KR102650329B1 - Pyromethene boron complex, light-emitting devices containing the same, display devices, and lighting devices - Google Patents

Abstract

A pyromethene boron complex represented by the general formula (1) provides a light-emitting material with a high fluorescence quantum yield and a sharp emission spectrum, and a light-emitting device with high luminous efficiency, color purity, and durability.

(R ¹ to R ⁶ are each independently 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, an arylether group, an arylthioether group, aryl group, heteroaryl group, amino group, silyl group, siloxanyl group and boryl group.These groups may further have substituents.However, at least one of R ¹ to R ⁴ is a hydrogen atom or an alkyl group. X ^{1 and} It is selected from the group consisting of aryl group, heteroaryl group, halogen and cyano group. These groups may further have substituents. R ⁷ is represented by the following general formula (2).

(R ⁸ to R ¹⁰ are each independently 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, an arylether group, an arylthioether group, aryl group, heteroaryl group, halogen, cyano group, aldehyde group, acyl group, carboxyl group, ester group, amide group, sulfonyl group, sulfonic acid ester group, sulfonamide group, amino group, nitro group, silyl group, siloxanyl group, It is selected from the group consisting of a boryl group and a phosphine oxide group.These groups may further have substituents.R ¹¹ is 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. , alkylthio group, aryl ether group, arylthioether group, aryl group, heteroaryl group, halogen, cyano group, aldehyde group, acyl group, carboxyl group, ester group, amide group, sulfonyl group, sulfonic acid ester group, sulfonamide group, It is selected from the group consisting of amino group, nitro group, silyl group, siloxanyl group, boryl group and phosphine oxide group.These groups may further have substituents.Ar ¹ is substituted or unsubstituted aryl group, or substituted or unsubstituted hetero It is an aryl group.)

Description

Pyromethene boron complex, light-emitting devices containing the same, display devices, and lighting devices

The present invention relates to pyromethene boron complex, light-emitting devices containing the same, display devices, and lighting devices.

Organic thin film light-emitting devices that emit light by recombining electrons injected from the cathode and holes injected from the anode within the light-emitting layer sandwiched between the two electrodes are thin, capable of low driving voltage and high-brightness light emission, and can also emit multicolor light by selecting the light-emitting material. It has a feature that makes this possible. In particular, by using a combination of a host material and a dopant material in the light emitting layer, a light emitting device that emits light of the three primary colors of blue, green, and red with high efficiency can be obtained.

As a dopant, a dye with a high fluorescence quantum yield is usually used. For example, a complex having a pyromethene skeleton is a compound that satisfies the requirements necessary to obtain high efficiency as a dopant, such as a high fluorescence quantum yield and a small Stokes shift and a small peak half width of the emission spectrum, and a pyromethene complex as a dopant. It is known that light-emitting devices using , exhibit good device characteristics (for example, see Patent Document 1). Additionally, in recent years, with the goal of high luminous efficiency, light-emitting devices containing TADF (Thermally Activated Delayed Fluorescence) materials and pyromethene boron complexes have been examined (for example, see Patent Document 2).

Japanese Patent Publication No. 2003-12676 International Publication No. 2016/056559

When using organic thin film light emitting devices as display devices or lighting devices, it is required to widen the color gamut. The color region determines the vertex coordinates representing the respective emission of red, green, and blue in the xy chromaticity diagram, and is represented by a triangle connecting them. In order to widen the color gamut, it is necessary to set the coordinates of each vertex of red, green, and blue to an appropriate chromaticity so that the area of the triangle is widened, and for this reason, various color designs are being implemented.

Chromaticity is determined by a combination of emission peak wavelength and color purity. Color purity is determined by the width of the emission spectrum, and as the width of the emission spectrum narrows and approaches monochromatic light, color purity increases. Increasing color purity is particularly important for wide color gamut, and light-emitting materials with a sharp emission spectrum are strongly required.

Additionally, when using an organic thin film light emitting device as a display device or lighting device, it is required to improve the durability of the light emitting device. In order to improve the durability of light-emitting devices, it is necessary to increase the stability of light-emitting materials.

On the other hand, organic thin film light emitting devices are required to have high luminous efficiency from the viewpoint of improving brightness and saving power. In particular, for mobile display devices whose use has been expanding in recent years, power saving has become a particularly important issue.

In this situation, pyromethene boron complex is a useful light-emitting material that can obtain a sharp emission spectrum when used as a dopant, but higher luminous efficiency and durability are required for light-emitting devices. However, it was difficult to achieve a light-emitting device with high luminous efficiency and high durability while maintaining a sharp luminescence spectrum.

The purpose of the present invention is to solve these problems of the prior art and provide a light-emitting material with a high fluorescence quantum yield and a sharp emission spectrum, and a light-emitting device with high luminous efficiency, color purity, and durability.

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

R ¹ to R ⁶ are each independently 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, an aryl ether group, an arylthioether group. , an aryl group, a heteroaryl group, an amino group, a silyl group, a siloxanyl group, and a boryl group. These groups may further have substituents. However, at least one of R ¹ to R ⁴ is a hydrogen atom or an alkyl group.

X ^{1 and} , heteroaryl group, halogen, and cyano group. These groups may further have substituents.

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

R ⁸ to R ¹⁰ are each independently 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, an aryl ether group, an arylthioether group. , aryl group, heteroaryl group, halogen, cyano group, aldehyde group, acyl group, carboxyl group, ester group, amide group, sulfonyl group, sulfonic acid ester group, sulfonamide group, amino group, nitro group, silyl group, siloxanyl group, bo It is selected from the group consisting of a reel group and a phosphine oxide group. These groups may further have substituents.

R ¹¹ is an alkyl group, cycloalkyl group, heterocyclic group, alkenyl group, cycloalkenyl group, alkynyl group, hydroxyl group, thiol group, alkoxy group, alkylthio group, arylether group, arylthioether group, aryl group, heteroaryl group, halogen , cyano group, aldehyde group, acyl group, carboxyl group, ester group, amide group, sulfonyl group, sulfonic acid ester group, sulfonamide group, amino group, nitro group, silyl group, siloxanyl group, boryl group and phosphine oxide group. is selected. These groups may further have substituents.

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 device having an anode, a cathode, and a light-emitting layer existing between the anode and the cathode, and the light-emitting layer emits light by electrical energy, wherein the light-emitting layer contains the pyromethene boron complex. It is a light emitting device.

By the present invention, it is possible to provide a light-emitting material with a high fluorescence quantum yield and a sharp emission spectrum, and a light-emitting device with high luminous efficiency, color purity, and durability.

Hereinafter, preferred embodiments of the pyromethene boron complex, light-emitting elements, display devices, and lighting devices containing the same according to the present invention 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 use.

<Pyromethene boron complex>

The pyromethene boron complex according to the present invention is represented by general formula (1).

R ¹ to R ⁶ are each independently 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, an aryl ether group, an arylthioether group. , an aryl group, a heteroaryl group, an amino group, a silyl group, a siloxanyl group, and a boryl group. These groups may further have substituents. However, at least one of R ¹ to R ⁴ is a hydrogen atom or an alkyl group.

X ^{1 and} , heteroaryl group, halogen, and cyano group. These groups may further have substituents.

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

R ⁸ to R ¹⁰ are each independently 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, an aryl ether group, an arylthioether group. , aryl group, heteroaryl group, halogen, cyano group, aldehyde group, acyl group, carboxyl group, ester group, amide group, sulfonyl group, sulfonic acid ester group, sulfonamide group, amino group, nitro group, silyl group, siloxanyl group, bo It is selected from the group consisting of a reel group and a phosphine oxide group. These groups may further have substituents.

R ¹¹ is an alkyl group, cycloalkyl group, heterocyclic group, alkenyl group, cycloalkenyl group, alkynyl group, hydroxyl group, thiol group, alkoxy group, alkylthio group, arylether group, arylthioether group, aryl group, heteroaryl group, halogen , cyano group, aldehyde group, acyl group, carboxyl group, ester group, amide group, sulfonyl group, sulfonic acid ester group, sulfonamide group, amino group, nitro group, silyl group, siloxanyl group, boryl group and phosphine oxide group. is selected. These groups may further have substituents.

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

In the pyromethene skeleton, the region substituted by R ⁷ may hereinafter be referred to as the “bridge position.”

In the present invention, those having a pyromethene skeleton represented by the following formula and those having a condensed ring structure in a part of the pyromethene skeleton and the ring structure being expanded are collectively referred to as “pyrromethene.”

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

In addition, in all of the above groups, substituents in case of substitution include alkyl group, cycloalkyl group, heterocyclic group, alkenyl group, cycloalkenyl group, alkynyl group, aryl group, heteroaryl group, hydroxyl group, thiol group, alkoxy group, and alkyl group. Thio group, aryl ether group, arylthioether group, halogen, cyano group, aldehyde group, acyl group, carboxyl group, ester group, amide group, acyl group, sulfonyl group, sulfonic acid ester group, sulfonamide group, amino group, nitro group, silyl group A group selected from the group consisting of a siloxanyl group, a boryl group, a phosphine oxide group, and an oxo group is preferred. Furthermore, in the description of each substituent described later, specific substituents that are said to be preferable are more preferable. In addition, these substituents may be further substituted with the substituents mentioned above.

