Organic electroluminescent device

Abstract

To provide an organic electroluminescent element which is low in drive voltage and has high luminous efficiency and excellent power efficiency.SOLUTION: There is provided an organic electroluminescent element including an electron transport layer at least one layer of which is a layer containing an adamantane compound represented by formula (1). (In the formula, Ad represents a fluorine atom, a 1-4C alkyl group, a carbonyl group or 1-adamantyl group or 2-adamantyl group that may be substituted with a cyano group; Ar1 is a group comprising a group consisting of a single bond, a 6-40C aryl group that may be substituted with one or more R1's or a 3-40C heteroaryl group that may be substituted with one or more R1's; and Ar2 is a group comprising a group consisting of a 6-40C aryl group that may be substituted with one or more R1's or a 3-40C heteroaryl group that may be substituted with one or more R1's.)SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an organic electroluminescent device. [Background technology]

[0002] Conventional organic electroluminescent devices have a higher driving voltage, lower luminance and luminous efficiency, and significantly lower power efficiency than inorganic light-emitting diodes, and have not been put to practical use. Although recent organic electroluminescent devices have been gradually improved, there is a demand for materials and combinations with better luminous efficiency, driving voltage, and power efficiency characteristics. Depending on the application, such as in-vehicle applications, high heat resistance may be required, and there is a general demand for elements that contain materials with high glass transition temperatures (Tg).

[0003] Examples of electron transport materials having excellent long life for organic electroluminescent devices include the azine compounds disclosed in Patent Documents 1 to 3. However, further improvements in voltage, luminous efficiency, and power efficiency of organic electroluminescent devices using such materials have been required. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2011-063584 A [Patent Document 2] JP 2008-280330 A [Patent Document 3] JP 2015-34159 A Summary of the Invention [Problem to be solved by the invention]

[0005] One aspect of the present invention is directed to providing an organic electroluminescent device that has low voltage, high efficiency and excellent power efficiency. [Means for solving the problem]

[0006] An organic electroluminescent device according to one aspect of the present invention comprises: An anode, a cathode, and at least one light-emitting layer; At least two electron transport layers are provided between the cathode and the light emitting layer, At least one of the electron transport layers is a layer containing an adamantane compound represented by formula (1).

[0007] [ka] (In the formula, Ad represents a 1-adamantyl group or a 2-adamantyl group which may be substituted with a fluorine atom, an alkyl group having 1 to 4 carbon atoms, a carbonyl group, or a cyano group; Ar 1 is a single bond, one or more R 1 an aryl group having 6 to 40 carbon atoms which may be substituted with one or more R 1 a heteroaryl group having 3 to 40 carbon atoms which may be substituted with Ar 2 is one or more R 1 an aryl group having 6 to 40 carbon atoms which may be substituted with one or more R 1 a heteroaryl group having 3 to 40 carbon atoms which may be substituted with R 1 is a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a CHO group, a CN group, a NO2 group, an alkyl group, an alkenyl group, a cycloalkyl group, a bicycloalkyl group, or a tricycloalkyl group having 1 to 20 carbon atoms, an adamantyl group, an alkoxy group having 1 to 10 carbon atoms, an aryl group having 6 to 40 carbon atoms, a heteroaryl group having 3 to 40 carbon atoms, P(=O)(Ar 3 )2, C(=O)Ar 3 , B(Ar 3 )2, B(OAr 3 )2, OSO2Ar 3 , S(=O)Ar 3 , Si(Ar 3 )3, R 1are identical or different for each occurrence, and two or more adjacent R 1 may form a ring with each other; Ar 3 each occurrence may be the same or different, and each occurrence represents a substituent selected from the group consisting of an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 40 carbon atoms, or a heteroaryl group having 3 to 40 carbon atoms, and two or more adjacent Ar 3 may form a ring with each other; n represents 1, 2, or 3.) Effect of the Invention

[0008] According to one aspect of the present invention, it is possible to provide an organic electroluminescent device that operates at a low voltage and has high efficiency and high power efficiency. [Brief description of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view of an organic electroluminescent device according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, embodiments of the present invention will be described in detail.

[0011] <Organic electroluminescent device> An organic electroluminescent device according to one embodiment of the present invention comprises: An anode, a cathode, and at least one light-emitting layer; At least two electron transport layers are provided between the cathode and the light emitting layer, At least one of the electron transport layers is a layer containing an adamantane compound represented by formula (1).

[0012] The adamantane compound represented by formula (1) has a structure in which an adamantyl group is combined with a highly electron-transporting skeleton such as triazine, pyrimidine, or pyridine. Conventionally, compounds having a triazine, pyrimidine, or pyridine skeleton have excellent electron transport ability and electron injection properties from the cathode due to their high acceptor properties, but have had the problem that their high acceptor properties create an electron injection barrier to adjacent layers, resulting in energy loss.

[0013] In contrast, the present inventors presume that in the adamantane compound represented by formula (1), the acceptor property of the compound is alleviated by the donor property of the adamantyl group, thereby improving the electron injection property into the adjacent layer.

[0014] Furthermore, the inventors speculate that the adamantyl group is an excellent component of the electron transport layer because it is a rigid cyclic aliphatic group that is not involved in a conjugated structure and therefore does not sacrifice electron transport properties, unlike other donor substituents (e.g., arylamino groups).

[0015] Based on the above effects, the inventors speculate that the adamantane compound represented by formula (1) has enhanced electron injection properties into adjacent layers, and that by combining it with a different electron transport layer, it is possible to achieve both low voltage and high efficiency.

