WO2019163355A1 - Organic electroluminescent element, luminescent thin film, display device, and luminescent device - Google Patents

Abstract

The present invention provides an organic electroluminescent element, a luminescent thin film, a display device, and a luminescent device which have high luminous efficiency and can also prolong luminescence lifespan. The organic electroluminescent element includes a positive electrode, a negative electrode, and a light emitting layer provided between the positive electrode and the negative electrode, wherein a compound having an energy level difference of 0.5 eV or less between the lowest excited singlet energy level and the lowest excited triplet energy level, and an aggregation-induced emission molecule are contained in the light emitting layer. This luminescent thin film contains a compound having an energy level difference of 0.5 eV or less between the lowest excited singlet energy level and the lowest excited triplet energy level, and an aggregation-induced emission molecule. The display device and the luminescent device each include an organic electroluminescent element in which a compound having an energy level difference of 0.5 eV or less between the lowest excited singlet energy level and the lowest excited triplet energy level, and an aggregation-induced emission molecule are contained in a light emitting layer.

Description

ORGANIC ELECTROLUMINESCENT ELEMENT, LIGHT EMITTING THIN FILM, DISPLAY DEVICE AND LIGHTING DEVICE

The present invention relates to an organic electroluminescence element, a light-emitting thin film, a display device, and a lighting device.

A display, which is a video display unit such as a television or a computer, is one of the electronic devices indispensable in modern society. In recent years, displays have been accelerating in size and thickness, and along with this, development of organic electroluminescence (hereinafter, sometimes referred to as “organic EL”) elements has also become active. The organic EL element is a self-luminous all-solid-state light-emitting element with a relatively simple structure and a wide viewing angle, and has ideal characteristics as a component of a display. Yes.

Generally, an organic EL element has a structure in which a functional thin film such as a light emitting layer is laminated between an anode and a cathode. For the light emitting layer provided between the anode and the cathode, an organic compound exhibiting light emitting properties is used. When a voltage is applied between the anode and the cathode, electrons injected from the cathode and holes injected from the anode recombine on the luminescent compound contained in the light emitting layer to generate excitons. When the exciton is deactivated from the excited state to the ground state, light is emitted by releasing energy as light.

In the development of organic EL elements, it is predicted that demands for lower prices, mass production, luminous efficiency, and improvement of element lifetime will increase more than ever. As a method for realizing cost reduction and mass production of organic EL elements, it is considered that a wet coating method in which a functional thin film is formed by coating or printing a solution is effective. Therefore, at present, development of a manufacturing process using a wet coating method instead of the vacuum deposition method which has been the mainstream has been widely promoted.

Also, the luminescent compound used for the light emitting layer has been studied from various viewpoints. As the light emitting compound, fluorescent light emitting compounds have been mainly used from the beginning of the development of the organic EL device. However, according to the recombination of electrons and holes, singlet excitons and triplet excitons are generated at a ratio of 1: 3 according to the spin statistics rule. Therefore, in the fluorescent compound in which transition from singlet excitons contributes to light emission, the internal quantum efficiency is limited to 25% at the maximum.

In contrast, at present, it has been clarified that 100% internal quantum efficiency can be theoretically realized by a phosphorescent compound in which transition from triplet exciton contributes to light emission. Examples of phosphorescent compounds include various phosphorescent metals that facilitate the energy transfer (intersystem crossing: ISC) from singlet excitons, which are originally forbidden, to the triplet excitons by the heavy atom effect. Complexes have been developed. However, phosphorescent metal complexes that exhibit a short-wavelength side emission color such as blue have a shorter emission lifetime than other phosphorescent metal complexes that exhibit a long-wavelength side emission color. So far, an organic EL element that achieves both high luminous efficiency and element lifetime at a high level has not been realized.

On the other hand, a process is known in which reverse energy transfer (Reverse Intersystem Crossing: RISC) from triplet excitons to singlet excitons, which has a very low transition probability, is possible. Among these, energy transfer is promoted by minimizing the absolute value (hereinafter referred to as ΔE _st ) of the energy difference between the excited singlet energy level (S ₁ ) and the excited triplet energy level (T ₁ ). There is a TADF (Thermally Activated Delayed Fluorescence) mechanism, and attempts have been made to improve the exciton generation efficiency using these mechanisms.

For example, Patent Document 1 discloses that in a light emitting layer of an organic EL element, a fluorescent light emitting material and a light emitting material exhibiting TADF (hereinafter referred to as TADF molecules) are used in combination to increase the light emission efficiency of the organic EL element. Techniques to improve are described. In patent document 1, the 3rd material which has a function as a dispersing material is used with these luminescent materials. When a third material having a function as a dispersing material is used, energy loss for TADF molecules that easily cause molecular association is suppressed, and the efficiency of the light-emitting element is improved (see paragraph 0193).

Japanese Patent No. 5905916

From the viewpoint of improving the internal quantum efficiency of the organic EL element, a phosphorescent material that utilizes the radiation transition of triplet excitons for light emission is effective. However, phosphorescent materials do not have a sufficient light emission lifetime and often have the disadvantage that a rare noble metal is required. Therefore, a technique of incorporating RISC in the process of energy transfer and emitting light after converting triplet excitons to singlet excitons is promising as an alternative or complementary technique. However, in the TADF molecule, since the ISC process and the RISC process usually compete, the triplet excitons are quenched when the ISC rate constant is high and a large amount of triplet excitons are accumulated. However, there is a problem that the deterioration easily proceeds.

Such a problem of quenching of the triplet exciton can be solved to some extent by using the TADF molecule as a material that mediates RISC rather than as a light emitting material, as described in Patent Document 1. it can. However, the light-emitting compound generally used conventionally has strong light emission when the molecules are isolated, but has a property of quenching when the concentration of the molecules increases and the molecules aggregate. Even if the TADF molecule is used in combination, the luminescent compound receiving energy from the compound may still cause concentration quenching, so the concentration of the luminescent compound is increased with the aim of improving the luminous efficiency of the organic EL device. However, it is difficult to achieve high luminous efficiency.

In addition, when a wet coating method is used to form a light emitting layer, the concentration of the light emitting compound in the solution used for coating increases, and molecules easily aggregate together. It is known that local thin film density and uniformity are likely to be reduced in a thin film. Such alteration due to aggregation also causes a decrease in luminous efficiency, but it is not easy to prevent sufficiently by a dispersing material as described in Patent Document 1.

Therefore, an object of the present invention is to provide an organic electroluminescence element, a light-emitting thin film, a display device, and a lighting device that exhibit high luminous efficiency and can extend the lifetime of light emission.

The above-mentioned problem according to the present invention is solved by the following means.

1. An anode, a cathode, and a light emitting layer provided between the anode and the cathode, wherein the energy difference between the lowest excited singlet energy level and the lowest excited triplet energy level is 0 in the light emitting layer. Organic electroluminescent element containing the compound and aggregation induced luminescent molecule | numerator which are 0.5 eV or less.

［但し、一般式（Ａ）中、Ａは、電子のアクセプター部位を表し、Ｄは、電子のドナー部位を表し、Ｌは、２価の連結基を表し、ｌ及びｍは、それぞれ独立して、１～４の整数を表す。］ 2. The organic electroluminescence device according to claim 1, wherein the compound is a conjugated compound represented by the following general formula (A).

[In the general formula (A), A represents an electron acceptor moiety, D represents an electron donor moiety, L represents a divalent linking group, and l and m each independently represent Represents an integer of 1 to 4; ]

3. 2. The organic electroluminescence device according to 1 above, wherein the aggregation-induced luminescent molecule is a tetraphenylethylene derivative or a silole derivative.

4. A luminescent thin film containing a compound having an energy difference between the lowest excited singlet energy level and the lowest excited triplet energy level of 0.5 eV or less and an aggregation-induced luminescent molecule.

5. 4. A display device comprising the organic electroluminescence element according to any one of 1 to 3 above.

The illuminating device which comprises the organic electroluminescent element in any one of said 1 to 3.

According to the present invention, it is possible to provide an organic electroluminescence element, a light-emitting thin film, a display device, and a lighting device that exhibit high luminous efficiency and can extend the lifetime of light emission.

It is a conceptual diagram explaining the aggregation induced luminescent property of an AIE molecule. It is the schematic diagram which showed an example of the display apparatus comprised from an organic EL element. 4 is a schematic diagram of a display unit A. FIG. It is a schematic diagram of a pixel. It is a schematic diagram of a passive matrix type full-color display device. It is the schematic of an illuminating device. It is a schematic diagram of an illuminating device.

Hereinafter, although the form for implementing this invention is demonstrated in detail, this invention is not limited to these.

As a result of intensive studies to achieve both the light emission efficiency and the light emission lifetime of the organic EL device and the light-emitting thin film, the present inventors have found that aggregation-induced emission (AIE) molecules exhibiting strong light emission due to aggregation, When used with a Delta] E _st small compound, as the concentration of the luminescent compound to some extent higher, to reduce the concentration quenching of the problems such as occur in conventional fluorescent compound of the entire organic EL element or a light-emitting thin film It has been found that the lifetime of the light emission as is prolonged and the luminous efficiency as a whole of the luminescent compound is improved.

When a conventional fluorescent compound is used as the light-emitting compound, it is known that if the concentration of the compound is increased with the aim of improving the light-emitting efficiency, concentration quenching occurs and the light-emitting efficiency is decreased. On the other hand, when AIE molecules are used as the light-emitting compound, when the concentration of the compound is increased, rather strong light emission occurs due to aggregation of the molecules. In addition, since a compound having a small ΔE _st is used in combination, RISC is promoted, and the utilization efficiency of triplet excitons that are easily quenched is increased. Therefore, techniques using both the AIE molecules and Delta] E _st small compound as a luminescent compound is considered to be an effective means to achieve both emission efficiency and emission lifetime.

Further, it is generally known that a change over time in the film structure that occurs in the light emitting layer or the like is a cause of deterioration of the organic EL element or the like. Usually, when a molecule of a luminescent compound is diffused by application of a voltage, the aggregation and crystallization of the molecule proceeds, and the film structure of a functional thin film such as a luminescent layer can be changed. Such a change in the film structure is considered to affect the luminous efficiency of the organic EL element as a whole. On the other hand, since AIE molecules can exhibit strong light emission in an aggregated state, the change in the film structure due to application of voltage is reduced by forming aggregates in advance before the molecules start to diffuse. be able to. According to this method, there is an advantage that the film structure can be kept stable even when driving for a long time.

In addition, since the AIE molecule can exhibit strong light emission in an aggregated state, contact with oxygen, moisture, etc. in the atmosphere can be reduced by forming aggregates in advance. The formation of aggregates is presumed to reduce the contact area with oxygen, moisture, etc., which are degradation factors of organic EL elements, and improve the stability of the luminescent compound in the atmosphere. Therefore, when sealing an organic EL element etc., it becomes possible to employ | adopt the sealing material of a lower performance than before, and it is anticipated that it will lead to cost reduction.

<< Organic EL element >>
First, the organic EL element according to this embodiment will be described. The organic EL device according to this embodiment includes an anode, a cathode, and a functional thin film that is disposed between the anode and the cathode and includes at least a light emitting layer. In this organic EL element, the energy difference (ΔE _st ) between the lowest excited singlet energy level and the lowest excited triplet energy level is 0.5 eV or less in the light emitting layer provided between the anode and the cathode. And a compound having a property of easily causing RISC (hereinafter referred to as RISC compound) and an aggregation-induced luminescent molecule.

<Aggregation-induced luminescent molecule (AIE molecule)>
Aggregation-induced light-emitting molecules (AIE molecules) do not emit light because the quantum yield is low or the emission intensity is weak when the molecules are dissolved or dispersed without aggregation in the liquid medium. In a state where the molecules are aggregated to form an aggregate, the molecule exhibits the property that the quantum yield increases and the emission intensity increases.

In the organic EL device according to this embodiment, an appropriate molecule exhibiting the above properties can be used as the AIE molecule. The type of AIE molecule is not particularly limited. As an AIE molecule, one kind may be used alone or a plurality of kinds may be used in combination in a single light emitting layer. A preferred form of the AIE molecule is a molecule having at least one of an aromatic hydrocarbon ring and an aromatic heterocyclic ring.

Specific examples of AIE molecules include benzofuro-oxazolo-carbazole-based aggregation-induced luminescent molecules, carborane-based aggregation-induced luminescent molecules, tetraphenylethylene-based aggregation-induced luminescent molecules, silole-based aggregation-induced luminescent molecules, rhodamine-based molecules. In addition to aggregation-induced light-emitting molecules, aromatic ring-containing metal complexes in which a site that suppresses molecular motion is introduced into the ligand, other hetero compounds having an aromatic heterocycle, and the like can be given. However, the type of AIE molecule is not limited to these.

(Benzofuro / oxazolo / carbazole-based aggregation-induced luminescent molecules)
Examples of the benzofuro-oxazolo-carbazole-based aggregation-inducing light-emitting molecule include benzofuro-oxazolo-carbazole derivatives having a benzofuro [2,3-c] oxazolo [4,5-a] carbazole skeleton represented by the following general formula (1) Can be used.

[In the general formula (1), R ₁ and R ₂ each independently represent a hydrogen atom or a substituent, R ₃ and R ₄ each independently represent a substituent, N represents an integer of 0 to 4, and n represents an integer of 0 to 4. ]

Examples of the substituent for substituting the benzofuro-oxazolo-carbazole derivative include various electron-donating groups and electron-withdrawing groups that exhibit an arbitrary substituent constant according to Hammett's rule, but in particular, an aliphatic hydrocarbon group, an aromatic group A hydrocarbon group or a heterocyclic group is preferred.

