 to} R ₃₂ , R _{41 to} R ₅₂ , and R _{61 to} R ₇₂ are hydrogen atoms, substituents, or L, respectively. It is a single bond used for binding with.
In formula (A1-2), R ₃₁ and R ₃₂ may be combined with each other to form a ring. The group represented by the formula (A1-2) may be bonded to L at any position on the ring formed from R ₃₁ and R ₃₂ . )

The group represented by the formula (A1) is preferably represented by any of the following formulas (A1-11) to (A1-16).
(In formulas (A1-11) to (A1-16), R is a single bond used for bonding with a substituent or L. m1 is an integer of 1 to 9, and m2 is an integer of 1 to 11. Yes, m3 is an integer of 1 to 13, m4 is an integer of 1 to 14. R is bonded to any position on the fused ring represented by the formulas (A1-11) to (A1-16). You may.)

In formula (A2), one or more combinations selected from R ₁₀₂ and R ₁₀₃ , R ₁₀₃ and R ₁₀₄ , and R ₁₀₁ and R ₁₁₀ may be combined with each other to form a ring.

The group represented by the formula (A2) is preferably represented by any of the following formulas (A2-1) to (A2-5).
(In formulas (A2-1) to (A2-5), R _{111 to} R ₁₂₀ , R _{121 to} R ₁₃₂ , and R _{141 to} R ₁₅₁ are used for bonding with a hydrogen atom, a substituent, or L, respectively. It is a single bond.
In formula (A2-1), one or more combinations selected from R ₁₁₁ and R ₁₁₂ , R ₁₁₂ and R ₁₁₃ , and R ₁₁₆ and R ₁₁₇ may be combined with each other to form a ring. The group represented by the formula (A2-1) may be bonded to L at any position on the ring formed from the combination.
In formula (A2-5), R ₁₄₂ and R ₁₄₃ may combine with each other to form a ring. The group represented by the formula (A2-5) may be bonded to L at any position on the ring formed from R ₁₄₂ and R ₁₄₃ . )

The group represented by the formula (A2) is preferably represented by any of the following formulas (A2-11) to (A2-17).
(In formulas (A2-11) to (A2-17), R is a single bond substituent used for bonding with or L. m11 is an integer of 1 to 9, and m12 is an integer of 1 to 11. Yes, m13 is an integer of 1 to 12, m14 is an integer of 1 to 10, m15 is an integer of 1 to 11. R is represented by the formulas (A2-11) to (A2-17). It may be bonded to any position on the fused ring.)

The HAR-substituted or unsubstituted aromatic heterocyclic group having 5 to 30 ring-forming atoms may be any of the following groups.
• Substituted or unsubstituted, monocyclic aromatic heterocyclic groups,
Sulfur-containing aromatic heterocyclic group or oxygen-containing aromatic heterocyclic group in which two rings are condensed, either substituted or unsubstituted.
A nitrogen-containing aromatic heterocyclic group in which two 6-membered rings are condensed, either substituted or unsubstituted.
-Sulfur-containing aromatic heterocyclic group or oxygen-containing aromatic heterocyclic group in which three rings are condensed, either substituted or unsubstituted.
-A nitrogen-containing aromatic heterocyclic group in which three substituted or unsubstituted three 6-membered rings are condensed.-Groups represented by the following formulas (HAr-1) to (HAR-4).
(In formulas (HAr-1) to (HAR-4), X _{1 to} X ₇ , X _{11 to} X ₂₁ , and X _{31 to} X ₃₉ are nitrogen atoms, NR'or CR', respectively. R'is A single bond used to bond with a hydrogen atom, substituent, or L.)

HAR is a pyrrolyl group, a furyl group, a thienyl group, a pyridyl group, an imidazole pyridyl group, a pyridazinyl group, a pyrimidinyl group, a pyrazinyl group, a triazinyl group, an imidazolyl group, an oxazolyl group, a thiazolyl group, a pyrazolyl group, an isooxazolyl group, an isothiazolyl group and an oxadiazolyl group. Group, thiadiazolyl group, triazolyl group, tetrazolyl group, indolyl group, isoindrill group, benzofuranyl group, isobenzofuranyl group, benzothiophenyl group, isobenzothiophenyl group, quinolidinyl group, quinolyl group, isoquinolyl group, synnolyl group, phthalazinyl Group, quinazolinyl group, quinoxalinyl group, benzimidazolyl group, benzoxazolyl group, benzthiazolyl group, indazolyl group, benzisoxazolyl group, benzisothiazolyl group, dibenzofuranyl group, dibenzothiophenyl group, carbazolyl group, It may be a 9-phenylcarbazolyl group, a phenanthridinyl group, an acridinyl group, a phenanthrolinyl group, a phenazinyl group, a phenothiazinyl group, a phenoxadinyl group or a xanthenyl group. These groups may further have substituents.

