JP2024058588A - Polycyclic aromatic compound - Google Patents

Abstract

To provide a novel compound useful as materials for organic devices such as an organic EL element.SOLUTION: The present invention provides a polycyclic aromatic compound represented by the formula (1). A-D rings each represent a substituted/unsubstituted aryl ring or a substituted/unsubstituted heteroaryl ring; X represents >N-RNX (RNX is a substituted/unsubstituted aryl or a substituted/unsubstituted heteroaryl or the like) or the like; RNX may bind to at least one of A ring and B ring through a linking group or a single bond; and L represents >C(-RCL)2 (RCL represents a substituted/unsubstituted aryl or an unsubstituted alkyl or the like, and two RCX may bond together to form a ring) or the like. In the formula (1), at least one selected from the group consisting of the aryl ring and the heteroaryl ring may be condensed with at least one cycloalkane, and in the formula (1), at least one hydrogen may be substituted with deuterium.SELECTED DRAWING: None

Description

The present invention relates to a polycyclic aromatic compound. The present invention also relates to organic devices, such as organic electroluminescent elements, organic field-effect transistors, and organic thin-film solar cells, that use the polycyclic aromatic compound, as well as display devices and lighting devices.

Display devices using electroluminescent light-emitting elements have been extensively studied because they can be made thin and energy-efficient. Furthermore, organic electroluminescent devices made from organic materials have been actively studied because they can be easily made large and lightweight. In particular, there has been active research into the development of organic materials that have the luminescence properties of blue and green, which are one of the three primary colors of light, and organic materials that have the ability to transport charges such as holes and electrons (potential to become semiconductors or superconductors), regardless of whether they are polymeric or low-molecular-weight compounds.

An organic EL element has a structure consisting of a pair of electrodes consisting of an anode and a cathode, and one or more layers containing an organic compound that are disposed between the pair of electrodes. Layers containing organic compounds include a light-emitting layer and a charge transport/injection layer that transports or injects charges such as holes and electrons, and various organic materials suitable for these layers have been developed.

Among these, Patent Documents 1 and 2 disclose that polycyclic aromatic compounds containing boron are useful as materials for organic electroluminescent devices and the like. It has been reported that organic electroluminescent devices containing these polycyclic aromatic compounds have good external quantum efficiency.

International Publication No. 2015/102118 International Publication No. 2021/075856

As described above, various materials have been developed for use in organic EL elements. However, in order to increase the options for materials for organic EL elements, it is desirable to develop materials made of compounds different from conventional ones.
An object of the present invention is to provide a novel compound useful as a material for organic devices such as organic EL elements.

The present inventors conducted extensive research to solve the above problems, and discovered that a polycyclic aromatic compound that enables the manufacture of organic EL elements with even longer life can be obtained from a compound having a boron-containing structure similar to the compound described in Patent Document 1, thereby completing the present invention. In other words, the present invention provides the following polycyclic aromatic compounds, and further provides materials for organic devices that contain the following polycyclic aromatic compounds.

<1> A polycyclic aromatic compound represented by formula (1);

In formula (1),
ring A, ring B, ring C, and ring D each independently represent a substituted or unsubstituted aryl ring or a substituted or unsubstituted heteroaryl ring;
X is >N-R ^NX , >O, >C(-R ^CX ) ₂ , >Si(-R ^IX ) ₂ , >S, or >Se, R ^NX is hydrogen, a substituted or unsubstituted aryl, a substituted or unsubstituted heteroaryl, a substituted or unsubstituted alkyl, or a substituted or unsubstituted cycloalkyl, R ^CX and R ^IX are each independently hydrogen, a substituted or unsubstituted aryl, a substituted or unsubstituted heteroaryl, a substituted or unsubstituted alkyl, or a substituted or unsubstituted cycloalkyl, two R ^CX may be bonded to each other to form a ring, two R ^IX may be bonded to each other to form a ring, and R ^NX , R ^CX , and R ^IX may be bonded to at least one selected from the group consisting of ring A and ring B via a linking group or a single bond,
L is >C(-R ^CL ) ₂ , >NR ^NL , >O, >S, >C=O, >S=O, >S(=O) ₂ , or >Se; R ^CL is hydrogen, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted alkyl, or substituted or unsubstituted cycloalkyl; two R ^CLs may be bonded to each other to form a ring; R ^NL is hydrogen, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted alkyl, or substituted or unsubstituted cycloalkyl;
At least one selected from the group consisting of aryl rings and heteroaryl rings in formula (1) may be condensed with at least one cycloalkane, the cycloalkane may be substituted with at least one substituent, and at least one -CH ₂ - in the cycloalkane may be replaced with -O-;
At least one hydrogen in formula (1) may be replaced with deuterium.

<2> The polycyclic aromatic compound according to <1>, wherein the ring A, the ring B, the ring C and the ring D are all substituted or unsubstituted benzene rings.
<3> The polycyclic aromatic compound according to <1> or <2>, wherein L is C(—R ^CL ) ₂ , >NR ^NL , >O, or >S.
<4> The polycyclic aromatic compound according to <3>, wherein L is >C(—R ^CL ) ₂ .
<5> The polycyclic aromatic compound according to <4>, wherein all R ^CLs are substituted or unsubstituted phenyl, all R CLs are substituted or unsubstituted phenyl and two R ^CLs are bonded to each other, or all R ^CLs are methyl.
<6> The polycyclic aromatic compound according to any one of <1> to <5>, wherein X is >N-R ^NX , and R ^NX is bonded to only one of ring A and ring B, or to neither of them.

式中、Ｍｅはメチルであり、ｔＢｕはｔ－ブチルである。 <7> The polycyclic aromatic compound according to <6>, represented by any one of the following formulas:

In the formula, Me is methyl and tBu is t-butyl.

式中、Ｍｅはメチルであり、ｔＢｕはｔ－ブチルである。 <8> The polycyclic aromatic compound according to <1>, represented by any one of the following formulas:

In the formula, Me is methyl and tBu is t-butyl.

<9> An organic electroluminescence device comprising a pair of electrodes consisting of an anode and a cathode, and an organic layer disposed between the pair of electrodes, the organic layer containing the polycyclic aromatic compound according to any one of <1> to <8>.
<10> The organic electroluminescent device according to <9>, wherein the organic layer is a light-emitting layer.
<11> The organic electroluminescent device according to <10>, wherein the light-emitting layer contains a host material and the polycyclic aromatic compound as a dopant material.
<12> The organic electroluminescent device according to <11>, wherein the host material is an anthracene compound, a fluorene compound, or a dibenzochrysene compound.
<13> The organic electroluminescent device according to <10>, wherein the light-emitting layer contains a host material, a thermally activated delayed fluorescent material or a phosphorescent material as an assisting dopant, and the polycyclic aromatic compound as an emitting dopant.
<14> A display device or a lighting device comprising the organic electroluminescent device according to any one of <9> to <13>.

The present invention provides a novel polycyclic aromatic compound that is useful as a material for organic devices such as organic electroluminescent devices. The polycyclic aromatic compound of the present invention can be used in the manufacture of organic devices such as organic electroluminescent devices.

FIG. 1 is a schematic cross-sectional view showing an example of an organic electroluminescent device.

The present invention will be described in detail below. The following description of the constituent elements may be based on a representative embodiment or a specific example, but the present invention is not limited to such an embodiment. In this specification, a numerical range expressed using "to" means a range including the numerical values before and after "to" as the lower and upper limits. In this specification, "hydrogen" in the explanation of the structural formula means "hydrogen atom (H)". Similarly, "carbon atom (C)" may be referred to as "carbon".
In this specification, the term "adjacent groups" refers to two groups bonded to two adjacent atoms (two atoms directly bonded by a covalent bond) in a structural formula.

In this specification, "Me" is methyl, "Et" is ethyl, "nBu" is n-butyl (normal butyl), "tBu" is t-butyl (tertiary butyl), "iBu" is isobutyl, "secBu" is secondary butyl, "nPr" is n-propyl (normal propyl), "iPr" is isopropyl, "tAm" is t-amyl, "2EH" is 2-ethylhexyl, "tOct" is t-octyl, "Ph" is phenyl, "Mes" is mesityl (2,4,6-trimethylphenyl), "Ad" is 1-adamantyl, "Tf" is trifluoromethanesulfonyl, "TMS" is trimethylsilyl, and "D" is deuterium.
In this specification, the organic electroluminescent element may be referred to as an organic EL element.

In this specification, chemical structures and substituents are sometimes expressed by the number of carbon atoms, but when a chemical structure is substituted with a substituent or when a substituent is further substituted with a substituent, the number of carbon atoms means the number of carbon atoms in each of the chemical structure and the substituent, and does not mean the total number of carbon atoms in the chemical structure and the substituent, or the total number of carbon atoms in the substituent and the substituent. For example, "substituent B of carbon number Y substituted with substituent A of carbon number X" means that "substituent B of carbon number Y" is substituted with "substituent A of carbon number X", and the carbon number Y is not the total number of carbon atoms in the substituents A and B. Also, for example, "substituent B of carbon number Y substituted with substituent A" means that "substituent B of carbon number Y" is substituted with "substituent A (with no carbon number limit)", and the carbon number Y is not the total number of carbon atoms in the substituents A and B.

<Explanation of Rings and Substituents>
First, the rings and substituents used in the present specification will be described in detail below.
As used herein, the "aryl ring" includes, for example, an aryl ring having 6 to 30 carbon atoms, preferably an aryl ring having 6 to 16 carbon atoms, more preferably an aryl ring having 6 to 12 carbon atoms, and particularly preferably an aryl ring having 6 to 10 carbon atoms.

Specific examples of "aryl rings" include a monocyclic benzene ring, a bicyclic bicyclic bicyclic naphthalene ring and an indene ring, a tricyclic terphenyl ring (m-terphenyl, o-terphenyl, p-terphenyl), a fused tricyclic acenaphthylene ring, a fluorene ring, a phenalene ring, a phenanthrene ring, and an anthracene ring, a fused tetracyclic tricyclic triphenylene ring, a pyrene ring, a naphthacene ring, and a chrysene ring, and a fused pentacyclic perylene ring and a pentacene ring. In addition, the fluorene ring, benzofluorene ring, and indene ring each include a structure in which a fluorene ring, a benzofluorene ring, and a cyclopentane ring are spiro-bonded. In addition, the fluorene ring, benzofluorene ring, and indene ring also include those in which two of the two hydrogen atoms of the methylene in the structure are replaced by alkyl such as methyl as the first substituent described below, resulting in a dimethylfluorene ring, dimethylbenzofluorene ring, dimethylindene ring, etc.

In this specification, examples of the "heteroaryl ring" include heteroaryl rings having 2 to 30 carbon atoms, preferably heteroaryl rings having 2 to 25 carbon atoms, more preferably heteroaryl rings having 2 to 20 carbon atoms, still more preferably heteroaryl rings having 2 to 15 carbon atoms, and particularly preferably heteroaryl rings having 2 to 10 carbon atoms. In addition, examples of the "heteroaryl ring" include heterocycles containing, in addition to carbon, 1 to 5 heteroatoms selected from oxygen, sulfur, nitrogen, boron, selenium, phosphorus, and tellurium as ring-constituting atoms.

Specific examples of the "heteroaryl ring" include a pyrrole ring, an oxazole ring, an isoxazole ring, a thiazole ring, an isothiazole ring, an imidazole ring, an oxadiazole ring (such as a furazan ring), a thiadiazole ring, a triazole ring, a tetrazole ring, a pyrazole ring, a pyridine ring, a pyrimidine ring, a pyridazine ring, a pyrazine ring, a triazine ring, an indole ring, an isoindole ring, a 1H-indazole ring, a benzimidazole ring, a benzoxazole ring, a benzothiazole ring, a 1H-benzotriazole ring, a quinoline ring, an isoquinoline ring, a cinnoline ring, a quinazoline ring, a quinoxaline ring, a phthalazine ring, a naphthyridine ring, a purine ring, a pteridine ring, a carbazole ring, an acridine ring, a phenoxathiin ring, a phenoxazine ring, a phenothiazine ring, a phenazine ring, a phenazasiline ring, an indolizine ring, a furan ring, a benzofuran ring, an isobenzofuran ring, a dibenzofuran ring, and a thiophene ring. , a benzothiophene ring, a dibenzothiophene ring, a thianthrene ring, an indolocarbazole ring, a benzoindolocarbazole ring, a dibenzoindolocarbazole ring, a naphthobenzofuran ring, a dioxin ring, a dihydroacridine ring, a xanthene ring, a thioxanthene ring, a dibenzodioxin ring, a dioxaboranaphthoanthracene ring (such as a 5,9-dioxa-13b-bora-13bH-naphtho[3,2,1-de]anthracene ring), a benzoselenophene ring, Examples of the ring include an aryl ring, a dibenzoselenophene ring, an azacarbazole ring, an azadibenzothiophene ring, an azadibenzofuran ring, an azadibenzoselenophene ring, an azatriphenylene ring, an imidazoimidazole ring, an indoloindole ring, a benzofurocarbazole ring, a benzothienocarbazole ring, an indenocarbazole ring, a selenophenocarbazole ring, a spiro[fluorene-9,9'-xanthene] ring, a spirobi[silafluorene] ring, etc. In addition, it is also preferable that the dihydroacridine ring, the xanthene ring, and the thioxanthene ring have two of the two hydrogen atoms of the methylene in the structure replaced by an alkyl such as methyl as the first substituent described later, to form a dimethyldihydroacridine ring, a dimethylxanthene ring, a dimethylthioxanthene ring, etc. In addition, bicyclic rings such as bipyridine ring, phenylpyridine ring, and pyridylphenyl ring, and tricyclic rings such as terpyridyl ring, bispyridylphenyl ring, and pyridylbiphenyl ring are also included as "heteroaryl rings." In addition, "heteroaryl ring" also includes a pyran ring.

In this specification, a substituent may be substituted with a further substituent. For example, a particular substituent may be described as "substituted or unsubstituted". This means that the particular substituent is substituted with at least one further substituent, or is not substituted. In a similar sense, the term "optionally substituted" may also be used. In this specification, the particular substituent may be referred to as a "first substituent" and the further substituent may be referred to as a "second substituent".

In this specification, the substituent group Zα consists of the substituents of the substituent group Z and the substituent represented by the formula (A30) described below.

In the present specification, the substituent group Z is
an aryl optionally substituted with at least one group selected from the group consisting of aryl, heteroaryl, alkyl, cycloalkyl, cyano, and halogen;
heteroaryl optionally substituted with at least one group selected from the group consisting of aryl, heteroaryl, alkyl, cycloalkyl, cyano, and halogen;
diarylamino which may be substituted with at least one group selected from the group consisting of aryl, heteroaryl, alkyl, cycloalkyl, cyano, and halogen (two aryls may be bonded to each other via a linking group);
diheteroarylamino optionally substituted with at least one group selected from the group consisting of aryl, heteroaryl, alkyl, cycloalkyl, cyano, and halogen (two heteroaryls may be bonded to each other via a linking group);
arylheteroarylamino which may be substituted with at least one group selected from the group consisting of aryl, heteroaryl, alkyl, cycloalkyl, cyano, and halogen (the aryl and heteroaryl may be bonded to each other via a linking group);
diarylboryl optionally substituted with at least one group selected from the group consisting of aryl, heteroaryl, alkyl, cycloalkyl, cyano, and halogen (two aryls may be bonded via a single bond or a linking group);
an alkyl group optionally substituted with at least one group selected from the group consisting of aryl, heteroaryl, cycloalkyl, cyano, and halogen;
cycloalkyl optionally substituted with at least one group selected from the group consisting of aryl, heteroaryl, alkyl, cycloalkyl, cyano, and halogen;
alkoxy optionally substituted with at least one group selected from the group consisting of aryl, heteroaryl, cycloalkyl, cyano, and halogen;
aryloxy optionally substituted with at least one group selected from the group consisting of aryl, heteroaryl, alkyl, cycloalkyl, cyano, and halogen;
Consists of substituted silyl, cyano, and halogen.
The aryl as the second substituent in each group of the substituent group Z may be further substituted with an aryl, heteroaryl, alkyl, cycloalkyl, cyano, or halogen; similarly, the heteroaryl as the second substituent may be substituted with an aryl, heteroaryl, alkyl, cycloalkyl, cyano, or halogen.

In this specification, when the term "substituent" is used, the type of the substituent is not particularly limited, but unless otherwise specified, it may be any group selected from the substituent group Z. For example, when a group that is "substituted or unsubstituted" is substituted, the group may be substituted with at least one group selected from the substituent group Z.

In this specification, "aryl" refers to, for example, an aryl having 6 to 30 carbon atoms, and preferably an aryl having 6 to 20 carbon atoms, an aryl having 6 to 16 carbon atoms, an aryl having 6 to 12 carbon atoms, or an aryl having 6 to 10 carbon atoms.

Specific examples of "aryl" include monovalent groups obtained by removing one hydrogen from the above-mentioned "aryl ring." For example, phenyl is a monocyclic ring system, biphenylyl (2-biphenylyl, 3-biphenylyl, or 4-biphenylyl) is a bicyclic ring system, naphthyl (1-naphthyl or 2-naphthyl) is a condensed bicyclic ring system, terphenylyl (m-terphenyl-2'-yl, m-terphenyl-4'-yl, m-terphenyl-5'-yl, o-terphenyl-3'-yl, o-terphenyl-4'-yl, p-terphenyl-2'-yl, m-terphenyl-2-yl, m-terphenyl-3-yl, m-terphenyl-4-yl, o-terphenyl-2-yl, o-terphenyl-3-yl, o-terphenyl-4-yl, p-terphenyl-2-yl, p-terphenyl-3-yl, or p-terphenyl-4-yl) is a condensed tricyclic ring system, acenaphthylene-(1-, 3-, 4-, or 5- m-)yl, fluoren-(1-, 2-, 3-, 4-, or 9-)yl, phenalen-(1- or 2-)yl, phenanthrene-(1-, 2-, 3-, 4-, or 9-)yl, or anthracene-(1-, 2-, or 9-)yl; the tetracyclic ring system quaterphenylyl (5'-phenyl-m-terphenyl-2-yl, 5'-phenyl-m-terphenyl-3-yl, 5'-phenyl-m-terphenyl-4-yl, or m-quaterphenyl); the fused tetracyclic ring system triphenylene-(1- or 2-)yl, pyren-(1-, 2-, or 4-)yl, or naphthacene-(1-, 2-, or 5-)yl; or the fused pentacyclic ring system perylene-(1-, 2-, or 3-)yl, or pentacene-(1-, 2-, 5-, or 6-)yl. Other examples include monovalent spirofluorene groups.

The aryl as the second substituent also includes a structure in which the aryl is substituted with at least one group selected from the group consisting of aryl such as phenyl (specific examples are the groups described above), alkyl such as methyl (specific examples are the groups described later), and cycloalkyl such as cyclohexyl or adamantyl (specific examples are the groups described later).
An example of such a group is a group in which the 9-position of fluorenyl as the second substituent is substituted with an aryl such as phenyl, an alkyl such as methyl, or a cycloalkyl such as cyclohexyl or adamantyl.

The "arylene" is, for example, an arylene having 6 to 30 carbon atoms, and preferably an arylene having 6 to 20 carbon atoms, an arylene having 6 to 16 carbon atoms, an arylene having 6 to 12 carbon atoms, or an arylene having 6 to 10 carbon atoms.
Specific examples of "arylene" include divalent groups obtained by removing one hydrogen from the above-mentioned "aryl" (monovalent group).

"Heteroaryl" is, for example, a heteroaryl having 2 to 30 carbon atoms, and preferably a heteroaryl having 2 to 25 carbon atoms, a heteroaryl having 2 to 20 carbon atoms, a heteroaryl having 2 to 15 carbon atoms, or a heteroaryl having 2 to 10 carbon atoms. "Heteroaryl" contains, in addition to carbon, one or more heteroatoms selected from oxygen, sulfur, nitrogen, etc., as ring-constituting atoms, preferably 1 to 5 heteroatoms.

Specific examples of "heteroaryl" include monovalent groups obtained by removing one hydrogen from the above-mentioned "heteroaryl ring". For example, pyrrolyl, oxazolyl, isoxazolyl, thiazolyl, isothiazolyl, imidazolyl, oxadiazolyl, thiadiazolyl, triazolyl, tetrazolyl, pyrazolyl, pyridyl, pyrimidinyl, pyridazinyl, pyrazinyl, triazinyl, indolyl, isoindolyl, 1H-indazolyl, benzimidazolyl, benzoxazolyl, benzothiazolyl, 1H-benzotriazolyl, quinolinyl, isoquinolinyl, cinnolinyl, quinazolinyl, quinoxalinyl, phenanthrolinyl, phthalazinyl, naphthyridinyl, purinyl, pteridinyl, carbazolyl, Acridinyl, phenoxathiinyl, phenoxazinyl, phenothiazinyl, phenazinyl, phenazasilinyl, indolizinyl, furanyl, benzofuranyl, isobenzofuranyl, dibenzofuranyl, naphthobenzofuranyl, thienyl, benzothienyl, isobenzothienyl, dibenzothienyl, naphthobenzothienyl, monovalent groups of benzophosphole oxide rings, monovalent groups of dibenzophosphole oxide rings, furazanyl, thianthrenyl, indolocarbazolyl, benzoindolocarbazolyl, dibenzoindolocarbazolyl, imidazolinyl, or oxazolinyl. Other examples include monovalent groups of spiro[fluorene-9,9'-xanthene], monovalent groups of spirobi[silafluorene], and monovalent groups of benzoselenophene.

The heteroaryl as the second substituent also includes a structure in which the heteroaryl is substituted with at least one group selected from the group consisting of aryl such as phenyl (specific examples are the groups described above), alkyl such as methyl (specific examples are the groups described below), and cycloalkyl such as cyclohexyl or adamantyl (specific examples are the groups described below).
An example of such a group is a group in which the 9-position of the carbazolyl as the second substituent is substituted with an aryl such as phenyl, an alkyl such as methyl, or a cycloalkyl such as cyclohexyl or adamantyl.Furthermore, the heteroaryl as the second substituent also includes groups in which a nitrogen-containing heteroaryl such as pyridyl, pyrimidinyl, triazinyl, or carbazolyl is further substituted with phenyl or biphenylyl.

The "heteroarylene" is, for example, a heteroarylene having 2 to 30 carbon atoms, and preferably a heteroarylene having 2 to 25 carbon atoms, a heteroarylene having 2 to 20 carbon atoms, a heteroarylene having 2 to 15 carbon atoms, or a heteroarylene having 2 to 10 carbon atoms. In addition, the "heteroarylene" is, for example, a divalent group such as a heterocycle containing, in addition to carbon, 1 to 5 heteroatoms selected from oxygen, sulfur, and nitrogen as ring-constituting atoms.
Specific examples of "heteroarylene" include divalent groups obtained by removing one hydrogen atom from the above-mentioned "heteroaryl" (monovalent group).

The term "diarylamino" refers to an amino group substituted with two aryl groups, and the details of the aryl group can be found in the above description of the "aryl".
The term "diheteroarylamino" refers to an amino group substituted with two heteroaryls. For details of the heteroaryl, the above description of the "heteroaryl" can be cited.
The term "arylheteroarylamino" refers to an amino group substituted with an aryl and a heteroaryl. For details of the aryl and the heteroaryl, the above descriptions of "aryl" and "heteroaryl" can be cited.

The two aryls in the diarylamino as the first substituent may be bonded to each other via a linking group, the two heteroaryls in the diheteroarylamino as the first substituent may be bonded to each other via a linking group, and the aryl and heteroaryl in the arylheteroarylamino as the first substituent may be bonded to each other via a linking group. Here, the expression "bonded via a linking group" means that, for example, the two phenyls in diphenylamino form a bond with a linking group as shown below. This explanation also applies to diheteroarylamino and arylheteroarylamino formed by aryls and heteroaryls.

Specific examples of the linking group include >O, >N-R ^X , >C(-R ^X ) ₂ , -C(-R ^X )=C(-R ^X )-, >Si(-R ^X ) ₂ , >S, >CO, >CS, >SO, >SO ₂ , >SeO, >SeO ₂ , >PO, >B(-R ^X ), and >Se. Each R ^X is independently an alkyl, cycloalkyl, aryl, or heteroaryl, which may be substituted with an alkyl, cycloalkyl, aryl, or heteroaryl. Furthermore, the two R ^Xs in each of >C(-R ^X ) ₂ , -C(-R ^X )=C(-R ^X )-, >Si(-R ^X ) ₂ , and >B(-R ^X ) may be bonded to each other via a single bond or a linking group X ^Y to form a ring. Examples of X ^Y include >O, >N-R ^Y , >C(-R ^Y ) ₂ , >Si(-R ^Y ) ₂ , >S, >CO, >CS, >SO, >SO ₂ , and >Se, and R ^Y is independently alkyl, cycloalkyl, aryl, or heteroaryl, which may be substituted with alkyl, cycloalkyl, aryl, or heteroaryl. However, when X ^Y is >C(-R ^Y ) ₂ or >Si(-R ^Y ) ₂ , the two R ^Ys do not bond to form a ring. Examples of the linking group include alkenylene. Any hydrogen of the alkenylene may be independently substituted with R ^2X , and each R ^2X is independently alkyl, cycloalkyl, substituted silyl, aryl, or heteroaryl, which may be substituted with alkyl, cycloalkyl, substituted silyl, or aryl. The two R ^X 's in -C(-R ^X )=C(-R ^X )- may be bonded to each other to form an aryl (such as a benzene ring) or heteroaryl ring together with the C=C to which they are bonded. That is, -C(-R ^X )=C(-R ^X )- may be an arylene (such as 1,2-phenylene) or heteroarylene.