Examples of the aliphatic hydrocarbon group that substitutes the benzofuro-oxazolo-carbazole derivative include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group. A linear or branched alkyl group such as a pentyl group, a hexyl group, an octyl group, a dodecyl group, a tridecyl group, a tetradecyl group or a pentadecyl group, or a cycloalkyl group such as a cyclopentyl group or a cyclohexyl group.

Examples of the aromatic hydrocarbon group replacing the benzofuro-oxazolo-carbazole derivative include phenyl group, mesityl group, tolyl group, xylyl group, naphthyl group, anthryl group, azulenyl group, acenaphthenyl group, fluorenyl group, phenanthryl group, indenyl Group, pyrenyl group, biphenylyl group and the like.

Examples of the heterocyclic group that substitutes the benzofuro-oxazolo-carbazole derivative include a pyridyl group, a pyridazyl group, a pyrimidinyl group, a pyrrolyl group, an imidazolyl group, a benzoimidazolyl group, a pyrazolyl group, a pyrazinyl group, a triazolyl group, a tetrazolyl group, an oxazolyl group, Thiazolyl group, benzoxazolyl group, benzothiazolyl group, isoxazolyl group, isothiazolyl group, thiadiazolyl group, oxadiazolyl group, furyl group, furazanyl group, thienyl group, quinolyl group, isoquinolyl group, benzofuryl group, dibenzofuryl group, benzothienyl group, Dibenzothienyl, indazolyl, carbazolyl, carbolinyl, diazacarbazolyl, quinoxalinyl, phenanthridyl, pyridazinyl, triazinyl, quinazolini Group, or an aromatic heterocyclic group such as a phthalazinyl group, a pyrrolidyl group, imidazolidyl group, morpholyl group, and a non-aromatic heterocyclic groups such as oxazolidyl group.

The benzofuro-oxazolo-carbazole derivatives are, for example, sulfonic acid group, carboxyl group, phosphoric acid group, phosphorous acid group, hydroxyl group, amino group, isocyanate group, silyl group, halogen atom, alkyl group, cycloalkyl group, alkenyl group, Alkynyl group, cycloalkenyl group, cycloalkynyl group, aryl group, aralkyl group, alkoxy group, aryloxy group, alkylthio group, arylthio group, alkoxycarbonyl group, aryloxycarbonyl group, sulfamoyl group, acyl group, acyloxy group, amide group , A carbamoyl group, a ureido group, an alkylsulfinyl group, an arylsulfinyl group, an alkylsulfonyl group, an arylsulfonyl group, a cyano group, a nitro group, a mercapto group, and other substituents represented by the general formula (1) , Aliphatic hydrocarbon group substituted in its backbone, an aromatic hydrocarbon group, or may have a heterocyclic group.

(Carborane-based aggregation-induced luminescent molecules)
As the carborane-based aggregation-inducing luminescent molecule, a 1,2-closo-dicarbadodecaborane derivative represented by C ₂ B ₁₀ H ₁₂ can be used. A particularly preferred form of the carborane-based aggregation-inducing luminescent molecule is a derivative of o-carborane represented by the following general formula (2). A derivative of o-carborane has a high electron withdrawing property in a cluster portion where π electrons are delocalized. It is generally known that a carborane derivative having a π-electron conjugated unit introduced at the 1- or 2-position carbon emits strong fluorescence (K. Kokado, et al., Macromolecules, 2009, 42, 1418-1420). Etc.).

[However, in General Formula (2), R ₅ and R ₆ each independently represent a hydrogen atom, an organic group, or an organometallic group, and at least one of R ₅ and R ₆ is a π-electron conjugated unit. Represents. In general formula (2), a white circle represents a carbon atom, and a black circle represents a boron atom to which a hydrogen atom is bonded. The carborane represented by the general formula (2) is a cluster molecule having a regular dihedral structure, and illustration of boron atoms and hydrogen atoms located on the back side is omitted in the formula.

Examples of the organic group for substituting carborane include saturated aliphatic hydrocarbon groups such as alkyl groups and cycloalkyl groups, unsaturated aliphatic hydrocarbon groups such as alkenyl groups, alkynyl groups, cycloalkenyl groups, and cycloalkynyl groups. And aromatic hydrocarbon groups and heterocyclic groups. Specific examples of these organic groups include the same groups as the substituents for substituting the benzofuro-oxazolo-carbazole derivative.

Examples of the organometallic group that substitutes carborane include an organic group in which metal atoms such as Ir, Pt, Rh, Ru, Ag, Cu, Os, and Re are coordinate-bonded. Specific examples of these organic groups include pyridine ring, pyridazine ring, pyrimidine ring, imidazole ring, benzimidazole ring, pyrazole ring, pyrazine ring, triazole ring, benzoxazole ring, benzothiazole ring, quinoline ring, isoquinoline ring, indazole Ring, quinoxaline ring, phenanthridine ring and the like.

The carborane has other substituents such as a sulfonic acid group, a carboxyl group, a phosphoric acid group, a phosphorous acid group, a hydroxyl group, an amino group, an isocyanate group, a silyl group, and a halogen atom, like the benzofuro-oxazolo-carbazole derivative. In addition, an organic group such as a saturated aliphatic hydrocarbon group, an unsaturated aliphatic hydrocarbon group, an aromatic hydrocarbon group, or a heterocyclic group substituted on the cluster portion may be included in the organic metal group.

In general formula (2), R ₅ and R ₆ may have the same structure or different structures as long as at least one is a π-electron conjugated unit. R ₅ and R ₆ may be condensed with each other to form a ring. R ₅ and R ₆ may be composed of a combination of an electron-donating π-electron conjugated unit and an electron-accepting π-electron conjugated unit, or an electron-donating π-electron conjugated unit and a non-conjugated atom. It may be configured in combination with a group.

Examples of the π-electron conjugated unit include an atomic group composed of an organic group such as an aromatic hydrocarbon group and an aromatic heterocyclic group, an organic metal group, and a linking group such as a conjugated diene group, an ethynylene group, and a hetero atom. Or a molecular chain. The π-electron conjugated unit is preferably composed of a planar molecular chain or atomic group in that the molecular motion of the π-electron conjugated unit is easily restricted by aggregation of carborane.

A particularly preferred form of the π-electron conjugated unit is an aromatic hydrocarbon group or an aromatic group from the viewpoint that molecular motion is easily restricted by aggregation of carborane, and that energy level control and molecular motion control can be performed appropriately. It is a heterocyclic group. As the aromatic hydrocarbon group constituting the π-electron conjugated unit, a phenyl group, a naphthyl group, an anthranyl group, a phenanthryl group, a pyrenyl group, and the like are preferable. Examples of the aromatic heterocyclic group constituting the π-electron conjugated unit include pyridyl group, pyrimidyl group, pyrrolyl group, imidazolyl group, pyrazolyl group, triazolyl group, oxazolyl group, thiazolyl group, thiadiazolyl group, oxadiazolyl group, triazinyl group, etc. Is preferred. Specifically, as R ₅ and R ₆ , a 9-carbazolylphenyl group, γ-carbonylylphenyl group, triphenylsilyl group and the like can be preferably used.

(Tetraphenylethylene-based aggregation-induced luminescent molecule)
As the tetraphenylethylene-based aggregation-inducing luminescent molecule, a tetraphenylethylene derivative having a tetraphenylethylene skeleton represented by the following general formula (3) can be used.

[In the general formula (3), R ₇ , R ₈ , R ₉ and R ₁₀ each independently represents an organic group or an organometallic group, and o, p, q and r are each independently Represents an integer of 0 to 5. ]

Examples of the organic group that substitutes the tetraphenylethylene derivative include an aliphatic hydrocarbon group, an aromatic hydrocarbon group, and a heterocyclic group. Specific examples of these organic groups include the same groups as the substituents for substituting the benzofuro-oxazolo-carbazole derivative.

Examples of the organometallic group that substitutes for the tetraphenylethylene derivative include organic groups in which metal atoms such as Ir, Pt, Rh, Ru, Ag, Cu, Os, and Re are coordinated. Specific examples of these organic groups include the same groups as the organometallic groups that substitute for the carborane.

The tetraphenylethylene derivative is the same as the benzofuro-oxazolo-carbazole derivative, and other sulfonic acid group, carboxyl group, phosphoric acid group, phosphorous acid group, hydroxyl group, amino group, isocyanate group, silyl group, halogen atom, etc. You may have a substituent in tetraphenylethylene frame | skeleton itself, organic groups, such as an aliphatic hydrocarbon group substituted by the frame | skeleton, an aromatic hydrocarbon group, and a heterocyclic group, or an organometallic group.

In general formula (3), R ₇ to R ₁₀ may have the same structure or different structures among one or more substituents substituted on the same ring. . Also, R ₇ to R ₁₀ may have the same structure or different structures. R ₇ to R ₁₀ may be condensed with substituents substituted on the same ring to form a ring, or condensed with substituents substituted on different rings to form a ring. It may be formed. Note that the tetraphenylethylene derivative has a structure in which two or more tetraphenylethylene skeletons represented by the general formula (3) are included and these skeletons are connected to each other via any one of R ₇ to R _10. May be.

Specific examples of the tetraphenylethylene-based aggregation-inducing luminescent molecule include tetraphenylethylene and a 9-carbazolylphenyl group, γ at the para-position of the benzene ring of the tetraphenylethylene derivative represented by the general formula (3). -Derivatives substituted with a carbonylylphenyl group, a 4,6-diphenyl-1,3,5-triazinyl group and the like are exemplified, but not limited thereto.

(Silole-based aggregation-induced luminescent molecules)
As the silole-based aggregation-inducing luminescent molecule, a silole derivative in which a π-electron conjugated unit is bonded to a silole ring can be used. A particularly preferred form of the silole-based aggregation-inducing luminescent molecule is a derivative in which the 3-position and 4-position carbon of the silole ring represented by the following general formula (4) is substituted with a benzene ring which may have a substituent. It is.

[In the general formula (4), R ₁₁ and R ₁₂ each independently represents a hydrocarbon group having 1 to 12 carbon atoms, and s and t each independently represents an integer of 0 to 5] R ₁₃ and R ₁₆ each independently represents an organic group, and R ₁₄ and R ₁₅ each independently represents an organic group having 1 to 20 carbon atoms. ]

Examples of R ₁₁ and R ₁₂ for substituting the silole derivative include a saturated aliphatic hydrocarbon group having 1 to 12 carbon atoms, an unsaturated aliphatic hydrocarbon group having 1 to 12 carbon atoms, and a carbon number of 1 -12 aromatic hydrocarbon groups. Specific examples of these organic groups include the same groups as the substituents for substituting the benzofuro-oxazolo-carbazole derivative. R ₁₁ and R ₁₂ are more preferably a hydrocarbon group having 1 to 6 carbon atoms, and still more preferably a hydrocarbon group having 1 to 4 carbon atoms. Further, s and t are preferably 0 or 1, and particularly preferably 0, that is, R ₁₁ and R ₁₂ are each a phenyl group.

Examples of R ₁₃ and R ₁₆ for substituting a silole derivative include an atomic group or a molecular chain composed of an aliphatic hydrocarbon group, an aromatic hydrocarbon group, or a heterocyclic group. Specific examples of these organic groups include the same groups as the substituents for substituting the carborane. R ₁₃ or R ₁₆ is one of a benzene ring, a naphthalene ring, a pyridine ring, a pyrrole ring, an imidazole ring, an imidazoline ring, a pyrazolyl ring, a pyrazine ring, an oxazole ring, a thiazole ring, a furan ring, and a thiophene ring. A π-electron conjugated unit constituted as described above is more preferable, a π-electron conjugated unit including one or more benzene rings is further preferable, and a phenyl group is particularly preferable.

Examples of R ₁₄ and R ₁₅ for substituting the silole derivative include a saturated aliphatic hydrocarbon group having 1 to 20 carbon atoms, an unsaturated aliphatic hydrocarbon group having 1 to 20 carbon atoms, and a carbon number of 1 Up to 20 aromatic hydrocarbon groups. Specific examples of these organic groups include the same groups as the substituents for substituting the benzofuro-oxazolo-carbazole derivative. The organic groups represented by R ₁₄ and R ₁₅ are not limited to hydrocarbons, and may have heteroatoms such as N, O, S, and Si. R ₁₄ and R ₁₅ are more preferably an organic group having 1 to 12 carbon atoms, more preferably a phenyl group or an alkyl group having 1 to 12 carbon atoms.

(Acquisition method of AIE molecule)
The above AIE molecule can be synthesized using a conventionally known method. For example, K.K. Kokado, et al. , Macromolecules, 2009, 42, 1418-1420, US Patent Application Publication No. 2012/299474, US Patent Application Publication No. 2013/179791, US Patent Application Publication No. 2013/89889, Qin W. , Et al. , Chem. Commun. , 2015, 51, 7321-7324, Kim J. et al. Y. , Et al. , Adv. Mater. 2013, 25, 2666-2671, Chen B. et al. , Et al. , Chem. Eur. J. et al. , 2014, 20, 1931-1939 can be used. Examples of rhodamine-based aggregation-inducing luminescent molecules include S. Kamino, et al. , Chem. Commun. , 2010, 46, 9013-9015 can be used.

(Aggregation-induced luminescence of AIE molecule)
FIG. 1 is a conceptual diagram illustrating aggregation-induced luminescence of AIE molecules. As shown in FIG. 1, a conventional fluorescent compound that does not exhibit aggregation-induced light emission causes quenching and a decrease in light emission intensity as the concentration increases. On the other hand, AIE molecules have the property that the emission intensity increases as the concentration increases. Whether or not the luminescent compound has such aggregation-induced luminescence can be confirmed by dispersing molecules in a solvent and comparing the luminescence intensity observed for each concentration.