In the description of this description, “unsubstituted” means that the atom bonded to the target basic skeleton or group is only a hydrogen atom or a deuterium atom. The same applies to the case of “substituted or unsubstituted” in the compounds or partial structures thereof described below.

An alkyl group refers to a saturated aliphatic hydrocarbon group such as, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, and tert-butyl group, which may be substituted or unsubstituted. . There is no particular limitation on the additional substituent when substituted, and examples include alkyl group, halogen, aryl group, heteroaryl group, etc. This point is also common to the description below. The number of carbon atoms in the alkyl group is not particularly limited, but is preferably in the range of 1 to 20, more preferably 1 to 8, from the viewpoint of availability and cost.

A cycloalkyl group refers to, for example, a saturated alicyclic hydrocarbon group such as a cyclopropyl group, cyclohexyl group, norbornyl group, or adamantyl group, which may be substituted or unsubstituted. The number of carbon atoms in the alkyl group portion is not particularly limited, but is preferably in the range of 3 to 20.

A heterocyclic group refers to an aliphatic ring having atoms other than carbon in the ring, such as, for example, a pyran ring, piperidine ring, or cyclic amide, and may be substituted or unsubstituted. The number of carbon atoms in the heterocyclic group is not particularly limited, but is preferably in the range of 2 to 20.

An alkenyl group refers to an unsaturated aliphatic hydrocarbon group containing a double bond, such as a vinyl group, an allyl group, or a butadienyl group, which may be substituted or unsubstituted. The number of carbon atoms in the alkenyl group is not particularly limited, but is preferably in the range of 2 to 20.

A cycloalkenyl group refers to an unsaturated alicyclic hydrocarbon group containing a double bond, such as a cyclopentenyl group, cyclopentadienyl group, or cyclohexenyl group, and may be substituted or unsubstituted. The number of carbon atoms in the cycloalkenyl group is not particularly limited, but is preferably in the range of 3 to 20.

An alkynyl group refers to an unsaturated aliphatic hydrocarbon group containing a triple bond such as an ethynyl group, which may be substituted or unsubstituted. The number of carbon atoms in the alkynyl group is not particularly limited, but is preferably in the range of 2 to 20.

An alkoxy group refers to a functional group to which an aliphatic hydrocarbon group is bonded through an ether bond, such as a methoxy group, ethoxy group, or propoxy group, and this aliphatic hydrocarbon group may be substituted or unsubstituted. The number of carbon atoms in the alkoxy group is not particularly limited, but is preferably in the range of 1 to 20.

An alkylthio group is one in which the oxygen atom of the ether bond of an alkoxy group is replaced with a sulfur atom. The hydrocarbon group of the alkylthio group may be substituted or unsubstituted. The number of carbon atoms of the alkylthio group is not particularly limited, but is preferably in the range of 1 to 20.

An aryl ether group refers to a functional group to which an aromatic hydrocarbon group is bonded through an ether bond, such as a phenoxy group, and the aromatic hydrocarbon group may be substituted or unsubstituted. The number of carbon atoms in the aryl ether group is not particularly limited, but is preferably in the range of 6 to 40.

An arylthioether group is one in which the oxygen atom of the ether bond of an arylether group is replaced with a sulfur atom. The aromatic hydrocarbon group in the arylthioether group may be substituted or unsubstituted. The number of carbon atoms in the arylthioether group is not particularly limited, but is preferably in the range of 6 to 40.

The aryl group may be either a monocyclic ring or a condensed ring, for example, phenyl group, naphthyl group, fluorenyl group, benzofluorenyl group, dibenzofluorenyl group, phenanthryl group, anthracenyl group, benzophenanthryl group, benzoanthra group. Represents aromatic hydrocarbon groups such as cenyl group, chrysenyl group, pyrenyl group, fluoranthenyl group, triphenylenyl group, benzofluoranthenyl group, dibenzoanthracenyl group, perylenyl group, and helisenyl group. Among them, a group selected from the group consisting of phenyl group, biphenyl group, terphenyl group, naphthyl group, fluorenyl group, phenanthryl group, anthracenyl group, pyrenyl group, fluoranthenyl group and triphenylenyl group is preferable. 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 through a single bond is treated as a phenyl group having an aryl group as a substituent. The number of carbon atoms in the aryl group is not particularly limited, but is preferably in the range of 6 to 40, more preferably in the range of 6 to 30. Additionally, in the phenyl group, when there are substituents on two adjacent carbon atoms in the phenyl group, the substituents may form a ring structure.

The heteroaryl group may be either a monocyclic ring or a condensed ring, for example, pyridyl group, furanyl group, thiophenyl group, quinolinyl group, isoquinolinyl group, pyrazinyl group, pyrimidyl group, pyridazinyl group, and triazinyl group. , naphthyridinyl group, cinnolinyl group, phthalazinyl group, quinoxalinyl group, quinazolinyl group, benzofuranyl group, benzothiophenyl group, indolyl group, dibenzofuranyl group, dibenzothiophenyl group, carbazolyl group, benzocar Bazolyl group, carbolinyl group, indolocarbazolyl group, benzofurocarbazolyl group, benzothienocarbazolyl group, dihydroindenocarbazolyl group, benzoquinolinyl group, acridinyl group, dibenzo Cyclic groups having atoms other than carbon and hydrogen, that is, heteroatoms, in one or more rings, such as acridinyl group, benzoimidazolyl group, imidazopyridyl group, benzoxazolyl group, benzothiazolyl group, phenanthrolinyl group, etc. Represents an aromatic group. As the hetero atom, a nitrogen atom, an oxygen atom, or a sulfur atom is preferable. The heteroaryl group may be substituted or unsubstituted. The number of carbon atoms in the heteroaryl group is not particularly limited, but is preferably in the range of 2 to 40, more preferably in the range of 2 to 30.

Halogen refers to an atom selected from fluorine, chlorine, bromine, and iodine.

A cyano group is a functional group whose structure is represented by -CN. Here, it is the carbon atom that bonds with the other group.

An aldehyde group is a functional group whose structure is represented by -C(=O)H. Here, it is the carbon atom that bonds with the other group.

An acyl group refers to a functional group bonded to an alkyl group, cycloalkyl group, alkenyl group, alkynyl group, aryl group, or heteroaryl group through a carbonyl group, for example, an acetyl group, propionyl group, benzoyl group, acrylyl group, etc. These substituents may be further substituted. The number of carbon atoms of the acyl group is not particularly limited, but is preferably 2 to 40, more preferably 2 to 30.

An ester group refers to a functional group in which, for example, an alkyl group, cycloalkyl group, aryl group, heteroaryl group, etc. are bonded through an ester bond. These substituents may be further substituted. The number of carbon atoms in the ester group is not particularly limited, but is preferably in the range of 1 to 20. More specifically, methyl ester groups such as methoxycarbonyl group, ethyl ester groups such as ethoxycarbonyl group, propyl ester groups such as propoxycarbonyl group, butyl ester groups such as butoxycarbonyl group, isopropoxymethoxycarbonyl group, etc. Hexyl ester groups such as propyl ester group and hexyloxycarbonyl group, and phenyl ester groups such as phenoxycarbonyl group.

An amide group refers to a functional group in which, for example, an alkyl group, cycloalkyl group, aryl group, heteroaryl group, etc. are bonded through an amide bond. These substituents may be further substituted. The number of carbon atoms in the amide group is not particularly limited, but is preferably in the range of 1 to 20. More specifically, methylamide group, ethylamide group, propylamide group, butylamide group, isopropylamide group, hexylamide group, phenylamide group, etc. are mentioned.

A sulfonyl group refers to a functional group in which, for example, an alkyl group, cycloalkyl group, aryl group, heteroaryl group, etc. are bonded through a -S(=O) ₂ - bond. These substituents may be further substituted. The number of carbon atoms in the sulfonyl group is not particularly limited, but is preferably in the range of 1 to 20.

The sulfonic acid ester group refers to a functional group in which, for example, an alkyl group, cycloalkyl group, aryl group, heteroaryl group, etc. are bonded through a sulfonic acid ester bond. Here, the sulfonic acid ester bond refers to the carbonyl portion of the ester bond, that is, -C(=O)-, being replaced with the sulfonyl portion, that is, -S(=O) ₂ -. Additionally, these substituents may be further substituted. The number of carbon atoms in the sulfonic acid ester group is not particularly limited, but is preferably in the range of 1 to 20.

