JP2016092280A - Luminescent thin film, organic electroluminescent element, illuminating device and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a luminescent thin film superior in emission lifetime; an organic electroluminescent element including the light emission thin film; a display device with the organic electroluminescent element; and an illuminating device.SOLUTION: A luminescent thin film of the present invention comprises: a luminescent compound of which the absolute value (ΔEst) of an energy difference between the lowest excited singlet energy and the lowest excited triplet energy is 0.5 eV or less; and a compound having a structure expressed by the general formula (I).SELECTED DRAWING: None

Description

  The present invention relates to a light-emitting thin film, an organic electroluminescence element, a display device, and a lighting device. More specifically, the present invention relates to a light-emitting thin film having an excellent light emission lifetime, an organic electroluminescence element using the same, a display device, and a lighting device.

An organic electroluminescence element (hereinafter also referred to as an organic EL element) has a configuration in which a luminescent thin film (luminescent layer) containing a luminescent compound is sandwiched between a cathode and an anode, and by applying an electric field, Excitons are generated by recombining holes injected from the anode and electrons injected from the cathode in the light emitting layer, and light is emitted when the excitons are deactivated (fluorescence / phosphorescence). It is a light emitting element using An organic EL element is an all-solid-state element composed of an organic material film having a thickness of only a submicron between electrodes, and can emit light at a voltage of several volts to several tens of volts. It is expected to be used for next-generation flat display and lighting.
As for the development of organic EL elements for practical use, Princeton University has reported organic EL elements that use phosphorescence emission from excited triplets, and since then, active research has been conducted on materials that exhibit phosphorescence at room temperature. It is becoming.
In addition, organic EL elements that utilize phosphorescence can in principle achieve a light emission efficiency that is approximately four times that of organic EL elements that utilize previous fluorescence. Research and development of device layer configurations and electrodes are performed all over the world.

  However, the phosphorescence emission method is a very high potential method, but in order to actually obtain high quantum efficiency in the phosphorescence emission method, it is necessary to use a complex using a rare metal such as iridium or platinum as the central metal. There is concern that the reserves of rare metals and the price of the metals themselves will become a major industrial issue in the future.

On the other hand, various developments have been made to improve the light emission efficiency in the fluorescent light emitting type, and a new movement has recently been made.
For example, reverse intersystem crossing from triplet excitons to singlet excitons (hereinafter referred to as “RISC” where appropriate) (thermally activated delayed fluorescence (“thermal excitation”)) occurs. (Also referred to as “type delayed fluorescence”): Thermally Activated Delayed Fluorescence (hereinafter abbreviated as “TADF” where appropriate), and the possibility of its use in organic EL devices has been reported (for example, , See Patent Document 1).

As shown in FIG. 1, the TADF mechanism is a material in which the difference (ΔEst) between the excited singlet energy and the excited triplet energy is smaller than that of a general fluorescent compound (in FIG. 1, ΔEst (TADF) is ΔEst (F ) Is a light emission mechanism that utilizes the phenomenon that reverse intersystem crossing from triplet excitons to singlet excitons occurs.
That is, since ΔEst is small, triplet excitons generated with a probability of 75% due to electric field excitation cannot contribute to light emission originally, but transition to a singlet excited state by thermal energy at the time of driving an organic EL element, From that state to the ground state, radiation is deactivated (also referred to as “radiation transition” or “radiation deactivation”), and fluorescence is emitted. If delayed fluorescence due to the TADF mechanism is used, it is considered that 100% internal quantum efficiency is theoretically possible even in fluorescence emission.

Furthermore, when a light emitting layer composed of a host compound and a light emitting compound contains a compound showing TADF (hereinafter also referred to as “TADF compound”) as a third component (assist dopant) in the light emitting layer, high light emission efficiency is exhibited. It is known that it is effective for (see, for example, Non-Patent Document 1). By generating 25% singlet excitons and 75% triplet excitons on the assist dopant by electric field excitation, the triplet excitons generate singlet excitons with reverse intersystem crossing (RISC). be able to.
The energy of the singlet exciton can be transferred to the luminescent compound by fluorescence resonance energy transfer (hereinafter abbreviated as “FRET” as appropriate), and light can be emitted by the energy transferred from the luminescent compound. It becomes. Therefore, theoretically, 100% exciton energy can be used to cause the luminescent compound to emit light, and high luminous efficiency is exhibited.

  As described above, in recent years, a light-emitting layer using a host compound and a light-emitting compound or a compound exhibiting TADF properties as an assist dopant has attracted attention, and various development studies have been conducted to achieve high light emission efficiency. However, on the other hand, the light emission lifetime has not been sufficiently studied, and satisfactory performance has not been obtained.

JP2013-116975A

H. Nakatanani, et al. , Nature Communication, 2014, 5, 4016-4022.

  The present invention has been made in view of the above-described problems and circumstances, and a solution to the problem is that a light-emitting thin film having an excellent light emission lifetime, an organic electroluminescence element including the light-emitting thin film, and the organic electroluminescence element are provided. Display device and lighting device.

In order to solve the above-mentioned problems, the inventors of the present invention provide a combination of a luminescent compound contained as a component constituting a composition for forming a luminescent thin film and a compound represented by the general formula (I). Focusing on the possibility that aggregation can be suppressed and the luminescence lifetime can be improved, and as a result of thorough examination on matching of the luminescent compound with the compound represented by the general formula (I), it is represented by the general formula (I). The present inventors have found that the above problem can be solved by appropriately selecting a compound having a structure to be achieved, and have reached the present invention.
That is, the said subject which concerns on this invention is solved by the following means.

[式中、Ｘ_１０１は、ＮＲ_１０１、酸素原子、硫黄原子、ＣＲ_１０２Ｒ_１０３又はＳｉＲ_１０２Ｒ_１０３を表す。ｙ_１〜ｙ_８は、各々、ＣＲ_１０４又は窒素原子を表す。Ｒ_１０１〜Ｒ_１０４は、各々、水素原子又は置換基を表し、互いに結合して環を形成してもよい。Ａｒ_１０１及びＡｒ_１０２は、各々、芳香族環を表し、それぞれ同一でも異なっていてもよい。ｎ１０１及びｎ１０２は、各々、０〜４の整数を表す。] 1. Contains a light-emitting compound whose absolute value (ΔEst) of energy difference between the lowest excited singlet energy and the lowest excited triplet energy is 0.5 eV or less, and a compound having a structure represented by the following general formula (I) A luminescent thin film characterized by:

[Wherein, X ₁₀₁ represents NR ₁₀₁ , an oxygen atom, a sulfur atom, CR ₁₀₂ R ₁₀₃ or SiR ₁₀₂ R ₁₀₃ . y _{1 to} y ₈ each represent CR ₁₀₄ or a nitrogen atom. R _{101 to} R ₁₀₄ each represent a hydrogen atom or a substituent, and may be bonded to each other to form a ring. Ar ₁₀₁ and Ar ₁₀₂ each represent an aromatic ring and may be the same or different. n101 and n102 each represent an integer of 0 to 4. ]

  2. 2. The light-emitting thin film according to item 1, wherein the light-emitting compound is a TADF compound and the compound having the structure represented by the general formula (I) is a host compound.

  3. An organic electroluminescence device comprising the luminescent thin film according to item 1 or 2 as a light emitting layer between an anode and a cathode.

  4). 4. At least one layer of the light emitting layer contains the TADF compound, the host compound, and at least one luminescent compound among a fluorescent compound and a phosphorescent compound. Organic electroluminescence element.

［式中、Ｘ_１０１、Ａｒ_１０１、Ａｒ_１０２、及びｎ１０２は、それぞれ、前記一般式（Ｉ）におけるＸ_１０１、Ａｒ_１０１、Ａｒ_１０２、及びｎ１０２と同義である。］ 5. Item 5. The organic electroluminescence device according to Item 3 or 4, wherein the host compound has a structure represented by the following general formula (II).

_{Wherein, X 101, Ar 101, Ar 102} , and n102, respectively, the same meanings as _{X 101, Ar 101, Ar 102} , and n102 in formula (I). ]

［式中、Ｘ_１０１、Ａｒ_１０２及びｎ１０２は、それぞれ、前記一般式（Ｉ）におけるＸ_１０１、Ａｒ_１０１、Ａｒ_１０２、及びｎ１０２と同義である。］ 6). 6. The organic electroluminescence device according to any one of items 3 to 5, wherein the host compound has a structure represented by the following general formula (III).

_Wherein, X _{101, Ar 102} and n102, respectively, the same meanings as _{X 101, Ar 101, Ar 102} , and n102 in formula (I). ]

7). 7. The organic electroluminescence device according to item 6, wherein Ar ₁₀₂ in the general formula (III) is a substituted or unsubstituted carbazole ring.

［一般式（１）において、Ａｒ¹〜Ａｒ^３は、各々独立に、置換又は無置換のアリール基を表し、少なくとも１つは下記一般式（２）で表される構造を有する基で置換されたアリール基を表す。］

［一般式（２）において、Ｒ^１〜Ｒ^８は、各々独立に、水素原子又は置換基を表す。Ｚは、Ｏ、Ｓ、Ｏ＝Ｃ、Ａｒ^４−Ｎ、又は化学結合を表す。Ａｒ^４は、置換又は無置換のアリール基を表す。Ｒ^１〜Ｒ^８のうち隣り合う基同士は、互いに結合を形成、又は、連結基を介して環を形成してもよい。］

［一般式（３）において、Ｒ^１〜Ｒ^５の少なくとも１つは、シアノ基を表し、Ｒ^１〜Ｒ^５の少なくとも１つは下記一般式（４）で表される構造を有する基を表し、残りのＲ^１〜Ｒ^５は水素原子又は置換基を表す。］

［一般式（４）において、Ｒ^２１〜Ｒ^２８は、各々独立に、水素原子又は置換基を表す。ただし、下記要件＜Ａ＞か＜Ｂ＞の少なくとも一方を満たす。
＜Ａ＞Ｒ^２５及びＲ^２６は、単結合を形成する。
＜Ｂ＞Ｒ^２７及びＲ^２８は、置換又は無置換のベンゼン環を形成するのに必要な原子団を表す。］

［一般式（５）において、Ｒ^１及びＲ^２は、各々独立に、下記一般式（６）で表される構造を有する基である。］

［一般式（６）において、Ｒ^１〜Ｒ^８は、各々独立に、水素原子又は置換基を表す。Ｚは、Ｏ、Ｓ、Ｏ＝Ｃ、Ａｒ^４−Ｎ、又は結合を表す。Ａｒ^４は、置換又は無置換のアリール基を表す。Ｒ^１〜Ｒ^８のうち隣り合う基同士は、互いに結合を形成、又は、連結基を介して環を形成してもよい。］ 8). The TADF compound has a structure represented by any one of the following general formulas (1), (3), or (5), according to any one of items 3 to 7 The organic electroluminescent element of description.

[In General Formula (1), Ar ^{1 to} Ar ³ each independently represents a substituted or unsubstituted aryl group, and at least one of them is substituted with a group having a structure represented by the following General Formula (2). Represents an aryl group. ]

[In General formula (2), R < ¹ > -R < ⁸ > represents a hydrogen atom or a substituent each independently. Z represents O, S, O═C, Ar ⁴ —N, or a chemical bond. Ar ⁴ represents a substituted or unsubstituted aryl group. Adjacent groups among R ^{1 to} R ⁸ may form a bond with each other or form a ring via a linking group. ]

[In the general formula ^(3), at least one of R 1 to R ⁵ represents a cyano ^group, at least one of R 1 to R ⁵ is a group having the structure represented by the following general formula (4) The remaining R ^{1 to} R ⁵ represent a hydrogen atom or a substituent. ]

[In the general formula ^{(4), R} 21 ~R ²⁸ independently represents a hydrogen atom or a substituent. However, at least one of the following requirements <A> or <B> is satisfied.
<A> R ²⁵ and R ²⁶ form a single bond.
<B> R ²⁷ and R ²⁸ represent an atomic group necessary for forming a substituted or unsubstituted benzene ring. ]

[In General Formula (5), R ¹ and R ² are each independently a group having a structure represented by the following General Formula (6). ]

[In General formula (6), R < ¹ > -R < ⁸ > represents a hydrogen atom or a substituent each independently. Z represents O, S, O═C, Ar ⁴ —N, or a bond. Ar ⁴ represents a substituted or unsubstituted aryl group. Adjacent groups among R ^{1 to} R ⁸ may form a bond with each other or form a ring via a linking group. ]

  9. A display device comprising the organic electroluminescence element according to any one of items 3 to 8.

10. An illuminating device comprising the organic electroluminescence element according to any one of items 3 to 8.

11. A lighting device according to item 10 and a display device comprising a liquid crystal element as a display means.

By the above means of the present invention, it is possible to provide a light-emitting thin film having an excellent light emission lifetime, an organic electroluminescence element including the light-emitting thin film, and a display device and a lighting device including the organic electroluminescence element.
The expression mechanism or action mechanism of the effect of the present invention is not clear, but is presumed as follows.
In a conventional organic electroluminescence device, it is presumed that the reason why a sufficient emission lifetime cannot be obtained is agglomeration of a luminescent compound or a host compound contained as a composition for forming a luminescent thin film. That is, it is considered that the aggregation of the composition is caused by activation of molecular motion of the luminescent compound or the host compound when the luminescent thin film is formed or when a driving current is applied. In particular, when the luminescent compound contained in the composition is aggregated, it is considered that a phenomenon such as excimer fluorescence in which excitons form a complex to emit light.
In the present invention, the combination of the luminescent compound and the compound having the structure represented by the general formula (I) allows the compound molecules themselves to be non-planar and the chemical structure difference between the two compounds. It is considered that aggregation was prevented by the property and steric hindrance.
Furthermore, by using a compound having a structure represented by any one of the general formulas (1), (3), or (5) as the TADF compound, aggregation of the compound is prevented and ΔEst is reduced. It is thought that it was possible.
As described above, according to the means of the present invention, it is possible to prevent aggregation of the compound having the structure represented by the general formula (I) and the luminescent compound (TADF compound), and to reduce ΔEst, so that organic It is assumed that the light emission lifetime of the EL element is improved.