Specifically, a predetermined concentration of a luminescent compound is dispersed in a good solvent at room temperature (25 ° C.), the emission spectrum of the excited luminescent compound is measured, and the peak intensity at the maximum emission wavelength is measured in the case of a dilute dispersion solution. It is possible to confirm whether or not it has aggregation-induced luminescence by obtaining the relative intensity with respect to. As shown in FIG. 1, the emission intensity at the maximum emission wavelength λmax detected from the dispersion solution with a concentration of 0.01 mM is I ₀ , and the emission intensity at the maximum emission wavelength λmax detected from the dispersion solution with a concentration of 10 mM is I ₁₀ . The light emitting compound satisfying the following mathematical formula (A) is defined as an AIE molecule.
I ₁₀ / I ₀ > 1 (A)

(AIE molecule concentration)
As long as the AIE molecule is used in combination with a RISC compound described later, the AIE molecule may be contained in the light emitting layer at an appropriate concentration. The concentration of AIE molecules in the light emitting layer can be, for example, 0.1% by mass or more and 99.9% by mass or less. If the charge transporting property of the AIE molecule is good, high luminous efficiency can be obtained even if the light emitting layer is formed in such a wide range of film concentrations. The light-emitting layer can be composed of only AIE molecules and RISC compounds, or can be composed of AIE molecules and RISC compounds, host compounds described later, and other light-emitting dopants.

The concentration of AIE molecules in the light emitting layer is preferably 2% by mass or more, more preferably 5% by mass or more, and still more preferably 10% by mass or more. When the concentration of AIE molecules in the film is 2% by mass or more, strong light emission due to aggregation of AIE molecules is easily obtained, and when the concentration is 10% by mass or more, the luminescent compound is more in comparison with a general light emitting layer. Since it exists in the aggregated state, light emission by the aggregated AIE molecules can be obtained reliably, and deterioration of the luminescent compound due to oxygen, moisture, etc. in the atmosphere can be avoided. The concentration of AIE molecules in the light emitting layer may be 70% by mass or less, or 70% by mass or more and 99.9% by mass or less. When the concentration of AIE molecules in the film is 70% by mass or less, high luminous efficiency can be obtained when a host compound or the like is used in addition to the RISC compound.

<RISC compound>
As the RISC compound, a compound in which the energy difference (ΔE _st ) between the lowest excited singlet energy level (S ₁ ) and the lowest excited triplet energy level (T ₁ ) is 0.5 eV or less is used as the AIE molecule. Can be used together. ΔE _st of the RISC compound is preferably 0.3 eV or less, more preferably 0.1 eV or less. Since the RISC compound has a small _ΔEst , the RISC compound has a property of causing a reverse intersystem crossing from a triplet exciton to a singlet exciton, which is spin-forbidden, with high probability even at room temperature.

In general, triplet excitons are theoretically generated at a rate of 75% under electric field excitation. However, in the conventional fluorescent compound, the generated triplet excitons are easily non-radiatively deactivated, so that theoretically, only a maximum emission quantum yield of 25% can be realized. On the other hand, when a RISC compound having a small ΔE _st is used, triplet excitons generated by electric field excitation can be inverted to singlet excitons by inverse intersystem crossing. Singlet excitons can generate an instantaneous radiative transition, and can generate a radiative transition after intermolecular energy transfer. Therefore, the internal quantum efficiency can be improved by using a RISC compound in the light emitting layer.

In the RISC compound, the compound itself may emit delayed luminescence due to the radiation transition of the singlet exciton, or the AIE molecule may emit light by transferring energy to the AIE molecule that uses the singlet exciton. When the AIE molecule used in combination emits light, it is preferable that the speed of intermolecular energy transfer is sufficiently faster than the speed of ISC, the speed of radiation transition from T ₁ , and the speed of non-radiation transition, and fluorescence resonance energy transfer (FRET). From the viewpoint of efficiency, it is preferable to use a combination having a large overlap integral between the absorption spectrum of the RISC compound and the absorption spectrum of the AIE molecule.

As the RISC compound, a conjugated compound represented by the following general formula (A) is particularly preferably used. According to the soot conjugated compound represented by the general formula (A), the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) in the molecule are spatially separated. Since the overlap of the wave functions of each other is reduced, a compound having a sufficiently small ΔE _st and easily generating RISC at room temperature can be obtained.

[In the general formula (A), A represents an electron acceptor moiety, D represents an electron donor moiety, L represents a divalent linking group, and l and m each independently represent Represents an integer of 1 to 4; ]

As the acceptor site A, an atomic group or a molecular chain that has a high electron withdrawing property and deepens the energy level of LUMO or HOMO in the molecule can be used. As the acceptor site A, an atomic group or molecular chain having aromaticity based on the Hückel rule is preferable, and an atomic group or molecular chain including an aromatic heterocyclic ring having a nitrogen atom is more preferable. Specific examples of the acceptor site A include a pyridine ring, pyrazine ring, pyrimidine ring, pyridazine ring, sarin ring, phthalazine ring, pteridine ring, phenanthridine ring, phenanthroline ring, and condensed rings containing these ring structures. . These acceptor sites A may have a substituent.

As the donor site D, it is possible to use an atomic group or a molecular chain that has a high electron donating property and has a low LUMO or HOMO energy level in the molecule. Specific examples of the donor site D include an aryl group substituted with an electron-donating group (benzene ring, indene ring, naphthalene ring, azulene ring, fluorene ring, phenanthrene ring, anthracene ring, acenaphthylene ring, biphenylene ring, naphthacene ring, Pyrene ring, pentalene ring, acanthrylene ring, heptalene ring, triphenylene ring, as-indacene ring, chrysene ring, s-indacene ring, preaden ring, phenalene ring, fluoranthene ring, perylene ring, acephenanthrylene ring, biphenyl Ring, terphenyl ring, tetraphenyl ring, etc.) and optionally substituted electron-donating heterocyclic groups (pyrrole ring, indole ring, carbazole ring, indoloindole ring, 9,10-dihydroacridine ring, phenoxy ring) Sazine ring, phenothiazine ring, dibenzothiophene Ring, benzofurylindole ring, benzothienoindole ring, indolocarbazole ring, benzofurylcarbazole ring, benzothienocarbazole ring, benzothienobenzothiophene ring, benzocarbazole ring, dibenzocarbazole ring, azacarbazole ring, and diazacarbazole ring Etc.), an amino group which may be substituted, or an alkyl group. Especially, since it has high electron donating property, it is preferable that it is the electron donating heterocyclic group which may be substituted.

As the linking group L, any of a structure that expands the cocoon conjugated system formed by each site and a structure that blocks the cocoon conjugated system formed by each site can be used. Further, it may be a rigid structure in which a change in molecular structure between the ground state and each excited state is small, or a structure having a high degree of freedom capable of suppressing reverse charge transfer from an intramolecular charge transfer state. Good. Specific examples of the linking group L include a divalent or higher valent group composed of a hydrocarbon group, an aromatic hydrocarbon group, an aromatic heterocyclic group, and the like. These linking groups L may have a substituent.

Examples of the substituent include an alkyl group (for example, methyl group, ethyl group, propyl group, isopropyl group, tert-butyl group, pentyl group, hexyl group, octyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, etc.) A cycloalkyl group (eg, cyclopentyl group, cyclohexyl group, etc.), an alkenyl group (eg, vinyl group, allyl group, etc.), an alkynyl group (eg, ethynyl group, propargyl group, etc.), an aromatic hydrocarbon group (aromatic hydrocarbon). Also referred to as cyclic group, aromatic carbocyclic group, aryl group, etc., for example, phenyl group, p-chlorophenyl group, mesityl group, tolyl group, xylyl group, naphthyl group, anthryl group, azulenyl group, acenaphthenyl group, fluorenyl group, phenanthryl Group, indenyl group, pyrenyl group, biphenylyl group, etc.), aromatic A cyclic group (for example, pyridyl group, pyrimidinyl group, furyl group, pyrrolyl group, imidazolyl group, benzoimidazolyl group, pyrazolyl group, pyrazinyl group, triazolyl group (for example, 1,2,4-triazol-1-yl group, 1, 2,3-triazol-1-yl group), oxazolyl group, benzoxazolyl group, thiazolyl group, isoxazolyl group, isothiazolyl group, furazanyl group, thienyl group, quinolyl group, benzofuryl group, dibenzofuryl group, benzothienyl group , A dibenzothienyl group, an indolyl group, a carbazolyl group, a carbolinyl group, a diazacarbazolyl group (in which one of the carbon atoms constituting the carboline ring of the carbolinyl group is replaced by a nitrogen atom), a quinoxalinyl group, a pyridazinyl group, Triazinyl group, quinazolinyl group, lid Dinyl group etc.), heterocyclic group (eg pyrrolidyl group, imidazolidyl group, morpholyl group, oxazolidyl group etc.), alkoxy group (eg methoxy group, ethoxy group, propyloxy group, pentyloxy group, hexyloxy group, octyloxy group) Group, dodecyloxy group, etc.), cycloalkoxy group (eg, cyclopentyloxy group, cyclohexyloxy group, etc.), aryloxy group (eg, phenoxy group, naphthyloxy group, etc.), alkylthio group (eg, methylthio group, ethylthio group, Propylthio group, pentylthio group, hexylthio group, octylthio group, dodecylthio group, etc.), cycloalkylthio group (eg, cyclopentylthio group, cyclohexylthio group, etc.), arylthio group (eg, phenylthio group, naphthylthio group, etc.), alkoxy Carbonyl group (for example, methyloxycarbonyl group, ethyloxycarbonyl group, butyloxycarbonyl group, octyloxycarbonyl group, dodecyloxycarbonyl group, etc.), aryloxycarbonyl group (for example, phenyloxycarbonyl group, naphthyloxycarbonyl group, etc.) Sulfamoyl group (for example, aminosulfonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group, butylaminosulfonyl group, hexylaminosulfonyl group, cyclohexylaminosulfonyl group, octylaminosulfonyl group, dodecylaminosulfonyl group, phenylaminosulfonyl group, Naphthylaminosulfonyl group, 2-pyridylaminosulfonyl group, etc.), acyl groups (for example, acetyl group, ethylcarbonyl group, propylcarbonyl group, Tilcarbonyl 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.), amide group (eg, methylcarbonylamino group, ethylcarbonylamino group, dimethylcarbonylamino group, propylcarbonylamino group, pentylcarbonylamino group) Group, cyclohexylcarbonylamino group, 2-ethylhexylcarbonylamino group, octylcarbonylamino group, dodecylcarbonylamino group, phenyl Carbonylamino group, naphthylcarbonylamino group, etc.), carbamoyl group (for example, aminocarbonyl group, methylaminocarbonyl group, dimethylaminocarbonyl group, propylaminocarbonyl group, pentylaminocarbonyl group, cyclohexylaminocarbonyl group, octylaminocarbonyl group, 2-ethylhexylaminocarbonyl group, dodecylaminocarbonyl group, phenylaminocarbonyl group, naphthylaminocarbonyl 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-pyridylaminoureido group, etc.), sulfinyl group (for example, Tylsulfinyl 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, dodecylsulfonyl group, etc.), arylsulfonyl group or heteroarylsulfonyl group (for example, phenylsulfonyl group, naphthylsulfonyl group, 2-pyridylsulfonyl group) Etc.), amino group (for example, amino group, ethylamino group, dimethylamino group, diphenylamino group, butylamino group, cyclopentylamino group, 2 Ethylhexylamino group, dodecylamino group, anilino group, naphthylamino group, 2-pyridylamino group, etc.), halogen atom (eg, fluorine atom, chlorine atom, bromine atom etc.), fluorinated hydrocarbon group (eg, fluoromethyl group, Trifluoromethyl group, pentafluoroethyl group, pentafluorophenyl group, etc.), cyano group, nitro group, hydroxy group, mercapto group, silyl group (for example, trimethylsilyl group, triisopropylsilyl group, triphenylsilyl group, phenyldiethylsilyl) Group), a phosphono group, and the like.

Among these, the substituent for substituting the conjugated compound represented by the general formula (A) includes an alkyl group, an aromatic hydrocarbon group, an aromatic heterocyclic group, an alkoxy group, an amino group, or a cyano group. Is preferred. Preferred examples of the aromatic hydrocarbon group and aromatic heterocyclic group include indole ring, indazole ring, benzothiazole ring, benzoxazole ring, benzimidazole ring, quinoline ring, isoquinoline ring, quinazoline ring, quinoxaline ring, isoindole. Ring, naphthyridine ring, phthalazine ring, carbazole ring, carboline ring, diazacarbazole ring, acridine ring, phenanthridine ring, phenanthroline ring, phenazine ring, azadibenzofuran ring, azadibenzothiophene ring and the like. These substituents can also be used as acceptor sites.

As the RISC compound, a compound having a benzene ring as the linking group L can be preferably used. The acceptor site A and the donor site D are preferably bonded to each other at the para position with respect to the linking group L composed of a benzene ring. Furthermore, it is preferable that one or more of the ortho positions of the bonding position to which the acceptor site A is bonded is a hydrogen atom. Moreover, it is preferable that one or more of the ortho positions of the bonding position to which the donor site D is bonded is an electron donating group. Specific examples of such RISC compounds include compounds A-1 to A-64 described in JP-A-2017-075121.

<Minimization design of ΔEst>
In order to reduce ΔEst of the compound represented by the general formula (A), it is most effective to reduce the spatial overlap between the highest occupied orbital (HOMO) and the lowest unoccupied orbital (LUMO) in the molecule. . Generally, it is known that HOMO is distributed in an electron donating site and LUMO is distributed in an electron withdrawing site in the electron orbit of a molecule. For this reason, for example, as described in "Applied Physics in the Stage of Practical Use", Applied Physics Vol. 82, No. 6, 2013, an electron-donating skeleton and electron-withdrawing properties are included in the molecule. When the skeleton of is introduced, the site where HOMO is localized and the site where LUMO is localized can be kept away.