In addition, in this specification, when the term "diarylamino", "diheteroarylamino", or "arylheteroarylamino" is used, unless otherwise specified, it is assumed that the following explanation is added: "The two aryls of the diarylamino may be bonded to each other via a linking group", "The two heteroaryls of the diheteroarylamino may be bonded to each other via a linking group", and "The aryl and heteroaryl of the arylheteroarylamino may be bonded to each other via a linking group", respectively.

"Diarylboryl" is a boryl substituted with two aryls, and the above description of "aryl" can be cited for details of the aryls. The two aryls may be bonded via a single bond or a linking group (e.g., -CH=CH-, -CR=CR-, -C≡C-, >N-R, >O, >S, >CO, >C=S, >S=O, >S(=O) ₂ , >Se(=O), >Se(=O) ₂ , >P(=O), >B(-R), >C(-R) ₂ , >Si(-R) ₂ , or >Se). Here, R in -CR=CR-, R in >N-R, R in >B(-R), R in >C(-R) ₂ , and R in >Si(-R) are aryl, heteroaryl, diarylamino, alkyl, alkenyl, alkynyl, cycloalkyl, alkoxy, or aryloxy, and at least one hydrogen in the R may be further substituted with aryl, heteroaryl, alkyl, alkenyl, alkynyl, or cycloalkyl. In addition, two adjacent R may be bonded to each other to form a ring, forming a cycloalkylene, arylene, or heteroarylene. For details of the substituents listed here, the explanations of "aryl", "arylene", "heteroaryl", "heteroarylene", and "diarylamino" above, and the explanations of "alkyl", "alkenyl", "alkynyl", "cycloalkyl", "cycloalkylene", "alkoxy", and "aryloxy" below can be cited. In addition, when the term "diarylboryl" is used simply in this specification, unless otherwise specified, it is assumed that the explanation that "the two aryls of the diarylboryl may be bonded to each other via a single bond or a linking group" is added.

"Alkyl" may be either straight-chain or branched-chain, for example, straight-chain alkyl having 1 to 24 carbon atoms or branched-chain alkyl having 3 to 24 carbon atoms, and preferably alkyl having 1 to 18 carbon atoms (branched-chain alkyl having 3 to 18 carbon atoms), alkyl having 1 to 12 carbon atoms (branched-chain alkyl having 3 to 12 carbon atoms), alkyl having 1 to 6 carbon atoms (branched-chain alkyl having 3 to 6 carbon atoms), alkyl having 1 to 5 carbon atoms (branched-chain alkyl having 3 to 5 carbon atoms), alkyl having 1 to 4 carbon atoms (branched-chain alkyl having 3 to 4 carbon atoms), etc.

Specific examples of "alkyl" include methyl, ethyl, n-propyl, isopropyl, 1-ethyl-1-methylpropyl, 1,1-diethylpropyl, 1,1,2-trimethylpropyl, 1,1,2,2-tetramethylpropyl, 1-ethyl-1,2,2-trimethylpropyl, n-butyl, isobutyl, s-butyl, t-butyl, 2-ethylbutyl, 1,1-dimethylbutyl, 3,3-dimethylbutyl, 1,1-diethylbutyl, 1-ethyl-1-methylbutyl, 1-propyl-1-methylbutyl, 1,1,3-trimethylbutyl, 1-ethyl-1,3-dimethylbutyl, n-pentyl, isopentyl, neopentyl, t-pentyl (t-amyl), 1-methylpentyl, 2-propylpentyl, 1,1-dimethylpentyl, 1-ethyl-1-methylpentyl, 1-propyl-1 -methylpentyl, 1-butyl-1-methylpentyl, 1,1,4-trimethylpentyl, n-hexyl, 1-methylhexyl, 2-ethylhexyl, 1,1-dimethylhexyl, 1-ethyl-1-methylhexyl, 1,1,5-trimethylhexyl, 3,5,5-trimethylhexyl, n-heptyl, 1-methylheptyl, 1-hexylheptyl, 1,1-dimethylheptyl, 2,2-dimethylhexyl, Methylheptyl, 2,6-dimethyl-4-heptyl, n-octyl, t-octyl (1,1,3,3-tetramethylbutyl), 1,1-dimethyloctyl, n-nonyl, n-decyl, 1-methyldecyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, n-octadecyl, or n-eicosyl.

"Alkylene" is a divalent group obtained by removing one of the hydrogen atoms from "alkyl", such as methylene, ethylene, and propylene.

For "alkenyl," please refer to the explanation of "alkyl" above. It is a group in which the C-C single bond in the "alkyl" structure is replaced with a C=C double bond, and includes groups in which not only one but two or more single bonds are replaced with double bonds (also called alkadien-yl or alkatriene-yl).

"Alkenylene" is a divalent group obtained by removing one of the hydrogen atoms from "alkenyl", for example vinylene.

For "alkynyl," please refer to the explanation of "alkyl" above. It is a group in which the C-C single bond in the "alkyl" structure is replaced with a C≡C triple bond, and also includes groups in which not only one but two or more single bonds are replaced with triple bonds (also called alkadiyn-yl or alkatriyn-yl).

"Cycloalkyl" is, for example, cycloalkyl having 3 to 24 carbon atoms, and preferably cycloalkyl having 3 to 20 carbon atoms, cycloalkyl having 3 to 16 carbon atoms, cycloalkyl having 3 to 14 carbon atoms, cycloalkyl having 3 to 12 carbon atoms, cycloalkyl having 5 to 10 carbon atoms, cycloalkyl having 5 to 8 carbon atoms, cycloalkyl having 5 to 6 carbon atoms, or cycloalkyl having 5 carbon atoms.

Specific examples of "cycloalkyl" include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, or alkyl (especially methyl) substituted derivatives of these having 1 to 5 or 1 to 4 carbon atoms, bicyclo[1.1.0]butyl, bicyclo[1.1.1]pentyl, bicyclo[2.1.0]pentyl, bicyclo[2.1.1]hexyl, bicyclo[3.1.0]hexyl, bicyclo[2.2.1]heptyl (norbornyl), bicyclo[2.2.2]octyl, adamantyl, diamantyl, decahydronaphthalenyl, and decahydroazulenyl.

The "cycloalkylene" is, for example, a cycloalkylene having 3 to 24 carbon atoms, and preferably a cycloalkylene having 3 to 20 carbon atoms, a cycloalkylene having 3 to 16 carbon atoms, a cycloalkylene having 3 to 14 carbon atoms, a cycloalkylene having 3 to 12 carbon atoms, a cycloalkylene having 5 to 10 carbon atoms, a cycloalkylene having 5 to 8 carbon atoms, a cycloalkylene having 5 to 6 carbon atoms, or a cycloalkylene having 5 carbon atoms.
Specific examples of "cycloalkylene" include structures obtained by removing one hydrogen from the above-mentioned "cycloalkyl" (monovalent group) to form a divalent group.

"Cycloalkenyl" refers to a group having a structure in which at least one pair of single bonds between two carbons in the above-mentioned "cycloalkyl" has become a double bond (for example, a group in which --CH ₂ --CH ₂ -- is replaced with --CH=CH--), and does not fall under the category of aryl. Specific examples include 1-cyclohexenyl and 1-cyclopentenyl.

"Alkoxy" is a group represented by "Alk-O- (Alk is alkyl)" and the details of this alkyl can be found in the explanation of "alkyl" above.

"Aryloxy" is a group represented by "Ar-O- (Ar is aryl)" and for details on the aryl, please refer to the explanation of "aryl" above.

"Substituted silyl" is, for example, a silyl substituted with at least one of aryl, alkyl, and cycloalkyl, and is preferably triarylsilyl, trialkylsilyl, tricycloalkylsilyl, dialkylcycloalkylsilyl, or alkyldicycloalkylsilyl.

The "triarylsilyl" is a silyl group substituted with three aryl groups. For details of the aryl groups, see the above description of the "aryl".
Specific "triarylsilyl" includes, for example, triphenylsilyl, diphenylmononaphthylsilyl, monophenyldinaphthylsilyl, trinaphthylsilyl, and the like.

The term "trialkylsilyl" refers to a silyl group substituted with three alkyl groups. For details of this alkyl group, see the above description of "alkyl."
Specific examples of "trialkylsilyl" include trimethylsilyl, triethylsilyl, tri-n-propylsilyl, triisopropylsilyl, tri-n-butylsilyl, triisobutylsilyl, tri-s-butylsilyl, tri-t-butylsilyl, ethyldimethylsilyl, n-propyldimethylsilyl, isopropyldimethylsilyl, n-butyldimethylsilyl, isobutyldimethylsilyl, s-butyldimethylsilyl, t-butyldimethylsilyl, methyldiethylsilyl, n-propyldiethylsilyl, isopropyldiethylsilyl, n-butyldiethylsilyl, s-butyldiethylsilyl, t-butyldiethylsilyl, methyldi-n-propylsilyl, ethyldi-n-propylsilyl, n-butyldi-n-propylsilyl, s-butyldi-n-propylsilyl, t-butyldi-n-propylsilyl, methyldiisopropylsilyl, ethyldiisopropylsilyl, n-butyldiisopropylsilyl, s-butyldiisopropylsilyl, and t-butyldiisopropylsilyl.

The term "tricycloalkylsilyl" refers to a silyl group substituted with three cycloalkyl groups. For details of this cycloalkyl, see the above description of the "cycloalkyl".
Specific "tricycloalkylsilyl" includes, for example, tricyclopentylsilyl or tricyclohexylsilyl.

"Dialkylcycloalkylsilyl" is a silyl group substituted with two alkyls and one cycloalkyl. For details on the alkyl and cycloalkyl, see the explanations of "alkyl" and "cycloalkyl" above.

"Alkyldicycloalkylsilyl" is a silyl group substituted with one alkyl and two cycloalkyl. For details of the alkyl and cycloalkyl, see the explanations of "alkyl" and "cycloalkyl" above.

"Halogen" is fluorine, chlorine, bromine or iodine, preferably fluorine, chlorine or bromine, more preferably fluorine or chlorine, and even more preferably fluorine.

When cyano or halogen is substituted, it is preferable that all or some of the hydrogen atoms in the aryl or heteroaryl in the structure are replaced with cyano or halogen.

The substituent represented by formula (A30) has the following structure.

In formula (A30),
Ak is hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted cycloalkyl, or substituted or unsubstituted cycloalkenyl, in which at least one -CH ₂ - may be replaced by -O- or -S-;
R ^Ak is a substituted or unsubstituted aryl, a substituted or unsubstituted heteroaryl, a substituted or unsubstituted alkyl, or a substituted or unsubstituted cycloalkyl, and R ^Ak may be bonded to Ak via a linking group or a single bond, and * indicates the bonding position.

In formula (A30), since Ak is the above-mentioned substituent, it does not conjugate with the unshared electron pair on N, and therefore the unshared electron pair can be conjugated with the π electron of the bonded group, allowing for a greater wavelength change than when an aryl or the like is present at the same position. The same applies to the effect on the multiple resonance effect, allowing for a greater improvement in thermally activated delayed fluorescence (TADF) properties.

R is ^preferably aryl optionally substituted with alkyl or cycloalkyl, heteroaryl optionally substituted with alkyl or cycloalkyl, alkyl or cycloalkyl, more preferably aryl optionally substituted with alkyl, heteroaryl optionally substituted with alkyl, alkyl or cycloalkyl, further preferably aryl optionally substituted with alkyl, and particularly preferably phenyl optionally substituted with methyl.

In formula (A30), Ak is preferably an alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 3 to 14 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms or a cycloalkyl group having 3 to 8 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, and even more preferably methyl.

R ^Ak and Ak may be the same or different, and are preferably different.

R ^Ak may be bonded to Ak via a linking group or a single bond. In this case, examples of the linking group include >O, >S, and >Si(-R) _2. R in >Si(-R) ₂ is hydrogen, an aryl having 6 to 12 carbon atoms, an alkyl having 1 to 6 carbon atoms, or a cycloalkyl having 3 to 14 carbon atoms. Examples of the structure in which R ^Ak is bonded to Ak via a linking group or a single bond include the following.

上記各式中、＊は結合位置である。

In the above formulas, * indicates a bonding position.

<When two groups bonded to the same atom are bonded to each other>
In this specification, when it is stated that two groups bonded to the same atom may be bonded to each other to form a ring, it is sufficient that they are bonded by a single bond or a linking group (collectively also referred to as a linking group). Examples of the linking group include _-CH2 - _CH2- , -CHR-CHR-, _-CR2 -CR2-, -CH=CH-, -CR=CR- _, -C≡C-, -N(-R)-, -O-, -S-, -C(-R) _2- , -C(=O)-, -C(=S)-, -S(=O)-, -S(=O) _2- , -Se(=O)-, -Se(=O) _2- , -P(=O)-, -B(-R)-, -Si(-R) _2- or -Se-, for example, the following structure. The R of -CHR-CHR-, the R of _{-CR2- CR2-} , the R of -CR=CR-, the R of -N(-R)-, the R of -C(-R) _2- , the R of -B(-R)-, and the R of -Si(-R) _2- are each independently hydrogen, aryl which may be substituted with alkyl or cycloalkyl, heteroaryl which may be substituted with alkyl or cycloalkyl, alkyl which may be substituted with cycloalkyl, alkenyl which may be substituted with alkyl or cycloalkyl, alkynyl which may be substituted with alkyl or cycloalkyl, or cycloalkyl which may be substituted with alkyl or cycloalkyl. Two adjacent Rs may be bonded to form a ring, forming a cycloalkylene, arylene, or heteroarylene.

As the bonding group, a single bond and the linking groups -CR=CR-, -N(-R)-, -O-, -S-, -C(-R) ₂ -, -Si(-R) ₂ -, and -Se- are preferred, a single bond and the linking groups -CR=CR-, -N(-R)-, -O-, -S-, and -C(-R) ₂ - are more preferred, a single bond and the linking groups -CR=CR-, -N(-R)-, -O-, and -S- are even more preferred, and a single bond is most preferred.

The position where the two R's are bonded by the linking group is not particularly limited as long as it is a position where bonding is possible, but it is preferable for them to be bonded at the most adjacent positions. For example, if the two groups are phenyl, it is preferable for them to be bonded at the ortho (2nd) positions based on the bonding position (1st position) of "C" or "Si" in the phenyl (see the structural formula above).

1. Polycyclic aromatic compounds <Explanation of the overall structure of the compound>
The polycyclic aromatic compound of the present invention has a structure represented by formula (1).

In formula (1),
Ring A, ring B, ring C, and ring D are each independently a substituted or unsubstituted aryl ring or a substituted or unsubstituted heteroaryl ring, X is >N-R ^NX , >O, >C(-R ^CX ) ₂ , >Si(-R ^IX ) ₂ , >S, or >Se, where R ^NX , R ^CX , and R ^IX may be bonded to at least one of ring A and ring B via a linking group or a single bond, and L is >C(-R ^CL ) ₂ , >NR ^NL , >O, >S, >C=O, >S=O, >S(=O) ₂ , or >Se. Details of each symbol will be described later.

The inventors have already found that polycyclic aromatic compounds in which aromatic rings are linked by hetero elements such as boron, nitrogen, oxygen, and sulfur have a large HOMO-LUMO gap (band gap Eg in a thin film). This is because six-membered rings containing hetero elements have low aromaticity, suppressing the decrease in the HOMO-LUMO gap associated with the expansion of the conjugated system. They also found that the HOMO-LUMO gap can be changed arbitrarily depending on the type and linking method of the hetero elements. This is thought to be because the HOMO and LUMO energies can be moved arbitrarily depending on the spatial extent and energy of the unoccupied orbitals or lone pairs of the hetero elements.

In these polycyclic aromatic compounds, the excited states SOMO1 and SOMO2 are localized on each atom due to electronic perturbation of the heteroatom, so that the half-width of the fluorescence emission peak is narrow, and when used as a dopant in an organic EL device, light emission with high color purity can be obtained. For the same reason, ΔE _S1T1 is small, and the compound exhibits thermally activated delayed fluorescence, and when used as an emitting dopant in an organic EL device, high efficiency can be obtained.
Furthermore, the introduction of a substituent group allows the HOMO and LUMO energies to be freely adjusted, making it possible to optimize the ionization potential and electron affinity depending on the surrounding materials.

The compound of the present invention has a rigid skeleton because an additional ring structure is bonded to the multiple rings directly bonded to boron in the above-mentioned conventional polycyclic aromatic compound having boron as a central element, and an organic EL device using this compound as a light-emitting material has a higher device life and quantum efficiency. Specifically, in formula (1), the A ring and the D ring are bonded by a single bond, and the D ring is further bonded to the C ring via L, making the structure rigid. In formula (1), the A ring and the D ring are bonded by a single bond, so that the distortion of the structure is small. In addition, the D ring is bonded to the C ring via L, so that the bond between boron and the A ring and the C ring is strong. Furthermore, the L is not a single bond, so that the skeleton is less likely to be distorted.
However, the present invention is not particularly limited by these principles.

<Explanation of ring structure in compound>
In formula (1), "A", "B", "C", and "D" in the circles are symbols indicating the ring structure represented by each circle. The structure represented by formula (1) has at least four aromatic rings, namely ring A, ring B, ring C, and ring D, connected with boron and hetero elements such as oxygen, sulfur, or nitrogen to form a ring structure. The ring structure formed is a fused ring structure composed of at least eight rings.

Ring A, ring B, ring C, and ring D are each independently a substituted or unsubstituted aryl ring or a substituted or unsubstituted heteroaryl ring.

The A ring forms a tetravalent group having bonds to four consecutive elements (preferably carbon) on the aryl or heteroaryl ring in the structure. These four bonds bond the A ring to the X, B, N, and D rings (single bond). The A ring, whose ring constituent elements are the elements having the above four bonds, is preferably a five-membered or six-membered ring, more preferably a six-membered ring. This ring may be further condensed with another ring. Examples of six-membered rings include a benzene ring, a pyridine ring, a pyrazine ring, and a pyrimidine ring. Examples of six-membered rings further condensed with another ring include a naphthalene ring, a quinoline ring, a dibenzofuran ring, a dibenzothiophene ring, and a carbazole ring. Examples of five-membered rings include a furan ring, a thiophene ring, a pyrrole ring, and a thiazole ring. Examples of five-membered rings further condensed with another ring include a benzofuran ring, a benzothiophene ring, and an indole ring. The aryl or heteroaryl ring in the A ring is preferably a benzene ring.

The C ring and the D ring each form a trivalent group having bonds to three consecutive elements (preferably carbon) on the aryl ring or heteroaryl ring in the structure. The C ring is bonded to B, N, and L through these three bonds, and the D ring is bonded to L, N, and the A ring (single bond). The rings having the above-mentioned three bonded elements as ring constituent elements in the C ring and the D ring are preferably 5-membered or 6-membered rings, and more preferably 6-membered rings. This ring may be further condensed with other rings. Examples of 6-membered rings include a benzene ring, a pyridine ring, a pyrazine ring, and a pyrimidine ring. Examples of 6-membered rings further condensed with other rings include a naphthalene ring, a quinoline ring, a dibenzofuran ring, a dibenzothiophene ring, and a carbazole ring. Examples of 5-membered rings include a furan ring, a thiophene ring, a pyrrole ring, and a thiazole ring. Examples of 5-membered rings further condensed with other rings include a benzofuran ring, a benzothiophene ring, and an indole ring. As the aryl or heteroaryl ring in rings C and D, a benzene ring is preferable.

The B ring forms a divalent group having bonds to two elements (preferably carbon) adjacent to each other on the aryl or heteroaryl ring in the structure. The B ring is bonded to X and B by the above two bonds. X may be further bonded to the B ring at another site as described below, so that the B ring becomes a trivalent group. In the B ring, the ring having the above elements having the above two bonds as ring constituent elements is preferably a 5-membered ring or a 6-membered ring. This ring may be further condensed with another ring. Examples of the 6-membered ring include a benzene ring, a pyridine ring, a pyrazine ring, and a pyrimidine ring. Examples of the 6-membered ring further condensed with another ring include a naphthalene ring, a quinoline ring, a benzofuran ring, a benzothiophene ring, an indole ring, a benzoselenophene ring, a dibenzofuran ring, a dibenzothiophene ring, a carbazole ring, and a dibenzoselenophene ring. Examples of the 5-membered ring include a furan ring, a thiophene ring, a pyrrole ring, a thiazole ring, and a selenophene ring. Examples of the five-membered ring further condensed with another ring include a benzofuran ring, a benzothiophene ring, an indole ring, an indene ring, a benzoselenophene ring, etc. As the aryl ring or heteroaryl ring in ring B, a benzene ring, a benzofuran ring, a benzothiophene ring, or a benzoselenophene ring is preferable, a benzene ring, a benzofuran ring, or a benzothiophene ring is more preferable, and a benzene ring or a benzothiophene ring is even more preferable.

In the substituted or unsubstituted aryl rings or substituted or unsubstituted heteroaryl rings in the A ring, the B ring, the C ring, and the D ring of formula (1), the substituents referred to as "substituted or unsubstituted" include at least one substituent selected from the substituent group Zα. The substituent may also be a substituted or unsubstituted diarylphosphino such as diphenylphosphino.

As the substituent, substituted or unsubstituted alkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, or substituted or unsubstituted diarylamino is preferable, and t-butyl, diphenylamino, or carbazolyl is more preferable. See also the examples of preferred substituents described below.

In formula (1), it is preferable that at least one of the A ring, B ring, C ring, and D ring is an aryl ring having at least one substituent or a heteroaryl ring having at least one substituent, it is more preferable that at least two of them are an aryl ring having at least one substituent or a heteroaryl ring having at least one substituent, it is even more preferable that at least three of them are an aryl ring having at least one substituent or a heteroaryl ring having at least one substituent, and it is particularly preferable that all of them are an aryl ring having at least one substituent or a heteroaryl ring having at least one substituent.

The polycyclic aromatic compound of the present invention is preferably a polycyclic aromatic compound represented by the following formula (1-a): In other words, formula (1-a) is a preferred embodiment of formula (1).

In formula (1-a), X and L have the same meanings as X and L in formula (1). Each Z is independently -C(-R ^Z )= or -N=, each R ^Z is independently hydrogen or a substituent, two adjacent R ^Z may be bonded to each other to form a substituted or unsubstituted aryl ring or a substituted or unsubstituted heteroaryl ring together with the carbons to which they are bonded, and each Z=Z may independently be >N-R ^NZ , >O, >C(-R ^CZ ) ₂ , >Si(-R ^IZ ) ₂ , >S, or >Se.

The number of Z which is -N= in each of ring b, ring c and ring d is preferably 0 to 2, and more preferably 0 to 1. The number of Z which is -N= in ring a is preferably 0 to 1. It is preferable that each Z is -C(-R ^Z )=.

The substituent ^RZ and the substituent on the formed ring include at least one substituent selected from the substituent group Zα, and is preferably substituted or unsubstituted alkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, or substituted or unsubstituted diarylamino, more preferably t-butyl. Examples of preferred substituents described below can also be referred to.

In the a ring, the position of the substituent R ^Z is the para position of boron (B) or the para position of nitrogen (N), and the para position of boron (B) is preferred. The other R ^Z is preferably hydrogen. In each of the b ring and the c ring, the position of the substituent R ^Z is preferably the para position of boron (B) or the para position of X or nitrogen (N), and the para position of X or nitrogen (N) is more preferred. The other R ^Z is preferably hydrogen. In terms of ease of production, good color, and stability in the element, it is particularly preferred that R ^Z at the ortho position of boron (B) is hydrogen. When R ^Z at the ortho position of boron (B) is hydrogen, the b ring and the c ring become planar, and the half width of the emission spectrum becomes narrow. In addition, the molecular distortion is small and stable, and when used as a light-emitting material in an element, it has a long life. In the d ring, the position of the substituent R ^Z is preferably the para position of nitrogen (N). The other R ^Z is preferably hydrogen.

Examples of the structure of a ring containing Z are shown below. In the following formula, R is a substituent and has the same meaning as R ^Z , but does not mean hydrogen and does not mean bonding between Rs. R ⁰ is hydrogen or a substituent and has the same meaning as R ^Z , but does not mean bonding between ^Rs . Furthermore, n is an integer of 0 to 4, R ^N and R ^C are hydrogen, aryl which may be substituted with alkyl or cycloalkyl, heteroaryl which may be substituted with alkyl or cycloalkyl, alkyl which may be substituted with cycloalkyl, or cycloalkyl which may be substituted with alkyl, and two R ^Cs may be bonded to each other to form a ring.

The above shows an example of the b-ring, but the same can be considered for the a-ring, c-ring and d-ring.
The structure of the ring containing Z (ring b) is preferably a benzene ring, a benzofuran ring, a benzothiophene ring, an indole ring, or a benzoselenophene ring, more preferably a benzene ring or a benzothiophene ring.

In each of the partial structures above, R is preferably an unsubstituted alkyl or a diarylamino which may be substituted with an alkyl. n is preferably 0 or 1. ^R is preferably hydrogen. ^R is preferably an aryl which may be substituted with an alkyl or cycloalkyl. ^R is preferably methyl.

<Explanation of L>
In formula (1), L is >C(-R ^CL ) ₂ , >NR ^NL , >O, >S, >C=O, >S=O, >S(=O) ₂ , or >Se. ^{R CL} is hydrogen, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted alkyl, or substituted or unsubstituted cycloalkyl, and two R ^CL may be bonded to each other to form a ring, and R ^NL is hydrogen, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted alkyl, or substituted or unsubstituted cycloalkyl. When L is any of these linking groups, the reactivity is reduced compared to, for example, when L is >Si(-R ^IL ) ₂ or the like (R ^IL is a substituent such as alkyl), and the life of the produced organic EL element can be extended when used to form an organic EL element.

