WO2016111216A1 - Organic electroluminescent device, organic-electroluminescent-device driving method, and illumination device - Google Patents

Abstract

In this organic electroluminescent device, which has a luminescent layer containing π-conjugated molecules, when the application of a current is stopped after the current is applied, light is emitted while the current is being applied and also after the application of the current is stopped.

Description

ORGANIC ELECTROLUMINESCENT ELEMENT, ORGANIC ELECTROLUMINESCENT ELEMENT DRIVING METHOD, AND LIGHTING DEVICE

The present invention relates to an organic electroluminescence element, a driving method of an organic electroluminescence element, and a lighting device, and particularly relates to an organic electroluminescence element having a light storage function.

Various attempts have been made to give various performances to organic light-emitting elements such as organic electroluminescence elements (organic EL elements) and to apply them to various uses, and to develop new uses.
For example, light emitted from a luminescent material can be broadly classified into fluorescence and phosphorescence. Of these, phosphorescence is stored when excitation light is applied to the luminescent material in the case of light emission by photoexcitation. It is known that a phosphorescent phenomenon in which light is emitted after the light is stopped can be seen. If this phosphorescence phenomenon is used for an organic light emitting device, it is considered that phosphorescence illumination or the like in which light emission remains even after the application of energy is stopped is realized. However, there has been no report that such a phosphorescent phenomenon has been observed for an organic electroluminescence element that emits light by current excitation.
For example, Non-Patent Document 1 reports that a phosphorescent spectrum was observed by driving an organic electroluminescence element using a fluorescent material as a light-emitting material in a pulsed manner. However, phosphorescence is observed in this organic electroluminescence element only in the on period in which the current is applied, and no phosphorescence is emitted in the off period in which the current application is stopped.

Therefore, the present inventors considered that selection of a light emitting material in consideration of a phosphorescent light emitting process is important in order to realize an organic electroluminescence element having a phosphorescent function, and proceeded with research.
That is, in an organic electroluminescence element, energy is generated by recombination of holes and electrons injected into the light-emitting layer by application of current, and the light-emitting material is excited to an excited singlet state and an excited triplet state by this energy. . The singlet excitons generated thereby return to the ground state while emitting fluorescence, and the triplet excitons return to the ground state while emitting phosphorescence. In order for the organic electroluminescence element to exhibit the phosphorescence phenomenon, it is necessary that the light emitting material excited in the excited triplet state stays in the excited state for a long time and then efficiently deactivates the radiation. However, while an extremely large number of light-emitting organic compounds have been reported, no indicator has been established for selecting one in which the excited triplet state lasts long. Even if an organic compound in which the excited triplet state persists for a long time can be selected, such an organic compound has a greater chance of non-radiative deactivation due to thermal motion while in the excited state. It is difficult to emit phosphorescence. In particular, in organic electroluminescence devices, triplet-triplet annihilation occurs when the current density increases, making it more difficult to use phosphorescence. For these reasons, it is considered that the realization of an organic electroluminescence element having a phosphorescent function is impossible, and the fact is that no investigation has been made.
Under such circumstances, the inventors of the present invention aimed to provide an organic electroluminescence device having a phosphorescent function, with respect to various organic compounds whose excited triplet state was considered to be maintained for a relatively long time by current excitation. A comprehensive study was conducted to evaluate the presence or absence of the phosphorescent phenomenon.

As a result of diligent investigation, the present inventors have used a π-conjugated planar molecule as a luminescent material, so that the phosphorescent type emits light both during and after the application of current. It was found that the organic electroluminescence device of the present invention was realized. Specifically, the present invention has the following configuration.
[1] having a pair of electrodes and at least one organic layer including a light emitting layer between the pair of electrodes,
The light emitting layer includes a π-conjugated planar molecule, and when the application of current is stopped after applying a current to the light emitting layer by the pair of electrodes, the application of the current is stopped while applying the current. An organic electroluminescence element characterized by emitting light later.
[2] The organic electroluminescence device according to [1], wherein fluorescence is emitted while an electric current is applied, and phosphorescence or delayed fluorescence is emitted after the application of the current is stopped.
[3] The organic electroluminescence device according to [1] or [2], wherein the π-conjugated planar molecule has at least one aromatic ring.
[4] The organic electroluminescence device according to [3], wherein the aromatic ring is a benzene ring or an aromatic ring having a condensed polycyclic structure in which two or more benzene rings are condensed.
[5] Any one of [1] to [4], wherein the π-conjugated planar molecule is a D-substituted product in which part or all of hydrogen atoms are substituted with ² H (deuterium D). 2. The organic electroluminescence device according to item 1.
[6] The π-conjugated planar molecule is a secondary amine or a tertiary amine having a structure in which an amino group is substituted for an atomic group constituting a π-conjugated system. [1] to [5] The organic electroluminescent element of any one of Claims.
[7] The organic electroluminescence device according to [6], wherein the amino group is at least one of a substituted or unsubstituted diarylamino group and a substituted or unsubstituted dialkylamino group.
[8] The organic electroluminescence device according to any one of [1] to [7], wherein the π-conjugated planar molecule has a substituted or unsubstituted fluorene ring.
[9] The π-conjugated planar molecule is a compound represented by the following formula, a derivative in which at least one hydrogen atom of the compound represented by the following formula is substituted with a substituent, or the compound or the derivative The organic electroluminescence device according to any one of [1] to [8], wherein a part or all of the hydrogen atoms in the compound is a D-substituted product in which ² H (deuterium D) is substituted.

[10] The organic electroluminescent element according to any one of [1] to [9], wherein the light emitting layer further includes a host material.
[11] The organic electro according to [10], wherein the lowest excited triplet energy level of the host material is 0.1 eV or more higher than the lowest excited triplet energy level of the π-conjugated planar molecule. Luminescence element.
[12] The host material includes a cyclic structure in which at least two cycloalkanes are condensed, a cyclic structure in which at least two cycloalkanes and at least one cycloalkene are condensed, and a substituted or unsubstituted carbazolyl group substituted in the cyclic structure. And [10] or [11], wherein the organic electroluminescence device is a compound having at least one of a substituted or unsubstituted diarylamino group.
[13] The organic electroluminescence device according to [12], wherein the substituent is a substituted or unsubstituted carbazolyl group.
[14] The organic electroluminescence device according to any one of [10] to [13], wherein the host material is a compound represented by the following general formula (1).

[In the general formula (1), Ar represents a substituent having at least one aromatic ring, m represents an integer of 1 to 5, Z represents a substituent other than Ar, and n represents 0 to 21. Represents any integer. When m is 2 or more, m Ar may be the same or different from each other. Ar may be bonded to any of the four rings constituting the androstane ring. When n is 2 or more, the n Zs may be the same as or different from each other. The bonding position of Z may be any of the four rings constituting the androstane ring. Bonds at the 1st and 2nd positions of the androstane ring, 2nd and 3rd positions, 3rd and 4th positions, 6th and 7th positions, 11th and 12th positions, 15th and 16th positions The bond and the one or more bonds selected from the group consisting of the 16-position and 17-position bonds may be double bonds. However, the 1st and 2nd bond, the 2nd and 3rd bond, the 2nd and 3rd bond, the 3rd and 4th bond, and the 15th and 16th bond and the 16th and 17th bond However, they are not simultaneously double bonds. ]
[15] A driving method for driving the organic electroluminescence device according to any one of [1] to [14], wherein the current is applied to the light emitting layer after the current is applied to the light emitting layer by the pair of electrodes. A method for driving an organic electroluminescence element, characterized in that light emission is generated both while the current is applied and after the current application is stopped.
[16] The method for driving an organic electroluminescence element according to [15], wherein a time for applying a current to the light emitting layer is 1 μsec or more.
[17] The current described in [15] or [16], wherein the current is applied to the light emitting layer in a pulsed pattern in which an on period in which current is applied and an off period in which current application is stopped are alternately repeated. Driving method of the organic electroluminescence element.
[18] The organic electroluminescence element driving method according to [17], wherein the on period is 1 μs to 10 seconds and the off period is 1 μs to 10 minutes.
[19] An illumination device comprising the organic electroluminescent element according to any one of [1] to [14].
[20] It has control means for controlling the organic electroluminescence element so as to apply a current to the light emitting layer in a pulsed pattern in which an on period in which current is applied and an off period in which application of current is stopped are alternately repeated. The lighting device according to [19], which is characterized.
[21] A compound represented by the general formula (1).