In order to reduce ΔEst, it is also effective to reduce the molecular structure change between the ground state and the excited state of the compound. As a method of reducing the molecular structure change, for example, there is a method of making a compound rigid. For example, a method of suppressing free rotation of the bond between rings, a method of reducing the number of sites that can move freely in the molecule, such as introducing a condensed ring having a large π-conjugated surface, and the like can be used. In particular, when the site involved in light emission in the compound is rigid, the structural change in the excited state can be reduced.

<Electron density distribution>
The distribution state of HOMO and LUMO in the compound can be obtained from the electron density distribution when the structure is optimized by molecular orbital calculation. Molecular orbital calculation can be performed using molecular orbital calculation software using B3LYP as a functional and 6-31G (d) as a basis function. The type of molecular orbital calculation software is not particularly limited. As software for molecular orbital calculation, for example, Gaussian 09 (Revision C.01, MJ Frisch, et al, Gaussian, Inc., 2010) manufactured by Gaussian in the United States can be used.

Also, Delta] E _st compounds after structural optimization by molecular orbital calculation, time-dependent density functional theory (DFT: Time-Dependent) to perform the calculations of the excited state energy by energy level of _{S 1} (E (S ₁ )) and the energy level of T ₁ (E (T ₁ )) can be obtained and calculated as ΔE _st = | E (S ₁ ) −E (T ₁ ) |. A smaller ΔE _st calculated indicates that HOMO and LUMO are more separated.

<Lowest excited singlet energy level S ₁ >
The energy (E (S ₁ )) of the lowest excited singlet energy level (S ₁ ) can be determined based on a known method as shown below. First, a compound to be measured is deposited on a quartz substrate to prepare a sample, and the absorption spectrum (vertical axis: absorbance, horizontal axis: wavelength) of the sample is measured at room temperature (300 K). Thereafter, a tangent line is drawn with respect to the rise of the obtained absorption spectrum on the long wavelength side, and calculation can be performed using a predetermined conversion formula based on the wavelength value at the intersection of the tangent line and the horizontal axis.

However, when the compound to be measured has a relatively high aggregation property, an error due to aggregation may occur in the measurement of the thin film. The peak value of the maximum emission wavelength measured in a solution state at room temperature (25 ° C.) is used as an approximate value on condition that the Stokes shift of the compound is relatively small and the molecular structure change between the ground state and the excited state is small. be able to. As the solvent, a solvent that has a small solvent effect and does not significantly affect the aggregation state of the compound, for example, a nonpolar solvent such as cyclohexane or toluene can be used.

<Lowest excited triplet energy level T ₁ >
The energy (E (T ₁ )) of the lowest excited triplet energy level (T ₁ ) can be determined based on the photoluminescence (PL) characteristics of the thin film or solution as shown below. For example, after making a thin dispersion of a compound to be measured into a thin film, transient PL characteristics are measured using a streak camera to separate a fluorescent component and a phosphorescent component. Then, the absolute value of the obtained energy difference can be set as ΔE _st and can be calculated from ΔE _st and S ₁ obtained in advance. The PL characteristics can be obtained by, for example, exciting a compound with laser light, measuring the internal quantum efficiency with an absolute PL quantum yield measuring device C9920-02 (manufactured by Hamamatsu Photonics), and measuring the emission lifetime with a streak camera C4334 (manufactured by Hamamatsu Photonics) Can be measured.

(RISC compound concentration)
The RISC compound may be contained in an appropriate concentration in the light emitting layer as long as it is used in combination with the AIE molecule. The concentration of the RISC compound in the light emitting layer is, for example, from 0.1% by mass to 50% by mass, preferably from 1% by mass to 30% by mass, and more preferably from 5% by mass to 30% by mass. Can do. When the concentration of the RISC compound in the film is 1% by mass or more, the luminous efficiency can be significantly improved by utilizing triplet excitons for light emission. Further, when the concentration of the RISC compound in the film is 30% by mass or less, light emission from the AIE molecule that hardly causes concentration quenching can be efficiently used.

<< Constituent layers of organic EL elements >>
The organic EL device according to the present invention can be provided, for example, as a structure having an anode and a cathode on a base material, and an organic constituent layer including a light emitting layer sandwiched between the anode and the cathode. As typical element configurations of the organic EL element according to the present invention, the following configurations 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

The organic EL element according to the present invention may be provided on the outside of the electrode by appropriately combining layers such as a sealing layer, a barrier layer, and a light extraction layer. In the above configuration, the layer excluding the anode and the cathode is also referred to as “organic layer”.

The light emitting layer may be composed of a single layer or a plurality of layers. When the light emitting layer is composed of a plurality of layers, a non-light emitting intermediate layer may be provided between the light emitting layers. Further, as 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. Further, 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 between the light emitting layer and the anode.

(Tandem structure)
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. Examples of typical element configurations having a tandem structure include the following configurations.
(I) Anode / first light emitting unit / second light emitting unit / third light emitting unit / cathode (II) anode / first light emitting unit / intermediate layer / second light emitting unit / intermediate layer / third light emitting unit / cathode

In the tandem organic EL element, the plurality of light emitting units may all have the same configuration or different configurations. Further, some of the light emitting units may have the same configuration, and the remaining light emitting units may have different configurations. The tandem organic EL element may be composed of two light emitting units, or may be composed of four or more light emitting units by providing a light emitting unit or an intermediate layer between the third light emitting unit and the cathode. May be. The light emitting units may be stacked adjacent to each other or may be stacked via an intermediate layer.

The intermediate layer is generally called an intermediate electrode, an intermediate conductive layer, a charge generation layer, an electron extraction layer, a connection layer, or an intermediate insulating layer. The intermediate layer is an electron adjacent to the anode side and the layer adjacent to the cathode side. Any layer having a function of supplying holes can be formed using a known material and structure.

Examples of the material of the intermediate layer include ITO (indium tin oxide), IZO (indium zinc oxide), ZnO ₂ , TiN, ZrN, HfN, TiOx, VOx, CuI, InN, GaN, CuAlO ₂ , and CuGaO. ₂ , conductive inorganic compound layers such as SrCu ₂ O ₂ , LaB ₆ , RuO ₂ , and Al, double-layer films such as Au / Bi ₂ O ₃ , SnO ₂ / Ag / SnO ₂ , ZnO / Ag / ZnO, Bi ₂ O ₃ / Au / Bi ₂ O ₃ , TiO ₂ / TiN / TiO ₂ , TiO ₂ / ZrN / TiO _{2 and} other multilayer films, C _{60 and} other fullerenes, conductive organic layers such as oligothiophene, Examples include, but are not limited to, conductive organic compound layers such as metal phthalocyanines, metal-free phthalocyanines, metal porphyrins, metal-free porphyrins, etc. Is not to be done.

A preferable configuration of the light emitting unit includes, for example, a configuration in which the anode and the cathode are removed from any one of the above-described element configurations (1) to (7), but is not limited thereto.

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, and US Pat. No. 6,872. 472, U.S. Pat. No. 6,107,734, U.S. Pat. No. 6,337,492, International Publication No. 2005/009087, JP-A 2006-228712, JP-A 2006-24791, JP-A 2006-. No. 49393, JP-A-2006-49394, JP-A-2006-49396, JP-A-2011-96679, JP-A-2005-340187, JP-A-4711424, JP-A-34966681, JP-A-3884564, JP-A-4213169 JP, 2010-192719, JP, 2009-076929, JP, 2008-078414, Examples include, but are not limited to, element configurations and constituent materials described in JP 2007-059848, JP 2003-272860, JP 2003-045676, and International Publication No. 2005/094130. .

In the organic EL device according to the present invention, the AIE molecule and the RISC compound may be included in a light emitting layer composed of a single layer or composed of a plurality of layers as long as they are used in the same light emitting layer. It may be included in one or more of the light emitting layers. In addition, as long as the AIE molecule and the RISC compound are used in the same light emitting layer, the light emitting units constituting the tandem type may be included in a single light emitting unit, or may be included in a plurality of light emitting units. May be included.

The organic EL device according to the present invention has either a configuration in which only light emission derived from AIE molecules is emitted, or a configuration in which both light emission derived from AIE molecules and light emission derived from a RISC compound are emitted. It may be said. The relationship between the energy level of the AIE molecule and the energy level of the RISC compound is not particularly limited. However, when a host compound is used for the light emitting layer, it is preferable that the lowest excited triplet energy level of the RISC compound is deeper than the lowest excited triplet energy level of the host compound.

In the organic EL device according to the present invention, the external extraction quantum efficiency of light emission at room temperature (25 ° C.) is preferably 1% or more, and more preferably 5% or more. Here, external extraction quantum efficiency (%) = number of photons emitted to the outside of the organic EL element / number of electrons flowed to the organic EL element × 100.

Hereinafter, each layer (hole injection layer, hole transport layer, hole blocking layer, electron blocking layer, electron transport layer, electron injection layer, light emitting layer) constituting the organic EL device according to the present invention will be described.

《Hole injection layer》
The hole injection layer is a layer provided between the anode and the light emitting layer in order to lower the driving voltage and improve the light emission luminance. For the hole injection layer, see “Organic EL devices and their industrialization front line (issued by NTT Corporation on November 30, 1998)”, Volume 2, Chapter 2, “Electrode Materials” (pages 123-166). It is described in detail. The hole injection layer can be provided as necessary. The hole injection layer may be provided, for example, between the anode and the light emitting layer, or between the anode and the hole transport layer.

Details of the hole injection layer are also described in JP-A-9-45479, JP-A-9-260062, JP-A-8-288069 and the like.

As the material of the hole injection layer, for example, the same material as the material of the hole transport layer described later can be used. As the material for the hole injection layer, one kind may be used alone, or a plurality kinds may be used in combination.

Examples of the material for the hole injection layer include phthalocyanine derivatives typified by copper phthalocyanine, hexaazatriphenylene derivatives as described in JP-A-2003-519432, JP-A 2006-135145, and vanadium oxide. Preferred are metal oxides, amorphous carbon, conductive polymers such as polyaniline (emeraldine) and polythiophene, orthometalated complexes represented by tris (2-phenylpyridine) iridium complex, and triarylamine derivatives.

《Hole transport layer》
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.

The total thickness of the hole transport layer is not particularly limited, but is usually 5 nm to 5 μm, preferably 2 to 500 nm, more preferably 5 to 200 nm.

As a material for the hole transport layer, any material having hole injection property, hole transport property, and electron barrier property may be used, and a known compound having such properties should be used. Can do. As the material for the hole transport layer, one kind may be used alone, or a plurality kinds may be used in combination.

Examples of the material for the hole transport layer include porphyrin derivatives, phthalocyanine derivatives, oxazole derivatives, oxadiazole derivatives, triazole derivatives, imidazole derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, hydrazone derivatives, stilbene derivatives, polyarylalkanes. Derivatives, triarylamine derivatives, carbazole derivatives, indolocarbazole derivatives, isoindole derivatives, acene derivatives such as anthracene and naphthalene, fluorene derivatives, fluorenone derivatives, polyvinyl carbazole, polymers with aromatic amines introduced into the main chain or side chain Polymer or oligomer, polysilane, conductive polymer or oligomer (for example, PEDOT: PSS, aniline copolymer, polyaniline, polythiol) Fen, etc.) and the like.

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 connecting core part of triarylamine.

In addition, as a material for the hole transport layer, hexaazatriphenylene derivatives as described in JP-T-2003-519432, JP-A-2006-135145, and the like can also be used.

As materials for the hole transport layer, JP-A-11-251067, J. Org. Huang, et. al. Inorganic semiconductors such as p-type-Si and p-type-SiC as described in the literature (Applied Physics Letters, 80 (2002), p. 139) can also be used. Further, ortho-metalated organometallic complexes having Ir or Pt as the central metal typified by Ir (ppy) ₃ are also preferably used.

The hole transport layer may be formed as a layer having a high p property by doping a doping material. Specific examples of the hole transport layer having such a structure are disclosed in JP-A-4-297076, JP-A-2000-196140, JP-A-2001-102175, J. Pat. Appl. Phys. 95, 5773 (2004), and the like.

As a material for the hole transport layer, a triarylamine derivative, a carbazole derivative, an indolocarbazole derivative, an azatriphenylene derivative, an organometallic complex, a polymer or an oligomer having an aromatic amine introduced into the main chain or side chain, and the like are preferably used. .

Specific examples of the material for the hole transport layer include compounds described in the following documents, but are not limited thereto. Appl. Phys. Lett. 69, 2160 (1996); 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. Met. 111, 421 (2000), SID Symposium Digest, 37, 923 (2006), J. Am. Mater. Chern. 3,319 (1993), Adv. Mater. 6, 677 (1994), Chern. Mater. , 15, 3148 (2003), U.S. Patent Publication No. 20030162053, U.S. Patent Publication No. 200201558242, U.S. Patent Publication No. 20060240279, U.S. Patent Publication No. 20080220265, U.S. Patent No. 5061569, International Publication No. 2007002683, International Publication. 2009018009, EP650955, U.S. Patent Publication No. 20080124572, U.S. Patent Publication No. 200707078938, U.S. Patent Publication No. 200880106190, U.S. Patent Publication No. 20080018221, International Publication No. 201212115034, Special Table No. 2003-519432, Special Publication No. 2006-135145, US Patent Application No. 13/585981, and the like.

《Hole blocking layer》
The hole blocking layer is a layer having a function of an electron transporting 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 holes while transporting electrons, the recombination probability of electrons and holes can be improved. Moreover, the said electron carrying layer can also be used as a hole-blocking layer as needed. The hole blocking layer is preferably provided adjacent to the cathode side of the light emitting layer.

The thickness of the hole blocking layer is not particularly limited, but is preferably 3 to 100 nm, more preferably 5 to 30 nm.

As the material for the hole blocking layer, materials for electron transport layers described later and materials used as host compounds described later are preferably used.