R ^CL is preferably a substituted or unsubstituted aryl or a substituted or unsubstituted alkyl, and more preferably a substituted or unsubstituted phenyl or an unsubstituted alkyl (preferably methyl). The two R ^CL in >C(-R ^CL ) ₂ may be the same or different, but are preferably the same. It is also preferable that both R ^CL are substituted or unsubstituted phenyl, and both are bonded via a single bond or a linking group.

R ^NL is preferably a substituted or unsubstituted aryl or a substituted or unsubstituted heteroaryl, more preferably a substituted or unsubstituted aryl, and further preferably a substituted or unsubstituted phenyl.

L is preferably >C(-R ^CL ) ₂ , >NR ^NL , >O or >S. In addition, polycyclic aromatic compounds represented by formula (1) in which L is >C(-R ^CL ) ₂ are preferred because they tend to produce short-wavelength blue light emission.

<Explanation of X>
X is >N-R ^NX , >O, >C(-R ^CX ) ₂ , >Si(-R ^IX ) ₂ , >S, or >Se; R ^NX is hydrogen, a substituted or unsubstituted aryl, a substituted or unsubstituted heteroaryl, a substituted or unsubstituted alkyl, or a substituted or unsubstituted cycloalkyl; R ^CX and R ^IX are each independently hydrogen, a substituted or unsubstituted aryl, a substituted or unsubstituted heteroaryl, a substituted or unsubstituted alkyl, or a substituted or unsubstituted cycloalkyl; two R ^CXs may be bonded to each other to form a ring; two R ^IXs may be bonded to each other to form a ring; and R ^NX , R ^CX , and R ^IX may be bonded to at least one of ring A and ring B via a linking group or a single bond.

R ^NX is preferably a substituted or unsubstituted aryl or a substituted or unsubstituted heteroaryl, more preferably a substituted or unsubstituted phenyl, and even more preferably an unsubstituted phenyl. R ^CX is preferably a substituted or unsubstituted aryl or a substituted or unsubstituted heteroaryl, and more preferably a substituted or unsubstituted phenyl. R ^IX is preferably a substituted or unsubstituted aryl or a substituted or unsubstituted heteroaryl, and more preferably a substituted or unsubstituted phenyl.

In the polycyclic aromatic compound represented by formula (1) used as an emitting dopant in the light-emitting layer of an organic EL device, X is preferably >N-R ^NX , >S, >O, or >Se, more preferably >N-R ^NX , >O, or >S, even more preferably >N-R ^NX or >S, and particularly preferably >N-R ^NX .

<Explanation of change in ring structure due to bonding between X and the ring>
R ^NX , R ^CX and R ^IX in X may be bonded to one or two rings including themselves to which X is bonded via a single bond or a linking group. Specifically, in formula (1), R ^NX , R ^CX and R ^IX in X may be bonded to at least one of ring A or ring B via a single bond or a linking group.

Examples of the linking group when R ^NX , R ^CX and R ^IX are each bonded to a ring include -CH ₂ -CH ₂ -, -CHR-CHR-, -CR ₂ -CR ₂ -, -CH=CH-, -CR=CR-, -C≡C-, -N(-R)-, -O-, -S-, -C(-R) ₂ -, -C(=O)-, -C(=S)-, -S(=O)-, -S(=O) ₂ -, -Se(=O)-, -Se(=O) ₂ -, -P(=O)-, -B(-R)-, -Si(-R) ₂ - and -Se-. Of these, -CH=CH-, -CR=CR-, -N(-R)-, -O-, -S- and -C(-R) ₂ - are preferred, -CH=CH-, -CR=CR-, -N(-R)-, -O- and -S- are more preferred, and -CR=CR-, -N(-R)-, -O- and -S- are even more preferred. The R of "-CHR-CHR-", the R of "-CR ₂ -CR ₂ -", the R of "-CR=CR-", the R of "-N(-R)-", the R of "-C(-R) ₂ -", the R of "-B(-R)-", and the R of "-Si(-R) ₂ -" are each independently hydrogen, aryl which may be substituted with an alkyl or cycloalkyl, heteroaryl which may be substituted with an alkyl or cycloalkyl, alkyl which may be substituted with an alkyl or cycloalkyl, alkenyl which may be substituted with an alkyl or cycloalkyl, alkynyl which may be substituted with an alkyl or cycloalkyl, or cycloalkyl which may be substituted with an alkyl or cycloalkyl. Two Rs bonded to the same element may be bonded to each other to form a ring. Furthermore, two adjacent Rs may be bonded to each other to form a cycloalkylene ring, an arylene ring, or a heteroarylene ring. These rings may also be substituted with an alkyl or cycloalkyl.

Examples of the fused ring formed by R ^NX in >N-R ^NX bonding to a benzene ring as an aryl ring in ring A or ring B include a carbazole ring (R ^NX which is a phenyl is bonded via a single bond), a phenoxazine ring (R ^NX which is a phenyl is bonded via -O-), a phenothiazine ring (R ^NX which is a phenyl is bonded via -S-), or an acridone ring (R ^NX which is a phenyl is bonded via -C(=O)-).

Furthermore, the following partial structure (A10) may be formed by the above-mentioned linkage.

In formula (A10), R ^A1 to R ^A4 are each independently hydrogen, an alkyl group which may be substituted, or a cycloalkyl group which may be substituted, and any two to four of R ^A1 to R ^A4 may be bonded to each other by a linking group or a single bond, and are bonded to one of the two rings to which X is bonded at the two * positions, and to the other ring at the ** position. That is, N in formula (A10) is N of >N-R ^NX when X is >N-R ^NX . The atoms on the rings bonded at the two * positions may be adjacent atoms (preferably carbon atoms). The partial structure represented by formula (A10) contains an N-C bond with a weak bond dissociation energy (BDE), but the presence of another bond forming a ring promotes a reverse reaction (recombination reaction) even when the N-C bond is broken, resulting in a more stable structure. Therefore, an organic EL device manufactured using a polycyclic aromatic compound having such a structure is expected to have a long device life. When the polycyclic aromatic compound contains a structure represented by formula (A10), the number of such structures may be one or two (preferably one).

In formula (A10), any two to four of R ^A1 to R ^A4 may be linked to each other via a linking group.
Of R ^A1 to R ^A4 , any two (R ^A1 and R ^A4 , R ^A1 and R ^A4 and R ^A2 and R ^A3 , R ^A1 and R ^A2 , R ^A3 and R ^A4 , R ^A1 and R ^A2 and R ^A3 and R ^A4 ) are preferably bonded to each other by a linking group or a single bond, and it is more preferable that R ^A1 and R ^A4 are bonded to each other by a linking group or a single bond. An example of the divalent group formed by bonding to each other is alkylene. At least one hydrogen atom in the alkylene may be substituted with an alkyl or cycloalkyl, and at least one (preferably one) -CH ₂ - in the alkylene may be substituted with -O- and -S-. As the divalent group formed by bonding to each other, a straight chain alkylene having 2 to 5 carbon atoms is preferable, a straight chain alkylene having 3 or 4 carbon atoms is more preferable, and a straight chain alkylene having 4 carbon atoms (-(CH ₂ ) ₄ -) is even more preferable. It is particularly preferred that the linear alkylene having 4 carbon atoms (--(CH ₂ ) ₄ --) is unsubstituted.

The remaining R ^A1 to R ^A4 that are not involved in the linking through the linking group are each preferably independently hydrogen or an alkyl which may be substituted, more preferably an alkyl having 1 to 6 carbon atoms which may be substituted, further preferably an unsubstituted alkyl having 1 to 6 carbon atoms, and most preferably methyl.
That is, the partial structure represented by formula (A10) is preferably a structure represented by the following formula (A11).

式（Ａ１１）中、Ｍｅはメチルであり、２つの＊の位置でＸが結合する２つの環の一方の環に、＊＊の位置で他方の環に結合している。

In formula (A11), Me is methyl and is bonded to one of the two rings to which X is bonded at the two * positions and to the other ring at the ** position.

[Polycyclic aromatic compound represented by formula (2)]
A polycyclic aromatic compound represented by the following formula (2) in which R ^NX in X of >N-R ^NX is a substituted or unsubstituted aryl or a substituted or unsubstituted heteroaryl and R ^NX is bonded to ring A via a single bond and to ring B via a linking group L′ is a preferred embodiment of the polycyclic aromatic compound represented by formula (1).

In formula (2), ring A, ring B, ring C, and ring D have the same meaning as ring A, ring B, ring C, and ring D in formula (1), respectively, and the preferred ranges are also the same. L has the same meaning as L in formula (1), and the preferred ranges are also the same. Ring E is a substituted or unsubstituted aryl ring or a substituted or unsubstituted heteroaryl ring, and the preferred ranges are the same as ring D in formula (1). L' has the same meaning as L in formula (1), and the preferred ranges are also the same.
At least one selected from the group consisting of aryl rings and heteroaryl rings in formula (2) may be condensed with at least one cycloalkane, the cycloalkane may be substituted with at least one substituent, and at least one -CH ₂ - in the cycloalkane may be replaced with -O-;
At least one hydrogen in formula (2) may be replaced with deuterium.

In formula (2), it is preferable that at least one of the A ring, B ring, C ring, D ring, and E ring is an aryl ring having at least one substituent or a heteroaryl ring having at least one substituent, more preferably that at least two of them are an aryl ring having at least one substituent or a heteroaryl ring having at least one substituent, even more preferably that at least three of them are an aryl ring having at least one substituent or a heteroaryl ring having at least one substituent, and particularly preferably that all of them are an aryl ring having at least one substituent or a heteroaryl ring having at least one substituent. By having an aromatic ring having a substituent as the A ring, B ring, C ring, D ring, or E ring, it is possible to obtain even higher luminous efficiency when the compound is used to form an organic EL device, and to extend the life of the organic EL device.

In formula (2), L and L' may be the same or different, but are preferably the same. Also, the D ring and the E ring may be the same or different, but are preferably the same. This is because synthesis is facilitated in either case.

<Preferable Substituents>
In polycyclic aromatic compounds used as emitting dopants (and in other compounds used as dopants), the tertiary alkyl represented by the following formula (tR) is one of the most preferred substituents containing an "alkyl". This is because such a bulky substituent increases the intermolecular distance, thereby improving the light emission quantum yield (PLQY). In addition, a substituent in which the tertiary alkyl represented by formula (tR) is substituted with another substituent as a second substituent is also preferred. Specifically, examples include diarylamino substituted with a tertiary alkyl represented by (tR), carbazolyl substituted with a tertiary alkyl represented by (tR) (preferably N-carbazolyl), or benzocarbazolyl substituted with a tertiary alkyl represented by (tR) (preferably N-benzocarbazolyl). Examples of the substitution form of the group of formula (tR) on diarylamino, carbazolyl, and benzocarbazolyl include examples in which some or all of the hydrogen atoms on the aryl ring or benzene ring in these groups are replaced with the group of formula (tR).

In formula (tR), R ^a , R ^b , and R ^c each independently represent an alkyl group having 1 to 24 carbon atoms, any —CH ₂ — in the alkyl group may be replaced by —O—, and the group represented by formula (tR) has * as the bonding position.

The "alkyl having 1 to 24 carbon atoms" of R ^a , R ^b and R ^c may be either linear or branched, and examples thereof include linear alkyl having 1 to 24 carbon atoms or branched alkyl having 3 to 24 carbon atoms, alkyl having 1 to 18 carbon atoms (branched alkyl having 3 to 18 carbon atoms), alkyl having 1 to 12 carbon atoms (branched alkyl having 3 to 12 carbon atoms), alkyl having 1 to 6 carbon atoms (branched alkyl having 3 to 6 carbon atoms), and alkyl having 1 to 4 carbon atoms (branched alkyl having 3 to 4 carbon atoms).

The total number of carbon atoms of R ^a , R ^b and R ^c in formula (tR) is preferably 3 to 20, and particularly preferably 3 to 10.

R ^a , R ^b , and R Specific examples of alkyl for ^c include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, n-pentyl, isopentyl, neopentyl, t-pentyl, n-hexyl, 1-methylpentyl, 4-methyl-2-pentyl, 3,3-dimethylbutyl, 2-ethylbutyl, n-heptyl, 1-methylhexyl, n-octyl, t-octyl, 1-methylheptyl, 2-ethylhexyl, 2-propylpentyl, n-nonyl, 2,2-dimethylheptyl, 2,6-dimethyl-4-heptyl, 3,5,5-trimethylhexyl, n-decyl, n-undecyl, 1-methyldecyl, n-dodecyl, n-tridecyl, 1-hexylheptyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, n-octadecyl, and n-eicosyl.

Examples of the group represented by formula (tR) include t-butyl, t-amyl, 1-ethyl-1-methylpropyl, 1,1-diethylpropyl, 1,1-dimethylbutyl, 1-ethyl-1-methylbutyl, 1,1,3,3-tetramethylbutyl, 1,1,4-trimethylpentyl, 1,1,2-trimethylpropyl, 1,1-dimethyloctyl, 1,1-dimethylpentyl, 1,1-dimethylheptyl, 1,1,5-trimethylhexyl, 1-ethyl-1-methylhexyl, 1-ethyl-1,3-dimethylbutyl, 1,1,2,2-tetramethylpropyl, 1-butyl-1-methylpentyl, 1,1-diethylbutyl, 1-ethyl-1-methylpentyl, 1,1,3-trimethylbutyl, 1-propyl-1-methylpentyl, 1,1,2-trimethylpropyl, 1-ethyl-1,2,2-trimethylpropyl, 1-propyl-1-methylbutyl, and 1,1-dimethylhexyl. Of these, t-butyl and t-amyl are preferred.

The substituent is preferably a substituent represented by formula (A30).

The emission wavelength can be adjusted by the steric hindrance, electron donating property and electron withdrawing property of the structure of the substituent possessed by the compound used as a dopant (assisting dopant or emitting dopant). The groups represented by the following structural formulas are preferred, and more preferred are methyl, t-butyl, t-amyl, t-octyl, neopentyl, adamantyl, phenyl, o-tolyl, p-tolyl, 2,4-xylyl, 2,5-xylyl, 2,6-xylyl, 2,4,6-mesityl, diphenylamino, di-p-tolylamino, bis(p-(t-butyl)phenyl)amino, carbazolyl, 3,6-dimethylcarbazolyl, 3,6-di-t-butyl and more preferably, methyl, t-butyl, t-amyl, t-octyl, neopentyl, adamantyl, phenyl, o-tolyl, 2,6-xylyl, 2,4,6-mesityl, diphenylamino, di-p-tolylamino, bis(p-(t-butyl)phenyl)amino, carbazolyl, 3,6-dimethylcarbazolyl, 3,6-di-t-butylcarbazolyl, and tribenzoazepinyl. From the viewpoint of ease of synthesis, a larger steric hindrance is preferred for selective synthesis, and specifically, t-butyl, t-amyl, t-octyl, adamantyl, o-tolyl, p-tolyl, 2,4-xylyl, 2,5-xylyl, 2,6-xylyl, 2,4,6-mesityl, di-p-tolylamino, bis(p-(t-butyl)phenyl)amino, 3,6-dimethylcarbazolyl, and 3,6-di-t-butylcarbazolyl are preferred.

In the following structural formula, * represents a bond position.

The polycyclic aromatic compound represented by formula (1) preferably has a structure containing at least one tertiary alkyl (such as t-butyl or t-amyl), neopentyl or adamantyl represented by the above formula (tR), and preferably contains a tertiary alkyl (such as t-butyl or t-amyl) represented by formula (tR). This is because such bulky substituents increase the intermolecular distance, thereby improving the luminescence quantum yield (PLQY). Diarylamino is also preferred as the substituent. Furthermore, diarylamino substituted with a group represented by formula (tR), carbazolyl (preferably N-carbazolyl) substituted with a group represented by formula (tR), or benzocarbazolyl (preferably N-benzocarbazolyl) substituted with a group represented by formula (tR) are also preferred. Examples of the substitution form of the group represented by formula (tR) on diarylamino, carbazolyl, and benzocarbazolyl include examples in which some or all of the hydrogen atoms on the aryl ring or benzene ring in these groups are substituted with a group represented by formula (tR).

In the structure represented by formula (1), the substituent on the aryl ring or heteroaryl ring may be a substituent represented by the following formula (A20).

The substituent represented by formula (A20) is bonded to two adjacent atoms on the ring of the aryl ring or heteroaryl ring at two *'s, respectively. In formula (A20), L is >N-R, >O, >Si(-R) ₂ or >S, R of the >N-R is substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted alkyl or substituted or unsubstituted cycloalkyl, R of the >Si(-R) ₂ is hydrogen, optionally substituted aryl, optionally substituted alkyl or optionally substituted cycloalkyl, and may be bonded to each other by a linking group, and at least one of R of the >N-R and the >Si(-R) ₂ may be bonded to the aryl ring or heteroaryl ring by a linking group or a single bond,
r is an integer from 1 to 4;
Each R ^A is independently hydrogen, substituted or unsubstituted alkyl, or substituted or unsubstituted cycloalkyl, and any R ^A may be bonded to any other R ^A via a linking group or a single bond.

Examples of the above-mentioned substituent include any of the following substituents.

In each formula, * may be bonded to two or three consecutive (adjacent) atoms on any aryl or heteroaryl ring.

<Cycloalkane condensation>
At least one selected from the group consisting of aryl rings and heteroaryl rings in the polycyclic aromatic compound represented by formula (1) may be condensed with at least one cycloalkane. The same applies to the polycyclic aromatic compound represented by formula (2) or formula (1-a), and the following description also applies to the polycyclic aromatic compound represented by formula (2) or formula (1-a).

The cycloalkane may be a cycloalkane having 3 to 24 carbon atoms. In this case, at least one hydrogen atom in the cycloalkane may be substituted with an aryl having 6 to 30 carbon atoms, a heteroaryl having 2 to 30 carbon atoms, an alkyl having 1 to 24 carbon atoms, or a cycloalkyl having 3 to 24 carbon atoms, and at least one -CH ₂ - in the cycloalkane may be replaced with -O-.

The cycloalkane is preferably a cycloalkane having 3 to 20 carbon atoms, in which at least one hydrogen atom may be substituted with an aryl having 6 to 16 carbon atoms, a heteroaryl having 2 to 22 carbon atoms, an alkyl having 1 to 12 carbon atoms, or a cycloalkyl having 3 to 16 carbon atoms.

Examples of "cycloalkanes" include cycloalkanes with 3 to 24 carbon atoms, cycloalkanes with 3 to 20 carbon atoms, cycloalkanes with 3 to 16 carbon atoms, cycloalkanes with 3 to 14 carbon atoms, cycloalkanes with 5 to 10 carbon atoms, cycloalkanes with 5 to 8 carbon atoms, cycloalkanes with 5 to 6 carbon atoms, and cycloalkanes with 5 carbon atoms.

Specific examples of cycloalkanes include cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane, norbornane (bicyclo[2.2.1]heptane), bicyclo[1.1.0]butane, bicyclo[1.1.1]pentane, bicyclo[2.1.0]pentane, bicyclo[2.1.1]hexane, bicyclo[3.1.0]hexane, bicyclo[2.2.2]octane, adamantane, diamantane, decahydronaphthalene, and decahydroazulene, as well as alkyl (especially methyl) substituted, halogen (especially fluorine) substituted, and deuterium substituted derivatives of these having 1 to 5 carbon atoms.

Among the above examples, a structure having at least one substituent on the α-position carbon of the cycloalkane (in a cycloalkane fused to an aryl ring or heteroaryl ring, the carbon adjacent to the carbon at the condensation site), such as that shown in the structural formula below, is preferred, a structure having two substituents on the α-position carbon is more preferred, and a structure having two substituents on each of the two α-position carbons (four substituents in total) is even more preferred. Examples of such substituents include alkyl groups having 1 to 5 carbon atoms (especially methyl), halogens (especially fluorine), and deuterium. In particular, a structure in which a partial structure represented by the following formula (B) is bonded to adjacent carbon atoms in an aryl ring or heteroaryl ring is preferred.

式（Ｂ）中、＊は結合位置を示す。

In formula (B), * indicates a bonding position.

The number of cycloalkanes fused to one aryl ring or heteroaryl ring is preferably 1 to 3, more preferably 1 or 2, and even more preferably 1. For example, the following shows an example in which one or more cycloalkanes are fused to one benzene ring (phenyl). * indicates the bonding position, and the position may be any carbon that constitutes the benzene ring but does not constitute the cycloalkane. Cycloalkanes fused to each other as in formula (Cy-1-4) and formula (Cy-2-4) may be fused together. The same applies when the fused ring (group) is an aryl ring or heteroaryl ring other than a benzene ring (phenyl), or when the fused cycloalkane is a cycloalkane other than cyclopentane or cyclohexane.

At least one -CH ₂ - in a cycloalkane may be replaced with -O-. For example, examples in which one or more -CH ₂ - in a cycloalkane fused to a benzene ring (phenyl) are replaced with -O- are shown below. The same applies when the fused ring (group) is an aryl ring or heteroaryl ring other than a benzene ring (phenyl) or when the fused cycloalkane is a cycloalkane other than cyclopentane or cyclohexane.

The cycloalkane may be substituted with at least one substituent, and the substituent may be any of the substituents selected from the group Z of substituents. Among these substituents, alkyl (e.g., alkyl having 1 to 6 carbon atoms) and cycloalkyl (e.g., cycloalkyl having 3 to 14 carbon atoms) are preferred. It is also preferred that any hydrogen atom is replaced with a halogen (e.g., fluorine) or deuterium. In addition, when cycloalkyl is substituted, it may be a substitution form that forms a spiro structure. For example, an example of a spiro structure formed in a cycloalkane condensed to one benzene ring (phenyl) is shown below. In each structural formula, * means that in the case of a benzene ring, it is a benzene ring included in the skeletal structure of the compound, and in the case of phenyl, it means a bond that substitutes in the skeletal structure of the compound.

Examples of cycloalkane condensation include those in which the aryl and heteroaryl rings in the A, B, C, and D rings (and E ring) of the polycyclic aromatic compound represented by formula (1) are condensed with a cycloalkane.

Other forms of cycloalkane condensation include examples where the polycyclic aromatic compound represented by formula (1) has, for example, >N-R ^NX , where R ^NX is an aryl fused with a cycloalkane, a diarylamino fused with a cycloalkane (fused to the aryl moiety), a carbazolyl fused with a cycloalkane (fused to the benzene ring moiety), or a benzocarbazolyl fused with a cycloalkane (fused to the benzene ring moiety).

By introducing a cycloalkane structure into the polycyclic aromatic compound represented by formula (1), it is expected that the melting point and sublimation temperature will be further reduced. This means that in the sublimation purification, which is almost essential as a purification method for materials for organic devices such as organic EL elements that require high purity, purification can be performed at a relatively low temperature, and thermal decomposition of the material can be avoided. This is also true for the vacuum deposition process, which is a powerful means for producing organic devices such as organic EL elements, and since the process can be performed at a relatively low temperature, thermal decomposition of the material can be avoided, resulting in a high-performance organic device. In addition, since the introduction of a cycloalkane structure improves solubility in organic solvents, it can also be applied to the production of elements using a coating process. However, the present invention is not particularly limited to these principles.

<Replacement with deuterium>
All or a part of the hydrogen atoms in the polycyclic aromatic compound represented by formula (1) may be deuterium. The same applies to the structure represented by formula (2) or formula (1-a), and the following description also applies to the polycyclic aromatic compound represented by formula (2) or formula (1-a).

For example, in the polycyclic aromatic compound represented by formula (1), hydrogen atoms in the aryl or heteroaryl rings in rings A, B, C, and D (and ring E) and in the substituents thereof may be replaced with deuterium atoms, and among these, there are embodiments in which all or part of the hydrogen atoms in the aryl or heteroaryl rings are replaced with deuterium atoms. From the viewpoint of durability, it is also preferable that all or part of the hydrogen atoms in the polycyclic aromatic compound represented by formula (1) are deuterated.

<Specific examples of polycyclic aromatic compounds>
Examples of the polycyclic aromatic compound represented by formula (1) include compounds represented by any of the following structural formulas.

<Method of producing polycyclic aromatic compound>
The polycyclic aromatic compound represented by formula (1) can be basically produced by first bonding the A ring (a ring) with the fused rings including the B ring (b ring) and the C ring (c ring) with a bonding group (a group including X) and a single bond to produce an intermediate (first reaction), and then bonding the A ring (a ring), the B ring (b ring) and the C ring (c ring) with boron to produce a final product (second reaction). In the first reaction, for example, if it is an etherification reaction, a general reaction such as a nucleophilic substitution reaction or an Ullmann reaction can be used, and if it is an amination reaction, a general reaction such as a Buchwald-Hartwig reaction, a nucleophilic substitution reaction or a Goldberg amination can be used. In addition, in the second reaction, a tandem hetero Friedel-Crafts reaction (sequential aromatic electrophilic substitution reaction, the same applies below) can be used.

As shown in the following scheme (1), the second reaction is a reaction to introduce boron to bond fused rings including ring A (ring a), ring B (ring b) and ring C (ring c). First, the halogen atom (Hal) between X and the nitrogen atom is halogen-metal exchanged with n-butyllithium, sec-butyllithium or t-butyllithium. Next, boron trichloride or boron tribromide is added to perform lithium-boron metal exchange, and then a Brønsted base such as N,N-diisopropylethylamine is added to carry out a tandem boron-Friedel-Crafts reaction to obtain the target product. In the second reaction, a Lewis acid such as aluminum trichloride may be added to promote the reaction. The halogen atom (Hal) in the formula may be any of F, Cl, Br and I, and can be appropriately selected in consideration of the reactivity of the substrate.

By appropriately selecting the raw materials used, it is possible to synthesize polycyclic aromatic compounds having substituents at the desired positions.

Specific examples of solvents used in the above reactions include t-butylbenzene and xylene.