HAR is preferably a pyridyl group, an imidazole pyridyl group, a pyridazinyl group, a pyrimidinyl group, a pyrazinyl group, a triazinyl group, a benzimidazolyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a carbazolyl group, a 9-phenylcarbazolyl group, It is a phenanthrolinyl group or a quinazolinyl group. These groups may further have substituents.

L is preferably a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms. The two single bonds that bind to L are preferably located at the para position on L.
n is preferably an integer of 1-5.
L is, for example, a divalent group represented by any of the following formulas.

The compound represented by the formula (1) preferably contains 1 to 3 nitrogen atoms.

The above compounds can be synthesized by using known alternative reactions or raw materials suitable for the desired product.

In the present specification, the hydrogen atom includes isotopes having different numbers of neutrons, that is, hydrogen (protium), deuterium (deuterium), and tritium (tritium).

In the present specification, the ring-forming carbon number constitutes the ring itself of a compound having a structure in which atoms are cyclically bonded (for example, a monocyclic compound, a fused ring compound, a crosslinked compound, a carbocyclic compound, or a heterocyclic compound). Represents the number of carbon atoms in an atom. When the ring is substituted with a substituent, the carbon contained in the substituent is not included in the ring-forming carbon number. The "ring-forming carbon number" described below shall be the same unless otherwise specified. For example, a benzene ring has 6 ring-forming carbon atoms, a naphthalene ring has 10 ring-forming carbon atoms, a pyridinyl group has 5 ring-forming carbon atoms, and a flanyl group has 4 ring-forming carbon atoms. When, for example, an alkyl group is substituted as a substituent on the benzene ring or naphthalene ring, the number of carbon atoms of the alkyl group is not included in the number of ring-forming carbon atoms. When, for example, a fluorene ring is bonded to the fluorene ring as a substituent (including a spirofluorene ring), the number of carbon atoms of the fluorene ring as a substituent is not included in the number of ring-forming carbon atoms.

In the present specification, the number of ring-forming atoms refers to a compound having a structure in which atoms are cyclically bonded (for example, a monocycle, a fused ring, or a ring assembly) (for example, a monocyclic compound, a fused ring compound, a crosslinked compound, a carbocyclic compound, or a complex). It represents the number of atoms constituting the ring itself of the ring compound). Atoms that do not form a ring and atoms included in the substituent when the ring is substituted by a substituent are not included in the number of ring-forming atoms. The "number of ring-forming atoms" described below shall be the same unless otherwise specified. For example, the pyridine ring has 6 ring-forming atoms, the quinazoline ring has 10 ring-forming atoms, and the furan ring has 5 ring-forming atoms. Hydrogen atoms bonded to carbon atoms of the pyridine ring and quinazoline ring and atoms constituting substituents are not included in the number of ring-forming atoms. When, for example, a fluorene ring is bonded to the fluorene ring as a substituent (including a spirofluorene ring), the number of atoms of the fluorene ring as a substituent is not included in the number of ring-forming atoms.

In the present specification, the "carbon number XX to YY" in the expression "ZZ group having substituted or unsubstituted carbon number XX to YY" represents the carbon number when the ZZ group is unsubstituted, and is substituted. If so, the carbon number of the substituent is not included.
In the present specification, the "atomic number XX to YY" in the expression "ZZ group of atomic number XX to YY substituted or unsubstituted" represents the number of atoms when the ZZ group is unsubstituted, and is substituted. If so, the number of atoms of the substituent is not included.
In the present specification, the term "unsubstituted" in the case of "substituted or unsubstituted" means that the substituent is not substituted and a hydrogen atom is bonded.

Each group represented by each of the above formulas will be described in detail below.