《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. By blocking electrons while transporting holes, the probability of recombination of electrons and holes can be improved. Moreover, the said hole transport layer can also be used as an electron blocking layer as needed. The electron blocking layer is preferably provided adjacent to the anode side of the light emitting layer.

The thickness of the electron blocking layer is not particularly limited, but is preferably 3 to 100 nm, more preferably 5 to 30 nm.

As the material for the electron blocking layer, a material for a hole transport layer described later and a material used as a host compound described later are preferably used.

《Electron transport layer》
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.

The total thickness of the electron transport layer is not particularly limited, but is usually 2 nm to 5 μm, preferably 2 to 500 nm, more preferably 5 to 200 nm.

In the organic EL element, when 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 positioned at the counter electrode of the electrode from which the light is extracted. It is known. When light is reflected by the cathode, this interference effect can be efficiently utilized by appropriately adjusting the total film thickness of the electron transport layer between several nanometers and several micrometers. On the other hand, when the thickness of the electron transport layer is increased, the voltage is likely to increase. Therefore, particularly when the thickness is large, the electron mobility of the electron transport layer is preferably 10 ⁻⁵ cm ² / Vs or more. .

As a material for the electron transport layer, any material that has any of electron injection property, electron transport property, and hole barrier property may be used, and a known compound having such properties can be used. . The material for the electron transport layer may be used alone or in combination of two or more.

Examples of the material for the electron transport layer include nitrogen-containing aromatic heterocyclic derivatives (carbazole derivatives, azacarbazole derivatives (one in which one or more carbon atoms constituting the carbazole ring are substituted with nitrogen atoms), pyridine derivatives, and pyrimidines. 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, benz Thiazole derivatives, dibenzofuran derivatives, dibenzothiophene derivatives, silole derivatives, aromatic hydrocarbon ring derivatives (naphthalene derivatives, anthracene derivatives, triphenyl Emissions, etc.) and the like.

As the material for the electron transport layer, 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) Etc., and metal complexes in which the central metal of these metal complexes is replaced with In, Mg, Cu, Ca, Sn, Ga, or Pb.

In addition, examples of the material for the electron transport layer include metal-free or metal phthalocyanine, or those whose ends are substituted with an alkyl group or a sulfonic acid group. Further, a distyrylpyrazine derivative that can be a material for the light emitting layer can be used, and an inorganic semiconductor such as n-type-Si, n-type-SiC, or the like can also be used. In addition, a polymer material in which these materials are introduced into a polymer chain, or a polymer material having these materials as a polymer main chain can be used.

The electron transport layer may be formed as a layer having a high n property by doping a doping material. Examples of the dopant include n-type dopants including metal complexes and metal compounds such as metal halides. Specific examples of the electron transport layer having such a structure are disclosed in JP-A-4-297076, JP-A-10-270172, JP-A-2000-196140, JP-A-2001-102175, J. Pat. Appl. Phys. 95, 5773 (2004), and the like.

Specific examples of the material for the electron transport layer include compounds described in the following documents, but are not limited thereto. U.S. Pat.No. 6,528,187, U.S. Pat.No. 7,230,107, U.S. Patent Publication No. 20050025993, U.S. Pat. Publication No. 2004036077, U.S. Pat. Publication No. 200901115316, U.S. Pat. Publication No. 20090101870, U.S. Pat. No. 2003060956, International Publication No. 20080832085, 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), U.S. Pat. No. 7,964,293, U.S. Patent Publication No. 2009030202, International Publication No. 20040980975, International Publication No. 2004063159, International Publication No. 2005085387, International Publication No. 20060606731, International Publication No. 2007086552. International Publication No. 20081414690, International Publication No. 2009090442, International Publication No. 2009066779, International Publication No. 200905253, International Publication No. 20101086935, International Publication No. 2010150593, International Publication No. 20110047707, EP23111826, JP2010- No. 251,675, JP-A 2009-209133, JP-A 2009-124114, JP-A 2008-277810, JP 2 06-156445, JP-2005-340122 discloses a JP 2003-45662, JP-2003-31367, JP 2003-282270, JP-WO 2012115034 or the like.

More preferable materials for the electron transport layer include pyridine derivatives, pyrimidine derivatives, pyrazine derivatives, triazine derivatives, dibenzofuran derivatives, dibenzothiophene derivatives, carbazole derivatives, azacarbazole derivatives, and benzimidazole derivatives.

《Electron injection layer》
The electron injection layer 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. The details of the electron injection layer are described in Volume 2, Chapter 2, “Electrode Materials” (pages 123 to 166) of “Organic EL devices and their industrialization front line (issued by NTT Corporation on November 30, 1998)”. It is described in. The electron injection layer can be provided as necessary. The electron injection layer may be provided, for example, between the cathode and the light emitting layer or between the cathode and the electron transport layer.

The electron injection layer is preferably a very thin film. The thickness of the electron injection layer is preferably 0.1 to 5 nm. The electron injection layer may be a non-uniform film in which constituent materials are intermittently present.

Details of the electron injection layer are also 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 include metals such as strontium and aluminum, alkali metal compounds such as lithium fluoride, sodium fluoride, and potassium fluoride, magnesium fluoride, and calcium fluoride. Examples thereof include alkaline earth metal compounds such as metal oxides, metal oxides such as aluminum oxide, and metal complexes such as lithium 8-hydroxyquinolate (Liq). It is also possible to use the same material as that of the electron transport layer. The material for the electron injection layer may be used alone or in combination of two or more.

<Light emitting layer>
The light emitting layer is a layer that provides a field for generating light emission. Electrons and holes injected from the electrode or an adjacent layer are recombined in the light emitting layer, and light emission occurs with deactivation of excitons generated by the recombination. The site that emits light may be within the layer of the light emitting layer, or may be the interface between the light emitting layer and an adjacent layer.

The total thickness of the light emitting layer is not particularly limited, but it is possible to improve the homogeneity of the film to be formed, to prevent the application of unnecessary high voltage during light emission, and to the drive current. From the viewpoint of improving the stability of the emission color, the thickness is preferably 2 nm to 5 μm, more preferably 2 to 500 nm, still more preferably 5 to 200 nm.

The individual thickness of the light emitting layer is preferably 2 nm to 1 μm, more preferably 2 to 200 nm, and still more preferably 3 to 150 nm.

The light emitting layer preferably contains a light emitting dopant (a light emitting dopant compound, a dopant compound, also simply referred to as a dopant) and a host compound (a matrix material, a light emitting host compound, also simply referred to as a host). In the organic EL device according to the present embodiment, the AIE molecule functions as a light emitting dopant. The RISC compound is treated as a luminescent dopant regardless of the presence or absence of radiative transition.

(1) Luminescent dopant As the luminescent dopant, there are a fluorescent luminescent dopant (also referred to as a fluorescent dopant or a fluorescent compound) and a phosphorescent dopant (also referred to as a phosphorescent dopant or a phosphorescent compound).

The concentration of the luminescent dopant in the luminescent layer can be arbitrarily determined based on the dopant used and the requirements of the device. The luminescent dopant may be distributed at a uniform concentration or a non-uniform arbitrary concentration with respect to the film thickness direction of the luminescent layer.

As the luminescent dopant, in addition to the AIE molecule and the RISC compound, other fluorescent luminescent dopants and phosphorescent luminescent dopants can be used in combination. For each fluorescent light-emitting dopant or each phosphorescent light-emitting dopant, one kind of light-emitting compound may be used, or a plurality of kinds of light-emitting compounds may be used in combination. Further, different light emitting dopants may be used in the same light emitting layer, or different light emitting dopants may be used for different light emitting layers. With such a combination, an arbitrary emission color can be obtained for the emission emitted from the organic EL element.

The emission color of the organic EL device or compound according to the present invention is shown in FIG. 4.16 on page 108 of “New Color Science Handbook” (edited by the Japan Society for Color Science, University of Tokyo Press, 1985). The result measured by Konica Minolta Sensing Co., Ltd. can be defined by the color when applied to the CIE chromaticity coordinates.

The organic EL device according to the present invention may be a device in which one or more light-emitting layers contain a plurality of light-emitting dopants having different light emission colors and exhibit white light emission. The combination of the luminescent dopants that emit white light is not particularly limited, and examples thereof include a combination of blue and orange, a combination of blue, green, and red.

The white light emitted by the organic EL device according to the present invention is not limited in hue and the like, and may be white near orange or white near blue. When measured by the method described above, the chromaticity in the CIE 1931 color system at 1000 cd / m ² may be in the region of x = 0.39 ± 0.09 and y = 0.38 ± 0.08. preferable.

(1.1) Phosphorescent dopant The phosphorescent dopant according to the present invention is a compound in which light emission from an excited triplet is observed. Specifically, it is a compound that emits phosphorescence at room temperature (25 ° C.), and is defined as a compound having a phosphorescence quantum yield of 0.01 or more at 25 ° C. The preferable phosphorescence quantum yield of a phosphorescent dopant is 0.1 or more.

The phosphorescence quantum yield can be measured by the method described in Spectroscopic II, page 398 (1992 edition, Maruzen) of Experimental Chemistry Course 4 of the 4th edition. The phosphorescence quantum yield in solution can be measured using various solvents, but the phosphorescent dopant according to the present invention achieves a phosphorescence quantum yield of 0.01 or more in any solvent. Just do it.

The principle of light emission of phosphorescent dopant is roughly divided into two types. One is that recombination of carriers occurs on the host compound to which carriers are transported to generate an excited state of the host compound, and this energy is transferred to the phosphorescent dopant to emit light from the phosphorescent dopant. Energy transfer type. The other is a carrier trap type in which a phosphorescent dopant becomes a carrier trap, and recombination of carriers occurs on the phosphorescent dopant to emit light from the phosphorescent dopant. In either case, it is a condition that the excited state energy of the phosphorescent dopant is lower than the excited state energy of the host compound.

In the organic EL device according to the present embodiment, an appropriate type used for a light emitting layer of a general organic EL device can be used as a phosphorescent dopant. The principle of light emission of the phosphorescent dopant may be based on any of the above principles. However, in the organic EL device according to the present embodiment, when a phosphorescent dopant is used together with the RISC compound, the light emission efficiency may be lowered. In such a case, the structure which does not use a phosphorescence dopant together is more preferable.

Specific examples of the phosphorescent dopant include compounds described in the following documents, but are not limited thereto. Nature, 395, 151 (1998), Appl. Phys. Lett. 78, 1622 (2001), Adv. Mater. , 19, 739 (2007), Chern. Mater. 17, 3532 (2005), Adv. Mater. , 17, 1059 (2005), International Publication No. 2009100991, International Publication No. 2008101842, International Publication No. 2003030257, United States Patent Publication No. 2006835469, United States Patent Publication No. 20060202194, United States Patent Publication No. 20070087321, United States Patent Publication. 20050244673, Inorg. Chern. , 40, 1704 (2001), Chern. Mater. 16, 2480 (2004), Adv. Mater. 16, 2003 (2004), Angew. Chern. lnt. Ed. , 2006, 45, 7800, Appl. Phys. Lett. 86, 153505 (2005), Chern. Lett. , 34, 592 (2005), Chern. Commun. , 2906 (2005), Inorg. Chern. , 42, 1248 (2003), International Publication No. 2009050290, International Publication No. 20022015645, International Publication No. 2009000673, United States Patent Publication No. 20020034656, United States Patent No. 7332232, United States Patent Publication No. 20090108737, United States Patent Publication No. 20090039776, U.S. Patent No. 6921915, U.S. Patent No. 6,687,266, U.S. Patent Publication No. 20070190359, U.S. Patent Publication No. 2006060008670, U.S. Patent Publication No. 20090165846, U.S. Patent Publication No. 20080015355, U.S. Pat. No. 7,250,226, U.S. Pat. Patent No. 7396598, U.S. Patent Publication No. 20060263635, U.S. Patent Publication No. 200301368657, U.S. Patent Publication No. 2003015280 Patent, US Patent No. 7090928, Angew. Chern. lnt. Ed. 47, 1 (2008), Chern. Mater. , 18, 5119 (2006), Inorg. Chern. 46, 4308 (2007), Organometallics, 23, 3745 (2004), Appl. Phys. Lett. , 74, 1361 (1999), International Publication No. 2002002714, International Publication No. 2006009024, International Publication No. 200606056418, International Publication No. 2005019373, International Publication No. 20050051873, International Publication No. 200500513873, International Publication No. 20070043380, International Patent Publication No. 2006082742, United States Patent Publication No. 20060251923, United States Patent Publication No. 20050260441, United States Patent No. 7393599, United States Patent No. 7,534,505, United States Patent No. 7,445,855, United States Patent Publication No. 20070190359, United States Patent Publication No. 20080297033. No. 7, U.S. Pat. No. 7,338,722, U.S. Patent Publication No. 200201334984, U.S. Pat. No. 7,279,704, U.S. Pat. No. 8120, U.S. Patent Publication No. 2006103874, International Publication No. 2005076380, International Publication No. 201303663, International Publication No. 2008140115, International Publication No. 2007705243, International Publication No. 20111134013, International Publication No. 2011157339, International Publication No. 201208989, International Publication No. WO200913646, International Publication No. 2012120327, International Publication No. 20111051404, International Publication No. 2011004639, International Publication No. 20111073149, US Patent Publication No. 20122225853, US Patent Publication No. 2012122126, JP2012 -0697737, JP2012-195554, JP2009-114086, JP2003-81988, JP200. No. -302671, a JP 2002-363552 and the like.

Hereinafter, specific examples of preferable compounds as phosphorescent dopants will be given, but the invention is not limited thereto.

(1.2) Fluorescent luminescent dopant The fluorescent luminescent dopant which concerns on this invention is a compound which can light-emit from an excitation singlet. The kind of the fluorescent light-emitting dopant is not particularly limited as long as light emission from the excited singlet is observed. However, in the organic EL device according to this embodiment, when another fluorescent light-emitting dopant that does not have aggregation-induced light emission is used together with the AIE molecule, the light emission efficiency may be lowered. Therefore, the structure which does not use other fluorescent luminescent dopant together is more preferable.