A sulfonamide group refers to a functional group in which, for example, an alkyl group, cycloalkyl group, aryl group, heteroaryl group, etc. are bonded through a sulfonamide bond. Here, the sulfonamide bond refers to the carbonyl portion of the ester bond, that is, -C(=O)-, being replaced with the sulfonyl portion, that is, -S(=O) ₂ -. Additionally, these substituents may be further substituted. The number of carbon atoms in the sulfonamide group is not particularly limited, but is preferably in the range of 1 to 20.

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

A silyl group refers to a functional group to which a substituted or unsubstituted silicon atom is bonded, for example, alkylsilyl groups such as trimethylsilyl group, triethylsilyl group, tert-butyldimethylsilyl group, propyldimethylsilyl group, and vinyldimethylsilyl group, or phenyldimethyl group. It represents arylsilyl groups such as silyl group, tert-butyldiphenylsilyl group, triphenylsilyl group, and trinaphthylsilyl group. Substituents on silicon may be further substituted. The number of carbon atoms in the silyl group is not particularly limited, but is preferably in the range of 1 to 30.

The siloxanyl group refers to a silicon compound group through an ether bond, such as a trimethylsiloxanyl group. Substituents on silicon may be further substituted.

A boryl group is a substituted or unsubstituted boryl group. Examples of the substituent in the case of substitution include an aryl group, heteroaryl group, straight-chain alkyl group, branched alkyl group, aryl ether group, alkoxy group, and hydroxyl group, and among them, an aryl group and an aryl ether group are preferable.

A phosphine oxide group is 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 pyromethene boron complex has a rigid and highly planar skeleton, it exhibits a high fluorescence quantum yield. Additionally, since the peak half width of the emission spectrum is small, efficient emission of light and high color purity can be achieved in the light emitting device.

In order to further improve the luminous efficiency, it is effective to suppress rotation and vibration of the substituents of the pyromethene boron complex, reduce energy loss, and improve the fluorescence quantum yield. In addition, in order to improve color purity, it is effective to reduce the vibration relaxation in the excited state of the pyromethene boron complex, thereby reducing the half width of the emission spectrum.

From this point of view, a substituent R ⁷ is introduced at the cusp of the pyromethene skeleton. By introducing R ⁷ , it is possible to provide a pyromethene boron complex with high fluorescence quantum yield and a small half width. Among them, among the substituents R ⁷ , Ar ¹ and R ¹¹ are each of the above groups, which is advantageous for improving luminous efficiency because intramolecular rotation of the cusp with respect to the pyromethene skeleton, resulting in energy deactivation, can be suppressed.

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

Additionally, the stability of the pyromethene boron complex affects the durability of the light emitting device. In order to further improve its stability, it is desirable to introduce bulky substituents on the cusp. By introducing a bulky substituent, the pyromethene skeleton can be protected from interaction with other surrounding molecules. Among the substituents R ⁷ , Ar ¹ and R ¹¹ are each of the above groups, thereby improving the stability of the pyromethene boron complex and improving the durability of the light emitting device. From this viewpoint, R ¹¹ is preferably a bulkier substituent, and is preferably a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group.

R ¹ and R ⁴ are selected from the above-described group and affect the peak emission wavelength, crystallinity, sublimation temperature, etc. of the pyromethene boron complex. From the viewpoint of making the half width of the emission spectrum smaller, R ¹ and R ⁴ are preferably hydrogen atoms or alkyl groups. Moreover, from the viewpoint of further improving the fluorescence quantum yield, it is more preferable that R ¹ and R ⁴ are alkyl groups.

R ² and R ³ are selected from the above-described group, and mainly affect the peak emission wavelength, half width of the emission spectrum, stability or crystallinity of the pyromethene boron complex. From the viewpoint of reducing the half width of the emission spectrum, improving stability, and ease of synthesis including recrystallization, at least one of R ² and R ³ , preferably both, is substituted with a hydrogen atom. Alternatively, it is preferably a group selected from the group consisting of an unsubstituted alkyl group, a substituted or unsubstituted aryl group, and a substituted or unsubstituted heteroaryl group. Moreover, from the viewpoint of further reducing the half width, it is more preferable that R ² and R ³ are alkyl groups.

R ⁵ and R ⁶ are selected from the above-mentioned group, and mainly affect the peak emission wavelength, half width of the emission spectrum, stability or crystallinity of the pyromethene boron complex. From the viewpoint of making the half width of the emission spectrum smaller, improving stability, and ease of synthesis including recrystallization purification, at least one of R ⁵ and R ⁶ , preferably both, is a hydrogen atom, or It is preferable that it is a substituted or unsubstituted alkyl group.

X ¹ and X ² are selected from the above. From the viewpoint of luminescence characteristics ^{and thermal} stability, desirable. Here, the haloalkyl group is an alkyl group substituted with at least one halogen. A haloaryl group is an aryl group substituted with at least one halogen.

In addition, from the viewpoint of stabilizing the excited state to obtain a higher fluorescence quantum yield and from the viewpoint of improving durability, X ^{1 and} It is more preferable that it is a group selected from the group consisting of a fluorine group, more preferably a fluorine atom or a cyano group, and most preferably a fluorine atom. These are electron withdrawing groups and can increase the stability of the compound by lowering the electron density of the pyromethene skeleton.

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

The pyromethene boron complex represented by general formula (1) is described in J. Org. Chem., vol.64, No.21, pp.7813-7819 (1999), Angew. Chem., Int. Ed. Engl., vol.36, pp.1333-1335 (1997), Org. It can be manufactured by referring to the method described in Lett., vol.12, pp.296 (2010), etc.

In addition, in order to introduce an aryl group or heteroaryl group into the pyromethene skeleton, for example, in the presence of a metal catalyst such as palladium, a coupling reaction between a halogenated derivative of the pyromethene boron complex and a boronic acid or boronic acid ester derivative is used to form a carbon-carbon reaction. Methods for creating a bond may be mentioned, but are not limited to this. Similarly, in order to introduce an amino group or carbazolyl group into the pyromethene skeleton, for example, a carbon-nitrogen bond is formed using a coupling reaction between a halogenated derivative of the pyromethene boron complex and an amine or carbazole derivative in the presence of a metal catalyst such as palladium. A method of generating a , but is not limited to this.

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

The purity of the pyromethene boron complex produced in this way is preferably 99% by weight or more from the viewpoint of enabling the light-emitting device to exhibit stable characteristics.

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

In order to achieve high color purity, it is preferable that the pyromethene boron complex represented by general formula (1) has a sharp emission spectrum of light emitted when irradiated with excitation light. Additionally, top emission elements, which are becoming mainstream in display devices and lighting devices, can achieve high brightness and high color purity due to the resonance effect caused by the micro-cavity structure. However, if the emission spectrum is sharp, this resonance effect is displayed more strongly, resulting in higher efficiency. It is advantageous to From this viewpoint, the half width of the emission spectrum is preferably 60 nm or less, more preferably 50 nm or less, further preferably 45 nm or less, and especially preferably 28 nm or less.

The luminous efficiency of a light-emitting device depends on the fluorescence quantum yield of the light-emitting material itself. Therefore, it is desired that the fluorescence quantum yield of the light-emitting material is as close to 100% as possible. The pyromethene boron complex represented by the general formula (1) has R ¹¹ and Ar ¹ as described above, thereby suppressing rotation and vibration on the cusp and reducing heat deactivation, thereby obtaining a high fluorescence quantum yield. From the above viewpoint, the fluorescence quantum yield of the pyromethene boron complex is preferably 90% or more, and more preferably 95% or more. However, the fluorescence quantum yield shown here is measured using an absolute quantum yield measuring device in a diluted solution using toluene as a solvent.

<Light-emitting device materials>

The pyromethene boron complex represented by general formula (1) is used as a light-emitting device material in light-emitting devices because it can achieve high luminous efficiency. Here, the light-emitting device material in the present invention refers to a material used in a certain layer of a light-emitting device, and as described later, it is a material used in a layer selected from a hole injection layer, a hole transport layer, a light-emitting layer, and an electron transport layer. , also includes materials used for the protective film (cap layer) of the electrode.

The pyromethene boron complex represented by General Formula (1) is preferably a material used in the light-emitting layer because it has high light-emitting performance.

<Light-emitting device>

Next, embodiments of the light-emitting device of the present invention will be described. The light emitting device of the present invention has an anode, a cathode, and an organic layer existing between the anode and the cathode. It is preferable that the organic layer includes at least a light-emitting layer, and that the light-emitting layer is an organic electroluminescent element that emits light by electrical energy.

The light emitting device 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 device includes, in addition to the structure consisting of only the light-emitting layer, 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 transport layer. 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/holes Stacked structures such as 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 can be mentioned.

Additionally, a tandem type light emitting element may be used in which a plurality of the above-described stacked structures are stacked with an intermediate layer interposed therebetween. The intermediate layer generally includes an intermediate electrode, an intermediate conductive layer, a charge generation layer, an electron withdrawal layer, a connection layer, an intermediate insulating layer, etc., and a known material composition can be used. As a preferred specific example of a tandem light emitting device, 9) a stacked configuration such as 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. can be mentioned.