In the organic electroluminescence device of the present invention, when the light emitting layer contains π-conjugated planar molecules, when the current application is stopped after the current is applied to the light emitting layer, the current is applied and the current is applied. It emits light after both stops. For this reason, according to this organic electroluminescent element, it is possible to realize phosphorescent illumination in which light emission remains even after the application of current is stopped. In addition, when the pulse driving method is applied to the organic electroluminescence element, light emission can be obtained in both the on period in which the current is applied and the off period in which the current application is stopped. Therefore, the off period is set to be relatively long. Thus, the current load can be reduced and the device life can be extended.

It is a schematic sectional drawing which shows the layer structural example of an organic electroluminescent element. It is the emission spectrum of the thin film of Test Example 1 during and after irradiation with ultraviolet light. It is an afterglow attenuation curve after stopping the ultraviolet light irradiation of the thin film of Test Example 2. It is the emission spectrum after stopping the application of the electric current while applying the electric current of the organic electroluminescent element of Example 1. It is the emission spectrum after stopping the application of an electric current while applying the electric current of the organic electroluminescent element of Example 3. It is a graph which shows the change of the phosphorescence emission intensity after the electric current application stop of the organic electroluminescent element of Example 3.

Hereinafter, the contents of the present invention will be described in detail. The description of the constituent elements described below may be made based on typical embodiments and specific examples of the present invention, but the present invention is not limited to such embodiments and specific examples. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value. In addition, the isotope species of the hydrogen atom present in the molecule of the compound used in the present invention is not particularly limited. For example, all the hydrogen atoms in the molecule may be ¹ H, or a part or all of them are ² H. (Deuterium D) may be used.

[Organic electroluminescence device]
The organic electroluminescence device of the present invention is configured to have an anode and a cathode (a pair of electrodes) and at least one organic layer including a light emitting layer between the anode and the cathode. The light-emitting layer contains π-conjugated planar molecules, and after applying a current to the light-emitting layer with a pair of electrodes, when the current application is stopped, both while applying the current and after stopping the current application It emits light.
In the present invention, “light emission after application of current is stopped” refers to light emission that lasts for 0.1 seconds or more after application of current is stopped. In the following description, “light emission after the application of current is stopped” is sometimes referred to as “light storage”, and the duration of light storage is sometimes referred to as “light storage life”.
The duration of phosphorescence means the time during which the emission intensity decreases to 37% after the application of current is stopped. The duration of light storage in the present invention is a value measured by a photomultiplier tube. The duration of phosphorescence is preferably 0.1 seconds or longer, more preferably 1 second or longer, and even more preferably 40 seconds or longer.
According to such an organic electroluminescence element, it is possible to realize phosphorescent illumination in which light emission remains even after the application of current is stopped. In addition, when the pulse driving method is applied to the organic electroluminescence element, light emission can be obtained in both the on period in which the current is applied and the off period in which the current application is stopped. Therefore, the off period is set to be relatively long. Thus, the current load can be reduced and the device life can be extended.
The organic layer may be composed only of the light emitting layer, or may have one or more organic layers in addition to the light emitting layer. Examples of such other organic layers include a hole transport layer, a hole injection layer, an electron blocking layer, a hole blocking layer, an electron injection layer, an electron transport layer, and an exciton blocking layer. The hole transport layer may be a hole injection / transport layer having a hole injection function, and the electron transport layer may be an electron injection / transport layer having an electron injection function. A specific example of the structure of an organic electroluminescence element is shown in FIG. In FIG. 1, 1 is a substrate, 2 is an anode, 3 is a hole injection layer, 4 is a hole transport layer, 5 is a light emitting layer, 6 is an electron transport layer, and 7 is a cathode.
Below, the structure of each part which comprises the organic electroluminescent element of this invention is explained in full detail.

[Light emitting layer]
The light emitting layer is a layer that emits light after excitons are generated by recombination of holes and electrons injected from the anode and the cathode, respectively. In the organic electroluminescence device of the present invention, the light-emitting layer includes π-conjugated planar molecules, and when the current application is stopped after applying the current to the light-emitting layer, the supply of current is stopped while the current is applied. It emits light after both. The light emitted during the application of the current and after the application of the current is stopped may be any of fluorescence, phosphorescence, and delayed fluorescence, or may be light in which two or more types of light are mixed. However, the radiation deactivation from the excited singlet state to the ground state is much faster than the radiation deactivation from the excited triplet state to the ground state. The emission is mainly fluorescence, and the emission after the application of current is stopped is mainly phosphorescence or delayed fluorescence. In this way, different light colors can be obtained during these periods by applying different types of light while applying current and after stopping applying current. Thereby, the change with time of the emission color can be used as an indicator of current on / off, and can be used as a light design. In addition, when the on period in which current is applied and the off period in which application of current is stopped are alternately repeated in a short cycle, a hue in which a plurality of emission colors are mixed can be visually recognized. By changing the pulse width in the off period, the visually recognized light can be adjusted to a desired hue.

In the present invention, the “π-conjugated planar molecule” means an atomic group that constitutes a π-conjugated system, and this atomic group has a planar structure (hereinafter referred to as “π-conjugated planar structure”). The π-conjugated planar molecule may be composed only of a π-conjugated planar structure, or may have a structure other than the π-conjugated planar structure.
In the π-conjugated planar molecule, the π-conjugated planar structure is preferably an aromatic ring. Π-conjugated planar molecules with an aromatic ring tend to be hard, and the radiative deactivation path proceeds more easily than the non-radiative deactivation path when relaxing from the excited triplet state. It is done. As a result, phosphorescence can be emitted efficiently. Examples of the aromatic ring include a benzene ring and a condensed polycyclic structure having a structure in which two or more benzene rings are condensed. Examples of the condensed polycyclic structure include naphthalene, phenanthrene, triphenylene, chrysene, pyrene, benzoperylene, coronene and the like.
The π-conjugated planar molecule is preferably a D-substituted product in which some or all of the hydrogen atoms are substituted with ² H (deuterium D). Since the CD bond is less likely to expand and contract than the CH bond, the D-substitution can suppress non-radiative deactivation from the excited triplet state more efficiently than the H form, and can emit phosphorescence more efficiently. it can. In addition, if a π-conjugated planar molecule in which some or all of hydrogen atoms are substituted with ² H (deuterium D) is used, the lifetime of the light-emitting element can be extended. In particular, the lifetime of the organic electroluminescence device can be extended more effectively by using it in the light emitting layer in combination with a host having a lowest excited triplet energy level higher than that of a π-conjugated planar molecule.
In the π-conjugated planar molecule, the π-conjugated planar structure may be substituted with a substituent. In particular, secondary amines and tertiary amines having a structure in which the π-conjugated planar structure is substituted with an amino group tend to emit phosphorescence having a large emission intensity at room temperature for a long time, and are preferably used as a phosphorescent material. Can do. The amino group is preferably a substituted or unsubstituted diarylamino group or a substituted or unsubstituted dialkylamino group, more preferably a substituted or unsubstituted diphenylamino group.

In the following, specific examples of π-conjugated planar molecules will be exemplified. However, π-conjugated planar molecules that can be used in the present invention should not be construed as being limited by these specific examples.
π-conjugated planar molecules include 2-dimethylaminotriphenylene, 2-diphenylaminotriphenylene, 2-diethylaminofluorene, 2-dipropylaminofluorene, 3-amino-2-dimethylfluorene, 2,7-bis (N-phenyl- N- (4′-N, N-diphenylamino-biphenyl-4-yl))-9,9-dimethyl-fluorene, 9,9-dimethyl-N, N′-diphenyl-N, N′-di-m -Tolylfluorene-2,7-diamine, 2,7-bis [phenyl (mtolyl) amino] -9,9'-spirofluorene, N, N, N ', N'-tetraphenylbenzidine, N, N' -Diphenyl-N, N'-di (m-tolyl) -benzidine, 3,3 ', 5,5'-tetramethyl-benzidine, 4,4'-bis [di (3,5-xylyl) amino] -4 "-phenyltriphenylamine, N, N, N ', N'-tetrakis (p-tolyl) benzidine, 4,4'-bis [N- (1-naphthyl) -N-phenylamino] -4" -Phenyltriphenylamine, N-phenyl-2-naphthylamine, N, N'-diphenyl-benzidine, (phenanthren-9-yl) -phenyl-amine, N-phenyl-N-pyren-3-yl-amine, diethyl- And pyren-1-yl-amine. By using these compounds (π-conjugated planar molecules), it is possible to observe light storage with a long lifetime and a high emission intensity at room temperature. In addition, a D-substituted product in which hydrogen atoms of aromatic rings of these compounds are substituted with ² H (deuterium D) and a halogen-substituted product in which halogen atoms such as fluorine are substituted are also preferably used as π-conjugated planar molecules. it can.

