TW202128719A - Pyrromethene boron complex, light-emitting element containing same, light-emitting element, display device, and illumination device - Google Patents

Abstract

By means of a pyrromethene boron complex represented by general formula (1), provided are: a light-emitting material having a high fluorescence quantum yield and a sharp light-emitting spectrum; and a light-emitting element having a high light-emitting efficiency, color purity, and a durability.

Description

Pyrrolomethylene boron complex, light-emitting element, display device and lighting device containing the same

The present invention relates to a pyrromethene boron complex, a light-emitting element, a display device and a lighting device containing the pyrromethene boron complex.

The organic thin-film light-emitting element that emits light by recombining electrons injected from the cathode and holes injected from the anode in the light-emitting layer sandwiched between the two poles has a thin profile and can achieve low driving voltage and high brightness light emission, and then by selecting The luminescent material realizes the characteristics of multi-color luminescence. In particular, by using a host material and a dopant material in combination in the light-emitting layer, a light-emitting element that efficiently emits light of the three primary colors of blue, green, and red can be obtained.

As the dopant, a pigment with a high fluorescence quantum yield can usually be used. For example, it is known that complexes with a pyrromethene skeleton are provided as a dopant with high fluorescence quantum yield, a Stokes shift and a small peak half-value width of the emission spectrum to obtain high efficiency. As a compound required for the necessary conditions, a light-emitting device using a pyrromethene complex as a dopant exhibits good device characteristics (for example, refer to Patent Document 1). Furthermore, in recent years, with the goal of high luminous efficiency, a light-emitting element comprising a thermally activated delayed fluorescence (TADF) material and a pyrromethene boron complex has been studied (for example, refer to Patent Document 2 ). [Prior Art Literature] [Patent Literature]

Patent Document 1: Japanese Patent Laid-Open No. 2003-12676 Patent Document 2: International Publication No. 2016/056559

[The problem to be solved by the invention] When the organic thin-film light-emitting element is used as a display device or a lighting device, it is required to expand the color gamut. The color gamut is determined in the xy chromaticity diagram to indicate the apex coordinates of red, green, and blue light, and is represented by a triangle connecting them. In order to expand the color gamut, the vertex coordinates of red, green, and blue must be adjusted to the appropriate chromaticity to expand the area of the triangle. For this reason, various color designs are being carried out.

The chromaticity is determined by the combination of the emission peak wavelength and the color purity. The color purity is determined by the width of the luminescence spectrum. The narrower the width of the luminescence spectrum, the closer to monochromatic light, the higher the color purity. In order to achieve a wide color gamut, it is particularly important to improve color purity, and there is a strong demand for luminescent materials with sharp emission spectra.

In addition, when an organic thin-film light-emitting element is used as a display device or a lighting device, it is required to improve the durability of the light-emitting element. In order to improve the durability of the light-emitting element, the stability of the light-emitting material must be improved.

On the other hand, from the viewpoint of brightness improvement and power saving, the organic thin-film light-emitting element desirably has high luminous efficiency. In particular, in mobile display devices that have been increasingly used in recent years, power saving has become a particularly important issue.

Under such circumstances, when pyrromethene boron complex is used as a dopant, although it is a useful light-emitting material that can obtain a sharp emission spectrum, it is required for light-emitting elements to have higher luminous efficiency and Higher durability. However, it is difficult to maintain a sharp emission spectrum and achieve a light-emitting element with high luminous efficiency and high durability.

The purpose of the present invention is to solve the aforementioned problems of the prior art and provide a luminescent material with high fluorescent quantum yield and sharp emission spectrum, and a luminescent element with high luminous efficiency, color purity and durability. [Means to solve the problem]

The present invention is a pyrromethene boron complex represented by the general formula (1).

[化1]

R ¹ to R ⁶ are each independently selected from a hydrogen atom, an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a hydroxyl group, a thiol group, an alkoxy group, an alkylthio group, and an aryl group. Ether group, aryl sulfide group, aryl group, heteroaryl group, amine group, silyl group, siloxyalkyl group and oxyboron group. These groups may further have a substituent. Among them, ^{at least one of R 1} to R ⁴ is a hydrogen atom or an alkyl group. X ¹ and X ² are each independently selected from alkyl, cycloalkyl, heterocyclic, alkenyl, cycloalkenyl, alkynyl, hydroxyl, thiol, alkoxy, alkylthio, aryl ether, Aryl sulfide group, aryl group, heteroaryl group, halogen and cyano group. These groups may further have a substituent. R ⁷ is represented by the following general formula (2).

[化2]

R ⁸ to R ¹⁰ are each independently selected from a hydrogen atom, an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a hydroxyl group, a thiol group, an alkoxy group, an alkylthio group, and an aryl group. Ether group, aryl sulfide group, aryl group, heteroaryl group, halogen, cyano group, aldehyde group, acyl group, carboxyl group, ester group, amide group, sulfonyl group, sulfonate group, sulfonamide group, Amine group, nitro group, silyl group, siloxyalkyl group, oxyboron group and phosphine oxide group. These groups may further have a substituent. R ^{11 is} selected from alkyl, cycloalkyl, heterocyclyl, alkenyl, cycloalkenyl, alkynyl, hydroxyl, thiol, alkoxy, alkylthio, aryl ether, aryl sulfide, Aryl, heteroaryl, halogen, cyano, aldehyde, amide, carboxyl, ester, amide, sulfonate, sulfonate, sulfonamide, amine, nitro, silyl, In the group consisting of siloxyalkyl, oxyboron and phosphine oxide groups. These groups may further have a substituent. Ar ¹ is a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group.

In addition, another aspect of the present invention is a light-emitting element that has an anode and a cathode, and a light-emitting layer existing between the anode and the cathode, and the light-emitting layer emits light by electric energy. The light-emitting layer contains the pyrromethene boron complex. [Effects of the invention]

With the present invention, it is possible to provide a luminescent material with high fluorescent quantum yield and a sharp emission spectrum, and a luminescent element with high luminous efficiency, color purity and durability.

Hereinafter, preferred embodiments of the pyrromethene boron complex of the present invention, a light-emitting element, a display device, and a lighting device containing the same will be described in detail. However, the present invention is not limited to the following embodiments, and can be implemented with various changes depending on the purpose or application.

＜Pyrromethene boron complexes＞ The pyrromethene boron complex of the present invention is represented by the general formula (1).

[化3]

R ¹ to R ⁶ are each independently selected from a hydrogen atom, an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a hydroxyl group, a thiol group, an alkoxy group, an alkylthio group, and an aryl group. Ether group, aryl sulfide group, aryl group, heteroaryl group, amine group, silyl group, siloxyalkyl group and oxyboron group. These groups may further have a substituent. Among them, ^{at least one of R 1} to R ⁴ is a hydrogen atom or an alkyl group.

X ¹ and X ² are each independently selected from alkyl, cycloalkyl, heterocyclic, alkenyl, cycloalkenyl, alkynyl, hydroxyl, thiol, alkoxy, alkylthio, aryl ether, Aryl sulfide group, aryl group, heteroaryl group, halogen and cyano group. These groups may further have a substituent.

R ⁷ is represented by the following general formula (2).

[化4]

R ⁸ to R ¹⁰ are each independently selected from a hydrogen atom, an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a hydroxyl group, a thiol group, an alkoxy group, an alkylthio group, and an aryl group. Ether group, aryl sulfide group, aryl group, heteroaryl group, halogen, cyano group, aldehyde group, acyl group, carboxyl group, ester group, amide group, sulfonyl group, sulfonate group, sulfonamide group, Amine group, nitro group, silyl group, siloxyalkyl group, oxyboron group and phosphine oxide group. These groups may further have a substituent.

R ^{11 is} selected from alkyl, cycloalkyl, heterocyclyl, alkenyl, cycloalkenyl, alkynyl, hydroxyl, thiol, alkoxy, alkylthio, aryl ether, aryl sulfide, Aryl, heteroaryl, halogen, cyano, aldehyde, amide, carboxyl, ester, amide, sulfonate, sulfonate, sulfonamide, amine, nitro, silyl, In the group consisting of siloxyalkyl, oxyboron and phosphine oxide groups. These groups may further have a substituent.

Ar ¹ is a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group.

In the pyrromethene skeleton, ^{the site substituted with R 7} may be referred to as the "bridgehead position" below.

In the present invention, those having a pyrromethene skeleton represented by the following formula, and those having a condensed ring structure in a part of the pyrromethene skeleton with an enlarged ring structure are collectively referred to as "pyrromethene".

[化5]

In all the groups described above, hydrogen may also be deuterium. The same applies to the compounds described below or partial structures thereof.

In addition, among all the groups, the substituents when substituted are preferably selected from the group consisting of alkyl, cycloalkyl, heterocyclyl, alkenyl, cycloalkenyl, alkynyl, aryl, heteroaryl, Hydroxyl group, thiol group, alkoxy group, alkylthio group, aryl ether group, aryl sulfide group, halogen, cyano group, aldehyde group, acyl group, carboxyl group, ester group, amide group, amide group, sulfonyl group Group, sulfonate group, sulfonamide group, amine group, nitro group, silyl group, siloxyalkyl group, oxyboron group, phosphine oxide group and pendant oxy group. Furthermore, it is more preferable to set it as a preferable concrete substituent in the description of each substituent mentioned later. In addition, these substituents may be further substituted with the above-mentioned substituents.

In the description of the present invention, the term "unsubstituted" means that the atom bonded to the target basic skeleton or group is only a hydrogen atom or a deuterium atom. In the compounds described below or partial structures thereof, the case of "substituted or unsubstituted" is also the same as described above.

The alkyl group means, for example, a saturated aliphatic hydrocarbon group such as a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, a second butyl group, and a tertiary butyl group, and it may be substituted or unsubstituted. The additional substituent at the time of substitution is not particularly limited, and examples thereof include an alkyl group, a halogen, an aryl group, a heteroaryl group, etc., and this aspect is also the same in the following description. The carbon number of the alkyl group is not particularly limited, but it is preferably in the range of 1 or more and 20 or less, more preferably in the range of 1 or more and 8 or less in terms of ease of availability and cost.

The cycloalkyl group means, for example, a saturated alicyclic hydrocarbon group such as a cyclopropyl group, a cyclohexyl group, a norbornyl group, and an adamantyl group, which may be substituted or unsubstituted. The carbon number of the alkyl moiety is not particularly limited, but is preferably in the range of 3 or more and 20 or less.

The heterocyclic group means, for example, a pyran ring, a piperidine ring, and a cyclic aliphatic ring having atoms other than carbon in the ring, which may be substituted or unsubstituted. The number of carbon atoms of the heterocyclic group is not particularly limited, but is preferably in the range of 2 or more and 20 or less.