Additionally, each of the above layers may be either a single layer or multiple layers, and may be doped. Additionally, a device configuration including a layer using a capping material to improve luminous efficiency due to the optical interference effect can also be mentioned.

The pyromethene boron complex represented by General Formula (1) may be used in any layer in the above device configuration, but is preferably used in the light-emitting layer because it has a high fluorescence quantum yield and thin film stability.

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

(Board)

It is preferable to form the light emitting device on a substrate because it maintains the mechanical strength of the light emitting device, reduces thermal deformation, and has barrier properties that prevent water vapor or oxygen from entering the light emitting layer. The substrate is not particularly limited, and examples include glass plates, ceramic plates, resin films, resin thin films, and metal thin plates. Among these, a glass substrate is suitably used from the viewpoint of being transparent and easy to process. In particular, a glass substrate with high transparency is desirable in a bottom emission element that extracts light through the substrate. Additionally, flexible displays and foldable displays are increasing in mobile devices such as smartphones, and resin films or resin thin films obtained by curing varnish are suitably used for this purpose. Heat-resistant films are used as resin films, and specific examples include polyimide films and polyethylene naphthalate films.

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

(anode)

An anode is formed on the substrate. Here, various wiring, circuits, and switching elements may be interposed between the substrate and the anode. The material used for the anode is not particularly limited as long as it is a material that can efficiently inject holes into the organic layer. However, in a bottom emission type device, it is preferable that it is a transparent or translucent electrode, and in a top emission type device, it is preferable that it is a reflective electrode. do.

Materials for transparent or translucent electrodes include conductive metal oxides such as zinc oxide, tin oxide, indium oxide, indium tin oxide (ITO), and indium zinc oxide (IZO); or metals such as gold, silver, aluminum, and chrome; Conductive polymers such as polythiophene, polypyrrole, and polyaniline are examples. However, when using a metal, it is desirable to make the film thickness thin so that it can semitransmit light. Among the above, indium tin oxide (ITO) is more preferable from the viewpoint of transparency and stability.

As a material for the reflecting electrode, it is desirable to have no absorption of all light and a high reflectance. Specifically, metals such as aluminum, silver, and platinum are exemplified.

The method for forming the anode can be an optimal method depending on the forming material, and examples include sputtering, vapor deposition, and inkjet methods. For example, when forming an anode with a metal oxide, a sputtering method is used, and when forming an anode with a metal, a vapor deposition method is used. The film thickness of the anode is not particularly limited, but is preferably from several nm to hundreds of nm.

In addition, these electrode materials may be used individually, or may be used by laminating or mixing a plurality of materials.

(cathode)

The cathode is formed on the surface opposite to the anode across the organic layer, and is particularly preferably formed on the electron transport layer or the electron injection layer. The material used for the cathode is not particularly limited as long as it is a material that can efficiently inject electrons into the light-emitting layer. However, in a bottom emission type device, it is preferable that it is a reflective electrode, and in a top emission type device, it is preferable that it is a translucent electrode.

The cathode material generally includes metals such as platinum, gold, silver, copper, iron, tin, aluminum, and indium; alloys or multilayer laminated films of these metals and low work function metals such as lithium, sodium, potassium, calcium, and magnesium; Alternatively, conductive metal oxides such as zinc oxide, indium tin oxide (ITO), and indium zinc oxide (IZO) are preferable. Among them, metals selected from aluminum, silver, and magnesium as the main components are preferable in terms of electrical resistance value, ease of film formation, film stability, luminous efficiency, etc. Additionally, it is preferable if the cathode is made of magnesium and silver because electron injection into the electron transport layer and electron injection layer in the present invention becomes easy and low voltage driving becomes possible.

(protective layer)

For cathode protection, it is desirable to laminate a protective layer (cap 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; inorganic substances such as silica, titania, and silicon nitride; Organic polymer compounds such as polyvinyl alcohol, polyvinyl chloride, and hydrocarbon-based polymer compounds can be mentioned. However, when the light emitting element has an element structure (top emission structure) that extracts light from the cathode side, the material used for the protective layer is selected from materials that are light transparent 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 may be one layer or may be a stack of multiple layers. The presence of a hole injection layer between the hole transport layer and the anode is preferable because lower voltage driving is possible and the durability of the device is improved, and the carrier balance of the device is further improved to improve luminous efficiency.

A preferred example of a hole injection material is an electron-donating hole injection material (donor material). These are materials that can reduce the energy barrier with the anode because the HOMO level is shallower than the hole transport layer and is close to the work function of the anode. Specifically, benzidine derivatives, 4,4',4"-tris(3-methylphenyl(phenyl)amino)triphenylamine (m-MTDATA), 4,4',4"-tris(1-naphthyl(phenyl) A group of aromatic amine materials such as starburst arylamine such as amino) triphenylamine (1-TNATA); Heterocyclic compounds such as carbazole derivatives, pyrazoline derivatives, stilbene-based compounds, hydrazone-based compounds, benzofuran derivatives, thiophene derivatives, oxadiazole derivatives, phthalocyanine derivatives, and porphyrin derivatives; In the polymer system, examples include polycarbonate and styrene derivatives having the above-described monomer in the side chain, polythiophene such as PEDOT/PSS, polyaniline, polyfluorene, polyvinylcarbazole, and polysilane. These materials may be used individually, or two or more types of materials may be mixed and used. Additionally, a hole injection layer may be formed by laminating a plurality of materials.

Additionally, another preferred example of the hole injection material is an electron-accepting hole injection material (acceptor material). Here, the hole injection layer may be composed of an acceptor material alone, or may be used by doping the donor material with an acceptor material. The acceptor material is a material that forms a charge transfer complex between the adjacent hole transport layer when used alone, and between the donor material when used by doping it with a donor material. The use of such materials is more preferable because it contributes to improving the conductivity of the hole injection layer and lowering the driving voltage of the device, and achieves effects such as improving luminous efficiency and improving durability. As the acceptor material, metal oxides such as molybdenum oxide, vanadium oxide, tungsten oxide, and ruthenium oxide; charge transfer complexes such as tris(4-bromophenyl)aminiumhexachloroantimonate (TBPAH); 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile (HAT-CN6), 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano n-type organic semiconductor compounds such as quinodimethane (F4-TCNQ) and fluorinated copper phthalocyanine; Fullerenes, etc. are exemplified. When the hole injection layer contains an acceptor material, the hole injection layer may be one layer or may be composed of a plurality of layers 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 a single layer or may be composed of a plurality of layers stacked.

The hole transport layer is formed by one type of hole transport material alone or by laminating or mixing two or more types of hole transport materials. Additionally, it is desirable that the hole transport material has high hole injection efficiency and transports the injected holes efficiently. For this purpose, a material is required that has an appropriate ionization potential, has high hole mobility, is excellent in stability, and is unlikely to generate impurities that become traps.

Substances that satisfy these conditions include, but are not particularly limited to, benzidine derivatives, a 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, oxa Heterocyclic compounds such as diazole derivatives, phthalocyanine derivatives, and porphyrin derivatives; In polymer systems, examples include polycarbonate, styrene derivatives, polythiophene, polyaniline, polyfluorene, polyvinylcarbazole, and polysilane, which have the above-mentioned monomers in their side chains.

(Emitting layer)

The light-emitting layer is a layer that emits light by excitation energy generated by recombination of holes and electrons. The light-emitting layer may be composed of a single material, but from the viewpoint of color purity, it is preferable to have a first compound and a second compound that is a dopant that exhibits strong light emission. Suitable examples of the first compound include host materials responsible for charge transfer and compounds with thermally activated delayed fluorescence.

The pyromethene boron complex represented by the general formula (1) has a particularly excellent fluorescence quantum yield and has a narrow half-width of the emission spectrum, so that high color purity can be achieved, so it is used as a second compound as a dopant of the light-emitting layer. It is desirable to use Since the concentration quenching phenomenon occurs when the dope amount of the second compound is too large, it is preferably 20% by weight or less, more preferably 10% by weight or less, even more preferably 5% by weight or less, based on the total weight of the light emitting layer. % or less is most preferable. Moreover, since sufficient energy transfer is difficult to occur when the dope concentration is too low, 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.

There is no need to limit the host material to only one type of compound, and two or more types may be mixed and used, or may be used by laminating them. The host material is not particularly limited, and includes compounds having a condensed aryl ring such as naphthacene, pyrene, anthracene, and fluoranthene, and derivatives thereof; Aromatic amine derivatives such as N,N'-dinaphthyl-N,N'-diphenyl-4,4'-diphenyl-1,1'-diamine; metal chelating oxinoid compounds including tris(8-quinolinato)aluminum(III); Bistyryl derivatives such as distyrylbenzene derivatives; Tetraphenylbutadiene derivatives, indene derivatives, coumarin derivatives, oxadiazole derivatives, pyrrolopyridine derivatives, perinone derivatives, pyrrolopyrrole derivatives, thiadiazolopyridine derivatives, dibenzofuran derivatives, carbazole derivatives, indolocarbazole derivatives , triazine derivatives; In polymer systems, polyphenylenevinylene derivatives, polyparaphenylene derivatives, polyfluorene derivatives, polyvinylcarbazole derivatives, polythiophene derivatives, etc. can be used. Particularly preferred host materials are anthracene derivatives or naphthacene derivatives.

