JP7769504B2 - Polycyclic aromatic compounds - Google Patents

Description

The present invention relates to polycyclic aromatic compounds, organic devices using the same, such as organic electroluminescent elements, organic field-effect transistors, and organic thin-film solar cells, as well as display devices and lighting devices.

Traditionally, display devices using electroluminescent light-emitting elements have been the subject of extensive research due to their potential for power saving and thinning. Furthermore, organic electroluminescent devices made from organic materials have been actively investigated due to their ease of being lightweight and large-sized. In particular, there has been active research into the development of organic materials that have the luminescent properties of blue and green, which are one of the three primary colors of light, as well as organic materials with the ability to transport charges such as holes and electrons (potentially becoming semiconductors or superconductors), regardless of whether they are polymeric or low-molecular-weight compounds.

Organic EL elements have a structure consisting of a pair of electrodes consisting of an anode and a cathode, and one or more layers containing organic compounds that are placed between the pair of electrodes. Layers containing organic compounds include light-emitting layers and charge transport/injection layers that transport or inject charges such as holes and electrons, and a variety of organic materials suitable for these layers have been developed.

Currently, three types of light-emitting materials are used for the light-emitting layer: fluorescent materials, phosphorescent materials, and thermally activated delayed fluorescence (TADF) materials. For example, fluorescent materials such as improved azaborine derivatives have been reported (Patent Document 1), phosphorescent materials such as noble metal complexes with multidentate ligands have been developed (Patent Document 2), and thermally activated delayed fluorescence (TADF) materials such as carbazonitrile compounds have been developed (Non-Patent Document 1).

In devices using either material, a material with a high minimum excited singlet energy or triplet energy is used in the layer adjacent to the emitting layer or as a host to prevent energy leakage from the emitting layer or surrounding layers, which would lead to a decrease in efficiency.

International Publication No. 2015/102118 Japanese Patent Application Laid-Open No. 2014-239225

Nature Vol.492 13 December 2012

As mentioned above, a variety of materials have been developed for use in organic EL devices, but to increase the options for materials for organic EL devices, there is a need for the development of materials made from compounds that differ from conventional ones. Furthermore, Patent Document 1 reports a boron-containing polycyclic aromatic compound and an organic EL device using the compound, but there is a need for materials for the emitting layer and peripheral layers that can improve the luminous efficiency and device lifespan to further improve device characteristics.

As a result of extensive research to solve the above problems, the inventors succeeded in producing a novel polycyclic aromatic compound and discovered that this compound is effective as a material with high singlet energy and triplet energy. They then discovered that an excellent organic EL device can be obtained by constructing an organic EL device, for example, by using such a polycyclic aromatic compound as a host material or a material for a layer adjacent to an emitting layer, and disposing an emitting layer between a pair of electrodes, the emitting layer containing a compound with a lower triplet energy as a dopant material, and thus completed the present invention. Specifically, the present invention provides the following polycyclic aromatic compounds, as well as materials for organic devices containing the following polycyclic aromatic compounds.

<1> A polycyclic aromatic compound having a structure consisting of one or more structural units represented by the following 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;
Ring B and ring C may be further bonded via a single bond or a linking group, when ^X2 is a single bond, ring C and ring D may be further bonded via a linking group, when ^X3 is a single bond, ring D and ring A may be further bonded via a linking group,
X ¹ , X ² and X ³ each independently represent >C(—R ^XC ) ₂ , >N—R ^XN , >O, >Si(—R ^XI ) ₂ , >S or a single bond, provided that X ¹ and X ² are not simultaneously single bonds;
R ^XC , R ^XN and R ^XI are each independently hydrogen, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted alkyl or substituted or unsubstituted cycloalkyl, or form a ring together with one or two rings selected from ring A to ring D bound to the same element, provided that two R ^XCs may be bonded to each other and two R ^XIs may be bonded to each other;
At least one hydrogen atom in the compound or structure represented by formula (1) may be replaced with deuterium, cyano, or halogen.

<2> The polycyclic aromatic compound according to <1>, having a structure consisting of one structural unit represented by formula (1).
<3> The polycyclic aromatic compound according to <1> or <2>, wherein the ring A, the ring B, the ring C, and the ring D are all substituted or unsubstituted benzene rings.
<4> The polycyclic aromatic compound according to any one of <1> to <3>, wherein X ¹ , X ² and X ³ are each independently >N—R ^XN , >O, >S or a single bond, and R ^XN is a substituted or unsubstituted aryl or a substituted or unsubstituted heteroaryl.

<5> The polycyclic aromatic compound according to <1>, represented by any one of the following formulas:

<6> A material for an organic device, comprising the polycyclic aromatic compound according to any one of <1> to <5>.
<7> 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 <5>.
<8> The organic electroluminescent device according to <7>, wherein the organic layer is a light-emitting layer.
<9> The organic electroluminescent device according to <8>, wherein the light-emitting layer contains the polycyclic aromatic compound as a host material and a dopant material.
<10> The organic electroluminescent device according to <7>, wherein the organic layer is an electron transport layer.
<11> The organic electroluminescent device according to <7>, wherein the organic layer is a hole transport layer.
<12> A display device or a lighting device comprising the organic electroluminescent device according to any one of <7> to <11>.

In a preferred embodiment of the present invention, an organic EL device is produced using a novel polycyclic aromatic compound, for example, as a host material in an emitting layer, as a component of the host material, or as a component of a layer adjacent to the emitting layer, thereby providing an organic EL device with excellent quantum efficiency and device life.

1 is a schematic cross-sectional view showing an organic EL element according to an embodiment of the present invention.

The present invention will be described in detail below. The following description of the constituent elements may be based on representative embodiments or specific examples, but the present invention is not limited to such embodiments. In this specification, a numerical range expressed using "to" means a range that includes the numerical values before and after "to" as the lower and upper limits.
In this specification, in explaining structural formulae, a "hydrogen atom (H)" may be referred to as "hydrogen." Similarly, a "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" represents methyl, "Et" represents ethyl, "nBu" represents n-butyl (normal butyl), "tBu" represents t-butyl (tertiary butyl), "iBu" represents isobutyl, "secBu" represents secondary butyl, "nPr" represents n-propyl (normal propyl), "iPr" represents isopropyl, "tAm" represents t-amyl, "2EH" represents 2-ethylhexyl, "tOct" represents t-octyl, "Ph" represents phenyl, "Mes" represents mesityl (2,4,6-trimethylphenyl), "Tf" represents trifluoromethanesulfonyl, "TMS" represents trimethylsilyl, and "D" represents 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 represented by the number of carbon atoms. However, when a chemical structure is substituted with a substituent, or when a substituent is further substituted with a substituent, the number of carbon atoms refers to the number of carbon atoms in the chemical structure or the substituent, and does not refer to 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 carbon number Y is not the total number of carbon atoms in substituents A and B. 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 restriction)," and carbon number Y is not the total number of carbon atoms in substituents A and B.

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

1. Polycyclic Aromatic Compound of the Present Invention The polycyclic aromatic compound of the present invention is a polycyclic aromatic compound having a structure consisting of one or more structural units represented by formula (1).

The inventors have discovered that the polycyclic aromatic compounds of the present invention, in which aromatic rings are linked by heteroatoms such as oxygen, nitrogen, and sulfur, have a large HOMO-LUMO gap (band gap Eg in thin films) and high triplet energy. This is thought to be because the rings containing heteroatoms have low aromaticity, which prevents the decrease in the HOMO-LUMO gap that accompanies the expansion of the conjugated system, and because a large HOMO-LUMO gap can be obtained by utilizing intramolecular distortion to prevent the expansion of the conjugated system.

In addition, the heteroatom-containing polycyclic aromatic compounds according to the present invention are useful as materials with high triplet energy, and are also useful as host compounds for phosphorescent organic EL devices and organic EL devices that utilize thermally activated delayed fluorescence, as well as electron blocking layers (electron blocking layers) and hole blocking layers (hole blocking layers) adjacent to the light-emitting layer, and as electron transport layers and hole transport layers. Furthermore, the HOMO and LUMO energies of these polycyclic aromatic compounds can be freely adjusted by introducing substituents, making it possible to optimize the ionization potential and electron affinity depending on the surrounding materials.

<Ring structure of structural unit represented by formula (1)>
In formula (1), "A,""B,""C," and "D" in the circle are symbols indicating the ring structure shown by the circle.

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.

In the substituted or unsubstituted aryl rings or substituted or unsubstituted heteroaryl rings in rings A, B, C, and D of the structural unit represented by formula (1), the substituents referred to as "substituted or unsubstituted" are preferably at least one substituent selected from the substituent group Z described below.

The structural unit represented by formula (1) has a structure in which at least four aromatic rings, namely ring A, ring B, ring C, and ring D, are linked by heteroatoms such as oxygen, nitrogen, and sulfur to form a further ring structure. The formed ring structure is a fused ring structure, composed of at least two rings, one of which contains a 7- to 9-membered ring structure. The structural unit represented by formula (1) has a structure in which ring A, ring B, ring C, and ring D are each further fused to this fused ring.

Ring A forms a trivalent group having bonds to three consecutive carbon atoms on the aryl ring or heteroaryl ring in its structure. These three bonds are bonded to ^X1 , N, and ^X3 , respectively. When Ring A is further bonded to another ring, it may become a tetravalent group. In Ring A, the ring having the carbon atoms having the above three bonds as ring constituent elements is preferably a 5- or 6-membered ring, more preferably a 6-membered ring. This ring may be further fused with another ring. An example of a 6-membered ring is a benzene ring. Examples of a benzene ring further fused with another ring include a naphthalene ring, a dibenzofuran ring, a dibenzothiophene ring, and a carbazole ring.

Ring B, Ring C, and Ring D each form a divalent group having bonds to two adjacent carbon atoms on the aryl or heteroaryl ring in the ring structure. Ring B is bonded to ^X1 and N through the two bonds, Ring C is bonded to N and ^X2 through the two bonds, and Ring D is bonded to ^X2 and ^X3 through the two bonds. When Ring B, Ring C, and Ring D are each bonded to another ring, they may form a trivalent group. In Ring B, Ring C, and Ring D, the rings containing the carbon atoms having the two bonds as ring constituent elements are preferably 5- or 6-membered rings, more preferably 6-membered rings. This ring may be further fused with another ring. An example of a 6-membered ring is a benzene ring. Examples of a benzene ring further fused with another ring include a naphthalene ring, a dibenzofuran ring, a dibenzothiophene ring, and a carbazole ring.

In the structural unit represented by formula (1), ring B and ring C may be further bonded via a single bond or a linking group, when ^X2 is a single bond ring C and ring D may be further bonded via a linking group, and when ^X3 is a single bond ring D and ring A may be further bonded via a linking group. Examples of the linking group include >N-R, >C(-R) ₂ , >Si(-R) ₂ , >O, and >S. In this case, each R is independently hydrogen, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted alkyl, or substituted or unsubstituted cycloalkyl, and two Rs in >C(-R) ₂ may be bonded to each other to form a ring, or two Rs in >Si(-R) ₂ may be bonded to each other to form a ring.

A structure in which ring A, ring B, ring C, and ring D of formula (1) are all substituted or unsubstituted benzene rings can be represented by formula (2) below, and the structural unit represented by formula (2) is a preferred example of the structural unit represented by formula (1).

The rings A, B, C and D in formula (1) correspond to the ring a and its substituents, the ring b and its substituents, the ring c and its substituents, and the ring d and its substituents in formula (2), respectively.
In formula (2), each R ^a is independently a substituent. This substituent is at least one substituent selected from the substituent group Z described below. "R ^a -" indicates that any of the substitutable elements constituting the ring to which the end of the line belongs may be substituted with the substituent represented by R ^a , and n1 to n4 indicate the number of substitutions. Note that when the ring to which the end of the line of "R ^a -" belongs forms a fused ring together with the dashed line, the substituent represented by R ^a may be substituted at any position of the fused ring. Specifically, n1 is an integer of 0 to 3, n2 is an integer of 0 to 4, n3 is an integer of 0 to 4, and n4 is an integer of 0 to 4. ^{X 1} , X ² , and X ³ have the same meanings as X ¹ , X ² , and X ³ in formula (1), respectively, and the preferred ranges are also the same.