Specific examples of the fluorescent luminescent dopant include anthracene derivatives, pyrene derivatives, chrysene derivatives, fluoranthene derivatives, perylene derivatives, fluorene derivatives, arylacetylene derivatives, styrylarylene derivatives, styrylamine derivatives, arylamine derivatives, boron complexes, coumarin derivatives, Examples include pyran derivatives, cyanine derivatives, croconium derivatives, squalium derivatives, oxobenzoanthracene derivatives, fluorescein derivatives, rhodamine derivatives, pyrylium derivatives, perylene derivatives, polythiophene derivatives, rare earth complex compounds, and the like.

In recent years, luminescent dopants using delayed fluorescence have been developed, and these may be used. Specific examples of the luminescent dopant using delayed fluorescence include compounds described in International Publication No. 2011/156793, Japanese Patent Application Laid-Open No. 2011-213643, Japanese Patent Application Laid-Open No. 2010-93181, and the like.

(2) Host Compound The host compound according to the present invention is a compound mainly responsible for charge injection and transport in the light emitting layer, and is a compound in which light emission itself is not substantially observed in the organic EL element. A compound having a phosphorescence quantum yield of phosphorescence emission of less than 0.1 at room temperature (25 ° C.) is preferred, and a compound having a phosphorescence quantum yield of less than 0.01 is more preferred.

Among the compounds contained in the light emitting layer, the host compound preferably has a mass ratio in the light emitting layer of 20% or more. Moreover, it is preferable that the excited state energy of a host compound is higher than the excited state energy of the light emission dopant contained in the same layer. In the organic EL device according to this embodiment, the light emitting layer may have a configuration in which a host compound is used in combination with an AIE molecule or a RISC compound, or a configuration in which a host compound is not used in combination. For combination with the structures of the host compound, _{S 1} and _{T 1} of the host compound is preferably higher than _{S 1} and _{T 1} of the _{S 1} and _{T 1} and RISC compound of AIE molecules.

As the host compound, an appropriate type used for a light emitting layer of a general organic EL element can be used. The host compound may be a low molecular compound or a high molecular compound having a repeating unit. Further, it may be a compound having a reactive group such as a vinyl group or an epoxy group. A host compound may be used individually by 1 type, and may use multiple types together. When a plurality of types of host compounds are used in combination, the movement of electric charges can be easily adjusted, so that the organic EL element can be made highly efficient.

As a host compound, it has a hole transporting ability or an electron transporting ability, prevents an increase in wavelength of light emission, and further allows the organic EL element to operate stably during high temperature driving or heat generated by driving. Therefore, it is preferable to have a high glass transition temperature (Tg). The glass transition temperature of the host compound is preferably 90 ° C. or higher, more preferably 120 ° C. or higher. The glass transition temperature (Tg) is a value determined by a method based on JIS-K-7121 using DSC (Differential Scanning Colorimetry).

Specific examples of the host compound include compounds described in the following documents, but are not limited thereto. JP-A-2001-257076, 2002-308855, 2001-313179, 2002-319491, 2001-357777, 2002-334786, 2002-8860, 2002-334787, 2002-15871, 2002-334788, 2002-43056, 2002-334789, 2002-75645, 2002-338579, 2002-105445 gazette, 2002-343568 gazette, 2002-141173 gazette, 2002-352957 gazette, 2002-203683 gazette, 2002-363227 gazette, 2002-231453 gazette, No. 003-3165, No. 2002-234888, No. 2003-27048, No. 2002-255934, No. 2002-260861, No. 2002-280183, No. 2002-299060, No. 2002. -302516, 2002-305083, 2002-305084, 2002-308837, US Patent Publication No. 20030175553, United States Patent Publication No. 20060280965, United States Patent Publication No. 20050112407, United States Patent Publication 20090017330, U.S. Patent Publication No. 20090030202, U.S. Patent Publication No. 20050238919, International Publication No. 2001039234, International Publication No. 200902126, International Publication No. No. 8056746, International Publication No. 2004093207, International Publication No. 2005089025, International Publication No. 20077063796, International Publication No. 2007076754, International Publication No. 2004078822, International Publication No. 2005030900, International Publication No. 20060146966, International Publication No. 2009086028 International Publication No. 2009003898, International Publication No. 20122023947, Japanese Unexamined Patent Application Publication No. 2008-074939, Japanese Unexamined Patent Application Publication No. 2007-254297, EP2034538, and the like.

<Contents>
The organic layer of the organic EL element may further contain other inclusions. Other inclusions include, for example, simple halogens and halogenated compounds such as bromine, iodine and chlorine, alkali metals such as Pd, Ca and Na, compounds of alkaline earth metals and transition metals, metal complexes and salts. Can be mentioned.

The amount of other inclusions is not particularly limited, but is preferably 1000 ppm or less, more preferably 500 ppm or less, and still more preferably 50 ppm or less with respect to the total mass of the layer containing the inclusions. However, the range is not limited to this range depending on the purpose of improving the transportability of electrons and holes, the purpose of making the energy transfer of excitons advantageous.

<Method for forming organic layer>
The formation method of the organic layer (a hole injection layer, a hole transport layer, a light emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer, etc.) is not particularly limited. A method (also referred to as a wet process) or the like can be used.

Examples of the wet method include spin coating method, casting method, ink jet method, printing method, die coating method, blade coating method, roll coating method, spray coating method, curtain coating method, LB method (Langmuir-Blodgett method) and the like. Can be mentioned. As the wet method, a method having high suitability for a roll-to-roll method such as a die coating method, a roll coating method, an ink jet method, or a spray coating method is preferable in that a homogeneous thin film is easily obtained and productivity is high. Used.

Examples of the liquid medium for dissolving or dispersing the organic layer material include ketones such as methyl ethyl ketone and cyclohexanone, fatty acid esters such as ethyl acetate, halogenated hydrocarbons such as dichlorobenzene, toluene, xylene, and mesitylene. And aromatic hydrocarbons such as cyclohexylbenzene, aliphatic hydrocarbons such as cyclohexane, decalin and dodecane, and organic solvents such as DMF and DMSO. As a dispersion method for dispersing the material of the organic layer, ultrasonic dispersion, high shear force dispersion, media dispersion, or the like can be used.

The organic layer may be formed using the same method for each layer, or may be formed using a different method for each layer. In the case of using the vacuum deposition method, the deposition conditions vary depending on the type of compound used, but generally, the boat heating temperature is 50 to 450 ° C., the degree of vacuum is 10 ⁻⁶ to 10 ⁻² Pa, the deposition rate is 0.01 to 50 nm / Second, substrate temperature −50 to 300 ° C., film thickness 0.1 nm to 5 μm, preferably 5 to 200 nm can be set as appropriate conditions.

It is preferable that the organic layer is produced from the anode side layer to the cathode side layer consistently by a single vacuum drawing. However, it may be taken out halfway and subjected to a different film forming method. When taking out on the way, it is preferable to perform the operation | work in that case in dry inert gas atmosphere.

"anode"
As the anode, a material having a work function (4 eV or more, preferably 4.5 eV or more) of a metal, an alloy, an electrically conductive compound, or a mixture thereof is 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 capable of forming a transparent conductive film such as IDIXO (In ₂ O ₃ —ZnO) may be used.

The anode can be formed as a thin film by depositing an electrode material by vapor deposition or sputtering. When forming the anode, a pattern having a desired shape may be formed by photolithography. Further, when high pattern accuracy is not required (in the case of about 100 μm or more), a pattern may be formed using a mask when performing vapor deposition or sputtering of the electrode material. Moreover, when using the electrode substance which can be apply | coated like an organic electroconductivity compound, wet methods, such as a printing system and a coating system, can also be used.

When taking out the light emission of the organic EL element from the anode, it is preferable that the transmittance of the anode is larger than 10%. The sheet resistance as the anode is preferably several hundred Ω / □ or less. Although the thickness of the anode depends on the electrode material, it is usually 10 nm to 1 μm, preferably 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, or a mixture thereof as an electrode material is preferably 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 (Al ₂ O ₃ ) Mixtures, indium, lithium / aluminum mixtures, aluminum, rare earth metals and the like.

As the electrode material of the cathode, a mixture of an electron injecting metal and a second metal which is a stable metal having a larger work function value than this, for example, magnesium / More preferred are silver mixtures, magnesium / aluminum mixtures, magnesium / indium mixtures, aluminum / aluminum oxide (Al ₂ O ₃ ) mixtures, lithium / aluminum mixtures, aluminum and the like.

The cathode can be formed as a thin film by depositing an electrode material by vapor deposition or sputtering.

The sheet resistance as the cathode is preferably several hundred Ω / □ or less. The thickness of the cathode is usually 10 nm to 5 μm, preferably 50 to 200 nm.

In addition, it is preferable that either one of the anode and the cathode of the organic EL element is transparent or semi-transparent from the viewpoint of transmitting the emitted light and improving the light emission luminance. For example, a transparent or semi-transparent cathode can be produced by depositing a metal as a cathode electrode material with a film thickness of 1 to 20 nm and then depositing the conductive transparent material thereon. it can.

《Support substrate》
As a support substrate (also referred to as a substrate, a substrate, a substrate, a support, or the like) of the organic EL element, glass, plastic, or the like can be used, and the type thereof is not particularly limited. The support substrate may be transparent or opaque. When extracting light from the support substrate side, the support substrate is preferably transparent. Examples of the transparent support substrate include glass, quartz, and a transparent resin film. A particularly preferable support substrate is a resin film that can give 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, cellulose acetate butyrate, and cellulose acetate propionate (CAP). ), Cellulose esters such as cellulose acetate phthalate (TAC), 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, polysulfone Cycloolefins such as amines, polyetherimide, polyetherketoneimide, polyamide, fluororesin, nylon, polymethylmethacrylate, acrylic or polyarylate, arton (trade name, manufactured by JSR) or appel (trade name, manufactured by Mitsui Chemicals) Based resins and the like.

On the surface of the resin film, an inorganic coating, an organic coating, an inorganic / organic hybrid coating, or the like may be formed. The resin film has a water vapor permeability (25 ± 0.5 ° C., relative humidity (90 ± 2)% RH) measured by a method according to JIS K 7129-1992 of 0.01 g / (m ² · 24 h) or less. The oxygen permeability measured by the method according to JIS K 7126-1987 is 10 ⁻³ ml / (m ² · 24 h · atm) or less, and the water vapor permeability is 10 ^−. A high barrier film of ⁵ g / (m ² · 24 h) or less is more preferable.

As a material of the barrier film formed on the barrier film, any material may be used as long as it has a function of suppressing the intrusion of an organic EL element such as moisture or oxygen, which may deteriorate. For example, silicon oxide, silicon dioxide, nitriding Silicon or the like can be used. In order to improve brittleness, the barrier film preferably has a laminated structure of an inorganic layer and an organic layer. The stacking order of the inorganic layer and the organic layer is not particularly limited, but it is preferable to stack the inorganic layer and the organic layer alternately a plurality of times.

The formation method of the barrier film is not particularly limited, and for example, vacuum deposition method, sputtering method, reactive sputtering method, molecular beam epitaxy method, cluster ion beam method, ion plating method, plasma polymerization method, atmospheric pressure A plasma polymerization method, a plasma CVD method, a laser CVD method, a thermal CVD method, a coating method, or the like can be used. As a method for forming the barrier film, an atmospheric pressure plasma polymerization method as described in JP-A-2004-68143 is particularly preferable.

As the opaque support substrate, for example, a metal plate such as aluminum or stainless steel, a film, a resin substrate, a ceramic substrate, or the like can be used.

<Sealing>
Examples of the method for sealing the organic EL element include a method in which a sealing member is bonded to an electrode or a support substrate with an adhesive. The sealing member should just be arrange | positioned so that the display area | region of an organic EL element may be covered, and may be concave plate shape and flat plate shape. Examples of the method for processing the sealing member into a concave shape include sand blasting and chemical etching. The transparency and electrical insulation of the sealing member are not particularly limited.

Specific examples of the sealing member 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 / film include those formed of polycarbonate, acrylic, polyethylene terephthalate, polyether sulfide, polysulfone and the like. Examples of the metal plate / film include those formed of metals and alloys such as stainless steel, iron, copper, aluminum, magnesium, nickel, zinc, chromium, titanium, molybdenum, silicon, germanium, and tantalum.

As the sealing member, a polymer film or a metal film can be preferably used because the organic EL element can be thinned. The polymer film, the oxygen permeability was measured by the method based on JIS K 7126-1987 is ^{1 × 10 -3 ml / m 2} / 24h or less, the water vapor permeability measured by the method based on JIS K 7129-1992 degrees (25 ± 0.5 ℃, relative humidity (90 ± 2)%) is preferably those of ^{1 × 10 -3 g / (m} 2 / 24h) or less.

Adhesives include photo-curing adhesives having a reactive vinyl group such as acrylic acid oligomers and methacrylic acid oligomers, thermosetting adhesives, moisture-curing adhesives such as 2-cyanoacrylates, and epoxy-based adhesives. And a thermosetting adhesive such as a chemical curing (two-component mixed) adhesive. In addition, hot melt adhesives such as polyamide, polyester, polyolefin, and the like, and cationic curing type ultraviolet curing epoxy resin adhesives can be used.

As the adhesive, since the organic EL element may be deteriorated by heat treatment, an adhesive that can be adhesively cured from room temperature to 80 ° C. is preferable. The adhesive may be one in which a desiccant is dispersed. Application | coating of the adhesive agent to a sealing part may be performed using a commercially available dispenser, and may be performed by printing like screen printing.