Examples of the aromatic hydrocarbon group (aryl group) include a phenyl group, a naphthyl group, an anthryl group, a phenanthryl group, a naphthacenyl group, a pyrenyl group, a chrysenyl group, a benzo [c] phenanthryl group, a benzo [g] chrysenyl group and a triphenylenyl group. Examples thereof include a group, a fluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a biphenylyl group, an o-terphenyl group, an m-terphenyl group, a p-terphenyl group, a fluoranthenyl group and the like.
The aromatic hydrocarbon group preferably has a ring-forming carbon number of 6 to 20, and more preferably 6 to 12.
Examples of the divalent or higher aromatic hydrocarbon group include divalent or higher valent groups corresponding to the above-mentioned examples of aryl groups.

Examples of the aromatic heterocyclic group (heteroaryl group) include pyrrolyl group, furyl group, thienyl group, pyridyl group, imidazole pyridyl group, pyridazinyl group, pyrimidinyl group, pyrazinyl group, triazinyl group, imidazolyl group, oxazolyl group and thiazolyl group. Group, pyrazolyl group, isooxazolyl group, isothiazolyl group, oxadiazolyl group, thiadiazolyl group, triazolyl group, tetrazolyl group, indolyl group, isoindryl group, benzofuranyl group, isobenzofuranyl group, benzothiophenyl group, isobenzothiophenyl group, indridinyl Group, quinolidinyl group, quinolyl group, isoquinolyl group, cinnolyl group, phthalazinyl group, quinazolinyl group, quinoxalinyl group, benzimidazolyl group, benzoxazolyl group, benzthiazolyl group, indazolyl group, benzisoxazolyl group, benzisothiazolyl Group, dibenzofuranyl group, dibenzothiophenyl group, carbazolyl group, 9-phenylcarbazolyl group, phenanthridinyl group, acridinyl group, phenanthrolinyl group, phenazinyl group, phenothiazine group, phenoxadinyl group or xanthenyl group And so on.
The number of ring-forming atoms of the aromatic heterocyclic group is preferably 5 to 20, and more preferably 5 to 14.
Examples of the divalent or higher aromatic heterocyclic group include divalent or higher valent groups corresponding to the above-mentioned examples of heteroaryl groups.

The above "carbazolyl group" also includes the following structures.

The heteroaryl group also includes the following structures.
(In the formula, X ^{1 to} X ⁶ and Y ^{1 to} Y ⁶ are oxygen atoms, sulfur atoms, nitrogen atoms or -NH- groups, respectively.)

The substituents of "substituted or unsubstituted ..." and "substituent" include halogen atoms, cyano groups, substituted or unsubstituted alkyl groups having 1 to 15 carbon atoms, and substituted or unsubstituted carbon atoms. 3 to 15 cyclic alkyl groups, substituted or unsubstituted alkylsilyl groups with 1 to 45 carbon atoms, substituted or unsubstituted arylsilyl groups with 6 to 50 carbon atoms, substituted or unsubstituted alkoxy having 1 to 15 carbon atoms. Group, substituted or unsubstituted ring-forming aryloxy group with 6 to 30 carbon atoms, substituted or unsubstituted alkylthio group with 1 to 15 carbon atoms, substituted or unsubstituted ring-forming arylthio group with 6 to 30 carbon atoms, substituted Alternatively, an arylamino group having 6 to 30 unsubstituted ring-forming carbon atoms, an aryl group having 6 to 30 substituted or unsubstituted ring-forming carbon atoms, or a heteroaryl group having 5 to 30 substituted or unsubstituted ring-forming atoms, etc. Can be mentioned.

The "substituents" of R _{1 to} R _{10 of} the formula (A1) and R _{101 to} R ₁₁₀ of the formula (A2) are halogen atoms, cyano groups, substituted or unsubstituted alkyl groups having 1 to 15 carbon atoms, substituted or substituted. An unsubstituted cyclic alkyl group having 3 to 15 carbon atoms, a substituted or unsubstituted alkylsilyl group having 1 to 45 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 15 carbon atoms, or a substituted or unsubstituted carbon number. It may be 1 to 15 alkylthio groups.

These substituents may be further substituted by the above substituents. Further, a plurality of these substituents may be bonded to each other to form a ring.