The dashed line in formula (2) indicates that the elements on both ends of the dashed line may be linked. Specifically, this is as follows:

A fused ring may be formed by a wavy line bonding ring a to two carbon atoms on ring a. A fused ring may be formed by a wavy line bonding ring b to either one of two carbon atoms on ring b. A fused ring may be formed by a wavy line bonding ring c to two carbon atoms on ring c. A fused ring may be formed by a wavy line bonding ring d to two carbon atoms on ring d. The ring formed may form a fused ring together with another ring indicated by a wavy line. The fused ring formed is preferably a naphthalene ring, a dibenzofuran ring, a dibenzothiophene ring, or a carbazole ring.

Furthermore, ring b and ring c may be further bonded by a wavy line that represents a single bond, >N-R ^XBC , >O, or >S. When ^{X 2} is a single bond, ring c and ring d may be further bonded by a wavy line that represents >N-R ^XCD , >O, or >S. When ^{X 3} is a single bond, ring d and ring a may be further bonded by a wavy line that represents >N-R ^XDA , >O, or >S. R ^XBC , R ^XCD , and R ^XDA are each independently hydrogen, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted alkyl, or substituted or unsubstituted cycloalkyl. Here, the substituent in the term "substituted or unsubstituted" includes at least one substituent selected from the substituent group Z described below.

The elements on different rings on either side of the dashed line are linked to form a fused ring of at least three rings. Examples of fused rings in this case include a carbazole ring, and when ring b and ring c are linked, a phenoxazine ring or a phenothiazine ring.

In formula (2), the number of dashed lines connecting the elements at both ends is preferably 0 to 3, more preferably 0 to 2, and even more preferably 0, in the structural unit represented by formula (2).

In formula (2), R ^a is preferably a substituted or unsubstituted aryl or a substituted or unsubstituted heteroaryl, and n1 to n4 are each preferably 0 or 1, and more preferably 0.

<X ¹ , X ² , X ³ >
^X1 , ^X2 , and ^X3 are each independently >C(—R ^XC ) ₂ , >N—R ^XN , >O, >Si(—R ^XI ) ₂ , >S, or a single bond. R ^XC , R ^XN , and R ^XI are each independently hydrogen, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted alkyl, or substituted or unsubstituted cycloalkyl, or form a ring together with one or two rings selected from rings A to D bonded to the same element, provided that two R ^XCs may be bonded to each other and two R ^XIs may be bonded to each other, and ^X1 and ^X2 are not simultaneously single bonds.

In R ^XC , R ^XN and R ^XI , when "substituted or unsubstituted" or the like is used, the substituent is at least one substituent selected from the substituent group Z, and preferably a substituted or unsubstituted aryl, a substituted or unsubstituted heteroaryl, an unsubstituted cycloalkyl or an unsubstituted alkyl. ^{R XN} is preferably a substituted or unsubstituted aryl or a substituted or unsubstituted heteroaryl, and for example, biphenylyl or diphenyltriazinyl, or a group having these as a substituent, is preferred. R ^XC and R ^XI are preferably a substituted or unsubstituted aryl or an unsubstituted alkyl.

The expression "that R ^XC , R ^XN , or R ^XI forms a ring together with one or two rings selected from rings A to D bonded to the same element" means that the ring is formed by any of the following bonds:

At least one R ^XC of ^X1 >C(—R ^XC ) ₂ is bonded to ring A and/or ring B; R ^XN of ^X1 >N—R ^XN is bonded to ring A and/or ring B;
X ¹ is >at least one R ^XI of Si(—R ^XI ) ₂ is bonded to ring A and/or ring B, and X ² is >at least one R ^XC of C(—R ^XC ) ₂ is bonded to ring C and/or ring D;
^X2 is >N-R ^XN , and R ^XN is bonded to ring C and/or ring D;
^X2 is Si(—R ^XI ) ₂ , and at least one R ^XI is bonded to ring C and/or ring D;
^X3 is >C(—R ^XC ) ₂ , at least one R ^XC is bonded to ring D and/or ring A:
^X3 is >N-R ^XN , and R ^XN is bonded to ring D and/or ring A;
X ³ is >Si(—R ^XI ) ₂ , and at least one R ^XI is bonded to ring D and/or ring A.

Of the above, any of the following is preferred:
^X2 is >NR ^XN , wherein R ^XN is bonded to ring C and/or ring D; or ^X3 is >NR ^XN , wherein R ^XN is bonded to ring D and/or ring A.
As described above, it is preferable that one or two, and more preferably one, of R ^XC , R ^XN , and R ^XI bonded to one or two rings selected from rings A to D in the structural unit represented by formula (1).

Examples of the ring structure formed are shown below. In the following, examples are shown in which R ^XN of ^X2 >N-R ^XN is bonded to ring C and/or ring D to form a ring structure.

X ¹ , X ² and X ³ are each independently preferably >N—R ^XN , >O, >S or a single bond, more preferably >O, >S or a single bond, and even more preferably a single bond.
^X1 is more preferably >O or a single bond. It is more preferable that both ^X2 and ^X3 are >N-R ^XN , or one of them is >N-R ^XN and the other is a single bond. ^{R XN} is preferably substituted or unsubstituted aryl or substituted or unsubstituted heteroaryl.

<When two groups bonded to the same atom are bonded to each other>
Two groups (two R ^{XC s} , two R XI ^s , other two R) bonded to the same atom in >C(-R ^XC ) ₂ , >Si(-R ^XI ) ₂ -, etc. may be bonded to each other to form a ring. They may be bonded by a single bond or a linking group (collectively referred to as a linking group), and examples of the linking group include -CH ₂ -CH ₂ -, -CHR-CHR-, -CR ₂ -CR ₂ -, -CH=CH-, -CR=CR-, -C≡C-, -N(-R)-, -O-, -S-, -C(-R) ₂ -, -Si(-R) ₂ -, or -Se-, for example, the following structure: The R of -CHR-CHR-, the R of -CR _{- CR-} , the R of -CR=CR-, the R of -N(-R)-, _the R of -C(-R)-, and the R of -Si(-R)- are _each independently hydrogen, aryl optionally substituted with alkyl or cycloalkyl, heteroaryl optionally substituted with alkyl or cycloalkyl, alkyl optionally substituted with cycloalkyl, alkenyl optionally substituted with alkyl or cycloalkyl, alkynyl optionally substituted with alkyl or cycloalkyl, or cycloalkyl optionally substituted with alkyl or cycloalkyl. Adjacent two Rs may form a ring to form a cycloalkylene, arylene, or heteroarylene.

As the linking 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 at which the two R groups 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) position relative to the bonding position (1st position) of the "C" or "Si" on the phenyl (see the structural formula above).

<Specific Description of Rings and Substituents>
Details of the rings and substituents described herein are provided below.

The "aryl ring" is, for example, an aryl ring having 6 to 30 carbon atoms, and preferably an aryl ring having 6 to 20 carbon atoms, an aryl ring having 6 to 16 carbon atoms, an aryl ring having 6 to 12 carbon atoms, or an aryl ring having 6 to 10 carbon atoms.

Specific examples of "aryl rings" include a monocyclic benzene ring, a fused bicyclic naphthalene ring, a fused tricyclic acenaphthylene ring, a fluorene ring, a phenalene ring, a phenanthrene ring, and an anthracene ring, a fused tetracyclic triphenylene ring, a pyrene ring, or a naphthacene ring, and a fused pentacyclic perylene ring or pentacene ring.

A "heteroaryl ring" is, for example, a heteroaryl ring having 2 to 30 carbon atoms, and preferably a heteroaryl ring having 2 to 25 carbon atoms, a heteroaryl ring having 2 to 20 carbon atoms, a heteroaryl ring having 2 to 15 carbon atoms, or a heteroaryl ring having 2 to 10 carbon atoms. Furthermore, a "heteroaryl ring" is, for example, a heterocyclic ring containing, in addition to carbon, 1 to 5 heteroatoms selected from oxygen, sulfur, and nitrogen 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, 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 phenanthroline ring, a phthalazine ring, a naphthyridine ring, a purine ring, a pteridine ring, a carbazole ring, a benzophenone ... Examples of such rings include a benzol 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, a naphthobenzofuran ring, a thiophene ring, a benzothiophene ring, an isobenzothiophene ring, a dibenzothiophene ring, a naphthobenzothiophene ring, a benzophosphole ring, a dibenzophosphole ring, a benzophosphole oxide ring, a dibenzophosphole oxide ring, a furazan ring, a thianthrene ring, an indolocarbazole ring, a benzoindolocarbazole ring, a dibenzoindolocarbazole ring, an imidazoline ring, and an oxazoline ring.

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

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 phenyl, a monocyclic ring system; biphenylyl (2-biphenylyl, 3-biphenylyl, or 4-biphenylyl) a bicyclic ring system; naphthyl (1-naphthyl or 2-naphthyl) a fused 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) a tricyclic ring system; and acenaphthylene-(1-, 3-, 4- , or 5-)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, 5'-phenyl-m-terphenyl-5-yl, 5'-phenyl-m-terphenyl-6-yl, 5'-phenyl-m-terphenyl-7-yl, 5'-phenyl-m-terphenyl-8-yl, 5'-phenyl-m-terphenyl-9-yl, 5'-phenyl-m-terphenyl-10-yl, 5'-phenyl-m-terphenyl-11-yl, 5'-phenyl-m-terphenyl-12-yl, 5'-phenyl-m-terphenyl-13-yl, 5'-phenyl-m-terphenyl-14-yl, 5'-phenyl-m-terphenyl-15-yl, 5'-phenyl-m-terphenyl-16-yl, 5'-phenyl-m-terphenyl-17-yl, 5'-phenyl-m-terphenyl-18-yl, 5'-phenyl-m-terphenyl-19-yl, 5'-phenyl-m-terphenyl-20-yl, 5'-phenyl-m-terphenyl-21-yl, 5'-phenyl-m-terphenyl-22-yl, 5'-phenyl-m-terphenyl-33-yl, 5'-phenyl-m-terphenyl-19-yl, 5'-phenyl-m-terphenyl-23-yl, 5'-phenyl-m-terphenyl-24-yl, 5'-phenyl-m Examples include fused tetracyclic ring systems such as m-terphenyl-4-yl or m-quaterphenyl, triphenylene-(1- or 2-)yl, pyrene-(1-, 2-, or 4-)yl, or naphthacene-(1-, 2-, or 5-)yl, and fused pentacyclic ring systems such as perylene-(1-, 2-, or 3-)yl or pentacene-(1-, 2-, 5-, or 6-)yl. Other examples include monovalent groups of spirofluorene.

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 aryls such as phenyl (specific examples are the groups described above), alkyls such as methyl (specific examples are the groups described later), and cycloalkyls 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 atom from the above-mentioned "aryl" (monovalent group).

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

Specific examples of "heteroaryl" include 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, and a Examples include clidinyl, phenoxathiinyl, phenoxazinyl, phenothiazinyl, phenazinyl, phenazasilinyl, indolizinyl, furanyl, benzofuranyl, isobenzofuranyl, dibenzofuranyl, naphthobenzofuranyl, thienyl, benzothienyl, isobenzothienyl, dibenzothienyl, naphthobenzothienyl, benzophosphoryl, dibenzophosphoryl, monovalent groups of benzophospholeoxide rings, monovalent groups of dibenzophospholeoxide rings, furazanyl, thianthrenyl, indolocarbazolyl, benzoindolocarbazolyl, dibenzoindolocarbazolyl, imidazolinyl, and oxazolinyl. Other examples include monovalent groups of spirofluorene, monovalent groups of spiro[fluorene-9,9'-xanthene], monovalent groups of spirobi[silafluorene], and monovalent groups of benzoselephene.