In the synthesis method of the above scheme (1), an example has been shown in which a tandem hetero Friedel-Crafts reaction was carried out by halogen-metal exchange of the halogen atom between ^X1 and the nitrogen atom with butyllithium or the like before adding boron trichloride, boron tribromide, or the like, but the reaction can also be carried out by adding boron trichloride, boron tribromide, or the like to a precursor in which the halogen has been converted to hydrogen.

The orthometalation reagent used in the above scheme (1) includes alkyllithium such as methyllithium, n-butyllithium, sec-butyllithium, and t-butyllithium, and organic alkali metal compounds such as lithium diisopropylamide, lithium tetramethylpiperidide, lithium hexamethyldisilazide, and potassium hexamethyldisilazide.

The metal-boron metal exchange reagent used in the above scheme (1) includes boron halides such as boron trifluoride, boron trichloride, boron tribromide, and boron triiodide, boron alkoxylates, and boron aryloxylates.

Examples of Bronsted bases used in the above scheme (1) include N,N-diisopropylethylamine, triethylamine, 2,2,6,6-tetramethylpiperidine, 1,2,2,6,6-pentamethylpiperidine, N,N-dimethylaniline, N,N-dimethyltoluidine, 2,6-lutidine, sodium tetraphenylborate, potassium tetraphenylborate, triphenylborane, tetraphenylsilane, Ar ₄ BNa, Ar 4 BK, Ar ₃ B, and _{Ar 4 Si} (wherein Ar is an aryl such as phenyl).

Examples of Lewis acids used in the above scheme (1) include _AlCl3 , _AlBr3 , _AlF3 , _BF3.OEt2 , _BCl3 , _BBr3 , _BI3 , _GaCl3 , _GaBr3 , _InCl3 , _InBr3 , In(OTf) ₃ , SnCl4, _SnBr4 , AgOTf, _{ScCl3 ,} Sc(OTf) ₃ , _ZnCl2 , ZnBr2, Zn(OTf) ₂ , MgCl2, MgBr2 _{, Mg(OTf)2, LiOTf, NaOTf, KOTf, Me3SiOTf, Cu(OTf)2 , CuCl2 , YCl3 , and Y (} OTf) _3. , _TiCl4 , _TiBr4 , _ZrCl4 , _ZrBr4 , _FeCl3 , _FeBr3 , _CoCl3 , _CoBr3 , etc.

In the above scheme (1), a Brönsted base or Lewis acid may be used to promote the tandem hetero Friedel-Crafts reaction. However, when a boron halide such as boron trifluoride, boron trichloride, boron tribromide, or boron triiodide is used, acids such as hydrogen fluoride, hydrogen chloride, hydrogen bromide, and hydrogen iodide are generated as the aromatic electrophilic substitution reaction proceeds, so it is effective to use a Brönsted base to capture the acid. On the other hand, when an amino halide of boron or an alkoxylated product of boron is used, amines and alcohols are generated as the aromatic electrophilic substitution reaction proceeds, so it is not necessary to use a Brönsted base in many cases, but since the amino and alkoxy have low elimination ability, it is effective to use a Lewis acid to promote their elimination.

The polycyclic aromatic compounds of the present invention also include those in which at least some of the hydrogen atoms are replaced with deuterium or halogens such as fluorine or chlorine, and such compounds can be synthesized in the same manner as above by using raw materials in which the desired sites are deuterated, fluorinated or chlorinated.

2. Organic Devices The polycyclic aromatic compound of the present invention can be used as a material for organic devices. Examples of organic devices include organic electroluminescence devices, organic field effect transistors, and organic thin-film solar cells. The polycyclic aromatic compound of the present invention is preferably used as a material for forming one or more organic layers in the organic electroluminescence devices.

2-1. Organic electroluminescent device
2-1-1. Structure of Organic Electroluminescent Device FIG. 1 is a schematic cross-sectional view showing an example of an organic EL device.
The organic EL element 100 shown in FIG. 1 has a substrate 101, an anode 102 provided on the substrate 101, a hole injection layer 103 provided on the anode 102, a hole transport layer 104 provided on the hole injection layer 103, a light emitting layer 105 provided on the hole transport layer 104, an electron transport layer 106 provided on the light emitting layer 105, an electron injection layer 107 provided on the electron transport layer 106, and a cathode 108 provided on the electron injection layer 107.

The organic EL element 100 may be fabricated in the reverse order, for example, with a substrate 101, a cathode 108 provided on the substrate 101, an electron injection layer 107 provided on the cathode 108, an electron transport layer 106 provided on the electron injection layer 107, a light-emitting layer 105 provided on the electron transport layer 106, a hole transport layer 104 provided on the light-emitting layer 105, a hole injection layer 103 provided on the hole transport layer 104, and an anode 102 provided on the hole injection layer 103.

Not all of the above layers are essential, and the minimum structural unit is the anode 102, the light-emitting layer 105, and the cathode 108, with the hole injection layer 103, the hole transport layer 104, the electron transport layer 106, and the electron injection layer 107 being layers that may be provided optionally. Each of the above layers may consist of a single layer or multiple layers.

In addition to the above-mentioned "substrate/anode/hole injection layer/hole transport layer/light-emitting layer/electron transport layer/electron injection layer/cathode" configuration, the layers constituting the organic EL element may be "substrate/anode/hole transport layer/light-emitting layer/electron transport layer/electron injection layer/cathode", "substrate/anode/hole injection layer/light-emitting layer/electron transport layer/electron injection layer/cathode", "substrate/anode/hole injection layer/light-emitting layer/electron transport layer/electron injection layer/cathode", "substrate/anode/hole injection layer/hole transport layer/light-emitting ... transport", The configuration may be "transport layer/cathode", "substrate/anode/light-emitting layer/electron transport layer/electron injection layer/cathode", "substrate/anode/hole transport layer/light-emitting layer/electron injection layer/cathode", "substrate/anode/hole transport layer/light-emitting layer/electron transport layer/cathode", "substrate/anode/hole transport layer/light-emitting layer/electron injection layer/cathode", "substrate/anode/hole injection layer/light-emitting layer/electron injection layer/cathode", "substrate/anode/hole injection layer/light-emitting layer/electron transport layer/cathode", "substrate/anode/light-emitting layer/electron transport layer/cathode", "substrate/anode/light-emitting layer/electron transport layer/cathode", or "substrate/anode/light-emitting layer/electron injection layer/cathode".

The organic EL element may further have one or both of an electron blocking layer (electron blocking layer) and a hole blocking layer (hole blocking layer). The electron blocking layer has a LUMO shallower than that of the light emitting layer and a HOMO close to that of the light emitting layer or the hole transport layer, and is disposed between the light emitting layer and the hole transport layer. Since electrons remain in the light emitting layer and do not leak to the hole transport layer, it is possible to prevent a shortened life due to deterioration of the hole transport layer and a decrease in efficiency due to a decrease in recombination efficiency. The hole blocking layer has a HOMO deeper than that of the light emitting layer and a LUMO close to that of the light emitting layer or the hole transport layer, and is disposed between the light emitting layer and the electron transport layer. Since holes remain in the light emitting layer and do not leak to the electron transport layer, it is possible to prevent a shortened life due to deterioration of the electron transport layer and a decrease in efficiency due to a decrease in recombination efficiency. The hole injection/transport layer may also serve as the electron blocking layer. The electron injection/transport layer may also serve as the hole blocking layer.

The organic EL element may further have a high T1 layer. The high T1 layer has a higher T1 than the host compound, assisting dopant compound, or emitting dopant compound used in the light-emitting layer, and is disposed between the light-emitting layer and the hole transport layer and/or between the light-emitting layer and the electron blocking layer. The value of the T1 energy varies depending on the light-emitting mechanism of the element, but has a higher T1 than the compound used in the host. By having a high T1 layer around the light-emitting layer, triplet energy can be trapped and triplet energy that does not normally lead to light emission in fluorescent molecules can be converted to singlet energy, resulting in high efficiency. The hole injection/transport layer or the electron blocking layer may also serve as the high T1 layer. The electron injection/transport layer or the hole blocking layer may also serve as the high T1 layer.

The polycyclic aromatic compound of the present invention is preferably used as a material for forming a light-emitting layer or a material for forming an electron transport layer, and more preferably used as a material for forming a light-emitting layer. The polycyclic aromatic compound of the present invention can be particularly preferably used as a blue light-emitting material.

2-1-2. Substrate in organic electroluminescence device The substrate 101 is a support for the organic EL element 100, and is usually made of quartz, glass, metal, plastic, or the like. The substrate 101 is formed into a plate, film, or sheet shape depending on the purpose, and for example, a glass plate, a metal plate, a metal foil, a plastic film, a plastic sheet, or the like is used. Among them, a glass plate and a plate made of a transparent synthetic resin such as polyester, polymethacrylate, polycarbonate, or polysulfone are preferred. For a glass substrate, soda lime glass or alkali-free glass is used, and the thickness is sufficient to maintain mechanical strength. In addition, in order to improve the gas barrier property, a gas barrier film such as a dense silicon oxide film may be provided on at least one side of the substrate 101, and it is preferable to provide a gas barrier film when a plate, film, or sheet made of a synthetic resin with low gas barrier property is used as the substrate 101.

The anode 102 plays a role of injecting holes into the light -emitting layer 105. When at least one layer of the hole injection layer 103 and the hole transport layer 104 is provided between the anode 102 and the light-emitting layer 105, holes are injected into the light-emitting layer 105 via these layers.

Materials for forming the anode 102 include inorganic and organic compounds. Inorganic compounds include, for example, metals (aluminum, gold, silver, nickel, palladium, chromium, etc.), metal oxides (indium oxide, tin oxide, indium-tin oxide (ITO), indium-zinc oxide (IZO), etc.), metal halides (copper iodide, etc.), copper sulfide, carbon black, ITO glass, and Nesa glass. Organic compounds include, for example, polythiophenes such as poly(3-methylthiophene), polypyrrole, polyaniline, and other conductive polymers. In addition, materials that are used as anodes in organic EL elements can be appropriately selected and used.

2-1-4. Hole injection layer and hole transport layer in organic electroluminescence element The hole injection layer 103 plays a role of efficiently injecting holes moving from the anode 102 into the light emitting layer 105 or the hole transport layer 104. The hole transport layer 104 plays a role of efficiently transporting holes injected from the anode 102 or holes injected from the anode 102 through the hole injection layer 103 to the light emitting layer 105. The hole injection layer 103 and the hole transport layer 104 are each formed by laminating or mixing one or more types of hole injection/transport materials. Alternatively, a layer may be formed by adding an inorganic salt such as iron (III) chloride to the hole injection/transport material.

The hole injection/transport material must be able to efficiently inject and transport holes from the positive electrode between electrodes to which an electric field is applied, and it is desirable for the hole injection efficiency to be high and for the injected holes to be efficiently transported. For this purpose, it is preferable for the material to have a small ionization potential, a large hole mobility, and excellent stability, and to be unlikely to generate impurities that act as traps during manufacture and use.

As the material for forming the hole injection layer 103 and the hole transport layer 104, any compound can be selected from compounds conventionally used as charge transport materials for holes in photoconductive materials, p-type semiconductors, and known compounds used in hole injection layers and hole transport layers of organic EL elements. Specific examples thereof include carbazole derivatives (N-phenylcarbazole, polyvinylcarbazole, etc.), biscarbazole derivatives such as bis(N-arylcarbazole) or bis(N-alkylcarbazole), triarylamine derivatives (polymers having an aromatic tertiary amino in the main chain or side chain, 1,1-bis(4-di-p-tolylaminophenyl)cyclohexane, N,N'-diphenyl-N,N'-di(3-methylphenyl)-4,4'-diaminobiphenyl, N,N'-diphenyl-N,N'-dinaphthyl-4,4'-diaminobiphenyl, N,N'-diphenyl-N,N'-di(3-methylphenyl)-4,4'-diphenyl-1,1'-diamine, N,N'-dinaphthyl-N,N'-diphenyl-4,4'-diphenyl-1,1'-diamine, N ⁴ ,N ^{4 '} -diphenyl-N ⁴ ,N ^{4 '} -Bis(9-phenyl-9H-carbazol-3-yl)-[1,1'-biphenyl]-4,4'-diamine, N ⁴ , N ⁴ , N ^{4 '} , N ^{4 '} -tetra[1,1'-biphenyl]-4-yl)-[1,1'-biphenyl]-4,4'-diamine, triphenylamine derivatives such as 4,4',4"-tris(3-methylphenyl(phenyl)amino)triphenylamine, starburst amine derivatives, etc.), stilbene derivatives, phthalocyanine derivatives (metal-free, copper phthalocyanine, etc.), pyrazoline derivatives, hydrazone compounds, benzofuran derivatives, thiophene derivatives, oxadiazole derivatives, quinoxaline derivatives (for example, 1,4,5,8,9,12-hexaazatriphenylene-2,3,6,7,10,11-hexacarbonitrile, etc.), heterocyclic compounds such as porphyrin derivatives, polysilanes, etc. As for polymers, polycarbonates and styrene derivatives having the above-mentioned monomers in the side chains, polyvinylcarbazole, polysilane, etc. are preferable, but there is no particular limitation as long as they are compounds that can form a thin film required for fabricating a light-emitting device, can inject holes from the anode, and can transport holes.

It is also known that the electrical conductivity of organic semiconductors is strongly influenced by their doping. Such organic semiconductor matrix substances consist of compounds with good electron donating or accepting properties. For doping with electron donating substances, strong electron acceptors such as tetracyanoquinone dimethane (TCNQ) or 2,3,5,6-tetrafluorotetracyano-1,4-benzoquinone dimethane (F4TCNQ) are known (see, for example, the literature "M. Pfeiffer, A. Beyer, T. Fritz, K. Leo, Appl. Phys. Lett., 73(22), 3202-3204 (1998)" and the literature "J. Blochwitz, M. Pfeiffer, T. Fritz, K. Leo, Appl. Phys. Lett., 73(6), 729-731 (1998)"). These generate so-called holes by an electron transfer process in the electron donating base substance (hole transport substance). The conductivity of the base material varies considerably depending on the number and mobility of holes. Matrix materials with hole transport properties include, for example, benzidine derivatives (such as TPD) or starburst amine derivatives (such as TDATA), or certain metal phthalocyanines (especially zinc phthalocyanine (ZnPc)) (JP 2005-167175 A).

The hole injection layer material and hole transport layer material described above can also be used as hole layer materials in the form of polymer compounds obtained by polymerizing a reactive compound substituted with a reactive substituent as a monomer, or a crosslinked polymer thereof, or a pendant polymer compound obtained by reacting a main chain polymer with the reactive compound, or a crosslinked pendant polymer thereof.

2-1-5. Light-emitting layer in organic electroluminescent device The light-emitting layer 105 is a layer that emits light by recombining holes injected from the anode 102 and electrons injected from the cathode 108 between electrodes to which an electric field is applied. The material that forms the light-emitting layer 105 may be a compound that is excited and emits light by the recombination of holes and electrons (light-emitting compound), and a compound that can be formed into a stable thin film shape and shows strong light-emitting (fluorescence) efficiency in a solid state is preferably used.

The light-emitting layer may be a single layer or multiple layers, each of which is formed from a material for a light-emitting layer. When the light-emitting layer is multiple layers, it is preferable that any one of the layers contains the polycyclic aromatic compound of the present invention. It is preferable that the light-emitting layer is a single layer.

The light-emitting layer is formed from materials for the light layer (host material, dopant material). The host material and the dopant material may each be one type or a combination of multiple types. For example, an emitting dopant and an assisting dopant may be used as the dopant material. It is also preferable that the light-emitting layer contains an emitting dopant and at least two selected from the group consisting of a hole-transporting host material, an electron-transporting host material, and an assisting dopant material. The dopant material may be contained in the entire host material or may be contained partially in the host material. As a doping method, the dopant material may be formed by a co-evaporation method with the host material, but it may also be mixed with the host material in advance and then evaporated at the same time. The light-emitting layer may also be formed by a wet film-forming method using a light-emitting layer-forming composition prepared by dissolving the material in an organic solvent.

The amount of the host material used varies depending on the type of host material, and may be determined according to the characteristics of the host material. The amount of the host material used is preferably 50 to 99.999% by mass, more preferably 80 to 99.95% by mass, and even more preferably 90 to 99.9% by mass, of the total mass of the materials for the light-emitting layer. When the host material is a combination of a hole-transporting host material and an electron-transporting host material, the amount of the host material used is the combined mass of the hole-transporting host material and the electron-transporting host material. The ratio of the amount of the hole-transporting host material to the amount of the electron-transporting host material used may be 1:9 to 9:1 by mass, preferably 4:6 to 6:4, and more preferably approximately 1:1.

The amount of emitting dopant used varies depending on the type of emitting dopant, and may be determined according to its characteristics. The amount of emitting dopant used is preferably 0.001 to 50% by mass of the total mass of the material for the light-emitting layer, more preferably 0.05 to 20% by mass, and even more preferably 0.1 to 10% by mass. The above range is preferable in that, for example, concentration quenching can be prevented.

In an organic electroluminescent device that uses an assisting dopant (thermally activated delayed fluorescent material or phosphorescent material) in addition to an emitting dopant, a low concentration of the emitting dopant material is preferable in terms of preventing concentration quenching. A high concentration of the assisting dopant is preferable in terms of the efficiency of energy transfer. A high concentration of the assisting dopant is preferable in terms of the efficiency of the thermally activated delayed fluorescence mechanism. In an organic electroluminescent device that uses a thermally activated delayed fluorescent material as an assisting dopant, a low concentration of the emitting dopant is preferable compared to the amount of the assisting dopant in terms of the efficiency of the thermally activated delayed fluorescence mechanism of the assisting dopant.

When an assisting dopant material is used, the approximate amounts of the host material, assisting dopant material, and emitting dopant material used are 40 to 99% by weight, 59 to 1% by weight, and 20 to 0.001% by weight, respectively, based on the total weight of the materials for the light-emitting layer, preferably 60 to 95% by weight, 39 to 5% by weight, and 10 to 0.01% by weight, respectively, and more preferably 70 to 90% by weight, 29 to 10% by weight, and 5 to 0.05% by weight.

The polycyclic aromatic compound represented by formula (1) is preferably used as a material for forming a light-emitting layer, more preferably as a dopant, and particularly preferably as an emitting dopant.

<Host Material>
Examples of the host material include condensed ring derivatives such as anthracene and pyrene, which have been known as light emitters for a long time, bisstyryl derivatives such as bisstyryl anthracene derivatives and distyrylbenzene derivatives, tetraphenylbutadiene derivatives, cyclopentadiene derivatives, fluorene derivatives, benzofluorene derivatives, N-phenylcarbazole derivatives, carbazonitrile derivatives, and dibenzochrysene derivatives. From the viewpoint of durability, it is also preferable that some or all of the hydrogen atoms of the host material are deuterated. Furthermore, it is also preferable to form the light emitting layer by combining a host compound in which some or all of the hydrogen atoms are deuterated with a dopant compound in which some or all of the hydrogen atoms are deuterated.

The host material may be one type or a combination of multiple types. When multiple types are used, a combination of a hole-transporting host material and an electron-transporting host material is preferable.

[Anthracene Compounds]
Examples of the anthracene compound as a host include a compound represented by the formula (3-H) and a compound represented by the formula (3-H2).

In formula (3-H),
X and ^Ar4 are each independently hydrogen, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted diarylamino, optionally substituted diheteroarylamino, substituted or unsubstituted arylheteroarylamino, substituted or unsubstituted alkyl, optionally substituted cycloalkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkoxy, substituted or unsubstituted aryloxy, substituted or unsubstituted arylthio, or substituted silyl, and all of X and ^Ar4 are not hydrogen at the same time.
At least one hydrogen in the compound represented by formula (3-H) may be substituted with halogen, cyano, deuterium or an optionally substituted heteroaryl.

A polymer (preferably a dimer) may be formed using the structure represented by formula (3-H) as a unit structure. In this case, for example, the unit structures represented by formula (3-H) may be bonded to each other via X, where X may be a single bond, an arylene (phenylene, biphenylene, naphthylene, etc.), or a heteroarylene (a pyridine ring, a dibenzofuran ring, a dibenzothiophene ring, a carbazole ring, a benzocarbazole ring, a phenyl-substituted carbazole ring, etc., which has a divalent bond).

For details of each group in the compound represented by formula (3-H), the explanation for formula (1) above can be cited, and further explanation is given in the section on preferred embodiments below.

Preferred embodiments of the above anthracene compound are described below. The symbols in the following structures are defined as above.

In formula (3-H), X is each independently a group represented by formula (3-X1), formula (3-X2) or formula (3-X3), and the group represented by formula (3-X1), formula (3-X2) or formula (3-X3) is bonded to the anthracene ring of formula (3-H) at *. Preferably, two Xs are not simultaneously a group represented by formula (3-X3). More preferably, two Xs are not simultaneously a group represented by formula (3-X2).

A polymer (preferably a dimer) may be formed using the structure represented by formula (3-H) as a unit structure. In this case, for example, the unit structures represented by formula (3-H) may be bonded to each other via X, where X may be a single bond, an arylene (phenylene, biphenylene, naphthylene, etc.), or a heteroarylene (a pyridine ring, a dibenzofuran ring, a dibenzothiophene ring, a carbazole ring, a benzocarbazole ring, a phenyl-substituted carbazole ring, etc., which has a divalent bond).

The naphthylene moieties in formula (3-X1) and formula (3-X2) may be condensed with one benzene ring. The condensed structures are as follows:

Ar ¹ and Ar ² are each independently hydrogen, phenyl, biphenylyl, terphenylyl, quaterphenylyl, naphthyl, phenanthryl, fluorenyl, benzofluorenyl, chrysenyl, triphenylenyl, pyrenyl, or a group represented by formula (A) (including carbazolyl, benzocarbazolyl, and phenyl-substituted carbazolyl). When Ar ¹ or Ar ² is a group represented by formula (A), the group represented by formula (A) is bonded to the naphthalene ring in formula (3-X1) or formula (3-X2) at the *.

Ar ³ is phenyl, biphenylyl, terphenylyl, quaterphenylyl, naphthyl, phenanthryl, fluorenyl, benzofluorenyl, chrysenyl, triphenylenyl, pyrenyl, or a group represented by formula (A) (including carbazolyl, benzocarbazolyl, and phenyl-substituted carbazolyl). When Ar ³ is a group represented by formula (A), the group represented by formula (A) is bonded to the single bond represented by a straight line in formula (3-X3) at the *. That is, the anthracene ring of formula (3-H) and the group represented by formula (A) are directly bonded.

In addition, Ar ³ may have a substituent, and at least one hydrogen atom in Ar ³ may be further substituted with an alkyl having 1 to 4 carbon atoms, a cycloalkyl having 5 to 10 carbon atoms, phenyl, biphenylyl, terphenylyl, naphthyl, phenanthryl, fluorenyl, chrysenyl, triphenylenyl, pyrenyl, or a group represented by formula (A) (including carbazolyl and phenyl-substituted carbazolyl). When the substituent in Ar ³ is a group represented by formula (A), the group represented by formula (A) bonds to Ar ³ in formula (3-X3) at the *.

Each Ar ⁴ is independently hydrogen, phenyl, biphenylyl, terphenylyl, naphthyl, or silyl substituted with alkyl having 1 to 4 carbon atoms (eg, methyl, ethyl, t-butyl) and/or cycloalkyl having 5 to 10 carbon atoms.

Examples of alkyl groups with 1 to 4 carbon atoms that substitute for silyl include methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, t-butyl, and cyclobutyl, and each of the three hydrogen atoms in the silyl is independently replaced by one of these alkyl groups.

Specific examples of "silyl substituted with alkyl having 1 to 4 carbon atoms" include trimethylsilyl, triethylsilyl, tripropylsilyl, triisopropylsilyl, tributylsilyl, trisec-butylsilyl, tri-t-butylsilyl, ethyldimethylsilyl, propyldimethylsilyl, isopropyldimethylsilyl, butyldimethylsilyl, sec-butyldimethylsilyl, t-butyldimethylsilyl, methyldiethylsilyl, propyldiethylsilyl, isopropyldiethylsilyl, butyldiethylsilyl, sec-butyldiethylsilyl, t-butyldiethylsilyl, methyldipropylsilyl, ethyldipropylsilyl, butyldipropylsilyl, sec-butyldipropylsilyl, t-butyldipropylsilyl, methyldiisopropylsilyl, ethyldiisopropylsilyl, butyldiisopropylsilyl, sec-butyldiisopropylsilyl, t-butyldiisopropylsilyl, and the like.

Examples of cycloalkyls having 5 to 10 carbon atoms that substitute for silyl include cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, bicyclo[1.1.1]pentyl, bicyclo[2.1.0]pentyl, bicyclo[2.1.1]hexyl, bicyclo[3.1.0]hexyl, bicyclo[2.2.1]heptyl (norbornyl), bicyclo[2.2.2]octyl, adamantyl, decahydronaphthalenyl, and decahydroazulenyl, and each of the three hydrogens in the silyl is independently replaced by one of these cycloalkyls.

Specific examples of "silyl substituted with cycloalkyl having 5 to 10 carbon atoms" include tricyclopentylsilyl and tricyclohexylsilyl.

Substituted silyls include dialkylcycloalkylsilyls, which are substituted with two alkyls and one cycloalkyl, and alkyldicycloalkylsilyls, which are substituted with one alkyl and two cycloalkyls. Specific examples of the alkyl and cycloalkyl substituents are the groups mentioned above.

In addition, hydrogen in the chemical structure of the anthracene compound represented by formula (3-H) may be replaced by a group represented by formula (A). When replaced by a group represented by formula (A), the group represented by formula (A) replaces at least one hydrogen in the compound represented by formula (3-H) at the *.

The group represented by formula (A) is one of the substituents that the anthracene compound represented by formula (3-H) may have.