[0016] <Adamantane compound represented by formula (1)>

[0017] [ka] (In the formula, Ad represents a 1-adamantyl group or a 2-adamantyl group which may be substituted with a fluorine atom, an alkyl group having 1 to 4 carbon atoms, a carbonyl group, or a cyano group; Ar 1 is a single bond, one or more R 1 an aryl group having 6 to 40 carbon atoms which may be substituted with one or more R 1a heteroaryl group having 3 to 40 carbon atoms which may be substituted with Ar 2 is one or more R 1 an aryl group having 6 to 40 carbon atoms which may be substituted with one or more R 1 a heteroaryl group having 3 to 40 carbon atoms which may be substituted with R 1 is a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a CHO group, a CN group, a NO2 group, an alkyl group, an alkenyl group, a cycloalkyl group, a bicycloalkyl group, or a tricycloalkyl group having 1 to 20 carbon atoms, an adamantyl group, an alkoxy group having 1 to 10 carbon atoms, an aryl group having 6 to 40 carbon atoms, a heteroaryl group having 3 to 40 carbon atoms, P(=O)(Ar 3 )2, C(=O)Ar 3 , B(Ar 3 )2, B(OAr 3 )2, OSO2Ar 3 , S(=O)Ar 3 , Si(Ar 3 )3, R 1 are identical or different for each occurrence, and two or more adjacent R 1 may form a ring with each other; Ar 3 each occurrence may be the same or different, and each occurrence represents a substituent selected from the group consisting of an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 40 carbon atoms, or a heteroaryl group having 3 to 40 carbon atoms, and two or more adjacent Ar 3 may form a ring with each other; n represents 1, 2, or 3.)

[0018] In the embodiment of the present invention, it is preferable to provide a layer containing another electron transporting compound having high injection ability from the cathode to the electron transporting layer as an adjacent layer on the cathode side of the layer containing the compound represented by formula (1). Furthermore, since the layer containing the compound represented by formula (1) has high electron injection ability to the adjacent organic layer, it exerts a further high effect when used at the interface with the light emitting layer which is likely to become an energy barrier.

[0019] Advertisement Ad is a 1-adamantyl group (hereinafter, Ad 1 ) or 2-adamantyl group (hereinafter, Ad 2 (also referred to as "1-adamantyl group"), and preferably a 1-adamantyl group.

[0020] The alkyl group having 1 to 4 carbon atoms is not particularly limited, but preferred examples include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, and a tert-butyl group.

[0021] In one embodiment of the present invention, it is preferable that the compound has a 1,3,5-triazine skeleton as a partial structure, and in another embodiment, it is preferable that the compound has a pyrimidine skeleton as a partial structure. These partial structures can enhance the electron transport property, and each of them has a function of emphasizing the mechanism of effect expression of the adamantane compound. The effect can be obtained if there is only one partial structure in one molecule of the adamantane compound.

[0022] ≪Ar 1 ≫ Ar 1 is a single bond, one or more R 1 an aryl group having 6 to 40 carbon atoms which may be substituted with one or more R 1 The group consisting of heteroaryl groups having 3 to 40 carbon atoms which may be substituted with

[0023] The aryl group having 6 to 40 carbon atoms is not particularly limited, but preferred examples include a phenyl group, a biphenyl group, a naphthyl group, a terphenyl group, a phenanthryl group, an anthryl group, a pyrenyl group, a triphenylenyl group, a chrysenyl group, a fluoranthenyl group, an acenaphthylenyl group, a fluorenyl group, a benzofluorenyl group, and a spirofluorenyl group, and may be a substituent having a structure in which a plurality of these groups are combined.

[0024] Examples of the heteroaryl group having 3 to 40 carbon atoms include, but are not limited to, a pyridyl group, a pyrazyl group, a pyrimidyl group, a pyridazyl group, a triazyl group, a quinolyl group, an isoquinolyl group, a phenanthridyl group, a benzoquinolyl group, an acridyl group, a pyridylphenyl group, a pyridylbiphenyl group, a pyridylnaphthyl group, a pyridylphenanthryl group, a pyridylanthryl group, a pyridylpyrenyl group, a pyridyltriphenylenyl group, a pyridylc group, a pyridylcyclohexyl ... Lysenyl group, pyridylfluoranthenyl group, pyridylacenaphthylenyl group, pyrimidylphenyl group, pyrimidylbiphenyl group, pyrimidylnaphthyl group, pyrimidylphenanthryl group, pyrimidylanthryl group, pyrimidylpyrenyl group, pyrimidyltriphenylenyl group, pyrimidylchrysenyl group, pyrimidylfluoranthenyl group, pyrimidylacenaphthylenyl group, pyrazylphenyl group, pyrazylbiphenyl group, pyrazylnaphthyl group , a pyrazylphenanthryl group, a pyrazylanthryl group, a pyrazylpyrenyl group, a pyrazyltriphenylenyl group, a pyrazylchrysenyl group, a pyrazylfluoranthenyl group, a pyrazylacenaphthylenyl group, a quinolylphenyl group, a quinolylbiphenyl group, a quinolylnaphthyl group, a quinolylphenanthryl group, a quinolylanthryl group, a quinolylpyrenyl group, a quinolyltriphenylenyl group, a quinolylchrysenyl group, a quinolylfluoranthenyl group, Preferred examples include a quinolylacenaphthylenyl group, an isoquinolylphenyl group, an isoquinolylbiphenyl group, an isoquinolylnaphthyl group, an isoquinolylphenanthryl group, an isoquinolylanthryl group, an isoquinolylpyrenyl group, an isoquinolyltriphenylenyl group, an isoquinolylchrysenyl group, an isoquinolylfluoranthenyl group, and an isoquinolylacenaphthylenyl group, and the like. The substituent may have a structure in which a plurality of these groups are combined.

[0025] ≪Ar 2 ≫ Ar 2 is one or more R 1 an aryl group having 6 to 40 carbon atoms which may be substituted with one or more R 1 The group consisting of heteroaryl groups having 3 to 40 carbon atoms which may be substituted with Preferable examples of the aryl group having 6 to 40 carbon atoms and the heteroaryl group having 3 to 40 carbon atoms include Ar 1 The same groups as those shown below can be mentioned.

[0026] ≪R 1 ≫ R 1 is a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a CHO group, a CN group, a NO2 group, an alkyl group, an alkenyl group, a cycloalkyl group, a bicycloalkyl group, or a tricycloalkyl group having 1 to 20 carbon atoms, an adamantyl group, an alkoxy group having 1 to 10 carbon atoms, an aryl group having 6 to 40 carbon atoms, a heteroaryl group having 3 to 40 carbon atoms, P(=O)(Ar 3 )2, C(=O)Ar 3 , B(Ar 3 )2, B(OAr 3 )2, OSO2Ar 3 , S(=O)Ar 3 , Si(Ar 3 )3, R 1 are identical or different for each occurrence, and two or more adjacent R 1 may form a ring together.