The dopant material is not particularly limited, but may contain a fluorescent material other than the pyromethene boron complex represented by general formula (1). Specifically, compounds having a condensed aryl ring such as naphthacene, pyrene, anthracene, and fluoranthene, and derivatives thereof; Compounds or derivatives thereof having a heteroaryl ring; Distyrylbenzene derivatives, aminostyryl derivatives, tetraphenylbutadiene derivatives, stilbene derivatives, aldazine derivatives, pyromethene derivatives, diketopyrrolo[3,4-c]pyrrole derivatives, coumarin derivatives, azole derivatives and metal complexes thereof, and aromatic amine derivatives.

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

From the viewpoint of increasing monochromatic purity, the dopant material is preferably one type of pyromethene boron complex represented by general formula (1).

In addition to the host material or dopant material, the light-emitting layer may further contain a third component for adjusting the carrier balance in the light-emitting layer or stabilizing the layer structure of the light-emitting layer. However, as the third component, a material that does not cause interaction with the host material and the dopant material is selected.

Thermal activation delayed fluorescent compounds, also commonly called TADF materials, reduce the energy gap between the energy level of the singlet excited state and the energy level of the triplet excited state, thereby converting the inverse interstitial state from the triplet excited state to the singlet excited state. It is a material that promotes crossover and improves the probability of singlet exciton creation. The difference between the lowest singlet excitation energy level and the lowest triplet excitation energy level (referred to as ΔEST) in the TADF material is preferably 0.3 eV or less. By using delayed fluorescence by this TADF mechanism, the theoretical internal efficiency can be increased to 100%. Additionally, when Förster-type energy transfer occurs from the singlet exciton of the first compound having thermally activated delayed fluorescence to the singlet exciton of the second compound, fluorescence emission from the singlet exciton of the second compound is observed. In order for this energy transfer to occur, it is preferable that the lowest singlet excitation energy level of the first compound is greater than the lowest singlet excitation energy level of the second compound. Here, when the second compound is a fluorescent material with a sharp emission spectrum, a light-emitting device with high efficiency and high color purity can be obtained. In this way, when the light-emitting layer contains a thermally activated delayed fluorescent compound, highly efficient light emission is possible, contributing to lower power consumption of the display. The heat-activated delayed fluorescent compound may be a compound that exhibits heat-activated delayed fluorescence with a single material, or may be a compound that exhibits heat-activated delayed fluorescence with a plurality of compounds, as in the case of forming an exciplex complex.

The heat-activated delayed fluorescent compound may be a single compound or a mixture of multiple compounds, and known materials can be used. Specifically, examples include benzonitrile derivatives, triazine derivatives, disulfoxide derivatives, carbazole derivatives, indolocarbazole derivatives, dihydrophenazine derivatives, thiazole derivatives, and oxadiazole derivatives. In particular, it is preferable that it is a compound having an electron donating part (donor part) and an electron withdrawing part (acceptor part) in the same molecule. The electron donating part (donor part) and the electron withdrawing part may be directly bonded through a single bond or spiro bond, or may be bonded through a linking group. Examples of such compounds include compounds containing a structure represented by the following general formula (3).

In the general formula (3), A is an electron-donating moiety, B is an electron-donating moiety, and L is a linking group. When there is a plurality of A, the plurality of A's may be the same or different from each other, and the A's may be bonded to each other to form a ring structure. When there are two or more Bs, the plurality of Bs may be the same or different from each other, and the Bs may be combined to form a ring structure.

L is a direct bond, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 ring carbon atoms, a substituted or unsubstituted heteroaromatic ring group having 5 to 30 ring atoms, a group in which 2 to 5 of these groups are linked to each other, and an alkyl fluoride group. It is a group selected from the group consisting of methylene groups having. Here, the direct bond includes a single bond and a spiro bond. However, the heterocyclic aromatic ring group does not include an aromatic amino group having electron donation or a π-electron-excessive heterocyclic functional group.

a and b are each independently integers of 1 to 5.

Two or more L may exist in the same molecule. When there is a plurality of L, the plurality of L's may be the same or different from each other, and the L's may be combined to form a saturated or unsaturated ring. Additionally, a plurality of L may be connected through A and/or B. When there are multiple A and/or B and L, multiple A and/or B may bind to the same L or may bind to different L.

Here, the electron donating region (donor region) refers to a region rich in electrons relative to adjacent regions. For example, an aromatic amino group or a π-electron-excessive heterocyclic functional group can be mentioned. Specifically, diarylamino group, carbazolyl group, benzocarbazolyl group, dibenzocarbazolyl group, indolocarbazolyl group, dihydroacridinyl group, phenoxazinyl group and dihydrophenazinyl group and these. Examples include groups where multiple groups are connected. These groups may or may not be further substituted. Examples of the substituent in the case of substitution include the preferable substituents described above.

Additionally, the electron withdrawing portion (acceptor portion) refers to a portion that is electron deficient relative to the adjacent portion. For example, a phenyl group or a π electron-deficient heterocyclic functional group having an electron withdrawing group or an electron withdrawing group as a substituent can be mentioned. Specifically, examples include an electron-withdrawing group selected from a carbonyl group, a sulfonyl group, a cyano group, and a fluorine atom, a phenyl group, a pyrimidinyl group, and a triazinyl group having an electron-withdrawing group as a substituent. These groups may or may not be further substituted. Examples of the substituent in the case of substitution include the preferable substituents described above.

Examples of the aromatic hydrocarbon group having 6 to 30 ring carbon atoms used as the linking group L include phenyl group, biphenyl group, terphenyl group, naphthyl group, fluorenyl group, benzofluorenyl group, dibenzofluorenyl group, phenanthryl group, Anthracenyl group, benzophenanthryl group, benzoanthracenyl group, chrysenyl group, pyrenyl group, fluoranthenyl group, triphenylenyl group, benzofluoranthenyl group, dibenzoanthracenyl group, perylenyl group, helicenyl group Examples include (a+b)-valent groups in which some hydrogen atoms are removed from an aryl group such as an aryl group.

Examples of the heteroaromatic ring group having 5 to 30 ring atoms used as the linking group L include pyridyl group, furanyl group, thiophenyl group, quinolinyl group, isoquinolinyl group, pyrazinyl group, pyrimidyl group, and pyridazinyl. group, triazinyl group, naphthyridinyl group, cinnolinyl group, phthalazinyl group, quinoxalinyl group, quinazolinyl group, benzofuranyl group, benzothiophenyl group, indolyl group, dibenzofuranyl group, dibenzothiophenyl group, benzoquinyl group Heteroaryl groups having atoms other than carbon and hydrogen, that is, heteroatoms, in one or more rings, such as nolinyl group, benzoimidazolyl group, imidazopyridyl group, benzoxazolyl group, benzothiazolyl group, and phenanthrolinyl group. An (a+b) cyclic aromatic group with some hydrogen removed from it can be mentioned. As the hetero atom, a nitrogen atom, an oxygen atom, or a sulfur atom is preferable. The heteroaromatic ring group may be substituted or unsubstituted.

Examples of such heat-activated delayed fluorescent compounds include, but are not particularly limited to, the following.

It is preferable that the first compound is a heat-activated delayed fluorescent compound, and the second compound is a pyromethene boron complex represented by the general formula (1). Additionally, when the first compound is a heat-activated delayed fluorescent compound, it is preferable that the light-emitting layer additionally includes a third compound whose singlet energy is greater than the singlet energy of the first compound. As a result, the third compound can have the function of confining the energy of the light-emitting material within the light-emitting layer, making it possible to emit light efficiently. Additionally, it is preferable that the lowest triplet excitation energy of the third compound is greater than the lowest triplet excitation energy of the first compound.

As this third compound, it is preferable that it is an organic compound that has a high charge transport ability and a high glass transition temperature. The third compound is not particularly limited, but examples include the following.

Additionally, the third compound may be single or may be composed of two or more types of materials. When using two or more types of materials as the third compound, it is preferable that it is 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 at an appropriate mixing ratio, the charge balance in the light-emitting layer can be adjusted and unevenness of the light-emitting region can be suppressed, thereby improving the reliability of the light-emitting device and improving durability. Additionally, an exciplex may be formed between the electron-transporting third compound and the hole-transporting third compound. In view of the above, it is preferable that the first compound and the third compound respectively satisfy the relational expressions of the following formulas 1 to 4. Additionally, it is more preferable to satisfy Equations 1 and 2, and it is even more preferable to satisfy Equations 3 and 4. Additionally, it is more preferable to satisfy all of Equations 1 to 4.