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

Alkyl groups include methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, s-butyl group, isobutyl group, t-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, Examples thereof include an n-octyl group.
The number of carbon atoms of the alkyl group is preferably 1 to 10, and more preferably 1 to 6. Of these, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, s-butyl group, isobutyl group, t-butyl group, n-pentyl group and n-hexyl group are preferable.

Examples of the cyclic alkyl group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a 4-methylcyclohexyl group, an adamantyl group, a norbornyl group and the like. The number of ring-forming carbons is preferably 3 to 10, more preferably 5 to 8, more preferably 3 to 8 ring-forming carbons, and particularly preferably 3 to 6 ring-forming carbons.

Alkylsilyl group is represented as -SiY _3, include examples of each of the above alkyl Examples of Y. Examples of the alkylsilyl group include a trimethylsilyl group, a triethylsilyl group, a t-butyldimethylsilyl group, a vinyldimethylsilyl group, a propyldimethylsilyl group, a triisopropylsilyl group and the like.

The arylsilyl group is a silyl group substituted with 1 to 3 aryl groups, and examples of the aryl group include the above-mentioned aryl examples. In addition to the aryl group, the above alkyl group may be substituted. Examples of the arylsilyl group include a triphenylsilyl group and a phenyldimethylsilyl group.

The alkoxy group is represented as -OY, and examples of Y include the above-mentioned alkyl examples. The alkoxy group is, for example, a methoxy group or an ethoxy group.

The aryloxy group is represented as -OZ, and examples of Z include the above-mentioned examples of aryl groups. The aryloxy group is, for example, a phenoxy group.

The alkylthio group is represented as -SY, and examples of Y include the above alkyl examples.
The arylthio group is represented as -SZ, and examples of Z include the above-mentioned examples of aryl groups.

Arylamino group is represented as -NZ _2, examples of the above aryl groups as examples of Z.
Aryl groups and heteroaryl groups are as described above.

Examples of the compound according to one aspect of the present invention are shown below.

2. 2. Organic EL Element A schematic diagram of the organic EL element according to one aspect of the present invention is shown in FIG.
The organic EL element 1 is provided with a first electrode 20, an organic layer 30B, a second electrode 40, and a capping layer 50 in this order on a substrate 10, and is configured to extract light from the capping layer 50 side. .. In this embodiment, the organic layer 30B is a three-layer organic layer composed of a first organic layer 32B, a blue light emitting layer 34B, and a second organic layer 36B, but the configuration is not limited to this and can be appropriately changed.
Hereinafter, each layer constituting the organic EL element will be described.

(1) Capping layer The capping layer is an organic layer constituting a laminated body of organic EL elements, and is a layer provided on the second electrode. In one embodiment of the present invention, the luminous efficiency of the organic EL device can be improved by using a specific compound for the capping layer.
The film thickness of the capping layer is preferably 200 nm or less, more preferably 40 to 100 nm.

(2) First Electrode As the material of the first electrode, a metal such as Ag, Al or Au or a metal alloy such as APC (Ag-Pd-Cu) is preferable. These metal materials and metal alloys may be laminated. Further, a transparent electrode layer such as indium tin oxide (ITO) or indium zinc oxide may be formed on the upper surface and / or lower surface of a metal, a metal alloy or a laminate thereof.

(3) Second electrode As the second electrode, a metallic material can be used. A metallic material is one in which the real part of the dielectric constant is a negative value. Such materials include not only metals but also organic / inorganic transparent electrode materials exhibiting metallic luster other than metals.
As the metal, materials such as Ag, Mg, Al, and Ca and those formed of alloys thereof are preferable. Further, in order to extract light in the front direction of the element while having a resonance function, it is preferable that the transmittance in the front direction is 20% or more and the light is translucent. When Ag, Mg, Al, Ca or an alloy thereof is used as the second electrode, the film thickness is preferably 30 nm or less in order to exhibit sufficient light transmission.

(4) Organic layer The organic layer is not particularly limited as long as it includes a light emitting layer, and for example, a multilayer film structure composed of a first organic layer / a light emitting layer / a second organic layer can be used. Specific examples thereof include a multilayer film structure composed of an anode / hole transport band / light emitting layer / electron transport band / cathode.
The hole transport zone is composed of a single layer or a plurality of layers of a hole injection layer and a hole transport layer. The electron transport band is composed of a single layer or a plurality of layers of an electron injection layer and an electron transport layer.