[0027] R 1 teeth 、 It is preferably a hydrogen atom, a fluorine atom, a methyl group, an adamantyl group, a cyano group, a phenyl group, a naphthyl group, a phenanthryl group, an anthryl group, a chrysenyl group, a pyrenyl group, a triphenylenyl group, a fluorenyl group, a dimethylfluorenyl group, a 9,9'-spirobifluorenyl group, a furanyl group, a benzofuranyl group, a dibenzofuranyl group, a thiophenyl group, a benzothiophenyl group, a dibenzothiophenyl group, a pyridyl group, a pyrimidyl group, a pyrazyl group, a quinolyl group, an isoquinolyl group, a quinazolyl group, a phenanthridyl group, an imidazolyl group, or a carbazolyl group, and may be a substituent having a structure in which a plurality of these are combined.Furthermore, it is preferably a hydrogen atom.

[0028] ≪Ar 3 ≫ Ar 3are the same or different at each occurrence, and each represents a group consisting of an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 40 carbon atoms, or a heteroaryl group having 3 to 40 carbon atoms, and two or more adjacent Ar 3 may form a ring together.

[0029] Preferable examples of the aryl group having 6 to 40 carbon atoms and the heteroaryl group having 3 to 40 carbon atoms include Ar 1 The same groups as those shown below can be mentioned.

[0030] <Azine compound represented by formula (2)> The organic electroluminescent device according to one embodiment of the present invention is characterized by having an electron transport layer containing an adamantane compound represented by formula (1) and an electron transport layer containing an azine compound represented by formula (2).

[0031] [ka]

[0032] ≪Z 1 , Z 2 , and Z 3 ≫ In formula (2), Z 1 , Z 2 , and Z 3 Each independently represents a nitrogen atom or CH. 1 , Z 2 , Z 3 At least one of the Ar groups is preferably a nitrogen atom, and more preferably all three of the Ar groups are nitrogen atoms. 1 and Ar 2 Each independently has the same meaning as the group described above.

[0033] <Azine compound represented by formula (1a)> The adamantane compound represented by formula (1) according to one embodiment of the present invention is preferably an azine compound represented by formula (1a).

[0034] [ka]

[0035] {In general formula (1a), Each Ad is independently the same as defined above and represents a 1-adamantyl group or a 2-adamantyl group optionally substituted with a fluorine atom, an alkyl group having 1 to 4 carbon atoms, a carbonyl group, or a cyano group; p and q each independently represent 0 or 1; Ar 4 and Ar 6 each independently represents a single bond (only when p is 1 or q is 1), a group consisting of an aryl group having 6 to 40 carbon atoms, or a heteroaryl group having 3 to 40 carbon atoms (these substituents may have, as a substituent, a fluorine atom, an alkyl group having 1 to 4 carbon atoms, an aryl group having 6 to 18 carbon atoms, an aryl group having 6 to 18 carbon atoms substituted with a fluorine atom, an aryl group having 6 to 18 carbon atoms substituted with an alkyl group having 1 to 4 carbon atoms, an aryl group having 6 to 18 carbon atoms substituted with a heteroaryl group having 3 to 13 carbon atoms, a heteroaryl group having 3 to 13 carbon atoms, or a heteroaryl group having 3 to 13 carbon atoms substituted with an alkyl group having 1 to 4 carbon atoms);

[0036] Ar 5 each independently represent a heteroaryl group having 3 to 13 carbon atoms or an aryl group having 6 to 18 carbon atoms (each of these substituents may independently have a fluorine atom, an alkyl group having 1 to 4 carbon atoms, an aryl group having 6 to 18 carbon atoms substituted with a fluorine atom, an aryl group having 6 to 18 carbon atoms substituted with an alkyl group having 1 to 4 carbon atoms, an aryl group having 6 to 18 carbon atoms substituted with a heteroaryl group having 3 to 13 carbon atoms, a heteroaryl group having 3 to 13 carbon atoms, or a heteroaryl group having 3 to 13 carbon atoms substituted with an alkyl group having 1 to 4 carbon atoms as a substituent);

[0037] X 1 , X 2 , X 3 and X 4each independently represents a single bond, an arylene group having 6 to 18 carbon atoms, or a heteroarylene group having 3 to 20 carbon atoms (which may be substituted with a fluorine atom, an alkyl group having 1 to 4 carbon atoms, a phenyl group, a biphenyl group, a naphthyl group, a furanyl group, a benzofuranyl group, a dibenzofuranyl group, a thiophenyl group, a benzothiophenyl group, or a dibenzothiophenyl group); r represents 0, 1 or 2; f represents 0, 1 or 2; Z 4 、 Z 5 and Z 6 each independently represents a nitrogen atom or CH; f +p+q is 1, 2 or 3.}

[0038] ≪Ar 4 and Ar 6 ≫ Ar 4 and Ar 6 each independently represents a single bond (only when p is 1 or q is 1), a group consisting of an aryl group having 6 to 40 carbon atoms, or a heteroaryl group having 3 to 40 carbon atoms (these substituents may have, as a substituent, a fluorine atom, an alkyl group having 1 to 4 carbon atoms, an aryl group having 6 to 18 carbon atoms, an aryl group having 6 to 18 carbon atoms substituted with a fluorine atom, an aryl group having 6 to 18 carbon atoms substituted with an alkyl group having 1 to 4 carbon atoms, an aryl group having 6 to 18 carbon atoms substituted with a heteroaryl group having 3 to 13 carbon atoms, a heteroaryl group having 3 to 13 carbon atoms, or a heteroaryl group having 3 to 13 carbon atoms substituted with an alkyl group having 1 to 4 carbon atoms).

[0039] ≪Ar 5 ≫ Ar 5each independently represent a heteroaryl group having 3 to 13 carbon atoms or an aryl group having 6 to 18 carbon atoms (each of these substituents may independently have a fluorine atom, an alkyl group having 1 to 4 carbon atoms, an aryl group having 6 to 18 carbon atoms substituted with a fluorine atom, an aryl group having 6 to 18 carbon atoms substituted with an alkyl group having 1 to 4 carbon atoms, an aryl group having 6 to 18 carbon atoms substituted with a heteroaryl group having 3 to 13 carbon atoms, a heteroaryl group having 3 to 13 carbon atoms, or a heteroaryl group having 3 to 13 carbon atoms substituted with an alkyl group having 1 to 4 carbon atoms as a substituent).