S1 (third compound with electron transport properties)>S1 (first compound) (Formula 1)

S1 (third hole-transporting compound) > S1 (first compound) (Formula 2)

T1 (third compound with electron transport properties)>T1 (first compound) (Formula 3)

T1 (third compound with hole transport properties)>T1 (first compound) (Formula 4)

Here, S1 represents the energy level of the lowest singlet excitation state of each compound, and T1 represents the energy level of the lowest triplet excitation state of each compound.

Examples of the third electron-transporting compound include compounds containing a π electron-deficient heteroaromatic ring. Specifically, 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD), 3-(4-biphenylyl)-4-phenyl- 5-(4-tert-butylphenyl)-1,2,4-triazole (TAZ), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazole- 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 -Heterocyclic compounds having a polyazole skeleton such as phenyl-1H-benzimidazole (mDBTBIm-II); 2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (2mDBTPDBq-II), 2-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (2mDBTBPDBq-II), 2-[4-( 3,6-diphenyl-9H-carbazol-9-yl)phenyl]dibenzo[f,h]quinoxaline (2CzPDBq-III), 7-[3-(dibenzothiophen-4-yl)phenyl] Dibenzo[f,h]quinoxaline (7mDBTPDBq-II) and 6-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (6mDBTPDBq-II), 2-[ Heterocyclic compounds having a quinoxaline skeleton or a dibenzoquinoxaline skeleton, such as 3'-(9H-carbazol-9-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (2mCzBPDBq); 4 ,6-bis[3-(phenanthren-9-yl)phenyl]pyrimidine (4,6mPnP2Pm), 4,6-bis[3-(9H-carbazol-9-yl)phenyl]pyrimidine (4, Heterocyclic compounds having a diazine skeleton (pyrimidine skeleton or pyrazine skeleton) such as 6mCzP2Pm) and 4,6-bis[3-(4-dibenzothienyl)phenyl]pyrimidine (4,6mDBTP2Pm-II); 3 ,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine (3,5DCzPPy), 1,3,5-tri[3-(3-pyridyl)phenyl]benzene (TmPyPB), 3 Heterocyclic compounds having a pyridine skeleton, such as ,3',5,5'-tetra[(m-pyridyl)-phen-3-yl]biphenyl (BP4mPy), are examples.

Additionally, examples of the third hole-transporting compound include compounds containing a π-electron-excessive heteroaromatic ring. Specifically, 1,3-bis(N-carbazolyl)benzene, 4,4'-di(N-carbazolyl)biphenyl (CBP), 3,3'-di(N-carbazolyl)bi. Phenyl (mCBP), 1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (TCPB), 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-car Bazole (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'-bicarbazole, 9-([1,1':4' ,1"-terphenyl]-4-yl)-9'-(naphthalen-2-yl)-9H,9'H-3,3'-bicarbazole, 9,9',9"-triphenyl- Compounds having a carbazole skeleton such as 9H,9'H,9"H-3,3':6',3"-tricarbazole are exemplified.

(electron transport layer)

The electron transport layer is a layer through which electrons are injected from the cathode and transports electrons. The electron transport material used in the electron transport layer is required to have high electron affinity, high electron mobility, excellent stability, and a material that is unlikely to generate trapping impurities. Additionally, since low molecular weight compounds tend to crystallize and deteriorate the film quality, compounds with a molecular weight of 400 or more are preferable.

The electron transport layer in the present invention also includes a hole blocking layer that can efficiently prevent the movement of holes. The hole blocking layer and the electron transport layer may be single or may be composed of a plurality of materials laminated.

Examples of electron transport materials include polycyclic aromatic derivatives, styryl-based aromatic ring derivatives, quinone derivatives, phosphorus oxide derivatives, quinolinol complexes such as tris(8-quinolinolato)aluminum(III), benzoquinolinol complexes, and hydroxyl. Various metal complexes such as azole complex, azomethine complex, tropolone metal complex, and flavonol metal complex can be mentioned. In order to reduce the driving voltage and obtain highly efficient light emission, it is preferable to use a compound having a heteroaryl group containing electron-accepting nitrogen. Here, electron-accepting nitrogen refers to a nitrogen atom forming a multiple bond with an adjacent atom. Since the heteroaryl group containing electron-accepting nitrogen has high electron affinity, electrons are easily injected from the cathode, enabling lower voltage driving. Additionally, the supply of electrons to the light-emitting layer increases, increasing the probability of recombination, thereby improving luminous efficiency. Compounds having a heteroaryl group structure containing an electron-accepting nitrogen include, for example, pyridine derivatives, triazine derivatives, pyrazine derivatives, pyrimidine derivatives, quinoline derivatives, quinoxaline derivatives, quinazoline derivatives, naphthyridine derivatives, and benzoquinoline derivatives. , phenanthroline derivatives, imidazole derivatives, oxazole derivatives, thiazole derivatives, triazole derivatives, oxadiazole derivatives, thiadiazole derivatives, benzimidazole derivatives, benzoxazole derivatives, benzthiazole derivatives, phenanthroimida Preferred compounds include sol derivatives and oligopyridine derivatives such as bipyridine and terpyridine. Among them, imidazole derivatives such as tris(N-phenylbenzimidazol-2-yl)benzene, 1,3-bis[(4-tert-butylphenyl)-1,3,4-oxadiazolyl]phenylene, etc. Oxadiazole derivatives of; Triazole derivatives such as N-naphthyl-2,5-diphenyl-1,3,4-triazole; Phenanthroline derivatives such as vasocuproin and 1,3-bis(1,10-phenanthrolin-9-yl)benzene; Benzoquinoline derivatives such as 2,2'-bis(benzo[h]quinolin-2-yl)-9,9'-spirobifluorene; Bipyridine derivatives such as 2,5-bis(6'-(2',2"-bipyridyl))-1,1-dimethyl-3,4-diphenylsilol; 1,3-bis(4'- (2,2':6'2"-terpyridinyl))terpyridine derivatives such as benzene; Naphthyridine derivatives such as bis(1-naphthyl)-4-(1,8-naphthyridin-2-yl)phenylphosphine oxide and triazine derivatives are preferably used from the viewpoint of electron transport ability.

In addition, it is more preferable if the electron transport material has a condensed polycyclic aromatic skeleton because the glass transition temperature is improved and the electron mobility is large, making it possible to lower the voltage. As such a condensed polycyclic aromatic skeleton, a fluoranthene skeleton, anthracene skeleton, pyrene skeleton, or phenanthroline skeleton is preferable, and a fluoranthene skeleton or phenanthroline skeleton is particularly preferable.

The electron transport material may be used alone or in combination of two or more types. Additionally, the electron transport layer may contain a donor material. Here, the donor material is a compound that facilitates electron injection from the cathode or electron injection layer into the electron transport layer by improving the electron injection barrier, and also improves the electrical 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 quinolinol, alkaline earth metals, inorganic salts containing alkaline earth metals, Examples include complexes of alkaline earth metals and organic substances, rare earth metals such as Eu and Yb, inorganic salts containing rare earth metals, and complexes of rare earth metals and organic substances. As the donor material, metallic lithium, rare earth metal or lithium quinolinol (Liq) is particularly preferred.

(electron injection layer)

In the present invention, an electron injection layer may 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 is made of a compound having a heteroaryl ring structure containing electron-accepting nitrogen or the donor material. For example, a phenanthroline derivative represented by general formula (4) described later is preferred.

Additionally, an insulator or semiconductor inorganic material can be used in the electron injection layer. The use of these materials is preferable because short circuiting of the light emitting element can be prevented and electron injection properties can be improved.

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

(charge generation layer)

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

The n-type charge generation layer includes an n-type dopant and an n-type host, and these can be made of conventional materials. For example, the donor material exemplified as the material of the electron transport layer is suitably used as the n-type dopant. Among these, alkali metals or salts thereof and rare earth metals are preferable, and materials selected from metal lithium, lithium fluoride (LiF), lithium quinolinol (Liq) and metal ytterbium are more preferable. Additionally, as the n-type host, those exemplified as electron transport materials are suitably used. Among these, materials selected from triazine derivatives, phenanthroline derivatives and oligopyridine derivatives are preferable, phenanthroline derivatives or terpyridine derivatives are more preferable, and phenanthroline derivatives represented by the following general formula (4) are even more preferable. do. That is, it is preferable that the charge generation layer contains a phenanthroline derivative represented by 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 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. Among Ar ² , the positions of substitution by p phenanthrolyl groups are arbitrary positions.

Examples of the aromatic hydrocarbon group and heteroaromatic ring group include those described in the examples of the aryl group and heteroaryl group described above, but are not limited thereto. The aromatic hydrocarbon group or heteroaromatic group may further have a substituent other than the phenanthryl group.