(Hole injection layer)
The hole injection layer is a layer containing a substance having a high hole injection property. Substances with high hole injection properties include molybdenum oxide, titanium oxide, vanadium oxide, renium oxide, ruthenium oxide, chromium oxide, zirconium oxide, hafnium oxide, tantalum oxide, silver oxide, etc. Tungsten oxides, manganese oxides, aromatic amine compounds, polymer compounds (oligoforms, dendrimers, polymers, etc.) and the like can also be used.

(Hole transport layer)
The hole transport layer is a layer containing a substance having a high hole transport property. An aromatic amine compound, a carbazole derivative, an anthracene derivative, or the like can be used for the hole transport layer. Polymer compounds such as poly (N-vinylcarbazole) (abbreviation: PVK) and poly (4-vinyltriphenylamine) (abbreviation: PVTPA) can also be used. However, any substance other than these may be used as long as it is a substance having a higher hole transport property than electrons. The layer containing a substance having a high hole transport property is not limited to a single layer, but may be a layer in which two or more layers made of the above substances are laminated.

(Guest material of light emitting layer)
The light emitting layer is a layer containing a substance having high light emitting property, and various materials can be used. For example, as a substance having high luminescence, a fluorescent compound that emits fluorescence or a phosphorescent compound that emits phosphorescence can be used. A fluorescent compound is a compound capable of emitting light from a singlet excited state, and a phosphorescent compound is a compound capable of emitting light from a triplet excited state.
As the blue-based fluorescent light emitting material that can be used for the light emitting layer, a pyrene derivative, a styrylamine derivative, a chrysene derivative, a fluoranthene derivative, a fluorene derivative, a diamine derivative, a triarylamine derivative and the like can be used. As a green fluorescent light emitting material that can be used for the light emitting layer, an aromatic amine derivative or the like can be used. As a red fluorescent light emitting material that can be used for the light emitting layer, a tetracene derivative, a diamine derivative, or the like can be used.
As a blue phosphorescent material that can be used for the light emitting layer, a metal complex such as an iridium complex, an osmium complex, or a platinum complex is used. An iridium complex or the like is used as a green phosphorescent material that can be used for the light emitting layer. As a red phosphorescent material that can be used for the light emitting layer, a metal complex such as an iridium complex, a platinum complex, a terbium complex, or a europium complex is used.

(Host material for light emitting layer)
The light emitting layer may have a structure in which the above-mentioned highly luminescent substance (guest material) is dispersed in another substance (host material). Various substances can be used as the substance for dispersing the highly luminescent substance, and the lowest empty orbital level (LUMO level) is higher than the highly luminescent substance, and the highest occupied orbital level (maximum occupied orbital level). It is preferable to use a substance having a low HOMO level).
Examples of the substance (host material) for dispersing a highly luminescent substance include 1) a metal complex such as an aluminum complex, a berylium complex, or a zinc complex, and 2) an oxadiazole derivative, a benzoimidazole derivative, a phenanthroline derivative, or the like. Complex aromatic compounds such as heterocyclic compounds, 3) carbazole derivatives, anthracene derivatives, phenanthrene derivatives, pyrene derivatives, or chrysene derivatives, 3) aromatic amine compounds such as triarylamine derivatives or condensed polycyclic aromatic amine derivatives. used.

(Electronic transport layer)
The electron transport layer is a layer containing a substance having a high electron transport property. The electron transport layer includes 1) a metal complex such as an aluminum complex, a berylium complex, and a zinc complex, 2) a complex aromatic compound such as an imidazole derivative, a benzimidazole derivative, an azine derivative, a carbazole derivative, and a phenanthroline derivative, and 3) a polymer compound. Can be used.

(Electron injection layer)
The electron injection layer is a layer containing a substance having a high electron injection property. The electron injection layer contains alkali metals such as lithium (Li), lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF ₂ ), lithium oxide (LiOx), and alkaline earth metals. , Or their compounds can be used.

(5) Substrate The substrate is used as a support for a light emitting element. As the substrate, for example, glass, quartz, plastic or the like can be used. Moreover, you may use a flexible substrate. The flexible substrate is a bendable (flexible) substrate, and examples thereof include a plastic substrate made of polycarbonate and polyvinyl chloride.