Schematic diagram showing energy diagrams of normal fluorescent compounds and TADF compounds

The organic electroluminescence device of the present invention includes a luminescent compound having an absolute value (ΔEst) of an energy difference of 0.5 eV or less between the lowest excited singlet energy and the lowest excited triplet energy, and the following general formula (I): It contains a compound having the structure represented. This feature is a technical feature common to the inventions according to claims 1 to 11.
As an embodiment of the present invention, from the viewpoint of manifesting the effects of the present invention, the luminescent compound is a TADF compound, and the compound having the structure represented by the general formula (I) is a host compound. preferable.
The luminescent thin film of the present invention can be suitably used as a light emitting layer between an anode and a cathode in an organic electroluminescence element.
As the organic electroluminescence element of the present invention, from the viewpoint of expression of the effect of the present invention,
It is preferable that at least one layer of the light emitting layer contains the TADF compound, the host compound, and at least one light emitting compound among a fluorescent compound and a phosphorescent compound. The host compound preferably has a structure represented by the general formula (II). Furthermore, it is preferable that the host compound has a structure represented by the general formula (III) from the viewpoint of preventing aggregation of the compound and transportability of electrons and holes. Furthermore, Ar ₁₀₂ in the general formula (III) is preferably a substituted or unsubstituted carbazole ring from the same viewpoint as described above.
The TADF compound preferably has a structure represented by any one of the general formulas (1), (3), and (5) from the viewpoint of preventing aggregation of the compound and reducing ΔEst.
The organic electroluminescent element of this invention is used suitably for a display apparatus and an illuminating device.
The illumination device of the present invention is suitably used for a display device provided with a liquid crystal element as a display means.
Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In addition, in this application, "-" is used in the meaning which includes the numerical value described before and behind that as a lower limit and an upper limit.

<Luminescent thin film>
The luminescent thin film of the present invention is represented by a luminescent compound having an absolute value (ΔEst) of an energy difference between the lowest excited singlet energy and the lowest excited triplet energy of 0.5 eV or less, and the following general formula (I). And a compound having a structure as described above.
As an embodiment of the light-emitting thin film of the present invention, the light-emitting compound is preferably a TADF compound, and the compound having a structure represented by the general formula (I) is preferably a host compound.

(Host compound)
When a TADF compound is used as the light-emitting compound, since the existence time of the triplet excited state is long, the lowest excited triplet energy of the host compound itself (T ₁ : “lowest triplet energy”, “triplet energy”, and , Simply referred to as “triplet state”), not having a low T ₁ state (state in which the lowest triplet energy is reduced) in a state where the host compounds are associated with each other, and a TADF compound the host compound and do not form an exciplex, such that the host compound does not form a electro-mer by the electric field, appropriate design is required of the molecular structure, such as a host compound does not lower T ₁ reduction (decrease lowest triplet energy) It becomes.
In order to satisfy these requirements, the host compound itself must have high electron hopping mobility, high hole hopping movement, and small structural change when it is in a triplet excited state. It is. Representative examples of host compounds that satisfy these requirements include a carbazole skeleton, an azacarbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, or an azadibenzofuran skeleton, which have a high minimum triplet energy and an extended π-conjugated skeleton having a 14π electron system. Preferred are those having a partial structure. In particular, when the light emitting layer contains a carbazole derivative, it is possible to promote appropriate carrier hopping and dispersion of the light emitting compound in the light emitting layer, and the effect of improving the light emitting performance of the device and the stability of the thin film can be obtained. Therefore, it is preferable.

Further, representative examples include compounds in which these rings have a biaryl and / or multiaryl structure. As used herein, “aryl” includes not only an aromatic hydrocarbon ring but also an aromatic heterocyclic ring.
More preferably, it is a compound in which a carbazole skeleton and a 14π-electron aromatic heterocyclic compound having a molecular structure different from that of the carbazole skeleton are directly bonded, and further a 14π-electron aromatic heterocyclic compound is incorporated in the molecule. A carbazole derivative having at least one is preferred. In particular, the carbazole derivative is preferably a compound having two or more conjugated structures having 14π electrons or more in order to further enhance the effects of the present invention.

The host compound according to the present invention is represented by the following general formula (I). In general, a condensed aromatic ring tends to have a low triplet energy (T ₁ ), but a compound represented by the general formula (I) has a high minimum triplet energy T ₁ and has a short emission wavelength (ie, It can be suitably used for a light-emitting compound having a high T ₁ and S ₁ .

In the general formula (I), X ₁₀₁ represents NR ₁₀₁ , an oxygen atom, a sulfur atom, CR ₁₀₂ R ₁₀₃ or SiR ₁₀₂ R ₁₀₃ . y _{1 to} y ₈ each represents CR ₁₀₄ or a nitrogen atom.

R _{101 to} R ₁₀₄ each represent a hydrogen atom or a substituent, and may be bonded to each other to form a ring.

Ar ₁₀₁ and Ar ₁₀₂ each represent an aromatic ring and may be the same or different.

  n101 and n102 each represent an integer of 0 to 4.

R _{101 to} R ₁₀₄ in the general formula (I) represent hydrogen or a substituent, and the substituent here refers to what may be contained within a range not inhibiting the function of the host compound used in the present invention, for example, In the case where a substituent is introduced in the synthesis scheme, the compound having the effect of the present invention is defined as being included in the present invention.

Examples of the substituent represented by each of R _{101 to} R ₁₀₄ include a linear or branched alkyl group (for example, methyl group, ethyl group, propyl group, isopropyl group, t-butyl group, pentyl group, hexyl group, octyl group). Group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, etc.), alkenyl group (eg, vinyl group, allyl group, etc.), alkynyl group (eg, ethynyl group, propargyl group, etc.), aromatic hydrocarbon ring group (aromatic Also called carbocyclic group, aryl group, etc. For example, benzene ring, biphenyl, naphthalene ring, azulene ring, anthracene ring, phenanthrene ring, pyrene ring, chrysene ring, naphthacene ring, triphenylene ring, o-terphenyl ring, m- Terphenyl ring, p-terphenyl ring, acenaphthene ring, coronene ring, indene ring, fluorene ring A group derived from a fluoranthrene ring, a naphthacene ring, a pentacene ring, a perylene ring, a pentaphen ring, a picene ring, a pyrene ring, a pyrantolen ring, an anthraanthrene ring, tetralin, etc.), an aromatic heterocyclic group (for example, a furan ring) , Dibenzofuran ring, thiophene ring, dibenzothiophene ring, oxazole ring, pyrrole ring, pyridine ring, pyridazine ring, pyrimidine ring, pyrazine ring, triazine ring, benzimidazole ring, oxadiazole ring, triazole ring, imidazole ring, pyrazole ring, Thiazole ring, indole ring, indazole ring, benzimidazole ring, benzothiazole ring, benzoxazole ring, quinoxaline ring, quinazoline ring, cinnoline ring, quinoline ring, isoquinoline ring, phthalazine ring, naphthyridine ring, carbazole ring, Borin ring, diazacarbazole ring (group derived from a ring in which one of the carbon atoms of the hydrocarbon ring constituting the carboline ring is further substituted with a nitrogen atom, etc. In addition, combining the carboline ring and the diazacarbazole ring Sometimes referred to as “azacarbazole ring”), non-aromatic hydrocarbon ring group (eg, cyclopentyl group, cyclohexyl group, etc.), non-aromatic heterocyclic group (eg, pyrrolidyl group, imidazolidyl group, morpholyl group, oxazolidyl) Group), alkoxy group (for example, methoxy group, ethoxy group, propyloxy group, pentyloxy group, hexyloxy group, octyloxy group, dodecyloxy group, etc.), cycloalkoxy group (for example, cyclopentyloxy group, cyclohexyloxy group) Etc.), aryloxy group (for example, phenoxy group, naphthyloxy) Group), alkylthio group (for example, methylthio group, ethylthio group, propylthio group, pentylthio group, hexylthio group, octylthio group, dodecylthio group, etc.), cycloalkylthio group (for example, cyclopentylthio group, cyclohexylthio group, etc.), arylthio group (Eg, phenylthio group, naphthylthio group, etc.), alkoxycarbonyl group (eg, methyloxycarbonyl group, ethyloxycarbonyl group, butyloxycarbonyl group, octyloxycarbonyl group, dodecyloxycarbonyl group, etc.), aryloxycarbonyl group (eg, , Phenyloxycarbonyl group, naphthyloxycarbonyl group, etc.), sulfamoyl group (for example, aminosulfonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group, butylaminosulfo group) Group, hexylaminosulfonyl group, cyclohexylaminosulfonyl group, octylaminosulfonyl group, dodecylaminosulfonyl group, phenylaminosulfonyl group, naphthylaminosulfonyl group, 2-pyridylaminosulfonyl group, etc.), acyl group (for example, acetyl group, ethyl group) Carbonyl group, propylcarbonyl group, pentylcarbonyl group, cyclohexylcarbonyl group, octylcarbonyl group, 2-ethylhexylcarbonyl group, dodecylcarbonyl group, phenylcarbonyl group, naphthylcarbonyl group, pyridylcarbonyl group, etc.), acyloxy group (for example, acetyloxy) Group, ethylcarbonyloxy group, butylcarbonyloxy group, octylcarbonyloxy group, dodecylcarbonyloxy group, phenylcarbonyloxy group, etc.) Amido group (for example, methylcarbonylamino group, ethylcarbonylamino group, dimethylcarbonylamino group, propylcarbonylamino group, pentylcarbonylamino group, cyclohexylcarbonylamino group, 2-ethylhexylcarbonylamino group, octylcarbonylamino group, dodecylcarbonylamino group) Group, phenylcarbonylamino group, naphthylcarbonylamino group, etc.), carbamoyl group (for example, aminocarbonyl group, methylaminocarbonyl group, dimethylaminocarbonyl group, propylaminocarbonyl group, pentylaminocarbonyl group, cyclohexylaminocarbonyl group, octylamino) Carbonyl group, 2-ethylhexylaminocarbonyl group, dodecylaminocarbonyl group, phenylaminocarbonyl group, naphthylamino Carbonyl group, 2-pyridylaminocarbonyl group, etc.), ureido group (for example, methylureido group, ethylureido group, pentylureido group, cyclohexylureido group, octylureido group, dodecylureido group, phenylureido group, naphthylureido group, 2-pyridylamino group) Ureido group, etc.), sulfinyl group (for example, methylsulfinyl group, ethylsulfinyl group, butylsulfinyl group, cyclohexylsulfinyl group, 2-ethylhexylsulfinyl group, dodecylsulfinyl group, phenylsulfinyl group, naphthylsulfinyl group, 2-pyridylsulfinyl group, etc. ), Alkylsulfonyl group (for example, methylsulfonyl group, ethylsulfonyl group, butylsulfonyl group, cyclohexylsulfonyl group, 2-ethylhexylsulfonyl group) Group, dodecylsulfonyl group, etc.), arylsulfonyl group or heteroarylsulfonyl group (eg, phenylsulfonyl group, naphthylsulfonyl group, 2-pyridylsulfonyl group, etc.), amino group (eg, amino group, ethylamino group, dimethylamino group) Butylamino group, cyclopentylamino group, 2-ethylhexylamino group, dodecylamino group, anilino group, naphthylamino group, 2-pyridylamino group, etc.), halogen atoms (eg fluorine atom, chlorine atom, bromine atom etc.), fluorine Hydrocarbon group (for example, fluoromethyl group, trifluoromethyl group, pentafluoroethyl group, pentafluorophenyl group, etc.), cyano group, nitro group, hydroxy group, thiol group, silyl group (for example, trimethylsilyl group, triisopropyl group) Silyl group, Triphe Rushiriru group, phenyl diethyl silyl group and the like), or the like deuterium atom.

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

The _y 1 ~y ₈ in the general formula _(I), preferably at least three of the y 1 ~y _4, or at least three of the _y 5 ~y ₈ is represented by _{CR 102,} more preferably y _{1 to} y ₈ are all CR ₁₀₂ . Such a skeleton is excellent in hole transport property or electron transport property, and can efficiently recombine and emit holes / electrons injected from the anode / cathode in the light-emitting thin film.

Among them, a compound in which X ₁₀₁ is NR ₁₀₁ , an oxygen atom, or a sulfur atom in general formula (I) is preferable as a structure having a low energy level of the lowest unoccupied molecular orbital (LUMO) and excellent electron transport properties. More preferably, the condensed ring formed with X ₁₀₁ and y _{1 to} y ₈ is a carbazole ring, an azacarbazole ring, a dibenzofuran ring or an azadibenzofuran ring.

Furthermore, for the purpose of preferably making the host compound rigid, when X ₁₀₁ is NR ₁₀₁ , R ₁₀₁ is an aromatic hydrocarbon ring group which is a π-conjugated skeleton among the substituents mentioned above. Or it is preferable that it is an aromatic heterocyclic group. Further, these R ₁₀₁ may be further substituted with a substituent represented by the aforementioned R _{101 to} R ₁₀₄ .