From the viewpoint of sublimation and thin film formation, p is preferably 2.

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

The p-type charge generation layer includes a p-type dopant and a p-type host, and conventional materials can be used. For example, as a p-type dopant, the acceptor material exemplified as the material of the hole injection layer, iodine, FeCl ₃ , FeF ₃ , SbCl ₅ , etc. are suitably used. Specifically, HAT-CN6, F4-TCNQ, tetracyanoquinodimethane derivatives, radialene derivatives, iodine, FeCl ₃ , FeF ₃ , SbCl ₅ , etc. are mentioned. Among these, HAT-CN6, (2E,2'E,2"E)-2,2',2"-(cyclopropane-1,2,3-triylidene)tris(2-(perfluorophenyl) )-acetonitrile), (2E,2'E,2"E)-2,2',2"-(cyclopropane-1,2,3-triylidene)tris(2-(4-cyano purple Radialene derivatives such as (luorophenyl)-acetonitrile) are more preferable. A thin film of p-type dopant may be formed, and the film thickness is preferably 10 nm or less. Additionally, as a p-type host, an arylamine derivative is preferable.

(Method of forming light emitting element)

The formation method of each layer constituting the light emitting device may be either a dry process or a wet process, and is not particularly limited, such as resistance heating evaporation, electron beam evaporation, sputtering, molecular stacking, coating, inkjet, or printing methods. However, resistance heating evaporation is usually preferable in terms of device characteristics.

The thickness of the organic layer cannot be limited because it depends on the resistance value of the light-emitting material, but is preferably 1 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 devices)

The light-emitting device according to the embodiment of the present invention has a function of converting electrical energy into light. Here, direct current is mainly used as electrical energy, but pulse current or alternating current can also be used. There are no particular restrictions on the current and voltage values, and the required characteristic values vary depending on the purpose of the device, but it is desirable to obtain high luminance at low voltage from the viewpoint of power consumption and lifespan of the device.

In the light-emitting device according to the embodiment of the present invention, from the viewpoint of improving color purity, the half width of the luminescence spectrum when energized is preferably 60 nm or less, more preferably 50 nm or less, further preferably 45 nm or less, and especially 30 nm or less. desirable.

Since the light emitting device of the present invention has a narrow half width of the light emission spectrum, it is more preferable to use it in a top emission type light emitting device. In a top emission type light emitting device, the narrower the half width is, the higher the luminous efficiency is due to the resonance effect caused by the micro cavity. Therefore, it becomes possible to achieve both high color purity and high luminous efficiency.

(Use of light-emitting device)

The light-emitting element according to the embodiment of the present invention is suitably used as a display device, such as a display displaying in a matrix and/or segment manner, for example.

Additionally, the light-emitting device according to the embodiment of the present invention is also preferably used as a backlight for various devices. Backlights are mainly used to improve the visibility of display devices such as displays that do not self-emit, and are used in display devices such as liquid crystal displays, clocks, audio devices, automobile panels, display boards, and signs. In particular, the light-emitting element of the present invention is preferably used in liquid crystal displays, and among them, backlights for personal computers whose thickness is being considered, and can provide backlights that are thinner and lighter than conventional ones.

Additionally, the light emitting element according to the embodiment of the present invention is also preferably used as various lighting devices. The light-emitting device according to the embodiment of the present invention is capable of achieving both high luminous efficiency and high color purity, and can also be thinner and lighter, making it possible to realize a lighting device that combines low power consumption, vivid luminous color, and high design.

Example

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

Synthesis Example 1

Method for synthesis of compound D-1

Compound D-1 was synthesized according to the reaction scheme below.

5.35 g of 2,6-dibromobenzaldehyde, 7.40 g of 4-t-butylphenylboronic acid, 5.38 g of sodium carbonate, 100 mL of dimethoxyethane, and 20 mL of water were added to the flask and purged with nitrogen. 142 mg of bis(triphenylphosphine)palladium(II) dichloride was added thereto, and the mixture was refluxed for 4 hours. The reaction solution was cooled to room temperature, the organic layer was separated, dried over magnesium sulfate, filtered, and the solvent was distilled off. Methanol was added to the obtained reaction product and filtered to obtain 4.03 g of 2,6-bis(p-t-butylphenyl)benzaldehyde as a white solid.

4.03 g of 2,6-bis(pt-butylphenyl)benzaldehyde and 2.17 g of 2,4-dimethylpyrrole thus obtained were placed in a reaction vessel, 360 mL of dichloromethane and 5 drops of trifluoroacetic acid were added, and the mixture was incubated at room temperature for 1 week. It was stirred. Additionally, 2.70 g of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) was added and stirred at room temperature for 4 days. After that, it was filtered and the solvent was distilled off. To the obtained reaction product, 360 mL of dichloromethane and 5.90 mL of diisopropylethylamine were added and stirred at room temperature for 30 minutes. Additionally, 4.10 mL of boron trifluoride diethyl ether complex was added and stirred at room temperature for 4 hours, and then the solvent was distilled off. After removing, water was added and stirred. The organic layer was separated and washed with saturated saline solution. This organic layer was dried with magnesium sulfate, filtered, and the solvent was distilled off. The obtained reaction product was purified by silica gel chromatography to obtain 580 mg 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-1, a pyromethene boron complex.

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 luminescent properties of compound D-1 in solution are shown below.

Absorption spectrum (solvent: toluene): λmax 513nm

Fluorescence spectrum (solvent: toluene): λmax 526nm, half width 23nm

Fluorescence quantum yield (solvent: toluene, excitation light: 460 nm): 100%.

Sublimation purification was performed to further increase purity. A metal container containing compound D-1 was installed in a glass tube, and this was heated at 190°C under a pressure of 1×10 ^-3 Pa using an oil diffusion pump to sublimate compound D-1. The solid attached to the glass tube wall was recovered and its purity was confirmed to be 99% by LC-MS analysis.

Synthesis Example 2

Method for synthesis of compound D-2

Compound D-2 was synthesized according to the reaction scheme below.

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

9.76 g of 2,4,6-tri(pt-butylphenyl)benzaldehyde and 5.54 g of 2,4-dimethylpyrrole obtained in this way were placed in a reaction vessel, 200 mL of toluene and 5 drops of trifluoroacetic acid were added, and the mixture was incubated at 40°C. After stirring for 30 minutes, water was added and stirred, and the organic layer was separated and washed with saturated saline solution. This organic layer was dried with magnesium sulfate, filtered, and the solvent was distilled off. The obtained reaction product, 8.81 g of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), and 200 mL of toluene were added to a flask and stirred at 40°C for 30 minutes. After that, 17.2 mL of diisopropylethylamine and 12.2 mL of boron trifluoride diethyl ether complex were added and stirred at room temperature for 30 minutes, then water was added and stirred. The organic layer was separated and washed with saturated saline solution. This organic layer was dried with magnesium sulfate, filtered, and the solvent was distilled off. The obtained reaction product was purified by silica gelation 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, a pyromethene 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 luminescent properties of compound D-2 in solution are shown below.

Absorption spectrum (solvent: toluene): λmax 513nm

Fluorescence spectrum (solvent: toluene): λmax 527nm, half width 22nm

Fluorescence quantum yield (solvent: toluene, excitation light: 460 nm): 100%.

Sublimation purification was performed to further increase purity. A metal container containing compound D-2 was installed in a glass tube, and this was heated at 240°C under a pressure of 1×10 ^-3 Pa using an oil diffusion pump to sublimate compound D-2. The solid attached to the glass tube wall was recovered and its purity was confirmed to be 99% by LC-MS analysis.

The pyromethene boron complex used in the following examples and comparative examples is the compound shown below. Additionally, Table 1 shows the molecular weight and emission characteristics of these pyromethene boron complexes measured in toluene solutions.

Example 1

(Fluorescent light emitting device evaluation)

A glass substrate (manufactured by Geomatec Co., Ltd., 11 Ω/□, sputtered product) on which 165 nm of ITO transparent conductive film was deposited as an anode was cut into 38 × 46 mm and etched. The obtained substrate was ultrasonic cleaned with "Semicoclean 56" (trade name, manufactured by Furuuchi Chemical Co., Ltd.) for 15 minutes, then washed with ultrapure water and dried.

This substrate was treated with UV-ozone for 1 hour immediately before device fabrication, installed in a vacuum evaporation device, and evacuated until the pressure in the device became 5×10 ^-4 Pa or less. By the resistance heating method, 10 nm of HAT-CN6 was first deposited as a hole injection layer, and 50 nm of HT-1 was deposited as a hole transport layer. Next, as a light emitting layer, H-1 as a host material and compound D-1 as a dopant material were deposited to a thickness of 20 nm at a dope concentration of 1.0% by weight. Additionally, ET-1 was used as an electron transport layer and 2E-1 was used as a donor material, and the ET-1 and 2E-1 were laminated to a thickness of 30 nm at a deposition rate ratio of 1:1. Next, 0.5 nm of 2E-1 was deposited as an electron injection layer, and then 1000 nm of magnesium and silver were co-deposited to serve as a cathode, and a 5 x 5 mm square device was produced.