The organic EL element according to one aspect of the present invention can be used for a flat light emitter such as a flat panel display of a wall-mounted television, a copying machine, a printer, a backlight of a liquid crystal display or a light source such as an instrument, a display board, an indicator light and the like. ..

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited thereto. Compounds 1 to 4 and Comparative Compound 1 used for the capping layer in Examples and Comparative Examples are shown.

Example 1 (Preparation of organic EL element)
Zinc oxide film (IZO) (film thickness 10 nm), APC (Ag-Pd-Cu) layer (reflection layer) (film thickness 100 nm), which is a silver alloy layer, and zinc oxide on a glass substrate to be a substrate for manufacturing elements. A film (IZO) (thickness 10 nm) was formed in this order by a sputtering method. Subsequently, using a normal lithography technique, this conductive material layer was patterned by etching using a resist pattern as a mask to form a lower electrode (anode). The substrate on which the lower electrode was formed was ultrasonically cleaned in isopropyl alcohol for 5 minutes, and then UV ozone cleaning was performed for 30 minutes. Then, using a vacuum vapor deposition method, HI was deposited on the lower electrode with a film thickness of 5 nm as a hole injection layer. Next, HT1 was deposited with a film thickness of 130 nm as the first hole transport layer. Further, following the film formation of the HT1 film, HT2 was deposited with a film thickness of 10 nm as the second hole transport layer. Following the film formation of the second hole transport layer, BH and BD were vapor-deposited at a film thickness of 25 nm at a weight ratio of 95: 5 to form a blue light emitting layer. Then, ET1 having a film thickness of 10 nm was formed on this film as an electron transport layer, and then ET2 having a film thickness of 20 nm was formed. Then, LiF was vapor-deposited on this film as an electron injection layer to form a LiF film with a film thickness of 1 nm. Mg and Ag were vapor-deposited on the LiF film at a film thickness of 10 nm at a film thickness of 9: 1 to form an upper electrode (cathode) made of a semi-transparent MgAg alloy. Next, a capping layer made of compound 1 was formed over the entire surface of the upper electrode to produce an organic EL device. An element having a capping layer thickness of 60 nm was produced.

The materials used in the examples are shown below.

(Evaluation of organic EL element)
The following evaluation was performed on the obtained organic EL device or compound 1.
(1) Refractive index, extinction coefficient, order parameter A material to be measured (Compound 1) is vacuum-deposited on a glass substrate with a film thickness of about 50 nm, and a spectroscopic ellipsometry apparatus (manufactured by JA Woolum (USA)). The measurement was performed every 5 ° in the range of the measurement angle of 45 ° to 75 ° by M-2000UI). In order to improve the measurement accuracy of the extinction coefficient, the transmission spectrum in the normal direction of the substrate (perpendicular to the surface of the organic EL element substrate) was also measured by the apparatus. The measurement of only the glass substrate was performed in the same manner. The obtained measurement information was fitted with the analysis software (Complete EASE) manufactured by the same company. As the fitting conditions, an anisotropic model of uniaxial rotational symmetry is used, and the parameter MSE indicating the square average error in the software is set to 3.0 or less, and the in-plane organic film formed on the substrate is formed. The refractive index in the direction and the normal direction, the extinction coefficient in the in-plane direction and the normal direction, and the order parameter were calculated. The order parameter was calculated based on the peak wavelength of S1 described later. An isotropic model was used for the glass substrate. The results are shown in Table 1. The refractive index and extinction coefficient in Table 1 are values in S1 energy.
In addition, the refractive indexes in the in-plane direction and the normal direction at wavelengths of 430 nm, 460 nm, 480 nm, 500 nm, 530 nm and 600 nm were measured. The results are shown in Table 2.

(2) Current-voltage-luminance characteristic A current is applied to the obtained organic EL element so as to be 10 mA / cm ^2, and the current-voltage-luminance characteristic of EL light emission emitted in the normal direction with respect to the element surface is obtained. The measurement was performed with a spectral radiance meter (CS-1000 manufactured by Konica Minolta), and the emission peak intensity, peak wavelength, and CIE color coordinate values were determined. The results are shown in Table 1.