In the general formula (I), examples of the aromatic ring represented by Ar ₁₀₁ and Ar ₁₀₂ include an aromatic hydrocarbon ring and an aromatic heterocyclic ring. The aromatic ring may be a monocyclic ring or a condensed ring, and may be unsubstituted or may have a substituent similar to the substituents represented by R _{101 to} R ₁₀₄ described above.

In the general formula (I), examples of the aromatic hydrocarbon ring represented by Ar ₁₀₁ and Ar ₁₀₂ include the aromatic hydrocarbon rings exemplified as the substituents represented by the aforementioned R _{101 to} R _104. Examples include the same ring as the group.

In the partial structure represented by the general formula (I), examples of the aromatic heterocycle represented by Ar ₁₀₁ and Ar ₁₀₂ include the substituents represented by R _{101 to} R ₁₀₄ described above. The same ring as an aromatic heterocyclic group is mentioned.

When considering purpose of host compounds represented by formula (I) have a high lowest triplet energy T _1, the aromatic ring itself of the lowest triplet energy represented by Ar ₁₀₁ and Ar ₁₀₂ T ₁ Benzene ring (including polyphenylene skeleton (including biphenyl, terphenyl, quarterphenyl) etc.), fluorene ring, triphenylene ring, carbazole ring, azacarbazole ring, dibenzofuran ring, azadibenzofuran ring A dibenzothiophene ring, a dibenzothiophene ring, a pyridine ring, a pyrazine ring, an indoloindole ring, an indole ring, a benzofuran ring, a benzothiophene ring, an imidazole ring or a triazine ring. More preferred are a benzene ring, a carbazole ring, an azacarbazole ring, and a dibenzofuran ring.

When Ar ₁₀₁ and Ar ₁₀₂ are a carbazole ring or an azacarbazole ring, it is more preferable that they are bonded at the N-position (or 9-position) or the 3-position.

When Ar ₁₀₁ and Ar ₁₀₂ are dibenzofuran rings, they are more preferably bonded at the 2-position or 4-position.

In addition to the above purpose, when considering the use of an organic EL element mounted in a vehicle, the environment temperature in the vehicle is assumed to be high, so the Tg of the host compound is high. Is also preferable. Therefore, for the purpose of increasing the Tg of the host compound represented by the general formula (I), each of the aromatic rings represented by Ar ₁₀₁ and Ar ₁₀₂ is preferably a condensed ring having three or more rings. .

  Specific examples of the aromatic hydrocarbon condensed ring in which three or more rings are condensed include naphthacene ring, anthracene ring, tetracene ring, pentacene ring, hexacene ring, phenanthrene ring, pyrene ring, benzopyrene ring, benzoazulene ring, chrysene ring , Benzochrysene ring, acenaphthene ring, acenaphthylene ring, triphenylene ring, coronene ring, benzocoronene ring, hexabenzocoronene ring, fluorene ring, benzofluorene ring, fluoranthene ring, perylene ring, naphthoperylene ring, pentabenzoperylene ring, benzoperylene ring, pentaphen A ring, a picene ring, a pyranthrene ring, a coronene ring, a naphtho- coronene ring, an ovalen ring, an anthraanthrene ring and the like. These rings may further have the above substituents.

  Specific examples of the aromatic heterocycle condensed with three or more rings include an acridine ring, a benzoquinoline ring, a carbazole ring, a carboline ring, a phenazine ring, a phenanthridine ring, a phenanthroline ring, a carboline ring, a cyclazine ring, Kindin ring, tepenidine ring, quinindrin ring, triphenodithiazine ring, triphenodioxazine ring, phenanthrazine ring, anthrazine ring, perimidine ring, diazacarbazole ring (any one of the carbon atoms constituting the carboline ring is a nitrogen atom Phenanthroline ring, dibenzofuran ring, dibenzothiophene ring, naphthofuran ring, naphthothiophene ring, benzodifuran ring, benzodithiophene ring, naphthodifuran ring, naphthodithiophene ring, anthrafuran ring, anthradifuran ring, A Tiger thiophene ring, anthradithiophene ring, thianthrene ring, phenoxathiin ring, such as thio fan Tren ring (naphthaldehyde thiophene ring), and the like. In addition, these rings may further have a substituent.

In general formula (I), n101 and n102 are each preferably an integer of 0 to 2, and more preferably n101 + n102 is an integer of 1 to 3. _Furthermore, since _{the R 101} is the n101 and n102 when the hydrogen atom is 0 at the same time, the molecular weight of the host compound represented by the general formula (I) is small, can only be achieved low glass transition temperature _{Tg, R 101} is hydrogen In the case of an atom, n101 represents an integer of 1 to 4.

  As the host compound used in the present invention, the carbazole derivative is preferably a compound having a structure represented by the general formula (II). This is because such a compound tends to have particularly excellent carrier transportability.

In formula _{(II), X 101, Ar} 101, Ar 102, and n102 are each synonymous with _{X 101, Ar 101, Ar 102} , and n102 in formula (I).

  n102 is preferably an integer of 0 to 2, more preferably 0 or 1.

In the general formula (II), the condensed ring formed containing X ₁₀₁ may further have a substituent other than Ar ₁₀₁ and Ar ₁₀₂ as long as the function of the host compound used in the present invention is not inhibited. .

  Furthermore, it is preferable that the compound represented by general formula (II) is represented by the following general formula (III).

In the general formula _{(III), X 101, Ar} 102, and n102 are synonymous with _{X 101, Ar 102,} and n102 in each of the general formula (II).

In the general formula (III), Ar ₁₀₂ is a substituted or unsubstituted carbazole ring.

Examples of the host compound used in the present invention include compounds having a structure represented by the general formula (I), (II), or (III) and other compound structures, but are not limited thereto. It is not something.

  The host compound used for this invention should just be a compound in which at least 1 type has a structure represented by general formula (I), and may be used in combination of multiple types. A preferred host compound may be a low molecular compound having a molecular weight sufficient for sublimation purification or a polymer having a repeating unit.

  In the case of a low molecular weight compound, sublimation purification is possible, so that there is an advantage that purification is easy and a high-purity material is easily obtained. The molecular weight is not particularly limited as long as sublimation purification is possible, but the preferred molecular weight is 3000 or less, more preferably 2000 or less.

  In the case of a polymer or oligomer having a repeating unit, there is an advantage that it is easy to form a film by a wet process, and since a polymer generally has a high glass transition temperature (Tg), it is preferable from the viewpoint of heat resistance.

  The polymer used as the host compound used in the present invention is not particularly limited as long as the desired device performance can be achieved, but preferably has a structure represented by the general formula (I), (II), or (III) Are preferably present in the main chain or side chain. Although there is no restriction | limiting in particular as molecular weight, Molecular weight 5000 or more is preferable or a thing with 10 or more repeating units is preferable.

  In addition, the host compound has a hole transporting ability or an electron transporting ability, prevents the emission of light from being long-wavelength, and is stable with respect to heat generated when the organic EL element is driven at a high temperature or during the driving of the element. From the viewpoint of operation, it is preferable to have a high glass transition temperature (Tg). Tg is preferably 90 ° C. or higher, more preferably 120 ° C. or higher.

  Here, the glass transition temperature (Tg) is a value obtained by a method based on JIS K 7121-2012 using DSC (Differential Scanning Colorimetry).

(Luminescent compound)
The luminescent thin film of the present invention includes, as a luminescent compound, at least a luminescent compound having an absolute value (ΔEst) of an energy difference between the lowest excited singlet energy and the lowest excited triplet energy of 0.5 eV or less. Features. In addition, as long as the effect of the present invention is not impaired, a fluorescent compound emitting fluorescence or a phosphorescent compound emitting phosphorescence can be used in combination as the luminescent compound.

(1) TADF compound The TADF compound is not particularly required to be a heavy metal complex such as a phosphorescent compound, and is a so-called organic compound composed of a combination of common elements such as carbon, oxygen, nitrogen and hydrogen. The compounds can be applied, and other non-metallic elements such as phosphorus, sulfur and silicon can be used, and complexes of typical metals such as aluminum and zinc can be used.

  The TADF compound in the present invention means a compound having ΔEst of 0.5 eV or less, which is a difference between excited singlet energy and excited triplet energy, although it does not have a heavy atom in the molecule.

  When ΔEst is 0.5 eV or less, reverse intersystem crossing from the triplet excited state to the singlet excited state occurs. Furthermore, since the rate constant of deactivation from singlet excited state to ground state (= fluorescence emission) is extremely large, triplet excitons themselves are thermally deactivated to ground state (non-radiative deactivation). It is more kinetically advantageous to return to the ground state while emitting fluorescence via the singlet excited state. Therefore, the TADF compound can ideally emit 100% fluorescence.

  In order to make ΔEst 0.5 eV or less, the distribution regions of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) distributed on the molecule are sufficient. It is considered preferable that they are separated. These can be achieved by adding an electron-accepting group and an electron-donating group to the luminescent compound.

  However, if the distribution areas of HOMO and LUMO are largely separated and become in a state close to the intramolecular charge transfer state, it can be formed between multiple molecules, resulting in various stabilization with a wide distribution. A state will exist, and the shape of the absorption spectrum and emission spectrum will be broad. From the viewpoint of suppressing the shapes of the absorption spectrum and emission spectrum from becoming broad, the TADF material according to the present invention preferably has a sharp emission spectrum shape and a small difference between the emission maximum wavelength and the rising wavelength of the emission spectrum. . These are achieved by reducing changes in the molecular structure of the singlet excited state and the triplet excited state.

In addition, in a TADF material that does not contain heavy metals, the transition that is deactivated from the triplet excited state to the ground state is a forbidden transition, and therefore the existence time (exciton lifetime) in the triplet excited state is from several hundred microseconds to millisecond. It becomes extremely long with second order. Therefore, even if the T ₁ energy of the host compound is higher than that of the luminescent compound, the reverse energy transfer from the triplet excited state of the luminescent compound to the host compound due to the length of its existence time. The probability of waking up increases. As a result, the reverse reverse crossing from the triplet excited state to the singlet excited state of the originally intended TADF material does not occur sufficiently, and unfavorable reverse energy transfer to the host compound becomes the mainstream, resulting in sufficient luminous efficiency. Inconvenience that cannot be obtained. Therefore, from the viewpoint of suppressing reverse energy transfer to the host compound, the TADF material according to the present invention preferably has a short triplet excited state existence time (exciton lifetime). These can be achieved by reducing the molecular structure change between the ground state and the triplet excited state, and introducing a substituent or an element suitable for unwinding the forbidden transition.

［一般式（１）において、Ａｒ¹〜Ａｒ^３は、各々独立に、置換又は無置換のアリール基を表し、少なくとも１つは下記一般式（２）で表される構造を有する基で置換されたアリール基を表す。］

［一般式（２）において、Ｒ^１〜Ｒ^８は、各々独立に、水素原子又は置換基を表す。Ｚは、Ｏ、Ｓ、Ｏ＝Ｃ、Ａｒ^４−Ｎ、又は化学結合を表す。Ａｒ^４は、置換又は無置換のアリール基を表す。Ｒ^１〜Ｒ^８のうち隣り合う基同士は、互いに結合を形成、又は、連結基を介して環を形成してもよい。］

［一般式（３）において、Ｒ^１〜Ｒ^５の少なくとも１つは、シアノ基を表し、Ｒ^１〜Ｒ^５の少なくとも１つは下記一般式（４）で表される構造を有する基を表し、残りのＲ^１〜Ｒ^５は水素原子又は置換基を表す。］

［一般式（４）において、Ｒ^２１〜Ｒ^２８は、各々独立に、水素原子又は置換基を表す。ただし、下記要件＜Ａ＞か＜Ｂ＞の少なくとも一方を満たす。
＜Ａ＞Ｒ^２５及びＲ^２６は、単結合を形成する。
＜Ｂ＞Ｒ^２７及びＲ^２８は、置換又は無置換のベンゼン環を形成するのに必要な原子団を表す。］

［一般式（５）において、Ｒ^１及びＲ^２は、各々独立に、下記一般式（６）で表される構造を有する基である。］

［一般式（６）において、Ｒ^１〜Ｒ^８は、各々独立に、水素原子又は置換基を表す。Ｚは、Ｏ、Ｓ、Ｏ＝Ｃ、Ａｒ^４−Ｎ、又は結合を表す。Ａｒ^４は、置換又は無置換のアリール基を表す。Ｒ^１〜Ｒ^８のうち隣り合う基同士は、互いに結合を形成、又は、連結基を介して環を形成してもよい。］ As the luminescent compound having the above-described molecular structure, compounds having structures represented by the following general formulas (1) to (6) are preferable.

[In General Formula (1), Ar ^{1 to} Ar ³ each independently represents a substituted or unsubstituted aryl group, and at least one of them is substituted with a group having a structure represented by the following General Formula (2). Represents an aryl group. ]

[In General formula (2), R < ¹ > -R < ⁸ > represents a hydrogen atom or a substituent each independently. Z represents O, S, O═C, Ar ⁴ —N, or a chemical bond. Ar ⁴ represents a substituted or unsubstituted aryl group. Adjacent groups among R ^{1 to} R ⁸ may form a bond with each other or form a ring via a linking group. ]

[In the general formula ^(3), at least one of R 1 to R ⁵ represents a cyano ^group, at least one of R 1 to R ⁵ is a group having the structure represented by the following general formula (4) The remaining R ^{1 to} R ⁵ represent a hydrogen atom or a substituent. ]

[In the general formula ^{(4), R} 21 ~R ²⁸ independently represents a hydrogen atom or a substituent. However, at least one of the following requirements <A> or <B> is satisfied.
<A> R ²⁵ and R ²⁶ form a single bond.
<B> R ²⁷ and R ²⁸ represent an atomic group necessary for forming a substituted or unsubstituted benzene ring. ]

[In General Formula (5), R ¹ and R ² are each independently a group having a structure represented by the following General Formula (6). ]

[In General formula (6), R < ¹ > -R < ⁸ > represents a hydrogen atom or a substituent each independently. Z represents O, S, O═C, Ar ⁴ —N, or a bond. Ar ⁴ represents a substituted or unsubstituted aryl group. Adjacent groups among R ^{1 to} R ⁸ may form a bond with each other or form a ring via a linking group. ]

  The TADF compound is exemplified below, but the present invention is not limited to this.