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 carbazolyl group as the second substituent, where the 9-position is substituted with an aryl such as phenyl, an alkyl such as methyl, or a cycloalkyl such as cyclohexyl or adamantyl. Also included in the heteroaryl group as the second substituent are groups in which a nitrogen-containing heteroaryl such as pyridyl, pyrimidinyl, triazinyl, or carbazolyl is further substituted with phenyl, biphenylyl, or the like.

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. Furthermore, 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).

"Diarylamino" is an amino substituted with two aryl groups, and the details of the aryl group can be found in the above explanation of "aryl".
"Diheteroarylamino" is an amino substituted with two heteroaryls, and the details of this heteroaryl can be found in the above description of "heteroaryl".
"Arylheteroarylamino" is amino substituted with aryl and heteroaryl, and the details of the aryl and heteroaryl can be found in the above explanations of "aryl" and "heteroaryl".

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 via a linking group, as shown below. This explanation also applies to diheteroarylamino and arylheteroarylamino formed from aryls or heteroaryls.

Specific examples of the linking group include >O, >N-R ^X , >C(-R ^X ) ₂ , >Si(-R ^X ) ₂ , >S, >CO, >CS, >SO, >SO ₂ , and >Se. Each R ^X is independently alkyl, cycloalkyl, aryl, or heteroaryl, which may be substituted with alkyl, cycloalkyl, aryl, or heteroaryl. Furthermore, R ^X in >C(-R ^X ) ₂ and >Si(-R ^X ) ₂ may be bonded 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 each 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. Further examples of the linking group include alkenylene. Any hydrogen atoms of the alkenylene may be independently replaced with R ^X , and each R ^X is independently alkyl, cycloalkyl, substituted silyl, aryl, or heteroaryl, which may be substituted with alkyl, cycloalkyl, substituted silyl, or aryl.

In addition, unless otherwise specified, when the term "diarylamino," "diheteroarylamino," or "arylheteroarylamino" is used in this specification, it is assumed that the following additional 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.

A "diarylboryl" is a boryl substituted with two aryls, and the above description of the "aryl" can be cited for details of the aryl. 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, >C(-R) ₂ , >Si(-R) ₂ , or >Se). Here, the R of -CR=CR-, the R of >N-R, the R of >C(-R) ₂ , and the R of >Si(-R) are aryl, heteroaryl, diarylamino, alkyl, alkenyl, alkynyl, cycloalkyl, alkoxy, or aryloxy, and these groups may be further substituted with an aryl, heteroaryl, alkyl, alkenyl, alkynyl, or cycloalkyl. Two adjacent Rs may form a ring, forming a cycloalkylene, arylene, or heteroarylene. For details of the substituents listed here, the above-mentioned explanations of "aryl,""arylene,""heteroaryl,""heteroarylene," and "diarylamino," as well as the below-mentioned explanations of "alkyl,""alkenyl,""alkynyl,""cycloalkyl,""cycloalkylene,""alkoxy," and "aryloxy" can be cited. Furthermore, when "diarylboryl" is simply described 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 also added.

"Alkyl" may be either straight-chain or branched-chain, for example, a straight-chain alkyl having 1 to 24 carbon atoms or a branched-chain alkyl having 3 to 24 carbon atoms. Preferred examples include 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), and alkyl having 1 to 4 carbon atoms (branched-chain alkyl having 3 to 4 carbon atoms).

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 Examples include 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, and n-eicosyl.

For "alkenyl," please refer to the explanation of "alkyl" above. It is a group in which a 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 alkadiene-yl or alkanetriene-yl).

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

"Cycloalkyl" is, for example, a cycloalkyl having 3 to 24 carbon atoms, and preferably a cycloalkyl having 3 to 20 carbon atoms, a cycloalkyl having 3 to 16 carbon atoms, a cycloalkyl having 3 to 14 carbon atoms, a cycloalkyl having 3 to 12 carbon atoms, a cycloalkyl having 5 to 10 carbon atoms, a cycloalkyl having 5 to 8 carbon atoms, a cycloalkyl having 5 to 6 carbon atoms, or a 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, norbornenyl, 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, 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 divalent groups obtained by removing one hydrogen atom from the above-mentioned "cycloalkyl" (monovalent group).

"Alkoxy" is a group represented by "Alk-O- (Alk is alkyl)", and for details on this alkyl, please refer to 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" refers to, for example, a silyl substituted with at least one of aryl, alkyl, and cycloalkyl, and is preferably triarylsilyl, trialkylsilyl, tricycloalkylsilyl, dialkylcycloalkylsilyl, or alkyldicycloalkylsilyl.

"Triarylsilyl" is a silyl group substituted with three aryl groups, and the details of the aryl groups can be found in the above description of "aryl".
Specific examples of "triarylsilyl" include triphenylsilyl, diphenylmononaphthylsilyl, monophenyldinaphthylsilyl, and trinaphthylsilyl.

"Trialkylsilyl" is a silyl group substituted with three alkyl groups, and the details of this alkyl can be found in the above description of "alkyl".
Specific examples of the "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.

"Tricycloalkylsilyl" is a silyl group substituted with three cycloalkyl groups, and the details of this cycloalkyl can be found in the above description of "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 for "alkyl" and "cycloalkyl" above.

"Alkyldicycloalkylsilyl" is a silyl group substituted with one alkyl and two cycloalkyl groups. For details about the alkyl and cycloalkyl groups, please refer to the explanations of "alkyl" and "cycloalkyl" above.

The substituents on the structural units of formula (1) may be selected depending on the intended use of the polycyclic aromatic compound having a structure consisting of one or more structural units represented by formula (1). Preferred are methyl, t-butyl, adamantyl, phenyl, o-tolyl, naphthyl, biphenylyl, terphenyl, diphenylamino, carbazolyl, dibenzofuranyl, dibenzothiophenyl, 3,5-dicarbazolylphenyl, carbazolyl-substituted phenyl, pyridyl, phenyl-substituted pyridyl, bipyridyl, piperidinyl, phenyl-substituted piperidinyl, pyrazinyl, phenyl-substituted pyrazinyl, triazinyl, 3,5-diphenyltriazinyl, biphenyl-substituted triazinyl, carbazolyl-substituted triazinyl, and cyano. When a polycyclic aromatic compound having a structure consisting of one or more structural units represented by formula (1) is used as a hole-transporting layer or a hole-transporting host, the substituent is more preferably diphenylamino, carbazolyl, dibenzofuranyl, dibenzothiophenyl, 3,5-dicarbazolylphenyl, or carbazolyl-substituted phenyl. When used as an electron-transporting layer or an electron-transporting host, the substituent is preferably pyridyl, phenyl-substituted pyridyl, bipyridyl, piperidinyl, phenyl-substituted piperidinyl, pyrazinyl, phenyl-substituted pyrazinyl, triazinyl, 3,5-diphenyl-triazinyl, biphenyl-substituted triazinyl, carbazolyl-substituted triazinyl, or cyano. When used as a host material, the substituents are preferably phenyl, naphthyl, biphenylyl, terphenyl, diphenylamino, carbazolyl, dibenzofuranyl, dibenzothiophenyl, 3,5-di-carbazolylphenyl, carbazolyl-substituted phenyl, pyridyl, phenyl-substituted pyridyl, bipyridyl, piperidinyl, phenyl-substituted piperidinyl, pyrazinyl, phenyl-substituted pyrazinyl, triazinyl, 3,5-diphenyl-triazinyl, biphenyl-substituted triazinyl, and carbazolyl-substituted triazinyl.

In R ^XC , R ^XN , R ^XI , R ^XBC , R ^XCD , and R ^XDA , examples of the substituent when referred to as "substituted or unsubstituted" include aryl (which may be substituted with an aryl or heteroaryl), substituted or unsubstituted heteroaryl (which may be substituted with an aryl or heteroaryl), alkyl, cycloalkyl, or a substituent represented by any of the following formulas:

<Structure consisting of one or more structural units>
The polycyclic aromatic compound of the present invention is a polycyclic aromatic compound having a structure consisting of one or more structural units represented by formula (1). The polycyclic aromatic compound having a structure consisting of one of the structural units is a polycyclic aromatic compound represented by the formula described above for the structural unit represented by formula (1). The polycyclic aromatic compound having a structure consisting of two or more structural units represented by formula (1) is a compound corresponding to a multimer of the polycyclic aromatic compound represented by the formula described above for the structural unit represented by formula (1). The multimer is preferably a dimer to a hexamer, more preferably a dimer to a trimer, and particularly preferably a dimer. The multimer may be in a form having a plurality of the above unit structures within a single compound, and may be in a form in which any ring (ring A, ring B, ring C, or ring D) contained in the above structural unit is bonded so as to be shared by multiple unit structures, or in a form in which any ring (ring A, ring B, ring C, or ring D) contained in the above unit structure is bonded so as to be fused to each other. Furthermore, the above unit structures may be bonded together by a linking group such as a single bond, alkylene having 1 to 3 carbon atoms, phenylene, naphthylene, etc. Among these, a bonded structure so as to share a ring is preferred.

<Deuterium, cyano, or halogen substitution explanation>
At least one hydrogen atom in the polycyclic aromatic compound of the present invention may be replaced by deuterium, cyano, or a halogen atom. The halogen atom is fluorine, chlorine, bromine, or iodine, preferably fluorine, chlorine, or bromine, and more preferably fluorine or chlorine.

<Specific Examples of Polycyclic Aromatic Compounds of the Present Invention>
Specific examples of the polycyclic aromatic compound of the present invention include compounds represented by any of the following structural formulas.

2. Method for Producing Polycyclic Aromatic Compounds The polycyclic aromatic compounds of the present invention are basically produced by preparing a fused ring structure of ring A and ring B in which the X3 position is halogenated, and a structure containing ring X2-ring D-X3 (in this case, ring C may belong to either structure), and finally cyclizing them.

Intermediates are synthesized using standard methods, and for cyclization reactions, for example, etherification reactions can be carried out using common reactions such as nucleophilic substitution or the Ullmann reaction, and amination reactions can be carried out using common reactions such as nucleophilic substitution or the Buchwald-Hartwig reaction.

There are two types of cyclization reactions, as shown in Schemes (1) and (2) below. However, in Schemes (1) and (2) below, the substituents used in the cyclization reaction, such as the leaving groups attached to Ring A, Ring B, Ring C, Ring D, X1, X2, and X3, are omitted.

The following describes the production method of the cyclization reaction for the above case, taking compounds (a), (b), and (c) in which ring A, ring B, ring C, and ring D are benzene rings as examples.

An example of case 1 is the method described in scheme (3).

In scheme (3), a cross-coupling reaction can be carried out using a copper catalyst or palladium catalyst to obtain the desired product.

In the above scheme (3), when a copper catalyst is used, copper powder, copper oxide, or copper halide is used. Bases used include cesium carbonate, potassium carbonate, sodium carbonate, calcium carbonate, magnesium carbonate, sodium bicarbonate, tripotassium phosphate, and sodium hydride. Reaction accelerators include crown ethers (e.g., 18-crown-6-ether), polyethylene glycol (PEG), and polyethylene glycol dialkyl ether (PEGDM). Reaction solvents include N,N-dimethylformamide, nitrobenzene, dimethyl sulfoxide, dichlorobenzene, o-dichlorobenzene, and quinoline. The reaction temperature is 160 to 250°C; however, if the substrate has low reactivity, the reaction can be carried out at higher temperatures using an autoclave or similar device.