As the π-conjugated planar molecule, a compound represented by the following formula can also be preferably used. The compound represented by the following formula is a D-substituted product in which at least one of the hydrogen atoms may be substituted with a substituent, or a part or all of the hydrogen atoms are substituted with ² H (deuterium D). Also good.

Among these π-conjugated planar molecules, a compound represented by the following formula, a derivative in which at least one hydrogen atom of the compound represented by the following formula is substituted with a substituent, or a compound represented by the following formula or It is preferable to use a D-substituted product in which part or all of the hydrogen atoms of the derivative are substituted with ² H (deuterium D).

In addition, a π-conjugated planar molecule having an excellent hole transport function can also be used as a material for the light emitting layer. For specific examples of the π-conjugated planar molecule having excellent hole transport ability, the following specific examples of the hole transport material can be referred to.
One kind of these π-conjugated planar molecules may be used alone, or two or more kinds may be used in combination.

The light emitting layer may be composed of only the π-conjugated planar molecule described above, but preferably includes a π-conjugated planar molecule and a host material. The host material is preferably selected so that the lowest excited triplet energy level is higher than the lowest excited triplet energy level of the π-conjugated planar molecule used in the light emitting layer. The energy difference is preferably 0.1 eV or more, more preferably 0.3 eV or more, and even more preferably 0.5 eV or more. In the present invention, host materials satisfying such conditions can be widely adopted.
As a host material, an organic semiconductor material in which a specific substituent is introduced into a cyclic structure having a structure in which at least two cycloalkanes are condensed, or a cyclic structure in which at least two cycloalkanes and at least one cycloalkene are condensed An organic semiconductor material into which a specific substituent is introduced can be suitably used. Here, the specific substituent is a substituent having a structure in which a hydrogen atom is removed from a compound generally used as an organic semiconductor host material, has a plurality of π bonds, and has a π conjugated system. A spreading substituent is preferred. The number of the specific substituents substituted on the cyclic structure is not particularly limited, and may be one or two or more, but preferably one. In addition, the cyclic structure may be substituted with a substituent other than the specific substituent described above. In the compound having such a structure, the distance between the hydrogen atom of the steroid and the carbon atom constituting the π-conjugated system is shorter than usual, and it is considered that there is a CH-π interaction between molecules. Therefore, even if the lowest excited triplet energy level of the compound is relatively low, it is considered that the compound can effectively contribute to the extension of the lifetime of the organic electroluminescence device using the compound. A material using a compound having such a structure has a relatively high oxygen barrier property. For this reason, deterioration of the organic electroluminescence element can be suppressed, and a relatively long life can be maintained even in the presence of oxygen.
Hereinafter, specific examples of the cyclic structure and the specific substituent introduced into the cyclic structure will be given. In the following formulae, each R independently represents a substituent. A dotted line in a specific example of the substituent R represents a binding site to the cyclic structure, and when there are two dotted lines, each represents a binding site to the same or different cyclic structure. In the following cyclic structure and substituent R, at least one of the hydrogen atoms may be substituted with a substituent. The substituent is preferably substituted with an aryl group, heteroaryl group, alkenyl group, alkynyl group or the like so as to spread the π-conjugated system, but may be substituted with other substituents. Other substituents include alkyl groups, alkoxy groups, thioalkoxy groups, aryloxy groups, thioaryloxy groups, heteroaryloxy groups, heterothioaryloxy groups, secondary amino groups, tertiary amino groups, cyano groups, etc. These substituents may be further substituted with a substituent.

In the present invention, a compound having a structure represented by the following general formula (1) can be preferably used as the host material.

In the general formula (1), Ar represents a substituent having at least one aromatic ring, m represents an integer of 1 to 5, Z represents a substituent other than Ar, and n represents 0 to 21. Represents any integer. When m is 2 or more, m Ar may be the same or different from each other. Ar may be bonded to any of the four rings constituting the androstane ring. When n is 2 or more, the n Zs may be the same as or different from each other. The bonding position of Z may be any of the four rings constituting the androstane ring. Bonds at the 1st and 2nd positions of the androstane ring, 2nd and 3rd positions, 3rd and 4th positions, 6th and 7th positions, 11th and 12th positions, 15th and 16th positions The bond and the one or more bonds selected from the group consisting of the 16-position and the 17-position bond may be a double bond (provided that the 1-position and 2-position bond, the 2-position and 3-position bond, and the 2-position And the bond at the 3-position, the bond at the 3-position and the 4-position, and the bond at the 15-position and the 16-position and the bond at the 16-position and the 17-position are not simultaneously double bonds. The positions 1 to 17 of the androstane ring are as follows.

The aromatic ring possessed by the substituent represented by Ar may be a benzene ring or a heteroaromatic ring. The heteroaromatic ring is preferably a 5- to 7-membered heteroaromatic ring, and the hetero atom constituting the ring is preferably one or more atoms selected from the group consisting of a nitrogen atom, an oxygen atom and a sulfur atom. . Specific examples of the heteroaromatic ring include pyridine ring, pyrimidine ring, pyridazine ring, pyrazine ring, triazine ring, pyrrole ring, furan ring, thiophene ring, imidazole ring, pyrazole ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole. A ring can be mentioned. In the substituent represented by Ar, a ring in which two or more aromatic rings are fused may exist. Specific examples of a ring in which two or more aromatic rings are fused include naphthalene ring, anthracene ring, quinoline ring, isoquinoline ring, phthalazine ring, buteridine ring, coumarin ring, chromone ring, benzodiazepine ring, indole ring, benzimidazole ring, benzofuran And a ring, a purine ring, an acridine ring, a phenoxazine ring, a phenothiazine ring, and a phenazine ring.

Ar is an aromatic ring contained in Ar directly bonded to an androstane ring or bonded to an androstane ring via an atom (preferably a nitrogen atom or a carbon atom) bonded to the androstane ring. It is preferable. Ar is, for example, a substituted or unsubstituted phenyl group, a substituted or unsubstituted naphthyl group, a substituted or unsubstituted N-carbazolyl group, a substituted or unsubstituted 2-carbazolyl group, a substituted or unsubstituted 3-carbazolyl group Substituted or unsubstituted 2-fluorenyl group, substituted or unsubstituted 3-fluorenyl group, substituted or unsubstituted 9-fluorenyl group, substituted or unsubstituted N-phenazyl group, substituted or unsubstituted N-phenoxazyl group And a substituted or unsubstituted N-phenothiazyl group. Examples of the substituent that can be substituted on the phenyl group include, for example, an alkyl group (preferably having 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, still more preferably 1 to 6 carbon atoms), an alkoxy group (preferably 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms), an alkylthio group (preferably 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, still more preferably carbon atoms). 1-6) and cyano groups. As specific Ar structural examples, the specific examples illustrated as R can be referred to.

In the general formula (1), m is an integer of 1 to 5, preferably 1 to 3, and more preferably 1 or 2. When m is 2 or more, a compound in which m Ars are identical to each other has an advantage that synthesis is easy. When m is 2 or more, a plurality of Ars may be bonded to the same ring among the four rings constituting the androstane ring, or Ar may be bonded to different rings.
Ar may be bonded to any position of the androstane ring. Preferred is Ar at one or more positions selected from the group consisting of 1st, 2nd, 3rd, 4th, 6th, 7th, 11th, 12th, 15th, 16th and 17th positions. It is a substituted compound. A compound in which at least one Ar is bonded to any one of positions 1 to 4 of the androstane ring is more preferable. Among the 1 to 4 positions, a compound bonded to the 2 or 3 position is preferable, and a compound bonded to the 3 position is more preferable. A compound in which at least one Ar is bonded to any of positions 15 to 17 of the androstane ring is also preferable, a compound bonded to the 16th position or the 17th position is preferable, and a compound bonded to the 17th position is preferable. Further preferred. Among these, a compound bonded to at least one of the 3-position and the 17-position is preferable.