The alkenyl group means, for example, an unsaturated aliphatic hydrocarbon group containing a double bond, such as a vinyl group, an allyl group, and a butadienyl group, which may be substituted or unsubstituted. The carbon number of the alkenyl group is not particularly limited, but is preferably in the range of 2 or more and 20 or less.

The cycloalkenyl group means, for example, an unsaturated alicyclic hydrocarbon group containing a double bond, such as a cyclopentenyl group, a cyclopentadienyl group, and a cyclohexenyl group, which may be substituted or unsubstituted. The carbon number of the cycloalkenyl group is not particularly limited, but is preferably in the range of 3 or more and 20 or less.

The alkynyl group means, for example, an unsaturated aliphatic hydrocarbon group containing a triple bond such as an ethynyl group, which may be substituted or unsubstituted. The carbon number of the alkynyl group is not particularly limited, but is preferably in the range of 2 or more and 20 or less.

The alkoxy group means, for example, a functional group to which an aliphatic hydrocarbon group is bonded via an ether bond, such as a methoxy group, an ethoxy group, and a propoxy group, and the aliphatic hydrocarbon group may be substituted or unsubstituted. The carbon number of the alkoxy group is not particularly limited, but is preferably in the range of 1 or more and 20 or less.

The term "alkylthio group" means that the oxygen atom of the ether bond of the alkoxy group is substituted with a sulfur atom. The hydrocarbyl group of the alkylthio group may be substituted or unsubstituted. The carbon number of the alkylthio group is not particularly limited, but is preferably in the range of 1 or more and 20 or less.

The aryl ether group means, for example, a functional group such as a phenoxy group to which an aromatic hydrocarbon group is bonded via an ether bond. The aromatic hydrocarbon group may be substituted or unsubstituted. The carbon number of the aryl ether group is not particularly limited, but is preferably in the range of 6 or more and 40 or less.

The aryl sulfide group refers to the one in which the oxygen atom of the ether bond of the aryl ether group is substituted with a sulfur atom. The aromatic hydrocarbon group in the aryl sulfide group may be substituted or unsubstituted. The carbon number of the aryl sulfide group is not particularly limited, but is preferably in the range of 6 or more and 40 or less.

The aryl group can be any one of a single ring or a condensed ring, for example, it represents a phenyl group, a naphthyl group, a fluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a phenanthryl group, an anthryl group, a triphenylphenanthryl group, and a benzanthracene group. Aromatic hydrocarbon groups such as fluoranthene group, triphenylene group, pyrene group, fluoranthene group, triphenylenyl group, benzofluoranthene group, dibenzoanthracene group, perylene group, helicenyl group, etc. Among them, preferred is a group selected from the group consisting of phenyl, biphenyl, terphenyl, naphthyl, fluorenyl, phenanthryl, anthracenyl, pyrenyl, fluoranthene, and triphenylene. The aryl group may be substituted or unsubstituted. In the present invention, a group in which a plurality of phenyl groups such as a biphenyl group and a terphenyl group are bonded via a single bond is regarded as a phenyl group having an aryl group as a substituent. The carbon number of the aryl group is not particularly limited, but is preferably 6 or more and 40 or less, more preferably 6 or more and 30 or less. In addition, in the phenyl group, when each of the two adjacent carbon atoms in the phenyl group has a substituent, these substituents may form a ring structure with each other.

The heteroaryl group can be any one of a single ring or a condensed ring, for example, pyridyl, furyl, thiophenyl group, quinolinyl, isoquinolinyl, pyrazinyl, pyrimidinyl, pyridazinyl , Triazinyl, naphthyridinyl, cinnolinyl, phthalazinyl, quinoxalinyl, quinazolinyl, benzofuranyl, benzothiophenyl, indolyl, dibenzofuranyl, diphenyl Acetylthio, carbazolyl, benzocarbazolyl, carbolinyl group, indolocarbazolyl, benzofurocarbazolyl, benzothienocarbazolyl, dihydroindeno Carbazolyl, benzoquinolinyl, acridinyl, dibenzoacridinyl, benzimidazolyl, imidazopyridyl, benzoxazolyl, benzothiazolyl, phenanthroline are equal to one or more A cyclic aromatic group having atoms other than carbon and hydrogen, that is, heteroatoms in the ring. As the hetero atom, a nitrogen atom, an oxygen atom or a sulfur atom is preferred. Heteroaryl groups may be substituted or unsubstituted. The carbon number of a heteroaryl group is not specifically limited, Preferably it is the range of 2 or more and 40 or less, More preferably, it is the range of 2 or more and 30 or less.

The term "halogen" means an atom selected from fluorine, chlorine, bromine and iodine.

The so-called cyano group refers to a functional group represented by the structure -CN. Here, it is a carbon atom that is bonded to other groups.

The so-called aldehyde group means a functional group represented by the structure -C(=O)H. Here, it is a carbon atom that is bonded to other groups.

The so-called acyl group means, for example, an acetyl group, a propionyl group, a benzyl group, a acryloyl group, etc., which are bonded via a carbonyl group to an alkyl group, a cycloalkyl group, an alkenyl group, alkynyl group, an aryl group, a heteroaryl group, etc. base. These substituents may be further substituted. The carbon number of the acyl group is not particularly limited, but is preferably 2 or more and 40 or less, and more preferably 2 or more and 30 or less.

The term "ester group" means, for example, a functional group formed by bonding an alkyl group, a cycloalkyl group, an aryl group, and a heteroaryl group via an ester bond. These substituents may be further substituted. The carbon number of the ester group is not particularly limited, but is preferably in the range of 1 or more and 20 or less. More specifically, examples include methyl ester groups such as methoxycarbonyl, ethyl ester groups such as ethoxycarbonyl, propyl ester groups such as propoxycarbonyl, butyl ester groups such as butoxycarbonyl, isopropyl Isopropyl ester groups such as oxymethoxycarbonyl, hexyl ester groups such as hexyloxycarbonyl, phenyl ester groups such as phenoxycarbonyl, and the like.

The amide group means, for example, a functional group formed by bonding an alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, etc. via an amide bond. These substituents may be further substituted. The carbon number of the amide group is not particularly limited, but is preferably in the range of 1 or more and 20 or less. More specifically, examples include methyl amide, ethyl amide, propyl amide, butyl amide, isopropyl amide, hexyl amide, phenyl amide, etc. .

The sulfonyl group means, for example, a functional group formed by bonding an alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, etc. via a -S(=O) _2-bond. These substituents may be further substituted. The carbon number of the sulfonyl group is not particularly limited, but is preferably in the range of 1 or more and 20 or less.

The sulfonate group means, for example, a functional group formed by bonding an alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, etc. via a sulfonate ester bond. Here, the sulfonate ester bond refers to a carbonyl part of an ester bond, that is, -C(=O)- is substituted with a sulfonate group, that is, -S(=O) ₂ -. In addition, these substituents may be further substituted. The carbon number of the sulfonate group is not particularly limited, but is preferably in the range of 1 or more and 20 or less.

The sulfonamide group means, for example, a functional group formed by bonding an alkyl group, a cycloalkyl group, an aryl group, and a heteroaryl group via a sulfonamide bond. Here, the sulfonamide bond refers to a carbonyl part of an ester bond, that is, -C(=O)- is substituted with a sulfonamide, that is, -S(=O) ₂ -. In addition, these substituents may be further substituted. The carbon number of the sulfonamide group is not particularly limited, but it is preferably in the range of 1 or more and 20 or less.

The so-called amine group refers to a substituted or unsubstituted amine group. Examples of the substituent in the case of substitution include an aryl group, a heteroaryl group, a linear alkyl group, and a branched alkyl group. As an aryl group and a heteroaryl group, a phenyl group, a naphthyl group, a pyridyl group, and a quinolinyl group are preferable. These substituents may be further substituted. The carbon number is not particularly limited, but is preferably 2 or more and 50 or less, more preferably 6 or more and 40 or less, and particularly preferably 6 or more and 30 or less.

The so-called silyl group refers to a functional group bonded with substituted or unsubstituted silicon atoms, such as trimethylsilyl group, triethylsilyl group, tertiary butyldimethylsilyl group, and propyldimethylsilyl group. Alkyl silyl groups such as silyl group and vinyl dimethyl silyl group; or aryl silyl groups such as phenyl dimethyl silyl group, tertiary butyl diphenyl silyl group, triphenyl silyl group, trinaphthyl silyl group, etc. base. Substituents on silicon can be further substituted. The carbon number of the silyl group is not particularly limited, but is preferably in the range of 1 or more and 30 or less.

The siloxyalkyl group means, for example, a silicon compound group such as a trimethylsiloxyalkyl group via an ether bond. Substituents on silicon can be further substituted.

The oxyboron group refers to a substituted or unsubstituted oxyboron group. Examples of substituents in the case of substitution include aryl groups, heteroaryl groups, linear alkyl groups, branched alkyl groups, aryl ether groups, alkoxy groups, and hydroxyl groups. Among them, aryl groups and aryl ether groups are preferred. base.

The phosphine oxide group means a group represented by -P(=O)R ⁵⁰ R ^51. R ⁵⁰ and R ⁵¹ are each independently selected from the same ^{group as R 1} to R ^6.

Since the pyrromethene boron complex has a strong and highly planar skeleton, it exhibits a high fluorescence quantum yield. In addition, the peak half-value width of the emission spectrum is small, so efficient light emission and high color purity can be achieved in the light-emitting element.

In order to further improve the luminous efficiency, it is effective to suppress the rotation and vibration of the substituent of the pyrromethene boron complex, reduce energy loss, and increase the fluorescence quantum yield. In addition, in order to improve the color purity, it is effective to reduce the vibrational relaxation in the excited state of the pyrromethene boron complex, and to reduce the half-value width of the emission spectrum.

From this viewpoint, the substituent R ⁷ is introduced to the bridgehead position of the pyrromethene skeleton. By introducing R ⁷ , a pyrromethene boron complex with high fluorescence quantum yield and small half-value width can be provided. Among them, in the substituent R ⁷ , Ar ¹ and R ¹¹ are each the above-mentioned groups, which can suppress the intramolecular rotation of the bridgehead position with respect to the pyrromethene skeleton to cause energy inactivation, thereby contributing to the improvement of luminous efficiency.

In addition, ^{since at least one of R 1} to R ⁴ is a hydrogen atom or an alkyl group, vibration relaxation in the excited state can be reduced, and the half-value width of the emission spectrum can be reduced.