  Hereinafter, various measurement methods relating to the TADF compound according to the present invention will be described.

(Electron density distribution)
In the luminescent compound according to the present invention, it is preferable that HOMO and LUMO are substantially separated in the molecule from the viewpoint of reducing ΔEst. The distribution states of these HOMO and LUMO can be obtained from the electron density distribution when the structure is optimized by molecular orbital calculation.
The structure optimization and the calculation of the electron density distribution by molecular orbital calculation of the luminescent compound in the present invention use molecular orbital calculation software using B3LYP as a functional and 6-31G (d) as a basis function as a calculation method. There is no particular limitation on the software, and any of them can be similarly calculated.
In the present invention, Gaussian 09 (Revision C.01, MJ Frisch, et al, Gaussian, Inc., 2010.) manufactured by Gaussian, USA was used as molecular orbital calculation software.
Further, “HOMO and LUMO are substantially separated” means that the HOMO orbital distribution calculated by the above molecular calculation and the central part of the LUMO orbital distribution are separated, more preferably the HOMO orbital distribution and the LUMO orbital. This means that the distributions of do not overlap.
As for the separation state of HOMO and LUMO, from the above-described structure optimization calculation using B3LYP as the functional and 6-31G (d) as the basis function, the time-dependent density functional method (Time-Dependent DFT) is used. It is also possible to calculate the energy of S ₁ and T ₁ (respectively E (S ₁ ) and E (T ₁ )) by calculating the excited state and calculate ΔEst = E (S ₁ ) −E (T ₁ ). It is. As the calculated ΔEst is smaller, HOMO and LUMO are more separated. In the present invention, ΔEst calculated using the same calculation method as described above is preferably 0.5 eV or less, more preferably 0.2 eV or less, and further preferably 0.1 eV or less.

(Minimum excitation singlet energy S ₁ )
The lowest excited singlet energy S ₁ of the luminescent compound in the present invention is also defined in the present invention as calculated in the same manner as a normal method. That is, a sample to be measured is deposited on a quartz substrate to prepare a sample, and the absorption spectrum (vertical axis: absorbance, horizontal axis: wavelength) of this sample is measured at room temperature (25 ° C.). A tangent line is drawn with respect to the rising edge of the absorption spectrum on the long wavelength side, and is calculated from a predetermined conversion formula based on the wavelength value at the intersection of the tangent line and the horizontal axis.
However, when the luminescent compound used in the present invention has a relatively high aggregation property of the molecule itself, an error due to aggregation may occur in the measurement of the thin film. In consideration of the fact that the luminescent compound in the present invention has a relatively small Stokes shift and that the structural change between the excited state and the ground state is small, the lowest excited singlet energy S ₁ in the present invention is light emission at room temperature (25 ° C.). The peak value of the maximum emission wavelength in the solution state of the active compound was used as an approximate value. Here, the solvent to be used may be a solvent that does not affect the aggregation state of the luminescent compound, that is, a solvent having a small influence of the solvent effect, for example, a nonpolar solvent such as cyclohexane or toluene.

(Measurement of Stokes shift)
An excitation (absorption) spectrum and an emission spectrum of a solution of a luminescent compound (using a suitable solvent such as dichloromethane and chloroform) are measured with a fluorescence spectrophotometer (for example, an RF-5300 type fluorescence spectrometer manufactured by Shimadzu Corporation, manufactured by Hitachi, Ltd.) F-4500 type fluorescence spectrometer or the like), and the difference between the fluorescence maximum wavelength and the excitation (absorption) maximum wavelength can be obtained as “Stokes shift”.

The concentration of the TADF compound in the luminescent thin film can be determined arbitrarily based on the TADF compound used and the requirements of the device, and is uniform in the layer thickness direction of the luminescent thin film. It may be contained and may have any concentration distribution.
In addition, the TADF compounds according to the present invention may be used in combination of plural kinds, or may be used in combination of TADF compounds having different structures, or in combination of a fluorescent compound and a phosphorescent compound. Thereby, arbitrary luminescent colors can be obtained.

The luminescent color of the compound according to the present invention is shown in FIG. 14.16 on page 108 of “New Color Science Handbook” (edited by the Japan Society for Color Science, University of Tokyo Press, 1985), with a spectral radiance meter CS-1000 (Konica Minolta). It is determined by the color when the result measured by (made by Co., Ltd.) is applied to the CIE chromaticity coordinates.
In the present invention, it is also preferable that the light-emitting thin film of one layer or a plurality of layers contains a plurality of light-emitting compounds having different emission colors and emits white light.
There are no particular limitations on the combination of the luminescent compounds exhibiting white, and examples include blue and orange, and a combination of blue, green and red.
The white color in the present invention means that the chromaticity in the CIE 1931 color system at 1000 cd / m ² is x = 0.39 ± 0.09, y = 0 when the 2-degree viewing angle front luminance is measured by the above-described method. Preferably in the region of .38 ± 0.08.

The method for forming the light-emitting thin film of the present invention is not particularly limited, and a conventionally known method such as a vacuum deposition method or a wet method (also referred to as a wet process) can be used.
Examples of the wet method include spin coating, casting, ink jet, printing, die coating, blade coating, roll coating, spray coating, curtain coating, and LB (Langmuir-Blodgett). From the viewpoint of obtaining a homogeneous thin film easily and high productivity, a method with high roll-to-roll method suitability such as a die coating method, a roll coating method, an ink jet method and a spray coating method is preferable.

  Examples of the liquid medium for dissolving or dispersing the π-conjugated compound used in the present invention include ketones such as methyl ethyl ketone and cyclohexanone, fatty acid esters such as ethyl acetate, halogenated hydrocarbons such as dichlorobenzene, toluene and xylene. Aromatic hydrocarbons such as mesitylene and cyclohexylbenzene, aliphatic hydrocarbons such as cyclohexane, decalin and dodecane, and organic solvents such as DMF and DMSO can be used.

Moreover, as a dispersion method, it can disperse | distribute by dispersion methods, such as an ultrasonic wave, high shear force dispersion | distribution, and media dispersion | distribution.
When a vapor deposition method is employed for film formation, the vapor deposition conditions vary depending on the type of compound used, but generally the boat heating temperature is in the range of 50 to 450 ° C., and the degree of vacuum is in the range of 10 ⁻⁶ to 10 ⁻² Pa. Of these, the deposition rate is appropriately selected within the range of 0.01 to 50 nm / second, the substrate temperature within the range of −50 to 300 ° C., the layer thickness within the range of 0.1 nm to 5 μm, and preferably within the range of 5 to 200 nm. desirable.
When a spin coat method is employed for film formation, it is preferable to perform the spin coater within a range of 100 to 1000 rpm and within a range of 10 to 120 seconds in a dry inert gas atmosphere.

≪Application of luminescent thin film≫
The luminescent thin film of this invention is used suitably for the light emitting layer of an organic EL element. As a result, an organic EL element, a display device, and a lighting device with improved light emission lifetime can be obtained.

≪Organic EL element≫
The organic EL device of the present invention is characterized by having at least one luminescent thin film of the present invention as a luminescent layer between an anode and a cathode.

As typical element structures in the organic EL element of the present invention, the following structures can be exemplified, but the invention is not limited thereto.
(1) Anode / light emitting layer // cathode (2) Anode / light emitting layer / electron transport layer / cathode (3) Anode / hole transport layer / light emitting layer / cathode (4) Anode / hole transport layer / light emitting layer / Electron transport layer / cathode (5) anode / hole transport layer / light emitting layer / electron transport layer / electron injection layer / cathode (6) anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / cathode (7) Anode / hole injection layer / hole transport layer / (electron blocking layer /) light emitting layer / (hole blocking layer /) electron transport layer / electron injection layer / cathode Among the above, the configuration of (7) is Although used preferably, it is not limited to this.
The light emitting layer according to the present invention is composed of a single layer or a plurality of layers, and when there are a plurality of light emitting layers, a non-light emitting intermediate layer may be provided between the light emitting layers.

If necessary, a hole blocking layer (also referred to as a hole blocking layer) or an electron injection layer (also referred to as a cathode buffer layer) may be provided between the light emitting layer and the cathode. An electron blocking layer (also referred to as an electron barrier layer) or a hole injection layer (also referred to as an anode buffer layer) may be provided therebetween.
The electron transport layer according to the present invention is a layer having a function of transporting electrons, and in a broad sense, an electron injection layer and a hole blocking layer are also included in the electron transport layer. Moreover, you may be comprised by multiple layers.
The hole transport layer according to the present invention is a layer having a function of transporting holes, and in a broad sense, a hole injection layer and an electron blocking layer are also included in the hole transport layer. Moreover, you may be comprised by multiple layers.
In the above-described typical element configuration, the layer excluding the anode and the cathode is also referred to as “organic layer”.

The formation method of the organic layer is not particularly limited, and a conventionally known formation method such as a vacuum deposition method or a wet method (also referred to as a wet process) can be used.
Examples of the wet method include spin coating, casting, ink jet, printing, die coating, blade coating, roll coating, spray coating, curtain coating, and LB (Langmuir-Blodgett). From the viewpoint of obtaining a homogeneous thin film easily and high productivity, a method with high roll-to-roll method suitability such as a die coating method, a roll coating method, an ink jet method and a spray coating method is preferable.

  Examples of the liquid medium for dissolving or dispersing the material forming the organic layer according to the present invention include ketones such as methyl ethyl ketone and cyclohexanone, fatty acid esters such as ethyl acetate, halogenated hydrocarbons such as dichlorobenzene, toluene, Aromatic hydrocarbons such as xylene, mesitylene and cyclohexylbenzene, aliphatic hydrocarbons such as cyclohexane, decalin and dodecane, and organic solvents such as DMF and DMSO can be used.

  Moreover, as a dispersion method, it can disperse | distribute by dispersion methods, such as an ultrasonic wave, high shear force dispersion | distribution, and media dispersion | distribution.

  After application, the solvent may be removed in a drying process. In the drying process, a drying furnace can be used. In the drying furnace, it is possible to change the temperature condition, change the wind speed, etc. by appropriately setting several zones according to the material of the organic compound layer.

  Heat treatment may be performed after removing the solvent. The heat treatment is not limited to any form as long as heat is transferred from the back surface, but the heat treatment is preferably performed at a glass transition temperature of ± 50 ° C. and at a temperature not exceeding the decomposition temperature and heat transfer from the back surface.

  By performing the heat treatment, the smoothness of the film, the removal of the residual solvent, and the curing of the coating film can be achieved, thereby improving the element characteristics during lamination.

After the heat treatment, the substrate may be stored under reduced pressure (10 ⁻⁶ Pa to 10 ⁻² Pa). You may apply temperature suitably. The storage period is preferably in the range of 1 to 200 hours, and the longer it is, the better. As a result, oxygen and trace moisture due to device deterioration are removed.

  After these layers are formed, a thin film made of a cathode material is formed thereon by a method such as vapor deposition or sputtering so as to have a film thickness of 1 μm or less, preferably in the range of 50 to 200 nm. By providing, a desired organic EL element can be obtained.

  In addition, it is also possible to reverse the production order and produce the cathode, the electron injection layer, the electron transport layer, the light emitting layer, the hole transport layer, the hole injection layer, and the anode in this order. When a DC voltage is applied to the multicolor display device thus obtained, light emission can be observed by applying a voltage of about 2 to 40 V with the positive polarity of the anode and the negative polarity of the cathode. An alternating voltage may be applied. The alternating current waveform to be applied may be arbitrary.

Further, the organic EL element according to the present invention may be an element having a so-called tandem structure in which a plurality of light emitting units including at least one light emitting layer are stacked.
As typical element configurations of the tandem structure, for example, the following configurations can be given.
Anode / first light emitting unit / intermediate layer / second light emitting unit / intermediate layer / third light emitting unit / cathode Here, the first light emitting unit, the second light emitting unit and the third light emitting unit are all the same, May be different. Two light emitting units may be the same, and the remaining one may be different.
A plurality of light emitting units may be laminated directly or via an intermediate layer, and the intermediate layer is generally an intermediate electrode, an intermediate conductive layer, a charge generation layer, an electron extraction layer, a connection layer, an intermediate layer. A known material structure can be used as long as it is also called an insulating layer and has a function of supplying electrons to the anode-side adjacent layer and holes to the cathode-side adjacent layer.

Examples of materials used for the intermediate layer include ITO (indium tin oxide), IZO (indium zinc oxide), ZnO ₂ , TiN, ZrN, HfN, TiO _x , VO _x , CuI, InN, GaN, Conductive inorganic compound layers such as CuAlO ₂ , CuGaO ₂ , SrCu ₂ O ₂ , LaB ₆ , RuO ₂ and Al, two-layer films such as Au / Bi ₂ O ₃ , SnO ₂ / Ag / SnO ₂ , ZnO / Multi-layer film such as Ag / ZnO, Bi ₂ O ₃ / Au / Bi ₂ O ₃ , TiO ₂ / TiN / TiO ₂ , TiO ₂ / ZrN / TiO ₂ , fullerenes such as C ₆₀ , conductivity such as oligothiophene Examples include organic material layers, conductive organic compound layers such as metal phthalocyanines, metal-free phthalocyanines, metal porphyrins, and metal-free porphyrins. The present invention is not limited thereto.
As a preferable configuration in the light emitting unit, for example, a configuration in which the anode and the cathode are excluded from the configurations (1) to (7) described in the above-described typical element configurations, and the like is described. It is not limited.