In the general formula (1), Z represents a substituent other than Ar. At this time, two Z bonded to one carbon atom constituting the ring skeleton of the androstan ring may be fused to form a single structure such as O = or S =. At this time, a carbonyl group (O = C <) or a thiocarbonyl group (S = C <) is formed by two Zs and one carbon atom to which they are bonded. On the other hand, preferred substituents that can be taken by a single Z include an alkyl group (preferably having 1 to 6 carbon atoms, more preferably 1 to 3 carbon atoms, still more preferably 1 or 2 carbon atoms), an alkoxy group (preferably carbon atoms). 1 to 6, more preferably 1 to 3, more preferably 1 or 2 carbon atoms), alkylthio group (preferably 1 to 6, more preferably 1 to 3, more preferably 1 carbon) Or 2), a cyano group can be mentioned. The number of chain long atoms of the substituent represented by Z is preferably 1 to 10, more preferably 1 to 7, still more preferably 1 to 4, and even more preferably 1 or 2. .

N in the general formula (1) is an integer of 0 to 21, preferably 0 to 8, and more preferably 0 to 4. When n is 2 or more, a plurality of Z may be bonded to the same ring among four rings constituting the androstane ring, or Z may be bonded to different rings. Z may be bonded to any position of the androstane ring.

A bond between the 1 and 2 positions of the androstane ring in the general formula (1), a bond between the 2 and 3 positions, a bond between the 3 and 4 positions, a bond between the 6 and 7 positions, a bond between the 11 and 12 positions, The one or more bonds selected from the group consisting of the 15th and 16th positions and the 16th and 17th positions may be double bonds. However, the 1st and 2nd position bonds and the 2nd and 3rd position bonds do not become double bonds at the same time, and the 2nd and 3rd position bonds and the 3rd and 4th position bonds become double bonds at the same time. In addition, the 15th and 16th position bonds and the 16th and 17th position bonds do not become double bonds at the same time. When a double bond is present in the androstane ring, the position is preferably either a 1-position or 2-position bond, a 2-position or 3-position bond, a 3-position or 4-position bond, More preferably, it is a bond at the 3-position, or a bond at the 3-position or 4-position.

The compound represented by the general formula (1) can be synthesized by appropriately combining known synthesis methods. For example, a desired compound can be synthesized by reacting Ar-H with the following androstane compound.

In the above formula, X is a halogen atom, preferably a chlorine atom, a bromine atom, or an iodine atom, and more preferably a bromine atom or an iodine atom. Other definitions are the same as those in the general formula (1). For details of the reaction conditions for this reaction, for example, Synthesis Example 1 described later can be referred to.
In the above formula, the synthesis reaction can also be performed using a compound in which X is N ₃ . By reacting a compound in which X is N ₃ with a compound represented by R ¹ —C≡C—H, a compound in which R ¹ is bonded to the X position via a 1,2,3-triazole ring is synthesized. can do. For details of the reaction conditions for this reaction, for example, Synthesis Example 2 described later can be referred to.

These host materials may be used individually by 1 type, and may be used in combination of 2 or more types.
As the host material, it is preferable to select an organic compound having at least the lowest excited triplet energy level higher than that of the π-conjugated planar molecule used for the light-emitting layer from these organic compounds. It is more preferable to select an organic compound having an energy difference of 0.1 eV or more, more preferable to select an organic compound having an energy difference of 0.3 eV or more, and an organic compound having an energy difference of 0.5 eV or more. Even more preferably, the compound is selected. It is more preferable to select an organic compound in which both the lowest excited triplet energy level and the lowest excited singlet energy level have values higher than those of the π-conjugated planar molecules used in the light emitting layer. Thereby, singlet excitons and triplet excitons generated in the π-conjugated planar molecule can be confined in the π-conjugated planar molecule, and the light emission efficiency can be sufficiently extracted.
In the organic electroluminescence device of the present invention, light emission is generated from a π-conjugated planar molecule contained in the light emitting layer. However, light emission from the host material may be partly or partly emitted.
When the host material is used, the amount of the compound of the present invention, which is a light emitting material, is preferably 0.1% by weight or more, more preferably 1% by weight or more, and 50% or more. It is preferably no greater than wt%, more preferably no greater than 20 wt%, and even more preferably no greater than 10 wt%.

[substrate]
The organic electroluminescence device of the present invention is preferably supported on a substrate. The substrate is not particularly limited and may be any substrate conventionally used for organic electroluminescence elements. For example, a substrate made of glass, transparent plastic, quartz, silicon, or the like can be used.

[anode]
As the anode in the organic electroluminescence element, an electrode material made of a metal, an alloy, an electrically conductive compound, or a mixture thereof having a high work function (4 eV or more) is preferably used. Specific examples of such electrode materials include metals such as Au, and conductive transparent materials such as CuI, indium tin oxide (ITO), SnO ₂ , and ZnO. Alternatively, an amorphous material such as IDIXO (In ₂ O ₃ —ZnO) that can form a transparent conductive film may be used. For the anode, a thin film may be formed by vapor deposition or sputtering of these electrode materials, and a pattern of a desired shape may be formed by photolithography, or when pattern accuracy is not so high (about 100 μm or more) ), A pattern may be formed through a mask having a desired shape at the time of vapor deposition or sputtering of the electrode material. Or when using the material which can be apply | coated like an organic electroconductivity compound, wet film-forming methods, such as a printing system and a coating system, can also be used. When light emission is extracted from the anode, it is desirable that the transmittance be greater than 10%, and the sheet resistance as the anode is preferably several hundred Ω / □ or less. Further, although the film thickness depends on the material, it is usually selected in the range of 10 to 1000 nm, preferably 10 to 200 nm.

[cathode]
On the other hand, as the cathode, a material having a low work function (4 eV or less) metal (referred to as an electron injecting metal), an alloy, an electrically conductive compound, and a mixture thereof as an electrode material is used. Specific examples of such electrode materials include sodium, sodium-potassium alloy, magnesium, lithium, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al ₂ O ₃ ) Mixtures, indium, lithium / aluminum mixtures, rare earth metals and the like. Among these, from the point of durability against electron injection and oxidation, a mixture of an electron injecting metal and a second metal which is a stable metal having a larger work function value than this, for example, a magnesium / silver mixture, Suitable are a magnesium / aluminum mixture, a magnesium / indium mixture, an aluminum / aluminum oxide (Al ₂ O ₃ ) mixture, a lithium / aluminum mixture, aluminum and the like. The cathode can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering. The sheet resistance as the cathode is preferably several hundred Ω / □ or less, and the film thickness is usually selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm. In order to transmit the emitted light, if either one of the anode or the cathode of the organic electroluminescence element is transparent or translucent, the emission luminance is advantageously improved.
In addition, by using the conductive transparent material mentioned in the description of the anode as a cathode, a transparent or semi-transparent cathode can be produced. By applying this, an element in which both the anode and the cathode are transparent is used. Can be produced.

[Injection layer]
The injection layer is a layer provided between the electrode and the organic layer for lowering the driving voltage and improving the luminance of light emission. There are a hole injection layer and an electron injection layer, and between the anode and the light emitting layer or the hole transport layer. Further, it may be present between the cathode and the light emitting layer or the electron transport layer. The injection layer can be provided as necessary.

[Blocking layer]
The blocking layer is a layer that can prevent diffusion of charges (electrons or holes) and / or excitons existing in the light emitting layer to the outside of the light emitting layer. The electron blocking layer can be disposed between the light emitting layer and the hole transport layer and blocks electrons from passing through the light emitting layer toward the hole transport layer. Similarly, a hole blocking layer can be disposed between the light emitting layer and the electron transporting layer to prevent holes from passing through the light emitting layer toward the electron transporting layer. The blocking layer can also be used to block excitons from diffusing outside the light emitting layer. That is, each of the electron blocking layer and the hole blocking layer can also function as an exciton blocking layer. The term “electron blocking layer” or “exciton blocking layer” as used herein is used in the sense of including a layer having the functions of an electron blocking layer and an exciton blocking layer in one layer.