[0040] <X 1 , X 2 , X 3 and X 4 ≫ X 1 , X 2 , X 3 and X 4 teeth 、 Each of them independently represents a single bond, an arylene group having 6 to 18 carbon atoms, or a heteroarylene group having 3 to 20 carbon atoms (which may be substituted with a fluorine atom, an alkyl group having 1 to 4 carbon atoms, a phenyl group, a biphenyl group, a naphthyl group, a furanyl group, a benzofuranyl group, a dibenzofuranyl group, a thiophenyl group, a benzothiophenyl group, or a dibenzothiophenyl group).

[0041] ≪Z 4 , Z 5 and Z 6 ≫ Z 4 , Z 5 and Z 6 each independently represents a nitrogen atom or CH.

[0042] <Compounds represented by formulae (2a), (2b), and (2c)> The azine compound represented by formula (2) which is one embodiment of the present invention is preferably a compound represented by formulae (2a), (2b) and (2c).

[0043] [ka]

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[0046] ≪Ar 7 ≫ In the formula, Ar 7 are each independently a group selected from the group consisting of a single bond, an aryl group having 6 to 40 carbon atoms, or a heteroaryl group having 3 to 40 carbon atoms (these groups may be substituted with a fluoro group, a cyano group, a methyl group, a phenyl group, a biphenylyl group, a naphthyl group, a phenanthryl group, an anthryl group, a pyridyl group, a pyrazyl group, a pyrimidyl group, a quinolyl group, or an isoquinolyl group).

[0047] ≪L, Ar 8 and Ar 9 ≫ L, Ar 8 and Ar 9 are each independently a group consisting of an aryl group having 6 to 40 carbon atoms or a heteroaryl group having 3 to 40 carbon atoms (these groups may be substituted with a fluoro group, a cyano group, a methyl group, a phenyl group, a biphenylyl group, a naphthyl group, a phenanthryl group, an anthryl group, a pyridyl group, a pyrazyl group, a pyrimidyl group, a quinolyl group, or an isoquinolyl group).

[0048] Particularly preferred specific examples of the compound represented by formula (1) include the following (A-1) to (A-456), but the present invention is not limited to these.

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[0087] The compound represented by formula (1) according to the embodiment of the present invention can be produced by the production method described in JP-A-2015-34159 or the like.

[0088] The adamantane compound of formula (1) according to the embodiment of the present invention significantly improves the electron transporting property from the cathode to the light emitting layer by combining with other electron transporting materials, and improves the driving voltage, light emitting efficiency and power efficiency.

[0089] Examples of electron transport materials that can be combined with the adamantane compound represented by formula (1) include those described in JP 2007-314503, JP 2010-155826, JP 2011-84553, JP 2011-121934, JP 2015-27986, JP 2011-063584, JP 2008-280330, JP 2016-121120, JP 2012-144523, JP 2014-141467, JP 2019-19126, WO2016-002864, WO2017-221974, and JP 2015-134. 743, compounds described in JP 2020-94034, 8-hydroxyquinolinato lithium (Liq), bis(8-hydroxyquinolinato) zinc, bis(8-hydroxyquinolinato) copper, bis(8-hydroxyquinolinato) manganese, tris(8-hydroxyquinolinato) aluminum, tris(2-methyl-8-hydroxyquinolinato) aluminum, tris(8-hydroxyquinolinato) gallium, bis(10-hydroxybenzo[h]quinolinato) beryllium, bis(10-hydroxybenzo [h]quinolinato)zinc, bis(2-methyl-8-quinolinato)chlorogallium, bis(2-methyl-8-quinolinato)(o-cresolato)gallium, bis(2-methyl-8-quinolinato)-1-naphtholatoaluminum, bis(2-methyl-8-quinolinato)-2-naphtholatogallium, Alq3 (tris(8-quinolinolato)aluminum), aluminum(III) bis(2-methyl-8-hydroxyquinoline)-4-phenylphenolate (BAlq), and other metal complexes, beryllium bis(benzoxy) Examples of suitable quinolin-10-olate (Bebq2) and other quinoline derivatives, 1,2,4-triazole derivatives (TAZ, NTAZ), anthracene derivatives such as 9,10-di(naphthalene-2-yl)anthracene (DNA), triazine derivatives, pyrimidine derivatives, pyridine derivatives, bipyridine derivatives, oxadiazole derivatives, triazole derivatives, phenanthroline derivatives, fluoranthene derivatives, phosphine oxide derivatives, triphenylene derivatives, and silole derivatives, and these may be used in combination.

[0090] It is preferred to combine with a compound according to formula (2), in particular with at least one compound selected from formulae (2a), (2b) and (2c).

[0091] Specific examples of the compound represented by formula (2) to be combined with formula (1) are shown below as compounds (B-1) to (B-291), but the present invention is not limited thereto.

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[0113] <Structure of organic electroluminescent device> A typical structure of an organic electroluminescent device that may benefit from embodiments of the present invention includes a substrate, an anode, a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and a cathode. <Substrate to light-emitting layer>

[0114] The anode and cathode of the organic electroluminescent device are connected to a power source via electrical conductors. The organic electroluminescent device is operated by applying an electric potential between the anode and the cathode. Holes are injected into the organic electroluminescent device from the anode, and electrons are injected into the organic electroluminescent device from the cathode.

[0115] The organic electroluminescent device is typically covered with a substrate, and the anode or cathode can be in contact with the substrate. The electrode in contact with the substrate is conveniently called the lower electrode. Generally, the lower electrode is an anode, but the organic electroluminescent device of the present invention is not limited to such a form.

[0116] The substrate may be light transmissive or opaque, depending on the intended direction of light emission. Light transmissive properties are desirable for viewing the electroluminescent emission through the substrate. Transparent glass or plastic are commonly employed as such substrates. The substrate may be a composite structure comprising multiple layers of materials.