When this light emitting device was made to emit light at 1000 cd/m2, the light emission characteristics were a peak emission wavelength of 529 nm, a half width of 26 nm, and an external quantum efficiency of 4.0%. In addition, durability was evaluated by continuously applying a current with an initial luminance of 1000 cd/m2 and at a time when the luminance was 90% of the initial luminance (hereinafter referred to as LT90). As a result, the LT90 of this light emitting device was 99 hours. In addition, in the above, HAT-CN6, HT-1, H-1, ET-1, and 2E-1 are compounds shown below, respectively.

Examples 2 to 15, Comparative Examples 1 to 3

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

As can be seen with reference to Table 2, in Examples 1 to 15, compared to Comparative Examples 1 to 3, the external quantum efficiency and device durability (LT90) were significantly improved while maintaining a small half width. In this regard, it can be seen that according to the present invention, a light emitting device with high color purity, high luminous efficiency, and high device durability can be obtained.

(Evaluation of thermally activated delayed fluorescent device)

Example 16

A glass substrate (manufactured by Geomatec Co., Ltd., 11 Ω/□, sputtered product) on which 100 nm of an ITO transparent conductive film was deposited as an anode was cut into 38 × 46 mm and etched. The obtained substrate was ultrasonic cleaned for 15 minutes with "Semicoclean 56" (trade name, manufactured by Furuuchi Chemical Co., Ltd.) and then washed with ultrapure water.

This substrate was treated with UV-ozone for 1 hour immediately before fabricating the device, placed in a vacuum evaporation device, and evacuated until the vacuum level in the device became 5×10 ^-4 Pa or less. By the resistance heating method, 10 nm of HAT-CN6 was first deposited as a hole injection layer, and 40 nm of HT-1 was deposited as a hole transport layer. Next, as a light emitting layer, host material H-2, compound D-1, and compound H-3, which is a TADF material, were deposited at a weight ratio of 79.5:0.5:20 to a thickness of 30 nm. In addition, as an electron transport layer, compound ET-1 was used as an electron transport material and 2E-1 was used as a donor material, and the deposition rate ratio of compound ET-1 and 2E-1 was 1:1, so that it was laminated to a thickness of 50 nm. . Next, 0.5 nm of 2E-1 was deposited as an electron injection layer, and then 1000 nm of magnesium and silver were co-deposited to serve as a cathode, and a 5 x 5 mm square device was produced.

When this light emitting device was made to emit light at 1000 cd/m2, the light emission characteristics were as follows: peak emission wavelength of 529 nm, half width of 28 nm, external quantum efficiency of 14.2%, and LT90 of 80 hours. In addition, in the above, H-2 and H-3 are compounds shown below.

Examples 17 to 20, Comparative Examples 4 to 6

A light-emitting device was manufactured and evaluated in the same manner as in Example 16, except that the compounds shown in Table 3 were used as dopant materials. The results are shown in Table 3.

As can be seen with reference to Table 3, in Examples 16 to 20, compared to Comparative Examples 4 to 6, the external quantum efficiency and device durability (LT90) were significantly improved while maintaining a small half width. In this regard, it can be seen that according to the present invention, a light emitting device with high color purity, high luminous efficiency, and high device durability can be obtained.

As described above, it was shown that the present invention enables the production of a light-emitting device with high color purity, luminous efficiency, and device durability. As a result, it was shown that luminous efficiency can be increased in the manufacture of display devices such as displays and lighting devices.

(Tandem type fluorescent light emitting device evaluation)

Example 21

A glass substrate (manufactured by Geomatec Co., Ltd., 11 Ω/□, sputtered product) on which 165 nm of ITO transparent conductive film was deposited as an anode was cut into 38 mm x 46 mm and etched. The obtained substrate was ultrasonic cleaned for 15 minutes using "Semicoclean 56" (trade name, manufactured by Furuuchi Chemical Co., Ltd.) and then washed with ultrapure water.

This substrate was treated with UV-ozone for 1 hour immediately before fabricating the device, placed in a vacuum evaporation device, and evacuated until the vacuum level in the device became 5×10 ^-4 Pa or less. By the resistance heating method, 5 nm of HAT-CN6 was first deposited as a hole injection layer, and then 50 nm of HT-1 was deposited as a hole transport layer. Next, as a hole blocking layer, H-1 was deposited to a thickness of 10 nm, and as a light emitting layer, the host material H-1 and the dopant compound D-1 were deposited at a weight ratio of 99.5:0.5 to a thickness of 20 nm. Additionally, ET-1 was laminated to a thickness of 10 nm as an electron blocking layer, and compound ET-3 was laminated to a thickness of 35 nm as an electron transport layer. Subsequently, as an n-type charge generation layer, compound ET-3 as an n-type host and metal lithium as an n-type dopant were laminated for 10 nm at a deposition rate ratio of 99:1. Additionally, 10 nm of HAT-CN6 was laminated as a p-type charge generation layer. On top of this, as above, a 50 nm hole transport layer, a 10 nm hole blocking layer, and a 20 nm light emitting layer were formed. Additionally, ET-2 was deposited to a thickness of 10 nm as an electron blocking layer, and ET-3 was deposited to a thickness of 35 nm as an electron transport layer. Next, 0.5 nm of 2E-1 was deposited as an electron injection layer, and then 1000 nm of magnesium and silver were co-deposited to serve as a cathode, and a 5 mm x 5 mm square tandem light emitting device was produced.

When this light emitting device was made to emit light at 1000 cd/m2, the light emission characteristics were as follows: peak emission wavelength of 530 nm, half width of 25 nm, external quantum efficiency of 4.3%, and LT90 of 110 hours. It was confirmed that durability was improved compared to Example 1, which had only one light-emitting layer. In addition, in the above, ET-2 and ET-3 are compounds shown below.

Claims (11)

Pyromethene boron complex, represented by general formula (1):

R ¹ to R ⁶ are each independently 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, an aryl ether group, an arylthioether group. , an aryl group, a heteroaryl group, an amino group, a silyl group, a siloxanyl group, and a boryl group; These groups may further have substituents; However, at least one of R ¹ to R ⁴ is a hydrogen atom or an alkyl group;
X ^{1 and} , is selected from the group consisting of heteroaryl group, halogen and cyano group; These groups may further have substituents;
R ⁷ is represented by the following general formula (2);

R ⁸ to R ¹⁰ are each independently 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, an aryl ether group, an arylthioether group. , aryl group, heteroaryl group, halogen, cyano group, aldehyde group, acyl group, carboxyl group, ester group, amide group, sulfonyl group, sulfonic acid ester group, sulfonamide group, amino group, nitro group, silyl group, siloxanyl group, bo selected from the group consisting of a reel group and a phosphine oxide group; These groups may further have substituents;
R ¹¹ is an alkyl group, cycloalkyl group, heterocyclic group, alkenyl group, cycloalkenyl group, alkynyl group, hydroxyl group, thiol group, alkoxy group, alkylthio group, arylether group, arylthioether group, aryl group, heteroaryl group, halogen , cyano group, aldehyde group, acyl group, carboxyl group, ester group, amide group, sulfonyl group, sulfonic acid ester group, sulfonamide group, amino group, nitro group, silyl group, siloxanyl group, boryl group and phosphine oxide group. is chosen; These groups may further have substituents;
Ar ¹ is a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group. The pyromethene boron complex according to claim 1, wherein R ¹¹ is a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group. The pyromethene boron complex according to claim 1, wherein R ¹ and R ⁴ are each independently a hydrogen atom or an alkyl group. The pyromethene boron complex according to claim 1, wherein R ² and R ³ are an alkyl group. A device having an anode, a cathode, and a light-emitting layer between the anode and the cathode, wherein the light-emitting layer emits light by electrical energy, wherein the light-emitting layer contains the pyromethene boron complex according to any one of claims 1 to 4. A light emitting device containing. The method of claim 5, wherein the light-emitting layer includes a first compound and a second compound, the first compound is a heat-activated delayed fluorescent compound, and the second compound is a pyromethene boron complex represented by the general formula (1). Phosphorus, light emitting device. The light emitting device according to claim 6, wherein the thermally activated delayed fluorescent compound is a compound having an electron donating moiety and an electron withdrawing moiety in the same molecule. The light-emitting device according to claim 5, comprising two or more light-emitting layers between the anode and the cathode, and one or more charge generation layers between each light-emitting layer. The light-emitting device according to claim 8, wherein the charge generation layer contains a phenanthroline derivative represented by 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 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; Among Ar ² , the positions of substitution by p phenanthrolyl groups are arbitrary positions. A display device comprising the light emitting element according to claim 5. A lighting device comprising the light-emitting element according to claim 5.