[Hole blocking layer]
The hole blocking layer has a function of an electron transport layer in a broad sense. The hole blocking layer has a role of blocking holes from reaching the electron transport layer while transporting electrons, thereby improving the recombination probability of electrons and holes in the light emitting layer. As the material for the hole blocking layer, the material for the electron transport layer described later can be used as necessary.

[Electron blocking layer]
The electron blocking layer has a function of transporting holes in a broad sense. The electron blocking layer has a role to block electrons from reaching the hole transport layer while transporting holes, thereby improving the probability of recombination of electrons and holes in the light emitting layer. .

[Exciton blocking layer]
The exciton blocking layer is a layer for preventing excitons generated by recombination of holes and electrons in the light emitting layer from diffusing into the charge transport layer. It becomes possible to efficiently confine in the light emitting layer, and the light emission efficiency of the device can be improved. The exciton blocking layer can be inserted on either the anode side or the cathode side adjacent to the light emitting layer, or both can be inserted simultaneously. That is, when the exciton blocking layer is provided on the anode side, the layer can be inserted adjacent to the light emitting layer between the hole transport layer and the light emitting layer, and when inserted on the cathode side, the light emitting layer and the cathode Between the luminescent layer and the light-emitting layer. Further, a hole injection layer, an electron blocking layer, or the like can be provided between the anode and the exciton blocking layer adjacent to the anode side of the light emitting layer, and the excitation adjacent to the cathode and the cathode side of the light emitting layer can be provided. Between the child blocking layer, an electron injection layer, an electron transport layer, a hole blocking layer, and the like can be provided. When the blocking layer is disposed, at least one of the excited singlet energy and the excited triplet energy of the material used as the blocking layer is preferably higher than the excited singlet energy and the excited triplet energy of the light emitting material.

[Hole transport layer]
The hole transport layer is made of a hole transport material having a function of transporting holes, and the hole transport layer can be provided as a single layer or a plurality of layers.
The hole transport material has any one of hole injection or transport and electron barrier properties, and may be either organic or inorganic. Known hole transport materials that can be used include, for example, triazole derivatives, oxadiazole derivatives, imidazole derivatives, carbazole derivatives, indolocarbazole derivatives, polyarylalkane derivatives, pyrazoline derivatives and pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, Examples include amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aniline copolymers, and conductive polymer oligomers, particularly thiophene oligomers. An aromatic tertiary amine compound and an styrylamine compound are preferably used, and an aromatic tertiary amine compound is more preferably used.

[Electron transport layer]
The electron transport layer is made of a material having a function of transporting electrons, and the electron transport layer can be provided as a single layer or a plurality of layers.
The electron transport material (which may also serve as a hole blocking material) may have a function of transmitting electrons injected from the cathode to the light emitting layer. Examples of the electron transport layer that can be used include nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyran dioxide oxide derivatives, carbodiimides, fluorenylidenemethane derivatives, anthraquinodimethane and anthrone derivatives, oxadiazole derivatives, and the like. Furthermore, in the above oxadiazole derivative, a thiadiazole derivative in which the oxygen atom of the oxadiazole ring is substituted with a sulfur atom, and a quinoxaline derivative having a quinoxaline ring known as an electron withdrawing group can also be used as an electron transport material. Furthermore, a polymer material in which these materials are introduced into a polymer chain or these materials are used as a polymer main chain can also be used.

The method for forming the light-emitting layer, injection layer, blocking layer, hole blocking layer, electron blocking layer, exciton blocking layer, hole transport layer, and electron transport layer is not particularly limited, and either dry process or wet process is used. You may produce by.

Below, the preferable material which can be used for an organic electroluminescent element is illustrated concretely. However, the material that can be used in the present invention is not limited to the following exemplary compounds. Moreover, even if it is a compound illustrated as a material which has a specific function, it can also be diverted as a material which has another function. In the structural formulas of the following exemplary compounds, R, R ′, and R ₁ to R ₁₀ each independently represent a hydrogen atom or a substituent. X represents a carbon atom or a hetero atom forming a ring skeleton, n represents an integer of 3 to 5, Y represents a substituent, and m represents an integer of 0 or more.

First, examples of preferred compounds that can be used as a hole injection material are given.

Next, preferred examples of compounds that can be used as a hole transport material are given.

Next, preferred examples of compounds that can be used as an electron blocking material are given.

Next, preferred examples of compounds that can be used as hole blocking materials are given.

Next, preferred compound examples that can be used as an electron transporting material are listed.

Next, preferred examples of compounds that can be used as an electron injection material will be given.

Further preferred compound examples are given as materials that can be added. For example, adding as a stabilizing material can be considered.

[Driving method and application]
The organic electroluminescence device of the present invention has a structure in which the current is applied to the light emitting layer after the current is applied to the light emitting layer by the positive electrode and the negative electrode, while the current is applied to the light emitting layer and after the current application is stopped. Both emit light. This light emission is presumed to be caused by the following mechanism.
That is, when current is applied by the positive and negative electrodes, holes are injected from the anode side into the light emitting layer, electrons are injected from the cathode side, and these holes and electrons recombine on the π-conjugated planar molecule. To generate energy. This energy causes the π-conjugated planar molecule to be excited into an excited singlet state and an excited triplet state, and of these excitons (singlet excitons) excited to the excited singlet state, Since the state is in a spin-permissive relationship, it easily returns to the ground state while emitting fluorescence while applying a current. On the other hand, excitons excited to the excited triplet state (triplet excitons) are less likely to return to the ground state because the excited triplet state and the ground state are in a spin-forbidden relationship, and are delayed from the singlet exciton. Return to the ground state while emitting phosphorescence. In the present invention, it is considered that the triplet exciton of the π-conjugated planar molecule stays in the excited state for a relatively long time, and that it is difficult to cause thermal motion and triplet-triplet annihilation, and the current application is stopped. After that, radiation is deactivated and phosphorescence is efficiently emitted. With the above mechanism, the organic electroluminescence element emits light both during application of the current and after the application of the current is stopped, so that the phosphorescent function can be reliably obtained.

The current application pattern to the organic electroluminescence element may be a one-cycle pattern in which the current application is stopped after the current is applied, or an on period in which the current is applied and an off period in which the current application is stopped. Alternatively, a pulse-like pattern that repeats the above may be used. By driving with a pattern of one cycle, the organic electroluminescence element can be used as phosphorescent illumination that utilizes light emission (afterglow) after application of current. In addition, when driving with a pulse pattern that alternately repeats the on period and the off period (pulse driving), light is emitted in both the on period and the off period, thereby flickering even when the off period is set relatively long. Is unlikely to occur. Thereby, it is possible to reduce the current load by setting the off period to be relatively long, and it is possible to extend the element life. Such a long-life organic electroluminescence element can be suitably used as illumination that is always lit, such as an emergency light. When the organic electroluminescence device is driven in one cycle, the current application time is preferably 1 μsec or more, and more preferably 30 μsec or more. In the case of driving with a pulse pattern in which the on period and the off period are alternately repeated, the pulse width of the on period is preferably 1 μsec or more, and more preferably 30 μsec to 1 sec. The pulse width in the off period is preferably 1 μsec to 10 minutes, and more preferably 100 μsec to 10 minutes.
The organic electroluminescence element of the present invention can be applied to any of a single element, an element having a structure arranged in an array, and a structure in which an anode and a cathode are arranged in an XY matrix. The organic light emitting device such as the organic electroluminescence device of the present invention can be further applied to various uses. For example, it is possible to produce an organic electroluminescence display device using the organic electroluminescence element of the present invention. For details, see “Organic EL Display” (Ohm Co., Ltd.) written by Shizushi Tokito, Chiba Adachi and Hideyuki Murata. ) Can be referred to. In particular, the organic electroluminescence device of the present invention can be applied to organic electroluminescence illumination and backlights that are in great demand.

Hereinafter, the features of the present invention will be described more specifically with reference to synthesis examples and examples. The following materials, processing details, processing procedures, and the like can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below. The evaluation of the luminescence properties was carried out by using a high performance UV-visible near-infrared spectrophotometer (Perkin Elmer: Lambda950), a fluorescence spectrophotometer (Horiba, Ltd .: FluoroMax-4), an absolute PL quantum yield measuring device (Hamamatsu). Photonics: C11347), source meter (Ceethley: 2400 series), semiconductor parameter analyzer (Agilent Technology: E5273A), optical power meter measuring device (Newport: 1930C), optical spectrometer ( The measurement was performed using a spectroradiometer (manufactured by Topcon Co., Ltd .: SR-3) and a multichannel spectrometer (PMA-50, manufactured by Hamamatsu Photonics Co., Ltd.).