When a palladium catalyst is used, palladium acetate, palladium chloride, palladium bromide, tris(dibenzylideneacetone)dipalladium(0), tris(dibenzylideneacetone)dipalladium chloroform complex(0), tetrakis(triphenylphosphine)palladium(0), [1,1'-bis(diphenylphosphino)ferrocene]palladium(II) dichloridodichloromethane complex (1:1), etc. are used. Bases that can be used include lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, cesium carbonate, sodium bicarbonate, sodium hydride, alkoxypotassium (e.g., potassium methoxy, potassium ethoxy, potassium n-propoxy, potassium isopropoxy, potassium n-butoxy, and potassium tert-butoxy), and alkoxysodium (e.g., sodium methoxy, sodium ethoxy, sodium n-propoxy, sodium isopropoxy, sodium n-butoxy, and sodium tert-butoxy). The reaction accelerators are 2,2'-(diphenylphosphino)-1,1'-binaphthyl, 1,1'-(diphenylphosphino)ferrocene, dicyclohexylphosphinobiphenyl, di-tert-butylphosphinobiphenyl, tri(tert-butyl)phosphine, 1-(N,N-dimethylaminomethyl)-2-(di-tert-butylphosphino)ferrocene, 1-(N,N-dibutylaminomethyl)-2-(di-tert-butylphosphino)ferrocene, and 1-(N,N-dibutylaminomethyl)-2-(di-tert-butylphosphino)ferrocene. )-2-(di-tert-butylphosphino)ferrocene, 1-(methoxymethyl)-2-(di-tert-butylphosphino)ferrocene, 1,1'-bis(di-tert-butylphosphino)ferrocene, 2,2'-bis(di-tert-butylphosphino)-1,1'-binaphthyl, 2-methoxy-2'-(di-tert-butylphosphino)-1,1'-binaphthyl, etc. are used. Aromatic hydrocarbon solvents such as benzene, toluene, xylene, and mesitylene are used as the reaction solvent. The solvents may be used alone or in combination. The reaction temperature is typically between 50 and 200°C, more preferably between 80 and 140°C.

Examples of Case 2 include the methods described in Scheme (4) and Scheme (5).

In Scheme (4) and Scheme (5), the desired product can be obtained by intramolecular cross-coupling using a copper catalyst or palladium catalyst. The reaction conditions are the same as those for Scheme (3).

In Scheme (4), the resulting ring-containing intermediate can then be cross-coupled with an aryl halide compound using a copper or palladium catalyst to obtain the desired product.

The above-described schemes (1) to (5) are representative methods for producing polycyclic aromatic compounds of the present invention, and other compounds can also be synthesized using similar methods. Furthermore, the polycyclic aromatic compounds of the present invention also include compounds in which at least some of the hydrogen atoms are replaced with deuterium, cyano, or halogen. These compounds can be produced in the same manner as above by using raw materials that are halogenated, such as deuterated, cyanated, fluorinated, or chlorinated, at the desired positions.

3. Organic Devices The polycyclic aromatic compound according to the present invention can be used as a material for organic devices, such as organic electroluminescent devices, organic field-effect transistors, and organic thin-film solar cells.

3-1 Organic Electroluminescent Device The organic EL device according to this embodiment will now be described in detail with reference to the drawings. Figure 1 is a schematic cross-sectional view showing the organic EL device according to this embodiment.

<Structure of Organic Electroluminescent Device>
The organic EL element 100 shown in FIG. 1 includes 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, to have 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, an emissive layer 105 provided on the electron transport layer 106, a hole transport layer 104 provided on the emissive 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; the minimum structural unit is the anode 102, light-emitting layer 105, and cathode 108, with the hole injection layer 103, hole transport layer 104, electron transport layer 106, and electron injection layer 107 being optional layers. Furthermore, each of the above layers may consist of a single layer or multiple layers.

The layers constituting an organic EL element may be configured in the above-mentioned "substrate/anode/hole injection layer/hole transport layer/light-emitting layer/electron transport layer/electron injection layer/cathode" configuration, as well as "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/hole transport layer/light-emitting layer/electron injection layer/cathode," "substrate/anode/hole injection layer/hole transport layer/light-emitting layer/electron injection layer/cathode," or "substrate/anode/hole injection layer/hole transport layer/light-emitting layer/electron transport" configuration. The configurations 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 injection 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", or "substrate/anode/light-emitting layer/electron injection layer/cathode".

The organic EL device may further include an electron blocking layer (electron blocking layer) and/or 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. Because electrons remain in the light-emitting layer and do not leak into the hole transport layer, this prevents a shortened lifetime 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. Because holes remain in the light-emitting layer and do not leak into the electron transport layer, this prevents a shortened lifetime 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 function as the electron blocking layer. The electron injection/transport layer may also function as the hole blocking layer.

The organic EL device 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 emitting layer, and is disposed between the emitting layer and the hole transport layer and/or between the emitting layer and the electron blocking layer. The T1 energy value varies depending on the light-emitting mechanism of the device, but has a higher T1 than the compound used as the host. By having a high T1 layer around the emitting layer, triplet energy can be trapped and converted into singlet energy, which would not normally lead to light emission in fluorescent molecules, 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 compounds of the present invention are preferably used as materials for organic electroluminescent devices. Generally, compounds having a donor structure can be used as hole-transporting host materials in the light-emitting layer and as hole-transporting layers, compounds having an acceptor structure can be used as electron-transporting host materials in the electron-transporting layers, and compounds having both a donor structure and an acceptor structure can be used in both the hole-transporting layer and the host and electron-transporting layers in the light-emitting layer. For donor and acceptor structures, see, for example, Advanced Functional Materials 2020, 2008332. More specifically, donor structures include triarylamine structures and carbazole structures, and acceptor structures include triazine structures, pyrimidine structures, and pyridine structures. Depending on the partial structure, the polycyclic aromatic compounds of the present invention can be used as host materials in the light-emitting layer, hole-transporting layer materials, electron-transporting layer materials, etc.

<Substrate in Organic Electroluminescent Device>
The substrate 101 is a support for the organic EL device 100 and is typically 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 examples thereof include glass plates, metal plates, metal foils, plastic films, and plastic sheets. Among these, glass plates and plates made of transparent synthetic resins such as polyester, polymethacrylate, polycarbonate, and polysulfone are preferred. For glass substrates, soda-lime glass or alkali-free glass may be used, and the thickness may be sufficient to maintain mechanical strength. Furthermore, to enhance gas barrier properties, the substrate 101 may be provided with a gas barrier film such as a dense silicon oxide film on at least one side. Providing a gas barrier film is particularly preferred when a synthetic resin plate, film, or sheet with poor gas barrier properties is used as the substrate 101.

<Anode in Organic Electroluminescent Device>
The anode 102 serves to inject holes into the light-emitting layer 105. When at least one 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), and conductive polymers such as polypyrrole and polyaniline. Other materials that can be appropriately selected from those used as anodes in organic EL elements can also be used.

<Hole injection layer and hole transport layer in organic electroluminescent device>
The hole injection layer 103 serves to efficiently inject holes migrating from the anode 102 into the light-emitting layer 105 or the hole transport layer 104. The hole transport layer 104 serves to efficiently transport holes injected from the anode 102 or holes injected from the anode 102 via 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 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. It is desirable for the hole injection/transport material to have high hole injection efficiency and efficiently transport the injected holes. To achieve this, the material should preferably have a low ionization potential, high hole mobility, excellent stability, and be less likely to generate impurities that can become traps during production or use. It is also preferable to use the polycyclic aromatic compound of the present invention as a material for the hole transport layer.

As materials 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 group 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, heterocyclic compounds such as benzofuran derivatives, thiophene derivatives, oxadiazole derivatives, quinoxaline derivatives (for example, 1,4,5,8,9,12-hexaazatriphenylene-2,3,6,7,10,11-hexacarbonitrile), porphyrin derivatives, polysilanes, etc. As polymers, polycarbonates, styrene derivatives, polyvinylcarbazole, polysilanes, etc. having the above-mentioned monomers in the side chains are preferred, but there is no particular limitation on the compound as long as it can form a thin film necessary for fabricating a light-emitting device, can inject holes from the anode, and can further transport holes.

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

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

<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 for the light-emitting layer 105 may be a compound that emits light upon excitation by the recombination of holes and electrons (light-emitting compound), and is preferably a compound that can be formed into a stable thin film and exhibits strong light-emitting (fluorescence) efficiency in a solid state. The polycyclic aromatic compound of the present invention is also preferably used as a material for the light-emitting layer.

The light-emitting layer may consist of a single layer or multiple layers, each formed from light-emitting layer materials (host material, dopant material). The host material and dopant material may each be one type, or a combination of multiple types. The dopant material may be contained entirely or partially in the host material. As a doping method, the dopant material can be formed by co-evaporation with the host material, but it can also be mixed with the host material in advance and then vapor-deposited simultaneously, or mixed with the host material together with an organic solvent in advance and then formed into a film by a wet film-forming method.

The amount of host material used varies depending on the type of host material and can be determined based on the characteristics of the host material. The recommended amount of host material used is preferably 50 to 99.999% by weight, more preferably 80 to 99.95% by weight, and even more preferably 90 to 99.9% by weight, based on the total weight of the light-emitting layer materials.

The amount of dopant material used varies depending on the type of dopant material and can be determined based on the characteristics of the dopant material. The recommended amount of dopant material used is preferably 0.001 to 50% by mass, more preferably 0.05 to 20% by mass, and even more preferably 0.1 to 10% by mass, based on the total mass of the light-emitting layer materials. The above ranges are preferable in that they can prevent concentration quenching, for example. Furthermore, from the perspective of durability, it is also preferable that some or all of the hydrogen in the dopant material is deuterated.

The dopant material may be a combination of an emitting dopant and an assisting dopant material. It is preferable to use a thermally activated delayed fluorescent material as the assisting dopant material. In organic electroluminescent devices using an assisting dopant material, a low concentration of the emitting dopant material is preferred in terms of preventing concentration quenching. A high concentration of the assisting dopant material is preferred in terms of the efficiency of the thermally activated delayed fluorescent mechanism. Furthermore, in organic electroluminescent devices using a thermally activated delayed fluorescent assisting dopant material, a low concentration of the emitting dopant material is preferred compared to the amount of the assisting dopant material in terms of the efficiency of the thermally activated delayed fluorescent mechanism of the assisting dopant material.

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, they are 60 to 95% by weight, 39 to 5% by weight, and 10 to 0.01% by weight, respectively, and more preferably, they are 70 to 90% by weight, 29 to 10% by weight, and 5 to 0.05% by weight.

<Host material>
Examples of the host material include fused ring derivatives of anthracene, pyrene, and the like, which have long been known as light emitters; bisstyryl derivatives such as bisstyrylanthracene derivatives and distyrylbenzene derivatives; tetraphenylbutadiene derivatives; cyclopentadiene derivatives; fluorene derivatives; benzofluorene derivatives; N-phenylcarbazole derivatives; and carbazonitrile derivatives.

From the viewpoint of promoting rather than inhibiting the generation of TADF in the light-emitting layer, the triplet energy of the host material is preferably higher than the triplet energy of the dopant or assisting dopant having the highest triplet energy in the light-emitting layer. Specifically, the triplet energy 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. A TADF-active compound may also be used as the host material.

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 preferred.

The polycyclic aromatic compound of the present invention can be preferably used as a host material. The polycyclic aromatic compound of the present invention may be used alone, or may be used as a hole-transporting host material or an electron-transporting host material.

[Hole-transporting host material (HH)]
Preferable examples of the hole-transporting host material (HH) include, in addition to the polycyclic aromatic compound of the present invention, a compound represented by formula (HH-1) and a compound having a partial structure represented by formula (HH-1).

In formula (HH-1),
Q is >O, >S, or >N-A;
In formula (HH-1), one carbon atom adjacent to the carbon atom to which Q is bonded in each of the two phenyl groups may be bonded to each other via L,
L is a single bond, >O, >S or >C(-A) ₂ ;
A is hydrogen, aryl, heteroaryl, diarylamino, alkyl, cycloalkyl, alkoxy or aryloxy, and two As in >C(-A) ₂ may be bonded to each other to form an aryl, heteroaryl or cycloalkyl.