Further, as a method for sealing the organic EL element, a method of forming a sealing film covering the organic layer and the electrode on the outside of the electrode provided on the opposite side of the support substrate can also be used. The sealing film may be provided by any one of an inorganic film, an organic film, an inorganic / organic hybrid film, and the like. As a material for the sealing film, any material may be used as long as it has a function of suppressing intrusion of substances that cause deterioration of the organic EL element such as moisture and oxygen. For example, silicon oxide, silicon dioxide, silicon nitride, or the like is used. Can do. In order to improve brittleness, the sealing film preferably has a laminated structure of an inorganic layer and an organic layer.

The method for forming the sealing film is not particularly limited. For example, the vacuum deposition method, the sputtering method, the reactive sputtering method, the molecular beam epitaxy method, the cluster ion beam method, the ion plating method, the plasma polymerization method, An atmospheric pressure plasma polymerization method, a plasma CVD method, a laser CVD method, a thermal CVD method, a coating method, or the like can be used.

An inert gas such as nitrogen or argon, or an inert liquid such as fluorinated hydrocarbon or silicon oil is injected into the gap between the sealing member and the display area of the organic EL element in both the gas phase and the liquid phase. It is preferable to do. In addition, the gap between the sealing member and the display area of the organic EL element may be a vacuum or may enclose a hygroscopic compound.

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, etc.). For sulfates, metal halides and perchloric acids, anhydrous salts are preferably used.

<Application>
The organic EL element according to the present invention can be used as a display device, a display, and various light sources. Examples of light sources include lighting devices (home lighting, interior lighting), clock backlights, liquid crystal backlights, signboard advertising light sources, traffic light sources, optical storage media light sources, electrophotographic copying machine light sources, Examples include a light source of an optical communication processor and a light source of an optical sensor. In particular, it can be effectively used as a backlight of a liquid crystal display device and an illumination light source.

(Display device)
Specifically, the organic EL element according to the present invention can be used as a pixel of a display device. The display device may be a single color display device or a multicolor display device. Below, a multicolor display device is demonstrated as an example of the display apparatus which comprises the organic EL element of this invention.

The configuration of the organic EL element provided in the display device can take various configurations including the above-described element configuration example. When a DC voltage is applied to the multicolor display device, 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. When an AC voltage is applied, light emission can be observed only when the anode is in the + state and the cathode is in the-state. The AC waveform to be applied is not particularly limited.

The multicolor display device can be used as, for example, a display device, a display, or various light sources. Examples of the display device and display include a television, a personal computer, a mobile device, an AV device, a character broadcast display, and an information display in a car. In display devices and displays, full-color display is possible when three types of organic EL elements of blue light emission, red light emission and green light emission are used. It can be used as a display device for reproducing still images and moving images, and a driving method for reproducing moving images may be either a simple matrix (passive matrix) method or an active matrix method.

FIG. 2 is a schematic view showing an example of a display device composed of organic EL elements. This display device displays image information by light emission of an organic EL element. The display 1 includes a display unit A having a plurality of pixels, a control unit B that performs image scanning of the display unit A based on image information, and a wiring unit that electrically connects the display unit A and the control unit B. Etc.

The control unit B sends a scanning signal and an image data signal to each of the plurality of pixels based on image information from the outside. Then, the pixels for each scanning line sequentially emit light according to the image data signal by the scanning signal, and image information is displayed by the display unit A.

FIG. 3 is a schematic diagram of the display unit A. The display unit A has a plurality of pixels 3, a plurality of scanning lines 5, and a plurality of data lines 6 on the substrate. FIG. 3 shows a case where light from each pixel 3 is extracted downward (in the direction of the white arrow).

The scanning line 5 and the data line 6 in the wiring part are each made of a conductive material. The scanning lines 5 and the data lines 6 are orthogonal to each other in a grid pattern, and are connected to the pixels 3 at the orthogonal positions. When a scanning signal is applied from the scanning line 5, the pixel 3 receives an image data signal from the data line 6 and emits light according to the received image data. Full color display is possible by appropriately arranging each of the red, green, and blue pixels of the emission color on the substrate.

FIG. 4 is a schematic diagram of a pixel. The pixel 3 includes an organic EL element 10, a switching transistor 11, a driving transistor 12, a capacitor 13, and the like. For the plurality of pixels 3 provided on the substrate, organic EL elements 10 of red, green and blue emission colors are used.

4, an image data signal is applied from the control unit B to the drain of the switching transistor 11 via the data line 6. When a scanning signal is applied from the control unit B to the gate of the switching transistor 11 via the scanning line 5, the driving of the switching transistor 11 is turned on, and the image data signal applied to the drain is driven by the capacitor 13. It is transmitted to the gate of the transistor 12.

By the transmission of the image data signal, the capacitor 13 is charged according to the potential of the image data signal, and the drive transistor 12 is turned on. The drive transistor 12 has a drain connected to the power supply line 7 and a source connected to the electrode of the organic EL element 10. A current is supplied from the power supply line 7 to the organic EL element 10 in accordance with the potential of the image data signal applied to the gate.

When the controller B sequentially scans and the scanning signal moves to the next scanning line 5, the driving of the switching transistor 11 is turned off. However, even if the driving of the switching transistor 11 is turned off, the capacitor 13 holds the potential of the charged image data signal. Therefore, the drive of the drive transistor 12 is kept on, and the light emission of the organic EL element 10 continues until the next scanning signal is applied. When the scanning signal is next applied by sequential scanning, the driving transistor 12 is driven according to the potential of the next image data signal synchronized with the scanning signal, and the organic EL element 10 emits light.

As described above, the organic EL element 10 emits light for each of the plurality of pixels by providing the switching transistor 11 and the driving transistor 12 which are active elements with respect to the organic EL element 10 used for each of the plurality of pixels 3. Can be configured. Such a light emission method is called an active matrix method.

The light emission of the organic EL element 10 may be light emission of a plurality of gradations by a multi-value image data signal having a plurality of gradation potentials, or by turning on / off a predetermined light emission amount by a binary image data signal. Light emission may be used. Further, the potential of the capacitor 13 may be continuously maintained until the next scanning signal is applied, or may be discharged immediately before the next scanning signal is applied.

Note that the light emission method of the display device is not limited to the above active matrix method, and may be a passive matrix method in which the organic EL element emits light according to the data signal only when the scanning signal is scanned.

FIG. 5 is a schematic diagram of a passive matrix type full-color display device. In FIG. 5, a plurality of scanning lines 5 and a plurality of image data lines 6 are provided in a lattice shape so as to face each other with the pixel 3 interposed therebetween. When the scanning signal of the scanning line 5 is applied by sequential scanning, the pixels 3 connected to the scanning line 5 emit light according to the image data signal. According to the passive matrix method, it is not necessary to provide an active element in the pixel 3, and the manufacturing cost is reduced.

<Lighting device>
Specifically, the organic EL element according to the present invention can be used as a light source of various lighting devices. The lighting device may be a device that generates an appropriate light source color, but is preferably a device that generates a white light source color.

White light emission can be obtained by causing a plurality of luminescent compounds to emit light at the same time and mixing the colors. The combination of the luminescent colors may be a combination of three primary colors of red, green and blue, or a combination of complementary colors such as blue and yellow, blue green and orange. Moreover, the pigment | dye which light-emits light from a luminescent compound as excitation light may be used together, and a color filter may be utilized.

In the illuminating device, organic EL elements that generate emission colors of respective colors may be arranged on the array to generate white emission, or the emission color of the organic EL element itself may be whitened. When the emission color of the organic EL element itself is white, patterning may be performed only on the light-emitting layer and the like, and the electrodes and the like may be collectively formed on one surface.

FIG. 6 is a schematic diagram of the lighting device. FIG. 7 is a schematic diagram of a lighting device. The lighting device can be formed, for example, by covering the organic EL element 101 according to the present invention with a glass cover 102 having a thickness of about 300 μm. By sealing the pair of electrodes 105 and 107 and the organic layer 106 with a glass cover 102 or the like having a sealing material applied around it, the organic layer 106 or the like is prevented from being deteriorated by oxygen or moisture in the atmosphere. Can do. For example, sealing is performed in a glove box under a nitrogen atmosphere (in an atmosphere of high-purity nitrogen gas with a purity of 99.999% or more), and the glass cover 102 is filled with an inert gas 108 such as nitrogen gas or trapped. It is possible to install a liquid 109 or the like.

Note that the organic EL element according to the above embodiment is not limited to the above description in terms of its configuration, manufacturing method, application, etc., and other known configurations and A manufacturing method can be applied, and the present invention can be used for other purposes. For example, JP2013-089608A, JP2014120334A, JP2015-201508A, and the like may be referred to for the known configuration, manufacturing method, application, and the like of the organic EL element.

<Light-emitting thin film>
Next, the luminescent thin film according to this embodiment will be described. The luminescent thin film according to the present embodiment includes a compound (RISC compound) in which the energy difference between the lowest excited singlet energy level and the lowest excited triplet energy level is 0.5 eV or less and an aggregation-induced luminescent molecule (AIE molecule). ) And. For example, a light-emitting functional thin film that can be used for various applications can be formed by forming a functional thin film containing a RISC compound and AIE molecules on a substrate. The concentration of the AIE molecule in the light-emitting thin film can be, for example, 0.1% by mass or more and 99.9% by mass or less. Moreover, the density | concentration in the light emitting thin film of a RISC compound can be 0.1 mass% or more and 99.9 mass% or less, for example.

The luminescent thin film according to the present embodiment can be used as a material such as an organic EL element, a photoelectric conversion element, or an organic functional thin film. Moreover, it can also be used as a light-emitting element constituting the display device or the lighting device. The method for forming the light-emitting thin film of the present invention is not particularly limited, and conventionally known methods such as a vacuum deposition method and a wet method can be used. In addition to the RISC compound and the AIE molecule, other luminescent compounds and host compounds may be blended in the luminescent thin film to be formed.

Examples of the wet method include spin coating method, casting method, ink jet method, printing method, die coating method, blade coating method, roll coating method, spray coating method, curtain coating method, LB method (Langmuir-Blodgett method) and the like. Can be mentioned. As the wet method, a method having high suitability for a roll-to-roll method such as a die coating method, a roll coating method, an ink jet method, or a spray coating method is preferable in that a homogeneous thin film is easily obtained and productivity is high. Used.

Examples of the liquid medium for dissolving or dispersing the RISC compound and the AIE molecule include ketones such as methyl ethyl ketone and cyclohexanone, fatty acid esters such as ethyl acetate, halogenated hydrocarbons such as dichlorobenzene, toluene, xylene, Examples thereof include aromatic hydrocarbons such as mesitylene and cyclohexylbenzene, aliphatic hydrocarbons such as cyclohexane, decalin and dodecane, and organic solvents such as DMF and DMSO. As a dispersion method for dispersing the material, ultrasonic dispersion, high shear force dispersion, media dispersion, or the like can be used.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In the examples, “%” means “% by mass” unless otherwise specified.

(Fluorescent compound)
The fluorescent compounds (A-1, A-2) used in the examples are shown below. Compound A-1 and Compound A-2 are conventional fluorescent compounds having no aggregation-induced light emission.

(RISC compound)
The RISC compounds (B-1, B-2, B-3) used in the examples are shown below. Incidentally, Delta] E _st of RISC Compound B-1 is 0.09 eV, Delta] E _st of RISC Compound B-2 is 0.11 eV, Delta] E _st of RISC Compound B-3 is 0.25 eV.

(Hole transport material)
The hole transport material (HT-1) used in the examples is shown below.

(Electron transport material)
The electron transport materials (ET-1, ET-2) used in the examples are shown below.

(Host compound)
The host compounds (H-1, H-2) used in the examples are shown below.

(AIE molecule)
The AIE molecules (AIE-1, AIE-2, AIE-3, AIE-4) used in the examples are shown below. AIE molecules are fluorescent compounds that emit strong fluorescence by aggregating to form aggregates.

Of the compounds used in the examples, AIE-1 and AIE-2 were prepared according to the method described in the publication (Qin W., et al., Chem. Commun., 2015, 51, 7321-7324). Based on the synthesis. AIE-3 was synthesized based on a method described in a publication (Kim JY, et al., Adv. Mater. 2013, 25, 2666-2671). AIE-4 was synthesized based on a method described in a publication (Chen B., et al., Chem. Eur. J., 2014, 20, 1931-1939). About other compounds, the commercial item (made by Wako Pure Chemical Industries Ltd.) was used.

[Example 1]
An organic EL device was prepared using the post-crosslinking type compound HT-1 for the hole transport layer and the light emitting compound shown in Table 1 for the light emitting layer, and the light emission efficiency was evaluated.

<Preparation of organic EL element 1-1>
(Preparation of anode)
On a 100 mm × 100 mm × 1.1 mm transparent support substrate (NH Techno Glass, NA-45), an ITO (indium tin oxide) film having a thickness of about 100 nm was formed as an anode and patterned. Subsequently, after ultrasonic cleaning with isopropyl alcohol and drying with dry nitrogen gas, UV ozone cleaning was performed for 5 minutes.

(Preparation of hole transport layer)
Subsequently, a solution obtained by diluting poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate (PEDOT: PSS, manufactured by Hereus Co., Ltd., trade name: CLEVIOS P VP AI 4083) to 70% with pure water was used. Then, a film was formed on the anode prepared on the transparent support substrate by spin coating under conditions of 3000 rpm and 30 seconds. And it dried at 200 degreeC for 1 hour, and formed the 30-nm-thick 1st positive hole transport layer. Next, the substrate was transferred to a nitrogen atmosphere, and a coating solution obtained by dissolving 9.0 mg of compound HT-1 in 1.1 g of chlorobenzene was applied on the first hole transport layer under conditions of 1500 rpm and 30 seconds. The film was formed by spin coating. Then, ultraviolet light was irradiated for 180 seconds, and photopolymerization / crosslinking of the post-crosslinking type compound HT-1 was performed to form a second hole transport layer having a thickness of about 20 nm.