Singlet energy levels and triplet energy levels were determined by the following methods.
(1) Singlet energy level A sample having a thickness of 100 nm was prepared on a Si substrate by co-evaporating a measurement target compound and mCBP so that the measurement target compound had a concentration of 6% by weight. The fluorescence spectrum of this sample was measured at room temperature (300K). By integrating the luminescence from immediately after the excitation light incidence to 100 nanoseconds after the incidence, a fluorescence spectrum having a luminescence intensity on the vertical axis and a wavelength on the horizontal axis was obtained. In the fluorescence spectrum, the vertical axis represents light emission and the horizontal axis represents wavelength. A tangent line was drawn with respect to the short-wave rise of the emission spectrum, and the wavelength value λedge [nm] at the intersection of the tangent line and the horizontal axis was obtained. A value obtained by converting this wavelength value into an energy value by the following conversion formula was defined as E _S1 .
Conversion formula: E _S1 [eV] = 1239.85 / λedge
For the measurement of the emission spectrum, a nitrogen laser (Lasertechnik Berlin, MNL200) was used as an excitation light source, and a streak camera (Hamamatsu Photonics, C4334) was used as a detector.
(2) Triplet energy E _T1
The same sample as the singlet energy E _S1 was cooled to 5 [K], the phosphorescence measurement sample was irradiated with excitation light (337 nm), and the phosphorescence intensity was measured using a streak camera. By integrating the light emission from 1 millisecond after the excitation light incidence to 10 milliseconds after the light incidence, a phosphorescence spectrum having a light emission intensity on the vertical axis and a wavelength on the horizontal axis was obtained. A tangent line was drawn with respect to the rising edge of the phosphorescence spectrum on the short wavelength side, and a wavelength value λ edge [nm] at the intersection of the tangent line and the horizontal axis was obtained. A value obtained by converting this wavelength value into an energy value by the following conversion formula was defined as _ET1 .
Conversion formula: E _T1 [eV] = 1239.85 / λedge
The tangent to the rising edge of the phosphorescence spectrum on the short wavelength side was drawn as follows. When moving on the spectrum curve from the short wavelength side of the phosphorescence spectrum to the maximum value on the shortest wavelength side among the maximum values of the spectrum, tangents at each point on the curve are considered toward the long wavelength side. The slope of this tangent line increases as the curve rises (that is, as the vertical axis increases). The tangent drawn at the point where the value of the slope takes the maximum value was taken as the tangent to the rising edge of the phosphorescence spectrum on the short wavelength side.
Note that the maximum point having a peak intensity of 10% or less of the maximum peak intensity of the spectrum is not included in the above-mentioned maximum value on the shortest wavelength side, and the slope value closest to the maximum value on the shortest wavelength side is the maximum The tangent drawn at the point where the value was taken was taken as the tangent to the rising edge of the phosphorescence spectrum on the short wavelength side.

Synthesis Example 1 Synthesis of Czste (1) Synthesis of 3-iodoandrost-2-ene [isomer mixture with 3-iodoandrost-3-ene] Androstan-3-one (4.00 g, 13.89 mmol ), Hydrazine (12 mL), triethylamine (12 mL), and ethanol (20 mL) were mixed and refluxed for 2 hours. After cooling, water was added and the mixture was concentrated under reduced pressure until a white precipitate was formed. The precipitate was collected by filtration, washed with water, and dried under reduced pressure. After drying, the mixture was dissolved in a mixed solvent of dioxane (60 mL) and triethylamine (30 mL), iodine was added little by little, and the mixture was stirred for 30 minutes. Then, an aqueous sodium sulfate solution was added, and the mixture was concentrated under reduced pressure until a white precipitate was formed. Extraction with dichloromethane and drying under reduced pressure gave a crude product. The crude product was purified by silica gel column chromatography (hexane: dichloromethane = 9: 1). Since the product was unstable, it was used in the next reaction without further purification. MS (FD-MS): m / z 384 [M] ^<+> .
(2) Synthesis of 3- (N-carbazoyl-androst-2-ene (Czste) [isomer mixture with 3- (N-carbazoyl-androst-3-ene, mixing ratio 81:19]] 3-iodo Androst-2-ene (2.5 g, 6.51 mmol), carbazole (1.6 g, 9.58 mmol), dipivaloylmethane (0.36 g, 1.96 mmol), copper iodide (0.2 g, 1.05 mmol), potassium carbonate ( 4.0 g, 28.99 mmol) and dehydrated dimethyl sulfoxide (30 mL) were heated for 24 hours at 100 ° C. After cooling, extracted with dichloromethane and concentrated under reduced pressure.The crude product was purified by silica gel column chromatography (dichloromethane: ethyl acetate). = 9: 1) The target compound was obtained as a white powder by sublimation purification (0.98 g, 2.31 mmol, 36%).
¹ H-NMR: (500 MHz, CDCl ₃ , 25 ° C): δ (ppm) = 8.08 [d, 2H, carbazole], 7.41 [m, 2H, carbazole], 7.36 [m, 2H, carbazole], 5.99 [ d, 0.81H, androst-2-ene], 5.72 [s, 0.19H, androst-3-ene], 2.41-1.97 [m, 4H, androstene], 1.86-1.58 [m, 7H, androstene], 1.57- 1.16 [m, 9H, androstene], 1.10 [s, 0.57H, CH ₃ of androst-3-ene], 1.05 [s, 2.43H, CH ₃ of androst-2-ene], 1.04-0.86 [m, 3H , androstene], 0.76 [s, 0.57H, CH ₃ of androst-3-ene], 0.75 [s, 2.43H, CH ₃ of androst-2-ene].
¹³ C-NMR: (125 MHz, CDCl ₃ , 25 ° C): δ (ppm) = 140.55, 133.19, 132.99, 132.28, 127.00, 125.60, 123.00, 120.23, 119.09, 109.72, 54.56, 54.53, 54.18, 53.51, 46.17 , 42.14, 41.02, 40.79, 40.46, 39.75, 38.91, 36.07, 36.00, 35.20, 34.69, 34.66, 32.46, 32.07, 31.89, 28.48, 27.38, 25.56, 25.52, 25.22, 21.47, 21.28, 20.54, 20.51, 17.72, 17.52 , 12.59, 12.25.
MS (FD-MS): m / z 423 [M] ⁺ .
Elemental Analysis: calcd.for C ₃₁ H ₃₇ N ₁ : C, 87.89; H, 8.80; N, 3.31; found: C, 87.71; H, 8.80; N, 3.28.
Sublimation temperature (1Pa, TGA) approx. 215 ° C, glass transition temperature (Tg) 63.8 ° C, melting point 240 ° C
Lowest excited singlet energy level 3.6eV, lowest excited triplet energy level 2.7eV, HOMO -6.0eV, LUMO -2.5eV

(Synthesis Example 2) Synthesis of TPste TPste was synthesized according to the following scheme.