In formula (A), Y is -O-, -S- or >N-R ²⁹ , R ²¹ to R ²⁸ are each independently hydrogen, optionally substituted alkyl, optionally substituted cycloalkyl, optionally substituted aryl, optionally substituted heteroaryl, optionally substituted alkoxy, optionally substituted aryloxy, optionally substituted arylthio, trialkylsilyl, tricycloalkylsilyl, dialkylcycloalkylsilyl, alkyldicycloalkylsilyl, optionally substituted amino, halogen, hydroxy or cyano, adjacent groups among R ²¹ to R ²⁸ may be bonded to each other to form a hydrocarbon ring, an aryl ring or a heteroaryl ring, and R ²⁹ is hydrogen or optionally substituted aryl.
In formula (A), Y is preferably --O--.

Adjacent groups among R ²¹ to R ²⁸ may be bonded to each other to form a hydrocarbon ring, an aryl ring, or a heteroaryl ring. The group represented by the following formula (A-1) does not form a ring, and examples of the group that forms a ring include the groups represented by the following formulas (A-2) to (A-14). At least one hydrogen atom in the group represented by any of formulas (A-1) to (A-14) may be substituted with alkyl, cycloalkyl, aryl, heteroaryl, alkoxy, aryloxy, arylthio, trialkylsilyl, tricycloalkylsilyl, dialkylcycloalkylsilyl, alkyldicycloalkylsilyl, diaryl (the two aryls may be bonded to each other via a linking group), substituted amino, diheteroaryl substituted amino, arylheteroaryl substituted amino, halogen, hydroxy, or cyano.

Examples of rings formed by bonding adjacent groups to each other include hydrocarbon rings such as cyclohexane rings, and examples of aryl rings and heteroaryl rings include the ring structures explained above for "aryl" and "heteroaryl" in R ^{to R} , and these rings are formed so as to be condensed with one or two benzene rings in formula (A-1).

The group represented by formula (A) is a group obtained by removing one hydrogen atom at any position of formula (A), and * indicates the position. That is, the group represented by formula (A) may have any position as a bonding position. For example, it may be any carbon atom on the two benzene rings in the structure of formula (A), an atom on any ring formed by bonding adjacent groups among R ²¹ to R ²⁸ in the structure of formula (A), any position in R ²⁹ in “>N-R ²⁹ ” as Y in the structure of formula (A), or a group directly bonded to N in “>N-R ²⁹ ” (R ²⁹ is a bond). The same applies to the groups represented by any of formulas (A-1) to (A-14).

Examples of the group represented by formula (A) include groups represented by any of formulas (A-1) to (A-14), with groups represented by any of formulas (A-1) to (A-5) and (A-12) to (A-14) being preferred, groups represented by any of formulas (A-1) to (A-4) being more preferred, groups represented by any of formulas (A-1), (A-3) and (A-4) being even more preferred, and groups represented by formula (A-1) being particularly preferred.

Examples of the group represented by formula (A) include the following groups: In the formula, Y and * are defined as above.

In the compound represented by formula (3-H), the group represented by formula (A) is preferably bonded to any one of the naphthalene ring in formula (3-X1) or formula (3-X2), the single bond in formula (3-X3), and Ar ³ in formula (3-X3).

In addition, all or some of the hydrogen atoms in the chemical structure of the anthracene compound represented by formula (3-H) may be deuterium.

The anthracene compound as the host may be, for example, a compound represented by the following formula (3-H2).

In formula (3-H2), Ar ^c is optionally substituted aryl or optionally substituted heteroaryl, R ^c is hydrogen, alkyl, or cycloalkyl, Ar ¹¹ , Ar ¹² , Ar ¹³ , Ar ¹⁴ , Ar ¹⁵ , Ar ¹⁶ , Ar ¹⁷ , and Ar ¹⁸ are each independently hydrogen, optionally substituted aryl, optionally substituted heteroaryl, optionally substituted diarylamino, optionally substituted diheteroarylamino, optionally substituted arylheteroarylamino, optionally substituted alkyl, optionally substituted cycloalkyl, optionally substituted alkenyl, optionally substituted alkoxy, optionally substituted aryloxy, optionally substituted arylthio, or optionally substituted silyl, and at least one hydrogen in the compound represented by formula (3-H2) may be replaced by halogen, cyano, or deuterium.

In formula (3-H2), the definitions of "optionally substituted aryl", "optionally substituted heteroaryl", "optionally substituted diarylamino", "optionally substituted diheteroarylamino", "optionally substituted arylheteroarylamino", "optionally substituted alkyl", "optionally substituted cycloalkyl", "optionally substituted alkenyl", "optionally substituted alkoxy", "optionally substituted aryloxy", "optionally substituted arylthio", and "optionally substituted silyl" are the same as those in formula (3-H) above, and the explanation in formula (3-H) can be cited.

The "optionally substituted aryl" is preferably a group represented by any one of the following formulas (3-H2-X1) to (3-H2-X8).

In formulae (3-H2-X1) to (3-H2-X8), * indicates a bonding position. In formulae (3-H2-X1) to (3-H2-X3), Ar ²¹ , Ar ²² , and Ar ²³ are each independently hydrogen, phenyl, biphenylyl, terphenylyl, quaterphenylyl, naphthyl, phenanthryl, fluorenyl, benzofluorenyl, chrysenyl, triphenylenyl, pyrenyl, anthracenyl, or a group represented by formula (A). In the explanation of formula (3-H2), the group represented by formula (A) is the same as that explained in the anthracene compound represented by formula (3-H).

In formulae (3-H2-X4) to (3-H2-X8), Ar ²⁴ , Ar ²⁵ , Ar ²⁶ , Ar ²⁷ , Ar ²⁸ , Ar ²⁹ , and Ar ³⁰ are each independently hydrogen, phenyl, biphenylyl, terphenylyl, naphthyl, phenanthryl, fluorenyl, chrysenyl, triphenylenyl, pyrenyl, or a group represented by formula (A). In addition, any one or more hydrogen atoms in each of the groups represented by formulae (3-H2-X1) to (3-H2-X8) may be substituted by alkyl having 1 to 6 carbon atoms (preferably methyl or t-butyl).

Furthermore, preferred examples of "optionally substituted aryl" include phenyl, biphenylyl, terphenylyl, naphthyl, phenanthryl, fluorenyl, chrysenyl, triphenylenyl, pyrenyl, and terphenylyl (particularly m-terphenyl-5'-yl) which may be substituted with one or more substituents selected from the group consisting of groups represented by formula (A).

An example of an "optionally substituted heteroaryl" is a group represented by formula (A). Other examples of "optionally substituted aryl" and "optionally substituted heteroaryl" include dibenzofuryl, naphthobenzofuryl, and phenyl-substituted dibenzofuryl.

At least one hydrogen atom in the compound represented by formula (3-H2) may be replaced by a halogen atom, cyano, or deuterium. In this case, "halogen" includes fluorine, chlorine, bromine, and iodine. In particular, a compound in which all hydrogen atoms in the compound represented by formula (3-H2) are replaced by deuterium is preferred.

In formula (3-H2), R ^c is hydrogen, alkyl, or cycloalkyl, preferably hydrogen, methyl, or t-butyl, and more preferably hydrogen.
In formula (3-H2), it is preferable that at least two of Ar ¹¹ to Ar ¹⁸ are optionally substituted aryl or optionally substituted heteroaryl. That is, it is preferable that the anthracene compound represented by formula (3-H2) has a structure in which at least three substituents selected from the group consisting of optionally substituted aryl and optionally substituted heteroaryl are bonded to an anthracene ring.

In the anthracene compound represented by formula (3-H2), two of Ar ¹¹ to Ar ¹⁸ are optionally substituted aryl or optionally substituted heteroaryl, and the remaining six are hydrogen, optionally substituted alkyl, optionally substituted cycloalkyl, optionally substituted alkenyl, or optionally substituted alkoxy. In other words, it is more preferable that the anthracene compound represented by formula (3-H2) has a structure in which three substituents selected from the group consisting of optionally substituted aryl and optionally substituted heteroaryl are bonded to the anthracene ring.

In the anthracene compound represented by formula (3-H2), any two of Ar ¹¹ to Ar ¹⁸ are optionally substituted aryl or optionally substituted heteroaryl, and the other six are hydrogen, methyl, or t-butyl.

Furthermore, in formula (3-H2), it is preferred that R ^c is hydrogen and any six of Ar ¹¹ to Ar ¹⁸ are hydrogen.

The anthracene compound represented by formula (3-H2) is preferably an anthracene compound represented by the following formula (3-H2-A), (3-H2-B), (3-H2-C), (3-H2-D), or (3-H2-E).

In formula (3-H2-A), (3-H2-B), (3-H2-C), (3-H2-D) or (3-H2-E), Ar ^c ', Ar ¹¹ ', Ar ¹² ', Ar ¹³ ', Ar ¹⁴ ', Ar ¹⁵ ', Ar ¹⁷ ' and Ar ¹⁸ ' are each independently phenyl, biphenylyl, terphenylyl, quaterphenylyl, naphthyl, phenanthryl, fluorenyl, benzofluorenyl, chrysenyl, triphenylenyl, pyrenyl, or a group represented by formula (A), and at least one hydrogen atom in these groups may be substituted by phenyl, biphenylyl, terphenylyl, quaterphenylyl, naphthyl, phenanthryl, fluorenyl, benzofluorenyl, chrysenyl, triphenylenyl, pyrenyl, or a group represented by formula (A). When all of the hydrogen atoms of the methylene in fluorenyl and benzofluorenyl are replaced by phenyl, these phenyls may be bonded to each other via a single bond. Methyl or t-butyl may be bonded to the carbon atom of the anthracene ring to which Ar ^c ', Ar ¹¹ ', Ar ¹² ', Ar ¹³ ', Ar ¹⁴ ', Ar ¹⁵ ', Ar ¹⁷ ', and Ar ¹⁸ ' are not bonded, instead of hydrogen.

When Ar ^c ', Ar ¹¹ ', Ar ¹² ', Ar ¹³ ', Ar ¹⁴ ', Ar ¹⁵ ', Ar ¹⁷ ', and Ar ¹⁸ ' are each substituted or unsubstituted phenyl or substituted or unsubstituted naphthyl, they are preferably a group represented by any of the above formulae (3-H2-X1) to (3-H2-X8).

It is more preferable that Ar ^c ', Ar ¹¹ ', Ar ¹² ', Ar ¹³ ', Ar ¹⁴ ', Ar ¹⁵ ', Ar ¹⁷ ', and Ar ¹⁸ ' are each independently phenyl, biphenylyl (particularly biphenyl-2-yl or biphenyl-4-yl), terphenylyl (particularly m-terphenyl-5'-yl), naphthyl, phenanthryl, fluorenyl, or a group represented by any of the above formulas (A-1) to (A-4), in which case at least one hydrogen atom in these groups may be substituted by phenyl, biphenylyl, naphthyl, phenanthryl, fluorenyl, or a group represented by any of the above formulas (A-1) to (A-4).

In addition, at least one hydrogen atom in the compound represented by formula (3-H2-A), (3-H2-B), (3-H2-C), (3-H2-D), or (3-H2-E) may be substituted with a halogen, cyano, or deuterium. Deuterated forms are preferred, and it is preferable that all anthracene rings are deuterated, or that all hydrogen atoms are deuterated.

Particularly preferred anthracene compounds represented by formula (3-H2) include those represented by formula (3-H2-Aa) below.

In formula (3-H2-Aa), Ar ^c ', Ar ¹⁴ ', and Ar ¹⁵ ' are each independently phenyl, biphenylyl, terphenylyl, naphthyl, phenanthryl, fluorenyl, benzofluorenyl, chrysenyl, triphenylenyl, pyrenyl, or a group represented by any one of formulas (A-1) to (A-11), and at least one hydrogen atom in these groups may be substituted by phenyl, biphenylyl, terphenylyl, naphthyl, phenanthryl, fluorenyl, benzofluorenyl, chrysenyl, triphenylenyl, pyrenyl, or a group represented by any one of formulas (A-1) to (A-11). When both hydrogen atoms of methylene groups in fluorenyl and benzofluorenyl are substituted by phenyl, these phenyl groups may be bonded to each other by a single bond. Furthermore, the carbon atoms on the anthracene ring to which Ar ^c ', Ar ¹⁴ ', and Ar ¹⁵ ' are not bonded may be substituted with methyl or t-butyl in place of hydrogen. At least one hydrogen in the compound represented by formula (3-H2-Aa) may be substituted with halogen or cyano, and at least one hydrogen in the compound represented by formula (3-H2-Aa) is substituted with deuterium.

In formula (3-H2-Aa), it is preferable that Ar ^c ', Ar ¹⁴ ', and Ar ¹⁵ ' are each independently phenyl, biphenylyl, terphenylyl, naphthyl, phenanthryl, fluorenyl, or a group represented by any one of the above formulas (A-1) to (A-4), and at least one hydrogen atom in these groups may be substituted by phenyl, naphthyl, phenanthryl, fluorenyl, or a group represented by any one of the above formulas (A-1) to (A-4).

In the compound represented by formula (3-H2-Aa), it is preferable that at least the hydrogen bonded to the carbon at the 10th position of the anthracene ring (the carbon bonded to Ar ^c ' is the 9th position) is substituted with deuterium. That is, the compound represented by formula (3-H2-Aa) is preferably a compound represented by the following formula (3-H2-Ab). In formula (3-H2-Ab), D is deuterium, and Ar ^c ', Ar ¹⁴ ', and Ar ¹⁵ ' are the same as those in formula (3-H2-Aa). D in formula (3-H2-Ab) indicates that at least this position is deuterium, and any one or more other hydrogen atoms in formula (3-H2-Ab) may be deuterium at the same time, and it is also preferable that all hydrogen atoms in formula (3-H2-Ab) are deuterium.

Specific examples of the anthracene compound include compounds represented by formulae (3-131-Y) to (3-182-Y), (3-183-N), (3-184-Y) to (3-284-Y), (3-500) to (3-557), (3-600) to (3-605), and (3-606-Y) to (3-626-Y). The hydrogen atoms in these formulae may be partially or completely replaced with deuterium, and particularly preferred forms of deuterium replacement are listed individually. Y in the formulae may be any of -O-, -S-, >N-R ²⁹ (R ²⁹ is the same as above) or >C(-R ³⁰ ) ₂ (R ³⁰ is an aryl or alkyl group which may be linked), where R ²⁹ is, for example, phenyl, and R ³⁰ is, for example, methyl. For example, when Y is O, the formula (3-131-Y) is made into the formula (3-131-O), and when Y is -S- or >N-R ²⁹ , it is made into the formula (3-131-S) or the formula (3-131-N), respectively.

上記式中、Ｄは重水素である。

In the above formula, D is deuterium.

Among these compounds, the compounds of the formula (3-131-Y) to the formula (3-134-Y), the formula (3-138-Y), the formula (3-140-Y) to the formula (3-143-Y), the formula (3-150-Y), the formula (3-153-Y) to the formula (3-156-Y), the formula (3-166-Y), the formula (3-168-Y), the formula (3-173-Y), the formula (3-177-Y), the formula (3-180-Y) to the formula (3-183-N), the formula (3-185-Y), the formula (3-190-Y), the formula (3-223-Y), the formula (3-241- Y), the formula (3-250-Y), the formula (3-252-Y) to the formula (3-254-Y), the formula (3-270-Y) to the formula (3-284-Y), the formula (3-501), the formula (3-507), the formula (3-508), the formula (3-509), the formula (3-513), the formula (3-514), the formula (3-519), the formula (3-521), the formula (3-538) to the formula (3-547), or the formula (3-600) to the formula (3-605), and the formula (3-606-Y) to the formula (3-626-Y) are preferred. Y is preferably -O- or >N-R ²⁹ , more preferably -O-. Deuterium substitution is also preferred.

The above anthracene compounds can be produced by applying Suzuki coupling, Negishi coupling, or other known coupling reactions using as starting materials a compound having a reactive group at a desired position of the anthracene skeleton, and a compound having a reactive group in a partial structure such as X, Ar ⁴ , and the structure of formula (A) in the case of an anthracene compound represented by formula (3-H). Examples of reactive groups in these reactive compounds include halogens and boronic acids. As a specific production method, for example, the synthesis method in paragraphs [0089] to [0175] of WO 2014/141725 can be referred to.

[Fluorene Compounds]
The compound represented by the formula (4-H) basically functions as a host.

In formula (4-H),
R ¹ to R ¹⁰ are each independently hydrogen, aryl, heteroaryl (the heteroaryl may be bonded to the fluorene skeleton in formula (4-H) via a linking group), diarylamino, diheteroarylamino, arylheteroarylamino, alkyl, cycloalkyl, alkenyl, alkoxy, or aryloxy, in which at least one hydrogen may be replaced by an aryl, heteroaryl, alkyl, or cycloalkyl, and R ¹ and R ² , R ² and R ³ , R ³ and R ⁴ , R ⁵ and R ⁶ , R ⁶ and R ⁷ , R ⁷ and R ⁸ , or R ⁹ and R ¹⁰ may each independently bond to form a fused ring or a spiro ring, and at least one hydrogen atom in the formed ring may be substituted with an aryl, a heteroaryl (the heteroaryl may be bonded to the formed ring via a linking group), a diarylamino, a diheteroarylamino, an arylheteroarylamino, an alkyl, a cycloalkyl, an alkenyl, an alkoxy, or an aryloxy, and at least one hydrogen atom in these may be substituted with an aryl, a heteroaryl, an alkyl, or a cycloalkyl, and at least one hydrogen atom in the compound represented by formula (4-H) may be substituted with a halogen, a cyano, or a deuterium.

For details of each group in the definition of formula (4-H), please refer to the explanation for the polycyclic aromatic compound of formula (1) above.

Examples of the alkenyl in R ¹ to R ¹⁰ include alkenyl having 2 to 30 carbon atoms, preferably alkenyl having 2 to 20 carbon atoms, more preferably alkenyl having 2 to 10 carbon atoms, further preferably alkenyl having 2 to 6 carbon atoms, and particularly preferably alkenyl having 2 to 4 carbon atoms. Preferred alkenyls are vinyl, 1-propenyl, 2-propenyl, 1-butenyl, 2-butenyl, 3-butenyl, 1-pentenyl, 2-pentenyl, 3-pentenyl, 4-pentenyl, 1-hexenyl, 2-hexenyl, 3-hexenyl, 4-hexenyl, or 5-hexenyl.

Specific examples of heteroaryl include monovalent groups represented by removing any one hydrogen atom from the compounds of the following formula (4-Ar1), (4-Ar2), (4-Ar3), (4-Ar4), or (4-Ar5).

In formulae (4-Ar1) to (4-Ar5), ^Y1 's are each independently O, S, or N-R, where R is phenyl, biphenylyl, naphthyl, anthracenyl, or hydrogen, and at least one hydrogen in the structures of formulae (4-Ar1) to (4-Ar5) may be substituted with phenyl, biphenylyl, naphthyl, anthracenyl, phenanthryl, methyl, ethyl, propyl, or butyl.

These heteroaryls may be bonded to the fluorene skeleton in formula (4-H) via a linking group. That is, the fluorene skeleton in formula (4-H) and the heteroaryl may be bonded directly or via _a linking group. Examples of the linking group include phenylene, biphenylene, naphthylene, anthracenylene _, methylene, ethylene, _{-OCH2CH2- , -CH2CH2O-} , and _-OCH2CH2O- .

In addition, R ¹ and R ² , R ² and R ³ , R ³ and R ⁴ , R ⁵ and R ⁶ , R ⁶ and R ⁷ , or R ⁷ and R ⁸ in formula (4-H) may each independently bond to a fused ring, and R ⁹ and R ¹⁰ may bond to a spiro ring. The fused ring formed by R ¹ to R ⁸ is a ring fused to the benzene ring in formula (4-H), and is an aliphatic ring or an aromatic ring. It is preferably an aromatic ring, and examples of the structure including the benzene ring in formula (4-H) include a naphthalene ring and a phenanthrene ring. The spiro ring formed by R ⁹ and R ¹⁰ is a ring spiro-bonded to the 5-membered ring in formula (4-H), and is an aliphatic ring or an aromatic ring. It is preferably an aromatic ring, and examples of the structure including the benzene ring in formula (4-H) include a fluorene ring.

The compound represented by formula (4-H) is preferably a compound represented by the following formula (4-H-1), formula (4-H-2) or formula (4-H-3), which is a compound in which R ¹ and R ² in formula (4-H) are bonded to form a condensed benzene ring, a compound in which R ³ and R ⁴ in formula (4-H) are bonded to form a condensed benzene ring, and a compound in which none of R ¹ to R ⁸ in formula (4-H) are bonded.

The definitions of R ¹ to R ¹⁰ in formulas (4-H-1), (4-H-2) and (4-H-3) are the same as the corresponding R ¹ to R ¹⁰ in formula (4-H), and the definitions of R ¹¹ to R ¹⁴ in formulas (4-H-1) and (4-H-2) are the same as the corresponding R ¹ to R ¹⁰ in formula (4-H).

The compound represented by formula (4-H) is more preferably a compound represented by the following formula (4-H-1A), formula (4-H-2A) or formula (4-H-3A), which is a compound in which R ⁹ and R ¹⁰ are bonded to form a spiro-fluorene ring in formula (4-H-1), formula (4-H-2) or formula (4-H-3), respectively.

The definitions of ^R2 to ^R7 in formulae (4-H-1A), (4-H-2A) and (4-H-3A) are the same as the corresponding ^R2 to R7 in formulae (4-H-1), (4-H-2) and (4-H-3), and the definitions of ^R11 to ^R14 in formulae (4-H-1A) and (4-H-2A) are the same as ^R11 to ^R14 in formulae (4-H- ¹ ) and (4-H-2).

In addition, all or some of the hydrogen atoms in the compound represented by formula (4-H) may be replaced with halogen, cyano, or deuterium.

More specific examples of the fluorene compound as a host include compounds represented by the following structural formulas.

[Dibenzochrysene Compounds]
The dibenzochrysene compound as the host is, for example, a compound represented by the following formula (5-H).

In formula (5-H), R ¹ to R ¹⁶ are each independently hydrogen, aryl, heteroaryl (the heteroaryl may be bonded to the dibenzochrysene skeleton in formula (5-H) via a linking group), diarylamino, diheteroarylamino, arylheteroarylamino, alkyl, cycloalkyl, alkenyl, alkoxy, or aryloxy, in which at least one hydrogen may be substituted with an aryl, heteroaryl, alkyl, or cycloalkyl, or adjacent groups among R ¹ to R ¹⁶ may be bonded to each other to form a condensed ring, in which at least one hydrogen in the formed ring may be substituted with an aryl, heteroaryl (the heteroaryl may be bonded to the formed ring via a linking group), diarylamino, diheteroarylamino, arylheteroarylamino, alkyl, cycloalkyl, alkenyl, alkoxy, or aryloxy, in which at least one hydrogen may be substituted with an aryl, heteroaryl, alkyl, or cycloalkyl, or in which at least one hydrogen in the compound represented by formula (5-H) may be substituted with a halogen, cyano, or deuterium.

For details of each group in the definition of formula (5-H), please refer to the explanation for the polycyclic aromatic compound of formula (1) above.

The alkenyl in the definition of formula (5-H) is, for example, an alkenyl having 2 to 30 carbon atoms, preferably an alkenyl having 2 to 20 carbon atoms, more preferably an alkenyl having 2 to 10 carbon atoms, even more preferably an alkenyl having 2 to 6 carbon atoms, and particularly preferably an alkenyl having 2 to 4 carbon atoms. Preferred alkenyls are vinyl, 1-propenyl, 2-propenyl, 1-butenyl, 2-butenyl, 3-butenyl, 1-pentenyl, 2-pentenyl, 3-pentenyl, 4-pentenyl, 1-hexenyl, 2-hexenyl, 3-hexenyl, 4-hexenyl, or 5-hexenyl.

Specific examples of heteroaryl include monovalent groups represented by removing any one hydrogen atom from the compounds of the following formula (5-Ar1), (5-Ar2), (5-Ar3), (5-Ar4), or (5-Ar5).

In formulae (5-Ar1) to (5-Ar5), ^Y1 's are each independently O, S or N-R, R is phenyl, biphenylyl, naphthyl, anthracenyl or hydrogen, and at least one hydrogen in the structures of formulae (5-Ar1) to (5-Ar5) may be substituted with phenyl, biphenylyl, naphthyl, anthracenyl, phenanthryl, methyl, ethyl, propyl or butyl.

These heteroaryls may be bonded to the dibenzochrysene skeleton in formula (5-H) via a linking group. That is, the dibenzochrysene skeleton in formula (5-H) and the heteroaryl may be bonded directly or via _a linking group. Examples of the linking group include phenylene, biphenylene, naphthylene, _{anthracenylene} , methylene, ethylene, _{-OCH2CH2- , -CH2CH2O-} , and _-OCH2CH2O- .

In the compound represented by formula (5-H), R ¹ , R ⁴ , R ⁵ , R ⁸ , R ⁹ , R ¹² , R ¹³ and R ¹⁶ are preferably hydrogen. In this case, it is preferable that R ² , R ³ , R ⁶ , R ⁷ , R ¹⁰ , R ¹¹ , R ¹⁴ and R ¹⁵ in formula (5-H) are each independently hydrogen, phenyl, biphenylyl, naphthyl, anthracenyl, phenanthryl, a monovalent group having a structure of formula (5-Ar1), formula (5-Ar2), formula (5-Ar3), formula (5-Ar4) or formula (5-Ar5) (the monovalent group having the structure may be bonded to the dibenzochrysene skeleton in formula (5-H) via phenylene, biphenylene, naphthylene, anthracenylene, methylene, ethylene, -OCH ₂ CH ₂ -, -CH ₂ CH ₂ O- or -OCH ₂ CH ₂ O-), methyl, ethyl, propyl or butyl.