(Production of light emitting layer)
Subsequently, a coating solution obtained by dissolving 6.75 mg of the host compound H-1 and 1.69 mg of the fluorescent compound A-1 in 1.1 g of chlorobenzene under a nitrogen atmosphere was used as the second hole transport layer. A film was formed thereon by spin coating under conditions of 1500 rpm and 30 seconds. Then, the solvent was completely removed by heating and drying at 130 ° C. under vacuum to form a light emitting layer having a thickness of about 50 nm.

(Preparation of electron transport layer)
Subsequently, the transparent support substrate on which the light emitting layer was formed was attached to a vacuum deposition apparatus, and then the vacuum chamber was depressurized to 4 × 10 ⁻⁴ Pa, and the compound ET-1 was added at 0.1 nm / second onto the light emitting layer. Evaporation was performed to form an electron transport layer having a thickness of about 35 nm.

(Preparation of electron injection layer / cathode)
Subsequently, using a vacuum deposition apparatus, lithium fluoride was deposited on the electron transport layer to form an electron injection layer having a thickness of about 1.0 nm. Next, aluminum was deposited on the electron injection layer to form a cathode having a thickness of about 110 nm.

(Sealing)
An epoxy photo-curing adhesive (Lux Track LC0629B, manufactured by Toagosei Co., Ltd.) containing a hygroscopic compound that adsorbs oxygen and moisture is applied to the periphery of the sealing glass cover. The electrode formed on the support substrate and the organic layer were covered, and the peripheral portion coated with an epoxy photocurable adhesive as a sealing material was adhered to the transparent support substrate. Thereafter, UV light was irradiated from the transparent support substrate side to a portion where no electrode or organic layer was formed, and the adhesive was cured to obtain a sealed organic EL element 1-1.

<Preparation of organic EL element 1-2>
The organic EL device 1 was prepared in the same manner as the organic EL device 1-1 except that 8.01 mg of the host compound H-1 and 0.42 mg of the RISC compound B-1 were used for the coating solution for forming the light emitting layer. 2 was produced.

<Preparation of organic EL element 1-3>
The organic EL device 1 except that 6.33 mg of the host compound H-1, 0.42 mg of the RISC compound B-1 and 1.69 mg of the fluorescent compound A-1 were used for the coating solution for forming the light emitting layer. Organic EL device 1-3 was produced in the same manner as -1.

<Preparation of organic EL elements 1-4 to 1-7>
Organic EL devices 1-4 to 1-7 were produced in the same manner as the organic EL device 1-3 except that the type of the luminescent compound was replaced with the compounds shown in Table 1.

<Evaluation of luminous efficiency>
At room temperature (25 ° C.), the organic EL element was turned on at a constant current density of ^2.5 mA / cm ² , and the emission luminance was measured with a spectral radiance meter CS-2000 (manufactured by Konica Minolta). The extraction quantum efficiency was determined. The results are shown in Table 1. The luminous efficiency in the table represents a relative value with the measured value of the organic EL element 1-3 as 100.

As shown in Table 1, the organic EL device 1-1 using only the fluorescent compound A-1 having no aggregation-induced light emission as the light emitting compound at a concentration of 20% by mass, or only the RISC compound B-1 is 20 In the organic EL element 1-2 used at a concentration of mass%, light emission was not substantially observed, and it is considered that concentration quenching occurred due to aggregation of the compounds. In the organic EL device 1-3 in which RISC compound B-1 and fluorescent compound A-1 are used in combination as the light emitting compound, organic EL device using fluorescent compound A-1 or RISC compound B-1 alone Compared with 1-1 to 1-2, the luminous efficiency was improved to some extent.

In contrast, in the organic EL elements 1-4 to 1-7 in which AIE molecules are added at the same concentration instead of the fluorescent compound A-1 and used together with the RISC compound, compared to the organic EL element 1-3, Further improvement in luminous efficiency was observed. From this result, even if the concentration is high enough to cause quenching in the conventional fluorescent compound, the AIE molecule can be made to emit light sufficiently, and it can be emitted in combination with the RISC compound. It was confirmed that the efficiency was greatly improved.

[Example 2]
In order to confirm the component that produced light emission in Example 1, a sample of a light-emitting thin film was prepared using the same light-emitting compound as in Example 1, and the emission spectrum was evaluated.

<Preparation of Sample 2-1>
The glass substrate of 300 mm × 300 mm × 1.1 mm was subjected to UV ozone cleaning treatment for 10 minutes. Thereafter, the coating solution used for forming the light emitting layer of the organic EL element 1-1 was formed on the substrate by spin coating under a nitrogen atmosphere at 1000 rpm for 30 seconds. Then, sealing was performed in the same procedure as that for the organic EL element 1-1 to obtain a sample 2-1.

<Preparation of Sample 2-2>
Sample 2 was prepared in the same manner as Sample 2-1, except that the coating solution used for forming the light emitting layer of the organic EL device 1-2 was used and the fluorescent compound A-1 was replaced with RISC compound B-1. 2 was produced.

<Preparation of Sample 2-3>
Sample 2-3 was prepared in the same manner as Sample 2-2, except that RISC compound B-1 was replaced with RISC compound B-2.

<Preparation of samples 2-4 to 2-5>
Samples 2-4 to 2-5 were prepared in the same manner as Sample 2-1, except that the fluorescent compound A-1 was replaced with AIE-1 or AIE-2.

<Preparation of Samples 2-6 to 2-9>
Sample 2-1 was prepared in the same manner as Sample 2-1, except that the coating solution used for forming the light-emitting layers of the organic EL devices 1-4 to 1-7 was used and the type of light-emitting compound was replaced with the compound shown in Table 2. 2-6 to 2-9 were produced.

<Spectrum evaluation>
The sample was made to emit light using the excitation method shown in Table 2, and the emission spectrum was measured at room temperature with a spectrofluorometer (Hitachi High-Tech Science Co., Ltd., F-7000) to confirm the emission maximum wavelength. Samples 2-1 to 2-5 were optically excited with light in a wavelength region including the visible light region, and samples 2-6 to 2-9 were excited with current at ^2.5 mA / cm ² .

As a result, the emission maximum wavelengths of Samples 2-6 to 2-9 using RISC compounds and AIE molecules in combination as the luminescent compounds are the same as those of Samples 2-4 and 2-5 using only AIE molecules, respectively. Matched. In Samples 2-6 to 2-9, luminescence derived from the AIE molecule was detected, and thus it was assumed that the exciton had transferred energy from the RISC compound to the AIE molecule.

[Example 3]
An organic EL device was prepared using the post-crosslinking compound HT-1 for the hole transport layer and the light-emitting compound shown in Table 3 for the light-emitting layer, and the luminous efficiency was evaluated.

<Production of organic EL elements 3-1 to 3-5>
Organic EL devices 3-1 to 3-5 were produced in the same manner as the organic EL device 1-1 except that the type of the luminescent compound was replaced with the compounds shown in Table 3.

<Evaluation of luminous efficiency>
As in Example 1, the organic EL element was turned on at a constant current density of ^2.5 mA / cm ² at room temperature (25 ° C.), and the emission luminance was measured with a spectral radiance meter CS-2000 (manufactured by Konica Minolta). The light emission efficiency (external extraction quantum efficiency) was determined by measurement. The results are shown in Table 3. The luminous efficiency in the table represents a relative value with the measured value of the organic EL element 3-3 as 100.

As shown in Table 3, in the organic EL device 3-1, in which only the fluorescent compound A-2 having no aggregation-inducing light-emitting property as the light-emitting compound was used at a concentration of 20% by mass, almost no light emission was observed. On the other hand, in the organic EL elements 3-4 to 3-5 in which AIE molecules are added at the same concentration instead of the fluorescent compound A-2 and used together with the RISC compound, compared with the organic EL element 3-3, High luminous efficiency was obtained. Therefore, when the concentration of the fluorescent compound is increased for the purpose of improving the luminous efficiency, it is presumed that the method using the AIE molecule is effective.

[Example 4]
In order to confirm the component that produced light emission in Example 3, a sample of a light-emitting thin film was prepared using the same light-emitting compound as in Example 3, and the emission spectrum was evaluated.

<Preparation of Sample 4-1>
In the same manner as in Example 2, a UV ozone cleaning treatment was performed for 10 minutes on a glass substrate of 300 mm × 300 mm × 1.1 mm. Thereafter, the coating liquid used for forming the light emitting layer of the organic EL element 3-1 was formed on the substrate by spin coating under a nitrogen atmosphere at 1000 rpm for 30 seconds. Then, sealing was performed in the same procedure as in the organic EL element 1-1 to obtain a sample 4-1.

<Preparation of Sample 4-2>
Sample 4 was prepared in the same manner as Sample 4-1, except that the coating solution used for forming the light emitting layer of the organic EL device 3-2 was used and the fluorescent compound A-2 was replaced with RISC compound B-3. 2 was produced.

<Preparation of samples 4-3 to 4-4>
Samples 4-3 to 4-4 were produced in the same manner as Sample 4-1, except that the fluorescent compound A-2 was replaced with AIE-3 or AIE-4.

<Preparation of samples 4-5 to 4-6>
Samples were obtained in the same manner as Sample 4-1, except that the coating solution used for forming the light emitting layers of the organic EL devices 3-4 to 3-5 was used and the types of the light emitting compounds were replaced with the compounds shown in Table 4. 4-5 to 4-6 were produced.

<Spectrum evaluation>
In the same manner as in Example 2, the sample was caused to emit light using the excitation method shown in Table 4, and the emission spectrum was measured at room temperature with a spectrofluorometer (Hitachi High-Tech Science Co., Ltd., F-7000). The wavelength was confirmed. Samples 4-1 to 4-4 were optically excited with light in a wavelength region including the visible light region, and samples 4-5 to 4-6 were excited with current at ^2.5 mA / cm ² .

As a result, the emission maximum wavelength of sample 4-5 using a RISC compound and an AIE molecule in combination as the luminescent compound is the emission maximum wavelength of sample 4-2 using only the RISC compound B-3, or only the AIE molecule. It was confirmed that the sample was located at two locations that approximate the emission maximum wavelength of Sample 4-3. Similarly, Sample 4-6 using a RISC compound and an AIE molecule in combination as the luminescent compound is similarly located at two locations that are close to the emission maximum wavelength of Sample 4-2 and the emission maximum wavelength of Sample 4-4. It was confirmed. Therefore, not all triplet excitons generated in the RISC compound are energy transferred to the AIE molecule, and it is assumed that a part of the triplet excitons may cause light emission on the RISC compound.

[Example 5]
An organic EL element containing AIE molecules as a luminescent compound was prepared and evaluated for resistance to moisture and oxygen.

<Preparation of organic EL element 5-1>
Organic EL device except that compound ET-1 used for forming the electron transport layer was replaced with compound ET-2, host compound H-1 was replaced with host compound H-2, and the device was completed without sealing Organic EL element 5-1 was produced in the same manner as in 1-3.

<Preparation of organic EL element 5-2>
Organic EL device except that compound ET-1 used for forming the electron transport layer was replaced with compound ET-2, host compound H-1 was replaced with host compound H-2, and the device was completed without sealing In the same manner as in 1-4, an organic EL element 5-2 was produced.

<Evaluation of resistance to moisture and oxygen>
The light emission efficiency of the organic EL element immediately after the production and the light emission efficiency of the organic EL element after being left in the atmosphere for 24 hours were determined, and the resistance to moisture and oxygen was evaluated based on the decrease in the light emission efficiency. The luminous efficiency (external extraction quantum efficiency) was determined in the same manner as in Example 1. The results are shown in Table 5. The luminous efficiency in the table represents a relative value for each organic EL element, with the measured value immediately after production (after 0 hour) being 100.

As shown in Table 5, the organic EL device 5-2 containing AIE molecules in the light emitting layer was confirmed to have high light emission efficiency even after being left in the air. The reason for this is not clear, but the AIE molecules form aggregates, which increases the diameter of the individual light emitters and reduces the contact area and the number of collisions with water molecules and oxygen that cause deterioration. Can be guessed. It should be noted that the phosphorescent metal complex used in this case had similar results when Dp-1 to Dp-59 described in this specification were used.

DESCRIPTION OF SYMBOLS 1 Display 3 Pixel 5 Scan line 6 Data line 7 Power supply line 10 Organic EL element 11 Switching transistor 12 Drive transistor 13 Capacitor 101 Organic EL element 102 in an illuminating device Glass cover 105 Cathode 106 Organic EL layer 107 Glass substrate 108 with a transparent electrode Nitrogen Gas 109 Water capturing agent A Display part B Control part

Claims (6)

An anode, a cathode, and a light emitting layer provided between the anode and the cathode, wherein the energy difference between the lowest excited singlet energy level and the lowest excited triplet energy level is 0 in the light emitting layer. Organic electroluminescent element containing the compound and aggregation induced luminescent molecule | numerator which are 0.5 eV or less. The organic electroluminescence device according to claim 1, wherein the compound is a conjugated compound represented by the following general formula (A).

[In the general formula (A), A represents an electron acceptor moiety, D represents an electron donor moiety, L represents a divalent linking group, and l and m each independently represent Represents an integer of 1 to 4; ] The organic electroluminescence device according to claim 1, wherein the aggregation-induced luminescent molecule is a tetraphenylethylene derivative or a silole derivative. A luminescent thin film containing a compound having an energy difference between the lowest excited singlet energy level and the lowest excited triplet energy level of 0.5 eV or less and an aggregation-induced luminescent molecule. A display device comprising the organic electroluminescence element according to any one of claims 1 to 3. An illumination device comprising the organic electroluminescence element according to any one of claims 1 to 3.

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