(3) Singlet energy S1
The peak on the long wavelength side of the extinction coefficient (in-plane direction) was defined as S1. The results are shown in Table 1.

(4) Order parameters A film of a low molecular weight material vacuum-deposited on a substrate usually has uniaxial rotational symmetry with the normal direction of the substrate as the rotation target axis. The angle formed by the molecular axis and the normal direction of the substrate in the thin film formed on the substrate is θ, and the parallel direction (Ordinary direction) and the vertical direction (Extra-Ordinary direction) of the substrate obtained by multi-incident angle spectroscopic ellipsometry measurement of the thin film When the extinction coefficients are ko and ke, respectively, S'represented by the following equation is the order parameter.
S'= 1- <cos2θ> = 2ko / (ke + 2ko) = 2/3 (1-S)
S = (1/2) <3cos2θ-1> = (ke-ko) / (ke + 2ko)
The method for evaluating the molecular orientation is a known method, and the details are described in Organic Electronics, 2009, Vol. 10, p. 127. The method for forming the thin film is a vacuum vapor deposition method.
The order parameter S'obtained from multi-angle spectroscopic ellipsometry measurements is 1.0 when all molecules are oriented parallel to the substrate. Further, when the molecules are not oriented and are random, the value is 0.66.

(5) External Quantum Efficiency The external quantum efficiency EQE (unit:%) was calculated from the obtained spectral radiance spectrum on the assumption that Lambasian radiation was performed. The results are shown in Table 1.

Examples 2-4, Comparative Example 1
As the compound used for the capping layer, an organic EL device was produced and evaluated in the same manner as in Example 1 except that the compound shown in Table 1 was used instead of compound 1. The results are shown in Tables 1 and 2.

From Table 1, it can be seen that the order parameters of Compounds 1 to 4 are closer to 1.0 as compared with Comparative Compound 1. This indicates that the molecules of Compounds 1 to 4 are more parallel to the substrate as compared with Comparative Compound 1. As a result, the organic EL devices obtained in Examples 1 to 4 show higher external quantum yields.
The extinction coefficient of compound 2 is higher than that of comparative compound 1. However, in compound 2, S1 is much larger than that of other materials and is in the ultraviolet light region, and even if the extinction coefficient is high in this region, there is no problem in the light extraction function. The fact that S1 is 3.91 eV means that the extinction coefficient is very small in both the plane direction and the normal direction in the blue wavelength region of 2.8 eV or less and becomes almost zero.

From Table 2, it can be seen that the refractive indexes of Compounds 1 to 4 are higher than those of Comparative Compound 1 at wavelengths of 430 nm to 600 nm. It is suggested that the compound used in the present invention can suppress the absorption of emission energy even on the longer wavelength side than blue.

1 Organic EL element 10 Substrate 20 First electrode 30B Organic layer 32B First organic layer 34B Blue light emitting layer 36B Second organic layer 40 Second electrode 50 Capping layer

Claims (10)