In the compound represented by formula (5-H), R ¹ , R ² , R ⁴ , R ⁵ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹² , R ¹³ , R ¹⁵ and R ¹⁶ are more preferably hydrogen. In this case, at least one (preferably one or two, more preferably one) of R ³ , R ⁶ , R ¹¹ and R ¹⁴ in formula (5-H) is a single bond, phenylene, biphenylene, naphthylene, anthracenylene, methylene, ethylene, -OCH ₂ CH ₂ -, -CH ₂ CH ₂ O-, or -OCH ₂ CH ₂ A monovalent group having a structure of formula (5-Ar1), (5-Ar2), (5-Ar3), (5-Ar4) or (5-Ar5) via O-, wherein the other than the at least one (i.e., other than the position substituted by the monovalent group having the structure) is hydrogen, phenyl, biphenylyl, naphthyl, anthracenyl, methyl, ethyl, propyl or butyl, and at least one hydrogen in these may be substituted with phenyl, biphenylyl, naphthyl, anthracenyl, methyl, ethyl, propyl or butyl.

In addition, when a monovalent group having a structure represented by formula (5-Ar1) to formula (5-Ar5) is selected as R ² , R ³ , R ⁶ , R ⁷ , R ¹⁰ , R ¹¹ , R ¹⁴ and R ¹⁵ in formula (5-H), at least one hydrogen atom in the structure may be bonded to any one of R ¹ to R ¹⁶ in formula (5-H) to form a single bond.

More specific examples of the dibenzochrysene compound as a host include compounds represented by the following structural formulas.

[Compound represented by any one of formulas (H1), (H2) and (H3)]
As the host material, for example, a compound represented by any one of the following formulas (H1), (H2), and (H3) can be used.

In formulae (H1), (H2) and (H3), L ¹ is a single bond or a divalent group containing at least an arylene or heteroarylene. Specifically, L ¹ may be a single bond, or may be an arylene having 6 to 24 carbon atoms, a heteroarylene having 2 to 24 carbon atoms, a heteroarylenearylene having 6 to 24 carbon atoms, or an aryleneheteroarylenearylene having 6 to 24 carbon atoms, or a divalent group formed by linking any two of these with -O-, -S-, -CH ₂ -, -Si(-Arx) ₂ - (Arx is aryl), or a cycloalkylene. The arylene in L ¹ is preferably an arylene having 6 to 16 carbon atoms, more preferably an arylene having 6 to 12 carbon atoms, and particularly preferably an arylene having 6 to 10 carbon atoms, and specifically includes divalent groups such as a benzene ring, a biphenyl ring, a terphenyl ring and a fluorene ring. L The heteroarylene in ¹ is preferably a heteroarylene having 2 to 24 carbon atoms, more preferably a heteroarylene having 2 to 20 carbon atoms, still more preferably a heteroarylene having 2 to 15 carbon atoms, and particularly preferably a heteroarylene having 2 to 10 carbon atoms. Specific examples thereof include a pyrrole ring, an oxazole ring, an isoxazole ring, a thiazole ring, an isothiazole ring, an imidazole ring, an oxadiazole ring (such as a furazan ring), a thiadiazole ring, a triazole ring, a tetrazole ring, a pyrazole ring, a pyridine ring, a pyrimidine ring, a pyridazine ring, a pyrazine ring, a triazine ring, an indole ring, and an isoindole ring. , 1H-indazole ring, benzimidazole ring, benzoxazole ring, benzothiazole ring, 1H-benzotriazole ring, quinoline ring, isoquinoline ring, cinnoline ring, quinazoline ring, quinoxaline ring, phthalazine ring, naphthyridine ring, purine ring, pteridine ring, carbazole ring, acridine ring, phenoxathiin ring, phenoxazine ring, phenothiazine ring, phenazine ring, indolizine ring, furan ring, benzofuran ring, isobenzofuran ring, dibenzofuran ring, thiophene ring, benzothiophene ring, dibenzothiophene ring, and thianthrene ring. At least one hydrogen atom in the compound represented by each of the above formulae may be substituted with at least one group selected from the substituent group Z or deuterium, and may be substituted with, for example, an alkyl group having 1 to 6 carbon atoms, cyano, halogen, or deuterium.

Preferred specific examples include compounds represented by any of the structural formulas listed below. In the structural formulas listed below, at least one hydrogen may be substituted with halogen, cyano, alkyl having 1 to 4 carbon atoms (e.g., methyl or t-butyl), phenyl, naphthyl, or the like.

[Hole-transporting host material (HH) and electron-transporting host material (EH)]
The hole-transporting host material (HH) and the electron-transporting host material (EH) satisfy the following relationship with respect to the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO).
The HOMO of the hole-transporting host material (HH) is shallower than the HOMO of the electron-transporting host material (EH), and the LUMO of the electron-transporting host material (EH) is deeper than the LUMO of the hole-transporting host material (HH).
It is also preferable that the HOMO of the emitting dopant is shallower than the HOMO of the hole-transporting host material (HH), or the LUMO of the emitting dopant is deeper than the LUMO of the electron-transporting host material (EH).

In addition, the lowest excited triplet energy level ( _ET1 ) of the hole-transporting host material (HH) and the electron-transporting host material (EH) is preferably higher than the _ET1 of the emitting dopant or assisting dopant having the highest _ET1 in the emitting layer, from the viewpoint of promoting the generation of TADF without inhibiting it in the emitting layer, and specifically, the _ET1 of the host material is preferably 0.01 eV or higher, more preferably 0.03 eV or higher, and even more preferably 0.1 eV or higher than the _ET1 of the emitting dopant or assisting dopant. In addition, the _ET1 of the host material is preferably 2.47 eV or higher, more preferably 2.49 eV or higher, and even more preferably 2.56 eV or higher.

It is also preferable to use a hole-transporting host material in the hole-transporting layer adjacent to the light-emitting layer, and an electron-transporting host material in the electron-transporting layer adjacent to this light-emitting layer. This is because carrier leakage and energy leakage from the light-emitting layer to the adjacent layer are less likely to occur, resulting in a highly efficient organic EL element. The host material in the light-emitting layer (hole-transporting host material) and the hole-transporting layer material may be the same or different. Also, the host material in the light-emitting layer (electron-transporting host material) and the electron-transporting layer material may be the same or different.

Preferred examples of the hole-transporting host material (HH) include compounds represented by formula (HH-1) or having a partial structure represented by formula (HH-1) and a structure containing at least three rings selected from the group consisting of aryl rings and heteroaryl rings. It is preferable that this compound does not contain any of an imine structure (-N=C-; including a partial structure of a heteroaryl ring), boron (>B-), and cyano (CN).

In formula (HH-1),
Q is >O, >S, or >N-A ^H ;
In formula (HH-1), one carbon atom adjacent to the carbon atom to which Q is bonded in each of the two phenyls may be bonded to each other via L,
L is a single bond, >O, >S, or >C(-A ^H ) ₂ ;
A ^H is hydrogen, aryl or heteroaryl, and the two A ^H in >C(-A ^H ) ₂ may be bonded to each other.

When the hole transporting host material contains a structure represented by formula (HH-1) as a partial structure, it may contain one of these partial structures, but it is also preferable to contain two or more of these partial structures. When it contains two or more partial structures, the two or more partial structures may be the same or different. The two or more partial structures may be bonded to each other by a single bond, may be bonded so that any ring contained in the partial structure is shared, or may be bonded so that any ring contained in the partial structure is condensed. The partial structure may further have a substituent selected from aryl, heteroaryl, diarylamino, or aryloxy.

The compound represented by the above formula (HH-1) or having a partial structure represented by formula (HH-1) has a structure containing at least three rings selected from the group consisting of aryl rings and heteroaryl rings. The number of rings contained is preferably 6 or more, and more preferably 8 or more. It is also preferably 20 or less, more preferably 15 or less, and even more preferably 10 or less. The number of rings refers to the number of single rings, and for fused rings, the number is the number of single rings that constitute the fused rings.

The hole-transporting host material is preferably a compound containing one or more partial structures selected from the group consisting of a triarylamine structure, a carbazole ring, a dibenzofuran ring, a dibenzothiophene ring, and a condensed polycyclic ring containing phenoxazine or phenothiazine. The hole-transporting host material may contain one such partial structure, but it is also preferable that it contains two or more. When it contains two or more, the two or more partial structures may be the same or different from each other.

Specific examples of the hole-transporting host material include the following compounds.

Of the above, HH-1-1, HH-1-2, HH-1-4 to HH-1-12, HH-1-17, HH-1-18, HH-1-20 to HH-1-24, HH-1-82, HH-1-84 to HH-1-89, HH-1-91, HH-1-92, HH-1-106 to HH-1-108, and HH-1-109 to HH-1-115 are preferred.

Examples of the electron transporting host material (EH) include compounds represented by formulae (EH-1A) to (EH-1D) or having a partial structure represented by formulae (EH-1A) to (EH-1D) and a structure containing at least three rings selected from the group consisting of aryl rings and heteroaryl rings.

In formulae (EH-1A) to (EH-1D),
Ar is a heteroaryl ring containing N═C as a partial structure constituting the ring;
Z is a single bond, —O—, —S—, or —N(-A ^E )—;
The carbon atom adjacent to the carbon atom to which Z is bonded and A ^E to which Z is bonded may be bonded to each other via L,
L is a single bond, >O, >S or >C(-A ^E ) ₂ ;
A ^E is aryl, heteroaryl, or triarylsilyl, and two A ^E in >C(-A ^E ) ₂ may be bonded to each other;
X is C, P or S;
When X is C, n=2 and m=1;
When X is P, n=3 and m=1;
When X is S, n=2 and m=1 to 2.

Compounds represented by the above formulae (EH-1A) to (EH-1D) or having a partial structure represented by formulae (EH-1A) to (EH-1D) have a structure containing at least three rings selected from the group consisting of aryl rings and heteroaryl rings. The number of rings contained is preferably 4 or more, more preferably 6 or more, and even more preferably 8 or more. It is also preferably 20 or less, more preferably 15 or less, and even more preferably 10 or less. The number of rings refers to the number of single rings, and for fused rings, the number is the number of single rings that constitute the fused rings.

When the electron transporting host material contains a structure represented by formulae (EH-1A) to (EH-1D) as a partial structure, it may contain one of these partial structures, but it is also preferable to contain two or more of them. When it contains two or more, the two or more partial structures may be the same or different. The two or more partial structures may be bonded to each other by a single bond, may be bonded so that any ring contained in the partial structure is shared, or may be bonded so that any ring contained in the partial structure is condensed. The partial structure may further have a substituent selected from aryl, heteroaryl, diarylamino, or aryloxy.

Specific examples of the electron transporting host material include the following compounds.

Other preferable examples of the electron-transporting host material (a compound having a partial structure represented by formula (EH-1)) include a polycyclic aromatic compound represented by formula (EH-1b) below, or a polymer of a polycyclic aromatic compound having a plurality of structures represented by formula (EH-1b) below.

In formula (EH-1b),
R ¹ , R ² , R ³ , R ⁴ and R ⁵ (hereinafter also referred to as “R ¹ etc.”) are each independently hydrogen or a substituent. The substituent may be any substituent selected from the substituent group Z.
In formula (EH-1b), X ¹ and X ² each independently represent >N—R (amine nitrogen), >O, >C(—R) ₂ , >S or >Se, and X ¹ and X ² are not both >C(—R) ₂ ;
R in the >N-R and >C(-R) ₂ are each independently hydrogen or a substituent selected from the substituent group Z, and may be further substituted with an aryl, heteroaryl, alkyl or cycloalkyl (these are the second substituents), and R in the >N-R and >C(-R) ₂ are each independently bonded to at least one of the ring a, ring b and ring c via a linking group or a single bond.
Y ¹ , Y ² , Y ³ , Y ⁴ , Y ⁵ and Y ⁶ (hereinafter also referred to as "Y ^1, etc.") are each independently ═C(—R)— or ═N— (pyridine nitrogen), at least one of which is ═N— (pyridine nitrogen);
Each R in the =C(-R)- is independently hydrogen or a substituent selected from the substituent group Z.
Adjacent groups among R ¹ , R ² , R ³ , R ⁴ and R ⁵ , and R of ═C(—R)— as Y ¹ to Y ⁶ may be bonded to each other to form an aryl ring or a heteroaryl ring together with at least one of the ring a, ring b and ring c, and at least one hydrogen atom in the formed ring may be substituted with an aryl, heteroaryl, diarylamino, diheteroarylamino, arylheteroarylamino, diarylboryl (two aryls may be bonded via a single bond or a linking group), alkyl, cycloalkyl, alkoxy or aryloxy (all of these are first substituents), and at least one hydrogen atom in these may be further substituted with an aryl, heteroaryl, alkyl or cycloalkyl (all of these are second substituents).
At least one hydrogen atom in the compound and structure represented by formula (EH-1b) may be substituted with cyano, halogen or deuterium.

In formula (EH-1b), it is preferable that R ¹ , R ² , R ³ , R ⁴ and R ⁵ are all hydrogen, or that R ³ and R ⁴ are all hydrogen, and at least one selected from the group consisting of R ¹ , R ² and R ⁵ is a substituent other than hydrogen, and the rest are hydrogen. As the substituent, an aryl which may be substituted with an alkyl, an alkyl or a heteroaryl, a heteroaryl which may be substituted with an alkyl or an aryl, or a diarylamino which may be substituted with an alkyl or an aryl is preferable. In this case, the alkyl is preferably an alkyl having 1 to 6 carbon atoms (methyl, t-butyl, etc.), the aryl is preferably phenyl or biphenyl, and the heteroaryl is preferably triazinyl, carbazolyl (2-carbazolyl, 3-carbazolyl, 9-carbazolyl, etc.), pyrimidinyl, pyridinyl, dibenzofuranyl or dibenzothienyl. Specific examples include phenyl, biphenyl, diphenyltriazinyl, carbazolyltriazinyl, monophenylpyrimidinyl, diphenylpyrimidinyl, carbazolyltriazinyl, pyridinyl, dibenzofuranyl and dibenzothienyl.

^Y1 and the like are each independently =C(-R)- or =N-, and at least one is =N-. Any of ^Y1 to ^Y6 may be =N-. Preferably, ^Y1 and ^Y6 are =N- (ring a is a pyrimidine ring), ^Y1 or ^Y6 are =N- (ring a is a pyridine ring), ^Y2 and ^Y5 are =N- (ring b and ring c are pyridine rings), ^Y3 and ^Y4 are =N- (ring b and ring c are pyridine rings), ^Y2 to ^Y5 are =N- (ring b and ring c are pyrimidine rings), ^Y1 , ^Y3 , ^Y4 and ^Y6 are =N- (ring a is a pyrimidine ring, ring b and ring c are pyridine rings), ^Y1 , ^Y2 , ^Y5 and ^Y6 are =N- (ring a is a pyrimidine ring, ring b and ring c are pyridine rings), ^Y1 to ^Y6 are =N- (ring a, ring b and ring c are pyridine rings), and ^Y2 or ^Y5 is =N- (ring b or ring c is a pyridine ring).

In addition to the above =N- configuration, X ¹ and X ² are preferably >O, and polycyclic aromatic compounds containing a partial structure represented by any of the following formulas are preferred.

In particular, a polycyclic aromatic compound containing a partial structure represented by formula (EH-1b-N1) has high E _S1 , high E _T1 and small ΔE _S1T1 as compared to a structure without N.
Specific examples of the polycyclic aromatic compound represented by formula (EH-1b) are shown below.

Of the above, EH-1-1 to EH-1-4, EH-1-10, EH-1-21 to EH-1-25, EH-1-32, EH-1-33, EH-1-51 to EH-1-59, EH-1-61, EH-1-66, EH-1-68, EH-1-71, EH-1-72, EH-1-90, EH-1-94 to EH-1-99, EH-1-100, EH-1-101, EH-1-104, EH-1-115, EH-1-117, EH-1-120, EH-1-122, EH-1-123, and EH-1-127 to EH-1-130 are preferred.

The combination of a hole-transporting host material and an electron-transporting host material is selected based on the HOMO, LUMO and lowest excited triplet energy level (E _T1 ) of the hole-transporting host material, the electron-transporting host material and the dopant material.
Regarding the HOMO and LUMO, a combination is selected in which the HOMO (HH) of the hole-transporting host material is shallower than the HOMO (EH) of the electron-transporting host material, and the LUMO (EH) of the electron-transporting host material is deeper than the LUMO (HH) of the hole-transporting host material. More specifically, the HOMO (HH) is shallower than the HOMO (EH) by 0.10 eV or more, and the LUMO (HH) is deeper than the HOMO (EH). A combination in which the HOMO(HH) is 0.20 eV or more shallower than the HOMO(EH) and the LUMO(HH) is 0.20 eV or more deeper than the HOMO(EH) is more preferable, and a combination in which the HOMO(HH) is 0.25 eV or more shallower than the HOMO(EH) and the LUMO(HH) is 0.25 eV or more deeper than the HOMO(EH) is even more preferable.

The hole transporting host material and the electron transporting host material may be combined to form an association called an exciplex. It is generally known that an exciplex is easily formed between a material having a relatively deep LUMO level and a material having a shallow HOMO level. The interaction between the hole transporting host material and the electron transporting host material, specifically, whether or not an exciplex is formed, can be determined by forming a single layer film consisting of only the hole transporting host material and the electron transporting host material under the same conditions as those for forming the light-emitting layer, measuring the emission spectrum (fluorescence spectrum, phosphorescence spectrum), and comparing the obtained emission spectrum with the emission spectrum shown by each of the hole transporting host material and the electron transporting host material alone. It can be determined by the spectrum of the mixed film containing the hole transporting host material and the electron transporting host material showing an emission wavelength different from both the spectrum of the film of the hole transporting host material and the spectrum of the film of the electron transporting host material. Specifically, it is sufficient to use the difference in the peak wavelength of the spectrum as an indicator by 10 nm or more.

Specific examples of the combination of a hole transporting host material and an electron transporting host material that do not form an exciplex include the following combinations. In order to satisfy the above-mentioned physical values of HOMO, LUMO, and E _T1 , the hole transporting host material is preferably a compound having carbazole, dibenzofuran, dibenzothiophene, triarylamine, indolocarbazole, and benzoxazinophenoxazine as a partial structure, more preferably a compound having carbazole, dibenzofuran, and dibenzothiophene as a partial structure, and even more preferably a compound having carbazole as a partial structure. Similarly, the electron transporting host material is preferably a compound having pyridine, triazine, phosphine oxide, benzofuropyridine, and dibenzoxasiline as a partial structure, more preferably a compound having triazine, phosphine oxide, benzofuropyridine, and dibenzoxasiline as a partial structure, and even more preferably a compound having triazine.

More specifically, the hole-transporting host material is preferably selected from the group consisting of HH-1-1, HH-1-2, HH-1-4 to HH-1-12, HH-1-17, HH-1-18, HH-1-20 to HH-1-24, HH-1-82, HH-1-84 to HH-1-89, HH-1-91, HH-1-92 and HH-1-106 to HH-1-108, and the electron-transporting host material is preferably selected from the group consisting of EH-1-1 to EH-1-4, EH -1-10, EH-1-21 to EH-1-25, EH-1-32, EH-1-33, EH-1-51 to EH-1-59, EH-1-61, EH-1-71, EH-1-72, EH-1-90, EH-1-100, EH-1-101, EH-1-104, EH-1-117, EH-1-120, EH-1-122, EH-1-123, and EH-1-127 to EH-1-130. Preferred examples of combinations include compound HH-1-1 and compound EH-1-22, compound HH-1-1 and compound EH-1-23, compound HH-1-1 and compound EH-1-24, compound HH-1-2 and compound EH-1-22, compound HH-1-2 and compound EH-1-23, compound HH-1-2 and compound EH-1-24, or compound HH-1-1 and compound EH-1-128.

Specific examples of the combination of the hole transporting host material and the electron transporting host material forming an exciplex include the following combinations. In order to satisfy the above-mentioned physical property values of HOMO, LUMO, and E _T1 , the hole transporting host material is preferably a compound having carbazole, triarylamine, indolocarbazole, and benzoxazinophenoxazine as a partial structure, more preferably a compound having triarylamine, indolocarbazole, and benzoxazinophenoxazine as a partial structure, and even more preferably a compound having triarylamine as a partial structure. Similarly, the electron transporting host material is preferably a compound having pyridine, triazine, phosphine oxide, and benzofuropyridine as a partial structure, more preferably a compound having triazine, phosphine oxide, benzofuropyridine, and dibenzoxasiline as a partial structure, and even more preferably a compound having phosphine oxide and triazine.

More specifically, the hole-transporting host material is preferably selected from the group consisting of HH-1-1, HH-1-2, HH-1-11, HH-1-12, HH-1-17, HH-1-18, HH-1-23, HH-1-24, and HH-1-115, and the electron-transporting host material is preferably selected from the group consisting of EH-1-1 to EH-1-4, EH-1-21 to EH-1-25, and EH-1-5. It is preferable that the compound is selected from the group consisting of EH-1-127 to EH-1-130. Preferred examples of combinations include compound HH-1-1 and compound EH-1-21, compound HH-1-2 and compound EH-1-21, compound HH-1-12 and compound EH-1-94, compound HH-1-12 and compound EH-1-117, compound HH-1-1 and compound EH-1-130, compound HH-1-33 and compound EH-1-117, compound HH-1-48 and compound EH-1-117, compound HH-1-49 and compound EH-1-117, or compound HH-1-115 and compound EH-1-99.

Other specific combinations of hole-transporting host materials and electron-transporting host materials are described in Organic Electronics 66 (2019) 227-24, Advanced. Functional Materials 25 (2015) 361-366, Advanced Materials 26 (2014) 4730-4734, and ACS Applied Materials and Interfaces 8 (2016) 32984-32991. , ACS Applied Materials and Interfaces 2016, 8, 9806-9810, ACS Applied Materials and Interfaces 2016, 8, 32984-32991, Journal of Materials Chemistry C, 2018, 6, 8784-8792, Angewante Chemie International Edition. 2018, 57, 12380-12384, Advanced Functional Materials, 24, 2014, 3970, Advanced Materials, 26, 2014, 5684, Synthetic Metals, 201, 2015, 49, and Nature Photonics, 16, 212-218 (2022) can be referenced.

<Assisting dopant (thermally activated delayed fluorescent material or phosphorescent material)>
The light-emitting layer preferably contains an assisting dopant together with the emitting dopant and the host material. The assisting dopant is preferably a thermally activated delayed fluorescent material or a phosphorescent material. The polycyclic aromatic compound represented by formula (1) can be preferably used as an emitting dopant in the TAF element or PSF element. The polycyclic aromatic compound of the present invention used as an emitting dopant in the TAF element or PSF element is preferably a polycyclic aromatic compound represented by formula (2).

In this embodiment, known host compounds can be used, such as compounds having at least one of a carbazole ring and a furan ring. Among them, it is preferable to use a compound in which at least one of furanyl and carbazolyl is bonded to at least one of arylene and heteroarylene. Specific examples include compounds represented by formulas (H1), (H2), and (H3), particularly mCP and mCBP, as well as compounds HH-1-115 and EH-1-99. A TADF-active compound may also be used as the host compound. In this embodiment, it is also preferable to use a combination of a hole-transporting host material and an electron-transporting host material as the host.

From the viewpoint of promoting the generation of TADF in the light-emitting layer without inhibiting it, the lowest excited triplet energy level E(1,T,Sh) of the emitting dopant or assisting dopant having the highest lowest excited triplet energy level in the light-emitting layer is preferably higher than the lowest excited triplet energy level E(2,T,Sh) or E(3,T,Sh). Specifically, the lowest excited triplet energy level E(1,T,Sh) of the host compound is preferably 0.01 eV or higher, more preferably 0.03 eV or higher, and even more preferably 0.1 eV or higher than E(2,T,Sh) or E(3,T,Sh). The lowest excited triplet energy level E of the host material is preferably 2.70 eV or higher, more preferably 2.73 eV or higher, and even more preferably 2.80 eV or higher.

[Thermally activated delayed phosphor]
The term "thermally activated delayed fluorescent material" refers to a compound that absorbs thermal energy, undergoes reverse intersystem crossing from the lowest excited triplet state to the lowest excited singlet state, and then radiatively deactivates from the lowest excited singlet state to emit delayed fluorescence. However, "thermally activated delayed fluorescent material" also includes compounds that undergo higher triplets in the process of excitation from the lowest excited triplet state to the lowest excited singlet state. For example, see the paper by Monkman et al. of Durham University (NATURE COMMUNICATIONS, 7:13680, DOI: 10.1038/ncomms13680), the paper by Hosokai et al. of the National Institute of Advanced Industrial Science and Technology (Hosokai et al., Sci. Adv. 2017;3: e1603282), the paper by Sato et al. of Kyoto University (Scientific Reports, 7:4820, DOI:10.1038/s41598-017-05007-7), and the paper by Sato et al. of Kyoto University (Scientific Reports, 7:4820, DOI:10.1038/s41598-017-05007-7). Examples of such reviews include a conference presentation by Sato et al. (98th Annual Meeting of the Chemical Society of Japan, Presentation No.: 2I4-15, Mechanism of Highly Efficient Emission in Organic Electroluminescence Using DABNA as an Emitting Molecule, Graduate School of Engineering, Kyoto University), a review by Bui et al. (DOI: 10.3762/bjoc.14.18), a review by Duan et al. (DOI: 10.1063/1.5143501), a review by Ding et al. (DOI: 10.1088/1674-4926/42/5/050201), and a review by Xie et al. (DOI: 10.1002/adom.202002204). In the present invention, when a sample containing the target compound is measured for its fluorescence lifetime at 300K, if a slow fluorescent component is observed, the target compound is determined to be a "thermally activated delayed fluorescent material". Here, a slow fluorescent component refers to one having a fluorescence lifetime of 0.1 μsec or more. The fluorescence lifetime can be measured, for example, using a fluorescence lifetime measuring device (manufactured by Hamamatsu Photonics KK, C11367-01).