[0117] When electroluminescent light emission is viewed through the anode, the anode is made transparent or substantially transparent to the light emission. Common transparent anode materials used in the present invention include indium-tin oxide (ITO), indium-zinc oxide (IZO), or tin oxide. In addition, other metal oxides such as aluminum or indium-doped tin oxide, magnesium-indium oxide, or nickel-tungsten oxide are preferably used.

[0118] In addition to these oxides, metal nitrides, such as gallium nitride, metal selenides, such as zinc selenide, or metal sulfides, such as zinc sulfide, can be used as the anode. The anode can be modified with plasma-deposited fluorocarbons. For applications where the electroluminescent emission is only seen through the cathode, the transmission characteristics of the anode are not important and any conductive material can be used, transparent, opaque, or reflective. Examples of conductors for this application include gold, iridium, molybdenum, palladium, and platinum.

[0119] A hole injection layer can be provided between the anode and the hole transport layer. The material of the hole injection layer improves the film formation properties of organic material layers such as hole transport layers and hole injection layers, and helps to facilitate the injection of holes into the hole transport layer. Examples of materials suitable for use in the hole injection layer include porphyrin compounds, plasma-deposited fluorocarbon polymers, and amines having aromatic rings such as biphenyl groups and carbazole groups, such as m-MTDATA (4,4',4''-tris[(3-methylphenyl)phenylamino]triphenylamine), 2T-NATA (4,4',4''-tris[(N-naphthalen-2-yl)-N-phenylamino]triphenylamine), triphenylamine, tritolylamine, tolyldiphenylamine, N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diphenylamine, and N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diphenylamine. amine, N,N,N'N'-tetrakis(4-methylphenyl)-1,1'-biphenyl-4,4'-diamine, MeO-TPD (N,N,N'N'-tetrakis(4-methoxyphenyl)-1,1'-biphenyl-4,4'-diamine), N,N'-diphenyl-N,N'-dinaphthyl-1,1'-biphenyl-4,4'-diamine, N,N'-bis(methylphenyl)-N,N'-bis(4-normal butylphenyl)phenanthrene-9,10-diamine, or N,N'-diphenyl-N,N'-bis(9-phenylcarbazol-3-yl)-1,1'-biphenyl-4,4'-diamine.

[0120] The hole transport layer of the organic electroluminescent device preferably contains one or more hole transport compounds (hole transport materials), such as aromatic tertiary amines. Aromatic tertiary amines are compounds that contain one or more trivalent nitrogen atoms that are bonded only to carbon atoms, one or more of which form an aromatic ring.

[0121] In particular, the aromatic tertiary amine can be an arylamine, such as a monoarylamine, diarylamine, triarylamine, or a polymeric arylamine.

[0122] The hole transport material may be an aromatic tertiary amine having one or more amine groups. Additionally, a polymeric hole transport material may be used.

[0123] For example, poly(N-vinylcarbazole) (PVK), polythiophene, polypyrrole, polyaniline, etc. can be used. Specific examples include NPD (N,N'-bis(naphthalene-1-yl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine), α-NPD (N,N'-di(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine), TPBi (1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene), TPD (N,N'-bis(3-methylphenyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine), etc.

[0124] A layer containing dipyrazino[2,3-f:2',3'-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile (HAT-CN) may be provided as a charge generating layer between the hole injection layer and the hole transport layer.

[0125] The light-emitting layer of an organic electroluminescent device contains a phosphorescent or fluorescent material where light emission occurs as a result of electron-hole pair recombination in this region. The light-emitting layer may be formed from a single material, including both small molecules and polymers, but is more commonly formed from a host material doped with a guest compound, such that light emission comes primarily from the dopant and can be of any color.

[0126] Another embodiment is a light-emitting layer that undergoes a light-emitting process using Thermally Activated Delayed Fluorescence (TADF).

[0127] Examples of the host material for the light-emitting layer include compounds having a cyano group, a triazyl group, a pyrimidyl group, an adamantyl group, a biphenyl group, a fluorenyl group, a triphenylsilyl group, a carbazole group, a pyrenyl group, a dibenzofuranyl group, or an anthranyl group.

[0128] Specific examples include DPVBi (4,4'-bis(2,2-diphenylvinyl)-1,1'-biphenyl), BCzVBi (4,4'-bis(9-ethyl-3-carbazovinylene)-1,1'-biphenyl), TBADN (2-tertiarybutyl-9,10-di(2-naphthyl)anthracene), ADN (9,10-di(2-naphthyl)anthracene), CBP (4,4'-bis(carbazol-9-yl)biphenyl), CDBP (4,4'-bis(carbazol-9-yl)-2,2'-dimethylbiphenyl), and 9,10-bis(biphenyl)anthracene.

[0129] The host materials in the light-emitting layer can be an electron-transporting material, as defined below, a hole-transporting material, as defined above, or another material or combination of these materials that support hole-electron recombination.

[0130] Examples of fluorescent dopants include anthracene derivatives, pyrene derivatives, arylamine derivatives, tetracene derivatives, xanthene derivatives, perylene derivatives, rubrene derivatives, coumarin derivatives, rhodamine derivatives, quinacridone derivatives, dicyanomethylenepyran derivatives, thiopyran derivatives, polymethine derivatives, pyrylium derivatives, thiapyrylium derivatives, fluorene derivatives, periflanthene derivatives, indenoperylene derivatives, bis(azinyl)amine boron derivatives, bis(azinyl)methane derivatives, and carbostyril derivatives.

[0131] Examples of phosphorescent dopants include organometallic complexes of transition metals such as iridium, platinum, palladium, osmium, and europium.

[0132] Examples of dopants include Alq3 (tris(8-hydroxyquinoline)aluminum), DPAVBi (4,4'-bis[4-(di-para-tolylamino)styryl]biphenyl), perylene, Ir(PPy)3 (tris(2-phenylpyridine)iridium(III), or FlrPic (bis(3,5-difluoro-2-(2-pyridyl)phenyl-(2-carboxypyridyl)iridium(III), etc.).