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 1, but it is also preferable for it to contain two or more. 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, or may be bonded so that any rings contained in the partial structures are shared, or may be bonded so that any rings contained in the partial structures are fused to each other. The partial structure may further have a substituent selected from aryl, heteroaryl, diarylamino, or aryloxy.

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 fused polycyclic ring containing phenoxazine or phenothiazine. The hole-transporting host material may contain one such partial structure 1, but preferably contains two or more. When two or more partial structures are contained, the two or more partial structures may be the same or different.

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, and HH-1-106 to HH-1-108 are preferred.

[Electron-Transporting Host Material (EH)]
Examples of the electron-transporting host material (EH) include the polycyclic aromatic compound of the present invention, as well as a compound represented by formula (EH-1) and a compound having a partial structure represented by formula (EH-1).

In formula (EH-1),
Each J is independently ═C(-A)- or ═N-, and at least three Js are ═C(-A)-;
Z is —O—, —S—, —C(═O)—, —P(═O)(-A)—, —P(═S)(-A)—, —N(-A)—, —B(-A)— or —S(═O) ₂ —;
J adjacent to the carbon atom to which Z is bonded and A to which Z is bonded may be bonded to each other via L,
L is a single bond, >O, >S or >C(-A) ₂ ;
A is hydrogen, aryl, heteroaryl, diarylamino, alkyl, cycloalkyl, triarylsilyl, alkoxy or aryloxy, and two A's in >C(-A) ₂ may be bonded to each other to form an aryl, heteroaryl or cycloalkyl;
When all J's are ═C(—A)—, either A or Z has a heteroatom.

For the aryl, heteroaryl, diarylamino, alkyl, cycloalkyl, triarylsilyl, alkoxy, or aryloxy represented by A in formula (EH-1), the explanation for A in formula (HH-1) can be referenced. For the aryl, heteroaryl, or cycloalkyl when two A's in formula (EH-1) bond together to form an aryl, heteroaryl, or cycloalkyl, the explanation for formula (HH-1) can also be referenced.

When the electron-transporting host material contains a structure represented by formula (EH-1) as a partial structure, it may contain one such partial structure, but it is also preferable that it contains two or more. 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, or may be bonded so that any rings contained in the partial structures are shared, or may be bonded so that any rings contained in the partial structures are fused to each other. 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 preferred 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 multimer 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 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 do not both represent >C(—R) ₂ ;
R in the >N-R and >C(-R) ₂ each independently represents hydrogen or a substituent selected from the substituent group Z, and R in the >N-R and >C(-R) ₂ each independently may be 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), and at least one 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 represented by Y ¹ to Y ⁶ may be bonded to each other to form an aryl ring or heteroaryl ring together with at least one ring of ring a, ring b and ring c, and the formed ring may be substituted with at least one group selected from substituent group Z.
At least one hydrogen atom in the compound and structure represented by formula (EH-1b) may be replaced 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. The substituent is preferably an aryl optionally substituted with an alkyl, an alkyl, or a heteroaryl, a heteroaryl optionally substituted with an alkyl or an aryl, or a diarylamino optionally substituted with an alkyl or an aryl. In this case, the alkyl is preferably an alkyl having 1 to 6 carbon atoms (e.g., methyl, t-butyl), the aryl is preferably phenyl or biphenyl, and the heteroaryl is preferably triazinyl, carbazolyl (e.g., 2-carbazolyl, 3-carbazolyl, 9-carbazolyl), pyrimidinyl, pyridinyl, dibenzofuranyl, or dibenzothienyl. Specific examples include phenyl, biphenyl, diphenyltriazinyl, carbazolyltriazinyl, monophenylpyrimidinyl, diphenylpyrimidinyl, carbazolyltriazinyl, pyridinyl, dibenzofuranyl and dibenzothienyl.

Y ¹ and the like are each independently =C(-R)- or =N-, and at least one is =N-. Any of ^{Y 1} to Y ⁶ may be =N-. Preferably, ^Y1 and ^Y6 are =N- (ring a is a pyrimidine ring), ^Y1 or ^Y6 is =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), or ^Y2 or ^Y5 is =N- (ring b or ring c is a pyridine ring).

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

In particular, polycyclic aromatic compounds containing a partial structure represented by formula (EH-1b-N1) have high E _S1 , high E _T1 and small ΔE _S1T1 compared to structures 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-1-100, 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.

[Combination of hole-transporting host material and electron-transporting host material]
The combination of a hole-transporting host material and an electron-transporting host material is selected depending on the HOMO, LUMO and excited triplet energy 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 shallower than the HOMO (EH) by 0.20 eV or more and the LUMO (HH) is deeper than the HOMO (EH) by 0.20 eV or more is preferred, a combination in which the HOMO (HH) is shallower than the HOMO (EH) by 0.20 eV or more and the LUMO (HH) is deeper than the HOMO (EH) by 0.20 eV or more is more preferred, and a combination in which the HOMO (HH) is shallower than the HMO (EH) by 0.25 eV or more and the LUMO (HH) is deeper than the HMO (EH) by 0.25 eV or more is even more preferred.

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 exciplexes are easily formed between a material with a relatively deep LUMO level and a material with a shallow HOMO level. The interaction between the hole-transporting host material and the electron-transporting host material, specifically, whether an exciplex has 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 for forming the light-emitting layer, measuring the emission spectrum (fluorescence spectrum, phosphorescence spectrum), and comparing the obtained emission spectrum with the emission spectrum of each of the hole-transporting host material and the electron-transporting host material alone. This can be determined by the spectrum of a mixed film containing the hole-transporting host material and the electron-transporting host material exhibiting an emission wavelength that is 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, a difference of 10 nm or more in the peak wavelength of the spectrum can be used as an indicator.

Specific examples of combinations of hole-transporting host materials and electron-transporting host materials that do not form exciplexes include the following combinations. To satisfy the above-mentioned physical properties of HOMO, LUMO, and excited triplet energy, the hole-transporting host material is preferably a compound having carbazole, dibenzofuran, dibenzothiophene, triarylamine, inderocarbazole, or benzoxazinophenoxazine as a partial structure, more preferably a compound having carbazole, dibenzofuran, or 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, or dibenzoxasiline as a partial structure, more preferably a compound having triazine, phosphine oxide, benzofuropyridine, or 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-1-2 -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 combinations of hole-transporting host materials and electron-transporting host materials that form exciplexes include the following combinations. To satisfy the above-mentioned physical properties of HOMO, LUMO, and excited triplet energy, the hole-transporting host material is preferably a compound having carbazole, triarylamine, inderocarbazole, or benzoxazinophenoxazine as a partial structure, more preferably a compound having triarylamine, inderocarbazole, or 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, or benzofuropyridine as a partial structure, more preferably a compound having triazine, phosphine oxide, benzofuropyridine, or dibenzoxasiline as a partial structure, and even more preferably a compound having phosphine oxide or 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, and HH-1-24, 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, EH- It is preferred that the compound is selected from the group consisting of EH-1-51 to EH-1-57, EH-1-59, EH-1-66, EH-1-68, 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-1-21, compound HH-1-2 and compound EH-1-21, 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, or compound HH-1-49 and compound EH-1-117.

For other specific combinations of hole-transporting host materials and electron-transporting host materials, see 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, and Synthetic Metals, 201, 2015, 49, etc., can be referenced.

<Dopant materials>
Known compounds can be used as the dopant material, and can be selected from a variety of materials depending on the desired emission color. Specific examples include fused ring derivatives of 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, and tetraphenylbutadiene. derivatives, cyclopentadiene derivatives, bisstyryl derivatives such as bisstyryl anthracene derivatives and distyrylbenzene derivatives (JP-A-1-245087), bisstyrylarylene derivatives (JP-A-2-247278), diazaindacene derivatives, furan derivatives, benzofuran derivatives, 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, oxobenzanthracene 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.

In the light-emitting layer, it is preferable to use the polycyclic aromatic compound of the present invention as a host material and a phosphorescent material or a TADF material (thermally activated delayed fluorescent material) as a dopant material.

[Phosphorescent materials]
Phosphorescent materials utilize the intramolecular spin-orbit interaction (heavy atom effect) of metal atoms to emit light from triplets. Examples of such phosphorescent materials include luminescent metal complexes. Examples of luminescent metal complexes include compounds represented by the following formulas (B-1) and (B-2):

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 "WXYZ" 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 formula (B-2), M is preferably Pt from the viewpoint of efficiency and life.
The ligand (X-Y) in formula (B-1) has at least one ligand selected from the group consisting of: The ligand (W-X-Y-Z) in formula (B-2) has at least one ligand selected from the group consisting of:

however,
--- bonded to the central metal M,
Y's are each 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 aromatic carbons C—H in the ring may each independently be replaced by N;
R _e and R _f may optionally be fused or joined to form a ring;
R _a , R _b , R _c , and R _d each independently may be unsubstituted or substituted with 1 to the maximum substitutable number;
R _a , R _b , R _c , R _d , R _e , and R _f are each independently hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, aryl, heteroaryl, nitrile, isonitrile, sulfanyl, or a combination 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(PF ₆ ), Ir(2-phq) ₃ , Ir(BT) ₂ (acac), Ir(DMP) ₃ , Ir(Mphq) ₃ IR(phq) ₂ tpy, fac-Ir(ppy) ₂ Pc, Ir(dp)PQ ₂ , Ir(Dpm)(Piq) ₂ , Hex-Ir(piq) ₂ (acac), Hex-Ir(piq) ₃ , Ir(dmpq) ₃ , Ir(dmpq) ₂ (acac), FPQIrpic, etc.

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

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

[TADF material (thermally activated delayed fluorescent substance)]
As the dopant material, it is also preferable to use a polycyclic aromatic compound containing boron described in International Publication No. 2015/102118, International Publication No. 2018/212169, International Publication No. 2020/162600, etc. The polycyclic aromatic compound having a boron atom may be a phosphor or a TADF material (thermally activated delayed fluorescent material). The polycyclic aromatic compound having a boron atom is preferably a blue-emitting compound.

By reducing the energy difference between the excited singlet state and the excited triplet state, reverse intersystem crossing from the excited triplet state, which normally has a low transition probability, to the excited singlet state can be efficiently achieved, resulting in emission from the singlet state (thermally activated delayed fluorescence, TADF). In normal fluorescence emission, 75% of the triplet excitons generated by current excitation pass through a thermal deactivation pathway and cannot be extracted as fluorescence. In contrast, with TADF, all excitons can be used for fluorescence emission, enabling the realization of highly efficient organic EL devices.

Preferred examples of the boron-containing polycyclic aromatic compound include compounds represented by the following formula (12), formula (13) or formula (14).

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;
Y is B (boron),
X ¹ , X ² , X ³ and X ⁴ each independently represent >O, >N—R, >S or >Se, R of the >N—R is a substituted or unsubstituted aryl, a substituted or unsubstituted heteroaryl or a substituted or unsubstituted alkyl, and R of the >N—R may be bonded to the A ring, the B ring, the C ring and/or the D ring via a linking group or a single bond;
R ¹ and R ² are each independently hydrogen, alkyl having 1 to 6 carbon atoms, aryl having 6 to 12 carbon atoms, heteroaryl having 2 to 15 carbon atoms, or diarylamino (wherein aryl has 6 to 12 carbon atoms);
^Z1 and ^Z2 are each independently a substituent selected from the substituent group Z, ^Z1 may be bonded to the ring A via a linking group or a single bond, ^Z2 may be bonded to the ring C via a linking group or a single bond, and
At least one hydrogen atom in the compound represented by formula (12) may be replaced by cyano, halogen, or deuterium.

In the rings A, B, C and D of formula (12), when the aryl ring or heteroaryl ring is substituted, the substituents and Z ¹ and Z ² include substituents selected from the substituent group Z.