In the light-emitting layer further containing "thermally activated delayed phosphor" as an assisting dopant, the polycyclic aromatic compound of the present invention can function as an emitting dopant. That is, the "thermally activated delayed phosphor" can function as an assisting dopant that assists the emission of the polycyclic aromatic compound of the present invention.
In this specification, an organic electroluminescent device using a thermally activated delayed fluorescent material as an assisting dopant may be referred to as a "TAF device" (TADF Assisting Fluorescence device).
The "host compound" in the TAF element means a compound whose lowest excited singlet energy level, determined from the shoulder on the short wavelength side of the peak of the fluorescence spectrum, is higher than that of the thermally activated delayed fluorescent material as the assisting dopant and the emitting dopant.

The thermally activated delayed fluorescent material (TADF compound) used in the TAF element is preferably a donor-acceptor type thermally activated delayed fluorescent material (D-A type TADF compound) designed to localize the HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) in the molecule using an electron-donating substituent called a donor and an electron-accepting substituent called an acceptor, thereby causing efficient reverse intersystem crossing.

In this specification, the term "electron-donating substituent" (donor) refers to a substituent or partial structure in which the HOMO is localized in the thermally activated delayed phosphor molecule, and the term "electron-accepting substituent" (acceptor) refers to a substituent or partial structure in which the LUMO is localized in the thermally activated delayed phosphor molecule.

In general, a thermally activated delayed phosphor using a donor or an acceptor has a large spin orbit coupling (SOC) due to its structure, and a small exchange interaction between HOMO and LUMO, and therefore a small ΔE _S1T1 , so that a very fast reverse intersystem crossing rate can be obtained. By using the polycyclic aromatic compound of the present invention as an emitting dopant and the thermally activated delayed phosphor (TADF material) as an assisting dopant, a device that satisfies any one or all of high efficiency, high color purity, and long life can be provided. The thermally activated delayed phosphor may be a compound whose emission spectrum at least partially overlaps with the absorption spectrum of the polycyclic aromatic compound of the present invention. The polycyclic aromatic compound of the present invention and the thermally activated delayed phosphor may both be included in the same layer, or may be included in an adjacent layer or other adjacent layers.

As the thermally activated delayed phosphor in the TAF element, for example, a compound in which a donor and an acceptor are bonded directly or via a spacer can be used. As the electron donor group (donor structure) and the electron acceptor group (acceptor structure) used in the thermally activated delayed phosphor of the present invention, for example, the structures described in Chemistry of Materials, 2017, 29, 1946-1963 can be used. Examples of the donor structure include carbazole, dimethylcarbazole, di-tert-butylcarbazole, dimethoxycarbazole, tetramethylcarbazole, benzofluorocarbazole, benzothienocarbazole, phenyldihydroindolocarbazole, phenylbicarbazole, bicarbazole, tercarbazole, diphenylcarbazolylamine, tetraphenylcarbazolyldiamine, phenoxazine, dihydrophenazine, phenothiazine, dimethyldihydroacridine, diphenylamine, bis(tert-butylphenyl)amine, N1-(4-(diphenylamino)phenyl)-N4,N4-diphenylbenzene-1,4-diamine, dimethyltetraphenyldihydroacridinediamine, tetramethyldihydroindenoacridine, and diphenyldihydrodibenzoazasiline. Examples of the acceptor structure include sulfonyldibenzene, benzophenone, phenylenebis(phenylmethanone), benzonitrile, isonicotinonitrile, phthalonitrile, isophthalonitrile, paraphthalonitrile, benzenetricarbonitrile, triazole, oxazole, thiadiazole, benzothiazole, benzobis(thiazole), benzoxazole, benzobis(oxazole), quinoline, benzimidazole, dibenzoquinoxaline, heptaazaphenalene, thioxanthone dioxide, dimethylanthracenone, anthracenedione, 5H-cyclopenta[1,2-b:5,4-b']dipyridine, fluorene dicarbonitrile, triphenyltriazine, pyrazine dicarbonitrile, pyrimidine, phenylpyrimidine, methylpyrimidine, pyridine dicarbonitrile, dibenzoquinoxaline dicarbonitrile, bis(phenylsulfonyl)benzene, dimethylthioxanthene dioxide, thianthrene tetraoxide, and tris(dimethylphenyl)borane. In particular, the compound having thermally activated delayed fluorescence in the TAF element is preferably a compound having at least one partial structure selected from carbazole, phenoxazine, acridine, triazine, pyrimidine, pyrazine, thioxanthene, benzonitrile, phthalonitrile, isophthalonitrile, diphenylsulfone, triazole, oxadiazole, thiadiazole, and benzophenone.

The compound used as the assisting dopant in the light-emitting layer of the TAF element is preferably a thermally activated delayed phosphor whose emission spectrum at least partially overlaps with the absorption peak of the emitting dopant.

[Phosphorescent materials (assisting dopants)]
In the light-emitting layer, a phosphorescent material may be used as an assisting dopant. In this specification, an organic electroluminescent device using a phosphorescent material as an assisting dopant may be referred to as a phosphorescence-assisted element, phosphor-sensitized fluorescent element, or PSF element. Phosphorescent materials utilize the intramolecular spin-orbit interaction (heavy atom effect) of metal atoms to obtain light emission from an excited triplet state. As such phosphorescent materials, for example, luminescent metal complexes can be used. As luminescent metal complexes, for example, compounds represented by the following formula (B-1) and the following formula (B-2) can be used.

In formula (B-1), M is at least one selected from the group consisting of Ir, Pt, Au, Eu, Ru, Re, Ag, and Cu, n is an integer of 1 to 3, and each "X-Y" is independently a bidentate ligand.
In formula (B-2), M is at least one selected from the group consisting of Pt, Re and Cu, and "W-X-Y-Z" is a tetradentate ligand.
In formula (B-1), M is preferably Ir and n is preferably 3, from the viewpoints of efficiency and life.
In the formula (B-2), M is preferably Pt from the viewpoints of efficiency and life.
The ligand (X-Y) in formula (B-1) has at least one ligand selected from the group consisting of the following: The ligand (W-X-Y-Z) in formula (B-2) has at least one ligand selected from the group consisting of the following as a part thereof:

In the formula,
--- is bonded to the central metal M,
Each Y is independently BR _e , NR _e , PR _e , O, S, Se, C═O, S═O, SO2, CR _e R _f , SiR _e R _f , or GeR _e R _f , and each aromatic carbon C—H in the ring may be independently replaced by N;
R _e and R _f may be optionally fused or joined to form a ring;
R _a , R _b , R _c , and R _d are each independently unsubstituted or substituted with from 1 to the maximum number of substituents possible;
_R , R, _R , _R , _R , R _, and _R are each independently hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, aryl, heteroaryl, nitrile, isonitrile, sulfanyl, or combinations thereof;
However, any two adjacent substituents in R _a , R _b , R _c , and R _d may be fused or linked to form a ring or to form a multidentate ligand.

Examples of the compound represented by formula (B-1) include Ir(ppy) ₃ , Ir(ppy) ₂ (acac), Ir(mppy) ₃ , Ir(PPy) ₂ (m-bppy), BtpIr(acac), Ir(btp) ₂ (acac), Ir(2-phq) ₃ , Hex-Ir(phq) ₃ , Ir(fbi) ₂ (acac), fac-Tris(2-(3-p-xylyl)phenyl)pyridine iridium(III), Eu(dbm) ₃ (Phen), Ir(piq) ₃ , Ir(piq) ₂ (acac), and Ir(Fliq) ₂ (acac), Ir(Flq) ₂ (acac), Ru(dtb-bpy) _3.2 ( _PF6 ), Ir(2-phq) ₃ , Ir(BT) ₂ (acac), Ir(DMP) ₃ , Ir(Mphq) _3IR (phq)2tpy, fac-Ir(ppy)2Pc, Ir(dp) _PQ2 , Ir(Dpm)(Piq) ₂ , Hex-Ir _{(piq)2 (acac), Hex-Ir(piq)3, Ir(dmpq)3, Ir(dmpq)2 ( acac ) , and} FPQIrpic.

Other examples of the compound represented by formula (B-1) include the following compounds:

In addition, iridium complexes described in JP 2006-089398 A, JP 2006-080419 A, JP 2005-298483 A, JP 2005-097263 A, and JP 2004-111379 A, U.S. Patent Application Publication No. 2019/0051845, etc., or platinum complexes described in Advanced Materials, 26: 7116-7121, NPG Asia Materials 13, 53 (2021), Applied Physics Letters, 117, 253301 (2020), Light-Emitting Diode - An Outlook On the Empirical Features and Its Recent Technological Advancements, Chapter 5 may be used.

<Other dopant materials>
The polycyclic aromatic compound represented by formula (1) may be used in combination with other dopant materials. However, the other dopant materials are preferably less than 100% by mass, more preferably 50% by mass or less, even more preferably 30% by mass or less, and particularly preferably 10% by mass or less, based on the total mass of the polycyclic aromatic compound represented by formula (1) in one light-emitting layer. Known compounds can be used as the other dopant materials, and can be selected from various materials according to the desired emission color. Specific examples of such compounds include condensed ring derivatives such as phenanthrene, anthracene, pyrene, tetracene, pentacene, perylene, naphthopyrene, dibenzopyrene, rubrene, and chrysene, benzoxazole derivatives, benzothiazole derivatives, benzimidazole derivatives, benzotriazole derivatives, oxazole derivatives, oxadiazole derivatives, thiazole derivatives, imidazole derivatives, thiadiazole derivatives, triazole derivatives, pyrazoline derivatives, stilbene derivatives, thiophene derivatives, tetraphenylbutadiene derivatives, cyclopentadiene derivatives, bisstyryl derivatives such as bisstyrylanthracene derivatives and distyrylbenzene derivatives (JP Patent Publication No. 2-245087), bisstyrylarylene derivatives (JP Patent Publication No. 2-247278), diazaindacene derivatives, furan derivatives, benzofuran derivatives, and isobenzofuran derivatives such as phenylisobenzofuran, dimesitylisobenzofuran, di(2-methylphenyl)isobenzofuran, di(2-trifluoromethylphenyl)isobenzofuran, and phenylisobenzofuran. coumarin derivatives such as dibenzofuran derivatives, 7-dialkylaminocoumarin derivatives, 7-piperidinocoumarin derivatives, 7-hydroxycoumarin derivatives, 7-methoxycoumarin derivatives, 7-acetoxycoumarin derivatives, 3-benzothiazolylcoumarin derivatives, 3-benzimidazolylcoumarin derivatives, and 3-benzoxazolylcoumarin derivatives, dicyanomethylenepyran derivatives, dicyanomethylenethiopyran derivatives, polymethine derivatives, cyanine derivatives, oxobenzoanthracene derivatives, xanthene derivatives, rhodamine derivatives, conductors, fluorescein derivatives, pyrylium derivatives, carbostyril derivatives, acridine derivatives, oxazine derivatives, phenylene oxide derivatives, quinacridone derivatives, quinazoline derivatives, pyrrolopyridine derivatives, furopyridine derivatives, 1,2,5-thiadiazolopyrene derivatives, pyrromethene derivatives, perinone derivatives, pyrrolopyrrole derivatives, squarylium derivatives, violanthrone derivatives, phenazine derivatives, acridone derivatives, deazaflavin derivatives, fluorene derivatives and benzofluorene derivatives.

As other dopant materials, it is also preferable to use polycyclic aromatic compounds containing boron as described in WO 2015/102118, WO 2020/162600, and paragraphs 0097 to 0269 of JP 2021-077890, etc.

2-1-6. Electron Injection Layer and Electron Transport Layer in Organic Electroluminescent Device The electron injection layer 107 plays a role of efficiently injecting electrons moving from the cathode 108 into the light emitting layer 105 or the electron transport layer 106. The electron transport layer 106 plays a role of efficiently transporting electrons injected from the cathode 108 or electrons injected from the cathode 108 via the electron injection layer 107 to the light emitting layer 105. The electron transport layer 106 and the electron injection layer 107 are each formed by laminating or mixing one or more types of electron transport/injection materials, or by a mixture of an electron transport/injection material and a polymer binder.

The electron injection/transport layer is a layer that is responsible for injecting electrons from the cathode and transporting the electrons. It is desirable for the electron injection layer to have a high electron injection efficiency and efficiently transport the injected electrons. For this purpose, it is preferable for the material to have a large electron affinity, a large electron mobility, and excellent stability, and to be a material that is unlikely to generate impurities that become traps during manufacture and use. However, when considering the balance between the transport of holes and electrons, if the material mainly plays a role in efficiently preventing holes from the anode from flowing to the cathode without recombining, even if the electron transport ability is not that high, it has the effect of improving the luminous efficiency equivalent to a material with a high electron transport ability. Therefore, the electron injection/transport layer in this embodiment may also include the function of a layer that can efficiently block the movement of holes.

The material (electron transport material) forming the electron transport layer 106 or the electron injection layer 107 can be arbitrarily selected from compounds conventionally used as electron transport compounds in photoconductive materials and known compounds used in the electron injection layer and electron transport layer of organic EL elements.

Materials used in the electron transport layer or electron injection layer preferably contain at least one selected from compounds consisting of aromatic rings or heteroaromatic rings composed of one or more atoms selected from carbon, hydrogen, oxygen, sulfur, silicon, and phosphorus, pyrrole derivatives and their condensed ring derivatives, and metal complexes having electron-accepting nitrogen. Specific examples include condensed ring aromatic ring derivatives such as naphthalene and anthracene, styryl aromatic ring derivatives such as 4,4'-bis(diphenylethenyl)biphenyl, perinone derivatives, coumarin derivatives, naphthalimide derivatives, quinone derivatives such as anthraquinone and diphenoquinone, phosphine oxide derivatives, arylnitrile derivatives, and indole derivatives. Metal complexes having electron-accepting nitrogen include, for example, hydroxyazole complexes such as hydroxyphenyloxazole complexes, azomethine complexes, tropolone metal complexes, flavonol metal complexes, and benzoquinoline metal complexes. These materials can be used alone or in combination with different materials.

Specific examples of other electron transport compounds include pyridine derivatives, naphthalene derivatives, anthracene derivatives, phenanthroline derivatives, perinone derivatives, coumarin derivatives, naphthalimide derivatives, anthraquinone derivatives, diphenoquinone derivatives, diphenylquinone derivatives, perylene derivatives, oxadiazole derivatives (such as 1,3-bis[(4-t-butylphenyl)1,3,4-oxadiazolyl]phenylene), thiophene derivatives, triazole derivatives (such as N-naphthyl-2,5-diphenyl-1,3,4-triazole), thiadiazole derivatives, metal complexes of oxine derivatives, quinolinol-based metal complexes, quinoxaline derivatives, polymers of quinoxaline derivatives, benzazole compounds, gallium complexes, pyrazole derivatives, perfluorinated phenylene derivatives, triazine derivatives, and pyrazine. Derivatives, benzoquinoline derivatives (such as 2,2'-bis(benzo[h]quinolin-2-yl)-9,9'-spirobifluorene), imidazopyridine derivatives, borane derivatives, benzimidazole derivatives (such as tris(N-phenylbenzimidazol-2-yl)benzene), benzoxazole derivatives, benzothiazole derivatives, quinoline derivatives, oligopyridine derivatives such as terpyridine, bipyridine derivatives, terpyridine derivatives (such as 1,3-bis(2,2':6',2"-terpyridin-4'-yl)benzene), naphthyridine derivatives (such as bis(1-naphthyl)-4-(1,8-naphthyridin-2-yl)phenylphosphine oxide), aldazine derivatives, carbazole derivatives, indole derivatives, phosphine oxide derivatives, and bisstyryl derivatives.

Metal complexes having an electron-accepting nitrogen can also be used, such as quinolinol metal complexes, hydroxyazole complexes such as hydroxyphenyloxazole complexes, azomethine complexes, tropolone metal complexes, flavonol metal complexes, and benzoquinoline metal complexes.

The above materials can be used alone or in combination with other materials.

Among the above-mentioned materials, borane derivatives, pyridine derivatives, fluoranthene derivatives, BO-based derivatives, anthracene derivatives, benzofluorene derivatives, phosphine oxide derivatives, pyrimidine derivatives, arylnitrile derivatives, triazine derivatives, benzimidazole derivatives, phenanthroline derivatives, and quinolinol-based metal complexes are preferred.

The electron transport layer or the electron injection layer may further contain a substance capable of reducing the material forming the electron transport layer or the electron injection layer. As the reducing substance, various substances can be used as long as they have a certain degree of reducing ability. For example, at least one selected from the group consisting of alkali metals, alkaline earth metals, rare earth metals, oxides of alkali metals, halides of alkali metals, oxides of alkaline earth metals, halides of alkaline earth metals, oxides of rare earth metals, halides of rare earth metals, organic complexes of alkali metals, organic complexes of alkaline earth metals, and organic complexes of rare earth metals can be preferably used.

Preferred reducing substances include alkali metals such as Na (work function 2.36 eV), K (2.28 eV), Rb (2.16 eV), or Cs (1.95 eV), and alkaline earth metals such as Ca (2.9 eV), Sr (2.0-2.5 eV), or Ba (2.52 eV), with substances with a work function of 2.9 eV or less being particularly preferred. Of these, more preferred reducing substances are alkali metals such as K, Rb, or Cs, more preferably Rb or Cs, and most preferably Cs. These alkali metals have particularly high reducing ability, and by adding a relatively small amount to the material forming the electron transport layer or electron injection layer, the luminance of the organic EL element can be improved and the lifespan can be extended. In addition, as a reducing substance having a work function of 2.9 eV or less, a combination of two or more of these alkali metals is also preferred, and in particular, a combination containing Cs, such as a combination of Cs and Na, Cs and K, Cs and Rb, or Cs, Na and K, is preferred. By containing Cs, the reducing ability can be efficiently exerted, and by adding it to the material forming the electron transport layer or electron injection layer, the luminance of the light emitted by the organic EL element can be improved and the life span can be extended.

2-1-7. Cathode in Organic Electroluminescent Device The cathode 108 plays a role in injecting electrons into the light-emitting layer 105 via the electron injection layer 107 and the electron transport layer 106 .

The material for forming the cathode 108 is not particularly limited as long as it can efficiently inject electrons into the organic layer, but the same material as the material for forming the anode 102 can be used. Among them, metals such as tin, indium, calcium, aluminum, silver, copper, nickel, chromium, gold, platinum, iron, zinc, lithium, sodium, potassium, cesium, and magnesium, or alloys thereof (magnesium-silver alloy, magnesium-indium alloy, aluminum-lithium alloy such as lithium fluoride/aluminum, etc.), etc. are preferred. In order to increase the electron injection efficiency and improve the device characteristics, lithium, sodium, potassium, cesium, calcium, magnesium, or alloys containing these low work function metals are effective. However, these low work function metals are generally unstable in air. To improve this point, for example, a method is known in which a trace amount of lithium, cesium, or magnesium is doped into the organic layer to use a highly stable electrode. Other dopants that can be used include inorganic salts such as lithium fluoride, cesium fluoride, lithium oxide, and cesium oxide. However, they are not limited to these.

Furthermore, preferred examples include laminating metals such as platinum, gold, silver, copper, iron, tin, aluminum, and indium, or alloys using these metals, as well as inorganic materials such as silica, titania, and silicon nitride, polyvinyl alcohol, vinyl chloride, and hydrocarbon polymer compounds, in order to protect the electrodes. There are no particular limitations on the method of producing these electrodes, and they can be produced by resistance heating, electron beam deposition, sputtering, ion plating, coating, or the like, as long as electrical conductivity can be obtained.

2-1-8. Method for Producing an Organic Electroluminescent Device Each layer constituting an organic EL device can be formed by forming the material to be formed into a thin film by a method such as vapor deposition, resistance heating vapor deposition, electron beam vapor deposition, sputtering, molecular lamination, printing, spin coating or casting, or coating. The thickness of each layer thus formed is not particularly limited and can be set appropriately according to the properties of the material, but is usually in the range of 2 nm to 5000 nm. The thickness can usually be measured with a quartz crystal oscillation type film thickness measuring device. When forming a thin film by vapor deposition, the vapor deposition conditions vary depending on the type of material, the desired crystal structure and association structure of the film, etc. It is generally preferable to set the vapor deposition conditions appropriately in the range of boat heating temperature +50 to +400°C, vacuum degree 10 ^-6 to 10 ^-3 Pa, vapor deposition speed 0.01 to 50 nm/sec, substrate temperature -150 to +300°C, and film thickness 2 nm to 5 μm.

When applying a DC voltage to the organic EL element obtained in this way, the anode should be set to + and the cathode to -. When a voltage of about 2 to 40 V is applied, light emission can be observed from the transparent or semi-transparent electrode side (anode or cathode, or both). This organic EL element also emits light when a pulsed current or AC current is applied. The waveform of the applied AC current can be any waveform.

Next, as an example of a method for producing an organic EL element, we will explain a method for producing an organic EL element consisting of an anode, a hole injection layer, a hole transport layer, a light emitting layer made of a host material and a dopant material, an electron transport layer, an electron injection layer, and a cathode.

<Vapor deposition method>
A thin film of an anode material is formed on a suitable substrate by vapor deposition or the like to prepare an anode, and then a thin film of a hole injection layer and a hole transport layer is formed on the anode. A host material and a dopant material are co-deposited on the anode to form a thin film as a light-emitting layer, an electron transport layer and an electron injection layer are formed on the light-emitting layer, and a thin film of a cathode material is further formed by vapor deposition or the like to prepare a cathode, thereby obtaining a desired organic EL element. Note that in the preparation of the above-mentioned organic EL element, the order of preparation can be reversed, and the layers can be prepared in the order of cathode, electron injection layer, electron transport layer, light-emitting layer, hole transport layer, hole injection layer, and anode.

<Wet film formation method>
The wet film formation method is carried out by preparing a low molecular weight compound capable of forming each organic layer of an organic EL element as a liquid composition for forming an organic layer, and using this. If there is no suitable organic solvent for dissolving this low molecular weight compound, the composition for forming an organic layer may be prepared from a polymer compound polymerized together with other monomers having a solubility function as a reactive compound in which a reactive substituent is substituted on the low molecular weight compound, or a main chain polymer.

In the wet film formation method, a coating film is generally formed through a coating process in which an organic layer forming composition is applied to a substrate and a drying process in which the solvent is removed from the applied organic layer forming composition. When the polymer compound has a crosslinkable substituent (also called a crosslinkable polymer compound), the polymer is further crosslinked by the drying process to form a crosslinked polymer. Depending on the difference in the coating process, the method using a spin coater is called the spin coat method, the method using a slit coater is called the slit coat method, the method using a plate is called the gravure, offset, reverse offset, or flexographic printing method, the method using an inkjet printer is called the inkjet method, and the method spraying in a mist form is called the spray method. The drying process includes air drying, heating, and drying under reduced pressure. The drying process may be performed only once, or may be performed multiple times using different methods and conditions. In addition, different methods may be used in combination, such as baking under reduced pressure.

A wet film formation method is a film formation method that uses a solution, and examples of this include some printing methods (inkjet methods), spin coating methods or casting methods, and coating methods. Unlike vacuum deposition methods, wet film formation methods do not require expensive vacuum deposition equipment, and can form films under atmospheric pressure. In addition, wet film formation methods allow for large area production and continuous production, which leads to reduced manufacturing costs.

On the other hand, compared to the vacuum deposition method, wet deposition methods can be difficult to layer. When using wet deposition methods to create layered films, it is necessary to prevent the lower layer from being dissolved by the composition of the upper layer, and therefore compositions with controlled solubility, crosslinking of the lower layer, and orthogonal solvents (solvents that are not mutually soluble) are used. However, even with these techniques, it can be difficult to use wet deposition methods to apply all films.

Therefore, a common method for producing organic EL elements is to use wet deposition methods for only a few layers and vacuum deposition for the rest.

For example, the procedure for producing an organic EL element by partially applying a wet film formation method will be described below.
(Step 1) Formation of an anode by vacuum deposition (Step 2) Formation of a hole injection layer-forming composition containing a hole injection layer material by wet deposition (Step 3) Formation of a hole transport layer-forming composition containing a hole transport layer material by wet deposition (Step 4) Formation of an emitting layer-forming composition containing a host material and a dopant material by wet deposition (Step 5) Formation of an electron transport layer by vacuum deposition (Step 6) Formation of an electron injection layer by vacuum deposition (Step 7) Formation of a cathode by vacuum deposition By going through these steps, an organic EL element consisting of an anode/hole injection layer/hole transport layer/emitting layer consisting of a host material and a dopant material/electron transport layer/electron injection layer/cathode is obtained.
Of course, the electron transport layer and the electron injection layer may also be formed by a wet film formation method using layer-forming compositions containing the electron transport layer material and the electron injection layer material, respectively. In this case, it is preferable to use a means for preventing dissolution of the lower light-emitting layer or a means for forming the film from the cathode side in the reverse order to the above procedure.

<Other film formation methods>
The composition for forming an organic layer can be formed into a film by laser thermal imaging (LITI). LITI is a method in which a compound attached to a substrate is heated and vapor-deposited by a laser, and the composition for forming an organic layer can be used as a material to be applied to the substrate.

<Optional Step>
Before and after each film-forming step, appropriate treatment steps, cleaning steps, and drying steps may be appropriately inserted. Examples of treatment steps include exposure treatment, plasma surface treatment, ultrasonic treatment, ozone treatment, cleaning treatment using an appropriate solvent, and heat treatment. Furthermore, a series of steps for preparing a bank may also be included.