[0133] <Electron transport layer> The electron transport layer of the organic electroluminescent device according to one embodiment of the present invention is a layer adjacent to the light-emitting layer, and is characterized in that it is composed of at least two layers, at least one of which contains an adamantane compound represented by formula (1). Hereinafter, the electron transport layer adjacent to the light-emitting layer is referred to as electron transport layer A. The electron transport layers present in order toward the cathode are referred to as electron transport layers B, C, etc.

[0134] The adamantane compound represented by formula (1) according to an embodiment of the present invention is preferably contained in the electron transport layer A. When both the electron transport layer A and the electron transport layer B contain the adamantane compound represented by formula (1), the compound contained in the electron transport layer A is not the same as the compound contained in the electron transport layer B. The difference may be due to the presence or absence of a dopant.

[0135] It is preferable that the electron transport layer A or B contains an azine compound represented by formula (2). The azine compound represented by formula (2) may be doped with a metal such as Na, Li, Cs, Yb, Au, Ca, Al, Mg, Sm, Ag, Cu, or Zn, a metal salt such as cesium carbonate, calcium carbonate, lithium fluoride, or barium oxide, an alkali metal complex such as lithium, sodium, or calcium, or an alkaline earth metal complex such as beryllium, magnesium, or calcium, and it is particularly preferable that the dopant is Liq.

[0136] The electron transport layer according to the embodiment of the present invention may contain an electron transport compound other than the compounds represented by formulas (1) and (2) as long as the effect of the present invention is not impaired.

[0137] Other electron transporting compounds include alkali metal complexes, alkaline earth metal complexes, earth metal complexes, etc. Desirable alkali metal complexes, alkaline earth metal complexes, and earth metal complexes include, for example, 8-hydroxyquinolinato lithium (Liq), bis(8-hydroxyquinolinato) zinc, bis(8-hydroxyquinolinato) copper, bis(8-hydroxyquinolinato) manganese, tris(8-hydroxyquinolinato) aluminum, tris(2-methyl-8-hydroxyquinolinato) aluminum, tris(8-hydroxyquinolinato) bis(10-hydroxybenzo[h]quinolinato)gallium, bis(10-hydroxybenzo[h]quinolinato)beryllium, bis(10-hydroxybenzo[h]quinolinato)zinc, bis(2-methyl-8-quinolinato)chlorogallium, bis(2-methyl-8-quinolinato)(o-cresolate)gallium, bis(2-methyl-8-quinolinato)-1-naphtholate aluminum, and bis(2-methyl-8-quinolinato)-2-naphtholate gallium.

[0138] Examples of the electron transport layer B and the like include triazine derivatives, pyrimidine derivatives, pyridine derivatives, fluoranthene derivatives, fluorenone derivatives, anthraquinodimethane derivatives, diphenoquinone derivatives, thiopyran dioxide derivatives, oxazole derivatives, oxadiazole derivatives, triazole derivatives, imidazole derivatives, perylene tetracarboxylic acid derivatives, fluorenylidenemethane derivatives, anthraquinodimethane derivatives, and anthrone derivatives.

[0139] In addition, the above-mentioned metal complexes, alkali metal oxides, alkaline earth oxides, rare earth oxides, alkali metal halides, alkaline earth halides, rare earth halides, SiO X , AlO X , SiN X , SiON, AlON, GeO X , LiO X , LiON, TiO X , TiON, TaO X ,TaON,TaN XInorganic compounds such as various oxides, nitrides, and oxynitrides of C, etc. may also be used.

[0140] <Cathode> When light emission is viewed only through the anode, the cathode used in the present invention can be formed from nearly any conductive material. Suitable cathode materials include sodium, sodium-potassium alloys, magnesium, lithium, magnesium / copper mixtures, magnesium / silver mixtures, magnesium / aluminum mixtures, magnesium / indium mixtures, aluminum / aluminum oxide (Al2O3) mixtures, indium, lithium / aluminum mixtures, rare earth metals, lanthanide metals such as ytterbium, and the like, and may be used in conjunction with an electron injection layer of a metal, a metal compound such as a metal oxide or metal fluoride, an organic compound, or an organometallic compound. EXAMPLES

[0141] Hereinafter, the present invention will be described in detail with reference to examples, although the present invention is not limited to these examples.

[0142] <Fabrication of Organic Electroluminescent Device> <Element Example 1> A glass substrate with an indium tin oxide (ITO) transparent electrode, on which a 2 mm wide striped pattern of ITO film (thickness 110 nm) was prepared, was used as the substrate. After cleaning this substrate with isopropyl alcohol, the surface was treated with ozone ultraviolet cleaning. After cleaning, the materials for each layer were vacuum-deposited on the substrate by vacuum deposition, and a 4 mm luminous area was formed, as shown in the cross section of Figure 1. 2 The organic electroluminescence device was produced. Each organic material was deposited by a resistance heating method. The materials used were as follows. The materials were purified by sublimation before use.

[0143] [ka]

[0144] [ka] (B-276) (B-271) (B-254)

[0145] [ka]

[0146] First, the glass substrate was placed in a vacuum deposition chamber and 1.0×10 -4 The pressure was reduced to 10 Pa.

[0147] Thereafter, a hole injection layer 2, a charge generation layer 3, a hole transport layer 4, a light-emitting layer 5, an electron transport layer 6 (corresponding to the electron transport layer A of the present invention), an electron injection layer 7 (corresponding to the electron transport layer B of the present invention), and a cathode layer 8 were formed as organic compound layers on a glass substrate with an ITO transparent electrode shown in FIG. 1 by laminating them in this order by vacuum deposition.

[0148] As the hole injection layer 2, a HIL was deposited to a thickness of 65 nm at a rate of 0.15 nm / sec.

[0149] As the charge generating layer 3, a film of HAT was formed at a speed of 0.05 nm / sec to a thickness of 5 nm.

[0150] As the hole transport layer 4, HTL was deposited to a thickness of 10 nm at a rate of 0.15 nm / sec.

[0151] As the light-emitting layer 5, EML-1 and EML-2 were deposited in a ratio of 95:5 to a thickness of 25 nm (deposition rate: 0.18 nm / sec).