  Specific examples of the tandem organic EL element include, for example, US Pat. No. 6,337,492, US Pat. No. 7,420,203, US Pat. No. 7,473,923, US Pat. No. 6,872,472, US Pat. No. 6,107,734, US Pat. No. 6,337,492, International JP 2005/009087, JP 2006-228712, JP 2006-24791, JP 2006-49393, JP 2006-49394, JP 2006-49396, JP 2011. No. -96679, JP 2005-340187, JP 47114424, JP 34096681, JP 3884564, JP 431169, JP 2010-192719, JP 2009-076929, JP Open 2008-0784 No. 4, JP 2007-059848 A, JP 2003-272860 A, JP 2003-045676 A, International Publication No. 2005/094130, and the like. The present invention is not limited to these.

  Hereinafter, each layer which comprises the organic EL element of this invention is demonstrated.

<Light emitting layer>
The light emitting layer according to the present invention is characterized by using the light emitting thin film of the present invention. A layer that provides a field where electrons and holes injected from an electrode or adjacent layer recombine and emit light via excitons, even if the light emitting portion is within the layer of the light emitting layer And an interface between adjacent layers. The structure of the light emitting layer according to the present invention is not particularly limited as long as it satisfies the requirements defined in the present invention.
The total thickness of the light emitting layer is not particularly limited, but it prevents the uniformity of the film to be formed, the application of unnecessary high voltage during light emission, and the improvement of the stability of the emission color against the drive current. From the viewpoint, it is preferable to adjust in the range of 2 nm to 5 μm, more preferably in the range of 2 to 500 nm, and still more preferably in the range of 5 to 200 nm.
In addition, the thickness of each light emitting layer of the present invention is preferably adjusted within a range of 2 nm to 1 μm, more preferably adjusted within a range of 2 to 200 nm, and further preferably within a range of 3 to 150 nm. Adjusted to

<Electron transport layer>
In the present invention, the electron transport layer is made of a material having a function of transporting electrons, and may have a function of transmitting electrons injected from the cathode to the light emitting layer.
Although there is no restriction | limiting in particular about the total layer thickness of the electron carrying layer of this invention, Usually, it exists in the range of 2 nm-5 micrometers, More preferably, it exists in the range of 2-500 nm, More preferably, it exists in the range of 5-200 nm. It is.
Further, in the organic EL element, when the light generated in the light emitting layer is extracted from the electrode, the light extracted directly from the light emitting layer interferes with the light extracted after being reflected by the electrode from which the light is extracted and the electrode located at the counter electrode. It is known to wake up. When light is reflected by the cathode, this interference effect can be efficiently utilized by appropriately adjusting the total thickness of the electron transport layer between several nanometers and several micrometers.
On the other hand, when the layer thickness of the electron transport layer is increased, the voltage is likely to increase. Therefore, particularly when the layer thickness is thick, the electron mobility of the electron transport layer is preferably 10 ⁻⁵ cm ² / Vs or more. .
The material used for the electron transport layer (hereinafter referred to as an electron transport material) may be any of electron injecting or transporting properties and hole blocking properties, and can be selected from conventionally known compounds. Can be selected and used.

  For example, nitrogen-containing aromatic heterocyclic derivatives (carbazole derivatives, azacarbazole derivatives (one or more carbon atoms constituting the carbazole ring are substituted with nitrogen atoms), pyridine derivatives, pyrimidine derivatives, pyrazine derivatives, pyridazine derivatives, Triazine derivatives, quinoline derivatives, quinoxaline derivatives, phenanthroline derivatives, azatriphenylene derivatives, oxazole derivatives, thiazole derivatives, oxadiazole derivatives, thiadiazole derivatives, triazole derivatives, benzimidazole derivatives, benzoxazole derivatives, benzthiazole derivatives, etc.), dibenzofuran derivatives, Dibenzothiophene derivatives, silole derivatives, aromatic hydrocarbon ring derivatives (naphthalene derivatives, anthracene derivatives, triphenylene derivatives, etc.) That.

In addition, a metal complex having a quinolinol skeleton or a dibenzoquinolinol skeleton as a ligand, for example, tris (8-quinolinol) aluminum (Alq), tris (5,7-dichloro-8-quinolinol) aluminum, tris (5,7- Dibromo-8-quinolinol) aluminum, tris (2-methyl-8-quinolinol) aluminum, tris (5-methyl-8-quinolinol) aluminum, bis (8-quinolinol) zinc (Znq) and the like, and their metal complexes A metal complex in which the central metal is replaced with In, Mg, Cu, Ca, Sn, Ga, or Pb can also be used as the electron transport material.
In addition, metal-free or metal phthalocyanine, or those having terminal ends substituted with an alkyl group or a sulfonic acid group can be preferably used as the electron transport material. In addition, the distyrylpyrazine derivative exemplified as the material of the light emitting layer can also be used as an electron transport material, and an inorganic semiconductor such as n-type-Si, n-type-SiC, etc. as in the case of the hole injection layer and the hole transport layer. Can also be used as an electron transporting material.
Further, a polymer material in which these materials are introduced into a polymer chain or these materials are used as a polymer main chain can also be used.

  In the electron transport layer according to the present invention, the electron transport layer may be doped with a doping material as a guest material to form an electron transport layer having a high n property (electron rich). Examples of the doping material include n-type dopants such as metal complexes and metal compounds such as metal halides. Specific examples of the electron transport layer having such a structure include, for example, JP-A-4-297076, JP-A-10-270172, JP-A-2000-196140, 2001-102175, J. Pat. Appl. Phys. , 95, 5773 (2004) and the like.

Specific examples of known preferable electron transport materials used in the organic EL device of the present invention include compounds described in the following documents, but the present invention is not limited thereto.
US Pat. No. 6,528,187, US Pat. No. 7,230,107, US Patent Application Publication No. 2005/0025993, US Patent Application Publication No. 2004/0036077, US Patent Application Publication No. 2009/0115316, US Patent Application Publication No. 2009/0101870, United States Patent Application Publication No. 2009/0179554, International Publication No. 2003/060956, International Publication No. 2008/132805, Appl. Phys. Lett. 75, 4 (1999), Appl. Phys. Lett. 79, 449 (2001), Appl. Phys. Lett. 81, 162 (2002), Appl. Phys. Lett. 81, 162 (2002), Appl. Phys. Lett. 79,156 (2001), US Patent No. 7964293, US Patent Application Publication No. 2009/030202, International Publication No. 2004/080975, International Publication No. 2004/063159, International Publication No. 2005/085387, International Publication No. Public Publication No. 2006/067931, International Publication No. 2007/086552, International Publication No. 2008/114690, International Publication No. 2009/066942, International Publication No. 2009/066779, International Publication No. 2009/054253, International Publication No. 2011/086935, International Publication No. 2010/150593, International Publication No. 2010/047707, EP23111826, JP2010-251675A, JP2009-209133A, JP2009-124114A, JP 2 JP 08-277810 A, JP 2006-156445 A, JP 2005-340122 A, JP 2003-45662 A, JP 2003-31367 A, JP 2003-282270 A, International Publication 2012. / 115034.

  More preferable electron transport materials in the present invention include aromatic heterocyclic compounds containing at least one nitrogen atom. For example, pyridine derivatives, pyrimidine derivatives, pyrazine derivatives, triazine derivatives, dibenzofuran derivatives, dibenzothiophene derivatives, azadibenzofuran derivatives. , Azadibenzothiophene derivatives, carbazole derivatives, azacarbazole derivatives, benzimidazole derivatives, and the like. The electron transport material may be used alone or in combination of two or more.

<Hole blocking layer>
The hole blocking layer is a layer having the function of an electron transport layer in a broad sense, and is preferably made of a material having a function of transporting electrons and a small ability to transport holes. By blocking the holes, the probability of recombination of electrons and holes can be improved.
Moreover, the structure of the electron carrying layer mentioned above can be used as a hole-blocking layer concerning this invention as needed.
The hole blocking layer provided in the organic EL device of the present invention is preferably provided adjacent to the cathode side of the light emitting layer.
The layer thickness of the hole blocking layer according to the present invention is preferably in the range of 3 to 100 nm, more preferably in the range of 5 to 30 nm.
As the material used for the hole blocking layer, the material used for the above-described electron transport layer is preferably used, and the material used as the above-described host compound is also preferably used for the hole blocking layer.

<Electron injection layer>
The electron injection layer (also referred to as “cathode buffer layer”) according to the present invention is a layer provided between the cathode and the light emitting layer in order to lower the driving voltage and improve the light emission luminance. It is described in detail in Chapter 2 “Electrode Materials” (pages 123 to 166) of the second edition of “The Forefront of Industrialization” (issued by NTT Corporation on November 30, 1998).
In the present invention, the electron injection layer may be provided as necessary, and may be present between the cathode and the light emitting layer or between the cathode and the electron transport layer as described above.
The electron injection layer is preferably a very thin film, and the layer thickness is preferably in the range of 0.1 to 5 nm, although it depends on the material. Moreover, the nonuniform layer (film | membrane) in which a constituent material exists intermittently may be sufficient.

The details of the electron injection layer are described in JP-A-6-325871, JP-A-9-17574, JP-A-10-74586, and the like. Specific examples of materials preferably used for the electron injection layer are as follows. , Metals typified by strontium and aluminum, alkali metal compounds typified by lithium fluoride, sodium fluoride, potassium fluoride, etc., alkaline earth metal compounds typified by magnesium fluoride, calcium fluoride, etc., oxidation Examples thereof include metal oxides typified by aluminum, metal complexes typified by 8-hydroxyquinolinate lithium (Liq), and the like. Further, the above-described electron transport material can also be used.
Moreover, the material used for said electron injection layer may be used independently, and may be used in combination of multiple types.

<Hole transport layer>
In the present invention, the hole transport layer is made of a material having a function of transporting holes and may have a function of transmitting holes injected from the anode to the light emitting layer.
Although there is no restriction | limiting in particular about the total layer thickness of the positive hole transport layer of this invention, Usually, it exists in the range of 5 nm-5 micrometers, More preferably, it exists in the range of 2-500 nm, More preferably, it is the range of 5-200 nm. Is within.
As a material used for the hole transport layer (hereinafter referred to as a hole transport material), any material that has either a hole injection property or a transport property or an electron barrier property may be used. Any one can be selected and used.
For example, porphyrin derivatives, phthalocyanine derivatives, oxazole derivatives, oxadiazole derivatives, triazole derivatives, imidazole derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, hydrazone derivatives, stilbene derivatives, polyarylalkane derivatives, triarylamine derivatives, carbazole derivatives , Indolocarbazole derivatives, isoindole derivatives, acene derivatives such as anthracene and naphthalene, fluorene derivatives, fluorenone derivatives, and polyvinyl carbazole, polymer materials or oligomers with aromatic amines introduced into the main chain or side chain, polysilane, conductive And polymer (for example, PEDOT / PSS, aniline copolymer, polyaniline, polythiophene, etc.).

Examples of the triarylamine derivative include a benzidine type typified by α-NPD, a starburst type typified by MTDATA, and a compound having fluorene or anthracene in the triarylamine linking core part.
In addition, hexaazatriphenylene derivatives such as those described in JP-A-2003-519432 and JP-A-2006-135145 can also be used as a hole transport material.
Furthermore, a hole transport layer having a high p property doped with impurities can also be used. Examples thereof include JP-A-4-297076, JP-A-2000-196140, 2001-102175, J. Pat. Appl. Phys. 95, 5773 (2004), and the like.

JP-A-11-251067, J. Org. Huang et. al. It is also possible to use so-called p-type hole transport materials and inorganic compounds such as p-type-Si and p-type-SiC, as described in the literature (Applied Physics Letters 80 (2002), p. 139). Further, ortho-metalated organometallic complexes having Ir or Pt as the central metal as typified by Ir (ppy) ₃ are also preferably used.
Although the above-mentioned materials can be used as the hole transport material, a triarylamine derivative, a carbazole derivative, an indolocarbazole derivative, an azatriphenylene derivative, an organometallic complex, or an aromatic amine is introduced into the main chain or side chain. The polymer materials or oligomers used are preferably used.

Specific examples of known preferred hole transport materials used in the organic EL device of the present invention include the compounds described in the following documents in addition to the documents listed above, but the present invention is not limited thereto. Not.
For example, Appl. Phys. Lett. 69, 2160 (1996), J. MoI. Lumin. 72-74,985 (1997), Appl. Phys. Lett. 78, 673 (2001), Appl. Phys. Lett. 90, 183503 (2007), Appl. Phys. Lett. 90, 183503 (2007), Appl. Phys. Lett. 51, 913 (1987), Synth. Met. 87, 171 (1997), Synth. Met. 91, 209 (1997), Synth. MeT111, 421 (2000), SID Symposium Digest, 37, 923 (2006), J. Am. Mater. Chem. 3,319 (1993), Adv. Mater. 6, 677 (1994), Chem. Mater. 15, 3148 (2003), U.S. Patent Application Publication No. 2003/0162053, U.S. Patent Application Publication No. 2002/0158242, U.S. Patent Application Publication No. 2006/0240279, U.S. Patent Application Publication No. 2008/2008. No. 0220265, U.S. Patent No. 5061569, International Publication No. 2007/002683, International Publication No. 2009/018009, EP650955, U.S. Patent Application Publication No. 2008/0124572, U.S. Patent Publication No. 2007/0278938. Specification, US Patent Application Publication No. 2008/0106190, US Patent Application Publication No. 2008/0018221, International Publication No. 2012/115034, Japanese Translation of PCT International Publication No. 2003-519432, Japanese Patent Application Laid-Open No. 2006-135145 , It is a country patent application number 13/585981 issue like. The hole transport material may be used alone or in combination of two or more.