(3α, 5β) -estran-3-ol (5.0 g), paratoluenesulfonyl chloride (2.0 g), and pyridine (50 mL) were reacted at 50 ° C. for 3 hours under argon. After the reaction, the solvent was distilled under reduced pressure, dissolved in ethyl acetate, washed with 1 mol / L HCl, and distilled under reduced pressure to obtain a yellow solid (8.5 g). This yellow solid was dissolved in DMF, NaN ₃ (1.5 g) was added, and the mixture was reacted at 60 ° C. for 24 hours. After the reaction, the solvent was distilled under reduced pressure, dissolved in ethyl acetate, washed with water, and distilled again under reduced pressure. Purification by silica gel column chromatography (hexane: ethyl acetate = 9: 1) gave 3-azide- (3β, 5β) estrane (3.2 g).
Next, 3-azide- (3β, 5β) estrane (1.5 g), 2-ethylpyridine (0.6 g), CuSO ₄ (0.2 g), sodium ascorbate (1.3 g), tetrahydrofuran (50 mL), A mixed solution of pure water (20 mL) was heated at 75 ° C. for 24 hours. The solvent was distilled under reduced pressure and extracted with dichloromethane. Purification by column chromatography (amino-modified silica gel, CH ₂ Cl ₂ : hexane = 4: 6) gave 1.2 g of TPste. As a result of X-ray analysis, the distance between the hydrogen atom of the steroid and the carbon atom of the pyridine ring is 2.89 mm, and the distance between the hydrogen atom of the steroid and the nitrogen atom of the pyridine ring is 2.70 mm, both of which are 2. It was confirmed that it was 9 cm or less. This suggested that there was a CH-π interaction.
¹ H NMR: (500 MHz, CDCl ₃ , 25 ° C): δ (ppm) = 8.59 [d, 1H, pyridine], 8.26 [s, 1H, triazole], 8.22 [d, 1H, pyridine], 7.79 [ td, 1H, pyridine], 7.23 [m, 1H, pyridine], 2.42 [m, 1H, androstane], 2.16-2.09 [m, 2H, androstane], 1.73-1.01 [m, 18H, androstane], 1.10 [s , 3H, CH ₃ of androstane], 0.68 [s, 1H, CH ₃ of androstane], 0.92-0.70 [m, 3H, androstane].
¹³ C NMR: (125 MHz, CDCl ₃ , 25 ° C): δ (ppm) = 150.68, 149.31, 147.76, 136.96, 122.72, 121.12, 120.26, 56.46, 54.42, 54.24, 40.76, 40.34, 39.91, 38.73, 35.91, 35.70, 33.23, 32.74, 31.96, 28.22, 25.44, 25.42, 20.72, 20.44, 17.51, 11.87.
MS (FD-MS): m / z 404 [M] ⁺ .
Elemental analysis: calcd.for C ₃₁ H ₃₇ N ₁ : C, 77.18; H, 8.97; N, 13.85; found: C, 77.44; H, 8.99; N, 13.98.
Sublimation temperature (1Pa, TG-DTA) approx. 180 ° C, glass transition temperature (Tg) 46 ° C, melting point 154 ° C
Lowest excited singlet energy level 4.1eV, lowest excited triplet energy level 3.1eV, HOMO -6.0eV, LUMO -1.8eV

(Test Example 1) Evaluation of luminous life of DMFLTPD films using various hosts DMFLTPD and the following six types under vacuum conditions of 5.0 × 10 ⁻⁴ Pa on a silicon substrate by vacuum deposition A selected host was deposited from a different deposition source, and a thin film having a DMFLTPD concentration of 1.0% by weight was formed to a thickness of 100 nm. Luminescence was observed when irradiated with ultraviolet light at 77 K for 2.4 seconds. The phosphorescent lifetime was measured for phosphorescence (afterglow) after the ultraviolet light irradiation was stopped. Further, for each of DMFLTPD and the following six types of hosts, the lowest excited triplet energy level was measured according to the above measurement method.

The luminous life when each host was used and the lowest excited triplet energy level of the host were as shown in the following table. The lowest excited triplet energy level of DMFLTPD was 2.5 eV. From the table below, it was confirmed that the phosphorescent lifetime can be extended by using a host having a lowest excited triplet energy level higher than that of DMFLTPD. On the other hand, Czste has a long photoluminescence lifetime, although the lowest excited triplet energy level is lower than mCP. The emission spectra of the thin film using Czste and the thin film using mCP are shown in FIG. 2, and the results of measuring the external quantum yield are shown in Table 2. In Table 2, F represents fluorescence, P represents phosphorescence, and all represents the sum of fluorescence and phosphorescence. When Czste was used, the quantum yield of phosphorescence was high, suggesting the existence of intermolecular interactions. Further, the thin film using Czste emitted phosphorescence at room temperature in the presence of oxygen, and it was confirmed that the stability against oxygen and the barrier property were high.

(Test Example 2) Evaluation of phosphorescence lifetime with and without deuteration A thin film was formed under the same conditions as in Test Example 1 using one type of host selected from Czste, mCP, DPEPO, and β-estradiol and DMFLTPD. Formed. At this time, for each host, two types were formed: one formed with deuterated DMFLTPD (d-form) and one formed with hydrogen substituted for deuterium (h-form). When each thin film was irradiated with ultraviolet light at 300K, light emission was observed. The phosphorescence (afterglow) was observed after the ultraviolet light irradiation was stopped. The results are shown in FIG. It was confirmed that the use of deuterated DMFLTPD (d-form) increased the phosphorescent lifetime. In particular, when it was used in combination with a host having a high lowest excited triplet energy level, a long life due to deuteration was remarkably recognized.

Example 1 Production and Evaluation of Organic Electroluminescence Device Using DMFLTPD and mCP An organic electroluminescence device was produced by the following method using DMFLTPD as a π-conjugated planar molecule and mCP as a host material.
Each thin film was laminated at a vacuum degree of 5.0 × 10 ⁻⁴ Pa by a vacuum deposition method on a glass substrate on which an anode made of indium tin oxide (ITO) having a thickness of 100 nm was formed. First, α-NPD was formed to a thickness of 30 nm on ITO, and mCP was formed to a thickness of 10 nm thereon. Next, DMFLTPD and mCP were co-evaporated from different evaporation sources to form a layer having a thickness of 30 nm as a light emitting layer. At this time, the concentration of DMFLTPD was 1% by weight. Next, TPBi is formed to a thickness of 60 nm, further, lithium fluoride (LiF) is vacuum-deposited to 0.8 nm, and then aluminum (Al) is evaporated to a thickness of 800 nm to form a cathode. An electroluminescence element was obtained.
About the manufactured organic electroluminescence device, after applying the current at 40 V for 5 μs, when the current application was stopped, the blue color was seen for a moment, it immediately turned green, and the green color gradually disappeared. I was able to confirm.
Simultaneously with this visual observation, the emission spectrum during current application and the emission spectrum at each time point 0.02 seconds and 0.13 seconds after the current application was stopped were measured, and the current application was further stopped. The phosphorescent lifetime from the time point was measured. The measured emission spectrum is shown in FIG. Moreover, the result of having measured the emission spectrum by light irradiation (296 nm excitation light) about the light emitting layer similar to what was formed by this organic electroluminescence is also shown in FIG.
As shown in FIG. 4, fluorescence emission was observed during the application of current, and phosphorescence emission was observed after the current application was stopped. The phosphorescent life of phosphorescence was 0.2 seconds.

(Example 2) Production and evaluation of organic electroluminescence device using DMFLTPD and Czste or mCP When forming a light emitting layer, it was the same as Example 1 except that Czste or mCP was used as a host material instead of mCP. Thus, an organic electroluminescence element was produced.
When a current was applied to the manufactured organic electroluminescence device under the same conditions as in Example 1 and then the current application was stopped, blue fluorescence was observed during the current application, and the green phosphorous was observed after the current application was stopped. Light emission was observed. Moreover, the luminous life of the organic electroluminescent element using Czste as the host is 0.4 seconds, and the luminous life of the organic electroluminescent element using mCP as the host is 0.27 seconds. As compared with the organic electroluminescence device, it was possible to obtain a long-lived light storage. In addition, it was confirmed that the use of Czste having a higher lowest excited triplet energy level has a longer lifetime. When any host was used, the maximum external quantum efficiency was 1.0%.
From these results, it was confirmed that by adopting the configuration of the present invention, a highly useful phosphorescent organic electroluminescence element was realized.

(Example 3) coronene and Czste coronene a (C ₂₄ H ₁₂₎ used as the Preparation and Evaluation π conjugated plane molecular organic electroluminescence device using the using the Czste as a host material, an organic electroluminescence device by the following method Was made.
Each thin film was laminated at a vacuum degree of 5.0 × 10 ⁻⁴ Pa by a vacuum deposition method on a glass substrate on which an anode made of indium tin oxide (ITO) having a thickness of 100 nm was formed. First, α-NPD was formed to a thickness of 30 nm on ITO, and mCP was formed to a thickness of 10 nm thereon. Next, coronene and Czste were co-evaporated from different vapor deposition sources to form a layer having a thickness of 60 nm as a light emitting layer. At this time, the concentration of coronene was 1% by weight. Next, TPBi is formed to a thickness of 60 nm, further lithium fluoride (LiF) is vacuum-deposited to 0.8 nm, and then aluminum (Al) is evaporated to a thickness of 80 nm to form a cathode. An electroluminescence element was obtained.
About the manufactured organic electroluminescence device, after applying the current at 40 V for 50 μsec, when the current application was stopped, the blue color was seen for a moment, it immediately turned yellow, and the yellow color gradually disappeared. I was able to confirm.
Simultaneously with this visual observation, the emission spectrum during current application and the emission spectrum at each time point 0.02 seconds and 0.13 seconds after the current application was stopped were measured, and the current application was further stopped. The phosphorescent lifetime from the time point was measured. The measured emission spectrum is shown in FIG.
As shown in FIG. 5, fluorescence emission was observed during current application (blue), and phosphorescence emission (orange) was observed after the current application was stopped. Further, from FIG. 6, the phosphorescent life of phosphorescence was 3.75 seconds.