[0152] As the electron transport layer 6, compound A-25 was deposited to a thickness of 5 nm (deposition rate: 0.15 nm / sec), and as the electron injection layer 7, ETL-1 (B-276) and Liq were deposited to a thickness of 25 nm in a ratio of 50:50 (mass ratio) (co-evaporation, deposition rate: 0.15 nm / sec).

[0153] Finally, a metal mask was placed so as to be perpendicular to the ITO stripes, and the cathode layer 7 was formed. The cathode layer 7 had a two-layer structure in which silver / magnesium (mass ratio 1 / 10) and silver were formed in this order to thicknesses of 80 nm (film formation rate 0.5 nm / sec) and 20 nm (film formation rate 0.2 nm / sec), respectively.

[0154] The thickness of each film was measured using a stylus film thickness gauge (DEKTAK).

[0155] Furthermore, this element was sealed in a nitrogen atmosphere glove box with oxygen and moisture concentrations of 1 ppm or less to produce an organic electroluminescent element Example 1. For sealing, a glass sealing cap and the film-formed substrate epoxy type ultraviolet curing resin (manufactured by Nagase ChemteX Corporation) were used.

[0156] <Element Example 2> Element Example 2 was prepared in the same manner as in Element Example 1, except that Compound A-50 was used in the electron transport layer 6 of Element Example 1.

[0157] <Element Example 3> Element Example 3 was produced in the same manner as Element Example 2, except that ETL-2 (B-271) was used for electron injection 7 in Element Example 2.

[0158] <Element Example 4> Element Example-4 was prepared in the same manner as in Element Example-1, except that ETL-3 (B-254) was used for the electron transport layer 6 of Element Example-1, and the compound A-170 and Liq were used for the electron injection layer 7 in a ratio of 50:50 (mass ratio).

[0159] <Comparative element example 1> Element Comparative Example-1 was produced in the same manner as Element Example-1, except that the electron transport layer 6 and the electron injection layer 7 were formed into 30 nm films of Compound A-25 and Liq in a ratio of 50:50 (mass ratio) (co-evaporation, film formation rate 0.15 nm / sec).

[0160] <Comparative element example 2> Element Comparative Example 2 was produced in the same manner as Element Example 1, except that the electron transport layer 6 and the electron injection layer 7 were formed into 30 nm films of ETL-1 (B-276) and Liq in a ratio of 50:50 (mass ratio) (co-evaporation, film formation rate 0.15 nm / sec).

[0161] <Comparative element example 3> Element Comparative Example 3 was prepared in the same manner as Element Example 1, except that T2T was used for the electron transport layer 6 of Element Example 1, and ETL-2 (B-271) and Liq were used for the electron injection layer 7 in a ratio of 50:50 (mass ratio).

[0162] <Comparative element example 4> Element Comparative Example 4 was produced in the same manner as Element Example 1, except that the electron transport layer 6 and the electron injection layer 7 were formed into 30 nm films of Compound A-170 and Liq in a ratio of 50:50 (mass ratio) (co-evaporation, film formation rate 0.15 nm / sec).

[0163] <Element evaluation> A direct current was applied to the prepared organic electroluminescent device, and the light-emitting characteristics were evaluated using a luminance meter, LUMINANCE METER (BM-9) manufactured by TOPCON. The light-emitting characteristics were evaluated using a current (current density 10 mA / cm 2 The voltage (V), current efficiency (cd / A) and power efficiency (lm / W) were measured when a current of 100 was passed through the capacitor, and the relative values ​​are shown in Table 1, with the value for Comparative Example 1 taken as 100. A smaller voltage value and a larger efficiency value indicate superiority in both cases. The measurements were carried out in an atmosphere of 23°C and 50% RH.

[0164] [Table 1]

[0165] As shown in Table 1, within the scope of the embodiments of the present invention, it is possible to obtain an organic electroluminescent device having high luminous efficiency and high power efficiency at a low voltage. It is also apparent that the effect is remarkable when the compound represented by formula (1) is adjacent to the light-emitting layer. [Explanation of symbols]

[0166] 1. Glass substrate with ITO transparent electrode 2. Hole injection layer 3. Charge generation layer 4. Hole transport layer 5.Emitting layer 6.Electron transport layer A 7.Electron transport layer B 8.Cathode

Claims

1. comprising an anode, a cathode and at least one light-emitting layer; At least two electron transport layers are provided between the cathode and the light emitting layer, the electron transport layer comprises an organic compound; An organic electroluminescent device, wherein at least one of the electron transport layers is a layer containing an adamantane compound represented by formula (1). 【Chemistry 1】 (In the formula, Ad represents a 1-adamantyl group or a 2-adamantyl group which may be substituted with a fluorine atom, an alkyl group having 1 to 4 carbon atoms, a carbonyl group, or a cyano group; Ar １ is a single bond, one or more R １ an aryl group having 6 to 40 carbon atoms which may be substituted with one or more R １ a heteroaryl group having 3 to 40 carbon atoms which may be substituted with Ar ２ is one or more R １ an aryl group having 6 to 40 carbon atoms which may be substituted with one or more R １ a heteroaryl group having 3 to 40 carbon atoms which may be substituted with R １ is a hydrogen atom, a deuterium atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a CHO group, NO ２ group, an alkyl group, an alkenyl group, a cycloalkyl group, a bicycloalkyl group, or a tricycloalkyl group having 1 to 20 carbon atoms, an adamantyl group, an alkoxy group having 1 to 10 carbon atoms, an aryl group having 6 to 40 carbon atoms, a heteroaryl group having 3 to 40 carbon atoms, P(═O)(Ar ３ ) ２ , C(=O)Ar ３ , B(Ar ３ ) ２ , B(OAr ３ ) ２ , OSO ２ Ar ３ , S(=O)Ar ３ , Si(Ar ３ ) ３ R １ are the same or different for each occurrence, and two or more adjacent R １ may form a ring together; Ar ３ each occurrence may be the same or different and represents a group consisting of an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 40 carbon atoms, or a heteroaryl group having 3 to 40 carbon atoms, and two or more adjacent Ar ３ may form a ring together; n represents 1, 2, or 3.