<Electron blocking layer>
The electron blocking layer is a layer having a function of a hole transport layer in a broad sense, and is preferably made of a material having a function of transporting holes and a small ability to transport electrons, while transporting holes. By blocking electrons, the probability of recombination of electrons and holes can be improved.
Moreover, the structure of the positive hole transport layer mentioned above can be used as an electron blocking layer according to the present invention, if necessary.
The electron blocking layer provided in the organic EL device of the present invention is preferably provided adjacent to the anode side of the light emitting layer.
The layer thickness of the electron blocking layer according to the present invention is preferably in the range of 3 to 100 nm, more preferably in the range of 5 to 30 nm.
As the material used for the electron blocking layer, the material used for the above-described hole transport layer is preferably used, and the material used as the above-described host compound is also preferably used for the electron blocking layer.

<Hole injection layer>
The hole injection layer (also referred to as “anode buffer layer”) according to the present invention is a layer provided between the anode and the light emitting layer for the purpose of lowering the driving voltage and improving the light emission luminance. It is described in detail in Chapter 2 “Electrode Materials” (pages 123 to 166) of the second edition of “The Forefront of Industrialization” (issued by NTT Corporation on November 30, 1998).
In the present invention, the hole injection layer may be provided as necessary, and may be present between the anode and the light emitting layer or between the anode and the hole transport layer as described above.
The details of the hole injection layer are also described in JP-A-9-45479, JP-A-9-260062, JP-A-8-288069, etc. Examples of the material used for the hole injection layer include: Examples thereof include materials used for the above-described hole transport layer.
Among them, phthalocyanine derivatives typified by copper phthalocyanine, hexaazatriphenylene derivatives as described in JP-T-2003-519432, JP-A-2006-135145, etc., metal oxides typified by vanadium oxide, amorphous carbon, polyaniline (emeral Din) and conductive polymers such as polythiophene, orthometalated complexes represented by tris (2-phenylpyridine) iridium complex, and triarylamine derivatives are preferred.
The materials used for the hole injection layer described above may be used alone or in combination of two or more.

<Additives>
The organic layer in the present invention described above may further contain other additives.
Examples of the additive include halogen elements such as bromine, iodine and chlorine, halogenated compounds, alkali metals such as Pd, Ca and Na, alkaline earth metals, transition metal compounds, complexes, and salts.
The content of the additive can be arbitrarily determined, but is preferably 1000 ppm or less, more preferably 500 ppm or less, and further preferably 50 ppm or less with respect to the total mass% of the contained layer. .
However, it is not within this range depending on the purpose of improving the transportability of electrons and holes or the purpose of favoring the exciton energy transfer.

(Formation method of organic layer)
A method for forming the organic layer (hole injection layer, hole transport layer, light emitting layer, hole blocking layer, electron transport layer, electron injection layer, etc.) of the present invention will be described.
The method for forming the organic layer of the present invention is not particularly limited, and a conventionally known method such as a vacuum deposition method or a wet method (also referred to as a wet process) can be used.
Examples of the wet method include spin coating, casting, ink jet, printing, die coating, blade coating, roll coating, spray coating, curtain coating, and LB (Langmuir-Blodgett). From the viewpoint of obtaining a homogeneous thin film easily and high productivity, a method with high roll-to-roll method suitability such as a die coating method, a roll coating method, an ink jet method and a spray coating method is preferable.
Examples of the liquid medium for dissolving or dispersing the organic EL material used in the present invention include ketones such as methyl ethyl ketone and cyclohexanone, fatty acid esters such as ethyl acetate, halogenated hydrocarbons such as dichlorobenzene, toluene, xylene, Aromatic hydrocarbons such as mesitylene and cyclohexylbenzene, aliphatic hydrocarbons such as cyclohexane, decalin, and dodecane, and organic solvents such as DMF and DMSO can be used.
Moreover, as a dispersion method, it can disperse | distribute by dispersion methods, such as an ultrasonic wave, high shear force dispersion | distribution, and media dispersion | distribution.
Further, different film forming methods may be applied for each layer. When employing a vapor deposition method for film formation, the vapor deposition conditions vary depending on the type of compound used, but generally a boat heating temperature of 50 to 450 ° C., a degree of vacuum of 10 ⁻⁶ to 10 ⁻² Pa, and a vapor deposition rate of 0.01 to It is desirable to select appropriately within a range of 50 nm / second, a substrate temperature of −50 to 300 ° C., and a layer (film) thickness of 0.1 nm to 5 μm, preferably 5 to 200 nm.
The organic layer of the present invention is preferably formed from the hole injection layer to the cathode consistently by a single evacuation, but may be taken out halfway and subjected to different film forming methods. In that case, it is preferable to perform the work in a dry inert gas atmosphere.

<Anode>
As the anode in the organic EL element, those having a work function (4 eV or more, preferably 4.5 V or more) of a metal, an alloy, an electrically conductive compound and a mixture thereof as an electrode material are preferably used. Specific examples of such electrode materials include metals such as Au, and conductive transparent materials such as CuI, indium tin oxide (ITO), SnO ₂ , and ZnO. Alternatively, an amorphous material such as IDIXO (In ₂ O ₃ —ZnO) capable of forming a transparent conductive film may be used.
The anode may be formed by depositing a thin film of these electrode materials by vapor deposition or sputtering, and a pattern having a desired shape may be formed by photolithography, or when pattern accuracy is not so high (about 100 μm or more) A pattern may be formed through a mask having a desired shape at the time of vapor deposition or sputtering of the electrode material.
Or when using the substance which can be apply | coated like an organic electroconductivity compound, wet film-forming methods, such as a printing system and a coating system, can also be used. When light emission is extracted from the anode, it is desirable that the transmittance be greater than 10%, and the sheet resistance as the anode is preferably several hundred Ω / □ or less.
Although the film thickness of the anode depends on the material, it is usually selected within the range of 10 nm to 1 μm, preferably within the range of 10 to 200 nm.

<Cathode>
As the cathode, a material having a work function (4 eV or less) metal (referred to as an electron injecting metal), an alloy, an electrically conductive compound, and a mixture thereof as an electrode material is used. Specific examples of such electrode materials include sodium, sodium-potassium alloy, magnesium, lithium, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al2O3) mixture. , Indium, lithium / aluminum mixtures, aluminum, rare earth metals and the like. Among these, from the point of durability against electron injection and oxidation, etc., a mixture of an electron injecting metal and a second metal which is a stable metal having a larger work function than this, for example, a magnesium / silver mixture, Magnesium / aluminum mixtures, magnesium / indium mixtures, aluminum / aluminum oxide (Al ₂ O ₃ ) mixtures, lithium / aluminum mixtures, aluminum and the like are preferred.

The cathode can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering. The sheet resistance as the cathode is preferably several hundred Ω / □ or less, and the film thickness is usually selected within the range of 10 nm to 5 μm, preferably within the range of 50 to 200 nm.
In order to transmit the emitted light, if either one of the anode or the cathode of the organic EL element is transparent or translucent, the emission luminance is advantageously improved.
Moreover, after producing the said metal with the film thickness in the range of 1-20 nm in a cathode, the transparent or semi-transparent cathode can be produced by producing the electroconductive transparent material mentioned by description of an anode on it. By applying this, an element in which both the anode and the cathode are transmissive can be manufactured.

<Support substrate>
The support substrate (hereinafter also referred to as a substrate, substrate, substrate, support, etc.) that can be used in the organic EL device of the present invention is not particularly limited in the type of glass, plastic, etc., and is transparent. Or opaque.
When extracting light from the support substrate side, the support substrate is preferably transparent. Examples of the transparent support substrate preferably used include glass, quartz, and a transparent resin film. A particularly preferable support substrate is a resin film capable of giving flexibility to the organic EL element.

  Examples of the resin film include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyethylene, polypropylene, cellophane, cellulose diacetate, cellulose triacetate (TAC), cellulose acetate butyrate, cellulose acetate propionate ( CAP), cellulose esters such as cellulose acetate phthalate, cellulose nitrate or derivatives thereof, polyvinylidene chloride, polyvinyl alcohol, polyethylene vinyl alcohol, syndiotactic polystyrene, polycarbonate, norbornene resin, polymethylpentene, polyether ketone, polyimide , Polyethersulfone (PES), polyphenylene sulfide, polysulfones, Cycloolefin resins such as polyetherimide, polyetherketoneimide, polyamide, fluororesin, nylon, polymethylmethacrylate, acrylic or polyarylate, Arton (trade name, manufactured by JSR) or Appel (trade name, manufactured by Mitsui Chemicals) Can be mentioned.

An inorganic film, an organic film, or a hybrid film of both may be formed on the surface of the resin film, and the water vapor permeability (25 ± 0.5 ° C.) measured by a method according to JIS K 7129-1992. , Relative humidity (90 ± 2)% RH) is preferably 0.01 g / m ² · 24 h or less barrier film, and moreover, oxygen permeability measured by a method according to JIS K 7126-1987 However, it is preferable that the film has a high barrier property of 1 × 10 ⁻³ ml / m ² · 24 h · atm or less and a water vapor permeability of 1 × 10 ⁻⁵ g / m ² · 24 h or less.

As a material for forming the barrier film, any material may be used as long as it has a function of suppressing intrusion of elements that cause deterioration of elements such as moisture and oxygen. For example, silicon oxide, silicon dioxide, silicon nitride, or the like can be used. Further, in order to improve the brittleness of the film, it is more preferable to have a laminated structure of these inorganic layers and organic material layers. Although there is no restriction | limiting in particular about the lamination | stacking order of an inorganic layer and an organic layer, It is preferable to laminate | stack both alternately several times.
The method for forming the barrier film is not particularly limited. For example, vacuum deposition, sputtering, reactive sputtering, molecular beam epitaxy, cluster ion beam, ion plating, plasma polymerization, atmospheric pressure plasma polymerization A plasma CVD method, a laser CVD method, a thermal CVD method, a coating method, or the like can be used, but an atmospheric pressure plasma polymerization method as described in JP-A-2004-68143 is particularly preferable.

Examples of the opaque support substrate include metal plates such as aluminum and stainless steel, films, opaque resin substrates, and ceramic substrates.
The external extraction quantum efficiency at room temperature (25 ° C.) of light emission of the organic EL device of the present invention is preferably 1% or more, and more preferably 5% or more.
Here, the external extraction quantum efficiency (%) = the number of photons emitted to the outside of the organic EL element / the number of electrons sent to the organic EL element × 100.
In addition, a hue improvement filter such as a color filter may be used in combination, or a color conversion filter that converts the emission color from the organic EL element into multiple colors using a phosphor may be used in combination.

<Sealing>
Examples of the sealing means used for sealing the organic EL element of the present invention include a method of bonding a sealing member, an electrode, and a support substrate with an adhesive. As a sealing member, it should just be arrange | positioned so that the display area | region of an organic EL element may be covered, and it may be concave plate shape or flat plate shape. Moreover, transparency and electrical insulation are not particularly limited.
Specific examples include a glass plate, a polymer plate / film, and a metal plate / film. Examples of the glass plate include soda-lime glass, barium / strontium-containing glass, lead glass, aluminosilicate glass, borosilicate glass, barium borosilicate glass, and quartz. Examples of the polymer plate include polycarbonate, acrylic, polyethylene terephthalate, polyether sulfide, and polysulfone. Examples of the metal plate include those made of one or more metals or alloys selected from the group consisting of stainless steel, iron, copper, aluminum, magnesium, nickel, zinc, chromium, titanium, molybdenum, silicon, germanium, and tantalum.

In the present invention, a polymer film and a metal film can be preferably used because the organic EL element can be thinned. Furthermore, the polymer film has an oxygen permeability measured by a method according to JIS K 7126-1987 of 1 × 10 ⁻³ ml / m ² · 24 h or less, and measured by a method according to JIS K 7129-1992. The water vapor permeability (25 ± 0.5 ° C., relative humidity 90 ± 2%) is preferably 1 × 10 ⁻³ g / m ² · 24 h or less.
For processing the sealing member into a concave shape, sandblasting, chemical etching, or the like is used.

Specific examples of the adhesive include photocuring and thermosetting adhesives having reactive vinyl groups such as acrylic acid oligomers and methacrylic acid oligomers, and moisture curing adhesives such as 2-cyanoacrylates. be able to. Moreover, heat | fever and chemical curing types (two-component mixing), such as an epoxy type, can be mentioned. Moreover, hot-melt type polyamide, polyester, and polyolefin can be mentioned. Moreover, a cationic curing type ultraviolet curing epoxy resin adhesive can be mentioned.
In addition, since an organic EL element may deteriorate by heat processing, what can be adhesive-hardened from room temperature to 80 degreeC is preferable. A desiccant may be dispersed in the adhesive. Application | coating of the adhesive agent to a sealing part may use commercially available dispenser, and may print like screen printing.