In addition, the stability of the pyrromethene boron complex affects the durability of the light-emitting element. In order to further improve its stability, it is preferable to introduce bulky substituents at the bridgehead position. By introducing bulky substituents, the pyrromethene skeleton can be protected from interaction with other surrounding molecules. ^{When Ar 1} and R ¹¹ are the above-mentioned groups in the substituent R ⁷ , the stability of the pyrromethene boron complex can be improved, and the durability of the light-emitting device can be improved. From this viewpoint, R ^{11 is} preferably a bulkier substituent, preferably a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group.

R ¹ and R ^{4 are} selected from the group and affect the emission peak wavelength, crystallinity, sublimation temperature, etc. of the pyrromethene boron complex. From the viewpoint of further reducing the half-value width of the emission spectrum, R ¹ and R ^{4 are} preferably hydrogen atoms or alkyl groups. Furthermore, from the viewpoint of further improving the fluorescence quantum yield, R ¹ and R ^{4 are more} preferably alkyl groups.

R ² and R ^{3 are} selected from the group, and mainly affect the emission peak wavelength of the pyrromethene boron complex, the half-value width of the emission spectrum, the stability or the crystallinity. From the viewpoint of further reducing the half-value width of the emission spectrum, the viewpoint of further improving the stability, and the viewpoint of the ease of synthesis including the formation of recrystallization, at least one of ^{R 2} and R ^{3 is preferably} Preferred for both is a group selected from the group consisting of a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, and a substituted or unsubstituted heteroaryl group. . Furthermore, from the viewpoint of further reducing the half-value width, R ² and R ^{3 are more} preferably alkyl groups.

R ⁵ and R ^{6 are} selected from the group, and mainly affect the emission peak wavelength of the pyrromethene boron complex, the half-value width of the emission spectrum, the stability or the crystallinity. From the viewpoint of further reducing the half-value width of the emission spectrum, the viewpoint of further improving the stability, and the viewpoint of the ease of synthesis including recrystallization and purification, at least one of ^{R 5} and R ^{6 is preferably} Preferred for both is a hydrogen atom, or a substituted or unsubstituted alkyl group.

X ¹ and X ^{2 are} selected from the group. From the viewpoint of luminescence characteristics and thermal stability, X ¹ and X ^{2 are} preferably selected from the group consisting of alkoxy, halogenated alkyl, halogenated alkoxy, aryl ether group, halogenated aryl ether group, halogenated aryl group, A group in the group consisting of a halogen atom and a cyano group. Here, the term "haloalkyl" refers to an alkyl group substituted with at least one halogen. The so-called halogenated aryl group refers to an aryl group substituted with at least one halogen.

^{In addition, X 1} and X ^{2 are more} preferably selected from the group consisting of fluorine atoms, fluorine-containing alkyl groups, and fluorine-containing alkoxy groups from the viewpoint of stable excited state and higher fluorescence quantum yield and the viewpoint that durability can be improved. The group in the group consisting of a fluorine-containing aryl group and a cyano group is more preferably a fluorine atom or a cyano group, and most preferably a fluorine atom. These are electron withdrawing groups, which can reduce the electron density of the pyrromethene skeleton and increase the stability of the compound.

An example of the pyrromethene boron complex compound represented by General formula (1) is shown below, but it is not limited to these.

[化6]

[化7]

[化8]

[化9]

[化10]

[化11]

[化12]

[化13]

[化14]

[化15]

[化16]

[化17]

[化18]

[化19]

[化20]

[化21]

For the pyrromethene boron complex represented by the general formula (1), please refer to "Journal of Organic Chemistry (J. Org. Chem.)" (vol. 64, No. 21, page 7813-page 7819 (1999)) ), "Angew. Chem., Int. Ed. Engl." (vol. 36, p. 1333-p. 1335 (1997)), "Org. Lett." ( vol. 12, page 296 (2010)).

Furthermore, in order to introduce an aryl group or a heteroaryl group into the pyrromethene skeleton, for example, the use of a halogenated derivative of a pyrromethene boron complex and a boric acid or boronic acid ester derivative under a metal catalyst such as palladium can be mentioned. The method of coupling reaction to form carbon-carbon bond is not limited to this. Similarly, in order to introduce an amine group or a carbazole group into the pyrromethene skeleton, for example, a halogenated derivative of a pyrromethene boron complex and an amine or carbazole derivative are used under a metal catalyst such as palladium. The method of coupling reaction to form a carbon-nitrogen bond is not limited to this.

The obtained pyrromethene boron complex is preferably purified by organic synthesis such as recrystallization or column chromatography, and then further purified by heating under reduced pressure, which is generally called sublimation purification, to remove low-boiling components. , Improve purity. The heating temperature in the sublimation purification is not particularly limited, but from the viewpoint of preventing thermal decomposition of the pyrromethene boron complex, it is preferably 330°C or lower, and more preferably 300°C or lower.

From the viewpoint that the light-emitting element can exhibit stable characteristics, the purity of the pyrromethene boron complex produced in the above manner is preferably 99% by weight or more.

The optical properties of the pyrromethene boron complex represented by the general formula (1) can be obtained by measuring the absorption spectrum and the emission spectrum of the diluted solution. The solvent is not particularly limited as long as it is a transparent solvent that dissolves the pyrromethene boron complex and the absorption spectrum of the solvent does not overlap the absorption spectrum of the pyrromethene boron complex. Specifically, toluene and the like can be exemplified. The concentration of the solution is not particularly limited as long as it has sufficient absorbance and does not undergo concentration quenching. It is preferably in the range of 1×10 ^-4 mol/L to 1×10 ^-7 mol/L, and more It is preferably in the range of 1×10 ^-5 mol/L to 1×10 ^-6 mol/L. The absorption spectrum can be measured by a general ultraviolet-visible spectrophotometer. In addition, the emission spectrum can be measured by a general fluorescent spectrophotometer. Furthermore, for the measurement of the fluorescence quantum yield, it is preferable to use an absolute quantum yield measuring device using an integrating sphere.

In order to achieve high color purity, the pyrromethene boron complex represented by the general formula (1) preferably has a sharp emission spectrum of light emitted by irradiation with excitation light. In addition, in display devices or lighting devices that have become the mainstream of top-emitting devices, the resonance effect brought by the microcavity structure can achieve high brightness and high color purity. If the emission spectrum is sharp, it will be more intense. Exhibiting this resonance effect contributes to high efficiency. From this viewpoint, the half-value width of the emission spectrum is preferably 60 nm or less, more preferably 50 nm or less, still more preferably 45 nm or less, and particularly preferably 28 nm or less.

The luminous efficiency of a light-emitting element depends on the fluorescence quantum yield of the light-emitting material itself. Therefore, the fluorescence quantum yield of the luminescent material is ideally as close to 100% as possible. Regarding the pyrromethene boron complex represented by the general formula (1), R ¹¹ and Ar ^{1 are} as described above to suppress the rotation and vibration of the bridgehead position and reduce thermal deactivation, thereby obtaining high fluorescence quantum Yield. From the above viewpoints, the fluorescence quantum yield of the pyrromethene boron complex is preferably 90% or more, more preferably 95% or more. Among them, the fluorescence quantum yield shown here is obtained by measuring a diluted solution using toluene as a solvent with an absolute quantum yield measuring device.

＜Light-emitting device materials＞ The pyrromethene boron complex represented by the general formula (1) can achieve high luminous efficiency, and therefore can be used as a light-emitting device material in a light-emitting device. Here, the light-emitting element material in the present invention means a material used in any layer of the light-emitting element, except for the layer selected from the group consisting of a hole injection layer, a hole transport layer, a light emitting layer, and an electron transport layer, as described later. In addition to the materials used, materials used in the protective film layer (covering layer) of the electrode are also included.

The pyrromethene boron complex represented by the general formula (1) has high light-emitting performance, and therefore is preferably a material used in the light-emitting layer.

＜Light-emitting components＞ Next, an embodiment of the light-emitting element of the present invention will be described. The light-emitting element of the present invention has an anode and a cathode, and an organic layer existing between the anode and the cathode. The organic layer includes at least a light-emitting layer, and the light-emitting layer is preferably an organic electroluminescence element that emits light by electric energy.

The light-emitting element of the present invention may be either a bottom emission type or a top emission type.

The layer structure of the organic layer between the anode and the cathode in this light-emitting element includes, in addition to the structure containing only the light-emitting layer, such as 1) light-emitting layer/electron transport layer, 2) hole transport layer/light-emitting layer, 3) Hole transport layer/light emitting layer/electron transport layer, 4) hole injection layer/hole transport layer/light emitting layer/electron transport layer, 5) hole transport layer/light emitting layer/electron transport layer/electron injection layer, 6 ) Hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection layer, 7) hole injection layer / hole transport layer / light emitting layer / hole blocking layer / electron transport layer / electron injection layer, 8) Hole injection layer/hole transport layer/electron blocking layer/light emitting layer/hole blocking layer/electron transport layer/electron injection layer-like laminated structure.

Furthermore, it may be a tandem type light-emitting element in which a plurality of the above-mentioned laminated structures are laminated via an intermediate layer. As the intermediate layer, generally, an intermediate electrode, an intermediate conductive layer, a charge generation layer, an electron draw layer, a connection layer, an intermediate insulating layer, etc. can be cited, and a known material structure can be used. As a preferable specific example of the tandem light-emitting element, such as 9) hole injection layer/hole transport layer/light emitting layer/electron transport layer/electron injection layer/charge generation layer/hole injection layer/hole transport Layer/light-emitting layer/electron transport layer/electron injection layer-like laminated structure.

In addition, each of the layers can be either a single layer or multiple layers, and can also be doped. Furthermore, the following element structure can also be cited, and the element structure includes a layer using a covering material for achieving an increase in luminous efficiency due to an optical interference effect.

The pyrromethene boron complex represented by the general formula (1) can be used in any layer in the device structure, but it is preferably used in the light-emitting layer due to the high fluorescence quantum yield and thin film stability.

Specific examples of the structure of the light-emitting element are listed below, but the structure of the present invention is not limited to these.

(Substrate) In order to maintain the mechanical strength of the light-emitting element, reduce thermal deformation, and have barrier properties to prevent water vapor or oxygen from entering the light-emitting layer, it is preferable to form the light-emitting element on a substrate. The substrate is not particularly limited, and examples thereof include glass plates, ceramic plates, resin films, resin films, and metal thin plates. Among them, a glass substrate can be preferably used from the viewpoint of transparency and ease of processing. In particular, in bottom light emitting devices that output light through a substrate, a glass substrate with high transparency is preferred. In addition, flexible displays or foldable displays have been added to mobile devices such as smartphones. For the purposes described above, a resin film or a resin film obtained by hardening a varnish can be preferably used. As the resin film, a heat-resistant film can be used. Specifically, a polyimide film, a polyethylene naphthalate film, and the like can be exemplified.