In formula (12), X ¹ , X ² , X ³ and X ⁴ each independently represent >O, >N—R, >S or >Se, and each R in the >N—R independently represents an aryl having 6 to 12 carbon atoms, a heteroaryl having 2 to 15 carbon atoms, a cycloalkyl having 3 to 12 carbon atoms or an alkyl having 1 to 6 carbon atoms.
In the compound represented by formula (12), from the viewpoint of high TADF properties, Z ¹ and Z ² are preferably diphenylamino which may have a substituent or N-carbazolyl which may have a substituent, and more preferably diphenylamino which may have a substituent. The diphenylamino which may have a substituent is preferably unsubstituted diphenylamino or diphenylamino having at least one alkyl having 1 to 4 carbon atoms, and more preferably unsubstituted diphenylamino or diphenylamino having at least one methyl at the m-position or o-position relative to N. From the viewpoint of ease of synthesis and emission wavelength, it is preferable that the aryl ring or heteroaryl ring in ring A, ring B, ring C and ring D has no substitution other than Z ¹ and Z ² , or has only alkyl having 1 to 6 carbon atoms as other substituents, and more preferably has no substitution other than Z ¹ and Z ² .
Examples of the compound represented by formula (12) are shown below.

In formula (13) and formula (14),
ring A ¹¹ , ring A ²¹ , ring A ³¹ , ring B ¹¹ , ring B ²¹ , ring C ¹¹ , and ring C ³¹ each independently represent a substituted or unsubstituted aryl ring or a substituted or unsubstituted heteroaryl ring;
Y ¹¹ , Y ²¹ , and Y ³¹ are B (boron);
X ¹¹ , X ¹² , X ²¹ , X ²² , X ³¹ , and X ³² each independently represent >O, >N—R, >S, or >Se, and R of the >N—R represents a substituted or unsubstituted aryl, a substituted or unsubstituted heteroaryl, or a substituted or unsubstituted alkyl, and R of the >N—R may be bonded to ring A ¹¹ , ring A ²¹ , ring A ³¹ , ring B ¹¹ , ring B ²¹ , ring C ¹¹ , and/or ring C ³¹ via a linking group or a single bond;
At least one hydrogen atom in the compounds represented by formulas (13) and (14) may be replaced by cyano, halogen or deuterium.

In the formula (13) and the formula (14), when the aryl ring or heteroaryl ring is substituted in ring ^A11 , ring ^A21 , ring ^A31 , ring ^B11 , ring ^B21 , ring ^C11 , and ring ^C31 , the substituents and ^Z1 and ^Z2 include substituents selected from the substituent group Z.

In formula (13) and formula (14), X ¹¹ , X ¹² , X ²¹ , X ²² , X ³¹ , and X ³² each independently represent >O, >N—R, >S, or >Se, and each R in the >N—R is independently an aryl having 6 to 12 carbon atoms, a heteroaryl having 2 to 15 carbon atoms, a cycloalkyl having 3 to 12 carbon atoms, or an alkyl having 1 to 6 carbon atoms.

Examples of the compound represented by formula (13) or formula (14) are shown below.

<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 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 the injection and transport of electrons from the cathode. It is desirable for the electron injection/transport layer to have high electron injection efficiency and efficiently transport the injected electrons. To achieve this, it is preferable for the material to have high electron affinity, high electron mobility, and excellent stability, and to be less likely to generate impurities that act as traps during manufacture and use. However, when considering the balance between hole and electron transport, if a material's primary function is to efficiently block holes from the anode from flowing toward the cathode without recombining, then even if its electron transport capacity is not that high, it can still have the same effect of improving luminous efficiency as a material with high electron transport capacity. Therefore, the electron injection/transport layer in this embodiment may also function as 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 devices. It is also preferable to use the polycyclic aromatic compound of the present invention as a material for the electron transport layer.

Materials used in the electron transport layer or electron injection layer preferably contain at least one selected from compounds consisting of aromatic or heteroaromatic rings composed of one or more atoms selected from carbon, hydrogen, oxygen, sulfur, silicon, and phosphorus; pyrrole derivatives and their fused ring derivatives; and metal complexes having electron-accepting nitrogen. Specific examples include fused ring aromatic derivatives such as naphthalene and anthracene; styryl aromatic derivatives such as 4,4'-bis(diphenylethenyl)biphenyl; perinone derivatives; coumarin derivatives; naphthalimide derivatives; quinone derivatives such as anthraquinone and diphenoquinone; phosphorus oxide derivatives; arylnitrile derivatives; and indole derivatives. Examples of metal complexes having electron-accepting nitrogen include 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 other materials.

Specific examples of other electron transfer 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, pyrazole derivatives, Examples of such compounds include azine 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(4'-(2,2':6'2"-terpyridinyl))benzene), naphthyridine derivatives (such as bis(1-naphthyl)-4-(1,8-naphthyridin-2-yl)phenylphosphine oxide), aldazine derivatives, carbazole derivatives, indole derivatives, phosphorus oxide derivatives, and bisstyryl derivatives.

Metal complexes having an electron-accepting nitrogen atom 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 materials mentioned above, 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 electron injection layer may further contain a substance capable of reducing the material forming the electron transport layer or electron injection layer. A variety of substances can be used as this reducing substance, as long as they have a certain level of reducing ability. For example, at least one selected from the group consisting of alkali metals, alkaline earth metals, rare earth metals, alkali metal oxides, alkali metal halides, alkaline earth metal oxides, alkaline earth metal halides, rare earth metal oxides, rare earth metal halides, alkali metal organic complexes, alkaline earth metal organic complexes, and rare earth metal organic complexes can be suitably 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). Substances with a work function of 2.9 eV or less are particularly preferred. Among these, alkali metals K, Rb, or Cs are more preferred, with Rb or Cs being even more preferred, and Cs being the most preferred. These alkali metals have particularly high reducing power, and adding relatively small amounts to the materials forming the electron transport layer or electron injection layer can improve the luminance and extend the life of organic EL devices. Combinations of two or more of these alkali metals are also preferred as reducing substances with a work function of 2.9 eV or less, and combinations containing Cs, such as Cs and Na, Cs and K, Cs and Rb, or Cs, Na and K, are particularly preferred. By including Cs, the reducing ability can be efficiently exerted, and adding it to the material that forms the electron transport layer or electron injection layer can improve the luminance and extend the life of the organic EL element.

<Cathode in Organic Electroluminescent Device>
The cathode 108 serves to inject electrons into the light-emitting layer 105 via the electron injection layer 107 and the electron transport layer 106 .

The material for the cathode 108 is not particularly limited as long as it can efficiently inject electrons into the organic layer, but the same materials as those for the anode 102 can be used. Among these, metals such as tin, indium, calcium, aluminum, silver, copper, nickel, chromium, gold, platinum, iron, zinc, lithium, sodium, potassium, cesium, and magnesium, or alloys thereof (e.g., magnesium-silver alloys, magnesium-indium alloys, and aluminum-lithium alloys such as lithium fluoride/aluminum alloys), are preferred. To increase electron injection efficiency and improve device performance, 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 address this issue, a known method is to dope the organic layer with trace amounts of lithium, cesium, or magnesium to create a highly stable electrode. Other dopants that can be used include, but are not limited to, inorganic salts such as lithium fluoride, cesium fluoride, lithium oxide, and cesium oxide.

Furthermore, for electrode protection, 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. There are no particular restrictions on the method for producing these electrodes, as long as electrical conductivity can be achieved, and methods such as resistance heating, electron beam evaporation, sputtering, ion plating, and coating can be used.

<Method for producing organic electroluminescent device>
Each layer constituting an organic EL device can be formed by forming the materials constituting each layer into a thin film using methods such as vapor deposition, resistance heating vapor deposition, electron beam vapor deposition, sputtering, molecular lamination, printing, spin coating, casting, and coating. The thickness of each layer formed in this manner is not particularly limited and can be set appropriately depending on the properties of the material, but is typically in the range of 2 nm to 5,000 nm. Film thickness can typically be measured using a quartz crystal oscillator film thickness measuring device. When forming a thin film using vapor deposition, the deposition conditions vary depending on the type of material, the desired crystal structure and association structure of the film, and other factors. Deposition conditions are generally preferably set as follows: boat heating temperature +50 to +400°C, vacuum level ^10-6 to ^10-3 Pa, deposition rate 0.01 to 50 nm/sec, substrate temperature -150 to +300°C, and film thickness in the range of 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 + polarity and the cathode to - polarity. When a voltage of approximately 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 pulse current or AC current is applied. The AC waveform applied can be any waveform.

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

<Vapor deposition method>
A thin film of an anode material is formed on a suitable substrate by vapor deposition or the like to form an anode, and then thin films of a hole injection layer and a hole transport layer are formed on the anode. A host material and a dopant material are co-deposited on the anode to form a thin film to form an emissive layer. An electron transport layer and an electron injection layer are formed on the emissive layer, and a thin film of a cathode material is further formed by vapor deposition or the like to form a cathode, thereby obtaining the desired organic EL device. It is also possible to reverse the order of fabrication of the above-described organic EL device, forming the layers in the order of cathode, electron injection layer, electron transport layer, emissive layer, hole transport layer, hole injection layer, and anode.

<Wet film formation method>
The wet film formation method is carried out by preparing a liquid organic layer-forming composition from a low molecular weight compound capable of forming each organic layer of an organic EL element, and using this. If there is no suitable organic solvent that can dissolve this low molecular weight compound, the organic layer-forming composition may be prepared from a reactive compound obtained by substituting a reactive substituent on the low molecular weight compound, such as another monomer having a solubility function as a reactive compound or a polymer compound polymerized together with a main-chain polymer.

Wet film formation methods generally involve a coating process in which an organic layer-forming composition is applied to a substrate, followed by a drying process in which the solvent is removed from the applied organic layer-forming composition to form a coating film. If the polymer compound has a crosslinkable substituent (also known as a crosslinkable polymer compound), the drying process results in further crosslinking to form a crosslinked polymer. Depending on the coating process, methods using a spin coater are called spin coating; methods using a slit coater are called slit coating; methods using a printing plate are called gravure, offset, reverse offset, or flexographic printing; methods using an inkjet printer are called inkjet printing; and methods spraying the composition in a mist are called spraying. Drying processes include air drying, heating, and vacuum drying. The drying process may be performed once, or multiple times using different methods and conditions. Different methods may also be used in combination, such as baking under reduced pressure.

Wet film formation methods are film formation methods that use solutions, and include some printing methods (inkjet methods), spin coating 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.

However, compared to vacuum deposition, wet deposition can be difficult to use for layering. When using wet deposition to create layered films, it is necessary to prevent the dissolution of the lower layer by the composition of the upper layer, and this requires the use of compositions with controlled solubility, crosslinking of the lower layer, and orthogonal solvents (solvents that are not soluble in each other). However, even with these techniques, it can be difficult to use wet deposition for applying all films.

Therefore, a common method for producing organic EL elements is to use wet film formation 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-forming 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 composed 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 method to prevent dissolution of the underlying light-emitting layer or a method to form the layer from the cathode side, in the reverse order of the above procedure.

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

<Optional step>
Before and after each film-forming step, appropriate treatment steps, cleaning steps, and drying steps may be added as appropriate. 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 create banks. Positive and negative resist materials can be used as bank materials for photolithography. Patternable printing methods such as inkjet printing, gravure offset printing, reverse offset printing, and screen printing can also be used. In these cases, permanent resist materials can also be used.

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

<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 film-forming properties, the presence or absence of defects in the coating film, surface roughness, and smoothness. Furthermore, during film formation using an inkjet method, it is possible to control meniscus stability at the pinhole of the inkjet head, thereby controlling and improving 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 lifespan of an organic EL device having an organic layer obtained from the organic layer-forming composition.