A first electrode, one or more organic layers including a light emitting layer, a second electrode, and a capping layer are provided in this order.
An organic electroluminescence device in which the capping layer contains a compound represented by the following formula (1).
(In the formula (1), A is any of the following formulas (A1-1) to (A1-4) or a group represented by the formula (A2-1).
L is a divalent group represented by any of the following formulas.
n is an integer of 1 to 5, and when n is 2 or more, the plurality of Ls may be the same or different.
HAR is an aromatic heterocyclic group having 5 to 30 substituted or unsubstituted ring-forming atoms.
(In formulas (A1-1) to (A1-4), R _{11 to} R ₂₀ , R _{21 to} R ₃₂ , R _{41 to} R ₅₂ , and R _{61 to} R ₇₂ are hydrogen atoms, substituents, or L, respectively. It is a single bond used for binding with.
In formula (A1-2), R ₃₁ and R ₃₂ may be combined with each other to form a ring. The group represented by the formula (A1-2) may be bonded to L at any position on the ring formed from R ₃₁ and R ₃₂ . )
In formula (A2-1), R _{111 to} R ₁₂₀ are single bonds used for bonding with a hydrogen atom, a substituent, or L, respectively.
In formula (A2-1), one or more combinations selected from R ₁₁₁ and R ₁₁₂ , R ₁₁₂ and R ₁₁₃ , and R ₁₁₆ and R ₁₁₇ may be combined with each other to form a ring. The group represented by the formula (A2-1) may be bonded to L at any position on the ring formed from the combination. ))) The organic electroluminescence device according to claim 1, wherein A is represented by the above formula (A1-3). The organic electroluminescence device according to claim 1, wherein A is represented by any of the following formulas (A1-11) to (A1-16).
(In formulas (A1-11) to (A1-16), R is a single bond used for bonding with a substituent or L. m1 is an integer of 1 to 9, and m2 is an integer of 1 to 11. Yes, m3 is an integer of 1 to 13, m4 is an integer of 1 to 14. R is bonded to any position on the fused ring represented by the formulas (A1-11) to (A1-16). You may.) The organic electroluminescence device according to claim 1, wherein the group represented by the formula (A2-1) is represented by any of the following formulas (A2-11) to (A2-15).
(In formulas (A2-11) to (A2-15), R is a single bond used for bonding with a substituent or L. m11 is an integer of 1 to 9, and m12 is an integer of 1 to 11. Yes, m13 is an integer of 1-12. R may be bonded to any position on the fused ring represented by the formulas (A2-11) to (A2-15).) HAR
Substituted or unsubstituted, monocyclic aromatic heterocyclic groups,
Sulfur-containing aromatic heterocyclic group or oxygen-containing aromatic heterocyclic group in which two rings are condensed, either substituted or unsubstituted.
Nitrogen-containing aromatic heterocyclic groups in which two 6-membered rings are condensed, either substituted or unsubstituted.
Sulfur-containing aromatic heterocyclic groups or oxygen-containing aromatic heterocyclic groups in which three rings are condensed, either substituted or unsubstituted.
Any of claims 1 to 4, which is a substituted or unsubstituted, nitrogen-containing aromatic heterocyclic group in which three 6-membered rings are condensed, or a group represented by the following formulas (HAr-1) to (HAR-4). The organic electroluminescence element described in Crab.
(In formulas (HAr-1) to (HAR-4), X _{1 to} X ₇ , X _{11 to} X ₂₁ , and X _{31 to} X ₃₉ are nitrogen atoms, NR'or CR', respectively. R'is A single bond used to bond with a hydrogen atom, substituent, or L.) HAR is substituted or unsubstituted, pyrrolyl group, furyl group, thienyl group, pyridyl group, imidazole pyridyl group, pyridazinyl group, pyrimidinyl group, pyrazinyl group, triazinyl group, imidazolyl group, oxazolyl group, thiazolyl group, pyrazolyl group, isooxazolyl. Group, isothiazolyl group, oxadiazolyl group, thiadiazolyl group, triazolyl group, tetrazolyl group, indolyl group, isoindrill group, benzofuranyl group, isobenzofuranyl group, benzothiophenyl group, isobenzothiophenyl group, quinolidinyl group, quinolyl group, isoquinolyl Group, cinnolyl group, phthalazinyl group, quinazolinyl group, quinoxalinyl group, benzimidazolyl group, benzoxazolyl group, benzthiazolyl group, indazolyl group, benzisoxazolyl group, benzisothiazolyl group, dibenzofuranyl group, dibenzothiol group Any of claims 1 to 5, which is a phenyl group, a carbazolyl group, a 9-phenylcarbazolyl group, a phenanthridinyl group, an acridinyl group, a phenanthrolinyl group, a phenazinyl group, a phenothiazine group, a phenoxadinyl group or a xanthenyl group. The organic electroluminescence element described in Crab. HAR is substituted or unsubstituted, pyridyl group, imidazole pyridyl group, pyridazinyl group, pyrimidinyl group, pyrazinyl group, triazinyl group, benzimidazolyl group, dibenzofuranyl group, dibenzothiophenyl group, carbazolyl group, 9-phenylcarbazoli The organic electroluminescence element according to claim 6, which is a group of phenyl, a group of phenylurinyl, or a group of quinazolinyl. The organic electroluminescence device according to any one of claims 1 to 7, which has an electron transport layer between the light emitting layer and the second electrode. The organic electroluminescence device according to any one of claims 1 to 8, which has a hole transport layer between the light emitting layer and the first electrode. An electronic device equipped with the organic electroluminescence device according to any one of claims 1 to 9.