In addition, it is also preferable that the electrode and the organic layer are coated on the outside of the electrode facing the support substrate with the organic layer interposed therebetween, and an inorganic or organic layer is formed in contact with the support substrate to form a sealing film. . In this case, the material for forming the film may be any material that has a function of suppressing intrusion of elements that cause deterioration of elements such as moisture and oxygen. For example, silicon oxide, silicon dioxide, silicon nitride, or the like may be used. it can.
Further, in order to improve the brittleness of the film, it is preferable to have a laminated structure of these inorganic layers and layers made of organic materials. There are no particular limitations on the method of forming these films. For example, vacuum deposition, sputtering, reactive sputtering, molecular beam epitaxy, cluster ion beam, ion plating, plasma polymerization, atmospheric pressure plasma A combination method, a plasma CVD method, a laser CVD method, a thermal CVD method, a coating method, or the like can be used.

In the gap between the sealing member and the display area of the organic EL element, an inert gas such as nitrogen or argon, or an inert liquid such as fluorinated hydrocarbon or silicon oil can be injected in the gas phase and liquid phase. preferable. A vacuum can also be used. Moreover, a hygroscopic compound can also be enclosed inside.
Examples of the hygroscopic compound include metal oxides (for example, sodium oxide, potassium oxide, calcium oxide, barium oxide, magnesium oxide, aluminum oxide) and sulfates (for example, sodium sulfate, calcium sulfate, magnesium sulfate, cobalt sulfate). Etc.), metal halides (eg calcium chloride, magnesium chloride, cesium fluoride, tantalum fluoride, cerium bromide, magnesium bromide, barium iodide, magnesium iodide etc.), perchloric acids (eg perchloric acid) Barium, magnesium perchlorate, and the like), and anhydrous salts are preferably used in sulfates, metal halides, and perchloric acids.

<Protective film, protective plate>
In order to increase the mechanical strength of the element, a protective film or a protective plate may be provided outside the sealing film or the sealing film on the side facing the support substrate with the organic layer interposed therebetween. In particular, when sealing is performed by the sealing film, the mechanical strength is not necessarily high, and thus it is preferable to provide such a protective film and a protective plate.
As a material that can be used for this, the same glass plate, polymer plate / film, metal plate / film, etc. used for the sealing can be used, but the polymer film is light and thin. Is preferably used.

<Light extraction improvement technology>
An organic EL element emits light inside a layer having a refractive index higher than that of air (within a refractive index of about 1.6 to 2.1), and is about 15% to 20% of light generated in the light emitting layer. It is generally said that it can only be taken out. This is because light incident on the interface (interface between the transparent substrate and air) at an angle θ greater than the critical angle causes total reflection and cannot be taken out of the device, or between the transparent electrode or light emitting layer and the transparent substrate. This is because light is totally reflected between the light and the light is guided through the transparent electrode or the light emitting layer, and as a result, the light escapes in the direction of the side surface of the device.

  As a technique for improving the light extraction efficiency, for example, a method of forming irregularities on the surface of the transparent substrate to prevent total reflection at the transparent substrate and the air interface (for example, US Pat. No. 4,774,435), A method for improving efficiency by providing light condensing property (for example, JP-A-63-314795), a method for forming a reflective surface on a side surface of an element (for example, JP-A-1-220394), a substrate, etc. A method of forming an antireflection film by introducing a flat layer having an intermediate refractive index between the substrate and the light emitter (for example, Japanese Patent Application Laid-Open No. 62-172691), lower refraction than the substrate between the substrate and the light emitter A method of introducing a flat layer having a refractive index (for example, Japanese Patent Application Laid-Open No. 2001-202827), and a method of forming a diffraction grating between any one of the substrate, the transparent electrode layer and the light emitting layer (including between the substrate and the outside) ( JP-A-11 No. 283,751 Publication), and the like.

In the present invention, these methods can be used in combination with the organic EL device of the present invention. However, a method of introducing a flat layer having a lower refractive index than the substrate between the substrate and the light emitter, or a substrate, transparent A method of forming a diffraction grating between any layers of the electrode layer and the light emitting layer (including between the substrate and the outside) can be suitably used.
In the present invention, by combining these means, it is possible to obtain an element having higher luminance or durability.

When a low refractive index medium is formed between the transparent electrode and the transparent substrate with a thickness longer than the wavelength of light, the light extracted from the transparent electrode has a higher extraction efficiency to the outside as the refractive index of the medium is lower. Become.
Examples of the low refractive index layer include aerogel, porous silica, magnesium fluoride, and a fluorine-based polymer. Since the refractive index of the transparent substrate is generally in the range of about 1.5 to 1.7, the low refractive index layer preferably has a refractive index of about 1.5 or less. Furthermore, it is preferable that it is 1.35 or less.
The thickness of the low refractive index medium is preferably at least twice the wavelength in the medium. This is because the effect of the low refractive index layer is diminished when the thickness of the low refractive index medium is about the wavelength of light and the electromagnetic wave exuded by evanescent enters the substrate.

  The method of introducing a diffraction grating into an interface that causes total reflection or in any medium has a feature that the effect of improving the light extraction efficiency is high. This method uses the property that the diffraction grating can change the direction of light to a specific direction different from refraction by so-called Bragg diffraction, such as first-order diffraction or second-order diffraction. The light that cannot be emitted due to total internal reflection between layers is diffracted by introducing a diffraction grating into any layer or medium (in the transparent substrate or transparent electrode). , Trying to extract light out.

The introduced diffraction grating desirably has a two-dimensional periodic refractive index. This is because light emitted from the light-emitting layer is randomly generated in all directions, so in a general one-dimensional diffraction grating having a periodic refractive index distribution only in a certain direction, only light traveling in a specific direction is diffracted. The light extraction efficiency does not increase so much.
However, by making the refractive index distribution a two-dimensional distribution, light traveling in all directions is diffracted, and light extraction efficiency is increased.
The position where the diffraction grating is introduced may be in any of the layers or in the medium (in the transparent substrate or the transparent electrode), but is preferably in the vicinity of the organic light emitting layer where light is generated. At this time, the period of the diffraction grating is preferably within a range of about 1/2 to 3 times the wavelength of light in the medium. The arrangement of the diffraction gratings is preferably two-dimensionally repeated, such as a square lattice, a triangular lattice, or a honeycomb lattice.

<Condensing sheet>
The organic EL element of the present invention can be processed to provide a structure on a microlens array, for example, on the light extraction side of a support substrate (substrate), or combined with a so-called condensing sheet, for example, in a specific direction, for example, the element Condensing light in the front direction with respect to the light emitting surface can increase the luminance in a specific direction.
As an example of the microlens array, quadrangular pyramids having a side of 30 μm and an apex angle of 90 degrees are arranged two-dimensionally on the light extraction side of the substrate. One side is preferably within a range of 10 to 100 μm. If it is smaller than this, the effect of diffraction is generated and colored, and if it is too large, the thickness becomes thick, which is not preferable.
As the condensing sheet, for example, a sheet that is put into practical use in an LED backlight of a liquid crystal display device can be used. As such a sheet, for example, a brightness enhancement film (BEF) manufactured by Sumitomo 3M Limited can be used. As the shape of the prism sheet, for example, a substrate may be formed with a triangle stripe having a vertex angle of 90 degrees and a pitch of 50 μm, or the vertex angle is rounded and the pitch is changed randomly. Other shapes may also be used.
Moreover, in order to control the light emission angle from an organic EL element, you may use a light-diffusion plate and a film together with a condensing sheet. For example, a diffusion film (light-up) manufactured by Kimoto Co., Ltd. can be used.

≪Usage≫
The organic EL element of the present invention can be used as an electronic device such as a display device, a display, and various light emitting devices.
Examples of light emitting devices include lighting devices (home lighting, interior lighting), clocks and backlights for liquid crystals, billboard advertisements, traffic lights, light sources of optical storage media, light sources of electrophotographic copying machines, light sources of optical communication processors, light Although the light source of a sensor etc. are mentioned, It is not limited to this, Especially, it can use effectively for the use as a backlight of a liquid crystal display device, and a light source for illumination.
In the organic EL element of the present invention, patterning may be performed by a metal mask, an ink jet printing method, or the like as needed during film formation. In the case of patterning, only the electrode may be patterned, the electrode and the light emitting layer may be patterned, or the entire layer of the element may be patterned. In the fabrication of the element, a conventionally known method is used. Can do.

  The light emission color of the organic EL device of the present invention and the compound of the present invention is shown in FIG. 14.16 on page 108 of “New Color Science Handbook” (Edited by the Japan Color Society, University of Tokyo Press, 1985). It is determined by the color when the result measured with a total of CS-1000 (manufactured by Konica Minolta Co., Ltd.) is applied to the CIE chromaticity coordinates.

When the organic EL element of the present invention is a white element, white means that the chromaticity in the CIE1931 color system at 1000 cd / m ² is X when the 2 ° viewing angle front luminance is measured by the above method. = 0.33 ± 0.07 and Y = 0.33 ± 0.1.

<Display device>
The display device including the organic EL element of the present invention may be single color or multicolor, but here, the multicolor display device will be described.

In the case of a multicolor display device, a shadow mask is provided only at the time of forming a light emitting layer, and a film can be formed on one surface by vapor deposition, casting, spin coating, ink jet, printing, or the like.
In the case of patterning only the light emitting layer, there is no limitation on the method, but a vapor deposition method, an inkjet method, a spin coating method, and a printing method are preferable.

  The configuration of the organic EL element provided in the display device is selected from the above-described configuration examples of the organic EL element as necessary.

  Moreover, the manufacturing method of an organic EL element is as having shown to the one aspect | mode of manufacture of the organic EL element of said invention.

  When a DC voltage is applied to the multicolor display device thus obtained, light emission can be observed by applying a voltage of about 2 to 40 V with the positive polarity of the anode and the negative polarity of the cathode. Further, even when a voltage is applied with the opposite polarity, no current flows and no light emission occurs. Further, when an AC voltage is applied, light is emitted only when the anode is in the + state and the cathode is in the-state. The alternating current waveform to be applied may be arbitrary.

  The multicolor display device can be used as a display device, a display, or various light emission sources. In a display device or display, full-color display is possible by using three types of organic EL elements of blue, red, and green light emission.

  Examples of the display device or display include a television, a personal computer, a mobile device, an AV device, a character broadcast display, and an information display in an automobile. In particular, it may be used as a display device for reproducing still images and moving images, and the driving method when used as a display device for reproducing moving images may be either a simple matrix (passive matrix) method or an active matrix method.

  Light-emitting devices include household lighting, interior lighting, clock and liquid crystal backlights, billboard advertisements, traffic lights, optical storage media light sources, electrophotographic copying machine light sources, optical communication processor light sources, optical sensor light sources, etc. However, the present invention is not limited to these.

<Lighting device>
The organic EL element of the present invention can also be used for a lighting device.
The organic EL element of the present invention may be used as an organic EL element having a resonator structure. Examples of the purpose of use of the organic EL element having such a resonator structure include a light source of an optical storage medium, a light source of an electrophotographic copying machine, a light source of an optical communication processing machine, and a light source of an optical sensor. It is not limited. Moreover, you may use for the said use by making a laser oscillation.
Further, the organic EL element of the present invention may be used as a kind of lamp for illumination or exposure light source, a projection device for projecting an image, or a type for directly viewing a still image or a moving image. It may be used as a display device (display).
The driving method when used as a display device for reproducing a moving image may be either a passive matrix method or an active matrix method. Alternatively, it is possible to produce a full-color display device by using two or more organic EL elements of the present invention having different emission colors.

  Moreover, the luminescent compound of this invention is applicable to the organic EL element which produces substantially white light emission as an illuminating device. For example, when a plurality of luminescent compounds are used, white emission can be obtained by simultaneously emitting a plurality of emission colors and mixing the colors. The combination of a plurality of emission colors may include three emission maximum wavelengths of three primary colors of red, green, and blue, or two of the complementary colors such as blue and yellow, blue green and orange, etc. The thing containing the light emission maximum wavelength may be used.

In addition, the method for forming the organic EL device of the present invention may be simply arranged by providing a mask only when forming a light emitting layer, a hole transport layer, an electron transport layer, or the like, and separately coating with the mask. Since the other layers are common, patterning of a mask or the like is unnecessary, and for example, an electrode film can be formed on one surface by a vapor deposition method, a cast method, a spin coating method, an ink jet method, a printing method, or the like, and productivity is improved.
According to this method, unlike a white organic EL device in which light emitting elements of a plurality of colors are arranged in parallel in an array, the elements themselves are luminescent white.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "mass part" or "mass%" is represented.
Moreover, the volume% of the compound in each Example is calculated | required from specific gravity by measuring the layer thickness to produce by the quartz crystal microbalance method, and calculating mass.

In addition, the compound used in a present Example is represented by the following chemical structural formula.

[Example 1]
(Preparation of organic EL element 1-1)
An ITO (indium tin oxide) film having a thickness of 150 nm was formed as an anode on a glass substrate having a size of 50 mm × 50 mm and a thickness of 0.7 mm, followed by patterning. Thereafter, the transparent substrate with the ITO transparent electrode is ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, and subjected to UV ozone cleaning for 5 minutes. Then, the transparent substrate is placed on a substrate holder of a commercially available vacuum deposition apparatus. Fixed.
Each of the vapor deposition crucibles in the vacuum vapor deposition apparatus was filled with the constituent material of each layer in an amount optimal for device fabrication. As the evaporation crucible, a crucible made of a resistance heating material made of molybdenum or tungsten was used.