After film formation, the organic solvent is removed from the coating film through a drying process using vacuum, reduced pressure, heating, or other methods. When heating, from the perspective of improving coating film formation, it is preferable to perform the heating at a temperature below the glass transition temperature (Tg) of at least one of the solutes +30°C. Furthermore, from the perspective of reducing residual solvent, it is preferable to heat at a temperature above the glass transition temperature (Tg) of at least one of the solutes -30°C. Even if the heating temperature is lower than the boiling point of the organic solvent, the film is thin enough that the organic solvent is sufficiently removed. Furthermore, drying may be performed multiple times at different temperatures, or 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 the good solubility, storage stability, and film-forming properties of each component in the composition for forming an organic layer, as well as the good film quality of the coating film obtained from the composition for forming an organic layer, good ejection properties when an inkjet method is used, and good electrical properties, light-emitting properties, efficiency, and lifespan of an organic EL element having an organic layer produced using the composition.

The organic layer-forming composition can be produced by appropriately selecting and performing known processes such as stirring, mixing, heating, cooling, dissolving, and dispersing the above-mentioned components. After preparation, the composition may be subjected to appropriate processes such as filtration, degassing, ion exchange, and inert gas replacement/filling.

<Application examples of organic electroluminescent devices>
The present invention can also be applied to a display device having an organic EL element or a lighting device having an organic EL element.
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 10-335066 A, JP 2003-321546 A, and JP 2004-281086 A). Display methods include, for example, matrix and segment methods. Note that matrix display and segment display may coexist on the same panel.

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

In the segment type, 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 and backlights for liquid crystal display devices (see, for example, JP 2003-257621 A, JP 2003-277741 A, and JP 2004-119211 A). Backlights are primarily used to improve the visibility of non-self-luminous display devices, and are used in liquid crystal display devices, clocks, audio equipment, automotive panels, display boards, signs, and the like. In particular, backlights for liquid crystal display devices, particularly those used in personal computers where thinning is an issue, are difficult to achieve because conventional systems use fluorescent lamps and light guide plates. Therefore, backlights using the light-emitting elements of this embodiment are characterized by their thinness and light weight.

3-2. Other Organic Devices The polycyclic aromatic compound according to the present invention can be used to produce organic field effect transistors or organic thin-film solar cells, in addition to the organic electroluminescent devices described above.

The present invention will be explained in more detail below using examples, but the present invention is not limited to these. First, an example of the synthesis of a polycyclic aromatic compound will be described below.

Synthesis of compound (1-1)

Under a nitrogen atmosphere, 66.1 g of 1,3-dichloro-2-nitrobenzene, 40 g of phenylboronic acid, 15.2 g of tetrakis(triphenylphosphine)palladium(0) (Pd(PPh ₃ ) ₄ ), 139.3 g of tripotassium phosphate, 4.2 g of tetrabutylammonium bromide (TBAB), 400 ml of toluene, and 40 ml of water were placed in a flask and refluxed with stirring for 4 hours. After the reaction solution was cooled to room temperature, water and toluene were added and the mixture was separated. The organic layer was then purified using a silica gel short-path column (eluent: toluene). This was followed by purification using silica gel column chromatography (eluent: toluene/heptane = 1/4) to obtain 58.7 g of the intermediate compound 3-chloro-2-nitro-1,1'-biphenyl.

Under a nitrogen atmosphere, 31.5 g of 3-chloro-2-nitro-1,1'-biphenyl, 123.8 g of triphenylphosphine, and 285 ml of 1,2,4-trichlorobenzene were placed in a flask, stirred, and refluxed for 15 hours. After the reaction was complete, the solvent was removed by distillation under reduced pressure, and the product was then purified by NH2 silica gel column chromatography (eluent: toluene/heptane = 1/4) to yield 19.8 g of the intermediate compound 1-chloro-9H-carbazole.

Under a nitrogen atmosphere, 1-chloro-9H-carbazole (10 g), 1-chloro-2-iodobenzene (17.7 g), copper (6.3 g), potassium carbonate (27.4 g), 18-crown-6 (1.3 g), and 1,2-dichlorobenzene (100 ml) were placed in a flask and refluxed with stirring for 20 hours. After the reaction was complete, the reaction solution was cooled to room temperature and purified using a silica gel short-path column (eluent: toluene). The resulting crude product was purified using silica gel column chromatography (eluent: toluene/heptane = 1/4) to yield 7.8 g of the intermediate compound 1-chloro-9-(2-chlorophenyl)-9H-carbazole.

Under a nitrogen atmosphere, 8.3 g of 1-chloro-9-(2-chlorophenyl)-9H-carbazole, 7.7 g of N,N-diphenylbenzene-1,2-diamine, 0.3 g of palladium acetate, 1.1 g of 2-dicyclohexylphosphino-2',6'-dimethoxy-1,1'-biphenyl (Sphos), 7.7 g of sodium t-butoxide (NaOtBu), and 116 ml of xylene were placed in a flask and refluxed with stirring for 16 hours. After the reaction was complete, the reaction solution was cooled to room temperature, and water and toluene were added to separate the layers. The organic layer was then purified using a silica gel short-path column (eluent: toluene), followed by silica gel column chromatography (eluent: toluene/heptane = 1/4), and further purified by sublimation to obtain the target compound (1-1) (5.4 g).

The structure of the compound of formula (1-1) was confirmed by MS spectrum and NMR measurements.
¹ H-NMR (CDCl ₃ ): δ = 6.97-7.06 (m, 8H), 7.14-7.15 (m, 3H), 7.25-7.38 (m, 10H), 7.71 (d, 1H), 7.87 (d, 1H), 7.93 (d, 1H), 8.54 (d, 1H).

Synthesis of compound (1-10)

Under a nitrogen atmosphere, 8.3 g of 1-chloro-9-(2-chlorophenyl)-9H-carbazole, 5.4 g of N-phenylbenzene-1,2-diamine, 0.3 g of palladium acetate, 1.1 g of 2-dicyclohexylphosphino-2',6'-dimethoxy-1,1'-biphenyl (Sphos), 7.7 g of sodium t-butoxide (NaOtBu), and 116 ml of xylene were placed in a flask and refluxed with stirring for 16 hours. After the reaction was complete, the reaction solution was cooled to room temperature, and water and toluene were added for phase separation. The organic layer was then purified using a silica gel short-path column (eluent: toluene) and then by silica gel column chromatography (eluent: toluene/heptane = 1/4) to yield 4-phenyl-4,9-dihydrodibenzo[5,6:8,9][1,4,7]triazonino[3,2,1-jk]carbazole (3.2 g).

Under a nitrogen atmosphere, 1.3 g of 4-phenyl-4,9-dihydrodibenzo[5,6:8,9][1,4,7]triazonino[3,2,1-jk]carbazole, 1.8 g of 9,9'-(5-bromo-1,3-phenylene)bis(9H-carbazole), 0.03 g of palladium acetate, 0.9 g of tri-tert-butylphosphine, 1.9 g of potassium phosphate, and 10 ml of xylene were placed in a flask and refluxed with stirring for 8 hours. After the reaction was complete, the reaction solution was cooled to room temperature and purified using a silica gel short-path column (eluent: toluene). The resulting crude product was washed with Solmix solvent and reprecipitated several times with heptane. The product was further purified using silica gel column chromatography (eluent: toluene/heptane = 1/3) and then purified by sublimation to obtain the target compound (1-10) (1.3 g).

The structure of the compound of formula (1-10) was confirmed by MS spectrum and NMR measurements.
¹ H-NMR (CDCl ₃ ): δ = 6.95 (d, 2H), 7.01-7.06 (m, 3H), 7.13 (s, 2H), 7.15 (s, 1H), 7.16-7.17 (m, 7H), 7.23 -7.42 (m, 12H), 7.68-7.69 (m, 5H), 7.87 (d, 1H), 7.96 (d, 1H), 8.30 (d, 4H), 8.53 (d, 1H).

Synthesis of compound (1-13)

Under a nitrogen atmosphere, 2.1 g of 4-phenyl-4,9-dihydrodibenzo[5,6:8,9][1,4,7]triazonino[3,2,1-jk]carbazole, 1.24 g of 55% sodium hydride (NaH), and 77 ml of dimethylformamide (DMF) were placed in a flask and stirred at room temperature for 1 hour. Then, 3.8 g of 2-chloro-4,6-diphenyl-1,3,5-triazine was added, and the mixture was stirred at room temperature for an additional 64 hours. After the reaction was completed, water was gradually added while cooling in an ice-water bath, and the mixture was extracted with ethyl acetate. The organic layer was then evaporated under reduced pressure, and the resulting crude product was purified by NH ₂ silica gel column chromatography (eluent: toluene/heptane = 1/2 (volume ratio)). The product was then reprecipitated several times with Solmix solvent and further purified by sublimation to obtain the target compound (1-13) (1.1 g).

The structure of the compound of formula (1-13) was confirmed by MS spectrum and NMR measurements.
¹ H-NMR (CDCl ₃ ): δ = 6.95 (d, 2H), 7.02-7.06 (m, 3H), 7.15-7.16 (m, 3H), 7.23-7.26 (m, 4H), 7.34-7.37 (m, 4H), 7.48 (m, 6H), 7.69 (d, 1H), 7.84 (d, 1H), 7.92 (d, 1H), 8.37 (d, 4H), 8.57 (d, 1H).

Synthesis of compound (1-68)

Under a nitrogen atmosphere, 13.1 g of 2-bromo-1-chloro-3-fluorobenzene, 7.5 g of 2-aminophenol, 21.6 g of potassium carbonate, and 90 ml of 1-methyl-2-pyrrolidone were placed in a flask and heated with stirring at 150°C for 6 hours. After the reaction was complete, the reaction solution was cooled to room temperature, and water and ethyl acetate were added to separate the liquid. The liquid was then purified by silica gel column chromatography (eluent: toluene/heptane = 3/1) to obtain 15.3 g of the intermediate compound 2-(2-bromo-3-chlorophenoxy)aniline.

Under a nitrogen atmosphere, 12.6 g of 2-(2-bromo-3-chlorophenoxy)aniline, 1.0 g of [1,1'-bis(diphenylphosphino)ferrocene]palladium(II) dichloritodichloromethane complex (1:1) (Pd(dppf)Cl ₂ -CH ₂ Cl ₂ ), 8.1 g of sodium t-butoxide (NaOtBu), and 315 ml of toluene were placed in a flask and refluxed with stirring for 2 hours. After completion of the reaction, the reaction solution was cooled to room temperature, and water and toluene were added to separate the layers. The organic layer was then purified using a silica gel short-path column (eluent: toluene) and then by silica gel column chromatography (eluent: toluene/heptane = 1/6) to obtain 6.3 g of the intermediate compound 1-chloro-10H-phenoxazine.

Under a nitrogen atmosphere, 50 g of 2-bromoaniline, 44.7 g of (2-fluorophenyl)boronic acid, 8.2 g of dichlorobis[di-t-butyl(4-dimethylaminophenyl)phosphino]palladium(II) (Pd-132, Johnson Matthey), 185.1 g of tripotassium phosphate, 4.7 g of tetrabutylammonium bromide (TBAB), 600 ml of toluene, and 100 ml of water were placed in a flask and refluxed with stirring for 4 hours. After the reaction mixture was cooled to room temperature, water and toluene were added and the mixture was separated. The mixture was then purified by silica gel column chromatography (eluent: toluene) to yield 51.5 g of the intermediate compound 2'-fluoro-[1,1'-biphenyl]-2-amine.

Under a nitrogen atmosphere, 5.8 g of 1-chloro-10H-phenoxazine, 5.5 g of 2'-fluoro-[1,1'-biphenyl]-2-amine, 0.3 g of palladium acetate, 1.1 g of 2-dicyclohexylphosphino-2',6'-dimethoxy-1,1'-biphenyl (Sphos), 7.7 g of sodium t-butoxide (NaOtBu), and 116 ml of xylene were placed in a flask and refluxed with stirring for 16 hours. After the reaction was complete, the reaction solution was cooled to room temperature, and water and toluene were added for phase separation. The organic layer was then purified using a silica gel short-path column (eluent: toluene) and then by silica gel column chromatography (eluent: toluene/heptane = 1/4) to obtain 3.5 g of the intermediate compound 5H-dibenzo[5,6:7,8][1,4]diazocino[3,2,1-kl]phenoxazine.