In addition, various wirings, circuits, and TFT-based switching elements for driving the organic EL may be provided on the surface of the substrate.

(anode) The anode is formed on the substrate. Here, various wirings, circuits, and switching elements may be interposed between the substrate and the anode. The material used in the anode is not particularly limited as long as it can efficiently inject holes into the organic layer. In bottom-emission type devices, transparent or semi-transparent electrodes are preferred. The reflective electrode is preferable in the element.

Examples of materials for the transparent or semi-transparent electrode include conductive metal oxides such as zinc oxide, tin oxide, indium oxide, indium tin oxide (ITO), and indium zinc oxide (IZO); or gold , Silver, aluminum, chromium and other metals; conductive polymers such as polythiophene, polypyrrole, and polyaniline. Among them, when metal is used, it is preferable to make the film thickness thin so that light can be semi-transmitted. Among the above, from the viewpoint of transparency and stability, indium tin oxide (ITO) is more preferable.

As the material of the reflective electrode, a material that does not absorb all light and has a high reflectance is preferable. Specifically, metals such as aluminum, silver, and platinum can be exemplified.

The method of forming the anode can be optimized according to its forming material, and examples thereof include a sputtering method, a vapor deposition method, and an inkjet method. For example, when the anode is formed of a metal oxide, a sputtering method can be used, and when the anode is formed of a metal, a vapor deposition method can be used. The thickness of the anode is not particularly limited, but it is preferably several nm to several hundreds of nm.

In addition, these electrode materials may be used alone, but multiple materials may be laminated or mixed for use.

(cathode) The cathode is formed on the surface on the opposite side of the anode with the organic layer interposed therebetween, and is particularly preferably formed on the electron transport layer or the electron injection layer. The material used in the cathode is not particularly limited as long as it can efficiently inject electrons into the light-emitting layer. It is preferably a reflective electrode in a bottom-emission type device, and more preferably a top-emission type device. It is a translucent electrode.

As the material of the cathode, in general, metals such as platinum, gold, silver, copper, iron, tin, aluminum, and indium are preferred; alloys of these metals with low work function metals such as lithium, sodium, potassium, calcium, and magnesium Or multilayer laminated film; or conductive metal oxides such as zinc oxide, indium tin oxide (ITO), indium zinc oxide (IZO), etc. Among them, the main component is preferably a metal selected from aluminum, silver, and magnesium in terms of resistance value, ease of film formation, film stability, luminous efficiency, and the like. In addition, if the cathode contains magnesium and silver, the electron injection into the electron transport layer and the electron injection layer in the present invention becomes easy, and low-voltage driving is possible, which is preferable.

(The protective layer) In order to protect the cathode, it is preferable to laminate a protective layer (covering layer) on the cathode. The material constituting the protective layer is not particularly limited, and examples include metals such as platinum, gold, silver, copper, iron, tin, aluminum, and indium; alloys using these metals; silicon dioxide, titanium oxide, and nitride Inorganic materials such as silicon; organic polymer compounds such as polyvinyl alcohol, polyvinyl chloride, and hydrocarbon-based polymer compounds. Wherein, in the case where the light-emitting element has an element structure (top emission structure) that outputs light from the cathode side, the material used in the protective layer is selected from materials that have translucency in the visible light region.

(Hole injection layer) The hole injection layer is a layer that is inserted between the anode and the hole transport layer to facilitate hole injection. The hole injection layer can be one layer or multiple layers. If there is a hole injection layer between the hole transport layer and the anode, lower voltage driving can be achieved, and the endurance life of the device is also improved. Not only that, the carrier balance of the device is improved, and the luminous efficiency is also improved. good.

As a preferable example of the hole injection material, an electron donating hole injection material (donor material) can be cited. These materials are materials that can reduce the energy barrier with the anode because the energy level of the Highest Occupied Molecular Orbital (HOMO) is shallower than that of the hole transport layer and close to the work function of the anode. Specifically, examples include benzidine derivatives, 4,4',4"-tris(3-methylphenyl(phenyl)amino)triphenylamine (4,4',4"-tris( 3-methylphenyl(phenyl)amino)triphenylamine, m-MTDATA), 4,4',4"-tris(1-naphthyl(phenyl)amino)triphenylamine (4,4',4"-tris (1-naphthyl(phenyl)amino)triphenylamine, 1-TNATA) and other aromatic amine-based materials such as starburst arylamines; carbazole derivatives, pyrazoline derivatives, and stilbene-based compounds , Hydrazone compounds, benzofuran derivatives, thiophene derivatives, oxadiazole derivatives, phthalocyanine derivatives, porin derivatives and other heterocyclic compounds; in the polymer system, the side chain has the monomer Carbonate or styrene derivatives, such as poly-3,4-Ethylenedioxythiophene (PEDOT)/polyphenylene sulfide (PPS) like polythiophene, polyaniline , Polyfluorene, polyvinyl carbazole and polysilane, etc. These materials can be used alone, or two or more materials can be used in combination. In addition, a plurality of materials may be laminated as a hole injection layer.

In addition, as another preferable example of the hole injection material, an electron-accepting hole injection material (acceptor material) can be cited. Here, the hole injection layer may be composed of the acceptor material alone, or the acceptor material may be doped into the donor material for use. The acceptor material is a material that forms a charge transfer complex between the adjacent hole transport layer when used alone, and forms a charge transfer complex between the donor material and the donor material when it is doped into the donor material. Compound. If such a material is used, the conductivity of the hole injection layer can be improved, and the driving voltage of the device can be reduced, the luminous efficiency can be improved, and the endurance life can be improved. Therefore, it is more preferable. As the acceptor material, for example, metal oxides such as molybdenum oxide, vanadium oxide, tungsten oxide, and ruthenium oxide; such as Tris(4-bromophenyl)Aminium hexachloroantimonate, TBPAH)-like charge transfer complex; such as 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile (1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile, HAT-CN6), 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane , F4-TCNQ), n-type organic semiconductor compounds like fluorinated copper phthalocyanine; fullerenes, etc. In the case where the hole injection layer contains an acceptor material, the hole injection layer may be one layer, or a plurality of layers may be laminated.

(Hole transport layer) The hole transport layer is a layer that transports holes injected from the anode to the light-emitting layer. The hole transport layer may be one layer, or multiple layers may be laminated.

The hole transport layer is formed by one type of hole transport material alone or by layering or mixing two or more types of hole transport materials. In addition, the hole transport material preferably has high hole injection efficiency and efficiently transmits the injected holes. Therefore, the hole transport material is required to be a substance that has an appropriate ionization potential, has a high hole mobility, and has excellent stability, and it is difficult to generate impurities that become traps.

The substance that satisfies such conditions is not particularly limited, and examples include: benzidine derivatives, group of aromatic amine materials called starburst arylamines; carbazole derivatives, pyrazoline derivatives , Stilbene-based compounds, hydrazone-based compounds, benzofuran derivatives, dibenzofuran derivatives, thiophene derivatives, benzothiophene derivatives, dibenzothiophene derivatives, fluorene derivatives, spirofluorene derivatives, Heterocyclic compounds such as oxadiazole derivatives, phthalocyanine derivatives, and porin derivatives; polycarbonate or styrene derivatives, polythiophenes, polyanilines, and Fluorene, polyvinyl carbazole and polysiloxane, etc.

(Light-emitting layer) The light-emitting layer is a layer that emits light by excitation energy generated by the recombination of holes and electrons. The light-emitting layer may be composed of a single material, and from the viewpoint of color purity, it is preferable to have a first compound and a dopant that exhibits strong luminescence, that is, a second compound. As the first compound, for example, a host material that is responsible for charge transfer, or a compound that has thermally activated delayed fluorescence properties can be cited as preferred examples.

The pyrromethene boron complex represented by the general formula (1) has particularly excellent fluorescence quantum yield and a narrow half-value width of the emission spectrum, which can achieve high color purity, so it is preferably used as a dopant for the light-emitting layer , That is, the second compound is used. If the doping amount of the second compound is too large, concentration quenching will occur. Therefore, relative to the weight of the entire light-emitting layer, it is preferably 20% by weight or less, more preferably 10% by weight or less, and still more preferably 5% by weight or less. The best content is 2% by weight or less. In addition, if the doping concentration is too low, sufficient energy transfer is unlikely to occur, so it is preferably 0.1% by weight or more, and more preferably 0.5% by weight or more with respect to the weight of the entire light-emitting layer.

The host material does not need to be limited to only one type of compound, and two or more types may be used in combination, and it may also be used in layers. The host material is not particularly limited, and compounds with condensed aryl rings such as naphthalene, pyrene, anthracene, and fluoranthene or derivatives thereof can be used; N,N'-dinaphthyl-N,N'-diphenyl- Aromatic amine derivatives such as 4,4'-diphenyl-1,1'-diamine; metal chelated oxinoid compounds represented by tris(8-hydroxyquinoline) aluminum (III) ；Distyryl derivatives such as stilbene benzene derivatives; Tetraphenylbutadiene derivatives, indene derivatives, coumarin derivatives, oxadiazole derivatives, pyrrolopyridine derivatives, percyclic ketones Derivatives, pyrrolopyrrole derivatives, thiadiazolopyridine derivatives, dibenzofuran derivatives, carbazole derivatives, indolocarbazole derivatives, triazine derivatives; can be used in polymer systems Polyphenylene acetylene derivatives, polyparaphenylene derivatives, polyfluorene derivatives, polyvinylcarbazole derivatives, polythiophene derivatives, and the like. Particularly preferred as the host material are anthracene derivatives or fused tetrabenzene derivatives.

The dopant material is not particularly limited, and may include fluorescent materials other than the pyrromethene boron complex represented by the general formula (1). Specifically, examples include: naphthalene, pyrene, anthracene, fluoranthene, and other compounds having condensed aryl rings or derivatives thereof; compounds having heteroaryl rings or derivatives thereof; distyrylbenzene derivatives, amino groups Styryl derivatives, tetraphenylbutadiene derivatives, stilbene derivatives, aldazine derivatives, pyrromethene derivatives, diketopyrrolo[3,4-c]pyrrole derivatives, fragrances Legginin derivatives, azole derivatives and metal complexes, aromatic amine derivatives, etc.

In addition, as a dopant material, a phosphorescent light-emitting material may also be included. As a dopant for phosphorescent light emission, it is preferable to include a dopant selected from the group consisting of iridium (Ir), ruthenium (Ru), palladium (Pd), platinum (Pt), osmium (Os), and rhenium (Re) The metal complex compound of at least one of the metals is more preferably an iridium complex or a platinum complex from the viewpoint of high-efficiency light emission. The ligand preferably has a nitrogen-containing heteroaryl group such as a phenylpyridine skeleton, a phenylquinoline skeleton, or a carbene skeleton, but is not limited to these.