After reducing the vacuum to 1 × 10 ⁻⁴ Pa, the deposition crucible containing HAT-CN was energized and heated, and deposited on the ITO transparent electrode at a deposition rate of 0.1 nm / second. A hole injection layer was formed.
Subsequently, the evaporation crucible containing TrisPCz was energized and heated, and evaporated at a deposition rate of 0.1 nm / second to form a hole transport layer having a layer thickness of 30 nm.
Next, mCBP as the host compound and D-1 as the TADF compound are co-evaporated at a deposition rate of 0.1 nm / second so that the volume percentage is 85% and 15%, respectively, to form a light emitting layer having a layer thickness of 30 nm. did.
Further, the deposition crucible containing T2T was energized and heated, and was deposited at a deposition rate of 0.1 nm / second to form an exciton blocking layer having a layer thickness of 10 nm.
Next, the deposition crucible containing BPy-TP2 was energized and heated, and deposited at a deposition rate of 0.1 nm / second to form an electron transport layer having a layer thickness of 40 nm.
On top of this, lithium fluoride was formed to a thickness of 0.8 nm, and then 100 nm of aluminum was deposited to form a cathode.
The non-light-emitting surface side of the above element was covered with a can-shaped glass case in an atmosphere of high purity nitrogen gas having a purity of 99.999% or more, and an electrode lead-out wiring was installed to prepare an organic EL element 1-1.

(Preparation of organic EL elements 1-2 to 1-109)
Organic EL devices 1-2 to 1-109 were produced in the same manner as the organic EL device 1-1 except that the host compound and the TADF compound were changed as shown in Tables 1 to 3.

<Evaluation of organic EL element>
The following evaluation was performed about the obtained organic EL element.

<Luminescent life>
When driven at a constant current of ^2.5 mA / cm ² , the time required for the luminance to drop to half of the luminance immediately after the start of light emission (initial luminance) was measured, and this was calculated as the half-life time (τ 0.5). As an index of life. In addition, the spectral radiance meter CS-2000 (made by Konica Minolta) was used for the measurement.

  Moreover, the measurement result of the light emission lifetime of Table 1-Table 3 was represented by the relative value when the measured value of the organic EL element 1-1 was set to 100.

(result)
From the results shown in Tables 1 to 3, it was confirmed that the organic EL device according to the present invention has a longer light emission lifetime than the organic EL device of the comparative example.

[Example 2]
(Preparation of organic EL element 2-1)
After patterning a 120 nm-thick ITO (indium tin oxide) substrate on a 30 mm × 30 mm × 0.7 mm glass substrate as an anode, the substrate provided with this ITO transparent electrode was ultrasonically cleaned with isopropyl alcohol. Then, it was dried with dry nitrogen gas, and UV ozone cleaning was performed for 5 minutes.

  A solution obtained by diluting poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate (PEDOT / PSS, Bayer, Baytron P Al 4083) to 70% with pure water on this substrate was spin-coated at 3000 rpm for 30 seconds. After forming into a film by the method, it was dried at 200 ° C. for 1 hour to provide a hole injection layer having a layer thickness of 30 nm.

  This substrate was transferred to a glove box under a nitrogen atmosphere in accordance with JIS B9920 with a measured cleanliness of class 100, a dew point temperature of −80 ° C. or lower, and an oxygen concentration of 0.8 ppm.

  A coating solution for a hole transport layer was prepared as follows in a glove box, and applied with a spin coater under conditions of 1500 rpm and 30 seconds.

This substrate was heated at 150 ° C. for 10 seconds, and irradiated with 30 mW / cm ² of ultraviolet light for 20 seconds using a high pressure mercury lamp (OHD-110M-ST, manufactured by Oak Manufacturing Co., Ltd.).

  Furthermore, it heated at 120 degreeC for 30 minute (s), and provided the positive hole transport layer. When the coating was performed under the same conditions on a separately prepared substrate and measured, the layer thickness was 20 nm.

(Coating liquid for hole transport layer)
Toluene 100g
HT-A 0.45g
HT-B 0.05g
Subsequently, the light emitting layer coating liquid was prepared as follows, and it apply | coated on the conditions which raise from 500 rpm to 5000 rpm in 30 seconds with a spin coater. Furthermore, it heated at 150 degreeC for 30 minutes, and provided the light emitting layer. When it applied and measured on the board | substrate prepared separately on the same conditions, the layer thickness was 40 nm.

(Light emitting layer coating solution)
Toluene 100g
mCBP 1.00g
DP-1 0.11g
Subsequently, the coating liquid for electron carrying layers was prepared as follows, and it apply | coated on the conditions of 1500 rpm and 30 seconds with a spin coater. Furthermore, it heated at 120 degreeC for 30 minutes, and provided the electron carrying layer. When the coating was performed under the same conditions on a separately prepared substrate and measured, the layer thickness was 30 nm.

(Coating liquid for electron transport layer)
2,2,3,3-tetrafluoro-1-propanol 100 g
ET-A 0.75g
Next, the substrate provided up to the electron transport layer was moved to a vapor deposition machine without being exposed to the atmosphere, and the pressure was reduced to 4 × 10 −4 Pa. Note that cesium fluoride and aluminum were each placed in a tungsten resistance heating boat and attached to a vapor deposition machine.

  First, a resistance heating boat containing cesium fluoride was energized and heated to provide a 3 nm electron injection layer made of cesium fluoride on the substrate. Subsequently, a resistance heating boat containing aluminum was energized and heated, and a cathode having a layer thickness of 100 nm made of aluminum was provided at a deposition rate of 1 to 2 nm / second.

  The substrate provided up to the cathode is moved to a glove box with a cleanness measured in accordance with JIS B9920 of class 100, a dew point temperature of -80 ° C. or less, and an oxygen concentration of 0.8 ppm without being exposed to the atmosphere. Then, sealing was performed with a glass sealing can attached with barium oxide which is a water-absorbing agent, and an electrode lead-out wiring was installed to prepare an organic EL element 2-1.

(Production of organic EL elements 2-2 to 2-109)
Organic EL elements 2-2 to 2-109 were produced in the same manner as the organic EL element 2-1, except that the host compound and the TADF compound were changed as shown in Tables 4 to 6.

<Evaluation of organic EL element>
The following evaluation was performed about the obtained organic EL element.

<Luminescent life>
When driven at a constant current of ^2.5 mA / cm ² , the time required for the luminance to drop to half of the luminance immediately after the start of light emission (initial luminance) was measured, and this was calculated as the half-life time (τ 0.5). As an index of life. In addition, the spectral radiance meter CS-2000 (made by Konica Minolta) was used for the measurement.

  Moreover, the measurement result of the light emission lifetime of Table 4-Table 6 was represented by the relative value when the measured value of the organic EL element 2-1 was set to 100.

(result)
From the results shown in Tables 4 to 6, it was confirmed that the organic EL device according to the present invention has a longer light emission lifetime than the organic EL device of the comparative example.

[Example 3]
(Preparation of organic EL element 3-1)
After patterning on a substrate (NH45 manufactured by NH Techno Glass Co., Ltd.) on which a 100 nm × 100 mm × 1.1 mm glass substrate was formed as a positive electrode on a 100 mm × 100 mm × 1.1 mm glass substrate, this transparent ITO electrode was provided. The supporting substrate was ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, and UV ozone cleaning was performed for 5 minutes.
On this transparent support substrate, using a solution obtained by diluting poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate (PEDOT / PSS, Bayer, Baytron P Al 4083) to 70% with pure water, 3000 rpm, A thin film was formed by spin coating under conditions of 30 seconds, and then dried at 200 ° C. for 1 hour to provide a hole injection layer having a layer thickness of 20 nm. This transparent support substrate was fixed to a substrate holder of a commercially available vacuum vapor deposition apparatus, and each of the vapor deposition crucibles in the vacuum vapor deposition apparatus was filled with a constituent material of each layer in an amount optimal for device fabrication. As the evaporation crucible, a crucible made of a resistance heating material made of molybdenum or tungsten was used.

After reducing the vacuum to 1 × 10 ⁻⁴ Pa, α-NPD (4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl) was added at a deposition rate of 0.1 nm / sec. Vapor deposition was performed on the hole injection layer to form a hole transport layer having a thickness of 40 nm. Next, using mCP as the host compound, TTPA as the dopant, and D-5 as the combination compound, the respective ratios were 75%, 10%, and 15% by volume, and the deposition rate was 0.1 nm / second. Evaporation was performed to form a light emitting layer with a layer thickness of 30 nm. Thereafter, TPBi (1,3,5-tris (N-phenylbenzimidazol-2-yl) benzene) was deposited at a deposition rate of 0.1 nm / second to form an electron transport layer having a layer thickness of 30 nm.
Furthermore, after forming sodium fluoride with a film thickness of 1 nm, 100 nm of aluminum was vapor-deposited to form a cathode.
The non-light-emitting surface side of the above element was covered with a can-shaped glass case in an atmosphere of high purity nitrogen gas having a purity of 99.999% or more, and an electrode lead-out wiring was installed to prepare an organic EL element 3-1.

(Preparation of organic EL element 3-2)
Organic EL except that H-115 was used as the host compound, TTPA as the dopant, and D-5 compound was used as the combined compound, and the light emitting layer was formed so that the respective ratios were 75%, 10%, and 15% by volume. The organic EL element 3-2 was produced in the same manner as in the production of the element 3-1.

(Evaluation)
The organic EL elements 3-1 and 3-2 were evaluated as follows.

<Luminescent life>
When driven at a constant current of ^2.5 mA / cm ² , the time required for the luminance to drop to half of the luminance immediately after the start of light emission (initial luminance) was measured, and this was calculated as the half-life time (τ 0.5). As an index of life. In addition, the spectral radiance meter CS-2000 (made by Konica Minolta) was used for the measurement.

  Moreover, the measurement result of the light emission lifetime of Table 7 was represented by the relative value when the measured value of the organic EL element 3-1 was 100.

(result)
From the results shown in Table 7, it was confirmed that the organic EL device according to the present invention has a longer light emission lifetime than the organic EL device of the comparative example.

Claims (11)

Contains a light-emitting compound whose absolute value (ΔEst) of energy difference between the lowest excited singlet energy and the lowest excited triplet energy is 0.5 eV or less, and a compound having a structure represented by the following general formula (I) A luminescent thin film characterized by:

[Wherein, X ₁₀₁ represents NR ₁₀₁ , an oxygen atom, a sulfur atom, CR ₁₀₂ R ₁₀₃ or SiR ₁₀₂ R ₁₀₃ . y _{1 to} y ₈ each represent CR ₁₀₄ or a nitrogen atom. R _{101 to} R ₁₀₄ each represent a hydrogen atom or a substituent, and may be bonded to each other to form a ring. Ar ₁₀₁ and Ar ₁₀₂ each represent an aromatic ring and may be the same or different. n101 and n102 each represent an integer of 0 to 4. ].   The luminescent thin film according to claim 1, wherein the luminescent compound is a TADF compound, and the compound having a structure represented by the general formula (I) is a host compound.   An organic electroluminescent device comprising the luminescent thin film according to claim 1 as a light emitting layer between an anode and a cathode.   The at least one layer of the light emitting layer contains the TADF compound, the host compound, and at least one light emitting compound among a fluorescent compound and a phosphorescent compound. Organic electroluminescence element. The organic electroluminescence device according to claim 3 or 4, wherein the host compound has a structure represented by the following general formula (II).

_{Wherein, X 101, Ar 101, Ar 102} , and n102, respectively, the same meanings as _{X 101, Ar 101, Ar 102} , and n102 in formula (I). ]. The organic electroluminescence device according to any one of claims 3 to 5, wherein the host compound has a structure represented by the following general formula (III).

_Wherein, X _{101, Ar 102} and n102, respectively, the same meanings as _{X 101, Ar 101, Ar 102} , and n102 in formula (I). ]. The organic electroluminescence device according to claim 6, wherein Ar ₁₀₂ in the general formula (III) is a substituted or unsubstituted carbazole ring. The TADF compound has a structure represented by any one of the following general formulas (1), (3), and (5), according to any one of claims 3 to 7. The organic electroluminescent element of description.

[In General Formula (1), Ar ^{1 to} Ar ³ each independently represents a substituted or unsubstituted aryl group, and at least one of them is substituted with a group having a structure represented by the following General Formula (2). Represents an aryl group. ]

[In General formula (2), R < ¹ > -R < ⁸ > represents a hydrogen atom or a substituent each independently. Z represents O, S, O═C, Ar ⁴ —N, or a chemical bond. Ar ⁴ represents a substituted or unsubstituted aryl group. Adjacent groups among R ^{1 to} R ⁸ may form a bond with each other or form a ring via a linking group. ]

[In the general formula ^(3), at least one of R 1 to R ⁵ represents a cyano ^group, at least one of R 1 to R ⁵ is a group having the structure represented by the following general formula (4) The remaining R ^{1 to} R ⁵ represent a hydrogen atom or a substituent. ]

[In the general formula ^{(4), R} 21 ~R ²⁸ independently represents a hydrogen atom or a substituent. However, at least one of the following requirements <A> or <B> is satisfied.
<A> R ²⁵ and R ²⁶ form a single bond.
<B> R ²⁷ and R ²⁸ represent an atomic group necessary for forming a substituted or unsubstituted benzene ring. ]

[In General Formula (5), R ¹ and R ² are each independently a group having a structure represented by the following General Formula (6). ]

[In General formula (6), R < ¹ > -R < ⁸ > represents a hydrogen atom or a substituent each independently. Z represents O, S, O═C, Ar ⁴ —N, or a bond. Ar ⁴ represents a substituted or unsubstituted aryl group. Adjacent groups among R ^{1 to} R ⁸ may form a bond with each other or form a ring via a linking group. ]   A display device comprising the organic electroluminescence element according to any one of claims 3 to 8.   An illuminating device comprising the organic electroluminescence element according to any one of claims 3 to 8.   11. A display device comprising the lighting device according to claim 10 and a liquid crystal element as display means.

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