Under a nitrogen atmosphere, 2.3 g of 5H-dibenzo[5,6:7,8][1,4]diazocino[3,2,1-kl]phenoxazine, 0.84 g of copper, 3.6 g of potassium carbonate, and 66 ml of iodobenzene were placed in a flask and refluxed with stirring for 6 hours. After the reaction was complete, the reaction solution was cooled to room temperature and purified using a silica gel short-path column (eluent: toluene). The resulting crude product was washed with Solmix solvent and reprecipitated several times with heptane. The product was further purified using silica gel column chromatography (eluent: toluene/heptane = 1/3) and then purified by sublimation to obtain the target compound (1-68) (2.3 g).

The structure of the compound of formula (1-68) was confirmed by MS spectrum and NMR measurements.
¹ H-NMR (CDCl ₃ ): δ = 7.89 (d, 2H), 7.27 (t, 2H), 7.16 (t, 2H), 7.05 (d, 2H), 6.98 (d, 2H), 6.8 2-6.77 (m, 3H), 6.63 (t, 1H), 6.52-6.45 (m, 3H), 6.39 (d, 2H), 6.34 (d, 1H).

Synthesis of compound (1-85)

Under a nitrogen atmosphere, 1.0 g of 5H-dibenzo[5,6:7,8][1,4]diazocino[3,2,1-kl]phenoxazine, 1.8 g of 9,9'-(5-bromo-1,3-phenylene)bis(9H-carbazole), 0.03 g of palladium acetate, 0.9 g of tri-tert-butylphosphine, 1.9 g of potassium phosphate, and 10 ml of xylene were placed in a flask and refluxed with stirring for 8 hours. After the reaction was complete, the reaction solution was cooled to room temperature and purified using a silica gel short-path column (eluent: toluene). The resulting crude product was washed with Solmix solvent and reprecipitated several times with heptane. The product was further purified using silica gel column chromatography (eluent: toluene/heptane = 1/3) and then purified by sublimation to obtain the target compound (1-85) (1.1 g).

The structure of the compound of formula (1-85) was confirmed by MS spectrum and NMR measurements.
¹ H-NMR (CDCl ₃ ): δ = 6.62 (d, 1H), 6.81 (t, 1H), 6.88 (d, 1H), 6.98-7.03 (m, 3H), 7.10 (s, 2H), 7.15 (s , 1H), 7.15-7.17 (m, 7H), 7.39-7.46 (m, 8H), 7.63 (d, 4H), 8.11 (d, 2H), 8.29 (d, 4H).

Synthesis of compound (1-88)

Under a nitrogen atmosphere, 1.7 g of 5H-dibenzo[5,6:7,8][1,4]diazocino[3,2,1-kl]phenoxazine, 1.24 g of 55% sodium hydride (NaH), and 77 ml of dimethylformamide (DMF) were placed in a flask and stirred at room temperature for 1 hour. Then, 3.8 g of 2-chloro-4,6-diphenyl-1,3,5-triazine was added, and the mixture was stirred at room temperature for an additional 64 hours. After the reaction was completed, water was gradually added while cooling in an ice-water bath, and the mixture was extracted with ethyl acetate. The organic layer was then distilled off under reduced pressure, and the resulting crude product was purified by NH ₂ silica gel column chromatography (eluent: toluene/heptane = 1/2 (volume ratio)). The product was then reprecipitated several times with Solmix solvent and further purified by sublimation to obtain the target compound (1-88) (1.2 g).

The structure of the compound of formula (1-88) was confirmed by MS spectrum and NMR measurements.
¹ H-NMR (CDCl ₃ ): δ = 6.62 (d, 1H), 6.84-6.85 (m, 2H), 6.94-7.02 (m, 3H), 7.12-7.13 (m, 3H), 7.37-7.38 (m, 4H), 7.51 (m, 6H), 8.09 (d, 2H), 8.36 (d, 4H).

By appropriately changing the raw material compounds, other polycyclic aromatic compounds of the present invention can be synthesized using methods similar to the synthesis examples described above.

Next, we will describe the evaluation of the basic physical properties of the compound of the present invention and the fabrication and evaluation of organic EL devices using the compound of the present invention. However, the application of the compound of the present invention is not limited to the examples shown below, and the film thickness and constituent materials of each layer can be changed as appropriate depending on the basic physical properties of the compound of the present invention.

<Evaluation of vapor-deposited organic EL elements>
Organic EL elements according to Examples 1-1 to 1-7, Examples 2-1 to 2-4, Examples 3-1 to 3-4, Examples 4-1 to 4, Comparative Examples 1-1, 2-1, and 4-1 to 4-2 were produced, and the external quantum efficiency at a luminance of 1000 cd/ ^m2 and LT50 (the time required to reach 500 cd/ ^m2 when continuously driven at a current density at an initial luminance of 1000 cd/ ^m2 ) were measured.
In the following tables, "host 1" corresponds to a hole-transporting host material, and "host 2" corresponds to an electron-transporting host material.

<Comparative 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 200 nm was formed by sputtering and polished to 50 nm was used as a transparent support substrate. This transparent support substrate was fixed to the substrate holder of a commercially available vapor deposition apparatus (manufactured by Showa Vacuum Co., Ltd.), and molybdenum vapor deposition boats containing HAT-CN, HTL-1, TcTa, ETL-1, and ET7, respectively, and tungsten vapor deposition boats containing LiF and aluminum, respectively, were attached.

The following layers were sequentially formed 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 vapor-deposited to a thickness of 5 nm to form a hole injection layer. Next, HTL-1 was heated and vapor-deposited to a thickness of 90 nm to form hole transport layer 1, and TcTa was further heated and vapor-deposited to a thickness of 10 nm to form hole transport layer 2. Next, ETL-1 and new-DABNA were simultaneously heated and vapor-deposited to a thickness of 20 nm to form a light-emitting layer. The vapor deposition rate was adjusted so that the mass ratio of ETL-1 to new-DABNA was approximately 99:1. Next, ETL-1 was heated and vapor-deposited to a thickness of 20 nm to form electron transport layer 1, and then ET7 was heated and vapor-deposited to a thickness of 10 nm to form electron transport layer 2. The vapor deposition rate for 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 at a deposition rate of 1 to 10 nm/sec to form a cathode, thereby obtaining an organic EL device.

The chemical structures of the compounds used in the comparative examples and examples are shown below.

(BN2/BSN-0230/S) was synthesized as follows.
Under a nitrogen atmosphere, boron tribromide (1.91 g, 7.6 mmol) was added dropwise to a solution of (BN2/BSN-0230/S-Pre) (1.96 g, 1.90 mmol) in o-dichlorobenzene (19 mL) at room temperature, followed by stirring at 170°C for 4 hours. The reaction solution was cooled to room temperature and poured into phosphate buffer (pH 7.0), and the aqueous layer was extracted with toluene. The resulting organic layer was washed with saturated saline and dried over anhydrous magnesium sulfate. The solution was concentrated under reduced pressure, and the residue was purified using a silica gel short-path column (eluent: toluene). Further, by performing heating and washing twice with ethyl acetate, compound (BN2/BSN-0230/S) was obtained as a yellow solid (0.41 g, yield 21%).

The structure of the obtained compound was confirmed by LC-MS measurement and NMR measurement.
LC-MS: [M+H ⁺ ]=1038.40
^1H -NMR (500MHz, _CDCl3 ): δ=10.20 (s, 1H), 9.10 (dd, J=7.7, 1.4Hz, 1H), 8.96 (dd, J=7.7, 1.4Hz, 1H), 7. 51-7.44 (m, 7H), 7.40-7.35 (m, 4H), 7.33 (t, J=7.7Hz, 1H), 7.28 (s, 1H), 7.24-7. 16 (m, 9H), 7.11-7.01 (m, 11H), 6.98-6.92 (m, 6H), 6.83 (d, J = 2.6Hz, 2H), 6.78 (d , J=8.6Hz, 1H), 6.75 (d, J=8.6Hz, 1H), 5.92 (d, J=2.3Hz, 1H), 5.68-5.63 (m, 2H).

<Examples 1-1 to 1-7, Examples 2-1 to 2-4, Examples 3-1 to 3-4, Examples 4-1 to 4, Comparative Examples 2-1, and Comparative Examples 4-1 and 4-2>
Each element was fabricated by changing the materials and concentrations of the hole transport layer 2, the light emitting layer, and the electron transport layer 1 of Comparative Example 1-1 to those shown in Table 1.

The evaluation results for each element are shown in Table 2.

Compared to Comparative Example 1-1, Examples 1-1 to 1-7 exhibited higher efficiency and longer device life. Furthermore, a comparison between the Examples indicates that host materials having a carbazole ring or triazine ring as a partial structure are preferable, with those having a triazine ring as a partial structure being even more preferable. Furthermore, when comparing the medium-membered ring moieties, those having the partial structure of compound (1-68) are preferable.

Compared to Comparative Example 2-1, Examples 2-1 to 2-4 exhibited higher efficiency and longer device life. Furthermore, comparing the Examples, those having a carbazole ring as a partial structure are preferable when used as a p-host, those having a triazine ring as a partial structure are preferable when used as an n-host, and those having the partial structure of compound (1-68) are preferable when comparing medium-sized ring moieties.

Compared to Comparative Example 2-1, Examples 3-1 to 3-4 exhibited higher efficiency and longer device life. Furthermore, a comparison between the Examples revealed that hole transport layer 2 preferably has a carbazole ring as a partial structure, and electron transport layer 1 preferably has a triazine ring as a partial structure. Furthermore, when comparing medium-sized ring moieties, those with the partial structure of compound (1-68) are preferred.

Compared to Comparative Examples 4-1 and 4-2, Examples 4-1 to 4-4 exhibited higher efficiency and longer device life. Furthermore, comparing the Examples, it was found that when used as a p-host, those having a carbazole ring as a partial structure are preferable, and when used as an n-host, those having a triazine ring as a partial structure are preferable. Furthermore, when comparing the medium-sized ring moieties, those having the partial structure of compound (1-68) are preferable.

The compound of the present invention can be used in hole transport layer 2, host 1, host 2, or electron transport layer 1, but is preferably used in electron transport layer 1, host 1, or host 2, more preferably used as host 1 or host 2, and most preferably used as host 2.

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 (9)

A polycyclic aromatic compound represented by the following formula (1) :
In formula (1),
ring A, ring B, ring C and ring D are all unsubstituted benzene rings ;
X1 ^is >O or a single bond;
X2 ^is >N—R ^XN or a single bond;
X3 ^is >N-R ^XN ;
However, X ¹ and X ² cannot be single bonds at the same time,
Each R ^XN is independently a substituted or unsubstituted aryl having 6 to 10 carbon atoms or a substituted or unsubstituted heteroaryl having 2 to 10 carbon atoms, and the substituent in the substituted group is at least one group selected from the group consisting of unsubstituted aryl having 6 to 10 carbon atoms and unsubstituted heteroaryl having 2 to 10 carbon atoms. The polycyclic aromatic compound according to claim 1, represented by any one of the following formulas:
A material for an organic device, comprising the polycyclic aromatic compound according to claim 1 or 2 . 3. 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 claim 1 . The organic electroluminescent device according to claim 4 , wherein the organic layer is a light-emitting layer. The organic electroluminescent device according to claim 5 , wherein the light-emitting layer contains the polycyclic aromatic compound as a host material and a dopant material. The organic electroluminescent device according to claim 4 , wherein the organic layer is an electron transport layer. The organic electroluminescent device according to claim 4 , wherein the organic layer is a hole transport layer. A display device or a lighting device comprising the organic electroluminescent device according to any one of claims 4 to 8 .