Among them, from the viewpoint of improving color purity, the dopant material is preferably a pyrromethene boron complex represented by the general formula (1).

In addition to the host material or dopant material, the light-emitting layer may further include a third component for adjusting the carrier balance in the light-emitting layer or for stabilizing the layer structure of the light-emitting layer. Among them, as the third component, a material that does not interact between the host material and the dopant material is selected.

Thermally activated delayed fluorescent compounds are generally called TADF materials, which promote the excitation from the triplet excited state to the singlet state by reducing the energy gap between the energy level of the singlet excited state and the energy level of the triplet excited state A material that increases the probability of singlet exciton generation by inverse intersystem crossing of states. The difference between the lowest excited singlet energy level and the lowest excited triplet energy level (set as ΔEST) in the TADF material is preferably 0.3 eV or less. By using the delayed fluorescence based on the TADF mechanism, the theoretical internal efficiency can be increased to 100%. Furthermore, when the Forster type energy transfer occurs from the singlet excitons of the first compound having thermally activated delayed fluorescence to the singlet excitons of the second compound, the second compound is observed Fluorescence of singlet excitons. In order to cause such energy transfer, it is preferable that the lowest excited singlet energy level of the first compound is greater than the lowest excited singlet energy level of the second compound. Here, in the case where the second compound is a fluorescent light-emitting material having a sharp emission spectrum, a light-emitting element with high efficiency and high color purity can be obtained. In this way, if the light-emitting layer contains a thermally activated delayed fluorescent compound, high-efficiency light emission can be achieved, which contributes to lower power consumption of the display. The thermally activated delayed fluorescence compound can be a compound that exhibits thermally activated delayed fluorescence by a single material, or can be a compound that exhibits thermally activated delayed fluorescence by forming an exciplex (exciplex). Fluorescent compounds.

As the thermally activated delayed fluorescent compound, a single compound may be used, or a plurality of compounds may be mixed and used, and known materials may be used. Specifically, for example, benzonitrile derivatives, triazine derivatives, disulfide derivatives, carbazole derivatives, indolocarbazole derivatives, dihydrophenazine derivatives, thiazole derivatives, oxazol Diazole derivatives and so on. In particular, a compound having an electron donating part (donor part) and an electron withdrawing part (acceptor part) in the same molecule is preferable. The electron donating part (donor part) and the electron withdrawing part may be directly bonded via a single bond or a screw bond, or may be bonded via a connecting base. As an example of such a compound, the compound containing the structure represented by the following general formula (3) is mentioned.

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In the general formula (3), A is an electron withdrawing part, B is an electron donating part, and L is a linking group. When there are a plurality of A, the plurality of A may be the same or different from each other, and the A may be bonded to each other to form a ring structure. When there are a plurality of Bs, the plurality of Bs may be the same as or different from each other, and the Bs may be bonded to each other to form a ring structure.

L is selected from a direct bond, a substituted or unsubstituted ring forming an aromatic hydrocarbon group having 6 to 30 carbons, a substituted or unsubstituted ring forming a heteroaromatic ring group having 5 to 30 atoms, and these groups A group consisting of two to five groups connected to each other, and a group consisting of a methylene group having a fluorinated alkyl group. Here, the so-called direct key includes single key and screw key. Among them, heteroaromatic ring groups do not include electron-donating aromatic amine groups or π-electron excess heterocyclic functional groups.

a and b are each independently an integer of 1-5.

There may be more than one L in the same molecule. When there are a plurality of Ls, the plurality of Ls may be the same as or different from each other, and the Ls may be bonded to each other to form a saturated or unsaturated ring. In addition, a plurality of L may be bonded via A and/or B. When there are multiple A and/or B and L respectively, multiple A and/or B may be bonded to the same L, or may be bonded to different L.

Here, the electron-donating portion (donor portion) refers to a portion where electrons are relatively abundant relative to an adjacent portion. For example, an aromatic amine group or a π-electron-excess type heterocyclic functional group can be mentioned. Specifically, diarylamino, carbazolyl, benzocarbazolyl, dibenzocarbazolyl, indolocarbazolyl, dihydroacridinyl, phenoxazinyl, and dihydromorphine can be exemplified The azinyl group and the group formed by connecting a plurality of these groups and the like. These groups may be further substituted or unsubstituted. As the substituent in the case of substitution, examples of the above-mentioned preferred substituents can be cited.

In addition, the electron withdrawing portion (acceptor portion) refers to a portion relatively lacking in electrons relative to an adjacent portion. For example, an electron withdrawing group or a phenyl group having an electron withdrawing group as a substituent, or a π electron-deficient heterocyclic functional group can be cited. Specifically, an electron withdrawing group selected from a carbonyl group, a sulfonyl group, a cyano group, and a fluorine atom, or a phenyl group, a pyrimidinyl group, or a triazinyl group having an electron withdrawing group as a substituent can be exemplified. These groups may be further substituted or unsubstituted. As the substituent in the case of substitution, examples of the above-mentioned preferred substituents can be cited.

Examples of the ring-forming aromatic hydrocarbon group having 6 to 30 carbons that can be used as the linking group L include phenyl, biphenyl, terphenyl, naphthyl, fluorenyl, benzofluorenyl, and dibenzofluorene. Group, phenanthryl group, anthracenyl group, triphenylphenanthryl group, benzoanthryl group, triphenylene group, pyrenyl group, fluoranthryl group, triphenylene group, benzofluoranthene group, dibenzoanthryl group, perylene group, spiral alkyl group, etc. The (a+b) valence group formed by removing part of the hydrogen atom in the aryl group.

Examples of the ring-forming heteroaromatic ring group having 5 to 30 atoms that can be used as the linking group L include pyridyl, furyl, thiophenyl, quinolyl, isoquinolyl, pyrazinyl, and pyrimidinyl. , Pyridazinyl, triazinyl, naphthyridinyl, cinnolinyl, phthalazinyl, quinoxalinyl, quinazolinyl, benzofuranyl, benzothiol, indolyl, dibenzofuran Group, dibenzothiophenyl, benzoquinolinyl, benzimidazolyl, imidazopyridyl, benzoxazolyl, benzothiazolyl, phenanthroline equal to one or more rings with carbon and hydrogen A (a+b)-valent cyclic aromatic group obtained by removing a part of hydrogen from the heteroaryl group of other atoms, that is, heteroatoms. As the hetero atom, a nitrogen atom, an oxygen atom or a sulfur atom is preferred. The heteroaromatic ring group may be substituted or unsubstituted.

It does not specifically limit as such a thermally activated delayed fluorescent compound, The following examples can be mentioned.

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Preferably, the first compound is a thermally activated delayed fluorescence compound, and the second compound is a pyrromethene boron complex represented by the general formula (1). In addition, when the first compound is a thermally activated delayed fluorescent compound, it is preferable that the light-emitting layer further contains a third compound having a singlet energy greater than that of the first compound. Thereby, the third compound can have the function of confining the energy of the light-emitting material in the light-emitting layer, and can emit light efficiently. In addition, it is also preferable that the lowest excited triplet energy of the third compound is greater than the lowest excited triplet energy of the first compound.

As such a third compound, an organic compound having a high charge transport ability and a high glass transition temperature is preferable. The third compound is not particularly limited, and the following examples can be given.

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In addition, the third compound may be composed of a single material, or may be composed of two or more materials. When two or more materials are used as the third compound, it is preferably a combination of an electron-transporting third compound and a hole-transporting third compound. By combining the electron-transporting third compound and the hole-transporting third compound in an appropriate mixing ratio, the charge balance in the light-emitting layer can be adjusted, the shift of the light-emitting region can be suppressed, and the reliability of the light-emitting device can be improved. Improve durability. In addition, an excited complex compound may be formed between the electron-transporting third compound and the hole-transporting third compound. From the above viewpoints, it is preferable that the first compound and the third compound satisfy the relational expressions of the following formulas 1 to 4, respectively. In addition, it is more preferable to satisfy formula 1 and formula 2, and it is still more preferable to satisfy formula 3 and formula 4. In addition, it is more preferable that all of Formula 1 to Formula 4 are satisfied. S1 (the third compound with electron transport properties)>S1 (the first compound) (Formula 1) S1 (the third compound with hole transport properties)> S1 (the first compound) (Formula 2) T1 (the third compound with electron transport properties)> T1 (the first compound) (Formula 3) T1 (the third compound with hole transport properties)> T1 (the first compound) (Formula 4) Here, S1 represents the energy level of the lowest excited singlet state of each compound, and T1 represents the energy level of the lowest excited triplet state of each compound.

As the third electron-transporting compound, a compound containing a π-electron-deficient heteroaromatic ring and the like can be cited. Specifically, examples include: 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD), 3-(4-biphenyl) Yl)-4-phenyl-5-(4-tertiary butylphenyl)-1,2,4-triazole (TAZ), 1,3-bis[5-(p-tertiary butylphenyl) -1,3,4-oxadiazol-2-yl]benzene (OXD-7), 9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl] -9H-carbazole (CO11), 2,2',2''-(1,3,5-benzenetriyl) tris(1-phenyl-1H-benzimidazole) (TPBI), 2-[3 -(Dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole (mDBTBIm-II) and other heterocyclic compounds with a polyazole skeleton; 2-[3-(dibenzothiophene -4-yl)phenyl]dibenzo[f,h]quinoxaline (2mDBTPDBq-II), 2-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]diphenyl And [f,h]quinoxaline (2mDBTBPDBq-II), 2-[4-(3,6-diphenyl-9H-carbazol-9-yl)phenyl]dibenzo[f,h]quine Oxaline (2CzPDBq-III), 7-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (7mDBTPDBq-II) and 6-[3-(二Benzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (6mDBTPDBq-II), 2-[3'-(9H-carbazol-9-yl)biphenyl-3- Yl]dibenzo[f,h]quinoxaline (2mCzBPDBq) and other heterocyclic compounds with a quinoxaline skeleton or a dibenzoquinoxaline skeleton; 4,6-bis[3-(phenanthrene-9-yl) Phenyl]pyrimidine (4,6mPnP2Pm), 4,6-bis[3-(9H-carbazol-9-yl)phenyl]pyrimidine (4,6mCzP2Pm), 4,6-bis[3-(4-bis Benzothienyl) phenyl] pyrimidine (4,6mDBTP2Pm-II) and other heterocyclic compounds having a diazine skeleton (pyrimidine skeleton or pyrazine skeleton); 3,5-bis[3-(9H-carbazole-9- Group) phenyl] pyridine (3,5DCzPPy), 1,3,5-tris [3-(3-pyridyl) phenyl] benzene (TmPyPB), 3,3',5,5'-tetra[(between Pyridyl)-phenyl-3-yl]biphenyl (BP4mPy) and other heterocyclic compounds with a pyridine skeleton.