(Example 4) Production and evaluation of organic electroluminescence device using DMFLTPD and DPEPO Each thin film was subjected to vacuum deposition on a glass substrate on which an anode made of indium tin oxide (ITO) having a thickness of 100 nm was formed. And a degree of vacuum of 5.0 × 10 ⁻⁴ Pa. First, α-NPD was formed to a thickness of 30 nm on ITO, and mCP was formed to a thickness of 10 nm thereon. Next, DMFLTPD and DPEPO were co-evaporated from different vapor deposition sources to form a layer having a thickness of 30 nm as a light emitting layer. At this time, the concentration of DMFLTPD was 1% by weight. Next, DPEPO is formed to a thickness of 10 nm, TPBi is formed to a thickness of 50 nm, lithium fluoride (LiF) is vacuum-deposited to 0.8 nm, and aluminum (Al) is then formed to a thickness of 800 nm. A cathode was formed by vapor deposition to obtain an organic electroluminescence element.
When a current was applied to the manufactured organic electroluminescence device under the same conditions as in Example 1 and then the current application was stopped, blue fluorescence was observed during the current application, and the green phosphorous was observed after the current application was stopped. Light emission was observed. The phosphorescent lifetime was 0.95 seconds and the maximum external quantum efficiency was 0.85%.

From these results, it was confirmed that by adopting the configuration of the present invention, a highly useful phosphorescent organic electroluminescence element was realized.

The organic electroluminescence device of the present invention emits light both during application of current and after application of current is stopped, and therefore can be suitably used as phosphorescent illumination or pulse drive illumination. For this reason, this invention has high industrial applicability.

DESCRIPTION OF SYMBOLS 1 Substrate 2 Anode 3 Hole injection layer 4 Hole transport layer 5 Light emitting layer 6 Electron transport layer 7 Cathode

Claims (21)

1. A pair of electrodes, and at least one organic layer including a light emitting layer between the pair of electrodes,
   The light emitting layer includes a π-conjugated planar molecule,
   When the current application is stopped after applying a current to the light emitting layer, the pair of electrodes emits light both during the application of the current and after the application of the current is stopped. Luminescence element.
2. 2. The organic electroluminescence device according to claim 1, wherein the organic electroluminescence device emits fluorescence while applying current, and emits phosphorescence or delayed fluorescence after the application of current is stopped.
3. 3. The organic electroluminescence device according to claim 1, wherein the π-conjugated planar molecule has at least one aromatic ring.
4. The organic electroluminescence device according to claim 3, wherein the aromatic ring is a benzene ring or an aromatic ring having a condensed polycyclic structure in which two or more benzene rings are condensed.
5. 5. The π-conjugated planar molecule is a D-substituted product in which part or all of hydrogen atoms are substituted with ² H (deuterium D). Organic electroluminescence device.
6. 6. The π-conjugated planar molecule is a secondary amine or a tertiary amine having a structure in which an amino group is substituted for an atomic group constituting a π-conjugated system, according to any one of claims 1 to 5. The organic electroluminescent element of description.
7. The organic electroluminescence device according to claim 6, wherein the amino group is at least one of a substituted or unsubstituted diarylamino group and a substituted or unsubstituted dialkylamino group.
8. The organic electroluminescent device according to any one of claims 1 to 7, wherein the π-conjugated planar molecule has a substituted or unsubstituted fluorene ring.
9. The π-conjugated planar molecule is a compound represented by the following formula, a derivative in which at least one hydrogen atom of the compound represented by the following formula is substituted with a substituent, or a hydrogen atom of the compound or the derivative 9. The organic electroluminescence device according to claim 1, wherein a part or all of the compound is a D-substituted product substituted with ² H (deuterium D).
   

   
10. The organic electroluminescence device according to any one of claims 1 to 9, wherein the light emitting layer further contains a host material.
11. The organic electroluminescence device according to claim 10, wherein the lowest excited triplet energy level of the host material is 0.1 eV or more higher than the lowest excited triplet energy level of the π-conjugated planar molecule.
12. The host material includes a cyclic structure in which at least two cycloalkanes are condensed or a cyclic structure in which at least two cycloalkanes and at least one cycloalkene are condensed, a substituted or unsubstituted carbazolyl group substituted with the cyclic structure, and a substituted or The organic electroluminescence device according to claim 11, wherein the organic electroluminescence device is a compound having at least one of unsubstituted diarylamino groups.
13. The organic electroluminescence device according to claim 12, wherein the substituent is a substituted or unsubstituted carbazolyl group.
14. 14. The organic electroluminescence device according to claim 10, wherein the host material is a compound represented by the following general formula (1).
    

    

    [In the general formula (1), Ar represents a substituent having at least one aromatic ring, m represents an integer of 1 to 5, Z represents a substituent other than Ar, and n represents 0 to 21. Represents any integer. When m is 2 or more, m Ar may be the same or different from each other. Ar may be bonded to any of the four rings constituting the androstane ring. When n is 2 or more, the n Zs may be the same as or different from each other. The bonding position of Z may be any of the four rings constituting the androstane ring. Bonds at the 1st and 2nd positions of the androstane ring, 2nd and 3rd positions, 3rd and 4th positions, 6th and 7th positions, 11th and 12th positions, 15th and 16th positions The bond and the one or more bonds selected from the group consisting of the 16-position and 17-position bonds may be double bonds. However, the 1st and 2nd bond, the 2nd and 3rd bond, the 2nd and 3rd bond, the 3rd and 4th bond, and the 15th and 16th bond and the 16th and 17th bond However, they are not simultaneously double bonds. ]
15. A driving method for driving the organic electroluminescence element according to any one of claims 1 to 14,
    The pair of electrodes is configured to stop the application of current after applying a current to the light emitting layer, and to emit light both during the application of current and after the application of current is stopped. A driving method of an organic electroluminescence element.
16. The method for driving an organic electroluminescence element according to claim 15, wherein the time for applying a current to the light emitting layer is 1 µsec or more.
17. 17. The organic electroluminescence device according to claim 15, wherein a current is applied to the light emitting layer in a pulse pattern in which an on period in which a current is applied and an off period in which the current application is stopped are alternately repeated. Driving method.
18. 18. The method of driving an organic electroluminescence element according to claim 17, wherein the on period is 1 μs to 10 seconds and the off period is 1 to 10 minutes.
19. A lighting device comprising the organic electroluminescence element according to any one of claims 1 to 14.
20. It has a control means for controlling the organic electroluminescence element so as to apply a current to the light emitting layer in a pulsed pattern in which an on period in which current is applied and an off period in which application of current is stopped are alternately repeated. The lighting device according to claim 19.
21. A compound represented by the following general formula (1).
    

    

    [In the general formula (1), Ar represents a substituent having at least one aromatic ring, m represents an integer of 1 to 5, Z represents a substituent other than Ar, and n represents 0 to 21. Represents any integer. When m is 2 or more, m Ar may be the same or different from each other. Ar may be bonded to any of the four rings constituting the androstane ring. When n is 2 or more, the n Zs may be the same as or different from each other. The bonding position of Z may be any of the four rings constituting the androstane ring. Bonds at the 1st and 2nd positions of the androstane ring, 2nd and 3rd positions, 3rd and 4th positions, 6th and 7th positions, 11th and 12th positions, 15th and 16th positions The bond and the one or more bonds selected from the group consisting of the 16-position and 17-position bonds may be double bonds. However, the 1st and 2nd bond, the 2nd and 3rd bond, the 2nd and 3rd bond, the 3rd and 4th bond, and the 15th and 16th bond and the 16th and 17th bond However, they are not simultaneously double bonds. ]

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