2. 2. The organic electroluminescence device according to claim 1, comprising an electron transport layer containing the adamantane compound represented by formula (1) and an electron transport layer containing the azine compound represented by formula (2). 【Chemistry 2】 (In the formula, Z １ , Z ２ , and Z ３ each independently represents a nitrogen atom or C-H; Ar １ and Ar ２ Each independently has the same meaning as the radicals described in claim 1.

3. 3. The organic electroluminescent device according to claim 1, wherein the layer containing the adamantane compound represented by formula (1) is adjacent to the light-emitting layer.

4. 4. The organic electroluminescent device according to claim 2, wherein the layer containing the azine compound represented by formula (2) is a mixed film with a metal or an organometallic compound.

5. 5. The organic electroluminescent device according to claim 2, wherein the layer containing the azine compound represented by the formula (2) is a mixed film with Liq.

6. 6. The organic electroluminescent device according to claim 1, wherein the light-emitting layer contains a compound having anthracene as a partial structure.

7. 6. The organic electroluminescent device according to claim 1, wherein the light-emitting layer contains a compound having dibenzofuran as a partial structure.

8. 8. The organic electroluminescent device according to claim 1, wherein the adamantane compound represented by formula (1) is an azine compound represented by formula (1a). 【Chemistry 3】 {In general formula (1a), Each Ad independently represents a 1-adamantyl group or a 2-adamantyl group optionally substituted with a fluorine atom, an alkyl group having 1 to 4 carbon atoms, a carbonyl group, or a cyano group; p and q each independently represent 0 or 1; Ar ４ and Ar ６ each independently represents a single bond (only when p is 1 or q is 1), a group consisting of an aryl group having 6 to 40 carbon atoms, or a heteroaryl group having 3 to 40 carbon atoms (these substituents may have, as a substituent, a fluorine atom, an alkyl group having 1 to 4 carbon atoms, an aryl group having 6 to 18 carbon atoms, an aryl group having 6 to 18 carbon atoms substituted with a fluorine atom, an aryl group having 6 to 18 carbon atoms substituted with an alkyl group having 1 to 4 carbon atoms, an aryl group having 6 to 18 carbon atoms substituted with a heteroaryl group having 3 to 13 carbon atoms, a heteroaryl group having 3 to 13 carbon atoms, or a heteroaryl group having 3 to 13 carbon atoms substituted with an alkyl group having 1 to 4 carbon atoms); Ar ５ each independently represent a heteroaryl group having 3 to 13 carbon atoms or an aryl group having 6 to 18 carbon atoms (each of these substituents may independently have as a substituent a fluorine atom, an alkyl group having 1 to 4 carbon atoms, an aryl group having 6 to 18 carbon atoms substituted with a fluorine atom, an aryl group having 6 to 18 carbon atoms substituted with an alkyl group having 1 to 4 carbon atoms, an aryl group having 6 to 18 carbon atoms substituted with a heteroaryl group having 3 to 13 carbon atoms, a heteroaryl group having 3 to 13 carbon atoms, or a heteroaryl group having 3 to 13 carbon atoms substituted with an alkyl group having 1 to 4 carbon atoms); X １ , X ２ , X ３ and X ４ each independently represents a single bond, an arylene group having 6 to 18 carbon atoms, or a heteroarylene group having 3 to 20 carbon atoms (which may be substituted with a fluorine atom, an alkyl group having 1 to 4 carbon atoms, a phenyl group, a biphenyl group, a naphthyl group, a furanyl group, a benzofuranyl group, a dibenzofuranyl group, a thiophenyl group, a benzothiophenyl group, or a dibenzothiophenyl group); r represents 0, 1 or 2; f represents 0, 1 or 2; Z4, Z ５ and Z ６ each independently represents a nitrogen atom or C-H; f+p+q is 1, 2 or 3.

9. 6. The organic electroluminescent device according to claim 2, 4 or 5, wherein the azine compound represented by formula (2) is selected from the compounds represented by formulas (2a), (2b) and (2c): 【Chemistry 4】 【Chemistry 5】 【Chemistry 6】 {During the ceremony, Ar ７ each independently represents a group selected from the group consisting of a single bond, an aryl group having 6 to 40 carbon atoms, or a heteroaryl group having 3 to 40 carbon atoms (these groups may be substituted with a fluoro group, a cyano group, a methyl group, a phenyl group, a biphenylyl group, a naphthyl group, a phenanthryl group, an anthryl group, a pyridyl group, a pyrazyl group, a pyrimidyl group, a quinolyl group, or an isoquinolyl group); L, Ar ８ and Ar ９ are each independently a group consisting of an aryl group having 6 to 40 carbon atoms or a heteroaryl group having 3 to 40 carbon atoms (these groups may be substituted with a fluoro group, a cyano group, a methyl group, a phenyl group, a biphenylyl group, a naphthyl group, a phenanthryl group, an anthryl group, a pyridyl group, a pyrazyl group, a pyrimidyl group, a quinolyl group, or an isoquinolyl group).

10. 10. The organic electroluminescent device according to claim 1, wherein Ad in the formula (1) is a 1-adamantyl group.

11. R in the formula (1) １ The organic electroluminescent device according to any one of claims 1 to 10, wherein is a hydrogen atom, a fluorine atom, a methyl group, an adamantyl group, a phenyl group, a naphthyl group, a phenanthryl group, an anthryl group, a chrysenyl group, a pyrenyl group, a triphenylenyl group, a fluorenyl group, a dimethylfluorenyl group, a 9,9'-spirobifluorenyl group, a furanyl group, a benzofuranyl group, a dibenzofuranyl group, a thiophenyl group, a benzothiophenyl group, a dibenzothiophenyl group, a pyridyl group, a pyrimidyl group, a pyrazyl group, a quinolyl group, an isoquinolyl group, a quinazolyl group, a phenanthridyl group, an imidazolyl group, or a carbazolyl group.

12. R in the formula (1) １ The organic electroluminescent device according to any one of claims 1 to 11, wherein is a hydrogen atom.

13. 13. The organic electroluminescent device according to claim 1, wherein the formula (1) has a 1,3,5-triazine skeleton as a partial structure.

14. 14. The organic electroluminescent device according to claim 1, wherein the formula (1) has a pyrimidine skeleton as a partial structure.

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