In addition, as the third compound having hole transport properties, a compound containing a π-electron-excess type heteroaromatic ring can be cited. Specifically, 1,3-bis(N-carbazolyl)benzene, 4, 4'-bis(N-carbazolyl)biphenyl (CBP), 3,3'-bis(N-carbazolyl)biphenyl (mCBP), 1,3,5-tris[4-(N-carb Azolyl)phenyl]benzene (TCPB), 9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (CzPA), 1,4-bis[4-(N- (Carbazolyl)phenyl)-2,3,5,6-tetraphenylbenzene, 9-phenyl-9H-3-(9-phenyl-9H-carbazol-3-yl)carbazole, 3, 6-Bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole (PCzPCA2), 3-[N-(1-naphthyl)-N -(9-Phenylcarbazol-3-yl)amino]-9-phenylcarbazole (PCzPCN1), 9-([1,1-biphenyl]-4-yl)-9'-([1 ,1':4',1''-terphenyl]-4-yl)-9H,9'H-3,3'-dicarbazole, 9-([1,1':4',1'' -Terphenyl)-4-yl)-9'-(naphthalen-2-yl)-9H,9'H-3,3'-dicarbazole, 9,9',9''-triphenyl-9H ,9'H,9''H-3,3':6',3''-tricarbazole and other compounds having a carbazole skeleton.

(Electron transport layer) The electron transport layer is a layer that injects electrons from the cathode and further transports electrons. As the electron transport material used in the electron transport layer, it is required to have a high electron affinity, high electron mobility, excellent stability, and a substance that does not easily generate impurities that become traps. In addition, a low-molecular-weight compound is likely to crystallize and deteriorate the film quality, so a compound having a molecular weight of 400 or more is preferred.

The electron transport layer in the present invention also includes a hole blocking layer that can efficiently block the migration of holes as the same meaning. The hole blocking layer and the electron transport layer can be constructed separately, or multiple materials can be laminated.

Examples of electron transport materials include polycyclic aromatic derivatives, styryl aromatic ring derivatives, quinone derivatives, phosphorus oxide derivatives, tris(8-hydroxyquinoline) aluminum (III) and other hydroxyquinoline complexes Complexes, benzohydroxyquinoline complexes, hydroxyazole complexes, azomethine complexes, tropolone metal complexes and flavonol metal complexes and other metal complexes Compound. In terms of lowering the driving voltage and obtaining high-efficiency light emission, it is preferable to use a compound having a heteroaryl group containing electron-accepting nitrogen. Here, the term “electron-accepting nitrogen” refers to a nitrogen atom that forms multiple bonds with adjacent atoms. The heteroaryl group containing electron-accepting nitrogen has a high electron affinity, and therefore it is easy to inject electrons from the cathode and can be driven at a lower voltage. In addition, more electrons are supplied to the light-emitting layer, and the probability of recombination becomes higher, so the luminous efficiency is improved. Examples of compounds having a heteroaryl structure containing electron-accepting nitrogen include pyridine derivatives, triazine derivatives, pyrazine derivatives, pyrimidine derivatives, quinoline derivatives, quinoxaline derivatives, and quinazoline Derivatives, naphthyridine derivatives, benzoquinoline derivatives, phenanthroline derivatives, imidazole derivatives, oxazole derivatives, thiazole derivatives, triazole derivatives, oxadiazole derivatives, thiadiazole derivatives, Benzimidazole derivatives, benzoxazole derivatives, benzothiazole derivatives, phenanthrimidazole derivatives, and oligopyridine derivatives such as bipyridine or terpyridine are preferred compounds. Among them, from the viewpoint of electron transport ability, imidazole derivatives such as tris(N-phenylbenzimidazol-2-yl)benzene, 1,3-bis[(4-tertiary butylbenzene) Yl)-1,3,4-oxadiazolyl] phenylene and other oxadiazole derivatives; N-naphthyl-2,5-diphenyl-1,3,4-triazole and other triazole derivatives; 2,9-Dimethyl-4,7-diphenyl-1,10-phenanthroline (bathocuproin) or 1,3-bis(1,10-phenantholin-9-yl)phenanthroline derivatives; 2,2'-bis(benzo[h]quinolin-2-yl)-9,9'-spirobifluorene and other benzoquinoline derivatives; 2,5-bis(6'-(2',2 "-Bipyridyl))-1,1-dimethyl-3,4-diphenylsilol and other bipyridine derivatives; 1,3-bis(4'-(2,2':6'2" -Terpyridyl)) benzene and other terpyridine derivatives; bis(1-naphthyl)-4-(1,8-naphthyridin-2-yl)phenylphosphine oxide and other naphthyridine derivatives and triazine derivatives .

In addition, if the electron transport material has a condensed polycyclic aromatic skeleton, the glass transition temperature will increase, and the electron mobility will increase, so that the voltage can be lowered, which is more preferable. As such a condensed polycyclic aromatic skeleton, a fluoranthene skeleton, an anthracene skeleton, a pyrene skeleton or a phenanthroline skeleton is preferable, and a fluoranthene skeleton or a phenanthroline skeleton is particularly preferable.

The electron transport material can be used alone or in a mixture of two or more. In addition, the electron transport layer may also contain a donor material. Here, the term “donor material” refers to a compound that facilitates electron injection from the cathode or the electron injection layer to the electron transport layer by improving the electron injection barrier, thereby improving the conductivity of the electron transport layer.

Preferred examples of donor materials include: alkali metals such as Li, inorganic salts containing alkali metals such as LiF, complexes of alkali metals and organic substances such as lithium quinolate, alkaline earth metals, and inorganic salts containing alkaline earth metals , Complexes of alkaline earth metals and organics, rare earth metals such as Eu or Yb, inorganic salts containing rare earth metals, complexes of rare earth metals and organics, etc. As the donor material, metallic lithium, rare earth metals, and lithium quinolate (Liq) are particularly preferred.

(Electron injection layer) In the present invention, an electron injection layer may also be provided between the cathode and the electron transport layer. Generally, the electron injection layer is formed for the purpose of assisting the injection of electrons from the cathode to the electron transport layer, and includes a compound having a heteroaryl ring structure containing electron-accepting nitrogen, or the donor material. Preferably, it is a phenanthroline derivative represented by general formula (4) mentioned later.

In addition, an insulator or a semiconductor inorganic substance may be used for the electron injection layer. By using these materials, the short circuit of the light-emitting element can be prevented, and the electron injection performance can be improved, so it is preferable.

As such an insulator, it is preferable to use at least one metal compound selected from the group consisting of alkali metal chalcogenides, alkaline earth metal chalcogenides, alkali metal halides, and alkaline earth metal halides.

(Charge generation layer) The charge generation layer in the present invention is a layer that generates or separates charges by applying a voltage and injects the charges into adjacent layers. The charge generation layer may be formed of one layer, or multiple layers may be stacked. Generally, those that easily generate electrons as charges are called n-type charge generation layers, and those that easily generate holes are called p-type charge generation layers. The charge generation layer preferably includes two layers, more preferably a pn junction type charge generation layer including an n-type charge generation layer and a p-type charge generation layer. The pn junction type charge generation layer generates charges by applying a voltage to the light-emitting element, or separates the charges into holes and electrons, and injects these holes and electrons into the light-emitting layer through the hole transport layer and the electron transport layer. Specifically, in a light-emitting element including a plurality of light-emitting layers, when a charge-generating layer is used as an intermediate layer, the n-type charge-generating layer supplies electrons to the first light-emitting layer existing on the anode side, and the p-type charge-generating layer Holes are supplied to the second light-emitting layer existing on the cathode side. Therefore, in a light-emitting device having two or more light-emitting layers, by having more than one charge generation layer between the light-emitting layer and the light-emitting layer, the efficiency of the device can be further improved, the driving voltage can be reduced, and the durability of the device can be further improved. .

The n-type charge generation layer includes an n-type dopant and an n-type host, and the previous materials can be used for these. For example, as the n-type dopant, the donor material exemplified as the material of the electron transport layer can be preferably used. Among these, preferred are alkali metals or their salts, and rare earth metals, and more preferred are materials selected from metallic lithium, lithium fluoride (LiF), lithium quinolate (Liq), and metallic ytterbium. In addition, as the n-type host, those exemplified as electron transport materials can be preferably used. Among these, materials selected from triazine derivatives, phenanthroline derivatives and oligopyridine derivatives are preferred, phenanthroline derivatives or terpyridine derivatives are more preferred, and the following general formula (4 ) Represented by the phenanthroline derivative. That is, it is preferable to contain the phenanthroline derivative represented by general formula (4) in the charge generation layer.

[化48]

In the general formula (4), Ar ^{2 is} selected from the group consisting of a p-valent aromatic hydrocarbon group and a p-valent heteroaromatic ring group. p is a natural number from 1 to 3. R ¹⁵ to R ²² may be the same or different, and are selected from the group consisting of a hydrogen atom, an alkyl group, a cycloalkyl group, a heterocyclic group, an aryl group, and a heteroaryl group. In Ar ² , the substitution positions of p phenanthroline groups are arbitrary positions.

As an aromatic hydrocarbon group and a heteroaromatic ring group, the group described in the example of the said aryl group and heteroaryl group can be mentioned, for example, but it is not limited to these groups. The aromatic hydrocarbon group or heteroaromatic ring group may further have a substituent in addition to the phenanthrene group.

From the standpoint of sublimability and film formation, p is preferably 2.

An example of the phenanthroline derivative represented by the general formula (4) is shown below.

[化49]

The p-type charge generation layer includes a p-type dopant and a p-type host, and the previous materials can be used for these. For example, as the p-type dopant, the acceptor material exemplified as the material of the hole injection layer, or iodine, FeCl ₃ , FeF ₃ , SbCl ₅ or the like can be preferably used. Specifically, HAT-CN6, F4-TCNQ, tetracyanoquinodimethane derivatives, axene derivatives, iodine, FeCl ₃ , FeF ₃ , SbCl ₅ and the like can be mentioned. Among these, HAT-CN6 or (2E, 2'E, 2''E)-2,2',2''-(cyclopropane-1,2,3-triylene) tris(2- (Perfluorophenyl)-acetonitrile), (2E,2'E,2``E)-2,2',2''-(cyclopropane-1,2,3-triylidene)tris(2-( 4-cyanoperfluorophenyl)-acetonitrile) isometric ene derivatives. A thin film of p-type dopant can be formed, and its thickness is preferably 10 nm or less. In addition, the p-type dopant is preferably an arylamine derivative.