Photolithography techniques can be used to fabricate the bank. Positive resist materials and negative resist materials can be used as bank materials that can be used with photolithography. In addition, patternable printing methods such as inkjet printing, gravure offset printing, reverse offset printing, and screen printing can also be used. In this case, permanent resist materials can also be used.

<Organic layer forming composition used in wet film formation method>
The composition for forming an organic layer is obtained by dissolving a low molecular weight compound capable of forming each organic layer of an organic EL element, or a polymer compound obtained by polymerizing the low molecular weight compound, in an organic solvent. For example, the composition for forming an emitting layer contains at least one polycyclic aromatic compound (or a polymer compound thereof) as a first component, which is a dopant material, at least one host material as a second component, and at least one organic solvent as a third component. The first component functions as a dopant component of the emitting layer obtained from the composition, and the second component functions as a host component of the emitting layer. The third component functions as a solvent that dissolves the first and second components in the composition, and gives a smooth and uniform surface shape due to the controlled evaporation rate of the third component itself during application.

<Organic solvent>
The organic layer forming composition contains at least one organic solvent. By controlling the evaporation rate of the organic solvent during film formation, it is possible to control and improve the film formability, the presence or absence of defects in the coating film, the surface roughness, and the smoothness. In addition, during film formation using the inkjet method, it is possible to control the meniscus stability at the pinhole of the inkjet head, and control and improve the ejection properties. In addition, by controlling the drying rate of the film and the orientation of the derivative molecules, it is possible to improve the electrical properties, light emitting properties, efficiency, and life of an organic EL element having an organic layer obtained from the organic layer forming composition.

After film formation, the organic solvent is removed from the coating film by a drying process such as vacuum, reduced pressure, or heating. When heating is performed, from the viewpoint of improving the coating film formation properties, it is preferable to perform the heating at a temperature of at least one of the solutes' glass transition temperature (Tg) +30°C or lower. From the viewpoint of reducing residual solvent, it is preferable to heat at at least one of the solutes' glass transition temperature (Tg) -30°C or higher. Even if the heating temperature is lower than the boiling point of the organic solvent, the organic solvent is sufficiently removed because the film is thin. Also, drying may be performed multiple times at different temperatures, and multiple drying methods may be used in combination.

(2) Specific examples of organic solvents Examples of organic solvents used in the organic layer-forming composition include, but are not limited to, alkylbenzene solvents, phenyl ether solvents, alkyl ether solvents, cyclic ketone solvents, aliphatic ketone solvents, monocyclic ketone solvents, solvents having a diester skeleton, and fluorine-containing solvents. The solvents may be used alone or in combination.

<Optional ingredients>
The composition for forming the organic layer may contain optional components, such as a binder and a surfactant, to the extent that the properties of the composition are not impaired.

<Composition and Properties of Organic Layer-Forming Composition>
The content of each component in the composition for forming an organic layer is determined taking into consideration good solubility, storage stability, and film-formability of each component in the composition for forming an organic layer, as well as good film quality of a coating film obtained from the composition for forming an organic layer, good ejection properties when an inkjet method is used, and good electrical characteristics, luminescent characteristics, efficiency, and life of an organic EL element having an organic layer produced using the composition.

The composition for forming the organic layer can be produced by appropriately selecting and performing stirring, mixing, heating, cooling, dissolving, dispersing, etc. of the above-mentioned components using a known method. In addition, after preparation, filtration, degassing (also called degassing), ion exchange treatment, and inert gas replacement/filling treatment, etc. may be appropriately selected and performed.

2-1-9. Application Examples of Organic Electroluminescent Devices The present invention can also be applied to display devices including organic EL devices or lighting devices including organic EL devices.
A display device or lighting device including an organic EL element can be manufactured by a known method, for example, by connecting the organic EL element according to this embodiment to a known driving device, and can be driven appropriately using a known driving method such as DC driving, pulse driving, or AC driving.

Examples of display devices include panel displays such as color flat panel displays, and flexible displays such as flexible color organic electroluminescent (EL) displays (see, for example, JP-A-10-335066, JP-A-2003-321546, JP-A-2004-281086, etc.). Examples of display methods include matrix and segment methods. Note that matrix display and segment display may coexist in the same panel.

In a matrix, the pixels for display are arranged two-dimensionally, such as in a grid or mosaic pattern, and a collection of pixels displays characters and images. The shape and size of the pixels are determined by the application. For example, square pixels with sides of 300 μm or less are usually used to display images and characters on computers, monitors, and televisions, and pixels with sides on the order of mm are used for large displays such as display panels. For monochrome display, pixels of the same color can be arranged, but for color display, red, green, and blue pixels are displayed side by side. In this case, there are typically delta types and stripe types. The driving method for this matrix can be either line sequential driving method or active matrix. Line sequential driving has the advantage of being simpler in structure, but when considering operating characteristics, active matrix may be superior, so it is necessary to use it according to the application.

In the segment method, a pattern is formed to display predetermined information, and a specific area is illuminated. Examples include the time and temperature displays on digital clocks and thermometers, the operating status displays on audio equipment and induction cookers, and panel displays on automobiles.

Examples of lighting devices include lighting devices for indoor lighting, backlights for liquid crystal display devices, etc. (see, for example, JP-A-2003-257621, JP-A-2003-277741, JP-A-2004-119211, etc.). Backlights are mainly used for the purpose of improving the visibility of non-self-luminous display devices, and are used in liquid crystal display devices, clocks, audio devices, automobile panels, display boards, signs, etc. In particular, for backlights for liquid crystal display devices, especially for personal computers where thinning is an issue, it is difficult to make them thin because conventional methods are made up of fluorescent lamps and light guide plates, so the backlights using the light-emitting elements according to this embodiment are characterized by their thinness and light weight.

2-2. Other Organic Devices The polycyclic aromatic compound according to the present invention can be used for producing organic field effect transistors or organic thin-film solar cells, in addition to the organic electroluminescent devices described above.

An organic field-effect transistor is a transistor that controls current by generating an electric field through voltage input, and has a gate electrode in addition to a source electrode and a drain electrode. When a voltage is applied to the gate electrode, an electric field is generated, and the flow of electrons (or holes) between the source electrode and drain electrode can be arbitrarily blocked to control the current. Field-effect transistors are easier to miniaturize than simple transistors (bipolar transistors), and are often used as elements in integrated circuits.

The structure of an organic field effect transistor may be such that a source electrode and a drain electrode are provided in contact with an organic semiconductor active layer formed using the polycyclic aromatic compound according to the present invention, and a gate electrode is provided sandwiching an insulating layer (dielectric layer) in contact with the organic semiconductor active layer. Examples of the element structure include the following structure.
(1) Substrate/gate electrode/insulator layer/source electrode/drain electrode/organic semiconductor active layer (2) Substrate/gate electrode/insulator layer/organic semiconductor active layer/source electrode/drain electrode (3) Substrate/organic semiconductor active layer/source electrode/drain electrode/insulator layer/gate electrode (4) Substrate/source electrode/drain electrode/organic semiconductor active layer/insulator layer/gate electrode An organic field effect transistor configured in this manner can be used as a pixel driving switching element for active matrix driving liquid crystal displays and organic electroluminescence displays.

An organic thin-film solar cell has a structure in which an anode such as ITO, a hole transport layer, a photoelectric conversion layer, an electron transport layer, and a cathode are laminated on a transparent substrate such as glass. The photoelectric conversion layer has a p-type semiconductor layer on the anode side and an n-type semiconductor layer on the cathode side. The polycyclic aromatic compound according to the present invention can be used as a material for a hole transport layer, a p-type semiconductor layer, an n-type semiconductor layer, and an electron transport layer depending on its physical properties. The polycyclic aromatic compound according to the present invention can function as a hole transport material or an electron transport material in an organic thin-film solar cell. In addition to the above, the organic thin-film solar cell may appropriately include a hole blocking layer, an electron blocking layer, an electron injection layer, a hole injection layer, a smoothing layer, and the like. For the organic thin-film solar cell, known materials used in organic thin-film solar cells can be appropriately selected and combined for use.

3. Wavelength conversion material The polycyclic aromatic compound of the present invention can be used as a wavelength conversion material. Currently, the application of multi-color technology using a color conversion method to liquid crystal displays, organic EL displays, lighting, and the like is being actively studied. Color conversion refers to converting the light emitted from a light emitter to light with a longer wavelength, for example, converting ultraviolet light or blue light to green light or red light emission. By forming this wavelength conversion material having color conversion function into a film and combining it with, for example, a blue light source, it becomes possible to extract the three primary colors of blue, green, and red from the blue light source, that is, to extract white light. By combining such a white light source, which is a combination of a blue light source and a wavelength conversion film having a color conversion function, with a liquid crystal driving part and a color filter as a light source unit, it becomes possible to manufacture a full-color display. Furthermore, if there is no liquid crystal driving part, it can be used as a white light source as it is, and can be applied as a white light source such as LED lighting. Furthermore, by using a blue organic EL element as a light source in combination with a wavelength conversion film that converts blue light into green light and red light, it becomes possible to manufacture a full-color organic EL display without using a metal mask. Furthermore, by using blue micro-LEDs as a light source in combination with wavelength conversion films that convert blue light into green and red light, it becomes possible to create low-cost full-color micro-LED displays.

The polycyclic aromatic compound of the present invention can be used as this wavelength conversion material. By using a wavelength conversion material containing the polycyclic aromatic compound of the present invention, light from a light source or a light-emitting element that generates ultraviolet light or shorter wavelength blue light can be converted into blue light or green light with high color purity suitable for use in a display device (a display device using an organic EL element or a liquid crystal display device). The converted color can be adjusted by appropriately selecting the substituent of the polycyclic aromatic compound of the present invention, the binder resin used in the wavelength conversion composition described below, and the like. The wavelength conversion material can be prepared as a wavelength conversion composition containing the polycyclic aromatic compound of the present invention. In addition, a wavelength conversion film may be formed using this wavelength conversion composition.

The wavelength conversion composition may contain, in addition to the polycyclic aromatic compound of the present invention, a binder resin, other additives, and a solvent. As the binder resin, for example, those described in paragraphs 0173 to 0176 of WO 2016/190283 can be used. As the other additives, the compounds described in paragraphs 0177 to 0181 of WO 2016/190283 can be used. As the solvent, the description of the solvent contained in the composition for forming the light-emitting layer above can be referred to.

The wavelength conversion film includes a wavelength conversion layer formed by curing the wavelength converting composition. Known film formation methods can be referred to as a method for producing a wavelength conversion layer from a wavelength converting composition. The wavelength conversion film may consist only of a wavelength conversion layer formed from a composition containing the polycyclic aromatic compound of the present invention, or may include other wavelength conversion layers (e.g., a wavelength conversion layer that converts blue light into green light or red light, or a wavelength conversion layer that converts blue light or green light into red light). The wavelength conversion film may further include a substrate layer and a barrier layer for preventing deterioration of the color conversion layer due to oxygen, moisture, or heat.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these.
In the examples, MALDI-TOF-MS means matrix-assisted laser desorption ionization time-of-flight mass spectrometry.

Synthesis Example (1):
Synthesis of compound (1-1)

Compound (S-1) (0.76 g) and tert-butylbenzene (7.0 ml) were added to a flask containing the compound (S-1) (0.76 g) and tert-butylbenzene (7.0 ml) under a nitrogen atmosphere at -30°C, and 1.6 M tert-butyllithium pentane solution (1.6 ml) was added. After the dropwise addition was completed, the temperature was raised to 60°C and the mixture was stirred for 2 hours, and then components with a boiling point lower than that of tert-butylbenzene were distilled off under reduced pressure. The mixture was cooled to -30°C, boron tribromide (0.63 g) was added, the mixture was heated to room temperature and stirred for 0.5 hours. Thereafter, the mixture was cooled again to 0°C, N,N-diisopropylethylamine (0.43 ml) was added, and the mixture was stirred at room temperature until the heat generation subsided, and then the mixture was heated to 120°C and stirred for 3 hours. The reaction solution was cooled to room temperature, and an aqueous sodium acetate solution cooled in an ice bath was added, followed by heptane, and the mixture was separated. Next, the residue was purified using a silica gel short-path column (eluent: toluene), and the solvent was distilled off under reduced pressure. The resulting solid was dissolved in toluene and reprecipitated by adding heptane to obtain compound (1-1) (0.35 g).
MALDI-TOF-MS: [M] ⁺ = 738.51

Synthesis Example (2):
Synthesis of compound (1-2)

It was synthesized according to the method of Synthesis Example (1).
MALDI-TOF-MS (M ⁺ )=794.48

Synthesis Example (3):
Synthesis of compound (1-3)

It was synthesized according to the method of Synthesis Example (1).
MALDI-TOF-MS (M ⁺ )=832.55

Synthesis Example (4):
Synthesis of compound (1-4)

It was synthesized according to the method of Synthesis Example (1).
MALDI-TOF-MS (M ⁺ )=860.52

Synthesis Example (5):
Synthesis of compound (1-5)

It was synthesized according to the method of Synthesis Example (1).
MALDI-TOF-MS (M ⁺ )=776.52

Synthesis Example (6):
Synthesis of compound (1-6)

It was synthesized according to the method of Synthesis Example (1).
MALDI-TOF-MS (M ⁺ )=1245.64

Manufacture and Evaluation of Organic EL Device The following organic EL device was manufactured using the polycyclic aromatic compound synthesized above.

<Examples 1-1 to 1-6, and Comparative Examples 1-1 to 1-5>
The material configurations of the layers in the organic EL elements of Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-5 are shown in Table 1 below.

In Table 1, "HI" is N ⁴ ,N ^4' -diphenyl-N ⁴ ,N ^4' -bis(9-phenyl-9H-carbazol-3-yl)-[1,1'-biphenyl]-4,4'-diamine, "HAT-CN" is 1,4,5,8,9,12-hexaazatriphenylene hexacarbonitrile, "HT-1" is N-[1,1'-biphenyl]-4-yl-9,9-dimethyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9H-fluoren-2-amine, and "HT-2" is N,N-bis(4-(dibenzo[b,d]furan-4-yl)fluoren-2-amine. "BH" is 2-(10-phenylanthracen-9-yl)dibenzo[b,d]furan; "ET-1" is 9,9'-[(5-(6-(1,1'-biphenyl)-4-yl)-2-phenylpyrimidin-4-yl)-1,3-phenylene]bis(9H-carbazole); and "ET-2" is 2-ethyl-1-(4-(10-phenylanthracen-9-yl)phenyl)-1H-benzo[d]imidazole. The chemical structures of "Liq" and comparative compounds (Ref-1) to (Ref-5) are shown below. The comparative compounds were synthesized in the same manner as in Synthesis Example 1.

[Example 1-1]
A 26 mm × 28 mm × 0.7 mm glass substrate (manufactured by Optoscience Co., Ltd.) on which an ITO film having a thickness of 180 nm was formed by sputtering and polished to 120 nm was used as a transparent support substrate. This transparent support substrate was fixed to a substrate holder of a commercially available deposition apparatus (manufactured by Showa Vacuum Co., Ltd.), and a molybdenum deposition boat containing HI, HAT-CN, HT-1, HT-2, BH, compound (1-1), ET-1, and ET-2, and an aluminum nitride deposition boat containing Liq, LiF, and aluminum were attached.

The following layers were formed in sequence on the ITO film of the transparent support substrate. The vacuum chamber was depressurized to 5×10 ⁻⁴ Pa, and first, HI was heated and evaporated to a thickness of 40 nm, then HAT-CN was heated and evaporated to a thickness of 5 nm, then HT-1 was heated and evaporated to a thickness of 45 nm, then HT-2 was heated and evaporated to a thickness of 10 nm to form a hole layer consisting of four layers. Next, BH and compound (1-1) were heated simultaneously and evaporated to a thickness of 25 nm to form a light-emitting layer. The evaporation rate was adjusted so that the mass ratio of BH to compound (1-1) was approximately 97:3. Furthermore, ET-1 was heated and evaporated to a thickness of 5 nm, then ET-2 and Liq were heated simultaneously and evaporated to a thickness of 25 nm to form an electronic layer consisting of two layers. The evaporation rate was adjusted so that the mass ratio of ET-2 to Liq was approximately 50:50. The evaporation rate of each layer was 0.01 to 1 nm/sec. Thereafter, LiF was heated and evaporated at a deposition rate of 0.01 to 0.1 nm/sec to a thickness of 1 nm, and then aluminum was heated and evaporated to a thickness of 100 nm to form a cathode, thereby obtaining an organic EL element.

[Examples 1-2 to 1-6, Comparative Examples 1-1 to 1-5]
An organic EL device was obtained in the same manner as in Example 1-1, except that a compound shown in Table 1 was used instead of compound (1-1).

[evaluation]
The evaluation items include driving voltage (V), emission wavelength (nm), CIE chromaticity (x, y), external quantum efficiency (%), maximum wavelength (nm) and half-width (nm) of the emission spectrum, etc. For these evaluation items, values at 1000 cd/ ^m2 emission can be used.

The quantum efficiency of a light-emitting element can be classified into internal quantum efficiency and external quantum efficiency. The internal quantum efficiency indicates the proportion of external energy injected as electrons (or holes) into the light-emitting layer of the light-emitting element that is converted purely into photons. On the other hand, the external quantum efficiency is calculated based on the amount of these photons that are emitted to the outside of the light-emitting element. Some of the photons generated in the light-emitting layer are absorbed or continue to be reflected inside the light-emitting element, and are not emitted to the outside of the light-emitting element, so the external quantum efficiency is lower than the internal quantum efficiency.

The method of measuring the spectral radiance (emission spectrum) and the external quantum efficiency is as follows. Using a voltage/current generator R6144 manufactured by Advantest Corporation, a voltage is applied so that the luminance of the element becomes 1000 cd/ ^m2 , and the element is made to emit light. Using a spectroradiometer SR-3AR manufactured by TOPCON Corporation, the spectral radiance of the visible light region is measured from a direction perpendicular to the light-emitting surface. Assuming that the light-emitting surface is a completely diffusing surface, the measured spectral radiance value of each wavelength component is divided by the wavelength energy and multiplied by π to obtain the number of photons at each wavelength. Next, the number of photons is integrated over the entire wavelength range observed to obtain the total number of photons emitted from the element. The value obtained by dividing the applied current value by the elementary charge is the number of carriers injected into the element, and the value obtained by dividing the total number of photons emitted from the element by the number of carriers injected into the element is the external quantum efficiency. The half-width of the emission spectrum is obtained as the width between the upper and lower wavelengths at which the intensity is 50% with respect to the maximum emission wavelength.

For the organic EL elements of Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-5, a direct current voltage was applied to the ITO electrode as the anode and the LiF/aluminum electrode as the cathode to measure the characteristics at 1000 cd/ ^m2 emission, and the time (lifetime) during which the luminance was maintained at 97% or more of the initial luminance was also measured.
The results are shown in Table 2.

Examples 1-1 to 1-6 were more efficient and had a longer life than the corresponding comparative examples.

<Examples 2 to 3 and Comparative Examples 2 to 3>
[Comparative Example 2-1]
A 26 mm x 28 mm x 0.7 mm glass substrate (manufactured by Optoscience Co., Ltd.) on which an ITO film having a thickness of 200 nm was formed by sputtering and polished to 120 nm was used as a transparent support substrate. This transparent support substrate was fixed to a substrate holder of a commercially available deposition apparatus (manufactured by Showa Vacuum Co., Ltd.), and a molybdenum deposition boat containing HAT-CN, HTL-1, TcTa, ETL-1, BCC-TPTA, compound (Ref-1), and ET7, and a tungsten deposition boat containing LiF and aluminum were attached.

The following layers were formed in sequence on the ITO film of the transparent support substrate. The vacuum chamber was depressurized to 5×10 ⁻⁴ Pa, and first, HAT-CN was heated and evaporated to a thickness of 5 nm to form a hole injection layer. Next, HTL-1 was heated and evaporated to a thickness of 90 nm to form a hole transport layer 1, and TcTa was further heated and evaporated to a thickness of 10 nm to form a hole transport layer 2. Next, TcTa, ETL-1, BCC-TPTA, and the compound (Ref-1) were simultaneously heated and evaporated to a thickness of 20 nm to form a light-emitting layer. The evaporation rate was adjusted so that the mass ratio of TcTa, ETL-1, BCC-TPTA, and the compound (Ref-1) was approximately 44.5:44.5:10:1. Next, ETL-1 was heated and evaporated to a thickness of 20 nm to form an electron transport layer 1, and ET7 was further heated and evaporated to a thickness of 10 nm to form an electron transport layer 2. The deposition rate of each layer was 0.01 to 1 nm/sec. Then, LiF was heated and deposited at a deposition rate of 0.01 to 0.1 nm/sec to a thickness of 1 nm, and then aluminum was heated and deposited to a thickness of 100 nm to form a cathode, thereby obtaining an organic EL device. At this time, the deposition rate of aluminum was adjusted to 1 to 10 nm/sec.

[Examples 2-1 to 2, Examples 3-1 to 2, Comparative Examples 2-2 to 5, Comparative Examples 3-1 to 5]
An organic EL element was obtained in the same manner as in Comparative Example 2-1, except that the assisting dopant and the emitting dopant were changed to those shown in Table 3.
In Table 3, "host 1" corresponds to a hole-transporting host material, and "host 2" corresponds to an electron-transporting host material.

The chemical structures of the compounds used to manufacture each of the above elements are shown below.

[evaluation]
For the organic EL elements of Examples 2-1 to 2, Examples 3-1 to 2, Comparative Examples 2-1 to 5, and Comparative Examples 3-1 to 5, a direct current voltage was applied to the ITO electrode as the anode and the LiF/aluminum electrode as the cathode, and the external quantum efficiency (EQE) and LT50 (the time until the luminance reaches 500 cd/ ^m2 when continuously driven at a current density at an initial luminance of 1000 cd/ ^m2 ) at a luminance of 1000 cd/ ^m2 were measured.
The evaluation results of each element are shown in Table 4.

The results show that the elements of the examples have higher efficiency and longer life than the elements of the comparative examples.

REFERENCE SIGNS LIST 100 Organic electroluminescent element 101 Substrate 102 Anode 103 Hole injection layer 104 Hole transport layer 105 Light-emitting layer 106 Electron transport layer 107 Electron injection layer 108 Cathode

Claims (14)

A polycyclic aromatic compound represented by formula (1);

In formula (1),
ring A, ring B, ring C, and ring D each independently represent a substituted or unsubstituted aryl ring or a substituted or unsubstituted heteroaryl ring;
X is >N-R ^NX , >O, >C(-R ^CX ) ₂ , >Si(-R ^IX ) ₂ , >S, or >Se, R ^NX is hydrogen, a substituted or unsubstituted aryl, a substituted or unsubstituted heteroaryl, a substituted or unsubstituted alkyl, or a substituted or unsubstituted cycloalkyl, R ^CX and R ^IX are each independently hydrogen, a substituted or unsubstituted aryl, a substituted or unsubstituted heteroaryl, a substituted or unsubstituted alkyl, or a substituted or unsubstituted cycloalkyl, two R ^CX may be bonded to each other to form a ring, two R ^IX may be bonded to each other to form a ring, R ^NX , R ^CX , and R ^IX may be bonded to at least one selected from the group consisting of ring A and ring B via a linking group or a single bond,
L is >C(-R ^CL ) ₂ , >NR ^NL , >O, >S, >C=O, >S=O, >S(=O) ₂ , or >Se; R ^CL is hydrogen, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted alkyl, or substituted or unsubstituted cycloalkyl; two R ^CLs may be bonded to each other to form a ring; R ^NL is hydrogen, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted alkyl, or substituted or unsubstituted cycloalkyl;
At least one selected from the group consisting of aryl rings and heteroaryl rings in formula (1) may be condensed with at least one cycloalkane, the cycloalkane may be substituted with at least one substituent, and at least one -CH ₂ - in the cycloalkane may be replaced with -O-;
At least one hydrogen in formula (1) may be replaced with deuterium. The polycyclic aromatic compound according to claim 1, wherein ring A, ring B, ring C, and ring D are all substituted or unsubstituted benzene rings. 2. The polycyclic aromatic compound of claim 1, wherein L is C(--R ^CL ) ₂ , >NR ^NL , >O, or >S. The polycyclic aromatic compound according to claim 3, wherein L is >C(-R ^CL ) ₂ . The polycyclic aromatic compound according to claim 4, wherein all of R ^CL are substituted or unsubstituted phenyl, all of R ^{CL are substituted or unsubstituted phenyl and two R CL} are bonded to each other, or all of R ^CL are methyl. 2. The polycyclic aromatic compound according to claim 1, wherein X is >N-R ^NX , and R ^NX is bonded to only one of ring A and ring B, or to neither of rings. The polycyclic aromatic compound according to claim 6, represented by any one of the following formulas:

In the formula, Me is methyl and tBu is t-butyl. The polycyclic aromatic compound according to claim 1, represented by any one of the following formulas:

In the formula, Me is methyl and tBu is t-butyl. An organic electroluminescence device having a pair of electrodes consisting of an anode and a cathode and an organic layer disposed between the pair of electrodes, the organic layer containing the polycyclic aromatic compound according to any one of claims 1 to 8. The organic electroluminescent device according to claim 9, wherein the organic layer is a light-emitting layer. The organic electroluminescent device according to claim 10, wherein the light-emitting layer contains a host material and the polycyclic aromatic compound as a dopant material. The organic electroluminescent device according to claim 11, wherein the host material is an anthracene compound, a fluorene compound, or a dibenzochrysene compound. The organic electroluminescent device according to claim 10, wherein the light-emitting layer contains a host material, a thermally activated delayed fluorescent material or a phosphorescent material as an assisting dopant, and the polycyclic aromatic compound as an emitting dopant. A display device or lighting device comprising the organic electroluminescent device according to claim 9.