(Method of forming light-emitting element) The method for forming the layers constituting the light-emitting element may be any of a dry process or a wet process, although it is not particularly limited to resistance heating vapor deposition, electron beam vapor deposition, sputtering, molecular stacking method, coating method, spraying method, etc. Ink method, printing method, etc., generally, resistance heating vapor deposition is preferable in terms of element characteristics.

The thickness of the organic layer depends on the resistance value of the light-emitting material, so it cannot be limited, but it is preferably 1 nm to 1000 nm. The film thicknesses of the light-emitting layer, the electron transport layer, and the hole transport layer are each preferably 1 nm or more and 200 nm or less, and more preferably 5 nm or more and 100 nm or less.

(Characteristics of light-emitting elements) The light-emitting element of the embodiment of the present invention has a function of converting electric energy into light. Here, as electric energy, direct current is mainly used, but pulse current or alternating current may also be used. The current value and the voltage value are not particularly limited, and the required characteristic values are different depending on the purpose of the element. From the viewpoint of the power consumption and the life of the element, it is preferable to obtain high brightness at a low voltage.

From the viewpoint of improving the color purity, the light-emitting element of the embodiment of the present invention preferably has a half-value width of the emission spectrum caused by energization of 60 nm or less, more preferably 50 nm or less, and still more preferably 45 nm or less, and most preferably Below 30 nm.

Since the light-emitting element of the present invention has a narrow half-value width of the emission spectrum, it is more preferably used for a top-emission type light-emitting element. The top-emission type light-emitting element uses the resonance effect brought by the microcavity, and the narrower the half-value width, the higher the luminous efficiency. Therefore, high color purity and high luminous efficiency can coexist.

(Use of light-emitting elements) The light-emitting element of the embodiment of the present invention can be preferably used as a display device such as a display that displays in a matrix and/or a segment.

In addition, the light-emitting element of the embodiment of the present invention can also be suitably used as a backlight for various devices and the like. The backlight is mainly used for the purpose of improving the visibility of display devices such as non-luminous displays, and can be used in display devices such as liquid crystal displays, clocks, audio devices, car panels, display panels, and signs. In particular, the light-emitting element of the present invention can be preferably used in a backlight for a personal computer in which thinning is being studied in a liquid crystal display, and can provide a thinner and lighter backlight than before.

In addition, the light-emitting element of the embodiment of the present invention can also be suitably used as various lighting devices. The light-emitting element according to the embodiment of the present invention can coexist high luminous efficiency and high color purity, and furthermore, can be thinned and lightened. Therefore, it is possible to realize a lighting device that combines low power consumption, bright luminous color, and high design. [Example]

Hereinafter, the present invention will be explained with reference to examples, but the present invention is not limited by these examples.

Synthesis example 1 Synthesis method of compound D-1 Compound D-1 was synthesized according to the following reaction scheme.

[化50]

Put 5.35 g of 2,6-dibromobenzaldehyde, 7.40 g of 4-tert-butylphenylboronic acid, 5.38 g of sodium carbonate, 100 mL of dimethoxyethane, and 20 mL of water into the flask, and perform nitrogen replacement . 142 mg of bis(triphenylphosphine)palladium(II) dichloride was added thereto, and refluxing was performed for 4 hours. The reaction solution was cooled to room temperature, and after the organic layer was separated, it was dried with magnesium sulfate, and after filtration, the solvent was distilled off. Methanol was added to the obtained reaction product and filtered, thereby obtaining 4.03 g of 2,6-bis(p-tert-butylphenyl)benzaldehyde as a white solid.

Put 4.03 g of 2,6-bis(p-tert-butylphenyl)benzaldehyde and 2.17 g of 2,4-dimethylpyrrole thus obtained into the reaction vessel, add 360 mL of dichloromethane and 5 drops of three Fluoroacetic acid, stirring at room temperature for 1 week. Furthermore, 2.70 g of 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (2,3-Dichloro-5,6-Dicyano-1,4-Benzoquinone, DDQ) was added, at room temperature Stir for 4 days. After that, it was filtered and the solvent was distilled off. Add 360 mL of dichloromethane and 5.90 mL of diisopropylethylamine to the resulting reaction product, stir at room temperature for 30 minutes, and then add 4.10 mL of boron trifluoride diethyl ether complex, and stir at room temperature After 4 hours, the solvent was distilled off, and water was added and stirred. The organic layer was separated and washed with saturated brine. The organic layer was dried with magnesium sulfate, and the solvent was distilled off after filtration. The obtained reaction product was purified by silica gel chromatography to obtain 580 mg of red powder. The powder obtained was analyzed by ¹ H-NMR (Nuclear Magnetic Resonance, NMR) and Liquid Chromatography-Mass Spectrometry (LC-MS), and it was confirmed that the red powder was complex as pyrromethene boron Compound D-1. ¹ H-NMR(CDCl ₃ (d=ppm)): 7.52(d, 1H), 7.43(d, 2H), 7.23-7.17(m, 4H), 7.10(d, 4H), 5.79(s, 2H) , 2.38(s, 6H), 1.52(s, 6H), 1.22(s, 18H) MS (m/z) molecular weight: 589.

The luminescence characteristics of compound D-1 in solution are shown below. Absorption spectrum (solvent: toluene): λmax is 513 nm Fluorescence spectrum (solvent: toluene): λmax is 526 nm, half-value width is 23 nm Fluorescence quantum yield (solvent: toluene, excitation light: 460 nm): 100%.

In order to further improve the purity, sublimation purification is performed. A metal container filled with compound D-1 was set in the glass tube, and the compound D-1 was sublimated by heating it at 190°C under a pressure of ^{1×10 -3 Pa using an oil diffusion pump.} The solid adhering to the wall of the glass tube was recovered, and the purity of 99% was confirmed by LC-MS analysis.

Synthesis Example 2 Synthetic method of compound D-2 Compound D-2 was synthesized according to the following reaction scheme.

[化51]

Put 4.16 g of 2,4,6-trichlorobenzaldehyde, 11.0 g of 4-tert-butylphenylboronic acid, 21.12 g of potassium phosphate, 100 mL of dioxane, and 20 mL of water into the flask, and perform nitrogen substitution. 229 mg of bis(dibenzylideneacetone)palladium(0) and 379 mg of XPhos were added thereto, and refluxing was performed for 2 hours. The reaction solution was cooled to room temperature, and after the organic layer was separated, it was dried with magnesium sulfate, and after filtration, the solvent was distilled off. The obtained reaction product was purified by silica gel chromatography to obtain 9.76 g of 2,4,6-tris(p-tert-butylphenyl)benzaldehyde as a white solid.

Put 9.76 g of 2,4,6-tris(p-tert-butylphenyl)benzaldehyde and 5.54 g of 2,4-dimethylpyrrole thus obtained into the reaction vessel, add 200 mL of toluene and 5 drops of Fluoroacetic acid was stirred at 40°C for 30 minutes, water was added and stirred, and the organic layer was separated and washed with saturated brine. The organic layer was dried with magnesium sulfate, and the solvent was distilled off after filtration. Put the obtained reaction product, 8.81 g of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and 200 mL of toluene into a flask, and stir at 40°C for 30 minutes . Then, 17.2 mL of diisopropylethylamine and 12.2 mL of boron trifluoride diethyl ether complex were added, and after stirring for 30 minutes at room temperature, water was added for stirring. The organic layer was separated and washed with saturated brine. The organic layer was dried with magnesium sulfate, and the solvent was distilled off after filtration. The obtained reaction product was purified by silica gel chromatography to obtain 3.63 g of red powder. The obtained powder was analyzed by ¹ H-NMR and LC-MS, and it was confirmed that the red powder was compound D-2 which is a pyrromethene boron complex. ¹ H-NMR(CDCl ₃ (d=ppm)): 7.72-7.63(m, 4H), 7.47(d, 2H), 7.23-7.12(m, 8H), 5.81(s, 2H), 2.38(s, 6H), 1.57(s, 6H), 1.32(s, 9H), 1.22(s, 18H) MS (m/z) molecular weight: 721.

The luminescence characteristics of compound D-2 in solution are shown below. Absorption spectrum (solvent: toluene): λmax is 513 nm Fluorescence spectrum (solvent: toluene): λmax is 527 nm, half-value width is 22 nm Fluorescence quantum yield (solvent: toluene, excitation light: 460 nm): 100%.

In order to further improve the purity, sublimation purification is performed. A metal container filled with compound D-2 was set in the glass tube, and the compound D-2 was sublimated by heating it at 240° C. under a pressure of ^{1×10 -3 Pa using an oil diffusion pump.} The solid adhering to the wall of the glass tube was recovered, and the purity of 99% was confirmed by LC-MS analysis.

The pyrromethene boron complexes used in the following examples and comparative examples are the compounds shown below. In addition, the molecular weight and luminescence characteristics measured in the toluene solution of these pyrromethene boron complexes are shown in Table 1.

[化52]

[化53]

[Table 1] [Table 1] Compound Molecular weight Absorption spectrum Luminous spectrum Fluorescence quantum yield λmax (nm) λmax (nm) Half-value width (nm) QY (%) D-1 589 513 526 twenty three 100 D-2 721 513 527 twenty two 100 D-3 607 516 531 twenty three 93 D-4 561 510 521 twenty three 94 D-5 563 507 519 twenty two 92 D-6 735 516 532 twenty four 100 D-7 649 513 526 twenty four 100 D-8 561 507 519 twenty two 100 D-9 801 507 518 twenty three 100 D-10 645 517 532 twenty three 100 D-11 448 517 532 twenty two 95 D-12 504 513 526 twenty three 100 D-13 601 550 572 30 100 D-14 601 558 598 30 95 D-15 533 513 527 twenty three 100 D-16 589 503 516 twenty three 84 D-17 338 504 518 25 90 D-18 400 508 521 twenty four 85

Example 1 (Evaluation of Fluorescent Light-Emitting Elements) A glass substrate (manufactured by Geomatec (stock), 11 Ω/□, sputtered product) on which a 165 nm ITO transparent conductive film was deposited as an anode was cut into 38 mm×46 mm, and then etched. The resulting substrate was ultrasonically cleaned with "Semico clean 56" (trade name, manufactured by Furuuchi Chemical Co., Ltd.) for 15 minutes, washed with ultrapure water, and dried.

The substrate was subjected to UV-ozone treatment for 1 hour immediately before the production of the element, set in a vacuum vapor deposition device, and exhausted until the pressure in the device became 5×10 ^-4 Pa or less. First, HAT-CN6 of 10 nm was evaporated as the hole injection layer by resistance heating method, and HT-1 of 50 nm was evaporated as the hole transport layer. Next, H-1 as a host material and compound D-1 as a dopant material were deposited to a thickness of 20 nm as a light-emitting layer so that the doping concentration became 1.0% by weight. Furthermore, ET-1 was used, 2E-1 was used as the donor material, and the deposition rate ratio of ET-1 to 2E-1 was 1:1, and the thickness of the stack was 30 nm as the electron transport layer. Next, after vapor-depositing 0.5 nm of 2E-1 as an electron injection layer, magnesium and silver were co-evaporated for 1000 nm to form a cathode, and a 5 mm×5 mm square element was fabricated.

When the light-emitting element was made to emit light at 1000 cd/m ² , the emission peak wavelength was 529 nm, the half-value width was 26 nm, and the external quantum efficiency was 4.0%. In addition, the durability was evaluated by continuously energizing the current at the initial brightness of 1000 cd/m ² within the time (hereinafter, referred to as LT90) for the brightness of 90% of the initial brightness. As a result, the LT90 of this light-emitting element was 99 hours. In addition, in the above, HAT-CN6, HT-1, H-1, ET-1, and 2E-1 are the compounds shown below, respectively.

[化54]

Example 2 to Example 15, Comparative Example 1 to Comparative Example 3 A light-emitting element was produced and evaluated in the same manner as in Example 1, except that the compound described in Table 2 was used instead of the compound D-1 as the dopant material. The results are shown in Table 2.

[Table 2]

Referring to Table 2, it can be seen that in Examples 1 to 15, compared with Comparative Examples 1 to 3, while keeping the half-value width small, the external quantum efficiency and device durability (LT90) are greatly improved . From this, it is understood that according to the present invention, a light-emitting element having high color purity, high luminous efficiency, and high element durability can be obtained.

(Evaluation of thermally activated delayed fluorescent element) Example 16 A glass substrate (manufactured by Geomatec (stock), 11 Ω/□, sputtered product) on which a 100-nm ITO transparent conductive film was deposited as an anode was cut into 38 mm×46 mm, and then etched. The resulting substrate was ultrasonically cleaned with "Semico clean 56" (trade name, manufactured by Furuuchi Chemical Co., Ltd.) for 15 minutes, and then cleaned with ultrapure water.

The substrate was subjected to UV-ozone treatment for 1 hour immediately before the production of the element, set in a vacuum vapor deposition device, and exhausted until the vacuum degree in the device became 5×10 ^-4 Pa or less. First, HAT-CN6 of 10 nm was evaporated as the hole injection layer by resistance heating method, and HT-1 of 40 nm was evaporated as the hole transport layer. Next, the host material H-2, the compound D-1, and the compound H-3 as the TADF material were vapor-deposited to a thickness of 30 nm in a weight ratio of 79.5:0.5:20, as a light-emitting layer. Furthermore, compound ET-1 was used as the electron transport material, 2E-1 was used as the donor material, and a thickness of 50 nm was laminated so that the vapor deposition rate ratio of compound ET-1 and 2E-1 became 1:1. Electron transport layer. Next, after vapor-depositing 0.5 nm of 2E-1 as an electron injection layer, magnesium and silver were co-evaporated for 1000 nm to form a cathode, and a 5 mm×5 mm square element was fabricated.

The emission characteristics when the light-emitting element was made to emit light at 1000 cd/m ² were that the emission peak wavelength was 529 nm, the half-value width was 28 nm, the external quantum efficiency was 14.2%, and the LT90 was 80 hours. In addition, in the above, H-2 and H-3 are the compounds shown below.

[化55]

Example 17 to Example 20, Comparative Example 4 to Comparative Example 6 Except for using the compound described in Table 3 as the dopant material, a light-emitting element was produced in the same manner as in Example 16, and evaluated. The results are shown in Table 3.

[table 3]

Referring to Table 3, it can be seen that in Examples 16 to 20, compared with Comparative Examples 4 to 6, while keeping the half-value width small, the external quantum efficiency and device durability (LT90) are greatly improved. . From this, it is understood that according to the present invention, a light-emitting element having high color purity, high luminous efficiency, and high element durability can be obtained.

As described above, it is shown that the present invention can produce a light-emitting element with high color purity, luminous efficiency, and element durability. In this way, the luminous efficiency can be improved during the manufacture of display devices such as displays or lighting devices.

(Evaluation of tandem fluorescent light-emitting element) Example 21 A glass substrate (manufactured by Geomatec (stock), 11 Ω/□, sputtered product) on which a 165 nm ITO transparent conductive film was deposited as an anode was cut into 38 mm×46 mm, and then etched. The resulting substrate was ultrasonically cleaned with "Semico clean 56" (trade name, manufactured by Furuuchi Chemical Co., Ltd.) for 15 minutes, and then cleaned with ultrapure water.

The substrate was subjected to UV-ozone treatment for 1 hour immediately before the production of the element, set in a vacuum vapor deposition device, and exhausted until the vacuum degree in the device became 5×10 ^-4 Pa or less. First, 5 nm HAT-CN6 was vapor-deposited as the hole injection layer by the resistance heating method, and then 50 nm HT-1 was vapor-deposited as the hole transport layer. Next, H-1 10 nm as a hole blocking layer, host material H-1 as a light-emitting layer, and dopant compound D-1 were vapor-deposited to a thickness of 20 nm so that the weight ratio becomes 99.5:0.5. Furthermore, ET-1 as an electron blocking layer was laminated with a thickness of 10 nm, and compound ET-3 as an electron transport layer was laminated with a thickness of 35 nm. Next, the compound ET-3 as the n-type host and the metal lithium as the n-type dopant were laminated for 10 nm so that the vapor deposition rate ratio became 99:1 to form an n-type charge generation layer. Furthermore, HAT-CN6 with a thickness of 10 nm was laminated as a p-type charge generation layer. A hole transport layer of 50 nm, a hole blocking layer of 10 nm, and a light emitting layer of 20 nm were formed thereon in the same manner as described above. Furthermore, ET-2 of 10 nm was deposited as the electron blocking layer, and ET-3 of 35 nm was deposited as the electron transport layer in this order. Next, after vapor-depositing 0.5 nm of 2E-1 as an electron injection layer, magnesium and silver were co-evaporated for 1000 nm to form a cathode, and a tandem light-emitting element of 5 mm×5 mm square was fabricated.

When the light-emitting element was made to emit light at 1000 cd/m ² , the emission peak wavelength was 530 nm, the half-value width was 25 nm, the external quantum efficiency was 4.3%, and the LT90 was 110 hours. It was confirmed that the durability was improved compared with Example 1 in which there was only one light-emitting layer. In addition, in the above, ET-2 and ET-3 are the compounds shown below.

[化56]

without

without

Claims (11)

A pyrromethene boron complex is represented by the general formula (1):

R ¹ to R ⁶ are each independently selected from a hydrogen atom, an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a hydroxyl group, a thiol group, an alkoxy group, an alkylthio group, and an aryl group. Ether group, aryl sulfide group, aryl group, heteroaryl group, amine group, silyl group, siloxyalkyl group and oxyboron group; these groups may further have substituents; wherein, R ¹ At least one of ~R ⁴ is a hydrogen atom or an alkyl group; X ¹ and X ² are each independently selected from an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a hydroxyl group, and a thiol group , Alkoxy, alkylthio, aryl ether, aryl sulfide, aryl, heteroaryl, halogen and cyano; these groups may further have substituents; R ⁷ is It is represented by the following general formula (2);

R ⁸ to R ¹⁰ are each independently selected from a hydrogen atom, an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a hydroxyl group, a thiol group, an alkoxy group, an alkylthio group, and an aryl group. Ether group, aryl sulfide group, aryl group, heteroaryl group, halogen, cyano group, aldehyde group, acyl group, carboxyl group, ester group, amide group, sulfonyl group, sulfonate group, sulfonamide group, Amine group, nitro group, silyl group, siloxyalkyl group, oxyboron group and phosphine oxide group; these groups may further have substituents; R ^{11 is} selected from the group consisting of alkyl, cycloalkyl, heterocyclic Group, alkenyl, cycloalkenyl, alkynyl, hydroxyl, thiol, alkoxy, alkylthio, aryl ether, aryl sulfide, aryl, heteroaryl, halogen, cyano, aldehyde Group, acyl group, carboxyl group, ester group, amide group, sulfonamide group, sulfonate group, sulfonamide group, amine group, nitro group, silyl group, siloxyalkyl group, oxyboron group and phosphine oxide group These groups may further have substituents; Ar ¹ is a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group. The pyrromethene boron complex according to claim 1, wherein R ¹¹ is a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group. The pyrromethene boron complex according to claim 1 or claim 2, wherein R ¹ and R ⁴ are each independently a hydrogen atom or an alkyl group. The pyrromethene boron complex according to any one of claims 1 to 3, wherein R ² and R ³ are alkyl groups. A light-emitting element is an element having an anode, a cathode, and a light-emitting layer existing between the anode and the cathode. The light-emitting layer emits light by electric energy, and the light-emitting layer contains items such as claims 1 to The pyrromethene boron complex according to any one of Item 4. The light-emitting element according to claim 5, wherein the light-emitting layer contains a first compound and a second compound, the first compound is a thermally activated delayed fluorescence compound, and the second compound is the general formula (1 ) Pyrromethene boron complex. The light-emitting element according to claim 5 or 6, wherein the thermally activated delayed fluorescent compound according to claim 6 is a compound having an electron donating part and an electron withdrawing part in the same molecule. The light-emitting element according to any one of claims 5 to 7, wherein there are two or more light-emitting layers between the anode and the cathode, and one or more charge generation layers are provided between each light-emitting layer and the light-emitting layer. The light-emitting element according to claim 8, wherein the charge generation layer contains the phenanthroline derivative represented by the general formula (4):

In the general formula (4), Ar ^{2 is} selected from the group consisting of a p-valent aromatic hydrocarbon group and a p-valent heteroaromatic ring group; p is a natural number from 1 to 3; R ¹⁵ to R ²² may be the same or the same. It may be different, and is selected from the group consisting of a hydrogen atom, an alkyl group, a cycloalkyl group, a heterocyclic group, an aryl group, and a heteroaryl group; in Ar ² , the substitution position of p phenanthroline groups is any position. A display device comprising the light-emitting element according to any one of claim 5 to claim 9. A lighting device comprising the light-emitting element according to any one of claim 5 to claim 9.